According to statistics, more than 80% of all traffic accidents involve cars. More than one million people die every year and about 500,000 are injured. In an effort to address this issue, every 3rd Sunday in November has been designated by the United Nations as "World Day of Remembrance for Road Traffic Victims". Modern car security systems are aimed at reducing the existing sad statistics on this issue. Designers of new cars always closely follow production standards and. To do this, they model various dangerous situations on crash tests. Therefore, before the release of the car, it undergoes a thorough check and suitability for safe use on road.
But it is impossible to completely eliminate this type of incidents at such a level of development of technology and society. Therefore, the main emphasis is on the prevention of an emergency and the elimination of consequences after it.
Auto safety tests
The main organization for assessing the safety of cars is the European New Car Testing Association. It has existed since 1995. Each new brand of car that has passed through is rated on a five-star scale - the more stars, the better.
For example, through tests, they have proven that the use of high airbags reduces the risk of head injury by 5-6 times.
Active Safety Options
Active car safety systems are a complex of constructive and operational properties aimed at reducing the likelihood of accidents on the road.
Let's analyze the main parameters that are responsible for the level active safety.
- Responsible for the efficiency of driving during braking braking properties, the serviceability of which and allows you to avoid accidents. The anti-lock braking system is responsible for adjusting the level and the wheel system as a whole.
- Traction properties cars affect the possibility of increasing the speed in motion, take part in overtaking, restructuring in lanes and other maneuvers.
- The production and tuning of the suspension, steering, brake system is carried out using new quality standards and modern materials, which improves reliability systems.
- Has an impact on safety and auto layout. Cars with a front-engine layout are considered more preferable.
- It is the responsibility of the vehicle stability.
- Vehicle handling- the ability of the car to move along the trajectory selected. One of the definitions characterizing controllability is the ability of a car to change the motion vector, provided that the steering wheel is stationary - understeer. Distinguish tire and roll understeer.
- informative- a property of the car, the task of which is to provide the driver with timely information about the intensity of traffic on the road, weather conditions and others. Distinguish internal information content, which depends on the viewing radius, the effective operation of the blower and glass heating; external, depending on overall dimensions, serviceable headlights, brake lights; and additional information content, which helps with fog, snowfall and at night.
- Comfort- a parameter responsible for creating favorable microclimate conditions while driving.
Active safety systems
The most popular active safety systems that significantly increase the efficiency of the braking system are:
1) Anti-Lock Braking System. It eliminates the blocking of the wheels during braking. The task of the system is to prevent the car from slipping if the driver loses control during emergency braking. ABS reduces the stopping distance, which will help you avoid hitting a pedestrian or driving into a ditch. anti-lock braking system is an anti-skid system and electronic control sustainability;
2) Anti-slip system. designed to improve vehicle control in difficult weather conditions and conditions of poor adhesion, using the mechanism of action on the drive wheels;
3) . Prevents unpleasant drifts of the car thanks to the use of an electronic computer, which controls the moment of force of the wheel or wheels at the same time. The computer-guided system takes control when the probability of loss of human control is close - therefore, it is a very effective car security system;
4) Brake force distribution system. Complements the anti-lock braking system. The main difference is that the CPT helps control the braking system throughout the vehicle's journey, not just during an emergency. It is responsible for the uniform distribution of braking forces on all wheels in order to maintain the trajectory set by the driver;
5) Electronic differential lock mechanism. The essence of its work is as follows: during skidding or sliding, a situation often arises that one of the wheels hangs in the air, continuing to spin, and the support wheel stops. The driver loses control of the car, which creates the risk of an accident on the road. In turn, the differential lock allows you to transfer torque to the axle shafts or cardan shafts, normalizing the movement of the car.
6) Mechanism of automatic emergency braking . It helps in cases where the driver does not have time to fully press the brake pedal, i.e. the system itself automatically applies brake pressure.
7) Pedestrian warning system. If a pedestrian is dangerously close to the car, the system will give an audible signal, which will help to avoid an accident on the road and save his life.
There are also safety systems (assistants) that come into operation before the onset of an accident, as soon as they feel a potential threat to the life of the driver, while they take responsibility for the steering and braking system. The breakthrough for the development of these mechanisms has given a breakthrough in the study of electronic systems: new ones are being produced, the usefulness of control units is increasing.
Ministry of Education and Science
Russian Federation
State educational institution higher
vocational education
CONTROL WORK No. 1, No. 2
in the discipline "Safety Vehicle»
Active and passive safety car
Introduction
1 Technical characteristics of the car
2 Active vehicle safety
3 Passive vehicle safety
4 Environmental Safety car
Conclusion
Literature
INTRODUCTION
A modern car by its nature is a device of increased danger. Considering the social significance of the car and its potential danger during operation, manufacturers equip their cars with means that contribute to its safe operation. From the complex of means with which a modern car is equipped, passive safety means are of great interest. The passive safety of the car must ensure the survival and minimization of the number of injuries to the passengers of the car involved in a traffic accident.
In recent years, the passive safety of cars has become one of the most important elements in terms of manufacturers. Huge amounts of money are invested in the study of this topic and its development due to the fact that companies care about the health of customers.
I will try to explain a few definitions hidden under the broad definition of "passive safety".
It is divided into external and internal.
The internal includes measures to protect people sitting in the car through special interior equipment. External passive safety includes measures to protect passengers by giving the body special properties, for example, the absence sharp corners, deformation.
Passive safety - a set of components and devices that allow you to save the life of car passengers in case of an accident. Includes, among other things:
1.Airbags;
2. crushable or soft elements of the front panel;
3.folding steering column;
4.travmobezopasny pedal assembly - in the event of a collision, the pedals are separated from the attachment points and reduce the risk of damage to the driver's legs;
5.inertial seat belts with pretensioners;
6.energy-absorbing elements of the front and rear parts of the car, crushed upon impact - bumpers;
7.seat headrests - protect the passenger's neck from serious injuries when the car hits from behind;
8.safety glasses: tempered, which, when broken, shatter into many non-sharp fragments and triplex;
9.roll bars, reinforced A-pillars and upper windshield frame in roadsters and convertibles, transverse bars in the doors.
1 Specifications car GAZ-66-11
Table 1 - Characteristics of GAS - 66 - 11
| Automobile model | GAZ - 66 - 11 |
| Year of issue | 1985 - 1996 |
| Dimensional parameters, mm | |
| Length | 5805 |
| Width | 2322 |
| Height | 2520 |
| Base | 3300 |
| Track, mm | |
| front wheels | 1800 |
| Rear wheels | 1750 |
| Weight characteristics | |
| Curb weight, kg | 3640 |
| Load capacity, kg | 2000 |
| Gross weight, kg | 3055 |
| Speed characteristics | |
| Maximum speed, km/h | 90 |
| Acceleration time to 100 km/h, sec | no data |
| Brake mechanisms | |
| front axle | Drum type with internal pads. Diameter 380 mm., width of overlays 80 mm. |
| rear axle | |
Table 2. - Values of steady-state deceleration.
2 Active vehicle safety
In scientific terms, this is a set of design and operational properties of a car aimed at preventing traffic accidents and eliminating the prerequisites for their occurrence associated with the design features of the car.
And to put it simply, these are the car systems that help in preventing an accident.
RELIABILITY
The reliability of components, assemblies and vehicle systems is a determining factor in active safety. Particularly high requirements are placed on the reliability of the elements associated with the implementation of the maneuver - the brake system, steering, suspension, engine, transmission, and so on. Increasing the reliability is achieved by improving the design, the use of new technologies and materials.
VEHICLE LAYOUT
The layout of cars is of three types:
a) Front-engine - the layout of the car, in which the engine is located in front of the passenger compartment. It is the most common and has two options: rear-wheel drive (classic) and front-wheel drive. The last type of layout - front-engine front-wheel drive - is now widely used due to a number of advantages over drive on rear wheels:
Better stability and handling when driving on high speed, especially on wet and slippery roads;
Ensuring the necessary weight load on the driving wheels;
Less noise level, which is facilitated by the absence of cardan shaft.
At the same time, front-wheel drive vehicles have a number of disadvantages:
At full load, acceleration on the rise and on wet roads deteriorates;
At the moment of braking, the distribution of weight between the axles is too uneven (70% -75% of the vehicle's weight falls on the wheels of the front axle) and, accordingly, the braking forces (see Braking properties);
The tires of the front driving steered wheels are loaded more, respectively, more subject to wear;
Front wheel drive requires the use of complex units - hinges of equal angular velocities(SHRUS)
The combination of the power unit (engine and gearbox) with the final drive complicates access to individual elements.
b) The layout with a central engine - the engine is located between the front and rear axles, for cars is quite rare. It allows you to get the most roomy interior for given dimensions and good distribution along the axes.
c) Rear-engined - the engine is located behind the passenger compartment. This arrangement was common in small cars. When transmitting torque to the rear wheels, it made it possible to obtain an inexpensive power unit and distribute such a load along the axles, in which the rear wheels accounted for about 60% of the weight. This had a positive effect on the car's cross-country ability, but negatively on its stability and controllability, especially at high speeds. Cars with this layout, at present, are practically not produced.
BRAKING PROPERTIES
The ability to prevent accidents is most often associated with intensive braking, so it is necessary that the braking properties of the car ensure its effective deceleration in all traffic situations.
To fulfill this condition, the force developed by the brake mechanism must not exceed the traction force, which depends on the weight load on the wheel and the condition of the road surface. Otherwise, the wheel will lock up (stop rotating) and begin to slide, which can lead (especially when several wheels are blocked) to skid the car and significantly increase the braking distance. To prevent blocking, the forces developed by the brake mechanisms must be proportional to the weight load on the wheel. This is realized through the use of more efficient disc brakes.
Modern cars use an anti-lock braking system (ABS) that adjusts the braking force of each wheel and prevents them from slipping.
In winter and summer, the condition of the road surface is different, so for best implementation braking properties, it is necessary to use tires that correspond to the season.
TRACTION PROPERTIES
Traction properties (traction dynamics) of the car determine its ability to intensively increase the speed. The confidence of the driver when overtaking, passing through intersections largely depends on these properties. Traction dynamics is especially important for emergency situations when it is too late to slow down and it is not possible to maneuver difficult conditions, and you can avoid an accident only by being ahead of the events.
As with braking forces, the traction force on the wheel should not be greater than the traction force, otherwise it will begin to slip. Prevents this traction control system (PBS). When the car accelerates, it slows down the wheel, the rotation speed of which is greater than that of the others, and, if necessary, reduces the power developed by the engine.
VEHICLE STABILITY
Stability - the ability of a car to keep moving along a given trajectory, opposing the forces that cause it to skid and roll over in various road conditions at high speeds.
There are the following types of sustainability:
Transverse with rectilinear movement (course stability).
Its violation is manifested in the yaw (change of direction) of the car on the road and can be caused by the action of the lateral force of the wind, different values of traction or braking forces on the wheels of the left or right side, their slipping or sliding. large play in steering, incorrect wheel alignment, etc .;
Transverse during curvilinear motion.
Its violation leads to skidding or capsizing under the action of centrifugal force. An increase in the position of the center of mass of the car especially worsens stability (for example, a large mass of cargo on a removable roof rack);
Longitudinal.
Its violation is manifested in the slipping of the drive wheels when overcoming long icy or snowy slopes and the car sliding back. This is especially true for road trains.
DRIVABILITY OF THE VEHICLE
Handling - the ability of the car to move in the direction set by the driver.
One of the characteristics of handling is understeer - the ability of a car to change direction when the steering wheel is stationary. Depending on the change in the turning radius under the influence of lateral forces (centrifugal force on a turn, wind force, etc.), understeer can be:
Insufficient - the car increases the turning radius;
Neutral - the turning radius does not change;
Excessive - the turning radius is reduced.
Distinguish tire and roll understeer.
Tire steering
Tire steering is related to the property of tires to move at an angle to a given direction during side slip (displacement of the contact patch with the road relative to the plane of rotation of the wheel). If you install tires of a different model, the understeer may change and the car will behave differently when cornering when driving at high speed. In addition, the amount of side slip depends on the pressure in the tires, which must correspond to that specified in the vehicle's operating instructions.
Roll Steering
Roll oversteer is due to the fact that when the body tilts (roll), the wheels change their position relative to the road and the car (depending on the type of suspension). For example, if the suspension is double-wishbone, the wheels lean in the direction of the roll, increasing the slip.
INFORMATION
Informativeness - the property of the car to provide the necessary information to the driver and other road users. Insufficient information from other vehicles on the road about the condition of the road surface, etc. often causes accidents. Internal provides the driver with the opportunity to perceive the information necessary to drive the car.
It depends on the following factors:
Visibility should allow the driver to receive all the necessary information about the traffic situation in a timely manner and without interference. Faulty or inefficiently operating washers, windshield and heating systems, windshield wipers, lack of regular rear-view mirrors sharply impair visibility under certain road conditions.
The location of the instrument panel, buttons and control keys, gear lever, etc. should provide the driver with a minimum amount of time to check indications, actions on switches, etc.
External informativeness - providing other road users with information from the car, which is necessary for proper interaction with them. It includes an external light signaling system, a sound signal, dimensions, shape and color of the body. The information content of passenger cars depends on the contrast of their color relative to the road surface. According to statistics, cars painted in black, green, gray and blue colors, are twice as likely to get into an accident due to the difficulty of distinguishing them in low visibility conditions and at night. Faulty direction indicators, brake lights, parking lights will not allow other road users to recognize the driver's intentions in time and make the right decision.
COMFORTABILITY
The comfort of the car determines the time during which the driver is able to drive the car without fatigue. An increase in comfort is facilitated by the use of automatic transmission, speed controllers (cruise control), etc. At present, cars are produced equipped with adaptive cruise control. It not only automatically maintains the speed at a given level, but also, if necessary, reduces it up to a complete stop of the car.
3 Passive vehicle safety
BODY
It provides acceptable loads on the human body from a sharp deceleration in an accident and saves the space of the passenger compartment after the deformation of the body.
In a severe accident, there is a risk that the engine and other components can enter the driver's cab. Therefore, the cabin is surrounded by a special "safety grid", which is an absolute protection in such cases. The same stiffening ribs and bars can be found in the doors of the car (in case of side collisions). This also includes areas of energy repayment.
In a severe accident, there is a sharp and unexpected deceleration to a complete stop of the car. This process causes huge overloads on the bodies of passengers, which can be fatal. It follows from this that it is necessary to find a way to "slow down" the deceleration in order to reduce the load on the human body. One way to solve this problem is to design areas of destruction that dampen the energy of a collision in the front and rear parts of the body. The destruction of the car will be more severe, but the passengers will remain intact (and this is compared to the old "thick-skinned" cars, when the car got off with a "light fright", but the passengers received severe injuries).
The design of the body provides that in the event of a collision, the parts of the body are deformed, as it were, separately. Plus, high-tensioned metal sheets are used in the design. This makes the car more rigid, and on the other hand allows it to be not so heavy.
SEAT BELTS
At first, cars were equipped with two-point belts that “held” riders by the stomach or chest. In less than half a century, engineers realized that the multi-point design is much better, because in the event of an accident it allows you to distribute the pressure of the belt on the surface of the body more evenly and significantly reduce the risk of injury to the spine and internal organs. In motorsport, for example, four-, five- and even six-point seat belts are used - they keep the person in the seat “tightly”. But on the “citizen”, because of their simplicity and convenience, three-point ones took root.
In order for the belt to work properly for its purpose, it must fit snugly against the body. Formerly belts I had to adjust, adjust according to the figure. With the advent of inertial belts, the need for “manual adjustment” has disappeared - in the normal state, the coil rotates freely, and the belt can wrap around a passenger of any build, it does not hinder actions, and every time a passenger wants to change the position of the body, the strap always fits snugly to the body. But at the moment when “force majeure” comes, the inertial coil will immediately fix the belt. In addition, on modern machines squibs are used in the belts. Small explosive charges detonate, pulling the belt, and he presses the passenger to the back of the seat, preventing him from hitting.
Seat belts are one of the most effective means accident protection.
That's why cars must be equipped with seat belts, if attachment points are provided for this. The protective properties of belts largely depend on their technical condition. Belt malfunctions, in which the vehicle is not allowed to be operated, include tears and abrasions of the fabric tape of the straps visible to the naked eye, unreliable fixation of the tongue of the strap in the lock or the absence of automatic ejection of the tongue when the lock is unlocked. At the seat belts inertial type the strap tape should be freely retracted into the coil and blocked when the car moves sharply at a speed of 15 - 20 km / h. Belts that have experienced critical loads during an accident in which the car body has received serious damage are subject to replacement.
AIRBAGS
One of the most common and effective safety systems in modern cars (after seat belts) are airbags. They began to be widely used already in the late 70s, but it was not until a decade later that they really took their rightful place in the safety systems of most manufacturers' cars.
They are located not only in front of the driver, but also in front of the front passenger, as well as from the sides (in the doors, pillars, etc.). Some car models have their forced shutdown due to the fact that people with heart problems and children may not be able to withstand their false operation.
Today, airbags are commonplace not only in expensive cars, but also in small (and relatively inexpensive) cars. Why are airbags needed? And what are they?
Airbags have been developed for both drivers and front seat passengers. For the driver, the pillow is usually installed on the steering, for the passenger - on the dashboard (depending on the design).
The front airbags will deploy upon receiving alarm from the control unit. Depending on the design, the degree of filling of the pillow with gas may vary. The purpose of the front airbags is to protect the driver and passenger from injury by solid objects (engine body, etc.) and glass fragments in frontal collisions.
Side airbags are designed to reduce damage to vehicle occupants in a side impact. They are installed on the doors or in the backs of the seats. In the event of a side impact, external sensors send signals to the central airbag control unit. This makes it possible for some or all of the side airbags to deploy.
Here is a diagram of how the airbag system works:
Studies of the effect of airbags on the likelihood of driver death in frontal collisions have shown that it is reduced by 20-25%.
If the airbags have deployed or been damaged in any way, they cannot be repaired. The entire airbag system must be replaced.
The driver's airbag has a volume of 60 to 80 liters, and the front passenger - up to 130 liters. It is easy to imagine that when the system is triggered, the interior volume decreases by 200-250 liters within 0.04 seconds (see figure), which gives a considerable load on the eardrums. In addition, a pillow flying at a speed of more than 300 km / h is fraught with a considerable danger to people if they are not fastened with a seat belt and nothing delays inertial motion body against the pillow.
There are statistics on the impact of airbags on injuries in an accident. What can be done to reduce the chance of injury?
If your car has an airbag, do not place rear-facing child seats on a vehicle seat where the airbag is located. When inflated, the airbag may move the seat and cause injury to the child.
Airbags in the passenger seat increase the risk of death for children under the age of 13 sitting in that seat. A child less than 150 cm tall can be hit in the head by an air bag that opens at a speed of 322 km/h.
HEADRESTS
The role of the head restraint is to prevent sudden movement of the head during an accident. Therefore, you should adjust the height of the head restraint and its position in correct position. Modern head restraints have two degrees of adjustment to prevent injuries to the cervical vertebrae during the “overlapping” movement, which are so characteristic of rear-end collisions.
Effective protection when using a head restraint can be achieved if it is located exactly on the center line of the head at the level of its center of gravity and no more than 7 cm from the back of it. Be aware that some seat options change the size and position of the head restraint.
SAFETY STEERING GEAR
Crash-safe steering is one of the constructive measures that ensure the passive safety of the car - the ability to reduce the severity of the consequences of traffic accidents. The steering gear can cause serious injury to the driver in a frontal collision with an obstacle when the front of the vehicle is crushed when the entire steering gear moves towards the driver.
The driver can also be injured from the steering wheel or steering shaft when moving forward sharply due to a frontal collision, when the movement is 300 ... 400 mm with a weak seat belt tension. To reduce the severity of injuries sustained by the driver in frontal collisions, which account for about 50% of all traffic accidents, various designs of safety steering mechanisms are used. To this end, in addition to the steering wheel with a recessed hub and two spokes, which can significantly reduce the severity of injuries on impact, a special energy-absorbing device is installed in the steering mechanism, and the steering shaft is often made composite. All this provides a slight movement of the steering shaft inside the car body in frontal collisions with obstacles, cars and other vehicles.
Other energy-absorbing devices that connect composite steering shafts are also used in safety steering controls of passenger cars. These include rubber couplings of a special design, as well as devices of the "Japanese flashlight" type, which is made in the form of several longitudinal plates welded to the ends of the connected parts of the steering shaft. In collisions, the rubber clutch is destroyed, and the connecting plates are deformed and reduce the movement of the steering shaft inside the body.
The main elements of a wheel assembly are a rim with a disk and a pneumatic tire, which can be tubeless or consist of a tire, a tube and a rim tape.
EMERGENCY EXITS
Roof hatches and windows of buses can be used as emergency exits for quick evacuation of passengers from the passenger compartment in case of an accident or fire. For this purpose, inside and outside the passenger compartment of buses, special means for opening emergency windows and hatches. So, glasses can be installed in the window openings of the body on two locking rubber profiles with a locking cord. In case of danger, it is necessary to pull out the lock cord using the bracket attached to it, and squeeze out the glass. Some windows are hung in the opening on hinges and are provided with handles for opening them outward.
Devices for actuation emergency exits Buses in service must be in working order. However, during the operation of buses, ATP employees often remove the bracket on emergency windows, fearing deliberate damage to the window seal by passengers or pedestrians in cases where this is not dictated by necessity. Such "prudence" makes it impossible for emergency evacuation of people from buses.
4 Vehicle environmental friendliness
Environmental Safety- this is a property of the car, which allows to reduce the harm caused to road users and the environment during its normal operation. measures to reduce harmful effects vehicles on the environment should be considered a reduction in exhaust emissions and noise levels.
The main pollutants during the operation of vehicles are:
– oil products during their evaporation;
– abrasion products of tires, brake pads and clutch discs, asphalt and concrete surfaces.
The main measures to prevent and reduce the harmful effects of vehicles on the environment should be considered:
1) the development of such car designs that would pollute less atmospheric air toxic components of the exhaust gases and would create a lower level of noise;
2) improving the methods of repair, maintenance and operation of vehicles in order to reduce the concentration of toxic components in exhaust gases, the level of noise produced by vehicles, and environmental pollution with operating materials;
3) compliance in the design and construction of roads, engineering structures, service facilities with such requirements as fitting an object into the landscape; a rational combination of elements of the plan and the longitudinal profile, ensuring the constancy of the speed of the car; protection of surface and ground waters from pollution; water and wind erosion control; prevention of landslides and collapses; conservation of flora and fauna; reduction of areas allocated for construction; protection of buildings and structures near the road from vibrations; combating traffic noise and air pollution; application of construction methods and technologies that bring the least damage to the environment;
4) the use of means and methods of organizing and regulating traffic, providing optimal modes the movement and characteristics of traffic flows, the reduction of stops at traffic lights, the number of gear shifts and the time of operation of engines in unsteady conditions.
Vehicle Noise Reduction Methods
To reduce the noise of the car, first of all, they strive to design less noisy mechanical components; reduce the number of processes accompanied by shocks; reduce the magnitude of unbalanced forces, the speed of flow around parts with gas jets, the tolerances of mating parts; improve lubrication; use plain bearings and noiseless materials. In addition, the reduction of vehicle noise is achieved by the use of noise-absorbing and noise-isolating devices.
Noise in the intake tract of the engine can be reduced with the help of a specially designed air cleaner with resonant and expansion chambers, and inlet pipe designs that reduce the speed of the air-fuel mixture flow around the internal surfaces. These devices allow you to reduce the intake noise level by 10-15 dB A-weighted.
Noise level, when exhaust gases are released(when they flow through the exhaust valves), can reach 120–130 dB on the A scale. To reduce exhaust noise, active or reactive silencers are installed. The most common simple and cheap active silencers are multi-chamber channels, the inner walls of which are made of sound-absorbing materials. The sound is damped as a result of the friction of the exhaust gases against the inner walls. The longer the muffler and the smaller the cross section of the channels, the more intense the sound is damped.
Jet silencers are a combination of elements of different acoustic elasticity; noise reduction in them occurs due to repeated reflection of sound and its return to the source. It should be remembered that the more efficient the muffler works, the more the effective engine power decreases. These losses can reach 15% or more. During the operation of vehicles, it is necessary to carefully monitor the serviceability (primarily tightness) of the intake and exhaust tracts. Even a small depressurization of the muffler dramatically increases the exhaust noise. Noise in the transmission, chassis and bodywork of a new serviceable vehicle can be reduced through design improvements. The gearbox uses synchronizers, helical gears of constant mesh, blocking tapered rings and a number of other design solutions. Intermediate propeller shaft supports, hypoid main gears, and less noisy bearings are gaining popularity. Improved suspension elements. In the structures of bodies and cabs, welding, noise-insulating gaskets and coatings are widely used. Noise in the above parts and mechanisms of cars can occur and reach significant values only in case of malfunctions of individual components and parts: breakage of the gear teeth, warpage of the clutch discs, imbalance of the cardan shaft, violation of the gaps between the gears in the main gear, etc. The noise of the car increases especially sharply in case of malfunction of various elements of the body. The main way to eliminate noise is the correct technical operation of the car.
CONCLUSION
Ensuring the good condition of the structural elements of the car, the requirements for which were considered earlier, can reduce the likelihood of an accident. However, it has not yet been possible to create absolute safety on the roads. That is why experts in many countries pay great attention to the so-called passive car safety, which allows to reduce the severity of the consequences of an accident.
LITERATURE
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3. Theory and design of the car and engine
Vakhlamov V.K., Shatrov M.G., Yurchevsky A.A.
4. Organization road transport and traffic safety 6 studies. allowance for students of higher education. institutions / A.E. Gorev, E.M. Oleshchenko .- M .: Publishing Center "Academy". 2006.(p.187-190)
Vehicle safety. Vehicle safety includes a set of design and operational properties that reduce the likelihood of traffic accidents, the severity of their consequences and the negative impact on the environment.
The concept of vehicle design safety includes active and passive safety.
Active safety structures are constructive measures aimed at preventing accidents. These include measures that ensure controllability and stability when driving, efficient and reliable braking, easy and reliable steering, low driver fatigue, good visibility, effective operation of external lighting and signaling devices, as well as improving the dynamic qualities of the car.
Passive safety structures are constructive measures that exclude or minimize the consequences of an accident for the driver, passengers and cargo. They provide for the use of safety steering column designs, energy-intensive elements on the front and rear of the car, upholstery of the cab and body and soft linings, seat belts, safety glass, sealed fuel system, reliable fire-fighting devices, locks for the hood and body with locking devices, safe layout of parts and whole cars.
In recent years, much attention has been paid to improving the safety of car design in all countries producing them. In the United States of America more widely. The active safety of a vehicle refers to its properties that reduce the likelihood of a traffic accident.
Active safety is provided by several operational features that allow the driver to confidently drive a car, accelerate and brake with the required intensity, and maneuver on the roadway, which is required by the traffic situation, without significant expenditure of physical strength. The main of these properties are: traction, braking, stability, controllability, cross-country ability, information content, habitability.
Under passive vehicle safety its properties that reduce the severity of the consequences of a traffic accident are understood.
Distinguish between external and internal passive safety of the car. The main requirement of external passive safety is to ensure such a constructive performance of the outer surfaces and elements of the car, in which the probability of human injury by these elements in the event of a traffic accident would be minimal.
As you know, a significant number of accidents are associated with collisions and collisions with a fixed obstacle. In this regard, one of the requirements for the external passive safety of cars is to protect drivers and passengers from injury, as well as the car itself from damage using external elements designs.
Figure 8.1 - Scheme of forces and moments acting on the car
Figure 8.1 - Vehicle safety structure
An example of a passive safety element can be a safety bumper, the purpose of which is to soften the impact of a car on obstacles at low speeds (for example, when maneuvering in a parking area).
The endurance limit of overloads for a person is 50-60g (g-acceleration of free fall). The limit of endurance for an unprotected body is the amount of energy perceived directly by the body, corresponding to a speed of about 15 km / h. At 50 km / h, the energy exceeds the allowable by about 10 times. Therefore, the task is to reduce the acceleration of the human body in a collision due to prolonged deformation of the front of the car body, in which as much energy as possible would be absorbed.
That is, the greater the deformation of the car and the longer it takes, the less overload the driver experiences when colliding with an obstacle.
External passive safety includes decorative elements of the body, handles, mirrors and other parts fixed on the car body. On modern cars, weary door handles are increasingly being used, which do not cause injury to pedestrians in the event of a traffic accident. Protruding emblems of manufacturers on the front of the car are not used.
There are two main requirements for the internal passive safety of a car:
Creation of conditions under which a person could safely withstand any overload;
Exclusion of traumatic elements inside the body (cabin). The driver and passengers in a collision after an instantaneous stop of the car still continue to move, maintaining the speed that the car had before the collision. It is at this time that most injuries occur as a result of hitting the head on the windshield, the chest on the steering wheel and steering column, and the knees on the lower edge of the instrument panel.
Analysis of traffic accidents shows that the vast majority of those killed were in the front seat. Therefore, when developing measures for passive safety, first of all, attention is paid to ensuring the safety of the driver and passenger in the front seat.
The design and rigidity of the car body are carried out in such a way that the front and rear parts of the body are deformed during collisions, and the deformation of the passenger compartment (cabin) is as minimal as possible to preserve the life support zone, that is, the minimum required space within which the squeezing of the human body inside the body is excluded .
In addition, the following measures should be provided to reduce the severity of the consequences of a collision:
The need to move the steering wheel and steering column and absorb impact energy, as well as evenly distribute the impact over the surface of the driver’s chest;
Elimination of the possibility of ejection or falling out of passengers and the driver (reliability of door locks);
Availability of individual protective and restraint means for all passengers and the driver (seat belts, head restraints, air bags);
Absence of traumatic elements in front of passengers and the driver;
Body equipment safety glasses. The effectiveness of the use of seat belts in combination with other activities is confirmed by statistical data. Thus, the use of belts reduces the number of injuries by 60 - 75% and reduces their severity.
One of the effective ways to solve the problem of limiting the movement of the driver and passengers in a collision is the use of pneumatic bags, which, when a car collides with an obstacle, are filled with compressed gas in 0.03 - 0.04 s, absorb the impact of the driver and passengers and thereby reduce the severity of injury.
Under vehicle crash safety its properties are understood in the event of an accident not to impede the evacuation of people, not to cause injuries during and after evacuation. The main measures of post-accident safety are fire-fighting measures, measures for the evacuation of people, emergency signaling.
The most severe consequence of a traffic accident is a car fire. Fires most often occur during severe accidents such as car collisions, collisions with fixed obstacles, and rollovers. Despite the low probability of fire (0.03 -1.2% of the total number of incidents), their consequences are severe.
They cause almost complete destruction of the car and, if evacuation is impossible, the death of people. In such accidents, fuel spills out of a damaged tank or from filler neck. Ignition occurs from hot parts of the exhaust system, from a spark from a faulty ignition system or from friction of body parts on the road or on the body of another car. There may be other causes of fire.
Under the environmental safety of the vehicle its ability to reduce the degree of negative impact on the environment is understood. Environmental safety covers all aspects of car use. The main environmental aspects associated with the operation of the car are listed below.
Loss of useful land area. The land necessary for the movement and parking of automobiles is excluded from the use of other branches of the national economy. The total length of the world network of paved roads exceeds 10 million km, which means the loss of the area of more than 30 million hectares. The expansion of streets and squares leads to “an increase in the territories of cities and the lengthening of all communications. In cities with a developed road network and car service enterprises, the areas allocated for traffic and car parking occupy up to 70% of the entire territory.
In addition, huge territories are occupied by factories for the production and repair of cars, services for ensuring the functioning of road transport: gas stations, service stations, campsites, etc.
Air pollution. The main mass of harmful impurities dispersed in the atmosphere is the result of the operation of vehicles. An average power engine emits about 10 m 3 of exhaust gases into the atmosphere in one day of operation, which include carbon monoxide, hydrocarbons, nitrogen oxides and many other toxic substances.
In our country, the following norms are established for the average daily maximum permissible concentrations of toxic substances in the atmosphere:
Hydrocarbons - 0.0015 g/m;
Carbon monoxide - 0.0010 g/m;
Nitrogen dioxide - 0.00004 g/m.
Use of natural resources. Millions of tons of high-quality materials are used for the production and operation of cars, which leads to the depletion of their natural reserves. With the exponential growth in per capita energy consumption that characterizes industrialized countries, there will soon come a point when existing energy sources will not be able to meet human needs.
A significant proportion of the energy consumed is spent by cars, efficiency. engines which is 0.3 0.35, therefore, 65 - 70% of the energy potential is not used.
Noise and vibration. The noise level that can be tolerated for a long time by a person without harmful consequences is 80 - 90 dB. On the streets of large cities and industrial centers, the noise level reaches 120 - 130 dB. Ground vibrations caused by the movement of vehicles have a detrimental effect on buildings and structures. To protect a person from the harmful effects of vehicle noise, various methods are used: improving the design of cars, noise protection structures and green spaces along busy city highways, organizing such a traffic mode when the noise level is the lowest.
The magnitude of the traction force is greater, the greater the engine torque and gear ratios gearboxes and final drive. But the magnitude of the traction force cannot exceed the force of adhesion of the driving wheels to the road. If the traction force exceeds the traction force of the wheels with the road, then the drive wheels will slip.
Adhesion force is equal to the product of the adhesion coefficient and the adhesion weight. For traction car the coupling weight is equal to the normal load on the braked wheels.
Adhesion coefficient depends on the type and condition of the road surface, on the design and condition of the tires (air pressure, tread pattern), on the load and speed of the vehicle. The value of the friction coefficient decreases on wet and damp road surfaces, especially with an increase in speed and a worn tire tread. For example, with a dry road with asphalt concrete surface, the coefficient of adhesion is 0.7 - 0.8, and for a wet road - 0.35 - 0.45. On an icy road, the friction coefficient drops to 0.1 - 0.2.
Gravity car is attached in the center of gravity. In modern cars, the center of gravity is located at a height of 0.45 - 0.6 m from the road surface and approximately in the middle of the car. Therefore, the normal load of a passenger car is distributed approximately equally along its axles, i.e. the coupling weight is equal to 50% of the normal load.
The height of the center of gravity for trucks is 0.65 - 1 m. For fully loaded trucks, the coupling weight is 60-75% of the normal load. At four-wheel drive vehicles the towing weight is equal to the normal load of the vehicle.
When the car is moving, these ratios change, since there is a longitudinal redistribution of the normal load between the axles of the car, when the driving wheels transmit traction, the rear wheels are more loaded, and when the car is braked, the front wheels are loaded. In addition, the redistribution of the normal load between the front and rear wheels occurs when the vehicle is moving uphill or downhill.
The redistribution of the load, changing the value of the adhesive weight, affects the amount of adhesion of the wheels to the road, the braking properties and the stability of the car.
Forces of resistance to movement. Traction force on the driving wheels of the car. When a car is moving uniformly on a horizontal road, such forces are: the rolling resistance force and the air resistance force. When the car moves uphill, a lifting resistance force arises (Fig. 8.2), and when the car accelerates, an acceleration resistance force (inertia force) arises.
Rolling resistance force occurs due to deformation of the tires and the road surface. It is equal to the product of the normal load of the car and the coefficient of rolling resistance.
Figure 8.2 - Scheme of forces and moments acting on the car
The rolling resistance coefficient depends on the type and condition of the road surface, the design of the tires, their wear and air pressure in them, and the speed of the vehicle. For example, for a road with asphalt concrete surface, the rolling resistance coefficient is 0.014 0.020, for a dry dirt road - 0.025-0.035.
On hard road surfaces, the coefficient of rolling resistance increases sharply with a decrease in air pressure in the tires, and increases with an increase in speed, as well as with an increase in braking and torque.
The force of air resistance depends on the coefficient of air resistance, the frontal area and the speed of the vehicle. The air resistance coefficient is determined by the type of car and the shape of its body, and the frontal area is determined by the wheel track (the distance between the centers of the tires) and the height of the car. The force of air resistance increases in proportion to the square of the speed of the car.
Lift resistance force the greater, the greater the mass of the car and the steepness of the road, which is estimated by the angle of elevation in degrees or the magnitude of the slope, expressed as a percentage. When the car is moving downhill, the force of resistance to lifting, on the contrary, accelerates the movement of the car.
On roads with asphalt concrete pavement, the longitudinal slope usually does not exceed 6%. If the coefficient of rolling resistance is taken equal to 0.02, then the total resistance of the road will be 8% of the normal load of the car.
Overclocking resistance force(inertial force) depends on the mass of the car, its acceleration (increase in speed per unit time) and the mass of rotating parts (flywheel, wheels), for the acceleration of which the traction force is also expended.
When the car accelerates, the acceleration resistance force is directed in the direction opposite to the movement. When the car is braking and slowing down its movement, the inertia force is directed in the direction of the car movement.
Vehicle braking. Braking agility is characterized by the vehicle's ability to quickly decelerate and stop. A reliable and efficient braking system allows the driver to confidently drive the car at high speed and, if necessary, stop it in a short section of the road.
Modern cars have four brake systems: working, spare, parking and auxiliary. Moreover, the drive to all circuits of the brake system is separate. Most important for control and safety is the service brake system. With its help, service and emergency braking of the car is carried out.
Service call braking with a slight deceleration (1-3 m / s 2). It is used to stop the car at a previously planned place or to smoothly reduce speed.
Emergency braking is called with a large deceleration, usually maximum, reaching up to 8 m / s2. It is used in a dangerous situation to prevent a pasture or an unexpected obstacle.
When the car is braking, it is not the traction force that acts on and about the wheels, but the braking forces Pt1 and Pt2, as shown in (Fig. 8.3). The force of inertia in this case is directed towards the movement of the car.
Consider the process of emergency braking. The driver, having noticed an obstacle, assesses the traffic situation, decides on braking and puts his foot on the brake pedal. The time t required for these actions (driver reaction time) is shown in (Fig. 8.3) segment AB.
During this time, the car travels the path S without slowing down. Then the driver presses the brake pedal and the pressure from the main brake cylinder (or brake valve) is transferred to the wheel brakes (the brake actuator response time tpt is the segment BC. The time tt depends mainly on the design of the brake actuator. It is equal to an average of 0.2-0, 4s for vehicles with hydraulic drive and 0.6-0.8 s with pneumatic. For road trains with a pneumatic brake drive, the time t can reach 2-3 s. The car travels the distance St in time t, also without slowing down.
Figure 8.3 - Stopping and braking distance of the car
After the time tpt, the brake system is fully applied (point C), and the vehicle speed begins to decrease. In this case, the deceleration first increases (segment CD, braking force rise time tnt), and then remains approximately constant (steady-state) and equal to jset (time tset, segment DE).
The duration of the period tnt depends on the mass of the vehicle, the type and condition of the road surface. The greater the mass of the car and the coefficient of adhesion of tires to the road, the greater the time t. The value of this time is in the range of 0.1-0.6 s. During the time tnt, the car moves a distance Snt, and its speed decreases slightly.
When driving with a steady deceleration (time tset, segment DE), the vehicle speed decreases by the same amount for every second. At the end of braking, it drops to zero (point E), and the car, having passed the path Sst, stops. The driver takes his foot off the brake pedal and braking occurs (braking time tot, section EF).
However, under the action of inertia, the front axle is loaded during braking, while the rear axle, on the contrary, is unloaded. Therefore, the reaction on the front wheels Rzl increases, and on the rear wheels Rz2 decreases. The traction forces change accordingly, so for most cars, full and simultaneous use of the clutch by all wheels of the car is extremely rare and the actual deceleration is less than the maximum possible.
In order to take into account the decrease in deceleration, it is necessary to introduce a correction factor for the braking efficiency K.e, equal to 1.1-1.15 for cars and 1.3-1.5 for trucks and buses, into the formula for determining jst. On slippery roads the braking forces on all wheels of the car almost simultaneously reach the value of the adhesion force.
The braking distance is less than the stopping distance, because during the reaction time of the driver, the car moves a considerable distance. Stopping and braking distances increase with an increase in speed and a decrease in the friction coefficient. The minimum permissible braking distances at an initial speed of 40 km / h on a level road with a dry, clean and even surface are standardized.
The efficiency of the brake system depends to a large extent on its technical condition and the technical condition of the tires. If oil or water enters the brake system, the coefficient of friction between the brake linings and drums (or discs) decreases, and the braking torque decreases. When the tire tread wears out, the friction coefficient decreases.
This entails a reduction in braking forces. In operation, often the braking forces of the left and right wheels of the car are different, which causes it to turn around a vertical axis. The reasons may be various wear brake pads and drums or tires, or oil or water entering the braking system on one side of the vehicle, reducing the coefficient of friction and reducing braking torque.
Vehicle stability. Stability is understood as the ability of a vehicle to resist skidding, slipping, and overturning. Distinguish between longitudinal and transverse stability of the car. More likely and dangerous loss of lateral stability.
The course stability of a car is called its ability to move in the right direction without corrective actions from the driver, i.e. with the steering wheel in the same position. A vehicle with poor directional stability changes direction unexpectedly all the time.
This poses a threat to other vehicles and pedestrians. The driver, driving an unstable car, is forced to carefully monitor road conditions and constantly adjust traffic to prevent going off the road. When driving such a car for a long time, the driver quickly gets tired, and the possibility of an accident increases.
The violation of directional stability occurs as a result of the action of disturbing forces, for example, gusts of side wind, wheel strikes on uneven roads, and also due to a sharp turn of the steered wheels by the driver. Loss of stability can be caused by technical malfunctions(incorrect adjustment of the brake mechanisms, excessive play in the steering or its jamming, tire puncture, etc.)
Especially dangerous is the loss of directional stability at high speed. The car, changing the direction of movement and deviating even on not high angle, may be in the oncoming lane after a short time. So, if a car moving at a speed of 80 km / h deviates from the straight direction of motion by only 5 °, then after 2.5 s it will move to the side by almost I m and the driver may not have time to return the car to the previous lane.
Figure 8.4 - Diagram of the forces acting on the car
Often the vehicle loses stability when driving on a road with a transverse slope (slope) and when turning on a level road.
If the car is moving along a slope (Fig. 8.4, a), gravity G makes an angle β with the road surface and it can be decomposed into two components: force P1, parallel to the road, and force P2, perpendicular to it.
Force P1, tend to move the car downhill and overturn it. The larger the angle of the slope β, the greater the force P1, therefore, the more likely the loss of lateral stability. When turning the car, the cause of the loss of stability is the centrifugal force Rc (Fig. 8.4, b), directed from the center of rotation and applied to the center of gravity of the car. It is directly proportional to the square of the speed of the car and inversely proportional to the radius of curvature of its trajectory.
Cross-slip of tires on the road is counteracted by traction forces, as already noted above, which depend on the coefficient of adhesion. On dry, clean surfaces, the traction forces are strong enough that the car does not lose stability even with a large lateral force. If the road is covered with a layer of wet mud or ice, the car may skid even when it is moving at low speed along a relatively gentle curve.
The maximum speed at which one can move along a curved section with a radius R without lateral tire slip is So, when turning on a dry asphalt concrete surface (jx = 0.7) at R = 50m, one can move at a speed of about 66 km/h. Overcoming the same turn after rain (jx = 0.3) without slipping, one can move only at a speed of 40-43 km/h. Therefore, before turning, you need to reduce the speed the more, the smaller the radius of the upcoming turn. The formula determines the speed at which the wheels of both axles of the car slide in the transverse direction at the same time.
This phenomenon is extremely rare in practice. Much more often, the tires of one of the axles - front or rear - begin to slide. Cross slip of the front axle occurs rarely and also stops quickly. In most, the wheels of the rear axle slide, which, starting to move in the transverse direction, slide faster and faster. This accelerating cross-slip is called a skid. To stop a skid that has begun, turn the steering wheel in the direction of the skid. At the same time, the car will begin to move along a more gentle curve, the turning radius will increase, and the centrifugal force will decrease. You need to turn the steering wheel smoothly and quickly, but not at a very large angle, so as not to cause a turn in the opposite direction.
As soon as the skid stops, you must also smoothly and quickly return the steering wheel to the neutral position. It should also be noted that in order to get out of a skid of a rear-wheel drive car, the fuel supply must be reduced, and on a front-wheel drive, on the contrary, it should be increased. Often skidding occurs during emergency braking, when the grip of the tires with the road has already been used to create braking forces. In this case, you should immediately stop or weaken the braking and thereby increase the lateral stability of the vehicle.
Under the action of a lateral force, the car can not only slide along the road, but also tip over on its side or on the roof. The possibility of overturning depends on the position of the center, the gravity of the car. The higher the center of gravity is from the surface of the vehicle, the more likely it is to roll over. Buses overturn especially often, as well as trucks employed in the transportation of light, bulky goods (hay, straw, empty containers, etc.) and liquids. Under the action of the transverse force, the springs on one side of the car are compressed and the body tilts, increasing the risk of rollover.
Vehicle handling. Under controllability is understood the property of the car to provide movement in the direction given by the driver. The drivability of a car, more than its other performance properties, is related to the driver.
To ensure good controllability, the design parameters of the car must correspond to the psychophysiological characteristics of the driver.
The controllability of the car is characterized by several indicators. The main ones are: the limit value of the curvature of the trajectory during the circular motion of the car, the limit value of the rate of change of the curvature of the trajectory, the amount of energy spent on driving the car, the amount of spontaneous deviations of the car from a given direction of movement.
The steered wheels constantly deviate from the neutral position under the influence of road irregularities. The ability of the steered wheels to maintain a neutral position and return to it after a turn is called steered wheel stabilization. Weight stabilization is provided by the transverse inclination of the front suspension pivots. When the wheels are turned, due to the transverse inclination of the kingpins, the car rises, but with its weight it strives to return the turned wheels to their original position.
The high-speed stabilizing moment is due to the longitudinal inclination of the pivots. The kingpin is located so that it upper end directed back, and the bottom forward. The pivot axis crosses the road surface in front of the wheel-to-road contact patch. Therefore, when the car is moving, the rolling resistance force creates a stabilizing moment about the king pin axis. With a working steering gear and steering mechanism after turning the car steered wheels and the steering wheel must return to the neutral position without the participation of the driver.
In the steering mechanism, the worm is located relative to the roller with a slight skew. In this regard, in the middle position, the gap between the worm and the roller is minimal and close to zero, and when the roller and bipod deviate in any direction, the gap increases. Therefore, when the wheels are in the neutral position, increased friction is created in the steering mechanism, which contributes to the stabilization of the wheels and high-speed stabilizing moments.
Incorrect adjustment of the steering mechanism, large gaps in the steering gear can cause poor stabilization of the steered wheels, causing the vehicle to oscillate. A car with poor stabilization of the steered wheels spontaneously changes direction, as a result of which the driver is forced to continuously turn the steering wheel in one direction or the other in order to return the car to its lane.
Poor stabilization of the steered wheels requires a significant amount of physical and mental energy of the driver, increases the wear of tires and steering gear parts.
When the car is moving on a turn, the outer and inner wheels roll along circles of different radii (Fig. 8.4). In order for the wheels to roll without slipping, their axes must intersect at one point. To fulfill this condition, the steered wheels must turn at different angles. Turning the wheels of the car at different angles provides a steering trapezoid. The outer wheel always turns at a smaller angle than the inner one, and this difference is greater, the greater the angle of rotation of the wheels.
Tire elasticity has a significant effect on the steering performance of a car. When a lateral force acts on the car (it does not matter, inertial forces or crosswinds), the tires are deformed and the wheels, together with the car, are displaced in the direction of the lateral force. This displacement is the greater, the greater the lateral force and the higher the elasticity of the tires. The angle between the plane of rotation of the wheel and the direction of its movement is called the slip angle 8 (Fig. 8.5).
With the same slip angles of the front and rear wheels, the car retains given direction movement, but rotated relative to it by the value of the slip angle. If the slip angle of the wheels of the front axle is greater than the slip angle of the wheels of the rear bogie, then when the car moves around a corner, it will tend to move along an arc of a larger radius than the one set by the driver. This property of the car is called understeer.
If the slip angle of the rear axle wheels is greater than the slip angle of the front axle wheels, then when the car moves around a corner, it will tend to move along an arc of a smaller radius than the one set by the driver. This property of a car is called oversteer.
The turning of the car can be controlled to some extent by using tires of different plasticity, changing the pressure in them, changing the distribution of the mass of the car along the axes (due to the placement of the load).
Figure 8.5 - Kinematics of the car turning and wheel slip scheme
An oversteered vehicle is more agile but requires more attention and high professional excellence from the driver. An understeer car requires less attention and skill, but makes the driver's job more difficult as it requires the steering wheel to be turned through large angles.
The influence of steering and on the movement of the car becomes noticeable and significant only at high speeds.
The controllability of the car depends on the technical condition of its chassis and steering. Reducing the pressure in one of the tires increases its rolling resistance and reduces the lateral stiffness. Therefore, a car with a flat tire is constantly deviating to its side. To compensate for this slip, the driver turns the steered wheels in the direction opposite to the slip, and the wheels begin to roll with side slip, while wearing out intensively.
The wear of the steering gear parts and the pivot connection leads to the formation of gaps and the occurrence of arbitrary vibrations of the wheels.
With large clearances and high speeds, the vibrations of the front wheels can be so significant that their traction is impaired. The cause of wheel oscillation may be their imbalance due to tire imbalance, patches on the tube, dirt on the wheel rim. To prevent vibrations of the wheels, they must be balanced on a special stand by installing balancing weights on the disk.
Vehicle passability. Cross-country ability is understood as the property of a car to move on uneven and difficult terrain without touching the lower contour of the body with irregularities. The passability of the car is characterized by two groups of indicators: geometric indicators of passability and traction indexes of passability. Geometric indicators characterize the probability of hitting the car over bumps, and the support-coupling characteristics characterize the possibility of driving on difficult road sections and off-road.
According to the cross-country ability, all cars can be divided into three groups:
General purpose vehicles (wheel formula 4x2, 6x4);
Cross-country vehicles (wheel formula 4x4, 6x6);
Cars high cross, having a special layout and design, multi-axle with all-wheel drive, tracked or half-tracked, amphibious vehicles and other vehicles specially designed to work only in off-road conditions.
Consider the geometric indicators of patency. Ground clearance is the distance between the lowest point of the vehicle and the road surface. This indicator characterizes the possibility of the car moving without touching the obstacles located on the way of movement (Fig. 8.6).
Figure 8.6 - Geometric indicators of patency
The radii of the longitudinal and transverse patency are the radii of the circles tangent to the wheels and the lowest point of the car, located inside the base (track). These radii characterize the height and shape of the obstacle that the car can overcome without hitting it. The smaller they are, the higher the car's ability to overcome significant irregularities without touching them with its lowest points.
The front and bottom corners of the overhang, respectively αp1 and αp2, are formed by the road surface and the plane tangent to the front or rear wheels and to the protruding lowest points of the front or rear of the car.
Max Height the threshold that the car can overcome for the driven wheels is 0.35 ... 0.65 of the wheel radius. The maximum threshold height overcome by the driving wheel can reach the radius of the wheel and is sometimes limited not by the traction capabilities of the vehicle or the grip properties of the road, but by small overhang or clearance angles.
The maximum required width of the passage at the minimum turning radius of the car characterizes the ability to maneuver on small areas, so the vehicle's cross-country ability in the horizontal plane is often considered as a separate operational property of maneuverability. The most maneuverable are cars with all steerable wheels. In the case of towing with a trailer or semi-trailers, the maneuverability of the car deteriorates, since when the road train turns, the trailer will mix towards the center of the turn, which is why the lane width of the road train is greater than that of a single car.
The following are related to the support-coupling indicators of patency. Maximum traction force - the greatest traction force that a car is capable of developing in low gear. Coupling weight - the force of gravity of the car attributable to the drive wheels. The more scenes you sing weight, the higher the car's cross-country ability.
Among vehicles with a 4x2 wheel arrangement, rear-engined rear-wheel drive and front-engine front-wheel drive vehicles have the greatest cross-country ability, since with this arrangement the driving wheels are always loaded with engine mass. The specific tire pressure on the supporting surface is defined as the ratio of the vertical load on the tire to the contact area, measured along the contour of the tire contact patch with the road q = GF.
This indicator is of great importance for the cross-country ability of the car. The lower the specific pressure, the less the soil is destroyed, the less the depth of the formed track, the lower the rolling resistance and the higher the car's cross-country ability.
The track matching ratio is the ratio of the front wheel track to the rear wheel track. With the full coincidence of the track of the front and rear wheels, the rear wheels roll on the ground compacted by the front wheels, and the rolling resistance is minimal. If the track of the front and rear wheels does not match, additional energy is expended to destroy the compacted walls of the track formed by the front wheels by the rear wheels. Therefore, in cross-country vehicles, single tires are often installed on the rear wheels, thereby reducing rolling resistance.
The patency of the car largely depends on its design. So, for example, in cross-country vehicles, limited-slip differentials, lockable interaxle and interwheel differentials, wide-profile tires with developed lugs, winches for self-pulling and other devices that facilitate the vehicle's off-road capability are used.
Informativeness of the car. Information content is understood as the property of the car to provide the necessary information to the driver and other road users. In all conditions, the information perceived by the driver is essential for safe driving. With insufficient visibility, especially at night, information content, among other operational properties of the car, has a special effect on traffic safety.
Distinguish between internal and external informativity.
Internal informativeness- this is the property of the car to provide the driver with information about the operation of units and mechanisms. It depends on the design of the instrument panel, devices that provide visibility, handles, pedals and vehicle control buttons.
The location of the instruments on the panel and their device should allow the driver to spend a minimum of time to observe the readings of the instruments. Pedals, handles, buttons and controls should be located so that the driver can easily find them, especially at night.
Visibility depends mainly on the size of the windows and wipers, the width and location of the cab pillars, the design of the windshield washers, the blowing and heating systems for the windows, the location and design of the rear-view mirrors. Visibility also depends on the comfort of the seat.
External informativeness- this is the property of the car to inform other road users about its position on the road and the driver's intentions to change direction and speed. It depends on the size, shape and color of the body, the location of retroreflectors, external light signaling, sound signal.
Trucks medium and heavy duty, road trains, buses due to their dimensions are more visible and better distinguishable than cars and motorcycles. Cars painted in dark colors (black, gray, green, blue), because of the difficulty of distinguishing them, are 2 times more likely to get into an accident than those painted in light and bright colors.
The external light signaling system must be distinguished by reliable operation and provide unambiguous interpretation of signals by road users in any visibility conditions. Dipped and main beam headlights, as well as other additional headlights (spotlight, fog lights) improve the internal and external information content of the car when driving at night and in conditions of poor visibility.
Vehicle habitability. The habitability of a vehicle is the properties of the environment surrounding the driver and passengers, which determine the level of comfort and aesthetic i and the places of their work and rest. Habitability is characterized by a microclimate, ergonomic characteristics of the cabin, noise and vibrations, gas contamination and smooth running.
The microclimate is characterized by a combination of temperature, humidity and air velocity. The optimal air temperature in the car cabin is considered to be 18 ... 24 ° С. A rise or fall in temperature, especially a long period time, affects the psychophysiological characteristics of the driver, leads to a slowdown in reaction and mental activity, to physical fatigue and, as a result, to a decrease in labor productivity and traffic safety.
Humidity and air velocity greatly affect the thermoregulation of the body. At low temperatures and high humidity, heat transfer increases and the body undergoes more intensive cooling. At high temperatures and humidity, heat transfer is sharply reduced, which leads to overheating of the body.
The driver begins to feel the movement of air in the cabin at its speed of 0.25 m/s. The optimum air velocity in the cabin is about 1m/s.
Ergonomic properties characterize the compliance of the seat and controls of the vehicle with the anthropometric parameters of a person, i.e. the size of his body and limbs.
The design of the seat should allow the driver to sit behind the controls, ensuring a minimum of energy consumption and constant readiness for a long time.
The color scheme inside the cabin also has a certain attention to the driver's psyche, which, of course, affects the driver's performance and traffic safety.
The nature of noise and vibrations is the same - mechanical vibrations of car parts. The sources of noise in a car are the engine, transmission, exhaust system, suspension. The effect of noise on the driver is the cause of an increase in his reaction time, a temporary deterioration in the characteristics of vision, a decrease in attention, impaired coordination of movements and functions of the vestibular apparatus.
Domestic and international regulations set the maximum permissible noise level in the cabin within 80 - 85 dB.
Unlike noise, which is perceived by the ear, vibrations are perceived by the surface of the driver's body. Just like noise, vibration causes great harm to the driver's condition, and with constant exposure for a long time, it can affect his health.
Gas pollution is characterized by the concentration of exhaust gases, fuel vapors and other harmful impurities in the air. Of particular danger to the driver is carbon monoxide - a colorless and odorless gas. Getting into the human blood through the lungs, it deprives it of the ability to deliver oxygen to the cells of the body. A person dies of suffocation, feeling nothing and not understanding what is happening to him.
In this regard, the driver must carefully monitor the tightness of the engine exhaust tract, prevent the suction of gases and vapors from engine compartment into the cab. It is strictly forbidden to start and, most importantly, warm up the engine in the garage when people are in it.
Passive safety is a set of design and operational properties of a car aimed at reducing the severity of a traffic accident. Passive safety combines the elements and systems of the car, which are put into operation immediately at the time of the accident. their main task is to save the lives of passengers and reduce the likelihood of injury to a minimum.
In the sixties of the last century, a book by Washington lawyer Ralph Nader was published, where he cited many facts of road accidents in the form of car collisions, their overturning and ignition, which led to human casualties and injuries, which, according to his conclusion, could have been avoided if cars designed with even minimal regard for safety factors. Powerful motorist rights organizations that emerged shortly after the publication of the book began the fight for vehicle safety, which was supported by the authorities in Europe and North America. Many of the demands of the general public were granted the force of law.
Automakers were forced to respond to what was happening and the first thing they did was to reconsider their approaches to the layout schemes and design of car bodies, where in the first place they demanded the protection of the driver and passengers in an accident. Briefly, these approaches can be formulated as follows:
The interior of the car is a capsule, a zone of maximum security, which should be invincible either from the front, or from the back, or from the sides.
None of the equipment in the cabin should be injurious to the driver and passengers.
Everything in the car around the safety capsule should dampen the kinetic energy of the collision, reducing the likelihood of damage to the capsule, and the engine, transmission units and suspension assemblies should "go" under it.
Accommodation fuel tank, fuel lines and other elements of the fuel system, as well as elements of electrical and electronic systems should be such that the likelihood of a fire is minimal.
Rollover resistance should be maximized.
Distinguish external and internal passive vehicle safety.
External passive safety reduces injuries to other road users: pedestrians, drivers and passengers of other vehicles involved in an accident, and also reduces mechanical damage the cars themselves. This is achieved by constructive exclusion of sharp corners, protruding handles, and other elements from the outer surface of the body.
Two main requirements are imposed on the internal passive safety of a car: the creation of conditions under which a person could safely withstand significant overloads and the exclusion of traumatic elements in the cabin (cabin).
The basis modern protection people - parts of the body that deform upon impact and absorb its energy, strong safety arcs, reinforced front roof pillars, safety (soft, without sharp corners, ribs, edges, etc.) car interior parts that create a certain "safety grid" for the driver and passengers. The current regulatory documents establish only the criteria for the severity of injuries to people in collisions under given conditions - in the direction of impact, speed, position of an obstacle, and the like. The ways in which these requirements are met are not regulated. In a severe accident, there is a sharp decrease in speed, which leads to significant overloads on the bodies of people, which can be fatal. Therefore, the task is to find a way to "stretch" this overload in time and over the surface of the body. The SRS2 passive safety system has been developed to keep a person in place in a car collision so that, while moving uncontrollably through the cabin, the driver and passengers do not injure each other or about the details of the body and interior. The system includes the following elements:
Seat belts, including inertial and preloaded;
Airbags;
Flexible or soft front panel elements;
Steering column, consisting in frontal impact;
Safety pedal assembly - in the event of a collision, the pedals are separated from the attachment points and reduce the risk of damage to the driver's legs;
Energy-absorbing elements of the front and rear of the car, crumple on impact (bumpers)
The headrests of the seats, the passenger's neck protect against serious injuries when the car hits from behind;
Safety glass - tempered, which, when destroyed, shatter into many non-sharp fragments and triplex;
Roll bars, reinforced A-pillars and upper windshield frame in roadsters and convertibles;
Crossbars in the doors.
The modern passive safety system of the car is electronically controlled, which ensures the effective interaction of most components. The control system includes:
Input sensors (two front and two side to determine the direction of impact, one control)
Control block;
Actuators of system components.
The input sensors fix the parameters at which an emergency occurs and convert them into electrical signals. The input sensors include;
1. Shock sensor. As a rule, two shock sensors are installed on each side of the car. They provide the appropriate airbags. In the rear, shock sensors are used when the vehicle is equipped with electrically operated active head restraints.
2. Seat belt buckle switch. The seat belt buckle switch detects the use of the seat belt.
3. Front passenger seat occupied sensor, driver and front passenger seat position sensor. The front passenger seat occupied sensor allows, in the event of an emergency and the absence of a passenger in the front seat, to save the corresponding airbag. Depending on the position of the driver's and front passenger's seats, which is fixed by the corresponding sensors, the order and intensity of the application of the system components changes.
As sensors of passive safety systems are widely used accelerometers.
Accelerometers are linear acceleration sensors for monitoring the angle of inclination of bodies, inertia forces, shock loads and vibration. In transport, accelerometers are used to control airbags, in inertial navigation systems (gyroscopes). There are mainly three types of accelerometers:
Piezo-fuel based on a multilayer piezoelectric polymer film. When the film is deformed under the action of an inertial force, a potential difference arises at the boundaries of the film layers. The parameters of the sensors depend on temperature and pressure, therefore they have low accuracy, are cheap, and are used to control airbags and control shock and vibration deformations.
Volumetric integral accelerometers, such as NAC - 201/3 from Lucas NovaSensor, which are also used in airbags. In them, a measuring silicon beam with an implanted piezoresistor flexes under the action of an inertial mass when a car collides. The output signal of the crystal is 50 - 100 mV.
Surface integrated circuits from Analog Devices ADXL105, 150, 190,202, having a collar crystal structure Hf 40 - 50 cells. These highly sensitive sensors are used in security systems. The mass of the weight is 0.1 mg, the sensitivity is 0.2 angstroms.
Based on the comparison of the sensor signals with the control parameters, the control unit recognizes the onset of an emergency and activates the necessary actuators of the system elements.
The actuators of the elements of the passive safety system are:
Airbag igniter;
Igniter tensioned seat belt;
Igniter (relay) for emergency disconnect battery;
Igniter for active head restraint drive mechanism (when using electrically driven head restraints);
The control lamp signaling about not fastened seat belts.
Activation of executive devices is done in a certain combination in accordance with the embedded software.
Seat belts. They prevent the occupant from coasting down and thus possibly colliding with the interior of the vehicle or other occupants (so-called secondary impacts), and ensure that the occupant is in a position that allows the airbags to deploy safely. In addition, during an accident, the seat belts stretch a little, thereby absorbing the kinetic energy of the passenger, which additionally slows down his movement, and distributes the braking force over a large surface. Seat belt stretching is carried out with the help of extension and cushioning devices provided with energy-absorbing technologies. It is also possible to use pre-tensioners in seat belts at the time of an accident.
According to the number of attachment points, the following types of seat belts are distinguished:
Two-point seat belts;
Three-point seat belts;
Four, five and six point seat belts.
A promising design is inflatable seat belts that fill with gas during an accident. They increase the area of contact with the passenger and, accordingly, reduce the load on the person. The inflatable section can be shoulder and waist. Tests show that this seat belt design provides additional side impact protection. As a measure against non-use of seat belts, automatic seat belts have been offered since 1981.
Modern cars are equipped with pretensioner seat belts ( pretensioners). Retractable seat belts are designed to prevent a person from moving forward (relative to vehicle movement) in an accident in advance. This is achieved by winding and reducing the freedom of fit of the seat belt on the signal of the sensor. Pull-on, usually mounted on the seat belt buckle. Less commonly retractable are installed on the seat belt fitting. According to the principle of operation, the following designs of cable tensioners are distinguished; ball; rotary; rail; tape.
These designs of tensioners are equipped with a mechanical or electric drive, which provides ignition of the squib. Structurally, they are divided into a mechanical drive, based on the occupation of the squib mechanically (piercing with a striker) an electric drive, which provides ignition of the squib by an electrical signal from the electronic control unit (or from a separate sensor).
The tensioner provides winding up to a segment of the seat belt up to 130 mm long in 13 ms.
Airbags. An airbag complements the seat belt, reducing the chance of the passenger's head and upper body hitting any part of the vehicle interior. They also reduce the risk of serious injury by distributing the impact force over the passenger's body. Airbag deployment by its very nature deploys a large object very quickly, so in some situations it can cause injury or even death to a passenger, can kill an unrestrained child who is sitting too close to the airbag or has been thrown forward by emergency braking force, so the placement of the child must be appropriate certain requirements.
Modern passenger cars have several airbags, which are located in different places in the car. Depending on the location, the following types of airbags are distinguished:
Front airbags;
Side airbags;
Head airbags;
knee airbags;
Central airbag.
For the first time, frontal airbags were used on Mercedes-Benz cars in 1981. Distinguish frontal airbag driver and front passenger. The front passenger airbag is usually deactivated. In a number of designs of front airbags, two-stage and also multi-stage operation is used, depending on the severity of the accident (the so-called adaptive airbags). The driver's frontal airbag is located in the steering wheel, the front passenger's - in the upper right part of the front.
Side airbags are designed to reduce the risk of injury to the pelvis, chest and abdomen in the event of an accident. The highest quality side airbags have a two-chamber design.
Head airbags (another name - "curtain" airbags) serve, as the name suggests, to protect the head in a side collision.
The knee airbag protects the driver's knees and shins from injury. In 2009, Toyota introduced a center airbag to reduce the severity of secondary injury to occupants in a side impact. It is located in the armrest of the front row of seats or the central part of the backrest of the rear seats.
Airbag device. The airbag consists of an elastic shell, filled with gas, a gas generator and a control system.
The gas generator is used to fill the pillow shell with gas. Together, the shell and the gas generator form an airbag module. The designs of gas generators are distinguished by their shape (dome-shaped and tubular), by the nature of their operation (with one-stage and two-stage operation), by the method of gas formation (solid fuel and hybrid).
The solid propellant gas generator consists of a housing, a squib and a solid propellant charge. The charge is a mixture of sodium oxide, potassium nitrate and silicon dioxide. The ignition of the fuel comes from the squib and is accompanied by the formation of nitrogen gas, which inflates the airbag shell.
The airbags are activated upon impact 3 milliseconds after the impact sensor is triggered. Within 20-40 ms, the pillow is completely inflated, and after 100 ms, the pillow is inflated. Depending on the direction of impact, only certain airbags are activated. If the impact force exceeds a predetermined level, the shock sensors transmit a signal to the control unit. After processing the signals from all sensors, the control unit determines the need and time for the deployment of certain airbags and other components of the passive safety system. Accordingly, the triggering conditions for different airbags are different. For example, frontal airbags are deployed under the following conditions: the force of a frontal impact exceeds a predetermined value; hitting a solid solid object (curb, sidewalk edge, pit wall) hard landing after a jump; car fall; oblique impact to the front of the car. The frontal airbags do not deploy in the event of a rear impact, side impact, or vehicle rollover. All airbags deploy when the vehicle catches fire.
Airbag deployment algorithms are constantly being improved and become more and more complex. Modern algorithms take into account the speed of the vehicle, the speed of its deceleration, the weight of the passenger and his location, the use of a seat belt, the presence of a child seat.
Headrest. Headrest - a protective device built into the upper part of the seat, there is a measure of emphasis for the back of the head of the driver or passenger of the car. The head restraints are either designed as part of the extended seat backs or are separate adjustable cushions above the seats. Head restraints are installed to reduce the effect of uncontrolled movement of the head, especially backwards, as a result of an accident due to a collision with another vehicle from behind. A very important role in protecting the cervical vertebrae in an accident is played by the correct installation and adjustment of the head restraint. A significant disadvantage of fixed head restraints is the need for their height adjustment.
Active head restraints equipped with special movable lever hidden in the back of the chair. In the event of a rear impact of the car, the driver's back, due to inertia from the push, is pressed into the seat and presses the lower end of the lever. The mechanism, which works, brings the headrest closer to the driver's head even before it rolls over, thereby reducing the impact force. Active head restraints are effective in low to medium speed collisions, where injuries are most common and only in certain types of rear-end collisions. After a collision, the head restraints return to their original position. Active head restraints must always be correctly adjusted. The implementation of the electric drive of the active head restraint requires the presence of an electronic control system. The control system includes shock sensors, a control unit and the actual drive mechanism. The basis of the mechanism is a squib with electric ignition.
In a frontal impact, depending on its severity, the following can be triggered: pretensioning seat belts, frontal airbags and pretensioning seat belts.
In a frontal-diagonal impact, depending on its strength and angle of impact, the following may work: tensioned seat belts; front airbags and retractable seat belts; matching (right or left) side airbags and retractable seat belts; appropriate side airbags, head airbags and retractable seat belts; frontal airbags, matching side airbags, head airbags and retractable seat belts.
In the event of a side impact, depending on the severity of the impact, the following may be triggered: the appropriate side airbags and retractable seat belts; appropriate head airbags and retractable seat belts; matching side airbags, head airbags and retractable seat belts.
In the event of a rear impact, depending on the force of the impact, the following may work: tensioned seat belts; battery disconnector; active headrests.
Emergency disconnect designed to prevent short circuit in the electrical system and possible vehicle fire. The emergency battery disconnect switch is fitted to vehicles in which the battery is installed in the passenger compartment or in the luggage compartment. Distinguish the following designs of emergency opening: squib for disconnecting the battery; battery disconnect relay.
Pedestrian protection system It is designed to reduce the consequences of a collision between a pedestrian and a car in a traffic accident. The systems are produced by a number of companies and since 2011 have been installed on mass-produced passenger cars of European manufacturers. These systems have a similar design (Fig. 6.11).
Figure 6.11 - Scheme of the pedestrian protection system
Like any electronic system, the pedestrian protection system includes the following structural elements:
input sensors;
Control block;
executive devices.
Acceleration sensors (Remote Acceleration Sensor, RAS) are used as input sensors. 2-3 such sensors are installed in the front bumper. Additionally, a contact sensor can be installed.
The principle of operation of the pedestrian protection system is based on the opening of the hood when a car collides with a pedestrian, which increases the space between the hood and engine parts and, accordingly, reduces human injury. In fact, the raised hood serves as an airbag.
When a vehicle collides with a pedestrian, the acceleration sensors and the contact sensor transmit signals to the electronic control unit. The control unit, in accordance with the programmed program, if necessary, initiates the actuation of the bonnet lifter squibs.
In addition to the presented system on cars for the protection of pedestrians, such constructive solutions as a "soft" hood are used; frameless brushes; soft bumper; sloped hood and windshield. Since 2012, Volvo has been offering a pedestrian airbag on its vehicles.
In such a complex unit as a car, it is very easy to forget about one of the most basic systems - the protection and safety system. And if active safety is always covered in detail both by the media and by the dealers or sellers themselves, then passive safety is nothing more than a gray mouse inside the complex structure of a vehicle.
What is passive car safety
Passive safety is a set of features and adaptations of a vehicle that have their own unique design and operational differences, however, functionally aimed at ensuring the maximum safe conditions when you get into an accident. Unlike an active safety system, the action of which is aimed at saving the car from accidents, the car's passive safety system is activated after the accident has taken place.
In order to reduce the consequences of an accident, a whole set of devices is used, the purpose of which is to reduce the severity of an accident. For a more accurate classification, a division into two main groups is used:
internal system - it includes:
- Airbags
- Seat belts
- Seat structure (headrests, armrests, etc.)
- Body energy absorbers
- Other soft interior elements
External system - Another, no less important group, is presented in the form:
- Bumpers
- Protrusions on the body
- glasses
- rack amplifiers
Recently, on the pages of well-known news agencies, they began to cover in detail the points that report on all the elements of passive safety in a car. In addition, we should not forget the activities of the independent organization Euro NCAP (European New Car Assessment Program). This committee has been crash-testing all models entering the market for quite some time now, awarding test reports for both active and passive safety systems. Anyone can get acquainted with the data on the results of crash tests, making sure of each of the components of the protection system.
The image shows how all passive safety systems work harmoniously during an emergency (seat belts, airbags, seat with headrest).
Internal passive safety
All passive safety elements included in this list are designed to protect everyone in the passenger compartment of a car that has had an accident. That is why, in addition to equipping the car, it is very important special equipment(in good condition), it must be used by all participants in the ride for its intended purpose. Only compliance with all the rules will allow you to get the highest protection. Next, we will consider the most basic items that are included in the list of internal passive safety.
- The body is the basis of the entire security system. The strength of the car and the possible deformation of its parts directly depend on the material, condition, and design features of the car body. To protect passengers from getting under the hood contents into the cabin, the designers specifically use a "safety grill" - a strong layer that does not allow breaking the cabin base.
- Interior safety from structural elements is a whole list of devices and technologies that are designed to protect the health of the driver and passengers. For example, many salons provide for a folding steering wheel that does not allow additional damage to the driver. Besides, modern cars equipped with a safety pedal assembly, the action of which provides for the disconnection of the pedals from the mounts, reducing the load on the lower limbs.
To count on maximum safety during the use of the head restraint, you must very clearly set its position to a certain height that suits you.
- Seat belts - from accepted standard lap 2-point belts, which held the passenger with a conventional tie through the stomach or chest, were abandoned in the middle of the last century. Similar passive means security required improvements, which came in the form of multi-point belts. The increased functionality of this type of device made it possible to evenly distribute the kinetics throughout the body without traumatizing individual areas of the body.
- Airbags are the second most important (seat belts confidently hold the first line here), a passive safety system. Recognized in the late 70s. they are tightly integrated into all vehicles. The modern auto industry began to be equipped with a whole set of airbag systems that surround the driver and passengers from all sides, blocking potential damage zones. A sharp opening of the chamber with pillow storage activates the rapid filling of the latter air mixture, which cushions a person approaching by inertia.
- Seats and head restraints - the seat itself is not additional features during an accident other than to restrain the passenger in place. However, the head restraints, on the contrary, reveal their functionality just at the moment of collision, preventing the head from tilting back with subsequent trauma to the cervical vertebrae.
- Other internal passive safety features - many vehicles are provided with highly stressed metal sheets. Such an upgrade allows you to make the car more impact-resistant, while reducing its mass. Many cars also use active system areas of destruction, which, upon collision, dampen the emerging kinetics, and are themselves destroyed at the same time (increased destruction of the car is nothing compared to human life and health).
On the example of a frame of a small body smart car, you can see how passive safety plays a fundamental role even at the design stage of a future car.
External passive safety
If in the previous paragraph we considered the means and devices of a car that protect passengers and drivers at the time of an accident, then this time we will talk about a complex that allows you to maximally protect the health of a pedestrian who has fallen under the wheels of the car in question.
- Bumpers - the design of modern bumpers includes several energy- and kinetic-absorbing elements that are present both at the front of the car and at the rear. Their purpose is to absorb the energy arising from the impact due to blocks prone to crushing. This not only reduces the risk of damage to a pedestrian, but also greatly reduces damage inside the car.
- External protrusions of cars - as a rule, to useful properties such elements are difficult to attribute. However, as it may seem at first glance, most of these elements have a similar principle of self-destruction, described earlier in paragraph 6. of the section "Internal passive safety".
- Devices for the protection of pedestrians - individual manufacturing companies represented by Bosch, Siemens, TRW and others, have been actively developing systems for providing additional safety to pedestrians involved in an accident for several decades. For example, the Electronic Pedestrian Protection system will allow you to raise the roof of the hood, increasing the area of \u200b\u200bit collision with the body of a pedestrian, while acting as a "shield" from the harder and uneven parts of the engine compartment.
