The steering gear includes steering wheel, a shaft enclosed in a steering column, and a steering gear connected to the steering gear. The steering mechanism allows you to reduce the effort applied by the driver to the steering wheel to overcome the resistance that occurs when turning the steered wheels of the machine due to friction between the tires and the road, as well as soil deformation when driving on dirt roads.
The steering gear is mechanical transmission(for example, a gear) installed in a housing (crankcase) and having a gear ratio of 15 - 30. The steering mechanism reduces the force applied by the driver to the steering wheel connected by means of a shaft to the gearbox by as many times. The more gear ratio steering gear, the easier it is for the driver to turn steered wheels. However, with an increase in the gear ratio of the steering gear, in order to turn the steered wheel connected through the drive parts to the gear output shaft through a certain angle, the driver needs to turn the steering wheel at a larger angle than with a small gear ratio. When the vehicle is moving with high speed it is more difficult to make a sharp turn at a large angle, since the driver does not have time to turn the steering wheel.
Steering gear ratio:
Up = (ap/ac) = (pc/pp)
where ap and ac are the angles of rotation, respectively, of the steering wheel and the output shaft of the gearbox; Рр, Рс - the force applied by the driver to the steering wheel, and the force on the output link of the steering mechanism (bipod).
So, to turn the bipod by 25° with a gear ratio of the steering gear equal to 30, the steering wheel must be turned by 750°, and with Up = 15 - by 375°. With a force on the steering wheel of 200 N and a gear ratio of Up = 30, the driver creates a force of 6 kN on the output link of the gearbox, and with Up = 15 - 2 times less. It is advisable to have a variable steering gear ratio.
At small steering angles (not more than 120°), a large gear ratio is preferable, which ensures easy and precise control of the car when driving at high speed. At low speeds a small gear ratio makes it possible to obtain significant angles of rotation of the steered wheels at small angles of rotation of the steering wheel, which ensures high maneuverability of the vehicle.
When choosing the gear ratio of the steering mechanism, it is assumed that the steered wheels must turn from the neutral position to maximum angle(35 ... 45 °) no more than 2.5 turns of the steering wheel.
Steering mechanisms can be of several types. The most common of these are "worm-three-ridged roller", "worm-gear" and "screw-ball nut-rack-gear". The gear in the steering mechanism is made in the form of a sector.
The steering mechanism converts the rotational movement of the steering wheel into the angular movement of the steering arm mounted on the output shaft of the steering gear. The steering gear when driving a fully loaded vehicle, as a rule, should provide a force on the steering wheel rim of not more than 150 N.
Free steering angle (play) for trucks should not normally exceed 25° (corresponding to a shower length of 120 mm measured at the rim of the steering wheel) when driving a truck in a straight line. For cars of other types, the steering wheel play is different. Backlash occurs due to wear in operation of steering parts and misalignment of the steering mechanism and drive. To reduce friction losses and protect parts of the steering gearbox from corrosion, special gear oil is poured into its crankcase, mounted on the frame of the machine.
When operating the vehicle, it is necessary to adjust the steering mechanism. Adjusting devices of steering gears are designed to eliminate, firstly, the axial play of the steering shaft or the leading element of the gearbox, and secondly, the play between the driving and driven elements.
Consider the design of the steering mechanism of the type "globoidal worm - three-ridged roller".
Rice. Steering gear type "globoidal worm-three-ridged roller":
1 - steering gear housing; 2 - head of the steering arm shaft; 3 - three-ridged roller; 4 - shims; 5 - worm; 6 - steering shaft; 7 - axis; 8 - bipod shaft bearing; 9 - lock washer; 10 - cap nut; 11 - adjusting screw; 12 - bipod shaft; 13 - stuffing box; 14 - steering arm; 15 - nut; 16 - bronze bushing; h - adjustable depth of engagement of the roller with the worm
Globoidal worm 5 is installed in the crankcase 1 of the steering gear on two bevel roller bearings, well perceiving axial forces arising from the interaction of the worm with the three-ridged roller 3. The worm, pressed onto the splines at the end of the steering shaft 6, provides, with a limited length, good engagement of the roller ridges with the thread of the worm. Due to the fact that the load action is dispersed over several ridges as a result of their contact with the worm, as well as the replacement of sliding friction in engagement with much lower rolling friction, high wear resistance of the mechanism and a sufficiently high efficiency are achieved.
The axis of the roller is fixed in the head 2 of the shaft 12 of the steering arm 14, and the roller itself is mounted on needle bearings, which reduce losses when the roller is scrolled relative to the axis 7. The bearings of the steering arm shaft are, on the one hand, a roller bearing, and on the other, a bronze bushing 76. The bipod is connected to the shaft with the help of small slots and secured with a washer and nut 15. An oil seal 13 is used to seal the bipod shaft.
The engagement of the worm with the ridges is carried out in such a way that, in a position corresponding to the rectilinear movement of the machine, free play the steering wheel is practically absent, and as the steering angle increases, it increases.
The steering shaft bearing tightening is adjusted by changing the number of gaskets installed under the crankcase cover, which rests with its plane against the end of the extreme tapered roller bearing. The engagement of the worm with the roller is adjusted by shifting the steering arm shaft in the axial direction using the adjusting screw 11. This screw is installed in the side cover of the crankcase, closed from the outside with a cap nut 10 and fixed with a lock washer 9.
On cars heavy duty steering mechanisms of the “worm-side sector (gear)” or “screw-ball nut-rack-gear” type are used, which have a large contact area of the elements and, as a result, low pressures between the surfaces of the working pairs of the gearbox.
The worm-side sector steering mechanism, the simplest in design, is used on some cars. The side sector 3 is engaged with the worm 2 in the form of a part of a gear with helical teeth. The side sector is made as a single unit with the shaft 1 bipod. The bipod is located on a shaft mounted on needle bearings.
The gap in engagement between the worm and the sector is not constant. The smallest gap corresponds to the middle position of the steering wheel. The clearance in the engagement is regulated by changing the thickness of the washer located between the side surface of the sector and the cover of the steering gear housing.
The design of the steering mechanism of the "screw-ball nut-rail-sector" type is shown in the figure. Steering wheel shaft through driveline connected to the screw 4, which interacts with the ball nut 5, which is fixed by the locking screw 15 in the piston rail 3. The thread of the screw and the nut is made in the form of semicircular grooves filled with balls 7 circulating along the thread when the screw rotates. The extreme threads of the nut are connected by a groove 6 with an outer tube that ensures the circulation of the balls. The rolling friction of these balls on the thread during the rotation of the screw is negligible, which causes high efficiency such a mechanism.
Rice. Steering gear type "worm-side sector":
1 - bipod shaft; 2 - worm; 3 - side sector
Rice. Steering gear type "screw-ball nut-rail-sector":
1 - cylinder cover; 2 - crankcase; 3 - piston rail; 4 - screw; 5 - ball nut; 6 - gutter; 7 - balls; 8 - intermediate cover; 9 - spool; 10 - control valve body; 11 - nut; 12 - top cover; 13 - plunger spring; 14 - plunger; 15 - locking screw; 16 - gear sector (gear); 17 - shaft; 18- bipod; 19 - side cover; 20 - retaining ring; 21 - adjusting screw; 22 - ball pin
When turning the car, the driver, using the steering wheel and shaft, rotates the screw, relative to the axis of which the ball nut moves on circulating balls. Together with the nut, the piston-rack also moves, turning the toothed sector (gear) 16, made as a single unit with the shaft 17. The bipod 18 is mounted on the shaft using splines, and the shaft itself is placed on bronze bushings in the crankcase 2 of the steering gear.
TO Category:
1Domestic cars
Purpose and steering device
Steering assignment. Steering is designed to ensure the movement of the car in the direction specified by the driver. It consists of a steering mechanism and a steering gear. The design of the steering mechanism and the steering drive must ensure the accuracy of driving the car, the reliability of the operation of all components and parts * do not require the driver to expend great effort and not transmit shocks perceived by the wheels of the car to the steering wheel.
In order for the car to move on a turn without lateral slip of the wheels, all wheels must roll along arcs described from one center lying on the continuation rear axle car. In this case, the front steered wheels of the car must be turned at different angles. The inner (in relation to the center of rotation) wheel should be turned at a greater angle, the outer wheel - at a smaller angle. Such a rotation scheme is achieved by using a trapezoid with swivel joints in the steering gear.
Steering gear. There are several types of steering gear. The most common of these are the worm - roller, worm - sector and screw - ball nut.
The worm-roller steering gear is used on most passenger cars and many trucks. On fig. 1 shows the device of the steering mechanism of this type of GAZ-53A car. In the crankcase of the steering gear, a globoidal worm mounted on the end of the steering shaft rotates on two tapered roller bearings.
Rice. 1. Scheme of rotation of the steered wheels of the car: a - the angle of rotation of the outer wheel, P - the angle of rotation of the inner wheel; 1 - tie rod, 2 - front axle, 3 - trunnion arms
The worm engages a three-ridged roller that rotates on two needle bearings. A spacer sleeve is installed between the bearings. The axis of the roller is fixed in the head of the steering arm shaft. The steering arm shaft is supported on one side by a roller bearing, and on the other side by a bronze bushing. The steering arm is connected to its shaft by small splines and secured with a nut 15. The end of the arm arm shaft is sealed with an oil seal. To adjust the tightening of the steering shaft bearings, gaskets are installed under the lower crankcase cover.
The engagement of the working pair of the steering mechanism is made in such a way that in the position corresponding to the rectilinear movement of the vehicle, there should be no free play of the steering wheel. As the steering wheel is turned in one direction or another, the gap between the worm and the roller and the free play I of the steering wheel increase. Adjustment of the engagement of the worm with the roller is carried out by shifting the steering arm shaft in the axial direction with the help of an adjusting screw. The screw is installed in the side cover! crankcase of the steering mechanism, is closed from the outside with a cap nut 8 and is fixed with a lock washer, secured with a pin.
The steering mechanism of the worm-roller type provides the lowest friction losses. Due to this, less driver effort is required to drive the car and wear of parts is reduced.
In heavy-duty vehicles, the steering mechanism has a larger gear ratio to facilitate control, while significant specific pressures between the surfaces of the working pair are not allowed.
In this regard, such vehicles use a steering mechanism such as a worm - a sector with a large engagement surface or a mechanism with two working pairs such as a screw - nut and a rack - sector.
The worm-type steering mechanism - the sector is the simplest in design. The globoidal worm engages with a side sector in the form of a part of a gear with spiral teeth, made integral with the fry shaft. The gap in the engagement of the worm with the sector is not constant. The smallest gap value corresponds to the middle position of the steering wheel.
Rice. 2. Worm-roller type steering mechanism: 1 - mechanism housing, 2 - bipod shaft, 3 - three-ridged roller, 4 - gasket. 5 - worm, b - plug, 7 - lock washer, 8 - cap nut, 9 - roller axle, 10 - steering shaft, 11 - adjusting screw, 12 - locking pin, 13 - stuffing box, 14 - steering arm, 15 - nut, 16 - bronze bushing
When the steering wheel is turned in one direction or another, the clearance increases depending on the angle of rotation, reaching a maximum value in the extreme positions. This distribution of clearance facilitates maneuvering with large steering angles and is achieved by gradually lowering the height of the teeth of the sector from the middle to the extreme points. During assembly, the correct installation of the mechanism is checked by the marks on the worm and sector.
The bipod is mounted on a shaft rotating in two needle bearings, between which a spacer sleeve is installed. At the same time, the gap in the engagement of the worm - the sector is easily adjusted by changing the thickness of the thrust washer located between the side surface of the sector and the cover of the steering mechanism housing.
Rice. 3. Steering gear with built-in hydraulic booster: 1 - pump drive pulley, 2 - hydraulic booster pump, 3 - pump reservoir, 4 - filter, 5 - safety valve filter, b-line drain, bypass valve, 8 safety valve, 9 - pipeline high pressure, 10 - piston rail. 11 - steering gear housing. 12 - screw, 13 - ball, 14 - ball nut, 15 - thrust ball bearing, 16 - control valve body, 17 - check valve, 18 - spool, 19 - adjusting nut, 20 - spring washer, 21 - jet plunger spring, 22 - jet plunger, 23 - toothed sector, 4 - bipod, 25 - pump stator, 26 - pump rotor, 27 - suction cavity, 28 - injection cavity, 29 - blades
The steering mechanism of the type screw - nut and rail - sector is used on many trucks (ZIL-130, KamAZ of all models, etc.), its device is shown in fig. 3.
Steering shaft mounted in ball bearings, has a screw at the end. A ball nut is fixed on the screw, which is included in the piston rail. When the steering shaft is turned, the rack-piston moves along its axis. The axial movement of the rack-piston, which has teeth on the outer surface, causes the rotation of the gear sector mounted on the bipod shaft. The bipod through the steering gear rotates the front wheels.
The nut and screw are provided with semicircular helical grooves. Balls roll freely in them. To prevent the balls from falling out of the helical grooves, stamped guides are inserted into the grooves of the nuts, which are a closed chute. Turning the screw causes the balls to roll along the chute. At the same time, they exit from one side of the nut and return to it from the opposite side. The presence of balls greatly facilitates the rotation of the steering shaft.
The steering mechanism is connected to the steering column shaft by means of a cardan shaft with two hinges. This is due to the difficulty of placing the steering conventional design on a vehicle with V-engine and the cabin as close as possible to it.
Safety steering column. In case of frontal impacts of the car, in the event of an accident, the driver may be injured by the steering wheel. To minimize the risk of the driver hitting the steering wheel, cars latest models install a trauma-safe steering column. So, on the Moskvich-1500 car, the telescopic steering column consists of tubular parts that can fit one into the other.
When hitting the steering wheel, the lower part of the steering shaft receives axial movement in a slotted elastic sleeve, and the upper and lower parts of the steering column tube enter the middle part of the tube. Impact energy is absorbed by friction between moving parts.
The steering wheel itself, with its recessed hub and soft grip, reduces the risk of being hit by it.
The driver, watching the road, controls the car using the steering. The purpose of the steering is to change the direction of the car so that when the car is turned, the rolling of its wheels along the road occurs as far as possible without slipping. The latter is very important, as tire side slip causes them to increased wear and degrades vehicle stability.
The steering consists of a steering mechanism and a steering gear. Sometimes in steering amplifier is on.
The steering mechanism is called a slow gear that converts the rotation of the steering wheel shaft into the rotation of the bipod shaft. This mechanism increases the driver's effort applied to the steering wheel and facilitates its operation.
The steering gear is called a system of rods and levers, which, together with the steering mechanism, turns the car. The steering drive (or steering trapezoid) is used to turn the steered wheels of the car at different angles, which is necessary for the wheels to roll without side slip. The steering trapezoid is a hinged quadrangle formed by central part front axle, tie rod and swing arms. The latter are connected to pivot pins on which steerable wheels are mounted.
Rice. Fig. 4. Scheme of turning the car and steering trapezoid: a - scheme of turning; b - scheme of the steering trapezoid; R - wheel turning radius; 1 to 8 - pivot pins; 2 and 6 - rotary levers; 3 - front axle; 4 - transverse steering rod; 5 - lever
The steering mechanism is connected to the left rotary pin, longitudinal steering rod and lever. The bipod of the steering mechanism moves the longitudinal tie rod forward or backward, causing the steered wheels to turn left or right.
Due to the presence of the steering trapezoid, the steered wheels turn at different angles: the inner (closest to the center of rotation) wheel at a greater angle than the outer one. The difference in the angles of rotation is determined by the angle of inclination of the trapezoid pivot arms.
The scheme of a steering drive of forward operated wheels shown on fig. 4, corresponds to the accepted on domestic cars the position of the steering wheel in right-hand traffic.
TO Category: - 1Domestic cars
Steering is used to ensure the movement of the car in the direction specified by the driver. The steering consists of a steering mechanism and a steering gear.
The steering mechanism serves to increase and transmit to the steering drive the effort applied by the driver to the steering wheel. In passenger cars, worm and rack-and-pinion steering gears are mainly used.
The advantages of the "worm-roller" mechanism include: low tendency to transfer shocks from road bumps, large angles of rotation of the wheels, the possibility of transferring large forces. The disadvantages are a large number of rods and articulations with ever-accumulating backlash, a “heavy” and uninformative steering wheel. In the end, the cons outweighed the pros. On modern cars, such devices are practically not used.
The most common today is a rack and pinion steering mechanism. Light weight, compact, low price, the minimum number of rods and hinges - all this led to wide application. The pinion-and-rack mechanism is ideally suited to the McPherson front-wheel drive layout and suspension, providing greater ease and precision in steering. However, there are also disadvantages: due to the simplicity of the design, any push from the wheels is transmitted to the steering wheel. And for heavy machines, such a mechanism is not entirely suitable.
The steering drive is designed to transfer force from the steering mechanism to the steered wheels, while ensuring their rotation at unequal angles. If both wheels are turned the same amount, the inner wheel will scrape on the road (slide sideways) which will reduce steering efficiency. This slip, which also creates additional heat and wheel wear, can be eliminated by turning the inner wheel at a greater angle than the outer wheel. When cornering, each of the wheels describes its own circle different from the other, and the outer (farthest from the center of the turn) wheel moves along larger radius than internal. And, since they have a common center of rotation, then, accordingly, the inner wheel must be turned at a greater angle than the outer one. This is ensured by the design of the so-called "steering trapezoid", which includes swing arms and tie rods with hinges. The necessary ratio of the angles of rotation of the wheels is provided by the selection of the angle of inclination of the steering levers relative to the longitudinal axis of the vehicle and the length of the steering levers and transverse link.
Steering gear worm type comprises:
- steering wheel with shaft,
– crankcase of a worm pair,
- a pair of "worm-roller",
- steering arm.
In the crankcase of the steering mechanism, a pair of "worm-roller" is in constant engagement. The worm is nothing more than the lower end of the steering shaft, and the roller, in turn, is located on the steering arm shaft. When the steering wheel is rotated, the roller begins to move along the screw thread of the worm, which leads to the rotation of the steering arm shaft.
Worm pair, like any other gear connection, requires lubrication, and therefore oil is poured into the crankcase of the steering mechanism, the brand of which is indicated in the instructions for the car. The result of the interaction of the "worm-roller" pair is the transformation of the rotation of the steering wheel into the rotation of the steering arm in one direction or another. And then the force is transferred to the steering drive and from it to the steered (front) wheels. Modern vehicles use a safety steering shaft that can fold or break if the driver hits the steering wheel during a crash to prevent serious chest injury.
The steering gear used with the worm-type mechanism includes:
– right and left side traction,
- medium thrust
- pendulum lever
– right and left rotary levers of wheels.
Each tie rod is articulated at its ends so that the moving parts of the steering gear can
freely rotate relative to each other and the body in different planes.
Rack and pinion steering
In the gear-rack steering mechanism, the force is transmitted to the wheels using a spur or helical gear mounted in bearings, and gear rack moving in guide bushings. To ensure backlash-free engagement, the rack is pressed against the gear by springs. The steering gear is connected by a shaft to the steering wheel, and the rack is connected to two transverse rods, which can be mounted in the middle or at the ends of the rack. These mechanisms have a small gear ratio, which makes it possible to quickly turn the steered wheels to the desired position. Full rotation of the steered wheels from one extreme position the other is carried out in 1.75 ... 2.5 turns of the steering wheel.
The steering gear consists of two horizontal rods and rotary levers. telescopic racks front suspension. The rods are connected to the swing arms using ball joints. The swing arms are welded to the front suspension struts. The rods transmit the force to the pivot arms of the telescopic wheel suspension struts and respectively turn them to the right or left.
Main steering malfunctions
Increased play of the steering wheel, as well as knocking, may be the result of loosening of the steering gear housing, steering arm or swingarm bracket, excessive wear of the steering rod joints or swingarm bushings, wear of the transmission pair (“worm-roller” or “gear-rack”) or violations of the adjustment of its engagement. To eliminate the malfunction, tighten all fasteners, adjust the gearing in the transmission pair, and replace worn parts.
Stiff rotation of the steering wheel may be due to incorrect gearing adjustment in the transmission pair, lack of lubrication in the steering gear housing, and violation of the front wheel alignment angles. To eliminate the malfunction, it is necessary to adjust the engagement in the transmission pair of the steering mechanism, check the level and, if necessary, add lubricant to the crankcase, adjust the front wheel alignment angles in accordance with the manufacturer's recommendations.
Steering Care
Everyone knows the expression: "The best treatment is prevention." Therefore, every time, communicating with your car from below (on viewing hole or overpass), one of the first things to check is the elements of the steering gear and mechanism. All protective rubber bands must be intact, the nuts must be cottered, the levers in the hinges must not dangle, the steering elements must not have mechanical damage and deformations. Backlash in the drive joints is easily determined when the assistant shakes the steering wheel, and you find by touch, by the mutual movement of the articulated parts. faulty node. Fortunately, the times of general shortages have passed, and there is an opportunity to purchase quality parts, and not those numerous fakes that fail after a week of operation, as was the case in the recent past.
A decisive role in the durability of car parts and components is played by driving style, road conditions and timely service. All this affects the service life of steering parts. When the driver constantly pulls the steering wheel, turns it in place, jumps over pits and arranges off-road racing, there is an intensive wear of all the swivel joints of the drive and steering gear parts. If, after a “hard” trip, your car began to divert to the side while driving, then in best case you will get by with adjusting the angles of the front wheels, but at worst, the costs will be more tangible, since you will have to replace damaged parts. After replacing any of the parts of the steering gear or when the vehicle is being moved away from a straight line, it is necessary to adjust the “camber” of the front wheels. Work on these adjustments should be carried out at the car service stand using special equipment.
Power Steering:
1 - steering arm;
2 - longitudinal steering rod;
3 - steering mechanism;
4 - suction hose;
5 - drain hose;
6 - tank;
7 - right side steering rod;
8 - right pendulum lever;
9 - transverse steering rod;
10 - input shaft steering mechanism;
11 - lower universal joint;
12 - cardan shaft;
13 - upper universal joint;
14 - steering column shaft;
15 - steering wheel;
16 - left pendulum lever;
17, 21 - tips of the left lateral thrust;
18 - adjusting tube clamp;
19 - left lever of the steering trapezoid;
20 - hinge cover;
22 - hinge;
23 - discharge hose;
24 - hydraulic booster pump
Steering modern cars With swivel wheels includes the following elements:
- a steering wheel with a steering shaft (steering column);
- steering gear ;
- steering gear (may contain a booster and (or) shock absorbers).
The steering wheel is located in the driver's cab and is located at such an angle to the vertical that provides the most convenient coverage of its rim by the driver's hands. The larger the diameter of the steering wheel, the less force on the steering wheel rim, ceteris paribus, but at the same time, the possibility of quickly turning the steering wheel when performing sharp maneuvers is reduced. The diameter of the steering wheel of modern passenger cars is in the range of 380–425 mm, heavy trucks and buses - 440–550 mm, the steering wheels of sports cars have the smallest diameters.
The steering mechanism is a mechanical gearbox, its main task is to increase the driver's effort applied to the steering wheel, which is necessary to turn the steered wheels. Steering controls without steering gears, when the driver directly turns the steered wheel, have survived only on very light vehicles, for example, on motorcycles. The steering mechanism has a sufficiently large gear ratio, therefore, to turn the steered wheels to a maximum angle of 30–45 °, it is necessary to make several turns of the steering wheel.
Truck articulated steering shaft
steering shaft connects the steering wheel to the steering mechanism and is often articulated, which allows for a more rational layout of the steering elements, and for trucks to use a tilting cab.
In addition, the articulated steering shaft improves the safety of the steering wheel in case of accidents, reducing the movement of the steering wheel into the passenger compartment and the possibility of injury to the driver's chest.
Steering shaft with collapsible elements:
1 - shaft before impact;
2 - shaft in the process of crushing;
3 - completely "folded" shaft;
4 - maximum stroke steering shaft
For the same purpose, collapsible elements are sometimes built into the steering shaft, and the steering wheel is covered with relatively soft material, which does not give sharp fragments during the destruction.
The steering drive is a system of rods and hinges connecting the steering gear with the steered wheels. Since the steering mechanism is fixed to the carrier system of the vehicle, and the steered wheels move up and down on the suspension relative to the carrier system during movement, the steering drive must provide the necessary angle of rotation of the wheels, regardless of vertical movements suspension (consistency of the kinematics of the steering gear and suspension). In this regard, the design of the steering gear, namely the number and location of steering rods and joints, depends on the type of vehicle suspension used. The most complex steering gear have vehicles with multiple controlled axles.
To further reduce the effort required to turn the steering wheel, power steering is used in the steering gear. The source of energy for the operation of the amplifier is, as a rule, the car engine. Initially, amplifiers were used only on heavy trucks and buses, now they are also used on cars.
To mitigate jerks and shocks that are transmitted to the steering wheel when driving on rough roads, damping elements are sometimes built into the steering gear - steering shock absorbers. The design of these shock absorbers does not fundamentally differ from the design of suspension shock absorbers.
TO Category:
Car maintenance
Steering gear and car drive
Steering gear. To convert the rotational movement of the steering shaft into the rocking movement of the bipod and increase the gain transmitted from the steering wheel to the steering arm, a steering mechanism is used. The presence in the steering mechanisms of a large gear ratio (from 15 to 30) facilitates driving. The gear ratio is determined by the ratio of the angle of rotation of the steering wheel to the angle of rotation of the steered wheels of the car.
Rice. 1. Car steering:
a - dependent suspension of the front wheels; b - independent suspension
Rice. 2. The steering mechanism of the car GAZ-53A
Steering mechanisms are divided into worm, screw, combined and rack and pinion (gear). Worm gears come with a worm-roller, worm-sector and worm-crank transmission. The roller can be two- or three-ridged, the sector - two- and multi-toothed, the crank - with one or two spikes. In screw mechanisms, the transmission of forces is carried out by means of a screw and a nut. In combined mechanisms, the transmission of forces is carried out through the following nodes: screw, nut - rail and sector; screw, nut and crank; nut and lever. rack mechanisms made of gear and gear rack. The most widely used transmission is a globoidal worm - a roller on rolling bearings. In such a pair, friction and wear are significantly reduced and the necessary clearances in the engagement are maintained. Steering mechanisms of this type are used on most cars of the GAZ, VAZ, AZLK, etc.
The worm steering mechanism installed on GAZ-BZA vehicles has a globoidal worm and a three-ridged roller that are engaged. The worm is pressed onto a hollow shaft and mounted in the steering gear housing on two tapered roller bearings. The roller rotates on an axle in needle bearings. The roller axle is pressed into the head of the bipod shaft, which rotates in a sleeve and a cylindrical roller bearing. A bipod is planted on the small conical splines of the end of the shaft. The engagement of the roller with the worm depends on the position of the adjusting screw, which is fixed with a lock washer, a pin and a cap nut screwed onto the screw.
The steering shaft is placed in a tube (steering column), the lower end of which is attached to top cover crankcase. In the upper part of the steering column, an angular contact bearing of the steering shaft is installed, which has small conical splines for installing the steering wheel. Oil is poured into the crankcase of the steering mechanism through a hole closed with a screw plug. Steering mechanisms of this type are installed on GAZ-24 Volga, GAZ-302 Volga, GAZ-66 cars, LAZ-695N buses, etc.
The screw steering mechanism installed on ZIL-130 vehicles consists of a crankcase, which is integral with the hydraulic booster cylinder, a screw with a ball nut and a piston rack with a gear sector.
Rice. 3. The steering mechanism of the car ZIL -130
Rice. 4. The steering mechanism of the car MAZ -5335
The sector is made in one piece with the steering arm shaft. The crankcase is closed with covers 1.8 and 12. The nut is fixed in the piston rail with screws. The screw is connected to the nut with balls that are placed in groove 6 of the nut and screw.
The steering mechanism with a screw and a nut on circulating balls is characterized by low friction losses and extended term services.
In the control valve body, two thrust ball bearings are mounted on the screw, and between them is the control valve spool. The clearance in these bearings is adjusted by a nut.
The gap in the engagement of the piston rack and the toothed sector is adjusted by displacing the steering arm shaft with a screw, the head of which enters the hole of the arm arm and rests on the thrust washer. Oil is drained into the crankcase of the steering mechanism through a hole closed with a magnetic plug.
When the steering wheel is turned, the screw moves the ball nut with the piston rack, and it turns the toothed sector with the bipod shaft. Further, the force is transferred to the steering drive, ensuring the rotation of the wheels of the car. This is how steering works without power steering, i.e. with idle engine.
The combined steering gear mounted on the MA3-5335 vehicle consists of a screw and a ball nut-rack meshed with a gear sector, the shaft of which is also the bipod shaft. The screw and nut have semi-circular helical grooves that are filled with balls. To create a closed system for rolling balls, stamped guides are inserted into the rail nut to prevent balls from falling out. The steering gear screw is installed in the crankcase in two conical bearings, and the sector shaft is in needle bearings.
Each steering mechanism is characterized gear ratio, which is equal to 20.0 for steering gears of ZIL-130 and KamAE-5320 trucks, 20.5 for GAZ-53A cars, 23.6 for MA3-5335-23.6 cars, 19.1 for RAF-2203 buses and buses LAZ -695N-23.5, and for cars it is in the range from 12 to 20.
On vehicles of the KamAZ family, the screw-nut type steering gear is arranged together with an angular gear reducer, which transmits torque from the steering shaft driveline to the steering gear screw.
On LiAZ-677M and LAZ-4202 buses, the angular gearbox is used to transmit torque at a right angle from the steering wheel through the cardan shaft to the worm-sector steering mechanism.
The rack and pinion steering mechanism has been widely used on front-wheel drive cars VAZ-2108 Sputnik and AZLK-2141 Moskvich. It is relatively easy to manufacture and allows you to reduce the number of steering rod joints.
The main parts of such a steering mechanism are a gear cut on the shaft and a rack that are engaged and placed in the crankcase. When the steering wheel shaft rotates, the gear, rotating, moves the rack in the longitudinal direction, which, through the hinges, transfers the force to the steering rods. Tie rods through the tie rod end and swing arms turn the steered wheels.
Steering gear. To transfer force from the steering mechanism to the steered wheels and for the correct relative position of the wheels when turning, the steering gear is used. Steering gears come with a solid trapezoid (with dependent suspension wheels) and with a dissected trapezoid (with independent suspension). In addition, the steering trapezoid can be rear or front, i.e. with a transverse link located behind the front beam or in front of it.
The parts of the steering gear with dependent wheel alignment include (see Fig. 16.2, a) steering arm, trailing link, trailing link arm, transverse link and steering levers of the pivot pins.
The steering arm can swing along an arc of a circle located in a plane parallel to the longitudinal axis of the vehicle, or in a plane parallel to the beam front axle. In the latter case, there is no longitudinal link, and the force from the bipod is transmitted through the middle link and two side tie rods to the pivot pins. The bipod is attached to the shaft on conical splines with a nut on all vehicles. For correct installation bipods during assembly on the shaft and bipod make special marks. At the lower end of the steering arm, which has a conical hole, a pin with a transverse link is fixed.
Longitudinal steering rod is made of a pipe with bulges along the edges for mounting parts of two hinges. Each hinge consists of a pin, liners, covering spherical surfaces ball head of the pin, spring, limiter and screw plug. When screwing the cork, the head of the finger is clamped by the inserts due to the spring. The spring softens the blows from the wheels to the steering arm and eliminates the gap when the parts are worn. Limiter 5 prevents excessive compression of the spring, and in case of breakage, prevents the pin from leaving the hinge.
Rice. 5. The steering mechanism of the car VAZ -2108 "Sputnik"
The steering levers are pivotally connected to the rods. The hinges have a different design and are carefully protected from dirt. Lubricant enters them through the grease fittings. In some car models, plastic inserts are used in the linkage joints that do not require lubrication during the operation of the car.
The tie rod also has a tubular section, on the ends of which tips are screwed. The ends of the transverse rod and, accordingly, the articulated tips have the right and left hand thread to change the length of the rod when adjusting the toe-in. The tips are fixed on the rod with coupling bolts.
Rice. 6. Tie rod joints:
a - longitudinal traction; b, c - transverse thrust
In the transverse steering rods, hinges are installed in which the movement of the pin is only allowed perpendicular to the rod. The tie rod with independent suspension of the front wheels consists of a medium rod and two lateral tie rods connected pivotally.
The hinge consists of a ball pin, which may have a head with spherical surfaces or a ball head, and two eccentric bushings pressed against the pin by a spring held by a plug. With such a device, the springs are not loaded by the forces acting on the tie rod, and the gap is eliminated when the hinge parts are worn out automatically. Ball pins are installed in the conical holes of the levers and secured with nuts.
Some passenger cars use energy-absorbing safety steering controls that reduce the force that causes injury to the driver in an accident.
So, on GAZ-302 Volga cars, a rubber clutch connecting two parts of the steering shaft serves as an energy-absorbing device, and on AZLK-2140 cars, the steering shaft and steering column are made composite, which makes it possible for the steering shaft to move slightly inside the passenger compartment during car collisions.
In addition, the steering wheel is made with a recessed hub and a soft pad, which significantly reduces the severity of injury received by the driver when hitting it. Other devices that increase the safety of the driver may also be used.
The following types of steering mechanisms are used in cars: a worm and a sector (Ural-375 car), a worm and a roller (three-ridge on ZIL-164A and ZIL-157 cars and two-ridge on GAZ-53A, ZAZ-965 Zaporozhets, Moskvich- 408", M-21 "Volga", etc.), screw and nut and combined. The latter include mechanisms that combine a screw and nut on circulating rollers and a rail with a sector (ZIL-130, ZIL-111, BelAZ-540 and BelAZ-548 cars).
In the worm and sector mechanism, both a conventional cylindrical worm and a globoidal worm with a threaded surface are used, the turns of which are made along an arc of a circle centered on the axis of rotation of the sector. In the latter case, even if sharp turns the car between the teeth of the sector and the worm remains a small gap.
The mechanism with a cylindrical worm and a sector is shown in fig. 6, a. With a worm mounted on the lower end of the steering shaft, a gear sector is engaged, made as one piece with the steering arm shaft.
On fig. 6, b shows a worm and roller type steering mechanism. At the lower end of the steering shaft there is a globoidal worm, which is engaged with a two-ridged roller, which engages with the turns of the worm and sits on an axis fixed in the fork of the shaft 8 of the steering arm. The mechanism of this type is the most wear-resistant and requires the least amount of effort from the driver when turning.
The worm can also be paired with a side sector. In mechanisms of this type, the contact between the teeth does not occur at separate points, as in the previously considered gears, but along lines, which makes it possible to transmit much greater forces. However, friction losses and wear of such a transmission are large. In addition, this type of mechanism is particularly sensitive to the precision of the engagement adjustment.
Rice. 6. Main types of steering mechanisms:
a - worm and sector; b - worm and roller; c - worm and side sector; 1 - steering shaft; 2 - cylindrical worm; 3 - gear sector; 4 - bipod shaft; 5 - steering arm; 6 - globoidal worm; 7 - roller; 8 - steering arm shaft; 9 - lateral gear sector
On fig. 7 shows a worm-type steering mechanism and a roller with a gear ratio of 20.5 of a GAZ-53F car.
A cast-iron steering gear housing is bolted to the left side member of the vehicle frame, inside which a globoidal worm and a two-ridge roller are placed in engagement. The steering shaft with a worm pressed onto its lower end is supported by a cylindrical roller bearing in the steering column and two tapered roller bearings in the steering gear housing. The last two bearings do not have inner rings and their rollers run directly on the surface of the worm. The roller is mounted on an axle on two ball bearings, on the inner ring of which a spring ring is installed. The axis of the roller is pressed into the head of the steering arm shaft and is offset from the axis of the worm towards the side cover of the crankcase by 5.75 mm.
The bipod is fixed on the small splines of the shaft with a nut and washer. Four double splines ensure the correct connection of the bipod with the shaft. The bipod shaft rotates in a cylindrical roller bearing and bushing and can be rotated through 90°. The sleeve is placed in the crankcase, and the bearing is in its side cover. In addition to the side, the crankcase also has top and bottom covers. Oil is poured into the crankcase through a hole closed by a plug.
The crankcase is attached to the steering column with a clamp and a coupling bolt. At the upper end of the steering shaft, a steering wheel and a signal button are attached. The signal wire runs inside the steering shaft in a tube; a sealing ring is installed between the tube and the shaft, pressed against the tube by a spring. Top end The shaft is sealed with an oil seal pressed by a spring. The bipod shaft is sealed with glands.
Rice. 7. The steering mechanism of the car GAE -53F:
1 - ring; 2 - inner ring of bearings; 3 - ball; 4 - roller axis; 5 - sealing ring; 6 - tube; 7 - signal wire; 8 and 17 - springs; 9 and 15 - covers; 10 and and - shims; 12 - tapered roller bearing; 13 - crankcase; 14 - cork; 16, 33 and 34 - oil seals; 18 - steering shaft; 19 - steering column; 20 - globoidal worm; 21 - two-ridge roller; 22 - steering arm shaft; 23 - bolt; 24 - collar; 25 and 32 - cylindrical roller bearings; 26 - side cover; 27 - adjusting screw; 28 - nut; 29 - bushing; 30 - steering wheel; 31 - steering arm
The engagement of the worm and the roller can be adjusted without disassembling the steering gear, with a screw, the groove of which includes the shank of the steering arm shaft. As already mentioned, the axes of the roller and the worm lie in different planes; therefore, to reduce the gap in the engagement, it is enough to move the bipod shaft towards the worm by screwing in the screw. An increase in clearance can be achieved by removing the screw. Outside, a cap nut is screwed onto the screw, which prevents oil from flowing out of the crankcase through the thread. To prevent the roller from disengaging from the worm, internal tides in the steering gear housing are used. They also limit the rotation of the steering arm shaft. The axial clearance of roller bearings is adjusted by removing cardboard with special impregnation (0.25 mm thick) and parchment (0.10-0.12 mm thick) gaskets from under the crankcase cover.
In the M-21 Volga car, the steering mechanism is the same in design.
In the ZIL-164A car, a steering mechanism with a worm and a three-ridged roller is used, which increases the possible angles of rotation of the steering arm without breaking the engagement.
On fig. 8 shows the steering gear of a MAZ-200 car of the cylindrical worm type and the side sector. The worm and side sector with spiral teeth are placed in the crankcase. The worm is pressed onto the lower end of the steering shaft. When the steering shaft and the worm turn, the sector rotates, the end teeth of which are engaged with the worm. Needle bearings serve as supports for the sector shaft.
Rice. 8. The steering mechanism of the car MAZ -200:
1 - worm; 2 - sector; h - gaskets; 4 - shaped nut; 5 - needle bearing; 6 - crankcase
Steering shaft bearings are adjusted by changing the thickness of the spacers under the flange of the shaped nut.
In the steering gear, the screw and nut of the MAZ-525 car have a screw thread on the lower end of the steering shaft. When the steering shaft rotates, the nut sitting on its lower end in the sleeve moves up or down along the shaft, turning the steering arm shaft installed in the sleeves in the crankcase and crankcase cover. The lower end of the steering shaft is not fixed, and the upper end has a swing bearing, consisting of a ball bearing and rubber rings. The steering column is connected with the lower and upper tips to the steering gear housing and the head housing.
The steering gear ratio is defined as the ratio of the steering wheel angle to the steering arm angle. The larger the gear ratio, the less effort is needed to turn the wheels. For quick turning, the gear ratio should not be too large.
The steering mechanisms of trucks have gear ratios of 20-40, and cars - 17-18.
Rice. 9. The steering mechanism of the car MAZ -525
The steering mechanism converts the rotational movement of the steering wheel into the angular movement of the steering gear links, it is performed with a large gear ratio (20-24) to reduce the effort expended by the driver.
On KamAZ vehicles, a power steering mechanism is used, which is shown in fig. 93. The actual steering mechanism includes a screw along which a nut mounted on circulating balls moves, and a piston-rack engaged with teeth with a gear sector.
Since the cab of KamAZ vehicles is moved forward and is made folding, it was necessary to introduce a swivel joint of the steering column with the steering mechanism and an additional angular gearbox.
Rice. 10. Diagram of the power steering mechanism:
1 - jet plunger; 2- oil radiator; 3 - high pressure hose; 4 - pump; 5 - steering column; 6 - cardan shaft; 7 - drive gear: 8 - driven gear; 9 - shaft soshkn; 10 - toothed sector of the bipod shaft; 11 - piston-turnip: 12 - screw; 13 - ball nut; 14 - ball bearings: 15 - thrust rear bearing; 16 - spool; 17 - control valve; 18 - hose low pressure; 19 - thrust front bearing
The steering column shaft is articulated with cardan shaft. The other end of the shaft is connected to the drive gear of the angular gearbox by means of a hinge. Angle gear consists of driving and driven bevel gears.
The drive gear is made in one piece with its shaft rotating on needle and ball bearings. The pinion ball bearing is located in the top cover of the crankcase. Driven gear 8 is mounted on a screw shaft rotating in two ball bearings. The nut moving along the screw is placed in the piston-rack. On its outer surface, teeth are cut, forming a rack and engaging with the toothed sector.
To facilitate the movement of the nut, semicircular helical grooves are made in it and in the screw, forming a spiral channel filled with balls. Balls falling out of the grooves is prevented by installing stamped guides consisting of two halves into the grooves of the nut. The trough thus formed creates two closed streams of rolling balls. On this chute, when the screw is turned, the balls roll, emerging from one side of the nut and returning to it from the other. Two thrust bearings with a control valve spool between them are installed on the propeller shaft. The bearings and spool are secured with a nut and spring washer. The spool is slightly longer than the seat in the control valve.
In the axial direction, the screw and spool can move within 1.1 mm in each direction from the middle position, to which they are returned by helical springs and reaction plungers, which are under pressure from the oil supplied through the discharge line from the vane pump. Each turn of the steering wheel is transmitted to the screw and causes a corresponding turn of the wheels. However, the wheels at the same time create resistance, which, being transferred to the propeller, tends to displace it in the axial direction. When this resistance exceeds the precompression force of the springs, the displacement of the screw will change the position of the spool. According to the direction of the screw shift, the spool will connect one cavity of the amplifier to the discharge line, and the other to the drain line. Under oil pressure, the piston-rack creates an additional force acting on the bipod sector and contributing to the rotation of the steered wheels of the vehicle.
As the resistance to turning the front wheels increases, the pressure in the working cavity of the hydraulic booster cylinder increases. At the same time, the pressure under the jet plungers also increases. Under the pressure of the springs and reactive plungers, the spool tends to return to the middle position.
The driver, driving a car, always retains a sense of the road, i.e., to turn the steering wheel, he needs to expend some effort.
With an increase in resistance to turning the front wheels and an increase in pressure in the cavity of the hydraulic booster cylinder, the force on the steering wheel also increases.
At the end of the impact on the steering wheel, the spool moves to the middle position, the connection of this cylinder cavity with the discharge line stops and the pressure in it drops.
In the middle position, the axial clearance between the piston-rack and the gear sector is the smallest. As the steering wheel is turned to the right and to the left, the clearance in this engagement increases.
When the engine is not running and there is no fluid supply from the power steering pump, the steering mechanism works in the usual way, however, the driver has to expend more effort to control the car.
In the lower part of the steering gear housing is located drain plug with a magnet, trapping metal particles falling into the liquid.
The cars of the Minsk Automobile Plant used a steering mechanism of the screw-ball nut type, with a separate hydraulic booster.
The steering gear shaft, mounted on two tapered roller bearings, has a screw along which the rack nut moves. A rail is cut on the outer surface of the nut, which engages with the toothed sector of the shaft. For easier movement of the nut, semicircular helical grooves are made in it and in the screw, forming a spiral channel filled with balls. Balls falling out of the grooves is prevented by installing stamped guides into the grooves of the nut, forming a tubular groove. On this chute, when the screw is turned, the balls roll, emerging from one side of the nut and returning to it from the other.
The shaft of the gear sector is mounted on three needle bearings, two of which are located on the side of the bipod attachment. A sector with five teeth engages with the rack teeth. The middle tooth of the sector is somewhat thicker than the others. At one end of the sector shaft, small splines are made for connection with the steering arm, which is kept from axial displacement by a nut. At the other end of the sector shaft there is an adjusting device that allows you to set the required axial clearance in the sector-nut engagement. It consists of an adjusting screw fixed with a lock nut.
The crankcase of the steering mechanism is cast from cast iron and closed from the sides with removable covers with sealing gaskets. The exit points of the rudder shaft and sector shaft from the crankcase are sealed rubber seals. At the top of the crankcase there is a plug that closes the oil filler hole. At the bottom there is a hole with the same plug for draining the oil.
On KrAZ vehicles, a steering mechanism was previously installed, consisting of a worm and a lateral gear sector with spiral teeth (there are many such vehicles in operation now), and currently a mechanism is used in the form of a screw and a ball nut-rack, i.e. of the same type, as well as on cars of the Minsk Automobile Plant, also with a separate hydraulic booster.
Rice. 11. Steering gear of MAZ cars:
1 - sector shaft; 2 - stuffing box; 3 - needle bearings; 4 - side cover: 5 - cork drain hole; 6 - adjusting nut; 7 - bearing; 8 - steering gear housing: 9 - nut-rail; 10 - balls; 11 - screw; 12 - filler plug; 13 - bearing
TO Category: - Car maintenance
