The gearbox, or otherwise the transmission, transmits the rotational force - the so-called torque - from the car's engine to the wheels. At the same time, depending on the driving conditions of the car, it can transmit torque in whole or in part.
A car going uphill should use a lower gear than a car going down a flat freeway. A lower gear sends more torque to the wheels. And this is required when the car is moving slowly, because it is hard for her. Higher gears are suitable for faster vehicle movement.
There are manual transmissions, but there are also automatic ones. To change gear in a manual transmission, the driver first presses the clutch pedal (picture on the left). In this case, the engine is disconnected from the gearbox. Then the driver moves the control lever to another gear and releases the clutch pedal. The engine is reconnected to the gearbox and can again transfer its energy to the wheels. In an automatic transmission, the position of the gas pedal (accelerator) is correlated with the speed of the car, and the gear changes automatically if necessary.
Manual transmission control
The adjacent diagrams show how the shift lever can be used to shift from one gear to another. Depending on the gear set, different proportions of the torque passing through the gearbox (red lines with arrows) get to the wheels. Neutral gear. Engine power is not transferred to the wheels.
Neutral gear. Engine power is not transferred to the wheels.
First transfer. The largest gear of the drive shaft is connected to its pair on the driven shaft. The machine moves slowly, but can overcome difficult sections of the road.
Second transfer. The second pair of gears work together with the clutch mechanism. In this case, the speed of the car is usually from 15 to 25 miles per hour.
Third gear. The third pair of gears works together with the clutch mechanism. The speed of the car is even greater, and the torque at the wheels is less.
Fourth gear. The input and output shafts are connected directly (direct transmission) - the speed of the car is maximum, and the torque is the lowest.
Reverse.(5th gear in the picture) When you turn on the transmission reversing its drive gear "rotates the output (drive) shaft in the opposite direction.
Accelerator operation
The number of engine revolutions per minute depends on how much fuel flows from the carburetor into the cylinders. The movement of fuel is controlled by the carburetor throttle, and the operation of the throttle is controlled by the accelerator pedal, which is located on the floor in front of the driver.
When the driver presses the accelerator pedal with his foot, throttle valve opens and more fuel enters the engine. If the driver releases the accelerator pedal, the damper is closed and the amount of incoming fuel is reduced. At the same time, both engine speed and vehicle speed decrease.
Automatic transmission
When to apply automatic transmission, the driver does not have a clutch pedal under his foot. Instead, a torque converter paired with planetary gear(figure on the right and below) automatically disconnect the engine from the drive shaft when, according to traffic conditions, it is necessary to change gear.
And after the gear has changed, the drive shaft is connected again. As soon as the driver puts the control lever in the working position, and the mechanism automatic box chooses the gear desired gear according to the driving conditions of the vehicle at the moment.
Engines internal combustion, both gasoline and diesel, have a fairly narrow operating range. mechanical box transmission is necessary to ensure optimal mode work power unit.
Changes in the gear ratio are carried out manually, usually by moving the lever from one position to another. To ensure switching, the power flow is interrupted by means of a mechanical clutch.
Excursion into history
On the first cars there was no gearbox familiar to us with gears, the force on the drive wheels was transmitted by a belt. This device was used Karl Benz- to increase the speed, the driver had to throw the ring from one pair of pulleys to another. Gears in the transmission were first used by Wilhelm Maybach, in cars of his design there were mechanical boxes.
The transmission of torque from it to the drive wheels was carried out using steel chain. Coaxial box at the beginning of the 20th century appeared on the cars of Louis Renault, who is also the inventor of the cardan shaft.
At first, the automotive industry was dominated by a spaced arrangement of units, in which the gearbox was located separately from the power unit. The transmission of torque in them took place through a special shaft, as was the case on the BMW 501 model.
The mechanical boxes of the first releases were very complex, their management required considerable effort and good skills. In 1928, the American engineer Charles Kettering from General Motors offered a device for synchronization. First lucky box, equipped with such a mechanism, was installed on a Corvette car. On the European continent, ZF has become a leader in the development of transmissions.
The firmly entrenched name of the manual transmission has the following decoding of the abbreviation - a manual gearbox. Earlier in the name, the first letter P was understood as the word for change, but over time it was replaced by a more appropriate one. Abbreviated name of the mechanical box in technical descriptions often appears with a number indicating the number of steps.
A modern manual transmission has a fairly advanced device that, in addition to shifting gears on the move, performs a number of functions:
- ensuring the movement of the car in reverse;
- separation of the transmission and the running engine of the car during short stops;
- the presence of the neutral position of the box allows you to start the engine.
Cars equipped with this kind of transmissions, other things being equal more economical than cars with automatic transmission.
The principle of operation of the manual transmission
Starting the car, driving slowly bad road causes a lot of resistance. A car with a manual transmission in this mode requires the maximum amount of torque.
At the same time, the gearbox performs the functions of a reduction gear, and even with high speed vehicle moving at a relatively low speed. After acceleration stops, the driver switches the mode, and the crankshaft speed returns to the optimal range.
Uniform movement along the plane requires less effort, which is provided by increased gears.
The principle of operation of a mechanical gearbox is to create connections between the drive (input) shaft and the driven (output) through combinations of gears with different numbers of teeth. This allows you to adjust the transmission to changing driving conditions of the vehicle.
For dummies, as non-specialists are commonly called, the principle of operation of a manual transmission can be explained in just a few words. The device provides normal work engine by changing the number of revolutions, increasing or decreasing the force on the drive wheels. This allows you to keep best mode operation of the power unit when starting off, accelerating and decelerating.
This principle of operation of the manual transmission is preserved in all cars: with full, and with rear, and with front-wheel drive. The transmission device in each of the cases has its own characteristics, but at the same time the main structural elements and their purpose are preserved. The change in gear ratio occurs due to the introduction of a certain combination of gears with a different number of teeth.
These ratios for each engine are selected individually in the course of design work and full-scale tests. This takes into account many factors and, first of all, the parameters of the engine. The physical principle of the manual transmission remains unchanged, the driver controls the mode change manually by moving the lever from one position to another.
Video - manual transmission, principle of operation:
A visual representation of the principle of operation of the manual transmission can be obtained after watching the video clip. A schematic animated image is the best way to demonstrate the interaction of parts with each other. Such materials provide an understanding of the ongoing processes, especially when switching operating modes.
Device
The design of the manual transmission has changed little since the main elements of it were made and patented. The mechanical gearbox consists of the following parts and assemblies:
- crankcase;
- input, output and intermediate shafts;
- synchronizers;
- driving and driven gears;
- gear shift mechanism.
The parts assembled in a single housing interact with each other, ensuring the transmission of torque. The device of a mechanical gearbox depends on the design features and the number of shafts - according to given feature they are divided into two- and three-shaft. The latter layout is called coaxial and in the technical literature it is commonly called classical.
Shafts and gear blocks
In this design, the drive and driven shafts are placed in the crankcase of the box one after the other. in shank input shaft a bearing is installed on which the end of the secondary rests. The absence of a rigid connection allows them to rotate independently of each other at different frequencies and in different directions. Below them is an intermediate shaft, the transmission of force occurs through gear blocks installed on these parts.
In order to reduce the noise of the gearbox, the gears in it are made helical. In the manufacture of these parts, a strict system of tolerances is used, and great attention is given to the quality of processing of mating surfaces.
On the drive shaft of a classic mechanical box, several gears of different diameters and, accordingly, with a different number of teeth, are rigidly fixed. In some cases, the knot is made integral, which provides it with maximum strength.
Gears on the output shaft can be installed in two ways:
- movable on slots;
- fixed on the hubs.
The connection with the drive shaft in the first version occurs due to the longitudinal movement of the driven gear along the splines until it engages in the drive gear. Such a scheme is simple and reliable and has become quite widespread.
In another design, the longitudinal movement of the parts is excluded and the connection takes place using a sliding clutch.
Video - how torque is transmitted in a manual transmission:
The angular velocities of the driving shaft and the driven shaft are equalized using special device, which is called a synchronizer. in gearboxes sports cars or machines special purpose Cam clutches can be used instead of these units.
Control mechanisms
Throughout the history of the development of motor transport, many original designs have been developed. The most common layout used in modern units.
The manual transmission is controlled by a special design consisting of the following elements:
- lever;
- drives;
- sliders;
- forks;
- castle;
- gear shift clutches.
Changes in the operating modes of the unit are made by the driver by moving the lever from one position to another. Sliders are activated through the drives. Protection against simultaneous activation is a special locking mechanism - a lock. In three-way boxes, it makes it impossible for two sliders to move while the third one moves.
This assembly actuates the shift fork, which causes the clutch to shift. This part is a thick-walled ring with slots on the inner surface. They are in constant engagement with the gear rim of the driven shaft, along which the clutch moves along it. There are similar slots on the side surface of the driven gear.
When shifting gears, the lever is first transferred to neutral, from which a selection is made. desired mode. During this time, the synchronizer equalizes the angular velocities, and the gear is blocked by the clutch. Torque from the input shaft is transmitted to the secondary and then through main gearbox on the drive wheels.
The synchronizer provides shockless switching, while its operation time does not exceed a few hundredths of a second.
Video - clutch device and manual transmission, a visual story from Toyota:
The softness of the operation of a manual transmission largely depends on general condition parts and, in particular, this unit.
The synchronizer is a bronze ring with a ring gear on inside. When the clutch moves, it first presses the part against the conical surface on the sidewall of the driven gear, the resulting friction force is sufficient to equalize the speed of the shafts. After synchronization, the gear wheel is locked by the shift clutch.
How to shift gears on a manual transmission
The operation of vehicles with a manual gearbox and their management has whole line features that the driver needs to know. A natural question arises: how to use a manual transmission? Learning to do this begins at, starting from showing the instructor to developing an automatic skill in gear shifting.
How to shift gears on a manual transmission is usually indicated on a diagram printed on the outer surface of the lever handle. In general, the process looks like this:
- the driver squeezes the clutch with his left foot;
- hand moves the lever from one position to another;
- gently release the clutch pedal and gently press the accelerator.
Gear shifting in a manual gearbox is carried out in accordance with the scheme, which is indicated in the technical documentation for the car. Experienced drivers It is recommended to adhere to the following rules, which will increase the resource of the unit:
- the use of direct gear (usually fourth) will significantly reduce fuel consumption;
- shifting gears on a manual gearbox should be carried out strictly in accordance with the instructions developed by the manufacturer;
- inclusion reverse gear perform only after a complete stop of the car;
- the clutch pedal is depressed quickly and all the way to the floor, but it should be released smoothly without jerking;
- on icy or wet road coasting is unacceptable;
- when cornering, it is not recommended to shift gears;
- effective on a free road is the reception of engine braking by successively downshifting to a minimum;
- periodic check of the oil level in the box and timely replacement in progress Maintenance will increase its resource.
Video - tips on how to shift gears on a manual transmission:
Learning how to drive a car requires constant practice. The actions of the instructor are shown in great detail, observing them will allow the novice driver to form the correct muscle reactions.
Oil for manual transmission
Maintenance of transmission units is carried out in accordance with the service book. In most manual transmission boxes, replacement operating fluid carried out every 50-60 thousand kilometers. During this period, wear products accumulate in it and lubricating properties are lost.
During maintenance, pour for a manual transmission, specified in the instruction manual. This is especially true for cars. foreign production use of the wrong oil can cause wear and even damage to the unit.
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To answer the question what kind of oil in the manual transmission, you should read the entries in service book, where a mark is made on the brand of technical fluid.
Despite the fact that in the past ten years it has been the automatic ones that have gained wild popularity, those who prefer a car with a manual transmission have not become much less. In addition, this one has the simplest principle of operation, and even a teapot can understand it. Today we will talk about what is the principle of operation of a manual transmission and what functional elements it consists of.
Main components
The main task of a manual transmission, like any other transmission, is to transfer torque from the engine to the drive wheels. Moreover, it is precisely such a device as a box that is able to vary this moment in such a way that the most optimal balance between efficiency and power, and the engine resource was spent as little as possible.
The simplest solution to this problem is the introduction of such a device into the nodes of the car, which would mechanically connect the wheels and the motor and make it so that the rotational and cardan speeds differ.
To better understand what is at stake, it is worth imagining the chain of an ordinary bicycle, which, probably, everyone had in childhood. As you know, usually the drive gear, which is engaged with the pedal drive, has enough big size, while the driven one, which is attached to the wheel hub, is quite small.
In modern bicycles, you can change gears by moving the chain on the gears. different sizes. This is done in order to change the ratio of cadence and wheel speed and, thus, change the speed of the bike itself.
It turns out that cars use a mechanism with a very similar device. Only instead of pedals it acts here crankshaft engine, and instead of the wheel hub - cardan shaft, which is connected to the gearbox and distributes the forces between the axle shafts.
The drive shaft, sometimes called the input shaft, is connected to the engine's crankshaft through a device such as a clutch. It is a rod on which gears of different sizes are welded. A similar view has a driven, or intermediate, shaft, which is connected to the cardan shaft.
The movement of the shafts, which have a spring mechanism, is carried out by a backstage, to which a lever is attached, which goes into the salon. The lever has its own switching pattern, which is always indicated on the lever head or in the vehicle's operating instructions.
A manual transmission is a device in which the parts are subjected to great friction and overheating, therefore, in its crankcase there is a lubricant that constantly reduces friction and the temperature of the interacting metal components.
How it works?
The primary rotates whenever it is in the home position and the pedal is released. Thus, the frequency of the input shaft always coincides with the frequency of rotation of the engine shaft, or simply with its revolutions.
The speed of the intermediate shaft, which is connected to the cardan, depends on what gear the car is in. For example, if the manual transmission is in neutral gear, then the shaft rotates at the same frequency as the drive wheels.
When the speed is on and the pedal is released, the shafts rotate at a variable speed. This speed depends solely on the engine speed, which is controlled by the accelerator pedal.
When it comes time to switch from one speed to another, enough difficult process consisting of several stages. So, first you need to press the clutch pedal. In this case, the drive shaft is disconnected from the engine and begins to rotate independently.
When the pedal is pressed, you can safely translate through the neutral position to desired speed. But here one significant difficulty arises: since the sizes of the gears on the shafts are different, they rotate at different frequencies. For this reason, the frequencies must be synchronized with each other.
Consider how the gearbox is arranged, we will also learn in more detail about the principle of its operation. The engine of the very first cars was directly connected to the drive wheels, which made it easier to care for the car and control, but the power left much to be desired. Modern cars allow you to transfer the energy of the engine to the drive wheels through the transmission, which is done by converting the constant rotation of the engine shaft by the gearbox, and the driver has the ability, depending on the speed he has chosen, to slow down or accelerate the movement of the car.
In addition, the gearbox allows you to change the value tractive effort, which is transmitted to the driving wheels of the machine, change the direction of their rotation and start the engine stationary car with the clutch engaged. You can see how the clutch of a car is arranged on our website.
But its main purpose is to change the torque transmitted from crankshaft engine to the drive wheels in size and direction by engaging gears of different diameters, as well as a long disconnection of the engine from the transmission. Simply put, the gearbox allows you to combine optimal number engine speed at different speeds. The number of steps depends on the number of pairs of gears engaged in certain combinations.
How does a manual transmission work?
The number of gears is directly related to the ability of the car to adapt to different conditions and overcome obstacles. The composition of the gearbox includes a set of gears (gears) that mesh with each other in various combinations and thereby form several gears, and the gears and gearbox shafts are located inside the crankcase, from which two interconnected shafts emerge - driven and driven. Gears are installed on the driven shaft, moving along it as a result of shifting the gear lever by the driver.
Main part modern cars equipped two-shaft three-way five-speed gearbox gear with constant mesh gears. In the gearbox housing, the primary and secondary shafts with gears and synchronizers are installed on bearings. There is also an axle with an intermediate reverse gear. gears forward are in constant engagement.
One of the gears of each forward gear is mounted on the shaft on bearings, and the torque when the gears are engaged is transmitted through synchronizers located on the shaft on splines. When forward gears are engaged, the input and output shafts rotate in opposite directions, and when reverse gear is engaged, they rotate in the same direction. The reverse gears (driving and driven) are connected through an intermediate gear.
It is mounted on an axle on a bearing and is engaged when the reverse gear is engaged. As a result of these processes, the intermediate gear provides a change in the direction of rotation output shaft.
The driver shifts gears with a special mechanism mounted on the gearbox housing. He engages gears with a lever that moves the synchronizer of the gear he has chosen to the corresponding gear with the help of forks. This ensures the transmission of torque from the gear through the synchronizer to the output shaft of the gearbox.
The inclusion of the first gear occurs as a result of moving the synchronizer gearbox to the right along the splines of the output shaft with the help of a fork and connecting it to the driven gear of the first gear, which is mounted on the shaft, on the bearing. The torque from the input shaft is transmitted through the drive gear mounted on it to the driven gear of the first gear and further to the output shaft of the gearbox through the synchronizer. In first gear, the speed of the car decreases, but the torque increases.
Second gear is engaged when the fork moves the synchronizer to the left and connects to the second gear driven gear. The torque from the input shaft to the secondary is transmitted through the second gear drive and driven gears and the synchronizer. When this gear is engaged, the speed of the machine increases, and the torque, on the contrary, slows down.
Third and fourth gears are switched on simultaneously with a fork when the synchronizer is moved along the splines of the secondary shaft in opposite directions, as a result of which it is connected to the driven gear of the third or fourth gear. The torque from the input shaft to the secondary is transmitted through the gears of the third or fourth gear. As a result of the inclusion of these speeds, the speed of the car increases significantly, and the torque does not change.
The gearbox device can also be clearly seen in the next video.
The mechanical transmission of a car is designed to change the torque and transfer it from the engine to the wheels. It disconnects the engine from the drive wheels of the machine. Let's explain what a manual gearbox consists of - how it works.
The mechanical "box" consists of:- crankcase;
- primary, secondary and intermediate shafts with gears;
- additional shaft and reverse gear;
- synchronizers;
- gear shift mechanism with locking and blocking devices;
- shift lever.
Scheme of work: 1 - input shaft; 2 - switching lever; 3 - switching mechanism; 4 - secondary shaft; 5 - drain plug; 6 - intermediate shaft; 7 - crankcase.
The crankcase contains the main parts of the transmission. It is attached to the clutch housing, which is attached to the engine. Because during operation, the gears are tested heavy loads they should be well lubricated. Therefore, the crankcase is half its volume filled with gear oil.
The shafts rotate in bearings mounted in the crankcase. They have sets of gears with different number teeth.
Synchronizers are necessary for smooth, silent and shockless gear shifting by equalizing the angular velocities of rotating gears.
Switch mechanism serves to change gears in the box and is controlled by the driver using a lever from the passenger compartment. At the same time, the locking device does not allow two gears to be switched on simultaneously, and the blocking device keeps them from being switched off spontaneously.
gearbox requirements
- Ensuring the best traction and fuel-economic properties
- high efficiency
- ease of control
- Shockless switching and quiet operation
- the impossibility of simultaneously engaging two gears or reverse when moving forward
- reliable retention of gears in the engaged position
- simplicity of design and small cost, small size and weight
- ease of maintenance and repair
Ease of control depends on the method of gear shifting and the type of drive. Gears are shifted using moving gears, gear couplings, synchronizers, friction or electromagnetic devices. For shockless switching, synchronizers are installed, which complicate the design, and also increase the size and weight of the transmission. That's why most widespread received those in which top gears they are switched by synchronizers, and the lower ones by gear couplings.
How do gears work?
Let's look at an example of how the torque value (speed) changes in different gears.
a) Gear ratio of one pair of gears
Take two gears and count the number of teeth. The first gear has 20 teeth, and the second 40. So with two revolutions of the first gear, the second will make only one revolution ( gear ratio equals 2).
b) Gear ratio of two gears
On the image b) the first gear (“A”) has 20 teeth, the second (“B”) has 40, the third (“C”) has 20, the fourth (“G”) has 40. Further, simple arithmetic. The input shaft and gear "A" rotate at a speed of 2000 rpm. Gear "B" rotates 2 times slower, i.e. it has 1000 rpm, and since gears "B" and "C" are fixed on the same shaft, then the third gear makes 1000 rpm. Then gear "G" will rotate even 2 times slower - 500 rpm. From the engine to the input shaft comes - 2000 rpm, and comes out - 500 rpm. On the intermediate shaft at this time - 1000 rpm.
IN this example the gear ratio of the first pair of gears is two, the second pair of gears is also two. The total gear ratio of this scheme is 2x2=4. That is, the number of revolutions on the secondary shaft decreases by 4 times, compared with the primary. Please note that if we disengage gears "B" and "G", then the secondary shaft will not rotate. At the same time, the transmission of torque to the driving wheels of the car is also stopped, which corresponds to a neutral gear.
Reverse gear, i.e. rotation of the output shaft in the opposite direction, is provided by an additional, fourth shaft with a reverse gear. An additional shaft is needed to get odd number pairs of gears, then the torque changes direction: 
Torque transmission scheme when reverse gear is engaged: 1 - input shaft; 2 - gear of the input shaft; 3 - intermediate shaft; 4 - gear and reverse gear shaft; 5 - secondary shaft.
gear ratios
Since there is a large set of gears in the "box", by engaging different pairs, we have the opportunity to change the general gear ratio. Let's look at the gear ratios:| Transfers | VAZ 2105 | VAZ 2109 |
| I | 3,67 | 3,636 |
| II | 2,10 | 1,95 |
| III | 1,36 | 1,357 |
| IV | 1,00 | 0,941 |
| V | 0,82 | 0,784 |
| R(Reverse) | 3,53 | 3,53 |
Such numbers are obtained by dividing the number of teeth of one gear by the divisible number of teeth of the second and further along the chain. If the gear ratio is equal to one (1.00), then this means that the secondary shaft rotates with the same angular velocity as primary. A gear in which the speed of rotation of the shafts is equalized is usually called - straight. As a rule, this is the fourth. The fifth (or highest) has a gear ratio less than one. It is needed for driving on the highway with minimal engine speeds.
First and reverse gear are the most “strong”. It is not difficult for the engine to turn the wheels, but the car in this case moves slowly. And when driving uphill in the "nimble" fifth and fourth gears, the motor does not have enough strength. Therefore, you have to switch to lower, but "strong" gears.
First gear is required to start moving so that the engine can move a heavy machine. Further, by increasing the speed and making some margin of inertia, you can switch to the second gear, more "weak", but more "fast", then to the third and so on. The usual driving mode - in fourth (in the city) or fifth (on the highway) - they are the fastest and most economical.
What are the faults?
Usually they appear as a result of rough work with the shift lever. If the driver constantly "pulls" the lever, i.e. transfers it from one gear to another with a quick, sharp movement - this will lead to a repair. With this handling of the lever, the switching mechanism or synchronizers will definitely fail.The shift lever shifts in a calm, smooth motion, with micro-pauses in the neutral position for the synchronizers to work, protecting the gears from breakage. With proper handling and periodic oil changes in the "box", it will not break until the end of its service life.
Noise during operation, which depends mainly on the type of gears installed, is significantly reduced when replacing spur gears with helical gears. Correct work also depends on the service on time.
