But now it would be nice to think about it! How does he move on the ground, our favorite car? The engine already knows how it works, and the wheels turn in the opposite direction, and even back and forth. And today we'll talk about the transmission and its structure. What is included in the transmission and the design features of this system.

In short, all the mechanisms that are located between the engine and the driving wheels are the transmission of the car. It performs the following functions:

• transmits torque from the engine to the drive axle;
• changes the value and direction of the moment;
• distributes the torque to the driving wheels.

What is included in the transmission of a car and what are its types

Depending on what type of energy is converted, this type of transmission can be:

• mechanical (converts and transfers mechanical energy);
• electrical (converts mechanical energy into electrical energy, and after feeding it to the driving wheels, back - electrical into mechanical);
• hydrovolume (converts mechanical energy into energy of fluid movement, and after feeding to the drive wheels, back - energy of fluid movement into mechanical);
• combined or hybrid (combination of electromechanical and hydromechanical).

The first option is most often used in modern cars. If the change in torque is automatic, then it is called automatic.

Design

The design of the device can assume the use of a pair of front and rear wheels as driving wheels.

If the rear pair of wheels is used as leading, then the car turns out to be rear-wheel drive, and if the front - front-wheel drive. If the car has a drive simultaneously to the rear and front wheels 4x4, then all-wheel drive.

Cars with different types of drive have their own transmission design, which often differs significantly in the composition of the elements and their design.

So in a rear-wheel drive car, these are sequentially located elements: clutch, gearbox, cardan and main gear, differential, axle shafts.

Clutch

Serves for a short disconnection of the engine from the transmission and the subsequent smooth connection of these elements after gear shifting, as well as protecting parts from excessive loads.

Changes torque, speed and direction of travel, and also decouples the engine and transmission for a long time. The boxes are mechanical, and (torque converter - planetary gears)

Cardan transmission

It is necessary for the translation of the moment from the secondary shaft of the box to the shaft of the main gear, which are at an angle relative to each other.

main gear

GP is needed to increase the torque, change direction and transfer it to the axle shaft. Usually, a hypoid main gear is used in a car (the gear teeth are not straight, as usual, but radial).

Differential

The differential distributes the torque to the drive wheels, and allows the axle shafts to rotate at different angular speeds from each other during the turning of the vehicle.

CV joint

The transmission of a front-wheel drive car is equipped with constant velocity joints (abbreviated SHRUS) and drive shafts (semi-axles).

The first ones are needed to remove the edge torque from the differential and feed it to the drive axle. As a rule, these are 2 hinges for communication with the differential (so-called internal hinges) and 2 more hinges for communication with the wheels (so-called external hinges).

Drive shafts are located between these joints.

The transmission of a car with an all-wheel drive assumes various options for the designs discussed earlier, which together form an all-wheel drive system.

It's that simple. Now you know what goes into the transmission of the car and it remains for us to understand in detail how each of the nodes of the transmission mechanism works. Follow the publications and do not skimp on knowledge, share with everyone.

And see you soon on the blog pages.

The power train of a car consists of a number of mechanisms that transfer forces from the engine to the drive wheels of the car and allow you to change the amount of this force in accordance with the driving conditions of the car, as well as to separate the engine from the drive wheels.

The GAZ-21 "Volga" car and a number of others have a rear axle drive, in which the power transmission consists of a clutch, gearbox, cardan gear, main gear, differential and semi-axles. The exception is the Zaporozhets minicar, in which the clutch, gearbox and main gear with differential and drive axle shafts are a compact unit connected to the engine and located together with it in the rear of the car.

In some models of two-axle vehicles with rear-axle drive (GAZ-13 "Chaika", ZIL-111 and ZIL-114), instead of a clutch and a gearbox, an automatic transmission is used in the power train, consisting of a torque converter and a planetary gearbox with automatic control.

Serves to temporarily disconnect the power train from the running engine and smooth their connection. Disconnection is necessary when stopping and braking the car, as well as when changing gears; smooth connection - when starting off and after disengaging gears. In addition, the clutch protects the components of the power train mechanisms from significant overloads. All passenger cars are fitted with single disc clutches. In the GAZ-21 Volga car, a hydraulic clutch drive is used, which consists of a suspended pedal, a master cylinder, a pipeline, a slave cylinder, a clutch release fork and a clutch release clutch with a thrust bearing. The hydraulic clutch master cylinder is molded in one piece with the brake master cylinder. The fluid reservoir in these cylinders is common and has a baffle in the lower part, so that a malfunction of one system does not affect the operation of the other.

Transmission is necessary to change the tractive effort on the wheels of the car, to obtain reverse gear and to separate the engine from the driving wheels.

The tractive effort on the wheels, required to overcome all the resistances that arise when the vehicle is moving, must vary depending on the operating conditions of the vehicle. The gearbox consists of a set of gears that mesh with one another in various combinations, forming several gears, or stages with different gear ratios (stepped gearbox).

The gearbox in the Volga car is two-way, three-stage, with the inclusion of the second and third gears using a synchronizer and with a shift lever located on the steering column.

Serves to transfer the rotational force from the gearbox or transfer case to the drive axle of the vehicle with varying angles of inclination between the shafts. The cardan transmission consists of a shaft, their bearings and cardan joints.

All domestic cars use double open cardan drives with rigid cardan joints on needle bearings.

The rigid cardan consists of two forks and a cross. The spikes of the cross fit into the holes of the forks and are fixed in them on needle bearings. The bearing consists of a steel cup, a set of thin rollers (needles) and an oil seal that retains the grease in the bearing. The bearings are secured in the holes of the forks with covers and screws or a lock ring.

There is another design of the universal joint needle bearing, in which rubber self-tightening seals are used, and the bearing cups are fixed in the forks with retaining rings. Such a cardan is used in the GAZ-21 Volga car.

The final drive, differential and axle shafts are included in the drive to the drive wheels of a two-axle vehicle with one rear drive axle. All these devices are contained in a common crankcase with semi-axial sleeves and are called the rear drive axle.

The main gear is used to transmit tractive effort to the drive wheels and provides rotation from the propeller shaft on the axle shaft at an angle of 90 °. The main gear uses single or double gear drives. In passenger cars, a single hypoid transmission is mainly used.

Provides rolling of the right and left driving wheels with different number of revolutions when turning the car and driving on uneven roads. The differential consists of a box, a crosspiece, bevel satellites and side gears.

The axle shafts are used to transfer rotation from the differential to the drive wheels. Depending on the location of the bearings, the axle shafts perceive various loads and are divided according to the work efforts into three main types: unloaded, three-quarters unloaded and semi-unloaded.

If the axle shaft does not perceive bending moments and transmits only torque, then it is called unloaded. Most trucks have this type of axle shaft.

The half-axle, unloaded by three quarters, differs from the unloaded one in that its outer end is connected to the drive wheel hub, which rests on the rear axle casing not through two, but through one bearing. Semi-axles of this type are installed in Pobeda passenger cars.

Semi-balanced axle shafts absorb all bending moments, and the outer ends of the axle shafts are directly supported by bearings installed in the rear axle housing. They are mainly used in passenger cars "Moskvich-408", GAZ-21 "Volga", GAZ-13 "Chaika". Cars ZAZ-965 and ZAZ-966 have unloaded swinging axle shafts.

The main gear of a car is a transmission element, in the most common version, consisting of two gears (driven and leading), designed to convert the torque coming from the gearbox and transmit it to the drive axle. Traction and speed characteristics of the vehicle and fuel consumption directly depend on the design of the main gear. Consider the device, principle of operation, types and requirements for the transmission mechanism.

Principle of operation

General view of the hypoid final drive

The principle of operation of the main gear is quite simple: while the car is moving, the torque from the engine is transmitted to the variable gearbox (gearbox), and then, through the main gear and, to the drive shafts of the car. Thus, the final drive directly changes the torque that is transmitted to the wheels of the machine. Accordingly, it also changes the speed of rotation of the wheels.

The main characteristic of this gearbox is the gear ratio. This parameter reflects the ratio of the number of teeth of the driven gear (connected to the wheels) to the leading one (connected to the gearbox). The higher the gear ratio, the faster the car accelerates (the torque increases), but the maximum speed decreases. Decreasing the gear ratio increases the top speed and the car accelerates more slowly. For each car model, the gear ratio is selected taking into account the characteristics of the engine, gearbox, wheel size, brake system, etc.

Device and basic requirements for the main gear

The structure of the mechanism under consideration is simple: the main gear consists of two gears (gear reducer). The pinion gear is smaller and is connected to the output shaft of the gearbox. The driven gear is larger than the driving gear, and it is connected with and, accordingly, with the wheels of the machine.

The scheme of the main transfer of the driving axle of the car: 1 - driving wheels; 2 - semi-axis; 3 - driven gear; 4 - driving shaft; 5 - driving gear

Consider the basic requirements for the main gear:

• minimum level of noise and vibration during operation;
• minimum fuel consumption;
• high efficiency;
• ensuring high traction and dynamic characteristics;
• manufacturability;
• minimum overall dimensions (to increase ground clearance and not raise the floor level in the car);
• minimum weight;
• high reliability;
• minimal need for maintenance.

The efficiency of the main gear can be increased by improving the quality of the teeth of both gears, as well as increasing the rigidity of the parts and using rolling bearings in the design. Note that minimizing vibration and noise during operation is most often required for gear reducers of passenger cars. Vibration and noise can be minimized by ensuring reliable lubrication of the teeth, improving the accuracy of the gearing of gears, increasing the diameter of the shafts, and other measures that increase the rigidity of the mechanism elements.

Classification of final drives

By the number of pairs of engagement

• Single - has only one pair of gears: driven and driven.
• Double - has two pairs of gears. Divided into double center or double spaced. The double central one is located only in the driving axle, and the double spaced one is also located in the hub of the driving wheels. It is used in freight transport, as it requires an increased gear ratio.

Single and double final drive

By the type of gear connection

• Cylindrical. It is used on cars with front-wheel drive, in which the engine and gearbox have a transverse arrangement. This type of connection uses gears with chevron and helical teeth.
• Conical. It is used on those rear-wheel drive cars in which the dimensions of the mechanisms are not important and there are no restrictions on the noise level.
• Hypoid is the most popular type of gear connection for rear wheel drive vehicles.
• Worm - in the design of the transmission of cars is practically not used.

Cylindrical final drive

By layout

• Placed in the gearbox or in the power unit. On front-wheel drive vehicles, the main gear is located directly in the gearbox housing.
• Placed separately from the checkpoint. In rear-wheel drive vehicles, the main gear pair is located in the drive axle housing along with the differential.

Note that in four-wheel drive vehicles, the location of the main gear pair depends on the type of drive.

Bevel final drive

Advantages and disadvantages

Worm final drive

Each type of gear joint has its own pros and cons. Consider them:

• Cylindrical final drive. The maximum gear ratio is limited to 4.2. Further increase in the ratio of the number of teeth leads to a significant increase in the size of the mechanism, as well as an increase in noise.
• Hypoid final drive. This type has a low tooth load and low noise level. At the same time, due to the displacement in the engagement of the gears, the sliding friction increases and the efficiency decreases, but at the same time it becomes possible to lower the propeller shaft as low as possible. Gear ratio for passenger cars - 3.5-4.5; for freight - 5-7 ;.
• Bevel final drive. It is rarely used due to its large size and noise.
• Worm final drive. This type of gear connection is practically not used due to the laboriousness of manufacture and the high cost of production.

The final drive is an integral part of the transmission, on which fuel consumption, maximum speed and acceleration time of the car depend. That is why, when tuning a transmission, a pair of gears is often changed to an improved version. This helps to reduce the load on the gearbox and clutch, as well as improve acceleration dynamics.

Transmission car ( power train) ensures the transfer of forces (torque) from the engine to the driving wheels, as well as the transformation (transformation) of these forces depending on the driving conditions. The transmission includes all components and mechanisms of the car that connect the engine to the drive wheels.

A distinction should be made between transmissions of vehicles with rear axle drive (a / m of the classic layout), with front-wheel drive and all-wheel drive vehicles. Also, the transmission of an all-wheel drive vehicle designed for off-road use (SUV) will differ from the transmission of an all-wheel drive vehicle designed for paved roads.

The wheel formulas of cars with rear or front wheel drive are written - 4x2 (i.e., four wheels, two of which are driving). The wheel formula of a car with a drive to the front and rear axles is written - 4x4 (i.e., four wheels are all driving).

Transmission mechanisms include: clutch, gearbox(including , transfer caseand power take-offfor auxiliary mechanisms) , cardan gear, final drive, differential, drive wheel drivesand some other mechanisms .

Final drive, gearbox and transfer case (if equipped) provide total gear ratio transmission of the car.

1). Clutch serves to connect the engine to the transmission, as well as to temporarily disconnect them (for example, at the time of gear shifting).

On cars are used "dry", one - or two-disc friction clutches with a mechanical (usually cable), or hydromechanical drive, as well as fluid couplings and torque converters.

The operation of friction clutches is based on the use of frictional forces between solid surfaces, in particular - between the clutch pressure plate, the friction linings of the clutch disc and the engine flywheel. The device of a single-plate dry friction clutch of a passenger car is shown in figure... Hydraulic and cable drive diagram

Hydromechanical clutches and torque converters transmit torque from the engine to the transmission by exposing the working parts of the mechanism to a fluid (usually a special oil) circulating inside the torque converter housing. The torque converter device is shown in figure... You can read about the operation of the simplest torque converter here.

2). Transmission serves to change the traction forces (torques) transmitted from the engine to the driving wheels, as well as to disconnect the engine from the transmission (including long-term ones) and ensure the car is moving in reverse.

The need to change the tractive effort on the wheels arises when the driving conditions of the vehicle (road conditions) change. The greatest effort on the drive wheels is required when starting the vehicle. When driving in difficult road conditions (for example, a steep hill or off-road), engine power will be spent to overcome the resistance to the movement of the car. When driving in favorable road conditions (for example, a flat highway), the engine power can be “spent” to accelerate the car.

Depending on the driving conditions, the driver selects (turns on) one or another gear in the gearbox, engaging gears with different gear ratios and, thereby, changes the torque on the driving wheels. In automatic transmissions, the gears are controlled by the engagement control systems, without the direct involvement of the driver.

When changing (increasing / decreasing) the torque on the driving wheels, the speed of their rotation changes in inverse proportion, by the same amount.

On modern automotive technology, two, - three-shaft gearboxes with simple gear transmission and spur gears of external engagement, as well as gears and gearboxes planetary type and variators... The number of forward gears can be within 3 - 7, reverse - 1 - 2. Gear ratios are given in the technical characteristics of the transmission of a particular vehicle.

The general structure of a shaft mechanical transmission can be viewed at rice.

The main parts of a shaft gearbox are shafts (primary, secondary, intermediate), gears, synchronizers, bearings, parts of the gearshift mechanism (for "manual" gearboxes - forks, rods, etc.). Planetary gearboxes include shafts (leading, driven, central), a set of planetary gears, consisting of a set of gears (satellites, sun and crown) and a carrier, friction-braking devices, a mechanism for hydraulic or electro-hydraulic control of gear shifting.

The operation of a simple gear and planetary gear is considered here.

Transfer case has a device similar to a gearbox, is installed behind the main gearbox (sometimes, the gearbox and the transfer case, are structurally combined in one housing) and serves to distribute (distribute) the effort to all available drive axles of the car. The transfer case, as a rule, has two gears - high (direct) and low, which doubles the total number of gears and allows you to select the gear ratios of the transmission for driving in difficult off-road conditions. A mechanism is placed in the box for turning on / off one of the axles and the main gear with an axle differential, if permanent all-wheel drive is provided. Also, there may be a locking mechanism for the center differential

3). Cardan transmission serves to transfer rotation from the gearbox (transfer case) to the main gear of the driving axle with constantly changing tilt angles and the distance between the axles of the vehicle (base).

The angle of inclination of the propeller shaft must change due to the fact that the driving axle of the car is attached to the body (frame) through the suspension elements (i.e., not rigidly) and has a certain degree of freedom. For the same reason, the distance between the axles of the car also changes. So, when the car accelerates, the rear drive axle tends to "catch up" with the front part of the body, and when braking, on the contrary, "lag behind" it.

The cardan transmission can include one or more shafts, cardan joints, flexible connecting and suspension couplings.

The cardan drive device of a passenger car can be viewed .

4). main gear transfers torque at an angle of 90º from the cardan shaft to the drives of the driving wheels, changes the torque in accordance with its gear ratio.

There are single and double main gears. Gears of gears can be bevel and / or cylindrical. Single simple gears include a drive and a driven gear. Small pinion gear - bevel, with spiral teeth is installed in rolling bearings and is driven from the propeller shaft, or directly from the gearbox shaft. The large driven gear, with spiral teeth, is bolted to the differential box. In hypoid gears, the axis of the small bevel gear is shifted downward relative to the axis of the large driven gear by 30 - 40 mm.

The gears of the hypoid gears are manufactured in “pairs” and are marked. Replacement of gears should be carried out only as a set.

The final drive device is shown in figure.

e). Differential distributes the torque between the driving wheels (axles) and allows the driving wheels of the car to rotate at different speeds, which is necessary when the car is passing bends and when the wheels hit different road conditions (for example, one wheel is on a flat surface, and the other moves over bumps).

The most widely used are differentials with bevel gears. The differential has a housing (differential box) in which bevel half-axle gears and satellite gears mounted on the axle are located.

The above property of the differential, in the case of existing differences in the adhesion of the driving wheels to the road surface, often leads to slipping of one of the wheels (wheels with a lower coefficient of adhesion to the road). To eliminate this undesirable effect on off-road vehicles, limited slip differentials (self-locking differentials) are used or differential lock mechanisms are used.

The differential device is shown in figure.

5). Wheel drives.

Driving axle shafts are installed in the axle sleeves of the driving axle beam and are used to transfer rotation from the differential to the wheels. According to the operating conditions, the axle shafts are divided into two main types: semi-unloaded and fully unloaded.

The semi-balanced axle shaft at one end lies in the differential box, and the other in the axle shaft bearing.

Fully unloaded axle shaft at one end lies in the differential box, and at the other, through a flange, is connected to the wheel hub. In turn, the wheel hub is mounted on bearings at the end of the semi-axial sleeve. With this setting, the axle shaft transmits only torque. All other forces are absorbed by the drive axle beam through the bearings.

The drive axle is a common casing (beam) with a central crankcase and semi-axial sleeves. The crankcase houses the final drive and differential. Half-shafts are installed in the half-axle sleeves.

In front wheel drives there is such an element as constant-velocity joint, providing uniform rotation of the wheels at their different spatial positions while turning the car.

The rear wheel drive of a classic vehicle is shown , front wheel drive is shown in figure... You can read about the constant velocity joint here.

Drive axles and wheel drive

The drive axle is a rigid hollow beam consisting of three main elements: two half-axle sleeves and a middle part - a crankcase, in which the main gear with a differential is located. In the hollow sleeves of the beams, steel tubular casing of the axle shafts are pressed, which serve to install the wheel hubs. According to the method of manufacturing, the beams of the driving axles are distinguished into cast and stamped-welded. On most cars and buses, the rear drive axle beams consist of two stamped steel halves welded together.

We will consider the structure and interaction of the main gear, differential and rear wheel drive units using the example of driving axles of cars and buses with different wheel formulas.

The drive axle of the ZIL -130 car (Fig. 14.33). The main gear of the rear axle of this car is double with a total gear ratio of 6.32. It consists of a pair of helical bevel gears and a pair of cylindrical helical gears. The drive bevel gear is made in one piece with the shaft and is connected to the cardan transmission by means of a flange. It rotates in roller bearings mounted in a housing bolted to the final drive housing. The oil for lubricating the pinion bearings is fed through a groove cast in the crankcase.

The driven bevel gear is attached to the intermediate shaft flange, with which the drive spur gear is manufactured as a whole. Spacers between the final drive boat and the hull are used to adjust the meshing of the drive gear and driven gear teeth.

A bearing cover with an oil seal is attached to the housing. A gasket is installed between the cover and the bearing housing, and a washer is installed between the flange sleeve / and the roller bearing. A spacer sleeve and two ground steel rings for bearing adjustment are located between the roller bearings.

The intermediate shaft is mounted on tapered roller bearings located in the crankcase covers. To adjust the bearings and the position of the driven bevel gear relative to the axis of the drive gear, spacers are placed under the covers. The driven spur gear is rigidly connected to two cups 20 and 23 of the differential box, in which the semi-axial bevel gears are located. The half-shafts, located in the rear axle beam, are installed with their inner ends in the slotted holes of the half-axle gears.

The differential box rotates on tapered roller bearings covered with covers. These bearings are adjusted with nuts. A cross is placed between the differential cups, on the spikes of which satellites sit, which are simultaneously meshing with semi-axial gears. To reduce friction, support washers made of low-carbon steel are installed under the half-axle gears and satellites.

When the main gear is operating, the gain from the driven gear is transmitted to the differential box, and through it to the crosspiece and satellites. The latter, being in engagement with the semi-axial gear wheels, ensure the rotation of the semi-axles.

Half shafts. The transmission of torque from the differential to the drive wheels is carried out by means of axle shafts. Each axle shaft with an inner end with splines, on which the axle gear sits, is installed in the differential box. At the outer end of the axle shaft there is a flange for fastening with studs to the wheel hub. In addition to the PEC torque acting on the shoulder RK (wheel radius), the axle shafts can perceive bending moments from the forces acting when the vehicle is moving.

Figure: 1. Leading axle of the car ZIL -130

The torque from the axle shaft to the drive wheel hub is transmitted through the bearing assembly. Depending on the location of the bearings of this unit relative to the casing in which the axle shafts are located, the loads acting on them are also different. In this regard, the axle shafts are divided into two main types: semi-unloaded and fully unloaded.

The semi-unloaded semi-axle is called the semi-shaft, which is supported by a ball bearing located inside its casing. Such a semiaxis not only transmits the torque that twists it, but also perceives bending moments.

Fully unloaded is a semi-axle that is unloaded from bending moments and transmits only torque. This is achieved by the fact that the wheel hub is mounted on the half-axle casing on two widely spaced roller bearings, as a result of which bending moments are absorbed by the casing, and the axle shafts transmit only torque.

Semi-unloaded axle shafts are installed on all passenger cars, buses of an especially small class and on many trucks of especially small and light carrying capacity. Fully unloaded axle shafts are installed on all medium and heavy duty trucks, as well as medium and large buses.

Figure: 2. Semiaxis schemes:
a - semi-unloaded; b - completely unloaded

As an example of a fully unloaded axle shaft in Fig. 3, a shows the drive of the rear driving wheels of a ZIL -130 vehicle assembled with a semiaxis. To install the axle shafts and hubs of the driving wheels, steel pipes are welded to the end part of the rear axle beam, which are the axle shafts. Two tapered roller bearings are mounted on the machined casing journals. The outer rings of these bearings are pressed into the wheel hub seats.

The hub mounted on the bearings is secured by an adjusting nut with a lock washer and a locknut that grips the oil seal, preventing lubricant from entering the hub from the rear axle housing. To prevent it from flowing out of the hub and getting into the brake drum, an oil seal is placed on the pipe. The axle shaft flange is attached to the hub with studs and nuts. To increase the reliability of the axle shafts fastening, conical expansion sleeves are installed on each stud, with the help of which a gap-free connection of the axle shaft flange on the studs is achieved. As a result, all studs work simultaneously when transmitting torque.

The brake drum is attached to the hub flange using studs, and on the other side

the wheel discs are attached to the same studs with nuts. Inside the brake drum there is an expanding fist that acts on the pads with friction linings riveted to them during braking.

In the considered design of the drive wheel drive unit, the semi-axle perceives only torque, and the hub bearings, located symmetrically relative to the middle plane of the wheel, perceive bending moments: and transfer them to the beam, while unloading the semi-axle.

The GAZ-53-12, GAZ-52-04 trucks have a similar design of the drive wheel drive unit.

A typical example of the design of the drive of the leading front wheels is the drive to the steered wheels of the GAZ-66-11 car. The front axle of this vehicle, while remaining steerable, transmits torque to the front drive wheels. Such bridges are often called combined (both driven and driving). Just like the rear axle, the driving front axle consists of a final drive, differential and axle shafts. In such a bridge, the outer part of the axle shaft casing ends with spherical cups, which are the bearings of the pivot pin. The pivot pin is made in the form of two studs welded to a spherical cup. Tapered roller bearings are installed on the spikes, which are closed with covers. The top cover is also the lever of the hollow pivot pin. Considering that the torque from the differential to the wheel hubs must be transmitted at varying angles, the axle shaft is made as one piece with the inner fork, and the shaft on which the wheel hub is installed is made together with the outer fork.

Figure: 3. Drive to the driving wheels of the car:
a - ZIL -130; b - GAZ -66-11

The inner fork is connected to the outer fork by a ball-type universal joint of equal angular velocities, which ensures the same rotation speeds of the forks regardless of the angle of the steered wheels. A flange is installed on the splines of the shaft, which is attached to the hub with pins. The wheel hub rotates on two tapered roller bearings mounted on a pivot pin.

Wheel (final) transmission. On buses LiAZ-677M, LAZ -4202 and cars of the MAZ family, the rear drive axle has a double spaced main gear, which consists of a central (main) gear and wheel gears located in the rear wheel hubs. The use of wheel reducers, or, as they are often called, the final drive, allows you to unload the differential and axle shafts, reduce the overall dimensions of the bridge and increase the vehicle's ground clearance.

The center gear consists of a pair of helical bevel gears and an interwheel differential.

The wheel reducer of the LiAZ-677M bus is made in the form of spur cylindrical gears with external and internal gearing (planetary type). It includes a fully balanced axle shaft, pinion (sun) gear, satellite gears, axles, carrier and ring gear.

The torque is supplied by the semi-axle to the drive gear and is transmitted to three satellite gears mounted on the axles, the ends of which are pressed into the carrier hole. The carrier is attached to the hub of a wheel rotating on a ball and roller bearings using studs. In a final drive of this type, the torque is transmitted to the wheel hub through the carrier, and the ring gear is a locked gear support, which is fixedly connected to the journal.

On MAZ-500A, MAZ -5335 vehicles, a wheel reducer with a locked carrier is used. It consists of a driving (sun) gear mounted on the splines of the outer end of the semi-axle, three satellite gears with axles and a ring gear with internal teeth.

The crown wheel is the driven element of the transmission and is screwed to the wheel hub. The carrier consists of two cups: outer and inner, connected by bolts. It is seated on the end of the axle shaft housing and is connected to it by a splined connection, therefore it does not rotate (locked).

Figure: 4. Wheel drive of the LiAZ-677M bus

The torque from the differential of the central transmission is supplied to the Y-axle, and from it to the leading (sun) gear of the reducer. From the drive gear, the torque is transmitted to three satellite gears, which rotate on axles in the direction opposite to the direction of rotation of the drive gear. From the satellites, the torque is transmitted to the driven (main) gear wheel, and from it to the wheel hub.

The considered wheel drive with a locked carrier is a gear drive with intermediate gears (three satellite gears). The gear ratio of such a transmission is equal to the ratio of the numbers of the teeth of the crown wheel and the sun (driving) gear and is usually in the range of 1.4-1.5.

Figure: 5. Wheel drive of MAZ family cars

On some cars, for example MAZ-500, a spaced double main gear is used. In this case, the second pair of gears is in the drive to each of the driving wheels and is called the wheel or final drive.

It is made in the form of a planetary gear reducer. The pinion (sun) gear is mounted on a semi-axle and meshes with three satellite gears. The axes of the satellites are installed in a fixed glass, which acts as a carrier and consists of an inner and outer cups, which are bolted together. The driven gear, which has internal teeth, is attached to the drive wheel hub.

The gear ratio of such a transmission is usually 1.4-1.5. The use of wheel gears makes it possible to reduce the dimensions of the main gear, increase the ground clearance and reduce the load on the differential and semi-axles.

TO Category: - Car maintenance