When beginners get behind the wheel of a car, they have problems with the gearbox at the stage of learning to drive, or rather, with the need for constant shifting. Many have thought more than once that without this "poker" the car would be more ideal. But, unfortunately, without the car could not work effectively. This is due to the characteristics of the internal combustion engine. Let's find out the purpose of its types, device and principle of operation.

Why do you need a gearbox in a car?

If you open the directories, it says that this mechanism is used to change the torque generated by the internal combustion engine. The gearbox also serves to temporarily turn off the torque from the engine and for reversing.

And now consider the appointment from the point of view of people far from the device and the theory of the car. It is also worth figuring out why you need to change the gearshift stages every time you drive.

The need to constantly change gears is directly related to the characteristics of the motors. internal combustion. Unlike electrical units, the torque of an internal combustion engine has an uneven characteristic.

ICE and electric motor

The main difference between electric motors and internal combustion engines is in the thrust characteristics. This characteristic describes how power and torque change with rpm. In the case of electric motors, the torque is available immediately, and as the speed increases, the torque will drop.

This characteristic is more suitable for a car - at the moment of starting and during acceleration, when you need to make a lot of effort to overcome inertia, it is better to have a large torque. To move further evenly, much less effort is required. The power of electric motors in any range of rotor speeds is close to the maximum, and in any modes it is realized and used almost completely. Therefore, electric motors are more suitable for use as a vehicle propulsion system. In ICE, things are a little different. When the crankshaft rpm is low, the power is also low. The rotational moment practically does not change.

If the resistance to movement increases and the speed begins to decrease, then the electric motor will increase the torque. In the case of an internal combustion engine, the moment will increase only quite a bit, and then decrease.

The traction characteristic of the internal combustion engine is considered completely unsatisfactory. But even now, in terms of efficiency, overall dimensions, and other qualities, they are significantly superior to modern electric power units. Based on these considerations, the engineers accepted the lack of internal combustion engines and created a gearbox to solve this problem. Its purpose is to change the gear ratio between the crankshaft and the driving pair of wheels. As a result, maximum torque is available in a narrow range of optimal rpm, but in different gears. So the engine runs more efficiently.

gear ratios

For a better understanding of the purpose of a gearbox in a car, one should remember the school physics course and some sections of mechanics.

In gear-based transmission systems where two gears operate, the diameter and number of teeth will determine the RPM and torque. The ratio of the number of teeth on the driven gear to the number of teeth on the drive gear is the gear ratio. When the drive gear has a smaller diameter than the driven gear, the revolutions on the latter will be lower, and the torque, on the contrary, will be higher.

With a gain in strength, there will be a loss in speed. And having won in speed, we will notice losses in strength. If there are several gears in the transmission mechanism, then the gear ratio is determined by multiplying the numbers of each pair of gears. The purpose of the gearbox is precisely to change the gear ratios.

To get the different torque that is needed to drive the car in different road conditions, there are several pairs of gears in the gearbox. They come with different gear ratios. If you install an intermediate gear in a pair of driving and driven gears, then the latter will rotate in the opposite direction - this is reverse gear.

Any type of vehicle gearbox is necessary in order for the internal combustion engine to operate at optimal speeds and in its normal operating modes, as well as in order to be able to effectively use engine power in all driving situations by simply changing the gear ratio.

When and how to switch gears?

In order to start moving in a car and pick up an initial low speed, as well as to move in off-road conditions, close to the maximum torque is needed. It can be achieved in the middle range of engine crankshaft speeds. In this case, there is no need for high speed. To do this, there are lower gears in the checkpoint - first, second, sometimes third. At the same time, even at high speeds in first gear, the car will drive quite slowly.

To move evenly at a higher speed, the wheels must rotate at a high frequency. In this case, the engine speed should be optimal. For this, there are higher gears - fourth, fifth (and if the gearbox is 6-speed, then sixth). Here the gear ratios are lower. The car will move quickly at the same optimal speed until the internal combustion engine reaches the maximum or maximum permissible speed. In higher gears, acceleration will no longer be as effective. Also, in higher gears, you will not be able to drive at low speed. The car will not be able to move. The engine simply can not provide the required torque.

Operating principle

Manual transmission device

In the world now there are a lot of different designs of manual transmission. Most front-wheel drive cars have two-shaft mechanisms. Three-shaft are installed on rear-wheel drive. I must say that even in our time, when technology is developing very quickly, mechanics are very popular. The fact is that repairs of this type are simple and inexpensive, unlike automatic transmissions and CVTs.

Double shaft box

It is based on the primary and secondary shaft of the gearbox. Also in the car's gearbox device there is also a block of gears along with synchronizers. The main gear mechanism and differential are installed in the metal transmission housing.

Using the input shaft, the vehicle's transmission can be connected to the clutch assembly. A block with gears is rigidly fixed on the shaft. The gearbox also has a secondary shaft. It is located parallel to the primary. It is also equipped with a block of gears. The latter are constantly in rigid engagement with the elements from the block on the input shaft. Also, the output shaft of the transmission is connected through a gear to the main gear. The gear block is equipped with synchronizers. In different designs, there may be several secondary shafts.

Additionally, the box is equipped with a gearshift mechanism. Most often it is remote. Since the car's transmission case is small, the elements are located under the hood.

Three-shaft checkpoint

The input shaft serves to connect the gearbox mechanism to the clutch assembly. On the shaft there are splines on which the driven disk is put on. The moment from the engine is transmitted through the gearbox gear, which is engaged with this element. An intermediate element is located in parallel. It is equipped with a block of gears that are in rigid engagement with the shaft.

The secondary shaft is on the same axis as the primary. The gears are not rigidly meshed and rotate freely. The gears of the intermediate and output shafts, as well as the part on the input shaft, are constantly engaged.

Synchronizers are installed between the gears. The shift mechanism is installed directly in the car's transmission housing. It is a shift lever, as well as sliders and forks.

Conclusion

So, we found out what a gearbox is. As you can see, this is a very important node in the design of any car. It is he who allows the movement of the car with different effort and speed. The movement of the car is largely determined by the gearbox.

Introduction

1. Appointment

2. General arrangement of the gearbox

3. Main gear with differential

4. Automatic transmissions

5. Transmission malfunctions

6. Conclusion

Literature

Introduction

The car has to move at speeds from very low to a hundred or two kilometers per hour - and therefore the range in which the wheel speed changes turns out to be huge - every 50 times. But the internal combustion engine is able to work effectively only in the range of 2000-6000 rpm, that is, change the speed of rotation of the crankshaft only three times. Therefore, it is necessary to put the same box between it and the wheels in order to obtain the required speed of movement at close to optimal engine speeds.

On different vehicles, the gearbox arrangement may differ, but circuit diagram stays about the same. In the second section, we will consider its general structure.

In the fourth section, we will find out whether it is possible to make the gearbox work by automatically adjusting to the driving mode. Consider the three most common options today.

The fifth section will discuss the main faults of the gearbox and how to fix them.

Purpose

The purpose of the gearbox is to change the traction force, speed and direction of the car. In automobile engines, with a decrease in the speed of the crankshaft, the torque increases slightly, reaches a maximum value, and with a further decrease in the speed, it also decreases. However, when the car is moving on hills, on bad roads, when starting off and quickly accelerating, it is necessary to increase the torque transmitted from the engine to the drive wheels. For this purpose, the gearbox serves, which also includes a gear that allows the car to move in reverse. In addition, the gearbox provides separation of the engine from the transmission.

A stepped gearbox consists of a set of gears that mesh in various combinations to form several gears or stages with different gear ratios. The greater the number of gears, the better the car "adapts" to different driving conditions. The gearbox should operate silently, with minimal wear; this is achieved by using gears with helical teeth.

Stepped gearboxes are divided into four- and five-speed according to the number of forward gears. Usually the gearboxes of passenger cars, small buses and trucks light-duty gearboxes have four gears, while the gearboxes of large buses and heavy-duty trucks have five gears.

Stepped gearboxes can be simple and planetary. Basically, simple speed gearboxes are used on cars, gear shifting in which occurs in two ways: by moving gears or moving clutches.

Sometimes cars are equipped with stepless gearboxes with a smooth change in gear ratio and combined gearboxes that use both methods of changing the gear ratio.

In a simple speed gearbox (Fig. 1) there are three shafts: the drive (primary) A, connected through the clutch to the engine crankshaft; driven (secondary) B, connected through a driveline and other mechanisms with the driving wheels of the car; intermediate B. With the drive shaft, the drive gear 1 is made as a whole, which is in constant engagement with the driven gear 8, rigidly connected to the intermediate shaft. When the clutch is engaged, the drive and intermediate shafts rotate.

Fig.1. Scheme of a three-speed gearbox: A - drive shaft; B - driven shaft; B - intermediate shaft; G - axis of the gear wheel of the reverse gear; 1–8 - gear wheels.

Movable gears 2 and 3 are mounted on the driven shaft, and gears 7, 6 and 4, as well as wheel 8, are rigidly connected to the intermediate shaft. The ratio of the number of teeth of the driven gear to the number of teeth of the drive wheel, inverse to the ratio of their rotational speeds, is called the gear ratio. For example, the gear ratio of a transmission consisting of gears 8 and 1,

where z8 is the number of teeth of the driven gear wheel 8; z1 is the number of teeth of the drive gear 1.

When any gear of the driven shaft engages with one of the gears of the intermediate shaft, the torque from the engine through the drive, intermediate and driven shafts of the gearbox is transmitted to the driveline and then to the drive wheels of the vehicle. To turn on the first gear, the wheel 3 is moved forward, engaging it with the gear 6 of the first gear of the intermediate shaft. The total gear ratio of the first gear is determined as the product of the gear ratios of individual pairs of gears, i.e.

where z3 and z6 are the numbers of teeth, respectively, of wheel 3 and gear 6.

When the first gear is engaged, the torque Mk on the driven shaft of the gearbox increases in comparison with the engine torque Md by u1 times, i.e.

and has a maximum value, since gear 6 is the smallest of the gears of the intermediate shaft, and wheel 3 is the largest of the gears of the driven shaft.

The first gear is used when the car is moving in the most difficult road conditions, on steep slopes, as well as when starting off on a bad road and with a load.

The second gear is provided by the inclusion of gears 2 and 7. Then

where z2 and z7 are the numbers of gear teeth, respectively 2 and 7.

The second gear is intermediate. In the above diagram of a three-stage box, it is the only one. Four- and five-speed gearboxes may have two or even three intermediate gears.

When the direct (in this case, third) gear is engaged, the drive and driven shafts are connected directly through gears 1 and 2 (u3 = 1). Direct gear is the main gear used when driving on a good road.

Gear shifting is performed with the clutch disengaged, introducing the movable gears (carriages) of the driven shaft into engagement with the fixed gears of the intermediate shaft. This engagement is accompanied by impacts of the ends of the teeth and their increased wear. Therefore, gearboxes with constant mesh gears are often used on cars, which are characterized by high durability.

With the gear wheel 4 of the intermediate shaft in constant engagement is the intermediate gear wheel 5 of the reverse gear, which in fig. 1 is conventionally shown in the plane of the drawing. To turn on the reverse gear, the gear wheel 3 is moved back, engaging it with the intermediate gear wheel 5 of the reverse gear, freely rotating on its axis.

General arrangement of the gearbox

On different vehicles, the gearbox arrangement may differ, but the circuit diagram remains approximately the same. In this section, we will consider its general structure.

The gearbox (Fig. 1) is mechanical, three-way, four-speed, with four gears forward and one reverse. The gears of the first, second, third and fourth gears are helical. Driving and driven reverse gears are spur gears. The intermediate gear wheel of the reverse gear is helical.

Gear ratios of pairs of gear wheels of a gearbox

first gear .............................................. 3.8

second gear ........................................ 2.118

third gear ........................................ 1.409

fourth gear .................................... 0.964

reversing ............................................... 4.156

gearbox housing is a block structure, divided by partitions into three sections. The main gear is located in the first section on the flywheel side. The second section contains gears of the first and second gears and reverse gears, and the third section contains gears of the third and fourth gears. The first and second sections communicate with each other and have a common oil drain hole, closed with a plug with a permanent magnet glued in to collect metal particles that have fallen into the oil. The third section communicates with the cavity of the back cover and also has an oil drain hole closed with the same plug. In the third section, between the gears of the third and fourth gears, a speedometer drive gear is installed. The clutch housing is attached to the front of the gearbox housing, and the rear cover is attached to the rear. The gearbox housing seats are machined together with the clutch housing, so they are replaced as a set.

Rice. 2. Gearbox:

1 - back cover; 2 - slider rod; 3 - sealant; 4 - rear sleeve; 5 - front sleeve; 6 - crankcase cover; 7 - gasket; 8 - bushing; 9 - drive gear of the fourth gear; 10 - washer; 11 - hub; 12 - clutch of the third and fourth gears; 13 - needle bearing; 14 - blocking ring; 15 - third gear gear; 16 - roller bearing; 17 - intermediate shaft; 18 - lever; 19 - retaining ring; 20 - transmission drive shaft; 21 - cover; 22 - drive gear (driven shaft) of the main gear; 23 - front bearing cover; 24 - oil drain plug; 25 - adjusting gasket; 26 - thrust bearing of the drive gear; 27 - adjusting gasket; 28 - driven gear of the first gear; 29 - washer; 30 - reverse driven gear; 31 - driven gear of the second gear; 32 - driven gear of the third gear; 33 - drive gear of the speedometer drive; 34 - driven gear of the fourth gear; 35 - rear bearing of the drive gear; 36 - gearbox housing; 37 - gasket; 38 - washer; 39 - nut; 40 - washer; 41 - splined shaft of the reverse drive gear; 42 - intermediate reverse drive gear; 43 - intermediate driven reverse gear; 44 - axle bushing; 45 - axis of the splined shaft; 46 - cracker; 47 - spring; 48 - plug; 49 - driven gear of the speedometer drive; 50 - sealant; 51 - drive gear; 52 - shaft; 53 - gearbox housing; 54 - gear; 55 - driven shaft. The scheme of the synchronizer: a - the neutral position of the gears; b - start of synchronization; in - transmission is on

Rice. 3.

drive shaft The gearbox rotates on two bearings: the front end of the shaft is on a needle bearing pressed into the flywheel bolt, and the rear end is on a bearing installed in the hole in the gearbox housing. A thrust split ring mounted on the drive shaft prevents the bearing and shaft from moving backwards. It is kept from moving forward by the rear bearing cover, which is bolted with a tightening torque of 1.6-2 kgf-m. At the front end of the drive shaft, splines are cut for a sliding fit of the clutch disc. In the middle part of the shaft, located inside the gearbox, a helical gear is cut, which is in constant engagement with the driven gear of the first gear and the intermediate driven gear of the reverse gear. The axial force that occurs when the torque is transmitted by the drive shaft is perceived by the ball bearing. Behind the gear, at the rear end of the input shaft, there are involute splines that engage with the intermediate shaft hub. The drive shaft is sealed by a self-adjusting rubber seal with an oil-driven thread.

intermediate shaft the gearbox is hollow, made integral with the second gear drive gear. The shaft rotates on two bearings: front roller and rear ball bearings installed in the hole of the gearbox housing. On the intermediate shaft on double-row needle bearings, the drive gears of the third and fourth gears rotate. Thrust shaped washers are installed to limit axial movements that occur on helical gears during torque transmission. The required axial run-up of the gears in the range of 0.26-0.39 mm is provided by the length of the bushings.

spline shaft reverse gear is pressed into the holes of the front and middle walls of the crankcase and is additionally held by the mustache of the cover, which is included in the groove at the front end of the axle. The diameter of the front end of the axle is 27 mm larger than the diameter of the rest of the axle by 0.04 mm. Accordingly, the hole in the front wall of the crankcase is also enlarged, which facilitates assembly and disassembly of the assembly.

driven shaft made integral with the drive gear of the final drive and rotates on three bearings pressed into the gearbox housing. The front bearing is double-row, thrust, tapered, pressed into the front back of the crankcase and perceives radial and axial forces from the final drive. From axial movements arising under the action of axial forces on steel teeth during torque transmission, the bearing is fixed by a cover, which is attached to the crankcase with four bolts with a torque of 3.2-4 kgf-m.

Synchronizers are designed to equalize the speeds of rotating parts of the power transmission when shifting gears. The gearbox has two synchronizers: for fourth and third gears and for second and first. Synchronizers have the same device and the same dimensions, but in the synchronizer of the second and first gears, the reverse driven gear serves as a clutch. The synchronizer hub is put on the splines of the intermediate shaft with internal splines and is held on it together with other parts, washers and a nut. Slots are cut on the outer surface of the hub, along which the synchronizer clutch can move. In addition to slots, three longitudinal grooves are cut out on the hub at different distances from one another, in which three stamped crackers with protrusions in the middle are placed. The crackers are pressed against the splines of the coupling by two spring rings, and the protrusions of the crackers enter the annular groove of the coupling. Brass blocking rings are installed on both sides of the hub. At the ends of these rings facing the hub, three grooves are made into which the ends of the crackers enter. The blocking rings have an internal conical surface that matches the conical surface of the gear synchronizer rims. Fine threads are cut on the conical surface of the rings. A gear shift fork enters the cylindrical groove on the upper surface of the synchronizer sleeve. It breaks the film between the blocking rings and the conical surface of the gear being engaged when they come into contact, as a result of which increased friction occurs between the ring and the conical surface. Outside, the rings have short straight teeth, the same as on the neighboring gear synchronizer rims. These teeth correspond to the depressions between the splines of the synchronizer clutch, as a result of which the clutch, moving in the axial direction, can engage with its splines with the teeth of the locking rings and with the gear rims. Couplings and hubs are matched at the factory in sets to ensure a smooth and easy glide

couplings on hubs with a minimum clearance. On a ZIL-130 car, an inertial-type synchronizer is used.

Rice. 4. Mechanisms for shifting and controlling the gearbox:

1 - lever; 2 - cover; 3, 33 - spring; 4 - persistent cup; 5 - ball cup; 6 - cover; 7 - support sleeve; 8 - insert; 9 - locking bolt; 10 - reverse gear lever; 11 - reverse gear shift rod; 12 - a rod of switching of the third and fourth transfers; 13 - lock of the upper rods; 14 - slider rod; 15 - lock pusher; 16 - gearshift slider; 17 - fork of the third and fourth gears; 18 - cover; 19 - spring; 20 - retainer ball; 21 - a rod of switching of the first and second transfers; 22 - lock of the lower rods; 23 - locknut; 24 - washer; 25 - bolt; 26 - nut; 27 - clutch; 28 - shaft; 29 - floor tunnel cover; 30 - cover; 31 - slider; 32 - guide cup; 34 - damping ring; 35 - bracket; 36 - mechanism fastening bolt; 37 - body; 38 - rug; 39 - retaining ring.

Gear shift is carried out with the help of couplings, forks and three movable rods (Fig. 4), parallel to each other and located in the same row. The rods move in holes bored in the rear and middle walls of the gearbox housing. The ends of the rods entering the cavity of the rear cover have grooves into which the switching slider enters. To fix the working positions of the rods, there are recesses on their surface, which include retainers in the form of balls pressed by springs located in the bushings. The bushings are pressed into the crankcase holes and closed with a common cover. To prevent the inclusion of two gears at once, a blocking device is installed, consisting of upper and lower locks and a pusher. The gearbox is controlled by a lever on the body floor tunnel. The lower pin of the lever is pivotally connected to the slider of the gearbox control mechanism. The slider is connected to the gearbox slider by means of a shaft and a rubber flexible coupling. On the rear cover of the gearbox, there is a switch for reversing lights, which is activated by a special protrusion made on the reversing rod.

Main gear with differential

The main gear increases the torque and transmits it from the cardan shaft to the axle shafts at a right angle. The main gear can be single, consisting of one pair of gears, and double, consisting of two pairs of gears. The gear ratios of the main gears of cars are as follows: ZIL - 130 - 6.45; GAZ - 53A - 6.83; GAZ - 24 Volga - 4.1.

The main gear with differential is located between the clutch housing and the gearbox housing and is structurally made in one block with the gearbox (Fig. 5). The drive gear of the main gear simultaneously performs the functions of the driven shaft of the gearbox, which rotates on three bearings. Adjusting shims are installed between the shoulder of the front bearing and the front wall of the crankcase, which determine the position of the drive gear. The main gear driven gear is bolted to the differential housing and rotates together with the differential on two tapered bearings installed in the housings. Bearing housings are inserted into the side holes of the gearbox and clutch housing and fastened to it with nuts. Tapered bearings of the driven gear are fastened with adjusting nuts, which set the side clearance in the engagement of the main pair within 0.1-0.22 mm. The locking of the adjusting nuts is carried out by stoppers included in their grooves. The differential housing contains satellites and side gears. Half-axle gears have a shaped groove into which the axle shaft is inserted with crackers. To protect the main gear from dust and dirt, as well as from leakage of lubricant from the crankcase, a protective rubber cover is installed on the axle shaft, inside which the cuff housing and cuff are placed. The cuff bodies have an oil-draining thread: the left body - left, right - right. To distinguish them, a groove (A) is made at the end of the sleeve of the left body. To protect the cuff device from dirt, a dirt deflector is installed on the axle shaft at a distance of 224 mm from the flange.

Rice. 5. Rear wheel hub, main gear and axle shafts:

1 - nut; 2 - cotter pin 3 - thrust washer; 4 - decorative cap; 5 - cuff; 6 - brake drum; 7 - wheel nut; 8 - brake shield; 9 - hub; 10 - rear suspension arm; 11 - leading cardan fork; 12 - flange; 13 - bolt; 14 - locking pin; 15 - axle shaft; 16 - cover; 17 - axle pin; 18 - cracker of the axle shaft; 19- right cuff body; 20 - axle gear; 21- cover; 22 - left body; 23 - cuff; 24 - mud deflector; 25 - cardan cross bearing; 26 - bearing needles; 27 - retaining ring; 28 - sealant; 29 - cap; 30 - grease fitting; 31 - crosses; 32, - driven fork; 33 - hub bearing; 34 - spacer sleeve; 35 - bearing housing; 36 - bolt; 37 - brake drum mounting bolt; 38 - wheel disk; A - groove on the left body 22.

The axle shaft is connected to the cardan joint with a spline connection and is locked with a pin. The universal joint consists of two forks, a cross, bearings, cuffs and lock rings. The rear wheel hub rotates on two tapered bearings (of the same size) pressed into the housing. A plastic spacer sleeve is installed between the inner races of the bearings. On both sides of the housing, the bearings are protected by cuffs. From the side of the wheel, the hub is inserted into the housing until it stops into the inner race of the bearing. The splined part of the hub includes a shaft with a cardan joint. The shaft is attached to the hub with a nut and splinted. The same nut adjusts the clearance in the bearings. The brake drum is attached to the hub flange with six bolts.

Automatic transmissions

There are three main types of automatic transmissions in use today.

The car has to move at speeds from a tortoise to a hundred or two kilometers per hour - and therefore the range in which the wheel speed changes turns out to be huge - every 50 times. there is a change in the speed of rotation of the crankshaft only three times. Therefore, it is necessary to put the same box between it and the wheels in order to obtain the required speed of movement at close to optimal engine speeds.

By the way, not all known motors require the use of such a converter on gears. For example, a steam engine and an electric motor develop a considerable torque, as they say, "from zero" - that is why in trolleybuses (as in steam locomotives) there is neither a third pedal nor a gear lever.

So, ICE for cars - the engine is not the best. And since there is no quick replacement for it yet, it will not be possible to do without a gearbox in the coming years. But here it is possible to make it work, automatically adjusting to the driving mode, and even in several ways. Consider the three most common options today.

PLANETARY GEAR WITH TORQUE CONVERTER

A paradox: the device, the most complex in terms of mechanics and hydraulics, took root on mass-produced cars, perhaps earlier than others - in 1955, the American technical literature already considered the designs of a good dozen "automatic machines" from different companies! And the very first three-speed planetary gearbox was created by Cadillac back in ... 1906.

Rice. 6. Classic "automatic": 1 - pump wheel; 2 – turbine wheel; 3 - casing; 4 - control unit (operates automatically or by commands from the lever or buttons on the steering wheel); 5 - sun gear; 6 - gears-satellites; 7 - ring gear.

The planetary gearboxes used in such "machines" got their name for the satellite gears rotating around the central (sun) gear, like planets. A story about the principle of operation of such systems would take up too much space. Let's just say that their use in automatic transmission is due to the extreme simplicity of changing the gear ratio: it is enough just to slow down one or another rotating element or connect them to each other by means of a special friction clutch. These processes are relatively easy to automate.

But simply shifting gears is not enough: the car should not accelerate jerkily. Therefore, such a box is always supplemented by a torque converter - it smoothly changes the ratio between the speeds of rotation of the input and output shafts (as well as between the input and output torque) in a rather narrow range (usually from 1:1 to 1:2.3). Now, when a complex hydromechanical unit (Fig. 1) has perched in place of the usual and small mechanical box with gears (Fig. 1), the driver can relax and almost forget about the lever under right hand and pedals under the left foot. Almost - because reverse gear or a special mode for difficult conditions (and recently there have been more modes for slippery roads, intense acceleration) still need to be turned on yourself.

Until recently, the Russian driver was not familiar with the charms of driving with an "automatic", except for LiAZ city buses, the gear shift in which was accompanied by noticeable jerks, and inaccessible government "member carriers".

Let us note here the characteristic shortcomings of this classical design: large power losses (which means excessive fuel consumption and loss of dynamics), high cost, complexity and bulkiness. As for reliability, in modern automatic transmissions this problem is solved and the resource, with proper maintenance, reaches hundreds of thousands of kilometers. (However, when buying a used foreign car, you should exercise maximum caution, because the former owner had to fill in the torque converter with something other than the branded Dexron (Dexron) or tow the capricious car without loading the drive wheels onto a tow truck - and you will be provided with a repair cost exceeding the most pessimistic expectations.)

STEPLESS VARIATOR

The device has been known for a long time and captivates with its apparent simplicity: a V-belt and a pair of split pulleys (Fig. 2). By shifting or expanding the disks of one of them, you can smoothly change the gear ratio over a fairly wide range. The variator has long been used in light vehicles such as snowmobiles, quadricycles, etc., but the problem of reliability arose on the way to implementation in a full-size car. The transmission of significant torque loaded the belt so much that it was not necessary to talk about its acceptable service life. Perhaps only the Dutch company DAF was the first to dare to put a variator on a serial passenger car, but on its "bigger" successor it was abandoned.

Rice. 7. V-belt variator: 1 - "belt" of the variator; 2 - split pulley; 3 - with a small gap between the cheeks of the pulley, the gear ratio is maximum; 4 - with a large gap - the minimum.

A breakthrough was brought by the technology of the late twentieth century: a type-setting "belt" consisting of a steel tape and steel trapezoidal segments strung on it. The system was called CVT (Continous Variable Transmission - continuously variable transmission). Now it is gaining ground in increasingly heavy classes of vehicles with powerful engines. Riding a Honda Civic with CVT gives a completely unusual feeling: you add gas, the tachometer needle freezes somewhere around 4000 and smooth, without jerks and dips, acceleration presses into the back of the seat, while the other arrow is the speedometer – will not get close to the number 200! The design of the variator made it easy to implement the manual control mode: it is enough to enter several fixed gear ratio values ​​\u200b\u200bin the computer's memory, and it can be switched manually with a lever or buttons. This is how it is done, for example, in the new FIAT-Punto, where there are ... seven gears! As for the resource, if properly performed, it also reaches hundreds of thousands of kilometers, and changing the "belt" is technically easy, except perhaps expensive.

By the way, the problem of transmitting a large torque that existed until recently has already been solved by the designers of Audi, who used a "belt", the steel links of which are interconnected by a complex interlacing and are capable of transmitting up to 280 N.m! And the Japanese suggest in the near future to do without a belt at all, using a conical friction variator.

Rice. 8. Conical friction variator.

QUASI-AUTOMATIC TRANSMISSION

Rice. 9. Quasi-automatic transmission: 1 - clutch release fork, controlled from the electronic unit; 2 - disc spring; 3 - driven disk; 4 - flywheel; 5 - gear shift clutches; 6 - gears; 7 - shafts.

Alas, nothing more suitable has yet been found in the automotive language: companies use their own names - "steptronic", "celespeed" .., the essence of which is the same. We are talking about the automatic control of a conventional five-speed gearbox and clutch (Fig. 3). We can say that here the problem is solved head on: instead of hands and feet, the pedal and lever are controlled by pneumatic hydraulic cylinders or solenoids, and the commands are given to them by an electronic brain connected to a variety of sensors. It is clear that such a solution has become possible only recently, but it has already begun to replace classical automata with might and main. After all, such a system, by definition, does not entail additional power losses, and therefore does not affect the economy and dynamics of the car. Moreover, a properly written control program will provide optimal overclocking, which usually only an ace driver is capable of. In addition, it is easy to introduce "manual" control - buttons on the steering wheel or a lever in the floor. Moreover, the automation will not allow the driver to make a serious mistake - for example, turn on reverse gear or a gear that does not correspond to the capabilities of the engine in this mode at the wrong time. The resource will not differ from the resource of a conventional box, and maybe even increase: after all, the automation will take care of smooth switching and clutch engagement. Well, electronics has now become, perhaps, more reliable than mechanics. Similar developments are being carried out in US, and if it were not for the chronic lack of money, we would have already reported on the tests of the "automatic" "Oka" or "Lada".

To what extent do “automatic” conveniences actually change the performance of cars? Let's turn to the curious tests of our German colleagues. They took a pair of exactly the same cars - with and without automatic transmission - and removed the characteristics. The classic "automatic" with a torque converter was represented by "Porsche" and "Opel", CVT - of course, "Honda", and the newfangled manual transmission with automatic control - "Alfa Romeo" and "Mercedes" A-class. The results confirmed: "automatic" with a torque converter is heavy, takes power and voracious; the variator is easier, also worsens the dynamics, but almost does not increase appetite; mechanics with automatic control is somewhat sluggish, but it saves gasoline. And the most curious option is automatic clutch in one of the A-class versions: it almost doesn’t spoil the dynamics, it even reduces fuel consumption. The fact that this is indeed the case is also proved by the editorial experience of operating the Oki-Prestige, equipped with an EPS system (for more details, see ZR, 1999, No. 7).

Well, now some omniscient statistics. Diagram 1 shows mechanical manual transmissions in warm colors and "automatic" transmissions in cold colors. As you can see, the share of cars with automatic transmissions is growing and by the year 2000 will be about 17%. At the same time, boxes with a torque converter, which in 1980 were the only option for "automatic machines", are just as steadily losing ground to systems of mechanical boxes with automatic control and variators. According to some forecasts, by 2010 the torque converter will become a relic. Although... "Citroen" has just offered an "automatic" "Ksara" with a planetary gearbox, the control algorithm of which allows you to save fuel compared to the "mechanics" controlled by the average driver! From the same diagram it is clear that in 2000 there will be no four-speed manual gearboxes on new cars - moreover, six-speed units will be more and more common. If we return to today, the share of cars equipped with automatic transmission is shown in diagram 2: it ranges from 4% (small class) to 93% (luxury class).

RATIO OF OUTPUT OF MACHINES WITH DIFFERENT TYPES OF TRANSMISSIONS

SHARE OF CARS WITH AUTOMATIC TRANSMISSION (by class)

Transmission malfunctions

Characteristic signs:

Difficulty shifting gear;

Spontaneous shutdown;

Noise, oil leak;

Simultaneous inclusion of two gears;

Strong knocking or grinding in work.

It is convenient to present the main gearbox malfunctions and ways to eliminate them in the form of a table.

Table 1.

CAUSES OF FAILURE	REMEDIES OR PREVENTION
Difficulty shifting gears
Loose fastening of the forks of the gearshift mechanism	Fasten the forks securely
Bent forks and sticking sliders	Straighten or replace bent forks. Eliminate jamming of sliders
Burrs on the inner surface of the teeth of the synchronizer couplings or the teeth of the gears	Deburr
Incorrect position of the reverse stop on the side cover of the gearbox	Adjust stop position
Simultaneous engagement of two gears	Wear of the locks of the rods or the pusher of the locks
Spontaneous transmission shutdown
Wear of the ends and the working surface of the teeth of the synchronizer couplings and the teeth of the clamps	Replace worn parts
Weakening of the springs of the detents	Replace springs
Incomplete gear engagement	Check stem and fork size. In case of excessive wear, replace
Increased clearance between reverse gear and hub	Replace worn mating parts
Significant wear on the reverse fork	Replace fork assembly with cracker
Spontaneous switching off of the switch, sliders	Unreliable fastening of the gearbox to the clutch housing Unreliable fastening of forks The spring of the sliders is weakened, the edges of the groove are worn out
Noise in the gearbox
Shaft bearing wear	Replace
Wear or chipping of the working surface of the gear teeth	Replace
Lack of oil in the gearbox or low oil level	Check oil level and top up if necessary
Incomplete engagement of the clutch	Carry out adjustment
Weakened nuts for fastening bearing caps and cardan flanges	Tighten nuts
Increased heating of the gearbox	Low oil level in the crankcase or a significant decrease in its viscosity Presence of metal particles or shavings in the oil Distortions in the meshing of gears or jamming of the shafts in the bearings
Oil leak from gearbox
Increased oil level in the gearbox crankcase	Check oil level
Deterioration of the oil seals of the gearbox	Replace damaged oil seals
Wear of the steel-babbit bushings of the extension	change extension assembly with bushings or press and bore new bushings
Breather clogged	breather clear
Loose crankcase and extension plugs, cover bolts	Tighten plugs, tighten bolts
Rupture of lid gaskets or nicks and damage to mating surfaces	Replace damaged gaskets or clean out nicks and grind mating surfaces

Conclusion

In this work, such issues as purpose, device, principle of operation, malfunctions, gearboxes were considered. We found out that, according to the principle of operation, gearboxes can be mechanical and automatic, we examined their differences.

We also found out that not all known motors require the use of such a converter on gears. For example, a steam engine and an electric motor develop a considerable torque, as they say, "from zero" - that is why in trolleybuses (as in steam locomotives) there is neither a third pedal nor a gear lever. ICE for cars - the engine is not the best. And since there is no quick replacement for it yet, it will not be possible to do without a gearbox in the coming years.

In one of the sections, the main malfunctions of the gearbox and how to eliminate them were considered.

This work can be used in the study of the course of cars, both at school and in secondary specialized and higher educational institutions.

Literature

1. Vershigora V.A., Pyatkov K.B., VAZ cars. - M .: "Transport" 1973. - 366 p.

2. Ignatov A.P., Novokshenov K.V., Pyatkov K.B., Album on the design and operation of VAZ-2108, VAZ-2109 cars. – M.: “Third Rome”, 1996. – 80 p.

3. V. M. Kalennikov, N. M. Ilyin, Yu. V. Buralev, Category B car, 4th ed., stereotype. M.: Transport, 1986. - 320 p., ill., tab.

4. Kalissky V.S. et al., Car: A Textbook for a Third Class Driver, Textbook. - M .: Transport 1978. - 448 p., ill.

5. Mikhailovsky E.V., Serebryakov K.B., Tur E.Ya., Vehicle device, Textbook. - M .: "Engineering" 1987. - 350 p.

6. V. L. Rogovtsev, A. G. Puzankov, V. D. Oldfield, Device and operation of vehicles, Textbook. - M .: "Transport" 1996. - 430 p.

) is one of the most common devices that can change the engine torques. This gearbox got its name in connection with the mechanical (manual) way of shifting gears.

A manual gearbox is referred to as a stepped gearbox, since the torques in it change with the help of steps. A step is a pair of interacting gears. Each of these stages provides a rotation function having a certain angular velocity, or in other words a certain gear ratio.

The gear ratio is the ratio of the number of teeth on the main gear to a certain number of teeth on the drive gear. Thus, different stages of a manual transmission can have different gear ratios. The low gear stage has a large gear ratio, and the highest one has the smallest ratio.

Gearbox designs are distinguished depending on the number of steps. The design of the gearbox can be four, five, six speed. Almost all modern cars are equipped with a five-speed gearbox.

Also, from a wide variety of mechanical gearboxes, there are two main types of gearboxes:

• three-shaft gearbox (manufacturers install on a rear-wheel drive car),
• and a two-shaft gearbox (used on passenger cars with front-wheel drive). The principle of operation and design of these boxes also have big differences, so they will be considered separately.

The three-shaft gearbox consists of the following parts:

• primary (leading) shaft;
• drive shaft gears;
• intermediate shaft;
• secondary (driven shaft);
• synchronizer clutches;
• crankcase (gearbox housing).

Functions of the main components of a manual transmission.

drive shaft makes a clutch connection. On the drive shaft there are splines necessary for the clutch disc. Torque is transmitted from the drive shaft through the gear.

intermediate shaft is parallel to the input shaft. On the intermediate shaft there is a block of gears, also located with it in engagement.

driven shaft located next to the drive shaft on the same axis. The technical process is carried out using a mechanical bearing located on the drive shaft. In this case, the gear block located on the driven shaft, as a rule, is not fixed with the shaft, thus, it performs free rotation on it. The block of gears of the driven and intermediate shaft and the gear of the intermediate shaft work in constant engagement.

Synchronizer couplings located between certain gears of the driven shaft. The actions of synchronizers are based on the compatibility of the angular velocities of the driven shaft with the angular velocities of the shaft itself using friction. These couplings can be firmly engaged with the driven shaft, and move along the driven shaft in the longitudinal direction by means of a spline connection. Further, at the ends of the coupling there are gear rims that are connected to the gear rims of the block of certain gears of the driven shaft. Almost all modern gearboxes are equipped with synchronizers installed in all gears.

Switching mechanism (device) three-shaft box is located on the box body. This mechanism consists of a control lever, as well as sliders with forks. The shift mechanism has a locking device that prevents two or three gears from being engaged at the same time. Also, this mechanism can be equipped with a remote control.

gearbox housing contains structural parts and mechanisms, and is also intended for storing oil. The crankcase can be made of magnesium or aluminum alloy.

Scheme of operation of a three-shaft gearbox

When the lever is in the neutral position, no torque is transmitted to the drive wheels. During the movement of the control lever, the required fork moves the synchronizer clutch. This clutch synchronizes the angular speeds of the input shaft and the required gear. After synchronization, the gear teeth of the clutch engage with the gear teeth, thus ensuring that the gear is locked on the driven shaft. The function of the gearbox is to transmit torque with a certain gear ratio to the drive wheels from the engine.

The gearbox also ensures that the car moves in reverse. Change of direction of rotation is carried out with the help of a reverse gear, which is mounted on a separate axle.

The composition of the two-shaft gearbox.

The two-shaft gearbox consists of the following parts:

• drive shaft;
• drive shaft gear block;
• secondary shaft;
• block of gears of a secondary shaft;
• synchronizer clutches;
• main gear;
• differential;
• gear shift mechanism;
• gearbox housing.

Two-shaft gearbox device

The main functions in a two-shaft gearbox are performed by the drive shaft, on which the gear unit is firmly fixed. It is the drive shaft that makes the connection with the clutch.

On the same axis with the drive shaft is the driven shaft with a certain gear block. These gears provide constant engagement with the drive shaft gears and can rotate on the shaft without any obstruction. Also, the drive gear is firmly fixed on the driven shaft. Between these gears are synchronizer clutches.

In order to reduce the linear dimensions and increase the number of steps in the box, two or three driven shafts are sometimes installed instead of one shaft. Each shaft has a firmly fixed final drive gear. This gear provides engagement with the driven gear, and performs the work of three main gears.

The main gear, together with the differential, can transmit torque to the front wheels of the car from the secondary shaft. The function of the differential is to ensure the rotation of the wheels with different angular speeds.

The shift mechanisms of a two-shaft gearbox have remote actions, and, as a rule, are located separately from the gearbox housing itself. The connection between the mechanism and the box is carried out with the help of rods and cables. The cable connection is the simplest, so it is more often used in switching mechanisms.

This mechanism consists of the following parts:

• control lever;
• gear selection cable;
• gear selection lever;
• shift cable;
• central shift rod with the necessary plugs;
• blocking device.

It should be noted that the concept of "gear selection" means the transverse movement of the control lever parallel to the axis of the vehicle. The term "shifting" means the longitudinal travel of the lever (movement or travel to a specific gear).

How a two-shaft manual transmission works.

The scheme of operation of a two-shaft gearbox is similar to a three-shaft gearbox. The main focus is on the gearshift mechanism.

When the required gear is engaged, the movement of the lever is divided into longitudinal and transverse. When the lateral movement of the lever is engaged, the main force will be transferred to the cable for selecting the desired gear. The cable will act on the gear selector control lever. This lever will rotate the central rods around its axis, thus providing a gear selection.

With the longitudinal stroke of the lever, the force will be transmitted to the gear shift cable, and then to the gear shift lever itself. Further, the lever will produce a horizontal movement of the rod with forks. A certain fork on the rod will move the synchronizer sleeve, and block the gear wheel of the driven shaft. Thus, torque from the engine will be transmitted to the drive wheels.

Automatic transmission

An automatic transmission, which has the abbreviated name automatic transmission, or often in everyday life it is also called automatic transmission, is a device that serves to change torque. Automatic transmission is used in automatic transmission of cars. A hydromechanical transmission is also often referred to as an automatic.
The automatic box consists of the following devices:

• Manual Transmission;
• torque converter;
• control system.
• working fluid pump;
• working fluid cooling system.

In automatic transmissions, which are installed on passenger cars with front-wheel drive, a differential and final drive are additionally included in the design.
A torque converter is a device that performs the function of transmitting and changing the engine torque to the gearbox.

The design of the torque converter consists of the following main parts:

• reactor wheel;
• turbine wheel;
• pump wheel;
• freewheel clutch;
• locking clutch;
• converter housing.

A pump wheel is connected to the crankshaft of the engine, when the turbine wheel is connected directly to a manual gearbox. In the space between the turbine and pump wheels there is a reactor wheel, which is a completely fixed part. The torque converter wheels have blades of a specific shape that allow the working fluid to pass freely. It should be noted that channels are provided on the blades for this purpose.

The lock-up clutch performs the function of blocking the transformer, which is necessary in some modes of vehicle operation. As a rule, all elements that are located in the torque converter housing are filled with working fluid. The torque converter works in a closed cycle. The fluid flow is transferred from the pump wheel to the turbine wheel and then to the reactor wheel. The speed flow is enhanced by the design of the blades. The torque is increased by the flow of the working fluid, which is directed to the impeller. Torque converter torque can develop the maximum value at the lowest speed. The crankshaft of the engine increases the speed of rotation with an increase in the angular velocity of the turbine and pump wheels, while the fluid flow changes its direction. The reactor wheel starts to rotate only when the freewheel is activated. In the fluid coupling mode, the torque converter can operate, while only transmitting torque.
The torque converter is blocked when the locking clutch is closed with a further increase in speed. There is a direct transmission of torque from the engine to the gearbox.

As part of an automatic transmission, a manual transmission is used to change the torque, and it can also provide the vehicle to move in reverse. Automatic gearboxes have planetary gearboxes in their design, which are characterized by their compactness and the possibility of autonomous operation. A mechanical gearbox consists of several planetary gearboxes, which are connected in series to work together. Some combination of planetary gearboxes can provide the required number of steps. Modern ones are equipped with six-speed, seven-speed and eight-speed gearboxes.
The planetary gearbox, as a rule, has a planetary gear set, which consists of the following parts:

• ring gear
• sun gear;
• satellites;
• carrier.

Under conditions of blocking of several elements of the planetary gear set, such as the ring gear, sun gear, carrier, rotation is transmitted. Friction brakes and clutch provides the necessary blocking. All elements of the planetary gear are blocked by the clutch, while providing the transmission with torque. Specific elements hold the brake due to the connection with the body of the box. The brake and clutch work with the help of hydraulic cylinders controlled from the distribution module. The overrunning clutch, which is located in the gearbox design, performs the function of holding the carrier from rotating in the opposite direction. The friction brake and clutch are the mechanisms by which gears are shifted in an automatic transmission.

The work of an automatic transmission is to perform some algorithm for turning off and on the brakes and clutch. The gear pump performs the function of transferring the working fluid in the automatic gearbox. The torque converter hub drives the pump. The automatic transmission has a corresponding system that cools the working fluid. The engine cooling system contains a heat exchanger that helps cool the working fluid. Some designs of automatic transmissions have a separate radiator in their design.
Modern automatic transmissions are controlled by an electronic system, which consists of the following elements:

• electronic transmission control unit;
• distribution module;
• input sensors;
• selector lever.

The system uses the following sensors in its work:

• working fluid temperature;
• selector lever position;
• gas pedal position.
• speed at the gearbox input.

The electronic control unit located in the automatic transmission processes the sensor signals and controls the signals going to the camshaft. This system in the course of its work, it uses a program that provides a flexible algorithm for switching to lower and higher gears. The engine control unit interacts with the gearbox control unit.

The automatic transmission system has a distribution module, which consists of solenoid valves that perform the function of controlling the working fluid and shifting gears. The electronic unit controls the operation of the solenoid valves.
The selector lever directly controls the automatic transmission.

The required mode of operation of the automatic transmission is performed by moving the lever to the appropriate position:

• N - neutral mode;
• D - moving forward in automatic gear shifting mode;
• Р – parking mode;
• R - reverse mode;
• S - sport mode.

Some transmissions allow you to quickly accelerate the car using the "Kick-Down" mode by quickly changing gears.

Variable speed drive

A variator is a special type of mechanical continuously variable transmission that is capable of smoothly changing the ratio of rotational speed and torque over the entire range of traction forces and speeds. The main advantage of a variator or continuously variable transmission is the optimal use of the engine by coordinating the load on the car with the operation of the crankshaft, which results in high fuel economy.

The variator has a universal name - Continuously Variable Transmission (transmission with a smoothly changing gear ratio) and an abbreviation - CVT. Given the maximum power of CVTs, they are usually used on passenger cars, however, taking into account new developments in the automotive industry, their scope is constantly expanding.

In a simplified form, the structure of the CVT gearbox is as follows:

• a device responsible for disconnecting the transmission and engine (that is, the neutral position);
• directly variator;
• a mechanism for reversing;
• gearbox control.

To ensure the neutral position of the gearbox, the following devices are designed:

• automatic centrifugal clutch. This type of clutch is implemented in the Transmatic system;
• electronically controlled electromagnetic clutch. An example is the Hyper CVT gearbox on brand cars;
• the so-called "wet" electronically controlled multi-plate clutch. Implemented in the system on cars of the brand and;
• torque converter or torque converter. Available in Lineartronic on cars, Ecotronic on cars and Extroid on cars.

In practice, two types of variator are used in the automotive industry - V-belt and toroid.

Description of the V-belt variator device.

Typically, a V-belt transmission has one or two belt drives in its device, which include two pulleys fastened with a V-belt. A pulley is a connection of two conical disks that move apart or move apart, thereby varying its diameter. The belt itself consists of conical metal plates. Thus, due to the friction that occurs between the pulley and the sidewall of the V-belt, rotation is transmitted. The Lineartronic variator uses a metal chain, which is why they are called wedge-chain.

Features of the V-belt variator

Due to the specifics of the device, the CVT transmission does not have the ability to reverse. To provide reverse gear in such gearboxes, special designs are used. Typically, in such designs, one of the classes of mechanical gearboxes is used - a differential (or planetary) gearbox.

Often, manufacturers equip the CVT transmission with electronic control systems that synchronize the diameter of the pulleys with the engine speed, and also control the clutch and operation of the planetary gearbox.

To control the variator there is a switch lever. These modes correspond to the operating modes of an automatic transmission. Sometimes the variator may have the ability to select gear ratios in one particular mode. This function is designed to eliminate the subjective factor of negative perception by the driver of the constancy of engine speed when accelerating.

Transfer case

The transmission of a car consists of many structural elements, but the most important of them, of course, is the gearbox. This module performs several functions at once:

• changes the engine torque;
• changes the speed and direction of the vehicle;
• serves for long-term separation of the engine and transmission.

There are several types of gearboxes that differ from each other in the principle of operation and in many ways form the type of car transmission:

• stepped boxes;
• stepless boxes;
• combination boxes.

In stepped gearboxes, the torque of the power unit changes in steps, that is, each stage provides rotation with a rigidly set angular velocity or, in other words, has a specific gear ratio. This term refers to the ratio between the number of teeth on the driven and driving gears. Thus, all stages in such a box have different gear ratios, with lower stages having large gear ratios, and higher ones correspondingly smaller.

In turn, speed gearboxes are divided into two types:

• mechanical boxes;
• robotic.

A manual gearbox (in everyday life it is often called simply "mechanics", and in short - manual transmission) is nothing more than a multi-stage spur gearbox, the gear shift in which occurs in manual mode. Such a gearbox can have a different number of steps and, accordingly, a manual gearbox can be four-, five-, six-, seven-speed, and in some cases have more steps.

Compared to other gearboxes, "mechanics" has several advantages. First of all, this is the simplicity of the design, from which the next advantage emerges - reliability. Another important feature is the possibility of manual control in all modes of vehicle movement. Such qualities have made a manual transmission the most common among all types of gearboxes. However, recently there has been an increase in the popularity of automatic transmissions, which will be discussed a little lower.

A robotic gearbox (sometimes also called an automated gearbox, but in everyday life just a “robot”) is a variation of a manual gearbox where the gear shifting and clutch engagement / disengagement functions are automated. Modern "robots" are equipped with a dual clutch, thanks to which the transmission of torque occurs without interrupting the flow of power. In addition, dual-clutch robotic gearboxes significantly reduce fuel consumption and provide higher acceleration dynamics compared to other types of gearboxes. Such qualities have brought "robots" high popularity, which only increases every year. In fact, the “robot” combines the convenience of an automatic transmission with the reliability and economy of a manual transmission. Today, preselective gearboxes can be seen both on budget cars from manufacturers such as, etc., and on premium cars (,). The most famous are the Direct Shift Gearbox (), Sequential M Gearbox (SMG) and Easytronic robotic gearboxes.

As for continuously variable gearboxes, they primarily include a CVT gearbox, which in everyday life is simply called a “CVT”. The main difference between such a box and its stepped counterparts is that the gear ratios in it change smoothly. This effect is achieved due to mechanical or hydraulic torque conversion.

Thanks to this design, cars equipped with CVTs have optimal dynamic characteristics. At the same time, CVT boxes have their limitations. One of the most significant is the limitation of the transmitted torque. In addition, some designs have problems with reliability and overall service life. As a rule, variators are installed on Japanese-made cars (,). As for European companies, here CVTs are most often used by the concern. The most famous CVT designs are Extroid and Multitronik.

In automatic gearboxes (in everyday life they are called "automatic machines", and for short) a combined principle of operation is used. A classic automatic transmission consists of a torque converter, which replaces the mechanical clutch and provides a stepless change in torque, and a manual gearbox, which, as a rule, has the form of a planetary gearbox. Also, a modern automatic gearbox includes such components as a working fluid cooling system, a working fluid supply pump and a box control system. Modern machines have seven (the so-called 7G-Tronic), and in some cases even eight gears.

Automatic boxes have both advantages and disadvantages. The advantages include high reliability and smooth gear shifting. The disadvantages of such boxes usually include low acceleration dynamics and increased (compared to other boxes) fuel consumption. Recently, automatic transmissions have appeared on the market, which provide a function to simulate manual shifting (Steptronic,).

Today, the term "automatic gearbox" means not only a classic gearbox based on a torque converter, but also CVT and robotic gearboxes. All these boxes are electronically controlled.

Another type of automatic transmission is the so-called adaptive transmission, which is able to adapt to the driver's driving style.

Clutch

The clutch of the car is designed for smooth and shock-free transmission of torque from the engine crankshaft to the gearbox. Now, the vast majority of cars are equipped with a single-plate clutch. This car assembly was developed at the end of the 90th century. Previously, the engine was connected to the gearbox via a variable tension leather belt. The car clutch has its own housing and is mounted on the engine and the gearbox is already attached to it.

The most important task of a modern clutch, regardless of its design and device, is the smooth disconnection and connection of the engine to the vehicle transmission. In addition, the clutch protects transmission parts and components from sudden overloads. Automotive clutch can be friction, hydraulic or electromagnetic. On this moment friction clutch is widespread, which in turn is divided into subspecies:

• single disk;
• two-disk;
• multidisk.

It is also worth noting that there is a so-called "wet clutch". In a wet clutch design, the driven and pressure plates operate in some kind of fluid, which is often a special oil. In a dry unit, no liquid is used and the engine and gearbox are connected by dry friction.

Clutch device

As already mentioned, at the moment, almost all passenger cars with a manual transmission use a dry single-plate clutch. Two- and multi-disc units are installed on trucks or powerful sports cars.

Dry single-plate clutch consists of the following main components:

The drive disc, which is also the flywheel on which the starter ring gear is mounted, is rigidly attached to the crankshaft of the car's engine. The flywheel can consist of one or two parts. The drive disc, consisting of two parts, is called dual-mass and allows you to smooth out jerks as much as possible when the clutch is engaged. Most cars have a simple flywheel.

The clutch pressure plate housing, which is often called the basket, is fixed on the flywheel. The pressure plate is directly installed in the basket, which is fixed in the housing with a special diaphragm spring. A driven disk is installed between the drive and pressure disk, which has splines on the hub for connection to the input shaft checkpoint and is firmly clamped between the flywheel and the clutch basket. Driven discs for most passenger cars are equipped with damper springs that help smooth out jerks and vibrations.

The pressure bearing, or as it is more commonly called, the release bearing, is located on the clutch release clutch, directly on the gearbox housing. The release bearing is designed to act on the diaphragm spring of the clutch basket, which in turn moves the pressure plate. The bearing is moved by means of a fork, which is acted upon by a cable or hydraulic clutch.

The dry-type double-disk clutch consists of almost the same structural elements. The differences are only in the presence of a second driven disk and a spacer between them. Such a clutch is able to transfer much more torque from the engine to the transmission and has a fairly long service life. However, as practice has shown, a simple single-disk unit is quite enough for a passenger car.

How an automobile clutch works

Despite the fact that the clutch device seems very complicated, the principle of its operation is quite simple. When you press the pedal, the fork with the release bearing acts on the diaphragm spring, thereby retracting the pressure plate from the flywheel to a certain distance and releasing the driven one - the clutch is disengaged and the engine is disconnected from checkpoint. When the clutch pedal is depressed, the driver has the ability to turn it on, off, or change gear.

When the pedal is released, the fork moves the thrust bearing away from the basket lugs, thereby pressing the pressure plate against the flywheel. Due to the fact that between the flywheel and the basket there is a driven disk with friction linings, there is a smooth transmission of torque. How smoothly the clutch pedal was released, the torque will be transferred so smoothly.

Tiptronic

An advanced gearshift mechanism that makes it possible to control the dynamics of the car in any mode of engine operation is commonly called tiptronic (Tiptronic). Whether you're braking, accelerating, or downshifting, Tiptronic does a great job of controlling dynamics, which sets the Tiptronic transmission apart from a conventional automatic transmission.

For the first time, motorists learned about the Tiptronic trademark in 1989 - it was then that the well-known giant of the German automobile industry registered it. Initially, Tiptronic was developed exclusively for sports cars that needed a convenient gearshift mechanism at high speeds. The system made it possible to change gears faster, due to the smaller trajectory of the control lever.
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Many cars of the concern are equipped with gearboxes with this system. The Tiptronic system is used in robotic gearboxes, S-Tronic and CVT. In cars, an analogue of Tiptronic is implemented - Steptronic (Steptronic). The name of the Tiptronic system has become a household name due to the spread of manual mode on automatic transmissions.

There is a misconception that Tiptronic is a separate element of an automatic transmission that allows you to switch to manual control, but this is not so. Tiptronic is not a design, but a function - the gearbox is designed and assembled already with the Tiptronic system. When choosing a car, many car enthusiasts who are interested in this system believe the seller's promises that Tiptronic can be installed in a classic gearbox later. Know that this is a scam!

To activate the Tiptronic mode, use the automatic transmission selector lever. To make it clearer, pay attention to the selector link - it has a special cutout on which the symbols "+" and "-" are indicated.

There are car models in which there is a special switch on the steering wheel that allows you to switch to manual control of the gearbox. These paddle shifters are often referred to as "paddles" and when you select a specific gear, you will see its image on the information display.

The electronic unit that controls the operation of the gearbox has a special program designed to start the system. Two devices are responsible for activating the Tiptronic function: a switch in the gear selector and a switch under the steering wheel.

The gear selector can be equipped with several switches (1-3). One switch is responsible for turning on and off, the other two allow you to switch to the lower and the highest gear. When the switch is pressed, the signal enters the electronic unit, in which the program algorithm is activated. Gear shifting is carried out through the control unit.

By pressing the petals, the driver activates the mechanism that transfers the automatic transmission to manual mode, without switching the selector lever. If the need to use the paddle shifters has disappeared, and the driver does not use them for a while, the system triggers an algorithm that returns the gearbox to automatic mode. This is very useful for novice motorists: even if the driver forgets to switch the mode, the “smart” algorithm will do everything by itself.

The Tiptronic function implemented in the variator is triggered as a result of the programmed algorithm of fixed gear ratios in the variator.

Multitronic

The multitronic CVT is the best continuously variable transmission ever made in the world. Thanks to the use of this device, not only does driving comfort increase, but an incredibly high fuel efficiency of the engine is achieved, and dynamic qualities are significantly improved. vehicle. Multitronic is installed, as a rule, on Audi premium cars.
This gearbox consists of eight devices that provide a truly perfect car ride. Wet clutch here is a combination of multi-plate clutch-frictions forward and reverse. In order to avoid overheating of the clutches, the gearbox provides for their forced cooling by means of a separate flow of the working fluid. The clutches installed in the multitronic compare favorably with the torque converters used in conventional automatic transmissions. Compared to the latter, the clutches are more compact, light and easy to handle.
To ensure comfortable driving when driving in reverse, a planetary mechanism is used. When the machine is moving forward, the forward clutch completely locks the gearbox. When moving in the opposite direction, the reverse clutch begins to act, blocking the ring gear, which causes the planetary gear to move in the other direction. At the same time, it will not work to develop an excessively high speed: when reversing, it is limited by electronics.

The multitronic also uses a variator, which is necessary for a smooth change in gear ratio. This device consists of driving and driven pulleys, each of which includes two discs with a conical surface. The drive drive is connected through an intermediate gear to the crankshaft, while the torque from the driven drive goes to the main gear. In addition, each pulley has one movable disk, which allows you to change the pulley diameter during operation.

For the first time, a technical solution was introduced in multitronics, which made it possible to significantly increase the number of gear ratios. This was achieved through the use of a metal chain that operates as quietly as possible. Noise reduction was achieved by using links with different sizes.
The drive of both pulleys includes clamping and adjusting hydraulic cylinders. If the first is necessary in order to press the chain against the discs, then the adjusting hydraulic cylinder serves to adjust the gear ratio.
Multitronic uses a unique transmission control system consisting of a hydraulic unit, input sensors and an electronic control unit.
The first of the listed elements is responsible for the operation of the friction clutches and their cooling with the help of an ejection pump, for the functioning of the pressure and control cylinders, and for regulating the pressure of the working fluid.
The circulation of the working fluid is provided by a gear-type oil pump. It is cooled by means of an oil-water heat exchanger, which is integral part engine cooling systems.

All input sensors are divided into the following devices:

• liquid pressure control sensor
• temperature sensor
• speed sensors at the output and input of the gearbox
• selector lever position sensor

The choice of the optimal gear ratio, depending on the wishes of the driver and road conditions, is made by the electronic control unit. Focusing on the signals from the sensors, the control unit determines the optimal pressure of the working fluid at a particular point in time and provides this pressure by acting on the solenoid valves.
The control modes of the multitronic, which has a mechanical connection with the selector lever, coincide with the automatic transmission modes. In addition, for the possibility of rapid acceleration of the car in this box there is a Kick-Down mode. The Tiptronic function is also implemented here, especially for those who are used to using a manual transmission.

Robotic DSG gearbox

Currently, AG has launched the production of a robotic DSG, known as the Direct Shift Gearbox, which is installed on almost all modern models of mass-produced passenger cars, and provides fast gear changes without interrupting engine power. It is these qualities of the box that attract the attention of motorists to a greater extent.

When using a robotic gearbox, a continuous supply of torque directly from the engine to the wheels is achieved through two clutches and their corresponding gear rows. The designs of the new DSG robotic box have six and seven steps.

The 7th gearbox has a torque of about 250 Nm and is installed on cars of class B and C, as well as some models of class D. The gearbox, which has six steps, generates a torque of almost 350 Nm. It is usually installed on passenger cars with a more powerful engine.

To the gearbox DSG The following devices have been included:

• - main gear
• - two gears
• - 2nd clutch
• - differentials
• - box control system
• - crankcase (body)

Diagram of the DSG box

In the new box, the torque is transmitted to two rows of gears by a clutch that includes a drive disc. Its operation is provided by a flywheel connected to the disc through the input hub, which, in turn, interacts with two friction multi-plate clutches connected to the gear rows using the same main hub.
The dual clutch of the six speed gearbox is a "wet" type, as it is filled with oil, while the seven speed has a conventional clutch. This design of the DSG allows oil consumption of just 1.7 liters, which significantly reduces energy costs and increases engine efficiency. An important role is also played by the electric oil pump, which replaced the hydraulic one.
The first row of gear mechanisms is used when reversing and has an odd number of gears. An even number of gearbox gears is responsible for the movement of the car in forward gear. Both rows have the form of primary and secondary shafts, equipped with gear blocks.
For gear shifting and clutch control, special systems have been developed that are equipped with:

• - input sensors
• - electronic control unit
• - executive mechanisms
• - electrohydraulic control unit.

The entire system is combined into a single module, known as Mechatronic, located in the crankcase. The input sensors control the speed at the input and output of the DSG robotic box, oil temperature and pressure, and the position of the forks when the gears are engaged. Electronic unit control is carried out by the gearbox control algorithm based on the sensor signals.
The operation of the hydraulic control circuits of the robotic box is monitored by an electro-hydraulic control unit, which has the following devices:

• - multiplexer
• - solenoid valves
• - distribution spools
• - pressure control valves

The multiplexer built into the gearbox controls the operation of the shift cylinders using solenoid valves. Pressure control valves and solenoid valves are the main mechanisms in the Direct Shift Gearbox control system. Solenoid valves shift gears, and spool valves are activated by means of the selector lever.
The operation of the new DSG is carried out by sequentially switching on the gears of all rows, and during the operation of one of the gears, the machine selects the second one and prepares it for switching on, which is carried out by the synchronizer and clutch. This operation is electronically controlled with a hydraulic booster.
All the innovations used in the DSG allow the car to pick up speed quickly, which is successfully used in sports cars and does not allow you to lose precious seconds. When it was created, the goal was to reduce the loss of torque, which creates heavy loads on the transmission and clutch. Motorists noted that the new model of the gearbox is softer, works well on cars with less torque and allows you to significantly save fuel.

The gearbox serves to change the traction force on the wheels of the car depending on the resistance to movement and allows the car to move in reverse. The gearbox allows, in addition, when the gears are turned off, to disconnect the driving wheels of the car from the engine, thereby ensuring the possibility of starting the engine and idling it.

The gearbox is a mechanism consisting of a set of gears that can be engaged in various combinations.

Each combination of gear box engagement is called a stage or gear. The number of steps (gears) in the gearbox depends on the design of the car and is usually from three to five (not counting the reverse gear). In accordance with this, the gearboxes are called three-speed, four-speed and five-speed.

Rice. Gearbox of GAZ-69 and GAZ-69A cars: 1 - oil seal; 2 - rear crankcase cover; 3 - ball bearing of the secondary shaft; 4 - gearbox housing; 5 - oil flinger ring; 6 - secondary shaft; 7 - fork for switching the gear (carriage) of the first gear and reverse gear; 8 - gear (carriage) of first gear and reverse; 9 - gear lever; 10 - upper crankcase cover; 11 - second gear gear; 12 - second gear bushing; 13 - ring gear of the second gear; 14 - carriage of the second and third gears; 15 - carriage fork of the second and third gears; 16 - toothed hub; 17 - shims; 18 - thrust ring; 19 - gear ring of the third gear; 20 - third gear; 21 - roller bearing; 22 - input shaft ball bearing; 23 - input shaft; 24 - front crankcase cover; 25 - oil flinger ring; 26 - intermediate shaft roller bearing; 27, 29, 32 and - gears of the intermediate shaft; 28 - crankcase drain plug; 30 - the axis of the intermediate shaft; 31 - intermediate shaft; 34 - intermediate reverse gear

The engagement of various pairs of gears is carried out with the help of carriages (gears) moving along the shafts of the box. Depending on the number of movable carriages, the boxes are divided into two-way (two carriages) and three-way (three carriages).

The principle of operation of automobile gearboxes

The principle of operation of automobile gearboxes regardless of their design and the number of gears is the same. Consider their design and operation using the example of a three-stage two-way gearbox of GAZ-69A and GAZ-69 cars.

The primary (drive) shaft 23 is made integral with the gear 20 of the third gear and with the ring gear 19. The input shaft is connected to the crankshaft of the engine through the clutch.

The secondary (driven) shaft 6 is, as it were, a continuation of the primary shaft and is located with it on the same axis. The output shaft shank sits in a roller bearing 21 mounted at the end of the input shaft. The secondary shaft can therefore rotate independently of the primary.

Two gears 8 and 11 and a toothed hub 16 are installed on the secondary shaft. Gear 8 (carriage) sits on the shaft on splines and can move along its axis. Gear 11 has a ring gear 13. It is mounted on the secondary shaft on a bronze bushing 12, therefore it rotates freely on the shaft. A carriage 14 of the second and third gears is installed on the hub, which moves along the hub.

The intermediate shaft 31 is a block of gears 27, 29, 32 and 33, freely rotating on the axis 30.

The reverse intermediate gear 34 is mounted on an axle on a bronze bushing and rotates freely on the axle.

The primary and secondary shafts are installed in the sockets of the crankcase of the box on ball bearings 22 and 3. The axis 30 of the intermediate shaft is fixed in the crankcase seats motionlessly, while the intermediate shaft 31 rotates on the axis on roller bearings 26. The axis of the intermediate reverse gear is motionlessly fixed in special sockets of the crankcase.

The gear 20 of the input shaft with the gear 27 of the intermediate shaft, as well as the gear 33 with the intermediate gear 34 reverse are in constant engagement. In constant engagement are also the gear 29 of the intermediate shaft and the gear 11 of the secondary shaft. The carriages 8 and 14 can move along the secondary shaft and engage: the carriage 14 with its internal teeth with the ring gear 19 of the gear 20 of the input shaft or with the ring gear 13 of the gear 11; carriage 8 with gear 32 or 34.

With the position of the carriages shown in the figure, the torque from the engine will be transmitted from the input shaft through gears 20 and 27 to the intermediate shaft gear set.

However, torque will not be transmitted to the secondary shaft, since with the depicted position of carriages 8 and 14, the secondary shaft is disconnected from both the primary and intermediate shafts. This position of the carriages is called neutral. The carriages are placed in the neutral position when the engine is started and the engine is idling (on the spot or when the vehicle is coasting).

Rice. Scheme of switching gears and transmitting torque in a three-speed gearbox of GAZ-69 and GAZ-69A cars: a - first gear; b - second gear; c - third gear; g - reverse; I - the position of the lever when the first gear is engaged; II - the position of the lever when the second gear is engaged; III - the position of the lever when the third gear is engaged; IV - lever position when reversing

To set the car in motion, it is necessary to transmit torque to the secondary shaft. To do this, the carriage 8 or 14 should be engaged with one of the gears of the intermediate shaft, which would ensure the highest gear ratio, and therefore the highest torque on the output shaft. Let's move the carriage 8 to the right and engage it with the gear 32 of the intermediate shaft, as shown in Fig. A. This position of the carriages corresponds to the first gear.

To turn on the second gear, it is necessary to disengage the carriage 8 from the gear 32, and then, moving (in Fig. b to the left) the carriage 14, enter the latter into engagement with the ring gear 13 of the gear 11, which is constantly engaged with the gear 29 of the intermediate shaft.

You need to switch from second gear to third in the same sequence as from first gear to second. In this case, the carriage 14 is disengaged from the ring gear 13 of the gear 11 and is engaged with the ring gear 19 of the gear 20 of the input shaft (Fig. C), the primary and secondary shafts begin to rotate as one.

To move in reverse, both carriages should be moved to the neutral position, and then the carriage 8 should be moved to the left and engaged with the intermediate gear 34 in reverse. In this case, the direction of rotation of the secondary shaft will change to the opposite.

For easy and shock-free gear shifting, it is necessary that the circumferential speeds of the gears engaged are the same. The peripheral speed of the gear depends on the number of revolutions of the shaft on which it sits, and on its diameter: the larger the diameter of the gear and the number of revolutions of the shaft, the greater its circumferential speed. To facilitate shockless gear shifting and reduce gear tooth wear in gearboxes, in particular in the gearbox of GAZ-69A and GAZ-69 cars, a special device is provided - a synchronizer for the second and third gears.

The synchronizer equalizes the circumferential speeds of rotation of the gears before engaging them. It is arranged as follows. At the end of the secondary shaft 1, the toothed hub 6 of the synchronizer is mounted on splines and secured with a retaining ring 14. On the outer teeth of the hub, a carriage 10 of the second and third gears is installed, covered by a fork 8. Sliders 11 of the blocking device are installed in three grooves of the hub, connected by means of balls 9 of the clamps to the carriage 10. On both sides of the hub there are blocking bronze rings 4. Each blocking ring has ring gear and grooves 47 for sliders; the inner surface of the ring is made cone-shaped.

The synchronizer is located between the gear rim 13 of the gear 15 of the input shaft and the gear rim 3 of the gear 2 of the second gear. The bases of the gear rims of gears 2 and 15 have conical surfaces.

Rice. The device and scheme of operation of the synchronizer of the gearbox: a - the position of the parts of the synchronizer when equalizing peripheral speeds; b - the position of the synchronizer parts with the gear engaged; in - details of the synchronizer; 1 - secondary shaft of the gearbox; 2 - second gear gear; 3 - ring gear of the second gear; 4 - blocking ring; 5 - thrust washer; 6 - gear hub; 7 - spring; 8 - carriage fork of the second and third gears; 9 - retainer ball; 10 - carriage of the second and third gears; 11 - slider; 12 - shims; 13 - gear rim of the input shaft gear; 14 - locking ring of the toothed hub; 15 - gear of the input shaft; 16 - input shaft; 17 - groove for the hub slider

When the second or third gear is turned on, the synchronizer carriage 10 moves along with the sliders 11 along the hub 6 with the help of a switching device. The sliders included in the grooves 17 of the blocking rings 4 press the ring against the conical surface of the corresponding gear ring gear. Due to the friction that occurs between the contacting tapered surfaces, the blocking ring is slightly shifted in the direction of rotation of the ring gear until the grooves stop against the side surfaces of the sliders. At the same time, the beveled surface of the ends of the teeth of the carriage 10, resting against the beveled surface of the ends of the teeth of the ring 4, does not allow the teeth to engage, as a result of which the ring 4 is strongly pressed against the conical surface of the ring gear. As a result of strong friction of the cones, the speeds of rotation of the shafts are equalized, the carriage 10 moves further, squeezing out the balls 9 of the retainers, and with its teeth enters the gaps of the teeth of the crown 13, silently turning on the corresponding gear.

The gearbox is controlled by lever 6; swinging in the ball joint of the gearbox housing cover.

In the same cover, two sliders 3 and 12 are installed in the sockets, which can move along their axes, while sliding in the sockets of the box cover. Each of these sliders is connected to a fork: slider 12 of the first gear and reverse carriage with fork 11, slider 3 of the carriage of second and third gears with fork 10.

The ends of the forks fit in the annular grooves in the carriages and do not prevent the carriages from rotating freely together with the secondary shaft. With the longitudinal movement of the forks, the carriages move along the shaft and thereby engage the corresponding gears. By moving the lever, and consequently, the forks with the carriages, the gears are changed in the box.

To prevent arbitrary disengagement of gears and the simultaneous inclusion of several gears, special devices are provided in the gear shift mechanism - clamps (stoppers) - to fix the lever in a certain position and locks that do not allow simultaneous inclusion of several gears.

In three-speed gearboxes with two sliders, the lock also acts as a lock.

Rice. The gearshift mechanism of the gearbox of GAZ-60 and GAZ-69A cars: 1 - latch spring; 2 - side cover of the gearbox housing; 3 - slider of the carriage fork of the second and third gears; 4 - squeezing bracket; 5 - spring of the squeezing bracket; 6 - gear lever; 7 - spring of the gear lever; 8 - cap; 9 - ball bearing; 10 - carriage fork of the second and third gears; 11 - carriage fork of first gear and reverse gear; 12 - slider of the carriage fork of the first gear and reverse gear; 13 - lock crackers

The latch consists of two hollow crackers 13 sliding in a special slot made in the gearbox cover. Under the action of spring 1, crackers jump into the recesses located in the corresponding places of the sliders. Crackers securely hold the sliders from spontaneous movement, and also prevent the possibility of simultaneous movement of both sliders.

It is impossible to move both sliders at once and turn on, thus, two gears at the same time for the following reason. As soon as one of the sliders moves so much that the cracker comes out of the recesses, both crackers will be pushed close to each other. The total length of the shifted crackers is selected so that the second cracker can no longer get out of the recess of the slider adjoining it, and thus the slider is securely locked.

To prevent accidental engagement of reverse gear, in the cover of the gearbox, slightly below the ball joint, there is a squeezing bracket 4 with a spring 5 that presses the end of lever 6. Therefore, to engage reverse gear (and first gear), an increased force must be applied to the lever so that move the bracket to the side.

It is poured into the gearbox housing up to the level of the control plug hole.

Any car with an internal combustion engine has a gearbox in its design. There are many varieties of this unit, but the most common type is a manual transmission (manual transmission). It is equipped with both domestic and foreign cars.

The gearbox is used to change the ratio of rotational speed from the engine to the wheels. The method of switching between the steps (gears) of this gearbox is manual (mechanical), which gave the name to the entire assembly. The driver independently decides which of the fixed gear ratio values ​​​​(gearing gears) should be included at the current moment.

Modern manual transmission

In addition, the manual transmission allows you to switch to reverse mode, in which the car moves in the opposite direction. There is also a neutral mode, when there is no transmission of rotation from the motor to the wheels.

Principle of operation and device

The gearbox is a multi-stage closed gearbox. Helical gears have the ability to alternately mesh and change the speed between the input shaft and the output. This is the principle of the gearbox.

Clutch

The manual box works in tandem with the clutch. This assembly allows you to temporarily disconnect the motor from the transmission. Such an operation makes it possible to painlessly switch gears (stages) without turning off the engine speed.

The clutch block is necessary, as significant torque passes through the manual transmission.

Gears and shafts

In any gearbox of a traditional design, they are located parallel to the axis of the shafts on which the gears are based. The common body is called the crankcase. The most popular are three-shaft and two-shaft companies.

In three-shaft there are three shafts:

• the first is the leader;
• the second is intermediate;
• the third is the follower.

The first shaft is connected to the clutch, splines are cut on its surface, along which the clutch disc moves. From this axis, rotation is transmitted to an intermediate axle rigidly connected to the input shaft gear.

The driven shaft of the manual transmission has a specific location. It is coaxial with the drive and is connected to it through a bearing located inside the first shaft. This ensures their independent rotation. Blocks of gears with a driven axle do not have a rigid fixation with it, and the gears are delimited by special synchronizer clutches. The latter just sit rigidly on the driven shaft, but are able to move along the axis along the splines.

The ends of the couplings are equipped with gear rims that can be connected to the same rims located on the ends of the driven shaft gears. The modern gearbox design assumes the presence of such synchronizers in all forward gears.

When the neutral mode is turned on, the gears rotate freely, and all synchronizer clutches are in the open position. When the driver squeezes the clutch and switches the lever to one of the steps, then at this time the fork in the gearbox moves the clutch into engagement with its pair at the end of the gear. So the gear is rigidly fixed to the shaft and does not scroll on it, but ensures the transmission of rotation and force.

Most manual transmissions use helical gears, which can withstand more force than spur gears, and they are also less noisy. They are made of high-alloy steel, after which hardening is carried out at HDTV and normalized to relieve stress. This ensures maximum service life.

For a two-shaft box, a connection of the drive shaft with the clutch block is also provided. Unlike a three-axle design, a block of gears is located on the drive axle, and not one. There is no intermediate shaft, and the driven shaft runs parallel to the leading one. The gears on both axles rotate freely and are always engaged.

The driven shaft is equipped with a rigidly fixed final drive gear. Synchronization clutches are located between the remaining gears. Such a scheme of a mechanical gearbox in terms of the operation of synchronizers is similar to a three-shaft scheme. The difference is that there is no direct transmission, and that each stage has only one pair of connected gears, rather than two pairs.

The two-shaft device of a manual transmission has a greater efficiency than the three-shaft, however, it has a limitation in increasing the gear ratio. Due to this feature, the design is used only in passenger cars.

Synchronizers

All modern mechanical gearboxes are equipped with synchronizers. Without them, the machines had to do a double squeeze so that the circumferential speeds of the gears were equal, and it was possible to switch gears. Also, synchronizers are not installed on gearboxes with a large number of gears, sometimes up to 18 steps, typical for special equipment, since this is technically impossible. For quick gear shifting, sports cars may not have synchronizers in the manual transmission.

Synchronizer manual transmission

The cars used by most drivers are equipped with synchronizers because the car's gearbox is less friendly without them. These elements ensure quiet operation and alignment of gear speeds.

The inner diameter of the hub has splined grooves, due to which movement is carried out along the axis of the secondary shaft. At the same time, such rigidity ensures the transmission of large forces.

The synchronizer works in this way. When the driver turns on the gear, the clutch is fed towards the desired gear. During movement, the force is transferred to one of the locking rings of the clutch. Due to the different speeds between the gear and the clutch, the conical surfaces of the teeth interact with the help of friction. She turns the blocking ring to the stop.

The work of synchronizers

The teeth of the latter are mounted against the teeth of the coupling, so subsequent displacement of the coupling becomes impossible. The clutch engages without resistance with a small crown on the gear. The gear due to such a connection is rigidly blocked with the clutch. This process takes place in a fraction of a second. One synchronizer usually provides two gears.

Gear change process

The corresponding mechanism is responsible for the switching procedure. For vehicles with rear-wheel drive, the lever is mounted directly on the manual transmission housing. The whole mechanism is hidden inside the body of the unit, and the shift knob directly controls it. This arrangement has its advantages and disadvantages.

• simple design solution;
• ensuring clarity of switching;
• more durable design for operation.

• there is no possibility to use a design with a rear motor;
• not used on front wheel drive vehicles.

Machines with a front drive axle are equipped with a gear lever in the following places:

• floor between the driver and front passenger seat;
• on the steering column;
• near the instrument panel.

Remote control of the box for front-wheel drive cars is carried out using rods or backstage. This design also has its own characteristics.

• comfortable more independent arrangement of the lever for gear shifting;
• vibration from the box is not transmitted to the manual transmission lever;
• provides more freedom for design and engineering layout.

• less durability;
• backlash may appear over time;
• periodic qualified adjustment of the rods is required;
• clarity is less accurate, as opposed to being located directly on the case.

Although there are various drives for the gear on / off mechanism, the mechanism itself in most gearboxes has a similar design. It is based on movable rods, which are located in the housing cover, as well as forks rigidly fixed on the rods.

Gearshift mechanism Lada Granta

The forks in a semicircle enter the groove of the synchronizer clutch. Additionally, in the manual transmission there are devices that will save the mechanism from non-engagement or from unauthorized disengagement of the gears, as well as from the simultaneous activation of two stages.

Advantages and disadvantages of manual transmissions

All types of mechanisms have their own advantages and disadvantages. Consider them at the manual transmission.

Advantages:

• the design has the lowest cost when compared with analogues;
• unlike hydromechanical, it has less weight and higher efficiency;
• does not need special cooling conditions compared to automatic transmissions;
• an average car with a manual transmission has more economical parameters and acceleration dynamics, unlike an average car with an automatic transmission;
• simplicity and engineering sophistication of the design;
• high degree of reliability and long service life;
• does not need specific maintenance and scarce consumables or repair materials;
• the driver has a wider range of driving techniques in extreme conditions of icy conditions, off-road, etc.;
• the car is easily started by pushing and can be towed at any speed and for any distance;
• there is a technical possibility of complete separation of the motor and transmission, in contrast to the hydromechanical automatic transmission.

Flaws:

• for gear shifting, a complete separation of the power plant and transmission is used, which affects the operation time;
• specific driving skills are required to ensure smooth gear shifting;
• inability to smoothly shift the gear ratio, since the number of steps is usually limited to a number from 4 to 7;
• low resource of the clutch assembly;
• the driver, when driving a car with a manual transmission for a long time, has more fatigue than when driving on an “automatic” transmission.

In most countries with a higher income of the population, the number of produced cars with manual transmission has been reduced to almost 10-15%.