Friction clutches: principle of operation, drawing. Frictions (friction discs)

Main clutch(see fig. 62). The main friction clutch is two-disc, dry friction, designed for short-term disconnection of the engine from the gearbox, for smooth starting the machine from its place and protecting the units power transmission and the engine from overloads with a sharp change in loads on the drive wheels.

The main clutch is located in a common crankcase with a gearbox and is separated from it by an internal partition.

The main clutch consists of driving and driven parts and a shutdown mechanism.

Leading parts are rigidly connected with crankshaft engine. These include the support disk 19, the drive drum 17 with internal teeth and the casing 14, which is attached together with the support disk with bolts 18 to the flywheel.

engine. The teeth of the drive disk 20 and pressure disk 22 engage with the teeth of the drive drum. Nine cups 24 are fixed in the casing 14, in which two concentric helical pressure springs 16 are placed.

The driven parts include two steel driven disks 21 with internal teeth with friction disks attached to them on both sides, made of a special friction mass KF-2 GOST 1786-57, and a driven drum 23, on the teeth of which the driven disks sit.

The driven drum is connected by splines with a hollow shaft 7, made integral with the drive bevel gear of the gearbox.

The shutdown mechanism consists of a booster 9 with a piston 10, a housing 13 with angular contact bearing 12, three retracting springs 5, three two-arm levers 1, fixed on the axles in the casing 14.

Rice. 62. Main clutch:

1 - two-arm lever; 2 - fork; 3 - adjusting nut; 4 - locking bar; 5 - withdrawal spring; 6 - plug holes for lubrication; 7 - transmission drive shaft; 8 - self-clamping cuff; 9 - booster main clutch; 10 - booster piston; 11 - seal body; 12 - bearing; 13 - bearing housing of the shutdown mechanism; 14 - casing of the main clutch; 15 - gearbox housing; 16 - pressure springs; 17 - driving drum; 18 - bolt; 19 - support disk; 20 - leading friction disk; 21 - driven friction disk; 22 - pressure plate; 23 - driven drum; 24 - a glass of springs; 25 - drive roller oil pump; 26 - piston stroke limiter ring; 27 and 29 - rubber rings; 28 - casing; 30 - a bolt of fastening of a lock lath; 31 - bearing housing cover; a is a cavity.

Appointment, general device planetary slewing mechanisms with stopping brakes, gearboxes, parking brake and onboard transmission BMP-2

Purpose of planetary rotation mechanisms- transmission of torque from the gearbox to the final drives, turning and a short-term increase in traction on the drive wheels without gear shifting (slow gear engagement).

Swing mechanisms- planetary, two-stage. The machine is equipped with two planetary turning mechanisms with stopping brakes of the same design. They are connected to the gearbox on both sides of the crankcase.

Purpose of stopping brakes- stopping, braking the car, exercising sharp turn and keeping the machine at a standstill.

Stop brakes- tape, floating.

The device of planetary rotation mechanisms. Each slewing mechanism consists of a single-row planetary gearbox, a locking clutch and a PMP disc brake.

Planetary reductor consists of an epicyclic gear 19 (see Fig. 62) mounted on the cargo shaft of the gearbox, carrier 34 with three satellites 8 on the axles, sun gear 35, which is rigidly connected to the outer drum 21 of the blocking clutch, as well as fastening parts of the planetary gearbox.

Locking clutch connects (locks) the epicyclic gear 19 with the sun gear 35, providing a direct transmission of torque from the cargo shaft of the gearbox to the final drive, and disconnects the sun and epicyclic gears to obtain a slow gear.

The locking clutch consists of four drive discs 18 with ceramic-metal friction surfaces, three driven discs 17, an outer drum 21, a pressure disc 7, pressure springs 20, a support disc and an inner drum (epicyclic gear 19). The locking clutch is permanently closed.

Brake PMP serves to stop the sun gear 35 to obtain a slow gear in the planetary rotation mechanism. It consists of a disc brake 24 (three steel discs and four discs with ceramic-metal friction surfaces), an outer drum 23, an inner drum that is integral with the outer drum 21 of the blocking clutch, a pressure plate 27, a support disc 5, springs 25, a piston 28 The PMP brake is permanently open.

Stop brake consists of a brake band made up of two halves, to inner surface of which reinforced friction linings are riveted, release springs that are attached to the brackets and to the brake band, two hydraulic cylinders, springs, adjusting nut, lever, stop and brake drum.

Drive control device for planetary rotation mechanisms. The steering drive of the machine is designed to turn the machine. It consists of a steering wheel located in the steering column, a roller, levers, rods, spools and a left and right turn.

A movable stop is rigidly fixed on the roller, and a bar is welded to the steering column tube, on which there are adjustable stops. The movable stop and limiters exclude the possibility of the spools hitting the body of the spool box when the steering wheel is deflected to the stop.

Two pins are pressed onto the roller, which fit into the grooves on the lever hubs. When the steering wheel is deflected, one pin rests against the edge of the groove and moves the lever, and the second pin at this time moves along the groove of the other lever, which is held by a spring and does not rotate.

The slow gear drive is designed to simultaneously turn off the locking clutches and turn on the brakes of both PMPs during straight-line movement, which provides an increase in torque by 1.44 times and a corresponding decrease in speed in each gear.

The drive for controlling the planetary mechanisms can be in the initial position, in the position of the included slow gear and in the positions corresponding to the rotation.

Operation of planetary rotation mechanisms and control drive. In the starting position the steering wheel is in a horizontal position, the slow gear lever is in top position, the levers of the spool box are pulled to the rear extreme position by springs, the locking clutches are on, and the PMP brakes are off. At the same time, the sun gears of the PMP are interlocked with the epicycles, they are one whole.

When the transmission is on the carriers of the PMP rotate at the same speed as the cargo shaft of the gearbox. The car moves at a speed determined by the gear included in the gearbox.

When the lever is moved down through the roller, the rods and levers move the spools of the spool box and open the channels for supplying oil to the boosters of the locking clutches and brakes of the PMP. Under oil pressure, the locking clutches are turned off, and the PMP brakes are turned on.

When the gear is engaged, the rotation from the cargo shaft of the gearbox is transmitted through satellites, which, rolling around the sun gears, rotate the planet carrier. A car moves in a straight line at a speed of 1.44 times less speed, determined by the transmission included in the CP.

Turning the machine is done by turning the steering wheel to the left or right. The change in the turning radius of the machine occurs smoothly, the greater the angle of rotation of the steering wheel from the initial position, the smaller the radius will be the turning of the machine.

When the steering wheel is turned at a small angle to the left, a lever is turned through the roller, which, through the rod, turns the lever of the spool box.

Rice. 63. Planetary rotation mechanism:

1 - outer sealing cuff; 2 - bronze bushing (bearing); 3 - support pin; 4, 11 - gaskets; 5 - platter; 6 - booster support; 7 - pressure plate of the locking clutch; 8 - satellite; 3 - needle bearing; 10 - satellite axis; 12 - carrier needle bearing; 13 - cargo shaft of the gearbox; 14 - crankcase mounting stud; 15 - nut: 16 - spacer; 17 - driven disk of the blocking clutch; 18 - drive disk; 19 - epicyclic gear of the planetary gear set (inner drum); 20 - spring of the blocking clutch; 21 - outer drum; 22 - bolts for fastening the drum to the spacer; 23 - drum; 24- disc brake; 25 - brake release spring; 26- brake drum; 27 - brake pressure disc; 28 - piston; 29- O-rings; 30 - ball bearing; 31 - cuff; 32 - gear clutch; 33 - cork drove; 34 - planet carrier; 35 - sun gear; 36 - internal sealing collar of the piston.

When the lever is turned, the spool moves and opens the oil supply channel to the booster of the blocking clutch of the left PMP.

Oil under the influence of gradually increasing pressure due to the bevel on the spool begins to move the pressure plate. The compression force of the disks decreases, the disks slip. As the compression force decreases, the amount of torque transmitted to the driven disks of the locking clutch of the left PMP, and, consequently, to the left drive wheel, decreases, the left track begins to lag behind and the machine with a large radius turns to the left.

When turning the steering wheel to a greater angle the spool, moving, opens the channel for supplying oil to the brake booster of the left PMP, while the channel for supplying oil to the booster of the blocking clutch remains open. Piston 28, together with the pressure plate, begins to move and compresses the friction discs of the PMP brake.

The gap between the friction discs gradually decreases, the discs begin to slip, the amount of torque transmitted to the planetary carrier increases, and the left track will lag behind the right track more and more, the turning radius of the machine will gradually decrease.

With fully applied brake and lockup clutch rotation of the left PMP is transmitted through the satellites, which, rolling around the braked sun gear, rotate the carrier of the left PMP at a speed 1.44 times less than the speed of rotation of the carrier of the right PMP, the machine will turn with a fixed turning radius.

When turning the steering wheel all the way the spool, moving, first opens the oil drain channel from the PMP brake booster, while the oil drains into the gearbox housing, and the brake piston returns to initial position, freeing friction discs. The lock-up clutch remains disengaged. Then the spool opens the oil supply channel to the hydraulic cylinder of the left stop brake.

Pressurized oil enters the cavity, the piston moves and presses the parking brake lever roller with its rod. The lever rotates around the axis and tightens the brake band. The left track brakes, the machine turns in place to the left.

When the steering wheel is in its original position the spool moves to its original position and opens the drain channel from the blocking clutch booster, while the oil is drained into the gearbox housing, and the blocking clutch is activated under the action of the springs. When the gear is engaged, the machine will move at a speed determined by the gear included in the gearbox.

Stop brake control drive. The stop brake control drive consists of a pedal located on the pedal bridge and held in its original position by a spring, a lever on the pedal bridge, levers and on the transition bridge, a rod, a stopping brake spool located in the spool box, hydraulic cylinders. Hydraulic cylinders are identical in design and consist of a body, piston, rod and fittings.

Operation of the stopping brakes and control drive. To brake the machine with stopping brakes, it is necessary to press the pedal, while the pipe rigidly connected to the pedal and the lever turn.

The lever, turning, moves the stop brake spool through the rod. The spool, moving, opens the channel for supplying oil to the hydraulic cylinders. Oil under pressure enters the cavity of the hydraulic cylinders, moving the pistons and tightening brake bands. The pressure in the hydraulic cylinders increases smoothly depending on the degree of pressing the pedal due to the presence of a tracking device.

With absence required pressure oils in the hydraulic control system, the stop brake bands are tightened with the help of compressed air coming from the pneumatic system of the machine: when the stop brake pedal is pressed, the bridge lever acts on the limit switch and closes its contact. The voltage through the pressure switch, the contact of which closes automatically when the pressure in the hydraulic control system drops below 0.25 MPa (2.6 kgf / cm2), and the limit switch is supplied to the electro-pneumatic valve of the pneumatic system, which opens, and compressed air through pipelines through the fitting enters the cavity of the hydraulic cylinder. The piston moves and presses the parking brake lever roller, the parking brake bands are tightened.

A multi-plate friction clutch is a type of torque transmission mechanism, consisting of a package of friction and steel discs. The moment is transmitted due to the friction force that occurs when the discs are compressed. Multi-plate clutches are widely used in various nodes car transmissions. Consider the device, the principle of operation, as well as the pros and cons of these mechanisms.

The principle of operation of the clutch

General form multi-plate friction clutch

The main task of a multi-plate clutch is to right moment smoothly connect and disconnect the input (drive) and output (driven) shafts using the friction force between the disks. In this case, torque is transmitted from one shaft to another. The disks are compressed due to the action of fluid pressure.

Note that the stronger the surfaces of the discs are in contact, the greater the value of the transmitted moment. During operation, the clutch can slip, while the driven shaft accelerates smoothly, without jerks and bumps.

The main difference between a multi-disk mechanism and others is that by increasing the number of disks, the number of contact surfaces increases, as a result of which it becomes possible to transmit more torque.

The basis of the normal operation of the friction clutch is the presence of a regulated gap between the discs. This interval must be equal to the value set by the manufacturer. If the gap between the clutch discs is less than the prescribed one, then the friction clutches will be constantly in a “compressed” state and, accordingly, wear out faster. If the distance is greater, then slippage of the clutch will be observed during operation. In this case, too, avoid rapid wear. Accurate adjustment of the gaps between the friction clutches during the repair of the clutch is the key to its correct operation.

Device and main components

A multi-plate friction clutch is structurally a package of steel and friction discs that alternate with each other. Their number directly depends on what torque must be transmitted between the shafts.

The principle of operation of a multi-plate clutch

So, in the clutch there are two types of discs - steel and friction. What is their difference? The thing is that the second type of disks has special coating called "friction". It is made of materials that have an increased coefficient of friction: ceramics, carbon composites, Kevlar threads, and so on.

Most often, friction discs are steel discs with a friction layer. However, steel is not always their basis; sometimes these parts of the coupling are made of durable plastic. The discs are attached to the hub of the drive shaft.

Ordinary steel discs without friction coatings are fixed in a drum connected to the driven shaft.

The clutch also includes a piston and a return spring. Under the action of fluid pressure, the piston presses on the disk pack, due to which a friction force arises between them, and torque is also transmitted. After the pressure is released, the spring returns the piston and the clutch disengages.

There are two types of multi-plate clutch: dry and wet. The second type of device is partially filled with oil. Lubricant is needed for:

more efficient heat dissipation;
lubrication of the coupling parts.

A wet multi-plate clutch has one drawback - it has low coefficient friction. This shortcoming manufacturers compensate by increasing the pressure on the discs, as well as through the use of the latest friction materials.

Advantages and disadvantages

Advantages of a multi-plate friction clutch:

compactness;
when using a multi-plate clutch, the dimensions of the assembly are significantly reduced;
transmission of significant torque with small dimensions of the mechanism (due to an increase in the number of disks);
smoothness of work;
the ability to coaxially connect the driving and driven shafts.

However, this mechanism not without flaws. For example, during operation, steel and friction discs may burn. Wet multi-plate clutches with viscosity changes lubricant the coefficient of friction also changes.

Coupling application

Multi-plate friction clutches are widely used in automobiles. This device used in the following systems:

clutch (in CVTs without a torque converter);
automatic transmission (automatic transmission): the clutch in the automatic transmission is used to transmit torque to the planetary gear set;
robotic box gears: disc pack with double clutch in the robot box is used for high-speed gear shifting;
systems all-wheel drive: friction device install in transfer box(clutch is needed here for automatic locking center differential);
differential: mechanical device performs the function of full or partial blocking.

) - a device for transmitting rotational motion by means of sliding friction force.

Principle of operation

By appointment, friction clutches can be coupling and safety.

Friction clutch (clutch) designed to separate and smoothly connect the input and output shafts through friction.

During the activation of the clutch friction clutches, the torque on the driven shaft increases progressively and in proportion to the increase in the force of mutual pressing of the friction surfaces. This makes it possible to connect shafts under load and with a significant initial difference in their angular velocities. In the process of switching on, the clutch slips, and the acceleration of the driven shaft is carried out smoothly, without shock.

The safety clutch is designed to disconnect the input and output shafts in case of exceeding the torque limit.

According to the type of rubbing surfaces, disc, cone, drum, drum-tape couplings are distinguished.

According to the method of creating friction forces, clutches with spring, cargo, centrifugal, cam, hydraulic, pneumatic and electromagnetic pressure are distinguished.

According to the type of friction forces, dry friction clutches and clutches operating in oil are distinguished.

Classification of friction clutches

Friction clutches according to the shape of the working surfaces are of the following types:

disk, the working surfaces of which are flat end surfaces of the disks.
conical.
cylindrical.

On mechanical vehicles applied clutch.

Crawler Tractor Friction Clutch

Serves to detach one of the sides when turning.

Device

Lead drum.
Leading discs.
driven drum.
driven disks.
Pressure springs.
Tie fingers.
Squeeze disc.
Release bearing.
Clutch release fork.

Operating principle

In rectilinear motion - the disc pack is pressed by the squeezing disc due to the springs, and the rotation is transmitted from central gear through the friction clutch to the final drive. When turning - the force from the control lever is transmitted through the servo mechanism to the clutch release fork. Fork pulls back release bearing and squeezing disc. It moves away from the disk pack and releases them, while the springs are compressed. Leading disks begin to slip relative to the driven ones.

Literature

Coupling // Great Soviet Encyclopedia: [in 30 volumes] / ch. ed. A. M. Prokhorov. - 3rd ed. - M.: Soviet Encyclopedia, 1969-1978.
Polyakov V.S., Barbash I.D., Ryakhovsky O.A. Handbook of couplings. - L .: Mashinostroenie (Leningrad department), 1974. - 352 p.
Anuryev V.I. Handbook of the designer-machine builder: In 3 volumes / Ed. I. N. Zhestkovoy. - 8th ed., revised. and additional .. - M .: Mashinostroenie, 2001. - T. 2. - 912 p. - ISBN 5-217-02964-1 (5-217-02962-5), BBC 34.42-2, UDC 621.001.66 (035).

This

Clutches (friction discs, clutch packs) - clutch elements between gears in, necessary to turn on and. The clutch consists of a base ( steel disk). A special friction lining is glued to the indicated disk.

The main task of the clutches is to close (compress) and open (unclench) at a strictly defined moment, due to which the desired gear, which corresponds to a particular gear, stops or starts to rotate. The clutches are compressed and decompressed under the pressure of the transmission ATF fluids.

Read in this article

The device of automatic transmission friction discs and the principle of operation

First of all, there are two types of frictions:

metal discs with a friction lining, which are engaged with the body of the automatic transmission. Such clutches are immovable.
soft clutches rotating simultaneously with the sun gears. Such clutches are made of a soft material (for example, pressed cardboard) and have a hardening coating (graphite, etc.)

Various automatic transmissions may have different types clutches. For example, in automatic transmissions made in the 20th century and which are now obsolete, the friction discs are one-sided, without pads. In fact, this means that there are two discs, one steel and the other cardboard.

More modern types Automatic transmissions received modified friction discs with adjustments, as a result of which the clutch resource was increased, heat dissipation was improved, etc. Friction discs are collected in so-called "packages" (friction package), when one disc is made of metal and the other is made of soft material. These pairs are duplicated several times to form a finished package. For example, a simple 4's step automatic has 2 or 3 sets of clutches.

If we talk about the principles of operation, you need to understand that the so-called planetary gear is used in the automatic transmission device. So, in a nutshell, when the gear is out, the friction discs rotate without restriction, that is, they are not pinched due to lack of oil pressure.

However, at the moment of switching on the transmission transmission fluid ATF under pressure passes through the channels of the valve body, as a result of which the discs are compressed (frictions are tightly pressed against each other). As a result, the desired gear is connected, while the remaining gears in the automatic transmission stop.

Clutch service life and major breakdowns

Many motorists are well aware that the most common malfunction of the automatic transmission is the wear of the friction discs (friction wear). At the same time, it is impossible to avoid such wear, however, competent maintenance and operation of the automatic transmission allows you to increase the resource of clutch packs up to 250-400 thousand km. run.

To do this, it is necessary to change the oil in the automatic gearbox in a timely manner (every 40-50 thousand km), monitor the oil level in the gearbox, prevent overheating, do not skid in a car with automatic transmission, etc. If the friction discs are out of order, as a rule, you can hear that the friction clutches have burned out. In practice, this manifests itself in such a way that automatic transmission gears do not turn on, gears slip, etc. Let's figure it out.

So, the friction discs themselves may well serve for a long time (a mileage indicator of about 500 thousand km is quite real), since these discs rotate in oil. So, their resource largely depends on the condition of the oil. If you do not change the oil in the machine and the oil filter, and at the same time subject the transmission to serious loads, it is quite possible that the clutches will also fail by 80-150 thousand km.

The reason is the loss of properties ATP oils and aging, pressure drop, contamination of the fluid itself with gearbox wear products, problems with valve body channels, solenoids, etc. Together, the oil pressure on the clutches will drop, the compression will not be as effective and the friction discs will slip in this case.

It turns out that they heat up and “burn out” from friction, and the friction packs are destroyed. Often, the smell of burning can also be noticed when analyzing the ATF fluid, when the oil in the automatic transmission box smells burnt precisely because of slipping and burning of the friction clutches.

What is the result

As you can see, the friction discs of an automatic transmission are a kind of clutch in a manual transmission. At the same time, the element is quite reliable, but only if everything is in order with the oil pressure in the “automatic” box and the liquid itself is clean.

A decrease in pressure usually occurs when:

the oil level (ATF) in the box is not correct;
the transmission fluid itself has lost its properties and / or is heavily contaminated;
there were problems with the oil pump, reduced throughput automatic transmission oil filter or oil cooler;
valve body channels are clogged, solenoids do not work correctly, etc.

In the presence of such problems, the transmission may switch jerkily,. As a rule, if the problem is not paid attention to, the friction discs are the first to fail, the friction clutches slip and burn. As a result ATF oil it smells burnt in the automatic transmission, the color of the oil in the automatic gearbox changes, etc.

To solve the problem in some cases, it may be enough to flush the oil cooler, change the oil in the automatic box, and also oil filter. In other situations, it may be necessary to disassemble the automatic transmission to replace the clutch packs, flush the valve body channels, and check the performance of the solenoids.

One way or another, when the first signs of clutch slippage are detected, it is necessary to stop the operation of the vehicle and deliver the car to the service station in order to conduct an in-depth diagnosis of the automatic transmission.