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Clutch Operation Principle And Clutch General Abnormal Problem Solved

Jun 03, 2017

The clutch is positioned in the flywheel housing between the engine and the gearbox, and the clutch assembly is fixed on the back plane of the flywheel by means of screws, and the output shaft of the clutch is the input shaft of the transmission. In the process of running a car, the driver may step on or loosen the clutch pedal as necessary, so that the engine is temporarily separated from the gearbox and gradually joined to cut off or transmit the power input from the engine to the transmission. Clutch is a commonly used component in mechanical transmission, which can separate or engage the drive system at any time. The basic requirements are: smooth engagement, quick and thorough separation; adjust and repair convenient; small size; quality; good wear resistance and sufficient heat dissipation capability; convenient and labor-saving operation, commonly divided into tooth type and friction type two.


Mechanical parts that can be joined or separated at any time as required by the active shaft and driven shaft. It can be used to control the starting, stopping, shifting and reversing of the machine drive system. Clutch types, according to the nature of the work can be divided into: control clutch. The electromagnetic manipulation methods include mechanical, pneumatic and hydraulic, such as embedded clutch (fitted through the teeth, or key torque), friction clutch (using friction torque), flexible clutch (air with oxytocin to manipulate the friction piece of clutch engagement or disengagement of the air compression, fetal expansion) electromagnetic slip clutch (magnetic force is generated to transfer torque with the magnetizing current), magnetic powder clutch (with the magnetic field coil magnetization, the formation of magnetic chain to transfer torque). Automatic clutch. By a simple mechanical method to complete the automatic joint or separate action, and divided into safety clutch (when the transfer torque reaches a certain value when the drive shaft can be automatically separated, so as to prevent overload, avoid damage to the important part of a machine), centrifugal clutch (when the drive shaft speed reaches a certain value, due to the centrifugal force can make the transmission shaft can automatically separate to join or exceed a speed), directional clutch (also called the clutch, the ratchet pawl engagement or roller, wedge wedge action of one-way transmission of motion or torque, when the driving shaft or reversal speed is lower than the driven shaft, the clutch is automatically separated).


1., ensure that the car started smoothly

Before starting the car in a static state, if the engine and gearbox are rigidly connected, once the gear, cars will be connected due to the sudden sudden rush, not only will cause mechanical damage, and the driving force is not enough to overcome the car before the enormous inertia force, the speed of the engine flameout declined sharply. If the clutch in starting the engine and gearbox will temporarily separated, then the clutch engagement gradually, because of the existence of the phenomenon of friction between the driving part and the driven part of the clutch, the clutch torque from zero to increase gradually, and the driving force of the automobile is increasing gradually, which make the car a smooth start.

2. easy to change gears

In the process of moving the car, different gear boxes are often changed to adapt to changing driving conditions. If there is no clutch to separate the engine from the gear box, then the transmission gear in the gearbox will not be removed due to the load, and the pressure between the teeth of the meshing surface is very large and difficult to separate. The other pair of meshing gears is difficult to mesh because of the unequal speed between the two sides. Even if forced into the meshing, it will produce a big tooth end impact, easy to damage parts. The clutch is used to shift the engine and the gearbox temporarily, and then a pair of gears engaged in the engagement are removed because of the load, and the pressure between the meshing surfaces is greatly reduced and is easy to separate. Another pair of gear to be engaged, separated by the driving gear and the engine inertia is small, so that the gears meshing circumferential speed to be equal or nearly equal by appropriate action can shift, so as to avoid or mitigate the impact of inter gear.

3. prevent the transmission from being overloaded

Automobile emergency brake wheel, sudden deceleration, and the engine with the transmission due to the rotation inertia, still maintain the original speed, this will often have the moment of inertia is much larger than the engine torque in the transmission system, the transmission system components easy to damage. Because the clutch is to transmit torque by friction torque transmission, so when the load is larger than the friction transmission, clutch and the driven part will automatically slip, so as to prevent the transmission of the overload effect.

4. reduce torsional vibration impact

The working principle of an automobile engine determines the unevenness of its output torque. In the work stroke, the combustion chamber gas explosion produces great impact torque, while in other strokes it relies on inertia to drag the engine. Although the inertia of the engine itself can reduce the torsional vibration, the remaining impact still has a negative impact on the transmission and transmission shaft. The damping spring (tangential distribution) in the clutch can significantly reduce the torsional vibration impact of the engine and prolong the life of the gear change.

Working principle

The active part and the driven part of the clutch by friction between the surfaces, or the use of liquid as the transmission medium (hydraulic coupling), or the use of magnetic drive (electromagnetic clutch) to transfer torque, which can be temporarily separated between the two, and gradually joined the two parts mutually rotate and allow in the transmission process.

At present, the friction clutch, which is called spring friction clutch, is widely used in automobiles.

The torque emitted by the engine is transmitted to the driven plate by the friction action between the flywheel and the pressure plate and the contact surface of the driven disk. When the driver depresses the clutch pedal, through mechanical transmission, the diaphragm spring platen drive after the shift, so the driven part and driving part separation.

Friction clutch shall be able to meet the following basic requirements:

(1) ensure that the maximum torque can be transmitted by the engine, and there is a certain torque transfer force.

(2) it can be separated thoroughly when it is separated, it is soft when jointing, and has good heat dissipation ability.

(3) the inertia of the driven part is as small as possible. Thus, when the clutch is shifted apart, the rotation speed of the part connected with the input shaft of the transmission gear is easy to change, thereby reducing the impact between gears.

(4) it has the ability of reducing the impact of the direction of rotation and attenuating the vibration of the direction, and the noise is small.

(5) the friction coefficient of the pressure plate and the friction plate changes little, and the work is stable.

(6) the operation is labor-saving, and the maintenance is convenient.


Automobile clutch has friction clutch, hydraulic torque converter (hydraulic coupler), electromagnetic clutch and so on. Friction clutch is divided into two types: wet and dry.

Hydraulic coupler

The torque is transferred by the working fluid (oil), and the casing is connected with the pump wheel as an integral body. The impeller is the driving element; the turbine is opposite to the pump wheel and is driven. When the pump wheel speed is low, the turbine can not be driven, the active component and the follower are separated; with the increase of the pump wheel speed, the turbine is driven, the active component and the follower are in a joint state.

Electromagnetic clutch

The engagement and separation of the clutch is controlled by the power off of the coil. If magnetic particles are placed between the active and the driven parts, the resultant force between them can be strengthened. Such a clutch is called a magnetic particle type electromagnetic clutch.

At present, the vast majority of clutch with manual transmission is dry friction clutch, according to the number of driven disk, it is divided into single disk type, double disc and multi disc and so on.

Wet friction clutch is usually multi disc, immersed in oil to facilitate heat dissipation. A number of spiral spring as the spring, and the spring along the circumferential distribution of the clutch is called multi coil spring clutch (as shown). The clutch with diaphragm spring as the compression spring is called diaphragm spring clutch.

Automatic clutch

With the application of electronic technology in automobiles, an automatic clutch system has also entered the automotive field. The control unit controls the clutch (ECU) has been used in some cars, make an important step - manual transmission shift clutch to disconnect and engage automatically timely, simplify the operation of the driver.

The traditional clutch has two kinds of pull and hydraulic type, and the automatic clutch is divided into two kinds: mechanical motor, automatic clutch and hydraulic automatic clutch. Automatic mechanical clutch motor ECU integration accelerator pedal, engine speed sensor, the speed sensor signal, after processing send commands to drive the servomotor driven clutch rod by mechanical form; automatic clutch hydraulic is sent by the ECU signal to drive the electric hydraulic system, hydraulic control clutch through.

Automatic hydraulic clutch diaphragm clutch on the basis of current general on the increase of the electronic control unit (ECU) and hydraulic system, the pedal clutch cylinder piston is changed to switch device controlled electric pump to operate the clutch cylinder piston. The transmission control unit (ECU) and the engine control unit (ECU) is integrated together, according to the accelerator pedal, gear box, transmission input / output shaft speed, engine speed, solar term door opening sensor feedback information, calculate the best time and speed clutch engagement.

The actuating mechanism of the automatic clutch is composed of an electric oil pump, an electromagnetic valve and a clutch cylinder. When the ECU sends out an instruction to drive the electric oil pump, the high-pressure oil produced by the electric oil pump is delivered to the clutch cylinder through an electromagnetic valve. Through the ECU control electromagnetic valve current quantity to control the oil flow and the oil liquid channel transformation, realizes the clutch cylinder piston movement, thus completes the automobile start and shift when the clutch movement.

ECU with automatic clutch device of automobile automatic transmission (AT) and continuously variable transmission (CVT) compared to cars, it has advantages in economic operation, because of its transmission or manual transmission, so the fuel consumption is relatively low, the manufacturing cost is lower than that of AT and CVT. Of course, car handling will be less convenient than AT and CVT. After all, it's a manual transmission, and still needs to shift manually.

Exception problem

Note that the clutch is slipping, several causes of this phenomenon, the main reason is the clutch pedal free travel is too small, the separation bearing often pressure in the diaphragm spring, the pressure plate is always in semi detached. Or the clutch pressure plate spring is too soft or broken, the clutch and flywheel connected screws loose, etc..

In the idle state of the engine, when the clutch pedal is pressed almost to the bottom, the clutch can be cut off. Depress the clutch pedal, feel the hang up or the gear gear crash, or the clutch pedal does not move, the vehicle begins to run, all of which indicate that the clutch of the car is not completely separated.

The clutch pedal to 3/4, clutch should firmly connected, otherwise check whether the trip right, available on the pedal at the measuring ruler to measure the highest position, then measure the height of the pedal, the pedal to feel resistance height values of the two numerical difference is the car clutch stroke.

Abnormal noise during clutch use is also abnormal. The trouble is that the bearings are worn seriously, the bearing back springs are too soft or broken, and the diaphragm spring supports are out of order.

fault diagnosis

(1) abnormal sound of clutch;

Phenomenon: an abnormal noise occurs when the clutch is separated or joined

The reason: lack of separation of bearing lubricant, caused by dry friction or bearing damage; the gap between the separation bearing and the separation between the sleeve and the inner end of the lever; bearing oil dirt serious separation catheter or separation bearing return spring and pedal return spring fatigue, broken off, so that the separation of bearing return driven disc spline hole and the poor; spline shaft with Songkuang; driven disc damping spring annealing fatigue or break; disc lining rivets loose or rivets loose or rivet head exposed; pin hole double clutch transmission pin and intermediate pressure plate and clutch wear open.

Diagnosis and exclusion: a clutch pedal so that the separation of bearing contact and separation lever, if there is a "rustling" sound for bearing noise, if the gas after noise, indicating excessive bearing wear, loose damage, should be replaced; on the clutch pedal, crash if a discontinuous, explain separation of traverse bearing, replace the separation bearing return spring; even if the clutch pedal, just engage or just when there was a noise separation, description driven disc rivet loose or exposed, should replace the clutch disc.

(2) the clutch is not completely separated

Phenomenon: when the engine is idle, press the clutch pedal. The gear is impacted by the gear and is difficult to hang in. If you barely hang it, the engine will stall completely when the clutch pedal is not completely relaxed.

Reason: the clutch pedal free travel is too large; the bending deformation, lever support looseness, bearing pin prolapse, separating the inner end of the height lever to adjust; lever to adjust properly, so that the inner side is not in the same plane or in the end height is too low; double clutch intermediate plate limit screw to adjust properly, individual separation spring fatigue, insufficient height or broken, intermediate plate in a drive pin or in the clutch drive window axial movement is not flexible; clutch plate warping, friction plate rupture or rivets loose; the friction plate is too thick or new and driven disc installed wrong; driven disc spline hole and the first transmission shaft spline a shaft; clutch hydraulic control mechanism of oil, air or oil shortage; diaphragm spring weakened; engine bearing wear or damage to the engine crankshaft and the input shaft of the transmission is different Axis.

Diagnosis and Troubleshooting: check the clutch pedal free travel, if free travel is too large to adjust for the hydraulic operating mechanism to check whether the oil storage tank is insufficient or pipe with air and the necessary check elimination; separation inside the lever end height, if the separation lever is too low or not in the same plane, then adjusted, otherwise check the clutch disc is reversed, if no problem is to check; check whether the warpage of driven disc rivet, driven disc is axially moving cassette if it is to replace or repair.

Contact person: Ms. Nancy Yue