What Is a Power Clutch?

The clutch is located in the flywheel housing between the engine and the gearbox. The clutch assembly is fixed on the rear plane of the flywheel with screws. The output shaft of the clutch is the input shaft of the gearbox. During the running of the car, the driver can step on or release the clutch pedal as needed to temporarily separate and gradually engage the engine and the gearbox to cut off or transfer the power input by the engine to the transmission. Clutches are a common component in mechanical transmissions, which can disengage or engage the transmission system at any time. The basic requirements are: stable joint, rapid and thorough separation; easy adjustment and repair; small outline size; low quality; good abrasion resistance and sufficient heat dissipation capacity; easy operation and labor saving, commonly used are tooth-embedded and Two types of friction.

Chinese name: clutch
Foreign name: Clutch

Classification: Electromagnetic clutch, magnetic powder clutch, etc.
Function: Cut off or transfer power from the engine
Location: Inside the flywheel housing between the engine and the transmission

Clutch definition

The function of the clutch Clutch, commonly known in Hong Kong as Kekko, comes from English Clutch, and Taiwanese often refers to it as Japanese or Japanese, which is a device that transmits the engine power of a car or other power machinery to the axle by means of a switch.

The clutch is installed between the engine and the transmission. It is an assembly directly connected to the engine in the automotive driveline. The clutch is usually installed with the flywheel set of the engine crankshaft, and it is the part that cuts off and transmits power between the engine and the vehicle drive train. During the entire process from the start of the car to normal driving, the driver can manipulate the clutch to temporarily separate or gradually engage the engine and drive train as needed to cut off or transfer the power output by the engine to the drive train. Its role is to make the engine and transmission gradually engage to ensure the smooth start of the car; temporarily cut off the connection between the engine and the transmission to facilitate shifting and reduce the impact of shifting; it can be started when the car is braked in an emergency The separation function prevents the transmission system and other transmission systems from being overloaded, thereby playing a certain protective role.

The clutch is similar to a switch. It engages or disengages the power transmission function. The active part and the driven part of the clutch mechanism can be temporarily separated, and can be gradually engaged, and it may be relatively rotated during transmission. No rigid connection can be used between the clutch's driving and driven parts. Any type of car has a clutch device, but only in a different form. ^[1]

Clutch classification

According to the analysis of " China's clutch manufacturing industry production and sales demand and investment forecast analysis report forecast " analysis, clutches are divided into electromagnetic clutches, magnetic powder clutches, friction clutches and hydraulic clutches:

Clutch electromagnetic clutch

The on and off of the coil is used to control the engagement and disengagement of the clutch.

Electromagnetic clutches can be divided into: dry single-plate electromagnetic clutches, dry multi-plate electromagnetic clutches, wet multi-plate electromagnetic clutches, magnetic powder clutches, slip-type electromagnetic clutches, and the like.

The working mode of electromagnetic clutch can be divided into: power-on combination and power-off combination.

Dry single-plate electromagnetic clutch: When the coil is energized, magnetic force is applied to the "armature" disc, and the clutch is in the engaged state; when the coil is de-energized, the "armature" springs back and the clutch is in the disengaged state.

Dry multi-plate, wet multi-plate electromagnetic clutches: The principle is the same as above, and additional friction is added. The same volume torque is larger than the dry single-plate electromagnetic clutch. The wet multi-plate electromagnetic clutch must be cooled by oil or other coolant when working .

Clutch magnetic powder clutch

A magnetic is placed between the driving and the driven parts. When the power is not applied, the magnetic powder is in a loose state. When the power is applied, the magnetic powder is combined, and the driving part and the driven part rotate at the same time. Advantages: The torque can be adjusted by adjusting the current, allowing for large slip. Disadvantages: The temperature rise is greater when the slip is large, and the relative price is high.

Slip type electromagnetic clutch: When the clutch is working, there must be a certain speed difference between the master and slave parts for torque transmission. The amount of torque depends on the strength of the magnetic field and the difference in speed. The excitation current remains unchanged, and the speed decreases sharply with increasing torque; when the torque remains unchanged, the excitation current decreases, and the speed decreases even more severely.

The slip type electromagnetic clutch has no mechanical connection between the main and driven parts, no wear and tear, no magnetic powder leakage, and no impact. Adjusting the excitation current can change the speed and use it as a continuously variable transmission. This is its advantage. The main disadvantage of this clutch is that the eddy current in the rotor generates heat, which is proportional to the speed difference. The efficiency at low speed is very low, the efficiency value is the main, the speed ratio of the driven shaft, that is = n2 / n1.

The mechanical transmission system suitable for high-frequency operation can combine or separate the driven part and the active part when the active part is running.

When the driving member and the driven member are in a separated state, the driving member is rotated, and the driven member is stationary; the driving member and the driven member are in an engaged state, and the driven member is driven to rotate.

Widely used in machine tools, packaging, printing, textiles, light industry, and office equipment.

Electromagnetic clutches are generally used in media with an ambient temperature of -20-50 ° C, humidity of less than 85%, and no risk of explosion, and the coil voltage fluctuations should not exceed ± 5% of the rated voltage.

Clutch friction clutch

Friction clutches are the most widely used and have the longest history. They are basically composed of a driving part, a driven part, a pressing mechanism and an operating mechanism. The main and driven parts and the pressing mechanism are the basic structures to ensure that the clutch is in the engaged state and can transmit power, and the operating mechanism of the clutch is mainly a device that releases the clutch. During the disengagement process, when the clutch pedal is depressed, the free clearance of the clutch is first eliminated during the free stroke, and then a release clearance is generated during the working stroke, and the clutch is disengaged. During the engagement process, the clutch pedal is gradually released, and the pressure plate moves forward under the action of the compression spring. First, the separation gap is eliminated, and sufficient pressure is exerted on the working surface of the pressure plate, driven disk and flywheel; The release bearing moves backwards under the action of the return spring, creating a free play and the clutch engages.

Clutch hydraulic clutch

Hydraulic clutch fluid (usually oil) is used as the transmission medium. Compared with mechanical clutches, in addition to various changes in transmission characteristics, it also mainly absorbs vibration and shock caused by the rotation of the driving and driven shafts.

The structure of the hydraulic clutch includes an input shaft with a speed-increasing gear train; a working fluid flow chamber composed of an impeller, a driven wheel, and an impeller shell; an output shaft with a driven wheel, and the driven wheel and the impeller It can be operatively combined together; generally, the impeller shell and the impeller are made of a material having a small specific gravity and a large stress tolerance range to reduce centrifugal stress.

Clutch principle

For models with manual transmission, the clutch is an important part of the vehicle's power system. It is responsible for cutting off and connecting the power to the engine. When driving on urban roads or complex roads, the clutch has become one of our most frequently used components. The use of the clutch directly reflects the level of driving and protects the vehicle. How to use the clutch correctly and master the principle of the clutch to solve the problem by using the clutch under special circumstances is something that every rider driving a manual transmission model should master.

The so-called clutch, as its name implies, uses "off" and "on" to transmit a proper amount of power. The clutch consists of a friction plate, a spring plate, a pressure plate, and a power output shaft. It is located between the engine and the gearbox and is used to transmit the torque stored on the engine flywheel to the gearbox to ensure that the vehicle is transmitted to the vehicle under different driving conditions. The right amount of driving force and torque of the drive wheels belongs to the category of powertrain. During semi-linkage, the speed difference between the power input end and the power output end of the clutch is allowed, that is, a proper amount of power is transmitted through the speed difference.

The clutch is divided into three working states, namely, non-interlocking when the clutch is stepped on, full interlocking when the clutch is not stepped on, and semi-interlocking when the clutch is partially stepped on. When the vehicle starts, the driver depresses the clutch, and the movement of the clutch pedal pulls the pressure plate back, that is, the pressure plate is separated from the friction plate. At this time, the pressure plate does not contact the flywheel at all, and there is no relative friction. When the vehicle is running normally, the pressure plate is tightly pressed against the friction plate of the flywheel. At this time, the friction between the platen and the friction plate is the largest, and the relative static friction between the input shaft and the output shaft is maintained. . The last is the semi-interlocked state of the clutch. The friction between the pressure plate and the friction plate is less than the fully-interlocked state. At this time, the clutch pressure plate and the friction plate on the flywheel are in a sliding friction state. The rotation speed of the flywheel is greater than the rotation speed of the output shaft, and the power transmitted from the flywheel is transmitted to the gearbox. In this state, the engine and the drive wheels are equivalent to a soft connection state.

Generally speaking, the clutch works when the vehicle starts and shifts. At this time, there is a speed difference between the first and second shafts of the gearbox. The power of the engine must be cut off from the first shaft to make the synchronizer good. The speed of one axis is kept synchronized with the two axes. After the gear is engaged, a shaft is combined with the engine power through the clutch, so that the power can continue to be transmitted. There is also an indispensable cushioning device in the clutch. It consists of two discs similar to a flywheel. A rectangular groove is punched on the disc, and a spring is arranged in the groove. When encountering a fierce impact, the spring between the two discs is elastic to each other. Function, buffering external stimuli, effectively protecting the engine and clutch.

Among the various parts of the clutch, the strength of the pressure plate spring, the friction coefficient of the friction plate, the diameter of the clutch, the position of the friction plate and the number of clutches are the key factors that determine the performance of the clutch. The greater the spring stiffness, the higher the friction coefficient of the friction plate, and the larger the clutch diameter, the better the clutch performance. ^[2]

Clutch typical clutch working process

The work of the diaphragm spring clutch can be divided into three processes: work, release and engagement.

1. Working process. When the diaphragm spring is inserted between the clutch cover and the pressure plate, the pressure on the pressure plate caused by the pre-compression deformation causes the main and driven parts of the clutch to be compressed, that is, the clutch is in an engaged state. The engine power is transmitted to the driven disk through the flywheel, clutch cover and pressure plate connected to the crankshaft, and then transmitted to the input shaft of the transmission through the driven disk splined bushing. The working characteristics of this process are that the torque and rotation speed of the clutch master and slave parts are the same, there is no speed difference between the master and slave parts, and there is no slip.

2. Separation process. The driver steps on the clutch pedal, the pedal moves to the left, the push rod moves to the left, and the diaphragm spring separation plate is pushed to the left by the cylinder and the working cylinder. Affected by this, the diaphragm spring uses the support pin fixed on the clutch cover as a fulcrum to move the big end to the right, and simultaneously pulls the pressure plate to the right by the action of the separation plate. Finally, there is a gap between the driven disk, the flywheel, and the pressure plate, and the clutch is released, and the clutch release process ends.

The working characteristic of the clutch during the disconnection process is that the power and movement of the engine cannot be transmitted to the driven disc after the disconnection. The driving part is still synchronized with the engine speed, while the driven part decreases rapidly.

3. The joining process. The driver releases the clutch pedal and returns to the original position under the action of a return spring, and simultaneously drives the push rod and the release bearing to return. That is, the movement of the manipulation mechanism in the joining process is the reverse process of the separation process. When a reserved gap appears between the release bearing and the diaphragm spring separation plate and the diaphragm spring re-presses the pressure plate against the driven plate, the engagement process ends and the clutch resumes transmitting power.

Working process of diaphragm spring clutch (1 sheet)

Clutch action

Clutch ensures smooth car start

This is the primary function of the clutch. Before the car starts, it is natural to start the engine. When the car starts, the car gradually accelerates from a completely stationary state. If the drive train (which links the entire car) is rigidly connected to the engine, the car will suddenly move forward as soon as the transmission is in gear, but it will not start. This is because the car has a large inertia from stationary to forward, causing a large resistance torque to the engine. Under the effect of this inertia resistance moment, the engine's speed drops sharply below the minimum stable speed (generally 300-500RPM) in an instant, and the engine will stop working and the car will not start.

Therefore, we need the help of the clutch. After the engine starts and before the car starts, the driver first depresses the clutch pedal, disengages the clutch, disengages the engine from the drive train, puts the transmission in gear, and then gradually releases the clutch pedal to gradually engage the clutch. During the engagement process, the engine's blocked torque gradually increases, so you should gradually step on the accelerator pedal at the same time, that is, gradually increase the fuel supply to the engine, so that the engine speed is always maintained at the minimum stable speed without stopping. At the same time, as the clutch tightness of the clutch gradually increases, the torque transmitted by the engine to the driving wheels through the drive train gradually increases. When the traction is sufficient to overcome the starting resistance, the car starts to move from standstill and gradually accelerates.

Clutch realizes smooth shifting

In the process of driving a car, in order to adapt to changing driving conditions, the drive train often needs to change gears to work. To realize gear shifting of a gear type transmission, generally, a gear or other gear shifting mechanism is shifted to push out one gear pair of the original gear position for transmission, and then bring the gear pair of the other gear position into operation. Before changing gears, you must step on the clutch pedal to interrupt the power transmission, so that the meshing pair of the original gear can be disengaged. At the same time, the speed of the meshing parts of the meshing pair of the new gear can be gradually synchronized, so that the impact when entering the mesh can be greatly Reduced, thus achieving smooth shifting. 3. Prevent overloading of the drive train

When the car is in emergency braking, if there is no clutch, the engine will reduce the speed sharply due to the rigid connection with the drive train, so all moving parts in it will generate a large inertia moment (its value may greatly exceed the value issued by the engine during normal operation) Maximum torque), causing the drive train to exceed its load carrying capacity and cause damage to the parts. With a clutch, this danger can be eliminated by relying on the relative movement that can occur between the driving and driven parts of the clutch. Therefore, we need clutches to limit the maximum torque experienced by the drive train to ensure safety.

Use, maintenance and maintenance of clutches

Clutch considerations

1. The clutch must be cleaned before installation to remove anti-rust grease and debris.

2. The clutch can be installed coaxially or in separate shafts. The axial direction must be fixed. No axial movement is allowed between the driving part and the driven part. When the shaft is installed, the shaft between the driving part and the driven part is coaxial. The degree should not be greater than 0.1mm.

3. When the wet electromagnetic clutch works, lubricating oil must be added between the friction plates. The lubrication method is (1) divided pouring oil lubrication; (2) oil bath lubrication, the part immersed in the oil is about 5 times the volume of the clutch; 3) Shaft lubrication and lubrication. Shaft lubrication should be used for high-speed and high-frequency operation.

4. When the tooth-embedded electromagnetic clutch is installed, there must be a certain gap between the end teeth, so that there is no tooth grinding during idling, but it must not be greater than .

5. The electromagnetic clutch and brake are Class B insulation, and the normal temperature rise is 40 ° C. The working temperature during extreme thermal equilibrium is not allowed to exceed 100 ° C, otherwise the coil and friction parts are prone to damage.

6. Power supply and control circuit. The clutch power supply is DC 24V (except for special order). It is obtained from three-phase or single-phase AC voltage through step-down and full-wave rectification (or bridge rectification). No voltage regulation and flat-wave require sufficient power. Half-wave rectified power is not allowed.

7. Requirements for clutches in automotive drive trains

Depending on the use of the clutch, it should meet the following main requirements:

The joint is smooth and soft to ensure the car starts smoothly.

Quick and thorough separation for easy gear shifting and engine start;

With proper reserve capacity, it can ensure the transmission of the maximum torque of the engine and prevent the drive train from overloading;

The driving inertia of the driven part should be as small as possible to reduce the impact when shifting;

It has good heat dissipation ability. When the car needs to operate the clutch frequently during driving, it will cause the master and driven parts of the clutch to relatively slip and generate frictional heat. If the heat is not released in time, it will seriously affect the reliability of its work And service life;

Light handling to reduce driver fatigue.

Clutch operation essentials

Three essentials of clutch operation: one fast, two slow, and three linkages. When lifting the clutch pedal, you must follow the "one fast, two slow, three linkage" operating principle. When starting, step on the clutch pedal to act neatly, with one foot in the end to completely disengage the clutch.

The so-called "one fast, two slow, and three linkages" is the process of lifting the clutch pedal in three stages. At first, it is quickly lifted. When you feel that the clutch pressure plate is gradually coupled to the half linkage, the pedal lift speed starts to slow down. In the process of semi-linkage to full engagement, the clutch pedal is slowly raised. When the clutch pedal is raised, you should gradually press down the accelerator pedal according to the power of the engine, so that the car can start smoothly. The throttle operation should be smooth and appropriate, and the throttle can only be increased when the clutch is fully engaged.

Clutch pedal failure

I. Failure phenomenon: Although the clutch pedal has been depressed to the bottom when the engine is idling, it is difficult to suspend gears and the transmission gear has an impact sound. After barely putting on the gear, the clutch pedal has not been released, and the car is running or stalled.

Second, check: Remove the clutch bottom cover, hang the transmission in neutral, and step on the clutch to the end. Then, use a screwdriver to turn the driven disk. If it can be turned easily, the clutch is well disengaged; if it cannot be turned, the clutch is not disengaged completely.

3. Exclusion:

1. Check whether the free travel of the clutch pedal is too large and adjust it.

2. Check whether the height of the separation lever is consistent or too low. Move the release fork under the car, so that the front end of the release bearing gently rests on the inner end surface of the release lever, and turn the clutch for one week to check. Inconsistent, should be adjusted. If the separation lever height is the same and the separation is still not complete, check the lever height. Adjust the separation levers to the same height. If they can be completely separated, it means that the original adjustment is improper or the wear is excessive. After the release lever is adjusted, the free travel of the clutch pedal must be readjusted.

3. If the separation is still not complete after the above adjustments are normal, remove the clutch, check whether the driven disk is reversely installed, whether the axial movement is difficult, whether the main driven disk is warped, whether the separation lever screw is loose, and the floating pin Whether it falls off.

4. For the clutch of the newly riveted friction plate, check whether the driven disk and the friction plate are too thick. If it is too thick, add a gasket between the clutch cover and the flywheel.

5. For the clutch of hydraulic transmission, in addition to the above-mentioned inspection, it should also check whether the brake fluid is lacking, whether the pipeline is leaking and the air in the hydraulic system is exhausted.

Clutch slip treatment

When clutch slippage occurs, correct failure cause analysis should be performed.

1.Causes of clutch slippage

The friction plate of the driven disk is excessively worn or the rivets are exposed;

The clutch pressure plate spring is too soft or broken;

The free travel of the clutch pedal is too small;

There is oil stain on the friction disc of the driven disc or it becomes aging and hardened;

The clutch and flywheel joint bolts are loose;

The oil return hole of the clutch master cylinder is blocked.

2. Troubleshooting order and orientation

Check the free travel of the pedal, if it does not meet the standard value, it should be adjusted;

If the free travel is normal, remove the clutch bottom cover and check whether the clutch cover and flywheel joint bolts are loose. If they are loose, tighten them;

Check if there is any oil stain on the edge of the friction plate of the clutch. If there is oil stain, remove it and wash it with gasoline or alkaline water and dry it. Then find out the source of the oil stain and remove it;

If it is found that the friction plate is severely worn, the rivet is exposed, hardened, burnt or soaked with oil, it should be replaced with a new one. The new friction plate must not be cracked or damaged, and the depth of the rivet should meet the requirements;

Check the oil return hole of the clutch master cylinder. If the oil return hole is blocked, it should be cleared.

If the fault cannot be eliminated after the above inspection, adjustment and repair, disassemble the clutch and check the spring force of the pressure plate spring. When the pressure plate spring is good, the length should be the same. If it is uneven, it should be replaced with a new one. If the spring force is slightly reduced and the length is not much different, you can adjust it by adding or subtracting a gasket under the spring.

Clutch problem

1. Pay attention to whether the clutch is slipping. There are several reasons for this phenomenon. The main reason is that the free travel of the clutch pedal is too small, and the release bearing is often pressed against the diaphragm spring, so that the pressure plate is always in a semi-detached state. Or the clutch pressure plate spring is too soft or broken, and the screws connecting the clutch to the flywheel are loose.

2. In the idle state of the engine, the clutch can only be cut off when the clutch pedal is pressed to almost bottom. Depress the clutch pedal and feel difficulty in gear-shifting or the harsh sound of transmission gears, or start the vehicle without lifting the clutch pedal after gear-shifting, which indicates that the car's clutch is not completely disengaged.

3. When the clutch pedal is depressed to 3/4, the clutch should be firmly engaged, otherwise check whether the stroke is appropriate. Use a ruler to measure at the pedal. First measure the highest position height of the pedal and then measure the pedal. The height of the resistance, the difference between the two values is the clutch stroke value of the car.

4. It is abnormal if abnormal noise occurs during the use of the clutch. The cause of the failure is severe wear of the separated bearing, too soft or broken bearing return spring, and failure of the diaphragm spring support.

Incomplete clutch release

There are two phenomena that the clutch is not completely separated:

(1) When the car starts, step down the clutch pedal and exceed the free travel, but still feel difficult to shift gear; if it is forced to shift into gear, but the clutch pedal has not been fully raised, the car will move forward or backward and cause the engine Turn off.

(2) It is difficult to shift gears while driving, or the gears cannot be shifted up, and the gear crashes in the transmission.

The main reasons for incomplete clutch release are:

The free travel of the clutch pedal is too large;

The inner ends of the separation levers are not on the same plane, and the individual separation levers are deformed, broken, and worn seriously;

The clutch driven disk is warped, the rivets are loose, or the friction plate of the new clutch is too thick;

The front and back sides of the clutch follower plate are installed in reverse;

The clearance between the key groove of the driven disc hub and the spline tooth of the first shaft of the transmission is too small or stuck, which makes it difficult to move.

The diagnosis method for this kind of failure is: drive the car on a flat road, put the gearshift lever in the neutral position, and press the clutch pedal. If only the driver is alone, you can use a wooden stick to press the clutch pedal down and press it Hold (pull up the brake handle to make the hand brake work). In the hole below the flywheel housing, use a screwdriver to push the clutch disc. If it can be pushed gently, it means that the clutch can still be cut off. If it can't be pushed, it means that the clutch cannot be disengaged.

The main reason for poor clutch release is that the free travel of the clutch pedal is too large. Then, after replacing the clutch driven disk, because the cleaning of the first shaft of the transmission was neglected, there were impurities, which caused the gap between the driven disk hub and the first shaft to be too small, the movement resistance was large, and the clutch release was not good. When purchasing the clutch driven disk assembly, the user should check for warpage, and its thickness should meet the standards. If it is warped or too thick, it should be replaced.