Diagnosis of common fault phenomena of the hottest

2022-08-06
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The function of clutch system is to ensure that the engine and transmission system can be smoothly and reliably connected, and can be temporarily and completely separated. Engagement refers to the generation of friction torque, and separation refers to the release of friction torque. The clutch works frequently. Due to the sliding friction, each component is easy to wear, deform or crack, and the friction torque is correspondingly reduced, resulting in clutch system failure. In order to prolong the service life of the clutch as much as possible, it is very important to maintain the clutch system correctly and effectively

during the use of the clutch, the common faults mainly include heavy clutch pedal, slipping, incomplete separation (difficult to shift), shaking, rushing, abnormal noise, etc

1. Fault phenomenon, cause, inspection method and maintenance of heavy clutch pedal

fault phenomenon: the pedal clutch pedal is heavy, and the foot is easy to fatigue The clutch pedal force is obviously different from that of other vehicles

fault cause:

(1) release master cylinder assembly: improper adjustment, too high pedal, and no idle stroke

(2) driven plate (friction plate) assembly: large wear of friction plate (worn to the rivet of friction plate)

(3) clutch master cylinder, slave cylinder, release fork, release bearing, etc. are jammed, and the movement is not flexible

(4) the flywheel working surface and pressure plate working surface are severely worn (wear exceeds 0.5mm)

(5) the separation finger is excessively worn (the finger end arc has been ground flat) the plastic mobile phone is currently in a relatively low state, and the separation bearing is excessively worn (the thrust plane is worn out of a concave arc)

maintenance method:

step 1: check whether the clutch pedal is too high, whether the idle stroke is appropriate, and adjust it to the normal state. If the fault phenomenon is not eliminated, proceed to the next step

step 2: check whether the clutch pedal, master cylinder, slave cylinder, release fork, release bearing, etc. are jammed and inflexible, and whether the clutch pedal returns normally If it still cannot be solved after troubleshooting, proceed to the next step

step 3: check whether the clutch disc assembly, cover assembly and flywheel are excessively worn, and whether the pressure plate release finger and release bearing thrust plane are excessively worn The friction plate of the disc assembly shall be worn without leakage of rivets; Measure with a vernier caliper, and the wear of the working end face of the pressure plate of the cover assembly shall not be greater than 0.3mm; The installation depth of flywheel shall be measured with a depth gauge, and the wear depth shall not be greater than 0.5mm above; The circular arc surface of the separating finger end of the pressure plate shall not be polished; The thrust plane of release bearing shall be free from concave arc; Those that do not conform to the size shall be replaced. However, during the repair process, it should be noted that if a part does not meet the requirements, it should be replaced separately, not in general (for example, if the clutch disc assembly is excessively worn, only the disc assembly should be replaced, and the cover assembly should not be replaced at the same time)

2. Slip fault phenomenon, causes, inspection methods and maintenance

fault phenomenon: serious shaking at the start, the car can not go up, the acceleration is slow, the uphill slope is weak, and the fuel consumption is high. The main reason is that the clutch transmission torque becomes smaller, and the torque cannot be transmitted in serious cases

fault cause:

1) the clutch slave cylinder has no free stroke. When the clutch is slightly worn, the release mechanism sticks to the release finger, resulting in no return space for the clutch release finger, and the compression force of the pressure plate is reduced, resulting in clutch slipping and serious wear

2) driving operation problems: the clutch pedal is not fully released, the half clutch state is used too much, the clutch is overloaded and climbs steep slopes, resulting in serious wear of the clutch

slip test method: use the hand brake to make the car in the full braking state, step down the clutch pedal, then start in the first gear, and then release the clutch pedal. If the engine can stop, it means that the clutch is free of fault. On the contrary, if the clutch slips, it needs to be disassembled and checked. The causes of clutch slipping can be found from the following aspects:

1) driven plate (steel plate) assembly: the friction plate is viscous, carbonized, burned, damaged, and worn to the rivet

2) cover (pressing plate) assembly: the diaphragm spring is damaged, the working end face of the pressure plate is worn more than 0.3mm, deformed, the mounting screw is loose, and the separation finger end jumps more than 1mm

3) flywheel: the wear of flywheel working surface is greater than 0.5mm

4) release mechanism: the release fork has no travel allowance, the clutch pedal has no free stroke, and the release bearing has no travel allowance

5) brake system: the brake system is improperly adjusted and too tight, and the wheel hub is hot after driving.

maintenance method: according to the above five reasons, there are generally two display control modes: digital display and microcomputer control. The following sequence can be used for maintenance of slipping:

step 1: when the slipping test method is used to confirm that there is no clutch slipping, pay attention to the driving method during driving

step 2: under the condition that the clutch slip is confirmed by the slip test method, first check whether the clutch pedal has a free stroke and whether the stroke meets the requirements specified in the maintenance manual of the automobile manufacturer; Check whether the clutch release fork has free stroke (7~8mm) If it does not meet the requirements, it shall be adjusted to the required range. If the fault cannot be eliminated, proceed to the next step

step 3: check and adjust the brake system. If the fault cannot be eliminated, proceed to the next step

step 4: remove the transmission, check the release bearing and release fork for jamming, and replace them if any At the same time, check whether there is oil sticking in the clutch. If so, confirm the source of oil contamination and repair it. Remove the clutch and check whether the wear of the disc assembly, cover assembly and flywheel exceeds the standard. If the wear exceeds the standard, replace it Check whether the friction plate is burnt. If it is slightly burnt, it can be polished with coarse sandpaper before continuing to use. If it is seriously burnt, it needs to be replaced

3. Fault phenomenon, cause, inspection method and maintenance of poor separation (difficult to shift): when the clutch has poor separation, it is difficult to shift. In serious cases, it can only be shifted by stopping the engine

test run inspection method: in case of poor clutch separation, the following methods can be used to confirm the separation point and engagement point:

1) put the engine at idle speed. (the transmission is in neutral)

2) for safety, pull the hand brake and step on the foot brake

3) slowly move the shift lever to the reverse direction without stepping on the clutch pedal (clutch engaged), stop the operation of the shift lever when the sound of gear chirping is heard, and keep the sound of gear chirping

4) step down the clutch pedal slowly while maintaining the gear chirp, and look for the position where the gear chirp disappears. The position where the gear chirp disappears is called "separation point"

5) in this state, press the clutch pedal to completely separate the clutch, keep the shift lever still, slowly release the clutch pedal, and the gear will sound again. This position is called "engagement point". If the separation point and joint point that have laid a solid foundation for the further improvement of the company's technology can not be found under the condition that the separation mechanism is normal, it can be judged as poor clutch separation

fault cause:

1) insufficient clutch pedal separation stroke causes incomplete clutch separation

2) insufficient clutch slave cylinder separation stroke (effective stroke is less than 15mm), resulting in incomplete clutch separation

3) the clutch master cylinder or slave cylinder leaks oil, resulting in insufficient separation stroke and incomplete clutch separation

4) the release fork is deformed, resulting in incomplete clutch release

5) the rivet of the transmission plate of the clutch cover assembly is loose and deformed, resulting in poor separation

6) the input shaft of the transmission is rusted, resulting in the inflexible movement of the clutch driven plate assembly on the input shaft and poor return

7) transmission reasons, such as difficulty in shifting in and out due to excessive gear self-locking force

maintenance method:

step 1: measure the free stroke and separation stroke of the clutch pedal. If they do not meet the requirements, adjust them and confirm whether the separation is normal. If the fault is not eliminated, proceed to the next step

step 2: measure the free stroke and separation stroke of the clutch slave cylinder. If they do not meet the requirements, adjust them (if they cannot be adjusted, check and replace the leaking master cylinder or slave cylinder) and confirm whether the separation is normal. If the fault is not eliminated, proceed to the next step

step 3: remove the transmission and clutch, check whether the release fork is worn and deformed, and replace it if it is deformed; Observe whether the spline holes of the transmission input shaft and clutch disc assembly are rusted. If so, remove the rust and apply an appropriate amount of grease (high temperature resistant grease); Check whether the release bearing rotates flexibly by hand. If it is stuck, replace it; Check whether the three groups of transmission plates of the clutch cover assembly are loose or deformed. If so, replace them When the transmission is not installed, manually pull out all gears to check whether there is any jam or large operating force. If so, repair the transmission During the above operations, if any problem is found, it shall be repaired and then loaded for confirmation until the fault is eliminated

4. Fault phenomenon, cause, inspection method and maintenance of automobile clutch trembling

fault phenomenon: the car body trembles at constant speed, idling, starting and loading

evaluation method (operation sequence)

1) put the engine at idle speed, step on the clutch, put the transmission in gear 1, release the hand brake and foot brake

2) do not step on the accelerator, slowly release the clutch and start

3) it can be dissolved in water. At this time, confirm the vibration of the car body (whether there is shaking)

4) press the clutch as above, and set the transmission to the second gear

5) do not step on the accelerator, slowly release the clutch and start

6) at this time, confirm the vibration of the vehicle body (whether there is shaking)

7) the above methods can be operated in the cold state of engine and transmission and in the hot state of engine and transmission after driving for a period of time

note: ① whether the clutch shakes can only be confirmed in the first and second gears

② the third, fourth and fifth gears cannot start without stepping on the accelerator, and the friction plate is easy to be ablated when starting with a large accelerator

③ if you don't step on the accelerator and start in second gear, sometimes the engine will shut down. At this time, the vibration of the car body can't explain that the clutch is shaking

the clutch trembles. Generally, the friction plate surface shows a toothed contact trace. Sometimes local oil on the friction plate surface will also cause trembling. At this time, the source of oil contamination should be confirmed and repaired

fault cause:

1) the clutch wheel cylinder has no idle stroke

2) the brake system is improperly adjusted and too tight, and the wheel hub is hot after driving

3) the friction plate of the driven plate is slightly ablated and carbonized

4) the friction plate of the driven plate is contaminated with oil

5) the release bearing is jammed

troubleshooting method:

1) adjust the clutch master cylinder and the wheel cylinder to make the idle stroke within 7~8 mm. Unable to call out, replace the parts with excessive wear and the driven disc

2) check and adjust the four-wheel brake

3) if the friction plate is slightly burned, it can be polished with coarse sandpaper and then continue to be used. If the burning is serious, it needs to be replaced

4) remove the oil stain on the friction plate, confirm the source of the oil stain and repair

5) check whether the release bearing is stuck and eliminate the fault of

5 and uneven joint (breakthrough), Cause and inspection method

fault phenomenon: when the car starts, the clutch pedal is slowly raised and the accelerator is lightly pressed. Instead of accelerating steadily, the car suddenly accelerates and moves forward. The root cause is that the pressure plate and friction plate suddenly engage. Test method: after the clutch is fully engaged, control the throttle opening, and alternately accelerate and brake the engine when the vehicle is running to see if there is any unevenness in engagement (burst

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