Clutch slave cylinder piston displacement measurement method

Abstract

The invention discloses a clutch slave cylinder piston displacement measurement method, which comprises the following steps that: when an induction guide rod moves along with a piston, an induction end sequentially passes through each Hall sensor to sequentially cause each Hall sensor to sense the intensity change of a surrounding magnetic field, so as to output a voltage signal to an operational amplifier; a voltage signal amplified by the operational amplifier is input to an ADC acquisition port of the MCU, the MCU controls a PWM output port to output a PWM signal to a vehicle ECU according to the acquired voltage signal, a corresponding relation between a PWM output signal value and the position of the piston is established in the vehicle ECU, and the vehicle ECU displays the position of the piston through the display device according to the PWM output signal value. According to the measuring method, the long-stroke displacement change of the piston can be measured in real time, real-time feedback of clutch control in the running process of the vehicle is achieved, and monitoring and data collection of clutch control can be achieved by a vehicle master controller.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile clutch operation, and relates to a clutch slave cylinder, and in particular to a clutch slave cylinder piston displacement measurement method. Background Art

[0002] The clutch slave cylinder (slave cylinder for short) is an important component in the automobile clutch control system. Its function is to control the engagement and disengagement of the clutch, thereby cutting off or transmitting the power output of the engine.

[0003] like Figure 1 As shown, in the automobile clutch operating system, the driver steps on the clutch pedal 1, and the push rod connected to the clutch pedal pushes the piston in the master cylinder 2 to move, and the brake fluid in the master cylinder oil pot flows outward under pressure. The low-pressure brake fluid enters the slave cylinder 3 through the oil pipe, which will push the air valve inside the slave cylinder 3 to open, and then the compressed air enters the air cavity inside the slave cylinder 3, and the compressed air pushes the piston of the slave cylinder to move, and then pushes the push rod connected to the piston to output thrust and displacement to the outside. Under the action of the push rod of the slave cylinder 3, the release fork 4 rotates around the fulcrum, and drives the release bearing and diaphragm spring in the clutch 5 to move in turn, so that the pressure applied by the diaphragm spring on the pressure plate 51 is released, so that the pressure plate 51 and the driven plate 52 are separated. When the driver releases the pedal, the brake fluid returns from the slave cylinder 3 to the master cylinder 2 oil pot, the internal air valve of the slave cylinder 3, and the compressed air in the air cavity of the slave cylinder 3 is discharged, and the slave cylinder does not output thrust and displacement, and the diaphragm spring of the clutch is reset, and the pressure plate 51 is pressed again to combine with the driven plate 52.

[0004] It can be seen from the above description that the piston of the slave pump 3 moves back and forth during the operation of the clutch, that is, the piston will have displacement changes, but the existing slave pump cannot measure the long-stroke displacement changes of the piston during operation. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a clutch slave cylinder piston displacement measurement method, which can automatically measure the long-stroke displacement change of the piston when the slave cylinder is working, so as to overcome the shortcomings of the prior art.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A clutch sub-pump piston displacement measurement method, the clutch has an air cavity, a piston is arranged in the air cavity, and also includes a displacement sensor, the displacement sensor includes a sensing guide rod and a circuit board, one end of the sensing guide rod is a connection end connected to the piston, and the other end is a magnetic sensing end, the circuit board includes an MCU, an operational amplifier and a plurality of Hall sensors distributed at equal intervals along a direction parallel to the sensing guide rod, the measurement method is:

[0008] When the sensing guide rod moves with the piston, the sensing end passes through each of the Hall sensors in sequence, causing each of the Hall sensors to sense changes in the surrounding magnetic field in sequence, and then output a voltage signal to the operational amplifier. The voltage signal amplified by the operational amplifier is input to the ADC acquisition port of the MCU. The MCU controls the PWM output port to output a PWM signal to the vehicle ECU based on the collected voltage signal. A corresponding relationship between the PWM output signal value and the position of the piston is established in the vehicle ECU. The vehicle ECU displays the position of the piston through a display device based on the PWM output signal value.

[0009] By adopting the above technical solution, when the clutch slave cylinder is working, the displacement sensor can measure the long-stroke displacement changes of the piston in real time, realizing real-time feedback of the clutch control of the vehicle during driving, which is beneficial for the vehicle main control to monitor and collect data on the clutch control.

[0010] In a specific implementation manner of the present invention, the MCU performs linear fitting on the voltage signals output by each of the Hall sensors after being collected by the ADC collection port, and the MCU controls the PWM output port to output a PWM signal according to the data after the linear fitting.

[0011] In a specific implementation manner of the present invention, the MCU only collects the voltage signal in the best linear region of the output voltage signal curve of each Hall sensor through the ADC acquisition port.

[0012] In a specific embodiment of the present invention, the standard voltage range of the optimal linear region collected by the MCU is V min To V max , when the actual range of the MCU acquisition narrows to V min窄 To V max窄 When calculating, the MCU dynamically compensates the collected voltage through the formula "V0 = K × V1 + B" and then maps it back to the standard voltage range, where V0 is the voltage value after dynamic compensation, V1 is the voltage value collected before dynamic compensation, K is the compensation coefficient, and B is the compensation constant. By adopting this technical solution, the present invention realizes dynamic compensation of voltage signals for the decrease in measurement accuracy of the displacement sensor, thereby ensuring the measurement accuracy and improving the accuracy of displacement measurement.

[0013] The measuring method of the present invention also realizes monitoring of the wear of the clutch pressure plate. The monitoring is that when the driver releases the clutch pedal, if the displacement position of the piston after returning measured by the measuring method deviates from the initial position and exceeds a set threshold, it indicates that the clutch pressure plate is severely worn. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0015] Figure 1 It is a schematic diagram of the structure of the clutch control system;

[0016] Figure 2 It is a three-dimensional structural schematic diagram of the slave pump of the present invention;

[0017] Figure 3 is an internal cross-sectional view of a slave pump of the present invention;

[0018] Figure 4 is a three-dimensional schematic diagram of a displacement sensor;

[0019] Figure 5 It is the main view of the displacement sensor;

[0020] Figure 6 It is the rear view of the displacement sensor;

[0021] Figure 7 for Figure 5 Middle MM section view;

[0022] Figure 8 for Figure 5 Middle NN section view;

[0023] Fig. 9 Schematic diagram of the bushing structure

[0024] Fig.10 This is the circuit board principle block diagram of the displacement sensor;

[0025] Fig.11 It is the voltage output curve of the Hall chip;

[0026] Fig.12 A schematic diagram showing the relationship between the magnetic field changes sensed by each Hall chip, the output voltage and the piston position;

[0027] Fig.13 A schematic diagram showing the relationship between the voltage digital value collected by each ADC acquisition port and the piston position;

[0028] Fig.14 A schematic diagram showing the relationship between the digital value and the piston position after data linear fitting is shown.

[0029] Fig.15 The schematic diagram shows the principle that the change of piston position causes the change of magnetic field and voltage in turn, and then the MCU performs linear fitting and generates a characteristic curve;

[0030] Fig.16 Schematic diagram of the narrowing of the optimal linear region after the Hall chip accuracy decreases. DETAILED DESCRIPTION

[0031] In order to clearly explain the present invention, the technical terms involved in the present invention are first explained as follows:

[0032] MCU-Microcontroller Unit, Chinese translation: micro control unit;

[0033] ADC-Analog to Digital Converter, Chinese translation: analog to digital converter;

[0034] ECU-Engine Control Unit, Chinese translation: engine control unit;

[0035] LDO-Low-dropout regulator, Chinese translation: low voltage difference regulator;

[0036] OA-Operational amplifier, Chinese translation: operational amplifier.

[0037] like Figure 2 , Figure 3 As shown, the clutch slave cylinder of the present invention includes a pump housing 100 , a piston, a push rod 300 and a displacement sensor 500 .

[0038] The pump housing 100 has an air cavity 110 and a liquid cavity 120 inside.

[0039] The liquid cavity 120 is located at the rear of the gas cavity 110, and the liquid cavity 120 and the gas cavity 110 are connected and coaxially arranged. The cross-sectional area of ​​the gas cavity 110 is larger than the cross-sectional area of ​​the liquid cavity 120. The front end opening of the gas cavity 110 is installed with a cover plate 111.

[0040] The piston includes a piston rod 210 and a piston disc 220. The piston disc 220 is disposed in the air cavity 110 and is movable in the air cavity 110. The piston rod 210 is disposed in the liquid cavity 120 and the front end thereof extends into the air cavity 110 and is connected to the piston disc 220. A return spring 230 is disposed between the piston disc 220 and the rear wall of the air cavity 110.

[0041] In order to measure the displacement of the piston (ie, the piston plate 220 ), the pump housing 100 further has a mounting hole 140 communicating with the air cavity 110 at the rear of the air cavity 110 . The displacement sensor 500 is fixed in the mounting hole 140 .

[0042] like Figures 4 to 9 As shown, the displacement sensor 500 includes a housing 510 , a circuit board 520 , a sensing guide rod 530 , a bushing 540 and a magnet 550 .

[0043] Among them, the shell 510 is fixed in the mounting hole 140, and a sealing ring is arranged between the two for sealing. The shell 510 is composed of a shell body 510a and an end cover 510b. The shell body 510a is divided into a circuit cavity 511, a guide rod cavity 512 and a pin interface 513. The guide rod cavity 512 is parallel to the circuit cavity 511. The guide rod cavity 512 has an opening leading to the air cavity 110, and the circuit cavity 511 has an opening away from the air cavity 110. The end cover 510b blocks the opening of the circuit cavity 511. The circuit board 520 is installed and fixed in the circuit cavity 511. The pin interface 513 is perpendicular to the circuit cavity 511, and a pin 513a electrically connected to the circuit board 520 is fixed inside. The signal generated by the sensor can be transmitted to the vehicle ECU by connecting the vehicle ECU through the pin interface 513 via the wiring harness.

[0044] The bushing 540 is fixed in the guide rod cavity 512 and has an opening leading to the air cavity 110. One end of the induction guide rod 530 is a connection end 530a connected to the piston disc 220, and the other end is a sensing end 530b located in the guide rod cavity 512. Accordingly, the induction guide rod 530 is divided into a thick rod portion 531 located in the bushing 540 near the sensing end 530b and a thin rod portion 532 located outside the bushing 540 near the connection end 503a. The length of the thick rod portion 531 is equivalent to the length of the bushing 540, and the thick rod portion 531 has a mounting cavity 533 at the position of the sensing end 530b. The magnet 550 is fixedly installed in the mounting cavity 533.

[0045] Hall chips are evenly spaced on the circuit board 520 along the length of the sensing rod 530. When the sensing rod 530 moves in the bushing 540, each Hall chip 523 generates different voltage signal outputs as the magnet 550 approaches and moves away, thereby measuring the displacement of the piston disk 220.

[0046] like Fig. 9 As shown, the inner wall of the bushing 540 is circumferentially distributed with semicircular ridges 541 extending in the axial direction, and the circumferential surface of the thick rod portion 531 is in line contact with the ridges 541. Such a structure reduces the friction between the bushing and the sensing guide rod, and allows a gap between the inner wall of the bushing and the sensing guide rod, so that the gas in the bushing can be discharged during the movement of the sensing guide rod, making the sliding of the sensing guide rod more stable and smooth. In addition, the outer wall of the bushing 540 has a convex ring 542 stuck in the shell body 510a. The bushing 540 and the shell body 510a can be fixed together by injection molding. With such a structure, the bushing 540 is firmly fixed in the shell 510, and loosening between the bushing 540 and the shell 510 is avoided, ensuring the reliable operation of the sensor. In this embodiment, the material of the bushing 540 is nylon, which has the effect of wear resistance and lubrication. Using nylon as the bushing is not only conducive to the smooth movement of the sensing guide rod in the bushing, but also can reduce the wear of the bushing.

[0047] like Fig.10 As shown, the circuit board 520 includes a power supply main module 521, an operational amplifier 522, an MCU, and a plurality of Hall chips 523. The MCU has an ADC acquisition port 524 and a PWM output port 525. In this embodiment, a total of five Hall chips 523 (i.e., hall1, hall2, hall3, hall4, and hall15) are used, and the voltage signals are respectively transmitted to five operational amplifiers 522 (i.e., operational amplifier 1, operational amplifier 2, operational amplifier 3, operational amplifier 4, and operational amplifier 5) for amplification processing. The MCU has five ADC acquisition ports 524 (i.e., ADC1, ADC2, ADC3, ADC4, and ADC5) for respectively acquiring the amplified voltage signals from the five operational amplifiers 522.

[0048] The power supply module 521 includes an input protection circuit and an LDO module. The input protection circuit has the functions of anti-reverse connection, anti-surge, anti-static, and anti-overvoltage. The LDO module has the functions of voltage regulation and voltage reduction, overcurrent protection, overtemperature protection, power supply isolation, and improving the power supply voltage noise suppression coefficient, filtering, and limiting. Since the input protection circuit and the LDO module are both mature circuit modules in the prior art, the detailed circuit structures of the two are not introduced in detail.

[0049] The input protection circuit obtains 5V voltage from the vehicle ECU and gives it to the LDO module for processing. The LDO module converts the 5V voltage obtained from the vehicle ECU into 3.3V voltage to power each Hall chip 523, each operational amplifier 522 and MCU respectively.

[0050] When the piston disc 220 moves in the air cavity 110, driving the magnet 550 at the inductive end of the inductive guide rod 530 to pass through each Hall chip 523 in sequence, each Hall chip 523 will sense the change of the surrounding magnetic field in sequence, and then generate a changing voltage signal. Since the voltage signal generated by the Hall chip 523 is relatively weak, it needs to be input into the operational amplifier 522 for amplification. For example, when the magnet passes through, each Hall chip 523 of this embodiment will sense the magnetic field change range of -8mT to +8mT, and the voltage signal range generated is 0.28V to 1.72V. This voltage signal is too weak, so the operational amplifier 522 needs to be amplified twice, thereby generating a voltage signal of 0.56V to 3.44V for the MCU.

[0051] like Fig.11 As shown, the voltage generated by the Hall chip has the best linearity in the range of 1.04V to 2.96V. Therefore, the ADC acquisition port 524 in the MCU only acquires the voltage in the best linear region, that is, between 1.04V and 2.96V.

[0052] Fig.12 The relationship between the magnetic field change sensed by each Hall chip, the output voltage and the piston position is shown. The output voltage of each Hall chip 523 corresponds to the position of the piston. Therefore, each position will correspond to the voltage collected by each Hall chip 523 and the 5-way ADC acquisition port 524. When the finished product is calibrated at the factory, the sensing guide rod 530 will be moved from 0 to 85mm. At this time, the five-way ADC voltage is collected, and the voltage and actual displacement data can be obtained, and this data is written to the register of the MCU. When the client uses it, the next time the sensing guide rod appears in the same position, the corresponding position can be read, and the relationship between the voltage and position can be obtained (for example: the voltage collected by ADC4 is 1.52V, and then it can be known that the position of the piston is 55mm).

[0053] Therefore, when the voltage collected by ADC1 is 2~2.96V, the corresponding piston position is 0-10mm; when the voltage collected by ADC2 is 1.04~2.96V, the corresponding piston position is 10-30mm; when the voltage collected by ADC3 is 1.04~2.96V, the corresponding piston position is 30-50mm; when the voltage collected by ADC4 is 1.04~2.96V, the corresponding piston position is 50-70mm; when the voltage collected by ADC5 is 1.04~2.96V, the corresponding piston position is 70-90mm.

[0054] And the PWM signal output value of the PWM output port 525 is also corresponding to the piston position. It is known that the piston moves 85mm, and the effective PWM signal output value is 10%-90%. Then (90-10) / 85=0.94% / mm, that is, for every 1mm of movement, the PWM signal output value changes by 0.94%. Therefore, when the ADC4 acquisition voltage is 1.52V, the PWM signal output value=10%+55×0.94%=61.77%.

[0055] When the ADC acquisition port is collecting voltage, it will convert the analog voltage signal into a digital value. For example, for a 12-bit ADC, 3.6V reference voltage, the converted digital value of the voltage 1.8V is 2048 (i.e. 1.8 / 3.6×4096=2048). Fig.13 The corresponding relationship between the piston displacement value and the voltage digital quantity collected by each ADC acquisition port is shown.

[0056] The digital quantities collected by each ADC acquisition port 524 are distributed on their own straight line segments, forming multiple line segments, but all of them change linearly and have the same slope. Therefore, the MCU can perform linear fitting on the digital quantities collected by the five ADC acquisition ports as a whole, fitting them into a continuous straight line, where the digital quantities change linearly and continuously from 1600 to 14400, such as Fig.14As shown in FIG. 2 , linearly fitting multiple segments of data to continuous data on a straight line is a prior art, which will not be elaborated here.

[0057] Then use the digital value (1600-14400) at the corresponding displacement position after fitting as the numerator of the PWM signal. Since the clock of the PWM output port is 8M and the frequency of the PWM output port is 500Hz (ie 0.5KHz, 0.0005MHz), 8 / 0.0005=16000 is the count of one cycle, which is used as the denominator. In this way, by dividing the numerator by the denominator, we can get the corresponding PWM signal output value at the corresponding position. For example, the corresponding digital value after fitting at the starting point 0mm is 1600, and the obtained PWM signal output value = 1600 / 16000×100%=10%; the corresponding digital value after fitting at the end point 85mm is 14400, and the obtained PWM signal output value = 14400 / 16000×100%=90%, and the corresponding digital value after fitting at the position 55mm is 9882.56, and the obtained PWM signal output value is 9882.56 / 16000×100%=61.77%. In this way, the MCU realizes the control of the PWM signal output.

[0058] In summary, since there is a one-to-one correspondence between the PWM signal output value and the piston position, this one-to-one correspondence can be stored in the vehicle ECU. Fig.15 As shown, when the piston disc 220 is displaced in the air cavity, the magnetic sensing end of the sensing guide rod 530 (i.e., the magnet 550) passes through each Hall chip in sequence, which will cause each Hall chip to sense different magnetic field sizes in sequence, and then output corresponding voltage signals, which are amplified by the operational amplifier and then digitally converted through the ADC acquisition port in the MCU. After the MCU performs data linear fitting, the voltage digital quantity corresponding to each piston position is obtained after fitting, and then the output characteristic curve of the linear corresponding piston position of the PWM signal output value is calculated and generated. Therefore, when the piston disc is displaced to different positions, the displacement sensor will output the corresponding PWM signal output value to the vehicle ECU, and finally the vehicle ECU controls the display device to display the position of the piston according to the one-to-one correspondence between the PWM signal output value and the position of the piston. The display device can be a vehicle dashboard, a central control display screen, or a terminal device connected to the vehicle ECU during maintenance.

[0059] After the displacement sensor works for a long time, the mechanical part will be worn and the magnetic field of the magnet will be attenuated, which will affect the accuracy of the product. Fig.16As shown in the figure, the best linear region collected by the MCU becomes narrower, with the highest point dropping from 2.96V to 2.9V and the lowest point rising from 1.04V to 1.1V. This phenomenon of the narrowing of the best linear region will reduce the measurement accuracy of the displacement sensor, resulting in inaccurate measurement position.

[0060] In order to offset the impact of mechanical wear and magnet magnetic field attenuation, dynamic compensation is required. The specific compensation methods are as follows:

[0061] When leaving the factory, the voltage range of each Hall chip output will be collected and calibrated to the standard voltage range V min To V max (In this embodiment, it is 1.04V to 2.96V). The MCU has a storage function to store the mapping relationship between the actual collected voltage signal and the standard voltage range. When working, the MCU will compare the collected voltage with the stored voltage. After running for a period of time, the output voltage range of the Hall chip becomes narrower, and the voltage range actually collected by the MCU will become V min窄 To V max窄 (i.e. the warning voltage range, for example, in this embodiment it is 1.1V-2.9V). At this time, the MCU will dynamically compensate the collected voltage signal through the formula "V0=K×V1+B" to map it back to the standard voltage range of 1.04-2.96V during calculation, where V0 is the voltage value after dynamic compensation, V1 is the voltage value collected before dynamic compensation, K is the compensation coefficient, and B is the compensation constant. In this embodiment, since the standard voltage range is 1.04V-2.96V and the warning voltage range is 1.1V-2.9V, the value of the compensation coefficient K is 1.067, and the value of the compensation constant B is -0.133. In this way, when the actual voltage range collected by the MCU is narrowed to the warning voltage range of 1.1V-2.9V, dynamic compensation is performed through the formula, and the lowest point voltage value V after dynamic compensation is 0min =1.1×1.067-0.133=1.04, the highest point voltage value after dynamic compensation V 0max =2.9×1.067-0.133=2.96, so that the voltage signal actually collected by the MCU is mapped back to the corresponding voltage in the standard voltage range of 1.04V-2.96V, ensuring the measurement accuracy. The MCU stores the mapping relationship between the new actual collected voltage signal and the standard voltage range. When the voltage range collected by the MCU is narrowed to 1.1V-2.9V again, the MCU will dynamically compensate the collected voltage signal through the formula "V0=K×V1+B" to map it back to the standard voltage range of 1.04-2.96V during calculation, and so on, thereby ensuring the measurement accuracy of the displacement sensor.

[0062] The clutch slave cylinder piston displacement measurement method of the present invention can also monitor the wear of the clutch pressure plate: when the driver releases the clutch pedal, the displacement position of the piston after returning to the position measured by the measurement method of the present invention deviates from the initial position by more than the set threshold value, indicating that the clutch pressure plate is seriously worn and needs to be replaced. For example, before the driver steps on the clutch pedal, the initial position of the piston in the air cavity is 40mm. When the clutch pedal is stepped on, the piston moves forward, driving the push rod, and then driving the clutch pressure plate to separate from the driven plate. When the driver releases the clutch pedal, if the clutch pressure plate is not worn, the piston will just return to the initial position of 40mm under the balanced action of the pressure plate reaction force and the return spring. However, when the pressure plate is worn, the pressure plate becomes thinner, which makes the piston deviate backward from the initial position when returning. The more serious the wear of the pressure plate, the more the piston deviates backward from the initial position when returning. For this reason, a threshold value can be set in the vehicle ECU. When the degree of deviation exceeds the set threshold value, it means that the clutch pressure plate is seriously worn and needs to be replaced. The vehicle ECU can also further issue an alarm based on this.

[0063] It can be seen from the above detailed description that the clutch slave cylinder piston displacement measurement method of the present invention realizes the accurate measurement of the long stroke of the piston displacement, and also has a dynamic compensation function, thereby ensuring the measurement accuracy and having the advantage of accurate measurement position.

Claims

1. A clutch sub-pump piston displacement measurement method, the clutch has an air cavity, a piston is arranged in the air cavity, and also includes a displacement sensor, the displacement sensor includes a sensing guide rod and a circuit board, one end of the sensing guide rod is a connection end connected to the piston, and the other end is a magnetic sensing end, the circuit board includes an MCU, an operational amplifier and a plurality of Hall sensors distributed at equal intervals along a direction parallel to the sensing guide rod, the measurement method is: When the sensing guide rod moves with the piston, the sensing end passes through each of the Hall sensors in sequence, causing each of the Hall sensors to sense changes in the surrounding magnetic field in sequence, and then output a voltage signal to the operational amplifier. The voltage signal amplified by the operational amplifier is input to the ADC acquisition port of the MCU. The MCU controls the PWM output port to output a PWM signal to the vehicle ECU based on the collected voltage signal. A corresponding relationship between the PWM output signal value and the position of the piston is established in the vehicle ECU. The vehicle ECU displays the position of the piston through a display device based on the PWM output signal value.

2. The clutch slave cylinder piston displacement measurement method according to claim 1, characterized in that: The MCU performs linear fitting on the voltage signals output by each of the Hall sensors after the voltage signals are collected by the ADC collection port, and the MCU controls the PWM output port to output a PWM signal according to the data after the linear fitting.

3. The clutch slave cylinder piston displacement measurement method according to claim 2, characterized in that: The MCU only collects the voltage signal in the best linear region of the output voltage signal curve of each Hall sensor through the ADC acquisition port.

4. The clutch slave cylinder piston displacement measurement method according to claim 4, characterized in that: The standard voltage range of the optimal linear region collected by the MCU is V min To V max , when the actual range of the MCU acquisition narrows to V min窄 To V max窄 When calculating, the MCU dynamically compensates the collected voltage through the formula "V0=K×V1+B" and then maps it back to the standard voltage range, where V0 is the voltage value after dynamic compensation, V1 is the voltage value collected before dynamic compensation, K is the compensation coefficient, and B is the compensation constant.

5. The clutch slave cylinder piston displacement measurement method according to claim 4, characterized in that: The measuring method monitors the wear of the clutch pressure plate. When the driver releases the clutch pedal, if the displacement position of the piston after returning measured by the measuring method deviates from the initial position and exceeds a set threshold, it indicates that the clutch pressure plate is severely worn.

6. The clutch slave cylinder piston displacement measurement method according to any one of claims 1 to 5, characterized in that: The displacement sensor further comprises a shell and a magnet. The shell is divided into a guide rod cavity and a circuit cavity which are parallel to each other. The magnet is installed in the sensing end, and the circuit board is installed in the circuit cavity.

7. The clutch slave cylinder piston displacement measurement method according to claim 6, characterized in that: A bushing is fixed in the guide rod cavity, and the sensing end is located in the bushing and slides.

8. The clutch slave cylinder piston displacement measurement method according to claim 7, characterized in that: The inner wall of the bushing is circumferentially provided with ridges extending in the axial direction, and the circumferential surface of the sensing end is in contact with the ridges.

9. The clutch slave cylinder piston displacement measurement method according to claim 7, characterized in that: The bushing is made of nylon.

Images