Wheel cylinder structure with displacement sensor

Abstract

The utility model discloses a wheel cylinder structure with a displacement sensor, which comprises a pump shell, a displacement sensor, an air inlet channel and a liquid inlet channel, the piston is provided with a piston disc arranged in the air cavity; the air valve is arranged in the air inlet channel; the push rod is connected with the piston; a displacement sensor is installed on the pump shell, and an induction guide rod of the displacement sensor extends into the air cavity to be connected with the piston disc. According to the utility model, the displacement of the piston of the wheel cylinder can be measured when the wheel cylinder works, the real-time feedback of the working state of the wheel cylinder in the running process of a vehicle is realized, and the monitoring and data acquisition of the wear state of a clutch driven disc can be realized by a vehicle master controller.

Description

Technical Field

[0001] The utility model belongs to the technical field of automobile clutch operation, and relates to a clutch slave cylinder, in particular to a slave cylinder structure with a displacement sensor. Background Art

[0002] The clutch slave cylinder (short for slave cylinder) is an important component of 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 a car clutch operating system, when the driver depresses the clutch pedal 1, the push rod connected to the clutch pedal pushes the piston in the master cylinder 2. The brake fluid in the master cylinder reservoir is pressurized and flows outward. The low-pressure brake fluid enters the slave cylinder 3 through the oil pipe, pushing the air valve inside the slave cylinder 3 to open, allowing compressed air to enter the air chamber inside the slave cylinder 3. The compressed air pushes the piston in the slave cylinder 3 to move, which in turn pushes the push rod connected to the piston, outputting thrust and displacement. Driven by the push rod of the slave cylinder 3, the release fork 4 rotates about the fulcrum, which in turn drives the release bearing and diaphragm spring in the clutch 5. This releases the pressure applied by the diaphragm spring on the pressure plate 51, allowing the pressure plate 51 to separate from the driven plate 52. When the driver releases the pedal, the brake fluid returns from the slave cylinder 3 to the oil tank of the master cylinder 2, the internal air valve of the slave cylinder 3 is closed, the compressed air in the air cavity of the slave cylinder 3 is discharged, the slave cylinder has no output thrust and displacement, the diaphragm spring of the clutch is reset, and the pressure plate 51 is re-pressed to engage with the driven plate 52, and the piston of the slave cylinder 3 is reset at the same time.

[0004] As can be seen from the above description, the piston of slave pump 3 moves back and forth during clutch operation, meaning its displacement varies. However, since the piston's motion within the slave pump cannot be directly observed, it is impossible to determine whether the piston's travel meets the required clutch disengagement stroke. Furthermore, due to wear and thinning of the clutch's driven disc during use, the slave pump piston's position continuously shifts back when not in operation. While existing slave pump structures can measure piston position using a wear indicator needle, manual operation is inconvenient and does not allow for integrated electrical signals and real-time monitoring of the driven disc's wear status via a central control instrument. Utility Model Content

[0005] The technical problem to be solved by the utility model is to provide a slave pump structure with a displacement sensor, so that the slave pump can measure the displacement change of the piston and monitor the wear condition of the driven plate of the clutch in real time when working, thereby overcoming the shortcomings of the existing technology.

[0006] In order to solve the above technical problems, the technical problems to be solved by this utility model are:

[0007] A slave pump structure with a displacement sensor, comprising:

[0008] A pump housing, wherein the pump housing has an air cavity, an air inlet channel and a liquid inlet channel;

[0009] a piston having a piston disc disposed in the air cavity;

[0010] an air valve, the air valve being arranged in the air inlet duct;

[0011] a push rod connected to the piston;

[0012] Brake fluid enters the air inlet passage through the fluid inlet passage to drive the air valve to open, and compressed air enters the air chamber through the air inlet passage to drive the piston disc and the push rod to move forward; when no brake fluid enters the air inlet passage through the fluid inlet passage, the air valve is reset to close, and the piston disc and the push rod are reset;

[0013] A displacement sensor is installed on the pump housing, and a sensing guide rod of the displacement sensor extends into the air cavity and is connected to the piston disc.

[0014] With the above technical solution, since a displacement sensor is installed on the pump housing, and the sensing guide rod of the displacement sensor extends into the air cavity and is connected to the piston disc, when the piston disc moves and displaces in the air cavity, the sensing guide rod of the displacement sensor also displaces accordingly, so that the displacement sensor can sense the displacement change of the piston disc, thereby measuring the displacement change of the piston of the slave cylinder, and can also judge the wear state of the clutch driven disc through the position offset data when the piston is reset.

[0015] In the present invention, the displacement sensor includes a housing, a circuit board, and the sensing guide rod. The housing is divided into a guide rod cavity and a circuit cavity that are parallel to each other. The sensing guide rod is divided into a connecting end connected to the piston disk and a sensing end that is located and slides in the guide rod cavity. A magnet is installed in the sensing end. The circuit board is installed in the circuit cavity, and a plurality of Hall chips are evenly spaced along the length of the sensing guide rod. Due to the long displacement stroke of the piston, a corresponding displacement sensor is not directly available on the market. The present invention distributes multiple Hall chips evenly spaced on the circuit board. When the magnet on the sensing guide rod moves in the guide rod cavity, it approaches or moves away from each Hall chip in turn. Each Hall chip will sense the change in the magnetic field in turn and can output a different voltage. Then, according to the positional relationship between the different voltages output by each Hall chip and the position of the piston disk, the long-stroke displacement change of the piston in the slave pump can be ultimately measured.

[0016] In the present invention, a bushing is fixed within the guide rod cavity, and the sensing end slides within the bushing. The sensing guide rod is divided into a thick rod portion located near the sensing end and capable of sliding within the bushing, and a thin rod portion located near the connecting end and outside the bushing. The bushing provides protection and guidance for the sliding of the sensing guide rod, while the thick rod and thin rod, allowing the thick rod to slide within the bushing, stabilize the sliding of the sensing guide rod.

[0017] In the present invention, the inner wall of the bushing is circumferentially provided with axially extending ridges, with the circumferential surface of the thick rod portion contacting these ridges. The use of ridges on the inner wall of the bushing reduces friction between the bushing and the sensing rod, and creates a gap between the inner wall of the bushing and the sensing rod, allowing gas within the bushing to escape during the movement of the sensing rod, resulting in smoother and more stable sliding of the sensing rod.

[0018] In the present invention, the outer wall of the bushing is provided with a convex ring which is clamped in the housing. Such a structure enables the bushing to be firmly fixed in the housing, avoids loosening between the bushing and the housing, and ensures reliable operation of the sensor.

[0019] In the present invention, the bushing is made of nylon, which is wear-resistant and lubricating. Using nylon as the bushing not only facilitates the smooth movement of the sensing guide rod in the bushing, but also reduces the wear of the bushing.

[0020] From the above detailed description, it can be seen that the utility model can measure the displacement of the slave cylinder piston when the slave cylinder is working, and realize real-time feedback of the working status of the slave cylinder during vehicle driving, which is beneficial for the vehicle main control to monitor and collect data on the wear status of the driven plate of the clutch. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0022] Figure 1 It is a structural diagram of the clutch control system;

[0023] Figure 2 This is a schematic diagram of the three-dimensional structure of the slave pump of the present utility model;

[0024] Figure 3 This is a front view of the slave pump of the present utility model;

[0025] Figure 4 It is a rear view of the slave pump of the present utility model;

[0026] Figure 5 for Figure 4 Middle AA section view;

[0027] Figure 6 for Figure 4 Middle CC section view;

[0028] Figure 6A for Figure 6 An enlarged view of the air valve in FIG.

[0029] Figure 7 for Figure 4 Middle DD section view;

[0030] Figure 7A for Figure 7 Enlarged view of point E in the middle;

[0031] Figure 7B for Figure 7 Enlarged view of point F in the middle;

[0032] Figure 7C for Figure 7 Enlarged view of point G in the middle;

[0033] Figure 8 for Figure 4 A cross-sectional view in the HH direction in the intake state;

[0034] Figure 8A for Figure 8 Enlarged view at point I in the middle;

[0035] Figure 9 for Figure 4 A cross-sectional view in the exhaust state along the HH direction;

[0036] Figure 9A for Figure 9 Enlarged view of J in the middle;

[0037] Figure 10 for Figure 4 Middle KK section view;

[0038] Figure 10A for Figure 10 Enlarged view of L in the middle;

[0039] Figure 11 for Figure 3 Middle BB section view;

[0040] Figure 12 This is a schematic diagram of the slave cylinder of the present invention being arranged next to the gearbox;

[0041] Figure 13 is a three-dimensional schematic diagram of a displacement sensor;

[0042] Figure 14 It is the main view of the displacement sensor;

[0043] Figure 15 It is the rear view of the displacement sensor;

[0044] Figure 16 for Figure 14 Middle MM section view;

[0045] Figure 17 for Figure 15 Middle NN section view;

[0046] Figure 18 It is a structural diagram of the bushing;

[0047] Figure 19 This is the principle block diagram of the displacement sensor circuit board;

[0048] Figure 20 This is the voltage output curve of the Hall chip;

[0049] Figure 21 A schematic diagram showing the relationship between the magnetic field changes sensed by each Hall chip, the output voltage and the piston position. DETAILED DESCRIPTION

[0050] like Figures 2 to 6 , combined Figure 7 、 Figure 11 As shown, the sub-pump structure with a displacement sensor of the present invention includes a pump housing 100 , a piston, a push rod 300 , an air valve 400 , and a displacement sensor 500 .

[0051] The pump housing 100 has an air cavity 110 , a liquid cavity 120 , an air inlet 410 and a liquid inlet 420 therein.

[0052] The liquid cavity 120 is located at the rear of the air cavity 110. The liquid cavity 120 and the air cavity 110 are connected and arranged coaxially. The cross-sectional area of ​​the air cavity 110 is larger than the cross-sectional area of ​​the liquid cavity 120. A cover plate 111 is installed at the front opening of the air cavity 110.

[0053] The piston includes a piston rod 210 and a piston plate 220. The piston rod 210 is disposed in the liquid chamber 120, with its front end extending into the air chamber 110. The piston plate 220 is disposed within the air chamber 110 and fixed to the front end of the piston rod 210. Furthermore, a return spring 230 is disposed within the air chamber 110. This return spring 230 is positioned within the air chamber 110 and between the piston plate 220 and the rear wall of the air chamber 110.

[0054] Combine Figure 7A As shown, there is a first gap between the piston rod 210 and the inner wall of the liquid chamber 120. A first sealing ring 131 and a second sealing ring 135 are provided in the liquid chamber 120 near the front end of the air chamber 11 to seal the first gap.

[0055] Combine Figure 7CAs shown, there is a second gap between the circumference of the piston disc 220 and the interior of the air cavity 110. A third sealing ring 141 is provided on the circumference of the piston disc 220 to seal the second gap.

[0056] Combine Figure 7B As shown, the front end face of the piston rod 210 is also provided with a ball socket 211. The push rod 300 passes through the cover plate 111, and its rear end has a semicircular ball head 301. The ball head 301 is installed in the ball socket 211 and is fixed by an elastic clip 302. The elastic clip 302 is a conical tubular structure that allows the ball head 301 to pass through. Its large end 302a is stuck on the hole wall of the ball socket 211, and the small end 302b is stuck on the ball head 301, fixing the ball head 301 to prevent the ball head 301 from falling out of the ball socket. In addition, this fixing method will not limit the rotation of the ball head 301 in the ball socket 211, thereby allowing the push rod 300 to swing appropriately when transmitting force outward.

[0057] For example Figure 7 and Figure 8 As shown, one end of return spring 230 abuts against a positioning groove 231 on the inner surface of piston plate 220, while the other end abuts against the rear wall of air chamber 110 and is positioned by a raised platform 232 protruding from the rear wall and surrounding the fluid chamber. The function of return spring 230 is to balance the reaction force of the external clutch pressure plate when there is no compressed air in air chamber 110 and no brake fluid in fluid chamber 120, ensuring that piston plate 220 always returns to its initial position in air chamber 110.

[0058] Combine Figure 2 、 Figure 6 and Figure 11 As shown, the air inlet 410 is arranged parallel to the liquid chamber 120. Figure 6 As shown, the air valve 400 is installed in the air intake duct 410. When brake fluid enters the air intake duct 410, it drives the air valve 400 to open, allowing compressed air to enter the air cavity 110 through the air intake duct 410, driving the piston plate 220 to move forward, thereby driving the push rod 300 forward. When the brake fluid stops entering the air intake duct, the air valve 400 will close, causing the piston plate 220 to retreat under the reaction force of the clutch pressure plate. When the piston plate 220 retreats, it discharges the compressed air in the air cavity 110 to the outside of the pump housing 100. Specifically, the air valve 400 includes a valve seat 401, a sealing plug 402, a cylinder 403, a first spring 404, a valve core 406, a second spring 407, and an end cover 408.

[0059] Combine Figure 8 and Figure 8AAs shown, the valve seat 401 and the cylinder 403 are fixed in the air inlet duct 410 by being compressed by the end cover 408. The valve seat 401 divides the air inlet duct 410 into a front chamber 410a and a rear chamber 410b. The sealing plug 402 is located in the rear chamber 410b, and its plug portion initially seals the valve seat opening 401a of the valve seat 401. The cylinder 403 is located behind the sealing plug 402. The plunger portion of the sealing plug 402 is located in the cylinder 403, and the two are sealed by a fourth sealing ring 403a. The sealing plug 402 can move axially forward and backward under the guidance of the cylinder 403. The first spring 404 is mounted on the cylinder 403 and is located between the flange at the rear end of the cylinder 403 and the plug portion of the sealing plug 402. The valve core 406 is arranged in the front cavity 410a, and the rear end of the valve core 406 has a head 406a that can pass through the valve seat opening 401a, and the second spring 407 is arranged between the valve seat 401 and the valve core 406. Under the elastic action of the second spring 407, in the initial state, there is a gap between the valve core 406 and the valve seat 401. The valve core 406 has an air passage 406b extending from the rear end face of the head 406a to the interior and a lateral air passage 406c connected from the air passage 406b to the side surface of the valve core 406. The position corresponding to the lateral air passage 406c in the front cavity 410a is provided with an exhaust channel 411a connected to the outside. The valve core 406 is provided with a fifth sealing ring 406d (such as Figure 6A A sealing gasket 402a is provided on the front end of the plug portion of the sealing plug 402, which provides a seal when in contact with the valve seat opening 401a of the valve seat 401 or the head portion 406a of the valve core 406. A fourth sealing ring 403a is provided on the circumferential surface of the plunger portion of the sealing plug 401.

[0060] Combined with Figure 2 As shown, the rear end of the air inlet 410 has an air inlet interface 405 that is horizontal and perpendicular to the air inlet 410. The air inlet interface 405 is connected to the rear cavity 410b. The air inlet interface 405 is used to connect to a compressed air source.

[0061] Combine Figure 2 、 Figure 10 and Figure 10A As shown, an air hole 411 b is provided in the front cavity 410 a near the valve seat 401 , and an internal air passage 411 extending from the air hole 411 b to the rear wall of the air cavity 110 is provided in the pump housing 100 .

[0062] Combine Figure 2 and Figure 11 As shown, the pump housing 100 also has a liquid inlet 420. The liquid inlet 420 is horizontally perpendicular to the air inlet 410 and intersects with the air inlet 410 and the liquid cavity 120, respectively, and then forms an air inlet liquid inlet hole 421 (as shown in FIG. Figure 6AAs shown), a liquid inlet hole 422 is formed at the top of the liquid cavity 120 near the guide sleeve 121 (as shown Figure 7A shown).

[0063] Since the air inlet duct 410 is parallel to the liquid chamber 120 and does not tilt upward, the slave pump can be arranged at multiple locations beside the transmission. Figure 12 As shown, the slave cylinder 001 can be arranged at the upper left corner, the left side, and the bottom of the gearbox 002.

[0064] For example Figure 6A As shown, a blocking step 410c is provided in the middle of the front chamber 410a to prevent the valve core 406 from moving to the bottom of the front end of the front chamber 410a. Thus, with the blocking step 410 preventing the valve core 406 from moving to the bottom of the front end of the front chamber 410a, a gap always exists between the front end of the valve core 406 and the bottom of the front end of the front chamber 410a when the valve core 406 is in the initial state. This gap allows brake fluid to smoothly enter the front chamber 410a from the intake port 421.

[0065] When the driver steps on the clutch pedal, the clutch pedal will control the main pump in the vehicle clutch system to output brake fluid. The brake fluid enters the front cavity 410a of the intake duct 410 through the intake duct liquid inlet hole 421 through the liquid inlet channel 420 and enters the liquid cavity 120 through the liquid cavity liquid inlet hole 422.

[0066] When the brake fluid enters the front chamber 410a of the intake passage 410, it drives the valve core 406 to push the sealing plug 402 open and separate from the valve seat 401, so that the valve seat port 401a is opened, so that the rear chamber 410b and the front chamber 410a are connected. At this time, the compressed air in the rear chamber 410b enters the front chamber 410a through the valve seat port 410b, and enters the air chamber 110 from the air hole 411b through the internal air passage 411 (that is, at this time, the intake interface 405, the rear chamber 410b, the valve seat port 401a of the valve seat 401, the front chamber 410a, the air hole 411, and the internal air passage 411 connected in sequence form an intake passage, as shown in FIG. Figure 8A and Figure 10A As shown by the arrow in the middle, the piston disc 220 in the air chamber 110, under the action of the compressed air, and the piston rod 110 in the liquid chamber 120, under the action of the brake fluid, move forward together, driving the push rod 300 forward, thereby driving the clutch pressure plate and movable plate to separate. As the valve core 406 pushes open the sealing plug 402, the sealing plug 402 simultaneously blocks the opening of the central air passage 406b, preventing the compressed air that has flowed into the front chamber 410a from leaking out of the central air passage 406b.

[0067] When the driver releases the clutch pedal, the clutch pedal no longer controls the master pump's output of brake fluid to the slave pump, and the brake fluid in both the front chamber 410a and the fluid chamber 120 loses pressure. Consequently, the valve core 406 in the intake duct 410, under the action of the second spring 407, returns to its initial position. The sealing plug 402, under the action of the first spring 404, returns to the initial sealing position of the valve seat opening 401a of the valve seat 401, thus severing the connection between the rear chamber 410b and the front chamber 410a. Simultaneously, the push rod 300, under the reaction force of the clutch pressure plate, drives the piston rod 210 and piston plate 220 back together. During the retraction process, the piston rod 210 discharges the brake fluid in the liquid chamber from the liquid chamber inlet hole 422 via the liquid inlet channel 420 back to the main pump, and the piston plate 220 discharges the gas in the air chamber 110 through the internal air channel 411, the air hole 411b, the gap between the valve core 406 and the valve seat 401, the middle air channel 406b, the lateral air channel 406c, and the exhaust channel 411a to the outside of the slave pump (that is, at this time, the internal air channel 411, the air hole 411b, the gap between the valve core 406 and the valve seat 401, the middle air channel 406b, the lateral air channel 406c, and the exhaust channel 411a are connected in sequence to form an exhaust channel, as shown in FIG. Figure 9 、 Figure 9A arrows).

[0068] The air valve 400 of the present invention can automatically switch between air intake and exhaust according to whether brake fluid is introduced, and the switching is fast and reliable without causing blowby problems.

[0069] From the above description, it can be seen that during the operation of the slave pump, the piston moves forward and backward. In order to measure the displacement of the piston,

[0070] like Figure 2 and Figure 5 As shown, the pump housing is located at the rear of the air cavity 110 and further has a mounting hole 140 communicating with the air cavity 110 . The displacement sensor 500 is fixed in the mounting hole 140 .

[0071] like Figures 13 to 17 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 .

[0072] Among them, the outer shell 510 is fixed in the mounting hole 140, and a sealing ring is provided between the two for sealing. The outer 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 facing 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. Through the pin interface 513, the signal generated by the sensor can be transmitted to the main control of the car.

[0073] The bushing 540 is fixed in the guide rod cavity 512 and has an opening leading to the air cavity 110. The sensing guide rod 530 has a connecting end 530a connected to the piston disc 220 at one end and a sensing end 530b located in the guide rod cavity 512 at the other end. Accordingly, the sensing 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 connecting end 503a. The length of the thick rod portion 531 is comparable to that of the bushing 440, and the thick rod portion 531 has a mounting cavity 533 located at the sensing end 530b. The magnet 550 is fixedly mounted in the mounting cavity 533.

[0074] Hall effect chips are evenly spaced along the length of the sensing rod 530 on the circuit board 520. As the sensing rod 530 moves within the bushing 540, each Hall effect chip 521 generates different voltage output signals as the magnet 550 approaches or moves away from it, thereby measuring the displacement of the piston disk 220. In this utility model, the spacing between the Hall effect chips is calculated and appropriately arranged so that the measurement ranges of each Hall effect chip are aligned end-to-end, enabling continuous measurement of the entire travel of the piston disk.

[0075] like Figure 18As shown, the inner wall of the bushing 540 is circumferentially distributed with semicircular ridges 541 extending axially, and the circumferential surface of the thick rod portion 531 is in line contact with the ridges 541. This structure reduces friction between the bushing and the sensing guide rod and creates a gap between the inner wall of the bushing and the sensing guide rod, allowing gas within the bushing to escape during the movement of the sensing guide rod, making the sensing guide rod slide more smoothly. In addition, the outer wall of the bushing 540 has a raised ring 542 that is retained within the housing body 510a. The bushing 540 and the housing body 510a can be fixed together using an injection molding structure. This structure ensures that the bushing 540 is firmly fixed within the housing 510, preventing loosening between the bushing 540 and the housing 510, and ensuring reliable operation of the sensor. In this embodiment, the bushing 540 is made of nylon, which is wear-resistant and lubricating. Using nylon as the bushing not only facilitates smooth movement of the sensing guide rod within the bushing but also reduces wear on the bushing.

[0076] like Figure 19 As shown, the circuit board 520 includes a power supply module 521, an operational amplifier 522, an MCU, and multiple Hall effect chips 523. The MCU has an ADC acquisition port 524 and a PWM output port 525. In this embodiment, a total of five Hall effect chips 523 are used (i.e., hall1, hall2, hall3, hall4, and hall15 shown in the figure), which respectively transmit voltage signals to five operational amplifiers 522 (i.e., op amp 1, op amp 2, op amp 3, op amp 4, and op amp 5 shown in the figure) for amplification. The MCU has five ADC acquisition ports 524 (i.e., ADC1, ADC2, ADC3, ADC4, and ADC5 shown in the figure), which are used to respectively collect the amplified voltage signals from the five operational amplifiers 522.

[0077] The main power supply module 521 includes an input protection circuit and an LDO module. The input protection circuit provides protection against reverse connection, surges, static electricity, and overvoltage. The LDO module provides voltage regulation and step-down, overcurrent protection, overtemperature protection, power supply isolation, improved power supply voltage noise suppression coefficient, filtering, and amplitude limiting. Since both the input protection circuit and the LDO module are well-established circuit modules, their detailed circuit structures will not be described in detail.

[0078] The input protection circuit obtains a 5V voltage from the vehicle ECU and provides it to the LDO module for processing. The LDO module converts the 5V voltage obtained from the vehicle ECU into a 3.3V voltage to power each Hall chip 523, each operational amplifier 522 and the MCU respectively.

[0079] When the piston disk 220 moves within the air cavity 110, driving the magnet 550 at the sensing end of the sensing guide rod 530 to sequentially pass through each Hall chip 523, each Hall chip 523 will sequentially sense changes in the surrounding magnetic field, thereby generating a varying voltage signal. Because 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, in this embodiment, each Hall chip 523 will sense a magnetic field variation ranging from -8mT to +8mT when a magnet passes by, and the resulting voltage signal range is 0.28V to 1.72V. This voltage signal is too weak, so the operational amplifier 522 needs to perform a double amplification process to generate a voltage signal of 0.56V to 3.44V for the MCU.

[0080] like Figure 20 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 collects the voltage in the best linear region, that is, between 1.04V and 2.94V.

[0081] Figure 21 The figure shows the relationship between the magnetic field changes sensed by each Hall chip, the output voltage and the piston position. The output voltage of each Hall chip 523 corresponds to the position of the piston. Therefore, each position corresponds 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).

[0082] 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.

[0083] The PWM signal output value of PWM output port 525 also corresponds to the piston position. Given that the piston moves 85 mm, the effective PWM signal output value is 10% - 90%. Therefore, (90 - 10) / 85 = 0.94% / mm, meaning that for every 1 mm of movement, the PWM signal output value changes by 0.94%. Therefore, when the ADC4 sampling voltage is 1.52 V, the PWM signal output value = 10% + 55 × 0.94% = 61.77%.

[0084] Since the voltage signals collected by each ADC acquisition port 523 and the PWM signal output values ​​output by the PWM output port 525 each correspond one-to-one to the piston position, for example, when the ADC4 acquisition voltage is 1.52V, the PWM signal output value = 10% + 55 × 0.94% = 61.77%, corresponding to the piston position of 55mm. Therefore, the MCU can control the PWM output port 525 to output the corresponding PWM signal output value based on the voltage signals collected by each ADC acquisition port. When the piston disk moves to different positions, the displacement sensor will output the corresponding PWM signal output value to the vehicle ECU. Ultimately, the vehicle ECU controls the display device to display the piston position based on the one-to-one correspondence between the PWM signal output value and the piston position. The display device can be the vehicle's instrument panel, central control display screen, or a terminal device connected to the vehicle ECU during maintenance.

[0085] The above is the structure of the slave cylinder with a displacement sensor in this utility model. Because the displacement sensor is mounted on the pump housing, and its sensing rod extends into the air cavity and connects to the piston disc, when the piston disc moves and shifts within the air cavity, the sensing rod also shifts. The displacement sensor senses the displacement change of the piston disc, thereby measuring the displacement change of the slave cylinder's piston. The displacement data measured by the displacement sensor can be transmitted to the vehicle ECU via a wiring harness and displayed on the master control instrument.

[0086] Because the slave cylinder can measure the displacement of the piston disc using a displacement sensor, it can also monitor the wear of the clutch disc by measuring the offset between the piston disc's return position and its initial position. For example, before the driver presses the clutch pedal, the piston initially positions 40mm in the air chamber. When the clutch pedal is pressed, the piston moves forward, driving the push rod, which in turn drives the clutch pressure plate and driven disc apart. When the driver releases the clutch pedal, if the clutch disc is not worn, the piston disc returns to its initial position of 40mm due to the balance between the pressure plate's reaction force and the return spring. However, if the driven disc is worn and thinner, the piston disc will deviate backward from its initial position when returning. The more severe the pressure plate wear, the further the piston deviates from its initial position when returning, and the position data measured by the displacement sensor will be greater than 40mm. Therefore, the slave cylinder can also monitor the wear of the clutch disc using the displacement sensor.

[0087] In addition, the utility model distributes multiple Hall chips at equal intervals on the circuit board. When the magnet on the induction guide rod moves in the guide rod cavity, it approaches or moves away from each Hall chip in turn. Each Hall chip will sense the change in the magnetic field in turn and can output different voltages. Then, according to the positional relationship between the different voltages output by each Hall chip and the position of the piston disk, the longer stroke displacement change of the piston in the sub-pump can be finally measured.

[0088] It can be seen from the above detailed description that the utility model can measure the displacement of the slave cylinder piston when the slave cylinder is working, and realize real-time feedback of the slave cylinder working status during vehicle driving, which is beneficial for the vehicle main control to monitor and collect data on the wear status of the clutch driven plate.

Claims

1. A slave pump structure with a displacement sensor, comprising: A pump housing, wherein the pump housing has an air cavity, an air inlet channel and a liquid inlet channel; a piston having a piston disc disposed in the air cavity; an air valve, the air valve being arranged in the air inlet duct; a push rod connected to the piston; Brake fluid enters the air inlet passage through the fluid inlet passage to drive the air valve to open, and compressed air enters the air chamber through the air inlet passage to drive the piston disc and the push rod to move forward; when no brake fluid enters the air inlet passage through the fluid inlet passage, the air valve is reset to close, and the piston disc and the push rod are reset; The invention is characterized in that a displacement sensor is installed on the pump housing, and a sensing guide rod of the displacement sensor extends into the air cavity and is connected to the piston disk.

2. The slave pump structure with a displacement sensor according to claim 1, characterized in that: The displacement sensor includes a shell, a circuit board, a magnet and the sensing guide rod. The shell is divided into a guide rod cavity and a circuit cavity that are parallel to each other. The sensing guide rod is divided into a connecting end connected to the piston disk and a sensing end that can slide in the guide rod cavity. The magnet is installed in the sensing end, and the circuit board is installed in the circuit cavity. A plurality of Hall chips are distributed on it at equal intervals along the length direction of the sensing guide rod.

3. The slave pump structure with a displacement sensor according to claim 2, characterized in that: A bushing is fixed in the guide rod cavity, and the sensing end is located in the bushing and slides.

4. The slave pump structure with a displacement sensor according to claim 3, characterized in that: The sensing guide rod is divided into a thick rod portion located at the sensing end side and capable of sliding in the bushing and a thin rod portion located at the connecting end side and outside the bushing.

5. The slave pump structure with a displacement sensor according to claim 4, 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 thick rod portion contacts the ridges.

6. The slave pump structure with a displacement sensor according to claim 3, characterized in that: The outer wall of the bushing is provided with a convex ring which is clamped in the shell.

7. The slave pump structure with a displacement sensor according to claim 3, characterized in that: The material of the bushing is nylon.

8. The slave pump structure with a displacement sensor according to claim 2, characterized in that: The pump housing has a liquid cavity in communication with the air cavity behind the air cavity. The piston also includes a piston rod disposed in the liquid cavity and connected to the piston disc. The liquid inlet channel is in communication with the liquid cavity.

9. The slave pump structure with a displacement sensor according to claim 8, characterized in that: The top of the liquid cavity is provided with a liquid cavity inlet hole, and the liquid cavity inlet hole is communicated with the liquid inlet channel.

10. The slave pump structure with a displacement sensor according to claim 8, characterized in that: The front end surface of the piston rod has a ball socket, and the rear end of the push rod has a ball head. The ball head is fixed in the ball socket through an elastic clamp. The large end of the elastic clamp is clamped on the inner wall of the ball socket, and the small end is clamped on the ball head.

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