Displacement sensor for wheel cylinder piston

Abstract

The utility model discloses a wheel cylinder piston displacement sensor which comprises a shell, a circuit board and an induction guide rod, a guide rod cavity and a circuit cavity which are parallel to each other are divided in the shell, and the induction guide rod is divided into a connecting end used for being connected with a piston of a wheel cylinder and an induction end which is located in the guide rod cavity, can slide and has magnetism. The circuit board is installed in the circuit cavity, and a plurality of Hall chips are distributed on the circuit board at equal intervals in the length direction of the induction guide rod. The device can be applied to the wheel cylinder to measure the long-stroke displacement change of the piston, and can realize the real-time feedback of the working state of the wheel cylinder in the running process of a vehicle.

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 piston 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 master cylinder 2 oil tank, 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 combine with the driven plate 52. At the same time, under the action of the diaphragm spring and the return spring in the slave cylinder, the release bearing, release fork and slave cylinder piston are pushed back to the starting position.

[0004] From the above description, it can be seen 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 displacement sensor cannot be applied to the slave pump to measure the long-stroke displacement changes of the piston. Utility Model Content

[0005] The technical problem to be solved by the utility model is to provide a slave pump piston displacement sensor which can be used in a slave pump to measure the long-stroke displacement change of the piston, 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 slave cylinder piston displacement sensor, characterized in that it 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 for connecting to the piston of the slave cylinder and a magnetic sensing end that can slide in the guide rod cavity, the circuit board is installed in the circuit cavity, and a plurality of Hall chips are distributed on it at equal intervals along the length direction of the sensing guide rod.

[0008] By adopting the above technical solution, the utility model is installed on the slave cylinder, and the connecting end of the sensing guide rod is connected to the piston of the slave cylinder. In this way, when the piston is displaced, the sensing guide rod of the displacement sensor also displaces. When the magnetic sensing end of the sensing guide rod passes through each Hall sensor, each Hall chip will sense the change in the magnetic field in turn and then output voltage signals of different sizes. Since the voltage signals of different sizes output by each Hall chip correspond one-to-one to the position of the piston, the long-stroke displacement change of the piston can eventually be measured.

[0009] The present invention further comprises a magnet, which is installed in the induction end. The present invention obtains magnetism by installing a magnet at the induction end.

[0010] 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.

[0011] In the present invention, the inner wall of the bushing is circumferentially distributed with axially extending ridges, with the circumferential surface of the thick rod portion contacting these ridges. These ridges are semicircular. The use of these 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 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.

[0012] 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.

[0013] 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.

[0014] In the present invention, the circuit board also includes a power supply module, an operational amplifier, and an MCU. The MCU has an ADC acquisition port and a PWM output port. The power supply module supplies power to the Hall chip, the operational amplifier, and the MCU. The output voltage signal of the Hall chip is amplified by the operational amplifier and then output to the MCU. The MCU controls the ADC acquisition port to perform analog-to-digital conversion on the input voltage signal and controls the PWM output port to output a PWM signal.

[0015] From the above detailed description, it can be seen that the present invention can be applied to measure the long-stroke displacement change of the piston in the slave cylinder, and can realize real-time feedback of the working status of the slave cylinder during the driving process of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0017] Figure 1 It is a structural diagram of the clutch control system;

[0018] Figure 2 Schematic diagram of the three-dimensional structure of the slave pump;

[0019] Figure 3 is an internal cross-sectional view of the slave pump;

[0020] Figure 4 This is a three-dimensional schematic diagram of the displacement sensor of the present utility model;

[0021] Figure 5 This is a front view of the displacement sensor of the present utility model;

[0022] Figure 6 This is a rear view of the displacement sensor of the present utility model;

[0023] Figure 7 for Figure 5 Middle MM section view;

[0024] Figure 8 for Figure 6 Middle NN section view;

[0025] Figure 9 Schematic diagram of the bushing structure

[0026] Figure 10 This is the principle block diagram of the displacement sensor circuit board;

[0027] Figure 11 This is the voltage output curve of the Hall chip;

[0028] Figure 12A schematic diagram showing the relationship between the magnetic field changes sensed by each Hall chip, the output voltage and the piston position. DETAILED DESCRIPTION

[0029] The technical terms involved in this utility model are:

[0030] MCU-Microcontroller Unit, Chinese translation: micro control unit;

[0031] ADC-Analog to Digital Converter, Chinese translation: analog to digital converter;

[0032] ECU-Engine Control Unit, Chinese translation: engine control unit;

[0033] LDO-Low-dropout regulator, Chinese translation: low voltage difference regulator;

[0034] OA-Operational amplifier, Chinese translation: operational amplifier.

[0035] In order to facilitate and clearly understand the present invention, the clutch slave cylinder is first introduced. Figure 2 、 Figure 3 As shown, the clutch slave cylinder includes a pump housing 100 , a piston, a push rod 300 and a displacement sensor 500 .

[0036] The pump housing 100 defines an air cavity 110 and a liquid cavity 120 therein.

[0037] 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.

[0038] The piston includes a piston rod 210 and a piston plate 220. The piston plate 220 is disposed within the air chamber 110 and is movable within the air chamber 110. The piston rod 210 is disposed within the liquid chamber 120, with its front end extending into the air chamber 110 and connected to the piston plate 220. A return spring 230 is disposed between the piston plate 220 and the rear wall of the air chamber 110.

[0039] In order to measure the displacement of the piston (ie, the piston plate 220 ), the pump housing 100 further has a mounting hole 140 at the rear of the air cavity 110 , which is in communication with the air cavity 110 . The displacement sensor 500 of the present invention is fixed in the mounting hole 140 .

[0040] like Figures 4 to 9As shown, the slave cylinder piston displacement sensor of the present invention includes a housing 510 , a circuit board 520 , a sensing guide rod 530 , a bushing 540 and a magnet 550 .

[0041] Among them, the shell 510 is fixed to the mounting hole 140, and a sealing ring is provided 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 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. The signal generated by the sensor can be transmitted to the vehicle ECU through the pin interface 513 via the wiring harness to connect to the vehicle ECU.

[0042] 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 bushings 440 and 540. 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.

[0043] Hall effect chips are evenly spaced on the circuit board 520 along the length of the sensing rod 530. When the sensing rod 530 moves within the bushing 540, each Hall effect chip 523 generates different voltage outputs as the magnet 550 approaches or moves away, thereby measuring the displacement of the piston plate 220.

[0044] like Figure 9As 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.

[0045] like Figure 10 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] like Figure 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 collects the voltage in the best linear region, that is, between 1.04V and 2.94V.

[0050] Figure 12 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).

[0051] 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.

[0052] 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%.

[0053] 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 x 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.

[0054] It can be seen from the above detailed description that the present invention can be applied to the slave cylinder to measure the long-stroke displacement change of the piston, and can realize the real-time feedback of the working status of the slave cylinder during the driving process of the vehicle.

Claims

1. A slave pump piston displacement sensor, characterized in that: It includes a shell, a circuit board and a 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 for connecting to the piston of the slave pump and a magnetic sensing end that can slide in the guide rod cavity. The circuit board is installed in the circuit cavity, and multiple Hall chips are distributed on it at equal intervals along the length direction of the sensing guide rod.

2. The slave cylinder piston displacement sensor according to claim 1, characterized in that: It also includes a magnet, and the magnet is installed in the induction end.

3. The slave cylinder piston displacement sensor according to claim 1, 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 cylinder piston 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 cylinder piston 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 cylinder piston displacement sensor according to claim 5, characterized in that: The convex ridge is a semicircular convex ridge.

7. The slave cylinder piston 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.

8. The slave cylinder piston displacement sensor according to claim 3, characterized in that: The material of the bushing is nylon.

9. The slave cylinder piston displacement sensor according to claim 1, characterized in that The circuit board also includes a power supply module, an operational amplifier, and an MCU. The MCU has an ADC acquisition port and a PWM output port. The power supply module supplies power to the Hall chip, the operational amplifier, and the MCU. The output voltage signal of the Hall chip is amplified by the operational amplifier and then output to the MCU. The MCU controls the ADC acquisition port to perform analog-to-digital conversion on the input voltage signal and controls the PWM output port to output a PWM signal.

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