Brake control device

Abstract

Provided is a brake control device that makes it possible for a magnet and a sensor to be closer together while ensuring waterproofing on the sensor side. The present invention is configured such that the opening of a shaft accommodation hole is sealed by a thin film of a sealing member.

Description

Brake control device

[0001] The present invention relates to a brake control device.

[0002] Patent Document 1 discloses a brake control device that controls brake fluid pressure using a pump driven by a motor, in which a magnet attached to the tip of the motor shaft and a magnetic flux detection sensor mounted on a control board are arranged opposite each other with a sealing member sandwiched between them, and the sensor detects the rotational position of the motor. The sealing member prevents brake fluid from seeping from the housing side to the sensor side, and closes the opening on the sensor side of the shaft accommodating hole in the housing.

[0003] Patent No. 6898888

[0004] However, in the above-mentioned Patent Document 1, a resin sealing member is used, which requires a thickness required for molding, and therefore the distance between the magnet and the sensor is increased, resulting in a problem of deterioration in the magnetic flux detection accuracy of the sensor. One of the objects of the present invention is to provide a brake control device that can arrange the magnet and sensor closer to each other while ensuring waterproofing on the sensor side.

[0005] A brake control device according to one embodiment of the present invention includes a sealing member attached to the opening of the shaft accommodating hole on the second surface of the housing and having a thin film that seals the opening.

[0006] Therefore, in one embodiment of the present invention, the magnet and the sensor can be arranged closer to each other while ensuring waterproofness on the sensor side.

[0007] 1 is a longitudinal sectional view of a brake control device 1 of Embodiment 1. FIG. 2 is an enlarged view of a main part of FIG. 1. FIG. 3 is a perspective view of a shaft accommodating hole 2d as viewed from the rear surface 22 side of a housing 2. FIG. 4(a) is an exploded perspective view of a sealing member 10 of Embodiment 1, and FIG. 4(b) is a sectional perspective view of the sealing member 10 of Embodiment 1. FIG. 5(a) is an exploded perspective view of a sealing member 10 of Embodiment 2, and FIG. 5(b) is a sectional perspective view of the sealing member 10 of Embodiment 2.

[0008] [Embodiment 1] FIG. 1 is a longitudinal cross-sectional view of a brake control device 1 of embodiment 1. The brake control device 1 is applied to, for example, an electric vehicle. The electric vehicle may be a hybrid vehicle equipped with an engine and a motor / generator as a prime mover for driving the wheels, or an electric vehicle equipped with only a motor / generator as a prime mover. In an electric vehicle, a regenerative braking system including a motor / generator can perform regenerative braking, which brakes the vehicle by converting the vehicle's kinetic energy into electrical energy through power generation. The brake control device 1 generates braking force by converting the vehicle's kinetic energy into thermal energy through friction. A brake actuation unit is attached to each wheel. The brake actuation unit is, for example, a disc type and has a hydraulic brake caliper.

[0009] The brake caliper has a brake disc and brake pads. The brake disc is a brake rotor that rotates integrally with the tire. The brake pads are positioned with a certain clearance from the brake disc and move due to the hydraulic pressure in the wheel cylinder. When the brake pads are pressed against the brake disc, the frictional force generates a braking force. The brake control device 1 has two brake piping systems: primary and secondary. The brake piping system is, for example, an X-piping system. However, other piping systems, such as front and rear piping, may also be used. The brake control device 1 is positioned between the master cylinder and each brake actuation unit, supplies brake fluid to each brake actuation unit, and controls the brake hydraulic pressure in the wheel cylinder.

[0010] The brake control device 1 is located in a motor compartment isolated from the driver's cab of the vehicle. The brake control device 1 has a housing 2, a motor 3, a stroke simulator (not shown), and a control unit 5. The housing 2 is fixed to the floor of the motor compartment via an insulator and a bracket (not shown). The bracket is fastened to the floor with multiple screws. The housing 2 is a housing that houses a pump 6, multiple solenoid valves 7, multiple hydraulic pressure sensors 8, etc. The housing 2 is a roughly rectangular block made of aluminum alloy. The housing 2 has two circuits, a primary and a secondary, through which brake fluid flows. The two circuits are composed of multiple fluid paths.

[0011] The motor 3 is a brushless motor and includes a motor case 31, a stator 32, a rotor shaft 33, a rotor 34, and a power connector 35. The motor case 31 is cylindrical, with a cylindrical portion 31a and two bottom portions 31b and 31c. The center of the bottom portion 31c is open. The motor case 31 is fastened to the front (first surface) 21 of the housing 2 using screws (not shown). The stator 32 is fixed to the inner circumferential surface of the cylindrical portion 31a. The rotor shaft 33 is cylindrical and rotatably attached to the motor case 31 about a rotation axis O1. Hereinafter, the X-axis is defined as the direction of the rotation axis O1, and the direction from the bottom portion 31b to the bottom portion 31c is defined as the positive X-axis direction. The radial direction is the direction radially outward from the rotation axis O1, and the circumferential direction is the direction around the rotation axis O1.

[0012] The X-axis negative end of rotor shaft 33 is rotatably supported relative to motor case 31 by bearing 37a attached to bottom 31b. The X-axis positive side of rotor shaft 33 is rotatably supported relative to motor case 31 by bearing 37b attached to bottom 31c. The X-axis positive end of rotor shaft 33 protrudes further toward the X-axis positive side than bottom 31c. Rotor 34 is fixed to the outer periphery of rotor shaft 33 and faces stator 32 in the radial direction. Rotor 34 rotates integrally with rotor shaft 33.

[0013] The power connector 35 is connected to a power supply unit 36a. The power supply unit 36a supplies power to the stator 32 from a first control board 52 (described later) of the control unit 5 via the power connector 35. The power supply unit 36a protrudes outside the motor case 31 and extends toward the positive X-axis direction along a through-hole 2a that penetrates the interior of the housing 2 in the X-axis direction. Most of the power supply unit 36a is covered with synthetic resin. The rotor shaft 33 is a rotating shaft for driving the pump 6. The positive X-axis end of the rotor shaft 33 is housed on the negative X-axis side of the back surface (second surface) 22 of the housing 2.

[0014] The stroke simulator (not shown) incorporates a plunger supported by a spring. The movement of the plunger absorbs the movement of the brake fluid discharged from the master cylinder and at the same time generates a reaction force on the brake pedal. Although not shown, the stroke simulator is fastened to the right side of the housing 2 using a screw.

[0015] The pump 6 is driven by the motor 3 to draw brake fluid from a reservoir tank (not shown) and discharge it toward the wheel cylinders. The pump 6 is shared by two systems: a primary system and a secondary system. In the first embodiment, five plunger pumps 6a with excellent noise and vibration performance are used as the pumps 6. The plunger pumps 6a are housed in five cylinder accommodating holes 2b formed in the housing 2. Two cylinder accommodating holes 2b are arranged on the right side of the housing 2, two on the left side, and one on the bottom surface 24, and are arranged at equal intervals around the circumference. Each cylinder accommodating hole 2b is connected to a cam chamber 2c. The cam chamber 2c forms part of the shaft accommodating hole 2d and opens to the front surface 21 of the housing 2.

[0016] The shaft accommodating hole 2d is a generally cylindrical hole with a bottom that extends in the X-axis direction and opens to the front surface 21 and rear surface 22 of the housing 2. When viewed from the X-axis direction, the center of the shaft accommodating hole 2d is on the rotation axis O1. The shaft accommodating hole 2d accommodates a sensor shaft 33b that is integrally formed with the end of the rotor shaft 33 facing the X-axis positive direction. A cam portion 33a is formed on the X-axis positive side of the rotor shaft 33. A cam bearing 62 is attached to the outer periphery of the cam portion 33a. When the cam portion 33a rotates due to the rotational drive of the motor 3, the plunger 6a1 abutting the outer ring of the cam bearing 62 in each plunger pump 6a reciprocates, causing the pump 6 to draw in and discharge brake fluid. A stopper 63 abuts the X-axis positive side of the cam bearing 62.

[0017] The multiple solenoid valves 7 and the like are solenoid valves that operate in response to control signals from the control unit 5. A valve element strokes in response to the energization of the solenoid, switching between opening and closing the fluid path (connecting and disconnecting the fluid path). The solenoid valves 7 and the like control the communication state of the above-mentioned circuit and adjust the flow state of the brake fluid, thereby generating a controlled fluid pressure. The solenoid valves 7 and the like are partially housed in multiple valve housing holes 2e. Each valve housing hole 2e extends in the X-axis direction and opens to the rear surface 22 of the housing 2.

[0018] The hydraulic pressure sensors 8 and the like detect the master cylinder hydraulic pressure, the primary and secondary wheel cylinder hydraulic pressures, and the discharge pressure of the pump 6. The hydraulic pressure sensors 8 and the like are partially housed in the sensor housing holes 2f. Each sensor housing hole 2f extends in the X-axis direction and opens to the rear surface 22 of the housing 2. When viewed from the X-axis direction, each valve housing hole 2e and each sensor housing hole 2f are disposed spaced apart from one another.

[0019] The control unit 5 receives inputs from a brake pedal stroke sensor, such as a hydraulic pressure sensor 8 attached to the housing 2, as well as information about the vehicle's driving conditions. The control unit 5 uses the input information to operate multiple solenoid valves 7 and the motor 3 according to a built-in program, thereby controlling the wheel cylinder hydraulic pressure of each wheel. This allows for various brake control functions (antilock brake control to prevent wheel slippage due to braking, boost control to reduce the driver's brake operation force, brake control for vehicle dynamics control, automatic brake control such as vehicle following control, and regenerative brake cooperative control). Vehicle dynamics control includes vehicle behavior stabilization control such as skid prevention. Regenerative brake cooperative control controls the wheel cylinder hydraulic pressure to achieve a target deceleration (target braking force) in coordination with the regenerative brake.

[0020] The control unit 5 includes a case 51, a first control board 52, and a second control board 53. The first control board 52 and the second control board 53 form a control board section. The second control board 53 is configured to be able to be housed between the multiple solenoid valves 7 and is smaller in size than the first control board 52. The case 51 includes a main body 511 and a cover 512. The main body 511 is recessed on the negative X-axis side and covers the solenoids 7a of the multiple solenoid valves 7 and other components. The main body 511 is fastened to the rear surface 22 of the housing 2 with screws (not shown). The main body 511 includes a first board housing section 511a on the positive X-axis side. The first control board 52 is housed in the first board housing section 511a. The housing side of the first board housing section 511a, i.e., the negative X-axis side, includes a second board housing section 511b. The second control board 53 is housed in the second board housing section 511b. When viewed from the axial direction, second control board 53 is installed in a position where at least a portion of it overlaps with rotation axis 01. First control board 52 and second control board 53 are electrically connected by a bus bar or the like (not shown). Cover 512 is fixed to the X-axis positive side of main body 511 and is a lid member that covers first board accommodating section 511a.

[0021] The first control board 52 is disposed in the board accommodating portion 511a parallel to the rear surface 22 of the housing 2. The first control board 52 has a motor control circuit, a motor drive circuit, a solenoid drive circuit, and a solenoid control circuit that control the power supply state to the motor 3 and each solenoid 7a. The motor control circuit has a microcomputer (or ASIC), memory, etc., and is a circuit that drives the motor drive circuit (its drive elements). The motor drive circuit has drive elements such as MOSFETs, and is a circuit that drives the motor 3. The solenoid control circuit has a microcomputer (or ASIC), memory, etc., and is a circuit that drives the solenoid drive circuit (its drive elements). The solenoid drive circuit has drive elements such as MOSFETs, and is a circuit that drives each solenoid 7a.

[0022] The second control board 53 is disposed in the second board housing portion 511b parallel to the first control board 52 and spaced a predetermined distance from the first control board 52 on the negative X-axis side. As shown in FIG. 2, a magnetic flux detector (motor rotation speed sensor, hereinafter abbreviated as sensor) 9c is mounted on the surface of the second control board 53 on the negative X-axis side. FIG. 2 is an enlarged view of the main components of FIG. 1. The sensor 9c is located adjacent to the magnet 9a attached to the sensor shaft 33b via the magnet holder 33c and faces the magnet 9a in the axial direction. The sensor 9c has a detection element, such as a Hall element, and detects changes in magnetic flux density associated with the rotation of the magnet 9a to detect the rotation angle (mechanical angle) of the rotor shaft 33, i.e., the motor rotation speed. The rotation angle of the rotor shaft 33 detected by the sensor 9c is output to the motor control circuit and solenoid control circuit of the first control board 52 and is used to control the motor 3 and each solenoid 7a.

[0023] 2 and 3, a sealing member 10 is attached to the opening 22a of the shaft accommodating hole 2d on the back surface 22 of the housing 2. The sealing member 10 includes a fixing portion 11 and a thin film 12. FIG. 4(a) is an exploded perspective view of the sealing member 10 of the first embodiment, and FIG. 4(b) is a cross-sectional perspective view of the sealing member 10 of the first embodiment.

[0024] Fixing portion 11 is formed in a generally annular shape using a thermoplastic resin by injection molding or the like. Fixing portion 11 fixes sealing member 10 to opening 22a and holds and fixes thin film 12, and has a cylindrical portion 11a, an outer flange portion 11b, and an inner flange portion 11c. Fixing portion 11 is fixed to the periphery of opening 22a by press-fitting or adhesive, ensuring liquid-tightness between the two. Cylindrical portion 11a is inserted into shaft accommodating hole 2d. Outer flange portion 11b abuts against the bottom surface of counterbore portion 22b formed on the periphery of opening 22a. The X-axis positive end of inner flange portion 11c is located closer to the X-axis negative end than the X-axis positive end of outer flange portion 11b.

[0025] Thin film 12 is used to seal opening 22a and is formed in a disk shape using a waterproof and breathable material (waterproof and breathable material). Thin film 12 is thinner than the other parts of fixed portion 11 (cylindrical portion 11a, outer flange portion 11b, and inner flange portion 11c) and is thinner than the thickness of fixed portion 11 in the X-axis direction. Thin film 12 is adhered or affixed to the X-axis positive end of inner flange portion 11c by heat welding or the like, thereby ensuring liquid-tightness between them. The X-axis positive end of thin film 12 is located further toward the X-axis negative end than the X-axis positive end of outer flange portion 11b.

[0026] Next, the effects of the first embodiment will be described. In recent years, brushless motors have increasingly been adopted in brake control devices compatible with autonomous driving in order to improve hydraulic response. Controlling a brushless motor requires the inclusion of a sensor that detects its rotational state. In conventional brake control devices, a magnet attached to the end of the motor shaft and a magnetic flux detection sensor mounted on a control board are arranged opposite each other with a sealing member sandwiched between them, and the sensor detects the rotational position of the motor. The sealing member is used to prevent brake fluid from seeping from the housing side to the sensor side, and it blocks the sensor-side opening of the shaft accommodating hole in the housing.

[0027] However, because conventional sealing members are integrally molded from resin, the necessary thickness must be ensured, making it impossible to place the magnet and sensor close to each other. This makes them susceptible to electrical disturbances from the solenoid valve's solenoid or printed circuit board circuit, as well as high-temperature demagnetization, resulting in a deterioration in the sensor's magnetic flux detection accuracy. While the deterioration in magnetic flux detection accuracy can be prevented by increasing the size of the magnet, this comes at the cost of doing so.

[0028] In contrast, the brake control device 1 of the first embodiment is provided with a sealing member 10 having a thin film 12 attached to the opening 22a of the shaft accommodating hole 2d and sealing the opening 22a. By providing the thin film 12 in the area where the magnet 9a and the sensor 9c face each other, the magnet 9a and the sensor 9c can be positioned close to each other, making them less susceptible to electrical disturbances and high-temperature demagnetization from the solenoid 7a of the solenoid valve 7, the second control board 53, and the like. As a result, the detection accuracy of the sensor 9c can be improved while ensuring waterproofing on the sensor 9c side. Furthermore, because there is no need to increase the size of the magnet, costs can be reduced.

[0029] The sealing member 10 of the first embodiment has a fixing portion 11 for fixing the thin film 12 to the housing 2, and the thin film 12 is formed thinner than the thickness of the fixing portion 11 in the axial direction of the rotor shaft 33. In other words, the thickness of the thin film 12 can be designed independently of the thickness of the resin fixing portion 11. Therefore, the fixing portion 11 can be formed thick to ensure the necessary strength, while the thin film 12 can be formed thinner to position the magnet 9a and the sensor 9c closer to each other. The thin film 12 of the first embodiment is formed of a waterproof material. This more reliably prevents brake fluid from seeping into the second control board 53, improving the reliability of the brake control device 1.

[0030] Furthermore, the thin film 12 is made of a waterproof, breathable material. This allows air to circulate between the motor 3, the control unit 5, and the outside air through the thin film 12 and the vent holes on the control unit 5 side, maintaining a constant equilibrium with the atmosphere even in cases where temperature changes cause internal pressure fluctuations between the motor 3 and the control unit 5. As a result, even if the internal pressure of the units increases due to temperature increases within the motor 3 and the control unit 5 during continuous high-load operation of the pump 6, damage to the low-pressure seal of the pump 6 and the sealing components of the case 51 can be suppressed. Furthermore, during an airtightness inspection performed after assembly of the brake control device 1, internal pressure is sealed in through the vent holes on the control unit 5 side, allowing the airtightness of the entire device, including the motor 3, to be confirmed in one go. This reduces the number of inspection steps during assembly of the brake control device 1, improving productivity.

[0031] The motor 3 in the first embodiment is a brushless motor. Therefore, compared to a brushed motor, this motor has improved hydraulic response, making it suitable for use as a brake control device for vehicles requiring high response, such as autonomous driving. The use of a brushless motor also offers benefits such as a longer life, easier maintenance, and quieter operation. The sensor 9c in the first embodiment is mounted on the second control board 53, which is positioned opposite the magnet 9a. Mounting the sensor 9c on the second control board 53 opposite the magnet 9a improves the layout flexibility of the sensor 9c.

[0032] 5(a) is an exploded perspective view of the sealing member 10 of embodiment 2, and FIG. 5(b) is a cross-sectional perspective view of the sealing member 10 of embodiment 2. Embodiment 2 differs from embodiment 1 in that a cross-shaped reinforcing rib 11d is provided on the inner periphery of the fixing portion 11. The addition of the reinforcing rib 11d can further improve the holding strength of the thin film 12.

[0033] While the embodiments for carrying out the present invention have been described above, the specific configuration of the present invention is not limited to the configuration of the embodiments, and the present invention also includes design changes and the like that do not deviate from the gist of the invention. For example, the material and shape of the fixing portion of the sealing member can be set as appropriate.

[0034] This application claims priority to Japanese Patent Application No. 2023-216497, filed December 22, 2023. The entire disclosure of Japanese Patent Application No. 2023-216497, filed December 22, 2023, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety.

[0035] REFERENCE SIGNS LIST 1...brake control device, 2...housing, 2d...shaft accommodating hole, 3...motor, 9a...magnet, 9c...magnetic flux detection unit (detection unit), 10...sealing member, 11...fixing unit, 12...thin film, 21...front surface (first surface), 22...back surface (second surface), 33b...sensor shaft (shaft), 53...second control board (board)

Claims

1. A brake control device comprising: a motor; a shaft rotated by the motor and having a first end and a second end; a control unit controlling the rotation of the motor; and a housing, wherein the housing has a first surface, a second surface, and a shaft accommodating hole, wherein the motor is disposed on the first surface, and the control unit is disposed on the second surface, which is spaced a predetermined distance from the first surface in the axial direction of the shaft, and the shaft accommodating hole penetrates between the first surface and the second surface and into which the second end of the shaft is inserted, the brake control device further comprising: a magnet attached to the second end of the shaft; a sealing member attached to an opening of the shaft accommodating hole in the second surface and having a thin film that seals the opening; and a detection unit provided on the control unit so as to face the magnet via the thin film, and which detects the rotation state of the shaft.

2. A brake control device as claimed in claim 1, wherein the sealing member has a fixing portion for fixing the thin film to the housing, and the thin film is formed to be thinner than the thickness of the fixing portion in the axial direction of the shaft.

3. A brake control device according to claim 1, wherein the thin film is made of a waterproof material.

4. A brake control device according to claim 1, wherein the thin film is made of a waterproof and moisture-permeable material.

5. A brake control device according to claim 1, wherein the motor is a brushless motor.

6. A brake control device according to claim 1, wherein the detection unit is mounted on a substrate disposed opposite the magnet.