Braking system for vehicle

Abstract

A braking system 100 comprises: an electric cylinder 51 that has a servo motor 513; a rotation angle sensor SE2; and a control unit 81. The rotation angle sensor SE2 is configured so as to detect a Z pulse, which is generated each time the servo motor 513 completes one full rotation, and a phase pulse, which is generated each time the servo motor 513 rotates by a prescribed rotation angle. The control unit 81 performs a rotation angle sensor checking process. In the rotation angle sensor checking process, the control unit 81 rotates the servo motor 513 such that a piston 512 retreats. The control unit 81 counts the number of phase pulses in the period from the detection of a first Z pulse to the detection of a second Z pulse. The control unit 81 determines that the rotation angle sensor SE2 is normal when the number of phase pulses is within a prescribed range.

Description

Vehicle braking system

[0001] The present invention relates to a braking system for a vehicle equipped with an electric cylinder.

[0002] Braking devices that can generate braking force using an electric cylinder with a piston that moves in response to the drive of an electric motor are known. For example, Patent Document 1 discloses a braking device in which brake fluid is supplied to a wheel cylinder by the operation of an electric cylinder.

[0003] Japanese Patent Application Laid-Open No. 2023-119255

[0004] The electric cylinder disclosed in Patent Document 1 can be controlled based on the rotation angle of an electric motor. The rotation angle of the electric motor can be detected by a rotation angle sensor. When the electric cylinder is controlled based on the rotation angle detected by the rotation angle sensor, if there is an error in the rotation angle detected by the rotation angle sensor, there is a problem that the accuracy of controlling the electric cylinder is reduced and control different from the intended control is executed.

[0005] A vehicle braking system for solving the above problem is a vehicle braking system including an electric cylinder that generates a braking force on a vehicle, the electric cylinder having a cylinder, a piston contained in the cylinder, a servomotor, a linear motion conversion mechanism that converts rotation of the servomotor into forward and backward movement of the piston, a rotation angle sensor that detects a rotation angle according to rotation of the servomotor, and a control unit that controls the servomotor, the electric cylinder is configured so that no hydraulic pressure is generated when the piston is in a position that is further back than a predetermined pressurization start position, and hydraulic pressure is generated when the piston moves forward than the pressurization start position, the rotation angle sensor is configured to detect a Z pulse generated for each rotation of the servomotor and a phase pulse generated for each rotation of the servomotor by the predetermined rotation angle, and the control unit converts the phase pulse detected by the rotation angle sensor into a Z pulse. The control unit is configured to detect the rotation angle of the servo motor by loading a current into each phase of the servo motor, and when the vehicle's braking system is activated, the control unit executes a rotation angle sensor check process to confirm whether the rotation angle sensor is normal.As a first check process in the rotation angle sensor check process, the control unit applies current in a predetermined pattern to each phase of the servo motor toward a first phase target rotation speed, thereby rotating the servo motor so that the piston retracts.The control unit counts the number of phase pulses in the period from the detection of the first Z pulse to the detection of the second Z pulse, with the Z pulse detected during the rotation of the servo motor being a first Z pulse and the Z pulse detected next to the first Z pulse being a second Z pulse.The control unit checks whether the number of phase pulses thus counted is within a specified range, and determines that the rotation angle sensor is normal if the number of phase pulses is within the specified range.

[0006] According to the present invention, the rotation angle sensor can be checked.

[0007] FIG. 1 is a schematic diagram showing one embodiment of a vehicle braking system. FIG. 2 is a cross-sectional view schematically showing the structure of an electric cylinder provided in the braking system of FIG. 1. FIG. 3 is a cross-sectional view schematically showing the structure of an electric cylinder provided in the braking system of FIG. 1. FIG. 4 is a flowchart showing the processing flow when the braking system of FIG. 1 checks a rotation angle sensor. FIG. 5 is a flowchart showing the processing flow when the braking system of FIG. 1 checks a rotation angle sensor. FIG. 6 is a schematic diagram explaining the position of a piston in an electric cylinder provided in the braking system of FIG. 1. FIG. 7 is a timing chart illustrating the relationship between the counter value of a phase pulse and a Z pulse when the braking system of FIG. 1 checks a rotation angle sensor. FIG. 8 is a timing chart explaining a braking system of a modified example.

[0008] A braking system 100, which is one embodiment of a braking system for a vehicle, will be described below with reference to Figures 1 to 7. As shown in Figure 1, the braking system 100 includes an electric cylinder 51. The braking system 100 also includes a control unit 81.

[0009] An example of a braking system 100 includes a braking device 20 and a control device 80. An example of the braking device 20 includes a first braking unit 50 and a second braking unit 23 as braking units. The first braking unit 50 includes an electric cylinder 51, which will be described in detail later. The control device 80 can control the braking device 20. The control device 80 includes a control unit 81.

[0010] 1 illustrates a plurality of wheels FL, FR, RL, and RR as wheels of a vehicle to which the braking system 100 is applied. The plurality of wheels FL, FR, RL, and RR include two front wheels FL and FR and two rear wheels RL and RR. The vehicle is equipped with a brake operating member 21. The brake operating member 21 can be operated by the driver of the vehicle. An example of the brake operating member 21 is a brake pedal.

[0011] The control unit 81 is an example of a processing circuit provided in the vehicle. The braking system 100 may include other processing circuits in addition to the control unit 81. Some of the functions realized by the control unit 81 may be realized by other processing circuits. The processing circuits provided in the vehicle may be connected to each other so that they can send and receive information to each other. For example, a configuration can be adopted in which each processing circuit is connected to an in-vehicle network provided in the vehicle. The processing circuits connected to the in-vehicle network can communicate with each other via the in-vehicle network. For example, detection systems such as various sensors provided in the vehicle may be connected to the in-vehicle network.

[0012] <Brake Device> The brake device 20 includes a brake mechanism 10 corresponding to each of the wheels FL, FR, RL, and RR. The brake mechanisms 10 can apply frictional braking forces to the respective wheels FL, FR, RL, and RR. The frictional braking forces applied by the respective brake mechanisms 10 to the wheels FL, FR, RL, and RR can be adjusted by the brake device 20.

[0013] An example of the braking device 20 is a hydraulic braking device. For example, the braking device 20 includes a reservoir tank 24 that stores brake fluid, and a hydraulic pressure generating device 22. An example of the hydraulic pressure generating device 22 is a so-called brake-by-wire type hydraulic pressure generating device. The hydraulic pressure generating device 22 can generate hydraulic pressure according to the amount of operation of the brake operating member 21. The hydraulic pressure generating device 22 is composed of a master device 30 and a first braking unit 50. The master device 30 can supply brake fluid to the second braking unit 23. The first braking unit 50 can supply brake fluid to the master device 30 and the second braking unit 23.

[0014] <Brake Mechanism> The brake mechanism 10 will now be described. The brake mechanism 10 includes a wheel cylinder 11 to which brake fluid is supplied, a rotating plate 12 that rotates integrally with the wheel, and a friction material 13 that moves relative to the rotating plate 12 in the thickness direction of the rotating plate 12. The brake mechanism 10 is configured such that the higher the WC pressure Pwc, which is the fluid pressure in the wheel cylinder 11, the more strongly the friction material 13 is pressed against the rotating plate 12. According to the brake mechanism 10, the higher the WC pressure Pwc, the greater the frictional braking force applied to the wheels FL, FR, RL, and RR.

[0015] <Master Device> An example of the master device 30 includes a master cylinder 31, a stroke simulator 32, a plurality of flow paths 331, 332, and 333 connected to the master cylinder 31, and a plurality of control valves 341 and 342 that control the flow of brake fluid. The stroke simulator 32 can generate a reaction force according to the amount of operation of the brake operating member 21.

[0016] The master cylinder 31 includes a main cylinder 41 and a cover cylinder 42. The master cylinder 31 includes a master piston 43 and an input piston 44. The master cylinder 31 includes a master spring 45 that applies a force to push the master piston 43, and an input spring 46 that applies a force to push the input piston 44. The master piston 43 and the input piston 44 can move relative to the main cylinder 41 and the cover cylinder 42.

[0017] An example of a master cylinder 31 will be described in more detail. The main cylinder 41 of the master cylinder 31 has a plate-shaped bottom wall 411 and a first peripheral wall 412 extending from the bottom wall 411 along the axis of the bottom wall 411. The main cylinder 41 further has a second peripheral wall 413 extending from the rear end of the first peripheral wall 412 along the axis of the first peripheral wall 412, and a first annular wall 414 extending from the rear end of the second peripheral wall 413 toward the axis of the second peripheral wall 413. Each of the first peripheral wall 412 and the second peripheral wall 413 is cylindrical. A hole is formed in the first annular wall 414, into which the rear end of the master piston 43 (described later) is inserted. The inner diameter of the first peripheral wall 412 is smaller than the inner diameter of the second peripheral wall 413.

[0018] Within the main cylinder 41, a master chamber Rm is defined by a bottom wall 411, a first peripheral wall 412, and the master piston 43. Hereinafter, in the master cylinder 31, the leftward direction in FIG. 1 of the movement of the master piston 43, i.e., the direction in which the volume of the master chamber Rm decreases, will be referred to as the "forward" direction. On the other hand, the opposite direction of the movement of the master piston 43 from the forward direction will be referred to as the "rearward" direction. The rearward direction is also the direction in which the volume of the master chamber Rm increases.

[0019] Within the main cylinder 41, a first fluid chamber R1 is defined by the second peripheral wall 413 and the master piston 43, and a servo chamber Rs is defined by the second peripheral wall 413, the first annular wall 414, and the master piston 43. The master chamber Rm is formed near the front end of the master cylinder 31. The first fluid chamber R1 is formed rearward of the master chamber Rm. The servo chamber Rs is formed rearward of the first fluid chamber R1. Within the main cylinder 41, the master chamber Rm, the first fluid chamber R1, and the servo chamber Rs are not connected to one another. The cross-sectional area of ​​the master chamber Rm is equal to the cross-sectional area of ​​the servo chamber Rs. Here, the cross-sectional area of ​​the servo chamber Rs refers to the cross-sectional area of ​​the servo chamber Rs when the master piston 43 is housed therein.

[0020] The cover cylinder 42 of the master cylinder 31 has a cylindrical third peripheral wall 421 and a second annular wall 422 extending from the rear end of the third peripheral wall 421 toward the axis of the third peripheral wall 421. The third peripheral wall 421 is attached to the first annular wall 414 so that its axis coincides with that of the second peripheral wall 413 of the main cylinder 41. The second annular wall 422 has a hole into which the rear end of the input piston 44 (described later) is inserted.

[0021] Within the cover cylinder 42, a second fluid chamber R2 is defined by the third peripheral wall 421, the second annular wall 422, and the first annular wall 414 of the main cylinder 41. In the master cylinder 31, the second fluid chamber R2 is formed rearward of the servo chamber Rs.

[0022] The master piston 43 is housed in the master cylinder 31 in surface contact with the inner circumferential surfaces of the first circumferential wall 412, the second circumferential wall 413, and the first annular wall 414 of the main cylinder 41. Therefore, when the master piston 43 moves axially, the master piston 43 slides on the inner circumferential surfaces of the first circumferential wall 412, the second circumferential wall 413, and the first annular wall 414. The rear end of the master piston 43 protrudes rearward beyond the first annular wall 414 and is located within the second fluid chamber R2. The area of ​​the rear end of the master piston 43 is equal to the cross-sectional area of ​​the first fluid chamber R1. The area of ​​the rear end of the master piston 43 is the area that receives axial force due to the hydraulic pressure in the second fluid chamber R2. The cross-sectional area of ​​the first fluid chamber R1 is the cross-sectional area of ​​the first fluid chamber R1 when the master piston 43 is housed therein.

[0023] The input piston 44 is housed in the master cylinder 31 in surface contact with the inner circumferential surface of the second annular wall 422 of the cover cylinder 42. Therefore, when the input piston 44 moves in the axial direction, the input piston 44 slides on the inner circumferential surface of the second annular wall 422. The rear end of the input piston 44 protrudes rearward beyond the second annular wall 422. The brake operating member 21 is connected to the rear end of the input piston 44. Therefore, the input piston 44 moves in a direction approaching the master piston 43 in accordance with the amount of operation of the brake operating member 21. Furthermore, a gap is formed between the input piston 44 and the master piston 43 in the second fluid chamber R2.

[0024] The master spring 45 is disposed in the master chamber Rm of the main cylinder 41. The master spring 45 applies a force to the master piston 43 that pushes the master piston 43 rearward. Therefore, when the master piston 43 moves forward, the master spring 45 is elastically compressed.

[0025] The input spring 46 is disposed in the second fluid chamber R2 of the cover cylinder 42. The input spring 46 applies a force to the input piston 44 that pushes the input piston 44 rearward. Therefore, when the input piston 44 moves forward, the input spring 46 is elastically compressed.

[0026] In the master cylinder 31, the master chamber Rm is connected to the reservoir tank 24. More specifically, a portion of the master chamber Rm near the rear end is connected to the reservoir tank 24 via a port formed in the first peripheral wall 412 of the main cylinder 41. Therefore, when the master piston 43 moves forward from the position shown in FIG. 1, the master chamber Rm and the reservoir tank 24 are no longer connected. As a result, as the master piston 43 moves forward, the hydraulic pressure in the master chamber Rm increases. For example, when the hydraulic pressure in the servo chamber Rs increases, the hydraulic pressure in the servo chamber Rs moves the master piston 43 forward. This increases the hydraulic pressure in the master chamber Rm.

[0027] The first flow path 331 connects the master chamber Rm and the second braking unit 23. That is, the first flow path 331 is a flow path that connects some of the multiple wheel cylinders 11 to the master chamber Rm. More specifically, the first flow path 331 connects the wheel cylinders 11 for the front wheels FL and FR to the master chamber Rm. The second flow path 332 connects the first fluid chamber R1 and the second fluid chamber R2. The third flow path 333 connects the reservoir tank 24 to the second flow path 332.

[0028] The first control valve 341 is a normally closed solenoid valve. The second control valve 342 is a normally open solenoid valve. The first control valve 341 is disposed between the second fluid chamber R2 and the connection point of the second fluid path 332 with the third fluid path 333. The second control valve 342 is disposed in the third fluid path 333. When the braking system 100 is operating, the first control valve 341 is opened and the second control valve 342 is closed.

[0029] The stroke simulator 32 is disposed between the first fluid chamber R1 and the first control valve 341 in the second flow path 332. For example, the stroke simulator 32 includes an internal piston that is biased by a spring. When brake fluid flows into the stroke simulator 32 from the second flow path 332, the internal piston displaces against the spring force, generating pressure in the brake fluid in response to the piston's displacement. The piston is not shown. Specifically, when the input piston 44 moves forward by operation of the brake operating member 21 with the first control valve 341 open and the second control valve 342 closed, the volume of the second fluid chamber R2 decreases by the volume of the input piston 44 entering the second fluid chamber R2. Therefore, brake fluid flowing from the second fluid chamber R2 into the second flow path 332 flows into the stroke simulator 32. As a result, the stroke simulator 32 generates the same pressure in the second fluid chamber R2 and the first fluid chamber R1, which are connected by the second flow path 332. If the area of ​​the rear end of the master piston 43 protruding into the second fluid chamber R2 is equal to the cross-sectional area of ​​the first fluid chamber R1, and the same pressure is generated in the second fluid chamber R2 and the first fluid chamber R1, the master piston 43 will not be moved axially by this pressure.

[0030] <First Brake Unit> The first brake unit 50 includes an electric cylinder 51 having a servo motor 513 as a power source. The first brake unit 50 can adjust the WC pressure Pwc by the electric cylinder 51 that operates in accordance with the drive amount of the servo motor 513. In other words, the electric cylinder 51 can generate braking forces on the wheels FL, FR, RL, and RR of the vehicle.

[0031] An example of the first braking unit 50 will be described. The first braking unit 50 includes an electric cylinder 51, a hydraulic pressure adjusting valve 551, and a check valve 552.

[0032] The first braking unit 50 includes a fourth flow path 54 that connects the electric cylinder 51 and the reservoir tank 24. The first braking unit 50 includes a sixth flow path 58 that connects the second braking unit 23 and the electric cylinder 51. The first braking unit 50 includes a fifth flow path 55 that connects the servo chamber Rs of the master cylinder 31 and the sixth flow path 58.

[0033] The hydraulic pressure adjustment valve 551 is provided in the fifth flow path 55. The hydraulic pressure adjustment valve 551 is an electromagnetic valve that adjusts the differential pressure between a portion of the fifth flow path 55 that is closer to the servo chamber Rs than the hydraulic pressure adjustment valve 551 and a portion of the fifth flow path 55 that is closer to the electric cylinder 51 than the hydraulic pressure adjustment valve 551. In other words, the hydraulic pressure adjustment valve 551 can adjust the amount of brake fluid supplied to the servo chamber Rs.

[0034] The check valve 552 is provided in the fifth flow path 55 in parallel with the hydraulic pressure regulating valve 551. The check valve 552 allows the flow of brake fluid through the check valve 552 from the servo chamber Rs toward the electric cylinder 51. On the other hand, the check valve 552 restricts the flow of brake fluid through the check valve 552 in the direction from the electric cylinder 51 to the servo chamber Rs.

[0035] <Electric Cylinder> The electric cylinder 51 included in the first braking unit 50 is provided between the fourth flow path 54 and the sixth flow path 58. The fourth flow path 54 is connected to an input port 515 of the electric cylinder 51. The sixth flow path 58 is connected to an output port 516 of the electric cylinder 51. The input port 515 and the output port 516 will be described later.

[0036] The configuration of the electric cylinder 51 will be described with reference to Figures 1, 2, and 3. The electric cylinder 51 includes a cylinder 511, a piston 512 housed in the cylinder 511, a servomotor 513, and a linear motion conversion mechanism 514. The piston 512 is slidably provided within the cylinder 511. The servomotor 513 is the power source of the electric cylinder 51. The linear motion conversion mechanism 514 converts the rotational motion of the output shaft of the servomotor 513 into linear motion of the piston 512. In other words, the linear motion conversion mechanism 514 converts the rotation of the servomotor 513 into forward and backward movement of the piston 512.

[0037] A brushless motor is an example of the servo motor 513. The coil provided in the servo motor 513 is, for example, a three-phase coil consisting of U-phase, V-phase, and W-phase. The servo motor 513 is driven by a three-phase AC.

[0038] Within the cylinder 511, a hydraulic pressure chamber Re into which brake fluid is introduced is defined by the peripheral wall of the cylinder 511 and the piston 512. The position of the piston 512 within the cylinder 511 can be changed by driving a servo motor 513. Hereinafter, the direction of movement of the piston 512 that reduces the volume of the hydraulic pressure chamber Re will be referred to as the "advance direction Za." The direction of movement of the piston 512 opposite to the advance direction Za will be referred to as the "rearward direction Zb." The rearward direction Zb is also the direction of movement of the piston 512 that increases the volume of the hydraulic pressure chamber Re.

[0039] When moving the piston 512, the control device 80 uses an end position EP and a pressurization start position OP. Figure 2 shows the electric cylinder 51 in a state where the piston 512 is located at the pressurization start position OP. The pressurization start position OP is a position where the piston 512 is moved a specified amount Xm in the forward direction Za from the end position EP. The pressurization start position OP serves as a base point when hydraulic pressure is generated by the electric cylinder 51. Here, the end position EP is a position where the piston 512 is moved to the end in the backward direction Zb.

[0040] As shown in FIGS. 2 and 3 , the electric cylinder 51 includes an elastic body 518. The elastic body 518 applies a force to the piston 512 that pushes the piston 512 in the forward direction Za when the piston 512 is located at the end position EP. The elastic body 518 is arranged so that contact of the piston 512 with the elastic body 518 restricts movement of the piston 512 in the backward direction Zb. For example, as shown in FIGS. 2 and 3 , the elastic body 518 is arranged so as to contact the rear inner wall 511 a of the cylinder 511. For example, the elastic body 518 is arranged so as to contact the end face of the piston 512 in the backward direction Zb when the piston 512 is located at the end position EP.

[0041] An example of the elastic body 518 is a disc spring. A leaf spring, a coil spring, or the like can also be used as the elastic body 518. An elastic member molded from an elastic material such as elastomer or rubber can also be used as the elastic body 518. Note that Figures 2 and 3 illustrate a disc spring as the elastic body 518 that can be deformed into a flat plate shape.

[0042] When the piston 512 moves in the backward direction Zb, causing the piston 512 to come into contact with the elastic body 518, and then the piston 512 continues to move in the backward direction Zb, the elastic body 518 elastically deforms. If the piston 512 moves further in the backward direction Zb while elastically deforming the elastic body 518, the elastic deformation will eventually reach its limit. The end position EP is set as a position between the position of the piston 512 where the elastic body 518 begins to deform elastically and the position of the piston 512 where the elastic body 518 deforms to its limit.

[0043] 3 shows the electric cylinder 51 in a state where the piston 512 has moved to the most retracted position BE in the backward direction Zb. The state where the piston 512 has moved to the most retracted position BE in the backward direction Zb is a state where the piston 512 cannot be retracted any further when moved in the backward direction Zb even if a maximum driving force is generated. Alternatively, the state where the piston has moved to the most retracted position BE in the backward direction Zb is a state where the piston 512 cannot be mechanically retracted any further when moved in the backward direction Zb.

[0044] 3 illustrates the electric cylinder 51 in a state in which the piston 512 has moved in the backward direction Zb from the end position EP and is abutting against the rear inner wall 511a of the cylinder 511 with the elastic body 518 sandwiched therebetween. At this time, the disc spring serving as the elastic body 518 is deformed to its limit and thus assumes a flat plate shape. For example, as shown in FIG. 3 , when the piston 512 abuts against the rear inner wall 511a via the elastic body 518, the end face of the piston 512 in the backward direction Zb has moved to the most retracted position BE in the backward direction Zb. If the electric cylinder were configured without an elastic body, the state in which the end face of the piston in the backward direction is in contact with the rear inner wall corresponds to the state in which the piston has moved to the end in the backward direction.

[0045] An input port 515 and an output port 516 are formed in the peripheral wall of the cylinder 511 as ports connecting the hydraulic chamber Re with the outside. A through hole 517 is formed in the piston 512. The through hole 517 is formed in a position that allows communication between the input port 515 and the hydraulic chamber Re when the piston 512 is located at the end position EP. As a result, when the piston 512 is located at the end position EP, the hydraulic chamber Re of the cylinder 511 is connected to the fourth flow path 54 via the input port 515 and the through hole 517. In other words, the hydraulic chamber Re of the cylinder 511 is connected to the reservoir tank 24 via the input port 515 and the through hole 517. As shown in FIGS. 2 and 3 , the input port 515 is open when the piston 512 is located between the end position EP and the pressurization start position OP. The electric cylinder 51 is configured so that when the piston 512 moves in the forward direction Za from the pressurization start position OP, the piston 512 closes the input port 515. If the piston 512 moves further in the forward direction Za after the input port 515 has been closed by the piston 512 in this way, the hydraulic pressure in the hydraulic pressure chamber Re increases. In other words, the electric cylinder 51 is configured so that no hydraulic pressure is generated when the piston 512 is in a position further back than the predetermined pressurization start position OP. The electric cylinder 51 is configured so that hydraulic pressure is generated when the piston 512 moves forward beyond the pressurization start position OP.

[0046] An output port 516 of the cylinder 511 is connected to the second braking unit 23 and the fifth flow path 55 via a sixth flow path 58. The output port 516 is always open regardless of the position of the piston 512. Therefore, when the input port 515 is blocked by the piston 512 and the piston 512 moves in the forward direction Za, the brake fluid in the hydraulic chamber Re is discharged from the output port 516 to the outside of the cylinder 511.

[0047] 1 to 3, the electric cylinder 51 of this embodiment does not include a spring that applies a force to push the piston 512 in the backward direction Zb. The electric cylinder 51 may include a spring that applies a force to push the piston 512 in the backward direction Zb.

[0048] As shown in FIG. 1 , the first braking unit 50 includes a release flow passage 56 and a release valve 57 disposed in the release flow passage 56. The release flow passage 56 is a flow passage that connects the reservoir tank 24 and the wheel cylinder 11 so as to bypass the electric cylinder 51. A first end of the release flow passage 56 is connected to the fourth flow passage 54, and a second end of the release flow passage 56 is connected to the sixth flow passage 58. Specifically, the release flow passage 56 connects the reservoir tank 24 and the input port 515 in the fourth flow passage 54 to the output port 516 and the second braking unit 23 in the sixth flow passage 58. The release valve 57 is a normally closed solenoid valve. Therefore, when control to open the release valve 57 is not being performed, the release flow passage 56 is closed.

[0049] <Second Brake Unit> A description will be given of an example of the second brake unit 23. The second brake unit 23 is a brake actuator that can individually adjust the WC pressure Pwc of each of the wheels FL, FR, RL, and RR.

[0050] 1, the second braking section 23 includes a front-wheel pressure adjusting unit 231 and a rear-wheel pressure adjusting unit 232. The front-wheel pressure adjusting unit 231 adjusts the hydraulic pressure in the wheel cylinders 11 for the front wheels FL, FR to generate a frictional braking force at the front wheels FL, FR. The rear-wheel pressure adjusting unit 232 adjusts the hydraulic pressure in the wheel cylinders 11 for the rear wheels RL, RR to generate a frictional braking force at the rear wheels RL, RR.

[0051] <Brake Device Detection System> As shown in Fig. 1, the detection system of the brake device 20 includes a plurality of sensors. Detection signals from the sensors are input to a control device 80 of the brake device 20. Fig. 1 shows the plurality of sensors, including a master hydraulic pressure sensor 351, an input hydraulic pressure sensor 352, a control pressure sensor 353, a stroke sensor SE1, and a rotation angle sensor SE2.

[0052] The master hydraulic pressure sensor 351 detects the hydraulic pressure in the master chamber Rm. For example, the master hydraulic pressure sensor 351 is provided in the first fluid flow path 331. The input hydraulic pressure sensor 352 detects the hydraulic pressure in the second fluid chamber R2. For example, the input hydraulic pressure sensor 352 is connected to the second fluid flow path 332 at a position between the first control valve 341 and the second fluid chamber R2.

[0053] The control pressure sensor 353 is a pressure sensor that detects the hydraulic pressure of the brake fluid supplied from the electric cylinder 51. For example, the control pressure sensor 353 is provided near the output port 516 of the electric cylinder 51. As an example, FIG. 1 shows a configuration in which the control pressure sensor 353 is connected between the release valve 57 in the release flow path 56 and the output port 516.

[0054] The stroke sensor SE1 detects the amount of operation of the brake operating member 21. The rotation angle sensor SE2 detects the rotation angle corresponding to the rotation of the servo motor 513, which is the power source of the electric cylinder 51. The rotation angle sensor SE2 is configured to detect a Z pulse generated every time the servo motor 513 rotates once, and a phase pulse generated every time the servo motor 513 rotates a predetermined rotation angle. The control unit 81 can detect the rotation angle of the servo motor 513 by counting the phase pulses detected by the rotation angle sensor SE2.

[0055] An example of the rotation angle sensor SE2 is a three-phase rotary encoder consisting of A-phase, B-phase, and Z-phase. The output pulse of the Z-phase corresponds to the Z-pulse. The A-pulse, which is the output pulse of the A-phase, and the B-pulse, which is the output pulse of the B-phase, correspond to the phase pulses. The phase of the A-phase is shifted from the phase of the B-phase by a specified period. Therefore, the rotation direction of the servo motor 513 can be determined based on the order in which the rising and falling edges of the A-phase output pulse and the rising and falling edges of the B-phase output pulse are output. A specified maximum value α of the A-phase output pulse and the B-phase output pulse is generated in total while the servo motor 513 makes one rotation. The specified maximum value α is a value determined by the specifications of the rotation angle sensor SE2.

[0056] <Control Device> The control device 80 can control the first braking unit 50 and the second braking unit 23. The control unit 81 is a functional unit that has the function of controlling the first braking unit 50 and the second braking unit 23. The control unit 81 can control the servo motor 513.

[0057] The control device 80 includes a drive circuit 82 for controlling the servo motor 513. The drive circuit 82 is, for example, an inverter circuit that converts direct current into three-phase alternating current and supplies the current to the coil of the servo motor 513. The control device 80 operates the drive circuit 82 to supply the servo motor 513 with a current SG for controlling the servo motor 513.

[0058] When the check start condition is met, the control unit 81 executes a rotation angle sensor check process to check whether the rotation angle sensor SE2 is normal. As an example, the check start condition is set to be met when the vehicle braking system 100 is started. The check start condition may be determined to be not met when the rotation angle sensor check process is executed. The check start condition may be determined to be not met when an abnormality determination or a normality determination, which will be described later, is stored as a result of executing the rotation angle sensor check process.

[0059] The check start condition may be set to be satisfied even when the abnormality determination stored as a result of executing the rotation angle sensor check process is reset. Here, "rotation angle sensor SE2 is normal" means that no abnormality has occurred in rotation angle sensor SE2. "rotation angle sensor SE2 is abnormal" means that pulses cannot be detected according to the specifications of rotation angle sensor SE2. For example, this may include a state in which one or more types of pulses cannot be detected while servo motor 513 is rotating.

[0060] [Rotation Angle Sensor Check Process] The rotation angle sensor check process will be described with reference to Figures 4 to 6. Figure 4 shows the flow of the process executed by the control unit 81. The control unit 81 can execute this process routine when the check start condition is met.

[0061] When this processing routine starts, first in step S101, the control unit 81 starts counting A / B pulses. Specifically, the control unit 81 updates the A / B counter value Cab by incrementing it by 1 each time an A pulse and a B pulse are detected. The initial value of the A / B counter value Cab is 0. After starting to count A / B pulses, the control unit 81 proceeds to step S102.

[0062] In step S102, the control unit 81 starts inspection driving to move the piston 512 toward the pressure reduction side. Specifically, it applies current in a predetermined pattern to each phase of the servo motor 513 so as to move the piston 512 in the backward direction Zb. The inspection driving is performed as rotation angle sensorless control. Rotation angle sensorless control is control that does not use a signal from a rotation angle sensor. In the inspection driving, the servo motor 513 is rotated at a constant rotation speed. The current value supplied to the servo motor 513 in the inspection driving is set to a current value that generates a torque greater than the resistance when the piston 512 slides within the cylinder 511 when the servo motor 513 is driven by that current value. After starting the inspection driving toward the pressure reduction side, the control unit 81 proceeds to step S103.

[0063] In step S103, if the piston 512 has reached the pressure reduction limit (S103: YES), the control unit 81 proceeds to step S105. On the other hand, if the piston 512 has not reached the pressure reduction limit (S103: NO), the control unit 81 proceeds to step S111.

[0064] The pressure reduction limit will now be described. For example, when the piston 512 is moved in the backward direction Zb by a specified backward limit distance by the test drive, it can be determined that the pressure reduction limit has been reached.

[0065] For example, when the servo motor 513 is rotated by an amount sufficient to move the reverse limit distance by the test drive, it can be determined that the pressure reduction limit has been reached. The rotation speed of the servo motor 513 corresponding to the reverse limit distance is set as the first phase target rotation speed. The first phase target rotation speed is, for example, two or more rotations.

[0066] For example, it can be determined that the pressure reduction limit has been reached when a first specified time has elapsed since the start of the test drive. An example of the first specified time can be set as the time required for the piston 512 to move in the backward direction Zb from a state in which the end face of the piston 512 in the forward direction Za is at the pressurization start position OP until the end face of the piston 512 in the backward direction Zb reaches the most retracted position BE. A value calculated in advance by an experiment or the like can be used as the first specified time.

[0067] In step S111, the control unit 81 executes a determination process. The determination process will be described later. When the determination process ends, the control unit 81 shifts the process to step S104. In step S104, if the determination end flag is not turned on (S104: NO), the control unit 81 shifts the process back to step S103.

[0068] On the other hand, if the determination end flag is set to ON (S104: YES), the control unit 81 proceeds to step S109. In step S109, the control unit 81 determines that the rotation angle sensor SE2 is normal. Thereafter, the control unit 81 ends this processing routine. In step S109, the control unit 81 may store information indicating that the rotation angle sensor SE2 is normal.

[0069] 5 shows the flow of the determination process executed by the control unit 81. The control unit 81 can start this processing routine in the process of step S111 shown in FIG. 4 and in the process of step S112 described later.

[0070] When this processing routine is started, first in step S201, the control unit 81 determines whether or not a Z pulse has been detected. If a Z pulse has not been detected (S201: NO), the control unit 81 ends this processing routine. On the other hand, if a Z pulse has been detected (S201: YES), the control unit 81 proceeds to step S202.

[0071] In step S202, the Z counter value Cz is updated by incrementing it by 1. The initial value of the Z counter value Cz is 0. After updating the Z counter value Cz, the control unit 81 proceeds to step S203.

[0072] In step S203, if the Z counter value Cz is less than 2, i.e., if the Z counter value Cz is 1 (S203: NO), the control unit 81 proceeds to step S205. In step S205, the control unit 81 resets the A / B counter value Cab to its initial value of 0. Thereafter, the control unit 81 ends this processing routine.

[0073] On the other hand, if the Z counter value Cz is equal to or greater than 2 in step S203 (S203: YES), the control unit 81 proceeds to step S204. In step S204, the control unit 81 stores the A / B counter value Cab as a saved counter value Cab'. Thereafter, the control unit 81 proceeds to step S206. In step S206, the control unit 81 resets the A / B counter value Cab to its initial value of 0. Thereafter, the control unit 81 proceeds to step S207.

[0074] In step S207, the control unit 81 determines whether the counter stored value Cab' is within a specified range. For example, the control unit 81 makes the determination as follows. The control unit 81 determines that the counter stored value Cab' is within the specified range if the counter stored value Cab' is equal to or greater than the "specified maximum value α-Yab / 2" and equal to or less than the "specified maximum value α+Yab / 2." The control unit 81 determines that the counter stored value Cab' is outside the specified range if the counter stored value Cab' is smaller than the "specified maximum value α-Yab / 2." The control unit 81 determines that the counter stored value Cab' is outside the specified range if the counter stored value Cab' is greater than the "specified maximum value α+Yab / 2." Here, "Yab / 2" means a tolerance. The tolerance Yab / 2 can be calculated as a predetermined ratio to the specified maximum value α.

[0075] In step S207, if the stored counter value Cab′ is outside the specified range (S207: NO), the control unit 81 ends this processing routine. On the other hand, if the stored counter value Cab′ is within the specified range (S207: YES), the control unit 81 proceeds to step S208.

[0076] In step S208, the control unit 81 turns on the determination end flag. The initial value of the determination end flag is off. When the control unit 81 turns on the determination end flag, it ends this processing routine.

[0077] 4, in step S105, the control unit 81 resets both the A / B counter value Cab and the Z counter value Cz to 0. After that, the control unit 81 proceeds to step S106.

[0078] In step S106, the control unit 81 starts inspection drive to move the piston 512 toward the pressurizing side. Specifically, current is applied in a predetermined pattern to each phase of the servo motor 513 so as to move the piston 512 forward in the direction Za. As with the inspection drive toward the depressurizing side, the inspection drive toward the pressurizing side is performed using rotation angle sensorless control. After starting the inspection drive toward the pressurizing side, the control unit 81 proceeds to step S107.

[0079] In step S107, if the piston 512 has not reached the pressure-side limit (S107: NO), the control unit 81 proceeds to step S112. On the other hand, if the piston 512 has reached the pressure-side limit (S107: YES), the control unit 81 proceeds to step S110.

[0080] The pressure-side limit will now be described. For example, when the piston 512 is moved in the forward direction Za by a specified forward limit distance by the test drive, it can be determined that the pressure-side limit has been reached.

[0081] For example, when the servo motor 513 is rotated by an amount sufficient to move the piston 512 the advance limit distance by test driving, it can be determined that the pressure-side limit has been reached. The rotation speed of the servo motor 513 corresponding to the advance limit distance is set to the second phase target rotation speed. The second phase target rotation speed is, for example, two rotations or more. The higher the second phase target rotation speed, the more times Z pulses are output, and therefore the more opportunities there are to determine the counter stored value Cab'. However, it is preferable to set the upper limit of the second phase target rotation speed based on the relationship between the piston 512 and the pressure start position OP, as will be described later.

[0082] For example, it can be determined that the pressure-side limit has been reached when a second specified time has elapsed since the start of the test drive. An example of the second specified time can be set as the time required for the piston 512 to move in the forward direction Za from a state in which the end face of the piston 512 in the backward direction Zb is at the most retracted position BE until the end face of the piston 512 in the forward direction Za reaches the pressure-applying start position OP. A value calculated in advance by an experiment or the like can be used as the second specified time.

[0083] In step S112, the control unit 81 executes the determination process. When the determination process ends, the control unit 81 shifts the process to step S108. In step S108, if the determination end flag is not turned on (S108: NO), the control unit 81 shifts the process back to step S107.

[0084] On the other hand, if the determination end flag is set to ON (S108: YES), the control unit 81 proceeds to step S109. In step S109, the control unit 81 determines that the rotation angle sensor SE2 is normal. Thereafter, the control unit 81 ends this processing routine.

[0085] In step S110, the control unit 81 determines that an abnormality has occurred in the rotation angle sensor SE2. Then, the control unit 81 ends this processing routine. In step S110, the control unit 81 may store information indicating that the rotation angle sensor SE2 is abnormal.

[0086] When the control unit 81 finishes the rotation angle sensor check process, it resets the A / B counter value Cab, the Z counter value Cz, the counter storage value Cab', and the determination end flag to their initial values.

[0087] <Position of piston moved in rotation angle sensor check process> The position of piston 512 moved in the rotation angle sensor check process of this embodiment will be described with reference to Fig. 6. Note that Figs. 1 to 3 and 6 are schematic examples, and the dimensions of each part in the figures do not represent actual dimensions.

[0088] The distance traveled by the piston 512 when it moves between a state where its front end is at the pressurization start position OP and a state where its rear end is at the most retracted position BE is defined as an idle distance Li. Here, the front end of the piston 512 is the end face of the piston 512 in the forward direction Za. The rear end of the piston 512 is the end face of the piston 512 in the backward direction Zb.

[0089] 6 shows the initial position X0, the first position X1, and the second position X2. The initial position X0, the first position X1, and the second position X2, for example, satisfy the relationship described below. The initial position X0 is located between the most retracted position BE and the pressure application start position OP. The initial position X0 is a position that satisfies the following relationship with the first position X1 and the second position X2.

[0090] The first position X1 represents the position of the rear end of the piston 512 when the piston 512 is moved in the retraction direction Zb by a first displacement LLb from a state in which the front end of the piston 512 is at the initial position X0. The first displacement LLb corresponds to the distance the piston 512 retracts according to the first phase target rotation speed. In other words, the first displacement LLb is equal to the retraction limit distance. The first position X1 is closer to the pressurization start position OP than the most retracted position BE. The upper limit of the value that can be set as the first phase target rotation speed is preferably a value that positions the first position X1 closer to the pressurization start position OP than the most retracted position BE.

[0091] The second position X2 represents the position of the front end of the piston 512 when the piston 512 is moved in the forward direction Za by a second displacement LLa from a state in which the rear end of the piston 512 is at the first position X1. The second displacement LLa corresponds to the distance the piston 512 advances according to the second phase target rotational speed. In other words, the second displacement LLa is equal to the forward limit distance. The second position X2 is closer to the most retracted position BE than the pressurization start position OP. The upper limit of the value that can be set as the second phase target rotational speed is preferably a value that positions the second position X2 closer to the most retracted position BE than the pressurization start position OP. More preferably, the upper limit of the value that can be set as the second phase target rotational speed is a value that positions the second position X2 slightly further in the backward direction Zb than the pressurization start position OP. Note that the idle distance Li is greater than the second displacement LLa. The magnitude relationship between the second displacement LLa and the first displacement LLb can be set as appropriate, but it is preferable that the second displacement LLa is larger than the first displacement LLb.

[0092] From the above, the following can be said: Even if the piston 512 moves in the backward direction Zb by the first displacement LLb from a state in which the front end of the piston 512 is at the initial position X0, the rear end of the piston 512 does not reach the most backward position BE. Even if the piston 512 moves in the forward direction Za by the second displacement LLa from a state in which the rear end of the piston 512 is at the first position X1, no hydraulic pressure is generated.

[0093] In addition, when the second displacement LLa is greater than the first displacement LLb, the second position X2 can also be considered to be a position where the piston 512 is moved in the forward direction Za from the initial position X0 by a distance obtained by subtracting a distance corresponding to the first displacement LLb from the second displacement LLa. Therefore, even if the piston 512 is moved in the forward direction Za from the initial position X0 by a distance obtained by subtracting a distance corresponding to the first displacement LLb from the second displacement LLa, no hydraulic pressure is generated.

[0094] <Termination Process> When shutting down the braking system 100, the control unit 81 may execute a termination process to move the piston 512 to a preset position and then terminate the braking system 100. A state in which the braking system 100 is terminated refers to a state in which the control unit 81 is not activated. A state in which the control unit 81 is not activated may also include a state in which the control unit 81 is inactive. As an example, the braking system 100 is terminated when the start switch of the vehicle is turned off.

[0095] In the termination process, for example, the control unit 81 may move the piston 512 so that the front end of the piston 512 is aligned with the initial position X0. For example, the control unit 81 may move the piston 512 so that the front end of the piston 512 is positioned between the initial position X0 and the pressurization start position OP.

[0096] If the rotation angle sensor check process is initiated when the vehicle braking system 100 is started, the position of the piston 512 after it has been moved by the termination process is the position of the piston 512 when the rotation angle sensor check process is initiated.

[0097] <Correspondence> When the Z counter value Cz is 2 or more, the latest Z pulse corresponds to the "second Z pulse." The Z pulse detected immediately before the latest Z pulse corresponds to the "first Z pulse." In other words, the Z pulse detected after the first Z pulse is the second Z pulse. Furthermore, the counter stored value Cab' corresponds to the "number of phase pulses in the period from the detection of the first Z pulse to the detection of the second Z pulse."

[0098] 4, the process consisting of steps S101, S102, S103, S111, S104, and S109 corresponds to the first check process. The process consisting of steps S106, S107, S112, S108, S109, and S110 corresponds to the second check process. The second check process is executed when the rotation angle sensor SE2 is not determined to be normal even after the first check process is executed. The condition for starting the second check process can be said to be when the piston 512 reaches the pressure reduction limit without being determined to be normal in the first check process.

[0099] <Functions and Effects> The functions and effects of this embodiment will be described. Fig. 7 shows the A / B counter value Cab and the Z pulse when the rotation angle sensor check process is executed. As an example, the first check process will be described.

[0100] As shown in (b) of Fig. 7, the first Z pulse is detected at timing t1. The second Z pulse is detected at timing t2. When the first Z pulse is detected at timing t1, the A / B counter value Cab is reset to 0 (S205), as shown in (a) of Fig. 7. Thereafter, the A / B counter value Cab is incremented each time an A pulse and a B pulse are detected. When the second Z pulse is detected at timing t2, the A / B counter value Cab at this time is stored as the counter saved value Cab' (S204).

[0101] If the A / B counter value Cab at the time when the second Z pulse is detected at timing t2 is within a specified range including the specified maximum value α based on the specifications of the rotation angle sensor SE2, the determination process ends (S208). As a result, it is determined that the rotation angle sensor SE2 is normal (S109). Note that FIG. 7 shows the range obtained by increasing or decreasing the allowable error Yab / 2 based on the specified maximum value α. If the counter stored value Cab' is within this range, it can be determined that the rotation angle sensor SE2 is normal.

[0102] If the A / B counter value Cab is not within the specified range, the determination process can be repeated until the piston 512 reaches the pressure reduction limit. If the piston 512 reaches the pressure reduction limit, the process can proceed to the second check process. In the second check process, the determination process can also be repeated until the piston 512 reaches the pressure increase limit.

[0103] As described above, according to this embodiment, it is possible to check whether the rotation angle sensor SE2 is normal. In the rotation angle sensor check process, the servo motor 513 is rotated using rotation angle sensorless control, which does not use the rotation angle sensor signal for control. This may cause the rotor of the servo motor 513 to not rotate smoothly. For example, the rotor of the servo motor 513 may fluctuate between the forward and reverse directions. This may cause the number of phase pulses per rotation detected in the rotation angle sensor check process to deviate from the specified maximum value α. Furthermore, due to the relationship between the timing at which the phase pulses are output and the calculation cycle of the control unit 81, the counter stored value Cab′ may deviate from the specified maximum value α. In this regard, this embodiment uses a specified range including the specified maximum value α to determine whether the A / B counter value Cab from the detection of the first Z pulse to the detection of the second Z pulse is within the specified range. Therefore, deviations in the number of phase pulses can be tolerated when checking the rotation angle sensor SE2.

[0104] Incidentally, in order to check whether the rotation angle sensor SE2 is normal, it is necessary to output a Z pulse and a phase pulse by rotating the servo motor 513 as described above. When checking the rotation angle sensor SE2, if the electric cylinder 51 generates hydraulic pressure in accordance with the rotation of the servo motor 513, a braking force corresponding to the hydraulic pressure is generated on the vehicle. If a braking force is generated when checking the rotation angle sensor SE2, the generated braking force will not correspond to the operation by the driver of the vehicle, which may cause the driver to feel uncomfortable.

[0105] In this regard, according to this embodiment, the rotation angle sensor check process can be performed without generating hydraulic pressure. For example, in the first check process, the servo motor 513 is rotated so that the piston 512 moves in the backward direction Zb, so no hydraulic pressure is generated. In the first check process, the first phase target rotation speed is two or more rotations, so the Z pulse is output at least two times. This provides an opportunity to count the phase pulses between the first Z pulse and the second Z pulse.

[0106] In this embodiment, the first phase target rotation speed is set so that the rear end of the piston 512 does not reach the most retracted position BE when the piston 512 is retracted by the first displacement LLb corresponding to the first phase target rotation speed. Since the rear end of the piston 512 can be prevented from reaching the most retracted position BE, excessive stress on the electric cylinder 51 can be prevented.

[0107] In this embodiment, the position of the piston 512 when the first check process is started is set to a position where the rear end of the piston 512 will not reach the most retracted position BE when the piston 512 is retracted by the first displacement LLb corresponding to the first phase target rotation speed. Since the rear end of the piston 512 can be prevented from reaching the most retracted position BE, excessive stress on the electric cylinder 51 can be prevented.

[0108] In the second check process, the second phase target rotation speed is set so that the front end of the piston 512 does not reach the pressurization start position OP when the piston 512 is advanced by the second displacement LLa corresponding to the second phase target rotation speed. This makes it possible to suppress the generation of hydraulic pressure even when the piston 512 is moved in the forward direction Za. In the second check process, because the second phase target rotation speed is two or more rotations, a Z pulse is output at least two times. This provides an opportunity to count the phase pulses between the first Z pulse and the second Z pulse.

[0109] In this embodiment, the idle distance Li is set to be greater than the second displacement LLa. Therefore, even if the rear end of the piston 512 has reached the most retracted position BE when the second check process is started, the front end of the piston 512, which is advanced by the second check process, does not reach the pressurization start position OP. This prevents hydraulic pressure from being generated during the second check process.

[0110] Even if the rotation angle sensor SE2 is normal, the first check process may not determine that the sensor is normal. For example, if the rear end of the piston 512 reaches the most retracted position BE due to the test drive toward the depressurization side in the first check process, the A / B counter value Cab does not increase after the rear end of the piston 512 reaches the most retracted position BE. Therefore, the counter stored value Cab' may be a value outside the specified range. If an abnormality were determined in the above situation, an abnormality may be erroneously determined even though the rotation angle sensor SE2 is normal.

[0111] In this regard, according to the present embodiment, if the first check process does not result in a normal determination, the process proceeds to the second check process, thereby continuing the check, thereby improving the accuracy of checking whether the rotation angle sensor SE2 is normal.

[0112] By moving the piston 512 by the termination process, the position of the piston 512 at the time when the rotation angle sensor check process is started can be set to a predetermined position, thereby enabling the rotation angle sensor check process to be performed without generating hydraulic pressure.

[0113] (Modifications) This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0114] In the above embodiment, the specified range is set as a range obtained by increasing or decreasing the allowable difference Yab / 2 with respect to the specified maximum value α. The specified range does not necessarily have to be centered around the specified maximum value α. For example, the specified range may be equal to or greater than the value obtained by subtracting the allowable decrease β from the specified maximum value α and equal to or less than the value obtained by adding the allowable increase γ (β > γ or γ > β) to the specified maximum value α.

[0115] In the above embodiment, the second check process is executed when the pressure reduction limit is reached in the first check process. Alternatively, an abnormality determination may be performed when the pressure reduction limit is reached.

[0116] In the above embodiment, if a negative determination is made in step S104, the process of step S103 is performed again. Alternatively, if a negative determination is made in step S104 and the Z counter value Cz is 2 or greater, the process may proceed to step S105. That is, if the determination as to whether the counter stored value Cab' is within the specified range does not result in the determination that the determination end flag is not turned on, the first check process may be terminated and the second check process may be initiated. Alternatively, if a negative determination is made in step S104 and the Z counter value Cz is 2 or greater, the process may proceed to step S110. That is, if the determination as to whether the counter stored value Cab' is within the specified range does not result in the determination that the determination end flag is not turned on, an abnormality determination may be performed.

[0117] In the above embodiment, if a negative determination is made in step S108, the process of step S107 is performed again. Alternatively, if a negative determination is made in step S108 and the Z counter value Cz is equal to or greater than 2, the process may proceed to step S110. In other words, if the determination end flag is not set on as a result of determining whether the counter stored value Cab' is within the specified range, an abnormality determination may be performed.

[0118] In the above embodiment, the control device 80 receives Z pulse and phase pulse signals from the rotation angle sensor SE2 to calculate the A / B counter value Cab. Unlike the above embodiment, even if the A / B counter value Cab is calculated on the rotation angle sensor side and the calculated A / B counter value Cab and the presence or absence of a Z pulse are periodically transmitted, the first check process and the second check process can be similarly executed to check whether the rotation angle sensor SE2 is normal.

[0119] More specifically, the rotation angle sensor SE2 calculates an A / B counter value Cab that correlates with the rotation angle. In this case, for example, the A / B counter value Cab is set to 0 (zero) at the Z pulse detection position. When the rotation angle sensor SE2 rotates forward from there, the A / B counter value Cab also increases in accordance with the rotation angle and reaches a specified maximum value α at the position immediately before the next Z pulse. On the other hand, when the rotation angle sensor SE2 rotates backward, the A / B counter value Cab decreases in accordance with the rotation angle and reaches 0 (zero) at the position of the next Z pulse. In this case, for example, the A / B counter value Cab is set to the specified maximum value α immediately after the Z pulse detection position and reaches 0 (zero) at the position immediately before the next Z pulse. Furthermore, the rotation angle sensor SE2 communicates at a predetermined communication interval CT. When a communication timing arrives, the rotation angle sensor SE2 transmits the A / B counter value Cab at that time and whether the Z pulse position has been passed between the previous communication timing and the current communication timing.

[0120] FIG. 8 shows the A / B counter value Cab before and after the Z pulse position for a normal rotation angle sensor SE2. As shown in FIG. 8B, FIG. 8 also displays the Z pulse passing position T1Z and the Z pulse passing position T2Z as the Z pulse detection positions. When the rotation angle sensor SE2 rotates in the forward direction Za during the second check process, the A / B counter value Cab changes over time from left to right in FIG. 8 (from the Z pulse passing position T1Z toward the Z pulse passing position T2Z). First, at communication timing T11 immediately after the first Z pulse, a value within a predetermined error range from 0 (zero) cleared at the Z pulse position is transmitted as the A / B counter value Cab, along with a notification that the first Z pulse has passed. At this time, the control device 80 sets the Z counter value Cz to 1. The control device 80 may further confirm that the A / B counter value Cab is within a predetermined error range from 0 (zero). The control device 80 stores the A / B counter value Cab as a counter storage value Cab' each time the A / B counter value Cab is transmitted. When the control device 80 receives the A / B counter value Cab from the rotation angle sensor SE2 at communication timing T20, which is immediately before the second Z pulse, the control device 80 also stores the A / B counter value Cab as a counter storage value Cab'. Then, at communication timing T21, which is immediately after the second Z pulse, the control device 80 transmits a value within a predetermined error range from 0 (zero) cleared at the position of the Z pulse as the A / B counter value Cab, along with a notification that the Z pulse has passed. Therefore, when the control device 80 receives notification from the rotation angle sensor SE2 at communication timing T21 that the second Z pulse has passed, it first sets the Z counter value Cz to 2. Next, before updating the counter storage value Cab', the control device 80 determines whether the stored counter storage value Cab' is within a specified range based on the predetermined error range using the specified maximum value α as a reference. This allows the control device 80 to determine whether the rotation angle sensor SE2 is normal. After making the determination, the control device 80 stores the A / B counter value Cab received from the rotation angle sensor SE2 as a stored counter value Cab'.

[0121] Similarly, when the rotation angle sensor SE2 rotates in the backward direction Zb in the first check process, the counter value changes over time from right to left in FIG. 8 (from Z pulse passing position T2Z toward Z pulse passing position T1Z). First, at T20, which is the communication timing immediately after the first Z pulse, a value within a predetermined error range from the specified maximum value α is transmitted as the A / B counter value Cab, and a notification that the first Z pulse has passed is transmitted. At this time, the control device 80 sets the Z counter value Cz to 1. The control device 80 may further confirm that the A / B counter value Cab is within a predetermined error range from the specified maximum value α. Each time the A / B counter value Cab is transmitted, the control device 80 stores the A / B counter value Cab as the counter stored value Cab'. When the rotation angle sensor SE2 transmits the A / B counter value Cab at T11, which is the communication timing immediately before the second Z pulse, the control device 80 also stores the A / B counter value Cab as the counter stored value Cab'. Then, at communication timing T10 immediately after the second Z pulse, a value within a predetermined error range from the specified maximum value α is transmitted as the A / B counter value Cab, along with a notification that the Z pulse has passed. Therefore, when the control device 80 receives, at communication timing T10, notification that the second Z pulse has passed from the rotation angle sensor SE2, it first sets the Z counter value Cz to 2. Next, before updating the counter storage value Cab', it determines whether the stored counter storage value Cab' is within a specified range based on the above-mentioned predetermined error range, with 0 (zero) as the reference. This makes it possible to determine whether the rotation angle sensor SE2 is normal. After this determination, the control device 80 stores the A / B counter value Cab received from the rotation angle sensor SE2 as the counter storage value Cab'.

[0122] The predetermined error range is preferably set taking into consideration the motor rotation speed and communication interval CT in the first check process, or the motor rotation speed and communication interval CT in the second check process.

[0123] Specifically, based on the motor rotation speed and communication interval CT in the first check process, the A / B counter value Cab at a time T1L from the Z pulse passing position T1Z before the communication interval CT is calculated to estimate the first communication error Y1 due to communication delay, or the A / B counter value Cab at a time T2L from the Z pulse passing position T2Z before the communication interval CT is calculated to estimate the second communication error Y2 due to communication delay, and a predetermined error range may be calculated from the allowable difference Yab / 2 and the first communication error Y1, and from the allowable difference Yab / 2 and the second communication error Y2.

[0124] In the above configuration, for example, the rotation angle sensor SE2 includes a processing circuit having the above functions. Specifically, the processing circuit has a function of calculating the A / B counter value Cab and a function of transmitting the A / B counter value Cab and the presence or absence of a Z pulse to the control device 80.

[0125] Note that Figure 8 is illustrated as follows: Figures 8(a) and 8(b) omit the passage of time between the above-mentioned time points T1L and T2L. Figure 8(a) omits part of the transition of the A / B counter value Cab between 0 (zero) and the specified maximum value α. Figure 8(b) shows the interval between the rising edge and the falling edge of one Z pulse smaller than that in Figure 7(b).

[0126] In the above embodiment, the braking system 100 is illustrated as including the braking device 20 configured with the first braking unit 50 and the second braking unit 23. The rotation angle sensor check process can be applied to a braking system different from the above embodiment as long as the braking system is configured to generate braking force in response to the driving of an electric cylinder.

[0127] The processing circuits such as the control unit 81 can be configured as follows: The processing circuit can be configured as a circuit including one or more processors that execute various processes according to a computer program. The processing circuit can be configured as a circuit including one or more hardware circuits that execute various processes. The processing circuit can be configured as a circuit that combines one or more processors that execute some of the various processes with one or more hardware circuits that execute the remaining of the various processes.

[0128] The processor includes a processing unit such as a CPU. The processor includes a memory such as a RAM and a ROM. The memory stores program code or instructions configured to cause the processing unit to perform a process. The memory, i.e., storage medium, includes any available medium accessible by a general-purpose or special-purpose computer. An example of a hardware circuit is an ASIC, which is an application-specific integrated circuit. Another example of a hardware circuit is an FPGA.

Claims

1. A vehicle braking system including an electric cylinder that generates a braking force on a vehicle, the electric cylinder having a cylinder, a piston contained in the cylinder, a servomotor, a linear motion conversion mechanism that converts rotation of the servomotor into forward and backward movement of the piston, a rotation angle sensor that detects a rotation angle corresponding to the rotation of the servomotor, and a control unit that controls the servomotor, the electric cylinder is configured such that no hydraulic pressure is generated when the piston is in a position retreated from a predetermined pressurization start position, and hydraulic pressure is generated when the piston advances from the pressurization start position, the rotation angle sensor is configured to detect a Z pulse generated every time the servomotor rotates once, and a phase pulse generated every time the servomotor rotates by a predetermined rotation angle, the control unit is configured to detect the rotation angle of the servomotor by counting the phase pulses detected by the rotation angle sensor, and the control unit executes a rotation angle sensor check process to confirm whether the rotation angle sensor is normal or not when the vehicle braking system is started, A vehicle braking system as a first check process in the rotation angle sensor check process, in which a current is applied in a predetermined pattern to each phase of the servo motor toward a first phase target rotation speed, thereby rotating the servo motor so that the piston retracts, and the Z pulse detected during the rotation of the servo motor is designated as a first Z pulse, and the Z pulse detected after the first Z pulse is designated as a second Z pulse, the number of phase pulses in the period from when the first Z pulse is detected to when the second Z pulse is detected is counted, and it is confirmed whether the number of counted phase pulses is within a specified range, and if the number of phase pulses is within the specified range, it is determined that the rotation angle sensor is normal.

2. If the control unit has executed the first check process but has not determined that the rotation angle sensor is normal, it executes a second check process in the rotation angle sensor check process, and in the second check process, it applies a current in a predetermined pattern to each phase of the servo motor toward a second phase target rotation speed, thereby rotating the servo motor so as to move the piston forward, and counts the number of phase pulses in the period from when the first Z pulse is detected to when the second Z pulse is detected, with the Z pulse detected during the rotation of the servo motor being the first Z pulse and the Z pulse detected after the first Z pulse being the second Z pulse, and confirms whether the number of counted phase pulses is within the specified range, and determines that the rotation angle sensor is normal if the number of phase pulses is within the specified range.

3. A vehicle braking system as described in claim 2, wherein an idle distance, which is the distance the piston moves from the most rearward position where it cannot be rearward any further to the pressurization start position, is set to be greater than a second displacement, which is the distance the piston advances due to the second phase target rotation speed.

Images