Braking device

Abstract

To prevent the rotation angle of an electric motor from changing in a step-like manner when gradually increasing or decreasing it. [Solution] The first processing circuit functions as a target setting unit M21 that sets a target torque TqTr based on a servo pressure deviation ΔPs, which is the deviation between a target servo pressure PsTr and a servo pressure Ps; a motor control unit M23 that drives the first electric motor 513 based on the target torque TqTr; and a determination unit M19 that determines whether the drive state of the first electric motor 513 is unstable when the target servo pressure PsTr is increasing or decreasing. If the target setting unit M21 determines that the drive state of the first electric motor 513 is unstable, it performs a compensation process that superimposes a compensation torque on the target torque TqTr.

Description

Technical Field

[0001] The present invention relates to a braking device that generates a braking force for a vehicle by pressing a friction portion against a rotating body that rotates integrally with a wheel.

Background Art

[0002] The braking device disclosed in Patent Document 1 can increase the braking force of a vehicle by driving an electric motor so that the rotation angle increases. In this braking device, the braking force is controlled by driving the electric motor to eliminate the deviation between the target rotation angle of the electric motor and the rotation angle detection value.

[0003] Cogging torque occurs in an electric motor. Also, frictional force occurs on the torque transmission path of the electric motor in the braking device. Therefore, when the target rotation angle gradually increases or decreases, the rotation of the electric motor may stop due to the influence of the frictional force and cogging torque.

[0004] In the braking device of Patent Document 1 described above, when the rotation angle detection value does not change even though the target rotation angle is increasing or decreasing, the electric motor is driven so that a pulsating compensation torque is superimposed on the output torque of the electric motor. Thereby, it is suppressed that the state where the rotation of the electric motor stops continues.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the braking device described above, a compensatory torque is superimposed on the output torque of the electric motor, provided that the rotation of the electric motor has stopped. Therefore, in the braking device described above, when gradually increasing or decreasing the target rotation angle, it is unavoidable that the braking force generated by the driving of the electric motor will change in a step-like manner. [Means for solving the problem]

[0007] A braking device for solving the above problems is a device equipped with a braking unit that generates braking force on a vehicle by pressing a friction part against a rotating body that rotates integrally with the wheel. The braking unit has an electric motor, a rotating part that rotates in conjunction with the driving of the electric motor, and a linear motion part that moves linearly in synchronization with the rotation of the rotating part, and is configured so that the pressing force, which is the force that presses the friction part against the rotating body, can be adjusted by moving the linear motion part linearly. The braking device includes a target setting unit that sets a target torque, which is a target value of the output torque of the electric motor, based on the deviation between a target value and a detected value of the correlation value of the pressing force, a motor control unit that drives the electric motor based on the target torque, and a determination unit that determines whether the driving state of the electric motor is an unstable state in which the linear motion of the linear motion part may stop when the target value of the correlation value of the pressing force increases or decreases. If the target setting unit determines that the driving state of the electric motor is the unstable state, it performs a compensation process in which it superimposes a compensation torque on the target torque. [Effects of the Invention]

[0008] The above-described braking device has the effect of suppressing step-like changes in the rotation angle when the rotation angle of an electric motor is gradually increased or decreased. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram showing a vehicle equipped with one embodiment of a braking system. [Figure 2]Figure 2 is a block diagram showing the functional configuration of the first controller in Figure 1. [Figure 3] Figure 3 is a flowchart showing a series of processes for determining whether the operating state of an electric motor is unstable. [Figure 4] Figures 4(a) to 4(d) show the timing charts for gradually increasing the target servo pressure. [Modes for carrying out the invention]

[0010] One embodiment of the braking device will be described with reference to Figures 1 to 4. Figure 1 shows a vehicle 10 equipped with a braking system 100. The vehicle 10 has two first wheels 11 and two second wheels 12. The vehicle 10 is equipped with multiple friction brakes 15 corresponding to each of the multiple wheels 11, 12.

[0011] <Configuration of friction brakes> Multiple friction brakes 15 generate braking force on the corresponding wheels 11 and 12. Each friction brake 15 comprises a wheel cylinder 16, a rotating body 17, and a friction part 18. Since the rotating body 17 rotates integrally with the wheels 11 and 12, the friction part 18 presses against the rotating body 17, generating braking force on the wheels 11 and 12. The pressing force, which is the force pressing the friction part 18 against the rotating body 17, increases with increasing wheel pressure, which is the hydraulic pressure inside the wheel cylinder 16. Therefore, the friction brake 15 can generate greater braking force on the wheels 11 and 12 as the wheel pressure increases.

[0012] Hereafter, the braking force generated at the wheels 11 and 12 by the operation of the friction brake 15 will be referred to as "friction braking force". The sum of the friction braking forces generated at multiple wheels 11 and 12 will be referred to as "friction braking force FbM of the vehicle 10" or simply "friction braking force FbM".

[0013] <Configuration of the braking system> The braking system 100 adjusts the braking force generated in the vehicle 10 by controlling the wheel pressure of multiple wheel cylinders 16. The braking system 100 comprises an upstream unit 110 and a downstream unit 120. Each of the upstream unit 110 and the downstream unit 120 is configured to control the wheel pressure of multiple wheel cylinders 16.

[0014] <Configuration of the upstream unit> The upstream unit 110 includes a hydraulic pressure generator 20 and a first controller 210 that controls the hydraulic pressure generator 20. The first controller 210 will be described later.

[0015] The hydraulic pressure generator 20 includes a reservoir tank 21, a braking operating member 22, a brake sensor 23, a master device 30, and an electrically operated pressurized unit 50. The pressurized unit 50 corresponds to the "braking unit".

[0016] The reservoir tank 21 stores brake fluid and is open to the atmosphere. The braking operation member 22 is a member operated by the driver of the vehicle 10 when adjusting the deceleration of the vehicle 10. An example of the braking operation member 22 is the brake pedal. The act of the driver operating the braking operation member 22 is called "braking operation". When braking operation is being performed, the hydraulic pressure generator 20 can generate wheel pressure in multiple wheel cylinders 16 according to the amount of operation of the braking operation member 22.

[0017] The brake sensor 23 detects information regarding the driver's operation of the braking control member 22. For example, the brake sensor 23 detects the amount of operation of the braking control member 22 by the driver as information regarding the operation of the braking control member 22. Hereafter, the amount of operation based on the detection signal of the brake sensor 23 will be referred to as "braking operation amount Ba".

[0018] <Master device> The master device 30 includes a master cylinder 31, a stroke simulator 32, a plurality of flow paths 331, 332, 333 connected to the master cylinder 31, and a plurality of control valves 341, 342 that control the flow of the brake fluid. The master device 30 includes a hydraulic pressure sensor 351 that detects the hydraulic pressure of the brake fluid.

[0019] The stroke simulator 32 can generate a reaction force according to the operation amount of the braking operation member 22. The master cylinder 31 includes a main cylinder 41, a cover cylinder 42, a master piston 43, and an input piston 44. Each of the master piston 43 and the input piston 44 can move relative to the main cylinder 41 and the cover cylinder 42. The master cylinder 31 includes a master spring 45 that biases the master piston 43 and an input spring 46 that biases the input piston 44.

[0020] The main cylinder 41 has a plate-shaped bottom wall 411, a cylindrical peripheral wall 412 extending along the axis of the bottom wall 411 from the bottom wall 411, and a first annular wall 413 extending from the rear end of the peripheral wall 412 toward the axis of the peripheral wall 412. A hole into which the rear end portion of the master piston 43 described later is inserted is formed in the first annular wall 413.

[0021] Inside the main cylinder 41, a master chamber Rm is defined by the bottom wall 411, the peripheral wall 412, and the master piston 43. Hereinafter, in the master cylinder 31, the moving direction of the master piston 43 on the left side in FIG. 1, which reduces the volume of the master chamber Rm, is referred to as "forward". On the other hand, the opposite direction of the forward direction is referred to as "rearward". The rearward direction is also the direction in which the volume of the master chamber Rm increases.

[0022] Rearward of the master chamber Rm within the main cylinder 41, the first fluid chamber R1 is partitioned by the circumferential wall 412 and the master piston 43. Rearward of the first fluid chamber R1 within the main cylinder 41, the servo chamber Rs is partitioned by the circumferential wall 412, the first annular wall 413 and the master piston 43. Within the main cylinder 41, the master chamber Rm, the first fluid chamber R1, and the servo chamber Rs are not connected to each other.

[0023] The cover cylinder 42 has a cylindrical circumferential wall 421 and a second annular wall 422 extending from the rear end of the circumferential wall 421 toward the axis of the circumferential wall 421. The circumferential wall 421 is attached to the first annular wall 413 so that its axis coincides with that of the circumferential wall 412 of the main cylinder 41. The second annular wall 422 is provided with a hole into which the rear end of the input piston 44, which will be described later, is inserted.

[0024] Within the cover cylinder 42, the second fluid chamber R2 is partitioned by the peripheral wall 421, the second annular wall 422, and the first annular wall 413 of the main cylinder 41. In the master cylinder 31, the second fluid chamber R2 is located behind the servo chamber Rs.

[0025] The master piston 43 is housed in the master cylinder 31 with a seal ring interposed between the master piston 43 and the inner surface of the circumferential wall 412 and the inner surface of the first annular wall 413 of the main cylinder 41. When the master piston 43 moves axially, it slides along the inner surface of the circumferential wall 412 and the inner surface of the first annular wall 413. The rear end of the master piston 43 protrudes rearward from the first annular wall 413 and is located within the second fluid chamber R2.

[0026] The input piston 44 is housed in the master cylinder 31 with a seal ring interposed between the input piston 44 and the inner circumferential surface of the second annular wall 422 of the cover cylinder 42. When the input piston 44 moves axially, it slides along the inner circumferential surface of the second annular wall 422. The rear end of the input piston 44 protrudes rearward from the second annular wall 422. A braking operating member 22 is connected to the rear end of the input piston 44. In the second fluid chamber R2, a gap is formed between the input piston 44 and the master piston 43. When the braking operating member 22 is operated, the input piston 44 moves in a direction toward the master piston 43.

[0027] The master spring 45 is positioned between the bottom wall 411 of the main cylinder 41 and the master piston 43. The master spring 45 biases the master piston 43 backward, so when the master piston 43 moves forward, the master spring 45 is elastically compressed.

[0028] The input spring 46 is positioned between the first annular wall 413 of the main cylinder 41 and the input piston 44. The input spring 46 biases the input piston 44 backward, so when the input piston 44 moves forward, the input spring 46 is elastically compressed.

[0029] In the master cylinder 31, the master chamber Rm is connected to the reservoir tank 21. More specifically, the rear end portion of the master chamber Rm is connected to the reservoir tank 21 via a port formed in the peripheral wall 412 of the main cylinder 41. Therefore, when the master piston 43 moves forward from the initial position shown in Figure 1, the connection between the master chamber Rm and the reservoir tank 21 is released. From this point onward, the hydraulic pressure in the master chamber Rm increases as the master piston 43 moves forward. For example, if the hydraulic pressure in the servo chamber Rs increases, the hydraulic pressure in the servo chamber Rs will move the master piston 43 forward. This will increase the hydraulic pressure in the master chamber Rm.

[0030] The first flow path 331 connects the first hydraulic circuit 711 of the braking actuator 70 (described later) to the master chamber Rm. The second flow path 332 connects the first liquid chamber R1 to the third flow path 333. The stroke simulator 32 is also connected to the second flow path 332. The third flow path 333 connects the second liquid chamber R2 to the reservoir tank 21.

[0031] 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 located in the third flow path 333, in the portion between the connection point with the second flow path 332 and the second liquid chamber R2. The second control valve 342 is located in the third flow path 333, in the portion opposite to the first control valve 341, with the connection point with the second flow path 332 in between. When the control device 200 is operating, the first control valve 341 is opened and the second control valve 342 is closed.

[0032] The hydraulic pressure sensor 351 detects the hydraulic pressure in the second liquid chamber R2. For example, the hydraulic pressure sensor 351 is installed in the portion of the third flow path 333 between the connection point with the second liquid chamber R2 and the first control valve 341. In the following description, the hydraulic pressure based on the detection signal from the hydraulic pressure sensor 351 will be referred to as the "input hydraulic pressure Pgs".

[0033] <Pressure Unit> The pressurizing unit 50 is equipped with an electric cylinder 51. The pressurizing unit 50 can adjust the wheel pressure of multiple wheel cylinders 16 by operating the electric cylinder 51.

[0034] The pressurizing unit 50 is equipped with a fourth passage 54, a fifth passage 55, and a sixth passage 56 as brake fluid passages. The fourth passage 54 is connected to the input port 515 of the electric cylinder 51 and the reservoir tank 21. The fifth passage 55 is connected to the servo chamber Rs of the master cylinder 31 and the output port 516 of the electric cylinder 51. The sixth passage 56 is connected to the second hydraulic circuit 712 of the brake actuator 70 (described later) and the fifth passage 55. Therefore, the electric cylinder 51 can supply brake fluid discharged from the output port 516 to both the servo chamber Rs and the second hydraulic circuit 712.

[0035] The pressurizing unit 50 includes a differential pressure regulating valve 551 installed in the portion of the fifth flow path 55 between the connection point with the sixth flow path 56 and the servo chamber Rs. The differential pressure regulating valve 551 is a normally open linear solenoid valve that adjusts the differential pressure between the portion of the fifth flow path 55 between the differential pressure regulating valve 551 and the servo chamber Rs and between the portion of the fifth flow path 55 between the differential pressure regulating valve 551 and the electric cylinder 51. By adjusting the indicated opening degree of the differential pressure regulating valve 551, the pressurizing unit 50 can adjust the amount of brake fluid supplied to the servo chamber Rs, i.e., the hydraulic pressure in the servo chamber Rs.

[0036] Furthermore, a check valve 552 is provided in parallel with the differential pressure regulating valve 551 in the fifth flow path 55. The check valve 552 allows the flow of brake fluid through it 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 it toward the servo chamber Rs toward the servo chamber Rs.

[0037] The electric cylinder 51 comprises a cylinder 511, a piston 512, a first electric motor 513, and a conversion mechanism 514. The piston 512 is slidably mounted within the cylinder 511. The first electric motor 513 functions as the power source for the electric cylinder 51. The output shaft 513a of the first electric motor 513 is connected to the conversion mechanism 514.

[0038] An example of the first electric motor 513 is a brushless motor having multiple phase coils. In this case, the motor rotation angle can be adjusted by adjusting the current flowing through the multiple phase coils. The motor rotation angle is the rotation angle of the output shaft of the first electric motor 513.

[0039] The conversion mechanism 514 converts the rotational motion of the output shaft 513a into the linear motion of the piston 512. The conversion mechanism 514 has a rotating part 514a that rotates in conjunction with the drive of the first electric motor 513, and a linear motion part 514b that is coaxially arranged with the rotating part 514a. Since the rotating part 514a is connected to the output shaft 513a, the rotating part 514a rotates in conjunction with the rotation of the output shaft 513a. The linear motion part 514b moves linearly in synchronization with the rotation of the rotating part 514a. Specifically, the linear motion part 514b moves linearly in a direction corresponding to the rotation direction of the rotating part 514a. The piston 512 is connected to this linear motion part 514b. Therefore, the piston 512 moves linearly in response to the drive of the first electric motor 513.

[0040] An example of a conversion mechanism 514 is a screw mechanism. In the example shown in Figure 1, the nut of the screw mechanism functions as the rotating part 514a, and the bolt functions as the linear part 514b. The conversion mechanism 514 is not limited to this configuration; a screw mechanism in which the bolt functions as the rotating part 514a and the nut functions as the linear part 514b may also be used as the conversion mechanism 514.

[0041] Inside cylinder 511, a hydraulic chamber Re into which brake fluid is introduced is partitioned by the peripheral wall of cylinder 511 and piston 512. The position of piston 512 inside cylinder 511 can be changed by driving first electric motor 513. Hereafter, the direction of linear movement of piston 512 when reducing the volume of hydraulic chamber Re will be described as "forward direction Za," and the opposite direction of forward direction Za will be described as "reverse direction Zb." Reverse direction Zb is also the direction of linear movement of piston 512 when increasing the volume of hydraulic chamber Re.

[0042] An input port 515 and an output port 516 are formed on the peripheral wall of the cylinder 511 as ports connecting the hydraulic chamber Re to the outside. A through hole 517 is formed in the piston 512. The through hole 517 is positioned so that the input port 515 and the hydraulic chamber Re can communicate when the piston 512 is in its rearmost position. As a result, when the piston 512 is in its rearmost position, the hydraulic chamber Re of the cylinder 511 communicates with the reservoir tank 21 via the through hole 517, the input port 515, and the fourth flow path 54. The input port 515 is open when the piston 512 is in its rearmost position and is configured to be closed by the piston 512 when the piston 512 moves forward in the Za direction from the rearmost position. Even after the input port 515 is closed by the piston 512, if the piston 512 moves forward in the Za direction, the hydraulic pressure in the hydraulic chamber Re increases.

[0043] The output port 516 is connected to the master cylinder 31 and the sixth flow path 56 via the fifth flow path 55. 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, the brake fluid from the hydraulic chamber Re is discharged from the output port 516 into the fifth flow path 55 as the piston 512 moves in the forward direction Za within the cylinder 511 in response to the drive of the first electric motor 513. On the other hand, as the piston 512 moves in the backward direction Zb within the cylinder 511 in response to the drive of the first electric motor 513, the brake fluid from the fifth flow path 55 is drawn into the hydraulic chamber Re from the output port 516.

[0044] In the hydraulic pressure generator 20, when brake fluid is discharged from the output port 516 of the electric cylinder 51, the brake fluid flows through the fifth passage 55. A portion of the brake fluid flowing through the fifth passage 55 flows towards the wheel cylinder 16 for the second wheel 12 via the sixth passage 56. The remaining brake fluid flows into the servo chamber Rs of the master device 30. As a result, the hydraulic pressure in the servo chamber Rs increases, causing the master piston 43 to move forward and increasing the hydraulic pressure in the master chamber Rm. This causes the brake fluid in the master chamber Rm to flow through the first passage 331 towards the wheel cylinder 16 for the first wheel 11.

[0045] On the other hand, when the electric cylinder 51 is drawing brake fluid through the output port 516, brake fluid flows out from each of the wheel cylinders 16 for the multiple wheels 11 and 12. As a result, the brake fluid flows in the sixth passage 56 toward the fifth passage 55. Also, in the first passage 331, brake fluid flows toward the master chamber Rm. As a result, the hydraulic pressure in the master chamber Rm increases, causing the master piston 43 to move backward. Consequently, the brake fluid in the servo chamber Rs flows out into the fifth passage 55. This causes the brake fluid to flow toward the electric cylinder 51 in the fifth passage 55.

[0046] The pressurizing unit 50 is equipped with a servo pressure sensor 58 and a rotation angle sensor 59. The servo pressure sensor 58 detects the servo pressure, which is the discharge pressure of the brake fluid from the electric cylinder 51. The rotation angle sensor 59 detects the motor rotation angle of the first electric motor 513. Hereafter, the servo pressure based on the detection signal of the servo pressure sensor 58 will be referred to as the "servo pressure detection value Ps". The motor rotation angle based on the detection signal of the rotation angle sensor 59 will be referred to as the "rotation angle detection value θmt".

[0047] <Downstream Unit> The downstream unit 120 includes a braking actuator 70 and a second controller 220 for controlling the braking actuator 70. An example of the braking actuator 70 is the actuator disclosed in "Japanese Patent Application Publication No. 2024-170913". The braking actuator 70 may have a different configuration from the actuator disclosed in the above publication, as long as it can individually adjust the wheel pressure of multiple wheel cylinders 16. The second controller 220 will be described later.

[0048] <Control device configuration> As shown in Figure 1, the control device 200 of the braking device 100 can operate the hydraulic pressure generator 20 and the braking actuator 70 based on detection signals from multiple sensors 351, 58, and 59. For example, the control device 200 can control the servo pressure by driving the first electric motor 513. This allows the control device 200 to generate wheel pressure in multiple wheel cylinders 16 according to the servo pressure. Furthermore, even when the pressurizing unit 50 of the hydraulic pressure generator 20 is not operating, the control device 200 can adjust the wheel pressure of multiple wheel cylinders 16 by operating the braking actuator 70.

[0049] The control device 200 includes the first controller 210 and the second controller 220 described above. The multiple controllers 210 and 220 can send and receive various information and commands from each other via the in-vehicle network 230.

[0050] The first controller 210 has a first processing circuit 211. The second controller 220 has a second processing circuit 221. An example of the processing circuits 211 and 221 is an electronic control unit. In this case, each of the multiple processing circuits 211 and 221 has a CPU and a memory that stores a control program executed by the CPU. The first processing circuit 211 operates the hydraulic pressure generator 20 by having the CPU execute the control program in the memory. The second processing circuit 221 operates the braking actuator 70 by having the CPU execute the control program in the memory.

[0051] <Functional Configuration of the First Controller> Referring to Figure 2, the functional configuration of the first controller 210 will be explained. The first processing circuit 211 of the first controller 210 functions as a plurality of functional units when the CPU executes a control program in memory. The plurality of functional units include a functional unit related to driving the first electric motor 513. The plurality of functional units include a target friction braking force derivation unit M11, a target servo pressure derivation unit M13, a servo pressure deviation derivation unit M15, a rotation speed derivation unit M17, a determination unit M19, a target setting unit M21, and a motor control unit M23.

[0052] The target friction braking force derivation unit M11 derives a target friction braking force FbMTr, which is a target value for the friction braking force FbM of the vehicle 10, at predetermined control cycles. The target friction braking force derivation unit M11 derives the target friction braking force FbMTr based on the braking operation amount Ba and the regenerative braking force FbE of the vehicle 10. For example, the target friction braking force derivation unit M11 derives the target braking force FbTr such that its value increases as the braking operation amount Ba increases. The target braking force FbTr is the target value of the sum of the regenerative braking force FbE and the friction braking force FbM. The target friction braking force derivation unit M11 derives the value obtained by subtracting the regenerative braking force FbE from the target braking force FbTr as the target friction braking force FbMTr.

[0053] The target servo pressure derivation unit M13 derives the target servo pressure PsTr based on the target friction braking force FbMTr at predetermined control cycles. The target servo pressure PsTr is the target value of the servo pressure Ps. The target servo pressure derivation unit M13 derives the target servo pressure PsTr such that its value increases as the target friction braking force FbMTr increases.

[0054] As the servo pressure increases, the wheel pressure of the multiple wheel cylinders 16 increases. As a result, the pressing force, which is the force pressing the friction part 18 against the rotating body 17, increases. In other words, the servo pressure is an example of a "correlation value of the pressing force." In this respect, the target servo pressure PsTr corresponds to the "target value of the correlation value of the pressing force," and the servo pressure Ps corresponds to the "detected value of the correlation value of the pressing force."

[0055] The servo pressure deviation derivation unit M15 derives the servo pressure deviation ΔPs, which is the deviation between the target servo pressure PsTr and the servo pressure Ps, at predetermined control cycles. For example, the servo pressure deviation derivation unit M15 derives the value obtained by subtracting the servo pressure Ps from the target servo pressure PsTr as the servo pressure deviation ΔPs. The servo pressure deviation ΔPs corresponds to the "deviation between the target value and the detected value of the correlation value of the pressing force".

[0056] The rotational speed derivation unit M17 derives the motor rotational speed Nmt, which is the rotational speed of the output shaft 513a of the first electric motor 513, as the operating speed at predetermined control cycles. For example, the rotational speed derivation unit M17 derives the motor rotational speed Nmt by taking the time derivative of the rotation angle detection value θmt.

[0057] The determination unit M19 determines whether the drive state of the first electric motor 513 is unstable when the target servo pressure PsTr increases or decreases. An unstable state is a drive state of the first electric motor 513 in which the linear motion of the linear motion unit 514b may stop even when the first electric motor 513 is being driven.

[0058] The determination unit M19 determines whether the drive state of the first electric motor 513 is unstable based on the target servo pressure PsTr, the servo pressure deviation ΔPs, and the motor rotation speed Nmt. The processing details of the determination unit M19 will be described later with reference to Figure 3.

[0059] The target setting unit M21 sets the target torque TqTr, which is the target value of the output torque of the first electric motor 513, at predetermined control cycles. For example, the target setting unit M21 includes a reference torque derivation unit M211, a feedback torque derivation unit M213, and a compensation processing unit M215. Hereafter, the feedback torque derivation unit M213 will be referred to as "F / B torque derivation unit M213".

[0060] The reference torque derivation unit M211 derives a reference torque Tqff, which is a reference value for the output torque of the first electric motor 513, based on the target servo pressure PsTr. For example, the reference torque derivation unit M211 derives the reference torque Tqff by feedforward control based on the target servo pressure PsTr. As a result, the reference torque Tqff increases as the target servo pressure PsTr increases.

[0061] The F / B torque derivation unit M213 derives a feedback-corrected torque Tqfb by feedback control that takes the servo pressure deviation ΔPs as input. The feedback control includes at least proportional control among proportional control, differential control, and integral control. The feedback-corrected torque Tqfb is referred to as "FB-corrected torque Tqfb".

[0062] The compensation processing unit M215 sets the target torque TqTr based on the reference torque Tqff, FB correction torque Tqfb, target servo pressure PsTr, and the determination result of the determination unit M19. The compensation processing unit M215 derives the sum of the reference torque Tqff and the FB correction torque Tqfb as the provisional value TqTr1 of the target torque. If the determination unit M19 determines that the drive state of the first electric motor 513 is not unstable, the compensation processing unit M215 sets the provisional value TqTr1 as the target torque TqTr.

[0063] On the other hand, if the determination unit M19 determines that the drive state of the first electric motor 513 is unstable, the compensation processing unit M215 sets the target torque TqTr by performing compensation processing. In the compensation processing, if the target servo pressure PsTr is increasing, the compensation processing unit M215 sets a positive torque as the compensation torque TqC, and then sets the sum of the compensation torque TqC and the provisional value TqTr1 as the target torque TqTr. Conversely, if the target servo pressure PsTr is decreasing, the compensation processing unit M215 sets a negative torque as the compensation torque TqC, and then sets the sum of the compensation torque TqC and the provisional value TqTr1 as the target torque TqTr. In this way, the compensation processing unit M215 can superimpose the compensation torque TqC on the target torque TqTr.

[0064] Here, when the first electric motor 513 is being driven, cogging torque is generated in the first electric motor 513. If the rate of increase of the motor torque Tq, which is the output torque of the first electric motor 513, is small, the rotation of the output shaft 513a may be suppressed due to the effect of the cogging torque. In addition, frictional force is generated in the torque transmission path of the first electric motor 513, for example, between the rotating part 514a and the linear moving part 514b. If the rate of increase of the motor torque Tq is small, the rotation of the output shaft 513a may be suppressed due to the effect of this frictional force.

[0065] Therefore, the magnitude of the compensation torque TqC is set based on the cogging torque and the magnitude of the frictional force generated between the rotating part 514a and the linear part 514b. In other words, the compensation torque TqC is set to a magnitude that can overcome the cogging torque and frictional force and continue the rotation of the output shaft 513a.

[0066] The motor control unit M23 derives a command value ITr for the motor current, which is the current supplied to the first electric motor 513, based on the target torque TqTr. Then, the motor control unit M23 activates the driver circuit for the first electric motor 513 according to the drive signal based on the command value ITr. In this way, the motor control unit M23 can drive the first electric motor 513.

[0067] <Processing details of the determination unit> Referring to Figure 3, the processing details of the determination unit M19 will be explained. The determination unit M19 performs the series of processes shown in Figure 3 at predetermined determination cycles when the target servo pressure PsTr is increasing or decreasing.

[0068] In step S11, the determination unit M19 determines whether the absolute value of the servo pressure deviation ΔPs is greater than or equal to a predetermined deviation determination value ΔPsth. If the absolute value of the servo pressure deviation ΔPs is small, it is possible that the servo pressure Ps is judged to be substantially equal to the target servo pressure PsTr, and the rotation angle detection value θmt is maintained. Therefore, the criterion for determining whether the servo pressure Ps is judged to be substantially equal to the target servo pressure PsTr is set as the deviation determination value ΔPsth. If the absolute value of the servo pressure deviation ΔPs is greater than or equal to the deviation determination value ΔPsth (S11: YES), the determination unit M19 proceeds to step S13. On the other hand, if the absolute value of the servo pressure deviation ΔPs is less than the deviation determination value ΔPsth (S11: NO), the determination unit M19 proceeds to step S17.

[0069] In step S13, the determination unit M19 determines whether the absolute value of the motor rotation speed Nmt is less than the speed determination value Nmtth. The speed determination value Nmtth is set as the criterion for determining whether the output shaft 513a is rotating very slowly. If the absolute value of the motor rotation speed Nmt is less than the speed determination value Nmtth (S13: YES), the determination unit M19 proceeds to step S15. On the other hand, if the absolute value of the motor rotation speed Nmt is greater than or equal to the speed determination value Nmtth (S13: NO), the determination unit M19 proceeds to step S17.

[0070] In step S15, the determination unit M19 determines that the drive state of the first electric motor 513 is unstable. That is, the determination unit M19 determines that the drive state of the first electric motor 513 is unstable if both of the following first and second conditions are met. The determination unit M19 then terminates the series of processes shown in Figure 3.

[0071] Condition 1: The absolute value of the servo pressure deviation ΔPs must be greater than or equal to the deviation judgment value ΔPsth. Second condition: The absolute value of the motor rotation speed Nmt must be less than the speed determination value Nmtth. In step S17, the determination unit M19 determines that the driving state of the first electric motor 513 is not unstable. That is, the determination unit M19 determines that the driving state of the first electric motor 513 is not unstable if at least one of the first and second conditions is not met. The determination unit M19 then terminates the series of processes shown in Figure 3.

[0072] <Operation and Effects of This Embodiment> (1) Referring to Figure 4, the operation and effects of this embodiment will be explained. In the example shown in Figure 4, the target servo pressure PsTr is increased gradually. When the braking operation amount Ba is increased very slowly by the driver's braking operation, the target servo pressure PsTr may be increased gradually. Figure 4(a) shows the change in the target servo pressure PsTr. Figure 4(b) shows the change in the servo pressure Ps in a comparative example in which the compensation torque TqC is not superimposed on the target torque TqTr. Figure 4(c) shows the change in the servo pressure Ps in this embodiment in which the compensation torque TqC is superimposed on the target torque TqTr. Figure 4(d) shows the change in the target torque TqTr in this embodiment.

[0073] As shown in Figure 4(a), the target servo pressure PsTr is increased from timing t1. Then, as shown in Figure 4(d), the target torque TqTr is increased. This causes the electric cylinder 51 to operate, and brake fluid is discharged from the electric cylinder 51. As a result, the servo pressure Ps increases in line with the increase in the target servo pressure PsTr.

[0074] Here, we will explain the comparative example described above. In the comparative example, even if the drive state of the first electric motor 513 becomes unstable, the compensation torque TqC is not superimposed on the target torque TqTr. As mentioned above, when the target servo pressure PsTr is increased slowly, the rate of increase of the target torque TqTr is small. In other words, the rate of increase of the motor torque Tq of the first electric motor 513 is also small. As a result, the rotation of the first electric motor 513 may stop due to the effects of cogging torque and friction force. Then, as shown in Figures 4(a) and (b), even though the target servo pressure PsTr is increasing, the servo pressure Ps is maintained, so the absolute value of the servo pressure deviation ΔPs becomes large. Then, the magnitude of the FB correction torque Tqfb becomes large and the target torque TqTr becomes large. As a result, the rotation of the first electric motor 513 resumes, and the increase of the servo pressure Ps resumes. When the servo pressure Ps starts to increase, the absolute value of the servo pressure deviation ΔPs becomes small. Then, the rotation of the first electric motor 513 stops again. In other words, in the comparative example, when the target servo pressure PsTr increases gradually, the servo pressure Ps may increase in a step-like manner. Also, when the target servo pressure PsTr decreases gradually, the servo pressure Ps may decrease in a step-like manner. This step-like change in servo pressure Ps means that the wheel pressure, and consequently the frictional braking force FbM of the vehicle 10, also changes in a step-like manner.

[0075] In this embodiment, if the drive state of the first electric motor 513 is determined to be unstable, a compensation torque TqC is superimposed on the target torque TqTr, as shown in Figure 4(d). Even if the motor rotation speed Nmt decreases due to the effects of cogging torque and friction force, the rotation of the first electric motor 513 is prevented from stopping by temporarily increasing the absolute value of the target torque TqTr in this way. As a result, if the target servo pressure PsTr is increasing, the servo pressure Ps continues to increase gradually, as shown in Figure 4(c). Therefore, the braking device 100 can prevent the rotation angle of the first electric motor 513 from changing in a step-like manner when gradually increasing or decreasing the rotation angle. In other words, the braking device 100 can prevent the friction braking force FbM from changing in a step-like manner when gradually increasing or decreasing the target servo pressure PsTr.

[0076] (2) When the target servo pressure PsTr is increasing or decreasing, a decrease in the absolute value of the motor rotation speed Nmt means that the rotation of the first electric motor 513 may eventually stop. Furthermore, when the motor rotation speed Nmt decreases, the rate of change of the servo pressure Ps also decreases. As a result, the absolute value of the servo pressure deviation ΔPs tends to increase.

[0077] Therefore, the first processing circuit 211 determines that the drive state of the first electric motor 513 is unstable if the absolute value of the servo pressure deviation ΔPs is greater than or equal to the deviation determination value ΔPsth, and the absolute value of the motor rotation speed Nmt is less than the speed determination value Nmtth. This allows the first processing circuit 211 to accurately determine whether or not the drive state of the first electric motor 513 is unstable. Furthermore, because the first processing circuit 211 can determine that the drive state of the first electric motor 513 is unstable before the rotation of the first electric motor 513 stops, it can superimpose the compensation torque TqC onto the target torque TqTr at an appropriate timing.

[0078] (3) The magnitude of the compensation torque TqC is set based on the cogging torque generated by the first electric motor 513 and the magnitude of the frictional force generated by the conversion mechanism 514. The first processing circuit 211 superimposes this compensation torque TqC onto the target torque TqTr. This allows the first processing circuit 211 to suppress the temporary cessation of the rotation of the first electric motor 513, i.e., the change in the frictional braking force FbM, when gradually increasing or decreasing the target servo pressure PsTr. Furthermore, by superimposing the compensation torque TqC onto the target torque TqTr, when the absolute value of the motor rotation speed Nmt becomes greater than or equal to the speed determination value Nmtth and the driving state of the first electric motor 513 is no longer unstable, the superimposition of the compensation torque TqC onto the target torque TqTr is terminated. Therefore, the period during which the compensation torque TqC is superimposed onto the target torque TqTr does not become too long, thus suppressing the occurrence of excessive changes in the servo pressure Ps. In most cases, when the compensation torque TqC is superimposed on the target torque TqTr, the absolute value of the motor rotation speed Nmt becomes equal to or greater than the speed judgment value Nmtth in a short time, so the superposition of the compensation torque TqC on the target torque TqTr ends in a short time.

[0079] Here, it is desirable that the determination of whether the absolute value of the motor rotation speed Nmt is less than the speed determination value Nmtth is performed at short intervals, so that if an unstable state occurs, the compensation torque TqC is quickly superimposed on the target torque TqTr, and if the unstable state is subsequently resolved, the superimposition of the compensation torque TqC on the target torque TqTr is quickly terminated. A "short interval" here means, for example, 3 ms or less, preferably 1 ms or less, and more preferably 200 μs or less.

[0080] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0081] The magnitude of the compensation torque TqC may be set by considering only one of the magnitudes of the cogging torque and the frictional force generated in the conversion mechanism 514. The first processing circuit 211, i.e., the determination unit M19, may determine whether the driving state of the first electric motor 513 is unstable using a method different from the method described in the above embodiment, provided that it can determine whether the driving state of the first electric motor 513 is unstable. For example, when the target servo pressure PsTr is increasing or decreasing, the first processing circuit 211 may determine that the driving state of the first electric motor 513 is unstable if the absolute value of the rate of change of the target servo pressure PsTr is less than or equal to a threshold, and the absolute value of the motor rotation speed Nmt is less than a speed determination value.

[0082] The first processing circuit 211, i.e., the target setting unit M21, may superimpose a pulse-shaped compensation torque TqC onto the target torque TqTr at predetermined intervals during periods when it is determined that the drive state of the first electric motor 513 is unstable.

[0083] The first processing circuit 211, i.e., the rotational speed derivation unit M17, may derive the moving speed of the piston 512 and the linear motion unit 514b, which move linearly in response to the drive of the first electric motor 513, as the operating speed. In this case, it is preferable that the first processing circuit 211, i.e., the determination unit M19, determines that the second condition is met when the absolute value of the moving speed of the piston 512 and the linear motion unit 514b is less than the speed determination value corresponding to that moving speed.

[0084] If the braking device 100 is equipped with a sensor for detecting wheel pressure, the first processing circuit 211, i.e., the target setting unit, may acquire the target value of the wheel pressure as the target for the correlation value of the pressing force. Alternatively, the first processing circuit 211, i.e., the target setting unit, may acquire the detected value of the wheel pressure as the detected value for the correlation value of the pressing force.

[0085] The braking unit may have a different configuration from the pressurizing unit 50 shown in Figure 1, as long as the pressing force can be adjusted by driving the first electric motor 513 to move the linear motion unit 514b in a straight line. The braking unit may be, for example, an electric braking device disclosed in "Japanese Patent Application Publication No. 2024-143525".

[0086] The first processing circuit 211 is not limited to one that includes a CPU and ROM and executes software processing. That is, the first processing circuit 211 may have any of the following configurations: (a), (b), and (c).

[0087] (a) The first processing circuit 211 comprises one or more processors that perform various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to perform the processes. The memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or dedicated computer.

[0088] (b) The first processing circuit 211 includes one or more dedicated hardware circuits that perform various processes. Examples of dedicated hardware circuits include application-specific integrated circuits, i.e., ASICs or FPGAs. ASIC is an abbreviation for "Application Specific Integrated Circuit". FPGA is an abbreviation for "Field Programmable Gate Array".

[0089] (c) The first processing circuit 211 comprises one or more processors that execute a portion of the various processes according to a computer program, and one or more dedicated hardware circuits that execute the remaining processes among the various processes.

[0090] <Other technological ideas> The technical concepts that can be understood from the above embodiments and modified examples are described below. [Note 1] Preferably, the determination unit determines that the driving state of the electric motor is not the unstable state if at least one of the first condition and the second condition is not met.

[0091] [Note 2] The aforementioned vehicle has friction brakes configured to increase the pressing force as the hydraulic pressure of the wheel cylinder increases. The braking unit includes an electric cylinder configured such that when the rotation angle of the electric motor increases, the piston is pushed forward within the cylinder by the linear motion part, causing brake fluid to be discharged from the cylinder through an output port. The aforementioned target setting unit, It is preferable to obtain the target value of the discharge pressure of the electric cylinder as the target value of the correlation value of the pressing force, and to obtain the detected value of the discharge pressure as the detected value of the correlation value of the pressing force.

[0092] [Note 3] A braking device comprising a braking unit that generates braking force by pressing a friction part against a rotating body that rotates integrally with the wheel, The braking unit comprises an electric motor, a rotating part that rotates in conjunction with the driving of the electric motor, and a linear motion part that moves linearly in synchronization with the rotation of the rotating part, and is configured so that the pressing force, which is the force that presses the friction part against the rotating body, can be adjusted by moving the linear motion part linearly. A target setting unit sets a target torque, which is the target output torque of the electric motor, based on the deviation between the target value and the detected value of the correlation value of the pressing force, The system includes a motor control unit that drives the electric motor based on the target torque, The aforementioned target setting unit, A braking device that, when the target value of the correlation value of the pressing force is increasing or decreasing, performs a compensation process in which a compensation torque is superimposed on the target torque when both of the following conditions are met: first, the absolute value of the deviation is greater than or equal to a predetermined deviation judgment value; and second, the absolute value of the operating speed, which is the rotational speed of the output shaft of the electric motor or the moving speed of the linear motion part, is less than a speed judgment value.

[0093] In this specification, the expression "at least one" means "one or more" of the desired options. For example, if there are two options, the expression "at least one" means "only one option" or "both of the two options." As another example, if there are three or more options, the expression "at least one" means "only one option" or "a combination of two or more arbitrary options." [Explanation of Symbols]

[0094] 10... Vehicles 11,12...Wheel 15… Friction brakes 16... Wheel cylinder 17…Rotational body 18...Friction part 50…Pressurizing unit (an example of a braking unit) 51…Electric Cylinder 511...Cylinder 512... Piston 513...First electric motor 513a... Output shaft 514...Conversion mechanism 514a... Rotating part 514b... Linear motion section 516…Output port 100...braking device 210...First controller 211...First processing circuit M19...judgment section M21... Goal Setting Department M23...Motor control unit

Claims

1. A braking device comprising a braking unit that generates braking force on a vehicle by pressing a friction part against a rotating body that rotates integrally with the wheel, The braking unit comprises an electric motor, a rotating part that rotates in conjunction with the driving of the electric motor, and a linear motion part that moves linearly in synchronization with the rotation of the rotating part, and is configured so that the pressing force, which is the force that presses the friction part against the rotating body, can be adjusted by moving the linear motion part linearly. A target setting unit sets a target torque, which is the target value of the output torque of the electric motor, based on the deviation between the target value and the detected value of the correlation value of the pressing force. A motor control unit that drives the electric motor based on the target torque, The system includes a determination unit that determines whether the driving state of the electric motor is in an unstable state in which the linear movement of the linear motion part may stop, when the target value of the correlation value of the pressing force increases or decreases. The target setting unit, when it determines that the driving state of the electric motor is in the unstable state, executes a compensation process that superimposes a compensation torque on the target torque. Braking device.

2. The determination unit determines that the driving state of the electric motor is in the unstable state if both of the following conditions are met: first, the absolute value of the deviation is greater than or equal to a predetermined deviation determination value; and second, the absolute value of the operating speed, which is the rotational speed of the output shaft of the electric motor or the moving speed of the linear motion part, is less than the speed determination value. The braking device according to claim 1.

3. The compensation torque is set based on the cogging torque generated by the electric motor and the magnitude of the frictional force generated between the rotating part and the linear motion part. The braking device according to claim 1 or claim 2.

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