Braking device

Abstract

To reduce fluctuation of brake fluid pressure caused by operation of a valve device.SOLUTION: A control unit 30 of a braking device includes an electric cylinder 20 for supplying brake fluid to wheel cylinders 10L, 10R by driving an electric motor 26, a fluid passage 21 through which the brake fluid discharged by the electric cylinder 20 flows, and holding valves 22L, 22R for opening and closing the fluid passage 21 to the wheel cylinders 10L, 10R. 10R 10L 22L 22R, when the holding valves 22L and 22R are opened, the relaxation control is performed to adjust the torque of the electric motor 26 so as to increase the discharge flow amount of the brake fluid from the electric cylinder 20 by the predicted flow amount.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a braking device. [Background technology]

[0002] As a braking device for a vehicle, there is a device having a wheel cylinder that generates a braking force for a wheel in response to the supply of brake fluid by an actuator. The braking devices for a vehicle described in Patent Documents 1 and 2 include a valve device that opens and closes a fluid passage connecting the actuator and the wheel cylinder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-154636 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-110633 Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of a braking system equipped with the above-described valve device, the hydraulic pressure in the hydraulic passage fluctuates in response to the operation of the valve device. [Means for solving the problem]

[0005] A braking device that solves the above problem comprises a brake fluid supply device that supplies brake fluid to a wheel cylinder by driving an electric motor, a fluid path through which brake fluid flows from the brake fluid supply device to the wheel cylinder, a valve device that switches between a closed state in which the fluid path is blocked to isolate the brake fluid supply device from the wheel cylinder and an open state in which the fluid path is opened to connect the brake fluid supply device to the wheel cylinder, and a control unit that controls the brake fluid supply device and the valve device, wherein the control unit is configured to predict changes in the state of the brake fluid in the fluid path that occur when the open state is switched between the closed state and the open state, and to perform mitigation control that adjusts the drive of the electric motor to mitigate the state change based on the predicted state change. [Effects of the Invention]

[0006] The braking device has the effect of reducing fluctuations in hydraulic pressure in the hydraulic passage caused by the operation of the valve device. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram schematically showing the configuration of a braking device according to a first embodiment. [Figure 2] FIG. 2 is a flowchart showing the procedure of the mitigation control executed by the control unit of the braking device of FIG. [Figure 3] FIG. 3(a) is a time chart showing the change in the holding valve opening degree, FIG. 3(b) is a time chart showing the change in the wheel servo pressure, FIG. 3(c) is a time chart showing the change in the servo pressure, and FIG. 3(d) is a time chart showing the change in the motor torque when the holding valve in the braking device of FIG. 1 is open. [Figure 4] FIG. 4 is a flowchart showing the procedure of the mitigation control executed by the control unit of the braking device of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] (First embodiment) Hereinafter, a first embodiment of the braking device will be described in detail with reference to FIGS. <About the braking system configuration> First, the configuration of the braking device of this embodiment will be described with reference to Fig. 1. The braking device of this embodiment is mounted on a vehicle, and generates a braking force for the vehicle by supplying brake fluid to wheel cylinders 10L, 10R of the left and right front wheels.

[0009] The braking system of this embodiment includes an electric cylinder 20 as a brake fluid supply device that supplies brake fluid to the wheel cylinders 10L, 10R. The electric cylinder 20 generates hydraulic pressure using the torque of an electric motor 26 (hereinafter referred to as motor torque). The electric cylinder 20 supplies brake fluid to the wheel cylinders 10L, 10R through a hydraulic line 21. Both wheel cylinders 10L, 10R are connected to the hydraulic line 21 via holding valves 22L, 22R, which are normally-open linear solenoid valves.

[0010] In this embodiment, the electric cylinder 20 is connected to the fluid line 21 via a cylinder cut valve 23, which is a normally closed solenoid valve. The electric cylinder 20 is connected to a reserve tank 11 that stores brake fluid via a refill check valve 24. In addition, both wheel cylinders 10L, 10R are connected to the reserve tank 11 via pressure reducing valves 25L, 25R, which are normally closed solenoid valves, respectively.

[0011] The braking system of this embodiment further includes a master cylinder 12. The master cylinder 12 generates hydraulic pressure in response to depression of a brake pedal 13 by the vehicle driver. The master cylinder 12 is connected to a stroke simulator 15 via a simulator cut valve 14, which is a normally closed solenoid valve. The master cylinder 12 is also connected to a hydraulic line 21 via a master cut valve 16, which is a normally open solenoid valve. In the braking system of this embodiment, the holding valves 22L, 22R correspond to the valve device. That is, the holding valves 22L, 22R are configured to switch between a closed state in which the hydraulic line 21 is closed to disconnect the electric cylinder 20 from the wheel cylinders 10L, 10R, and an open state in which the hydraulic line 21 is opened to connect the electric cylinder 20 to the wheel cylinders 10L, 10R.

[0012] The braking system can switch between first and second operating modes by opening and closing the simulator cut valve 14, the master cut valve 16, and the cylinder cut valve 23. In the first operating mode, the braking system generates braking force by having the master cylinder 12 supply brake fluid to the wheel cylinders 10L, 10R. The first operating mode is achieved by opening the master cut valve 16 and closing the simulator cut valve 14 and the cylinder cut valve 23. In the second operating mode, the braking system generates braking force by having the electric cylinder 20 supply brake fluid to the wheel cylinders 10L, 10R. The second operating mode is achieved by closing the master cut valve 16 and opening the simulator cut valve 14 and the cylinder cut valve 23. The braking system normally operates in the second operating mode and switches to the first operating mode in the event of a power failure, etc.

[0013] The braking device of this embodiment further includes a control unit 30. The control unit 30 includes an arithmetic processing unit 31 and a memory 32. Programs and data for controlling the braking device are stored in the memory 32. The control unit 30 executes various processes related to the control of the braking device by having the arithmetic processing unit 31 execute the programs stored in the memory 32. Detection signals from sensors such as a pedal stroke sensor 33, an M / C pressure sensor 34, a servo pressure sensor 35, a motor rotation angle sensor 36, and wheel speed sensors 37L, 37R are input to the control unit 30. The pedal stroke sensor 33 is a sensor that detects the pedal stroke, which is the amount of depression of the brake pedal 13. The M / C pressure sensor 34 is a sensor that detects the M / C pressure, which is the hydraulic pressure generated by the master cylinder 12. The servo pressure sensor 35 is a sensor that detects the servo pressure, which is the hydraulic pressure in the liquid passage 21. The motor rotation angle sensor 36 is a sensor that detects the rotation angle of the electric motor 26 of the electric cylinder 20. The wheel speed sensors 37L, 37R are sensors that detect the wheel speed, which is the rotational speed of the left and right front wheels, respectively. Then, the control unit 30 controls the electric motor 26 of the electric cylinder 20 and each solenoid valve (14, 16, 22L, 22R, 23, 25L, 25R) based on the detection results of these sensors.

[0014] <Overview of Servo Pressure Control> During the second operation mode, the control unit 30 calculates the target servo pressure based on the M / C pressure, pedal stroke, etc. Then, the control unit 30 performs feedback control of the motor torque of the electric cylinder 20 to make the detected value of the servo pressure by the servo pressure sensor 35 coincide with the target servo pressure. If the holding valves 22L, 22R are open and the pressure reducing valves 25L, 25R are closed at this time, braking force is generated on the left and right front wheels by the brake fluid supplied from the electric cylinder 20 to the wheel cylinders 10L, 10R.

[0015] <Regarding ABS Control> Next, the ABS control executed by the control unit 30 will be described. During vehicle braking, the control unit 30 checks whether deceleration slippage is occurring in the wheels based on the detection results of the wheel speed sensors 37L, 37R of the wheels. If the control unit 30 determines that deceleration slippage is occurring, it starts ABS control. When ABS control starts, the control unit 30 first performs a pressure reduction process. This process reduces the wheel pressure of the wheel where deceleration slippage has been confirmed. Specifically, the control unit 30 performs this process by closing the pressure retention valves 22L, 22R and keeping the pressure reduction valves 25L, 25R open. This causes the brake fluid in the wheel cylinders 10L, 10R of the wheels where deceleration slippage has occurred to be discharged into the reserve tank 11, thereby reducing the wheel pressure. If the control unit 30 then determines that the deceleration slippage has been resolved, it performs a pressure increase process. This process increases the wheel pressure of the wheels where deceleration slippage has been resolved. Specifically, the control unit 30 closes the pressure-reducing valves 25L, 25R and opens the pressure-holding valves 22L, 22R as a pressure-increasing process. This stops the discharge of brake fluid from the wheel cylinders 10L, 10R and resumes the supply of brake fluid from the electric cylinder 20, increasing the wheel pressure of the wheel for which it has been confirmed that deceleration slip has been resolved. The control unit 30 alternately repeats the pressure-reducing process and pressure-increasing process during ABS control.

[0016] In this embodiment, the control unit 30 opens the pressure holding valves 22L, 22R at the start of the pressure increase process to increase the wheel pressure to a pressure slightly lower than the pressure at which deceleration slip occurs in the wheels. The control unit 30 adjusts the opening of the pressure holding valves 22L, 22R to gradually increase the wheel pressure until it confirms the occurrence of deceleration slip.

[0017] <Regarding pressure boost start processing> Next, the pressure increase start process that the control unit 30 performs when starting the pressure increase process under ABS control will be described with reference to Fig. 2. Fig. 2 shows the processing procedure of the control unit 30 during the pressure increase start process. The control unit 30 performs the process of Fig. 2 when it is confirmed that the deceleration slip has been resolved and a request is made to start the pressure increase process during the pressure reduction process under ABS control.

[0018] When the start of pressure increase processing is requested, the control unit 30 first predicts a change in the state of the brake fluid in step S110 based on the opening degree, valve opening time, servo pressure, required wheel pressure, etc. of the retention valves 22L, 22R. Here, a change in the outflow flow rate will be used as an example of the change in the state of the brake fluid. The outflow flow rate represents the flow rate of brake fluid flowing from the fluid passage 21 to the wheel cylinders 10L, 10R in response to the opening of the retention valves 22L, 22R. Next, in step S120, the control unit 30 calculates, as an FF (feedforward) correction amount, an increase in motor torque required to discharge brake fluid at a flow rate equal to the outflow flow rate into the electric cylinder 20.

[0019] Next, in step S130, the control unit 30 commands the holding valves 22L, 22R to open. After that, the control unit 30 waits for a predetermined waiting time TD to elapse (S140), and then reflects the FF correction amount in the command value of the motor torque of the electric cylinder 20 (S150). Then, the control unit 30 ends the pressure increase start processing. The reflection of the FF correction amount in the command value of the motor torque may be stopped when the pressure increase processing ends. Alternatively, after the FF correction amount is reflected in the command value of the motor torque, the value of the FF correction amount may be gradually decreased over time.

[0020] The standby time TD is set to the difference between the following delay times Δ1 and Δ2 (=Δ1-Δ2). The delay time Δ1 represents the response delay between when the control unit 30 commands the holding valves 22L and 22R to open and when the holding valves 22L and 22R actually open. The delay time Δ2 represents the response delay between when the control unit 30 commands the motor torque to increase and when the discharge flow rate of the electric cylinder 20 actually increases in response to that command. The holding valves 22L and 22R open and close by moving the built-in valve disc. The movement of the valve disc requires a certain amount of time due to sliding resistance and hydraulic resistance. The motor torque command value commands the current or voltage to be applied to the electric motor 26. The time required for a change in the command value to be reflected in the actual motor torque is shorter than the time required for the holding valves 22L and 22R to open. Therefore, the delay time Δ1 is longer than the delay time Δ2 (Δ1>Δ2).

[0021] In this pressure-increase start process, the control unit 30 predicts the flow rate of brake fluid that will flow from the fluid passage 21 to the wheel cylinders 10L, 10R when the valve is switched from the closed state to the open state (S110). The control unit 30 also calculates, as the FF correction amount value (S120), the increase in motor torque required to increase the brake fluid discharge flow rate of the electric cylinder 20 to the fluid passage 21 by an amount equal to the flow rate predicted in step S110. The control unit 30 then increases the brake fluid discharge flow rate of the electric cylinder 20 by reflecting the FF correction amount in the command value for the motor torque (S150). In this way, in the pressure-increase start process, the control unit 30 predicts the flow rate of brake fluid that will be discharged from the fluid passage 21 to the wheel cylinders 10L, 10R when the valve is switched from the closed state to the open state. Then, when switching from the closed state to the open state, the control unit 30 increases the discharge flow rate of the brake fluid from the electric cylinder 20 to the fluid path 21 based on the predicted outflow flow rate. In this embodiment, the control of the electric cylinder 20 by the control unit 30 in the pressure increase start process corresponds to relaxation control.

[0022] <Actions and Effects of the First Embodiment> FIG. 3 shows an example of a control mode at the start of the pressure increase process in the braking system of this embodiment. FIG. 3(a) shows the change in the opening degree of the holding valves 22L, 22R, FIG. 3(b) shows the change in the wheel pressure, FIG. 3(c) shows the change in the servo pressure, and FIG. 3(d) shows the change in the motor torque of the electric cylinder 20. The change in the command value of the holding valves 22L, 22R is shown by a two-dot chain line in FIG. 3(a), and the change in the command value of the motor torque is shown by a two-dot chain line in FIG. 3(d). Furthermore, both FIG. 3(c) and FIG. 3(d) also show the change in the servo pressure and motor torque when the electric cylinder 20 is controlled only by feedback of the servo pressure without reflecting the FF correction amount in the process of FIG. 2. Furthermore, within the time shown in FIG. 3, the target servo pressure is maintained at a constant value.

[0023] In FIG. 3 , the control unit 30 instructs the brake fluid retention valves 22L and 22R to open at time t1. Then, at time t3, a delay time Δ1 has elapsed since time t1, the brake fluid retention valves 22L and 22R are fully open. In FIG. 3 , the control unit 30 then instructs the brake fluid retention valves 22L and 22R to reduce their opening at time t4, thereby slowing the rate at which the wheel pressure increases. When the brake fluid retention valves 22L and 22R open, brake fluid flows from the fluid passage 21 to the wheel cylinders 10L and 10R. If the brake fluid discharge flow rate from the electric cylinder 20 remains constant before and after the opening of the brake fluid retention valves 22L and 22R, the servo pressure decreases in response to the outflow of brake fluid. Servo pressure feedback alone can only increase the motor torque after the servo pressure has decreased. Therefore, if the electric cylinder 20 is controlled solely by servo pressure feedback, the servo pressure temporarily decreases after the brake fluid retention valves 22L and 22R open.

[0024] In contrast, the control unit 30 of this embodiment predicts the flow rate of oil flowing into the wheel cylinders 10L, 10R in response to the opening of the holding valves 22L, 22R. The control unit 30 then calculates the motor torque increase amount required to increase the discharge flow rate of the electric cylinder 20 by the predicted flow rate as the FF correction amount. The control unit 30 then reflects the FF correction amount in the command value of the motor torque at time t2, when the wait time TD has elapsed since time t1, when the command to open the holding valves 22L, 22R is issued. As described above, the wait time TD is set to the difference between the response delay time Δ1 from the command to open the valves to the actual opening of the holding valves 22L, 22R, and the response delay time Δ2 until the change in the command value is reflected in the actual motor torque. Therefore, the actual change in motor torque in response to the reflection of the FF correction amount at time t2 occurs at time t3, when the holding valves 22L, 22R open.

[0025] The increase in motor torque due to this FF correction amount increases the flow rate of brake fluid discharged from the electric cylinder 20 to the fluid passage 21. The increase in the flow rate at this time is approximately equal to the flow rate of fluid flowing into the wheel cylinders 10L, 10R in response to the opening of the retention valves 22L, 22R. Therefore, even after the retention valves 22L, 22R open, the servo pressure hardly decreases and is maintained at a pressure approximately equal to the target servo pressure.

[0026] In this way, the control unit 30 predicts the outflow rate of brake fluid from the fluid path 21 that accompanies the opening of the retention valves 22L, 22R at the start of the pressure increase process. Then, when the retention valves 22L, 22R are opened, the control unit 30 increases the motor torque based on the prediction result, thereby increasing the discharge rate of brake fluid from the electric cylinder 20 to the fluid path 21. Therefore, the discharge rate of the electric cylinder 20 can be increased before a drop in servo pressure that accompanies the opening of the retention valves 22L, 22R actually occurs. Therefore, the braking device of this embodiment has the effect of mitigating the drop in servo pressure that accompanies the opening of the retention valves 22L, 22R at the start of the pressure increase process.

[0027] Furthermore, after instructing the hold valves 22L, 22R to open, the control unit 30 waits a predetermined waiting time TD before instructing the electric cylinder 20 to increase the discharge flow rate. Therefore, regardless of differences in the responsiveness of the hold valves 22L, 22R and the electric cylinder 20, it is possible to synchronize the opening of the hold valves 22L, 22R with the increase in the discharge flow rate of the electric cylinder 20.

[0028] (Modification of the first embodiment) This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0029] Similar to the pressure increase start process, it is also possible to perform control to mitigate the increase in servo pressure associated with the closure of the holding valves 22L, 22R at the start of the pressure reduction process. Closing the holding valves 22L, 22R stops the outflow of brake fluid from the fluid line 21 to the wheel cylinders 10L, 10R. If the electric cylinder 20 continues to discharge brake fluid into the fluid line 21 after the valves are closed, the amount of brake fluid in the fluid line 21 increases, causing the servo pressure to rise. This increase in servo pressure associated with the closure of the holding valves 22L, 22R can be mitigated by performing the following process at the start of the pressure reduction process. In this case, when a pressure reduction process is requested, the control unit 30 predicts a decrease in the outflow rate of brake fluid from the fluid line 21 associated with the closure of the holding valves 22L, 22R. Then, when the control unit 30 closes the holding valves 22L, 22R, the control unit 30 reduces the discharge flow rate of brake fluid from the electric cylinder 20 by the amount of the predicted decrease in the outflow rate by reducing the motor torque. In this case as well, it is desirable to wait a waiting time TD after issuing a command to close the holding valves 22L, 22R before issuing a command to reduce the discharge flow rate to the electric cylinder 20. In this case, the waiting time TD should be set to the difference between the response delay time from the command to fully close until the holding valves 22L, 22R actually become fully closed, and the response delay time from the command to reduce the discharge flow rate until the discharge flow rate of the electric cylinder 20 actually decreases.

[0030] The mitigation control may be performed at the start of both the pressure increase process and the pressure decrease process. The mitigation control here predicts a change in the flow rate of brake fluid from the fluid passage 21 due to the opening and closing of the retention valves 22L, 22R, and, based on the prediction result, increases or decreases the discharge flow rate of the electric cylinder 20 in accordance with the opening and closing of the retention valves 22L, 22R.

[0031] In cases such as when there is a small difference between the delay time in the response to the opening and closing of the holding valves 22L, 22R and the delay time in the response to the change in the flow rate of the electric cylinder 20, mitigation control may be performed without setting the standby time TD. In other words, the instruction to open or close the holding valves 22L, 22R and the instruction to increase or decrease the discharge flow rate of the electric cylinder 20 may be simultaneously executed in mitigation control.

[0032] (Second embodiment) Next, a second embodiment of the braking device will be described in detail with reference to Fig. 4. In this embodiment, components common to the first embodiment are assigned the same reference numerals and detailed description thereof will be omitted. The braking device of this embodiment has the same hardware configuration as in Fig. 1, but the control unit 30 is configured to perform mitigation control that is different from that of the first embodiment.

[0033] <Regarding mitigation controls> 4 shows the processing procedure of the mitigation control performed by the control unit 30 of the braking system of this embodiment. The control unit 30 repeatedly executes the processing of FIG. 4 at every predetermined control cycle during ABS control.

[0034] 4 starts, the control unit 30 first determines in step S200 whether or not pressure increase processing is being performed. If pressure increase processing is being performed (YES), the control unit 30 proceeds to step S210, and if pressure increase processing is not being performed (NO), that is, if pressure reduction processing is being performed, the control unit 30 ends the processing for the current control cycle.

[0035] In step S210, the control unit 30 calculates a predicted increase in the servo pressure. The predicted increase in the servo pressure here represents the increase in the servo pressure that would occur if the pressure reduction process were started under the current circumstances and the holding valves 22L, 22R were closed. The control unit 30 calculates the predicted increase in the servo pressure based on, for example, the servo pressure, the motor rotation speed, etc.

[0036] During the pressure increase process, brake fluid discharged from the electric cylinder 20 flows into the hydraulic line 21, while brake fluid flows out to the wheel cylinders 10L and 10R. When the pressure reduction process begins and the holding valves 22L and 22R are closed, the flow of brake fluid from the hydraulic line 21 to the wheel cylinders 10L and 10R immediately stops. Meanwhile, when the pressure reduction process begins, the electric cylinder 20 continues to discharge brake fluid into the hydraulic line 21, just as it did before the process began. Therefore, immediately after the pressure reduction process begins, the flow rate of brake fluid flowing into the hydraulic line 21 becomes excessive, causing a temporary rise in servo pressure. As described above, the electric cylinder 20 is controlled by feedback based on the servo pressure. Therefore, the electric cylinder 20 continues to discharge brake fluid into the hydraulic line 21 for a while even after the holding valves 22L and 22R close. The amount of brake fluid discharged from the electric cylinder 20 into the hydraulic line 21 after the holding valves 22L and 22R close can be calculated from the motor rotation speed when the valves are closed. The amount of increase in servo pressure after the valves are closed is calculated based on the amount of brake fluid discharged into the fluid passage 21 after the retention valves 22L, 22R are closed and the servo pressure at the time of valve closure. In this way, the predicted amount of increase in servo pressure is calculated as a function of the current servo pressure and the motor rotation speed of the electric cylinder 20.

[0037] Next, in step S220, the control unit 30 determines whether the predicted increase amount exceeds a predetermined threshold value. The threshold value is determined based on the pressure resistance performance of the components of the braking device, etc. If the predicted increase amount exceeds the threshold value (YES), the control unit 30 proceeds to step S230, and if the predicted increase amount is equal to or less than the threshold value (NO), the control unit 30 ends the processing for the current control cycle.

[0038] In step S230, the control unit 30 calculates the motor rotation speed at which the predicted increase amount is equal to the threshold value as the speed limit. As described above, the increase amount of servo pressure after the holding valves 22L, 22R are closed can be calculated as a function of the servo pressure and motor rotation speed at the time of valve closure. Therefore, the motor rotation speed at which the predicted increase amount is equal to the threshold value can be calculated from the current servo pressure. In the next step S240, the control unit 30 adjusts the motor torque of the electric cylinder 20 so that the motor rotation speed is equal to or less than the speed limit, and then ends the processing for the current control cycle. Specifically, in step S240, the control unit 30 calculates the brake torque as a value proportional to the deviation between the speed limit and the current motor rotation speed. Then, the control unit 30 sets the value obtained by subtracting the brake torque from the value set by feedback based on the servo pressure as the motor torque command value for the electric cylinder 20.

[0039] <Actions and Effects of the Second Embodiment> The control unit 30 in the braking system of this embodiment predicts the amount of increase in servo pressure that will occur when the holding valves 22L, 22R are closed with the start of the pressure reduction process during ABS control while the pressure increase process is being performed. If the predicted amount of increase in servo pressure exceeds a threshold, the control unit 30 performs mitigation control to reduce the motor torque of the electric cylinder 20. The braking system of this embodiment can reduce the motor torque of the electric cylinder 20 even without a command to close the holding valves 22L, 22R, thereby achieving the effect of further mitigating the increase in servo pressure that will occur when the holding valves 22L, 22R are closed.

[0040] (Modification of the second embodiment) There may be cases where the absolute value of the servo pressure is required to be equal to or less than a certain value even after the holding valves 22L, 22R are closed. In such cases, the mitigation control of Fig. 4 may be performed as follows. In step S210 of Fig. 4, the peak value of the servo pressure that increases as the holding valves 22L, 22R are closed is predicted, and in step S220, it is determined whether the predicted peak value exceeds a threshold value. Then, in step S230, the motor rotation speed at which the peak value is equal to the threshold value is set as the speed limit.

[0041] (Other change examples) In the above embodiment, the amount of brake fluid flowing out of the hydraulic line 21 and changes in the hydraulic pressure (servo pressure) in the hydraulic line 21 due to the opening and closing of the retention valves 22L and 22R are predicted, and the prediction results are reflected in the control of the electric cylinder 20, thereby mitigating fluctuations in the servo pressure. Mitigation control may also be performed by predicting other changes in the state of the brake fluid in the hydraulic line 21, such as the amount of brake fluid in the hydraulic line 21, and reflecting the prediction results in the control of the electric cylinder 20. For example, changes in the state of the brake fluid in the hydraulic line 21 due to the opening and closing of the retention valves 22L and 22R may be predicted taking into account changes in the rotational speed of the electric motor 26 obtained based on the acceleration of the electric motor 26. Furthermore, if the rate of change in the state of the brake fluid in the hydraulic line 21 due to the opening and closing of the retention valves 22L and 22R is equal to or greater than a predetermined threshold, the motor torque may be adjusted to maintain the current rotational speed of the electric motor 26. In the above embodiment, mitigation control is performed by adjusting the torque of the electric motor 26. However, mitigation control may also be performed by adjusting the drive amount of the electric motor 26 by means other than torque adjustment.

[0042] The mitigation control of the above embodiment may be implemented as control for mitigating servo pressure fluctuations when the holding valves 22L, 22R are opened and closed in control other than ABS control. In the braking device of the above embodiment, the electric cylinder 20 supplies brake fluid to the wheel cylinders 10L, 10R of the left and right front wheels. However, the number and positions of the wheel cylinders to which the electric cylinder 20 supplies brake fluid may be changed.

[0043] Instead of the electric cylinder 20, another brake fluid supply device that supplies brake fluid to the wheel cylinder by driving an electric motor may be used. Other valve devices that can switch between a closed state in which the fluid path 21 for the wheel cylinders 10L, 10R is blocked and an open state in which the fluid path 21 for the wheel cylinders 10L, 10R is open may be used in place of the retention valves 22L, 22R.

[0044] The mitigation control of the above embodiment can also be applied to braking systems having a configuration different from that shown in Fig. 1. If the braking system includes a valve device interposed between the wheel cylinder and a fluid passage through which the brake fluid discharged from the brake fluid supply device flows, the adoption of the mitigation control of the above embodiment can mitigate servo pressure fluctuations that accompany the operation of the valve device.

[0045] The control unit 30 may be configured as a circuit including one or more processors operating according to a computer program, one or more dedicated hardware circuits such as dedicated hardware for performing at least some of the various processes, or a combination thereof. Dedicated hardware may include, for example, an application-specific integrated circuit (ASIC). The processor includes a CPU and memory such as RAM and ROM, which stores program code or instructions configured to cause the CPU to perform processes. The memory, i.e., storage medium, includes any available medium accessible by a general-purpose or dedicated computer. [Explanation of symbols]

[0046] 10L, 10R...Wheel cylinder 20...Electric cylinder (brake fluid supply device) 21…Liquid path 22L, 22R...Retention valve (valve device) 26...Electric motor 30...Control unit

Claims

1. a brake fluid supply device that supplies brake fluid to the wheel cylinder by driving an electric motor; a fluid passage through which the brake fluid flows to be supplied from the brake fluid supply device to the wheel cylinder; a valve device that switches between a closed state in which the fluid passage is closed to disconnect the brake fluid supply device from the wheel cylinder and an open state in which the fluid passage is opened to connect the brake fluid supply device to the wheel cylinder; a control unit for controlling the brake fluid supply device and the valve device; It is equipped with The control unit predicts a change in state of the brake fluid in the fluid path that accompanies switching between the open state and the closed state, and performs mitigation control to adjust the drive of the electric motor to mitigate the change in state based on the predicted result of the change in state. Braking device.

2. 2. The braking device according to claim 1, wherein, in the mitigation control, after instructing the valve device to switch between the open state and the closed state, the control unit instructs the brake fluid supply device to adjust the drive of the electric motor based on the prediction result after a predetermined waiting time has elapsed.

3. The braking device of claim 1, wherein the control unit predicts a change in the state of the brake fluid in the fluid path that accompanies switching from the open state to the closed state, and performs the mitigation control by adjusting the drive amount of the electric motor in response to switching from the open state to the closed state based on the predicted result of the state change.

4. 2. The braking device according to claim 1, wherein the control unit predicts, in the open state, at least one of the amount of increase in hydraulic pressure in the hydraulic path that accompanies switching to the closed state and the peak value of hydraulic pressure in the hydraulic path that accompanies switching to the closed state, and if the amount of increase or the peak value exceeds a predetermined threshold, performs the mitigation control by reducing the driving amount of the electric motor in the open state.

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