Electric brake device

Abstract

To suppress heat generation of an electric actuator when holding a brake force applied to a vehicle.SOLUTION: An electric brake device (1) selectively executes, during holding a brake force, first holding control for making a drive amount of a partial electric actuator of a plurality of electric actuators (A1 to A4) larger than a drive amount other then the partial electric actuator, and second holding control for making the drive amount other than the partial electric actuator larger than the drive amount of the partial electric actuator.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electric braking device. [Background technology]

[0002] 2. Description of the Related Art There is known an electric braking device that applies a braking force to a vehicle by linearly moving a piston in a cylinder in response to the drive of an electric motor (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] DE 102019215313 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the electric actuator is continuously driven in order to maintain the braking force applied to the vehicle, there is a problem in that the electric actuator becomes hot. An aspect of the present disclosure aims to suppress heat generation in an electric actuator when maintaining a braking force applied to a vehicle. [Means for solving the problem]

[0005] In order to solve the above problems, an electric braking device according to one embodiment of the present disclosure includes a plurality of electric actuators capable of applying a braking force to a vehicle by linear movement of a piston in a cylinder in response to driving of an electric motor, and is capable of maintaining the braking force to be applied to the vehicle by continuing to drive the electric actuators.The electric braking device further includes a retention control unit that selectively executes, when maintaining the braking force, a first retention control that maintains the braking force by making the drive amount of some of the electric actuators among the plurality of electric actuators larger than the drive amount of the electric actuators other than the some of the electric actuators. The electric braking device according to each aspect of the present disclosure may be realized by a computer. In this case, a control program for the electric braking device that causes a computer to operate as each part (software element) of the electric braking device to realize the electric braking device, and a computer-readable recording medium on which the control program is recorded, also fall within the scope of the present disclosure. Effect of the Invention

[0006] According to one aspect of the present disclosure, heat generation in an electric actuator can be suppressed when maintaining the braking force applied to a vehicle. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic configuration diagram of a braking system for a vehicle equipped with an electric braking device according to a first embodiment of the present disclosure. [Diagram 2] 13 is a flowchart showing a process flow of a retention control process. [Diagram 3] FIG. 11 is a schematic configuration diagram of a braking system for a vehicle equipped with an electric braking device according to a second embodiment of the present disclosure. [Figure 4] FIG. 11 is a schematic configuration diagram of a braking system for a vehicle equipped with an electric braking device according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Embodiment 1] FIG. 1 is a schematic configuration diagram of a braking system of a vehicle equipped with an electric braking device according to a first embodiment of the present disclosure. The vehicle shown in FIG. 1 includes wheels W1-W4. The wheels W1-W4 are provided with calipers each including a wheel cylinder WC1-WC4. In FIG. 1, the wheels W1-W4 are the left front wheel FL, the right front wheel FR, the left rear wheel RL, and the right rear wheel RR of the vehicle, respectively. Hereinafter, the wheels W1 and W2 may be referred to as the front wheels W1 and W2. The wheels W3 and W4 may be referred to as the rear wheels W3 and W4.

[0009] The vehicle shown in FIG. 1 includes an electric braking device 1 according to the first embodiment of the present disclosure, changeover valves VL1-VL4, a master cylinder 23, and a stroke simulator 30.

[0010] The electric braking device 1 includes electric actuators A1-A4 and a control unit . The electric actuators A1-A4 correspond one-to-one to the wheel cylinders WC1-WC4, respectively. The electric actuators A1-A4 are electric cylinders and include a cylinder C, a piston P, an electric motor M, and a rotation angle sensor R. The electric actuators A1-A4 discharge brake fluid to the wheel cylinders WC1-WC4 by linear motion of the piston P in the cylinder C in response to driving of the electric motor M. In the wheels W1-W4, braking force is generated by pressing a friction member (not shown) against a rotating member that rotates integrally with the wheels W1-W4 due to the hydraulic pressure of the wheel cylinders WC1-WC4. The control unit 10 is an example of a holding control unit, and is, for example, an ECU including a microcomputer.

[0011] The changeover valves VL1-VL4 are provided in the paths between the master cylinder 23 and the wheel cylinders WC1-WC4, respectively. The stroke simulator 30 is connected to a path between the master cylinder 23 and the wheel cylinders WC3-WC4 via a simulator cut valve 31. The stroke simulator 30 generates a reaction force according to the operation mode of the brake pedal 26 when the switching valves VL1-VL4 are closed.

[0012] The vehicle shown in FIG. 1 is provided with sensors SE1-SE6 for detecting brake fluid pressure. The sensors SE1 and SE2 detect the brake fluid pressure in the path between the master cylinder 23 and the wheel cylinders WC1-WC4. The sensors SE3-SE6 detect the brake fluid pressure in the path between the electric actuators A1-A4 and the wheel cylinders WC1-WC4. The sensors SE1-SE6 may also function as temperature sensors. For example, the control unit 10 may estimate the temperature of the electric actuators A1-A4 based on the detection values ​​of the sensors SE3-SE6. In addition, the temperature of the electric actuators A1-A4 may be detected by a thermistor (not shown) provided in the control unit 10, and the control unit 10 may estimate the actuator temperature based on the detected temperature.

[0013] The control unit 10 receives the detection results of the sensors SE1-SE6 and the rotation angle sensor R. The control unit 10 may further receive information relating to the wheel speed of the vehicle, the operation mode of the brake pedal 26, and the like. The control unit 10 can perform drive control of the electric motors M of the electric actuators A1-A4, and open / close control of the simulator cut valve 31 and the switching valves VL1-VL4.

[0014] Brake fluid is discharged to the wheel cylinders WC1-WC4 from the master cylinder 23 or the electric actuators A1-A4. When brake fluid is discharged from the master cylinder 23 to the wheel cylinders WC1-WC4, the changeover valves VL1-VL4 are open. On the other hand, when brake fluid is discharged from the electric actuators A1-A4 to the wheel cylinders WC1-WC4, the changeover valves VL1-VL4 are closed. When brake fluid is supplied to the wheel cylinders WC1-WC4, the wheel cylinder pressure increases and a braking torque according to the wheel cylinder pressure is applied to the wheels W1-W4, thereby applying a braking force to the vehicle.

[0015] (Maintaining braking force) The control unit 10 executes a hold control process for holding the braking force applied to the vehicle. The hold control process includes a first hold control and a second hold control, the details of which will be described later. The control unit 10 selectively executes either the first hold control or the second hold control.

[0016] In the first hold control, the control unit 10 energizes the electric motors M of the electric actuators A1 and A2 while closing the switching valves VL1-VL4, and stops energizing the electric motors M of the electric actuators A3 and A4. As a result, the control unit 10 drives the electric actuators A1 and A2 to supply brake fluid from the electric actuators A1 and A2 to the wheel cylinders WC1 and WC2 to continue applying braking torque to the front wheels W1 and W2 of the vehicle, and stops driving the electric actuators A3 and A4. The electric actuators A3 and A4 release heat while their driving is stopped, thereby decreasing their temperature.

[0017] In the second hold control, the control unit 10 energizes the electric motors M of the electric actuators A3 and A4 while closing the switching valves VL1-VL4, and stops energizing the electric motors M of the electric actuators A1 and A2. As a result, the control unit 10 drives the electric actuators A3 and A4 to supply brake fluid from the electric actuators A3 and A4 to the wheel cylinders WC3 and WC4 to continue applying braking torque to the rear wheels W3 and W4 of the vehicle, and stops driving the electric actuators A1 and A2. The electric actuators A1 and A2 release heat while their driving is stopped, thereby decreasing their temperature.

[0018] In order to reliably maintain the braking force applied to the vehicle, when switching from the first hold control to the second hold control, the control unit 10 stops the drive of the electric actuators A1 and A2 after sufficiently increasing the drive amount of the electric actuators A3 and A4. When switching from the second hold control to the first hold control, the control unit 10 stops the drive of the electric actuators A3 and A4 after sufficiently increasing the drive amount of the electric actuators A1 and A2.

[0019] The control unit 10 changes the selection of the hold control process to the second hold control when a predetermined first judgment condition is satisfied as a result of continuing the first hold control. Also, the control unit 10 changes the selection of the hold control process to the first hold control when a predetermined second judgment condition is satisfied as a result of continuing the second hold control. The first judgment condition is, for example, that the temperature of the electric actuators A1 and A2 driven by the first hold control exceeds a predetermined threshold value. The temperature of the electric actuators A1 and A2 may be estimated based on the detection values ​​of the sensors S3 and S4 or thermistors, or may be estimated by the control unit 10 based on the time during which the electric actuators A1 and A2 are continuously driven. The second judgment condition is, for example, that the temperature of the electric actuators A3 and A4 driven by the second hold control exceeds a predetermined threshold value. The temperature of the electric actuators A3 and A4 may be estimated based on the detection values ​​of the sensors S5 and S6 or thermistors, or may be estimated by the control unit 10 based on the time during which the electric actuators A3 and A4 are continuously driven.

[0020] Fig. 2 is a flow chart showing the flow of the holding control process. The control unit 10 repeatedly executes the process of Fig. 2, and once the process of Fig. 2 is completed, the control unit 10 starts the process of the next cycle.

[0021] In S100, the control unit 10 judges whether or not to maintain the braking force applied to the vehicle. For example, when the shift position of the vehicle is in the parking position, the control unit 10 judges to maintain the braking force applied to the vehicle (S100: YES), and proceeds to the process of S200. In S200, it judges whether or not the first hold control or the second hold control is currently in progress. If the first hold control or the second hold control is in progress (S200: YES), the process proceeds to the process of S600, and if neither the first hold control nor the second hold control is in progress (S200: NO), the process proceeds to the process of S300.

[0022] In S300, it is determined whether or not a third judgment condition is satisfied. In the third judgment condition, the control unit 10 determines, for example, whether or not any of the temperatures of the electric actuators A1-A4 exceeds a predetermined threshold. If the third judgment condition is not satisfied (S300: NO), the control unit 10 performs normal hold control in which hold control is performed by driving all of the electric actuators A1-A4 (S400), ends the processing of the current cycle, and starts the processing of the next cycle. If the third judgment condition is satisfied (S300: YES), the process proceeds to S500 to select the first hold control or the second hold control. In S500, the control unit 10 may select which hold control to start from based on information such as the current temperature, continuous operation time, cumulative operation time, and cumulative operation count of the electric actuators A1-A4, or may select which hold control to start from based on information stored in advance.

[0023] In S600, it is determined whether or not the first hold control is currently being performed. If the first hold control is being performed (S600: YES), the process proceeds to S700. If the second hold control is being performed (S600: NO), the process proceeds to S800.

[0024] In S700, the control unit 10 judges whether or not the first judgment condition is satisfied. For example, the control unit 10 judges whether or not the temperature of the electric actuators A1 and A2 exceeds a predetermined threshold. If the first judgment condition is satisfied (S700: YES), the control unit 10 performs the second hold control (S900), ends the processing of the current cycle, and starts the processing of the next cycle. If the first judgment condition is not satisfied (S700: NO), the control unit 10 performs the first hold control (S1000), ends the processing of the current cycle, and starts the processing of the next cycle.

[0025] In S800, the control unit 10 judges whether or not the second judgment condition is satisfied. For example, the control unit 10 judges whether or not the temperature of the electric actuators A3 and A4 exceeds a predetermined threshold. If the second judgment condition is satisfied (S800: YES), the control unit 10 performs the first hold control (S1000), ends the processing of the current cycle, and starts the processing of the next cycle. If the second judgment condition is not satisfied (S800: NO), the control unit 10 performs the second hold control (S900), ends the processing of the current cycle, and starts the processing of the next cycle.

[0026] Here, the third judgment condition is set to be easier to satisfy than the first judgment condition and the second judgment condition. For example, in the case of the electric actuator temperature, the threshold value of the third judgment condition is set lower than the first judgment condition and the second judgment condition, and in the case of the electric actuator continuous operation time, the threshold value of the third judgment condition is set shorter than the first judgment condition and the second judgment condition.

[0027] In S100, when the shift position of the vehicle is not in the parking position, the control unit 10 determines that the braking force applied to the vehicle is not to be held (S100: NO), and proceeds to processing of S1100. In S600, the control unit 10 determines whether a predetermined time has passed since the holding of the braking force was released. For example, if the predetermined time has passed since the timing when the shift position of the vehicle was changed from the parking position to the drive position (S1100: YES), the control unit 10 drives the electric actuators A1-A4 or the master cylinder 23 to apply a predetermined braking force to the vehicle (S1200). The predetermined braking force is a braking force that can suppress unintended movement of the vehicle, and is determined based on the gradient of the road surface on which the vehicle is located, the road surface conditions, the vehicle specifications, and the like. For example, if a predetermined time or more has passed since the shift position of the vehicle was changed from the parking position to the drive position (S1100: NO), the control unit 10 ends the processing of the current cycle and starts the processing of the next cycle.

[0028] [Embodiment 2] Other embodiments of the present disclosure will be described below. For ease of explanation, the same reference numerals will be used to designate members having the same functions as those described in the first embodiment, and the description thereof will not be repeated.

[0029] Fig. 3 is a schematic configuration diagram of a vehicle braking system equipped with an electric braking device according to embodiment 2 of the present disclosure. The vehicle braking system shown in Fig. 3 differs from the braking system of embodiment 1 in that it has switching valves VL5 and VL6 and in that it has electric actuators A1-A4 that are driven under first hold control and second hold control.

[0030] The switching valve VL5 is located closer to the master cylinder 23 than a branch point B1 between the path between the master cylinder 23 and the wheel cylinder WC1 and the path between the master cylinder 23 and the wheel cylinder WC2. The switching valve VL6 is located closer to the master cylinder 23 than a branch point B2 between the path between the master cylinder 23 and the wheel cylinder WC3 and the path between the master cylinder 23 and the wheel cylinder WC4.

[0031] In the first hold control in the second embodiment, the control unit 10 closes the changeover valves VL5 and VL6 and opens the changeover valves VL1-VL4, energizes the electric motors M of the electric actuators A2 and A4, and stops energizing the electric motors M of the electric actuators A1 and A3. As a result, the control unit 10 drives the electric actuators A2 and A4 to supply brake fluid from the electric actuators A2 and A4 to the wheel cylinders WC1-WC4 to continue applying braking torque to the wheels W1-W4, and stops driving the electric actuators A1 and A3. The electric actuator A2 supplies brake fluid to the wheel cylinder WC2, and also supplies brake fluid to the wheel cylinder WC1 corresponding to the electric actuator A1 via a connection path RT5 shown by a dashed line in Fig. 3. The connection path RT5 connects a connection path RT1, which is a path between the electric actuator A1 and the wheel cylinder WC1, to a connection path RT2, which is a path between the electric actuator A2 and the wheel cylinder WC2. The connection path RT2 is an example of a first connection path. The connection path RT1 is an example of a second connection path. The electric actuator A4 supplies brake fluid to the wheel cylinder WC4, and also supplies brake fluid to the wheel cylinder WC3 corresponding to the electric actuator A3 via a connection path RT6 shown by a dashed line in Fig. 3. The connection path RT6 connects the connection path RT3, which is a path between the electric actuator A3 and the wheel cylinder WC3, to the connection path RT4, which is a path between the electric actuator A4 and the wheel cylinder WC4. The connection path RT4 is an example of a first connection path. The connection path RT3 is an example of a second connection path.

[0032] In the second hold control, the control unit 10 closes the changeover valves VL5 and VL6 and opens the changeover valves VL1-VL4, energizes the electric motors M of the electric actuators A1 and A3, and stops energizing the electric motors M of the electric actuators A2 and A4. As a result, the control unit 10 drives the electric actuators A1 and A3 to supply brake fluid from the electric actuators A1 and A3 to the wheel cylinders WC1-WC4 to continue applying braking torque to the wheels W1-W4, and stops driving the electric actuators A2 and A4. As a result, the electric actuator A1 supplies brake fluid to the wheel cylinder WC1, and also supplies brake fluid to the wheel cylinder WC2 via the connecting path RT5. The electric actuator A3 supplies brake fluid to the wheel cylinder WC3, and also supplies brake fluid to the wheel cylinder WC4 via the connecting path RT6.

[0033] When switching from the first hold control to the second hold control, the control unit 10 increases the drive amounts of the electric actuators A1 and A3 while decreasing the drive amounts of the electric actuators A2 and A4. On the other hand, when switching from the second hold control to the first hold control, the control unit 10 increases the drive amounts of the electric actuators A2 and A4 while decreasing the drive amounts of the electric actuators A1 and A3.

[0034] [Embodiment 3] Fig. 4 is a schematic configuration diagram of a vehicle braking system equipped with an electric braking device according to embodiment 3 of the present disclosure. The vehicle braking system shown in Fig. 4 differs from the braking system of embodiment 1 in that the master cylinder 23 is changed to an air master cylinder and that an air-over-hydraulic (AOH) type braking device 20 is used.

[0035] The braking device 20 supplies air to the air master cylinder 23 in response to the operation of the brake pedal 26. The air master cylinder 23 converts the air pressure into brake fluid pressure. Here, the braking device 20 has air pressure circuits separated for each system, and air pressure is sent from each air pressure circuit to the air master cylinder 23 separated for each system. Also, the braking device 20 can maintain the brake fluid pressure by maintaining the air pressure by continuously applying electricity to a solenoid valve (not shown).

[0036] In the third embodiment, in the first hold control, the control unit 10 energizes the electric motors M of the electric actuators A1-A4 with the changeover valves VL1-VL4 closed. In the first hold control, no current is applied to the solenoid valves (not shown) of the braking device 20, so that the temperature of the solenoid valves can be lowered. Then, in the second hold control, the control unit 10 opens the changeover valves VL1-VL4 to supply brake fluid from the air master cylinder 23 to the wheel cylinders WC1-WC4, and holds the braking force applied to the vehicle. In the second hold control, no current is applied to the electric motors M of the electric actuators A1-A4, so that the temperature of the electric actuators A1-A4 can be lowered. Here, in the third embodiment, when switching from the second hold control to the first hold control, it is preferable to set the air pressure in the front system (or rear system) to atmospheric pressure, then drive the electric actuators A1-A2 in the front system (or rear system), and then set the air pressure in the rear system (or front system) to atmospheric pressure, and then drive the electric actuators A3-A4 in the rear system (or front system). If the electric actuators A1-A4 are driven while the brake fluid is pressurized by the air master cylinder 23, the pistons of the electric actuators need to be advanced while the load on the electric actuators is high, so that the electric motors of the electric actuators are likely to generate heat. In this regard, the above-mentioned method of operation can suppress the heat generation of the electric motors when the hold control is switched, while suppressing the braking force from falling below the braking force required to hold the vehicle stopped. In the third embodiment, the switching valves VL5 and VL6 may be provided as in the second embodiment.

[0037] [Modifications] In the above-mentioned embodiment 1, the electric actuators A1-A4 are electric cylinders, and brake fluid is discharged to the wheel cylinders WC1-WC4 by linearly moving the piston P in the cylinder C in response to the driving of the electric motor M, thereby maintaining the braking force of the vehicle. However, the electric actuators A1-A4 are not limited to electric cylinders. For example, the piston P may be driven by the electric motor M of the electric actuators A1-A4 to directly linearly move a friction member without using brake fluid, thereby pressing the friction member against a rotating member.

[0038] In the above-described first embodiment, the first judgment condition is that the temperature of the electric actuators A1 and A2 driven by the first hold control exceeds a predetermined threshold value. However, the first judgment condition may be determined based on a parameter other than the temperature of the electric actuators A1 and A2 driven by the first hold control. For example, the control unit 10 may determine whether the first judgment condition is satisfied based on the time during which the electric actuators A1 and A2 are continuously driven, the accumulated time during which the electric actuators A1 and A2 are driven during the first hold control, or the number of times the electric actuators A1 and A2 are driven during the first hold control. In the above-mentioned embodiment 1, the second judgment condition is that the temperature of the electric actuators A3 and A4 driven by the second hold control exceeds a predetermined threshold value. However, the second judgment condition may be determined based on a parameter other than the temperature of the electric actuators A3 and A4 driven by the first hold control. For example, the control unit 10 may determine whether the second judgment condition is satisfied based on the time during which the electric actuators A3 and A4 are continuously driven, the accumulated time during which the electric actuators A3 and A4 are driven during the second hold control, or the number of times the electric actuators A3 and A4 are driven during the second hold control.

[0039] In the above-mentioned first embodiment, in the first hold control, the control unit 10 energizes the electric motors M of the electric actuators A1 and A2 while stopping the energization of the electric motors M of the electric actuators A3 and A4 with the switching valves VL1-VL4 closed, but is not limited to this. The control unit 10 only needs to make the drive amount of the electric actuators A3 and A4 smaller than the drive amount of the electric actuators A1 and A2, and does not need to stop the electric actuators A3 and A4. In the above-mentioned first embodiment, in the second hold control, the control unit 10 energizes the electric motors M of the electric actuators A3 and A4 while stopping the energization of the electric motors M of the electric actuators A1 and A2 with the switching valves VL1-VL4 closed, but is not limited to this. The control unit 10 only needs to make the drive amount of the electric actuators A1 and A2 smaller than the drive amount of the electric actuators A3 and A4, and does not need to stop the electric actuators A1 and A2.

[0040] In the first embodiment, in the first hold control, the control unit 10 energizes the electric motors M of the electric actuators A1 and A2 while closing the switching valves VL1-VL4, while stopping the energization of the electric motors M of the electric actuators A3 and A4. Then, in the second hold control, the control unit 10 energizes the electric motors M of the electric actuators A3 and A4 while closing the switching valves VL1-VL4, while stopping the energization of the electric motors M of the electric actuators A1 and A2. However, the actuators to be driven in the first hold control and the second hold control are not limited to this. (1) In the first hold control, the control unit 10 may energize the electric motors M of the electric actuators A2 and A3 while keeping the changeover valves VL1-VL4 closed, and may stop energizing the electric motors M of the electric actuators A1 and A4. In the second hold control, the control unit 10 may energize the electric motors M of the electric actuators A1 and A4 while keeping the changeover valves VL1-VL4 closed, and may stop energizing the electric motors M of the electric actuators A2 and A3. (2) If the vehicle is provided with a parking lock mechanism that locks the rotation of the drive transmission shaft that transmits the output of the drive source that drives the vehicle to the drive wheels, the braking force that is insufficient when holding the vehicle stopped using the parking lock mechanism may be compensated for by the braking force generated by driving the electric actuators A1-A4 during the first hold control or the second hold control.

[0041] In the above-mentioned second embodiment, the control unit 10 may shift the timing of switching between driving and stopping the electric actuators A1 and A2 on the front wheels W1 and W2 side and the timing of switching between driving and stopping the electric actuators A3 and A4 on the rear wheels W3 and W4 side by a predetermined time in the first hold control and the second hold control. The predetermined time may be set to at least a temperature at which the temperature of the electric actuators A1-A4 does not exceed a predetermined threshold value.

[0042] In the above-described first and second embodiments, the control unit 10 may be able to select a hold control process other than the first hold control and the second hold control. For example, when the temperature of the electric actuators A1-A4 exceeds a predetermined threshold, the control unit 10 may execute a third hold control that supplies brake fluid from the master cylinder 23 to the wheel cylinders WC1-WC4 to hold the braking force applied to the vehicle.

[0043] [Software implementation example] The functions of the electric braking device 1 (hereinafter referred to as the "device") can be realized by a program for causing a computer to function as the device, and by a program for causing a computer to function as each control block of the device (particularly each part included in the control unit 10). In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program to realize each function described in each of the above embodiments. The program may be non-transitory and may be recorded in one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be provided to the device via any wired or wireless transmission medium. In addition, some or all of the functions of each of the control blocks can be realized by a logic circuit. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of the present disclosure. In addition, the functions of each of the control blocks can be realized by, for example, a quantum computer.

[0044] 〔summary〕 An electric braking device according to one embodiment of the present disclosure includes a plurality of electric actuators capable of applying a braking force to a vehicle by linear movement of a piston in a cylinder in response to driving of an electric motor, and is capable of maintaining the braking force to be applied to the vehicle by continuing to drive the electric actuators.The electric braking device further includes a retention control unit that selectively executes, when maintaining the braking force, a first retention control that maintains the braking force by making the drive amount of some of the electric actuators larger than the drive amount of the electric actuators other than the some of the electric actuators. In the first hold control, the drive amount of some of the electric actuators is made larger than the drive amount of the rest of the electric actuators, so heat generation in the electric actuators other than the rest of the electric actuators can be suppressed. In the second hold control, the drive amount of the rest of the electric actuators is made larger than the drive amount of the rest of the electric actuators, so heat generation in the rest of the electric actuators can be suppressed. By selectively executing the first hold control and the second hold control, heat generation in some or all of the electric actuators can be suppressed. In the case of large vehicles that require a large braking force when stopping on a slope, the vehicle can be kept stopped for longer than before by suppressing heat generation in the electric actuator when the braking force is maintained.

[0045] In an electric braking device according to one embodiment of the present disclosure, each of the plurality of electric actuators is an electric cylinder capable of applying a braking force to the vehicle by ejecting brake fluid toward a wheel cylinder corresponding to the electric actuator in accordance with the linear motion of the piston, and the device is provided with a plurality of connection paths connecting each of the plurality of electric actuators to the wheel cylinder corresponding to the electric actuator, and a communication passage that communicates a first connection path among the plurality of connection paths that corresponds to some of the electric actuators and a second connection path that corresponds to the electric actuators other than the some of the electric actuators, and the first hold control continues to drive the some of the electric actuators among the plurality of electric actuators and stops the electric actuators other than the some of the electric actuators among the plurality of electric actuators, and the second hold control stops the some of the electric actuators among the plurality of electric actuators and continues to drive the electric actuators other than the some of the electric actuators among the plurality of electric actuators. By connecting the first and second connection passages through a communication passage, the brake fluid discharged from the electric cylinders can be supplied not only to the wheel cylinders corresponding to some of the electric cylinders, but also to the wheel cylinders corresponding to the remaining electric cylinders. Therefore, by driving some of the electric cylinders, it is possible to supply brake fluid to the multiple wheel cylinders, and the retained braking force can be maintained. When multiple connection paths are connected by a communication passage, the pressure in the piping system becomes the same. In this case, if the pressure in the piping system is further increased to generate the required braking force, the electric cylinder needs to be driven against the pressure in the piping system. If some and other electric cylinders are driven with different drive amounts, the pressure in the piping system is increased, so that the electric cylinder with the smaller drive amount also needs to have a larger current flow through its electric motor to increase the torque, which reduces the heat generation reduction effect. Therefore, according to the above configuration, the hold control section stops all but a portion of the electric cylinders in the first hold control, and stops a portion of the electric cylinders in the second hold control, thereby making it possible to increase the heat reduction effect.

[0046] In an electric braking device according to one embodiment of the present disclosure, the some of the electric actuators and the electric actuators other than the some of the electric actuators each include at least one electric cylinder that ejects brake fluid into the wheel cylinder arranged on the front wheels of the vehicle, and at least one electric cylinder that ejects brake fluid into the wheel cylinder arranged on the rear wheels of the vehicle, and when changing from a state in which one of the first hold control and the second hold control is being executed to a state in which the other is being executed, the timing for changing the electric cylinder on the front wheel side to be driven and the timing for changing the electric cylinder on the rear wheel side to be driven are shifted by a predetermined time. According to the above configuration, by shifting the timing for changing the electric cylinders to be driven on the front wheel side and the rear wheel side, it is possible to optimize the transition of the braking force applied to the vehicle when switching between the first hold control and the second hold control.

[0047] In an electric braking device according to one aspect of the present disclosure, the hold control unit holds a braking force that suppresses movement of the vehicle unintended by the occupant for a predetermined time from the timing at which the hold of the braking force applied to the vehicle is released. At the timing when the retention of the braking force is released, the vehicle may move unintended by the occupants. For example, if the parking lock mechanism is released when the vehicle is stopped on a slope, the vehicle may start to go down the slope. According to the above configuration, by retaining the braking force for a predetermined time from the timing when the retention of the braking force is released, it is possible to prevent the vehicle from moving unintended by the occupants at the timing when the retention of the braking force is released.

[0048] [Additional Notes] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0049] 1 Electric braking device 10 Control section 11 Storage section 23 Master cylinder A1, A2, A3, A4 Electric Actuators RT1, RT2, RT3, RT4 connection RT5, RT6 connecting road WC1, WC2, WC3, WC4 Wheel Cylinders

Claims

1. An electric braking device includes a plurality of electric actuators capable of applying a braking force to a vehicle by linearly moving a piston in a cylinder in response to driving of an electric motor, and capable of maintaining the braking force applied to the vehicle by continuously driving the electric actuators, an electric braking device comprising: a holding control unit which selectively executes, when maintaining a braking force, a first holding control which holds the braking force by making a drive amount of some of the electric actuators among the plurality of electric actuators larger than a drive amount of the electric actuators other than the some of the electric actuators; and a second holding control which holds the braking force by making a drive amount of some of the electric actuators among the plurality of electric actuators larger than a drive amount of the electric actuators other than the some of the electric actuators.

2. each of the plurality of electric actuators is an electric cylinder capable of applying a braking force to the vehicle by discharging brake fluid toward a wheel cylinder corresponding to the electric actuator in accordance with linear motion of the piston; a plurality of connection paths connecting each of the plurality of electric actuators to the wheel cylinder corresponding to the electric actuator; a communication passage that communicates a first connection passage corresponding to the part of the electric actuators and a second connection passage corresponding to the electric actuators other than the part of the electric actuators, among the plurality of connection passages; In the first hold control, the some of the electric actuators among the plurality of electric actuators are continuously driven, and the electric actuators other than the some of the electric actuators among the plurality of electric actuators are stopped, 2. The electric braking device according to claim 1, wherein in the second hold control, some of the electric actuators among the plurality of electric actuators are stopped, and the electric actuators other than the some of the electric actuators among the plurality of electric actuators are allowed to continue to be driven.

Images