Electric braking device

Abstract

An electric braking device (1) selectively executes, when holding braking force, a first holding control for making the driving amount of some electric actuators from among a plurality of electric actuators (A1-A4) greater than the driving amount of the electric actuators other than said some electric actuators, and a second holding control for making the driving amount of the electric actuators other than said some electric actuators greater than the driving amount of said some electric actuators.

Description

electric braking device

[0001] The present disclosure relates to an electric braking system.

[0002] 2. Description of the Related Art Electric braking devices are known that apply braking force to a vehicle by linearly moving a piston in a cylinder in response to the driving of an electric motor (see, for example, Patent Document 1).

[0003] DE 102019215313

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

[0005] In order to solve the above problems, an electric braking device according to one aspect of the present disclosure includes a plurality of electric actuators capable of applying braking force to a vehicle by linearly moving pistons in cylinders in response to drive of an electric motor, and capable of maintaining the braking force applied to the vehicle by continuing to drive the electric actuators, and further includes a maintenance control unit that selectively executes, when maintaining the braking force, a first maintenance control that maintains the braking force by making the drive amount of some of the electric actuators greater than the drive amount of the remaining electric actuators, and a second maintenance control that maintains the braking force by making the drive amount of the remaining electric actuators greater than the drive amount of the remaining 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 unit (software element) of the electric braking device to realize the electric braking device by a computer, and a computer-readable recording medium having the program recorded thereon, are also within the scope of the present disclosure.

[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.

[0007] Fig. 1 is a schematic configuration diagram of a braking system for a vehicle equipped with an electric braking device according to embodiment 1 of the present disclosure. Fig. 2 is a flowchart showing a processing flow of holding control processing. Fig. 3 is a schematic configuration diagram of a braking system for a vehicle equipped with an electric braking device according to embodiment 2 of the present disclosure. Fig. 4 is a schematic configuration diagram of a braking system for a vehicle equipped with an electric braking device according to embodiment 3 of the present disclosure.

[0008] [Embodiment 1] Fig. 1 is a schematic configuration diagram of a braking system for a vehicle equipped with an electric braking device according to embodiment 1 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, switching 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 10. The electric actuators A1-A4 correspond one-to-one to the wheel cylinders WC1-WC4. Each electric actuator A1-A4 is an electric cylinder and includes 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 as the piston P in the cylinder C moves linearly in response to the driving of the electric motor M. At the wheels W1-W4, braking force is generated when the hydraulic pressure in the wheel cylinders WC1-WC4 presses friction members (not shown) against rotating members that rotate integrally with the wheels W1-W4. The control unit 10 is an example of a holding control unit and is, for example, an ECU including a microcomputer.

[0011] The switching 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 the paths between the master cylinder 23 and the wheel cylinders WC3-WC4 via a simulator cut valve 31. When the switching valves VL1-VL4 are closed, the stroke simulator 30 generates a reaction force corresponding to the operation mode of the brake pedal 26.

[0012] The vehicle shown in FIG. 1 is provided with sensors SE1-SE6 that detect brake fluid pressure. Sensors SE1 and SE2 detect the brake fluid pressure in the path between the master cylinder 23 and the wheel cylinders WC1-WC4. Sensors SE3-SE6 detect the brake fluid pressure in the path between the electric actuators A1-A4 and the wheel cylinders WC1-WC4. Sensors SE1-SE6 may also function as temperature sensors. For example, the control unit 10 may estimate the temperatures of the electric actuators A1-A4 based on the detected values ​​of sensors SE3-SE6. Furthermore, the temperature of the electric actuators A1-A4 may be detected by a thermistor (not shown) or the like 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. Information relating to the vehicle wheel speed, the operation mode of the brake pedal 26, and the like may also be input to the control unit 10. The control unit 10 can control the drive of the electric motors M of the electric actuators A1-A4, and control the opening and closing 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 corresponding 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 maintenance control process to maintain the braking force applied to the vehicle. The maintenance control process includes a first maintenance control and a second maintenance control, which will be described in detail later. The control unit 10 selectively executes either the first maintenance control or the second maintenance control.

[0016] In the first hold control, the control unit 10 energizes the electric motors M of the electric actuators A1 and A2 while keeping the selector valves VL1-VL4 closed, 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, thereby continuing to apply 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 radiate heat while their drive 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 keeping the selector valves VL1-VL4 closed, 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, thereby continuing to apply 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 radiate heat while they are 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 determination condition is satisfied as a result of continuing the first hold control. Furthermore, the control unit 10 changes the selection of the hold control process to the first hold control when a predetermined second determination condition is satisfied as a result of continuing the second hold control. The first determination condition is, for example, that the temperatures of the electric actuators A1 and A2 driven under the first hold control exceed a predetermined threshold. The temperatures of the electric actuators A1 and A2 may be estimated based on the detection values ​​of the sensors S3 and S4 or thermistors, or the control unit 10 may estimate the temperatures based on the duration of continuous drive of the electric actuators A1 and A2. The second determination condition is, for example, that the temperatures of the electric actuators A3 and A4 driven under the second hold control exceed a predetermined threshold. The temperatures of the electric actuators A3 and A4 may be estimated based on the detection values ​​of the sensors S5 and S6 or thermistors, or the control unit 10 may estimate the temperatures based on the duration of continuous drive of the electric actuators A3 and A4.

[0020] 2 is a flowchart 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 determines whether or not to maintain the braking force applied to the vehicle. For example, when the vehicle's shift position is in the park position, the control unit 10 determines to maintain the braking force applied to the vehicle (S100: YES), and proceeds to processing in S200. In S200, the control unit 10 determines whether 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 control unit 10 proceeds to processing in S600. If neither the first hold control nor the second hold control is in progress (S200: NO), the control unit 10 proceeds to processing in S300.

[0022] In S300, the control unit 10 determines whether a third determination condition is met. In the third determination condition, the control unit 10 determines, for example, whether the temperature of any of the electric actuators A1-A4 exceeds a predetermined threshold. If the third determination condition is not met (S300: NO), the control unit 10 performs normal hold control, which drives all of the electric actuators A1-A4 to perform hold control (S400), ends the processing of the current cycle, and starts the processing of the next cycle. If the third determination condition is met (S300: YES), the control unit 10 proceeds to S500 and selects either the first hold control or the second hold control. In S500, the control unit 10 may select which hold control to start based on information such as the current temperature of the electric actuators A1-A4, the continuous operating time, the accumulated operating time, and the accumulated number of operations, or may select which hold control to start based on pre-stored information.

[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 determines whether a first determination condition is met. For example, the control unit 10 determines whether the temperatures of the electric actuators A1 and A2 exceed a predetermined threshold. If the first determination condition is met (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 determination condition is not met (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 determines whether a second determination condition is met. For example, the control unit 10 determines whether the temperatures of the electric actuators A3 and A4 exceed a predetermined threshold. If the second determination condition is met (S800: YES), the control unit 10 performs first hold control (S1000), ends the processing of the current cycle, and starts the processing of the next cycle. If the second determination condition is not met (S800: NO), the control unit 10 performs second hold control (S900), ends the processing of the current cycle, and starts the processing of the next cycle.

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

[0027] In S100, when the vehicle's shift position is not in the Park position, the control unit 10 determines not to maintain the braking force applied to the vehicle (S100: NO) and proceeds to processing in S1100. In S600, the control unit 10 determines whether a predetermined time has elapsed since the braking force maintenance was released. For example, if the predetermined time has elapsed since the vehicle's shift position was changed from the Park 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 sufficient to prevent the vehicle from moving unintentionally and is determined based on the gradient of the road surface on which the vehicle is located, road conditions, vehicle specifications, etc. For example, if a predetermined time or more has elapsed since the vehicle's shift position was changed from the Park 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] Another embodiment of the present disclosure will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the first embodiment, and the description thereof will not be repeated.

[0029] 3 is a schematic configuration diagram of a braking system for a vehicle equipped with an electric braking device according to embodiment 2 of the present disclosure. The braking system for the vehicle shown in Fig. 3 differs from the braking system of embodiment 1 in that it includes switching valves VL5 and VL6 and in that it includes 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 wheel cylinder WC1 and the path between the master cylinder 23 and 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 wheel cylinder WC3 and the path between the master cylinder 23 and wheel cylinder WC4.

[0031] In the first hold control in the second embodiment, the control unit 10 closes the selector valves VL5 and VL6 and opens the selector valves VL1-VL4, energizing the electric motors M of the electric actuators A2 and A4 while deenergizing 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, thereby applying braking torque to the wheels W1-W4, while deactivating the electric actuators A1 and A3. The electric actuator A2 supplies brake fluid to the wheel cylinder WC2 and also to the wheel cylinder WC1 corresponding to the electric actuator A1 via a connecting path RT5 shown by a dashed line in FIG. 3 . The connecting path RT5 connects the connecting path RT1, which is the path between the electric actuator A1 and the wheel cylinder WC1, and the connecting path RT2, which is the 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, with 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 brake hold control, the control unit 10 closes the selector valves VL5 and VL6 and opens the selector valves VL1-VL4, energizing the electric motors M of the electric actuators A1 and A3 while deenergizing 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, thereby applying braking torque to the wheels W1-W4, while deactivating the electric actuators A2 and A4. As a result, the electric actuator A1 supplies brake fluid to the wheel cylinder WC1 and also to the wheel cylinder WC2 via the connecting path RT5. The electric actuator A3 supplies brake fluid to the wheel cylinder WC3 and also 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 amount of the electric actuators A1 and A3 while decreasing the drive amount 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 amount of the electric actuators A2 and A4 while decreasing the drive amount of the electric actuators A1 and A3.

[0034] [Embodiment 3] Fig. 4 is a schematic configuration diagram of a braking system for a vehicle equipped with an electric braking device according to embodiment 3 of the present disclosure. The braking system for the vehicle 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 an air-over-hydraulic (AOH) type braking device 20 is employed.

[0035] The braking device 20 supplies air to an air master cylinder 23 in response to operation of a brake pedal 26. The air master cylinder 23 converts air pressure into brake fluid pressure. The braking device 20 has air pressure circuits separated into systems, and air pressure is sent from each air pressure circuit to the air master cylinder 23 separated into systems. The braking device 20 can also maintain brake fluid pressure by maintaining air pressure by continuously energizing 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, the solenoid valves (not shown) of the braking device 20 are not energized, thereby allowing the temperature of the solenoid valves to 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, thereby maintaining the braking force applied to the vehicle. In the second hold control, the electric motors M of the electric actuators A1-A4 are not energized, thereby allowing the temperature of the electric actuators A1-A4 to be lowered. In the third embodiment, when switching from the second brake hold control to the first brake 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). Driving the electric actuators A1-A4 while the brake fluid is pressurized by the air master cylinder 23 requires the pistons of the electric actuators to advance under high loads on the electric actuators, which makes the electric motors of the electric actuators prone to heat generation. In this regard, the above-described operation method can suppress heat generation in the electric motors when brake hold control is switched on while preventing the braking force from falling below the level required to hold the vehicle. Note that the third embodiment may also be configured with the switching valves VL5 and VL6, as in the second embodiment.

[0037] [Modification] In the first embodiment, 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 drive 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 drive of the electric motor M of the electric actuators A1-A4 may cause the piston P to directly linearly move a friction member without the intervention of brake fluid, thereby pressing the friction member against a rotating member.

[0038] In the first embodiment, the first determination condition is that the temperature of the electric actuators A1 and A2 driven under the first hold control exceeds a predetermined threshold. However, the first determination condition may be determined based on a parameter other than the temperature of the electric actuators A1 and A2 driven under the first hold control. For example, the control unit 10 may determine whether the first determination condition is satisfied based on the continuous drive time of the electric actuators A1 and A2, the cumulative drive time of the electric actuators A1 and A2 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 first embodiment, the second determination condition is that the temperature of the electric actuators A3 and A4 driven under the second hold control exceeds a predetermined threshold. However, the second determination condition may be determined based on a parameter other than the temperature of the electric actuators A3 and A4 driven under the first hold control. For example, the control unit 10 may determine whether the second determination condition is met based on the time for which the electric actuators A3 and A4 are continuously driven, the cumulative time for 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 first embodiment, during the first hold control, the control unit 10 energizes the electric motors M of the electric actuators A1 and A2 while closing the selector valves VL1-VL4, while stopping the energization of the electric motors M of the electric actuators A3 and A4. However, this is not limited to this. The control unit 10 only needs to make the drive amounts of the electric actuators A3 and A4 smaller than the drive amounts of the electric actuators A1 and A2, and does not need to stop the electric actuators A3 and A4. In the first embodiment, during the second hold control, the control unit 10 energizes the electric motors M of the electric actuators A3 and A4 while closing the selector valves VL1-VL4, while stopping the energization of the electric motors M of the electric actuators A1 and A2. However, this is not limited to this. The control unit 10 only needs to make the drive amounts of the electric actuators A1 and A2 smaller than the drive amounts of the electric actuators A3 and A4, and does not need to stop the electric actuators A1 and A2.

[0040] In the first embodiment, during the first hold control, the control unit 10 energizes the electric motors M of the electric actuators A1 and A2 while closing the selector valves VL1-VL4, while stopping the energization of the electric motors M of the electric actuators A3 and A4. During the second hold control, the control unit 10 energizes the electric motors M of the electric actuators A3 and A4 while closing the selector valves VL1-VL4, while stopping the energization of the electric motors M of the electric actuators A1 and A2. However, the actuators driven during the first hold control and the second hold control are not limited to these. (1) During the first hold control, the control unit 10 may energize the electric motors M of the electric actuators A2 and A3 while closing the selector valves VL1-VL4, while stopping the energization of 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 closing the selector valves VL1-VL4, 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 by the parking lock mechanism may be compensated for by the braking force generated by driving the electric actuators A1-A4 in the first hold control or the second hold control.

[0041] In the 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 and the timing of switching between driving and stopping the electric actuators A3 and A4 on the rear wheels W3 and W4 by a predetermined time during the first hold control and the second hold control. The predetermined time may be set to a temperature at least such that the temperatures of the electric actuators A1 to A4 do not exceed a predetermined threshold.

[0042] In the first and second embodiments, the control unit 10 may be configured 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 to supply 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 that causes a computer to function as the device, and that causes the computer to function as each control block (particularly each unit included in the control unit 10) of the device. 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 functions described in each of the above embodiments are realized by executing the program using the control device and storage device. The program may be stored non-transitory on one or more computer-readable storage media. The storage media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium. Furthermore, some or all of the functions of each control block may be realized by a logic circuit. For example, an integrated circuit in which a logic circuit functioning as each control block is formed is also within the scope of the present disclosure. Alternatively, the functions of each control block may be realized by, for example, a quantum computer.

[0044] [Summary] An electric braking device according to one aspect of the present disclosure includes a plurality of electric actuators capable of applying braking force to a vehicle by linearly moving pistons in cylinders in response to drive of an electric motor, and capable of maintaining the braking force applied to the vehicle by continuously driving the electric actuators. The electric braking device further includes a hold control unit that selectively executes, when maintaining the braking force, a first hold control that maintains the braking force by increasing the drive amount of some of the electric actuators to be greater than the drive amount of the remaining electric actuators, and a second hold control that maintains the braking force by increasing the drive amount of the remaining electric actuators to be greater than the drive amount of the remaining electric actuators. The first hold control increases the drive amount of some of the electric actuators to be greater than the drive amount of the remaining electric actuators, thereby suppressing heat generation in the electric actuators other than some of the electric actuators. The second hold control increases the drive amount of the remaining electric actuators to be greater than the drive amount of the remaining electric actuators, thereby suppressing heat generation in the remaining electric actuators. Selectively executing the first hold control and the second hold control can suppress heat generation in the remaining electric actuators and the remaining electric actuators. 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 maintaining braking force.

[0045] In one aspect of the present disclosure, the electric braking device includes a plurality of connection paths connecting each of the electric actuators to the wheel cylinder corresponding to the electric actuator, and a communication path connecting a first connection path corresponding to some of the electric actuators among the connection paths to a second connection path corresponding to the electric actuators other than the some of the electric actuators, wherein the first hold control continues to drive some of the electric actuators and stops the other electric actuators, and the second hold control stops some of the electric actuators and continues to drive the other electric actuators. The communication path between the first connection path and the second connection path allows the brake fluid discharged from the electric cylinder to be supplied not only to the wheel cylinders corresponding to some of the electric cylinders but also to the wheel cylinders corresponding to the other electric cylinders. Therefore, by driving some of the electric cylinders, brake fluid can be supplied to multiple wheel cylinders, maintaining the required braking force. When multiple connecting passages are connected via a communication passage, the pressure in the piping system is equalized. In this case, if the pressure in the piping system is further increased to generate the required braking force, the electric cylinders must be driven against the pressure in the piping system. If some and the rest of the electric cylinders are driven with different drive amounts, the increased pressure in the piping system requires a larger current to be passed through the electric motor of the electric cylinder with the smaller drive amount to increase torque, thereby reducing the heat generation reduction effect. Therefore, with the above configuration, the hold control unit stops the rest of the electric cylinders with the first hold control and the rest of the electric cylinders with the second hold control, thereby increasing the heat generation reduction effect.

[0046] In one aspect of the electric braking system according to 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 discharges brake fluid to the wheel cylinders arranged on the front wheels of the vehicle and at least one electric cylinder that discharges brake fluid to the wheel cylinders arranged on the rear wheels of the vehicle, and when switching from a state in which one of the first hold control and the second hold control is being performed to a state in which the other is being performed, the timing of changing the electric cylinder on the front wheel side to be driven and the timing of changing the electric cylinder on the rear wheel side to be driven are shifted by a predetermined time. With this configuration, by shifting the timing of changing the electric cylinder on the front wheel side to be driven and the electric cylinder on 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 applied to the vehicle to prevent the vehicle from moving unintentionally by the occupant for a predetermined time from the timing at which the hold control unit releases the hold control unit of the braking force. At the timing at which the hold control unit releases the braking force, the vehicle may move unintentionally by the occupant. For example, if the parking lock mechanism is released when the vehicle is stopped on a slope, the vehicle may start to move down the slope. According to the above configuration, by holding the braking force for a predetermined time from the timing at which the hold control unit releases the braking force, the vehicle may move unintentionally by the occupant at the timing at which the hold control unit releases the braking force.

[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.

Claims

1. An electric braking device having 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 the drive of an electric motor, and capable of maintaining the braking force to be applied to the vehicle by continuing to drive the electric actuators, characterized in that the electric braking device further comprises a hold control unit which selectively executes, when maintaining the braking force, a first hold control which maintains the braking force by making the drive amount of some of the electric actuators among the plurality of electric actuators greater than the drive amount of the remaining electric actuators among the plurality of electric actuators, and a second hold control which maintains the braking force by making the drive amount of the remaining electric actuators among the plurality of electric actuators greater than the drive amount of the remaining electric actuators among the remaining electric actuators.

2. The electric braking device according to claim 1, wherein 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 the linear motion of the piston, and the electric braking device comprises: 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 path connecting a first connection path corresponding to some of the electric actuators among the plurality of connection paths and a second connection path corresponding to the electric actuators other than the some of the electric actuators, wherein 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.

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