JP2024083033A - Electric parking brake device - Google Patents

Abstract

To set an appropriate target current value according to an individual difference in performance of an electric motor in an electric parking brake device.SOLUTION: An electric parking brake device of an embodiment comprises: a linear-motion member which, during vehicle braking control, is moved in a forward direction by driving of an electric motor to generate electric braking force, and which, during braking release control, is moved in a backward direction opposite to the forward direction by driving of the electric motor to release the electric braking force; and a controller for controlling the electric motor. When controlling the electric motor, the controller acquires at least one of a first elapsed time from when energization is started to when a change gradient of a current value of the electric motor with respect to time becomes a first threshold value or less during the braking release control, and a second elapsed time from when energization is started to when the change gradient of the current value of the electric motor with respect to time becomes a second threshold value or more during the braking control. The controller sets a target current value for energization of the electric motor during the braking control on the basis of the acquired elapsed time(s).SELECTED DRAWING: Figure 6

Description

The present invention relates to an electric parking brake device.

In recent years, electric parking brake devices (EPBs) have been widely adopted in vehicles (such as passenger cars). In an electric parking brake device, a controller drives an electric motor, for example, to move a linear member in the forward direction to generate an electric braking force, or to move the linear member in the backward direction to release the electric braking force. When generating an electric braking force, if the current value passing through the electric motor reaches a target current value, it is determined that the target electric braking force has been generated, and the drive of the electric motor is stopped.

In this case, the controller obtains information such as the temperature and idling speed of the electric motor from the sensor, and determines the target current value based on that information. Specifically, for example, relationship information between information such as the temperature and idling speed of the electric motor and the magnitude of the target current value is stored in advance, and the target current value is set based on that relationship information.

JP 2007-515344 A

However, in the above-mentioned conventional technology, the related information is unrelated to the individual differences in the performance of the electric motor, so it is not possible to set an appropriate target current value according to the individual differences in the performance of the electric motor.

The objective of the present invention is to provide an electric parking brake device that can set an appropriate target current value according to individual differences in the performance of electric motors.

The electric parking brake device according to the present invention includes, for example, a linear motion member that generates an electric braking force by moving in a forward direction by driving an electric motor during braking control of the vehicle, and releases the electric braking force by moving in a backward direction, which is the opposite direction to the forward direction, by driving the electric motor during braking release control, and a controller that controls the electric motor. When controlling the electric motor, the controller obtains at least one of a first elapsed time from the start of energization until the gradient of change in the current value of the electric motor with respect to time becomes equal to or less than a first threshold value during the braking release control, and a second elapsed time from the start of energization until the gradient of change in the current value of the electric motor with respect to time becomes equal to or greater than a second threshold value during the braking control, and sets a target current value to be applied to the electric motor during the braking control based on the first elapsed time or the second elapsed time that has been obtained.

FIG. 1 is a schematic diagram showing an overall outline of a vehicle brake device according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a rear wheel brake mechanism provided in the vehicle brake device of the embodiment. FIG. 3 is a graph showing how the current value of the electric motor changes over time in the embodiment. FIG. 4 is a graph showing a first example of the relationship between the no-load determination time and the target current value in the embodiment. FIG. 5 is a graph showing a second example of the relationship between the no-load determination time and the target current value in the embodiment. FIG. 6 is a flowchart showing a process executed by the electric parking brake device of the embodiment.

Below, exemplary embodiments of the present invention are disclosed. The configurations of the embodiments shown below, and the actions and results (effects) brought about by said configurations, are examples. The present invention can also be realized with configurations other than those disclosed in the following embodiments. Furthermore, according to the present invention, it is possible to obtain at least one of the various effects (including derivative effects) obtained by the following configurations.

The following embodiment will be described using as an example a vehicle brake device that uses a disc brake type EPB in the rear wheel system.

Figure 1 is a schematic diagram showing an overall overview of a vehicle brake device according to an embodiment. Figure 2 is a schematic cross-sectional view of a rear wheel brake mechanism provided in the vehicle brake device according to an embodiment.

As shown in Figures 1 and 2, the vehicle brake device of this embodiment includes a service brake 1 (hydraulic brake device) and an EPB 2 (electric parking brake device).

The service brake 1 generates hydraulic braking force (service brake force) by using hydraulic pressure to press the brake pads 11 against the brake discs 12 that rotate together with the vehicle wheels.

The EPB2 generates an electric braking force by driving the EPB motor 10 (electric motor) to press the brake pads 11 against the brake disc 12.

The service brake 1 is a hydraulic brake mechanism that generates brake fluid pressure based on the depression of the brake pedal 3 by the driver, and generates a service brake force based on this brake fluid pressure. Specifically, the service brake 1 boosts the depression force corresponding to the depression of the brake pedal 3 by the driver using a booster device 4, and then generates brake fluid pressure corresponding to the boosted depression force in the M/C (master cylinder) 5. The brake fluid pressure is then transmitted to the W/C (wheel cylinder) 6 provided in the wheel brake mechanism of each wheel, thereby generating a service brake force. In addition, an actuator 7 for controlling the brake fluid pressure is provided between the M/C 5 and the W/C 6. The actuator 7 adjusts the service brake force generated by the service brake 1 and performs various controls (e.g., anti-skid control, etc.) to improve the safety of the vehicle.

Various controls using the actuator 7 are executed by the ESC (Electronic Stability Control)-ECU 8, which controls the service brake force. For example, the ESC-ECU 8 outputs a control current for controlling various control valves and a motor for driving the pump provided in the actuator 7, thereby controlling the hydraulic circuit provided in the actuator 7 and controlling the W/C pressure transmitted to the W/C 6. This prevents wheel slippage and improves the safety of the vehicle. For example, the actuator 7 is equipped with a pressure increase control valve for each wheel that controls the application of the brake hydraulic pressure generated in the M/C 5 or the brake hydraulic pressure generated by the pump drive to the W/C 6, and a pressure reduction control valve that reduces the W/C pressure by supplying the brake fluid in each W/C 6 to a reservoir, and is configured to be able to increase, maintain, and reduce the W/C pressure. In addition, the actuator 7 makes it possible to realize an automatic pressurization function of the service brake 1, and based on the control of the pump drive and various control valves, the W/C 6 can be automatically pressurized even when the brakes are not being operated.

On the other hand, the EPB2 generates an electric braking force by driving a wheel brake mechanism with an EPB motor 10, and is configured with an EPB-ECU 9 (controller) that controls the driving of the EPB motor 10. The EPB-ECU 9 and the ESC-ECU 8 transmit and receive information, for example, via CAN (Controller Area Network) communication.

The wheel brake mechanism is a mechanical structure that generates a braking force (braking force) in the vehicle brake device of the embodiment. The wheel brake mechanism for the front wheels is structured to generate a service brake force by operating the service brake 1. On the other hand, the wheel brake mechanism for the rear wheels is structured to generate a braking force in response to both the operation of the service brake 1 and the operation of the EPB 2. The wheel brake mechanism for the front wheels is a wheel brake mechanism that has been commonly used in the past, but does not have a mechanism for generating an electric braking force based on the operation of the EPB 2, as compared to the wheel brake mechanism for the rear wheels. Therefore, a description of the wheel brake mechanism for the front wheels is omitted here, and the following describes the wheel brake mechanism for the rear wheels.

In the rear wheel brake mechanism, not only when the service brake 1 is activated but also when the EPB 2 is activated, the brake pad 11, which is the friction material shown in FIG. 2, is pressed, and the brake pad 11 pinches the brake disc 12 (12RL, 12RR, 12FR, 12FL), which is the friction material, generating a frictional force between the brake pad 11 and the brake disc 12, thereby generating a braking force.

Specifically, the wheel brake mechanism rotates the EPB motor 10, which is fixed directly to the body 14 of the W/C 6 for pressing the brake pads 11 as shown in FIG. 2, in the caliper 13 shown in FIG. 1, thereby rotating the spur gear 15 provided on the drive shaft 10a of the EPB motor 10. The rotational force of the EPB motor 10 is then transmitted to the spur gear 16 meshed with the spur gear 15, thereby moving the brake pads 11 and generating an electric braking force by the EPB 2.

In addition to the W/C 6 and brake pads 11, the caliper 13 also contains a portion of the end face of the brake disc 12, sandwiched between the brake pads 11. The W/C 6 is configured to generate W/C pressure in the hollow portion 14a, which is a brake fluid storage chamber, by introducing brake fluid pressure through a passage 14b into the hollow portion 14a of the cylindrical body 14, and is configured with a rotating shaft 17, a drive shaft 18, a piston 19 (linear member), and the like, within the hollow portion 14a.

One end of the rotating shaft 17 is connected to the spur gear 16 through an insertion hole 14c formed in the body 14, and when the spur gear 16 is rotated, the rotating shaft 17 is rotated in conjunction with the rotation of the spur gear 16. A male screw groove 17a is formed on the outer circumferential surface of the rotating shaft 17 at the end of the rotating shaft 17 opposite the end connected to the spur gear 16. Meanwhile, the other end of the rotating shaft 17 is supported by being inserted into the insertion hole 14c. Specifically, the insertion hole 14c is provided with a bearing 21 together with an O-ring 20, and the other end of the rotating shaft 17 is supported by the bearing 21 while the O-ring 20 prevents brake fluid from leaking out between the rotating shaft 17 and the inner wall surface of the insertion hole 14c.

The drive shaft 18 is composed of a nut made of a hollow cylindrical member, and a female screw groove 18a that screws into the male screw groove 17a of the rotating shaft 17 is formed on the inner wall surface. The drive shaft 18 is configured, for example, as a cylindrical or polygonal column equipped with a rotation prevention key, so that it cannot rotate around the center of rotation of the rotating shaft 17 even if the rotating shaft 17 rotates. Therefore, when the rotating shaft 17 is rotated, the engagement between the male screw groove 17a and the female screw groove 18a converts the rotational force of the rotating shaft 17 into a force that moves the drive shaft 18 in the axial direction of the rotating shaft 17. When the drive of the EPB motor 10 is stopped, the drive shaft 18 stops in the same position due to the frictional force caused by the engagement between the male screw groove 17a and the female screw groove 18a. If the drive of the EPB motor 10 is stopped when the target electric braking force is reached, the drive shaft 18 is held in that position, and the desired electric braking force is maintained and self-locked (hereinafter simply referred to as "locked").

The piston 19 generates an electric braking force by moving in the forward direction due to the drive of the EPB motor 10 during vehicle braking control, and releases the electric braking force by moving in the reverse direction, which is the opposite direction to the forward direction, due to the drive of the EPB motor 10 during brake release control. Specifically, it is as follows.

The piston 19 is arranged to surround the outer periphery of the drive shaft 18, and is composed of a cylindrical member or a polygonal tube member with a bottom, and is arranged so that its outer periphery contacts the inner wall surface of the hollow portion 14a formed in the body 14. A seal member 22 is provided on the inner wall surface of the body 14 to prevent brake fluid leakage between the outer periphery of the piston 19 and the inner wall surface of the body 14, and the structure is such that W/C pressure can be applied to the end surface of the piston 19. The seal member 22 is used to generate a reaction force to pull back the piston 19 during release control after apply control (lock control). Because this seal member 22 is provided, even if the brake pad 11 and the piston 19 are pushed in by the brake disc 12 tilted during turning within a range that does not exceed the elastic deformation amount of the seal member 22, they can be pushed back to the brake disc 12 side so that a predetermined clearance is maintained between the brake disc 12 and the brake pad 11.

In addition, if the drive shaft 18 is provided with a key for preventing rotation, the piston 19 is provided with a key groove for the key to slide in, so that the piston 19 cannot rotate around the center of rotation of the drive shaft 17 even when the drive shaft 17 rotates. If the drive shaft 18 is made into a polygonal column, the piston 19 is made into a polygonal cylinder of a corresponding shape.

The brake pad 11 is disposed at the tip of the piston 19, and the brake pad 11 is moved left and right as the piston 19 moves. Specifically, the piston 19 is movable leftward as the drive shaft 18 moves leftward, and is movable leftward independently of the drive shaft 18 when W/C pressure is applied to the end of the piston 19 (the end opposite the end where the brake pad 11 is disposed). When the drive shaft 18 is in the release position (the state before the EPB motor 10 is rotated), which is the standby position during normal release, if no brake fluid pressure is applied in the hollow portion 14a (W/C pressure = 0), the piston 19 is moved rightward by the elastic force of the seal member 22 described later, and the brake pad 11 is separated from the brake disc 12. In addition, when the EPB motor 10 is rotated and the drive shaft 18 is moved from its initial position to the left on the page, even if the W/C pressure becomes 0, the moved drive shaft 18 restricts the movement of the piston 19 to the right on the page, and the brake pad 11 is held in place.

In the wheel brake mechanism configured as above, when the service brake 1 is operated, the piston 19 is moved to the left on the paper based on the W/C pressure generated by the operation, and the brake disc 12 is pressed against the brake pad 11, generating a service brake force. When the EPB 2 is operated, the EPB motor 10 is driven to rotate the spur gear 15, which in turn rotates the spur gear 16 and the rotating shaft 17, and the drive shaft 18 is moved toward the brake disc 12 (to the left on the paper) based on the meshing of the male screw groove 17a and the female screw groove 18a. Then, the tip of the drive shaft 18 comes into contact with the bottom surface of the piston 19 and presses the piston 19, and the piston 19 is also moved in the same direction, which presses the brake disc 12 against the brake pad 11, generating an electric braking force. This makes it possible to create a shared wheel brake mechanism that generates braking forces in response to both the operation of the service brake 1 and the operation of the EPB 2.

In addition, by acquiring the current detection value from a current sensor (not shown) that detects the current of the EPB motor 10, it is possible to confirm the state of electric braking force generated by the EPB 2 and recognize the current detection value.

The longitudinal G sensor 25 detects G (acceleration) in the longitudinal direction (travel direction) of the vehicle and transmits a detection signal to the EPB-ECU 9.

The M/C pressure sensor 26 detects the M/C pressure in the M/C 5 and transmits a detection signal to the EPB-ECU 9.

The temperature sensor 28 detects the temperature of the wheel brake mechanism (e.g., the brake disc) and transmits a detection signal to the EPB-ECU 9.

The wheel speed sensor 29 detects the rotation speed of each wheel and transmits a detection signal to the EPB-ECU 9. In practice, one wheel speed sensor 29 is provided for each wheel, but detailed illustration and description are omitted here.

The EPB-ECU 9 is configured with a well-known microcomputer equipped with a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), I/O, etc., and performs parking brake control by controlling the rotation of the EPB motor 10 according to a program stored in the ROM, etc.

The EPB-ECU 9 inputs signals corresponding to the operation state of an operation SW (switch) 23 provided on an instrument panel (not shown) inside the vehicle cabin, for example, and drives the EPB motor 10 according to the operation state of the operation SW 23. Furthermore, the EPB-ECU 9 executes apply control, release control, and the like based on the current detection value of the EPB motor 10, and recognizes, based on the control state, that apply control is in progress and the wheels are locked due to apply control, and that release control is in progress and the wheels are released due to release control (EPB released state). The EPB-ECU 9 then outputs signals to display various information to indicator lamps 24 provided on the instrument panel.

In the vehicle brake device configured as described above, basically, the service brake 1 generates a service brake force when the vehicle is traveling, thereby generating a braking force for the vehicle. When the vehicle is stopped by the service brake 1, the driver presses the operation SW 23 to operate the EPB 2 to generate an electric braking force to maintain the stopped state, and then releases the electric braking force. That is, when the driver operates the brake pedal 3 while the vehicle is traveling, the service brake 1 operates by transmitting the brake fluid pressure generated in the M/C 5 to the W/C 6 to generate a service brake force. The EPB 2 operates by driving the EPB motor 10 to move the piston 19, pressing the brake pad 11 against the brake disc 12 to generate an electric braking force to lock the wheels, or by separating the brake pad 11 from the brake disc 12 to release the electric braking force to release the wheels.

In other words, the apply/release control generates and releases the electric braking force. In the apply control, the EPB2 is actuated by rotating the EPB motor 10 forward, and the rotation of the EPB motor 10 is stopped at a position where the desired electric braking force can be generated by the EPB2, and this state is maintained. In this way, the desired electric braking force is generated. In the release control, the EPB2 is actuated by rotating the EPB motor 10 backward, and the electric braking force generated by the EPB2 is released.

Below, with reference to Figures 3 to 5, a technique for setting an appropriate target current value according to individual differences in the performance of the EPB motor 10 will be described. Note that in the following, power transmission efficiency means the efficiency of power transmission from the EPB motor 10 to the piston 19. This power transmission efficiency can change due to various factors such as aging of the wheel brake mechanism and environmental temperature and humidity. When the target current value passed through the EPB motor 10 during braking control is the same, the higher the power transmission efficiency, the greater the generated electric braking force, and the lower the power transmission efficiency, the smaller the generated electric braking force.

In the following, for the sake of simplicity, two relative states will be described as examples: a high power transmission efficiency state in which the power transmission efficiency is high, and a low power transmission efficiency state in which the power transmission efficiency is low.

Figure 3 is a graph showing the change over time in the current value of the EPB motor 10 in the embodiment. As shown in (A), during brake release control, the current value C11 is in a high power transmission efficiency state, and the current value C12 is in a low power transmission efficiency state.

In this case, the current value C11 rises sharply at time t1 due to an inrush current, and at time t2, the gradient of change in the current value C11 with respect to time becomes equal to or less than the first threshold value. The first threshold value is a threshold value used to determine the no-load determination time of the EPB motor 10 during brake release control, and is a threshold value of the gradient of change in the current value with respect to time. The time T11 from time t1 to time t2 is the first elapsed time from the start of current flow to the EPB motor 10 in a high power transmission efficiency state until the gradient of change in the current value of the EPB motor 10 with respect to time becomes equal to or less than the first threshold value.

The current value C12 rises sharply at time t1 due to an inrush current, and at time t3, the gradient of change in the current value C12 with respect to time is equal to or less than the first threshold value. The time T12 from time t1 to time t3 is the first elapsed time in the low power transmission efficiency state.

In this way, the length of the first elapsed time is correlated with the power transmission efficiency state. Therefore, by using this first elapsed time, it is possible to set an appropriate target current value according to individual differences in the performance of the EPB motor 10.

Also, as shown in (B), during braking control (apply control), current value C21 is in a state of high power transmission efficiency, and current value C22 is in a state of low power transmission efficiency.

In this case, the current value C21 rises sharply at time t11 due to an inrush current, and at time t13, the gradient of change in the current value C21 with respect to time is equal to or greater than the second threshold value. The second threshold value is a threshold value used to determine the no-load determination time during braking control, and is a threshold value of the gradient of change in the current value with respect to time. The time T21 from time t11 to time t13 is the second elapsed time from the start of current flow to the EPB motor 10 in a high power transmission efficiency state until the gradient of change in the current value of the EPB motor 10 with respect to time becomes equal to or greater than the second threshold value.

In addition, the current value C22 rises sharply at time t11 due to an inrush current, and at time t12, the gradient of change in the current value C22 with respect to time is equal to or greater than the second threshold value. The time T22 from time t11 to time t12 is the second elapsed time in the low power transmission efficiency state.

In this way, the length of the second elapsed time is correlated with the power transmission efficiency state. Therefore, by using this second elapsed time, it is possible to set an appropriate target current value according to individual differences in the performance of the EPB motor 10.

Figure 4 is a graph showing a first example of the relationship between the no-load judgment time and the target current value in an embodiment. As shown in (A), when the no-load judgment time during brake release control is used, the EPB-ECU 9 sets the target current value TC1 when the no-load judgment time is less than the threshold value SH1, and sets the target current value TC2 (>TC1) when the no-load judgment time is equal to or greater than the threshold value SH1.

Also, as shown in (B), when the EPB-ECU 9 uses the no-load determination time during braking control (apply control), it sets a target current value TC3 when the no-load determination time is less than the threshold value SH2, and sets a target current value TC4 (<TC3) when the no-load determination time is equal to or greater than the threshold value SH2.

Figure 5 is a graph showing a second example of the relationship between the no-load determination time and the target current value in an embodiment. As shown in (A), when the EPB-ECU 9 uses the no-load determination time during brake release control, the longer the no-load determination time, the larger the target current value is set.

Also, as shown in (B), when the EPB-ECU 9 uses the no-load determination time during braking control (apply control), the longer the no-load determination time is, the smaller the target current value is set.

Based on the above, the control flow of the EPB-ECU 9 will be explained with reference to FIG. 6. FIG. 6 is a flowchart showing the processing executed by the electric parking brake device of the embodiment.

When controlling the EPB motor 10 (step S1), the EPB-ECU 9 acquires at least one of a first elapsed time from the start of energization until the gradient of change in the current value of the EPB motor 10 with respect to time becomes equal to or less than a first threshold value during brake release control, and a second elapsed time from the start of energization until the gradient of change in the current value of the EPB motor 10 with respect to time becomes equal to or greater than a second threshold value during brake control (step S2). Note that steps S1 and S2 may be executed simultaneously with the brake control or brake release control, or may be executed at a timing independent of the brake control or brake release control.

Next, in step S3, the EPB-ECU 9 determines whether or not to execute braking control. If the answer is Yes, the EPB-ECU 9 proceeds to step S4, and if the answer is No, the EPB-ECU 9 returns to step S3.

In step S4, the EPB-ECU 9 sets a target current value to be applied to the EPB motor 10 during braking control based on either the first elapsed time or the second elapsed time, whichever is acquired in step S2 (FIGS. 4 and 5). Note that the setting of the target current value in step S4 may be performed before step S3.

Next, in step S5, the EPB-ECU 9 controls the EPB motor 10 using the target current value set in step S4.

In this way, according to the electric parking brake device of the embodiment, by setting the target current value to be passed through the EPB motor 10 during braking control based on at least one of the first elapsed time and the second elapsed time described above, it is possible to set an appropriate target current value according to individual differences in the performance of the EPB motor 10. This makes it possible to prevent the electric parking brake device from being subjected to a load more than necessary.

In addition, if the target current value is set to be larger the longer the first elapsed time (no-load determination time) based on the first elapsed time (Figures 4(A) and 5(A)), the change in current due to a decrease in power transmission efficiency is larger during brake release control than during brake control, so the target current value can be set with greater accuracy.

The change in current due to a decrease in power transmission efficiency is greater during brake release control than during brake control because, in general, a smaller current value is required when the EPB motor 10 is rotating in reverse than when it is rotating in forward direction.

In addition, if the target current value is set to be smaller the longer the second elapsed time (no-load determination time) based on the second elapsed time (Figures 4(B) and 5(B)), the second elapsed time can be obtained sooner than the first elapsed time when the electric parking brake device is in the released state as a reference, and an appropriate target current value can be set sooner based on the second elapsed time.

Although the embodiments of the present invention have been described above, the above-mentioned embodiments are merely examples and are not intended to limit the scope of the invention. The novel embodiments described above can be implemented in various forms, and various omissions, substitutions, or modifications can be made without departing from the gist of the invention. Furthermore, the above-mentioned embodiments are included within the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

For example, in the above embodiment, the rear wheels are electrically braked wheels, but this is not limited thereto, and the front wheels may be electrically braked wheels.

Furthermore, the present invention is not limited to disc brake type EPBs, but can also be applied to drum brake type EPBs.

In addition, in Figures 4 and 5, linear graphs are used to simplify the illustration and explanation, but this is not limited to this and non-linear graphs (e.g., graphs showing quadratic functions, exponential functions, logarithmic functions, etc.) may also be used.

1...service brake (hydraulic brake device), 2...EPB (electric parking brake device), 5...M/C, 6...W/C, 7...actuator, 8...ESC-ECU, 9...EPB-ECU (controller), 10...EPB motor (electric motor), 11...brake pad, 12...brake disc, 13...caliper, 14...body, 14a...hollow portion, 14b...passage, 17...rotating shaft, 17a...male thread groove, 18...propeller shaft, 18a...female thread groove, 19...piston (linear member), 23...operating switch, 24...indicator lamp, 25...front/rear G sensor, 26...M/C pressure sensor, 28...temperature sensor, 29...wheel speed sensor.

Claims (3)

a linear motion member that generates an electric braking force by moving in a forward direction by driving an electric motor during a braking control of the vehicle, and releases the electric braking force by moving in a backward direction, which is a direction opposite to the forward direction, by driving the electric motor during a brake release control;
A controller for controlling the electric motor;
In an electric parking brake device comprising:
The controller:
When controlling the electric motor, at least one of a first elapsed time from the start of energization until a gradient of change in a current value of the electric motor with respect to time becomes equal to or less than a first threshold value during the brake release control and a second elapsed time from the start of energization until a gradient of change in a current value of the electric motor with respect to time becomes equal to or greater than a second threshold value during the brake control is obtained;
an electric parking brake device that sets a target current value to be applied to the electric motor during the braking control based on the acquired one of the first elapsed time and the second elapsed time. The controller:
The electric motor is controlled during the brake release control to obtain the first elapsed time.
The electric parking brake device according to claim 1 , wherein, during the braking control, the target current value is set to be larger based on the first elapsed time as the first elapsed time is longer. The controller:
controlling the electric motor during the braking control to obtain the second elapsed time;
3 . The electric parking brake device according to claim 1 , wherein, during the braking control, the target current value is set smaller based on the second elapsed time as the second elapsed time is longer. 4 .

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