Electric parking brake for vehicles

Abstract

To prevent a linear motion member from getting too close to a retraction side regulation part by execution of release processing without increasing the size of an actuator.SOLUTION: An actuator 30 of an electric parking braking device 20 includes an electric motor 31, a linear motion member 55 and a flange part 53. When the linear motion member 55 moves in a forward direction X1, a brake shoe is pressed against the inner peripheral surface of a brake drum to generate a parking brake. A control device 80 of the electric parking braking device 20 executes, when releasing the parking brake, release processing of reversely driving the electric motor 31 from the time point at which it is determined that the motor current becomes constant to the elapse of the release time. The control device 80 executes shortening processing of changing the release time such that the release time becomes shorter as the interval between the brake shoe and the inner peripheral surface at the time of non-actuation of the drum brake is narrower.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electric parking brake system for a vehicle. [Background technology]

[0002] Patent Document 1 describes an example of an electric parking brake system that applies parking brakes to a vehicle by operating a drum brake. The actuator of this system includes an electric motor and a linearly moving member that moves linearly when driven by the electric motor. To apply the parking brake, the electric motor drives the actuator in the forward direction, causing the linearly moving member to move forward. This causes the brake shoes of the drum brake to be pressed against the inner peripheral surface of the brake drum. When it is determined that the force pressing the brake shoes against the brake drum has exceeded a predetermined value, the forward rotation of the electric motor is stopped.

[0003] In such a device, when the parking brake is released, a release process is performed to drive the electric motor in the reverse direction. When the electric motor drives in the reverse direction, the linearly-acting member moves in the reverse direction, which is the opposite direction to the forward direction, and the brake shoe moves away from the inner peripheral surface of the brake drum. When a predetermined release time has elapsed from the reference point at which it is determined that the motor current, which is the value of the current flowing through the electric motor, has become constant, the reverse driving of the electric motor is stopped.

[0004] The actuator of the electric parking brake device has a restricting portion that restricts the movement range of the linearly moving member. When the linearly moving member moves in the reverse direction due to the release process, it is preferable to prevent the linearly moving member from coming too close to the reverse-side restricting portion that is located further in the reverse direction than the linearly moving member. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-172293 Summary of the Invention [Problem to be solved by the invention]

[0006] Depending on how the drum brake is used during service braking, the standby interval, which is the distance between the inner circumferential surface of the brake drum and the brake shoes when the drum brake is not in operation, can become very narrow. If the electric motor is driven in the forward direction to apply the parking brake when the standby interval is very narrow, the force pressing the brake shoes against the brake drum increases quickly, resulting in a shorter drive time for the electric motor compared to when the standby interval is relatively wide. If the release process is subsequently performed in this case, the electric motor will continue to drive in the reverse direction from the reference point until the predetermined release time has elapsed, causing the linearly moving member to approach the reverse-side restrictor very closely. To prevent the linearly moving member from approaching the reverse-side restrictor too closely when the release process is performed, the range of movement of the linearly moving member must be widened. However, the larger the range of movement, the larger the actuator will be. [Means for solving the problem]

[0007] An electric parking brake system for a vehicle that solves the above-mentioned problems is applied to a vehicle equipped with drum brakes that apply braking force to wheels by pressing a friction member against the inner circumferential surface of a cylindrical portion that rotates integrally with the wheels. This electric parking brake system includes an actuator and a control device that controls the actuator. The actuator includes an electric motor, a linearly-acting member that moves forward when the electric motor is driven in the forward direction and moves in a reverse direction, which is the opposite direction to the forward direction, when the electric motor is driven in the reverse direction, and a reverse-side limiting portion that limits the movement range of the linearly-acting member and is located further in the reverse direction than the linearly-acting member. When the linearly-acting member moves forward in the forward direction due to the forward rotation of the electric motor, the actuator presses the friction member against the inner circumferential surface, thereby applying a parking brake to the vehicle. The control device executes an apply process that drives the electric motor in the forward direction until it is determined that the force pressing the friction member against the inner peripheral surface has reached a predetermined value or more, a release process that releases the parking brake by driving the electric motor in the reverse direction from the point in time when it is determined that the value of the current flowing through the electric motor has reached a constant value until a predetermined release time has elapsed, and a shortening process that changes the release time so that the release time becomes shorter as the standby interval, which is the gap between the friction member and the inner peripheral surface when the drum brake is not in operation, becomes narrower.

[0008] In the above configuration, the shortening process changes the release time so that the shorter the standby interval, the shorter the release time. By setting a shorter release time, the amount of backward movement of the linearly moving member caused by the reverse rotation of the electric motor during the release process can be reduced. This prevents the linearly moving member from coming too close to the backward restriction portion during the release process, even if the amount of forward movement of the linearly moving member caused by the forward rotation of the electric motor during the apply process is small. In other words, the release process can prevent the linearly moving member from coming too close to the backward restriction portion without increasing the size of the actuator to expand the range of movement of the linearly moving member. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an electric parking brake device and a drum brake according to an embodiment. [Figure 2] FIG. 2 is a configuration diagram showing a cross section of an actuator and a control device in the electric parking brake device. [Figure 3] FIG. 3 is a cross-sectional view showing the actuator of the electric parking brake device. [Figure 4] FIG. 4 is a flowchart showing the flow of processing when the processing circuit of the control device executes the apply processing. [Figure 5] FIG. 5 is a time chart showing the transition of the motor current when the apply process is executed. [Figure 6] FIG. 6 is a time chart showing the transition of the motor current when the linearly moving member comes into contact with the forward movement regulating portion during the application process. [Figure 7] FIG. 7 is a flowchart showing the flow of processing when the processing circuit executes the release processing. [Figure 8] FIG. 8 is a time chart showing the transition of the motor current when the release process is executed. [Figure 9] FIG. 9 is a flowchart showing the flow of processing when the processing circuit executes shortening processing or extension processing. [Figure 10] FIG. 10 is a time chart showing the transition of the motor current when the apply process is executed. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, one embodiment of an electric parking brake device for a vehicle will be described with reference to FIGS. FIG. 1 shows a drum brake 10 provided on a wheel, and an electric parking brake device 20 that applies a parking brake to the wheel by actuating the drum brake 10.

[0011] <Drum brakes> The drum brake 10 comprises a backing plate 11 fixed to the vehicle body and a brake drum 12 fixed to the axle of the wheel. The brake drum 12 has a cylindrical portion 121 that is centered on the rotation axis 100 of the wheel. This cylindrical portion 121 rotates integrally with the wheel. The inner peripheral surface of the cylindrical portion 121 is referred to as the "inner peripheral surface 12a of the brake drum 12."

[0012] The brake drum 12 includes two brake shoes 15 and 16 arranged inside a cylindrical portion 121, and a wheel cylinder (not shown). The brake shoes 15 and 16 correspond to the "friction member."

[0013] Both brake shoes 15, 16 have an arc shape that follows the shape of the inner peripheral surface 12a of the brake drum 12. Both brake shoes 15, 16 each have a friction material 17. The upper ends of the brake shoes 15, 16 in FIG. 1 are referred to as "first ends of the brake shoes 15, 16," and the lower ends of the brake shoes 15, 16 in FIG. 1 are referred to as "second ends of the brake shoes 15, 16." At this time, during service braking, when the hydraulic pressure in the wheel cylinder is increased, the wheel cylinder displaces both brake shoes 15, 16 so that the first ends of the brake shoes 15 and 16 move away from each other. As a result, the friction materials 17 of both brake shoes 15, 16 are pressed against the inner peripheral surface 12a of the brake drum 12.

[0014] A second end of the brake shoe 15 is supported by the backing plate 11 in a state where it can rotate around a rotation center J1, and a second end of the brake shoe 16 is supported by the backing plate 11 in a state where it can rotate around a rotation center J2. Therefore, during service braking, the wheel cylinder presses both brake shoes 15, 16 against the inner peripheral surface 12a of the brake drum 12, thereby applying a braking force to the wheel.

[0015] <Electric parking brake system> As shown in FIGS. 1 and 2, the electric parking brake device 20 includes a parking lever 21, a parking cable 22, a shoe strut 24, an actuator 30, and a control device 80.

[0016] The parking lever 21 is supported by one of the two brake shoes 15, 16, the brake shoe 15. As shown in FIG. 1, the parking lever 21 extends generally in the vertical direction of the vehicle. The upper end of the parking lever 21 in FIG. 1 is referred to as the "first end 21a of the parking lever 21," and the lower end of the parking lever 21 in FIG. 2 is referred to as the "second end 21b of the parking lever 21." In this case, the first end 21a of the parking lever 21 is supported by the brake shoe 15 in a manner that allows it to rotate around the rotation shaft 18. Meanwhile, a parking cable 22 is connected to the second end 21b of the parking lever 21.

[0017] The shoe strut 24 is disposed between the two brake shoes 15, 16. During parking braking, the actuator 30 is activated to pull the parking cable 22, displacing the second end of the brake shoe 15 in the braking direction D1. At this time, the parking lever 21 attempts to rotate around the rotation axis 18, causing the shoe strut 24 to tension between the two brake shoes 15, 16. This tension of the shoe strut 24 presses the brake shoe 16 against the shoe strut 24. The resulting reaction force presses the brake shoe 15. As a result, the friction materials 17 of the brake shoes 15, 16 are pressed against the inner circumferential surface 12a of the brake drum 12. This applies a parking braking force to the wheels, i.e., the parking brake is activated. The force pressing the brake shoes 15, 16 against the inner circumferential surface 12a is also referred to as the "pressing force."

[0018] On the other hand, when the parking brake is released, the actuator 30 is activated to reduce the tension of the parking cable 22. This causes the second end 21b of the parking lever 21 to be displaced in the release direction D2, which is the opposite direction to the braking direction D1, thereby reducing the parking braking force applied to the wheels. When the brake shoes 15, 16 are eventually separated from the inner peripheral surface 12a of the brake drum 12, the parking brake is released.

[0019] The shoe strut 24 has an adjuster function that adjusts the standby interval Hw. The standby interval Hw is the distance between the inner peripheral surface 12a of the brake drum 12 and the brake shoes 15, 16 when the drum brake 10 is not in operation. In this embodiment, the shoe strut 24 is configured to perform the adjuster function only when the service brake is applied, out of the parking brake and service brake. Because this adjuster function is well known, a detailed description will be omitted. However, the adjuster function works to change the standby interval Hw to the reference interval HwB. However, when the value indicating the standby interval Hw is within a predetermined interval range, the adjuster function works, but when the value indicating the standby interval Hw is outside the predetermined interval range, the adjuster function does not work. The value indicating the reference interval HwB is a value within the predetermined interval range.

[0020] As shown in FIGS. 2 and 3, the actuator 30 includes an electric motor 31, a reduction mechanism 40, and a linear motion conversion mechanism 50. An output shaft 32 that rotates integrally with the rotor of the electric motor 31 is connected to the electric motor 31. The electric motor 31 rotates the output shaft 32 in a first rotational direction, and in a second rotational direction that is the opposite direction to the first rotational direction. Driving the electric motor 31 to rotate the output shaft 32 in the first rotational direction is called "forward driving," and driving the electric motor 31 to rotate the output shaft 32 in the second rotational direction is called "reverse driving."

[0021] The reduction gear 40 transmits the rotational motion of the electric motor 31 to the linear motion conversion mechanism 50. In this embodiment, the reduction gear 40 has a plurality of gears that mesh with each other. Of the plurality of gears, a first gear 41 is connected to the output shaft 32, and rotates in response to the rotation of the output shaft 32. Of the plurality of gears, a second gear 42 is fixed to the linear motion conversion mechanism 50.

[0022] The linear motion conversion mechanism 50 converts the rotational motion transmitted from the reduction gear mechanism 40 into linear motion and outputs the linear motion to the parking cable 22. The linear motion conversion mechanism 50 is, for example, a ball screw mechanism or a feed screw mechanism. The linear motion conversion mechanism 50 has a rotating member 51, a linear motion member 55, and a rotation prevention member 57. The rotating member 51 has a cylindrical portion 52 and a flange portion 53 extending radially outward from the cylindrical portion 52. The second gear 42 is fixed to the flange portion 53. The rotating member 51 is disposed coaxially with the second gear 42, and rotates integrally with the second gear 42.

[0023] Of the two directions along the central axis of the cylindrical portion 52 of the rotating member 51, the right direction in FIGS. 2 and 3 is referred to as the "forward direction X1," and the left direction in FIGS. 2 and 3 is referred to as the "rearward direction X2."

[0024] The anti-rotation member 57 is disposed radially outward of the linear motion member 55. The anti-rotation member 57 is configured to restrict rotation of the linear motion member 55. A protrusion 58 that protrudes radially inward is provided at an end of the anti-rotation member 57 in the forward movement direction X1.

[0025] The linear moving member 55 is capable of linear movement along the extension direction of the cylindrical portion 52. When the rotating member 51 rotates, the rotation of the linear moving member 55 is restricted by the anti-rotation member 57, and therefore the linear moving member 55 moves linearly in a direction (forward direction X1 or backward direction X2) corresponding to the rotation direction of the rotating member 51. In this embodiment, when the output shaft 32 is rotated in a first rotation direction by the forward driving of the electric motor 31, the linear moving member 55 moves in the forward direction X1. On the other hand, when the output shaft 32 is rotated in a second rotation direction by the reverse driving of the electric motor 31, the linear moving member 55 moves in the backward direction X2.

[0026] As shown in FIGS. 2 and 3 , the parking cable 22 is inserted inside the rotating member 51, and the forward direction X1 end 22a of the parking cable 22 is positioned further in the forward direction X1 than the forward direction X1 end of the linearly moving member 55. A locking member 23 is fixed to the forward direction X1 end 22a of the parking cable 22. The linearly moving member 55 supports the locking member 23. Therefore, when the linearly moving member 55 moves in the forward direction X1, the locking member 23 also moves in the forward direction X1. As a result, the parking cable 22 is pulled by the actuator 30, and the tension of the parking cable 22 increases. As a result, the second end 21b of the parking lever 21 is displaced in the braking direction D1, and the parking braking force increases. On the other hand, when the linearly moving member 55 moves in the reverse direction X2, the locking member 23 is pulled by the parking cable 22 and also moves in the reverse direction X2. As a result, the tension of the parking cable 22 decreases. As a result, the second end 21b of the parking lever 21 is displaced in the release direction D2, thereby reducing the parking braking force.

[0027] The linear moving member 55 moves linearly within a predetermined movement range AR shown in FIG. 2 by being driven by the electric motor 31. That is, when the linear moving member 55 moves in the backward direction X2 by being driven in the reverse direction by the electric motor 31, the backward direction X2 end of the linear moving member 55 approaches the backward side boundary, which is the boundary on the backward direction X2 side of the movement range AR. When the backward direction X2 end of the linear moving member 55 reaches the backward side boundary, the linear moving member 55 comes into contact with the flange portion 53 of the rotating member 51, and further movement of the linear moving member 55 in the backward direction X2 is restricted by the flange portion 53. On the other hand, when the linear moving member 55 moves in the forward direction X1 by being driven in the forward direction by the electric motor 31, the forward direction X1 end of the linear moving member 55 approaches the forward side boundary, which is the boundary on the forward direction X1 side of the movement range AR. Then, when the end of the linear moving member 55 in the forward direction X1 reaches the forward side boundary, the linear moving member 55 comes into contact with the protrusion 58 of the anti-rotation member 57, and further movement of the linear moving member 55 in the forward direction X1 is restricted by the protrusion 58.

[0028] That is, in this embodiment, the flange portion 53 restricts the movement range AR of the linear moving member 55 and corresponds to a "rearward-moving-side restricting portion" located further in the rearward direction X2 than the linear moving member 55. The protruding portion 58 restricts the movement range AR of the linear moving member 55 and corresponds to an "advancement-side restricting portion" located further in the forward direction X1 than the linear moving member 55.

[0029] The actuator 30 has a self-locking function. The self-locking function here means a function that maintains the position of the linearly moving member 55 when the driving of the electric motor 31 is stopped. Therefore, if the driving of the electric motor 31 is stopped while the parking braking force is being applied to the wheels, the parking braking force is maintained.

[0030] 2, the control device 80 includes a processing circuit 81. The processing circuit 81 has a CPU 82 and a memory 83. The memory 83 stores various control programs that the CPU 82 executes.

[0031] The processing circuit 81 executes an apply process, a release process, a shortening process, and an extension process by having the CPU 82 execute a control program. The apply process is a process for applying the parking brake. The release process is a process for releasing the parking brake. The shortening process and the extension process are processes for changing the release time Tbkth that defines the drive time of the electric motor 31 during the release process. Details of the release time Tbkth will be described later.

[0032] <Apply processing> The flow of processing when the processing circuit 81 executes the apply processing will be described with reference to Figures 4 to 6. When the parking brake is requested, the processing circuit 81 executes the processing routine shown in Figure 4. Figures 5 and 6 show the transition of the motor current Imt accompanying the execution of the apply processing. The motor current Imt is the value of the current flowing through the electric motor 31 when the electric motor 31 is driven.

[0033] 4, in step S11, the processing circuit 81 starts the forward rotation of the electric motor 31. That is, the processing circuit 81 starts the apply process. As shown in FIG. 5, an inrush current flows through the electric motor 31 when the electric motor 31 is started. That is, during the starting period from timing t11 when the electric motor 31 starts to timing t12, the motor current Imt is relatively large. However, after timing t12, the effect of the inrush current also decreases, and the brake shoes 15, 16 are no longer in contact with the inner circumferential surface 12a of the brake drum 12, so the motor load applied to the electric motor 31 is small. Therefore, the motor current Imt is small. In other words, the magnitude of the motor load is correlated with the magnitude of the motor current Imt. Then, when the brake shoes 15, 16 come into contact with the inner circumferential surface 12a, the motor load increases, and the motor current Imt also increases.

[0034] 4, when the electric motor 31 starts to be driven in the forward direction, the processing circuit 81 proceeds to step S13. In step S13, the processing circuit 81 determines whether the linear moving member 55 has come into contact with the protrusion 58 of the anti-rotation member 57 due to the movement of the linear moving member 55 in the forward direction X1 caused by the forward rotation of the electric motor 31.

[0035] In Fig. 6, the solid line shows the change in the motor current Imt when the linearly moving member 55 comes into contact with the protrusion 58 while the electric motor 31 is rotating in the forward direction. The dashed line shows the change in the motor current Imt when the linearly moving member 55 does not come into contact with the protrusion 58 while the electric motor 31 is rotating in the forward direction. When the linearly moving member 55 comes into contact with the protrusion 58 as shown by the solid line in Fig. 6, the motor load increases suddenly because the protrusion 58 restricts further movement of the linearly moving member 55 in the forward direction X1. As a result, the motor current Imt increases suddenly.

[0036] Therefore, the processing circuit 81 determines whether or not both of the following two conditions (A1) and (A2) are satisfied. If both of the two conditions (A1) and (A2) are satisfied, the processing circuit 81 determines that the linearly moving member 55 is in contact with the protrusion 58. On the other hand, if at least one of the two conditions (A1) and (A2) is not satisfied, the processing circuit 81 determines that the linearly moving member 55 is not in contact with the protrusion 58. (A1) The time elapsed since the start of forward rotation of the electric motor 31 exceeds the initial drive time Tda. (A2) The motor current Imt is equal to or greater than the contact determination current value ImtAa.

[0037] During the period from the start of forward rotation of the electric motor 31 until the elapse of the initial drive time Tda, the motor current Imt may be relatively large due to the influence of an inrush current. Therefore, the initial drive time Tda is set as a criterion for determining whether an inrush current is flowing through the electric motor 31. The contact determination current value ImtAa is set as a criterion for determining whether the motor load is excessive.

[0038] 4, if it is determined that the linearly moving member 55 is in contact with the protrusion 58 (S13: YES), the processing circuit 81 proceeds to step S15. In step S15, the processing circuit 81 sets the contact flag FLG0 to ON. If it is determined that the linearly moving member 55 is in contact with the protrusion 58, the contact flag FLG0 is set to ON, whereas if it is determined that the linearly moving member 55 is not in contact with the protrusion 58, the contact flag FLG0 is set to OFF. Thereafter, the processing circuit 81 proceeds to step S21.

[0039] On the other hand, if it is determined in step S13 that the linear moving member 55 is not in contact with the protrusion 58 (NO), the processing circuit 81 proceeds to step S17. In step S17, the processing circuit 81 determines whether the pressing force pressing both brake shoes 15, 16 against the inner peripheral surface 12a of the brake drum 12 has reached or exceeded a predetermined value.

[0040] 5, once the elapsed time from the start of forward rotation of the electric motor 31 exceeds the initial drive time Tda, the motor current Imt changes in accordance with changes in the motor load. That is, when the brake shoes 15, 16 are not in contact with the inner circumferential surface 12a of the brake drum 12, the motor load is small and the motor current Imt is small. Then, when the brake shoes 15, 16 come into contact with the inner circumferential surface 12a as a result of forward rotation of the electric motor 31, the motor load increases and the motor current Imt increases.

[0041] In this embodiment, the processing circuit 81 determines whether the motor current Imt has reached or exceeded the stop determination current value Imtth1. As the pressing force, which is the force pressing the brake shoes 15, 16 against the inner peripheral surface 12a of the brake drum 12, increases, the motor load increases, and the motor current Imt therefore increases. Therefore, the stop determination current value Imtth1 is set as a criterion for determining whether the pressing force has reached or exceeded a predetermined value. However, the stop determination current value Imtth1 is smaller than the contact determination current value ImtAa.

[0042] The processing circuit 81 determines that the pressing force has reached a predetermined value or more if both of the following two conditions (A3) and (A4) are met. On the other hand, the processing circuit 81 determines that the pressing force has not reached a predetermined value or more if at least one of the two conditions (A3) and (A4) is not met. (A3) The time elapsed since the start of forward rotation of the electric motor 31 exceeds the initial drive time Tda. (A4) The motor current Imt is equal to or greater than the stop determination current value Imtth1.

[0043] Returning to FIG. 4, if it is determined in step S17 that the pressing force is not equal to or greater than the predetermined value (NO), the processing circuit 81 proceeds to step S13. On the other hand, if it is determined that the pressing force is equal to or greater than the predetermined value (S17: YES), the processing circuit 81 proceeds to step S19. In step S19, the processing circuit 81 sets the contact flag FLG0 to OFF. Then, the processing circuit 81 proceeds to step S21.

[0044] In step S21, the processing circuit 81 stops the forward rotation of the electric motor 31. That is, the processing circuit 81 ends the apply process. Subsequently, in step S23, the processing circuit 81 acquires the first measurement time Tx.

[0045] Here, the acquisition of the first measurement time Tx will be explained. When the brake shoes 15, 16 begin to contact the inner peripheral surface 12a of the brake drum 12 due to forward rotation of the electric motor 31, the motor load increases, and the motor current Imt begins to increase, as shown by both the solid and dashed lines in FIG. 5. The motor current Imt then exceeds the reference current Imtk. The reference current Imtk is set as a criterion for determining whether or not the brake shoes 15, 16 may have begun to contact the inner peripheral surface 12a. In this case, the reference current Imtk is smaller than the stop determination current value Imtth1. The processing circuit 81 determines that the brake shoes 15, 16 have contacted the inner peripheral surface 12a when the duration during which the motor current Imt is equal to or greater than the reference current Imtk exceeds the determination time Th. The processing circuit 81 then acquires, as a first measurement time Tx, the elapsed time from the start of forward rotation of the electric motor 31 to the time when it is determined that the brake shoes 15, 16 have contacted the inner circumferential surface 12a of the brake drum 12. In Fig. 5, the dashed line represents the transition of the motor current Imt when the apply process is executed when the standby interval Hw is relatively wide, and the solid line represents the transition of the motor current Imt when the apply process is executed when the standby interval Hw is relatively narrow. In this embodiment, the standby interval Hw can be estimated based on the length of the first measurement time Tx.

[0046] When the processing circuit 81 acquires the first measurement time Tx, it ends the processing routine shown in FIG. <Release process> The flow of processing when the processing circuit 81 executes the release processing will be described with reference to Figures 7 and 8. When a request is made to release the parking brake, the processing circuit 81 executes the processing routine shown in Figure 7. Figure 8 shows the transition of the motor current Imt accompanying the execution of the release processing.

[0047] 7, in step S31, the processing circuit 81 starts reverse driving of the electric motor 31. That is, the processing circuit 81 starts the release process. As shown in Figure 8, an inrush current flows through the electric motor 31 when the electric motor 31 begins to start. That is, during the startup period from timing t31 when the electric motor 31 starts to timing t32, the motor current Imt is relatively large due to the influence of the inrush current. After timing t32, the influence of the inrush current also decreases, and the pressing force described above gradually decreases as the electric motor 31 is driven in the reverse direction, thereby reducing the motor load. That is, the motor current Imt decreases. Then, at timing t33, just before and after both brake shoes 15, 16 separate from the inner circumferential surface 12a of the brake drum 12, the motor current Imt becomes approximately constant.

[0048] Returning to FIG. 7, when reverse driving of the electric motor 31 is started, the processing circuit 81 shifts the processing to step S33. In step S33, the processing circuit 81 determines whether the motor current Imt has become constant. For example, if the rate of change of the motor current Imt is equal to or greater than the rate of change determination value, the processing circuit 81 determines that the motor current Imt has not become constant. On the other hand, if the rate of change of the motor current Imt is less than the rate of change determination value, the processing circuit 81 determines that the motor current Imt has become constant. If the processing circuit 81 determines that the motor current Imt has not become constant (S33: NO), the processing circuit 81 repeats the determination of step S33 until it can determine that the motor current Imt has become constant. Then, if the processing circuit 81 determines that the motor current Imt has become constant (S33: YES), the processing circuit 81 shifts the processing to step S35.

[0049] In step S35, the processing circuit 81 determines whether the linear moving member 55 has come into contact with the flange portion 53 of the rotating member 51 as the linear moving member 55 moves in the backward direction X2 as the electric motor 31 is driven in the reverse direction.

[0050] 8, the solid line shows the transition of the motor current Imt when the linearly moving member 55 comes into contact with the flange portion 53 while the electric motor 31 is driving in the reverse direction. When the linearly moving member 55 comes into contact with the flange portion 53, the flange portion 53 restricts further movement of the linearly moving member 55 in the backward direction X2, and therefore the motor load increases suddenly. As a result, the motor current Imt increases suddenly.

[0051] Therefore, the processing circuit 81 determines whether or not both of the following two conditions (B1) and (B2) are satisfied. If both of the two conditions (B1) and (B2) are satisfied, the processing circuit 81 determines that the linear motion member 55 is in contact with the flange portion 53. On the other hand, if at least one of the two conditions (B1) and (B2) is not satisfied, the processing circuit 81 determines that the linear motion member 55 is not in contact with the flange portion 53. (B1) The time elapsed from the start of reverse rotation of the electric motor 31 exceeds the initial drive time Tdb. (B2) The motor current Imt is equal to or greater than the contact determination current value ImtAb.

[0052] During the period from the start of reverse rotation of the electric motor 31 until the elapse of the initial drive time Tdb, the motor current Imt may be relatively large due to the influence of an inrush current. Therefore, the initial drive time Tdb is set as a criterion for determining whether an inrush current is flowing through the electric motor 31. The contact determination current value ImtAb is set as a criterion for determining whether the motor load is excessive.

[0053] 7, if it is determined that the linearly moving member 55 is in contact with the flange portion 53 (S35: YES), the processing circuit 81 proceeds to step S37. In step S37, the processing circuit 81 sets the contact flag FLG1 to ON. If it is determined that the linearly moving member 55 is in contact with the flange portion 53, the contact flag FLG1 is set to ON, whereas if it is determined that the linearly moving member 55 is not in contact with the flange portion 53, the contact flag FLG1 is set to OFF. Thereafter, the processing circuit 81 proceeds to step S43.

[0054] On the other hand, if it is determined in step S35 that the linearly moving member 55 is not in contact with the flange portion 53 (NO), the processing circuit 81 proceeds to step S39. In step S39, the processing circuit 81 determines whether the return time Tbk is equal to or greater than a predetermined release time Tbkth. The return time Tbk is the elapsed time from the point in time when it is determined that the motor current Imt has become constant, i.e., from the point in time when the determination result in step S33 changes from NO to YES. The release time Tbkth is set as a criterion for determining whether both brake shoes 15, 16 have separated from the inner circumferential surface 12a of the brake drum 12.

[0055] If the return time Tbk is less than the release time Tbkth (S39: NO), the processing circuit 81 proceeds to step S35. On the other hand, if the return time Tbk is equal to or greater than the release time Tbkth (S39: YES), the processing circuit 81 proceeds to step S41. In step S41, the processing circuit 81 sets the contact flag FLG1 to OFF. Then, the processing circuit 81 proceeds to step S43.

[0056] In step S43, the processing circuit 81 stops the reverse rotation of the electric motor 31. That is, the processing circuit 81 ends the release process. Thereafter, the processing circuit 81 ends this processing routine.

[0057] <Shortened and extended processing> The flow of processing when the processing circuit 81 executes the shortening processing or the extension processing will be described with reference to Figures 9 and 10. When the apply processing or the release processing is executed, the processing circuit 81 executes the processing routine shown in Figure 9. Figure 10 shows the transition of the motor current Imt accompanying the execution of the apply processing.

[0058] In step S61 of this processing routine shown in FIG. 9, the processing circuit 81 determines whether a decrease flag FLG2, which will be described later, is set to OFF. If the decrease flag FLG2 is set to OFF (S61: YES), the processing circuit 81 proceeds to step S63. In step S63, the processing circuit 81 determines whether a shortening condition, which is a condition for shortening the release time Tbkth, is met. In this embodiment, the processing circuit 81 determines that the shortening condition is met when at least one of the following two conditions (C1) and (C2) is met. (C1) The contact flag FLG1 is set to ON. (C2) The first measurement time Tx is equal to or less than the first time judgment value Txth.

[0059] If the contact flag FLG1 is set to ON, it can be determined that the linearly moving member 55 contacted the flange portion 53 when the previous release process was executed. It can be inferred that the shorter the first measurement time Tx acquired during the previous execution of the apply process, the shorter the standby interval Hw. If the standby interval Hw is short, there is a possibility that the linearly moving member 55 will come extremely close to the flange portion 53 when the release process is executed. Therefore, a first time judgment value Txth is set as a criterion for determining whether there is a possibility that the linearly moving member 55 will come extremely close to the flange portion 53 when the release process is executed.

[0060] If the shortening condition is not met (S63: NO), the processing circuit 81 ends this processing routine. That is, the processing circuit 81 does not execute either the shortening process or the extension process at this timing. On the other hand, if the shortening condition is met (S63: YES), the processing circuit 81 proceeds to step S65.

[0061] In step S65, the processing circuit 81 sets a decrease correction amount ΔTd. For example, when the processing of step S65 is executed because the contact flag FLG1 is set to ON, the processing circuit 81 sets a predetermined value as the decrease correction amount ΔTd. Furthermore, when the processing of step S65 is executed because the first measurement time Tx is equal to or less than the first time determination value Txth, the processing circuit 81 sets a larger value as the first measurement time Tx is shorter as the first measurement time Tx is shorter. It can be inferred that the shorter the first measurement time Tx is, the shorter the standby interval Hw is. Therefore, it can be said that the processing circuit 81 sets a larger value as the standby interval Hw is shorter as the standby interval Hw is shorter. Note that when the processing of step S65 is executed because the contact flag FLG1 is set to ON, the processing circuit 81 preferably sets a larger value as the decrease correction amount ΔTd compared to when the processing of step S65 is executed because the first measurement time Tx is equal to or less than the first time determination value Txth.

[0062] Next, in step S67, the processing circuit 81 executes a shortening process to reduce the release time Tbkth using the decrease correction amount ΔTd. In the shortening process, the processing circuit 81 subtracts the decrease correction amount ΔTd from the release time Tbkth and sets the result as a new release time Tbkth. By executing the shortening process, the processing circuit 81 changes the release time Tbkth so that the release time Tbkth becomes shorter as the standby interval Hw becomes shorter.

[0063] After the shortening process is executed, the processing circuit 81 proceeds to step S69. In step S69, the processing circuit 81 sets the reduction flag FLG2 to ON. That is, if the release time Tbkth has been reduced by the shortening process, the reduction flag FLG2 is set to ON. On the other hand, if the release time Tbkth has not been reduced by the shortening process, the reduction flag FLG2 is set to OFF. Thereafter, the processing circuit 81 sets the contact flag FLG1 to OFF in step S71, and then ends this processing routine.

[0064] On the other hand, if the reduction flag FLG2 is set to ON in step S61 (NO), the processing circuit 81 proceeds to step S81. In step S81, the processing circuit 81 determines whether or not it has detected that maintenance of the drum brake 10, including at least one of replacement of the friction material 17 of the brake shoes 15, 16 and adjustment of the waiting interval Hw, has been performed by an operator. If it has determined that it has detected that maintenance has been performed by an operator (S81: YES), the processing circuit 81 proceeds to step S87. On the other hand, if it has determined that it has not detected that maintenance has been performed by an operator (S81: NO), the processing circuit 81 proceeds to step S83.

[0065] In step S83, the processing circuit 81 determines whether the contact flag FLG0 is set to ON. If the contact flag FLG0 is set to ON, it can be assumed that the linearly moving member 55 was in contact with the protrusion 58 when the previous apply process was executed. Therefore, if the contact flag FLG0 is set to ON (S83: YES), the processing circuit 81 shifts the process to step S87. On the other hand, if the contact flag FLG0 is set to OFF (S83: NO), the processing circuit 81 shifts the process to step S85.

[0066] In step S85, the processing circuit 81 determines whether the first measured time Tx is longer than a second time judgment value Txth2. The first measured time Tx is correlated with the width of the standby interval Hw. The second time judgment value Txth2 is set as a criterion for determining whether the standby interval Hw has become wider.

[0067] FIG. 10 shows the change in the motor current Imt during execution of the apply process as the standby interval Hw is extended. In FIG. 10, the dashed line shows the change in the motor current Imt when the standby interval Hw is narrow, and the solid line shows the change in the motor current Imt when the standby interval Hw is extended. As shown by the dashed line in FIG. 10, when the standby interval Hw is narrow, the first measurement time Tx is shorter than the second time judgment value Txth2. However, when the standby interval Hw is extended beyond the case where the dashed line in FIG. 10 shows the change in the motor current Imt, the first measurement time Tx becomes longer.

[0068] 9, if the first measured time Tx is longer than the second time judgment value Txth2 in step S85 (YES), the processing circuit 81 proceeds to step S87. On the other hand, if the first measured time Tx is equal to or shorter than the second time judgment value Txth2 (S85: NO), the processing circuit 81 ends this processing routine. That is, the processing circuit 81 does not execute the extension process at this timing.

[0069] In step S87, the processing circuit 81 sets the increased correction amount ΔTi. For example, when the processing of step S87 is executed because maintenance has been detected, the processing circuit 81 sets a first predetermined value as the increased correction amount ΔTi. Also, when the processing of step S87 is executed because the contact flag FLG0 has been set to ON, the processing circuit 81 sets a second predetermined value as the increased correction amount ΔTi. The second predetermined value may be the same as the first predetermined value or may be a value different from the first predetermined value. Also, when the processing of step S87 is executed because the first measurement time Tx is longer than the second time determination value Txth2, for example, the processing circuit 81 sets a larger value as the first measurement time Tx is longer as the increased correction amount ΔTi. Therefore, it can be said that the processing circuit 81 sets a larger value as the standby interval Hw is wider as the standby interval Hw is wider.

[0070] Next, in step S89, the processing circuit 81 executes an extension process to increase the release time Tbkth using the increased correction amount ΔTi. In the extension process, the processing circuit 81 sets the sum of the release time Tbkth and the increased correction amount ΔTi as a new release time Tbkth. By executing the extension process, the processing circuit 81 thereby changes the release time Tbkth so that the release time Tbkth becomes longer as the waiting interval Hw becomes wider.

[0071] After the extension process is completed, the process circuit 81 proceeds to step S91. In step S91, the process circuit 81 sets the reduction flag FLG2 to OFF. Thereafter, the process circuit 81 ends this process routine.

[0072] <Actions and Effects of This Embodiment> If the drum brake 10 is activated by the service brake while the vehicle is traveling for a long period of time, the brake shoes 15, 16 are pressed against the inner circumferential surface 12a of the brake drum 12 for a long period of time. As a result, frictional heat generated between the brake drum 12 and the brake shoes 15, 16 causes the brake drum 12 to thermally expand, increasing the diameter of the cylindrical portion 121. In this case, the standby interval Hw becomes wider, and the adjuster function adjusts the standby interval Hw to the reference interval HwB. However, if the temperature of the brake drum 12 drops after the adjuster function adjusts the standby interval Hw, reducing the diameter of the cylindrical portion 121, the standby interval Hw becomes narrower. If the release process is performed in this state, the linearly acting member 55 may come extremely close to the flange portion 53 during the release process.

[0073] When the apply process is performed with the standby interval Hw being narrow in this manner, the amount of movement of the linearly moving member 55 in the forward direction X1 caused by the forward rotation of the electric motor 31 is reduced. In other words, with the parking brake applied, the movable inner gap, which is the gap between the linearly moving member 55 and the flange portion 53, does not become very wide.

[0074] In this embodiment, when the standby interval Hw becomes shorter, the shortening process is executed to change the release time Tbkth so that the release time Tbkth becomes shorter as the standby interval Hw becomes shorter. By setting the release time Tbkth to a shorter time, the amount of movement of the linearly moving member 55 in the reverse direction X2 caused by the reverse drive of the electric motor 31 in the release process can be reduced. As a result, even when the release process is executed when the movable inner gap is not very wide, the amount of movement of the linearly moving member 55 in the reverse direction X2 caused by the reverse drive of the electric motor 31 can be reduced, thereby preventing the linearly moving member 55 from coming too close to the flange portion 53. In other words, even without increasing the size of the actuator 30 to expand the movement range AR of the linearly moving member 55, the execution of the release process can prevent the linearly moving member 55 from coming too close to the flange portion 53. In other words, when the parking brake is released, the movable inner gap can be kept wide to a certain extent.

[0075] In this embodiment, the following effects can be further obtained. (1) It can be inferred that the shorter the time for which the electric motor 31 is driven during the application process, i.e., the shorter the first measurement time Tx, the shorter the standby interval Hw. Therefore, in this embodiment, if the first measurement time Tx is equal to or shorter than the first time determination value Txth, it can be determined that the standby interval Hw has become shorter than the predetermined interval, and therefore the shortening process is executed. As a result, when the release process is executed next time onwards, the amount of movement of the linearly moving member 55 in the retreating direction X2 is reduced, thereby preventing the linearly moving member 55 from coming too close to the flange portion 53.

[0076] In this embodiment, the shortening process is not executed when the first measurement time Tx is longer than the first time determination value Txth. This is because it can be determined that the linearly moving member 55 will not come too close to the flange portion 53 when the release process is executed without changing the release time Tbkth. Therefore, it is possible to prevent the shortening process from being executed when it is not necessary to shorten the release time Tbkth.

[0077] (2) When the shortening process is executed because the first measurement time Tx is equal to or shorter than the first time determination value Txth, the decrease correction amount ΔTd of the release time Tbkth is changed depending on the first measurement time Tx. That is, the shorter the first measurement time Tx, the narrower the standby interval Hw is estimated to be, so the decrease correction amount ΔTd is increased. This can enhance the effect of preventing the linearly moving member 55 from getting too close to the flange portion 53 when the release process is executed.

[0078] (3) If the linear moving member 55 comes into contact with the flange portion 53 when the linear moving member 55 is moved in the backward direction X2 by executing the release process, the shortening process is executed. As a result, when the release process is executed next time and thereafter, the amount of movement of the linear moving member 55 in the backward direction X2 can be reduced, thereby preventing the linear moving member 55 from coming into contact with the flange portion 53. Therefore, it is possible to prevent the linear moving member 55 from coming into contact with the flange portion 53 every time the release process is executed.

[0079] (4) When the release time Tbkth is shortened by executing the shortening process, the standby interval Hw may become longer than when the shortening process was executed due to subsequent actuation of the drum brake 10, etc. In this embodiment, when the release time Tbkth is shortened by executing the shortening process and it is determined that the standby interval Hw is longer than when the shortening process was executed, the extension process is executed to increase the release time Tbkth. By lengthening the release time Tbkth in this manner, the amount of movement of the linearly moving member 55 in the backward direction X2 during the next and subsequent executions of the release process increases. This increases the distance between the linearly moving member 55 and the protruding portion 58 at the end of the release process. This prevents the linearly moving member 55 from getting too close to the protruding portion 58 or from contacting the protruding portion 58 when the linearly moving member 55 moves in the forward direction X1 during the next execution of the apply process.

[0080] (5) In this embodiment, when the apply process is executed under conditions in which the release time Tbkth has been shortened by executing the shortening process, if the first measured time Tx at that time is longer than the second time determination value Txth2, it can be determined that the standby interval Hw has become wider than when the shortening process was executed. If it is determined that the standby interval Hw has become wider, the extension process is executed to increase the release time Tbkth. In this case, the longer the first measured time Tx, the larger the increase correction amount ΔTi of the release time Tbkth. This can enhance the effect of preventing the linearly moving member 55 from getting too close to the protruding portion 58 or from coming into contact with the protruding portion 58 when the linearly moving member 55 moves in the forward direction X1 by executing the next apply process.

[0081] (6) If the above-described maintenance is detected under the circumstances where the release time Tbkth has been shortened by executing the shortening process, it can be determined that the waiting interval Hw has become wider than when the shortening process was executed. Therefore, the release time Tbkth is corrected and increased by executing the extension process. This prevents the release time Tbkth from remaining short even though the waiting interval Hw has been optimized by the maintenance.

[0082] (7) If the linearly moving member 55 comes into contact with the protruding portion 58 during the application process in a situation where the release time Tbkth has been shortened by executing the shortening process, the release time Tbkth is corrected and increased by executing the extension process. By executing the release process using such a release time Tbkth, it is possible to move the linearly moving member 55 sufficiently away from the protruding portion 58 before the start of the next application process. Therefore, it is possible to prevent the linearly moving member 55 from coming into contact with the protruding portion 58 during the next and subsequent application processes.

[0083] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0084] If it is detected that the linearly moving member 55 has come into contact with the protrusion 58 during the application process in a situation where the release time Tbkth has been shortened by the execution of the shortening process, the release time Tbkth does not need to be increased. Even in this case, the execution of the release process can prevent the linearly moving member 55 from coming too close to the flange portion 53.

[0085] The release time Tbkth does not have to be increased when maintenance is performed, including at least one of extending the standby interval Hw and replacing the brake shoes 15, 16. If the apply process is executed after such maintenance is performed, the first measured time Tx will be longer than the second time determination value Txth2. Therefore, the extension process is executed on the condition that the first measured time Tx is longer than the second time determination value Txth2, and the release time Tbkth is increased.

[0086] In the above embodiment, when the extension process is executed on the condition that the first measurement time Tx is longer than the second time determination value Txth2, the increase correction amount ΔTi of the release time Tbkth is varied depending on the first measurement time Tx, but this is not limiting. That is, the increase correction amount ΔTi does not have to be varied depending on the first measurement time Tx.

[0087] If the extension process is executed in response to the maintenance being performed, the extension process does not have to be executed even if it is determined that the first measurement time Tx is longer than the second time determination value Txth2.

[0088] If it is determined that the linearly-acting member 55 has come into contact with the protrusion 58 during the application process, the extension process may be executed to increase the release time Tbkth, regardless of whether the reduction flag FLG2 is set to on or not.

[0089] When it is detected that the above-described maintenance has been performed, the extension process may be executed to increase the release time Tbkth, regardless of whether the reduction flag FLG2 is set to ON.

[0090] If the shortening process is executed when the linear member 55 comes into contact with the flange portion 53 during the execution of the release process, the shortening process does not have to be executed even if it is determined that the first measurement time Tx has become equal to or less than the first time determination value Txth.

[0091] It can be inferred that the longer the vehicle's mileage, the more frequently the drum brake 10 is activated, and the more wear there is in the friction material 17 of the brake shoes 15, 16. Furthermore, it can be inferred that the more frequently the drum brake 10 functions as a service brake while traveling, the more wear there is in the friction material 17 of the brake shoes 15, 16. The greater the degree of wear of the friction material 17 of the brake shoes 15, 16, the more likely the standby interval Hw is to become longer. Therefore, the degree of wear of the friction material 17 may be estimated based on at least one of the mileage and the number of times the drum brake 10 functions as a service brake while traveling, and the greater the estimated degree of wear, the smaller the reduction correction amount ΔTd of the release time Tbkth in the shortening process may be.

[0092] Alternatively, the extension process may be executed when the estimated value of the degree of wear is equal to or greater than a threshold value. In this manner, when determining whether to execute the shortening process based on the degree of wear, the extension process may not be executed even if the first measurement time Tx is equal to or less than the first time determination value Txth.

[0093] In the above embodiment, when the shortening process is executed on the condition that the first measurement time Tx becomes equal to or less than the first time determination value Txth, the decrease correction amount ΔTd of the release time Tbkth is varied depending on the first measurement time Tx, but this is not limiting. That is, the decrease correction amount ΔTd does not have to be varied depending on the first measurement time Tx.

[0094] In the above embodiment, if the release time Tbkth is corrected to decrease by the release process, the release time Tbkth is not further corrected to decrease, but this is not limited to this. For example, if it is determined that the waiting interval Hw has become even narrower after the release time Tbkth has been reduced by the release process, the release process may be executed again to further correct the release time Tbkth to decrease.

[0095] In the above embodiment, the decrease correction amount ΔTd is set to a larger value because it can be estimated that the standby interval Hw is shorter as the first measurement time Tx is shorter, but this is not limited to this. For example, if the drum brake 10 is provided with a detection system that can measure the standby interval Hw, the decrease correction amount ΔTd may be set to a larger value as the standby interval Hw detected by the detection system is shorter.

[0096] The processing circuit 81 is not limited to one equipped with a CPU 82 and memory 83 and executing software processing. For example, it may be equipped with a dedicated hardware circuit that performs hardware processing on at least a portion of what was software processed in the above embodiment. An example of a dedicated hardware circuit is an ASIC. ASIC is an abbreviation for "Application Specific Integrated Circuit." In other words, the processing circuit 81 may have any of the following configurations (a) to (c): (a) The processing circuit 81 includes a processing device that executes all of the above processes according to a program, and a program storage device such as a ROM that stores the program. (b) The processing circuitry 81 includes a processing device and a program storage device that execute part of the above processing in accordance with a program, and dedicated hardware circuits that execute the remaining processing. (c) The processing circuit 81 includes a dedicated hardware circuit for executing all of the above processes. Here, there may be a plurality of software execution devices including a processing device and a program storage device, and a plurality of dedicated hardware circuits.

[0097] In the actuator 30, the flange portion 53 does not have to function as a retraction-side restricting portion. In this case, a stopper that functions as a retraction-side restricting portion may be disposed between the flange portion 53 and the linearly moving member 55.

[0098] The electric parking brake device 20 may have a configuration different from that shown in Figures 1 and 2, as long as it can vary the parking braking force by moving the linearly acting member 55 and has an adjuster function that operates during service braking. [Explanation of symbols]

[0099] 10...Drum brake 12...Brake drum 121...Cylindrical part 12a...Inner peripheral surface 15, 16...Brake shoes (an example of a friction member) 20...Electric parking brake 30...Actuator 31...Electric motor 55...Linear motion member 58...Protrusion (an example of a forward-side restricting portion) 53...Flange portion (an example of a retreat side restricting portion) 80...Control device 81...Processing circuit

Claims

1. The present invention is applied to a vehicle equipped with a drum brake that applies a braking force to a wheel by pressing a friction member against the inner peripheral surface of a cylindrical portion that rotates integrally with the wheel, An actuator and a control device that controls the actuator, The actuator is a linearly moving member that moves in a forward direction when the electric motor is driven in a forward direction, and moves in a backward direction, which is the opposite direction to the forward direction, when the electric motor is driven in a reverse direction; and a backward-side restricting portion that restricts the movement range of the linearly moving member and is located in the backward direction relative to the linearly moving member; When the linearly moving member moves in the forward direction due to the forward rotation of the electric motor, the friction member is pressed against the inner circumferential surface to generate a parking brake on the vehicle, The control device an applying process of driving the electric motor in a forward direction until it is determined that the force pressing the friction member against the inner peripheral surface has reached a predetermined value or more; a release process for releasing the parking brake, which drives the electric motor in the reverse direction from the time when it is determined that the value of the current flowing through the electric motor has become constant until a predetermined release time has elapsed; a shortening process for changing the release time so that the release time becomes shorter as the standby gap, which is the gap between the friction member and the inner circumferential surface when the drum brake is not in operation, becomes narrower. Electric parking brake for vehicles.

2. The control device determines whether the standby interval has become shorter than a predetermined interval, and executes the shortening process when it determines that the standby interval has become shorter than the predetermined interval.

2. An electric parking brake system for a vehicle according to claim 1.

3. The control device determines whether the standby interval has become wider than when the shortening process was executed under the condition that the release time has been shortened by executing the shortening process, and corrects the release time to increase it when it determines that the standby interval has become wider than when the shortening process was executed.

3. An electric parking brake device for a vehicle according to claim 1 or 2.

4. When the control device detects that maintenance including at least one of extension of the standby interval and replacement of the friction member has been performed under the condition that the release time has been shortened by executing the shortening process, the control device corrects the release time by increasing it.

3. An electric parking brake device for a vehicle according to claim 1 or 2.

5. the actuator restricts a movement range of the linearly moving member and has an advancement-side restricting portion located further in the advancement direction than the linearly moving member, The control device corrects the release time by increasing it when the forward movement of the linearly moving member is restricted by the forward movement restricting portion during forward rotation of the electric motor in the apply process. An electric parking brake device for a vehicle according to any one of claims 1 to 4.

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