Electric parking brake control device

Abstract

To stabilize a release position of a moving member switching the state of a parking brake.SOLUTION: An electric parking brake control device includes a motor, a moving member moved by the motor, a state quantity change member, and a control part. The moving member is moved between an apply position where the parking brake is in an apply state, and a release position where the parking brake is in a release state. The state quantity change member becomes a resistance of movement of the moving member, in a process of moving the moving member to the release position, and thereby changes the state quantity (differential value of the number of rotations of motor) of the motor. The control part acquires a current and a voltage supplied to the motor, after start of energization to the motor, when the moving member is moved to the release position, calculates the state quantity of the motor on the basis of a motor parameter estimated by the acquired current and voltage (time t13), and stops the motor when the calculated state quantity of the motor satisfies a predetermined condition (time t15).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an electric parking brake control device. [Background technology]

[0002] Conventionally, a known electric parking brake control device controls an electric actuator that swings a parking lever inside a drum brake (see Patent Document 1). In this technology, the electric actuator includes a rod connected to the parking lever, a motor for moving the rod back and forth, and a disc spring for applying a load to the rod.

[0003] The rod is movable between an apply position and a release position. When the rod moves from the release position to the apply position, the rod pulls the parking lever, generating braking force from the drum brake. When the rod moves from the apply position to the release position, the braking force from the drum brake is released.

[0004] The disc spring is positioned so that it contacts the rod as it moves from the apply position to the release position. When the rod comes into contact with the disc spring, a load is applied to the motor, causing the motor current to increase. In conventional control, the motor is stopped and the rod is placed in the release position when the motor current reaches a predetermined value. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6213032 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventional technology, the release position is determined based only on the current value of the motor, so there is a risk that the release position may not be stable due to the influence of variations in temperature and motor performance.

[0007] Therefore, an object of the present invention is to stabilize the release position of a moving member for switching the operating state of a parking brake. [Means for solving the problem]

[0008] In order to solve the above problem, the electric parking brake control device of the present invention is a device that changes the state of the parking brake between an applied state in which braking force is generated and a released state in which the braking force is released. The electric parking brake control device includes a motor, a conversion mechanism that converts the rotational motion of the motor into linear motion, a moving member that is moved by the conversion mechanism, a state quantity changing member, and a control unit that controls the driving of the motor. The movable member is movable between an apply position where the parking brake is in an applied state and a release position where the parking brake is in a released state. The state quantity changing member changes the state quantity of the motor by acting as resistance to the movement of the moving member during the process in which the moving member moves from the apply position to the release position. When the control unit moves the movable member from the apply position to the release position, after starting to energize the motor, it acquires the current and voltage supplied to the motor, calculates the state quantity of the motor based on motor parameters estimated from the acquired current and voltage, and stops driving the motor when the calculated state quantity of the motor satisfies predetermined conditions. [Effects of the Invention]

[0009] According to the present invention, the control unit acquires both the current and voltage supplied to the motor, estimates motor parameters from the acquired current and voltage, and calculates the motor state quantities based on the estimated motor parameters, so that it is possible to stop the motor drive based on the motor state quantities that are less affected by variations in temperature and motor performance, thereby stabilizing the release position of the moving member. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a configuration diagram of a vehicle equipped with an electric parking brake control device according to an embodiment of the present invention. [Figure 2] 1A and 1B are diagrams showing a drum brake and a parking brake mechanism, in which FIG. 1A shows a state in which the brakes are not applied, and FIG. 1B shows a state in which the brakes are applied by the parking brake mechanism. [Figure 3] 1A and 1B are cross-sectional views showing an electric actuator of a parking brake mechanism, in which FIG. 1A shows a released state and FIG. 1B shows an applied state. [Figure 4] 1A is a time chart showing a conventional apply process, and FIG. 1B is a time chart showing a conventional release process. [Figure 5] 10A and 10B are diagrams for explaining problems caused by variations in release position. [Figure 6] FIG. 1(a) shows a first table for setting threshold values ​​based on motor parameters, FIG. 1(b) shows a second table for setting threshold values ​​based on motor voltage, and FIG. 1(c) shows three tables for setting threshold values ​​based on motor parameters and motor voltage. [Figure 7] 10 is a flowchart showing a release process performed by a control unit. [Figure 8] 10 is a time chart showing parameters that change during a release process. [Figure 9] 10 is a flowchart showing a modified example of the release process. [Figure 10]10 is a time chart showing parameters that change during a release process according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. As shown in FIG. 1, the vehicle CR includes a drum brake D as an example of a parking brake, a parking brake mechanism 200, and a brake fluid pressure control device 100 for a vehicle.

[0012] A drum brake D is provided on each of the four wheels W. The parking brake mechanism 200 is a mechanism that mechanically operates the drum brakes D, and is provided for the drum brakes D provided on the two rear wheels W.

[0013] The vehicle brake hydraulic control device 100 is for appropriately controlling the braking force applied to each wheel W of the vehicle CR, and mainly comprises a hydraulic unit 10 provided with oil passages (hydraulic pressure passages) and various components, and a control unit 20 for appropriately controlling the various components within the hydraulic unit 10. The hydraulic unit 10 is connected via an oil passage to a master cylinder MC that generates brake hydraulic pressure when the brake pedal BP is depressed, and is also connected via an oil passage to wheel cylinders D4 of each drum brake D. The hydraulic unit 10 comprises valves, pumps, etc. for controlling the brake hydraulic pressure applied to the wheel cylinders D4.

[0014] The control unit 20 has the function of controlling the valves and pumps in the hydraulic unit 10. The control unit 20 is connected to a wheel speed sensor 91 that detects the wheel speed of the wheel W and a parking switch 92 that switches the state of the drum brake D between an applied state and a released state. Here, the applied state refers to a state in which braking force is generated by the drum brake D. Furthermore, the released state refers to a state in which the braking force of the drum brake D is released.

[0015] The parking switch 92 is switchable between an apply position and a release position. When the parking switch 92 is in the apply position, it outputs an apply signal to the control unit 20 to put the drum brakes D into an apply state, and when the parking switch 92 is in the release position, it outputs a release signal to the control unit 20 to put the drum brakes D into a release state.

[0016] The control unit 20 is equipped with, for example, a CPU, RAM, ROM, and input / output circuits, and performs control by performing various arithmetic processing based on inputs from the wheel speed sensor 91, parking switch 92, etc., and programs and data stored in the ROM.

[0017] 2(a) and 2(b), the drum brake D includes a drum D1, a brake shoe D2, a return spring D3, and a wheel cylinder D4. The drum D1 is a member having a cylindrical portion that rotates integrally with the wheel W.

[0018] The brake shoe D2 is an arc-shaped member that extends along the inner circumferential surface of the drum D1, and is pressed against the inner circumferential surface of the drum D1 to apply a braking force to the wheel W. Two brake shoes D2 are provided along the inner circumferential surface of the drum D1. One end of each of the two brake shoes D2 is rotatably supported by a support member D5, allowing them to rotate toward and away from each other.

[0019] The return spring D3 biases the other ends of the two brake shoes D2 toward each other. The wheel cylinder D4 biases the two brake shoes D2 toward the inner circumferential surface of the drum D1 by brake fluid pressure supplied from the hydraulic unit 10.

[0020] The parking brake mechanism 200 includes a strut 210, a parking lever 220, a wire 230, and an electric actuator 240 shown in Fig. 3. The strut 210 is engaged with the other end of each of the two brake shoes D2.

[0021] One end of the parking lever 220 is rotatably supported by one brake shoe D2 via a pin 221. A wire 230 is connected to the other end of the parking lever 220. A portion of the parking lever 220 between one end and the other end, closer to the one end, engages with the strut 210.

[0022] When the wire 230 is pulled to the right in the figure, the parking lever 220 rotates about the pin 221, causing the parking lever 220 to press the other brake shoe D2 against the inner circumferential surface of the drum D1 via the strut 210. When the wire 230 is pulled further, the parking lever 220 rotates about the portion where it engages with the strut 210, causing the parking lever 220 to press the one brake shoe D2 against the inner circumferential surface of the drum D1 via the pin 221.

[0023] As a result, the brake shoes D2 are pressed against the inner peripheral surface of the drum D1 by the pulling action of the wire 230. When the wire 230 is loosened to the left in the figure, the biasing force of the return spring D3 moves the brake shoes D2 away from the inner peripheral surface of the drum D1.

[0024] As shown in Fig. 3, the electric actuator 240 is a device for pulling the wire 230. The electric actuator 240, together with the control unit 20, constitutes an electric parking brake control device 1. The electric parking brake control device 1 is a device that changes the state of the drum brake D between an applied state and a released state. The electric actuator 240 includes a motor 241, a conversion mechanism 2, a screw shaft 244 as an example of a moving member, a housing 245, a retainer 246, and a plurality of disc springs 247 as an example of a state quantity changing member and an elastic member.

[0025] The conversion mechanism 2 is a mechanism that converts the rotational motion of the motor 241 into linear motion, and includes a plurality of gears 242 and a nut 243 . The nut 243 is connected to the motor 241 via a plurality of gears 242. The nut 243 has a female screw portion 243A that meshes with a male screw portion 244A of the screw shaft 244.

[0026] The screw shaft 244 is a member that is moved linearly by the conversion mechanism 2. The screw shaft 244 is supported by the housing 245 so as to be movable in the axial direction, and the wire 230 is fixed to the tip. A flange 244B that protrudes in the radial direction is formed on the end of the screw shaft 244 opposite to the tip.

[0027] The retainer 246 is a disk member having a hole in the center, and engages with the flange portion 244B of the screw shaft 244 from the tip side of the screw shaft 244. A plurality of disc springs 247 are arranged between the retainer 246 and the nut 243 in the axial direction of the screw shaft 244.

[0028] In this electric actuator 240, when the motor 241 is rotated in the forward direction, the screw shaft 244 moves in the direction of being housed in the housing 245, thereby pulling the wire 230 and bringing the drum brake D into the applied state. When the motor 241 is rotated in the reverse direction, the screw shaft 244 moves in the direction of protruding from the housing 245, thereby loosening the wire 230 and bringing the drum brake D into the released state.

[0029] In the following description, the position of the screw shaft 244 when the drum brake D is in the applied state is also referred to as the "apply position," and the position of the screw shaft 244 when the drum brake D is in the released state is also referred to as the "release position." Specifically, the release position is the position shown in Figure 3(b), and the apply position is the position shown in Figure 3(a).

[0030] When the screw shaft 244 is located at the release position, the plurality of disc springs 247 are sandwiched in a deformed state between the retainer 246 and the nut 243. When the screw shaft 244 is located at the apply position, the retainer 246 is prevented from moving by contact with the housing 245, and the flange portion 244B of the screw shaft 244 is separated from the retainer 246. In the process of the screw shaft 244 moving from the apply position to the release position, the disc springs 247 are deformed by the screw shaft 244.

[0031] The control unit 20 controls the driving of the motor 241 based on a signal from the parking switch 92. The control unit 20 has the function of executing an apply process and a release process. In the following description, the output of the apply signal from the parking switch 92 will also be referred to as an "apply command," and the output of the release signal from the parking switch 92 will also be referred to as a "release command."

[0032] The apply process is a process for driving the electric actuator 240 so that the drum brake D is in the applied state. In other words, the apply process is a process for controlling the electric actuator 240 so that the brake shoe D2 moves in a direction pressing against the drum D1. Specifically, upon receiving an apply command, the control unit 20 rotates the motor 241 forward to move the screw shaft 244 to the apply position, thereby putting the drum brake D in the applied state.

[0033] The release process is a process for driving the electric actuator 240 so that the drum brake D is in a released state. In other words, the release process is a process for controlling the electric actuator 240 so that the brake shoe D2 moves in a direction away from the drum D1. Specifically, upon receiving a release command, the control unit 20 reversely rotates the motor 241 to move the screw shaft 244 to the release position, thereby putting the parking brake mechanism 200 into the released state.

[0034] Conventionally, the apply process and the release process are performed by monitoring the value of the current flowing through the motor 241. Hereinafter, the conventional methods for each process will be described.

[0035] 4(a), when the control unit 20 receives an apply command, it starts the apply process by supplying a current to the motor 241 to rotate the motor 241 in the forward direction (time t41). When the current starts to flow to the motor 241, an inrush current occurs, but the inrush current subsides after a predetermined time (time t42). When the inrush current subsides, the motor 241 starts to rotate.

[0036] As a result, the screw shaft 244 starts to move from the release position toward the apply position. As the screw shaft 244 moves from the release position toward the apply position, the resistance force applied to the screw shaft 244 from the disc spring 247 gradually decreases, and the current gradually decreases. When the screw shaft 244 moves away from the retainer 246, the resistance force applied to the screw shaft 244 is no longer applied (time t43), and thereafter the current becomes constant.

[0037] Thereafter, when the brake shoe D2 comes into contact with the drum D1 (time t44), the resistance force acting on the screw shaft 244 gradually increases, causing the current supplied to the motor 241 to increase. Thereafter, when the current becomes equal to or greater than the apply threshold IA (time t45), the control unit 20 stops the current supply and completes the apply process.

[0038] 4(b), upon receiving the release command, the control unit 20 starts the release process by supplying a current to the motor 241 to rotate the motor 241 in the reverse direction (time t51). When the current starts to flow to the motor 241, an inrush current occurs, but the inrush current subsides after a predetermined time (time t52). When the inrush current subsides, the motor 241 starts to rotate.

[0039] As a result, the threaded shaft 244 moves from the apply position toward the release position, and the brake shoe D2 moves in a direction away from the drum D1. As the threaded shaft 244 moves from the apply position toward the release position, the resistance force applied to the threaded shaft 244 by the brake shoe D2 gradually decreases, and the current gradually decreases. When the brake shoe D2 moves away from the drum D1, the load on the threaded shaft 244 is released (time t53), and thereafter the current becomes constant.

[0040] Thereafter, when the screw shaft 244 comes into contact with the retainer 246 (time t54), the resistance force applied to the screw shaft 244 by the disc spring 247 gradually increases, and the current supplied to the motor 241 increases. At this time, the disc spring 247 acts as a resistance to the movement of the screw shaft 244 in the process of the screw shaft 244 moving from the apply position to the release position, thereby changing the rotation speed N(t) of the motor 241, which is a state quantity of the motor 241. Thereafter, when the current becomes equal to or greater than the release threshold IR (time t55), the control unit 20 stops the current supply and completes the release process.

[0041] In conventional apply and release processes that monitor the current, variations in temperature and motor performance can cause the release position to vary. When the release position varies, the load on the disc spring 247 at the release position changes, and the tightening force of the screw shaft 244 against the nut 243 also changes.

[0042] Fig. 5 is a diagram showing changes in current when the apply process is performed from a state in which the screw shaft 244 is located at the release position. As shown by the dashed line in Fig. 5, when the spring load is greater than normal at the release position, the falling interval TB of the inrush current is shorter than the falling interval TA under normal conditions. More specifically, when the spring load is greater than normal, the motor 241 starts to rotate at a high current value IB, and the load on the motor 241 gradually decreases as the motor 241 rotates, thereby decreasing the current value.

[0043] When the falling section TB of the inrush current becomes shorter in this way, the accuracy of the axial force F(t) of the screw shaft 244 deteriorates. Here, the current value i(t1) shown in Fig. 5 is the current value at time t1, and i(t2) is the current value at time t2. When the spring load is normal, the current values ​​at the two points are i(t1) and i(t2), but when the spring load is large, the current value at time t2 of the two current values ​​becomes i(t2)', which is larger than i(t2), and the estimation accuracy of the axial force F(t) deteriorates.

[0044] Therefore, in this embodiment, the control unit 20 positions the screw shaft 244 at the release position using the following method, thereby suppressing variations in the release position. When the control unit 20 moves the screw shaft 244 from the apply position to the release position, it drives the motor 241 to start moving the screw shaft 244. After the movement of the screw shaft 244 starts, the control unit 20 acquires the current and voltage supplied to the motor 241. The control unit 20 calculates the rotation speed N(t) of the motor 241 based on the motor parameters Km and Rm estimated from the acquired current and voltage.

[0045] When the calculated rotation speed N(t) of the motor 241 satisfies a predetermined condition, the control unit 20 stops driving the motor 241. In this embodiment, the control unit 20 stops driving the motor 241 on the condition that the differential value of the calculated rotation speed N(t) of the motor 241 reaches a predetermined threshold value TH1.

[0046] The predetermined threshold TH1 may be set in advance, or may be, for example, a fixed value, or may be a value set according to conditions.

[0047] Below, a method for calculating the axial force F(t) of the screw shaft 244 and the rotation speed N(t) of the motor 241, and a method for setting the threshold value TH1 in the case where the threshold value TH1 is set depending on conditions will be described. The control unit 20 calculates the axial force F(t) using the following equations (1) and (2).

[0048] The following formula is formula (1) for calculating the axial force F(t).

number

[0049] The following equation is equation (2) for calculating ω(t).

number

[0050] The control unit 20 calculates the rotation speed N(t) of the motor 241 using the following equation (3). N(t)=ω(t)×60 / 2π (3) ω(t): Angular velocity of the motor calculated using equation (2)

[0051] The units of each parameter are as follows: N(t):[rpm] ω(t):[rad / s] Km: [N·m / A] Rm:[Ω] Ub,U(t):[V] i(t),i(t-1),Ii,Imax:[A] L: [mH]

[0052] Next, a method for setting the threshold value TH1 in a case where the threshold value TH1 is set depending on conditions will be described. For example, the threshold value TH1 can be set based on a first table TB1 shown in FIG. 6(a). The first table TB1 is a table showing the relationship between the threshold value TH1 and the motor parameter Km. The first table TB1 is set so that the threshold value TH1 increases as the motor parameter Km increases. More specifically, the threshold value TH1 is calculated using the following formula (4). TH1 = a1 Km + b1 (4) a1: Slope coefficient b1: Intercept

[0053] The slope coefficient a1 and intercept b1 may be set based on the specifications of the motor 241 and the axial force F(t) that should be generated when the motor 241 is stopped at the release position. The control unit 20 uses the first table TB1 to change the threshold value TH1 based on the motor parameter Km.

[0054] The threshold value TH1 can also be set based on a second table TB2 shown in FIG. 6(b). The second table TB2 is a table showing the relationship between the threshold value TH1 and the voltage Vm (measured value) applied to the motor 241. The second table TB2 is set so that the threshold value TH1 increases as the voltage Vm increases. More specifically, the threshold value TH1 is calculated using the following equation (5). TH1 = a2 Vm + b2 (5) a2: Slope coefficient b2: Intercept

[0055] The slope coefficient a2 and the intercept b2 may be set based on the specifications of the motor 241 and the axial force F(t) that should be generated when the motor 241 is stopped at the release position. The control unit 20 uses the second table TB2 to change the threshold value TH1 based on the voltage Vm supplied to the motor 241.

[0056] The threshold value TH1 can also be set based on the third table TB3, fourth table TB4, and fifth table TB5 shown in FIG. 6(c). The third table TB3 is a table showing the relationship between the threshold value TH1 and the motor parameter Km when the voltage Vm (measured value) applied to the motor 241 is within a first range. The fourth table TB4 is a table showing the relationship between the threshold value TH1 and the motor parameter Km when the voltage Vm is within a second range higher than the first range. The fifth table TB5 is a table showing the relationship between the threshold value TH1 and the motor parameter Km when the voltage Vm is within a third range higher than the second range.

[0057] Each of the tables TB3 to TB5 is set so that the threshold value TH1 increases as the motor parameter Km increases. Each of the tables TB3 to TB5 is set so that the threshold value TH1 increases as the voltage Vm increases. The slope coefficient and intercept of each of the tables TB3 to TB5 may be set based on the specifications of the motor 241, the axial force F(t) that should be generated when stopping the motor 241 at the release position, and the voltage Vm. The control unit 20 uses the tables TB3 to TB5 to change the threshold value TH1 based on the motor parameter Km and the voltage Vm of the motor 241.

[0058] Next, the release process performed by the control unit 20 will be described. 7, in the release process, the control unit 20 first determines whether or not a release command has been issued from the parking switch 92 (S1). If it is determined in step S1 that a release command has not been issued (No), the control unit 20 ends this process.

[0059] If it is determined in step S1 that a release command has been issued (Yes), the control unit 20 applies a voltage to the motor 241 to drive the motor 241 (S2). After step S2, the control unit 20 starts acquiring the voltage applied to the motor 241 and the current flowing through the motor 241 (S3). More specifically, the motor 241 is provided with a voltage sensor that detects the voltage and a current sensor that detects the current, and the control unit 20 starts acquiring the voltage and current from the voltage sensor and the current sensor. After starting to acquire the voltage and current in step S3, the control unit 20 acquires the voltage and current at a predetermined cycle.

[0060] After a predetermined time has elapsed since step S3, specifically after the current value of motor 241 has become constant, control unit 20 estimates motor parameters Km and Rm based on the acquired voltage and current (S4). After step S4, control unit 20 calculates the rotation speed N(t) of motor 241 based on the estimated motor parameters Km and Rm and equations (2) and (3), and then calculates the derivative of rotation speed N(t) (S5).

[0061] After step S5, the control unit 20 determines whether the derivative of the rotation speed N(t) is equal to or less than the threshold value TH1 (S6). If it is determined in step S6 that the derivative of the rotation speed N(t) is not equal to or less than the threshold value TH1 (No), the control unit 20 returns to the processing of step S5. If it is determined in step S6 that the derivative of the rotation speed N(t) is equal to or less than the threshold value TH1, the control unit 20 stops the motor 241 (S7) and ends this processing.

[0062] Next, the release process by the control unit 20 will be described with reference to the time chart of FIG. 8, upon receiving a release command (time t11), the control unit 20 applies a voltage to the motor 241 to drive the motor 241. When the voltage is applied to the motor 241, an inrush current occurs, but the inrush current converges after a predetermined time (time t12). The voltage applied to the motor 241 gradually increases from the start of the voltage application.

[0063] The control unit 20 starts acquiring the voltage and current of the motor 241 from the start of voltage application, and when the current becomes constant (time t13), it estimates the motor parameters Km and Rm based on the acquired voltage and current, and calculates the rotation speed N(t) and the derivative of the rotation speed N(t).

[0064] Specifically, the control unit 20 estimates the motor parameters Km and Rm based on the voltage value U(t) and current value i(t) acquired at time t13. Next, the control unit 20 calculates the angular velocity ω(t) of the motor 241 based on the voltage value U(t) and current value i(t) acquired at time t13, the previous current value i(t-1) acquired immediately before the current value i(t), Rm, Km, and equation (2).

[0065] Thereafter, the control unit 20 calculates the rotation speed N(t) of the motor 241 based on ω(t) and equation (3). Then, the control unit 20 calculates the differential value of the rotation speed N(t) of the motor 241 based on the rotation speed N(t) of the motor 241.

[0066] Thereafter, when the screw shaft 244 comes into contact with the retainer 246 (time t14), the current of the motor 241 gradually increases, and the rotation speed N(t) of the motor 241 and the derivative of the rotation speed N(t) gradually decrease. When the derivative of the rotation speed N(t) becomes equal to or less than the threshold value TH1 (time t15), the control unit 20 stops the supply of electricity to the motor 241. This stops the driving of the motor 241, and the screw shaft 244 stops at the release position.

[0067] As described above, according to this embodiment, the following effects can be obtained. The control unit 20 acquires both the current and voltage supplied to the motor 241, estimates motor parameters Km and Rm from the acquired current and voltage, and calculates the differential value of the rotation speed N(t) of the motor 241 based on the estimated motor parameters Km and Rm, so that it is possible to stop driving the motor 241 based on the differential value of the rotation speed N(t), which is less affected by variations in temperature and motor performance. This makes it possible to stabilize the release position of the screw shaft 244.

[0068] The present invention is not limited to the above-described embodiment, but can be used in various forms as exemplified below. In the following description, the same reference numerals are used to designate components and processes having substantially the same structures as those in the above-described embodiment, and the description thereof will be omitted.

[0069] The state quantity of motor 241 is not limited to the differential value of the rotation speed N(t) of motor 241, but may be the rotation speed N(t) of motor 241 or the axial force F(t). Furthermore, since the load applied from screw shaft 244 to disc spring 247 has the same value as the axial force F(t), the state quantity of motor 241 may be the load applied to disc spring 247 or the differential value of the load applied to disc spring 247. In the following description, the load applied to disc spring 247 will also be simply referred to as the "spring load."

[0070] When the state quantity of the motor 241 is the differential value of the spring load, the control unit 20 executes the release process shown in Fig. 9. The release process shown in Fig. 9 includes the processes of steps S1 to S4 and S7 described above, as well as new steps S21 and S22.

[0071] 9 and 10, when the control unit 20 receives a release command (time t31), it starts driving the motor 241 and starts acquiring the current and voltage of the motor 241 (S1: Yes → S2 → S3). When the current value of the motor 241 becomes constant (time t32), the control unit 20 estimates the motor parameters Km and Rm based on the current and voltage of the motor 241 (S4).

[0072] After step S4, the control unit 20 calculates the spring load, i.e., the axial force F(t), based on the motor parameters Km and Rm, and then calculates the derivative of the spring load (S21). After step S21, the control unit 20 determines whether the derivative of the spring load is equal to or greater than a threshold value TH2 (S22). If it is determined in step S22 that the derivative of the spring load is not equal to or greater than the threshold value TH2 (No), the control unit 20 returns to the processing of step S21.

[0073] Thereafter, when the screw shaft 244 comes into contact with the retainer 246 (time t33), the current of the motor 241 gradually increases, and the spring load and the load derivative gradually increase. When the load derivative becomes equal to or greater than the threshold value TH1 (time t34), the control unit 20 determines that the spring load derivative is equal to or greater than the threshold value TH2 (S22: Yes), and stops driving the motor 241 (S7).

[0074] Even when the motor 241 is stopped based on the differential value of the spring load in this way, the current and voltage of the motor 241 are used to calculate the differential value of the spring load, so the effects of variations in temperature and motor performance can be reduced and the release position of the screw shaft 244 can be stabilized.

[0075] In the above embodiment, the parking brake mechanism 200 installed on the drum brake D is exemplified, but the present invention is not limited to this, and may be, for example, a parking brake mechanism installed on a disc brake.

[0076] In the above embodiment, the control unit is exemplified as the control unit 20 of the vehicle brake fluid pressure control device 100, but the present invention is not limited to this, and the control unit may be a control device other than the vehicle brake fluid pressure control device, for example, the vehicle's ECU (Electronic Control Unit).

[0077] The elastic member is not limited to a disc spring, but may be, for example, a coil spring or rubber.

[0078] The elements described in the above-described embodiment and modified examples may be implemented in any combination. [Explanation of symbols]

[0079] 1 Electric parking brake control device 2 Conversion mechanism 20 Control unit 200 Parking brake mechanism 241 Motor 244 Screw shaft 247 Disc spring (state quantity changing member, elastic member)

Claims

1. An electric parking brake control device that changes the state of a parking brake between an applied state in which braking force is generated and a released state in which the braking force is released, A motor; a conversion mechanism for converting the rotational motion of the motor into linear motion; a movable member that is moved by the conversion mechanism and that is movable between an apply position where the parking brake is in the applied state and a release position where the parking brake is in the released state; a state quantity changing member that changes a state quantity of the motor by acting as resistance to movement of the moving member during a process in which the moving member moves from the apply position to the release position; a control unit that controls the driving of the motor, The control unit When the moving member is moved from the apply position to the release position, After the start of energization of the motor, the current and voltage supplied to the motor are acquired; Calculating the state quantity of the motor based on the motor parameters estimated from the acquired current and voltage; An electric parking brake control device characterized in that, when a calculated state quantity of the motor satisfies a predetermined condition, driving of the motor is stopped.

2. 2. The electric parking brake control device according to claim 1, wherein the predetermined condition is that a state quantity of the motor reaches a predetermined threshold value.

3. 3. The electric parking brake control device according to claim 2, wherein the predetermined threshold value is set in advance.

4. 3. The electric parking brake control device according to claim 2, wherein the control unit changes the predetermined threshold value based on a voltage supplied to the motor.

5. 3. The electric parking brake control device according to claim 2, wherein the control unit changes the predetermined threshold value based on the motor parameter.

6. 3. The electric parking brake control device according to claim 2, wherein the control unit changes the predetermined threshold value based on the motor parameters and the voltage of the motor.

7. 7. The electric parking brake control device according to claim 1, wherein the control unit stops driving the motor when a differential value of a state quantity of the motor satisfies a predetermined condition.

8. 7. The electric parking brake control device according to claim 1, wherein the state quantity of the motor is a rotation speed of the motor.

9. 7. The electric parking brake control device according to claim 1, wherein the state quantity changing member is an elastic member that is deformed by the moving member moving from the apply position to the release position.

10. The control unit 10. The electric parking brake control device according to claim 9, wherein the driving of the motor is stopped based on the load acting on the elastic member calculated from the motor parameters.

11. 11. The electric parking brake control device according to claim 10, wherein the elastic member is composed of a plurality of disc springs.

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