Brake control device

Abstract

Disclosed is a brake control device that generates brake force capable of stopping a vehicle even when the slope of the road surface is large while minimizing the cost of the motor. The brake control device (control part 20) controls a hydraulic braking device (hydraulic unit 10) that presses a friction member (brake shoe D2) against a rotational solid (drum D1) that rotates integrally with vehicle wheels W, and a parking brake mechanism (200) that presses a friction member against the rotational solid by using the driving force of the motor to move a connecting member connected to the friction member. The brake control device acquires the road surface slope upon receiving an apply request when the vehicle is stopped, executes first braking control for pressing the friction member against the rotational solid using only the parking brake mechanism (200) when the road surface slope is less than a predetermined slope, and executes second braking control for pressing the friction member against the rotational solid using both the hydraulic braking device and the parking brake mechanism (200) when the road surface slope is equal to or greater than the predetermined slope.

Description

[Technical Field]

[0001] The present disclosure relates to a brake control device that controls a parking brake mechanism. [Background technology]

[0002] A conventional brake control device is known that determines whether a vehicle is parked on an uphill or downhill slope based on the inclination angle of the road surface acquired from an inclination sensor, and adjusts the parking brake force generated by the parking brake mechanism by changing the current flowing to the motor of the parking brake mechanism based on the determination result (see Japanese Patent Laid-Open Publication No. 2002-096721).This technology generates appropriate parking brake forces corresponding to uphill and downhill slopes, making it possible to stop the vehicle smoothly on both uphill and downhill slopes. Summary of the Invention

[0003] In order to generate a large parking brake force corresponding to a large gradient of the road surface, the motor capacity must be increased, which poses a problem of increased cost.

[0004] It is desirable to generate a braking force that can stop a vehicle even when the road surface has a large gradient, while keeping the cost of the motor low.

[0005] In view of the above background, the present invention discloses a brake control device that controls a hydraulic braking device that generates hydraulic braking force by using hydraulic pressure to press a friction member against a rotating body that rotates integrally with the wheel, and a parking brake mechanism that generates parking braking force by pressing the friction member against the rotating body by moving a connecting member connected to the friction member with the driving force of a motor. The brake control device acquires the road surface gradient when receiving a request to generate the parking brake force while the vehicle is stopped. When the road surface gradient is less than a predetermined gradient, the brake control device executes a first braking control by using only the parking brake mechanism to press the friction member against the rotating body, and when the road surface gradient is equal to or greater than the predetermined gradient, the brake control device executes a second braking control by using both the hydraulic braking device and the parking brake mechanism to press the friction member against the rotating body.

[0006] With this configuration, when the road gradient is equal to or greater than a predetermined gradient, the hydraulic braking device and the parking brake mechanism are used together to press the friction member against the rotor, thereby generating a braking force that is sufficient to stop the vehicle even when the road gradient is large. Furthermore, because the hydraulic braking device and the parking brake mechanism are used together when the road gradient is equal to or greater than a predetermined gradient, there is no need to increase the motor capacity of the parking brake mechanism in consideration of the road gradient, which allows for cost reduction.

[0007] Furthermore, in the second braking control, the brake control device may start the operation of the hydraulic braking device after starting the supply of current to the motor.

[0008] According to this configuration, the operating time of the hydraulic braking device can be shortened compared to, for example, a case where the hydraulic braking device is operated before the supply of current to the motor is started.

[0009] Furthermore, in the second braking control, the brake control device may start operation of the hydraulic braking device after the parking brake mechanism starts to operate.

[0010] With this configuration, the operating time of the hydraulic braking device can be further shortened.

[0011] Furthermore, in the second braking control, the brake control device may start supplying current to a hydraulic motor provided in the hydraulic braking device to start increasing the pressure of the brake fluid before starting to supply current to the motor, and may start supplying current to the motor after stopping the supply of current to the hydraulic motor.

[0012] According to this configuration, current is not passed through the motor and the hydraulic motor at the same time, so that an excessive voltage drop can be prevented.

[0013] Furthermore, in the second braking control, the brake control device may close a valve provided in the hydraulic braking device to maintain hydraulic pressure while the motor is being driven.

[0014] Furthermore, the brake control device may stop supplying current to the hydraulic motor when the hydraulic pressure increased by driving the hydraulic motor reaches a maximum value in the hydraulic braking device.

[0015] According to this configuration, the braking force of the hydraulic braking device can be utilized to the maximum extent possible, so the motor capacity can be reduced and costs can be further reduced.

[0016] In addition, the brake control device may be capable of acquiring longitudinal acceleration from a longitudinal acceleration sensor, and if there is no abnormality in the longitudinal acceleration sensor, the road surface gradient may be estimated based on the longitudinal acceleration, and if there is an abnormality in the longitudinal acceleration sensor, the road surface gradient may be set to the maximum gradient value.

[0017] According to this configuration, if there is an abnormality in the longitudinal acceleration sensor, the road surface gradient is set to the maximum gradient value, so when stopping on a slope when there is an abnormality in the longitudinal acceleration sensor, the vehicle can be stopped regardless of the gradient of the slope. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a configuration diagram of a vehicle equipped with an electric parking brake control device according to an embodiment; [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]FIG. 2 is a cross-sectional view showing an electric actuator of the parking brake mechanism. [Figure 4] 1 is a brake fluid pressure circuit diagram of a vehicle brake fluid pressure control device; [Figure 5] FIG. 1 shows the relationship between the distance from the contact point of the parking lever with the strut to the contact point of the brake shoe with the strut, where FIG. 1(a) shows the distance when the parking brake mechanism is in the applied state, and FIG. 1(b) shows the distance when the brake shoe rotates in response to the rotation of the drum after the parking brake mechanism is in the applied state. [Figure 6] 4 is a flowchart showing the operation of a parking brake control unit. [Figure 7] 10 is a flowchart showing a road surface gradient estimation process. [Figure 8] 4 is a flowchart showing the operation of a hydraulic pressure control unit. [Figure 9] 10A shows an example of the operation of the control unit, where FIG. 10A shows the change in hydraulic pressure and pulling force over time, FIG. 10B shows the change in motor current over time, FIG. 10C shows the change in hydraulic mode over time, and FIG. 10D shows the change in the driving state of the hydraulic motor over time. [Figure 10] 10 is a flowchart showing the operation of a parking brake control unit according to a modified example. [Figure 11] 10 is a flowchart showing the operation of a hydraulic pressure control unit according to a modified example. [Figure 12] 10A and 10B are diagrams showing an example of the operation of the control unit according to the modified example, in which FIG. 10A shows the change in hydraulic pressure and pulling force over time, FIG. 10B shows the change in motor current over time, FIG. 10C shows the change in hydraulic mode over time, and FIG. 10D shows the change in the driving state of the hydraulic motor over time. DETAILED DESCRIPTION OF THE INVENTION

[0019] Next, one embodiment will be described in detail with reference to the drawings as appropriate. As shown in FIG. 1, the vehicle CR includes a drum brake D, a parking brake mechanism 200, and a brake fluid pressure control device 100 for a vehicle.

[0020] 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.

[0021] 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 as an example of a hydraulic braking device, and a control unit 20 for appropriately controlling 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 structure of the hydraulic unit 10 will be described in detail later.

[0022] The control unit 20 is an example of a brake control device. The control unit 20 has a parking brake control unit 21 that controls the parking brake mechanism 200, and a hydraulic pressure control unit 22 that controls the hydraulic pressure unit 10. The control unit 20 is connected to a wheel speed sensor 91, a parking switch 92, a longitudinal acceleration sensor 93, and a pressure sensor 94. The wheel speed sensor 91 detects the wheel speed of the wheel W. The parking switch 92 switches the state of the parking brake mechanism 200 between an applied state and a released state. The longitudinal acceleration sensor 93 detects longitudinal acceleration. The pressure sensor 94 is provided in the hydraulic pressure unit 10. Here, the applied state refers to a state in which the parking brake mechanism 200 generates braking force. Furthermore, the released state refers to a state in which the parking brake mechanism 200 releases the braking force.

[0023] The control unit 20 includes, for example, a CPU, RAM, ROM, and input / output circuits, and is capable of acquiring information from a wheel speed sensor 91, a parking switch 92, a longitudinal acceleration sensor 93, and a pressure sensor 94. The control unit 20 executes control by performing various arithmetic processes based on inputs from the various sensors and switches, and programs and data stored in the ROM.

[0024] 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 a signal to the control unit 20 as an apply request to put the parking brake mechanism 200 into an apply state, and when the parking switch 92 is in the release position, it outputs a signal to the control unit 20 as a release request to put the parking brake mechanism 200 into a release state.

[0025] As shown in Figures 2(a) and 2(b), the drum brake D includes a drum D1 as an example of a rotating body, a brake shoe D2 as an example of a friction member, 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. Here, Figure 2 and Figure 5, which will be described later, show the drum brake D provided on the right rear wheel as a representative example.

[0026] 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.

[0027] A return spring D3 biases the other ends of the two brake shoes D2 in a direction that brings them closer together. The wheel cylinder D4 biases the two brake shoes D2 toward the inner circumferential surface of the drum D1 by using brake fluid pressure supplied from the hydraulic unit 10. In other words, the hydraulic unit 10 uses the brake fluid pressure to press the brake shoes D2 against the inner circumferential surface of the drum D1, generating hydraulic braking force.

[0028] The parking brake mechanism 200 includes a strut 210, a parking lever 220 as an example of a connecting member, 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.

[0029] One end of the parking lever 220 is rotatably connected to one brake shoe D2 by 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.

[0030] 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.

[0031] As a result, the pulling action of the wire 230 presses each brake shoe D2 against the inner circumferential surface of the drum D1. In other words, the parking brake mechanism 200 generates a parking brake force by moving the parking lever 220 with the driving force of the electric actuator 240, thereby pressing the brake shoes D2 against the inner circumferential surface of the drum D1. Note that when the wire 230 is loosened to the left in the figure, the biasing force of the return spring D3 moves each brake shoe D2 away from the inner circumferential surface of the drum D1.

[0032] 3, the electric actuator 240 is a device for pulling the wire 230. The electric actuator 240 includes a motor 241, a plurality of gears 242, a nut 243, a screw shaft 244, a housing 245, a retainer 246, and a plurality of disc springs 247.

[0033] Nut 243 is connected to motor 241 via multiple gears 242. Nut 243 has a female thread portion 243A that meshes with a male thread portion 244A of screw shaft 244. Screw shaft 244 is supported by housing 245 so as to be movable in the axial direction, and wire 230 is fixed to the tip. A flange portion 244B that protrudes radially is formed on the end of screw shaft 244 opposite to the tip.

[0034] The retainer 246 is a disk member having a hole in the center, and engages with the flange 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 flange 244B and the nut 243 in the axial direction of the screw shaft 244.

[0035] In this electric actuator 240, when the motor 241 is rotated forward, the screw shaft 244 moves in a direction to be housed in the housing 245, thereby pulling the wire 230, and the parking brake mechanism 200 enters an applied state in which the parking brake is applied. When the motor 241 is rotated reversely, the screw shaft 244 moves in a direction to protrude from the housing 245, thereby loosening the wire 230, and the parking brake mechanism 200 enters a released state in which the parking brake is released. In the released state, the multiple disc springs 247 are sandwiched between the retainer 246 and the nut 243 in a deformed state.

[0036] As shown in FIG. 4, the hydraulic unit 10 is configured by a pump body 11, which is a base body having hydraulic passages (hydraulic passages) through which brake fluid flows, and various electromagnetic valves arranged therein. The output ports M1 and M2 of the master cylinder MC are connected to the input port 11a of the pump body 11, and the output port 11b of the pump body 11 is connected to each wheel cylinder D4. Under normal conditions, the hydraulic passages from the input port 11a to the output port 11b in the pump body 11 are connected to each other, so that the depression force of the brake pedal BP is transmitted to each wheel cylinder D4. The hydraulic system connected to the output port M1 of the master cylinder MC is connected to the wheel cylinder D4 of the left front wheel and the wheel cylinder D4 of the right rear wheel. The hydraulic system connected to the output port M2 of the master cylinder MC is connected to the wheel cylinder D4 of the right front wheel and the wheel cylinder D4 of the left rear wheel. These hydraulic systems have substantially the same configuration.

[0037] Each hydraulic system is provided with a pressure regulating valve 12, a normally open proportional solenoid valve, on a hydraulic line connecting the input port 11a and the output port 11b, which can adjust the difference in hydraulic pressure between the upstream and downstream sides in response to the supplied current. A check valve 12a is provided in parallel with the pressure regulating valve 12, allowing flow only to the output port 11b.

[0038] The hydraulic line on the wheel cylinder D4 side of the pressure regulating valve 12 branches off midway, and each branch is connected to the output port 11b. An inlet valve 13, which is a normally-open proportional solenoid valve, is provided on each hydraulic line corresponding to each output port 11b. A check valve 13a that allows flow only toward the pressure regulating valve 12 is provided in parallel with each inlet valve 13.

[0039] A return hydraulic line 19B is provided from the hydraulic line between each output port 11b and the corresponding inlet valve 13, and connects between the pressure regulating valve 12 and the inlet valve 13 via an outlet valve 14, which is a normally closed solenoid valve.

[0040] Arranged on this return hydraulic line 19B, in this order from the outlet valve 14 side, are a reservoir 16 that temporarily absorbs excess brake fluid, a check valve 16a, a pump 17, and an orifice 17a. The check valve 16a is positioned so as to allow only flow between the pressure regulating valve 12 and the inlet valve 13. The pump 17 is driven by a hydraulic motor 31 and is provided to generate pressure between the pressure regulating valve 12 and the inlet valve 13. The hydraulic motor 31 is a common motor for driving the pumps 17 of each hydraulic system, and only one hydraulic motor 31 is provided for each of the two pumps 17. The orifice 17a dampens pressure pulsations of the brake fluid discharged from the pump 17 and pulsations generated by the operation of the pressure regulating valve 12.

[0041] An intake hydraulic pressure line 19C connects an intake hydraulic pressure line 19A connecting the input port 11a and the pressure regulating valve 12 to a portion of the return hydraulic pressure line 19B between the check valve 16a and the pump 17. An intake valve 15, which is a normally closed solenoid valve, is disposed in the intake hydraulic pressure line 19C.

[0042] The hydraulic pressure introduction passage 19A is provided with a pressure sensor 94 only on the side corresponding to the output port M2 of the master cylinder MC.

[0043] In the hydraulic unit 10 configured as described above, the solenoid valves are normally de-energized. Brake fluid pressure introduced through the input port 11a passes through the pressure regulator valve 12 and the inlet valve 13 and is output to the output port 11b, directly applied to each wheel cylinder D4. To reduce excess brake fluid pressure in a wheel cylinder D4, such as during anti-lock brake control, the corresponding inlet valve 13 is closed and the outlet valve 14 is opened, allowing brake fluid to flow through the return hydraulic line 19B to the reservoir 16 and drain the brake fluid from the wheel cylinder D4. To pressurize the wheel cylinder D4 without the driver operating the brake pedal BP, the intake valve 15 is opened and the hydraulic motor 31 is driven, actively supplying brake fluid to the wheel cylinder D4 using the pressure of the pump 17. Furthermore, the degree of pressurization of the wheel cylinder D4 can be adjusted by adjusting the current flowing through the pressure regulator valve 12.

[0044] However, when the vehicle CR is stopped using only the parking brake mechanism 200 as described above, the following problem occurs. As shown in Figure 5(a), when the vehicle CR is stopped on flat ground with the parking brake mechanism 200 in the applied state, the distance from the contact point P1 of the parking lever 220 with the strut 210 to the contact point P2 of the brake shoe D2 with the strut 210 is L1. Furthermore, when the parking brake mechanism 200 is put into the applied state on a steep downhill slope, for example, the parking brake mechanism 200 first assumes the state shown in Figure 5(a), causing the vehicle CR to temporarily stop.

[0045] However, when the vehicle CR moves slightly forward down a slope due to gravity acting on the vehicle CR, the drum D1 may rotate slightly, as shown in FIG. 5(b). In this case, the brake shoe D2 pressed against the drum D1 rotates slightly following the drum D1, causing the distance from the contact point P1 to the contact point P2 to become L2, which is slightly larger than L1. This phenomenon also occurs when the vehicle is stopped on an uphill slope. Therefore, the parking brake force may be weaker on a steep slope than on flat ground. Therefore, in this embodiment, the control unit 20 shown in FIG. 1 executes the following control to suppress a decrease in the parking brake force on a steep slope.

[0046] The control unit 20 has a function of selecting and executing a first braking control or a second braking control based on the road gradient when the vehicle is stopped. In the first braking control, the brake shoe D2 is pressed against the drum D1 using only the parking brake mechanism 200. In the second braking control, the brake shoe D2 is pressed against the drum D1 using both the hydraulic unit 10 and the parking brake mechanism 200. Specifically, when the control unit 20 receives an apply request when the vehicle is stopped, it first obtains the road gradient.

[0047] Specifically, when there is no abnormality in the longitudinal acceleration sensor 93, the control unit 20 estimates the road surface gradient based on the longitudinal acceleration acquired from the longitudinal acceleration sensor 93. Furthermore, when there is an abnormality in the longitudinal acceleration sensor, the control unit 20 sets the road surface gradient to the maximum gradient value.

[0048] Here, the maximum gradient value is the maximum gradient value that can be actually assumed for the road surface. The method for determining whether the vehicle is stopped includes a method for determining whether the vehicle speed is equal to or lower than a predetermined speed. The vehicle speed is calculated based on, for example, a signal from the wheel speed sensor 91.

[0049] When the road surface gradient is less than a predetermined gradient, the control unit 20 executes the first braking control. Specifically, in the first braking control, the control unit 20 supplies current to the motor 241, and stops the supply of current when the current becomes equal to or greater than an apply threshold, thereby putting the parking brake mechanism 200 into an apply state.

[0050] When the road surface gradient is equal to or greater than a predetermined gradient, the control unit 20 executes the second braking control. Specifically, in the second braking control, the control unit 20 starts supplying current to the motor 241, and then starts supplying current to the hydraulic motor 31, thereby starting operation of the hydraulic unit 10. More specifically, in the second braking control, the control unit 20 starts supplying current to the hydraulic motor 31 after the parking brake mechanism 200 starts to operate.

[0051] 9(b), when the supply of current to the motor 241 starts, an inrush current with a momentary high current value occurs. While this inrush current is occurring, the motor 241 does not move, and after the inrush current subsides, the motor 241 starts to move (time t2). Therefore, the timing at which the parking brake mechanism 200 starts to move (time t2) is later than the timing at which the supply of current to the motor 241 starts (time t1).

[0052] Furthermore, in the second braking control, the control unit 20 closes the inlet valve 13 of the hydraulic unit 10 to maintain the hydraulic pressure while the motor 241 is being driven. Furthermore, the control unit 20 stops the supply of current to the hydraulic motor 31 when the hydraulic pressure increased by the driving of the hydraulic motor 31 reaches its maximum value in the hydraulic unit 10.

[0053] The operation of the control unit 20 described above is specifically executed by the parking brake control unit 21 and the hydraulic pressure control unit 22. The operation of the parking brake control unit 21 and the hydraulic pressure control unit 22 will be described in detail below.

[0054] The parking brake control unit 21 repeatedly executes the process shown in FIG. 6, the parking brake control unit 21 first determines whether or not the vehicle CR has stopped (S1). If it is determined in step S1 that the vehicle CR has stopped (Yes), the parking brake control unit 21 determines whether or not an apply request has been made (S2).

[0055] If it is determined in step S2 that an apply request has been made (Yes), the parking brake control unit 21 starts supplying current to the motor 241 (S3). After step S3, the parking brake control unit 21 determines whether a predetermined time T1 has elapsed since the start of supplying current to the motor 241 (S4).

[0056] Here, the predetermined time T1 is the time from when current starts to flow to the motor 241 (time t1) to when the inrush current converges (time t2), as shown in Figure 9(b), and is set to an appropriate value through experiments, simulations, etc.

[0057] The parking brake control unit 21 repeatedly executes the process of step S4 until the predetermined time T1 has elapsed (S4: No). If it is determined in step S4 that the predetermined time T1 has elapsed (Yes), the parking brake control unit 21 executes a road surface gradient estimation process (S5) to obtain the road surface gradient S. The road surface gradient estimation process will be described in detail later.

[0058] After step S5, the parking brake control unit 21 determines whether the road surface gradient S is equal to or greater than a predetermined gradient Sth (S6). If it is determined in step S6 that S≧Sth (Yes), the parking brake control unit 21 outputs a pressure increase request and a target hydraulic pressure value to the hydraulic pressure control unit 22 (S7). Here, the target hydraulic pressure value is set to the maximum value of the hydraulic pressure in the hydraulic unit 10.

[0059] After step S7, the parking brake control unit 21 sets flag F, which indicates that a pressure increase request or the like has been output to the hydraulic unit 10, to 1 (S8). After step S8, the parking brake control unit 21 determines whether the current of the motor 241 is equal to or greater than the apply threshold value (S9). Furthermore, if it is determined in step S6 that S≧Sth is not true (No), the parking brake control unit 21 skips the processes of steps S7 and S8 and proceeds to the process of step S9.

[0060] The parking brake control unit 21 repeatedly executes the process of step S9 until the current of the motor 241 becomes equal to or greater than the apply threshold (S9: No). If it is determined in step S9 that the current has become equal to or greater than the apply threshold (Yes), the parking brake control unit 21 determines whether the flag F is 1, thereby determining whether the hydraulic unit 10 is operating (S10).

[0061] If it is determined in step S10 that flag F is 1 (Yes), the parking brake control unit 21 outputs a pressure reduction request to the hydraulic pressure control unit 22 (S11). After step S11, the parking brake control unit 21 sets flag F to 0 (S12) and ends this process. The parking brake control unit 21 also ends this process if it determines No in steps S1, S2, and S10.

[0062] 7, the parking brake control unit 21 first determines whether or not the longitudinal acceleration sensor 93 is abnormal (S31). As a method for determining whether or not an abnormality has occurred, for example, there is a method of setting an abnormality flag when the output value output from the longitudinal acceleration sensor 93 does not change while the vehicle CR is traveling.

[0063] If it is determined in step S31 that there is no abnormality (No), the parking brake control unit 21 estimates the road surface gradient S based on the longitudinal acceleration acquired from the longitudinal acceleration sensor 93 (S32), and ends this process. If it is determined in step S31 that there is an abnormality (Yes), the parking brake control unit 21 sets the road surface gradient S to the maximum gradient value Smax (S33), and ends this process.

[0064] The hydraulic pressure control unit 22 repeatedly executes the process shown in FIG. 8 while the vehicle CR is stopped. In the process shown in FIG. 8, the hydraulic pressure control unit 22 first determines whether or not it has received a pressure increase request and a target hydraulic pressure value from the parking brake control unit 21 (S51).

[0065] If it is determined in step S51 that the pressure increase request and the target hydraulic pressure value have been acquired (Yes), the hydraulic control unit 22 starts supplying current to the hydraulic motor 31 to drive the hydraulic motor 31 (S52). After step 52, the hydraulic control unit 22 determines whether the hydraulic pressure increased by driving the hydraulic motor 31 has reached or exceeded the target hydraulic pressure value (S53).

[0066] The hydraulic pressure control unit 22 repeatedly executes the process of step S53 until the hydraulic pressure reaches the target hydraulic pressure value (S53: No). If it is determined in step S53 that the hydraulic pressure has reached or exceeded the target hydraulic pressure value (Yes), the hydraulic pressure control unit 22 stops the supply of current to the hydraulic motor 31 to stop the hydraulic motor 31, and applies current to the inlet valve 13 to close the inlet valve 13 (S54). This maintains the hydraulic pressure at the target hydraulic pressure value.

[0067] After step S54, the hydraulic pressure control unit 22 determines whether or not a pressure reduction request has been received from the parking brake control unit 21 (S55). If it is determined in step S55 that a pressure reduction request has been received (Yes), the hydraulic pressure control unit 22 applies a current to the outlet valve 14 to open the outlet valve 14 (S56). This reduces the hydraulic pressure.

[0068] If the pressure reduction is completed in step S56, the hydraulic control unit 22 stops the supply of current to the inlet valve 13 and the outlet valve 14, thereby opening the inlet valve 13 and closing the outlet valve 14, and ends this process. If it is determined in step S51 that a pressure increase request and a target hydraulic pressure value have not been acquired (No), the hydraulic control unit 22 proceeds to the process of step S55. If it is determined in step S55 that a pressure reduction request has not been acquired (No), the hydraulic control unit 22 ends this process. As a result, the hydraulic control unit 22 does not operate the hydraulic unit 10 in the first braking control in which no request is received from the parking brake control unit 21, and operates the hydraulic unit 10 in the second braking control in which a request is received from the parking brake control unit 21.

[0069] Next, an example of the operation of the control unit 20 will be described in detail with reference to Fig. 9. Here, Fig. 9(d) is a graph showing the state of the hydraulic motor 31, where "ON" indicates a state in which current is flowing to the hydraulic motor 31, and "OFF" indicates a state in which current is not flowing to the hydraulic motor 31.

[0070] When the vehicle CR is stopped on a slope with a gradient Sth or greater, upon receiving an apply request (time t1), the control unit 20 starts supplying current to the motor 241, as shown in Fig. 9(b). Thereafter, the control unit 20 waits until a predetermined time T1 has elapsed, during which the inrush current converges. After the predetermined time T1 has elapsed (time t2), the motor 241 starts rotating.

[0071] As a result, the threaded shaft 244 shown in Fig. 3 starts to move from the release position toward the apply position. As the threaded shaft 244 moves from the release position toward the apply position, the load applied to the threaded shaft 244 from the disc spring 247 gradually decreases, and the current of the motor 241 gradually decreases after time t2, as shown in Fig. 9(b). When the threaded shaft 244 moves away from the retainer 246, the load on the threaded shaft 244 is no longer applied (time t3), and thereafter the current becomes constant.

[0072] After a predetermined time T1 has elapsed since the start of energizing the motor 241 (time t2), the control unit 20 starts supplying current to the hydraulic motor 31 as shown in Fig. 9(d), causing the hydraulic unit 10 to start increasing the hydraulic pressure in the wheel cylinder D4 (see Figs. 9(a) and 9(c)). As a result, while the hydraulic pressure is being increased, the wheel cylinder D4 starts to move the brake shoe D2, and the brake shoe D2 is pressed against the drum D1.

[0073] As shown in Figure 9(a), when the hydraulic pressure in wheel cylinder D4 becomes equal to or greater than the target hydraulic pressure value (time t4), the control unit 20 switches the hydraulic mode from boost to hold by stopping the supply of current to hydraulic motor 31 and closing inlet valve 13, as shown in Figures 9(c) and 9(d). Thereafter, when the parking lever 220 begins to press brake shoe D2 via strut 210 (time t5), as shown in Figures 9(a) and 9(b), the pulling force that pulls wire 230 by motor 241 begins to increase, and a load is applied to motor 241, causing the current of motor 241 to begin to increase.

[0074] Here, the graph shown by the two-dot chain line in Figure 9(b) represents the current in the first braking control in which braking force is generated only by the parking brake mechanism 200. In the first braking control, the position of the brake shoe D2 before a load is applied to the motor 241 is the position shown in Figure 2(a), that is, a position away from the drum D1. Therefore, in the first braking control, a load begins to be applied to the motor 241 and the current of the motor begins to increase at an earlier timing than in the second braking control.

[0075] In contrast, in the second braking control, after hydraulic pressure is increased and before a load is applied to the motor 241 (for example, from time t4 to t5), the position of the brake shoe D2 is the position shown in Fig. 2(b), that is, the position where it contacts the drum D1. Therefore, in the second braking control, the timing at which a load begins to be applied to the motor 241 is later than in the first braking control, and the amount of tension on the wire 230 can be increased.

[0076] Thereafter, when the current becomes equal to or greater than the apply threshold IA (time t6), the control unit 20 stops the supply of current to the motor 241 and completes the apply process. Thereafter, as shown in Figures 9(a) and 9(c), the control unit 20 switches the hydraulic pressure mode from hold to reduce, thereby reducing the hydraulic pressure (times t7-t8).

[0077] When the hydraulic braking force decreases due to a decrease in hydraulic pressure, the braking force applied to the wheel W decreases, causing the wheel W to rotate slightly, which may cause the brake shoe D2 to rotate in response to the rotation of the drum D1. However, in the second braking control, the wire 230 is pulled more strongly than in the first braking control, so the amount of rotation of the brake shoe D2 can be kept small, preventing a significant decrease in the parking brake force. Therefore, the vehicle CR can be stopped smoothly even on a slope with a gradient Sth or greater.

[0078] As described above, the following effects can be obtained in this embodiment. When the road surface gradient S is equal to or greater than a predetermined gradient Sth, the hydraulic unit 10 and the parking brake mechanism 200 are used together to press the brake shoe D2 against the drum D1, thereby generating a braking force that is sufficient to stop the vehicle CR even on a steep slope. Furthermore, when the road surface gradient S is equal to or greater than the predetermined gradient Sth, the hydraulic unit 10 and the parking brake mechanism 200 are used together, so there is no need to increase the capacity of the motor 241 of the parking brake mechanism 200 in consideration of the road surface gradient S, thereby reducing costs.

[0079] In the second braking control, the hydraulic unit 10 starts operating after the supply of current to the motor 241 is started, so the operating time of the hydraulic unit 10, more specifically the time for which current is passed through the inlet valve 13 to maintain hydraulic pressure, can be shortened compared to, for example, when the hydraulic unit is operated before the supply of current to the motor is started.

[0080] In particular, in this embodiment, in the second braking control, the hydraulic unit 10 starts operating after the parking brake mechanism 200 starts to operate, so the operating time of the hydraulic unit 10 can be shortened compared to, for example, when the hydraulic unit is operated before the parking brake mechanism starts to operate.

[0081] In the second braking control, when the hydraulic pressure increased by driving the hydraulic motor 31 reaches the maximum value in the hydraulic unit 10, the supply of current to the hydraulic motor 31 is stopped, thereby making it possible to make maximum use of the braking force from the hydraulic unit 10 when stopping the vehicle CR on a steep slope, thereby making it possible to lower the capacity of the motor 241 and reduce costs.

[0082] If there is an abnormality in the longitudinal acceleration sensor 93, the road surface gradient S is set to the maximum gradient value Smax, so when stopping on a slope when there is an abnormality in the longitudinal acceleration sensor 93, the vehicle CR can be stopped regardless of the gradient of the slope.

[0083] The above-described embodiment can be modified in various ways as exemplified below. In the following description, the same reference numerals are used to designate components having substantially the same structures as those in the above-described embodiment, and the description thereof will be omitted.

[0084] In the above embodiment, the hydraulic unit 10 is operated after the start of the supply of current to the motor 241. However, for example, as shown in FIG. 12 , in the second braking control, the control unit 20 may start supplying current to the hydraulic motor 31 to start increasing the brake fluid pressure at a time (time t21) before the start of the supply of current to the motor 241 (time t1). Also, the control unit 20 may start supplying current to the motor 241 (time t1) after the supply of current to the hydraulic motor 31 is stopped (time t1). Here, "after the supply of current to the hydraulic motor 31 is stopped" means after the supply of current to the hydraulic motor 31 is stopped, and includes the timing simultaneous with the stop.

[0085] Specifically, in this embodiment, the parking brake control unit 21 executes the process shown in Fig. 10. The process shown in Fig. 10 is a process obtained by partially modifying the process shown in Fig. 6. Specifically, the process shown in Fig. 10 is a process in which the processes of steps S3 and S4 of the process shown in Fig. 6 are moved between steps S8 and S9, and a new process of step S71 is added between steps S8 and S3.

[0086] In this embodiment, the hydraulic control unit 22 executes the process shown in Fig. 11. The process shown in Fig. 11 is a partial modification of the process shown in Fig. 8. Specifically, the process shown in Fig. 11 is a process in which a new step S81 is added between step S54 and step S55 of the process shown in Fig. 8.

[0087] 10, the parking brake control unit 21 executes the processes of steps S1 and S2 as in the above embodiment, and if it determines Yes in step S2, it executes the road surface gradient estimation process (S5). After step S5, the parking brake control unit 21 executes the process of step S7 as in the above embodiment. That is, the parking brake control unit 21 outputs a pressure increase request and a target hydraulic pressure value to the hydraulic pressure control unit 22 (S7) before executing the process of step S3 to start supplying current to the motor 241.

[0088] 11, when the hydraulic pressure control unit 22 receives a pressure increase request and a target hydraulic pressure value from the parking brake control unit 21 (S51: Yes), it performs steps S52 to S54 in the same manner as in the previous embodiment, thereby completing the process of increasing the hydraulic pressure. After step S54, the hydraulic pressure control unit 22 outputs a pressure increase completion signal indicating that the pressure increase has been completed to the parking brake control unit 21 (S81). After step S81, the hydraulic pressure control unit 22 performs steps S55 and S56 in the same manner as in the previous embodiment.

[0089] 10, the parking brake control unit 21 executes the processes of steps S7 and S8 in the same manner as in the above embodiment, and then determines (S71) whether or not a pressure increase completion signal has been received from the hydraulic pressure control unit 22. The parking brake control unit 21 repeatedly executes the process of step S71 until a pressure increase completion signal is received from the hydraulic pressure control unit 22 (S71: No).

[0090] If it is determined in step S71 that the pressure increase completion signal has been acquired (Yes), the parking brake control unit 21 starts supplying current to the motor 241 (S3). That is, the parking brake control unit 21 starts supplying current to the motor 241 after the hydraulic pressure control unit 22 stops supplying current to the hydraulic motor 31.

[0091] After step S3, the parking brake control unit 21 executes the process of step S4 in the same manner as in the above embodiment. After step S4, the parking brake control unit 21 executes the processes of steps S9 to S12 in the same manner as in the above embodiment.

[0092] According to this configuration, as shown in FIG. 12, the period during which current flows to the hydraulic motor 31 (time t21-t1) and the period during which current flows to the motor 241 do not overlap, so that excessive voltage drop caused by current flowing simultaneously to the hydraulic motor 31 and the motor 241 can be prevented.

[0093] 9, the supply of current to the hydraulic motor 31 is started immediately (at the time) after the parking brake mechanism 200 starts to operate, but the supply of current to the hydraulic motor 31 may be started at any timing as long as the timing is such that the pulling force starts to increase after the hydraulic pressure increase is completed. For example, the supply of current to the hydraulic motor 31 may be started at the time (time t3) when the current of the motor 241 switches from a decreasing trend to a constant current.

[0094] In the above embodiment, the control unit 20 of the vehicle brake fluid pressure control device 100 is exemplified as the brake control device, but a control device other than the vehicle brake fluid pressure control device, for example, an ECU (Electronic Control Unit) of the vehicle, may also be used as the brake control device.

[0095] In the above embodiment, the parking brake mechanism 200 is installed in the drum brake D, but it may be installed in a disc brake, for example. In this case, the rotor that rotates integrally with the wheel corresponds to the rotating body, the pad pressed against the rotor corresponds to the friction member, and the member connected to the friction member corresponds to the connecting member.

[0096] The elements described in the above-described embodiment and modified examples may be implemented in any combination.

Claims

1. a hydraulic braking device that generates hydraulic braking force by pressing a friction member against a rotating body that rotates integrally with the wheel using hydraulic pressure; a parking brake mechanism that generates a parking brake force by pressing the friction member against the rotating body by moving a connecting member connected to the friction member with a driving force of a motor; A brake control device that controls When a request to generate the parking brake force is received while the vehicle is stopped, the road surface gradient is acquired; When the road surface gradient is less than a predetermined gradient, a first braking control is executed by using only the parking brake mechanism to press the friction member against the rotating body; When the road surface gradient is equal to or greater than the predetermined gradient, a second braking control is executed in which the hydraulic braking device and the parking brake mechanism are used in combination to press the friction member against the rotating body; A brake control device characterized in that, in the second braking control, the hydraulic braking device starts operating after the supply of current to the motor starts.

2. 2. The brake control device according to claim 1, wherein, in the second braking control, the hydraulic braking device starts to operate after the parking brake mechanism starts to operate.

3. A hydraulic braking device that generates hydraulic braking force by pressing a friction member against a rotating body that rotates integrally with the wheel using hydraulic pressure; a parking brake mechanism that generates a parking brake force by pressing the friction member against the rotating body by moving a connecting member connected to the friction member with a driving force of a motor; A brake control device that controls When a request to generate the parking brake force is received while the vehicle is stopped, the road surface gradient is acquired; When the road surface gradient is less than a predetermined gradient, a first braking control is executed by using only the parking brake mechanism to press the friction member against the rotating body; When the road surface gradient is equal to or greater than the predetermined gradient, a second braking control is executed in which the hydraulic braking device and the parking brake mechanism are used in combination to press the friction member against the rotating body; In the second braking control, before starting to supply current to the motor, starting to supply current to a hydraulic motor provided in the hydraulic braking device to start increasing the pressure of the brake fluid; after stopping the supply of current to the hydraulic motor, starting the supply of current to the motor; A brake control device characterized in that when the hydraulic pressure increased by driving the hydraulic motor reaches a maximum value in the hydraulic braking device, the supply of current to the hydraulic motor is stopped.

4. In the second braking control, 4. The brake control device according to claim 3, wherein a valve provided in the hydraulic braking device is closed to maintain hydraulic pressure while the motor is in operation.

5. The longitudinal acceleration can be acquired from the longitudinal acceleration sensor, If there is no abnormality in the longitudinal acceleration sensor, the road surface gradient is estimated based on the longitudinal acceleration; 5. The brake control device according to claim 1, wherein when an abnormality occurs in the longitudinal acceleration sensor, the road surface gradient is set to a maximum gradient value.

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