JP7594602B2 - Brake Control Device - Google Patents

Description

The present disclosure relates to a brake control device that controls a parking brake mechanism.

A conventional brake control device is known that adjusts the parking brake force generated by the parking brake mechanism by controlling the motor of the parking brake mechanism based on the temperature of a friction member that can come into contact with a contact member fixed to the wheel (see JP 2005-255038 A). Specifically, in this technology, the brake control device controls the motor so that the parking brake force increases as the temperature of the friction member increases.

In order to generate a large parking brake force that can correspond to high temperatures of the friction materials, the motor's capacity must be increased, which creates the problem of high costs.

It is desirable to generate braking force capable of stopping the vehicle when the friction materials are at high temperatures while keeping motor costs down.

In consideration of the above-mentioned background, the present invention discloses a brake control device that controls a hydraulic braking device that uses hydraulic pressure to press a friction member against a rotating body that rotates integrally with the wheel to generate a hydraulic braking force, and 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 the driving force of a motor.
The brake control device obtains the temperature of the friction members when a request to generate the parking brake force is received.
When the temperature is below a predetermined temperature, the brake control device executes a first braking control using only the parking brake mechanism to press the friction member against the rotating body, and when the temperature is equal to or higher than the predetermined temperature, the brake control device executes a second braking control using both the hydraulic braking device and the parking brake mechanism to press the friction member against the rotating body.

According to this configuration, when the temperature of the friction member is equal to or higher than a predetermined temperature, the hydraulic braking device and the parking brake mechanism are used together to press the friction member against the rotating body, so that a braking force capable of stopping the vehicle can be generated even when the temperature of the friction member is high. In addition, when the temperature of the friction member is equal to or higher than a predetermined temperature, the hydraulic braking device and the parking brake mechanism are used together, so there is no need to increase the motor's capacity in consideration of the high temperature of the friction member, and costs can be reduced.

In addition, in the second braking control, the brake control device may start operation of the hydraulic braking device after starting to supply current to the motor.

With this configuration, the operating time of the hydraulic braking device can be shortened, for example, compared to when the hydraulic braking device is operated before current supply to the motor begins.

In addition, in the second braking control, the brake control device may start operation of the hydraulic braking device after the parking brake mechanism begins to move.

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

In addition, 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 brake fluid pressure 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.

With this configuration, current is not passed through the motor and hydraulic motor at the same time, preventing excessive voltage drops.

In addition, 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.

The brake control device may also 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.

With this configuration, the braking force provided by the hydraulic braking device can be utilized to the maximum extent possible, allowing the motor capacity to be lowered and costs to be reduced.

The brake control device may also estimate the temperature of the friction member based on at least the hydraulic pressure and the wheel speed.

With this configuration, there is no need to install a temperature sensor to detect the temperature of the friction member, which reduces costs.

1 is a configuration diagram of a vehicle equipped with an electric parking brake control device according to an embodiment; 1A is a diagram 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. FIG. 2 is a cross-sectional view showing an electric actuator of the parking brake mechanism. 1 is a brake fluid pressure circuit diagram of a vehicle brake fluid pressure control device. FIG. 1A is a diagram showing 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; FIG. 1B is a diagram showing the distance when the parking brake mechanism is in the applied state, and FIG. 1B is a diagram showing 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. 5 is a flowchart showing the operation of a parking brake control unit. 5 is a flowchart showing a hydraulic pressure operation determination process. 5 is a flowchart showing the operation of a hydraulic pressure control unit. 11A is a diagram showing an example of the operation of the control unit, in which FIG. 11A shows the change in hydraulic pressure and pulling force over time, FIG. 11B shows the change in motor current over time, FIG. 11C shows the change in hydraulic mode over time, and FIG. 11D shows the change in the driving state of the hydraulic motor over time. 10 is a flowchart showing the operation of a parking brake control unit according to a modified example. 10 is a flowchart showing the operation of a hydraulic pressure control unit according to a modified example. 10A shows an example of the operation of a control unit according to a modified example, in which FIG. 10A shows changes in hydraulic pressure and pulling force over time, FIG. 10B shows changes in motor current over time, FIG. 10C shows changes in hydraulic mode over time, and FIG. 10D shows changes in the driving state of a hydraulic motor over time.

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

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.

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 parts within the hydraulic unit 10. The hydraulic unit 10 is connected via an oil line to a master cylinder MC that generates brake hydraulic pressure when the brake pedal BP is depressed, and is also connected via an oil line to the wheel cylinders D4 of each drum brake D. The structure of the hydraulic unit 10 will be described in detail later.

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 control unit 22 that controls the hydraulic unit 10. A wheel speed sensor 91, a parking switch 92, a longitudinal acceleration sensor 93, and a pressure sensor 94 are connected to the control unit 20. The wheel speed sensor 91 detects the wheel speed of the wheel W. The parking switch 92 is for switching 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 unit 10. Here, the applied state refers to a state in which the parking brake mechanism 200 generates a braking force. Also, the released state refers to a state in which the parking brake mechanism 200 releases the braking force.

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 calculation processes based on inputs from the various sensors and switches, and on programs and data stored in the ROM.

The parking switch 92 can be switched 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.

2(a) and (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, FIG. 2 and FIG. 5, which will be described later, show the drum brake D installed on the right rear wheel as a representative example.

The brake shoes D2 are arc-shaped members that extend along the inner circumferential surface of the drum D1, and are 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.

The 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 surface of the drum D1 by the 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 surface of the drum D1, generating a hydraulic braking force.

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 engages with the other end of each of the two brake shoes D2.

One end of the parking lever 220 is rotatably connected to one of the brake shoes 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.

When the wire 230 is pulled to the right in the figure, the parking lever 220 rotates around the pin 221, and the parking lever 220 presses the other brake shoe D2 against the inner surface of the drum D1 via the strut 210. Furthermore, when the wire 230 is pulled, the parking lever 220 rotates around the engagement portion with the strut 210, and the parking lever 220 presses one brake shoe D2 against the inner surface of the drum D1 via the pin 221.

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 pressing the brake shoes D2 against the inner circumferential surface of the drum D1 by moving the parking lever 220 with the driving force of the electric actuator 240. Note that when the wire 230 is loosened to the left in the figure, the biasing force of the return spring D3 causes each brake shoe D2 to move away from the inner circumferential surface of the drum D1.

As shown in Figure 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.

The nut 243 is connected to the motor 241 via multiple gears 242. The nut 243 has a female threaded portion 243A that meshes with a male threaded portion 244A of the screw shaft 244. 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 portion 244B that protrudes radially is formed on the end of the screw shaft 244 opposite to the tip.

The retainer 246 is a disk member with 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.

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, pulling the wire 230 and placing the parking brake mechanism 200 in an applied state with the parking brake applied. When the motor 241 is rotated reversely, the screw shaft 244 moves in a direction to protrude from the housing 245, loosening the wire 230 and placing the parking brake mechanism 200 in a released state with the parking brake released. In the released state, the multiple disc springs 247 are clamped in a deformed state between the retainer 246 and the nut 243.

As shown in FIG. 4, the hydraulic unit 10 is configured by arranging hydraulic lines and various electromagnetic valves in the pump body 11, which is a base body having hydraulic lines (hydraulic lines) through which brake fluid flows. 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. Normally, the hydraulic lines from the input port 11a to the output port 11b in the pump body 11 are connected to each wheel cylinder D4, so that the 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, and 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. Each of these hydraulic systems has a substantially similar configuration.

Each hydraulic system is provided with a pressure regulating valve 12, which is a normally open proportional solenoid valve that can adjust the difference in hydraulic pressure between the upstream and downstream sides according to the current supplied, on the hydraulic path connecting the input port 11a and the output port 11b. In parallel with the pressure regulating valve 12, a check valve 12a is provided that allows flow only to the output port 11b.

The hydraulic line on the wheel cylinder D4 side of the pressure regulating valve 12 branches off along the way, 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 to the pressure regulating valve 12 side is provided in parallel with each inlet valve 13.

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

On this return hydraulic line 19B, in order from the outlet valve 14 side, a reservoir 16 that temporarily absorbs excess brake fluid, a check valve 16a, a pump 17, and an orifice 17a are arranged. The check valve 16a is arranged 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 is provided for each of the two pumps 17. The orifice 17a attenuates the pressure pulsation of the brake fluid discharged from the pump 17 and the pulsation generated by the operation of the pressure regulating valve 12.

The intake hydraulic pressure line 19A, which connects the input port 11a and the pressure regulating valve 12, and the portion of the return hydraulic pressure line 19B between the check valve 16a and the pump 17 are connected by the intake hydraulic pressure line 19C. The intake hydraulic pressure line 19C is provided with an intake valve 15, which is a normally closed solenoid valve.

In addition, a pressure sensor 94 is provided only on the side of the intake hydraulic passage 19A that corresponds to the output port M2 of the master cylinder MC.

In the hydraulic unit 10 configured as described above, under normal conditions, each solenoid valve is not energized, and the brake fluid pressure introduced from the input port 11a is output to the output port 11b through the pressure regulating valve 12 and the inlet valve 13, and is directly applied to each wheel cylinder D4. When excessive brake fluid pressure in the wheel cylinder D4 is to be reduced, such as when performing antilock brake control, the corresponding inlet valve 13 is closed and the outlet valve 14 is opened to allow the brake fluid to flow through the return hydraulic pressure path 19B to the reservoir 16, and the brake fluid in the wheel cylinder D4 can be drained. When the wheel cylinder D4 is pressurized without the driver operating the brake pedal BP, the intake valve 15 is opened and the hydraulic motor 31 is driven, so that the brake fluid can be actively supplied to the wheel cylinder D4 by the pressure of the pump 17. Furthermore, when it is desired to adjust the degree of pressurization of the wheel cylinder D4, the current flowing through the pressure regulating valve 12 can be adjusted.

However, when the vehicle CR is stopped using only the parking brake mechanism 200 as described above, the following problems arise.
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. Also, when the parking brake mechanism 200 is put into the applied state on a steep downhill slope that is equal to or greater than a first predetermined gradient, the parking brake mechanism 200 first goes into the state shown in Figure 5(a), and the vehicle CR temporarily stops.

However, when the vehicle CR moves forward slightly downhill due to gravity acting on the vehicle CR, the drum D1 may rotate slightly, as shown in Figure 5(b). In this case, the brake shoe D2 pressed against the drum D1 rotates slightly following the drum D1, and the distance from the contact part P1 to the contact part P2 described above becomes L2, which is slightly larger than L1. This phenomenon also occurs when the vehicle is stopped on an uphill road. Therefore, the parking brake force may be weaker on a steep slope that is equal to or greater than the first predetermined gradient, compared to flat ground.

In addition, for example, when the temperature of the brake shoe D2 is high on a downhill slope with a second predetermined gradient or more that is smaller than the first predetermined gradient, the frictional force between the brake shoe D2 and the drum D1 is reduced, and the vehicle CR may move forward slightly in the direction of descending the downhill slope after stopping once. In this case, the distance from the contact part P1 to the contact part P2 described above becomes L2, which is slightly larger than L1. This phenomenon also occurs when the vehicle is stopped on an uphill slope. Therefore, even if the slope has a gradient less than the first predetermined gradient, if the slope has a gradient of the second predetermined gradient or more and the temperature of the brake shoe D2 is high, the parking brake force may be weaker than on flat ground. Therefore, in this embodiment, the control unit 20 shown in FIG. 1 executes the control shown below to suppress the decrease in the parking brake force when the vehicle is stopped on a slope with a gradient of the first predetermined gradient or more, or when the temperature of the brake shoe D2 is high and the slope has a gradient of the second predetermined gradient or more.

The control unit 20 has a function of selecting and executing the first braking control and the second braking control based on the road gradient when the vehicle is stopped and the temperature of the brake shoe D2. 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 acquires the road gradient and the current estimated temperature of the brake shoe D2.

In detail, 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. In addition, when there is an abnormality in the longitudinal acceleration sensor, the control unit 20 sets the road surface gradient to the maximum gradient value.

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

In addition, the control unit 20 constantly estimates the temperature of the brake shoe D2. In detail, the control unit 20 sets the temperature of the brake shoe D2 to an initial value when the vehicle CR is started, such as when the engine is started, and each time the brakes are applied while the vehicle CR is traveling, the control unit 20 sets the amount of temperature rise of the brake shoe D2 due to braking, and estimates the temperature of the brake shoe D2 by adding the amount of temperature rise to the initial value.

The control unit 20 sets the amount of temperature rise during braking based on the brake fluid pressure and wheel speed. In particular, the amount of temperature rise of the brake shoe D2 is set to a value that is greater the greater the brake fluid pressure during braking and the greater the wheel speed during braking. In addition, while the vehicle CR is traveling with no braking, the control unit 20 gradually reduces the temperature of the brake shoe D2 over time.

The control unit 20 executes the first braking control when the road surface gradient is less than the second predetermined gradient, or when the road surface gradient is equal to or greater than the second predetermined gradient and the estimated temperature of the brake shoe D2 is less than the predetermined temperature. In more detail, 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 the apply threshold, thereby putting the parking brake mechanism 200 into the apply state.

The control unit 20 executes the second braking control when the road surface gradient is equal to or greater than a first predetermined gradient, or when the road surface gradient is equal to or greater than a second predetermined gradient and the estimated temperature of the brake shoe D2 is equal to or greater than a predetermined temperature. In detail, 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 move.

When the current supply to the motor 241 starts, an inrush current with a momentary high current value occurs, as shown in Fig. 9(b). When this inrush current occurs, the motor 241 does not move, and after the inrush current converges, 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 start of the current supply to the motor 241 (time t1).

In addition, 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. In addition, the control unit 20 stops the supply of current to the hydraulic motor 31 when the hydraulic pressure rising due to the driving of the hydraulic motor 31 reaches its maximum value in the hydraulic unit 10.

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.

The parking brake control unit 21 repeatedly executes the process shown in FIG.
6, the parking brake control unit 21 first determines whether 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 an apply request has been made (S2).

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 the current supply to the motor 241 (S4).

Here, the specified time T1 is the time from when current begins 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.

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 hydraulic operation determination process to determine whether or not to operate the hydraulic unit 10 (S5). If the parking brake control unit 21 determines in the hydraulic operation determination process that the hydraulic unit 10 is to be operated, it sets the hydraulic operation flag Fa to 1 to operate the hydraulic unit 10. The hydraulic operation determination process will be described in detail later.

After step S5, the parking brake control unit 21 determines whether the hydraulic operation flag Fa is 1 (S6). If it is determined in step S6 that the hydraulic operation flag Fa is 1 (Yes), the parking brake control unit 21 outputs a pressure increase request and a target hydraulic pressure value to the hydraulic control unit 22 (S7). Here, the target hydraulic pressure value is set to the maximum hydraulic pressure in the hydraulic unit 10.

After step S7, the parking brake control unit 21 sets flag F to 1, which indicates that a pressure increase request or the like has been output to the hydraulic unit 10 (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 (S9). If the parking brake control unit 21 determines in step S6 that the hydraulic operation flag Fa is not 1 (No), the parking brake control unit 21 skips steps S7 and S8 and proceeds to step S9.

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 in operation (S10).

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 control unit 22 (S11). After step S11, the parking brake control unit 21 sets flag F and hydraulic operation flag Fa 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.

In the hydraulic pressure operation determination process shown in Fig. 7, the parking brake control unit 21 first determines whether the longitudinal acceleration sensor 93 is abnormal (S31). As a method of determining whether an abnormality exists, 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.

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). 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).

After step S32 or step S33, the parking brake control unit 21 determines whether the road surface gradient S is equal to or greater than the first predetermined gradient Sth1 (S34). If it is determined in step S34 that S≧Sth1 (Yes), the parking brake control unit 21 sets the hydraulic operation flag Fa to 1 (S37) and ends this process.

If it is determined in step S34 that S is not equal to or greater than Sth1 (No), the parking brake control unit 21 determines whether the road surface gradient S is equal to or greater than a second predetermined gradient Sth2 that is smaller than the first predetermined gradient Sth1 (S35). If it is determined in step S35 that S is equal to or greater than Sth2 (Yes), the parking brake control unit 21 determines whether the estimated temperature Tb of the brake shoe D2 is equal to or greater than a predetermined temperature Tth (S36).

If it is determined in step S36 that Tb ≧ Tth (Yes), the parking brake control unit 21 sets the hydraulic pressure operation flag Fa to 1 (S37) and ends this process. If it is determined in step S35 or step S36 that No, the parking brake control unit 21 ends this process without setting the hydraulic pressure operation flag Fa to 1.

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 a pressure increase request and a target hydraulic pressure value have been acquired from the parking brake control unit 21 (S51).

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).

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 is equal to or greater than 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.

After step S54, the hydraulic 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 control unit 22 passes a current through the outlet valve 14 to open the outlet valve 14 (S56). This reduces the hydraulic pressure.

When 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. When 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. When 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, in the first braking control where no request is received from the parking brake control unit 21, the hydraulic control unit 22 does not operate the hydraulic unit 10, and in the second braking control where a request is received from the parking brake control unit 21, the hydraulic control unit 22 operates the hydraulic unit 10.

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 a state in which current is flowing through the hydraulic motor 31 is shown as "ON" and a state in which no current is flowing through the hydraulic motor 31 is shown as "OFF".

When the vehicle CR is stopped on a slope with a first predetermined gradient Sth1 or more, or when the vehicle CR is stopped on a slope with a second predetermined gradient Sth2 or more with the estimated temperature Tb of the brake shoe D2 being equal to or higher than the predetermined temperature Tth, the control unit 20 receives an apply request (time t1) and starts supplying current to the motor 241 as shown in FIG. 9(b). The control unit 20 then waits until a predetermined time T1 has elapsed, during which the inrush current converges. When the predetermined time T1 has elapsed (time t2), the motor 241 starts rotating.

As a result, the screw shaft 244 shown in Figure 3 starts to move from the release position towards the apply position. As the screw shaft 244 moves from the release position towards the apply position, the load on the screw shaft 244 from the disc spring 247 gradually decreases, so that the current of the motor 241 gradually decreases after time t2, as shown in Figure 9 (b). When the screw shaft 244 moves away from the retainer 246, the load on the screw shaft 244 is no longer applied (time t3), and the current then becomes constant.

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) to cause the hydraulic unit 10 to start increasing the hydraulic pressure in the wheel cylinder D4 (see Figs. 9(a) and (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.

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

Here, the graph shown by the two-dot chain line in Figure 9 (b) is 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 is applied to the motor 241 and the motor current begins to rise at an earlier timing than in the second braking control.

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 in the position shown in Figure 2(b), that is, in the position where it is in contact with the drum D1. Therefore, in the second braking control, the timing at which a load begins to be applied to the motor 241 is delayed compared to the first braking control, and the amount of pulling on the wire 230 can be increased.

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

When the hydraulic braking force decreases due to a reduction in hydraulic pressure, the braking force applied to the wheel W decreases, causing the wheel W to rotate slightly and 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 than in the first braking control, so the amount of rotation of the brake shoe D2 can be kept small and a large decrease in the parking brake force can be prevented. Therefore, when the vehicle CR is stopped on a slope with a first predetermined gradient Sth1 or more, or when the vehicle CR is stopped on a slope with a second predetermined gradient Sth2 or more in a state in which the estimated temperature Tb of the brake shoe D2 is equal to or higher than the predetermined temperature Tth, the vehicle CR can be stopped satisfactorily.

As described above, the following effects can be obtained in this embodiment.
In the case of Sth2≦S<Sth1 and Tb≧Tth, that is, when the vehicle CR stops on a slope with a not so steep gradient in a state where the temperature of the brake shoe D2 is high, the amount of movement of the vehicle CR after stopping on the slope may increase due to a decrease in the frictional force between the brake shoe D2 and the drum D1. In contrast, in this embodiment, when Sth2≦S<Sth1 and Tb≧Tth, the hydraulic unit 10 and the parking brake mechanism 200 are used in combination to press the brake shoe D2 against the drum D1, so that a braking force capable of stopping the vehicle CR can be generated even when the vehicle CR stops on a slope with a not so steep gradient in a state where the temperature of the brake shoe D2 is high. In addition, when Sth2≦S<Sth1 and Tb≧Tth, the hydraulic unit 10 and the parking brake mechanism 200 are used in combination, so that it is not necessary to increase the capacity of the motor 241 of the parking brake mechanism 200 in consideration of the temperature of the brake shoe D2, and costs can be reduced.

When the road surface gradient S is equal to or greater than the first predetermined gradient Sth1, the hydraulic unit 10 and the parking brake mechanism 200 are used together to press the brake shoe D2 against the drum D1, so that a braking force capable of stopping the vehicle CR can be generated even on a steep slope. In addition, when the road surface gradient S is equal to or greater than the first predetermined gradient Sth1, 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, and costs can be reduced.

In the second braking control, operation of the hydraulic unit 10 begins after the supply of current to the motor 241 is started, so that the operation 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, a case in which the hydraulic unit is operated before the supply of current to the motor is started.

In particular, in this embodiment, in the second braking control, operation of the hydraulic unit 10 begins after the parking brake mechanism 200 starts to operate, so that the operation time of the hydraulic unit 10 can be shortened compared to, for example, a case in which the hydraulic unit is operated before the parking brake mechanism starts to operate.

In the second braking control, when the hydraulic pressure increased by driving the hydraulic motor 31 reaches its maximum value in the hydraulic unit 10, the supply of current to the hydraulic motor 31 is stopped, so that the braking force from the hydraulic unit 10 can be maximized when stopping the vehicle CR on a steep slope, thereby lowering the capacity of the motor 241 and further reducing costs.

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 that 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.

Since the temperature of the brake shoe D2 is estimated, there is no need to install a temperature sensor to detect the temperature of the brake shoe D2, which reduces costs.

The above embodiment can be modified in various ways as shown below. In the following description, components that have substantially the same structure as the above embodiment are given the same reference numerals and their description is omitted.

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

Specifically, in this embodiment, the parking brake control unit 21 executes the process shown in Figure 10. The process shown in Figure 10 is a process in which the process shown in Figure 6 has been partially modified. Specifically, the process shown in Figure 10 is a process in which steps S3 and S4 of the process shown in Figure 6 have been moved between steps S8 and S9, and a new step S71 has been added between steps S8 and S3.

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

In the process shown in Figure 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 hydraulic operation determination 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 control unit 22 (S7) before executing the process of step S3 to start supplying current to the motor 241.

As shown in Figure 11, when the hydraulic pressure control unit 22 acquires a pressure increase request and a target hydraulic pressure value from the parking brake control unit 21 (S51: Yes), it performs the processes of 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 the processes of steps S55 and S56 in the same manner as in the previous embodiment.

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

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). In other words, the parking brake control unit 21 starts supplying current to the motor 241 after the hydraulic control unit 22 stops supplying current to the hydraulic motor 31.

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 process of steps S9 to S12 in the same manner as in the above embodiment.

According to this embodiment, as shown in FIG. 12, the period during which current is passed through the hydraulic motor 31 (time t21-t1) and the period during which current is passed through the motor 241 do not overlap, thereby preventing excessive voltage drop caused by passing current through the hydraulic motor 31 and the motor 241 simultaneously.

In the above embodiment, the first braking control and the second braking control are selected based on the road gradient and the temperature of the brake shoe, but the first braking control and the second braking control may be selected based only on the temperature of the brake shoe. In this case, the second braking control is executed when the temperature of the brake shoe is high regardless of the road gradient, so that, for example, it is possible to prevent a car parked on flat ground from moving due to the wind in a typhoon or a vehicle loaded on a ship from moving due to the rocking of the ship.

In the above embodiment, the first braking control and the second braking control are selected and executed when the vehicle is stopped, but for example, the control unit may select and execute the first braking control and the second braking control based on the temperature of the brake shoes when an apply request is received while the vehicle is traveling.

In the above embodiment, the temperature of the brake shoe D2 was estimated based on the hydraulic pressure and the wheel speed, but the temperature may also be estimated based on, for example, the hydraulic pressure, the wheel speed, and other parameters.

9, the current supply to the hydraulic motor 31 is started immediately (at the time) when the parking brake mechanism 200 starts to move, but the current supply to the hydraulic motor 31 may be started at any timing as long as the pulling force starts to increase after the hydraulic pressure increase is completed. For example, the current supply 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.

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 the vehicle's ECU (Electronic Control Unit), may also be used as the brake control device.

In the above embodiment, the parking brake mechanism 200 installed in the drum brake D is exemplified, but it may be, for example, a parking brake mechanism installed in a disc brake. 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.

The elements described in the above embodiments and variants may be implemented in any combination.

Claims (3)

a hydraulic braking device that generates a hydraulic braking force by pressing a friction member against a rotating body that rotates integrally with the wheel by 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 by a driving force of a motor;
A brake control device for controlling
obtaining a temperature of the friction member when a request to generate the parking brake force is received;
When the temperature is lower than a predetermined temperature, a first braking control is executed to press the friction member against the rotating body using only the parking brake mechanism;
When the temperature is equal to or higher than the predetermined temperature, 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 ;
2. The brake control device according to claim 1, wherein in the second braking control, the hydraulic braking device starts operating after the supply of current to the motor starts . 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. The brake control device according to claim 1 , wherein the temperature of the friction member is estimated based on at least a hydraulic pressure and a wheel speed.

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