Brake control device, brake control method, and brake control program

Abstract

To provide a technique that enables appropriate parking of a vehicle upon detecting that one of parking brake devices respectively provided on its right and left wheels is in an abnormal state.SOLUTION: A brake control device 20 includes: an output control unit 40 configured to, upon detecting that only one of right and left parking brake devices 24 is in an abnormal state, cause the other parking brake device 24 to output a first braking force; and a movement detection processing unit 34 configured to detect movement of the vehicle when the first braking force is output. When detecting no vehicle movement during the output of the first braking force, the output control unit 40 causes the other the parking brake device to output a second braking force larger than the first braking force to park the vehicle.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technique for controlling a parking brake device, and more particularly to control when one of the parking brake devices provided on the left and right sides enters an abnormal state. [Background technology]

[0002] Patent Document 1 discloses an electric parking brake device that includes a parking brake provided on the rear wheels of a vehicle, an actuator unit that applies braking force to the parking brake, and a parking brake control device that controls the actuator unit. This electric parking brake control device prohibits activation of the parking brake when an abnormality is detected in the electric parking brake control device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-123797 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology disclosed in Patent Document 1 prohibits the operation of the parking brake when an abnormality is detected in the electric parking brake control device, but depending on the location of the abnormality in the electric parking brake device, it may be possible to activate the parking brake and park the vehicle, which may be inconvenient.

[0005] An object of the present invention is to provide a technology that enables appropriate parking when it is detected that one of the parking brake devices provided on the left and right wheels is in an abnormal state. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the present invention is a brake control device that controls parking brake devices provided on left and right wheels, and includes an output control unit that, when an abnormal state of only one of the left and right parking brake devices is detected, causes the other parking brake device to output a first braking force, and a movement detection processing unit that detects vehicle movement when the first braking force is output. If the output control unit does not detect vehicle movement while outputting the first braking force, it causes the other parking brake device to output a second braking force greater than the first braking force to park the vehicle.

[0007] Another aspect of the present invention is a brake control method using a brake control device that controls parking brake devices provided on left and right wheels, and includes the steps of: when an abnormal state of only one of the left and right parking brake devices is detected, causing the other parking brake device to output a first braking force; detecting vehicle movement when the first braking force is output; and, if no vehicle movement is detected while the first braking force is being output, causing the other parking brake device to output a second braking force greater than the first braking force to park the vehicle.

[0008] Another aspect of the present invention is a brake control program that causes a computer to operate brake control devices that control parking brake devices provided on left and right wheels, respectively, to execute the following steps: when an abnormal state is detected in only one of the left and right parking brake devices, causing the other parking brake device to output a first braking force, detecting vehicle movement when the first braking force is output, and, if no movement of the vehicle is detected while the first braking force is being output, causing the other parking brake device to output the second braking force that is greater than the first braking force to park the vehicle. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a technique that allows appropriate parking when it is detected that either one of the parking brake devices provided on the left and right wheels is in an abnormal state. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram illustrating a functional configuration of a brake control system. [Figure 2] FIG. 10 is a diagram showing the flow of parking brake control using the detection result of the slope detection processing unit. [Figure 3] FIG. 10 is a diagram showing the flow of parking brake control for accurately checking whether the vehicle is sliding downhill. [Figure 4] 4 is a flowchart of parking brake control according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1 is a diagram showing the functional configuration of a brake control system 10. Each function of the brake control system 10 can be configured in terms of hardware using circuit blocks, memory, and other LSIs, and in terms of software, can be realized by system software, application programs, etc. loaded into memory. Therefore, those skilled in the art will understand that each function of the brake control system 10 can be realized in various forms using only hardware, only software, or a combination thereof, and is not limited to any one of these. The brake control system 10 may be installed in a vehicle, and the vehicle may be capable of autonomous driving.

[0012] The brake control system 10 includes a pedal operation detection sensor 12, an input unit 14, a movement detection sensor 16, a slope detection sensor 18, a brake control device 20, a hydraulic brake device 22, and a parking brake device 24.

[0013] The pedal operation detection sensor 12 detects the amount of brake pedal operation and transmits the detection result to the brake control device 20. The pedal operation detection sensor 12 is, for example, a stroke sensor that detects the amount of brake pedal depression. The input unit 14 is a switch or touch sensor for switching the parking brake device 24 on / off, and transmits the driver's input result to the brake control device 20.

[0014] The movement detection sensor 16 detects the movement of the vehicle. For example, the movement detection sensor 16 may be a wheel speed sensor that transmits the rotation speed of the wheel to the brake control device 20. The movement detection sensor 16 may also detect the rotation of the axle.

[0015] The slope detection sensor 18 is a sensor for detecting whether the location where the vehicle is located is a slope or not, and transmits the detection result to the brake control device 20. The slope detection sensor 18 is, for example, an inclination sensor or an optical radar. The vehicle is also provided with sensors for detecting information about the vehicle's running state, such as a brake pressure sensor, an acceleration sensor, and a vehicle speed sensor.

[0016] The brake control device 20 controls a hydraulic brake device 22 and a parking brake device 24. The hydraulic brake device 22 uses hydraulic pressure to move a piston back and forth. When the piston advances due to increased pressure, it presses the brake pads toward the brake discs, thereby applying braking force to the wheels.

[0017] The parking brake device 24 operates in response to the input result of the input unit 14, and applies a braking force to the wheels when parking. The parking brake device 24 is provided on each of the left and right wheels. The parking brake device 24 may be provided only on the rear wheels. The parking brake device 24 includes a motor, a screw, brake pads, and a brake disc. In the following description, the parking brake device 24 may be referred to as an EPB (Electric Parking Brake).

[0018] The motor rotates the screw to move it forward and backward. As the screw moves forward and backward, it moves the brake pads forward and backward toward the brake disc. When the power is turned off during parking, the screw stops moving forward and backward, so the brake pads remain pressed against the brake disc. The parking brake device 24 can adjust the braking force by the amount of drive of the motor, i.e., the distance the screw moves forward and backward. The time it takes for the parking brake device 24 to exert braking force is longer than that of the hydraulic brake device 22. An EPB sensor may also be provided that detects the amount of operation of the parking brake device 24, i.e., the braking force exerted by the parking brake device 24. The EPB sensor may detect the distance the screw moves forward and backward, or it may detect the number of rotations of the screw.

[0019] The brake pads and brake discs of the parking brake device 24 are the same as those of the hydraulic brake device 22. That is, like the hydraulic brake device 22, the parking brake device 24 exerts braking force by pressing the brake pads against the brake disc. For example, the screws of the parking brake device 24 are provided inside the piston of the hydraulic brake device 22. When the driver turns on the input unit 14 while depressing the brake pedal, both the hydraulic brake device 22 and the parking brake device 24 act to press the brake pads against the brake disc.

[0020] The brake control device 20 includes an acquisition unit 30, a braking amount determination unit 32, a movement detection processing unit 34, a slope detection processing unit 36, a judgment unit 38, and an output control unit 40. The acquisition unit 30 acquires detection results from the pedal operation detection sensor 12, the input unit 14, the movement detection sensor 16, and the slope detection sensor 18.

[0021] The braking amount determination unit 32 determines the braking amount of the hydraulic brake device 22 based on the detection result of the pedal operation detection sensor 12. The braking amount determination unit 32 determines the braking amount to be exerted by the hydraulic brake device 22 in accordance with the operation amount of the brake pedal. The output control unit 40 controls the hydraulic brake device 22 in accordance with the determination result of the braking amount determination unit 32.

[0022] The movement detection processing unit 34 detects the movement of the vehicle based on the detection results of the movement detection sensor 16. The movement detection processing unit 34 determines that the vehicle has moved when the wheel speed sensor detects the rotation of any wheel, and determines that the vehicle is not moving when the rotation of all wheels is not detected. If there is an abnormality in one of the parking brake devices 24 and the vehicle is parked using only the parking brake device 24 on one side, the wheels on the abnormal side may rotate while the wheels on the normal side remain locked, causing the vehicle to slide down. The movement detection processing unit 34 detects the vehicle sliding down.

[0023] The slope detection processing unit 36 ​​detects whether the location where the vehicle is located is a slope based on the detection result of the slope detection sensor 18. For example, if the inclination sensor detects an angle within plus or minus 0.5 degrees, the slope detection processing unit 36 ​​determines that the road is not a slope, and if the inclination sensor detects an angle outside the range of plus or minus 0.5 degrees, the slope detection processing unit 36 ​​determines that the road is a slope.

[0024] The determination unit 38 receives information indicating on / off from the input unit 14 and starts processing to activate or release the parking brake devices 24. The determination unit 38 determines the target braking force to be generated by the parking brake devices 24. If both the left and right parking brake devices 24 are in an abnormal state, a warning display is turned on, so that the driver can recognize that the parking brake devices 24 cannot be activated. The determination unit 38 may determine whether the parking brake devices 24 are in an abnormal state based on the detection result of the EPB sensor.

[0025] When only one of the left and right parking brake devices 24 is detected to be in an abnormal state, the determination unit 38 determines to have the other parking brake device 24 output a first braking force. The first braking force is a target braking force. The output control unit 40 causes the other parking brake device 24 to output the first braking force according to the determination result of the determination unit 38. The movement detection processing unit 34 detects movement of the vehicle when the first braking force is output. In other words, the movement detection processing unit 34 detects whether the vehicle is sliding downhill. If the determination unit 38 does not detect movement of the vehicle while outputting the first braking force, it determines to have the other parking brake device 24 output a second braking force greater than the first braking force. The output control unit 40 causes the other parking brake device 24 to output the second braking force according to the determination result of the determination unit 38, thereby parking the vehicle. The second braking force is a target braking force greater than the first braking force. In other words, when one side of the parking brake device 24 is malfunctioning, the brake control device 20 stops the vehicle with a small first braking force to check whether the vehicle is rolling over, and if the vehicle is not rolling over, parks the vehicle with the normal second braking force. If the vehicle does not roll over with the small first braking force, it is confirmed that the possibility of the vehicle rolling over is extremely low. As a result, when parking the vehicle with the parking brake device 24 that is malfunctioning on one side, it is confirmed that the vehicle will not roll over, and the vehicle can be parked appropriately.

[0026] The second braking force is a normal target braking force that is used when no abnormal state exists. The first braking force is determined by experiment or the like, and may be set in the range of 0.25 to 0.75 times the second braking force, for example.

[0027] If the determination unit 38 detects movement of the vehicle while the first braking force is being output, it determines to release the parking brake device 24, terminate the operation of the parking brake device 24, and issue a warning that parking is not possible, so that the driver receives the warning and parks the vehicle in another location.

[0028] If neither of the left and right parking brake devices 24 is in an abnormal state, the determination unit 38 determines to cause both parking brake devices 24 to output the second braking force. The output control unit 40 parks the vehicle by causing both parking brake devices 24 to output the second braking force in accordance with the determination result of the determination unit 38. As a result, if there is no abnormality in the parking brake devices 24, the vehicle is parked with the normal second braking force.

[0029] Next, the control for parking after checking whether the vehicle is on a slope will be described with reference to Fig. 2. Fig. 2 is a diagram showing the flow of parking brake control using the detection result of the slope detection processing unit 36. The horizontal axis in Fig. 2 represents the same time axis. In Fig. 2, only one of the left and right parking brake devices 24 is in an abnormal state.

[0030] At time t0, the vehicle is on a slope and the driver is depressing the brake pedal. At this time, the wheel speed is zero and the vehicle is not rolling downhill.

[0031] At time t1, the driver turns on the input unit 14, which is the EPB switch, and the determination unit 38 starts parking brake control. When the slope detection processing unit 36 ​​detects that the parking position is on a slope, the determination unit 38 determines to cause the other parking brake device 24 to output a first braking force Bf. The output control unit 40 causes the other parking brake device 24 to output the first braking force Bf in accordance with the determination result of the determination unit 38.

[0032] At time t2, the driver releases the brake pedal, reducing the pressure in the hydraulic brake device 22. The movement detection processing unit 34 detects whether the vehicle is rolling downhill between time t2 and time t3, that is, after the hydraulic brake device 22 is released. The time period for confirming whether the vehicle is rolling downhill, that is, the time period from time t2 to time t3, is determined by experimentation or the like, but is set in the range of, for example, one second to several seconds.

[0033] At time t3, if the determination unit 38 does not detect movement of the vehicle while outputting the first braking force Bf, it determines to cause the other parking brake device 24 to output a second braking force Bs greater than the first braking force Bf. The output control unit 40 causes the other parking brake device 24 to output the second braking force Bs and parks the vehicle in accordance with the determination result of the determination unit 38. In this way, when the parking position is on a slope, the brake control device 20 confirms that the small first braking force Bf will not cause the vehicle to roll over, and then parks the vehicle with the second braking force Bs.

[0034] If the movement detection processing unit 34 detects that the vehicle is sliding down between time t2 and time t3, the judgment unit 38 decides to terminate the operation of the parking brake device 24 and to issue a warning that parking is not possible.

[0035] If the determination unit 38 detects at time t1 that the parking position is not on a slope, it determines to output a second braking force Bs greater than the first braking force Bf without going through the stage of outputting the first braking force Bf and detecting vehicle movement. The output control unit 40, in accordance with the determination result of the determination unit 38, outputs the second braking force Bs to park the vehicle without going through the stage of maintaining the first braking force Bf from time t1. If the parking position is not on a slope, the vehicle will not roll over, so the brake control device 20 parks the vehicle at the first braking force Bf without checking for roll over.

[0036] Next, control for parking by checking whether the vehicle is sliding down without taking into account the influence of the hydraulic brake device 22 will be described with reference to Fig. 3. Fig. 3 is a diagram showing the flow of parking brake control for accurately checking whether the vehicle is sliding down. The horizontal axis in Fig. 3 represents the same time axis. In Fig. 3, only one of the left and right parking brake devices 24 is in an abnormal state.

[0037] The parking brake device 24 exerts braking force by pressing the same brake pads as the hydraulic brake device 22 against the brake disc. Therefore, when the driver turns on the parking brake device 24 while depressing the brake pedal, both forces are applied to the brake pads. As a result, a braking force greater than the first braking force may be exerted when detecting whether the vehicle is rolling downhill. Therefore, the brake control device 20 checks whether the vehicle is rolling downhill after reducing the pressure in the hydraulic brake device 22.

[0038] At time t0, the driver depresses the brake pedal, and braking force is applied to the non-EPB controlled wheels and the EPB controlled wheels by the hydraulic brake device 22 using brake hydraulic pressure. At time t0, the wheel speeds of the non-EPB controlled wheels and the EPB controlled wheels are zero, and no skid has occurred. The non-EPB controlled wheels are the front wheels and the rear wheels corresponding to the parking brake device 24 in an abnormal state. The EPB controlled wheels are the rear wheels corresponding to the parking brake device 24 in a normal state.

[0039] At time t1, the driver turns on the input unit 14, which is the EPB switch, and the determination unit 38 starts parking brake control. The determination unit 38 determines to reduce the pressure of the hydraulic brake device 22 of the EPB-controlled wheel that is the same as the other parking brake device 24, causing the other parking brake device 24 to output a first braking force. In accordance with the determination result of the determination unit 38, the output control unit 40 reduces the pressure of the hydraulic brake device 22 of the EPB-controlled wheel from time t1, causing the other parking brake device 24 to output the first braking force. This eliminates the influence of the hydraulic brake device 22 only on the EPB-controlled wheel. Because the hydraulic brake devices 22 of the non-EPB-controlled wheels are operating, the vehicle does not roll over. In this way, by first turning off the hydraulic brake device 22 of only the EPB-controlled wheels while the driver is depressing the brake pedal, it is possible to safely and accurately detect the occurrence of vehicle rollover.

[0040] At time t2, the driver releases the brake pedal. The determination unit 38 determines to reduce the pressure of the hydraulic brake device 22 of the non-EPB controlled wheel, and the output control unit 40 reduces the pressure of the hydraulic brake device 22 of the non-EPB controlled wheel. The hydraulic brake device 22 has a faster response than the parking brake device 24 and is immediately turned off. As a result, only the parking brake device 24 of the EPB controlled wheel is braking with the first braking force.

[0041] The movement detection processing unit 34 detects a vehicle skid between time t2 and time t3, that is, after the hydraulic brake device 22 is turned off, while only the parking brake device 24 of the EPB-controlled wheel is braking with the first braking force. In FIG. 3, the non-EPB-controlled wheel starts to rotate from time t2, and the EPB-controlled wheel rotates in response, causing a skid 50. The movement detection processing unit 34 detects the movement of the vehicle and determines that a skid has occurred. By creating a state in which no braking force is being applied by the hydraulic brake device 22 to the EPB-controlled wheel and only the parking brake device 24 of the EPB-controlled wheel is braking with the first braking force, it is possible to accurately determine whether the vehicle is skidding.

[0042] At time t3, the occurrence of the vehicle rolling over causes the determination unit 38 to terminate the operation of the parking brake device 24 and to decide to issue a warning that parking is not possible. In response to this warning, at time t4, the driver depresses the brake pedal, and braking force is applied to both the EPB-controlled wheels and the non-EPB-controlled wheels by the operation of the hydraulic brake device 22.

[0043] If the vehicle does not roll down between time t2 and time t3, the output control unit 40 causes the other parking brake device 24 to output the second braking force Bs to park the vehicle.

[0044] 4 is a flowchart of the parking brake control according to the embodiment. When the driver turns on the input unit 14, the determination unit 38 starts the parking brake control (S10). The slope detection processing unit 36 ​​determines whether the parking position is on a slope based on the detection result of the slope detection sensor 18 (S12).

[0045] The determination unit 38 determines whether only one of the parking brake devices 24 is malfunctioning (S14). The determination unit 38 may determine whether the parking brake device 24 is in an abnormal state based on the motor drive amount and the detection result of the EPB sensor of the parking brake device 24. If both of the parking brake devices 24 are in an abnormal state, the operation of the parking brake device 24 is terminated.

[0046] If it is determined that the parking brake devices 24 on both sides are not faulty (N in S14), the judgment unit 38 decides to output the normal second braking force, and the output control unit 40 causes the parking brake devices 24 that are not faulty to output the second braking force (S26), thereby completing the parking brake control.

[0047] If it is determined that one of the parking brake devices 24 has failed (Y in S14), the determination unit 38 determines whether the parking position is on a slope (S16). If the parking position is not on a slope (N in S16), the determination unit 38 determines to output the normal second braking force, and the output control unit 40 causes the parking brake device 24 that is not failed to output the second braking force (S26), thereby completing the parking brake control.

[0048] If the parking position is on a slope (Y in S16), the determination unit 38 determines to reduce the brake fluid pressure at the EPB-controlled wheels. The output control unit 40 reduces the brake fluid pressure at the EPB-controlled wheels in accordance with that determination (S18). The EPB-controlled wheels are wheels that correspond to parking brake devices 24 that are not malfunctioning. At this time, while the driver is depressing the brake pedal, the brake fluid pressure at the non-EPB-controlled wheels remains.

[0049] The determination unit 38 determines to cause the parking brake device 24 after pressure reduction to output the first braking force, and the output control unit 40 causes the parking brake device 24 corresponding to the EPB controlled wheel to output the first braking force (S20). The movement detection processing unit 34 detects movement of the vehicle, i.e., the vehicle rolling downhill, and the determination unit 38 determines whether the vehicle has moved while operating with the first braking force (S22).

[0050] If the vehicle is not moving while the first braking force is operating (N in S22), the judgment unit 38 decides to output the normal second braking force, and the output control unit 40 causes the parking brake device 24 that is not malfunctioning to output the second braking force (S26), completing the parking brake control.

[0051] If the vehicle is moving while the first braking force is being applied (Y in S22), the determination unit 38 determines to terminate the operation of the parking brake device 24 and issue a warning that parking is not possible. The output control unit 40 releases the operation of the parking brake device 24 in accordance with that determination (S24).

[0052] Although the embodiment has been described in which the output control unit 40 outputs the same second braking force when the parking brake devices 24 on both sides are not malfunctioning (N in S14), when the parking position is not on a slope (N in S16), and when the vehicle is not moving while operating with the first braking force (N in S22), the embodiment is not limited to this. For example, the second braking force may be different depending on the situation.

[0053] The present disclosure has been described above based on examples. The present disclosure is not limited to the above examples, and various modifications such as design changes may be made based on the knowledge of those skilled in the art. [Explanation of symbols]

[0054] 10 Brake control system, 12 Pedal operation detection sensor, 14 Input unit, 16 Movement detection sensor, 18 Slope detection sensor, 20 Brake control device, 22 Hydraulic brake device, 24 Parking brake device, 30 Acquisition unit, 32 Braking amount determination unit, 34 Movement detection processing unit, 36 Slope detection processing unit, 38 Judgment unit, 40 Output control unit.

Claims

1. A brake control device that controls parking brake devices provided on left and right wheels, an output control unit that, when an abnormal state of only one of the left and right parking brake devices is detected, causes the other parking brake device to output a first braking force; a movement detection processing unit that detects movement of the vehicle when the first braking force is output, a second braking force greater than the first braking force output from the other parking brake device to park the vehicle if the output control unit does not detect movement of the vehicle while outputting the first braking force;

2. Further provided is a slope detection processing unit for detecting a slope, 2. The brake control device according to claim 1, wherein the output control unit, when detecting that the parking position is not on a slope, outputs a second braking force greater than the first braking force to park the vehicle without going through a step of outputting the first braking force and detecting movement of the vehicle.

3. The parking brake device exerts braking force by pressing brake pads against a brake disc, the same as in a hydraulic brake device, 3. The brake control device according to claim 1, wherein, when an abnormal state of only one of the left and right parking brake devices is detected, the output control unit reduces the pressure of the hydraulic brake device of the same wheel as the other parking brake device, causing the other parking brake device to output a first braking force.

4. A brake control method using a brake control device that controls parking brake devices provided on left and right wheels, When an abnormal state of only one of the left and right parking brake devices is detected, outputting a first braking force to the other parking brake device; detecting a movement of the vehicle when the first braking force is output; and if no movement of the vehicle is detected while the first braking force is being output, causing the other parking brake device to output a second braking force greater than the first braking force to park the vehicle.

5. A computer for operating a brake control device that controls parking brake devices provided on each of the left and right wheels, When an abnormal state of only one of the left and right parking brake devices is detected, outputting a first braking force to the other parking brake device; detecting a movement of the vehicle when the first braking force is output; and if no movement of the vehicle is detected while the first braking force is being output, causing the other parking brake device to output a second braking force greater than the first braking force to park the vehicle.

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