Brake control device

Abstract

A brake control device 50 controls the braking force applied to a vehicle 10. If the reversing vehicle 10 is to be stopped, a processing circuit 51 of the brake control device 50 functions as a control unit M15 which performs first stopping control for controlling the braking force so as to suppress a change in the attitude of the vehicle 10 caused by stopping.

Description

Braking control device

[0001] The present invention relates to a brake control device provided in a vehicle.

[0002] Patent Document 1 discloses a device that controls the braking force and driving force of a vehicle to stop the vehicle at a predetermined stopping position when the vehicle is reversed and stopped.

[0003] Japanese Patent Application Publication No. 11-105686

[0004] SUMMARY OF THE INVENTION An object of the present invention is to improve the comfort of vehicle occupants when a vehicle moving backward is brought to a stop.

[0005] A braking control device for solving the above problem is a device for controlling a braking force applied to a vehicle, and the braking control device includes a control unit that performs a first stopping control for controlling the braking force when stopping a vehicle moving backward so as to suppress a change in the attitude of the vehicle caused by stopping the vehicle.

[0006] The braking control device has the effect of improving the comfort of the vehicle occupants when stopping a vehicle moving backward.

[0007] Fig. 1 is a schematic diagram showing a vehicle equipped with a brake control device according to an embodiment. Fig. 2 is a timing chart showing an example of a second vehicle stop control being performed when a braking force is applied to a forward-moving vehicle to stop the vehicle. Fig. 3 is a flowchart showing a series of processes executed by the brake control device of Fig. 1. Fig. 4 is a timing chart showing an example of a first vehicle stop control being performed when a braking force is applied to a backward-moving vehicle to stop the vehicle.

[0008] An embodiment of a brake control device will be described below with reference to Figures 1 to 4. Figure 1 illustrates a vehicle 10 equipped with a brake control device 50. The vehicle 10 includes a brake operating member 11, a shift device 15, a plurality of wheels, a plurality of friction brakes, and a brake actuator 30. The plurality of wheels includes two front wheels 12 and two rear wheels 13.

[0009] <Vehicle Operation System> The brake operating member 11 is a member that is operated by the driver when applying a braking force to the vehicle 10. An example of the brake operating member 11 is a brake pedal.

[0010] The shift device 15 is operated by the driver of the vehicle 10 to select one range from a plurality of ranges. The plurality of ranges include D range, R range, N range, and P range. D range is the forward range. R range is the reverse range. N range is the neutral range. P range is the parking range. The shift device 15 outputs information regarding the range selected by the driver's operation to the brake control device 50.

[0011] <Friction Brakes> The multiple friction brakes each apply a braking force to the corresponding wheel. Of the multiple friction brakes, the friction brake corresponding to the front wheel 12 is referred to as the "friction brake 20A," and the friction brake corresponding to the rear wheel 13 is referred to as the "friction brake 20B." The friction brakes 20A and 20B each have a wheel cylinder 21, a rotating body 22, and a friction portion 23. The rotating body 22 rotates integrally with the wheel. Therefore, braking force is applied to the wheel by pressing the friction portion 23 against the rotating body 22. The force pressing the friction portion 23 against the rotating body 22 increases as the wheel hydraulic pressure, which is the hydraulic pressure in the wheel cylinder 21, increases. Therefore, the friction brakes 20A and 20B can apply a greater vehicle braking force to the wheel as the wheel hydraulic pressure increases.

[0012] In the following description, the braking force applied to the front wheels 12 by the friction brake 20A will be referred to as the "front wheel friction braking force BPFF." The braking force applied to the rear wheels 13 by the friction brake 20B will be referred to as the "rear wheel friction braking force BPFR." The sum of the braking forces applied to the multiple wheels 12, 13 will be referred to as the "vehicle braking force BPAl." In the vehicle 10, the sum of the front wheel friction braking force BPFF and the rear wheel friction braking force BPFR corresponds to the vehicle braking force BPAl.

[0013] <Brake Actuator> The brake actuator 30 controls the wheel hydraulic pressure of the plurality of wheel cylinders 21 to control the braking force applied to the wheels 12, 13. For example, the brake actuator 30 has a pressure source that supplies brake fluid to the plurality of wheel cylinders 21. The pressure source is, for example, an electric pump and an electric cylinder. The brake actuator 30 can adjust the front wheel hydraulic pressure and the rear wheel hydraulic pressure separately.

[0014] <Detection System> The detection system of the vehicle 10 includes a plurality of sensors that output detection signals to the braking control device 50. The plurality of sensors includes a brake sensor 101, a plurality of wheel speed sensors 102, and a longitudinal acceleration sensor 103.

[0015] The brake sensor 101 detects information related to the operation of the brake operating member 11 by the driver. An example of the brake sensor 101 is a stroke sensor that detects the amount of operation of the brake operating member 11 by the driver. The amount of operation based on the detection signal of the brake sensor 101 is referred to as the "braking operation amount X." The detection system may also include a sensor that detects the operating force of the brake operating member 11 by the driver.

[0016] A wheel speed sensor 102 is provided for each of the plurality of wheels. Each of the plurality of wheel speed sensors 102 detects the rotational speed of the corresponding wheel. The rotational speed of the wheel based on the detection signal of the wheel speed sensor 102 is referred to as the "wheel speed VW." The traveling speed of the vehicle 10 calculated based on the wheel speeds VW of the plurality of wheels 12, 13 is referred to as the "vehicle speed VS."

[0017] The longitudinal acceleration sensor 103 detects the longitudinal acceleration of the vehicle 10 out of the accelerations acting on the vehicle 10. The longitudinal acceleration of the vehicle 10 based on the detection signal of the longitudinal acceleration sensor 103 is referred to as "longitudinal acceleration Gx."

[0018] <Brake Control Device> The brake control device 50 includes a processing circuit 51. One example of the processing circuit 51 is an electronic control device. In this case, the processing circuit 51 includes a CPU 52, a first memory 53, and a second memory 54. The first memory 53 stores a control program executed by the CPU 52. The second memory 54 stores calculation results of the CPU 52, etc. When the CPU 52 executes the control program in the first memory 53, the processing circuit 51 controls the brake actuator 30 to activate the plurality of friction brakes 20A, 20B. In other words, the processing circuit 51 can adjust the vehicle braking force BPAl by activating the plurality of friction brakes 20A, 20B.

[0019] <Outline of Vehicle-Stopping Braking Control> The processing circuit 51 performs vehicle-stopping braking control when the driver is operating the brake operating member 11. The vehicle-stopping braking control is an example of "vehicle-stopping control" that controls the vehicle braking force BPAl to suppress changes in the posture of the vehicle 10 that occur when the vehicle 10 is stopped by applying a braking force to the vehicle 10 to stop it.

[0020] The second vehicle-stopping braking control, which is one of the vehicle-stopping braking controls, will be described with reference to Figure 2. The second vehicle-stopping braking control is a vehicle-stopping braking control performed when stopping the forward-moving vehicle 10. In other words, the second vehicle-stopping braking control corresponds to a "second vehicle-stopping control" that is performed when stopping the forward-moving vehicle 10 just before the vehicle 10 stops.

[0021] At timing t11 while the vehicle 10 is moving forward, the driver begins to operate the brake operating member 11. In this case, as shown in FIG. 2B, the processing circuit 51 derives a required braking force BPRq. The required braking force BPRq is a required value for the vehicle braking force BPAl. For example, the processing circuit 51 derives a required braking force BPRq such that the greater the braking operation amount X of the brake operating member 11, the greater the required braking force BPRq. When the vehicle body speed VS of the vehicle 10 is greater than the first vehicle body speed determination value VSth1, as before timing t12, the processing circuit 51 sets the required braking force BPRq as the command braking force BPTr, as shown in FIG. 2D. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPAl becomes the command braking force BPTr.

[0022] When a braking force is applied to the vehicle 10 in this manner, the vehicle speed VS decreases as shown in Fig. 2A. Also, as shown in Fig. 2C, the absolute value of the longitudinal acceleration Gx increases as the vehicle braking force BPAl increases.

[0023] When the vehicle speed VS reaches the first vehicle speed determination value VSth1 at timing t12, the processing circuit 51 starts the second stationary braking control. The first vehicle speed determination value VSth1 is an example of a threshold value for setting the start timing of the stationary braking control. From timing t12, the processing circuit 51 starts an increasing correction process for the second stationary braking control. In the increasing correction process, the processing circuit 51 sets a vehicle braking force greater than the required braking force BPRq as the commanded braking force BPTr. For example, the processing circuit 51 sets the sum of the required braking force BPRq and the offset value ΔBP as the commanded braking force BPTr. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPAl becomes the commanded braking force BPTr. As a result, even if the required braking force BPRq remains the same, the absolute value of the longitudinal acceleration Gx of the vehicle 10 becomes greater by the amount of the offset value ΔBP than before timing t12.

[0024] At timing t13, the vehicle speed VS becomes the second vehicle speed determination value VSth2. A vehicle speed smaller than the first vehicle speed determination value VSth1 is set as the second vehicle speed determination value VSth2. When the vehicle speed VS is equal to or less than the second vehicle speed determination value VSth2, it is determined that the vehicle 10 is approaching the predicted stop position PS. The predicted stop position PS is a predicted position where the vehicle 10 will stop. The processing circuit 51 shifts the processing of the second stop-time braking control from an increase correction processing to a decrease correction processing when the vehicle 10 is about to stop. In the decrease correction processing, the processing circuit 51 reduces the command braking force BPTr. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPAl becomes the command braking force BPTr. By performing the decrease correction processing in this manner, the processing circuit 51 causes the vehicle braking force BPAl to become smaller than the required braking force BPRq. As a result, even if the required braking force BPRq remains the same, the absolute value of the longitudinal acceleration Gx of the vehicle 10 gradually decreases.

[0025] At timing t14, the command braking force BPTr becomes equal to the holding braking force BPh. At timing t14, in the decrease correction process, the processing circuit 51 holds the command braking force BPTr at the holding braking force BPh. In the second stop-state braking control, the stop-state maintaining braking force BPth is set as the holding braking force BPh. The stop-state maintaining braking force BPth is the minimum vehicle braking force required to keep the vehicle 10 stopped on the road surface on which the vehicle 10 is traveling, or a vehicle braking force slightly greater than the minimum vehicle braking force.

[0026] Of the reduction correction processes, the process of reducing the command braking force BPTr to the held braking force BPh is referred to as a "reduction process." Of the reduction correction processes, the process of maintaining the command braking force BPTr at the held braking force BPh is referred to as a "maintenance process."

[0027] Before the vehicle 10 stops, a deceleration inertia force, which is an inertia force resulting from deceleration, acts on the vehicle 10. The deceleration inertia force is correlated with the vehicle braking force BPAl and acts on the vehicle 10 in the traveling direction. Before the vehicle 10 stops, the longitudinal acceleration Gx has a value corresponding to the deceleration inertia force. However, when the vehicle 10 stops at timing t15, the deceleration inertia force becomes 0 (zero). Therefore, as shown in FIG. 2C , the longitudinal acceleration Gx fluctuates before and after the vehicle 10 stops.

[0028] When the vehicle-stop braking control is being implemented, the vehicle braking force BPAl when the vehicle is stopped is smaller than the required braking force BPRq. Therefore, when the vehicle is stopped while the vehicle-stop braking control is being implemented, the fluctuation in the longitudinal acceleration Gx when the vehicle is stopped is smaller than when the vehicle is stopped without the vehicle-stop braking control being implemented. As described above, the smaller the fluctuation in the longitudinal acceleration Gx, the smaller the change in the posture of the vehicle 10 caused by stopping, thereby improving the comfort of the occupants when the vehicle is stopped. On the other hand, if the vehicle braking force BPAl when the vehicle is stopped is reduced to improve the comfort of the occupants when the vehicle is stopped, the feeling of stopping felt by the occupants when the vehicle is stopped is reduced. The feeling of stopping is the sensation felt by the occupants that the vehicle 10 has stopped.

[0029] In the example shown in FIG. 2 , when the processing circuit 51 determines that the vehicle 10 has stopped at timing t15, it transitions the processing of the second stationary braking control from the reduction correction processing to the degeneration processing. In the degeneration processing, the processing circuit 51 increases the command braking force BPTr. For example, the processing circuit 51 increases the command braking force BPTr to the required braking force BPRq. The processing circuit 51 controls the brake actuator 30 based on the command braking force BPTr, thereby increasing the vehicle braking force BPAl. When the command braking force BPTr becomes equal to the required braking force BPRq at timing t16, the processing circuit 51 ends the second stationary braking control.

[0030] <Functional Configuration of Processing Circuit> The functional configuration of the processing circuit 51 will be described with reference to Fig. 1. The CPU 52 executes the control program in the first memory 53, causing the processing circuit 51 to function as multiple functional units. These multiple functional units are functional units for applying braking force to the vehicle 10 to bring it to a stop. The multiple functional units include an acquisition unit M11, a detection unit M13, and a control unit M15.

[0031] <Acquisition Unit> The acquisition unit M11 acquires the traveling direction of the traveling vehicle 10. For example, when the D range is selected by the shift device 15, the acquisition unit M11 acquires the forward direction as the traveling direction. When the R range is selected by the shift device 15, the acquisition unit M11 acquires the reverse direction as the traveling direction.

[0032] The acquisition unit M11 may acquire the traveling direction of the vehicle 10 based on information other than the range selected by the shift device 15. For example, if the vehicle 10 is equipped with a camera that captures images of the outside of the vehicle, the acquisition unit M11 may acquire the traveling direction by analyzing images captured by the camera. The acquisition unit M11 may also acquire the traveling direction of the vehicle 10 based on detection signals from on-board sensors such as the wheel speed sensor 102 and the longitudinal acceleration sensor 103.

[0033] <Detection Unit> The detection unit M13 detects that the wheels 12, 13 have come into contact with the wheel chock. When the vehicle 10 is moving backward, the detection unit M13 detects that the rear wheel 13 has come into contact with the wheel chock, and when the vehicle 10 is moving forward, the detection unit M13 detects that the front wheel 12 has come into contact with the wheel chock.

[0034] When the wheels come into contact with the wheel stoppers, the vehicle speed VS drops sharply or the vehicle 10 stops. Therefore, the detection unit M13 detects that the wheels 12, 13 have come into contact with the wheel stoppers, for example, based on the transition of the vehicle speed VS.

[0035] <Control Unit> The control unit M15 performs stopping-time braking control, which is an example of stopping control, when stopping the vehicle 10 by applying a braking force. When stopping the advancing vehicle 10, the control unit M15 performs the second stopping-time braking control shown in FIG. 2. When stopping the reversing vehicle 10, the control unit M15 performs the first stopping-time braking control. The first stopping-time braking control corresponds to the "first stopping control" that is performed when stopping the reversing vehicle 10 just before it comes to a stop.

[0036] When the vehicle 10 is decelerating due to the application of braking force, the control unit M15 selects control from the first stationary braking control and the second stationary braking control based on the traveling direction of the vehicle 10 acquired by the acquisition unit M11. Then, when the start condition for the stationary braking control is met, the control unit M15 implements the selected stationary braking control.

[0037] Both the first stationary braking control and the second stationary braking control include an increasing correction process, a decreasing correction process, and a degenerating process. In the increasing correction process of the stationary braking control, the control unit M15 derives the sum of the required braking force BPRq and the offset value ΔBP as the command braking force BPTr. Then, the control unit M15 operates the brake actuator 30 based on the command braking force BPTr.

[0038] When a condition for transitioning from the increasing correction process to the decreasing correction process is met during the execution of the increasing correction process, the control unit M15 ends the increasing correction process and starts the decreasing correction process. In the decreasing process of the decreasing correction process, the control unit M15 reduces the command braking force BPTr toward the held braking force BPh. When the command braking force BPTr decreases to the held braking force BPh, the control unit M15 executes the holding process of the decreasing correction process to hold the command braking force BPTr at the held braking force BPh. Then, the control unit M15 operates the brake actuator 30 based on the command braking force BPTr at that time.

[0039] When a condition for transitioning from the reduction correction process to the degeneration process is met during the execution of the reduction correction process, the control unit M15 terminates the reduction correction process and starts the degeneration process. In the degeneration process, the control unit M15 increases the command braking force BPTr to the required braking force BPRq. Then, the control unit M15 operates the brake actuator 30 based on the command braking force BPTr at that time.

[0040] The first stationary braking control is a control that reduces the degree of suppression of changes in the posture of the vehicle 10 when the vehicle is stopped, compared to the second stationary braking control. As described above, the smaller the fluctuation in the longitudinal acceleration Gx when the vehicle is stopped, the smaller the change in the posture of the vehicle 10 that occurs when the vehicle is stopped. Therefore, in this embodiment, when the first stationary braking control is performed, the control unit M15 sets the holding braking force BPh to a vehicle braking force that is greater than when the second stationary braking control is performed.

[0041] The holding braking force BPh when the first stationary braking control is implemented is greater than the holding braking force BPh when the second stationary braking control is implemented. Therefore, the travel distance of the vehicle 10 from the start of the first stationary braking control to the time of stopping is likely to be shorter than the travel distance of the vehicle 10 from the start of the second stationary braking control to the time of stopping. Also, the time required from the start of the first stationary braking control to the time of stopping is likely to be shorter than the time required from the start of the second stationary braking control to the time of stopping.

[0042] Therefore, when the first stationary braking control is performed, the control unit M15 sets the first vehicle body speed determination value VSth1 to a vehicle body speed that is lower than when the second stationary braking control is performed. Furthermore, when the first stationary braking control is performed, the control unit M15 may set the second vehicle body speed determination value VSth2 to a vehicle body speed that is lower than when the second stationary braking control is performed. The control unit M15 then sets the reduction rate of the command braking force BPTr in the reduction process of the first stationary braking control to be greater than the reduction rate of the command braking force BPTr in the reduction process of the second stationary braking control.

[0043] This allows the control unit M15 to delay the start timing of the first stationary braking control relative to the start timing of the second stationary braking control. Also, the control unit M15 can shorten the time required from the start of the first stationary braking control until the vehicle stops relative to the time required from the start of the second stationary braking control until the vehicle stops.

[0044] When the control unit M15 is performing stationary braking control to park the vehicle 10 in a parking lot, the wheels 12, 13 may come into contact with a wheel stopper. Therefore, if the detection unit M13 detects that the rear wheels 13 have come into contact with a wheel stopper while the first stationary braking control is being performed, the control unit M15 executes a degeneration process to terminate the first stationary braking control. Similarly, if the detection unit M13 detects that the front wheels 12 have come into contact with a wheel stopper while the second stationary braking control is being performed, the control unit M15 executes a degeneration process to terminate the second stationary braking control.

[0045] <Flow of processing for controlling vehicle braking force> A series of processing steps executed by the processing circuit 51 when performing stationary braking control will be described with reference to Fig. 3. The processing circuit 51 repeatedly executes the series of processing steps shown in Fig. 3 when braking the vehicle.

[0046] In step S11, the processing circuit 51 acquires the traveling direction of the vehicle 10. In the next step S13, the processing circuit 51 determines whether the traveling direction of the vehicle 10 is a reverse direction. If the processing circuit 51 determines that the traveling direction is a reverse direction (S13: YES), the processing circuit 51 proceeds to step S41. On the other hand, if the processing circuit 51 determines that the traveling direction is a forward direction (S13: NO), the processing circuit 51 proceeds to step S15.

[0047] In step S15, the processing circuit 51 sets the vehicle stop maintenance braking force BPth as the holding braking force BPh. In the next step S17, the processing circuit 51 sets a first vehicle body speed determination value VSth1 and a second vehicle body speed determination value VSth2 based on the holding braking force BPh.

[0048] Then, in step S19, the processing circuit 51 determines whether the start condition for the second stationary braking control is satisfied. The processing circuit 51 determines that the start condition is satisfied when the vehicle body speed VS becomes equal to or less than the first vehicle body speed determination value VSth1 from a state in which the vehicle body speed VS is greater than the first vehicle body speed determination value VSth1. If the processing circuit 51 determines that the start condition is satisfied (S19: YES), the processing circuit 51 proceeds to step S21. On the other hand, if the processing circuit 51 determines that the start condition is not satisfied (S19: NO), the processing circuit 51 temporarily ends the series of processes shown in FIG. 3 .

[0049] In step S21, the processing circuit 51 executes the second stationary braking control. Specifically, when the vehicle speed VS is greater than the second vehicle speed determination value VSth2, the processing circuit 51 executes an increasing correction process. In the increasing correction process, the processing circuit 51 sets a vehicle braking force greater than the required braking force BPRq as the command braking force BPTr to compensate for the extension of the braking distance of the vehicle 10 resulting from the execution of the decreasing correction process. That is, the offset value ΔBP shown in FIG. 2D is the braking force correction amount for compensating for the extension of the braking distance of the vehicle 10 resulting from the execution of the decreasing correction process. The processing circuit 51 operates the brake actuator 30 based on the command braking force BPTr.

[0050] When the vehicle speed VS becomes equal to or less than the second vehicle speed determination value VSth2, the processing circuit 51 shifts the processing from the increasing correction processing to the decreasing correction processing. When the commanded braking force BPTr is greater than the held braking force BPh, the processing circuit 51 executes the decreasing correction processing. In the decreasing processing, the processing circuit 51 reduces the commanded braking force BPTr to the held braking force BPh. Then, the processing circuit 51 operates the brake actuator 30 based on the commanded braking force BPTr. When the commanded braking force BPTr becomes equal to or less than the held braking force BPh, the processing circuit 51 executes the holding processing of the decreasing correction processing. In the holding processing, the processing circuit 51 holds the commanded braking force BPTr at the held braking force BPh. Then, the processing circuit 51 operates the brake actuator 30 based on the commanded braking force BPTr.

[0051] When the reduction correction process of the second stationary braking control is started as described above, the processing circuit 51 executes the process of step S23. In step S23, the processing circuit 51 determines whether an interruption condition of the second stationary braking control is satisfied. For example, if it is detected that the front wheels 12 of the forward-moving vehicle 10 have come into contact with a wheel stopper, the interruption condition can be considered to be satisfied. If the processing circuit 51 determines that the interruption condition is satisfied (S23: YES), the processing circuit 51 proceeds to step S27. On the other hand, if the processing circuit 51 determines that the interruption condition is not satisfied (S23: NO), the processing circuit 51 proceeds to step S25.

[0052] In step S25, the processing circuit 51 determines whether a transition condition to degeneration processing is satisfied. For example, the processing circuit 51 determines that the transition condition is satisfied when it is determined that the vehicle 10 has stopped. If the processing circuit 51 determines that the transition condition is not satisfied (S25: NO), the processing circuit 51 transitions the processing to step S23. On the other hand, if the processing circuit 51 determines that the transition condition is satisfied (S25: YES), the processing circuit 51 transitions the processing to step S27.

[0053] In step S27, the processing circuit 51 executes a degeneration process. In the degeneration process, the processing circuit 51 increases the command braking force BPTr to the required braking force BPRq. Then, the processing circuit 51 operates the brake actuator 30 based on the command braking force BPTr.

[0054] In the following step S29, the processing circuit 51 determines whether the termination condition for the degeneration process is satisfied. For example, if the command braking force BPTr is equal to the required braking force BPRq, the termination condition is deemed to be satisfied. On the other hand, if the command braking force BPTr is less than the required braking force BPRq, the termination condition is deemed to be not satisfied. If the processing circuit 51 determines that the termination condition is not satisfied (S29: NO), the processing circuit 51 proceeds to step S27 to execute the degeneration process. On the other hand, if the processing circuit 51 determines that the termination condition is satisfied (S29: YES), the processing circuit 51 terminates the degeneration process. Then, the processing circuit 51 terminates the second stationary braking control and ends the series of processes shown in FIG. 3.

[0055] In step S41, the processing circuit 51 sets the sum of the vehicle stop maintenance braking force BPth and the offset braking force α as the holding braking force BPh. The offset braking force α is set to a magnitude such that the sum of the vehicle stop maintenance braking force BPth and the offset braking force α is less than the required braking force BPRq. In the next step S43, the processing circuit 51 sets a first vehicle body speed determination value VSth1 and a second vehicle body speed determination value VSth2 based on the holding braking force BPh set in step S41.

[0056] Then, in step S45, the processing circuit 51 determines whether the start condition for the first stationary braking control is satisfied. The processing circuit 51 determines that the start condition is satisfied when the vehicle body speed VS becomes equal to or less than the first vehicle body speed determination value VSth1 from a state in which the vehicle body speed VS is greater than the first vehicle body speed determination value VSth1. If the processing circuit 51 determines that the start condition is satisfied (S45: YES), the processing circuit 51 proceeds to step S47. On the other hand, if the processing circuit 51 determines that the start condition is not satisfied (S45: NO), the processing circuit 51 temporarily ends the series of processes shown in FIG. 3 .

[0057] In step S47, the processing circuit 51 performs the first stationary braking control. Specifically, when the vehicle speed VS is greater than the second vehicle speed determination value VSth2, the processing circuit 51 performs an increasing correction process. In the increasing correction process, the processing circuit 51 sets a vehicle braking force greater than the required braking force BPRq as the command braking force BPTr to compensate for the extension of the braking distance of the vehicle 10 resulting from the execution of the decreasing correction process. For example, the processing circuit 51 sets the command braking force BPTr to the sum of the required braking force BPRq and the offset value ΔBP. The offset value ΔBP in the first stationary braking control may be the same as or different from the offset value ΔBP in the second stationary braking control. The processing circuit 51 activates the brake actuator 30 based on the command braking force BPTr.

[0058] When the vehicle speed VS becomes equal to or less than the second vehicle speed determination value VSth2, the processing circuit 51 shifts the processing from the increasing correction processing to the decreasing correction processing. The decreasing correction processing of the first stationary braking control is substantially the same as the decreasing correction processing of the second stationary braking control. Therefore, a description of the decreasing correction processing of the first stationary braking control will be omitted here.

[0059] When the reduction correction process of the first stationary braking control is started, the processing circuit 51 executes the process of step S49. In step S49, the processing circuit 51 determines whether or not an interruption condition of the first stationary braking control is satisfied. For example, if it is detected that the rear wheels 13 of the vehicle 10 moving backward have come into contact with a wheel stopper, the interruption condition can be considered to be satisfied. If the processing circuit 51 determines that the interruption condition is satisfied (S49: YES), the processing circuit 51 proceeds to step S53. On the other hand, if the processing circuit 51 determines that the interruption condition is not satisfied (S49: NO), the processing circuit 51 proceeds to step S51.

[0060] In step S51, the processing circuit 51 determines whether a transition condition to degeneration processing is satisfied. For example, the processing circuit 51 determines that the transition condition is satisfied when it is determined that the vehicle 10 has stopped. If the processing circuit 51 determines that the transition condition is not satisfied (S51: NO), the processing circuit 51 transitions the processing to step S49. On the other hand, if the processing circuit 51 determines that the transition condition is satisfied (S51: YES), the processing circuit 51 transitions the processing to step S53.

[0061] In step S53, the processing circuit 51 executes a degeneration process. The content of the degeneration process for the first stationary braking control is substantially the same as the content of the degeneration process for the second stationary braking control. Therefore, a description of the degeneration process for the first stationary braking control will be omitted here.

[0062] In the following step S55, the processing circuit 51 determines whether the termination condition for the degeneration processing is satisfied, as in step S29. If the processing circuit 51 determines that the termination condition is not satisfied (S55: NO), the processing circuit 51 proceeds to step S53, thereby executing the degeneration processing. On the other hand, if the processing circuit 51 determines that the termination condition is satisfied (S55: YES), the processing circuit 51 terminates the degeneration processing. Then, the processing circuit 51 terminates the first stationary braking control, thereby terminating the series of processing steps shown in FIG. 3.

[0063] <Operations and Effects of the Present Embodiment> With reference to FIG. 4, the operations and effects when braking force is applied to stop the vehicle 10 moving backward will be described.

[0064] 4A, 4B, and 4C, when a braking force is applied to the vehicle 10, the vehicle speed VS decreases. When the vehicle 10 is moving backward, the vehicle braking force BPh is set to be greater than the vehicle stop maintenance braking force BPth. Furthermore, the greater the holding braking force BPh, the smaller the first vehicle speed determination value VSth1 and the second vehicle speed determination value VSth2 become.

[0065] When the vehicle speed VS reaches the first vehicle speed determination value VSth1 at timing t21, the processing circuit 51 starts the first stationary braking control. The processing circuit 51 starts an increasing correction process for the first stationary braking control. In the increasing correction process, the processing circuit 51 sets the commanded braking force BPTr to the sum of the required braking force BPRq and the offset value ΔBP. The processing circuit 51 then controls the brake actuator 30 so that the vehicle braking force BPAl becomes the commanded braking force BPTr. As a result, as shown in FIGS. 4A and 4C, the vehicle braking force BPAl is increased even though the required braking force BPRq is constant. As a result, the absolute value of the longitudinal acceleration Gx increases, as shown in FIG. 4B.

[0066] When the vehicle speed VS reaches the second vehicle speed determination value VSth2 at timing t22, the processing circuit 51 transitions from the increasing correction process to the decreasing correction process. Specifically, just before the vehicle 10 comes to a stop, the processing circuit 51 starts the decreasing process of the decreasing correction process. In the decreasing process, the processing circuit 51 decreases the commanded braking force BPTr toward the held braking force BPh. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPAl becomes the commanded braking force BPTr. As a result, the vehicle braking force BPAl becomes smaller than the required braking force BPRq. As a result, even if the required braking force BPRq remains the same, the absolute value of the longitudinal acceleration Gx of the vehicle 10 gradually decreases.

[0067] When the command braking force BPTr becomes equal to the held braking force BPh at timing t23 during the reduction process, the processing circuit 51 starts the holding process of the reduction correction process. In the holding process, the processing circuit 51 holds the command braking force BPTr at the held braking force BPh. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPAl is held.

[0068] If it is determined that the vehicle 10 has stopped at timing t24 while the holding process is being executed, the processing circuit 51 transitions from the reduction correction process to the degeneration process. In the degeneration process, the processing circuit 51 increases the command braking force BPTr to the required braking force BPRq. Then, the processing circuit 51 operates the brake actuator 30 so that the vehicle braking force BPAl becomes the command braking force BPTr. As a result, the vehicle braking force BPAl is increased to the required braking force BPRq.

[0069] In this embodiment, the absolute value of the longitudinal acceleration Gx immediately before the vehicle 10 is stopped is reduced by performing the first stationary braking control. As a result, the fluctuation range of the longitudinal acceleration Gx before and after the vehicle 10 is stopped is reduced, and therefore, the change in the posture of the vehicle 10 caused by the vehicle stopping is reduced.

[0070] Therefore, the brake control device 50 can improve the comfort of the occupants when stopping the vehicle 10 moving backward. In this embodiment, the following effects can be further obtained.

[0071] (1) When the driver is operating the vehicle 10 in reverse, it is more difficult for the driver to check the direction of travel of the vehicle 10 than when the vehicle 10 is moving forward. Therefore, if the driver does not feel a sense of stopping, the driver is likely to feel uneasy.

[0072] Therefore, in this embodiment, when the retreating vehicle 10 is stopped, the first vehicle-stop braking control is executed to reduce the degree of suppression of the change in the posture of the vehicle 10 caused by stopping. As a result, the degree of change in the posture of the vehicle 10 caused by stopping becomes larger compared to when the second vehicle-stop braking control is executed to stop the retreating vehicle 10.

[0073] Therefore, when stopping a vehicle 10 moving backward, the brake control device 50 can simultaneously give the occupants a sense of stopping and improve the comfort of the occupants when the vehicle is stopped.

[0074] (2) In this embodiment, when the first vehicle stop braking control is performed, the processing circuit 51 sets the vehicle braking force holding braking force BPh to be greater than the vehicle stop maintaining braking force BPth. This allows the brake control device 50 to increase the absolute value of the longitudinal acceleration Gx immediately before stopping the vehicle 10 compared to when stopping a forward moving vehicle 10. As a result, when stopping a backward moving vehicle 10, the brake control device can provide the occupants with a stronger feeling of stopping than when stopping a forward moving vehicle 10.

[0075] (3) When the reduction process is being executed, the vehicle braking force BPAl is reduced, causing the pitch angle of the vehicle 10 to change during deceleration. In this case, if the reduction rate of the vehicle braking force BPAl is small, the rate of change of the pitch angle is small, improving the comfort of the occupants. On the other hand, if the reduction rate of the vehicle braking force BPAl is large, the rate of change of the pitch angle is large, making it easier for the occupants to feel the change in the attitude of the vehicle 10.

[0076] Therefore, the processing circuit 51 sets the reduction rate of the command braking force BPTr in the reduction process of the first stationary braking control to be greater than the reduction rate in the second stationary braking control. As a result, the rate of change in the posture of the vehicle 10 increases immediately before the vehicle 10 comes to a stop while moving backward. As a result, the brake control device 50 can more easily give the occupants a greater sense of stopping when stopping the vehicle 10 while moving backward.

[0077] (4) When the reduction correction process of the vehicle-stop braking control is being executed, the vehicle braking force BPAl becomes smaller than the required braking force BPRq. Furthermore, if the wheels 12, 13 come into contact with the wheel stoppers while the reduction correction process is being executed, the vehicle 10 will temporarily stop. In this case, if the vehicle braking force BPAl remains smaller than the required braking force BPRq, there is a risk that the vehicle 10 will start moving again.

[0078] Therefore, when the processing circuit 51 detects that the wheels 12, 13 have come into contact with the wheel chocks under the condition that the vehicle braking force BPAl has become smaller than the required braking force BPRq due to the execution of the reduction correction process, the processing circuit 51 increases the vehicle braking force BPAl to the required braking force BPRq by executing the reduction process. As a result, when the wheels 12, 13 come into contact with the wheel chocks and the vehicle 10 has stopped, the brake control device 50 can prevent the vehicle 10 from moving again.

[0079] <Modifications> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0080] Wheel chocks are structures set up in parking lots. Therefore, the processing circuit may transition to degenerate processing when it detects that a wheel has come into contact with a wheel chock in a situation where it has been determined by a navigation device or the like that the vehicle 10 is located in a parking lot. In other words, if it has been determined by a navigation device or the like that the vehicle 10 is not located in a parking lot, the processing circuit may not transition to degenerate processing even if it detects that a wheel has come into contact with a wheel chock. Furthermore, if it has been determined by a navigation device or the like that the vehicle 10 is not located in a parking lot, the processing circuit may not detect that a wheel has come into contact with a wheel chock.

[0081] The holding braking force BPh in the second stationary braking control may be different in magnitude from the stationary maintenance braking force BPth, as long as it is smaller than the holding braking force BPh in the first stationary braking control.

[0082] In the above embodiment, the offset braking force α is fixed at a predetermined value, but this is not limiting. For example, the processing circuit may vary the offset braking force α based on the vehicle speed VS at the start of the first stationary braking control, the required braking force BPRq, etc.

[0083] The braking force BPh held in the first braking control during a stop may be equal to the braking force BPh held in the second braking control during a stop. In this case, by making the execution time of the holding process of the first braking control during a stop shorter than the execution time of the holding process of the second braking control during a stop, the braking control device can reduce the degree to which the change in the posture of the vehicle 10 caused by stopping is suppressed.

[0084] Furthermore, if the second stationary braking control is a control that includes a holding process, the first stationary braking control may be a control that does not include a holding process. - If the held braking force BPh in the first stationary braking control is made larger than the held braking force BPh in the second stationary braking control, the decrease rate of the command braking force BPTr in the decrease process of the first stationary braking control does not have to be larger than the decrease rate of the command braking force BPTr in the decrease process of the second stationary braking control.

[0085] - The processing circuit (i.e., the control unit) may perform the first stationary braking control so that the time required from the start of the first stationary braking control to the vehicle coming to a stop is the same as the time required from the start of the second stationary braking control to the vehicle coming to a stop.

[0086] The processing circuit (i.e., the control unit) does not need to delay the start timing of the first stationary braking control later than the start timing of the second stationary braking control. In the above embodiment, the processing circuit 51 determines the start timing of the increasing correction process and the start timing of the decreasing correction process of the stationary braking control in accordance with changes in the vehicle body speed VS. However, the processing circuit 51 may determine the start timing of each process using a parameter other than the vehicle body speed VS, as long as the parameter value decreases as the vehicle 10 approaches the predicted stationary position PS. Examples of the other parameters include a stopping distance and a predicted stationary time. The stopping distance is the distance from the current position of the vehicle 10 to the predicted stationary position PS. The predicted stationary time is the time required for the vehicle 10 to stop. An example of the predicted stationary time is TTC. TTC is an abbreviation for "Time To Collision."

[0087] - If the vehicle-stop braking control includes a decrease correction process, it does not have to include an increase correction process. - If the decrease correction process includes a decrease process, it does not have to include a maintenance process. - When performing the vehicle-stop braking control, the brake control device may control not only the friction braking force but also the regenerative braking force. In this case, the sum of the total friction braking force applied to the vehicle 10 and the total regenerative braking force applied to the vehicle 10 becomes the vehicle braking force BPAl.

[0088] In the above embodiment, the processing circuit 51 performs the vehicle-stop braking control when the driver brakes the vehicle in response to the operation of the brake operating member 11. However, the processing circuit 51 may perform the vehicle-stop braking control when automatic braking is performed.

[0089] The processing circuit 51 may perform control other than the above-described vehicle-stop braking control as the vehicle stopping control. For example, the processing circuit 51 may perform control as the vehicle stopping control to adjust the pitch angle of the vehicle 10 during vehicle braking by changing the distribution of the braking force applied to the front wheels 12 and the braking force applied to the rear wheels 13. In this case, the processing circuit 51 can suppress changes in the posture of the vehicle 10 that occur when the vehicle is stopped by increasing the proportion of the braking force applied to the rear wheels 13 in the vehicle braking force BPAl.

[0090] The processing circuitry 51 may be configured as a circuit including one or more processors operating according to a computer program, one or more dedicated hardware circuits such as dedicated hardware for performing at least some of the various processes, or a combination thereof. Examples of dedicated hardware include an application-specific integrated circuit (ASIC). The processor includes a CPU and memory such as RAM and ROM, which store program code or instructions configured to cause the CPU to perform processes. The memory, i.e., storage medium, includes any available medium accessible by a general-purpose or dedicated computer.

[0091] <Other Technical Ideas> The following describes technical ideas that can be understood from the above-described embodiment and modified examples. [Supplementary Note 1] It is preferable that the first stop control is control for reducing the braking force to a first braking force and then setting the vehicle body speed of the vehicle to 0 (zero) when the vehicle is about to stop, and that the second stop control is control for reducing the braking force to a second braking force that is smaller than the first braking force and then setting the vehicle body speed of the vehicle to 0 (zero) when the vehicle is about to stop.

[0092] [Appendix 2] The vehicle is provided with an acquisition unit that acquires the direction of travel of the traveling vehicle, and when applying a braking force to the traveling vehicle to stop it, the control unit preferably performs one of the first stopping control and the second stopping control in accordance with the direction of travel acquired by the acquisition unit.

[0093] It should be noted that the expression "at least one" used in this specification means "one or more" of the desired options. As an example, the expression "at least one" used in this specification means "only one option" or "both of two options" if the number of options is two. As another example, the expression "at least one" used in this specification means "only one option" or "any combination of two or more options" if the number of options is three or more.

Claims

1. A braking control device that controls the braking force applied to a vehicle, comprising a control unit that performs first stop control for controlling the braking force to suppress a change in the posture of the vehicle accompanying stopping when stopping the vehicle that is moving backward.

2. When the control unit stops the vehicle that is moving forward, the control unit performs second stop control for controlling the braking force to suppress a change in the posture of the vehicle accompanying stopping, and in the first stop control, the degree of suppression of the change in the posture of the vehicle due to the implementation of the first stop control is smaller than the degree of suppression of the change in the posture of the vehicle due to the implementation of the second stop control, and the braking force is controlled as described in claim 1 of the braking control device.

3. The control unit makes the start timing of the first stop control later than the start timing of the second stop control, as described in claim 2 of the braking control device.

4. The control unit performs the first stop control so that the time required from the start point of the first stop control to stopping is shorter than the time required from the start point of the second stop control to stopping, as described in claim 3 of the braking control device.

5. When the vehicle is about to stop, the first stop control and the second stop control are controls that execute a decrease process for decreasing the braking force and then set the vehicle body speed of the vehicle to 0 (zero). When the control unit is in the decrease process of the first stop control, the control unit increases the decrease speed of the braking force more than when the decrease process of the second stop control is executed, as described in any one of claims 2 to 4 of the braking control device.

6. When the vehicle is about to stop, the first stop control is a control that executes a decrease process for decreasing the braking force and then sets the vehicle body speed of the vehicle to 0 (zero). When it is detected during the implementation of the first stop control that the wheels of the vehicle have come into contact with wheel stops, the control unit executes a retraction process for increasing the braking force to the required value of the braking force and terminates the first stop control, as described in claim 1 or claim 2 of the braking control device.

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