Brake control device

Abstract

To enable improvement in vehicle occupant comfort when stopping a reversing vehicle.SOLUTION: A brake control device 50 controls the braking force applied to a vehicle 10. When 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.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

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

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to improve the comfort of the vehicle occupants when stopping a reversing vehicle.

Means for Solving the Problems

[0005] The braking control device for solving the above problems is a device that controls the braking force applied to a vehicle. The braking control device includes 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 reversing vehicle.

Effects of the Invention

[0006] The above braking control device has an effect of being able to improve the comfort of the vehicle occupants when stopping a reversing vehicle.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0008] Hereinafter, an embodiment of the braking control device will be described with reference to FIGS. 1 to 4. FIG. 1 illustrates a vehicle 10 including a braking control device 50. The vehicle 10 includes a braking operation 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 Operating System> The braking operation member 11 is a member that a driver operates when applying a braking force to the vehicle 10. An example of the braking operation member 11 is a brake pedal.

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

[0011] <Friction Brake> A plurality of friction brakes respectively apply braking forces to corresponding wheels. Among the plurality of friction brakes, the friction brake corresponding to the front wheel 12 is referred to as "friction brake 20A", and the friction brake corresponding to the rear wheel 13 is referred to as "friction brake 20B". The friction brakes 20A and 20B have a wheel cylinder 21, a rotating body 22, and a friction portion 23. The rotating body 22 rotates integrally with the wheel. Therefore, by pressing the friction portion 23 against the rotating body 22, a braking force is applied to the wheel. The force for 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 wheels as the wheel hydraulic pressure increases.

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

[0013] <Brake actuator> The brake actuator 30 controls the braking force applied to the wheels 12 and 13 by controlling the wheel hydraulic pressure of the plurality of wheel cylinders 21. 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 individually.

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

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

[0016] The wheel speed sensors 102 are provided for each of the plurality of wheels. The plurality of wheel speed sensors 102 respectively detect the rotational speed of the corresponding wheels. The rotational speed of the wheels based on the detection signals of the wheel speed sensors 102 is referred to as "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 "vehicle body speed VS".

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

[0018] <Braking control device> The braking control device 50 includes a processing circuit 51. An example of the processing circuit 51 is an electronic control unit. In this case, the processing circuit 51 has 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 the calculation results of the CPU 52 and the like. By the CPU 52 executing the control program in the first memory 53, the processing circuit 51 controls the braking actuator 30 to operate the plurality of friction brakes 20A, 20B. That is, the processing circuit 51 can adjust the vehicle braking force BPAl by operating the plurality of friction brakes 20A, 20B.

[0019] <Outline of braking control during parking> When the driver operates the braking operation member 11, the processing circuit 51 performs braking control at the time of stopping. The braking control at the time of stopping is an example of "stopping control" that controls the vehicle braking force BPAl in order to suppress changes in the posture of the vehicle 10 accompanying stopping when applying a braking force to the vehicle 10 to stop it.

[0020] Referring to FIG. 2, the second braking control at the time of stopping, which is one of the braking controls at the time of stopping, will be described. The second braking control at the time of stopping is the braking control at the time of stopping the advancing vehicle 10. That is, the second braking control at the time of stopping corresponds to the "second stopping control" that is performed when stopping the vehicle 10 immediately before stopping the advancing vehicle 10.

[0021] At timing t11 when the vehicle 10 is advancing, the driver starts operating the braking operation member 11. In this case, as shown in FIG. 2(B), the processing circuit 51 derives the required braking force BPRq. The required braking force BPRq is the required value of the vehicle braking force BPAl. For example, the processing circuit 51 derives the required braking force BPRq so that the magnitude increases as the braking operation amount X of the braking operation member 11 increases. 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, as shown in FIG. 2(D), the processing circuit 51 sets the required braking force BPRq 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.

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

[0023] When the vehicle body speed VS reaches the first vehicle body speed determination value VSth1 at timing t12, the processing circuit 51 starts the second stop-time braking control. The first vehicle body speed determination value VSth1 is an example of a threshold value for setting the start timing of the stop-time braking control. From timing t12, the processing circuit 51 starts the augmentation correction process of the second stop-time braking control. In the augmentation 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 braking actuator 30 so that the vehicle braking force BPAl becomes the commanded braking force BPTr. As a result, even when the required braking force BPRq is the same, the absolute value of the longitudinal acceleration Gx of the vehicle 10 becomes larger than before timing t12 by the amount of the offset value ΔBP.

[0024] At timing t13, the vehicle body speed VS reaches the second vehicle body speed determination value VSth2. A vehicle body speed smaller than the first vehicle body speed determination value VSth1 is set as the second vehicle body speed determination value VSth2. When the vehicle body speed VS is less than or equal to the second vehicle body speed determination value VSth2, it can be considered that the vehicle 10 has approached the stop prediction position PS. The stop prediction position PS is the predicted position where the vehicle 10 stops. When the vehicle 10 is approaching a stop, the processing circuit 51 shifts the process of the second stop-time braking control from the augmentation correction process to the reduction correction process. In the reduction correction process, the processing circuit 51 decreases the commanded braking force BPTr. Then, the processing circuit 51 controls the braking actuator 30 so that the vehicle braking force BPAl becomes the commanded braking force BPTr. By the processing circuit 51 executing the reduction correction process in this way, the vehicle braking force BPAl becomes smaller than the required braking force BPRq. As a result, even when the required braking force BPRq is the same, the absolute value of the longitudinal acceleration Gx of the vehicle 10 gradually becomes smaller.

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

[0026] Note that, among the deceleration correction processes, the process of reducing the commanded braking force BPTr to the holding braking force BPh is referred to as the "reduction process". Among the deceleration correction processes, the process of holding the commanded braking force BPTr at the holding braking force BPh is referred to as the "holding process".

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

[0028] When the stop-time braking control is being carried out, the vehicle braking force BPAl at the time of stopping is smaller than the required braking force BPRq. Therefore, when stopping in a state where the stop-time braking control is being carried out, compared with the case of stopping in a state where the stop-time braking control is not being carried out, the fluctuation of the longitudinal acceleration Gx at the time of stopping is smaller. Thus, the smaller the fluctuation of the longitudinal acceleration Gx, the smaller the change in the posture of the vehicle 10 accompanying the stop, so the comfort of the passengers at the time of stopping is improved. On the other hand, when the vehicle braking force BPAl at the time of stopping is reduced in order to improve the comfort of the passengers at the time of stopping, the sense of stopping felt by the passengers at the time of stopping becomes smaller. The sense of stopping is the feeling that the passengers feel when the vehicle 10 has stopped.

[0029] In the example shown in FIG. 2, at timing t15, when the processing circuit 51 determines that the vehicle 10 has stopped, the processing of the second stop-time braking control shifts from the reduction correction process to the degradation process. In the degradation process, the processing circuit 51 increases the indicated braking force BPTr. For example, the processing circuit 51 increases the indicated braking force BPTr to the required braking force BPRq. By controlling the braking actuator 30 based on the indicated braking force BPTr by the processing circuit 51, the vehicle braking force BPAl increases. When the indicated braking force BPTr becomes equal to the required braking force BPRq at timing t16, the processing circuit 51 ends the second stop-time braking control.

[0030] <Functional Configuration of Processing Circuit> Referring to FIG. 1, the functional configuration of the processing circuit 51 will be described. By the CPU 52 executing the control program of the first memory 53, the processing circuit 51 functions as a plurality of functional units. These plurality of functional units are functional units for stopping the vehicle 10 by applying a braking force to the vehicle 10. The plurality of 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 backward direction as the traveling direction.

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

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

[0034] When the wheel comes into contact with the wheel stopper, the vehicle body speed VS drops sharply or the vehicle 10 stops. Therefore, the detection unit M13 detects that the wheels 12 and 13 have come into contact with the wheel stopper based on, for example, the change in the vehicle body speed VS.

[0035] <Control unit> When stopping the vehicle 10 by applying braking force, the control unit M15 performs parking braking control, which is an example of parking control. When stopping the forward-moving vehicle 10, the control unit M15 performs the second parking braking control shown in FIG. 2. When stopping the reversing vehicle 10, the control unit M15 performs the first parking braking control. The first parking braking control corresponds to the "first parking control" performed when stopping the vehicle 10 immediately before it stops while the vehicle 10 is reversing.

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

[0037] Both the first parking braking control and the second parking braking control include an augmentation correction process, a reduction correction process, and a degradation process. In the augmentation correction process of the parking braking control, the control unit M15 derives the indicated braking force BPTr as the sum of the required braking force BPRq and the offset value ΔBP. Then, the control unit M15 operates the brake actuator 30 based on the indicated braking force BPTr.

[0038] During the execution of the augmentation correction process, when the condition for shifting the process from the augmentation correction process to the reduction correction process is satisfied, the control unit M15 ends the augmentation correction process and starts the reduction correction process. In the reduction process of the reduction correction process, the control unit M15 decreases the indicated braking force BPTr toward the holding braking force BPh. When the indicated braking force BPTr decreases to the holding braking force BPh, the control unit M15 holds the indicated braking force BPTr at the holding braking force BPh by executing the holding process of the reduction correction process. Then, the control unit M15 operates the braking actuator 30 based on the indicated braking force BPTr at that time.

[0039] During the execution of the reduction correction process, when the condition for shifting the process from the reduction correction process to the degeneracy process is satisfied, the control unit M15 ends the reduction correction process and starts the degeneracy process. In the degeneracy process, the control unit M15 increases the indicated braking force BPTr to the required braking force BPRq. Then, the control unit M15 operates the braking actuator 30 based on the indicated braking force BPTr at that time.

[0040] The first stop-time braking control is a control that reduces the degree of suppression of the change in the posture of the vehicle 10 during stopping compared to the second stop-time braking control. As described above, the smaller the fluctuation of the longitudinal acceleration Gx during stopping, the smaller the change in the posture of the vehicle 10 accompanying the stop. Therefore, in the present embodiment, when the control unit M15 implements the first stop-time braking control, the control unit M15 sets a larger vehicle braking force as the holding braking force BPh than when implementing the second stop-time braking control.

[0041] The holding braking force BPh when the first stop-time braking control is implemented is larger than the holding braking force BPh when the second stop-time braking control is implemented. Therefore, the traveling distance of the vehicle 10 from the start of the first stop-time braking control until stopping is likely to be shorter than the traveling distance of the vehicle 10 from the start of the second stop-time braking control until stopping. Also, the time required from the start point of the first stop-time braking control until stopping is likely to be shorter than the time required from the start point of the second stop-time braking control until stopping.

[0042] Therefore, when the control unit M15 performs the first stop-time braking control, it sets a vehicle speed as the first vehicle speed determination value VSth1 that is lower than the vehicle speed when performing the second stop-time braking control. Further, when the control unit M15 performs the first stop-time braking control, it may set a vehicle speed as the second vehicle speed determination value VSth2 that is lower than the vehicle speed when performing the second stop-time braking control. Then, the control unit M15 makes the decreasing speed of the commanded braking force BPTr in the decreasing process of the first stop-time braking control greater than the decreasing speed of the commanded braking force BPTr in the decreasing process of the second stop-time braking control.

[0043] Thereby, the control unit M15 can make the start timing of the first stop-time braking control later than the start timing of the second stop-time braking control. Also, the control unit M15 can make the time required from the start point of the first stop-time braking control until stopping shorter than the time required from the start point of the second stop-time braking control until stopping.

[0044] When the control unit M15 is performing the stop-time braking control when parking the vehicle 10 in a parking lot, the wheels 12, 13 may come into contact with the wheel stopper. Therefore, when the detection unit M13 detects that the rear wheel 13 has come into contact with the wheel stopper during the execution of the first stop-time braking control, the control unit M15 executes a fallback process to end the first stop-time braking control. Similarly, when the detection unit M13 detects that the front wheel 12 has come into contact with the wheel stopper during the execution of the second stop-time braking control, the control unit M15 executes a fallback process to end the second stop-time braking control.

[0045] <Flow of process for controlling vehicle braking force> Referring to FIG. 3, a series of processes executed by the processing circuit 51 when performing the stop-time braking control will be described. The processing circuit 51 repeatedly executes the series of processes shown in FIG. 3 during vehicle braking.

[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 the reverse direction. When the processing circuit 51 determines that the traveling direction is the reverse direction (S13: YES), the process proceeds to step S41. On the other hand, when the processing circuit 51 determines that the traveling direction is the forward direction (S13: NO), the process proceeds to step S15.

[0047] In step S15, the processing circuit 51 sets the stop-maintaining braking force BPth as the holding braking force BPh. In the next step S17, the processing circuit 51 sets a first vehicle speed determination value VSth1 and a second vehicle 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 stop-time braking control is satisfied. When the vehicle speed VS decreases from a state where it is greater than the first vehicle speed determination value VSth1 to a value less than or equal to the first vehicle speed determination value VSth1, the processing circuit 51 determines that the start condition is satisfied. When the processing circuit 51 determines that the start condition is satisfied (S19: YES), the process proceeds to step S21. On the other hand, when the processing circuit 51 determines that the start condition is not satisfied (S19: NO), the series of processes shown in FIG. 3 is temporarily terminated.

[0049] In step S21, the processing circuit 51 performs the second stop-time braking control. Specifically, when the vehicle speed VS is greater than the second vehicle speed determination value VSth2, the processing circuit 51 executes an additional correction process. In the additional correction process, the processing circuit 51 sets a vehicle braking force greater than the required braking force BPRq as the commanded braking force BPTr in order to compensate for the extension of the braking distance of the vehicle 10 caused by the execution of the reduction correction process. That is, the offset value ΔBP shown in FIG. 2(D) is the correction amount of the braking force for compensating for the extension of the braking distance of the vehicle 10 caused by the execution of the reduction correction process. The processing circuit 51 operates the brake actuator 30 based on the commanded braking force BPTr.

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

[0051] When starting the decreasing correction process of the second stop-time braking control as described above, the processing circuit 51 executes the process of step S23. In step S23, the processing circuit 51 determines whether or not the interruption condition of the second stop-time braking control is satisfied. For example, when it is detected that the front wheels 12 of the forward moving vehicle 10 have contacted the wheel stopper, it can be regarded that the interruption condition is satisfied. When the processing circuit 51 determines that the interruption condition is satisfied (S23: YES), the process proceeds to step S27. On the other hand, when the processing circuit 51 determines that the interruption condition is not satisfied (S23: NO), the process proceeds to step S25.

[0052] In step S25, the processing circuit 51 determines whether or not the shift condition to the degeneracy process is satisfied. For example, when the processing circuit 51 can determine that the vehicle 10 has stopped, it determines that the shift condition is satisfied. When the processing circuit 51 determines that the shift condition is not satisfied (S25: NO), the process proceeds to step S23. On the other hand, when the processing circuit 51 determines that the shift condition is satisfied (S25: YES), the process proceeds to step S27.

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

[0054] In the subsequent step S29, the processing circuit 51 determines whether the end condition of the degradation process is satisfied. For example, when the commanded braking force BPTr becomes equal to the required braking force BPRq, it is regarded that the end condition is satisfied. On the other hand, when the commanded braking force BPTr is less than the required braking force BPRq, it is regarded that the end condition is not satisfied. When the processing circuit 51 determines that the end condition is not satisfied (S29: NO), the processing circuit 51 executes the degradation process by shifting the process to step S27. On the other hand, when the processing circuit 51 determines that the end condition is satisfied (S29: YES), the degradation process is terminated. Then, the processing circuit 51 terminates the second stop-time braking control and terminates the series of processes shown in FIG. 3.

[0055] In step S41, the processing circuit 51 sets the sum of the parking 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 parking 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 of the first stop-time braking control is satisfied. The processing circuit 51 determines that the start condition is satisfied when the vehicle body speed VS becomes less than or equal to the first vehicle body speed determination value VSth1 from a state where the vehicle body speed VS is greater than the first vehicle body speed determination value VSth1. When the processing circuit 51 determines that the start condition is satisfied (S45: YES), the process proceeds to step S47. On the other hand, when the processing circuit 51 determines that the start condition is not satisfied (S45: NO), the series of processes shown in FIG. 3 is temporarily terminated.

[0057] In step S47, the processing circuit 51 performs first stop-time braking control. Specifically, when the vehicle body speed VS is greater than the second vehicle body speed determination value VSth2, the processing circuit 51 executes an increase correction process. In the increase correction process, the processing circuit 51 sets a vehicle braking force greater than the required braking force BPRq as the commanded braking force BPTr in order to compensate for the extension of the braking distance of the vehicle 10 caused by the execution of the decrease correction process. 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. The offset value ΔBP in the first stop-time braking control may be the same magnitude as the offset value ΔBP in the second stop-time braking control, or may be a different magnitude. The processing circuit 51 operates the brake actuator 30 based on the commanded braking force BPTr.

[0058] When the vehicle body speed VS becomes equal to or less than the second vehicle body speed determination value VSth2, the processing circuit 51 shifts the process from the increase correction process to the decrease correction process. The content of the decrease correction process in the first stop-time braking control is substantially equivalent to the content of the decrease correction process in the second stop-time braking control. Therefore, the description of the decrease correction process in the first stop-time braking control is omitted here.

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

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

[0061] In step S53, the processing circuit 51 executes the degradation process. The content of the degradation process of the first stop-time braking control is substantially equivalent to the content of the degradation process of the second stop-time braking control. Therefore, the description of the degradation process of the first stop-time braking control is omitted here.

[0062] In the subsequent step S55, the processing circuit 51 determines whether the end condition of the degradation process is satisfied, in the same manner as in step S29 above. If the processing circuit 51 determines that the end condition is not satisfied (S55: NO), the process proceeds to step S53 to execute the degradation process. On the other hand, if the processing circuit 51 determines that the end condition is satisfied (S55: YES), the degradation process ends. Then, the processing circuit 51 ends the first stop-time braking control and ends the series of processes shown in FIG. 3.

[0063] <Actions and Effects of the Present Embodiment> Referring to FIG. 4, the actions and effects when the vehicle 10 moving backward is stopped by applying a braking force will be described.

[0064] As shown in FIGS. 4(A), 4(B), and 4(C), when a braking force is applied to the vehicle 10, the vehicle body speed VS decreases. When the vehicle 10 is moving backward, a vehicle braking force greater than the stop-maintaining braking force BPth is set as the holding braking force BPh. Also, the higher the holding braking force BPh, the lower the first vehicle body speed determination value VSth1 and the second vehicle body speed determination value VSth2.

[0065] When the vehicle body speed VS reaches the first vehicle body speed determination value VSth1 at timing t21, the processing circuit 51 starts the first stop-time braking control. The processing circuit 51 starts the additional correction processing of the first stop-time braking control. In the additional correction processing, the processing circuit 51 sets the sum of the required braking force BPRq and the offset value ΔBP as the instructed braking force BPTr. Then, the processing circuit 51 controls the braking actuator 30 so that the vehicle braking force BPAl becomes the instructed braking force BPTr. As a result, as shown in FIGS. 4(A) and 4(C), even though the required braking force BPRq is constant, the vehicle braking force BPAl increases. Consequently, as shown in FIG. 4(B), the absolute value of the longitudinal acceleration Gx becomes larger.

[0066] When the vehicle body speed VS reaches the second vehicle body speed determination value VSth2 at timing t22, the processing circuit 51 shifts the processing from the additional correction processing to the subtractive correction processing. Specifically, when the vehicle 10 is about to stop, the processing circuit 51 starts the decreasing processing among the subtractive correction processing. In the decreasing processing, the processing circuit 51 decreases the instructed braking force BPTr toward the holding braking force BPh. Then, the processing circuit 51 controls the braking actuator 30 so that the vehicle braking force BPAl becomes the instructed braking force BPTr. As a result, the vehicle braking force BPAl becomes smaller than the required braking force BPRq. Consequently, even if the required braking force BPRq is the same, the absolute value of the longitudinal acceleration Gx of the vehicle 10 gradually becomes smaller.

[0067] When the instructed braking force BPTr becomes equal to the holding braking force BPh at timing t23 during the execution of the decreasing processing, the processing circuit 51 starts the holding processing among the subtractive correction processing. In the holding processing, the processing circuit 51 holds the instructed braking force BPTr with the holding braking force BPh. Then, the processing circuit 51 controls the braking actuator 30 so that the vehicle braking force BPAl is held.

[0068] If it can be determined that the vehicle 10 has stopped at the timing t24 during the execution of the holding process, the processing circuit 51 shifts the process from the reduction correction process to the degradation process. In the degradation process, the processing circuit 51 increases the commanded 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 commanded braking force BPTr. As a result, the vehicle braking force BPAl is increased to the required braking force BPRq.

[0069] In this embodiment, by performing the first stop-time braking control, the absolute value of the longitudinal acceleration Gx immediately before stopping becomes small. As a result, since the variation range of the longitudinal acceleration Gx before and after the stop of the vehicle 10 becomes small, the change in the attitude of the vehicle 10 accompanying the stop becomes small.

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

[0071] (1) When the vehicle 10 is being moved backward by the driver's vehicle operation, it is more difficult for the driver to confirm the traveling direction of the vehicle 10 compared to the case where the vehicle 10 is being moved forward. Therefore, if the stopping feeling is small, the driver is likely to feel uneasy.

[0072] Therefore, in this embodiment, when stopping the vehicle 10 that is moving backward, by performing the first stop-time braking control, the degree of suppression of the change in the attitude of the vehicle 10 accompanying the stop is reduced. As a result, compared to the case where the second stop-time braking control is performed when stopping the vehicle 10 that is moving backward, the degree of change in the attitude of the vehicle 10 accompanying the stop becomes larger.

[0073] Therefore, the braking control device 50 can achieve both giving the occupants a stopping feeling and improving the comfort of the occupants at the time of stopping when stopping the vehicle 10 that is moving backward.

[0074] (2) In this embodiment, when the processing circuit 51 performs the first stop-time braking control, it sets a vehicle braking force greater than the stop-maintaining braking force BPth as the holding braking force BPh. Thereby, the braking control device 50 can increase the absolute value of the longitudinal acceleration Gx immediately before stopping compared to the case of stopping the forward-moving vehicle 10. As a result, when the braking control device stops the reverse-moving vehicle 10, it can give the occupant a greater sense of stopping than when stopping the forward-moving vehicle 10.

[0075] (3) When the reduction process is being executed, since the vehicle braking force BPAl is reduced, the pitch angle of the vehicle 10 changes during deceleration. At this time, if the reduction rate of the vehicle braking force BPAl is small, the change rate of the pitch angle becomes small, improving the comfort of the occupant. On the other hand, if the reduction rate of the vehicle braking force BPAl is large, the change rate of the pitch angle becomes large, and the occupant feels the change in the posture of the vehicle 10 too much.

[0076] Therefore, in the reduction process of the first stop-time braking control, the processing circuit 51 makes the reduction rate of the commanded braking force BPTr larger than the reduction rate of the second stop-time braking control. Thereby, immediately before stopping the reverse-moving vehicle 10, the change rate of the posture of the vehicle 10 becomes large. As a result, the braking control device 50 can easily increase the sense of stopping given to the occupant when stopping the reverse-moving vehicle 10.

[0077] (4) When the reduction correction process of the stop-time braking control is being executed, the vehicle braking force BPAl is smaller than the commanded braking force BPRq. Also, when the wheels 12, 13 come into contact with the wheel stops during the execution of the reduction correction process, the vehicle 10 stops momentarily. At this time, if the vehicle braking force BPAl remains smaller than the commanded braking force BPRq, the vehicle 10 may start moving again.

[0078] Therefore, when the processing circuit 51 detects that the wheels 12 and 13 have come into contact with the wheel stopper in a situation where the vehicle braking force BPAl is smaller than the required braking force BPRq by executing the subtraction correction process, the processing circuit 51 increases the vehicle braking force BPAl to the required braking force BPRq by executing the degradation process. Thereby, when the wheels 12 and 13 come into contact with the wheel stopper and the vehicle 10 stops, the braking control device 50 can suppress the vehicle 10 from starting to move again.

[0079] <Modified Example> The above embodiment can be implemented with the following modifications. The above embodiment and the following modified examples can be implemented in combination with each other as long as they do not technically conflict with each other.

[0080] · The wheel stopper is a structure set in the parking lot. Therefore, when the processing circuit detects that the wheel has come into contact with the wheel stopper in a situation where it can be determined by a navigation device or the like that the vehicle 10 is located in the parking lot, the processing may be shifted to the degradation process. That is, when the processing circuit cannot determine by a navigation device or the like that the vehicle 10 is not located in the parking lot, even if it detects that the wheel has come into contact with the wheel stopper, it may not shift the processing to the degradation process. Further, when the processing circuit cannot determine by a navigation device or the like that the vehicle 10 is not located in the parking lot, it may not detect that the wheel has come into contact with the wheel stopper.

[0081] · If the holding braking force BPh in the second stop-time braking control is smaller than the holding braking force BPh in the first stop-time braking control, it may have a magnitude different from the stop-maintaining braking force BPth.

[0082] · In the above embodiment, the offset braking force α is fixed at a predetermined value, but it is not limited to this. For example, the processing circuit may vary the offset braking force α based on the vehicle body speed VS, the required braking force BPRq, etc. at the start point of the first stop-time braking control.

[0083] ·The holding braking force BPh in the first stop braking control may be the same magnitude as the holding braking force BPh in the second stop braking control. In this case, by making the execution time of the holding process in the first stop braking control shorter than the execution time of the holding process in the second stop braking control, the braking control device can reduce the degree of suppression of the change in the attitude of the vehicle 10 accompanying the stop.

[0084] Also, if the second stop braking control is a control including a holding process, the first stop braking control may be a control not including a holding process. ·If the holding braking force BPh in the first stop braking control is made larger than the holding braking force BPh in the second stop braking control, the decreasing speed of the commanded braking force BPTr in the decreasing process of the first stop braking control does not necessarily have to be larger than the decreasing speed of the commanded braking force BPTr in the decreasing process of the second stop braking control.

[0085] ·The processing circuit (i.e., the control unit) may perform the first stop braking control so that the time required from the start point of the first stop braking control until the stop is the same as the time required from the start point of the second stop braking control until the stop.

[0086] ·The processing circuit (i.e., the control unit) does not necessarily have to make the start timing of the first stop braking control later than the start timing of the second stop braking control. ·In the above embodiment, the processing circuit 51 determines the start timing of the boosting correction process and the start timing of the decreasing correction process of the stop braking control according to the change in the vehicle body speed VS. However, if it is a parameter whose value becomes smaller as the vehicle 10 approaches the predicted stop position PS, the processing circuit 51 may use other parameters than the vehicle body speed VS to determine the start timing of each process. Examples of other parameters include the stopping distance and the predicted stopping time. The stopping distance is the distance from the current position of the vehicle 10 to the predicted stop position PS. The predicted stopping time is the time required for the vehicle 10 to stop. An example of the predicted stopping time is TTC. TTC is an abbreviation of "Time To Collision".

[0087] · If the braking control during parking includes a reduction correction process, it does not necessarily have to include an increase correction process. · If the reduction correction process includes a decrease process, it does not necessarily have to include a holding process. · When executing the braking control during parking, the braking control device may control not only the frictional braking force but also the regenerative braking force. In this case, the sum of the total frictional braking force applied to the vehicle 10 and the total regenerative braking force applied to the vehicle 10 is the vehicle braking force BPAl.

[0088] · In the above embodiment, when the vehicle is braked due to the operation of the braking operation member 11 by the driver, the processing circuit 51 performs the braking control during parking. However, the processing circuit 51 may perform the braking control during parking during automatic braking.

[0089] · As a parking control, the processing circuit 51 may perform a control other than the above-described braking control during parking. For example, the processing circuit 51 may perform, as a parking control, a control for adjusting 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 the change in the posture of the vehicle 10 accompanying parking by increasing the ratio of the braking force applied to the rear wheels 13 in the vehicle braking force BPAl.

[0090] · The processing circuit 51 can be configured as a circuit including one or more processors that operate according to a computer program, one or more dedicated hardware circuits such as dedicated hardware that executes at least a part of various processes, or a combination thereof. Examples of the dedicated hardware include, for example, an ASIC (Application Specific Integrated Circuit) which is an integrated circuit for a specific purpose. The processor includes a CPU and a memory such as a RAM and a ROM, and the memory stores program codes or instructions configured to cause the CPU to execute processes. The memory, that is, the storage medium, includes any available medium that can be accessed by a general-purpose or dedicated computer.

[0091] <Other technical ideas> Describe the technical idea that can be grasped from the above embodiments and modification examples. [Appendix 1] The one-stop control is a control in which, when the vehicle is about to stop, the braking force is reduced to a first braking force and then the vehicle body speed of the vehicle is set to 0 (zero). It is preferable that the two-stop control is a control in which, when the vehicle is about to stop, the braking force is reduced to a second braking force smaller than the first braking force and then the vehicle body speed of the vehicle is set to 0 (zero).

[0092] [Appendix 2] It is provided with an acquisition unit that acquires the traveling direction of the traveling vehicle. When applying a braking force to the traveling vehicle to stop it, it is preferable that the control unit implements control according to the traveling direction acquired by the acquisition unit among the first stop control and the second stop control.

[0093] Note 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 the 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.

Explanation of reference numerals

[0094] 10…Vehicle 12, 13…Wheels 15…Shift device 30…Brake actuator 50…Brake control device 51…Processing circuit M11…Acquisition unit M13…Detection unit M15…Control unit

Claims

1. A braking control device for controlling the braking force applied to a vehicle, comprising a control unit that implements a first stop control for controlling the braking force to suppress a change in the attitude of the vehicle associated with stopping when stopping the vehicle that is reversing. A braking control device.

2. When the control unit stops the vehicle that is moving forward, it implements a second stop control for controlling the braking force to suppress a change in the attitude of the vehicle associated with stopping, and in the first stop control, controls the braking force so that the degree of suppression of the change in the attitude of the vehicle due to the implementation of the first stop control is smaller than the degree of suppression of the change in the attitude of the vehicle due to the implementation of the second stop control. The braking control device according to Claim 1.

3. The control unit makes the start timing of the first stop control later than the start timing of the second stop control. The braking control device according to Claim 2.

4. The control unit implements 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. The braking control device according to Claim 3.

5. At the verge of the vehicle stopping, the first stop control and the second stop control are controls for reducing the braking force and then setting the body speed of the vehicle to 0 (zero). The control unit increases the reduction speed of the braking force in the reduction process of the first stop control compared to when the reduction process of the second stop control is executed. The braking control device according to any one of Claims 2 to 4.

6. At the verge of the vehicle stopping, the first stop control is a control for reducing the braking force and then setting the 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 stoppers, the control unit executes a retreat process for increasing the braking force to the required value of the braking force and terminates the first stop control. The braking control device according to Claim 1 or Claim 2. ​ ​ ​ ​ ​

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