Braking control device

Abstract

To provide a braking control device, which is configured to suppress a change in attitude of a vehicle when stopping the vehicle, without making a driver feel strangeness, when the driver changes a braking operation in the middle of braking.SOLUTION: A processing circuit 51 of a braking control device 50 functions as: a control part M11 that decreases vehicle braking force down to predetermined braking force that is smaller than required braking force and then executes a decrease-correcting process for decreasing the vehicle body speed of a vehicle 10 down to 0 (zero), when applying braking force to the vehicle 10 to stop the vehicle; and a setting part M15 that when sensing change of braking operation before starting the decrease correcting process, under a situation where a driver is performing the braking operation, sets a time for executing the decrease correcting process to a time shorter than that when not sensing the change of the braking operation.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a braking control device that controls the braking force applied to a vehicle.

Background Art

[0002] Patent Document 1 discloses a vehicle control device that performs stop control for suppressing a change in the posture of a vehicle at the time of stopping by reducing the braking force applied to the vehicle immediately before stopping.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the braking force is reduced in accordance with the execution of the above-described stop control, if the braking operation of the driver of the vehicle is changed, a deviation may occur between the behavior of the vehicle intended by the driver and the actual behavior of the vehicle. If such a deviation occurs, the driver may feel a sense of discomfort due to the occurrence of the deviation.

Means for Solving the Problems

[0005] The braking control device for solving the above problems, when applying a braking force to the vehicle to stop it, reduces the braking force applied to the vehicle to a predetermined braking force smaller than the required value of the braking force, and then executes a deceleration correction process for setting the vehicle body speed of the vehicle to 0 (zero). When the change in the braking operation is detected before the start of the deceleration correction process in a situation where the driver of the vehicle is performing a braking operation, a setting unit that sets the execution time of the deceleration correction process to a shorter time than when the change in the braking operation is not detected.

Effects of the Invention

[0006] When the braking operation is changed by the driver during braking, the above braking control device can suppress the change in the posture of the vehicle at the time of stopping without making the driver feel uncomfortable.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0008] Hereinafter, an embodiment of the braking control device will be described with reference to FIGS. 1 to 8. FIG. 1 illustrates a vehicle 10 including a braking control device 50. The vehicle 10 includes a braking operation member 11, a plurality of wheels, a plurality of friction brakes 20, and a braking actuator 30. The plurality of wheels includes two front wheels 12 and two rear wheels 13. 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. Operating the braking operation member 11 by the driver is referred to as "braking operation".

[0009] <Friction brake> The plurality of friction brakes 20 respectively apply a braking force to the corresponding wheels. The friction brake 20 has 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 brake 20 can apply a greater braking force to the wheel as the wheel hydraulic pressure increases.

[0010] <Braking actuator> The braking actuator 30 controls the braking force applied to the wheels 12, 13 by controlling the wheel hydraulic pressure of the plurality of wheel cylinders 21. For example, the braking actuator 30 has a pressurizing source that supplies brake fluid to the plurality of wheel cylinders 21. The pressurizing source is, for example, an electric pump and an electric cylinder. The braking actuator 30 can individually adjust the wheel hydraulic pressure of the wheel cylinder 21 for the front wheels 12 and the wheel hydraulic pressure of the wheel cylinder 21 for the rear wheels 13.

[0011] In the following description, the sum of the braking forces applied to the plurality of wheels 12, 13 is also referred to as "vehicle braking force BPAl". <Detection system> The detection system of vehicle 10 includes a plurality of sensors that output detection signals to the braking control device 50. The plurality of sensors include a brake sensor 101, a plurality of wheel speed sensors 102, and a longitudinal and lateral acceleration sensor 103.

[0012] 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.

[0013] 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 wheel. The rotational speed of the wheel based on the detection signal of the wheel speed sensor 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".

[0014] The longitudinal and lateral acceleration sensor 103 detects the acceleration in the longitudinal and lateral directions of the vehicle 10 among the accelerations acting on the vehicle 10. The acceleration in the longitudinal and lateral directions of the vehicle 10 based on the detection signal of the longitudinal and lateral acceleration sensor 103 is referred to as "longitudinal and lateral acceleration Gx".

[0015] <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 20. That is, the processing circuit 51 can adjust the vehicle braking force BPAl by operating the plurality of friction brakes 20.

[0016] <Overview of Braking Control at Stop> When the driver operates the braking operation member 11, the processing circuit 51 performs braking control at stop. The braking control at stop is braking control for suppressing changes in the posture of the vehicle 10 when stopping.

[0017] Referring to FIG. 2, the braking control at stop will be described. FIG. 2 illustrates an example in which the braking operation amount X does not change during the execution of the braking control at stop. At timing t11 when the vehicle 10 is running, the driver starts operating the braking operation member 11. In this case, as shown in FIG. 2(B), the processing circuit 51 derives a required braking force BPRq. The required braking force BPRq is a required value of the vehicle braking force BPAl. For example, the processing circuit 51 derives the required braking force BPRq such that the value 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.

[0018] When the 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 and lateral acceleration Gx increases as the vehicle braking force BPAl increases.

[0019] When the vehicle body speed VS reaches the first vehicle body speed determination value VSth1 at timing t12, the processing circuit 51 starts the 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 supplementary correction processing of the stop-time braking control. In the supplementary correction processing, the processing circuit 51 sets a 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 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.

[0020] 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 equal to or lower than the second vehicle body speed determination value VSth2, it can be considered that the vehicle 10 has approached the stop position PS. The stop position PS is the predicted position where the vehicle 10 stops. The processing circuit 51 shifts the processing of the stop-time braking control from the supplementary correction processing to the reduction correction processing. In the reduction correction processing, the processing circuit 51 decreases the commanded braking force BPTr at a constant speed. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPAl becomes the commanded braking force BPTr. By the processing circuit 51 executing the reduction correction processing 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.

[0021] At timing t14, the commanded braking force BPTr becomes equal to the holding braking force BPth for stopping. As the holding braking force BPth for stopping, the minimum braking force necessary to maintain the stop of the vehicle 10 on the current traveling road surface of the vehicle 10, or a braking force slightly greater than the braking force, is set. This holding braking force BPth for stopping is an example of the "predetermined braking force". From timing t14, in the subtraction correction process, the processing circuit 51 holds the commanded braking force BPTr at the holding braking force BPth for stopping.

[0022] At timing t15, since the processing circuit 51 determines that the vehicle 10 has stopped, the process of braking control at the time of stopping is shifted from the subtraction correction process to the degradation process. In the degradation process, the processing circuit 51 increases the commanded braking force BPTr. For example, the processing circuit 51 increases the commanded braking force BPTr to the required braking force BPRq. By the processing circuit 51 controlling the brake actuator 30 based on the commanded braking force BPTr, the vehicle braking force BPAl increases. When the commanded braking force BPTr becomes equal to the required braking force BPRq at timing t16, the processing circuit 51 ends the braking control at the time of stopping.

[0023] <Functional configuration of the 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, for example, a control unit M11, an acquisition unit M13, and a setting unit M15.

[0024] <Control unit> When the control unit M11 applies braking force to the vehicle 10 to stop it, it performs stop-time braking control. That is, when the start condition of the stop-time braking control is satisfied, the control unit M11 executes the additional correction process of the stop-time braking control. In the additional correction process, the control unit M11 sets the commanded braking force BPTr to a vehicle braking force greater than the required braking force BPRq. The offset value ΔBP, which is the additional correction amount of the commanded braking force BPTr at this time, 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 subsequent reduction correction process. The control unit M11 operates the brake actuator 30 based on the commanded braking force BPTr.

[0025] During the execution of the additional correction process, when the transition condition from the additional correction process to the reduction correction process is satisfied, the control unit M11 ends the additional correction process and starts the reduction correction process. In the reduction correction process, the control unit M11 reduces the commanded braking force BPTr to the stop-maintaining braking force BPth smaller than the required braking force BPRq and then sets the vehicle body speed VS to 0 (zero). At this time, the control unit M11 reduces the commanded braking force BPTr to the stop-maintaining braking force BPth before the vehicle body speed VS becomes 0 (zero). After the commanded braking force BPTr reaches the stop-maintaining braking force BPth, the control unit M11 holds the commanded braking force BPTr at the stop-maintaining braking force BPth. The control unit M11 operates the brake actuator 30 based on the commanded braking force BPTr at that time.

[0026] During the execution of the reduction correction process, when the transition condition from the reduction correction process to the degradation process is satisfied, the control unit M11 ends the reduction correction process and starts the degradation process. In the degradation process, the control unit M11 increases the commanded braking force BPTr to the required braking force BPRq. The control unit M11 operates the brake actuator 30 based on the commanded braking force BPTr.

[0027] <Acquisition unit> The acquisition unit M13 acquires at least one of the braking operation amount X and the change speed dX of the braking operation amount X as a braking operation related value. For example, the acquisition unit M13 acquires the braking operation related value each time during the execution of the augmentation correction process. In the present embodiment, the acquisition unit M13 acquires at least the braking operation amount X among the braking operation amount X and the change speed dX of the braking operation amount X.

[0028] <Setting unit> When the setting unit M15 detects a change in the braking operation before the start of the reduction correction process in a situation where the driver is performing a braking operation, the setting unit M15 sets the execution time TMD of the reduction correction process to a shorter time than when no change in the braking operation is detected. For example, the setting unit M15 detects a change in the braking operation based on the transition of the braking related value acquired by the acquisition unit M13 before the start of the reduction correction process. In the present embodiment, the acquisition unit M13 acquires the braking operation amount X as the braking related value. Therefore, the setting unit M15 detects a change in the braking operation based on the transition of the braking operation amount X before the start of the reduction correction process. At this time, the setting unit M15 detects that the braking operation has changed when the change amount ΔX of the braking operation amount X from the start time of the augmentation correction process becomes equal to or greater than the first change amount ΔXth1.

[0029] The setting unit M15 sets the execution time TMD of the reduction correction process depending on whether or not a change in the braking operation is detected before the start of the reduction correction process. In the present embodiment, when the change amount ΔX of the braking operation amount X from the start time of the augmentation correction process becomes equal to or greater than the first change amount ΔXth1, the setting unit M15 makes the execution time TMD shorter than when the change amount ΔX does not become equal to or greater than the first change amount ΔXth1.

[0030] For example, using the map shown in FIG. 3, the setting unit M15 may set the execution time TMD of the subtraction correction process. As shown in FIG. 3, when the change amount ΔX is less than the first change amount ΔXth1, the setting unit M15 sets the reference execution time TMDB as the execution time TMD of the subtraction correction process on the assumption that it cannot detect the change in the braking operation before the start of the subtraction correction process. When the change amount ΔX is greater than or equal to the first change amount ΔXth1 and less than the second change amount ΔXth2, the setting unit M15 sets a shorter time as the execution time TMD of the subtraction correction process as the change amount ΔX is larger. The second change amount ΔXth2 is smaller than the first change amount ΔXth1. When the change amount ΔX is greater than or equal to the second change amount ΔXth2, the setting unit M15 sets the minimum time TMDMin as the execution time TMD of the subtraction correction process. The minimum time TMDMin is shorter than the reference execution time TMDB.

[0031] <Flow of processing during vehicle braking> Referring to FIG. 4, a series of processes when the processing circuit 51 executes the stop-time braking control will be described. When the driver is performing a braking operation, the processing circuit 51 repeatedly executes the series of processes shown in FIG. 4.

[0032] In step S11, the processing circuit 51 determines whether the start condition of the stop-time braking control is satisfied. For example, as shown in FIG. 2, when the vehicle body speed VS changes from a state where it is greater than the first vehicle body speed determination value VSth1 to a state where it is less than or equal to the first vehicle body 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 (S11: YES), the process proceeds to step S13. On the other hand, when the processing circuit 51 determines that the start condition is not satisfied (S11: NO), the series of processes shown in FIG. 4 is temporarily terminated.

[0033] In step S13, the processing circuit 51 acquires the braking operation amount X at that time as the reference operation amount XB. This reference operation amount XB is the braking operation amount X at the start point of the augmentation correction process. In the subsequent step S15, the processing circuit 51 executes the augmentation correction process for the stop-time braking control. In the augmentation correction process, the processing circuit 51 sets the sum of the required braking force BPRq and the offset value ΔBP as the indicated braking force BPTr in order to compensate for the extension of the braking distance of the vehicle 10 due to the execution of the reduction correction process. The processing circuit 51 operates the brake actuator 30 based on the indicated braking force BPTr.

[0034] In the next step S17, the processing circuit 51 acquires the braking operation amount X at that time. That is, the processing circuit 51 acquires the braking operation amount X during the execution of the augmentation correction process. Then in step S19, the processing circuit 51 sets the execution time TMD of the reduction correction process. Specifically, the processing circuit 51 derives the magnitude of the difference between the braking operation amount X acquired in step S17 and the reference operation amount XB as the change amount ΔX of the braking operation amount. The processing circuit 51 sets the execution time TMD corresponding to the change amount ΔX using, for example, the map shown in FIG. 3.

[0035] In the subsequent step S21, the processing circuit 51 sets the second vehicle body speed determination value VSth2 to a vehicle body speed corresponding to the execution time TMD set in step S19. At this time, the processing circuit 51 sets the second vehicle body speed determination value VSth2 such that the value becomes smaller as the execution time TMD becomes shorter. The stop-time braking control is a control for making the vehicle body speed VS zero (zero) during the execution of the subtraction correction process. Therefore, for example, if the second vehicle body speed determination value VSth2 is not decreased even when the execution time TMD becomes shorter, there is a high possibility that the vehicle body speed VS will not become zero (zero) by the end of the subtraction correction process. Thus, when the execution time TMD of the subtraction correction process is variable as in this embodiment, it is necessary to change the second vehicle body speed determination value VSth2 according to the set execution time TMD. Therefore, during the execution of the subtraction correction process, the processing circuit 51 sets the second vehicle body speed determination value VSth2 so that the vehicle body speed VS becomes zero (zero) within the holding period during which the commanded braking force BPTr is held at the stop-maintaining braking force BPth. When the processing circuit 51 sets the second vehicle body speed determination value VSth2, the process proceeds to step S23.

[0036] In step S23, the processing circuit 51 determines whether or not the condition for shifting from the addition correction process to the subtraction correction process is satisfied. For example, when the vehicle body speed VS changes from a state where it is greater than the second vehicle body speed determination value VSth2 to a state where the vehicle body speed VS is less than or equal to the second vehicle body speed determination value VSth2, the processing circuit 51 determines that the shift condition is satisfied. The second vehicle body speed determination value VSth2 used here is the one set in step S21. When the processing circuit 51 determines that the shift condition is not satisfied (S23: NO), the process proceeds to step S15. That is, the processing circuit 51 executes the addition correction process. On the other hand, when the processing circuit 51 determines that the shift condition is satisfied (S23: YES), the process proceeds to step S25.

[0037] In step S25, the processing circuit 51 executes a reduction correction process for stop-time braking control. In the reduction correction process, the processing circuit 51 reduces the commanded braking force BPTr to the holding braking force for stop BPth. After the commanded braking force BPTr reaches the holding braking force for stop BPth, the processing circuit 51 holds the commanded braking force BPTr at the holding braking force for stop BPth. Then, the processing circuit 51 operates the brake actuator 30 based on the commanded braking force BPTr.

[0038] In the present embodiment, the processing circuit 51 changes the commanded braking force BPTr so that the reduction correction process can be completed within the execution time TMD set in step S19. First, the processing circuit 51 sets the length of the reduction period, which is the period during which the commanded braking force BPTr is reduced to the holding braking force for stop BPth, and the length of the holding period, which is the period during which the commanded braking force BPTr is held at the holding braking force for stop BPth. If the length of the reduction period is shortened, the reduction speed of the commanded braking force BPTr during the reduction period tends to increase. Therefore, the processing circuit 51 shortens the length of the holding period as the execution time TMD becomes shorter. Then, during the reduction period, the processing circuit 51 increases the reduction speed of the commanded braking force BPTr as the set length of the reduction period becomes shorter. When the reduction period ends and the commanded braking force BPTr reaches the holding braking force for stop BPth, the processing circuit 51 holds the commanded braking force BPTr at the holding braking force for stop BPth.

[0039] In subsequent step S27, the processing circuit 51 determines whether the transition condition from the subtraction correction process to the degradation process is satisfied. For example, as shown in FIG. 2, when the processing circuit 51 determines that the vehicle 10 has stopped, it determines that the transition condition is satisfied. Therefore, before the actual execution time of the subtraction correction process reaches the above execution time TMD, the processing circuit 51 may determine that the transition condition is satisfied. Conversely, after the actual execution time of the subtraction correction process exceeds the above execution time TMD, the processing circuit 51 may determine that the transition condition is satisfied. When the processing circuit 51 determines that the transition condition is not satisfied (S27: NO), the process proceeds to step S25. That is, the processing circuit 51 executes the subtraction correction process. On the other hand, when the processing circuit 51 determines that the transition condition is satisfied (S27: YES), the process proceeds to step S29.

[0040] In step S29, the processing circuit 51 executes the degradation process of the stop-time braking control. 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 based on the commanded braking force BPTr.

[0041] In the next step S31, 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 (S31: NO), the process proceeds to step S29. That is, the processing circuit 51 executes the degradation process. On the other hand, when the processing circuit 51 determines that the end condition is satisfied (S31: YES), the degradation process ends. Then, the processing circuit 51 ends the stop-time braking control and ends the series of processes shown in FIG. 4.

[0042] In this embodiment, each of the processes in steps S15 and S23 to S31 is executed by the processing circuit 51 functioning as the control unit M11. Each of the processes in steps S13 and S17 is executed by the processing circuit 51 functioning as the acquisition unit M13. Each of the processes in steps S19 and S21 is executed by the processing circuit 51 functioning as the setting unit M15.

[0043] <Actions and effects of this embodiment when the braking operation amount X is decreased> Referring to FIGS. 5 and 6, the case where the braking operation amount X is decreased before the start of the subtraction correction process will be described. FIG. 5 illustrates a first comparative example in which the execution time TMD of the subtraction correction process is not changed even if the braking operation amount X is decreased before the start of the subtraction correction process. FIG. 6 illustrates this embodiment in which the execution time TMD of the subtraction correction process is changed when the braking operation amount X is decreased before the start of the subtraction correction process.

[0044] <First comparative example> As shown in FIGS. 5(A), 5(B), and 5(C), at the timing t21 when the driver is applying braking force to the vehicle 10 by performing a braking operation, the processing circuit determines that the start condition of the stop-time braking control is satisfied. Therefore, the processing circuit starts the addition correction process. During the execution of the addition correction process, the indicated braking force BPTr is set to a vehicle braking force that is greater than the required braking force BPRq. Therefore, the vehicle braking force BPAl becomes greater than the required braking force BPRq.

[0045] From the timing t22 during the execution of such an addition correction process, the driver's braking operation changes. Specifically, since the braking operation amount X decreases, the required braking force BPRq decreases as shown in FIG. 5(A). As a result, the indicated braking force BPTr also decreases while maintaining a state greater than the required braking force BPRq. Thereby, the vehicle braking force BPAl also decreases.

[0046] At a subsequent timing t23, since the transition condition from the positive correction process to the negative correction process is satisfied, the processing circuit ends the positive correction process and starts the negative correction process. In the negative correction process, the commanded braking force BPTr is decreased to the holding braking force BPth for stopping. Therefore, the vehicle braking force BPAl decreases toward the holding braking force BPth for stopping. Then, at timing t24, the commanded braking force BPTr becomes the holding braking force BPth for stopping. Therefore, after timing t24, the commanded braking force BPTr is held at the holding braking force BPth for stopping. As a result, the vehicle braking force BPAl is held.

[0047] Here, in the first comparative example, during the execution of the positive correction process before the start of the negative correction process, the vehicle braking force BPAl decreases in response to the decrease in the braking operation amount X. Then, as shown in (C) of FIG. 5, due to the start of the negative correction process from timing t23 during which the braking operation amount X is decreasing, the decreasing speed of the vehicle braking force BPAl increases. That is, although the decreasing speed of the braking operation amount X is constant, the decreasing speed of the vehicle braking force BPAl increases midway. In the first comparative example, the period from timing t23 to timing t24 is a period during which the vehicle braking force BPAl decreases at a speed higher than the speed corresponding to the decreasing speed of the braking operation amount X. Further, in the first comparative example, in the period from timing t24 to timing t25, although the braking operation amount X is decreasing, the vehicle braking force BPAl is not decreased.

[0048] That is, in the first comparative example, a deviation occurs between the behavior of the vehicle inferred from the mode of the driver's braking operation and the actual behavior of the vehicle. If the period during which such a deviation occurs is long, the driver may feel a sense of discomfort with respect to the occurrence of the deviation.

[0049] <This Embodiment> As shown in FIGS. 6(A), 6(B), and 6(C), at the timing t31 when the driver performs a braking operation and braking force is being applied to the vehicle 10, the processing circuit 51 starts the supplementary correction process for the stop-time braking control. As a result, the vehicle braking force BPAl becomes greater than the required braking force BPRq. From the timing t32 during the execution of such a supplementary correction process, the driver's braking operation changes. Specifically, since the braking operation amount X decreases, the required braking force BPRq decreases as shown in FIG. 6(A). As a result, as shown in FIG. 6(C), the commanded braking force BPTr and the vehicle braking force BPAl also decrease.

[0050] The timing t33 in FIG. 6 corresponds to the timing t23 in FIG. 5. That is, in the first comparative example, the reduction correction process starts from the timing t33. In contrast, in the present embodiment, when a change in the braking operation is detected before the start of the reduction correction process, the execution time TMD of the reduction correction process is set to a shorter time than when no change in the braking operation is detected. As a result, the start timing of the reduction correction process is delayed compared to the case of the first comparative example. In the example shown in FIG. 6, between the timing t34 after the timing t33 and the timing t36, the processing circuit 51 executes the reduction correction process. Specifically, between the timing t34 and the timing t35, the processing circuit 51 decreases the commanded braking force BPTr to the stop-maintaining braking force BPth. Then, between the timing t35 and the timing t36, the processing circuit 51 holds the commanded braking force BPTr at the stop-maintaining braking force BPth.

[0051] The length of the period from timing t34 to timing t36 is shorter than the length of the period from timing t23 to timing t25, which is the execution period of the subtraction correction process in the first comparative example. As a result, the length of the period during which a deviation occurs between the behavior of the vehicle inferred from the manner of the driver's braking operation and the actual behavior of the vehicle becomes shorter compared to the case of the first comparative example. Therefore, even if the subtraction correction process is executed, it is difficult for the driver to feel discomfort due to the occurrence of the above deviation. Accordingly, even when the decrease in the braking operation amount X starts before the start of the subtraction correction process, the braking control device 50 can suppress the change in the posture of the vehicle 10 at the time of stopping without making the driver feel discomfort.

[0052] <Actions and effects of the present embodiment when the braking operation amount X increases> With reference to FIGS. 7 and 8, the case where the braking operation amount X increases before the start of the subtraction correction process will be described. FIG. 7 illustrates a second comparative example in which the execution time TMD of the subtraction correction process is not changed even when the braking operation amount X increases before the start of the subtraction correction process. FIG. 8 illustrates the present embodiment in which the execution time TMD of the subtraction correction process is changed when the braking operation amount X increases before the start of the subtraction correction process.

[0053] <Second comparative example> As shown in FIGS. 7(A), (B), and (C), at the timing t41 when the braking force is being applied to the vehicle 10 by the driver's braking operation, the processing circuit starts the addition correction process for the stop-time braking control. Therefore, the vehicle braking force BPAl becomes larger than the required braking force BPRq. From the timing t42 during the execution of such an addition correction process, the driver's braking operation changes. Specifically, since the braking operation amount X increases, the required braking force BPRq increases as shown in FIG. 7(A). As a result, as shown in FIG. 7(C), the commanded braking force BPTr and the vehicle braking force BPAl also increase.

[0054] At a subsequent timing t43, since the transition condition from the positive correction process to the negative correction process is satisfied, the processing circuit ends the positive correction process and starts the negative correction process. In the negative correction process, the commanded braking force BPTr is decreased to the holding braking force BPth for stopping. At timing t44, the commanded braking force BPTr becomes the holding braking force BPth for stopping. Therefore, the commanded braking force BPTr is held after timing t44.

[0055] Here, in the second comparative example, the braking operation amount X is increased during the execution of the positive correction process before the start of the negative correction process. Therefore, the vehicle body speed VS reaches the second vehicle body speed determination value VSth2 earlier. As a result, the execution time of the positive correction process becomes shorter. Thereby, there is a possibility that the braking distance of the vehicle becomes longer.

[0056] Also, when the negative correction process is executed by an amount corresponding to the shortening of the braking distance by the execution of the positive correction process, the following problems may occur. That is, there is a possibility that the commanded braking force BPTr cannot be decreased to the holding braking force BPth for stopping by the negative correction process by the amount by which the execution time of the positive correction process has become shorter. In this case, the vehicle braking force BPAl at the time of stopping will be greater than the holding braking force BPth for stopping. As a result, the effect of suppressing the change in the posture of the vehicle at the time of stopping becomes smaller.

[0057] Furthermore, in the second comparative example, the period from timing t43 to timing t45 is a period during which the vehicle braking force BPAl decreases even though the braking operation amount X is increasing. In other words, the period from timing t43 to timing t45 is a period in which a deviation occurs between the behavior of the vehicle inferred from the manner of the driver's braking operation and the actual behavior of the vehicle. If such a deviation occurs for a long period, the driver may feel a sense of discomfort with respect to the occurrence of the deviation.

[0058] <This Embodiment> As shown in FIGS. 8(A), 8(B), and 8(C), at the timing t51 when the driver performs a braking operation and braking force is being applied to the vehicle 10, the processing circuit 51 starts the supplementary correction process for the stop-time braking control. For this reason, the vehicle braking force BPAl becomes greater than the required braking force BPRq. From the timing t52 during the execution of such a supplementary correction process, the driver's braking operation changes. Specifically, since the braking operation amount X increases, the required braking force BPRq increases as shown in FIG. 8(A). As a result, as shown in FIG. 8(C), the commanded braking force BPTr and the vehicle braking force BPAl also increase.

[0059] In the present embodiment, when a change in the braking operation is detected before the start of the reduction correction process, the execution time TMD of the reduction correction process is set to a shorter time than when no change in the braking operation is detected. As a result, the start timing of the reduction correction process is delayed compared to the case of the second comparative example. Thereby, the execution time of the supplementary correction process becomes longer than in the case of the second comparative example. As a result, the braking control device 50 can suppress an increase in the braking distance by as much as the execution time of the supplementary correction process can be made longer compared to the second comparative example.

[0060] Also, by as much as the execution time of the supplementary correction process can be made longer, the braking distance can be shortened by the execution of the supplementary correction process compared to the second comparative example. Therefore, in the reduction correction process executed next to the supplementary correction process, the commanded braking force BPTr, that is, the vehicle braking force BPAl, is decreased to the stop-maintaining braking force BPth. As a result, the braking control device 50 can enhance the effect of suppressing a change in the posture of the vehicle 10 at the time of stopping compared to the second comparative example.

[0061] Furthermore, in the present embodiment, the period from timing t53 to timing t54 is the execution period of the subtraction correction process. In the example shown in FIG. 8, since the braking operation amount X is increasing during the execution of the addition correction process, the length of the period from timing t53 to timing t54 is shorter than the length of the period from timing t43 to timing t45, which is the execution period of the subtraction correction process in the second comparative example. Therefore, the length of the period during which a deviation occurs between the behavior of the vehicle inferred from the driving behavior of the driver and the actual behavior of the vehicle is shorter than that in the second comparative example. Therefore, even if the subtraction correction process is executed, it is difficult for the driver to feel discomfort caused by the occurrence of the above deviation. Therefore, the braking control device 50 can suppress a change in the posture of the vehicle 10 at the time of stopping without making the driver feel discomfort even when the increase in the braking operation amount X starts before the start of the subtraction correction process.

[0062] <Other effects> (1) It can be inferred that the greater the change amount ΔX of the braking operation amount before the start of the subtraction correction process, the stronger the driver's intention to change the braking mode. Therefore, the braking control device 50 sets a shorter time as the execution time TMD of the subtraction correction process as the change amount ΔX of the braking operation amount before the start of the subtraction correction process becomes larger. Thereby, the braking control device 50 can shorten the period during which the behavior of the vehicle 10 intended by the driver who performs the braking operation and the actual behavior of the vehicle 10 deviate, as the driver's intention to change the braking mode becomes stronger.

[0063] (2) As described above, the longer the period during which the vehicle braking force BPAl does not change despite the driver changing the braking operation amount X, the easier it is for the driver to feel discomfort. Therefore, when the braking control device 50 detects a change in the braking operation before the start of the subtraction correction process, the length of the holding period during which the instructed braking force BPTr is held at the stop maintaining braking force BPth in the execution time of the subtraction correction process is made shorter than when no change in the braking operation is detected. Thereby, when the braking control device 50 detects a change in the braking operation before the start of the subtraction correction process, it can shorten the period during which the vehicle braking force BPAl does not change despite the driver changing the braking operation amount X, so that it is difficult for the driver to feel discomfort.

[0064] <Modified Example> The above-described embodiment can be implemented with the following modifications. The above-described 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.

[0065] · The processing circuit 51 (i.e., the acquisition unit M13) may acquire the change rate dX of the braking operation amount X as a braking operation-related value. FIG. 9 illustrates a part of a series of processes when setting the execution time TMD of the subtraction correction process based on the change rate dX.

[0066] As shown in FIG. 9, when the processing circuit 51 determines that the start condition of the braking control at stop is satisfied (S11: YES), the process proceeds to step S131. In step S131, the processing circuit 51 functions as the acquisition unit M13 to acquire the change rate dX of the braking operation amount at that time as the reference change rate dXB. At this time, the processing circuit 51 may acquire the value obtained by differentiating the braking operation amount X with respect to time as the change rate dX. In the next step S15, the processing circuit 51 executes the addition correction process of the braking control at stop. In the subsequent step S171, the processing circuit 51 functions as the acquisition unit M13 to acquire the change rate dX at that time. That is, the processing circuit 51 acquires the change rate dX during the execution of the addition correction process.

[0067] Then, in step S191, the processing circuit 51 functions as the setting unit M15 to set the execution time TMD according to the magnitude of the difference between the change rate dX acquired in step S171 and the reference change rate dXB. The magnitude of the difference between the change rate dX and the reference change rate dXB is referred to as the "change rate change amount". For example, when the change rate change amount is equal to or greater than the threshold value, the processing circuit 51 shortens the execution time TMD compared to the case where the change rate change amount is less than the threshold value. The criterion for determining whether a change in the braking operation can be detected is set as a threshold value. Thereby, when the processing circuit 51 detects a change in the braking operation before the start of the subtraction correction process, it can set the execution time TMD to a shorter time than when no change in the braking operation is detected.

[0068] ·The processing circuit 51 (i.e., the setting unit M15) may set the execution time TMD of the deceleration correction process in consideration of both the change amount ΔX of the braking operation amount acquired before the start of the deceleration correction process and the change amount of the change speed.

[0069] ·When the processing circuit 51 (i.e., the setting unit M15) detects a change in the braking operation before the start of the deceleration correction process, it may not vary the execution time TMD according to the degree of change in the braking operation.

[0070] ·When the processing circuit 51 (i.e., the setting unit M15) detects a change in the braking operation before the start of the deceleration correction process, it may shorten the execution time TMD of the deceleration correction process by omitting the holding period during which the commanded braking force BPTr is held at the vehicle stop maintaining braking force BPth. FIG. 10 shows a time chart illustrating the transition of the commanded braking force BPTr when the holding period is omitted. Even in this case, since the execution time of the deceleration correction process is shortened, the same effects as those of the above-described embodiment can be obtained.

[0071] ·When the processing circuit 51 detects a change in the braking operation before the start of the deceleration correction process, if it can shorten the execution time TMD of the deceleration correction process, it does not necessarily have to shorten the length of the decreasing period during which the commanded braking force BPTr is decreased. Even in this case, the processing circuit 51 can shorten the execution time TMD of the deceleration correction process by shortening the length of the holding period during which the commanded braking force BPTr is held.

[0072] ·In the above-described embodiment, the vehicle stop maintaining braking force BPth is set as the predetermined braking force, but it is not limited thereto. A vehicle braking force different from the vehicle stop maintaining braking force BPth may be set as the predetermined braking force. Also, the magnitude of the predetermined braking force may be changed according to the situation.

[0073] · If the stop-time braking control includes a reduction correction process, it may not include an increase correction process. In this case, the reference time point is the time point that is a predetermined time before the start timing of the reduction correction process. Then, when the processing circuit 51 detects a change in the braking operation during the period from the reference time point to the start timing of the reduction correction process, it is preferable to set the execution time of the reduction correction process to a shorter time than when no change in the braking operation is detected during this period. In this case, the "predetermined time" may be several seconds.

[0074] · If the processing circuit 51 shortens the execution time TMD of the reduction correction process when the braking operation amount X decreases before the start of the reduction correction process, it may not change the execution time TMD when the braking operation amount X increases before the start of the reduction correction process.

[0075] · If the processing circuit 51 shortens the execution time TMD of the reduction correction process when the braking operation amount X increases before the start of the reduction correction process, it may not change the execution time TMD when the braking operation amount X decreases before the start of the reduction correction process.

[0076] · In the above embodiment, the processing circuit 51 determines the start timing of the increase correction process and the start timing of the reduction correction process of the stop-time braking control according to the change in the vehicle body speed VS. However, if it is a parameter whose value decreases as the vehicle 10 approaches the 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 stop distance and the stop prediction time. The stop distance is the distance from the current position of the vehicle 10 to the stop position PS. The stop prediction time is the time required for the vehicle 10 to stop. An example of the stop prediction time is TTC. TTC is an abbreviation of "Time To Collision".

[0077] · When executing the stop-time braking control, 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 sum of the total regenerative braking force applied to the vehicle 10 becomes the vehicle braking force BPAl.

[0078] ·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 for executing at least some of various processes, or a combination thereof. Examples of the dedicated hardware include, for example, an ASIC which is an application-specific integrated circuit. The processor includes a CPU and memories such as a RAM and a ROM, and the memories store 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.

[0079] <Other technical ideas> Describe the technical ideas that can be grasped from the above embodiments and modification examples. [Appendix 1] It is provided with an acquisition unit that acquires at least one of the amount of the braking operation and the rate of change of the amount of the braking operation. Preferably, the setting unit detects a change in the braking operation based on the transition of the value acquired by the acquisition unit before the start of the subtraction correction process.

[0080] [Appendix 2] In the subtraction correction process, the control unit preferably reduces the braking force applied to the vehicle to the predetermined braking force, and after the braking force reaches the predetermined braking force, holds the braking force at the predetermined braking force and then sets the vehicle body speed to 0 (zero).

[0081] [Appendix 3] When the setting unit detects a change in the braking operation before the start of the subtraction correction process, it is preferable to set the time for holding the braking force applied to the vehicle at the predetermined braking force during the execution time of the subtraction correction process to be shorter than the case where no change in the braking operation is detected.

[0082] [Appendix 4] When the setting unit detects a change in the braking operation before the start of the reduction correction process, it is preferable to shorten the execution time of the reduction correction process by omitting the period during which the braking force applied to the vehicle is held at the predetermined braking force.

[0083] [Appendix 5] When applying a braking force to the vehicle to stop it, the control unit executes an increase correction process of making the braking force applied to the vehicle greater than the required value of the braking force before executing the reduction correction process. When the setting unit detects a change in the braking operation during the execution of the increase correction process, it is preferable to set the execution time of the reduction correction process to a shorter time than when no change in the braking operation is detected.

[0084] 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

[0085] 10…Vehicle 11, 12…Wheels 20…Friction Brake 30…Braking Actuator 50…Braking Control Device 51…Processing Circuit M11…Control Unit M13…Acquisition Unit M15…Setting Unit

Claims

1. When applying braking force to a vehicle to stop it, a control unit that executes a deceleration correction process of reducing the braking force applied to the vehicle to a predetermined braking force smaller than the required value of the braking force and then setting the vehicle body speed of the vehicle to 0 (zero); A setting unit that, when a change in the braking operation is detected before the start of the deceleration correction process in a situation where the driver of the vehicle is performing a braking operation, sets the execution time of the deceleration correction process to a shorter time than when no change in the braking operation is detected. A braking control device comprising: Braking control device.

2. The setting unit sets the execution time of the deceleration correction process to a shorter time as the degree of change in the braking operation before the start of the deceleration correction process is greater. The braking control device according to claim 1.

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