Brake control device

Abstract

This invention relates to a braking control device. The processing circuit (51) of the braking control device (50) functions as a control unit (M11) and a setting unit (M15). When the vehicle (10) is stopped by applying braking force, the control unit (M11) performs stop braking control so that the vehicle speed of the vehicle (10) becomes 0 (zero) after the vehicle braking force is reduced to a specified braking force. The greater the moving force acting on the vehicle (10) during the execution of stop braking control, the shorter the execution time of the stop braking control holding process is set by the setting unit (M15).

Description

Technical Field

[0001] This invention relates to a braking control device for controlling the braking force applied to a vehicle. Background Technology

[0002] In recent years, a control device has been developed to implement parking control by reducing the braking force applied to the vehicle just before it stops, thereby suppressing changes in the vehicle's posture during parking. For example, the control device disclosed in Patent Document 1 estimates the timing at which the vehicle speed becomes 0 (zero) during parking control, i.e., the parking estimation timing. Then, the control device reduces the braking force so that the braking force becomes 0 (zero) at the parking estimation timing.

[0003] However, the actual timing when the vehicle speed reaches 0 (zero) is sometimes earlier than the estimated stopping time mentioned above. In this case, the control device described above cannot sufficiently reduce the braking force before stopping, and therefore may not be able to sufficiently reduce the change in the vehicle's posture when stopping.

[0004] In contrast, the control device disclosed in Patent Document 2 implements parking control as follows: the braking force is sufficiently reduced before the estimated parking time, and then the braking force is maintained. Therefore, even if the actual vehicle speed reaches 0 (zero) earlier than the estimated parking time, the braking force becomes sufficiently small when the vehicle speed actually reaches 0 (zero). Furthermore, the rate of reduction of the braking force is 0 (zero) just before stopping. Therefore, even if the actual vehicle speed reaches 0 (zero) deviates from the estimated parking time, changes in the vehicle's posture during parking can be suppressed.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-28913

[0006] Patent Document 2: Japanese Patent Application Publication No. 2022-152781

[0007] The force acting on the vehicle to move it. This force can be, for example, the driving force transmitted from the vehicle's power source to the wheels, or the downhill component of the gravitational acceleration acting on the vehicle traveling on a slope. When performing the parking control disclosed in Patent Document 2 under conditions where such a force causing vehicle movement is relatively large, it may cause a sense of disorientation for the driver when the vehicle is stopped. For example, the vehicle may move after its speed reaches 0 (zero). Furthermore, on an uphill road, the vehicle may sometimes slide downhill. Summary of the Invention

[0008] The braking control device for solving the above-mentioned problem is a device that performs stop braking control when the vehicle is stopped by applying braking force, and then reduces the braking force applied to the vehicle to a predetermined braking force to bring the vehicle's speed to 0 (zero). This braking control device includes: a control unit that performs a reduction process and a holding process in the stop braking control, wherein the reduction process reduces the braking force applied to the vehicle to the predetermined braking force, and the holding process is the next process after the reduction process and is performed before the vehicle's speed reaches 0 (zero), maintaining the braking force applied to the vehicle at the predetermined braking force; and a setting unit that sets the execution time of the holding process to be shorter as the force acting on the vehicle to move the vehicle during the execution of the stop braking control increases.

[0009] The aforementioned braking control device achieves the following effect: when the vehicle is brought to a stop by implementing stop-on braking control, it can suppress changes in the vehicle's posture during parking without causing any sense of incongruity to the driver. Attached Figure Description

[0010] Figure 1 This is a structural diagram showing a vehicle equipped with the braking control device of the first embodiment.

[0011] Figure 2 It is a timing diagram for the case where a vehicle stops on a level road.

[0012] Figure 3 This is a diagram illustrating an example of the mapping used when setting the execution time of a process to maintain or reduce its execution time.

[0013] Figure 4 This is a flowchart illustrating a series of processes performed by the braking control device of the first embodiment.

[0014] Figure 5 This is a timing diagram for the case where the vehicle stops on a slope, as shown in the comparative example.

[0015] Figure 6 This is a timing diagram of the braking control device in the first embodiment, when the vehicle is stopped on a slope.

[0016] Figure 7 This is a flowchart illustrating a series of processes performed by the braking control device of the second embodiment.

[0017] Figure 8 This is a timing diagram of the braking control device in the second embodiment, when the vehicle stops on a slope.

[0018] Figure 9This is a diagram of an example of a mapping used to represent the reliability of deriving road surface slope. Detailed Implementation

[0019] (First Implementation)

[0020] The following is in accordance with Figures 1-6 The first embodiment of the braking control device will be described.

[0021] Figure 1 The diagram illustrates a vehicle 10 equipped with a brake control device 50. The vehicle 10 includes a brake operating member 11, multiple wheels, multiple friction brakes 20, and a brake actuator 30. The brake operating member 11 is operated by the driver when braking force is applied to the vehicle 10. An example of the brake operating member 11 is a brake pedal. The multiple wheels include two front wheels 12 and two rear wheels 13.

[0022] <Friction Brake>

[0023] Multiple friction brakes 20 apply braking force to their respective wheels. Each friction brake 20 has a wheel cylinder 21, a rotating body 22, and a friction part 23. The rotating body 22 rotates integrally with the wheel. Therefore, braking force is applied to the wheel by pressing the friction part 23 against the rotating body 22. The higher the hydraulic pressure in the wheel cylinder 21, i.e., the higher the wheel hydraulic pressure, the greater the force that presses the friction part 23 against the rotating body 22. Therefore, the higher the wheel hydraulic pressure, the greater the braking force that the friction brake 20 can apply to the wheel.

[0024] <Brake Actuator>

[0025] The brake actuator 30 controls the braking force applied to the wheels 12 and 13 by controlling the wheel hydraulic pressure of multiple wheel cylinders 21. For example, the brake actuator 30 has a pressurization source that supplies brake fluid to the multiple wheel cylinders 21. The pressurization source is, for example, an electric pump and an electric cylinder. The brake actuator 30 can individually adjust the wheel hydraulic pressure of the wheel cylinders 21 for the front wheels 12 and the wheel hydraulic pressure of the wheel cylinders 21 for the rear wheels 13.

[0026] In later records, the sum of the braking forces applied to multiple wheels 12 and 13 will also be referred to as "vehicle braking force BPA1".

[0027] <Detection System>

[0028] The detection system of vehicle 10 includes multiple sensors that output detection signals to braking control device 50. The multiple sensors include brake sensor 101, multiple wheel speed sensors 102, and front and rear acceleration sensors 103.

[0029] Brake sensor 101 detects information related to the driver's operation of brake operating member 11. An example of brake sensor 101 is a stroke sensor that detects the amount of operation by the driver on brake operating member 11. The amount of operation based on the detection signal from brake sensor 101 is referred to as "brake operation amount X". Alternatively, the detection system may also include a sensor that detects the force applied by the driver to brake operating member 11.

[0030] A wheel speed sensor 102 is provided for each of the multiple wheels. The multiple wheel speed sensors 102 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 called "wheel speed VW". The driving speed of the vehicle 10 calculated based on the wheel speeds VW of the multiple wheels 12 and 13 is called "vehicle speed VS".

[0031] The front and rear acceleration sensors 103 detect the acceleration in the front-rear direction of the vehicle 10 in the acceleration acting on the vehicle 10. The front-rear acceleration of the vehicle 10 based on the detection signal of the front and rear acceleration sensors 103 is called "front-rear acceleration Gx".

[0032] <Brake Control Device>

[0033] The brake control device 50 includes a processing circuit 51. An example of the processing circuit 51 is an electronic control device. In this case, the processing circuit 51 includes a CPU 52, a first memory 53, and a second memory 54. The first memory 53 stores the control program executed by the CPU 52. The second memory 54 stores the calculation results of the CPU 52, etc. By executing the control program in the first memory 53 through the CPU 52, the processing circuit 51 controls the brake actuator 30 to operate the multiple friction brakes 20. That is, the processing circuit 51 can adjust the vehicle braking force BPA1 by operating the multiple friction brakes 20.

[0034] <Overview of braking control during stop>

[0035] When the vehicle 10 is brought to a stop by applying braking force, the processing circuit 51 implements stop-time braking control. Stop-time braking control is a braking control used to suppress changes in the posture of the vehicle 10 when it is stopped.

[0036] Reference Figure 2 The braking control during stopping is explained. Figure 2 The illustration shows an example of implementing stop-on-time braking control when bringing vehicle 10 to a stop on a level road.

[0037] At time t11, while the vehicle 10 is in motion, the driver begins to operate the brake operating component 11. In this situation, as... Figure 2As shown in (B), the processing circuit 51 derives the requested braking force BPRq. The requested braking force BPRq is the requested value of the vehicle's braking force BPA1. For example, the processing circuit 51 derives the requested braking force BPRq in such a way that the larger the braking operation amount X of the braking operation member 11, the larger the value. If, as before time t12, the vehicle body speed VS of the vehicle 10 is greater than the first vehicle body speed determination value VSth1, then... Figure 2 As shown in (D), the processing circuit 51 sets the requested braking force BPRq to the indicated braking force BPTr. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPA1 becomes the indicated braking force BPTr.

[0038] Thus, when braking force is applied to vehicle 10, such as Figure 2 As shown in (A), the vehicle speed VS decreases. Additionally, as... Figure 2 As shown in (C), the absolute value of the front and rear acceleration Gx increases as the vehicle's braking force BPA1 increases.

[0039] When the vehicle speed VS reaches the first vehicle speed determination value VSth1 at time t12, the processing circuit 51 initiates stop-on-time braking control. The first vehicle speed determination value VSth1 is an example of a threshold used to set the start timing of stop-on-time braking control. From time t12, the processing circuit 51 initiates an increase correction process for stop-on-time braking control. In the increase correction process, the processing circuit 51 sets a braking force greater than the requested braking force BPRq as the indicated braking force BPTr. For example, the processing circuit 51 sets the sum of the requested braking force BPRq and the offset value ΔBP as the indicated braking force BPTr. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPA1 becomes the indicated braking force BPTr. Thus, even if the requested braking force BPRq is the same, the absolute value of the vehicle 10's front-to-rear acceleration Gx increases by the amount of the offset value ΔBP compared to before time t12.

[0040] At time t13, the vehicle speed VS becomes the second vehicle speed determination value VSth2. Vehicle speeds smaller than the first vehicle speed determination value VSth1 are set as the second vehicle speed determination value VSth2. When the vehicle speed VS is below the second vehicle speed determination value VSth2, the vehicle 10 can be considered to be approaching the stopping position PS. The stopping position PS refers to the predicted stopping position of the vehicle 10. The processing circuit 51 transfers the braking control processing at the time of stopping from the increase correction processing to the decrease correction processing. In the decrease correction processing, the processing circuit 51 reduces the indicated braking force BPTr at a certain speed. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPA1 becomes the indicated braking force BPTr. Thus, by performing the decrease correction processing through the processing circuit 51, the vehicle braking force BPA1 is less than the requested braking force BPRq. As a result, even if the requested braking force BPRq is the same, the absolute value of the vehicle 10's front-to-rear acceleration Gx gradually decreases.

[0041] At time t14, the indicated braking force BPTr is equal to the parking sustaining braking force BPth. The parking sustaining braking force BPth is set as the minimum braking force required to keep the vehicle 10 at a stop on the road surface where it is currently traveling, or a braking force slightly greater than that. This parking sustaining braking force BPth is an example of a "prescribed braking force". Starting from time t14, during the reduction correction process, the processing circuit 51 maintains the indicated braking force BPTr at the parking sustaining braking force BPth.

[0042] Furthermore, the process in the reduction correction process that reduces the indicated braking force BPTr to the parking sustaining braking force BPth will be referred to as the "reduction process." The process in the reduction correction process that maintains the indicated braking force BPTr at the parking sustaining braking force BPth will be referred to as the "holding process." The holding process begins after the reduction process and is performed until the vehicle speed VS reaches 0 (zero). More specifically, it is preferable to begin the holding process just before the vehicle speed VS reaches 0 (zero).

[0043] At time t15, the processing circuit 51 determines that the vehicle 10 has stopped, and therefore switches the braking control process from reduction correction (i.e., holding process) to retraction process. In the retraction 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 requested braking force BPRq. The processing circuit 51 controls the brake actuator 30 based on the indicated braking force BPTr, thereby increasing the vehicle braking force BPA1. When at time t16, the indicated braking force BPTr equals the requested braking force BPRq, the processing circuit 51 terminates the braking control at stop.

[0044] <Functional Structure of Processing Circuit>

[0045] Reference Figure 1 The functional structure of the processing circuit 51 will be described. The CPU 52 executes the control program from the first memory 53, thereby enabling the processing circuit 51 to function as multiple functional units. These multiple functional units are for stopping the vehicle 10 by applying braking force. These multiple functional units include, for example, a control unit M11, a movement force output unit M13, and a setting unit M15.

[0046] <Control Department>

[0047] When the control unit M11 applies braking force to the vehicle 10 to bring it to a stop, it implements stop-and-go braking control. That is, when the start condition for stop-and-go braking control is met, the control unit M11 performs an increase correction process. In the increase correction process, the control unit M11 sets the indicated braking force BPTr to a vehicle braking force greater than the requested braking force BPRq. The increase correction amount of the indicated braking force BPTr at this time, i.e., the offset value ΔBP, is a correction amount of braking force used to compensate for the increase in braking distance of the vehicle 10 caused by the execution of the decrease correction process described later. The control unit M11 activates the brake actuator 30 based on this indicated braking force BPTr.

[0048] During the execution of the increase correction process, when the transition condition from the increase correction process to the decrease correction process is met, the control unit M11 ends the increase correction process and begins the decrease correction process. In the decrease correction process, after reducing the indicated braking force BPTr to the parking sustaining braking force BPth, the control unit M11 sets the vehicle speed VS to 0 (zero). Specifically, the control unit M11 reduces the indicated braking force BPTr to the parking sustaining braking force BPth by executing the decrease process in the decrease correction process. In this embodiment, during the decrease process, the control unit M11 reduces the indicated braking force BPTr to a parking sustaining braking force BPth that is less than the requested braking force BPRq. The control unit M11 activates the brake actuator 30 based on the indicated braking force BPTr at this time. After the indicated braking force BPTr becomes the parking sustaining braking force BPth, the control unit M11 maintains the indicated braking force BPTr at the parking sustaining braking force BPth by executing the hold process in the decrease correction process. The control unit M11 begins the hold process before the vehicle speed VS becomes 0 (zero). The control unit M11 activates the brake actuator 30 based on the indicated braking force BPTr at this time.

[0049] As detailed below, in this embodiment, the setting unit M15 sets the execution time TMD for the reduction process. Therefore, the control unit M11 reduces the indicated braking force BPTr to the stop-holding braking force BPth within the execution time TMD set by the setting unit M15. Thus, during the reduction process, the control unit M11 calculates the difference between the indicated braking force BPTr and the stop-holding braking force BPth at the start time of the reduction process as the braking force difference. The control unit M11 calculates the reduction rate of the indicated braking force BPTr by dividing this braking force difference by the execution time TMD. Then, the control unit M11 reduces the indicated braking force BPTr at this reduction rate.

[0050] During the execution of the reduction correction process, when the transition condition from the reduction correction process to the retraction process is met, the control unit M11 ends the reduction correction process and begins the retraction process. In the retraction process, the control unit M11 increases the indicated braking force BPTr to the requested braking force BPRq. At this time, the control unit M11 increases the indicated braking force BPTr such that the rate of increase of the indicated braking force BPTr is greater than the rate of decrease of the indicated braking force BPTr during the reduction process. Then, the control unit M11 activates the brake actuator 30 based on this indicated braking force BPTr.

[0051] <Mobility Force Output Department>

[0052] The moving force output unit M13 outputs the moving force FM that acts on the vehicle 10 when the vehicle 10 brakes. The moving force FM is the force that causes the vehicle 10 to move. More specifically, the moving force FM is the force that acts on the front or rear of the vehicle 10.

[0053] The moving force FM includes, for example, the driving force FD of the vehicle 10 and the gravity acting on the vehicle 10. The greater the magnitude of the driving force FD, the greater the force required to move the vehicle 10 in the direction of travel. In addition, when the vehicle 10 is traveling on a slope, the greater the magnitude of the component of gravity in the downhill direction (i.e., the component of gravitational acceleration FG), the greater the force required to move the vehicle 10 in the downhill direction.

[0054] Therefore, the moving force output unit M13 outputs the moving force FM in such a way that the larger the magnitude of the driving force FD of the vehicle 10 when the vehicle 10 is braking, the larger the value of the moving force FM.

[0055] Furthermore, the motion force extraction unit M13 extracts the slope of the road surface on which the vehicle 10 travels, i.e., the road slope θ. For example, the motion force extraction unit M13 extracts the road slope θ by the principle that the larger the difference between the differential value of the vehicle 10's body speed VS and the front-rear acceleration Gx, the larger the value. The motion force extraction unit M13 can also obtain the road slope θ based on road-related information obtained from the navigation device. In addition, if the vehicle 10 is equipped with a sensor that detects the tilt of the vehicle body, the motion force extraction unit M13 can also obtain the detection value of the sensor as the road slope θ. Furthermore, the motion force extraction unit M13 can also extract the road slope θ by analyzing images captured by the onboard camera.

[0056] The motion force deriving unit M13 derives the motion force FM in such a way that the larger the road surface slope θ, the larger the value. This is because the larger the road surface slope θ, the larger the magnitude of the aforementioned gravitational acceleration component FG.

[0057] When vehicle 10 is moving uphill, the direction of the driving force FD is opposite to the direction of the gravitational acceleration component FG. Therefore, the moving force derivation unit M13 derives the difference between the magnitude of the gravitational acceleration component FG (which can be estimated based on the road slope θ) and the magnitude of the driving force FD as the moving force FM.

[0058] When vehicle 10 is moving downhill, the direction of the driving force FD is the same as the direction of the gravitational acceleration component FG. Therefore, the moving force derivation unit M13 derives the sum of the magnitude of the gravitational acceleration component FG (which can be estimated based on the road slope θ) and the magnitude of the driving force FD as the moving force FM.

[0059] <Settings Department>

[0060] The setting unit M15 sets the execution time TMH of the holding process and the execution time TMD of the reduction process in the reduction correction process based on the movement force FM acting on the vehicle 10 during the execution of braking control at a stop. Specifically, the larger the movement force FM, the shorter the execution time TMH of the holding process is set by the setting unit M15. In addition, the setting unit M15 sets the execution time TMD of the reduction process in such a way that the shorter the execution time TMH of the holding process, the larger the value.

[0061] Figure 3 The diagram illustrates an example of a mapping used to set the execution time TMH for maintaining the current processing speed and the execution time TMD for reducing the current processing speed. For example... Figure 3As shown, when the movement force FM is less than the decision movement force FMth, the execution time TMH of the hold process is set to the base execution time TMH1, and the execution time TMD of the reduce process is set to the base execution time TMD1. On the other hand, when the movement force FM is greater than or equal to the decision movement force FMth, the execution time TMH of the hold process is set to be less than the base execution time TMH1, and the execution time TMD of the reduce process is longer than the base execution time TMD1. In detail, when the movement force FM is greater than or equal to the decision movement force FMth, the larger the movement force FM, the shorter the execution time TMH of the hold process. Moreover, the shorter the execution time TMH of the hold process, the shorter the execution time TMD of the reduce process.

[0062] In addition, Figure 3 In the example shown, the sum of the execution time TMH of the maintenance process and the execution time TMD of the reduction process, i.e., the execution time of the reduction correction process, is constant and independent of the magnitude of the movement force FM. However, the execution time of the reduction correction process can also vary depending on the magnitude of the movement force FM. For example, the larger the magnitude of the movement force FM, the shorter the execution time of the reduction correction process.

[0063] <Procedure for handling vehicle braking>

[0064] Reference Figure 4 This section describes a series of processes performed by the processing circuit 51 during braking control at a stop. The processing circuit 51 repeatedly executes these processes when the vehicle 10 brakes. Figure 4 The series of processes shown.

[0065] In step S11, the processing circuit 51 outputs the moving force FM.

[0066] In the next step S13, the processing circuit 51 sets the execution time TMH of the holding process based on the movement force FM. Additionally, the processing circuit 51 sets the execution time TMD of the reduction process based on the execution time TMH of the holding process.

[0067] In step S15, the processing circuit 51 determines whether the starting condition for braking control at the time of stopping is met. For example, if... Figure 2 As shown, when the vehicle speed VS changes from being greater than the first vehicle speed determination value VSth1 to being less than the first vehicle speed determination value VSth1, the processing circuit 51 determines that the start condition is met. If the start condition is met (S15: Yes), the processing circuit 51 moves the processing to step S17. Conversely, if the start condition is not met (S15: No), the processing circuit 51 temporarily terminates the process. Figure 4 The series of processes shown.

[0068] In step S17, the processing circuit 51 implements braking control when stopping.

[0069] Specifically, in step S19, the processing circuit 51 performs an increase correction process. In this increase correction process, to compensate for the increase in braking distance of the vehicle 10 caused by the decrease correction process, the processing circuit 51 sets the sum of the requested braking force BPRq and the offset value ΔBP as the indicated braking force BPTr. The processing circuit 51 then activates the brake actuator 30 based on this indicated braking force BPTr.

[0070] In step S21, the processing circuit 51 determines whether the transition condition from the increase correction process to the decrease correction process is met. For example, when the vehicle speed VS changes from a state where it is greater than the second vehicle speed determination value VSth2 to a state where the vehicle speed VS is less than or equal to the second vehicle speed determination value VSth2, the processing circuit 51 determines that the transition condition is met. If the processing circuit 51 determines that the transition condition is not met (S21: No), the processing moves to step S19. That is, the processing circuit 51 performs the increase correction process. On the other hand, if the processing circuit 51 determines that the transition condition is met (S21: Yes), the processing moves to step S23.

[0071] In step S23, the processing circuit 51 performs a reduction process in the reduction correction process. In the reduction process, the processing circuit 51 reduces the indicated braking force BPTr to the parking sustaining braking force BPth. Specifically, the processing circuit 51 reduces the indicated braking force BPTr such that the execution time TMD of the reduction process set in step S13 becomes the parking sustaining braking force BPth. Then, the processing circuit 51 activates the brake actuator 30 based on the indicated braking force BPTr at this time.

[0072] In the next step S25, the processing circuit 51 determines whether the indicated braking force BPTr is below the parking sustaining braking force BPth. Here, the processing circuit 51 may also determine whether the actual execution time of the reduction process is the same as the aforementioned reduction process execution time TMD. If the processing circuit 51 determines that the indicated braking force BPTr is not below the parking sustaining braking force BPth (S25: No), the processing moves to step S23. That is, the processing circuit 51 performs the reduction process. On the other hand, if the processing circuit 51 determines that the indicated braking force BPTr is below the parking sustaining braking force BPth (S25: Yes), the processing moves to step S27.

[0073] In step S27, the processing circuit 51 performs a holding process within the reduction correction process. In the holding process, the processing circuit 51 maintains the indicated braking force BPTr at the parking holding braking force BPth. Then, the processing circuit 51 activates the brake actuator 30 based on this indicated braking force BPTr.

[0074] In the next step S29, the processing circuit 51 determines whether the end condition of the holding process is met. In this embodiment, if at least one of the conditions (A1) and (A2) shown below is met, the processing circuit 51 determines that the end condition of the holding process is met. On the other hand, if neither of the conditions (A1) nor (A2) shown below is met, the processing circuit 51 determines that the end condition of the holding process is not met.

[0075] (A1) The actual execution time of the hold process reaches the execution time TMH of the hold process mentioned above.

[0076] (A2) It can be determined that vehicle 10 has stopped.

[0077] If the processing circuit 51 determines that the termination condition is not met (S29: No), it moves the processing to step S27. That is, the processing circuit 51 performs the holding process. On the other hand, if the processing circuit 51 determines that the termination condition is met (S29: Yes), it moves the processing to step S31.

[0078] In step S31, the processing circuit 51 performs a retraction process. During the retraction process, the processing circuit 51 increases the indicated braking force BPTr to the requested braking force BPRq. Then, the processing circuit 51 activates the brake actuator 30 based on this indicated braking force BPTr.

[0079] In the next step S33, the processing circuit 51 determines whether the termination condition of the retraction process is met. For example, if the indicated braking force BPTr is equal to the requested braking force BPRq, the termination condition is considered met. On the other hand, if the indicated braking force BPTr is less than the requested braking force BPRq, the termination condition is considered not met. If the processing circuit 51 determines that the termination condition is not met (S33: No), the processing moves to step S31. That is, the processing circuit 51 performs the retraction process. On the other hand, if the processing circuit 51 determines that the termination condition is met (S33: Yes), the retraction process ends. Then, the processing circuit 51 ends the braking control at the stop and terminates the process. Figure 4 The series of processes shown.

[0080] In this embodiment, the processing of step S11 is performed by the processing circuit 51 as the moving force output unit M13. The processing of step S13 is performed by the processing circuit 51 as the setting unit M15. The processing of step S17 is performed by the processing circuit 51 as the control unit M11.

[0081] <Function and Effects of This Implementation Method>

[0082] Reference Figure 5 and Figure 6 The function and effects of this implementation method are explained. Figure 5 and Figure 6 The example shown is a case of stopping a vehicle 10 that is traveling on a slope by applying braking force. Figure 5 This section presents a comparison of the execution time TMH for maintaining the process without changing the mobility force FM and the execution time TMD for reducing the process. Figure 6 This embodiment describes the execution time TMH of the maintenance process and the execution time TMD of the reduction process based on the change in mobility force FM.

[0083] <Comparative Example>

[0084] like Figure 5 As shown by the dashed line in (C), the parking holding braking force BPth is greater when the vehicle 10 is traveling on a slope than when the vehicle 10 is traveling on a level road.

[0085] like Figure 5 As shown in (A), (B), and (C), at time t21 during the process of applying braking force to vehicle 10, the processing circuit determines that the start condition for braking control at a stop has been met. Therefore, the processing circuit begins the increase correction process. During the execution of the increase correction process, the indicated braking force BPTr is set to be greater than the vehicle braking force requested by the braking force BPRq. Therefore, the vehicle braking force BPA1 is greater than the requested braking force BPRq.

[0086] At time t22, the transition condition from the increase correction process to the decrease correction process is met. Therefore, the processing circuit begins the decrease process in the decrease correction process. As a result, the vehicle braking force BPA1 decreases to the parking sustaining braking force BPth. Then, at time t23, since the indicator braking force BPTr becomes the parking sustaining braking force BPth, the processing circuit begins the hold process in the decrease correction process. As a result, the vehicle braking force BPA1 is held. When time t24 is reached, the hold process ends and the retraction process begins, so the vehicle braking force BPA1 is increased.

[0087] Here, the parking holding braking force BPth is set based on the magnitude of the road slope θ. Therefore, if the accuracy of deriving the road slope θ is low, the parking holding braking force BPth may deviate from the actual value of the parking holding braking force. In particular, if the parking holding braking force BPth is less than the actual value of the parking holding braking force, during the period when the vehicle braking force BPA1 is maintained by the holding process, the vehicle 10 may start moving downhill once the vehicle speed VS becomes 0 (zero). The greater the slope of the road, the greater the magnitude of the gravitational acceleration component FG, i.e., the greater the moving force FM. The greater the moving force FM, the easier it is to advance the timing of the start of the vehicle 10 moving downhill.

[0088] Furthermore, when vehicle 10 begins to move downhill, the braking force BPA1 is increased through the retraction process, and vehicle 10 comes to a stop. However, the driver may experience a sense of disorientation when vehicle 10 stops after it has begun to move downhill.

[0089] <This implementation method>

[0090] like Figure 6 As shown in (A), (B), and (C), during the timing t31 of applying braking force to vehicle 10, the processing circuit 51 begins to perform a brake control increase correction process when it stops. Therefore, the vehicle braking force BPA1 is greater than the requested braking force BPRq.

[0091] In this embodiment, before performing the reduction correction process, the processing circuit 51 sets the execution time TMH of the holding process. Specifically, the processing circuit 51 sets the execution time TMH of the holding process in such a way that the larger the movement force FM is, the shorter the value.

[0092] Therefore, in situations where the moving force FM is relatively large, such as when vehicle 10 is traveling on a slope, the processing execution time TMH is shortened.

[0093] exist Figure 6 In the example shown, the reduction process in the correction process begins at time t32, thereby reducing the vehicle's braking force BPA1. Then, the hold process in the correction process begins at time t33. Since the hold process is executed until time t34, the rollback process begins at time t34, thus increasing the vehicle's braking force BPA1.

[0094] The duration of the hold operation, i.e., the time from time t33 to time t34, is shorter than the duration of the hold operation in the comparative example, i.e., the time from time t23 to time t24. Therefore, even if the parking brake force BPth is less than the actual value of the parking brake force, the likelihood that the vehicle 10 will begin to move downhill once the vehicle speed VS reaches 0 (zero) during the period when the vehicle brake force BPA is maintained by the hold operation is lower than in the comparative example. Therefore, the likelihood of the driver experiencing the same sense of disharmony as in the comparative example is reduced.

[0095] Therefore, when the braking control device 50 stops the vehicle 10 by implementing stop braking control, it can suppress the change in the posture of the vehicle 10 when it stops without causing the driver any sense of incongruity.

[0096] <Other Effects>

[0097] (1-1) When the execution time TMH of the holding process is shortened due to the relatively large moving force FM, the brake control device 50 extends the execution time TMD of the reduction process. As a result, the reduction rate of the vehicle's braking force BPA1 during the reduction process can be reduced. Consequently, when the moving force FM is relatively large, the brake control device 50 can smooth the front and rear bumping motion of the vehicle 10 that is performing the reduction correction process.

[0098] (1-2) The braking control device 50 derives the moving force FM in such a way that the value increases as the road surface slope θ increases. Therefore, the braking control device 50 can improve the suppression effect of the vehicle 10 sliding downhill when the vehicle 10 is stopped by applying braking control when stopping on a slope with a large road surface slope θ.

[0099] (Second Implementation)

[0100] according to Figure 7 and Figure 8 A second embodiment of the braking control device will be described. Furthermore, the difference between the second and first embodiments lies in the selection of braking control upon stopping, which is appropriate to the magnitude of the moving force. In the following description, the differences from the first embodiment will be primarily explained; the same reference numerals will be used for components identical to those in the first embodiment, and repeated descriptions will be omitted.

[0101] In this embodiment, the braking control device 50 is configured to perform both a first stop braking control and a second stop braking control as stop braking control. The first stop braking control and the second stop braking control each include an increase correction process, a decrease correction process, and a decrease process. The decrease correction process of the first stop braking control includes a decrease process and a hold process. The decrease correction process of the second stop braking control includes a decrease process but does not include a hold process.

[0102] <Procedure for handling vehicle braking>

[0103] Reference Figure 7 This section describes a series of processes performed by the processing circuit 51 of the brake control device 50 during braking control at a stop. The processing circuit 51 repeatedly executes these processes when the vehicle 10 brakes. Figure 7 The series of processes shown.

[0104] In step S51, similar to step S11 above, the processing circuit 51 outputs the moving force FM.

[0105] In the next step S53, similar to step S15 above, the processing circuit 51 determines whether the start condition for braking control at the time of stopping is met. If the processing circuit 51 determines that the start condition is met (S53: Yes), the processing moves to step S55. On the other hand, if the processing circuit 51 determines that the start condition is not met (S53: No), the processing circuit temporarily terminates. Figure 7 The series of processes shown.

[0106] In step S55, the processing circuit 51 determines whether the movement force FM is less than the threshold FMth1. If braking control is implemented when the movement force FM is relatively large, during the reduction correction process, the vehicle 10 may start moving after the vehicle speed VS becomes 0 (zero). Therefore, the criterion for determining whether the movement force FM is relatively large is set to the threshold FMth1. If the processing circuit 51 determines that the movement force FM is less than the threshold FMth1 (S55: Yes), the processing moves to step S60. On the other hand, if the processing circuit 51 determines that the movement force FM is greater than or equal to the threshold FMth1 (S55: No), the processing moves to step S80.

[0107] In step S60, the processing circuit 51 implements the first stop braking control as stop braking control.

[0108] Specifically, in step S61, processing circuit 51 performs an increase correction process. This increase correction process is the same as the increase correction process performed in step S19. In the next step S63, similar to step S21, processing circuit 51 determines whether the transition condition from the increase correction process to the decrease correction process is met. If the processing circuit 51 determines that the transition condition is not met (S63: No), it moves the processing back to step S61. That is, processing circuit 51 performs the increase correction process. On the other hand, if the processing circuit 51 determines that the transition condition is met (S63: Yes), it moves the processing back to step S65.

[0109] In step S65, the processing circuit 51 performs a reduction process in the reduction correction process. In the reduction process, the processing circuit 51 reduces the indicated braking force BPTr to the parking sustaining braking force BPth. Then, the processing circuit 51 activates the brake actuator 30 based on the indicated braking force BPTr at this time.

[0110] In the next step S67, the processing circuit 51 determines whether the indicated braking force BPTr is below the parking sustaining braking force BPth. If the processing circuit 51 determines that the indicated braking force BPTr is not below the parking sustaining braking force BPth (S67: No), the processing moves to step S65. That is, the processing circuit 51 performs a reduction process. On the other hand, if the processing circuit 51 determines that the indicated braking force BPTr is below the parking sustaining braking force BPth (S67: Yes), the processing moves to step S69.

[0111] In step S69, similar to step S27 described above, the processing circuit 51 performs the hold process in the reduction correction process. In the next step S71, the processing circuit 51 determines whether the vehicle 10 has stopped. If the processing circuit 51 determines that the vehicle 10 has not stopped (S71: No), the processing moves to step S69. That is, the processing circuit 51 performs the hold process. On the other hand, if the processing circuit 51 determines that the vehicle 10 has stopped (S71: Yes), the processing moves to step S73.

[0112] In step S73, similarly to step S31, the processing circuit 51 performs the retraction process. In the following step S75, similarly to step S33, the processing circuit 51 determines whether the end condition of the retraction process is met. If the processing circuit 51 determines that the end condition is not met (S75: No), the processing moves to step S73. That is, the processing circuit 51 performs the retraction process. On the other hand, if the processing circuit 51 determines that the end condition is met (S75: Yes), the retraction process ends. Then, the processing circuit 51 ends the first stop braking control and terminates... Figure 7 The series of processes shown.

[0113] In step S80, the processing circuit 51 implements a second stop-time braking control as a stop-time braking control. Specifically, in step S81, the processing circuit 51 performs an increase correction process. The content of this increase correction process is the same as the increase correction process performed in step S19 above. In the next step S83, similarly to step S21 above, the processing circuit 51 determines whether the transition condition from the increase correction process to the decrease correction process is met. If the processing circuit 51 determines that the transition condition is not met (S83: No), the processing moves to step S81. That is, the processing circuit 51 performs the increase correction process. On the other hand, if the processing circuit 51 determines that the transition condition is met (S83: Yes), the processing moves to step S85.

[0114] In step S85, the processing circuit 51 performs a reduction process in the reduction correction process. In the reduction process, the processing circuit 51 reduces the indicated braking force BPTr to the parking sustaining braking force BPth. Then, the processing circuit 51 activates the brake actuator 30 based on the indicated braking force BPTr at this time.

[0115] In the next step S87, the processing circuit 51 determines whether the indicated braking force BPTr is below the parking sustaining braking force BPth. If the processing circuit 51 determines that the indicated braking force BPTr is not below the parking sustaining braking force BPth (S87: No), the processing moves to step S85. That is, the processing circuit 51 performs a reduction process. On the other hand, if the processing circuit 51 determines that the indicated braking force BPTr is below the parking sustaining braking force BPth (S87: Yes), the processing moves to step S89.

[0116] In step S89, similar to step S31 above, the processing circuit 51 performs the retraction process. In the next step S91, similar to step S33 above, the processing circuit 51 determines whether the end condition of the retraction process is met. If the processing circuit 51 determines that the end condition is not met (S91: No), the processing moves to step S89. That is, the processing circuit 51 performs the retraction process. On the other hand, if the processing circuit 51 determines that the end condition is met (S91: Yes), the processing circuit 51 ends the retraction process. Then, the processing circuit 51 ends the second stop braking control and ends the process. Figure 7 The series of processes shown.

[0117] <Function and Effects of This Implementation Method>

[0118] Reference Figure 8 The function and effect of the second braking control during stop are explained. Figure 8 The example shown is a case of stopping a vehicle 10 that is traveling on a slope by applying braking force.

[0119] like Figure 8 As shown in (A), (B), and (C), at time t41 during the process of applying braking force to vehicle 10, processing circuit 51 determines that the start condition for stop braking control is met. In this case, processing circuit 51 can determine that the moving force FM is greater than or equal to the threshold FMth1, and therefore implements second stop braking control. That is, starting from time t41, processing circuit 51 begins the increase correction process for second stop braking control. During the execution of the increase correction process, the indicated braking force BPTr is set to be greater than the vehicle braking force requested by braking force BPRq. Therefore, the vehicle braking force BPA1 is greater than the requested braking force BPRq.

[0120] At time t42, the transition condition from the increase correction process to the decrease correction process is met. Therefore, the processing circuit 51 executes the decrease process in the decrease correction process. As a result, the vehicle braking force BPA1 is reduced to the parking sustaining braking force BPth. Then, at time t43, the indicated braking force BPTr becomes the parking sustaining braking force BPth. Thus, the processing circuit 51 shifts the processing from the decrease correction process to the retraction process. That is, in the case of implementing the second stop braking control, no period is set for maintaining the vehicle braking force BPA1. At the subsequent time t44, the indicated braking force BPTr reaches the requested braking force BPRq, so the processing circuit 51 ends the second stop braking control.

[0121] In this embodiment, there is no period during which the vehicle braking force BPA1 is maintained at the parking sustaining braking force BPth. Therefore, when the indicated braking force BPTr becomes the parking sustaining braking force BPth through the reduction process, the indicated braking force BPTr is immediately increased toward the requested braking force BPRq. As a result, even if the parking sustaining braking force BPth is less than the actual value of the parking sustaining braking force, the likelihood that the vehicle 10 will start moving downhill after the vehicle speed VS becomes 0 (zero) is lower than in the comparative example described above. Therefore, the likelihood of the driver experiencing the same sense of disharmony as in the comparative example is reduced.

[0122] Therefore, when the braking control device 50 stops the vehicle 10 by implementing stop braking control, it can suppress the change in the posture of the vehicle 10 when it stops without causing the driver any sense of incongruity.

[0123] (Example of the change)

[0124] The above-described embodiments can be implemented by modification as follows. The above-described embodiments and the following modifications can be combined with each other to implement them within the scope of technical inconsistency.

[0125] • The processing circuit 51 may also not function as the moving force output unit M13. In this case, in the first embodiment, it is preferable that the larger the road surface slope θ, the shorter the processing execution time TMH of the processing circuit 51 (i.e., the setting unit M15) will be. This is because it can be predicted that the larger the road surface slope θ, the greater the moving force acting on the vehicle 10.

[0126] Furthermore, in the second embodiment, the processing circuit 51 (i.e., the setting unit M15) can determine that the moving force is large when the road surface slope θ is greater than or equal to the slope threshold, and therefore it is preferable to implement the second stop braking control. On the other hand, the processing circuit 51 can determine that the moving force is not large when the road surface slope θ is less than the slope threshold, and therefore it is preferable to implement the first stop braking control.

[0127] • In the first embodiment, the processing circuit 51 (i.e., the setting unit M15) may also set the execution time TMH of the process to be shorter than that when the road surface on which the vehicle 10 is traveling is a slope.

[0128] In the first embodiment, the processing circuit 51 (i.e., the setting unit M15) makes the execution time TMD of the reduction process variable according to the execution time TMH of the holding process, but is not limited thereto. For example, the processing circuit 51 (i.e., the setting unit M15) may also set the predetermined time to the execution time TMD of the reduction process regardless of the length of the execution time TMH of the holding process.

[0129] In several embodiments, the processing circuit 51 (i.e., the control unit M11) may also vary the rate at which the indicator braking force BPTr increases during the retraction process based on the movement force FM. For example, the processing circuit 51 (i.e., the control unit M11) may also set the rate at which the indicator braking force BPTr increases during the retraction process in such a way that the larger the movement force FM is, the larger the value becomes.

[0130] • If the braking control at a stop includes both reduction correction processing and retraction processing, it may not include increase correction processing.

[0131] In the above embodiments, the processing circuit 51 determines the start timing of the increase correction process and the decrease correction process for braking control when stopping based on the change in vehicle speed VS. However, as long as the value of a parameter decreases as the vehicle 10 approaches the stopping position PS, the processing circuit 51 may also use parameters other than vehicle speed VS to determine the start timing of each process. Examples of such parameters include stopping distance and stopping prediction time. The stopping distance is the distance from the current position of the vehicle 10 to the stopping position PS. The stopping prediction time is the time required until the vehicle 10 comes to a stop. An example of stopping prediction time is TTC. TTC is an abbreviation for "Time To Collision".

[0132] When the braking control device performs braking control at a stop, it can control not only the friction braking force but also the regenerative braking force. In this case, the sum of the friction braking force applied to the vehicle 10 and the sum of the regenerative braking force applied to the vehicle 10 constitutes the vehicle braking force BPA1.

[0133] In the above embodiments, when the vehicle brakes in conjunction with the driver's operation of the brake operating member 11, the processing circuit 51 performs stop-time braking control. However, the processing circuit 51 may also perform stop-time braking control during automatic braking.

[0134] The processing circuit 51 (i.e., the movement force derivation unit M13) sometimes derives the road slope θ based on the difference between the differential value of the vehicle body speed VS of the vehicle 10 and the front and rear acceleration Gx. Various noise signals are superimposed on the detection signals from the front and rear acceleration sensors 103 and the wheel speed sensors 102. Therefore, it is difficult to say that the derived road slope θ has high accuracy. For example, even if the driving surface is level, sometimes a value corresponding to the error component is derived as the road slope θ. In this case, as the parking holding braking force BPth, a value larger than the value that should be set is derived. Therefore, when deriving the road slope θ, the processing circuit 51 (i.e., the movement force derivation unit M13) should preferably use... Figure 9 The mapping shown.

[0135] Figure 9 This represents a mapping between road surface slope θ and reliability. The road surface slope, defined as the difference between the differential value of the vehicle speed VS and the front-to-back acceleration Gx, is set as the "road surface slope calculation value θE". In this mapping, when the road surface slope calculation value θE is above the first boundary slope value θth1 and below the second boundary slope value θth2, the reliability α is 0 (zero). For example, the value obtained by reversing the sign of the second boundary slope value θth2 is the first boundary slope value θth1. When the road surface slope calculation value θE is less than the first boundary slope value θth1, the larger the absolute value of the road surface slope calculation value θE, the larger the reliability α. When the road surface slope calculation value θE is greater than the second boundary slope value θth2, the larger the absolute value of the road surface slope calculation value θE, the larger the reliability α.

[0136] Furthermore, the processing circuit 51 (i.e., the moving force output unit M13) outputs based on Figure 9 The product of the reliability α derived from the mapping shown and the calculated road slope value θE is taken as the road slope θ. Then, the processing circuit 51 (i.e., the movement force derivation unit M13) preferably derives a value corresponding to such road slope θ as the movement force FM.

[0137] • The specified braking force can also be a different value from the parking brake force BPth. For example, the vehicle braking force BPA1, which is slightly larger than the parking brake force BPth, can also be set as the specified braking force.

[0138] The processing circuit 51 can be configured as a circuit including one or more processors that operate according to a computer program, dedicated hardware that performs at least a portion of various processes, or a combination thereof. Examples of dedicated hardware include, for instance, ASICs (Integrated Circuits for a Specific Purpose). The processor includes a CPU and memories such as RAM and ROM, which store program code or instructions configured to cause the CPU to perform processes. Memory, or storage medium, includes all available media accessible to general-purpose or special-purpose computers.

[0139] (Other technical ideas)

[0140] The technical ideas that can be grasped from the above-mentioned multiple implementation methods and variations are recorded.

[0141] [Note 1] Preferably, the above-mentioned braking control at stop includes a retraction process, which is a process following the execution of the above-mentioned holding process, and increases the braking force applied to the vehicle.

[0142] In the aforementioned retraction process, the control unit increases the braking force applied to the vehicle at a speed greater than the rate at which the braking force applied to the vehicle is reduced when the aforementioned reduction process is performed.

[0143] [Appendix 2] A braking control device, when stopping a vehicle by applying braking force, performs stop-time braking control, wherein after reducing the braking force of the vehicle to a predetermined braking force, the vehicle speed is reduced to 0 (zero), the braking control device comprising:

[0144] The control unit, in the aforementioned stop braking control, performs a reduction process and a holding process. In the reduction process, the braking force applied to the vehicle is reduced to the aforementioned predetermined braking force. The holding process is the next process after the reduction process and begins before the vehicle's body speed VS reaches 0 (zero), maintaining the braking force applied to the vehicle at the aforementioned predetermined braking force; and

[0145] The setting unit sets the execution time of the holding process to be shorter than the time when the road surface on which the vehicle is traveling is a slope.

[0146] [Appendix 3] A braking control device performs stop braking control when the vehicle is stopped by applying braking force, wherein the vehicle speed is reduced to 0 after the braking force of the vehicle is reduced to a predetermined braking force.

[0147] The aforementioned braking control device includes a control unit that implements a first stop-time braking control including a reduction process and a holding process, and a second stop-time braking control including the reduction process but not the holding process. In the reduction process, the braking force applied to the vehicle is reduced to the predetermined braking force. The holding process is the next process after the reduction process and begins before the vehicle's body speed VS reaches 0 (zero), maintaining the braking force applied to the vehicle at the predetermined braking force.

[0148] When the moving force is less than a threshold, the control unit implements the first stop braking control, and when the moving force is greater than or equal to the threshold, it implements the second stop braking control, wherein the moving force is the force acting on the vehicle that causes the vehicle to move.

[0149] Furthermore, the term "at least one" as used in this specification refers to "more than one" of the desired options. As an example, if the number of options is two, "at least one" as used in this specification means "only one option" or "both of the two options". As another example, if the number of options is three or more, "at least one" as used in this specification means "only one option" or "any combination of two or more options".

Claims

1. A braking control device that performs stop-time braking control when a vehicle is stopped by applying braking force, wherein, in the stop-time braking control, after reducing the braking force applied to the vehicle to a predetermined braking force, the vehicle speed is reduced to 0, the braking control device comprising: The control unit, in the aforementioned stop-and-brake control, performs a reduction process and a holding process. In the reduction process, the braking force applied to the vehicle is reduced to the aforementioned predetermined braking force. The holding process is the next process after the reduction process and is performed before the vehicle's body speed reaches 0, maintaining the braking force applied to the vehicle at the aforementioned predetermined braking force; and The setting unit sets the execution time of the holding process to be shorter as the force acting on the vehicle during the execution of the braking control at the stop is greater.

2. The braking control device according to claim 1, wherein, The aforementioned setting unit sets the execution time of the aforementioned reduction process in such a way that the shorter the execution time of the aforementioned maintenance process, the larger the value.

3. The braking control device according to claim 1 or 2, wherein, The vehicle is equipped with a force-exporting unit. The greater the slope of the road surface on which the vehicle travels, the greater the force output by the force-exporting unit becomes as a force to move the vehicle.

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