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 control unit (M11) applies braking force to the vehicle (10) to stop, it performs a reduction correction process that reduces the vehicle's braking force to a predetermined braking force smaller than the requested braking force, and then reduces the vehicle's speed to 0 (zero). If a change in braking operation is detected before the reduction correction process begins when the driver performs braking operation, the setting unit (M15) sets the execution time of the reduction correction process to be shorter than the time when no change in braking operation is detected.

Description

Technical Field

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

[0002] Patent document 1 discloses a vehicle control device that implements parking control by reducing the braking force applied to the vehicle before it stops, thereby suppressing changes in the vehicle's posture during parking.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2016-28913

[0004] When braking force is reduced while implementing parking control as described above, if the driver changes the braking operation, a discrepancy occurs between the driver's intended vehicle behavior and the actual vehicle behavior. In the event of this discrepancy, the driver may experience a sense of incongruity due to the discrepancy. Summary of the Invention

[0005] A braking control device for solving the above-mentioned problem includes: a control unit that performs a reduction correction process when applying braking force to a vehicle to stop it, wherein the reduction correction process reduces the braking force applied to the vehicle to a predetermined braking force smaller than the requested value of the braking force, and then sets the vehicle speed to 0 (zero); and a setting unit that, when the driver of the vehicle performs braking operation, if a change in the braking operation is detected before the reduction correction process begins, sets the execution time of the reduction correction process to be shorter than the time when no change in the braking operation is detected.

[0006] The aforementioned braking control device achieves the following effect: if the driver changes the braking operation during braking, it can suppress changes in the vehicle's posture when stopping without causing the driver to feel any sense of incongruity. Attached Figure Description

[0007] Figure 1 This is a structural diagram showing a vehicle equipped with a braking control device according to an embodiment.

[0008] Figure 2 This is a timing diagram showing the situation where the braking operation remains unchanged when the vehicle is brought to a stop by applying braking force.

[0009] Figure 3 This is a diagram illustrating an example of a mapping used to set a reduction in the execution time of the correction process.

[0010] Figure 4 It means by Figure 1 A flowchart of a series of processes performed by the braking control device.

[0011] Figure 5 This is a timing diagram of the case in the first comparative example where the reduction of braking operation amount began before the reduction correction process started.

[0012] Figure 6 Is Figure 1 The timing diagram shows the case where the reduction in braking operation amount begins before the reduction correction process starts in the braking control device.

[0013] Figure 7 This is a timing diagram of the second comparative example, where the increase in braking operation amount began before the reduction correction process started.

[0014] Figure 8 Is Figure 1 The timing diagram shows the situation where the braking operation amount increases before the reduction correction process begins in the braking control device.

[0015] Figure 9 It is a flowchart representing a part of a series of processes performed by the brake control device of the modified example.

[0016] Figure 10 This is a timing diagram illustrating a modified example of braking control during stopping. Detailed Implementation

[0017] The following is in accordance with Figures 1 to 8 One embodiment of the braking control device will be described.

[0018] Figure 1 The diagram illustrates a vehicle 10 equipped with a brake control device 50. The vehicle 10 includes a brake operating component 11, multiple wheels, multiple friction brakes 20, and brake actuators 30. The multiple wheels include two front wheels 12 and two rear wheels 13. The brake operating component 11 is a component operated by the driver when braking force is applied to the vehicle 10. An example of the brake operating component 11 is a brake pedal. The driver's operation of the brake operating component 11 is referred to as "brake operation."

[0019] <Friction Brake>

[0020] 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.

[0021] <Brake Actuator>

[0022] 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.

[0023] 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".

[0024] <Detection System>

[0025] 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.

[0026] Brake sensor 101 detects information related to the driver's operation of brake operating component 11. An example of brake sensor 101 is a stroke sensor that detects the amount of operation by the driver on brake operating component 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 component 11.

[0027] 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".

[0028] 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".

[0029] <Brake Control Device>

[0030] 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.

[0031] <Overview of braking control during stop>

[0032] The processing circuit 51 implements stop-time braking control when the driver operates the brake operation component 11. Stop-time braking control is a braking control used to suppress changes in the posture of the vehicle 10 when it is stopped.

[0033] Reference Figure 2 The braking control during stopping is explained. Figure 2 The illustration shows an example where the braking operation amount X remains unchanged during the implementation of braking control at a stop.

[0034] 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 2 As 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 component 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] At time t14, the indicated braking force BPTr is equal to the parking sustaining braking force BPth. The parking sustaining braking force BPth is the minimum braking force required to keep the vehicle 10 at a stop on the current road surface, or a slightly greater braking force. 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.

[0039] At time t15, the processing circuit 51 determines that the vehicle 10 has stopped, and therefore switches the braking control process from reduction correction to retraction. 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.

[0040] <Functional Structure of Processing Circuit>

[0041] Reference Figure 1 The functional structure of the processing circuit 51 will be described. The CPU 52 executes the control program of 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, an acquisition unit M13, and a setting unit M15.

[0042] <Control Department>

[0043] 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 for stop-and-go braking control. In this 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 decrease correction process described later. The control unit M11 actuates the brake actuator 30 based on this indicated braking force BPTr.

[0044] 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 a parking sustaining braking force BPth that is smaller than the requested braking force BPRq, the control unit M11 sets the vehicle speed VS to 0 (zero). At this time, before the vehicle speed VS becomes 0 (zero), the control unit M11 reduces the indicated braking force BPTr to the parking sustaining braking force BPth. 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. The control unit M11 activates the brake actuator 30 based on the indicated braking force BPTr at this time.

[0045] 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 terminates 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. Based on this indicated braking force BPTr, the control unit M11 activates the brake actuator 30.

[0046] <Acquisition Department>

[0047] The acquisition unit M13 acquires at least one of the braking operation amount X and the rate of change of the braking operation amount X dX 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 increase correction process. In this embodiment, the acquisition unit M13 acquires at least the braking operation amount X from the braking operation amount X and the rate of change of the braking operation amount X dX.

[0048] <Settings Department>

[0049] When the driver is performing braking operations, if the setting unit M15 detects a change in braking operation before the reduction correction process begins, it sets the execution time TMD of the reduction correction process to be shorter than the time when no change in braking operation is detected. For example, the setting unit M15 detects the change in braking operation based on the shift of braking-related values ​​acquired by the acquisition unit M13 before the reduction correction process begins. In this embodiment, the acquisition unit M13 acquires the braking operation amount X as a braking-related value. Therefore, the setting unit M15 detects the change in braking operation based on the shift of the braking operation amount X before the reduction correction process begins. At this time, the setting unit M15 detects a change in braking operation if the change ΔX of the braking operation amount X from the start time of the increase correction process is a first change ΔXth1 or more.

[0050] The setting unit M15 sets the execution time TMD of the reduction correction process based on whether a change in braking operation is detected before the reduction correction process begins. In this embodiment, if the change ΔX of braking operation amount X from the start time of the increase correction process is a first change ΔXth1 or more, the setting unit M15 sets the execution time TMD to be shorter than if the change ΔX is not a first change ΔXth1 or more.

[0051] For example, the M15 setting unit is best used Figure 3 The mapping shown is used to set the TMD (Time Management Method) to reduce the execution time of the correction process. For example... Figure 3As shown, when the change amount ΔX is less than the first change amount ΔXth1, the setting unit M15 considers it impossible to detect the change in braking operation before the reduction correction process begins, and sets the reference execution time TMDB as the execution time TMD of the reduction correction process. When the change amount ΔX is greater than or equal to the first change amount ΔXth1 but less than the second change amount ΔXth2, the setting unit M15 sets the execution time TMD of the reduction correction process to be shorter as the change amount ΔX increases. 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 reduction correction process. The minimum time TMDMin is shorter than the reference execution time TMDB.

[0052] <Procedure for handling vehicle braking>

[0053] Reference Figure 4 This section explains a series of processes performed by the processing circuit 51 during stop braking control. The processing circuit 51 repeatedly executes the following steps when the driver performs the braking operation: Figure 4 The series of processes shown.

[0054] In step S11, the processing circuit 51 determines whether the start 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 (S11: Yes), the processing circuit 51 moves the processing to step S13. Conversely, if the start condition is not met (S11: No), the processing circuit 51 temporarily terminates the process. Figure 4 The series of processes shown.

[0055] In step S13, the processing circuit 51 acquires the braking operation amount X at this time as the reference operation amount XB. This reference operation amount XB is the braking operation amount X at the start time of the increase correction process. In the next step S15, the processing circuit 51 executes the increase correction process for braking control at stop. In the increase correction process, in order to compensate for the increase in braking distance of the vehicle 10 caused by the execution of 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 activates the brake actuator 30 based on this indicated braking force BPTr.

[0056] In the next step S17, the processing circuit 51 obtains the braking operation amount X at this time. That is, the processing circuit 51 obtains the braking operation amount X during the execution of the increase correction process.

[0057] Then, in step S19, the processing circuit 51 sets the execution time TMD for the reduction correction process. Specifically, the processing circuit 51 derives the difference between the braking operation amount X obtained in step S17 and the reference operation amount XB as the change in braking operation amount ΔX. The processing circuit 51 uses, for example... Figure 3 The mapping shown sets the execution time TMD corresponding to the change ΔX.

[0058] In the next step S21, the processing circuit 51 sets the second vehicle speed determination value VSth2 to a vehicle speed corresponding to the execution time TMD set in step S19. At this time, the processing circuit 51 sets the second vehicle speed determination value VSth2 in such a way that the shorter the execution time TMD, the smaller the value. Stop braking control is the control that makes the vehicle speed VS reach 0 (zero) during the execution of the reduction correction process. Therefore, for example, if the second vehicle speed determination value VSth2 is not reduced even if the execution time TMD is shortened, the possibility that the vehicle speed VS will not reach 0 (zero) before the end time of the reduction correction process becomes higher. Therefore, when the execution time TMD of the reduction correction process is variable as in this embodiment, it is necessary to change the second vehicle speed determination value VSth2 according to the set execution time TMD. Therefore, the processing circuit 51 sets the second vehicle speed determination value VSth2 so that the vehicle speed VS reaches 0 (zero) during the period when the indicated braking force BPTr is maintained at the stop holding braking force BPth during the execution of the reduction correction process. When the second vehicle speed determination value VSth2 is set, the processing circuit 51 moves the processing to step S23.

[0059] In step S23, 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. The second vehicle speed determination value VSth2 used here is the value set in step S21. If the processing circuit 51 determines that the transition condition is not met (S23: No), the processing moves to step S15. 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 (S23: Yes), the processing moves to step S25.

[0060] In step S25, the processing circuit 51 performs a reduction correction process for the braking control during stop. In this reduction correction process, the processing circuit 51 reduces the indicated braking force BPTr to the parking sustaining braking force BPth. After the indicated braking force BPTr becomes the parking sustaining braking force BPth, the processing circuit 51 maintains the indicated braking force BPTr at the parking sustaining braking force BPth. Then, the processing circuit 51 activates the brake actuator 30 based on this indicated braking force BPTr.

[0061] In this embodiment, the processing circuit 51 modifies the indicated braking force BPTr to enable the reduction correction process to end at the execution time TMD set in step S19. First, the processing circuit 51 sets the length of the period during which the indicated braking force BPTr is reduced to the parking sustaining braking force BPth (i.e., the reduction period) and the length of the period during which the indicated braking force BPTr is held at the parking sustaining braking force BPth (i.e., the holding period). If the length of the reduction period is shortened, the rate of reduction of the indicated braking force BPTr during the reduction period tends to increase. Therefore, the shorter the execution time TMD, the shorter the holding period set by the processing circuit 51. Furthermore, the shorter the set length of the reduction period, the greater the rate of reduction of the indicated braking force BPTr by the processing circuit 51. When the reduction period ends and the indicated braking force BPTr becomes the parking sustaining braking force BPth, the processing circuit 51 holds the indicated braking force BPTr at the parking sustaining braking force BPth.

[0062] In the next step S27, the processing circuit 51 determines whether the transition condition from the reduction correction process to the reduction process is met. For example, as Figure 2 As shown, processing circuit 51 determines that the transfer condition is met when it can determine that vehicle 10 has stopped. Therefore, sometimes processing circuit 51 determines that the transfer condition is met before the actual execution time of the reduction correction process reaches the aforementioned execution time TMD. Conversely, sometimes processing circuit 51 determines that the transfer condition is met after the actual execution time of the reduction correction process exceeds the aforementioned execution time TMD. If processing circuit 51 determines that the transfer condition is not met (S27: No), it moves the processing to step S25. That is, processing circuit 51 performs the reduction correction process. On the other hand, if processing circuit 51 determines that the transfer condition is met (S27: Yes), it moves the processing to step S29.

[0063] In step S29, the processing circuit 51 performs a retraction process for the braking control upon stopping. In this 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.

[0064] In the next step S31, 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 (S31: No), the processing moves to step S29. 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 (S31: 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.

[0065] In this embodiment, each of steps S15 and S23 to S31 is executed by the processing circuit 51 as a control unit M11. Each of steps S13 and S17 is executed by the processing circuit 51 as an acquisition unit M13. Each of steps S19 and S21 is executed by the processing circuit 51 as a setting unit M15.

[0066] <The function and effects of this embodiment when the braking operation amount X is reduced>

[0067] Reference Figure 5 and Figure 6 The following explains the case where the braking operation amount X is reduced before the reduction correction process begins. Figure 5 The illustration shows a first comparative example where the braking operation amount X is reduced before the reduction correction process begins, but the execution time TMD of the reduction correction process is not changed. Figure 6 The illustration shows this implementation where the execution time TMD of the reduction correction process is changed when the braking operation amount X is reduced before the reduction correction process begins.

[0068] <First Comparative Example>

[0069] like Figure 5 As shown in (A), (B), and (C), at time t21 during the process of the driver applying braking force to vehicle 10, the processing circuit determines that the starting 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 a vehicle braking force greater than the requested braking force BPRq. Therefore, the vehicle braking force BPA1 is greater than the requested braking force BPRq.

[0070] Starting from time t22 during the execution of this increased correction process, the driver's braking operation changes. Specifically, because the braking operation amount X decreases, therefore... Figure 5As shown in (A), the requested braking force BPRq decreases. As a result, the indicated braking force BPTr also decreases while remaining greater than the requested braking force BPRq. Consequently, the vehicle's braking force BPA1 also decreases.

[0071] At time t23, since the transition condition from the increase correction process to the decrease correction process is met, the processing circuit ends the increase correction process and begins the decrease correction process. In the decrease correction process, the indicated braking force BPTr is reduced to the parking sustaining braking force BPth. Therefore, the vehicle braking force BPA1 decreases towards the parking sustaining braking force BPth. Then, at time t24, the indicated braking force BPTr becomes the parking sustaining braking force BPth. Therefore, after time t24, the indicated braking force BPTr is maintained at the parking sustaining braking force BPth. Thus, the vehicle braking force BPA1 is maintained.

[0072] Here, in the first comparative example, from the execution of the increase correction process before the decrease correction process begins, the vehicle braking force BPA decreases according to the decrease in braking operation amount X. Furthermore, as... Figure 5 As shown in (C), since the correction process begins at time t23 during the period when the braking operation amount X decreases, the rate of decrease in vehicle braking force BPA increases. That is, although the rate of decrease in braking operation amount X is constant, the rate of decrease in vehicle braking force BPA increases midway. In the first comparative example, the period from time t23 to time t24 is the period during which vehicle braking force BPA decreases at a rate greater than the rate corresponding to the rate of decrease in braking operation amount X. Furthermore, in the first comparative example, during the period from time t24 to time t25, although braking operation amount X decreases, vehicle braking force BPA does not decrease.

[0073] That is, in the first comparative example, there is a discrepancy between the vehicle's behavior inferred from the driver's braking action and the actual vehicle behavior. If this discrepancy persists for a long period, the driver may experience a sense of incongruity regarding its occurrence.

[0074] <This implementation method>

[0075] like Figure 6 As shown in (A), (B), and (C), at time t31 during the process of the driver applying braking force to the vehicle 10, the processing circuit 51 begins to perform an increase correction process for braking control when it stops. As a result, the vehicle braking force BPA1 is greater than the requested braking force BPRq. From time t32 during the execution of this increase correction process, the driver's braking operation changes. Specifically, because the braking operation amount X decreases, therefore... Figure 6 As shown in (A), the requested braking force BPRq is reduced. The result is as follows: Figure 6As shown in (C), the indicated braking force BPTr and the vehicle braking force BPA1 also decrease.

[0076] Figure 6 The timer t33 in the middle is equivalent to Figure 5 The timing t23. That is, in the first comparative example, the correction process is reduced starting from timing t33.

[0077] In contrast, in this embodiment, when a change in braking operation is detected before the reduction correction process begins, the execution time (TMD) of the reduction correction process is set to a shorter time than in the case where no change in braking operation is detected. As a result, the start timing of the reduction correction process is later than in the first comparative example. Figure 6 In the example shown, during the period from time t34 (which follows time t33) to time t36, the processing circuit 51 performs a reduction correction process. Specifically, during the period from time t34 to time t35, the processing circuit 51 reduces the indicated braking force BPTr to the parking sustaining braking force BPth. Then, during the period from time t35 to time t36, the processing circuit 51 maintains the indicated braking force BPTr at the parking sustaining braking force BPth.

[0078] The length of the period from time t34 to time t36 is shorter than the execution period of the reduction correction process in the first comparative example, that is, the period from time t23 to time t25. As a result, the length of the period during which the vehicle's behavior, inferred from the driver's braking operation, deviates from the actual vehicle behavior is shorter than in the first comparative example. Therefore, even if the reduction correction process is performed, the driver is less likely to feel any disharmony caused by the aforementioned deviation. Therefore, even if the braking operation amount X begins to decrease before the reduction correction process begins, the brake control device 50 can suppress changes in the vehicle 10's posture during parking without causing the driver to feel any disharmony.

[0079] <The function and effect of this embodiment when the braking operation amount X is increased>

[0080] Reference Figure 7 and Figure 8 The following explains the case where the braking operation amount X is increased before the reduction correction process begins. Figure 7 The illustration shows a second comparative example where the execution time TMD of the reduction correction process is not changed even if the braking operation amount X is increased before the reduction correction process begins. Figure 8 The illustration shows this embodiment of changing the execution time TMD of the reduction correction process when the braking operation amount X is increased before the reduction correction process begins.

[0081] <Second Comparative Example>

[0082] like Figure 7 As shown in (A), (B), and (C), at time t41 during the process of the driver applying braking force to vehicle 10, the processing circuit begins to perform an increase correction process for braking control when it stops. Therefore, the vehicle braking force BPA1 is greater than the requested braking force BPRq. From time t42 during the execution of this increase correction process, the driver's braking operation changes. Specifically, because the braking operation amount X increases, therefore... Figure 7 As shown in (A), the requested braking force BPRq is increased. The result is as follows: Figure 7 As shown in (C), the indicated braking force BPTr and the vehicle braking force BPA also increase.

[0083] At time t43, the transition condition from the increase correction process to the decrease correction process is met, so the processing circuit ends the increase correction process and begins the decrease correction process. In the decrease correction process, the indicated braking force BPTr is reduced to the parking sustaining braking force BPth. At time t44, the indicated braking force BPTr becomes the parking sustaining braking force BPth. Therefore, after time t44, the indicated braking force BPTr is maintained.

[0084] Here, in the second comparative example, the braking operation amount X is increased from the execution of the increase correction process before the decrease correction process begins. Therefore, the vehicle speed VS reaches the second vehicle speed determination value VSth2 earlier. As a result, the execution time of the increase correction process is shortened. Consequently, the vehicle's braking distance may increase.

[0085] Furthermore, if the braking distance can be shortened by performing an increase correction process, then performing a decrease correction process may lead to the following problem: The execution time of the increase correction process becomes shorter, and consequently, the decrease correction process may not be able to reduce the indicated braking force BPTr to the parking sustaining braking force BPth. In this case, the vehicle braking force BPA1 is greater than the parking sustaining braking force BPth when the vehicle is stopped. As a result, the effect of suppressing changes in vehicle posture when stopped is reduced.

[0086] Furthermore, in the second comparative example, the period from time t43 to time t45 is the period during which the vehicle's braking force BPA decreases despite an increase in the amount of braking operation X. In other words, the period from time t43 to time t45 is the period during which the vehicle's behavior inferred from the driver's braking operation deviates from the actual vehicle behavior. If this period of deviation is long, the driver may experience a sense of incongruity regarding the occurrence of this deviation.

[0087] <This implementation method>

[0088] like Figure 8As shown in (A), (B), and (C), at time t51 during the process of the driver applying braking force to the vehicle 10, the processing circuit 51 begins to perform an increase correction process for braking control when it stops. Therefore, the vehicle braking force BPA1 is greater than the requested braking force BPRq. From time t52 during the execution of this increase correction process, the driver's braking operation changes. Specifically, because the braking operation amount X increases, therefore... Figure 8 As shown in (A), the requested braking force BPRq is increased. The result is as follows: Figure 8 As shown in (C), the indicated braking force BPTr and the vehicle braking force BPA also increase.

[0089] In this embodiment, when a change in braking operation is detected before the reduction correction process begins, the execution time TMD of the reduction correction process is set to be shorter than the time when no change in braking operation is detected. As a result, the start timing of the reduction correction process is later than in the second comparative example. Consequently, the execution time of the increase correction process is longer than in the second comparative example. As a result, compared to the second comparative example, the braking control device 50 can extend the execution time of the increase correction process, thus suppressing the increase in braking distance.

[0090] Furthermore, the execution time of the increase correction process can be extended, and correspondingly, compared with the second comparative example, the braking distance can be shortened by executing the increase correction process. Therefore, in the decrease correction process executed after the increase correction process, the indicated braking force BPTr, i.e., the vehicle braking force BPA1, is reduced to the parking sustaining braking force BPth. As a result, compared with the second comparative example, the brake control device 50 can improve the suppression effect of changes in the vehicle 10's posture when parking.

[0091] Furthermore, in this embodiment, the period from time t53 to time t54 becomes the execution period for the reduction correction process. Figure 8 In the example shown, because the braking operation amount X is increased during the execution of the increase correction process, the length of the period from time t53 to time t54 is shorter than the execution period of the decrease correction process in the second comparative example, that is, the period from time t43 to time t45. Therefore, the length of the period during which the vehicle's behavior, inferred from the driver's braking operation, deviates from the actual vehicle behavior is shorter than in the second comparative example. Therefore, even when the decrease correction process is executed, the driver is unlikely to feel any disharmony caused by the aforementioned deviation. Therefore, even when the braking operation amount X begins to increase before the decrease correction process begins, the brake control device 50 can suppress changes in the vehicle 10's posture during parking without causing the driver any disharmony.

[0092] <Other Effects>

[0093] (1) It can be inferred that the greater the change in braking operation amount ΔX before the reduction correction process begins, the stronger the driver's desire to change the braking mode. Therefore, the greater the change in braking operation amount ΔX before the reduction correction process begins, the shorter the execution time TMD of the reduction correction process will be set by the brake control device 50. As a result, the stronger the driver's desire to change the braking mode, the more the brake control device 50 can shorten the period during which the driver's intention to perform the braking operation deviates from the actual behavior of the vehicle 10.

[0094] (2) As described above, the longer the period during which the vehicle's braking force BPA remains unchanged despite the driver changing the amount of braking operation X, the more likely the driver is to feel a sense of disharmony. Therefore, when a change in braking operation is detected before the reduction correction process begins, the brake control device 50 shortens the length of the period during which the indicated braking force BPTr is maintained at the parking sustaining braking force BPth during the execution time of the reduction correction process compared to the case where no change in braking operation is detected. Thus, when a change in braking operation is detected before the reduction correction process begins, the brake control device 50 can shorten the period during which the vehicle's braking force BPA remains unchanged despite the driver changing the amount of braking operation X, making it less likely for the driver to feel a sense of disharmony.

[0095] <Example of Change>

[0096] 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 within the scope of technical inconsistency.

[0097] The processing circuit 51 (i.e., the acquisition unit M13) can also acquire the rate of change dX of the braking operation amount X as a braking operation related value. Figure 9 The diagram illustrates a series of processes in the case of reducing the execution time of the correction process (TMD) based on the rate of change dX.

[0098] like Figure 9 As shown, when the processing circuit 51 determines that the start condition for braking control at a stop is met (S11: Yes), the processing moves to step S131. In step S131, the processing circuit 51 functions as the acquisition unit M13, thereby acquiring the rate of change of the braking operation amount dX at this time as the reference rate of change dXB. At this time, the processing circuit 51 preferably acquires the value obtained by differentiating the braking operation amount X over time as the rate of change dX. In the next step S15, the processing circuit 51 performs an increase correction process for braking control at a stop. In the next step S171, the processing circuit 51 functions as the acquisition unit M13, thereby acquiring the rate of change dX at this time. That is, the processing circuit 51 acquires the rate of change dX during the execution of the increase correction process.

[0099] Then, in step S191, the processing circuit 51 functions as a setting unit M15, thereby setting the execution time TMD based on the magnitude of the difference between the change rate dX obtained 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 called the "change rate change amount". For example, if the change rate change amount is above a threshold, the processing circuit 51 sets the execution time TMD to be shorter than if the change rate change amount is less than the threshold. The criterion for determining whether a change in braking operation can be detected is set to a threshold. Thus, if a change in braking operation is detected before the reduction correction process begins, the processing circuit 51 can set the execution time TMD to be shorter than if no change in braking operation is detected.

[0100] The processing circuit 51 (i.e., the setting unit M15) may also set the execution time TMD of the reduction correction process by considering both the change in braking operation amount ΔX obtained before the reduction correction process begins and the change in speed.

[0101] • If the processing circuit 51 (i.e., the setting unit M15) detects a change in the braking operation before the reduction correction process begins, the execution time TMD can be made variable regardless of the degree of change in the braking operation.

[0102] • If the processing circuit 51 (i.e., the setting unit M15) detects a change in braking operation before the reduction correction process begins, it can also shorten the execution time TMD of the reduction correction process by omitting the period during which the indicated braking force BPTr is maintained at the parking sustaining braking force BPth. Figure 10 The diagram illustrates the timing of the indicated braking force BPTr when the holding period is omitted. Even in this case, the same effect as the above-described embodiment can be achieved because the execution time of the reduction correction process is shortened.

[0103] If the processing circuit 51 detects a change in braking operation before the reduction correction process begins, it may not shorten the length of the reduction period that reduces the indicated braking force BPTr, provided that the execution time TMD of the reduction correction process can be shortened. Even in this case, the processing circuit 51 can shorten the execution time TMD of the reduction correction process by shortening the length of the holding period of the indicated braking force BPTr.

[0104] In the above embodiments, the parking sustaining braking force BPth is set as the prescribed braking force, but it is not limited to this. A vehicle braking force different from the parking sustaining braking force BPth may also be set as the prescribed braking force. Furthermore, the magnitude of the prescribed braking force may be changed depending on the situation.

[0105] • When stopping, braking control may or may not include an increase correction process if it includes a decrease correction process. In this case, a timing interval that is a predetermined time earlier than the start timing of the decrease correction process is used as the reference time. Then, if the processing circuit 51 detects a change in braking operation during the period from the reference time to the start timing of the decrease correction process, it preferably sets the execution time of the decrease correction process to be shorter than the time during which no change in braking operation is detected. In this case, the "predetermined time" is preferably a few seconds.

[0106] • Processing circuit 51 can shorten the execution time TMD of the reduction correction process by reducing the braking operation amount X before the reduction correction process begins, and can also maintain the execution time TMD by increasing the braking operation amount X before the reduction correction process begins.

[0107] • Processing circuit 51 can shorten the execution time TMD of the reduction correction process by increasing the braking operation amount X before the reduction correction process begins, and can also keep the execution time TMD unchanged by decreasing the braking operation amount X before the reduction correction process begins.

[0108] In the above embodiment, 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 can 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".

[0109] When the braking control device performs stop braking control, 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 is the vehicle braking force BPA1.

[0110] 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.

[0111] <Other Technological Ideas>

[0112] The technical ideas that can be grasped from the above implementation methods and variations are recorded.

[0113] [Note 1] Preferably, the system includes 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.

[0114] The setting unit detects changes in the braking operation based on the shift in the value obtained by the acquisition unit before the reduction correction process begins.

[0115] [Note 2] Preferably, in the reduction correction process, the control unit reduces the braking force applied to the vehicle to the specified braking force, maintains the braking force at the specified braking force after the braking force reaches the specified braking force, and then makes the vehicle speed 0 (zero).

[0116] [Appendix 3] Preferably, if a change in the braking operation is detected before the reduction correction process begins, the setting unit sets the time during which the braking force applied to the vehicle is maintained at the specified braking force during the execution time of the reduction correction process to be shorter than the time when no change in the braking operation is detected.

[0117] [Note 4] Preferably, if a change in the braking operation is detected before the reduction correction process begins, the setting unit shortens the execution time of the reduction correction process by omitting the period during which the braking force applied to the vehicle is maintained at the specified braking force.

[0118] [Appendix 5] Preferably, when the control unit applies braking force to the vehicle to stop it, before performing the reduction correction process, it performs an increase correction process to make the braking force applied to the vehicle greater than the requested value of the braking force.

[0119] If the setting unit detects a change in the braking operation during the execution of the increase correction process, it sets the execution time of the decrease correction process to be shorter than the time when no change in the braking operation is detected.

[0120] 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, comprising: The control unit performs a reduction correction process when applying braking force to the vehicle to bring it to a stop. In this reduction correction process, after reducing the braking force applied to the vehicle to a predetermined braking force smaller than the requested braking force value, the vehicle's speed is reduced to 0. The setting unit, when the driver of the vehicle is performing braking operation, if a change in the braking operation is detected before the reduction correction process begins, sets the execution time of the reduction correction process to be shorter than the time when no change in the braking operation is detected.

2. The braking control device according to claim 1, wherein, The greater the degree of change in the braking operation before the reduction correction process begins, the shorter the execution time of the reduction correction process will be set by the setting unit.

Images