Brake control device and brake control method

Abstract

A brake control device (50) is provided with: a parking distance acquisition unit (M11) configured so as to acquire, as a parking-related value, a distance traveled by a traveling vehicle (10) until the traveling vehicle (10) stops or a vehicle speed until the vehicle (10) stops; a replacement control unit (M15) configured so as to adjust the friction braking force to a stop maintaining braking force and adjust the regenerative braking force in accordance with a braking request for the vehicle (10) when the parking-related value becomes smaller than a first parking determination value while the regenerative braking force is being applied to the vehicle (10); and a regenerative braking reduction control unit (M17) configured so that, when the parking-related value becomes smaller than the second parking determination value, the regenerative braking force is reduced so that the regenerative braking force becomes zero before the parking-related value becomes zero.

Description

Technical Field

[0001] The present disclosure relates to a brake control device and a brake control method for controlling a braking force applied to a vehicle. Background Art

[0002] Patent Document 1 discloses a control device that uses the regenerative braking force generated by an electric generator and the friction braking force generated by a hydraulic actuator to perform braking control to suppress changes in the vehicle's posture when the vehicle stops. If the vehicle speed falls below a specified speed, the control device controls the electric generator to reduce the regenerative braking force toward 0 (zero). Furthermore, if the vehicle speed reaches 0 (zero), the control device increases the friction braking force by activating the hydraulic actuator. This allows the control device to suppress sudden changes in the vehicle's posture when the vehicle stops and maintain the vehicle's stopped state.

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

[0004] Immediately before a vehicle stops, the accuracy of vehicle speed derivation decreases. Therefore, when applying regenerative braking force to the vehicle until just before the vehicle stops, the control device must actually cause the motor generator to repeat regeneration and power running until the vehicle stops. This, in turn, may degrade the vehicle's energy efficiency. Summary of the Invention

[0005] A brake control device according to one aspect of the present disclosure is configured to control regenerative braking force and friction braking force during vehicle braking. The brake control device includes: a parking-related value acquisition unit configured to acquire the distance traveled by a traveling vehicle until it stops or the vehicle speed until the vehicle stops as a parking-related value; a switching control unit configured to adjust the friction braking force to a braking force for maintaining the vehicle stopped on the road surface on which the vehicle is traveling, i.e., a stop-maintaining braking force, when the parking-related value becomes less than a first stop determination value while the regenerative braking force is being applied to the vehicle; and to adjust the regenerative braking force based on a braking request to the vehicle; and a regenerative braking reduction control unit configured to reduce the regenerative braking force so that the regenerative braking force reaches zero before the parking-related value reaches zero, when the parking-related value becomes less than a second stop determination value, wherein the second stop determination value is smaller than the first stop determination value.

[0006] Another aspect of the present disclosure provides a braking control method for controlling regenerative braking force and friction braking force during vehicle braking. The braking control method includes: obtaining a distance traveled by a moving vehicle until it stops, or a vehicle speed until the vehicle stops, as a stop-related value; adjusting the friction braking force to a braking force for maintaining the vehicle stopped on the road surface on which the vehicle is traveling, i.e., a stop-maintaining braking force, when the stop-related value becomes less than a first stop determination value while the regenerative braking force is being applied to the vehicle; and adjusting the regenerative braking force based on a braking request to the vehicle; and reducing the regenerative braking force to zero before the stop-related value becomes zero, when the stop-related value becomes less than a second stop determination value, wherein the second stop determination value is smaller than the first stop determination value. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a schematic configuration diagram showing a vehicle equipped with the brake control device according to the first embodiment.

[0008] Figure 2 Yes Figure 1 Flowchart of the first half of a series of processes executed by a processing circuit of a brake control device.

[0009] Figure 3 Yes Figure 1 Flowchart of the latter half of a series of processes executed by a processing circuit of a brake control device.

[0010] Figure 4 Is used to illustrate Figure 1 Timing diagram of the function of the brake control device.

[0011] Figure 5 This is a flowchart showing the processing executed by the processing circuit of the brake control device according to the second embodiment.

[0012] Figure 6 Is used to illustrate Figure 5 Timing diagram of the function of the brake control device.

[0013] Figure 7 It is a timing chart for explaining the operation of the brake control device according to the modified example.

[0014] Figure 8 This is a block diagram showing the functional configuration of a brake control device according to a modified example. DETAILED DESCRIPTION

[0015] (First embodiment)

[0016] The following, according to Figures 1 to 4A first embodiment of a brake control device and a brake control method will be described.

[0017] Figure 1 The figure shows a vehicle 10 equipped with a brake control device 50. Vehicle 10 includes a brake operating member 11, multiple wheels, multiple friction brakes 20, a braking device 30, and a regeneration device 40. The multiple wheels include front wheels 12 and rear wheels 13. Brake operating member 11 is a member operated by the driver to apply braking force to vehicle 10. For example, brake operating member 11 is a brake pedal or a brake lever.

[0018] <Regeneration device>

[0019] The regeneration device 40 includes a motor generator 41 for the rear wheels 13 and a regeneration control device 45 that controls the motor generator 41. The motor generator 41 functions as a motor to transmit driving force to the rear wheels 13. On the other hand, the motor generator 41 functions as a generator to apply a regenerative braking force to the rear wheels 13 corresponding to the amount of power generated by the motor generator 41.

[0020] The regeneration control device 45 includes a processing circuit 46 that controls the motor generator 41. For example, the processing circuit 46 is an electronic control unit. In this case, the processing circuit 46 includes a CPU and memory. The memory stores a control program executed by the CPU. The CPU executes this control program, thereby controlling the motor generator 41. Furthermore, the regeneration control device 45 can send and receive various information to and from the brake control device 50. Therefore, the processing circuit 46 coordinates with the brake control device 50 to adjust the regenerative braking force during vehicle braking.

[0021] Friction brakes

[0022] Multiple friction brakes 20 apply friction braking force to corresponding wheels. Each friction brake 20 includes a wheel cylinder 21, a rotating body 22, and a friction portion 23. Since the rotating body 22 rotates integrally with the wheel, friction braking force is applied to the wheel by pressing the friction portion 23 against the rotating body 22. The higher the hydraulic pressure within the wheel cylinder 21, or the wheel hydraulic pressure, the greater the force pressing the friction portion 23 against the rotating body 22. Therefore, the higher the wheel hydraulic pressure, the greater the friction braking force that the friction brake 20 can apply to the wheel.

[0023] Braking system

[0024] The braking system 30 adjusts the friction braking force applied to the front wheels 12 and rear wheels 13 by controlling the wheel hydraulic pressures in the multiple wheel cylinders 21. For example, the braking system 30 includes a pressurizing source for supplying brake fluid to the multiple wheel cylinders 21. Examples of the pressurizing source include an electric pump and an electric cylinder. The braking system 30 can independently control the wheel hydraulic pressures in the wheel cylinders 21 for the front wheels 12 and the wheel hydraulic pressures in the wheel cylinders 21 for the rear wheels 13.

[0025] Detection System

[0026] like Figure 1 As shown, a detection signal is input from the detection system to the brake control device 50. The detection system includes multiple sensors. The multiple sensors include a brake sensor 101, a longitudinal acceleration sensor 102, and multiple wheel speed sensors 103. The brake sensor 101 detects information related to the driver's operation of the brake operating member 11. Examples of the brake sensor 101 include a sensor that detects the amount of operation of the driver's brake operating member 11 and a sensor that detects the force of the driver's operation of the brake operating member 11. The longitudinal acceleration sensor 102 detects the longitudinal acceleration of the vehicle 10. A wheel speed sensor 103 is provided for each of the multiple wheels. The wheel speed sensor 103 detects the rotational speed of the corresponding wheel. In addition, the longitudinal acceleration based on the detection signal of the longitudinal acceleration sensor 102 is referred to as "fore-and-aft acceleration Gx". The rotational speed of the wheel based on the detection signal of the wheel speed sensor 103 is referred to as "wheel speed VW".

[0027] <Brake control system>

[0028] like Figure 1 As shown, the brake control device 50 controls the brake device 30. The brake control device 50 communicates with the regeneration control device 45 of the regeneration device 40.

[0029] The brake control device 50 includes a processing circuit 51. For example, the processing circuit 51 is an electronic control unit. In this case, the processing circuit 51 includes a CPU 52 and a memory 53. The memory 53 stores a control program executed by the CPU 52. The CPU 52 executes this control program, allowing the processing circuit 51 to control the brake device 30, causing it to apply friction braking force to the vehicle 10. Furthermore, the processing circuit 51 transmits instructions regarding regenerative braking force to the regenerative control device 45, causing it to apply regenerative braking force to the vehicle 10.

[0030] <Regeneration coordinated control>

[0031] The regenerative coordination control performed by the processing circuit 51 will be described. The processing circuit 51 derives the required braking force BPRq, which is the required braking force for the vehicle 10. When the brake operating member 11 is operated, the processing circuit 51 derives a value corresponding to the detection signal of the brake sensor 101 as the required braking force BPRq. Furthermore, when another control device requests deceleration of the vehicle 10, the processing circuit 51 derives a value corresponding to the required deceleration value of the vehicle 10 as the required braking force BPRq. The processing circuit 51 transmits the required braking force BPRq to the regeneration control device 45. In this way, the processing circuit 51 receives from the regeneration control device 45 the regenerative braking force BPE actually applied to the vehicle 10 by the regeneration device 40.

[0032] The processing circuit 51 derives a target friction braking force BPFtr, or target friction braking force, for the vehicle 10 based on the regenerative braking force BPE and the required braking force BPRq. If the regenerative braking force BPE and the required braking force BPRq are equal, the processing circuit 51 derives 0 (zero) as the target friction braking force BPFtr. On the other hand, if the regenerative braking force BPE is less than the required braking force BPRq, the processing circuit 51 derives the difference between the required braking force BPRq and the regenerative braking force BPE as the target friction braking force BPFtr. The processing circuit 51 then operates the brake device 30 based on the target friction braking force BPFtr.

[0033] <Functional Department>

[0034] The processing circuit 51 functions as a stopping distance acquisition unit M11, a stop-maintaining braking force derivation unit M13, a switching control unit M15, a regenerative braking reduction control unit M17, and a friction braking increase control unit M19, as the CPU 52 executes a control program stored in the memory 53. In this embodiment, the stopping distance acquisition unit M11 corresponds to a "parking-related value acquisition unit" that acquires a parking-related value. The parking-related value is a parameter whose value decreases as the vehicle 10 approaches a stop position.

[0035] When a braking request is issued for a moving vehicle 10, the stopping distance acquisition unit M11 acquires the stopping distance DS, which is the distance the vehicle 10 travels until it stops. Specifically, the stopping distance acquisition unit M11 acquires the stopping distance DS as a parking-related value. For example, the stopping distance acquisition unit M11 derives the stopping distance DS based on the vehicle body speed VS0 and the deceleration DVS. For example, the stopping distance acquisition unit M11 acquires the vehicle body speed VS0, which is the vehicle body speed of the vehicle 10 based on the wheel speeds VW of the front wheels 12 and the rear wheels 13. The stopping distance acquisition unit M11 acquires the time-differentiated value of the vehicle body speed VS0 as the deceleration DVS of the vehicle 10. The stopping distance acquisition unit M11 then estimates the stopping position, which is the position where the vehicle 10 stops, based on the vehicle body speed VS0 and the deceleration DVS. The stopping distance acquisition unit M11 acquires the distance from the current position of the vehicle 10 to the stopped position as the stopping distance DS.

[0036] The stopping-maintaining braking force derivation unit M13 derives the braking force used to maintain the vehicle 10 stopped on the road surface on which the vehicle 10 is traveling, namely, the stopping-maintaining braking force BPST. For example, the stopping-maintaining braking force derivation unit M13 derives the minimum value of the braking force capable of maintaining the vehicle 10 stopped on the road surface, or a braking force slightly greater than the minimum value, as the stopping-maintaining braking force BPST. Therefore, the greater the absolute value of the road surface gradient, the greater the stopping-maintaining braking force BPST derived by the stopping-maintaining braking force derivation unit M13. For example, the greater the difference between the longitudinal acceleration GX and the deceleration DVS of the vehicle 10, the greater the stopping-maintaining braking force BPST derived by the stopping-maintaining braking force derivation unit M13.

[0037] The switching control unit M15 executes switching control in which the friction braking force BPR is set to the stop-maintaining braking force BPST while adjusting the regenerative braking force BPE according to the braking request for the vehicle 10. Specifically, during the switching control, the switching control unit M15 increases the friction braking force BPF to the stop-maintaining braking force BPST, thereby adjusting the friction braking force BPR to the stop-maintaining braking force BPST. Furthermore, the switching control unit M15 adjusts the regenerative braking force BPE according to the braking request for the vehicle 10 by reducing the regenerative braking force BPE such that the greater the increase in the friction braking force BPF, the greater the decrease in the regenerative braking force BPE. The switching control unit M15 initiates switching control when the stopping distance DS is less than a first stopping distance determination value DSth1 while the regenerative braking force BPE is being applied to the vehicle 10. The first stopping distance determination value DSth1 is set to a value indicating whether the vehicle 10 is approaching the boundary of the stop position. The first stopping distance determination value DSth1 corresponds to the "first stopping determination value." The switching control unit M15 executes switching control when it can be determined that the vehicle 10 has approached the aforementioned stop position.

[0038] Specifically, during the switching control, the switching control unit M15 increases the target friction braking force BPFtr toward the stop-maintaining braking force BPST at each predetermined control cycle when the friction braking force BPF is less than the stop-maintaining braking force BPST. The switching control unit M15 then operates the brake device 30 based on the latest value of the target friction braking force BPFtr. Furthermore, the switching control unit M15 derives, at each control cycle, a value obtained by subtracting the previous value from the latest value of the target friction braking force BPFtr as the braking force reduction amount ΔBP. The previous value of the target friction braking force BPFtr refers to the target friction braking force BPFtr derived in the previous control cycle. At each control cycle, the switching control unit M15 derives, at each control cycle, a value obtained by subtracting the braking force reduction amount ΔBP from the current regenerative braking force BPE, and transmits this target regenerative braking force BPEtr to the regenerative control unit 45. Consequently, the regenerative control unit 45 operates the motor generator 41 based on the target regenerative braking force BPEtr, thereby reducing the regenerative braking force BPE to the target regenerative braking force BPEtr.

[0039] Then, when the friction braking force BPF becomes equal to or greater than the stop maintaining braking force BPST, the switching control unit M15 ends the switching control.

[0040] On the other hand, when the stopping distance DS becomes less than the first stopping distance determination value DSth1 and the friction braking force BPF is greater than the stop-maintaining braking force BPST, the switching control unit M15 limits the adjustment of the friction braking force BPF and the regenerative braking force BPE. Specifically, the switching control unit M15 limits the increase in the friction braking force BPF and the decrease in the regenerative braking force BPE. In this embodiment, the switching control unit M15 maintains the friction braking force BPF and the regenerative braking force BPE by not executing the switching control.

[0041] The regenerative braking reduction control unit M17 executes regenerative braking reduction control to reduce the regenerative braking force BPE so that the regenerative braking force BPE reaches 0 (zero) before the stopping distance DS reaches 0 (zero). The regenerative braking reduction control unit M17 initiates the regenerative braking reduction control when the stopping distance DS becomes less than a second stopping distance determination value DSth2. The second stopping distance determination value DSth2 is set to a distance shorter than the first stopping distance determination value DSth1. For example, the second stopping distance determination value DSth2 is set to a value indicating whether the vehicle 10 has reached the boundary immediately before the aforementioned stop position. The second stopping distance determination value DSth2 corresponds to the "second stopping determination value."

[0042] During regenerative braking reduction control, the regenerative braking reduction control unit M17 reduces the target regenerative braking force BPEtr at a predetermined reduction rate. Furthermore, the regenerative braking reduction control unit M17 transmits the latest value of the target regenerative braking force BPEtr to the regenerative control device 45. This causes the regenerative control device 45 to operate the motor generator 41 based on the target regenerative braking force BPEtr, thereby reducing the regenerative braking force BPE. When the regenerative braking force BPE reaches 0 (zero), the regenerative braking reduction control unit M17 terminates the regenerative braking reduction control.

[0043] The friction brake increase control unit M19 performs friction brake increase control to increase the friction braking force BPF when the vehicle 10 is stopped. For example, the friction brake increase control unit M19 determines that the vehicle 10 is stopped when the following conditions (A1), (A2), and (A3) are all met.

[0044] (A1) The stopping distance DS is 0 (zero).

[0045] (A2) The regenerative braking force BPE is 0 (zero).

[0046] (A3) The front wheels 12 and the rear wheels 13 are not rotating.

[0047] During friction brake increase control, the friction brake increase control unit M19 increases the target friction braking force BPFtr at a predetermined increase rate to the required braking force BPRq. Furthermore, the friction brake increase control unit M19 operates the braking device 30 based on the latest value of the target friction braking force BPFtr. In this embodiment, the friction brake increase control unit M19 increases both the front and rear wheel friction braking forces so that the front and rear wheel hydraulic pressures are equal. At this time, the friction brake increase control unit M19 increases the front and rear wheel hydraulic pressures so that the total friction braking force, the sum of the front and rear wheel friction braking forces, equals the target friction braking force BPFtr. The front wheel hydraulic pressure refers to the wheel hydraulic pressure in the wheel cylinders 21 for the front wheels 12, and the rear wheel hydraulic pressure refers to the wheel hydraulic pressure in the wheel cylinders 21 for the rear wheels 13. The front wheel friction braking force is the friction braking force applied to the front wheels 12, and the rear wheel friction braking force is the friction braking force applied to the rear wheels 13.

[0048] <Smooth stop processing>

[0049] Reference Figure 2 as well as Figure 3 The smooth stop process performed by the processing circuit 51 will now be described. The smooth stop process is a series of processes for suppressing the shaking of the vehicle body when the vehicle 10 stops by adjusting the braking force of the vehicle 10. The processing circuit 51 repeatedly performs the smooth stop process as the CPU 52 executes a control program stored in the memory 53.

[0050] like Figure 2 As shown, in step S11, the processing circuit 51 determines whether a braking request has been issued. For example, if the brake operating member 11 is operated, a braking request is considered to have been issued. Alternatively, for example, if another control device requests deceleration of the vehicle 10, a braking request is considered to have been issued. If the processing circuit 51 determines that a braking request has been issued (S11: Yes), the process proceeds to step S15. On the other hand, if the processing circuit 51 determines that no braking request has been issued (S11: No), the process proceeds to step S13.

[0051] In step S13, the processing circuit 51 turns off the replacement completion flag FLG1 and temporarily ends the smooth stop process.

[0052] In step S15, the processing circuit 51 derives the required braking force BPRq. Then, the processing circuit 51 shifts the process to step S17.

[0053] In step S17 , the processing circuit 51 functions as the stop maintaining braking force deriving unit M13 to obtain the stop maintaining braking force BPST .

[0054] In step S19, the processing circuit 51 functions as a parking-related value acquisition unit to acquire a parking-related value. In this embodiment, the processing circuit 51 functions as a parking distance acquisition unit M11 to acquire the parking distance DS as the parking-related value. The processing circuit 51 then proceeds to step S21.

[0055] In step S21, the processing circuit 51 determines whether the stopping distance DS acquired in step S19 is less than the first stopping distance determination value DSth1. If the stopping distance DS is less than the first stopping distance determination value DSth1 (S21: Yes), the processing circuit 51 proceeds to step S31. On the other hand, if the stopping distance DS is greater than or equal to the first stopping distance determination value DSth1 (S21: No), the processing circuit 51 proceeds to step S23.

[0056] In step S23, the processing circuit 51 performs normal braking control. That is, the processing circuit 51 performs the above-mentioned regenerative coordination control as normal braking control. Then, the processing circuit 51 temporarily ends the smooth stop process.

[0057] In step S31, the processing circuit 51 determines whether the replacement completion flag FLG1 is set to on. If the replacement completion flag FLG1 is set to on (S31: Yes), the processing circuit 51 proceeds to step S43. On the other hand, if the replacement completion flag FLG1 is set to off (S31: No), the processing circuit 51 proceeds to step S33.

[0058] In step S33, the processing circuit 51 determines whether the target friction braking force BPFtr is greater than the stop-maintaining braking force BPST. If the target friction braking force BPFtr is greater than the stop-maintaining braking force BPST (S33: Yes), the processing circuit 51 proceeds to step S41. On the other hand, if the target friction braking force BPFtr is less than the stop-maintaining braking force BPST (S33: No), the processing circuit 51 proceeds to step S35.

[0059] In step S35, the processing circuit 51, functioning as the switching control unit M15, increases the target friction braking force BPFtr and, based on this target friction braking force BPFtr, operates the braking device 30. In the following step S37, the processing circuit 51, functioning as the switching control unit M15, instructs the regeneration control device 45 to reduce the regeneration braking force BPEtr. Specifically, the processing circuit 51 reduces the target regeneration braking force BPEtr and transmits this target regeneration braking force BPEtr to the regeneration control device 45. In this embodiment, steps S35 and S37 correspond to switching control. The processing circuit 51 then temporarily terminates the smooth stop process.

[0060] like Figure 3 As shown, in step S41, the processing circuit 51 turns on the replacement completion flag FLG1. That is, the processing circuit 51 ends the replacement control. Then, the processing circuit 51 moves the process to step S43.

[0061] In step S43, the processing circuit 51 determines whether the stopping distance DS is less than the second stopping distance determination value DSth2. If the stopping distance DS is less than the second stopping distance determination value DSth2 (S43: Yes), the processing circuit 51 proceeds to step S45. On the other hand, if the stopping distance DS is greater than or equal to the second stopping distance determination value DSth2 (S43: No), the processing circuit 51 temporarily terminates the smooth stop process. In this case, the processing circuit 51 maintains the friction braking force BPF and the regenerative braking force BPE.

[0062] In step S45, the processing circuit 51 determines whether the regenerative braking force BPE is 0 (zero). For example, if the target regenerative braking force BPEtr is 0 (zero), the processing circuit 51 determines that the regenerative braking force BPE is 0 (zero). If the processing circuit 51 determines that the regenerative braking force BPE is 0 (zero) (S45: Yes), the processing proceeds to step S51. On the other hand, if the processing circuit 51 determines that the regenerative braking force BPE is not 0 (zero) (S45: No), the processing proceeds to step S47.

[0063] In step S47, the processing circuit 51 functions as the regenerative braking reduction control unit M17 and instructs the regenerative control device 45 to reduce the regenerative braking force BPE. Specifically, the processing circuit 51 decreases the target regenerative braking force BPEtr toward 0 (zero) and transmits this target regenerative braking force BPEtr to the regenerative control device 45. In this embodiment, step S47 corresponds to regenerative braking reduction control. The processing circuit 51 then temporarily terminates the smooth stop process.

[0064] In step S51, the processing circuit 51 functions as the friction brake increase control unit M19 to determine whether the vehicle 10 is stopped. If the processing circuit 51 determines that the vehicle 10 is stopped (S51: Yes), the processing proceeds to step S53. If the processing circuit 51 determines that the vehicle 10 is not stopped (S51: No), the smooth stop process is temporarily terminated. In this case, the processing circuit 51 maintains the friction braking force BPF.

[0065] In step S53, the processing circuit 51, functioning as the friction brake increase control unit M19, determines whether the friction braking force BPF is greater than the required braking force BPRq. If the friction braking force BPF is greater than the required braking force BPRq (S53: Yes), the processing circuit 51 terminates the smooth stop process. On the other hand, if the friction braking force BPF is less than the required braking force BPRq (S53: No), the processing proceeds to step S55.

[0066] In step S55, the processing circuit 51 functions as the friction brake increase control unit M19 to increase the friction braking force BPF toward the required braking force BPRq. Specifically, the processing circuit 51 increases the target friction braking force BPFtr and activates the brake device 30 based on this target friction braking force BPFtr. In this embodiment, step S55 corresponds to the friction brake increase control. The processing circuit 51 then temporarily terminates the smooth stop process.

[0067] <Functions and Effects of the First Embodiment>

[0068] Reference Figure 4 , explaining the role and effect of vehicle braking.

[0069] like Figure 4 As shown in (A), if the brake operating member 11 is operated at time t11 while the vehicle is traveling, the processing circuit 51 begins to determine that a braking request has been issued. Consequently, the processing circuit 51 derives the required braking force BPRq and acquires the stopping distance DS at each predetermined control cycle. From time t11 to time t13, the processing circuit 51 determines that the stopping distance DS is greater than or equal to the first stopping distance determination value DSth1, and therefore executes regenerative cooperative control as normal braking control. The sum of the friction braking force BPF and the regenerative braking force BPE is referred to as the "total braking force BPA."

[0070] In the regenerative cooperative control, the processing circuit 51 controls the braking device 30 and the regenerative device 40 so that the total braking force BPA becomes equal to the required braking force BPRq. Figure 4 In the example shown, Figure 4As shown in (C), (D), and (E), the processing circuit 51 controls the braking device 30 and the regeneration device 40 so that the regenerative braking force BPE becomes equal to the required braking force BPRq.

[0071] Figure 4 The translational motion of vehicle 10 shown in (B) refers to the fore-aft acceleration of vehicle 10 excluding the sprung motion. This fore-aft acceleration is referred to as vehicle body fore-aft acceleration GxB. When vehicle 10 is decelerating, vehicle body fore-aft acceleration GxB is negative. Furthermore, the greater the total braking force BPA, the greater the absolute value of vehicle body fore-aft acceleration GxB. Furthermore, the greater the absolute value of vehicle body fore-aft acceleration GxB, the more likely the pitch angle of vehicle 10 increases.

[0072] exist Figure 4 In the example shown, the required braking force BPRq is substantially maintained from timing t12 onward. At timing t13, while the required braking force BPRq is maintained, the processing circuit 51 determines that the stopping distance DS is less than the first stopping distance determination value DSth1. Furthermore, at timing t13, the processing circuit 51 determines that the friction braking force BPF is less than the stop-maintaining braking force BPST. Therefore, the processing circuit 51 executes switching control to increase the friction braking force BPF to the stop-maintaining braking force BPST and, in conjunction with the increase in the friction braking force BPF, reduce the regenerative braking force BPE. This reduces the regenerative braking force BPE even as the friction braking force BPF increases. Therefore, even when the friction braking force BPF increases, the processing circuit 51 can maintain the total braking force BPA equal to the required braking force BPRq.

[0073] When the friction braking force BPF reaches the stop maintaining braking force BPST, the processing circuit 51 maintains the friction braking force BPF and the stop maintaining braking force BPST to be equal, and maintains the regenerative braking force BPE.

[0074] At timing t14 after the replacement control ends, the processing circuit 51 determines that the stopping distance DS is less than the second stopping distance determination value DSth2. Then, the processing circuit 51 executes the regenerative braking reduction control to reduce the regenerative braking force BPE to 0 (zero). The processing circuit 51 reduces the target regenerative braking force BPEtr so that the regenerative braking force BPE becomes 0 (zero) before the stopping distance DS becomes 0 (zero). Figure 4 In the example shown, when the regenerative braking force BPE becomes 0 (zero) at timing t15, the processing circuit 51 maintains the regenerative braking force BPE at 0 (zero) and holds the friction braking force BPF.

[0075] Here, after the above-mentioned replacement control is completed, the friction braking force BPF is maintained at the stop maintaining braking force BPST. Therefore, even if the vehicle 10 stops directly, the brake control device 50 can maintain the state in which the vehicle 10 is stopped.

[0076] In the brake control device 50, the friction braking force BPF is increased to the stop-maintaining braking force BPST before the regenerative braking force BPE becomes 0 (zero). Therefore, the electric generator 41 does not need to repeat the regeneration and power operation immediately before the vehicle 10 stops. In addition, the regenerative braking force BPE is reduced to 0 (zero) before the vehicle 10 stops, and the total braking force BPA is reduced accordingly. Therefore, the vehicle 10 stops in a state where the magnitude of the longitudinal acceleration GxB of the vehicle body is reduced to a certain extent. As a result, the change in the longitudinal acceleration GxB of the vehicle body caused by the stopping of the vehicle 10 is small. Therefore, the brake control device 50 can suppress the deterioration of the energy efficiency of the vehicle 10 and suppress the posture of the vehicle 10 from changing significantly when the vehicle 10 stops.

[0077] exist Figure 4 In the example shown, the processing circuit 51 determines at time t16 that the vehicle 10 has stopped. Therefore, the processing circuit 51 executes friction brake boost processing to increase the friction braking force BPF. At time t17, the friction braking force BPF reaches the required braking force BPRq. Therefore, after time t17, the processing circuit 51 maintains the friction braking force BPF equal to the required braking force BPRq. This allows the brake control device 50 to eliminate the discrepancy between the required braking force BPRq and the total braking force BPA.

[0078] In the first embodiment, the following effects can be further obtained.

[0079] (1-1) Figure 4 In (D) and (E), the dotted lines show the changes in the friction braking force BPF and the regenerative braking force BPE when the normal switching control is executed. In the normal switching control, the regenerative braking force BPE becomes 0 (zero) before timing t14.

[0080] In contrast, the brake control device 50 can provide the regenerative braking force BPE to the vehicle 10 until the timing t15. Therefore, the brake control device 50 can improve the energy efficiency of the vehicle 10 compared to the case where the normal switching control is performed. Specifically, the brake control device 50 can improve the energy efficiency of the vehicle 10 by Figure 4 The amount corresponding to the area ER surrounded by the dotted line in (C).

[0081] (1-2) In the brake control device 50, if the friction braking force BPF is increased to the stop-maintaining braking force BPST through the execution of the replacement control, the friction braking force BPF is maintained until the vehicle 10 is determined to have stopped. In other words, the brake control device 50 may not repeatedly increase or decrease the friction braking force BPF immediately before the vehicle 10 stops. Therefore, the brake control device 50 can suppress the generation of body vibrations of the vehicle 10 caused by fluctuations in the friction braking force BPF immediately before the vehicle 10 stops. Furthermore, the brake control device 50 may not repeatedly increase or decrease the friction braking force BPF, thereby suppressing energy consumption in the brake device 30.

[0082] (1-3) There are cases where the friction braking force BPF is already greater than the stop-maintaining braking force BPST at the time the stopping distance DS is determined to be less than the first stopping distance determination value DSth1. In the brake control device 50, if the friction braking force BPF is greater than the stop-maintaining braking force BPST at the time the stopping distance DS is determined to be less than the first stopping distance determination value DSth1, the processing circuit 51 does not execute the switching control. In other words, the processing circuit 51 limits the increase in the friction braking force BPF and the decrease in the regenerative braking force BPE until the stopping distance DS is determined to be less than the second stopping distance determination value DSth2. Thus, the brake control device 50 can suppress the decrease in the regenerative braking force BPE, thereby improving the energy efficiency of the vehicle 10.

[0083] (Second embodiment)

[0084] according to Figure 5 as well as Figure 6 A second embodiment of a brake control device will be described. The second embodiment differs from the first embodiment in the details of the replacement control. The following description will focus on the differences from the first embodiment. Components identical to those in the first embodiment will be denoted by the same reference numerals, and duplicate descriptions will be omitted.

[0085] exist Figure 5 The diagram in the middle shows Figure 2 The details of the process of step S35 are shown.

[0086] When the smooth stop process is being executed, if the following three conditions are all satisfied, the processing circuit 51 moves the process to step S35 .

[0087] It is determined that the stopping distance DS is smaller than the first stopping distance determination value DSth1 ( S21 : YES).

[0088] The replacement completion flag FLG1 is on (S31: No).

[0089] The friction braking force BPF is smaller than the stop maintaining braking force BPST ( S33 : NO).

[0090] like Figure 5 As shown, the process of step S35 includes the processes of steps S351, S353, and S355. The processing circuit 51 executes steps S351, S353, and S355 by functioning as the replacement control unit M15.

[0091] In the first step S351, the processing circuit 51 determines whether the braking force BPST for stopping and maintaining is equal to or greater than the determination braking force BPSTth. The determination braking force BPSTth is a criterion for determining whether the braking force BPST for stopping and maintaining is relatively large.

[0092] Here, consider the case where both the front wheel friction braking force BPFF and the rear wheel friction braking force BPFR are increased while the stop-maintaining braking force BPST is relatively low. In this case, both the front wheel friction braking force BPFF and the rear wheel friction braking force BPFR are relatively low. Therefore, naturally, both the front wheel hydraulic pressure and the rear wheel hydraulic pressure are relatively low. As a result, there is a possibility of brake squealing in at least one of the friction brakes 20 for the front wheels 12 and the friction brakes 20 for the rear wheels 13. Therefore, the determination braking force BPSTth is set to a value that indicates the boundary between whether brake squealing is likely to occur in the friction brakes 20 when both the front wheel friction braking force and the rear wheel friction braking force are increased as in the first embodiment described above. If the stop-maintaining braking force BPST is less than the determination braking force BPSTth, it is considered that increasing both the front wheel friction braking force BPFF and the rear wheel friction braking force BPFR will likely result in brake squealing in the friction brakes 20. On the other hand, when the stop maintaining braking force BPST is equal to or greater than the determination braking force BPSTth, it is considered that no brake squealing sound is generated in the friction brake 20 even if both the front wheel friction braking force BPFF and the rear wheel friction braking force BPFR are increased.

[0093] If the stopping and maintaining braking force BPST is greater than the determination braking force BPSTth (S351: YES), the processing circuit 51 proceeds to step S353. On the other hand, if the stopping and maintaining braking force BPST is less than the determination braking force BPSTth (S351: NO), the processing circuit 51 proceeds to step S355.

[0094] In step S353, the processing circuit 51 increases both the front wheel friction braking force BPFF and the rear wheel friction braking force BPFR. For example, the processing circuit 51 increases both the target of the front wheel friction braking force BPFF, that is, the target front wheel friction braking force, and the target of the rear wheel friction braking force BPFR, that is, the target rear wheel friction braking force. At this time, the processing circuit 51 increases the target front wheel friction braking force and the target rear wheel friction braking force in such a manner that the sum of the target front wheel friction braking force and the target rear wheel friction braking force is equal to the target friction braking force BPFtr. Moreover, the processing circuit 51 operates the brake device 30 in such a manner that the front wheel hydraulic pressure PwcF becomes a hydraulic pressure corresponding to the target front wheel friction braking force. The processing circuit 51 operates the brake device 30 in such a manner that the rear wheel hydraulic pressure PwcR becomes a hydraulic pressure corresponding to the target rear wheel friction braking force. Thereafter, the processing circuit 51 ends Figure 5 Specifically, the processing circuit 51 adjusts the total friction braking force, which is the sum of the front wheel friction braking force and the rear wheel friction braking force, to the stopping maintenance braking force, while adjusting the regenerative braking force BPE according to the braking request to the vehicle 10 .

[0095] In step S355, the processing circuit 51 increases only the friction braking force of either the front wheel friction braking force BPFF or the rear wheel friction braking force BPFR, that is, the target friction braking force. In the second embodiment, the rear wheel friction braking force BPFR corresponds to the target friction braking force. Therefore, the processing circuit 51 increases the rear wheel friction braking force BPFR, and on the other hand, maintains the front wheel friction braking force BPFF. In this case, the processing circuit 51 maintains the target front wheel friction braking force, and on the other hand, increases the target rear wheel friction braking force. In addition, the processing circuit 51 increases the target rear wheel friction braking force in such a manner that the sum of the target front wheel friction braking force and the target rear wheel friction braking force is equal to the target friction braking force BPFtr. Moreover, the processing circuit 51 operates the brake device 30 in such a manner that the front wheel hydraulic pressure PwcF is maintained and the rear wheel hydraulic pressure PwcR becomes a hydraulic pressure corresponding to the target rear wheel friction braking force. Thereafter, the processing circuit 51 ends Figure 5 The series of processing shown in Figure 2 That is, the processing circuit 51 can adjust the target friction braking force to the stop-maintaining braking force, and at the same time adjust the regenerative braking force BPE according to the braking request to the vehicle 10 .

[0096] <Functions and Effects of Second Embodiment>

[0097] Reference Figure 6 The following description will focus on the actions and effects during vehicle braking in the second embodiment that differ from those in the first embodiment.

[0098] like Figure 6 As shown in (A) to (G) of FIG. 1 , at timing t21 during vehicle braking, the processing circuit 51 determines that the stopping distance DS is smaller than the first stopping distance determination value DSth1. Figure 6 In the example shown, at time t21, the friction braking force BPF is less than the stop-maintaining braking force BPST. Therefore, the processing circuit 51 performs switching control to increase the friction braking force BPF to the stop-maintaining braking force BPST and decrease the regenerative braking force BPE in conjunction with the increase in the friction braking force BPF.

[0099] That is, the processing circuit 51 determines whether the stopping and maintaining braking force BPST is equal to or greater than the determination braking force BPSTth. Figure 6 In (F) and (G), the dotted lines show the transitions of the front wheel fluid pressure PwcF and the rear wheel fluid pressure PwcR when both the front wheel friction braking force BPFF and the rear wheel friction braking force BPFR are increased.

[0100] exist Figure 6 In the example shown, the processing circuit 51 determines that the stopping and maintaining braking force BPST is less than the determined braking force BPSTth, and therefore increases only the rear wheel friction braking force BPFR of the front wheel friction braking force BPFF and the rear wheel friction braking force BPFR. In other words, when it is predicted that increasing both the front wheel friction braking force BPFF and the rear wheel friction braking force BPFR will cause a brake squeal on at least one of the front wheels 12 and the rear wheels 13, the processing circuit 51 increases only the rear wheel friction braking force BPFR of the front wheel friction braking force BPFF and the rear wheel friction braking force BPFR. As a result, Figure 6 As shown in (G), the rear wheel hydraulic pressure PwcR is higher than when both the front wheel friction braking force BPFF and the rear wheel friction braking force BPFR are increased. The lower the wheel hydraulic pressure, the more likely it is that brake squealing noise will occur in the friction brake 20. Therefore, the brake control device 50 can suppress brake squealing noise in the friction brake 20 when the friction braking force BPF is increased by executing the switching control.

[0101] At time t22 after the completion of the switching control, the processing circuit 51 determines that the stopping distance DS is less than the second stopping distance determination value DSth2. Therefore, the processing circuit 51 executes regenerative braking reduction control to reduce the regenerative braking force BPE to 0 (zero). At time t23, with the regenerative braking force BPE at 0 (zero), the processing circuit 51 determines that the vehicle 10 has stopped. Consequently, the processing circuit 51 executes friction braking increase control to increase the friction braking force BPF to the required braking force BPRq. At this time, the processing circuit 51 adjusts both the front wheel friction braking force BPFF and the rear wheel friction braking force BPFR so that the front wheel hydraulic pressure PwcF and the rear wheel hydraulic pressure PwcR are at the same pressure.

[0102] (Change Example)

[0103] The above-mentioned multiple embodiments can be implemented by modifying them as follows. The above-mentioned multiple embodiments and the following modified examples can be implemented in combination with each other within the scope of no technical contradiction.

[0104] If the regenerative braking reduction control is executed immediately before the vehicle 10 stops, the total braking force BPA tends to decrease, and accordingly the braking distance of the vehicle 10 tends to increase. Figure 7 As shown in (A) to (E) of FIGURE 3, processing circuit 51 determines that stopping distance DS is less than the third stopping distance determination value at time t31, before switching control starts at time t32. The third stopping distance determination value is set to a distance greater than first stopping distance determination value DSth1. In this manner, processing circuit 51 can also execute braking increase control, starting at time t31, to increase total braking force BPA relative to required braking force BPRq. Preferably, the amount of increase in total braking force BPA in this case is set so that the braking distance does not increase even if regenerative braking reduction control is subsequently executed.

[0105] exist Figure 7 In the example shown, the processing circuit 51 increases the regenerative braking force BPE by executing the brake increase control. Thus, the brake control device of the modified example can improve the energy efficiency of the vehicle 10 and suppress an increase in the braking distance.

[0106] When the processing circuit 51 determines that the stopping distance DS is less than the first stopping distance determination value DSth1, and if it is possible to increase the regenerative braking force BPE, the processing circuit 51 may execute the following process. Specifically, the processing circuit 51 may execute a different switching control from the switching control when the friction braking force BPF is greater than the stopping-maintaining braking force BPST. In this other switching control, the processing circuit 51 may decrease the friction braking force BPF toward the stopping-maintaining braking force BPST and increase the regenerative braking force BPE in response to the decrease in the friction braking force BPF.

[0107] In the second embodiment, when the stopping distance DS is determined to be less than the first stopping distance determination value DSth1 and the stopping and maintaining braking force BPST is greater than or equal to the determination braking force BPSTth, the processing circuit 51 may increase only the front wheel friction braking force BPFF of the front wheel friction braking force BPFF and the rear wheel friction braking force BPFR. In this case, the front wheel friction braking force BPFF corresponds to the target friction braking force.

[0108] In the second embodiment, even when it is determined that the stopping distance DS is less than the first stopping distance determination value DSth1, the processing circuit 51 may increase only one of the front wheel friction braking force BPFF and the rear wheel friction braking force BPFR while the stopping and maintaining braking force BPST is equal to or greater than the determination braking force BPSTth.

[0109] During the friction brake increase control, the processing circuit 51 may not set the friction braking force BPF to be equal to the required braking force BPRq, as long as the friction braking force BPF is increased. Specifically, the processing circuit 51 may set a predetermined braking force that is different from the required braking force BPRq and increase the friction braking force BPF to the predetermined braking force.

[0110] Even if the friction brake increase control is not executed, the vehicle 10 can be maintained in a stopped state. Therefore, even if the processing circuit 51 determines that the vehicle 10 is stopped, the friction brake increase control does not need to be executed.

[0111] The processing circuit 51 may also obtain the vehicle body speed VS0 of the vehicle 10, that is, the vehicle speed SP, as the parking-related value instead of the parking distance DS. Figure 8 As shown, in the brake control device 50A, the processing circuit 51 can also function as a vehicle speed acquisition unit M21. In this case, the vehicle speed acquisition unit M21 functions as a "parking-related value acquisition unit." In this case, when the vehicle speed SP falls below the first parking speed determination value, the processing circuit 51 functions as a switching control unit M15 to execute the aforementioned switching control. The first parking speed determination value corresponds to the "first parking determination value." Furthermore, when the vehicle speed SP falls below the second parking speed determination value, the processing circuit 51 functions as a regenerative braking reduction control unit M17 to execute regenerative braking reduction control. The second parking speed determination value is set to a vehicle speed lower than the first parking speed determination value. The second parking speed determination value corresponds to the "second parking determination value."

[0112] The processing circuit 51 can be configured as one or more processors operating according to a computer program, one or more dedicated hardware circuits such as dedicated hardware that performs at least a portion of various processes, or a circuit comprising a combination thereof. Examples of dedicated hardware include application-specific integrated circuits, or ASICs. A processor includes a CPU and memory such as RAM and ROM, which stores program code or instructions configured to cause the CPU to execute processes. Memory, or computer-readable media, encompasses all available media that can be accessed by general-purpose or dedicated computers.

[0113] Furthermore, the expression "at least one" as used in this specification refers to "one or more" of the desired options. For example, when the number of options is two, the expression "at least one" as used in this specification refers to "only one option" or "both options." As another example, when the number of options is three or more, the expression "at least one" as used in this specification refers to "only one option" or "any combination of two or more options."

Claims

1. A brake control device configured to control regenerative braking force and friction braking force during vehicle braking, wherein: have: a parking-related value acquiring unit configured to acquire, as the parking-related value, a distance traveled by the vehicle until the vehicle stopped or a vehicle speed until the vehicle stopped; a replacement control unit configured to adjust the friction braking force to a braking force for maintaining the vehicle stopped on the road surface on which the vehicle is traveling, i.e., a stop-maintaining braking force, when the stop-related value becomes less than a first stop determination value while the regenerative braking force is being applied to the vehicle, and to adjust the regenerative braking force based on a braking request to the vehicle; as well as The regenerative braking reduction control unit is configured to reduce the regenerative braking force so that the regenerative braking force becomes zero before the parking-related value becomes zero when the parking-related value becomes smaller than a second parking determination value that is smaller than the first parking determination value.

2. The brake control device according to claim 1, wherein: The vehicle further includes a friction brake increase control unit configured to increase the friction braking force when the vehicle is stopped.

3. The brake control device according to claim 1 or 2, wherein: The vehicle has front wheels, rear wheels, and a brake device. The brake device is configured to independently adjust the friction braking force applied to the front wheel, that is, the front wheel friction braking force, and the friction braking force applied to the rear wheel, that is, the rear wheel friction braking force. The friction braking force of either the front wheel friction braking force or the rear wheel friction braking force is the target friction braking force. The replacement control unit is further configured to increase only the target friction braking force to the stop-maintaining braking force when the parking-related value becomes smaller than the first parking determination value in the state where the regenerative braking force is applied to the vehicle, and on the other hand, adjust the regenerative braking force according to the required braking of the vehicle.

4. The brake control device according to claim 1 or 2, wherein: The vehicle has front wheels, rear wheels, and a brake device. The brake device is configured to independently adjust the friction braking force applied to the front wheel, that is, the front wheel friction braking force, and the friction braking force applied to the rear wheel, that is, the rear wheel friction braking force. The friction braking force of either the front wheel friction braking force or the rear wheel friction braking force is the target friction braking force. The switching control unit is further configured to, when the parking-related value becomes smaller than the first parking determination value in a state where the regenerative braking force is applied to the vehicle, When the stop-maintaining braking force is greater than the determination braking force, the sum of the front wheel friction braking force and the rear wheel friction braking force, i.e., the total friction braking force, is adjusted to the stop-maintaining braking force by increasing both the front wheel friction braking force and the rear wheel friction braking force. On the other hand, the regenerative braking force is adjusted according to the required braking of the vehicle. When the stop-maintaining braking force is smaller than the determination braking force, only the target friction braking force is increased to the stop-maintaining braking force, while the regenerative braking force is adjusted according to the braking request for the vehicle.

5. The brake control device according to claim 1 or 2, wherein: The replacement control unit is further configured to limit the adjustment of the friction braking force and the regenerative braking force until the parking-related value becomes less than the second parking judgment value when the friction braking force is greater than the stop-maintaining braking force at the moment when the parking-related value becomes less than the first parking judgment value.

6. The brake control device according to claim 1 or 2, wherein: The vehicle further includes a stop-maintaining braking force deriving unit configured to derive the stop-maintaining braking force.

7. The brake control device according to claim 1 or 2, wherein: The vehicle has front wheels, rear wheels, and a brake device. The brake device is configured to independently adjust the friction braking force applied to the front wheel, that is, the front wheel friction braking force, and the friction braking force applied to the rear wheel, that is, the rear wheel friction braking force. The friction braking force of either the front wheel friction braking force or the rear wheel friction braking force is the target friction braking force. The replacement control unit is further configured to, when the parking-related value becomes smaller than the first parking determination value in a state where the regenerative braking force is applied to the vehicle, adjust only the target friction braking force to the stop-maintaining braking force when it can be predicted that a brake sound will be generated on at least one of the front wheels and the rear wheels if both the front wheel friction braking force and the rear wheel friction braking force are increased, and on the other hand, adjust the regenerative braking force according to the braking requirement for the vehicle.

8. A braking control method for controlling regenerative braking force and friction braking force during vehicle braking, wherein: Include: obtaining a distance traveled by the moving vehicle until it stops or a vehicle speed until the moving vehicle stops as a parking-related value; When the parking-related value becomes less than a first parking determination value while the regenerative braking force is being applied to the vehicle, the friction braking force is adjusted to a braking force for maintaining the vehicle stopped on the road surface on which the vehicle is traveling, i.e., a stop-maintaining braking force, and the regenerative braking force is adjusted according to a braking request for the vehicle. as well as When the parking-related value becomes smaller than a second parking determination value that is smaller than the first parking determination value, the regenerative braking force is reduced so as to become zero before the parking-related value becomes zero.

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