Vehicle brake control device

Abstract

The invention relates to a vehicle brake control device. A control device (50) is provided with a control unit (M19) that implements ABS control that suppresses locking of left and right wheels of a vehicle by adjusting the braking force of the left and right wheels. The method is executed in the ABS control. The control unit (M19) alternately switches between a right wheel period in which the right wheel of the left and right wheels is set as a first wheel in which the braking force is increased and the left wheel is set as a second wheel in which the braking force is adjusted within a range smaller than the braking force of the first wheel. And a left wheel period crossing process in which the left wheel is set as the first wheel and the right wheel is set as the second wheel, and a crossing process in which the braking force of the second wheel is increased during either the left wheel period or the right wheel period.

Description

Technical Field

[0001] The present invention relates to a vehicle brake control device for implementing anti-lock brake control for adjusting the braking force of left and right wheels of a vehicle. Background Art

[0002] Patent Document 1 discloses a control device that performs anti-lock braking control to stabilize vehicle behavior by suppressing wheel locking of a vehicle. The control device performs anti-lock braking control based on a downshifting method of the wheel with the lower wheel speed among left and right wheels.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2008-126859

[0004] When the control device implements the anti-lock brake control of the downshift method, the braking force of the left and right wheels is set to a magnitude corresponding to the wheel with the lower wheel speed, so that the braking force may be applied to the two wheels more than necessary. In this case, the braking efficiency may be reduced. Summary of the invention

[0005] The vehicle brake control device for solving the above-mentioned problem includes a control unit, which implements anti-lock braking control for suppressing the locking of the left and right wheels by adjusting the braking forces of the left and right wheels of the vehicle. In the anti-lock braking control, the control unit performs a crossover process in which a first period and a second period are alternately switched, and the braking force of the second wheel is increased during any of the first period and the second period, wherein in the first period, one of the left and right wheels is set as the first wheel for increasing the braking force, and the other of the left and right wheels is set as the second wheel for adjusting the braking force within a range smaller than the braking force of the first wheel, and in the second period, the other wheel is set as the first wheel, and the one wheel is set as the second wheel.

[0006] When the above-mentioned vehicle brake control device performs cross processing of anti-lock brake control, there is a period in which the braking force of the first wheel and the braking force of the second wheel of the left and right wheels are both increased. However, during this period, the braking force of the second wheel is maintained to be less than the braking force of the first wheel. Therefore, the degree of deceleration slip in the second wheel is difficult to increase compared with the first wheel. That is, the second wheel is less likely to lock than the first wheel. Therefore, it is possible to suppress the reduction of braking efficiency during the implementation of anti-lock brake control. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a schematic configuration diagram showing a vehicle including a control device as one embodiment of a vehicle brake control device.

[0008] Figure 2 This is a block diagram showing the functional structure of the control device.

[0009] Figure 3 This is a timing chart when the cross process is executed as the anti-lock braking control for both the left and right wheels.

[0010] Figure 4 This is a timing chart when the separated road surface processing is executed as the anti-lock braking control for both the left and right wheels.

[0011] Figure 5 This is a flowchart showing a processing routine executed by the execution device of the control device.

[0012] Figure 6 This is a flowchart showing a processing routine executed by the execution device.

[0013] Figure 7 It is a timing chart for explaining the process of determining whether or not the two-wheel locking state has occurred.

[0014] Figure 8 This is a timing chart for a case where it is determined that the two wheels are in a locked state during the anti-lock braking control for both the left and right wheels. DETAILED DESCRIPTION

[0015] Below, according to Figures 1 to 8 An embodiment of a vehicle brake control device will be described.

[0016] like Figure 1 As shown, the vehicle 10 includes a plurality of wheels and a braking system for adjusting the braking force applied to the plurality of wheels. The plurality of wheels include a left front wheel 11, a right front wheel 12, a left rear wheel 13, and a right rear wheel 14. The braking system includes a front wheel braking device 20, two rear wheel braking devices 30, and a control device 50. In this embodiment, the control device 50 corresponds to a "vehicle braking control device".

[0017] <Front wheel brake system>

[0018] The front wheel brake device 20 includes two friction brakes 21 and a brake actuator 27. Among the plurality of friction brakes 21, one is provided for the left front wheel 11, and the remaining one is provided for the right front wheel 12. The plurality of friction brakes 21 respectively include a friction portion 22, a friction portion 23, and a wheel cylinder 24. Since the friction portion 22 rotates integrally with the front wheels 11, 12, the friction brake 21 can apply a braking force to the front wheels 11, 12 by pressing the friction portion 23 to the friction portion 22. The higher the hydraulic pressure in the wheel cylinder 24, the greater the force that presses the friction portion 23 to the friction portion 22. That is, the friction brake 21 can adjust the braking force of the front wheels 11, 12 by adjusting the hydraulic pressure in the wheel cylinder 24.

[0019] The brake actuator 27 is configured to be able to individually control the hydraulic pressures in the wheel cylinders 24 of the plurality of friction brakes 21. The brake actuator 27 adjusts the braking force of the front wheels 11 and 12 by controlling the hydraulic pressures in the wheel cylinders 24.

[0020] <Rear wheel brake system>

[0021] Of the two rear wheel brake devices 30, one is provided for the left rear wheel 13, and the remaining one is provided for the right rear wheel 14. The plurality of rear wheel brake devices 30 are respectively provided with a friction portion 31, a friction portion 32, an electric motor 33, a speed reduction mechanism 34, and a direct motion conversion mechanism 35. The friction portion 31 rotates integrally with the rear wheels 13 and 14, so the rear wheel brake device 30 can apply a braking force to the rear wheels 13 and 14 by pressing the friction portion 32 to the friction portion 31.

[0022] The speed reduction mechanism 34 reduces the speed of the rotational motion of the electric motor 33 and outputs it to the direct motion conversion mechanism 35. The direct motion conversion mechanism 35 converts the rotational motion input from the speed reduction mechanism 34 into a linear motion and outputs it to the friction portion 32. Therefore, in the rear wheel brake device 30, when the electric motor 33 is driven, the output torque of the electric motor 33 is transmitted to the friction portion 32 via the speed reduction mechanism 34 and the direct motion conversion mechanism 35. As a result, the friction portion 32 approaches the friction portion 31, or the friction portion 32 is separated from the friction portion 31. That is, by increasing the output torque of the electric motor 33, the braking force of the rear wheels 13 and 14 is increased.

[0023] <Control device>

[0024] Signals are input to the control device 50 from the detection system. The detection system includes four wheel speed sensors 61, 62, 63, and 64, a front and rear acceleration sensor 65, and a brake sensor 66. The wheel speed sensors 61 to 64 output signals corresponding to the rotation speeds of the corresponding wheels 11 to 14. The front and rear acceleration sensor 65 outputs a signal corresponding to the front and rear acceleration of the vehicle 10. The brake sensor 66 outputs a signal corresponding to information related to the operation of the brake pedal 16 by the driver of the vehicle 10. For example, the brake sensor 66 may be a sensor that detects the operating force of the driver's brake pedal 16 or a force related to the operating force, or may be a sensor that detects the amount of operation of the brake pedal 16. Furthermore, the control device 50 controls the brake actuator 27 and the plurality of electric motors 33 based on the signals input from the various sensors.

[0025] In addition, the rotation speed of the wheel based on the detection values ​​of the wheel speed sensors 61 to 64 is referred to as "wheel speed VW". Specifically, the wheel speed VW of the left front wheel 11 is referred to as "wheel speed VW1", the wheel speed VW of the right front wheel 12 is referred to as "wheel speed VW2", the wheel speed VW of the left rear wheel 13 is referred to as "wheel speed VW3", and the wheel speed VW of the right rear wheel 14 is referred to as "wheel speed VW4". The longitudinal acceleration of the vehicle 10 based on the detection value of the longitudinal acceleration sensor 65 is referred to as "longitudinal acceleration GX".

[0026] The control device 50 implements anti-lock braking control to suppress wheel locking when the vehicle 10 is decelerated. Hereinafter, the anti-lock braking control is referred to as "ABS control". The control device 50 implements ABS control on each of the front wheels 11 and 12 individually. On the other hand, when the control device 50 determines that at least one of the left and right rear wheels 13 and 14 is likely to lock, it implements ABS control on the left and right rear wheels 13 and 14.

[0027] The control device 50 includes an execution device 51 and a storage device 52. For example, the execution device 51 is a CPU. The storage device 52 stores a control program executed by the execution device 51.

[0028] like Figure 2 As shown, the execution device 51 executes the control program to function as a vehicle body speed derivation unit M11, a slip value derivation unit M13, a wheel acceleration derivation unit M15, a two-wheel lock determination unit M17, and a control unit M19.

[0029] The vehicle body speed deriving unit M11 derives the vehicle body speed VS0 of the vehicle 10 based on the wheel speeds VW1 to VW4 of the plurality of wheels 11 to 14. For example, when the vehicle 10 is braked, the vehicle body speed deriving unit M11 derives the vehicle body speed VS0 based on the wheel speed VW of the rear wheel 13, 14 having the higher wheel speed VW.

[0030] The slip value deriving unit M13 derives a slip value, which is a value indicating the degree of deceleration slip of the plurality of wheels 11 to 14. In the present embodiment, the slip value deriving unit M13 derives the slip ratio SLP of the wheel as the slip value. The slip value deriving unit M13 derives a value obtained by subtracting the wheel speed VW from the vehicle body speed VS0 and dividing it by the vehicle body speed VS0 as the slip ratio SLP. The slip ratio SLP of the left front wheel 11 is referred to as "slip ratio SLP1", the slip ratio SLP of the right front wheel 12 is referred to as "slip ratio SLP2", the slip ratio SLP of the left rear wheel 13 is referred to as "slip ratio SLP3", and the slip ratio SLP of the right rear wheel 14 is referred to as "slip ratio SLP4".

[0031] The wheel acceleration derivation unit M15 derives the wheel acceleration DVW of the plurality of wheels 11 to 14. Specifically, the wheel acceleration derivation unit M15 derives a value obtained by time-differentiating the wheel speed VW as the wheel acceleration DVW. Therefore, when the wheel speed VW increases, the wheel acceleration derivation unit M15 derives a positive value as the wheel acceleration DVW, and on the other hand, when the wheel speed VW decreases, a negative value is derived as the wheel acceleration DVW. The wheel acceleration DVW of the left front wheel 11 is referred to as "wheel acceleration DVW1", the wheel acceleration DVW of the right front wheel 12 is referred to as "wheel acceleration DVW2", the wheel acceleration DVW of the left rear wheel 13 is referred to as "wheel acceleration DVW3", and the wheel acceleration DVW of the right rear wheel 14 is referred to as "wheel acceleration DVW4".

[0032] The two-wheel lock determination unit M17 determines whether the two-wheel lock state in which both the left and right rear wheels 13 and 14 are locked occurs when the ABS control is performed on the left and right rear wheels 13 and 14. The specific contents of the process of determining whether the two-wheel lock state occurs will be described later.

[0033] The control unit M19 implements ABS control. Specifically, when the slip ratio SLP1 of the left front wheel 11 exceeds the threshold value SLPth1 for start determination, the control unit M19 can determine that the left front wheel 11 may be locked, so the ABS control of adjusting the braking force Fx1 of the left front wheel 11 is implemented. When the slip ratio SLP2 of the right front wheel 12 exceeds the threshold value SLPth1 for start determination, the control unit M19 can determine that the right front wheel 12 may be locked, so the ABS control of adjusting the braking force Fx2 of the right front wheel 12 is implemented. When the slip ratio SLP of at least one of the left and right rear wheels 13 and 14 exceeds the threshold value SLPth1 for start determination, the control unit M19 can determine that the rear wheel may be locked, so the ABS control of adjusting the braking forces Fx3 and Fx4 of the two rear wheels 13 and 14 is implemented. In addition, the braking forces Fx1 to Fx4 of the wheels controlled by the control unit M19 are indication values ​​of the braking force applied to the wheels.

[0034] The ABS control for the left and right rear wheels 13 and 14 includes a crossover process and a split road process. The crossover process refers to the ABS control when the road surface on which the vehicle 10 is traveling is not a split road surface. The split road process refers to the ABS control when the road surface on which the vehicle 10 is traveling is a split road surface. A split road surface refers to a road surface where the μ value of the road surface where the left wheel contacts the ground and the road surface where the right wheel contacts the ground are greatly different.

[0035] Reference Figure 3 , the cross processing is explained. Figure 3In (A), the dotted line indicates the change of the braking force Fx3 of the left rear wheel 13, and the dashed line indicates the change of the braking force Fx4 of the right rear wheel 14. Figure 3 In (B), the dotted line indicates the change in the slip ratio SLP3 of the left rear wheel 13, and the dashed line indicates the change in the slip ratio SLP4 of the right rear wheel 14. Figure 3 In (C), the dotted line indicates the change in the wheel speed VW3 of the left rear wheel 13, the dashed line indicates the change in the wheel speed VW4 of the right rear wheel 14, and the solid line indicates the change in the vehicle body speed VS0.

[0036] exist Figure 3 In the example shown, the braking forces Fx3 and Fx4 are applied to the two rear wheels 13 and 14 from time t11. As a result, the wheel speed VW3 of the left rear wheel 13, the wheel speed VW4 of the right rear wheel 14, and the vehicle body speed VS0 all begin to decrease. As the braking forces Fx3 and Fx4 of the rear wheels 13 and 14 increase, the slip ratio SLP3 of the left rear wheel 13 and the slip ratio SLP4 of the right rear wheel 14 increase. Then, at time t12, the slip ratios SLP3 and SLP4 of the two rear wheels 13 and 14 exceed the threshold value SLPth1 for starting determination, so the control unit M19 starts to implement ABS control. Specifically, the control unit M19 starts the cross processing of ABS control.

[0037] The cross processing is an ABS control in which one of the left and right rear wheels 13 and 14 is set as the first wheel for increasing the braking force, and the other rear wheel is set as the second wheel for adjusting the braking force within a range smaller than the braking force of the first wheel. In the cross processing, the control unit M19 alternately switches between the right wheel period in which the right rear wheel 14 is set as the first wheel and the left rear wheel 13 is set as the second wheel, and the left wheel period in which the left rear wheel 13 is set as the first wheel and the right rear wheel 14 is set as the second wheel. For example, when the right wheel period is set as the first period, the left wheel period is equivalent to the second period. On the contrary, when the left wheel period is set as the first period, the right wheel period is equivalent to the second period. The slip rate SLP of the first wheel is set to "slip rate SLPa", and the slip rate SLP of the second wheel is set to "slip rate SLPb". For example, when the left rear wheel 13 is the first wheel, the slip rate SLP3 of the left rear wheel 13 corresponds to the slip rate SLPa, and the slip rate SLP4 of the right rear wheel 14 corresponds to the slip rate SLPb.

[0038] In the crossover process, when the slip ratio SLPa of the first wheel exceeds the deceleration slip determination value SLPth2 while the slip ratio SLPb of the second wheel is less than the deceleration slip determination value SLPth2, the control unit M19 switches the first wheel and the second wheel. A value smaller than the start determination threshold value SLPth1 is set as the deceleration slip determination value SLPth2. For example, in the right wheel period, when the slip ratio SLP4 of the right rear wheel 14 as the first wheel exceeds the deceleration slip determination value SLPth2 while the slip ratio SLP3 of the left rear wheel 13 as the second wheel is less than the deceleration slip determination value SLPth2, the control unit M19 ends the right wheel period and starts the left wheel period. In addition, during the left wheel period, when the slip ratio SLP4 of the right rear wheel 14 as the second wheel is less than the deceleration slip judgment value SLPth2 and the slip ratio SLP3 of the left rear wheel 13 as the first wheel exceeds the deceleration slip judgment value SLPth2, the control unit M19 ends the left wheel period and starts the right wheel period.

[0039] The control unit M19 sequentially executes a non-increasing mode and an increasing mode as modes for adjusting the braking force of the second wheel in cross processing. The non-increasing mode is a mode in which the braking force of the second wheel is not increased. Specifically, the non-increasing mode is a mode in which the slip ratio SLPb of the second wheel is reduced by reducing and maintaining the braking force of the second wheel. The increasing mode is a mode in which the braking force of the second wheel is increased. Specifically, the increasing mode increases the braking force of the second wheel within a range in which the ratio of the braking force of the second wheel to the braking force of the first wheel is below a prescribed ratio. The prescribed ratio is a value less than 100%. For example, a value greater than 70% and less than 90% is set as the prescribed ratio.

[0040] In addition, the control unit M19 changes the mode from the non-increasing mode to the increasing mode on the condition that the slip ratio SLPb of the second wheel in the adjustment of the braking force of the second wheel in the non-increasing mode is less than the slip elimination determination value SLPth3. The slip elimination determination value SLPth3 is a criterion for determining whether the deceleration slip of the wheel has been eliminated. As the slip elimination determination value SLPth3, a value smaller than the deceleration slip determination value SLPth2 is set.

[0041] When the control unit M19 executes the intersection processing, the slip ratio SLPb of the second wheel may exceed the deceleration slip determination value SLPth2 when the slip ratio SLPa of the first wheel is less than the deceleration slip determination value SLPth2. In this case, it can be determined that the road surface on which the vehicle 10 is traveling has become a separated road surface, so the control unit M19 ends the intersection processing and executes the separated road surface processing.

[0042] Reference Figure 4 , the separation road treatment is explained. Figure 4 In (A), the dotted line indicates the change of the braking force Fx3 of the left rear wheel 13, and the dashed line indicates the change of the braking force Fx4 of the right rear wheel 14. Figure 4 In (B), the dotted line indicates the change in the slip ratio SLP3 of the left rear wheel 13 , and the dashed line indicates the change in the slip ratio SLP4 of the right rear wheel 14 .

[0043] exist Figure 4 In the example shown, the braking forces Fx3 and Fx4 are applied to the two rear wheels 13 and 14 from time t21. As the braking forces Fx3 and Fx4 increase, the slip ratios SLP3 and SLP4 increase in either the left rear wheel 13 or the right rear wheel 14. Then, at time t22, the slip ratio SLP3 of the left rear wheel 13 of the two rear wheels 13 and 14 exceeds the start determination threshold SLPth1, so the control unit M19 starts to implement ABS control. The processing of the control unit M19 after time t22 is a separation road surface processing.

[0044] The split road surface processing is an ABS control in which the rear wheel with the smaller slip ratio SLP of the left and right rear wheels 13 and 14 is set as the first wheel, and the rear wheel with the larger slip ratio SLP is set as the second wheel. The control unit M19 does not switch between the first wheel and the second wheel in the split road surface processing. Figure 4 In the example shown, the control unit M19 adjusts the braking forces Fx3 and Fx4 of the left rear wheel 13 and the right rear wheel 14 on the basis of maintaining the state in which the right rear wheel 14 is the first wheel and the left rear wheel 13 is the second wheel, so that the slip ratios SLP3 and SLP4 of the left rear wheel 13 and the right rear wheel 14 are both below the deceleration slip determination value SLPth2. Specifically, the control unit M19 adjusts the braking forces of the first wheel and the second wheel while stopping the exchange of the first wheel and the second wheel to maintain the state in which the braking force of the second wheel is greater than the braking force of the first wheel. For example, when the slip ratio SLPb of the second wheel exceeds the deceleration slip determination value SLPth2, the control unit M19 reduces the braking forces of both the first wheel and the second wheel. If the slip ratio SLPb of the second wheel becomes less than the slip elimination determination value SLPth3 by reducing the braking force, the control unit M19 increases the braking forces of both the first wheel and the second wheel.

[0045] When the control unit M19 executes the split road surface processing, the slip ratio SLPa of the first wheel sometimes exceeds the deceleration slip determination value SLPth2 when the slip ratio SLPb of the second wheel is less than the deceleration slip determination value SLPth2. In this case, it can be determined that the road surface on which the vehicle 10 is traveling is not a split road surface, so the control unit M19 ends the split road surface processing and executes the intersection processing.

[0046] <Processing flow when ABS control is applied to both rear wheels>

[0047] Reference Figure 5 The following describes a processing routine for determining whether to start ABS control for the left and right rear wheels 13 and 14, or determining whether to end the ABS control. The execution device 51 repeatedly executes this processing routine at each predetermined control cycle by executing the control program.

[0048] In this processing routine, in step S11, the execution device 51 functions as the control unit M19 to determine whether the ABS implementation flag FLG1 is set to OFF. When the ABS control is implemented for the left and right rear wheels 13 and 14, the ABS implementation flag FLG1 is set to ON. On the other hand, when the ABS control is not implemented, the ABS implementation flag FLG1 is set to OFF. When the ABS implementation flag FLG1 is set to OFF (S11: YES), the execution device 51 moves the processing to step S13. On the other hand, when the ABS implementation flag FLG1 is set to ON (S11: NO), the execution device 51 moves the processing to step S21.

[0049] In step S13, the actuator 51 functions as the control unit M19 to determine whether the start condition for the ABS control of the left and right rear wheels 13 and 14 is satisfied. If at least one of the following two conditions is satisfied, the start condition is deemed to be satisfied. On the other hand, if neither of the two conditions is satisfied, the start condition is deemed to be unsatisfactory.

[0050] The slip ratio SLP3 of the left rear wheel 13 exceeds the start determination threshold value SLPth1.

[0051] The slip ratio SLP4 of the right rear wheel 14 exceeds the start determination threshold value SLPth1.

[0052] When the execution device 51 determines that the start condition is satisfied (S13: Yes), the processing proceeds to step S15. On the other hand, when the execution device 51 determines that the start condition is not satisfied (S13: No), the processing routine is temporarily terminated.

[0053] In step S15, the execution device 51 sets the ABS implementation flag FLG1 to on by functioning as the control unit M19. In step S17, the execution device 51 sets the condition coefficient KN to 1 by functioning as the control unit M19. The condition coefficient KN is a coefficient for determining whether to perform the intersection process or the separation road process. In the present embodiment, when the start condition is satisfied and the ABS control is started, the condition coefficient KN is set to 1 in order to select the intersection process. Thereafter, the execution device 51 temporarily ends the present processing routine.

[0054] In step S21, the actuator 51 functions as the control unit M19 to determine whether the termination condition for terminating the ABS control of the left and right rear wheels 13 and 14 is satisfied. For example, if the vehicle 10 stops or the braking request for the rear wheels 13 and 14 disappears, the actuator 51 determines that the termination condition is satisfied. If the actuator 51 determines that the termination condition is satisfied (S21: Yes), the processing moves to step S27. On the other hand, if the actuator 51 determines that the termination condition is not satisfied (S21: No), the processing moves to step S23.

[0055] In step S23, the execution device 51 functions as the two-wheel lock determination unit M17 to determine whether the two-wheel lock state has occurred. When the execution device 51 determines that the two-wheel lock state has occurred (S23: Yes), the processing moves to step S25. On the other hand, when the execution device 51 determines that the two-wheel lock state has not occurred (S23: No), the present processing routine is temporarily terminated.

[0056] In step S25, the execution device 51 functions as the control unit M19 to turn on the two-wheel lock flag FLG2. Thereafter, the execution device 51 temporarily terminates this processing routine.

[0057] In step S27, the execution device 51 functions as the control unit M19 to set both the ABS implementation flag FLG1 and the two-wheel lock flag FLG2 to OFF. Thereafter, the execution device 51 temporarily terminates this processing routine.

[0058] Reference Figure 6 , a processing routine for implementing ABS control of the left and right rear wheels 13, 14 is described. The execution device 51 repeatedly executes this processing routine in each predetermined control cycle by executing the control program. The multiple steps S41 to S63 constituting this processing routine are processes executed by the execution device 51 functioning as the control unit M19.

[0059] In this processing routine, in step S41, the execution device 51 determines whether the ABS implementation flag FLG1 is set to on. When the ABS implementation flag FLG1 is set to on (S41: Yes), the execution device 51 moves the process to step S43. On the other hand, when the ABS implementation flag FLG1 is set to off (S41: No), the execution device 51 temporarily ends this processing routine.

[0060] In step S43, the execution device 51 determines whether the two-wheel lock flag FLG2 is set to OFF. When the two-wheel lock flag FLG2 is set to OFF (S43: YES), the execution device 51 moves the process to step S45. On the other hand, when the two-wheel lock flag FLG2 is set to ON (S43: NO), the execution device 51 moves the process to step S53.

[0061] In step S45, the execution device 51 determines whether the condition coefficient KN is 1. If the condition coefficient KN is 1 (S45: Yes), the execution device 51 moves the process to step S47. On the other hand, if the condition coefficient KN is not 1 (S45: No), the execution device 51 moves the process to step S59.

[0062] In step S47, the actuator 51 executes the above-mentioned intersection processing as ABS control for the left and right rear wheels 13 and 14. In step S49, the actuator 51 determines whether the following two conditions are met. If both conditions are met, the road surface on which the vehicle 10 is traveling is considered to be a separated road surface.

[0063] The first wheel slip ratio SLPa is less than or equal to the deceleration slip determination value SLPth2

[0064] The second wheel slip ratio SLPb is larger than the deceleration slip determination value SLPth2.

[0065] When both conditions are satisfied (S49: Yes), the execution device 51 moves the process to step S51. On the other hand, when at least one of the two conditions is not satisfied (S49: No), the execution device 51 temporarily ends the present processing routine.

[0066] In step S51 , the execution device 51 sets the condition coefficient KN to 2. Thereafter, the execution device 51 temporarily ends this processing routine.

[0067] In step S53, the actuator 51 instructs the first wheel and the second wheel to be swapped. That is, if the actuator 51 determines that the two wheels are locked, the first wheel and the second wheel are swapped. Then, in step S55, the actuator 51 sets the two-wheel lock flag FLG2 to off.

[0068] In step S57, the execution device 51 determines whether to execute the cross process as the ABS control of the left and right rear wheels 13 and 14. When the execution device 51 executes the cross process (S57: Yes), the processing moves to step S47. That is, when the execution device 51 determines that the two wheels are locked during the execution of the cross process, the cross process is continued after the first wheel and the second wheel are switched. On the other hand, when the execution device 51 does not execute the cross process (S57: No), the processing moves to step S59 because the separated road surface processing is being executed. That is, when the execution device 51 determines that the two wheels are locked during the execution of the separated road surface processing, the separated road surface processing is continued after the first wheel and the second wheel are switched.

[0069] In step S59, the actuator 51 executes the above-mentioned split road surface processing as ABS control for the left and right rear wheels 13 and 14. In step S61, the actuator 51 determines whether the following two conditions are met. If both conditions are met, it is considered that the road surface on which the vehicle 10 is traveling is not a split road surface.

[0070] The slip ratio SLPa of the first wheel is larger than the deceleration slip determination value SLPth2.

[0071] The second wheel slip ratio SLPb is less than or equal to the deceleration slip determination value SLPth2.

[0072] When both conditions are satisfied (S61: Yes), the execution device 51 moves the process to step S63. On the other hand, when at least one of the two conditions is not satisfied (S61: No), the execution device 51 temporarily ends the present processing routine.

[0073] In step S63 , the execution device 51 sets the condition coefficient KN to 1. Thereafter, the execution device 51 temporarily ends this processing routine.

[0074] <Determination of whether the two wheels are locked>

[0075] Reference Figure 7 , the process of determining whether the two wheels are locked is described. The execution device 51 executes this process by functioning as a two-wheel lock determination unit M17. Figure 7 In (A), the dotted line indicates the change of the wheel speed VW3 of the left rear wheel 13, the dashed line indicates the change of the wheel speed VW4 of the right rear wheel 14, the solid line indicates the actual value VS of the vehicle speed, and the double-dashed line indicates the change of the vehicle speed VS0. Figure 7 In (B), the dotted line indicates the change in the slip ratio SLP3 of the left rear wheel 13 , and the dashed line indicates the change in the slip ratio SLP4 of the right rear wheel 14 .

[0076] When the ABS control is performed on the rear wheels 13 and 14 , that is, when the intersection process or the separated road process is executed, the execution device 51 executes a process of determining whether the two wheels are in a locked state.

[0077] like Figure 7 As in the period from time t31 to time t32 in FIG. 1 , the actuator 51 determines that the two-wheel locking state is in effect, taking as a condition that the slip ratios SLP3 and SLP4 of the two rear wheels 13 and 14 are both greater than the two-wheel deceleration slip determination value SLPth4. As the two-wheel deceleration slip determination value SLPth4, a value that is less than the deceleration slip determination value SLPth2 and greater than the slip elimination determination value SLPth3 is set. Specifically, when the duration of the state in which the slip ratios SLP3 and SLP4 are both greater than the two-wheel deceleration slip determination value SLPth4 is greater than a predetermined time, the actuator 51 determines that the two-wheel locking state is in effect. As the predetermined time, a length of time that allows determination of whether the actual value of the slip ratio of the left rear wheel 13 and the actual value of the slip ratio of the right rear wheel 14 are both greater than the two-wheel deceleration slip determination value SLPth4 is set.

[0078] As in the period between time t33 and time t34, there is a case where the degree of deceleration slip of the two rear wheels 13 and 14 gradually increases. In this case, as the wheel speeds VW3 and VW4 of the two rear wheels 13 and 14 decrease, as shown in FIG. Figure 7 The vehicle body speed VS0 indicated by the double-dashed line also decreases. Therefore, even if deceleration slip occurs at the two rear wheels 13 and 14, the slip ratios SLP3 and SLP4 will not increase. That is, both slip ratios SLP3 and SLP4 will not become greater than the two-wheel deceleration slip determination value SLPth4.

[0079] Therefore, the actuator 51 determines that the two-wheel locking state is in place when both the following conditions (A1) and (A2) are satisfied. Specifically, the actuator 51 determines that the two-wheel locking state is in place when the duration of the state in which both the two conditions (A1) and (A2) are satisfied is longer than a predetermined time.

[0080] (A1) The difference between the slip ratio SLP3 of the left rear wheel 13 and the slip ratio SLP4 of the right rear wheel 14 is smaller than a predetermined difference.

[0081] (A2) The wheel acceleration DVW3 of the left rear wheel 13 and the wheel acceleration DVW4 of the right rear wheel 14 are both less than or equal to the wheel acceleration determination value DVWth.

[0082] When the difference between slip ratios SLP3 and SLP4 is smaller than a predetermined difference, it is considered that there is almost no difference between slip ratios SLP3 and SLP4. Wheel acceleration determination value DVWth is a criterion for determining whether wheel speeds VW3 and VW4 of rear wheels 13 and 14 are reduced.

[0083] <Functions and Effects of the Present Embodiment>

[0084] (1) When a braking force is applied to the vehicle 10, if the slip ratio SLP of at least one of the two rear wheels 13, 14 exceeds the start determination threshold value SLPth1, the cross process is started as ABS control of the two rear wheels 13, 14. Figure 3 As shown, in the crossing process, the left wheel period in which the left rear wheel 13 is the first wheel and the right rear wheel 14 is the second wheel and the right wheel period in which the right rear wheel 14 is the first wheel and the left rear wheel 13 is the second wheel are alternately switched.

[0085] The cross processing has a non-increasing mode and an increasing mode as modes for controlling the braking force of the second wheel. When the braking force of the second wheel is adjusted in the increasing mode, the braking force of the second wheel is increased within a range that is smaller than the braking force of the first wheel. That is, when the cross processing is performed, there is a period in which the braking force of the first wheel and the braking force of the second wheel are both increased. However, during this period, the state in which the braking force of the second wheel is smaller than the braking force of the first wheel is maintained. Therefore, compared with the first wheel, the deceleration slip in the second wheel is not easy to become larger. Therefore, it is possible to prevent the left and right rear wheels 13 and 14 from being locked during the implementation of the ABS control. In other words, it is possible to prevent the braking efficiency from being reduced during the implementation of the ABS control.

[0086] (2) As a method of suppressing the state where both the left and right rear wheels 13 and 14 are locked during the implementation of ABS control, a method of not increasing the braking force of the second wheel is also conceivable. In this case, although it is possible to suppress the state where both the rear wheels 13 and 14 are locked, the difference in braking force between the left and right rear wheels 13 and 14 becomes large, and the yaw moment of the vehicle 10 becomes large. In addition, it is difficult for the braking force of the entire vehicle 10 to become large, so it is difficult for the deceleration of the vehicle 10 to become large. In this regard, in the present embodiment, since the braking force of the second wheel is also increased, it is possible to suppress the difference in braking force between the left and right rear wheels 13 and 14 from becoming large, and it is also possible to suppress the reduction in the braking force of the entire vehicle 10 caused by the implementation of ABS control. Therefore, during the implementation of ABS control, it is possible to suppress the reduction in the deceleration of the vehicle 10 while suppressing the increase in the yaw moment of the vehicle 10.

[0087] (3) Figure 3The thick dashed line in (C) shows the transition of the vehicle body speed VS1 derived when the left and right wheel independent ABS control is implemented. If both rear wheels 13 and 14 are locked, the wheel speeds VW3 and VW4 of the two rear wheels 13 and 14 are greatly reduced, so there is a case where the vehicle body speed VS1 is greatly reduced compared to the actual value of the vehicle body speed. In this case, the accuracy of deriving the slip rates SLP1 to SLP4 of the wheels 11 to 14 is reduced.

[0088] In this regard, by implementing the above-mentioned control as the ABS control for the left and right rear wheels 13 and 14, it is possible to prevent both rear wheels 13 and 14 from being locked. Therefore, it is possible to prevent the estimation accuracy of the vehicle body speed VS0 during braking of the vehicle 10 from being reduced. Therefore, it is also possible to prevent the derivation accuracy of the slip ratios SLP1 to SLP4 of the wheels 11 to 14 from being reduced.

[0089] (4) When the braking force of the second wheel is increased in the increasing mode, the braking force of the second wheel is increased within a range where the ratio of the braking force of the second wheel to the braking force of the first wheel is less than a predetermined ratio. Therefore, it is possible to suppress a sharp increase in the braking force of the second wheel when the mode is switched from the non-increasing mode to the increasing mode. Therefore, it is possible to suppress a decrease in the stability of the behavior of the vehicle 10 caused by increasing the braking force of the second wheel.

[0090] (5) In this embodiment, if the non-increasing mode is executed as the mode for adjusting the braking force of the second wheel, then Figure 3 As shown in FIG. 1 , when the braking force of the second wheel is reduced to a certain degree of braking force, the braking force of the second wheel is maintained. Furthermore, if the slip ratio SLPb of the second wheel is less than the slip elimination determination value SLPth3, it can be determined that the deceleration slip of the second wheel has been eliminated, so the mode is shifted from the non-increasing mode to the increasing mode. That is, the braking force of the second wheel starts to be increased after the deceleration slip of the second wheel is eliminated. Therefore, the effect of suppressing the state where both rear wheels 13 and 14 are locked during the implementation of ABS control can be further improved.

[0091] In addition, even if the braking force of the second wheel is maintained at a certain level in the non-increasing mode, the deceleration slip of the second wheel may not be eliminated. In this case, the deceleration slip of the second wheel is eliminated by further reducing the braking force of the second wheel.

[0092] (6) When the intersection processing is executed, the slip ratio SLPb of the second wheel may exceed the deceleration slip determination value SLPth2 when the slip ratio SLPa of the first wheel is less than the deceleration slip determination value SLPth2. In this case, the vehicle 10 may be traveling on a separated road surface where the μ value of the road surface where the second wheel is in contact is lower than the μ value of the road surface where the first wheel is in contact. Therefore, the intersection processing is terminated and the separated road surface processing is started.

[0093] like Figure 4 As shown, in the separation road surface processing, the switching between the first wheel and the second wheel is stopped. And, while maintaining the state that the braking force of the first wheel is larger than the braking force of the second wheel, the braking forces of the first wheel and the second wheel are adjusted. Specifically, if the braking force of the first wheel and the braking force of the second wheel are increased, the slip ratio SLPb of the second wheel that is in contact with the low μ road becomes larger. And, if the slip ratio SLPb of the second wheel exceeds the deceleration slip determination value SLPth2, the braking force of the first wheel and the braking force of the second wheel are reduced. And, if the slip ratio SLPb of the second wheel is less than the slip elimination determination value SLPth3, it can be determined that the deceleration slip of the second wheel is eliminated, so the braking force of the first wheel and the braking force of the second wheel are both increased.

[0094] In this way, in the separation road surface processing, even if the braking force of the first wheel in contact with the high μ road is made larger than the braking force of the second wheel in contact with the low μ road, the slip ratio SLPa of the first wheel can be suppressed from increasing. Therefore, it is possible to suppress the state where both the left and right rear wheels 13 and 14 are locked. In addition, by deriving the vehicle body speed VS0 based on the wheel speed VW of the first wheel, it is possible to suppress the reduction in the estimation accuracy of the vehicle body speed VS0.

[0095] (7) Even if the intersection process or the split road process is executed, the two-wheel lock state may occur, in which both the left and right rear wheels 13 and 14 are locked. For example, if any one of the following conditions (B1), (B2), (B3) and (B4) is satisfied, the two-wheel lock state may occur during the execution of the intersection process or the split road process.

[0096] (B1) There is a large difference between the braking characteristics of the rear wheel brake device 30 for the left rear wheel 13 and the braking characteristics of the rear wheel brake device 30 for the right rear wheel 14.

[0097] (B2) There is a large difference between the μ value of the road surface on which the left rear wheel 13 contacts the ground and the μ value of the road surface on which the right rear wheel 14 contacts the ground.

[0098] (B3) There is a large difference between the μ value of the tire of the left rear wheel 13 and the μ value of the tire of the right rear wheel 14 .

[0099] (B4) There is a large difference between the diameter of the tire of the left rear wheel 13 and the diameter of the tire of the right rear wheel 14.

[0100] Here, the braking characteristic of the braking device refers to the ratio of the indicated value of the braking force to the actual value of the braking force, that is, the braking ratio. If the braking ratio is small, the actual value of the braking force is smaller than the indicated value of the braking force.

[0101] Reference Figure 8 ABS control in a case where there is a large divergence between the braking characteristics of the rear wheel brake device 30 for the left rear wheel 13 and the braking characteristics of the rear wheel brake device 30 for the right rear wheel 14 will be described. Figure 8 The example shown is a case where the braking ratio of the rear wheel brake device 30 for the left rear wheel 13 is smaller than the braking ratio of the rear wheel brake device 30 for the right rear wheel 14. Figure 8 In (A), the dotted line indicates the change in the slip ratio SLP3 of the left rear wheel 13, and the dashed line indicates the change in the slip ratio SLP4 of the right rear wheel 14. Figure 8 In (B), the thinner dotted line indicates the change of the indicated value Fx3 of the braking force of the left rear wheel 13, the thinner dashed line indicates the change of the indicated value Fx4 of the braking force of the right rear wheel 14, and the thick dashed line indicates the change of the actual value Fx4R of the braking force of the right rear wheel 14. In this example, although a large divergence occurs between the indicated value Fx4 of the braking force and the actual value Fx4R of the braking force in the right rear wheel 14, there is almost no divergence between the indicated value Fx3 of the braking force and the actual value of the braking force in the left rear wheel 13.

[0102] At time t41 when the vehicle 10 is subjected to braking force, ABS control of the left and right rear wheels 13 and 14 is started. At time t42 when the separation road surface processing is executed in which the right rear wheel 14 is set as the first wheel and the left rear wheel 13 is set as the second wheel, the actuator 51 determines that the two wheels are locked. Therefore, the actuator 51 continues the separation road surface processing after switching the first wheel and the second wheel. That is, after time t42, the left rear wheel 13 becomes the first wheel and the right rear wheel 14 becomes the second wheel. Therefore, the indication value Fx3 of the braking force of the left rear wheel 13 is increased, and the indication value Fx4 of the braking force of the right rear wheel 14 is reduced, so that the indication value Fx3 of the braking force of the left rear wheel 13 is greater than the indication value Fx4 of the braking force of the right rear wheel 14. The indication value Fx4 of the braking force of the right rear wheel 14 is not increased until the difference in braking force between the right rear wheel 14 and the left rear wheel 13 reaches a certain level.

[0103] exist Figure 8In the example shown, at time t43, when the slip ratio SLP4 of the right rear wheel 14 as the second wheel is less than the deceleration slip determination value SLPth2, the slip ratio SLP3 of the left rear wheel 13 as the first wheel exceeds the deceleration slip determination value SLPth2. Therefore, the separation road surface processing is terminated and the intersection processing is performed. In this way, the first wheel and the second wheel are switched. Moreover, the indication value Fx4 of the braking force of the right rear wheel 14 as the first wheel is increased, and on the other hand, the indication value Fx3 of the braking force of the left rear wheel 13 as the second wheel is reduced. In the intersection processing, the indication value Fx3 of the braking force of the left rear wheel 13 is increased from the time t44 when the deceleration slip of the left rear wheel 13 is eliminated.

[0104] After time t44, the actual value of the braking force of the left rear wheel 13 and the actual value Fx4R of the braking force of the right rear wheel 14 are almost the same. Therefore, the slip ratio SLP3 of the left rear wheel 13 and the slip ratio SLP4 of the right rear wheel 14 both gradually increase. That is, the above-mentioned conditions (A1) and (A2) are both satisfied. Then, at time t45 during the execution of the cross process, the execution device 51 determines that the two wheels are locked, and continues to execute the cross process after switching the first wheel and the second wheel.

[0105] If it is determined that the two wheels are locked during the implementation of the ABS control, the first wheel and the second wheel are switched. As a result, the braking force of the rear wheel whose slip ratio SLP is difficult to increase is suppressed from increasing. As a result, the slip ratio SLP of the rear wheel whose slip ratio SLP is difficult to increase can be suppressed from increasing. Therefore, even if the two wheels are locked due to the execution of the intersection process or the split road process, the two wheels can be eliminated as soon as possible.

[0106] (8) For example, when the slip ratios SLP3 and SLP4 of the two rear wheels 13 and 14 are both equal to or greater than the two-wheel deceleration slip determination value SLPth4, it is determined that the two-wheel lock state has occurred. In addition, even when the slip ratios SLP3 and SLP4 of the two rear wheels 13 and 14 do not increase, it is determined that the two-wheel lock state has occurred if both of the above conditions (A1) and (A2) are satisfied. Therefore, the accuracy of determining whether the two-wheel lock state has occurred can be improved.

[0107] <Change Example>

[0108] The above-mentioned embodiment can be implemented with modifications as follows. The above-mentioned embodiment and the following modifications can be implemented in combination with each other within the scope of no technical contradiction.

[0109] When it is determined that the two wheels are locked, ABS control may be implemented while maintaining the braking force of one of the left and right rear wheels 13, 14 and adjusting the braking force of the other rear wheel. Also, when it is determined that the two wheels are locked, ABS control may be implemented to adjust the braking force of the two rear wheels 13, 14 so that the difference between the braking forces of the left and right rear wheels 13, 14 is greater.

[0110] When the intersection process or the split road process is executed, it is not necessary to execute the process of determining whether the two wheels are locked.

[0111] When the slip ratio SLPb of the second wheel becomes larger than the slip ratio SLPa of the first wheel during execution of the intersecting process, the execution device 51 may terminate the intersecting process and start the separated road surface process.

[0112] The execution device 51 may terminate the separate road surface processing and start the intersection processing when the slip ratio SLPa of the first wheel is larger than the slip ratio SLPb of the second wheel during the execution of the separate road surface processing.

[0113] As long as the intersection process is executed as the ABS control for the rear wheels 13, 14, the split road surface process does not necessarily have to be executed.

[0114] In the above embodiment, when the cross processing is executed, if the slip ratio SLPa of the first wheel exceeds the deceleration slip determination value SLPth2, the first wheel and the second wheel are switched, but the present invention is not limited thereto. For example, when the left rear wheel 13 is set as the first wheel, if the duration of the state of increasing the braking force Fx3 of the left rear wheel 13 reaches a predetermined duration, the left rear wheel 13 is set as the second wheel and the right rear wheel 14 is set as the first wheel, so that the braking force of the left rear wheel 13 is reduced, and the braking force Fx4 of the right rear wheel 14 is increased.

[0115] In the above embodiment, when the braking force of the second wheel is adjusted, if the slip ratio SLPb of the second wheel is less than the slip elimination determination value SLPth3, the mode is shifted from the non-increasing mode to the increasing mode, but the present invention is not limited thereto. For example, if a predetermined time has passed from the start time point of the non-increasing mode, the mode may be shifted from the non-increasing mode to the increasing mode. In this case, the time assumed to be able to eliminate the deceleration slip of the second wheel may be set to the predetermined time.

[0116] In the cross processing, if at least one of the following two conditions (C1) and (C2) is satisfied, the mode for adjusting the braking force of the second wheel may be switched from the non-increasing mode to the increasing mode.

[0117] (C1) The second wheel slip ratio SLPb is smaller than the slip elimination determination value SLPth3.

[0118] (C2) A predetermined time has passed since the start time of the non-increase mode.

[0119] When the braking force of the second wheel is adjusted in the non-increasing mode, a period for maintaining the braking force may not be provided as long as a period for reducing the braking force can be provided.

[0120] In the intersection process, if the braking force of the second wheel is not greater than the braking force of the first wheel, the ratio of the braking force of the second wheel to the braking force of the first wheel may be made greater than a predetermined ratio by increasing the second braking force.

[0121] When the start condition for the ABS control of the left and right rear wheels 13, 14 is satisfied, the separated road surface processing may be executed from the beginning when the difference in slip ratio between the two rear wheels 13, 14 is equal to or larger than the determination slip ratio difference.

[0122] In the cross process, the control unit may switch the first wheel and the second wheel when both of the following two conditions (D1) and (D2) are satisfied.

[0123] (D1) The second wheel slip ratio SLPb (second wheel slip value) is less than or equal to the deceleration slip determination value SLPth2.

[0124] (D2) When the wheel acceleration DVW of the second wheel is greater than the wheel acceleration judgment value DVWth, the slip ratio SLPa of the first wheel (slip value of the first wheel) exceeds the deceleration slip judgment value SLPth2, and the wheel acceleration DVW of the first wheel is less than the wheel acceleration judgment value DVWth.

[0125] The control unit may also terminate the crossover process and execute a separation road process of stopping the switching between the first wheel and the second wheel to maintain the braking force of the first wheel greater than the braking force of the second wheel and adjusting the braking force of the first wheel and the second wheel when both of the following two conditions (E1) and (E2) are satisfied during the implementation of the ABS control.

[0126] (E1) The slip ratio SLPa of the first wheel (the slip value of the first wheel) is less than or equal to the deceleration slip determination value SLPth2, and the wheel acceleration DVW of the first wheel is greater than or equal to the wheel acceleration determination value DVWth.

[0127] (E2) When the condition (E1) is satisfied, the second wheel slip ratio SLPb (second wheel slip value) exceeds the deceleration slip determination value SLPth2, and the wheel acceleration DVW of the second wheel is less than or equal to the wheel acceleration determination value DVW.

[0128] In the above embodiment, the slip ratio SLP is derived as the slip value indicating the degree of deceleration slip of the wheel, but the present invention is not limited thereto. For example, the slip amount obtained by subtracting the wheel speed VW from the vehicle body speed VS0 may be derived as the slip value.

[0129] In the above embodiment, the case where the intersection process or the separated road surface process is executed for the left and right rear wheels 13 and 14 is described. However, the intersection process and the separated road surface process may be executed for the left and right front wheels 11 and 12.

[0130] The control device 50 can be configured as one or more processors that operate according to a computer program, one or more dedicated hardware circuits such as dedicated hardware that performs at least a part of various processes, or a circuit including a combination thereof. As dedicated hardware, for example, an application-specific integrated circuit, i.e., an ASIC, can be cited. The processor includes a CPU, and a memory such as a RAM and a ROM, and the memory stores a program code or an instruction configured to cause the CPU to execute a process. The memory, i.e., the storage medium, includes all available media that can be accessed by a general-purpose or special-purpose computer.

[0131] The braking system may be a single-brake system as long as it can adjust the braking force of the plurality of wheels 11 to 14 individually. Figure 1 The brake systems shown have different configurations.

[0132] In addition, the expression "at least one" used in this specification means "one or more" of the desired options. As an example, the expression "at least one" used in this specification means "only one option" or "both options" when the number of options is two. As another example, the expression "at least one" used in this specification means "only one option" or "any combination of two or more options" when the number of options is three or more.

[0133] <Other technical ideas>

[0134] Next, technical ideas that can be grasped from the above-mentioned embodiment and modified examples are described as supplementary notes.

[0135] (Supplementary Note 1) Preferably, when the slip value of at least one of the left and right wheels exceeds the start determination threshold, the control unit starts the anti-lock brake control.

[0136] A value smaller than the above-mentioned start determination threshold value is set as the deceleration slip determination value.

[0137] (Supplementary Note 2) It is preferred to include a two-wheel lock determination unit, which determines whether a two-wheel lock state in which both the left and right wheels are locked occurs when the anti-lock braking control is implemented.

[0138] In the anti-lock brake control, the control unit switches the first wheel and the second wheel when it is determined that the two-wheel locked state has occurred.

[0139] (Supplementary Note 3) It is preferable to include a slip value deriving unit for deriving a slip value, the slip value being a value indicating the degree of deceleration slip of the wheel.

[0140] The two-wheel lock determination unit determines that the two-wheel lock state occurs on the condition that both the slip value of the first wheel and the slip value of the second wheel are equal to or greater than a two-wheel deceleration slip determination value.

[0141] (Supplementary Note 4) It is preferable to include: a slip value deriving unit that derives a slip value that is a value indicating the degree of deceleration slip of the wheel; and

[0142] a wheel acceleration deriving unit for deriving a wheel acceleration which is an increasing speed of the rotation speed of the wheel;

[0143] The two-wheel lock determination unit determines that the two-wheel lock state is in place when the difference between the slip value of the first wheel and the slip value of the second wheel is less than a specified difference, and the wheel acceleration of the first wheel and the wheel acceleration of the second wheel are both below a wheel acceleration determination value.

Claims

1. A vehicle brake control device, A control unit is provided for implementing anti-lock braking control for suppressing locking of the left and right wheels by adjusting the braking forces of the left and right wheels of the vehicle. In the anti-lock brake control, the control unit performs a crossover process in which the first period and the second period are alternately switched, and the braking force of the second wheel is increased in any of the first period and the second period, wherein: During the first period, one of the left and right wheels is set as the first wheel for increasing the braking force, and the other of the left and right wheels is set as the second wheel for adjusting the braking force within a range smaller than the braking force of the first wheel. During the second period, the other wheel is set as the first wheel, and the one wheel is set as the second wheel.

2. The vehicle brake control device according to claim 1, wherein: In the intersection process, the control unit increases the braking force of the second wheel within a range where a ratio of the braking force of the second wheel to the braking force of the first wheel is equal to or less than a predetermined ratio.

3. The vehicle brake control device according to claim 1, wherein: A slip value deriving unit is provided for deriving a slip value indicating a degree of deceleration slip of the wheel. In the cross processing, the control unit sequentially executes a non-increasing mode in which the braking force of the second wheel is reduced and maintained, and an increasing mode in which the braking force of the second wheel is increased, as a mode for adjusting the braking force of the second wheel. And the mode is shifted from the non-increasing mode to the increasing mode on the condition that the slip value of the second wheel is smaller than a slip elimination determination value in the adjustment of the braking force of the second wheel in the non-increasing mode.

4. The vehicle brake control device according to claim 1 or 2, wherein: A slip value deriving unit is provided for deriving a slip value indicating a degree of deceleration slip of the wheel. In the crossover process, when the slip value of the first wheel exceeds the deceleration slip determination value while the slip value of the second wheel is equal to or less than a deceleration slip determination value, the control unit switches between the first wheel and the second wheel.

5. The vehicle brake control device according to claim 1 or 2, wherein: A slip value deriving unit is provided for deriving a slip value indicating a degree of deceleration slip of the wheel. In the implementation of the above-mentioned anti-lock braking control, when the slip value of the above-mentioned second wheel exceeds the above-mentioned deceleration slip judgment value under the condition that the above-mentioned slip value of the above-mentioned first wheel is below the above-mentioned deceleration slip judgment value, the above-mentioned control unit ends the above-mentioned cross processing and executes the above-mentioned separation road surface processing. In the above-mentioned separation road surface processing, the replacement of the above-mentioned first wheel and the above-mentioned second wheel is stopped to maintain the state in which the braking force of the first wheel is greater than the braking force of the second wheel, and the braking forces of the above-mentioned first wheel and the above-mentioned second wheel are adjusted so that the above-mentioned slip values ​​of the above-mentioned first wheel and the above-mentioned second wheel are all below the above-mentioned deceleration slip judgment value.

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