Vehicle braking control system

Abstract

To restrain braking efficiency from being deteriorated during execution of ABS control.SOLUTION: A control device 50 comprises a control unit M19 that performs ABS control for adjusting the braking power of both the left and right wheels of a vehicle so as to prevent the left and right wheels from locking. In the ABS control, the control unit M19 performs cross processing for alternately switching between a right-wheel period in which the right wheel from among the left and right wheels is set as a first wheel for which braking power is increased and the left wheel is set as a second wheel for which braking power is adjusted within a range less than the braking power of the first wheel, and a left-wheel period in which the left wheel is set as the first wheel and the right wheel is set as the second wheel, and also performs cross processing for increasing the braking power of the second wheel during both the left-wheel period and the right-wheel period.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a vehicle braking control device that performs antilock 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 antilock brake control for suppressing the locking of vehicle wheels and stabilizing vehicle behavior. The control device performs select-low type antilock brake control based on the wheel with the lower wheel speed among the left and right wheels.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the control device performs select-low type antilock brake control, in order to set the braking force of the left and right wheels to a magnitude corresponding to the wheel with the lower wheel speed, there is a possibility that an excessive braking force is applied to the two wheels. In this case, there is a possibility that the braking efficiency decreases.

Means for Solving the Problems

[0005] A vehicle braking control device for solving the above problems includes a control unit that performs anti-lock brake control to suppress the locking of both left and right wheels by adjusting the braking force of both left and right wheels of the vehicle. The control unit alternately switches between a first period in which one of the left and right wheels is designated as a first wheel whose braking force is increased, and the other of the left and right wheels is designated as a second wheel whose braking force is adjusted to a range less than that of the first wheel, and a second period in which the other wheel is designated as the first wheel and the one wheel is designated as the second wheel, and performs a cross process to increase the braking force of the second wheel in both the first and second periods.

[0006] When the above-mentioned vehicle braking control device is performing cross-processing of anti-lock brake control, there is a period in which the braking force of both the first wheel and the second wheel of the left and right wheels are increased. However, during this period, the braking force of the second wheel remains less than that of the first wheel. Therefore, the degree of deceleration slip is less likely to increase in the second wheel compared to the first wheel. In other words, the second wheel is less likely to lock up compared to the first wheel. Consequently, a decrease in braking efficiency during the implementation of anti-lock brake control can be suppressed. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram showing a vehicle equipped with a control device, which is one embodiment of a vehicle braking control device. [Figure 2] Figure 2 is a block diagram showing the functional configuration of the control device. [Figure 3] Figure 3 is a timing chart for when cross-processing is performed as anti-lock brake control for both the left and right wheels. [Figure 4] Figure 4 is a timing chart for when split road surface handling is performed as anti-lock brake control for both the left and right wheels. [Figure 5]Figure 5 is a flowchart showing the processing routine executed by the execution unit of the control device. [Figure 6] Figure 6 is a flowchart showing the processing routine executed by the execution device. [Figure 7] Figure 7 is a timing chart illustrating the process for determining whether or not both wheels are locked. [Figure 8] Figure 8 is a timing chart for when it is determined that both wheels are locked while anti-lock brake control is being applied to both the left and right wheels. [Modes for carrying out the invention]

[0008] An embodiment of a vehicle braking control device will be described below with reference to Figures 1 to 8. As shown in Figure 1, the vehicle 10 includes a plurality of wheels and a braking system that adjusts the braking force applied to the plurality of wheels. The plurality of wheels include the left front wheel 11, the right front wheel 12, the left rear wheel 13, and the 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".

[0009] <Front wheel braking device> The front wheel braking system 20 comprises two friction brakes 21 and a braking actuator 27. Of the multiple friction brakes 21, one is provided for the left front wheel 11, while the other is provided for the right front wheel 12. Each of the multiple friction brakes 21 has a friction-receiving part 22, a friction part 23, and a wheel cylinder 24. Since the friction-receiving part 22 rotates integrally with the front wheels 11 and 12, the friction brake 21 can apply braking force to the front wheels 11 and 12 by pressing the friction part 23 against the friction-receiving part 22. The higher the hydraulic pressure in the wheel cylinder 24, the greater the force pressing the friction part 23 against the friction-receiving part 22. In other words, the friction brake 21 can adjust the braking force of the front wheels 11 and 12 by adjusting the hydraulic pressure in the wheel cylinder 24.

[0010] The braking actuator 27 is configured to individually control the hydraulic pressure in the wheel cylinders 24 of multiple friction brakes 21. The braking actuator 27 adjusts the braking force of the front wheels 11 and 12 by controlling the hydraulic pressure in the wheel cylinders 24.

[0011] <Rear wheel braking device> Of the two rear wheel braking devices 30, one is provided for the left rear wheel 13, while the other is provided for the right rear wheel 14. Each of the multiple rear wheel braking devices 30 comprises a friction-receiving part 31, a friction part 32, an electric motor 33, a reduction mechanism 34, and a linear motion conversion mechanism 35. Since the friction-receiving part 31 rotates integrally with the rear wheels 13 and 14, the rear wheel braking device 30 can apply braking force to the rear wheels 13 and 14 by pressing the friction part 32 against the friction-receiving part 31.

[0012] The reduction mechanism 34 reduces the rotational motion of the electric motor 33 and outputs it to the linear motion conversion mechanism 35. The linear motion conversion mechanism 35 converts the rotational motion input from the reduction mechanism 34 into linear motion and outputs it to the friction part 32. Therefore, in the rear wheel braking device 30, when the electric motor 33 is driven, the output torque of the electric motor 33 is transmitted to the friction part 32 via the reduction mechanism 34 and the linear motion conversion mechanism 35. As a result, the friction part 32 approaches the friction-bearing part 31, or the friction part 32 moves away from the friction-bearing part 31. In other words, by increasing the output torque of the electric motor 33, the braking force of the rear wheels 13 and 14 increases.

[0013] <Control device> A signal is input into the control device 50 from the detection system. The detection system includes four wheel speed sensors 61, 62, 63, 64, a longitudinal and lateral acceleration sensor 65, and a brake sensor 66. The wheel speed sensors 61 to 64 output signals corresponding to the rotational speeds of the corresponding wheels 11 to 14. The longitudinal and lateral acceleration sensor 65 outputs a signal corresponding to the longitudinal and lateral acceleration of the vehicle 10. The brake sensor 66 outputs a signal corresponding to information regarding 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 correlated with the operating force, or may be a sensor that detects the operation amount of the brake pedal 16. Then, the control device 50 controls the braking actuator 27 and the plurality of electric motors 33 based on the signals input from the various sensors.

[0014] Note that the rotational speed of the wheels 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 and lateral acceleration of the vehicle 10 based on the detection value of the longitudinal and lateral acceleration sensor 65 is referred to as "longitudinal and lateral acceleration GX".

[0015] The control device 50 performs antilock brake control to suppress the wheels from locking during deceleration of the vehicle 10. Hereinafter, the antilock brake control is referred to as "ABS control". The control device 50 individually performs ABS control for each wheel with respect to the front wheels 11, 12. On the other hand, when the control device 50 determines that there is a possibility that at least one of the left and right rear wheels 13, 14 locks, the control device 50 performs ABS control on both the left and right rear wheels 13, 14.

[0016] 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.

[0017] As shown in FIG. 2, by executing the control program, the execution device 51 functions 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.

[0018] The vehicle body speed derivation 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 braking, the vehicle body speed derivation unit M11 derives the vehicle body speed VS0 based on the wheel speed VW of the rear wheel with the higher wheel speed among the left and right rear wheels 13 and 14.

[0019] The slip value derivation 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 derivation unit M13 derives the slip ratio SLP of the wheel as the slip value. The slip value derivation unit M13 derives, as the slip ratio SLP, a value obtained by dividing the value obtained by subtracting the wheel speed VW of the wheel from the vehicle body speed VS0 by the vehicle body speed VS0. 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".

[0020] The wheel acceleration derivation unit M15 derives the wheel accelerations DVW of the plurality of wheels 11 to 14. Specifically, the wheel acceleration derivation unit M15 derives, as the wheel acceleration DVW, a value obtained by differentiating the wheel speed VW with respect to time. Therefore, when the wheel speed VW increases, the wheel acceleration derivation unit M15 derives a positive value as the wheel acceleration DVW, while when the wheel speed VW decreases, the wheel acceleration derivation unit M15 derives a negative value 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".

[0021] The dual-wheel lock determination unit M17 determines whether a dual-wheel lock state has been reached, where both the left and right rear wheels 13 and 14 are locked, when ABS control is being performed on both rear wheels 13 and 14. The specific details of the process for determining whether a dual-wheel lock state has been reached will be described later.

[0022] The control unit M19 performs ABS control. Specifically, if the slip ratio SLP1 of the left front wheel 11 exceeds the start determination threshold SLPth1, the control unit M19 determines that there is a possibility of the left front wheel 11 locking up, and therefore performs ABS control by adjusting the braking force Fx1 of the left front wheel 11. If the slip ratio SLP2 of the right front wheel 12 exceeds the start determination threshold SLPth1, the control unit M19 determines that there is a possibility of the right front wheel 12 locking up, and therefore performs ABS control by adjusting the braking force Fx2 of the right front wheel 12. If the slip ratio SLP of at least one of the left and right rear wheels 13 and 14 exceeds the start determination threshold SLPth1, the control unit M19 determines that there is a possibility of the said rear wheel locking up, and therefore performs ABS control by adjusting the braking forces Fx3 and Fx4 of both rear wheels 13 and 14. The braking forces Fx1 to Fx4 of the wheels controlled by the control unit M19 are the instructed values ​​of the braking force to be applied to the wheels.

[0023] The ABS control for both the left and right rear wheels 13 and 14 includes cross-field processing and split-surface processing. Cross-field processing can be described as ABS control when the road surface on which the vehicle 10 is traveling is not a split-surface surface. Split-surface processing can be described as ABS control when the road surface on which the vehicle 10 is traveling is a split-surface surface. A split-surface surface is a road surface where the μ value differs significantly between the road surface on which the left wheel makes contact and the road surface on which the right wheel makes contact.

[0024] Refer to Figure 3 to explain the cross-processing. In Figure 3(A), the dashed line shows the change in braking force Fx3 of the left rear wheel 13, and the dashed line shows the change in braking force Fx4 of the right rear wheel 14. In Figure 3(B), the dashed line shows the change in slip ratio SLP3 of the left rear wheel 13, and the dashed line shows the change in slip ratio SLP4 of the right rear wheel 14. In Figure 3(C), the dashed line shows the change in wheel speed VW3 of the left rear wheel 13, the dashed line shows the change in wheel speed VW4 of the right rear wheel 14, and the solid line shows the change in vehicle speed VS0.

[0025] In the example shown in Figure 3, braking forces Fx3 and Fx4 are applied to both rear wheels 13 and 14 starting at timing 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 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, respectively. Then, at timing t12, the slip ratios SLP3 and SLP4 of both rear wheels 13 and 14 exceed the start determination threshold SLPth1, so the control unit M19 starts ABS control. Specifically, the control unit M19 starts the cross-processing of ABS control.

[0026] Cross-control is an ABS control system that uses one of the two rear wheels 13 and 14 on the left and right sides as the first wheel, which increases braking force, and the other rear wheel as the second wheel, which adjusts braking force within a range less than that of the first wheel. The control unit M19 alternately switches between a right-wheel period, in which the right rear wheel 14 is the first wheel and the left rear wheel 13 is the second wheel, and a left-wheel period, in which the left rear wheel 13 is the first wheel and the right rear wheel 14 is the second wheel. For example, if the right-wheel period is the first period, the left-wheel period corresponds to the second period. Conversely, if the left-wheel period is the first period, the right-wheel period corresponds to the second period. The slip ratio SLP of the first wheel is denoted as "Slip Ratio SLPa", and the slip ratio SLP of the second wheel is denoted as "Slip Ratio SLPb". For example, if the left rear wheel 13 is the first wheel, the slip ratio SLP3 of the left rear wheel 13 corresponds to the slip ratio SLPa, and the slip ratio SLP4 of the right rear wheel 14 corresponds to the slip ratio SLPb.

[0027] In cross-processing, the control unit M19 switches between the first and second wheels when the slip rate SLPa of the first wheel exceeds the deceleration slip determination value SLPth2 while the slip rate SLPb of the second wheel is less than or equal to the deceleration slip determination value SLPth2. The deceleration slip determination value SLPth2 is set to a value smaller than the start determination threshold SLPth1. For example, during the right wheel period, if the slip rate SLP3 of the second wheel (left rear wheel 13) is less than or equal to the deceleration slip determination value SLPth2 while the slip rate SLP4 of the first wheel (right rear wheel 14) exceeds the deceleration slip determination value SLPth2, the control unit M19 ends the right wheel period and starts the left wheel period. Furthermore, during the left wheel period, if the slip ratio SLP4 of the second wheel, the right rear wheel 14, is less than or equal to the deceleration slip determination value SLPth2, and the slip ratio SLP3 of the first wheel, the left rear wheel 13, exceeds the deceleration slip determination value SLPth2, the control unit M19 terminates the left wheel period and starts the right wheel period.

[0028] The control unit M19 sequentially executes a non-increase mode and an increase mode as modes for adjusting the braking force of the second wheel during cross-traffic processing. The non-increase mode is a mode in which the braking force of the second wheel is not increased. Specifically, the non-increase mode is a mode that aims to reduce the slip ratio SLPb of the second wheel by decreasing and maintaining the braking force of the second wheel. The increase mode is a mode that increases the braking force of the second wheel. Specifically, the increase 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 less than or equal to a specified ratio. The specified ratio is a value less than 100%. For example, a value of 70% or more and 90% or less is set as the specified ratio.

[0029] Furthermore, the control unit M19 switches the mode from non-increase mode to increase mode when the slip ratio SLPb of the second wheel becomes less than the slip elimination judgment value SLPth3 while adjusting the braking force of the second wheel in non-increase mode. The slip elimination judgment value SLPth3 is the criterion for determining whether or not the deceleration slip of the wheel has been eliminated. The slip elimination judgment value SLPth3 is set to a value smaller than the deceleration slip judgment value SLPth2.

[0030] When the control unit M19 is performing cross-processing, the slip ratio SLPb of the second wheel may exceed the deceleration slip determination value SLPth2 while the slip ratio SLPa of the first wheel is less than or equal to the deceleration slip determination value SLPth2. In this case, the control unit M19 can determine that the road surface on which the vehicle 10 is traveling has become a split road surface, and therefore terminates the cross-processing and performs split road surface processing.

[0031] Refer to Figure 4 to explain how to handle a split road surface. In Figure 4(A), the dashed line shows the change in braking force Fx3 of the left rear wheel 13, and the dashed line shows the change in braking force Fx4 of the right rear wheel 14. In Figure 4(B), the dashed line shows the change in slip ratio SLP3 of the left rear wheel 13, and the dashed line shows the change in slip ratio SLP4 of the right rear wheel 14.

[0032] In the example shown in Figure 4, braking forces Fx3 and Fx4 are applied to both rear wheels 13 and 14 starting at timing t21. As the braking forces Fx3 and Fx4 increase, the slip ratios SLP3 and SLP4 increase for both the left rear wheel 13 and the right rear wheel 14. At timing t22, the slip ratio SLP3 of the left rear wheel 13 exceeds the start determination threshold SLPth1, so the control unit M19 starts ABS control. The processing performed by the control unit M19 from timing t22 onward is split road surface processing.

[0033] Split road surface handling is an ABS control system that designates the rear wheel with the smaller slip ratio SLP as the first wheel and the rear wheel with the larger slip ratio SLP as the second wheel. The control unit M19 does not switch between the first and second wheels during split road surface handling. In the example shown in Figure 4, the control unit M19 maintains the state where the right rear wheel 14 is the first wheel and the left rear wheel 13 is the second wheel, and adjusts the braking forces Fx3 and Fx4 of the left rear wheel 13 and the right rear wheel 14 so that the slip ratios SLP3 and SLP4 of both the left rear wheel 13 and the right rear wheel 14 are less than or equal to the deceleration slip judgment value SLPth2. Specifically, the control unit M19 stops switching between the first and second wheels and adjusts the braking forces of the first and second wheels while maintaining the state where the braking force of the second wheel is greater than the braking force of the first wheel. For example, if the slip ratio SLPb of the second wheel exceeds the deceleration slip detection value SLPth2, the control unit M19 reduces the braking force of both the first and second wheels. If the slip ratio SLPb of the second wheel falls below the slip elimination detection value SLPth3 due to the reduction in braking force, the control unit M19 increases the braking force of both the first and second wheels.

[0034] When the control unit M19 is performing split road surface processing, the slip ratio SLPa of the first wheel may exceed the deceleration slip determination value SLPth2 while the slip ratio SLPb of the second wheel is less than or equal to the deceleration slip determination value SLPth2. In this case, the control unit M19 can determine that the road surface on which the vehicle 10 is traveling is no longer a split road surface, and therefore terminates the split road surface processing and performs cross-road processing.

[0035] <Processing flow when implementing ABS control for both left and right rear wheels> Referring to Figure 5, a processing routine for determining whether to start ABS control for both the left and right rear wheels 13 and 14, and whether to terminate the said ABS control, will be explained. The execution device 51 executes this processing routine repeatedly at predetermined control cycles by executing the control program.

[0036] In this processing routine, in step S11, the execution device 51, functioning as the control unit M19, determines whether the ABS implementation flag FLG1 is set to off. If ABS control is being performed on both the left and right rear wheels 13 and 14, the ABS implementation flag FLG1 is set to on, while if the ABS control is not being performed, the ABS implementation flag FLG1 is set to off. If the ABS implementation flag FLG1 is set to off (S11: YES), the execution device 51 proceeds to step S13. On the other hand, if the ABS implementation flag FLG1 is set to on (S11: NO), the execution device 51 proceeds to step S21.

[0037] In step S13, the execution device 51, functioning as the control unit M19, determines whether the conditions for starting ABS control for both the left and right rear wheels 13 and 14 are met. If at least one of the following two conditions is met, the start condition is considered to be met. On the other hand, if neither of the two conditions is met, the start condition is considered not to be met. • The slip ratio SLP3 of the left rear wheel 13 exceeds the threshold SLPth1 used for determining the start of the race. • The slip ratio SLP4 of the right rear wheel 14 exceeds the threshold SLPth1 used for determining the start of the race.

[0038] If the execution device 51 determines that the start condition is met (S13: YES), it proceeds to step S15. On the other hand, if the execution device 51 determines that the start condition is not met (S13: NO), it terminates this processing routine.

[0039] In step S15, the execution device 51, functioning as the control unit M19, sets the ABS implementation flag FLG1 to ON. In step S17, the execution device 51, functioning as the control unit M19, sets the condition coefficient KN to 1. The condition coefficient KN is a coefficient used to determine whether to perform cross-processing or split-road surface processing. In this embodiment, when the start condition is met and ABS control is started, the condition coefficient KN is set to 1 in order to select cross-processing. After that, the execution device 51 terminates this processing routine.

[0040] In step S21, the execution device 51, functioning as the control unit M19, determines whether the termination conditions for ending ABS control for both the left and right rear wheels 13 and 14 have been met. For example, the execution device 51 determines that the termination conditions have been met when the vehicle 10 stops or when there are no more braking requests for the rear wheels 13 and 14. If the execution device 51 determines that the termination conditions have been met (S21: YES), it proceeds to step S27. On the other hand, if the execution device 51 determines that the termination conditions have not been met (S21: NO), it proceeds to step S23.

[0041] In step S23, the execution device 51 functions as a double-wheel lock determination unit M17 to determine whether or not the wheels are locked. If the execution device 51 determines that the wheels are locked (S23: YES), it proceeds to step S25. On the other hand, if the execution device 51 determines that the wheels are not locked (S23: NO), it terminates this processing routine.

[0042] In step S25, the execution device 51, acting as the control unit M19, sets the wheel lock flag FLG2 to ON. After that, the execution device 51 terminates this processing routine.

[0043] In step S27, the execution device 51, acting as the control unit M19, sets both the ABS implementation flag FLG1 and the dual wheel lock flag FLG2 to off. After that, the execution device 51 terminates this processing routine.

[0044] Referring to Figure 6, the processing routine for implementing ABS control for both the left and right rear wheels 13 and 14 will be described. The execution device 51 executes this processing routine repeatedly at predetermined control cycles by executing the control program. The multiple steps S41 to S63 that constitute this processing routine are processes that are performed by the execution device 51 functioning as the control unit M19.

[0045] In this processing routine, step S41, the execution device 51 determines whether the ABS implementation flag FLG1 is set to ON. If the ABS implementation flag FLG1 is set to ON (S41: YES), the execution device 51 proceeds to step S43. On the other hand, if the ABS implementation flag FLG1 is set to OFF (S41: NO), the execution device 51 terminates this processing routine.

[0046] In step S43, the execution device 51 determines whether the dual wheel lock flag FLG2 is set to off. If the dual wheel lock flag FLG2 is set to off (S43: YES), the execution device 51 proceeds to step S45. On the other hand, if the dual wheel lock flag FLG2 is set to on (S43: NO), the execution device 51 proceeds to step S53.

[0047] In step S45, the execution device 51 determines whether the condition coefficient KN is 1 or not. If the condition coefficient KN is 1 (S45: YES), the execution device 51 proceeds to step S47. On the other hand, if the condition coefficient KN is not 1 (S45: NO), the execution device 51 proceeds to step S59.

[0048] In step S47, the execution device 51 performs the above cross processing as ABS control for both the left and right rear wheels 13 and 14. In step S49, the execution device 51 determines whether the following two conditions are met. If both conditions are met, the road surface on which the vehicle 10 is traveling can be considered to have become a split road surface. • The slip ratio SLPa of the first wheel must be less than or equal to the deceleration slip detection value SLPth2. • The slip ratio SLPb of the second wheel is greater than the deceleration slip detection value SLPth2.

[0049] If both conditions are met (S49: YES), the execution device 51 proceeds to step S51. On the other hand, if at least one of the two conditions is not met (S49: NO), the execution device 51 terminates this processing routine.

[0050] In step S51, the execution device 51 sets the condition coefficient KN to 2. After that, the execution device 51 terminates this processing routine. In step S53, the execution device 51 instructs the first wheel and the second wheel to be swapped. That is, when the execution device 51 determines that both wheels are locked, it swaps the first wheel and the second wheel. Then, in step S55, the execution device 51 sets the two-wheel lock flag FLG2 to off.

[0051] In step S57, the execution device 51 determines whether or not it is performing cross-wheel processing as ABS control for both the left and right rear wheels 13 and 14. If the execution device 51 is performing cross-wheel processing (S57: YES), it proceeds to step S47. That is, if the execution device 51 determines that both wheels have locked up during the execution of cross-wheel processing, it swaps the first wheel and the second wheel and continues the cross-wheel processing. On the other hand, if the execution device 51 is not performing cross-wheel processing (S57: NO), it is performing split road surface processing, and therefore proceeds to step S59. That is, if the execution device 51 determines that both wheels have locked up during the execution of split road surface processing, it swaps the first wheel and the second wheel and continues the split road surface processing.

[0052] In step S59, the execution device 51 performs the above-mentioned split road surface processing as ABS control for both the left and right rear wheels 13 and 14. In step S61, the execution device 51 determines whether the following two conditions are met. If both conditions are met, the road surface on which the vehicle 10 is traveling can be considered to be no longer a split road surface. • The slip ratio SLPa of the first wheel is greater than the deceleration slip detection value SLPth2. • The slip ratio SLPb of the second wheel must be less than or equal to the deceleration slip detection value SLPth2.

[0053] If both conditions are met (S61: YES), the execution device 51 proceeds to step S63. On the other hand, if at least one of the two conditions is not met (S61: NO), the execution device 51 terminates this processing routine.

[0054] In step S63, the execution device 51 sets the condition coefficient KN to 1. After that, the execution device 51 terminates this processing routine. <Determining whether both wheels are locked or not> Referring to Figure 7, the process for determining whether or not both wheels are locked will be explained. The execution device 51 performs this process by functioning as a two-wheel lock determination unit M17. In Figure 7(A), the dashed line shows the change in the wheel speed VW3 of the left rear wheel 13, the dashed line shows the change in the wheel speed VW4 of the right rear wheel 14, the solid line shows the actual value VS of the vehicle speed, and the dashed line shows the change in the vehicle speed VS0. In Figure 7(B), the dashed line shows the change in the slip ratio SLP3 of the left rear wheel 13, and the dashed line shows the change in the slip ratio SLP4 of the right rear wheel 14.

[0055] The execution device 51 performs a process to determine whether or not both wheels are locked when ABS control is being performed on both rear wheels 13 and 14, that is, when cross-road processing or split-road surface processing is being performed.

[0056] As shown in Figure 7, from timing t31 to timing t32, the execution device 51 determines that both wheels are locked if the slip ratios SLP3 and SLP4 of both rear wheels 13 and 14 are equal to or greater than the deceleration slip determination value SLPth4. The deceleration slip determination value SLPth4 is set to be less than or equal to the deceleration slip determination value SLPth2 and greater than the slip release determination value SLPth3. Specifically, the execution device 51 determines that both wheels are locked if the duration of the state in which both slip ratios SLP3 and SLP4 are equal to or greater than the deceleration slip determination value SLPth4 exceeds a specified time. The specified time is set to the length of time during which it is possible to determine whether the actual slip ratio of the left rear wheel 13 and the actual slip ratio of the right rear wheel 14 are equal to or greater than the deceleration slip determination value SLPth4.

[0057] During periods such as from timing t33 ​​to timing t34, the degree of deceleration slip of both rear wheels 13 and 14 may gradually increase. In this case, in line with the decrease in wheel speeds VW3 and VW4 of both rear wheels 13 and 14, the vehicle speed VS0 also decreases, as shown by the dashed line in Figure 7. Therefore, even if deceleration slip occurs in both rear wheels 13 and 14, the slip ratios SLP3 and SLP4 do not increase. In other words, neither of the slip ratios SLP3 and SLP4 will exceed the two-wheel deceleration slip judgment value SLPth4.

[0058] Therefore, the execution device 51 determines that both wheels are locked when both of the following conditions (A1) and (A2) are met. Specifically, the execution device 51 determines that both wheels are locked when the duration of the state in which both of the two conditions (A1) and (A2) are met exceeds a specified time. (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 less than a predetermined difference. (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 judgment value DVWth.

[0059] If the difference between slip ratio SLP3 and slip ratio SLP4 is less than a predetermined difference, the difference between slip ratio SLP3 and slip ratio SLP4 can be considered to be almost negligible. The wheel acceleration judgment value DVWth is the criterion for determining whether or not the wheel speeds VW3 and VW4 of the rear wheels 13 and 14 are decreasing.

[0060] <Operation and Effects of This Embodiment> (1) When braking force is applied to the vehicle 10, if the slip ratio SLP of at least one of the two rear wheels 13 and 14 exceeds the start determination threshold SLPth1, cross-processing is started as ABS control for both rear wheels 13 and 14. As shown in Figure 3, in cross-processing, 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.

[0061] The cross-control system has two modes for controlling the braking force of the second wheel: a non-increase mode and an increase mode. When adjusting the braking force of the second wheel in the increase mode, the braking force of the second wheel is increased to a level less than that of the first wheel. In other words, when the cross-control system is running, there is a period during which both the braking force of the first wheel and the braking force of the second wheel are increased. However, during this period, the braking force of the second wheel remains less than that of the first wheel. Therefore, deceleration slip is less likely to occur in the second wheel compared to the first wheel. Consequently, it is possible to suppress the locking of both the left and right rear wheels 13 and 14 during ABS control. In other words, it is possible to suppress a decrease in braking efficiency during ABS control.

[0062] (2) As a method to suppress the state in which both the left and right rear wheels 13 and 14 lock up while ABS control is being performed, a method of not increasing the braking force of the second wheel can also be considered. In this case, although the state in which both rear wheels 13 and 14 lock up can be suppressed, the difference in braking force between the left and right rear wheels 13 and 14 will increase, and the yaw moment of the vehicle 10 will increase. Also, the overall braking force of the vehicle 10 will not increase easily, so the deceleration of the vehicle 10 will not increase easily. In this embodiment, however, since the braking force of the second wheel is also increased, it is possible to suppress the increase in the difference in braking force between the left and right rear wheels 13 and 14, and also to suppress the decrease in the overall braking force of the vehicle 10 caused by the implementation of ABS control.Therefore, while suppressing the decrease in the deceleration of the vehicle 10, it is possible to suppress the increase in the yaw moment of the vehicle 10 while ABS control is being performed.

[0063] (3) The thick dashed line in Figure 3(C) shows the change in vehicle speed VS1 derived when independent left and right wheel ABS control is implemented. When both rear wheels 13 and 14 lock up, the wheel speeds VW3 and VW4 of both rear wheels 13 and 14 decrease significantly, so the vehicle speed VS1 may become significantly smaller compared to the actual vehicle speed. In this case, the accuracy of deriving the slip ratios SLP1 to SLP4 of wheels 11 to 14 decreases.

[0064] In this regard, by implementing the above-described control as ABS control for both the left and right rear wheels 13 and 14, it is possible to suppress the condition in which both rear wheels 13 and 14 lock up. Therefore, it is possible to suppress a decrease in the estimation accuracy of the vehicle speed VS0 when the vehicle 10 is braking. Consequently, it is also possible to suppress a decrease in the derivation accuracy of the slip ratios SLP1 to SLP4 of the wheels 11 to 14.

[0065] (4) When increasing the braking force of the second wheel in the amplification 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 or equal to a specified ratio. Therefore, when the mode switches from the non-amplification mode to the amplification mode, a sudden increase in the braking force of the second wheel can be suppressed. Therefore, a decrease in the stability of the vehicle 10's behavior caused by increasing the braking force of the second wheel can be suppressed.

[0066] (5) In this embodiment, when the non-increase mode is executed as the mode for adjusting the braking force of the second wheel, as shown in Figure 3, once the braking force of the second wheel is reduced to a certain level, the braking force of the second wheel is maintained. When the slip ratio SLPb of the second wheel becomes less than the slip elimination judgment value SLPth3, it can be determined that the deceleration slip of the second wheel has been eliminated, and the mode transitions from the non-increase mode to the increase mode. That is, the deceleration slip of the second wheel is eliminated before the braking force of the second wheel is increased. Therefore, the effect of suppressing the state in which both rear wheels 13 and 14 lock up during ABS control can be further enhanced.

[0067] Furthermore, even when the braking force of the second wheel is maintained at a certain level using the non-increasing mode, the deceleration slip of the second wheel may not be easily resolved. In this case, the deceleration slip of the second wheel can be resolved by further reducing the braking force of the second wheel.

[0068] (6) When cross processing is being performed, the slip ratio SLPb of the second wheel may exceed the deceleration slip judgment value SLPth2 while the slip ratio SLPa of the first wheel is less than or equal to the deceleration slip judgment value SLPth2. In this case, it is possible that the vehicle 10 is traveling on a split road surface where the μ value of the road surface in contact with the second wheel is lower than the μ value of the road surface in contact with the first wheel. Therefore, cross processing is terminated and split road surface processing is started.

[0069] As shown in Figure 4, in split road surface handling, the switching between the first and second wheels is stopped. Then, while maintaining a state where the braking force of the first wheel is greater than that of the second wheel, the braking forces of the first and second wheels are adjusted. Specifically, increasing the braking forces of both the first and second wheels increases the slip ratio SLPb of the second wheel in contact with the low-μ surface. When the slip ratio SLPb of the second wheel exceeds the deceleration slip judgment value SLPth2, the braking forces of both the first and second wheels are reduced. When the slip ratio SLPb of the second wheel falls below the slip elimination judgment value SLPth3, it is determined that the deceleration slip of the second wheel has been eliminated, and therefore the braking forces of both the first and second wheels are increased.

[0070] In this split surface treatment, the braking force of the first wheel in contact with the high-μ surface can be made greater than the braking force of the second wheel in contact with the low-μ surface, while suppressing an increase in the slip ratio SLPa of the first wheel. Therefore, it is possible to suppress a state in which both the left and right rear wheels 13 and 14 lock up. Furthermore, by deriving the vehicle speed VS0 based on the wheel speed VW of the first wheel, it is possible to suppress a decrease in the estimation accuracy of the vehicle speed VS0.

[0071] (7) Even when cross-traverse or split-traverse is being performed, it is possible that both rear wheels 13 and 14 may lock up, resulting in a double-wheel lock condition. For example, if any of the following conditions (B1), (B2), (B3), and (B4) are met, it is possible that both wheels may lock up during cross-traverse or split-traverse. (B1) There is a large discrepancy between the braking characteristics of the rear brake system 30 for the left rear wheel 13 and the braking characteristics of the rear brake system 30 for the right rear wheel 14. (B2) There is a large discrepancy between the μ value of the road surface in contact with the left rear wheel 13 and the μ value of the road surface in contact with the right rear wheel 14. (B3) There is a large discrepancy between the μ value of the left rear wheel 13 and the μ value of the right rear wheel 14. (B4) There is a large discrepancy between the diameter of the left rear wheel 13 and the diameter of the right rear wheel 14.

[0072] Here, the braking characteristic of the braking system is the braking ratio, which is the ratio of the indicated braking force to the actual braking force. A small braking ratio means that the actual braking force is smaller than the indicated braking force. Referring to Figure 8, we will explain ABS control when there is a large discrepancy between the braking characteristics of the rear brake system 30 for the left rear wheel 13 and the braking characteristics of the rear brake system 30 for the right rear wheel 14. The example shown in Figure 8 is when the braking ratio of the rear brake system 30 for the left rear wheel 13 is smaller than the braking ratio of the rear brake system 30 for the right rear wheel 14. In Figure 8(A), the dashed line shows the change in the slip ratio SLP3 of the left rear wheel 13, and the dashed line shows the change in the slip ratio SLP4 of the right rear wheel 14. In Figure 8(B), the thin dashed line shows the change in the indicated value Fx3 of the braking force of the left rear wheel 13, the thin dashed line shows the change in the indicated value Fx4 of the braking force of the right rear wheel 14, and the thick dashed line shows the change in the actual value Fx4R of the braking force of the right rear wheel 14. In this example, a large discrepancy occurs between the indicated braking force Fx4 and the actual braking force Fx4R for the right rear wheel 14, but there is almost no discrepancy between the indicated braking force Fx3 and the actual braking force for the left rear wheel 13.

[0073] At timing t41, while braking force is being applied to the vehicle 10, ABS control is initiated for both the left and right rear wheels 13 and 14. At timing t42, while split road surface processing is being performed with the right rear wheel 14 as the first wheel and the left rear wheel 13 as the second wheel, the execution device 51 determines that both wheels are locked. Therefore, the execution device 51 swaps the first and second wheels and continues the split road surface processing. That is, from timing t42 onward, the left rear wheel 13 becomes the first wheel and the right rear wheel 14 becomes the second wheel. Therefore, the instruction value Fx3 for the braking force of the left rear wheel 13 is increased, while the instruction value Fx4 for the braking force of the right rear wheel 14 is decreased, so that the instruction value Fx3 for the braking force of the left rear wheel 13 becomes greater than the instruction value Fx4 for the braking force of the right rear wheel 14. The indicated braking force Fx4 for the right rear wheel 14 will not increase until the difference in braking force between the right rear wheel 14 and the left rear wheel 13 becomes large enough.

[0074] In the example shown in Figure 8, at timing t43, the slip ratio SLP4 of the second wheel, the right rear wheel 14, is less than or equal to the deceleration slip detection value SLPth2, while the slip ratio SLP3 of the first wheel, the left rear wheel 13, exceeds the deceleration slip detection value SLPth2. Therefore, the split road surface processing is completed and the cross processing is executed. Then, the first and second wheels are switched. The instructed braking force value Fx4 of the first wheel, the right rear wheel 14, is increased, while the instructed braking force value Fx3 of the second wheel, the left rear wheel 13, is decreased. In the cross processing, the instructed braking force value Fx3 of the left rear wheel 13 is increased from timing t44, when the deceleration slip of the left rear wheel 13 is eliminated.

[0075] From timing t44 onward, the actual braking force of the left rear wheel 13 and the actual braking force of the right rear wheel 14, Fx4R, become approximately the same. As a result, both the slip ratio SLP3 of the left rear wheel 13 and the slip ratio SLP4 of the right rear wheel 14 gradually increase. In other words, both of the above conditions (A1) and (A2) become satisfied. Then, at timing t45 during the execution of the cross-wheel process, the execution device 51 determines that both wheels are locked, swaps the first wheel and the second wheel, and continues the execution of the cross-wheel process.

[0076] If it is determined that both wheels are locked during ABS control, the first and second wheels are switched. This suppresses the increase in braking force of the rear wheel that is less prone to a large slip ratio (SLP) among the first and second wheels. As a result, it is possible to suppress an increase in the SLP of the rear wheel that is less prone to a large slip ratio. Therefore, even if both wheels are locked due to cross-slip or split-slip road surface treatment, the two-wheel lock condition can be resolved quickly.

[0077] (8) For example, if the slip ratios SLP3 and SLP4 of both rear wheels 13 and 14 both become greater than or equal to the deceleration slip determination value SLPth4, it is determined that both wheels are locked. Also, even if the slip ratios SLP3 and SLP4 of both rear wheels 13 and 14 do not increase, if both of the above conditions (A1) and (A2) are met, it is determined that both wheels are locked. Therefore, the accuracy of determining whether or not both wheels are locked can be increased.

[0078] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0079] If it is determined that both wheels are locked, ABS control may be implemented to maintain the braking force of one of the left and right rear wheels 13 and 14 while adjusting the braking force of the other rear wheel. Alternatively, if it is determined that both wheels are locked, ABS control may be implemented to adjust the braking force of both rear wheels 13 and 14 so that the difference in braking force between the left and right rear wheels 13 and 14 becomes larger.

[0080] When performing cross-wheel processing or split-wheel processing, it is not mandatory to perform a process to determine whether or not both wheels are locked. The execution device 51 may terminate the cross-processing and start split road surface processing if the slip ratio SLPb of the second wheel becomes greater than the slip ratio SLPa of the first wheel during the execution of the cross-processing.

[0081] The execution device 51 may terminate the split road surface treatment and start the cross treatment if the slip ratio SLPa of the first wheel becomes greater than the slip ratio SLPb of the second wheel during the execution of the split road surface treatment.

[0082] If cross-straightening is performed as ABS control for the rear wheels 13 and 14, then split-straightening is not essential. In the above embodiment, when cross processing is performed, the system switches between the first and second wheels when the slip ratio SLPa of the first wheel exceeds the deceleration slip determination value SLPth2, but it is not limited to this. For example, when the left rear wheel 13 is the first wheel, when the duration of the state in which the braking force Fx3 of the left rear wheel 13 is increased reaches a predetermined duration, the system may change the left rear wheel 13 to the second wheel and the right rear wheel 14 to the first wheel, thereby decreasing the braking force of the left rear wheel 13 while increasing the braking force Fx4 of the right rear wheel 14.

[0083] In the above embodiment, when adjusting the braking force of the second wheel, the mode is set to transition from the non-increasing mode to the increasing mode when the slip ratio SLPb of the second wheel becomes less than the slip elimination judgment value SLPth3, but this is not limited to this. For example, the mode may be set to transition from the non-increasing mode to the increasing mode after a predetermined time has elapsed from the start of the non-increasing mode. In this case, the predetermined time should be set to the time in which it is assumed that the deceleration slip of the second wheel can be eliminated.

[0084] In the cross-processing, if at least one of the following two conditions (C1) and (C2) is met, the mode for adjusting the braking force of the second wheel may be changed from the non-increasing mode to the increasing mode. (C1) The slip ratio SLPb of the second wheel becomes less than the slip resolution value SLPth3. (C2) A predetermined time has elapsed since the start of the non-increasing mode.

[0085] When adjusting the braking force of the second wheel in non-increasing mode, if it is possible to provide a period for reducing the braking force, then it is acceptable not to provide a period for maintaining the braking force. In cross-wheel braking, if the braking force of the second wheel does not exceed 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 become greater than the specified ratio by increasing the braking force of the second wheel.

[0086] When the conditions for starting ABS control for both the left and right rear wheels 13 and 14 are met, and the difference in slip ratios between the two rear wheels 13 and 14 is greater than or equal to the difference in determined slip ratios, the split road surface processing may be performed from the beginning.

[0087] The control unit may switch between the first wheel and the second wheel during cross-processing if both of the following two conditions (D1) and (D2) are met. (D1) The slip ratio of the second wheel SLPb (slip value of the second wheel) is less than or equal to the deceleration slip detection value SLPth2. (D2) Under the condition that the wheel acceleration DVW of the second wheel is equal to or greater than the wheel acceleration judgment value DVWth, the slip ratio SLPa (slip value of the first wheel) of the first wheel exceeds the deceleration slip judgment value SLPth2, and the wheel acceleration DVW of the first wheel is equal to or less than the wheel acceleration judgment value DVWth.

[0088] The control unit may, during ABS control, terminate the cross-processing and stop the swapping of the first and second wheels, maintaining a state in which the braking force of the first wheel is greater than the braking force of the second wheel, while performing split road surface processing to adjust the braking forces of the first and second wheels if both of the following two conditions (E1) and (E2) are met. (E1) The slip ratio SLPa (slip value of the first wheel) of the first wheel is less than or equal to the deceleration slip judgment value SLPth2, and the wheel acceleration DVW of the first wheel is greater than or equal to the wheel acceleration judgment value DVWth. (E2) Under the conditions (E1) are met, the slip ratio SLPb (slip value of the second wheel) of the second wheel exceeds the deceleration slip judgment value SLPth2, and the wheel acceleration DVW of the second wheel is less than or equal to the wheel acceleration judgment value DVW.

[0089] In the above embodiment, the slip ratio SLP was derived as a slip value indicating the degree of deceleration slip of the wheels, but this is not limited to this. For example, the slip amount, which is the value obtained by subtracting the wheel speed VW from the vehicle speed VS0, may be derived as the slip value.

[0090] The above embodiment describes the case where cross-tracing and split-road surface treatment are performed on both the left and right rear wheels 13 and 14. However, cross-tracing and split-road surface treatment may also be performed on both the left and right front wheels 11 and 12.

[0091] The control device 50 may be configured as a circuit including one or more processors that operate according to a computer program, one or more dedicated hardware circuits that perform at least some of the various processes, or a combination thereof. Examples of dedicated hardware include application-specific integrated circuits (ASICs). The processor includes a CPU and memory such as RAM and ROM, where the memory stores program code or instructions configured to cause the CPU to perform the processes. The memory, i.e., storage medium, includes any available medium that can be accessed by a general-purpose or dedicated computer.

[0092] The braking system may have a different configuration from the one shown in Figure 1, as long as it allows for individual adjustment of the braking force of multiple wheels 11-14. In this specification, the expression "at least one" means "one or more" of the desired options. For example, if there are two options, the expression "at least one" means "only one option" or "both of the two options." As another example, if there are three or more options, the expression "at least one" means "only one option" or "a combination of two or more arbitrary options."

[0093] <Other technological ideas> Next, the technical concepts that can be understood from the above embodiments and modified examples are described as an addendum. (Note 1) The control unit is configured to start the anti-lock brake control when the slip value of at least one of the left and right wheels exceeds the threshold for determining when to start. It is preferable that the deceleration slip determination value is set to a value smaller than the start determination threshold.

[0094] (Note 2) When the anti-lock brake control is being implemented, the vehicle is equipped with a dual-wheel lock determination unit that determines whether or not both the left and right wheels are locked, resulting in a dual-wheel lock state. In the anti-lock brake control, it is preferable that the control unit switches between the first wheel and the second wheel when it determines that both wheels are locked.

[0095] (Note 3) The vehicle is equipped with a slip value derivation unit that derives a slip value which is a value indicating the degree of deceleration slip of the wheel, Preferably, the two-wheel lock determination unit determines that the two-wheel lock state has occurred when both the slip value of the first wheel and the slip value of the second wheel become equal to or greater than the two-wheel deceleration slip determination value.

[0096] (Note 4) A slip value derivation unit that derives a slip value which is a value indicating the degree of deceleration slip of the wheel, The system includes a wheel acceleration derivation unit that derives the wheel acceleration, which is the rate at which the rotational speed of the wheel increases. Preferably, the two-wheel lock determination unit determines that the two-wheel lock state has occurred on the condition that both of the following conditions are met: the difference between the slip value of the first wheel and the slip value of the second wheel is less than a predetermined difference, and the wheel acceleration of both the first wheel and the second wheel is less than or equal to a wheel acceleration determination value. [Explanation of Symbols]

[0097] 10... Vehicles 11~14…Wheel 50…Control device 51…Execution device 52...Storage device M13... Slip value derivation section M17... Wheel lock detection unit M19... Control Unit

Claims

1. The vehicle includes a control unit that performs anti-lock brake control to suppress the locking of both left and right wheels by adjusting the braking force of those wheels, The control unit alternately switches between a first period in which one of the left and right wheels is designated as a first wheel that increases braking force, and the other of the left and right wheels is designated as a second wheel that adjusts braking force within a range less than the braking force of the first wheel, and a second period in which the other wheel is designated as the first wheel and one of the wheels is designated as the second wheel, and in both the first and second periods, it performs a cross processing to increase the braking force of the second wheel. The control unit increases the braking force of the second wheel in the cross-processing 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 or equal to a specified ratio. Vehicle braking control system.

2. A control unit that performs anti-lock brake control to suppress the locking of both left and right wheels by adjusting the braking force of both left and right wheels of the vehicle, The system includes a slip value derivation unit that derives a slip value, which is a value indicating the degree of deceleration slip of the wheel, The control unit alternately switches between a first period in which one of the left and right wheels is designated as a first wheel that increases braking force, and the other of the left and right wheels is designated as a second wheel that adjusts braking force within a range less than the braking force of the first wheel, and a second period in which the other wheel is designated as the first wheel and one of the wheels is designated as the second wheel, and in both the first and second periods, it performs a cross processing to increase the braking force of the second wheel. The control unit, in the cross processing, As a mode for adjusting the braking force of the second wheel, the following are executed in sequence: a non-increase mode in which at least the braking force of the second wheel is decreased and maintained, and an increase mode in which the braking force of the second wheel is increased. If, during the adjustment of the braking force of the second wheel in the non-increase mode, the slip value of the second wheel falls below the slip elimination judgment value, the mode is changed from the non-increase mode to the increase mode. Vehicle braking control system.

3. A control unit that performs anti-lock brake control to suppress the locking of both left and right wheels by adjusting the braking force of both left and right wheels of the vehicle, The system includes a slip value derivation unit that derives a slip value, which is a value indicating the degree of deceleration slip of the wheel, The control unit alternately switches between a first period in which one of the left and right wheels is designated as a first wheel that increases braking force, and the other of the left and right wheels is designated as a second wheel that adjusts braking force within a range less than the braking force of the first wheel, and a second period in which the other wheel is designated as the first wheel and one of the wheels is designated as the second wheel, and in both the first and second periods, it performs a cross processing to increase the braking force of the second wheel. The control unit switches between the first and second wheels in the cross-processing when the slip value of the first wheel exceeds the deceleration slip determination value while the slip value of the second wheel is less than or equal to the deceleration slip determination value. Vehicle braking control system.

4. A control unit that performs anti-lock brake control to suppress the locking of both left and right wheels by adjusting the braking force of both left and right wheels of the vehicle, The system includes a slip value derivation unit that derives a slip value, which is a value indicating the degree of deceleration slip of the wheel, The control unit alternately switches between a first period in which one of the left and right wheels is designated as a first wheel that increases braking force, and the other of the left and right wheels is designated as a second wheel that adjusts braking force within a range less than the braking force of the first wheel, and a second period in which the other wheel is designated as the first wheel and one of the wheels is designated as the second wheel, and in both the first and second periods, it performs a cross processing to increase the braking force of the second wheel. During the execution of the anti-lock brake control, if the slip value of the second wheel exceeds the deceleration slip determination value while the slip value of the first wheel is less than or equal to the deceleration slip determination value, the control unit terminates the cross processing, stops the swapping of the first and second wheels, maintains a state in which the braking force of the first wheel is greater than the braking force of the second wheel, and performs split road surface processing to adjust the braking forces of the first and second wheels so that the slip values ​​of both the first and second wheels are less than or equal to the deceleration slip determination value. Vehicle braking control system.

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