Brake control device

Abstract

To suppress a vehicle that banks during steering from side-slipping.SOLUTION: A brake control device 10 is applicable to a vehicle 90 that enables a vehicle body and a wheel to bank during steering. The brake control device 10 controls a braking device 70 that applies braking force to the wheel. The brake control device 10 comprises a side-slip acceleration calculating part 11 that calculates side-slip acceleration which is side-slip acceleration at which the wheel moves in a lateral direction. The brake control device 10 comprises an ABS control part 13 that executes ABS control. The brake control device 10 comprises a filter processing part 12 that applies filter processing for suppressing the side-slip acceleration from varying in a deceleration direction with respect to the side-slip acceleration during execution of the ABS control. The ABS control part 13 executes side-slip suppression processing during execution of the ABS control. The side-slip suppression processing is processing which decreases braking force that is applied to the wheel when the side-slip acceleration subjected to the filter processing is large in an acceleration direction, more in comparison with when the side-slip acceleration is not large.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a braking control device for a vehicle capable of tilting a vehicle body and wheels during turning.

Background Art

[0002] In a vehicle such as a motorcycle capable of tilting a vehicle body and wheels during turning, the gyro effect accompanying the rotation of the wheels contributes to the stability of the vehicle. Patent Document 1 discloses a control device for suppressing the skidding of wheels in such a vehicle. In the control device disclosed in Patent Document 1, when the skidding acceleration of the wheels is equal to or greater than a threshold value, the braking force is decreased to reduce the longitudinal force so that the resultant force of the longitudinal force and the lateral force is within the friction circle, thereby suppressing skidding.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Even if the skidding acceleration becomes small after skidding of the wheels has occurred, skidding may continue. That is, if the control for suppressing skidding is terminated because the skidding acceleration becomes smaller than the threshold value, there is a risk that the skidding is not eliminated and the stability of the vehicle decreases.

Means for Solving the Problems

[0005] The braking control device for solving the above problems is applied to a vehicle capable of banking the vehicle body and wheels during turning, and is a braking control device that controls a braking device that applies a braking force to the wheels. The braking control device includes a lateral slip acceleration calculation unit that calculates a lateral slip acceleration, which is an acceleration of lateral slip in which the wheels move laterally with respect to the traveling direction of the wheels or the vehicle body, an anti-lock braking control (ABS) control unit that performs anti-lock braking control to decrease and increase the braking force applied to the wheels based on the slip amount of the wheels, and a filter processing unit that performs a filter process to suppress a change in the lateral slip acceleration in the deceleration direction during the execution of the anti-lock braking control. The ABS control unit executes a lateral slip suppression process during the execution of the anti-lock braking control. The gist of the lateral slip suppression process is that when the lateral slip acceleration after the filter process by the filter processing unit is large in the acceleration direction, the braking force applied to the wheels is decreased compared to the case where it is not so.

[0006] According to the above configuration, the lateral slip acceleration is less likely to change rapidly in the deceleration direction by the filter process. For this reason, the lateral slip suppression process, which is a process of decreasing the braking force when the lateral slip acceleration is large in the acceleration direction, is likely to continue. That is, the braking force is likely to be decreased during the execution of anti-lock braking control (hereinafter also referred to as "ABS control"). As a result, the longitudinal force is likely to be decreased, and the lateral slip is likely to be eliminated.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the braking control device will be described with reference to FIGS. 1 to 6. FIG. 1 shows a braking control device 10 and a vehicle 90 to which the braking control device 10 is applied. 〈Vehicle〉 The vehicle 90 is, for example, a motorcycle as shown in FIG. 2. The motorcycle is an example of a saddle-type vehicle in which a driver rides straddling the vehicle body 93. When the motorcycle turns a curve, the vehicle body 93 and the wheels are banked, so that the vehicle body 93 and the wheels tilt from the upright state about the longitudinal direction of the vehicle body 93 toward the inside of the curve, that is, the turning center side. Terms for expressing tilting the vehicle body 93 and the wheels during turning include bank, lean, roll, etc. In the present embodiment, the description will be made using bank.

[0009] As shown in FIG. 1, the vehicle 90 includes a front wheel 91 and a rear wheel 92 as wheels. The front wheel 91 is a steered wheel that can be operated via a steering operation member such as a handlebar. The rear wheel 92 is a drive wheel to which the driving force from the power source of the vehicle 90 is transmitted. An example of the power source of the vehicle 90 is an internal combustion engine. The power source is not limited to the internal combustion engine, and an electric motor or the like can also be adopted.

[0010] The vehicle 90 includes a suspension that connects the wheels and the vehicle body 93. The vehicle 90 includes, for example, a front fork that connects the front wheel 91 and the frame of the vehicle body 93. The vehicle 90 includes, for example, a swing arm that connects the rear wheel 92 and the frame of the vehicle body 93.

[0011] 〈Braking Device〉 As shown in FIG. 1, the vehicle 90 is provided with a braking device 70. An example of the braking device 70 is a friction braking device. FIG. 1 shows a hydraulic braking device as an example of the friction braking device.

[0012] The braking device 70 includes a front-wheel braking mechanism 81 corresponding to the front wheels 91 and a rear-wheel braking mechanism 82 corresponding to the rear wheels 92. The front-wheel braking mechanism 81 can apply a braking force to the front wheels 91. The rear-wheel braking mechanism 82 can apply a braking force to the rear wheels 92. Each braking mechanism 81, 82 is composed of a wheel cylinder, a rotating body that rotates integrally with the wheel, and a friction material that can be pressed against the rotating body. An example of the braking mechanisms 81, 82 is a disc brake. The braking mechanisms 81, 82 may be drum brakes.

[0013] As shown in FIG. 1, the braking device 70 includes a first master cylinder 71 and a second master cylinder 72. The braking device 70 includes a hydraulic pressure adjustment device 73 to which brake fluid is supplied from the first master cylinder 71 and the second master cylinder 72. The hydraulic pressure adjustment device 73 includes a hydraulic passage connecting the first master cylinder 71 and the wheel cylinder of the front-wheel braking mechanism 81. The hydraulic pressure adjustment device 73 includes a hydraulic passage connecting the second master cylinder 72 and the wheel cylinder of the rear-wheel braking mechanism 82.

[0014] The first master cylinder 71 is connected to a braking operation member for the front wheels 91 that can be operated by the driver of the vehicle 90. The first master cylinder 71 generates hydraulic pressure according to the operation amount of the braking operation member for the front wheels 91. The hydraulic pressure generated by the first master cylinder 71 is referred to as the front-wheel MC pressure. An example of the braking operation member for the front wheels 91 is a brake lever. The brake lever is attached to the handlebar of the vehicle 90.

[0015] The second master cylinder 72 is connected to a braking operation member for the rear wheels 92 that can be operated by the driver of the vehicle 90. The second master cylinder 72 generates hydraulic pressure according to the operation amount of the braking operation member for the rear wheels 92. The hydraulic pressure generated by the second master cylinder 72 is referred to as the rear-wheel MC pressure. An example of the braking operation member for the rear wheels 92 is a brake pedal. The brake pedal is disposed near the step of the vehicle 90.

[0016] In the front-wheel braking mechanism 81, brake fluid is supplied from the first master cylinder 71 to the wheel cylinder. The front-wheel braking mechanism 81 can generate a frictional braking force on the front wheels 91 according to the hydraulic pressure in the wheel cylinder.

[0017] In the rear-wheel braking mechanism 82, brake fluid is supplied from the second master cylinder 72 to the wheel cylinder. The rear-wheel braking mechanism 82 can generate a frictional braking force on the rear wheels 92 according to the hydraulic pressure in the wheel cylinder.

[0018] Each braking mechanism 81, 82 is configured such that the higher the hydraulic pressure in the wheel cylinder, the greater the force pressing the friction material against the rotating body. That is, each braking mechanism 81, 82 can apply a greater braking force to the wheels as the hydraulic pressure in the wheel cylinder increases. The hydraulic pressure in the wheel cylinder is an example of a value indicating the pressing force for pressing the friction material against the rotating body.

[0019] The hydraulic pressure adjustment device 73 can adjust the hydraulic pressure supplied to the wheel cylinders of each braking mechanism 81, 82. For example, the hydraulic pressure adjustment device 73 includes a pump, a motor for driving the pump, and a solenoid valve. The hydraulic pressure is adjusted by controlling the motor and the solenoid valve. Note that the hydraulic pressure adjustment device 73 may be constituted by a device having a liquid passage connected to the first master cylinder 71 and a device having a liquid passage connected to the second master cylinder 72.

[0020] <Sensor> Vehicle 90 is equipped with various sensors. FIG. 1 shows, as an example of various sensors, a first wheel speed sensor SE1, a second wheel speed sensor SE2, and a behavior detection sensor SE3. Detection signals from the various sensors are input to the braking control device 10.

[0021] The first wheel speed sensor SE1 and the second wheel speed sensor SE2 are sensors that detect the wheel speed VW of the wheels. The braking control device 10 can calculate the wheel speed VW of the front wheels 91 based on the detection signal from the first wheel speed sensor SE1. The braking control device 10 can calculate the wheel speed VW of the rear wheels 92 based on the detection signal from the second wheel speed sensor SE2. The braking control device 10 can calculate the vehicle body speed VS based on each wheel speed VW. The vehicle body speed VS indicates the traveling speed of the vehicle 90. Also, the braking control device 10 can calculate the wheel acceleration DVW, for example, by time-differentiating the wheel speed VW.

[0022] The behavior detection sensor SE3 is an inertial sensor that detects the behavior of the vehicle 90. The behavior detection sensor SE3 is attached to the vehicle body 93 of the vehicle 90. The behavior detection sensor SE3 is, for example, a sensor unit composed of an acceleration sensor and a gyro sensor. The braking control device 10 can calculate the longitudinal acceleration, lateral acceleration, vertical acceleration, pitch rate, roll rate, and yaw rate based on the detection signal from the behavior detection sensor SE3.

[0023] 〈Braking Control Device〉 The braking control device 10 has a function of controlling the hydraulic pressure adjustment device 73. The braking control device 10 can adjust the braking force applied to the front wheels 91 and the braking force applied to the rear wheels 92 respectively by controlling the hydraulic pressure adjustment device 73.

[0024] Hereinafter, control for the front wheels 91 among the wheels of the vehicle 90 will be described. In the following description, detection values or calculated values such as the wheel speed VW, the wheel acceleration DVW, and values calculated based on the wheel acceleration DVW are values related to the front wheels 91 that are the control targets. Note that the braking control device 10 can perform the same control for the rear wheels 92 as the control for the front wheels 91.

[0025] The braking control device 10 is a processing circuit configured by a plurality of functional units that execute various controls. FIG. 1 shows, as an example of the functional units, a sideslip acceleration calculation unit 11, a filter processing unit 12, and an ABS control unit 13. Each functional unit included in the braking control device 10 can transmit and receive information to and from each other.

[0026] The sideslip acceleration calculation unit 11 calculates a sideslip acceleration Gssb, which is the acceleration of a sideslip in which the wheel moves in the lateral direction with respect to the traveling direction of the wheel or the vehicle body 93. As an example, the sideslip acceleration Gssb generated in the front wheels 91 will be described. The sideslip acceleration calculation unit 11 can calculate the sideslip acceleration Gssb based on, for example, the following relational expression (Expression 1).

[0027]

Equation

[0028] The bank angle θ will be described with reference to FIG. 2. The bank angle θ can be calculated as the inclination angle of the vehicle body 93. For example, the bank angle θ is calculated based on the lateral acceleration and the roll rate.

[0029] Figure 2 shows a state in which the vehicle 90 in an upright state, where the vehicle body 93 and the wheels are perpendicular to the horizontal road surface RD, is viewed from the front. As shown by the white arrow in Figure 2, the vehicle 90 can tilt to the left or right. The tilt angle of the vehicle body 93 at this time is the bank angle θ. The bank angle θ is set to "0" when the vehicle 90 is in an upright state, that is, when the vehicle 90 is perpendicular to the horizontal plane. The bank angle θ is calculated as a positive value when the vehicle body 93 is tilted to one side. In this case, the greater the tilt of the vehicle body 93, the larger the value of the bank angle θ. The bank angle θ is calculated as a negative value when the vehicle body 93 is tilted to the other side. In this case, the greater the tilt of the vehicle body 93, the smaller the value of the bank angle θ. That is, the larger the absolute value of the bank angle θ, the greater the tilt of the vehicle body 93. In the present embodiment, the description is made assuming that the road surface is horizontal.

[0030] According to the above relational expression (Expression 1), the sideslip acceleration Gssb has different positive and negative values depending on the direction of the sideslip. In the present embodiment, the sideslip acceleration calculation unit 11 calculates the sideslip acceleration Gssb so that the greater the sideslip acceleration in the positive direction, the greater the sideslip acceleration in the acceleration direction. For example, when the bank angle θ is negative, the sideslip acceleration calculation unit 11 multiplies the value calculated according to the above relational expression (Expression 1) by "-1".

[0031] The filter processing unit 12 performs filter processing for suppressing fluctuations in the sideslip acceleration in the deceleration direction with respect to the sideslip acceleration during the execution of the ABS control. The filter processing unit 12 performs low-pass filter processing.

[0032] As shown in FIG. 3, the filter processing unit 12 acquires the lateral sliding acceleration Gssb from the lateral sliding acceleration calculation unit 11. The filter processing unit 12 performs low-pass filter processing on the lateral sliding acceleration Gssb with a cut-off frequency fc, and calculates the processed value as the filtered lateral sliding acceleration Gsslp. The filtered lateral sliding acceleration Gsslp is a value from which components having a frequency higher than the cut-off frequency fc are removed. The cut-off frequency fc can be set to a value of 1.0 Hz or less, for example. The upper limit of the value that can be set as the cut-off frequency fc is preferably 0.75 Hz, and more preferably 0.5 Hz.

[0033] The ABS control unit 13 can perform antilock brake control to suppress wheel lock during braking of the vehicle 90. The ABS control unit 13 starts ABS control when the ABS start condition is satisfied. The ABS start condition is determined to be satisfied, for example, when the slip amount of the wheel is equal to or greater than a threshold value. The slip amount of the wheel can be calculated based on the vehicle body speed VS and the wheel speed VW. When the ABS control unit 13 starts ABS control, it operates the braking device 70 so as to adjust the braking force according to the slip amount. According to the ABS control, the slip amount is reduced by switching between a pressure reduction control for reducing the braking force, a holding control for keeping the braking force constant, and a pressure increase control for increasing the braking force, according to the slip amount. In the pressure reduction control, a specified gradient is set as the reduction gradient for reducing the braking force. In the pressure increase control, a specified gradient is set as the pressure increase gradient for increasing the braking force. Note that increasing the pressure means increasing the pressing force, which corresponds to increasing the hydraulic pressure in the wheel cylinder. Reducing the pressure means reducing the pressing force, which corresponds to reducing the hydraulic pressure in the wheel cylinder. Holding corresponds to holding the hydraulic pressure in the wheel cylinder. In the ABS control of the present embodiment, there are a pressure reduction mode and a pressure increase mode as control modes. In the pressure reduction mode, pressure reduction control and holding control are performed. In the pressure increase mode, pressure increase control is performed.

[0034] During the execution of ABS control, the yaw rate suppression control unit 13 performs yaw rate suppression processing to suppress the yaw of the vehicle 90. The yaw rate suppression processing is processing aimed at causing the resultant force of the longitudinal force and the lateral force to fall within the friction circle by reducing the longitudinal force. Although details will be described later, by performing the yaw rate suppression processing, the yaw rate suppression control unit 13 reduces the braking force applied to the wheels when the yaw acceleration is large in the acceleration direction compared to when it is not so.

[0035] In order to execute the yaw rate suppression processing, the yaw rate suppression control unit 13 acquires the yaw acceleration of the vehicle 90 as the control yaw acceleration Gss. As shown in FIG. 3, the yaw acceleration Gssb is input to the yaw rate suppression control unit 13 from the yaw acceleration calculation unit 11. The filtered yaw acceleration Gsslp is input to the yaw rate suppression control unit 13 from the filter processing unit 12. The yaw rate suppression control unit 13 uses the yaw acceleration Gssb or the filtered yaw acceleration Gsslp as the control yaw acceleration Gss.

[0036] Using FIG. 4, the flow of the processing executed by the yaw rate suppression control unit 13 will be described. This processing routine is repeatedly executed at a predetermined cycle. When this processing routine is started, first, the yaw rate suppression control unit 13 executes the processing of step S101. If the yaw rate suppression control unit 13 is performing ABS control (S101: YES), the processing proceeds to step S102.

[0037] In step S102, if the control mode of the ABS control is the pressure reduction mode (S102: YES), the yaw rate suppression control unit 13 proceeds to step S103. In step S103, the yaw rate suppression control unit 13 determines whether the yaw acceleration is tending to decrease. Here, for example, when the current yaw acceleration Gssb(n) is smaller than the previous filtered yaw acceleration Gsslp(n - 1), the yaw rate suppression control unit 13 determines that the yaw acceleration is tending to decrease. On the other hand, when the current yaw acceleration Gssb(n) is greater than or equal to the previous filtered yaw acceleration Gsslp(n - 1), the yaw rate suppression control unit 13 determines that the yaw acceleration is not tending to decrease.

[0038] When the lateral sliding acceleration is decreasing (S103: YES), the ABS control unit 13 proceeds to step S104. On the other hand, when the lateral sliding acceleration is not decreasing (S103: NO), the ABS control unit 13 proceeds to step S107.

[0039] In step S104, the ABS control unit 13 sets the filtered lateral sliding acceleration Gsslp as the control lateral sliding acceleration Gss. Then, the ABS control unit 13 ends this processing routine. That is, when the ABS control is in the pressure reduction mode and the lateral sliding acceleration is decreasing, the filtered lateral sliding acceleration Gsslp is set as the control lateral sliding acceleration Gss.

[0040] In step S107, the ABS control unit 13 sets the lateral sliding acceleration Gssb as the control lateral sliding acceleration Gss. Then, the ABS control unit 13 ends this processing routine. That is, when the ABS control is in the pressure reduction mode and the lateral sliding acceleration is not decreasing, the lateral sliding acceleration Gssb is set as the control lateral sliding acceleration Gss.

[0041] In the process of step S101, when the ABS control is not being performed (S101: NO), the ABS control unit 13 proceeds to step S107. Then, the ABS control unit 13 ends this processing routine with the lateral sliding acceleration Gssb as the control lateral sliding acceleration Gss.

[0042] In the process of step S102, when the control mode of the ABS control is not the pressure reduction mode (S102: NO), the ABS control unit 13 proceeds to step S105. In step S105, when the control mode of the ABS control is not the pressure increase mode (S105: NO), the ABS control unit 13 proceeds to step S107. Then, the ABS control unit 13 ends this processing routine with the lateral sliding acceleration Gssb as the control lateral sliding acceleration Gss.

[0043] On the other hand, when the control mode of the ABS control is the boost mode (S105: YES), the ABS control unit 13 transfers the process to step S106. In step S106, when boosting has started (S106: YES), the ABS control unit 13 transfers the process to step S107. Thereafter, the ABS control unit 13 terminates this processing routine with the lateral slip acceleration Gssb as the control lateral slip acceleration Gss. That is, when the ABS control is in the boost mode and boosting has started, the lateral slip acceleration Gssb is set as the control lateral slip acceleration Gss.

[0044] In the process of step S106, when boosting has not started (S106: NO), the ABS control unit 13 transfers the process to step S103. Thereafter, when the lateral slip acceleration is decreasing (S103: YES), the ABS control unit 13 terminates this processing routine with the filtered lateral slip acceleration Gsslp as the control lateral slip acceleration Gss. That is, when the ABS control is in the boost mode but boosting has not started and the lateral slip acceleration is decreasing, the filtered lateral slip acceleration Gsslp is set as the control lateral slip acceleration Gss. On the other hand, when the lateral slip acceleration is not decreasing (S103: NO), the ABS control unit 13 terminates this processing routine with the lateral slip acceleration Gssb as the control lateral slip acceleration Gss. That is, when the ABS control is in the boost mode but boosting has not started and the lateral slip acceleration is not decreasing, the lateral slip acceleration Gssb is set as the control lateral slip acceleration Gss.

[0045] As described above, the ABS control unit 13 sets the control lateral slip acceleration Gss according to the control mode of the ABS control. The ABS control unit 13 sets the control lateral slip acceleration Gss according to whether the lateral slip acceleration is decreasing. Note that when the ABS control unit 13 starts to increase the braking force during the execution of the ABS control, it sets the lateral slip acceleration Gssb as the control lateral slip acceleration Gss.

[0046] Using FIG. 5, an example of the skid suppression process executed by the ABS control unit 13 will be described. The processing routine shown in FIG. 5 is repeatedly executed by the ABS control unit 13 during the implementation of ABS control.

[0047] When this processing routine starts, first in step S201, the ABS control unit 13 determines whether the control skid acceleration Gss exceeds the start determination value Gssth in the acceleration direction. Here, the start determination value Gssth is set to a positive value calculated in advance through experiments or the like. If the control skid acceleration Gss is less than or equal to the start determination value Gssth (S201: NO), the ABS control unit 13 temporarily ends this processing routine. On the other hand, if the control skid acceleration Gss is greater than the start determination value Gssth (S201: YES), the ABS control unit 13 proceeds to step S202.

[0048] In step S202, the ABS control unit 13 prohibits the recovery hold implemented in the pressure reduction mode. The recovery hold is to confirm whether the slip amount decreases during a predetermined period by holding the braking force constant during a predetermined period after reducing the braking force. In the process of step S202, this recovery hold is prohibited. As a result, the holding of the braking force by the recovery hold is no longer performed. After prohibiting the recovery hold, the ABS control unit 13 proceeds to step S203.

[0049] In step S203, the ABS control unit 13 increases the reduction gradient when reducing the braking force. As a result, the braking force reduced per unit time becomes larger. Then, the ABS control unit 13 proceeds to step S204.

[0050] In step S204, the ABS control unit 13 changes the rapid pressure increase start determination value. The rapid pressure increase start determination value is a threshold value set to start the rapid pressure increase process. The rapid pressure increase process is a process for quickly increasing the braking force when a rapid recovery of the wheel speed VW is detected during the implementation of ABS control. The ABS control unit 13 can start the rapid pressure increase process when the wheel acceleration DVW is greater than the rapid pressure increase start determination value. The rapid pressure increase start determination value is set as a prescribed positive value. For example, the rapid pressure increase start determination value can be set to a value of 3.0G or more. In the process of step S204, the ABS control unit 13 increases the rapid pressure increase start determination value. For example, the ABS control unit 13 changes the rapid pressure increase start determination value to 2 times or more of the prescribed value. As a result, the rapid pressure increase process will not start unless the wheel acceleration DVW is a larger value. When the rapid pressure increase start determination value is changed, the ABS control unit 13 ends this processing routine.

[0051] When the control lateral acceleration Gss decreases and becomes equal to or less than the start determination value Gssth, the ABS control unit 13 restores the changes made in steps S202 to S204. That is, the ABS control unit 13 permits recovery hold. The ABS control unit 13 decreases the decreasing gradient to a prescribed gradient. The ABS control unit 13 decreases the rapid pressure increase start determination value and changes it to the prescribed value.

[0052] The ABS control unit 13 can use the value after the filter processing by the filter processing unit 12 as the control lateral acceleration Gss during the period when the pressure reduction mode during the implementation of ABS control is being performed. According to the lateral slip suppression process executed by the ABS control unit 13, the brake device 70 is controlled as follows. When the control lateral acceleration Gss, which is a value in the acceleration direction, exceeds the start determination value Gssth in the acceleration direction, the braking force applied to the wheels is decreased compared to the case where the control lateral acceleration Gss does not exceed the start determination value Gssth in the acceleration direction.

[0053] <Function and Effect> The function and effect of this embodiment will be described. FIG. 6 shows an example of the case where the ABS control is performed by the ABS control unit 13. In FIG. 6, the example in the present embodiment is shown by a solid line. That is, the solid line is an example of the case where the filter lateral acceleration Gsslp is used. The dashed line in FIG. 6(a) indicates the vehicle body speed VS. The dashed line shown in FIG. 6(b) corresponds to the front wheel MC pressure. In FIG. 6(c), the control lateral acceleration Gss is shown by a solid line. In FIG. 6(c), the lateral acceleration Gssb is shown by a two-dot chain line.

[0054] In the example shown in FIG. 6, braking is started by the operation of the driver of the vehicle 90 from the timing t11. As shown by the solid line in FIG. 6(b), the braking force increases after the timing t11. As shown in FIG. 6(a), after the timing t11, the vehicle body speed VS and the wheel speed VW gradually deviate from each other. The difference between the vehicle body speed VS and the wheel speed VW corresponds to the slip amount.

[0055] As shown in FIG. 6(b), the ABS control is started from the timing t12. The pressure reduction mode is performed during the period from the timing t12 to the timing t15. From the timing t15, the pressure increase mode is started. In the example shown by the solid line in FIG. 6(b), the pressure increase is started without delay at the start of the pressure increase mode at the timing t15.

[0056] Before the timing t13, the lateral acceleration Gssb is set as the control lateral acceleration Gss. That is, as shown in Fig. 6(c), the control lateral acceleration Gss indicated by the solid line coincides with the lateral acceleration Gssb indicated by the chain double-dashed line. During the period from timing t13 to timing t15, since the lateral acceleration tends to decrease, the filtered lateral acceleration Gsslp is set as the control lateral acceleration Gss (S104). Therefore, during the period from timing t13 to timing t15, as shown in Fig. 6(c), the control lateral acceleration Gss indicated by the solid line has its variation in the deceleration direction suppressed as compared with the lateral acceleration Gssb indicated by the chain double-dashed line. By setting the cut-off frequency fc in the filter processing unit 12 to a preferable value, the filtered lateral acceleration Gsslp can be calculated so as to connect the vertices of the portions where the lateral acceleration Gssb indicated by the chain double-dashed line is convex upward. Thus, according to the braking control device 10, when the lateral acceleration tends to decrease, the filtered lateral acceleration Gsslp is set as the control lateral acceleration Gss, whereby the variation of the control lateral acceleration Gss in the deceleration direction can be suppressed.

[0057] In Fig. 6(a) and Fig. 6(b), the comparative examples are shown by the chain double-dashed lines. The comparative examples are cases where the lateral acceleration Gssb is used as the control lateral acceleration Gss even during the period in which the pressure reduction mode is performed in the example indicated by the solid line, that is, during the period from timing t12 to timing t15.

[0058] As shown in Fig. 6(c), the lateral slip acceleration Gssb is small during the period from timing t13 to timing t14. In the comparative example, since the lateral slip acceleration Gssb becomes small, as shown in Fig. 6(b), the increase in braking force starts at a timing t14 earlier than timing t15. Here, even if the acceleration of lateral slip becomes small after the occurrence of wheel lateral slip, the lateral slip may continue. Particularly on a low-μ road where the road surface friction coefficient is relatively low, the lateral slip tends to continue even when the acceleration of lateral slip becomes small. If the braking force is increased in such a case, there is a risk that the lateral slip is not eliminated and the stability of the vehicle decreases. In the case of the comparative example, as shown in Fig. 6(a), after timing t14, the decrease in the wheel speed VW is difficult to be eliminated, and slip and lateral slip are likely to occur again.

[0059] On the other hand, according to the braking control device 10, since the variation in the deceleration direction of the control lateral slip acceleration Gss is suppressed, it is possible to suppress the temporary decrease in the lateral slip acceleration as compared with the case of the comparative example shown by the two-dot chain line. For this reason, it is less likely that the lateral slip acceleration becomes larger than the start determination value again after the lateral slip acceleration becomes equal to or less than the start determination value. That is, the process of suppressing lateral slip is likely to continue without being terminated. As a result, it is possible to suppress the start of the increase in the braking force before the lateral slip is eliminated. Even if the road surface on which the vehicle 90 is traveling is a low-μ road, the stability of the vehicle can be ensured.

[0060] In the lateral slip suppression process, the braking control device 10 prohibits recovery holding. As a result, the period during which the braking force decreases is likely to be longer compared to the case where recovery holding is not prohibited. By prohibiting recovery holding, the braking force can be decreased even during the period when recovery holding is originally performed. For this reason, the braking force is more likely to be decreased.

[0061] In the lateral slip suppression process, the braking control device 10 increases the decreasing gradient of the braking force. As a result, the braking force is more likely to be decreased. In the braking control device 10, in the yaw slip suppression process, the rapid pressure increase start determination value is increased. As a result, the rapid pressure increase process is not started unless the wheel acceleration DVW is a larger value. By suppressing the start of the rapid pressure increase process, the decrease in braking force is more likely to continue.

[0062] (Modified example) This embodiment can be implemented with the following modifications. This embodiment and the following modified examples can be implemented in combination with each other within a technically non - conflicting range.

[0063] · In the above embodiment, the braking control device 10 changes the setting of the control yaw slip acceleration Gss according to whether or not the pressure increase is started in the pressure increase mode. Instead of this, when it is in the pressure increase mode, the yaw slip acceleration Gssb may be used as the control yaw slip acceleration Gss. That is, the processes of step S105 and step S106 shown in FIG. 4 may be omitted. In this case, when a negative determination is made in step S102, the process may proceed to step S107.

[0064] · The yaw slip suppression process in the above embodiment is an example. Any one of the processes shown in steps S202 to S204 may be performed, or any two of the processes may be performed. Also, yaw slip can be suppressed by a process different from the processes shown in steps S202 to S204.

[0065] · In the above embodiment, an example is shown in which when the bank angle θ is negative, the value calculated according to the above relational expression (Expression 1) is multiplied by “−1”, but this process is not essential. For example, the absolute value of the yaw slip acceleration Gssb calculated according to the above relational expression (Expression 1) may be used. In this case, when the control yaw slip acceleration Gss set based on the absolute value is larger than the start determination value, it can be determined that the yaw slip acceleration exceeds the start determination value in the acceleration direction.

[0066] Alternatively, for example, the lateral acceleration Gssb calculated according to the above relational expression (Expression 1) may be used as it is. In this case, it is advisable to use the start determination value as the first determination value and the value obtained by multiplying the start determination value by "-1" as the second determination value. According to this, when the lateral acceleration is greater than the first determination value, or when the lateral acceleration is less than the second determination value, it means that the lateral acceleration exceeds the start determination value in the acceleration direction.

[0067] · The braking control device 10, which is a processing circuit, may have any of the following configurations [a] to [c]. [a] A circuit including one or more processors that execute various processes according to a computer program. The processor includes a processing device. Examples of the processing device are a CPU, a DSP, and a GPU, etc. The processor includes a memory. Examples of the memory are a RAM, a ROM, and a flash memory, etc. The memory stores program codes or instructions configured to cause the processing device to execute the processing. The memory, that is, the computer-readable medium, includes any available medium accessible by a general-purpose or dedicated computer. [b] A circuit including one or more hardware circuits that execute various processes. Examples of the hardware circuit are an ASIC (Application Specific Integrated Circuit), a CPLD (Complex Programmable Logic Device), and an FPGA (Field Programmable Gate Array), etc. [c] A circuit including a processor that executes a part of various processes according to a computer program and a hardware circuit that executes the remaining processes of the various processes.

[0068] · A part of the functions realized by the braking control device 10 may be realized by other processing circuits connected to the braking control device 10. For example, the vehicle may be equipped with another control device having a function of calculating the longitudinal acceleration, lateral acceleration, vertical acceleration, pitch rate, roll rate, yaw rate, etc. based on the detection signal from the behavior detection sensor SE3.

[0069] ·In the above embodiment, a hydraulic braking device was exemplified as the friction braking device. The friction braking device is not limited to a hydraulic braking device, and may be a mechanical friction braking device that presses a friction material against a rotating body by mechanically transmitting the driving amount of an electric motor.

[0070] ·The braking control device 10 may be applied to a vehicle capable of applying braking force to the front wheels and the rear wheels based on the operation of one braking operation member. ·The vehicle 90 to which the braking control device 10 is applied is not limited to a motorcycle, and may be a three-wheeled vehicle or a four-wheeled vehicle as long as it is a vehicle capable of banking the vehicle body and wheels during turning. The three-wheeled vehicle may have two front wheels or two rear wheels. The vehicle 90 may be a vehicle in which only one of the front wheels and the rear wheels banks. Also, the vehicle 90 is not limited to a saddle-riding type vehicle.

[0071] ·In the above embodiment, the bank angle is detected based on the vertical direction, but the bank angle may be detected based on the direction perpendicular to the road surface. As a method for detecting the bank angle based on the direction perpendicular to the road surface, for example, there are the following methods. Note that the method for detecting the bank angle is not limited to the exemplified method.

[0072] One example is a method of installing a sensor such as an ultrasonic distance sensor on a banking part of the vehicle and detecting the bank angle based on the distance between a predetermined position and the road surface. Another example is, for example, in the case where there are a banking part and a non-banking part in the above three-wheeled vehicle, installing a sensor such as a rotation angle sensor or a displacement sensor at the connection part between the banking part and the non-banking part and detecting the angle formed by both connected parts. An example of the banking part is a part of the vehicle including the front wheels, and an example of the non-banking part is a part of the vehicle including the rear wheels.

Explanation of Signs

[0073] 10…Braking control device 11…Acceleration calculation unit 12…Filter processing unit 13…ABS control unit 70…Brake device 81…Front wheel braking mechanism 82…Rear wheel braking mechanism 90…Vehicle 91…Front wheel 92…Rear wheel 93…Vehicle body SE1…First wheel speed sensor SE2…Second wheel speed sensor SE3…Behavior detection sensor

Claims

1. A braking control device that is applied to a vehicle capable of banking the vehicle body and wheels during turning and controls a braking device that applies a braking force to the wheels, a lateral slip acceleration calculation unit that calculates a lateral slip acceleration, which is an acceleration of lateral slip in which the wheels move laterally with respect to the traveling direction of the wheels or the vehicle body, an ABS control unit that performs antilock brake control to decrease the braking force applied to the wheels and increase the braking force applied to the wheels based on the slip amount of the wheels, and a filter processing unit that performs a filter process to suppress a change in the lateral slip acceleration in the deceleration direction with respect to the lateral slip acceleration during the execution of the antilock brake control. The ABS control unit executes a lateral slip suppression process during the execution of the antilock brake control, and the lateral slip suppression process is a process of decreasing the braking force applied to the wheels when the lateral slip acceleration after the filter process by the filter processing unit is large in the acceleration direction compared to when it is not. Braking control device.

2. During a specified period while the ABS control unit is performing the antilock brake control, the value after the filter process by the filter processing unit is used as a control lateral slip acceleration. In the lateral slip suppression process, when the control lateral slip acceleration, which is a value in the acceleration direction, exceeds a specified start determination value in the acceleration direction, the braking force applied to the wheels is decreased compared to when the control lateral slip acceleration does not exceed the start determination value in the acceleration direction. The braking control device according to Claim 1.

3. The specified period is a period in which the braking force applied to the wheels is decreased. The braking control device according to Claim 2. ​

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