JP7707880B2 - Brake Control Device - Google Patents

Description

The present invention relates to a braking control device for a vehicle that can tilt the body and wheels when turning.

In vehicles such as motorcycles, where the body and wheels can be tilted when turning, the gyro effect that accompanies the rotation of the wheels contributes to the stability of the vehicle. Patent Document 1 discloses a control device that suppresses wheel skid in such a vehicle. The control device disclosed in Patent Document 1 reduces the braking force when the wheel skid acceleration is equal to or greater than a threshold value, thereby reducing the longitudinal force and suppressing the lateral skid by making the resultant longitudinal force and lateral force fall within a friction circle.

International Publication No. 2013/014945

Even if the skid acceleration decreases after the wheel skid occurs, the skid may continue. In other words, if the control to suppress the skid is terminated just because the skid acceleration becomes smaller than the threshold value, the skid may not be resolved and the stability of the vehicle may decrease.

The braking control device for solving the above problem is applied to a vehicle that can bank the vehicle body and wheels when turning, and controls a braking device that applies braking force to the wheels. The braking control device includes a skid acceleration calculation unit that calculates a skid acceleration, which is the acceleration of a skid in which the wheel moves laterally relative to the traveling direction of the wheel or the vehicle body, an ABS control unit that performs anti-lock brake control that reduces the braking force applied to the wheel and increases the braking force applied to the wheel based on the amount of slip of the wheel, and a filter processing unit that performs a filter process on the skid acceleration to suppress fluctuations in the deceleration direction of the skid acceleration while the anti-lock brake control is being performed, and the ABS control unit executes a skid suppression process while the anti-lock brake control is being performed, and the skid suppression process is a process that reduces the braking force applied to the wheel when the skid acceleration after filtering by the filter processing unit is large in the acceleration direction compared to when this is not the case.

According to the above configuration, the filter process makes it difficult for the skid acceleration to suddenly change in the deceleration direction. This makes it easier to continue the skid suppression process, which is a process that reduces the braking force when the skid acceleration is large in the acceleration direction. In other words, the braking force is more likely to be reduced while anti-lock brake control (hereinafter sometimes referred to as "ABS control") is being implemented. This makes it easier to reduce the longitudinal force, making it easier to eliminate skid.

FIG. 1 is a schematic diagram showing an embodiment of a vehicle braking control device and a vehicle that is an object to be controlled by the braking control device. FIG. 2 is a front view showing the vehicle. FIG. 3 is a block diagram showing the brake control device. FIG. 4 is a flowchart showing the flow of the process executed by the brake control device. FIG. 5 is a flowchart showing the flow of the skid suppression process executed by the brake control device. FIG. 6 is a diagram showing the transition of the sideslip acceleration filtered by the brake control device, and the transition of the wheel speed and the braking force controlled by the brake control device.

Hereinafter, an embodiment of a brake control device will be described with reference to FIGS.
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. A motorcycle is an example of a saddle-ride type vehicle in which a driver straddles a body 93 to ride. When a motorcycle turns a curve, the body 93 and wheels are banked, so that the body 93 and wheels are tilted from an upright state to the inside of the curve, i.e., toward the center of the turn, with the fore-and-aft direction of the body 93 as an axis. Terms used to describe the tilting of the body 93 and wheels when turning include bank, lean, roll, and the like. In this embodiment, a description will be given using bank.

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

The vehicle 90 has a suspension that connects the wheels to the body 93. The vehicle 90 has, for example, a front fork that connects the front wheel 91 to the frame of the body 93. The vehicle 90 has, for example, a swing arm that connects the rear wheel 92 to the frame of the body 93.

<Brake device>
As shown in Fig. 1, a 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.

The braking device 70 includes a front wheel braking mechanism 81 corresponding to the front wheel 91, and a rear wheel braking mechanism 82 corresponding to the rear wheel 92. The front wheel braking mechanism 81 can apply a braking force to the front wheel 91. The rear wheel braking mechanism 82 can apply a braking force to the rear wheel 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 also be drum brakes.

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 adjusting device 73 to which brake fluid is supplied from the first master cylinder 71 and the second master cylinder 72. The hydraulic pressure adjusting device 73 includes a hydraulic passage that connects the first master cylinder 71 and the wheel cylinder of the front wheel braking mechanism 81. The hydraulic pressure adjusting device 73 includes a hydraulic passage that connects the second master cylinder 72 and the wheel cylinder of the rear wheel braking mechanism 82.

The first master cylinder 71 is connected to a brake operating 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 amount of operation of the brake operating member for the front wheels 91. The hydraulic pressure generated by the first master cylinder 71 is called the front wheel MC pressure. An example of a brake operating member for the front wheels 91 is a brake lever. The brake lever is attached to the handlebar of the vehicle 90.

The second master cylinder 72 is connected to a brake operating 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 amount of operation of the brake operating member for the rear wheels 92. The hydraulic pressure generated by the second master cylinder 72 is called the rear wheel MC pressure. An example of a brake operating member for the rear wheels 92 is a brake pedal. The brake pedal is located near the step of the vehicle 90.

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 fluid pressure in the wheel cylinder.

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 wheel 92 according to the fluid pressure in the wheel cylinder.

Each braking mechanism 81, 82 is configured so that the higher the hydraulic pressure in the wheel cylinder, the greater the force with which the friction material is pressed against the rotating body. In other words, each braking mechanism 81, 82 can apply a greater braking force to the wheel the higher the hydraulic pressure in the wheel cylinder. The hydraulic pressure in the wheel cylinder is an example of a value that indicates the pressure with which the friction material is pressed against the rotating body.

The hydraulic pressure adjusting device 73 can adjust the hydraulic pressure supplied to the wheel cylinders of each of the braking mechanisms 81, 82. For example, the hydraulic pressure adjusting device 73 includes a pump, a motor that drives the pump, and a solenoid valve. The hydraulic pressure is adjusted by controlling the motor and the solenoid valve. The hydraulic pressure adjusting device 73 may be configured with a device having a hydraulic line connected to the first master cylinder 71 and a device having a hydraulic line connected to the second master cylinder 72.

Sensors
The vehicle 90 is equipped with various sensors. In Fig. 1, a first wheel speed sensor SE1, a second wheel speed sensor SE2, and a behavior detection sensor SE3 are shown as examples of the various sensors. Detection signals from the various sensors are input to the brake control device 10.

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 brake 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 brake 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 brake 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. In addition, the brake control device 10 can calculate the wheel acceleration DVW, for example, by differentiating the wheel speed VW with respect to time.

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 body 93 of the vehicle 90. The behavior detection sensor SE3 is a sensor unit that is composed of, for example, 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.

Braking control device
The brake control device 10 has a function of controlling the hydraulic pressure adjusting device 73. The brake control device 10 can adjust the braking force applied to the front wheels 91 and the braking force applied to the rear wheels 92 by controlling the hydraulic pressure adjusting device 73.

The following describes control for the front wheels 91 of the vehicle 90. In the following description, detected 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 object of control. Note that the braking control device 10 can also perform control similar to the control for the front wheels 91, but for the rear wheels 92.

The braking control device 10 is a processing circuit that is composed of multiple functional units that execute various types of control. FIG. 1 shows a sideslip acceleration calculation unit 11, a filter processing unit 12, and an ABS control unit 13 as examples of functional units. Each functional unit of the braking control device 10 is capable of transmitting and receiving information to and from each other.

The lateral slip acceleration calculation unit 11 calculates the lateral slip acceleration Gssb, which is the acceleration of the lateral slip of the wheel moving laterally relative to the traveling direction of the wheel or vehicle body 93. As an example, the lateral slip acceleration Gssb occurring in the front wheel 91 will be described. The lateral slip acceleration calculation unit 11 can calculate the lateral slip acceleration Gssb based on the following relational expression (Equation 1), for example.

In the relational expression (Equation 1), ωz represents the detected value of the yaw rate. θ represents the bank angle. g represents the gravitational acceleration. Ay represents the detected value of the lateral acceleration. If represents the horizontal distance between the sensor that detects the lateral acceleration and the center of the target wheel. In other words, If is the horizontal distance between the mounting position of the behavior detection sensor SE3 and the center of the front wheel 91.

The bank angle θ will be explained using 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.

2 shows the vehicle 90 in an upright state with the body 93 and wheels perpendicular to the horizontal road surface RD, as viewed from the front. The vehicle 90 can tilt to the left or right as shown by the white arrow in FIG. 2. The tilt angle of the body 93 at this time is the bank angle θ. The bank angle θ is set to "0" when the vehicle 90 is upright, i.e., when the vehicle 90 is perpendicular to the horizontal plane. The bank angle θ is calculated as a positive value when the body 93 is tilted to one side. In this case, the more the body 93 is tilted, the larger the bank angle θ. The bank angle θ is calculated as a negative value when the body 93 is tilted to the other side. In this case, the more the body 93 is tilted, the smaller the bank angle θ. In other words, the larger the absolute value of the bank angle θ, the more the body 93 is tilted. In this embodiment, the road surface is described as being horizontal.

According to the above relational equation (Equation 1), the sideslip acceleration Gssb has a positive or negative value depending on the direction of the sideslip. In this embodiment, the sideslip acceleration calculation unit 11 calculates the sideslip acceleration Gssb so that the greater the value of the sideslip acceleration in the positive direction, the greater the sideslip acceleration in the accelerating 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 equation (Equation 1) by "-1."

The filter processing unit 12 performs a filter process on the sideslip acceleration during ABS control to suppress fluctuations in the deceleration direction of the sideslip acceleration. The filter processing unit 12 performs low-pass filtering.

As shown in FIG. 3, the filter processing unit 12 acquires the sideslip acceleration Gssb from the sideslip acceleration calculation unit 11. The filter processing unit 12 performs low-pass filtering on the sideslip acceleration Gssb using the cutoff frequency fc, and calculates the processed value as the filtered sideslip acceleration Gsslp. The filtered sideslip acceleration Gsslp is a value from which frequency components higher than the cutoff frequency fc have been removed. The cutoff frequency fc can be set to a value of, for example, 1.0 Hz or less. The upper limit of the value that can be set as the cutoff frequency fc is preferably 0.75 Hz, and more preferably 0.5 Hz.

The ABS control unit 13 can implement anti-lock brake control that suppresses wheel locking during braking of the vehicle 90. The ABS control unit 13 starts ABS control when an ABS start condition is satisfied. The ABS start condition is determined to be satisfied, for example, when the amount of slip of the wheels is equal to or greater than a threshold value. The amount of slip of the wheels can be calculated based on the vehicle speed VS and the wheel speed VW. When the ABS control unit 13 starts ABS control, it operates the braking device 70 to adjust the braking force according to the amount of slip. According to the ABS control, the amount of slip is reduced by switching between a pressure reduction control that reduces the braking force, a holding control that keeps the braking force constant, and a pressure increase control that increases the braking force according to the amount of slip. In the pressure reduction control, a prescribed gradient is set as a reduction gradient that reduces the braking force. In the pressure increase control, a prescribed gradient is set as a pressure increase gradient that increases the braking force. Note that pressure increase means increasing the pressing force, which corresponds to increasing the hydraulic pressure in the wheel cylinder. Pressure reduction means decreasing the pressing force, which corresponds to decreasing the hydraulic pressure in the wheel cylinder. "Holding" corresponds to holding the hydraulic pressure in the wheel cylinder. In the ABS control of this embodiment, there are a pressure reduction mode and a pressure increase mode as control modes. In the pressure reduction mode, pressure reduction control and pressure holding control are performed. In the pressure increase mode, pressure increase control is performed.

The ABS control unit 13 performs skid suppression processing to suppress skid of the vehicle 90 while ABS control is being executed. The skid suppression processing is intended to reduce the longitudinal force so that the resultant force of the longitudinal force and the lateral force falls within the friction circle. Details will be described later, but by performing the skid suppression processing, the ABS control unit 13 reduces the braking force applied to the wheels when the lateral slip acceleration is large in the acceleration direction, compared to when this is not the case.

To execute the skid suppression process, the ABS control unit 13 acquires the acceleration of the skid of the vehicle 90 as the control skid acceleration Gss. As shown in FIG. 3, the ABS control unit 13 receives the skid acceleration Gssb from the skid acceleration calculation unit 11. The ABS control unit 13 receives the filtered skid acceleration Gsslp from the filter processing unit 12. The ABS control unit 13 uses the skid acceleration Gssb or the filtered skid acceleration Gsslp as the control skid acceleration Gss.

The flow of processing executed by the ABS control unit 13 will be described with reference to Fig. 4. This processing routine is repeatedly executed at predetermined intervals.
When this processing routine is started, first, the ABS control unit 13 executes the processing of step S101. If the ABS control is being performed (S101: YES), the ABS control unit 13 proceeds to the processing of step S102.

In step S102, if the control mode of the ABS control is the pressure reduction mode (S102: YES), the ABS control unit 13 proceeds to step S103.
In step S103, the ABS control unit 13 judges whether or not the sideslip acceleration is decreasing. Here, the ABS control unit 13 judges that the sideslip acceleration is decreasing, for example, when the current sideslip acceleration Gssb(n) is smaller than the previous filtered sideslip acceleration Gsslp(n-1). On the other hand, the ABS control unit 13 judges that the sideslip acceleration is not decreasing, when the current sideslip acceleration Gssb(n) is equal to or larger than the previous filtered sideslip acceleration Gsslp(n-1).

If the skid acceleration is decreasing (S103: YES), the ABS control unit 13 proceeds to step S104. On the other hand, if the skid acceleration is not decreasing (S103: NO), the ABS control unit 13 proceeds to step S107.

In step S104, the ABS control unit 13 sets the filtered sideslip acceleration Gsslp as the control sideslip acceleration Gss. After that, the ABS control unit 13 ends this processing routine. In other words, when the ABS control is in the pressure reduction mode and the sideslip acceleration is tending to decrease, the filtered sideslip acceleration Gsslp is set as the control sideslip acceleration Gss.

In step S107, the ABS control unit 13 sets the skid acceleration Gssb as the control skid acceleration Gss. After that, the ABS control unit 13 ends this processing routine. In other words, when the ABS control is in the pressure reduction mode and the skid acceleration is not decreasing, the skid acceleration Gssb is set as the control skid acceleration Gss.

If ABS control is not being performed in the process of step S101 (S101: NO), the ABS control unit 13 proceeds to step S107. After that, the ABS control unit 13 sets the skid acceleration Gssb as the control skid acceleration Gss, and ends this processing routine.

In the process of step S102, if 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, if the control mode of the ABS control is not the pressure increase mode (S105: NO), the ABS control unit 13 proceeds to step S107. Thereafter, the ABS control unit 13 sets the skid acceleration Gssb as the control skid acceleration Gss, and ends this processing routine.

On the other hand, if the control mode of the ABS control is the boost mode (S105: YES), the ABS control unit 13 proceeds to step S106. If boosting has started in step S106 (S106: YES), the ABS control unit 13 proceeds to step S107. Thereafter, the ABS control unit 13 sets the skid acceleration Gssb as the control skid acceleration Gss and ends this processing routine. In other words, if the ABS control is in the boost mode and boosting has started, the skid acceleration Gssb is set as the control skid acceleration Gss.

In the process of step S106, if pressure increase has not started (S106: NO), the ABS control unit 13 proceeds to step S103. After that, if the skid acceleration is decreasing (S103: YES), the ABS control unit 13 sets the filtered skid acceleration Gsslp as the control skid acceleration Gss and ends this process routine. That is, if the ABS control is in the boost mode but pressure increase has not started and the skid acceleration is decreasing, the filtered skid acceleration Gsslp is set as the control skid acceleration Gss. On the other hand, if the skid acceleration is not decreasing (S103: NO), the ABS control unit 13 sets the skid acceleration Gssb as the control skid acceleration Gss and ends this process routine. That is, if the ABS control is in the boost mode but pressure increase has not started and the skid acceleration is not decreasing, the skid acceleration Gssb is set as the control skid acceleration Gss.

As described above, the ABS control unit 13 sets the control skid acceleration Gss according to the control mode of the ABS control. The ABS control unit 13 sets the control skid acceleration Gss according to whether or not the skid acceleration is tending to decrease. When the ABS control unit 13 starts to increase the braking force while ABS control is being performed, it sets the skid acceleration Gssb as the control skid acceleration Gss.

An example of the skid suppression process executed by the ABS control unit 13 will be described with reference to FIG. 5. The process routine shown in FIG. 5 is repeatedly executed by the ABS control unit 13 while ABS control is being performed.

When this processing routine is started, 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, etc. If the control skid acceleration Gss is equal to or less than 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.

In step S202, the ABS control unit 13 prohibits recovery hold that is performed in the pressure reduction mode. Recovery hold is a process in which the braking force is held constant for a predetermined period of time after the braking force is reduced, thereby checking whether the amount of slippage decreases during the predetermined period of time. In the process of step S202, this recovery hold is prohibited. As a result, the braking force is no longer maintained by recovery hold. When recovery hold is prohibited, the ABS control unit 13 transitions to the process of step S203.

In step S203, the ABS control unit 13 increases the gradient of the decrease in the braking force. As a result, the braking force that is decreased per unit time increases. After that, the ABS control unit 13 transitions the process to step S204.

In step S204, the ABS control unit 13 changes the sudden increase pressure start judgment value. The sudden increase pressure start judgment value is a threshold value that is set for starting the sudden increase pressure processing. The sudden increase pressure processing is a process for quickly increasing the braking force when a sudden recovery of the wheel speed VW is detected during the implementation of ABS control. The ABS control unit 13 can start the sudden increase pressure processing when the wheel acceleration DVW is larger than the sudden increase pressure start judgment value. The sudden increase pressure start judgment value is set as a specified positive value. For example, the sudden increase pressure start judgment value can be set to a value of 3.0 G or more. In the process of step S204, the ABS control unit 13 increases the sudden increase pressure start judgment value. For example, the ABS control unit 13 changes the sudden increase pressure start judgment value to a value twice the specified value or more. As a result, the sudden increase pressure processing will not be started unless the wheel acceleration DVW is a larger value. When the sudden increase pressure start judgment value is changed, the ABS control unit 13 ends this processing routine.

When the control skid 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 reduces the decrease gradient to a specified gradient. The ABS control unit 13 reduces the sudden pressure increase start determination value to a specified value.

The ABS control unit 13 can use the value filtered by the filter processing unit 12 as the control skid acceleration Gss during the period when the pressure reduction mode is being performed while ABS control is being performed. According to the skid suppression process performed by the ABS control unit 13, the braking device 70 is controlled as follows. When the control skid 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 reduced compared to when the control skid acceleration Gss does not exceed the start determination value Gssth in the acceleration direction.

<Action and Effects>
The operation and effects of this embodiment will be described.
Fig. 6 shows an example of the case where ABS control is performed by the ABS control unit 13. In Fig. 6, an example in this embodiment is shown by a solid line. That is, the solid line is an example of the case where the filtered skid acceleration Gsslp is used. The dashed line in Fig. 6(a) shows 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 skid acceleration Gss is shown by a solid line. In Fig. 6(c), the skid acceleration Gssb is shown by a two-dot chain line.

In the example shown in FIG. 6, braking is initiated by the driver of the vehicle 90 at time t11. As shown by the solid line in FIG. 6(b), the braking force increases after time t11. As shown in FIG. 6(a), after time t11, the vehicle speed VS and the wheel speed VW gradually diverge. The difference between the vehicle speed VS and the wheel speed VW corresponds to the amount of slip.

As shown in FIG. 6B, ABS control is started at time t12. The pressure reduction mode is performed from time t12 to time t15. The pressure increase mode is started at time t15. In the example shown by the solid line in FIG. 6B, pressure increase is started without delay from the start of the pressure increase mode at time t15.

In the period before timing t13, the side-slip acceleration Gssb is set as the control side-slip acceleration Gss. That is, as shown in FIG. 6C, the control side-slip acceleration Gss shown by the solid line coincides with the side-slip acceleration Gssb shown by the two-dot chain line. In the period from timing t13 to timing t15, the side-slip acceleration is on a decreasing trend, so the filter side-slip acceleration Gsslp is set as the control side-slip acceleration Gss (S104). Therefore, in the period from timing t13 to timing t15, as shown in FIG. 6C, the control side-slip acceleration Gss shown by the solid line is less likely to fluctuate in the deceleration direction than the side-slip acceleration Gssb shown by the two-dot chain line. By setting the cutoff frequency fc in the filter processing unit 12 to a preferred value, the filter side-slip acceleration Gsslp can be calculated so as to connect the vertices of the part of the side-slip acceleration Gssb shown by the two-dot chain line that is convex upward. In this way, according to the braking control device 10, when the skid acceleration is on a decreasing trend, the filter skid acceleration Gsslp is set as the control skid acceleration Gss, thereby suppressing fluctuations in the control skid acceleration Gss in the deceleration direction.

In Figures 6(a) and 6(b), a comparative example is shown by a two-dot chain line. The comparative example is an example in which the side-slip acceleration Gssb is used as the control side-slip acceleration Gss even during the period in which the pressure reduction mode is performed in the example shown by the solid line, that is, the period from timing t12 to timing t15.

As shown in FIG. 6C, the skid acceleration Gssb is small from time t13 to time t14. As the skid acceleration Gssb is small, in the comparative example, as shown in FIG. 6B, the braking force starts to increase from time t14, which is earlier than time t15. Here, even if the acceleration of the skid decreases after the wheel skid occurs, the skid may continue. In particular, on a low μ road with a relatively low road friction coefficient, the skid is likely to continue even if the acceleration of the skid decreases. In such a case, if the braking force is increased, the skid may not be resolved and the stability of the vehicle may decrease. In the comparative example, as shown in FIG. 6A, the decrease in the wheel speed VW is difficult to resolve after time t14, making it easier for slip and skid to occur again.

In contrast, according to the brake control device 10, by suppressing fluctuations in the deceleration direction with respect to the control skid acceleration Gss, it is possible to suppress a temporary decrease in the skid acceleration compared to the comparative example shown by the two-dot chain line. Therefore, it is difficult for the skid acceleration to become greater than the start judgment value again after it has fallen below the start judgment value. In other words, the process of suppressing skid is likely to continue without being terminated. This makes it possible to suppress the start of an increase in the braking force before the skid is resolved. It is possible to ensure the stability of the vehicle 90 even if the road surface on which the vehicle 90 is traveling is a low μ road.

The brake control device 10 prohibits recovery hold during skid prevention processing. This makes it easier for the period during which the braking force is reduced to be longer than when recovery hold is not prohibited. By prohibiting recovery hold, the braking force can be reduced even during periods when recovery hold would normally be performed. This makes it easier for the braking force to be reduced.

In the skid prevention process, the brake control device 10 increases the gradient of the decrease in the braking force, thereby making it easier for the braking force to be decreased.
In the skid prevention process, the brake control device 10 increases the sudden pressure increase start determination value. As a result, the sudden pressure increase process is not started unless the wheel acceleration DVW has a larger value. By suppressing the start of the sudden pressure increase process, the reduction in the braking force is more likely to continue.

(Example of change)
This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that they are not technically inconsistent.

- In the above embodiment, the brake control device 10 changes the setting of the control skid acceleration Gss depending on whether or not pressure increase has started in the boost mode. Alternatively, in the boost mode, the skid acceleration Gssb may be set to the control skid acceleration Gss. In other words, the processing of steps S105 and S106 shown in FIG. 4 may be omitted. In this case, if a negative determination is made in step S102, the processing may proceed to step S107.

The skid 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. In addition, skid suppression may be performed by a process different from the processes shown in steps S202 to S204.

In the above embodiment, the value calculated according to the above relational expression (Equation 1) is multiplied by "-1" when the bank angle θ is negative. However, this process is not essential.
For example, the absolute value of the sideslip acceleration Gssb calculated according to the above-mentioned relational expression (Equation 1) may be used. In this case, if the control sideslip acceleration Gss set based on the absolute value is greater than the start determination value, it can be determined that the sideslip acceleration exceeds the start determination value in the accelerating direction.

Also, for example, the skid acceleration Gssb calculated according to the above relational expression (Equation 1) may be used as is. In this case, the start judgment value may be used as the first judgment value, and the value obtained by multiplying the start judgment value by "-1" may be used as the second judgment value. According to this, when the skid acceleration is greater than the first judgment value, or when the skid acceleration is less than the second judgment value, it is determined that the skid acceleration exceeds the start judgment value in the acceleration direction.

The braking control device 10, which is a processing circuit, may have any of the following configurations [a] to [c]. [a] A circuit having one or more processors that execute various processes according to a computer program. The processor has a processing device. Examples of the processing device are a CPU, a DSP, and a GPU. The processor has a memory. Examples of the memory are a RAM, a ROM, and a flash memory. The memory stores program code or instructions configured to cause the processing device to execute the processes. The memory, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or special-purpose computer. [b] A circuit having 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). [c] A circuit having a processor that executes some of the various processes according to a computer program and a hardware circuit that executes the remaining processes of the various processes.

Some of the functions implemented by the brake control device 10 may be implemented by another processing circuit connected to the brake control device 10 .
For example, the vehicle may be equipped with another control device having a function of calculating longitudinal acceleration, lateral acceleration, vertical acceleration, pitch rate, roll rate, yaw rate, etc. based on the detection signal from the behavior detection sensor SE3.

- In the above embodiment, a hydraulic braking device is exemplified as a 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 force of an electric motor.

The brake control device 10 may be applied to a vehicle in which braking forces can be applied to the front wheels and the rear wheels based on the operation of a single brake operating member.
The vehicle 90 to which the brake 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 the vehicle body and wheels can be banked when turning. A three-wheeled vehicle may be a vehicle with two front wheels or a vehicle with two rear wheels. The vehicle 90 may be a vehicle in which only one of the front and rear wheels can bank. Furthermore, the vehicle 90 is not limited to a saddle-ride type vehicle.

- In the above embodiment, the bank angle is detected based on the vertical direction, but the bank angle may be detected based on a direction perpendicular to the road surface. The following methods, for example, can be used to detect the bank angle based on a direction perpendicular to the road surface. Note that the method of detecting the bank angle is not limited to the exemplified method.

One example is a method of installing a sensor such as an ultrasonic distance sensor on the banking portion of the vehicle and detecting the bank angle based on the distance between a predetermined position and the road surface.
Another example is a method in which, for example, in the case of a three-wheeled vehicle having a banking portion and a non-banking portion, a sensor such as a rotation angle sensor or a displacement sensor is installed at the connection between the banking portion and the non-banking portion to detect the angle between the two connected portions. An example of a banking portion is a portion of the vehicle including the front wheels, and an example of a non-banking portion is a portion of the vehicle including the rear wheels.

REFERENCE SIGNS LIST 10 Brake control device 11 Acceleration calculation section 12 Filter processing section 13 ABS control section 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 (3)

A brake control device that is applied to a vehicle that can bank a vehicle body and wheels when turning, and controls a brake device that applies a braking force to the wheels, comprising:
a sideslip acceleration calculation unit that calculates a sideslip acceleration, which is an acceleration of a sideslip caused by the wheel moving in a lateral direction relative to a traveling direction of the wheel or the vehicle body;
an ABS control unit that performs antilock brake control by decreasing a braking force applied to the wheel and increasing a braking force applied to the wheel based on an amount of slip of the wheel;
a filter processing unit that performs a filter process on the sideslip acceleration to suppress fluctuations of the sideslip acceleration in a deceleration direction while the antilock brake control is being performed,
The ABS control unit executes a skid suppression process while the antilock brake control is being performed,
The skid suppression process is a process for reducing the braking force applied to the wheels when the skid acceleration after the filtering process by the filtering processor is large in the acceleration direction, compared to when the skid acceleration is not large. 2. The brake control device according to claim 1, wherein the ABS control unit sets a value after filtering by the filtering unit as a control skid acceleration during a specified period while the anti-lock brake control is being performed, and in the skid suppression process, when the control skid acceleration, which is a value in the acceleration direction, exceeds a specified start determination value in the acceleration direction, the ABS control unit reduces the braking force applied to the wheels compared to when the control skid acceleration does not exceed the start determination value in the acceleration direction. The brake control device according to claim 2 , wherein the specified period is a period during which the braking force applied to the wheel is reduced.