JP7259249B2 - Braking control device - Google Patents

Description

The present invention relates to a braking control device.

Some braking control devices are capable of executing control (downhill control) for the vehicle to travel downhill at a constant speed. On the other hand, many braking control devices are configured to perform anti-skid control to reduce the braking force on the wheels according to changes in the slip ratios of the wheels. Here, for example, in the device disclosed in Japanese Unexamined Patent Application Publication No. 2006-224946, execution of antiskid control is suppressed in order to reliably maintain the target speed on a downhill road. Specifically, in this device, the set slip ratio, which is the threshold for determining whether antiskid control can be executed, is set larger than the normal value during downhill control, thereby suppressing the execution of antiskid control.

JP 2006-224946 A

However, in the above device, although the execution frequency of the antiskid control is suppressed, the road surface condition of the downhill road is not taken into consideration when executing the antiskid control, and there is room for improvement.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a braking control device capable of executing anti-skid control in accordance with the road surface conditions on a downhill road and improving the vehicle speed retention accuracy. With the goal.

The present invention provides a method for controlling a wheel speed related to a wheel speed of a vehicle during execution of downhill control for applying a braking force to the wheels of the vehicle so that the vehicle speed does not exceed a target vehicle speed when the vehicle is running on a downhill road. A braking control device that performs anti-skid control to reduce the braking force on the wheels in accordance with a change in value, wherein the degree of intervention of the anti-skid control is reduced based on a road surface condition during execution of the downhill control. a determination unit for determining whether or not to reduce the intervention degree of the antiskid control when the determination unit determines that the antiskid control intervention degree should be decreased; and a regenerative braking device that applies regenerative braking force to the wheels. In the specific control, the degree of intervention of the antiskid control is reduced by reducing the degree of reduction of the regenerative braking force in the antiskid control .

For example, when the road surface changes from a normal road surface to a road surface on which anti-skid control is executed, and then returns to the normal road surface, on a downhill road, when the normal road surface is restored, anti-skid control is performed. There is a possibility that the vehicle speed will increase due to the influence of the decrease in braking force due to the execution of the control. However, according to the present invention, the amount of reduction in braking force due to anti-skid control becomes smaller depending on the road surface conditions. Power, that is, high braking force can be exhibited. That is, according to the present invention, anti-skid control can be executed in accordance with road surface conditions on a downhill road, and vehicle speed retention accuracy can be improved.

1 is a configuration diagram of a vehicle braking system including a braking control system of this embodiment; FIG. It is an explanatory view for explaining specific control of this embodiment. It is an explanatory view for explaining the 2nd modification of this embodiment.

An embodiment of the present invention will be described below with reference to the drawings. Each figure used for explanation is a conceptual diagram. As shown in FIG. 1, the vehicle braking device A of this embodiment includes a braking control device 1, a hydraulic braking device 2, a regenerative braking device 3, and wheels 41, 42, 43, and 44. there is For example, wheel 41 is the right front wheel, wheel 42 is the left front wheel, wheel 43 is the right rear wheel, and wheel 44 is the left rear wheel. Each wheel 41-44 is provided with a wheel speed sensor 6 for detecting the wheel speed. The wheel speed sensor 6 transmits the detection result (wheel speed information) to the braking control device 1 . The vehicle is also equipped with a plurality of sensors 7 for detecting longitudinal acceleration, lateral acceleration, vertical acceleration, yaw rate, pitching rate, and the like. A detection result of each sensor 7 is transmitted to the braking control device 1 . The hydraulic braking device 2 and the regenerative braking device 3 are known devices, and will be briefly described below with an example.

The hydraulic braking device 2 generates hydraulic pressure (wheel pressure) in wheel cylinders 51, 52, 53, and 54 provided on each of the wheels 41 to 44, thereby applying hydraulic braking force (friction braking force) to the wheels 41 to 44. ) is a device that generates The hydraulic braking device 2 includes a master cylinder mechanism 21 that generates a master pressure according to a driver's brake operation, an actuator 22 that is supplied with the master pressure and adjusts the pressure of each wheel, and wheels 41 to 44 that control the wheel pressure according to the wheel pressure. and a friction braking device 23 for generating a braking force.

The actuator 22 is a known ESC actuator, and is composed of a plurality of solenoid valves, an electric pump, a reservoir, etc. (not shown). The actuator 22 can independently perform pressurization control, depressurization control, holding control, or the like for each of the wheel cylinders 51 to 54 based on a command from the braking control device 1 . Further, the actuator 22 can perform anti-skid control (ABS control), skid prevention control, etc. based on the command from the braking control device 1 .

The friction braking device 23 is, for example, a disc brake device or a drum brake device, and is provided for each wheel 41-44. Each friction braking device 23 is provided with a corresponding wheel cylinder 51-54. The higher the wheel pressure, the higher the hydraulic braking force applied to the wheels 41-44.

The regenerative braking device 3 is a device that applies regenerative braking force to the wheels 41-44. The regenerative braking device 3 includes a hybrid ECU, a generator, an inverter, and a battery (not shown). The hybrid ECU and the braking control device 1 execute cooperative regenerative control such as setting a target regenerative braking force and a target hydraulic braking force for a target deceleration. A detailed description of the regenerative braking device 3 is omitted.

The braking control device 1 is an ECU (electronic control unit) including a microcomputer or the like, and is a device that controls the hydraulic braking device 2 and the regenerative braking device 3 . The braking control device 1 calculates a target deceleration (target braking force) of the vehicle based on the driving conditions or the driver's braking operation, and calculates a target wheel pressure (target hydraulic braking force) for each wheel 41 to 44 based on the target deceleration. ) and set the target regenerative braking force. The braking control device 1 controls the actuator 22 according to each target wheel pressure.

The braking control device 1 is configured to be able to execute descending slope control that applies braking force to the wheels of the vehicle so that the vehicle speed does not exceed a target vehicle speed when the vehicle is running on a descending slope. The braking control device 1 executes descending slope control in accordance with an instruction (operation) from the driver. The braking control device 1 controls the actuator 22 to keep the vehicle speed constant at a predetermined target speed in descending slope control, thereby controlling the braking force.

In addition, the braking control device 1 performs anti-skid control to reduce the braking force on the wheels 41-44 in accordance with changes in the slip ratios or wheel decelerations of the wheels 41-44. Based on the detection result of the wheel speed sensor 6, the braking control device 1 detects the wheels 41 to 44 whose wheel-related values regarding the wheel speed exceed a predetermined threshold value, and executes antiskid control for the detected wheels 41 to 44. do. A wheel-related value is a slip ratio or wheel deceleration that can be calculated using wheel speed. The braking control device 1 controls the actuator 22 to perform antiskid control. The braking control device 1 performs anti-skid control even during execution of downhill control.

(specific control)
The braking control device 1 is configured to be able to execute specific control that changes the degree of intervention of antiskid control in accordance with the road surface condition during antiskid control during downhill control. Specifically, the braking control device 1 has a determination section 11 and a control section 12 as functions.

The determination unit 11 determines the road surface condition during execution of downhill control. For example, based on the detection results of the wheel speed sensor 6 and the plurality of sensors 7, the determination unit 11 determines whether the wheels 41 to 44 have entered a step (recess). For example, when the wheel-related value (for example, the slip ratio) of the wheels 41 increases sharply and the forward acceleration of the vehicle slightly increases, the determination unit 11 determines that the wheels 41 enter a step and the vehicle slightly accelerates. Therefore, it can be determined that the road surface is in a "stepped state". The determination unit 11 of the present embodiment determines the road surface condition (in this case, whether or not there is a step) based on a determination condition different from the determination condition on whether antiskid control can be executed. Note that the step determination can be performed using the pitching rate, the detection result of the image sensor, or the like, and a known determination method can be applied.

As another example of grasping the road surface condition, the determination unit 11 can also estimate the road surface condition ahead based on the road surface data of the navigation system 8 using the position information by GPS. For example, information such as travel data of other vehicles and road maintenance conditions accumulated in the external server is transmitted to the navigation system 8 by wireless communication or the like, and road surface condition information is updated. The determination unit 11 can determine whether or not there is uneven ground such as a step or mud ahead based on the road surface condition information from the navigation system 8 and the position of the host vehicle.

Then, the determining unit 11 determines whether or not the degree of intervention of the anti-skid control should be reduced based on the determined (estimated) road surface condition during execution of the descending slope control. If the determination unit 11 determines that the road surface condition is a stepped state, the determination unit 11 determines that the intervention degree of the antiskid control should be reduced. Determination of the degree of intervention by the determining unit 11, for example, when the change in the wheel-related value is one of the determining factors, as in the step determination described above, results in, for example, the antiskid It is done just before control execution.

When the determining unit 11 determines that the antiskid control intervention degree should be reduced, the control unit 12 reduces the antiskid control intervention degree more than when the determining unit 11 determines that the antiskid control intervention degree should not be decreased. Execute specific control that reduces the degree of antiskid control intervention. That is, as shown in FIG. 2, when the determination unit 11 determines that the intervention degree of the antiskid control should be reduced, the control unit 12 controls the normal braking force reduction amount in the antiskid control (reduction of the wheel pressure). Anti-skid control is performed with a smaller amount of braking force reduction than the amount). When the specific control is executed, the braking force reduction amount is reduced, and the braking force applied to the wheels 41-44 is maintained higher than that of normal antiskid control. A situation in which the determination unit 11 determines that the antiskid control intervention degree should not be reduced corresponds to a situation in which the determination unit 11 does not determine that the antiskid control intervention degree should be reduced. The determination unit 11 determines whether specific control should be executed according to road surface conditions.

According to this embodiment, it is possible to reduce the amount of reduction in braking force due to antiskid control according to the road surface conditions, and to suppress an increase in vehicle speed after antiskid control is executed, which may occur when traveling on a downhill road. In other words, the braking control device 1 detects a specific road surface condition that is likely to change from a road surface with a relatively high coefficient of friction to a road surface with a relatively low coefficient of friction, and then quickly change to a road surface with a relatively high coefficient of friction, before executing antiskid control. Judgment/estimation and execution of specific control. As a result, even in such a situation, the braking force can be maintained at a high level, and the vehicle speed can be maintained with high accuracy.

For example, if the road surface ahead is uneven terrain such as a small depression or mud, anti-skid control is executed when the vehicle enters a small uneven terrain on a downhill road, and anti-skid control is executed when the vehicle exceeds the uneven terrain. There is a possibility that the vehicle speed will increase due to the effect of the decrease in braking force due to the execution of However, according to this embodiment, since specific control is executed according to the road surface condition, braking force that is relatively similar to that before antiskid control can be exerted even after overcoming a small uneven terrain. As described above, according to the present embodiment, it is possible to perform anti-skid control according to the road surface conditions on a downhill road, and improve the accuracy of maintaining the vehicle speed.

To give a more specific example, when the wheels 41 enter a step, the wheels 41 are temporarily separated from the ground, and the friction coefficient of the road surface of the wheels 41 is reduced. Then, when the wheel 41 comes into contact with the ground and goes over the step, the coefficient of friction recovers (increases). In this step-over state, the friction coefficient increases, and the reduction in braking force due to anti-skid control directly leads to a reduction in the braking force of the vehicle. According to the present embodiment, when the wheels 41 enter a bump, anti-skid control and specific control are executed, so it is possible to suppress an increase in vehicle speed after the vehicle climbs over the bump due to a decrease in braking force.

Further, when executing the specific control, the controller 12 reduces the intervention degree of the anti-skid control as the gradient of the downhill road increases. As a result, even in a state where the tendency of the vehicle speed to increase due to gravity is high, it is possible to more appropriately suppress the increase in the vehicle speed after the execution of the anti-skid control. The slope of the downhill road can be calculated based on the detection result (acceleration) of the sensor 7, for example.

Note that even when the road surface becomes uneven and the specific control is executed, it is conceivable that the uneven road continues for a long time contrary to the determination by the determination unit 11 . This can be detected, for example, by the wheel-related value not recovering for a predetermined period of time. In this case, the determination unit 11 determines that the specific control should be stopped, and accordingly the control unit 12 stops the specific control. In other words, even if a road surface condition contrary to the judgment of the judging section 11 appears, appropriate anti-skid control can be executed. The determination by the determination unit 11 that the specific control should be stopped corresponds to the determination by the determination unit 11 that the degree of antiskid control intervention should not be reduced.

(First modification)
The determination unit 11 may determine that the anti-skid control intervention degree should be reduced by a predetermined amount or a predetermined ratio, using execution of downhill control as a trigger. That is, the determination unit 11 determines that the road surface condition is off-road because the descending slope control is selected. The control unit 12 reduces the amount of decrease in the braking force by a predetermined amount or a predetermined ratio when executing the anti-skid control during execution of the downhill control. In other words, the control unit 12 executes the suppressed anti-skid control during execution of the downhill control.

Then, the determination unit 11 determines whether or not to stop the specific control based on the road surface condition during execution of the specific control. For example, when the road surface changes from a relatively high friction coefficient state to a relatively low friction coefficient state, the anti-skid control (anti-skid control+specific control) suppressed as described above is executed. If the wheel-related value (slip ratio, etc.) does not recover within a predetermined period of time during execution of the specific control, the determination unit 11 determines that the road surface with a relatively low coefficient of friction continues, and should stop the specific control. judge. In this case, the control unit 12 stops the specific control and returns to normal antiskid control. As a result, the grip force of the wheels 41 to 44 can be maximized according to the road surface conditions, and the vehicle speed can be prevented from exceeding the target vehicle speed.

The predetermined time for the stop determination of the specific control may be set, for example, to the time required to travel a distance corresponding to the wheelbase at the target vehicle speed. This predetermined time corresponds to the time from when the front wheels 41 and 42 enter the rough terrain until the rear wheels 43 and 44 enter the rough terrain. In this case, it can be estimated that the front wheels 41 and 42 continue to be on the uneven ground, and that the rear wheels 43 and 44 are likely to be on the uneven ground as well, because the wheel-related values do not recover for the predetermined time. When the front and rear wheels 41 to 44 are on uneven ground, stopping the specific control and switching to normal anti-skid control allows the wheels 41 to 44 to exert an appropriate gripping force. In other words, stopping the specific control in such a situation improves the vehicle speed retention accuracy.

(Second modification)
Further, the control unit 12 may reduce the degree of reduction of the braking force of the vehicle during the antiskid control by at least a predetermined value or a predetermined ratio when executing the antiskid control while the downhill control is being executed. In other words, the control unit 12 may execute anti-skid control for descending slope control in which the degree of intervention is set to be small in advance.

In this case, as shown in FIG. 3, the regenerative braking device 3 applies a predetermined regenerative braking force to the wheels 41 so that at least part of the braking force of the vehicle is exerted by the regenerative braking force during downhill control. to 44. According to this configuration, a reduction in braking force due to anti-skid control is suppressed during execution of downhill control, so an increase in vehicle speed after execution of anti-skid control can be suppressed, and electric power generated by regenerative braking force can be recovered. becomes. That is, it is possible to improve the accuracy of holding the vehicle speed and improve the fuel efficiency.

For example, as shown by the dotted line in FIG. 3, when anti-skid control is executed with a normal braking force reduction amount during execution of downhill control, the target braking force is relatively large each time anti-skid control is executed. will decrease in proportion. On this premise, when executing cooperative control in which the target braking force is achieved by the sum of the hydraulic braking force and the regenerative braking force, it is necessary to control the increase and decrease of the regenerative braking force in accordance with the execution of the anti-skid control. Control becomes very complicated. However, as in the second modified example, if anti-skid control for downhill control, in which the degree of decrease in braking force is relatively small during execution of downhill control, is executed, a certain amount of large constant regenerative braking force can be obtained. generated, there is no need to change the regenerative braking force by anti-skid control, and it can be dealt with only by changing the hydraulic braking force. In other words, it is possible to collect a large amount of electric power through simple control in addition to improving the vehicle speed retention accuracy.

As in the first modification, the configuration of this second modification assumes that the road surface is off-road when the downhill control is started. It can also be said that the configuration continues to determine that the degree should be reduced. However, even in the configuration of the second modification, the determination unit 11 determines the road surface condition, and the control unit 12 determines the determination result of the determination unit 11 with respect to the braking force reduction amount of the anti-skid control for downhill control. , the braking force reduction amount may be further reduced.

Further, as shown in FIG. 3, the braking control device 1 is configured to achieve the target braking force with the regenerative braking force and the hydraulic braking force even during downhill control. Alternatively, the antiskid control intervention degree may be reduced by reducing the reduction degree of the regenerative braking force in the antiskid control. When normal anti-skid control is executed, the braking control device 1 must reduce not only the hydraulic braking force but also the regenerative braking force, as indicated by the dotted line in FIG. However, according to the above configuration, as shown by the solid line in FIG. ), the anti-skid control in the specific control can be executed only by reducing the hydraulic braking force. This makes it possible to improve fuel efficiency.

(others)
The present invention is not limited to the above embodiments. For example, the braking control device 1 can reduce the degree of intervention of the antiskid control to the limit. good too. The degree of antiskid control intervention can also be said to be a braking force reduction amount for reducing the braking force by antiskid control.

DESCRIPTION OF SYMBOLS 1... Braking control apparatus, 11... Judgment part, 12... Control part, 2... Hydraulic braking apparatus, 3... Regenerative braking apparatus, 41-44... Wheel, 51-54... Wheel cylinder, 6... Wheel speed sensor.

Claims (1)

During execution of downhill control for applying braking force to the wheels of the vehicle so that the vehicle speed does not exceed a target vehicle speed when traveling on a downhill road, changes in wheel-related values relating to the wheel speed of the wheels. A braking control device that executes anti-skid control to reduce the braking force on the wheel accordingly,
a determination unit that determines whether or not the degree of intervention of the anti-skid control should be reduced based on the road surface condition during execution of the downhill control;
When the determination unit determines that the degree of intervention of the antiskid control should be reduced, the antiskid control is more effective than when the determination unit determines that the degree of intervention of the antiskid control should not be reduced. a control unit that executes specific control that reduces the degree of control intervention;
A regenerative braking device that applies regenerative braking force to the wheels,
The braking control device, wherein the control unit reduces the degree of intervention of the antiskid control by reducing the degree of reduction of the regenerative braking force in the antiskid control in the specific control.

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