JP2004224306A - Brake control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the delay of boosting control from occurring when wheels ride over a step on a road surface in braking while avoiding the deterioration of feeling in braking on a flat road with a high coefficient of friction in a brake control device for a vehicle controlled by a pressure regulation control means controlled by the operation of a pressure regulating means so as to perform anti-lock brake control for switching the reduction, holding, and boosting of brake fluid pressure. <P>SOLUTION: A wheel acceleration/deceleration speed calculated by a wheel acceleration/deceleration calculation means 20 is differentiated by a differentiating means 21. A step ride over determination means 22 determines that a vehicle is in a step ride over state when the differentiated value of the wheel acceleration/deceleration exceeds a threshold at the time of braking in a non-antilock brake control state. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a pressure adjusting means capable of adjusting a brake fluid pressure acting on a wheel brake during a braking operation, and a pressure reducing means for reducing a brake fluid pressure acting on a wheel brake when a wheel is likely to be locked during braking. And a pressure control means for controlling the operation of the pressure control means so as to execute antilock brake control for switching between holding and pressure increase.
[0002]
[Prior art]
Conventionally, such a vehicle brake control device is already known, for example, from Patent Document 1 and the like.
[0003]
[Patent Document 1]
JP-B 64-70256 [0004]
[Problems to be solved by the invention]
By the way, there is a case where a wheel gets over a step on a road surface at the time of braking, and in this case, the wheel speed drops rapidly due to the wheel floating off the road surface, and the vehicle may go in a locking direction. When the anti-lock brake control is executed in response to such a rapid change in the wheel speed, the brake fluid pressure of the wheel brake is reduced, but the wheel reaction force recovers even if the wheel touches the ground. Since the pressure-reducing state is maintained until this time, the state in which the brake fluid pressure of the wheel brakes is low will continue for a long time, causing inconveniences such as a delay in the pressure increase control. Therefore, in the above-described conventional device, when the wheel acceleration / deceleration exceeds a threshold value, it is determined that the vehicle is over a step, based on a change in wheel speed when the vehicle crosses a step. However, if the state of overcoming a step is determined using wheel acceleration / deceleration, there is a possibility that the state of overcoming a step is erroneously determined under the influence of vehicle acceleration / deceleration.
[0005]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vehicle brake control device that can accurately determine a state over a step without being affected by vehicle acceleration / deceleration. I do.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes a pressure adjusting means capable of adjusting a brake fluid pressure acting on a wheel brake during a braking operation, and a pressure adjusting means for controlling when a wheel is likely to fall into a locked state during braking. A brake control device for controlling the operation of the pressure control means so as to execute antilock brake control for switching between reduction, holding and pressure increase of brake fluid pressure acting on the wheel brake. A wheel speed detector, wheel acceleration / deceleration calculating means for calculating wheel acceleration / deceleration from wheel speeds detected by the wheel speed detector, and wheel acceleration / deceleration calculated by the wheel acceleration / deceleration calculation means. A differentiating means for differentiating the deceleration, and a stepping over state according to a differential value of the wheel acceleration / deceleration obtained by the differentiating means at the time of braking in a non-antilock brake control state being equal to or larger than a threshold. Characterized in that it comprises a a determining step overcome determining means that.
[0007]
According to such a configuration, the differential value of the wheel acceleration / deceleration becomes equal to or larger than the threshold value based on the fact that the wheel speed suddenly rises instantaneously when the wheel passes over the step during braking. It is determined that the vehicle is over a step, and the differential value of the wheel acceleration / deceleration is used without using the wheel acceleration / deceleration. The overcoming state can be determined.
[0008]
According to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, the pressure regulation control means starts within a predetermined time after the step overrun determination section determines that the vehicle is over a step. The operation of the pressure regulating means is controlled so that the pressure increasing rate in the first pressure increasing mode of the anti-lock brake control is larger than that in the non-stepping over state. Since the pressure increase rate in the first pressure increase mode in the anti-lock brake control started due to the step over is set to be higher than that in the non-step over state, the delay in the pressure increase control is prevented. Can be. Especially on a road surface with a high coefficient of friction, the feeling of vehicle deceleration depends on the pressure increase rate.Therefore, by increasing the pressure increase rate by judging that the vehicle is over a step, the feeling of braking can be worsened. It can be effectively avoided.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described based on an embodiment of the present invention shown in the attached drawings.
[0010]
1 to 4 show one embodiment of the present invention. FIG. 1 is a hydraulic circuit diagram of a vehicle brake device, FIG. 2 is a block diagram showing a partial configuration of a control unit, and FIG. FIG. 4 is a timing chart of differential values of wheel acceleration / deceleration, wheel speed and brake fluid pressure, and FIG. 4 is a diagram showing changes in differential values of wheel acceleration / deceleration and wheel acceleration / deceleration with respect to vehicle body acceleration / deceleration. .
[0011]
First, in FIG. 1, a tandem type master cylinder M is provided with first and second output ports 1A and 1B for generating a brake fluid pressure according to a depression force applied to a brake pedal P by a vehicle driver, and is used for a left front wheel. Wheel brake 2A, right rear wheel brake 2B, right front wheel brake 2C, left rear wheel brake 2D, and first and second individually connected to the first and second output ports 1A, 1B. Pressure adjusting means 4 is provided between the output hydraulic pressure paths 3A and 3B, and first and second proportional pressure reducing valves 5A and 5B are provided between the pressure adjusting means 4 and the right and left rear wheel brakes 2B and 2D. Are interposed respectively.
[0012]
The pressure adjusting means 4 includes first, second, third and third wheel brakes respectively corresponding to the front left wheel brake 2A, the rear right wheel brake 2B, the front right wheel brake 2C and the rear left wheel brake 2D. 4 normally-open solenoid valves 6A to 6D, first, second, third and fourth check valves 7A to 7D connected in parallel to the normally-open solenoid valves 6A to 6D, respectively, and the wheel brakes 2A. , 2, 3, and 4 normally closed solenoid valves 8 A to 8 D individually corresponding to the first and second output hydraulic pressure paths 3 A, 3 B, respectively. Drives two reservoirs 9A, 9B, plunger-type first and second pumps 10A, 10B connected to first and second reservoirs 9A, 9B via suction valves 11A, 11B, respectively, and both pumps 10A, 10B. One common electric motor 12 Comprises the normally open solenoid valves 6A-6D, and a control unit 16 for controlling the operation of the normally closed solenoid valve 8A~8D and the electric motor 12.
[0013]
The first normally open solenoid valve 6A is provided between the first output hydraulic pressure passage 3A and the left front wheel brake 2A, and the second normally open solenoid valve 6B is provided between the first output hydraulic pressure passage 3A and the first proportional hydraulic passage 3A. The third normally open solenoid valve 6C is provided between the pressure reducing valve 5A, the third normally open solenoid valve 6C is provided between the second output hydraulic pressure passage 3B and the right front wheel brake 2C, and the fourth normally open solenoid valve 6D is provided with the second output solenoid valve 6D. It is provided between the hydraulic path 3B and the second proportional pressure reducing valve 5B.
[0014]
The first to fourth check valves 7A to 7D are connected in parallel to the normally open solenoid valves 6A to 6D so as to allow the flow of the brake fluid from the corresponding wheel brakes 2A to 2D to the master cylinder M. Is done.
[0015]
The first normally closed solenoid valve 8A is provided between the left front wheel brake 2A and the first reservoir 9A, and the second normally closed solenoid valve 8B is provided between the first proportional pressure reducing valve 5A and the first reservoir 9A. The third normally closed solenoid valve 8C is provided between the right front wheel brake 2C and the second reservoir 9B, and the fourth normally closed solenoid valve 8D is provided between the second proportional pressure reducing valve 5B and the second reservoir 9B. Is provided.
[0016]
During normal braking, in which there is no possibility that each wheel locks, such pressure adjusting means 4 connects between the master cylinder M and the wheel brakes 2A to 2D and shuts off between the wheel brakes 2A to 2D and the reservoirs 9A and 9B. I do. That is, the normally-open solenoid valves 6A to 6D are demagnetized and opened, and the normally-closed solenoid valves 8A to 8D are demagnetized and closed, and output from the first output port 1A of the master cylinder M. The brake fluid pressure acts on the left front wheel brake 2A via the first normally open solenoid valve 6A, and acts on the right rear wheel via the second normally open solenoid valve 6B and the first proportional pressure reducing valve 5A. Acts on the wheel brake 2B. The brake fluid pressure output from the second output port 1B of the master cylinder M acts on the right front wheel brake 2C via the third normally-open solenoid valve 6C, and also acts on the fourth normally-open solenoid valve 6D. It acts on the left rear wheel brake 2D via the second proportional pressure reducing valve 5B.
[0017]
When the wheels are about to enter the locked state during the above-described braking, the pressure adjusting means 4 shuts off the master cylinder M and the wheel brakes 2A to 2D at a portion corresponding to the wheels about to enter the locked state. At the same time, communication is made between the wheel brakes 2A to 2D and the reservoirs 9A and 9B. That is, among the first to fourth normally-open solenoid valves 6A to 6D, the normally-open solenoid valves corresponding to the wheels that are about to enter the locked state are excited and closed, and the first to fourth normally-closed solenoid valves are opened. Of the solenoid valves 8A to 8D, the normally closed solenoid valves corresponding to the wheels are excited and opened. As a result, a part of the brake fluid pressure of the wheel that is about to enter the locked state is absorbed by the first reservoir 9A or the second reservoir 9B, and the brake fluid pressure of the wheel that is about to enter the locked state is reduced. .
[0018]
When the brake fluid pressure is kept constant, the pressure adjusting means 4 is in a state in which the wheel brakes 2A to 2D are cut off from the master cylinder M and the reservoirs 9A and 9B. That is, the normally open solenoid valves 6A to 6D are excited and closed, and the normally closed solenoid valves 8A to 8D are demagnetized and closed. When the brake fluid pressure is further increased, the normally open solenoid valves 6A to 6D may be demagnetized and opened, and the normally closed solenoid valves 8A to 8D may be demagnetized and closed.
[0019]
By controlling the demagnetization and excitation of each of the normally-open solenoid valves 6A to 6D and each of the normally-closed solenoid valves 8A to 8D by the control unit 16 in this manner, braking can be efficiently performed without locking the wheels. .
[0020]
By the way, when braking in a state in which the anti-lock brake control is not executed, the wheels may get off the road surface by climbing over the bumps on the road surface, and the wheel speed may drop sharply and go in the locking direction. Antilock brake control to avoid falling into a state may be started. In this case, the brake fluid pressure is first reduced by the start of the anti-lock brake control. However, even if the wheels touch the ground, the reduced pressure continues until the wheel reaction force recovers. The low state continues for a long time, and the pressure increase control may be delayed. In order to avoid such a delay in the pressure increasing control, the control unit 16 executes the anti-lock brake control so that the pressure increasing rate is made larger at the time of going over a step than at the time of getting over a non-step. In order to cope with such a step over, the portion corresponding to, for example, the left front wheel of the control unit 16 is configured as shown in FIG.
[0021]
In FIG. 2, the control unit 16 controls the opening and closing of the normally open solenoid valve 6A and the normally closed solenoid valve 8A corresponding to the left front wheel in the pressure adjusting means 4, so that the left front wheel is likely to be locked during braking. In the event that the pressure becomes negative, a pressure control means 19 for executing anti-lock brake control for switching between reduction, holding and pressure increase of the brake fluid pressure acting on the wheel brake 2A is provided. The detection values of the wheel speed detectors 17A, 17B, 17C, and 17D that detect the wheel speeds of the front wheel, the right rear wheel, the right front wheel, and the left rear wheel are input.
[0022]
Further, the control unit 16 includes a wheel acceleration / deceleration calculating means 20 for calculating wheel acceleration / deceleration from the wheel speed detected by the wheel speed detector 17A, and a wheel acceleration / deceleration calculating means 20 A differentiating means 21 for differentiating acceleration / deceleration, and a step-over state when the differential value of the wheel acceleration / deceleration obtained by the differentiating means 21 at the time of braking in the non-antilock brake control state becomes equal to or larger than a threshold value. And a signal indicating whether or not the antilock brake control is being performed is input from the pressure regulation control means 19 to the step difference determining means 22.
[0023]
Moreover, the pressure regulation control means 19 sets the pressure increase rate in the first pressure increase mode of the antilock brake control, which is started within a predetermined time, for example, 300 msec, after the step difference determination means 22 determines that the vehicle is over the step. The opening / closing of the normally-open solenoid valve 6A and the normally-closed solenoid valve 8A in the pressure adjusting means 4 is controlled so as to be larger than when the vehicle is over a step.
[0024]
When detecting that the brake pedal P has been suddenly braked based on the detection value of the brake operation amount detecting means 18, the pressure regulation control means 19 enters the pressure reduction control state of the second cycle in the antilock brake control. At this time, or when either of the cases where the antilock brake control is completed is satisfied, the pressure increase rate increase correction in the pressure increase mode is stopped.
[0025]
According to the control of the control unit 16, as shown in FIG. 3, when the wheel goes over a step on the road surface during braking in which the brake fluid pressure is increased in response to the braking operation, the wheel acceleration / deceleration is controlled. At time t1 when the differential value of exceeds a threshold value, the counting of a timer for counting a predetermined time, for example, 300 msec, is started. In addition, the wheel speed suddenly dropped due to the wheel floating off the road surface due to overcoming the step, and the wheel speed decreased, and the anti-lock brake control was started until the time measured by the timer reached "0". In some cases, the pressure increase rate from the start time t2 of the pressure increase mode in the antilock brake control is set to be larger than that at the time of crossing a non-step difference indicated by a chain line. Thereafter, for example, at the end time t3 of the antilock brake control, the correction to the increasing side of the pressure increasing rate ends.
[0026]
Next, the operation of this embodiment will be described. The differential value of the wheel acceleration / deceleration becomes equal to or larger than the threshold value based on the fact that the wheel speed suddenly rises suddenly when the wheel goes over the step during braking. In this way, it is determined that the vehicle is over a step, and the differential value of the wheel acceleration / deceleration is used without using the wheel acceleration / deceleration. Thus, it is possible to determine the state of climbing over a step. That is, as shown in FIG. 4, when the brake fluid pressure is applied to the wheel brake to reduce the wheel speed, the vehicle acceleration and the deceleration and the differential value of the wheel acceleration and deceleration are interposed between the vehicle acceleration and the vehicle acceleration. -The difference in acceleration / deceleration components of the vehicle body is caused by the effect of the deceleration. Thus, it is possible to determine the state of climbing over a step without receiving the information.
[0027]
Further, since the pressure increase rate in the first pressure increase mode in the anti-lock brake control started due to the step over is made larger than that in the non-step over state, the delay of the pressure increase control is prevented. be able to. Moreover, since the pressure increase rate in the pressure increase mode is not set high in advance in anticipation of a delay in the pressure increase control, the brake pressure does not excessively increase on a flat road, and the braking pressure is not increased. The ring does not get worse.
[0028]
Further, increasing the pressure increasing rate in the pressure increasing mode is limited to a case where the anti-lock brake control is started within a predetermined time after it is determined that the vehicle is over the bump, and is started for a cause other than climbing over the bump. Unnecessarily increasing the pressure increase rate during the antilock brake control performed can be prevented.
[0029]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the claims. It is.
[0030]
【The invention's effect】
As described above, according to the first aspect of the present invention, it is possible to accurately determine the state of overcoming a step without being affected by vehicle acceleration / deceleration.
[0031]
According to the second aspect of the present invention, when the vehicle is traveling over a step, the pressure increase rate in the antilock brake control can be increased to prevent a delay in the pressure increase control. It is also possible to avoid deterioration in feeling when braking on a flat road. Also, it is possible to prevent the pressure increase rate from being unnecessarily increased during the anti-lock brake control started due to a cause other than climbing over a step.
[Brief description of the drawings]
FIG. 1 is a hydraulic circuit diagram of a vehicle brake device.
FIG. 2 is a block diagram showing a partial configuration of a control unit.
FIG. 3 is a timing chart of a timer, a differential value of wheel acceleration / deceleration, a wheel speed, and a brake fluid pressure.
FIG. 4 is a diagram showing changes in wheel acceleration / deceleration and derivative values of wheel acceleration / deceleration with respect to vehicle body acceleration / deceleration.
[Explanation of symbols]
2A, 2B, 2C, 2D Wheel brake 4 Pressure adjusting means 17A, 17B, 17C, 17D Wheel speed detector 19 Pressure control means 20 Wheel acceleration / deceleration Calculating means 21... Differentiating means 22...

Claims (2)

A pressure adjusting means (4) capable of adjusting the brake fluid pressure acting on the wheel brakes (2A, 2B, 2C, 2D) during the braking operation, and a wheel brake (2A) when the wheels are about to be locked during braking. And 2D) pressure control means (19) for controlling the operation of the pressure control means (4) so as to execute antilock brake control for switching between reduction, holding and pressure increase of the brake fluid pressure. In the vehicle brake control device provided, a wheel speed detector (17A, 17B, 17C, 17D) and a wheel acceleration / deceleration for calculating wheel acceleration / deceleration from wheel speeds detected by the wheel speed detectors (17A to 17D) are provided. Deceleration calculating means (20); differentiating means (21) for differentiating the wheel acceleration / deceleration obtained by the wheel acceleration / deceleration calculating means (20); A step-override determining means (22) for determining that the vehicle is over a step when the differential value of the wheel acceleration / deceleration obtained by the differentiating means (21) is equal to or greater than a threshold value; Vehicle brake control device. The pressure adjustment control means (19) increases the pressure increase rate in the first pressure increase mode of the anti-lock brake control started within a predetermined time after the step difference determination means (22) determines that the vehicle is over the step. The brake control device for a vehicle according to claim 1, wherein the operation of the pressure adjusting means (4) is controlled so as to be larger than when the vehicle is not over a step.

Images