JPH11115718A - Antilock brake control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve breaking force in the low speed territory in antilock brake control by stopping pressure reducing of brake fluid pressure, when estimated vehicle speed is less than a fixed speed in the low speed territory and a pressure reducing time in a pressure mode in over a fixed time. SOLUTION: When antilock brake control is in a pressure reducing mode (S1), a fixed time is added to the pressure reducing time T (n-1) in the last time computation cycle, so as to set the pressure reducing time T (n) of the present computation cycle (S2). Next, estimated vehicle sped Vref is compared with a threshold value Vh (S3), and when the estimated vehicle speed Vref is larger than the threshold value Vh, this routine is completed. When the estimated vehicle speed is less than the threshold value Vh, a pressure reducing time T (n) is compared with a threshold value Th (S4), and when the T (n) is smaller than Th, this routine is completed, and when the pressure reducing time T(n) is larger than the threshold value Th, brake fluid pressure is held in this state (S5) and the routine is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to antilock brake control for a vehicle.

[0002]

2. Description of the Related Art Conventionally, in anti-lock brake control, if the brake fluid pressure is reduced to prevent the wheels from locking, the brake fluid pressure after wheel recovery is lower than the maximum fluid pressure on the road surface μ. Road surface μ cannot be used to the maximum extent due to the occurrence of In particular, it is difficult to control the vehicle in a low speed range, and a slight increase in the brake fluid pressure or a change in the road surface results in locking (slip ratio of 100%). Therefore, in order to prevent locking or to quickly recover from wheel slip, the braking force tends to be lower, and the deceleration tends to decrease.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to increase the braking force in a low speed range in antilock brake control.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a vehicle equipped with a wheel speed sensor for detecting the rotational speed of a wheel, and an electronic control unit for receiving and processing the signal from the wheel speed sensor. If the pressure is equal to or lower than a predetermined speed in a low-speed range and the decompression time in the decompression mode is equal to or longer than a predetermined time, the depressurization of the brake fluid pressure is stopped. In a vehicle equipped with a wheel speed sensor that detects the vehicle speed and an electronic control unit that receives and processes the signal from the wheel speed sensor, the estimated vehicle speed is equal to or lower than a predetermined speed in a low speed range, and the decompression time in the decompression mode is reduced. When the vehicle deceleration is equal to or longer than a predetermined time and the vehicle deceleration is equal to or higher than a predetermined value, the pressure reduction of the brake fluid pressure is stopped.
An anti-lock brake control method or a wheel speed sensor for detecting wheel rotational speed, a device for detecting acceleration / deceleration of the vehicle body, and a signal for receiving and calculating each signal of a wheel speed sensor and a device for detecting acceleration / deceleration of the vehicle body If the estimated vehicle speed is equal to or lower than a predetermined speed in a low speed range, the decompression time in the decompression mode is equal to or longer than a predetermined time, and the vehicle deceleration is equal to or higher than a predetermined value, Stopping the depressurization of the hydraulic pressure, or the anti-lock brake control method, wherein in the anti-lock brake control method, depressurizing the brake fluid pressure of the front wheels is stopped. Or the anti-lock brake control method, wherein the estimated vehicle speed is 20 km / h or less. Located in.

[0005]

Embodiments of the present invention will be described below with reference to the drawings.

<A> Outline of Antilock Brake Control Device The antilock brake control device includes an electronic control device for instructing antilock brake control, and a hydraulic device (hydraulic device) that operates based on a control command from the electronic control device. For example, as shown in FIG. 1, the flow path of the hydraulic pressure generated by the brake pedal 11, the main reservoir 13, and the master cylinder 12 passes through the hydraulic unit 20 to each wheel (the left front wheel 1). , Right front wheel 2, left rear wheel 3, and right rear wheel 4).

In the antilock brake control, when a wheel slips, the electronic control unit 30 controls each wheel speed based on a signal from a wheel speed sensor 31 or a device (for example, a G sensor) 32 for detecting acceleration / deceleration of the vehicle body. Then, a wheel acceleration / deceleration (wheel acceleration and deceleration), a vehicle acceleration / deceleration, a signal for brake control, and the like are obtained, and the hydraulic pressure unit 20 is controlled to perform optimal brake control on the wheels. The electronic control unit 30 has a configuration of a dedicated hardware device or a general computer device such as a microcomputer.

<B> Hydraulic Unit The hydraulic unit 20 includes a first hydraulic circuit 21 and a second hydraulic circuit 22 that connect the master cylinder 12 and the wheel cylinder 14 in the example of the X pipe shown in FIG. Have.
The first hydraulic circuit 21 and the second hydraulic circuit 22 are both provided with a main hydraulic flow path I and a main hydraulic flow path II with an inlet valve 23 interposed therebetween, and a main hydraulic flow path II with an outlet valve 24. , An auxiliary reservoir 27, a pump 25, a damping chamber DC, and a return flow path 29 returning to the main hydraulic pressure flow path I via a check valve 28.

Hereinafter, the operation of the antilock brake control device will be described.

<A> Normal Brake Control In normal brake control, when the brake pedal 11 is depressed, brake fluid pressure is generated in the master cylinder 12, and the inlet valve 23 is opened and the outlet valve 24 is closed. Therefore, the brake fluid pressure generated in the master cylinder 12 is directly applied to the wheel cylinder 14, and the wheels are braked.

<B> Antilock Brake Control The electronic control unit 30 receives a signal from the wheel speed sensor 31 or the like, detects the state of the wheel, and calculates the slip amount of the wheel, the deceleration of the wheel, and the like. When the wheels are braked and the wheels are locked, anti-lock brake control such as opening / closing control of the inlet valve 23 and outlet valve 24 and driving control of the pump 25 by the motor 26 are performed.

In the antilock brake control, the brake fluid pressure is controlled by repeatedly increasing and decreasing the pressure in each cycle. In the one-cycle pressure increasing mode, for example, the opening and closing of the inlet valve 23 is controlled and the outlet valve 24 is controlled. In the closed state, the pressure of the brake fluid in the wheel cylinder 14 is increased.

An antilock brake control method in a low speed range will be described below.

<A> Conditions for control in the low speed range In the low speed range as compared with the high speed range, the slippage of the wheels does not greatly impair the safety. Control.

For this reason, the estimated vehicle speed Vref is in a low speed range, is equal to or lower than a predetermined estimated vehicle speed, that is, the threshold value Vh of the estimated vehicle speed, and the decompression time T (n) in the decompression mode is a predetermined decompression time. That is, when the condition is equal to or more than the threshold value Th of the pressure reduction time, the pressure reduction of the wheel brake pressure is stopped and the hydraulic pressure is maintained. The threshold value Vh of the estimated vehicle body speed is a speed at which the safety is not greatly impaired by the slip of the wheels, and approximately 20 km / hr is suitable. Further, the threshold value Th of the decompression time is a decompression time during which the wheels recover under the normal control, and varies depending on the state of the traveling road surface.
For example, on a high μ road, about 10 ms is suitable.

Further, in addition to the above conditions, when the vehicle body deceleration is equal to or more than a predetermined value, the reduction of the brake pressure of the wheels may be stopped to maintain the hydraulic pressure. When this condition is added, the frictional state of the road surface is further taken into account. The predetermined value of the vehicle body deceleration changes depending on the condition of the road surface. For example, about 0.4 G is suitable for a high μ road.

The front wheels have an effect on the braking force, and a sufficient effect can be exerted by applying the control in the low speed range to the brake control of the front wheels.

<B> Calculation of estimated vehicle speed The estimated vehicle speed is obtained by a generally used calculation method.
For example, in the case of a two-wheel drive vehicle, it is estimated from the wheel speed of the non-drive wheels, and in the case of four-wheel drive, it is estimated in consideration of the maximum wheel speed and the output value of the G sensor. It is checked whether the estimated vehicle speed Vref is equal to or lower than the threshold value Vh of the estimated vehicle speed.

<C> Measurement of deceleration time In the antilock brake control, it is checked whether or not the decompression time after entering the decompression mode for depressurizing the brake fluid pressure is equal to or longer than the decompression time threshold Th.

<D> Antilock Brake Control in Low Speed Range FIG. 3 shows the relationship between the wheel speed, the estimated vehicle speed, and the brake fluid pressure, and FIG. 4 shows the control at that time. In the antilock brake control, for example, at time t1, it is determined whether or not the pressure reduction mode is being performed (S1). Since the pressure reduction mode is not being performed, the pressure reduction time is set to 0 (S6), and this routine is ended. At time t2, since the decompression mode is set (S1), a predetermined time α is added to the decompression time T (n-1) of the previous operation cycle, and the decompression time T of the current operation cycle is calculated.
(N) (S2). Next, it is checked whether or not the estimated vehicle speed Vref is equal to or lower than the threshold value Vh of the estimated vehicle speed (S3). Since the estimated vehicle speed Vref is larger than the threshold value Vh, this routine is terminated. At time t3, since the mode is the pressure reduction mode (S1), the pressure reduction time T of the previous calculation cycle
A predetermined time α is added to (n−1) to obtain a pressure reduction time T (n) in the current operation cycle (S2). Next, the estimated vehicle speed V
Since ref is equal to or lower than the threshold value Vh of the estimated vehicle speed (S
3) It is checked whether or not the pressure reduction time T (n) is greater than the threshold value Th of the pressure reduction time (S4). Since this pressure reduction time T34 is smaller than the threshold value Th, this routine is terminated.
At time t5, since the mode is the pressure reduction mode (S1),
A predetermined time α is added to the decompression time T (n−1) of the previous operation cycle to obtain the decompression time T (n) of the current operation cycle (S2). Next, since the estimated vehicle speed Vref is equal to or less than the threshold value Vh of the estimated vehicle speed (S3), the decompression time T (n)
Is greater than or equal to the threshold value Th of the decompression time (S
4) Since the pressure reduction time T56 is longer than the threshold value Th, the brake fluid pressure is maintained in this state (S5), and this routine ends.

Further, a step (S7) for determining whether or not the vehicle body deceleration D (n) is greater than the threshold value Dh is added as required, as shown in FIG. If the vehicle body deceleration D (n) is greater than the threshold value Dh, control is performed to maintain the brake fluid pressure (S5).

[0022]

According to the present invention, the following effects can be obtained. <A> In the anti-lock brake control, control can be performed in a low-speed region without lowering the deceleration.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a brake system of a vehicle.

FIG. 2 is an explanatory view of a hydraulic unit.

FIG. 3 is a relationship diagram between wheel speed, estimated vehicle speed, and brake fluid pressure;

FIG. 4 is a flowchart of antilock brake control in a low speed range.

FIG. 5 is another flowchart of the antilock brake control in a low speed range.

[Explanation of symbols]

 12, master cylinder 14, wheel cylinder 20, hydraulic unit 21, first hydraulic circuit 22, second hydraulic circuit 23, inlet valve 24, outlet valve 25, pump 26, motor 29 ・ ・ Return channel 30 ・ ・ Electronic control device 31 ・ ・ Wheel speed sensor 32 ・ ・ G sensor

Claims (5)

[Claims] 1. A vehicle comprising: a wheel speed sensor for detecting a rotation speed of a wheel; and an electronic control unit for receiving and processing a signal from the wheel speed sensor. An anti-lock brake control method, characterized in that when the decompression time in the decompression mode is equal to or longer than a predetermined time, the decompression of the brake fluid pressure is stopped. 2. A vehicle comprising: a wheel speed sensor for detecting a rotation speed of a wheel; and an electronic control unit for receiving and processing a signal from the wheel speed sensor, wherein the estimated vehicle speed is equal to or lower than a predetermined speed in a low speed range. An anti-lock brake control method, wherein when the decompression time in the decompression mode is equal to or longer than a predetermined time and the vehicle body deceleration is equal to or higher than a predetermined value, the depressurization of the brake fluid pressure is stopped. 3. An electronic device for receiving and calculating signals of a wheel speed sensor for detecting a rotation speed of a wheel, a device for detecting acceleration / deceleration of a vehicle body, and a wheel speed sensor and a device for detecting acceleration / deceleration of the vehicle body. When the estimated vehicle speed is equal to or lower than a predetermined speed in a low speed range, the decompression time in the decompression mode is equal to or longer than a predetermined time, and the vehicle deceleration is equal to or higher than a predetermined value, the vehicle is provided with a control device. An anti-lock brake control method, characterized by stopping pressure reduction. 4. The anti-lock brake control method according to claim 1, wherein the reduction of the front wheel brake fluid pressure is stopped. 5. The anti-lock brake control method according to claim 1, wherein the estimated vehicle speed is 20 km / h or less.