JPH02216356A - Antilock control method for vehicle - Google Patents

Abstract

PURPOSE:To prevent a rear wheel speed from dropping down by starting in the initial cycle of a control the antilock control of a rear wheel in response to an antilock control signal in a front wheel side, in the case of a vehicle performing the antilock control for front and rear wheels through a separate control system. CONSTITUTION:In the time of braking, being based on a change of system speeds Vs1, Vs2 corresponding to right and left front wheel speeds Vw1, Vw2, a hold signal and a decay signal, generated in each control logic circuit 9, 10, are given to each modulator 14, 15. While of the right and left rear wheel speeds Vw3, Vw4, a wheel speed in a low speed side is set to a system speed Vs3 output to the third control logic circuit 12 controlling a modulator 17 through a control mode decision-select circuit 16. This circuit 16 is constituted, in case of outputting a hold signal from the control logic circuit 12, stopping an output of a pulse signal to a hold valve of the modulator 17 thereafter giving to the modulator 17 the output of the control logic circuit 12 left as it is.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an anti-lock control method for preventing wheels from locking during braking of a vehicle.

(Prior Art) In general, anti-lock control devices for vehicles use electric power to detect wheel speeds detected by wheel speed sensors in order to ensure the vehicle's steering performance and driving stability during braking, and to shorten braking distance. Based on the signal, the brake fluid pressure control mode is determined, and a hold valve consisting of a normally open solenoid valve and a decay valve consisting of a normally closed solenoid valve are opened and closed.
Accordingly, a control unit 2 including a microcomputer is used to increase, maintain, or reduce the brake fluid pressure.

Figure 4 shows wheel speed Vw, wheel acceleration/deceleration dVw/dt, and brake fluid in such anti-lock control.
FIG. 4 is a control state diagram showing changes in P w and a hold signal H3 and a decay signal DS for opening and closing a hold valve and a decay valve.

When the brake is not operated while the vehicle is running, the brake fluid pressure pw is not pressurized, and both the hold signal H3 and the decay signal DS are OFF'F.
Therefore, the hold valve is open and the Decay Pulp is closed, but as the brake is being used, the brake fluid pressure Pw is pressurized rapidly from time t to (normal mode).
, As a result, the wheel speed 1/w decreases. A pseudo wheel speed Vr is set that follows this wheel speed Vw with a speed difference lower by a constant speed Δ■, and this pseudo wheel speed V is , wheel deceleration (negative acceleration) dVw
/dL is a predetermined threshold value at time t1, for example -I
When G is reached, anti-lock control is started from this point [l]. This pseudo wheel speed Vr is -1 after time tl.
It is set to decrease linearly with a deceleration gradient θ of G. Then, at time t2 when the wheel deceleration dVw/dt reaches a threshold value -G□8 for achieving a predetermined maximum deceleration, the hold signal H3 is turned ON to close the hold valve and maintain the brake fluid pressure Pw.

By maintaining this brake fluid pressure Pw, the wheel speed Vw further decreases, and at time (3), the wheel speed Vw and the pseudo wheel speed Vr become equal, but at this time t3, the decay signal DS is turned ON and the decay valve is opened. The pressure reduction of the brake fluid pressure Pw is started. Due to this pressure reduction, the wheel speed turns to acceleration after reaching the low peak at time t4, but at this low peak time t4, the decay signal DS is turned OFF, the decay valve is closed, and the brake fluid pressure is reduced. The wheel speed Vw reaches a high peak at time t7, when the pressure reduction of Pw is finished and the brake fluid pressure Pw is maintained, but the brake fluid pressure Pw starts to be increased again from this time t7.The increase in pressure here is as follows. By turning the hold signal H3 on and off in relatively small increments, the brake fluid pressure Pw is alternately pressurized and held, thereby reducing the brake fluid pressure Pw.
is slowly increased to reduce the wheel speed Vw, and at time t8
D3 compatible) to generate the decompression mode again. Note that the speed Vb (-VJ+0.lY) is increased from the low peak speed v1 by an amount corresponding to 10% of the speed difference Y between the wheel speed Va and the low peak speed v1 at the pressure reduction start time t3.
Nimate+! ! The time t5 when I recovered and the above speed difference Y of 80
% is detected from the low peak speed Vl to the speed Vc (=Vf+0.8Y), and the first pressurization period Tx starting from the time t7 is the same as the time t5. It is determined by determining the road surface friction coefficient μ based on the calculation of the average acceleration (Vc-Vb)/ΔT during the period ΔT between The vehicle body speed is controlled by controlling the wheel speed Vw without locking the wheels by a combination of pressurization, holding, and hydraulic pressure of the brake fluid pressure Pw, which is determined based on the wheel deceleration dVw/dt, which is determined based on the wheel deceleration dVw/dt. can be reduced.

By the way, the brake force distribution between the front and rear wheels is normally limited so that the front wheels always lock first, so the fact that the front wheels have started anti-lock control means that if the hydraulic pressure in the mask cylinder continues to rise, it will happen soon. This means that anti-lock control will always start for the rear wheels as well.

In addition, when anti-lock control is started, the gradient of the increase in hydraulic pressure in the mask cylinder will be quite high if the driver presses the brake pedal hard, and as a result, the wheel deceleration will be large and anti-lock control will begin, causing the hydraulic pressure to rise considerably. Even if the pressure is lowered, the slip rate of the wheels will increase, especially if the slip rate of the rear wheels is high, there is a problem that the yaw of the vehicle body becomes large and the engine tends to stop in rear-wheel drive vehicles.

(Objective of the Invention) Therefore, an object of the present invention is to provide an anti-lock control device that improves the directional stability of a rear-wheel drive vehicle during braking and does not cause engine stop during braking.

(Structure of the Invention) In order to achieve the above object, in the present invention, in the first control cycle, anti-lock control of the rear wheel control system is started in response to a control signal generated in the front wheel control system. It is characterized by

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing a three-system anti-lock control device that utilizes the present invention, in which the outputs of wheel speed sensors 1 to 4 are sent to calculation circuits 5 to 8 for calculation, and each wheel speed ffVwl is
-Vw4 respectively, a signal is obtained. Then, the left front wheel speed Vwl and the right front wheel speed Vw2 remain at the first level.
The system speed Vsl and $22 system speed V32 are sent to Ml and the second control logic circuit 9 and 0, respectively, but the left rear wheel speed Vw3 and right rear wheel speed Vw4 are sent to the low select circuit ll811, and their The wheel speed on the low speed side is selected and the third system speed Vs3 is set as the third system speed Vs3.
control logic circuit 12.

The control logic circuit 9.10 sets the first and second system speeds Vsl, Vs2 as controlled target wheel speeds, and generates hold signals H5I, H52 and decay signals DSI, DS2 based on changes in the system speeds Vsl, Vs2.
and feed them to the modulator E4.15.

In addition, t4 vs logic time ll812 is the third system achievement level V
Hold signal H33 and decay signal DS3 are generated based on the change in s3, but these signals H33 and D
S3 is applied to the modulator 17 via the control mode determination/switching circuit 16.

Furthermore, f4111! Hold signals H3I and H32 output from logic circuits 9 and 10 are 02
The output of the OR circuit 13 is sent to the control mode determination/switching circuit 16.

FIG. 2 is a flowchart showing a control mode determination/switching routine executed by the circuit 16. First, in step S1, the third system! The presence or absence of the hold signal HS3 and decay signal DS3 output from the four-control logic circuit 12 is detected to determine whether anti-lock 111m for the rear wheels has started. If this determination is rNOJ, the process proceeds to step S2, and it is determined based on the output of the OR circuit 13 whether anti-lock control for the front wheels has been started. When the determination in step S2 is also rNOJ, the process returns to step S1.

Next, in a state where the determination in step S1 is rNOJ,
If the determination in step S2 is rYEsJ, step S3
, outputs a pulse signal to the hold valve of the rear wheel modulator 17, opens and closes this hold valve at a certain timing, and adjusts the brake fluid pressure to the rear wheels in steps, as shown by symbol A in Figure @3. and then return to step S1.

The control mode determination/switching circuit 16 includes the control logic circuit 1
If hold signal 1 (S3) is output from 2, it is determined that anti-lock control for the rear wheels has started, and the process proceeds from step S1 to step S4, in which a pulse signal is output to the hold valve of the rear wheel modulator 17. Then, the constant timing operation of the hold valve is stopped.From this point on, the output of the control loop circuit 12 is directly applied to the rear wheel modulator 17, and anti-lock control is performed in the normal mode.

Due to the operation of the control mode determination/switching circuit 16, the rear wheel AM hydraulic pressure in the first cycle gradually increases in a stepwise manner, so that the drop in the rear wheel speed becomes smaller as is clear from FIG. 3.

(Effects of the Invention) As is clear from the above description, in the present invention, in the first cycle, the antilock t4vs of the rear wheel control system is activated in response to the antilock t4 control signal generated in the front wheel control system. This prevents the rear wheel speed from dropping as in the conventional case. Therefore, the directional stability at the start of anti-lock tuf+ in a rear-wheel drive vehicle is improved, and loss of control due to engine stop is also eliminated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a three-system anti-lock 11 control device that utilizes the present invention, FIG. 2 is a flowchart of the control executed by the $lrn mode determination switching circuit, and FIG. 3 is a timing chart for explaining the present invention. FIG. 4 is a timing chart showing a conventional anti-lock control method, and FIG. 5 is a timing chart illustrating problems in the conventional anti-lock control method. 1 to 4-Wheel speed sensors 5 to 8--Arithmetic circuit 9, l0, 12-mrIIC+') Tsukrf
BIa11- Low select circuit 13---OR circuit 14.15.17-Modulator 16-Control mode judgment switching circuit Agent Patent attorney Yamamoto Shu 2 Concave control mode judgment switching routine Hayabusa diagram collection diagram

Claims (1)

[Claims] In a vehicle anti-lock control method in which anti-lock control for front wheels and anti-lock control for rear wheels are performed through separate control systems, in the first control cycle, anti-lock control occurring in the front wheel control system is An anti-lock control method characterized in that anti-lock control of a rear wheel control system is started in response to a lock control signal.