JPH02249751A - Antilock control method for vehicle - Google Patents

Abstract

PURPOSE:To prevent a condition of no-brake by setting an antilock control basic inhibition time from the point of time starting a brake operation and, when deceleration of a wheel speed reaches a predetermined value in the point of time this inhibition time passes, so as to start an antilock control by setting a dummy wheel speed. CONSTITUTION:The largest of each wheel speed signal is selected in a dummy car body speed arithmetic circuit 13, and a speed, limiting a follow-up limit of this maximum wheel speed to + or -1.1G, is output to each control logic circuit 9, 10, 12 as a dummy car body speed Vv. Each control logic circuit 9, 10, 12 sets a speed, decreased less than the wheel speed by the predetermined value, as a dummy car body speed Vr in the point of time the decelerated wheel speed by braking action reaches the predetermined deceleration -1.1G, and in the point of time a car body speed reaches the speed Vr, a pressure of brake fluid is started to be reduced. In this case, the lapse of time from the point of time for starting a brake operation is measured, and the setting of speed Vr is inhibited until this lapse of time reaches the predetermined time.

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, and in particular to an anti-lock control method that improves braking characteristics on rough roads. Regarding the method.

(Prior art) In general, anti-lock control devices for vehicles convert wheel speeds detected by wheel speed sensors into electric signals for the purpose of ensuring vehicle steering performance and running stability and shortening braking distance during braking. Based on this, 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 to increase, maintain, or reduce the brake fluid pressure. It is controlled by a control unit containing a microcomputer.

Figure 4 shows wheel speed Vw, wheel acceleration/deceleration dVw/dt, and brake fluid pressure P in such anti-lock control.
Changes in w and hold signal H3 and decay signal DS for opening and closing the hold valve and decay valve
FIG.

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, so the hold valve is open and the decay valve is closed. condition, but the brake fluid pressure Pw decreases with brake operation.
is pressurized rapidly from time to (normal mode), and as a result, the wheel speed Vw decreases, and the wheel deceleration (
When the negative acceleration) dVw/dt reaches a predetermined dark value, for example -1.1G, at time t1, anti-lock control is started from this time t1. On the other hand, at time t1, a speed (V
A pseudo wheel speed Vr is set that decreases linearly from w-ΔV) with a deceleration gradient θ of −1.IG. Then, at time t2 when the wheel deceleration dVw/dt reaches a threshold value -G, □ 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 the wheel speed Vw becomes equal to the pseudo wheel speed Vr at time t3. At this time t3, the decay signal DS is turned ON to open the decay valve and brake the brake fluid. Start reducing the hydraulic pressure Pw. Due to this pressure reduction, the wheel speed starts to accelerate after reaching a 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 pressure reduction of the brake fluid pressure Pw is completed. The wheel speed Vw reaches a high peak at time t7 when Pw is maintained, but the brake fluid pressure Pw starts to be increased again from this time t7. The pressurization here is performed by alternately repeating pressurization and holding of the brake fluid pressure Pw by turning the hold signal H9 on and off in relatively small steps, thereby increasing the brake fluid pressure Pw.
is slowly increased to reduce the wheel speed Vw, and at time t8
(corresponding to t3), the decompression mode is generated again. In addition,
The speed V b (= V l +
0.15 Y) The point t5 of recovery L and R is the time t6 when the speed has recovered to the speed Vc (=Vj!+0.8Y) increased from the low peak speed Vl by an amount corresponding to the speed difference Y080% above. The period Tx of the first pressurization that is detected and starts from time t7 is determined by the determination of the road surface friction coefficient μ based on the calculation of the average acceleration (Vc-Vb)/ΔT in the period ΔT between the above-mentioned times t5 and t6. The brake fluid pressure pw is determined based on the wheel deceleration dVw/dt detected immediately before the holding or pressurizing period.
By combining pressurization, holding, and depressurization, it is possible to reduce the vehicle speed by controlling the wheel speed Vw without locking the wheels.

FIG. 5 is a flowchart showing a pseudo wheel speed setting routine in a conventional anti-lock control method. First, in step S1, it is determined whether the deceleration dVw/dt of the wheel speed Vw is less than -1.IG. This deceleration d
This determination is repeated until Vw/dt reaches -1.1G since it is rNOJ. Deceleration dVw/dt is -1,
If it reaches 1G, the determination in step S1 is rYE.
Since it becomes sJ, the process proceeds to step S2, and -1, the IG generation point flag is turned ON, and then the process proceeds to step S3, where a pseudo wheel speed (Vr=Vw-ΔV) is set.

By the way, when a brake device is activated while a vehicle equipped with a conventional anti-lock control device is traveling on a rough road, the wheel speed suddenly drops. Due to this drop in wheel speed, the control logic circuit generates a pressure reduction mode almost at the same time as the start of operation, so the brake fluid pressure does not increase, resulting in insufficient braking force and a so-called no-brake state.

(Objective of the Invention) Therefore, the present invention prevents a no-brake state due to the occurrence of a brake fluid pressure depressurization mode when braking while driving on a rough road,
An object of the present invention is to provide an anti-lock control method that can ensure braking force.

(Structure of the Invention) In order to achieve the above object, in the present invention, a basic anti-lock control prohibition time T1 is set from the start of brake operation, and a pseudo wheel speed is set until time T1 elapses from the start of brake operation. Settings are prohibited.

(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 (three-channel) anti-lock control device to which the present invention is applied, in which the outputs of wheel speed sensors l to 4 are sent to calculation circuits 5 to 8 and calculated, and each wheel speed Vw -Vw4, respectively, are obtained. Then, the left front wheel speed Vwl and the right front wheel speed are changed to the first system speed Vsl and the second system speed Vs2, respectively, to the first and second M control logic circuits 9.10.
However, the left rear wheel speed Vw3 and the right rear wheel speed Vw
The lower wheel speed among the four wheel speeds is selected by the low select circuit 11 and sent to the third control logic circuit 12 as the third system speed Vs3. Each control logic circuit 9.10.
In step 12, the above-mentioned system speeds Vsl to Vs3 are respectively set as controlled target wheel speeds Vw, and the hold valve HV and the decay valve DV are turned on based on this wheel speed Vw.
・Perform oFF*Jf211.

In addition, a signal that causes each wheel Vwl to Vw4 to be damaged is sent to the pseudo vehicle speed calculation circuit 13, where the four wheel speeds VW
The fastest wheel speed among I to Vw4 is selected (high select), and the following limit of this fastest wheel speed is set to ±1.
The speed limited to 1G is output to each control logic circuit 9.10.12 as a pseudo vehicle speed Vv.

Each control logic circuit 9, 10, 12 receives a signal from a switch SWI that operates in conjunction with the brake pedal BP. In addition, the control logic circuits 9, 10, 12 are provided with -1, 1C generation point detection circuits 14, 15, 16.
After a predetermined time T1 has passed since the time when the switch S
W2 to SW4 are turned on, and the -1,1C departure point output circuits 14 to 16 are activated.

FIG. 2 is a flowchart showing a pseudo wheel speed setting routine in the anti-lock control method according to the present invention. First, in step SIO, it is determined whether a predetermined time TI has elapsed since the start of brake operation. Until this time T1 has elapsed, the determination in step SIO is “N
Since the result is "O", this determination is repeated. and step S
Step S only when the judgment in step 10 is rYESJ.
The control routine after step S1 is the same as that after step S1 in the flowchart shown in FIG. Determine whether or not. Since the answer is "NO", this determination is repeated until the deceleration dVw/dt reaches -1.1G. Deceleration dVw
When /dt reaches -1 and IG, this step S1
Since the determination of is rYESJ, the process proceeds to step S2, and -
1. The IG generation point flag turns ON, and then step S
Proceed to step 3 and set the vJ-like wheel speed (VrwVw-ΔV).

FIG. 3 is an explanatory diagram showing the anti-lock control method according to the present invention, in which the setting of the pseudo wheel speed Vr is prohibited until a predetermined time T1 has elapsed from the brake activation start time to, and at a time tlO when the time T1 has elapsed. , if the deceleration dVw/dt of the wheel speed Vw has reached -1.1G, a pseudo wheel speed Vr that linearly decreases from that point P with a deceleration of -1.1C is set, and the wheel speed Vw is The brake fluid pressure pw starts to be reduced from the point Q (time t3 in FIG. 4) when it becomes equal to the pseudo wheel speed Vr.

In the conventional method, since the predetermined time TI for prohibiting the setting of this pseudo wheel speed Vr was not set, when the brake device is operated on a rough road, the wheel speed Vw
The pseudo wheel speed Vr is set at the point P' where the deceleration of the vehicle reaches -1, I However, according to the present invention, the setting of the simulated vehicle transport speed Vr is limited to after a predetermined period of time TI has elapsed from the start of operation of the brake system. , sufficient braking force can be obtained.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, the anti-lock control basic inhibition time T from the start of brake operation
1, and when this time elapses, the deceleration dVw/dt of the wheel speed Vw is set to a predetermined value (-1 in the example, IG
), the virtual wheel speed Vr is set and anti-lock control is entered, thereby preventing a no-brake state when the brakes are applied while driving on a rough road and ensuring braking force. .

[Brief explanation of drawings]

Figure 1 shows three systems of anti-lock to which the present invention is applied.
Fig. 2 is a flowchart showing the pseudo wheel speed setting routine, Fig. 3 is an explanatory diagram of the present invention, Fig. 4 is a control state diagram in conventional anti-lock control, and Fig. 5 is a flowchart showing the pseudo wheel speed setting routine. 5 is a flowchart of a pseudo wheel speed setting routine in the method. 1 to 4 -- Wheel speed sensors 5 to 8 -- Calculation circuit 9.10.12 -- Control logic circuit II -- Low select circuit 13 -- Pseudo vehicle speed calculation circuit

Claims (1)

[Claims] At the time when the wheel speed Vw, which has been decelerated due to an increase in brake fluid pressure based on the operation of the brake device, reaches a predetermined deceleration -aG, a predetermined value ΔV is lower than the wheel speed Vw.
A pseudo wheel speed Vr is set that linearly descends from the speed (Vw - ΔV) by the predetermined deceleration -aG, and from the time when the wheel speed Vw becomes equal to the pseudo wheel speed Vr, the brake is applied. In the anti-lock control method for a vehicle that starts reducing the hydraulic pressure, the elapsed time from the start of operation of the brake device is measured,
An anti-lock control method for a vehicle, characterized in that setting of the pseudo wheel speed Vr is prohibited until the elapsed time reaches a predetermined time T1.