JPH02200557A - Anti-lock controlling method for vehicle - Google Patents

Abstract

PURPOSE:To prevent the braking distance from being extended by changing the control speed to the middle speed between the front wheel speed and the rear wheel speed when a low friction coefficient of the road face is detected and the gear engaged state of a transmission is detected. CONSTITUTION:When a control logic circuit 20 judges the gear engaged state via the output of a comparing circuit 21 and judges that a vehicle is running on a low-mu road, it operates a switch driving circuit 22 and transfers transfer switches S1 and S2 to positions shown by broken lines. A front wheel speed Vw5 and a rear wheel speed Vw6 are fed to an average value arithmetic circuit 23 in place of a low-select circuit 19. The circuit 23 calculates the average speed between the front wheel speed Vw5 and the rear wheel speed Vw6 and outputs it to the circuit 20 as the control speed Vw8. The circuit 20 controls a hold valve HV and a decay valve DV on or off provided on modulators 3A and 3B respectively based on the control speed Vw8, and the one-channel anti-lock control is performed.

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 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 the microcomputer controls the brake fluid pressure to be increased, maintained, or reduced by opening and closing the hold valve and decay valve, which are electromagnetic valves included in the modulator. ing.

Figure 5 shows wheel speed VW and acceleration/deceleration dVw/d of wheel speed Vw in an example of such anti-lock control.
Changes in t and brake fluid pressure Pw, and hold signal H3 for opening and closing the hold valve and decay valve
FIG. 3 is a control state diagram showing the decay signal DS and the decay signal DS.

Note that the pseudo vehicle speed Vv is an approximate vehicle speed obtained by selecting the highest wheel speed from among the wheel speeds of the four wheels.

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 pulp is open and the decay valve is closed. condition, but the brake fluid pressure Pw decreases with brake operation.
is pressurized rapidly from time point to (normal mode), and as a result, the wheel speed Vw decreases. This wheel speed V
A pseudo wheel speed V7 that follows w with a speed difference lower by a constant speed Δ■ is set, and this 114E
l Wheel speed ■ is wheel deceleration (negative acceleration) dVw
/di is a predetermined threshold at time [l, e.g. -1, O
When reaching G, anti-lock control is started from this point [1]. After time t1, the lii-like wheel attainment speed is set to decrease linearly with a deceleration gradient θ of -1.0C. and wheel deceleration dVw/
Time point L2 when dt reaches a predetermined threshold (-G,,,)
At this point, the hold signal H3 is turned ON, the hold pulp is closed, and the brake fluid pressure pw is maintained.

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 ■7 at time t3, but the first cycle of anti-lock control starts from this time t3. , Decay signal D
Turn on S, open the decay valve, and reduce the brake fluid pressure p.
Depressurize w. Due to this pressure reduction, the wheel speed turns to acceleration after reaching the low beak speed v1 at time L4.
At this low peak time t4, or when the speed has recovered to the speed Vb (=Vl+0.IY) increased from the low peak speed v1 by an amount corresponding to 10% of the speed iY between the wheel speed Va and the low peak speed V1 at the pressure reduction start time L3 At t5, the Decay signal DS is turned off,
The decay valve is closed to finish reducing the brake fluid pressure Pw, and the brake fluid pressure Pw is maintained (Figure 5 shows the case where the Decay signal is turned off at time t5).Next, the wheel speed Vw is changed to the time when the pressure reduction starts ( 3 + ttHtOL speed 1tV c (= V l + Q
, 9Y) After the time t6 when the vehicle has recovered to d, the high beak is reached at the time t7. In addition, the pseudo vehicle speed vT mentioned above
, a threshold value is set lower than that by a predetermined speed, and only when the wheel speed Vw exceeds the threshold value, the brake fluid is applied again from the point L7 when the wheel speed Vw reaches the high peak speed vh. The application of pressure Pw is started. Pressurization here is achieved by turning the hold signal H3 on and off in relatively small steps to increase the brake fluid pressure P.
Alternately repeating pressurization and holding of w, thereby slowly increasing brake fluid pressure Pw and decreasing wheel speed Vw,
The second cycle of decompression mode is generated again from time t8 (corresponding to t3). Note that the first pressurization period Tx starting from time point [7] is the period ΔT between time points t5 and t6.
The subsequent holding period or pressurization period is determined by determining the friction coefficient μ of the road surface based on the calculation of the average acceleration (Vc”Vb)/ΔT at Determined based on.

By combining the pressurization, holding, and depressurization of the brake fluid pressure Pw as described above, the vehicle speed can be reduced by controlling the wheel speed Vw by f and II without locking the wheels.

By the way, in a rear wheel drive vehicle in which the left and right rear wheels are driving wheels and the left and right front wheels are driven wheels, generally the brake devices for the left and right rear wheels are the first hydraulic piping system, and the brake devices for the left and right front wheels are the second hydraulic piping system.
A hydraulic piping system has been adopted, but when performing anti-lock control as mentioned above, especially in freight vehicles,
To simplify control, one-channel control schemes are widely used. In this case, the lowest wheel speed is selected from among the four wheel speeds (SELECT LOW), and anti-lock control is performed using this as the control target wheel speed (hereinafter referred to as "control speed").

However, when anti-lock control is performed on a road surface with a low friction coefficient (low μ road), when the transmission is in gear, the left and right rear wheels, which are the drive wheels, are connected to the engine via the transmission. Because the rotational inertia is large, as is clear from the timing chart in Figure 6 showing changes in front wheel speed, rear wheel speed, control speed, and brake fluid pressure, the front wheel speed (in this case, the lower of the left and right front wheel speeds) Even if the side wheel speed (determined as the side wheel speed) recovers to the i-like vehicle body speed Vv, the rear wheel speed (in this case, the lower left and right rear wheel speed) does not recover immediately; The time period during which the vehicle remains depressed becomes longer, the high peak cannot be reached, and furthermore, the vehicle body speed does not exceed a threshold value set to have a predetermined speed difference with respect to the pseudo vehicle speed Vv.

As mentioned above, in 1-channel anti-lock control,
The lowest wheel speed among the four wheel speeds is '#Al3
Since it is selected as the 1st speed, while the rear wheel speed, which is the control speed, is decreasing, re-pressurization of the brake fluid pressure is not started, and the reduced pressure state of the brake fluid pressure for the front wheels is maintained, and the U The moving distance will increase.

(Object of the Invention) Therefore, an object of the present invention is to provide a one-channel anti-lock control method that can prevent the braking distance from increasing even when the gear is engaged when braking on a low μ road. shall be.

(Structure of the Invention) The present invention is a one-channel anti-lock i! that controls brake fluid pressure using the speed obtained by select low of four wheel speeds in a rear-wheel drive vehicle as the control speed.
In the lr1g method, means for detecting the level of the friction coefficient of the road surface and means for detecting the gear engagement state of the transmission are provided, and when the low friction coefficient of the road surface is detected and the transmission is in the gear engagement state, If detected, flJI3 above
It is characterized in that the II speed is changed to a speed intermediate between the front wheel speed and the f&transport speed.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

4TIl shows a schematic diagram of the brake hydraulic piping system applied to the implementation of the present invention, 1 is a tandem mask cylinder operated by the brake pedal 2, 3A and 3B are modulators each equipped with a hold valve and a decay valve. be. One liquid chamber of the mask cylinder l is connected to the wheel cylinders 4.5 of the left and right front wheels FL, FR through the generator 3A, and the other liquid chamber of the mask cylinder l is connected to the left and right rear wheels RLSRR through the modulator 3B.
is connected to the wheel cylinder 6.7. The rotational speed of each wheel is detected as a frequency signal by speed sensors 8.9.10.11 respectively attached to these wheels, and the control circuit 12
It performs various calculations based on the output of and controls the modulators 3A and 3B.

FIG. 1 is a block diagram functionally showing a control system of a one-channel anti-lock control device applied to the implementation of the present invention. 8 is a left front wheel speed sensor, 9 is a right front wheel speed sensor, lO is a left rear wheel speed sensor, and 11 is a right rear wheel speed sensor, and these speed sensors 8 to 11 each receive frequency signals f1 to 1 proportional to the rotational speed of the wheels. Generate f4. Each frequency signal f.

~f4 are arithmetic circuits 13 to 16 in the control circuit 12, respectively.
is sent to and calculated, and outputs representing the respective wheel speeds Vwl to Vw4 are obtained. The left and right front wheel speeds Vwl, Vw2 are sent to the low select circuit 17, and the lower wheel speed of Vwl, Vw2 is selected, and the front wheel speed Vw5 is obtained. Similarly, the left and right rear wheel speeds Vw3 and Vw4 are sent to the low select circuit 18, and the lower wheel speed of Vw3 and Vw4 is selected to obtain the rear wheel speed Vw6.

Sl and S2 control the function of the changeover switches, and at the start of anti-lock control, the movable contacts of these changeover switches S1 and S2 are in the position shown by the solid line in Fig. 1, so that the front wheel speed Vw5 and the rear wheel speed Vw6 are low. The speed is sent to the select circuit 19, and the lower speed of Vw5 and Vw6 is selected, and this is given to the control logic circuit 20 as the control speed Vw7. That is, this control speed Vw7 is a speed obtained by selecting low of the wheel speeds Vwl-NVw4 of the four wheels. And control logic episode v112
0 controls ON/OFF of the hold valve HV and decay valve DV provided in each of the modulators 3A and 3B based on the control speed Vw7, thereby performing one-channel anti-lock control similar to the conventional one.

On the other hand, the front wheel speed Vw5 obtained by selecting the left and right front wheel speeds Vw1 s V w 2 and the rear wheel speed Vw6 obtained by selecting the left and right rear wheel speeds Vw3 and VW4 are the same as when the transmission is in gear. A comparison is made in the comparison [i8) path 21 to detect whether the state is present or not. This comparison circuit 21 generates an output when Vw5>Vw6, and sends this output to the control logic circuit 20.

When the vsm logic circuit 20 determines that the gear is in the gear state based on the output of the comparison circuit 21 and determines that the vehicle is traveling on a low μ road, the switch drive circuit 22
1 to switch the changeover switches S1 and S2 to the positions shown by broken lines in FIG. By this switching, the front wheel speed V
w5 and rear wheel speed Vw6 are sent to an average value calculation circuit 23 instead of the low select circuit 19. This circuit 23 operates at an average speed (Vw5+) of the front wheel speed Vw5 and the rear wheel speed Vw6.
Vw6)/2 is calculated and outputted to the control logic circuit 20 as the tsm speed Vw8. Therefore, the control logic circuit 20 is the modulator 3A.

The hold valve HV and decay valve DV provided in 3B are set to O based on the above control speed Vw8.
One channel antilock control is performed by N/OFF control.

In addition, in the above embodiment, the control speed Vw8 in the low μ road/in-gear state is calculated as the average value of the front wheel speed Vw5 and the rear wheel speed Vw6, but instead of the average value, Vw5
, Vw6 may be appropriately weighted to obtain an intermediate value (for example, Vw8=0.7Vw5+0.3Vw6
).

FIG. 2 shows a flowchart of the control speed switching logic in the above-described embodiment.

First, in step S1, it is determined whether or not it is the first cycle of anti-lock control.
Determine whether it is a road or not. This determination is made, for example, by the average acceleration (Vc-Vb)/
This can be done by changing the value of ΔT. Then, if the average acceleration value is smaller than a predetermined value, it is determined that the road is a low μ road. If it is determined that the road is a low μ road, it is determined in the next step S3 whether or not the transmission is in a gear. In this embodiment, front wheel speed Vw5>rear wheel speed Vw
5, it is determined that the gear is engaged. Then, when the determination in step S1 is rYEsJ, or when either of the determinations in steps S2 and S3 is "NO", the process advances to step S4, and the four-wheel speed Vwl~Vw
Let the speed Vw7 obtained by the select low of 4 be the tsm speed.

On the other hand, if the determination in step S1 is "NO" and the determinations in steps S2 and S3 are both rYEsJ, the process advances to step S5 and the average speed of the front wheel speed Vw5 and the rear wheel speed Vw6 is (Vw5+Vw6)/2 is the control speed Vw9.

(Effect of the invention) Figure 3 shows the front wheel speed Pw5 when the anti-lock 11 control according to the present invention is performed on a low μ road and in a gear engaged state.
, is a timing chart showing changes in rear wheel speed Pw6, control speed Pw8, and brake fluid pressure Pw. Third
As is clear from the figure, according to the present invention, the rear wheel speed Vw6
Since the brake fluid pressure Pw is increased even while the brake fluid pressure Pw is decreasing, the braking distance can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a professional diagram functionally showing the t11 control system of a one-channel anti-lock control device used in the implementation of the present invention.
7, FIG. 2 is a flowchart showing the control speed switching logic, FIG. 3 is a timing chart explaining the effects of the present invention, and FIG. 4 is a schematic diagram of the brake hydraulic piping system to which the present invention is applied. 5 is a control state diagram of the anti-lock 11 control, and FIG. 6 is a timing chart when conventional one-channel anti-lock control is performed on a low μ road and in a gear engaged state. 3A, 3B --- Modulators 8 to 11 -- Wheel speed sensor 12 -- Control circuit 17 to 19 -- Low select circuit 20 -- Control ROSIC circuit 21 -- Comparison circuit 22 -- Switch drive circuit 23 -- Average value calculation circuit cost Attorney Patent Attorney Yamamoto Figure 2) Figure 5 (t3)

Claims (1)

[Scope of Claims] Brake fluid pressure is controlled using the speed obtained by select low of four wheel speeds in a rear wheel drive vehicle in which the left and right rear wheels are driving wheels and the left and right front axles are driven wheels. In a one-channel anti-lock control method, a means for detecting the level of a coefficient of friction of a road surface and a means for detecting a gear engagement state of a transmission are provided, and a low coefficient of friction of the road surface is detected, and An anti-lock control method for a vehicle, comprising changing the speed of the controlled wheels to a speed between a front wheel speed and a rear wheel speed when a gear shift state of a transmission is detected.