JPS60229852A - Antiskid brake device - Google Patents

Abstract

PURPOSE:To improve the drive feeling of a vehicle and as to shorten the braking distance thereof, by restraining the upper limit of saw-like variations in the cylinder pressure of a brake cylinder below a limiting value at which a tire lock is generated, when the vehicle speed is lowered. CONSTITUTION:Control circuits 5a, 5b which are provided, corresponding to front and rear wheels, respectively, and deliver their control outputs to the energizing coils of control valves 2a, 2b, respectively. The upper limit of saw-like pressure in a brake cylinder is sequentially lowered, and is set at a value slightly lower than a theoretically optimum averaged brake force just before stopping. Further, the trends of saw-like variations in the brake pressure is beforehand stored in a memory in each control circuit including a microcomputer, and are selected in accordance with an actual road surface condition to control the brake operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an anti-skid brake device for a large vehicle equipped with a fluid brake.

[Description of prior art]

With conventional anti-skid brake systems, there is a lot of back-and-forth motion just before the vehicle comes to a stop, which impairs ride comfort, and if the brake pressure is lowered to avoid this, the braking distance increases. Furthermore, the adjustment of braking force depending on the road surface condition is left entirely to the experience of the driver.

Figure 1 shows this characteristic, and the upper row shows the vehicle speed
represents the relationship between and time t. Moreover, the lower row represents the fluctuation of the brake force P at each time. Bo in the upper row indicates the braking starting point, and the dotted line indicates the circumferential speed of the wheel. Between R, B, and R2B2, the tires are in a state of local tire lock. Lower chain vAu-
■ is the average value of the theoretical optimum braking force on that road surface,
xy indicates the upper limit value of the braking force. In this conventional system, the difference in braking force values between xy and uv is large in a low speed range of the vehicle, so the braking force changes in a sawtooth pattern until immediately before stopping. Therefore, as mentioned above, back and forth movement occurred, and there was room for improvement in terms of ride comfort. Furthermore, since the upper limit of the braking force is constant, there is a problem that the braking distance becomes longer.

[Purpose of the invention]

The present invention aims to improve ride comfort and shorten braking distance when anti-skid brakes are activated.

[Features of the invention]

The present invention is characterized by generating appropriate brake horns depending on the road surface condition when the anti-skid brake of a large vehicle is activated.

In other words, in an anti-skid brake system, the trend of saw-tooth variation in braking force is set in a control circuit including a microcomputer, and the theoretical optimum brake required is determined by each selection operation according to the actual road surface condition. It is characterized by obtaining a braking force as close as possible to the average value of the force.

[Explanation based on examples]

FIG. 2 shows a brake system diagram of the device according to the first embodiment of the present invention. The solid arrows in the figure represent electrical wiring, and the dotted lines represent air piping connections.

The air piping for the brake valve l operated by the driver using a brake vector (not shown) passes through two sets of control valves 2a or 2b to the play-1 cylinder '38 or 3 corresponding to each wheel 4a or 4b.
She is concubined by b. The reason for this change to the 2-no system is that there is a difference in braking force between the front wheels and the rear wheels of the vehicle body.

On the other hand, a control circuit 5a or 5b including a microcomputer is provided corresponding to each of the front wheels and rear wheels, and this is connected to a wheel center 6a or 6b control circuit 5a or 5b mounted on each wheel. The control output of the control circuit 5a or 5b is connected to the Hff coil of the control valve 2a or 2b.

The control valve 2a or 2b has a known structure that adjusts the air pressure sent from the valve section to the brake cylinder 3d or 3b on the load side depending on the current value of the respective excitation coil.

The vehicle speed ■ and the brake pressure P according to the present invention change over time t
Figure 3 shows the characteristics for

Now, in the lower part of Fig. 3, the upper limit values P+, Pz, etc. of the sawtooth pressure of the brake cylinder are successively reduced to P, p2 P3, and just before the vehicle stops, the value of the chain line x-y is set to the theoretical optimum. If the average braking force uv can be set slightly lower than the value of the average braking force uv, the vehicle body will be able to stop without causing a tire bump, and the riding comfort will be improved.

But in the actual case, u-V! Since the position of α changes greatly depending on the road surface condition, the value of α at the front cannot be kept constant. Because the set x-y line is
If it is lower than the u-y line determined by the road surface condition, the braking force will be too small and the braking distance will be extended. On the contrary x
-If it falls below the y line, the tires will lock up. Therefore, if the value of α, which varies depending on the road surface condition, is determined in advance by measuring the skid resistance number, etc., and set in the control circuit, the driver can select the value as appropriate according to changes in the road surface condition. By doing this, the current value of the excitation coil of the control valve is controlled,
An appropriate value of α can be obtained.

FIG. 4 is a brake system diagram of the second embodiment of the present invention. This example is of a liquid brake. Dotted arrows in the figure represent air piping, thick lines represent liquid piping, and thin lines represent electrical piping. Compared to the first embodiment, this embodiment is characterized by the provision of a brake booster 7a or 7b that converts air pressure into hydraulic pressure.

In this case as well, an appropriate value of α can be obtained, the braking distance is short, and the ride comfort is improved.

FIG. 5 shows a brake system diagram according to a third embodiment of the present invention. In this example, one set of complicated control valves is replaced with two sets of simple electromagnetic valves by detecting the pressure of the brake cylinder.

For convenience, FIG. 5 shows half of the front wheel portion, and the symbols 1, 3a, 4a, 5a, and 6a on the M side are all the same as those in FIG. 2. In addition, 9a-1 is a solenoid valve for closing the brake cylinder, 9a-2 is also a solenoid valve for loosening, 1Oa-1 is a check valve with a throttle, 10a-2 is a check valve, and 8a detects the impact pressure of the brake cylinder. This is a pressure sensor.

In this configuration, for example, in order to control the pressure P+ shown in FIG. Since the start-up is slightly delayed, the control circuit can demagnetize the solenoid valve and set the impulse pressure in the brake cylinder 3a to a desired value.

If a local tire lock occurs, such as at R or B shown in the upper row of FIG. 3, the release solenoid valve 9a-2 is energized by the command from the control circuit 5a upon detection by the wheel sensor 6a, and the brake is activated. The cylinder pressure is vented to atmosphere and the brake is released.

Next, the pressure at P2 is similarly controlled. In this way, the control distance is shortened and ride comfort is improved.

〔Effect of the invention〕

By suppressing the upper limit of the saw-tooth variation in brake cylinder pressure to below the limit that causes tire locking when the vehicle speed decreases, it is possible to improve ride comfort and shorten braking distance as much as possible. .

[Brief explanation of drawings]

Figure 1 shows the characteristic curve of a conventional anti-skid brake device. FIG. 2 is a brake system diagram of an embodiment of the air pressure system according to the present invention. FIG. 3 is a characteristic curve of the anti-skid brake device according to the present invention. Figure 4 is a hydraulic brake system diagram. No. 5M is a brake system diagram of an air pressure system equipped with a simple solenoid valve. l... Brake valve, 2a, 2b... Control valve, 3a, 3b... Brake cylinder, 4a. 4b...Wheel, 5a, 5b...Control circuit including microcomputer, 6a, 6b...Wheel sensor,
7a, 7b... Brake booster, 8a... Pressure sensor, 9a-1... Closing solenoid valve, 9a-2... Loosening solenoid valve, 10a-1... Throttle stop valve, 10a- 2・
··non-return valve. hi 沁一---→-t ′fJZ Figure BO-□を子4 En

Claims (1)

[Claims] (11) An on-off valve provided in a fluid passage from a fluid pressure source to a brake cylinder, a control circuit including a microcomputer that controls the on-off valve, and a wheel that detects the rotational speed of the wheel. In the anti-skid brake device, the control circuit includes a control means for receiving the output of the wheel sensor as an input and controlling fluid pressure supplied to the brake cylinder in a sawtooth manner during braking. , an anti-skid brake device characterized in that it includes means for controlling the upper limit value of the fluid pressure controlled in a sawtooth pattern so that it gradually decreases as the vehicle speed decreases. Claim No. 3 is a control valve that changes the supply pressure accordingly.
The anti-skid brake device according to item 11. (3) The anti-skid brake device according to claim 11, wherein the opening/closing valve is a closing solenoid valve and a releasing solenoid valve.