Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1995-08-08
2001-09-11
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S116100, C701S071000, C701S083000
Reexamination Certificate
active
06286914
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims priority from Japanese Patent Application No. Hei. 6-112729 filed Aug. 8, 1994, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automotive brake-fluid pressure control apparatus employed for example in traction control during acceleration slippage.
2. Description of the Related Art
Conventionally, hydraulic circuits of various types of structure have been proposed as an automotive brake-fluid pressure control apparatus employed for example in traction control during acceleration slippage; in recent years in particular, as shown in for example
FIG. 13
, a hydraulic circuit has been considered which can realize antiskid control and traction control and so on, and which has a structure driving two hydraulic pumps P
1
and P
2
with one hydraulic motor MR.
This hydraulic circuit performs traction control on a vehicle of front-wheel drive (FF) of a front-mounted engine, and valves and the like to perform traction control are disposed in a conduit of brake fluid reaching from a master cylinder M/C to wheel cylinders W/C of left and right front wheels FL and FR. Specifically, these are a master-cylinder cutoff valve (SM valve) which cuts off brake fluid from the master cylinder M/C, a reservoir cutoff valve (SR valve) which cuts off communication from a reservoir R on the M/C side to the intake side of the hydraulic pumps P
1
and P
2
, and also electromagnetic-type valves V
1
and V
2
which perform holding and release of high brake-fluid pressure given to a wheel cylinder W/C.
Accordingly, in a case of executing traction control with this hydraulic circuit (hereinafter described with reference to the FL wheel), braking force was controlled with holding and release of brake-fluid pressure performed by valves V
1
and V
2
in a state where the conduit had been interrupted by the SM valve. Additionally, normal brake operation corresponding to depression of a brake pedal BP by a driver was made possible after termination of traction control by causing the hydraulic pump P
1
to be stopped along with switching to a state wherein the SM valve was communicated, the valve V
1
was communicated, and the valve V
2
was interrupted.
However, problems such as described hereinafter existed in a case where the respective valves and the like are established in the above-described manner so that normal braking operation can be operated after termination of traction control.
That is to say, high-pressure brake fluid used in traction control must be expelled when the SM valve and the valves V
1
and V
2
are switched so as to enable normal braking operation after termination of traction control. However, there existed the problem in that time is required to expel the brake fluid, and setup for normal braking operation is delayed. If the SM valve and the valves V
1
and V
2
are switched in a state where this high-pressure brake fluid is not expelled, high pressure is applied to the master cylinder M/C at the time of normal braking operation, and there exists a possibility of damaging the master cylinder M/C.
Additionally, in a case where the SM valve and the valves V
1
and V
2
are switched to release the high-pressure brake fluid to the low-pressure side in the foregoing manner after termination of traction control, the hydraulic-pressure differential of the low-pressure side and high-pressure side is large, and so oil-shock noise was generated particularly on the master-cylinder side which has small capacity, and there was considerably unpleasantness for the driver.
SUMMARY OF THE INVENTION
To solve the above-described problems, it is an object of the present invention to provide an automotive brake-fluid pressure control apparatus which can quickly expel high-pressure brake fluid immediately after brake-force control such as traction control and which also can alleviate oil-shock noise.
An automotive brake-fluid pressure control apparatus according to the present invention causes a pump to be operated together with placing a first switching valve at an interrupted position and placing a second switching valve at a communicated position by a termination-control device as well as driving a pressure-control valve to a state which causes brake fluid to be expelled from a wheel cylinder at a time of termination of control of motion characteristics of a vehicle such as traction control or the like.
That is to say, valves are switched at a time of termination of traction control or the like so that braking operation by a driver becomes possible. At this time, according to the present invention, a pump is not caused to stop as in the prior art but conversely causes a pump to operate to expel brake fluid from a hydraulic circuit on a wheel-cylinder side, and so high-pressure brake fluid is rapidly expelled and hydraulic pressure can be reduced. As a result thereof, damage to the master cylinder can be prevented. Additionally, generation of oil-shock noise at a time of termination of traction control or the like can be alleviated by this rapid reduction of hydraulic pressure.
Additionally, in a case where acceleration slippage is detected by an acceleration-slippage detection device, it is also acceptable to apply brake-fluid pressure to the wheel cylinder of the vehicle wheel by brake-fluid pressure application device. In this case, acceleration slippage can accurately be prevented.
Furthermore, it is also acceptable to drive a termination-control device at a time of termination of traction control in an apparatus which performs antiskid control (ABS control) and traction control (TRC control).
That is to say, a motor is normally driven by a relay, but delays are established at ON-→OFF and OFF-→ON in a case of a mechanical relay to prevent contact-point melting. For this reason, there is a delay when the relay is switched off at a time of termination of TRC control until the relay subsequently is switched on. For this reason, in a case during TRC control when ABS control is started (with TRC control being stopped), there exists a problem wherein start timing of the ABS control is delayed. Consequently, according to the present invention, the motor is continued to be caused to operate even with the timing whereby this relay is switched off in a case where ABS control is started. Because of this, there exists an advantage whereby a pressure-reduction delay due to ABS control does not occur. That is to say, when a termination-control device is driven at a time of termination of traction control, not only are damage due to high hydraulic pressure prevented and oil-shock noise alleviated, but ABS control as well can be executed favorably.
Moreover, a method identical to a normal pressure-reducing method in ABS control can be employed to the foregoing termination-control device.
Furthermore, when pressure of brake fluid discharged by a pump has exceeded a predetermined pressure, it is preferred that brake fluid be expelled to a master-cylinder side by a pressure-regulating valve. Through this, brake-fluid pressure can be maintained in a safe uniform range.
Additionally, a valve to expel brake fluid from a discharge side of the pump to the reservoir of the master cylinder and a valve to expel brake fluid from the discharge side of the pump to the conduit connected to the master cylinder can be employed as the pressure-regulating valve.
In addition, a device to take in brake fluid from the reservoir of the master cylinder and a device to take in brake fluid from the reservoir of the master cylinder via the master cylinder can be employed as the pump.
In a case where it has been determined by a braking-determination device that a driver has performed braking, it is preferred that control by the above-described termination-control device be stopped, the pump be caused to be stopped by the braking-control device, and along with this, the first switching valve be placed at an interrupted position and second switching valve b
Okazaki Kouji
Sawada Mamoru
Nippondenso Co. Ltd.
Oberleitner Robert J.
Pillsbury & Winthrop LLP
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