Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1994-05-20
1996-01-30
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303 10, B60T 1318
Patent
active
054875978
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic brake circuit intended to equip a motor vehicle provided with at least one electrically pilot-controlled braking function, and including at least one master cylinder, an electric pump, first and second brake motors, first and second respective solenoid valves, and a low-pressure capacity, this capacity comprising a variable-volume accumulation chamber which is connected to the remainder of the circuit by an inlet and is defined within a cylinder by a piston stressed towards this inlet by means of a first spring generating a first force which acts in a direction capable of reducing the volume of this chamber to a minimum value.
Hydraulic circuits of this type have been known for a long time and equip all vehicles provided, for example, with an antilock braking function.
A problem commonly encountered in the design of circuits of this type concerns the reduction in their degree of complexity, in particular with a view to reduced costs and increased reliability.
In particular, the reduction of the number of active members, such as the solenoid valves, or of members with a complex structure such as the slide-valve distributors, is a constant object in the design of new brake circuits provided with at least one electrically pilot-controlled braking function.
Such is the context for the present invention which provides means for carrying out simply a plurality of functions in this type of circuit.
SUMMARY OF THE INVENTION
More precisely, the hydraulic circuit of the invention is essentially characterized in that the capacity comprises, in addition to the accumulation chamber, an access chamber which has first and second inlets and an outlet communicating with the inlet of the communication chamber, in that a sealing member, which can move between first and second extreme positions, is arranged in the access chamber in order selectively to the first inlet of the access chamber in its first position and the outlet of the access chamber in its second position, in that this sealing member is selectively placed in its first position by the first spring acting on this member via the piston when the volume of the accumulation chamber is close to the minimum value, in that this sealing member is placed in its second position by a second spring acting counter to the first spring and generating a second force smaller than the first force, when the volume of the accumulation chamber is substantially greater than its minimum value, and in that the second inlet is in permanent communication with the inside of the access chamber.
By virtue of this arrangement, the accumulation chamber constitutes a true state-memory facility for the hydraulic circuit, which can be used directly by the simplified distributor constituted by the access chamber.
In a preferred application of the essential features outlined above, the outlet of the access chamber has a sealing cross section which is smaller than the cross section of the piston, and the first inlet of the access chamber has a sealing cross section which is smaller than that of the outlet of this chamber.
The invention can, for example, make it possible, without the addition of any active element, to perform an antiskid function on a vehicle which is initially provided just with an antilock function.
In this case, the first inlet of the access chamber is connected to the outlet of the pump, on the one hand, and at least to the inlet of the first brake motor, on the other hand, via the first solenoid valve, and the second inlet of the access chamber is connected to the outlet of the master cylinder.
Moreover, the inlet of the accumulation chamber is connected to the inlet of the pump, and the outlet of the master cylinder may be connected to the second brake motor via a non-return valve preventing flow towards the master cylinder.
Lastly, it is possible to arrange for the outlet of the master cylinder to be connected to the first inlet of the access chamber by a non-return valve preventing flow towards this
REFERENCES:
patent: 5152586 (1992-10-01), Burgdorf
AlliedSignal Europe Services Techniques
McCormick Jr. Leo H.
Muratori Alfred
Oberleitner Robert J.
Palguta Larry J.
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