Booster with prefilling without limitation in flowrate

Power plants – Pressure fluid source and motor – Pulsator

Patent

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Details

60588, 60589, B60T 13565

Patent

active

059340754

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a boosted braking device for a motor vehicle, comprising: a master cylinder exhibiting at least one primary hydraulic chamber filled with a brake fluid and closed by a main hydraulic piston designed to receive an actuating force composed of an input force and of a boost force both acting in an axial direction; and a pneumatic booster capable of applying the actuating force to the main hydraulic piston, in response to the application of the input force on an operating rod controlling the opening of a valve borne by a pneumatic piston which can move with the operating rod, the booster itself including a rigid casing divided in leaktight fashion into two chambers by means at least of a moving partition which can be urged by a pressure difference established selectively between the two chambers through the opening of the valve, the input force being transmitted via a reaction disk against which the pneumatic piston also bears in order to supply it with a first part at least of the boost force, the moving partition being slidably mounted on the pneumatic piston, and the main hydraulic piston of the master cylinder comprising an annular piston sliding in leaktight fashion in a bore of the master cylinder, and an internal piston sliding in leaktight fashion inside the annular piston.


BACKGROUND OF THE INVENTION

A device of this type is known in the prior art, at least from document FR-A-2,700,513.
Such a braking device has the advantage, resulting from the use of a moving partition mounted so as to be able to slide relative to the pneumatic piston until it comes into abutment with the latter, that the braking force increases more uniformly, as a function of the travel of the operating rod and therefore of the brake pedal, than in the prior devices.
However, the obtaining of a uniform increase in the braking force can still be improved in braking devices of this type, insofar as the moment at which the pneumatic piston is carried along by the moving wall depends on conditions of depression of the brake pedal and insofar as mastering the effects of the pneumatic piston being carried along by the moving wall assumes tricky optimization of a multitude of parameters.


SUMMARY OF THE INVENTION

The object of the present invention is precisely to improve this known device in order to make it possible easily to produce a boosted braking device using hydraulic reaction which can exert an increasing braking force over the entire travel of the brake pedal, in a very uniform manner.
To this end, the device of the present invention is essentially characterized in that the reaction disk bears against the annular piston, in that the moving partition bears against the internal piston in order to transmit a second part of the boost force thereto, in that the main hydraulic piston comprises, apart from the annular piston and the internal piston, an additional piston capable of receiving from the internal piston a thrust able to make it slide in the bore, in that the annular, internal and additional pistons together define, inside the bore, a variable annular volume which is connected to a low-pressure brake fluid supply circuit for as long as the annular piston has not gone beyond a position where braking is initiated, and in that communication means are provided to establish, between the annular volume and the primary hydraulic chamber, a communication allowing the passage of brake fluid only provided at least that the additional piston is distant from the annular piston merely by a distance not exceeding a length of predetermined magnitude.
According to a first possible embodiment of the invention, the communication means comprise a hollow bearing surface integral with the additional piston and pointing towards the primary hydraulic chamber, a seal sliding over this hollow bearing surface between a bearing face of a collar of outside diameter d and a stop ring, both integral with the bearing surface, and a sliding ring sliding in the bore, and of which a first end bears against the annular pi

REFERENCES:
patent: 3911681 (1975-10-01), Sisco
patent: 3914941 (1975-10-01), Gardner
patent: 4033131 (1977-07-01), Gardner
patent: 4417445 (1983-11-01), Furuta

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