Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Patent
1997-05-28
1999-03-16
Lopez, F. Daniel
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
91434, F15B 910
Patent
active
058816283
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a pneumatic booster, especially one which can be used to boost the braking in motor vehicles, comprising: a rigid casing divided in leaktight fashion into at least two working chambers, the first of which is connected to a first pressure source delivering a first pressure, and the second of which can be connected selectively, by means of a three-way valve, to the first source or to a second pressure source delivering a pressure different from the first; a moving partition delimiting the two working chambers inside the casing and including a rigid skirt, it being possible for this moving partition to be urged by a boost force resulting from a difference in pressure set up selectively between the two working chambers by actuation of the three-way valve; a pneumatic piston capable of carrying the skirt along in a first axial direction and containing the three-way valve; an operating rod also accommodated in the piston and able to receive an input force controlling the actuation of the three-way valve; a push rod able to move axially with respect to the operating rod and able to receive, in order to transmit it on, an output force which is orientated in the first axial direction and which is composed of the input force and of the boost force; and reaction means interposed between the operating rod and the push rod in order to apply to the operating rod, counter to the input force, a reaction which can increase with the boost force.
Devices of this type, well known in the prior art, are applied to a very great number of motor vehicles these days to provide assistance with braking.
These devices generally use a reaction disc formed of an elastomeric material, by way of essential reaction means, and this is entirely satisfactory and will undoubtedly continue to be so for a long time.
However, and despite the traditional nature of the techniques involved, boosters continue to be the subject of substantial amounts of research aiming to optimize their operating characteristics.
Included among this research there feature especially current attempts at improving the definition of the dynamic performance of boosters, and more precisely at reducing the tolerances on those of their operating characteristics which are liable to vary as a function of the speed with which they are actuated.
The present invention falls within this context, and its object is to provide a booster which, for mass-production, has greater reproducibility of operation than current boosters, together with a response time which is selectively shorter.
To this end, the booster of the invention is essentially characterized in that the reaction means comprise: a fixed volume defined, in a central region of the skirt, between first and second rigid walls with which this skirt is equipped and which point respectively towards the first and second working chambers; a moving divider dividing the fixed volume into first and second reaction chambers respectively delimited in part by the second and first rigid walls; first and second communications respectively connecting the first working chamber and first reaction chamber together, and connecting the second working chamber and second reaction chamber together; and a selective valve capable of closing the second communication off at least partially in response to an air flow higher than a predetermined value established from the second working chamber towards the second reaction chamber, the first rigid wall of the skirt being shaped so that it can, at least indirectly, carry the push rod along in the first axial direction, and the divider being shaped so that it can, at least indirectly, carry the operating rod along in a direction which is the opposite direction to the first axial direction.
Although the author of the present invention is already the author of a related device which is not yet known publicly, but has already been the subject, on 31 Mar. 1995, of the filing of French Patent Application FR 95 03839, the booster proposed here can be distinguished from the prior
REFERENCES:
patent: 2796154 (1957-06-01), Stelzer
Bosch Systems De Frenado, S.L.
Comstock Warren
Lopez F. Daniel
McCormick Jr. Leo H.
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