Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Patent
1996-03-08
1999-03-16
Nguyen, Hoang
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
92 98R, F15B 910
Patent
active
058816275
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 integral with the skirt 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 slide in a first axial direction with respect to the operating rod and able to receive, in order to transmit it on, an output force which is orientated in this first axial direction and 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 increases with the boost force.
BACKGROUND OF THE INVENTION
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.
Such a device is for instance disclosed in document EP-A-0 151 028 which pertains to a tandem booster, i.e. a booster equipped with two amplification stages, the second of which is incorporated into the rigid skirt and controlled in pressure by an electronic circuit, the single reaction means of this tandem booster being nevertheless constituted by a traditional reaction disc formed of an elastomeric material.
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.
SUMMARY OF THE INVENTION
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.
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; and 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, 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
Such a device is for instance disclosed in document EP-A-0 151 028 which pertains to a tandem booster, i.e. a booster equipped with two amplification stages, the second of which is incorporated into the rigid skirt and controlled in pressure by an electronic circui
REFERENCES:
patent: 4426915 (1984-01-01), Maucher et al.
patent: 5027693 (1991-07-01), Wilkinson
Comstock Warren
McCormick Jr. Leo H.
Nguyen Hoang
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