Power plants – Pressure fluid source and motor – Pulsator
Reexamination Certificate
1999-11-29
2001-11-20
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Pulsator
Reexamination Certificate
active
06318081
ABSTRACT:
The present invention relates in general to hydraulic braking systems for motor vehicles.
More specifically, the present invention relates to a master cylinder with hydraulic reaction of the type which comprise: a cylindrical body pierced with a main axial bore delimiting a variable-volume working chamber filled with brake fluid; a main piston closing the working chamber and sliding selectively in the main bore from a position of rest and in a first axial direction to reduce the volume of this working chamber; a secondary axial bore pierced in the main piston and delimiting a variable-capacity reaction chamber subjected to a variable pressure and communicating with the working chamber; a reaction piston closing the reaction chamber and sliding selectively in the secondary bore from a position of rest and in the first axial direction to reduce the capacity of the reaction chamber; a first actuating member for displacing the main piston from its position of rest; a second actuating member for displacing the reaction piston from its position of rest; a spring that is preloaded in compression, an upstream end of which rests, in the position of rest, on the first actuating member and a downstream end of which rests, in a position of rest, on a stop integral with the main piston, this spring being arranged in the main piston around the reaction piston; and a drive surface defined on the reaction piston for selectively driving the downstream end of the spring in a second axial direction that is the opposite of the first axial direction and correspondingly increasing the compression of the spring.
BACKGROUND OF THE INVENTION
A master cylinder of this type is well known in the prior art and is, for example, incorporated into the braking devices described in patent EP-0,662,894 and patent document FR-2,751,602, such braking devices having the advantage of optimizing the intensity of the braking force in the event of a sharp application of the brakes.
More recently, there has arisen, in the design of new braking systems, a preoccupation with having very fine control over the feeling felt at the pedal by the driver, so as to standardize this feeling as far as possible and allow drivers to change vehicles without having to make any particular effort to adapt to the various braking systems used in various vehicles.
The present invention falls within this context and is intended to provide a master cylinder with hydraulic reaction of simple structure and which offers this feature.
SUMMARY OF THE INVENTION
To this end, the master cylinder of the present invention, which in other respects is in accordance with the generic definition given in the above preamble, is essentially characterized in that it further comprises movement-transmission means allowing the second actuating member to drive the upstream end of the spring along and correspondingly increase the compression of the spring when this second drive member displaces the reaction piston in the first axial direction.
This arrangement thus makes it possible, using one and the same spring, to fulfill two distinct functions namely, on the one hand, offering resistance to a movement of the reaction piston in the opposite direction from its actuating direction and, on the other hand, offering resistance to the displacement, in the actuating direction, of the second actuating member by the driver.
In the preferred embodiment of the invention, the movement-transmission means comprise a sliding ring arranged in the main piston around the reaction piston and inserted between the upstream end of the spring and the first actuating member, this ring being shaped to be driven along by the second actuating member when this second drive member displaces the reaction piston in the first axial direction.
Furthermore, the spring is preferably always in a state of compression such that at least one of its upstream and downstream ends is in its position of rest.
Other features and advantages of the invention will emerge clearly from the description thereof given hereafter with no limitation implied, with reference to the appended drawings.
REFERENCES:
patent: 6079208 (2000-06-01), Verbo et al.
Bosch Sistemas de Frenado S.L.
Comstock Warren
Lazo Thomas E.
Look Edward K.
McCormick Jr. Leo H.
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