Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Patent
1993-11-04
1995-08-01
Look, Edward K.
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
91376R, F15B 910
Patent
active
054372178
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to pneumatic boosters, and more particularly of the type which are used to provide boosted braking for motor vehicles.
Boosters of this type conventionally comprise a casing inside which a piston formed from a rear tubular part supporting a skirt defines, with the aid of an unrolling membrane, a front chamber, permanently connected to a vacuum source, and a rear chamber alternately connected to the front chamber or to the atmosphere via a valve means actuated by a control rod capable of bearing, by means of a plunger, on one of the faces of a reaction disk securely fastened to a thrust rod. The valve means comprises a valve element interacting via an active part with a first valve seat formed on the plunger and a second valve seat formed on the piston, the valve normally being stressed forwards by an elastic means.
Such boosters are conventionally located in the engine compartment of the vehicle, where available space is decreasing as the constructors desire to provide an increasing number of accessories, for example anti-lock devices for wheels, devices for preventing wheel spin on acceleration, anti-theft systems, etc., whilst taking the aerodynamics of the bonnet into account.
The constructors thus tend to want to integrate various systems into a single system, whilst, of course, respecting the safety standards.
On the other hand, various situations exist in which it is desirable to generate the increase in pressure in the braking circuit independently of the will of the driver of the vehicle, such as, for example, in order to prevent the wheels from spinning on acceleration, in order to fulfil an anti-theft function, for hill starts, etc.
Known anti-theft systems act on various control or maneuvering members of the vehicle, and are in each case elements which are added to the engine compartment. Some actuate the brakes if the vehicle is occupied by an unauthorized driver and, in this case, are also complex, bulky and costly systems.
In order to provide an aid to driving, constructors also develop systems for assisting with hill starts.
These systems maintain the application of the brakes for as long as the accelerator pedal is not actuated. These systems are further added to the preceding ones and have the same drawbacks.
The document U.S. Pat. No. 5,096,267 discloses a booster of the type recalled hereinabove in which the plunger is formed of two parts which can move with respect to each other, the first valve seat being formed on one of these parts of the plunger. The other part receives the control rod and is capable of bearing on the reaction disk. One or two electromagnets may be actuated in order to move the part carrying the first valve seat with respect to the other part on which the control rod bears in order to fulfil the functions of preventing the wheels from locking or, in the case of acceleration, from spinning. One or two compression springs are interposed between these two parts.
Such an arrangement with a floating valve seat has numerous drawbacks. Indeed, the length of the plunger, that is to say the axial distance between the front face of the plunger intended to interact with the reaction disk and the valve seat formed on the plunger, must be determined with very low tolerances if the neutral travel and response time of the booster as well as the latter's operational jump is to be controlled precisely. A floating mounting of the valve seat thus no longer makes it possible to control these significant features of the booster.
The subject of the present invention is therefore a pneumatic brake booster whose neutral travel, response time and jump are perfectly determined, which integrates additional functions such as an aid to hill starts and/or an anti-theft device for the vehicle, and which does so in a simple, reliable, and inexpensive fashion in accordance with the safety standards.
In accordance with the invention, this result is obtained with the aid of actuation means for stressing the active part of the valve element forwards in simultaneous intera
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Castel Philippe
Meynier Guy
AlliedSignal Europe Services Techniques
Look Edward K.
McCormick Jr. Leo H.
Nguyen Hoang
Palguta Larry J.
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