Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Patent
1993-05-04
1996-01-30
Look, Edward K.
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
91376R, F15B 910
Patent
active
054873240
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to pneumatic boosters, more particularly of the type used in order to boost the braking of motor vehicles.
Boosters of this type are well known, for example from document U.S. Pat. No. 4,765,226, and conventionally comprise, in order to equip a vehicle comprising an engine compartment and a passenger space which are separated by an apron, a casing formed of a front shell and of a back shell and inside which is located a piston formed of a back tubular part supporting a skirt which, with the aid of an unrolling membrane, defines a first chamber, or front chamber, connected permanently to a source of partial vacuum and a second chamber, or back chamber, connected selectively to the front chamber or to the atmosphere by a valve means actuated by a control rod, the casing of the booster comprising means for securing the booster to the apron of the vehicle.
Such boosters, although giving satisfactory operation, nevertheless have some disadvantages. Thus, during a braking action, air at atmospheric pressure is sucked in toward the back chamber of the booster via a valve passage of reduced cross section, after having passed through an air filter to prevent the intrusion of dust or of impurities into the booster. Conventionally, as for example in the above-mentioned document, this air filter is disposed in the back tubular part of the piston, which part projects outside the back shell of the booster inside the passenger space of the vehicle.
During a braking action, the presence of the air filter slows the movement of the air in the direction of the back chamber of the booster and consequently increases the response time of the latter. Furthermore, the valve passage of reduced cross section as well as various components of the booster, such as springs for example, are located in the path taken by the air and generate various noises and hisses in the passenger space, which can become annoying.
It has already been proposed, as in U.S. Pat. No. 5,031,507, to displace the air suction orifice in order to combat the operation noise of the booster. Such a solution then has other disadvantages, since additional chicanes and filters are introduced into the path of the air in movement, which lead to increased response times, sometimes in unacceptable proportions.
The object of the present invention is therefore to design a booster whose response time is as short as possible, and which is silent in operation for the vehicle passengers.
To achieve this, the present invention provides a booster of the type set out above, which comprises a third chamber connected permanently to the atmosphere through a filter element, and selectively and directly to the second chamber by the valve means, this third chamber having a volume at least equal to the minimal volume of the second chamber.
Such a third chamber thus constitutes a reserve of air from which the booster can draw during its operation, without obstructing the movement of the air, and therefore reducing the response time of the booster.
Advantageously, this third chamber is formed between the back shell of the booster and the apron of the vehicle, so that the orifice for suction of the air at atmospheric pressure is located in the engine compartment. The booster operating noises are therefore produced in this compartment, which is by construction acoustically insulated from the passenger space.
The invention will now be described by way of example with reference to the accompanying drawings in which:
FIG. 1 is a view in cross section of a booster constructed according to a first embodiment of the invention,
FIG. 2 is a view in cross section along line 2--2 of FIG. 1,
FIG. 3 is a view in cross section of a variant of the view of FIG. 2,
FIG. 4 is a view in cross section of a variant of a detail of FIG. 1,
FIG. 5 is a view in partial cross section of a booster constructed according to a second embodiment of the invention, and
FIG. 6 is a view in cross section of a third chamber for the booster of FIG. 3.
FIG. 1 gives a view in cross section of a pne
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Gautier Jean P.
Perez Miguel
Verbo Ulysse
AlliedSignal Europe Services Techniques
Look Edward K.
McCormick Jr. Leo H.
Nguyen Hoang
Palguta Larry J.
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