Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Patent
1993-08-06
1996-10-15
Lopez, F. Daniel
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
91376R, F15B 910
Patent
active
055643264
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a valve type control device for a pneumatic brake-booster.
The control rod which can be displaced, from a position of rest, in a first axial direction through the action of an input force. The rod being capped by a plunger which in turn has an axially support end face.
An annular valve surrounding the control rod, urged elastically in a first axial direction is actuated by the displacement of the control rod.
A first valve seat is formed by an annular portion of the plunger on the end opposite the support face.
A pneumatic piston located in the booster housing is movable in the first axial direction, from a position of rest, through the action of a pressure difference caused by actuation of the valve. The piston having an annular axial surface surrounding the plunger.
A reaction disk housed in a cup has a free face which engages an annular axial surface of the pneumatic piston. The support face of the plunger can apply combined forces developed through the movement of the plunger and piston for action on a push rod.
A second valve seat having an annular shape is concentric to and outside the first seat on the plunger. In the position of rest of the control rod, the second valve seat occupies a position further ahead than that of the first valve seat in the sense of the first axial direction. The valve engages the first seat in the position of rest and against the second seat on being actuated.
Devices of this kind are well known in the prior art, and one example thereof, among many others, is given in U.S. Pat. No. 4,491,058.
The conjoint utilization in motor vehicles of pneumatic brake-booster systems and electronic systems intended to prevent wheel locking has recently given rise to the to improve, by shortening it, the response time of such brake-booster systems so as to bring it closer to the very short response times in such electronic systems.
In this context the present invention has precisely the object of shortening the response time of a pneumatic brake-booster, i.e., the time between application of the brake by the driver of a vehicle and the occurrence of a brake-boosting force of significant amplitude.
According to the invention this object is achieved by a valve type control device for a booster essentially characterized by having a second seat of the valve is formed by an end face of a sleeve sealingly slidably mounted relative to a piston and configured to undergo, relative to a cup on an output rod, no movement in a sense of the first axial direction when the valve is actuated.
As a result of the structural relationship between the valve, sleeve and cup arrangement, the distance between the first and second valve seats on the actuation of the valve is increase and as a consequence a pressure difference generating the brake-boosting force is established more quickly in the booster.
In a first embodiment of the invention the sleeve forming the second valve seat bears against the cup, at least by means of an axial extension.
In a second possible embodiment of the invention the sleeve forming the second valve seat is disposed between the plunger and a movable wall formed by the piston. The sleeve has a second end face against which, on the actuation of the valve, the free face of the reaction disk comes to bear before coming into contact with the plunger. The sleeve as a result then under goes movement relative to the cup, in a second axial direction opposite to the first or actuation direction.
Other features and advantages of the invention will clearly emerge from the description thereof given below, with reference to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view in section of a prior art pneumatic brake-booster which illustrates the operating principle of such brake boosters.
FIG. 2 is a partial sectional view of a booster, having a first control valve made according to the teachings of the invention; and
FIG. 3 is a similar view to that in FIG. 2 and relates to a second embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTI
REFERENCES:
patent: 4633757 (1987-01-01), Kubota
patent: 4784038 (1988-11-01), Gautier
patent: 5172964 (1992-12-01), Levrai et al.
Gautier Jean Pierre
Perez Revilla Miguel
Verbo Ulysse
Bendix Europe Services Techniques
Lopez F. Daniel
McCormick Jr. Leo H.
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