Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Patent
1993-07-23
1996-02-27
Look, Edward K.
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
605471, F15B 910
Patent
active
054939496
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a braking device for motor vehicles, which in particular is equipped with a brake pedal and a pneumatic brake-booster, the latter in turn comprising: connected, permanently in the case of the first and selectively by operation of the pedal in the case of the second, to respective first and second pressure sources delivering pressures the difference between which is not zero, the operation of the pedal enabling brake-boosting work to occur as the result of a displacement of the movable wall through the action of said pressure difference; between the two chambers, this communication being interrupted from the commencement of each operation of the pedal and being restored only at the end of its release; communication between the second chamber and the second pressure source, this communication being established in the course of each operation of the pedal and interrupted on the commencement of its release, and adapted to establish additional selective communication between the chambers.
Devices of this kind are for example known from the documents EP-A-0 171 585, EP-A-0 173 054 and EP-A-0 201 689, which are incorporated by reference in the present description.
Despite their interest, these devices of the prior art necessarily make use of a solenoid valve to constitute the third valve means, the relatively high cost of which valve considerably restricts its field of application.
The present invention has in particular the object of overcoming this difficulty and does so by providing a device in which the third valve means comprise an inclinometric valve reacting to the inclination of the vehicle to prevent, at least in a determined direction and at a determined amplitude of inclination of the vehicle, communication between the two chambers.
This device, generally intended for a motor vehicle equipped with a clutch mechanism, may then advantageously comprise in addition control means reacting to a movement of said clutch mechanism to bring about the opening of the third valve means in response to said movement.
Although the utilization of clutch pedal-controlled inclinometric valves for holding back a vehicle on a downslope is known, for example from the patents U.S. Pat. Nos. 2,030,288 and 2,251,787, which are in turn incorporated herein by reference, these valves have hitherto been used only on the hydraulic brake circuit, with the disadvantage of having to resist high pressures, of having to be provided in duplicate for dual brake circuits, and of making the ending of the braking of the vehicle very highly and abruptly sensitive to the release of the clutch pedal, all of these disadvantages being also eliminated by the present invention.
In particular, the slight pressure difference existing on the two sides of a pneumatic device (a maximum of a few bars and usually less than one bar), in comparison with a hydraulic device, and also the use of a single circuit instead of a dual circuit therefore give rise to greatly reduced sensitivity, and therefore disturbance, at the clutch pedal.
In addition, the device provided can be used in a very simple manner, without additional external piping.
Other features and advantages of the invention will emerge clearly from the description thereof given below, by way of indication and without limitation, with reference to the accompanying drawings, in which:
FIG. 1 is a schematic view in section of a brake system utilizing the invention;
FIG. 2 is a view in section of an inclinometric valve utilizable in a device according to the invention; and
FIG. 3 is a partial view in section of a pneumatic booster, showing in side view the valve illustrated in FIG. 2.
Inasmuch as the invention relates only to an improvement made to pneumatic brake-booster systems and as the general constitution and the functioning of the latter are well known to those versed in the art, these systems will be rapidly recalled here solely to permit full understanding of the improvement provided by the invention.
Schematically, a system of this type comprises a booster 1 a
REFERENCES:
patent: 2030288 (1936-02-01), Freeman
patent: 2251787 (1941-08-01), Gardiner
patent: 4576004 (1986-03-01), Bach
patent: 4893691 (1990-01-01), Park
patent: 5117738 (1992-06-01), Horner
patent: 5400693 (1995-03-01), Schluter
Castel Philippe
Levrai Roland
Pressaco Pierre
Bendix Europe Services Techniques
Look Edward K.
McCormick Jr. Leo H.
Nguyen Hoang
Palguta Larry J.
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