Power plants – Pressure fluid source and motor – Pulsator
Patent
1997-09-24
2000-07-11
Lopez, F. Daniel
Power plants
Pressure fluid source and motor
Pulsator
B60T 1320
Patent
active
060855223
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to boosted braking devices for motor vehicles, comprising a master cylinder controlling the hydraulic pressure in the brake circuit connected to the brakes of the vehicle, this master cylinder being capable of being actuated by a pneumatic booster when the driver of the vehicle depresses the brake pedal.
In the conventional way, the master cylinder is filled with a brake fluid and equipped with a main hydraulic piston intended to receive an actuating force composed of an input force and of a boost force both acting in an axial direction.
Furthermore, the pneumatic booster can be operated by applying the input force to an operating rod controlling the opening of a valve, so as to exert the actuating force on the main hydraulic piston of the master cylinder, the booster including a rigid casing divided in leaktight fashion into two chambers by means of a moving partition which can be acted upon by a difference in pressure between the two chambers resulting from the opening of the valve and of driving along a pneumatic piston which can move with respect to the casing and bearing the valve, the input force being transmitted via a plunger which is also subject to the hydraulic pressure prevailing in the master cylinder.
In these devices, the main hydraulic piston of the master cylinder itself includes a hollow moving cylinder communicating with the master cylinder, receiving at least part of the boost force, and inside which there slides, in leaktight fashion and in the axial direction, a reaction piston capable of receiving at least the input force, elastic means exerting an elastic force between the reaction piston and the moving cylinder and urging the reaction piston in the direction of the master cylinder, at least one opening being made in the moving cylinder in order to make the interior of the latter communicate with the interior of the master cylinder.
Such a device is described, for example, in document FR-A-2,658,466.
These devices with hydraulic reaction have as their main advantage the fact that however intense the braking action and however great the rate of application of the input force, their characteristic operating curve, namely the curve giving the pressure in the master cylinder as a function of the intensity of the input force of the booster, is unchanged. These devices therefore show no lengthening in the response time in the case of emergency braking.
They do, however, have the drawback of having substantial hysteresis between the actuation and release phases, this being particularly significant in the most commonplace braking actions, namely those which have no emergency nature.
The present invention falls within this context, and its object is to propose a boosted braking device with hydraulic reaction which has improved operating characteristics in the case of emergency braking and which has no hysteresis, without the need for sensors or a complicated electronic circuit, and which is therefore of lower cost, while operating reliably under all circumstances.
To this end, the present invention proposes a boosted braking device for a motor vehicle, comprising on the one hand a master cylinder filled with a brake fluid and equipped with a main hydraulic piston intended to receive an actuating force composed of an input force and of a boost force both acting in an axial direction, and on the other hand a pneumatic booster which can be operated by applying the input force to an operating rod secured to a plunger controlling the opening of a three-way valve, so as to exert the actuating force on the main hydraulic piston, the booster including a rigid casing divided in leaktight fashion into at least two chambers by means of at least one moving partition which can be acted upon by a difference in pressure between the two chambers resulting from the opening of the three-way valve and of driving along a pneumatic piston which can move with respect to the casing, bearing the three-way valve and contributing at least to transmitting the boost force, the main hydraul
REFERENCES:
patent: 2959011 (1960-11-01), Randol
patent: 3387455 (1968-06-01), Eggstein
Comstock Warren
Lopez F. Daniel
McCormick, Jr. Leo H
Robert Bosch Technology Corporation
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