Boosted braking device with simplified automatic control

Details Boosted braking device with simplified automatic control Boosted braking device with simplified automatic control

1994-03-07

1998-01-27

Nguyen, Hoang

Power plants

Pressure fluid source and motor

Pulsator

91376R, B60T 1300, F15B 910

Patent

active

057111529

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a boosted braking device for a motor vehicle comprising, on the one hand, a master cylinder filled with a braking 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 suitable for exerting said actuating force on the main hydraulic piston and including a rigid casing separated by at least one sealed movable partition into at least two chambers the first of which at least is capable of being subjected selectively to a first pressure which is at least close to that which prevails in the second chamber, or to a second pressure which is different from the first one by means of at least one of two selective communication members comprising a solenoid valve and a valve controlled by the application of said input force on a control rod, said movable partition being capable of being forced by a pressure difference between the two chambers in order to entrain a pneumatic piston which can be moved with respect to the casing and carries said valve.
Devices of this type are known in the prior art and some examples thereof are given in documents EP-A2-0,171,588 and EP 0 347 583.
Such braking devices exhibit the potential interest, resulting from the use of a solenoid valve, of being capable of being actuated automatically by an electric signal without any intervention of the driver, for example in the event of detecting a situation requiring immediate braking of the vehicle or the wheels.
However, devices of this type up until now have known very few applications, essentially due to their cost still being too high and due to the reticence of users to see an automatic device depress the brake pedal in their place.
The present invention lies in this context, and its object is to propose a boosted braking device capable of being controlled automatically, but nevertheless of simple design, of low cost and respecting the usual reflexes of the users.
To this end, the device of the present invention is essentially characterized in that the main hydraulic piston of the master cylinder itself includes a hollow movable cylinder which communicates with the master cylinder, which interacts with the movable partition so as to receive at least a first part of the boost force communicated via the latter, and inside which there slides, in a sealed fashion and in the axial direction, a secondary hydraulic piston capable of receiving at least the said input force coming from the control rod, in that the movable partition is mounted slidingly on the pneumatic piston so as to be able to slide with respect to it over a predetermined stroke towards the master cylinder from an initial relative position in which it is in abutment against the pneumatic piston in a direction opposite to the one which points towards the master cylinder as far as a final position in which this movable partition may entrain the movable cylinder towards the master cylinder.
Moreover, it is possible to make provision for the valve to be forced closed by a spring and to isolate the two chambers from one another in the absence of an input force.
According to a preferred embodiment of the invention, the device further includes a reaction disk in contact with said pneumatic piston and suitable for transmitting to the secondary hydraulic piston a second part of the boost force coming from the pneumatic piston.
Other features and advantages of the invention will emerge clearly from the description thereof which is given hereafter, by way of non-limiting example, with reference to FIG. 1 which is a sectional view of a device in accordance with the invention, and to FIG. 2, which represents an enlarged detail of FIG. 1.
Insofar as the invention relates solely to an improvement made to pneumatic brake boosting systems and in which the general make-up and operation of the latter are well known to the person skilled in the art, these systems will be recalled but briefly here so as to all

REFERENCES:
patent: 4856412 (1989-08-01), Kawasumi et al.
patent: 4966420 (1990-10-01), Schiel et al.
patent: 5005464 (1991-04-01), Takaku
patent: 5910880 (1995-05-01), Schluter

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