Brake servo device for motor vehicles

Motors: expansible chamber type – Working member position feedback to motive fluid control – Plural input signal means for single motor valve

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Details

91376R, B60T 1372

Patent

active

059377275

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a brake power booster for automotive vehicles including a booster housing having its interior subdivided by a movable wall into a first chamber (vacuum chamber) and a second chamber (working chamber), and a control valve which controls a pneumatic pressure differential that acts upon the movable wall, the control valve having at least two sealing seats, which interact with an elastic valve member, and being operable by an actuating rod, on the one hand, and by a solenoid irrespective of the actuating rod, on the other hand, the armature of the solenoid being in force-transmitting cooperation with one of the sealing seats.
A brake power booster of this type is disclosed in international patent application No. WO 94/11226, for example. A disadvantage in the prior art brake power booster is the drop of forces in the force-travel characteristic curve of the control valve which occurs especially during the inflow of outside air into the working chamber and causes instabilities. To adapt the course of the force characteristic curve of the solenoid to the mentioned consumer characteristic curve, a highly dynamic and precise, complicated control system is required which needs data about the actuating travel of a sleeve. The sleeve carries the sealing seat operable by the solenoid. A sophisticated sensor structure is required to this end.
Therefore, an object of the present invention is to disclose measures which permit eliminating the need for the sensor structure and simplifying the control system in addition. More particularly, the objective is to position unstable points on the consumer characteristic curve.


SUMMARY OF THE INVENTION

According to the present invention, this object will be achieved by the armature which includes two parts that are movable relative to each other and interact with stops which are axially offset in the housing of the solenoid in the actuating direction of the latter.
To specify the idea of the present invention, in a preferred aspect of the present invention, the armature is comprised of two cylindrical parts which are coaxial to each other and guided telescopically in each other, and the distance between the radially outwardly arranged part and its associated stop is smaller than the distance between the radially inwardly arranged part and its associated stop.
To minimize the friction which occurs between the two armature parts and to optimize the course of the magnetic flux, it is appropriate to provide an insulating sliding layer, e.g., a foil, between the two parts.
Preferably, the sealing seat of the control valve operable by the armature may be either that sealing seat opening of which permits ventilating the second chamber (working chamber). Or, the sealing seat may be a third sealing seat which is arranged concentrically to the sealing seats and, upon operation of the control valve by the solenoid, replaces the sealing seat in terms of function which, when opened, permits a pneumatic connection between the two chambers.
The present invention will the explained in detail in the following description making reference to an embodiment and the accompanying drawing .


BRIEF DESCRIPTION OF THE DRAWING

The only FIGURE in the drawing shows a longitudinal cross-sectional view of a design of the brake power booster of the present invention, partially broken off.


DETAILED DESCRIPTION OF THE DRAWING

The booster housing 1 (shown only schematically) of the vacuum brake power booster of the present invention (as shown) is subdivided by an axially movable wall 2 into a working chamber 3 and a vacuum chamber 4. The axially movable wall 2 includes a diaphragm plate 8, deep-drawn from sheet metal, and a flexible diaphragm 18 which abuts thereon (not shown). The diaphragm, configured as a rolling diaphragm, provides a sealing between the outside periphery of the diaphragm plate 8 and the booster housing 1.
A control valve 12 operable by an actuating rod 7 is accommodated in a control housing 5, which is sealed and guided in t

REFERENCES:
patent: 5493946 (1996-02-01), Schluter
patent: 5605088 (1997-02-01), Balz et al.
patent: 5658055 (1997-08-01), Dieringer et al.

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