Power plants – Pressure fluid source and motor – Pulsator
Patent
1991-03-13
1993-05-18
Look, Edward K.
Power plants
Pressure fluid source and motor
Pulsator
60561, 60589, B60T 1320
Patent
active
052110192
DESCRIPTION:
BRIEF SUMMARY
INTRODUCTION
The invention is related to a brake actuating unit of a well known type comprised of a vacuum brake power booster and a tandem master cylinder mounted thereto The power booster housing is divided by a movable wall into a vacuum chamber and a power chamber which is ventable by means of a control valve being accommodated in a control valve housing fixed to the movable wall
The master brake cylinder comprises two pressure chambers within a cylinder housing and has a connection to an unpressurized hydraulic fluid reservoir may be shut off or opened by means of two valves. A primary piston defines the first, primary pressure chamber, and is of two-part construction consisting of an external piston which is in power-transmitting connection with the booster movable wall, and of an internal piston which is sealedly guided within the external pisto.n The internal piston is slidable to a limited extent relative to the external piston, and is directly actuatable by an operating element comprised of the actuating brake pedal, the internal piston integral with a valve piston actuating the booster control valve.
BACKGROUND OF THE INVENTION
An actuating unit of this kind has already become known by the German patent application published without examination, No. 3,401,402. It is the special feature of this state-of-the-art actuating unit that the valve piston sealedly passes through a wall of the master brake cylinder and in the event of an actuation is advanced into the primary pressure chamber of the master cylinder. The purpose achieved by these provisions is that in the event of a failure of the boosting power, the operating element will act on a piston area whose active cross-sectional area is smaller than the piston area which undergoes the action of the boosting power.
Mounting of the prior-art actuating unit to the splash wall of the automotive vehicle is carried out by means of fixing bolts which are secured to the booster housing and which are inserted through openings in the splash wall and are provided with nuts.
The state-of-the-art arrangement in which the operating element, the vacuum brake power booster, and the master brake cylinder are in series with one another has the following disadvantages:
a) The reaction resulting from the hydraulic pressure which exists within the master brake cylinder is transmitted to the splash wall through the booster housing. As a result, deformations of the booster housing are caused which have a negative effect on the brake system.
b) Expansions are caused by elevated temperatures in the engine compartment and must be balanced by longer actuating travels of the operating element.
c) A relatively large overall axial length results which causes considerable problems as to mounting within the engine compartment.
d) Elevated transverse forces are created during actuation which are absorbed by an outward bending of the piston rod which actuates the valve piston and by the sealing ring guiding and sealing the control housing within the booster housing, which are transmitted to the master brake cylinder, so that they cause problems of guiding in the master cylinder.
e) The tolerances of the elements which participate in the power transmission between the operating element and the master cylinder are stacked.
f) Noises are caused by the aspiration of the air from the passenger compartment.
g) A reduction of the cross-sectional suction area of the air inlet opening in the control valve housing the presence of the piston rod.
SUMMARY OF THE INVENTION
It is, therefore, the object of the present invention to propose an actuating unit of the type described in which the aforementioned disadvantages are largely eliminated and which makes it possible to minimize the actuating travel of the operating element required for the pressure build-up and obtain a reduction in the length of the overall mounting space necessary inside the engine compartment.
In accordance with the invention, this object is achieved by the combination of the following feature: The operating elemen
REFERENCES:
patent: 1978738 (1934-10-01), Bragg et al.
patent: 2767548 (1956-10-01), Ayers
patent: 2934042 (1960-04-01), Stelzer
patent: 4468926 (1984-09-01), Hodkinson
patent: 4553470 (1985-11-01), Shimazu
patent: 5044161 (1991-09-01), Schiel et al.
Alfred Teves GmbH
Lewis J. Gordon
Look Edward K.
Lopez F. Daniel
Seitter Robert P.
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