Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1990-02-22
1993-01-26
Graham, Matthew C.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031133, B60T 840
Patent
active
051817691
DESCRIPTION:
BRIEF SUMMARY
INTRODUCTION
The present invention is related to an automotive vehicle brake unit with anti-locking device, with a vacuum brake power booster arranged between the brake pedal and the master brake cylinder as to its action with at least two power chambers divided from each other by a movable wall, the first of which being connectible to a vacuum source and the second one being aeratable through a control valve actuatable by means of an input member coupled to the brake pedal, in order to generate a boosting power being proportional to the power of the brake pedal, said first power chamber in the event of a slip control action being aeratable by means of a first valve arrangement and wheel cylinders being connected to a primary and to a secondary pressure chamber of the master brake cylinder through brake lines, with sensors which are associated with the wheels to be braked and which monitor the rotating behaviour of the wheels in order to detect any locking and whose output signals are conveyable to a central electronic control unit by means of the control signals of which electromagnetically actuatable hydraulic fluid inlet and outlet valves are controllable which are inserted in the brake lines for slip control.
BACKGROUND OF THE INVENTION
An automotive vehicle brake unit of this kind is, for example, known from the earlier patent application No. P 38 17 785.4 of the applicant. The particular feature of this prior-art brake unit consists in that it is furnished with pneumatic means which in the event of a slip control action render it possible to aerate the first power chamber and/or to evacuate the second power chamber in order to activate, respectively to inactivate the boosting power of the vacuum brake power booster in a direction opposed to the actuating apparatus of the master brake cylinder.
The brake pedal pulsating along in the event of a control action is felt to be of disadvantage in the prior-art brake unit. It is considered a further disadvantage that the second power chamber of the vacuum brake power booster requires to be evacuated in order to completely cancel the hydraulic pressure existing in the master brake cylinder, so that the vacuum requirements become comparatively large.
BRIEF DESCRIPTION OF THE INVENTION
It is, therefore, the object of the present invention to configurate a brake unit of the kind mentioned in the beginning in such a way that the said pulsation of the brake pedal in the event of a control action is eliminated. In addition, the vacuum requirements are to be considerably reduced.
According to the invention, these objects are achieved in that the movable all of the vacuum brake power booster is movable independently of the input member and in that a hydraulic chamber being in active connection with the input member is provided whose link with a pressureless hydraulic fluid reservoir allows to be shut off.
According to an advantageous embodiment of the invention, it is envisaged that the primary piston of the master brake cylinder is formed by an external piston which is axially guided in the longitudinal bore of said master brake cylinder and is in connection with the movable wall, and by an internal piston which is guided therein and is in connection with the input member. This provision allows to transmit the power of reaction to the brake pedal in a particularly space-saving way.
In order to give the driver the feeling of braking in the event of a failure of the primary brake circuit, it is envisaged in a development of the subject matter of the present invention that in the primary pressure chamber a reaction device is arranged which in the event of a failure of the brake circuit connected to it renders possible the build-up of a pressure in the secondary pressure chamber proportional to the input power and in accordance with a characteristic curve fixed previously.
The reaction device is either formed by one each annular surface being configurated at the external piston, respectively at the internal piston and interacting with an annular elastic reaction
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patent: 4576004 (1986-03-01), Bach
patent: 4643486 (1987-02-01), Belart et al.
patent: 4659153 (1987-04-01), Klein
patent: 4767165 (1988-08-01), Burgdorf
patent: 4828337 (1989-05-01), Wagner et al.
patent: 4932727 (1990-06-01), Wagner et al.
Jung Christoph
Rueffer Manfred
Schiel Lothar
Von Gruenberg Hubertus
Wagner Wilfried
Graham Matthew C.
ITT Corporation
Lewis J. Gordon
Seitter Robert P.
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