Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1994-05-23
1995-08-22
Ballato, Josie A.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031171, B60T 842
Patent
active
054433088
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on a pressure modulator for a hydraulic brake system, especially a motor vehicle brake system. A pressure modulator that is used to modulate the pressure of the pressure fluid in the wheel brake cylinders is already known from German Patent Disclosure DE 37 41 310 A1, U.S. Pat. No. 4,461,116. This pressure modulator has a first cylinder with a servo piston, a second cylinder with a control piston, and a guide bore which connects the first cylinder with the second cylinder and in which a control tappet is disposed. The control tappet is located in the first cylinder at one face end of the servo piston and in the second cylinder at one face end of the control piston. In the second cylinder, a shutoff valve is disposed offset from a longitudinal axis of the pressure modulator. In this kind of pressure modulator, exact guidance of the servo piston in the first cylinder is not always assured, because the imposition of pressure on the servo piston by the pressure fluid creates the danger of a skewed position and therefore of leakage from the pressure modulator. The production of the eccentrically disposed shutoff valve requires high production expense.
ADVANTAGES OF THE INVENTION
The pressure modulator according to the invention has the advantage over the prior art of very exact guidance of the servo piston in the first cylinder by its tappet extension in the guide bore of the housing. In this way, skewing of the servo piston in the first cylinder is prevented, and the danger of resultant leakage from the pressure modulator is reduced. The pressure modulator can be manufactured economically. When used in a motor vehicle brake system with an anti-lock and traction control system, it enables simpler design and a smaller number of individual units in the brake system.
Advantageous further features of and improvements to the brake system are possible with the provisions recited hereinafter.
For an especially simple, economical design and exact actuation of the shutoff valve, it is advantageous if the control tappet, on its end protruding from the guide bore, has a recess open toward its face end toward the control piston, into which recess the actuation member protrudes with a crossbar extending at right angles to the longitudinal axis, the length of the recess in the direction of the longitudinal axis being greater than the length of the crossbar in the direction of the longitudinal axis, and if an actuation pin of the actuation member, which protrudes into the through bore of the control piston, extends in the direction toward the closing body, beginning at the crossbar.
It is advantageous if the actuation member is embodied as a part stamped from a metal material, so that it can be manufactured simply and economically.
To assure reliable closure of the shutoff valve, it is advantageous if the shutoff valve has the second compression spring, which exerts a spring force in the direction of the valve seat upon the closing body.
It is advantageous if the second compression spring is supported on a spring plate that in turn is pressed by the first compression spring against the control piston. This produces a very compact embodiment of the pressure modulator, which has a short structural length.
For the same reason, it is likewise advantageous if the second compression spring is embodied as a leaf spring with a spring tongue.
It is advantageous if the through bore of the control piston, on one end, has at least one radially inward-pointing retention protrusion, and if the closing body is disposed between the valve seat and the at least one retention protrusion, so that the stroke of the closing body is limited in the direction remote from the valve seat.
BRIEF DESCRIPTION OF THE DRAWING
Exemplary embodiments of the invention are shown in simplified form in the drawings and described in detail in the ensuing description. Shown are
FIG. 1, a circuit diagram of a hydraulic brake system with a pressure modulator in accordance with a first exemplary embodiment of th
REFERENCES:
patent: 4773715 (1988-09-01), Farr
patent: 4799742 (1989-01-01), May et al.
patent: 4861116 (1989-09-01), Bernhardt et al.
patent: 5273348 (1993-12-01), Yagi et al.
patent: 5328257 (1994-07-01), Tsukamoto
Ballato Josie A.
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
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