Fluid-pressure and analogous brake systems – Abs throttle control
Patent
1992-05-28
1993-10-12
Graham, Matthew C.
Fluid-pressure and analogous brake systems
Abs throttle control
303 975, 3031135, B60T 826, B60T 1134
Patent
active
052519694
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is related to a rear brake pressure proportioning valve or controller having an electrically actuated lockout arrangement.
Various brake pressure proportioning valves or controllers have been proposed in which an electromagnetically moved tappet extends through an axial bore in a pressure control piston, keeping the closing member of the control valve spaced from its valve seat as long as the anti-locking control is operational. An increased degree of safety is attained by the additional incorporation of such a controller since the brake pressure acting on the rear wheels is thus reduced when the anti-locking control malfunctions.
Starting from this principle, the present invention has the object to create further functional improvements, in particular, low force actuation of the lockout arrangement. This is of the special importance in case of twin-type brake power controllers for a diagonal combination of the brake circuits in order to allow locking out and releasing both brake circuits by a single actuator.
SUMMARY OF THE INVENTION
This object is achieved by an electromagnetically driven locking pin normally held in an axially shifted lockout position intermediate radially movable locking elements. The locking elements are received in openings in a fixed member and engaged by a radially acting wedging surface on a spring urged valve actuator member, which prevents axial closing movement of the valve control piston, initially positioned in the open position, as long as locking pin is held in its shifted position. The locking pin is released when an antiskid control fails by deenergization of the electromagnetic drive, and radial movement of the locking elements is allowed, so that normal proportioning action occurs by closing movement of the valve control piston. Due to the exclusively radial locking direction, unlocking is enabled with small forces. Upon repair of the anti-locking control, the controller valve member is easily locked again, because the brake lines will then be unpressurized and the control piston shifted to the open position by a spring, the interlocking elements easily moved radially out by the locking pin to again engage the wedge surface of the valve actuating element.
This set-up of the lockout arrangement is suited especially well for twin-type controllers because an electromagnet in common furnishes sufficient force to lock both control units.
The change-over pressure of the controller may be set, as load dependently by substituting for the control spring which generates a fixed bias force which acts upon the valving control piston a load variable force generating mechanical, pneumatic, hydraulic or electromagnet means.
A solution which provides particularly reliable lock out operation is achieved by locating the components of the arrangement in a chamber outside the hydraulic control circuit. A sophisticated and expensive sealing of the lockout arrangement is thus not needed.
That is, in lieu of a direct actuation of valve closing members by means of a tappet--as proposed in past solutions--the control piston or control pistons are directly acted upon in the present invention, each control piston sealedly projecting out of its bore into a chamber housing the lockout arrangement, which chamber is free of pressure fluid.
If and when the anti-locking control fails during operation of the brakes, the full pressure will exist at the outlet since the controller is locked until then.
Although the control piston will immediately travel into its pressure reducing position, the output pressure already existing would lock the rear wheel brakes if it were not reduced. For this reason, an additional pressure reducing apparatus is expedient which brings about an increase of the volume of the outlet-side section of the bore when the valve in the control piston is closed. At the least, the stroke of the control piston in the unlocked condition should definitely be larger than the closing travel of the valve of the control piston to achieve the increa
REFERENCES:
patent: 3727989 (1973-04-01), Keady
patent: 4472000 (1984-09-01), Leiber
patent: 4982999 (1991-01-01), Rossigno et al.
patent: 5139316 (1992-08-01), Watanabe et al.
Cezanne Rudolf
Heuer Rudolph
Alfred Teves GmbH
Graham Matthew C.
Lewis J. Gordon
Seitter Robert P.
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