Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Patent
1995-03-29
1996-10-08
Nguyen, Hoang
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
180417, 403328, F15B 910
Patent
active
055620167
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a centering device, in particular for steering valves in motor vehicles. In steering gears with a centering device, there are provided a drive part and a power takeoff part, and these parts are connected with each other by means of a torsion bar and are elastically rotatable against each other. The drive part is made in sleeve-fashion and encloses the torsion rod. The power takeoff part again partly encloses the drive part.
2. Description of the Prior Art
Such a centering device can be used advantageously for steering valves in the rotary slide or rotary piston design. EP0244449 contains a model based on this design. This centering device reveals a metallic shock absorber with axial spring action that is attached to the drive part and that acts upon the power takeoff part via a mid-position catch device with prestress. The mid-position catch device consists of the oblique surfaces associated with the two structural parts with roller bodies in between. In this way, one gets, on the drive part, a resetting force that depends on the twisting of the two structural parts and that is added to the twisting force of the torsion bar. The mid-position catch device here primarily takes care of the exact centering of the two structural parts that can be rotated against each other. This mid-position catch device needs an axial and radial installation space mostly on account of the metal shock absorber. Besides, this device requires a comparatively high production effort because one must fasten a centering piece and an end piece to the shock absorber and a centering piece on the power takeoff part.
The task of the invention is to find a centering device combined with a torsion bar that can be made at reasonable cost with a very small axial space requirement.
This problem is solved by the centering device of the present invention. Other more preferred embodiments are also disclosed.
SUMMARY OF THE INVENTION
In a radial borehole of the power takeoff part, a pin loaded by a spring is guided in a radial direction; this pin engages an oblique surface groove of the drive part. Because the spring, the pin, and the oblique surface groove lie in a radial plane, in other words, on top of each other, one can save considerable structural space. The wall thickness of the drive part is completely sufficient to house the centering elements, and one needs no additional axial and radial construction space.
According to a preferred embodiment, one provides a ring groove worked into the front face of the power takeoff part and a slitted, ring-shaped spring is inserted in that ring groove. The spring partly rests in the ring groove and in the area of an anchoring arrangement with the pin, has a flattened section that deviates from the circular shape. In this way, one can get good radial spring properties and adequate clear space for the fastening of the pin.
According to another preferred embodiment, one crimps the ends of the ring-shaped spring inward so that the spring motion in the ring groove will not be impaired by friction losses.
According to yet another preferred embodiment, one best makes the pin end in a ball shape. That improves the gliding properties,
The invention will be described in greater detail below with the help of a practical example illustrated in the drawing:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal profile through the centering device according to the invention and
FIG. 2 is a lateral profile along line II--II in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to FIGS. 1 and 2, the centering device has a torsion bar 1 that at its thickened ends is pinned together with a drive part 2 and a power takeoff part 3. Drive part 1 in its extension, for example, carries a rotary slide 2A that encloses the active part of torsion bar 1 almost over its entire length. Adjoining drive part 3 is a valve bushing 3A that is nonrotatably connected with said part, and in it, the rotary slide 2A can perform a
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patent: 3698748 (1972-10-01), Petri
patent: 4711315 (1987-12-01), Kitamura
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patent: 5070957 (1991-12-01), Harkrader et al.
patent: 5109753 (1992-05-01), Kobayashi
patent: 5190119 (1993-03-01), Nomura et al.
Nguyen Hoang
ZF Friedrichshafen AG
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