Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
2000-11-16
2001-07-31
Rivell, John (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C137S625230, C091S37500R
Reexamination Certificate
active
06267144
ABSTRACT:
The invention relates to a rotary slide valve for power steering in motor vehicles, according to the type defined in more detail in the preamble to claim
1
.
The rotary slide valve contains two valve elements that are disposed so that they can move coaxially inside each other and, in order to execute a control path, are disposed so that they can rotate in relation to each other in a limited fashion.
The first valve element, which is connected to the valve inlet member, is embodied as a radially inner rotary slide. The second valve element is non-rotatably connected to the valve outlet member and is embodied as a radially outer control bushing. The rotary slide is also connected to a drive pinion via a lost motion coupling that defines the control path. A pin, which is press-fitted without play into the drive pinion, engages in the control bushing to produce a rotary drive connection.
Both valve elements have control longitudinal grooves which are at least partially limited in their axial span and are used to direct a pressure fluid to or from one of the two working areas of a servomotor. A torsion bar spring is used to restore the two valve elements from a deflected position back into their neutral position.
A rotary slide valve of this kind has been disclosed, for example, by U.S. Pat. No. 3,746,045. This rotary slide valve contains a rotary slide that is guided in an axial bore of a control bushing. The rotary slide is connected to a valve outlet member via a torsion bar and a lost motion coupling. This lost motion coupling limits the relative rotation of the two valve elements in relation to each other and constitutes a mechanical stop for the valve after the rotation path of the lost motion coupling has been exhausted. In the event of a failure of the hydraulic assistance, this mechanical stop must be able to transmit the entire mechanical steering force.
Another rotary slide valve has been disclosed by DE-41 08 597 A1. This rotary slide valve is distinguished by virtue of the fact that in order to reduce the wear on the pin that is press-fitted into the drive pinion, during assembly of the rotary slide valve, the center axis of the inner diameter of the control bushing intersects with the center axis of the pin hole, and the center axis of the inner diameter of the control bushing is shifted from the center axis of the valve assembly toward the side of the valve assembly, which is disposed opposite from the pin hole.
In the known rotary slide valve as well, during assembly, the control bushing is connected to the pin that is press-fitted into the drive pinion. In order make this assembly step possible, the connection of the control bushing and pin must have play.
As a result of the existing play between the control bushing and pin, a relative movement can occur between the rotary slide and the control bushing without a detectable steering moment being introduced by means of the steering wheel. This leads to undesirable oil flows to the working cylinder. In addition, the play in the steering wheel makes itself negatively perceptible by means of moment discontinuities. These steering moment discontinuities that occur are noticed as self-steering effects in the steering wheel and cause the driver to feel unsafe.
The object of the current invention is to produce a play-free rotary slide valve which can compensate for the negative effects of assembly-related tolerances on the steering behavior.
This object is attained by means of a rotary slide valve of this generic type which also has the characterizing features of the main claim.
The embodiment according to the invention can be realized in at least three structural variants. In a first structural variant, the play required for assembly is compensated for through the use of a split, radially resilient pin. The second constructive variant provides a split tubular bushing for tolerance compensation, and the third alternative produces the play-free connection by means of a split receiving bore in the control bushing.
Advantageous and suitable embodiments of the invention are disclosed in the dependent claims. However, the invention is not limited to the feature combinations of the claims; on the contrary, an expert will form other useful possible combinations of claims and individual claim features from the stated object.
REFERENCES:
patent: 5738182 (1998-04-01), Birsching et al.
patent: 5845557 (1998-12-01), Speidel et al.
patent: 6009903 (2000-01-01), Rohringer et al.
patent: 6082242 (2000-07-01), Suzuki
patent: 4232813 (1994-03-01), None
patent: 4300612 (1994-07-01), None
de Maight Winfried
Ertle Peter
Hafermalz Jens-Uwe
Urban Karl-Heinz
Larson & Taylor PLC
Rivell John
Schoenfeld Meredith H
ZF Lenksysteme GmbH
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