Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
1999-08-30
2001-10-02
Rivell, John (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C091S37500R
Reexamination Certificate
active
06296018
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to power assisted rack and pinion steering systems for vehicles. More specifically, the present invention relates to the connection between a pinion and a valve sleeve, and the connection between a torsion bar and an input shaft, in a fluid power assisted rack and pinion steering gear assembly.
2. Description of the Prior Art
In a typical fluid power assisted steering system for a vehicle, a rotary valve directs the flow of hydraulic fluid under pressure to a hydraulic motor. The motor moves steering linkage to effect turning of the steerable wheels of the vehicle. The rotary valve includes a valve core and a valve sleeve which are relatively rotatable. A steering input shaft extending from the vehicle steering hand wheel has a portion formed as the valve core. One end of a torsion bar is rotationally fixed to the input shaft. An output member is rotationally fixed to the valve sleeve. The other end of the torsion bar is rotationally fixed to the output member.
When there is a resistive load on the output member from the steerable vehicle wheels, steering torque transmitted through the input shaft causes the torsion bar to twist. This action actuates the valve from a neutral condition and changes the rotary position of the valve core relative to the valve sleeve, in turn changing the fluid flow through the valve and to the motor. The motor moves the steering linkage to turn the steerable vehicle wheels. Steering linkage movement moves the output member in a follow-up manner to rotate the valve sleeve relative to the valve core and return the rotary valve to its neutral condition.
In a fluid power assisted rack and pinion steering gear assembly, the pinion is the output member. One end of the torsion bar is press fitted to the pinion. The other end of the torsion bar is pinned to the input shaft by a drilling, reaming and pinning operation. One such rack and pinion steering gear is shown in U.S. Pat. No. 4,996,905. In such a steering gear assembly, the input shaft and the pinion are supported for rotation at only three places along their length. These parts unavoidably undergo small bending movements because of forces applied to the steering gear assembly.
One location where such movement is manifested is the location where the valve sleeve is connected for rotation with the pinion. Typically, a cylindrical hitch pin is press fitted in the pinion and extends through a cylindrical opening in the valve sleeve. The opening in the valve sleeve is slightly larger than the diameter of the hitch pin, because of manufacturing tolerances. This size difference allows for radial and axial movement of the hitch pin in the opening resulting from the above-mentioned bending of the parts. This size difference, however, undesirably allows some relative angular movement between the pinion and the valve sleeve.
Another location where such bending movement is manifested is the location where the inner end of the torsion bar rotates within the input shaft. Typically, the adjoining surfaces of these parts are closely fitted to limit relative radial movement of the parts while still allowing relative rotational movement. For example, in U.S. Pat. No. 4,996,905, a bearing surface on an inner end portion of the torsion bar supports a portion of the input shaft for rotation relative to the torsion bar. Machining the parts to close tolerances as needed to operate in this manner is difficult and expensive.
SUMMARY OF THE INVENTION
The present invention is a rack and pinion steering gear assembly comprising an input shaft having a cylindrical inner surface defining an internal bore in the input shaft, and a pinion coaxial with the input shaft. An axially extending torsion bar has a first end portion rotationally fixed to the input shaft, a second end portion rotationally fixed to the pinion, and a torsionally flexible portion disposed axially between the first and second end portions. A first valve member is rotatable with the input shaft. A second valve member is rotatable with the pinion and is disposed concentrically about the first valve member.
In one embodiment, a support portion of the torsion bar is rotatable within the internal bore of the input shaft and has a circumferential groove. A compliant ring is disposed in the groove on the support portion of the torsion bar. The ring engages the cylindrical inner surface in the input shaft to enable rotation of the support portion of the torsion bar within the internal bore of the input shaft while limiting relative radial movement between the support portion of the torsion bar and the input shaft.
In another embodiment, the second valve member and the pinion each have a hitch pin opening. A hitch pin has a first portion disposed in the hitch pin opening in the pinion and a second portion disposed in the hitch pin opening in the second valve member. A portion of the material of the second valve member is deformed into engagement with the second portion of the hitch pin to limit relative angular movement between the hitch pin and the second valve member about the primary axis of the steering gear assembly.
REFERENCES:
patent: 3817151 (1974-06-01), Kawabata et al.
patent: 4378030 (1983-03-01), Duffy
patent: 4877100 (1989-10-01), Emori et al.
patent: 5571238 (1996-11-01), Breitweg et al.
patent: 5593166 (1997-01-01), Lovell et al.
patent: 5851006 (1998-12-01), Spillner et al.
patent: 6009903 (2000-01-01), Rohringer et al.
Rivell John
Schoenfeld Meredith H.
Tarolli, Sundheim, Covell Tummino & Szabo L.L.P.
TRW Inc.
LandOfFree
Rack and pinion steering system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rack and pinion steering system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rack and pinion steering system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2574734