Motor vehicles – Steering gear – With fluid power assist
Patent
1996-01-17
1998-01-27
Hurley, Kevin
Motor vehicles
Steering gear
With fluid power assist
180417, 91375A, B62D 508
Patent
active
057113955
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a rotary slide valve for power-assisted steering mechanisms of motor vehicles. The rotary slide valve contains two valve elements--namely a rotary slide and a valve sleeve--, which are arranged coaxially movable within each other and are connected with each other via a torsion rod and a backlash coupling in such a way that they are rotatable around each other by maximally the pivot path of the backlash coupling. The one valve element is connected with a valve inlet element member and the other valve element with a valve outlet member, fixed against relative rotation. A part of the backlash coupling is formed on the radially inner valve element by claws which project in relation to the front face of the valve element.
2. Description of the Prior Art
Such a rotary slide valve is known, for example, from DE-OS 17 55 438. In this rotary slide valve the inner and the outer valve elements are provided with stops or claws in case the torsion rod should break or the hydraulic installation should fail. These stops and claws come into play if one of the mentioned defects occurs. In such a case the steering gear can continue to be manually operated.
With normal steering movements the stops and claws, which together constitute the backlash coupling, limit the control path of the rotary slide valve, so that oversteering is not possible. In addition, the movement of the torsion rod is limited to its proportional range.
With the arrangement proposed in DE-OS 17 55 438, however, the claws which cooperate with the stops of the outer valve element are disposed approximately in the center of the valve element constituting the rotary slide. But it is only possible to produce a component with radially projecting claws arranged in this way by means of a considerable outlay of material and production effort.
In another known rotary slide valve (DE-C2-33 03 063) the claws project from the rotary slide in the axial direction in relation to its front face. Such claws can be produced relatively simply. But the openings of the outer valve element, which are provided with parallel lateral walls, are more difficult to produce. Relatively expensive broaching tools are required for this.
In addition, with this rotary slide valve there is an open connection through the broached openings of the outer valve element between its inner chamber and the exterior environment. Therefore the use of such a rotary slide valve is limited to structures in which the same pressure is present at this point inside and outside of the outer valve element and therefore no connection with different cylinder chambers is permitted. If this were the case, a great effort would be required to close and seal the broached openings from both sides.
The object of the invention lies in designing a rotary slide valve in such a way that the disadvantages of the known designs are avoided. It is intended in particular to produce the backlash coupling by simple means. It is intended to employ the rotary slide valve in many ways, without an additional outlay, particularly in respect to additional sealing steps.
SUMMARY OF THE INVENTION
This object is attained by the rotary slide valve of the present invention. Further advantageous and practical embodiments of the invention are described herein. The attainment of the object consists in particular in that the other part of the backlash coupling is constituted by two pins which are disposed parallel with each other in the radially outer valve element, whose axes are located in a plane extending perpendicularly in respect to the axis of the rotary slide valve. The bores for the pins can be produced particularly simply if the axes of the pins lie symmetrically with each other in respect to the axis of the rotary slide valve. In this case the pins can also be automatically mounted. The pins can be pressed oil-proof into the outer valve element in a simple manner by an appropriate selection of the fit between the pins and the bores. This results in th
REFERENCES:
patent: 5147009 (1992-09-01), Chikuma et al.
patent: 5241893 (1993-09-01), Guasch et al.
patent: 5396969 (1995-03-01), Joerg et al.
Breu Gunther
Schurr Rudolf
Hurley Kevin
ZF Friedrichshafen AG
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