Motor vehicles – Including one or more ski-like or runner members – With at least one surface-engaging propulsion element
Patent
1990-06-20
1992-02-11
Rice, Kenneth R.
Motor vehicles
Including one or more ski-like or runner members
With at least one surface-engaging propulsion element
180148, 180132, 91401, 92 135, 92 138, B62D 512, F15B 910
Patent
active
050868640
DESCRIPTION:
BRIEF SUMMARY
The invention is concerned with a hydraulic auxiliary-power steering device.
BRIEF DESCRIPTION OF THE PRIOR ART
Auxiliary-power steering devices with a working or drive piston installed in the steering gear housing are equipped with cut-off devices that cut off the auxiliary power in the surge chamber which is under working pressure at that time, before the limit stops are reached. In that process, seat valves connected with push rods are used which are pressed into their closed position by the combined power of a spring and the working pressure. When the final position of the piston in reached, a push rod abuts a housing wall and the proper by-pass valve opens. The high pressure that is acting in the working chamber is then reduced through a through-drilled hole or bore containing the cut-off device and through the working chamber that is relieved of the pressure. Such cut-off devices are known from DE-PS 25 04 892 and DE-OS 29 30 49B, for example.
From a prospectus of the Ross Gear Division, TRW Steering Components Group, 8000 Heath St., Lafayette, Ind. 47902, U.S.A., entitled "Integral Power Steering Gear--Applications Guide," from 1987, it is apparent that manual adjustment of the by-pass valve in the final positions of the steering movement are no longer performed during the initial assembling process. Instead, the by-pass valves are adjusted automatically after the assembly of the steering mechanism in the vehicle by a single mechanical rotation against the wheel limit stops. According to the prospectus, the steering limiter is constructed in such a way that a bushing or seat is pressed into an outer bushing or sleeve. The outer bushing is seated firmly in an axial through-drilled hole in the working piston. The inner bushing projects far beyond the outer bushing and the working piston after the assembly of the steering mechanism. Upon mechanical rotation against the wheel limit stops, the inner bushing touches a radial housing wall early and is pushed to the required setting in the through-drilled hole.
The inner bushing comprises the seat for the by-pass valve, whose piston is spring-loaded. A push rod of the cut-off piston directed outwardly projects from the working piston by a few millimeters so that the hydraulic pressure is reduced as soon as the push rod comes into contact with the radial housing wall.
In this known automatically adjustable steering limiter, the fit between the outer and the inner bushings must be produced with very great precision. With even small variations, the possibility of endangering the steering function, and thereby the safety of travel, cannot be excluded. Specifically, if the pressing of the two bushings is too slight, the inner bushing can creep outward axially as a result of the operating pressure. The operating pressure acts through the surge chamber, which is under operating pressure, and the by-pass valve in the working piston adjoining that surge chamber in the inside of the through drilled hole, and by that means it also acts on the by-pass valve that is under operating pressure.
Furthermore, the danger of the "creeping" outward of the inner bushing is increased by the fact that the working pressure, when traveling over obstacles, can achieve for a brief period of time an increase of more than 50 percent of the maximum pressure adjusted by a pressure limitation valve, as a result of the oil's mass moment of inertia.
SUMMARY OF THE INVENTION
Therefore it is the object of the invention to provide a self-adjusting hydraulic steering limiter with which a satisfactory cut-off function is assured under all operating conditions.
According to the invention, bushings are provided as a limit stop for the push rod of the by-pass valve in the radial walls of the housing to limit the piston travel.
In that situation, the open side of the bushing is turned toward the push rod. This shortens the axial space requirement. The vehicle is jacked up for assembly and adjustment of the auxiliary-power steering device. Therefore the steering gear and the steered wheels can e
REFERENCES:
patent: 2912935 (1955-12-01), Wick et al.
patent: 4736674 (1988-04-01), Stoll
patent: 4773303 (1988-09-01), Stroud
Integral Power Steering Gear Applications Guide.
Boehler Anne Marie
Rice Kenneth R.
Zahnradfabrik Friedrichshafen AG.
Zalkind Albert M.
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