Motor vehicles – Steering gear – No mechanical connection between steering shaft and steering...
Patent
1996-05-13
1998-06-02
Hurley, Kevin
Motor vehicles
Steering gear
No mechanical connection between steering shaft and steering...
180442, B62D 508
Patent
active
057587396
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a hydraulic steering circuit for slow-moving vehicles and to a hydraulic steering apparatus therefor, which includes a control valve and a metering pump, wherein the control valve includes an interior control piston, controllable by the steering wheel, and an outer control sleeve connected mechanically to the metering pump, wherein both are disposed concentrically relative to each other, and wherein both are rotatable to a limited degree relative to each other against the force of a spring, and wherein the control piston and the control sleeve have grooves cooperating with each other for connecting the metering pump to connectors of a steering cylinder.
2. Brief Description of the Background of the Invention Including Prior Art
Steering circuits of this kind are sufficiently known. They comprise essentially a tank, a supply pump, a hydraulic steering apparatus, and a hydraulic steering cylinder. The steering apparatus has, on the one hand, a feed connector and a discharge connector, which are both connected to the tank, and, on the other hand, two cylinder connectors, which are in connection with the two cylinder volumes of the steering cylinder. The steering cylinder, in general, is furnished with a one-sided piston rod, wherein the piston rod transfers its motion mechanically through a steering linkage to the guiding wheels.
Based on the one-sided piston rod, the two cylinder volumes have naturally different volumes. Upon actuation of the steering apparatus in one rotation direction, metered oil is transported through the steering apparatus in one of the two cylinder volumes and at the same time the oil is displaced from the other cylinder volume and fed thereby again to the tank through the steering apparatus. For this purpose, the same grooves in the control piston are available in the steering apparatus for the two directions of rotation.
The function of such a steering circuit with a corresponding steering apparatus is always satisfactory in cases where, corresponding to the circumstances, a sufficient steering load has to be overcome.
However, in certain individual application cases and application locations, pulling forces can occur at the piston of the steering cylinder, as is the case, for example, upon fast travel and a high rotation speed of the steered wheel of articulated frame steered vehicles. This pulling load at the cylinder piston can lead to the elimination of the steering load, based on the small oil volume, on the piston rod side when steering against the floor of the cylinder piston. Thereby, the steering cylinder runs in advance of the steering motion. An uncontrolled steering behavior is the consequence and is associated with all its danger.
A circuit with such a steering apparatus is described in the Printed Patent document WO-A-9112985, wherein a one-way restrictor is furnished in the working line between the control valve and the working area of the steering cylinder on the piston rod side for decreasing the influence of a negative damping relative to the dynamics of vehicle movement. The check valve is thereby blocked in the direction from the steering cylinder to the control valve.
This circuit increases the equipment-technological expenditures substantially.
A corresponding steering apparatus is presented in the printed patent document DE-A-2810902, wherein longitudinal control grooves are furnished in the control piston subdivided in two parts relative to their length for the purpose of decreasing the interior leak flows.
This solution does not eliminate the uncontrolled behavior of the steering cylinder in case of a pulling load.
SUMMARY OF THE INVENTION
It is an object of the present invention to create a hydraulic steering circuit and a corresponding steering apparatus which assures a sufficient steering load in the two steering directions in case of a steering cylinder with a one-sided and pullingly loaded or tension-loaded piston rod.
These and other objects and advantages of the present
REFERENCES:
patent: 4553390 (1985-11-01), Liebert et al.
patent: 5056311 (1991-10-01), Tischer
Bergmann Erhard
Voss Gerhard
Hurley Kevin
Hydraulik Nord GmbH
Kasper Horst M.
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