Motor vehicles – Surface effect vehicles – Dynamic seal or fluid curtain
Patent
1984-11-21
1986-10-21
Love, John J.
Motor vehicles
Surface effect vehicles
Dynamic seal or fluid curtain
180132, 180143, B62D 508
Patent
active
046180176
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
An auxiliary power boost steering system having an emergency pump which operates with a first and a second pump has been known, for example, in the German Pat. No. 27 31 975 (U.S. Pat. No. 4,237,993). A two-pump operation is always desirable since at times heavy trucks become unsteerable because of the failure of the engine driven first pump. In this case, a vehicle may be safely pulled out of traffic while the vehicle is rolling, for example, with the second pump (emergency steering pump) driven by the gearing in vehicle movement. The known auxiliary power steering arrangement shows a so-called emergency valve which, in the case of a defect of the engine driven first pump, separates the latter from the hydraulic steering circuit and connects in the emergency steering pump. Whenever the engine driven first pump is fully operational, the emergency steering pump in the standby mode circulates a volume of oil with a certain idling pressure required for the maintenance of the hydraulic circuit. Since a failure of the engine driven first pump occurs only very rarely during operation time of a vehicle, the continuing standby operation of the vehicle driven emergency steering pump means a steady loss of power.
BRIEF DESCRIPTION OF THE INVENTION
According to the invention, the engine driven pump is a variable displacement adjustable output pump, but the emergency steering pump is vehicle driven by a shaft or axle of the vehicle. A steering flow control valve has, in the neutral position, a construction so that output flow of the emergency steering pump regulates the variable displacement engine driven pump. Moreover, for the regulation of the variable displacement pump, a comparator valve connected between the pressure line connections to the booster cylinder has been provided connecting the effective pressure side of the booster cylinder with the pressure operated actuator of the variable displacement pump to set the extent of the stroke. At a low speed of travel, the emergency steering pump has an output flow sufficient for slow steering movements for usual steering in the directions of travel. In this case, the opened area of the inlet flow control gaps of a slidable steering control valve effect pressures for the actuator means of the variable displacement pump for zero stroke. Thus, when the vehicle travels at medium or higher speeds, in the normal operating range of the auxiliary power steering, the vehicle driven emergency steering pump supplies booster oil for steering purposes while the variable displacement pump remains in zero stroke position thereby absorbing no engine power, and being in a standby mode.
The vehicle driven emergency steering pump is the main pump relied on for steering at or above a predetermined vehicle speed, e.g., 10 KM/h. However, the term "emergency" is used to indicate that if the variable displacement pump flow fails when needed, the vehicle driven pump can at least provide pressure flow to steer the vehicle off the road.
However, for low speeds of travel, e.g., in sharp curves, the flow required in the booster cylinder can no longer be produced by the slowed speed of the vehicle driven steering pump alone. Due to the wide opening of an inlet valving gap, the control edges 12 or 13, respectively, the pressure difference decreases toward zero. As a result of the small or no pressure difference in the control lines 26 and 28, an actuator means swashplate is acted on by a spring force in the direction of increased volume discharge. The variable displacement pump therefore provides a pressure flow of oil whenever the travel conditions require supplemental feed to the booster cylinder. When the pressure in a chamber of the booster cylinder rises, such pressure chamber being connected through a comparator valve with the actuator means regulates the stroke of the pump to provide additional flow. Of course, should that pump fail, e.g., due to engine trouble or other reason, the vehicle driven emergency pump can at least function to steer the vehicle out o
REFERENCES:
patent: 3246472 (1966-04-01), Kries
patent: 3784328 (1974-01-01), Pedersen
patent: 4184560 (1980-01-01), Tischer
patent: 4204584 (1980-05-01), deMaight
patent: 4237993 (1980-12-01), Jablonsky
patent: 4293051 (1981-10-01), Nishikawa
patent: 4557342 (1985-12-01), Drutchas
Liebert Karl-Heinz
Wiedemann Erwin
Love John J.
McGiehan Donn
Zahnradfabrik Friedrichshafen AG.
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