Motor vehicles – Surface effect vehicles – Dynamic seal or fluid curtain
Patent
1992-01-10
1993-12-14
Hill, Mitchell J.
Motor vehicles
Surface effect vehicles
Dynamic seal or fluid curtain
180235, 280432, 2804461, B60D 132, B62D 509
Patent
active
052693899
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a pilot type fully hydraulic steering system having a steering device of a vehicle such as a wheel loader, fork lift truck and is capable of preventing the deterioration of a steering operation property of a wheel due to deviation of a wheel position when a vehicle body travels straight and of correcting deviation of the wheel position, which is caused by frequent turning of the wheel.
BACKGROUND
A conventional pilot type fully hydraulic steering system will be described with reference to FIG. 13.
In the same figure, if a wheel H is turned from a straight position H.sub.2 to a left turning position H.sub.1 or to a right turning position H.sub.3, a directional control valve b is changed over from a straight position b.sub.2 to a left turning position b.sub.3 so that an oil under pressure supplied through a hydraulic pump A is supplied to a metering unit c and returned to the directional control valve b. In the case of left turning, a directional control valve d of a steering valve is switched over to a left turning position d.sub.1 so that the oil under pressure from hydraulic pumps M (steering pump) and N (switching pump) is supplied to a head side D.sub.h of a left steering cylinder D and a bottom side E.sub.b of a right steering cylinder E. In the case of right turning, the oil under pressure is supplied to a bottom side D.sub.b of the left steering cylinder D and a head side E.sub.h of the right steering cylinder E so that vehicle bodies F and G are turned relative to each other, whereby the steering operation is made. The oil under pressure, which is returned from left and right steering cylinders D and E, is returned to a tank T through the directional control valve b. Designated at L is a working machine valve P.sub.1 and P.sub.2, which are denoted at two dotted and one chain line and show that the directional control valve b and the metering unit c are operated by the wheel H.
In the conventional pilot type fully hydraulic steering system, it is necessary to correct the deviation of the wheel position since the turning angle of the wheel and the turning angle of the vehicle body do not always accord with each other at the same ratio because of leakage of the oil under pressure inside each hydraulic device, indifference of the steering valve to a pilot oil and revolution of turning of the steering wheel.
Accordingly, the present invention is to eliminate the drawbacks of the conventional pilot type fully hydraulic steering system and to provide a wheel position correcting device capable of eliminating such a drawback that the steering of the wheel is deteriorated due to the gradual deviation of the wheel position when the vehicle body travels straight.
SUMMARY OF THE INVENTION
To achieve the above object, the present invention provides a wheel position correcting device for pilot type fully hydraulic steering system provided with a hydraulic circuit to connect a steering unit operated by a wheel to steering cylinders for turning the vehicle body, characterized in comprising a sensor to detect a turning angle of the wheel, a sensor to detect a turning angle of the vehicle body, a controller to compare outputs (such as voltage and pulse) from these two sensors to drive a wheel position correcting solenoid valve according to the difference between the outputs, a pilot type diverting valve to allow wheel position correcting oil to branch from a switch pump circuit to a wheel position correcting solenoid valve, and a safety valve to close a drain port of the pilot type diverting valve only when the driver performs steering with the wheel so that the pilot type diverting valve feeds correcting oil to the correcting valve.
With such an arrangement, it is possible to correct the deviation of the wheel position by supplying a wheel position correcting oil from the wheel position correcting solenoid valve to the steering cylinder toward the position for correcting the deviation of the wheel or by draining part of the oil discharged from the steering valve
REFERENCES:
patent: 4081054 (1978-03-01), Yates
patent: 4106792 (1978-08-01), Schultz et al.
patent: 4365685 (1982-12-01), Ratsko et al.
patent: 4688818 (1987-08-01), Grassmuck
patent: 4763916 (1988-08-01), Ratsko et al.
patent: 5020618 (1991-06-01), Nagao
Nozawa Toshiro
Tomiyoshi Yasumasa
Hill Mitchell J.
Kabushiki Kaisha Komatsu Seisakusho
Komatsu Mec Kabushiki Kaisha
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