Motor vehicles – Steering by driving – Combined with manual steering
Patent
1991-01-29
1992-12-01
Hill, Mitchell J.
Motor vehicles
Steering by driving
Combined with manual steering
60466, 137493, 180 648, 180 91, 303 842, B60K 1714, F16H 3950
Patent
active
051672910
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national phase application of PCT/EP/00936 filed Aug. 8, 1989 and based, in turn, upon German National Application P3827205.9 filed Aug. 11, 1988 under the International Convention.
FIELD OF THE INVENTION
The invention relates to a hydrostatic drive system for vehicles, particularly crawlers with a hydromotor mounted in the hub of a drive wheel, in or on whose control housing, besides control valves, wheel brake valves are provided, which are arranged in pressure lines and regulate the cross section of the return flow, steering it respectively on and off, depending on the operational pressure of the hydromotor.
BACKGROUND OF THE INVENTION
Hydrostatic drive units for vehicles are known (DE C 2 32 35 378). Thereby, it is required that the drive unit be so compact, especially in the axial direction, that it does not project laterally over the width of a caterpillar track of a crawler excavator or of the wheel of a vehicle. At the same time, the radial dimensions in the area of the seat of the centering device have to be selected so that drive system can be inserted and removed as a completely preassembled unit. These requirements are difficult to meet, when in or on the control housing of the hydromotor wheel brake valves are mounted in addition to other control valves. However, the arrangement of the valves directly on the control housing is advantageous because of increasing the response sensitivity of the drive due to short control lines
OBJECTS OF THE INVENTION
It is the object of the invention to provide a hydrostatic drive system having a particular valves, particularly of the wheel brake valves.
SUMMARY OF THE INVENTION
Due to configuration according to the invention, the wheel brake valves serve simultaneously as a pressure relief valve, so that additional pressure relief valves can be eliminated. This makes possible to keep the dimensions of the control lid with the valves small and to integrate the wheel brake valves in the control lid, so that in the assembled state they can be slid through the seat of the centering device of the drive system.
In order to increase the cross section of the inflow during traction, without increasing the overall construction volume of the wheel brake valves, parallel to each of the wheel brakes valve a bypass line is provided which is equipped with a return valve opening in the direction of the hydromotor. These valves require only a small space and can be lodged in the control lid in suitable places. Further, it is possible to use the same hydromotor with the same control lid for various flow volumes by simply changing the bypass.
In order to sustain the operation of the hydromotor with two pressure lines and one control line, according to the invention the pressure lines on the side of the wheel brake valves facing away from the hydromotor are interconnected by a control line with a two-way valve and a control pressure line for an adjusting mechanism of the hydromotor starting out from this valve.
The wheel brake valve of the drive system of the invention has in the area of the valve seat a throttle gap gradually widening with the opening of the wheel brake valve. As a result, the cross section of the opening can be precisely and continuously controlled over a long control path. Oscillations of the control piston in the area of the closing position are prevented. Further, according to the invention, the control piston has a compensation space with a compensation opening designed as a throttling point in the frontal surface facing the hydromotor. The compensation space is closed by a supporting piston on the frontal side opposite to the compensation opening, the effective cross section of this supporting piston being slightly smaller than the pressure-impacted surface enclosed by the valve seat. As a result, in spite of high system pressures, the compression springs can be designed with small dimensions. Since at opening and closing, through the throttling compensation opening an oil flows out
REFERENCES:
patent: 3261645 (1966-07-01), Alfieri et al.
patent: 4016903 (1977-04-01), Akashi et al.
Dubno Herbert
Hill Mitchell J.
Zahnradfabrik Friedrichshafen AG
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