Motor vehicles – Surface effect vehicles – Dynamic seal or fluid curtain
Patent
1990-04-18
1991-12-17
Marmor, Charles A.
Motor vehicles
Surface effect vehicles
Dynamic seal or fluid curtain
60384, 60422, 60450, 91516, 91518, B62D 506
Patent
active
050728024
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a control mechanism for two hydraulic adjustment devices supplied by a high-pressure pump via separate flow lines.
BRIEF DESCRIPTION OF THE PRIOR ART
Such control mechanisms are already known from German published patent application No. 35 40 236 and German published patent application No. 36 03 988. Here, a flow divider valve subdivides the oil flow, generated by a high-pressure pump, into two flow branches. One branch conducts a working flow via a steering valve to a first adjustment device such as a steering motor, and the other branch supplies a second adjustment device such as a hydraulic lifting unit with a residual flow. The flow divider valve is constructed so that it will supply oil pressure as needed to the steering function which is decisive as regards driving safety.
A measurement diaphragm is located behind a control edge of the flow divider valve for the working flow of the steering function. A small pilot flow constantly flows via this measurement diaphragm to the steering valve in its neutral position. This pilot flow serves for the initial regulation of a pressure in the steering motor and for tempering the steering valve, regardless of the load on the steering motor. This latter measure prevents a situation where the steering valve might get stuck due to heat expansion.
In the aforementioned German application No. 35 40 236, a constant pump is used for the purpose of supplying the control mechanism, and this pump always provides maximum pressure and maximum quantity. In the second German application No. 36 03 988, on the other hand, there is an adjustable pump which varies according to the requirements of the particular highest pressure in the first or second adjustment device. In this case, two control lines are needed which scan the particular working pressure of both adjustment devices and which guide it to the lifting element of the adjustment pump. The coordination of the known control mechanism is accomplished, as regards the combination here, with hydrostatic steering gears.
Such steering gears do not have any fixed rod connections to the drive wheels of the vehicle. By way of a steering valve, there is provided a metering pump which can be activated by a manual steering wheel and which feeds the working flow, depending on the direction of rotation, via high-pressure lines to one or the other pressure chamber of the steering motor. A vehicle equipped with this kind of steering valve, for example, can be used at construction sites and in agriculture. The maximum speed is restricted to 50 km/hr by law for safety reasons.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a hydraulic auxiliary power steering assembly instead of a hydrostatic steering assembly in the control mechanism. According to the invention, the first adjustment mechanism includes a hydraulic steering valve with a mechanical connection between the manual steering wheel and the steered wheels of the vehicle. The steering valve for controlling the working piston is coupled with a pilot valve that is connected in a pilot flow line so that the steering and pilot valves can be adjusted together as the manual steering wheel is turned. In the neutral position, the pilot valve allows the oil to flow off into the tank. As soon as the operator initiates a movement of the manual steering wheel, the steering valve is shifted so that a working flow line is connected with a pressure side of the steering motor. Simultaneously, the pilot valve regulates a pressure--via the flow divider valve--in this working flow line. By using a pilot valve coupled with the steering valve, it is also possible to regulate an auxiliary power steering assembly (i.e. a rod set connection to the wheels) via a pilot flow. A vehicle with this kind of design of its hydraulic control mechanism is also licensed for speeds above 50 km/hr for fast-moving vehicles.
The control mechanism can be operated advantageously with a constant pump or a variable pump. When one uses a variable pump, there are provided on
REFERENCES:
patent: 4043419 (1977-08-01), Larson et al.
patent: 4470260 (1984-09-01), Miller et al.
patent: 4664210 (1987-05-01), Yamaoka et al.
patent: 4665195 (1987-05-01), Rau et al.
Kagen Alan M.
Marmor Charles A.
Zahnradfabrik Friedrichshafen AG
Zalkind Albert M.
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