Power plants – Pressure fluid source and motor – Having distinct cooling or lubricating structure
Reexamination Certificate
2000-03-14
2001-11-13
Look, Edward K. (Department: 3746)
Power plants
Pressure fluid source and motor
Having distinct cooling or lubricating structure
C060S452000
Reexamination Certificate
active
06314729
ABSTRACT:
BACKGROUND OF THE INVENTION
Hydraulic fan drive systems for buses and the like have traditionally required a dedicated flow source to allow sufficiently accurate control of fan speed. This requires either a dedicated fan drive pump, or a dedicated flow amount from a priority flow source from a pump. It is desirable, however, in some applications, to use only a portion of the total flow from an existing hydraulic pump, and share the total pump flow with other work functions on the machine.
It is therefore a principal object of this invention to provide a speed modulating hydraulic fan drive system which shares flow from one source with other work functions.
A further object of this invention is to provide a speed modulating hydraulic fan drive system which will reduce the number of pumps required for the total work system.
A still further object of this invention is to provide a speed modulating hydraulic fan drive system which utilizes a pressure reducing valve which will allow only enough fluid to pass to develop the desired fan motor pressure drop.
A still further object of this invention is to provide a speed modulating hydraulic fan drive system which makes use of an electronic controller to command the pressure level of the pressure reducing valve, and which can respond directly to a communication signal of the electronic controller of the engine of the vehicle.
These and other objects will be apparent to those skilled in the art.
SUMMARY OF THE INVENTION
A specific type of hydraulic fan drive system is provided for engine driven machines, such as on road and off road machines, such as buses, construction equipment, agricultural equipment, and so on. The hydraulic fan drive systems turn a cooling fan which provides airflow to cool the engine on such machines. This system uses a proportional pressure reducing valve (or combination of valves providing a pressure reducing function) between the pump and the fan motor. This valve or (combination of valves) controls the pressure drop across the fan motor based on a control signal from an electronic controller. The valve allows as little or as much flow to pass as is required to maintain this pressure drop at the load (the fan motor).
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Crull Stanley W.
Peterson Mark A.
Lazo Thomas E.
Look Edward K.
Sauer-Danfoss Inc.
Zarley McKee Thomte Voorhees & Sease
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