Power plants – Pressure fluid source and motor – Having distinct cooling or lubricating structure
Patent
1996-05-17
1998-01-20
Lopez, F. Daniel
Power plants
Pressure fluid source and motor
Having distinct cooling or lubricating structure
F16D 3102
Patent
active
057090858
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The invention relates to a method for cooling the hydraulic oil present in the operating circuit of a construction machine, in particular a hydraulic excavator, in that the hydraulic oil is guided at least partially over an oil cooler and thereafter flows into a hydraulic oil tank.
BACKGROUND OF THE INVENTION
At present two methods are used for cooling the hydraulic oil in construction machines, in particular hydraulic excavators.
According to one method, all partial flows flow into a central tank, in which subsequently an appropriate mixing temperature ensues. A partial amount of this hydraulic oil is aspirated by a pump and guided over an oil cooler, which cooperates with a blower motor, before it cause the oil to flow back into the tank. To assure an appropriate operating temperature of the hydraulic oil in the tank, it is necessary either to aspirate a large amount of oil out of it or the oil cooler must be embodied to be of an appropriate size.
According to another method defined partial flows are directly led to the collecting tank and the heated oil from the hydraulic operating system (operating cylinders) is supplied to an oil cooler before reaching the collecting tank. The advantages of the above are that for thermodynamic reasons, the hottest part of the oil is provided to the cooler part, since in this way a higher cooling output can be achieved. Disadvantages are based on the fact that hydraulic operating system (operating cylinders) of the construction machine is not continuously operated and, therefore the temperature in the collecting tank may attain critical values.
It is an object of the invention to achieve an optimization of the degree of efficiency at the hydraulic oil cooler in order to assure in every case that the temperature present in the collecting tank cannot attain critical values. Further more, it is another object of the invention to reduce the cooling surface of the oil cooler.
SUMMARY OF THE INVENTION
The above objects are attained in accordance with the invention in that the hydraulic oil returning from the operating area(s), in particular the operating cylinders, having a very high temperature, is intermediately stored prior to entering the hydraulic oil tank, i.e. that it is spatially separated from the oil in the hydraulic oil tank, and is aspirated from there via a pump which sends the hydraulic oil which is at a high temperature level to the oil cooler before it flows back into the hydraulic oil tank at an appropriately lower temperature and is mixed there with the hydraulic oil of a different temperature level which is present there.
The pump preferably aspirates hydraulic oil from the hydraulic oil tank, if needed through a bypass, as soon as the amount of oil present in the intermediate reservoir falls below a preset filling amount or a preset filling level. The aspiration of secondary air is prevented by this step. In the same way the pump can automatically aspirate the hotter hydraulic oil from the intermediate reservoir when the filling amount or the filling level are exceeded.
A device for cooling the hydraulic oil present in the operating circuit of a construction machine is distinguished in that a further container in the form of an intermediate reservoir is provided in the area of the hydraulic oil tank, wherein the container in accordance with a further concept of the invention constitutes a partial area of the hydraulic oil tank. Accordingly, separate components which require structural space become superfluous, particularly since the total oil amount is not changed and instead is merely provided at different places of the hydraulic oil tank. The hot hydraulic oil provided in the intermediate reservoir is supplied to the oil cooler via a separate aspirating pump designed as a cooling oil pump, wherein this aspirating pump automatically aspirates oil from the hydraulic oil tank when there is too low a filling amount or filling level in the intermediate reservoir.
If a separate bypass line is used, at least one measuring device is pr
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patent: 3960174 (1976-06-01), Latimer et al.
patent: 3976124 (1976-08-01), Brown
patent: 4220015 (1980-09-01), Johansing, Jr.
patent: 5109672 (1992-05-01), Chenoweth et al.
patent: 5317872 (1994-06-01), Ingvast
Lopez F. Daniel
O & K Orenstein & Koppel AG
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