Oil-level controller for compressor

Details Oil-level controller for compressor Oil-level controller for compressor

1996-02-12

1997-11-18

Vrablik, John J.

Pumps

With condition responsive control of coolant or lubricant

418 556, 418 88, 418100, 1841031, F04B 3902, F04C 2902, F01M 1112

Patent

active

056881096

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION

This invention relates generally to refrigerating compressors. More particularly, it pertains to an oil-level controller, for use by a refrigerating compressor, for controlling the level of a lubricating oil (hereinafter called a lubricant) stored in the bottom of a compressor casing.


DESCRIPTION OF THE PRIOR ART

Many types of compressors have been proposed. JP Pat. Appln., laid open under Pub. No. 2-305392, discloses one. A compression mechanism is located in an upper space of a casing of the compressor, and located in a lower space thereof is a motor. A crankshaft extends up from the motor for linkage to the compression mechanism. The motor drives the crankshaft, and the crankshaft rotates, and the compression mechanism performs compression operations.
A lubricant is stored in the bottom of the casing, and the lower end of the crankshaft lies in the lubricant. The crankshaft lower end is provided with a pump mechanism, e.g., a centrifugal pump. Additionally, a flow passage is formed through the crankshaft. When the motor drives the crankshaft to rotate, the pump mechanism draws up a lubricant from the casing bottom. This lubricant travels through the flow passage to each of slide sections of the compressor for lubrication.
In the above-noted compressor, a lubricant is stored by a predetermined amount, and the level of the lubricant is, in any case, maintained to fall within a predetermined range, taking into account the fact that the oil level varies between when the compressor is stopped and when the compressor is driven.
In other words, the oil level is high when stopped while it is low when driven. Therefore the oil level is set such that it stays below a rotor of the motor in the stopped state while it stays above the lower end of the crankshaft in the drive state.
However, in spite of the above arrangement, the oil level may not fall in the predetermined range depending upon the operating conditions. If a compressor has not been run for a long period of time, or if a compressor is run in humid conditions, then a liquid refrigerant is likely to be mixed with a lubricant stored in a lubricant reservoir. In other words, in addition to the lubricant the liquid refrigerant is now stored in the lubricant reservoir, which may result in increasing the oil level above a predetermined high-limit point.
As the oil level goes beyond a predetermined point, the area of the crankshaft that is soaked in the lubricant stored in the lubricant reservoir increases. Additionally the motor rotor, too, is soaked in the lubricant. The crankshaft and the motor rotor must rotate against resistance produced by the lubricant. In this case electrical input must be increased so as to maintain the rotation of the crankshaft constant. This, however, produces input loss.
Also, in such a situation, both the crankshaft and the motor rotor stir the lubricant and the temperature of the lubricant increases. This increases the temperature of an entire casing space. As a result the efficiency of compression drops.
JP Pat. Appln., laid open under Pub. No. 4-214983, discloses an oil-level control technique known in the art as a forced differential pressure method. In this forced differential pressure method, two compressors are connected together by an oil-level equalizing pipe and there is produced a difference in pressure between the compressors. Most of the lubricant brought back from a refrigerant circulation circuit is introduced into one of the two compressors that is provided on the high-pressure side, and part of the brought-back lubricant is supplied through the oil-level equalizing pipe to the other compressor provided on the low-pressure side because of the aforesaid pressure difference.
The above-described organization, however, requires two compressors. In other words, it is difficult to accomplish a forced differential pressure technique with a single compressor.
Bearing in mind the above-described problems with the prior art techniques the present invention was made. In accordance with the

REFERENCES:
patent: 5000669 (1991-03-01), Shimizu et al.

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