Patent Application
20080213116
The present invention relates to a rotary compressor which is compressed in a multi-stage, and more particularly, to a multi-stage rotary compressor capable of optimizing compression efficiency, using a plurality of compression units all together.
A compressor is a device for compressing an operation gas and thus enhancing pressure by receiving power from a power generator such as an electric motor and compressing air, a refrigerant gas or other specific gas, which has been being used throughout industries. The compressor may be divided into a positive displacement compressor and a turbo compressor according to how to compress. The positive displacement compressor has a compressing method in which pressure is increased by decreasing volume, while the turbo compressor achieves a compression by converting a kinetic energy of a gas into a pressing energy. A rotary compressor, one of the positive displacement compressor, is generally applied to an air conditioning apparatus such as an air-conditioner. Recently, it is the trend that the air-conditioner has various functions. In response, the rotary compressor requires a product capable of varying capacity thereof.
The rotary compressor has used a refrigerant containing a CFC-based chlorine. However, the refrigerant is known to destroy the earth's ozone layer, which causes a global warming. As a result, its use is legally regulated and extensive researches have been made for an alternative refrigerant with respect to the existing refrigerant. Carbon dioxide is expected as the alternative refrigerant. Moreover, the global warming is led to a problem of improvement of an energy efficiency of instruments as well as a problem of the alternative of the refrigerant. This is because the carbon dioxide occurred by burning fossil fuel (a great deal of electric energy is still obtained by burning the fossil fuel) is the chief culprit of the global warming.
Accordingly, in the compressor which corresponds to the core part of a refrigeration system, it is the most considerable matter how to applying alternative refrigerants harmless for a global environment to the existing compressor without loss of performance thereof.
There is a multi-stage rotary compressor having a plurality of compression units capable of varying capacity thereof and of using an alternative refrigerant.
A typical multi-stage rotary compressor has a plurality of compression units for sucking, compressing and discharging a refrigerant, respectively; and a driving unit for driving the compression units, all of which are accommodated in a sealed container.
In the compression unit, a plurality of eccentric cams are integrally formed at a rotating shaft rotated by the driving unit. A rolling piston is fit-fixed to an outer circumferential surface of each eccentric cam. The rolling piston is positioned in a cylinder and rolledly-moved when it is contact with an inside diameter of the cylinder. The cylinder is divided therein into a suction chamber and a compression chamber by a vane contacting the rolling piston. The driving unit is composed of a motor for rotating the rotating axis, and accommodated in the sealed container together with the compression unit.
This typical multi-stage rotary compressor sequentially performs suction, compression and discharge of a refrigerant when the rolling piston is contact with the inside diameter of the cylinder at one point. If respective compression units are driven, a great deal of load is generated thereby to obtain a great capacity (hereinafter, referred to a power mode). At this time, the capacity of the compressor may correspond to the sum of refrigerants discharged from the respective compression units. If it is expected that the load is decreased thereby to obtain less capacity and power saving effect (hereinafter, referred to a saving mode), it may be achieved by cutting off the refrigerants sucked in several compression units, or by idling the rolling piston without allowing the compression of the refrigerant by means of moving the vane back and fixing it with such as a piece thereby to remove a boundary between the suction chamber and the compression chamber.
Or, the capacity of the refrigerant may be varied by speed variation using an inverter motor having a control drive as a driving unit.
The structure of the typical rotary compressor and a driving method therefor have the following problems.
First, in case of cutting off a refrigerant sucked in the compression unit, various capacity variation may not be implemented.
Second, during the saving mode in process, the method of moving back and fixing the vane requires an additional component like the piece and a space to install it, and increases the number of manufacturing processes.
Third, as the piece repeatedly impacts on the vane, it may result in damaging a surface thereof as the time elapses, and cause abrasion or generation of impurity thereby to degrade reliability of the compressor.
Fourth, in cases of idling the rolling piston or cutting off a suction of the refrigerant, because several compression units are not used, it may degrade efficiency of the compressor.
Fifth, in case of using the inverter motor as the driving unit, it requires generally a high price so as to increase manufacturing costs. Therefore, there is a need for realizing a capacity variation even using a constant-seed motor which requires relatively low price.
Therefore, it is an object of the present invention to provide a multi-stage rotary compressor capable of maximizing a compression efficiency, even using a plurality of compression units al together, and of decreasing power consumption to be suitable for a saving mode.
To achieve these objects, there is provided a multi-stage rotary compressor, comprising: a casing having a sealed space therein; a driving unit installed in the casing, for generating a driving force; a plurality of compression units for receiving the driving force from the driving unit and compressing a refrigerant; and a connection unit for connecting the plurality of compression units and guiding the refrigerant discharged from a compression unit to be sucked directly into the neighboring compression unit and then to be re-compressed.
As described so far, the multi-stage rotary compressor according to the present invention has effects as follows.
First, by re-compressing a previously-compressed refrigerant, a high discharge pressure can be obtained and a volume efficiency can be improved. Also, a leakage into a casing can be reduced and a heat quantity transferred to a low temperature refrigerant of a suction side can be remarkably decreased by using the previously compressed refrigerant during the re-compression.
Second, the present invention does not need an additional component and a space to install it in comparison with a method in which a vane is moved back and fixed during a saving mode in process, thereby simplifying manufacturing processes. Also, because a piece for moving back and fixing the vane is not required, there can not be no problem related to abrasion, a generation of impurity, and the like, thereby improving reliability of the compressor.
Third, by using every plurality of compression units during the saving mode, efficiency of a motor or the compressor can be improved. Furthermore, compared with a power mode, since the previously-compressed refrigerant is re-compressed, power requirement becomes less, which results in a power saving effect.
Fourth, manufacturing costs can be reduced by varying capacity using a low price of a constant-speed motor.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/KR04/03290 | 12/14/2004 | WO | 00 | 3/26/2008 |
