Refrigeration – Automatic control – Diverse – cascade or compound refrigeration-producing system
Reexamination Certificate
2003-03-13
2004-06-15
Norman, Marc (Department: 3748)
Refrigeration
Automatic control
Diverse, cascade or compound refrigeration-producing system
C062S196400, C062S510000
Reexamination Certificate
active
06748754
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a multistage compression type rotary compressor (hereinafter referred to as multistage rotary compressor) comprising an electric element in a hermetic shell case, and first and second rotary compression elements which are driven by the electric element, wherein a refrigerant which is compressed by the first rotary compression element and discharged is drawn into and compressed and discharged by the second rotary compression element, and a refrigeration circuit system using the multistage rotary compressor.
BACKGROUND OF THE INVENTION
In a conventional multistage rotary compressor of this type, for example, in a multistage rotary compressor of an internal intermediate pressure type, for example, as disclosed in JP-H 2-294586 and JP-H 2-294587 and a refrigeration circuit system using the multistage rotary compressor, a refrigerant is drawn into a low pressure chamber of a cylinder through a suction port of a first rotary compression element (first stage compression mechanism), and it is compressed during the operation of a roller and a vane and is changed into a refrigerant having an intermediate pressure (hereinafter referred to as intermediate pressure refrigerant) and the intermediate pressure refrigerant is discharged from a high pressure chamber of the cylinder to a hermetic shell case through a discharge port and a noise eliminating chamber.
The intermediate pressure refrigerant in the hermetic shell case is drawn into the low pressure chamber of the cylinder through a suction port of a second rotary compression element (second stage compression mechanism), where it is subjected to a second stage compressions during the operation of the roller and vane and is changed into a refrigerant having a high temperature and high pressure (hereinafter referred to as high temperature and high pressure refrigerant), which in turn flows from the high pressure chamber into a radiator or the like such as an external gas cooler or the like constituting a refrigeration circuit system unit through a discharge port and the noise eliminating chamber, where the heat is radiated to perform heating operation, then throttled by an expansion valve (pressure reducing device) and enters an evaporator, where heat of the refrigerant is withdrawn and the refrigerant is evaporated, thereafter it is drawn into the first rotary compression element. This cycle is repeated.
In such a multistage rotary compressor, the cylinders of the first and second rotary compression elements and the noise eliminating chamber communicate with each other by the discharge port. A discharge valve for freely opening and closing the discharge port is provided in the noise eliminating chamber. The discharge valve is formed of an elastic member made of longitudinal substantially rectangular metal sheet wherein one side of the discharge valve is brought into contact with the discharge port to seal it and the other side of the discharge valve is fixed to an attachment port by a caulking pin with a predetermined distance relative to the discharge port.
The refrigerant which is compressed by the cylinder to reach a predetermined pressure pushes the discharge valve which closes the discharge port to open the discharge port and then it is discharged into the noise eliminating chamber. When the discharge of the refrigerant approaches an end time, the discharge vale is structured to block off the discharge port. At this time, the refrigerant remains in the discharge port which is returned to the cylinder and is expanded again.
Although the re-expansion of the refrigerant remaining in the discharge port incurs the lowering of the compression efficiency, the conventional multistage rotary compressor sets the ratio of S2 to S1 (S2/S1) to be the same as the ratio of V2 to V1 (V2/V1) where SI is an area of a discharge port of the first rotary compression element and S2 is an area of a discharge port of the second rotary compression element, V1 is displacement of the first rotary compression element and V2 is displacement of the second rotary compression element.
Meanwhile, in a refrigeration circuit system such as a cooling, heating and hot water supply unit using refrigerant, e.g., Carbon dioxide (CO
2
), which is large in difference between high and low pressures, a discharge pressure of the second rotary compression element (second stage) is normally controlled to a very high pressure ranging from 10 MPa to 13 MPa so that volume flow at the discharge port of the second compression element is very small. Accordingly, even if the area of the discharge port of the second rotary compression element is made small, it is hardly susceptible to a passage resistance. Nonetheless, if the ratio of S2/S1 of the discharge port is set to a conventional ratio in the multistage rotary compressor using such a refrigerant, there arises a problem that a compression efficiency (operation efficiency) is lowered.
In the multistage rotary compressor using such a refrigerant, a discharge refrigerant pressure reaches 1 MPa at a refrigerant discharge side of the second rotary compression element (second stage compression mechanism) which becomes a high pressure at an ambient temperature of about +20° C. as shown in
FIG. 5
, while it reaches 9 MPa at the first rotary compression element forming a lower stage, which in turn becomes an intermediate pressure in the hermetic shell case (pressure in a case). A pressure (low pressure) drawn by the first rotary compression element is about 5 MPa.
However, if an evaporation temperature of the refrigerant increases when an ambient temperature increases, a pressure drawn by the first rotary compression element increases so that a pressure at the refrigerant discharge side (first stage discharging pressure) also increases as shown in FIG.
5
. When the ambient temperature becomes not less than +32° C., the pressure at the refrigerant discharge side (intermediate pressure) of the first rotary compression element becomes higher than that (second stage discharging pressure) of the second rotary compression element so that there occurs an inverse of the pressure between the intermediate pressure and a high pressure, arising a problem that a vane of the second rotary compression element is prone to jump to generate noises and the operation of the second rotary compression element becomes unstable.
Although in the conventional multistage rotary compressor, a pressure reversing phenomenon, between the pressure (intermediate pressure) at the refrigerant drawing side of the second rotary compression element and the pressure (high pressure) at the refrigerant discharge side of the first rotary compression element caused by excessive compression by the first rotary compression element is avoided by controlling the amount of circulation of the refrigerant by the expansion valve in the refrigeration circuit, namely, by restraining (throttling) the amount of refrigerant which is introduced into the first rotary compression element. However, in such a case, there arises a problem that the performance of the multistage rotary compressor is lowered because the amount of refrigerant which circulates in the refrigeration circuit is reduced. In addition, the pressure in the hermetic shell case increases, arising a problem that the pressure exceeds an allowable limit of the hermetic shell case.
SUMMARY OF THE INVENTION
The invention has been developed to solve the technical problems of the conventional multistage rotary compressor. It is a first object of the invention to provide a multistage rotary compressor using a refrigerant such as carbon dioxide (CO
2
) which becomes high in a discharge pressure, and improving operating efficiency by appropriately setting the ratio between the air volumes of the respective rotary compression elements and the areas of discharge port thereof. It is another object of the invention to provide a multistage rotary compressor capable of avoiding a pressure reversing phenomenon where discharge pressures of the first and second rotary compression elements
Matsumoto Kenzo
Sato Kazuya
Tadano Masaya
Tsuda Noriyuki
Yamasaki Haruyuki
Armstrong Kratz Quintos Hanson & Brooks, LLP
Norman Marc
Sanyo Electric Co,. Ltd.
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