Rotary compressor

Abstract: A two stage rotary compressor is disclosed and includes first and second cylinders (38,40) separated by an intermediate partition plate (36) and first and second compressing elements (42,44) disposed in the first and second cylinders (38,40) respectfully, the compressing elements (42,44) being formed on a rotary shaft (16) spaced from each other by a portion of the shaft (90) that extends through an aperture (36a) in the intermediate partition plate (36). The portion (90) of the shaft (16) between the compressing elements (42,44) has a larger cross-sectional area than the cross sectional area of the remainder of the shaft (16).

Description: The present invention relates to a rotary compressor and, in particular, to a two-cylinder type two-stage compression rotary compressor having a cylinder on either side of an intermediate partition plate. In a conventional rotary compressor such as those used in a refrigeration circuit and in which a refrigerant such as carbon dioxide (CO 2 ) is used, the pressure difference between the high and low pressure side may be very high. For example, the refrigerant pressure may reach approximately 100 kg/cm 2 G on the high pressure side (high stage side), whilst being approximately 30 kg/cm 2 G on the low pressure side (low stage side). Therefore, the pressure difference between the high and low pressure sides can be in the region of 70 kg/cm 2 G. A rotary compressor of the type referred to above includes a rotary shaft having two eccentric portions thereon, one eccentric portion, with a phase difference of 180° with respect to the other, being disposed in each cylinder separated by the intermediate partition plate. The rotary shaft includes a connecting portion between the two eccentric portions that extends through an aperture in the intermediate partition plate. A disadvantage with a conventional rotary compressor is that the connecting portion of the shaft is placed under high loads which can cause it to deform elastically. This problem particularly occurs when refrigerant having a high working pressure, such as carbon dioxide, is used. When the rotary shaft becomes elastically deformed, it may contact a bearing or other component of the compressor causing abnormal abrasion and an increase in wear. This reduces the durability of the compressor and generates vibration and noise. It is known from US 4563137 to provide a two-stage rotary compressor including first and second cylinders (38,40) separated by an intermediate partition plate (36) and first and second eccentric compressing portions (42,44) disposed in the first and second cylinders (38,40) respectfully, the eccentric compressing portions (42,44) being formed on a rotary shaft (16) spaced from each other by a portion (90) of the shaft (16) that extends through an aperture (36a) in the intermediate partition plate (36) and having a phase difference of 180°. It is an object of the present invention to overcome or alleviate the disadvantages with a conventional compressor mentioned above. A two-stage rotary compressor according to the invention is characterised in that the portion (90) of the eccentric compressing portions (42,44) has a cross-sectional shape such that the thickness in a direction orthogonal to an eccentric direction is larger than the thickness in the eccentric direction. Preferably, the cross section of the portion of the shaft between the compressing elements is non-circular in shape. Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates a two-cylinder type two-stage compression rotary compressor of an internal low pressure type; Figure 2 is a partial cross-sectional view through a cylinder of the compressor shown in Figure 1; Figure 3 is a side elevation of the rotary shaft including upper and lower eccentric portions, shown in the compressor of Figure 1; Figures 4(a) and (b) are cross-sectional views taken along the line A-A and the line B-B respectively; Figure 5 is a side elevation of another rotary shaft for use in the compressor shown in Figure 1; and Figures 6(a) and (b) are cross-sectional views taken along the line C-C and line D-D respectively, shown in Figure 5. A two-cylinder type two-stage compression rotary compressor 10 which is of an internal low pressure type according to an embodiment of the present invention includes: a cylindrical closed steel container 12; an electric motor 14 disposed in the closed container 14; and a rotary compression mechanism 18 drivable by a rotary shaft 16 of the electric motor 14. The cylindrical closed container 12 includes an oil tank it is base and comprises a container main body 12A for accommodating therein the electric motor 14 and the rotary compression mechanism 18, and a bowl-like cover 12B for closing the upper opening of the container main body 12A. Further, a terminal (wiring is omitted) 20 for supplying power to the electric motor portion 14 is provided on the cover 12B. The electric motor 14 includes stator 22 annually attached along the inner peripheral surface of the upper space of the cylindrical closed container 12, and a rotor 24 inserted and arranged inside the stator 22 with a small gap therebetween. The rotating shaft 16 extending through the centre in the vertical direction is fixed to the rotor 24. The stator 22 has a layered product 26 on which a ring-like electromagnetic steel plate is superimposed thereon and a stator coil 28 wound around the layered product 26. In addition, the rotor 24 is formed by a layered product 30 which is an electromagnetic steel plate similar to the stator 22. The rotor and stator 22 together constitute an alternating current motor. However, it will be apparent that the alternating current motor can be substituted by a DC motor in which a permanent magnet is embedded. The rotary compression mechanism 18 includes: a low stage side compression portion 32; a high stage side compression portion 34; and an intermediate partition plate 36 which is sandwiched between the compression portions 32, 34 and has an aperture 36a through which a portion of the rotating shaft extends. Each compression portion 32, 34 comprises the intermediate partition plate 36; upper and lower cylinders 38 and 40 arranged on the upper and lower sides of the intermediate partition plate 36 respectively, upper and lower rollers 46 and 48 which are fitted to upper and lower eccentric portions 42 and 44 provided on the rotary shaft 16 with a phase difference of 180 degrees in the upper and lower cylinders 38 and 40; upper and lower vanes 50 and 52 which are in contact with the upper and lower rollers 46 and 48 to partition the insides of each of the upper and lower cylinders 38 and 40 into a low pressure chamber side 38a, 40a and a high pressure chamber side 38b, 40b; and upper and lower support members 54, 56 which closes the upper and lower cylinders 38 and 40 and serve as bearings for the rotating shaft 16. Inlet passages 58, 60 communicate with the inside of the upper and lower cylinders 38, 40 and outlet sound absorbing chambers 62 and 64 are formed on the upper and lower support members 54, 56. The openings to both of the outlet sound absorbing chambers 62, 64 are closed by an upper and lower plate 66, 68. As shown in Figure 2, the upper and lower vanes 50, 52 are arranged and accommodated in radial guide grooves 60, 72 formed in the cylinder walls of the upper and lower cylinders 38, 40 so as to be capable of reciprocal movement therein. The vanes 50, 52 are constantly pushed against the upper and lower rollers 46, 48 by springs 74, 76. The compression operation of the first stage (low stage side) is carried out in the upper cylinder 38, and the compression operation of the second stage (high stage side) for further compressing the refrigerant gas which has been compressed in the upper cylinder 38 to be boosted to have an intermediate pressure is performed in the lower cylinder 40. Among elements constituting the above-described rotary compression mechanism 18, the upper support member 54, the upper cylinder 38, the intermediate partition plate 36, the lower cylinder 40 and the lower supporting member 56 are arranged in the stated order and are further integrally connected and fixed together with the upper plate 66 and the lower plate 68 using a plurality of fixing bolts 78. An oil hole 80 orthogonal to the axis of rotation of the shaft is formed near the lower end of the rotating shaft 16 and lateral fill holes 82, 84 are formed to this oil hole 80. The portion 90 of the shaft between the upper and lower eccentric portions 42, 44 is formed integrally with the shaft 16 and has a cross-sectional area is larger than the circular cross section of the remainder of the rotary shaft 16 to increase the rigidity of the rotary shaft 16. The cross section may be non-circular in shape. The cross-sectional shape of the connecting portion is shown more clearly in Figures 3 and 4. Although the connecting portion 90 for connecting the upper and lower eccentric portions 42, 44 is coaxial with the rotating shaft 16, its cross section is such that its thickness in a direction orthogonal to the direction in which the upper and lower eccentric portions 42, 44 extend from the rotary shaft 16 is greater than the thickness in the same direction in which the eccentric portions extend from the rotary shaft 16. More specifically, from Figures 4(a) and (b), a thickness d1 in the direction in which the upper and lower eccentric portions 42, 44 extend from the shaft 16 is the same as the diameter d of the rotary shaft 16. However, the thickness D1 in a direction orthogonal to the direction in which the eccentric portions 42, 44 extend is larger than the former thickness (D1 > d1 = d). Therefore, a non-circular cross-sectional area S1 of the connecting portion 90 is larger than a circular cross-sectional area S of the rotating shaft 16 (S1 > S). It is to be noted that the cross-sectional form of the connecting portion 90 in this case is vertically and horizontally asymmetric. Another embodiment is shown in Figures 5 and 6. In this embodiment, the thickness d2 in the same direction as the direction in which the eccentric portions extend from the rotary shaft 16 is larger than the diameter of d of the rotating shaft 16, and a thickness D2 in a direction orthogonal to the direction in which the eccentric sections extend from the rotary shaft 16 is larger than the former (= d2) (D2 > d2 > d)), as will be apparent from Figures 6(a) and (b). In this case, the non-circular cross-sectional area S2 of the connecting portion 90 is similarly larger than the non-circular cross-sectional area S1 in the foregoing embodiment (S2 > S1 > S). In this case, the connecting portion 90 has such a cross-sectional shape as that the thickness on the eccentricity side of the lower eccentric portion 44 is larger than the thickness on the eccentricity side of the upper eccentric portion 42. As a result, the cross-sectional area of the connecting portion 90 for connecting the upper and lower eccentric portions 42 and 44 integrally formed with the rotating shaft 16 is larger to increase the geometric secondary moment so that the strength (rigidity) of the rotary shaft is enhanced, thereby improving durability and reliability of the compressor. Specifically, when compressing a refrigerant having a high working pressure in two stages, although a large difference between a high pressure and a low pressure increases a load imposed on the rotating shaft 16, the increased cross-sectional area of the connecting portion 90 improves the strength (rigidity) of the shaft 16 and prevents the rotating shaft 16 from being elastically deformed. In this embodiment, carbon dioxide (CO 2 ) is used as a refrigerant and any existing oil such as mineral oil, alkylbenzene oil, ether oil, ester oil is used as lubricating oil. Refrigerant inlet pipes 92, 94 for leading the refrigerant gas into the upper and lower cylinders 38, 40 through the inlet passages 58 and 60 and the outlet sound absorbing chambers 62 and 64 and refrigerant outlet pipes 96 and 98 for discharging the compressed refrigerant gas are respectively connected to the upper and lower support members 54, 56. Additionally, refrigerant pipes 100, 102, 104 and 106 are respectively connected to these refrigerant inlet pipes 92, 94 and the refrigerant outlet pipes 96, 98. Also, an accumulator 108 is connected between the refrigerant pipings 102, 104. It is to be noted that a mounting seat 110 is provided on the outer bottom surface of the closed container 112. Operation of the above-described compressor will now be described. When the coil 28 of the electric motor 14 is energised through the terminal 20, the electric motor 14 is activated to rotate the rotor 24. This rotation causes the upper and lower rollers 46 and 48 fitted to the upper and lower eccentric portions 42 and 44 integrally provided to the rotating shaft 16 to eccentrically rotate in the upper and lower cylinders 38, 40. Consequently, as shown in Figure 2, the low-pressure refrigerant gas is sucked from an inlet port 112 into the low pressure chamber side 38a of the upper cylinder 38 through the refrigerant piping 100, the refrigerant inlet pipe 92 and the inlet passage 58 formed to the upper supporting member 54 and is compressed by the operation of the upper and roller 46 and the upper vane 50 to an intermediate pressure. It is then sent from the high pressure chamber side 38b of the upper cylinder 38 to the accumulator 108 on the outside of the closed container 12 through the outlet portion 114, the outlet sound absorbing chamber 62 formed to the upper supporting member 54, the refrigerant outlet pipe 96 and the refrigerant piping 102. The refrigerant gas with an intermediate pressure which has been sucked from the inlet portion 116 to the low pressure chamber side 40a of the lower cylinder 40 through the accumulator 108, the refrigerant piping 104, the refrigerant inlet pipe 94 and the inlet passage 60 formed to the lower supporting member 56 is subjected to the second-stage compression by the operation of the lower roller 48 and the lower vane 52 to become a high-pressure refrigerant gas. It is then sent from the high pressure chamber side 40b to an external refrigerant circuit (not shown) constituting a freezing cycle through the outlet port 118, the outlet sound absorbing chamber 64 formed to the lower supporting member 56, the refrigerant outlet pipe 98 and the refrigerant piping 106. Rotation of the rotating shaft 16 causes the lubricating oil reserved at the bottom of the closed container 12 to move up through the vertical oil hole 80 formed to the shaft centre of the rotating shaft 16, and the oil then flows out from the lateral fill holes 82 and 84 and is supplied to the bearing portion of the rotating shaft 16 and the upper and lower eccentric portions 42 and 44. As a result, the rotating shaft 16 and the upper and lower eccentric portions 42 and 44 can smoothly rotate. Although the foregoing embodiments have described the two-cylinder type two-stage compression rotary compressor having the rotating shaft 16 provided in the lengthwise direction, the present invention can be similarly applied to the two-cylinder type two-stage compression rotary compressor having the rotating shaft provided in the crosswise direction. According to the above-described present invention, the rotating shaft can be prevented from being elastically deformed even if a difference between a high pressure and a low pressure is large, and the two-cylinder type two-stage compression rotary compressor having the excellent durability and the high reliability can be provided.

Claims: A two stage rotary compressor including first and second cylinders (38, 40) separated by an intermediate partition plate (36) and first and second eccentric compressing portions (42, 44) disposed in the first and second cylinders (38, 40) respectively, the eccentric compressing portions (42, 44) being formed on a rotary shaft (16) spaced from each other by a portion (90) of the shaft (16) that extends through an aperture (36a) in the intermediate partition plate (36) and having a phase difference of 180°, characterised in that the portion (90) of the eccentric compressing portions (42,44) has a cross-sectional shape such that the thickness in a direction orthogonal to an eccentric direction is larger than the thickness in the eccentric direction. The two-cylinder type two-stage compression rotary compressor according to claim 1, wherein the cross-sectional shape of said connecting portion is non-circular. The two-cylinder type two-stage compression rotary compressor according to claim 1 or claim 2, wherein a cross-sectional area of said connecting portion is larger than a cross-sectional area of said rotating shaft.

Inventors: EBARA TOSHIYUKI, IMAI SATOSHI, ODA ATSUSHI, TADANO MASAYA, YAMAKAWA TAKASHI, EBARA, TOSHIYUKI, IMAI, SATOSHI, ODA, ATSUSHI, TADANO, MASAYA, YAMAKAWA, TAKASHI
Applicants: SANYO ELECTRIC CO, SANYO ELECTRIC CO., LTD.
Application year: 2000
Main classification: F04C11
IPC codes: F04C11, F04C18, F04C23, F04C29