A main bearing is disposed on one surface of a first cylinder, an intermediate plate is disposed on another surface of the first cylinder, the intermediate plate is disposed on one surface of a second cylinder, and an auxiliary bearing is disposed on another surface of the second cylinder. A shaft is constituted by a main shaft portion, a first eccentric portion, a second eccentric portion, and an auxiliary shaft portion. A first eccentric portion center position (H1/2) which is the center position of the first eccentric portion in height (H1) is located at a position closer to the main bearing than a first piston center position (P1/2) which is the center position of a first piston in height (P1). A second eccentric portion center position (H2/2) which is the center position of the second eccentric portion in height (H2) is located at a position closer to the auxiliary bearing than a second piston center position (P2/2) which is the center position of a second piston in height (P2).

BACKGROUND

1. Technical Field

The present disclosure relates to a two-cylinder hermetic compressor used for an outdoor unit of an air conditioner and a freezer.

2. Description of the Related Art

Generally, a hermetic compressor used for an outdoor unit of an air conditioner and a freezer includes an electric motor unit and a compression mechanism unit in a sealed container. The electric motor unit and the compression mechanism unit are connected to each other by a shaft, and a piston attached to an eccentric portion of the shaft revolves with the rotation of the shaft. A main bearing and an auxiliary bearing are mounted on both end surfaces of a cylinder having the piston provided therein, and the shaft is supported by the main bearing and the auxiliary bearing. Generally, one-cylinder hermetic compressor is often used.

Meanwhile, in comparison to a one-cylinder hermetic compressor that has conventionally been used most often, the two-cylinder hermetic compressor disclosed in PTL 1 to PTL 4 has a shaft provided with two eccentric portions, wherein a sliding loss of the eccentric portions can be reduced by decreasing the outer diameter and the height of the eccentric portions.

However, due to the reduction in the outer diameter and height of the eccentric portions, the sliding areas of the eccentric portions are undesirably decreased, which entails a problem of an increase in maximum stress on the eccentric portions.

SUMMARY

The present disclosure is accomplished in view of the foregoing problem, and aims to provide a two-cylinder hermetic compressor configured such that the center position of an eccentric portion and the center position of a piston differ from each other, thereby being capable of reducing maximum stress on the eccentric portion to suppress an amount of sliding frictional wear on the eccentric portion.

Specifically, in a two-cylinder hermetic compressor according to one example of an exemplary embodiment of the present disclosure, a first eccentric portion center position (H1/2) which is the center position of a first eccentric portion in height (H1) is located at a position closer to a main bearing than a first piston center position (P1/2) which is the center position of a first piston in height (P1). In addition, a second eccentric portion center position (H2/2) which is the center position of a second eccentric portion in height (H2) is located at a position closer to an auxiliary bearing than a second piston center position (P2/2) which is the center position of a second piston in height (P2).

In addition, in the two-cylinder hermetic compressor according to one example of the exemplary embodiment of the present disclosure, a distance (LH) between a first eccentric portion center position (H1/2) that is the center position of a first eccentric portion in height (H1) and a second eccentric portion center position (H2/2) that is the center position of a second eccentric portion in height (H2) is set larger than a distance (LP) between a first piston center position (P1/2) that is the center position of a first piston in height (P1) and a second piston center position (P2/2) that is the center position of a second piston in height (P2).

According to the configuration in which the first eccentric portion center position (H1/2) is located at a position closer to the main bearing than the first piston center position (P1/2) and the second eccentric portion center position (H2/2) is located at a position closer to the auxiliary bearing than the second piston center position (P2/2), or the distance (LH) is set larger than the distance (LP), maximum stress on the first eccentric portion and the second eccentric portion can be reduced, whereby an amount of sliding frictional wear can be suppressed. Thus, the heights of the first eccentric portion and the second eccentric portion can be decreased, whereby a sliding loss can be reduced.

DETAILED DESCRIPTION

Hereinafter, a description will be given of an example of an exemplary embodiment of the present disclosure with reference to the drawings.

FIG. 1is a sectional view of a two-cylinder hermetic compressor according to one example of the exemplary embodiment of the present disclosure.

Two-cylinder hermetic compressor1according to the present exemplary embodiment includes electric motor unit20and compression mechanism unit30in sealed container10. Electric motor unit20and compression mechanism unit30are connected to each other by shaft40.

Electric motor unit20includes stator21fixed on an inner surface of sealed container10and rotor22rotating in stator21.

The two-cylinder hermetic compressor according to the present exemplary embodiment includes first compression mechanism unit30A and second compression mechanism unit30B as compression mechanism unit30.

First compression mechanism unit30A includes first cylinder31A, first piston32A disposed in first cylinder31A, and a vane (not illustrated) that partitions the interior of first cylinder31A. First compression mechanism unit30A suctions a low-pressure refrigerant gas and compresses this refrigerant gas due to the revolution of first piston32A in first cylinder31A.

Similar to first compression mechanism unit30A, second compression mechanism unit30B includes second cylinder31B, second piston32B disposed in second cylinder31B, and a vane (not illustrated) that partitions the interior of second cylinder31B. Second compression mechanism unit30B suctions a low-pressure refrigerant gas and compresses this refrigerant gas due to the revolution of second piston32B in second cylinder31B.

Main bearing51is disposed on one surface of first cylinder31A, and intermediate plate52is disposed on another surface of first cylinder31A.

In addition, intermediate plate52is disposed on one surface of second cylinder31B, and auxiliary bearing53is disposed on another surface of second cylinder31B.

That is to say, intermediate plate52partitions first cylinder31A and second cylinder31B. Intermediate plate52has an opening larger than the diameter of shaft40.

Shaft40is constituted by main shaft portion41which has rotor22attached thereto and is supported by main bearing51, first eccentric portion42having first piston32A attached thereto, second eccentric portion43having second piston32B attached thereto, and auxiliary shaft portion44supported by auxiliary bearing53.

First eccentric portion42and second eccentric portion43are formed to have a phase difference of 180 degrees, and connection shaft portion45is formed between first eccentric portion42and second eccentric portion43.

First compression chamber33A is formed between main bearing51and intermediate plate52and between the inner peripheral surface of first cylinder31A and the outer peripheral surface of first piston32A. In addition, second compression chamber33B is formed between intermediate plate52and auxiliary bearing53and between the inner peripheral surface of second cylinder31B and the outer peripheral surface of second piston32B.

The volume of first compression chamber33A and the volume of second compression chamber33B are the same. Specifically, the inner diameter of first cylinder31A and the inner diameter of second cylinder31B are the same, and the outer diameter of first piston32A and the outer diameter of second piston32B are the same. In addition, the height of first cylinder31A on the inner periphery thereof and the height of second cylinder31B on the inner periphery thereof are the same, and the height of first piston32A and the height of second piston32B are the same.

Oil reservoir11is formed at the bottom of sealed container10, and oil pickup12is provided at the lower end of shaft40.

Although not illustrated, an oil feed path is formed inside shaft40in the axial direction, and a communication path for feeding oil to a sliding surface of compression mechanism unit30is formed in the oil feed path.

First suction pipe13A and second suction pipe13B are connected to the side surface of sealed container10, and discharge pipe14is connected to the top of sealed container10.

First suction pipe13A is connected to first compression chamber33A, and second suction pipe13B is connected to second compression chamber33B, respectively. Accumulator15is provided at the upstream side of first suction pipe13A and second suction pipe13B. Accumulator15separates the refrigerant returning from a freezing cycle into a liquid refrigerant and a gas refrigerant. The gas refrigerant flows through first suction pipe13A and second suction pipe13B.

Due to the rotation of shaft40, first piston32A and second piston32B revolve in first compression chamber33A and second compression chamber33B, respectively.

The gas refrigerant suctioned from first suction pipe13A and second suction pipe13B into first compression chamber33A and second compression chamber33B is compressed in first compression chamber33A and second compression chamber33B due to the revolution of first piston32A and second piston32B, and then, discharged into sealed container10. While the gas refrigerant discharged into sealed container10rises through electric motor unit20, oil is separated therefrom, and then, the resultant gas refrigerant is discharged outside of sealed container10from discharge pipe14.

The oil sucked from oil reservoir11due to the rotation of shaft40is fed into compression mechanism unit30from the communication path to allow the sliding surface of compression mechanism unit30to be smooth.

FIG. 2is a side view of the shaft and the pistons used in the two-cylinder hermetic compressor according to one example of the exemplary embodiment of the present disclosure.

Shaft40is constituted by main shaft portion41, first eccentric portion42, second eccentric portion43, auxiliary shaft portion44, and connection shaft portion45.

First communication path12A which is in communication with the oil feed path formed inside shaft40is open at the end of main shaft portion41on the side of first eccentric portion42, and second communication path12B which is in communication with the oil feed path formed inside shaft40is open at the end of auxiliary shaft portion44on the side of second eccentric portion43.

The diameter is set to be smaller than the diameter of main shaft portion41on the position where first communication path12A is open, and the diameter is set to be smaller than the diameter of auxiliary shaft portion44on the position where second communication path12B is open, whereby oil can be reliably fed to compression mechanism unit30.

Third communication path12C which is in communication with the oil feed path formed inside shaft40is open at the side surface of first eccentric portion42, and fourth communication path12D which is in communication with the oil feed path formed inside shaft40is open at the side surface of second eccentric portion43.

Thrust receiving portion46is provided to second eccentric portion43on the side of auxiliary shaft portion44. The diameter of thrust receiving portion46is smaller than the diameter of second eccentric portion43and larger than the diameter of auxiliary shaft portion44.

The end face of thrust receiving portion46is in contact with the surface of auxiliary bearing53on the side of second cylinder31B illustrated inFIG. 1.

Two-cylinder hermetic compressor1according to the present exemplary embodiment receives thrust loads of shaft40on the surface of auxiliary bearing53on the side of second cylinder31B through the end face of thrust receiving portion46, thereby being capable of stably receiving thrust loads as compared to the configuration of receiving thrust loads on auxiliary shaft portion44.

In two-cylinder hermetic compressor1according to the present exemplary embodiment, first eccentric portion center position (H1/2) which is the center position of first eccentric portion42in height (H1) is located at a position closer to main bearing51than first piston center position (P1/2) which is the center position of first piston32A in height (P1). In addition, in two-cylinder hermetic compressor1according to the present exemplary embodiment, second eccentric portion center position (H2/2) which is the center position of second eccentric portion43in height (H2) is located at a position closer to auxiliary bearing53than second piston center position (P2/2) which is the center position of second piston32B in height (P2).

In addition, in two-cylinder hermetic compressor1according to the present exemplary embodiment, distance (LH) between first eccentric portion center position (H1/2) that is the center position of first eccentric portion42in height (H1) and second eccentric portion center position (H2/2) that is the center position of second eccentric portion43in height (H2) is set larger than distance (LP) between first piston center position (P1/2) that is the center position of first piston32A in height (P1) and second piston center position (P2/2) that is the center position of second piston32B in height (P2).

According to the configuration in which first eccentric portion center position (H1/2) is located at a position closer to main bearing51than first piston center position (P1/2) and second eccentric portion center position (H2/2) is located at a position closer to auxiliary bearing53than second piston center position (P2/2), or distance (LH) is set larger than distance (LP), maximum stress on first eccentric portion42and second eccentric portion43can be reduced, whereby an amount of sliding frictional wear can be suppressed. Thus, heights (H1and H2) of first eccentric portion42and second eccentric portion43can be decreased, whereby a sliding loss can be reduced.

The ratio of height (H1) of first eccentric portion42to height (P1) of first piston32A can be set to be 40% to 75%, and the ratio of height (H2) of second eccentric portion43to height (P2) of second piston32B can be set to be 40% to 75%.

FIGS. 3 and 4illustrate test results of maximum stress values on the auxiliary shaft portion in the two-cylinder hermetic compressor according to the exemplary embodiment of the present disclosure.

FIG. 3shows the specification of Comparative Examples in which eccentric portion center position (H/2) and piston center position (P/2) are aligned with each other, and Examples in which there is a distance between eccentric portion center position (H/2) and piston center position (P/2).

In Example 1, height (H) of an eccentric portion is set to be 24.0 mm, height (P) of a piston is set to be 32.0 mm, distance (e) between eccentric portion center position (H/2) and piston center position (P/2) is set to be 0.6 mm, and ratio (H/P) of height (H) of the eccentric portion to height (P) of the piston is set to be 75%.

In Example 2, height (H) of an eccentric portion is set to be 22.0 mm, height (P) of a piston is set to be 32.0 mm, distance (e) between eccentric portion center position (H/2) and piston center position (P/2) is set to be 1.6 mm, and ratio (H/P) of height (H) of the eccentric portion to height (P) of the piston is set to be 69%.

In Example 3, height (H) of an eccentric portion is set to be 19.2 mm, height (P) of a piston is set to be 32.0 mm, distance (e) between eccentric portion center position (H/2) and piston center position (P/2) is set to be 3.0 mm, and ratio (H/P) of height (H) of the eccentric portion to height (P) of the piston is set to be 60%.

In Example 4, height (H) of an eccentric portion is set to be 17.0 mm, height (P) of a piston is set to be 32.0 mm, distance (e) between eccentric portion center position (H/2) and piston center position (P/2) is set to be 4.1 mm, and ratio (H/P) of height (H) of the eccentric portion to height (P) of the piston is set to be 53%.

In Example 5, height (H) of an eccentric portion is set to be 15.0 mm, height (P) of a piston is set to be 32.0 mm, distance (e) between eccentric portion center position (H/2) and piston center position (P/2) is set to be 5.1 mm, and ratio (H/P) of height (H) of the eccentric portion to height (P) of the piston is set to be 47%.

In Example 6, height (H) of an eccentric portion is set to be 13.0 mm, height (P) of a piston is set to be 32.0 mm, distance (e) between eccentric portion center position (H/2) and piston center position (P/2) is set to be 6.1 mm, and ratio (H/P) of height (H) of the eccentric portion to height (P) of the piston is set to be 41%.

FIG. 4Ais a graph showing the test result of maximum stress values on the first eccentric portion and the second eccentric portion in Comparative Examples and Examples.

As shown in Comparative Examples 1 to 3 inFIG. 4A, when height (H) of eccentric portion is decreased with height (P) of piston being fixed, a maximum stress value is increased on eccentric portions42and43.

In Example 1, height (P) of the piston is the same as that in Comparative Example 1, height (H) of the eccentric portion is larger than that in Comparative Example 1 by 2.0 mm, and distance (e) between eccentric portion center position (H/2) and piston center position (P/2) is set to be 0.6 mm. The maximum stress value on first eccentric portion42in Example 1 is lower than that in Comparative Example 1 by 13%, and the maximum stress value on second eccentric portion43in Example 1 is lower than that in Comparative Example 1 by 26%.

In Example 2, height (P) of the piston and height (H) of the eccentric portion are the same as those in Comparative Example 1, and distance (e) between eccentric portion center position (H/2) and piston center position (P/2) is set to be 1.6 mm. The maximum stress value on first eccentric portion42in Example 2 is lower than that in Comparative Example 1 by 11%, and the maximum stress value on second eccentric portion43in Example 2 is lower than that in Comparative Example 1 by 25%.

In Example 3, height (P) of the piston and height (H) of the eccentric portion are the same as those in Comparative Example 2, and distance (e) between eccentric portion center position (H/2) and piston center position (P/2) is set to be 3.0 mm. As compared to Comparative Example 1, the maximum stress value on first eccentric portion42in Example 3 is lower by 7%, while the maximum stress value on first eccentric portion42in Comparative Example 2 is higher by 17%, and the maximum stress value on second eccentric portion43in Example 3 is lower by 22%, while the maximum stress value on second eccentric portion43in Comparative Example 2 is higher by 12%.

In Example 4, height (P) of the piston and height (H) of the eccentric portion are the same as those in Comparative Example 3, and distance (e) between eccentric portion center position (H/2) and piston center position (P/2) is set to be 4.1 mm. As compared to Comparative Example 1, the maximum stress value on first eccentric portion42in Example 4 is lower by 1%, while the maximum stress value on first eccentric portion42in Comparative Example 3 is higher by 24%, and the maximum stress value on second eccentric portion43in Example 4 is lower by 17%, while the maximum stress value on second eccentric portion43in Comparative Example 3 is higher by 25%.

In Example 5, height (H) of the eccentric portion is further decreased and distance (e) between eccentric portion center position (H/2) and piston center position (P/2) is further increased, with respect to Example 4, and in Example 6, height (H) of the eccentric portion is further decreased and distance (e) between eccentric portion center position (H/2) and piston center position (P/2) is further increased, with respect to Example 5.

The maximum stress value in Example 6 is increased with respect to Example 4, and the maximum stress value in Example 6 is increased with respect to Example 5. However, the maximum stress values in Examples 5 and 6 are lower than those in Comparative Example 3 in which the height of the eccentric portion is larger.

FIG. 4Bshows the ratio of maximum stress on second eccentric portion in Examples 1 to 6 inFIG. 4A.

FIG. 4Bshows that the maximum stress on second eccentric portion43is not significantly increased when H/P that is the ratio of eccentric portion height (H) to piston height (P) ranges from 0.40 to 0.75. Specifically,FIG. 4Bshows that satisfactory effect can be provided within the range of 40% to 75% of the ratio of eccentric portion height (H) to piston height (P) with respect to Comparative Examples in which eccentric portion center position (H/2) and piston center position (P/2) are aligned with each other.

As described above, the present disclosure provides a two-cylinder hermetic compressor configured such that the center position of an eccentric portion and the center position of a piston differ from each other, thereby being capable of reducing maximum stress on the eccentric portion to suppress an amount of sliding frictional wear on the eccentric portion. Accordingly, the present disclosure is applicable not only to a two-cylinder hermetic compressor but also to a multi-stage compressor provided with a plurality of, such as three or more, cylinders.