Double-cylinder rotary compressor

Abstract

A double-cylinder rotary compressor is provided with a head connected to an air suction pipe, a first cylinder in which a first piston eccentrically rotates, a second cylinder in which a second piston eccentrically rotates, an intermediate plate provided between the first cylinder and the second cylinder, and a main flow path that passes from the air suction pipe through the head, the first cylinder, and the intermediate plate and passes through the second cylinder. A first branch flow path branching from the main flow path inside the first cylinder; and a second branch flow path branching from the main flow path inside the second cylinder.

Description

Technical Field

[0001] This invention relates to a twin-cylinder rotary compressor. Background Technology

[0002] Patent Document 1 discloses a two-cylinder rotary compressor having a compression mechanism and a rotary drive. Patent Document 1 discloses that working gas is introduced into the two-cylinder chamber from a suction pipe connected to a partition plate through two suction passages branched by a branch provided in the partition plate.

[0003] [Existing Technical Documents]

[0004] [Patent Documents]

[0005] [Patent Document 1] Patent No. 5070097 Summary of the Invention

[0006] [The problem the invention aims to solve]

[0007] In rotary compressors, the compression mechanism is flattened in order to improve performance.

[0008] This invention provides a technique for flattening the compression mechanism in a twin-cylinder rotary compressor.

[0009] [Methods for solving the problem]

[0010] The first invention's twin-cylinder rotary compressor has the following features:

[0011] The head that connects to the inhalation tube,

[0012] The first piston rotates eccentrically inside the first cylinder.

[0013] The second piston rotates eccentrically inside the second cylinder.

[0014] The middle plate located between the first cylinder and the second cylinder,

[0015] The main flow path from the intake pipe through the head, the first cylinder, and the middle plate to the second cylinder is as follows:

[0016] The first branch flow path, which branches off from the main flow path inside the first cylinder, and

[0017] The main flow path branches off from the second branch flow path inside the second cylinder.

[0018] According to the first invention, the dual-cylinder rotary compressor can be flattened.

[0019] According to the first invention's twin-cylinder rotary compressor, in the second invention's twin-cylinder rotary compressor, the flow path area of ​​the main flow path is greater than or equal to the flow path area of ​​the suction port connected to the suction pipe.

[0020] In the twin-cylinder rotary compressor according to any one of the first or second inventions, and in the twin-cylinder rotary compressor of the third invention, the flow area of ​​the second branch flow path is different from the flow area of ​​the first branch flow path.

[0021] In the twin-cylinder rotary compressor according to any one of the first to third inventions, and in the twin-cylinder rotary compressor of the fourth invention, the sum of the flow path area of ​​the first branch flow path and the flow path area of ​​the second branch flow path is greater than or equal to the flow path area of ​​the main flow path.

[0022] The dual-cylinder rotary compressor according to any one of the first to fourth inventions, and the dual-cylinder rotary compressor of the fifth invention, further include the first piston, and a first compression chamber formed between the first cylinder and the first piston, a first partition separating a first high-pressure chamber and a first low-pressure chamber, and the center of a first connection port connecting the first branch flow path to the first low-pressure chamber is located on the side of the first partition relative to the line connecting the main flow path and the rotation center of the first piston. The compressor also includes the second piston, and a second compression chamber formed between the second cylinder and the second piston, a second partition separating a second high-pressure chamber and a second low-pressure chamber, and the center of a second connection port connecting the second branch flow path to the second low-pressure chamber is located on the side of the second partition relative to the line connecting the main flow path and the rotation center of the second piston.

[0023] The dual-cylinder rotary compressor according to any one of the first to fifth inventions, and the dual-cylinder rotary compressor of the sixth invention, further include a retaining member for retaining the head, the first cylinder, the middle plate and the second cylinder, a container that internally houses the head, the first cylinder, the middle plate, the second cylinder and the retaining member, and a liquid reservoir connected to the suction pipe, the retaining member being fixed to the container, and the lower part of the liquid reservoir being disposed below the retaining member.

[0024] The twin-cylinder rotary compressor according to any one of the first to sixth inventions, and the twin-cylinder rotary compressor of the seventh invention, uses carbon dioxide as the refrigerant.

[0025] According to any one of the first to seventh inventions, in the dual-cylinder rotary compressor of the eighth invention, the first cylinder has a first through hole extending in the thickness direction outside the inner diameter of the first cylinder, and a first groove formed from the first through hole to the interior of the first cylinder; the middle plate has a second through hole extending in the thickness direction; the second cylinder has a longitudinal hole extending in the thickness direction outside the inner diameter of the second cylinder, and a second groove formed from the longitudinal hole to the interior of the second cylinder; the first through hole, the second through hole, and the longitudinal hole each constitute a part of the main flow path; the first groove constitutes the first branch flow path; and the second groove constitutes the second branch flow path. Attached Figure Description

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Figure 1

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Figure 2

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Figure 3

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Figure 4

[0030]

Figure 5

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Figure 6

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Figure 7

[0033]

Figure 8

[0034]

Figure 9

[0035] Specific examples of the rotary compressor of the present invention will be described below with reference to the accompanying drawings. Furthermore, the present invention is not limited to these examples, but is intended to include all modifications shown in the patent claims, which are equivalent in meaning and scope to the patent claims.

[0036] Furthermore, in the descriptions and drawings related to each embodiment, the same symbols are sometimes used for constituent elements that have substantially the same or corresponding functions, thereby omitting repeated descriptions. Also, for ease of understanding, the scales of various parts in the drawings may sometimes differ from the actual scales.

[0037] The directions, such as parallel, right angle, perpendicular intersection, horizontal, vertical, up and down, left and right, and front and back, are allowed to deviate to a degree that does not impair the effect of the implementation. The shape of the corner is not limited to right angles and may include arcs. Parallel, right angle, perpendicular intersection, horizontal, and vertical can each include approximately parallel, approximately right angle, approximately perpendicular intersection, approximately horizontal, and approximately vertical.

[0038] For example, roughly parallel means that two lines or two surfaces are not completely parallel to each other, but can be treated as parallel within the limits of manufacturing tolerances. Other terms such as roughly right angle, roughly perpendicular intersection, roughly horizontal, and roughly perpendicular are also intended to mean that, similarly to roughly parallel, the positional relationship between two lines or two surfaces, if within the limits of manufacturing tolerances, also falls into this category.

[0039] This embodiment describes a rotary compressor. The rotary compressor includes a head connected to an intake pipe, a first cylinder in which a first piston rotates eccentrically, a second cylinder in which a second piston rotates eccentrically, and a middle plate disposed between the first and second cylinders. The rotary compressor also includes a main flow path extending from the intake pipe head through the first cylinder and the middle plate to the second cylinder. Furthermore, the rotary compressor includes a first branch flow path branching from the main flow path inside the first cylinder, and a second branch flow path branching from the main flow path inside the second cylinder.

[0040] The rotary device involved in this embodiment will be described using a rotary compressor 1 as an example of the rotary device involved in this embodiment. Figure 1 This is a perspective view of rotary compressor 1, which is an example of a rotary compressor according to this embodiment. Figure 2 This is a cross-sectional view of rotary compressor 1, which is an example of a rotary compressor according to this embodiment. Figure 3 This is an enlarged cross-sectional view of rotary compressor 1, which is an example of a rotary compressor according to this embodiment.

[0041] Furthermore, for ease of explanation in the accompanying drawings, an imaginary three-dimensional coordinate system (XYZ perpendicularly intersecting coordinate system) is sometimes defined by mutually perpendicular intersecting X, Y, and Z axes (XYZ axes). For example, when a black circle is displayed within the circle representing a coordinate axis perpendicular to the paper, it indicates that the coordinate axis is facing the surface of the paper. Conversely, when a cross is displayed within the circle representing a coordinate axis, it indicates that the coordinate axis is facing the back side of the paper.

[0042] Here, the coordinates are set for illustrative purposes and are not intended to limit the orientation of the rotary compressor or the like involved in this embodiment.

[0043] Furthermore, in the following figures, the piston of the rotary compressor rotates in a plane parallel to the X-axis and Y-axis, namely the XY plane.

[0044] The view of an object viewed along the Z-axis from the +Z side in the opposite direction to the Z-axis is called the top view. The view of an object viewed along the Z-axis from the -Z side in the direction to the Z-axis is called the bottom view. The view of an object viewed along the Z-axis from the -Z side in the direction to the Z-axis is called the bottom view.

[0045] The rotary compressor 1 compresses refrigerant. The refrigerant used in the rotary compressor 1 is, for example, carbon dioxide. However, the refrigerant is not limited to carbon dioxide; it can also be, for example, a fluorocarbon-based refrigerant. The rotary compressor 1 includes a compressor body 10 and a receiver 20.

[0046] [Compressor Body 10]

[0047] The compressor body 10 includes a container 11, an intake pipe 12, an exhaust pipe 13, and power terminals 15. In addition, a plate 14 is provided in the container 11 for mounting the compressor body 10.

[0048] The compressor body 10 internally includes a compression section 70 and an electric motor 80. The electric motor 80 rotates the main shaft 81. The compression section 70 compresses the refrigerant supplied from the suction pipe 12. The refrigerant compressed in the compression section 70 is discharged from the discharge pipe 13 to the outside of the rotary compressor 1. The compression section 70 constitutes a compression mechanism.

[0049] The electric motor 80 rotates the main shaft 81. In the compression unit 70, the rotation of the main shaft 81 by the electric motor 80 causes pistons 61 and 62 to rotate independently. Pistons 61 and 62 rotate eccentrically as the main shaft 81 rotates. Through the independent rotation of pistons 61 and 62, the refrigerant is compressed in the compression unit 70.

[0050] The compression unit 70 includes a head 31, a cylinder 41, a middle plate 50, a cylinder 42, and a head 32. The head 31, cylinder 41, middle plate 50, cylinder 42, and head 32 are stacked sequentially from bottom to top. Each of the head 31, cylinder 41, middle plate 50, cylinder 42, and head 32 passes through a main shaft 81.

[0051] The compression unit 70 includes a piston 61 that rotates eccentrically via a main shaft 81 inside the cylinder 41. Furthermore, the compression unit 70 includes a piston 62 that rotates eccentrically via a main shaft 81 inside the cylinder 42.

[0052] [Head 31]

[0053] Explanation of head 31. Figure 4 This is a top view of the lower head 31 of a rotary compressor 1, which is an example of a rotary compressor according to this embodiment.

[0054] The head 31 has a through hole 31h extending along the X-axis and extending along the Z-axis from the middle. One side of the through hole 31h is connected to the intake pipe 12. The other side of the through hole 31h is connected to the through hole 41h of the cylinder 41.

[0055] The head 31 has an upper surface 31S. A cylinder 41 is mounted above the upper surface 31S. Furthermore, a piston 61 rotates above the upper surface 31S.

[0056] [Cylinder 41]

[0057] Next, we will explain cylinder 41. Figure 5 This is a top view of cylinder 41 in rotary compressor 1, which is an example of a rotary compressor according to this embodiment. Figure 6 This is a bottom view of cylinder 41 in rotary compressor 1, which is an example of a rotary compressor according to this embodiment. Furthermore, Figure 5 and Figure 6 The diagram also shows a piston 61 that rotates eccentrically inside cylinder 41.

[0058] The cylinder 41 has a through hole 41h extending along the thickness direction, i.e., the Z-axis. The through hole 41h is located on the outer side of the inner diameter of the cylinder 41. One side of the through hole 41h is connected to the through hole 31h of the head 31. The other side of the through hole 41h is connected to the through hole 50h of the middle plate 50. In addition, the cylinder 41 has a groove 41g, which is a groove formed from the through hole 41h to the interior of the cylinder 41.

[0059] The center 41gc of the connection port in the groove 41g of the cylinder 41 is located on the side of the partition 61b of the piston 61, relative to the line L1 of the rotation center 41c of the piston 61 and the center of the through hole 41h.

[0060] [Medium plate 50]

[0061] Next, we will explain the 50mm medium plate. Figure 7 This is a top view of the middle plate 50 in rotary compressor 1, which is an example of a rotary compressor according to this embodiment.

[0062] The middle plate 50 has a through hole 50h extending along the thickness direction, i.e., the Z-axis. One side of the through hole 50h is connected to the through hole 41h of the cylinder 41. The other side of the through hole 50h is connected to the longitudinal hole 42h of the cylinder 42.

[0063] [Cylinder 42]

[0064] Next, we will explain cylinder 42. Figure 8 This is a top view of cylinder 42 in rotary compressor 1, which is an example of a rotary compressor according to this embodiment. Figure 9 This is a bottom view of cylinder 42 in rotary compressor 1, which is an example of a rotary compressor according to this embodiment. Furthermore, Figure 8 and Figure 9 The piston 62, which rotates eccentrically inside cylinder 42, is also shown.

[0065] The cylinder 42 has a longitudinal hole 42h formed along the thickness direction, i.e., the Z-axis, extending to the middle of the thickness of the cylinder 42. The longitudinal hole 42h is located on the outer side of the inner diameter of the cylinder 42. The longitudinal hole 42h is connected to the through hole 50h of the middle plate 50. In addition, the cylinder 42 has a groove 42g, which is a groove formed from the longitudinal hole 42h to the interior of the cylinder 42.

[0066] The center 42gc of the connection port in the groove 42g of the cylinder 42 is located on the side of the partition 62b of the piston 62, relative to the line L2 of the rotation center 42c of the piston 62 and the center of the longitudinal hole 42h.

[0067] [Head 32]

[0068] The head 32 holds the head 31, cylinder 41, middle plate 50, and cylinder 42. Furthermore, the head 32 is fixed to the container 11. For example, the head 32 is fixed to the container 11 by welding. Additionally, the lower part of the reservoir 20 is located below the head 32.

[0069] [Pistons 61]

[0070] The piston 61 rotates eccentrically inside the cylinder 41. The piston 61 has a partition 61b that divides the compression chamber 41CS of the cylinder 41 into a high-pressure chamber 41HS and a low-pressure chamber 41LS. The partition 61b is fixed to the cylinder 41 by a bushing 41b.

[0071] [Piston 62]

[0072] Piston 62 rotates eccentrically inside cylinder 42. Piston 62 has a partition 62b that divides the compression chamber 42CS of cylinder 42 into a high-pressure chamber 42HS and a low-pressure chamber 42LS. Partition 62b is fixed to cylinder 42 by bushing 42b.

[0073] [Mainstream Road MFP]

[0074] like Figure 3 As shown, the rotary compressor 1 has a main flow path MFP, which passes through the intake pipe 12, head 31, cylinder 41 and middle plate 50, and through through holes 31h, 41h, 50h and longitudinal hole 42h to cylinder 42.

[0075] The flow path area SM of the main flow path MFP can be greater than or equal to the flow path area SSC of the suction port connected to the suction pipe 12. In this invention, the flow path area is the area of ​​the flow path cross-section cut off by a plane perpendicular to the direction of refrigerant flow. For example, the flow path area SM is the cross-sectional area cut off by a plane parallel to the XY plane in the through hole 41h, through hole 50h, and longitudinal hole 42h. Furthermore, the flow path area SM is the cross-sectional area cut off by a plane parallel to the YZ plane in the X-axis extended portion of the through hole 41h, or the cross-sectional area cut off by a plane parallel to the XY plane in the Y-axis extended portion of the through hole 41h.

[0076] [Branch path SFP1, Branch path SFP2]

[0077] like Figure 3 As shown, the rotary compressor 1 includes a branch flow path SFP1 that branches off from the main flow path MFP inside the cylinder 41 via a groove 41g. Furthermore, the rotary compressor 1 includes a branch flow path SFP2 that branches off from the main flow path MFP inside the cylinder 42 via a groove 42g.

[0078] The flow area SS2 of branch flow path SFP2 may differ from the flow area SS1 of branch flow path SFP1. For example, the flow area SS1 of branch flow path SFP1 and the flow area SS2 of branch flow path SFP2 may be determined in a way that optimizes the refrigerant flow rates in branch flow path SFP1 and branch flow path SFP2. Alternatively, the flow area SS1 of branch flow path SFP1 and the flow area SS2 of branch flow path SFP2 may be determined by making the refrigerant flow rates in branch flow path SFP1 and branch flow path SFP2 equal.

[0079] The sum of the flow area SS1 of branch flow path SFP1 and the flow area SS2 of branch flow path SFP2 can be greater than or equal to the flow area SM of the main flow path MFP. By ensuring that the sum of the flow area SS1 of branch flow path SFP1 and the flow area SS2 of branch flow path SFP2 is greater than or equal to the flow area SM of the main flow path MFP, the pressure loss in branch flow paths SFP1 and SFP2 can be reduced.

[0080] Furthermore, the flow area SS1 of branch flow path SFP1 is the cross-sectional area of ​​the groove 41g cut off by a plane perpendicular to the direction of extension of the groove 41g. The flow area SS2 of branch flow path SFP2 is the cross-sectional area of ​​the groove 42g cut off by a plane perpendicular to the direction of extension of the groove 42g.

[0081] Refrigerant from the main flow path MFP branch, via the branch flow path SFP1, is supplied to cylinder 41. For example, if cylinder 41 were directly connected to the intake pipe 12, it would be impossible for cylinder 41 to be thinner than the outer diameter of the intake pipe 12. By passing through the main flow path MFP and the branch flow path SFP1, refrigerant from the intake pipe 12 is supplied to cylinder 41, thus allowing cylinder 41 to be thinner. Similarly, by passing through the main flow path MFP and the branch flow path SFP2, refrigerant from the intake pipe 12 is supplied to cylinder 42, thus allowing cylinder 42 to be thinner.

[0082] Furthermore, for example, as disclosed in Patent Document 1, when the middle plate 50 is directly connected to the suction pipe 12, it is impossible to make the middle plate 50 thinner than the outer diameter of the suction pipe 12. Since the middle plate 50 is not connected to the suction pipe 12, the middle plate 50 can be made thinner.

[0083] In addition, cylinder 41 is an example of the first cylinder, cylinder 42 is an example of the second cylinder, branch flow path SFP1 is an example of the first branch flow path, and branch flow path SFP2 is an example of the second branch flow path.

[0084] Summary

[0085] According to the twin-cylinder rotary compressor of this embodiment, the compression mechanism can be flattened by thinning the first cylinder, the second cylinder, and the intermediate plate. According to the twin-cylinder rotary compressor of this embodiment, the main shaft can be shortened by flattening the compression mechanism. According to the twin-cylinder rotary compressor of this embodiment, the influence of main shaft deflection can be reduced by shortening the main shaft.

[0086] Furthermore, in the dual-cylinder rotary compressor according to this embodiment, the head is connected to the suction pipe, so the suction port of the cylinder can be designed regardless of the cylinder shape. The dual-cylinder rotary compressor according to this embodiment allows for the design of the cylinder suction port regardless of the cylinder shape, thus increasing design flexibility.

[0087] Furthermore, according to the twin-cylinder rotary compressor of this embodiment, the number of components around the suction section can be reduced. By reducing the number of components around the suction section, the manufacturing cost of the twin-cylinder rotary compressor according to this embodiment can be reduced.

[0088] According to the twin-cylinder rotary compressor of this embodiment, by making the flow path area of ​​the main flow path greater than or equal to the flow path area of ​​the suction port connected to the suction pipe, the refrigerant pressure loss inside the twin-cylinder rotary compressor can be reduced.

[0089] According to the twin-cylinder rotary compressor of this embodiment, the flow area of ​​the second branch flow path is different from that of the first branch flow path, thereby optimizing the amount of refrigerant allocated to the first cylinder and the second cylinder respectively.

[0090] According to the twin-cylinder rotary compressor of this embodiment, the sum of the flow area of ​​the first branch flow path and the flow area of ​​the second branch flow path is greater than or equal to the flow area of ​​the main flow path, thereby reducing the refrigerant pressure loss inside the twin-cylinder rotary compressor.

[0091] According to the twin-cylinder rotary compressor of this embodiment, the center of the first connection port in the first branch flow path is located on the side of the first partition plate relative to the line connecting the main flow path and the rotation center of the first piston. This allows for faster closure of the first connection port. In other words, the twin-cylinder rotary compressor of this embodiment reduces the angle at which the first connection port closes. Similarly, according to the twin-cylinder rotary compressor of this embodiment, the center of the second connection port in the second branch flow path is located on the side of the second partition plate relative to the line connecting the main flow path and the rotation center of the second piston. This allows for faster closure of the second connection port. In other words, the twin-cylinder rotary compressor of this embodiment reduces the angle at which the second connection port closes.

[0092] According to the twin-cylinder rotary compressor of this embodiment, by positioning the lower part of the liquid reservoir below the holding member, a lower center of gravity can be achieved. According to the twin-cylinder rotary compressor of this embodiment, by lowering the center of gravity of the twin-cylinder rotary compressor, vibration can be reduced.

[0093] According to the twin-cylinder rotary compressor of this embodiment, the main flow path is formed by a through hole and a longitudinal hole, and a branch flow path is formed by a groove, thereby increasing the design freedom of the shape in the cylinder's suction section. Furthermore, according to the twin-cylinder rotary compressor of this embodiment, the branch flow path formed by the groove simplifies the machining of the cylinder's suction section. Therefore, by simplifying the machining of the cylinder's suction section, the manufacturing cost of the twin-cylinder rotary compressor of this embodiment can be reduced.

[0094] The above describes the implementation methods, but it should be understood that various changes in form and detail are possible without departing from the spirit and scope of the patent claims. Various modifications and improvements, such as combinations or substitutions with other embodiments, are also possible.

[0095] This application claims priority to basic patent application No. 2023-057481 filed with the Japan Patent Office on March 31, 2023, the entire contents of which are incorporated herein by reference.

[0096] [Attached image labels]

[0097] 1. Rotary compressor

[0098] 10 Compressor body

[0099] 11 Containers

[0100] 12 Inhalation tubes

[0101] 13 Exhaust pipe

[0102] 20 Liquid Reservoirs

[0103] 31 Head

[0104] 31h Through Hole

[0105] 32 heads

[0106] 41, 42 cylinders

[0107] 41b, 42b bushings

[0108] Rotation center of 41c, 42c

[0109] 41g, 42g groove

[0110] 41gc, 42gc center

[0111] 41h Through Hole

[0112] 42h longitudinal hole

[0113] Compression chambers 41CS and 42CS

[0114] 41HS, 42HS High-Pressure Chamber

[0115] 41LS, 42LS low-pressure chamber

[0116] 50 medium plate

[0117] 50h through hole

[0118] Pistons 61 and 62

[0119] 61b, 62b spacers

[0120] 70 Compression Section

[0121] 80 Electric Section

[0122] 81 Spindle

[0123] MFP mainstream path

[0124] SFP1, SFP2 branch flow paths

[0125] SM, SS1, SS2, SSC flow path area

Claims

1. A twin-cylinder rotary compressor, comprising: The head that connects to the inhalation tube, The first piston rotates eccentrically inside the first cylinder. The second piston rotates eccentrically inside the second cylinder. The middle plate located between the first cylinder and the second cylinder, The main flow path from the intake pipe through the head, the first cylinder, and the middle plate to the second cylinder is as follows: The first branch flow path, which branches off from the main flow path inside the first cylinder, and The main flow path branches off from the second branch flow path inside the second cylinder.

2. The dual-cylinder rotary compressor according to claim 1, wherein the flow path area of ​​the main flow path is greater than or equal to the flow path area of ​​the suction port connected to the suction pipe.

3. The twin-cylinder rotary compressor according to any one of claims 1 or 2, wherein the flow area of ​​the second branch flow path is different from the flow area of ​​the first branch flow path.

4. The twin-cylinder rotary compressor according to any one of claims 1 to 3, wherein the sum of the flow area of ​​the first branch flow path and the flow area of ​​the second branch flow path is greater than or equal to the flow area of ​​the main flow path.

5. The twin-cylinder rotary compressor according to any one of claims 1 to 4, It also includes the first piston and a first compression chamber formed between the first cylinder and the first piston, and a first partition separating the first high-pressure chamber and the first low-pressure chamber. Relative to the line connecting the main flow path and the rotation center of the first piston, the center of the first connection port connecting the first branch flow path to the first low-pressure chamber is located on the side of the first partition plate. It also includes the second piston and a second partition that divides the second compression chamber formed between the second cylinder and the second piston into a second high-pressure chamber and a second low-pressure chamber. Relative to the line connecting the main flow path and the rotation center of the second piston, the center of the second connection port connecting the second branch flow path and the second low-pressure chamber is located on the side of the second partition plate.

6. The twin-cylinder rotary compressor according to any one of claims 1 to 5, further comprising: A retaining component that holds the head, the first cylinder, the middle plate, and the second cylinder. A container that houses the head, the first cylinder, the middle plate, the second cylinder, and the retaining member inside. The reservoir connected to the suction pipe, The retaining component is fixed to the container. The lower part of the reservoir is located on the lower side of the retaining component.

7. The twin-cylinder rotary compressor according to any one of claims 1 to 6, wherein the refrigerant used is carbon dioxide.

8. The twin-cylinder rotary compressor according to any one of claims 1 to 7, wherein the first cylinder comprises: On the outer side of the inner diameter of the first cylinder, a first through hole extends in the thickness direction, and The first groove formed from the first through hole to the interior of the first cylinder The middle plate has a second through hole extending through the thickness direction. The second cylinder has: On the outer side of the inner diameter of the second cylinder, there is a longitudinal hole extending in the thickness direction, and The second groove formed from the longitudinal hole to the interior of the second cylinder The first through hole, the second through hole, and the longitudinal hole each constitute a part of the main flow path. The first channel constitutes the first branch flow path. The second groove constitutes the second branch flow path.

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