Compressor and refrigeration cycle device

Abstract

A refrigerant is a single component refrigerant composed of a hydrocarbon refrigerant, or a refrigerant mixture containing the hydrocarbon refrigerant. Refrigerating machine oil present at a level of a suction port (71a) or lower in an oil reservoir (35) has a solution viscosity η of 5.0 [mPa·s] or more.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a compressor and a refrigeration cycle apparatus.BACKGROUND ART

[0002] Patent Document 1 discloses a refrigeration cycle apparatus. The refrigeration cycle apparatus includes a refrigerant circuit. The refrigerant circuit includes a compressor, a radiator, an expansion valve, and an evaporator. Once the compressor operates, the refrigerant in the refrigerant circuit circulates to perform a refrigeration cycle.

[0003] In the compressor, the refrigerant compressed by the compression mechanism flows out of the discharge pipe through the space inside the casing to the refrigerant circuit. In this manner, the inside of the casing is filled with the high-pressure refrigerant.

[0004] An oil reservoir that stores the refrigerating machine oil is formed at the bottom of the casing. The refrigerating machine oil is used to lubricate sliding portions in the compressor. The refrigerating machine oil in the oil reservoir is sucked through a suction port of the oil supply pump, and is supplied through an oil supply passage in the rotary shaft to a sliding portion of the bearing and a sliding portion of the eccentric portion.CITATION LISTPATENT DOCUMENT

[0005] Patent Document 1: Japanese Unexamined Patent Publication No. 2023-162986SUMMARY OF THE INVENTIONTECHNICAL PROBLEMS

[0006] As a refrigerant used in a refrigerant circuit of a refrigeration cycle apparatus, there is a hydrocarbon refrigerant, such as propane. A hydrocarbon refrigerant is a natural refrigerant and has a significantly low global warming potential. On the other hand, the hydrocarbon refrigerant has a hydrocarbon bond like the refrigerating machine oil and has a molecular structure similar to that of the refrigerating machine oil, and thus has characteristics of being easily dissolvable in the refrigerating machine oil. Accordingly, once the hydrocarbon refrigerant dissolves in the refrigerating machine oil inside the casing of the compressor, the solution viscosity of the refrigerating machine oil may decrease. Once such a refrigerating machine oil is supplied to a sliding portion of a bearing or a sliding portion of an eccentric portion, the amount of wear of the sliding portion increases.

[0007] It is an object of the present disclosure to provide a compressor capable of reducing wear of sliding portions.SOLUTION TO THE PROBLEMS

[0008] A first aspect is directed to a compressor. The compressor includes: an electric motor (25, 125); a rotary shaft (30,130) connected to the electric motor (25,125); a bearing (44, 45, 152, 156, 157) rotatably supporting the rotary shaft (30,130); a compression mechanism (40,140) configured to be driven by the rotary shaft (30,130) and compress a refrigerant; an oil supply mechanism (70,170); and a casing (21, 121) housing the electric motor (25, 125), the rotary shaft (30, 130), the bearing (44, 45, 152, 156, 157), the compression mechanism (40, 140), and the oil supply mechanism (70, 170), and filled with a high-pressure refrigerant discharged from the compression mechanism (40, 140). The rotary shaft (30, 130) includes a shaft body (31, 131) and an eccentric portion (32A, 32B, 132) eccentric from an axis of the shaft body (31, 131). The oil supply mechanism (70,170) includes: an oil supply pump (71, 171) having a suction port (71a, 171a) for sucking the refrigerating machine oil in an oil reservoir (35, 135) at a bottom of the casing (21, 121); and an oil supply passage (72, 172) configured to supply the oil sucked through the suction port (71a, 171a) to a sliding portion of the bearing (44, 45, 152, 156, 157) and a sliding portion of the eccentric portion (32A, 32B, 132). The refrigerant is a single component refrigerant composed of a hydrocarbon refrigerant or a refrigerant mixture containing the hydrocarbon refrigerant. The refrigerating machine oil is separated into two layers at a pressure of the refrigerant of 1.9 [Mpa] and a temperature of the refrigerating machine oil of 75°C. The refrigerating machine oil present at a level of the suction port (71a, 171a) or lower in the oil reservoir (35, 135) has a solution viscosity η of 5.0 [mPa·s] or more.

[0009] In the first aspect, the refrigerating machine oil in the oil reservoir (35, 135) flows through the suction port (71a, 171a) via the oil supply passage (72, 172) and is supplied to the sliding portion of the bearing (44, 45, 152, 156, 157) and the sliding portion of the eccentric portion (32A, 32B, 132). The refrigerating machine oil present at the level of the suction port (71a, 171a) or lower has the solution viscosity η of 5.0 [mPa·s] or more. This can reduce the supply of the refrigerating machine oil with a low viscosity to the sliding portion. As a result, the wear of the sliding portion can be reduced.

[0010] A second aspect is an embodiment of the first aspect. In the second aspect, the compression mechanism is a rotary compression mechanism (40) including an annular cylinder (51A, 51B), an annular roller (52A, 52B) configured to eccentrically rotate in the cylinder (51A, 51B), and a vane (53A, 53B) for defining a compression chamber in the cylinder (51A, 51B).

[0011] In the second aspect, the wear of the sliding portion can be reduced in the rotary compressor.

[0012] In the third aspect, when a displacement volume of the rotary compression mechanism (40) is defined as Vc [cc], the solution viscosity η is (-0.00101 × Vc + 0.12286) / (0.0000146 × Vc + 0.00505) or less.

[0013] An excessively high solution viscosity of the refrigerating machine oil increases the sliding loss at the sliding portion and the friction loss. Here, the sliding loss at the eccentric portion (32A, 32B) is influenced by a projected area when the eccentric portion (32A, 32B) is viewed from the radially outer side. The projected area of the eccentric portion (32A, 32B) increases with an increase in the displacement volume Vc of the rotary compression mechanism (40). As a result of studies in view of the above points, the upper limit of the solution viscosity for reducing the sliding loss at the eccentric portion (32A, 32B) can be expressed by the above functional expression including the displacement volume Vc [cc]. In the third aspect, since this solution viscosity η is lower than or equal to than the upper limit, an excessively high sliding loss at the eccentric portion (32A, 32B) can be reduced.

[0014] A fourth aspect of the present disclosure is an embodiment of the first aspect. In the fourth aspect, the compression mechanism is a scroll compression mechanism (140) including a fixed scroll (141) and a movable scroll (160).

[0015] In the fourth aspect, the wear of the sliding portion can be reduced in the scroll compressor.

[0016] A fifth aspect is an embodiment of the fourth aspect. In the fifth aspect, when a displacement volume of the scroll compression mechanism (140) is defined as Vcs [cc], the solution viscosity η is (0.000195 × Vcs + 0.0696) / 0.00714 or less.

[0017] An excessively high solution viscosity of the refrigerating machine oil increases the sliding loss at the sliding portion and the friction loss. Here, the sliding loss in the scroll compressor is dominated by the sliding loss at the bearing. The area of the sliding portion of the bearing increases with an increase in the displacement volume Vcs of the scroll compression mechanism (140). As a result of studies in view of the above points, the upper limit of the solution viscosity for reducing the sliding loss at the bearing (152, 156, 157) can be expressed by the above functional expression including the displacement volume Vcs [cc]. In the fifth aspect, since this solution viscosity η is lower than or equal to the upper limit, excessively high sliding loss at the sliding portion and the eccentric portion can be reduced.

[0018] A sixth aspect is an embodiment of any one of the first to fifth aspects. In the sixth aspect, the refrigerating machine oil includes polyalkylene glycol, polyvinyl ether, or polyol ester.

[0019] In the sixth aspect, the refrigerating machine oil includes the polyalkylene glycol, the polyvinyl ether, or the polyol ester. In these refrigerating machine oils, the hydrocarbon refrigerant is relatively less soluble. This can reduce an excessive decrease in the solution viscosity of the refrigerating machine oil due to the dissolution of the hydrocarbon refrigerant in the refrigerating machine oil.

[0020] A seventh aspect is an embodiment of any one of the first to sixth aspects. In the seventh aspect, the refrigerating machine oil contains at least one of an extreme pressure additive of a phosphoric acid ester, an antioxidant, or an acid scavenger.

[0021] An eighth aspect is an embodiment of any one of the first to seventh aspects. In the eighth aspect, the refrigerating machine oil contains the antioxidant or the acid scavenger in an amount of 0.1 wt% or more and 0.5 wt% or less.

[0022] In the eighth aspect, the content of the antioxidant or the acid scavenger is set to 0.5 wt% or less with respect to the weight of the refrigerating machine oil. This can reduce an excessive decrease in the solution viscosity of the refrigerating machine oil due to an increase in the content of the antioxidant or the acid scavenger.

[0023] A ninth aspect is an embodiment of any one of the first to eighth aspects. In the ninth aspect, the refrigerating machine oil contains an extreme pressure additive in an amount of 1.0 wt% or more and 5.0 wt% or less.

[0024] In the ninth aspect, since the content of the extreme pressure additive is set to 5.0 wt% or less with respect to the weight of the refrigerating machine oil. This can reduce an excessive decrease in the solution viscosity of the refrigerating machine oil due to an increase in the content of the extreme pressure additive.

[0025] A tenth aspect is an embodiment of any one of the first to ninth aspects. In the tenth aspect, the refrigerating machine oil has a molecular weight of 1000 or more and 1800 or less.

[0026] In the tenth aspect, the molecular weight of the refrigerating machine oil is set to 1000 or more and 1800 or less. This can reduce the dissolution of the hydrocarbon refrigerant in the refrigerating machine oil.

[0027] An eleventh aspect is an embodiment of any one of the first to tenth aspects. In the eleventh aspect, the refrigerating machine oil present at a level of the suction port (71a, 171a) or lower in the oil reservoir (35, 135) has a solution viscosity η of 6.0 [mPa·s] or more.

[0028] In the eleventh aspect, the supply of the refrigerating machine oil with a low viscosity to the sliding portion can be further reduced, thereby further reducing wear at the sliding portion.

[0029] A twelfth aspect is directed to a refrigeration cycle apparatus. The refrigeration cycle apparatus includes a refrigerant circuit (10) including the compressor (20) of any one of the first to eleventh aspects, and configured to circulate the hydrocarbon refrigerant to perform a refrigeration cycle.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] [FIG. 1] FIG. 1 is a piping system diagram of a refrigeration cycle apparatus of a first embodiment. [FIG. 2] FIG. 2 is a vertical sectional view of a compressor. [FIG. 3] FIG. 3 is an enlarged vertical sectional view of a main part of the compressor. [FIG. 4] FIG. 4 is a horizontal sectional view of a first compression element. [FIG. 5] FIG. 5 is a horizontal sectional view of a second compression element. [FIG. 6] FIG. 6 is a table showing test conditions of an evaluation test of the amount of wear of sliding portions. [FIG. 7] FIG. 7 is a graph showing a relationship between the amount of wear of the sliding portions and the solution viscosity of refrigerating machine oil. [FIG. 8] FIG. 8 is a graph showing a relationship between the solution viscosity of refrigerating machine oil and the loss percentage at eccentric portions in each of a plurality of compressors with different displacement volumes. [FIG. 9] FIG. 9 is a vertical sectional view of a compressor according to a second embodiment. [FIG. 10] FIG. 10 is a graph showing a relationship between the solution viscosity of refrigerating machine oil and the loss percentage at bearings in each of a plurality of compressors with different displacement volumes. DESCRIPTION OF EMBODIMENTS

[0031] Embodiments of the present disclosure will be described in detail below with reference to the drawings. The present disclosure is not limited to the embodiments shown below, and various changes can be made within the scope without departing from the technical concept of the present disclosure. Since each of the drawings is intended to illustrate the present disclosure conceptually, dimensions, ratios, or numbers may be exaggerated or simplified as necessary for ease of understanding.<First Embodiment>(1) General Configuration

[0032] A refrigeration cycle apparatus of the present disclosure is applied to a stationary air conditioner (1). As shown in FIG. 1, the air conditioner (1) is of a pair type having one outdoor unit (OU) installed outdoors and one indoor unit (IU) installed indoors. The outdoor unit (OU) and the indoor unit (IU) are connected to each other via two connection pipes.

[0033] The air conditioner (1) further includes a refrigerant circuit (10). The refrigerant circuit (10) is filled with a refrigerant. The refrigerant circulates in the refrigerant circuit (10) to perform a refrigeration cycle. The refrigerant circuit (10) includes a compressor (20), an outdoor heat exchanger (11), an expansion valve (12), and an indoor heat exchanger (13). The refrigerant circuit (10) further includes a four-way switching valve (14) for switching between a cooling cycle and a heating cycle. The compressor (20), the outdoor heat exchanger (11), and the expansion valve (12) are provided in the outdoor unit (OU), and the indoor heat exchanger (13) is provided in the indoor unit (IU). The expansion valve (12) may be provided in the indoor unit (IU).

[0034] The compressor (20) sucks and compresses a low-pressure refrigerant in the refrigerant circuit (10). The compressor (20) discharges the compressed refrigerant as a high-pressure refrigerant to the refrigerant circuit (10). The outdoor heat exchanger (11) is a fin-and-tube heat exchanger. The outdoor heat exchanger exchanges heat between the refrigerant of the refrigerant circuit (10) and the outdoor air transported by an outdoor fan (15). The expansion valve (12) is an example of the decompression mechanism that decompresses the refrigerant. The expansion valve (12) is an electronic expansion valve whose opening degree is adjustable. The indoor heat exchanger (13) is a fin-and-tube heat exchanger. The indoor heat exchanger exchanges heat between the refrigerant of the refrigerant circuit (10) and the outdoor air transported by an indoor fan (16).

[0035] The four-way switching valve (14) has a first port (P1), a second port (P2), a third port (P3), and a fourth port (P4). The four-way switching valve (14) switches between a first state indicated by solid curves in FIG. 1 and a second state indicated by broken curves in FIG. 1. The four-way switching valve (14) in the first state makes the first port (P1) and the second port (P2) communicate with each other, and the third port (P3) and the fourth port (P4) communicate with each other at the same time. When the four-way switching valve (14) is in the first state, the compressor (20) operates to perform a cooling cycle in which the outdoor heat exchanger (11) functions as a radiator (or a condenser) and the indoor heat exchanger (13) functions as an evaporator. The four-way switching valve (14) in the second state makes the first port (P1) and the third port (P3) communicate with each other, and the second port (P2) and the fourth port (P4) communicate with each other at the same time. When the four-way switching valve (14) is in the second state, the compressor (20) operates to perform a heating cycle in which the indoor heat exchanger (13) functions as a radiator (or a condenser) and the outdoor heat exchanger (11) functions as an evaporator.(2) Compressor

[0036] A configuration of the compressor (20) will be described with reference to FIGS. 2 to 5. In the following description, the terms for directions such as "upper" and "lower" refer to the directions of the arrows in FIG. 2. In the following description, an "axial direction" means a direction in which an axis (A) of a rotary shaft (30) shown in FIG. 2 extends, a "radial direction" means a direction passing through the axis (A) of the rotary shaft (30) and orthogonal to the axis (A), and a "circumferential direction" means a rotation direction of the rotary shaft (30).

[0037] The compressor (20) is a rotary compressor. The rotary compressor according to this embodiment is of a so-called swing type in which vanes (53A, 53B) formed integrally with rollers (52A, 52B) swing in accordance with eccentric rotation of the rollers (52A, 52B).

[0038] The compressor (20) includes a casing (21) and a plurality of components housed in the casing (21). The plurality of components include an electric motor (25), the rotary shaft (30), a rotary compression mechanism (40), bearings (44, 45), and an oil supply mechanism (70). The electric motor (25) is a drive source of the compression mechanism (40). The rotary shaft (30) is connected to the electric motor (25). The bearings (44, 45) rotatably support the rotary shaft (30). The compression mechanism (40) is driven to rotate by the rotary shaft (30), thereby compressing the refrigerant. The oil supply mechanism (70) supplies refrigerating machine oil, which is a lubricant, to a plurality of sliding portions.(2-1) Casing

[0039] The casing (21) is a hollow closed container. In other words, the compressor (20) is a hermetic compressor. The casing (21) has therein an internal space (S). The casing (21) is formed vertically long and extends in the axial direction, strictly, in the vertical direction. The casing (21) includes a cylindrical barrel (21a) extending in the vertical direction, an upper lid (21b) closing the upper end of the barrel (21a), and a lower lid (21c) closing the lower end of the barrel (21a). The lower lid (21c) constitutes the bottom of the casing (21).

[0040] The internal space (S) of the casing (21) is filled with a discharge refrigerant discharged from the compression mechanism (40). That is, the compressor (20) is of a so-called high-pressure dome type.

[0041] An oil reservoir (35) that stores the refrigerating machine oil is formed at the bottom of the casing (21). In the oil reservoir (35), the oil level of the refrigerating machine oil changes in accordance with the operating conditions of the compressor (20) and the air conditioner (1).(2-2) First Suction Pipe, Second Suction Pipe, and Discharge Pipe

[0042] A first suction pipe (23A), a second suction pipe (23B), and a discharge pipe (24) are connected to the casing (21). The first suction pipe (23A) and the second suction pipe (23B) penetrate the barrel (21a) in the radial direction. The first suction pipe (23A) and the second suction pipe (23B) are connected to a low-pressure line of the refrigerant circuit (10). The discharge pipe (24) penetrates the upper lid (21b) in the axial direction. The discharge pipe (24) is connected to a high-pressure line of the refrigerant circuit (10).(2-3) Electric Motor

[0043] The electric motor (25) is located in an upper portion of the internal space (S). The electric motor (25) has a stator (26) and a rotor (27). The stator (26) is fixed to the inner circumferential surface of the barrel (21a). The stator (26) is formed in a cylindrical shape as viewed in a cross section (i.e., the horizontal cross section) perpendicular to the axial direction. The rotor (27) is disposed radially inside the stator (26). The rotor (27) is fixed to the outer circumferential surface of the rotary shaft (30). The electric motor (25) is configured such that its number of revolutions can be adjusted by an inverter device. In other words, the electric motor (25) is an inverter electric motor with a variable operation frequency.(2-4) Rotary Shaft

[0044] The rotary shaft (30) is located at the center of the internal space (S) in the radial direction. The rotary shaft (30) extends in the vertical direction. The rotary shaft (30) includes a shaft body (31), and a first eccentric portion (32A) and a second eccentric portion (32B) that are eccentric from the axis (A) of the shaft body (31) in the radial direction. The rotor (27) of the electric motor (25) is connected to an upper portion of the shaft body (31). The first eccentric portion (32A) and the second eccentric portion (32B) are formed in a lower portion of the shaft body (31). The first eccentric portion (32A) is located above the second eccentric portion (32B). The direction in which the first eccentric portion (32A) is eccentric from the axis (A) and the direction in which the second eccentric portion (32B) is eccentric from the axis are different by 180° in the circumferential direction.(2-5) General Configuration of Compression Mechanism

[0045] The compression mechanism (40) is disposed below the electric motor (25). The compression mechanism (40) includes a front head (41), a first cylinder (51A), a middle plate (42), a second cylinder (51B), and a rear head (43) in this order from top to bottom. These members are fixed to each other by bolts extending in the axial direction.

[0046] The compression mechanism (40) according to this embodiment includes a first compression element (C1) and a second compression element (C2). The first compression element (C1) includes a first roller (52A) and a first vane (53A). The second compression element (C2) includes a second roller (52B) and a second vane (53B). In the compression mechanism (40) according to this embodiment, the rollers (52A, 52B) and the vanes (53A, 53B) are integrally formed, and the vanes (53A, 53B) swing in accordance with eccentric rotation of the rollers (52A, 52B).

[0047] The first cylinder (51A) has therein a first cylinder chamber (54A). The first cylinder chamber (54A) penetrates the first cylinder (51A) in the axial direction. The second cylinder (51B) has therein a second cylinder chamber (54B). The second cylinder chamber (54B) penetrates the second cylinder (51B) in the axial direction.(2-5-1) Closing Member

[0048] The front head (41), the middle plate (42), and the rear head (43) are examples of the closing member that closes the cylinder chambers (54A, 54B) in the axial direction. The front head (41) includes a first closing portion (41a) in the shape of a flat plate slightly thick in the axial direction, and an upper bearing portion (41b) extending upward from the center of the first closing portion (41a) in the radial direction.

[0049] The lower surface of the first closing portion (41a) closes the upper opening surface of the first cylinder chamber (54A). As shown in FIG. 4, the first closing portion (41a) is provided with a first discharge port (55A) communicating with the high-pressure chamber (i.e., the compression chamber) of the first cylinder chamber (54A). The first discharge port (55A) is opened and closed by a first discharge valve (not shown).

[0050] The upper bearing portion (41b) is formed in a tubular shape extending along the rotary shaft (30) in the axial direction. The rotary shaft (30) penetrates through the inside of the upper bearing portion (41b). A first bearing (44) is formed on the inner circumferential surface of the upper bearing portion (41b). The first bearing (44) rotatably supports the main shaft portion of the rotary shaft (30). The first bearing (44) is a sliding bearing, more specifically, a journal bearing.

[0051] The middle plate (42) is disposed between the first cylinder (51A) and the second cylinder (51B). The middle plate (42) is formed in an annular shape. The rotary shaft (30) penetrates through the inside of the middle plate (42). The upper surface of the middle plate (42) closes the lower opening surface of the first cylinder chamber (54A). The lower surface of the middle plate (42) closes the upper opening surface of the second cylinder chamber (54B).

[0052] The rear head (43) includes a second closing portion (43a) in the shape of a flat plate slightly thick in the axial direction, and a lower bearing portion (43b) extending downward from the center of the second closing portion (43a) in the radial direction. The upper surface of the second closing portion (43a) closes the lower opening surface of the second cylinder chamber (54B). As shown in FIG. 5, the second closing portion (43a) is provided with a second discharge port (55B) communicating with the high-pressure chamber (i.e., the compression chamber) of the second cylinder chamber (54B). The second discharge port (55B) is opened and closed by a second discharge valve (not shown).

[0053] The lower bearing portion (43b) is formed in a tubular shape extending along the rotary shaft (30) in the axial direction. The rotary shaft (30) penetrates the inside of the lower bearing portion (43b). A second bearing (45) is formed on an inner circumferential surface of the lower bearing portion (43b). The second bearing (45) rotatably supports the auxiliary shaft portion of the rotary shaft (30). The second bearing (45) is a sliding bearing, strictly, a journal bearing.(2-5-2) Details of First Compression Element

[0054] The first compression element (C1) shown in FIG. 4 includes the first eccentric portion (32A), the first cylinder (51A), the first roller (52A), the first vane (53A), and a pair of first bushes (56A).

[0055] The first cylinder (51A) is an annular member slightly thick in the axial direction. The first cylinder (51A) has therein the first cylinder chamber (54A). The first cylinder chamber (54A) is formed in a circular shape as viewed in the axial direction. The first cylinder (51A) is provided with a first suction passage (57A) and a first bush groove (58A). The first suction passage (57A) penetrates the first cylinder (51A) in the radial direction. The first suction passage (57A) communicates with the first suction pipe (23A).

[0056] The first roller (52A) is disposed in the first cylinder chamber (54A). The first roller (52A) is formed in an annular shape as viewed in the axial direction. The first eccentric portion (32A) is fitted inside the first roller (52A). The inner circumferential surface of the first roller (52A) and the outer circumferential surface of the first eccentric portion (32A) slide relative to each other. The first eccentric portion (32A) eccentrically rotates the first roller (52A). The first roller (52A) eccentrically rotates along the inner circumferential surface of the first cylinder chamber (54A), while forming a seal portion between the first roller (52A) and the inner circumferential surface of the first cylinder chamber (54A).

[0057] The first bush groove (58A) is formed on the top dead center side (i.e., an upper side in FIG. 3) in the first cylinder (51A). The first bush groove (58A) is formed in a circular shape as viewed in the axial direction. The pair of first bushes (56A) are fitted into the first bush groove (58A). Each of the pair of first bushes (56A) has an arc portion in a shape along the inner surface of the first bush groove (58A), and a flat portion being continuous with both ends of the arc portion. The pair of first bushes (56A) are disposed in the first bush groove (58A) with the flat portions thereof facing each other. The flat portions of the pair of first bushes (56A) hold the first vane (53A). The pair of first bushes (56A) are swingable along an inner surface of the first bush groove (58A). The first vane (53A) is reciprocally movable in the radial direction between the pair of first bushes (56A).

[0058] The first vane (53A) constitutes a partitioning member partitioning the first cylinder chamber (54A) into a low-pressure chamber (L) and a high-pressure chamber (H). A radially inner portion of the first vane (53A) is continuous with the outer circumferential surface of the first roller (52A). The low-pressure chamber (L) of the first cylinder chamber (54A) communicates with the first suction passage (57A) and constitutes a suction chamber into which the low-pressure refrigerant flows. The high-pressure chamber (H) of the first cylinder chamber (54A) is isolated from the first suction passage (57A) and constitutes a compression chamber for compressing the refrigerant.(2-5-3) Details of Second Compression Element

[0059] The second compression element (C2) shown in FIG. 5 includes the second eccentric portion (32B), the second cylinder (51B), the second roller (52B), the second vane (53B), and a pair of second bushes (56B). The basic structures of the second eccentric portion (32B), the second cylinder (51B), the second roller (52B), the second vane (53B), and the pair of second bushes (56B) are the same as those of the first eccentric portion (32A), the first cylinder (51A), the first roller (52A), the first vane (53A), and the pair of first bushes (56A), respectively. Detailed description thereof will thus be omitted. The second cylinder (51B) is provided with the second cylinder chamber (54B), a second suction passage (57B), and a second bush groove (58B). The basic structures of the second cylinder chamber (54B), the second suction passage (57B), and the second bush groove (58B) are the same as those of the first cylinder chamber (54A), the first suction passage (57A), and the first bush groove (58A), respectively. Detailed description thereof will thus be omitted. The second suction pipe (23B) communicates with the second suction passage (57B). The first roller (52A) and the second roller (52B) are different in phase by 180° in the eccentric rotation.(2-6) Oil Supply Mechanism

[0060] The oil supply mechanism (70) shown in FIG. 3 supplies the refrigerating machine oil in the oil reservoir (35) to a plurality of sliding portions. The oil supply mechanism (70) is provided under the rotary shaft (30). The oil supply mechanism (70) includes an oil supply pump (71) and an oil supply passage (72).

[0061] The oil supply pump (71) is provided at the lower end of the rotary shaft (30). The oil supply pump (71) is located at a position lower than the oil level of the oil reservoir (35). The oil supply pump (71) transports the refrigerating machine oil in the oil reservoir (35). The oil supply pump (71) has a suction port (71a) for sucking the refrigerating machine oil in the oil reservoir (35). The suction port (71a) is open downward toward the bottom of the casing (21). The oil supply pump (71) is a differential pressure, centrifugal, or positive-displacement pump.

[0062] The rotary shaft (30) has therein the oil supply passage (72). The oil supply passage (72) communicates with the discharge side of the oil supply pump (71). The oil supply passage (72) includes a main flow passage (73) extending in the vertical direction so as to pass through the axis of the rotary shaft (30), and a plurality of flow divider passages extending from the main flow passage (73) in the radial direction. The plurality of flow divider passages include the first flow divider passage (74a), the second flow divider passage (74b), the third flow divider passage (74c), and the fourth flow divider passage (74d) in order from the top to the bottom.

[0063] The first flow divider passage (74a) is located at the same level as the upper bearing portion (41b). The outflow port of the first flow divider passage (74a) is open toward the first bearing (44). In other words, the first flow divider passage (74a) is open toward the sliding portion between the first bearing (44) and the rotary shaft (30). The second flow divider passage (74b) is formed in the first eccentric portion (32A). The outflow port of the second flow divider passage (74b) is open toward the inner circumferential surface of the first roller (52A). In other words, the second flow divider passage (74b) is open toward the sliding portion between the first roller (52A) and the first eccentric portion (32A). The third flow divider passage (74c) is formed in the second eccentric portion (32B). The outflow port of the third flow divider passage (74c) is open toward the inner circumferential surface of the first roller (52A). In other words, the third flow divider passage (74c) is open toward the sliding portion between the second roller (52B) and the second eccentric portion (32B). The fourth flow divider passage (74d) is at the same level as the lower bearing portion (43b). The outflow port of the fourth flow divider passage (74d) is open toward the second bearing (45). In other words, the fourth flow divider passage (74d) is open toward the sliding portion between the second bearing (45) and the rotary shaft (30).(2-7) Operation

[0064] Once the rotary shaft (30) is driven to rotate by the electric motor (25), the first eccentric portion (32A) and the second eccentric portion (32B) rotate eccentrically. In the first compression element (C1), the low-pressure refrigerant is sucked through the first suction pipe (23A) into the low-pressure chamber (L) of the first cylinder chamber (54A) in accordance with the eccentric rotation of the first roller (52A). At the same time, the refrigerant is compressed in the high-pressure chamber (H) of the first cylinder chamber (54A). In the second compression element (C2), the low-pressure refrigerant is sucked through the second suction pipe (23B) into the low-pressure chamber (L) of the first cylinder chamber (54A) in accordance with the eccentric rotation of the second roller (52B). At the same time, the refrigerant is compressed in the high-pressure chamber of the second cylinder chamber (54B).

[0065] Once the internal pressure of the compression chamber of the first compression element (C1) rises and the first reed valve opens, the high-pressure refrigerant is discharged through the first discharge port (55A) to the internal space (S). Once the internal pressure of the compression chamber of the second compression element (C2) rises and the second reed valve opens, the high-pressure refrigerant is discharged through the second discharge port (55B) to the internal space (S). The high-pressure refrigerant around the compression mechanism (40) passes upward through the electric motor (25) and is discharged through the discharge pipe (24) to the refrigerant circuit (10).

[0066] Once the rotary shaft (30) rotates, the oil supply pump (71) rotates together with the rotary shaft (30). As a result, the refrigerating machine oil in the oil reservoir (35) is sucked in through the suction port (71a). The oil supply pump (71) sends the refrigerating machine oil sucked through the suction port (71a) via the main flow passage (73) to the flow divider passages (71a, 71b, 71c, 71d). The refrigerating machine oil in the first flow divider passage (74a) is used for lubricating the sliding portion of the first bearing (44). The refrigerating machine oil in the second flow divider passage (74b) is used for lubricating the sliding portion of the first eccentric portion (32A). The refrigerating machine oil in the third flow divider passage (74c) is used for lubricating the sliding portion of the second eccentric portion (32B). The refrigerating machine oil in the fourth flow divider passage (74d) is used for lubricating the sliding portion of the second bearing (45).(3) Refrigerant

[0067] The refrigerant according to this embodiment is a hydrocarbon refrigerant. The hydrocarbon refrigerant according to this embodiment is a single component refrigerant composed of propane (R290). Propane has a significantly low global warming potential and is environmentally friendly. On the other hand, a hydrocarbon refrigerant, such as propane, has a molecular structure similar to that of the refrigerating machine oil and thus has characteristics of being easily dissolvable in the refrigerating machine oil.

[0068] The hydrocarbon refrigerant may be a single component refrigerant composed of isobutane. The refrigerant of the refrigerant circuit (10) may be a refrigerant mixture containing the hydrocarbon refrigerant and at least one of other refrigerants. As the other refrigerant, for example, a hydrofluorocarbon (HFC) refrigerant, a hydrofluoroolefin (HFO) refrigerant, or trifluoroiodomethane (CF 3 I) is used.(4) Refrigerating Machine Oil

[0069] Next, the refrigerating machine oil used in the refrigerant circuit (10) will be described. Note that the refrigerating machine oil referred to here means a fluid containing additives, such as an extreme pressure additive, an antioxidant, and an acid scavenger in addition to the component (i.e., the lubricating oil) used for lubricating the sliding portions.(4-1) Components and Characteristics of Refrigerating Machine Oil

[0070] The refrigerating machine oil used in the refrigerant circuit (10) according to this embodiment includes any of polyalkylene glycol (PAG), polyvinyl ether (PVE), or polyol ester (POE). The refrigerating machine oil contains PAG, PVE or POE as a main component.

[0071] A hydrocarbon refrigerant, such as propane, has a molecular structure similar to that of the refrigerating machine oil and thus has characteristics of being easily dissolvable in the refrigerating machine oil. In contrast, PAG, PVE, or POE has a relatively low compatibility with a hydrocarbon refrigerant. Using PAG, PVE, or POE as the refrigerating machine oil, the dissolution of the refrigerant in the refrigerating machine oil can be reduced. The refrigerating machine oil may be alkylbenzene or mineral oil.

[0072] The refrigerating machine oil has characteristics of being separated into two layers at a pressure of the refrigerant of 1.9 [MPa] and a temperature of the refrigerating machine oil of 75°C. That is, the refrigerating machine oil in the oil reservoir (35) is separated into two layers when the refrigerant in the casing (21) has a pressure of 1.9 [MPa] and the refrigerating machine oil has a temperature of 75[°C].

[0073] In general, the refrigerating machine oil uniformly dissolves in the refrigerant. However, when the refrigerating machine oil with a low solubility to the refrigerant is used, the concentration gradient occurs between the refrigerating machine oil and the refrigerant in the oil reservoir (35), and the refrigerating machine oil then becomes a so-called two-layer separation state. The refrigerating machine oil near the oil level of the oil reservoir (35) forms a layer with a high solubility for the refrigerant because the refrigerant has low density. The refrigerating machine oil near the bottom of the oil reservoir (35) forms a layer with a low solubility for the refrigerant because the refrigerant has high density. The solution viscosity of the refrigerating machine oil changes in accordance with the solubility of the refrigerant. The solution viscosity of the refrigerating machine oil can thus be secured by lowering the solubility to the refrigerant. The state in which the refrigerant and the refrigerating machine oil do not dissolve and are separated into two layers, or in which the refrigerant and the refrigerating machine oil are emulsified, when the refrigerant and the refrigerating machine oil are mixed, is referred to as the two-layer separation state.

[0074] The molecular weight of the refrigerating machine oil is preferably 1000 or more and 1800 or less.

[0075] The refrigerating machine oil includes at least one additive of an extreme pressure additive of a phosphoric acid ester, an antioxidant, or an acid scavenger.

[0076] As the extreme pressure additive of phosphoric acid ester, one of those containing phosphoric acid ester, phosphorous acid ester, acidic phosphoric acid ester, acidic phosphorous acid ester, and amine salt of acidic phosphorous acid ester.

[0077] As the acid scavenger, an epoxy compound, such as phenyl glycidyl ether, alkyl glycidyl ether, alkylene glycol glycidyl ether, cyclohexene oxide, α-olefin oxide, or epoxidized soybean oil can be used.

[0078] As the antioxidant, a phenol-based antioxidant or an amine-based antioxidant can be used.

[0079] The refrigerating machine oil contains an extreme pressure additive in an amount of 1.0 wt% or more and 5.0 wt% or less. The refrigerating machine oil contains an antioxidant or an acid scavenger in an amount of 0.1 wt% or more and 0.5 wt% or less.

[0080] The surface tension of the refrigerating machine oil according to this embodiment is 0.25 [N / m] or more and 0.40 [N / m] or less at 20°C. The surface tension of the refrigerating machine oil is measured by a method in accordance with JIS K 2241.(4-2) Solution Viscosity of Refrigerating Machine Oil in Oil Reservoir

[0081] The solution viscosity of the refrigerating machine oil in the oil reservoir (35) of the casing (21) of the compressor (20) will be described in detail. The refrigerating machine oil located at the level h1 of the suction port (71a) of the oil supply pump (71) or lower in the oil reservoir (35) is defined as a first refrigerating machine oil. The level h1 of the suction port (71a) means an absolute height of the horizontal plane passing through the suction port (71a). The solution viscosity η of the first refrigerating machine oil according to this embodiment is a first solution viscosity η1 or more and a second solution viscosity η2 or less. In other words, the refrigerating machine oil is configured such that the solution viscosity η of the first refrigerating machine oil in the oil reservoir (35) is η1 or more and η2 or less. Here, the "solution viscosity" means the viscosity of a fluid with the refrigerant dissolved in the refrigerating machine oil. This viscosity of the fluid is measured by a method in accordance with JIS K 2283. The solution viscosity of the refrigerating machine oil changes in accordance with the content of the extreme pressure additive, the antioxidant, or the oxygen scavenger described above.

[0082] The temperature and pressure conditions of the oil reservoir (35) change in accordance with the operating conditions of the compressor (20) and the refrigerant circuit (10). This temperature condition is, for example, within a range from 72 [°C] to 80 [°C], and the pressure condition is 1.9 [MPa]. Under these operating conditions, the refrigerating machine oil is configured such that the solution viscosity η of the first refrigerating machine oil at 72 [°C] to 80 [°C] and 1.9 [Mpa] is the first solution viscosity η1 or more and the second solution viscosity η2 or less. The solution viscosity under the operating conditions can be measured by a viscometer attached to the casing (21), for example. The viscometer is attached to the barrel (21a) or the lower lid (21c) of the casing (21). The viscometer can measure the solution viscosity of the first refrigerating machine oil at h1 or lower in the oil reservoir (35).(4-2-1) Lower Limit of Solution Viscosity

[0083] The first solution viscosity η1, which is the lower limit of the solution viscosity of the first refrigerating machine oil, is 5.0 [mPa·s]. In other words, the solution viscosity η of the first refrigerating machine oil is 5.0 [mPa·s] or more. This can reduce the amount of wear of the sliding portions of the first bearing (44), the second bearing (45), the first eccentric portion (32A), the second eccentric portion (32B), and other parts. The test results of verifying the relationship between the amount of wear of the sliding portion and the solution viscosity of the refrigerating machine oil will be described with reference to FIGS. 6 and 7.

[0084] FIG. 6 shows the test conditions of this test. The amount of wear of the sliding portions was evaluated by the FALEX test under the ASTM standard D3233-19. In the FALEX test, cast iron (FC250) corresponding to the material of the sliding portions of the compressor (20) are used as test pieces (i.e., pins). Propane as a hydrocarbon refrigerant was dissolved in a refrigerating machine oil to prepare a plurality of refrigerating machine oils with different solution viscosities. For each refrigerating machine oil, a test piece (pin) lubricated with the refrigerating machine oil was clamped between two blocks and rotated for 60 minutes under a predetermined load (150 [lbs]) applied, and the amount of wear at this time was measured. At this time, the ambient temperature of the test piece was 80°C, which corresponds to the temperature in the casing (21) in a normal refrigeration cycle.

[0085] FIG. 7 shows the relationship between the solution viscosity of the refrigerating machine oil and the amount of wear of the test pieces, which was measured by the FALEX test. As a test result of the test, the test pieces with solution viscosities within a range from 6 [mPa·s] to 10 [mPa·s] were not worn. It was confirmed that the test pieces with the solution viscosities less than 6 [mPa·s] were worn, and that the amount of wear rapidly increased at solution viscosities of less than 5 [mPa·s]. At a solution viscosity of 5 [mPa·s] or more, the amount of wear can be reduced to 1 [mg] or less. From this, the solution viscosity may be set to 5.0 [mPa·s] or more, more preferably 6.0 [mPa·s] or more, in order to reduce the wear of the sliding portions. In the compressor (20) according to this embodiment, the wear of the sliding portions can be reduced properly using the refrigerating machine oil with a solution viscosity of 5.0 [mPa·s] or more.

[0086] In this embodiment, the first refrigerating machine oil has a solution viscosity η of 5.0 [mPa·s] or more at the level h1 of the suction port (71a) or lower. Accordingly, the oil supply mechanism (70) can supply the refrigerating machine oil with a solution viscosity of 5.0 [mPa·s] or more to the sliding portions of the first bearing (44), the second bearing (45), the first eccentric portion (32A), and the second eccentric portion (32B). As a result, the wear of the sliding portions can be reduced.(4-2-2) Upper Limit of Solution Viscosity

[0087] A result of studying the second solution viscosity η2 will be described, which is the upper limit of the solution viscosity of the first refrigerating machine oil. FIG. 8 shows a result of verifying the relationship between the solution viscosity of the refrigerating machine oil, the displacement volume Vc of the compression mechanism, and the loss percentage γ at the eccentric portions. In FIG. 8, a line segment L1 represents a compressor with a displacement volume Vc of 17.2 cc, a line segment L2 represents a compressor with a displacement volume Vc of 25.9 cc, and a line segment L3 represents a compressor with a displacement volume Vc of 35.0 cc. FIG. 8 shows the relationship between the solution viscosity of the refrigerating machine oil and the loss percentage γ at the eccentric portions in each of three compressors with different displacement volumes Vc.

[0088] The displacement volume Vc is the volume of the high-pressure chamber (i.e., the compression chamber) when the low-pressure chamber is completely closed in the cylinder and the high-pressure chamber (i.e., the compression chamber) is defined, and corresponds to the maximum volume of the compression chamber. When the compression mechanism is of a two cylinder type, Vc defined here is the sum of the displacement volume Vc-1 of the first cylinder and the displacement volume Vc-2 of the second cylinder. When the number of cylinders is n and the displacement volumes of the respective cylinders are Vc-n, Vc-n + 1, . . ., the displacement volume Vc is the sum of the displacement volumes Vc-n, Vc-n + 1, . . . .

[0089] The loss percentage γ at the eccentric portions is the percentage [%] of the sliding loss [W] at the eccentric portions with respect to the input [W] to the compressor. The sliding loss at the eccentric portions is the sum of the sliding losses at two eccentric portions in the case of a two cylinder type, and is the sum of the sliding losses at n eccentric portions (32A, 32B) in the case where there are n cylinders.

[0090] As can be seen from FIG. 8, the loss percentage γ at the eccentric portions increases with an increase in the displacement volume Vc. With an increase in the displacement volume Vc of the compression mechanism, the sizes of the eccentric portions and the projected area of the eccentric portions as viewed from the radially outer side increase. In an eccentric rotation of the eccentric portions, a load acts on the roller from the eccentric portion in a portion corresponding to this projected area, and the load greatly influences the sliding loss [W]. That is, with an increase in the displacement volume Vc, the projected area increases and the sliding loss and further the loss percentage γ at the eccentric portions increase.

[0091] The rotary compressor may include, in addition to the sliding portions between the eccentric portions (32A, 32B) and the rollers (52A, 52B), sliding portions in the thrust direction (thrust sliding portions) between the eccentric portions (32A, 32B) and the bearing. However, the thrust sliding portions may only need to have a minimum area required to reduce vertical vibrations of the rotary shaft (30), and the sliding area thereof is desirably small. Thus, in the rotary compressor, the number of sliding portions other than the sliding portions between the eccentric portions (32A, 32B) and the rollers (52A, 52B) is small, and the sliding loss of the other sliding portions is minor. As a result, the proportion of sliding loss of the eccentric portions (32A, 32B) relative to the input of the rotary compressor becomes large. Therefore, in the rotary compressor, with an increase in the displacement volume Vc, the loss percentage γ of the eccentric portions (32A, 32B) also increases.

[0092] As can be seen from FIG. 8, with an increase in the solution viscosity of the refrigerating machine oil, the loss percentage γ at the eccentric portions increases. This is because the sliding loss at the eccentric portions increases with an increase in the solution viscosity of the refrigerating machine oil.

[0093] In view of the above points, a relational expression (1) of the upper limit of the solution viscosity (i.e., the second solution viscosity η2) for setting the loss percentage γ at the eccentric portions to 10% or less was obtained based on the displacement volume Vc, the solution viscosity of the refrigerating machine oil, and the loss percentage γ at the eccentric portions shown in FIG. 8. η 2 = − 0.00101 × Vc + 0.12286 / 0.0000146 × Vc + 0.00505

[0094] Here, Vc in the relational expression (1) is the displacement volume [cc] of the compression mechanism (40) described above. By setting the solution viscosity of the refrigerating machine oil to η2 or less, the loss percentage γ at the eccentric portions can be set to 10% or less.

[0095] In this embodiment, the solution viscosity η of the first refrigerating machine oil is (-0.00101 × Vc + 0.12286) / (0.0000146 × Vc + 0.00505) or less. In this embodiment, the sliding loss at the eccentric portions (32A, 32B) of the compression mechanism (40) can thus be reduced to 10% or less of the input of the compressor (20). Here, the sliding loss at the eccentric portions (32A, 32B) accounts for a large proportion of the friction loss of the entire compressor (20). The loss percentage γ of 10% or less can effectively reduce the decrease in the efficiency of the compressor (20).

[0096] In addition, since a relatively large amount of refrigerating machine oil is supplied to the sliding portions of the eccentric portions (32A, 32B), fluid lubrication regions are formed between the eccentric portions (32A, 32B) and the rollers (52A, 52B). The sliding loss at the eccentric portions (32A, 32B) is thus easily influenced by the solution viscosity of the refrigerating machine oil. By setting the solution viscosity of the refrigerating machine oil to be the upper limit or less of the above relational expression (1), an increase in the sliding loss at the eccentric portions (32A, 32B) can be effectively reduced.(4-3) First Refrigerating Machine Oil

[0097] As described above, the first refrigerating machine oil is the refrigerating machine oil at the level of the suction port (71a) or lower in the oil reservoir (35). However, it is preferable that the first refrigerating machine oil is present below the suction port (71a), near the suction port (71a), or inside the suction port (71a). By setting the solution viscosity η of such a refrigerating machine oil to η1 or more, wear of the sliding portions can be particularly reduced. By setting the solution viscosity η of the refrigerating machine oil to η2 or less, the sliding loss at the eccentric portions (32A, 32B) can be reduced.(5) Advantages of First Embodiment

[0098] (5-1) The refrigerant according to this embodiment is a hydrocarbon refrigerant. The hydrocarbon refrigerant according to this embodiment is a single component refrigerant of propane. Propane has a significantly low global warming potential and is environmentally friendly. On the other hand, a hydrocarbon refrigerant, such as propane, has a molecular structure similar to that of the refrigerating machine oil and thus has characteristics of being easily dissolvable in the refrigerating machine oil. Accordingly, excessive dissolution of the refrigerant into the refrigerating machine oil may cause a decrease in the solution viscosity of the refrigerating machine oil. With a decrease in the solution viscosity of the refrigerating machine oil, the viscosity of the refrigerating machine oil supplied to the sliding portions of the first bearing (44), the second bearing (45), the first eccentric portion (32A), and the second eccentric portion (32B) also decreases. This may cause poor lubrication of these sliding portions.

[0099] In this embodiment, the first refrigerating machine oil present at the level of the suction port (71a) or lower in the oil reservoir (35) has a solution viscosity η of 5.0 [mPa·s] or more.

[0100] Accordingly, the refrigerating machine oil with a solution viscosity of 5.0 [mPa·s] or more can be supplied to the sliding portions of the bearings (44, 45) and the sliding portions of the eccentric portions (32A, 32B). This can reduce the wear of these sliding portions, thereby increasing the reliability of the compressor (20) and extending the life of the compressor (20). In particular, by setting the solution viscosity of the refrigerating machine oil to 6.0 [mPa·s] or more, the wear of the sliding portions can be further reduced.

[0101] (5-2) The solution viscosity η of the first refrigerating machine oil is (-0.00101 × Vc + 0.12286) / (0.0000146 × Vc + 0.00505) or less.

[0102] This can reduce the sliding loss at the eccentric portions (32A, 32B). Specifically, the sliding loss at the eccentric portions (32A, 32B) can be reduced to 10% or less with respect to the input to the compressor (20). This can reduce the friction loss of the compressor (20), thereby increasing the efficiency of the compressor (20) and improving the coefficient of performance (COP) of the refrigerant circuit (10).

[0103] (5-3) The refrigerating machine oil includes polyalkylene glycol, polyvinyl ether, or polyol ester.

[0104] With the use of these refrigerating machine oils, the hydrocarbon refrigerant is less likely to dissolve in the refrigerating machine oil. Once the hydrocarbon refrigerant dissolves in the refrigerating machine oil, the solution viscosity of the first refrigerating machine oil decreases. In contrast, with the use of these refrigerating machine oils, an excessive decrease in the solution viscosity of the first refrigerating machine oil can be reduced.

[0105] In particular, by setting the molecular weight of the refrigerating machine oil to 1000 or more and 1800 or less, the dissolution of the hydrocarbon refrigerant in the refrigerating machine oil can be effectively reduced.

[0106] Since hydrocarbon refrigerant is a highly flammable refrigerant, the amount of refrigerant filling the refrigerant circuit (10) may be limited. Accordingly, excessive dissolution of the hydrocarbon refrigerant into the refrigerating machine oil may make it difficult to ensure a sufficient amount of the refrigerant for use in the refrigeration cycle. In contrast, by reducing dissolution of the hydrocarbon refrigerant in the refrigerating machine oil in this manner, the amount of the refrigerant used in the refrigeration cycle can be secured.

[0107] (5-4) The refrigerating machine oil contains at least one of an extreme pressure additive of a phosphoric acid ester, an antioxidant, or an acid scavenger.

[0108] When the refrigerating machine oil contains an antioxidant, the amount of the antioxidant in the refrigerating machine oil is 0.1 wt% or more and 0.5 wt% or less. The hydrocarbon refrigerant has a chemically stable structure and is less likely to decompose during the refrigeration cycle compared to HFC refrigerant and HFO refrigerant. Even when the amount of the antioxidant in the refrigerant is 0.5 wt% or less, the refrigerant can be stably used for a long period of time. By limiting the amount of the antioxidant to 0.5 wt% or less, a decrease in the viscosity of the refrigerating machine oil can be reduced. As a result, the solution viscosity η of the first refrigerating machine oil can be more like to be increased to 5.0 [mPa·s] or more, thereby reducing the wear of the sliding portions. By reducing dissolution of the hydrocarbon refrigerant in the refrigerating machine oil in this manner, the amount of the refrigerant used in the refrigeration cycle can be secured.

[0109] When the refrigerating machine oil contains an acid scavenger, the amount of the acid scavenger is 0.1 wt% or more and 0.5 wt% or less. As described above, the hydrocarbon refrigerant has a chemically stable structure and is less likely to decompose during the refrigeration cycle compared to HFC refrigerant and HFO refrigerant. Even when the amount of the acid scavenger in the refrigerant is 0.5 wt% or less, the refrigerant can be stably used for a long period of time. By limiting the amount of the acid scavenger to 0.5 wt% or less, a decrease in the viscosity of the refrigerating machine oil can be reduced. As a result, the solution viscosity η of the first refrigerating machine oil can be more like to be increased to 5.0 [mPa·s] or more, thereby reducing the wear of the sliding portions. By reducing dissolution of the hydrocarbon refrigerant in the refrigerating machine oil in this manner, the amount of the refrigerant used in the refrigeration cycle can be secured.

[0110] When the refrigerating machine oil contains an extreme pressure additive, the amount of the extreme pressure additive is 1.0 wt% or more and 5.0 wt%. By limiting the amount of the extreme pressure additive to 5.0 wt% or less, a decrease in the viscosity of the refrigerating machine oil can be reduced. As a result, the solution viscosity η of the first refrigerating machine oil can be more like to be increased to 5.0 [mPa·s] or more, thereby reducing the wear of the sliding portions. By reducing dissolution of the hydrocarbon refrigerant in the refrigerating machine oil in this manner, the amount of the refrigerant used in the refrigeration cycle can be secured.<Second Embodiment>

[0111] A compressor according to a second embodiment is a scroll compressor (120).(6-1) General Configuration

[0112] As shown in FIG. 9, the scroll compressor (hereinafter also referred to as the compressor (120)) includes a casing (121) and a plurality of components housed in the casing (121). The plurality of components include an electric motor (125), a rotary shaft (130), a scroll compression mechanism (140), bearings (152, 156, 157), and an oil supply mechanism (170). The electric motor (125) is a drive source of the compression mechanism (140). The rotary shaft (130) is connected to the electric motor (125). The bearings (152, 156, 157) rotatably support the rotary shaft (130). The compression mechanism (140) is driven to rotate by the rotary shaft (130) to compress the refrigerant. The oil supply mechanism (170) supplies a refrigerating machine oil, which is a lubricant, to the plurality of sliding portions.

[0113] The casing (121) is a hollow closed container. In other words, the compressor (120) is a hermetic compressor. The casing (121) has therein an internal space (S). The casing (121) is formed vertically long and extends in the axial direction, strictly, in the vertical direction. The casing (121) includes a cylindrical barrel (121a) extending in the vertical direction, an upper end plate (121b) closing the upper end of the barrel (121a), and a lower end plate (121c) closing the lower end of the barrel (121a). The lower end plate (121c) constitutes the bottom of the casing (121).

[0114] The internal space (S) of the casing (121) is filled with a discharge refrigerant discharged from the compression mechanism (140). That is, the compressor (120) is of a so-called high-pressure dome type. The internal space (S) includes a first space (S1) above the compression mechanism (140), and a second space (S2) below the compression mechanism (140).

[0115] An oil reservoir (135) that stores the refrigerating machine oil is formed at the bottom of the casing (121). In the oil reservoir (135), the oil level of the refrigerating machine oil changes in accordance with the operating conditions of the compressor (120) and the air conditioner (1).

[0116] A suction pipe (123) and a discharge pipe (124) are connected to the casing (121). The suction pipe (123) penetrates the upper end plate (121b) in the axial direction. The outflow end of the suction pipe (123) is connected to the suction side of the compression mechanism (140). The discharge pipe (124) penetrates the barrel (121a) in the radial direction. The discharge pipe (124) communicates with the internal space (S) to be filled with the high-pressure refrigerant.

[0117] The electric motor (125) is located in a lower portion of the internal space (S). The electric motor (125) includes a stator (126) and a rotor (127). The stator (126) is fixed to the inner circumferential surface of the barrel (121a). The rotor (127) is fixed to the outer circumferential surface of the rotary shaft (130). The electric motor (125) is configured such that its number of revolutions can be adjusted by an inverter device. In other words, the electric motor (125) is an inverter electric motor with a variable operation frequency.

[0118] The rotary shaft (130) is located at the center of the internal space (S) in the radial direction. The rotary shaft (130) extends in the vertical direction. The rotary shaft (130) includes a shaft body (131) and an upper eccentric portion (132) that is eccentric from the axis of the shaft body (131) in the radial direction. The rotor (127) of the electric motor (125) is connected to the shaft body (131). The upper eccentric portion (132) is formed at an upper end of the shaft body (131).

[0119] A housing (150) is provided inside the casing (121). The housing (150) is located above the electric motor (125) and is fixed to the inner surface of the barrel (121a). A recess (151) is formed in the upper surface of the housing (150). An upper bearing (152) is provided at the center of the lower portion of the recess (151). The upper bearing (152) rotatably supports an upper portion of the shaft body (131). The recess (151) has therein a crank chamber (153) in which the upper eccentric portion (132) is movable.

[0120] A lower bearing member (155) is provided inside the casing (121). The lower bearing member (155) is fixed to a lower portion of the inner surface of the barrel (121a). A lower bearing (156) is provided at the center of the lower bearing member (155). The lower bearing (156) rotatably supports a lower portion of the shaft body (131).

[0121] The compression mechanism (140) includes a fixed scroll (141) and a movable scroll (160). The fixed scroll (141) is fixed to the upper surface of the housing (150). The movable scroll (160) is disposed between the fixed scroll (141) and the housing (150). A compression chamber (C) is formed between the fixed scroll (141) and the movable scroll (160).

[0122] The fixed scroll (141) includes a fixed end plate (142), a fixed wrap (143), and an outer circumferential wall (144). The fixed end plate (142) is formed at the upper end of the fixed scroll (141). The fixed wrap (143) protrudes downward from the fixed end plate (142). The fixed end plate (142) is formed in a spiral shape in a cross-sectional view in the axial direction. The outer circumferential wall (144) is formed on the outer peripheral edge of the fixed scroll (141) so as to surround the fixed end plate (142). The outer circumferential wall (144) is provided with a suction port (146) communicating with the suction pipe (123). A discharge port (147) communicating with the internal space (S) is formed in a central portion of the fixed end plate (142).

[0123] The movable scroll (160) includes a movable end plate (161), a movable wrap (162), and a boss (163). The movable end plate (161) is located above the upper eccentric portion (132). The movable wrap (162) protrudes upward from the movable end plate (161). The fixed end plate (142) is formed in a spiral shape in a cross-sectional view in the axial direction. The boss (163) protrudes downward from a central portion of the movable end plate. The upper eccentric portion (132) is fitted in the boss (163). Strictly speaking, a pin bearing (157) is provided between the inner surface of the boss (163) and the upper eccentric portion (132).(6-2) Oil Supply Mechanism

[0124] The oil supply mechanism (170) supplies the refrigerating machine oil in the oil reservoir (135) to the plurality of sliding portions. The oil supply mechanism (170) is provided under the rotary shaft (130). The oil supply mechanism (170) includes an oil supply pump (171) and an oil supply passage (172).

[0125] The oil supply pump (171) is provided at the lower end of the rotary shaft (130). The oil supply pump (171) is located at a position lower than the oil level of the oil reservoir (135). The oil supply pump (171) transports the refrigerating machine oil in the oil reservoir (135). The oil supply pump (171) has a suction port (171a) for sucking the refrigerating machine oil in the oil reservoir (135). The suction port (171a) is open downward toward the bottom of the casing (121). The oil supply pump (171) is a differential pressure, centrifugal, or positive-displacement pump.

[0126] The oil supply passage (172) communicates with the discharge side of the oil supply pump (171). The oil supply passage (172) includes a main flow passage (173) extending inside the rotary shaft (130) in the axial direction, and a plurality of flow divider passages (174a, 174b, 174c) extending from the main flow passage (173) in the radial direction. The plurality of flow divider passages include the fifth flow divider passage (174a), the sixth flow divider passage (174b), and the seventh flow divider passage (174c) in order from bottom to top.

[0127] The fifth flow divider passage (174a) is at the same level as the lower bearing (156). The outflow port of the fifth flow divider passage (174a) is open toward the lower bearing (156). In other words, the fifth flow divider passage (174a) is open toward the sliding portion between the lower bearing (156) and the rotary shaft (130). The sixth flow divider passage (174b) is at the same level as the upper bearing (152). The outflow port of the sixth flow divider passage (174b) is open toward the upper bearing (152). In other words, the sixth flow divider passage (174b) is open toward the sliding portion between the upper bearing (152) and the rotary shaft (130). The seventh flow divider passage (174c) is at the same level as the pin bearing (157). The outflow port of the seventh flow divider passage (174c) is open toward the pin bearing (157). In other words, the seventh flow divider passage (174c) is open toward the sliding portion between the pin bearing (157) and the upper eccentric portion (132).

[0128] The oil supply mechanism (170) according to the second embodiment includes an oil introduction passage (175) for introducing the refrigerating machine oil into the compression mechanism (140). The oil introduction passage (175) includes an oil groove (176), a housing-side flow passage (177), and a fixed flow passage (178). The oil groove (176) is an annular groove around the upper bearing (152). The refrigerating machine oil flowing out to the crank chamber (153) flows into the oil groove (176). The housing-side flow passage (177) is formed in the housing (150) and has an inflow end communicating with the oil groove (176). The fixed flow passage (178) is formed in the fixed scroll (141), and the inflow end of the fixed flow passage (178) communicates with the housing-side flow passage (177). The oil in the fixed flow passage (178) is supplied to a sliding portion in the thrust direction between the fixed scroll (141) and the movable scroll (160).(6-3) Operation

[0129] Once the rotary shaft (130) is driven to rotate by the electric motor (125), the upper eccentric portion (132) rotates eccentrically, and the movable scroll (160) turns accordingly. The refrigerant in the suction pipe (123) flows through the suction port (146) into the compression mechanism (140). The volume of the compression chamber between the movable wrap (162) and the fixed wrap (143) gradually decreases, and the refrigerant is compressed in the compression chamber. The compressed refrigerant flows out to the first space (S1). The refrigerant in the first space (S1) flows out through a passage (not shown) around the compression mechanism (140) to the second space (S2). A part of the refrigerant flows downward through a core cut (not shown) around the electric motor (125) and is used to cool the electric motor (125). The refrigerant in the first space (S1) flows out through the discharge pipe (124) into the refrigerant circuit (10).(6-4) Refrigerant and Refrigerating Machine Oil

[0130] The refrigerant and the refrigerating machine oil in the second embodiment are basically the same as those in the first embodiment. In other words, any of the refrigerants and refrigerating machine oils described in the first embodiment can be used as the refrigerant and the refrigerating machine oil in the second embodiment. In the second embodiment, the solution viscosity can be measured by a viscometer attached to the casing (121), for example. The viscometer is attached to the barrel (121a) or the lower end plate (121c) of the casing (121). The viscometer can measure the solution viscosity of the first refrigerating machine oil at h1 or lower in the oil reservoir (135).

[0131] In the second embodiment as well, the refrigerating machine oil located at the level h1 of the suction port (171a) of the oil supply pump (171) or lower is defined as a first refrigerating machine oil. In the second embodiment, the first solution viscosity η1, which is the lower limit of the solution viscosity of the first refrigerating machine oil, is 5.0 [mPa·s]. In other words, the solution viscosity η of the first refrigerating machine oil is 5.0 [mPa·s] or more. The solution viscosity of the first refrigerating machine oil is more preferably 6.0 [mPa·s] or more. This can reduce the amount of wear of the sliding portions in the scroll compressor (120). The sliding portions referred to here include sliding portions of not only the upper bearing (152), the lower bearing (156), and the pin bearing (157) but also a sliding portion in the thrust direction between the fixed scroll (141) and the movable scroll (160). The relationship between the amount of wear and the solution viscosity of the refrigerating machine oil is the same as that shown in FIG. 7, and the detailed description thereof will thus be omitted.

[0132] A result of studying the second solution viscosity η2 in the second embodiment, which is the upper limit of the solution viscosity of the first refrigerating machine oil, will be described. FIG. 10 shows a result of verifying the relationship between the solution viscosity of the refrigerating machine oil, the displacement volume Vcs of the scroll compression mechanism, and the bearing loss percentage γ2. In FIG. 10, a line segment L4 represents a compressor with a displacement volume Vcs of 98 cc, a line segment L5 represents a compressor with a displacement volume Vcs of 56 cc, and a line segment L6 represents a compressor with a displacement volume Vcs of 35 cc. FIG. 10 shows the relationship between the solution viscosity of the refrigerating machine oil and the bearing loss percentage γ2 in each of three scroll compressors with different displacement volumes Vcs.

[0133] The displacement volume Vcs is the maximum volume of the compression chamber when being completely closed by the compression mechanism. The bearing loss percentage γ2 is a percentage [%] of a sliding loss [W] at the bearings with respect to an input [W] to the compressor. The sliding loss at the bearings here is, strictly, the sum of the sliding losses at the upper bearing, the lower bearing, and the pin bearing.

[0134] As can be seen from FIG. 10, with a decrease in the displacement volume Vcs, the bearing loss percentage γ2 increases. To describe this in detail, in the scroll compressor, with an increase in the displacement volume, the outer diameter of the bearing also increases, and the outer diameters of the fixed scroll (141) and the movable scroll (160) increase even more. The scroll compressor is configured such that the movable scroll (160) is pressed against the fixed scroll (141) by back pressure to form the compression chamber. The fixed scroll (141) and the movable scroll (160) thus come into contact in the thrust direction. Therefore, with an increase in the outer diameters of the fixed scroll (141) and the movable scroll (160), the contact area between contact portions of the fixed scroll (141) and the movable scroll (160) (sliding portions in the thrust direction) increases, resulting in a significant increase in the sliding loss of the fixed scroll (141) and the movable scroll (160). Furthermore, with an increase in the displacement volume Vcs, the back pressure of the movable scroll (160) increases, resulting in an increased thrust force pressing the movable scroll (160) in the thrust direction. Accordingly, the sliding loss at the thrust sliding portions increases. For the above reasons, in the scroll compressor, with an increase in the displacement volume Vcs, the sliding loss at the thrust sliding portions relative to the input of the compressor increases, and accordingly, the proportion of the bearing sliding loss relative to the input, i.e., the bearing loss percentage γ2 decreases. Conversely, in the scroll compressor, with a decrease in the displacement volume Vcs, the bearing loss percentage γ2 increases. As can be seen from FIG. 10, with an increase in the solution viscosity of the refrigerating machine oil, the bearing loss percentage γ2 increases. This is because the sliding loss at the bearings increases with an increase in the solution viscosity of the refrigerating machine oil.

[0135] In view of the above points, a relational expression (2) of the upper limit of the solution viscosity (i.e., the second solution viscosity η2) for setting the bearing loss percentage γ2 to 10% or less was obtained based on the displacement volume Vcs, the solution viscosity of the refrigerating machine oil, and the bearing loss percentage γ2 shown in FIG. 10. η 2 = 0.000195 × Vcs + 0.0696 / 0.00714

[0136] In the relational expression (2), Vcs represents the above-described displacement volume [cc] of the compression mechanism (140). By setting the solution viscosity of the refrigerating machine oil to η2 or less, the bearing loss percentage γ2 can be set to 10% or less. In other words, when Vcs is within the range in FIG. 10, the solution viscosity is preferably set to 10 [mPa·s] or less.

[0137] In the second embodiment, the solution viscosity η of the first refrigerating machine oil is (0.000195 × Vcs + 0.0696) / 0.00714 or less. The second embodiment can reduce the sliding loss at each of the bearings (44, 45) of the compression mechanism (140) to 10% or less with respect to the input to the compressor (120). Thus, by setting the bearing loss percentage γ2 to 10% or less, a decrease in the efficiency of the scroll compressor (120) can be effectively reduced.(7) Other Embodiments

[0138] The rotary compressor may be of a so-called rolling piston type in which the roller eccentrically rotates with a vane separate from the roller abutting on the roller. The rotary compressor may be of a so-called hinge vane type in which the roller eccentrically rotates with the tip of the vane rotatably fitted into the recess in the outer circumferential surface of the roller.

[0139] The compression mechanism (40) may include only one cylinder, or may include three or more cylinders. In other words, the compression mechanism (40) may include only one compression unit, or may include three or more compression units.

[0140] The scroll compressor may be of an asymmetric or symmetric spiral type.

[0141] The air conditioner (1) may be of a multi-indoor type having a plurality of indoor units. The air conditioner (1) may be a movable type that adjusts the temperature of air in a target space of a vehicle, for example. The refrigeration cycle apparatus may be a hot water supply apparatus for generating hot water or a cooling apparatus for generating cold water. The refrigeration cycle apparatus may be an internal cooling apparatus that cools inside air. The internal cooling apparatus may be a stationary type for a warehouse, or a movable type for the inside of a transport container or a trailer.

[0142] While the embodiments and the variation thereof have been described above, it will be understood that various changes in form and details may be made without departing from the spirit and scope of the claims. The embodiments, the variation thereof, and the other embodiments may be combined and replaced with each other without deteriorating intended functions of the present disclosure.

[0143] The expressions of "first," "second," "third," . . . described above are used to distinguish the words to which these expressions are given, and the number and order of the words are not limited.INDUSTRIAL APPLICABILITY

[0144] As described above, the present disclosure is useful for a compressor and a refrigeration cycle apparatus.DESCRIPTION OF REFERENCE CHARACTERS

[0145] 1 Air Conditioner (Refrigeration Cycle Apparatus) 10 Refrigerant Circuit 20, 120 Compressor 21, 121 Casing 25, 125 Electric Motor 30, 130 Rotary Shaft 32A, 32B, 132 Eccentric Portion 40, 140 Compression Mechanism 44, 45, 152, 156, 157 Bearing 51A, 51B Cylinder 52A, 52B Roller 53A, 53B Vane 70, 170 Oil Supply Mechanism 71, 171 Oil Supply Pump 71a, 171a Suction Port 72, 172 Oil Supply Passage A Axis

Claims

1. A compressor comprising: an electric motor (25, 125); a rotary shaft (30,130) connected to the electric motor (25,125); a bearing (44, 45, 152, 156, 157) rotatably supporting the rotary shaft (30,130); a compression mechanism (40,140) configured to be driven by the rotary shaft (30,130) and compress a refrigerant; an oil supply mechanism (70,170); and a casing (21, 121) housing the electric motor (25, 125), the rotary shaft (30, 130), the bearing (44, 45, 152, 156, 157), the compression mechanism (40, 140), and the oil supply mechanism (70, 170), and filled with a high-pressure refrigerant discharged from the compression mechanism (40, 140), wherein the rotary shaft (30, 130) includes a shaft body (31, 131) and an eccentric portion (32A, 32B, 132) eccentric from an axis of the shaft body (31, 131), the oil supply mechanism (70,170) includes: an oil supply pump (71, 171) having a suction port (71a, 171a) for sucking the refrigerating machine oil in an oil reservoir (35, 135) at a bottom of the casing (21, 121); and an oil supply passage (72, 172) configured to supply the refrigerating machine oil sucked through the suction port (71a, 171a) to a sliding portion of the bearing (44, 45, 152, 156, 157) and a sliding portion of the eccentric portion (32A, 32B, 132), the refrigerant is a single component refrigerant composed of a hydrocarbon refrigerant or a refrigerant mixture containing the hydrocarbon refrigerant, the refrigerating machine oil is separated into two layers at a pressure of the refrigerant of 1.9 [Mpa] and a temperature of the refrigerating machine oil of 75°C, and the refrigerating machine oil present at a level of the suction port (71a, 171a) or lower in the oil reservoir (35, 135) has a solution viscosity η of 5.0 [mPa·s] or more.

2. The compressor of claim 1, wherein the compression mechanism is a rotary compression mechanism (40) including an annular cylinder (51A, 51B), an annular roller (52A, 52B) configured to eccentrically rotate in the cylinder (51A, 51B), and a vane (53A, 53B) for defining a compression chamber in the cylinder (51A, 51B).

3. The compressor of claim 2, wherein when a displacement volume of the rotary compression mechanism (40) is defined as Vc [cc], the solution viscosity η is: − 0.00101 × Vc + 0.12286 / 0.0000146 × Vc + 0.00505 or less.

4. The compressor of claim 1, wherein the compression mechanism is a scroll compression mechanism (140) including a fixed scroll (141) and a movable scroll (160).

5. The compressor of claim 4, wherein when a displacement volume of the scroll compression mechanism (140) is defined as Vcs [cc], the solution viscosity η is (0.000195 × Vcs + 0.0696) / 0.00714 or less.

6. The compressor of any one of claims 1 to 5, wherein the refrigerating machine oil includes polyalkylene glycol, polyvinyl ether, or polyol ester.

7. The compressor of any one of claims 1 to 6, wherein the refrigerating machine oil contains at least one of an extreme pressure additive of a phosphoric acid ester, an antioxidant, or an acid scavenger.

8. The compressor of any one of claims 1 to 7, wherein the refrigerating machine oil contains the antioxidant or the acid scavenger in an amount of 0.1 wt% or more and 0.5 wt% or less.

9. The compressor of any one of claims 1 to 8, wherein the refrigerating machine oil contains the extreme pressure additive in an amount of 1.0 wt% or more and 5.0 wt% or less.

10. The compressor of any one of claims 1 to 9, wherein the refrigerating machine oil has a molecular weight of 1000 or more and 1800 or less.

11. The compressor of any one of claims 1 to 10, wherein the refrigerating machine oil present at a level of the suction port (71a, 171a) or lower in the oil reservoir (35, 135) has a solution viscosity η of 6.0 [mPa·s] or more.

12. A refrigeration cycle apparatus comprising: a refrigerant circuit (10) including the compressor (20, 120) of any one of claims 1 to 11, and configured to circulate the hydrocarbon refrigerant to perform a refrigeration cycle.

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