Rotary compressor and equipment

Abstract

A compression mechanism part 30 includes a cylinder 31, a piston 32 disposed inside the cylinder 31, and a vane 33 that partitions the interior of the cylinder 31. A shaft 40 has an eccentric part 42. A vane groove 36 in which to dispose the vane 33 is formed in the cylinder 31. The eccentric part 42 is disposed inside the cylinder 31, and the piston 32 fits into the eccentric part 42. A cylindrical groove 32a with an arc angle α exceeding 180° is formed in the piston 32. A cylinder part 33b to be disposed in the cylindrical groove 32a is formed at an end portion of the vane 33. The vane 33 operates without separating from the piston 32. The Vickers hardness at the surface of the piston 32 is set to Hv 400 or less, thereby facilitating the formation of the cylindrical groove 32a in the piston 32. The above thus provides a rotary compressor 1 with high wear resistance between the piston 32 and the vane 33, as well as equipment using the rotary compressor 1.

Description

Rotary compressors and equipment

[0001] The present invention relates to a rotary compressor in which vanes operate without separating from pistons, and to a device using this rotary compressor.

[0002] Patent Document 1 discloses a rotary compressor in which a cylindrical groove is formed in the piston and a cylindrical portion is formed at the end of the vane to be placed in the cylindrical groove, thereby enabling the vane to operate without separating from the piston. Furthermore, to improve sliding performance with the vane, the piston is subjected to a hardening treatment to increase the surface hardness by heat treatment or surface coating (Patent Document 2).

[0003] JP-A-3-185291 JP-A-7-145787

[0004] It is not easy to form arc-shaped grooves on the outer periphery of a hardened piston, such as the piston described in Patent Document 1. Hardened pistons can cause material structures to chip off from the piston surface during machining. This also shortens the life of tools used to machine the piston. Furthermore, the machining time for the piston becomes extremely long. In a typical rotary compressor, the vanes that slide in the vane grooves are treated with a high-hardness surface. When a vane with a high-hardness surface slides against a piston, the sliding portion of the piston wears out if the piston is not hardened.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a rotary compressor in which cylindrical grooves can be easily formed in the piston and in which the wear resistance between the piston and the vane is high, and a device using this rotary compressor.

[0006] A rotary compressor (1) of the present invention according to a first aspect includes an electric motor unit (20) and a compression mechanism unit (30) housed in a sealed container (10), the electric motor unit (20) and the compression mechanism unit (30) being connected by a shaft (40), the compression mechanism unit (30) having a cylinder (31), a piston (32) arranged in the cylinder (31), and a vane (33) dividing the interior of the cylinder (31), the shaft (40) having an eccentric portion (42), the cylinder (31) having a vane groove (36) in which the vane (33) is arranged, the eccentric portion (42) being arranged in the cylinder (31), the piston (32) being fitted into the eccentric portion (42), the piston (32) having a cylindrical groove (32a) with an arc angle α exceeding 180°, and an end of the vane (33) having a cylindrical portion (33b) arranged in the cylindrical groove (32a), The present invention according to claim 2 is characterized in that, in the rotary compressor 1 according to claim 1, the piston 32 is made of gray cast iron. The present invention according to claim 3 is characterized in that, in the rotary compressor 1 according to claim 1 or claim 2, a surface treatment is performed on the side surface of the vane 33, and the Vickers hardness of the side surface of the vane 33 exceeds Hv 1000. The present invention according to claim 4 is characterized in that, in the rotary compressor 1 according to claim 3, the surface treatment is a nitriding treatment or a DLC treatment. The device according to claim 5 is a device using the rotary compressor 1 according to claim 1 or claim 2, and is characterized in that the rotary compressor 1, the condenser 2, the pressure reducing device 3, and the evaporator 4 are connected in a circular shape by piping.

[0007] According to the present invention, the use of a low-hardness material for the piston makes it easy to form a cylindrical groove, and the surface support between the cylindrical portion and the cylindrical groove provides high wear resistance.

[0008] 1 is a cross-sectional view showing a rotary compressor according to an embodiment of the present invention; FIG. 2 is a view taken along the line A-A in FIG. 1; FIG. 3 is a view showing a piston and a vane used in the rotary compressor according to the embodiment; FIG. 4 is a view showing a manufacturing process for a vane used in the rotary compressor according to the embodiment;

[0009] In the rotary compressor according to the first embodiment of the present invention, the Vickers hardness of the surface of the piston is set to be equal to or less than Hv 400. According to this embodiment, the use of a low-hardness material for the piston makes it easy to form a cylindrical groove, and the surface bearing between the cylindrical portion and the cylindrical groove also provides high wear resistance.

[0010] In the second embodiment of the present invention, the pistons in the rotary compressor according to the first embodiment are made of gray cast iron. According to this embodiment, it is easy to form cylindrical grooves.

[0011] In a third embodiment of the present invention, in the rotary compressor according to the first or second embodiment, the side surfaces of the vanes are surface-treated so that the Vickers hardness of the side surfaces of the vanes exceeds Hv 1000. According to this embodiment, it is possible to provide the vane grooves with sufficient sliding resistance.

[0012] A fourth embodiment of the present invention is the rotary compressor according to the third embodiment, wherein the surface treatment is nitriding or DLC treatment. According to this embodiment, nitriding or DLC treatment is suitable for the hard coating treatment.

[0013] A device according to a fifth embodiment of the present invention is a device using the rotary compressor according to the first or second embodiment, in which the rotary compressor, a condenser, a pressure reducing device, and an evaporator are connected in a ring shape by piping. According to this embodiment, a highly reliable device can be provided.

[0014] FIG. 1 is a cross-sectional view showing a rotary compressor according to an embodiment of the present invention, and FIG. 2 is a view taken along line A-A in FIG. 1 . The rotary compressor 1 according to this embodiment includes an electric motor unit 20 and a compression mechanism unit 30 housed within a sealed container 10. The electric motor unit 20 and the compression mechanism unit 30 are connected by a shaft 40. The electric motor unit 20 is composed of a stator 21 fixed to the inner surface of the sealed container 10 and a rotor 22 that rotates within the stator 21. The compression mechanism unit 30 includes a cylinder 31, a piston 32 disposed within the cylinder 31, and vanes 33 (see FIG. 2 ) that divide the interior of the cylinder 31. An upper bearing 51 is disposed on one side of the cylinder 31, and a lower bearing 52 is disposed on the other side of the cylinder 31. The shaft 40 is composed of a main shaft portion 41 to which the rotor 22 is attached and supported by the upper bearing 51, an eccentric portion 42 to which the piston 32 is attached, and a counter shaft portion 43 supported by the lower bearing 52. The upper bearing 51 is fixed to the sealed container 10. The piston 32 is rotatably fitted to the eccentric portion 42 of the shaft 40 that passes through the cylinder 31. An upper cover 53 is provided above the upper bearing 51. A silencing chamber 54 is formed between the upper bearing 51 and the upper cover 53. High-pressure refrigerant gas compressed by the compression mechanism 30 is discharged into the silencing chamber 54. The high-pressure refrigerant gas discharged into the silencing chamber 54 is discharged into the sealed container 10.

[0015] An oil sump 11 is formed at the bottom of the sealed container 10. The oil sump 11 stores refrigerant oil. An in-shaft oil supply passage 46 is formed axially inside the shaft 40. A communication passage 47 is formed inside the eccentric portion 42 for supplying refrigerant oil to the sliding surface of the compression mechanism 30. The refrigerant oil in the oil sump 11 is introduced into the in-shaft oil supply passage 46 from the lower end of the shaft 40. A portion of the refrigerant oil introduced into the in-shaft oil supply passage 46 is supplied to the sliding surface of the compression mechanism 30 through the communication passage 47. A suction pipe 12 is connected to the side of the sealed container 10, and a discharge pipe 13 is connected to the top of the sealed container 10. The suction pipe 12 guides refrigerant to the compression mechanism 30. The discharge pipe 13 guides refrigerant compressed by the compression mechanism 30 and discharged into the sealed container 10 out of the sealed container 10. An accumulator 14 is provided upstream of the suction pipe 12.

[0016] In the rotary compressor 1 according to this embodiment, a condenser 2, a pressure reducing device 3, and an evaporator 4 are connected in a ring shape by piping. The condenser 2 condenses the refrigerant discharged from a discharge pipe 13. The pressure reducing device 3 reduces the pressure of the refrigerant condensed by the condenser 2. The evaporator 4 evaporates the refrigerant reduced in pressure by the pressure reducing device 3. The refrigerant evaporated by the evaporator 4 is returned to the accumulator 14. The accumulator 14 includes an outer cylinder 14a, a refrigerant suction pipe 14b, and a separator plate 14c. An outer cylinder inlet 14d is provided at the top of the outer cylinder 14a, through which refrigerant from the evaporator 4 is introduced. The refrigerant suction pipe 14b has a suction pipe inlet 14e inside the outer cylinder 14a. The separator plate 14c is disposed between the outer cylinder inlet 14d and the suction pipe inlet 14e. A liquid reservoir 14f is formed at the inner bottom of the outer cylinder 14a. Liquid refrigerant is stored in the liquid reservoir 14f. Liquid refrigerant can be stored up to a height H of the suction pipe inlet 14e. Therefore, the volume of the liquid reservoir 14f is up to the height H of the suction pipe inlet 14e. The specific driving method of the rotary compressor 1 is not particularly limited. For example, the rotary compressor 1 may be driven by simple on-off control, or may be inverter-driven at multiple operating frequencies. In inverter drive, in order to optimize the operational control of the rotary compressor 1, a low rotation range in which the rotation speed of the electric motor unit 20 decreases and a high rotation range in which the rotation speed of the electric motor unit 20 increases occur.

[0017] The compression chamber 34 shown in FIG. 2 is formed between the inner circumferential surface of the cylinder 31 and the outer circumferential surface of the piston 32, between the upper bearing 51 and the lower bearing 52. The suction pipe 12 is connected to the suction passage 35 of the compression mechanism 30. The suction passage 35 is connected to the compression chamber 34. Rotation of the shaft 40 causes the piston 32 to revolve. The vane 33 reciprocates in the vane groove 36 as the piston 32 revolves along the inner wall surface of the cylinder 31. The vane 33 divides the compression chamber 34 into an suction space 34a that communicates with the suction passage 35 and a compression space 34b that communicates with the discharge hole 37. The suction volume formed in the cylinder 31 is the volume of the suction space 34a when the suction passage 35 is blocked by the piston 32, and is the volume when the suction space 34a is at its maximum. The gas refrigerant is drawn into the compression chamber 34 through the suction pipe 12 and the suction passage 35 by the revolution of the piston 32, is compressed in the compression chamber 34, and then discharged from the discharge hole 37 into the silencing chamber 54. The refrigerant gas discharged into the silencing chamber 54 is discharged into the sealed container 10 and then discharged from the discharge pipe 13 to the outside of the sealed container 10. The high-pressure refrigerant gas discharged to the outside of the sealed container 10 passes through the condenser 2, the pressure reducing device 3, and the evaporator 4, becomes low-pressure refrigerant gas, and is returned to the compression mechanism 30 via the accumulator 14.

[0018] 3A and 3B are diagrams showing a piston and a vane used in the rotary compressor according to the embodiment, in which FIG. 3A is a perspective view of the piston and the vane separated from each other, FIG. 3B is a plan view of the piston and the vane separated from each other, and FIG. 3C is a perspective view of the vane seen from a different direction.

[0019] A cylindrical groove 32a with an arc angle α exceeding 180° is formed on the outer peripheral surface of the piston 32. The cylindrical groove 32a extends from one end face of the piston 32 to the other end face. The vane 33 has a vane side surface 33a that slides along the vane groove 36, a cylindrical portion 33b disposed in the cylindrical groove 32a, and a constricted portion 33c connecting the vane side surface 33a and the cylindrical portion 33b. The cylindrical portion 33b is formed at the end of the vane 33. By engaging the cylindrical portion 33b with the cylindrical groove 32a, the vane 33 operates without separating from the piston 32. The cylindrical portion 33b has a notch 33d formed in the cylindrical portion 33b that extends from one end face to the other end face. The notch 33d divides the arc surface 33e of the cylindrical portion 33b into multiple sections. In this manner, the outer peripheral surface of the cylindrical portion 33b is formed with at least two separated arcuate surfaces 33e by the cutout portions 33d. Each arcuate surface 33e has an arc angle β greater than 90° and less than 180°, and the cutout portions 33d have an arc angle γ less than 45°. Preferably, the arc angle β is greater than 110° and less than 150°. By setting the cutout portions 33d to an arc angle γ less than 45°, the contact area between the cylindrical groove 32a and the cylindrical portion 33b can be increased, thereby reliably preventing refrigerant leakage. In this embodiment, the cutout portions 33d are formed at the vane tip portions of the vanes 33. That is, the cutout portions 33d are formed at the tip of the cylindrical portion 33b. The vane tip is less likely to be subjected to load, and forming the notch 33d at the vane tip allows the suction-side arcuate surface 33e1 and the discharge-side arcuate surface 33e2 to be symmetrical. While the notch 33d is formed as a flat surface in this embodiment, the notch 33d may be curved or not formed as a single flat surface, as long as it is cut out so that the inner surface is closer to the arcuate outer circumferential surface of the cylindrical portion 33b. It is preferable to position the two arcuate surfaces 33e closest to the imaginary plane X of the vane side surface 33a. Having the point of the cylindrical portion 33b closest to the imaginary plane X of the vane side surface 33a on the arcuate surface 33e reliably prevents refrigerant leakage.

[0020] The Vickers hardness of the surface of the piston 32 is set to Hv 400 or less. Using a low-hardness material for the piston 32 itself makes it easy to form the cylindrical groove 32a, and the surface support between the cylindrical portion 33b and the cylindrical groove 32a provides high wear resistance. The Vickers hardness of the surface of the piston 32 is preferably in the range of Hv 80 to Hv 400, and more preferably in the range of Hv 180 to Hv 250. The piston 32 is preferably made of gray cast iron, which makes it easy to form the cylindrical groove 32a. The piston 32 can be made of a sintered material. If a sintered material is used for the piston 32, the Vickers hardness is preferably set to Hv 400 or less.

[0021] The vane side surface portion 33a, i.e., the side surface of the vane 33, is subjected to a surface treatment so that the side surface of the vane 33 has a Vickers hardness exceeding Hv 1000. This provides sufficient sliding resistance to the vane groove 36. Nitriding or DLC treatment is suitable for the surface treatment of the vane side surface portion 33a. By performing nitriding or DLC treatment, the vane side surface portion 33a can be hard-coated.

[0022] The surface hardness of at least a portion of the cylindrical portion 33b is lower than the surface hardness of the vane side surface 33a. Note that "at least a portion of the cylindrical portion 33b" refers to the arcuate surface 33e. The same applies to the following description. By making the surface hardness of at least a portion of the cylindrical portion 33b lower than the surface hardness of the vane side surface 33a, the cylindrical portion 33b is provided with sliding resistance against the vane groove 36, and by making the surface hardness of at least a portion of the cylindrical portion 33b lower than the surface hardness of the vane side surface 33a, the processability and toughness of the cylindrical portion 33b can be improved. It is preferable that the Vickers hardness of at least a portion of the cylindrical portion 33b be lower by at least Hv 200 than the Vickers hardness of the vane side surface 33a. That is, by performing a hard coating treatment on the vane side surface portion 33a, the Vickers hardness of the vane side surface portion 33a can be made at least 200 Hv higher than the Vickers hardness of at least a portion of the cylindrical portion 33b, thereby providing sufficient sliding resistance to the vane groove 36. The surface hardness of the constricted portion 33c is also made lower than that of the vane side surface portion 33a. By making the surface hardness of the constricted portion 33c lower than that of the vane side surface portion 33a, the workability and toughness of the constricted portion 33c can be improved. By making the surface hardness of the vane side surface portion 33a higher than that of the constricted portion 33c, sliding resistance to the vane groove 36 can be provided. The surface hardness of the constricted portion 33c is preferably made lower than that of the cylindrical portion 33b. By making the surface hardness of the constricted portion 33c lower than the surface hardness of the vane side surface portion 33a and the cylindrical portion 33b, the workability and toughness of the constricted portion 33c can be improved. Furthermore, the surface hardness of the arcuate surface 33e is preferably lower than the surface hardness of the cutout portion 33d. By making the surface hardness of the arcuate surface 33e lower than the surface hardness of the cutout portion 33d, the workability and toughness of the arcuate surface 33e can be improved.

[0023] FIG. 4 illustrates a manufacturing process for a vane used in a rotary compressor according to the embodiment. FIG. 4(a) shows the base material of the vane 33. The vane 33 is made of an iron alloy containing iron (Fe) as the main component and chromium (Cr), or a high-carbon steel material containing metals such as chromium (Cr), tungsten (W), vanadium (V), and molybdenum (Mo). Using a steel material without tungsten (W) or vanadium (V) for the vane 33 can reduce costs. Alternatively, stainless steel (e.g., SUS440C) can be used for the vane 33. FIG. 4(b) shows the base material of the vane 33 shown in FIG. 4(a) after a hard coating treatment. As shown in FIG. 4(c), the hard-coated base material of the vane 33 is fixed to a jig Y, and a cutting tool Z is used to machine a cylindrical portion 33b and a constricted portion 33c. As shown in Figure 4(c), forming a cylindrical portion 33b with an arc angle α exceeding 180° requires finishing in two or more steps, which reduces the machining accuracy of the connecting surface M of the machined surface. However, by dividing the arc surface 33e of the cylindrical portion 33b into multiple parts using the cutout portion 33d and setting each arc surface 33e to an arc angle β of less than 180°, the machining accuracy of the arc surface 33e of the cylindrical portion 33b can be improved. In particular, by forming the cutout portion 33d at the connecting surface M, i.e., the tip of the cylindrical portion 33b, it is possible to perform the machining in just two finishing steps: finishing the suction-side arc surface 33e1 and finishing the discharge-side arc surface 33e2.

[0024] The working fluid described as a refrigerant in this embodiment and the refrigerating machine oil are in a two-phase separation state at a temperature of 25°C. Thus, by using a refrigerating machine oil that has low compatibility with the working fluid, particularly in the low rotational speed range of the rotary compressor 1, lubrication performance can be ensured and a good sliding condition can be maintained even when liquid compression operation is unavoidable. Here, the low rotational speed range refers to a rotational speed range of 900 rpm or less, particularly 600 rpm or less, and even 360 rpm or less. Liquid compression is likely to occur in the low rotational speed range. By ensuring lubrication performance in the low rotational speed range where liquid compression is likely to occur, operation in the low rotational speed range, i.e., low-capacity operation, can be performed stably. Furthermore, at temperatures between 0°C and 25°C, a mixture in which the working fluid is dissolved to the maximum extent in the refrigerating machine oil has a working fluid ratio of 1 wt% or more but less than 30 wt%. Thus, by using a refrigerating machine oil that has low compatibility with the working fluid, particularly in the low rotational speed range, lubrication performance can be ensured and a good sliding condition can be maintained even when liquid compression operation is unavoidable.

[0025] Although the present embodiment has been described with the accumulator 14 provided upstream of the suction pipe 12, the accumulator 14 can be omitted. That is, by using a refrigerating machine oil with low compatibility with the working fluid, the lubricating performance of the refrigerating machine oil can be ensured and a good sliding condition can be maintained even when liquid compression operation is unavoidable, so the accumulator 14 is not necessary. Furthermore, the volume of the liquid reservoir 14f of the accumulator 14 can be set to less than twice the suction volume formed in the cylinder 31. That is, by using a refrigerating machine oil with low compatibility with the working fluid, the lubricating performance can be ensured and a good sliding condition can be maintained even when liquid compression operation is unavoidable, so the accumulator 14 can be made smaller. Furthermore, in this embodiment, the compression mechanism 30 is described with one cylinder 31 and one piston 32, but the compression mechanism 30 may be with two cylinders 31 and two pistons 32. Because such a two-piston rotary compressor is suitable for low-speed operation, it is preferable that the vanes 33 operate without separating from each piston 32. Furthermore, an example of an apparatus using the rotary compressor 1 suitable for low-speed operation is an air conditioner, particularly a room air conditioner (household air conditioner). As described in this embodiment, the compression mechanism 30 in which the vanes 33 operate without separating from the pistons 32 can realize a highly efficient rotary compressor.

[0026] In particular, by using R32 as the working fluid and alkylbenzene oil as the refrigerating machine oil, compatibility is low, lubrication performance can be ensured, and a good sliding state can be maintained. The same applies to working fluids containing at least R32. Furthermore, by using carbon dioxide as the working fluid and polyalkylene glycol oil as the refrigerating machine oil, compatibility is low, lubrication performance can be ensured, and a good sliding state can be maintained. The same applies to working fluids containing at least carbon dioxide. Furthermore, by using R290 as the working fluid and polyalkylene glycol oil as the refrigerating machine oil, compatibility is low, lubrication performance can be ensured, and a good sliding state can be maintained. The same applies to working fluids containing at least R290. Note that the kinetic viscosity of the refrigerating machine oil is preferably 35 mm / s or less; however, when the working fluid contains, for example, carbon dioxide or R290, the refrigerating machine oil may have a kinetic viscosity exceeding 35 mm / s. In addition, in a rotary compressor in which the vane 33 operates without separating from the piston 32, R1234yf, HFO1123, a working fluid containing R1234yf, or a working fluid containing HFO1123 can be used, and in terms of lubrication performance, for working fluids containing R1234yf or R1234yf, it is preferable to use alkylbenzene oil as the refrigerating machine oil, and for working fluids containing HFO1123 or HFO1123, it is preferable to use ester oil or ether oil as the refrigerating machine oil.

[0027] The equipment according to this embodiment, in which the rotary compressor 1, the condenser 2, the pressure reducing device 3, and the evaporator 4 are connected in a ring shape by piping, is highly reliable.

[0028] An apparatus using the rotary compressor of the present invention is useful as a refrigeration cycle apparatus such as a hot water heating apparatus, an air conditioner, a water heater, a refrigerator, a showcase, a chiller, a dehumidifier, or a refrigerator.

[0029] REFERENCE SIGNS LIST 1 rotary compressor 2 condenser 3 pressure reducing device 4 evaporator 10 sealed container 11 oil reservoir 12 suction pipe 13 discharge pipe 14 accumulator 14a outer cylinder 14b refrigerant suction pipe 14c separation plate 14d outer cylinder inlet 14e suction pipe inlet 14f liquid reservoir 20 motor section 21 stator 22 rotor 30 compression mechanism section 31 cylinder 32 piston 32a cylindrical groove 33 vane 33a vane side section 33b cylindrical section 33c constricted section 33d notch section 33e circular arc surface 33e1 suction side circular arc surface 33e2 discharge side circular arc surface 34 compression chamber 34a suction space 34b compression space 35 suction passage 36 Vane groove 37 Discharge hole 40 Shaft 41 Main shaft portion 42 Eccentric portion 43 Sub-shaft portion 46 Oil supply passage in shaft 47 Communication passage 51 Upper bearing 52 Lower bearing 53 Upper cover 54 Silencer chamber H Height M Joint surface X Extended virtual surface Y Jig Z Cutting tool α, β, γ Arc angles

Claims

1. A rotary compressor comprising an electric motor unit and a compression mechanism unit housed within a sealed container, the electric motor unit and the compression mechanism unit being connected by a shaft, the compression mechanism unit having a cylinder, a piston disposed within the cylinder, and a vane that divides the interior of the cylinder, the shaft having an eccentric part, the cylinder forming a vane groove in which the vane is disposed, the eccentric part being disposed within the cylinder, the piston being fitted to the eccentric part, the piston forming a cylindrical groove with an arc angle exceeding 180°, and an end of the vane forming a cylindrical part that is disposed in the cylindrical groove, the vane operating without separating from the piston, and the piston having a Vickers hardness of Hv400 or less on its surface.

2. The rotary compressor according to claim 1, characterized in that the piston is made of gray cast iron.

3. A rotary compressor according to claim 1 or 2, characterized in that the side surfaces of the vanes are surface-treated, and the Vickers hardness of the side surfaces of the vanes exceeds Hv1000.

4. The rotary compressor according to claim 3, wherein the surface treatment is a nitriding treatment or a DLC treatment.

5. Equipment using the rotary compressor according to claim 1 or 2, characterized in that the rotary compressor, condenser, pressure reducing device, and evaporator are connected in a ring shape by piping.

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