Refrigerant compressor

Abstract

The invention provides a refrigerant compressor, which is environment-friendly and improves the reliability of a sliding surface formed by a combination of a metal bearing and a rotating shaft. This refrigerant compressor (1) is used in a refrigeration cycle, stores a refrigerating oil as a lubricating oil in a sealed container (700), and compresses at least a refrigerant, and is provided with: a compression mechanism unit (720) that compresses the refrigerant; and a rotating shaft (300) for driving the compression mechanism part (720), the rotating shaft (300) is provided with a sliding bearing (10) on at least one of an engagement part between the rotating shaft (300) and the compression mechanism part (720) and a rotation support part of the rotating shaft (300), and the surface energy of a sliding surface between the rotating shaft (300) and a target material and the surface energy of a sliding surface between the rotating shaft (300) and the sliding bearing (10) and the target material are both 500 mN / m or more and 1000 mN / m or less. A recess (130) capable of holding the refrigerator oil is formed in the sliding surface of at least one of the rotating shaft (300) and the sliding bearing (10).

Description

Technical Field

[0001] The invention relates to a refrigerant compressor. Background Art

[0002] In current air conditioning equipment and refrigeration equipment, from the perspective of preventing global warming, it is required to switch to low global warming coefficient refrigerants (low GWP (Global Warming Potential) refrigerants). As low GWP refrigerants, there are natural refrigerants such as propane (R290) and CO2, and HFO refrigerants with double bonds in the chemical structure. These low GWP refrigerants are low in polarity like the existing HFC refrigerants, so refrigeration oil is easy to dissolve and it is difficult to form an oil film on the sliding surface. Therefore, maintaining the reliability of the sliding surface becomes a problem.

[0003] The properties required for the sliding surface of a refrigerant compressor include a low friction coefficient in addition to wear resistance and seizure resistance. PTFE (polytetra fluoroethylene) is one of the resins that meets these properties. It is very cheap and is therefore widely used in the sliding surface of a refrigerant compressor, such as a sliding bearing.

[0004] However, recently, the regulation of PFAS (Per- and Poly FluoroAlkyl Substances; perfluoroalkyl compounds and polyfluoroalkyl compounds) has been studied in consideration of the environment. PTFE is listed as one of the substances to be regulated.

[0005] Various technologies have been studied to cope with such a situation. For example, in a refrigerant compressor using a sliding bearing, in order to improve the wear resistance and seizure resistance of the sliding surface, the sliding bearing is composed of a sliding surface formed by mixing a solid lubricant such as molybdenum disulfide and graphite with a resin.

[0006] In addition, for example, Patent Document 1 describes a sliding bearing device, which includes a bearing; a shaft supported by the bearing while sliding; and a gas supply unit that supplies dry gas to a bearing sliding surface where the bearing and the shaft slide. In this sliding bearing device, at least the sliding surface of the bearing is composed of a resin composite material in which a carbon material is mixed with a resin. In addition, the shaft is made of metal and has a groove extending in a direction different from the sliding direction on the sliding surface. In addition, Patent Document 1 describes that as the resin, for example, polyamide, polyphthalamide, polyamideimide, polyacetal, polyphenylene sulfide, polyetherimide, ultra-high molecular weight polyethylene, polyetheretherketone, etc. can be used.

[0007] In addition, for example, Patent Document 2 describes a sintered oil-impregnated bearing having a cylindrical inner peripheral surface supporting a rotating shaft. The sintered oil-impregnated bearing has a plurality of convex portions and concave portions formed on the inner peripheral surface in a circumferentially arranged state. In addition, the porosity of the surface of the convex portion, i.e., the bearing surface, is lower than the porosity of the concave portion and is 10% at most.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: International Publication No. 2011 / 070621

[0011] Patent Document 2: Japanese Patent Application Publication No. 2020-060284 Summary of the invention

[0012] Problems to be solved by the invention

[0013] In the sliding surface through the lubricating oil, the wettability of the oil is related to the reduction of the friction coefficient. Regarding wettability, the larger the surface free energy (hereinafter, sometimes described as "surface energy" in this specification) on the solid side compared to the surface tension on the liquid side (the surface tension of the lubricating oil in the refrigerant compressor), the easier it is to wet. In addition, the effect becomes greater by increasing the surface area of ​​the sliding surface.

[0014] On the other hand, in a refrigerant compressor in actual operation, there is a situation where liquid refrigerant flows into the compressor from the circulation side. In such a case, the viscosity of the liquid is reduced, and the thickness of the oil film cannot be ensured, which easily leads to mixed lubrication in which solid surface contact occurs on the sliding surface in the compressor composed of the sliding bearing and the rotating shaft.

[0015] A rotary shaft having fine grooves formed by a collection of multiple grooves extending in a direction different from the sliding direction as disclosed in Patent Document 1 requires an additional process during machining, which may significantly reduce the effect of heat treatment applied to the sliding surface of the rotary shaft.

[0016] In addition, in Patent Document 2, a sliding bearing made of a sintered metal material without using resin and a rotating shaft are combined. In this case, oil is contained in the pores formed by the sintered material to avoid oil cutoff (oil film rupture). However, in a lubrication environment mixed with a liquid refrigerant, there is a problem of mixed lubrication and boundary lubrication in which metal contact between the sintered metal bearing and the rotating shaft is likely to occur.

[0017] Furthermore, as mentioned above, recently, environmental protection requirements are imposed on refrigerant compressors.

[0018] The present invention has been made in view of the above-mentioned situation. An object of the present invention is to provide a refrigerant compressor which is environmentally friendly and has improved reliability of a sliding surface composed of a combination of a metal bearing and a rotating shaft.

[0019] Solutions to Solve Problems

[0020] The refrigerant compressor of the present invention that solves the above-mentioned problem is a refrigerant compressor used in a refrigeration cycle and storing refrigeration oil as lubricating oil in a closed container and compressing at least a refrigerant, comprising: a compression mechanism portion that compresses the refrigerant; and a rotating shaft that drives the compression mechanism portion, at least one of the engaging portion between the rotating shaft and the compression mechanism portion and the rotating support portion of the rotating shaft comprises a sliding bearing, the surface energy of the sliding surface between the rotating shaft and the sliding bearing and the counterpart material is both greater than 500mN / m and less than 1000mN / m, and a recessed portion capable of retaining the refrigeration oil is formed on the sliding surface of at least one of the rotating shaft and the sliding bearing.

[0021] Effects of the Invention

[0022] The refrigerant compressor of the present invention can improve the reliability of the sliding surface composed of the combination of the metal bearing and the rotating shaft while being environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a longitudinal sectional view showing a refrigerant compressor 1 according to an embodiment of the present invention.

[0024] Figure 2 These are explanatory diagrams showing a case where a hole portion 131 is provided as an example of the recessed portion 130 . The left figure is a perspective view seen from the side, and the right figure is a plan view.

[0025] Figure 3 These are explanatory diagrams showing a case where a groove portion 132 is provided as another example of the recessed portion 130 . The left figure is a perspective view seen from the side, and the right figure is a plan view.

[0026] Figure 4 It is a graph of a Stribeck curve showing the relationship between the Sommerfeld number and the friction coefficient in Examples and Comparative Examples.

[0027] Figure 5 It is a plan view showing a state where a hole portion 131 and a groove portion 132 are used together as an example of the recessed portion 130 .

[0028] Figure 6 It is a plan view showing a case where a hole portion 131 and a groove portion 132 are used together as another example of the recessed portion 130 .

[0029] Figure 7It is a plan view showing a case where a hole portion 131 and a groove portion 132 are used together as another example of the recessed portion 130 .

[0030] Figure 8 It is a plan view showing an example of the arrangement form of the recessed portion 130 .

[0031] Fig. 9 It is a plan view showing another example of the arrangement of the recessed portion 130 .

[0032] Explanation of symbols

[0033] 1—refrigerant compressor, 10—sliding bearing, 100—fixed scroll, 101—bottom plate, 102—wrap plate, 103—intake port, 104—discharge port, 130—recess, 131—hole, 132—groove, 200—orbiting scroll, 201—bottom plate, 202—wrap plate, 203—boss, 210—orbiting bearing (sliding bearing), 220—oil supply path, 300—rotating shaft, 301—crank pin, 310—pump joint, 311—oil Passage, 400—upper frame, 401—main bearing (sliding bearing), 402—sealing part, 408—drain pipe, 500—crosshead coupling, 600—motor, 700—sealed container, 701—discharge pipe, 710—discharge chamber, 711—suction pipe, 720—compression mechanism part, 800—lower frame, 801—auxiliary bearing, 802—bearing housing, 900—pump part, A—portion of sliding surface with high surface pressure, B—portion with particularly high surface pressure. DETAILED DESCRIPTION

[0034] Hereinafter, a refrigerant compressor according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings as appropriate. Figure 1 It is a longitudinal sectional view showing a refrigerant compressor 1 according to an embodiment of the present invention. Figure 1 The present invention is shown as an example of being applied to a scroll compressor as a refrigerant compressor 1. That is, the refrigerant compressor 1 is used in a refrigeration cycle, and refrigeration oil serving as lubricating oil is stored in a sealed container 700, and at least a refrigerant is compressed.

[0035] [Refrigerator compressor 1]

[0036] like Figure 1 As shown, the refrigerant compressor 1 includes a sealed container 700. In the sealed container 700, a compression mechanism 720 is disposed at the top, a motor 600 is disposed at the center, and an oil reservoir 730 is disposed at the bottom. In the sealed container 700, the compression mechanism 720 and the motor 600 are connected via a rotating shaft 300 made of an iron material. That is, the rotating shaft 300 drives the compression mechanism 720.

[0037] The compression mechanism 720 includes a fixed scroll 100 having a spiral wrap 102 standing on a bottom plate 101 and an orbiting scroll 200 having a spiral wrap 202 standing on a bottom plate 201, and the wraps 102 and 202 are meshed with each other. The compression mechanism 720 can at least compress (gas) refrigerant according to its structure.

[0038] The fixed scroll 100 is further provided with a suction port 103 and a discharge port 104 .

[0039] The rotating shaft 300 is supported by a main bearing 401 of an upper frame 400 provided above the motor 600 and a sub-bearing 801 of a lower frame 800 provided below the motor 600. The main bearing 401 corresponds to an engaging portion between the rotating shaft 300 and the compression mechanism 720.

[0040] The upper frame 400 and the lower frame 800 are fixed to the sealed container 700 .

[0041] A crank pin (eccentric shaft) 301 made of an iron material is provided at the front end of the rotating shaft 300. The crank pin 301 is inserted into and engaged with a boss portion 203 protrudingly provided below the bottom plate 201 of the orbiting scroll 200.

[0042] A slewing bearing 210 is provided in the boss portion 203 so as to slide with the crank pin 301. The boss portion 203 is equivalent to a rotation support portion of the rotating shaft 300. In addition, in this embodiment, the main bearing 401 and the slewing bearing 210 are equivalent to the sliding bearing 10. In this embodiment, Figure 1 As shown, it is preferable to provide at least one of the main bearing 401 and the orbiting bearing 210 as the sliding bearing 10. In addition, in the present embodiment, the sliding bearing 10 may be arranged in the auxiliary bearing 801.

[0043] Furthermore, an Oldham coupling 500 is disposed on the back surface of the bottom plate 201 of the orbiting scroll 200. The Oldham coupling 500 allows the orbiting scroll 200 to orbit relative to the fixed scroll 100 without rotating.

[0044] When the rotating shaft 300 connected to the rotor is rotated by the motor 600, the crank pin 301 provided at the front end of the rotating shaft 300 rotates eccentrically by the rotation. The orbiting scroll 200 performs an orbiting motion relative to the fixed scroll 100 without rotating by utilizing the self-rotation prevention mechanism of the crosshead coupling 500. Thus, the gaseous refrigerant is sucked into the closed chamber formed by the spiral wrap 102 and the wrap 202 via the suction pipe 711 and the suction port 103. The gaseous refrigerant moves toward the center side together with the above-mentioned closed chamber and the above-mentioned gyratory motion, and its volume is compressed. The compressed gaseous refrigerant is discharged from the discharge port 104 to the discharge chamber 710. The gaseous refrigerant discharged to the discharge chamber 710 circulates around the compression mechanism 720 and the motor 600, and is then discharged from the discharge pipe 701 to the outside of the refrigerant compressor 1.

[0045] Next, the oil supply path is described. A bearing housing 802 that accommodates the auxiliary bearing 801 is installed on the lower frame 800, and a pump unit 900 is provided at the lower end of the bearing housing 802. The pump unit 900 is driven via a pump joint 310 installed on the lower end of the rotating shaft 300. When the rotating shaft 300 rotates, the refrigeration oil in the oil reservoir 730 is sucked up by the pump unit 900, and reaches the upper part of the crank pin 301 from the pump unit 900 through the oil passage 311 formed in the rotating shaft 300. After lubricating the swivel bearing 210 from the upper part of the crank pin 301, the refrigeration oil flows to the main bearing 401. The refrigeration oil that has lubricated the main bearing 401 returns to the oil reservoir 730 through the oil drain pipe 408.

[0046] In addition, a part of the refrigeration oil after lubricating the orbiting bearing 210 flows into the back side of the bottom plate 201 of the orbiting scroll 200 through the sealing portion 402 provided between the lower surface of the boss portion 203 of the orbiting scroll 200 and the upper frame 400. The refrigeration oil flowing into the back side of the bottom plate 201 passes from here through the oil supply path 220 formed in the bottom plate 201 of the orbiting scroll 200, lubricates the sliding portion between the fixed scroll 100 and the orbiting scroll 200 and between the wraps 102 and 202, and is discharged to the discharge chamber 710 together with the compressed gaseous refrigerant. The refrigeration oil discharged to the discharge chamber 710 is then returned to the oil reservoir 730 at the lower part of the sealed container 700.

[0047] In the present embodiment, in the refrigerant compressor 1 having the above-described structure, the above-mentioned rotating shaft 300 and the sliding bearing 10 are as follows.

[0048] First, in the present embodiment, the surface energy of the sliding surfaces of the rotating shaft 300 and the sliding bearing 10 with respect to the counterpart material is 500 mN / m or more and 1000 mN / m or less.

[0049] Thus, the surface energy of the sliding surface is greater than the surface tension of the refrigerating machine oil, so the wettability is improved. In addition, from the viewpoint of further improving the wettability of the refrigerating machine oil, the surface energy is preferably 600 mN / m or more and 1000 mN / m or less, more preferably 700 mN / m or more and 1000 mN / m or less, further preferably 800 mN / m or more and 1000 mN / m or less, and still further preferably 900 mN / m or more and 1000 mN / m or less.

[0050] Furthermore, if the surface energy of the sliding surface with the counterpart material is less than 500 mN / m, wettability may be insufficient, and thus oil film breakage may occur.

[0051] On the other hand, if the surface energy of the sliding surface with the counterpart material exceeds 1000 mN / m, the material becomes the same as that of the rotating shaft made of an iron system, and there is a problem of causing adhesion wear.

[0052] The sliding surface having the above surface energy can satisfy the above conditions as long as it is formed of metal, ceramic, carbon, diamond-like carbon, etc. In other words, a material satisfying the above conditions can be appropriately selected and used from materials formed of these materials.

[0053] The surface energy of the sliding surface can be measured, for example, according to JIS R3257: 1999 (Wettability test method for substrate glass surface). The measurement is preferably carried out at 25°C ± 5°C and humidity 50 ± 10% as described in JIS. In addition, the test is preferably performed by dropping a drop of pure water on a solid sample with a flat surface and measuring the contact angle of the pure water. In addition, the contact angle can be measured using a liquid different from water, such as glycerin, to calculate the interfacial energy. The test can measure 5 points on 1 sample and calculate the average value.

[0054] In addition, in the present embodiment, a recessed portion 130 (see FIG. 1 ) capable of retaining the refrigerating machine oil is formed on the sliding surface of at least one of the rotating shaft 300 and the sliding bearing 10. Figure 2 ).

[0055] In the present embodiment, since the recessed portion 130 is formed, an oil film is easily formed and the sliding property is less likely to be impaired.

[0056] That is, the refrigerant compressor 1 of the present embodiment improves the wettability of the refrigeration oil by using the rotating shaft 300 and the sliding bearing 10 whose sliding surfaces have the above-mentioned surface energy, and further improves the durability of the oil in the above-mentioned recessed portion 130 .

[0057] Here, Figure 2 These are explanatory diagrams showing a case where a hole portion 131 is provided as an example of the recessed portion 130 . The left figure is a perspective view seen from the side, and the right figure is a plan view. Figure 3These are explanatory diagrams showing a case where a groove portion 132 is provided as another example of the recessed portion 130 . The left figure is a perspective view seen from the side, and the right figure is a plan view.

[0058] In the present embodiment, the recess 130 is preferably at least one of the hole 131 and the groove 132 having a depth of 0.005 mm or less. In this way, the mechanical strength of the rotating shaft 300 and the sliding bearing 10 is not easily reduced. From the viewpoint of not reducing the mechanical strength, the depth of the recess 130 and the groove 132 is more preferably 0.004 mm or less, and further preferably 0.003 mm or less.

[0059] The recess 130 is, for example, 0.3 mm wide and is provided in a plurality in a row at a pitch of 3.5 mm. In addition, multiple rows can be provided at a pitch of 3.5 mm for adjacent rows, but the present invention is not limited thereto. The recess 130 can be formed at positions in one row that are consistent with those in other rows, or can be staggered ( Figure 2 The staggered manner is shown in the figure). In addition, the pitch in the present embodiment refers to the length of two corresponding points of mutually adjacent recesses 130 (holes 131) and mutually adjacent rows of recesses 130 (rows of holes 131, grooves 132) measured parallel to the axis in a cross section of the axis including the center of the recess 130.

[0060] In addition, in the present embodiment, the surface area S1 of the sliding surface formed with the recessed portion 130 is preferably 1.04 times or more of the surface area S0 of the sliding surface when the recessed portion 130 is not formed. In other words, the formation density of the recessed portion 130 having a predetermined area is preferably set so that the surface area S1 is 1.04 times or more relative to the surface area S0. In this way, the surface area is increased by the recessed portion 130, and the refrigerating machine oil can be reliably retained according to the increased surface area. Therefore, compared with the case where the recessed portion 130 is not formed, the durability of the refrigerating machine oil is improved, and the oil film on the sliding surface is less likely to break. From the viewpoint of less likely to break the oil film, the surface area S1 is more preferably 1.05 times or more relative to the surface area S0, more preferably 1.06 times or more, and more preferably 1.07 times or more. In addition, in addition to the above lower limit relative to the surface area S0, the surface area S1 is preferably 1.1 times or less relative to the surface area S0, more preferably 1.09 times or less, and more preferably 1.08 times or less. In this way, it is possible to suppress an excessive increase in the difficulty of processing or an increase in processing cost.

[0061] The dissolution of refrigerant and refrigeration oil has the following characteristics: substances with similar polarity are easy to dissolve in each other, while substances with different polarity are difficult to dissolve.

[0062] For example, according to document 1 (Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers, 37(1), p.73-80, 2020) and surface tension data calculated by refrigerant manufacturers, when comparing the surface tension under pressure conditions of 1.4 PaG, the HFC refrigerant, i.e., R32, is 7.9 mN / m, while R1234yf is 3.04 mN / m, R1234ze(Z) is 4.37 mN / m, R1270 is 6.02 mN / m, and R290 is a low value of 5.09 mN / m.

[0063] In the refrigerant compressor 1 of the present embodiment, the refrigerant can use at least one of R1234yf, R1234ze, R290 and R1270, or at least one of them can be mixed with other refrigerants. That is, these refrigerants can be selected from several of these refrigerants for mixing. In addition, the refrigerant can also be a substance obtained by further mixing one or several of them with other refrigerants. In addition, when other refrigerants are mixed, the polarity of the mixed refrigerant is made lower than that of the refrigeration oil.

[0064] In addition, the refrigerating machine oil preferably has a surface tension of 10 mN / m or more. This makes it easy to form an oil film and ensures the thickness of the oil film.

[0065] However, the surface tension of the refrigeration oil is preferably smaller than the surface free energy of the sliding surface of the rotating shaft 300, the sliding bearing 10, etc. In this way, the wettability of the sliding surface of the rotating shaft 300, the sliding bearing 10, etc. can be reliably improved. Therefore, the oil film on the sliding surface of the rotating shaft 300, the sliding bearing 10, etc. is less likely to break.

[0066] In addition, the surface tension of refrigerating machine oil can be measured according to JISK2241, for example.

[0067] In the refrigerant compressor 1 using the rotating shaft 300 and the sliding bearing 10 whose surface energy of the sliding surface with the counterpart material is 500 mN / m or more and 1000 mN / m or less, the refrigerant having a low surface tension (10 mN / m or less) has low compatibility with the refrigeration oil having a surface tension higher than that of the refrigerant. Therefore, it is difficult for the refrigeration oil to return to the refrigerant compressor 1, and the oil film may be broken.

[0068] However, if the refrigerant and the refrigeration oil are respectively set as described above, in this embodiment, the recessed portion 130 is formed on the sliding surface of the rotating shaft 300 and the sliding bearing 10, so that an oil film can be easily formed on the sliding surface of the rotating shaft 300 and the sliding bearing 10. Therefore, the oil film is less likely to break.

[0069] As the refrigerating machine oil that can be used in the present embodiment, there are exemplified those satisfying a molecular weight of 500 or more and a density of 0.9 g / cm 3 The above conditions and the refrigeration oil having a hydroxyl group at the end of the chemical structure. If the refrigeration oil has these characteristics, the polarity becomes higher, so the solubility of the refrigerant relative to the refrigeration oil is reduced. Therefore, the reduction in oil viscosity during operation can be suppressed. In addition, the polarity of the refrigeration oil also acts on the sliding property of the sliding surface. If the sliding surface of the rotating shaft 300 and the sliding bearing 10 (that is, the main bearing 401 and the slewing bearing 210) has a surface energy higher than the surface tension of the refrigeration oil, the wettability of the sliding surface with the refrigeration oil is improved. In addition, by providing a recess 130 on any one of the sliding surfaces, the effect is improved. Therefore, it is not easy for the oil film to rupture on the sliding surface of the rotating shaft 300 and the sliding bearing 10, and the reliability of the sliding surface of the refrigerant compressor 1 is further improved.

[0070] The refrigerating machine oil preferably has at least one of an ester bond and an ether bond in the chemical structure. This can more reliably reduce the solubility of the refrigerant in the refrigerating machine oil.

[0071] As the refrigeration oil that can be used in this embodiment, specifically, ether-based refrigeration oil, polyalkylene glycol oil, polyethylene glycol oil, polyol ester oil, etc. can be cited. In addition, if it is polyalkylene glycol oil, polypropylene glycol oil with an ethanol group at the end can be used. In addition, if it is polyethylene glycol oil, it is a polymer of ethylene oxide and a polyol, and H[OCH(CH3)CH2] can be used. n PEG400 represented by OH, etc. In addition, in the case of a polyol ester oil, a hindered polyol ester oil, such as a mixed fatty acid ester oil of dipentaerythritol-based valeric acid and 2-methylbutyric acid, etc. can be used.

[0072] In the present embodiment, only the above-mentioned refrigerating machine oil can be used, but the above-mentioned refrigerating machine oil can also be mixed with other refrigerating machine oils for use. Examples of other refrigerating machine oils include mineral oils.

[0073] In this embodiment, the molecular weight of the refrigerating machine oil is preferably 600 or more, more preferably 750 or more, and further preferably 1000 or more. In addition, the molecular weight of the refrigerating machine oil is preferably 2000 or less, more preferably 1800 or less, further preferably 1750 or less, and further preferably 1500 or less. When the molecular weight of the refrigerating machine oil is within such a preferred range, the properties (solubility) of the refrigerating machine oil become more preferred, and the reliability of the sliding surface of the refrigerant compressor 1 can be further maintained.

[0074] In this embodiment, the density of the refrigeration oil is preferably 1.0 g / cm 3 In addition, the density of the refrigeration oil is preferably 1.2 g / cm 3 Below, more preferably 1.1 g / cm 3 When the density of the refrigerating machine oil is within such a preferred range, the properties (solubility) of the refrigerating machine oil become more preferable, and the reliability of the sliding surface of the refrigerant compressor 1 can be further maintained.

[0075] The molecular weight of the refrigerating machine oil is preferably 500 or more under the conditions of 1.4 MPa and 60° C. as described above. The density of the refrigerating machine oil is preferably 0.9 g / cm 3 As described above, the properties (solubility) of the refrigeration oil are further preferred, and the reliability of the sliding surface of the refrigerant compressor 1 can be further maintained.

[0076] The molecular weight of the refrigerating machine oil can be measured, for example, by a boiling point rise method or a freezing point depression method. In addition, the molecular weight of the refrigerating machine oil can be measured, for example, by using a gas chromatography method in accordance with JISK0114.

[0077] The density of the refrigerating machine oil can be measured in accordance with JISK2249, for example.

[0078] In the present embodiment, the ten-point average roughness (Rz) of the surface of the portion where the recessed portion 130 is not formed, that is, the surface of the flat portion, of the sliding surface of the rotating shaft 300 and the sliding bearing 10 is JIS ) is preferably 0.8 μm or less. In this way, the surface is smooth, so the sintering property can be improved, and the refrigeration oil can be retained, so the overall lubricity is improved. From the viewpoint of further improving these, the surface Rz of the portion of the sliding surface where the recess 130 is not formed is JIS More preferably, it is 0.5 μm or less.

[0079] [Formation of concave portion 130]

[0080] The recessed portion 130 in the present embodiment can be suitably formed by forming the recessed portion 130 on the sliding surface and then performing mirror finishing, but the present invention is not limited thereto.

[0081] In this embodiment, the sliding surface may be mirror-finished first and then the recessed portion 130 may be formed. When the recessed portion 130 is formed after mirror-finishing, if burrs or the like are generated, a finishing process (mirror-finishing again) may be performed to remove the burrs or the like as needed.

[0082] The recessed portion 130 can be formed by, for example, etching, laser processing, machining, or the like.

[0083] Furthermore, when forming the recessed portion 130 , mirror finishing is not necessarily required.

[0084] [Example]

[0085] (Stribeck curve)

[0086] Figure 4 Graphs of Stribeck curves showing the relationship between the Sommerfeld number and the friction coefficient for the embodiment and the comparative example. In the figure, the horizontal axis represents the Sommerfeld number and the vertical axis represents the friction coefficient. In addition, the embodiment is an example in which a rotating shaft 300 made of an iron-based material having the above-mentioned recessed portion 130 on the sliding surface and a sliding bearing 10 whose sliding surface is made of a sintered metal material are combined. The comparative example is an example in which a rotating shaft 300 made of an iron-based material having no above-mentioned recessed portion 130 on the sliding surface and a sliding bearing 10 whose sliding portion is made of a sintered metal material are combined. That is, the comparative example is a structure in which the recessed portion 130 is not provided on the rotating shaft 300 and the sliding bearing 10.

[0087] In this test for obtaining the Stribeck curve, the rotating shaft 300 having the recess 130 was formed as a hole 131 having a width of 0.3 mm and a depth of 0.005 mm, and a plurality of holes 131 were arranged in a row at a pitch of 3.5 mm, and a plurality of rows were arranged at a pitch of 3.5 mm for adjacent rows. The surface area S1 of the sliding surface having the recess 130 formed was 1.04 times or more the surface area S0 of the sliding surface when the recess 130 was not formed.

[0088] In addition, in this test, HFC refrigerant was used as the refrigerant, and ether-based refrigeration oil was used as the refrigeration oil. In addition, in this test, in these atmospheres (viscosity η: 0.5 to 2 mPa·s), the test load was changed to 500 to 7000 N at a rotation speed of 30 rps, and the Stribeck curve was obtained.

[0089] Generally, if the load increases, the surface pressure increases and the Sommerfeld number decreases. If the Sommerfeld number decreases, metal contact becomes easier and the friction coefficient increases. That is, the smaller the Sommerfeld number, the stricter the operating conditions.

[0090] On the other hand, the smaller the friction coefficient is, the higher the friction characteristics are.

[0091] That is, in Figure 4 In the graph shown, although the driving conditions become more severe toward the lower left of the graph, the friction coefficient is low and the evaluation is good. That is, it is determined that the reliability of the refrigerant compressor 1 is high.

[0092] like Figure 4 As shown, it is confirmed that the embodiment has a lower Sommerfeld number and a lower friction coefficient than the comparative example. That is, it is confirmed that the embodiment is evaluated better than the comparative example, and the reliability of the refrigerant compressor 1 is high, specifically, the reliability of the sliding surface is high. In addition, it can be seen that the embodiment can ensure the reliability of the refrigerant compressor 1 under a low-viscosity lubrication environment. In addition, the embodiment does not use PTFE, so it is environmentally friendly (environmentally friendly).

[0093] In the above-described embodiment, the rotating shaft 300 made of an iron-based material is used, but the same effect can be obtained as long as the surface energy is 500 mN / m or more and 1000 mN / m or less.

[0094] In addition, in the above-mentioned embodiment, the hole portion 131 is provided, but the same effect can be obtained when the groove portion 132 is provided as described below. That is, the groove portion 132 is formed with a width of 0.3 mm×a depth of 0.005 mm, and multiple rows are provided in adjacent rows at a pitch of 3.5 mm. In addition, the number of the groove portions 132 is set so that the surface area S1 of the sliding surface formed with the groove portion 132 is 1.04 times or more relative to the surface area S0 of the sliding surface when the groove portion 132 is not formed.

[0095] (Variation examples, etc.)

[0096] The refrigerant compressor 1 of one embodiment of the present invention has been described in detail above, but the main purpose of the present invention is not limited thereto, and includes various modified examples. For example, the above-mentioned embodiment is an example described in detail in order to easily explain the present invention, and is not necessarily limited to having all the structures described. In addition, a part of the structure of a certain embodiment can be replaced with the structure of another embodiment, and the structure of another embodiment can be added to the structure of a certain embodiment. In addition, with respect to a part of the structure of each embodiment, other structures can be added, deleted, or replaced.

[0097] For example, as described above, the recess 130 can be at least one of the hole 131 and the groove 132. Figure 5 As shown, the recess 130 can use both the hole 131 and the groove 132. Figure 5 FIG. 1 is a plan view showing a state where a hole 131 and a groove 132 are used together as an example of the recess 130. Figure 5 In the embodiment, the hole portions 131 and the groove portions 132 are alternately provided. However, this modification is not limited to this. Figure 6 as well as Figure 7 1 is a top view showing another example of the recess 130 in which the hole 131 and the groove 132 are used. Figure 6 As shown, multiple rows (in Figure 6 In the present modification, for example, Figure 7 As shown, a plurality of holes (in Figure 7 There are two grooves 132 in the figure.

[0098] The hole 131 and the groove 132 can be appropriately provided in consideration of the pressure on the sliding surface, the characteristics related to the oil retention of the refrigerating machine oil (e.g., viscosity, etc.), etc. When providing the hole 131 and the groove 132, it is preferable to analyze the pressure on the sliding surface, the characteristics related to the oil retention of the refrigerating machine oil, etc. by simulation, etc.

[0099] In addition, the recessed portion 130 can also be provided on the entire surface of the rotating shaft 300 or the sliding bearing 10, but is not limited thereto. Figure 8 1 is a top view showing an example of the arrangement of the recess 130. Figure 8 , a case where all the holes 131 are provided as the recessed portions 130 is shown. Fig. 9 1 is a top view showing another example of the arrangement of the recess 130. Fig. 9 The figure shows a case where both the hole portion 131 and the groove portion 132 are used as the recessed portion 130 .

[0100] like Figure 8 As shown, for example, the recessed portion 130 can be provided only in a portion A (for example, Figure 8 In this way, the durability of the refrigeration oil in the portion A with high surface pressure on the sliding surface is improved, and the oil film on the sliding surface is less likely to break. In addition, the processing of the recessed portion 130 is also facilitated. In addition, as Figure 8 As shown, the formation density of the holes 131 can be increased arbitrarily.

[0101] And, if Fig. 9As shown, for the recessed portion 130, the surface pressure of the portion B (for example, Fig. 9 The arrangement density of the recessed portion 130 can also be increased by only using the left half of the left half of the rotating shaft 300, the sliding bearing 10, etc. Fig. 9 In the embodiment, the groove 132 is provided on the sliding surface in a manner consistent with the portion A with high surface pressure, and the hole 131 is provided in a manner consistent with the portion B with particularly high surface pressure. In this way, the density of the recesses 130 at any position can be increased, so that the durability of the refrigeration oil in the portion A with high surface pressure and the portion B with particularly high surface pressure on the sliding surface is improved, and the oil film on the sliding surface is less likely to rupture. In addition, in Fig. 9 In the embodiment, the hole portion 131 and the groove portion 132 are used together, but the structure may be composed of only the hole portion 131 or only the groove portion 132.

Claims

1. A refrigerant compressor used in a refrigeration cycle, storing refrigeration oil as lubricating oil in a sealed container and compressing at least a refrigerant, characterized in that: The invention comprises: a compression mechanism part which compresses the refrigerant; and a rotating shaft which drives the compression mechanism part. At least one of the engaging portion between the rotating shaft and the compression mechanism portion and the rotation support portion of the rotating shaft includes a sliding bearing. The surface energy of the sliding surface between the rotating shaft and the sliding bearing and the counterpart material is 500 mN / m or more and 1000 mN / m or less. A recessed portion capable of retaining the refrigerating machine oil is formed on the sliding surface of at least one of the rotating shaft and the sliding bearing.

2. The refrigerant compressor according to claim 1, characterized in that: The recessed portion is at least one of a hole portion and a groove portion having a depth of 0.005 mm or less.

3. The refrigerant compressor according to claim 1 or 2, characterized in that: The surface area of ​​the sliding surface where the recessed portion is formed is 1.04 times or more relative to the surface area of ​​the sliding surface when the recessed portion is not formed.

4. The refrigerant compressor according to claim 1 or 2, characterized in that: The refrigerant is at least one of R1234yf, R1234ze, R290 and R1270, or at least one of them is mixed with other refrigerants. The refrigerating machine oil has a surface tension of 10 mN / m or more.

5. The refrigerant compressor according to claim 1 or 2, characterized in that: A ten-point average roughness of a surface of a portion of the sliding surface where the recessed portion is not formed is 0.8 μm or less.

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