Refrigerant compressor

Abstract

To provide a refrigerant compressor in which reliability of a sliding surface configured by combining a metal bearing and a rotary shaft is improved while in consideration of the environment.SOLUTION: A refrigerant compressor 1 is for use in a refrigeration cycle and stores refrigerating machine oil serving as lubricant in an airtight container 700, and compresses at least a refrigerant, the refrigerant compressor 1 comprises: a compression mechanical portion 720 compressing the refrigerant; a rotary shaft 300 driving the compression mechanical portion 720; and a plain bearing 10 provided at least one of an engagement portion between the rotary shaft 300 and the compression mechanical portion 720 and the rotation support portion of the rotary shaft 300. The rotary shaft 300 and the plain bearing 10 both have a surface energy on the sliding surface with respect to an opposite material, of 500 mN / m or more and 1000 mN / m or less, and a recess 130 capable of retaining the refrigerating machine oil is formed on the sliding surface of at least either one of the rotary shaft 300 and the plain bearing 10.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] In order to prevent global warming, there is a demand for current air conditioners and refrigeration equipment to switch to low global warming potential refrigerants (low GWP (Global Warming Potential) refrigerants). Low GWP refrigerants include natural refrigerants such as propane (R290) and CO2, and HFO refrigerants that have double bonds in their chemical structure. Like current HFC refrigerants, these low GWP refrigerants have low polarity, so refrigeration oil dissolves easily and it is difficult for an oil film to form on the sliding surfaces. This has made it difficult to maintain the reliability of the sliding surfaces. The properties required for the sliding surfaces of refrigerant compressors include a low coefficient of friction as well as resistance to wear and seizure. PTFE (polytetrafluoroethylene) is one of the resins that satisfies these properties, and since it is very inexpensive, it is widely used for the sliding surfaces of refrigerant compressors, such as sliding bearings.

[0003] However, in recent years, due to environmental considerations, restrictions on PFAS (Per- and Polyfluoroalkyl Substances) are being considered, and PTFE is listed as one of the substances to be regulated.

[0004] Various technologies to deal with such a situation have been studied. For example, in refrigerant compressors using sliding bearings, some sliding bearings have sliding surfaces that are made of a mixture of a solid lubricant material such as molybdenum disulfide or graphite and a resin in order to improve the wear resistance and seizure resistance of the sliding surfaces.

[0005] For example, Patent Document 1 describes a plain bearing device including a bearing, a shaft supported by the bearing while sliding, and a gas supply unit that supplies dry gas to the bearing sliding surface on which the bearing and the shaft slide. In this plain bearing device, at least the sliding surface of the bearing is made of a resin composite material in which a carbon material is mixed with a resin. The shaft is made of metal, and has a groove on the sliding surface that extends in a direction different from the sliding direction. Patent Document 1 also describes that, for example, polyamide, polyphthalamide, polyamideimide, polyacetal, polyphenylene sulfide, polyetherimide, ultra-high molecular weight polyethylene, polyetheretherketone, etc. can be used as the resin.

[0006] Also, for example, Patent Document 2 describes a sintered oil-impregnated bearing having a cylindrical inner peripheral surface that supports a rotating shaft. This sintered oil-impregnated bearing has a plurality of protrusions and recesses formed on the inner peripheral surface, aligned in the circumferential direction. In addition, the porosity of the bearing surface, which is the surface of the protrusions, is lower than the porosity of the recesses, being a maximum of 10%. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2011 / 070621 [Patent Document 2] JP 2020-060284 A Summary of the Invention [Problem to be solved by the invention]

[0008] In sliding surfaces that use lubricating oil, the reduction in the coefficient of friction is related to the wettability of the oil. The wettability increases as the surface free energy (hereinafter, in this specification, sometimes referred to as "surface energy") of the solid side is greater than the surface tension of the liquid side (surface tension of the lubricating oil in a refrigerant compressor). Furthermore, the effect increases as the surface area of ​​the sliding surface increases.

[0009] On the other hand, in a refrigerant compressor in operation, liquid refrigerant may flow into the compressor from the cycle side. In such a case, the liquid viscosity decreases, the oil film thickness cannot be secured, and mixed lubrication occurs easily, where solid surfaces come into contact with each other on the sliding surfaces inside the compressor, which are the sliding bearing and the rotating shaft.

[0010] A rotating shaft having a microgroove having a collection of multiple grooves extending in a direction different from the sliding direction, as in Patent Document 1, requires a separate process for machining and may significantly reduce the effect of the heat treatment applied to the sliding surface of the rotating shaft.

[0011] Also, in Patent Document 2, a sliding bearing made of a sintered metal material without using resin is combined with a rotating shaft. In this case, oil shortage (oil film shortage) can be avoided by impregnating the pores formed by the sintered material. However, in a lubrication environment where liquid refrigerant is mixed, there is a problem that the sintered metal bearing and the rotating shaft are likely to come into metal contact, resulting in mixed lubrication or boundary lubrication.

[0012] Furthermore, as mentioned above, there is a growing demand these days for refrigerant compressors to be environmentally friendly.

[0013] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a refrigerant compressor which is environmentally friendly and has improved reliability of a sliding surface formed by combining a metal bearing and a rotating shaft. [Means for solving the problem]

[0014] The refrigerant compressor of the present invention which solves the above-mentioned problems is a refrigerant compressor used in a refrigeration cycle, which stores refrigeration oil as a lubricant in a sealed container and compresses at least a refrigerant, and comprises a compression mechanism which compresses the refrigerant, a rotating shaft which drives the compression mechanism, and a plain bearing in at least one of an engagement portion between the rotating shaft and the compression mechanism and a rotation support portion of the rotating shaft, both of the rotating shaft and the plain bearing have surface energies of 500 mN / m or more and 1000 mN / m or less at the sliding surfaces with a mating material, and a recess capable of holding the refrigeration oil is formed in the sliding surface of at least one of the rotating shaft and the plain bearing. Effect of the Invention

[0015] The refrigerant compressor according to the present invention is environmentally friendly and can improve the reliability of the sliding surface formed by the combination of a metal bearing and a rotating shaft. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a vertical cross-sectional view showing a refrigerant compressor 1 according to an embodiment of the present invention. [Diagram 2] 1 is an explanatory diagram showing a state in which a hole 131 is provided as an example of a recess 130, the left diagram being a perspective view seen from the side, and the right diagram being a plan view. [Diagram 3] 11 is an explanatory diagram showing a state in which a groove portion 132 is provided as another example of the recess 130, the left diagram being a perspective view seen from the side, and the right diagram being a plan view. [Figure 4] 1 is a graph showing Stribeck curves illustrating the relationship between Sommerfeld number and coefficient of friction for examples and comparative examples. [Diagram 5] 1 is a plan view showing an example of a recess 130 in which a hole 131 and a groove 132 are used together. [Figure 6] FIG. 13 is a plan view showing another example of recess 130 in which hole 131 and groove 132 are used together. [Figure 7] FIG. 13 is a plan view showing another example of recess 130 in which hole 131 and groove 132 are used together. [Figure 8] FIG. 2 is a plan view showing an example of an arrangement of a recess 130. [Figure 9] 13 is a plan view showing another example of an arrangement of the recess 130. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, a refrigerant compressor according to an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the drawings to be referred to, Fig. 1 is a vertical cross-sectional view showing a refrigerant compressor 1 according to an embodiment of the present invention. Fig. 1 shows an example in which the present invention is applied to a scroll compressor as the refrigerant compressor 1. That is, the refrigerant compressor 1 is used in a refrigeration cycle, and stores refrigeration oil as a lubricant in a sealed container 700 to compress at least a refrigerant.

[0018] [Refrigerant compressor 1] As shown in Fig. 1, 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 in the middle, 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-based material. That is, the rotating shaft 300 drives the compression mechanism 720.

[0019] The compression mechanism 720 has a fixed scroll 100 having a spiral wrap 102 standing upright on a base plate 101, and an orbiting scroll 200 having a spiral wrap 202 standing upright on a base plate 201, and is formed by meshing the wraps 102, 202 with each other. With this configuration, the compression mechanism 720 can at least compress the (gaseous) refrigerant.

[0020] The fixed scroll 100 is also provided with an intake port 103 and a discharge port 104 . The rotating shaft 300 is supported by a main bearing 401 provided on an upper frame 400 above the electric motor 600, and a sub-bearing 801 provided on a lower frame 800 below the electric motor 600. The main bearing 401 corresponds to an engagement portion between the rotating shaft 300 and the compression mechanism portion 720.

[0021] The upper frame 400 and the lower frame 800 are fixed to the sealed container 700 . A crank pin (eccentric shaft) 301 made of an iron-based material is provided at the tip of the rotating shaft 300. This crank pin 301 is inserted into and engaged with a boss portion 203 protruding downward from the base plate 201 of the orbiting scroll 200. A slewing bearing 210 is provided in the boss portion 203 and configured to slide with the crank pin 301. The boss portion 203 corresponds to a rotation support portion of the rotating shaft 300. In this embodiment, the main bearing 401 and the slewing bearing 210 correspond to the plain bearing 10. In this embodiment, as shown in FIG. 1, it is preferable to provide at least one of the main bearing 401 and the slewing bearing 210 as the plain bearing 10. In this embodiment, the plain bearing 10 may be disposed as the sub-bearing 801.

[0022] An Oldham coupling 500 is disposed on the back surface of the base plate 201 of the orbiting scroll 200. This Oldham coupling 500 allows the orbiting scroll 200 to orbit relative to the fixed scroll 100 without rotating on its axis.

[0023] When the electric motor 600 rotates the rotating shaft 300 connected to the rotor, the rotation causes the crank pin 301 provided at the tip of the rotating shaft 300 to rotate eccentrically. The rotating scroll 200 performs an orbital motion without rotating relative to the fixed scroll 100 due to the rotation prevention mechanism of the Oldham coupling 500. As a result, the gaseous refrigerant is sucked into the sealed chamber formed by the spiral wrap 102 and wrap 202 through the suction pipe 711 and the suction port 103. The gaseous refrigerant is compressed in volume by the sealed chamber moving toward the center side along with the orbital motion. 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 electric motor 600, and is then discharged from the discharge pipe 701 to the outside of the refrigerant compressor 1.

[0024] Next, the oil supply path will be described. A bearing housing 802 that houses a sub-bearing 801 is attached to 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 attached to the lower end of the rotating shaft 300. When the rotating shaft 300 rotates, the refrigeration oil in the oil sump 730 is sucked up by the pump unit 900, and reaches the upper part of the crank pin 301 through an oil passage 311 formed in the rotating shaft 300 from the pump unit 900. The refrigeration oil lubricates the orbiting bearing 210 from the upper part of the crank pin 301, and then flows to the main bearing 401. The refrigeration oil that has lubricated the main bearing 401 passes through an oil drain pipe 408 and returns to the oil sump 730.

[0025] Furthermore, a portion of the refrigeration oil after lubricating the orbiting bearing 210 passes through a seal portion 402 provided between the lower surface of the boss portion 203 of the orbiting scroll 200 and the upper frame 400, and flows into the back surface of the base plate 201 of the orbiting scroll 200. The refrigeration oil that has flowed into the back surface of the base plate 201 passes through an oil supply passage 220 formed in the base plate 201 of the orbiting scroll 200, lubricates the sliding portions between the fixed scroll 100 and the orbiting scroll 200 and between the wraps 102, 202, and is discharged into the discharge chamber 710 together with the compressed gaseous refrigerant. The refrigeration oil discharged into the discharge chamber 710 then returns to an oil reservoir 730 at the bottom of the sealed container 700.

[0026] In this embodiment, in the refrigerant compressor 1 having the configuration described above, the rotating shaft 300 and the plain bearing 10 are configured as follows.

[0027] First, in this embodiment, the surface energy of the sliding surfaces of the rotating shaft 300 and the plain bearing 10 that slide against the counterpart material is set to 500 mN / m or more and 1000 mN / m or less.

[0028] In this way, the surface energy of the sliding surface is greater than the surface tension of the refrigerating machine oil, and thus the wettability is improved. 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, even more preferably 800 mN / m or more and 1000 mN / m or less, and even more preferably 900 mN / m or more and 1000 mN / m or less.

[0029] If the surface energy of the sliding surface with the counter material is less than 500 mN / m, the wettability may be insufficient, which may cause the oil film to break. On the other hand, if the surface energy of the sliding surface with the counter material exceeds 1000 mN / m, the material becomes the same type as that of a rotating shaft made of iron, which can cause adhesive wear.

[0030] The sliding surface having the above-mentioned surface energy can satisfy the above-mentioned conditions if it is formed using metal, ceramics, carbon, diamond-like carbon, etc. In other words, it is possible to appropriately select and use one that satisfies the above-mentioned conditions from among those formed from these materials.

[0031] The surface energy of the sliding surface can be measured, for example, in accordance with JIS R 3257:1999 "Test method for wettability of glass substrate surface." The measurement should be performed at 25°C±5°C and humidity 50±10% as specified in the JIS. The test should be performed by dropping a drop of pure water onto a solid sample with a flat surface and measuring the contact angle of the pure water. Furthermore, the contact angle should be measured with a liquid other than water, such as glycerin, and the interfacial energy should be calculated. The test should be performed by measuring five points on one sample and calculating the average value.

[0032] In this embodiment, the sliding surface of at least one of the rotating shaft 300 and the sliding bearing 10 is formed with the recess 130 (see FIG. 2) capable of holding the above-mentioned refrigeration oil. In this embodiment, since the recesses 130 are formed, an oil film is easily formed and slidability is not easily impaired.

[0033] In other words, the refrigerant compressor 1 according to this embodiment improves the wettability of the refrigeration oil by using the rotating shaft 300 and the plain bearing 10 whose sliding surfaces have the above-mentioned surface energy, and further improves the oil retention by the above-mentioned recess 130.

[0034] Here, Fig. 2 is an explanatory diagram showing a state where a hole 131 is provided as an example of the recess 130, the left figure being a perspective view seen from the side, and the right figure being a plan view. Fig. 3 is an explanatory diagram showing a state where a groove 132 is provided as another example of the recess 130, the left figure being a perspective view seen from the side, and the right figure being a plan view. In this embodiment, it is preferable that the recess 130 is 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 plain bearing 10 is less likely to decrease. From the viewpoint of preventing a decrease in the mechanical strength, the depth of the recess 130 and the groove 132 is more preferably 0.004 mm or less, and even more preferably 0.003 mm or less.

[0035] The recesses 130 may have a width of, for example, 0.3 mm, and may be provided in a row with a pitch of 3.5 mm, and may be provided in a row with a pitch of 3.5 mm, but are not limited thereto. The recesses 130 may be formed in the same position in one row as in another row, or may be formed in a shifted position (FIG. 2 shows a shifted state). Note that the pitch in this embodiment refers to the length measured parallel to the axis between two corresponding points of adjacent recesses 130 (holes 131) or rows of adjacent recesses 130 (rows of holes 131, grooves 132) in a cross section including the central axis of the recesses 130.

[0036] In this embodiment, the surface area S1 of the sliding surface on which the recesses 130 are formed is preferably 1.04 times or more the surface area S0 of the sliding surface when the recesses 130 are not formed. In other words, the formation density of the recesses 130 having a predetermined area is preferably set so that the surface area S1 is 1.04 times or more the surface area S0. In this way, the surface area is increased by the recesses 130, and the refrigerating machine oil can be reliably held by the increased surface area. Therefore, the refrigerating machine oil is held better than when the recesses 130 are not formed, and the oil film on the sliding surface is more unlikely to break. From the viewpoint of making the oil film less likely to break, the surface area S1 is more preferably 1.05 times or more the surface area S0, more preferably 1.06 times or more, and even more preferably 1.07 times or more. In addition to the above-mentioned lower limit for the surface area S0, the surface area S1 is preferably 1.1 times or less, more preferably 1.09 times or less, and even more preferably 1.08 times or less, the surface area S0. In this way, it is possible to prevent the processing difficulty and processing costs from becoming excessively high.

[0037] The refrigerant and the refrigerating machine oil have a characteristic that those with similar polarities dissolve easily, while those with different polarities do not dissolve easily. For example, when comparing the surface tension at a pressure condition of 1.4 PaG based on data calculated by refrigerant manufacturers and reference 1 (Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers, 37 (1), p.73-80, 2020), the HFC refrigerant R32 has a surface tension of 7.9 mN / m, while R1234yf has a surface tension of 3.04 mN / m, R1234ze(Z) has a surface tension of 4.37 mN / m, R1270 has a surface tension of 6.02 mN / m, and R290 has a surface tension of 5.09 mN / m, which are all lower values. In the refrigerant compressor 1 according to the present embodiment, the refrigerant may be at least one of R1234yf, R1234ze, R290, and R1270, or at least one of these may be mixed with another refrigerant. In other words, several of these refrigerants may be selected and mixed. The refrigerant may be one or more of these refrigerants mixed together and further mixed with another refrigerant. When another refrigerant is mixed, the polarity of the mixed refrigerant is set to be lower than that of the refrigerating machine oil.

[0038] In addition, the refrigeration oil preferably has a surface tension of 10 mN / m or more, which makes it easier to form an oil film and ensures a sufficient oil film thickness. However, it is preferable that the surface tension of the refrigeration oil is smaller than the surface free energy of the sliding surfaces of the rotating shaft 300, the plain bearing 10, etc. In this way, it is possible to reliably increase the wettability of the sliding surfaces of the rotating shaft 300, the plain bearing 10, etc. Therefore, oil film breakage on the sliding surfaces of the rotating shaft 300, the plain bearing 10, etc. becomes less likely to occur. The surface tension of the refrigerating machine oil can be measured in accordance with JIS K 2241, for example.

[0039] In the refrigerant compressor 1 using the rotating shaft 300 and the plain bearing 10 whose surface energy at the sliding surface with the counter material is 500 mN / m or more and 1000 mN / m or less, a refrigerant with low surface tension (10 mN / m or less) has low compatibility when combined with a refrigerating machine oil having a higher surface tension than that of the refrigerant. Therefore, the refrigerating machine oil is difficult to return to the refrigerant compressor 1, and the oil film may break. However, when the refrigerant and the refrigeration oil are in the above-mentioned form, in this embodiment, the recesses 130 are formed on the sliding surfaces of the rotating shaft 300 and the plain bearing 10, so that it is possible to easily form an oil film on the sliding surfaces of the rotating shaft 300 and the plain bearing 10. Therefore, the oil film is less likely to break.

[0040] The refrigeration oil that can be used in this embodiment has a molecular weight of 500 or more and a density of 0.9 g / cm3 Examples of the refrigeration oil include those that satisfy the above conditions and have a hydroxyl group at the end of the chemical structure. If the refrigeration oil has these characteristics, the polarity will be high, and the solubility of the refrigerant in the refrigeration oil will decrease. Therefore, it is possible to suppress the decrease in oil viscosity during operation. The polarity of the refrigeration oil also affects the slipperiness of the sliding surface. If the sliding surfaces of the rotating shaft 300 and the plain bearing 10 (i.e., the main bearing 401 and the orbiting bearing 210) are made to have a surface energy higher than the surface tension of the refrigeration oil, the wettability of the sliding surface with the refrigeration oil will improve. Furthermore, the effect will be improved by providing a recess 130 on any of the sliding surfaces. Therefore, the oil film will be less likely to break on the sliding surfaces of the rotating shaft 300 and the plain bearing 10, and the reliability of the sliding surfaces of the refrigerant compressor 1 will be further improved.

[0041] The refrigerating machine oil preferably has at least one of an ester bond and an ether bond in the chemical structure, which can more reliably reduce the solubility of the refrigerant in the refrigerating machine oil. Specific examples of refrigeration oils that can be used in this embodiment include ether-based refrigeration oils, polyalkylene glycol oils, polyethylene glycol oils, polyol ester oils, etc. In addition, polypropylene glycol oils having an ethanol group at the end can be used as polyalkylene glycol oils. In addition, polyethylene glycol oils are polymers of ethylene oxide and polyhydric alcohols, and are represented by the formula H[OCH(CH3)CH2] n PEG400 represented by OH can be used. In addition, in the case of polyol ester oils, hindered type polyol ester oils such as dipentaerythritol-based mixed fatty acid ester oils of pentanoic acid and 2-methylbutanoic acid can be used.

[0042] 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, such as mineral oils.

[0043] In this embodiment, the molecular weight of the refrigerating machine oil is preferably 600 or more, more preferably 750 or more, and even more preferably 1000 or more. The molecular weight of the refrigerating machine oil is preferably 2000 or less, more preferably 1800 or less, even more preferably 1750 or less, and even more preferably 1500 or less. When the molecular weight of the refrigerating machine oil is in 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.

[0044] In this embodiment, the density of the refrigerating machine oil is 1.0 g / cm 3 The density of the refrigerating machine oil is preferably 1.2 g / cm or more. 3 It is preferable that the density is 1.1 g / cm or less. 3 When the density of the refrigerating machine oil is in such a preferable 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 more effectively maintained.

[0045] The molecular weight of the refrigerating machine oil is preferably 500 or more under an environment of 1.4 MPa and 60° C., as described above. In addition, the density of the refrigerating machine oil is preferably 0.9 g / cm under an environment of 1.4 MPa and 60° C., as described above. 3 This is preferable. By doing so, 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. The molecular weight of the refrigerating machine oil can be measured, for example, by a boiling point elevation method or a freezing point depression method. The molecular weight of the refrigerating machine oil can also be measured, for example, by gas chromatography in accordance with JIS K 0114. The density of the refrigerating machine oil can be measured in accordance with JIS K 2249, for example.

[0046] In this embodiment, the ten-point average roughness (Rz JIS ) is preferably 0.8 μm or less. In this way, the surface is smooth and the seizure resistance can be improved, and the refrigerating machine oil can be retained, improving the overall lubrication. From the viewpoint of further improving these, the Rz of the surface of the portion where the recess 130 is not formed on the sliding surface is preferably 0.8 μm or less. JIS It is more preferable that the thickness is 0.5 μm or less.

[0047] [Formation of recess 130] In the present embodiment, the recess 130 can be suitably formed by forming the recess 130 on the sliding surface and then performing mirror finishing, but is not limited to this. In this embodiment, the sliding surface may be mirror-finished first, and then the recess 130 may be formed. When the recess 130 is formed after the mirror-finishing, if burrs or the like are generated, a finishing process (re-mirror-finishing) may be performed to remove the burrs or the like as necessary. The recess 130 can be formed by, for example, etching, laser processing, machining, or the like. In addition, when forming the recess 130, mirror finishing is not necessarily required. EXAMPLES

[0048] (Stribeck curve) FIG. 4 is a graph showing Stribeck curves showing the relationship between the Sommerfeld number and the friction coefficient for the examples and the comparative examples. In the figure, the horizontal axis shows the Sommerfeld number, and the vertical axis shows the friction coefficient. The examples are a combination of a rotating shaft 300 made of an iron-based material having the above-mentioned recess 130 on the sliding surface, and a plain bearing 10 whose sliding surface is made of a metal sintered material. The comparative examples are a combination of a rotating shaft 300 made of an iron-based material not having the above-mentioned recess 130 on the sliding surface, and a plain bearing 10 whose sliding portion is made of a metal sintered material. In other words, the comparative examples are a combination of the rotating shaft 300 and the plain bearing 10 whose sliding portion is made of a metal sintered material.

[0049] In this test to obtain the Stribeck curve, for a rotating shaft 300 having recesses 130, the recesses 130 were formed as holes 131 with a width of 0.3 mm and a depth of 0.005 mm, and a plurality of recesses 130 were provided in one row with a pitch of 3.5 mm, and adjacent rows were provided with a pitch of 3.5 mm. The surface area S1 of the sliding surface on which the recesses 130 were formed was 1.04 times or more larger than the surface area S0 of the sliding surface when the recesses 130 were not formed. In this test, an HFC refrigerant was used as the refrigerant and an ether-based refrigerant oil was used as the refrigerant oil. In this test, the Stribeck curve was obtained in these atmospheres (viscosity η: 0.5 to 2 mPa s) with a rotation speed of 30 rps and a test load of 500 to 7000 N.

[0050] Generally, as the load increases, the surface pressure increases and the Sommerfeld number decreases. As the Sommerfeld number decreases, metal contact becomes more likely and the friction coefficient increases. In other words, the smaller the Sommerfeld number, the harsher the operating conditions become. On the other hand, the smaller the friction coefficient, the higher the frictional properties. 4, the friction coefficient decreases and the evaluation improves as one moves to the bottom left of the graph, despite the severe operating conditions. In other words, the reliability of the refrigerant compressor 1 is determined to be high.

[0051] As shown in Fig. 4, it was confirmed that the Examples had a lower Sommerfeld number and a lower friction coefficient compared to the Comparative Example. In other words, the Examples were evaluated better than the Comparative Example, and it was confirmed that the reliability of the refrigerant compressor 1 was high, specifically, that the reliability of the sliding surface was high. This also showed that the Examples were able to ensure the reliability of the refrigerant compressor 1 in a low-viscosity lubrication environment. Furthermore, the Examples are environmentally friendly (environmentally considerate) because they do not use PTFE.

[0052] In the above embodiment, the rotating shaft 300 was made of an iron-based material, but similar effects were obtained with any material having a surface energy of 500 mN / m or more and 1000 mN / m or less. In the above embodiment, the above-mentioned hole 131 was provided, but the same effect was obtained when the groove 132 described below was used. That is, the groove 132 was formed with a width of 0.3 mm and a depth of 0.005 mm, and was provided in a plurality of rows with a pitch of 3.5 mm between adjacent rows. The number of grooves 132 was set so that the surface area S1 of the sliding surface on which the grooves 132 were formed was 1.04 times or more the surface area S0 of the sliding surface when the grooves 132 were not formed.

[0053] (Variations, etc.) Although the refrigerant compressor 1 according to one embodiment of the present invention has been described in detail above, the gist of the present invention is not limited to this and includes various modified examples. For example, the above-mentioned embodiment has been described in detail to easily explain the present invention, and the present invention is not necessarily limited to having all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0054] For example, as described above, the recess 130 can be at least one of the hole 131 and the groove 132. Therefore, the recess 130 can use the hole 131 and the groove 132 in combination as shown in FIG. 5. FIG. 5 is a plan view showing a state in which the hole 131 and the groove 132 are used in combination as an example of the recess 130. In FIG. 5, the hole 131 and the groove 132 are alternately provided. However, this modification is not limited to this. FIGS. 6 and 7 are plan views showing a state in which the hole 131 and the groove 132 are used in combination as another example of the recess 130. In this modification, for example, as shown in FIG. 6, a plurality of rows of the hole 131 (two rows in FIG. 6) can be provided between a pair of the grooves 132. In addition, in this modification, for example, as shown in FIG. 7, a plurality of grooves 132 (two rows in FIG. 7) can be provided between a pair of the rows of the hole 131. The holes 131 and the grooves 132 can be appropriately provided in consideration of the pressure on the sliding surface, the characteristics of the refrigeration oil related to oil retention (e.g., viscosity, etc.), etc. When providing the holes 131 and the grooves 132, it is advisable to analyze the pressure on the sliding surface, the characteristics of the refrigeration oil related to oil retention, etc. by simulation or the like.

[0055] The recesses 130 can also be provided on the entire surfaces of the rotating shaft 300 or the plain bearing 10, but are not limited to this. Here, Fig. 8 is a plan view showing an example of an installation mode of the recesses 130. Note that Fig. 8 illustrates a state in which all the recesses 130 are provided with hole portions 131. Fig. 9 is a plan view showing another example of an installation mode of the recesses 130. Note that Fig. 9 illustrates a state in which the hole portions 131 and the groove portions 132 are used together as the recesses 130.

[0056] As shown in Fig. 8, the recesses 130 can be provided only in a portion A where the surface pressure is high on the sliding surface of, for example, the rotating shaft 300 or the plain bearing 10 (for example, only the left half of the rotating shaft 300 or the plain bearing 10 in Fig. 8). In this way, the refrigeration oil is retained better in the portion A where the surface pressure is high on the sliding surface, making it more difficult for the oil film to break on the sliding surface. Also, machining of the recesses 130 becomes easier. Also, as shown in Fig. 8, the formation density of the holes 131 can be increased as desired.

[0057] Furthermore, as shown in FIG. 9, the recesses 130 can be arranged so that the installation density is high in a portion B where the surface pressure is particularly high in a portion A where the surface pressure is high on the sliding surface (for example, only the left half of the left half of the rotating shaft 300 or the sliding bearing 10 in FIG. 9). In FIG. 9, a groove 132 is provided so as to match the portion A where the surface pressure is high on the sliding surface, and a hole 131 is provided so as to match the portion B where the surface pressure is particularly high. In this way, the installation density of the recesses 130 at any position can be increased, so that the refrigeration oil is retained better in the portion B where the surface pressure is particularly high in the portion A where the surface pressure is high on the sliding surface, and the oil film on the sliding surface is less likely to break. Note that, although the hole 131 and the groove 132 are used in combination in FIG. 9, the recesses 130 may be configured with only the hole 131 or only the groove 132. [Explanation of symbols]

[0058] 1 Refrigerant compressor 10. Plain bearings 100 Fixed Scroll 101 Base plate 102 Lap 103 Intake port 104 Discharge port 130 Recess 131 Hole 132 Groove 200 Swivel Scroll 201 Base plate 202 Lap 203 Boss 210 Swing bearing (slide bearing) 220 Fuel Line 300 Rotational Axis 301 Crank pin 310 Pump joint 311 Oil passage 400 Upper Frame 401 Main bearing (slide bearing) 402 Seal part 408 Oil Drain Pipe 500 Oldham coupling 600 electric motor 700 Airtight container 701 Discharge pipe 710 Discharge chamber 711 Suction pipe 720 Compression mechanism 800 Lower Frame 801 Sub-bearing 802 Bearing housing 900 Pump section A: Area with high surface pressure on the sliding surface B Part where surface pressure is particularly high

Claims

1. A refrigerant compressor used in a refrigeration cycle, storing refrigeration oil as a lubricant in a sealed container, and compressing at least a refrigerant, A compression mechanism that compresses the refrigerant; A rotating shaft that drives the compression mechanism; a slide bearing is provided in at least one of an engagement portion between the rotating shaft and the compression mechanism portion and a rotation support portion of the rotating shaft, The rotating shaft and the plain bearing each have a surface energy of 500 mN / m or more and 1000 mN / m or less at a sliding surface with a counter material, A recess capable of holding the refrigerating machine oil is formed on the sliding surface of at least one of the rotating shaft and the sliding bearing. A refrigerant compressor comprising:

2. 2. The refrigerant compressor according to claim 1, The recess is at least one of a hole and a groove having a depth of 0.005 mm or less. A refrigerant compressor comprising:

3. The refrigerant compressor according to claim 1 or 2, The surface area of ​​the sliding surface on which the recess is formed is 1.04 times or more the surface area of ​​the sliding surface in a case where the recess is not formed. A refrigerant compressor comprising:

4. The refrigerant compressor according to claim 1 or 2, The refrigerant is at least one of R1234yf, R1234ze, R290, and R1270, or a mixture of at least one of these with another refrigerant, The refrigerating machine oil has a surface tension of 10 mN / m or more. A refrigerant compressor comprising:

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

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