Hermetic refrigerant compressor and refrigeration equipment using the same

Abstract

Provided is a hermetic refrigerant compressor that can achieve high efficiency and good reliability even when using a lubricating oil with a lower viscosity and reducing the sliding area of ​​a shaft supported by a bearing. The lubricating oil has a kinematic viscosity of 1mm at 40°C. 2 / S~7mm 2 / S, and its average mass molecular weight is 150 to 400, and it contains 0.5 mass% or more of high molecular weight components. The mass molecular weight of the high molecular weight components is 500 or more. In a crankshaft, which is the shaft part of the compression element, the sliding surface of the main shaft is divided into a first sliding surface and a second sliding surface via a non-sliding outer peripheral surface. When the axial length of the sliding surface with the shortest axial length among these sliding surfaces is defined as a single sliding length L, the ratio L / D of the single sliding length L to the outer diameter D of the main shaft is 2.0 or less.

Description

[Technical Field]

[0001] The present invention relates to a hermetic refrigerant compressor used in refrigerators, air conditioners, etc., and to a freezing / refrigerating device using the same. [Background technology]

[0002] In recent years, efforts have been made to develop highly efficient hermetic refrigerant compressors that reduce the use of fossil fuels in order to protect the global environment. For example, in order to achieve high efficiency, it has been proposed to form various coatings on the sliding surfaces of sliding members included in hermetic refrigerant compressors and to use lubricating oils with lower viscosities.

[0003] A hermetic refrigerant compressor contains lubricating oil in a sealed container and houses an electric element and a compression element. The compression element includes sliding members such as a crankshaft, pistons, and connecting rods, and the crankshaft main shaft and main bearing, piston and bore, piston pin and connecting rod, and crankshaft eccentric shaft and connecting rod all form sliding parts.

[0004] An example of a hermetic refrigerant compressor using a lubricant oil with a lower viscosity is the reciprocating compressor disclosed in Patent Document 1. The lubricant oil used in this reciprocating compressor has a kinematic viscosity of 3 mm at 40°C. 2 / S~10mm 2 Items within the / S range are listed.

[0005] If the viscosity of the lubricating oil is low, it becomes difficult for an oil film to form. However, in the reciprocating compressor (sealed refrigerant compressor) disclosed in Patent Document 1, a special treatment is applied to the surfaces of the sliding members that make up the sliding part, making it easier for an oil film to form.

[0006] Specifically, the piston and connecting rod, which are sliding components, are made of sintered iron and then steam-treated. The piston surface is machined to remove the steam layer, and the connecting rod is nitrided after steam treatment. This prevents wear and seizure in the piston and connecting rod, even when a low-viscosity lubricating oil is used and the oil film is thin.

[0007] Furthermore, in the hermetic compressor (hermetic refrigerant compressor) disclosed in Patent Document 2, the dimensions of the crankshaft main shaft and main bearing are specified to reduce vibration. Specifically, when the length (bearing length) of the bearing at the support portion of the crankshaft main shaft and main bearing is L and the diameter (shaft diameter) of the crankshaft is D, the ratio of bearing length / shaft diameter (referred to as "α" in Patent Document 2) is set to less than 2.5 (L / D<2.5). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 5222244 [Patent Document 2] Japanese Patent Application Publication No. 2017-014992 Summary of the Invention [Problem to be solved by the invention]

[0009] The crankshaft of a hermetic refrigerant compressor forms a shaft of a compression element driven by an electric element, and this shaft is rotatably supported by a bearing. To improve the efficiency of a hermetic refrigerant compressor, it is expected that the sliding area between the shaft and the bearing (supporting portion) will be reduced. However, if this sliding area is too small, the efficiency will actually decrease.

[0010] In the reciprocating compressor (sealed refrigerant compressor) disclosed in the aforementioned Patent Document 1, the kinematic viscosity at 40°C is 3 mm 2 / S~10mm 2Although a low-viscosity lubricant in the range of 1 / s is used, the target for improving wear resistance is the piston and connecting rod. Therefore, Patent Document 1 does not consider measures to be taken when using a low-viscosity lubricant for a configuration where a bearing is used, such as a crankshaft. Patent Document 1 also does not consider reducing the sliding area of ​​a bearing part, such as a crankshaft, in order to improve efficiency.

[0011] On the other hand, in the hermetic compressor disclosed in the aforementioned Patent Document 2, as mentioned above, vibration is reduced by setting the bearing length / shaft diameter ratio to less than 2.5 (L / D<2.5). However, Patent Document 2 discloses that when the bearing length / shaft diameter ratio is 2.0 or less (L / D≦2.0), the loss within the bearing increases. That is, Patent Document 2 discloses that when L / D≦2.0, the sliding area becomes too small, so the loss within the bearing increases and the efficiency of the hermetic compressor deteriorates.

[0012] The present invention has been made to solve the above problems, and an object of the present invention is to provide a hermetic refrigerant compressor that can achieve high efficiency and good reliability even when a lubricating oil with a lower viscosity is used and the sliding area of ​​the shaft supported by the bearing is reduced. [Means for solving the problem]

[0013] In order to solve the above-mentioned problems, the present invention provides a hermetic refrigerant compressor comprising a hermetic container for storing lubricating oil, an electric element housed in the hermetic container, and a compression element driven by the electric element for compressing a refrigerant, wherein the lubricating oil has a kinematic viscosity of 1 mm at 40°C. 2 / S~7mm 2 / S, and has an average mass molecular weight of 150 to 400, and contains 0.5 mass% or more of a high molecular weight component, the high molecular weight component having a mass molecular weight of 500 or more, the compression element includes a crankshaft having a main shaft and an eccentric shaft as a shaft portion, and a main bearing supporting the main shaft and an eccentric bearing supporting the eccentric shaft as a bearing portion supporting the shaft portion, the sliding surface of the main shaft with the main bearing being a single surface or being divided into multiple surfaces, and when the sliding surface is a single surface, when the axial length of the sliding surface is defined as a single sliding length L, or when the sliding surface is divided into multiple surfaces, when the axial length of the sliding surface with the shortest axial length is defined as the single sliding length L, the ratio L / D of the single sliding length L to the outer diameter D of the main shaft is 2.0 or less.

[0014] According to the above configuration, in the crankshaft, whether the sliding surface of the main shaft is a single surface or multiple surfaces, the ratio L / D of the single sliding length L to the outer diameter D is 2.0 or less, and even if the lubricating oil used is lower in viscosity, the average molecular weight of the lubricating oil is within a predetermined range, and the lubricating oil contains 0.5 mass% or more of a high-molecular-weight component with a relatively large molecular weight. This allows a suitable oil film to be formed even with a low-viscosity lubricating oil due to the high-molecular-weight component, even when the sliding area is reduced so that the ratio L / D is 2.0 or less. As a result, even when a lower-viscosity lubricating oil and a bearing with a reduced sliding area are used, the friction coefficient of the shaft supported by the bearing can be reduced. This effectively reduces friction in the sliding parts of the crankshaft, resulting in a hermetic refrigerant compressor that is both highly efficient and reliable.

[0015] In addition, the refrigeration / freezing device according to the present invention is configured to include a refrigerant circuit that includes the hermetic refrigerant compressor of the above configuration, a radiator, a pressure reducing device, and a heat absorber, and that connects these in a ring shape with piping.

[0016] According to the above configuration, the hermetic refrigerant compressor uses a low-viscosity lubricant oil to reduce the sliding area and has good shaft reliability. By providing a refrigeration / freezing device with such a highly efficient and reliable hermetic refrigerant compressor, the device can reduce its power consumption and achieve high reliability.

[0017] The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings. [Effects of the Invention]

[0018] With the above-described configuration, the present invention has an effect of providing a hermetic refrigerant compressor that can achieve high efficiency and good reliability even when a lubricating oil with a lower viscosity is used and the sliding area of ​​the shaft portion journaled by the bearing portion is reduced. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a hermetic refrigerant compressor according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic side view showing an example of the configuration of a crankshaft included in the hermetic refrigerant compressor shown in FIG. [Figure 3] FIG. 3A is a schematic diagram showing an example of the configuration of the crankshaft shown in FIG. 2 when the sliding surface is a single surface, and FIGS. 3B and 3C are schematic diagrams showing an example of the configuration of the crankshaft shown in FIG. 2 when the sliding surface is divided into multiple surfaces. [Figure 4] FIG. 4 is a schematic diagram showing an example of the configuration of a freezing / refrigeration device equipped with the hermetic refrigerant compressor shown in FIG. [Figure 5]FIG. 5A is a graph showing an example of the molecular weight distribution of the lubricating oil used in the hermetic refrigerant compressor shown in FIG. 1 , FIG. 5B is a graph showing an example of the molecular weight distribution of a conventional lubricating oil, and FIG. 5C is a graph showing an example of the molecular weight distribution of a high molecular weight component added to the lubricating oil according to the present disclosure. [Figure 6] FIG. 6 is a graph showing an example of the relationship between L / D and the friction coefficient of the crankshaft in the hermetic refrigerant compressor shown in FIG. 1 using the lubricating oil shown in FIG. 5A. [Figure 7] FIG. 7 is a graph showing an example of the relationship between the content of high molecular weight components contained in the lubricating oil shown in FIG. 5A and the coefficient of performance of the hermetic refrigerant compressor shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] The hermetic refrigerant compressor according to the present disclosure includes a sealed container for storing lubricating oil, an electric element housed in the sealed container, and a compression element driven by the electric element for compressing a refrigerant, wherein the lubricating oil has a kinematic viscosity of 1 mm at 40°C. 2 / S~7mm 2 / S, and has an average mass molecular weight of 150 to 400, and contains 0.5 mass% or more of a high molecular weight component, the high molecular weight component having a mass molecular weight of 500 or more, the compression element includes a crankshaft having a main shaft and an eccentric shaft as a shaft portion, and a main bearing supporting the main shaft and an eccentric bearing supporting the eccentric shaft as a bearing portion supporting the shaft portion, the sliding surface of the main shaft with the main bearing being a single surface or being divided into multiple surfaces, and when the sliding surface is a single surface, when the axial length of the sliding surface is defined as a single sliding length L, or when the sliding surface is divided into multiple surfaces, when the axial length of the sliding surface with the shortest axial length is defined as the single sliding length L, the ratio L / D of the single sliding length L to the outer diameter D of the main shaft is 2.0 or less.

[0021] According to the above configuration, in the crankshaft, whether the sliding surface of the main shaft is a single surface or multiple surfaces, the ratio L / D of the single sliding length L to the outer diameter D is 2.0 or less, and even if the lubricating oil used is lower in viscosity, the average molecular weight of the lubricating oil is within a predetermined range, and the lubricating oil contains 0.5 mass% or more of a high-molecular-weight component with a relatively large molecular weight. This allows a suitable oil film to be formed even with a low-viscosity lubricating oil due to the high-molecular-weight component, even when the sliding area is reduced so that the ratio L / D is 2.0 or less. As a result, even when a lower-viscosity lubricating oil and a bearing with a reduced sliding area are used, the friction coefficient of the shaft supported by the bearing can be reduced. This effectively reduces friction in the sliding parts of the crankshaft, resulting in a hermetic refrigerant compressor that is both highly efficient and reliable.

[0022] In the hermetic refrigerant compressor having the above configuration, the ratio L / D may be 0.4 or more.

[0023] According to the above configuration, if the ratio L / D is 0.4 or more, the risk of excessive reduction in the sliding area can be avoided or suppressed. Therefore, even when the sliding area is reduced, the oil film formed by the low-viscosity lubricating oil containing high-molecular-weight components can effectively reduce the friction coefficient of the shaft portion. This can more effectively achieve low friction in the sliding portion of the crankshaft.

[0024] In the hermetic refrigerant compressor having the above configuration, the lubricating oil may contain an oiliness agent.

[0025] According to the above configuration, the low-viscosity lubricating oil containing high-molecular-weight components further contains an oiliness agent, which makes it easier for the lubricating oil to form an oil film, thereby more effectively achieving low friction in the sliding parts of the crankshaft.

[0026] In the hermetic refrigerant compressor having the above configuration, the oiliness agent may be an ester compound.

[0027] According to the above configuration, the oiliness agent contained in the lubricating oil is an ester compound, and therefore the oiliness agent has an ester bond. Therefore, the polarity resulting from this ester bond can improve the oil film forming ability of the oiliness agent. This can more effectively reduce friction in the sliding parts of the crankshaft.

[0028] In the hermetic refrigerant compressor having the above configuration, the lubricating oil may have a distillation fraction of 0.1% or more at a distillation temperature of 300°C and an end point of 440°C or more.

[0029] According to the above configuration, a low-viscosity lubricating oil containing high-molecular-weight components contains components with high distillation temperatures. Therefore, even if the temperature of the sliding parts increases by reducing the sliding area, evaporation of the lubricating oil can be effectively avoided or suppressed, and the lubricating oil can more stably form an oil film. This allows for more optimal reduction in friction of the sliding parts of the crankshaft.

[0030] In the hermetic refrigerant compressor having the above configuration, the lubricating oil may contain a sliding property improver in an amount of 100 ppm or more when converted into elemental sulfur weight.

[0031] According to the above configuration, a suitable amount of a sulfur-based sliding property modifier is added to a low-viscosity lubricating oil containing a high-molecular-weight component. This sliding property modifier improves the wear resistance of the sliding surface, thereby promoting low friction in the sliding parts of the crankshaft. Therefore, even when the sliding area is reduced, low friction in the sliding parts can be more effectively achieved.

[0032] In the hermetic refrigerant compressor having the above configuration, the lubricating oil may contain a phosphorus-based extreme pressure additive.

[0033] According to the above configuration, a phosphorus-based extreme pressure additive is added to a low-viscosity lubricating oil containing a high-molecular-weight component. This extreme pressure additive improves the wear resistance of the sliding surface, thereby promoting low friction in the sliding parts of the crankshaft. Therefore, even when the sliding area is reduced, low friction in the sliding parts can be more effectively achieved.

[0034] In the hermetic refrigerant compressor having the above configuration, the lubricating oil may be at least one selected from the group consisting of mineral oil, alkylbenzene oil, and ester oil.

[0035] According to the above-mentioned configuration, although the lubricating oil itself is not particularly limited, at least one of mineral oil, alkylbenzene oil, and ester oil is used as the lubricating oil, which makes it possible to easily reduce the friction coefficient of the shaft portion even when the sliding area is reduced by reducing the viscosity of the lubricating oil and adding a high molecular weight component.

[0036] In the hermetic refrigerant compressor having the above configuration, the electric element may be inverter-driven at a plurality of operating frequencies.

[0037] According to the above configuration, a suitable oil film is formed on the sliding parts by the low-viscosity lubricating oil containing high-molecular-weight components, even during low-speed or high-speed inverter-driven operation. Even with a reduced sliding area, the friction coefficient of the shaft can be effectively reduced. This allows the sliding parts of the crankshaft to have a low friction coefficient and good wear resistance regardless of the operating speed, thereby improving the efficiency and reliability of the hermetic refrigerant compressor.

[0038] The refrigeration / freezing device according to the present disclosure may be configured to include a refrigerant circuit that includes a hermetic refrigerant compressor of the above-described configuration, a radiator, a pressure reducing device, and a heat absorber, and that connects these in a ring shape with piping.

[0039] According to the above configuration, the hermetic refrigerant compressor uses a low-viscosity lubricant oil to reduce the sliding area and has good shaft reliability. By providing a refrigeration / freezing device with such a highly efficient and reliable hermetic refrigerant compressor, the device can reduce its power consumption and achieve high reliability.

[0040] Representative embodiments of the present invention will be described below with reference to the drawings. Note that the same or corresponding elements will be designated by the same reference numerals throughout the drawings, and redundant description will be omitted.

[0041] (Embodiment 1) [Refrigerant compressor configuration] First, a representative configuration example of a hermetic refrigerant compressor according to a first embodiment of the present disclosure will be specifically described with reference to Figures 1 and 2. Figure 1 is a schematic cross-sectional view showing an example of the configuration of a hermetic refrigerant compressor 100 (hereinafter simply referred to as refrigerant compressor 100) according to the first embodiment of the present disclosure. Figure 2 is a schematic side view showing an example of the configuration of a crankshaft 108, which is a shaft part provided in refrigerant compressor 100.

[0042] As shown in Fig. 1, the refrigerant compressor 100 is filled with, for example, R600a as a refrigerant in a sealed container 101, and mineral oil is stored at the bottom as lubricating oil 103. In this disclosure, as the lubricating oil 103, a lubricating oil having a kinematic viscosity of 1 mm at 40°C is used as the lubricating oil, as will be described later. 2 / S~7mm 2 The lubricating oil 103 used in the present embodiment is a lubricating oil having a viscosity of 1000 to 10000 / S, an average mass molecular weight of 150 to 400, and a high molecular weight component of 0.5 mass% or more. The high molecular weight component has a mass molecular weight of 500 or more. In the present embodiment, a low-viscosity mineral oil is used as the lubricating oil 103, but the present invention is not limited to this. For example, as will be described later, an oily substance other than mineral oil may be used, and an oiliness agent or an extreme-pressure additive may be contained.

[0043] Also housed within the sealed container 101 are an electric element 106 and a compression element 107. The electric element 106 is composed of a stator 104 and a rotor 105. The compression element 107 is a reciprocating element driven by the electric element 106, and includes a crankshaft 108, a cylinder block 112, a piston 120, etc.

[0044] 2, crankshaft 108 is made up of main shaft 109 to which rotor 105 is press-fitted and eccentric shaft 110 formed eccentrically with respect to main shaft 109. In the first embodiment, the outer peripheral surface of main shaft 109 of crankshaft 108 includes first sliding surface 111a, second sliding surface 111b, and non-sliding outer peripheral surface 111c. An oil supply pump (not shown) is provided at the lower end of crankshaft 108.

[0045] In the first embodiment, cylinder block 112 is made of, for example, cast iron, and has a substantially cylindrical bore 113 formed therein, as well as a main bearing 114 that supports main shaft 109 of crankshaft 108. The inner peripheral surface of main bearing 114 is in slidable contact with first sliding surface 111a and second sliding surface 111b of the outer peripheral surface of main shaft 109, but is in contact with non-sliding outer peripheral surface 111c.

[0046] 1, the eccentric shaft 110 of the crankshaft 108 is located above the refrigerant compressor 100, and the main shaft 109 is located below the refrigerant compressor 100. Therefore, this up-down positional relationship (direction) will be used when describing the position of the crankshaft 108. For example, the upper end of the eccentric shaft 110 faces the upper inner surface of the sealed container 101, and the lower end of the eccentric shaft 110 is connected to the main shaft 109. The upper end of the main shaft 109 is connected to the eccentric shaft 110, and the lower end of the main shaft 109 faces the lower inner surface of the sealed container 101, and the lower end of the main shaft 109 is immersed in the lubricating oil 103.

[0047] In this disclosure, the term "sliding surface" refers to a surface of the outer circumferential surface of the shaft portion that is in slidable contact with the inner circumferential surface of the bearing portion. Non-sliding outer circumferential surface 111c constitutes part of the outer circumferential surface of main shaft 109, but unlike first sliding surface 111a and second sliding surface 111b, non-sliding outer circumferential surface 111c is a surface that is recessed (or concave) from the sliding surfaces (first sliding surface 111a and second sliding surface 111b) so as not to contact the inner circumferential surface of the bearing portion. In other words, the diameter or radius of the portion of main shaft 109 that becomes the sliding surface is larger than the diameter or radius of the portion that becomes non-sliding outer circumferential surface 111c.

[0048] A piston 120 is inserted into the bore 113 so as to be able to reciprocate, thereby forming a compression chamber 121. The piston pin 115 has, for example, a substantially cylindrical shape, and is disposed parallel to the eccentric shaft 110. The piston pin 115 is engaged in a piston pin hole formed in the piston 120 so as not to be able to rotate.

[0049] The connecting means 117 is made of, for example, an aluminum casting, and includes an eccentric bearing 119 that supports the eccentric shaft 110, and connects the eccentric shaft 110 to the piston 120 via a piston pin 115. The connecting means 117 is also called a connecting rod. The end face of the bore 113 is sealed with a valve plate 122.

[0050] In this disclosure, the main shaft 109 and eccentric shaft 110 of the crankshaft 108 are collectively referred to as the "shaft portion." Also, the main bearing 114 of the cylinder block 112 that supports the main shaft 109 and the eccentric bearing 119 of the connecting means 117 that supports the eccentric shaft 110 are collectively referred to as the "bearing portion."

[0051] The cylinder head 123 forms a high-pressure chamber (not shown) and is fixed to the valve plate 122 on the opposite side to the bore 113. A suction tube (not shown) is fixed to the sealed container 101 and connected to the low-pressure side (not shown) of the refrigeration cycle to guide refrigerant gas into the sealed container 101. A suction muffler 124 is sandwiched between the valve plate 122 and the cylinder head 123.

[0052] Here, the main shaft 109 and main bearing 114 of the crankshaft 108, the piston 120 and bore 113, the piston pin 115 and the connecting rod of the connecting means 117, the eccentric shaft 110 of the crankshaft 108 and the eccentric bearing 119 of the connecting means 117, etc. all form sliding parts with respect to each other.

[0053] In the refrigerant compressor 100 configured as described above, first, electric power is supplied from a commercial power source (not shown) to the electric element 106, causing the rotor 105 of the electric element 106 to rotate. The rotor 105 rotates the crankshaft 108, and the eccentric motion of the eccentric shaft 110 drives the piston 120 via the connecting means 117 and the piston pin 115. The piston 120 reciprocates within the bore 113, sucking in the refrigerant gas that has been introduced into the sealed container 101 via the suction tube through the suction muffler 124 and compressing it in the compression chamber 121.

[0054] The specific driving method of the refrigerant compressor 100 is not particularly limited. For example, the refrigerant compressor 100 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 refrigerant compressor 100, there are times when the refrigerant compressor 100 is operated at low speeds where the amount of oil supplied to each sliding part is reduced, and times when the rpm of the electric element 106 is increased.

[0055] In the refrigerant compressor 100 according to the present disclosure, as will be described later, the sliding areas of the shaft portion and bearing portion (shaft support portion) of the crankshaft 108 are reduced, and as will be described later, the lubricating oil 103 is low-viscosity and contains a high-molecular-weight component. This effectively reduces the friction coefficient of the shaft portion, and therefore the sliding portion of the crankshaft 108 (for example, the main shaft 109) can have a low friction coefficient and good wear resistance regardless of the operating speed, thereby improving the efficiency and reliability of the hermetic refrigerant compressor.

[0056] Of the multiple sliding parts included in the refrigerant compressor 100, the main shaft 109 of the crankshaft 108 is rotatably fitted to the main bearing 114 to form a sliding part. Therefore, for convenience of explanation, the sliding part formed by the main shaft 109 and the main bearing 114 will be referred to as the "main shaft sliding part." Similarly, the eccentric shaft 110 of the crankshaft 108 is rotatably fitted to the eccentric bearing 119 to form a sliding part. Therefore, for convenience of explanation, the sliding part formed by the eccentric shaft 110 and the eccentric bearing 119 will be referred to as the "eccentric shaft sliding part." Furthermore, the "main shaft sliding part" and the "eccentric shaft sliding part" will be collectively referred to as the "shaft sliding part."

[0057] As the crankshaft 108 rotates, the lubricating oil 103 is supplied from the oil supply pump to each sliding part, thereby lubricating each sliding part. The lubricating oil 103 also serves to seal between the piston 120 and the bore 113. In this disclosure, as will be described later, the lubricating oil 103 is low-viscosity and contains high-molecular-weight components. This type of lubricating oil 103 can not only effectively lubricate each sliding part, but also effectively seal between the piston 120 and the bore 113.

[0058] [Configuration of shaft sliding part] Next, an example of a specific configuration of the shaft sliding part according to the present disclosure will be described in detail with reference to Figures 3A to 3C. Figure 3A is a schematic diagram showing an example of the configuration of the crankshaft 108 shown in Figure 2 when the sliding surface is a single surface, and Figures 3B and 3C are schematic diagrams showing an example of the configuration of the crankshaft 108 shown in Figure 2 when the sliding surface is divided into multiple surfaces.

[0059] In the example shown in FIG. 2, the main shaft 109 of the crankshaft 108, which is a shaft portion, has a first sliding surface 111a and a second sliding surface 111b, so it can be said that the sliding surface of the main shaft 109 is divided into multiple surfaces. The configuration of the main shaft 109 shown in FIG. 2, i.e., the configuration in which the sliding surface is divided into two surfaces, corresponds to the schematic diagram shown in FIG. 3B. The shaft portion according to the present disclosure is not limited to this and may have a single surface. For example, as shown in FIG. 3A, the outer peripheral surface of the main shaft 109 may not be divided into multiple sliding surfaces but may have only a single sliding surface 111.

[0060] The specific configuration for dividing the sliding surface into multiple sections is not particularly limited, but typically, a recessed portion recessed (concave) toward the central axis from the sliding surface is formed between the multiple sliding surfaces. As shown in FIGS. 2 and 3B, this recessed portion constitutes the non-sliding outer peripheral surface 111c. The specific shape of the recessed portion is also not particularly limited, and for example, its depth may be any depth as long as it does not affect the rigidity, strength, etc. of the main shaft 109. Similarly, the width of the recessed portion (i.e., the distance between the multiple sliding surfaces) is also not particularly limited, and can be set appropriately depending on the degree to which the width of the sliding surface (sliding area) is narrowed (decreased or reduced).

[0061] When the sliding surface is divided into multiple parts, the number of sliding surfaces is not particularly limited. As shown in FIGS. 2 and 3B, the sliding surface may be divided into two surfaces, a first sliding surface 111a and a second sliding surface 111b. As shown in FIG. 3C, the sliding surface may be divided into three surfaces, a first sliding surface 111d, a second sliding surface 111e, and a third sliding surface 111f. Alternatively, the sliding surface may be divided into four or more surfaces. In the configuration shown in FIG. 3C, a first non-sliding outer peripheral surface 111g, which is a recess similar to the non-sliding outer peripheral surface 111c, is located between the first sliding surface 111d and the second sliding surface 111e. A second non-sliding outer peripheral surface 111h, which is a similar recess, is located between the second sliding surface 111e and the third sliding surface 111f.

[0062] Here, in the shaft portion according to the present disclosure, by setting the ratio of the axial length of the sliding surface to the outer diameter (diameter) of the portion that becomes the sliding surface to a predetermined value or less, the sliding area can be reduced without substantially affecting the wear resistance. Specifically, when the sliding surface is a single surface (for example, refer to FIG. 3A), the axial length of the sliding surface is defined as the single sliding length L. When the sliding surface is divided into a plurality of surfaces (for example, FIGS. 3B or 3C), the axial length of the sliding surface with the minimum axial length is defined as the single sliding length L. And when the outer diameter (diameter) of the portion that becomes the sliding surface in the shaft portion is the outer diameter D, the shaft portion is designed such that the ratio L / D of the single sliding length L to the outer diameter D of the shaft portion is 2.0 or less.

[0063] In FIG. 3A, for the convenience of explaining the outer diameter D and the single sliding length L, the length L (single sliding length L) of the single sliding surface 111 with respect to the outer diameter D is shown enlarged. If it is as shown in this FIG. 3A, the ratio L / D exceeds 2.0. However, actually, for example, by forming a recess (non-sliding outer peripheral surface) in the upper part (eccentric shaft 110 side) or the lower part (lubricating oil 103 side) of the main shaft 109 as viewed from the single sliding surface 111, the ratio L / D can be set to 2.0 or less (L / D≤2.0).

[0064] In FIG. 3B, the sliding surface is divided into a first sliding surface 111a and a second sliding surface 111b. In the example shown in FIG. 3B, the axial length La of the upper first sliding surface 111a is smaller than the axial length Lb of the lower second sliding surface 111b (La < Lb). In this case, since the first sliding surface 111a becomes the "sliding surface with the minimum length", its length La corresponds to the single sliding length L (L = La). In this example, it is sufficient that La / D is 2.0 or less in the first sliding surface 111a (La / D≤2.0).

[0065] In addition, in FIG. 3B as well, similar to FIG. 3A, for the sake of convenience of explanation, the length La of the first sliding surface 111a is shown enlarged with respect to the outer diameter D. Also in this case, by increasing the axial length of the non-sliding outer peripheral surface 111c or providing a non-sliding outer peripheral surface (recess) not shown above the first sliding surface 111a, the ratio L / D can be set to 2.0 or less.

[0066] In FIG. 3C, the sliding surface is divided into a first sliding surface 111d, a second sliding surface 111e, and a third sliding surface 111f. In the example shown in FIG. 3C, the length Le of the second sliding surface 111e in the central part is smaller than the axial length Ld of the upper first sliding surface 111d, and the length Ld is smaller than the length Lf of the lower third sliding surface 111f (Le < Ld < Lf). In this case, since the second sliding surface 111e becomes the "sliding surface with the minimum length", its length Le corresponds to the single sliding length L (L = Le). In this example, it is sufficient if Le / D is 2.0 or less on the second sliding surface 111e (Le / D ≤ 2.0).

[0067] In the present disclosure, the lower limit value of the ratio L / D is not particularly limited. However, as shown in the examples described later (Examples 2 and Comparative Example 3, and see FIG. 6), as an example of a preferable lower limit value, 0.4 or more can be mentioned. Therefore, the preferable range of the ratio L / D in the present disclosure can be within the range of 0.4 to 2.0.

[0068] When the ratio L / D exceeds 2.0, basically the sliding area becomes too large. Therefore, even when a low-viscosity lubricating oil 103 containing a high molecular weight component described later is used, sufficient high efficiency cannot be obtained in the refrigerant compressor 100. On the other hand, if the ratio L / D is less than 0.4, depending on various conditions of the shaft portion, the sliding area may become too narrow. In this case, there is a possibility that the effect of reducing the friction coefficient by the lubricating oil 103 cannot be sufficiently obtained.

[0069] For example, in the examples described below, the friction coefficient is minimal when the ratio L / D is in the range of 0.5 to 0.7, and even when the ratio L / D is less than 0.4, the friction coefficient is similar to that when the ratio L / D is in the range of approximately 1.0 to 1.2 (see FIG. 6). In other words, when the sliding area is narrowed so that the ratio L / D is less than 0.4, the friction coefficient increases to the same extent as when the ratio L / D is in the range of approximately 1.0 to 1.2. Considering the minimal value of the friction coefficient, it is possible to set a ratio L / D of 0.4 or more as a "threshold" that can effectively achieve the effects of narrowing the sliding area and reducing the friction coefficient.

[0070] As mentioned above, depending on the various conditions of the shaft portion (for example, the specific shape and material of crankshaft 108, the specific configuration of compression element 107 including crankshaft 108, etc.), the relationship between ratio L / D and the friction coefficient may shift to a position where the minimum value of the friction coefficient becomes smaller than the range of 0.5 to 0.7. In this case, the lower limit of ratio L / D may be set to less than 0.4.

[0071] On the other hand, in the present disclosure, the upper limit of the ratio L / D is set to 2.0 or less regardless of the various conditions of the shaft portion. Patent Document 2 states that by setting the ratio L / D within the range of 2.0 to 2.5, it is possible to achieve both vibration reduction and suppression of losses within the bearing. However, in the examples described below, the rate of increase in the friction coefficient tends to increase once the ratio L / D exceeds 2.0 (see FIG. 6). This tendency can be interpreted as meaning that if the sliding area becomes too large, the effect of reducing the friction coefficient provided by the lubricating oil 103 (which has a low viscosity and contains high molecular weight components) in the present disclosure cannot be fully exerted (in other words, it can be fully exerted when the sliding area is smaller than before).

[0072] Thus, in the present disclosure, when low-viscosity lubricating oil 103 containing high-molecular-weight components is used, the upper limit of the ratio L / D of crankshaft 108 may be 2.0 or less, and although there is no particular lower limit, a preferable example is 0.4 or more. Although it depends on various conditions, a ratio L / D of 0.4 or more can avoid or suppress the risk of excessive reduction in sliding area.

[0073] Therefore, even when the sliding area is reduced, the oil film formed by the low-viscosity lubricating oil 103 containing high-molecular-weight components effectively prevents a sudden increase in the friction coefficient of the shaft portion, thereby more effectively reducing friction at the sliding portion of the crankshaft 108, thereby favorably achieving high efficiency and wear resistance of the refrigerant compressor 100.

[0074] 3A to 3C, the ratio L / D has been described for the main shaft 109 of the crankshaft 108 as the shaft portion, but the present disclosure is not limited to this and is similarly applicable to the eccentric shaft 110. That is, when the sliding surface of the eccentric shaft 110 with the eccentric bearing 119 is a single surface, and the axial length of the sliding surface is defined as a single sliding length L, or when the sliding surface of the eccentric shaft 110 is divided into multiple surfaces, and the axial length of the sliding surface with the shortest axial length is defined as the single sliding length L, the ratio L / D of the single sliding length L to the outer diameter D of the eccentric shaft 110 may be 2.0 or less.

[0075] Therefore, in the refrigerant compressor 100 according to the present disclosure, it is sufficient that the ratio L / D is 2.0 or less in at least one of the shaft parts, that is, the main shaft 109 and the eccentric shaft 110, and it is sufficient that at least one of the main shaft 109 and the eccentric shaft 110 satisfies this requirement.

[0076] [Lubricant composition] Next, a more specific configuration of the lubricating oil 103 stored in the sealed container 101 will be described in detail.

[0077] The lubricating oil 103 used in the refrigerant compressor 100 according to the present disclosure is a lubricating oil having a kinematic viscosity of 1 mm at 40°C. 2 / S~7mm 2 / S, and has an average mass molecular weight of 150 to 400, and further contains 0.5 mass % or more of a component with a relatively large molecular weight, that is, a high molecular weight component with a mass molecular weight of 500 or more. The specific material of the lubricating oil 103 is not particularly limited, and typically, at least one oily substance selected from the group consisting of mineral oil, alkylbenzene oil, and polyalkylene glycol oil can be suitably used.

[0078] The lubricating oil 103 used in the present disclosure may originally contain high-molecular-weight components, or may be configured to have an oily substance corresponding to the high-molecular-weight components added so that the content is 0.5% by mass or more. An example of the former is mineral oil. When preparing (producing) the lubricating oil 103 by refining unrefined or roughly refined raw mineral oil, the refining conditions or refining method for the raw oil may be adjusted so that 0.5% by mass or more of the high-molecular-weight components remain. An example of the latter is a lubricating oil 103 in which mineral oil, alkylbenzene oil, or polyalkylene glycol oil is used as the "main component" and an oily substance that becomes the high-molecular-weight component is added to this main component as an "additive component."

[0079] The average mass molecular weight of the lubricating oil 103 used in the present disclosure may be within the range of 150 to 400, as described above. If the average mass molecular weight of the lubricating oil 103 is within this range, the aforementioned range of kinematic viscosity at 40°C can be satisfactorily achieved, and when the high molecular weight component is contained in an amount of 0.5 mass% or more, a suitable oil film can be formed even when the sliding area is reduced so that the ratio L / D is 2.0 or less. Furthermore, the average mass molecular weight of the lubricating oil 103 may be within the range of 200 to 300. If the average mass molecular weight of the lubricating oil 103 is within this range, a suitable oil film can be more easily formed when the sliding area is reduced so that the ratio L / D is 2.0 or less, although this depends on various conditions.

[0080] When lubricating oil 103 is configured by adding a high molecular weight component to the main component, the specific material or type of the high molecular weight component is not particularly limited as long as it is an oily substance with a mass molecular weight of 500 or more. For example, when the main component is mineral oil, the high molecular weight component may also be mineral oil, alkylbenzene oil, polyalkylene glycol oil, or another oily substance.

[0081] The method for measuring the average mass molecular weight of the lubricating oil and the mass molecular weight of the high molecular weight component is not particularly limited, but in this disclosure, the standard polystyrene equivalent method using GPC (Gel Permeation Chromatography) used in the examples described below can be used. That is, the average mass molecular weight (weight average molecular weight) of the lubricating oil can be measured as a weight (mass) average molecular weight converted to polystyrene using the GPC method. In addition, whether the mass molecular weight of the high molecular weight component is 500 or more can be determined by measuring a molecular weight distribution graph showing the relationship between differential molar mass distribution and mass molecular weight using the GPC method and determining whether a peak with a mass molecular weight of 500 or more is present.

[0082] The content of the high molecular weight components in the lubricating oil 103 used in the present disclosure may have a lower limit of 0.5 mass %, and the upper limit is not particularly limited as long as it does not affect the function or effect of the lubricating oil 103. According to the examples described later (see Example 3 and FIG. 7), even when the lubricating oil 103 contains only 0.5 mass % of high molecular weight components, the coefficient of performance (COP) of the refrigerant compressor 100 is improved compared to when the lubricating oil 103 does not contain any high molecular weight components (0 mass %).

[0083] Furthermore, according to the examples described later (see Example 3 and FIG. 7), a preferred example of the upper limit of the content of the high molecular weight component is 7.0% by mass or less, more preferably 6.0% by mass or less, and even more preferably 5.0% by mass. Compared to when the lubricating oil 103 does not contain the high molecular weight component (0% by mass), the coefficient of performance is improved even when the high molecular weight component exceeds 7.0% by mass. However, if the content exceeds 7.0% by mass, the effect of improving the coefficient of performance commensurate with the content of the high molecular weight component may not be obtained. Therefore, in the present disclosure, the upper limit of the content of the high molecular weight component is 7.0% by mass or less.

[0084] Furthermore, according to the examples described later, when comparing the coefficient of performance when the content of the high molecular weight component exceeds 6.0% by mass with the coefficient of performance when the content is 6.0% by mass or less, a better coefficient of performance is observed in the range of 6.0% by mass or less. Therefore, in the present disclosure, a preferred upper limit of the content of the high molecular weight component can be 6.0% by mass or less. Furthermore, according to the examples described later, the coefficient of performance reaches a maximum when the content of the high molecular weight component is around 2.0 to 2.5% by mass, and even around 5.0% by mass, the coefficient of performance is similar to the lower limit of the content, 0.5% by mass. Therefore, in the present disclosure, a more preferred upper limit of the content of the high molecular weight component can be 5.0% by mass or less.

[0085] Therefore, the preferred range of the content of the high molecular weight component in the present disclosure is 0.5% to 7.0% by mass, more preferably 0.5% to 6.0% by mass, and even more preferably 0.5% to 5.0% by mass. Depending on the conditions of the refrigerant compressor 100 or the shaft to be lubricated, the maximum value of the coefficient of performance may shift toward a lower or higher content of the high molecular weight component. In this case, the upper limit of the content of the high molecular weight component may be set to a value greater than 7.0% by mass or less than 0.5% by mass.

[0086] If the content of high molecular weight components in lubricating oil 103 is within the above range, it is basically determined that the average mass molecular weight of lubricating oil 103 is within the range of 150 to 400. In other words, if the ratio of high molecular weight components contained in lubricating oil 103 is within the above range, it can be considered that the high molecular weight components have almost no effect on the increase in the average mass molecular weight when viewed as a whole of lubricating oil 103 (the average mass molecular weight of lubricating oil 103 does not exceed 400). Therefore, the upper limit of the content of high molecular weight components in lubricating oil 103 can be set within a range that does not affect the function of lubricating oil 103 and does not excessively increase the average mass molecular weight.

[0087] In the present disclosure, the reason why the coefficient of performance of the refrigerant compressor 100 is improved by the lubricating oil 103 containing a high molecular weight component is that, from the results of the examples described later, the lubricating oil 103 has a low viscosity (a kinematic viscosity of 1 mm at 40°C). 2 / S~7mm 2 This is thought to be because, even if the lubricating oil 103 is in the range of 1 / S, the high molecular weight components contribute to the formation of a good oil film at the sliding part. In other words, the high molecular weight components can be present on the outer peripheral surface (sliding surface) of the main shaft 109 and the inner peripheral surface (sliding surface) of the main bearing 114, which constitute the sliding part, without being involved in the overall flow of the lubricating oil 103 that occurs at the sliding part when the crankshaft 108 slides, and this is thought to result in the good formation of an oil film by the lubricating oil 103.

[0088] In the present disclosure, only one type of oily substance may be used, or two or more types may be used in appropriate combination as the lubricating oil 103. The combination of two or more types of oily substances here includes not only a combination of two or more different oily substances that fall under the category of mineral oil, but also a combination of one or more oily substances that fall under the category of mineral oil with one or more oily substances that fall under the category of alkylbenzene oil (or one or more oily substances that fall under the category of polyalkylene glycol oil).

[0089] Furthermore, when the lubricating oil 103 is a main component to which a high molecular weight component is added as an additive component, for example, one type of oily substance may be used as the main component and one type of oily substance different from the main component as the high molecular weight component. Alternatively, two or more types of oily substances may be used as the main component and one type of oily substance as the high molecular weight component, or one type of oily substance may be used as the main component and two or more types of oily substances as the high molecular weight component. Alternatively, two or more types of mixtures of oily substances in which a high molecular weight component is added to a main component may be further mixed.

[0090] In the present disclosure, the oily substance itself is not particularly limited, but at least one of mineral oil, alkylbenzene oil, and ester oil may be used as the main component or the high molecular weight component (or both) of the oily substance. The lubricating oil 103 obtained thereby can effectively achieve the effect of reducing the friction coefficient of the shaft portion even when the sliding area is reduced.

[0091] The physical properties of the lubricating oil 103 (oily substance or lubricating oil composition) used in the present disclosure are not particularly limited except for the kinematic viscosity at 40°C described above, but an example of a preferred physical property is a distillation characteristic in which the lubricating oil 103 has a distillation fraction of 0.1% or more at a distillation temperature of 300°C and an end point of 440°C or higher. The method for measuring these distillation characteristics is not particularly limited, but in the present disclosure, a measurement method in accordance with JIS K2254:1998 Petroleum products - Distillation test methods or JIS K2601:1998 Crude oil test methods is used.

[0092] In a sliding part consisting of a shaft and a bearing, heat is generated by friction between the sliding surfaces during sliding, and it is known that a momentary high temperature called the flash temperature occurs in the early stages of friction. The outer peripheral surface of the shaft and the inner peripheral surface of the bearing are configured as smooth sliding surfaces to achieve good sliding properties. However, even if the sliding surfaces are smooth macroscopically, minute protrusions exist microscopically. During sliding, the minute protrusions on one sliding surface repeatedly adhere to and break off from the other sliding surface. When the minute protrusions break off, the thermal energy released concentrates, causing a momentary high temperature, which is called the flash temperature.

[0093] For example, Reference 1: JP 2006-097096 A discloses a carburized or carbonitrided bearing steel part, and this Reference 1 states that seizure generally occurs when the flash temperature exceeds approximately 140° C. It is known that the flash temperature in sliding parts can reach several hundred degrees, but in this disclosure, it has been determined that when using a low-viscosity lubricating oil 103 containing high-molecular-weight components, the conditions under which the flash temperature in sliding parts reaches 300° C. or higher are important.

[0094] Therefore, the lubricating oil 103 (oily substance or lubricating oil composition) used in the present disclosure preferably has distillation characteristics such that the distillation fraction (volume fraction) at a distillation temperature of 300°C is 0.1% or more and the end point is 440°C or more. When the distillation characteristics of the lubricating oil 103 satisfy this condition, evaporation of the oil film by the lubricating oil 103 can be effectively suppressed or prevented even if a flash temperature of 300°C or more occurs at the sliding part. Therefore, even if the lubricating oil 103 is a low-viscosity oil containing high-molecular-weight components and the sliding area is reduced, and the temperature of the sliding part increases, the oil film by the lubricating oil 103 can be more stably formed.

[0095] The lubricating oil 103 used in the present disclosure may be a low-viscosity oily substance containing high-molecular-weight components, and various additives may be added to this oily substance. In other words, the lubricating oil 103 used in the present disclosure may be a lubricating oil composition containing components other than the oily substance. As mentioned above, the oily substance used as the lubricating oil 103 may be one type or two or more types, but the use of two or more types of oily substances may also be defined as a "lubricating oil composition." Alternatively, the use of two or more types of oily substances may be defined as a "mixed oil," and the use of components other than the oily substance may be defined as a "lubricating oil composition."

[0096] When the lubricating oil 103 used in the present disclosure is a lubricating oil composition containing components (other components) other than oily substances, the specific other components are not particularly limited, but typical examples include additives known in the field of lubricating oils 103. In particular, in the present disclosure, it is preferable that the lubricating oil 103 contains an oiliness agent. Adding an oiliness agent to the lubricating oil 103 makes it easier for the lubricating oil 103 to form an oil film on the sliding surfaces of the sliding parts. This makes it possible to more effectively achieve low friction in the sliding parts.

[0097] The specific type of oily agent is not particularly limited, but representative examples include higher fatty acids, higher alcohols, esters (ester compounds), ethers, amines, amides, metal soaps, etc. These oily agents may be used alone or in combination of two or more. The amount of oily agent added is not particularly limited, but may be, for example, in the range of 0.01 to 1% by weight.

[0098] In the present disclosure, an ester-based compound can be mentioned as a more preferred oily agent. The ester-based compound may be a compound having an ester structure obtained by reacting an alcohol with a carboxylic acid. The alcohol may be a monohydric alcohol or a polyhydric alcohol having two or more hydric groups. Similarly, the carboxylic acid may be a monocarboxylic acid, a dicarboxylic acid, or a tricarboxylic acid (which may have four or more carboxy groups). Generally, commercially available ester-based oily agents can be suitably used.

[0099] As described above, the lubricating oil 103 used in the present disclosure is a low-viscosity lubricating oil containing high-molecular-weight components. However, if such lubricating oil 103 is a lubricating oil composition containing an oiliness agent, the oil film formation ability can be further improved. As described above, since the lubricating oil 103 used in the present disclosure contains high-molecular-weight components, the high-molecular-weight components are present on the sliding surfaces of the main shaft 109 and main bearing 114, which form the sliding part, and it is believed that this enables the formation of a good oil film. Furthermore, since the lubricating oil 103 contains an oiliness agent, this oiliness agent is adsorbed to the sliding surfaces of the main shaft 109 and main bearing 114, which is believed to further facilitate the formation of an oil film by the lubricating oil 103 (lubricating oil composition).

[0100] In particular, if the oiliness agent is an ester compound, the oiliness agent will have an ester bond. Therefore, the polarity resulting from this ester bond can make it easier for the oil film of the lubricating oil 103 (lubricating oil composition) to adhere to the sliding parts (improve the adhesion of the oil film). This further improves the oil film forming ability of the lubricating oil 103, thereby further reducing the friction coefficient and more effectively achieving low friction on the sliding parts.

[0101] The lubricating oil 103 used in the present disclosure may contain, as an additive, a sulfur-based sliding property modifier in addition to the oiliness agent described above. Examples of sulfur-based sliding property modifiers include those capable of reacting with sulfur and the material used in the shaft portion (shaft portion material). Therefore, the sliding property modifier may be sulfur itself, or a sulfur compound containing sulfur and capable of reacting with the shaft portion material.

[0102] In the present disclosure, an iron-based material is used as the material for the shaft portion, and therefore examples of sulfur compounds that can be used as sliding property modifiers include sulfurized olefins, sulfide compounds (e.g., dibenzyl (di)sulfide (DBDS)), xanthates, thiadiazoles, thiocarbonates, sulfurized oils and fats, sulfurized esters, dithiocarbamates, and sulfurized terpenes.

[0103] The content of the sulfur-based sliding properties modifier in lubricating oil 103 is not particularly limited, but preferably the sliding properties modifier is added to lubricating oil 103 so that the content is 100 ppm or more when converted to elemental sulfur weight. There is no particular upper limit to the amount of sliding properties modifier added, as long as it does not affect the physical properties of lubricating oil 103 (lubricating oil composition) (for example, 1000 ppm or less).

[0104] As described above, the lubricating oil 103 used in the present disclosure is a low-viscosity lubricating oil containing high-molecular-weight components, but if such lubricating oil 103 is a lubricating oil composition containing a sliding property modifier in addition to an oiliness agent, the sliding property modifier can improve the wear resistance of the sliding surface. Therefore, even if the sliding area is reduced, low friction of the sliding part can be more suitably achieved.

[0105] The lubricating oil 103 used in the present disclosure may contain known extreme-pressure additives in addition to the oiliness agents and sliding property improvers described above. Specific extreme-pressure additives that can be used suitably include known additives, and are not particularly limited. Examples include phosphorus-based compounds such as phosphate esters, and halogenated compounds such as chlorinated hydrocarbons or fluorinated hydrocarbons. Only one type of these extreme-pressure additives may be added to the lubricating oil composition (lubricating oil 103), or two or more types may be added in appropriate combination.

[0106] Among these extreme pressure additives, phosphorus-based compounds are preferably used. Typical phosphorus-based compounds include tricresyl phosphate (TCP), tributyl phosphate (TBP), and triphenyl phosphate (TPP), with TCP being more preferably used. By adding a phosphorus-based extreme pressure additive to the lubricating oil 103 in addition to a sulfur-based sliding property modifier, it is possible to achieve good wear reduction in the sliding parts of the shaft.

[0107] The amount of the extreme pressure additive added to the lubricating oil composition is not particularly limited. For example, when the main component of the lubricating oil 103 is a low-polarity substance such as mineral oil or alkylbenzene oil, a suitable amount to be added is in the range of 0.5 to 8.0% by weight, and a more preferred range is 1 to 3% by weight.

[0108] As described above, the lubricating oil 103 used in this disclosure is a low-viscosity lubricating oil containing high-molecular-weight components. However, if such a lubricating oil 103 is a lubricating oil composition containing an extreme-pressure additive in addition to an oiliness agent, the extreme-pressure additive can improve the wear resistance of the sliding surface. In particular, if both a sliding property modifier and an extreme-pressure additive are contained, the synergistic effect can further reduce wear on the sliding surface. Therefore, even when the sliding area is reduced, low friction of the sliding part can be more effectively achieved.

[0109] Additionally, in the refrigerant compressor 100 according to the present disclosure, various known additives other than the oiliness agent, the sliding property improver, and the extreme pressure additive may be added to the lubricating oil 103. As such additives, various additives known in the field of lubricating oil 103 can be suitably used, and representative examples include antioxidants, acid scavengers, metal deactivators, antifoaming agents, corrosion inhibitors, dispersants, etc.

[0110] In other words, the lubricating oil 103 used in the refrigerant compressor 100 used in the present disclosure may be a low-viscosity oily substance containing a high-molecular-weight component (which may be one type or a mixture of two or more types of oil), and preferably a lubricating oil composition in which an oily substance has been added with an oiliness agent (composed of an oily substance and an oiliness agent). Another preferred example is a lubricating oil composition that contains a sliding property improver or an extreme-pressure additive, or both, as additives.

[0111] As described above, in the refrigerant compressor 100 according to the present disclosure, (1) the lubricating oil 103 is a lubricating oil having a kinematic viscosity of 1 mm at 40°C. 2 / S~7mm 2 The lubricating oil 103 satisfies the following conditions: (1) the lubricating oil 103 has a mass average molecular weight of 150 to 400 and contains 0.5 mass % or more of a high-molecular-weight component having a mass average molecular weight of 500 or more; and (2) the ratio L / D of the single sliding length L to the outer diameter D of the shaft portion is 2.0 or less. The condition (2) applies whether the sliding surface of the shaft portion is a single surface or multiple surfaces, as long as the ratio L / D is 2.0 or less. In addition to the conditions (1) and (2), a preferable example may also satisfy the condition (3) that the lubricating oil 103 contains an oiliness agent (especially an ester-based agent).

[0112] As a result, even if the viscosity of the lubricating oil 103 is reduced and the sliding area is reduced so that the ratio L / D is 2.0 or less, a good oil film of the lubricating oil 103 can be formed at the sliding portion between the shaft portion and the bearing portion due to the high molecular weight component having a mass molecular weight of 500 or more. This reduces the friction coefficient of the sliding portion and effectively suppresses wear of the sliding portion. This improves the reliability of the shaft portion supported by the bearing portion. As a result, the efficiency and reliability of the refrigerant compressor 100 can be further improved.

[0113] As described above, the refrigerant compressor 100 according to the present disclosure may be inverter-driven at a plurality of operating frequencies. In inverter drive, the electric element 106 may be operated at a low rotation speed (low-speed operation) or a high rotation speed (high-speed operation). When operated at a low rotation speed, the amount of lubricating oil 103 supplied to the sliding shaft portion decreases. In the present disclosure, the sliding area of ​​the sliding shaft portion is reduced, but high efficiency and good wear resistance can be achieved even when the amount of lubricating oil 103 supplied decreases.

[0114] Furthermore, good wear resistance can be achieved even when the rotation speed changes from low to high (when the rotation speed of the electric element 106 increases). Therefore, an oil film derived from the component having a mass molecular weight of 500 or more and the ester-based oily agent can be formed on the sliding portion of the shaft, even during low-speed or high-speed operation in inverter drive. As a result, the reliability of the refrigerant compressor 100 can be improved, and the operating efficiency can also be improved.

[0115] (Embodiment 2) In the present second embodiment, an example of a refrigeration / freezing device including the refrigerant compressor 100 described in the first embodiment will be specifically described with reference to Fig. 4. Fig. 4 schematically shows the general configuration of a refrigeration / freezing device including the refrigerant compressor 100 according to the first embodiment. Therefore, in the present second embodiment, only the general outline of the basic configuration of the refrigeration / freezing device will be described.

[0116] As shown in Fig. 4, the refrigeration / freezing device according to the second embodiment includes a main body 275, a partition wall 278, a refrigerant circuit 270, and the like. The main body 275 is composed of a heat-insulating box and a door, and the box has one side open, and the door opens and closes the opening of the box. The interior of the main body 275 is partitioned by the partition wall 278 into an item storage space 276 and a machine room 277. A blower (not shown) is provided in the storage space 276. The interior of the main body 275 may be partitioned into spaces other than the storage space 276 and the machine room 277.

[0117] Refrigerant circuit 270 is configured to cool the inside of storage space 276, and includes, for example, refrigerant compressor 100 described in the first embodiment, a radiator 272, a pressure reducing device 273, and a heat absorber 274, which are connected in a ring shape by piping. Heat absorber 274 is disposed in storage space 276. The cooling heat of heat absorber 274 is agitated by a blower (not shown) so as to circulate within storage space 276, as indicated by the dashed arrows in FIG. 4. This cools the inside of storage space 276.

[0118] As described in the first embodiment, the refrigerant compressor 100 provided in the refrigerant circuit 270 uses, as the lubricating oil 103, a lubricating oil having a kinematic viscosity of 1 mm at 40°C. 2 / S~7mm 2 The present invention satisfies the following conditions: (1) the average mass molecular weight of the refrigerant compressor 100 is 150 to 400, and ... refrigerant compressor 100 contains 0.5 mass % or more of a high molecular weight component having a mass molecular weight of 500 or more; (2) the ratio L / D of the single sliding length L to the outer diameter D of the shaft portion is 2.0 or less; and preferably (3) the use of an ester-based oil agent. This makes it possible to improve the efficiency of the refrigerant compressor 100 and further improve its reliability.

[0119] As described above, the refrigeration / freezer according to the second embodiment is equipped with the refrigerant compressor 100 according to the first embodiment. In this refrigerant compressor 100, low viscosity lubricant oil 103 is used to reduce (lower) the sliding area of ​​the shaft sliding parts, and the shaft has good reliability. By providing the refrigeration / freezer with such a highly efficient and reliable hermetic refrigerant compressor, the power consumption of the refrigeration / freezer can be reduced and reliability can be improved. [Example]

[0120] The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited thereto. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention.

[0121] (lubricant and refrigerant compressor) In the following examples, a low-viscosity lubricating oil 103 (lubricating oil 103 in this example) containing a high-molecular-weight component with a mass molecular weight of 500 or more was used, and the kinematic viscosity at 40°C was 2.7 mm. 2 / S, and a mineral oil containing 2.0 mass % of high molecular weight components was used except for Example 3. In lubricating oil 103 of this example, both the main component and the high molecular weight component are mineral oils.

[0122] In the following examples and comparative examples, a reciprocating compressor TKD91E (product name, manufactured by Panasonic Corporation) was used as the refrigerant compressor 100.

[0123] Example 1 The molecular weight distribution of the lubricating oil 103 of this example was measured by GPC. The results are shown in Figure 5A. In the molecular weight distribution graph of Figure 5A, the vertical axis represents the differential molar mass distribution (dW / dlogM) and the horizontal axis represents the mass molecular weight. The GPC conditions were as follows: a differential refractive index detector (RI) was used as the detector, a column with a diameter of 6.0 mm and a length of 15 cm was used, tetrahydrofuran (THF) was used as the solvent, and monodisperse polystyrene was used as the standard sample; the flow rate was 0.45 mL / min and the column temperature was 40 °C.

[0124] (Comparative Example 1) The molecular weight distribution of a conventional lubricant (manufactured by JXTG Nippon Oil & Energy Corporation, product name FREOL S3) was measured by GPC in the same manner as in Example 1. The results are shown in Figure 5B. Note that in the molecular weight distribution graph of Figure 5B, as in Figure 5A, the vertical axis represents the differential molar mass distribution (dW / dlogM) and the horizontal axis represents the mass molecular weight.

[0125] (Comparative Example 2) The molecular weight distribution of only the high molecular weight components contained in lubricating oil 103 of this example was measured by GPC in the same manner as in Example 1. The results are shown in Figure 5C. Note that in the molecular weight distribution graph of Figure 5C, as in Figure 5A, the vertical axis represents the differential molar mass distribution (dW / dlogM) and the horizontal axis represents the mass molecular weight.

[0126] Example 2 The lubricating oil 103 of this embodiment (see Example 1) was used in the refrigerant compressor 100, and the ratio L / D of the crankshaft 108 was varied within a range of 0.3 to 2.5 to evaluate the coefficient of friction of the sliding parts. The results are shown by the solid line in Figure 6. In the graph of Figure 6, the vertical axis represents the coefficient of friction and the horizontal axis represents the ratio L / D. The coefficient of friction of the sliding parts of the crankshaft 108 was measured by a friction force measurement method using a load cell.

[0127] (Comparative Example 3) The coefficient of friction of the sliding parts was evaluated by using a conventional lubricating oil (see Comparative Example 1) in the refrigerant compressor 100 and varying the L / D ratio of the crankshaft 108 within the range of 0.3 to 2.5. The results are shown by the dashed line in Figure 6.

[0128] Example 3 The content of high molecular weight components in the lubricating oil 103 of this example was varied within a range of 0% by mass to approximately 8% by mass, and the coefficient of performance of the refrigerant compressor 100 was evaluated. The results are shown in Figure 7. In the graph of Figure 7, the vertical axis represents the coefficient of performance, and the horizontal axis represents the content of high molecular weight components. The coefficient of performance (COP) is the ratio of refrigeration capacity to consumed energy (input) (refrigeration capacity / input).

[0129] (Comparison between Examples and Comparative Examples) As is clear from a comparison of Figures 5A to 5C, the lubricating oil 103 of this embodiment contains 0.5 mass% or less of high molecular weight components corresponding to Figure 5C, as shown by the block arrow in Figure 5A, while conventional lubricating oils do not contain high molecular weight components.

[0130] In the refrigerant compressor 100 using the lubricating oil 103 of this embodiment, a good friction coefficient can be achieved when the ratio L / D is 2.0 or less, as shown by the solid line in Figure 6. On the other hand, in the refrigerant compressor 100 using a conventional lubricating oil, the friction coefficient is higher overall regardless of changes in the ratio L / D than when the lubricating oil 103 of this embodiment is used, as shown by the dashed line in Figure 6. In other words, it can be seen that the refrigerant compressor 100 using the lubricating oil 103 of this embodiment can reduce the friction coefficient compared to the conventional lubricating oil, and can reduce the friction coefficient of the sliding parts particularly under conditions where the ratio L / D is 2.0 or less (conditions where the sliding area is reduced).

[0131] Furthermore, in the refrigerant compressor 100 using the lubricating oil 103 of this embodiment, as shown in Figure 7, it can be seen that the coefficient of performance can be effectively reduced by including at least 0.5 mass% or more of high molecular weight components in the lubricating oil 103.

[0132] Thus, the hermetic refrigerant compressor according to the present disclosure includes a sealed container for storing lubricating oil, an electric element housed in the sealed container, and a compression element driven by the electric element for compressing a refrigerant, and the lubricating oil has a kinematic viscosity of 1 mm at 40°C. 2 / S~7mm 2 / S, and has an average mass molecular weight of 150 to 400, and contains 0.5 mass% or more of a high molecular weight component, the high molecular weight component having a mass molecular weight of 500 or more, the compression element includes a crankshaft having a main shaft and an eccentric shaft as a shaft portion, and a main bearing supporting the main shaft and an eccentric bearing supporting the eccentric shaft as a bearing portion supporting the shaft portion, the sliding surface of the main shaft with the main bearing being a single surface or being divided into multiple surfaces, and when the sliding surface is a single surface, when the axial length of the sliding surface is defined as a single sliding length L, or when the sliding surface is divided into multiple surfaces, when the axial length of the sliding surface with the shortest axial length is defined as the single sliding length L, the ratio L / D of the single sliding length L to the outer diameter D of the main shaft is 2.0 or less.

[0133] According to this configuration, whether the sliding surface of the main shaft of the crankshaft is a single surface or multiple surfaces, the ratio L / D of the single sliding length L to the outer diameter D is 2.0 or less, and even if the lubricating oil used is lower in viscosity, the average molecular weight of the lubricating oil is within a predetermined range, and the lubricating oil contains 0.5 mass% or more of a high-molecular-weight component with a relatively high molecular weight. This allows for a suitable oil film to be formed even with a low-viscosity lubricating oil due to the high-molecular-weight component, even when the sliding area is reduced so that the ratio L / D is 2.0 or less. As a result, even when a lower-viscosity lubricating oil and a bearing with a reduced sliding area are used, the friction coefficient of the shaft supported by the bearing can be reduced. This effectively reduces friction in the sliding parts of the crankshaft, resulting in a hermetic refrigerant compressor that is both highly efficient and reliable.

[0134] From the above description, many modifications and other embodiments of the present invention will be apparent to those skilled in the art. Therefore, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure and / or function thereof may be substantially changed without departing from the spirit of the present invention.

[0135] Furthermore, the present invention is not limited to the description of the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments or multiple modified examples are also included in the technical scope of the present invention. [Industrial Applicability]

[0136] As described above, the present invention provides a highly efficient and reliable refrigerant compressor that uses low-viscosity lubricating oil, and a freezing / refrigeration device that uses this refrigerant compressor. Therefore, the present invention can be widely applied to various devices that use a refrigeration cycle. [Explanation of symbols]

[0137] 100: Refrigerant compressor 101: Airtight container 103: Lubricating oil 106:Electric element 107: Compression element 108: Crankshaft 109: Main shaft (shaft part) 110: Eccentric shaft (shaft) 111: Single sliding surface 111a: First sliding surface 111b: Second sliding surface 111c: Non-sliding outer peripheral surface 111d: First sliding surface 111e: Second sliding surface 111f: Third sliding surface 111g: First non-sliding outer surface 111h: Second non-sliding outer surface 112: Cylinder block 114: Main bearing (bearing part) 119: Eccentric bearing (bearing part) 270: Refrigerant circuit 272: Heat sink 273: Pressure reducing device 274: Heat absorber

Claims

1. The compressor includes a sealed container that stores lubricating oil, an electric element housed in the sealed container, and a compression element that is driven by the electric element and compresses a refrigerant, The compression element is a crankshaft having a main shaft and an eccentric shaft as a shaft portion; The bearing portion supporting the shaft portion includes a main bearing supporting the main shaft and an eccentric bearing supporting the eccentric shaft, a sliding surface of the main shaft with respect to the main bearing is divided into a total of two surfaces, i.e., a first sliding surface and a second sliding surface, via a non-sliding outer peripheral surface that is recessed so as not to come into contact with an inner peripheral surface of the bearing portion, When the axial length of the sliding surface having the shortest axial length among the first sliding surface and the second sliding surface is defined as a single sliding length L, a ratio L / D of the single sliding length L to the outer diameter D of the main shaft is 2.0 or less; The lubricating oil has a kinematic viscosity of 1 mm at 40°C. 2 / S to 7mm 2 / S, and the average mass molecular weight is 150 to 400, Furthermore, the lubricating oil contains 0.5 mass % or more of a high molecular weight component having a mass molecular weight of 500 or more, and the upper limit of the average mass molecular weight of the high molecular weight component does not exceed 400. Hermetic refrigerant compressor.

2. The ratio L / D is 0.4 or more.

2. The hermetic refrigerant compressor according to claim 1.

3. The lubricating oil is characterized in that it contains an oiliness agent.

3. The hermetic refrigerant compressor according to claim 1 or 2.

4. The oily agent is an ester compound.

4. The hermetic refrigerant compressor according to claim 3.

5. The lubricating oil is characterized in that its distillation fraction at a distillation temperature of 300°C is 0.1% or more and its end point is 440°C or more.

5. The hermetic refrigerant compressor according to claim 1 or 4.

6. The lubricating oil contains a sliding property improver in an amount of 100 ppm or more when converted to sulfur element weight. The hermetic refrigerant compressor according to any one of claims 1 to 5.

7. The lubricating oil is characterized in that it contains a phosphorus-based extreme pressure additive. The hermetic refrigerant compressor according to any one of claims 1 to 6.

8. The lubricating oil is at least one selected from the group consisting of mineral oil, alkylbenzene oil, and ester oil. The hermetic refrigerant compressor according to any one of claims 1 to 7.

9. The electric element is inverter-driven at a plurality of operating frequencies.

9. The hermetic refrigerant compressor according to claim 1.

10. A refrigerant circuit including the hermetic refrigerant compressor according to any one of claims 1 to 9, a radiator, a pressure reducing device, and a heat absorber, and these are connected in a ring shape by piping. Refrigeration and freezing equipment.

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