JP2011021530A - Reciprocating compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high reliability and long life reciprocating compressor using a bearing material, which prevents wear and seizure in a bearing of a compressor in boundary lubrication conditions under which the oil film is temporarily thin and mixed lubrication conditions and has high wear resistance and high seizure resistance, in a reciprocating compressor using low viscosity oil as lubricating oil. <P>SOLUTION: A sliding portion is formed of a ball provided to a connecting rod and a ball receiving hole provided to the piston which are slidably ball-jointed to each other in an reciprocating compressor converting the rotation of a motor to reciprocating motion of the piston in a cylinder by the crank mechanism. Lubricating oil is then supplied to the sliding portion ball-jointed. The piston and the connecting rod, which are made of an iron-based sintered material containing iron as a main component, are respectively subjected to a steam treatment. A steam layer is removed from the piston surface by cutting. The connecting rod is subjected to a nitriding treatment after the steam treatment. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a reciprocating compressor, and is a hermetic refrigerant compressor used for a refrigerator, an air conditioner, etc., and particularly a reciprocating compressor excellent in wear characteristics of a bearing portion of a piston when a low-viscosity lubricating oil is used. About.

  In recent years, refrigerants in the refrigeration cycle have shifted from HFC (hydrofluorocarbon) to natural refrigerants from the viewpoint of global environmental conservation. In particular, with respect to hydrocarbon refrigerants, R600a (isobutane) is already used in refrigerators from the viewpoint of a low global warming potential.

  On the other hand, lubricating oil is used in a refrigerant compressor and plays a role of lubrication, sealing, cooling, insulation, etc. of the sliding part. In recent years, compressors are required to save energy, reduce size, reduce noise, and increase efficiency, and accordingly, lubricating oil tends to have a low viscosity. For this reason, the compressor is required to ensure the reliability of the sliding portion.

As disclosed in Patent Document 1, the ball joint structure of the reciprocating compressor piston and connecting rod is subjected to steam treatment on the iron-based sintered metal piston, and black tetroxide is formed on the holes and on the surface. Structures that form iron (Fe ₃ O ₄ ) are known.

  Further, as disclosed in Patent Document 2, as a ball joint structure of a piston and a connecting rod of a compressor, nitriding treatment and manganese phosphate treatment are applied to a spherical receiving hole (ball receiving hole) and / or a ball portion. A structure using a high carbon chromium steel material for the ball portion is known.

JP-A-2005-113842 JP 2003-214343 A

  Patent Document 1 employs a structure in which a piston and a connecting rod are connected by a ball joint method. As a piston connected to the piston rod of the reciprocating compressor, an unnecessary portion is removed by machining such as cutting before forming an oxide film on the spherical surface, and then steam treatment is performed. After that, finish machining is performed as necessary. Thereby, it becomes possible to suppress the roughness of the situation accompanying processing, and the movement of the piston rod can be made smooth, so that the compression efficiency of the compressor can be improved.

  However, the reliability of the sliding portion between the piston having the oxide film on the sintered metal and the counterpart material piston rod is not considered for the low-viscosity oil whose use tends to be expanded in the future. That is, when a low-viscosity oil is used as a lubricant, it is difficult to form an oil film, so it is expected that the friction / wear characteristics between the oxide film formed on the sintered metal and the counterpart material will deteriorate.

  Also, Patent Document 2 adopts a structure in which a piston and a connecting rod are connected by a ball joint method, and a ball seat provided on the piston is molded by plastic working. In this Patent Document 2, there is a structure that may cause a problem in sliding between the piston and the connecting rod. That is, in order to ensure a connection state, since it processes in the direction which closes a ball seat part, the channel | path of the lubricating oil supplied to a connection part becomes narrow, and lubricating oil may not fully be supplied. Therefore, the lubricating oil cannot be sufficiently supplied to the connecting portion, which may cause a temperature rise and damage to the spherical bearing portion.

  Therefore, in a reciprocating compressor using isobutane, which is a natural refrigerant, and low-viscosity oil as a lubricant, boundary lubrication and mixed lubrication may occur temporarily when the low-viscosity oil is used. In order to provide a highly reliable and long-life refrigerant compressor using a bearing material having high wear resistance and seizure resistance, which prevents wear and seizure in the bearing portion of the machine, a conventional refrigerant compressor Compared to the above, a highly reliable hermetic refrigerant compressor with improved wear resistance of the sliding portion is desired.

  The present invention has been made to solve the above-described problems, and its purpose is to perform compression in a boundary lubrication and mixed lubrication state where the oil film is temporarily thin in a reciprocating compressor using low-viscosity oil as a lubricant. An object of the present invention is to provide a highly reliable and long-life reciprocating compressor using a piston / rod having high wear resistance and seizure resistance that prevents wear and seizure in the piston / rod portion of the machine.

The reciprocating compressor of the present invention is configured as follows.
(1) In a reciprocating compressor that converts rotation of an electric motor into reciprocating motion of a piston in a cylinder by a crank mechanism, the crank mechanism includes a crankshaft, a crankpin that changes the rotation of the crankshaft to eccentric motion, and the crankpin A sliding portion in which one end is inserted into the connecting rod and the other end is connected to the piston, and a ball provided in the connecting rod and a ball receiving hole provided in the piston are slidably ball-jointed. And a low-viscosity lubricating oil is supplied to the ball-joined sliding portion, and the piston and the connecting rod are iron-based sintered materials mainly containing iron, and the piston and the connecting rod Each of the pistons is subjected to steam treatment, and the piston surface is cut to remove the steam layer and Has a structure subjected to nitriding treatment after steaming.

Thereby, while being able to avoid the sliding form of the same kind material, a hardness difference can be provided in a sliding part and a friction and wear characteristic improves.
(2) Moreover, the iron-based sintered material of the piston can ensure the strength of the sintered material by setting the density to 6 to 7.5 g / cm ³ .
(3) Further, in the iron-based sintered material of the piston, the ratio of the steam film remaining in the pores after removing the steam layer by cutting to the base material is 10 to 30%. As a result, the piston becomes a composite structure of a hard base material portion and a hard oxide film, and a hardness difference can be imparted at the sliding portion, thereby improving the friction and wear characteristics.
(4) In addition, the iron-based sintered material of the piston can have stable friction / wear characteristics when the surface roughness after cutting is Ra 1.0 μm or less.
(5) Moreover, it is a reciprocating compressor which compresses a refrigerant | coolant, Comprising: By using R600a as said refrigerant | coolant and polyol ester oil as said lubricating oil, the friction and wear characteristic of a sliding part improves.
(6) Moreover, when the viscosity of the lubricating oil is 3 to 10 mm ² / S at a kinematic viscosity at 40 ° C., the friction and wear characteristics of the sliding portion are stabilized.

  Furthermore, as a configuration of the refrigeration apparatus, at least the reciprocating compressor having the above-described configuration is used in a refrigeration apparatus that performs refrigeration by a refrigeration cycle including a compressor, a condenser, an expansion mechanism, an evaporator, and a refrigerant pipe that connects these. Mount.

  As described above, according to the present invention, even when the sliding member such as the piston or the rod is in the boundary lubrication or mixed lubrication state in which the oil film is thin, a sliding characteristic with a stable friction coefficient can be obtained and wear can be reduced. In addition, although the example which cuts the steam layer of a piston and performs the nitriding process of a connecting rod was demonstrated above, the same effect is acquired even when the nitriding process is performed to a piston and the cutting process of a connecting rod is performed.

  According to the present invention, in a reciprocating compressor using low-viscosity oil as a lubricant, wear and seizure in a piston / rod portion of a compressor that is temporarily in a boundary lubrication and mixed lubrication state where an oil film is thin, A highly reliable and long-life reciprocating compressor using a piston / rod having high wear resistance and seizure resistance can be provided.

It is sectional drawing of the hermetic refrigerant compressor concerning one embodiment of the present invention. FIG. 3 is a diagram showing an inner side of a piston 4 as viewed from a rotor shaft 7. It is AA sectional drawing of FIG. FIG. 3 is a cross-sectional view taken along the line BB in FIG. 2. 2 is a perspective view of a connecting rod 2. FIG. It is a perspective view which shows a rotation stopper. It is a perspective view of a ball joint structure. It is a perspective view which shows a mode when piston 4 reciprocates. It is a photograph of the sintered material of the piston as it is fired. It is the photograph with the steam processing of the sintered material of a piston. It is the photograph after the lapping after the steam processing of the sintered material of the piston. It is a cross-sectional photograph after the steam processing of the sintered material of the piston. It is a schematic diagram of the cross section after the steam process of the sintered material of a piston. It is the photograph of the cut surface cut after the steam processing of the sintered material of the piston. It is the schematic diagram of the cut surface cut after the steam process of the sintered material of a piston. It is a refrigerating cycle block diagram of a freezing apparatus. 6 is a graph showing a relationship between a test time and a friction coefficient in a wear test of Comparative Example 1. 6 is a graph showing a relationship between a test time and a friction coefficient in a wear test of Comparative Example 2. 6 is a graph showing a relationship between a test time and a friction coefficient in a wear test of Comparative Example 3.

  Hereinafter, embodiments according to the present invention will be described with reference to FIGS.

First, the overall structure of a hermetic refrigerant compressor according to an embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a cross-sectional view of a hermetic refrigerant compressor according to an embodiment of the present invention.

  This refrigerant compressor is a reciprocating type (reciprocating type) in which a piston 4 reciprocates in a cylinder 1 integrally formed with a bearing 1a and a frame 1b provided in a sealed case that also serves as an oil sump to realize a compression function. ) Compressor.

  At the lower part of the frame 1b, a stator 5 and a rotor 6 constituting an electric motor are provided as electric elements, and a crankpin 7a is provided at a position eccentric from the rotation center of the crankshaft 7.

  The crankshaft 7 extends through the bearing portion 1a of the frame and extends from the lower portion to the upper portion of the frame 1b, and the crankpin 7a is provided so as to be positioned above the frame 1b. The lower portion of the crankshaft 7 is directly connected to the rotor 6, and the crankshaft 7 is rotated by the power of the electric motor. The crankpin 7a and the piston 4 are connected by a connecting rod 2, and the rotation of the crankshaft is changed to an eccentric motion of the crankpin 7a, and the piston 4 reciprocates via the crankpin 7a and the connecting rod 2. It has a configuration.

  As described above, the hermetic refrigerant compressor according to the present embodiment stores the compression elements such as the cylinder 1 and the piston 4 and the elements such as the electric motor in the hermetic container, and the crankshaft 7 rotates the electric elements from the electric element. It presupposes a structure that conveys power.

Next, details of the structure of each part of the hermetic refrigerant compressor according to the embodiment of the present invention will be described with reference to FIGS.
FIG. 2 is a view showing the internal side of the piston 4 as viewed from the rotor shaft 7.
3 is a cross-sectional view taken along the line AA in FIG.
4 is a cross-sectional view taken along the line BB in FIG.
FIG. 5 is a perspective view of the connecting rod 2.
FIG. 6 is a perspective view showing a detent.
FIG. 7 is a perspective view of the ball joint structure.
FIG. 8 is a perspective view showing a state when the piston 4 reciprocates.

  As shown in FIG. 2, the piston 4 has a ball receiving portion (inner spherical surface) 4a. The ball receiving portion (inner spherical surface) 4a of the piston 4 is shaped to wrap at an angle of 180 degrees or more from the tip of the ball (outer spherical surface) 2a of the connecting rod 2 in the AA cross section shown in FIG. The cross section taken along the line B-B shown in FIG. 2 wraps the ball (outer spherical surface) 2a only at an angle of 180 degrees or more from the tip of the ball (outer spherical surface) 2a of the connecting rod 2. Accordingly, the ball joint structure has a sliding area smaller than that of the AA cross section, and the path through which the lubricating oil passes is short, so that the lubricating oil can easily flow and the lubricating oil can be sufficiently supplied.

  As shown in FIG. 5 and FIG. 8, the connecting rod 2 includes a ball (outer spherical surface) 2a into which a ball receiving portion (inner spherical surface) 4a of the piston 4 is inserted, and a crank bearing portion 2b into which a crank pin 7a is inserted, It is comprised from the rod part 2c which connects the ball | bowl (outer spherical surface) 2a and the crank bearing part 2b. The oil supply hole 2d is provided so as to penetrate the inside of the ball (outer spherical surface) 2a and the rod portion 2c. Lubricating oil flows through the oil supply hole 2d and is supplied from the crank bearing portion 2b to the sliding portion of the ball (outer spherical surface) 2a. The ball (outer spherical surface) 2a has a structure in which a part of the spherical surface is cut out similarly to the ball receiving portion (inner spherical surface) 4a of the piston 4, and has a cutout portion 2f. Therefore, the route through which the lubricating oil passes is short by the amount of the notch 2f, and the lubricating oil can easily flow and the lubricating oil can be supplied sufficiently.

  The connecting rod 2 prevents the ball (outer spherical surface) 2a from rotating off so that the ball (outer spherical surface) 2a ball-joined by the detent 10 shown in FIG. 6 does not fall out of the ball receiving hole (inner spherical surface) 4a. FIG. 7 shows a ball joint structure with a detent 10.

  The rotation of the ball (outer spherical surface) 2a with respect to the ball receiving hole (inner spherical surface) 4a is a swinging rotational motion in which the rod portion 2c of the connecting rod 2 swings the neck.

Next, the composition of the piston 4 and the connecting rod 2 and the manufacturing method will be described with reference to FIGS.
FIG. 9 is a photograph of the sintered material of the piston as it is fired.
FIG. 10 is a photograph of the piston sintered material as it is with the steam treatment.
FIG. 11 is a photograph after the lapping after the steam treatment of the sintered material of the piston.
FIG. 12 is a cross-sectional photograph of the piston sintered material after the steam treatment.
FIG. 13 is a schematic view of a cross section after the steam treatment of the sintered material of the piston.
FIG. 14 is a photograph of the cut surface cut after the steam treatment of the sintered material of the piston.
FIG. 15 is a schematic view of a cut surface cut after the steam treatment of the piston sintered material.

  The piston 4 and the connecting rod 2 employ an iron-based sintered material. The sintered material is a porous body in which a powder is molded and pressed and fired, and has a large number of pores.

  The photograph shown in FIG. 9 shows the as-sintered structure of the ball receiving hole 4 a of the piston 4, and the base material 9 is mixed with holes 10 that appear black and large in various sizes. In such a porous body, the lubricating oil is absorbed in the pores, and the oil film is not sufficiently formed in the sliding portion.

  Here, when the surface steam treatment is performed after the ball receiving hole 4a of the piston 4 is sintered, the result is shown in FIG. Since the pores are sealed by the oxide film formed by the steam treatment in this way, an oil film is easily formed on the sliding portion between the piston 4 and the rod 2.

  Next, when the steam layer 8 is lapped after the steam treatment, the surface is as shown in FIG. On the surface of the ball receiving hole 4a that has been lapped, the steam layer formed by the steam treatment remains and an oil film is easily formed.

  The manufacturing process of the piston 4 of the present embodiment is to cut the steam layer 8 formed on the surface of the ball receiving hole 4a after the steam treatment. The cutting of the steam layer 8 in the present embodiment can improve the friction and wear resistance of the sliding portion by cutting the ball receiving hole 4a of the piston 4 and reduce the wear damage of the sliding portion.

  FIG. 12 shows a cross section of the ball receiving hole 4a of the piston 4 after the steam process. An oxide film formed in a large and small number of pores in the substrate 9 and a steam layer of several μm exist on the surface portion. When the photograph of FIG. 12 is schematically shown as a cross-section after the steam treatment of the ball receiving hole 4a of the piston 4, it is as shown in FIG.

  FIG. 14 shows the structure of the sliding surface after the ball receiving hole 4a of the piston 4 is cut. 14 is schematically shown as a structure of the sliding surface after the ball receiving hole 4a of the piston 4 is cut, as shown in FIG.

When the steam treatment is performed on the sintered material and the surface steam layer is cut, the surface of the sintered material is composed of the base material 9, the pores 10, and the oxide film 8a. The base material 8 is iron-based and soft, and the oxide film 8a is hard with triiron tetroxide (Fe ₃ O ₄ ). By making such a composite structure, friction and wear characteristics are exhibited even in a low-viscosity oil. . That is, the friction coefficient is reduced and the sliding of the ball receiving hole 4a of the piston 4 and the ball (outer spherical surface) 2a is smooth even in low viscosity oil that is difficult to form an oil film.

Usually, the sliding part does not use a combination of the same kind of materials or the same hardness. In the combination of materials, by making a hardness difference, the surface of the harder material is prevented from being roughened, and wear powder is swept away by the rolling or lubricating oil while deforming the surface of the soft material and discharged out of the friction surface. Can do. Furthermore, after the wear powder is discharged, the softer material is familiar with the harder material surface shape, and the surface can be restored to a smooth shape before the formation and discharge of the wear powder. That is, the soft base material 9 receives the hard ball 2a in sliding with the connecting rod 2, and the hard oxide film present in the pores 10 becomes wear resistance, so that the overall balance is achieved and the friction / wear characteristics are improved. The density of the iron-based sintered material of the piston 4 and the rod 2 is preferably 6 g / cm ³ or more in consideration of the strength of the material. When the density is 6 g / cm ³ or less, the number of pores formed at the time of firing is large, and formation of large pores is also a concern, so that the overall proportion of the pores in the substrate increases, leading to a decrease in strength.

Further, in consideration of the area of the holes formed during firing, the density of the iron-based sintered material of the piston 4 and the rod 2 is desirably 7.5 g / cm ³ or less.

  As for the ratio of the oxide film 8a to the base material 9 after cutting the steam layer 8 of the ball receiving hole 4a of the piston 4, 10-30% is desirable. That is, when the ratio is 10% or less, the oxide film 8a that becomes wear resistance during sliding is small, and the friction / wear characteristics deteriorate. On the other hand, if the ratio is 30% or more, the density of the piston 4 itself is low, the strength is insufficient, and the reliability is lacking.

  The surface roughness after cutting of the piston 4 used in the present embodiment is preferably Ra (arithmetic average roughness) of 1.0 μm or less in consideration of sliding with the counterpart ball 2a. On the other hand, when the surface of the ball receiving hole 4a slides between the ball receiving hole 4a and the ball 2a and the surface roughness of Ra is 1.0 μm or more, the oil film is easily cut off, resulting in mixed lubrication and boundary lubrication, increasing wear, and galling and seizing. Is not preferable. Further, this surface roughness is desirably Ra 1.0 μm or less even in the ball 2 a of the rod 2.

The refrigerant used in the refrigerant compressor of the present embodiment is R600a (isobutane) and does not contain chlorine in the molecule, so the lubricity of the refrigerant itself cannot be expected, and the wear resistance of the compressor is reduced. Here, the lubricity of the refrigerant / lubricating oil mixture can be ensured by using a polyol ester lubricating oil. As the polyol ester oil, a hindered type synthesized from a polyhydric alcohol and a monovalent fatty acid and excellent in thermal stability is preferable. Regarding the viscosity of the lubricating oil (measured in accordance with JIS K2283), in the case of a reciprocating compressor, the viscosity at 40 ° C. is preferably in the range of 3 to 10 mm ² / s. When the viscosity is less than 3 mm ² / s, the viscosity in which the refrigerant is dissolved becomes low, the oil film inside the compressor is not sufficiently maintained, and the lubricity is poor, and it is always exposed to a mixed lubrication or boundary lubrication state. Furthermore, the sealing performance of the compression part cannot be maintained. On the other hand, when the viscosity exceeds 10 mm ² / s, mechanical losses such as viscous resistance and frictional resistance increase, and the compressor efficiency decreases.

  In this way, the ball receiving hole 4a of the piston 4 is cut after the steam treatment, so that a difference in hardness is imparted by sliding the iron-based sintered material with the ball 2a of the connecting rod 2 subjected to the steam treatment and further nitriding treatment. In addition, galling and adhesion are prevented, and friction and wear characteristics are improved.

Next, the refrigeration cycle of the refrigeration apparatus in which the refrigerant compressor of the present embodiment is used will be briefly described with reference to FIG.
FIG. 16 is a configuration diagram of the refrigeration cycle of the refrigeration apparatus.

  In the refrigeration apparatus including the refrigerant compressor 11, the condenser 12, the decompression device 13, and the evaporator 14, the refrigerant compressor 11 compresses the low-temperature and low-pressure refrigerant gas, discharges the high-temperature and high-pressure refrigerant gas, and supplies the condenser 12. send. The refrigerant gas sent to the condenser 12 becomes a high-temperature and high-pressure refrigerant liquid while releasing its heat into the air, and is sent to the decompression device 13. The high-temperature and high-pressure refrigerant liquid that passes through the decompression device 13 becomes low-temperature and low-pressure wet steam due to the throttling effect and is sent to the evaporator 14. The refrigerant that has entered the evaporator 14 absorbs heat from the surroundings and evaporates, and the low-temperature and low-pressure refrigerant gas that has left the evaporator 14 is sucked into the compressor 11, and the same cycle is repeated thereafter.

  In this refrigeration cycle, a refrigerator or the like requires a low evaporator temperature (−40 ° C. or lower). Here, if lubricating oil having poor compatibility with the refrigerant is used, the refrigeration oil separated from the refrigerant by the heat exchanger or the expansion mechanism accumulates, and there is a possibility that the oil return property to the compressor may be lowered.

  According to the composition and manufacturing method of the piston 4 and the connecting rod 2 of the present embodiment, even if the sliding member is low viscosity oil, it exhibits high sliding characteristics even under mixed lubrication and boundary lubrication conditions where the oil film is thin. Can do.

  Hereinafter, the friction characteristics of the present embodiment will be described using FIGS. 17 and 18 in comparison with comparative examples of other manufacturing methods.

  FIG. 17 is a graph showing the relationship between the test time and the friction coefficient in the wear test of Comparative Example 1.

  FIG. 18 is a graph showing the relationship between the test time and the friction coefficient in the wear test of Comparative Example 2.

  FIG. 19 is a graph showing the relationship between the test time and the friction coefficient in the comparative example 3 wear test.

  Table 1 shows a list of combinations of piston and rod manufacturing processes in the wear test.

  Comparative Example 1 is a combination in which the steam layers of both the ball receiving hole 4a and the spherical body portion 2a are cut. Comparative Example 2 is a combination in which the ball receiving hole 4a remains steam-treated and the sphere 2a is subjected to gas soft nitriding after the steam treatment. Comparative Example 3 is a combination in which the ball receiver 4a is subjected to the cutting process after the steam process and the spherical body part 2a is subjected to the gas soft nitriding process after the steam process. The comparative example 3 is an example showing a method for manufacturing the piston and the rod of the present embodiment.

The wear test was performed by immersing the piston 4 in a movable piece and the connecting rod 2 in a fixed piece. As the lubricating oil, a polyol ester oil having a kinematic viscosity of 8 cm ² / s was used.

  The load was 588 N, the speed was 0.48 m / s, and the target test time was 2 hours.

  As shown in FIG. 17, the result in Comparative Example 1 is that when a main load of 588 N is applied, the friction coefficient increases in 4 minutes, and the temperature of the sliding portion increases to 480 ° C. A wear test was not possible. It can be seen that adhesion occurs on the sliding portions of the piston 4 and the rod 2 after the test, and the friction and wear characteristics are insufficient.

Also in Comparative Example 2, the wear test was performed by immersing the oil in oil with the piston 4 as a movable piece and the connecting rod 2 as a fixed piece. As the lubricating oil, a polyol ester oil having a kinematic viscosity of 8 cm ² / s was used.

  The load was 588 N, the speed was 0.48 m / s, and the target test time was 2 hours.

  As shown in FIG. 18, the result in Comparative Example 2 is that a load of 588 N is applied, the friction coefficient increases in 17 minutes, the temperature of the sliding part increases to 350 ° C., and the target wear for 2 hours. The test was not possible. Although the wear amount of the piston portion was 17 minutes, the wear loss was reduced by 1.5 μm.

In Comparative Example 3 of this embodiment, the piston 4 was a movable piece and the connecting rod 2 was a fixed piece, which was immersed in oil. As the lubricating oil, a polyol ester oil having a kinematic viscosity of 8 cm ² / s was used. The load was 588 N, the speed was 0.48 m / s, and the target test time was 2 hours.

  As shown in FIG. 19, the result in Comparative Example 3 was that a stable low friction after applying a main load of 588 N and a wear test for 2 hours at a low sliding temperature of 100 ° C. or less were possible. . The abrasion amount of the piston 4 after the test was 5 μm, which was ½ that of Comparative Example 2.

Based on the above, a 45-day actual machine evaluation test was conducted using a hermetic refrigerant compressor equipped with the connecting rod 2 having the configuration shown in FIG. A polyol ester oil having a kinematic viscosity at 40 ° C. of 8 mm ² / s was used as the refrigerant and R600a as the refrigerating machine oil. An antioxidant and an acid scavenger are added to this lubricating oil. Abnormal wear does not occur in the ball receiving hole (inner spherical surface) 4a portion after the test and the ball 2a of the rod 2, no deterioration is seen in the lubricating oil, and good characteristics with high reliability are obtained. It was.

  As described above, according to the present invention, according to the present invention, even in a mixed lubrication and boundary lubrication state where the oil film is temporarily thin, stable sliding characteristics can be exhibited and the wear amount can be reduced. A highly reliable refrigerant compressor without deterioration and a refrigeration cycle using the same can be provided.

DESCRIPTION OF SYMBOLS 1 ... Cylinder, 2 ... Connecting rod, 2a ... Ball, 4 ... Piston, 4a ... Ball receiving hole, 7 ... Crankshaft, 8 ... Steam layer, 8a ... Oxide film, 9 ... Base material, 10 ... Hole, 11 ... Oxidation Film,
DESCRIPTION OF SYMBOLS 11 ... Refrigerant compressor, 12 ... Condenser, 13 ... Decompression apparatus, 14 ... Evaporator.

Claims (7)

In a reciprocating compressor that converts rotation of an electric motor into reciprocating motion of a piston in a cylinder by a crank mechanism,
The crank mechanism has a crankshaft, a crankpin for changing the rotation of the crankshaft to an eccentric motion, and a connecting rod having one end inserted into the crankpin and the other end connected to the piston,
The ball provided on the connecting rod and the ball receiving hole provided on the piston form a sliding part that is slidably ball-joined, and lubricating oil is supplied to the sliding part that is ball-joined,
The piston and the connecting rod are iron-based sintered materials containing iron as a main component, each of the piston and the connecting rod is subjected to a steam treatment, and the surface of the piston has a steam layer removed by cutting, 2. The reciprocating compressor according to claim 1, wherein the connecting rod is subjected to nitriding after steaming. The reciprocating compressor according to claim 1, wherein the iron-based sintered material of the piston has a density of 6 to 7.5 g / cm ³ .   The iron-based sintered material of the piston is characterized in that the ratio of the steam film remaining in the pores after removing the steam layer by cutting to the base material is 10 to 30%. The reciprocating compressor according to claim 2.   The reciprocating compressor according to any one of claims 1 to 3, wherein the iron-based sintered material of the piston has a surface roughness Ra of 1.0 µm or less after cutting.   The reciprocating compressor according to any one of claims 1 to 4, wherein the reciprocating compressor compresses a refrigerant, and R600a is used as the refrigerant, and polyol ester oil is used as the lubricating oil. The reciprocating compressor according to claim 1, wherein the lubricating oil has a kinematic viscosity of 40 ° C. and 3 to 10 mm ² / S.   The reciprocating compressor according to any one of claims 1 to 6, wherein at least a compressor, a condenser, an expansion mechanism, an evaporator, and a refrigeration apparatus configured to be refrigerated by a refrigeration cycle configured by connecting refrigerant pipes. Onboard refrigeration equipment.

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