JP2011026991A - Refrigerant compressor and refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerant compressor using an R600a refrigerant having a long service life by using a sliding material capable of preventing wear or seizure and having excellent wear resistance and seizure resistance in a piston and a rod of the compressor to which lubricating oil may not be temporarily supplied. <P>SOLUTION: In the refrigerant compressor using R600a (isobutane) for an operating refrigerant, as a surface treatment method of a sliding member, a pure chromium film layer is formed on a lower layer and a tungsten carbide layer and Me-DLC layer are formed as intermediate layers so that a diffusion permeation layer is surely formed on a surface of a base material, and DLC processing is applied to an uppermost part, and a DLC coating layer is formed. Thus, seizure or abnormal wear can be prevented, and the refrigerant compressor having the long service life and the refrigerating device with the compressor can be provided. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a hermetic refrigerant compressor used for a refrigerator, an air conditioner, etc., and more particularly to a hermetic refrigerant compressor having a reciprocating piston.

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

  On the other hand, refrigeration oil is used in refrigerant compressors and plays a role of lubrication, sealing, cooling, insulation, etc. of the sliding part. In recent years, compressors are required to save energy, downsize, reduce noise, and increase efficiency, and the use conditions of refrigeration oil have become severe. For this reason, lubricity is requested | required from the surface of ensuring the reliability of a compressor.

  Now, as a compressor of a refrigerator, as a hermetic refrigerant compressor having a reciprocating piston, a structure in which a crankshaft and a piston are connected by a connecting rod and the motion of the rotating shaft is changed to a reciprocating motion is common. is there. Among these, as a connecting structure between the piston and the connecting rod, a piston pin is used as a connecting portion between the piston and the connecting rod as described in JP-A-2004-27969 (Patent Document 1), and this piston pin serves as a shaft. As a simple structure, both are connected.

  Further, as a ball joint structure of a piston and a connecting rod of a compressor, as in JP-A-2003-214343 (Patent Document 2), both nitriding treatment and manganese phosphate treatment are performed on both spherical receiving holes (ball receiving holes) and ball portions or A structure using a high carbon chrome steel material on a spherical surface is known.

  Further, Japanese Patent Application Laid-Open No. 2007-64199 (Patent Document 3) is known in which a rotation restricting portion is provided on the piston side instead of the connecting rod side in the ball joint structure.

  Moreover, as a DLC process, a hermetic compressor in which a vane material that is a sliding component is coated with a DLC-Si film is known in Japanese Patent Application Laid-Open No. 2007-1000051 (Patent Document 4).

  As refrigeration oil for R600a (isobutane), naphthenic mineral oil and paraffinic mineral oil are widely used because they have good compatibility with refrigerants and are inexpensive.

  However, since R600a (isobutane) is highly compatible with these refrigerating machine oils, there is a concern about poor lubrication of the compressor caused by a decrease in the viscosity of the refrigerant / refrigerating machine oil mixture. Moreover, since R600a (isobutane) does not contain chlorine or fluorine in the molecule, the lubricity of the refrigerant itself cannot be expected.

  Therefore, Japanese Patent Application Laid-Open No. 2007-248020 (Patent Document 5) discloses a method of using a highly lubricating polyol ester oil as a refrigerating machine oil in order to improve lubricity.

JP 2004-27969 A JP 2003-214343 A JP 2007-64199 A JP 2007-1000051 A JP 2007-248020 A

  In Patent Document 1, the piston and the connecting rod are connected by a piston pin. This connecting structure has a bearing portion on the connecting rod side with the piston pin inserted into the piston side as an axis. Therefore, if the piston side shaft is inserted into the connecting rod side bearing, there may be a problem with sliding. That is, the sliding part between the piston pin and the connecting rod becomes local, and the contact surface pressure between the two becomes excessive at this time, so that the reliability may be lowered due to wear of the sliding part. In Patent Document 1, the supply of lubricating oil is stabilized to improve the reliability, but it does not solve the localization itself of the sliding portion caused by the shaft structure.

  Patent Document 2 employs a structure in which a piston and a connecting rod are connected by a ball joint method. Since the ball seat provided on the piston is molded by plastic working, the above-mentioned problem does not occur, but the structure may cause a problem in sliding between the piston and the connecting rod. That is, in order to secure the connected state, the ball seat portion is processed in the closing direction, so that the passage of the lubricating oil supplied to the connecting portion becomes narrow, and the lubricating oil may not be sufficiently supplied. Therefore, the lubricating oil cannot be sufficiently supplied to the connecting portion, and the temperature of the spherical bearing portion may be increased and damaged.

  Further, when a high carbon chrome steel material is used for the spherical surface (ball), the high carbon chrome steel material has a high hardness, which causes a problem in workability. That is, there has been a demand for a material that has not only high wear resistance but also excellent workability.

  In Patent Document 3, a rotation restricting portion is provided on the piston side to restrict the relative rotation of the piston and connecting rod, and the piston and connecting rod are made of an iron-based sintered material sealed with an oxide film to improve workability. Using. However, as the compressor's performance improves, the refrigerating machine oil supply to the sliding part and the oil film formation decrease as the viscosity of the refrigerating machine oil decreases. This may increase wear between the rod and the piston. For this reason, it is necessary to ensure sufficient wear resistance of the sliding portion.

  Patent Document 4 discloses a hermetic compressor in which a base material of a sliding part of a compressor is subjected to nitriding treatment to form a nitriding diffusion layer, and further, DLC-Si treatment is applied on the nitriding diffusion layer. . However, the DLC-Si coating contains Si in DLC, and although a reduction in the friction coefficient can be expected, there is a problem in terms of wear amount, so-called wear resistance.

  In Patent Document 5, the polyol ester oil, which is a refrigerating machine oil, is likely to be hydrolyzed when coexisting with water, and this also causes blockage of the refrigeration cycle and corrosive wear at the sliding portion. Further, as the viscosity decreases, it is difficult to form an oil film, and it is necessary to cope with deterioration of the refrigerating machine oil due to heat generation at the sliding portion.

  Therefore, in the refrigerant compressor using isobutane which is a natural refrigerant, the wear resistance of the sliding portion can be improved as compared with the conventional refrigerant compressor, and the highly reliable hermetic refrigerant compressor. Is desired. In other words, a long-life refrigerant using a sliding material having high wear resistance and seizure resistance that prevents wear and seizure in the piston / rod portion of the compressor that may not be supplied with lubricating oil temporarily. An object of the present invention is to provide a compressor and a refrigeration cycle apparatus using the compressor.

  Then, an object of this invention is to implement | achieve a long-life refrigerant compressor and the refrigerating-cycle apparatus using the same.

The object of the present invention is as follows.
In a hermetic compressor in which a compression element and an electric element are housed in a hermetic container, and a crankshaft and a piston driven by the electric element portion are connected by a connecting rod in a ball joint structure,
This is achieved by forming a Diamond Like Carbon coating (DLC coating) layer on the ball joint.

  According to the present invention, it is possible to provide a long-life refrigerant compressor and a refrigeration cycle apparatus using the refrigerant compressor.

It is sectional drawing explaining a hermetic refrigerant compressor. It is a figure which shows a piston inner surface structure. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG. It is a perspective view of a connecting rod. It is a perspective view of a rotation stopper. It is an assembly state figure of a piston and a connecting rod. It is a refrigeration cycle block diagram for basic refrigerators. It is a fragmentary figure which shows the internal structure in the surface treatment of this invention. It is a figure which shows the internal structure in the conventional surface treatment. It is a friction coefficient comparison figure. It is a wear amount comparison figure.

  Hereinafter, the present invention will be described in detail with reference to examples.

  FIG. 1 is a sectional view of a reciprocating hermetic refrigerant compressor according to the present invention.

  This refrigerant compressor is of a reciprocating type in which a piston 4 reciprocates in a cylinder 1 formed integrally with a bearing 1a and a frame 1b provided in a sealed case that also serves as an oil reservoir, and constitutes a compressor element. It is a compressor.

  A lower part of the frame 1b is provided with a stator 5 and a rotor 6 constituting an electric motor as electric elements, and a crank pin 7a is provided at a position eccentric from the rotation center of the crank shaft 7.

  The crankshaft 7 penetrates 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 part 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 crank pin 7 a and the piston 4 are connected by a connecting rod 2, and the piston 4 reciprocates via the crank pin 7 a and the connecting rod 2.

  In other words, the hermetic refrigerant compressor of this embodiment includes a compression element such as a cylinder 1 and a piston 4 and an electric element such as an electric motor housed in a hermetic container, and the crankshaft 7 applies a rotational force from the electric element to the piston. 4 is assumed. The crankshaft 7 and the piston 4 are connected by a connecting rod 2 with a ball joint structure.

  The piston of the compression element will be described in detail with reference to FIGS.

  FIG. 2 is a view showing the inside of the piston 4 when the piston 4 is viewed from the crankshaft 7 side, that is, when viewed from the left in FIG. 1, and has a ball receiving portion (inner spherical surface) 4a. 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. The ball receiving portion (inner spherical surface) 4a of the piston has a shape including the ball (outer spherical surface) 2a of the connecting rod 2 in the AA cross section. The image is an image in which the normal of the joint portion end surface 2e of the connecting rod 2 in FIG. However, since the AA cross section of the piston 4 has a shape as shown in FIG. 3, the connecting rod 2 does not fit into the piston 4 in the direction of FIG. 5. Once the connecting rod 2 is rotated 90 degrees and inserted into the piston 4, the connecting rod 2 is rotated 90 degrees so that the connecting rod 2 is fitted to the piston 4.

  As can be seen from FIG. 5, the ball joint portion with respect to rotation around the y axis, that is, the sliding area of the ball (outer spherical surface) 2a is small, and the sliding area of the ball (outer spherical surface) 2a with respect to rotation around the z axis is large. Therefore, the ball joint structure having a smaller sliding area than the AA cross section in the BB cross section and the path through which the lubricating oil passes are short, so that the lubricating oil can easily flow and the lubricating oil can be sufficiently supplied. Note that the xyz axes shown in FIG. 5 are shown only for explanation. The x-axis passes through the center of an oil supply hole 2d described later, and the z-axis passes through the center of the crank bearing portion 2b.

  FIG. 5 is a perspective view of the connecting rod 2. The connecting rod 2 includes a ball (outer spherical surface) 2a inserted into the ball receiving portion (inner spherical surface) 4a of the piston 4, a crank bearing portion 2b into which the crankshaft 7a is inserted, a ball (outer spherical surface) 2a and the crank bearing portion 2b. It is comprised from the rod part 2c to connect. 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. Further, the ball (outer spherical surface) 2 a has a structure in which a part of the spherical surface is cut out in the same manner as the ball receiving portion (inner spherical surface) 4 a of the piston 4. The end face 2e is obtained by this notch. Accordingly, the sliding area of the ball (outer spherical surface) 2a with respect to the rotation about the BB cross section, that is, around the y axis is small. That is, since the route through which the lubricating oil passes is short, the lubricating oil can easily flow and the lubricating oil can be supplied sufficiently.

FIG. 6 is a perspective view showing a detent. FIG. 7 is a perspective view of the ball joint structure. 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 rotation stopper 10 does not fall off from the ball receiving hole (inner spherical surface) 4a.
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. That is, the z-axis itself does not rotate but revolves around the axis of the crankshaft 7 parallel to the z-axis. In the ball joint portion, the ball (outer spherical surface) 2a and the ball receiving hole (inner spherical surface) 4a move relative to each other as a revolving motion about the z axis. More specifically, the ball (outer spherical surface) 2a rotates in a range of several tens of degrees to the left and right within the ball receiving hole (inner spherical surface) 4a and moves back and forth.

  The piston 4 and the connecting rod 2 employ an iron-based sintered material (sintered material containing iron as a main component). Steam processing is performed to seal the pores of the sintered material, and by forming an oxide film, it is prevented that process auxiliary materials such as processing oil are contained in the pores and incorporated into the product. When these process sub-materials are brought into the cycle, they may elute into the cycle during operation and promote deterioration of the refrigerating machine oil. Moreover, when the hole treatment is not performed, the lubricating oil is absorbed in the holes, and the oil film formation on the sliding portion becomes insufficient. Further, in order to reliably form a DLC (Diamond Like Carbon) coating layer, an oxide film layer is formed and subjected to surface roughness processing, and then DLC treatment is performed.

  This DLC treatment is applied to the ball (outer spherical surface) 2a of the ball joint portion to improve the wear resistance of the sliding portion and reduce wear damage of the sliding portion.

  FIG. 8 shows a refrigeration cycle configuration diagram for a 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 sends the refrigerant gas to the condenser 12. . 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 passing 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 exited 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, when the refrigerating machine oil having poor compatibility with the refrigerant is used, the refrigerating machine oil separated from the refrigerant by the heat exchanger or the expansion mechanism is accumulated, and the oil return property to the compressor is lowered.

  Since the refrigerant of this example is R600a (isobutane) and does not contain chlorine in the molecule, the lubricity of the refrigerant itself cannot be expected, and the wear resistance of the compressor is lowered. By using the refrigerating machine oil described above, the lubricity of the refrigerant / refrigerating machine oil mixture can be ensured. The aforementioned polyol ester oil is preferably a hindered type synthesized from a polyhydric alcohol and a monovalent fatty acid and excellent in thermal stability. For example, examples of the polyhydric alcohol include pentaerythritol and dipentaerythritol. Monovalent fatty acids include pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, 2-methylbutanoic acid, 2-methylpentanoic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, isooctanoic acid, 3, 5, 5 -Trimethylhexanoic acid and the like are used alone or in combination of two or more kinds.

  In particular, the base oil in the refrigerating machine oil is preferably at least one selected from the group of fatty acid ester oils represented by the formula (1), (2) or (3) having at least two ester bonds in the molecule.

(R ¹ —CH ₂ ) ₂ —C— (CH ₂ —O—CO—R ² ) ₂ ... (1)
(In the formula (1), R ¹ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R ² represents an alkyl group having 5 to 12 carbon atoms each independently)
(R ¹ —CH ₂ ) —C— (CH ₂ —O—CO—R ² ) ₃ ... (2)
(In the formula (2), R ¹ and R ² are as defined above.)
C— (CH ₂ —O—CO—R ² ) ₄ ... (3)
(In formula (3), R ² has the same meaning as described above.)
Regarding the viscosity of the refrigerating machine oil (measured in accordance with JIS K2283), in the case of a reciprocating compressor, the kinematic viscosity at 40 ° C. is preferably in the range of 5 to 15 mm ² / s. When the viscosity is less than 5 mm ² / s, the viscosity of the dissolved refrigerant becomes low, and the oil film inside the compressor is not sufficiently maintained, so that the lubricity cannot be maintained. Furthermore, the sealing performance of the compression part cannot be maintained. On the other hand, if the viscosity exceeds 15 mm ² / s, mechanical loss such as viscous resistance and frictional resistance increases, and the compressor efficiency decreases.

  In this embodiment, there is no problem even if an antioxidant, an acid scavenger, an antifoaming agent, a metal deactivator, or the like is added to the refrigerating machine oil. In particular, polyol ester oils are prone to oxidative degradation and have high hygroscopic properties, so that the amount of moisture brought in increases and degradation due to hydrolysis of motor insulating materials such as PET films is likely to occur. Antioxidants or acid scavengers Is necessary. As the antioxidant, DBPC (2,6-di-t-butyl-p-cresol) which is a phenol type is preferable. Examples of the acid scavenger include an epoxy type and a carbodiimide type, but an aliphatic epoxy compound is generally used.

  FIG. 9 is a partial view showing an internal configuration in the surface treatment of this embodiment. FIG. 10 shows an internal configuration in the conventional surface treatment. Conventionally, the base material of the connecting rod 2 was only subjected to the steam treatment to form the oxide film layer 15, but the surface was subjected to DLC treatment in order to improve the wear resistance of the sliding member. As the structure of the surface treatment layer, first, in order to ensure that the diffusion / permeation layer can be formed on the substrate surface of the sliding member, a pure chromium film layer 16 is disposed as a lower layer, and the diffusion / permeation layer (intermediate layer) is formed. A tungsten carbide layer 17 and a Me-DLC layer (Metal-Diamond Like Carbon) 18 are formed, and a DLC (Diamond Like Carbon) process is performed on the top to form a DLC coating layer 19.

  In the DLC coating layer 19, carbon has an amorphous bond including a diamond bond and a graphite bond. Features include a diamond structure and extremely high hardness, and since it has no crystal grain boundary, the surface after film formation is smooth, and it is lubricated by graphite bonding and has low friction. By using the DLC film as a protective film, the hardness is greatly improved, so that the thickness of the protective film can be reduced. Thereby, the film thickness accuracy at the time of film formation can be improved.

  When the film thickness is 2 μm or less, the film thickness does not reach a sufficient level, and when the surface layer is worn away and lost, the base material comes into direct contact, and the amount of wear increases. Moreover, the DLC processing method of a present Example is sputtering method with the film-forming temperature of 250 degrees C or less, and a maximum film thickness is 5-6 micrometers. Therefore, the total film thickness of the DLC coating is 2 to 6 μm. Furthermore, since it has low friction and a smooth surface, it has the effect of greatly improving the problems such as seizure and wear of the sliding portion. The presence of the diffusion / penetration layer improves the adhesion between the substrate and the DLC coating layer. Since the sliding surface of the sliding member is a DLC having good seizure resistance and wear resistance, even when it comes into solid contact, aggressive wear and seizure peculiar to metal contact hardly occur.

  FIG. 11 shows a comparison of the wear coefficient by a wear test conducted to confirm the wear resistance of the DLC film of this example. The test method used was a plate / ring type wear tester. As a test piece, the plate was subjected to steam treatment on SKH51 and the ring was subjected to 14EPC, and then a DLC film was formed. The film thickness of the DLC film was 2.5 μm. As a comparative example, 14EPC material without DLC treatment was used. As a result of wear test with no lubricating oil, sliding speed of 0.12 m / s and surface pressure of 9.8 MPa, 14 EPC material subjected to DLC treatment has a coefficient of friction of about 1/2 compared to untreated 14 EPC material. Decreased. In the untreated sample, the test piece was completely worn out at the time of 2.5 hr, and the test was stopped.

  FIG. 12 shows the amount of wear in the wear test. The wear amount of the DLC coating was 1 μm, whereas the untreated one had the test piece completely worn, and the wear amount was 3000 μm, that is, 3 mm.

  From these results, it can be seen that the sliding member of this example has high sliding characteristics even under non-lubrication.

  As described above, if the sliding member on which the DLC film is formed is used, not only CFC refrigerant and HCFC refrigerant, but also HFC refrigerant and HC refrigerant having poor lubricity because they do not contain chlorine, and natural systems that are in an ultra-high pressure state. The present invention can be applied to a refrigerant compressor using a refrigerant, and can provide high performance and high reliability of the compressor. Furthermore, it can be applied to an air conditioner, a refrigerator, and a water heater using the above-described refrigerant compressor, and can provide high performance and high reliability.

Based on the above, a 45-day actual machine evaluation test was performed using a hermetic refrigerant compressor equipped with a connecting rod 2 having the configuration shown in FIG. R600a was used as the refrigerant, and polyol ester oil having a kinematic viscosity at 40 ° C. of 8 mm ² / s was used as the refrigerating machine oil. Even if it is about ± 2 mm ² / s due to various factors, it is actually equivalent. An antioxidant and an acid scavenger are added to the refrigerating machine oil. Abnormal wear did not occur in the ball joint after the test, and no deterioration was observed in the refrigerating machine oil, so that good characteristics could be maintained.

  A highly reliable refrigeration cycle apparatus can be obtained by connecting a compressor, an expansion mechanism, an evaporator, and also the compressor obtained as described above in order with a refrigerant pipe to form a refrigeration cycle apparatus. . According to the above embodiment, even when the sliding member such as the piston or the rod is lubricated and the friction coefficient is increased, the wear resistance can be maintained and the sliding wear can be reduced.

1 Cylinder 2 Connecting rod 2a Ball 4 Piston 4a Ball receiving hole 7 Crankshaft 11 Compressor 12 Condenser 13 Expansion mechanism 14 Evaporator 15 Oxide film layer 16 Pure chromium film layer 17 Tungsten carbide layer 18 Me-DLC layer 19 DLC coating layer

Claims (10)

In a hermetic compressor in which a compression element and an electric element are housed in a hermetic container, and a crankshaft and a piston driven by the electric element portion are connected by a connecting rod in a ball joint structure,
A refrigerant compressor in which a Diamond Like Carbon coating (DLC coating) layer is formed on the ball joint. In claim 1,
The refrigerant compressor according to claim 1, wherein the piston and the connecting rod are made of a sintered material mainly composed of iron. In claim 2,
A refrigerant compressor in which an oxide film is formed on surfaces of the piston and the connecting rod. In claim 3,
A pure chromium film layer, a tungsten carbide layer, and a metal-diamond like carbon layer (Me-DLC layer) are formed as a lower layer of the DLC coating layer, and the DLC coating layer is formed on the Me-DLC layer. A refrigerant compressor characterized in that is formed. In claim 4,
A refrigerant compressor, wherein the total film thickness of the DLC coating layer is 2 to 6 μm. In any of claims 1 to 5,
A refrigerant compressor using R600a as a refrigerant. In claim 6,
A refrigerant compressor using a refrigerating machine oil together with the R600a, wherein the refrigerating machine oil has a kinematic viscosity at 40 ° C. of 5 to 15 mm ² / S. In claim 7,
A refrigerant compressor characterized by using polyol ester oil as the refrigerating machine oil and having a kinematic viscosity of 6 to 10 mm ² / S at a kinematic viscosity of 40 ° C. In claim 8,
A refrigerant compressor, wherein at least one of an acid scavenger and an antioxidant is added to the polyol ester oil. In the refrigeration cycle apparatus, the compressor, the condenser, the expansion mechanism and the evaporator, and also the compressor are sequentially connected by a refrigerant pipe.
A refrigeration cycle apparatus characterized in that the compressor is the compressor according to claim 1.

Images