JPH0719189A - Compressor for refrigerator - Google Patents

Abstract

PURPOSE:To improve a fatigue life for lubricating oil generating organic acid and the like by hydrolysis by using specific corrosion resistant material as the material of both or one of a rolling element and a bearing ring in a rolling bearing for bearing the reaction of torque generated at the compressed time of refrigerant gas. CONSTITUTION:In a scroll compressor, the respective laps 5, 6 of both fixed and turning scrolls 1, 2 are engaged with each other to form a compression mechanism part. The turning scroll member 2 is put in turning motion by a crankshaft 7, action converting mechanism connected to a rotary shaft. As a result, the volume of a compression chamber 8 is gradually reduced to compress refrigerant gas. In order to bear the reaction of torque generated at the compressed time of the refrigerant gas, a radial cylindrical roller bearing 11 is disposed between the crankshaft 7 and a frame 10. In this case, corrosion resistant material containing 3.5wt.% or more of chrome at least is used as the material of both or one of a rolling element and a bearing ring in the roller bearing 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a room air conditioner, a package air conditioner or the like which uses a refrigerant composed of difluoromethane alone or a mixture of plural kinds of fluorohydrocarbons in a group of fluorohydrocarbon refrigerants and synthetic refrigerating machine oil. The present invention relates to a compressor for a refrigeration system, and more particularly, to a material suitable for suppressing the peeling phenomenon of a rolling bearing.

[0002]

2. Description of the Related Art Conventionally, rolling bearing materials of rolling bearings and rolling element materials used in refrigeration compressors are JIS G 4805.
High-carbon chromium steel generally used as the bearing steel shown in (1970), carbon tool steel shown in JIS G 4401 (1972), and chromium molybdenum steel shown in JIS G 4105 (1979).

Further, since HCFC22 having chlorine as a refrigerant has been conventionally used in this type of refrigeration cycle, mineral oil or alkylbenzene has been mainly used as refrigerating machine oil. However, due to recent environmental problems, HCFC22 may be replaced with difluoroethane (HFC32) alone or with a mixture of this and at least one fluorohydrocarbon from a fluorohydrocarbon (HFC) refrigerant group. Became. However, this refrigerant has a drawback that its compatibility with general mineral oil-based lubricating oil is extremely poor [refrigeration 60 rolls].
816 (1985)]. This is probably because none of these refrigerants has chlorine in the molecule like HCFC22 [Asure Guide and Data].
Book (ASHRAE Guide and Data Book) 307p (1
969)]. Therefore, mineral oil cannot be used in terms of reliability (lubrication) of the compressor. Therefore, an ester-based synthetic refrigerating machine oil having a polar group is used to ensure compatibility with the refrigerant. However, the ester oil has a high hygroscopicity because it has a polar group, and therefore, there is a concern that it will be hydrolyzed to produce a fatty acid, which will shorten the fatigue life of the bearing. Therefore, using a chlorine-free refrigerant and an ester synthetic oil, a compressor was subjected to a severe test by intentionally adding water so that the refrigerant and the lubricating oil each have a saturated water content. As a result, H
A peeling phenomenon occurred on the rolling elements of the bearing in a short time such as 18 to 35% of the life of the CFC22 / mineral oil system. in this way,
The HFC / synthetic oil system has a drawback of reducing the bearing life of the compressor.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a refrigeration cycle using a fluorocarbon as a working refrigerant and a lubricating oil that produces an organic acid by hydrolysis like an ester in a refrigerating machine oil. In order to improve the fatigue life of the compressor rolling bearing.

[0005]

That is, according to the present invention, a martensitic steel containing chromium in an amount of 3.5% by weight or more is used as the material of the rolling bearing of the compressor for a refrigerator.

[0006]

By using such a material, the corrosion resistance of the bearing material can be improved and the fatigue strength can be improved.
As a result, the bearing life can be improved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

For room air conditioners and package air conditioners, energy saving, low noise, optimum cooling and heating are aimed at, and from the viewpoints of high efficiency of compressor, low torque fluctuation, easy control of rotation speed by inverter, etc., FIG. The scroll compressors shown are becoming mainstream. This compressor sucks and compresses the refrigerant by causing two spiral wraps having substantially the same shape to face each other and mesh with each other and swirling the other wrap with respect to one wrap.

At present, monochlorodifluoromethane (CHClF ₂ ; HCFC22), which is a kind of halogenated hydrocarbon, is used as a refrigerant for refrigerators such as room air conditioners and package air conditioners. Further, as the lubricating oil, naphthene-based or paraffin-based mineral oil is widely used because it has good compatibility with the refrigerant.

However, due to the environmental problem of depleting the ozone layer of the earth, the use of HCFC22 is regulated, and a refrigerant to replace them is required.

One of the possible refrigerants is HC.
Hydrofluorocarbon or fluorocarbon having a boiling point close to that of FC22. Currently, alternative refrigerant candidates for HCFC22 are (a) (A) difluoromethane (CH ₂ F ₂ ;
HFC32) alone, or (b) (B) 1,1,1,2- tetrafluoroethane _{(CF 3 CH 2 F; HFC134a} ), trifluoromethane (CHF _3; HFC23), pentafluoroethane (CHF ₂ CF _3; HFC125), 1,1,2,2
- tetrafluoroethane (CHF ₂ CHF _2; HFC13
4), 1,1,1-trifluoroethane (CF ₃ CH ₃ ; H
FC143a), 1,1,1,2,3,3,3- heptafluoropropane (CF ₃ CHFCF _3; HFC227e
a) A mixed refrigerant in which at least one kind of the fluorohydrocarbon-based refrigerant group represented by the following formula (1) is mixed with (A), or a mixed refrigerant in which plural kinds of (c) and (B) are mixed. Has been.

[0012]

[Chemical formula 1] C _{X HY} F _Z (Chemical formula 1) Here, an integer of X = 1 to 2, Y = 1 to 5, Z = 1 to 5 is a lubricating oil dissolved in these fluorohydrocarbon refrigerants. As
Polyalkylene glycol (US Pat. No. 4,755,316), fatty acid ester, carbonic acid ester, silicone oil and the like have been proposed. Among them, it is said that polyalkylene glycol cannot be used in a refrigeration compressor incorporating an electric motor because of its low electric insulation resistance. Carbonate ester and silicone oil are slightly inferior in lubricity, but can be used by adding an extreme pressure agent. On the other hand, the fatty acid ester is inexpensive and excellent in lubricity because it is synthesized by removing water from alcohol and fatty acid, and it is most promising as a lubricating oil for room air conditioners and package air conditioners.

FIG. 1 is a cross-sectional view of a scroll compressor widely used in room air conditioners and package air conditioners. This compressor wraps a spiral wrap 5 standing upright on an end plate 3 of a fixed scroll member 1 and an orbiting scroll member 2 consisting of an end plate 4 and a wrap 6 of substantially the same shape as the fixed scroll member 1. 5 and the wrap 6 face each other and engage with each other to form a compression mechanism portion, and the orbiting scroll member 2 is caused to orbit by a crankshaft 7 which is a motion converting mechanism connected to a rotating shaft. Of the compression chambers 8 (8a, 8b ...) Formed by the fixed scroll member 1 and the orbiting scroll member 2, the compression chambers located at the outermost sides are gradually reduced in volume with the orbiting motion, It moves toward the centers of the scroll members 1 and 2.

When both compression chambers 8a, 8b reach near the centers of both scroll members 1, 2, both compression chambers 8a, 8b communicate with the discharge port 9 so that the compressed gas in both compression chambers is discharged and fixed. The gas passes through a gas passage (not shown) provided in the scroll member 1 and the frame 10 to reach the inside of the pressure container 11 at the lower part of the frame, and is discharged to the outside of the compressor from a discharge pipe 12 provided on a side wall of the pressure container 11.

In this compressor, the electric motor 13 is built in the pressure vessel 11, and the crankshaft 7 rotates at a rotation speed corresponding to the voltage controlled by an inverter (not shown) outside the compressor to perform compression operation. To do.

In this compressor, a radial cylindrical roller bearing 16 is installed between the frame 10 and the crankshaft 7 in order to bear the reaction force of the torque generated when compressing the refrigerant gas. Further, an oil sump portion is provided below the motor 13, and this oil passes through an oil hole 14 provided in the crankshaft to prevent the orbiting scroll from rotating (Oldham ring) 15, the orbiting scroll member 2 and the crank. It is used for lubrication of the sliding portion with the shaft 7 and the radial cylindrical roller bearing 16.

As shown in FIG. 2, the structure of the radial cylindrical roller bearing is such that a cylindrical roller 19 is installed between an inner ring 17 and an outer ring 18, the rollers are in contact with each other, or have a constant value in the traveling direction of the roller. It is held by the cage 20 so as not to have an angle above.

In the refrigeration cycle using the present compressor, a mixed refrigerant containing 30% by weight of HFC32 and 70% by weight of HFC134a as a refrigerant, and a lubricating oil such as neopentyl glycol and n-nonanoic acid having a kinematic viscosity of about 32 cSt at 40 ° C. After encapsulating a polyol ester synthesized from adipic acid and adding water so that the refrigerant and the refrigerating machine oil would have a saturated water content at room temperature and operated for 100 days under overload conditions, the rolling element of the rolling bearing ( (Roller) peeling phenomenon occurred on the surface. The reason for this is that (a) friction between the roller and the cage or (b) particle Sakai corrosion due to the fatty acid generated by hydrolysis of the ester oil, etc. causes active microcracks on the roller surface. (C) It is presumed that water molecules present in the lubricating oil penetrated, decomposed, and generated hydrogen expanded cracks (so-called hydrogen embrittlement), resulting in peeling.

The present invention is intended to avoid the peeling by suppressing the generation of microcracks due to the above (b) and using a material having a resistance to hydrogen embrittlement due to (c) for the bearing. As its material, martensitic stainless steel containing 3.5% by weight or more of chromium is used. Examples will be described below.

The radial cylindrical roller bearing used in the present compressor has an inner diameter of 25 to 35 mm. Here, an experiment was conducted using an inner diameter of 25 mm. The basic specifications of the bearing are an inner diameter of 25 mm, an outer diameter of 47 mm, a width of 12 mm, and a dynamic load rating of 1320 kg. In the experiment, first, in order to examine the effect of chromium on the bearing life, as shown in Experiment 1 of Table 1, the bearing rings (inner ring and outer ring) and the rollers were made of high carbon chromium steel (class 2) (JIS G). 480
5 (1970) and below, referred to as SUJ2), the cage for radially arranging the rollers is a high strength brass casting (JIS H 5
102 (1979) and hereinafter referred to as HBsC), as well as bearings made of the materials shown in Experiments 2 to 4. Table 2 shows the JIS standard for the chemical composition of the material.

[0021]

[Table 1]

[0022]

[Table 2]

As described above, the refrigerant and the lubricating oil are HFC3.
2 is 30 wt%, HCF134a is 70 wt%, and a polyol ester synthesized from neopentyl glycol having a kinematic viscosity of about 32 cSt at 40 ° C., n-nonanoic acid and adipic acid is enclosed, and at room temperature. Add water so that the refrigerant and refrigerating machine oil have saturated water contents (1500 pp
m), with the tested bearing completely immersed in the lubricating oil,
The oil temperature was 130 ° C, the rotation speed was 6000 rpm, and the bearing load was constant at 1000 kg. During operation, a vibration accelerometer is installed on the side of the container containing the test bearing to detect the vibration acceleration.
(Manufactured by Company K), the operation was stopped when the vibration acceleration exceeded a certain value. The ratio k between the operating time t and the rated fatigue life L of the test bearing calculated by the formulas 1, 2 and 3 was obtained as the bearing life ratio and is shown in Table 1.

[0024]

[Equation 1]

[0025]

[Formula 2] f _h = f _n · C _a / P (Formula 2)

[0026]

[Equation 3]

As a result, the conventional material SUJ2 has a bearing life ratio k of 0.53, whereas SKH2 (the measured chromium content is 3.5% by weight) has k = 0.86, It can be seen that the bearing life is significantly increased in the case of a bearing made of a material having an amount of chromium of 3.5% by weight or more.

The results of measuring the total acid value of the lubricating oil after the experiment are also shown in Table 1. In the experiment, a predetermined amount of lubricating oil sampled immediately after the end of the test was neutralized with a potassium hydroxide solution, and the total acid number was determined by the weight of potassium hydroxide per unit weight of lubricating oil. According to this, although a large difference is not recognized depending on the material, the total acid value slightly increases compared to before the experiment, and the bearing having a larger k value tends to increase the total acid value.

Summarizing these results, the operating time is short for SUJ2 having a low chromium content,
The bearing is damaged in a short time despite the small amount of fatty acid produced by the hydrolysis of the ester oil. On the other hand, SUS440C, which contains a large amount of chromium, has a long operating time.
Despite the large amount of fatty acid produced and the increase in total acid value, the bearing life is extended. This is clearly an effect of the presence of chromium. That is, chromium in the steel prevents the generation of intergranular cracks and prevents the generation of microcracks, and suppresses hydrogen embrittlement due to hydrogen that is generated when water in lubricating oil enters the microcracks and decomposes. It is presumed that this is because

Next, the fatigue life of bearings having different rollers and inner / outer ring materials was measured. As Experiment 5 and Experiment 6 in Table 3, the bearing material, the fatigue life ratio K, and the total acid value of the lubricating oil after the experiment are also shown.

[0031]

[Table 3]

As a result, the bearings whose inner and outer rings were made of SKH2 (chromium content: 3.5% by weight) were replaced with SKH2 rollers.
It can be seen that the bearing with the longer life has a longer life. The reason for this is that the roller has more severe conditions than the inner and outer rings, including the fact that the roller slips between itself and the cage. However, it has been found that the bearing life can be extended by using SKH2 for all of the inner and outer rings of the roller bearing, the rollers, or the inner and outer rings, and the rollers, that is, using steel containing 3.5% by weight or more of chromium. . Although stainless steel includes martensite and austenite, martensite has low hardness (about 1/4 of martensite) and cannot be used for bearings.

As described above, by using martensitic steel containing chromium in an amount of 3.5% by weight or more for the rolling bearing or the bearing ring, in particular, a lubricating oil having a carbonyl group in the molecule is used. Even when the amount of water in oil is large, the life of the bearing can be improved.

In this embodiment, only the case of the radial cylindrical roller bearing has been described. However, considering the reason for the improvement of the bearing life described in the present invention, the rolling element and the metal cage are directly connected to each other among the rolling bearings in general. Rolling bearings that are in contact with each other, such as radial ball bearings, thrust needle roller bearings, thrust ball bearings, thrust cylindrical roller bearings, and tapered roller bearings, have different degrees of effect, but the bearing life is improved. In this sense, the bearing life can be improved by using martensitic steel containing chromium in an amount of 3.5% by weight or more for the rolling element in the bearing used in a bad environment.

In this embodiment, HFC32 and H are used as the refrigerant.
Only the mixed refrigerant of FC134a was explained, but HC
As long as it uses a chlorine-free refrigerant instead of FC22,
Regardless of HFC system alone or a mixture of these,
As a lubricating oil, there is no choice but to use a synthetic oil having a larger saturated water content than the conventionally used mineral oil. When the type or composition of the mixed refrigerant changes, it is necessary to change the molecular structure of the lubricating oil from the viewpoint of compatibility with the refrigerant. For example,
HFC32, HFC125, HFC134a, HFC1
Regarding the compatibility between the simple substance 43a and a general polyol ester, the HFC125 and the HFC134a are substantially equivalent and the highest, and then the HFC32 and the HFC143a are deteriorated in this order. Therefore, for example, the ester oil selected for HFC125 cannot be diverted to HFC32 as it is,
(1) When the molecular structure of the alcohol is not changed, the number of carbon atoms in the fatty acid is decreased, a branched chain fatty acid is used, (2) an alcohol having a large number of —OH is used,
The molecular structure of the ester needs to be changed. However, since it is an ester, the saturated moisture content reaches about 40 times that of mineral oil, and hydrolysis cannot be avoided. Therefore, by using the above-mentioned martensitic stainless steel for a bearing used in such an atmosphere, The bearing life can be improved regardless of the type and composition of the refrigerant. However, since chrome steel has inherently lower fatigue strength than carbon steel, for example, (1) When using SUS440C instead of the conventional SUJ2 as the material of the radial cylindrical roller bearing or conical bearing, the radial direction When the size is restricted, the axial length of the roller is increased. When the axial size is restricted, the diameter of the roller is reduced to increase the number of rollers. (2) Radial ball bearings and thrust ball bearings In this case, it is necessary to reduce the diameter of the balls and increase the number of balls. Also, (3)
In the case of needle thrust roller bearings, because the sliding speeds of the inner and outer diameter sides of the roller are different, the wear between the rollers and the bearing ring and the friction between the rollers and the cage are suppressed. From the viewpoint, the length of the roller cannot be increased beyond a certain value. Therefore, the desired fatigue life may not be satisfied only by reducing the diameter of the rollers and increasing the number of rollers. In this case, in addition to changing the bearing material, the cage is made of resin and the roller ends are sufficiently crowned (the end faces are finely tapered),
It is desirable to take measures such as dimple treatment (providing fine irregularities) on the surface of the roller and addition of a rust preventive agent to the lubricating oil, if necessary.

The mixed refrigerant may be a simple substance of (A) or a mixed refrigerant of the refrigerants of the (B) group.
Even if hydrocarbons such as methane, ethane, propane, butane, and dimethyl ether are mixed with these mixed refrigerants in order to improve the compatibility of the refrigerant and the synthetic oil, the bearing life can be similarly improved.

If necessary, an antifoaming agent for suppressing foaming of the lubricating oil, an extreme pressure agent for improving the lubricity, a viscosity index improving agent for adjusting the viscosity index, and oxidative deterioration are prevented. Similarly, the addition of antioxidants, acid scavengers for suppressing hydrolysis, etc., also improves the bearing life.

[0038]

The life of the bearing can be improved by using martensitic steel containing chromium in an amount of 3.5% by weight or more for the rolling bearing which is used in a bad environment.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a scroll compressor used in a room air conditioner or a package air conditioner, showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a radial cylindrical roller bearing that is the object of the present invention.

[Explanation of symbols]

1 ... Fixed scroll member, 2 ... Orbiting scroll member,
3, 4 ... End plate, 5, 6 ... Wrap, 7 ... Crank shaft, 8 ... Compression chamber, 9 ... Discharge port, 10 ... Frame, 11 ...
Pressure vessel, 12 ... Discharge pipe, 13 ... Electric motor, 14
... Oil hole, 15 ... Oldham ring, 16 ... Radial cylindrical roller bearing.

Claims (2)

[Claims] 1. A refrigerant comprising (A): a simple substance of difluoromethane or (B): a mixed refrigerant of (A) and at least one kind of a fluorohydrocarbon-based refrigerant group other than (A) or (B). Any one of the mixed refrigerants in which two or more kinds are mixed in the refrigerant group, a lubricating oil, a synthetic oil as a working medium, a drive shaft, an eccentric movement of the rotary motion of the drive shaft connected to the drive shaft, or A refrigerator having a motion conversion mechanism for converting into a reciprocating motion, a compression mechanism for sucking and compressing a refrigerant by the motion conversion mechanism, and a rolling bearing for supporting a force generated on the drive shaft when the refrigerant is compressed by the compression mechanism. In a compressor, a refrigerating machine characterized by using a corrosion-resistant material containing at least 3.5% by weight of chromium as a material of one or both of the rolling elements and the races that compose the rolling bearing. Compressor. 2. The compressor for a refrigerator according to claim 1, wherein the corrosion resistant material is martensitic stainless steel.