JPH03281687A - Working medium for refrigerator and refrigerator using the same - Google Patents

Abstract

PURPOSE:To prevent the roller bearing of a refrigerator from undergoing flaking which is ascribed to water contained in a lubricating oil by using a working medium made of a fluorohydrocarbon-based refrigerant, an aliphatic synthetic lubricating oil and a specific dialkyl nitrite and/or a specific dialkylamine salt. CONSTITUTION:A refrigerant based on a fluorohydrocarbon of formula I (wherein (x) is 1 to 3; and (y) and (z) are each 1 to 7) which has a critical temperature of 40 deg.C or more (e.g. 1,1,1,2-tetrafluoroethane); an aliphatic synthetic lubricating oil (e.g. polyalkylene glycol); and a dialkyl nitrite of formula II (wherein R<1> is cyclohexyl or isopropyl) and/or a dialkylamine salt of formula III (wherein R<2> is octyl) are blended. The amount of the dialkyl nitrite and/or the dialkylamine salt accounts for 0.01wt.% or more of the amount of the aliphatic synthetic lubricating oil.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a working medium for a refrigerator, and in particular to a working medium for a refrigeration compressor having a roller bearing in the rotational drive part of a car air conditioner, etc., and a working medium for the working medium. Regarding the refrigeration equipment used.

[Prior art] In recent years, in order to improve the interior comfort of automobiles, there has been a trend toward proper heating and cooling, and low noise.
Refrigerators have appeared that automatically control the flow rate of refrigerant, which is the working medium of the refrigeration compressor, depending on the indoor temperature.

The above-mentioned refrigeration compressor is a single swash plate type having a piston on one side, and the refrigeration capacity can be controlled by arbitrarily changing the inclination angle of this swash plate depending on the indoor temperature. This swash plate is supported by a bearing, but since the load is large, a roller bearing with a large load capacity is used for the rotational drive part of the bearing.

Dichlorodifluoromethane (CCΩ
2F x ; R12) is used.

Furthermore, naphthenic and paraffinic mineral oils are widely used as lubricating oils because of their good compatibility with the refrigerant.

However, due to the environmental problem of destroying the earth's ozone layer, the use of R12 has been regulated, and an alternative to it has been required.

Possible refrigerants to replace R12 include hydrofluorocarbons or fluorocarbons that have a boiling point close to that of R12. Currently, 1,1,1,2-tetrafluoroethane (CF, CHF2; R134a) is being considered for practical use as an alternative refrigerant.

However, this refrigerant has the disadvantage of extremely poor compatibility with general mineral oil-based lubricating oils [Refrigerating 608] 6 (1,
985)]. The reason for this is thought to be that it does not contain chlorine in the molecule like R12.
Guide Ant Data Book (ASRAE Gu
ide and DataBook) 307
Page (1969)].

[Problems to be Solved by the Invention] Polyalkylene glycol has been proposed as a lubricating oil that dissolves in the hydrofluorocarbon (R134a) (US Pat. No. 4,755,316).

However, this polyalkylene glycol has the problem of high hygroscopicity, and when a refrigeration compressor is operated using such a lubricating oil with a high water content, fatigue-induced flaking (relatively large areas of flaking and falling off) occurs on the roller bearing surface. (phenomenon) may occur, which may cause the vehicle to become inoperable.

In order to prevent this flaking, a polyalkylene glycol in which the water content in the oil is reduced to 200 ppm or less has been proposed (Japanese Patent Laid-Open No. 1-198694).

However, since polyalkylene glycol has the property of easily absorbing water, it is not easy to dehydrate it.

Furthermore, when used in power air conditioners, it is extremely difficult to prevent moisture from penetrating through the rubber hoses of the piping. Therefore, the current situation is that it has no choice but to be used in a state that contains a certain amount of moisture.

FIG. 1 is a sectional view showing an example of a swash plate type refrigeration compressor for a car air conditioner.

The refrigeration compressor is driven by using the rotational force of the engine as V bell)・(
(not shown) to the pulley 1. The compressor is operated and stopped by connecting and disengaging the clutch by turning on or cutting off current to the coil 2 of the magnetic clutch.

A swash plate 6 attached to the shaft 3 by engagement of the clutch
By rotating the piston 8, the piston 8 is moved from side to side via the connecting rod 7. The reciprocating movement of the piston 8 compresses the refrigerant gas in the cylinder into high-pressure refrigerant gas, which is adiabatically expanded by an expansion valve provided outside the compressor to obtain cold heat.

A roller bearing 5 is installed between the swash plate 6 and the piston support 9 of the compressor, and a roller bearing 4 is installed to support the reaction force of the piston applied to the swash plate 6.

The roller bearings 4 and 5 are lubricated by supplying a working medium, which is a mixture of refrigerant and lubricating oil retained at the bottom of the front cover 10, by splashing due to the rotational movement of the swash plate, thereby reducing friction and seizing of the bearings. We are trying to prevent this.

At this time, if the refrigeration compressor is operated using a lubricating oil such as polyalkylene gellicol with a high water content, corrosion will occur in the microcracks that occur on the roller bearing surface, and the microcracks will expand due to this corrosion. I have experienced subsequent flaking. This flaking is thought to be caused by brittle fracture caused by hydrogen that occurs as the bearing material corrodes.

Also, in the case of mineral oil-based lubricating oil, the water content in the oil is 25.1
As the amount increases to 0.400 ppm, the time until flaking occurs becomes shorter. For example, it has been reported that if 1100 ppm of water is 1, then 400 ppm is 0.52 [ASLE Trans, 20 (1977) 244].

As described above, the water content in oil is greatly involved in the occurrence of flaking. Therefore, in order to suppress the occurrence of flaking, it is most desirable to reduce the water content in the oil, but when using a lubricating oil such as polyalkylene glycol, which has a high hygroscopicity, it is very difficult to remove the hygroscopic water. It is difficult to

In view of the above circumstances, an object of the present invention is to provide a working medium for a refrigerator that suppresses flaking of a roller bearing due to moisture in lubricating oil, and a refrigerator using the medium.

[Means for Solving the Problems] The gist of the present invention for achieving the above object is as follows.

(1,) (a) Fluorinated hydrocarbon refrigerant, (b) aliphatic synthetic lubricant, (c) -Large quantity [1] and [■] HNo2 \/ R”-N-R1 (1) R2 \/R1-N-R" [1] (wherein, R
1 is a cyclohexyl group or an isopropyl group, R2 is an octyl group), and at least one of dialkyl nitrite and dialkylamine salt is added to the lubricating oil.
A working medium for a refrigerator, characterized in that the working medium contains 0.01% by weight or more.

(2) (a) a fluorinated hydrocarbon refrigerant, (b) a synthetic lubricating oil consisting of at least one of polyalkylene glycol, neopentyl polyol ester, and polyether-modified siloxane, (C) the above - large amount CI] and (U ) (wherein, R1 is a cyclohexyl group, an isopropyl group, R
2 is an octyl group) A working fluid for a refrigerator, comprising at least 0.01% by weight of at least one of a dialkyl nitrite and a dialkylamine salt, based on the lubricating oil.

The fluorinated hydrocarbon refrigerant has the general formula [■] Cx Hy
F z (m) (X is 1 to 3
, y is an integer from 1 to 7.2), and at least one type of refrigerant selected from refrigerants having a critical temperature of 40° C. or higher is used. For example, refrigerants that do not contain chlorine in their molecules, such as 1,1,1,2-tetrafluoroethane and 1,1,2°2-tetrafluoroethane, are used.

Examples of the dialkyl nitrite represented by the large amount (1) include dicyclohexyl nitrite (VPI powder manufactured by Showa Shell Sekiyu), diisopropyl nitrite, or a mixture thereof with the above (Ranran manufactured by Johoku Kagaku Kogyo), etc. There is a rust inhibitor.

Further, examples of the dialkylamine salt represented by the above-mentioned large amount [11] include dicyclohexylamine offtate (VARDEN-100E, manufactured by Nippon Ferroguard Co., Ltd.).

As lubricating oils, for example, Nilasan Uniloop MB-11 (manufactured by NOF Corporation) is used as a polyalkylene gellicol, and Nilasan
Examples include UNISTA H3O8B (manufactured by NOF Corporation) and PS555 (manufactured by Chisso Corporation) as a polyether-modified siloxane.

The reason why the amount of the dialkyl nitrite or dialkylamine salt is set to 0.01% by weight or more based on the lubricating oil is that if the amount is less than 0.01% by weight, a sufficient effect of suppressing the occurrence of flaking cannot be obtained. Note that depending on the coexistence of the refrigerant or the type of lubricating oil, the aliphatic salts may precipitate.
Since there is a risk of clogging the nozzle of the expansion valve of the refrigerator, the content is preferably 5% by weight or less.

Note that an antifoaming agent, a lateral pressure agent for improving lubrication properties, etc. may be added to the working medium as long as it does not impede the object of the present invention.

[Effect] The dialkyl nitrite added to a lubricating oil.

Amine salts are originally rust preventive agents that vaporize in a closed atmosphere containing steel members, etc., and prevent rust on steel by forming a rust preventive film on the surface of the steel material.

In the present invention, it is considered that the dialkyl nitrite and dialkylamine salt suppress flaking of roller bearings because they suppress moisture, which is the source of hydrogen generation. That is, the aliphatic salt added to the working medium penetrates into the highly active micro-cracks on the bearing surface caused by repeated loads (fatigue) on the roller bearing, and is adsorbed onto the surface to block moisture. This is thought to prevent the generation of hydrogen, thereby suppressing the expansion of microcracks and suppressing the occurrence of flaking.

If hydrogen generation does not occur, the microcracks will be immediately joined and will not expand.

[Example] Next, the present invention will be specifically explained using examples.

For polyalkylene glycol, neopentyl polyol ester, and polyether-modified siloxane having a viscosity of 50 to 60 cSt at 40°C, the fatigue life of roller bearings was compared with and without the dialkyl nitrite and dialkylamine salt.

A fatigue life test of the above roller bearing was conducted as follows.

A high-pressure atmosphere friction tester with a mechanical seal installed between the rotating shaft and the test container was used as the tester. A thrust needle bearing (basic dynamic load rating: 1680 kgf) with an inner diameter of 30 mm was installed in the test container, and the lubricating oil was filled so that the bearing was submerged. After evacuating this, 2 kgf/cm2G of 1.1,1,2-tetrafluoroethane was introduced into the container. 1100 without load
Perform a break-in operation at 0 rpm for 30 minutes.

Next, add a load equal to the basic dynamic load rating of the bearing,
Start operation at 200 rpm. During operation, a vibration tester (bearing monitor made by N'SK) is installed on the side of the container.
The value of is monitored, and when the value increases significantly due to the occurrence of flaking, the operation is stopped and the operation time until then (1)
and the rated fatigue life (L) of the test bearing calculated using the following equations (1) to (3).

L=500− f h1a/a−・−・−−−−−−(
1) f h=f n-Ca/P -----(2) f
n=(3,33/n)''--(3) However, L:
Roller bearing fatigue life time (h) Ca: Basic dynamic load rating (
kg f) p: bearing load (kgf) n: rotational speed (rpm) At this time, if lubrication is sufficient, the ratio (t/L) to the rated fatigue life will be 1 or more. If it is lower than 1, it indicates that there is a defect in lubricity.

The t/L of Examples and Comparative Examples are shown in Tables 1 to 3.

Table 3 As is clear from Table 1, in the case of the oils containing dialkyl nitrite and dialkylamine 7 in Examples 1 to 6, the rated fatigue life is 0.01% or more by weight of the acid salt. The ratio is 0.9 or more to 2, and an inhibitory effect on flaking based on moisture in the oil is recognized.

On the other hand, the t/I of Comparative Examples 1 to 3 in which the dialkyl nitrite and dianol kylamine salts are not blended is 0.3 to 0.
．． It is 5.

Table 2 shows the results of comparing the blending effects of the dialkyl nitrite and dialkylamine salts for three types of highly hygroscopic lubricating oils. The t/L is increased by adding salt to each oil well.

Table 3 shows the t/L when the above-mentioned dialkyl nitrite and amine salt were blended with polyalkylene glycol having a water content of 11,000 pp as a lubricating oil and operated.

In both cases, the effect of blending the aliphatic nitrite and aliphatic amine salt is recognized.

[Effects of the Invention] The working medium for a refrigerating machine of the present invention has the effect of suppressing corrosion and flaking on the bearing surface of a refrigerating compressor, and improves the life of air conditioners and refrigerators using the working medium. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a swash plate compressor for a car air conditioner. 1...Pulley, 2...Coil, 3...Shaft,
4, 5... Roller bearing, 6... Swash plate, 7... Connecting rod. 8... Piston. 9. Piston support. 0...Front cover

Claims (1)

[Claims] 1. (a) Fluorinated hydrocarbon refrigerant, (b) Aliphatic synthetic lubricant, (c) General formulas [I] and [II] ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [I] ▲There are mathematical formulas, chemical formulas, tables, etc.▼[II] (In the formula, R^1 is a cyclohexyl group, an isopropyl group,
A working fluid for a refrigerator, characterized in that it contains at least one of a dialkyl nitrite and a dialkylamine salt represented by (R^2 is an octyl group) in an amount of 0.01% by weight or more based on the lubricating oil. 2. (a) Fluorinated hydrocarbon refrigerant, (b) Synthetic lubricating oil consisting of at least one of polyalkylene glycol, neopentyl polyol ester, and polyether-modified siloxane, (c) General formulas [I] and [II] ▲ There are mathematical formulas, chemical formulas, tables, etc.▼[I] ▲There are mathematical formulas, chemical formulas, tables, etc.▼[II] (In the formula, R^1 is a cyclohexyl group, an isopropyl group,
A working fluid for a refrigerator, characterized in that it contains at least one of a dialkyl nitrite and a dialkylamine salt represented by (R^2 is an octyl group) in an amount of 0.01% by weight or more based on the lubricating oil. 3. The fluorinated hydrocarbon refrigerant has the general formula [III] CxH
yFz [III] (However, x is an integer from 1 to 3, y is from 1 to 7, and z is an integer from 1 to 7)
The working fluid for a refrigerator according to any one of claims 1 to 3, characterized in that the working fluid is at least one selected from refrigerants having a critical temperature of 40° C. or higher. 4. In a refrigeration system equipped with a refrigeration compressor having a roller bearing in the rotation drive part, the working medium of the refrigeration compressor is (a) a fluorinated hydrocarbon refrigerant, (c) polyalkylene glycol, neopentyl polyol ester, and Synthetic lubricating oil consisting of at least one type of polyether-modified siloxane, (c) General formulas [I] and [II] ▲ Contains mathematical formulas, chemical formulas, tables, etc. ▼ [ I ] ▲ Contains mathematical formulas, chemical formulas, tables, etc. ▼ [II ] (In the formula, R^1 is a cyclohexyl group, an isopropyl group,
A refrigeration system characterized by using a working medium containing at least one of a dialkyl nitrite and a dialkylamine salt represented by R^2 is an octyl group in an amount of 0.01% by weight or more based on the lubricating oil.