WO2007029884A1

WO2007029884A1 - Refrigerant compressor, cooling system and refrigerator

Info

Publication number: WO2007029884A1
Application number: PCT/JP2006/318318
Authority: WO
Inventors: Hiromitsu Iwata; Makoto Katayama; Ikutomo Umeoka; Yuuki Yoshimi; Hirotaka Kawabata; Yoshinori Ishida; Masato Ishiwata
Original assignee: Matsushita Electric Industrial Co., Ltd.; Fuji Manufacturing Co., Ltd.
Priority date: 2005-09-08
Filing date: 2006-09-08
Publication date: 2007-03-15
Also published as: JP2009508029A; US20090136375A1; EP1926912A1; KR20080042124A; CN200985869Y; CN1928362A

Abstract

A refrigerant compressor having a compression element comprising sliding components made of metallic materials, wherein a mixed layer is formed by solid-dissolving molybdenum disulfide in at least one of the sliding faces of the sliding components, and a single molybdenum disulfide layer is further formed on the surface of the mixed layer. With this configuration, initial break-in is done using the single layer, and sliding loss is reduced. Even if the single layer peels off, because the molybdenum disulfide of the mixed layer is cleaved at a low friction coefficient, solid lubrication action is attained, the friction coefficient of the sliding section is lowered, and sliding loss is reduced.

Description

DESCRIPTION REFRIGERANT COMPRESSOR, COOLING SYSTEM AND REFRIGERATOR

TECHNICAL FIELD

The present invention relates to a refrigerant compressor being used mainly for household electric refrigerator-freezers

and the like.

BACKGROUND ART

In recent years, highly efficient compressors consuming less fossil fuel have been being developed for the protection of global environment.

In a conventional compressor, one of the sliding members constituting a sliding section is made of a nitrided iron-based material treated with manganese phosphate, and the other sliding member is made of anodized aluminum die cast (for example, refer to Japanese Patent Application Laid-open No. Hei 6-117371). FIG. 14 is a sectional view showing a conventional refrigerant compressor disclosed in Japanese Patent Application Laid-open No. Hei 6-117371. As shown in FIG. 14, in a closed container 1, oil 2 is accumulated at the bottom thereof, and the closed container 1 accommodates an electric driving element 5 comprising a stator 3 and a rotor 4, and also accommodates a reciprocating compression element 6 that is driven using the electric driving element 5.

Next, the details of the compression element 6 will be

described below.

A crankshaft 7 comprises a main shaft section 8 on which the rotor 4 is pressure-fitted so as to be secured thereto and

an eccentric shaft 9 formed so as to be eccentric with respect to the main shaft section 8. The crankshaft 7 is provided with an oil pump 10. A compression chamber 13 having a nearly-

cylindrical bore section 12 is formed in a cylinder block 11, and the cylinder block 1 is provided with a bearing section 14

for journaling the main shaft section 8.

A piston 15, loosely fitted in the bore section 12, is connected to the eccentric shaft 9 via a piston pin 16 and a connecting rod 17 serving as a connecting means. The end face of the bore section 12 is sealed with a valve plate 18.

A head 19 in which a high-pressure chamber is formed is secured to the valve plate 18 on the opposite side of the bore section 12. A suction tube 20 is secured to the closed container 1 and connected to the low-pressure side (not shown) of a refrigerating cycle so as to introduce refrigerant gas (not shown) into the closed container 1. A suction muffler 21 is held between the valve plate 18 and the head 19.

Sliding sections are respectively formed between the main shaft section 8 of the crankshaft 7 and the bearing section 14, between the piston 15 and the bore section 12, between the

piston pin 16 and the connecting rod 17, and between the

eccentric shaft 9 of the crankshaft 7 and the connecting rod 17. One of the sliding members constituting the sliding section is

made of a nitrided iron-based material treated with manganese phosphate, and the other sliding member is made of anodized aluminum die cast.

The operation of the refrigerant compressor configured as described above will be described next. The power supplied from the commercial power supply (not shown) is supplied to the electric driving element 5 to rotate the rotor 4 of the electric driving section 5. The rotor 4 rotates the crankshaft 7, and the eccentric operation of the eccentric shaft 9 is transmitted from the connecting rod 17 serving as a connecting means to the

piston pin 16 to drive the piston 15. Hence, the piston 15 reciprocates inside the bore section 12, and the refrigerant gas introduced into the closed container 1 through the suction tube 20 is sucked through the suction muffler 21 and compressed continuously inside the compression chamber 13. As the crankshaft 7 is rotated, the oil 2 is supplied from

the oil pump 10 to the respective sliding sections to lubricate the sliding sections. In addition, the oil 2 supplied serves as

a seal between the piston 15 and the bore section 12.

The piston 15 is loosely fitted in the bore section 12 while a very small clearance is provided therebetween to reduce

leakage loss. As a result, the piston 15 and the bore section 12 may make partial contact with each other owing to fluctuations in shape and accuracy thereof. However, because

one of the sliding members in the sliding section is treated

with manganese phosphate that is low in hardness and density, even if they make contact with each other, the manganese phosphate at the contact portion is abraded, whereby the shapes of the two mating members can be adapted to each other (initial break-in) . Hence, sliding loss can be reduced at the sliding section between the piston 15 and the bore section 12.

In the refrigerant compressor described in the above- mentioned Japanese Patent Application Laid-open No. Hei 6-117371, because one of the sliding members in the sliding section is

treated with manganese phosphate that is low in hardness and density, the sliding section has good initial break-in performance. However, for example, if the sliding members make contact with each other repeatedly at the time of startup or the like during which no oil film is formed between the sliding

members, the manganese phosphate layer is abraded and lost, and

the base materials of the sliding members may make metallic contact with each other. As a result, the friction coefficient

rises and sliding loss increases in the refrigerant compressor. If the heat generated from the sliding members increases, abrasion may increase and abnormal abrasion may occur.

If abrasion occurs between the piston 15 and the bore

section 12 in particular, the clearance therebetween increases, the compressed refrigerant gas may leak from the clearance between the piston 15 and the bore section 12, and the

efficiency may be lowered.

In addition, metal powder generated by the abrasion reacts

with degraded substances in the oil, and sludge is formed. This sludge adheres to the inner wall of a capillary tube having a minute flow path, and an expansion valve, being generally used as an expander in a cooling system, and may inhibit the

circulation of the refrigerant.

Furthermore, according to another conventional technology, a mixed layer is formed by solid-dissolving molybdenum disulfide

(M0S2) serving as a solid lubricant in the sliding surface of the sliding member so as to function as a sliding material for a compressor (for example, refer to _/ the pamphlet of WO 04/055371) .

FIG. 15 shows the cross-section of a mixed layer formed by solid-dissolving molybdenum disulfide according to the

conventional technology described in the pamphlet of WO 04/055371.

As shown in FIG. 15, a mixed layer 33 is formed by solid- dissolving molybdenum disulfide in the sliding face of a sliding

component that is made of a metallic material and constitutes a compression element. With this configuration, even if metallic

contact occurs between the piston 15 and the bore section 12 at

the top dead center and the bottom dead center of the piston 15 wherein the speed of the piston 15 becomes zero, the friction coefficient is lowered owing to the solid lubrication of the

molybdenum disulfide in the mixed layer 33 formed on the surface of the piston 15, and friction loss can be reduced. Furthermore, minute pits 34 formed in the surface of the sliding section serve as labyrinth seals during compression, whereby leakage loss can be reduced and abrasion resistance can be improved.

According to the specifications described in the pamphlet of the above-mentioned WO 04/055371, even if solid-to-solid contact occurs, the molybdenum disulfide of the mixed layer 33 is cleaved at low friction coefficient, and self-lubrication action is achieved. However, according to the specifications, the mixed layer has hardness close to that of the base material, and the effect of initial break-in is hardly obtained. Hence, sliding loss cannot be reduced, and there is a problem of lowering the efficiency of the compressor. Additionally, although the mixed layer has self-

lubrication action, if the mixed layer or the sliding face of the mating sliding component is abraded, there is a problem of generating metal powder and metallic salts.

For example, in the case that a mixed layer is formed by solid-dissolving molybdenum disulfide in a sliding face, as

described in the pamphlet of WO 04/055371, and that the

manganese phosphate treatment described in Japanese Patent Application Laid-open No. Hei 6-117371 is further carried out on

the mixed layer, it is conceived that the advantages of using the two methods are obtained. However, if the manganese phosphate treatment is carried out on the mixed layer, the surface of the sliding component and the mixed layer formed by solid-dissolving molybdenum disulfide in the surface are corroded and lost because of the chemical reactions carried out during the manganese phosphate treatment according to the chemical reaction formulas: (chemical formula 1), (chemical formula 2) and (chemical formula 3) described below. For this reason, it is almost impossible to realize the configuration described above.

2H₃PO₄ + Fe → Fe(H₂PO₄J₂ + H₂ (Chemical formula 1)

Me (H₂PO₄ )₂ → MeHPO₄ + H₃PO₄ (Chemical formula 2)

3MeHPO₄ → Me₃ (PO₄) ₂ + H₃PO₄ (Chemical formula 3) where Me is a divalent metallic salt (Fe, Mn), Me(H₂PO₄J₂ is a primary phosphate, MeHPO^ is a secondary phosphate, and Me₃ (PO₄) ₂

is a tertiary phosphate.

DISCLOSURE OF THE INVENTION

The present invention has been made to solve the conventional problems described above, and is intended to

provide a refrigerant compressor being capable of reducing sliding loss and having high reliability and high efficiency.

For the purpose of solving the conventional problems

described above, a refrigerant compressor according to the present invention is characterized in that a mixed layer is formed by solid-dissolving molybdenum disulfide in at least one

of the sliding faces of the sliding components made of metallic materials, and a single molybdenum disulfide layer is further formed on the surface of the mixed layer. With this configuration, initial break-in is done using the single molybdenum disulfide layer. This produces effects of reducing sliding loss, suppressing abrasion on the base material and the mixed layer or the sliding face of the mating sliding component, and preventing generation of metal powder. Furthermore, in the refrigerant compressor according to the present invention, even if the single layer peels off and solid-to-solid contact occurs, because the molybdenum disulfide of the mixed layer has a hexagonal closed packing crystal structure, the molybdenum disulfide is cleaved at a low friction coefficient, whereby

solid lubrication action is attained. This produces effects of lowering the friction coefficient of the sliding component and

reducing sliding loss.

In the refrigerant compressor according to the present invention, a mixed layer is formed by solid-dissolving

molybdenum disulfide in a sliding face, and a single molybdenum

disulfide layer is further formed on the surface of the mixed layer as described above. With this configuration, the friction

coefficient can be reduced, and it is possible to provide a refrigerant compressor having high reliability and high efficiency. Furthermore, in the refrigerant compressor

according to the present invention, it is possible to suppress generation of metal abrasion powder from the mixed layer, the base material and the sliding face of the mating sliding component. Hence, the amounts of metallic salts formed by the reaction between the metal abrasion powder and degraded oil are reduced. As a result, even if the refrigerant paths have minute paths, such as a capillary tube and an expansion valve, the minute paths can be prevented from being clogged with metallic salts .

An invention set forth in claim 1 is characterized in that a compression element comprises sliding components made of metallic materials, and that a mixed layer is formed by solid- dissolving molybdenum disulfide in at least one of the sliding

faces of the sliding components, and a single molybdenum disulfide layer is further formed on the surface of the mixed layer. With this configuration, the friction coefficient is

lowered by the self-lubrication action of the molybdenum disulfide of the single molybdenum disulfide layer. This produces an effect of reducing sliding loss. Furthermore,

according to the invention set forth in claim 1, even if the single layer peels off and solid-to-solid contact occurs, because the molybdenum disulfide of the mixed layer has a

hexagonal closed packing crystal structure, the molybdenum disulfide is cleaved at a low friction coefficient, whereby solid lubrication action is attained. This lowers the friction

coefficient of the sliding component and reduces sliding loss. Hence, according to the invention set forth in claim 1, it is

possible to suppress metal abrasion on the mixed layer, the base material and the sliding face of the mating sliding component, whereby it is possible to provide a refrigerant compressor having high reliability and high efficiency. An invention set forth in claim 2 is characterized in that the maximum concentration of the molybdenum disulfide in the mixed layer according to the invention set forth in claim 1 is 5

wt% or more. Hence, the self-lubrication of the molybdenum disulfide of the mixed layer is stabilized, and the friction coefficient is lowered further. For this reason, according to the invention set forth in claim 2, it is possible to suppress metal abrasion on the mixed layer, the base material and the

sliding face of the mating sliding component, in addition to the

effects of the invention set forth in claim 1, whereby it is possible to provide a refrigerant compressor having high

reliability and high efficiency.

An invention set forth in claim 3 is characterized in that the thickness of the mixed layer according the invention set

forth in claim 1 is 0.1 to 2.0 μm. By the setting of the thickness of the mixed layer at 0.1 to 2.0 μm, the solid lubrication action of the molybdenum disulfide of the mixed layer can be attained stably. Hence, according to the invention set forth in claim 3, the friction coefficient of the sliding component is lowered, and sliding loss can be reduced. For this reason, according to the invention set forth in claim 3, it is possible to suppress metal abrasion on the mixed layer, the base material and the sliding face of the mating sliding component, in addition to the effects of the invention set forth in claim 1, whereby it is possible to provide a refrigerant compressor having high reliability and high efficiency.

An invention set forth in claim 4 is characterized in that the purity of the molybdenum disulfide of the single molybdenum disulfide layer according to the invention set forth in claim 1

is 98% or more. Hence, the amounts of impurities having friction coefficients higher than that of the molybdenum disulfide become very small, whereby the friction coefficient of the single molybdenum disulfide layer can be lowered, and

sliding loss can be reduced. For this reason, according to the invention set forth in claim 4, it is possible to suppress metal

abrasion on the mixed layer, the base material and the sliding

face of the mating sliding component, in addition to the effects of the invention set forth in claim 1, whereby it is possible to

provide a refrigerant compressor having high reliability and

high efficiency.

An invention set forth in claim 5 is characterized in that the thickness of the single molybdenum disulfide layer according to the invention set forth in claim 1 is 0.1 to 2.0 μm. Even if the single layer having a thickness of 0.1 to 2.0 μm peels off, the amount of leakage from between the piston and the bore section does not increase excessively, and freezing capacity is not lowered. For this reason, according to the invention set

forth in claim 5, it is possible to provide a refrigerant compressor having higher efficiency, in addition to the effects of the invention set forth in claim 1. ■

An invention set forth in claim 6 provides the refrigerant compressor set forth in any one of claims 1 to 5, wherein oil is accumulated and a compression element is accommodated in a closed container, the compression element is a reciprocating compression element comprising a crankshaft equipped with a main shaft and an eccentric shaft; a thrust section, one end of which

is integrated with the crankshaft and the other end of which is integrated with a bearing section; the bearing section rotatably journaling the main shaft; a cylinder block in which a

cylindrical bore section is formed; a piston reciprocating

inside the cylindrical bore section; a piston pin disposed in parallel with the eccentric shaft and secured to the piston; and a connecting rod for connecting the eccentric shaft to the

piston, and the sliding component made of a metallic material is at least either one of the crankshaft, the thrust section, the cylinder block, the piston, the piston pin, and the connecting rod. With this configuration of the invention set forth in claim 6, initial break-in is done using the single molybdenum disulfide layer. This produces an effect of reducing sliding loss. Even if the single layer peels off and solid-to-solid contact occurs, because the molybdenum disulfide of the mixed layer has a hexagonal closed packing crystal structure, the molybdenum disulfide is cleaved at a low friction coefficient, whereby solid lubrication action is attained. This produces

effects of lowering the friction coefficient of the sliding component and reducing sliding loss. For this reason, according to the invention set forth in claim 6, it is possible to suppress metal abrasion on the mixed layer, the base material and the sliding face of the mating sliding component, whereby it is possible to provide a refrigerant compressor comprising a

reciprocating compression element and having high reliability

and high efficiency. An invention set forth in claim 7 provides the refrigerant

compressor according to the invention set forth in any one of

claims 1 to 5, wherein oil is accumulated and a compression element is accommodated in a closed container, the compression

element comprises a crankshaft equipped with a main shaft and an eccentric shaft; a thrust section, one end of which is integrated with the crankshaft and the other end of which is integrated with a bearing section; the bearing section rotatably

journaling the main shaft; a cylinder block in which a cylindrical bore section is formed; a piston reciprocating inside the cylindrical bore section; and a connecting rod to which a ball is secured on the side connected to the piston, the piston in which the ball is movably held by crimping constitutes a reciprocating compression element, and the sliding component made of a metallic material is at least either one of the crankshaft, the thrust section, the cylinder block, the piston, and the connecting rod. With this configuration of the invention set forth in claim 7, initial break-in is done using the single molybdenum disulfide layer. This produces an action

of reducing sliding loss. Even if the single layer peels off and solid-to-solid contact occurs, because the molybdenum disulfide of the mixed layer has a hexagonal closed packing

crystal structure, the molybdenum disulfide is cleaved at a low friction coefficient, whereby solid lubrication action is attained. This produces effects of lowering the friction

coefficient of the sliding component and reducing sliding loss. For this reason, according to the invention set forth in claim 7, it is possible to suppress metal abrasion on the mixed layer, the base material and the sliding face of the mating sliding

component. As a result, the amount of metal abrasion powder that enters the crimped section between the piston and the ball and is trapped therebetween is reduced. Hence the free movement of the ball cannot be restricted, and it is possible to provide a reciprocating refrigerant compressor comprising a reciprocating compression element and having high reliability

and high efficiency.

An invention set forth in claim 8 provides the refrigerant compressor according to the invention set forth in any one of claims 1 to 5, wherein oil is accumulated and a compression element is accommodated in a closed container, the compression element is a rolling-piston-type compression element comprising a shaft having an eccentric section; a cylinder in which a compression chamber is formed in coaxial with the rotation center of the shaft; a rolling piston that is loosely fitted on

the eccentric section and rolls inside the compression chamber; a vane that partitions the compression chamber into the high-

pressure side and the low-pressure side thereof when made contact with the rolling piston under pressure; a main bearing and an auxiliary bearing that are used to seal both end faces of

the cylinder and to journal the shaft on the side of an electric

driving element and on the opposite side of the electric driving element, respectively; an oil supply spring secured to one end

of_, the shaft; and an oil supply pipe that accommodates the oil supply spring and one end of which is open and immersed in the oil, and the sliding component made of a metallic material is at

least either one of the shaft, the cylinder, the rolling piston, the vane, the main bearing, the auxiliary bearing, the oil supply spring and the oil supply pipe. With this configuration of the invention set forth in claim 8, initial break-in is done using the single molybdenum disulfide layer. This produces an effect of reducing sliding loss. Even if the single layer peels

off and solid-to-solid contact occurs, because the molybdenum disulfide of the mixed layer has a hexagonal closed packing crystal structure, the molybdenum disulfide is cleaved at a low friction coefficient, whereby solid lubrication action is attained. This produces effects of lowering the friction coefficient of the sliding component and reducing sliding loss. For this reason, according to the invention set forth in claim 8,

it is possible to suppress metal abrasion on the mixed layer, the base material and the sliding face of the mating sliding

component. It is therefore possible to provide a refrigerant compressor comprising a rotary compression element and having high reliability and high efficiency.

An invention set forth in claim 9 provides a cooling

system comprising the refrigerant compressor set forth in any one of claims 1 to 8, and an expander equipped with either a

capillary tube or an expansion valve. According to the invention set forth in claim 9, the amount of metal abrasion powder discharged from the compressor is small, and the amounts of metallic salts formed by the reaction between the metal abrasion powder and degraded oil and adhering to the inner wall of the capillary tube serving as a minute path and the minute paths inside the expansion valve are reduced. Hence, the circulation of the refrigerant is not obstructed, and it is possible to provide a cooling system having high reliability.

An invention set forth in claim 10 provides a refrigerator, such as a household refrigerator, having a cooling system comprising the refrigerant compressor set forth in any one of

claims 1 to 8, and an expander equipped with either a ^'capillary tube or an expansion valve that is more minute than those of general-purpose refrigerated warehouses and industrial refrigerators having large amounts of refrigerant circulation.

Because the invention set forth in claim 10 has the cooling system set forth in claim 9, the amount of metal abrasion powder discharged from the compressor is small, and the amounts of

metallic salts formed by the reaction between the metal abrasion powder and degraded oil and adhering to the inner wall of the

capillary tube serving as a minute path and the minute paths

inside the expansion valve are reduced. Hence, the circulation of the refrigerant is not obstructed, and it is possible to provide a household refrigerator having high reliability, for

example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a refrigerant compressor according to Embodiment 1 of the present invention;

FIG. 2 is a magnified view of portion A in FIG. 1;

FIG. 3 is a magnified view of portion B in FIG. 2;

FIG. 4 is a view showing how molybdenum disulfide is formed according to Embodiment 1 of the present invention; FIG. 5 is a characteristic graph showing the relationship between the freezing capacity and the clearance between the

piston and the bore section of the refrigerant compressor according to Embodiment 1 of the present invention;

FIG. 6 is a view showing the concentration distribution of

molybdenum disulfide according to Embodiment 1 of the present

invention;

FIG. 7 is a characteristic graph showing the relationship

between the concentration of molybdenum disulfide and the efficiency according to Embodiment 1 of the present invention; FIG. 8 is a connecting rod assembly drawing showing a ball

secured to a connecting rod and connected to a piston by

crimping so as to be movable freely according to Embodiment 1 of the present invention; FIG. 9 is a view showing the configuration of a household

refrigerator according to Embodiment 1 of the present invention;

FIG. 10 is a sectional view showing an expansion valve according to Embodiment 1 of the present invention;

FIG. 11 is a sectional view showing a refrigerant compressor according to Embodiment 2 of the present invention;

FIG. 12 is a sectional view taken on line C-D in 'FIG. 11;

FIG. 13 is a magnified view of portion E in FIG. 12;

FIG. 14 is a sectional view showing the conventional refrigerant compressor; and FIG. 15 is a sectional view showing the conventional mixed layer formed by solid-dissolving molybdenum disulfide.

BEST MODES FOR CARRYING OUT THE INVENTION (Embodiment 1) FIG. 1 is a sectional view showing a refrigerant

compressor according to Embodiment 1 of the present invention, FIG. 2 is a magnified view of portion A in FIG. 1, FIG. 3 is a

magnified view of portion B in FIG. 2, FIG. 4 is a view showing

how molybdenum disulfide is formed according to Embodiment 1, FIG. 5 is a characteristic graph showing the relationship

between the freezing capacity and the clearance between the

piston and the bore section of the refrigerant compressor according to Embodiment 1, FIG. 6 is a view showing the concentration distribution of molybdenum disulfide according to

Embodiment 1, FIG. 7 is a characteristic graph showing the relationship between the concentration of molybdenum disulfide

and the efficiency according to Embodiment 1, FIG. 8 is a connecting rod assembly drawing showing a ball secured to a connecting rod and connected to a piston by crimping so as to be movable freely according to Embodiment 1, FIG. 9 is a view showing the configuration of a household refrigerator according to Embodiment 1, and FIG. 10 is a sectional view showing an expansion valve according to Embodiment 1. In FIGS. 1, 2 and 3, a closed container 101 is filled with refrigerant gas 102, R600a, and oil 103 is accumulated at the bottom of the closed container 10,1. Furthermore, the closed container 101 accommodates an electric driving element 106 comprising a stator 104 and a rotor 105, and also accommodates a reciprocating compression element 107 that is driven using the

electric driving element 106.

The details of the compression element 107 will be described below.

A crankshaft 108 comprises a main shaft 109 on which the rotor 105 is pressure-fitted so as to be secured thereto and an

eccentric shaft 110 formed so as to be eccentric with respect to

the main shaft 109. An oil pump 111 communicating with the bottom of the closed container 101 in which the oil 103 is accumulated is provided at the lower end of the crankshaft 108. A nearly cylindrical bore section 113 is formed in a cylinder block 112 made of cast iron, and the cylinder block 112 is provided with a bearing section 114 for journaling the main

shaft 109. In addition, a flange face 120 is formed on the rotor 105,

and a thrust section 122 is formed on the upper end face of the bearing section 114. A thrust washer 124 is inserted between the flange face 120 and the thrust section 122 of the bearing section 114. The flange face 120, the thrust section 122 and the thrust washer 124 constitute a thrust bearing section 126.

A piston 132 made of an iron-based material is loosely fitted in the bore section 113 while having a constant clearance therebetween. The piston 132 and the bore section 113 form a compression chamber 134. The piston 132 is connected to the eccentric shaft 110 via a piston pin 137 and a connecting rod

138 serving as a connecting means. The end face of the bore section 113 is sealed with a valve plate 139.

A head 140 in which a high-pressure chamber is formed is

secured to the valve plate 139 on the opposite side of the bore section 113. A suction tube (not shown) is secured to the

closed container 101 and connected to the low-pressure side (not

shown) of a refrigerating cycle so as to introduce refrigerant gas 102 into the closed container 101. A suction muffler 142 is held between the valve plate 139 and the head 140.

Sliding sections are respectively formed between the piston 132 and the bore section 113, between the main shaft 109 and the bearing section 114, between the thrust section 122 and the thrust washer 124, between the piston pin 137 and the connecting rod 138, and between the eccentric shaft 110 and the

connecting rod 138. In at least one of the sliding members constituting the sliding section, a mixed layer 150 is formed by solid-dissolving molybdenum disulfide in the surface of the base material, and a single molybdenum disulfide layer 160 is further formed on the surface of this mixed layer 150.

The configuration of the sliding member will be described below in detail, taking the piston 132 as an example.

In the sliding section provided between the piston 132 and the bore section 113, the mixed layer 150 is formed by solid- dissolving molybdenum disulfide in the sliding surface of the

piston 132, that is, the surface of an iron-based material serving as the base material thereof, and the single molybdenum

disulfide layer 160 is further formed on the surface of the

mixed layer 150. It is preferable that the purity of the molybdenum disulfide should be 98% or more, that the thickness

of the single molybdenum disulfide layer 160 should be 0.1 to

2.0 urn, that the thickness of the mixed layer 150 should be 0.1 to 2.0 urn, and that the maximum concentration of the molybdenum

disulfide in the mixed layer 150 should be 5 wt% or more and 50

wt% or less .

As a method for forming the mixed layer 150 in which molybdenum disulfide is solid-dissolved and further forming the single molybdenum disulfide layer 160 on the surface of the mixed layer 150, a method for colliding the particles of molybdenum disulfide having a purity of 98% or more with the sliding face made of a metal serving as the base material of a sliding component at a speed of a certain level or more is used in Embodiment 1 of the present invention. It is preferable that the projection pressure of molybdenum disulfide at this time should be 1.0 to 1.5 MPa. With this method, the oxygen in the surface of the base material is diffused using the thermal energy generated during the collision, and the single molybdenum disulfide layer 160 is formed. In addition, by the collision of the particles of

molybdenum disulfide, some of the particles are melted into the base material and bonded metallically. As a result, it is found

that the mixed layer 150 in which molybdenum disulfide is solid-

dissolved and the single molybdenum disulfide layer 160 can be formed simultaneously.

The piston 132 is loosely fitted in the bore section 113

while a very small clearance of approximately 5 to 15 μm for example in a diametric direction is provided therebetween to

reduce leakage loss.

The operation of the refrigerant compressor according to Embodiment 1 configured as described above will be described . below.

The power supplied from the commercial power supply (not shown) is supplied to the electric driving element 106 to rotate the rotor 105 of the electric driving element 106. By the rotation of the rotor 105, the crankshaft 108 is rotated, and the eccentric shaft 110 is rotated eccentrically. The eccentric operation of the eccentric shaft 110 is transmitted from the connecting rod 138 serving as a connecting means to the piston pin 137 to drive the piston 132. Hence, the piston 132 reciprocates inside the bore section 113. As a result, the refrigerant gas 102 introduced into the closed container 101 through the suction tube (not shown) is sucked through the suction muffler 142 and compressed inside the compression

chamber 134.

As the crankshaft 108 is rotated, the oil 103 is supplied

from the oil pump 111 to the respective sliding sections to

lubricate the sliding sections. In addition, the oil 103 supplied serves as a seal between the piston 132 and the bore

section 113.

Because the clearance between the piston 132 and the bore section 113 is very small, the piston 132 and the bore section

113 may make partial contact with each other during the sliding

operation owing to fluctuations in shape and accuracy thereof.

In Embodiment 1, because the molybdenum disulfide of the single molybdenum disulfide layer 160 has a property of being cleaved

very easily, the shapes. of the two mating members can be adapted to each other, and initial break-in is done appropriately. As a result, the molybdenum disulfide of the single molybdenum disulfide layer 160 making contact with the surface of the mating sliding member is abraded and adapted to the shape of the

surface. Therefore, sliding loss can be reduced, and it is possible to provide a refrigerant compressor having high efficiency.

The relationship between freezing capacity and the amount of leakage from between the piston 132 and the bore section 113 will be described below referring to FIG. 5. The horizontal axis of FIG. 5 represents the clearance between the piston 132 and the bore section 113, and the vertical axis represents the freezing capacity.

According to the results shown in FIG. 5, when it is

assumed that the specified clearance is in the range of A to B μm, the freezing capacity lowers abruptly when the clearance

exceeds B + 4 μm.

Hence, the single molybdenum disulfide layer 160 on the sliding surface of the piston 132 is formed to have a thickness of .0.1 to 2.0 μm. With this configuration, even if the single molybdenum disulfide layer 160 peels off during operation, the increase in the clearance between the piston 132 and the bore

section 113 is limited to 4.0 μm at the maximum. As a result, in the configuration of Embodiment 1, the amount of leakage from between the piston 132 and the bore section 113 does not increase excessively, and the freezing capacity is not reduced excessively. It is thus possible to provide a refrigerant compressor having stably higher efficiency.

Next, in the refrigerant compressor according to Embodiment 1 of the present invention, the effects of the single molybdenum disulfide layer 160 and the mixed layer 150 formed on

the sliding surface will be described below.

When the piston 132 is positioned at the top dead center and at the bottom dead center, its speed becomes 0 m/s, no oil pressure is generated theoretically, and no oil film is formed.

Hence, metallic contact occurs frequently at the top dead center and the bottom dead center.

Furthermore, when the piston 132 of the refrigerant

compressor is positioned at the top dead center, the piston 132 receives a large compression load due to the compressed high-

pressure refrigerant. This compression load is transmitted to

the crankshaft 108 via the piston pin 137 and the connecting rod 138, and the crankshaft 108 is pressed by the piston 132

positioned near the top dead center and then tilted. This tilting of the crankshaft 108 generates a force of tilting the piston 132 inside the bore section 113. As a result, an end of the upper end face of the piston 132 on one side thereof and an end of the lower end face of the piston 132 on the other side thereof make contact with the bore section 113, and prying

occurs. Because of this prying, the piston 132 and the bore section 113 rub against each other, and abrasion occurs. In the case of the refrigerant compressor having the cantilevered bearing according to Embodiment 1, the tilting of the crankshaft 108 becomes large, and the prying occurs significantly.

As a result, the single molybdenum disulfide layer 160 is abraded, and the mixed layer 150 is exposed on the surface and

may be used as a sliding face.

In Embodiment 1, the molybdenum disulfide of the mixed layer 150 has a hexagonal closed packing crystal structure, and

the size of its molecule is very small, approximately 6 * lO^"14 μm. Hence the molybdenum disulfide is cleaved at a low friction

coefficient. Therefore, even if metallic contact occurs between the piston 132 and the bore section 113, the friction coefficient of the sliding section becomes low, and the sliding

loss is reduced. It is thus possible to provide a refrigerant compressor having high reliability.

FIG. 6 shows the concentration distribution of the

molybdenum disulfide formed on the sliding surface of the piston

132 according to Embodiment 1 of the present invention.

An energy dispersive X-ray analyzer is generally used to

measure the concentration of the molybdenum disulfide that is formed on the sliding face of the piston 132 and shown in FIG. 6, This energy dispersive X-ray analyzer will be described below

briefly.

Electrons emitted from the energy dispersive X-ray analyzer to the sliding surface of the piston 132 penetrate into

the sliding surface to a certain depth, and a characteristic X- ray is generated. A vacancy is formed when an electron orbiting the atomic nucleus of an atom is ejected outside from the atom

by an electron having penetrated to the certain depth, and an electron at a higher energy level makes a transition to the vacancy. At the time of the transition, excessive energy is

generated as an X-ray being characteristic to each element, and the X-ray is referred to as the characteristic X-ray.

Because the energy dispersive X-ray analyzer can analyze

the elements constituting the sliding surface of the piston 132

using the characteristic X-ray, the analyzer can measure the concentration of the molybdenum disulfide formed on the sliding

surface. The maximum concentration of the molybdenum disulfide

in the mixed layer 150 is obtained near the most outer surface, and can be detected by measuring the concentration near the most

outer surface.

As shown in FIG. 6, the thickness of the mixed layer 150 containing the molybdenum disulfide is 0.1 to 2.0 μm, and its maximum concentration is 5 to 20 wt%. When the molybdenum

disulfide of the mixed layer 150 described above is formed as described above, the self-lubrication of the molybdenum

disulfide is stabilized, and the friction coefficient is reduced further.

Next, the relationship between the maximum concentration

of the molybdenum disulfide in the mixed layer 150 and the efficiency of the refrigerant compressor will be described below in detail referring to FIG. 7. FIG. 7 shows the relationship between the maximum concentration of the molybdenum disulfide in

the mixed layer 150 and the efficiency (C. O. P.: Coefficient of performance) of the refrigerant compressor. The refrigerant compressor having been operated for a certain period was used to

obtain the relationship. As described above, the piston 132 being tilted reciprocates inside the bore section 113, and an

end of the upper end face of the piston 132 on one side thereof

and an end of the lower end face of the piston 132 on the other side thereof make contact with the bore section 113, and prying

occurs. The mixed layer 150 of the piston 132 serves as a

sliding face.

As shown in FIG. 7, the efficiency of the refrigerant

compressor rises abruptly when the maximum concentration of the molybdenum disulfide in the mixed layer 150 exceeds 5 wt% . The efficiency of the refrigerant compressor becomes almost constant when the, maximum concentration exceeds 15 wt%. Hence, it is conceived that the self-lubrication of the molybdenum disulfide is stabilized when the maximum concentration of the molybdenum

disulfide in the mixed layer 150 is at least 5 wt% .

On the other hand, for the purpose of raising the maximum concentration of the molybdenum disulfide in the mixed layer 150,

the particles of the molybdenum disulfide must be collided against a metallic sliding face for a long time, that is, numerous particles must be collided. For this reason, it is

practical that the maximum concentration should remain approximately 20 wt% in consideration of the cost and productivity of the molybdenum disulfide. Hence, the maximum concentration of the molybdenum

disulfide in the mixed layer 150 according to Embodiment 1 is controlled between 5 to 20 wt%.

In Embodiment 1 according to the present invention, the compressor operating at a constant speed has been described above. As more and more refrigerant compressors have been being

driven using inverters in recent years, the speeds of the

refrigerant compressors become lower. In the case of very slow operation at less than 20 Hz in particular, fluid lubrication is

hardly attained, and metallic contact is apt to occur. For this reason, the effects of the present invention are further significant .

It has been described that Embodiment 1 of the present invention is configured so that the mixed layer 150 is formed by solid-dissolving molybdenum disulfide in the sliding surface of the piston 132, and the single molybdenum disulfide layer 160 is further formed on the surface of the mixed layer 150. However, in the refrigerant compressor according to the present invention, the mixed layer 150 and the single molybdenum disulfide layer 160 may be formed on the sliding surface of the bore section 113 or on the - sliding surfaces of both the piston 132 and the bore

section 113. By the use of the mixed layer 150 and the single molybdenum disulfide layer 160 formed on both the sliding members, higher abrasion resistance is obtained. In Embodiment 1 of the present invention, the

configuration wherein the mixed layer 150 is formed by solid- dissolving molybdenum disulfide in the sliding surface of the

piston 132 and the single molybdenum disulfide layer 160 is further formed on the surface of the mixed layer 150 has been taken as an example and described in detail. However, even if

the mixed layer 150 and the single molybdenum disulfide layer

160 are formed at the sliding sections between the main shaft 109 of the crankshaft 108 and the bearing section 114, between

the flange face 120 of the rotor 105 and the thrust washer 124, between the thrust section 122 on the upper end face of the bearing section 114 and the thrust washer 124, between the piston pin 137 and the connecting rod 138, and between the

eccentric shaft 110 and the connecting rod 138, similar excellent effects are obtained.

In Embodiment 1 of the present invention, the thrust bearing section 126 comprising the flange face 120, the thrust section 122 and the thrust washer 124 has been taken as an

example and described. However, even if the thrust bearing comprises the thrust face 172 of the crankshaft 108, provided on the flange section 170 between the main shaft 109 and the eccentric shaft 110 of the crankshaft 108 on the opposite side of the eccentric shaft 110, and the thrust section 122 of the bearing section 114, similar excellent effects are obtained. In addition, the piston 181 shown in FIG. 8 is provided

with a connecting rod 183 to which a ball 182 is secured on the side connected to the piston 181. The piston 181 is configured

so that the ball 182 is crimped so as to be freely movable in

the piston 181. In the case of a joint generally referred to as a ball joint, the amount of metal abrasion powder that enters

the crimped free movement section and is trapped therein is

reduced. Hence the free movement cannot be restricted, and high efficiency obtained immediately after production can be

maintained.

A resin member 184 is held between the piston 181 and the ball 182 as an intervening member that is used to ensure smooth sliding therebetween as shown in FIG. 8.

A capillary tube 188 is used for the expander of a household refrigerator shown in FIG. 9. For the purpose of obtaining the four-star performance according to Japanese

Industrial Standards (JIS) and maintaining the temperature of the freezer compartment at -18⁰C, the amount of decompression in the capillary tube 188 is increased, that is, the inside diameter thereof is designed so as to be less than 1 mm, so that the temperature of the evaporator 196 is approximately -30⁰C. Adhesion of foreign substances to minute paths as typified by the capillary tube 188 and to refrigerant paths inside the high- temperature compressor 197 becomes a major cause of reduction in

cooling capacity. For this reason, intrusion of foreign

substances is strictly limited during the production of household refrigerators, consumer durables having a service life

of 10 or more years. Hence, regulations are enforced with

respect to the purity of refrigerant and oil, and with respect to residual moisture, metalworking oil, etc. Furthermore,

because residual air becomes a cause of occurrence of foreign

substances owing to oxidation, vacuuming is carried out to attain high vacuum, and refrigerant is hermetically sealed. _, Next, the flow of the refrigerant will be described below.

The refrigerant is compressed using the compressor 197 and passes through the condenser 198, and the heat of the

refrigerant is radiated. Then, the refrigerant is decompressed using the capillary tube 188, the heat inside the refrigerator 199 is absorbed using the evaporator 196, and the refrigerant returns to the compressor 197.

The refrigerant flows complicatedly in a state of gas- liquid mixed current at the entrance (not shown) and the exit (not shown) of the capillary tube. Hence, foreign substances that are hard to be dissolved in oil adhere generally to the entrance and the exit, thereby restricting the circulation of the refrigerant. In the household refrigerator 195 according to Embodiment 1, because intrusion of foreign substances during production is strictly limited, adhesion of foreign substances

to the entrance and the exit of the capillary tube, described above, rarely occurs. In addition, the amount of metal abrasion powder in the household refrigerator configured as described

above is small. Hence, the amounts of metallic salts formed by the reaction between the metal abrasion powder and degraded oil and adhering to the refrigerant paths are reduced, and foreign substances adhering .to the refrigerant paths can be limited very

strictly. Therefore, the circulation amount of the refrigerant is not reduced, and it is possible to provide a household refrigerator having high reliability.

Furthermore, although the capillary tube 188 is used in Embodiment 1, even when the expansion valve 189, an example of which is shown in FIG. 10, is used, the restriction of the circulation of the refrigerant owing to foreign substances adhering to the valve seat face 190 thereof can be prevented,

and excellent effects can be obtained.

(Embodiment 2)

FIG. 11 is a sectional view showing a refrigerant compressor according to Embodiment 2 of the present invention, FIG. 12 is a sectional view taken on line C-D in FIG. 11, and FIG. 13 is a magnified view of portion E in FIG. 12.

In FIGS. 11, 12 and 13, a closed container 201 accommodates an electric driving element 204 comprising a stator

202 and a rotor 203, and a rolling-piston-type compression element 205 driven using the electric driving element 204, together with oil 206.

The compression element 205 comprises a shaft 210 having

an eccentric section 207, a main shaft section 208 and an auxiliary shaft section 209; a cylinder 212 in which a

compression chamber 211 is formed; a main bearing 213 and an

auxiliary bearing 214 that are used to seal both end faces of the cylinder 212 and to journal the main shaft section 208 and the auxiliary shaft section 209, respectively; a rolling piston

215 that is loosely fitted on the eccentric section 207 and rolls inside the compression chamber 211; and a plate-shaped

vane 216 that is pressed against the rolling piston 215 and is used to partition the compression chamber 211 into the high- pressure side and the low-pressure side thereof. The rotor 203 is secured to the main shaft section 208

An oil pump 217 secured to the auxiliary bearing 214 comprises an oil supply pipe 220 and an oil supply spring 222 loosely fitted in this oil supply pipe 220. The oil pump 217 supplies the oil 206 to each of the sliding sections formed between the eccentric section 207 and the rolling piston 215,

between the main shaft section 208 and the main bearing 213, and between the auxiliary shaft section 209 and the auxiliary bearing 214.

In Embodiment 2, a mixed layer 224 is formed by solid- dissolving molybdenum disulfide in the sliding surfaces of the eccentric section 207, the main shaft section 208 and the

auxiliary shaft section 209 of the shaft 210, that is, the surface of an iron-based (Fe-based) material serving as the base material thereof, and a single molybdenum disulfide layer 228 is

further formed on the surface of the mixed layer 224.

It is preferable that the purity of the molybdenum disulfide should be 98% or more, that the thickness of the single molybdenum disulfide layer 228 should be 0.1 to 2.0 μm, that the thickness of the mixed layer 224 should be 0.1 to 2.0 μm, and that the maximum concentration of the molybdenum disulfide in the mixed layer 224 should be 5 wt% or more and 50

wt% or less . The operation of the refrigerant compressor according to Embodiment 2 configured as described above will be described below.

As the rotor 203 is rotated, the shaft 210 is rotated, and the rolling piston 215 loosely fitted in the eccentric section 207 rolls inside the compression chamber 211. Hence, the volumes of the high-pressure side chamber and the low-pressure side chamber of the compression chamber 211 are changed continuously, whereby refrigerant gas is compressed continuously. Furthermore, the compressed refrigerant gas is discharged into the closed container 201, and high-pressure atmosphere is created inside the closed container 201. Moreover, because the pressure inside the closed container 201 is high, the atmospheric pressure inside the closed container 201 acts as a

back pressure for the vane 216 and presses the tip of the vane 216 against the outer circumferential surface of the rolling

piston 215.

Additionally, as the shaft 210 is rotated, the oil supply spring 222 loosely fitted in the oil supply pipe 220

continuously supplies the oil 206 to the respective sliding

sections .

In the rolling-piston-type refrigerant compressor, the rolling piston 215 is loosely fitted on the eccentric section 207 so as to be rotatable. Hence, the relative speed between the rolling piston 215 and the eccentric section 207 is lower than the relative speed between the main shaft section 208 and the main bearing 213 and the relative speed between the auxiliary shaft section 209 and the auxiliary bearing 214. This means that Sommerfeld number S (Expression 1) that indicates the characteristic of a journal bearing and is obtained using the radius R, the radial clearance C and the speed N of the bearing, the viscosity μ of oil, and the face pressure P of the bearing becomes small, resulting in a disadvantageous condition in which a metallic contact is apt to occur during sliding lubrication. S = μ x N/P x (R/C)² (Expression 1)

In the rolling-piston-type refrigerant compressor, a condensation pressure is generally created inside the closed container 201, its inner pressure is high, and the refrigerant

is apt to be dissolved in the oil 206. As a result, the viscosity of the oil is lowered, and the above-mentioned Sommerfeld number S (Expression 1) indicating the characteristic

of the journal bearing becomes small/ resulting in a disadvantageous condition during sliding lubrication.

However, the mixed layer 224 is formed by solid-dissolving molybdenum disulfide in the sliding surfaces of the eccentric section 207, the main shaft section 208 and the auxiliary shaft

section 209 of the shaft 210, and the single molybdenum disulfide layer 228 is further formed on the surface of the mixed layer 224. With this configuration, even in the disadvantageous condition wherein Sommerfeld number S (Expression 1) becomes small during sliding lubrication, the molybdenum disulfide of the single layer 228 has a property of being cleaved very easily. Hence, the shapes of the two mating members can be adapted to each other, and initial break-in is done appropriately. As a result, the molybdenum disulfide of the single molybdenum disulfide layer 228 making contact with

the surface of the mating member is abraded and adapted to the shape of the surface. Therefore, the sliding loss of the rolling-piston-type refrigerant compressor can be reduced, and

it is possible to provide a refrigerant compressor having high efficiency.

Furthermore, even if the single molybdenum disulfide layer

228 is abraded and peels off owing to metallic contact between the sliding members, the molybdenum disulfide of the mixed layer

224 has a hexagonal closed packing crystal structure, and the

size of its molecule is very small, approximately 6 x 1(T¹⁴ urn. Hence the molybdenum disulfide is cleaved at a low friction coefficient. Therefore, even if metallic contact occurs between

the rolling piston 215 and the eccentric section 207, between the main shaft section 208 and the main bearing 213, and between the auxiliary shaft section 209 and the auxiliary bearing 214, the friction coefficient of the sliding section becomes low, and the sliding loss is reduced. Therefore, with the configuration

of Embodiment 2, it is possible to provide a refrigerant compressor having high reliability.

Moreover, the thickness of the mixed layer 224 is set at 0.1 to 2.0 μm, and the maximum concentration of molybdenum

disulfide in the mixed layer 224 is set at 5 wt% or more and 20 wt% or less. Hence, the self-lubrication of the molybdenum

disulfide is stabilized, and the friction coefficient is reduced further. Therefore, with the configuration described above, it is possible to provide a refrigerant compressor having high reliability and high efficiency.

In Embodiment 2 of the present invention, the mixed layer 224 is formed by solid-dissolving molybdenum disulfide in the

sliding surfaces of the eccentric section 207, the main shaft section 208 and the auxiliary shaft section 209, and the single molybdenum disulfide layer 228 is further formed on the surface

of the mixed layer 224. However, the mixed layer 224 and the

single molybdenum disulfide layer 228 may be formed on the inner circumferential surface of the rolling piston 215, and the

surfaces of the main bearing 213 and the auxiliary bearing 214.

Furthermore, the mixed layer 224 and the single molybdenum disulfide layer 228 may be formed on both of the surface of the eccentric section 207 and the inner circumferential surface of

the rolling piston 215, both the surfaces of the main shaft section 208 and the main bearing 213, and both the surfaces of the auxiliary shaft section 209 and the auxiliary bearing 214.

By the use of the mixed layer 224 and the single molybdenum disulfide layer 228 formed on the surfaces of both the sliding members, it is possible to obtain an excellent effect capable of providing a refrigerant compressor having high reliability and high efficiency.

Furthermore, in the case that the mixed layer 224 is formed by solid-dissolving molybdenum disulfide in the sliding surfaces of the sliding members in the sliding sections between the rolling piston 215 and the vane 216, between the main bearing 213 and the vane 216, between the auxiliary bearing 214 and the vane 216, between the main bearing 213 and the rolling piston 215, between the auxiliary bearing 214 and the rolling piston 215, between the cylinder 212 and the vane 216, between the cylinder 212 and the rolling piston 215, and between the oil

supply pipe 220 and the oil supply spring 222, and that the

single molybdenum disulfide layer 228 is further formed on the surface of the mixed layer 224, the friction coefficient at each

sliding section is reduced, and it is possible to provide a refrigerant compressor having high reliability and high efficiency.

In Embodiment 2 according to the present invention, a compressor operating at a constant speed has been described above. As more and more refrigerant compressors have been being driven using inverters in recent years, the speeds of the refrigerant compressors become lower. In the case of very slow operation at less than 20 Hz in particular, the problem of abnormal abrasion becomes more serious. For this reason, the effects of the present invention are further significant.

INDUSTRIAL APPLICABILITY

As described above, in the refrigerant compressor according to the present invention, the mixed 'layer is formed by solid-dissolving molybdenum disulfide in the sliding surface of

a sliding component, and the single molybdenum disulfide layer is further formed on the surfaces of the mixed layer. Hence, the friction coefficient of the sliding surface is reduced, and

it is possible to provide a compressor having high reliability and high efficiency. The present invention is thus widely

applicable to apparatuses having a refrigerating cycle.

Claims

1. A refrigerant compressor wherein a compression element

comprises sliding components made of metallic materials, and a mixed layer is formed by solid-dissolving molybdenum disulfide in at least one of the sliding faces of said sliding components, and a single molybdenum disulfide layer is further formed on the

surface of said mixed layer.

2. The refrigerant compressor according to claim 1, wherein the maximum concentration of the molybdenum disulfide in said mixed layer is 5 wt% or more.

3. The refrigerant compressor according to claim 1, wherein the thickness of said mixed layer is 0.1 to 2.0 μm.

4. The refrigerant compressor according to claim 1, wherein the purity of the molybdenum disulfide of said single molybdenum disulfide layer is 98% or more.

5. The refrigerant compressor according to claim 1, wherein

the thickness of said single molybdenum disulfide layer is 0.1

to 2.0 μm.

6. The refrigerant compressor according to any one of claims

1 to 5, wherein oil is accumulated and a compression element is

accommodated in a closed container, said compression element is a reciprocating compression element comprising a crankshaft equipped with a main shaft and an eccentric shaft; a thrust section, one end of which is

integrated with said crankshaft and the other end of which is integrated with a bearing section; said bearing section rotatably journaling said main shaft; a cylinder block in which a cylindrical bore section is formed; a piston reciprocating inside said cylindrical bore section; a piston pin disposed in parallel with said eccentric shaft and secured to said piston; and a connecting rod for connecting said eccentric shaft to said piston, and said sliding component made of a metallic material is at least either one of said crankshaft, said thrust section, said cylinder block, said piston, said piston pin, and said connecting rod.

7. The refrigerant compressor according to any one of claims

1 to 5, wherein

oil is accumulated and a compression element is accommodated in a closed container,

said compression element comprises a crankshaft equipped

with a main shaft and an eccentric shaft; a thrust section, one end of which is integrated with said crankshaft and the other end of which is integrated with a bearing section; said bearing

section rotatably journaling said main shaft; a cylinder block in which a cylindrical bore section is formed; a piston reciprocating inside said cylindrical bore section; and a

connecting rod to which a ball is secured on the side connected to said piston, said piston in which said ball is movably held by crimping constitutes a reciprocating compression element, and said sliding component made of a metallic material is at least either one of said crankshaft, said thrust section, said cylinder block, said piston, and said connecting rod.

8. The refrigerant compressor according to any one of claims 1 to 5, wherein oil is accumulated and a compression element is accommodated in a closed container,

said compression element is a rolling-piston-type compression element comprising a shaft having an eccentric section; a cylinder in which a compression chamber is formed in

coaxial with the rotation center of said shaft; a rolling piston that is loosely fitted on said eccentric section and rolls

inside said compression chamber; a vane that partitions said compression chamber into the high-pressure side and the low- pressure side thereof when made contact with said rolling piston

under pressure; a main bearing and an auxiliary bearing that are used to seal both end faces of said cylinder and to journal said shaft on the side of an electric driving element and on the opposite side of said electric driving element, respectively; an

oil supply spring secured to one end of said shaft; and an oil supply pipe that accommodates said oil supply spring and one end of which is open and immersed in said oil, and said sliding component made of a metallic material is at least either one of said shaft, said cylinder, said rolling piston, said vane, said main bearing, said auxiliary bearing,

said oil supply spring, and said oil supply pipe.

9. A cooling system comprising said refrigerant compressor according to any one of claims 1 to 8, and an expander equipped with either a capillary tube or an expansion valve.

10. A refrigerator having a cooling system comprising said refrigerant compressor according to any one of claims 1 to 8,

and an expander equipped with either a capillary tube or an expansion valve.