Patent Description:
A refrigeration cycle device such as an air conditioner for cooling and heating a room, a refrigerator, a refrigeration showcase or a heat pump water heater incorporates a sealed compressor therein, and circulates a refrigerant such as an HFC-based refrigerant or a natural refrigerant such as an HC based or CO<NUM> refrigerant.

The sealed compressor comprises a sealed container, an electric motor part housed in the sealed container, and a compression mechanism part connected to the electric motor part via a rotary shaft. A cylinder is provided in the compression mechanism part. A roller is arranged in the cylinder, and the tip of a blade elastically contacts the peripheral surface of the roller. When the roller is driven and rotated by the electric motor part via the shaft, the roller and the blade slide with each other. Since these sliding members are slid with each other, the wear resistance of their sliding surfaces needs to be improved.

<CIT> discloses a sealed compressor comprising a compression mechanism part. At least one of sliding members of the compression mechanism part, for example, a blade is formed of tool steel. On the sliding surface of the tip of the blade with a roller, a single layer of chromium, a chromium and tungsten carbide alloy layer, an amorphous carbon layer containing tungsten, and an amorphous carbon layer containing carbon and hydrogen without containing metal are stacked in this order from the surface of the substrate of the tool steel. The document <CIT> discloses a compressor which sliding parts provide a predetermined hardness and carbon percentage within the material.

However, according to the sealed compressor described in the above publication, for example, if one-sided contact occurs during the sliding of the roller and the blade, sufficient wear resistance may not be ensured.

The present invention provides a sealed compressor capable of ensuring wear resistance even in a sliding environment in which a first member and a second member sliding with each other of a compression mechanism part, for example, a blade and a roller are in a one-sided contact state, and a refrigeration cycle device comprising the compressor.

According to one embodiment, there is provided a sealed compressor comprising a compression mechanism part compressing a refrigerant in a sealed container, and a refrigerator oil. The compression mechanism part comprises a first member and a second member sliding with each other. The first member is a substrate which is made of iron-based metal and has a diamond-like carbon film on a surface of the substrate. The second member is formed of cast iron with magnesium added, has an amount of carbide precipitation on a sliding surface with the first member of less than or equal to <NUM>% in area ratio, and has a Rockwell hardness (HRC) of greater than or equal to <NUM> but less than or equal to <NUM>.

Mode for Carrying Out the Invention Embodiments will be described hereinafter with reference to the accompanying drawings.

<FIG> is a schematic view showing a refrigeration cycle device <NUM> according to an embodiment. The refrigeration cycle device <NUM> comprises a sealed compressor <NUM>, a condenser <NUM>, an expander <NUM> and an evaporator <NUM>. A refrigerant is circulated from the discharge side of the sealed compressor <NUM> to the suction side of the sealed compressor <NUM> via the condenser <NUM>, the expander <NUM>, the evaporator <NUM> and an accumulator <NUM>.

The sealed compressor <NUM> is, for example, a vertical rotary compressor, and comprises a sealed container <NUM>, a compression mechanism part <NUM> and an electric motor part <NUM> as main components.

The sealed container <NUM> has a cylindrical peripheral wall 10a, and is raised along the vertical direction. A discharge pipe 10b is provided at the upper end of the sealed container <NUM>. The discharge pipe 10b is connected to the condenser <NUM>. In addition, an oil reservoir part 10c which stores a refrigerator oil I for lubricating the compression mechanism part <NUM> is provided in the lower part of the sealed container <NUM>.

The compression mechanism part <NUM> is housed in the lower part of the sealed container <NUM> such that the compression mechanism part <NUM> is immersed in the refrigerator oil I. The compression mechanism part <NUM> has a twin cylinder structure, and comprises a first cylinder <NUM>, a second cylinder <NUM>, a rotary shaft <NUM>, a first roller <NUM>, a second roller <NUM>, a first blade 30a and a second blade 30b as main components.

The first cylinder <NUM> is fixed to the inner peripheral surface of the peripheral wall 10a of the sealed container <NUM>. The second cylinder <NUM> is fixed to the lower surface of the first cylinder <NUM> via an intermediate partition plate <NUM>.

A first bearing <NUM> is fixed to the upper surface of the first cylinder <NUM>. The first bearing <NUM> covers the inner diameter part of the first cylinder <NUM> from above, and protrudes toward above the first cylinder <NUM>. A space enclosed by the inner diameter part of the first cylinder <NUM>, the intermediate partition plate <NUM> and the first bearing <NUM> constitute a first cylinder chamber <NUM>. The intermediate partition plate <NUM> and the first bearing <NUM> are the closing members of the first cylinder chamber <NUM>.

A second bearing <NUM> is fixed to the lower surface of the second cylinder <NUM>. The second bearing <NUM> covers the inner diameter part of the second cylinder <NUM> from below, and protrudes toward below the second cylinder <NUM>. A space enclosed by the inner diameter part of the second cylinder <NUM>, the intermediate partition plate <NUM> and the second bearing <NUM> constitute a second cylinder chamber <NUM>. The intermediate partition plate <NUM> and the second bearing <NUM> are the closing members of the second cylinder chamber <NUM>. The first cylinder chamber <NUM> and the second cylinder chamber <NUM> are located coaxially with respect to a central axis O1 of the sealed container <NUM>.

As shown in <FIG>, the first cylinder chamber <NUM> and the second cylinder chamber <NUM> are connected to the accumulator <NUM> via suction pipes 25a and 25b. The gas-phase refrigerant separated from the liquid-phase refrigerant in the accumulator <NUM> is guided to the first cylinder chamber <NUM> and the second cylinder chamber <NUM> through the suction pipes 25a and 25b.

The rotary shaft <NUM> is coaxially located on the central axis O1 of the sealed container <NUM>, and penetrates the first cylinder chamber <NUM>, the second cylinder chamber <NUM> and the intermediate partition plate <NUM>. The rotary shaft <NUM> has a first journal part 27a, a second journal part 27b and a pair of eccentric parts 28a and 28b. The first journal part 27a is rotatably supported by the first bearing <NUM>. The second journal part 27b is rotatably supported by the second bearing <NUM>.

Furthermore, the rotary shaft <NUM> has a connecting part 27c coaxially extending from the first journal part 27a. A rotor <NUM> of the electric motor part <NUM> is firmly attached to the connecting part 27c.

The eccentric parts 28a and 28b are located between the first journal part 27a and the second journal part 27b. The eccentric parts 28a and 28b have a phase difference of, for example, <NUM> degrees, and have the same amount of eccentricity with respect to the central axis O1 of the sealed container <NUM>. One eccentric part 28a is housed in the first cylinder chamber <NUM>. The other eccentric part 28b is housed in the second cylinder chamber <NUM>.

The ring-shaped first roller <NUM> is fitted to the outer peripheral surface of the one eccentric part 28a. When the rotary shaft <NUM> rotates, the first roller <NUM> rotates eccentrically in the first cylinder chamber <NUM>, and a part of the outer peripheral surface of the first roller <NUM> slidably makes line contact with the inner peripheral surface of the first cylinder chamber <NUM> via an oil film.

The ring-shaped second roller <NUM> is fitted to the outer peripheral surface of the other eccentric part 28b. When the rotary shaft <NUM> rotates, the second roller <NUM> rotates eccentrically in the second cylinder chamber <NUM>, and a part of the outer peripheral surface of the second roller <NUM> slidably makes line contact with the inner peripheral surface of the second cylinder chamber <NUM> via an oil film.

As shown in <FIG>, the first blade 30a is supported by the first cylinder <NUM>. The tip of the first blade 30a is slidably pressed against the outer peripheral surface of the first roller <NUM>. The first blade 30a cooperates with the first roller <NUM>, and partitions the first cylinder chamber <NUM> into a suction region and a compression region. In addition, the first blade 30a follows the eccentric motion of the first roller <NUM>, and moves in a direction of protruding into the first cylinder chamber <NUM> or retreating from the first cylinder chamber <NUM>. This operation of the first blade 30a changes the volumes of the suction region and the compression region of the first cylinder chamber <NUM>, and compresses the gas-phase refrigerant sucked from the suction pipe 25a into the first cylinder chamber <NUM>.

The second blade 30b is supported by the second cylinder <NUM>. The tip of the second blade 30b is slidably pressed against the outer peripheral surface of the second roller <NUM>. The second blade 30b and the second roller <NUM> cooperate with each other in the same manner as the first blade 30a and the first roller <NUM>. Therefore, when the second roller <NUM> moves eccentrically in the second cylinder chamber <NUM>, the volumes of the suction region and the compression region of the second cylinder chamber <NUM> are changed, and the gas-phase refrigerant sucked from the suction pipe 25b into the second cylinder chamber <NUM> is compressed.

The high-temperature and high-pressure gas-phase refrigerant compressed in the first cylinder chamber <NUM> and the second cylinder chamber <NUM> is discharged into the sealed container <NUM> via an unillustrated discharge valve mechanism. The discharged gas-phase refrigerant rises in the sealed container <NUM>.

The electric motor part <NUM> is housed in the intermediate part along the axial direction of the sealed container <NUM> such that the electric motor part <NUM> is located between the compression mechanism part <NUM> and the discharge pipe 10b as shown in <FIG>. The electric motor part <NUM> is what is called an inner roller type motor, and comprises the rotor <NUM> and a stator <NUM>.

At the upper end of the rotator <NUM> of the electric motor part <NUM>, a centrifugal oil separator <NUM> which separates the refrigerator oil I contained in the gas-phase refrigerant in the sealed container <NUM> is installed.

Next, the materials and physical properties of the first member (for example, first and second blades 30a and 30b) and the second member (for example, first and second rollers <NUM> and <NUM>) sliding with each other, the shaft (rotary shaft <NUM>) and the closing members, which constitute the compression mechanism part <NUM> of the sealed compressor <NUM> described above, will be described in detail.

The first member (for example, the first and second blades 30a and 30b) has a structure in which the surface of a substrate made of iron-based metal is coated with a diamond-like carbon film (DLC film).

The iron-based metal is metal which is primarily composed of iron, and contains carbon and metal other than iron such as Cr, Ni, Mn or Si. Preferred iron-based metal is high-speed tool steel (SKH steel), specifically, tungsten-based SKH2 to SKH4, etc., or molybdenum-based SKH50 to SKH59, etc. In addition, SKD11 (alloy steel, die steel) can also be used.

Examples of diamond-like carbon (DLC) are hydrogen-free DLC, hydrogen-containing DLC, and Si-containing DLC.

The DLC film may be formed on at least the sliding surface of the substrate with the second member. It is preferable that the DLC film should have a thickness of greater than or equal to <NUM> but less than or equal to <NUM>.

It is preferable that the DLC film should have a base layer between it and the substrate in order to improve adhesion to the substrate. It is preferable that the base layer should be composed of a first layer made of a single layer of chromium, a second layer made of a chromium-tungsten carbide alloy layer, and a third layer made of a metal-containing amorphous carbon layer containing at least one of tungsten and tungsten carbide from the surface side of the substrate. It is preferable that the second layer should have a concentration gradient of chromium and tungsten carbide, and the content of chromium should be higher on the first layer side than on the third layer side and the content of tungsten carbide should be higher on the third layer side than on the first layer side. It is preferable that the third layer should have a concentration gradient of tungsten or tungsten carbide, and the content of tungsten or tungsten carbide should be higher on the second layer side than on the DLC film side.

The second member (for example, the first and second rollers <NUM> and <NUM>) is formed of cast iron with magnesium added, and the amount of carbide precipitation on the sliding surface with the first member is less than or equal to <NUM>% in area ratio. In addition, the second member has a Rockwell hardness (HRC) of greater than or equal to <NUM> but less than or equal to <NUM>.

The addition of magnesium serves to spheroidize carbon in cast iron, and the amount of magnesium added is preferably greater than or equal to <NUM>% by weight but less than or equal to <NUM>% by weight. It is preferable that the magnesium-added cast iron should contain at least greater than or equal to <NUM>% by weight but less than or equal to <NUM>% by weight of magnesium, greater than or equal to <NUM>% by weight but less than or equal to <NUM>% by weight of carbon, and less than or equal to <NUM>% by weight of phosphorus, and the rest should be iron.

In the second member, the amount of carbide precipitation (area ratio) on the sliding surface with the first member means a value obtained by specifying a measurement field of view of an area of (<NUM> to <NUM>) × (<NUM> to <NUM>) from a photograph of the sliding surface with the first member taken at a magnification of greater than or equal to <NUM> times but less than or equal to <NUM> times and determining the amount of carbide precipitated in the field of view in terms of area ratio. The precipitated carbide is, for example, cementite. If the amount of carbide precipitation of the second member exceeds <NUM>% in area ratio, the amount of wear of the diamond-like carbon film (DLC film) of the first member may increase during the sliding of the first member and the second member. In addition, non-uniform contact (one-sided contact) in the axial direction may occur between the sliding surfaces of the first member and the second member. In the second member, the amount of carbide precipitation on the sliding surface with the first member is preferably less than or equal to <NUM>% in area ratio.

The Rockwell hardness (HRC) of the second member can be determined by a test specified in JIS G2245. The Rockwell hardness (HRC) of the second member is set to greater than or equal to <NUM> but less than or equal to <NUM> so that adaptive wear is more likely to occur during the sliding with the DLC film of the first member. As a result, localized abnormal wear of the second member can be prevented, and high long-term reliability can be realized. If the Rockwell hardness (HRC) is set to less than <NUM>, wear is likely to progress on the sliding surface of the second member. On the other hand, if the Rockwell hardness (HRC) exceeds <NUM>, adaptive wear is less likely to occur during the sliding with the DLC film of the first member. Therefore, the surface pressure locally increases, and abnormal wear occurs. The Rockwell hardness (HRC) of the second member is more preferably greater than or equal to <NUM> but less than or equal to <NUM>.

The second member can have a Rockwell hardness (HRC) of greater than or equal to <NUM> but less than or equal to <NUM> by, for example, the following heat treatment. That is, after heating and holding at <NUM> for one hour, quenching is performed so that a martensitic structure is obtained. After that, tempering which is a process of reheating at a temperature of greater than or equal to <NUM> but less than or equal to <NUM> and holding for two hours is performed so that the martensitic structure is tempered. The tempering temperature is preferably greater than or equal to <NUM> but less than or equal to <NUM>, and is more preferably greater than or equal to <NUM> but less than or equal to <NUM>. Sub-zero treatment (also referred to as deep cooling) can also be performed after quenching. Here, deep cooling is a process of cooling at a temperature of less than or equal to <NUM> after quenching.

It is preferable that the shaft should be made of spheroidal graphite cast iron in which graphite is crystallized in a spherical shape and which has excellent lubricity and high rigidity (high Young's modulus).

It is preferable that the intermediate partition plate <NUM>, the first bearing <NUM>, and the second bearing <NUM>, which are the closing members, should be made of flake graphite cast iron in which graphite is crystallized in a fine flake form as compared with spheroidal graphite cast iron.

It should be noted that any of the first member (for example, the blade), the shaft and the closing members which slide with the second member (for example, the roller) may have its sliding surface coated with a solid lubricant such as manganese phosphate or molybdenum disulfide, for example.

Examples of the refrigerator oil I which lubricates the compression mechanism part <NUM> are polyol ester oil, polyvinyl ether oil, polyalkylene glycol oil, and mineral oil. It is preferable that the refrigerator oil should not contain any extreme pressure additive or the extreme pressure additive, if any, should be less than or equal to <NUM>% by weight. For example, tricresylphosphate can be used as the extreme pressure additive. When the refrigerator oil contains an extreme pressure additive, smaller is better, and the amount of the extreme pressure additive is preferably less than or equal to <NUM>% by weight and is more preferably less than or equal to <NUM>% by weight.

The refrigerant used in the sealed compressor is preferably a chlorine-free refrigerant, and examples are R448A, R449A, R449B, R407G, R407H, R449C, R456A, R516A, R460B, R463A, R744, and HC-based refrigerants.

The sealed compressor according to the above embodiment comprises the compression mechanism part which compresses the refrigerant in the sealed container, and the compression mechanism part comprises the first member, for example, the blade and the second member, for example, the roller which slide with each other. The blade has a structure in which the surface of the substrate made of iron-based metal is coated with the diamond-like carbon film (DLC film). The roller which slides with the DLC film of the blade is formed of cast iron with magnesium added, and the amount of carbide precipitation on the sliding surface with the DLC film of the blade is specified to less than or equal to <NUM>% in area ratio. According to these configurations, the wear of the DLC film of the blade can be suppressed, the roller itself can cause appropriate adaptive wear, and the surface pressure on the DLC film of the blade can be reduced. Furthermore, the Rockwell hardness (HRC) of the roller is specified to greater than or equal to <NUM> but less than or equal to <NUM> so that the relationship between the amount of wear of the DLC film and the amount of adaptive wear of the roller (which is larger than the amount of wear of the DLC film) can be maintained in an appropriate state during the sliding with the DLC film of the blade.

Therefore, in the first member and the second member which slide with each other, for example, in the blade and the roller, the coating film on the surface of the substrate of the blade is specified to an DLC film, the roller is formed of magnesium-added cast iron, and the amount of carbide precipitation (area ratio) on the sliding surface with the DLC film of the blade and the HRC are specified to specific ranges so that wear characteristics, etc., occurring between these components can be optimized and abnormal wear caused by one-sided contact between the DLC film of the blade and the roller can be prevented. As a result, the sealed compressor which can compress the refrigerant in the sealed container with high stability and reliability over a long period of time can be provided.

In addition, since the extreme pressure additive of the refrigerator oil which lubricates the compression mechanism part has a function of preventing wear, in the second member (roller) which slides with the DLC film of the first member (blade), the adaptive wear of the second member is inhibited. In one embodiment, the refrigerator oil does not contain any extreme pressure additive or the extreme pressure additive is set to less than or equal to <NUM>% by weight so that the adaptive wear of the roller can be developed and the abnormal wear between the sliding surfaces of the DLC film of the blade and the roller can be prevented.

Since chlorine contained in the refrigerant acts as an extreme pressure additive, that is, has a function of preventing wear, in the second member (roller) which slides with the DLC film of the first member (blade), the adaptive wear of the second member is inhibited. Therefore, in one embodiment, a refrigerant which does not contain chlorine is used so that the adaptive wear of the roller can be developed and the abnormal wear between the sliding surfaces of the DLC film of the blade and the roller can be prevented.

In one embodiment, the first member is applied to the blade and the second member is applied to the roller as the sliding members having the most severe lubrication environment in the rotary compressor so that the compressor having excellent long-term reliability can be provided.

In one embodiment, the shaft and the closing members of the cylinder chamber which slide with the roller are further provided, and the roller is formed of cast iron with magnesium added, and the amount of carbide precipitation (area ratio) on the sliding surface with the DLC film of the blade and the HRC are specified to specific ranges so that the roller causes appropriate adaptive wear during the sliding with the DLC film, and the surface pressure is reduced. In addition, the shaft which slides with the inner peripheral surface of the roller is formed of spheroidal graphite cast iron having a high Young's modulus so that the rigidity of the shaft (suppression of runout) can be increased and the inclination of the roller engaging with the shaft can be suppressed, and one-sided contact with the DLC film of the blade can be suppressed. Furthermore, the closing members which slide with the upper and lower end faces of the roller are formed of flake graphite cast iron in which graphite is crystallized in a fine form and oil retention is improved as compared with spheroidal graphite cast iron so that oil film breakage at the sliding surfaces of the closing members and the roller can be suppressed, and the wear of the roller end surfaces which slide with the closing members can be prevented. According to these effects, a compressor having excellent long-term reliability can be realized.

Next, examples of the present invention will be described in detail.

The amount of carbide precipitation (area ratio) of the roller described in the following examples was determined by photographing the sliding surface with the blade at a magnification of <NUM> times, specifying a measurement field of view of an area of <NUM> × <NUM> from the photograph, and determining the amount of carbide precipitated in the field of view.

A first member, for example, a blade composed of a substrate made of SKH51 and having a Rockwell hardness (HRC) of <NUM> and a diamond-like carbon film (DLC film) having a thickness of <NUM> and coating the surface of the substrate by the CVD method was produced.

In addition, a second member, for example, a roller composed of spheroidal graphite cast iron in which Mg constitutes <NUM>% by weight, C constitutes <NUM>% by weight, Si constitutes <NUM>% by weight, Mn constitutes <NUM>% by weight, P constitutes <NUM>% by weight, S constitutes <NUM>% by weight, and Fe constitutes the rest, and having a Rockwell hardness (HRC) of <NUM> was produced. In this roller, the amount of phosphorus (P) which is a component of spheroidal graphite cast iron was adjusted, and the amount of carbide precipitation on the sliding surface with the blade was thereby changed from <NUM> to <NUM>% in area ratio.

The obtained blade and roller were incorporated into the compression mechanism part of the rotary compressor. In addition, R410A was used as the refrigerant and polyol ester oil was used as the refrigeration machine oil, and the operation was performed for <NUM> hours under a high compression ratio condition, and the amount of wear of the DLC film of the blade was determined. Here, the specific high compression ratio condition is Pd (discharge pressure)/Ps (suction pressure) = <NUM> MPa/<NUM> MPa. The results are shown in <FIG>.

As is clear from <FIG>, when the roller having an amount of carbide precipitation exceeding <NUM>% in area ratio was used, during the sliding of the blade and the roller, the amount of wear of the DLC film increased, and non-uniform contact (one-sided contact) in the axial direction was observed between the sliding surfaces of the blade and the roller.

On the other hand, when the roller having an amount of carbide precipitation of less than or equal to <NUM>% in area ratio was used, during the sliding of the blade and the roller, the amount of wear of the DLC film did not increase, and one-sided contact could be remarkably prevented.

A roller made of the same cast iron as Example <NUM>, having an amount of carbide precipitation on a sliding surface with a blade of <NUM>% in area ratio, and having a Rockwell hardness (HRC) changing from <NUM> to <NUM> by adjusting the heating condition was produced. The roller was incorporated into the compression mechanism part of the rotary compressor together with the same blade as Example <NUM>, and the amount of wear of the DLC film of the blade and the amount of wear of the roller were determined under the same operation condition. The results are shown in <FIG>.

As is clear from <FIG>, when the roller having a hardness (HRC) in a range of greater than or equal to <NUM> but less than or equal to <NUM> was used, during the sliding of the blade and the roller, the amount of wear of the DLC film of the blade and the amount of wear of the roller did not increase but could be maintained constant, and one-sided contact could be remarkably prevented.

A roller made of the same cast iron as Example <NUM>, having an amount of carbide precipitation on a sliding surface with a blade of <NUM>% in area ratio, and having a Rockwell hardness (HRC) of <NUM> was produced.

A roller was produced from spheroidal graphite cast iron (JIS G <NUM>:<NUM>).

A roller was produced from monichrome cast iron, that is, special alloy cast iron in which Mo, Ni and Cr are added to spheroidal graphite cast iron [JIS G <NUM>: <NUM>].

Each of the obtained rollers of Example <NUM> and Comparative Examples <NUM> and <NUM> was incorporated into the refrigerator of the rotary compressor together with the same blade as Example <NUM>, and the amount of wear of the DLC film coating the surface of the substrate of the blade was determined under the same operation condition as Example <NUM>. The results are shown in <FIG>. In <FIG>, the wear limit is a value at which the DLC film on the surface of the substrate is worn and the surface of the substrate is exposed.

As is clear from <FIG>, in the sliding combination of the roller of Example <NUM> and the DLC film of the blade, the amount of wear of the DLC film was remarkably reduced, and was sufficiently below the wear limit.

On the other hand, in the sliding combination of the roller made of monochrome cast iron of Comparative Example <NUM> and the DLC film of the blade, the amount of wear of the DLC film was high and exceeded the wear limit as shown in <FIG>.

In addition, in the sliding combination of the roller made of spheroidal graphite cast iron of Comparative Example <NUM> and the DLC film of the blade, the amount of wear of the DLC film was extremely high and greatly exceeded the wear limit as shown in <FIG>.

A blade was produced by coating the surface of a substrate made of SKH51 and having a Rockwell hardness (HRC) of <NUM> with a diamond-like carbon film (DLC film) having a Vickers hardness (Hv) of <NUM> and having a thickness of <NUM> by the CVD method.

A blade was produced by nitriding the surface of a substrate made of SUS440C and having a Rockwell hardness (HRC) of <NUM> to form a nitride film having a Vickers hardness (Hv) of <NUM> and having a thickness of <NUM>.

A blade was produced by coating the surface of a substrate made of SKH51 and having a Rockwell hardness (HRC) of <NUM> with a CrN film having a Vickers hardness (Hv) of <NUM> and having a thickness of <NUM> by the CVD method.

Each of the obtained blades of Example <NUM> and Comparative Examples <NUM> and <NUM> was incorporated with the same roller as Example <NUM> into the refrigerator of the rotary compressor in the same manner as Example <NUM>, and the wear resistance of the coating film on the surface of the blade was evaluated under the same operation condition as Example <NUM>.

As a result, when the blade of Example <NUM> in which the surface of the substrate made of SKH51 is coated with the DLC film was slid with the roller having an amount of carbide precipitation on a sliding surface of <NUM>% in area ratio and having an HRC of <NUM>, the wear mount of the DLC film was small, and the wear resistance was high.

On the other hand, when the blade of Comparative Example <NUM> in which the substrate of SUS440C is nitrided to form the nitride film and the blade of Comparative Example <NUM> in which the surface of the substrate of SKH51 is coated with the CrN film were slid with the same roller as Example <NUM>, the wear of the nitride film of the blade and the wear of the CrN film of the blade were larger than that of the DLC film of Example <NUM>.

Based on the evaluation results of the comparison of different roller materials as the counterpart with respect to the DLC film of the blade between Example <NUM> and Comparative Examples <NUM> and <NUM>, and the comparison of different coating films on the surface of the blade as the counterpart with respect to the roller material (having a specific amount of carbide precipitation and having a specific Rockwell hardness (HRC)) between Example <NUM> and Comparative Examples <NUM> and <NUM>, the combination of the DLC film coating the surface of the blade and the roller made of magnesium-added cast iron, having an amount of carbide precipitation on a sliding surface of less than or equal to <NUM>% in area ratio, and having a Rockwell hardness (HRC) of greater than or equal to <NUM> but less than or equal to <NUM> can optimize the wear of the DLC film and the adaptive wear of the roller and achieve an effect of preventing abnormal wear caused by one-sided contact between the DLC film and the roller.

Polyol ester oil which is a refrigeration machine oil containing <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>% or <NUM>% by weight of tricresylphosphate which is an extreme pressure additive was used, and the same blade as Example <NUM> and a roller made of the same cast iron as Example <NUM>, having an amount of carbide precipitation on a sliding surface with the blade of <NUM>% in area ratio, and having an HRC of <NUM> were incorporated into the compression mechanism part of the rotary compressor, and the amount of wear of the DLC film of the blade was determined under the same operating condition as Example <NUM>. The results are shown in <FIG>.

As is clear from <FIG>, the wear of the DLC film of the blade can be suppressed by using polyol ester oil which is a refrigeration machine oil in which the content of tricresylphosphate which is an extreme pressure additive is less than or equal to <NUM>% by weight.

Claim 1:
A sealed compressor comprising:
a compression mechanism part compressing a refrigerant in a sealed container; and
a refrigerator oil, wherein
the compression mechanism part comprises a first member and a second member sliding with each other, characterised in that the first member is a substrate which is made of iron-based metal and has a diamond-like carbon film on a surface of the substrate and
the second member is formed of cast iron with magnesium added, has an amount of carbide precipitation on a sliding surface with the first member of less than or equal to <NUM>% in area ratio, and has a Rockwell hardness (HRC) of greater than or equal to <NUM> but less than or equal to <NUM>.