ROTARY COMPRESSOR

Technical Field

The present invention relates to assurance of reliability of a rotary compressor that uses a refrigerant mainly containing a chlorine atom-free, carbon-carbon double bond-containing hydrofluoroolefin having low global warming potential as its operating refrigerant, for use in refrigeration cycles such as room air conditioners, refrigerators and other air conditioning apparatuses.

Background Art

HFC (hydrofluorocarbon) systems, which have zero ozone depletion potential, are increasingly used as the operating refrigerants for conventional refrigeration apparatuses, but on the other hand, the HFC-based refrigerants are also causing problems recently, because they have very high global warming potentials. Thus, under study are refrigeration apparatuses that use a refrigerant mainly containing a chlorine atom-free, carbon-carbon double bond-containing hydrofluoroolefin that has low global warming potential. Various studies are made on vanes and pistons used in these kinds of rotary compressors employing the conventional HFC-based refrigerants, for improvement in reliability (see, for example, Patent Document 1).

Figure 3 is a horizontal crosssectional view illustrating the rotary compressor used with a conventional HFC (hydrofluorocarbon)-based refrigerant described in Patent Document 1. In the configuration, a piston 43, which is inserted along the internal surface of a cylinder 41, revolves with revolution of a shaft 42, suctioning and compressing a refrigerant gas respectively in a suction chamber 45 and a compression chamber 46 partitioned by a vane 44. The region of the rotary compressor severely damaged by abrasion in the mechanical configuration above is the area where the tip of the vane 44 and the peripheral surface of the piston 43 are in contact with each other, and it is a boundary abrasion region where the tip of the vane 44 is pressed onto the peripheral surface of the piston 43 under large force from the rear face of the vane 44 because of the pressure difference between discharge and suction pressures.

For that reason, the vane is subjected to nitridization treatment or the surface thereof to CrN or TiN ion plating, for improvement in abrasion resistance and reliability.

Citation List

• Patent Document 1:JP-A No.11-236890 SUMMARY OF THE INVENTION

Technical Problem

However, when the rotary compressor for a refrigeration apparatus employing an refrigerant mainly containing a chlorine atom-free, carbon-carbon double bond-containing hydrofluoroolefin having low global warming potential as the operating refrigerant is considered, there was a problems that, hydrogen fluoride is generated when the refrigerant above reacts with water and oxygen and it leads to acceleration of abrasive wear of the sliding parts, in particular the vane and the piston which are exposed to particularly severe sliding force, and also to degradation of the refrigeration oil and thus deterioration in reliability. In addition, conventional vanes were very expensive, because they were treated by nitridization or ion plating.

An object of the present invention, which was made to solve the problems in conventional technology, is to reduce production cost and assure reliability of a compressor for an extended period of time, by improving abrasion resistance of the vane, as the iron component thereof remains exposed on the surface, by nitridizing the vane made of a high-speed tool steel or sintering and quenching that made of a sintered alloy steel.

Solution to Problem The rotary compressor according to the present invention, which achieved the object above, is characterized in that: a refrigerant containing a carbon- carbon double bond-containing hydrofluoroolefin as the base component is used therein as operating refrigerant; a refrigeration oil miscible with the refrigerant is used therein; its compressing mechanism unit has a piston and a vane in a cylinder; and the vane is made of a high-speed tool steel and nitridized or the vane is made of a sintered alloy steel and sintered and quenched, and it is possible in the rotary compressor to suppress abrasive wear, because hydrogen fluoride generated by decomposition of the refrigerant in the region between the vane tip and the piston peripheral surface, where the sliding force is severe, is converted to iron fluoride. It is also possible to obtain a hardened structure containing carbides of W, Mo, Cr and V dispersed in a fine martensite matrix and thus reduces the production cost by sintering and quenching the vane.

Advantageous Effects of Invention

Because the vane of the rotary compressor is made of a high-speed tool steel and nitridized or made of a sintered alloy steel and sintered and quenched in the present invention, it is possible to prevent abrasive wear caused by hydrogen fluoride generated in reaction of a refrigerant mainly containing a chlorine atom-free, carbon-carbon double bond-containing hydrofluoroolefin having low global warming potential with water and oxygen, as hydrogen fluoride is converted to iron fluoride, and thus, provide an inexpensive compressor higher in reliability for an extended period of time.

Brief Description of Drawings

Figure 1 is a vertical crosssectional view illustrating the compressing mechanism unit in the rotary compressor in embodiment 1 of the present invention.

Figure 2 is a horizontal crosssectional view illustrating the compressing mechanism unit in the rotary compressor in embodiment 1 of the present invention.

Figure 3 is a horizontal crosssectional view illustrating the compressing mechanism unit in a conventional rotary compressor.

Description of Embodiments

The first aspect of the invention relates to a rotary compressor comprising: a refrigerant containing a carbon- carbon double bond-containing hydrofluoroolefin as the base component and used as operating refrigerant; a refrigeration oil miscible with the refrigerant; and a compressing mechanism unit having a piston and a vane in a cylinder, the vane being made of a high-speed tool steel and nitridized or made of a sintered alloy steel and sintered and quenched, and it is possible in the rotary compressor to suppress abrasive wear because hydrogen fluoride generated by decomposition of the refrigerant in the region between the vane tip and the piston peripheral surface, where the sliding force is severe, is converted to iron fluoride. It is also possible to obtain a hardened structure containing carbides of W, Mo, Cr and V dispersed in a fine martensite matrix and thus to reduce the production cost, by sintering and quenching the vane made of a sintered alloy steel.

The second aspect of the invention relates to a rotary compressor comprising: a refrigerant containing a carbon- carbon double bond-containing hydrofluoroolefin as the base component and used as operating refrigerant; a refrigeration oil miscible with the refrigerant; a motor placed in a tightly sealed container; a compressing mechanism unit having a shaft driven by the motor, the compressing mechanism unit having bearings on both faces of a cylinder; a piston rotated eccentrically by the shaft installed in the cylinder; and a vane partitioning the cylinder into a suction chamber and a compression chamber and having its tip pressed to the peripheral surface of the piston, the vane being made of a high-speed tool steel and nitridized or made of a sintered alloy steel and sintered and quenched, and it is possible in the rotary compressor to suppress abrasive wear, because hydrogen fluoride generated by decomposition of the refrigerant in the region between the vane tip and the piston peripheral surface, where the sliding force is severe, is converted to iron fluoride.

The third aspect of the invention relates to the first or second aspect of the invention, wherein the sintered alloy steel is a high-speed tool steel, and it is thus possible to make the vane superior in abrasion resistance to other sintered alloy steels.

The fourth aspect of the invention relates to any one of the first to third aspects of the invention, wherein the refrigeration oil is polyvinylethers, polyol esters or polyalkylene glycols, and it is thus possible to assure reliability of the rotary compressor, because a refrigeration oil miscible with the refrigerant can be used.

The fifth aspect of the invention relates to any one of the first to fourth aspects of the invention, wherein the refrigeration oil contains no extreme pressure additive. It is thus possible to prevent acceleration of decomposition of the refrigerant by action of the extreme pressure additive contained in the refrigeration oil.

Hereinafter, favorable embodiments of the present invention will be described with reference to drawings, but it should be understood that the present invention is not restricted by these embodiments.

Embodiment 1

Figure 1 is a vertical crosssectional view illustrating the rotary compressor in embodiment 1 of the present invention. As shown in Figure 1, a stator 2a of a motor 2 is fixed in the upper region of a tightly sealed container 1 and a compressing mechanism unit 5 having a shaft 4 driven by a rotor 2b in the lower region of the tightly sealed container 1. A main bearing 7 is fixed to the top face and a sub- bearing 8 to the bottom face of the cylinder 6 of compressing mechanism unit 5 with a bolt, for example. In the cylinder 6, a piston 9 is placed in an eccentric region 4a of the shaft 4 for eccentric rotation of the shaft.

In addition, stored in the bottom region of the tightly sealed container 1 is a refrigeration oil 3 of polyvinylethers, polyol esters or polyalkylene glycols containing no extreme pressure additive, which is miscible with a refrigerant containing a carbon-carbon double bond-containing hydrofluoroolefin (for example, HFO1234yf) as its base component (hereinafter, referred to as refrigerant R).

Figure 2 is a horizontal crosssectional view illustrating the compressing mechanism unit 5 in the rotary compressor according to the present invention. As shown in Figure 2, a vane 10 is inserted into a vane slot 6a of the cylinder 6 and a vane spring 11 is placed on the rear face 10b of the vane 10, so that the tip region 10a of the vane 10 is urged to become in contact with the peripheral surface of the piston 9. The material for the vane 10 is made of a SKH high- speed tool steel and nitridized or made of a sintered alloy steel such as high-speed tool steel and sintered and quenched.

The operation and action of the rotary compressor in the configuration above will be described below. First, a refrigerant gas of refrigerant R is suctioned into the suction chamber 13 through an inlet hole 12 formed in the cylinder 6. The refrigerant gas in the compression chamber 14 is compressed by leftward revolution (arrow direction) of the piston 9 and discharged through a discharge cutout 15 out of an outlet (not shown in the Figure) into the tightly sealed container 1. The compressed refrigerant gas discharged into the tightly sealed container 1 is fed through the space surrounding the motor 2 and discharged through a discharge pipe 16 at the top of the tightly sealed container 1, together with the refrigeration oil mist present therein.

A significant large force is applied to the rear face 10b of the vane 10 by the pressure difference with the pressure in the cylinder, because the pressure from the vane spring 11 and also the high discharge pressure are applied thereto and thus, the tip region 10a of the vane 10 and the peripheral surface of the piston 9 are in contact with each other under boundary abrasion and placed in a severe environment at high temperature. Thus, the refrigerant R there is decomposed, generating hydrogen fluoride and others.

According to the present invention, in which the material for the vane 10 is made of SKH high-speed tool steel and nitridized or made of a sintered alloy steel and quenched for assurance of reliability of the vane 10 and the piston 9 placed under such a severe environment, the iron component thereof, which is present in the state exposed on the surface, reacts with the hydrogen fluoride generated by decomposition of the refrigerant R, forming iron fluoride on the surface of the vane tip region 10a and the peripheral surface of the piston 9. It is thus possible to reduce sliding resistance and abrasive wear and to assure the reliability of the sliding units such as vane 10. In addition, sintering and quenching treatments of the sintered vane give a hardened structure containing carbides of W, Mo, Cr and V dispersed in fine martensite matrix and reduces the production cost.

It is also possible to suppress decomposition of the refrigerant itself, because the refrigeration oil contains no extreme pressure additive. Because a refrigeration oil miscible with the refrigerant R of polyvinylethers, polyol esters or polyalkylene glycols is used as the refrigeration oil, the refrigeration oil scattered and circulated in the refrigeration cycle can be recovered into the rotary compressor, thus assuring high reliability of the rotary compressor.

Although a high-speed tool steel (SKH) was used as the sintered material for vane 10 in the present embodiment 1, other sintered alloy steels such as alloy tool steel (SKD) and stainless steel (SUS) may be used for more cost- effective production. It is well known that sintering and quenching treatments and additional annealing treatment of a sintered alloy steel lead to further improvement in toughness.

Sliding parts of rolling piston-type rotary compressor, the vane 10 and the piston 9, have been described, but the present invention is applicable similarly to other rotary compressors such as sliding vane-type compressors, scrolls of scroll compressors and other sliding parts such as shafts and bearings, for reduction of the sliding resistance and improvement in reliability and cost effectiveness when the refrigerant R is used.

Although a motor was installed as the drive mechanism of the compressing mechanism unit in the tightly sealed container in the present embodiment 1, the embodiment of the drive mechanism is not limited thereto, and a motor may be installed outside the tightly sealed container or an engine may be used for operation.

Industrial Applicability

As described above, the compressor according to the present invention, which can assure reliability of the compressor even when a refrigerant containing a carbon- carbon double bond-containing hydrofluoroolefin as the base component is used, can be used in applications such as compressors for water heaters, compressors for car air conditioners, compressors for freezing refrigerators, compressors for dehumidifiers and others.