KR20070060007A - Hermetic compressor - Google Patents

Abstract

A hermetic compressor is provided to have high reliability and reduce wear of a ball joint part by using a material having a high wear resistant property. A hermetic compressor includes a hermetic container, a compressing element, a crank unit, and a ball(2a). The compressing element is received in the hermetic container. The compressing element has a cylinder and a piston(4). The piston reciprocates inside of the cylinder. The crank unit has a connecting rod(2) connected to the piston. The ball is installed on the connecting rod and is ball-jointed on the piston by rotating a ball receiving hole formed on the piston. A lubricant is provided to the sliding moving part of the ball joint.

Description

Hermetic Compressor {HERMETIC COMPRESSOR}

1 is a longitudinal cross-sectional view of a hermetic compressor in accordance with an embodiment of the present invention;

2 is a view showing the piston inner structure in accordance with an embodiment of the present invention;

3 is a sectional view taken along the line A-A of FIG.

4 is a sectional view taken along line B-B in FIG.

5 is a perspective view of a cone rod in accordance with an embodiment of the present invention.

Figure 6 relates to an embodiment of the present invention, a perspective view of the anti-rotation part.

7 is a view showing an assembled state of a piston and a cone rod in accordance with an embodiment of the present invention.

8 is a view showing an embodiment of the present invention, with the anti-rotation part added to the assembled state of the piston and the cone rod.

9 is a cross-sectional view showing a relationship between a piston, a cone rod, and a rotation preventing portion in accordance with another embodiment of the present invention.

10 is a perspective view of a rotation preventing portion in accordance with another embodiment of the present invention.

11 is a cross-sectional view of a crankshaft and a crank bearing part in accordance with another embodiment of the present invention.

Fig. 12 is a view showing the wear test results of the piston material and the cone rod material in accordance with the embodiment of the present invention.

FIG. 13 is a view showing a hardness measurement result of a sintered material in accordance with an embodiment of the present invention. FIG.

14 is a view showing the hardness measurement results of various steel materials in accordance with an embodiment of the present invention.

Fig. 15 relates to an embodiment of the present invention and shows wear test results of the piston material and the cone rod material.

<Explanation of symbols for the main parts of the drawings>

1: cylinder

4: piston

2: cone rod

2a: ball

4a: ball gutter hole

[Document 1] Japanese Unexamined Patent Publication No. 2003-214343

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to hermetic compressors for use in refrigerators, air conditioners and the like, and more particularly to hermetic compressors having reciprocating pistons.

Conventionally, as a ball joint structure in a piston and a cone rod of a compressor, as in Japanese Patent Laid-Open No. 2003-214343 (Patent Document 1), nitriding treatment and manganese phosphate treatment are both spherical receiving holes (ball receiving holes) or balls. The structure which carried out to one side and used the high carbon chromium steel for the spherical surface is known.

[Patent Document 1] Japanese Unexamined Patent Publication No. 2003-214343

However, the structure of patent document 1 had the following subjects.

In the connection structure of patent document 1, the hardness of the high carbon chromium steel used for a spherical surface is large, and processing is difficult. In addition, the passage of the lubricating oil supplied to the ball joint mechanism, that is, the spherical bearing (ball and ball receiving hole) becomes narrow when the piston is drawn out of the cylinder and becomes a contact portion between the piston and the cylinder.

Lubrication oil may not flow sufficiently through this gap, and as a result, the temperature of the spherical bearings (ball and ball receiving hole) may rise and be damaged.

In addition, the hermetic compressor has a vessel, ie a chamber, which is sealed by welding after insertion of the internal instrument.

Inevitably, the molten droplet at the time of welding, ie, a sputter particle, mixes and remains in a container. It can be seen that when the remaining sputter particles enter the circulating lubricating oil and enter the sliding part, the surface of the sliding part is damaged, and scratches are generated, leading to wear and sticking.

In addition, abrasion generated in each sliding surface is also mixed with the lubricating oil, and in particular, when entering a narrow sliding portion such as a ball joint portion, wear and seizure, like sputter particles, significantly lower the reliability of the compressor.

SUMMARY OF THE INVENTION The present invention aims to solve the above-mentioned problems, and aims to improve the performance and reliability of a compressor by connecting a piston and a rod by spherical bearings, supplying sufficient lubricating oil, and using a material having high wear resistance. do.

The present invention has a cone rod connected to the piston, the ball provided in the cone rod and the ball receiving hole provided in the piston is a ball joint so as to be able to rotate and slide, the lubricant is supplied to the sliding portion of the ball joint In a hermetic compressor, one of the piston and the cone rod is an alloy material containing iron as a main component, and the other material is harder than the hardness of the surface layer of the alloy material containing iron as a main component.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described based on drawing, respectively.

1 shows a reciprocating motion of a piston 4 coupled to a crankshaft 7a by a cone rod 2 in a cylinder 1 of a compression element integrally formed with a bearing 1a and a frame 1b in a closed container. There is shown a reciprocating hermetic compressor applying the present invention to construct a compression element.

In the lower part of the frame 1a, the stator 5 and the rotor 6 which comprise an electric motor which are electric elements are provided. The crankshaft 7a is in a position eccentric than the center of rotation of the rotor shaft 7 of the rotor 6.

The rotor shaft 7 penetrates through the bearing portion 1a of the frame 1. The rotor shaft 7 and the rotor 6 are directly connected to each other, and the piston 4 is reciprocated through the cone rod 2 by the rotation (rotating clockwise) of the rotor shaft 7. Exercise

The crankshaft 7a and the cone rod 2 of the rotor shaft 7 are referred to as a crank mechanism.

The piston of the compression element will be described in detail with reference to FIGS. 2, 3 and 4.

2 is a view showing the inner side of the piston 4 viewed from the rotor shaft 7, and has a ball receiving portion (inner surface) 4a. 3 is a cross-sectional view taken along the line A-A of FIG. 4 is a cross-sectional view taken along line B-B in FIG.

The ball receiving portion (durable surface) 4a of the piston is a shape that is enclosed at an angle of 180 degrees or more from the distal end of the ball (outer surface) 2a of the cone rod 2 in the AA cross section, but is 180 degrees or less in the BB cross section. The shape surrounds the ball (outer surface) 2a of the cone rod 2 only at an angle.

Therefore, in the B-B cross section, the ball joint structure has a smaller sliding area than the A-A cross section, and since the path through which the lubricating oil passes is short, the lubricating oil easily flows, and the structure can be sufficiently supplied with the lubricating oil.

The cone rod will be described with reference to FIG.

5 is a perspective view of the cone rod 2. The cone rod 2 includes a ball (outer surface) 2a inserted into the ball receiving portion (inner surface) 4a of the piston 4, a crank bearing portion 2b into which the crank shaft 7a is inserted, It consists of the rod part 2c which connects the ball (outer surface) 2a and the crank bearing part 2b.

The oil supply hole 2d is provided to penetrate the inside of the ball (outer surface) 2a and the rod part 2c. Lubricating oil flows through this oil supply hole 2d and is supplied from the crank bearing part 2b to the sliding part of the ball (outer surface) 2a.

The ball (outer surface) 2a has a structure in which a part of the spherical surface is cut out similarly to the ball receiving portion (inner surface) 4a of the piston 4. Therefore, the path through which the lubricating oil passes is short, the lubricating oil easily flows, and the structure can sufficiently supply the lubricating oil.

The anti-rotation unit will be described with reference to FIGS. 6, 7 and 8.

6 is a perspective view showing a rotation preventing portion. 7 is a perspective view of a state in which the anti-rotation part is assembled into the ball joint structure. Fig. 8A is a view of the anti-rotation part assembled as the ball joint structure seen from the crank bearing part side. Fig. 8B is a perspective view equivalent to Fig. 7 in which the viewpoint is changed.

Before explaining the rotation prevention part, description is given about the ball (outer surface) of a cone rod, and the ball receiving part (inner surface) of a piston.

The ball (outer surface) 2a has a pair of flat surfaces 2e formed symmetrically along the longitudinal direction of the cone rod 2.

The ball receiving hole (durable surface) 4a has a pair of insertion cutout openings 4b formed equal to or somewhat larger than the thickness width between the two flat surfaces 2c. The width of the notch opening 4b for insertion is L. FIG. The piston 4 has a pair of holding recesses 4c having a semicircular shape on the outside of the pair of inserting notch openings 4b.

The piston 4 has a circular hole 4f larger than the ball receiving hole (durable surface) 4a in the front where the ball receiving hole (durable surface) 4a is formed. That is, the ball receiving hole (inner surface) 4a is formed so that it may be recessed in the center bottom part of the circular hole 4f.

The oil reservoir 4d is formed at the bottom of the center of the ball receiving hole (durable surface) 4a. Lubricating oil supplied through the oil supply hole 2d is stored in this oil storage part 4d. The lubricating oil stored therein lubricates the sliding surface between the ball receiving hole (inner surface) 4a and the ball (outer surface) 2a sufficiently to perform smooth rotation.

The ball (outer surface) 2a is inserted into the ball receiving hole (inner surface) 4a, and the ball (outer surface) 2a is turned so that the flat surface 2c is brought into the insertion notch opening 4b. The fall prevention of the ball joint which engages so that a receiving hole (inner surface) 4a and the ball (outer surface) 2a slides smoothly is performed.

The rotation prevention part 10 prevents rotation of the ball (outer surface) 2a so that the ball-jointed ball (outer surface) 2a does not fall out of the ball receiving hole (inner surface) 4a.

The anti-rotation part 10 extends over a pair of fitting legs 10a inserted into a pair of holding recesses 4c provided on the piston 4 and a pair of fitting legs 10a. It has a connecting portion 10b. The pair of fitting legs 10a has a flat plate portion 10a1 and two circular arc portions 10a2 that are folded outwardly from both end portions of the flat plate portion 10a1 and extend to approach each other while drawing an arc.

Moreover, it is provided in the center of the flat plate part 10a1 so that it may be concave inward, and has the recessed part 10a3 joined to the flat surface 2c of the ball (outer spherical surface) 2a. The anti-rotation part 10 is formed by bending the steel sheet. It is made using a spring-like metal plate including a steel sheet or a phosphor bronze plate.

The anti-rotation part 10 is provided in the piston 4 as shown in FIG. The rotation prevention part 10 inserted from the circular hole 4f of the piston 4 is hold | maintained by the insertion leg 10a inserted in the holding recessed part 4c. The fitting leg 10a is not easily detached because the two circular arc portions 10a2 are fitted to the holding concave portions 4c so as to bend using elasticity.

By using the anti-rotation part 10 provided with this elastic circular arc part 10a2, the ball receiving hole (inner surface) 4a of the piston 4 and the ball (outer surface) of the cone rod 2 are deformed. It becomes possible to assemble a ball joint structure without making it become a ball joint structure excellent in sliding mobility.

In the state where the anti-rotation part 10 is provided in the piston 4, the recessed part 10a3 of the flat plate part 10a1 is joined to the flat surface 2c of the ball (outer surface) 2a. For this reason, rotation of the ball (outer surface) 2a in the direction of releasing the bonding between the flat surface 2c and the recessed portion 10a3 is prevented. By this rotation blocking, the ball joint to which the ball (outer surface) 2a and the ball receiving hole (inner surface) 4a engage is held so as not to fall off.

The rotation of the ball (outer surface) 2a with respect to the ball receiving hole (inner surface) 4a becomes a rotational operation of the swinging motion of the rod portion 2c of the cone rod 2.

Another embodiment of the anti-rotation will be described with reference to FIGS. 9 and 10.

As shown in Fig. 10, the anti-rotation part 10 is provided with a locking hook 10c at the connecting part 10b. In addition, it has a structure common to the rotation prevention part mentioned above.

The piston 4 is characterized in that an annular fixing groove 4g is provided in the circular hole 4f as shown in FIG. Others have a configuration common to the piston described above.

By engaging the locking hook 10c with the fixing groove 4g, the rotation preventing portion 10 does not come out of the circular hole 4f. Since the engagement of the locking hook 10c is applied to the holding by the elasticity of the two circular arc parts 10a2, the anti-rotation part 10 is hold | maintained more reliably.

Another embodiment of the supply of lubricating oil will be described with reference to FIG.

The crankshaft 7a has the oil distribution hole 110 of the lubricating oil extended in the axial direction, and the oil outflow hole 111 which penetrates to an outer periphery. Further, the crank bearing portion 2b has an annular oil receiving groove 112 on the sliding surface. The oil supply hole 2d communicates with this oil receiving groove 112.

Lubricant flowing through the oil distribution hole 110 is supplied to the crank bearing portion 2b via the oil outflow hole 111 and the oil receiving groove 112 to slide the surface of the crank bearing portion 2b and the crankshaft 7a. To lubricate. Since the lubricating oil in the oil receiving groove 112 also flows into the oil supply hole 2d, the sliding surfaces of the ball receiving hole (inner surface) 4a and the ball (outer surface) 2a are also lubricated.

Since the oil receiving groove 112 for oil storage is provided in the crank bearing portion 2b, the lubricating oil is well supplied to the sliding surfaces of the crank bearing portion 2b and the crank shaft 7a. In addition, since the oil supply hole 2d communicates with the oil receiving groove 112 that is the oil storage, the supply of lubricating oil is supplied to the sliding surfaces of the ball receiving hole (inner surface) 4a and the ball (outer surface) 2a. Well done.

Next, the material for ensuring the reliability of the ball joint part suitable for the structure in which the lubricating oil is supplied sufficiently will be described.

12 shows the results of the sliding test performed by the ring-on block friction tester on the materials used for the piston 4 and the cone rod 2.

In this test, the sliding speed was 1.01 m / s and the test load was 123.5 N in lubricating oil. From the test results, it was confirmed that the sintered material 4 that was sealed by performing steam treatment on only the material of the piston 4 without sealing the material of the cone rod 2 was found to have a large amount of wear.

This is because the oil film is not formed because it is not sealed. On the other hand, in the case of employing a cast iron having no pores or a sintered material which is sealed on both sides, the wear of the material of the cone rod 2 tends to decrease, and the required amount of limit wear is determined by the cone rod 2. I was satisfied with the material.

However, it is also confirmed that the wear of the piston 4 material increases. In the case of the sintered materials, the combination of the sintered material 4SN and the sintered material 8S of the piston 4 material which does not nitride is combined with the material of the cone rod 2 as the material of the nitrided cone rod 2. Although it was below the wear limit, it resulted in increasing the wear of the piston 4 material that is not nitrided.

In the case of nitriding on both sides, wear increased. In the counterpart material A3 and the sintered material 8S which were subjected to the heat treatment (treatment condition 103) described below on the mold steel and the sintered material 8S, both the material of the cone rod 2 and the material of the piston 4 improved wear resistance. It was below the limit. From these tests and trials, it was found that the ratio of the hardness of the surface of the materials to be combined greatly influenced the improvement of wear resistance.

Fig. 13 shows the surface hardness measurement results of the sintered material. The comparison between the surface hardness of the sintered material 4SN and the sintered material 8S is about 1.4 times, and it can be inferred that the wear limit value shown in Fig. 12 can be satisfied by increasing the hardness ratio.

Table 1

Treatment number Quenching temperature Tempering temperature Nitriding Method Nitriding treatment temperature Average hardness of surface layer Average hardness inside the material 101 1030 ℃ 200 ℃ Gas soft nitriding 575 ℃ HV750 HV500 103 1030 ℃ 520 ℃ Gas soft nitriding 575 ℃ HV760 HV550 104 1030 ℃ 520 ℃ Greed Nitriding 480 ℃ HV900 HV680

Table 1 relates to the examples of the present invention, which summarizes the treatment conditions and hardness measurement results of the mold steel quenching nitride material.

Table 1 is a counterpart material, and in order to increase the hardness ratio, surface hardness and internal hardness of the counterpart materials A1, A3, and A4 subjected to heat treatment and nitriding using SKD11 equivalent cold die steel in order to increase the hardness ratio. Indicates.

It can be seen that the surface hardness is increased by increasing the tempering temperature, and the surface layer and the interior are both hardened by lowering the temperature of the nitriding treatment. By using this highest material (relative material A4), the ratio of hardness can be approximately three times, and as shown in Fig. 11, both the material of the cone rod 2 and the material of the piston 4 are shown. It can be seen that wear can be suppressed.

Curing the counterpart material becomes difficult to process at the same time, and therefore, considering the workability, the counterpart material was examined. In addition to the counterparts A1, A3, and A4 shown in Table 1, the counterparts B6 and B8 shown in Fig. 14 were prepared by nitriding and high frequency quenching using the SCM415 material (case hardening steel) in JIS. It was.

FIG. 15 shows the results of the wear test combined with the sintered material 8S under the same test conditions as FIG.

From this result, when the ratio of the hardness of the surface layer is 1.5 times or more, it turns out that desired durability can be obtained regarding normal wear.

In addition, using the counterparts B6 and B8, the sliding test was performed again by a ring-on block friction tester as shown in Fig. 12 in combination with the sintered material 8S. In the retest, the sliding speed was 1.01 m / s and the test load was 123.5 N for a short time in the lubricating oil mixed with a welding sputter during mild steel welding adjusted to an average particle diameter of 10 microns.

As a result of observing the friction surface after the test, damage caused by sputter particles, i.e., abrasion wear marks, was observed on the surface of the counterpart material B6, but there was almost no abrasion wear trace on the surface of the counterpart material B8. Did.

As a result of the above results, the sintered material was sealed by steam treatment as the material of the piston 4, and the nitrate and the mold steel were quenched after sealing the sintered material by steam treatment as the material of the cone rod 2, and the high temperature was quenched. After tempering, what nitrided below the tempering temperature was used.

[First Embodiment]

As a material of the piston 4, a sintered material of Fe-Cu (1 to 2%)-C (0.7 to 1.0%) subjected to a sealing process by steam treatment was used, and an iron-based alloy was used as the material of the cone rod 2. The compressor used was produced.

This iron-based alloy contains Cr (11 to 13 wt%)-Mo (0.8 to 1.2 wt%)-Mn (0.3 to 0.6 wt%)-C (0.6 to 1.6 wt%) and other unavoidable elements as a solvent. After quenching the iron-based alloy of the remaining portions of iron at 1010 ° C to 1040 ° C, tempering was performed twice at 520 ° C for 2 hours, followed by nitriding for 90 minutes in a salt bath at 480 ° C.

Isobutane as a refrigerant and ester oil as lubricating oil were enclosed in the refrigeration cycle equipped with this hermetic compressor and operated for 30 days at 4900 revolutions per minute and discharge pressure of 1.6 MPa. The result was that mobility can be maintained.

As a result of the same test in which the discharge pressure was increased to 2.0 MPa, good characteristics could be maintained without abnormal wear on the ball joint structure.

In addition, as a result of manufacturing a compressor in which the sputter particles by welding were added to the lubricating oil 10 times the upper limit of the management, and operated for 5 days under the same conditions, it was possible to operate stably without stopping the rotation, and fine friction damage to the friction surface. There was no abnormal wear other than this observed.

As described above, when the embodiments of the present invention are applied, abnormal wear does not occur on the ball receiving portion (inner surface) 4a and the ball (outer surface) 2a of the ball joint structure, and thus, Reliability is ensured and the efficiency of the hermetic compressor can be improved by reducing the sliding loss in the operation of the hermetic compressor.

According to the present invention, wear of the ball joint portion can be reduced, and a highly reliable compressor can be obtained.

In addition, the present invention will be described in detail.

The present invention is characterized in that one of the piston and the cone rod is an alloy material containing iron as a main component, and the other material has a hardness of 1.5 times or more in the Vickers hardness of the alloy material containing iron as the main component.

Furthermore, in the present invention, the lubricant is supplied through an oil supply port passing through the inside of the cone rod provided in the ball joint part, and an oil film is formed on the contact surface (ball and ball receiving hole) between the piston and the cone rod, thereby reducing the frictional force. In addition, the efficiency of the wear can be improved by reducing the solid contact between the piston and the cone rod by the oil film.

In addition, it is preferable that the piston side is an iron type sintering material in order to improve the moldability of the durable surface of a ball receiving hole. On the other hand, the cone rod is preferably a sintered material for forming, processing, and lubricating holes on the outer surface of the ball, but a solvent material can also be applied to combinations in consideration of wear durability.

The iron-based sintered material needs to have sufficient strength on the piston or the cone rod or both to compress the gas by reciprocating the rotational force from the crank pin, so that the iron-based sintered material has a density of 6.6 g / cm 3 or more.

In order to lubricate sufficiently to effectively form the oil film, the sintered material used for the combination of the ball joints must be more dense.

After sintering the raw material powder, an appropriate shape is processed and subjected to steam treatment to seal the holes in the inside and the surface with the oxide film formed on the hole surface, so that the lubricant film is not easily discharged through the holes. Oxide of the sealing portion by steam treatment also has the effect of improving the strength of the sintered material and preventing adhesion wear.

Depending on the operating conditions of the refrigerant compression, a high load may be temporarily applied to the ball joint, so that even if a solid contact occurs on the friction surface, one surface may be nitrided or sulfided or a mixed layer thereof so as not to be in contact with each other. Heterogeneous goods by using.

Lubricating oil supplied to the sliding parts (ball and ball receiving hole) contains abrasion powder particles produced by the taming operation at the start of use or temporary high load operation in the compressor and sputter particles during chamber sealing. In the material on the soft side, the wear powder, in which the work hardening layer on the surface of the sliding part (ball and ball receiving hole) is dropped or dropped, is deformed in the gap between the sliding surface, so that the hardness is 1.5 times to the original material. Doubled.

In the sliding part (ball and ball receiving hole), by making the surface hardness of the hard side 1.5 times or more of the soft side, the surface roughness of the material of the hard side is prevented, and the surface of the material whose wear is soft Can be discharged by rolling movement or lubricating oil and discharged out of the friction surface.

In addition, after the discharge of the wear powder, the material of the soft side is tamed with the shape of the surface of the material on the hard side, and can be restored to a surface similar to the smooth shape before the formation and discharge of the wear powder.

The gap between the sliding parts (ball and ball receiving hole) in normal operation is at most 10 micrometers or less, which is effective for improving the compression efficiency, and the size of the particles which are formed in the gap or infiltrate with the lubricant is about 10 Since it becomes less than a micrometer, the effective depth of a surface-diffusion process is ensured to the depth of 2 times or more compared with the size of a surface particle so that a hard material may not be deformed and abraded by the particle | grains which move cloud.

The sputtered particles are solidified again in space by molten iron chamber material in the chamber welding. Some spherical particles have a viscous hardness of about 800. Although a filter can be provided in the improvement of a welding method, or a lubrication path, a filter may lower lubrication efficiency and worsen lubrication. Therefore, it is effective to further improve the hardness of the hard side in order to prevent damaging wear of the ball joint part by sputter particles.

Although the iron-based material is hardened by quenching, the wear resistance can be improved, but when the surface is metallic and in combination with the iron-based sintered material, adhesion with the counterpart is likely to occur. In addition, by nitriding or carburizing the surface, the hardness is increased, and further non-metallization is performed to prevent adhesion to the counterpart material and deformation and abrasion due to abrasion. Sulfide treatment is also effective for nonmetallization. You may combine these diffusion processes suitably. In the diffusion treatment, it is necessary to be able to temper at a temperature higher than the diffusion treatment temperature in order to maintain the internal hardness after quenching.

Lubricating oil used in the structure of the present invention is effective to use an iron-based sintered material and an ester-based synthetic oil having good adsorption on a nitrided or carburized or sulfided surface in order to firmly hold the oil film. Even if mineral oil and ester oil are mixed, ester molecules can selectively adhere to the surface of the sliding part to prevent solid contact.

Sealing treatment is necessary to hold an oil film of the lubricating oil to be supplied. However, by allowing the lubricant to be filled in the remaining hole inevitably, even when wear occurs and the hole is exposed on the surface, the filled lubricant can prevent the metal contact of the wear portion to prevent wear.

Moreover, this invention is set as the structure which supplies the lubricating oil from the inside of a cone rod in the compressor which has a connection structure of a piston and a cone rod, and a connection structure (ball and ball receiving hole) does not fall off. .

Advantageous Effects of Invention The present invention provides a hermetic compressor effective for the compression of isobutane refrigerants or non-chlorine refrigerants such as R134a that can not exert the effect of preventing abrasion with the refrigerant itself.

By the above-described configuration, the ball joint mechanism having excellent lubricity can be configured, and the performance and reliability of the hermetic compressor can be improved.

Claims (20)

And a crank mechanism for transmitting the compression force, the transmission element, and the rotational force of the transmission element accommodated in the closure container to the compression element. The compression element has a cylinder and a piston reciprocating in the cylinder, The crank mechanism has a cone rod connected to the piston, In a hermetic compressor in which a ball provided in the cone rod and a ball receiving hole provided in the piston are rotated so as to be slidably movable, and lubricating oil is supplied to the sliding portion of the ball joint. One of the piston and the cone rod is an alloy material containing iron as a main component, The other material is the hermetic compressor of 1.5 times or more in Vickers hardness with respect to the hardness of the surface layer of the said alloy material which has iron as a main component. The hermetic compressor according to claim 1, wherein the iron-based alloy material is a sintered material, and the density of the sintered material is 6.6 g / cm 3 or more. The hermetic compressor according to claim 2, wherein the sintered material is sealed by an oxide film. 4. The hermetic compressor according to claim 3, wherein the sealing treatment is a sealing treatment of vacancy remaining in the sintered material by steam treatment after forming and cutting the piston or the cone rod. The hermetic compressor of claim 1, wherein the front surface portion or the sliding portion is subjected to surface diffusion treatment of any one of nitriding treatment, carbonization treatment, carburizing treatment, and immersion nitriding treatment. The nitride layer or sulfide layer formed by the surface diffusion treatment, or the mixed layer of sulfide and nitride is a surface hardened layer, and the range of the hardness of 1.5 times or more is at least 20 microns or more from the outermost surface. Hermetic compressor. The hermetic compressor according to claim 5, wherein the surface diffusion treatment is a surface diffusion treatment performed at or below the tempering temperature of the material. The hermetic compressor of claim 1, wherein the lubricating oil is an lubricating oil mixed with an ester lubricating oil or an ester lubricating oil and a mineral oil. 3. The hermetic compressor according to claim 2, wherein the lubricating oil obtained by mixing the ester lubricating oil or the ester lubricating oil with the mineral oil is filled and impregnated into the pores remaining in the sintered material. The hermetic compressor according to claim 1, wherein the refrigerant compressed by the cylinder is isobutane. The hermetic compressor according to claim 1, wherein a non-chlorine refrigerant such as R134a having compatibility with an ester lubricant is used as the refrigerant to be compressed in the cylinder. The hermetic compressor according to claim 1, further comprising an oil supply hole that vertically penetrates the cone rod and falls out toward the sliding part of the ball. And a crank mechanism for transmitting the compression force, the transmission element, and the rotational force of the transmission element accommodated in the closure container to the compression element. The compression element has a cylinder and a piston reciprocating in the cylinder, The crank mechanism has a cone rod connected to the piston, In a hermetic compressor in which a ball provided in the cone rod and a ball receiving hole provided in the piston are rotated so as to be slidably movable, and lubricating oil is supplied to the sliding portion of the ball joint. The ball has a pair of flat surfaces formed symmetrically along the longitudinal direction of the cone rod, The ball receiving hole has a pair of insertion cutout openings formed equal to or somewhat larger than the thickness width between the two flat surfaces, The ball inserted into the ball receiving hole is turned so that the flat surface is in the insertion cutout opening, thereby preventing the ball joint from being pulled out. One of the piston and the cone rod is an alloy material containing iron as a main component, The other material is the hermetic compressor of 1.5 times or more in Vickers hardness with respect to the hardness of the surface layer of the said alloy material which has iron as a main component. And a crank mechanism for transmitting the compression force, the transmission element, and the rotational force of the transmission element accommodated in the closure container to the compression element. The compression element has a cylinder and a piston reciprocating in the cylinder, The crank mechanism has a cone rod connected to the piston, In a hermetic compressor in which a ball provided in the cone rod and a ball receiving hole provided in the piston are rotated so as to be slidably movable, and lubricating oil is supplied to the sliding portion of the ball joint. The ball has a pair of flat surfaces symmetrically formed along the longitudinal direction of the cone rod, The ball receiving hole has a pair of insertion cutout openings formed to be equal to or somewhat larger than the thickness width between the two flat surfaces, The ball inserted into the ball receiving hole is turned so that the flat surface is in the insertion cutout opening, thereby preventing the ball joint from being pulled out. The piston has a pair of holding recesses having a substantially semicircular shape on the outside of the pair of cutout openings, And a rotation preventing portion for preventing the ball inserted into the ball receiving hole from turning in a direction of falling out The anti-rotation portion has a pair of fitting legs inserted into the pair of holding recesses and a connecting portion spanning the pair of fitting legs, One of the piston and the cone rod is an alloy material containing iron as a main component, The other material is the hermetic compressor of 1.5 times or more in Vickers hardness with respect to the hardness of the surface layer of the said alloy material which has iron as a main component. 15. The hermetic compressor according to claim 14, wherein the pair of fitting legs has a flat plate portion and two circular arc portions which are folded outwardly from both end sides of the flat plate portion and extend close to each other while drawing an arc. The hermetic compressor according to claim 15, wherein the fitting leg is provided to be concave inward in the center of the flat plate portion and has a concave portion joined to the flat surface of the ball. 15. The hermetic compressor according to claim 14, wherein the connection part of the anti-rotation part has a locking hook which engages in a fixing groove provided in the piston. The hermetic compressor of claim 14, wherein the anti-rotation part is formed of a metal plate including a steel plate. And a crank mechanism for transmitting the compression force, the transmission element, and the rotational force of the transmission element accommodated in the closure container to the compression element. The compression element has a cylinder and a piston reciprocating in the cylinder, The crank mechanism has a cone rod connected to the piston, In a hermetic compressor in which a ball provided in the cone rod and a ball receiving hole provided in the piston are rotated so as to be slidably movable, and lubricating oil is supplied to the sliding portion of the ball joint. The cone rod has a crank bearing installed on the opposite side of the ball, The crank mechanism has a crankshaft provided on the transmission element side, and a crank bearing provided on the end of the cone rod on the opposite side of the ball and rotatably supporting the crankshaft, The crank bearing has an annular oil receiving groove on the sliding surface, The cone rod has a lubrication hole coming out of the oil receiving groove toward the sliding portion of the ball, One of the piston and the cone rod is an alloy material containing iron as a main component, The other material is the hermetic compressor of 1.5 times or more in Vickers hardness with respect to the hardness of the surface layer of the said alloy material which has iron as a main component. And a crank mechanism for transmitting the compression force, the transmission element, and the rotational force of the transmission element accommodated in the closure container to the compression element. The compression element has a cylinder and a piston reciprocating in the cylinder, The crank mechanism has a cone rod connected to the piston, In a hermetic compressor in which a ball provided in the cone rod and a ball receiving hole provided in the piston are rotated so as to be slidably movable, and lubricating oil is supplied to the sliding portion of the ball joint. The ball receiving hole has an oil reservoir at the bottom, One of the piston and the cone rod is an alloy material containing iron as a main component, The other material is the hermetic compressor of 1.5 times or more in Vickers hardness with respect to the hardness of the surface layer of the said alloy material which has iron as a main component.

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