EP1926911A1

EP1926911A1 - Hermetic compressor

Info

Publication number: EP1926911A1
Application number: EP07807305A
Authority: EP
Inventors: Takayuki Okamoto; Fumio Matsuki
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp
Priority date: 2006-09-13
Filing date: 2007-09-07
Publication date: 2008-06-04
Also published as: CN101351643A; KR20080059446A; WO2008032810A1; US20100129244A1; JP2009504956A

Abstract

A hermetic compressor includes a shaft having a connecting section formed between an eccentric shaft portion and a countershaft portion, the connecting section provided with an axial length sufficient for shifting a large end hole of a connecting rod to a position coaxial with the eccentric shaft portion. The shaft also has an extended surface of the eccentric shaft portion formed on the connecting section at one side opposite an eccentric axis thereof. This structure facilitates alignment of the center of axes of the eccentric shaft portion and the large end hole by simply sliding the extended surface of the shaft along a sliding surface of the large end hole, so as to ease insertion of the eccentric shaft portion into the large end hole, and prevent damages to the sliding surfaces of the eccentric shaft portion and the large end hole, thereby improving workability and productivity of assembling the shaft as well as reliability of the compressor.

Description

DESCRIPTION

HERMETIC COMPRESSOR

TECHNICAL FIELD

The present invention relates to hermetic compressors used mainly for domestic refrigerators.

BACKGROUND ART A conventional hermetic compressor is disclosed in Japanese Patent

Unexamined Publication, No. 2004-137926, which employs a shaft of such configuration that a countershaft portion and a main shaft portion are unitary formed in a coaxial manner with an eccentric shaft portion between them. Description is provided hereinafter of the conventional hermetic compressor noted above with reference to the drawings.

Fig. 15 is a longitudinally sectioned view of the conventional hermetic compressor, Fig. 16 is an enlarged view of a principal portion of a conventional shaft, and Fig. 17 to Fig. 21 are enlarged sectional views of the principal portion around the shaft for detailing the assembling steps of the shaft.

As shown in Fig. 15 to Fig. 21, hermetically sealed container 1 houses motor element 9 included of stator 5 having winding 3 and rotor 7, and compressor element 11 driven by motor element 9. Compressor element 11 includes shaft 19 having countershaft portion 15 and main shaft portion 17 provided in a coaxial manner at the upper side and the lower side of eccentric shaft portion 13, cylinder block 23 having compression chamber 21 of a substantially cylindrical shape, and piston 25 for making reciprocating motion inside compression chamber 21.

Compressor element 11 is also provided with connecting rod 27 having small end hole 33 and large end hole 37 formed unitary for connection with piston 25 and eccentric shaft portion 13, and they are assembled into one body with cylinder block 23. Compressor element 11 is further provided with countershaft bearing 29 for axially supporting countershaft portion 15, and main shaft bearing 31 made of an aluminum-based material and fixed to cylinder block 23 for axially supporting main shaft portion 17. A screw or the like means is used for fixing main shaft bearing 31 to cylinder block 23. The hermetic compressor constructed as above operates in a manner, which will be described hereinafter.

When rotor 7 of motor element 9 turns shaft 19, rotary motion of eccentric shaft portion 13 is transferred to piston 25 through connecting rod 27 to make piston 25 move reciprocally inside compression chamber 21. As a result, refrigerant gas is introduced into compression chamber 21 from a cooling system (not shown in the figures), compressed, and discharged again to the cooling system.

Description is provided next of the steps of assembling the shaft.

First, piston 25 and connecting rod 27 are connected with piston pin 35 in small end hole 33, as shown in Fig. 17, to assemble piston con-rod assembly 43. After that, piston 25 is installed into compression chamber 21 of cylinder block 23. Cylinder block 23 is then placed with compression chamber 21 facing downward. Since piston con-rod assembly 43 is not fixed to cylinder block 23, it slides down by its own weight to top side 23a of cylinder block 23.

Next, countershaft portion 15 of shaft 19 is inserted into cylinder block 23 from the opposite side of countershaft bearing 29. During this step, countershaft portion 15 is inserted into large end hole 37 of connecting rod 27 while lifting piston con-rod assembly 43.

Next, in order to insert countershaft portion 15 into countershaft bearing 29 of cylinder block 23, shaft 19 is shifted upward while lifting piston con-rod assembly 43 up to such a height that the center of axis of countershaft portion 15 comes into alignment with the axis of countershaft bearing 29, as shown in Fig. 18. Then, countershaft portion 15 is pushed to bring it inserted in countershaft bearing 29.

As the leading end of countershaft portion 15 begins to get into countershaft bearing 29, countershaft portion 15 passes completely through large end hole 37, as shown from Fig. 19 to Fig. 21. Piston con-rod assembly

43 hence falls upon curved surface 41 of connecting section 39 by its own weight after countershaft portion 15 has cleared through large end hole 37.

In order to fit eccentric shaft portion 13 to large end hole 37, piston con-rod assembly 43 in its resting position on curved surface 41 is lifted again, and eccentric shaft portion 13 is then fitted into large end hole 37 when the axis of eccentric shaft portion 13 comes in alignment with that of large end hole 37.

After completion of assembling shaft 19 in the manner as described above, main shaft bearing 31 is fitted to main-shaft portion 17 of shaft 19 and fixed to cylinder block 23 with screw 45.

In the conventional assembling steps described above, however, the axis of eccentric shaft portion 13 cannot be aligned easily with the axis of large end hole 37 when shaft 19 is fitted while lifting piston con-rod assembly 43 upward from curved surface 41 whereon large end hole 37 is resting. It thus has a drawback of poor workability and low productivity because sliding surfaces can be damaged when eccentric shaft portion 13 and large end hole 37 are forcibly rubbed with each other, and the assembling requires a considerable time. SUMMARY OF THE INVENTION

The present invention addresses the above problem of the prior art, and it aims to provide a hermetic compressor featuring good workability and high productivity in assembling while preventing damages to sliding surfaces during insertion of an eccentric shaft portion of a shaft into a large end hole.

The hermetic compressor of the present invention includes a compressor element enclosed in a hermetically sealed container. The compressor element includes a cylinder block constituting a compression chamber of a substantially cylindrical shape, and a shaft having an eccentric shaft portion, a countershaft portion and a main shaft portion integrally-formed, the countershaft portion and the main shaft portion being formed in a coaxial manner with the eccentric shaft portion between them. The compressor element also includes a countershaft bearing formed at the cylinder block for axially supporting the countershaft portion, a main shaft bearing also formed at the cylinder block for axially supporting the main shaft portion, a piston for making a reciprocating motion inside the compression chamber, and a connecting rod for connecting the piston and the eccentric shaft portion, the connecting rod provided with a large end hole which is fitted to the eccentric shaft portion. Connecting section is formed between the eccentric shaft portion and the countershaft portion of the shaft, the connecting section has an axial length sufficient to allow the large end hole to move into a position coaxial with the eccentric shaft portion, and an extended surface of the eccentric shaft portion is formed at a side, which is opposite to an eccentric axis, of the connecting section.

According to this structure, the eccentric shaft portion of the shaft can be inserted easily into the large end hole by taking advantage of the extended surface of the connecting section after making the countershaft portion clear through the large end hole. This structure can thus has advantages of preventing damages to the sliding surfaces of the large end hole and the eccentric shaft portion of the shaft, and improving workability and productivity in the assembling process.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is a longitudinally sectioned view of a hermetic compressor according to a first exemplary embodiment of the present invention;

Fig. 2 is an enlarged view of a principal portion of a shaft according to this exemplary embodiment;

Fig. 3 is an enlarged sectional view of the principal portion around the shaft for detailing assembling steps of the shaft according to this exemplary embodiment;

Fig. 4 is another enlarged sectional view of the principal portion around the shaft for detailing the assembling steps of the shaft according to this exemplary embodiment;

Fig. 5 is another enlarged sectional view of the principal portion around the shaft for detailing the assembling steps of the shaft according to this exemplary embodiment; Fig. 6 is still another enlarged sectional view of the principal portion around the shaft for detailing the assembling steps of the shaft according to this exemplary embodiment;

Fig. 7 is a perspective view of a main portion of the shaft according to this exemplary embodiment; Fig. 8 is yet another enlarged sectional view of the principal portion around the shaft for detailing the assembling steps of the shaft according to this exemplary embodiment;

Fig. 9 is a longitudinally sectioned view of a hermetic compressor according to a second exemplary embodiment of the present invention;

Fig. 10 is an enlarged view of a principal portion of a shaft according to this exemplary embodiment;

Fig. 11 is an enlarged sectional view of the principal portion around the shaft for detailing assembling steps of the shaft according to this exemplary embodiment;

Fig. 12 is another enlarged sectional view of the principal portion around the shaft for detailing the assembling steps of the shaft according to this exemplary embodiment; Fig. 13 is still another enlarged sectional view of the principal portion around the shaft for detailing the assembling steps of the shaft according to this exemplary embodiment;

Fig. 14 is yet another enlarged sectional view of the principal portion around the shaft for detailing the assembling steps of the shaft according to this exemplary embodiment;

Fig. 15 is a longitudinally sectioned view of a conventional hermetic compressor;

Fig. 16 is an enlarged view of a principal portion of a conventional shaft;

Fig. 17 is an enlarged sectional view of the principal portion around the conventional shaft for detailing assembling steps of the shaft;

Fig. 18 is another enlarged sectional view of the principal portion around the conventional shaft for detailing the assembling steps of the shaft;

Fig. 19 is another enlarged sectional view of the principal portion around the conventional shaft for detailing the assembling steps of the shaft; Fig. 20 is still another enlarged sectional view of the principal portion around the conventional shaft for detailing the assembling steps of the shaft; and

Fig. 21 is yet another enlarged sectional view of the principal portion around the conventional shaft for detailing the assembling steps of the shaft.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Description will he provided hereinafter of exemplary embodiments of the present invention by referring to the drawings.

FIRST EXEMPLARY EMBODIMENT

Fig. 1 is a longitudinally sectioned view of a hermetic compressor according to the first exemplary embodiment of the present invention, Fig. 2 is an enlarged view of a principal portion of a shaft, and Fig. 3 through Fig. 6 are sectional views of the principal portion around the shaft for detailing assembling steps of the shaft. Fig. 7 is a perspective view of a principal portion of the shaft, and Fig. 8 is another enlarged sectional view of the principal portion around the shaft for detailing the assembling steps. Referring now to Fig. 1 through Fig. 8, description is provided hereinafter of the hermetic compressor according to this exemplary embodiment of the invention.

In Fig. 1 to Fig. 8, hermetically sealed container 101 is filled with a refrigerant (not shown), and it also stores refrigerating machine oil (not shown). In one instance here, the refrigerant is a hydrocarbon group refrigerant of R600a, and the refrigerating machine oil is a mineral oil having good compatibility with the refrigerant.

Motor element 103 includes stator 105 connected to an external power supply (not shown), and rotor 107 disposed inside stator 105 with a predetermined space.

Compressor element 109 includes shaft 117 having countershaft portion

113 and main shaft portion 115 formed in a coaxial manner at the upper side and the lower side of eccentric shaft portion 111, cylinder block 121 made of a material such as iron-based cast material and having compression chamber 119 of a substantially cylindrical shape formed therein, and piston 127 for making reciprocating motion inside compression chamber 119.

Compressor element 109 also includes connecting rod 129 provided with small end hole 130 and large end hole 131 formed therein for connecting piston 127 and eccentric shaft portion 111. Compressor element 109 further includes countershaft bearing 123 provided in cylinder block 121 for axially supporting countershaft portion 113 of shaft 117. Furthermore, compressor element 109 includes main shaft bearing 125 made of an aluminum -based material, which is fixed to cylinder block 121 for axially supporting main shaft portion 115 of shaft 117. Screw 132 is used for fixing main shaft bearing 125 to cylinder block 121.

An outer diameter of countershaft portion 113 of shaft 117 is smaller than an outer diameter of eccentric shaft portion 111. Connecting section 133 is formed between eccentric shaft portion 111 and countershaft portion 113 of shaft 117, and connecting section 133 has an axial length sufficient to allow large end hole 131 of connecting rod 129 inserted from eccentric shaft portion 111 to move into a position coaxial with eccentric shaft portion 111. Extended surface 135 of eccentric shaft portion 111 is formed at a side, which is opposite to an eccentric axis, of connecting section 133. Extended surface 135 is processed simultaneously with a finishing process of eccentric shaft portion 111.

In other words, extended surface 135 formed on connecting section 133 is coaxial with eccentric shaft portion 111, and they both have same curvature with a high precision. Eccentric shaft portion 111 is provided with chamfered edge 136 on end surface 137 nearer to countershaft portion 113.

In . addition, curved configuration 139 is formed between the eccentric axis side of connecting section 133 and end surface 137, which is a side of countershaft portion 113, of eccentric shaft portion lllof shaft 117. Curved configuration 143 is formed between one side of connecting section 133 opposite the eccentric axis side and end surface 141, which is a side of the eccentric shaft portion 111, of the countershaft portion 113 of shaft 117. Rotor 105 is fitted to main shaft portion 115 of shaft 117. Stator 105 is fixed in a position underneath cylinder block 121.

The hermetic compressor constructed as above operates in a manner, which will be described hereinafter.

Rotor 107 of motor element 103 rotates shaft 117. When this occurs, the rotary motion of eccentric shaft portion 111 is transferred to piston 127 through connecting rod 129. This makes piston 127 moves reciprocally in compression chamber 119. As a result, the refrigerant gas is introduced into compression chamber 119 from a cooling system (not shown), compressed, and discharged again to the cooling system. Description is provided next of the steps of assembling shaft 117.

Piston con-rod assembly 147 is assembled beforehand, as shown in Fig. 3, in which piston 127 and small end hole 130 in connecting rod 129 are connected with piston pin 145. After piston 127 of piston con-rod assembly 147 is built into compression chamber 119 of cylinder block 121, cylinder block 121 is placed with compression chamber 119 facing downward. Since piston con-rod assembly 147 is not fixed, it slides down by its own weight to top side 121a of cylinder block 121.

Next, countershaft portion 113 of shaft 117 is inserted into cylinder block 121 from the opposite side of countershaft bearing 123. During this step, countershaft portion 113 is inserted into large end hole 131 of connecting rod 129 while lifting piston con-rod assembly 147.

Next, in order to insert countershaft portion 113 into countershaft bearing 123 of cylinder block 121, shaft 117 is shifted upward while lifting piston con-rod assembly 147 up to such a height that the axis of countershaft portion 113 comes into alignment with the axis of countershaft bearing 123, as shown in Fig. 4. Then, countershaft portion 113 is pushed in a manner to be inserted in countershaft bearing 123. As the leading end of countershaft portion 113 begins to get into countershaft bearing 123, countershaft portion 113 clears completely through large end hole 131 at about the same time, as shown in Fig. 5. Piston con-rod assembly 147 then falls by its own weight upon connecting section 133 provided with extended surface 135 having the same curvature as that of the inner wall of large end hole 131 at the opposite side of the eccentric axis.

In this instance, curved configuration 143 is formed between one side of connecting section 133 opposite the eccentric axis and end surface 141, which is a side of eccentric shaft portion 111, of countershaft portion 113, as shown in Fig. 6. Therefore, piston con-rod assembly 147 can slide along curved configuration 143 to extended surface 135 while keeping an inner sliding surface of large end hole 131 in contact with curved configuration 143. This structure prevents damages to the inner sliding surface of large end hole 131 of connecting rod 129 since it can alleviate an impact, which occurs when large end hole 131 falls upon connecting section 133. As shown in Fig. 6 and Fig. 7, there is also curved configuration 139 formed between the eccentric axis side of connecting section 133 and end surface 137 of eccentric shaft portion 111. It is therefore possible to increase a circumferential dimension of extended surface 135 at the side closer to eccentric shaft portion 111. It can hence reduce the possibility of large end hole 131 to become tilted with respect to extended surface 135. Additionally, it helps ease the alignment of the center of axes before fitting eccentric shaft portion 111, which substantially improves the workability of inserting eccentric shaft portion 111 into large end hole 131. Afterwards, shaft 117 can be pushed further by taking advantage of extended surface 135, as shown in Fig. 8, since the center of axis of eccentric shaft portion 111 is already in alignment to the axis of large end hole 131. As a result, large end hole 131 slides over extended surface 135 to easily fit to eccentric shaft portion 111, and to thereby complete the process of fitting countershaft portion 113 to countershaft bearing 123 of cylinder block 121.

Although the combination of refrigerant and refrigerating machine oil described here is an example using R600a and mineral oil, this invention can be embodied with any type of refrigerant selected from the group of R290, a mixture containing this and other refrigerants, Rl34a, R152, R407C, R404A and R410, and any kind of refrigerating machine oil compatible with the above refrigerants.

The hermetic compressor of this exemplary embodiment includes compressor element 109 enclosed inside hermetically sealed container 101, as described above. Compressor element 109 is provided with cylinder block 121 constituting compression chamber 119 of a substantially cylindrical shape, and shaft 117 having eccentric shaft portion 111, countershaft portion 113 and main shaft portion 115 integrally-formed, countershaft portion 113 and main shaft portion 115 being formed in the coaxial manner with eccentric shaft portion 111 between them. Compressor element 109 also includes countershaft bearing 123 formed at cylinder block 121 for axially supporting countershaft portion 113, main shaft bearing 125 also formed at cylinder block 121 for axially supporting main shaft portion 115, piston 127 for making reciprocating motion inside compression chamber 119, and connecting rod 129 for connecting piston 127 and eccentric shaft portion 111, connecting rod 129 provided with large end hole 131 which is fitted to eccentric shaft portion 111. Connecting section 133 is formed between eccentric shaft portion 111 and countershaft portion 113 of shaft 117, and connecting section 133 has an axial length sufficient to allow large end hole 131 to move into a position coaxial with eccentric shaft portion 111. Extended surface 135 of eccentric shaft portion 111 is formed on at a side, which is opposite the eccentric axis, of connecting section 133. In the assembling step for fitting eccentric shaft portion 111 of shaft 117 to large end hole 131 in connecting rod 129, all what is required is to slide the sliding surface of large end hole 131 over the extended surface of eccentric shaft portion 111 after inserting countershaft portion 113 of shaft 117 into large end hole 131 of connecting rod 129, to easily complete the alignment of the center of axes of eccentric shaft portion 111 and large end hole 131, and insertion of eccentric shaft portion 111 into large end hole 131. Accordingly, this structure can prevent the sliding surfaces of eccentric shaft portion 111 of shaft 117 and large end hole 131 of connecting rod 129 from being damaged. The structure can thus improve workability and productivity of the assembling process, thereby providing the hermetic compressor of high reliability and high productivity.

In the hermetic compressor according to this exemplary embodiment, extended surface 135 next to eccentric shaft portion 111 is processed simultaneously with the finishing process of eccentric shaft portion 111, and in a shape of circular arc in cross section having the same curvature as that of the inner wall of large end hole 131, as described above. Accordingly, the center of axis of eccentric shaft portion 111 can be aligned easily with that of extended surface 135 conjoining eccentric shaft portion 111, since extended surface 135 and eccentric shaft portion 111 are processed at the same time into shapes of the same curvature with that of the inner wall of large end hole 131. As a result, the above structure can further improve the workability and productivity in assembling of shaft 117, and provide the hermetic compressor of high reliability and high productivity. Moreover, the hermetic compressor of this exemplary embodiment is provided with curved configuration 139 formed between the eccentric axis side of connecting section 133 and end surface 137, which is a side of countershaft portion 113, of eccentric shaft portion 111, as described above. This structure can therefore prevent connecting section 133 at the side of eccentric shaft portion 111 from damaging the inner sliding surface of large end hole 131 during insertion of shaft 117 into large end hole 131 of connecting rod 129. It can also reduce the possibility of large end hole 131 to become tilted with respect to extended surface 135 so as to help ease the alignment of the center of axes since extended surface 135 has a larger circumferential dimension at the side closer to eccentric shaft portion 111. Accordingly, it can further prevent the sliding surface of large end hole 131 in connecting rod 129 from being damaged. As a result, it can improve the workability and productivity in assembling the shaft, and provide the hermetic compressor of high reliability and high productivity.

Additionally, the hermetic compressor of this exemplary embodiment is provided with curved configuration 143 formed between one side of connecting section 133 opposite the eccentric axis and end surfaces 141, which is a side of eccentric shaft portion 111, of countershaft portion 113, as described above. This structure can alleviate an impact when large end hole 131 falls upon connecting section 133 since large end hole 131 slides along curved configuration 143 of connecting section 133 when it falls upon connecting section 133 after clearing through countershaft portion 113. It can thus positively prevent the sliding surfaces of eccentric shaft portion 111 of shaft 117 and large end hole 131 of connecting rod 129 from being damaged. Accordingly, it can further improve the workability and productivity in assembling the shaft, and provide the hermetic compressor of even higher reliability and productivity. SECOND EXEMPLARY EMBODIMENT

Fig. 9 is a longitudinally sectioned view of a hermetic compressor according to a second exemplary embodiment of the present invention, Fig. 10 is an enlarged view of a principal portion of a shaft, and Fig. 11 through Fig.

14 are sectional views of the principal portion around the shaft for detailing assembling steps of the shaft.

With reference to Fig. 9 through Fig. 14, description is provided hereinafter of the hermetic compressor according to this exemplary embodiment of the invention.

In Fig. 9 to Fig. 14, hermetically sealed container 201 is filled with a refrigerant (not shown), and it also stores refrigerating machine oil (not shown). In this instance, the refrigerant is a hydrocarbon group refrigerant of R600a, and the refrigerating machine oil is a mineral oil having good compatibility with the refrigerant.

Motor element 203 includes stator 205 connected to an external power supply (not shown), and rotor 207 disposed inside stator 205 with a predetermined space.

Compressor element 209 includes shaft 217 having countershaft portion 213 and main shaft portion 215 formed in a coaxial manner at the upper side and the lower side of eccentric shaft portion 211, cylinder block 221 made of a material such as iron-based cast material and having compression chamber

219 of a substantially cylindrical shape formed therein, and piston 227 for making reciprocating motion inside compression chamber 219. Compressor element 209 also includes connecting rod 229 provided with small end hole 230 and large end hole 231 formed therein for connecting piston 227 and eccentric shaft portion 211. Compressor element 209 further includes countershaft bearing 223 provided in cylinder block 221 for axially supporting countershaft portion 213 of shaft 217. Furthermore, compressor element 209 includes main shaft bearing 225 made of an aluminum-based material, which is fixed to cylinder block 221 for axially supporting main shaft portion 215 of shaft 217. Screw 232 is used for fixing main shaft bearing 225 to cylinder block 221.

An outer diameter of countershaft portion 213 of shaft 217 is of same size as that of eccentric shaft portion 211. Connecting section 233 is formed between eccentric shaft portion 211 and countershaft portion 213 of shaft 217, and connecting section 233 has an axial length sufficient to allow large end hole 231 of connecting rod 229 inserted from eccentric shaft portion 211 to move into a position coaxial with eccentric shaft portion 211. Extended surface 235 of eccentric shaft portion 211 is formed on at a side, which is opposite the eccentric axis, of connecting section 233. Extended surface 235 is processed simultaneously with the finishing process of eccentric shaft portion 211.

In other words, extended surface 235 formed on connecting section 233 is coaxial with eccentric shaft portion 211, and they both have same curvature with a high precision. Eccentric shaft portion 211 is provided with chamfered edge 236 on end surface 237 nearer to countershaft portion 213. Moreover, extended surface 238 of countershaft portion 213 is formed on connecting section 233 at the side of eccentric shaft portion 211 of shaft 217, and extended surface 238 is processed simultaneously with the finishing process of countershaft portion 213.

In other words, extended surface 238 formed on connecting section 233 is coaxial with countershaft portion 213, and they both have same curvature with a high precision.

In addition, curved configuration 239 is formed between the eccentric axis side of connecting section 233 and end surface 237 of eccentric shaft portion 211 at the side nearer to countershaft portion 213 of shaft 217. Curved configuration 243 is formed between one side of connecting section 233 opposite the eccentric axis and end surface 241, which is a side of eccentric shaft portion 211, of countershaft portion 213 of shaft 217. Rotor 207 is fitted to main shaft portion 215 of shaft 217. Stator 205 is fixed in a position underneath cylinder block 221.

Rotor 207 of motor element 203 rotates shaft 217. When this occurs, the rotary motion of eccentric shaft portion 211 is transferred to piston 227 through connecting rod 229. This makes piston 227 move reciprocally inside compression chamber 219. As a result, the refrigerant gas is introduced into compression chamber 219 from a cooling system (not shown), compressed, and discharged again to the cooling system. Description is provided next of the steps of assembling shaft 217.

Piston con-rod assembly 247 is assembled beforehand, as shown in Fig. 11, in which piston 227 and small end hole 230 in connecting rod 229 are connected with piston pin 245. After piston 227 of piston con-rod assembly 247 is built into compression chamber 219 of cylinder block 221, cylinder block 221 is placed with compression chamber 219 facing downward. Piston con-rod assembly 247 receives a force of shifting toward top side 221a of cylinder block 221 by its own weight. However, accessory device 248 is used in this case to hold connecting rod 229 in the vicinity of large end hole 231, so as to keep piston con-rod assembly 247 lifted. In this way, the position of connecting rod 229 is maintained at a height where the center of axis of large end hole 231 is in alignment to that of countershaft bearing 223.

Next, countershaft portion 213 of shaft 217 is inserted into cylinder block 221 from the opposite side of countershaft bearing 223. Countershaft portion 213 is thus inserted into large end hole 231 of connecting rod 229. During this step, countershaft portion 213 can fit to large end hole 231 with a small gap since the outer diameter of countershaft portion 213 is made to be same size as that of eccentric shaft portion 211 where large end hole 231 is fitted, and this can prevent countershaft portion 213 and large end hole 231 from hitting against each other to avoid damages to their sliding surfaces during insertion. As a result, this structure can positively prevent damages to the sliding surfaces of countershaft portion 213 of shaft 217 and large end hole 231 of connecting rod 229. Next, shaft 217 is pushed further in a manner to insert countershaft portion 213 into countershaft bearing 223 while still maintaining the position of piston con-rod assembly 247 with accessory device 248, as shown in Fig. 12. During this step, extended surface 238 formed on connecting section 233 can continue to move on the sliding surface of large end hole 231 even after countershaft portion 213 has cleared therethrough because extended surface 238 of connecting section 233 is coaxial with countershaft portion 213 and they both have the same curvature with a high precision. This structure can make the position of shaft 217 stable, which help ease the process of insertion. When shaft 217 is pushed by sliding it on the sliding surface of large end hole 231, large end hole 231 comes in contact to curved configuration 239 formed between the eccentric axis side of connecting section 233 and end surface 237 of eccentric shaft portion 211 at the side nearer to countershaft portion 213, as shown in Fig. 13. Piston con-rod assembly 247 is then depressed with accessory device 248 along curved configuration 239 while pushing shaft 217 further. This causes connecting rod 229 to steadily and gradually move over curved configuration 239 up to end surface 237 of eccentric shaft portion 211. When connecting rod 229 is depressed further downward along end surface 237, the sliding surface of large end hole 231 can be brought into contact steadily upon extended surface 235.

In addition, curved configuration 239 between the eccentric axis side of connecting section 233 and end surface 237 of eccentric shaft portion 211 can increase a circumferential dimension of extended surface 235 at the side closer to eccentric shaft portion 211, as shown in Fig. 14. It can hence reduce the possibility of large end hole 231 to become tilted with respect to extended surface 235. As a result, it further helps ease the alignment of the center of axes before fitting eccentric shaft portion 211, which substantially improves the workability of inserting eccentric shaft portion 211 into large end hole 231.

Afterwards, large end hole 231 can slide on extended surface 235 when shaft 217 is pushed further since the axis of large end hole 231 is already in alignment to the axis of eccentric shaft portion 211 by making use of extended surface 235. Accordingly, large end hole 231 can be brought easily to fit to eccentric shaft portion 211, to thereby complete the process of fitting countershaft portion 213 to countershaft bearing 223 of cylinder block 221.

Although the combination of refrigerant and refrigerating machine oil described here is an example using R600a and mineral oil, this invention can be embodied with any type of refrigerant selected from the group of R290, a mixture containing this and other refrigerants, R134a, R152, R407C, R404A and R410, and any kind of refrigerating machine oil compatible with the above refrigerants.

As described above, the hermetic compressor of this exemplary embodiment includes countershaft portion 213 provided with the same outer diameter as that of eccentric shaft portion 211, which fits to large end hole 231. This structure can therefore prevent damages to the sliding surfaces of eccentric shaft portion 211 of shaft 217 and large end hole 231 of connecting rod 229 during the assembling step of fitting eccentric shaft portion 211 of shaft 217 to large end hole 231 of connecting rod 229, since countershaft portion 213 can fit to large end hole 231 with a small gap. The structure can also improve the workability and productivity of the assembling process, and provide the hermetic compressor of high reliability and high productivity.

INDUSTRIAL APPLICABILITY

Hermetic compressors of the present invention are suitable for many applications such as vending machines and air conditioning equipment, besides refrigerators.

Claims

1. A hermetic compressor comprising^ a compressor element enclosed in a hermetically sealed container, the compressor element including- a cylinder block constituting a compression chamber of a substantially cylindrical shape! a shaft having an eccentric shaft portion, a countershaft portion and a main shaft portion integrally "formed, the countershaft portion and the main shaft portion being formed in a coaxial manner with the eccentric shaft portion between them; a countershaft bearing formed at the cylinder block for axially supporting the countershaft portion; a main shaft bearing formed at the cylinder block for axially supporting the main shaft portion," a piston for making reciprocating motion inside the compression chamber; and a connecting rod for connecting the piston and the eccentric shaft portion, the connecting rod provided with a large end hole which is fitted to the eccentric shaft portion, wherein a connecting section is formed between the eccentric shaft portion and the countershaft portion of the shaft, the connecting section has an axial length sufficient to allow the large end hole to move into a position coaxial with the eccentric shaft portion, and wherein an extended surface of the eccentric shaft portion is formed at a side, which is opposite to an eccentric axis, of the connecting section.

2. The hermetic compressor of claim 1, wherein the extended surface of the eccentric shaft portion is processed simultaneously with a finishing process of the eccentric shaft portion, into a shape of circular arc in cross section having a curvature equal to a curvature of an inner wall of the large end hole.

3. The hermetic compressor of claim 1 or claim 2, wherein a curved configuration is formed between the eccentric axis side of the connecting section and an end surface, which is a side of the countershaft portion, of the eccentric shaft portion.

4. The hermetic compressor of claim 1 or claim 2, wherein a curved configuration is formed between one side of connecting section opposite the eccentric axis side and an end surface, which is a side of the eccentric shaft portion, of the countershaft portion.

5. The hermetic compressor of claim 1 or claim 2, wherein the countershaft portion has an outer diameter of same size as an outer diameter of the eccentric shaft portion for fitting to the large end hole.