The present invention relates to a relatively compact reciprocating compressor employed in a refrigerator for home use or the like.
Recently, various improvements for more compactness and facilitation of assembly have been made in reciprocating-compressors and there are users"" demands for higher efficiency and lower noises.
Reciprocating compressors of this kind are disclosed in, for example, Japanese Patent Laid-Open Publication No. 4-164174 (1992) and Japanese Patent Publication No. 5-84837 (1993).
In the known reciprocating compressor disclosed in Japanese Patent Publication No. 5-84837 (1993), a compressor body 1 is suspended in a housing 3 by a spring 2 so as to be supported as shown in FIG. 35. A crank case 4 includes a mounting portion 4a for mounting a motor stator 5 thereon, a bearing portion 4b for supporting a crank shaft 7 and a cylinder 4c for reciprocating a piston 8 therein, which are formed integrally. A motor rotor 6 is mounted on the crank shaft 7 and the crank shaft 7 includes an eccentric shaft 7a. 
A detailed construction of a connecting rod 10 is shown in FIG. 37. The connecting rod 10 includes a small end portion 11 and a large end portion 14. The small end portion 11 includes a cylindrical portion 11e having a small hole 11a and a rod portion 11b having a rectangular cross-sectional shape, which are formed integrally. The rod portion 11b extends radially outwardly from the cylindrical portion 11e and has a pair of parallel side faces 11d and a V-shaped distal end 11c. Meanwhile, the large end portion 14 includes a cylindrical portion 14d having a large hole 14a and a boss 14b projecting radially outwardly from the cylindrical portion 14d, which are formed integrally. A bore 14c for fitting the distal end 11c of the rod portion 11b of the small end portion 11 thereinto is formed at a central portion of an end face of the boss 14b. 
This known reciprocating compressor is assembled as shown in FIG. 36. Namely, the small end portion 11 of the connecting rod 10 is coupled with the piston 8 by a piston pin 9 and is fitted into the cylinder 4c from an outer side, i.e., a right side in FIG. 36. Then, a valve plate 12 and a cylinder head 13 are fixed to the cylinder 4c. On the other hand, the eccentric shaft 7a of the crank shaft 7 is fitted into the large hole 14a of the large end portion 14 of the connecting rod 10. Subsequently, the distal end 11c of the rod portion 11b of the small end portion 11 is fitted into the bore 14c of the boss 14b of the large end portion 14 and then, the small end portion 11 and the large end portion 14 are coupled with each other by welding, etc.
Therefore, by coupling the small end portion 11 and the large end portion 14 of the connecting rod 10 as described above, rotation of the crank shaft 7 is converted into reciprocation of the piston 8 so as to compress refrigerant sucked into the cylinder 4c. 
However, in the above described arrangement of the known reciprocating compressor, the small end portion 11 and the large diameter portion 14 of the connecting rod 10 are joined to each other by welding, etc. after fitting of the distal end 11c of the rod portion 11b of the small end portion 11 into the bore 14c of the large diameter portion 14. Thus, such an inconvenience is incurred that the distal end 11c of the rod portion 11b and the bore 14c of the large end portion 14 should be finished to highly accurate surface roughness.
Furthermore, even if an axis of the large hole 14a and an axis of the bore 14c deviate from each other even slightly or parallel of the parallel surfaces 11d of the rod portion 11b to an axis of the small holes 11a is out of order even slightly, there is a risk that the axis of the large holes 14a and the axis of the small hole 11a are subjected to torsion so as to increase rotational load during compression and suction processes upon rotation of the crank shaft 7, thereby resulting in drop of efficiency.
Meanwhile, in the known reciprocating compressor, there is also a risk that vibrations produced at the piston 8, the piston pin 9 and the small end portion 11 are directly transmitted to the large end portion 14, thus resulting in production of abnormal noises between the large end-portion 14 and the eccentric shaft 7a. 
Moreover, in this known reciprocating compressor, since small end portion 11 and the large end portion 14 of the connecting rod 10 are coupled with each other by welding or bonding, the number of its assembly steps increases. In addition, since the small end portion 11 and the large end portion 14 of the connecting rod 10 are fixed to each other immovably by welding or bonding, distortion or torsion of the axes of the small hole 11a and the large hole 14a is not absorbed by coupling between the small end portion 11 and the large end portion 14. As a result, machining accuracy of the small hole 11a, the large hole 14a, the distal end 11c and the bore 14c should be raised.
Accordingly, the present invention has for its object to provide, with a view to eliminating the above mentioned disadvantages of prior art, a reciprocating compressor in which its parts can be machined and assembled with high precision easily and rotational load caused by torsion of axes of a large hole and a small hole of a connecting rod is lessened such that not only efficiency of the reciprocating compressor is raised but noises and vibrations of the reciprocating compressor are reduced.
In order to accomplish this object, a reciprocating compressor according to the present invention comprises: a connecting rod which includes a small end portion and a large end portion coupled with each other; wherein the small end portion has a small hole and is coupled with a piston by a piston pin loosely fitted into the small hole, while the large end portion has a large hole such that an eccentric shaft of a crank shaft is loosely fitted into the large hole; wherein the large end portion is formed with a cylindrical bore having an axis passing through a center of the large hole and a fixing hole communicating with the cylindrical bore; wherein the small end portion includes a cylindrical portion having the small hole and a rod portion extending radially outwardly from the cylindrical portion such that the cylindrical portion and the rod portion are formed integrally; wherein a cylindrical retaining portion is provided at a distal end portion of the rod portion of the small end portion; wherein after the cylindrical retaining portion has been loosely fitted into or lightly press fitted into the cylindrical bore, not only the cylindrical retaining portion is retained in the cylindrical bore by inserting a locking pin into the fixing hole while a small torsional degree of freedom about an axis of the rod portion is being imparted to the rod portion but axes of the small hole and the large hole of the connecting rod are maintained on an identical plane.
Therefore, in the reciprocating compressor of the present invention, increase of rotational load upon rotation of the crank shaft during compression and suction processes and drop of efficiency due to this increase of rotational load can be obviated. Furthermore, machining properties of its parts can be upgraded and production and assembly of the reciprocating compressor can be facilitated.