Hermetic compressor

Abstract: A hermetic compressor with an improved operating efficiency for use in a cold storage, freezing chamber or the like, in which a suction pipe (21,23) is formed by a material having heat conductivity lower than that of a casing (1) of the hermetic compressor so that heat of the closed casing (1) is not easily transmitted to the suction pipe (21,23) for less heating of the cooling medium gas drawn in, and thus, cooling efficiency can be improved by preventing discharge of the low density cooling medium into the cooling system through compression of the expanded cooling medium gas.

Description: The invention relates to a hermetic compressor comprising a closed casing, a compressing unit having a cylinder and a piston, an electric motor for reciprocating the piston, a suction muffler communicating with a suction port of said compressing unit, and a suction pipe including a first section inserted with its one end in said suction muffler, a second section fixed to said closed casing and leading to the outside of said closed casing and a flexible third section which connects said first section with said second section. It has been a recent trend to improve the compression of a reciprocating type cooling medium compressor in a cooling system such as a cold storage, freezing chamber or the like. As one technique for meeting such a requirement, it has been proposed to eliminate the disadvantage that a suction gas is heated and expanded in the compressor so that the suction gas with a low density is drawn into a cylinder for being compressed, whereby reduction in density of the suction gas is prevented for higher suction efficiency. From US-A-4,531,894 a hermetic compressor of the kind described above is known, in which a suction pipe including a flexible section is mounted with its one end to the suction muffler, and with its second end being fixed to the closed casing. In this arrangement, however, the suction pipe is generally made of copper, so that the suction is heated through heat exchange with respect to the casing of the compressor, with consequent heating of the suction gas. Therefore, only a poor improvement of the compression efficiency can be obtained. It is an object of the present invention to provide an improved hermetic compressor in which heating of the suction gas of the cooling medium compressor by the casing is avoided. According to the invention the hermetic compressor of the kind described above is characterized in that said second section is made of material having a heat conductivity which is lower than that of said closed casing. By such an arrangement, a hermetic compressor is provided which is superior in compression efficiency, with substantial elimination of disadvantages inherent in the conventional arrangements of this kind. Preferable embodiments are defined in the dependent claims. These and other objects and features of the present invention will become apparent from the following description taken in conjunction with the preferred embodiment thereof with reference to the accompanying drawings, in which; Fig. 1 is a side sectional view of a hermetic compressor according to one preferred embodiment of the present invention, Fig. 2 is a cross section taken along the line II-II in Fig. 1, and Fig. 3 is also a fragmentary cross section taken along the line III-III in Fig. 1. Before the description of the present invention proceeds, it is to be noted that like parts are designated by like reference numerals throughout the accompanying drawings. Referring now to the drawings, there is shown in Figs. 1 to 3, a hermetic compressor C1 according to a preferred embodiment of the present invention, which generally includes a closed casing 1, a compressing unit 6 provided with a cylinder block 10 having a cylinder 9 formed with an opening 7 and accommodated in the closed casing 1 and a piston 8 accommodated in the cylinder 9, an electric motor 2 for reciprocating the piston 8 of the compressing unit 6, a valve plate 12 provided to cover the opening 7 of the cylinder 9 and provided with valves at a suction port and a discharge port thereof, a header provided for the valve seat 12 at its side remote from the cylinder 9, a suction muffler 17 for leading a cooling medium to the suction port of the valve plate 12, a discharge muffler 15 into which the cooling medium from the discharge port of the valve plate 12 flows so as to be led to outside of the closed casing 1, and a suction pipe 21 fixed to the closed casing 1 for leading the suction gas to the suction muffler 17. More specifically, the closed casing 1 made, for example, of iron is constituted by an upper casing 1a fitted over a peripheral edge of a lower casing 1b, with a junction therebetween being welded for combination. On the upper side of the casing 1, there is provided the electric motor 2 connected through wires W, with an electric plug 3 provided in the lower casing 1b at the left side in Fig. 2, with a crank shaft 5 which extends vertically in Fig. 2 being mounted on a rotor 4 of said motor 2. The compressing unit 6 located at the lower side of the closed casing 1 includes the cylinder block 10 provided with the cylinder 9 having the opening 7 at its one side, and the piston 8 movably accommodated therein. Said piston 8 is connected with said crank shaft 5 through a connecting rod 11 so as to transmit rotation of the crank shaft 5 to the piston 8 following the reciprocating movement thereof. On the opening 7 of the cylinder 9, the valve plate 12 having the suction port, discharge port, and valves provided at both ports (not particularly shown), and a cylinder head 13 are attached. As shown in Figs. 1 and 2, this cylinder head 13 is fixed to the cylinder block 10 through the valve plate 12 by set screws 14. The discharge muffler 15 which once receives the flow of the compressed cooling medium gas discharged from said discharge port, and then, leads said gas out of the closed casing 1 is fixed to the cylinder block 10 by a screw 16. The suction muffler 17 arranged to guide the cooling medium into said suction port is made, for example, of a plastic material, and is divided into an upper chamber 17a and a lower chamber 17b through a partition plate 19 formed with a hole 18 and provided therein, with the lower chamber 17b being arranged to lead the cooling medium to said suction port through a communicating pipe 20, while the upper chamber 17a has a hole 17d formed in its side wall 17c. The suction pipe 21 extending from the exterior of the closed casing 1 to the suction muffler 17 inside said casing 1 is folded in generally an L-shape, and includes a first passage 21a having its one end inserted through the hole 17d, into the upper chamber 17a of the suction muffler 17 so as to be positioned therein, a second passage 12b fixed to the lower casing 1b of the closed casing 1 and also folded generally in an L-shape so as to be positioned, at its one end, outside the closed casing 1, and a third passage 21c formed by closely winding a wire material in a coil shape for connecting said first passage 21a with said second passage 21b. In the suction pipe 21 having the construction as described above, at least the second passage 21b is formed by stainless steel having a heat conductivity lower than that of iron which is the material for the closed casing 1. It is to be noted here that the first passage 21a and the third passage 21c may be formed either of copper or stainless steel. In the above arrangement, the cooling medium gas returned from the suction pipe 21 is compressed by the piston 8 in the cylinder 9 through the suction muffler 17 so as to be further discharged outside via the discharge muffler 15. It should be particularly noted here that according to the hermetic compressor C1 of the present invention as described so far, owing to the construction that the second passage 21b of the suction pipe 21 contacting the closed casing 1 is made of stainless steel, the heat of the closed casing 1 is not readily conducted to said second passage 21b, and thus, the cooling medium gas is free from expansion by heating at this second passage 21b, whereby density lowering of the drawn-in cooling medium gas may be advantageously prevented.

Claims: A hermetic compressor comprising a closed casing (1), a compressing unit (6) having a cylinder (9) and a piston (8), an electric motor (2) for reciprocating the piston (8), a suction muffler (17) communicating with a suction port of said compressing unit (6), and a suction pipe (21) including a first section (21a) inserted with its one end in said suction muffler (17), a second section (21b) fixed to said closed casing (1) and leading to the outside of said closed casing (1) and a flexible third section (21c) which connects said first section (21a) with said second section (21b); characterized in that said second section (21b) is made of material having a heat conductivity lower than that of said closed casing (1). A hermetic compressor as claimed in claim 1, wherein said third section (21c) is formed by a coil spring pipe. A hermetic compressor as claimed in claim 1 or 2, wherein said closed casing (1) is made of iron, said suction pipe (21, 23), or said second section (21b) being formed of stainless steel.

Inventors: KAWAI HIDEKI, OHTA TOSHIHIKO, SASANO HIROSHI, KAWAI, HIDEKI, OHTA, TOSHIHIKO, SASANO, HIROSHI
Applicants: MATSUSHITA REFRIGERATION, MATSUSHITA REFRIGERATION COMPANY
Application year: 1989
Main classification: F04B39
IPC codes: F04B39