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 (23) is located with its one end (23e) in the vicinity of an inlet opening (22) of a suction muffler (17) so that heat of a closed casing (1) is not easily transmitted to the suction pipe (23) for less heating of the cooling medium gas drawn in, and thus, cooling efficiency is 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 communicating with said suction muffler, being fixed with its one end to, and leading to the outside of said closed casing. 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 pipe 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. From US-A-4,370,104 a suction muffler for a compressor is known in which a pipe connected to the cylinder head comprises a flaring horn the outer end surface of which is placed in the vicinity of the inner opening of a return line. Moreover, from GB-A-2,136,511 a similar solution is known in which the upper part of a suction muffler comprises a flared opening section which is placed in the vicinity of the inner opening of a refrigerant return line. 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 the suction pipe is open, at its other end, in the vicinity of an inlet opening of said suction muffler, and that said suction pipe is made of a material having a heat conductivity 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. 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 and 2, a hermetic compressor 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 plate 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 23 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 22 formed in its side wall 17c as an inlet opening. The suction pipe 23 extending from the exterior of the closed casing 1 to the suction muffler 17 inside said casing 1 is folded in generally double-L-shape, and has its one end 23b fixed to the lower casing 1b of the closed casing 1 so as to be positioned, at its one end, outside the closed casing 1. The hole 22 formed in the sidewall 17c of the suction muffler 17 has a diameter larger than that of the suction pipe 23. The other end of the suction pipe, i.e. its open end portion 23e, is positioned close to said hole 22 as illustrated in the drawings. The suction pipe 23 is made of stainless steel having a heat conductivity lower than that of the closed casing 1. In the above arrangement, the cooling medium gas returned from the suction pipe 23 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. Since most of the cooling medium gas sucked in through the suction pipe 23 is introduced into the suction muffler 17, there is no possibility that the expanded cooling medium gas is compressed for lowering in density. Moreover, since the suction pipe 23 is lower in the heat conductivity than the closed casing 1, heat from the closed casing 1 is not readily conducted, with a consequent difficulty in heating the cooling medium sucked in, and therefore, undesirable compression of the expanded cooling medium gas is eliminated, whereby reduction of cooling performance by the density lowering of the cooling medium gas can 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 (23) communicating with said suction muffler (17), being fixed with its one end (23b) to, and leading to the outside of said closed casing (1), characterized in that the suction pipe (23) is open, at its other end (23e), in the vicinity of an inlet opening (22) of said suction muffler (17), and that said suction pipe (23) is made of a material having a heat conductivity lower than that of said closed casing (1). A hermetic compressor as claimed in claim 1, wherein said suction pipe (23) is made of stainless steel. A hermetic compressor as claimed in claim 1, wherein said closed casing (1) is made of iron, said suction pipe (23) 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