The present invention relates to a hermetic reciprocating compressor including a hermetic casing, a compressing portion having a cylinder and a piston reciprocating inside the cylinder and a motor for driving the piston.
A hermetic compressor is generally employed in a cooling system such as a refrigerator or an air conditioner, so as to compress a gaseous refrigerant received from an evaporator and supply the compressed refrigerant to a condenser.
FIGS. 3 and 4 show front and side sectional views of a conventional hermetic reciprocating compressor, respectively. As shown in the drawings, the conventional compressor includes a casing 101 forming a closed internal space, a driving motor 110 installed inside the casing 101 and a compressing portion 120 which is driven by the driving motor 110 to compress a refrigerant. The driving motor 110 includes a stator 112, a rotor 111 rotatably installed inside the stator 112 and a crank shaft 117 fitted into the rotor 111 and rotating therewith while supported within a support member member. The compressing portion 120 includes a cylinder 113, a piston 123 reciprocating inside the cylinder 113 and a cylinder head 127. The piston 123 is connected to an eccentric portion 119 of the crank shaft 117 by a connecting rod 121 and reciprocates inside the cylinder 113 according to a rotational movement of the rotor 111, thereby inhaling and compressing the refrigerant. A suction muffler 141 is installed on the cylinder head 127 to guide the refrigerant to be compressed into an internal space 125 of the cylinder 113. A suction pipe 129 for transferring the refrigerant from an evaporator (not shown) to the compressor is connected to the suction muffler 141 after passing through a wall of the casing 101.
Referring to FIG. 5, the suction muffler 141 has an internal space for receiving the refrigerant, an inlet 142 to which the suction pipe 129 is connected and an outlet which communicates with a refrigerant inlet 143 provided in the cylinder head 127. A coil spring 145 is installed between the inlet 142 of the suction muffler 141 and the suction pipe 129. One end of the coil spring 145 is fixedly inserted into the inlet 142 of the suction muffler 141 and the other end thereof is fitted outside the leading end of the suction pipe 129, so as to guide the refrigerant passing through the suction pipe 129 into the suction muffler 141.
The gaseous refrigerant from the evaporator flows into the suction muffler 141 via the suction pipe 129 and the coil spring 145, and is then supplied to the internal space 125 of the cylinder 113 through the cylinder head 127. On the other hand, the gaseous refrigerant supplied from the evaporator to the cylinder 113 contains liquid oil for lubrication and rust prevention for internal parts of the refrigerant circulation system. Since the refrigerant is vaporized in the evaporator by absorbing heat from the surroundings, whereas the oil maintains the liquid state due to its having a higher evaporation point than that of the refrigerant, the oil in the liquid state flows together with the gaseous refrigerant. The mixture of the liquid oil and the gaseous refrigerant contained in the internal space 125 of the cylinder 113 may damage the piston 123, the inner wall of the cylinder 113 or a valve plate (not shown) of the compressing portion 120, due to a liquid compression phenomenon of the liquid oil. Also, the liquid oil, having a relatively high specific volume, may obstruct the compression of the gaseous refrigerant, thereby decreasing the compression efficiency of the compressor.