1. Field of the Invention
The present invention relates to a gas compressor which is to be favorably assembled into a refrigerating machine or an air conditioner as a refrigerant compressor. Particularly, the invention favorably relates to a motor-driven gas compressor into which an electric motor is assembled as a driving source for a gas-compressing mechanism.
2. Related Art Statement
Heretofore, a vane rotary type gas compressor is used as the gas compressor of this type (For example, see JP-A 2003-254244). As shown in FIG. 4, a compressing mechanism 3 is housed in a housing 2 of such a vane rotary type gas compressor 1. The housing 2 is provided with a suction port and a discharge port not shown. The compressing mechanism 3 has a cylinder 4 and a rotor 5 rotatably housed in the cylinder. The cylinder 4 defines a cylinder chamber 6 having an elliptical cross-sectional shape. In the cylinder chamber 6, the rotor 5 is provided with vanes 7 which divide the cylinder chamber 6 into a plurality of compressing chambers 6a in a circumferential direction. The volume of each of the compressing chambers 6a increases or decreases with the rotation of the rotor 5.
When the volume of the compressing chamber 6a increases with the rotation of the rotor 5, a refrigerant is sucked into a suction chamber (not shown) inside the housing 2 through the suction port, and further is sucked from this suction chamber into the compression chamber 6a via a suction passage (not shown) extending in the cylinder 4 and a suction inlet 8 opened to the cylinder chamber 6. On the other hand, when the volume of the compressing chamber 6a decreases with the rotation of the rotor 5, the refrigerant inside the compression chamber is compressed. The compressed refrigerant is guided, via the discharge outlet 9 opened to the cylinder chamber 6, to a discharge space 9a formed by a cut portion defined between the cylinder 4 and the housing surrounding the cylinder 2, into the discharge port communicating with the discharge space. In the discharge space 9a is provided a check valve mechanism 9b for preventing the compressed refrigerant from flowing back into the compressing chamber 6a. 
Although not shown, an electric motor is arranged as a driving force for the rotor inside the suction chamber in communication with the suction port of the housing so that the motor may be cooled with the refrigerant flowing in the housing. The actuation of the electric motor operates the gas-compressing mechanism, the refrigerant is sucked into the gas compressor via the suction port of the housing from a compressor (not shown) as mentioned above, and the refrigerant compressed by the gas compressor is fed to a condenser through the discharge port formed in the housing under pressure.
In the conventional gas compressor, the suction inlet 8 is opened at an end wall of the cylinder chamber 6 for taking the refrigerant into the cylinder chamber 6, and the refrigerant is sucked from the suction passage into the compressing chamber 6a through the suction inlet 8 opened at the end face of the cylinder chamber 6. On the other hand, the refrigerant compressed in the compressing chamber 6a is discharged into the discharge space 9 formed between the cylinder 4 and the housing 2 covering the cylinder, through the discharge outlet 9a opened in the peripheral wall of the cylinder chamber 6. Therefore, the high pressure of the compressed refrigerant acts as an internal pressure upon a portion of the housing 2 covering the outer peripheral portion of the cylinder of the housing. Consequently, in order to withstand such a high pressure, the housing 2 is made thick, so that the increased thickness may cause the larger dimension and increased weight of the housing.
Further, according to the conventional structure in which the discharge pressure acts upon the outer peripheral portion of the cylinder, it was not easy to assuredly prevent internal leakage from occurring due to the leakage of the high pressure at the outer peripheral portion of the cylinder toward a low-pressure side such as the suction passage.