A refrigerant compressor for a vehicle air-conditioning apparatus is normally mounted in an engine compartment and is driven by power received from the vehicle engine. Accordingly, the rotation-speed of the compressor depends on the operating state of the vehicle engine, and so the rotation-speed of the compressor may also change drastically following a sudden change in the rotation-speed of the engine, and the refrigerant temperature and pressure in the compressor may be changed drastically. In particular, under severe climatic conditions, there have been cases where the pressure in the compressor increased abnormally. Therefore, for safety reasons, a refrigerant compressor for a vehicle air-conditioning apparatus is provided with a safety valve that releases the abnormal pressure externally when the pressure in the compressor has increased abnormally.
The safety valve is provided so as to communicate with an exhaust pathway in the compressor and is configured such that, when the pressure in the exhaust pathway reaches a set pressure or more, the valve is opened to discharge some of the refrigerant from a discharge port to the outside. However, there is a problem in that since this safety valve is exposed to a severe environment in the engine compartment, the refrigerant, into which oil has being mixed, is released from the safety valve, and white smoke is formed when the refrigerant contacts a high-temperature body, such as the engine, thereby staining the devices in the engine compartment. There has been a risk that the valve is blocked by the discharge port becoming clogged with foreign matter such as mud and sand, or the valve is stayed in a constantly-opened state by the discharge port becoming jammed with foreign matter and so forth.
Thus, proposed that a cap that covers the discharge port is attached to the safety valve, and the cap is provided with a guide port for releasing the refrigerant discharged from the discharge port in a specific direction (see PTL 1); a safety valve is provided with an attachable and detachable cover, an elastic body is interposed between this cover and a valve main body, and the elastic body is provided with a groove having a starting end facing the discharge port and a terminal end reaching the outer edge to form a gas discharge flow path, and further, the terminal end part of the groove of the elastic body is provided with a labyrinth (see PTL 2); and so forth.
{Citation List}
{Patent Literature}
{PTL 1}
    Publication of Japanese Patent No. 3266985{PTL 2}    Publication of Japanese Patent No. 3038681