Compressor ( 1 ) having a region of pressure intermediate between discharge pressure and suction pressure (especially, crank chamber ( 10 )), characterized in that a valve mechanism ( 21 ) is provided for introducing discharge gas into the region of intermediate pressure so as to render constant the difference between intermediate pressure and suction pressure. A compressor structure is provided which can stably introduce a mixture of discharge gas and refrigerating machine oil into the crank chamber without using pressure reducing means such as an aperture and in a manner easy to form a passageway, thereby improving the lubricity of rolling part and slide part in the crank chamber.
1. A compressor having a region of pressure intermediate between discharge pressure and suction pressure characterized in that a valve mechanism is provided for introducing discharge gas into said region of intermediate pressure so as to render constant a pressure difference between intermediate pressure and suction pressure;
wherein said valve mechanism comprises an intermediate pressure introducing path communicating with said region of intermediate pressure, a suction pressure introducing path communicating with a region of suction pressure, a discharge gas introducing path capable of introducing discharge gas, a valve body having an intermediate pressure sensitive surface sensing intermediate pressure introduced from said intermediate pressure introducing path and a suction pressure sensitive surface sensing suction pressure introduced from said suction pressure introducing path on respective sides in a movement direction and having therein a communication path capable of communicating said intermediate pressure introducing path and said discharge gas introducing path with each other by movement, and a spring capable of giving a force corresponding to said constant pressure difference to said valve body.
2. The compressor according to claim 1 , wherein a first stopper is provided to an intermediate pressure introducing path side of said valve body for stopping said valve body having been moved at a position at which said intermediate pressure introducing path and said discharge gas introducing path communicate with each other through said communication path.
3. The compressor according to claim 2 , wherein a first pressure equalizing hole is provided to said first stopper for communicating both sides of said stopper at a state where said valve body has been stopped by said stopper at said position at which said intermediate pressure introducing path and said discharge gas introducing path communicate with each other and for introducing intermediate pressure onto said intermediate pressure sensitive surface.
4. The compressor according to claim 1 , wherein a second stopper is provided to a suction pressure introducing path side of said valve body for stopping said valve body having been moved at a predetermined position.
5. The compressor according to claim 4 , wherein a second pressure equalizing hole is provided to said second stopper for communicating both sides of said stopper at a state where said valve body has been stopped by said stopper at said predetermined position and for introducing suction pressure onto said suction pressure sensitive surface.
6. The compressor according to claim 1 , wherein said compressor is a piston type variable displacement compressor in which crank chamber pressure is intermediate pressure and which has a displacement control valve and a plurality of cylinder bores, and said displacement control valve controls a pressure difference between crank chamber pressure and suction pressure in a range capable of increasing displacement from a minimum displacement operation condition at which said displacement control valve is completely closed.
7. The compressor according to claim 6 , wherein said displacement control valve comprises an electromagnetic valve, and crank chamber pressure is controlled by an on/off signal sent thereto.
8. The compressor according to claim 6 , wherein said displacement control valve comprises a valve which can sense an index for displacement control, which can change a target index for displacement control by an external signal, and which is closed until a sensed index for displacement control reaches said target index determined by said external signal.
9. The compressor according to claim 6 , wherein said compressor is a clutchless compressor.
10. The compressor according to claim 1 , wherein said compressor is a piston type fixed displacement compressor in which crank chamber pressure is intermediate pressure and which has a plurality of cylinder bores.
11. The compressor according to claim 1 , wherein discharge gas is introduced into said region of intermediate pressure from a lower portion of an oil separator or an oil storage chamber.
12. The compressor according to claim 1 , wherein said compressor compresses carbon dioxide refrigerant.
13. The compressor according to claim 1 , wherein said compressor is used in an air conditioning system for vehicles.