US Patent 7419371 Scroll fluid machine

In a scroll fluid machine, a driving shaft extends axially to allow an orbiting scroll to revolve with respect to a fixed scroll thereby compressing a gas introduced from the outer circumference of the fixed scroll in a compressing chamber formed between the orbiting and fixed scrolls. From one end of the driving shaft, external air is introduced in a cooling hole extending axially of the driving shaft to cool the driving shaft. A cooling fan is rotatably secured at one end of the driving shaft to rotate by the driving shaft to cool the fixed scroll. The cooling fan comprises a base plate having a main fin on one side surface facing the side of the fixed scroll and a plurality of auxiliary fins on the other side surface to prevent cooling-finished air from invading into the cooling hole of the driving shaft.