The present invention relates to a scroll fluid machine having compressing and expanding regions, and especially to a scroll fluid machine connected to a fuel cell or used as an air expanding cooler.
In a fuel cell, electrolytes are put between an anode and a cathode. Hydrogen is fed as cell active material to the cathode. Electrons are released to create hydrogen ions and pass through an external circuit to the anode. Oxygen is fed to the anode and receives electrons from the external circuit. Oxygen ions react with hydrogen ions in the electrolytes to produce water. Thus, electrons flow from the cathode to the anode, or electric currents flows from the anode to the cathode.
Generally air that contains oxygen is fed to the anode, so that there are not only water but also unreactive oxygen and nitrogen which is main ingredient of air. To combine hydrogen with oxygen is exothermic reaction, so that temperature elevates from that of fed air. A gas that mainly contains nitrogen must be discharged from the anode.
Air pressurized by a compressor is fed to the anode, and the gas at the anode has higher pressure than atmospheric pressure. The gas is discharged to air and lost without doing work. Thus, the gas is fed to an expander to obtain energy retrieval. Hence, both compressor and expander are preferably, provided in the fuel cell.
U.S. Pat. No. 6,506,512 B1 to Mori et al. discloses a compression regenerative machine for a fuel cell, comprising a compressor and an expander in a single fluid machine. An orbiting scroll of the scroll fluid machine has a scroll wrap in each side. The scroll wrap in one side compresses sucked fluid, while the other-side scroll wrap expands the fluid to do work.
However, in the compression regenerative machine, the scroll wrap is provided on each side of the orbiting scroll to increase the length of the scroll. The orbiting scroll has at the center a bearing boss for supporting the orbiting scroll. So the scroll wrap is wound at the position outer than the outer circumference of the bearing boss to increase the external diameter of the scroll end plate. The wrap is provided on each side of the orbiting scroll thereby causing troublesome working.