| 摘要 |
A fixed scroll 2 is provided with a plate-like spiral tooth 6 on a base plate (4, Fig 1) having at its centre a discharge port 5 for high-pressure gas. A spiral tooth 15 on the base plate 13 of an orbiting scroll 12 engages the spiral tooth 6 to form a compression space periodically consisting of a low pressure chamber 30, an intermediate pressure chamber 29, and a high pressure chamber 28. At least one of the base plates (4), 13 has a counterboring or recess 36,37 adjacent the inner end portion of the spiral tooth 6,15. During the motion of the orbiting scroll 12 the counterboring 36,37 communicates with the intermediate pressure chamber 29 after the high pressure chamber 28 and the intermediate pressure chamber 29 communicate with each other via the side surfaces of the spiral teeth 6,15.
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