| 摘要 |
PROBLEM TO BE SOLVED: To sufficiently improve the operation rate of a rotating speed fixed type exhaust device.SOLUTION: When reducing the exhaust amount in the state of setting vacuum pumps 2a, 2b in operation together with a vacuum pump 3, if the rotating speed of the vacuum pump 2a is higher than 30%, an exhaust system reduces the rotating speeds of the vacuum pumps 2a, 2b without stopping the vacuum pump 3, if the vacuum pump 2b set in operation exists in addition to the vacuum pump 2a and the rotating speed of the vacuum pump 2a is 30%, the exhaust system stops the vacuum pump 2b and increases the rotating speed of the vacuum pump 2a without stopping the vacuum pump 3, and if the vacuum pump 2b is in a stopped state and the rotating speed of the vacuum pump 2a is 30%, the exhaust system stops the vacuum pump 3, increases the rotating speed of the vacuum pump 2a continuously set in operation, and starts the operation of the vacuum pump 2b. |
