| 摘要 |
PROBLEM TO BE SOLVED: To carry out control so as to prevent back pressure of a vacuum pump from attaining a constant value, and avoid overload operation so as to stabilize an operation by connecting a vacuum chamber to an atmosphere opening part through an exhaust piping, and arranging the vacuum pump capable of varying rotating speed and a control unit for controlling rotating speed in the exhaust piping. SOLUTION: A vacuum chamber 10 is connected to an intake port 32 of a vacuum exhaust system 30, and an exhaust piping 34 is connected to a discharge port 32b. A dry pump is used in the vacuum pump 32, and a brushless d.c. motor having a rotating speed control unit 42 is used in a driving motor 40. A back pressure sensor 44 for detecting back pressure of the vacuum pump 32 is arranged on a position in the vicinity of the discharge port 32b of the exhaust piping 34, and a signal outputted from the sensor 44 is inputted into the rotating speed control unit 42. In the case where the vacuum pump 32 is operated, rotating speed of the pump 32 is controlled so as to hold a restricting value wherein back pressure of the vacuum pump 32 is set beforehand. As a result, a desired time is extended, and stable operation is held, back pressure is reduced after the desired time is lapsed, and the operation is shifted to a normal operation.
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