| 摘要 |
PROBLEM TO BE SOLVED: To always maintain the concentration of gas included in the cleaning liquid to the stable and optimum condition without relation to temperature changes or the like of the cleaning liquid by controlling capability of a vacuum pump for functioning a deairing module depending on the concentration of gas included in the cleaning liquid having passed the deairing module. SOLUTION: When a water supply pump 3 operates, the cleaning liquid in the supply source 1 is supplied to an ultrasonic wave application nozzle 14 via a supply pipe 2, a deairing module 4, a gas monitor 11 and a flow meter 12. In this case, an inverter 13 operates to drive a vacuum pump 8 with its output power. Thereby the deairing module 4 functions to isolate and remove the oxygen in the cleaning liquid. When the cleaning liquid from which oxygen is isolated and removed flows out of the deairing module 4, the concentration of oxygen existing in the cleaning liquid is detected with a gas monitor 11 and an output frequency of the inverter 31 is controlled to set the detection result to the value preset with the manipulation part 33.
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