Operation control device and method of vacuum pumps

Abstract

An operation control devices and operation methods thereof so as to eliminates the difficulties in such a case of introduction of vacuum sensors and/or inverter control is disclosed. The disclosure relates to a control of plural sets of vacuum pumps. In order to comply with the subjects to overcome the difficulties, the disclosure proposes to utilize current detection approach instead of direct pressure detection approach, while showing how to estimate a vacuum degree achieved under the operation of the pumps as well as presenting a method on the control of the number of pumps. It is also described how organically a current detecting device, a vacuum degree estimating device, a working pump control device and related methods to satisfy the subjects are linked. The usefulness of the disclosure is also revealed.

1 . An operation control device of plural vacuum pumps for depressurizing gas inside at least one tank and/or chamber and so on, comprising:
 a current detecting means which detects a current flowing in a motor that drives the vacuum pumps; and   a control means which reduces the number of the vacuum pumps under operation, while judging whether a target vacuum and/or substantially vacuum condition is reached, based on the situation that a current value detected by said current detection means converges within a predetermined range.   
   
   
       2 . The operation control device of  claim 1 , wherein the control means further comprises a vacuum-degree-estimation means to judge that a threshold criterion value is reached when a current value of the motor under watch reaches the predetermined range, the threshold criterion value being predetermined in advance of a target-vacuum value and to conclude that said target-vacuum value is reached in case when the current value stays within the predetermined range for a predetermined span of time after the threshold criterion value is reached; wherein when the vacuum-degree-estimation means concludes that the threshold criterion value or the target-vacuum value within the predetermined range is reached, the number of the pumps under operation is reduced. 
   
   
       3 . The operation control device of  claim 1 , wherein the target-vacuum value within the predetermined range is reset at a lower value as an operation hours of the vacuum pumps is accumulated. 
   
   
       4 . The operation control device of  claim 2 , wherein the control means further comprises a pump operation control means; which designates one of the plural pumps as a pump under watch, stops at least one pump other than the pump under watch when said vacuum-degree-estimation means concludes, based on a current value of the motor driving the pump under watch, that said threshold criterion value or said target-vacuum value within the predetermined range is reached and shifts the pump under watch evenly one by one among the whole pumps. 
   
   
       5 . The operation control device of  claim 4 , wherein in a case where any one of the vacuum pumps is unable or difficult to be operated, the operation of the pump unable or difficult to be operated is skipped and the other next pump is designated as a pump under watch. 
   
   
       6 . An operation control method for plural vacuum pumps for depressurizing a gas inside at least one tank and/or chamber, comprising the steps of:
 detecting a current flowing into a motor that drives the vacuum pumps; and   reducing the number of the vacuum pumps under operation, while judging whether a target vacuum and/or substantially vacuum condition is reached, based on the situation that a current value detected by said current detection means converges within a predetermined range.   
   
   
       7 . The operation control method of  claim 6 , further comprising the steps of: designating one of the plural pumps as a pump under watch; judging that a threshold criterion value is reached when a current value of the motor under watch reaches the predetermined range, the threshold criterion value being predetermined in advance of a target-vacuum value; concluding that said target-vacuum value is reached in case when the current value stays within the predetermined range for a predetermined span of time after the threshold criterion value is reached; stopping at least one pump other than the pump under watch when it is concluded that said threshold criterion value and/or said target-vacuum value within the predetermined range is reached, based on a current value of the motor driving the pump under watch; and shifting said pump under watch evenly to the other next pump one by one among the whole pumps.