Title:
DETECTION OF EXHAUST FLOW RATE FOR TURBO MOLECULAR PUMP
Document Type and Number:
Japanese Patent JPH0252223
Kind Code:
A
Abstract:
PURPOSE:To accurately detect an exhaust flow rate by constituting a tubro molecular pump so that the output torque for a motor is kept constant in the manner of feeding back the detected load condition of a rotary blade. CONSTITUTION:In the case an induction motor is controlled so as to keep the V/F constant (where, V is a voltage impressed to the motor, F is a frequency to drive the motor), the motor is being operated with the set values V,F (point a) at the normal time, but when the load is changed, the torque to actuate the rotary blade is changed, thereby an operating point of the motor is conformed to a torque characteristic curve of the motor and the number of rotation is changed, if V and F are remained constant. In the case the exhaust speed can be kept constant by a pump which is connected to a discharge side of the turbo molecular pump, a balanced point (point c) for the load torque and the rotating torque of the motor is found by changing the number of rotation for the rotary blade with V/F remained constant, if a gas molecular flow rate is constant. That is, the values of V and F are set to optimum values by conforming with the load condition and remaining the value of V/F constant, and a slip of the motor is controlled to be constant, then the exhaust flow rate is detected by measuring V or F at this time.
Inventors:
YAMAMURA AKIRA
Application Number:
JP20333888A
Publication Date:
February 21, 1990
Filing Date:
August 16, 1988
Export Citation:
Assignee:
NIPPON FERROFLUIDICS KK
International Classes:
G01F9/00; F04D19/04; (IPC1-7): F04D19/04; G01F9/00
Domestic Patent References:
| JPS60128996A | 1985-07-10 | |||
| JPS61292847A | 1986-12-23 |
Attorney, Agent or Firm:
Masahiro Nishimori
Next Patent: MEASURING APPARATUS FOR MEASUREMENT OF LOAD WEIGHT