Patent ID: 8112182
Filing Date: 2012-02-07
Classification: G01F,G05D,Y10T

Abstract:
1. A mass flow rate controlling apparatus comprising a mass flow rate-detecting means attached to a fluid flow path, through which a fluid is supplied, for detecting a mass flow rate at predetermined time intervals, a flow rate-controlling valve mechanism attached to said fluid flow path for changing a valve-opening degree in response to a valve operating signal to control said mass flow rate, a controlling means for supplying said valve-operating voltage to said flow rate controlling valve mechanism, and a pressure-detecting means attached to said fluid flow path for detecting the pressure of said fluid at predetermined time intervals; wherein a pressure variation is obtained from the detected pressure; wherein said controlling means uses a first control mode for controlling said mass flow rate when said pressure variation is less than a predetermined threshold value; wherein in said first control mode, said controlling means stores a newest detected mass flow rate, a newest detected pressure and a newest valve-operating voltage for a current time interval; wherein in said first control mode, said controlling means compares a present mass flow rate signal obtained from said mass flow rate-detecting means with an externally input flow rate-setting signal to determine said valve-operating voltage; wherein said controlling means switches said first control mode to a second control mode when said pressure variation becomes equal to or more than said predetermined threshold value; and wherein in said second control mode, said controlling means determines said valve-operating voltage from the newest mass flow rate, the newest detected pressure and the newest valve operating voltage stored in said first control mode, a currently detected pressure, and valve characteristics stored in advance.