Patent ID: 8356729

Claim:
A material metering method for metering one batch material till a final target value is obtained in multi stages of large amount metering, middle amount metering and small amount metering in which material drop amount per unit time is gradually reduced while material is supplied into a metering device from a material outlet of a hopper: wherein target metering time and an initial value of a supply mass switch value are given for each of said middle amount metering and said small amount metering, said target metering time defining as a target lower limit unstable metering time whose drop amount per unit time after being changed from a prior stage of said metering to the next stage is unstable; and wherein said method comprises the steps of: calculating said supply mass switch value for said large amount metering by subtracting supply mass switch values for said middle amount metering and said small amount metering from said final target value; metering one batch material till said final target value is obtained and measuring actual metering time at said each stage in such a manner that material drop amount per unit time is stepwisely reduced each time material mass value measured with said metering device reaches a supply mass switch value at each stage; and calculating correction amount for the next one batch metering for each of said middle amount metering and said small amount metering based on the difference between actual metering time and target metering time of said middle amount metering and said small amount metering and executing correction by subtracting said calculated correction amount from the last supply mass switch value.