PURPOSE: To execute control with high accuracy by knowing exactly internal pressure in an air tube at the time of pressurization, even if a fluctuation of a voltage or a voltage drop occurs.
CONSTITUTION: A relation of a duct line pressure loss and internal pressure in an air tube at the time of two different voltage of an air pump 14 to be used is shown by a linear function, respectively. The relation of the duct line pressure loss and the internal pressure in the air tube derived by these two linear function is registered as data in a control means 6. At the time of actual measurement, initial pressure in the air tube is measured. Subsequently, by measuring a measured value immediately after pressurization is started, a duct line pressure loss at the time of actual measurement is derived. The duct line pressure loss in the actually measured value at this time and the duct line pressure loss at the time of two different voltage are compared and a relation interpolation of the internal pressure in the air tube at the time of actual measurement and the duct line pressure loss is executed by a proportional distribution, by which actual pressure in the air tube is derived.
NISHIYAMA TAKANOBU
OSAWA KEIKO
FUKUI HIROO
