| 摘要 |
PROBLEM TO BE SOLVED: To eliminate the influence of characteristic dispersion of a pressure detecting means by correcting the detection value of a pressure state on the basis of the output value of the pressure detecting means and an atmospheric pressure release setting means for setting the installed place of the pressure detecting means into an atmospheric pressure release state. SOLUTION: A purge cut-off valve 15 and a vent control valve 19 are closed, and a negative pressure cut-off valve by-pass valve 17 is opened to confirm that purge line pressure rises and a pressure sensor 18 reaches the output value VPO corresponding to positive pressure Po. The vent control valve 19 is then opened, while the purge cut-off valve 15 and the purge control valve 14 are closed, and the installed place of the pressure sensor 18 of a purge passage 10 is set into an atmosphere release state. After the specified time, the output value VAO of the pressure sensor 18 is read. The output value VPO for pressure judgment is set by an expression VPO=VAO+ΔVo, whereΔVo is the deviation between the output value at the time of detectiong the specified positive pressure Po and the output value at the time of detecting atmospheric pressure, and is previously obtained as a fixed value.
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