To surely detect the seating of a valve element by controlling the switching of a driving valve to keep the driving current flowing in an electromagnetic coil of a solenoid valve approximately constant, and detecting the seating of the valve element on the basis of the parameter corresponding to a duty ratio of the driving voltage.
When a transistor Q2 is switched on, the switching of a transistor Q1 is controlled to keep the coil current ICOIL approximately constant corresponding to the reference voltage VREF. A time measuring part 23 has a timer for measuring a period when the coil voltage VCOIL is in a high level when a judgement of seating permitting signal SDET supplied from a CPU 24 is in a high level. When the high level time TON is over a seating judgement value, the CPU 24 judges the seating. According to this construction, as the judgement is executed on the basis of the high level time TON of the coil voltage VCOIL, the seating of the valve element can be surely detected even in the switching driving of the coil of the solenoid.
IMURA AKIO
YAMAKI TOSHIHIRO
FUJIMOTO JIRO
TORII MINORU
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