Energization control apparatus for glow plug

Claim 1

An energization control apparatus for a glow plug, comprising: a battery; a glow plug having a low rated voltage which allows rapid heating at a low battery voltage during cranking of a diesel engine in a severe wintertime condition; power control means, arranged between said battery and said glow plug, for controlling a power supplied to said glow plug; and energization control means for controlling said power control means so as to control a root-mean-square value of a voltage applied to said glow plug to be equal to the low rated voltage when a voltage applied to said glow plug at the start of the diesel engine is detected to be higher than the low battery voltage, wherein said energization control means controls a duty ratio for controlling an ON/OFF operation of said power control means, and said energization control means comprises: first and second timers started in association with a key switch operation, said first timer setting a rapid heating time at an initial period of energization; reference voltage setting means controlled in accordance with an output from said first timer; battery voltage detecting means; and duty ratio control means for controlling the duty ratio for controlling the ON/OFF operation of said power control means, said first timer counting a time shorter than that of said second timer, said second timer setting an after glow time, and said reference voltage setting means changing the reference voltage by an ON/OFF operation of said first timer.