Control circuit for a glow plug assembly serving as an engine preheating means

Abstract

A control circuit for a glow plug assembly serving as an engine preheating means is designed so as to effect a temperature control in harmony with the specified position established by selective operation of a key switch having three switching positions, i.e., OFF, ON and START positions. The control circuit is capable of effecting three modes of operation: One is that, when the key switch is switched from OFF position to ON position, the glow plug assembly is energized to rapidly effect a preheating of the engine, and is deenergized when the temperature thereof reaches a predetermined value; Second is that, when the key switch is switched from ON position to START position, the voltage smaller than that at the time of the preheating is applied to the glow plug assembly to effect a first heat retention having substantially the same temperature as that of the aforesaid predetermined value; Third is that, when the key switch is switched from START position to ON position, power is intermittently fed to the glow plug assembly to effect a second heat retention having the temperature lower than or closer to the aforesaid predetermined value.

Dependencies are inferred from the claim text.