| 摘要 |
PURPOSE:To enable an engine preheating plug to be automatically changed over to the energized condition through a resistor by doubling an energizing path to said plug to form one of electric control means of the resistor having current value adjusting action and detect the disconnection of the preheating plug according to the energizing current value. CONSTITUTION:A relay 13 keeps closing the contact if it is not under disconnected condition, and energizes or deenergizes a relay 12 in response to current value showing temperature of preheating plugs 1-4 to intermittently close the contact. Thus, the preheating plugs 1-4 are maintained at about 700 deg.C-900 deg.C. If one of the preheating plugs is disconnected, a disconnection selecting circuit 22 generates H level output delayed some time after closing a switch 6 to turn on all transitors 23-25. By turning on the transistor 23 is lit a disconnection indicating lamp 15, the relay 13 is deenergized by turning on the transistor 24 and the relay 12 deenergized by turning on the transistor 25. Thus, the preheating plugs 1-4 are supplied with current only through resistances 10, 11 to supply large current to the preheating plugs and give abruptly exothermic reaction to same. |
