| 摘要 |
PURPOSE:To decrease consumption of electric power for a heating unit and improve its thermal efficiency, by equipping an arithmetic unit for reducing a conduction current to the heating unit on the basis of an output signal corresponding to limit temperature output from a temperature detector unit. CONSTITUTION:A heating unit 17 is mounted to a required part in an intake passage further in such a manner that a surface of the unit contacted to a mixture is used as a heated surface. A reference resistance 4 is connected in series to the heating unit 17, and a change of terminal voltage of said reference resistor 4 in accordance with a heat generating condition of the heating unit is utilized, then an additional resistor 6 is inserted and connected in series to the heating unit 17 on the basis terminal voltage drop to not higher than a preset voltage value. If temperature of the heating unit 17 exceeds an upper limit value of an adequate range, the heating unit 17, being of a positive temperature characteristic, increases its resistance, and terminal voltage of the reference resistor 4 lowers. If this voltage drop reaches preset voltage, an arithmetic circuit 7 is operated to excite a relay excitation coil 2. As a result, a contact 5 is turned ON, and a current, flowing in the heating unit 17, decreases to lower heating temperature of the heating unit itself. |
