| 摘要 |
PURPOSE:To prevent the abrupt deterioration of a heater by having an electric power source supplying means which conducts electricity to the heater according to the operating condition of an engine. CONSTITUTION:When an ignition switch turns on in the stage of low temp. starting of an engine, the output of a comparator 9 is at a low level; therefore a switch circuit 7 is off and no electricity is conducted to a heater 4, but when a waste gas is fed into an exhaust pipe and the temp. in the exhaust pipe rises and attains a prescribed temp., the output of the comparator 9 inverts from the low level to a high level according to the output voltage of a temp. sensor 8, by which the circuit 7 is turned on, thus the temp. of a ceramic pipe for heating of the heater 4 rises to high temp., the operating characteristics of the oxygen concn. sensor are improved and the air to fuel ratio is controlled adequately. When the temp. in the exhaust pipe attains a prescribed temp. T2, the output of the comparator 9 inverts from the high level to the low level according to the output voltage of the sensor 8 and the circuit 7 goes on again, thereby stopping the conduction of electricity to the heater 4. |
