| 摘要 |
PURPOSE:To obtain the air/fuel ratio sensor of an engine always holding a sensor temp. in a predetermined range, reduced in an error and having a heater with a long working life, by mounting a heater to a sensor and heating the sensor by supplying a current to the heater when the sucking air amount of an engine is small while cutting off a current to the heater when the air intake volume is great. CONSTITUTION:An air/fuel ratio sensor 2 is constituted of a solid electrolyte oxygen pump 6 formed by respectively providing latinum electrodes 4, 5 to both side surfaces of a flat shaped ion conductive solid electrolyte 3 with a thickness of about 0.5mm., a solid electrolyte oxygen sensor 10 formed by respectively providing platinum electrodes 8, 9 to both side surfaces of a flat plate shaped ion conductive solid electrolyte 7 and a support stand 11 for supporting the oxygen pump 6 and the oxygen sensor 10 so as to oppose both of them through a minute gap (d) of about 0.1mm. and inserted into an exhaust pipe 1. A nichrome wire is used in a heater 13 for heating the air/fuel ratio sensor 2 and the heater 13 is connected to a DC power source B at one terminal thereof and connected to a transistor TR2 at the other terminal thereof. The control terminal 14 of the transistor TR2 inputs the intake air volume of an engine or a signal corresponding thereto to perform the ON/OFF operation of the transistor TR2. |
