| 摘要 |
PURPOSE:To prevent the deterioration of an oxygen sensor by detecting the increase of the oxygen concn. in an exhaust pipe to the prescribed oxygen concn. or above, for example, the atm. state by means of an oxygen sensor and stopping the pump current to the oxygen sensor when an engine stops. CONSTITUTION:The oxygen sensor (a) is provided in the exhaust pipe of an internal-combustion engine and the concn. is measured by a means (b) for measuring the oxygen concn. The sensor (a) is so constituted that one side of an oxygen ion conductive electrolyte contacts with the atm. air and the other side contacts with the exhaust gas. The pump current is passed to the sensor so as to maintain the specified oxygen partial pressure ratio on both sides thereof and the oxygen concn. is detected from the pump current value by the means (b). The signal to stop the pump current is emitted from a means (c) for generating the stop signal to stop the current on discrimination that the atmosphere of the oxygen sensor is in the state above the prescribed oxygen concn. when the internal-combustion engine stops. The supply of the overcurrent for a long period is thus obviated and the deterioration of the oxygen sensor is thus prevented as the pump current is stopped while the atmosphere of the oxygen sensor is above the prescribed oxygen concn.
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