Exhaust gas sensor temperature detection system

摘要

In a mixture control system having an exhaust gas sensor located in an exhaust system of an internal combustion engine for controlling the air-fuel ratio of the mixture supplied to the engine, a detection system for detecting when the temperature of the exhaust gas sensor is within its normal operating range. A deviation signal is derived from the exhaust gas sensor to represent the deviation of the air-fuel ratio within the exhaust system from a desired air-fuel ratio. The peak value of the deviation signal is detected and stored in a storage circuit and compared with a threshold which represents the normal operating temperature of the exhaust gas sensor to provide a disabling signal for the mixture control system to suspend feedback control operation when the temperature of the sensor falls below its normal operating temperature. The exhaust gas sensor is then supplied with a current in response to the presence of the disabling signal so that the voltage across the sensor's internal impedance increases because of its high impedance value at low sensor temperatures. The output from the gas sensor is compared with a preset value higher than the maximum output level of the sensor when operating at or above its normal operating temperature but lower than the minimum output level of the sensor when operating below its normal operating temperature with the current being fed. When the gas sensor output falls below the preset value, the system determines that the temperature of the gas sensor has risen above its normal operating temperature to resume feedback control operation.