| 摘要 |
The invention relates to a control system for feedback control of the air/fuel ratio in an internal combustion engine which uses a three-way catalyst to purify the exhaust gas, and which may be an automotive engine, by using an exhaust sensor to detect actual values of air/fuel ratio in the engine. The control system has the function of varying the target value of air/fuel ratio according to operating conditions of the engine such that the target value becomes super-stoichiometric at least in a portion of a steady zone of the engine operating conditions. The control system includes means to detect the temperature of the three-way catalyst and means to vary the feed of fuel or air to the engine when the catalyst temperature is above a predetermined level, e.g. 750 DEG C., while the target value of the air/fuel ratio is super-stoichiometric such that the actual air/fuel ratio decreases to a predetermined value, e.g. stoichiometric value, which is optimum for the activities of the three-way catalyst, or to a still lower value. Such intentional change in the air/fuel ratio under the high exhaust temperature condition is effective in preventing early deterioration of the three-way catalyst.
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