| 摘要 |
PURPOSE:To enable an air-fuel ratio to be controlled correctly by providing an actual air-fuel ratio detecting means capable of detecting an actual air-fuel ratio based on the output from both a changing direction detecting means and an air-furl ratio sensor and sending said actual air-fuel ratio to an air-fuel ratio control means. CONSTITUTION:An air-fuel ratio control means 25 controls the air-fuel ratio of a mixture to be supplied to an engine 1 on the basis of a presently existent air-fuel ratio. An air-fuel ratio changing means 26 changes the air-fuel ratio of a mixture by an assigned amount. A changing direction detecting means 27 detects the changing direction of the output from an air-fuel ratio sensor 24. An actual air-fuel ratio detecting means 28 finds out the presently existent air-fuel ratio making use of the output from the changing direction detecting means 27 and the air-fuel ratio sensor 24. Thus, the air-fuel ratio control can be carried out correctly regardless whether the control mode is rich or lean.
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