| 摘要 |
PURPOSE:To make it possible to restrict the increase of NOx, by controlling the air-fuel ratio to the lean side, and at the same time, cutting off the secondary air feed from an air suction valve, at the partial loaded time. CONSTITUTION:When it is decided by a control unit 12 that the operating condition of an engine 1 which has a carburetor 11, is the time of partial load, through informations from a rotation sensor 13, a negative pressure sensor 14 and a water temperature sensor 15, an air-fuel ratio control signal is output so as to control the air-fuel ratio of the carburetor 11 to the lean side. At the same time, the secondary air is shut off, by turning off a solenoid 5, and leading atmosphere to the negative pressure chamber 6b of an air suction valve 6, through a solenoid valve 4. On the other hand, when the operating condition of the engine 1 becomes idle running or acceleration running, which are the operating conditions other than rare operating condition, the air-fuel ratio is controlled to the stoichiometric or the rich side, and the secondary air is led in by turning on the solenoid 5. In this way, the increase of NOx can be restricted under the rare operating condition, and HC, CO can be decreased under the operating conditions other than the rare operating condition.
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