| 摘要 |
PURPOSE:To simplify a control method and system, by varying a secondary air quantity to be led into an exhaust system in front of the catalyzing unit and installing an air fuel ratio controlling device which forcibly alter the exhaust air fuel ratio at an intake port of the unit before and behind a theoretical air- fuel ratio in between. CONSTITUTION:An air-fuel ratio controlling device 16 consisting of a lead valve 18, a solenoid valve 20, etc., which vary secondary air quantity to be led into an exhaust system in front of a catalyzing unit 12 and forcibly alter an exhaust fuel-air ratio at an intake port of the catalyzing unit 12 before and behind a theoretical fuel-air ratio in between. Then, the solenoid valve 20 is properly opened or closed whereby the exhaust air-fuel ratio at the catalyzing unit 12 intake port can be altered at both sides before and behind the theoretical air-fuel ratio interposed between, while characteristics capable of indicating a smooth purification ratio is attainable. Owing to this, although it is of a simple make-up, highly efficient purification can be achieved with a ternary catalyzer and, in respect of catalyst durability, a fluctuating cycle of the air-fuel ratio comes possible to be set for an ideal one without difficulty, leading to still more improvement in the durability of catalyst. |
