Secondary air control system for an internal combustion engine
AssigneeToyota Kidosha Kogyo Kabushiki Kaisha
InventorKeiso Takeda
Life of this patent
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Abstract
Disclosed is a double feedback loop type of secondary air control system for an internal combustion engine, in which a valve provided in a secondary air feed passage for regulating a quantity of the secondary air fed into an exhaust passage of the engine is operated in response to a first error signal indicative of a deviation of the actual secondary air quantity from the desired secondary air quantity and a second error signal indicative of a deviation of the actual air-fuel ratio from the desired air-fuel ratio, thereby effecting a precise control of the air-fuel ratio.
Claims6
A secondary air control system in an exhaust gas purifying system for an internal combustion engine including a three-way catalyzer in an exhaust passage of the engine and a secondary air feed device for feeding secondary air via a secondary air passage into said exhaust passage upstream of said catalyzer, said secondary air control system comprising:
- a control valve in said secondary air passage for regulating the flow rate of the secondary air fed therethrough;
- means for generating a signal indicative of a desired quantity of the secondary air determined by the quantity of an intake air supplied into the engine via a carburetor, the basic air-fuel ratio set by said carburetor and the desired air-fuel ratio for said catalyzer;
- first feedback means for generating a signal indicative of an actual quantity of the secondary air fed via said secondary air valve;
- means for generating a signal indicative of the desired air-fuel ratio;
- second feed back means for generating a signal indicative of an actual air-fuel ratio in the exhaust passage between the secondary air feeding position and said catalyzer;
- means responsive to said actual secondary air quantity signal and said desired secondary air quantity signal for generating a first error signal indicative of a deviation of the actual secondary air quantity from the desired secondary air quantity;
- means responsive to said actual air-fuel ratio signal and said desired air-fuel ratio signal for generating a second error signal indicative of a deviation of the actual air-fuel ratio from the desired air-fuel ratio;
- and
- actuator means responsive to said first and second error signals for operating said secondary air valve, said system further comprising means for generating an auxiliary signal, and signal selector means responsive to a temperature of said catalyzer for interrupting the feeding of said second error signal to said actuator means when the catalyzer temperature rises higher than a predetermined temperature, while feeding said auxiliary signal to said actuator means, so as to effect the secondary air control to prevent said catalyzer from being overheated.
Dependencies are inferred from the claim text.