Device for detecting deterioration of a catalytic converter for an engine
First Claim
1. A device for detecting a deterioration of a three-way catalytic converter for an internal combustion engine, said engine comprising, a plurality of cylinders divided into cylinder groups, individual exhaust passages connected to the respective cylinder groups, a common exhaust passage into which said individual exhaust passages are merged, upstream air-fuel ratio sensors disposed in said respective individual exhaust passages for detecting air-fuel ratios of the exhaust gases in said individual exhaust passages, a downstream air-fuel ratio sensor disposed in said common exhaust passage for detecting an air-fuel ratio of the exhaust gas in said common exhaust passage, at least one three-way catalytic converter disposed in exhaust passage between said upstream air-fuel ratio sensors and said downstream air-fuel ratio sensor, and a means for individually controlling the air-fuel ratio of each cylinder group based on outputs of said respective upstream air-fuel ratio sensors, said device comprising:
- an estimating means for estimating the air-fuel ratio of a mixture of the exhaust gases from said respective individual exhaust passages flowing into said common exhaust passage based on the output signals of said upstream air-fuel ratio sensors; and
a determining means for determining whether or not said three-way catalytic converter has deteriorated based on the output signal of said downstream air-fuel ratio sensor and said estimated air-fuel ratio of the mixture of the exhaust gas flowing into said common exhaust passage.
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Accused Products
Abstract
In an engine having two or more cylinder groups and a common exhaust passage with which exhaust passages individually connected to the respective cylinder groups are merged, the exhaust gases in the respective individual exhaust passage mix each other in the common exhaust passage before flowing into catalytic converter disposed in the common exhaust gas passage, therefore, when the air-fuel ratios of the respective cylinder groups are individually controlled, the air-fuel ratio of the exhaust gas in the common exhaust passage does not correspond to air-fuel ratio of the exhaust gas in any of the individual exhaust passages, and this makes it difficult to detect the deterioration of the catalyst based on the output of the upstream O2 sensor disposed in the individual exhaust passage and the downstream O2 sensor disposed in the common exhaust passage. In the present invention, the control circuit estimates the air-fuel ratio of the exhaust gas after mixed by averaging the outputs of the upstream air-fuel ratio sensors disposed in the respective individual exhaust passages, and detects the catalyst deterioration using the average output of the upstream air-fuel ratio sensor and the output of the downstream O2 sensor.
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Citations
16 Claims
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1. A device for detecting a deterioration of a three-way catalytic converter for an internal combustion engine, said engine comprising, a plurality of cylinders divided into cylinder groups, individual exhaust passages connected to the respective cylinder groups, a common exhaust passage into which said individual exhaust passages are merged, upstream air-fuel ratio sensors disposed in said respective individual exhaust passages for detecting air-fuel ratios of the exhaust gases in said individual exhaust passages, a downstream air-fuel ratio sensor disposed in said common exhaust passage for detecting an air-fuel ratio of the exhaust gas in said common exhaust passage, at least one three-way catalytic converter disposed in exhaust passage between said upstream air-fuel ratio sensors and said downstream air-fuel ratio sensor, and a means for individually controlling the air-fuel ratio of each cylinder group based on outputs of said respective upstream air-fuel ratio sensors, said device comprising:
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an estimating means for estimating the air-fuel ratio of a mixture of the exhaust gases from said respective individual exhaust passages flowing into said common exhaust passage based on the output signals of said upstream air-fuel ratio sensors; and a determining means for determining whether or not said three-way catalytic converter has deteriorated based on the output signal of said downstream air-fuel ratio sensor and said estimated air-fuel ratio of the mixture of the exhaust gas flowing into said common exhaust passage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification