Exhaust system for internal combustion engine
First Claim
1. An exhaust system for an internal combustion engine having a plurality of cylinders divided into two groups, which are independently connected to exhaust lines comprising an individual exhaust passage and a common exhaust passage, said exhaust system comprising:
- air-fuel ratio detecting means, disposed in each individual exhaust passage, for detecting an air-fuel ratio based on an emission level of exhaust gas;
catalytic convertor means, disposed in said common exhaust passage, for purifying exhaust gas;
an oxygen sensor, disposed in said common exhaust passage downstream from said catalytic convertor means, for detecting an oxygen level of exhaust gas passed through said catalytic convertor means; and
control means for feedback controlling air-fuel ratios for said cylinder groups independently based on emission levels detected by said air-fuel ratio detecting means, respectively, for detecting vehicle driving conditions, for feedback controlling an air-fuel ratio for said cylinder groups all together based on either one of the air-fuel ratios only when detecting a specific vehicle driving condition, and for detecting deterioration of said catalytic convertor means based on a signal representative of an oxygen level detected by said oxygen sensor while an air-fuel ratio is feedback controlled for said cylinder groups all together based on said one of said air-fuel ratios, thereby determining a critical deterioration of said catalytic convertor means.
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Accused Products
Abstract
An exhaust system for an automobile engine having two groups of cylinders has a catalytic device. Deterioration of the catalytic device is detected based on an oxygen level in exhaust gas passed through the catalytic device. A feedback control of an air-fuel ratio is conducted for the cylinder groups all together, based on either of the air-fuel ratios determined, based on emission levels of exhaust gas discharged, for one of two of the groups of cylinders, only when a specific vehicle driving condition is detected.
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Citations
17 Claims
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1. An exhaust system for an internal combustion engine having a plurality of cylinders divided into two groups, which are independently connected to exhaust lines comprising an individual exhaust passage and a common exhaust passage, said exhaust system comprising:
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air-fuel ratio detecting means, disposed in each individual exhaust passage, for detecting an air-fuel ratio based on an emission level of exhaust gas; catalytic convertor means, disposed in said common exhaust passage, for purifying exhaust gas; an oxygen sensor, disposed in said common exhaust passage downstream from said catalytic convertor means, for detecting an oxygen level of exhaust gas passed through said catalytic convertor means; and control means for feedback controlling air-fuel ratios for said cylinder groups independently based on emission levels detected by said air-fuel ratio detecting means, respectively, for detecting vehicle driving conditions, for feedback controlling an air-fuel ratio for said cylinder groups all together based on either one of the air-fuel ratios only when detecting a specific vehicle driving condition, and for detecting deterioration of said catalytic convertor means based on a signal representative of an oxygen level detected by said oxygen sensor while an air-fuel ratio is feedback controlled for said cylinder groups all together based on said one of said air-fuel ratios, thereby determining a critical deterioration of said catalytic convertor means. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An exhaust system as defined for an internal combustion engine having a plurality of cylinders divided into two groups, which are independently connected to exhaust lines comprising an individual exhaust passage and a common exhaust passage, said exhaust system comprising:
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air-fuel ratio detecting means, disposed in each individual exhaust passage, for detecting an air-fuel ratio based on an emission level of exhaust gas; catalytic convertor means, disposed in said common exhaust passage, for purifying exhaust gas; an oxygen sensor, disposed in said common exhaust passage downstream from said catalytic convertor means, for detecting an oxygen level of exhaust gas passed through said catalytic convertor means; and control means for feedback controlling air-fuel ratios for both said cylinder groups independently based on emission levels detected by said air-fuel ratio detecting means, respectively, for detecting vehicle driving conditions, for monitoring a difference between phases in change of air-fuel ratios for both said groups of said cylinders based on an emission level of exhaust gas detected by said air-fuel ratio detecting means only when detecting a specific vehicle driving condition, and for detecting deterioration of said catalytic convertor means based on a signal representative of an oxygen level detected by said oxygen sensor only when detecting no difference between said phases, thereby determining a critical deterioration of said catalytic convertor means. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. An exhaust system as defined for an internal combustion engine having a plurality of cylinders divided into two groups, which are independently connected to exhaust lines comprising an individual exhaust passage and a common exhaust passage, said exhaust system comprising:
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air-fuel ratio detecting means, disposed in each individual exhaust passage, for detecting an air-fuel ratio based on an emission level of exhaust gas; catalytic convertor means, disposed in said common exhaust passage, for purifying exhaust gas; an oxygen sensor, disposed in said common exhaust passage downstream from said catalytic convertor means, for detecting an oxygen level of exhaust gas passed through said catalytic convertor means; and control means for feedback controlling air-fuel ratios for said cylinder groups independently based on emission levels detected by said air-fuel ratio detecting means, respectively, for detecting vehicle driving conditions, for conducting a feedback control of an air-fuel ratio for both said cylinder groups based on either one of said air-fuel ratios for a predetermined period only when detecting a specific vehicle driving condition, for detecting a reversal frequency of a signal representative of an oxygen level detected by said oxygen sensor during said feedback control of an air-fuel ratio for both said cylinder groups based on said one of said air-fuel ratios for a predetermined period, for conducting a feedback control of an air-fuel ratio for both said cylinder groups based on the other one of said air-fuel ratios for said predetermined period only when detecting a specific vehicle driving condition, for detecting a reversal frequency of a signal representative of an oxygen level detected by said oxygen sensor during said feedback control of an air-fuel ratio for both said cylinder groups based on said the other one of said air-fuel ratios for a predetermined period, and for detecting deterioration of said catalytic convertor means based on an average reversal frequency of said reversal frequencies, thereby determining a critical deterioration of said catalytic convertor means. - View Dependent Claims (15, 16, 17)
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Specification