# US 9,435,279 B2 · Inter-cylinder air-fuel ratio variation abnormality detection apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,435,279 B2 - Document ID: US9435279B2 - Status: Granted - Kind: B2 - Application number: 14/223,418 - Filed: 2014-03-24 - Published: 2014-10-16 - Granted: 2016-09-06 - Earliest claimed: 2013-04-16 - Assignees: Toyota Jidosha Kabushiki Kaisha - Applicants: Yasushi Iwazaki; Kenji Suzuki - Inventors: Yasushi Iwazaki; Kenji Suzuki - Web page: https://patentgrep.com/patent/US9435279B2 ## CPC - F02D 41/1454: {the characteristics being an oxygen content or concentration or the air-fuel ratio} - F02D 41/0085: {Balancing of cylinder outputs, e.g. speed, torque or air-fuel ratio} - F02D: CONTROLLING COMBUSTION ENGINES (vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed B60K31/00; conjoint control of vehicle sub-units of different type or different function, road vehicle drive control systems for purposes other than the control of a single sub-unit B60W) ## Abstract When two abnormal cylinders are causing variation abnormality, these abnormal cylinders are identified. A parameter correlated with a degree of fluctuation of output from an air-fuel ratio sensor installed in an exhaust passage common to a plurality of cylinders is calculated. Based on the calculated parameter, inter-cylinder air-fuel ratio variation abnormality is detected. The following steps are carried out: (A) a step of forcibly changing amounts of fuel injected for two of the plurality of cylinders and calculating the parameter, (B) a step of changing the two cylinders to other two cylinders and repeating the step (A), and (C) a step of identifying two cylinders causing variation abnormality based on a plurality of the parameters calculated in the steps (A) and (B). ## Claims ### Claim 1 An inter-cylinder air-fuel ratio variation abnormality detection apparatus comprising: an air-fuel ratio sensor installed in an exhaust passage common to a plurality of cylinders to detect inter-cylinder air-fuel ratio variation abnormality based on a calculated parameter; and an electronic control unit configured to carry out: (A) a step of forcibly changing amounts of fuel injected for two of the plurality of cylinders and calculating the parameter that correlates with a degree of fluctuation of output from the air-fuel ratio sensor; (B) a step of changing the two cylinders to two other cylinders and repeating the step (A); and (C) a step of identifying two cylinders causing the inter-cylinder air-fuel ratio variation abnormality based on a plurality of the parameters calculated in the steps (A) and (B). ### Claim 2 (depends on 1) The inter-cylinder air-fuel ratio variation abnormality detection apparatus according to claim 1, wherein the electronic control unit is further configured to identify, in the step (C), two cylinders corresponding to one of the plurality of calculated parameters which minimizes a degree of a variation in air-fuel ratio as two cylinders causing the variation abnormality. ### Claim 3 (depends on 1) The inter-cylinder air-fuel ratio variation abnormality detection apparatus according to claim 1, wherein the electronic control unit is further configured to repeat the step (A) in the step (B) to carry out the change in the amount of injected fuel and the calculation of the parameter for all combinations of two cylinders. ### Claim 4 (depends on 1) The inter-cylinder air-fuel ratio variation abnormality detection apparatus according to claim 1, wherein the electronic control unit is further configured to carry out: (D) a step of forcibly changing the amount of fuel injected for one of the plurality of cylinders and calculating the parameter; and (E) a step of changing the one cylinder to another cylinder and repeating the step (D), wherein, in step (C), one cylinder or two cylinders causing the variation abnormality are identified based on a plurality of the parameters calculated in steps (A), (B), (D), and (E). ### Claim 5 (depends on 1) The inter-cylinder air-fuel ratio variation abnormality detection apparatus according to claim 1, wherein the electronic control unit is, further configured to also identify a type of the variation abnormality in the step (C). ### Claim 6 (depends on 1) The inter-cylinder air-fuel ratio variation abnormality detection apparatus according to claim 1, wherein, in the step (A), the change in the amount of injected fuel is an increase in the amount of injected fuel. ### Claim 7 An inter-cylinder air-fuel ratio variation abnormality detection apparatus comprising: a plurality of fuel injectors that inject an amount of fuel for each of a plurality of cylinders; an air-fuel ratio sensor installed in an exhaust passage common to the plurality of cylinders to detect inter-cylinder air-fuel ratio variation abnormality based on a calculated parameter; and an electronic control unit operatively connected to the plurality of fuel injectors, the electronic control unit configured to carry out: (A) a step of controlling two of the plurality of fuel injectors to forcibly changing the amounts of fuel injected for two of the plurality of cylinders and calculating the parameter that correlates with a degree of fluctuation of output from the air-fuel ratio sensor; (B) a step of changing the two fuel injectors and two cylinders to two other fuel injectors and two other cylinders and repeating the step (A); and (C) a step of identifying two cylinders causing the inter-cylinder air-fuel ratio variation abnormality based on a plurality of the parameters calculated in the steps (A) and (B). ### Claim 8 (depends on 7) The inter-cylinder air-fuel ratio variation abnormality detection apparatus according to claim 7, wherein the electronic control unit is further configured to identify, in the step (C), two cylinders corresponding to one of the plurality of calculated parameters which minimizes a degree of a variation in air-fuel ratio as two cylinders causing the variation abnormality. ### Claim 9 (depends on 7) The inter-cylinder air-fuel ratio variation abnormality detection apparatus according to claim 7, wherein the electronic control unit is further configured to repeat the step (A) in the step (B) to carry out the change in the amount of injected fuel and the calculation of the parameter for all combinations of two cylinders. ### Claim 10 (depends on 7) The inter-cylinder air-fuel ratio variation abnormality detection apparatus according to claim 7, wherein the electronic control unit is further configured to carry out: (D) a step of controlling one of the plurality of fuel injectors to forcibly changing the amount of fuel injected for one of the plurality of cylinders and calculating the parameter; and (E) a step of changing the one fuel injector and one cylinder to another fuel injector and another cylinder and repeating the step (D), wherein, in step (C), one cylinder or two cylinders causing the variation abnormality are identified based on a plurality of the parameters calculated in steps (A), (B), (D), and (E). ### Claim 11 (depends on 7) The inter-cylinder air-fuel ratio variation abnormality detection apparatus according to claim 7, wherein the electronic control unit is, further configured to also identify a type of the variation abnormality in the step (C). ### Claim 12 (depends on 7) The inter-cylinder air-fuel ratio variation abnormality detection apparatus according to claim 7, wherein, in the step (A), the change in the amount of injected fuel is an increase in the amount of injected fuel.