# US 10,371,687 B2 · Air-fuel ratio detection device for internal combustion engine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,371,687 B2 - Document ID: US10371687B2 - Status: Granted - Kind: B2 - Application number: 15/123,737 - Filed: 2015-01-14 - Published: 2017-01-19 - Granted: 2019-08-06 - Earliest claimed: 2014-03-07 - Assignees: Toyota Jidosha Kabushiki Kaisha - Applicants: Toyota Jidosha Kabushiki Kaisha - Inventors: Yukihiro Nakasaka - Web page: https://patentgrep.com/patent/US10371687B2 ## CPC - G01N 33/22: Fuels; Explosives - F02D 41/0085: {Balancing of cylinder outputs, e.g. speed, torque or air-fuel ratio} - F02D 41/1458: {with determination means using an estimation} - G01L 23/26: Details or accessories - G01M 15/08: by monitoring pressure in cylinders - F02D 2200/0402: the parameter being determined by using a model of the engine intake or its components - F02D 2200/0406: Intake manifold pressure - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - 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) - G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G) - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR ## Abstract An in-cylinder pressure sensor is provided. It is determined whether a cylinder for which the in-cylinder air-fuel ratio is to be calculated is a rich cylinder or a lean cylinder. A polytropic index in the expansion stroke is calculated from the in-cylinder pressure detected by the in-cylinder pressure sensor. The calculated polytropic index m is corrected based on an operational condition parameter of an internal combustion engine. An in-cylinder air-fuel ratio is calculated based on the corrected polytropic index m in the expansion stroke, the result of the determination of whether the cylinder is a rich cylinder or a lean cylinder, and an m-A/F curve. ## Claims ### Claim 1 An air-fuel ratio detection device for an internal combustion engine including one or more cylinders and each cylinder including a fuel injection valve to directly inject a fuel into the cylinder, the air-fuel ratio detection device comprising: an in-cylinder pressure detector configured to detect an in-cylinder pressure; and an ECU, the ECU programmed to: (a) determine whether a cylinder for which an index value of an in-cylinder air-fuel ratio is to be calculated is a rich cylinder, for which the in-cylinder air-fuel ratio is richer than a stoichiometric air-fuel ratio, or a lean cylinder, for which the in-cylinder air-fuel ratio is leaner than the stoichiometric air-fuel ratio; (b) calculate a polytropic index in an expansion stroke from the in-cylinder pressure detected by the in-cylinder pressure detector; (c) correct the calculated polytropic index based on an operational condition parameter of the internal combustion engine; and (d) calculate the index value of the in-cylinder air-fuel ratio based on the corrected polytropic index in the expansion stroke, a result of the determination of whether the cylinder for which the index value of the in-cylinder air-fuel ratio is to be calculated is a rich cylinder or a lean cylinder, and relationship information that prescribes a relationship between the polytropic index in the expansion stroke and the index value of the in-cylinder air-fuel ratio under a reference operational condition; wherein said ECU is further programmed to control the fuel injection valve in each cylinder, based on the index value of the in-cylinder air-fuel ratio, to adjust a fuel injection amount for each cylinder so as to set an air-fuel ratio of exhaust gas from said one or more cylinders to a stoichiometric air-fuel ratio. ### Claim 2 (depends on 1) The air-fuel ratio detection device according to claim 1, wherein the operational condition parameter used for the correction of the polytropic index in the expansion stroke is at least one of an engine speed, a temperature of engine cooling water, an ignition timing, an EGR rate and an engine load factor. ### Claim 3 (depends on 2) The air-fuel ratio detection device according to claim 2, wherein the ECU is programmed to correct the polytropic index in the expansion stroke so as to be smaller as the engine speed is higher, as the temperature of the engine cooling water is higher, as the ignition timing is retarded, as the EGR rate is higher, or as the engine load factor is higher. ### Claim 4 (depends on 1) The air-fuel ratio detection device according to claim 1, wherein the ECU is programmed to calculate an amount of heat release or a burning velocity from the in-cylinder pressure detected by the in-cylinder pressure-detector and determines that the cylinder for which the index value of the in-cylinder air-fuel ratio is to be calculated is a rich cylinder when the calculated amount of heat release or burning velocity is greater than a predetermined value. ### Claim 5 (depends on 1) The air-fuel ratio detection device according to claim 1, wherein the ECU is programmed to calculate the polytropic index in the expansion stroke from in-cylinder pressures and in-cylinder volumes at two or more points in the expansion stroke at or after a combustion end point and before an opening timing of an exhaust valve. ### Claim 6 (depends on 1) The air-fuel ratio detection device according to claim 1, wherein the internal combustion engine includes a plurality of cylinders, wherein the in-cylinder pressure detector is configured to detect an in-cylinder pressure of each of the plurality of cylinders, and wherein the ECU is programmed to determine that the air-fuel ratio is imbalance between cylinders when a difference in air-fuel ratio between the cylinders based on the calculated index value of the in-cylinder air-fuel ratio is greater than a predetermined criterion value. ### Claim 7 (depends on 1) The air-fuel ratio detection device according to claim 1, wherein the reference operational condition is an operational condition where the operational condition parameter equals an arbitrary reference value. ### Claim 8 (depends on 1) The air-fuel ratio detection device according to claim 1, wherein the relationship information is a curve that prescribes a relationship between the polytropic index in the expansion stroke and the index value of the in-cylinder air-fuel ratio in an X-Y plane with an X axis indicating the index value of the in-cylinder air-fuel ratio and a Y axis indicating the polytropic index in the expansion stroke.