# US 11,898,509 B2 · EGR estimation method for internal combustion engine and EGR estimation 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 11,898,509 B2 - Document ID: US11898509B2 - Status: Granted - Kind: B2 - Application number: 17/916,326 - Filed: 2020-04-02 - Published: 2023-05-18 - Granted: 2024-02-13 - Earliest claimed: 2020-04-02 - Assignees: Nissan Motor Co., Ltd. - Applicants: Nissan Motor Co., Ltd. - Inventors: Taichi Ando; Kenji Suzuki - Web page: https://patentgrep.com/patent/US11898509B2 ## CPC - F02D 41/0072: {Estimating, calculating or determining the EGR rate, amount or flow (sensors in EGR systems F02M26/45)} - F02D 41/005: {according to engine operating conditions} - F02D 41/123: {the fuel injection being cut-off} - F02M 26/06: Low pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust downstream of the turbocharger turbine and reintroduced into the intake system upstream of the compressor - F02M 26/49: Detecting, diagnosing or indicating an abnormal function of the EGR system - Y02T 10/40: Engine management systems - 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) - F02M: SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract An EGR estimation method for an internal combustion engine 1 estimates an EGR rate in an intake and exhaust system 10, 20 of an internal combustion engine, the intake and exhaust system 10, 20 of an internal combustion engine including an intake system 10, an exhaust system 20, and an EGR device 40, the EGR device 40 includes an EGR passage 41 and an EGR valve 43. The EGR estimation method includes determining a gas replacement state by exhaust gas and fresh air in an upstream EGR passage, which is a portion of the EGR passage between the EGR valve and the exhaust passage, when fuel cut of the internal combustion engine is started and the EGR valve is fully closed; and estimating the EGR rate based on a result of the determination. ## Claims ### Claim 1 An exhaust gas recirculation (EGR) estimation method for estimating an EGR rate in an intake and exhaust system of an internal combustion engine, the EGR estimation method comprising: providing the intake and exhaust system, which comprises: an intake passage that is connected to the internal combustion engine, an exhaust passage that is connected to the internal combustion engine, an EGR valve in which a gap occurs even when the EGR valve is fully closed, due to a structure of the EGR valve, and an EGR passage comprising an upstream EGR passage that connects the exhaust passage to the EGR valve, and a downstream EGR passage that connects the EGR valve to the intake passage; when a fuel cut of the internal combustion engine is started with the EGR valve fully closed: maintaining the EGR valve fully closed during the execution of the fuel cut of the internal combustion engine, and during the execution of the fuel cut of the internal combustion engine and/or after fuel injection of the internal combustion engine is restarted, determining a gas replacement state by exhaust gas and fresh air in the upstream EGR passage; and estimating the EGR rate based on a result of the determination of the gas replacement state. ### Claim 2 (depends on 1) The EGR estimation method for an internal combustion engine according to claim 1, wherein: whether an inside of the upstream EGR passage is not filled with the exhaust gas due to inflow of the fresh air is determined according to an execution time of the fuel cut. ### Claim 3 (depends on 2) The EGR estimation method for an internal combustion engine according to claim 2, wherein: when it is determined that the upstream EGR passage is not filled with the exhaust gas due to the inflow of the fresh air, the EGR rate after EGR is restarted is estimated to be zero. ### Claim 4 (depends on 1) The EGR estimation method for an internal combustion engine according to claim 1, wherein: after fuel injection of the internal combustion engine is restarted, it is determined whether the inside of the upstream EGR passage is replaced with the exhaust gas based on a flow rate of EGR gas flowing through the upstream EGR passage. ### Claim 5 (depends on 4) The EGR estimation method for an internal combustion engine according to claim 4, further comprising: setting a period until the EGR rate after the EGR is restarted starts to increase to be shorter as the flow rate of the EGR gas increases. ### Claim 6 (depends on 4) The EGR estimation method for an internal combustion engine according to claim 4, further comprising: setting a degree of increase in the EGR rate after the EGR is restarted to be larger as the flow rate of the EGR gas increases. ### Claim 7 (depends on 1) The EGR estimation method for an internal combustion engine according to claim 1, wherein: the gas replacement state is determined based on at least an amount of exhaust gas or an amount of fresh air leaking from the gap of the EGR valve. ### Claim 8 An exhaust gas recirculation (EGR) estimation device for estimating an EGR rate in an intake and exhaust system, the intake and exhaust system comprising: an intake passage that is connected to the internal combustion engine, an exhaust passage that is connected to the internal combustion engine, an EGR valve in which a gap occurs even when the EGR valve is fully closed, due to a structure of the EGR valve, and an EGR passage comprising an upstream EGR passage that connects the exhaust passage to the EGR valve, and a downstream EGR passage that connects the EGR valve to the intake passage, the EGR estimation device comprising: a determination control unit configured to, when a fuel cut of the internal combustion engine is started the EGR valve fully closed: maintain the EGR valve fully closed during the execution of a fuel cut of the internal combustion engine, and during the execution of the fuel cut of internal combustion engine and/or after fuel injection of the internal combustion engine is restarted, determine a gas replacement state by exhaust gas and fresh air in the upstream EGR passage; and an estimation control unit configured to estimate the EGR rate based on a result of the determination of the gas replacement state.