# US 9,038,611 B2 · NOx feedback for combustion control > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,038,611 B2 - Document ID: US9038611B2 - Status: Granted - Kind: B2 - Application number: 13/295,648 - Filed: 2011-11-14 - Published: 2013-05-16 - Granted: 2015-05-26 - Earliest claimed: 2011-11-14 - Assignees: Ford Global Technologies, LLC - Applicants: Peter Mitchell Lyon; Chris Riffle; Michiel J. Van Nieuwstadt; Frank M. Korpics; Jeff Reich; Dean Pennala - Inventors: Peter Mitchell Lyon; Chris Riffle; Michiel J. Van Nieuwstadt; Frank M. Korpics; Jeff Reich; Dean Pennala - Web page: https://patentgrep.com/patent/US9038611B2 ## CPC - F02D 21/08: the other gas being the exhaust gas of engine - F02D 41/0065: {Specific aspects of external EGR control (constructional details of EGR system F02M26/00)} - F02D 41/146: {the characteristics being an NOx content or concentration} - F02D 41/1461: {of the exhaust gases emitted by the engine} - F02M 26/05: High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor - 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 26/08: for engines having two or more intake charge compressors or exhaust gas turbines, e.g. a turbocharger combined with an additional compressor - F02M 26/24: with two or more coolers - F02M 26/38: with two or more EGR valves disposed in parallel - F02B 37/007: with exhaust-driven pumps arranged in parallel {, e.g. at least one pump supplying alternatively} - F02B 2075/125: {Direct injection in the combustion chamber for spark ignition engines, i.e. not in pre-combustion chamber} - F02D 13/0207: {changing valve lift or valve lift and timing} - F02D 13/0219: {by shifting the phase, i.e. the opening periods of the valves are constant} - F02D 2250/36: Control for minimising NOx emissions - F02M 26/15: in relation to engine exhaust purifying apparatus - Y02T 10/12: Improving ICE efficiencies - 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 - F02B: INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL (gas-turbine plants F02C; hot-gas or combustion-product positive-displacement engine plants F02G) - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A method for controlling combustion in an engine is provided. The method comprises under a first condition, adjusting an EGR amount of a total cylinder charge in response to engine out NOx levels being below a first threshold. In this way, NOx levels may be used as feedback to control combustion stability. ## Claims ### Claim 1 A method for controlling combustion in an engine, comprising: under a first condition, decreasing an EGR amount of a total cylinder charge in response to engine out NOx levels being below a first threshold and increasing the EGR amount of the total cylinder charge in response to the engine out NOx levels being above a second threshold, the first threshold being lower than the second threshold; and under a second condition, maintaining the EGR amount of the total cylinder charge even when NOx levels are below the first threshold. ### Claim 2 (depends on 1) The method of claim 1, wherein increasing the EGR amount of the total cylinder charge comprises adjusting an EGR valve to increase a percentage of EGR in the total cylinder charge. ### Claim 3 (depends on 1) The method of claim 1, wherein the first condition includes one or more of a reductant amount in an SCR system being above a first level and an efficiency of one or more emission control devices being above an efficiency threshold, and wherein the second condition includes one or more of the reductant amount being below the first level and the efficiency of the one or more emission control devices being below the efficiency threshold. ### Claim 4 (depends on 1) The method of claim 1, wherein decreasing the EGR amount of the total cylinder charge further comprises closing an EGR valve to decrease an EGR percentage of total cylinder charge. ### Claim 5 (depends on 4) The method of claim 4, further comprising opening an intake throttle concurrently with the EGR valve. ### Claim 6 (depends on 1) The method of claim 1, further comprising adjusting an EGR percentage of total cylinder charge based on engine speed and load. ### Claim 7 (depends on 1) The method of claim 1, further comprising adjusting one or more of a throttle and fuel injection timing in response to the engine out NOx levels being above the second threshold. ### Claim 8 (depends on 1) The method of claim 1, further comprising adjusting injection timing in response to the engine out NOx levels being below the first threshold. ### Claim 9 A system comprising: an engine including at least one cylinder and an exhaust passage coupled to at least one emission control device; an exhaust gas recirculation (EGR) system to divert a portion of exhaust from the engine to an air intake of the engine; a NOx sensor arranged in the exhaust passage upstream of the at least one emission control device; and a controller including instructions to: decrease an EGR amount of a total cylinder charge in response to NOx levels in the exhaust being below a first threshold, the NOx levels determined by the NOx sensor; increase the EGR amount of the total cylinder charge in response to the NOx levels in the exhaust being above a second threshold, the first threshold being lower than the second threshold; and not decreasing the EGR amount of the total cylinder charge in response to NOx levels in the exhaust being below the first threshold when an amount of reductant for injection is low. ### Claim 10 (depends on 9) The system of claim 9, wherein the EGR system comprises a high pressure EGR system (HP-EGR) controlled by an HP-EGR valve and a low pressure EGR system (LP-EGR) controlled by an LP-EGR system. ### Claim 11 (depends on 10) The system of claim 10, wherein the controller includes instructions to decrease the EGR amount of total cylinder charge by adjusting the HP-EGR valve or the LP-EGR valve based on the NOx levels in the exhaust from the engine. ### Claim 12 (depends on 11) The system of claim 11, wherein the controller includes instructions to decrease the EGR amount of total cylinder charge by adjusting the HP-EGR valve under low load conditions, and decrease the EGR amount of total cylinder charge by adjusting the LP-EGR valve under medium to high load conditions. ### Claim 13 (depends on 9) The system of claim 9, wherein the controller includes instructions to increase the EGR amount of the total cylinder charge in response to NOx levels in the exhaust being above a second threshold, greater than the first threshold. ### Claim 14 A method of reducing vehicle emissions, comprising: under a first condition, delivering HP-EGR to one or more cylinders of an engine; under a second condition, delivering LP-EGR to one or more cylinders of the engine; and under both the first and second conditions, decreasing an EGR amount of total cylinder charge in response to engine out NOx levels being below a first threshold; increasing the EGR amount of total cylinder charge in response to engine out NOx levels being above a second threshold, higher than the first threshold; and not decreasing the EGR amount of the total cylinder charge in response to NOx levels in the exhaust being below the first threshold when efficiency of an emissions control device is low. ### Claim 15 (depends on 14) The method of claim 14, wherein the first condition comprises medium to high engine load. ### Claim 16 (depends on 14) The method of claim 14, wherein the second condition comprises low engine load. ### Claim 17 (depends on 14) The method of claim 14, further comprising decreasing internal EGR when NOx levels are below the first threshold by adjusting one or more of intake and exhaust valve timing. ### Claim 18 (depends on 14) The method of claim 14, further comprising opening an intake throttle when NOx levels are below the first threshold. ### Claim 19 (depends on 14) The method of claim 14, further comprising adjusting fuel injection timing when NOx levels are below the first threshold.