# US 11,306,666 B2 · Method for detecting coking in the inlet section of an internal combustion engine with a variable inlet valve lift controller > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,306,666 B2 - Document ID: US11306666B2 - Status: Granted - Kind: B2 - Application number: 17/281,656 - Filed: 2019-10-15 - Published: 2021-12-02 - Granted: 2022-04-19 - Earliest claimed: 2018-10-25 - Assignees: Bayerische Motoren Werke Aktiengesellschaft - Applicants: Bayerische Motoren Werke Aktiengesellschaft - Inventors: Joerg Koehler - Web page: https://patentgrep.com/patent/US11306666B2 ## CPC - F02D 13/0226: {changing valve lift or valve lift and timing} - F02D 41/0002: {Controlling intake air} - F02D 41/1456: {with sensor output signal being linear or quasi-linear with the concentration of oxygen} - F02D 41/22: Safety or indicating devices for abnormal conditions {(in air/fuel ratio feedback systems F02D41/1495, in electric control linkage F02D11/107, in purge control systems F02M25/0809)} - F02D 41/2451: {characterised by what is learned or calibrated} - F02D 2041/001: {for engines with variable valve actuation} - F02D 2041/002: {by simultaneous control of throttle and variable valve actuation} - 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) - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A method detects coking in the inlet section of an internal combustion engine with direct fuel injection, a throttle valve and a variable inlet valve lift controller. A correction value calculated by the inlet valve lift controller as an offset value with a preset valve lift is determined. In parallel, a first quantity deviation test is carried out by which a first air ratio value is determined, which is formed from a first lambda value measured during the first quantity deviation test and a desired lambda value of the fuel combustion in the combustion chambers of the internal combustion engine, wherein, in the first quantity deviation test a load control process is carried out by way of the variable inlet valve lift controller. In a second quantity deviation test, a second air ratio value is determined which is formed from a lambda value measured during the second quantity deviation test and a desired lambda value of the fuel combustion. In the second quantity deviation test a load control process is carried out by way of the throttle valve. A comparison value is formed from the first air ratio value and the second air ratio value. Whether coking is present in the inlet section of the internal combustion engine is determined by combined evaluation of the comparison result and of the correction value. ## Claims ### Claim 1 A method for detecting coking in an inlet section of an internal combustion engine with direct fuel injection, a throttle flap and a variable inlet valve lift controller, comprising: ascertaining a correction value which is offset as an offset value against a preset valve lift by the inlet valve lift controller; carrying out a first quantity deviation test by way of which a first air ratio value is ascertained which is formed from a lambda value measured during the first quantity deviation test and a desired lambda value of a fuel combustion in combustion chambers of the internal combustion engine, wherein, in the first quantity deviation test, load control is performed by way of the variable inlet valve lift controller; carrying out a second quantity deviation test by way of which a second air ratio value is ascertained which is formed from a lambda value measured during the second quantity deviation test and a desired lambda value of the fuel combustion in the combustion chambers of the internal combustion engine, wherein, in the second quantity deviation test, load control is performed by way of the throttle flap; determining a comparison result from the first air ratio value and the second air ratio value; and determining whether coking is present in the inlet section of the internal combustion engine by combined evaluation of the comparison result and the correction value. ### Claim 2 (depends on 1) The method according to claim 1, wherein the correction value is read out of an engine controller. ### Claim 3 (depends on 1) The method according to claim 1, wherein the correction value is a value ascertained in relation to a running time of the internal combustion engine by the engine controller. ### Claim 4 (depends on 3) The method according to claim 3, wherein the correction value is a value adapted in relation to the running time of the internal combustion engine by the engine controller, wherein an adaptation is performed from a theoretically calculated air mass value of air flowing into the combustion chambers of the internal combustion engine and a measured air mass value. ### Claim 5 (depends on 1) The method according to claim 1, wherein the correction value is compared with a predefined limit value, and a presence of a fault in the inlet section is inferred when the correction value exceeds the predefined limit value. ### Claim 6 (depends on 5) The method according to claim 5, wherein a fault signal which represents coking is output when, additionally, the first air ratio value and the second air ratio value are different. ### Claim 7 (depends on 1) The method according to claim 1, wherein the first and/or the second quantity deviation test are carried out during idling operation of the internal combustion engine. ### Claim 8 (depends on 1) The method according to claim 1, wherein the first quantity deviation test is carried out with a small or minimal lift of the inlet valve and with the throttle flap open. ### Claim 9 (depends on 8) The method according to claim 8, wherein the second quantity deviation test is carried out with a maximum lift of the inlet valve and with the throttle flap substantially closed. ### Claim 10 (depends on 1) The method according to claim 1, wherein the second quantity deviation test is carried out with a maximum lift of the inlet valve and with the throttle flap substantially closed. ### Claim 11 (depends on 1) The method according to claim 1, wherein the first air ratio value and the second air ratio value are ascertained on a cylinder-specific basis, and the comparison result is determined on a cylinder-specific basis. ### Claim 12 (depends on 1) The method according to claim 1, wherein the first air ratio value is formed by the quotient of the lambda value measured during the first quantity deviation test and the desired lambda value, and the second air ratio value is formed by the quotient of the lambda value measured during the second quantity deviation test and the desired lambda value. ### Claim 13 (depends on 1) The method according to claim 1, wherein the presence of coking in the inlet section is inferred when the first air ratio value is lower than a predefined first threshold value and the second air ratio value is higher than the predefined first threshold value. ### Claim 14 A computer product comprising a non-transitory computer readable medium having stored thereon program code which, when executed on a processor, carries out the acts of: ascertaining a correction value which is offset as an offset value against a preset valve lift by the inlet valve lift controller; carrying out a first quantity deviation test by way of which a first air ratio value is ascertained which is formed from a lambda value measured during the first quantity deviation test and a desired lambda value of a fuel combustion in combustion chambers of the internal combustion engine, wherein, in the first quantity deviation test, load control is performed by way of the variable inlet valve lift controller; carrying out a second quantity deviation test by way of which a second air ratio value is ascertained which is formed from a lambda value measured during the second quantity deviation test and a desired lambda value of the fuel combustion in the combustion chambers of the internal combustion engine, wherein, in the second quantity deviation test, load control is performed by way of the throttle flap; determining a comparison result from the first air ratio value and the second air ratio value; and determining whether coking is present in the inlet section of the internal combustion engine by combined evaluation of the comparison result and the correction value. ### Claim 15 An apparatus, comprising: an engine test unit that detects faults in an inlet section of an internal combustion engine, wherein the engine test unit is operatively configured to: ascertain a correction value which is offset as an offset value against a preset valve lift by the inlet valve lift controller; carry out a first quantity deviation test by way of which a first air ratio value is ascertained which is formed from a lambda value measured during the first quantity deviation test and a desired lambda value of a fuel combustion in combustion chambers of the internal combustion engine, wherein, in the first quantity deviation test, load control is performed by way of the variable inlet valve lift controller; carry out a second quantity deviation test by way of which a second air ratio value is ascertained which is formed from a lambda value measured during the second quantity deviation test and a desired lambda value of the fuel combustion in the combustion chambers of the internal combustion engine, wherein, in the second quantity deviation test, load control is performed by way of the throttle flap; determine a comparison result from the first air ratio value and the second air ratio value; and determine whether coking is present in the inlet section of the internal combustion engine by combined evaluation of the comparison result and the correction value.