# US 10,118,608 B1 · Method for engine laser ignition system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,118,608 B1 - Document ID: US10118608B1 - Status: Granted - Kind: B1 - Application number: 15/793,246 - Filed: 2017-10-25 - Granted: 2018-11-06 - Earliest claimed: 2017-10-25 - Assignees: Ford Global Technologies, LLC - Applicants: Ford Global Technologies, LLC - Inventors: Aed M. Dudar - Web page: https://patentgrep.com/patent/US10118608B1 ## CPC - B60W 20/50: Control strategies for responding to system failures, e.g. for fault diagnosis, failsafe operation or limp mode - B60W 10/06: including control of combustion engines - B60W 10/08: including control of electric propulsion units, e.g. motors or generators - F02P 17/00: Testing of ignition installations, e.g. in combination with adjusting (testing fuel injection apparatus F02M65/00; testing ignition installations in general F23Q23/00); Testing of ignition timing in compression-ignition engines - F02P 23/04: Other physical ignition means, e.g. using laser rays - B60W 2710/065: Idle condition - F02P 17/12: Testing characteristics of the spark, ignition voltage or current (testing of sparking plugs H01T13/60) - B60W: CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT - F02P: IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES ({anti-pollution means for internal-combustion engines F02B17/00}; specially adapted for rotary-piston or oscillating-piston engines F02B53/12; {ignition of gas turbine plants F02C7/26; ignition of jet propulsion plants F02K9/95; starting of combustion engines F02N9/00}; ignition of combustion apparatus in general, glowing plugs F23Q; measuring of physical variables in general G01; controlling in general G05; data processing in general G06; electrical components in general see Section H; {ignition coils H01F38/12}; sparking plugs H01T13/00) ## Abstract Methods and systems are provided for diagnosing a laser ignition system of an engine. In one example, a controller may operate the laser in a sealed cylinder hours after key-off. Then, the cylinder may be unsealed and a change in exhaust temperature may be correlated with laser functionality. ## Claims ### Claim 1 A method, comprising: spinning an engine unfueled to establish a baseline exhaust temperature and then seal a cylinder at a position of negative valve overlap; operating a laser ignition device in the sealed cylinder; spinning the engine unfueled to unseal the cylinder; and diagnosing the laser ignition device based on a change in measured exhaust temperature relative to the baseline exhaust temperature. ### Claim 2 (depends on 1) The method of claim 1, wherein the diagnosing includes: responsive to the measured exhaust temperature exceeding the baseline exhaust temperature by a threshold, indicating that the laser ignition device is not degraded; and responsive to the measured exhaust temperature not exceeding the baseline exhaust temperature by the threshold, indicating that the laser ignition device is degraded. ### Claim 3 (depends on 2) The method of claim 2, further comprising selecting the threshold as a function of ambient conditions including ambient humidity. ### Claim 4 (depends on 3) The method of claim 3, wherein the threshold is decreased from a nominal value as the ambient humidity increases. ### Claim 5 (depends on 2) The method of claim 2, further comprising: responsive to the indicating that the laser ignition device is degraded, adjusting a misfire threshold of the cylinder. ### Claim 6 (depends on 2) The method of claim 2, wherein the cylinder is a first cylinder of the engine and wherein indicating that the laser ignition device is degraded includes setting a diagnostic code with a unique identifier for the first cylinder. ### Claim 7 (depends on 6) The method of claim 6, further comprising, after the indicating, re-spinning the engine unfueled to reestablish the baseline exhaust temperature and then diagnosing a second cylinder. ### Claim 8 (depends on 1) The method of claim 1, wherein spinning the engine unfueled includes spinning the engine via an electric motor, the electric motor including a starter motor and a hybrid vehicle driveline motor. ### Claim 9 (depends on 1) The method of claim 1, wherein spinning the engine unfueled includes: initially spinning the engine at a first speed for a first duration to establish the baseline exhaust temperature; then spinning the engine at a second speed, lower than the first speed, and for a second duration, smaller than the second duration to seal the cylinder by moving to the position of negative valve overlap; and then spinning the engine at the second speed for a third duration, smaller than the second duration, to unseal the cylinder by moving to another position where at least an exhaust valve is open. ### Claim 10 (depends on 1) The method of claim 1, wherein the exhaust temperature is measured via a temperature sensor coupled to a particulate filter in an exhaust passage of the engine. ### Claim 11 (depends on 1) The method of claim 1, wherein spinning the engine unfueled includes waking up an engine controller and spinning the engine after a threshold duration has elapsed since an engine key-off event. ### Claim 12 A method for an engine, comprising: operating a laser ignition device in a sealed, unfueled engine cylinder after an engine key-off; comparing a measured exhaust temperature after the operating to a baseline exhaust temperature established via unfueled engine spinning; and diagnosing the laser ignition device based on the comparing. ### Claim 13 (depends on 12) The method of claim 12, wherein the comparing includes calculating a difference between the measured exhaust temperature and the baseline exhaust temperature, and comparing the difference to a threshold, the threshold adjusted as a function of ambient humidity. ### Claim 14 (depends on 13) The method of claim 13, wherein the diagnosing includes: when the difference is higher than the threshold, indicating that the laser ignition device of the engine cylinder is not degraded; and when the difference is lower than the threshold, indicating that the laser ignition device of the engine cylinder is degraded. ### Claim 15 (depends on 14) The method of claim 14, further comprising: maintaining a misfire threshold of the cylinder when the laser ignition device is indicated to not be degraded; and adjusting the misfire threshold of the cylinder when the laser ignition device is indicated to be degraded. ### Claim 16 (depends on 12) The method of claim 12, further comprising, sealing the engine cylinder by spinning the engine, unfueled, via an electric motor to a position where each of an intake valve and an exhaust valve of the cylinder is closed. ### Claim 17 An engine system, comprising: an engine cylinder; a laser ignition device coupled to the cylinder; an exhaust temperature sensor; an electric motor; and a controller with computer-readable instructions stored on non-transitory memory for: waking up a powertrain control module from a sleep mode when a threshold duration has elapsed following an engine key-off; spinning the engine, unfueled via the motor, to establish a baseline exhaust temperature; sealing the cylinder by spinning the engine, unfueled via the motor, to a position where all cylinder valves are closed; operating the laser ignition device in the sealed cylinder for a duration; unsealing the cylinder by re-spinning the engine, unfueled via the motor, to a position where at least an exhaust valve is open; and diagnosing the laser ignition device by comparing an exhaust temperature measured after the operating with the baseline exhaust temperature. ### Claim 18 (depends on 17) The system of claim 17, further comprising a humidity sensor for estimating an ambient humidity, wherein the comparing includes comparing a difference between the measured exhaust temperature and the baseline exhaust temperature to a threshold based on an estimated ambient humidity, and wherein the diagnosing includes indicating that the laser ignition device is degraded when the difference is higher than the threshold. ### Claim 19 (depends on 18) The system of claim 18, wherein the controller includes further instructions for, responsive to the indicating that the laser ignition device of the cylinder is degraded, during a subsequent engine restart from rest, disabling fueling and operation of the laser ignition device of the cylinder, and adjusting a misfire threshold of the cylinder. ### Claim 20 (depends on 17) The system of claim 17, wherein spinning the engine, unfueled, includes spinning the engine at an engine speed lower than engine cranking speed.