# US 9,518,551 B2 · Laser ignition safety interlock system and method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,518,551 B2 - Document ID: US9518551B2 - Status: Granted - Kind: B2 - Application number: 13/870,327 - Filed: 2013-04-25 - Published: 2014-10-30 - Granted: 2016-12-13 - Earliest claimed: 2013-04-25 - Assignees: Ford Global Technologies, LLC - Applicants: Ford Global Technologies, LLC - Inventors: Douglas Raymond Martin; Kenneth James Miller - Web page: https://patentgrep.com/patent/US9518551B2 ## CPC - F02N 15/10: Safety devices not otherwise provided for - F02P 23/04: Other physical ignition means, e.g. using laser rays - F02D 2041/0092: {Synchronisation of the cylinders at engine start} - F02N 11/0814: {comprising means for controlling automatic idle-start-stop} - F02N: STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR - 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) - 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) ## Abstract A safety interlock system and method is provided for a laser ignition system. The laser device can be disabled upon receiving an indication that the laser device has been removed from the cylinder. The removal can be inferred based on an estimated distance between the cylinder piston and the laser ignition device. ## Claims ### Claim 1 An engine method, comprising: operating a laser ignition device of a cylinder in a low power mode to infer a distance between the laser ignition device and a piston of the cylinder; and adjusting a power output of laser pulses emitted by the laser ignition device into the cylinder based on the inferred distance relative to a threshold, the threshold based on a length of the cylinder, wherein adjusting the power output includes maintaining operation of the device in the low power mode when the inferred distance is within the threshold, and reducing the power output of the laser pulses when the inferred distance is outside the threshold. ### Claim 2 (depends on 1) The method of claim 1, further comprising: reading a barcode located on a top surface of the piston; and indicating that the laser ignition device has been removed from the cylinder. ### Claim 3 (depends on 1) The method of claim 1, wherein reducing the power output of the laser pulses includes disabling operation of the device. ### Claim 4 (depends on 3) The method of claim 3, wherein the adjusting includes reducing the power output of the laser pulses in response to the inferred distance indicating the device is removed from the cylinder. ### Claim 5 (depends on 1) The method of claim 1, wherein the inferred distance is based on a time elapsed since emission of a laser pulse from the laser ignition device into the cylinder and detection of the laser pulse following reflection off the piston. ### Claim 6 (depends on 1) The method of claim 1, wherein the threshold is further based on a distance between the laser ignition device and the piston when the piston is at a bottom dead center position and a distance when the piston is at a top dead center position. ### Claim 7 (depends on 1) The method of claim 1, further comprising: operating the laser ignition device of the cylinder in a high power mode to initiate cylinder combustion responsive to the inferred distance for all engine cylinders being within the threshold. ### Claim 8 An engine method, comprising: operating a cylinder laser ignition device to estimate a distance between the laser ignition device and a piston of a cylinder; and disabling the laser ignition device in response to the estimated distance being larger than a threshold distance. ### Claim 9 (depends on 8) The method of claim 8, wherein the threshold distance is based on a length of the cylinder. ### Claim 10 (depends on 9) The method of claim 9, wherein disabling the laser ignition device includes disabling a laser emitter of the device. ### Claim 11 (depends on 10) The method of claim 10, wherein operating the laser ignition device to estimate the distance includes operating the laser ignition device at a lower power, the laser ignition device operated at a higher power when operating the laser ignition device to ignite a cylinder air-fuel mixture. ### Claim 12 (depends on 11) The method of claim 11, wherein the operating includes operating the laser ignition device before a first combustion event from rest. ### Claim 13 (depends on 8) The method of claim 8, wherein the operating to estimate the distance includes, emitting a low power laser pulse from the device towards an interior of the cylinder, the emitted laser pulse reflected off the piston; detecting the reflected laser pulse; and estimating the distance based on a time elapsed between the emitting and the detecting. ### Claim 14 (depends on 13) The method of claim 13, wherein the threshold distance is based on a time elapsed when the piston is at bottom dead center. ### Claim 15 (depends on 14) The method of claim 14, further comprising indicating removal of the laser ignition device from the cylinder in response to the estimated distance being larger than the threshold distance. ### Claim 16 (depends on 15) The method of claim 15, wherein a top surface of the piston includes a barcode, the method further comprising reading the barcode to identify the cylinder from which the laser ignition device is removed. ### Claim 17 A method for an engine, comprising: disabling a laser ignition device coupled to an engine cylinder in response to an indication of removal of the device from the cylinder, wherein the indication includes a measured distance between a piston of the cylinder and the laser ignition device being higher than a threshold. ### Claim 18 (depends on 17) The method of claim 17, wherein disabling the laser ignition device includes, upon receiving a command to emit a laser pulse, emitting no laser pulse. ### Claim 19 (depends on 17) The method of claim 17, wherein disabling the laser ignition device includes disabling via hardware and/or software adjustments. ### Claim 20 (depends on 17) The method of claim 17, further comprising maintaining the laser ignition device disabled until an indication of installation of the device into the cylinder is received, and then re-enabling the laser ignition device.