# US 9,038,445 B2 · Method and apparatus for diagnosing engine fault > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,038,445 B2 - Document ID: US9038445B2 - Status: Granted - Kind: B2 - Application number: 14/006,446 - Filed: 2012-02-24 - Published: 2014-01-09 - Granted: 2015-05-26 - Earliest claimed: 2011-03-24 - Assignees: Honda Motor Co., Ltd. - Applicants: Hiroshi Ito; Takayuki Abe; Tetsuya Ohno; Mahito Shikama - Inventors: Hiroshi Ito; Takayuki Abe; Tetsuya Ohno; Mahito Shikama - Web page: https://patentgrep.com/patent/US9038445B2 ## CPC - G01M 15/11: by detecting misfire - F02D 41/123: {the fuel injection being cut-off} - F02D 41/1498: {measuring engine roughness} - 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)} - G01M 15/046: {by monitoring revolutions (for detecting misfire G01M15/11)} - F02D 2200/021: Engine temperature - F02D 2200/023: Temperature of lubricating oil or working fluid - F02D 2200/1015: Engines misfires - F02D 2200/503: Battery correction, i.e. corrections as a function of the state of the battery, its output or its type - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR - 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 According to a method and an apparatus of the present invention for diagnosing a fault of an engine, a cranking rotation state is created by rotating a crank shaft while explosions in each cylinder are stopped; a variation of angular velocity of the crank shaft is detected for each cylinder in the cranking rotation state; a cylinder the compression pressure of which is insufficient is detected based on the variation; and if a cylinder indicated as a misfiring cylinder by a fault code is the same as the cylinder detected as being insufficient in compression pressure in the cranking rotation state, the cylinder is specified. ## Claims ### Claim 1 A method of diagnosing an engine for a fault, which is monitored by a misfire monitor for judging a misfiring cylinder that suffers from a misfire while an engine having a plurality of cylinders is in operation, and storing a diagnostic trouble code representative of the misfiring cylinder, comprising: detecting variations in angular velocity of a crankshaft in a power stroke of the engine for each of the cylinders while the engine is in normal operation, and determining one of the cylinders, which exhibits small variations in angular velocity, as the misfiring cylinder; detecting variations in angular velocity of the crankshaft in a power stroke of the engine for each of the cylinders while the engine is being cranked to rotate the crankshaft while canceling fuel explosion in all of the cylinders simultaneously, and determining one of the cylinders, which exhibits small variations in angular velocity, as the compression pressure shortage cylinder; and identifying one of the cylinders, as a cylinder to be repaired, which coincides with the misfiring cylinder represented by the diagnostic trouble code and the compression pressure shortage cylinder that is determined while the engine is being cranked. ### Claim 2 (depends on 1) The method of diagnosing an engine for a fault according to claim 1, further comprising: while the engine is being cranked, comparing individual average values, which represent average values of the individual variations of the cylinders, with a total average value, which represents an average value of the variations of the cylinders; and determining one of the cylinders, which exhibits a smaller individual average value than the total average value, as the compression pressure shortage cylinder. ### Claim 3 (depends on 2) The method of diagnosing an engine for a fault according to claim 2, further comprising: displaying, in a plurality of stages, a degree of difference from the total average value, in connection with individual average values that are smaller than the total average value. ### Claim 4 (depends on 1) The method of diagnosing an engine for a fault according to claim 1, wherein the variations in angular velocity of the crankshaft while the engine is being cranked start being detected upon elapse of a predetermined time from start of a motor that actuates the crankshaft. ### Claim 5 (depends on 1) The method of diagnosing an engine for a fault according to claim 1, further comprising: monitoring a voltage of a battery for energizing the motor that actuates the crankshaft; and stopping determination of a compression pressure shortage cylinder if the voltage of the battery drops from a predetermined voltage. ### Claim 6 A method of diagnosing an engine for a fault, which is monitored by a misfire monitor for detecting variations in angular velocity of a crankshaft of an engine having a plurality of cylinders, in a power stroke of the engine for each of the cylinders, and judging a misfiring cylinder that suffers from a misfire based on the detected variations, comprising: cranking the engine to rotate the crankshaft while canceling fuel explosion in all of the cylinders simultaneously, detecting variations in angular velocity of the crankshaft in the power stroke for each of the cylinders while the engine is being cranked, and determining one of the cylinders, which exhibits variations in angular velocity that are equal to or smaller than a predetermined value, as a compression pressure shortage cylinder that suffers from a shortage of compression pressure. ### Claim 7 (depends on 6) The method of diagnosing an engine for a fault according to claim 6, further comprising: while the engine is being cranked, comparing individual average values, which represent average values of the individual variations of the cylinders, with a total average value, which represents an average value of the variations of the cylinders; and determining one of the cylinders, which exhibits a smaller individual average value than the total average value, as the compression pressure shortage cylinder. ### Claim 8 (depends on 7) The method of diagnosing an engine for a fault according to claim 7, further comprising: displaying, in a plurality of stages, a degree of difference from the total average value, in connection with individual average values that are smaller than the total average value. ### Claim 9 (depends on 6) The method of diagnosing an engine for a fault according to claim 6, wherein the variations in angular velocity of the crankshaft while the engine is being cranked start being detected upon elapse of a predetermined time from start of a motor that actuates the crankshaft. ### Claim 10 (depends on 6) The method of diagnosing an engine for a fault according to claim 6, further comprising: monitoring a voltage of a battery for energizing the motor that actuates the crankshaft; and stopping determination of a compression pressure shortage cylinder if the voltage of the battery drops from a predetermined voltage. ### Claim 11 An apparatus for diagnosing an engine for a fault, which is monitored by a misfire monitor for judging a misfiring cylinder that suffers from a misfire while an engine having a plurality of cylinders is in operation, and storing a diagnostic trouble code representative of the misfiring cylinder, wherein: the apparatus detects variations in angular velocity of the crankshaft in a power stroke of the engine for each of the cylinders while the engine is in normal operation, and determines one of the cylinders, which exhibits small variations in angular velocity, as the misfiring cylinder; the apparatus detects variations in angular velocity of the crankshaft for each of the cylinders while the engine is being cranked to rotate a crankshaft while canceling fuel explosion in all of the cylinders simultaneously, and determines one of the cylinders, which exhibits small variations in angular velocity, as the compression pressure shortage cylinder; and the apparatus identifies one of the cylinders as a cylinder to be repaired, which coincides with the misfiring cylinder represented by the diagnostic trouble code and the compression pressure shortage cylinder that is determined while the engine is being cranked. ### Claim 12 (depends on 11) The apparatus for diagnosing an engine for a fault according to claim 11, wherein: while the engine is being cranked, the apparatus compares individual average values, which represent average values of the individual variations of the cylinders, with a total average value, which represents an average value of the variations of the cylinders; and the apparatus determines one of the cylinders, which exhibits a smaller individual average value than the total average value, as the compression pressure shortage cylinder. ### Claim 13 (depends on 12) The apparatus for diagnosing an engine for a fault according to claim 12, wherein: the apparatus displays, in a plurality of stages, a degree of difference from the total average value, in connection with individual average values that are smaller than the total average value. ### Claim 14 (depends on 9) The apparatus for diagnosing an engine for a fault according to claim 9, wherein: the apparatus starts detecting the variations in angular velocity of the crankshaft while the engine is being cranked upon elapse of a predetermined time from start of a motor that actuates the crankshaft. ### Claim 15 (depends on 9) The apparatus for diagnosing an engine for a fault according to claim 9, wherein: the apparatus monitors a voltage of a battery for energizing the motor that actuates the crankshaft; and the apparatus stops determination of a compression pressure shortage cylinder if the voltage of the battery drops from a predetermined voltage. ### Claim 16 An apparatus for diagnosing an engine for a fault, which is monitored by a misfire monitor for detecting variations in angular velocity of a crankshaft of an engine having a plurality of cylinders, in a power stroke of the engine for each of the cylinders, and judging a misfiring cylinder that suffers from a misfire based on the detected variations, wherein the apparatus cranks the engine to rotate the crankshaft while canceling fuel explosion in all of the cylinders simultaneously, detects variations in angular velocity of the crankshaft in the power stroke for each of the cylinders while the engine is being cranked, and determines one of the cylinders, which exhibits variations in angular velocity that are equal to or smaller than a predetermined value, as a compression pressure shortage cylinder that suffers from a shortage of compression pressure. ### Claim 17 (depends on 11) The apparatus for diagnosing an engine for a fault according to claim 11, wherein: while the engine is being cranked, the apparatus compares individual average values, which represent average values of the individual variations of the cylinders, with a total average value, which represents an average value of the variations of the cylinders; and the apparatus determines one of the cylinders, which exhibits a smaller individual average value than the total average value, as the compression pressure shortage cylinder. ### Claim 18 (depends on 17) The apparatus for diagnosing an engine for a fault according to claim 17, wherein: the apparatus displays, in a plurality of stages, a degree of difference from the total average value, in connection with individual average values that are smaller than the total average value. ### Claim 19 (depends on 16) The apparatus for diagnosing an engine for a fault according to claim 16, wherein: the apparatus starts detecting the variations in angular velocity of the crankshaft while the engine is being cranked upon elapse of a predetermined time from start of a motor that actuates the crankshaft. ### Claim 20 (depends on 16) The apparatus for diagnosing an engine for a fault according to claim 16, wherein: the apparatus monitors a voltage of a battery for energizing the motor that actuates the crankshaft; and the apparatus stops determination of a compression pressure shortage cylinder if the voltage of the battery drops from a predetermined voltage.