# US 2014/0190449 A1 · System and method for randomly adjusting a firing frequency of an engine to reduce vibration when cylinders of the engine are deactivated > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0190449 A1 - Document ID: US20140190449A1 - Status: Published application - Kind: A1 - Application number: 13/798,775 - Filed: 2013-03-13 - Published: 2014-07-10 - Earliest claimed: 2013-01-07 - Assignees: GM Global Technology Operations LLC - Applicants: GM Global Technology Operations LLC - Inventors: ANDREW W. PHILLIPS - Web page: https://patentgrep.com/patent/US20140190449A1 ## CPC - F02D 41/0087: {Selective cylinder activation, i.e. partial cylinder operation (deceleration cut-off F02D41/123)} - F02D 37/02: one of the functions being ignition - 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 system according to the principles of the present invention includes a firing fraction module, an offset generation module, and a firing fraction module. The firing fraction module determines a firing fraction based on a driver torque request. The offset generation module randomly generates an offset. The firing control module adds the firing fraction to a running total each time that a crankshaft of an engine rotates through a predetermined angle, adds the offset to the running total, and executes a firing event in a cylinder of the engine when the running total is greater than or equal to a predetermined value. ## Claims ### Claim 1 A system comprising: a firing fraction module that determines a firing fraction based on a driver torque request; an offset generation module that randomly generates an offset; and a firing control module that: adds the firing fraction to a running total each time that a crankshaft of an engine rotates through a predetermined angle; adds the offset to the running total; and executes a firing event in a cylinder of the engine when the running total is greater than or equal to a predetermined value. ### Claim 2 (depends on 1) The system of claim 1 wherein the firing fraction module sets the firing fraction equal to a ratio of the driver torque request to a torque output of the engine when each cylinder in the engine is active. ### Claim 3 (depends on 1) The system of claim 1 wherein the firing control module subtracts the offset from the running total after determining whether the running total is greater than or equal to the predetermined value. ### Claim 4 (depends on 1) The system of claim 1 wherein the firing control module subtracts the predetermined value from the running total after executing the firing event. ### Claim 5 (depends on 1) The system of claim 1 further comprising a firing frequency module that determines a firing frequency of the engine based on an amount of crankshaft rotation between firing events. ### Claim 6 (depends on 1) The system of claim 1 wherein the firing control module adds the offset to the running total each time that the crankshaft rotates through the predetermined angle. ### Claim 7 (depends on 6) The system of claim 6 wherein the firing control module adds the offset to the running total when a firing frequency of the engine is within a predetermined range of a resonant frequency of a vehicle structure. ### Claim 8 (depends on 1) The system of claim 1 wherein the offset generation module randomly selects the offset from an offset range having a mean value of zero. ### Claim 9 (depends on 8) The system of claim 8 wherein the offset generation module increases the offset range when a difference between a firing frequency of the engine and a resonant frequency of a vehicle structure decreases. ### Claim 10 (depends on 8) The system of claim 8 wherein the offset generation module increases the offset range from zero to a non-zero value when a firing frequency of the engine is within a predetermined range of a resonant frequency of a vehicle structure. ### Claim 11 A method comprising: determining a firing fraction based on a driver torque request; randomly generates an offset; adding the firing fraction to a running total each time that a crankshaft of an engine rotates through a predetermined angle; adding the offset to the running total; and executing a firing event in a cylinder of the engine when the running total is greater than or equal to a predetermined value. ### Claim 12 (depends on 11) The method of claim 11 further comprising setting the firing fraction equal to a ratio of the driver torque request to a torque output of the engine when each cylinder in the engine is active. ### Claim 13 (depends on 11) The method of claim 11 further comprising subtracting the offset from the running total after determining whether the running total is greater than or equal to the predetermined value. ### Claim 14 (depends on 11) The method of claim 11 further comprising subtracting the predetermined value from the running total after executing the firing event. ### Claim 15 (depends on 11) The method of claim 11 further comprising determining a firing frequency of the engine based on an amount of crankshaft rotation between firing events. ### Claim 16 (depends on 11) The method of claim 11 further comprising adding the offset to the running total each time that the crankshaft rotates through the predetermined angle. ### Claim 17 (depends on 16) The method of claim 16 further comprising adding the offset to the running total when a firing frequency of the engine is within a predetermined range of a resonant frequency of a vehicle structure. ### Claim 18 (depends on 11) The method of claim 11 further comprising randomly selecting the offset from an offset range having a mean value of zero. ### Claim 19 (depends on 18) The method of claim 18 further comprising increasing the offset range when a difference between a firing frequency of the engine and a resonant frequency of a vehicle structure decreases. ### Claim 20 (depends on 18) The method of claim 18 further comprising increasing the offset range from zero to a non-zero value when a firing frequency of the engine is within a predetermined range of a resonant frequency of a vehicle structure.