# US 9,518,552 B2 · Ignition circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,518,552 B2 - Document ID: US9518552B2 - Status: Granted - Kind: B2 - Application number: 13/707,131 - Filed: 2012-12-06 - Published: 2013-06-13 - Granted: 2016-12-13 - Earliest claimed: 2011-12-07 - Assignees: Andreas Stihl AG & Co. KG - Applicants: Andreas Stihl AG & Co. KG - Inventors: Heiko Daeschner; Arno Kinnen; Ernst Buck - Web page: https://patentgrep.com/patent/US9518552B2 ## CPC - F02P 1/08: Layout of circuits - F02P 1/083: {for generating sparks by opening or closing a coil circuit} - F02P 3/055: with protective means to prevent damage to the circuit, {e.g. semiconductor devices} or the ignition coil - F02P 11/02: Preventing damage to engines or engine-driven gearing - B27B 17/00: Chain saws; Equipment therefor {(slotting or mortising machines equipped with chain cutters B27F5/06)} - B27B 17/0033: {Devices for attenuation of vibrations} - F02B 63/02: for hand-held tools - F02D 17/04: rendering engines inoperative or idling, e.g. caused by abnormal conditions (dependent on lubricating conditions F01M1/22; dependent on cooling F01P5/14) - 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 2400/06: Small engines with electronic control, e.g. for hand held tools - 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) - B27B: SAWS FOR WOOD OR SIMILAR MATERIAL; COMPONENTS OR ACCESSORIES THEREFOR (saws specially adapted for pruning or debranching A01G3/08; sawing apparatus specially adapted for felling trees A01G23/091; features not restricted to a particular type of wood saw B23D, e.g. attaching saw blades B23D51/00; machine tool frames, beds, pillars or like members, in general B23Q1/01) - F02B: INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL (gas-turbine plants F02C; hot-gas or combustion-product positive-displacement engine plants F02G) - 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 An ignition circuit for a combustion engine has an ignition coil and a control unit for the coil. The coil and the control unit are included in a common component as an ignition module. The module is supplied with voltage by a generator driven by the engine. A spark plug and the coil form a power circuit which includes a line segment to a reference potential outside the module. A sensor detects data of the engine and the output of the sensor is supplied to the module. The sensor is supplied with voltage via a sensor circuit. The sensor circuit and the power circuit use the line segment as a common connection to the reference potential, so that for a defect of the line segment, a missing connection to the reference potential in the high voltage circuit is recognized via the change of the sensor output signals. ## Claims ### Claim 1 An ignition circuit for a combustion engine having a combustion chamber, the ignition circuit comprising: a spark plug arranged in said combustion chamber; an ignition coil configured to generate a high voltage for triggering an ignition spark at said spark plug; a control unit configured to control said ignition coil; said control unit and said ignition coil being consolidated in a common component as an ignition module; a generator driven by said combustion engine; said ignition module being connected to said generator; said spark plug being disposed outside of said ignition module; said spark plug and said ignition coil, which is disposed in said ignition module, conjointly forming a high-voltage circuit; a reference potential source defining a reference potential outside of said ignition module; said high-voltage circuit including a line segment connecting said ignition module to said reference potential; a sensor configured to detect operating parameters of the combustion engine and to transmit an output signal to said ignition module; said sensor being electrically connected to said ignition module; an electric sensor circuit providing a supply voltage to said sensor; said electric sensor circuit being connected between said ignition module and said reference potential; said electric sensor circuit being connected via said line segment to said reference potential source; said high-voltage circuit being connected via said line segment to said reference potential so as to permit both said electric sensor circuit and said high-voltage circuit to be connected via said line segment to said reference potential; said line segment being a cable; said combustion engine defining a vibration exciting first unit; a second unit for accommodating said ignition module therein; said first and second units being vibration decoupled from each other and conjointly defining a vibration gap therebetween; and, said cable being arranged so as to bridge said vibration gap between said first and second units; said electric sensor circuit and said high-voltage circuit being interrupted when said line segment is mechanically interrupted; said output signal of said sensor transmitted to said ignition module being defective when said electric sensor circuit is interrupted; and, said control unit of said ignition module being configured to detect that said output signal is defective and to control said high-voltage circuit to prevent undefined high voltage conditions when said defective output signal is detected. ### Claim 2 (depends on 1) The ignition circuit of claim 1, wherein the combustion engine includes a cylinder, and wherein: said spark plug is fixed on said cylinder via a fastening and connected to said reference potential via said fastening; and, said high-voltage circuit is closed via said line segment to said reference potential. ### Claim 3 (depends on 1) The ignition circuit of claim 1, wherein: the combustion engine includes a fastening configured to fix said sensor on the combustion engine; said sensor has a voltage connection connected to said reference potential via said fastening; said sensor circuit is closed to said reference potential via said ignition module and said line segment. ### Claim 4 (depends on 1) The ignition circuit of claim 1, wherein said line segment is a flexible cable. ### Claim 5 (depends on 1) The ignition circuit of claim 1, wherein the combustion engine has a crankcase and said sensor is fixed on said crankcase. ### Claim 6 (depends on 1) The ignition circuit of claim 1, wherein said sensor is a first sensor configured to output a first sensor signal, said ignition module further comprising: a second sensor configured to be supplied with voltage via said sensor circuit and to output a second sensor signal; and, said control unit being configured to perform an evaluation of said first and said second sensor signals and to intervene in the ignition in dependence on said evaluation. ### Claim 7 (depends on 6) The ignition circuit of claim 6, wherein: said control unit is configured to switch off the ignition when said first and said second output signals are the same. ### Claim 8 (depends on 6) The ignition circuit of claim 6, wherein: said control unit is configured to switch off the ignition when said first and said second output signals are the same maximum signal. ### Claim 9 (depends on 1) The ignition circuit of claim 1, wherein said sensor has a voltage connection, said ignition circuit further comprising: a reverse biased diode; said voltage connection of said sensor being connected to said reference potential via said reverse biased diode. ### Claim 10 (depends on 9) The ignition circuit of claim 9, further comprising: a suppressor diode; and, said high-voltage circuit being connected to said reference potential via said suppressor diode and said voltage connection of said sensor. ### Claim 11 (depends on 10) The ignition circuit of claim 10, wherein said suppressor diode is arranged in said ignition module. ### Claim 12 (depends on 1) The ignition circuit of claim 1, wherein said sensor has a voltage connection, said ignition circuit further comprising: a freewheel diode; and, said voltage connection of said sensor being connected to said reference potential via said freewheel diode. ### Claim 13 (depends on 1) The ignition circuit of claim 1, wherein said reference potential source is the combustion engine. ### Claim 14 (depends on 1) The ignition circuit of claim 1, wherein the combustion engine has a crankcase and said reference potential source is the crankcase. ### Claim 15 (depends on 1) The ignition circuit of claim 1, wherein the combustion engine is a combustion engine of a handheld work apparatus. ### Claim 16 An ignition circuit for a combustion engine having a combustion chamber, the ignition circuit comprising: a spark plug arranged in said combustion chamber; an ignition coil configured to generate a high voltage for triggering an ignition spark at said spark plug; a control unit configured to control said ignition coil; said control unit and said ignition coil being consolidated in a common component as an ignition module; a generator driven by said combustion engine; said ignition module being connected to said generator; said spark plug being disposed outside of said ignition module; said spark plug and said ignition coil, which is disposed in said ignition module, conjointly forming a high-voltage circuit; a reference potential source defining a reference potential outside of said ignition module; said high-voltage circuit including a line segment connecting said ignition module to said reference potential; a first sensor configured to detect operating parameters of the combustion engine, to transmit an output signal to said ignition module, and to output a first sensor signal; said first sensor being electrically connected to said ignition module; an electric sensor circuit providing a supply voltage to said first sensor; said electric sensor circuit being connected between said ignition module and said reference potential; said electric sensor circuit being connected via said line segment to said reference potential source; a second sensor configured to be supplied with voltage via said electric sensor circuit and to output a second sensor signal; said control unit being configured to perform an evaluation of said first and said second sensor signals and to intervene in the ignition in dependence on said evaluation; said control unit being configured to switch off the ignition when said first and said second output signals are the same; said high-voltage circuit being connected via said line segment to said reference potential so as to permit both said electric sensor circuit and said high-voltage circuit to be connected via said line segment to said reference potential; said line segment being a cable; said combustion engine defining a vibration exciting first unit; a second unit for accommodating said ignition module therein; said first and second units being vibration decoupled from each other and conjointly defining a vibration gap therebetween; and, said cable being arranged so as to bridge said vibration gap between said first and second units.