Ignition circuit

Patent metadata

Field	Value
Publication number	US-9518552-B2
Application number	US-201213707131-A
Country	US
Kind code	B2
Filing date	Dec 6, 2012
Priority date	Dec 7, 2011
Publication date	Dec 13, 2016
Grant date	Dec 13, 2016

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.

First claim

What is claimed is:

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.

2. 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.

3. 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.

4. The ignition circuit of claim 1 , wherein said line segment is a flexible cable.

5. The ignition circuit of claim 1 , wherein the combustion engine has a crankcase and said sensor is fixed on said crankcase.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. The ignition circuit of claim 10 , wherein said suppressor diode is arranged in said ignition module.

12. 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.

13. The ignition circuit of claim 1 , wherein said reference potential source is the combustion engine.

14. The ignition circuit of claim 1 , wherein the combustion engine has a crankcase and said reference potential source is the crankcase.

15. The ignition circuit of claim 1 , wherein the combustion engine is a combustion engine of a handheld work apparatus.

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

Assignees

• Stihl Ag & Co Kg Andreas

Inventors

• Daeschner Heiko
• Kinnen Arno
• Buck Ernst

Classifications

• F02P3/055

  with protective means to prevent damage to the circuit, {e.g. semiconductor devices} or the ignition coil · CPC title

• F02D2400/06

  Small engines with electronic control, e.g. for hand held tools · CPC title

• B27B17/00

  Chain saws; Equipment therefor {(slotting or mortising machines equipped with chain cutters B27F5/06)} · CPC title

• F02B63/02

  for hand-held tools · CPC title

• F02P1/083

  for generating sparks by opening or closing a coil circuit · CPC title