GB1581434A - Electronic ignition systems for internal combustion engines - Google Patents

Description

(54) ELECTRONIC IGNITION SYSTEMS FOR INTERNAL COMBUSTION ENGINES (71) We, LUCAS INDUSTRIES LIMITED, a British Company of Great King Street, Birmingham B10 2XF, do hereby declare the invention for which we pray that a Patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to electronic ignition systems for internal combustion engines.

Conventionally an electronic ignition system includes a transducer driven by the engine, an electronic signal processing circuit connected to the transducer, an ignition transformer having its primary current controlled by the processing circuit and its secondary winding connected via an ignition distributor to the spark plugs of the engine.

It has now been mooted that failure of the processing circuit could occur in circumstances such that there is considerable danger to life, such as failure during high speed driving of a motor vehicle on a crowded highway. It is accordingly an object of the invention to provide an ignition system in which overall reliability is improved.

An ignition system in accordance with the invention comprises the combination of a single high tension system connected in use to the engine spark plugs, a pair of separate identical electronic signal processing circuits, transducer means normally operating said processing circuits in synchronism, and coil means for combining the outputs of the processing circuits and providing a high tension output to the high tension system.

Preferably the transducer means may be a single transducer connected to the input terminals of the processing circuits. The coil means may be two separate ignition transformers with their secondary coutputs combined (e.g. in parallel), but preferably the coil means consists of two primary windings on a common core assembly carrying a single secondary winding connected to the high tension system. The core assembly may be of a substantially 8 shaped configuration with the primary windings on the two loops of the 8 respectively and the secondary winding wound through both loops. In this case each loop of the core may have an air gap, preferably within the associated primary winding.

The system preferably also includes a warning system for indicating when either of the processing circuits has failed. The warning system may for example comprise a neon lamp connected between the output terminals of the two processing circuits so that it is only lit when the processing circuits are not operating in synchronism. The high tension system may comprise an ignition distributor.

In the accompanying drawings: Figure 1 is a circuit diagram of one example of the invention and Figure 2 is a diagrammatic view of a coil assembly used in the circuit of Figure 1.

The circuit of Figure 1 utilises a common engine shaft position transducer ]0 which feeds triggering pulses at set engine shaft positions to two identical electronic signal processing circuits 11, 12. The circuits 11, 12 each contain known circuit arrangements which vary the phase relationship between the signals received from the transducer and the output signals from the circuits 11, 13 in a predetermined manner in accordance with the engine speed.

Thus each circuit produces an output current pulse for each cylinder of the engine, the end of the current pulse being timed to coincide with the desired instant of ignition. When the circuits are operating normally the output pulses therefrom will be closely synchr onised.

Coil means are provided for combining the outputs of the two circuits 11, 12. Such coil means comprises a pair of primary windings 13, 14 and a secondary winding 15 on a common core 16. As shown in Figure 2, the core assembly is formed from two C-cores butted together along the side opposite the air gap so as to make up a core assembly of generally 8shaped configuration with an air gap in each loop of the 8. Alternatively the core assembly can be made up of an interleaved stack of E and U laminations. The windings 13 and 14 surround the two gapped sides of the respective loops and the secondary winding 1 5 surrounds the two abutted sides linking the two loops.

The secondary winding 15 is connected to a distributor 17 which connects it in turn to the spark plugs 18, 19, 20 and 21.

In normal operation interruption of the flux induced in the two loops of the core assembly by the two primary windings produces a predetermined high voltage in the secondary winding, the effect of the two windings 13, 14 being additive. If there is a failure such that one of the windings 13, 14 is continuously energised (i.e. a short circuit failure of the output transistor of the circuit or a failure of another component such that the output transistor remains switched on), the change in the total flux which occurs when current ceases to flow in the other primary winding will still be sufficient to generate a high enough secondary voltage to generate good sparks.In the event that an open circuit fault occurs in the output stage of the circuit 11 or 12, the provision of the air gaps in the two loops of the core assembly ensure that the loop associated with the failed circuit does not magnetically short circuit the other loop and sparks are still obtained. The overall performance of the ignition system in extreme speed and load conditions may be worsened by either type of fault condition, but it will still be possible to keep the engine running and delivering some power.

As shown in Figure 1 a warning system is provided for indicating when a failure of one circuit has occured. This system consists quite simply of a neon lamp 22 connected in series with a current limiting resistor 23, between the output terminals of the two circuits 11,12.

Normally, when the circuits 11, 12 operate in synchronism there is no voltage across the neon lamp. In the event of either mode of failure of either circuit 11 or 12 pulses will appear across the neon lamp which will cause it to glow.

It is to be appreciated that the present invention may be used with any type of high tension system. Where, as in the example hereinbefore described, the high tension system comprises an ignition distributor, the ignition distributor may be any type of distributor, for example, a convention rotor arm type or the type in which the secondary coil is connected at each end to a spark plug, the connections between the secondary coil and the spark plugs being earthed alternately so as to cause a spark to be produced at the other spark plug, and reference herein to an ignition distributor are to be construed accordingly.

Also, in alternative embodiments, the transducer may include in its construction signal processing circuit elements, for example, the low power, highly reliable part of the normal electronic ignition circuitry, and the word transducer is herein to be understood to cover a transducer which includes signal processing circuit elements.

WHAT WE CLAIM IS: 1. An electronic ignition system for an internal combustion engine comprising the combination of a single high tension system connected in use to the engine spark plugs, a pair of separate identical electronic signal processing circuits, transducer means normally operating said processing circuits in synchronism, and coil means for combining the outputs of the processing circuits and providing a high tension output to the high tension system.

2. An electronic ignition system as claimed in Claim 1 in which said transducer comprises a single transducer connected to the input terminals of both processing circuits.

3. An electronic ignition system as claimed in Claim 1 or Claim 2 in which the coil means comprises two separate ignition transforniers with their secondary outputs in parallel.

4. An electronic ignition system as claimed in Claim 1 or Claim 2 in which said coil means comprises two primary windings on a common core assembly carrying a single secondary winding connected to the high tension system.

5. An electronic ignition system as claimed in Claim 4 in which said common core is of 8shaped configuration with the primary windings wound through the two loops of the 8 respectively and the secondary winding wound through both loops.

6. An electronic ignition system as claimed in Claim 5 in which each loop of the 8-shaped core is formed with an air gap.

7. An electronic ignition system as claimed in Claim 6 in which each air gap is disposed within the associated primary winding.

8. An electronic ignition system as claimed in any preceding claim including a warning system for indicating when either of the processing circuits has failed.

9. An electronic ignition system as claimed in Claim 8 in which said warning system comprises a neon lamp connected between the output terminals of the two processing circuits, so that it is lit except when the processing circuits are operating in synchronism.

10. An electronic ignition system as claimed in any preceding claim in which the high tension system comprises an ignition distributor.

11. An electronic ignition system for an internal combustion engine substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. predetermined high voltage in the secondary winding, the effect of the two windings 13, 14 being additive. If there is a failure such that one of the windings 13, 14 is continuously energised (i.e. a short circuit failure of the output transistor of the circuit or a failure of another component such that the output transistor remains switched on), the change in the total flux which occurs when current ceases to flow in the other primary winding will still be sufficient to generate a high enough secondary voltage to generate good sparks.In the event that an open circuit fault occurs in the output stage of the circuit 11 or 12, the provision of the air gaps in the two loops of the core assembly ensure that the loop associated with the failed circuit does not magnetically short circuit the other loop and sparks are still obtained. The overall performance of the ignition system in extreme speed and load conditions may be worsened by either type of fault condition, but it will still be possible to keep the engine running and delivering some power. As shown in Figure 1 a warning system is provided for indicating when a failure of one circuit has occured. This system consists quite simply of a neon lamp 22 connected in series with a current limiting resistor 23, between the output terminals of the two circuits 11,12. Normally, when the circuits 11, 12 operate in synchronism there is no voltage across the neon lamp. In the event of either mode of failure of either circuit 11 or 12 pulses will appear across the neon lamp which will cause it to glow. It is to be appreciated that the present invention may be used with any type of high tension system. Where, as in the example hereinbefore described, the high tension system comprises an ignition distributor, the ignition distributor may be any type of distributor, for example, a convention rotor arm type or the type in which the secondary coil is connected at each end to a spark plug, the connections between the secondary coil and the spark plugs being earthed alternately so as to cause a spark to be produced at the other spark plug, and reference herein to an ignition distributor are to be construed accordingly. Also, in alternative embodiments, the transducer may include in its construction signal processing circuit elements, for example, the low power, highly reliable part of the normal electronic ignition circuitry, and the word transducer is herein to be understood to cover a transducer which includes signal processing circuit elements. WHAT WE CLAIM IS:

1. An electronic ignition system for an internal combustion engine comprising the combination of a single high tension system connected in use to the engine spark plugs, a pair of separate identical electronic signal processing circuits, transducer means normally operating said processing circuits in synchronism, and coil means for combining the outputs of the processing circuits and providing a high tension output to the high tension system.

2. An electronic ignition system as claimed in Claim 1 in which said transducer comprises a single transducer connected to the input terminals of both processing circuits.

3. An electronic ignition system as claimed in Claim 1 or Claim 2 in which the coil means comprises two separate ignition transforniers with their secondary outputs in parallel.

4. An electronic ignition system as claimed in Claim 1 or Claim 2 in which said coil means comprises two primary windings on a common core assembly carrying a single secondary winding connected to the high tension system.

5. An electronic ignition system as claimed in Claim 4 in which said common core is of 8shaped configuration with the primary windings wound through the two loops of the 8 respectively and the secondary winding wound through both loops.

6. An electronic ignition system as claimed in Claim 5 in which each loop of the 8-shaped core is formed with an air gap.

7. An electronic ignition system as claimed in Claim 6 in which each air gap is disposed within the associated primary winding.

8. An electronic ignition system as claimed in any preceding claim including a warning system for indicating when either of the processing circuits has failed.

9. An electronic ignition system as claimed in Claim 8 in which said warning system comprises a neon lamp connected between the output terminals of the two processing circuits, so that it is lit except when the processing circuits are operating in synchronism.

10. An electronic ignition system as claimed in any preceding claim in which the high tension system comprises an ignition distributor.

11. An electronic ignition system for an internal combustion engine substantially as hereinbefore described with reference to and as shown in the accompanying drawings.