GB2256456A - Ic engine multi-spark ignition system - Google Patents

Abstract

When a single pulse from the input driver 22 is fed through the Schmidtt detector 23 into the multi-spark frequency modulation oscillator 27 it is converted into a series of pulses which are fed through the power MOSFET driver 28 into the power MOSFET output stage where each pulse causes the primary windings of the ignition coil to be energised producing a series of sparks. The Schmidtt detector also provides signals for a static timing indicator 24, a tachometer output driver 26 and a no run clamp 25 which disables the MOSFET driver 28 when the engine is stationary. <IMAGE>

Description

MULTI-SPARK ELECTRONIC IGNITION SYSTEMS FIELD OF THE INVENTION THIS INVENTION RELATES TO AN ELECTRONIC IGNITION SYSTEM WHICH COMBINES HIGH ENERGY SPARKING WITH MULTI-SPARK INTENSITY AND IMPROVED COMBUSTION.

BACKGROUND TO THE INVENTION Spark ignition systems are basically the same on all modern cars and the system employs two metal electrodes which project into the combustion chamber. A normal battery delivers only 6 to 12 volts and this must be boosted thousands of times by the coil. The voltage needed must be at least 14,000 volts but to allow for losses in the system this is enhanced to around 30,000 volts. The number of sparks an ignition system can provide during a given time is one factor limiting the speed of an engine. The most a conventional ignition system can reliably produce is about 24,000 sparks a minute but multi-cylinder, high speed cars may need 70,000 sparks a minute or more,are even made. Such cars have a transistorised or electronic system because this is a way of producing powerful sparks at unusually high engine speeds.

When a conventional ignition system is operating at exceptionally high sparking rates, there is not enough time between sparks for a high enough voltage to be built up in the secondary circuit of the coil. The advantage of a transistor is that, though only a small amount of current reaches it, the transistor can 'trigger' a much higher amount to the coil for efficient sparking, no matter what the engine speed.

MULTI-SPARK ELECTRONIC IGNITION SYSTEMS This principle is used in the simplest form of electronic ignition, the 'transistor-assisted contacts' system; here the contacts carry only triggering current, which is about one fifteenth of that going through the points of a conventional contact-breaker. In a fully transistorised design for example, the triggering pulses are generated in a stationary pick-up coil in the distributor by a rotating magnet. The pulses are fed to a transistorised control unit which acts as an electronic switch.

It is one objective of the present invention to switch the primary current of the ignition coil many times during each compression stroke of the internal combustion engine.

According to another aspect of the present invention the system may include external control to disable the Multi-spark to simulate conventional spark system during engine servicing.

The first objective of the present invention is achieved by complying with the terms of a mathematical formula where: V=L di/dt E= L1 T=R/L V=coil induced voltage L=Primary coil inductance di/dt=Rata of collapse of primary current E=Stored coil energy I=Primary coil current MULTI-SPARK ELECTRONIC IGNITION SYSTEMS T=Time for primary coil current to charge to 63.2% of steady state.

R=Total primary resistance.

If the rate of collapse of the primary current di/dt is increased nearly 1000 times the induced voltage V in the coil is very high and as a concequence the primary coil induction can be greatly reduced. Should the primary coil inductance L be reduced then it becomes necessary to increase the primary coil current I to ensure sufficient energy is available.

If the primary coil current is doubled then only one quarter of the primary coil inductance is needed to produce the same energy, and this would require four times the rate of collapse of the primary current to maintain the induced voltage. Since only one quarter of the primary coil inductance is in circuit, the operating frequency limit is quadrupled because the required charge time is reduced by four - that is a 10,000 revolutions per minute engine may now run at 40,000 revolutions per minute with similar spark energy and voltage.

The Multi-Spark Electronic Ignition System comprises an 'inputdriver' which would accept and condition input signals from any position sensor - such as a contact-breaker, an optical device, Hall effect, reluctor or other system. The appropriate Multi Spark signal is generated by a Multi-Spark Frequency Modulation Oscillator and means whereby its Multi-Spark rate can be regulated or adjusted to suit the ignition coil in use, may be included.

MULTI-SPARK ELECTRONIC IGNITION SYSTEMS The circuit can also include a 'Schmitt Detector' Circuit to increase noise immunity. The primary coil current is switched by a 'Power Metal-oxide-semi-conductor field-effect transistor' (MOSFET) Output Stage Unit. This can be triggered by logical level or driven through an appropriate 'Power "MOSFET" Driver' the gate voltage of which may include clamping to limit the coil current.

Additionally the circuit may comprise a 'MOSFET' Protection Circuit to ensure the 'power Mosfet Output Stage' operates within its safe operating area as required by the manufacturers of this commercially available device.

A specific embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 illustrates a conventional sparking circuit for a motor vehicle.

Figure 2 indicates where the Multi-Spark Unit would be sited.

Figure 3 is a block diagram of the system.

Figure 4 is an electronic diagram of the system.

According to Figure 1 the conventional ignition system of an internal combustion motor car engine comprises of the battery 11, the ignition key 12, the primary circuit 13 of the coil 14, the secondary circuit 15 of the coil 14, the output high tension supply TThiCh cable 16 from the coil 14 A transmits the current to the distributor 17 supplying the high tension current to the four spark plugs 18.

It will be obvious the number of spark plugs will relate to the number of cylinders provided for the engine.

MULTI-SPARK ELECTRONIC IGNITION SYSTEMS Interruption of the current from the primary windings 13 of the coil 14 is provided by the contact breaker 19 and to prevent arcing or burning of these contact points a condenser 20 is inserted into the primary circuit. The spark plugs 18, the condenser 20, the contact breaker 19 and the battery 11 are suitably earthed to complete the circuit.

As previously stated, when the magnetic field collapses in the coil 14 a voltage is induced in the primary windings 13 which is high enough to cause an arc across the opening contact-breaker points 21. The condenser 20 will suppress burning or arcing across these contact points 21 and since the energy cannot pass through the condenser 20 it will flow back through the primary windings 13 of the coil 11 to rapidly initiate the collapse of the magnetic field and increase the voltage in the secondary winding.

It will be obvious this brief description of the conventional sparking circuit of a motor car engine is not original to this specification and no claim is entered for this prior art.

It is included to qualify the introduction of the Multi-Spark Electronic Ignition System embodied in this specification.

Reference should now be made to Figure 2 which illustrates the essential components of the sparking circuit and identifies the position at which the Multi-Spark Electronic Ignition unit 10 is installed in the circuit.

MULTI-SPARK ELECTRONIC IGNITION SYSTEMS According to Figure 2 the Multi-Spark Electronic Ignition System for an internalcombustion engine comprises similar components to those of conventional ignition system as in Figure 1.

The condensor is omitted and the multi-spark ignition circuit intercepts the contact breaker 21 to negative terminal of ignition coil 14. Power to the circuit is via the ignition switch 12 to the battery,and the circuit must be suitably earthed.

Alternative distributors may be used that include alternative triggering devices.

The multi-spark circuit may provide an additional output terminal to supply any vehicle tachometer.

The RPM detector clamp terminal may be wired to a 'plus' 12 volt supply in order to force the ignition to continually multi-spark independent of the distributor in order to adjust the multisparking rate via potentiameter Vrl. Additionally if this terminal is grcunded (earthed) the ignition is disabled, offering an immobilisation feature.

Any bailast component may be removed since the circuit can control current limiting.

According to Figure 3 the Multi Spark Electronic Ignition System comprises the initial input driver 22 which will accept signals from an engine distributor which may be transmitted by any one of a number of accepted methods. (Already mentioned, optical, Hall effect, reluctor). These signals are switched by the Schmitt Detector 23 via four outlets - the timing indicator 24, the no-run clamp 25, the tachometer output driver 26 and the main output channel, the Multi-Spark Frequency Modulator Oscillator 27.

The frequency modulator 27 will transfer the input signal into MULTI-SPARK ELECTRONIC IGNITION SYSTEMS a multi-spark signal and transmit this to the power metal oxide semi-conductor field-effect transistor (MOSFET) 28. This transistor 28 can also receive signals from the clamp 25 should the ignition need to be 'disabled' when the engine is stationary.

The driver signal from 28 is transmitted to the power transistor 29 (MOSFET) which directs it to the negative terminal of the engine ignition coil 30. Additionally the MOSFET protection circuit 31 clamps the primary coil voltage induced at the negative terminal of the ignition coil 30 and throughout the MOSFET 29 within the safe operating area of the MOSFET 29 as specified by the MOSFET's manufacturer. Otherwise this voltage would be very large due to the very much faster switching response of the MOSFET.

The above description is now indicated diagramatically in Figure 4 to which attention is directed.

The integrated circuits 1C1 and 1C3B form the input driver (22) and the Schmitt Detector (23) stage which accept the signals from the contact breaker, optical triggering or Hall effect device.

Integrated circuit 1C2 and its associated components form the Multi-Spark Frequency Modulation Oscillator (27) where VR1 adjusts the Multi-Spark Rate, 1C3a forms the Power Mosfet driver (28) and TR2 forms the Mosfet output stage 29. It can be seen that ;01 adds the protection stage (31). C2 to TR1 forms the engine stationary 'no run clamp' (25) and LED1 is the static timing indicator (24). The TR3 transistor forms the tachometer out put driver (26).

MULTI-SPARK ELECTRONIC IGNITION SYSTEMS According to Figure 4 the power distribution is diagramatically indicated by the circuit 4a which comprises semi-conductor diodes D6 ZD2 and ZD3, a capacitor C8 and resistors R13, R14 and R15. The voltage from the 12 volt battery is received via the ignition switch (12).

It can thus be seen from the description given in this specification of this embodiment of the invention that a Multi Spark capability can be provided for internal combustion-engines which can improve combustion efficiency and enhance flame front propogation across the cylinder with the resultant effect of increased engine torque and reduced fuel consumption. The Multi Spark system as herein described will also improve cold-weather starting since the overall spark duration is increased from approximately 0.5 to approximately 60 of crank shaft rotation whilst being cranked by the starter motor.

Claims (10)

1 An electronic ignition for internal combustion engines combining high energy sparking with multi-spark intensity, by switching the primary coil current many times during each compression stroke using a power Metal Oxide Semiconductor Field Effect Transistor (MOSFET).

2 An electronic ignition as claimed in Claim 1 to reduce premature flame front extinguishing and / or enhance flame front propagation.

3 An electronic ignition as claimed in the above claims to increase engine efficiency and / or performance.

4 An electronic ignition as claimed in the above claims in which primary coil current is controlled to regulate spark energies.

5 An electronic ignition as claimed in the above claims in which external control is included to allow simulation of conventional ignitions for servicing.

6 An electronic ignition as claimed in the above claims in which means maybe provided to adjust the multi-sparking frequency to suit the coil in use.

7 An electronic ignition as claimed in the above claims in which means are provided to drive a tachometer at the current engine RPM.

8 An electronic ignition as claimed in the above claims wherein input signal conditioning is used to allow any signal to drive the ignition with good noise immunity.

9 An electronic ignition as claimed in the above claims wherein suitable protection is provided to ensure the power MOSFET is within its safe operating area.

10 An electronic ignition as claimed in the above claims in which multi-sparking is prohibited and / or coil current stopped whilst the engine is stationary? 11 An electronic ignition substantially as described herein with reference to Figures 1-4 of the accompanying drawings.