IGNITION MONITOR

Abstract: An apparatus and method for visually monitoring and testing in situ the operation of an engine ignition system. A gas discharge device (12), typically a neon trigger tube, glow lamp or gas diode, is provided in the electrical circuit connecting each spark plug to its high voltage source so that the gas discharge device is triggered by firing of the spark plug. Defects in the ignition system, such as faulty ignition coil, high voltage leads, or spark plugs, can be visually detected from the failure of the discharge devices to flash, or a degradation in the illumination of the discharge devices. Each gas discharge device (12) can be incorporated into a connector unit (10) between the distributor (20) and a respective high voltage lead (30).

Description: "IGNITION MONITOR" The present invention relates to an apparatus and method for monitoring the operation of an engine ignition system. In particular, the invention is directed to a method and apparatus for visually monitoring or testing the operation of the ignition circuit of an internal combustion engine. BACKGROUND ART Faults which may occur in an ignition system include defective distributor, defective breaker points and their associated capacitor, defective ignition coil unit, faulty high voltage cables and defective spark plugs. Due to the multiplicity of possible faults, expertise in the art is required in order to ascertain which part of the ignition system is defective. Even with such expertise, the locatio of the fault is time consuming and increases service costs. In known methods of testing the components of an engine ignition system, such as the spark plugs, ignition coil and high voltage leads, it has been necessary to . disconnect and remove such components and test them individually. It is an object of the present invention to overcome, or substantially ameliorate the abovedescribed disadvantage by providing a novel method and apparatus for testing the ignition system in situ which enables the fault to be located quickly and accurately. DISCLOSURE OF INVENTION In one broad form, the present invention provides apparatus for monitoring the operation of an engine ignitio system, said apparatus being adapted to be inserted in the electrical circuit connecting an engine spark plug to its high voltage source and comprising a gas discharge device which is triggerable in response to firing of the spark plu According to another aspect of the present invention, there is provided a method of monitoring the operation of a engine ignition system, said method comprising the steps of inserting a gas discharge device in the electrical circuit connecting an engine spark plug to its high voltage source, whereby said gas discharge device is triggered by firing of said spark plug. Typically, the gas discharge device is a small neon trigger tube, glow lamp or gas diode which is connected in the circuit linking the ignition coil to the distributor, or the distribuor to the individual spark plugs. The neon trigger tube is connected in series with a current limiting resistor and in parallel with a by-pass resistance. The current drawn by the spark plug on firing creates a voltage across the by-pass resistance which, in turn, triggers the neon trigger tube. If the spark plug is not firing, the neon trigger tube will not be illuminated. Further, if the spark plug is not firing properly or the ignition coil is not developing sufficient voltage or energy, there will be a corresponding degradation in the illumination of the neon trigger tube. Typically, the ignition monitoring apparatus of the present invention is incorporated into a connector unit which is insertable into the distributor cap and connectable to the high voltage leads to the ignition coil and spark plugs. A preferred embodiment of the present invention will now be described with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a plan view of a distributor cap incorporating a preferred embodiment of the present invention. Fig. 2 is a sectional elevational view of the distributor cap of Fig. 1, and Fig. 3 is an electrical circuit diagram of the ignition monitor of the preferred embodiment. BEST MODE OF CARRYING OUT THE INVENTION The monitoring apparatus of the preferred embodiment comprises a neon cold cathode trigger tube or glow lamp NT connected in series with a current limiting resistor Rl, and a by-pass resistance R2 connected in shunt with the series connection of Rl and NT. as shown in Fig. 3. Although a neon trigger tube is used in the preferred embodiment, it will be apparent to those skilled in the art that any suitable gas discharge device can be used ; such as illuminating gas diodes. Such gas discharge devices typically comprise small hermetically sealed gas-filled envelopes containing two opposed and spaced apart electrode connected to terminals on the outside of the envelope. An appropriate inert gas, for example neon or argon, or mercur vapour is used. When the voltage between the electrodes exceeds a "breakdown voltage", there will be an electrical discharge through the gas which, in turn, illuminates the envelope. In the preferred embodiment, a neon trigger tube 12 and its associated resistors are encapsulated in clear epox resin or alternatively injection molded into clear plastic material and incorporated into a connector unit 10 having one connection terminal 13 designed for insertion into the distributor cap 20 and another connection terminal 11 which is designed for connection to a high voltage lead 30 from a respective spark plug (not shown). A respective connector unit 10, 10A, 10B, IOC is provided in the circuit connectin each spark plug to the distributor cap. Each connector uni 10 has a cutaway or transparent portion 14 on the uppermost side thereof in which the envelope of the neon trigger tube is arranged so that the illumination or flashing of the neo trigger tube 12 can be seen easily. Another connector unit 15, incorporating the ignition monitor of the preferred embodiment, is connected between the input of the distributor cap 20 and a high voltage lead 35 from the ignition coil (not shown) . The connector unit 15 also includes a cutaway or transparent viewing portion 1 through which the neon trigger tube 16 of its respective ignition monitor can be seen. Thus, the ignition monitors are inserted in the electrical circuit between the ignition coil and the distributor, and the distributor and the respective spark plugs. Operation of each ignition monitor will now be described with reference to Fig. 3. If the ignition monitor is incorporated into a connector unit 10, terminal A will be connected to the output of the distributor while terminal B will be connected -* ΪEAtr OMPI to the respective spark plug (not shown) . When a voltage pulse is produced at the distributor output for the respective spark plug, it will be transmitted to the spark plug via the ignition monitor and high voltage lead. Upon firing of the spark plug, a current is drawn through the by-pass resistance R2 which, for a spark plug voltage of 25 kV, is typically 2-5 kOhms. The current drawn through the by-pass resistance will develop a voltage across the electrodes of the neon trigger tube NT. When the voltage across the neon trigger tube exceeds the threshold or breakdown voltage, the tube will flash as a result of the gas discharge. The current through the neon trigger tube NT is limited by resistor Rl which typically is 1200-200° Ohms but naturally, the value of the current limiting resistor will depend on the maximum current rating of the neon trigger tube. It will be apparent that if the spark plug does not fire, no current will be drawn through the by-pass resistance and therefore, the trigger tube will not flash. If the spark plug is firing correctly on each revolution of the engine, the neon trigger tube will appear to be of constant illumination due to the high rate of firing. On the other hand, if the plug is not firing on each revolution, or is firing at reduced energy, there will be corresponding degradation in the illumination of the neon trigger tube and the fault can be discerned quickly and easily. Similarly, if the neon trigger tube in the connector unit 15 connected to the ignition coil lead is not flashing, or is flashing at reduced illumination, it will be apparent that there is a fault in the ignition coil or the coil lead. By visually inspecting the various trigger tubes while the engine is running, it is possible to locate and identify faults such as (i) failure of power supply from ignition switch to the breaker points, (ii) failure of the breaker points, (iii) failure of the points suppressor, (iv) partial or complete failure of the ignition coil, (v) defective rotor button, (vi) internal fault within distributor, (vii) open circuit high voltage lead and (viii) OMPI defective spark plug. For example, if one of the ignition monitors has a markedly increased light output from its neo trigger tube, then logically the corresponding spark plug electrode is shorted to earth. If there is a partial failure in the ignition coil, for example shorted turns in the windings, then the neon trigger tube in the coil lead will have reduced illumination. INDUSTRIAL APPLICABILITY It will be apparent to those skilled in the art that the present invention is applicable to all internal combustion engines as a simple, economical and effective means of visually monitoring and testing the operation of the ignition system. The invention has particular application to automobile engines and reduces the time and expense of locating and rectifying faults in the ignition system. O PI \

Claims: CLAIMS 1. A method of monitoring the operation of an engine ignition system, said method comprising the steps of inserting a gas discharge device in the electrical circuit connecting an engine spark plug to its high voltage source, whereby said gas discharge device is triggered by firing of said spark plug. 2. A method as claimed in claim 1, wherein said gas discharge device is a neon trigger tube or gas diode. 3. A method as claimed in claim 2, wherein a respective neon trigger tube or gas diode is inserted between the ignition coil and distributor, and between the distributor and each spark plug. 4. Apparatus for monitoring the operation of an engine ignition system, said apparatus being adapted to be inserted in the electrical circuit connecting an engine spark plug to its high voltage source and comprising a gas discharge device which is triggerable in response to firing of the spark plug. 5. Apparatus as claimed in claim 1, further comprising a current limiting resistance connected in series with said gas discharge device, and a by-pass resistance connected in parallel with the series connection of the current limiting resistance and said gas discharge device, said apparatus being connected in series between an ignition coil and distributor, and/or between the distributor and each spark plug. 6. Apparatus as claimed in claim 5 wherein said gas discharge device is a neon trigger tube or illuminating gas diode. 7. Apparatus as claimed in claim 6 wherein said neon trigger tube, current limiting resistance and by-pass resistance are encapsulated in a clear plastic or epoxy resin capsule. 8. Apparatus as claimed in claim 7, wherein said capsule is incorporated in a connector unit having one terminal adapted for connection to a distributor cap and another terminal for connection to a high voltage lead of said ignition system. 9. Apparatus as claimed in claim 8, wherein said connector unit has a cutaway or transparent portion on the uppermost side thereof through which illumination of the neon trigger tube or gas diode is visible. 10. Apparatus as claimed in claim 4 when used in an automobile ignition system. O PI

Inventors: DANIEL KELVIN JAMES, DANIEL, KELVIN, JAMES
Applicants: KELDAN IND, KELDAN INDUSTRIES LIMITED
Application year: 1984
Main classification: F02P17
IPC codes: F02P11, F02P17