GB2275505A

GB2275505A - Multiple electrode spark plug

Info

Publication number: GB2275505A
Application number: GB9303773A
Authority: GB
Inventors: Roy Targonski
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-02-25
Filing date: 1993-02-25
Publication date: 1994-08-31
Also published as: GB9303773D0

Abstract

Separate electrodes 4, 5, are provided within the insulator 3 which combine with one or more ground electrodes 6, 7, to provide a series of spark gaps 8, 9. The pairs of live and ground electrodes can be used in the same or separate ignition systems and can be fired simultaneously or separately. <IMAGE>

Description

IMPROVED SPARK PLUG The present invention relates to an improved spark plug for use in internal combustion engines.

Spark plugs are generally designed to have a central "live" electrode encased in a ceramic material in a screw threaded metallic body portion for releasable location in the cylinder head of an internal combustion engine, one or more ground electrodes extending from the metal body towards the centro-electrode to define a spark gap therebetween.

Various attempts have been made to improve the efficiency with which this type of spark plug ignites the combustion mixture, generally a fuel/oxygen mixture such as petrol/air. However such attempts have generally concentrated on varying the design of that part of plug in the area of the spark gap, for example encasing the two electrodes in a "pre-chamber" open to the main combustion chamber.

It is current practice, especially in aircraft engines, to use two spark plugs to improve combustion efficiency and also for safety reasons, each plug being part of a separate ignition system thereby providing multi-ignition systems.

I have now developed an improved form of spark plug that provides enhanced efficiency in the ignition of a combustion mixture and can also be used with multi-ignition systems.

My improved spark plug comprises a body portion capable of releasable location in a cylinder head port, an insulating material encased in said body and having an end portion extending through the body towards a combustion chamber associated with the cylinder head, and multiple live electrodes extending from said end portion of said insulating material, the plug further including at least one ground electrode extending towards the said live electrodes to define multiple spark gaps.

The live electrodes may be part of a single ignition system or each may be part of a separate ignition system thereby providing the same advantages as multi-ignition systems.

The body portion may comprise a conventional metal casing from which the ground electrodes may extend towards the live electrodes. Preferably there is one ground electrode for each live electrode.

The insulating material may be ceramic or any other suitable material and the live electrodes may extend in a substantially parallel relationship through the ceramic material and be formed of conventional materials such as copper or silicon carbide.

One embodiment of my invention will now be described with reference to the accompanying drawing which is a cross sectional view of an illustrative spark plug.

In the drawing the spark plug comprises an outer steel casing 1 screw threaded at 2 for location in a correspondingly threaded port in the cylinder head of an internal combustion engine.

A ceramic insulator 3 is contained within body 1 and has a lower end 31 surrounded by a circular shroud formed by extended portion 11 of body 1.

Live copper electrodes 4 and 5 extend in parallel through the insulator 3 and have end portions 41 and 51 extending below lower end 31 of the insulator and ends 42, 52 extending through the opposite end 32 of insulator 3.

Ground electrodes 6 and 7 are provided extending from portion 11 of body 1 and extend radially inwardly towards end portions 41 and 51 of the live electrodes to provide spark gaps 8 and 9.

Ends 42 and 52 of live electrodes 4 and 5 may be connected by conventional means to either a single ignition system or to separate ignition systems as required.

It is, of course, not essential that the electrodes extend completely through the insulator they must, however, have portions 41, 51 extending below the end of the insulator, and being located within the insulator, or a support extending from the insulator, means must also be provided for connection of the live electrodes to the ignition system or systems.

The invention is not limited to the use of two electrodes or to the electrodes of a circular cross-section. Thus four electrodes of triangular cross-section might be employed.

Furthermore the electrodes may be formed of any suitable material.

In use the spark plug of my invention has the safety and other advantages of a multi-plug ignition system when the live electrodes are linked to separate ignition systems. In use the spark plug also provides an improved spark dissipated over a larger volume which will lead to improved combustion leading to enhanced fuel economy and a reduction in pollutants.

When used in a multiple ignition system the spark plug also allows the production of a cascade spark which extends the spark duration and leads to improved combustion efficiency. Spark duration can, for example, be extended by firing each electrode in sequence or any other permutation that befits the engine state. In a three electrode plug, for example, all three electrodes may be fired simultaneously or in a sequence of 1, 2, 3; or 1, 2 and then 3; or 1 and 2 + 3. The spark is thus particularly suitable for use with computer controlled engine management systems.

Claims

CLAIMS:

1. A spark plug comprises a body portion capable of releasable location in a cylinder head port, an insulating material encased in said body and having an end portion extending through the body towards a combustion chamber associated with the cylinder head, and multiple live electrodes extending from said end portion of said insulating material, the plug further including at least one ground electrode extending towards the said live electrodes to define multiple spark gaps.

2. A spark plug according to claim 1 in which the body portion comprises a metal casing from which the ground electrodes extend towards the live electrodes.

3. A spark plug according to claim 1 or claim 2 in which there is one ground electrode for each live electrode.

4. A spark plug according to any preceding claim in which one or more ground electrodes have radially inward extending end portions.

5. A spark plug according to any preceding claim in which the live electrodes extend in a substantially parallel relationship through the ceramic material.

6. A spark plug according to any preceding claim in which the ceramic insulator is contained within the body and has a lower end surrounded by a circular shroud formed by an extended portion of the body.

7. A spark plug according to any preceding claim in which the live electrodes may be connected to either a single ignition system or to separate ignition systems as required.

8. A spark plug adapted to allow the production of a cascade spark which extends the spark duration and leads to improved combustion efficiency.