WO1993005528A1

WO1993005528A1 - Ignition device for combustion chamber

Info

Publication number: WO1993005528A1
Application number: PCT/US1992/007692
Authority: WO
Inventors: William G. Spare
Original assignee: Spare William G
Priority date: 1991-09-11
Filing date: 1992-09-11
Publication date: 1993-03-18
Also published as: AU2672992A

Abstract

A spark plug (10) having an open-vertex triangular grounding electrode (22) opposed to a central electrode (20) surrounded by and flush with an insulator (16). Spark initiation occurs across the insulator surface, across a spark gap, or both simultaneously. Sparks climb the triangular structure to emerge at the open-vertex to extend into a combustion chamber. A surface gap is set at about 0.050 inches and an air gap at about 0.037 inches.

Description

IGNITION DEVICE FOR COMBUSTION CHAMBER

BACKGROUND OF THE INVENTION The present invention relates generally to ignition devices for initiating combustion of flammable mixtures in combustion chambers. More specifically, the present invention relates to a spark plug for an internal combustion engine.

Spark plugs are well-known devices used in internal combustion engines to ignite compressed mixtures of fuel and air. The ignition of the fuel and air mixture drives pistons in the engine which rotate a crankshaft. Rotation of the crankshaft provides power to rotate wheels of an automobile, for example. A spark plug directly contributes to an efficiency of, and emissions resulting from, conversion of the fuel and air mixture to power.

Improving spark plugs of the prior art can contribute to cleaner burning, fuel efficient automobiles having improved power. Fig. 5 illustrates a conventional spark plug 100 design typically used in a majority of the automobiles today. This design includes a central electrode 102 surrounded by an insulator 104. The central electrode 102 extends beyond the insulator 104 at a first end to form a first gap surface 106. The central electrode 102 extends beyond the insulator 104 at a second end (not shown) to facilitate connection of a voltage source. A housing 108 includes threads for engaging the combustion chamber and surrounds the insulator 104. Connected to the housing 108 is a grounding electrode 110 having a first part 112 and second part 114. The first part 112, connected to the housing 108, extends along an line parallel to an axis of the central electrode 102. A second part 114 of the grounding electrode 110 extends at right angles to the first part 112 and is disposed to overlie the first gap surface 106. The second part 114, opposed to the first gap surface 106 thereby forms a second gap surface 116. In operation, the spark plug 100 is threaded into a complementary threaded aperture in an engine. The aperture i the engine permits the spark gap surfaces 106 and 116 to exte into a combustion chamber. A battery having positive and negative voltage terminals has its negative terminal coupled the engine which grounds the housing 108 in turn. An ignitio system couples the positive terminal to the second end of the spark plug 100. The ignition system periodically applies a sufficiently high voltage to the second end of the central electrode 102 to initiate a spark across the spark gap surfac 106 and 116. The required voltage to initiate the spark depends upon a distance separating the first and second spark gap surfaces 106 and 116, as well as the conditions inside th combustion chamber. The combustion chamber generally has a compressed mixture of fuel and air. Sparking characteristics are dependent upon the amount of compression, the relative amounts of fuel and air, the temperature and type of fuel. A location of sparking across the spark gap surfaces 106 and 116 varies with each spark. The spark location is difficult to predict in the spark plug 100.

This spark plug 100 used as a spark plug in automobiles has a number of drawbacks. One disadvantage is th amount of voltage required to initiate sparking. Typically, the spark gap surfaces are separated by a distance requiring about 40,000 volts to initiate a spark. The orientation of th spark gap surfaces results in an increase in spark gap separation as the grounding electrode 110 erodes through sparking. The increase in spark gap separation results in an increase in a requirement for spark initiation voltage. If this requirement increases beyond a particular margin, the ignition system will fail to provide sufficient voltage to initiate a spark.

Another disadvantage is that the design of the overlying ground electrode partially shields the spark from extending into the combustion chamber. Sparks which do not extend into the combustion chamber initiate combustion less efficiently than a spark extending further into the combustion chamber. As the spark gap is solely a "combustion air" gap, the spark initiation voltage varies as the combustion air properties vary. This variation can adversely affect performance. Still another disadvantage of the conventional desig is that the design permits the spark plugs to foul. Fouling results from incomplete combustion which allows carbon and oil deposits to form on the electrodes. As the carbon and oil deposits increase, the spark initiation voltages required to ionize the spark gap also increase. When the spark initiation voltage required is more than the voltage available, the plug will misfire.

SUMMARY OF THE INVENTION The present invention provides apparatus for initiating a spark in a combustion chamber. The invention permits spark initiation at decreased voltages. Sparks initiated with the device extend further into a combustion chamber and provide an ignition device resistant to fouling. The improved sparking permits improved power, fuel efficiency and better fuel emissions. The ignition device operates more efficiently which reduces undesirable pinging of the combustio engine. Additionally, initiation of sparking is less dependen upon combustion air than previous designs, which permits bette performance predictions.

According to one aspect of the invention, it include a housing having threads for engaging complementary threads in an aperture of a combustion chamber. An elongated insulator inside the housing surrounds a central electrode. One end of the insulator and central electrode extends into the aperture of the combustion chamber. The central electrode within the combustion chamber has a flat exposed electrode surface for on end of the spark gap which is coplanar to and flush with the end of the insulator within the combustion chamber. The other end of the central electrode conventionally extends beyond a second end of the insulator to provide a connection for a voltage source. A pair of grounding electrodes are used for the complementary end of the spark gap, each grounding electrode having two parts. The first part connects to the housing and extends to a position adjacent the end of the insulator flush with the central electrode. The first parts of the pair of grounding electrodes extend to positions on the insulator tha are opposite to each other. The second parts of the pair of grounding electrodes extend from the positions adjacent the insulator at an angle of about forty-five degrees away from a over the first gap surface. The second parts extend toward each other without touching, forming an open-vertex triangle with the first gap surface. The second parts are contained in a plane that includes the central electrode, and forms two gap producing surfaces: one gap extends from the central electrod to the ends of the first parts, and the second gap exists from the second parts of the grounding electrodes to the central electrode.

The invention provides improved performance over existing ignition devices. Spark plugs embodying the inventio produce longer sparks at reduced voltage levels without fouling. Initiation of a spark is relatively independent of the characteristics of the typical combustion environments.

Reference to the remaining portions of the specification and the drawings may realize a further understanding of the nature and advantages of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of a spark plug 10 embodying a preferred embodiment of the present invention; Fig. 2 is an enlarged view of threaded housing portion 14 showing a pair of opposed grounded electrodes; Fig. 3 is an end view of the spark plug 10; Fig. 4 is an end view showing an alternative embodiment of the present invention; Fig. 5 is a spark plug 100 of conventional design;

Fig. 6 is an illustration of a feature of the presen invention showing a flame 40 emerging from an open-vertex of the spark electrodes during operation; and

Fig. 7 is an illustration of a flame 40- emerging from a conventional spark plug 100.

DESCRIPTION OF THE PREFERRED EMBODIMENT Fig. 1 is a side view of a spark plug 10 embodying a preferred embodiment of the present invention. Spark plug 10 includes a housing 12 having a threaded portion 14. An insulator 16 surrounds a central electrode 20 disposed along a axis of the insulator 16. A ground electrode 22, connected to the threaded portion 14, extends to a first end 24 of the insulator 16. The central electrode 20, generally flush with the first end 24 of the insulator 26, extends to a coupler 26. The coupler permits application of a voltage source to the spark plug 10 for initiation of a spark. The ground electrode 22 connects to the threaded portion 14 at a ground connection point 28.

In operation, threading the spark plug 10 into a complementary-threaded aperture of a grounded combustion chamber grounds the housing 12 and the threaded portion 14. A ignition voltage applied to the coupler 26 initiates a spark between the ground electrode and the central electrode 20 proximate the first end 24 of the insulator 16. Fig. 2 is an enlarged view of threaded portion 14 having a pair of opposed grounded electrodes 22. A first grounded electrode 22a and a second grounded electrode 22b extend from a common connection point, the ground connection point 28 shown in Fig. 1, to the first end 24 of the insulator 16. As shown, the first grounded electrode 22a contacts the first end 24 of the insulator and extends to a position overlying the central electrode 20. Similarly, the second electrode contacts the first end 24 of the insulator at a position diametrically opposed to a position the first ground electrode 22a contacts the first end. The second ground electrode 22b also extends towards and over the central electrode 20. The first ground electrode 22a and the second ground electrode 22b each extend at about a forty-five degree angle from their contact positions on the insulator. The fir ground electrode 22a and the second ground electrode 22b together with the first end 24 of the insulator, define an open-vertex triangle spark gap. The central electrode 20 defines a first spark gap surface and the two grounded electrode each define a second spark gap surface.

In operation, application of the spark voltage to th coupler 26 of Fig. 1 initiates a spark across the spark gap between the first gap surface and one of the second spark gap surfaces. In a preferred embodiment of the present invention the electrodes have a surface gap of about 0.050 inches and an air gap of about 0.037 inches. The spark voltage initiates sparks directly across the spark gap, across the surface of th first end 24 of the insulator, or both. Sparks, whether initiated across the surface of the insulator or directly across the spark gap, advance towards the open-vertex. The open-vertex permits a spark to extend away from the spark plug 10 into a combustion chamber (not shown.) Permitting multiple sparking paths, having differing spark initiation voltage requirements is one important aspect of the preferred embodiment of the present invention. The surface spark initiation voltage requirement is on the order of 10,000 volts and the spark gap spark initiation voltage requirement is on the order of 10,000 volts.

An advantage of the open-vertex triangular structure is that the spark is unshielded and extends into the combustio chamber. Spark initiation voltage requirements are reduced. The net effect produces a hotter spark at reduced voltages improving combustion efficiency. The improved combustion efficiency improves emissions and power output as well as easier cold starting, smoother and more quiet engine operation less fuel consumption, reduction of detonation (pinging) , and less carbon formation on valves, pistons and combustion chambers.

Fig. 3 is an end view of the spark plug 10 illustrating one preferred embodiment. The first ground electrodes 22a and the second ground electrode 22b have first portions extending from the common connection point 28 to positions diametrically opposed to each other across the firs end 24 of the insulator 16. Each ground electrode includes a second portion extending away from and over the central electrode 20. In the preferred embodiment, the first portion of the ground electrodes do not touch the threaded ground portion except at the common connection point 28. This prevents the spark plug tip from cooling, allowing better operation. Better operation results from thin, convoluted ground electrodes. These electrodes cool faster, helping to prevent pre-ignition. The electrodes also heat enough to bur off carbon deposits. These thin, convoluted electrodes last longer and remain in relatively "new" condition. Gap adjustments are not generally required.

Fig. 4 is an end view showing an alternative embodiment of the present invention. In this alternative embodiment, the first and second ground electrodes connect to the threaded portions at different positions. In one embodiment, the connection points to the threaded portion are diametrically opposed across the threaded portion 14.

Fig. 6 is an illustration of a feature of the prese invention showing a flame 40 emerging from an open-vertex of the spark electrodes during operation. The operation illustrated is representative of using a preferred embodiment of the present invention to produce an unobstructed flame entering into an ignition chamber.

Fig. 7 is an illustration of a flame 40- emerging from a conventional spark plug 100. As noted, the overlying ground electrode of the conventional sparkplug inhibits the flame 40' from entering into an ignition chamber.

In conclusion, the present invention provides many advantages over existing devices, including more efficient engine operation, plugs are long lasting with long new like performance, less engine wear and maintenance through less oi contamination. While the above is a complete description of the preferred embodiments of the invention, various alternatives, modifications, and equivalents may be used. Fo example, platinum electrodes may be used for even better performance and durability. Therefore, the above description should not be taken as limiting the scope of the invention which is defined by the appended claims.

Claims

WHAT IS CLAIMED IS;

1. An ignition device for a combustion chamber, comprising: a housing having means for engaging the combustion chamber; an elongated insulator, having a central axis and carried by said housing, said insulator having a first end to extend within said chamber, and a second end; an elongated central electrode disposed along said central axis of said insulator, said central electrode having first end with a peripheral surface generally flush with said first end of said insulator to define a first surface of a spark gap, and a second end extending beyond said second end o said insulator for connection to a voltage source for spark initiation; and a second electrode having a first portion and a second portion, said first portion connected to said housing and extending to a position adjacent said first end of said insulator and said second portion extending therefrom at an angle away from and over said first surface of said spark gap.

2. The spark initiation device of claim 1 wherein said second portion of said first electrode extends at about a forty-five degree angle.

3. The spark initiation device of claim 1 wherein said second portion of said first electrode is disposed in a plane containing said central electrode.

4. The spark initiation device of claim 1 wherein said central electrode has a circular cross-section.

5. The spark initiation device of claim 1 further comprising a third electrode having a first portion and a second portions, said first portion connected to said housing and extending to a position adjacent said first end of said insulator and said second portion extending therefrom at an angle away from and over said first surface of said spark gap.

6. The spark initiation device of claim 2 wherein said second and third electrodes are connected to said housing at a first position and said first portions of said second and third electrodes extending to opposing sides of said insulator

7. The spark initiation device of claim 2 wherein said second and third electrodes are connected to said housing at a first position and a second position respectively, said first and said second positions diametrically opposed to each other on said housing and said first portions of said second and third electrodes extending to opposing sides of said insulator.

8. The spark initiation device of claim 3 wherein said second portions of said first and second electrodes exten at about a forty-five degree angle.

9. The spark initiation device of claim 4 wherein said second portions of said first and second electrodes exten at about a forty-five degree angle.

10. The spark initiation device of claim 3 wherein said second portions of said first and second electrodes are disposed in a plane containing said central electrode.

11. The spark initiation device of claim 5 wherein said second portions of said first and second electrodes are disposed in a plane containing said central electrode.

12. The spark initiation device of claim 4 wherein said second portions of said first and second electrodes are disposed in a plane containing said central electrode.

13. The spark initiation device of claim 6 wherein said second portions of said first and second electrodes are disposed in a plane containing said central electrode.

14. The spark initiation device of claim 7-10 wherein said second portions of said second and third electrodes each include a terminal end extending toward and separated from each other by a second gap.

15. The spark initiation device of claim 11 wherei said central electrode has a circular cross section having a diameter and wherein said second gap is less than said diamet of said central electrode.

16. A spark initiation device comprising: a first electrode coaxial with an insulator; and a second and third electrode proximate said insulator, said second and third electrodes forming an open- vertex triangle with said insulator, having said first electrode opposed to the open-vertex.

17. The spark initiation device of claim 16 having: a surface gap of about 0.050 inches and an air gap about 0.037 inches.