WO2000001047A1

WO2000001047A1 - Corona wind spark plug

Info

Publication number: WO2000001047A1
Application number: PCT/US1999/014756
Authority: WO
Inventors: Chris W. Witherspoon; Katherine B. Wright
Original assignee: Witherspoon Chris W; Wright Katherine B
Priority date: 1998-06-29
Filing date: 1999-06-29
Publication date: 2000-01-06
Also published as: AU4845899A

Abstract

A corona wind spark plug (20) for internal combustion engines includes a multi-pointed electrode (22).

Description

CORONA WIND SPARK PLUG

FIELD OF THE INVENTION

This invention relates to the ignition systems for internal combustion engines and more particularly to a high efficiency spark plug for internal combustion engines that incorporates the corona wind phenomenon without relying on an accessory voltage source to create the corona wind.

DESCRIPTION OF THE PRIOR ART There have been many attempts to develop spark plugs which decrease pollutants, have a longer life, and which increase horsepower. Some of these prior attempts have focused on generating an enlarged spark plasma to minimize misfires by igniting enough of the air/fuel mixture, to produce a large enough flame kernel, and to efficiently consume a higher volume of fuel to reduce emissions and produce a gain in power. With prior art spark plugs, there is little or no provision for disbursement of the flame kernel into the swirling air/fuel charge. Indeed, conventional spark plugs rely primarily on the size of the flame kernel for completing combustion.

It has been noted that when turbulence or pressurized air from an outside source is applied to a capacitive center electrode spark plug, the spark kernel was amplified by several magnitudes. What is needed is a method of generating a wind source within the cylinder itself to effectively speed the spark kernel and help aid in more efficient combustion.

There is another approach to spark plug technology that incorporates an electric or corona wind phenomenon to literally blow the flame front into the air fuel mixture. See SAE Technical Paper Series 920810, "A Corona Spark Plug System for Spark-Ignition Engines," by E. Sher and J. Ben-Ya'ish of Ben-Gurion University of Neyev, Israel, and A. Pokryvailo and Y. Spector, of Spectronix, Ltd., presented at the International Congress Exposition, Detroit, Michigan, February 24-28, 1999. In the E. Sher et al. approach, a modified electrical system including an accessory voltage source applies a constant current continuously to a modified spark plug with a pointed positive central electrode with a surrounding negative ring electrode. While the spark plug and system of Sher et al. operate to reduce CO and HC emissions at low rpm and low load conditions (e.g. below 2500 rpm), once the rpm and/or engine load increase, there is no noticeable advantage compared to conventional spark plugs with a conventional ignition system. Moreover, without the constant current applied, the Sher et al plug does not reduce CO or HC emissions. In the Sher et al system, the implementation of the outside electrical current brings a limitation to this singular, pointed, positive center electrode design because at approximately 2500 RPM or less the force of the air fuel charge is greater than the force of corona wind generated, overcoming the corona wind and degenerating into conventional spark and flame kernel propagation. The singular pointed center electrode has very limited capacitive properties and when spark occurs the corona wind is temporarily halted and the high energy of the spark is therefore only able to generate a plasma kernel of common magnitude. However when the corona wind resumes it can carry the heat that would normally transfer to the spark generating electrodes out into the fuel charge. Thus, as combustion chamber pressures rise, as RPM rise, the corona wind breaks down and the ignition device becomes only as effective as a common spark plug. Since the corona wind is ineffectual the sharp point of the center electrode is now subject to erosion and deterioration caused by retention of the extreme heat of ion transfer and plasma kernel formation. U.S. Patent No. 4,695,758 to Nishida et al. discloses a spark plug that can be made in smaller diameter than conventional spark plugs, yet which eliminates the chanelling phenomenon. No corona wind is generated by the Nishida et al. spark plug.

U.S. Patent No. 5,704,321 to Suckewer et al. discloses a traveling spark ignition system, the three embodiments of which all require a separate, constant voltage source applied to the center electrode of a so-called Marshall gun plasm generator spark plug.

Lastly, U.S. Patent No. 5,731,655 to Corrado discloses a spark plug with a 360-degree firing tip. In the Corrado spark plug, the center electrode has a plate located at its terminal end. The plate is either perfectly flat or has a circumferential raised lip with vertical sidewalls or slanted sidewalls, but in all cases forming a single, continuous edge. The plate is disposed in an opposed orientation to a ground electrode rim. The insulator surrounding a central positive electrode extends downwardly to the plate. The Corrado spark plug is alleged to reduce carbon buildup, and is designed to provide for a more widely dispersed sparking pattern. No corona wind is generated by the Corrado spark plug.

There accordingly remains a need for a spark plug that incorporates the corona wind phenomena to provide an improved spark plug capable of generating a large flame kernel using a conventional ignition system.

SUMMARY OF THE INVENTION

In a first aspect, the present invention is characterized by a first multi-pointed electrode that is spaced apart from a second electrode to form a sparking gap therebetween. Conventional spark plugs include a spaced apart positive electrode and ground electrode that are configured to generate a discharge spark therebetween. In contrast, the first multi-pointed electrode of the present invention and its relationship to the ground electrode creates a capacitive effect in conjunction with the ground electrode. The capacitive effect of the multi-pointed electrode increases ionic buildup and thus increases plasma discharge at multiple preselected points around the spark plug. A spark plasma discharge may then occur at the point that has least resistance.

The capacitive effect of the present invention efficiently utilizes the electrical energy produced by conventional ignition systems without modification and without requiring an accessory or supplemental system to apply constant current. This also permits the use of inexpensive spark plug wires.

In another aspect, the present invention creates an enlarged spark generated plasma kernel and then blows it into the compressing air/fuel mixture, thereby accelerating combustion propagation and producing a more complete burn. This rapid movement of heat mass into the air/fuel mixture creates a more complete combustion of fuel particulates thereby producing less harmful emissions of hydrocarbons and No_χ. The flame front thus generated may also be used to ignite extremely lean air/fuel mixtures that are presently difficult to ignite efficiently.

Another further aspect of the present invention, the spark plug generates a corona wind without the introduction of an outside electrical current.

In another still further aspect of the present invention, the spark plug generates a corona wind that resists break down at pressures exceeding those created by any conventional internal combustion engine including those producing RPM in excess of 13,000.

In yet a further aspect, the invention provides a means to increase engine efficiency and horsepower, yet decrease emissions.

In another aspect of the invention, there is provided a spark plug which runs cooler yet which is less subject to fouling and carbon build up than conventional spark plugs.

In a further aspect, the invention provides a design which allows lower cost materials to be utilized. These and other features and advantages of this invention will become further apparent from the detailed description and accompanying figures that follow. In the figures and description, numerals indicate the various features of the invention, like numerals referring to like features throughout both the drawings and the description.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a side view of a conventional prior art spark plug.

Fig.2 is a side view of one embodiment of a spark plug according to the present invention.

Fig. 3 is a cross section view of the spark plug of Fig. 2 taken along 3-3.

Fig. 4 is an end view of the spark plug of Fig. 2. Fig. 5 is a partial perspective view of the lower end of an alternate design for a multi- pointed electrode of Fig. 2.

Fig. 6 is a side view of a second embodiment of a spark plug according to the present invention.

Fig. 7 is an end view of the spark plug of Fig. 6. Fig. 8 is a cross section view of the spark plug of Fig. 6 taken along 8-8. Fig. 9 is a side view of a third embodiment of a spark plug according to the present invention.

Fig. 10 is an end view of the spark plug of Fig. 9

Fig. 11 is a side view of a fourth embodiment of a spart plug according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to Figure 1, there is shown a side view of a conventional prior art spark plug 2, which has a center electrode 4, a ground electrode 6, and a base shell 8. A spark plug wire 10 is connected to a terminal end or nut 12 connected to center electrode 4. An insulator nose 14 extends down somewhat, but does not cover the lower end of center electrode 4. In negative ground engines, sparks propagate from center electrode 4 to ground electrode 6.

In conventional spark plugs 2, the gap g between center electrode 4 and ground electrode 6 is normally about 0.7 to 0.9 mm, but can be as small as 0.3 mm (e.g. in racing engines) to 1.7 mm or more (in lean fuel-air mixtures). In these conventional spark plugs, combustion is initiated by electrical discharge across the electrodes 4 and 6 of the spark plug. The high- temperature plasm discharge between the electrodes ignite the air-fuel mixture in the immediate vicinity and the combustion reaction spreads outwardly from there. At first, the flame front, because of its small original size, does not generate enough energy to quickly heat the surrounding gases and thus propagates very slowly. This, in turn, raises the cylinder pressure slowly, and little compression heating is experienced. Only after the first 5-10% of the air-fuel mass is burned does the flame velocity reach higher values with the corresponding fast rise in pressure in the flame propagation region.

The various embodiments of the corona wind spark plugs of the invention are similar to conventional spark plugs except for important differences at the firing end.

Referring now to Figs. 2 to 4, a first, positive corona wind spark plug 20 includes a multi- pointed electrode 22. Spark plug body 24 may be similar to that of conventional spark plugs. In the spark plug 20, there is no ground wire and the lower end of the center electrode 32 includes multi-pointed electrode 22 with a plurality of points 24. Center electrode 32 has a terminal end 30 for connection to spark plug wire (not shown). Multi-pointed electrode 22 may be flat or dished slightly having a generally spherical radius of curvature between ³Λ" and 3", with the concavity and points 24 directed towards a lower end 26 of base shell 28, which in a negative ground engine acts as the ground electrode, or spark contact area 26.

Referring now to Fig. 3, spark contact area 26 of base shell 28 may be preferably chamfered 45 degrees from the long axis L of spark plug 20. This chamfering creates a situation that causes the spark to discharge at a 45 degree angle to long axis L of the spark plug 20. The angle Q of spark contact area 26 may vary between 0 and 90 degrees with 45 degrees being optimum. As shown, a terminal nut 30 is in communication with center electrode 32. Multi- pointed electrode 22 may be integral with or otherwise securely connected to lower end of center electrode 32. Insulative material (e.g. ceramic) 34 surrounds center electrode 32, and preferably extends down into contact with an upper surface 36 of multi-pointed electrode 22. Multi-pointed electrode 22 has a capacitive effect and acts to produce an intense spark with a shorter spark duration. The build up of electric charge on multi-pointed electrode 22 also creates a very stable spark, able to withstand extreme pressure and turbulence of RPM'S in excess of 13,000. Multi- pointed electrode 22 also partially shrouds lower end 38 of insulator 20 making spark plug 20 highly tolerant to fouling. In spark plug 20 of Figs. 1-4, multi-pointed electrode 22 is generally disk-shaped, and as a result its electrode points 24 are generally upwardly curved. Electrode points 24 preferably have relatively sharp points to provide for spark initiation points.

Referring to Figure 5, an alternate design for a multi-pointed electrode 24b is shown, having a flat plate 40, with a plurality of upwardly extending teeth 42 with pointed tips 44 extending from the perimeter 46 of the plate 40. Teeth 42 are disposed with these tips 44 facing spark contact area 26 on bottom of base shell 28. Referring now to Fig. 4, multi-pointed electrode 22 includes eight electrode points 24.

The number of pointed and preferably curved electrodes 24 in spark plug 20 plays a particular role in the optimum performance of the creation of corona wind and spark kernel. A balance of electrode points 24 in ratio to supplied voltage is selected for optimum performance. If an ignition system is older and produces less than 10,000 volts, 4 to 6 points is optimum (not shown), although fewer points may also be be used. Indeed, a single point might be able to produce some limited corona wind effects if the mass/capacitance of the electrode is adjusted accordingly. In typical modern passenger car high energy ignition systems, the number of points for balance is from six to eight electrode points (with eight points 24 shown in Fig. 4). In extremely high energy systems, such as for racing applications, up to 20 points may be used (not shown).

Referring back again to Figs. 2 and 3, the interaction of electrode points 24 on multipoint electrode 22 with spark contact 26 generate an outwardly direct corona wind W. This corona wind W is created when the electrical charge jumps from electrode points 24 of multi-point electrode 22 to spark contact 26 of base shell 28. The electric charge between electrode points 24 and spark contact 16 produce an inert wind W that accelerates the flame front (not shown) from spark plug 20 to the point of ignition. The corona wind W also focuses and thus intensifies the heat of the flame front. Since the flame front is accelerated and intensified, it is better able to burn fuel particles that have separated from the air fuel vapor that would normally remain as unbumed hydrocarbons that exit the cylinders. The multi-pointed electrode, corona wind generating spark plug's basic premise is to retain electric charge capabilities in the multi-pointed electrode 22 until it reaches a critical stage which occurs at a much higher level of accumulated charge than conventional spark plugs. The multi-point electrode 22 is preferably enlarged so as to store up the electric charge and utilize the stored charge to generate a corona wind that will force the flame front out into the air/fuel mixture. This corona wind W takes the heat that would normally be transferred to the spark generating electrodes out with the corona wind W. As the flame front moves away from the origin, it not only carries away the heat of the ignition, but the corona wind intensifies the heat of the flame front. This rapidly advancing, super heated flame front can then combust the air/fuel much more effectively. Even though the actual mass combustion occurs at an accelerated rate, generally the ignition timing may remain the same as used with conventional spark plugs. This is due to the fact that when current is discharged from the coil (or from other components of the ignition system) it collects in the enlarged multi-pointed electrode 22, and while collecting, there occurs an ionic bleed to all the sharp points 24 in the spark plug 20 causing the collision of ions between the sharp curved electrodes 24 and the spark contact area 26 that begins producing the corona wind W. Therefore, it takes a slightly longer period of time between actual spark discharges, thereby allowing the piston to travel higher up the cylinder before combustion begins and the piston is then forced back down with more thrust from a more complete and more rapid burning fuel charge.

By using a multiple-pointed capacitive electrode 22 in the present invention an outside source of electrical current can thus be eliminated. Instead, the high energy of a conventional ignition system is efficiently utilized to create the corona wind W. It does this by accumulating charge on all the multiple points and allowing some to bleed off to create the corona wind W, not only prior to sparking but during the occurrence of the spark, thereby focusing and thus enhancing the heat of the spark and ensuing plasma kernel development. Since the source of electrical current is high voltage and short duration the corona wind W is therefore very powerful and short. Basically, a flame front is blasted out into the fuel charge.

As air- fuel intake velocities rise with increased RPM, the high energy corona wind W developed by the spark plug 20 of the present invention resists break down, unlike the situation with the prior Sher et al. corona wind ignition system with its single, sharp center electrode and required accessory electrical system to supply a constant current to the spark plug. Under extreme conditions of high RPM engines where very high voltage systems are used, the spark plug of the present invention will nonetheless continue to generate a sufficiently strong corona wind as a result of the higher voltage.

The balance stems from the amount of ion bleed creating the corona wind and the amount of ions necessary to create the critical stage for spark discharge. If a lower energy system is bleeding off too many ions to too many points, this will weaken the spark kernel, and alter the timing of actual ignition. Therefore an optimum balance of ion bleed to spark kernel intensity should preferably be determined and a spark plug of the invention with the optimum number of points should be selected. As noted above, the spark plug embodiments of Figs. 1-5 provide for a positive corona wind spark plug. The term positive corona wind spark plug reflects the facts that sparks will jump from one or more of electrode points 24 to the spark contact surface 26.

Referring now to Figs. 6-8, another embodiment of a positive corona wind spark plug 50 is shown. Positive corona wind spark plug 50 has a ground electrode 52 and a terminal end 54.

Insulative material 56 surrounds center electrode 52, except at terminal nut end 54 and a lower end 58. At lower end 58, a multi-pointed electrode 60 is located. Multi-pointed electrode 60 is surrounded by a lower end 62 of base shell 64. At least one aperture 66 is formed in sidewalls of lower end 58 of base shell 64. As best shown in Fig. 8, lower end 62 of base shell 64 has a bottom opening 68. Formed near or around an inner perimeter surface of base shell is a spark contact surface 70. Multi-pointed electrode 60 has a plurality of points 72, which are generally directed outwardly and downwardly towards spark contact surface 70. In Figs. 6-8, multi- pointed electrode 60 is shown as being cupped and with six points 72. However, multi-pointed electrode 60 can have other shapes (e.g. like that shown generally in Fig. 5). Also, spark contact surface 70 can be formed with a bevel if desired. Aperture 66 can comprise two or more slot- shaped apertures, but apertures of other shapes can be provided as well.

Turning to Figs. 9 and 10, a first embodiment of a negative corona wind spark plug 80 is shown. In spark plug 80, a plurality of electrode points 82 are formed on a lower portion of base shell 84. A central electrode runs between a terminal nut 88 at the top of the spark plug 80 to a bottom electrode 86 which is preferably generally circular. Bottom electrode 86 may have a beveled edge 90 to define a spark contact surface. Base shell 84 has a thickness, and is spaced away from insulative material 92 that surrounds central electrode. Optionally, one or more base shell cent apertures 94 can be provided in base shell 84 and one or more bottom electrode vent apertures 96 can be formed through bottom electrode 86. These vents 94 and/or 96 can aid in generating improved corona wind. In the embodiment of Figs.9 and 10, electrode points of Figs. 9 and 10, electrode points 82 can be formed by removing material from sidewalls of base shell 84.

Turning to Fig. 11, a first embodiment of combination negative/positive corona wind spark plug 100 is shown. In spark plug 100, a plurality of electrode points 102 are formed on a lower portion of base shell 104, with unpointed regions defined therebetween to define a shell base rim portion 106 . A central electrode runs between a terminal nut 108 at the top of the spark plug 100 to a bottom electrode 110. Bottom electrode 110, like lower portion of base shell 104 has a plurality of electrode points 112 separated by unpointed regions which define a bottom electrode rim portion 114. The plurality of electrode points 102 on lower portion of base shell 104 are aligned over shell base electrode rim portion 114, and the plurality of electrode points 112 on bottom electrode 110 are aligned under shell base rim portion 106. Oriented as such, sparks can move between the electrode points (102 and 112) of the two electrodes (104 and 110, respective) to the rim portions (114 and 106, respectively), and thus the name positive/negative corona wind spark plug. Base shell 104 has a thickness, and is spaced away from insulative material 116 that surrounds central electrode. Optionally, one or more base shell vents 118 can be provided in base shell 104 and one or more bottom electrode vents 120 can be formed through bottom electrode 110. These vents 118 and/or 120 can aid in generating improved corona wind. The combination positive/negative spark plug 100, as with the other above noted spark plugs, functions to reduce emissions and slightly increase horsepower and torque.

It has been the inventors' experience that the negative corona wind spark plug tend to be more efficient in reducing emissions than the positive corona wind spark plug designs. However, both are superior to conventional spark plugs from a standpoint of CO and HC emission reduction, allow for leaner fuel-air mixtures, and actually increase the horsepower somewhat.

As stated above, the corona wind W helps push the flame front out into the cylinder away from the electrode points. This acts to help prevent excess heating, and reduces build-up of carbon, fouling, and other effects that might damage or decrease the efficiency of the spark plug.

Unlike some present spark plugs that use expensive materials, such as platinum and gold plating in lieu of lower cost metals, because of the corona wind effect, the spark plugs of the instant invention obviate the need for these costly materials, which further reduce their costs.

Moreover, the corona wind generating spark plugs of the instant invention can be used with conventional internal combustion engines and other electrical ignition components without requiring any accessory electrical changes and/or higher than normal electrical changes being supplied to the spark plugs.

In a test conducted on a small displacement Briggs & Stratton 5 H.P. internal combustion engine, a baseline was established using a conventional Champion® RJ 19CM spark plug, and was compared to a positive corona wind spark plug, substantially as shown in Figs. 9 and 10 (but without the optional vents.) Significant reduction in unbumed hydrocarbons (HC) and carbon monoxide (CO) were observed, and in the weighted specific emissions, significant reduction were experienced in HC + NO_χ (nitrous oxides) at idle (1750 RPM) and at 3060 RPM with a range of engine loads from 10% to 100%, as follows:

Table I

ENGINE EMISSION DATA

(with Conventional Spark Plugs)

Table II

WEIGHTED SPECIFIC EMISSIONS (With Conventional Spark Plug)

Table III

ENGINE & EMISSION DATA (With Positive Corona Wind Spark Plug)

TABLE IV

WEIGHTED SPECIFIC EMISSIONS (With Positive Corona Wind Spark Plug)

The unbumed hydrocarbons were reduced by 20% with the positive corona wind spark plug, and the HC + NO_χ reduction was 13%. Even better emission reducing results were observed with the negative corona wind spark plug.

In a test conducted using a 5 H.P. Brigg & Stratton engine, a slight increase in horsepower and torque were observed with a negative corona wind spark plug similar in design to that of Figs. 9 and 10, (but without vents,) compared to a convention Champion® RJ 19 LM spark plug.

Table V

HORSEPOWER & TORQUE

(Conventional Spark Plug)

Test #1

Test #2

Table VI

HORSEPOWER & TORQUE

(Negative Corona Wind Spark Plug)

Test #1

Test #2

As can be seen, the corona wind spark plug of the invention decrease emissions while at the same time actually slightly increasing torque and horsepower.

Numerous variations and modifications within the spirit of the present invention will of course occur to those of ordinary skill in the art in view of the preferred embodiments that have been disclosed herein. Such variations, as well as any other systems embodying any of the following claims, all remain within the scope of the present invention.

Claims

1. A corona wind generating ignition device for internal combustion engines, comprising a positive electrode and a ground electrode, at least one of the positive and ground electrodes having a plurality of points.

2. The corona wind generating ignition device for internal combustion engines of claim 1, wherein the ignition device comprises a spark plug in which the positive electrode is located near a lower region of the spark plug and comprises a member with the plurality of points pointing generally upwardly towards an underside of the ground electrode, the ground electrode comprising a lower edge of a base shell of the spark plug.

3. The corona wind generating ignition device for internal combustion engines of claim 2, wherein the lower edge of the base shell is beveled, and forms a spark contact area.

4. The corona wind generating ignition device for internal combustion engines of claim 2, wherein insulation material extends downwardly from a lower end of the base shell to an upper surface of the positive electrode.

5. The corona wind generating ignition device for internal combustion engines of claim 2, wherein the positive electrode is generally disk-shaped and the multiple points extend upwardly and outwardly therefrom.

6. The corona wind generating ignition device for internal combustion engines of claim 2, wherein the positive electrode is generally dish-shaped and the multiple points extend upwardly and outwardly therefrom.

7. The corona wind generating ignition device for internal combustion engines of claim 1 , wherein the ignition device comprises a spark plug in which the positive electrode is located near a lower region of the spark plug and comprises a member with the plurality of points pointing generally outwardly towards a lower region of a base shell of the spark plug, the lower region of the base shell having an inner spark contact surface.

8. The corona wind generating ignition device for internal combustion engines of claim 7, wherein at least one aperture is formed in a wall of the lower region of the base shell of the spark plug.

9. The corona wind generating ignition device for internal combustion engines of claim 7, wherein the inner spark contact surface is beveled.

10. The corona wind generating ignition device for internal combustion engines of claim 1 , wherein the ignition device comprises a spark plug in which the positive electrode is located near a lower region of the spark plug and comprises an enlarged member with a perimeter surface, and wherein the ground electrode comprises a lower region of a base shell of the spark plug with a plurality of points pointing generally downwardly therefrom towards an upper surface of the enlarged member of the positive electrode.

11. The corona wind generating ignition device for internal combustion engines of claim 10, wherein the enlarged member of the positive electrode is generally disk-shaped.

12. The corona wind generating ignition device for internal combustion engines of claim 10, wherein the enlarged member of the positive electrode is generally disk-shaped has a beveled perimeter edge which defines a spark contact area.

13. The corona wind generating ignition device for internal combustion engines of claim 10, further comprising at least one aperture formed in at least one of the enlarged member of the positive electrode and a sidewall of the base shell.

14. The corona wind generating ignition device for internal combustion engines of claim 1, wherein at least two points are provided, and the number of points is determined by the type of electrical ignition system of the internal combustion engine, and where more points are provided for higher power ignition systems.

15. The corona wind generating ignition device for internal combustion engines of claim 1 comprising a spark plug that is adapted to be used with conventional spark plug wires and conventional ignitions systems without additional electricity being delivered to the spark plug.

16. The corona wind generating ignition device for internal combustion engines of claim 1 , wherein the ignition device comprises a spark plug in which the positive electrode is located near a lower region of the spark plug and comprises a member with the plurality of points separated by unpointed regions, the ground electrode comprising a plurality of points separated by unpointed regions on a lower portion of a base shell of the spark plug, wherein the plurality of points of the positive electrode point towards the unpointed regions of the negative electrode, and the plurality of points of the negative electrode point towards the unpointed regions of the positive electrode.