Spark Plug

Abstract

A spark plug having in combination an adjustable axial air gap spark and circumferentially interrupted ground electrode means which creates a surface flame spark. The surface flame and air gap spark are transverse to each other, permitting adjustment of the shorter air gap spark electrode. The spark plug comprises a central electrode within an insulator, an air gap surrounding the insulator and a ground electrode carrying a pin which extends over the central electrode. In one embodiment, the air gap is relatively narrow, and carbon-reducing slots are formed in the ground electrode. In a second embodiment, radially adjustable surface flame ground electrode pins are provided. In another embodiment, a non-adjustable pin is carried by the ground electrode for the surface flame. In still another embodiment, a single J-shaped pin acts both as an adjustable air gap spark electrode and an adjustable surface flame electrode.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to spark plugs for internal combustion engines, and particularly to installations where misfire may be caused by electrical resistance elements of radios or other components which are disposed between the high voltage ignition coil and the spark plug itself. More particularly, the invention relates to spark plugs of the type having the combination of an air gap spark electrode and a surface flame electrode. It is an object of the invention to provide such a spark plug which furnishes easier low voltage cold motor starting, smoother motor performance, greater gas mileage, more horsepower and longer plug life.

2. Description of the Prior Art

Beesch U.S. Pat. No. 3,313,972 shows a spark plug with combined high tension gap and creepage spark gap. This patent, however, has several shortcomings with respect to the present invention. Among others, the high tension gap is not at right angles to the creepage gap and is not adjustable. Burley, et al. U.S. Pat. Nos. 3,488,544 and 3,488,556 show a spark plug with a semiconductor teaser gap. This construction has several shortcomings compared with the present invention, including the possibility of carbon formation on the face of the semiconductor which could cause malfunction of the plug. Lang U.S. Pat. No. 895,030 shows another spark plug designed to produce two sparks, but which is constructed and functions differently than the present invention. Other patents found in a search but which are not deemed to anticipate the present invention are the following:

Re 15,304 2,563,625 1,315,935 2,578,754 1,815,423 2,609,808 1,962,869 2,852,713 1,984,952 2,870,363 2,017,364 2,890,365 2,136,206 2,899,585 3,313,972

BRIEF SUMMARY OF THE INVENTION

Briefly, the invention comprises a spark plug having an elongated central electrode surrounded by an insulator body, the latter being in turn surrounded by a ground electrode with an end face spaced from the insulator and circumferentially interrupted means for producing a surface flame spark across the end face of the insulator. A pin is secured to the ground electrode end face and extends outwardly and then over the central electrode, the spacing between this pin and the central electrode being substantially less than the spacing between the central and ground electrodes across the insulator and face. The short air gap between the central electrode and pin is adjustable by bending the pin. In a preferred example, the air gap spark is 0.030 inch and the spark across the insulator end face, or surface flame spark, is 0.060 inch, giving a combined right angle spark length of 0.090 inch.

With this construction it has been found that detrimental surface flame misfire, caused for example by radio or other resistance components positioned between the high voltage ignition coil and plug, are eliminated. During low voltage cold motor starting, the invention provides maximum electrode spark and surface flame fire areas. The construction also provides smoother motor performance, greater gas mileage, more horsepower and longer plug life, and is excellent for higher compression liquefied petroleum propane operation. The novel spark plug further furnishes effective sparking through the surface flame when high compression cylinder turbulence tends to squeeze or blow out the air gap spark. The adjustable nature of the pin permits the spark plug to be adapted to any of various cylinder compression and ignition voltage conditions. The positioning of the short air gap pin over the central electrode reduces the likelihood of excessive carbon, scale or crust accumulation on the end of the central electrode, thus contributing to greater surface flame firing. The short air gap electrode pin also acts as a standby electrode to eliminate excessive or continuous arcing and overload of the surface flame path on the insulator. Moreover, the shorter air gap spark will automatically take over and operate satisfactorily in case the surface flame path of the insulator becomes cracked or otherwise damaged from the severe heat and pressure in the combustion chamber.

In a first embodiment of the invention, the end face of the ground electrode is relatively close to the insulator end face, and angularly spaced radial slots are formed in the ground electrode end face to reduce the surface flame area and the possibility of carbon fouling deposits. This will reduce the likelihood of misfire or quenching of the surface flame which is generally caused by excessive carbon buildup and oil formation. The pin in this embodiment is arched or curved to permit a more even distribution of the surface flame between the central and ground electrodes. The construction shown in this embodiment is suitable for use over a relatively broad temperature range.

In a second embodiment of the invention, a plurality of angularly spaced pins are threadably mounted in the ground electrode and extend radially inwardly, thus serving as adjustable surface flame electrodes. This construction is adapted for installation on previously manufactured conventional spark plugs or may be utilized in original manufacture without requiring extensive changes in molds, dies or the like used for forming conventional spark plugs. It may also be used to convert conventional spark plugs to high compression racing plugs, and high compression plugs for propane fuel operation.

A third embodiment of the invention utilizes a relatively short radially extending pin in addition to the first-mentioned pin, this second pin acting as a non-adjustable surface flame electrode.

In a fourth embodiment of the invention, the pin which extends outwardly and then over the central electrode, extends past the central electrode and then inwardly. The pin thus serves a dual purpose, namely an adjustable short air gap spark electrode and an adjustable surface flame electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view, partly sectioned, showing a first embodiment of the spark plug incorporating the principles of this invention.

FIG. 2 is a bottom plan view of the plug of FIG. 1 showing the slotted ground electrode.

FIG. 3 is a fragmentary elevational view, partly sectioned, showing a second embodiment of the invention with adjustable flame ground electrodes.

FIG. 4 is a bottom plan view of the embodiment of FIG. 3 showing the locations of the adjustable surface flame ground electrodes.

FIG. 5 is a fragmentary cross-sectional view in elevation showing a third embodiment of the invention in which the ground electrode is provided with a pin for the surface flame.

FIG. 6 is a partially sectioned fragmentary elevational view showing a fourth embodiment of the invention in which a single pin extending from the ground electrode acts both as an adjustable air gap spark electrode and an adjustable surface flame electrode, and

FIG. 7 is a chart showing the relative performance of a conventional single gap spark plug and the plug of this invention under varying pressures.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to the embodiment shown in FIGS. 1 and 2, the spark plug is generally indicated at 11 and comprises a central electrode 12 of tapered shape extending through an insert cap 13 in the upper end of an insulator 14 fabricated of porcelain or similar material. A terminal 15 surmounts the central electrode and is in electrical contact therewith. The lower end of insulator 14 is surrounded by a ground electrode 16 with gaskets 17 and 18 being disposed between the ground electrode and insulator. The lower end 19 of ground electrode 16 is threaded for mounting in the engine.

In this embodiment, the end surfaces 21 and 22 of the central electrode and insulator respectively are substantially flush. An air gap 23 is provided between the lower end 19 of ground electrode 16 and the outer edge of end surface 22 of the insulator. In a preferred construction, the radial distance from end surface 21 of the central electrode to end surface 24 of the ground electrode could be 0.060 inches.

A plurality of relatively large radial slots 25 are provided in the end face 24 of ground electrode 16. These slots are seen best in FIG. 2, four being shown in the present embodiment. The presence of slots 25 will greatly reduce the fire area of the ground electrode, in this case to approximately one-half that which would be present with an uninterrupted end surface. The purpose of the slots is to reduce the possibility of misfire or quenching of the surface flame which could be caused by excessive carbon buildup and oil formation, bearing in mind that the air gap 23 in the embodiment of FIGS. 1 and 2 is relatively narrow.

A pin 26 is secured at one end to end surface 24 of ground electrode 16 and extends inwardly, the other end being disposed directly over end surface 21 of central electrode 12. End 26 thus forms an adjustable spark air gap with the central electrode which is at right angles to the surface flame spark. Preferably, end 26 is arched or curved as shown to reduce the tendency of the surface flame to follow a channel path under the pin, which might occur if the pin were too close to the end surface 22 of insulator 14. The arched construction of the pin will permit the surface flame to distribute itself more evenly around the end surface 24 of the ground electrode. In a preferred example, the air gap between electrode 12 and pin 26 is 0.030 inches.

A series of tests of the novel spark plug (the two embodiments of FIGS. 1 to 4) in a transparent chamber, with various pressures, disclosed the following spark and surface flame performance (FIG. 7) with a standard 12 volt primary and high volt secondary ignition input, compared with a conventional spark plug. At atmospheric pressure both surface flame and air gap sparks fire, the short spark master firing. As the pressure increases, the spark and surface flame brighten and the lower resistance surface flame begins to predominate and master fires. Although both the short the spark and surface flame may fire simultaneously, depending on resistance and voltage reserve, or can shift back and forth, the surface flame tends to dominate as the pressure increases. At still higher pressures, approximately 90 to 220 p.s.i. or higher, the larger surface flame will completely predominate and will fire until squeezed out. In comparison, a conventional plug with 0.035 inch air gap was squeezed out at approximately 130 p.s.i.

Tests have indicated that the occasional dead spot or flameout misfire which occurs through the fuel acceleration cycle due, for example, to radio resistance wires installed between the high voltage ignition coil and plugs, tend to be corrected by the invention, namely the presence of the adjustable short air gap spark and the large surface flame right angle combination.

FIGS. 3 and 4 illustrate a second embodiment of the invention which incorporates the basic principles described above but has a plurality of adjustable pins on the ground electrode for the surface flame portion of the firing combination. The spark plug is generally indicated at 101 and comprises a central electrode 102, an insulator 103 and a ground electrode 104. In this case, the end face 105 of the ground electrode is more widely spaced from the end face 106 of the central electrode than in the previous embodiment, leaving a larger air gap 107. Moreover, the end face 108 of insulator 103 is recessed from the end face 106 of central electrode 102. Pin 109 in L-shaped, one end being secured to end face 105 (which is uninterrupted in this embodiment) and the other end extending over central electrode 102 to form a relatively short spark gap at right angles to the surface flame spark.

A plurality of pins 111 are threadably mounted in threaded portion 112 of central electrode 104 and extend inwardly toward insulator 103 adjacent its end face 108. Pins 111 are adjustable toward or away from central electrode 102 by their threaded nature. They will act as surface flame ground electrodes, similar to the segments of end surface 24 in the previous embodiment. Four such pins are shown in FIG. 4 although the number and size of pins could be varied to suit requirements. This construction could be adapted for installation on previously manufactured conventional spark plugs such as by drilling and tapping the threaded portions of the ground electrode to receive pins 111. Such an arrangement could be used to convert conventional plugs into high compression racing plugs.

FIG. 5 illustrates a third embodiment of the invention which again has the same principles but incorporates a non-adjustable surface flame electrode pin. The spark plug is generally indicated at 201 and has a central electrode 202, an insulator 203 and a ground electrode 204 with a threaded portion 205. The end face 206 of insulator 203 is recessed from the end surface 207 of central electrode 202, and an air gap 208 is formed between the uninterrupted annular end surface 209 of ground electrode 204 and insulator 203. An L-shaped pin 211 is secured to the ground electrode end surface and extends over central electrode 202 as in the previous embodiment.

A second L-shaped pin 212 is secured to end surface 209 of ground electrode 204 opposite pin 211. Pin 212 serves as a non-adjustable surface flame ground electrode, extending toward the end surface 206 of insulator 203. As in the previous embodiments, the flame surface spark will be substantially longer than the air gap spark. In a typical example, the air gap spark will be 0.025 inches and the surface flame spark 0.060 inches.

FIG. 6 illustrates a fourth embodiment of the invention generally indicated at 301. The spark plug in this case has a central electrode 302, an insulator 303 and a ground electrode 304. As in the embodiment of FIG. 5, end surface 305 of central electrode 302 extends outwardly past end surface 306 of insulator 303. End surface 307 of ground electrode 304 is spaced radially outwardly from the insulator to form an air gap 308.

The pin in FIG. 6 is generally indicated at 309 and comprises a relatively short leg 311 fixed to end surface 307 of the ground electrode, a relatively long leg 312 extending over and past end surface 305 of central electrode 302, and a relatively short outer end 313 which extends back inwardly parallel to the spark plug axis toward air gap 308. Portion 312 of pin 309 will act to induce a relatively short air gap spark with the central electrode as in the previous embodiment. Portion 313, however, being disposed between end surface 307 of ground electrode 304 and end surface 306 of the insulator, will induce a surface flame spark at right angles to the air spark. The positions of both portions 312 and 313 of pin 309 will be adjustable with respect to the central electrode by bending pin 311 at corners 314 and 315 respectively. A slight air gap 316 is provided between end 313 of pin 309 and insulator end face 306 to increase resistance and force firing of the surface flame.

The exposed ends of the central electrode in embodiments of FIGS. 3, 5 and 6 are utilized to gain additional electrode fire area and increase the depth and/or width of the surface flame to pins 111, 212, or pin portion 313 as the case may be. Normally, the surface flame spark will occupy the shortest distance or path from the exposed portion of the central electrode to ground. Carbon buildup on and around the end face of the insulator and the exposed portion of the central electrode will shift the surface flame to a new path of least resistance which could be a curved path anywhere around the exposed "neck" of the central electrode to the ground.

Claims

What is claimed is:

1. In a spark plug, a central electrode, an insulator surrounding said electrode and having an end surface, a ground electrode surrounding said insulator, a pin secured to said ground electrode and extending over the end surface of said central electrode to form a relatively short adjustable air gap spark extending in the direction of the spark plug axis, said air gap spark being adjustable by bending said pin, and means spaced radially outwardly from the end surface of said insulator to form circumferentially interrupted means on said ground electrode inducing a relatively long surface flame spark transverse to said air gap spark.

2. The combination according to claim 1, said last-mentioned means comprising a circumferentially interrupted end surface on said ground electrode.

3. The combination according to claim 2, said pin being arched so that its mid-portion is further away from the end face of said insulator than its end portion is from said central electrode end face.

4. The combination according to claim 1, said last-mentioned means comprising a plurality of circumferentially spaced pins mounted on said ground electrode and extending inwardly toward the said insulator.

5. The combination according to claim 4, said pins being threadably mounted in said ground electrode so as to be adjustable toward and away from the insulator.

6. The combination according to claim 1, said last-mentioned means comprising a second pin secured to the end surface of said ground electrode and angularly spaced from said first pin, the second pin extending toward said insulator end face.

7. The combination according to claim 1, said central electrode having a neck portion extending outwardly beyond the end surface of said insulator.

8. The combination according to claim 1, said last-mentioned means comprising an end portion on said pin extending axially inwardly toward said insulator end face, the air gap between said last-mentioned pin portion and the insulator end face being adjustable by bending the pin.

9. The combination according to claim 1, the length of said air gap spark being 0.030 inches, the length of said surface flame spark being 0.060 inches.

10. The combination according to claim 1, the length of said flame surface spark being approximately 0.060 inches.