JP2013098171A - Spark plug with undercut insulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spark plug for an internal combustion engine with reduced loads on an insulator.SOLUTION: The spark plug comprises: an elongated center electrode having a center electrode tip 28 at one end and a terminal proximate to the other end; an insulator 14 substantially surrounding the center electrode, the insulator 14 having a channel formed in an exterior surface of the insulator 14; and an outer shell 16 surrounding the insulator 14, the outer shell having a jam nut portion and a distal end extending from the jam nut portion, where the distal end of the outer shell 16 is aligned so as to be received in and engage the channel of the outer shell 16.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit of US Provisional Application No. 61 / 407,716, filed Oct. 28, 2010, the contents of which are hereby incorporated by reference.

The present application relates generally to spark plugs for internal combustion engines, and more specifically to a retaining nut-to-insulator interface that reduces the load on the insulator of the spark plug.
Conventional spark plug structures include an annular metal case having a thread near one end and a ceramic insulator extending from the threaded end through the metal case and beyond the opposite end. The center electrode is exposed near the threaded end, passes through an internal insulator, and is electrically connected to a terminal extending from the opposite end of the insulator, to which the spark plug is connected. Ignition cord is attached.

  The force applied to seal the spark plug at the tip is due to the torque transmitted by the threaded metal case, so the threaded part of the metal case must be sturdy and of considerable size . A portion of the metal case is formed to be engaged by a socket tool to impart torque to the threaded portion. The threaded portion is disposed away from the portion engaged by the socket tool.

  To facilitate efficient control of gas exhaust from the combustion chamber, the size of the valve may be increased. This inevitably reduces the size of the spark plug, reduces the size and robustness of the threaded metal case end, and is particularly effective for screwing the spark plug metal hole inner diameter and spark plug. It should be accompanied by a reduction in the combustion chamber wall area.

  As a result, the maximum diameter of the ceramic insulator is determined by the size of the hexagon nut or retaining nut portion of the outer shell. Therefore, for smaller hexagon nuts, the barrel diameter of the ceramic insulator is reduced. The diameter of the ceramic insulator is also defined by the clearance required for the shell hex nuts and pleats in addition to the shoulders required to keep the ceramic in place throughout its operating life.

  So far, for 14 mm and 16 mm hexagon nut spark plugs (12 mm spark plugs), the ceramic insulator diameter is different for each application and requires a separate spark boot. For example, a 14 mm hexagonal nut uses a 9.0 mm diameter ceramic barrel, and a 16 mm hexagonal nut uses a 10.5 mm diameter ceramic cylinder.

Accordingly, it would be desirable to provide a 14 mm hexagon nut spark plug that can use a larger diameter insulator than a 16 mm hexagon nut spark plug.
As the spark plug diameter decreases, the ability to hold the spark plug to its ground shield when removed may also decrease. Higher strength steel retaining nuts have been proposed to address this problem, but higher strength steel retaining nuts are assembled to insulators with greater load than lower strength steel retaining nuts, and therefore The impact strength of the insulator can be adversely affected.

US Pat. No. 5,091,672 US Pat. No. 5,697,334 US Pat. No. 5,918,571 US Pat. No. 6,104,130 US Patent Application Publication No. 2008/0272683 US Patent Application Publication No. 2009/0079319 US Patent Application Publication No. 2009/0121603 US Patent Application Publication No. 2009/0189503 US Patent Application Publication No. 2009/0189505 US Patent Application Publication No. 2009/0189506

  Accordingly, the inventor has recognized that it is desirable to provide a retaining nut-to-insulator interface that reduces the load on the insulator. The inventor also generally uses a smaller spark plug hex nut design with a ceramic insulator cylinder and spark cord associated with a larger spark plug hex nut design. Recognized that desirable.

  Exemplary embodiments of the present invention relate to spark plugs for internal combustion engines. This spark plug has an elongated center electrode having a center electrode tip at one end and a terminal close to the other end, and an insulator that substantially surrounds the center electrode, and has a channel formed on the outer surface of the insulator. And an outer shell surrounding the insulator, the outer shell having a retaining nut portion and a distal end extending from the retaining nut portion, the distal end of the outer shell being the outer shell's Housed in the channel and aligned to engage with it.

  Exemplary embodiments of the present invention also relate to a method of forming a spark plug. The method includes inserting an insulator into an outer shell of a spark plug, the insulator having a first portion, a second portion, and a third portion, wherein the first portion is an insulator. Disposed at one end, a third portion disposed at the opposite end of the insulator, a channel disposed between the second portion and the third portion, the second portion comprising the first portion and the third portion Thicker than the portion, the insulator further comprising a shoulder disposed between the channel and the second portion, and contacting the shoulder with the distal end of the outer shell, the distal end being Extending from the retaining nut portion of the outer shell, another shoulder of the insulator disposed between the first and second portions of the insulator and the distal end opposite the outer shell Securing a ground shield between.

1 is a side view of a spark plug according to an exemplary embodiment of the present invention. FIG. FIG. 2 is a cross-sectional side view of the exemplary spark plug shown in FIG. 1. It is a figure which shows the visual field along line 3-3 of FIG. FIG. 3 is an enlarged view of a part of FIG. 2.

  1-4 show the overall structure of an exemplary embodiment of the present invention. A spark plug 10 is shown and designed for an internal combustion engine. When the spark plug 10 is installed in the internal combustion engine, the spark plug 10 protrudes into a combustion chamber (not shown) of the engine through a threaded hole provided in an engine tip (not shown). This is realized by fitting the spark plug 10 as described above. The spark plug 10 comprises a cylindrical center electrode 12 extending along the axial length of the spark plug, an insulator 14 made of ceramic or the like that concentrically surrounds the center electrode 12, An outer shell 16 concentrically surrounding the insulator 14 is included.

  In the illustrated embodiment, the center electrode 12 has a cylindrical body with a tip 18 at one end, and the end 20 of the center electrode 12 opposite the tip 18 is through a conductive glass seal 24. It is electrically connected to the cylindrical terminal stud 22. In one embodiment, the conductive glass seal may be a fired-in seal. The glass seal serves as an electrical connection between the terminal stud and the center electrode. The terminal stud further includes a terminal nut 26 that is configured to be attached to an ignition cable (not shown) that supplies current to the plug when the plug is installed and protrudes from the insulator. In an alternative embodiment, a resistive element may be disposed between the terminal stud and the center electrode.

  The center electrode is covered by a longer coating than a conventional one with a highly heat and corrosion resistant metal material such as Inconel, another nickel-based alloy, or other suitable metal or alloy, such as copper May be provided with a core made of a thermally conductive metal material. In addition, the center electrode improves the heat transfer and maintains a spark gap to allow precious metal tips 28 such as those made from gold, palladium, or platinum alloys to function properly. In this way, it is bonded to the center electrode tip 18 and has any suitable form such as a flat one or a thin wire. As is known in the related art, the terminal stud can comprise a steel or steel-based alloy material with a nickel plating finish.

  As shown, the insulator is a substantially cylindrical elongated body having a first insulator section 30, a second insulator section 32, and a third insulator section 34, each having a different diameter. Having a body. The first insulator section substantially surrounds the central electrode and terminates at a distal end 36 having a tapered or flared configuration 38. The second insulator section is disposed between the first insulator section and the third insulator section, and the diameter of the second insulator section is larger than the diameters of the other two insulator sections. . The second insulator section and the narrower first insulator section are separated from each other by the shoulder 40.

  The spark plug further includes an outer shell 16 and a ground shield 44. The outer shell further comprises a retaining nut portion 46 at one end and an internal combustion engine seat portion 48 at the opposite end. A plurality of threads 50 are arranged between the retaining nut portion and the internal combustion engine seat surface portion that are configured to threadably engage a thread portion of a generally cylindrical opening that communicates with the combustion chamber of the internal combustion engine. The thread portion of the outer shell is configured to surround the second section of the insulator. The lock nut portion is formed integrally with the outer shell so that the spark plug can be removed in a spiral pattern when the lock nut screw is loosened and is easily and directly removed with very little inclination. In order to screw the spark plug into and out of the engine hole, a suitable socket tool can be engaged with the lock nut of the outer shell.

  The internal shell portion of the outer shell is aligned below the threaded section of the outer shell and juxtaposed with the insulator shoulder 40 when the spark plug assembly is complete. It includes a flare portion overlying a complementary flare section 52 of the ground shield. At this connection point, the ground shield and the outer shield are fixed to each other, and the insulator is captured therein.

  Next, with particular reference to FIGS. 2 and 4, the insulator further comprises a channel, groove or relief groove 54 formed in the outer surface of the insulator, the channel comprising a second portion of the insulator and a third portion. Resulting in an insulator section 56 disposed between the two portions. The section 56 has a reduced thickness that is thinner than adjacent portions of the second and third sections. The channel is also arranged to be aligned with a distal end 58 extending from the retaining nut portion.

  The distal end 58 further includes an inner shoulder 62 configured to engage the complementary shoulder 64 of the insulator. As shown, shoulder 64 is disposed between insulator channel portion 54 and second portion 32.

  At the opposite end of the channel, the insulator wall thickness increases at point 68 and a third insulator section projects from the distal end of the outer shell. As such, when the hexagonal portion of the retaining nut is 14 mm, the size of the third insulator section and the corresponding terminal stud insulator is to be used with a spark plug having a retaining nut with a dimension of 16 mm. Can be the same size. For example, a spark plug having a hexagonal nut size of 14 mm generally has a cylindrical portion size of 9 mm or a third section size, and a spark plug having a hexagonal nut size of 16 mm has a cylindrical shape of 10.5 mm. It will have the dimension of the part or the dimension of the third section. Furthermore, the size of the resulting terminal stud will vary according to the dimensions of the cylindrical portion. Therefore, by providing a pleat or channel 54 in the spark plug insulator, it is possible to use an insulator with a cylindrical portion dimension of 10.5 mm and a corresponding terminal stud with a spark plug having a hexagon nut size of 14 mm. it can. Of course, the foregoing ranges and dimensions are provided as examples only, and the exemplary embodiments of the present invention are intended to be limited to the specific ranges and dimensions disclosed herein. Absent.

  During assembly, the insulator is inserted axially into the outer shell in the direction of arrow 72, and then the internal combustion engine seat surface portion 48 is pressed over the flared portion 52 of the ground shield, The distal end 58 is channeled or relieved so that it is captured in the outer shell and ground shield assembly by the insulator shoulders 64 and 40 and the distal end 58 and the internal shell seat portion of the outer shell. It is pushed into the groove 56.

  Thus, the assembled outer shell and ground shield function as a unit. In an alternative configuration, the outer shell internal combustion engine seat portion and the ground shield portion 52 also use a joining technique such as brazing, laser welding, resistance welding, or plasma welding to secure the ground shield and retainer together. Can be joined together. In an exemplary embodiment of the invention, the internal combustion engine seat portion of the outer shell is “hot compressed” relative to the flare portion of the ground shield. The ground shield may also include a grounding strap for the ground electrode that extends above the center electrode tip. Moreover, the spark plug may have a variety of other configurations. Non-limiting examples of spark plug and ground shield / ground strap configurations include US Pat. No. 5,091,672, US Pat. No. 5,697,334, US Pat. No. 5,918,571, and US Pat. 6,104,130, as well as US Patent Application Publication No. 2008/0272683, US Patent Application Publication No. 2009/0079319, US Patent Application Publication No. 2009/0121603, US Patent Application Publication No. 2009/0189503, US Patent Application Publication No. 2009/0189505 and US Patent Application Publication No. 2009/0189506, each incorporated herein by reference.

  The outer shell will comprise a conductive metallic material, such as a nickel-plated carbon steel-based alloy, and the threaded section may have a thread outer diameter of about 12-16 mm or less and is threaded. The non-section can have an outer diameter of about 6-10 mm to provide a large engine space by providing a small diameter spark plug, as described above.

  The shape, size, and specific structure of the outer shell and insulator can, of course, vary significantly from design to design, so the attributes of the aforementioned dimensions of the outer shell and spark plug are merely a non-limiting illustration. As provided, exemplary embodiments of the present invention contemplate larger or smaller sizes than these values.

  Furthermore, the noble metal tip can be joined to the center electrode tip and the ground electrode strap by any suitable joining technique such as brazing, laser welding, resistance welding, or plasma welding.

  The insulator is formed from a non-conductive ceramic material, such as, for example, an alumina ceramic so as to hold the center electrode firmly while preventing an electrical short between the center electrode and the ground shield. Of course, other suitable equivalent materials may be used.

  Although the present invention has been described with reference to exemplary embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the scope of the present invention and equivalents thereof. It will be understood that this can be substituted for In addition, many modifications may be made to adapt a particular situation or material to the same scope without departing from the basic scope of the teachings of the invention. Accordingly, the invention is not limited to the specific embodiments disclosed as the best mode contemplated for carrying out the invention, but to the appended claims and their legal equivalents. It is intended to include all embodiments that fall within.

DESCRIPTION OF SYMBOLS 10 Spark plug 12 Center electrode 14 Insulator 16 Outer shell 18 Tip 20 Termination 22 Terminal stud 24 Conductive glass seal 26 Terminal nut 28 Precious metal tip 30 1st insulator area 32 2nd insulator area 34 3rd insulator Section 36 distal end 38 configuration 40 shoulder 44 ground shield 46 retaining nut section 48 internal combustion engine seat surface section 50 thread 52 section 54 channel 56 section 58 distal end 62 inner shoulder 64 shoulder 68 point 72 arrow

Claims (16)

A spark plug for an internal combustion engine,
An elongated center electrode having a center electrode tip at one end and a terminal proximate to the other end;
An insulator substantially surrounding the center electrode, the insulator having a channel formed on an outer surface of the insulator;
An outer shell surrounding the insulator, the outer shell having a retaining nut portion and a distal end extending from the retaining nut portion, wherein the distal end of the outer shell is the outer shell of the outer shell; An ignition plug for an internal combustion engine comprising: an outer shell received in the channel and aligned to engage with the channel.   The spark plug according to claim 1, wherein the retaining nut portion is formed integrally with the outer shell, and an outer surface of the outer shell adjacent to the retaining nut portion has a threaded portion.   3. The spark plug of claim 2, wherein the retaining nut portion is disposed between the distal end and a threaded portion of the outer shell, and the distal end opposite the outer shell is the outer shell. An internal combustion engine seat surface portion is defined, and the threaded portion is disposed between the retaining nut portion and the internal combustion engine seat surface portion.   4. The spark plug according to claim 3, wherein the insulator has a first portion, a second portion, and a third portion, and the first portion is disposed at one end of the insulator. The third portion is disposed on an opposite end of the insulator, the channel is disposed between the second portion and the third portion, and the second portion is disposed on the second portion. Spark plug thicker than part 1 and the third part.   5. The spark plug according to claim 4, wherein the insulator further comprises a shoulder disposed between the channel and the second portion, the shoulder being the distal end of the outer shell. A spark plug configured to engage a portion of the outer shell proximate to the outer shell.   6. The spark plug according to claim 5, wherein the insulator is made of a non-conductive ceramic material, the diameter of the retaining nut portion is approximately 14 mm, and the diameter of the section of the insulator is approximately 10 mm. plug.   6. The spark plug according to claim 5, wherein the center electrode extends from one end of the insulator and a terminal extends from the opposite end of the insulator.   5. The spark plug according to claim 4, wherein the insulator further includes another shoulder disposed between the first portion and the second portion. A spark plug configured to engage a distal end of a ground shield disposed between the internal combustion engine seat portion of the outer shell and the other shoulder. A method of forming a spark plug, comprising:
Inserting an insulator into an outer shell of the spark plug, the insulator having a first portion, a second portion, and a third portion, wherein the first portion is a portion of the insulator; Disposed at one end, the third portion is disposed at the opposite end of the insulator, a channel is disposed between the second portion and the third portion, and the second portion is The insulator further comprises a shoulder disposed between the channel and the second portion, the insulator being thicker than the first portion and the third portion;
Contacting the shoulder with a portion of the outer shell proximate to a distal end of the outer shell, the distal end extending from a retaining nut portion of the outer shell;
Securing a ground shield between another shoulder of the insulator and a distal end opposite the outer shell, wherein the other shoulder includes the first portion of the insulator and the first portion; A step disposed between the second portions.   10. The method of claim 9, wherein the retaining nut portion is integrally formed with the outer shell and the outer surface of the outer shell proximate to the retaining nut has a threaded portion.   11. The method of claim 10, wherein the retaining nut portion is disposed between the distal end and the threaded portion of the outer shell, and the distal end opposite the outer shell is the outer shell. The internal combustion engine seat surface portion is defined, and the threaded portion is disposed between the retaining nut portion and the internal combustion engine seat surface portion.   12. The method of claim 11, wherein the insulator has a first portion, a second portion, and a third portion, the first portion being disposed at one end of the insulator. The third portion is disposed at an opposite end of the insulator, the channel is disposed between the second portion and the third portion, and the second portion is disposed on the first portion. And thicker than the third part.   14. The method of claim 12, wherein the insulator further comprises a shoulder disposed between the channel and the second portion, the shoulder being the distal end of the outer shell. A method configured to engage.   14. The method of claim 13, wherein the insulator is made from a non-conductive ceramic material, the retaining nut portion dimension is approximately 14 mm, and the section diameter of the insulator is approximately 10 mm.   14. The method of claim 13, wherein the center electrode extends from one end of the insulator and a terminal extends from the opposite end of the insulator.   13. The method of claim 12, wherein the insulator further comprises another shoulder disposed between the first portion and the second portion, wherein the another shoulder is the outer side. A method configured to engage a distal end of a ground shield disposed between the internal combustion engine seat surface portion of the shell and the another shoulder.

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