Spark plug extension

Abstract

The present invention relates to a spark plug extension body connecting an ignition coil with a spark plug for a spark ignited internal combustion engine, as well as a method for providing such a spark plug extension body for reduction of partial electrical discharges in the spark plug extension body. In conventional spark plug extensions are coil springs used as electrical conductor against the spark plug terminal and/or ignition coil terminal. These coil springs cause Corona effects and short circuiting requiring replacement of the spark plug extension. With the invention the entire electrical conductor (CR.sub.u, 64, CR.sub.L) is in a rod like form and at least both ends (CR.sub.u, CR.sub.L) of the electrical conductor (CR.sub.u, 64, CR.sub.L) are made as a monolith in a flexible and electrically conducting polymeric material, preferably electrically conducting rubber.

Claims

1. A spark plug extension body connecting an ignition coil with a spark plug comprising: a spark plug boot; an extension housing; and an ignition coil connector; wherein said spark plug extension body includes a main axis and is configured for insertion into and/or removal out of a well associated with an internal combustion engine; wherein an elongated portion of the extension housing includes at least an electrical conductor and an electrical insulator arranged around the electrical conductor, wherein an upper portion of the ignition coil connector is removably connected to an ignition coil terminal, wherein a lower portion of the spark plug boot is removably connected to the spark plug, and wherein the electrical conductor is in a rod like form, the electrical conductor has a length that is between 100-500 mm, and at least both ends of the electrical conductor are made as a monolith in a flexible and electrically conducting polymeric material.

2. spark plug extension body according to claim 1, wherein at least a part of the electrical conductor is made in a solid rod like form.

3. A spark plug extension body according to claim 1, wherein at least a part of the electrical conductor is made in a tubular rod like form.

4. A spark plug extension body according to claim 1, wherein an entire length of the electrical conductor is made as a monolith in a flexible and electrically conducting polymeric material.

5. A spark plug extension body according to claim 1, wherein at least both ends of the electrical conductor are made in an electrically conductive rubber material.

6. A spark plug extension body according to claim 5, wherein the electrically conductive rubber material is selected from any of graphite rubber, nickel-graphite rubber, silver-copper-rubber or silicone rubber, and made by an extrusion or die moulding forming process.

7. A spark plug extension body according to claim 1, wherein the electrical conductor is located in a center of the elongated portion of the extension body completely filling a center volume.

8. A spark plug extension body according to claim 1, wherein an upper end portion of the electrical conductor includes a first end connector for connecting to an ignition coil terminal, and wherein a lower end portion of the electrical conductor includes a second end connector for a spark plug terminal, wherein the first and second ends are integral parts of the electrical conductor.

9. A spark plug extension body according to claim 8, wherein at least one end connector is a cylindrical sleeve made by the electrically conducting polymeric material, and wherein the cylindrical sleeve is arranged concentric with at least the ignition coil terminal or the spark plug terminal connected thereto and with an internal diameter of the cylindrical sleeve, before mounting the cylindrical sleeve on an ignition coil contact or the spark plug terminal, smaller than an outer diameter of the ignition coil terminal or the spark plug terminal.

10. The A spark plug extension body according to claim 8, wherein at least one end connector is a slotted cylindrical metal sleeve, wherein the slotted cylindrical sleeve is arranged concentric with at least an ignition coil contact or the spark plug terminal connected thereto and with the slotted cylindrical sleeve mounted by press fitting on an exterior of a lower flexible end element.

11. The spark plug extension body according to claim 1, wherein the electrical conductor as well as the electrical insulator are made by a flexible material, wherein the extension body is arranged to be transversally bendable in relation to the main axis so that an upper end portion and a lower end portion of the extension body may assume an angle (a) in relation to each other.

12. The spark plug extension body according to claim 1, wherein the electrical insulator is covered on an outer surface facing the a cylinder head around the well with an electrically conducting cover including a thin layer of an electrically conducting polymeric material.

13. The A method for reduction of partial electrical discharges in a spark plug extension body comprising: providing the spark plug extension body with an electrical conductor including a length that is between 100-500 mm, and an electrical insulator arranged around the electrical conductor; providing an upper ignition coil connector to an ignition coil terminal and a lower spark plug boot connectable to the spark plug in the spark plug extension body; and wherein the electrical conductor is provided in a rod like form with at least both ends of the electrical conductor made as a monolith in a flexible and electrically conducting polymeric material, and without air radial air gaps between the electrical conductor and a surrounding of the electrical insulator; wherein the electrical conductor is in a rod like form, the electrical conductor has a length that is between 100-500 mm, and at least both ends of the electrical conductor are made as a monolith in a flexible and electrically conducting polymeric material.

14. The method of claim 13, wherein the electrical conductor has a length that is at least 150 mm.

15. The spark plug extension body according to claim 1, wherein the electrical conductor has a length that is at least 150 mm.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1a is a side view of a spark plug extension body according to a first embodiment of the invention;

(2) FIG. 1b is a cross sectional view of the spark plug extension body as seen in view A-A in FIG. 1a;

(3) FIG. 1c is an enlarged detail view of the spark plug boot om FIG. 1b;

(4) FIG. 2a is a side view of a spark plug extension body according to a second embodiment of the invention;

(5) FIG. 2b is a cross sectional view of the spark plug extension body as seen in view B-B in FIG. 2a;

(6) FIG. 2c is an enlarged detail view of the spark plug boot om FIG. 2b;

(7) FIG. 3a is a side view of a spark plug extension body according to a second embodiment of the invention;

(8) FIG. 3b is a cross sectional view of the spark plug extension body as seen in view C-C in FIG. 3a;

(9) FIG. 3c is an enlarged detail view of the spark plug boot in FIG. 3b;

(10) FIG. 4a is an enlarged detail view of the spark plug boot according to an alternative inventive embodiment;

(11) FIG. 4b is a detail view of the end connector 66 seen in FIG. 4a, and

(12) FIG. 5 showing an alternative design of the electrical conductor 64.

DETAILED DESCRIPTION

(13) The invention will hereinafter be described in more detail with reference to the appended drawings. The following description should be considered as preferred form only, and is not decisive in a limiting sense.

First Embodiment

(14) In FIG. 1a is shown a side view of a first embodiment of a spark plug extension body according to the invention, and FIG. 1b shows a cross section of the spark plug extension body as seen in view A-A in FIG. 1 through the main axis CC. FIG. 1c shows an enlarged view of the spark plug boot in FIG. 1.b.

(15) The main parts of the spark plug extension body comprise a spark plug boot 10, an upper ignition coil connector 3 connectible to an ignition coil and an elongated extension housing 6.

(16) The spark plug extension body is configured for insertion in a well of a cylinder head in a conventional manner which well is associated with an internal combustion engine.

(17) The spark plug boot 10 and the coil connector 3 are connected to each other by means of the elongated extension housing 6 which comprises an inner conductor 64.

(18) In this first embodiment the inner conductor 64 may be any suitable conductor material, in form of a flexible or solid homogenous conductor.

(19) According to the invention at least both ends CR.sub.U and CR.sub.L of the electrical conductor 64 are made as a monolith in a flexible and electrically conducting polymeric material. Thus, the upper end element CR.sub.U and the lower end element CR.sub.L are preferably made as a solid body of electrically conductive material, more preferably electrically conductive rubber material. CR.sub.U and CR.sub.L may be die moulded with a recess for the spark plug terminal 2e in the lower end element CR.sub.L.

(20) The flexible upper end element CR.sub.U and the lower flexible end element CR.sub.L both provides for a positive bias force in the connecting points to the terminal 2e of the spark plug and the coil terminal (not shown) that may have a protruding pin that penetrates into the upper end element CR.sub.U when mounting the coil connector 3 to the ignition coil. The coil connector 3 may as seen in FIGS. 1a and 1b comprise a metallic or sturdy sleeve which may have surfaces for applying a spanner, and with internal threads that may be tightened to corresponding threads on the ignition coil housing.

(21) Further, the entire spark plug extension body may be provided with an outer electrically insulating housing 61 that may be casted thermoplastic material or similar, stretching all the way from the coil connector 3 and to the lower end of the spark plug boot 10. An elastic electrically insulating rubber sleeve 62 may also be provided for sealing the gap between the lower end of the boot 10 and the ceramic insulator 2i of the spark plug.

(22) Depending upon if the spark plug extension body needs to be flexible or not is the material of the insulating housing 61 and the inner conductor 64 chosen.

Second Embodiment

(23) In FIG. 2a is shown a side view of a second embodiment of a spark plug extension body according to the invention, and FIG. 2b shows a cross section of the spark plug extension body as seen in view B-B in FIG. 2 through the main axis CC. FIG. 2c shows an enlarged view of the spark plug boot in FIG. 2b.

(24) The main parts of the spark plug extension body comprise a spark plug boot 10, an upper ignition coil connector 3 connectible to an ignition coil and an elongated extension housing 6.

(25) As in the first embodiment are the spark plug boot 10 and the coil connector 3 connected to each other by means of the elongated extension housing 6 which comprises an inner conductor 64.

(26) In this second embodiment the inner conductor 64 may be any suitable conductor material, in form of a flexible or solid homogenous conductor, but here shaped as a hollow tube. This tube may or may not be void of any filler in the centre, or have a filling rod of any suitable filler material. The tube may also have a coil spring embedded in the tube material or have a supporting coil spring on the inside of the tube.

(27) According to the invention at least both ends CR.sub.U and CR.sub.L of the electrical conductor 64 are made as a monolith in a flexible and electrically conducting polymeric material. Thus, the upper end element CR.sub.U and the lower end element CR.sub.L are preferably made as a solid body of electrically conductive material, more preferably electrically conductive rubber material. CR.sub.U and CR.sub.L may be die moulded with a recess for the spark plug terminal 2e in the lower end element CR.sub.L.

(28) The flexible upper end element CR.sub.U and the lower flexible end element CR.sub.L both provides for a positive bias force in the connecting points to the terminal 2e of the spark plug and the coil terminal (not shown), which coil terminal may have a protruding pin that penetrates into the upper end element CR.sub.U when mounting the coil connector 3 to the ignition coil.

(29) The coil connector 3 may as seen in FIGS. 2a and 2b comprise a metallic or sturdy sleeve which may have surfaces for applying a spanner, and with internal threads that may be tightened to corresponding threads on the ignition coil housing.

(30) Further, the entire spark plug extension body may be provided with an outer electrically insulating housing 61 that may be casted thermoplastic material or similar, stretching all the way from the coil connector 3 and to the lower end of the spark plug boot 10. An elastic electrically insulating rubber sleeve 62 may also be provided for sealing the gap between the lower end of the boot 10 and the ceramic insulator 2i of the spark plug.

(31) Depending upon if the spark plug extension body needs to be flexible or not is the material of the insulating housing 61 and the inner conductor 64 chosen.

Third Embodiment

(32) In FIG. 3a is shown a side view of a third embodiment of a spark plug extension body according to the invention, and FIG. 3b shows a cross section of the spark plug extension body as seen in view C-C in FIG. 3a through the main axis CC. FIG. 3c shows an enlarged view of the spark plug boot 10 in FIG. 3b.

(33) The main parts of the spark plug extension body comprises as in previous embodiments of a spark plug boot 10, an upper ignition coil connector 3 connectible to an ignition coil and an elongated extension housing 6.

(34) The spark plug boot 10 and the coil connector 3 are connected to each other by means of the elongated extension housing 6 which comprises an inner conductor 64.

(35) In this third embodiment the inner conductor 64 may be any suitable conductor material, in form of a flexible or solid homogenous conductor.

(36) According to the invention at least both ends CR.sub.U and CR.sub.L of the electrical conductor 64 are made as a monolith in a flexible and electrically conducting polymeric material. Thus, the upper end element CR.sub.U and the lower end element CR.sub.L are preferably made as a solid body of electrically conductive material, more preferably electrically conductive rubber material. CR.sub.U and CR.sub.L may be die moulded with a recess for the spark plug terminal 2e in the lower end element CR.sub.L.

(37) The flexible upper end element CR.sub.U and the lower flexible end element CR.sub.L both provides for a positive bias force in the connecting points to the terminal 2e of the spark plug and the coil terminal (not shown) which coil terminal may have a protruding pin that penetrates into the upper end element CR.sub.U when mounting the coil connector 3 to the ignition coil.

(38) The coil connector 3 in the upper end may as seen in FIGS. 3a and 3b comprise a metallic or sturdy sleeve which may have surfaces for applying a spanner, and with internal threads that may be tightened to corresponding threads on the ignition coil housing.

(39) Further, the entire spark plug extension body may be provided with an outer electrically insulating housing in two parts 61a and 61b respectively that may be casted thermoplastic material or similar, which together are stretching all the way from the coil connector 3 and to the lower end of the spark plug boot 10. The upper part of the insulating housing 61a covers the coil connector 3 and a larger part of the elongated housing 61a and 61b, and may preferably be made in a flexible material allowing the extension body to be bent. The lower part 61b of the insulating housing covers the plug boot 10 and only a smaller part, at the most 50% of the length, of the elongated housing 61a and 61b.

(40) An elastic electrically insulating rubber sleeve 62 may also be provided for sealing the gap between the lower end of the boot 10 and the ceramic insulator 2i of the spark plug.

(41) Depending upon if the spark plug extension body needs to be flexible or not is the material of the insulating housing 61 and the inner conductor 64 chosen.

Fourth embodiment

(42) In FIG. 4a is shown an alternative detail embodiment, which otherwise have all other details similar to the third embodiment. Here is the lower flexible end element CR.sub.L also equipped with a slotted cylindrical metal sleeve 66, with the sleeve arranged concentric with the spark plug terminal 2e connected thereto and with the sleeve mounted by press fitting on the exterior of the lower flexible end element CR.sub.L. The slot 66a allows the sleeve 66 to expand when mounting on top of the spark plug terminal 2e, and the inner diameter of the sleeve has a diameter slightly less than the outer diameter of the spark plug terminal 2e, typically by 0.1-1 mm. Also in this embodiment may the end face of the ignition plug terminal 2e come into abutting contact with the lower flexible end element CR.sub.L, avoiding any air pockets therebetween.

Fifth Embodiment

(43) In FIG. 5 is shown yet an alternative detail embodiment, where not only the ends CR.sub.U and CR.sub.L of the electrical conductor 64 are made as a monolith in a flexible and electrically conducting polymeric material but instead the entire electrical conductor, with the ends CR.sub.U and CR.sub.L as well as the intermediate connector 64 all made in the same material, and thus forms one single monolith body of electrically conducting polymeric material. As seen here is the lower flexible end part CR.sub.L equipped with a recess for the spark plug terminal in the same way as in embodiments shown in FIG. 1-3, but may also have an end like the embodiment shown in FIG. 4.

SUMMARY

(44) The spark plug extension body according the invention provides with a solution avoiding usage of the conventional coil springs that are used to establish electrical contact with the spark plug terminal and/or the ignition coil terminal. The risk of corona effects in these coil springs is radically reduced and the spark plug extension body obtains an extended MTBF and thus saves operating costs and increased operability of the spark ignited engine.

(45) The invention is not to be seen as limited by the embodiments described above, but can be varied within the scope of the appended claims. For instance, the flexible material of the extension body may be a material other than rubber, and further the extension body may vary in length depending on the depth of the well 90.

(46) Many other variations are also possible, as will be readily understood by the person skilled in the art.