JP2013016296A - Ignition plug and gasket - Google Patents

Abstract

PROBLEM TO BE SOLVED: To significantly reduce labor and time when a gasket is replaced.SOLUTION: An ignition plug 1 includes: a cylindrical main body metal fitting 3 extending along an axis line CL1; and a solid annular gasket 18 provided in the outer periphery of the main body metal fitting 3. The metal body metal fitting 3 includes a mounting male screw part 15 formed in the outer periphery on the tip side thereof; and a seat part 16 which is formed at the rear end side from the male screw part 15 and swollen to the radially outer side. The gasket 18 of which the inner diameter is made smaller than a screw diameter of the male screw part 15 is provided between the male screw part 15 and the seat part 16. A female screw part 41 capable of being screwed to the male screw part 15 is formed in the inner periphery of the gasket 18.

Description

  The present invention relates to a spark plug used for an internal combustion engine or the like, and a gasket used for the spark plug.

  The spark plug is attached to a combustion device such as an internal combustion engine (engine), and is used for igniting an air-fuel mixture in the combustion chamber. In general, a spark plug is composed of an insulator having a shaft hole, a center electrode inserted through the distal end side of the shaft hole, a metal shell provided on the outer periphery of the insulator, and a base end portion at the tip of the metal shell. A ground electrode that is joined and has a tip portion that forms a spark discharge gap with the center electrode is provided. In addition, a male screw part for attaching the spark plug to the combustion device is formed on the metal shell, and a solid annular gasket may be attached to the screw neck of the male screw part (see, for example, Patent Document 1). When the spark plug is attached to the combustion device, the gasket ensures airtightness between the spark plug (metal shell) and the combustion device. The gasket has an inner diameter that is larger than the thread diameter of the male thread before mounting to the metal shell, and after being placed around the screw neck, a predetermined jig is pressed against the inside in the radial direction. By being plastically deformed (for example, clawed out), the inner diameter thereof is made smaller than the screw diameter of the male screw portion, and as a result, it is attached to the metal shell.

JP 2008-135370 A

  By the way, in the spark plug removed from the combustion device, the gasket may be crushed and deformed, or may be softened due to the influence of heat associated with the use of the combustion device. If the spark plug is reattached to the combustion device while the gasket remains in this state, the airtightness may be reduced.

  Therefore, in order to prevent a decrease in airtightness, it is conceivable to replace the gasket with a new one before reattaching the spark plug. However, in order to remove the gasket attached by plastic deformation as described above from the metal shell, it takes time-consuming work such as cutting the gasket, and when attaching a new gasket to the metal shell, The above-described processing needs to be performed on the gasket. Therefore, much labor and time are required for the gasket replacement operation.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ignition plug or the like that can drastically reduce labor and time when a gasket is replaced.

  Hereinafter, each configuration suitable for solving the above-described object will be described in terms of items. In addition, the effect specific to the corresponding structure is added as needed.

Configuration 1. The spark plug of this configuration includes a cylindrical metal shell extending along the axis,
A solid annular gasket provided on the outer periphery of the metal shell,
The metallic shell is
A male screw part for mounting formed on the outer periphery of the tip side of itself,
A seat portion formed on the rear end side of the male screw portion and bulging radially outward;
The gasket is an ignition plug having an inner diameter smaller than the screw diameter of the male screw portion and provided between the male screw portion and the seat portion,
A female screw part that can be screwed into the male screw part is formed on the inner periphery of the gasket.

  According to the said structure 1, the internal thread part which can be screwed with respect to the external thread part of a metal shell is formed in the inner periphery of a gasket. Therefore, when the gasket is attached to the metal shell, the gasket can be easily attached between the male screw portion and the seat portion by being inserted (screwed) while rotating the gasket relative to the male screw portion. Further, since the inner diameter of the gasket is made smaller than the thread diameter of the male thread portion, it is possible to prevent the attached gasket from falling off the metal shell.

  On the other hand, when removing the gasket from the metal shell, the gasket can be easily removed by retreating (screwing) while rotating the gasket relative to the male thread portion. That is, according to the said structure 1, both attachment and removal of a gasket can be performed easily, and the effort and time which replacement | exchange of a gasket require can be reduced drastically. Further, by replacing the gasket with a new one, it is possible to more reliably prevent a decrease in airtightness when the spark plug is attached to the combustion device again.

  Configuration 2. The spark plug of this configuration is characterized in that, in the above configuration 1, any one of the following (a) to (c) is satisfied.

(A) The screw diameter of the male screw portion is M14 and the inner diameter of the gasket is 13.2 mm or more. (B) The screw diameter of the male screw portion is M12 and the inner diameter of the gasket is 11.2 mm or more. (C) The thread diameter of the male threaded portion is M10, and the inner diameter of the gasket is 9.4 mm or more. The “inner diameter of the gasket” is defined in “Messenger” defined in JIS B0205-4. This refers to the reference dimension d1 of the screw inner diameter.

  When the gasket is attached to a combustion apparatus such as an internal combustion engine, the gasket is crushed and deformed, and the inner peripheral portion of the gasket projects radially inward. By setting according to the screw diameter, there is a sufficient gap between the inner periphery of the gasket and the male screw portion even when the deformed gasket is removed from the metal shell. Therefore, the gasket can be removed more easily, and as a result, the gasket can be replaced more easily.

  Configuration 3. The spark plug of this configuration is characterized in that, in the above configuration 1 or 2, the thickness of the gasket along the radial direction is 0.20 mm or more in the valley portion of the female screw portion.

  When the rigidity of the gasket is insufficient, the gasket may be easily deformed due to unintentional dropping or the like when handling the spark plug. If the gasket is deformed, the airtightness may not be sufficiently secured when the spark plug is attached to the combustion device.

  In this regard, according to Configuration 3, the thickness of the gasket along the radial direction is 0.20 mm or more in the valley portion of the female screw portion, and the gasket has sufficient rigidity. Therefore, the deformation of the gasket due to dropping or the like can be prevented more reliably, and as a result, the deterioration of the airtightness can be more reliably prevented.

  Configuration 4. The spark plug of this configuration is characterized in that in any one of the above configurations 1 to 3, the gasket is made of copper or an alloy containing copper as a main component.

  According to the said structure 4, the gasket is comprised with the alloy which has copper or copper as a main component, and is equipped with the outstanding heat conductivity. Therefore, in the spark plug attached to the combustion device, the heat of the metal shell can be efficiently conducted to the combustion device side through the gasket. As a result, the malfunction of the spark plug due to overheating (for example, consumption of the center electrode) can be prevented more reliably.

  Configuration 5. The spark plug of this configuration is characterized in that, in any one of the above configurations 1 to 3, the gasket is made of iron or an alloy containing iron as a main component.

  According to the configuration 5, the gasket can be manufactured at a low cost while ensuring the thermal conductivity of the gasket to some extent.

  Configuration 6. The gasket of this configuration is used for the spark plug according to any one of the above configurations 1 to 5.

  By using the gasket of the above configuration 6 for a spark plug in which a male screw part is formed on the metal shell, the same effects as the above configuration 1 and the like can be obtained.

It is a partially broken front view which shows the structure of a spark plug. It is a partial expanded sectional view which shows the structure of a gasket, etc.

  Hereinafter, an embodiment will be described with reference to the drawings. FIG. 1 is a partially cutaway front view showing a spark plug 1. In FIG. 1, the direction of the axis CL <b> 1 of the spark plug 1 is the vertical direction in the drawing, the lower side is the front end side of the spark plug 1, and the upper side is the rear end side.

  The spark plug 1 is composed of a cylindrical insulator 2, a cylindrical metal shell 3 that holds the insulator 2, and the like.

  As is well known, the insulator 2 is formed by firing alumina or the like, and in its outer portion, a rear end side body portion 10 formed on the rear end side, and a front end than the rear end side body portion 10. A large-diameter portion 11 that protrudes radially outward on the side, a middle body portion 12 that is smaller in diameter than the large-diameter portion 11, and a tip portion that is more distal than the middle body portion 12. The leg length part 13 formed in diameter smaller than this on the side is provided. Of the insulator 2, the large-diameter portion 11, the middle trunk portion 12, and most of the leg long portions 13 are accommodated inside the metal shell 3. A stepped portion 14 tapering toward the distal end is formed at the connecting portion between the middle body portion 12 and the leg long portion 13, and the insulator 2 is locked to the metal shell 3 at the stepped portion 14. ing.

  Further, a shaft hole 4 is formed through the insulator 2 along the axis CL1. A center electrode 5 is inserted on the tip side of the shaft hole 4. The center electrode 5 includes an inner layer 5A made of copper, a copper alloy or the like excellent in thermal conductivity, and an outer layer 5B made of a Ni alloy containing nickel (Ni) as a main component. Further, the center electrode 5 has a rod shape (cylindrical shape) as a whole, and a tip portion thereof protrudes from the tip of the insulator 2. Further, a noble metal tip 31 made of a noble metal alloy (for example, an iridium alloy or a platinum alloy) is joined to the tip of the center electrode 5.

  A terminal electrode 6 is inserted and fixed on the rear end side of the shaft hole 4 in a state of protruding from the rear end of the insulator 2.

  Further, a cylindrical resistor 7 is disposed between the center electrode 5 and the terminal electrode 6 of the shaft hole 4. Both ends of the resistor 7 are electrically connected to the center electrode 5 and the terminal electrode 6 through conductive glass seal layers 8 and 9, respectively.

  In addition, the metal shell 3 is formed in a cylindrical shape from a metal such as low carbon steel, and a spark plug 1 is attached to the outer peripheral surface of the metal shell 3 in a mounting hole for a combustion device (for example, an internal combustion engine or a fuel cell reformer). A male screw portion 15 is formed to be attached to. A flange-shaped seat 16 bulging radially outward is formed on the rear end side of the male screw portion 15, and is formed on the outer periphery of a cylindrical screw neck 17 positioned between the male screw portion 15 and the seat portion 16. Is fitted with a ring-shaped gasket 18 (the configuration of the gasket 18 will be described in detail later). Furthermore, a tool engagement portion 19 having a hexagonal cross section for engaging a tool such as a wrench when the metal shell 3 is attached to the combustion device is provided on the rear end side of the metal shell 3. A caulking portion 20 for holding the insulator 2 is provided. In addition, in this embodiment, the screw diameter of the male screw portion 15 is M14. In addition, the screw diameter of the external thread part 15 is changeable, for example, it is good also as M12 and M10.

  Further, a tapered step portion 21 for locking the insulator 2 is provided on the distal end side of the inner peripheral surface of the metal shell 3. The insulator 2 is inserted from the rear end side to the front end side of the metal shell 3, and the rear end of the metal shell 3 is engaged with the step portion 14 of the metal shell 3. It is fixed to the metal shell 3 by caulking the opening on the side inward in the radial direction, that is, by forming the caulking portion 20. An annular plate packing 22 is interposed between the stepped portions 14 and 21. Thereby, the airtightness in the combustion chamber is maintained, and the fuel gas entering the gap between the leg long portion 13 of the insulator 2 exposed to the combustion chamber and the inner peripheral surface of the metal shell 3 is prevented from leaking outside.

  Further, in order to make the sealing by caulking more complete, annular ring members 23 and 24 are interposed between the metal shell 3 and the insulator 2 on the rear end side of the metal shell 3, and the ring member 23 , 24 is filled with powder of talc (talc) 25. That is, the metal shell 3 holds the insulator 2 via the plate packing 22, the ring members 23 and 24, and the talc 25.

  In addition, a ground electrode 27 is joined to the front end portion 26 of the metal shell 3 with its middle portion bent back and the side surface of the front end portion facing the front end portion (the noble metal tip 31) of the center electrode 5. The ground electrode 27 is formed of an outer layer 27A formed of a Ni alloy [for example, Inconel 600 or Inconel 601 (both are registered trademarks)], a copper alloy, pure copper, or the like, which is a better heat conductive metal than the Ni alloy. And an inner layer 27B. Further, a spark discharge gap 33 is formed between the tip surface of the noble metal tip 31 and the tip of the ground electrode 27, and spark discharge is performed in the spark discharge gap 33 in a direction substantially along the axis CL1. It has come to be.

  Next, the structure of the gasket 18 which is a characteristic part of the present invention will be described.

  The gasket 18 is made of copper having excellent thermal conductivity or an alloy containing copper as a main component, and has a solid annular shape. As shown in FIG. 2, the inner diameter D of the gasket 18 is made smaller than the screw diameter of the male screw portion 15 and the outer diameter of the seat portion 16 in order to prevent the gasket 18 from falling off the metal shell 3. The gasket 18 may be formed of iron or an alloy containing iron as a main component.

  Furthermore, an internal thread portion 41 that can be screwed into the external thread portion 15 of the metal shell 3 is provided on the inner periphery of the gasket 18. In the present embodiment, as described above, since the screw diameter of the male screw portion 15 is M14, the inner diameter D of the gasket 18 is 13.2 mm or more. When the screw diameter of the male screw portion 15 is M12, the inner diameter D of the gasket 18 is 11.2 mm or more. When the screw diameter of the male screw portion 15 is M10, the inner diameter of the gasket is 9.4 mm. It is said above. Here, “the inner diameter D of the gasket 18” refers to the “reference dimension d1 of the inner diameter of the female screw” defined in JIS B0205-4.

  Further, in the valley portion 42 of the female screw portion 41, the thickness T of the gasket 18 along the radial direction (the direction orthogonal to the axis CL1) is set to 0.20 mm or more.

  As described above in detail, according to the present embodiment, the female screw portion 41 that can be screwed into the male screw portion 15 of the metal shell 3 is formed on the inner periphery of the gasket 18. Therefore, when the gasket 18 is attached to the metal shell 3, the gasket 18 is easily moved between the male screw portion 15 and the seat portion 16 by being inserted (screwed) while being relatively rotated with respect to the male screw portion 15. Can be installed. Further, since the inner diameter of the gasket 18 is smaller than the screw diameter of the male screw portion 15 and the outer diameter of the seat portion 16, it is possible to more reliably prevent the attached gasket 18 from falling off the metal shell 3.

  On the other hand, when removing the gasket 18 from the metal shell 3, the gasket 18 can be easily removed by retreating (screwing) while rotating the gasket 18 relative to the male screw portion 15. That is, according to this embodiment, both the attachment and removal of the gasket 18 can be easily performed, and the labor and time required for the replacement work of the gasket 18 can be drastically reduced. Further, by replacing the gasket 18 with a new one, it is possible to more reliably prevent a decrease in airtightness when the spark plug 1 is attached to the combustion device again.

  Furthermore, the inner diameter D of the gasket 18 is set as described above in accordance with the thread diameter of the male screw portion 15, so that the inner circumference of the gasket 18 can be removed even when the deformed gasket 18 is removed from the metal shell 3. And a sufficient gap exists between the male screw portion 15 and the male screw portion 15. Therefore, the gasket 18 can be removed more easily, and as a result, the gasket 18 can be replaced more easily.

  In addition, the thickness T of the gasket 18 along the radial direction is 0.20 mm or more, and the gasket 18 has sufficient rigidity. Therefore, the deformation of the gasket 18 due to dropping or the like can be prevented more reliably, and as a result, a decrease in airtightness can be more reliably prevented.

  The gasket 18 is made of copper or an alloy containing copper as a main component, and has excellent thermal conductivity. Therefore, in the spark plug 1 attached to the combustion device, the heat of the metal shell 3 can be efficiently conducted to the combustion device via the gasket 18. As a result, the malfunction of the spark plug 1 due to overheating (for example, wear of the center electrode 5) can be prevented more reliably.

  Next, in order to confirm the operational effects achieved by the above embodiment, an ignition in which gaskets with variously changed inner diameters D are attached to the metal shell with the male thread portion having a thread diameter of M14, M12, or M10. Plug samples were prepared and each sample was attached to a chamber simulating an internal combustion engine with a predetermined tightening torque (at this time, the gasket was crushed and deformed by being sandwiched between the chamber and the seat). Then, after removing the sample from the chamber, it was confirmed whether or not the gasket could be removed (unscrewed) from the metal shell. Here, if the gasket can be easily removed from the metal shell by hand, an evaluation of “○” is given. On the other hand, if it is difficult to remove the gasket by hand, an evaluation of “△” is given. I decided to give it. Table 1 shows the test results of the sample with the male screw part having a screw diameter of M14, Table 2 shows the test result of the sample with the male screw part having a screw diameter of M12, and Table 3 shows the screw diameter of the male screw part. The test result of the sample set to M10 is shown. In each sample, the inner diameter D of the gasket was made smaller than the thread diameter of the male thread portion.

  As shown in Tables 1 to 3, in the sample in which the screw diameter of the male screw portion is M14, the inner diameter D of the male screw portion is M12 by setting the inner diameter D of the gasket to 13.2 mm or more. It was clarified that the gasket can be easily removed by setting the inner diameter D to 9.4 mm or more in the sample in which the screw diameter of the male screw portion is M10 by setting the diameter to 11.2 mm or more. This is because, when the gasket is crushed and deformed, the inner peripheral portion protrudes radially inward, but when the inner diameter D is set in the above range, the crushed and deformed gasket is removed from the metal shell. This is probably because a sufficient gap exists between the inner periphery of the gasket and the male screw portion.

  As a result of the above test, when the thread diameter of the male thread portion is M14 so that the gasket can be easily removed (screwed off) from the metal shell after the spark plug is attached to the combustion device, the inner diameter of the gasket Is 13.2 mm or more, the inner diameter of the gasket is 11.2 mm or more when the thread diameter of the male thread is M12, and the inner diameter of the gasket is 9.4 mm when the thread diameter of the male thread is M10. It can be said that the above is preferable.

  Next, with respect to the annular member made of copper or iron, the internal thread portion is prepared so that the thickness T along the radial direction in the valley portion is different by a predetermined manufacturing apparatus (tapping machine), Gaskets with various thicknesses T were manufactured. Then, the manufactured gasket was attached to the metal shell, and the presence or absence of deformation of the attached gasket was confirmed. Here, the gasket confirmed to be deformed is likely to be deformed due to a drop or the like when the spark plug is handled, and the evaluation of “x” is given because there is a possibility that airtightness may be lowered. On the other hand, the gaskets that were not confirmed to be deformed were evaluated as “◯” because they had sufficient rigidity and sufficient airtightness could be secured. Table 4 shows the test results when the gasket is made of copper, and Table 5 shows the test results when the gasket is made of iron.

  As shown in Tables 4 and 5, it was confirmed that sufficient rigidity can be secured in both the gasket formed of copper and the gasket formed of iron by setting the thickness T to 0.20 mm or more. .

  From the results of the above test, it can be said that the gasket thickness T along the radial direction is preferably 0.20 mm or more from the viewpoint of preventing deformation of the gasket and ensuring sufficient airtightness.

  In addition, it is not limited to the description content of the said embodiment, For example, you may implement as follows. Of course, other application examples and modification examples not illustrated below are also possible.

  (A) In the said embodiment, although copper, iron, etc. are mentioned as a constituent material of the gasket 18, the constituent material of the gasket 18 is not limited to these, For example, aluminum, zinc, or these The gasket 18 may be formed of an alloy containing at least one kind.

  (B) In the above embodiment, the gasket 18 is used in the spark plug 1 that generates a spark discharge in the spark discharge gap 33, but the spark plug that can use the gasket 18 is not limited thereto. Therefore, for example, a cylindrical cavity portion (space) formed by the tip surface of the center electrode and the inner peripheral surface of the shaft hole is provided at its tip portion, and the cavity is generated by generating plasma in the cavity portion. The gasket 18 may be used for an ignition plug (so-called plasma jet ignition plug) that ejects plasma from the opening of the part.

  (C) In the above embodiment, the spark discharge gap 33 is formed between the noble metal tip 31 and the ground electrode 27, but the noble metal tip is joined to the tip of the ground electrode 27 and provided on both electrodes 5, 27. A spark discharge gap may be formed between the two precious metal chips. Further, a spark discharge gap may be formed between the tip of the center electrode 5 and the ground electrode 27 or the noble metal tip joined to the ground electrode 27 without providing the center electrode 5 with the noble metal tip 31.

  (D) In the above embodiment, the case where the ground electrode 27 is joined to the distal end portion 26 of the metal shell 3 is embodied. However, a part of the metal shell (or the tip metal fitting previously welded to the metal shell) The present invention can also be applied to the case where the ground electrode is formed so as to cut out a part of (see Japanese Patent Laid-Open No. 2006-236906, etc.).

  (E) In the above embodiment, the tool engaging portion 19 has a hexagonal cross section, but the shape of the tool engaging portion 19 is not limited to such a shape. For example, it may be a Bi-HEX (deformed 12-angle) shape [ISO 22777: 2005 (E)].

  (F) In the above embodiment, the center electrode 5 and the ground electrode 27 have a two-layer structure, but the center electrode 5 and the ground electrode 27 may be formed of a single material. Further, the center electrode 5 or the like may have a multilayer structure of three or more layers.

DESCRIPTION OF SYMBOLS 1 ... Spark plug 3 ... Main metal fitting 15 ... Male thread part 16 ... Seat part 18 ... Gasket 41 ... Female thread part 42 ... Valley part CL1 ... Axis line

Claims (6)

A cylindrical metal shell extending along the axis;
A solid annular gasket provided on the outer periphery of the metal shell,
The metallic shell is
A male screw part for mounting formed on the outer periphery of the tip side of itself,
A seat portion formed on the rear end side of the male screw portion and bulging radially outward;
The gasket is an ignition plug having an inner diameter smaller than the screw diameter of the male screw portion and provided between the male screw portion and the seat portion,
A spark plug characterized in that an internal thread portion that can be screwed into the external thread portion is formed on an inner periphery of the gasket. The spark plug according to claim 1, wherein any one of the following (a) to (c) is satisfied.
(A) The screw diameter of the male screw portion is M14 and the inner diameter of the gasket is 13.2 mm or more. (B) The screw diameter of the male screw portion is M12 and the inner diameter of the gasket is 11.2 mm or more. (C) The male thread portion has a thread diameter of M10, and the gasket has an inner diameter of 9.4 mm or more.   3. The spark plug according to claim 1, wherein a thickness of the gasket along a radial direction is 0.20 mm or more in a valley portion of the female screw portion.   The spark plug according to any one of claims 1 to 3, wherein the gasket is made of copper or an alloy containing copper as a main component.   The spark plug according to any one of claims 1 to 3, wherein the gasket is made of iron or an alloy containing iron as a main component.   The gasket used for the spark plug of any one of Claims 1 thru | or 5.

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