Spark plug with gasket

Abstract

To provide a gasket to be used when mounting a spark plug on an internal combustion engine, for reducing the occurrence of such an event that it comes off or falls down from the spark plug while securing air tightness.SOLUTION: A gasket 20 which is arranged between the spark plug and a cylinder head when threading and mounting a screw part of the spark plug to the cylinder head of the internal combustion engine, includes an annular body part 23 arranged on a screw hollowed-out part where no thread is formed on the root side of the screw part, and a protruded part having an inclination portion protruded from the body part 23 while inclining inside in the radial direction. A relationship of φb≤φa≤φc-0.9 mm is established where φa [mm] is the inner diameter of a circle S1 centering on an annular center Cp of the body part 23 and passing through a protruded end 26a of the inclination portion, φb [mm] is the outer diameter of the screw hollowed-out part, and φc [mm] is the screw nominal diameter of the screw part.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a gasket used when attaching a spark plug to an internal combustion engine.

Background Art

[0002] Conventionally, a spark plug having a center electrode and a ground electrode is known (see Patent Document 1 below). The spark plug is attached to an internal combustion engine and is configured to ignite an air-fuel mixture in the combustion chamber of the internal combustion engine by generating a discharge spark in a spark discharge gap between the center electrode and the ground electrode. The spark plug is provided with a mounting portion having a thread formed on its outer periphery. When attaching the spark plug to the internal combustion engine, the thread of the mounting portion is screwed into a threaded hole provided in a wall portion forming the combustion chamber of the internal combustion engine. Thereby, the center electrode and the ground electrode are inserted into the combustion chamber of the internal combustion engine.

[0003] In order to ensure airtightness between the internal combustion engine and the spark plug, a gasket may be interposed between the wall portion around the threaded hole of the internal combustion engine and the seat portion of the spark plug. As the configuration of this gasket, for example, in Patent Document 1, a plurality of convex portions protruding radially inward from the main body portion are formed on the inner peripheral edge portion of the gasket. The plurality of convex portions include a plurality of first extension portions extending toward the side of a specific surface which is the surface on the wall portion side of the main body portion in the axial direction of the main body portion. The first extension portion is separated from the main body portion except for the connection portion with the convex portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Patent Document 1 focuses on improving the airtightness of the gasket, but does not consider the gasket falling off the spark plug, or even if it does not fall off, the gasket falling into the threads of the spark plug.

[0006] The present disclosure aims to provide a gasket used when installing a spark plug to an internal combustion engine, which ensures airtightness while reducing the occurrence of events such as the spark plug falling out or sinking into the gasket. [Means for solving the problem]

[0007] gaskets of this disclosure Spark plug This refers to a gasket (20) that is placed between the spark plug and the wall when the threaded portion (11B) of the spark plug is screwed into the wall of the cylinder head of an internal combustion engine. Spark plug with gasket And, The gasket is The screw-stealing portion (11D) is positioned at the base of the screw portion where no threads (16) are formed, and has an annular main body portion (23) having an inner circumferential surface (24) that follows a circle, It comprises a convex portion (25) having an inclined portion (26) that protrudes radially inward from the main body, The inner diameter φa [mm] of the circle (S1) centered on the annular center (Cp) of the main body and passing through the protruding end (26a) of the inclined part, the outer diameter φb [mm] of the screw-removing part, and the nominal screw diameter φc [mm] of the screw part are defined as follows: With the spark plug not attached to the cylinder head wall (32) is, By setting the protruding end (26a) to engage with the thread (16) forming the first incomplete thread, and the inner surface (24) on the opposite side to engage with the thread (16) forming the second incomplete thread, Gasket It will not detach from the spark plug, nor will it fall in. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a gasket used when installing a spark plug to an internal combustion engine that ensures airtightness while reducing the occurrence of events such as the spark plug falling off or sinking into the engine. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a half-cross-sectional view of a spark plug. [Figure 2] Figure 2 is an enlarged cross-sectional view of portion A in Figure 1. [Figure 3] Figure 3 is a plan view of the gasket in the embodiment. [Figure 4] Figure 4 is a diagram illustrating the effect of the gasket in the embodiment. [Figure 5] Figure 5 is a diagram illustrating the effect of the gasket in the embodiment. [Figure 6] Figure 6 is a diagram illustrating the effect of the gasket in the embodiment. [Figure 7] Figure 7 is a plan view of the gasket in the first modified example. [Figure 8] Figure 8 is a plan view of the gasket in the second modified example. [Modes for carrying out the invention]

[0010] This embodiment will now be described with reference to the attached drawings. To facilitate understanding of the explanation, the same reference numerals are used for identical components in each drawing whenever possible, and redundant explanations are omitted.

[0011] As shown in FIG. 1, the spark plug 10 includes a cylindrical housing 11 formed of a metallic material such as iron. Inside the housing 11, the lower end of a cylindrical insulator 12 is coaxially inserted. The insulator 12 is formed of an insulating material such as alumina. The upper end portion 11A of the housing 11 is caulked to the insulator 12, whereby the housing 11 and the insulator 12 are integrally joined. And in the lower part of the insulator 12, a center electrode 13 is inserted and held in a through-hole 12A.

[0012] The center electrode 13 is formed in a columnar shape with a Ni alloy excellent in heat resistance or the like as a base material. Specifically, the inner material (center material) of the center electrode 13 is formed of copper, and the outer material (outer skin material) is formed of a Ni (nickel) - based alloy. The tip portion 13A of the center electrode 13 is exposed from the lower end of the insulator 12.

[0013] At a position facing the tip portion 13A of the center electrode 13, a ground electrode 14 that integrally curves and extends from the lower end surface of the housing 11 is disposed. The ground electrode 14 is connected to the housing 11 and is curved so that the tip portion 14A of the ground electrode 14 faces the tip surface of the center electrode 13. The ground electrode 14 is also formed of a Ni - based alloy.

[0014] A terminal portion 15 is electrically connected to the upper part of the center electrode 13. An external circuit for applying a high voltage for generating a spark is connected to the terminal portion 15.

[0015] A screw portion 11B as an attachment portion is formed on the outer periphery of the lower part of the housing 11. A thread 16 is provided on the outer periphery of the screw portion 11B. The thread 16 is for attaching the spark plug 10 to a screw hole 33 provided in a wall portion 32 of a cylinder head 30 of an internal combustion engine. By screwing the thread 16 and the screw hole 33 together, the spark plug 10 is attached to the wall portion 32 of the cylinder head 30. The nominal diameter of the thread 16 is also referred to as the nominal diameter rc.

[0016] With the spark plug 10 attached to the wall portion 32 of the cylinder head 30, the center electrode 13 and the ground electrode 14 of the spark plug 10 are exposed in the combustion chamber 31.

[0017] On the upper part of the threaded portion 11B of the housing 11, a seat portion 11C having a diameter larger than that of the threaded portion 11B is formed. The seat portion 11C protrudes radially outward of the spark plug 10 from the threaded portion 11B and is formed so as to cover the threaded hole 33 when the threaded portion 11B is attached to the threaded hole 33. Also, a thread theft prevention portion 11D is formed between the threaded portion 11B and the seat portion 11C of the housing 11.

[0018] FIG. 2 shows an enlarged cross-sectional view of the thread theft prevention portion 11D. FIG. 2 is an enlarged cross-sectional view of the region shown at A in FIG. 1.

[0019] The thread theft prevention portion 11D is formed so that its diameter is equal to the valley diameter of the thread crest 16 of the threaded portion 11B and functions as a relief portion of the swaging die when forming the thread crest 16 using a swaging die. The outer diameter of the thread theft prevention portion 11D is also referred to as the thread theft prevention diameter rb.

[0020] The housing 11 is formed by machining a metal pipe formed by cold forging. The plug seat surface 17, which is the surface of the seat portion 11C on the side of the thread theft prevention portion 11D, is formed as a tapered surface that reduces in diameter toward the thread theft prevention portion 11D. For this reason, when forming the housing 11 by machining, when forming the plug seat surface 17 by moving the cutting tool radially inward with respect to the metal pipe that rotates around the axis, and then when moving the cutting tool radially outward, it is possible to suppress damage to the plug seat surface 17 by the cutting tool. The inclination angle of the plug seat surface 17 with respect to the axial direction is, for example, 3°.

[0021] An annular gasket 20 is provided on the outer circumference of the screw-removing portion 11D. The gasket 20 is used for attachment to the cylinder head 30. Specifically, a wall seating surface 34 perpendicular to the axial direction of the spark plug 10 is formed on the outer surface of the wall portion 32 of the cylinder head 30. When the spark plug 10 is attached to the wall portion 32 of the cylinder head 30, the gasket 20 comes into contact with the wall seating surface 34 and the plug seating surface 17, maintaining an airtight seal between the cylinder head 30 and the spark plug 10. The gasket 20 has a first contact surface 21 that contacts the plug seating surface 17 and a second contact surface 22 that contacts the wall seating surface 34.

[0022] The gasket 20 comprises an annular body portion 23. The body portion 23 is a solid annular shape, and its cross-sectional shape is substantially rectangular. The gasket 20 also comprises a plurality of protrusions 25 that project radially inward from the body portion 23. The protrusions 25 are arc-shaped along the inner circumferential surface 24 of the body portion 23.

[0023] The protrusion 25 has an inclined portion 26 that extends inclined away from the main body portion 23. The tip portion of the inclined portion 26 is the protruding end 26a. The protruding end 26a is the innermost part of the protrusion 25.

[0024] The inclined portion 26 is inclined from the main body portion 23 starting from the separation point 26b, and is provided so that the protruding end 26a is furthest from the main body portion 23. With respect to the thickness tg1 of the main body portion 23, the length dp1 along the thickness direction of the main body portion 23 is provided such that the ratio of the length dp1 from the second contact surface 22 where the gasket 20 abuts against the wall portion 34 to the separation point 26b is between 50% and 91%.

[0025] The thickness tg1 of the main body portion 23 is the length of the main body portion 23 along the longitudinal direction of the spark plug 10. Similarly, the length dp1 from the second contact surface 22 to the separation point 26b is the length from the second contact surface 22 to the separation point 26b along the longitudinal direction of the spark plug 10.

[0026] Next, the gasket 20 will be explained further with reference to Figure 3. As shown in Figure 3, the gasket 20 is annular in shape. The annular center Cp of the gasket 20 is also the center of the circle along the inner circumferential surface 24. The annular center Cp of the gasket 20 is also the annular center Cp of the main body portion 23.

[0027] The circumferential length L1 of the protruding end 26a can also be defined as being the same as the circumferential length of the protrusion 25. The circumferential length L1 of the protruding end 26a can also be defined literally as the circumferential length of the protruding end 26a.

[0028] The sum of the circumferential lengths L1 of the protruding ends 26a is between 50% and 80% of the total circumference of the circle S1 passing through the protruding ends 26a. In the example shown in Figure 3, there are three protruding ends 26a at intervals of θ = 120°, so the sum of the circumferential lengths L1 of the protruding ends 26a is 3 × L1. As shown in Figure 6, by making the sum of the circumferential lengths L1 of the protruding ends 26a between 50% and 80% of the total circumference of the circle S1 passing through the protruding ends 26a, the occurrence of drop defects can be suppressed. Furthermore, when the inclined portion 26 is manufactured relative to the convex portion 25 using a known crimping method, the crimping load can be set within an appropriate range.

[0029] In this embodiment, the relationship f01 holds true for the inner diameter φa [mm] of the circle S1 centered on the annular center Cp of the main body 23 and passing through the protruding end 26a of the convex portion 25, the screw stealing diameter φb [mm] which is the outer diameter of the screw stealing portion 11D, and the nominal screw diameter φc [mm] of the screw portion 11B. φb≦φa≦φc-0.9mm (f01)

[0030] As shown in Figure 4, when the spark plug 10 is not attached to the wall portion 32 of the cylinder head 30, the gasket 20 moves below the thread-loosening portion 11D. When the gasket 20 and the spark plug 10 satisfy the relationship of equation f01, for example, the protruding end 26a engages with the thread 16 that forms the first incomplete thread, and the inner circumferential surface 24 on the opposite side engages with the thread 16 that forms the second incomplete thread. In the state shown in Figure 4, the gasket does not fall off the spark plug 10, and no sagging occurs.

[0031] On the other hand, as shown in Figure 5, if the gasket 20cp and spark plug 10, which are used as comparative examples, do not satisfy the relationship of formula f01, then even if the protruding end engages with the thread 16 that forms the first incomplete thread, for example, the inner surface on the opposite side will not engage with the thread 16 that forms the second incomplete thread, resulting in a drop.

[0032] As explained with reference to Figure 3, the gasket 20 has three protruding ends 26a evenly spaced in the circumferential direction. The configuration of the protruding ends is not limited to this. In the modified gasket 20A shown in Figure 7, there is one protruding end 26a similar to that in Figure 3, and a protruding end 26Aa formed by connecting two protruding ends 26a. In the modified gasket 20C shown in Figure 8, the protruding end 26a of the gasket 20A is eliminated, and a protruding end Ca is provided, which is an extension of the protruding end 26Aa of the gasket 20A.

[0033] [Note] Notes 1 through 4 below can be combined in any way as long as they do not contradict each other technically.

[0034] [Note 1] A gasket 20 is placed between the spark plug 20 and the wall portion 32 when the threaded portion 11B of the spark plug 20 is screwed into the wall portion 32 of the cylinder head 30 of an internal combustion engine, An annular main body portion 23 is positioned on the screw-stealing portion 11D where no threads 16 are formed at the base of the threaded portion 11B, It comprises a protruding portion 25 having an inclined portion 26 that protrudes radially inward from the main body portion 23, The relationship φb ≤ φa ≤ φc - 0.9 mm holds true for the inner diameter φa [mm] of the circle S1 centered on the annular center Cp of the main body 23 and passing through the protruding end 26a of the inclined portion 26, the outer diameter φb [mm] of the screw-stealing portion 11D, and the nominal screw diameter φc [mm] of the screw portion 11B.

[0035] According to Appendix 1, as explained with reference to Figures 3 and 4, the gasket 20 does not fall beyond the second thread of the incomplete thread portion of the threaded portion 11B, and the protruding end 26a of the gasket 20 can be securely hooked onto the thread 16.

[0036] [Note 2] The gasket 20 as described in Appendix 1, wherein the total circumferential length L1 of the protruding end 26a is 50% or more and 80% or less of the total circumferential length of the circle S1 passing through the protruding end 26a.

[0037] According to Appendix 2, since the sum of the circumferential lengths L1 of the protruding ends 26a is 50% or more of the total circumference of the circle S1, the area where the protruding ends 26a are formed is larger than other areas, and the protruding ends 26a can be reliably hooked onto the screw threads 16. Since the sum of the circumferential lengths L1 of the protruding ends 26a is 80% or less of the total circumference of the circle S1, when forming the inclined portion 26 with a crimp, the crimping load is not made excessive, and the lifespan of the crimping die is not worsened.

[0038] [Note 3] The gasket 20 as described in Appendix 1 or 2, wherein any straight line passing through the annular center Cp of the main body portion 23 intersects the protruding end 26a at at least one point.

[0039] According to Appendix 3, in the relationship between the gasket 20 and the thread 16, there are no opposing portions where the protruding end 26a is not formed, and the protruding end 26a can be reliably hooked onto the thread 16.

[0040] [Note 4] The inclined portion 26 is inclined from the convex portion 25 at the separation point 26b, The gasket 20 according to any one of the appendices 1 to 3, wherein the ratio of the length dp1 from the contact surface 22 where the gasket 20 abuts the wall portion 32 to the separation point 26b, which is the length along the thickness direction of the main body portion 23 with respect to the thickness tg1 of the main body portion 23, is 50% or more and 91% or less.

[0041] The embodiments have been described above with reference to specific examples. However, this disclosure is not limited to these specific examples. Modifications made to these specific examples by those skilled in the art are also included within the scope of this disclosure, as long as they retain the features of this disclosure. The elements, their arrangement, conditions, shapes, etc., of each of the aforementioned specific examples are not limited to those illustrated and can be modified as appropriate. The elements of each of the aforementioned specific examples can be combined in different ways as appropriate, as long as no technical inconsistencies arise. [Explanation of Symbols]

[0042] 10: Spark plug 11B: Threaded section 11D: Screw Theft Unit 20: Gasket 22: Second contact surface (contact surface) 23: Main body 25: Convex part 26: Inclined part 26a:Protruding end 26b: Separation point

Claims

1. A spark plug with a gasket, having a gasket (20) positioned between the spark plug and the wall when the threaded portion (11B) provided on the spark plug is screwed into the wall of the cylinder head of an internal combustion engine, The aforementioned gasket is The screw-stealing portion (11D) is positioned at the base of the aforementioned screw portion where no threads (16) are formed, and has an annular main body portion (23) having an inner circumferential surface (24) that follows a circle, The present invention comprises a convex portion (25) having an inclined portion (26) that protrudes radially inward from the main body, The inner diameter φa [mm] of the circle (S1) centered on the annular center (Cp) of the main body and passing through the protruding end (26a) of the inclined portion, the outer diameter φb [mm] of the screw-steel portion, and the nominal screw diameter φc [mm] of the screw portion are defined as follows: When the spark plug is not attached to the wall portion (32) of the cylinder head, the protruding end (26a) engages with the thread (16) that forms the first incomplete thread, and the inner circumferential surface (24) on the opposite side engages with the thread (16) that forms the second incomplete thread, A spark plug with a gasket, wherein the gasket does not detach from the spark plug and does not fall in.

2. The spark plug with gasket according to claim 1, wherein the sum of the circumferential lengths (L1) of the protruding ends is 50% or more and 80% or less of the total circumference of the circle passing through the protruding ends.

3. The spark plug with gasket according to claim 1 or 2, wherein any straight line passing through the annular center of the main body intersects the protruding end at least at one point.

4. The inclined portion is inclined from the convex portion at the separation point (26b), The spark plug with gasket according to claim 1, wherein the ratio of the length (dp1) from the contact surface (22) where the gasket abuts the wall to the separation point to the thickness (tg1) of the main body, which is a length along the thickness direction of the main body, is 50% or more and 91% or less.

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