JP6619769B2 - Spark plug - Google Patents

Description

  The present specification relates to a spark plug for igniting fuel gas in an internal combustion engine.

  The spark plug is attached to the internal combustion engine by screwing a screw portion formed on the metal shell into a screw hole of the internal combustion engine. When the spark plug is attached to the internal combustion engine, the metal shell of the spark plug and the internal combustion engine (for example, the cylinder head) are hermetically sealed so that the gas in the combustion chamber of the internal combustion engine does not leak to the outside. Is required. For this reason, spark plugs have been proposed in which various devices have been devised in the gasket for ensuring the sealing performance between the metal shell and the internal combustion engine.

  For example, in the gasket described in Patent Document 1, a cross section cut along a plane including the axis has an S shape. According to the shape, the plastic deformation of the gasket can be suppressed.

Japanese Patent Laid-Open No. 2006-136524

  However, in the above technique, since the amount of deformation of the gasket is large, the mounting position of the spark plug in the axial direction may vary.

  The present specification discloses a technique capable of ensuring a sealing property between the metal shell and the internal combustion engine while suppressing variations in the mounting position of the spark plug in the axial direction.

  The technology disclosed in this specification can be implemented as the following application examples.

[Application Example 1]
In the mounting state attached to the internal combustion engine, the outer peripheral surface has a screw portion that is screwed into the screw hole of the internal combustion engine,
A metal shell having a projecting portion projecting radially outward on the rear end side of the threaded portion and connected to the internal combustion engine over the entire circumference in the circumferential direction via a gasket in the attached state A spark plug comprising:
The gasket has a solid cross section cut along a plane including the axis,
When the portion of the gasket that contacts the projecting portion is a rear end side contact portion, and the portion of the gasket that contacts the internal combustion engine is a front end side contact portion,
The annular first center line passing through the center of the rear end side contact portion is either radially outer or radially inner than the annular second center line passing through the center of the tip contact portion. A spark plug characterized by being displaced over the entire circumference.

  According to the above configuration, since the cross section cut along the plane including the axis is solid, the amount of deformation of the gasket is reduced, and variations in the mounting position of the spark plug in the axial direction can be suppressed. Furthermore, in addition to the sealing pressure due to the elasticity of the gasket material itself, a sealing pressure is generated due to the gasket acting as a disc spring, so that the sealing performance between the metal shell and the internal combustion engine is improved. Can do. As a result, it is possible to ensure the sealing performance between the metal shell and the internal combustion engine while suppressing variations in the mounting position of the spark plug in the axial direction.

[Application Example 2] The spark plug according to Application Example 1,
A spark plug in which a radial distance between the first center line and the second center line is 0.25 mm or more over the entire circumference.

  According to the above configuration, the sealing pressure due to the gasket operating as a disc spring becomes higher, so that the sealing performance between the metal shell and the internal combustion engine can be further improved.

[Application Example 3] The spark plug according to Application Example 1 or 2,
An ignition plug in which an average value of positions of the rear end side contact portion in the radial direction at a position over the entire circumference in the circumferential direction is shorter than an average length of the distal end side contact portion in the radial direction.

  According to the said structure, the contact area of a gasket and an internal combustion engine can be comparatively enlarged by making the average length of the radial direction of a front end side contact part comparatively long, and damage to an internal combustion engine can be suppressed. Thereby, the sealing performance when the spark plug is repeatedly attached by replacing the spark plug or the like can be secured. In addition, by making the average length in the radial direction of the contact portion on the rear end side relatively short, the contact area between the gasket and the metal shell is made relatively small, the seal pressure between the metal shell and the gasket is increased, and the seal Can be improved.

[Application Example 4] The spark plug according to any one of Application Examples 1 to 3,
The spark plug has a Vickers hardness of 100 Hv or more.

  According to the said structure, since a gasket has sufficient hardness, the plastic deformation of a gasket can be suppressed. As a result, it can suppress that the seal pressure resulting from a gasket operating as a disc spring falls by plastic deformation.

[Application Example 5] The spark plug according to any one of Application Examples 1 to 4,
The spark plug having an average value at a position over the entire circumference in the circumferential direction of the length in the radial direction of the tip side contact portion is 1 mm or more and 1.4 mm or less.

  When the contact area between the gasket and the internal combustion engine is excessively small, damage to the internal combustion engine occurs, and when the contact area is excessively large, the seal pressure between the gasket and the internal combustion engine decreases. Sealing performance is reduced. According to the above configuration, the seal pressure between the gasket and the internal combustion engine can be improved while suppressing damage to the internal combustion engine.

[Application Example 6] The spark plug according to any one of Application Examples 1 to 5,
The spark plug, wherein an average value of positions of the rear end side contact portion in the radial direction over the entire circumference in the circumferential direction is 1 mm or less.

  When the contact area between the gasket and the metal shell is excessively large, the seal pressure between the gasket and the metal shell is lowered, so that the sealing performance is lowered. According to the above configuration, the sealing pressure between the gasket and the metal shell can be improved.

Application Example 7 The spark plug according to any one of Application Examples 1 to 6,
A spark plug in which the thread diameter of the thread portion of the metal shell is M10 or less.

  The smaller the screw diameter, the smaller the diameter of the gasket. The smaller the diameter of the gasket, the higher the sealing pressure resulting from operating as a disc spring. According to the above configuration, the sealing pressure resulting from operating as a disc spring is sufficiently high, so that the sealing performance between the metal shell and the internal combustion engine can be further improved.

  The technology disclosed in the present specification can be realized in various modes. For example, an ignition device using an ignition plug or an ignition plug, an internal combustion engine equipped with the ignition plug, or an ignition plug thereof The present invention can be realized in the form of an internal combustion engine equipped with an ignition device using the above, an electrode of a spark plug, and the like.

It is sectional drawing of the spark plug 100 of this embodiment. It is explanatory drawing of the gasket 90. FIG. It is a figure explaining shaping | molding of the gasket 90. FIG. It is sectional drawing of the intermediate body 90M and the gasket 90. FIG. It is explanatory drawing of the attachment state of the spark plug. It is the graph which plotted the test result of the 1st evaluation test. It is the graph which plotted the test result of the 2nd evaluation test. It is the graph which plotted the test result of the 3rd evaluation test. It is the graph which plotted the test result of the 4th evaluation test. It is the graph which plotted the test result of the 5th evaluation test. It is explanatory drawing of the gasket of a modification.

A. Embodiment:
A-1. Spark plug configuration:
FIG. 1 is a cross-sectional view of a spark plug 100 of the present embodiment. The dashed line in FIG. 1 indicates the axis CO (also referred to as axis CO) of the spark plug 100. A direction parallel to the axis CO (vertical direction in FIG. 1) is also referred to as an axis direction. A radial direction of a circle on the plane that is centered on the axis CO and is perpendicular to the axis CO is simply referred to as a “radial direction”, and a circumferential direction of the circle is also simply referred to as a “circumferential direction”. The lower direction in FIG. 1 is referred to as a front end direction FD, and the upper direction is also referred to as a rear end direction BD. The lower side in FIG. 1 is called the front end side of the spark plug 100, and the upper side in FIG.

  The spark plug 100 generates a discharge in a gap (discharge gap) formed between the center electrode 20 and the ground electrode 30, which will be described in detail later. The spark plug 100 is attached to the internal combustion engine and used to ignite the fuel gas in the combustion chamber of the internal combustion engine. The spark plug 100 includes an insulator 10 as an insulator, a center electrode 20, a ground electrode 30, a terminal fitting 40, a metal shell 50, and a gasket 90.

  The insulator 10 is formed by firing alumina or the like. The insulator 10 is a substantially cylindrical member that extends along the axial direction and has a shaft hole 12 that is a through-hole penetrating the insulator 10. The insulator 10 includes a flange part 19, a rear end side body part 18, a front end side body part 17, a step part 15, and a leg length part 13. The rear end side body portion 18 is located on the rear end side of the flange portion 19 and has an outer diameter smaller than the outer diameter of the flange portion 19. The distal end side body portion 17 is located on the distal end side from the flange portion 19 and has an outer diameter smaller than the outer diameter of the flange portion 19. The long leg portion 13 is positioned on the distal end side from the distal end side body portion 17 and has an outer diameter smaller than the outer diameter of the distal end side body portion 17. The leg portion 13 is exposed to the combustion chamber when the spark plug 100 is attached to an internal combustion engine (not shown). The step portion 15 is formed between the leg long portion 13 and the distal end side body portion 17.

  The metal shell 50 is formed of a conductive metal material, specifically, a low carbon steel material, and is a cylindrical metal fitting for fixing the spark plug 100 to an engine head (not shown) of an internal combustion engine. The metal shell 50 is formed with a through hole 59 penetrating along the axis CO. The metal shell 50 is disposed around the insulator 10 in the radial direction (that is, the outer periphery). That is, the insulator 10 is inserted and held in the through hole 59 of the metal shell 50. The tip of the insulator 10 protrudes from the tip of the metal shell 50 toward the tip side. The rear end of the insulator 10 protrudes toward the rear end side from the rear end of the metal shell 50.

  The metal shell 50 is formed between a hexagonal column-shaped tool engagement portion 51 with which a spark plug wrench engages, an attachment screw portion 52 for attachment to an internal combustion engine, and the tool engagement portion 51 and the attachment screw portion 52. And an overhanging portion 54.

  The mounting screw portion 52 includes a thread formed on the outer peripheral surface, and is screwed into a screw hole (not shown) provided in the engine head of the internal combustion engine when the spark plug 100 is mounted on the internal combustion engine. The nominal diameter of the mounting screw portion 52 is, for example, M10 or less, for example, M10 or M8.

  The overhang portion 54 is a hook-like portion that protrudes radially outward on the rear end side of the mounting screw portion 52. As will be described later, the overhang portion 54 is connected to the mounting surface of the internal combustion engine over the entire circumference via the gasket 90 in a mounting state in which the spark plug 100 is mounted to the internal combustion engine.

  Between the mounting screw portion 52 and the overhang portion 54 of the metal shell 50, a metal annular gasket 90, which will be described in detail later, is fitted. The gasket 90 seals a gap between the spark plug 100 and the internal combustion engine (engine head) when the spark plug 100 is attached to the internal combustion engine.

  The metal shell 50 further includes a thin caulking portion 53 provided on the rear end side of the tool engaging portion 51, and a thin compression deformation portion provided between the overhang portion 54 and the tool engaging portion 51. 58. An annular region formed between the inner peripheral surface of the portion of the metal shell 50 from the tool engaging portion 51 to the crimping portion 53 and the outer peripheral surface of the rear end side body portion 18 of the insulator 10 has an annular shape. Ring members 6 and 7 are arranged. Between the two ring members 6 and 7 in the said area | region, the powder of the talc (talc) 9 is filled. The rear end of the crimping portion 53 is bent radially inward and fixed to the outer peripheral surface of the insulator 10. The compression deformation portion 58 of the metal shell 50 is compressed and deformed when the crimping portion 53 fixed to the outer peripheral surface of the insulator 10 is pressed toward the distal end side during manufacture. By the compression deformation of the compression deformation portion 58, the insulator 10 is pressed toward the front end side in the metal shell 50 through the ring members 6, 7 and the talc 9. Accordingly, the step portion 15 (insulation) of the insulator 10 is formed by the step portion 56 (metal step portion) formed on the inner periphery of the mounting screw portion 52 of the metal shell 50 through the metal annular plate packing 8. The body side step) is pressed. As a result, the gas in the combustion chamber of the internal combustion engine is prevented by the plate packing 8 from leaking outside through the gap between the metal shell 50 and the insulator 10.

  The center electrode 20 includes a rod-shaped center electrode main body 21 extending in the axial direction and a center electrode tip 29. The center electrode main body 21 is held at the tip end portion inside the shaft hole 12 of the insulator 10. The center electrode main body 21 has a structure including an electrode base material 21A and a core portion 21B embedded in the electrode base material 21A. The electrode base material 21A is formed using, for example, nickel or an alloy containing nickel as a main component (for example, NCF600, NCF601). The core portion 21B is made of copper, which is superior in thermal conductivity to the alloy forming the electrode base material 21A, or an alloy containing copper as a main component, in this embodiment, copper.

  The center electrode main body 21 includes a flange portion 24 (also referred to as a flange portion) provided at a predetermined position in the axial direction, and a head portion 23 (electrode head portion) that is a portion on the rear end side of the flange portion 24. And a leg portion 25 (electrode leg portion) that is a portion on the tip side of the collar portion 24. The flange 24 is supported by the step 16 of the insulator 10. The distal end portion of the leg portion 25, that is, the distal end of the center electrode body 21 protrudes toward the distal end side from the distal end of the insulator 10.

  The center electrode tip 29 is a member having a substantially cylindrical shape, and is joined to the tip of the center electrode main body 21 (tip of the leg portion 25) using, for example, laser welding. The center electrode tip 29 is formed of a material mainly composed of a high melting point noble metal. The center electrode tip 29 is a noble metal tip formed using, for example, a noble metal such as iridium (Ir) or Ir, or an alloy containing the noble metal as a main component.

  The ground electrode 30 includes a ground electrode body 31 joined to the tip of the metal shell 50 and a square pole-shaped ground electrode tip 39. The ground electrode main body 31 is a rod-shaped body having a square cross section. The ground electrode main body 31 has a free end face 311 and a joining end face 312 as both end faces. The joining end surface 312 is joined to the front end surface 50A of the metal shell 50 by, for example, resistance welding. Thereby, the metal shell 50 and the ground electrode body 31 are electrically connected.

  The ground electrode main body 31 is formed using, for example, nickel or an alloy containing nickel as a main component (for example, NCF600, NCF601). The ground electrode body 31 is formed using a base material made of a highly corrosion-resistant metal (for example, nickel alloy) and a metal having a high thermal conductivity (for example, copper), and is a core embedded in the base material. And a two-layer structure including a portion. Similarly to the center electrode tip 29, the ground electrode tip 39 is a noble metal tip formed using a noble metal such as iridium (Ir) or Ir or an alloy containing the noble metal as a main component. The ground electrode tip 39 is joined to the surface on the rear end side in the vicinity of the free end surface 311 of the ground electrode main body 31 by using, for example, laser welding or resistance welding.

  The first discharge surface 295 that is the front end surface of the center electrode tip 29 and the second discharge surface 395 that is the rear end surface of the ground electrode tip 39 form the above-described discharge gap.

  The terminal fitting 40 is a rod-shaped member extending in the axial direction. The terminal fitting 40 is formed of a conductive metal material (for example, low carbon steel), and a metal layer (for example, Ni layer) for corrosion protection is formed on the surface of the terminal fitting 40 by plating or the like. The terminal fitting 40 includes a collar part 42 (terminal jaw part) formed at a predetermined position in the axial direction, a cap mounting part 41 located on the rear end side of the collar part 42, and a leg part 43 on the distal side of the collar part 42. (Terminal leg). The cap mounting portion 41 of the terminal fitting 40 is exposed on the rear end side from the insulator 10. The leg 43 of the terminal fitting 40 is inserted into the shaft hole 12 of the insulator 10. A plug cap connected to a high voltage cable (not shown) is attached to the cap attachment portion 41, and a high voltage for generating discharge is applied.

  In the shaft hole 12 of the insulator 10, radio noise at the time of discharge is generated between the tip of the terminal fitting 40 (tip of the leg 43) and the rear end of the center electrode 20 (back of the head 23). A resistor 70 for reduction is arranged. The resistor 70 is formed of, for example, a composition including glass particles that are main components, ceramic particles other than glass, and a conductive material. In the shaft hole 12, a gap between the resistor 70 and the center electrode 20 is filled with a conductive seal 60. A gap between the resistor 70 and the terminal fitting 40 is filled with a conductive seal 80. The conductive seals 60 and 80 are formed of a composition containing, for example, glass particles and metal particles (Cu, Fe, etc.).

A-2. Configuration of Gasket 90 FIG. 2 is an explanatory diagram of the gasket 90. FIG. 2A shows a schematic view in which the gasket 90 is viewed along the axis CO toward the rear end direction BD. FIG. 2B is a perspective view showing an outline of the gasket 90. The gasket 90 is formed using a metal material, for example, a metal material having a Vickers hardness of 100 Hv or more, specifically, iron.

  The gasket 90 has an annular shape. The outer diameter R3 of the gasket 90 is substantially equal to the outer diameter of the overhanging portion 54 of the metal shell 50. The gasket 90 includes a plurality (eight in the example of FIG. 2) small inner diameter portions 91 and a plurality (eight in the example of FIG. 2) large inner diameter portions 92. The inner diameter R1 of the small inner diameter portion 91 is smaller than the inner diameter R2 of the large inner diameter portion 92. The inner diameter R <b> 1 of the small inner diameter portion 91 is slightly smaller than the maximum outer diameter of the mounting screw portion 52. The inner diameter R <b> 2 of the large inner diameter portion 92 is slightly larger than the maximum outer diameter of the large inner diameter portion 92. A claw portion 913 (described later) on the radially inner side of the small inner diameter portion 91 is fitted into a groove portion 55 (FIG. 1) formed between the overhang portion 54 and the mounting screw portion 52 in the metal shell 50. Yes. As a result, the gasket 90 is engaged with the metal shell 50.

  The plurality of small inner diameter portions 91 and the plurality of large inner diameter portions 92 are alternately arranged along the circumferential direction. That is, the plurality of small inner diameter portions 91 are disposed at a plurality of dispersed positions in the circumferential direction of the gasket 90. Thereby, the gasket 90 is appropriately fixed to the metal shell 50. The circumferential length W1 of the plurality of small inner diameter portions 91 and the circumferential length W2 of the plurality of large inner diameter portions 92 are not limited to this, but are substantially equal in the example of FIG. .

  FIG. 3 is a diagram for explaining the molding of the gasket 90. An annular intermediate 90M shown in FIG. 3 is prepared. The intermediate body 90M has an annular shape with an outer diameter substantially equal to the outer diameter R3 of the gasket 90 and an inner diameter substantially equal to the inner diameter R2 of the large inner diameter portion 92 of the gasket 90.

  The mounting screw portion 52 of the metal shell 50 is inserted into the hole of the intermediate body 90M, and the intermediate body 90M comes into contact with the rear end surface of the intermediate body 90M and the front end surface 54S (FIG. 1) of the overhang portion 54. Thus, it arrange | positions with respect to the metal shell 50. In this state, as shown by eight arrows in FIG. 3, among the inner portion 902M of the intermediate body 90M, eight portions that should form the small inner diameter portion 91 are formed by a predetermined pressing member 300 (described later). It is pressed toward the rear end direction BD from the front end side. As a result, eight portions of the inner portion 902M that should form the small inner diameter portion 91 are pressed against the distal end surface 54S of the overhang portion 54 and crushed. As a result, eight small inner diameter portions 91 are formed, and the gasket 90 is completed, and the gasket 90 is engaged with the metal shell 50.

  This will be described in more detail with reference to FIG. FIG. 4 is a cross-sectional view of the intermediate 90M and the gasket 90. In FIG. 4, the upper direction is the front end direction FD, and the lower direction is the rear end direction BD. The left side is a direction ID from the outside to the inside along the radial direction, and the right side is a direction OD from the inside to the outside along the radial direction.

  The cross-sectional view of FIG. 4A shows a cross-section CSM obtained by cutting the intermediate 90M along a plane including the axis CO (FIG. 3). The cross-section CSM has a line-symmetric shape with respect to a line CL that passes through the center in the axial direction (tip direction FD) and is perpendicular to the axial direction. As shown in the cross section CSM, the intermediate body 90M includes the inner portion 902M and the outer portion 901M described above. The radially inner (direction ID) surface IVM and the radially outer (direction OD) surface OVM of the intermediate body 90M are parallel to the axial direction. The rear end surface IBM and the front end surface IFM of the inner part 902M are inclined with respect to the line CL perpendicular to the axial direction. For this purpose, in the cross section CSM, the inner part 902M has a trapezoidal shape. The rear end surface OBM and the front end surface OFM of the outer portion 901M are parallel to a line CL perpendicular to the axial direction. For this purpose, in the cross section CSM, the outer portion 901M has a rectangular shape.

  As shown in FIG. 4A, when the inner portion 902M of the intermediate body 90M is pressed in the rear end direction BD by the pressing member 300, the rear end surface IBM of the inner portion 902M is the front end surface of the overhanging portion 54. The rear end surface OBM of the outer portion 901M is in contact with the front end surface 54S. Therefore, when the inner portion 902M is pressed in the rear end direction BD by the pressing member 300, the inner portion 902M is moved to the outer end direction BD in the rear end direction BD as shown by arrows AR1 and AR2. A force for twisting the portion 901M in the distal direction FD is applied. That is, a rotational moment that twists the cross section CSM of FIG. 4A counterclockwise is applied to the intermediate 90M. Thus, as described above, the small inner diameter portion 91 is formed, and the gasket 90 is molded so as to function as a disc spring.

  4B shows a cross section CS1 (cross section AA in FIG. 2) obtained by cutting the small inner diameter portion 91 of the gasket 90 along a plane including the axis CO (FIG. 2). The small inner diameter portion 91 includes an inner portion 912 and an outer portion 911.

  In the cross section CS1, the outer portion 911 has a substantially rectangular shape. The front end surface OF1 of the outer portion 911 is inclined at an angle θ1 with respect to the direction perpendicular to the axial direction so that the radially inner side is located in the rear end direction BD than the radially outer side. Similarly, the rear end surface OB1 of the outer portion 911 is inclined at an angle θ2 with respect to the direction perpendicular to the axial direction so that the radially inner side is located in the rear end direction BD rather than the radially outer side. ing. The surface OV1 of the outer portion 911 is inclined with respect to the axial direction.

  The inner portion 912 includes a claw portion 913 that is formed by pressing with the pressing member 300 and fits into the groove portion 55 of the metal shell 50. In the cross section CS <b> 1, the distal end surface IF <b> 1 of the inner portion 912 and the radially inner surface IV <b> 1 of the inner portion 912 are greatly deformed by pressing by the pressing member 300. The rear end surface IB1 of the inner portion 912 is inclined at an angle θ3 with respect to the direction perpendicular to the axial direction so that the radially inner side is located in the distal direction FD than the radially outer side.

  4C shows a cross section CS2 (BB cross section in FIG. 2) obtained by cutting the large inner diameter portion 92 of the gasket 90 along a plane including the axis CO (FIG. 2). The large inner diameter portion 92 includes an inner portion 922 and an outer portion 921.

  In the cross section CS2, the outer portion 921 has a substantially rectangular shape similar to the outer portion 911 of the small inner diameter portion 91. The front end surface OF2 of the outer portion 921 is inclined at an angle θ4 with respect to the direction perpendicular to the axial direction so that the radially inner side is located in the rear end direction BD than the radially outer side. Similarly, the rear end surface OB2 of the outer portion 921 is inclined at an angle θ5 with respect to the direction perpendicular to the axial direction so that the inner side in the radial direction is located in the rear end direction BD than the outer side in the radial direction. ing. The surface OV2 of the outer portion 921 is inclined with respect to the axial direction.

  In the cross section CS2, the inner portion 922 has a distorted substantially trapezoidal shape. The front end surface IF <b> 2, the radially inner surface IV <b> 2, and the rear end surface IB <b> 2 of the inner portion 922 are deformed by the influence of the molding of the small inner diameter portion 91 by the pressing member 300. The rear end surface IB2 of the inner portion 922 is inclined at an angle θ6 with respect to the direction perpendicular to the axial direction so that the radially inner side is positioned in the distal direction FD than the radially outer side.

  As shown in FIGS. 4B and 4C, the gasket 90 is solid in any cross section including the axis CO including the cross sections CS1 and CS2. That is, no space is formed inside the gasket 90. For example, as a type of gasket different from the gasket 90, there is a gasket of a type in which a string-like member formed by bending a thin metal plate is formed into an annular shape. Not real.

  FIG. 5 is an explanatory diagram of an attached state in which the spark plug 100 is attached to the engine head 500 of the internal combustion engine. FIG. 5 shows a cross section CS3 obtained by cutting the spark plug 100 in the attached state along a plane including the axis CO (FIGS. 1 and 2). In the mounted state, as shown in FIG. 5, the mounting screw portion 52 of the metal shell 50 is screwed into the screw hole 510 of the engine head 500. As a result, the overhanging portion 54 is connected to the engine head 500 via the gasket 90. In the mounted state, the distal end surface 54S of the overhanging portion 54 and the mounting surface 500S of the engine head 500 are opposed to each other in the axial direction with the gasket 90 interposed therebetween. A cross section of the small inner diameter portion 91 of the gasket 90 appears in the cross section CS3 of FIG.

  In the mounted state, the mounting surface 500 </ b> S of the engine head 500 contacts the tip side of the gasket 90. A portion where the mounting surface 500S and the gasket 90 are in contact with each other is referred to as a tip side contact portion CFF (FIG. 5). The tip side contact portion CFF is on the tip surface OF1 (FIGS. 4B and 5) of the outer portion 911 of the small inner diameter portion 91 and the tip surface OF2 of the outer portion 921 of the large inner diameter portion 92 (FIG. 4C). Located in.

  The front end side contact portion CFF attaches the spark plug 100 to the engine head 500 in a state where a pre-sheet (sheet type prescale) made by Fuji Film is sandwiched between the gasket 90 and the mounting surface 500S. Can be identified by removing and checking the pre-sheet. The pre-sheet has a property that the color of the region to which the contact pressure is applied changes.

  As described above, the front end surfaces OF1 and OF2 form angles θ1 and θ4 with respect to the direction perpendicular to the axial direction so that the radially inner side is positioned in the rearward direction BD than the radially outer side. It is inclined (FIGS. 4B and 4C). For this reason, as shown in the cross-section CS3, the front end side contact portion CFF is a radially outer portion of the front end surfaces OF1 and OF2 of the outer portions 911 and 921 of the gasket 90.

  In the attached state, the front end surface 54S of the overhanging portion 54 contacts the rear end side of the gasket 90. A portion where the front end surface 54S of the overhanging portion 54 and the gasket 90 are in contact is referred to as a rear end side contact portion CFB (FIG. 5). The rear end side contact portion CFB includes a portion (FIGS. 4B and 5) including a boundary between the rear end surface OB1 of the outer portion 911 and the rear end surface IB1 of the inner portion 912 in the small inner diameter portion 91, and the large inner diameter portion 92. In FIG. 4 (C) including the boundary between the rear end surface OB2 of the outer portion 921 and the rear end surface IB2 of the inner portion 922.

  The rear end side contact portion CFB is the pre-sheet described above between the gasket 90 and the front end surface 54S of the metal shell 50, and the spark plug 100 is attached to the engine head 500 and the spark plug 100 is removed to check the pre-sheet. Can be identified.

  As described above, the rear end surfaces OB1 and OB2 form the angles θ2 and θ5 with respect to the direction perpendicular to the axial direction so that the radially inner side is positioned in the rearward direction BD than the radially outer side. It is inclined (FIGS. 4B and 4C). The rear end surfaces IB1 and IB2 are inclined at angles θ3 and θ6 with respect to the direction perpendicular to the axial direction so that the radially inner side is positioned in the distal direction FD than the radially outer side. (FIGS. 4B and 4C). For this reason, as shown in the cross section CS3, the rear end side contact portion CFB includes the radially inner portion of the rear end surfaces OB1 and OB2 of the outer portions 911 and 921 of the gasket 90, the inner portion 912 of the gasket 90, 922 is a radially outer portion of the rear end surfaces IB1 and IB2 of the 922.

  Thus, the front end side contact part CFF is shifted to the outside in the radial direction as a whole with respect to the rear end side contact part CFB.

  Here, let L1 (FIG. 5) be the length in the radial direction of the tip side contact portion CFF at each site in the circumferential direction. And the center of the radial direction of the front end side contact part CFF in each site | part of the circumferential direction is set to CF. FIG. 2A shows an annular line CFL that connects the radial center CF at each circumferential portion. The annular line CFL can also be referred to as a first center line CFL passing through the center of the distal end side contact portion CFF.

  The length in the radial direction of the rear end side contact portion CFB in each circumferential portion is L2 (FIG. 5). And the center of the radial direction of the rear end side contact part CFB in each site | part of the circumferential direction is set to CB. FIG. 2 shows an annular line CBL connecting the radial centers CB at each circumferential portion. The annular line CBL can also be referred to as a second center line CBL passing through the center of the rear end side contact portion CFB.

  As shown in FIG. 2A, the first center line CFL is deviated from the second center line CBL to the outside in the radial direction over the entire circumference in the circumferential direction. As a result, the gasket 90 functions as a disc spring. That is, when compressed in the axial direction by the front end surface 54S of the overhanging portion 54 and the mounting surface 500S of the engine head 500, the outer side in the radial direction is the rear end as shown by arrows AR3 and AR4 in FIG. It is deformed by receiving a force so as to rotate in the clockwise direction in FIG. 5 so as to face in the direction BD and radially inward in the distal direction FD. As the repulsive force against the deformation, as shown by arrows AR5 and AR6 in FIG. 5, the mounting surface 500S of the engine head 500 is pressed toward the front end direction FD, and the front end surface 54S of the overhanging portion 54 is moved in the rear end direction. A force for pressing toward the BD is generated.

  As described above, the gasket 90 of the present embodiment generates a sealing pressure due to the gasket 90 operating as a disc spring in addition to the sealing pressure due to the elasticity of the material of the gasket 90 itself. The sealing performance between the engine head 500 and the engine head 500 can be improved.

  Furthermore, since the gasket 90 has solid sections CS1 and CS2 (FIGS. 4B and 4C) cut along the plane including the axis CO, the deformation amount of the gasket 90 is reduced, and the spark plug 100 Variations in the mounting position in the axial direction can be suppressed.

  As described above, in the spark plug 100 of the present embodiment, the sealing performance between the metal shell 50 and the engine head 500 can be ensured while suppressing variations in the mounting position of the spark plug 100 in the axial direction.

  Here, the radial distance between the first center line CFL and the second center line CBL in FIG. 2A, in other words, the radial center in the tip side contact portion CFF in FIG. A distance between the CF and the radial center CB in the rear end side contact portion CFB is defined as La (also referred to as a center-to-center distance La).

  In the spark plug 100 of the present embodiment, the center-to-center distance La is preferably 0.25 mm or more over the entire circumferential direction. By doing so, the sealing pressure resulting from the gasket 90 operating as a disc spring becomes higher, so that the sealing performance between the metal shell 50 and the engine head 500 can be further improved.

  Furthermore, in the spark plug 100 of the present embodiment, the average length in the radial direction of the rear end side contact portion CFB, that is, the average value at the position over the entire circumference in the circumferential direction of the length L2 in FIG. It is preferable that the average length in the radial direction of the portion CFF, that is, the average value at the position over the entire circumference in the circumferential direction of the length L1 in FIG. Generally, the material of the engine head 500 (for example, aluminum die cast) has a lower hardness than the material of the metal shell 50 (for example, low carbon steel). For this reason, the engine head 500 is more susceptible to damage such as scratches than the metal shell 50. Since the contact area between the gasket 90 and the engine head 500 can be increased by making the average length in the radial direction of the tip side contact portion CFF relatively long, damage to the mounting surface 500S of the internal combustion engine can be suppressed. Thereby, the sealing performance when the spark plug 100 is repeatedly attached by replacement of the spark plug 100 or the like can be secured. For example, if damage such as a scratch occurs on the mounting surface 500S, when the spark plug 100 is mounted again, the combustion gas tends to leak through the scratch. Further, since the engine head 500 has a lower hardness than the metal shell 50, the adhesiveness with the gasket 90 is good. For this reason, by increasing the contact area between the gasket 90 and the engine head 500, the sealing performance can be ensured even if the sealing pressure is somewhat reduced. Moreover, since the contact area between the gasket 90 and the metal shell 50 can be reduced by relatively shortening the average length in the radial direction of the rear end side contact portion CFB, the sealing pressure between the metal shell 50 and the gasket 90 is increased. Thus, the sealing performance can be improved. Since the metal shell 50 has a higher hardness than the engine head 500, the adhesion with the gasket 90 is not good. For this reason, it is highly necessary to reduce the contact area between the gasket 90 and the metal shell 50 to increase the sealing pressure. On the other hand, since the metal shell 50 is harder than the engine head 500, even if the contact area is reduced and the seal pressure is increased, the metal shell 50 is not easily damaged.

  Furthermore, in the spark plug 100 of this embodiment, the gasket 90 preferably has a Vickers hardness of 100 Hv or more. By doing so, since the gasket 90 has sufficient hardness, plastic deformation of the gasket 90 can be suppressed. As a result, it can suppress that the seal pressure resulting from the gasket 90 operate | moving as a disk spring falls by plastic deformation.

  Furthermore, in the spark plug 100 of the present embodiment, it is preferable that the average length in the radial direction of the tip side contact portion CFF is 1 mm or more and 1.4 mm or less. When the contact area between the gasket 90 and the mounting surface 500S of the engine head 500 is excessively small, the mounting surface 500S is damaged, and when the contact area is excessively large, the gasket 90 and the mounting surface 500S. And the sealing pressure is reduced. According to the above configuration, the seal pressure between the gasket 90 and the mounting surface 500S can be improved while suppressing damage to the mounting surface 500S of the internal combustion engine.

  Furthermore, in the spark plug 100 of the present embodiment, the average length in the radial direction of the rear end side contact portion CFB is preferably 1 mm or less. When the contact area between the gasket 90 and the metal shell 50 (tip surface 54S of the overhanging portion 54) is excessively large, the seal pressure between the gasket 90 and the metal shell 50 is lowered, so that the sealing performance is lowered. According to the above configuration, the sealing pressure between the gasket 90 and the metal shell 50 can be improved.

  Furthermore, in the spark plug 100 of the present embodiment, the screw diameter of the mounting screw portion 52 of the metal shell 50 is preferably M10 or less. The smaller the screw diameter, the smaller the diameter of the gasket 90. The smaller the diameter of the gasket 90, the higher the sealing pressure due to operating as a disc spring. According to the above configuration, the sealing pressure resulting from operating as a disc spring is sufficiently high, so that the sealing performance between the metal shell 50 and the engine head 500 can be further improved. Further, in a small spark plug 100 having a screw diameter of M10 or less, it is difficult to increase the tightening torque of the mounting screw portion 52. Therefore, the seal pressure between the metal shell 50, the engine head 500, and the gasket 90 is difficult. Tend to be low. In the spark plug 100 of the present embodiment, since the decrease in the seal pressure can be compensated by the seal pressure caused by operating as a disc spring, the sealing performance of the small spark plug 100 of M10 or less can be effectively improved. .

B. Evaluation test B-1. First Evaluation Test In the first evaluation test, the center distance La is 0 mm, 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0 Three samples were created for each of the 11 types of samples set at .45 mm and 0.5 mm. The center-to-center distance La was changed by adjusting the radial length and inclination angle of the rear end surface IBM of the inner portion 902M of the intermediate body 90M and the amount of pressing by the pressing member 300. The sample in which the center distance La is set to 0 mm is a sample for comparison, and the sample in which the center distance La is set to 0.05 mm is a sample of the spark plug 100 of the present embodiment.

Items common to each sample are as follows.
Maximum thickness H of gasket 90 (length in axial direction, FIG. 4 (B)): 1.7 mm
Outer diameter R3 of the gasket 90 (FIG. 2): 16.8 mm
Nominal diameter of mounting screw 52: M12
Material of gasket 90: Iron Average value of length L1 in the radial direction of tip side contact portion CFF: 1.2 mm
Average length L2 in the radial direction of the rear end side contact portion CFB: 0.9 mm

  In this test, a desktop cooling test and a vibration test were performed with each sample attached to an aluminum bush with a tightening torque of 25 N · m. In the desktop cooling test, the heating and cooling cycle near the tip of the sample (near the discharge gap) was repeated eight times. Specifically, in one cycle, the vicinity of the tip of each sample was heated for 60 minutes and then cooled in air for 60 minutes. The target temperature for heating was 200 degrees Celsius, and the target temperature for cooling was 50 degrees Celsius.

  In the vibration test, each sample after the desktop cooling / heating test was attached to a vibration tester, and was vibrated for 8 hours in the axial direction and in the direction perpendicular to the axial direction. A log sweep vibration with an acceleration of 30 G was used for the vibration. In the log sweep vibration, the frequency was increased from 50 Hz to 500 Hz by logarithmic sweep, and then one cycle of decreasing the frequency from 500 Hz to 50 Hz by logarithmic sweep was performed for 6 minutes and 30 seconds.

  For each sample after the vibration test, the amount of air leakage from the gasket 90 was measured by a method based on ISO11565. Specifically, with the chamber heated to 200 degrees Celsius, the air pressure on the tip side of the sample was increased to 2.0 MPa, and the amount of air leakage per minute (unit: cc / min) was measured. Then, the evaluation of the sample having a leakage amount of more than 5 cc / min was rejected, and the evaluation of the sample having a leakage amount of 5 cc / min or less was evaluated as evaluation.

  FIG. 6 is a graph plotting the test results of the first evaluation test. Evaluation of all the samples whose center distance La is 0.25 mm or more was acceptable, and evaluation of all the samples whose center distance La was less than 0.25 mm was unacceptable. From this result, it was confirmed that when the center distance La is 0.25 m or more, the sealing performance is significantly improved as compared with the case where the center distance La is less than 0.25.

  Moreover, the tendency for the amount of leakage to fall was confirmed, so that the center distance La became long. In other words, the center-to-center distance La is more preferably 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, and 0.5 mm from the viewpoint of improving the sealing performance in the range of 0.25 mm or more. It could be confirmed.

B-2. Second Evaluation Test In the second evaluation test, the average value of the length L1 in the radial direction of the tip side contact portion CFF is 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1 mm, 1.2 mm, 1 Three samples were created for each of the eight types of samples set at .4 mm and 1.6 mm. The length L1 was changed by adjusting the inclination angle of the distal end surface OFM of the outer portion 901M of the intermediate body 90M. In this test, the center-to-center distance La was fixed to 0.5 mm in each sample. Items common to the other samples are the same as those in the first evaluation test described above.

  In the second evaluation test, each sample was attached to an aluminum bush at a tightening torque of 20 N · m, which was lower than that in the first evaluation test, in order to evaluate under more severe conditions. Then, for each sample, the same amount of leakage (unit: cc / min) was measured by the same method as the first evaluation test after the same desk cooling test and vibration test as those in the first evaluation test were executed. Then, the evaluation of the sample having a leakage amount of more than 5 cc / min was rejected, and the evaluation of the sample having a leakage amount of 5 cc / min or less was evaluated as evaluation.

  FIG. 7 is a graph plotting test results of the second evaluation test. The evaluation of all samples in which the average value of the length L1 in the radial direction of the tip side contact portion CFF is 1.4 mm or less is a pass, and the average value of the length L1 is three that is 1.6 mm. The sample evaluation was unacceptable. In particular, there is a relatively large difference in leakage amount of about 2 cc / mim on average between three samples with an average length L1 of 1.4 mm and three samples with 1.6 mm. Admitted. From this result, when the average value of the length L1 in the radial direction of the distal end side contact portion CFF is 1.4 mm or less, it is significant as compared with the case where the average value of the length L1 exceeds 1.4 mm. It was confirmed that the sealing performance was improved.

  In addition, at least in the range where the average value of the length L1 is 0.8 mm or more, it was confirmed that the leakage amount tends to decrease as the average value of the length L1 becomes shorter. That is, in the range of 0.8 mm or more and 1.4 mm or less, the average value of the length L1 is more preferable from the viewpoint of improving the sealing performance as it becomes shorter as 1.4 mm, 1.2 mm, 1 mm, and 0.8 mm. Was confirmed.

B-3. Third Evaluation Test In the third evaluation test, one for each of the three types of samples in which the average value of the length L1 in the radial direction of the tip side contact portion CFF is set to 0.9 mm, 1 mm, and 1.1 mm. Each sample was created. Items common to the other samples are the same as those in the second evaluation test described above.

  In the third evaluation test, each sample was attached to an aluminum bush with a tightening torque of 20 N · m, as in the second evaluation test. For each sample, the same amount of leakage (unit: cc / min) was measured by the same method as in the second evaluation test after the same desk cooling test and vibration test as in the second evaluation test were performed. And about each sample after measuring the leakage amount, once the sample was removed from the bush, it was attached again with a tightening torque of 20 N · m. For each sample, the same desk-top cooling test and vibration test, and measurement of the leakage amount were repeated. In this manner, for each sample, the sample tightening, the desktop cooling / heating test and the vibration test, and the measurement of the leakage amount were repeatedly performed five times.

  Then, the evaluation of the sample having a leakage amount of more than 5 cc / min was rejected, and the evaluation of the sample having a leakage amount of 5 cc / min or less was evaluated as evaluation.

  FIG. 8 is a graph plotting test results of the third evaluation test. In the sample in which the average value of the length L1 in the radial direction of the tip side contact portion CFF is 0.9 mm, it was confirmed that the amount of leakage increased as the number of repetitions increased. And the evaluation of the sample whose average value of the length L1 is 0.9 mm was acceptable when the number of repetitions was 3 or less, but failed when the number of repetitions was 4 or more. there were.

  On the other hand, in the sample in which the average value L1 in the radial direction of the tip side contact portion CFF is 1 mm and 1.1 mm, it is possible to confirm the tendency that the leakage amount increases even if the number of repetitions increases. There wasn't. And the evaluation of the sample whose average value of this length L1 is 1 mm and 1.1 mm was a pass in the whole range of 1-5 times of repetition.

  From the above, when the average value of the length L1 in the radial direction of the tip side contact portion CFF is 1 mm or more, it is confirmed that a decrease in sealing performance when the ignition plug 100 is repeatedly tightened (attached) can be suppressed. did it.

  By combining the results of the second evaluation test and the third evaluation test, it was confirmed that the average value of the length L1 in the radial direction of the tip side contact portion CFF is preferably 1 mm or more and 1.4 mm or less. .

B-4. Fourth Evaluation Test In the fourth evaluation test, the average value of the length L2 in the radial direction of the rear end side contact portion CFB is 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1 mm, 1.2 mm, Three samples were prepared for each of the seven types of samples set to 1.4 mm. The length L2 was changed by adjusting the inclination angle of the rear end surface IBM of the inner portion 902M of the intermediate body 90M. In this test, in each sample, the average value of the length L1 in the radial direction of the tip side contact portion CFF was fixed to 1.2 mm. Items common to the other samples are the same as those in the second and third evaluation tests described above.

  In the fourth evaluation test, each sample was attached to an aluminum bush at a tightening torque of 15 N · m, which was lower than that in the second evaluation test, in order to evaluate under more severe conditions. Then, for each sample, the same amount of leakage (unit: cc / min) was measured by the same method as the first evaluation test after the same desk cooling test and vibration test as those in the first evaluation test were executed. Then, the evaluation of the sample having a leakage amount of more than 5 cc / min was rejected, and the evaluation of the sample having a leakage amount of 5 cc / min or less was evaluated as evaluation.

  FIG. 9 is a graph plotting test results of the fourth evaluation test. The evaluation of all samples in which the average value of the length L2 in the radial direction of the rear end side contact part CFB is 1 mm or less is a pass, and the average value of the length L1 is 1.2 mm and 1.4 mm. The evaluation of three samples was unacceptable. In particular, when the average value of the length L2 exceeded 1 mm, it was confirmed that the amount of leakage greatly increased. From this result, when the average value of the length L2 in the radial direction of the rear end side contact portion CFB is 1 mm or less, the sealing performance is significantly higher than that when the average value of the length L2 exceeds 1 mm. Was confirmed to improve.

  Moreover, the tendency for the amount of leaks to decline was confirmed, so that the average value of this length L2 became short. That is, in the range of 1 mm or less, it was confirmed that the average value of the length L2 was more preferable from the viewpoint of improving the sealing property as the average value was shortened to 0.8 mm, 0.6 mm, 0.4 mm, and 0.2 mm. .

B-5. Fifth Evaluation Test In the fifth evaluation test, one for each of the nine types of samples in which the Vickers hardness of the gasket 90 is set to 50 Hv, 75 Hv, 100 Hv, 125 Hv, 150 Hv, 175 Hv, 200 Hv, 225 Hv, 250 Hv. A sample has been created. The Vickers hardness of the gasket 90 was adjusted by deforming the material of the gasket 90. In this test, the center-to-center distance La was fixed to 0.5 mm in each sample. Items common to the other samples are the same as those in the first evaluation test described above.

  In the fourth evaluation test, each sample was attached to an aluminum bush with a tightening torque of 20 N · m. Then, for each sample, the same amount of leakage (unit: cc / min) was measured by the same method as the first evaluation test after the same desk cooling test and vibration test as those in the first evaluation test were executed. And in order to evaluate on severer conditions, the evaluation of the sample whose leakage amount is more than 10 cc / min was rejected, and the evaluation of the sample whose leakage amount was 10 cc / min or less was evaluated as evaluation.

  FIG. 10 is a graph plotting the test results of the fifth evaluation test. Evaluation of a sample in which the Vickers hardness of the gasket 90 is 100 Hv or more, that is, a sample in which the Vickers hardness is 100 Hv, 125 Hv, 150 Hv, 175 Hv, 200 Hv, 225 Hv, and 250 Hv was acceptable. The evaluation of the sample in which the Vickers hardness of the gasket 90 is less than 100 Hv, that is, the sample in which the Vickers hardness is 50 Hv and 75 Hv was unacceptable. From this result, it was confirmed that when the Vickers hardness of the gasket 90 is 100 Hv or more, the sealing performance is significantly improved as compared with the case where the Vickers hardness is less than 100 Hv.

  Moreover, when the Vickers hardness is in a range of 150 Hv or less, it was confirmed that the leakage amount tends to decrease as the Vickers hardness of the gasket 90 increases. On the other hand, in the range where the Vickers hardness exceeds 150 Hv, even if the Vickers hardness of the gasket 90 is increased, there is no tendency for the leakage amount to further decrease. That is, it has been found that the Vickers hardness is more preferably 125 Hv or more and particularly preferably 150 Hv or more in the range of 100 Hv or more.

C. Modification (1) The cross sections CS1 and CS2 (FIGS. 4B and 4C) of the gasket 90 of the above embodiment are merely examples, and the present invention is not limited thereto. FIG. 11 is an explanatory diagram of a gasket according to a modification. FIGS. 11A to 11G show cross sections of the gaskets 90A to 90G according to the modified examples cut along the plane including the axis CO. The groove portions CH formed in the front end surfaces IFA to IFG of the inner portions 902A to 902G of the gaskets 90A to 90G are respectively inserted into the holes of the gaskets 90A to 90G after the mounting screw portion 52 of the metal shell 50 is inserted. It is formed by a predetermined pressing member (not shown). As a result, the radially inner ends (left side in the figure) of the inner portions 902A to 902G of the gaskets 90A to 90G extend radially inward, and these gaskets 90A are provided with the groove portions 55 (FIG. 1) of the metal shell 50. Engage with.

  Like these gaskets 90A to 90G, the distal end surfaces OFA to OFG of the outer portions 901A to 901G are positioned in the distal direction FD relative to the distal surfaces IFA to IFG of the inner portions 902A to 902G, and the outer portion 901A. The rear end surfaces OBA to OBG of ˜901G are preferably located in the front end direction FD rather than the rear end surfaces IBA to IBG of the inner portions 902A to 902G. In this way, as in the embodiment, the annular first center line passing through the center of the front end side contact portion is more radially outward than the annular second center line passing through the center of the rear end side contact portion. Sneak away. As a result, the gaskets 90A to 90G function as disc springs.

  For example, in the gasket 90A of FIG. 11A, the front end surface OFA of the outer portion 901A and the rear end surface IBA of the inner portion 902A are perpendicular to the axial direction, and the rear end surface OBA of the outer portion 901A and the inner portion 902A. The distal end surface IFA is inclined with respect to a direction perpendicular to the axial direction. The radially inner surface IVA of the inner portion 902A and the radially outer surface OVA of the outer portion 901A are parallel to each other and inclined with respect to the axial direction.

  In the gasket 90B of FIG. 11B, the radially outer surface OVB of the outer portion 901B is parallel to the axial direction. Other configurations of the gasket 90B in FIG. 11B are the same as the gasket 90A in FIG.

  In the gasket 90C of FIG. 11C, the front end surface IFC and the rear end surface IBC of the inner portion 902C and the front end surface OFC and the rear end surface OBC of the outer portion 901C are parallel to each other and perpendicular to the axis. The outer portion 901C is shifted in the distal direction FD from the inner portion 902C. Therefore, there is a step between the front end surface IFC of the inner portion 902C and the front end surface OFC of the outer portion 901C, and between the rear end surface IBC of the inner portion 902C and the rear end surface OBC of the outer portion 901C. Has a step.

  In the gasket 90D of FIG. 11D, each corner of the cross section is chamfered. The other structure of the gasket 90D in FIG. 11D is the same as that of the gasket 90C in FIG.

  In the gasket 90E of FIG. 11E, among the corners of the cross section, the corners between the front end surface IFE and the rear end surface IBE of the inner portion 902E and the radially inner surface IVE, and the front end of the outer portion 901E Corners between the surface OFE and the rear end surface OBE and the radially outer surface OVE are chamfered. The other structure of the gasket 90E in FIG. 11E is the same as that of the gasket 90C in FIG.

  In the gasket 90F of FIG. 11 (F), the tip surface IFF of the inner portion 902F and the tip surface OFF of the outer portion 901F are connected by an inclined surface. Similarly, the rear end surface IBF of the inner portion 902F and the rear end surface OBF of the outer portion 901F are connected by an inclined surface. The other structure of the gasket 90F in FIG. 11F is the same as that of the gasket 90D in FIG.

  In the gasket 90G of FIG. 11G, the front end surface IFG of the inner portion 902G and the front end surface OFG of the outer portion 901G are the same surface and are inclined with respect to the direction perpendicular to the axis. In addition, the rear end surface IBG of the inner portion 902G and the rear end surface OBG of the outer portion 901G are the same surface and are inclined with respect to the direction perpendicular to the axis. The front end surfaces IFG and OFG of the gasket 90G and the rear end surfaces IBG and OBG are parallel to each other.

(2) In the gasket 90 of the embodiment, as described above, the annular first center line CFL passing through the center of the front end side contact portion CFF is the annular second center passing through the center of the rear end side contact portion CFB. The line CBL is displaced outward in the radial direction. Instead of this, even if the annular first center line passing through the center of the front end side contact portion is shifted inward in the radial direction from the annular second center line passing through the center of the rear end side contact portion. good. As a result, the gasket functions as a disc spring. For example, the front end surface of the outer portion of the gasket is positioned in the rear end direction BD with respect to the front end surface of the inner portion, and the rear end surface of the outer portion is positioned in the rear end direction BD with respect to the rear end surface of the inner portion. If you do.

(3) Specific dimensions of the gasket 90 are examples and are not limited to these. For example, the center-to-center distance La does not have to be 0.25 mm or more over the entire circumferential direction, and may be less than 0.25 mm at some or all circumferential positions. Further, the annular first center line CFL and the second center line CBL do not have to be perfect circles, and may be, for example, annular lines wavy at some or all circumferential positions. . The center-to-center distance La may be different depending on the position in the circumferential direction.

  Further, the average value of the length L2 in the radial direction of the rear end side contact portion CFB may be shorter or the same as the average value of the length L1 in the radial direction of the front end side contact portion CFF. Moreover, the average value of the length L1 in the radial direction of the distal end side contact portion CFF may be less than 1 mm or may be greater than 1.4 mm. Further, the Vickers hardness of the gasket 90 may be less than 100 Hv. Furthermore, the average value of the length L2 in the radial direction of the rear end side contact portion CFB may be larger than 1 mm. Furthermore, the nominal diameter of the mounting screw portion 52 of the gasket 90 may be M12, M14, M16 larger than M10.

  The material forming the gasket 90 may be a material different from the material of the embodiment, for example, another metal such as aluminum or brass, or a material different from a metal such as resin.

(4) The specific configuration of the spark plug 100 of the above embodiment is an example, and can be modified as appropriate. For example, the materials, dimensions, shapes, and the like of the ground electrode 30, the metal shell 50, the center electrode 20, the insulator 10, and the like can be variously changed. For example, the material of the metal shell 50 may be low-carbon steel plated with zinc or nickel, or low-carbon steel that is not plated. The material of the insulator 10 may be various insulating ceramics other than alumina.

  As mentioned above, although this invention was demonstrated based on embodiment and a modification, embodiment mentioned above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the spirit and scope of the claims, and the present invention includes equivalents thereof.

  6 ... Ring member, 8 ... Plate packing, 9 ... Talc, 10 ... Insulator, 12 ... Shaft hole, 13 ... Leg long part, 15 ... Step part, 16 ... Step part, 17 ... Front end side body part, 18 ... Rear end Side body part, 19 ... collar part, 20 ... center electrode, 21 ... center electrode body, 21A ... electrode base material, 21B ... core part, 23 ... head part, 24 ... collar part, 25 ... leg part, 29 ... center electrode Tip: 30 ... Ground electrode, 31 ... Ground electrode body, 39 ... Ground electrode tip, 40 ... Terminal fitting, 41 ... Cap mounting part, 42 ... Hut, 43 ... Leg, 50 ... Metal fitting, 51 ... Tool engagement , 52 ... Mounting screw part, 53 ... Caulking part, 54 ... Overhang part, 55 ... Groove part, 56 ... Step part, 58 ... Compression deformation part, 59 ... Through hole, 60 ... Conductive seal, 70 ... Resistor 80 ... conductive seal, 90, 90A to 90G ... gasket, 90M ... intermediate, 91 ... small inner diameter portion, 92 ... large Diameter portion, 100 ... Spark plug, 295 ... First discharge surface, 300 ... Press member, 311 ... Free end surface, 312 ... Joining end surface, 395 ... Second discharge surface, 500 ... Engine head, 500S ... Mounting surface, 510 ... Screw Hole, 911, 921, 901A to 901G ... outer part, 912,922, 902A to 902G ... inner part

Claims (7)

In the mounting state attached to the internal combustion engine, the outer peripheral surface has a screw portion that is screwed into the screw hole of the internal combustion engine,
A metal shell having a projecting portion projecting radially outward on the rear end side of the threaded portion and connected to the internal combustion engine over the entire circumference in the circumferential direction via a gasket in the attached state A spark plug comprising:
The gasket has a solid cross section cut along a plane including the axis,
When the portion of the gasket that contacts the projecting portion is a rear end side contact portion, and the portion of the gasket that contacts the internal combustion engine is a front end side contact portion,
The annular first center line passing through the center of the rear end side contact portion is either radially outer or radially inner than the annular second center line passing through the center of the tip contact portion. A spark plug characterized by being displaced over the entire circumference. The spark plug according to claim 1,
A spark plug in which a radial distance between the first center line and the second center line is 0.25 mm or more over the entire circumference. The spark plug according to claim 1 or 2,
The average value at the position over the entire circumference in the circumferential direction of the radial length of the rear end side contact portion is more than the average value at the position over the entire circumference in the circumferential direction of the radial length of the tip side contact portion. Short, spark plug. The spark plug according to any one of claims 1 to 3,
The spark plug has a Vickers hardness of 100 Hv or more. The spark plug according to any one of claims 1 to 4,
The spark plug having an average value at a position over the entire circumference in the circumferential direction of the length in the radial direction of the tip side contact portion is 1 mm or more and 1.4 mm or less. The spark plug according to any one of claims 1 to 5,
The spark plug, wherein an average value of positions of the rear end side contact portion in the radial direction over the entire circumference in the circumferential direction is 1 mm or less. The spark plug according to any one of claims 1 to 6,
A spark plug in which the thread diameter of the thread portion of the metal shell is M10 or less.

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