JP5166492B2 - Threaded member having sealing member and spark plug - Google Patents

Description

  The present invention relates to a threaded member and a spark plug having a sealing member for sealing an airtight leak through an attachment hole.

  Generally, a spark plug is attached to an engine by screwing a screw thread formed on the outer periphery of a metal shell to a female screw formed in a mounting hole of an internal combustion engine such as an engine. On the outer periphery of the metal shell, a sealing member (gasket) formed by folding an annular metal plate over the entire circumference in the thickness direction is attached to prevent airtight leakage in the combustion chamber through the mounting hole. When the spark plug is attached, the gasket is compressed by being sandwiched between the overhanging portion of the metal shell and the opening peripheral portion of the attachment hole. The gasket is deformed as the screw is tightened, and improves the adhesion and axial force (reaction force acting in the axial direction due to compression accompanying the tightening) with respect to each of the overhanging portion and the opening peripheral portion, thereby sealing the airtight leak.

  By the way, in the direct injection type engine, the positional relationship among the ground electrode protruding into the combustion chamber, the fuel injection port, and the spark discharge gap affects the ignitability. Therefore, when the spark plug is attached to the engine, it is desired that the direction of the ground electrode (the positional relationship in the combustion chamber) can be freely adjusted by rotating the screw. Then, what secured the magnitude | size (change amount of a compression displacement) which can collapse a gasket is known, maintaining torque, by screwing at the time of attaching a spark plug (for example, refer patent document 1). In Patent Document 1, the amount of change in the compression displacement of the gasket is secured by 0.5 mm or more, so that the rotation of the screw is secured by 0.5 to 1 or more while maintaining a predetermined axial force, and the direction of the ground electrode is set. It can be adjusted.

JP 2000-266186 A

  However, in patent document 1, the part which becomes a crushing margin for ensuring the variation | change_quantity of the compression displacement of a gasket is ensured largely in the radial direction rather than the axial direction of a gasket. Since the gasket tends to spread in the radial direction due to crushing at the time of attachment, a gasket having a large crushing margin in the radial direction may protrude from the overhanging portion.

  The present invention has been made in order to solve the above-mentioned problems, and is a screwed member having a sealing member that can secure a sufficiently large crushing margin while suppressing the protrusion from the overhanging portion when crushing. And to provide a spark plug.

  According to the first aspect of the present invention, a thread is formed on the outer periphery of the projecting part, and the projecting part forms a form that makes a round in the circumferential direction while projecting outward from the outer periphery of the thread toward the base end side of the thread. In the state where the threaded member has an annular shape that is concentrically mounted from the outside, and the threaded member is screwed into the mounting hole in which the female thread is formed, In the threaded member having a sealing member, the sealing member having a sealing member that is compressed between the opening peripheral portion of the mounting hole and seals between the projecting portion and the opening peripheral portion. When the cross-section of the sealing member is viewed on a plane including the central axis of the stop member, the cross-section continues from one end to the other end while the other end is more than the one end. Has a spiral shape located inside, and one end of itself is the one end. Toward the other end of the sealing member that is located radially inward of the sealing member rather than the one end of the sealing member, so that the component along the radial direction is larger than the component along the axial direction of the sealing member, A first extending portion extending substantially linearly; a second extending portion extending substantially linearly so that the component along the axial direction is larger than the component extending along the radial direction; From a component along the radial direction at a position on the radially outer side than the second extending portion, a first connecting portion that connects the end and one end of the second extending portion with a curve of a radius of curvature r The third extending portion extending substantially linearly so that the component along the axial direction is larger, the other end of the second extending portion, and one end of the third extending portion from the first extending portion. A second connecting portion connected by a curve that bends in a direction away from the other end of the third extending portion; The other end of itself is the other end, and the first extending portion and the second connection are positioned between the first extending portion and the second connecting portion in the axial direction. A third connecting portion having a portion overlapping with the portion, and the sealing member is located on a side where the first extending portion contacts the protruding portion of the threaded member, and the threaded member is The threaded member is attached to the threaded member so as to be positioned radially inward of the second extending portion, and the threaded member is attached to the threaded member before the sealing member is screwed into the mounting hole. In the mounted state, the axial height of the sealing member is h, the thickness of the second extending portion at a position satisfying h / 2 is t, and further, in the radial direction of the sealing member, Of the third extending portion, the center of the sealing member R1 is a radial distance from the central axis in a part farthest from the axis, and R2 is a radial distance from the central axis in a part of the second extending portion closest to the central axis of the sealing member. Then, a threaded member having a sealing member satisfying 2 ≧ t ≦ r ≦ (R1−R2) / 2 and satisfying h ≧ (R1−R2) is provided.

  By defining the cross-sectional shape of the sealing member, the size when the sealing member is compressed can be secured, and the circumferential direction of the screwed member is adjusted while maintaining the airtightness of the sealing member. be able to. Specifically, the moldability of the sealing member can be ensured by satisfying 2 × t ≦ r. By setting r ≦ (R1-R2) / 2, the size of the crushing allowance when the sealing member is compressed can be ensured, and the circumferential direction of the threaded member can be adjusted. By setting h ≧ (R1−R2), the collapse allowance can be increased in the central axis direction, and the bulge in the radial direction when the collapse is ensured while securing the collapse allowance can be suppressed.

  In the first aspect, in the cross section of the sealing member, the other end may be located closer to the central axis than the one end in the radial direction. In the cross-sectional shape of the sealing member, if the other end is located closer to the central axis than the other end, the contact position between the first extending portion and the overhang portion and the central axis are equivalent to the radius. The friction diameter can be made smaller than the equivalent friction diameter having the radius of the contact position between the second connection portion and the opening peripheral edge and the central axis. Thereby, since the fastening torque at the time of attaching a threaded member can be made small and the return torque at the time of removing can be enlarged, loosening resistance can be ensured.

  In the first aspect, the sealing member may be made of stainless steel. Since stainless steel has high rigidity, it has high durability against creep deformation caused by a heating / cooling cycle that accompanies driving / resting of a device to which a threaded member is attached, and is effective.

In the first aspect, the compression load when compressing the sealing member in the axial direction is F, and the applied pressure P to the sealing member is calculated by F / {π (R1 ² −R2 ² )}. Sometimes, when the additional pressure P is in a range of 60 MPa to 130 MPa, a rotation angle when the threaded member is screwed into the mounting hole may be 90 ° or more and less than 360 °. Furthermore, a rotation angle when the threaded member is screwed into the mounting hole when the additional pressure P is in a range of 60 MPa to 130 MPa may be 180 ° or more and less than 360 °.

  If 90 ° or more can be secured as the rotation angle, the circumferential direction of the threaded member can be adjusted so as not to affect the drive of the device to which the threaded member is attached. Furthermore, if a rotation angle of 180 ° or more can be secured, the circumferential direction of the threaded member can be adjusted in a preferable direction in driving the device to which the threaded member is attached. The rotation angle of less than 360 ° is necessary and sufficient if the rotation angle is 360 ° because the circumferential direction of the threaded member can be adjusted to an arbitrary direction.

  In the first aspect, before screwing the threaded member into the mounting hole, the section of the sealing member mounted on the threaded member satisfies the h / 2, and the center of the thickness t When the hardness of the sealing member is measured at the position of the second extending portion, the Vickers hardness may be 200 Hv or more and 450 Hv or less. If the sealing member can secure a Vickers hardness of 200 Hv or more and 450 Hv or less, the sealing member can obtain a sufficient spring property, and a sufficient axial force can be secured when adjusting the circumferential direction of the threaded member. .

  In the first aspect, when the cross-section of the sealing member before being attached to the threaded member is viewed, a direction from one end side of the third connection portion toward the other end portion side is the axial direction. On the other hand, they may intersect at an angle of 40 ° to 70 °. In the cross section of the sealing member, if the direction from the one end side of the third connecting portion to the other end side intersects the axial direction at an angle of 40 ° or more, the third member is compressed when the sealing member is compressed. The second stretched portion and the third stretched portion are swelled in the radial direction to cause deformation with a spring property, thereby securing a sufficient axial force. In addition, it is difficult to manufacture a sealing member having the angle larger than 70 °.

  According to the second aspect of the present invention, there is provided a spark plug that uses the sealing member of the threaded member having the sealing member according to the first aspect while being mounted on a metal shell. If the spark plug is equipped with the sealing member according to the first aspect, it can sufficiently withstand the load caused by the heating / cooling cycle accompanying the driving / stopping of the internal combustion engine. Therefore, since the direction of the ground electrode can be adjusted while ensuring airtightness and looseness resistance, ignitability can be ensured.

1 is a partial cross-sectional view of a spark plug 1. FIG. It is a figure which shows the circumferential direction cross section in the state before mounting | wearing with the spark plug 1 of the gasket 100. FIG. It is a figure which shows the circumferential direction cross section in the state after mounting | wearing with the spark plug 1 of the gasket 100. FIG. FIG. 3 is a partial cross-sectional view showing a state in which the spark plug 1 is attached to the engine head 90 and compressed by sandwiching the gasket 100 between the overhanging portion 54 of the metal shell 50 and the opening peripheral edge portion 92 of the attachment hole 91. It is a graph which shows the relationship between the direction of the ground electrode 30, and ignition advance angle (BTDC).

  Hereinafter, an embodiment of a spark plug embodying the present invention will be described with reference to the drawings. First, with reference to FIG. 1, the structure of the spark plug 1 equipped with a gasket 100 as an example of a sealing member according to the present invention will be described. A metal shell 50 described later will be described as an example of a threaded member in the present invention. However, the spark plug 1 is completed by assembling each component to the metal shell 50. Therefore, for the sake of convenience, the following description will be made assuming that the axis of the metal shell 50 coincides with the axis O of the spark plug 1. In FIG. 1, the axis O direction 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.

  As shown in FIG. 1, the spark plug 1 has an insulator 10 that holds the center electrode 20 on the front end side in the shaft hole 12 and holds the terminal fitting 40 on the rear end side. The spark plug 1 has a metal shell 50 that surrounds the periphery of the insulator 10 in the circumferential direction and holds the insulator 10. The ground electrode 30 is joined to the front end surface 57 of the metal shell 50. The ground electrode 30 is bent so that the tip 31 side faces the center electrode 20, and has a spark discharge gap GAP between the noble metal tip 80 provided on the center electrode 20.

  First, the insulator 10 will be described. As is well known, the insulator 10 is formed by firing alumina or the like, and has a cylindrical shape having a shaft hole 12 extending in the direction of the axis O at the center of the shaft. At the approximate center of the insulator 10 in the direction of the axis O, a flange portion 19 having the largest outer diameter is formed. A rear end side body portion 18 is formed on the rear end side (upper side in FIG. 1) from the flange portion 19. A front end side body portion 17 having an outer diameter smaller than that of the rear end side body portion 18 is formed on the front end side (lower side in FIG. 1) from the flange portion 19. A long leg portion 13 having an outer diameter smaller than that of the front end side body portion 17 is formed on the front end side of the front end side body portion 17. The outer diameter of the long leg portion 13 is reduced toward the distal end side. When the spark plug 1 is attached to the engine head 90 (see FIG. 4) of the internal combustion engine, the leg long portion 13 is exposed to the combustion chamber (not shown) of the engine. A step portion 15 is formed between the leg long portion 13 and the distal end side trunk portion 17.

  Next, the center electrode 20 will be described. As described above, the insulator 10 holds the center electrode 20 on the distal end side of the shaft hole 12. The center electrode 20 has a structure in which a metal core 25 made of copper or the like having excellent thermal conductivity is disposed inside a base material 24 made of a nickel-based alloy such as Inconel (trade name) 600 or 601. The distal end portion 22 of the center electrode 20 protrudes from the distal end surface of the insulator 10, and the outer diameter is reduced toward the distal end side. A noble metal tip 80 is joined to the distal end surface of the distal end portion 22 in order to improve spark wear resistance. The insulator 10 has a seal body 4 and a ceramic resistor 3 in the shaft hole 12. The center electrode 20 is electrically connected to the terminal fitting 40 held on the rear end side of the shaft hole 12 via the seal body 4 and the ceramic resistor 3. When the spark plug 1 is used, an ignition coil (not shown) is connected to the terminal fitting 40 and a high voltage is applied.

  Next, the ground electrode 30 will be described. The ground electrode 30 is an electrode formed of a metal having high corrosion resistance (for example, a nickel alloy such as Inconel (trade name) 600 or 601) and formed in a rod shape having a substantially rectangular cross section. The ground electrode 30 has a base portion 32 on one end side joined to the distal end surface 57 of the metal shell 50 by welding. The ground electrode 30 is bent at the tip end 31 side at the other end toward the tip end 22 side of the center electrode 20. A spark discharge gap GAP is formed between the tip 31 of the ground electrode 30 and the noble metal tip 80 of the center electrode 20.

  Next, the metal shell 50 will be described. The metal shell 50 is a cylindrical metal fitting made of a low carbon steel material. As described above, the metal shell 50 surrounds the portion from the part of the rear end side body portion 18 of the insulator 10 to the long leg portion 13 and holds the insulator 10. The metal shell 50 includes a tool engaging portion 51 into which a spark plug wrench (not shown) is fitted, and an attachment portion 52 in which a screw thread is formed to be engaged with an internal thread of an attachment hole 91 (see FIG. 4) of the engine head 90. Have The metal shell 50 of the present embodiment is manufactured in accordance with a standard in which the nominal diameter of the thread of the mounting portion 52 is M12. The nominal diameter is not limited to M12, and may be M10, M14, or M8. Further, a Ni plating layer is formed on the surface of the metal shell 50.

  Between the tool engaging portion 51 and the attachment portion 52 of the metal shell 50, an overhang portion 54 is formed that projects radially outward in a bowl shape. A portion between the attachment portion 52 and the overhang portion 54 is referred to as a screw neck 59, and a gasket 100 described later is fitted into the screw neck 59.

  A caulking portion 53 having a small thickness is provided on the rear end side of the metal fitting 50 from the tool engaging portion 51. A thin buckled portion 58 is provided between the overhang portion 54 and the tool engaging portion 51 in the same manner as the caulking portion 53. A step portion 56 is formed at the position of the attachment portion 52 on the inner periphery of the metal shell 50, and the annular plate packing 8 is disposed on the step portion 56. Annular ring members 6, 7 are interposed between the inner peripheral surface of the metal shell 50 from the tool engaging portion 51 to the caulking portion 53 and the outer peripheral surface of the rear end side body portion 18 of the insulator 10. The talc (talc) 9 powder is filled between the ring members 6 and 7. The crimping portion 53 is crimped so as to be bent inward, thereby pressing the insulator 10 toward the distal end side in the metal shell 50 via the ring members 6, 7 and the talc 9. The insulator 10 pressed by the crimping portion 53 is integrated with the metal shell 50 with the step portion 15 supported by the step portion 56 of the metal shell 50 via the plate packing 8. The airtightness between the metal shell 50 and the insulator 10 is maintained by the plate packing 8, and the outflow of combustion gas is prevented. The above-described buckling portion 58 is configured to bend and deform outwardly with the addition of a compressive force during caulking, and the compression length of the talc 9 in the direction of the axis O is increased to improve airtightness. Is increasing.

  Next, the gasket 100 will be described. The gasket 100 is produced in an annular shape by applying a process of turning back in the thickness direction to a single annular plate made of austenitic stainless steel or ferritic stainless steel. When the gasket 100 is attached to the metal shell 50, the center axis of the annular gasket 100 (for convenience, the axis Q (see FIG. 3)) is aligned in the direction of the axis O and is fitted into the screw neck 59. At this time, the gasket 100 is placed so that the first extending portion 110 described later is directed to the overhanging portion 54 of the metal shell 50 and the screw neck 59 is positioned radially inward from the second extending portion 120 described later. Attached to the screw neck 59. The gasket 100 shown in FIG. 1 is deformed so as to be compressed in the axis Q direction and expanded in the radial direction when attached to the metal shell 50, and is prevented from coming off from the screw neck 59. . In the following, the gasket 100 (that is, not compressed in the direction of the axis Q) before being attached to the metal shell 50 will be described.

  As shown in FIG. 2, the gasket 100 according to the present embodiment has a cross section orthogonal to the circumferential direction (in other words, a plane including the axis Q) by folding the above-described annular plate material at three locations in the thickness direction. 100 and is hereinafter referred to as a “circumferential cross section”). More specifically, the gasket 100 has a spiral shape in which the end 102 is located on the inner side of the end 101 while continuing from one end 101 to the other end 102 in the circumferential cross section. For example, in order to produce a gasket that has four or more turns, or a circumferential cross section that is not spiral, and includes a turn in the reverse thickness direction, processing by press molding of at least five steps is required. And The gasket 100 of the present embodiment can be manufactured by so-called unidirectional bending in which one surface side of the plate material is always a valley side, and can be specifically formed by press molding in four steps, and thus has excellent formability. . Hereinafter, although the form of the gasket 100 is demonstrated, the circumferential direction cross section of the gasket 100 has the 1st extending | stretching part 110, the 2nd extending | stretching part 120, the 3rd extending | stretching part 130, the 1st connection part 140, the 2nd connection part 150 for convenience. , And the third connection part 160.

  The first extending portion 110 is a portion having a shape extending linearly toward the other end 112 of the gasket 100 with the one end portion 101 of the gasket 100 as its one end 111 in the circumferential cross section. The other end 112 of the first extending portion 110 is disposed inside the one end 111 in the radial direction. The second extending portion 120 is a portion having a shape extending linearly from one end 121 to the other end 122 such that the component in the axis Q direction is larger than the component in the radial direction in the circumferential cross section. is there. One end 121 of the second extending portion 120 is disposed closer to the first extending portion 110 than the other end 122. Similarly, the third extending portion 130 has a shape extending linearly from one end 131 to the other end 132 so that the component in the axis Q direction is larger than the component in the radial direction in the circumferential cross section. It is a part. The other end 132 of the third extending portion 130 is disposed closer to the first extending portion 110 than the one end 131. Further, the third extending portion 130 is disposed outside the second extending portion 120 in the radial direction.

  The first connection part 140 is a part that connects the other end 112 of the first extension part 110 and one end 121 of the second extension part 120. The first connection portion 140 is one of the three portions that are bent when the gasket 100 is manufactured. As will be described later, when the gasket 100 is compressed when the metal shell 50 is attached to the screw neck 59, the first connecting portion 140 has a shape in which the shape of the circumferential cross section follows the curve of the radius of curvature r. The extending part 110 and the second extending part 120 are connected. Since the first connecting portion 140 is bent in advance when the gasket 100 is manufactured, the first connecting portion 140 is formed in a shape along the curve of the radius of curvature r when the gasket 100 is compressed at the time of mounting.

  The second connecting portion 150 is a portion that connects the other end 122 of the second extending portion 120 and one end 131 of the third extending portion. The second connection part 150 is one of the parts that are bent when the gasket 100 is manufactured, like the first connection part 140 described above. The second connecting portion 150 is bent so that the shape of the circumferential cross section thereof is a shape along a U-shaped curve that bends away from the first extending portion 110 in the axis Q direction.

  The third connection part 160 is a part where one end 161 of the third connection part 160 is connected to the other end 132 of the third extension part 130 and the other end 162 of the third connection part 160 is the other end part 102 of the gasket 100. Similarly, the third connecting portion 160 is one of the parts that are bent when the gasket 100 is manufactured. The other end 162 of the third connecting portion 160 is bent so as to be located inside the one end 161 in the radial direction. At that time, the other end 162 is positioned between the second extended portion 120 and the third extended portion 130 in the radial direction, and in the axis Q direction, the first extended portion 110 and the second connecting portion 150 Located between. As a result, the other end 162 of the third connection portion 160 is disposed at a position overlapping the first extending portion 110 and the second connection portion 150 in the axis Q direction inside the spiral shape formed by the gasket 100. .

  As described above, the gasket 100 is formed so that the circumferential cross section thereof is spiral, so that a space is secured in the gasket 100. This internal space functions as a collapse allowance for the gasket 100 to be crushed when the spark plug 1 is attached to the engine head 90. In the present embodiment, when the spark plug 1 is attached to the engine head 90, the gasket 100 is desired to have a sufficient amount of collapse to adjust the direction of the ground electrode 30 protruding into the combustion chamber. In addition, when the gasket 100 is compressed, the second extending portion 120 and the third extending portion 130 of the gasket 100 may be deformed so as to expand in the radial direction in order to obtain a sufficient axial force for ensuring airtightness. desired. Therefore, when the gasket 100 is manufactured, the bending angle θ when the third connecting portion 160 is bent is defined. Specifically, the third connecting portion 160 is directed from the one end 161 side connected to the other end 132 of the third extending portion 130 toward the other end 162 side that is the other end portion 102 of the gasket 100. Is defined to intersect with the axis Q direction at an angle of 40 ° to 70 °.

  In a state before the third connecting portion 160 is bent, the direction from the one end 161 to the other end 162 of the third connecting portion 160 coincides with the direction from the one end 131 to the other end 132 of the third extending portion 130, and a straight line It extends in a shape. When the third connecting portion 160 is bent, an angle θ intersecting the direction from the one end 161 to the other end 162 of the third connecting portion 160 with the direction from the one end 131 to the other end 132 of the third extending portion 130 is The third connecting portion 160 is bent so as to be 40 ° or more and 70 ° or less. However, after the third connecting portion 160 is bent, the direction from the one end 161 toward the other end 162 differs depending on the bending position. In the present embodiment, it is assumed that the bending of the third connecting portion 160 at the time of manufacturing the gasket 100 is performed in the vicinity of one end 161 and the stretching direction is maintained in the vicinity of the other end 162. Therefore, for the sake of convenience, an angle θ at which the extending direction of the third connecting portion 160 in the vicinity of the other end 162 (indicated by the imaginary straight line 163) intersects the extending direction of the third extending portion 130 (indicated by the imaginary straight line 164) will be considered.

  According to Example 1 to be described later, it is impossible to mold a case where the angle θ at which the virtual straight line 163 intersects the virtual straight line 164 is greater than 70 °. When the angle θ at which the virtual straight line 163 and the virtual straight line 164 intersect is less than 40 °, the second extending portion 120 and the third extending portion 130 have a diameter in compression when the gasket 100 is attached to the metal shell 50. There is a risk of not swelling in the direction.

  Next, the gasket 100 attached to the metal shell 50 (compressed in the direction of the axis Q and deformed so as to expand in the radial direction) will be described with reference to FIGS. When the gasket 100 is attached to the metal shell 50 (see FIG. 1), it is compressed in the direction of the axis Q as shown in FIG. Due to compression, the circumferential cross section of the gasket 100 swells in the radial direction, and the inner diameter becomes a size that is smaller than the outer diameter of the thread of the metal shell 50, so that the gasket 100 is prevented from coming off from the screw neck 59. . Note that partial compression for further reducing the inner diameter of the gasket 100 may be performed at several locations in the circumferential direction of the gasket 100.

  In the spark plug 1 shown in FIG. 4, the metal shell 50 is mounted in the mounting hole 91 of the engine head 90, and the gasket 100 is sandwiched between the overhanging portion 54 of the metal shell 50 and the opening peripheral edge 92 of the mounting hole 91. It is a thing of the state. In the state of FIG. 4, the gasket 100 has not yet been compressed in the direction of the axis Q by tightening the metal shell 50. When further tightened from this state, although not shown, the gasket 100 is compressed in the axial Q direction between the overhanging portion 54 of the metal shell 50 and the opening peripheral edge portion 92 of the mounting hole 91, so that the radial direction This causes the deformation to swell. At this time, the second extending portion 120 and the third extending portion 130 are bent with a spring property in a direction away from each other, so that the gasket 100 has an axial force (tightening) on the protruding portion 54 and the opening peripheral portion 92. The reaction force is deformed while maintaining the reaction force acting in the direction of the axis Q due to compression.

In order to ensure the airtightness of the gasket 100 compressed between the overhanging portion 54 and the opening peripheral edge portion 92, it is important to apply an appropriate compressive force to the gasket 100. Therefore, the compression load when compressing the gasket 100 in the axis Q direction is F, and the pressure (additional pressure) P to which an appropriate compressive force is applied to the gasket 100 is P = F / {π (R1 ² −R2 ² )}. As shown in FIG. 3, in the circumferential cross section of the gasket 100, the radial distance from the axis Q in the portion farthest from the axis Q in the third extending portion 130 is R1. Similarly, the radial distance from the axis Q at the portion closest to the axis Q in the second extending portion 120 is R2.

  According to Example 2 described later, it was found that the range of the applied pressure P is desirably 60 MPa or more and 130 MPa or less. If the applied pressure P is less than 60 MPa, it is difficult to ensure airtightness with the gasket 100. If the applied pressure P is greater than 130 MPa, it is difficult to ensure the strength, and the metal shell 50 may be broken by tightening.

  In order to secure the range of the additional pressure P, it is also necessary to obtain a spring property by securing the hardness of the gasket 100 so that a sufficient axial force can be obtained when the gasket 100 is compressed. . According to Example 3 to be described later, it was found that when the hardness of the gasket 100 was measured at the point S of the circumferential cross section of the gasket 100 shown in FIG. 3, the Vickers hardness should be 200 Hv or more and 450 Hv or less. . In addition, in the circumferential cross section of the gasket 100 in a state where it is attached to the metal shell 50 before being attached to the engine head 90 shown in FIG. The thickness of the 2nd extending | stretching part 120 is set to t in the site | part where the height of the axis Q direction becomes h / 2. The center position of the thickness t is defined as the above S point.

  When the Vickers hardness of the gasket 100 at the point S is less than 200 Hv, the gasket 100 cannot obtain a sufficient spring property and may be plastically deformed and loosened when compressed by tightening. When the Vickers hardness of the gasket 100 at the point S is greater than 450 Hv, the gasket 100 may be cracked or cracked when compressed by tightening.

  Further, as described above, the gasket 100 of the present embodiment is provided with a crush margin for adjusting the direction of the ground electrode 30 protruding into the combustion chamber. However, since it is necessary to ensure airtightness as the gasket 100, it is desirable that the range of the applied pressure P is 60 MPa or more and 130 MPa or less even when the collapse allowance is collapsed. Therefore, according to Example 4 to be described later, in order to ensure the ignitability of the spark plug 1 while ensuring the range of the additional pressure P, the orientation of the ground electrode 30 can be adjusted by at least 90 ° or more. desired. When the angle at which the direction of the ground electrode 30 can be adjusted is less than 90 °, it may be difficult to adjust the direction of the ground electrode 30 to a direction that can reduce the influence on the ignitability. Note that the direction of the ground electrode 30 can be adjusted in all directions as long as it can be adjusted by 360 ° (for one rotation), so the upper limit is set to 360 °.

  Furthermore, according to Example 4 described later, it was found that if the orientation of the ground electrode 30 can be adjusted by 180 ° or more, the ignitability of the spark plug 1 can be reliably ensured. When the angle at which the direction of the ground electrode 30 can be adjusted is less than 180 °, it may be difficult to adjust the direction of the ground electrode 30 to a direction that can reduce the influence on the ignitability. The point that the upper limit of the orientation adjustment of the ground electrode 30 is 360 ° is the same as described above.

  Further, in the present embodiment, the circumferential direction of the gasket 100 is used so as to secure a crushing allowance large enough to adjust the orientation of the ground electrode 30 and not to protrude from the overhanging portion 54 even if it is crushed. There is a provision for the shape of the cross section. As described above, the height in the axis Q direction of the gasket 100 is h, the thickness of the second extending portion 120 at the position of h / 2 is t, and the radius of curvature of the first connection portion 140 is r. Further, the radial distance at the portion farthest from the axis Q of the third extending portion 130 is R1, and similarly, the radial distance at the portion closest to the axis Q of the second extending portion 120 is R2. At this time, 2 × t ≦ r ≦ (R1-R2) / 2 is satisfied and h ≧ (R1-R2) is satisfied.

  In the gasket 100, the second extending portion 120 and the third extending portion 130 are portions that swell in the radial direction by being crushed when the crushed allowance is crushed in the axis Q direction. The second extending portion 120 and the third extending portion 130 ensure the size of the crushing margin in the direction of the axis Q. In order to adjust the orientation of the ground electrode 30 as described above, it is necessary to secure a certain size as the size of the collapse in the axis Q direction. Therefore, when h is smaller than R1-R2 and the crushing margin is larger in the radial direction than the axis Q direction, the radial size when the gasket 100 is crushed becomes larger than that when h is R1-R2 or more. . Then, the gasket 100 may protrude from the overhanging portion 54 or may be caught by the screw neck 59, and there is a possibility that sufficient tightening cannot be performed. According to Example 5 described later, it has been found that there is a possibility that a sufficient angle (specifically, 180 ° or more) cannot be secured as an angle for adjusting the direction of the ground electrode 30.

  Next, in order to secure the size that the gasket 100 is crushed in the direction of the axis Q, the radius of curvature r of the first connecting portion 140 may be made smaller. The larger the radius of curvature r, the larger the size occupied by the first connecting portion 140 in the direction of the axis Q. Then, it becomes difficult to secure the size of the second extending portion 120 in the axis Q direction, and there is a possibility that a sufficient crushing allowance cannot be secured. According to Example 5 described later, it has been found that when the radius of curvature r is larger than (R1−R2) / 2, a sufficient crushing margin cannot be secured.

  On the other hand, the smaller the radius of curvature r, the larger the amount of distortion caused by the bending process at the first connecting portion 140 when the gasket 100 is manufactured. Then, the load due to the bending load causes wrinkles toward the bending trace of the first connecting portion 140, and when the gasket 100 is compressed, the folding trace starts from the folding trace and the spring property of the second extending portion 120 is increased. It may be difficult to secure. According to Example 6 to be described later, when the radius of curvature r is less than twice the thickness t of the second extending portion 120, the first connection portion 140 may be folded or crushed when the gasket 100 is manufactured. I understood.

  In addition, as a material of the gasket 100, for example, stainless steel (SUS) having the following standard number defined in JIS (Japanese Industrial Standard) can be used. Examples of austenitic stainless steels include SUS201, SUS202, SUS301, SUS301J, SUS302, SUS302B, SUS304, SUS304L, SUS304N1, SUS304N2, SUS304LN, SUS305, SUS309S, SUS310S, SUS316, US3316L, S3316L, S3316L, S3316L, S3316L, S3316L, S3316L, S3316L SUS317L, SUS317J1, SUS321, SUS347, SUSXM15J1, etc. can be used. Examples of ferritic stainless steel include SUS405, SUS410L, SUS429, SUS430, SUS430LX, SUS430JIL, SUS434, SUS436L, SUS436JIL, SUS444, SUS445J1, SUS445J2, SUS447J1, and SUS447M27.

  Gaskets made using stainless steel such as these have higher rigidity than commonly used gaskets made of Fe. Therefore, the durability against creep deformation caused by heating / cooling accompanying driving / resting of the engine is high, and screwing due to deformation of the gasket is less likely to occur. According to Example 7 which will be described later, it is confirmed that there is a difference in looseness resistance between the case where stainless steel (SUS) is used for the gasket 100 and the case where iron (Fe) is used. It has become clear that it is preferable to use stainless steel.

  Furthermore, it was confirmed by Example 7 that will be described later that there is a difference in looseness resistance depending on the direction in which the gasket 100 is attached to the screw neck 59 of the metal shell 50. Specifically, the gasket 100 according to the present embodiment is manufactured in a shape in which the second extending portion 120 side is disposed radially inward and the third extending portion 130 side is disposed radially outward in the circumferential cross section. It is attached to the screw neck 59 with the extending portion 110 side facing the overhang portion 54. On the other hand, it is produced in a shape in which the second extending portion side is arranged radially outside and the third extending portion side is arranged radially inside, and the first extending portion side is directed to the overhanging portion 54 and is attached to the screw neck 59. There is a gasket (sample 43) in the form of being mounted. Further, the second extending portion side is prepared in a shape arranged radially inward and the third extending portion side is arranged radially outside, and the second connecting portion side is directed to the overhanging portion 54 and attached to the screw neck 59. There is one form of gasket (sample 44). It was found that the gasket of any form has a smaller axial force (return torque) required for screw removal (loosening) than the gasket 100 of the present embodiment, and the looseness resistance is lowered.

  This phenomenon is explained by a comparison of equivalent friction diameters. As shown in FIG. 4, the gasket 100 is compressed in the direction of the axis Q as described above when mounted on the screw neck 59 of the metal shell 50. When the metal shell 50 to which the gasket 100 is attached is attached to the attachment hole 91 and the screw is tightened, the gasket 100 comes into contact with the overhanging portion 54 at one point X at the initial stage of compression. When a known equivalent friction diameter serving as an index for evaluating a substantial friction force generated between the gasket 100 and the overhanging portion 54 is examined, the diameter of a virtual circle whose radius is the radial distance of the point X is the gasket. This corresponds to an equivalent friction diameter between 100 and the overhanging portion 54. Similarly, the gasket 100 also contacts the opening peripheral edge 92 of the mounting hole 91 at one point Y. For this reason, the equivalent friction diameter between the gasket 100 and the opening peripheral edge 92 corresponds to the diameter of a virtual circle whose radius is the radial distance of the point Y.

  Here, the equivalent friction diameter refers to “the diameter of a circle when an annular contact is replaced with a circular contact having the same rotational friction force with respect to the rotational friction force”. In order to increase the looseness resistance, the frictional force between the gasket, the metal shell and the engine head may be increased to increase the return torque. The inventors have used an aluminum bush simulating an engine head, and observed the state of slip that occurs between the gasket and the metal shell and the aluminum bush when the metal shell is screwed into the mounting hole provided in the aluminum bush. did. As a result, it was found that when tightening, slipping was likely to occur between the gasket and the metal shell, and slipping was less likely to occur between the gasket and the aluminum bush. On the other hand, when loosened, it was found that slipping was less likely to occur between the gasket and the metal shell, and slipping was likely to occur between the gasket and the aluminum bush. Therefore, if the frictional force between the gasket and the aluminum bush, that is, the engine head, is increased rather than the frictional force between the gasket and the metal shell, the resistance to loosening of the screwing (relaxation resistance) can be increased. .

  According to Example 7, the gasket of the sample 43 has the same equivalent friction diameter between the peripheral edge of the opening as compared with the gasket 100 (sample 41) of the present embodiment, but between the extended portion and the gasket. The equivalent friction diameter is large. That is, if the metal shell to which the gasket of the sample 43 is attached is not tightened with a larger torque at the time of tightening, the same fastening force as that of the metal shell 50 to which the gasket 100 of this embodiment is attached cannot be obtained. In other words, when the metal shell to which the gasket of the sample 43 is attached and the metal shell 50 to which the gasket 100 of this embodiment is attached are tightened with the same torque, the return torque is the same as that of the gasket 100 of this embodiment. The mounted metal shell 50 is large.

  In addition, the gasket of the sample 44 has a smaller equivalent friction diameter with the peripheral edge of the opening and a larger equivalent friction diameter with the overhanging portion as compared with the gasket 100 (sample 41) of the present embodiment. Therefore, when both are tightened with the same torque, both the tightening force and the return torque of the metal shell 50 to which the gasket 100 of the present embodiment is attached are larger than those of the metal shell to which the gasket of the sample 44 is attached. large.

  Needless to say, the present invention can be modified in various ways. The gasket 100 is produced by folding an annular plate material at three places in the thickness direction, but may be produced by folding at two places or four or more places. Further, the circumferential cross section of the gasket 100 may not have the same shape over the entire circumference of the gasket 100. That is, the gasket 100 may partially have a circumferential cross-sectional shape shown in FIG. 3 in the circumferential direction of the gasket 100.

  The shape of the cross section in the circumferential direction of the gasket 100 shown in FIG. 3 shows a shape compressed in the direction of the axis Q when being attached to the screw neck 59 of the metal shell 50. Not only this but the shape of the circumferential cross section shown in FIG. 2 is formed in the state where the gasket 100 is attached to the screw neck 59, and the circumferential cross section shown in FIG. 3 is formed by compression when the spark plug 1 is tightened in the mounting hole 91. You may have a shape.

  At the time of producing the gasket 100, the effect of defining the bending angle θ when bending the third connecting portion 160 was confirmed. First, it was confirmed by simulation whether or not molding by a press molding machine according to the difference in the angle θ was possible. In the circumferential cross section of the gasket 100 shown in FIG. 2, a gasket having a bending angle θ of the third connecting portion 160 of 0 ° to 70 ° can be molded by simulating a molding process by a press molding machine. Since it was, it evaluated as (circle). However, a gasket with an angle θ of 90 ° was simulated by the molding process and found that it could not be processed by a press molding machine, and was evaluated as x.

  Next, the difference in behavior when the molded gasket was compressed due to the difference in the angle θ was confirmed by simulation. The simulation was performed by a known FEM analysis. In the case of a gasket having an angle θ of 40 ° or more, when compressed in the direction of the axis Q, the first extending portion 110 is pressed, the first connecting portion 140 is bent, and the one end 111 side of the first extending portion 110 moves downward. Is done. And the 1st extending part 110 contacted the other end 162 of the 3rd connection part 160, and the other end 162 was pushed by the 1st extending part 110 as it was, and was moved below so that it might be wound inside the crushing allowance . When the compression is further continued, the second extending portion 120 is pressed through the first connecting portion 140 by the first extending portion 110 that receives a drag force from the other end 162 of the third connecting portion 160, and the second extending portion 120 has a diameter. Bending occurred inward in the direction, and the length of the second extending portion 120 in the axis Q direction was shortened. Similarly, the third connecting portion 160 that receives a drag force from the first extending portion 110 at the other end 162 presses the third extending portion 130, and the third extending portion 130 bends radially outward. The length of the three extending portions 130 in the axis Q direction is shortened. As a result, the crushing allowance was compressed in the direction of the axis Q while expanding in the radial direction, and crushed in a desirable form.

  On the other hand, in the case of the gasket having an angle θ of less than 40 °, the first connecting portion 140 is bent by the compression in the axis Q direction, and the first extending portion 110 is in contact with the other end 162 of the third connecting portion 160 as described above. Then, the other end 162 of the third connection part 160 is pressed from the first extension part 110, but the third connection part 160 is pressed in a state in which the third connection part 160 abuts in a direction perpendicular to the surface of the first extension part 110. Will be. Thereby, the 3rd connection part 160 will bend radially outward with the 3rd extending | stretching part 130, and a crushing allowance will deform | transform like a parallelogram. The crushing allowance causes crushing in the direction of the axis Q without causing bending in the radial direction in the second extending portion 120 and the third extending portion 130. For this reason, although the collapse allowance collapsed, the spring property by the 2nd extending | stretching part 120 and the 3rd extending | stretching part 130 was not acquired, and since axial force was not securable, it evaluated as x. The results of the evaluation test are shown in Table 1.

  Obviously from Table 1, when the gasket 100 is manufactured, if the bending angle θ when bending the third connecting portion 160 is defined to be 40 ° or more and 70 ° or less, the desired form of collapse in both formability and deformation during compression is obtained. It was found that a gasket 100 having a margin can be obtained.

Next, an evaluation test was performed to confirm the applied pressure P necessary for the gasket 100 to ensure airtightness and looseness resistance. Five samples of the gasket 100 were produced by processing by press molding an annular plate made of stainless steel and having a thickness of 0.5 mm. At this time, as shown in FIG. 3, when the respective dimensions in the circumferential cross section of the gasket 100 were confirmed, the radius of curvature r of the first connecting portion 140 was 1 mm, the radial distance R1 was 8.15 mm, and the radial distance R2 was It became 6 mm. Five samples of the spark plug 1 in which the sample of the gasket 100 was attached to the screw neck 59 of the metal shell 50 were attached to an aluminum bush (not shown) with different tightening torques (compression loads F). Specifically, the applied pressure P (calculated by P = F / {π (R1 ² −R2 ² )} as described above) when attaching the sample of each spark plug 1 is 30, 60, 100, respectively. , 130, 190 [MPa]. At this time, in the sample of the spark plug 1 attached with the additional pressure P of 190 MPa, the metal shell 50 was broken. Therefore, it was evaluated as “x” in terms of strength, and no evaluation test was performed on the following looseness resistance and airtightness.

  The vibration test shown in ISO11565 was performed on the aluminum bush to which the sample of the spark plug 1 was attached. Specifically, with the aluminum bush to which the sample of the spark plug 1 is attached heated to 200 ° C., vibration of an acceleration of 30 G ± 2 G, a frequency of 50 to 500 Hz, and a sweep rate of 1 octave / min. The direction and its orthogonal direction were each given 8 hours. After the vibration test, the aluminum bush with the sample of the spark plug 1 attached is covered with a case filled with a liquid (for example, ethanol), and the aluminum bush is attached to the mounting hole of the aluminum bush from the opening corresponding to the combustion chamber side. An air pressure of 5 MPa was applied, and the amount of air leakage per minute was measured. Those having an air leakage amount of 5 cc or less were evaluated as “good” because the airtightness by the gasket 100 could be sufficiently maintained, and those having an air leakage amount of more than 5 cc were evaluated as “poor” because the airtightness could not be maintained.

  Further, the spark plug 1 is removed from the aluminum bush, and at this time, the torque (return torque) required for removing the metal shell 50 is measured, and the ratio of the return torque to the tightening torque (return torque / tightening torque) is obtained as a percentage. It was. When the return torque is 10% or more of the tightening torque, it is evaluated as “good” because the resistance to loosening (loose resistance) is good, and when it is less than 10%, it is evaluated as “poor” because the resistance to loosening is low. did. The results of the evaluation test are shown in Table 2.

  As shown in Table 2, all of the samples of the gasket 100 attached with an applied pressure P of 30 to 130 [MPa] had good resistance to loosening. Regarding the airtightness, the sample of the gasket 100 attached with the additional pressure P of 60 to 130 [MPa] was able to maintain sufficient airtightness, but the gasket 100 attached with the additional pressure P of 30 [MPa]. This sample could not maintain airtightness. Therefore, if the additional pressure P at the time of attaching the spark plug 1 is 60 to 130 [MPa], the second extending portion 120 and the third extending portion 130 are deformed while maintaining the spring property, so that the collapse allowance is crushed. As a result, it has been found that a sufficient axial force can be obtained as the gasket 100 and the looseness resistance and the airtightness can be secured.

  Next, an evaluation test was performed in order to confirm the hardness required for the second extending portion 120 and the third extending portion 130 to be deformed while maintaining the spring property when the collapse allowance is crushed. Nine types of 0.5 mm thick plate materials having different Vickers hardness were prepared by changing various annealing conditions in the stainless steel manufacturing process. And the sample of the gasket 100 provided with the dimension conditions similar to Example 2 using each said 9 types of board | plate material was produced. Moreover, when the same sample as the sample of nine gaskets 100 was produced separately and the Vickers hardness at the S point of each sample was measured, 150, 180, 200, 250, 325, 380, 400, 450, 460 [ Hv]. The Vickers hardness is measured with a test load of 1.961 N and a load holding time of 10 seconds in a test method based on JIS Z2244. Then, nine samples of the spark plug 1 fitted with the prepared sample of the gasket 100 were attached to an aluminum bush (not shown) with a predetermined tightening torque, and a vibration test was performed under the same conditions as in Example 2. After the test, the spark plug 1 was removed from the aluminum bush, the return torque was measured, and the loosening resistance was evaluated in the same manner as in Example 2. The same applies to the evaluation of the loosening resistance. However, when the return torque was 20% or more of the tightening torque, the loosening resistance was further evaluated as と し て.

  In addition, each of the spark plug 1 samples on which the nine types of gasket 100 samples were mounted was again attached to the aluminum bush, and at this time, the tightening torque was increased stepwise. And when the fracture | rupture (for example, damage of a screw thread) arises in the metal shell 50, the sample of the gasket 100 was removed and the external appearance was observed. When a crack or crack occurred in the sample of the gasket 100, it was evaluated as x, and when it did not occur, it was evaluated as o. The results of the evaluation test are shown in Table 3.

  As shown in Table 3, the gasket 100 having a Vickers hardness of 450 Hv or less did not crack or crack even when compressed with a tightening torque that would cause the metal shell 50 to break, but if it exceeds 450 Hv, the crack or crack It was found that Further, it has been found that the gasket 100 having a Vickers hardness of less than 200 Hv undergoes plastic deformation due to heat and vibration, and the axial force decreases. And it was found that if the Vickers hardness of the gasket 100 is 250 Hv or more, sufficient loosening resistance can be secured. Therefore, if the Vickers hardness of the gasket 100 is 200 Hv or more and 450 Hv or less, the second stretched portion 120 and the third stretched portion 130 can obtain sufficient spring properties, and a sufficient axial force as the gasket 100 is obtained. It was found that looseness can be secured.

  Next, an evaluation test was performed in order to examine the adjustable angle of the direction of the ground electrode 30 necessary for ensuring the ignitability of the spark plug 1. Here, the direction of the ground electrode 30 is adjusted in the range of 0 ° to 180 ° by having a size that allows the crushing amount to be crushed to a size corresponding to ½ pitch at the thread pitch of the mounting portion 52. Eight samples of possible gaskets 100 were prepared. Each sample of the gasket 100 was attached to a sample of the spark plug 1, and each spark plug 1 was attached to a test automobile engine (1.6 L, 4 cylinders) at an applied pressure P of 60 MPa. At this time, the orientation of the ground electrode 30 in the combustion chamber (not shown) is set to 0 ° for the best ignitability, and the orientation of the ground electrodes 30 of the eight samples is shifted by 45 °, For convenience, the samples were designated as Samples 21 to 28 in order from 0 °. The ignition advance angle (BTDC) when the orientation of the ground electrode 30 is not adjusted is 42, 41, 37.5, 37, 35, 37.5, 41, 41.5 [°] in order from the sample 21. It became. The results of this evaluation test are shown in Table 4.

  As shown in Table 4, when the gasket 100 is not crushed and the orientation of the ground electrode 30 cannot be adjusted, the spark plug 1 is oriented in the direction of the ground electrode 30 (180 °) at which the ignition advance angle is 35 ° as in the sample 25. Has been attached, the ignition advance angle could not be changed from 35 °, and the ignitability could not be improved. If the collapse amount of the gasket 100 is small and the direction of the ground electrode 30 can be adjusted only up to 45 °, even if the spark plug 1 is attached like the sample 25, by adjusting the direction of the ground electrode 30 by + 45 °, The ignition advance angle could be improved from 35 ° to 37.5 °. On the other hand, when the spark plug 1 is attached in the direction (45 °) of the ground electrode 30 where the ignition advance angle is 41 ° as in the sample 22, if the direction of the ground electrode 30 is adjusted by + 45 °, the ignition The advance angle may fall to 37.5 °. In this case, if the direction of the ground electrode 30 was not adjusted, 41 ° could be obtained as the ignition advance angle. Similarly, when the crushing margin of the gasket 100 is slightly large and the direction of the ground electrode 30 can be adjusted to 90 °, the ignition advance angle of the sample 25 is adjusted from 35 ° by adjusting the direction of the ground electrode 30 by + 90 °. It was possible to improve to 41 °. Furthermore, when the crushing margin of the gasket 100 is large and the direction of the ground electrode 30 can be adjusted to 180 °, the ignition advance angle of the sample 25 can be improved from 35 ° to 42 °.

  Thus, the greater the angle at which the orientation of the ground electrode 30 can be adjusted, the greater the degree of freedom in adjusting the ignition advance. As shown in Table 4, for example, when the gasket 100 capable of adjusting the orientation of the ground electrode 30 to 90 ° is attached, the orientation of the ground electrode 30 is adjusted within a range of + 90 ° for each of the samples 21 to 28. Thus, 42, 41, 37.5, 37.5, 41, 41.5, 42, and 42 [°] were obtained in order as the best value (maximum value) of the ignition advance angle. The smallest value among these maximum values was the maximum ignition advance angle 37.5 ° indicated by the samples 23 and 24. Compared to the case where the orientation of the ground electrode 30 cannot be adjusted, if the orientation of the ground electrode 30 can be adjusted to 90 °, the minimum value of the ignition advance is reduced from 35 ° (sample 25 when the orientation of the ground electrode 30 cannot be adjusted) to 37. It was confirmed that it could be improved to 5 °. Here, as shown in FIG. 5, it can be seen that the ignition advance is greatly reduced when the direction of the ground electrode 30 is in the range of 135 ° to 225 ° (indicated by the oblique lines in the graph). If the orientation of the ground electrode 30 can be adjusted by at least 90 ° or more, at least the minimum value of the ignition advance angle can be set to 37.5 ° as described above. Accordingly, it was found that the range of the spark advance angle of 37 ° or less indicated by the oblique lines in FIG. 5 can be avoided, and the ignitability of the spark plug 1 can be secured.

  Furthermore, as shown in Table 4, when the gasket 100 capable of adjusting the orientation of the ground electrode 30 to 180 ° is attached, the orientation of the ground electrode 30 is similarly adjusted for each of the samples 21 to 28, thereby igniting. As the maximum value of the advance angle, 42, 41, 41, 41.5, 42, 42, 42, and 42 [°] were obtained in this order. The minimum value among these maximum values was the maximum value 41 ° of the ignition advance indicated by the samples 22 and 23. Thus, it was confirmed that if the orientation of the ground electrode 30 could be adjusted to 180 °, the minimum ignition advance angle could be improved from 35 ° to 41 ° indicated by the sample 25 when the orientation of the ground electrode 30 could not be adjusted. . As shown in FIG. 5, the average value of the ignition advance taking a value in the range of 35 ° to 42 ° is 39 °. However, if the orientation of the ground electrode 30 can be adjusted by at least 180 ° or more, the average value is surely greater than the average value. It was found that the spark plug 1 can be adjusted to have a high ignition advance, and the ignitability of the spark plug 1 can be reliably ensured.

  Next, an evaluation test was performed in order to confirm the effect of providing the regulation on the shape of the circumferential cross section of the gasket 100. First, a plurality of annular plate materials made of stainless steel having different thicknesses are prepared, and the folding position and the folding angle at the time of press molding are adjusted to produce samples 1 to 16 of 16 types of gaskets 100 shown in Table 5. did. In Samples 1 to 16, the radius of curvature r of the first connection portion 140 was different in the range of 0.4 mm to 1.2 mm. Moreover, the thickness t of the 2nd extending | stretching part 120 became different in the range of 0.3 mm-0.5 mm. Further, the combination of the sizes of the radial distance R1 and the radial distance R2 is also changed, and the size of (R1−R2) / 2 that is worth half the crushing margin (for convenience, W) is The difference was in the range of 0.8 mm to 1.075 mm. And when the aspect ratio C of the crushing allowance was calculated | required by h / (R1-R2), C became different in the range of 0.938-1.475. Table 5 shows a table comparing the thickness t, the radius of curvature r, the size W of half of the crushing allowance, and the aspect ratio C of the crushing allowance of each sample.

  Each sample 1-16 shown in Table 5 was attached to the sample of the spark plug 1, and the spark plug 1 was attached to the aluminum bush with a tightening torque of 60-130 MPa. At this time, a sample in which the crushing margin was able to be crushed to a size corresponding to ½ pitch with the thread pitch of the mounting portion 52 (that is, a sample in which the direction of the ground electrode 30 was adjusted by 180 ° or more) was confirmed. About the sample which could be adjusted, it determined with (circle) and the sample which was not able to be determined with x. The results of this evaluation test are shown in Table 6. Table 6 focuses on the relationship between the curvature radius r of each sample and the aspect ratio C of the crushing allowance.

  As shown in Table 6, Samples 1 to 9, 13, and 14 were able to adjust the orientation of the ground electrode 30 by 180 ° or more. It was found that the samples 11 to 12, 15, and 16 in which the aspect ratio C is less than 1 and the crushing allowance is large in the radial direction cannot adjust the direction of the ground electrode 30 by 180 ° or more. Further, it was found that the sample 10 having the curvature radius r larger than W cannot adjust the direction of the ground electrode 30 by 180 ° or more. Therefore, if the radius of curvature r is W (that is, (R1-R2) / 2) or less and the aspect ratio C is 1 or more (that is, the crushing margin is large in the direction of the axis Q, h ≧ (R1-R2) It is confirmed that the orientation of the ground electrode 30 can be adjusted by 180 ° or more.

  Furthermore, for each of the above samples 1 to 16, the moldability when forming the first connection portion 140 was also evaluated. After bending the first connection part 140 by press molding when producing the gaskets 100 of the samples 1 to 16, the state of the bending trace was observed. At that time, a sample that was confirmed to be wrinkled toward the bending trace of the first connection portion 140 and confirmed that the folding or crushing occurred was evaluated as x, and a sample in which the bending trace formed a smooth curved surface was evaluated as ◯. Table 7 shows the results of the evaluation test. In Table 7, attention was paid to the relationship between the radius of curvature r of each sample and the thickness t.

  As shown in Table 7, Samples 2, 3, 6, 9, 10, and 12 in which the radius of curvature r is more than twice the thickness t are smooth curved surfaces with no creases in the first connecting portion 140. Was formed and the moldability was good. On the other hand, in samples 1, 4, 5, 7, 8, 11, 13 to 16 having a radius of curvature r less than twice the thickness t, it was confirmed that the bending marks of the first connection portion 140 were wrinkled. . In Example 5, the spark plug 1 attached to the aluminum bush was removed, and the bending traces of the first connection portion 140 of each sample were observed. As a result, samples 1, 4, 5, and 7 having a radius of curvature r less than twice the thickness t , 8, 11, 13 to 16 were confirmed to be broken or crushed.

  Next, an evaluation test was performed in order to confirm the influence of the looseness resistance depending on the material of the gasket 100, the direction in which the gasket 100 is attached to the metal shell 50, the difference in the shape of the circumferential cross section, and the like. First, similarly to Example 2, an annular plate material made of stainless steel having a thickness of 0.5 mm was subjected to processing by press molding to produce a sample 41 of the gasket 100 of the present embodiment. Regarding the dimensions in the circumferential cross section of the gasket 100, the radius of curvature r of the first connecting portion 140 was 1 mm, the radial distance R1 was 8.15 mm, and the radial distance R2 was 6 mm. A sample 42 having the same dimensions as the sample 41 and made of iron (Fe) was produced. Further, a sample 43 having a circumferential cross-sectional shape forming a mirror image with the sample 41 was produced. A sample of the spark plug 1 in which each sample is attached to the screw neck 59 of the metal shell 50 is prepared. Further, a sample 41 and a sample of the spark plug 1 in which the sample 44 with the axis Q direction inverted is attached to the screw neck 59 are prepared. did.

  The spark plug 1 on which each of the samples 41 to 44 was mounted was attached to an aluminum bush with a tightening torque of 15 N · m, and the same vibration test as in Example 2 was performed. Further, the spark plug 1 was removed from the aluminum bush, and at this time, the torque (return torque) necessary for removing the metal shell 50 was measured. The results of this evaluation test are shown in Table 8.

  As shown in Table 8, the return torque of sample 41 was 7.9 N · m, whereas samples 42 to 44 were 4.7, 6.7, and 4.4 [N · m], respectively. It has been found that the loosening resistance decreases. For samples 41 and 43, the equivalent friction diameter was determined from the contact mark (indicated by point X) with the overhanging portion 54 and found to be 13.5 mm and 14.8 mm, respectively. The equivalent friction diameter based on the contact mark (indicated by the point Y) with the opening peripheral portion 92 is the same for the samples 41 and 43, and when the circumferential cross section forms a mirror image, the overhang portion 54 side and the opening peripheral portion It was confirmed that the difference in the ratio of the equivalent friction diameter to the 92 side affects the return torque.

DESCRIPTION OF SYMBOLS 1 Spark plug 10 Insulator 12 Shaft hole 30 Ground electrode 50 Metal fitting 54 Overhang | projection part 90 Engine head 91 Mounting hole 92 Opening peripheral part 100 Gasket 101 One end part 102 Other end part 110 First extending part 111,121, 131,161 One end 112,122,132,162 The other end 120 The second extension part 130 The third extension part 140 The first connection part 150 The second connection part 160 The third connection part

Claims (8)

A thread is formed on the outer periphery of the thread, and a threaded member having a projecting portion that forms a round in the circumferential direction while projecting outward from the outer periphery of the thread on the base end side of the thread is concentric from the outside. In the state where the threaded member is screwed into the mounting hole in which the female thread is formed, the annular member is attached to the mounting hole and the opening peripheral edge of the mounting hole. In a threaded member having a sealing member, which includes a sealing member that is compressed and sealed between the projecting portion and the peripheral edge portion of the opening.
When looking at the cross section of the sealing member in a plane including the central axis of the sealing member,
While the cross section is continuous from one end to the other end, the other end forms a spiral shape located on the inner side of the one end,
One end of itself is the one end, and toward the other end of the sealing member positioned radially inward of the sealing member, the radial direction is more than the component along the axial direction of the sealing member. A first extending portion extending substantially linearly, so that the component along
A second extending portion extending substantially linearly so that the component along the axial direction is larger than the component along the radial direction;
A first connecting portion that connects the other end of the first extending portion and one end of the second extending portion with a curve of a radius of curvature r;
A third extending portion extending substantially linearly so that the component along the axial direction is larger than the component along the radial direction at a position outside the second extending portion in the radial direction;
A second connecting portion for connecting the other end of the second extending portion and one end of the third extending portion with a curve bent in a direction away from the first extending portion;
One end of itself is connected to the other end of the third extending portion, and the other end of itself is the other end portion, and in the axial direction, between the first extending portion and the second connecting portion. A third connecting portion having a portion overlapping the first extending portion and the second connecting portion while being positioned,
The sealing member is such that the first extending portion is located on a side of the threaded member that contacts the protruding portion, and the threaded member is located on the radially inner side of the second extending portion. Attached to the threaded member,
Before the sealing member is screwed into the mounting hole, the threaded member is attached to the threaded member.
The axial height of the sealing member is h,
The thickness of the second stretched portion at a position satisfying h / 2 is t,
Furthermore, in the radial direction of the sealing member,
Of the third extending portion, R1 is a radial distance from the central axis at a portion farthest from the central axis of the sealing member,
Of the second extending portion, when the radial distance from the central axis at the portion closest to the central axis of the sealing member is R2,
2 × t ≦ r ≦ (R1-R2) / 2
While satisfying
h ≧ (R1-R2)
A screwed member having a sealing member characterized by satisfying   2. The sealing member according to claim 1, wherein, in the cross section of the sealing member, the other end portion is located closer to the central axis than the one end portion in the radial direction. A threaded member.   The screw member having a sealing member according to claim 1 or 2, wherein the sealing member is made of stainless steel. When the compression load when compressing the sealing member in the axial direction is F, and the applied pressure P to the sealing member is calculated by F / {π (R1 ² −R2 ² )}, the addition The rotation angle at the time of screwing the threaded member into the mounting hole when the pressure P is in a range of 60 MPa to 130 MPa is 90 ° or more and less than 360 °. A threaded member having the sealing member according to 1.   5. The rotation angle when the threaded member is screwed into the mounting hole when the additional pressure P is in a range of 60 MPa to 130 MPa is 180 ° or more and less than 360 °. A threaded member having a sealing member.   Before the threaded member is screwed into the mounting hole, the second stretch that satisfies the h / 2 and becomes the center of the thickness t in the cross section of the sealing member mounted on the threaded member When the hardness of the said sealing member is measured in the position of a part, it is 200Hv or more and 450Hv or less by Vickers hardness, The screw attachment which has the sealing member in any one of Claims 1-5 characterized by the above-mentioned Element.   When the cross section of the sealing member before being attached to the threaded member is viewed, the direction from the one end side of the third connection portion toward the other end portion side is 40 ° with respect to the axial direction. The threaded member having a sealing member according to any one of claims 1 to 6, characterized by intersecting at an angle of 70 ° or less.   A spark plug using the sealing member of the threaded member having the sealing member according to any one of claims 1 to 7 mounted on a metal shell.

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