JP2018045892A - Spark plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spark plug which can suppress the deformation owing to a thermal stress and suppress an electrode chip from being damaged.SOLUTION: A spark plug comprises a grounding electrode which includes: an electrode chip having a chip main body mainly including a noble metal; and an intermediate member surrounding a side face of the chip main body. The intermediate member surrounding the side face the chip main body includes an alloy mainly including Ni or Ni. A fusing part athwart the chip main body and the intermediate member includes: a first fusing part containing 30-70 mass% of a noble metal component; and a second fusing part containing 80 mass% or more of a Ni component. In a cross section perpendicular to an axis of the chip main body, a portion of the first fusing part, which is formed in the chip main body, is generally present in a first region having a given angle of 90° or less with respect to the axis of the chip main body.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a spark plug, and more particularly to a spark plug in which an electrode tip containing a noble metal is provided on a ground electrode.

  There is known a spark plug in which an electrode chip in which an intermediate member surrounding a side surface of a chip body mainly composed of a noble metal and the chip body are joined by a melting portion is fitted in a recess formed in an electrode base material of a ground electrode. (Patent Document 1). In the technique disclosed in Patent Document 1, the intermediate member is joined to the electrode base material.

JP 2009-283262 A

  However, in the conventional technique described above, when the chip body and the intermediate member are firmly joined by the melted portion, the electrode base material is deformed due to the thermal stress caused by the thermal expansion difference between the chip body and the electrode base material. The chip body may break. Further, when a crack occurs at the interface between the melted portion and the chip body or the melted portion due to thermal stress, and the crack proceeds excessively, the chip body may fall off the intermediate member.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a spark plug that can suppress deformation due to thermal stress and breakage of an electrode tip.

Means for Solving the Problems and Effects of the Invention

  In order to achieve this object, according to the spark plug of the first aspect, the center electrode extending along the axis is disposed in the axial hole of the insulator formed along the axis. A ground electrode is joined to the metal shell disposed on the outer periphery of the insulator. The electrode base material of the ground electrode has a first end joined to the metal shell and a second end facing the center electrode. The electrode tip of the ground electrode is joined to the electrode base material in a state where at least a part thereof is fitted in a recess formed at a position facing the center electrode of the electrode base material. The electrode tip includes a tip body mainly composed of a noble metal and an intermediate member that surrounds the side surface of the tip body, and a melting portion is formed across the intermediate member and the tip body.

  The intermediate member is made of an alloy mainly containing Ni or Ni, and the melting part includes a first melting part containing 30 to 70% by mass of a noble metal component and a second melting part containing 80% by mass or more of the Ni component. Composed. As a result, the linear expansion coefficient of the second melting part in the environment where the spark plug is used can be brought close to the linear expansion coefficient of the intermediate member, while the linear expansion coefficient of the first melting part is set to the linear expansion coefficient of the chip body and the intermediate member. Between the linear expansion coefficient. As a result, the first melting part relaxes thermal stress between the intermediate member and the chip body.

  In the cross section perpendicular to the axis of the chip body, the part of the first melted portion formed on the chip body has a predetermined angle that the angle formed by two straight lines passing through the axis of the chip body is 90 ° or less. It exists in one area. Since the volume of the 1st fusion part is restricted, the force which acts on the 1st fusion part by thermal stress can be controlled. As a result, since the breakage of the first melting part can be suppressed in the environment where the spark plug is used, the first melting part joins the intermediate member and the chip body. Moreover, since it can prevent that the joining strength of the intermediate member and chip | tip main body by a 1st fusion | melting part becomes excessive, it can suppress that an electrode base material deform | transforms or a chip | tip main body fractures | ruptures.

  On the other hand, since the second melted portion has a large thermal expansion difference from the chip body, it is possible to easily generate a crack at the interface between the second melted portion and the chip body before the first melted portion or the chip body is broken. When a crack occurs at the interface between the second melting part and the chip body, the thermal stress in the melting part is released. As a result, it is possible to suppress breakage of the first melting part and the chip body and deformation of the electrode base material. Therefore, there is an effect that the deformation of the electrode base material and the damage of the electrode tip due to the thermal stress can be suppressed.

  According to the spark plug of claim 2, the first region is a virtual plane perpendicular to a plane including the axis of the electrode base material extending from the first end to the second end and the axis of the chip body. The first end portion side of the virtual plane including the axis of the chip body exists. As a result, even if the interface between the second melting portion and the chip body is broken, a conductive path from the metal shell to the chip body can be secured by the first melting portion existing on the first end side. Compared with the case where the first melting portion is present on the second end side, the conductive path through the first melting portion from the metal shell to the chip body can be shortened. There is an effect that it is difficult to cause deterioration.

  According to the spark plug of the third aspect, since the first region has a predetermined angle of 20 ° or more, the cross-sectional area of the first melting portion can be secured. As a result, in addition to the effect of Claim 1 or 2, there exists an effect which can ensure the intensity | strength of a 1st fusion | melting part.

  According to the spark plug of the fourth aspect, at least a part of the second melted portion formed on the chip body is present on the second end side of the virtual plane. As a result, in addition to the effect of the second aspect, there is an effect that the chip body can be held on the intermediate member in a balanced manner by the second melting portion and the first melting portion existing on the first end side.

  According to the spark plug of claim 5, in the cross section perpendicular to the axis of the chip body, at least a part of the second melted portion formed on the chip body is at least partially formed on the chip body of the first melted portion. Two tangent lines that are in contact with the portion to be formed and pass through the axis of the chip main body are present in a second region formed by extending the axis of the chip main body to the side opposite to the first melting portion. As a result, in addition to the effect of any one of the first to fourth aspects, there is an effect that the chip main body can be held on the intermediate member in a balanced manner by the second melting portion and the first melting portion existing in the first region.

It is a half sectional view of the spark plug in the first embodiment of the present invention. It is a top view of a ground electrode. It is sectional drawing of the ground electrode in the III-III line of FIG. It is sectional drawing of the ground electrode in the IV-IV line | wire of FIG. It is sectional drawing of the ground electrode of the spark plug in 2nd Embodiment. It is sectional drawing of the ground electrode of the spark plug in 3rd Embodiment. It is sectional drawing of the ground electrode of the spark plug in 4th Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a one-side cross-sectional view showing an outline view (on the left side of the paper) and a full cross-sectional view (on the right side of the paper) taken along a plane including the axis O with respect to the spark plug 10 according to the first embodiment of the present invention. It is. In FIG. 1, the lower side of the drawing is referred to as the front end side of the spark plug 10, and the upper side of the drawing is referred to as the rear end side of the spark plug 10. As shown in FIG. 1, the spark plug 10 includes a metal shell 11, a ground electrode 12, an insulator 17, and a center electrode 19.

  The metal shell 11 is a substantially cylindrical member fixed to a screw hole (not shown) of the internal combustion engine. The ground electrode 12 is joined to a metal base material 13 (for example, a nickel base alloy) whose first end portion 14 is joined to the tip of the metal shell 11 and a second end portion 15 of the electrode base material 13. The electrode tip 16 (refer FIG. 2, FIG. 3) is provided. The electrode base material 13 is a rod-shaped member whose second end 15 side is bent toward the center electrode 19 with respect to the first end 14.

  The insulator 17 is a substantially cylindrical member formed of alumina or the like having excellent mechanical properties and insulation at high temperatures. The insulator 17 has a shaft hole 18 extending along the axis O, and the metal shell 11 is fixed to the outer periphery. The center electrode 19 is a rod-shaped electrode that is inserted into the shaft hole 18 and held by the insulator 17 along the axis O. The center electrode 19 faces the ground electrode 12 through a spark gap. The terminal fitting 20 is a rod-like member to which a high voltage cable (not shown) is connected, and the distal end side is disposed in the insulator 17.

  The spark plug 10 is manufactured by the following method, for example. First, the center electrode 19 is inserted into the shaft hole 18 of the insulator 17. The center electrode 19 is disposed so that the tip is exposed to the outside from the shaft hole 18. After the terminal fitting 20 is inserted into the shaft hole 18 and the conduction between the terminal fitting 20 and the center electrode 19 is ensured, the metal shell 11 to which the electrode base material 13 has been joined in advance is assembled to the outer periphery of the insulator 17. After joining the electrode tip 16 to the electrode base material 13, the electrode base material 13 is bent so that the electrode tip 16 faces the center electrode 19 in the direction of the axis O to obtain the spark plug 10.

  With reference to FIG. 2, the electrode base material 13 to which the electrode tip 16 is bonded will be described. FIG. 2 is a plan view of the ground electrode 12 (viewed from the rear end side in the axis O direction of the spark plug 10). In FIG. 2, the second end portion 15 of the electrode base material 13 is illustrated, and the illustration of the first end portion 14 side of the electrode base material 13 is omitted.

  The electrode base material 13 is an alloy mainly composed of Ni or a member made of Ni, and a recess 21 is formed at a position facing the tip of the center electrode 19 (see FIG. 1). The recess 21 is a part into which at least a part of the electrode tip 16 is fitted. The electrode tip 16 fitted in the recess 21 faces the center electrode 19 through a spark gap.

  The electrode chip 16 includes a chip body 23 and an intermediate member 26 that surrounds a side surface 25 of the chip body 23. The chip body 23 is joined to the intermediate member 26 by a melting part (first melting part 27 and second melting part 28), and the intermediate member 26 is joined to the electrode base material 13 by a melting part 29. The melting portion 29 is provided over the entire outer periphery of the intermediate member 26. In the present embodiment, the melting portion 29 is continuously formed by scanning with a pulsed laser beam.

  The chip body 23 is a member made of a noble metal such as platinum, iridium, ruthenium, or rhodium that has a higher resistance to spark consumption than the electrode base material 13 or an alloy containing a noble metal as a main component. In the present embodiment, the chip body 23 is a plate material having a circular plan view. Further, the chip body 23 is arranged such that an axis 24 passing through its center coincides with the axis O of the center electrode 19 (see FIG. 1). The intermediate member 26 is an alloy mainly composed of Ni or a member made of Ni. In the present embodiment, the intermediate member 26 is an annular member having the same axial thickness and radial width in the circumferential direction.

  3 is a cross-sectional view of the ground electrode 12 taken along line III-III in FIG. As shown in FIG. 3, the electrode base material 13 has a shaft 22 that extends from the first end portion 14 (see FIG. 1) side to the second end portion 15. The axis 22 of the electrode base material 13 is orthogonal to the axis O. The recess 21 is a bottomed recess formed in the electrode base material 13. The electrode tip 16 is accommodated in the recess 21 with the tip body 23 slightly protruding from the electrode base material 13.

  The first melting part 27 and the second melting part 28 straddling the intermediate member 26 and the chip body 23 have a wedge shape (conical shape) in which the cross-sectional area gradually decreases from the intermediate member 26 toward the shaft 24 of the chip body 23. Is formed. In the direction orthogonal to the axis 24 (the left-right direction in FIG. 3), the length of the first melting part 27 is set longer than the length of the second melting part 28. The melting part 29 is a part extending along the axis 24 of the chip body 23, and is formed in a columnar shape straddling the intermediate member 26 and the electrode base material 13.

  The first melting part 27 and the second melting part 28 irradiate a laser beam in a direction perpendicular to the axis 24 from the side surface (outer periphery) of the intermediate member 26 with the chip body 23 inserted inside the intermediate member 26. It is formed. By the first melting part 27 and the second melting part 28, the electrode chip 16 in which the chip body 23 and the intermediate member 26 are joined is produced. As a laser for forming the first melting part 27 and the second melting part 28, for example, a solid laser such as a YAG laser, a disk laser, or a fiber laser can be used.

  The melting part 29 irradiates a laser beam parallel to the axis 24 toward the boundary between the intermediate member 26 and the electrode base material 13 in a state where the electrode chip 16 is fitted in the recess 21 of the electrode base material 13. It is formed over the entire circumference of the member 26. The electrode tip 16 and the electrode base material 13 (concave portion 21) may be resistance-welded before irradiating the laser beam for forming the melted portion 29. The melting portion 29 is formed by melting the outer peripheral portion of the intermediate member 26, the outer peripheral portions of the first melting portion 27 and the second melting portion 28, and the inner peripheral portion of the concave portion 21 (electrode base material 13). The components of the chip body 23 and the electrode base material 13 are mixed.

  The components of the intermediate member 26 and the electrode base material 13 melted by the laser beam are melted almost uniformly into the outer peripheral portions of the first melting portion 27 and the second melting portion 28, so that the first melting portion 27 and the second melting portion 28 This component depends on the ratio between the volume of the melted intermediate member 26 and the volume of the chip body 23. Since the first melting portion 27 has a length in the radial direction that is longer than a length in the radial direction of the second melting portion 28, the first melting portion 27 is melted compared to the second melting portion 28. The volume ratio is high. Therefore, the first melting part 27 includes more components derived from the chip body 23 than the second melting part 28, and the second melting part 28 includes the components derived from the intermediate member 26 in the first melting part 27. Compared to many.

  The electrode base material 13 and the intermediate member 26 are made of an alloy or Ni mainly containing Ni, and the chip body 23 is made of an alloy or noble metal mainly containing a noble metal. Therefore, the linear expansion coefficient of the chip body 23 in the environment where the spark plug 10 is used is smaller than the linear expansion coefficients of the electrode base material 13 and the intermediate member 26. The 1st fusion | melting part 27 contains 30-70 mass% of noble metal components, and the 2nd fusion | melting part 28 is set so that 80 mass% or more of Ni components may be contained. Therefore, the linear expansion coefficient of the first melting portion 27 in the above use environment can be set between the linear expansion coefficient of the intermediate member 26 and the linear expansion coefficient of the chip body 23. Therefore, since the 1st fusion | melting part 27 relieve | moderates a thermal stress between the intermediate member 26 and the chip | tip main body 23, the 1st fusion | melting part 27 connects both in the use environment of the spark plug 10. FIG.

  Elemental analysis of the first melting part 27 and the second melting part 28 can be performed by, for example, EDX (energy dispersive X-ray analysis), EPMA (electron beam microanalyzer), or the like. The analysis position of the first melting part 27 and the second melting part 28 by EDX, EPMA or the like is substantially the center of the first melting part 27 or the second melting part 28. In order to prevent the analysis from being performed at a position where the element concentration distribution is not uniform, such as a portion of the first melting portion 27 or the second melting portion 28 close to the axis 24 of the chip body 23 or near the boundary with the melting portion 29. It is.

  4 is a cross-sectional view of the ground electrode 12 taken along line IV-IV in FIG. 3, and shows a cross section perpendicular to the axis 24 of the chip body 23. FIG. The first melting part 27 is one continuous melting part formed by slightly shifting the two irradiation positions of the pulsed laser beam in the circumferential direction. The first melting portion 27 includes a portion 31 formed on the intermediate member 26 and a portion 32 formed on the chip body 23. The boundary between the portion 31 and the portion 32 is a boundary between the chip body 23 and the intermediate member 26 (side surface 25 of the chip body 23) before the first melting portion 27 is formed (before melting). The portion 32 formed on the chip body 23 in the first melting portion 27 is entirely present in the first region 35. The first area 35 is an area in which an angle θ formed by two straight lines passing through the axis 24 of the chip body 23 is set to a predetermined angle of 90 ° or less.

  Since the first region 35 including the first melting part 27 is set to a predetermined angle of 90 ° or less, the volume of the first melting part 27 is restricted. Since the region where the first melting part 27 connects the intermediate member 26 and the chip body 23 is restricted, the force acting on the first melting part 27 due to the thermal expansion difference between the intermediate member 26 and the chip body 23 can be suppressed. The breakage of the first melting part 27 can be suppressed. Moreover, since it can suppress that the joining strength of the intermediate member 26 and the chip | tip main body 23 by the 1st fusion | melting part 27 becomes excessive, it can suppress that the electrode base material 13 deform | transforms or the chip | tip main body 23 fractures | ruptures.

  Since it is possible to prevent the electrode base material 13 from being deformed by thermal stress, it is possible to prevent a gap from being formed between the electrode tip 16 and the concave portion 21, and a spark between the center electrode 19 (see FIG. 1) and the tip body 23. The gap can be prevented from narrowing or widening.

  In the first region 35, the angle θ formed is set to 20 ° or more. In that case, it is preferable that a part of the portion 32 formed in the chip body 23 exists in addition to the region included in the first region 35 and the angle θ formed by the portion 32. This is to secure a volume of the first melting part 27 that only holds the chip body 23. As a result, the first melting part 27 can hold the chip body 23 on the intermediate member 26 against the force acting on the first melting part 27 due to the thermal expansion difference between the intermediate member 26 and the chip body 23.

  The second melting portions 28 are five melting portions that are independent of each other and are formed by shifting the irradiation position of the pulsed laser beam five times in the circumferential direction. The second melting portion 28 includes a portion 33 formed on the intermediate member 26 and a portion 34 formed on the chip body 23. The boundary between the portion 33 and the portion 34 is a boundary between the chip body 23 and the intermediate member 26 (side surface 25 of the chip body 23) before the second melting portion 28 is formed (before melting). At least a part (all in the present embodiment) of the part 34 formed in the chip body 23 in the second melting part 28 exists outside the first region 35.

  Since the second melting portion 28 contains 80 mass% or more of the Ni component, the linear expansion coefficient of the second melting portion 28 can be brought close to the linear expansion coefficients of the intermediate member 26 and the electrode base material 13. Further, since the difference in thermal expansion between the second melting part 28 and the chip body 23 is larger than that between the first melting part 27 and the chip body 23, before the first melting part 27 or the chip body 23 breaks. Cracks are likely to occur at the interface between the second melting part 28 and the chip body 23.

  If a crack occurs at the interface between the second melting part 28 and the chip body 23, the thermal stress of the first melting part 27 and the second melting part 28 is released, so the first melting part 27 and the chip body 23 do not break. You can In addition, the bonding strength with the chip body 23 can be reduced by the second melting portion 28 as compared with the case where a melting portion containing 30 to 70 mass% of the noble metal component is provided instead of all the second melting portions 28. As a result, since the thermal stress is released, it is possible to suppress the electrode base material 13 from being deformed or the chip body 23 from being broken. Since it is possible to prevent the electrode base material 13 from being deformed by thermal stress, it is possible to prevent a gap from being formed between the electrode tip 16 and the recess 21, and a spark gap between the center electrode 19 (see FIG. 1) and the tip body 23 It can be prevented from becoming narrower or wider.

  Note that the second melting part 28 in which the crack has occurred at the interface is wedge-shaped and bites into the side surface 25 of the chip body 23 (see FIG. 3), so the second melting part 28 locks the chip body 23. Therefore, even if a crack occurs at the interface between the second melting portion 28 and the chip body 23, the chip body 23 can be prevented from being detached from the intermediate member 26 or inclined with respect to the intermediate member 26 due to vibration or impact.

  The first region 35 is perpendicular to the plane including the axis 22 of the electrode base material 13 and the axis 24 of the chip body 23, and more than the virtual plane 39 including the axis 24 (the plane perpendicular to the plane of FIG. 4). 1 on the first end portion 14 (see FIG. 1) side (left side in FIG. 4). The first melting portion 27 exists in the first region 35. Since the first melting part 27 connects the intermediate member 26 and the chip body 23 without breaking even when a crack occurs at the interface between the second melting part 28 and the chip body 23, the first melting part 27 A conductive path from the electrode base material 13 to the chip body 23 can be secured.

  As a result, the first melting from the electrode base material 13 to the chip body 23 is performed as compared with the case where the first region 35 exists on the second end 15 (see FIG. 1) side (right side in FIG. 4) from the virtual plane 39. The conductive path passing through the portion 27 can be shortened. Since the distance of the conductive path through which the discharge current flows can be shortened, loss and characteristic deterioration can hardly occur. Therefore, it is possible to suppress the occurrence of spark discharge between the chip body 23 and the center electrode 19 (see FIG. 1).

  When the first region 35 is present on the first end portion 14 (see FIG. 1) side of the virtual plane 39, the first melting portion 27 has the axis of the electrode base material 13 in the direction of the axis 24 of the chip body 23. 22 is formed at a position overlapping with 22. Thereby, compared with the case where the 1st fusion | melting part 27 does not overlap with the axis | shaft 22, the electrically conductive path | route via the 1st fusion | melting part 27 from the electrode base material 13 to the chip | tip main body 23 can be shortened. Since the distance of the conductive path can be further shortened, loss and characteristic deterioration can be made less likely to occur.

  In the present embodiment, at least part of the portion 34 formed in the chip body 23 of the second melting portion 28 is at the second end portion 15 (see FIG. 1) side (right side in FIG. 4) with respect to the virtual plane 39. Exists. When a crack occurs at the interface between the second melting part 28 and the chip body 23, the second melting part 28 bites into the chip body 23 and physically locks the chip body 23. On the other hand, the first melting part 27 joins the chip body 23 and the intermediate member 26. Since at least a part of the second melting part 28 and the first melting part 27 exist on both sides of the virtual plane 39, the chip body 23 can be held on the intermediate member 26 in a well-balanced manner.

  At least a portion 34 of the second melting portion 28 formed on the chip body 23 is in contact with a portion 32 of the first melting portion 27 formed on the chip body 23 and passes through the shaft 24 of the chip body 23 2. The two tangent lines 36 and 37 are present in a second region 38 formed by extending to the opposite side of the first melting portion 27 across the shaft 24 of the chip body 23. Since at least part of the portion 34 exists in the second region 38 on the opposite side of the first melting portion 27 across the shaft 24, even if a crack occurs at the interface between the second melting portion 28 and the chip body 23, The chip body 23 can be held on the intermediate member 26 with good balance.

  Next, a second embodiment will be described with reference to FIG. In the first embodiment, the first melting part 27 is a continuous melting part formed by two times of laser beam irradiation, and the second melting part 28 is formed by five times of laser beam irradiation. The case where there are five melted parts independent of each other has been described. In the second embodiment, a case will be described in which the first melting portion 41 and the second melting portion 44 are formed by changing the number of times of laser beam irradiation from that of the first embodiment. In addition, about the part same as the part demonstrated in 1st Embodiment, the same code | symbol is attached | subjected and the following description is abbreviate | omitted.

  FIG. 5 is a cross-sectional view of the ground electrode of the spark plug 40 according to the second embodiment, and shows a cross section perpendicular to the shaft 24 of the chip body 23. The first melting part 41 is one continuous melting part formed by three irradiations in which the irradiation position of the pulsed laser beam is slightly shifted in the circumferential direction. The first melting part 41 includes a part 42 formed on the intermediate member 26 and a part 43 formed on the chip body 23. The boundary between the portion 42 and the portion 43 is a boundary (side surface 25) between the chip body 23 and the intermediate member 26 before the first melting portion 41 is formed (before melting). The first melting part 41 contains 30 to 70% by mass of a noble metal component, and the part 43 formed in the chip body 23 of the first melting part 41 is entirely present in the first region 35.

  The second melting portions 44 are four melting portions that are independent of each other and are formed by shifting the four irradiation positions of the pulsed laser beam in the circumferential direction. The second melting portion 44 includes a portion 45 formed on the intermediate member 26 and a portion 46 formed on the chip body 23. The boundary between the portion 45 and the portion 46 is a boundary (side surface 25) between the chip body 23 and the intermediate member 26 before the second melting portion 44 is formed (before melting). The 2nd fusion part 44 contains 80 mass% or more of Ni ingredients.

  At least part (all in the present embodiment) of the portion 46 formed in the chip main body 23 of the second melting portion 44 exists on the second end portion 15 (see FIG. 1) side of the virtual plane 39. . Further, at least a part of the portion 46 extends two tangent lines 47 and 48 that are in contact with the portion 43 of the first melting portion 41 and pass through the shaft 24 to the opposite side of the first melting portion 41 across the shaft 24. It exists in the 2nd area | region 49 formed in this way. According to the second embodiment, the same operational effects as those of the first embodiment can be realized.

  Next, a third embodiment will be described with reference to FIG. In the second embodiment, a case has been described in which the pulsed laser beam is irradiated four times to form the second melting portion 44 that is four melting portions independent of each other. In the third embodiment, a case where the second melting part 54 is formed by irradiating a continuous wave laser beam will be described. In addition, about the part same as the part demonstrated in 1st Embodiment and 2nd Embodiment, the same code | symbol is attached | subjected and the following description is abbreviate | omitted. FIG. 6 is a cross-sectional view of the ground electrode of the spark plug 50 according to the third embodiment, and shows a cross section perpendicular to the shaft 24 of the chip body 23.

  The second melting portion 54 is a series of melting portions formed by scanning a continuous wave laser beam in the circumferential direction. The second melting portion 54 includes a portion 55 formed on the intermediate member 26 and a portion 56 formed on the chip body 23. The boundary between the portion 55 and the portion 56 is a boundary (side surface 25) between the chip body 23 and the intermediate member 26 before the second melting portion 54 is formed (before melting). The 2nd fusion part 54 contains 80 mass% or more of Ni ingredients.

  At least part (all in the present embodiment) of the portion 56 formed in the chip body 23 of the second melting portion 54 exists on the second end portion 15 (see FIG. 1) side of the virtual plane 39. . Further, at least a part of the portion 56 exists in the second region 49. According to the third embodiment, the same function and effect as those of the first embodiment can be realized.

  Next, a fourth embodiment will be described with reference to FIG. In the first to third embodiments, a case has been described in which the first melting portions 27 and 41 are one continuous melting portion formed by a plurality of times of laser beam irradiation. In the fourth embodiment, a case will be described in which first melted portions 61 that are independent from each other are formed by multiple times of laser beam irradiation. In addition, about the part same as the part demonstrated in 1st Embodiment, the same code | symbol is attached | subjected and the following description is abbreviate | omitted.

  FIG. 7 is a cross-sectional view of the ground electrode of the spark plug 60 in the fourth embodiment, and shows a cross section perpendicular to the axis 24 of the chip body 23. The first melting part 61 is two melting parts that are independent of each other and are formed by shifting the irradiation position of the pulsed laser beam twice in the circumferential direction. The first melting part 61 includes a part 62 formed on the intermediate member 26 and a part 63 formed on the chip body 23. The boundary between the portion 62 and the portion 63 is a boundary (side surface 25) between the chip body 23 and the intermediate member 26 before the first melting portion 61 is formed (before melting). The first melting part 61 contains 30 to 70% by mass of a noble metal component, and the part 63 formed in the chip body 23 of the first melting part 61 is entirely present in the first region 35.

  The second melting portion 64 is three melting portions that are independent from each other and are formed by shifting the irradiation position of the pulsed laser beam three times in the circumferential direction. The second melting portion 64 includes a portion 65 formed on the intermediate member 26 and a portion 66 formed on the chip body 23. The boundary between the portion 65 and the portion 66 is a boundary (side surface 25) between the chip body 23 and the intermediate member 26 before the second melting portion 64 is formed (before melting). The 2nd fusion part 64 contains 80 mass% or more of Ni ingredients.

  At least a part (all in the present embodiment) of the portion 66 formed in the chip body 23 in the second melting part 64 is present on the second end 15 (see FIG. 1) side with respect to the virtual plane 39. . Further, at least a part of the portion 66 extends two tangent lines 67 and 68 that are in contact with the portion 63 of the first melting portion 61 and pass through the shaft 24 to the opposite side of the first melting portion 61 across the shaft 24. The second region 69 is formed. According to the fourth embodiment, it is possible to realize the same operation and effect as the first embodiment.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1
The intermediate member was made of a nickel alloy (Inconel 600 (registered trademark)), and had an annular shape with dimensions of an inner diameter of 2.5 mm, an outer diameter of 3.3 mm, and a thickness of 0.85 mm. The chip body was made of a noble metal alloy having a composition of 80Ir-11Ru-8Rh-1Ni (numerical value is mass%), and had a disk shape with an outer diameter of 2.5 mm and a thickness of 1 mm. A plurality of portions of the outer periphery of the intermediate member into which the chip body is fitted are irradiated with a pulsed laser beam, so that the first melting portion (one melting portion) and the second melting portion (the five melting portions) described in the first embodiment Various electrode tips with melted portions) were obtained. The laser beam (typical example) that formed the first melted part has an energy of 1200 W, an irradiation rate of 24 Hz, and the number of irradiations is 2. The laser beam (typical example) that formed the second melted part has an energy of 500 W, an irradiation rate of 8 Hz, and irradiation. The number was five.

  The cross section of the electrode tip perpendicular to the axis of the tip body was observed with an X-ray fluoroscope, and the angle θ of the first region where the first melted part was formed was determined. In this embodiment, the angle formed by two tangents that contact the portion of the first melted portion formed on the chip body and pass through the axis of the chip body is defined as the angle θ of the first region. Further, the ratio (mass%) of the noble metal component in the first melting part and the ratio (mass%) of the Ni component in the second melting part are measured by EDX, and the angle θ (representative value) shown in Table 1 by the first melting part is measured. ) And noble metal component ratio (representative value). In all the electrode tips, the ratio of the Ni component in the second melting part was 80% by mass or more.

第１端部と第２端部とを有する断面矩形の棒状のニッケル合金（インコネル６００（登録商標））製の電極母材を準備し、第２端部に内径３．３ｍｍ、深さ０．８５ｍｍの凹部を形成した。凹部に電極チップを嵌め込んだ後、中間部材と電極母材との境界にレーザビームを照射して中間部材と電極母材とを溶接し、種々のサンプルを得た。なお、電極チップは、第１溶融部が形成された部分を、電極母材の第１端部側に向けて凹部に嵌め込んだ。

An electrode base material made of a nickel alloy (Inconel 600 (registered trademark)) having a rectangular cross section having a first end and a second end is prepared, and an inner diameter of 3.3 mm and a depth of 0.3 mm are prepared at the second end. A recess of 85 mm was formed. After fitting the electrode chip into the recess, the laser beam was applied to the boundary between the intermediate member and the electrode base material to weld the intermediate member and the electrode base material to obtain various samples. In addition, the electrode tip was fitted in the concave portion with the portion where the first melting portion was formed facing the first end portion side of the electrode base material.

  For all samples, after heating with a burner for 2 minutes so that the temperature of the second end of the electrode base material holding the first end is 950 ° C., letting it cool for 1 minute is one cycle, A cold test was performed in which 1000 cycles were applied to the electrode matrix.

  After the cooling test, the cross section of the electrode tip perpendicular to the axis of the tip body was observed with a metal microscope, and the length of the circumferential crack present in the first melting part (including the interface with the tip body) was measured. If the total length (total) of cracks existing in the first melted portion is 1/3 or more of the circumferential length of the first melted portion (the length of the boundary between the tip main body and the intermediate member before welding), the “breaking” (×) ”, and if it was less than 1/3, it was evaluated as“ not broken (◯) ”. The results are shown in Table 1.

  As shown in Table 1, the first molten part containing 30 to 70% by mass of the noble metal component and having an angle θ of 20 to 90 ° was not broken. From this result, it was confirmed that the first melting part containing 30 to 70% by mass of the noble metal component and having an angle θ of 20 to 90 ° can hold the chip body on the intermediate member. Therefore, it was also clear that the conductive path of the discharge current can be secured by the first melting part.

  Note that the interface between the first melted portion containing 25% by mass of the noble metal component and the chip body was mainly broken. It is presumed that the linear expansion coefficient of the first melting part is closer to the linear expansion coefficient of the intermediate member than the linear expansion coefficient of the chip body. Further, in the first molten part containing 75% by mass of the noble metal component, a part mainly close to the intermediate member was broken. It is presumed that the linear expansion coefficient of the first melting part is closer to the linear expansion coefficient of the chip body than the linear expansion coefficient of the intermediate member. As for the 1st fusion part whose angle theta is 100 degrees or more, the inside of the 1st fusion part fractured. This is presumably because the volume of the first melted portion increased and the force resulting from the difference in linear expansion between the intermediate member and the chip body increased.

(Example 2)
Example in which the ratio of the Ni component in the second melted portion is different from that in Example 1 except that the first melted portion including the angle θ of 70 ° and containing 65 mass% of the noble metal component is formed in all the electrode tips. Two samples were obtained. The ratio of the Ni component in the second melted portion was measured by EDX, and the electrode tip having the Ni melt proportion (representative value) shown in Table 2 was extracted.

全てのサンプルについて実施例１と同じ冷熱試験を行った。冷熱試験後、チップ本体の軸に垂直な電極チップの断面を金属顕微鏡で観察して、第２溶融部（チップ本体との界面を含む）のどこが破断したかを調べた。第２溶融部の内部で破断したものは「×」、第２溶融部とチップ本体との界面が破断したものは「○」と評価した。結果は表２に記した。

All the samples were subjected to the same cooling test as in Example 1. After the thermal test, the cross section of the electrode tip perpendicular to the axis of the tip body was observed with a metal microscope to examine where the second melted portion (including the interface with the tip body) broke. Those that broke inside the second melt zone were evaluated as “x”, and those that broke the interface between the second melt zone and the chip body were rated as “◯”. The results are shown in Table 2.

  As shown in Table 2, the second melting part containing 80 mass% or more of the Ni component was broken at the interface between the second melting part and the chip body. The second molten part releases thermal stress by breaking at the interface. Since the second melting part bites into the side surface of the chip body, the second melting part locks the chip body after the interface breaks. In addition, since the linear expansion coefficient leaves | separates from the linear expansion coefficient of an intermediate member as the ratio of Ni component becomes small, it is estimated that a 2nd fusion | melting part fractures inside.

  According to Example 1 and Example 2, since the second melting part releases thermal stress, it is possible to suppress the deformation of the electrode base material, the breakage of the chip body, and the progress of the crack, and the chip body as an intermediate member It is clear that it can be held stably.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. It can be easily guessed. For example, the shape and number of the first melting parts 27, 41, 61 and the second melting parts 28, 44, 54, 64 are examples, and can be set as appropriate.

  In each of the above embodiments, the case where the shape of the chip body 23 is a disk shape (columnar shape) has been described. However, the shape is not necessarily limited to this, and other shapes can naturally be adopted. Examples of the shape of the other chip body include a truncated cone shape, an elliptical column shape, and a polygonal column such as a triangular column and a quadrangular column.

  In each of the above embodiments, since the chip body 23 is cylindrical, the case where the intermediate member 26 surrounding the side surface 25 of the chip body 23 is annular has been described. However, the shape is not necessarily limited to this, and naturally, various shapes such as a cylindrical shape, an annular shape, and a rectangular tube shape can be adopted according to the shape of the chip body.

  In each of the above embodiments, the case where the intermediate member 26 is a bottomless annular shape has been described, but the present invention is not necessarily limited thereto. Since the intermediate member 26 only needs to be able to surround the side surface 25 of the chip body 23, it is naturally possible to employ the bottomed intermediate member 26 provided with a bottom portion that covers the bottom of the chip body 23.

  In each of the above embodiments, the case where the cross section of the electrode base material 13 is rectangular has been described. However, the present invention is not necessarily limited to this, and it is naturally possible to employ an electrode base material having another cross sectional shape. Examples of other cross-sectional shapes of the electrode base material include a circular shape, an elliptical shape, a polygonal shape such as a triangular shape and a pentagonal shape, and the like.

  In each of the above-described embodiments, the case where the melting portion 29 is provided over the entire outer periphery of the intermediate member 26 has been described, but the present invention is not necessarily limited thereto. The first melting portions 27, 41, 61 and the second melting portions 28, 44 are not mixed with the first melting portions 27, 41, 61 or the second melting portions 28, 44, 54, 64 and the melting portion 29. Of course, it is possible to use spot welding in which the melted portion 29 is independent of the.

  In this case, since the electrode chip 16 is fitted in the recess 21, the first melting portions 27, 41, 61 and the second melting portions 28, 44, 54, 64 exposed on the side surface of the intermediate member 26 are not formed in the recess 21. Can be accommodated. As a result, the first melting part 27 and the second melting part 28 can be prevented from being directly exposed to the outside air. It is known that an alloy containing a noble metal tends to cause oxidative corrosion when the proportion of the noble metal contained in the component increases. However, since the first melting part 27, 41, 61 and the second melting part 28, 44, 54, 64 can be prevented from being directly exposed to the outside air, the first melting part 27, 41, 61 and the second melting part 28, The oxidative corrosion of 44, 54 and 64 can be suppressed.

  In each of the above-described embodiments, the case where the melted portion 29 that joins the electrode tip 16 to the electrode base material 13 is formed by seam welding using a pulsed laser is not necessarily limited to this. It is naturally possible to join the electrode tip 16 to the electrode base material 13. Examples of other means include seam welding, arc welding, resistance welding, and the like using a continuous wave laser.

  In the above embodiments, the case where the second end 15 side of the electrode base material 13 in which the first end 14 is joined to the metal shell 11 is bent has been described. However, it is not necessarily limited to this. Naturally, instead of using the bent electrode base material 13, it is possible to use a linear electrode base material. In this case, the front end side of the metal shell 11 is extended in the direction of the axis O, the first end of the linear electrode base material is joined to the metal shell 11, and the second end of the electrode base material is connected to the center electrode 19. To face.

  In each of the above embodiments, the axis O of the center electrode 19 and the axis 24 of the chip body 23 are aligned, and the electrode base material 13 is disposed so that the electrode tip 16 faces the center electrode 19 in the direction of the axis O. explained. However, the present invention is not necessarily limited to this, and the positional relationship between the electrode tip 16 and the center electrode 19 can be set as appropriate. As another positional relationship between the electrode tip 16 and the center electrode 19, for example, the electrode base material 13 is disposed so that the axis O of the center electrode 19 and the axis 24 of the tip body 23 intersect, For example, the electrode base material 13 may be disposed so that the side surface and the electrode tip 16 face each other, and the electrode base material 13 may be disposed such that the shaft 22 and the axis O of the electrode base material 13 cross each other at an angle.

  In the third embodiment, the case where the second melted portion 54 is formed by scanning the continuous wave laser beam in the circumferential direction of the intermediate member 26 has been described. However, the present invention is not necessarily limited to this, and it is naturally possible to form the continuous second melting portion 54 by scanning the pulsed laser beam in the circumferential direction of the intermediate member 26.

10, 40, 50, 60 Spark plug 11 Metal shell 12 Ground electrode 13 Electrode base material 14 First end 15 Second end 16 Electrode tip 17 Insulator 18 Axis hole 19 Central electrode 21 Recess 22 Axis 23 Tip body 24 Axis 25 Side 26 Intermediate member 27, 41, 61 First melting part (part of melting part)
28, 44, 54, 64 Second melting part (part of melting part)
35 First region 36, 37, 47, 48, 67, 68 Tangent 38, 49, 69 Second region 39 Virtual plane O Axis

Claims (5)

A center electrode extending along an axis;
An insulator in which the center electrode is disposed in an axial hole formed along the axis;
A metal shell disposed on the outer periphery of the insulator;
A ground electrode joined to the metal shell,
The ground electrode includes an electrode base material having a first end joined to the metal shell and a second end facing the center electrode, and a recess formed at a position of the electrode base material facing the center electrode. An electrode chip joined to the electrode base material in a state in which at least a portion is fitted, and
The electrode tip comprises a tip body mainly composed of a noble metal, and an intermediate member surrounding a side surface of the tip body,
It is a spark plug formed by forming a melting part straddling the intermediate member and the chip body,
The intermediate member is made of an alloy mainly containing Ni or Ni,
The melting part includes a first melting part containing 30 to 70% by mass of a noble metal component and a second melting part containing 80% by mass or more of a Ni component,
In a cross section perpendicular to the axis of the chip body, a portion of the first melted portion formed on the chip body has an angle formed by two straight lines passing through the axis of the chip body of 90 ° or less. A spark plug characterized by being in a first region having a predetermined angle.   The first region is a virtual plane perpendicular to a plane including an axis of the electrode base material extending from the first end portion to the second end portion and the axis of the chip body. The spark plug according to claim 1, wherein the spark plug exists on the first end side with respect to a virtual plane including the axis.   The spark plug according to claim 1 or 2, wherein the predetermined angle of the first region is 20 ° or more.   3. The spark plug according to claim 2, wherein at least a part of the second melting portion formed on the chip body is present on the second end side with respect to the virtual plane.   In a cross section perpendicular to the axis of the chip body, at least a part of the second melting portion formed in the chip body is a portion formed in the chip body of the first melting portion. Two tangents that contact and pass through the axis of the chip body are present in a second region formed by extending the axis of the chip body to the opposite side of the first melting portion. The spark plug according to any one of claims 1 to 4.

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