JP4564741B2 - Manufacturing method of spark plug - Google Patents

Description

  The present invention relates to a method of manufacturing a spark plug for an internal combustion engine in which a chip is joined to an electrode that performs spark discharge.

  Conventionally, spark plugs for ignition are used in internal combustion engines. In this spark plug, generally, the ground electrode is welded to the tip of the metal shell that holds the insulator in which the center electrode is inserted, and the other end of the ground electrode is opposed to the tip of the center electrode. Thus, a spark discharge gap is formed. Then, a spark discharge is performed between the center electrode and the ground electrode. Further, a noble metal tip for improving the spark wear resistance is formed at a portion where a spark discharge gap is formed between the center electrode and the ground electrode.

By the way, as a method of joining the noble metal tip to the center electrode of the spark plug, a recess (small diameter portion) is provided at the tip of the center electrode, the tip (discharge noble metal electrode) is resistance-welded to the recess, and the side surface portion of the tip is further provided. Is welded to the tip of the center electrode over the entire circumference, thereby increasing the bonding strength between the tip and the tip of the center electrode (see, for example, Patent Document 1).
JP-A-7-22155

  On the other hand, when a noble metal tip is joined to the ground electrode, the noble metal tip is resistance-welded to the other end of the ground electrode, and the side surface of the noble metal tip is laser welded over the entire circumference, as in Patent Document 1. it can. However, when performing such a method, it is necessary to weld the ground electrode to the metal shell in advance by resistance welding or the like before joining the noble metal tip to the ground electrode. This requires a highly accurate positional relationship between the tip of the noble metal tip of the ground electrode with respect to the tip of the noble metal tip of the center electrode. This is because the above-mentioned requirement may not be obtained by the welding method. That is, the noble metal tip is joined to the ground electrode by resistance welding the noble metal tip to the other end of the ground electrode welded to the metal shell and laser welding the side surface of the noble metal tip over the entire circumference.

  However, when laser welding the noble metal tip to the ground electrode joined to the metal shell over the entire circumference, the tip of the center electrode may interfere with the laser light depending on the laser beam irradiation angle, and laser welding may not be possible over the entire circumference. There is. Therefore, it is necessary to perform laser welding at an irradiation angle of the laser beam that does not interfere with the center electrode tip, but when laser welding is performed at such an irradiation angle of the laser beam, the ground electrode and the noble metal tip are melted to each other. There was a risk that sink marks occurred and the outer diameter of the noble metal tip was narrowed (see the state of being removed: see FIG. 19). For this reason, the bonding strength of the noble metal tip is lowered, which may cause the tip to fall off. Further, since the heat conduction path for releasing the heat of the noble metal tip to the ground electrode is narrowed, it is difficult to draw the heat of the noble metal tip, and the durability may be lowered.

  The present invention has been made to solve the above problems, and provides a spark plug manufacturing method capable of maintaining the durability of the chip without impairing the bonding strength of the chip bonded to the ground electrode. The purpose is to do.

In order to achieve the above object, a spark plug manufacturing method according to a first aspect of the present invention includes a center electrode, an axial hole in the axial direction, and an insulator that holds the center electrode at a tip end side of the axial hole. A metal shell that surrounds the insulator and holds the insulator, one end of which is joined to the metal shell, and a columnar noble metal tip facing the center electrode is joined to the other end A spark plug comprising: an electrode; and an inner surface of the other end, which is a surface of the other end of the ground electrode facing the center electrode, and a surface opposite to the facing surface of the noble metal tip. A resistance that forms a flange that expands the outer diameter of the noble metal tip at the bottom of the noble metal tip while performing resistance welding with the bottom surface so that the protruding dimension of the noble metal tip is not less than 0.3 mm and not more than 1.5 mm Welding process; Serial in either irradiation angle of 5 degrees to 80 degrees with respect to the other end portion the inner surface of the ground electrode, by performing laser light irradiation over the entire periphery of the flange portion of the noble metal tip, dissolved entire flange portion A laser welding step of melting the ground electrode and welding the noble metal tip and the ground electrode, and in the resistance welding step, the cross-sectional area of the flange in the axial direction of the noble metal tip is Resistance welding of the noble metal tip is performed so that the area of the facing surface is 1.3 times or more.

  According to a second aspect of the present invention, there is provided a spark plug manufacturing method comprising: a center electrode; an insulator having an axial hole in an axial direction; and holding the center electrode on a tip end side of the axial hole; A metal shell that surrounds the periphery and holds the insulator, and a columnar noble metal tip facing the center electrode in a state where one end is joined to the metal fitting and a pedestal chip is sandwiched between the other end A spark plug having a thermal expansion coefficient between the noble metal chip and the ground electrode, wherein the pedestal chip has a thermal expansion coefficient between the noble metal chip and the ground electrode. Protrusion dimension of the noble metal tip by performing resistance welding between the pedestal tip joined to the inner surface of the other end, which is a surface facing the center electrode, and a bottom surface opposite to the facing surface of the noble metal tip 0.3 mm or more 1.5 a resistance welding step of forming a flange portion having an expanded outer diameter of the noble metal tip at the bottom of the noble metal tip while having a size of m or less, and any of 5 to 80 degrees with respect to the inner surface of the other end of the ground electrode A laser welding step of irradiating laser light over the entire circumference of the flange of the noble metal tip at a given irradiation angle, and welding the noble metal tip and the ground electrode, the noble metal tip comprising: In the resistance welding process, the resistance of the noble metal tip is such that the cross-sectional area of the flange in the axial direction of the noble metal tip is 1.2 times or more the area of the facing surface. Welding is performed.

  According to a third aspect of the present invention, there is provided a spark plug manufacturing method comprising: a center electrode; an insulator having an axial hole in an axial direction; and holding the center electrode on a tip end side of the axial hole; A metal shell that surrounds the periphery and holds the insulator, and a columnar noble metal tip facing the center electrode in a state where one end is joined to the metal fitting and a pedestal chip is sandwiched between the other end A spark plug having a thermal expansion coefficient between the noble metal chip and the ground electrode, wherein the pedestal chip has a thermal expansion coefficient between the noble metal chip and the ground electrode. Protrusion of the noble metal tip is performed by resistance welding between the inner surface of the other end, which is a surface facing the center electrode, and the pedestal tip joined to the bottom surface of the noble metal tip opposite to the facing surface. Dimension 0.3 mm or more 1 A resistance welding process for forming a flange portion having an expanded outer diameter of the noble metal tip at the bottom of the noble metal tip while having a size of 5 mm or less, and any of 5 to 80 degrees with respect to the inner surface of the other end of the ground electrode A laser welding step of irradiating laser light over the entire circumference of the flange of the noble metal tip at a given irradiation angle, and welding the noble metal tip and the ground electrode, the noble metal tip comprising: In the resistance welding process, the resistance of the noble metal tip is such that the cross-sectional area of the flange in the axial direction of the noble metal tip is 1.2 times or more the area of the facing surface. Welding is performed.

  Further, in the spark plug manufacturing method of the invention according to claim 4, in addition to the configuration of the invention according to any one of claims 1 to 3, in the laser welding step, the irradiation of the laser beam to the flange portion is It is performed at an irradiation angle of 5 to 60 degrees with respect to the inner surface of the other end of the ground electrode.

  Further, in the spark plug manufacturing method of the invention according to claim 5, in addition to the structure of the invention according to any of claims 1 to 4, the noble metal tip is mainly composed of iridium, rhodium, platinum, nickel, It is made of an alloy to which at least one of tungsten, palladium, ruthenium, and osmium is added.

  Further, in the spark plug manufacturing method of the invention according to claim 6, in addition to the configuration of the invention according to any one of claims 1 to 5, the noble metal tip is mainly composed of platinum, rhodium, iridium, nickel, It is made of an alloy to which at least one of tungsten, palladium, ruthenium, and osmium is added.

  In the spark plug manufacturing method according to the first aspect of the present invention, the irradiation angle is set to any one of 5 to 80 degrees with respect to the inner surface of the other end, which is the surface facing the center electrode of the other end of the ground electrode. Thus, the laser beam is irradiated over the entire circumference of the noble metal tip. For this reason, when irradiating a laser beam, the noble metal tip can be easily welded to the ground electrode without disturbing the tip of the center electrode.

  However, when laser welding is performed by irradiating laser light at the above-mentioned irradiation angle, sink marks may occur in the melted portion between the ground electrode and the noble metal tip, and the outer diameter of the noble metal tip may be reduced. Therefore, in the spark plug manufacturing method according to the first aspect of the present invention, a flange is formed at the bottom of the noble metal tip to be bonded to the inner surface of the other end of the ground electrode, and laser light is irradiated to the flange. Since laser welding is performed, thinning of the outer diameter of the noble metal tip can be reduced even if sink marks occur in the melted portion between the ground electrode and the noble metal tip after laser welding. Therefore, the bonding strength of the noble metal tip can be maintained, and the durability of the noble metal tip can be maintained. Moreover, in the invention which concerns on Claim 1, the protrusion dimension of a noble metal tip shall be the magnitude | size of 0.3 mm or more and 1.5 mm or less. If the projecting dimension of the noble metal tip is smaller than 0.3 mm, the problem of thinning is unlikely to occur, and this is not applicable in the present invention. In addition, when the protrusion dimension of the noble metal tip is larger than 1.5 mm, the reduction of the extinguishing action on the flame nucleus formed in the spark discharge gap is not further improved, and the spark wear resistance is lowered.

  Further, if the cross-sectional area of the collar portion of the noble metal tip is 1.3 times or more of the area of the opposing surface, the outer diameter of the portion where sink marks after laser welding have occurred will not be smaller than the outer diameter of the original noble metal tip. Therefore, the thinning of the outer diameter of the noble metal tip can be prevented. On the other hand, if the cross-sectional area of the collar portion of the noble metal tip is less than 1.3 times the area of the facing surface, the above effect cannot be obtained effectively. In addition, the cross-sectional area of the collar part of a noble metal tip means the maximum diameter of the collar part after resistance welding.

  In the spark plug manufacturing method according to the second aspect of the present invention, the irradiation angle is set to any one of 5 degrees to 80 degrees with respect to the inner surface of the other end which is a surface facing the center electrode of the other end of the ground electrode. Thus, the laser beam is irradiated over the entire circumference of the noble metal tip. For this reason, when irradiating a laser beam, the noble metal tip can be easily welded to the ground electrode without disturbing the tip of the center electrode.

However, when laser welding is performed by irradiating laser light at the above-mentioned irradiation angle, sink marks may occur in the melted portion between the ground electrode and the noble metal tip, and the outer diameter of the noble metal tip may be reduced. Therefore, in the spark plug manufacturing method according to the third aspect of the present invention, a flange is formed at the bottom of the noble metal tip that is joined to the inner surface of the other end of the ground electrode with a pedestal tip interposed, and a laser is applied to the flange. Since laser welding is performed by irradiating light, the thinning of the outer diameter of the noble metal tip can be reduced even if sink marks occur in the melted portion between the ground electrode and the noble metal tip after laser welding. Furthermore, since the pedestal tip is crushed so as to cover the buttock when forming the buttock, the thickness of the noble metal tip in the vicinity of the buttock can be increased without enlarging the bulge of the buttock, so that after laser welding The thinning of the outer diameter of the noble metal tip due to sink can be effectively reduced. Therefore, the bonding strength of the noble metal tip can be maintained, and the durability of the noble metal tip can be maintained. As the base chip, a metal having a coefficient of thermal expansion between the noble metal chip and the ground electrode is used. This further increases the bonding strength between the noble metal tip and the ground electrode. Moreover, in the invention which concerns on Claim 3, the protrusion dimension of a noble metal tip shall be 0.3 mm or more and 1.5 mm or less. If the projecting dimension of the noble metal tip is smaller than 0.3 mm, the problem of thinning is unlikely to occur, and this is not applicable in the present invention. In addition, when the protrusion dimension of the noble metal tip is larger than 1.5 mm, the reduction of the extinguishing action on the flame nucleus formed in the spark discharge gap is not further improved, and the spark wear resistance is lowered.
Also, if the cross-sectional area of the collar portion of the noble metal tip is 1.2 times or more the area of the opposing surface by interposing the base tip, the outer diameter of the part where the sink mark has occurred after laser welding is the original noble metal. Since it is not thinner than the outer diameter of the tip, it is possible to prevent the outer diameter of the noble metal tip from being reduced. On the other hand, if the cross-sectional area of the collar portion of the noble metal tip is less than 1.2 times the area of the facing surface, the above effect cannot be obtained effectively.

  In the spark plug manufacturing method of the invention according to claim 3, the irradiation angle is set to any one of 5 degrees to 80 degrees with respect to the inner surface of the other end which is the surface facing the center electrode of the other end of the ground electrode. Thus, the laser beam is irradiated over the entire circumference of the noble metal tip. For this reason, when irradiating a laser beam, the noble metal tip can be easily welded to the ground electrode without the front end of the center electrode interfering.

  However, when laser welding is performed by irradiating laser light at the above-mentioned irradiation angle, sink marks may occur in the melted portion between the ground electrode and the noble metal tip, and the outer diameter of the noble metal tip may be reduced. Accordingly, in the spark plug manufacturing method according to the fourth aspect of the present invention, a collar portion is formed at the bottom of the noble metal tip that is joined to the inner surface of the other end portion of the ground electrode with a base chip interposed, and a laser is applied to the collar portion. Since laser welding is performed by irradiating light, the thinning of the outer diameter of the noble metal tip can be reduced even if sink marks occur in the melted portion between the ground electrode and the noble metal tip after laser welding. Furthermore, since the pedestal tip is crushed so as to cover the buttock when forming the buttock, the thickness of the noble metal tip in the vicinity of the buttock can be increased without enlarging the bulge of the buttock, so that after laser welding The thinning of the outer diameter of the noble metal tip due to sink can be effectively reduced. Therefore, the bonding strength of the noble metal tip can be maintained, and the durability of the noble metal tip can be maintained. Moreover, in the invention which concerns on Claim 4, the protrusion dimension of a noble metal chip | tip is taken as the magnitude | size of 0.3 mm or more and 1.5 mm or less. If the projecting dimension of the noble metal tip is smaller than 0.3 mm, the problem of thinning is unlikely to occur, and this is not applicable in the present invention. In addition, when the protrusion dimension of the noble metal tip is larger than 1.5 mm, the reduction of the extinguishing action on the flame nucleus formed in the spark discharge gap is not further improved, and the spark wear resistance is lowered.

  Moreover, if the cross-sectional area of the collar portion of the noble metal tip is 1.2 times or more the area of the opposing surface by interposing the base tip, the outer diameter of the portion where sink marks after laser welding have occurred is the original noble metal. Since it is not thinner than the outer diameter of the tip, it is possible to prevent the outer diameter of the noble metal tip from being reduced. On the other hand, if the cross-sectional area of the collar portion of the noble metal tip is less than 1.2 times the area of the facing surface, the above effect cannot be obtained effectively.

  Further, in the spark plug manufacturing method of the invention according to claim 4, in addition to the effect of the invention according to any of claims 1 to 3, the irradiation angle of the laser beam at the time of laser welding is set to 5 with respect to the inner surface of the tip portion. If the angle is any one of 60 degrees to 60 degrees, the outer diameter of the noble metal tip is not reduced.

  Moreover, in the spark plug manufacturing method of the invention according to claim 5, in addition to the effect of the invention according to any one of claims 1 to 4, the noble metal tip for performing spark discharge is mainly composed of iridium, rhodium, platinum, When formed from an alloy to which at least one of nickel, tungsten, palladium, ruthenium, and osmium is added, a noble metal tip having excellent wear resistance can be provided.

  Further, in the spark plug manufacturing method of the invention according to claim 6, in addition to the effect of the invention according to any of claims 1 to 5, the noble metal tip for performing spark discharge is mainly composed of platinum, rhodium, iridium, When formed from an alloy to which at least one of nickel, tungsten, palladium, ruthenium, and osmium is added, a noble metal tip having excellent wear resistance can be provided.

Here, the cross-sectional area of the axial cross-section of the noble metal tip which is the other end resistance-welded to the inner surface of the ground electrode in the resistance welding process is desirably 0.12 mm ² or more 1.15 mm ² or less. When the cross-sectional area of the noble metal tip is smaller than 0.12 mm ² , it becomes difficult to effectively release the heat of the flame kernel formed in the spark discharge gap to the ground electrode, and the spark wear resistance is reduced. Further, if the cross-sectional area of the noble metal tip is made larger than 1.15 mm ² , the heat dissipation effect of the noble metal tip is not affected even if the laser welding process causes a narrowing.

  Embodiments of a spark plug manufacturing method embodying the present invention will be described below with reference to the drawings. First, the structure of a spark plug 100 as an example of the spark plug in the first embodiment will be described with reference to FIG. FIG. 1 is a partial cross-sectional view of a spark plug 100.

  As shown in FIG. 1, the spark plug 100 is roughly provided with an insulator 1 that constitutes an insulator, and a metal shell 5 that is provided at a substantially central portion in the longitudinal direction of the insulator 1 and holds the insulator 1. A center electrode 2 held in the axial direction in the insulator 1, a ground electrode 60 whose one end is welded to the tip portion 57 of the metal shell 5, and the other end faces the tip portion 22 of the center electrode 2, and the center electrode 2 and the terminal metal fitting 4 provided at the upper end portion.

  Next, the insulator 1 constituting the insulator of the spark plug 100 will be described. As is well known, the insulator 1 is formed by firing alumina or the like, and a corrugation 11 for increasing the creeping distance is formed at the rear end portion (upper portion in FIG. 1). Further, a leg length portion 13 that is exposed to the combustion chamber of the internal combustion engine is provided at the tip portion (lower portion in FIG. 1) of the insulator 1. Further, a central through hole 12 is formed at the axial center of the insulator 1, and the central electrode 2 is held in the central through hole 12. The center electrode 2 has at least a surface layer portion of an electrode base material 21 made of a nickel-based alloy such as Inconel (trade name) 600 or 601. The central through hole 12 corresponds to the “shaft hole” in the present invention.

  The distal end portion 22 of the center electrode 2 protrudes from the distal end surface of the insulator 1 and is formed so as to become smaller in diameter toward the distal end side. A columnar noble metal tip 23 is welded to the tip surface of the tip portion 22 in the axial direction of the center electrode 2. The center electrode 2 is electrically connected to the upper terminal fitting 4 via a seal body 14 and a ceramic resistor 3 provided in the center through hole 12. A high voltage cable (not shown) is connected to the terminal fitting 4 via a plug cap (not shown) so that a high voltage is applied.

  Next, the metal shell 5 will be described. As shown in FIG. 1, the metal shell 5 is for holding the insulator 1 and fixing the spark plug 100 to an internal combustion engine (not shown). The insulator 1 is supported by being surrounded by a metal shell 5. The metal shell 5 is formed of a low carbon steel material, and a hexagonal portion 51 that is a tool engaging portion into which a spark plug wrench (not shown) is fitted, and a screw portion that is screwed into an engine head provided on the internal combustion engine (not shown). 52. As an example of the standard of the screw portion 52, M14 or the like is used. In the metal shell 5, the caulking portion 53 is caulked, whereby the insulator 1 is supported on the step portion 56 via the plate packing 8, and the metal shell 5 and the insulator 1 are integrated. In order to complete sealing by caulking, annular ring members 6 and 7 are interposed between the metal shell 5 and the insulator 1, and talc (talc) 9 powder is interposed between the ring members 6 and 7. Filled. A flange 54 is formed at the center of the metal shell 5, and the gasket 10 is inserted into the vicinity of the rear end side (upper part in FIG. 1) of the screw 52, that is, the seat surface 55 of the flange 54. ing. In addition, the opposite side dimension of the hexagonal part 51 is 16 mm as an example, and the length from the seating surface 55 of the metal shell 5 to the tip part 57 is 19 mm as an example.

  Next, the ground electrode 60 will be described. The ground electrode 60 is made of a metal having high corrosion resistance. As an example, a nickel alloy such as Inconel (trade name) 600 or 601 is used. The ground electrode 60 has a substantially rectangular cross section in the longitudinal direction, and one end (base 62) is joined to the tip 57 of the metal shell 5 by welding. The other end portion (tip portion 61) of the ground electrode 60 is bent so as to face the tip portion 22 of the center electrode 2. An inner surface 63 of the ground electrode 60 that is a surface facing the center electrode 2 is substantially orthogonal to the axial direction of the center electrode 2. A cylindrical noble metal tip 70 projects from the inner surface 63, and the facing surface 71 of the noble metal tip 70 faces the facing surface 24 of the noble metal tip 23 of the center electrode 2. The facing surface 71 is a plane orthogonal to the axial direction of the noble metal tip 70.

  As an example of the noble metal tip 70, a platinum-rhodium alloy mainly composed of platinum having excellent wear resistance is used in the first embodiment. The noble metal chip 70 may be made of an alloy containing platinum as a main component and at least one of iridium, nickel, tungsten, palladium, ruthenium, and osmium. Alternatively, an alloy containing iridium as a main component and at least one of rhodium, platinum, nickel, tungsten, palladium, ruthenium, and osmium may be used. The reason why the alloy made of these noble metals is used as the noble metal tip 70 is to improve the wear resistance.

  Next, a first embodiment of the spark plug manufacturing method of the present invention will be described. Hereinafter, the welding process of the noble metal tip 70 will be described with reference to FIGS. 2-4 is a figure which shows the welding process of the noble metal tip 70 to the inner surface 63 of the ground electrode 60 in 1st Embodiment.

  In the method for manufacturing the spark plug 100 according to the first embodiment, the spark plug 100 in which the ground electrode 60 is joined to the metal shell 5 assembled with the insulator having the center electrode by a known manufacturing method is used as the welding jig ( The welding position is determined by the welding electrode 90 of the welding jig holding the noble metal tip 70. As described above, the ground electrode 60 is joined to the metal shell 5 in an unbent state in advance, and on the intersection line between the inner surface 63 of the ground electrode 60 and the surface that includes the axis of the center electrode 2 and is orthogonal to the inner surface 63, The noble metal tip 70 is positioned.

  As shown in FIG. 2, the noble metal tip 70 positioned with respect to the inner surface 63 is in a state in which the bottom surface 72 opposite to the facing surface 71 is pressed against the inner surface 63 of the ground electrode 60 by the welding electrode 90. Resistance welding is performed at (resistance welding process). The portion excluding the vicinity of the bottom surface 72 (bottom portion) of the noble metal tip 70 is held by the welding electrode 90, and the exposed portion of the noble metal tip 70 swells when the noble metal tip 70 is pressed toward the inner surface 63, and the collar portion 73. Is formed. As shown in FIG. 3, the cross-sectional area of the flange 73 of the noble metal tip 70 temporarily joined to the inner surface 63 (the crossing in the axial direction of the noble metal tip 70 at the portion where the outer diameter of the flange 73 shown in FIG. A pressing force is applied during the resistance welding so that the area of the surface is 1.3 times or more of the area of the facing surface 71 of the columnar noble metal tip 70 based on an experimental result (Example 1) described later. .

  Next, as shown in FIG. 4, the collar 73 is irradiated with laser light at an irradiation angle θ with respect to the inner surface 63. Laser welding is performed by a known YAG laser, and welding is performed over the entire circumference of the noble metal tip 70 (laser welding process). At this time, the collar portion 73 and the tip portion 61 of the ground electrode 60 are joined, and sink marks occur in the portion irradiated with the laser beam (melting portion 80). However, since the flange 73 swells larger than the body 74 of the noble metal tip 70, even if the cross-sectional area of the flange 73 is reduced by sinking, the area of the facing surface 71, that is, the body in the axial direction of the noble metal tip 70. It is difficult to be smaller than the cross-sectional area of 74. Then, the spark plug 100 can be completed by bending the ground electrode 60 so as to face the tip 22 of the center electrode 2 by a known method.

[Example 1]
Here, the relationship between the cross-sectional area of the flange 73 with respect to the area of the facing surface 71 of the noble metal tip 70 and sink marks generated by laser welding will be described with reference to FIGS.

  In the first embodiment, the following experiment was conducted as Example 1. By the resistance welding, the amount of swelling, that is, the cross-sectional area of the flange 73 with respect to the area of the facing surface 71 of the noble metal tip 70, was 1.3 times, 1.2 times, 1.1 times, and 1 time (no swelling). In each case, laser welding was performed with the irradiation angle θ set in the range of 5 to 80 degrees. Each experimental condition at this time is as follows. The noble metal tip 70 is made of a platinum-rhodium alloy having an outer diameter of 0.7 mm and a height of 0.8 mm. The ground electrode 60 is made of a nickel-based alloy having a width (length in the short direction) of 2.5 mm and a thickness of 1.4 mm. Resistance welding was performed by pressing the noble metal tip 70 against the inner surface 63 of the ground electrode 60 with a load of 150 N and applying a current of 1000 A. Laser welding was performed with a YAG laser having a laser pulse energy of 2 J and a pulse width of 2 msec. In each table, “the presence or absence of occurrence of chip thinning”, “thinning” represents that the outer diameter of the welded portion becomes thinner than before welding due to sink marks generated after laser welding. And when the cross-sectional area of the portion with the smallest cross-sectional area with respect to the area of the opposing surface 71 of the noble metal tip 70 is 0.8 times or less, “thinning” is “occurrence” and is larger than 0.8 times Is classified as “thinning” and “no occurrence”. In this case, for example, the presence or absence of thinning was confirmed for 1000 samples, and the occurrence rate was determined.

  FIG. 5 is a table showing the relationship between the laser irradiation angle and the presence or absence of tip taper when the bulge amount is 1.3 times. FIG. 6 is a table showing the relationship between the laser irradiation angle and the presence or absence of tip taper when the bulge amount is 1.2 times. FIG. 7 is a table showing the relationship between the laser irradiation angle and the presence or absence of tip taper when the bulge amount is 1.1 times. FIG. 8 is a table showing the relationship between the laser irradiation angle and the presence or absence of chip taper when there is no bulge.

  As shown in FIG. 5, when the bulge amount is 1.3 times, the laser irradiation angle θ is 5, 10, 20, 30, 30, 40, 50, and 60 degrees. Did not occur. Further, when the laser irradiation angle θ was 70 degrees and 80 degrees, thinning occurred, but the occurrence rate was 1% or less.

  As shown in FIG. 6, when the bulge amount was 1.2 times, no thinning occurred when the laser irradiation angle θ was 5, 10, or 20 degrees. Further, in the case of 30 degrees, 40 degrees, 50 degrees, and 60 degrees, thinning occurred, but the occurrence rate was 1% or less. Further, in the case of 70 degrees and 80 degrees, thinning occurred, but the incidence was greater than 1% and 10% or less.

  As shown in FIG. 7, when the bulge amount was 1.1 times, no thinning occurred when the laser irradiation angle θ was 5, 10, or 20 degrees. Further, in the case of 30 degrees, 40 degrees, 50 degrees, and 60 degrees, thinning occurred, but the occurrence rate was 1% or less. Further, in the case of 70 degrees and 80 degrees, thinning occurred, and the incidence was greater than 1% and 10% or less.

  As shown in FIG. 8, when there is no bulge, that is, when the bulge amount is 1 time, the laser irradiation angle θ is 5 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees. The thinning occurred, and the incidence was greater than 1% and 10% or less. In the case of 70 degrees and 80 degrees, the occurrence rate of thinning was 10% or more.

  From the above experimental results, it can be seen that as the cross-sectional area of the flange 73 with respect to the bulge amount, that is, the area of the facing surface 71 of the noble metal tip 70 increases, the influence of sink marks decreases. If the bulge amount is 1.3 times, the incidence of thinning is 1% or less in the laser irradiation angle θ range of 5 degrees to 80 degrees. Therefore, in this laser irradiation angle θ range (5 to 80 degrees), if resistance welding of the noble metal tip 70 is performed so that the bulge amount is 1.3 times or more, thinning due to sink marks is caused after laser welding. It turned out not to be a problem. In particular, when the laser irradiation angle θ is in the range of 5 degrees to 60 degrees, if resistance welding of the noble metal tip 70 is performed so that the bulge amount is 1.3 times or more, thinning does not occur after laser welding, which is more preferable. is there.

  Next, a spark plug 200 according to a second embodiment of the present invention will be described. In addition, the spark plug 200 has a form in which the joint portion between the ground electrode 60 and the noble metal tip 70 of the spark plug 100 described above is different, and an enlarged cross-sectional view of the principal portion of the joint portion is shown in FIG. Except for the above-described joint portion, the configuration is the same as that of the spark plug 100 according to the first embodiment. To do.

  As shown in FIG. 9, in the spark plug 200, a noble metal tip 70 is joined to the tip portion 61 of the ground electrode 60 via a pedestal tip 75. The pedestal chip 75 has a coefficient of thermal expansion between the ground electrode 60 and the noble metal chip 70. Specifically, a platinum-nickel alloy or the like can be used. Since the ground electrode 60 and the noble metal tip 70 are interposed via the base tip 75, the bonding strength of the noble metal tip 70 to the ground electrode 60 is further improved.

  Next, the manufacturing method of the spark plug 200 of 2nd Embodiment is demonstrated. The welding process of the noble metal tip 70 to the inner surface 63 of the ground electrode 60 in the second embodiment will be described below with reference to FIGS. 10-13 is a figure which shows the welding process of the noble metal tip 70 to the inner surface 63 of the ground electrode 60 in 2nd Embodiment.

  In the method for manufacturing the spark plug 200 according to the second embodiment, the spark plug 200 in which the ground electrode 60 is joined to the metal shell 5 assembled with the insulator having the center electrode by a known manufacturing method is used as a welding jig ( The welding position of the pedestal tip 75 is positioned. Then, as shown in FIG. 10, resistance welding is performed by the welding electrode 91 and temporarily joined to the inner surface 63.

  Next, the resistance welding process and laser welding process of the noble metal tip 70 shown in FIGS. 11 to 13 are substantially the same as those in the first embodiment. In the first embodiment, positioning is performed on the inner surface 63 of the ground electrode 60, and resistance welding is performed on the inner surface 63. However, in the second embodiment, the pedestal chip 75 is fixed. Positioning is performed, and resistance welding is performed on the base chip 75. At this time, the cross-sectional area of the flange 73 of the noble metal tip 70 temporarily joined to the inner surface 63 shown in FIG. 12 (the axial direction of the noble metal tip 70 in the portion where the outer diameter of the flange 73 shown in FIG. The area of the cross section) is based on the experimental result (Example 2) described later, and a pressing force is applied during this resistance welding so that it is 1.2 times or more the area of the opposing surface 71 of the columnar noble metal tip 70. It is done. The base chip 75 is crushed so as to surround the flange 73 of the noble metal chip 70.

[Example 2]
Next, FIG. 14 shows the relationship between the cross-sectional area of the flange 73 with respect to the area of the facing surface 71 of the noble metal tip 70 and sink marks generated by laser welding when the pedestal tip 75 of the second embodiment is interposed. A description will be given with reference to FIG.

  In the second embodiment, the following experiment was performed as Example 2. The amount of swelling by resistance welding with the pedestal tip 75 interposed, that is, the cross-sectional area of the flange 73 with respect to the area of the facing surface 71 of the noble metal tip 70 is 1.2 times, 1.1 times, and 1 time (not regarded as swelling) In each case, laser welding was performed with the irradiation angle θ set in the range of 5 to 80 degrees. Each experimental condition at this time is as follows. The base chip 75 is a circular disk-shaped chip, and is made of a platinum-nickel alloy having a diameter of 1 mm and a thickness of 0.1 mm. Other experimental conditions are the same as those in the first embodiment.

  FIG. 14 is a table showing the relationship between the laser irradiation angle and the presence or absence of tip taper when the bulge amount is 1.2 times. FIG. 15 is a table showing the relationship between the laser irradiation angle and the presence / absence of tip taper when the bulge amount is 1.1 times. FIG. 16 is a table showing the relationship between the laser irradiation angle and the presence / absence of chip taper when there is no swelling.

  As shown in FIG. 14, when the bulge amount is 1.2 times, the laser irradiation angle θ is 5 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, and 60 degrees, the thinning is performed. Did not occur. Further, when the laser irradiation angle θ was 70 degrees and 80 degrees, thinning occurred, but the occurrence rate was 1% or less.

  As shown in FIG. 15, when the bulge amount was 1.1 times, no thinning occurred when the laser irradiation angle θ was 5 degrees or 10 degrees. In addition, thinning occurred at 20 degrees, 30 degrees, 40 degrees, 50 degrees, and 60 degrees, but the occurrence rate was 1% or less. Further, in the case of 70 degrees and 80 degrees, thinning occurred, but the incidence was greater than 1% and 10% or less.

  As shown in FIG. 16, when there is no bulge, that is, when the amount of bulge is 1 time and when the laser irradiation angle θ is 5 degrees, although the thinning occurs, the incidence is 1% or less. Further, when the laser irradiation angle θ was 10, 20, 30, 40, 50, and 60 degrees, thinning occurred, and the incidence was greater than 1% and less than 10%. In the case of 70 degrees and 80 degrees, the occurrence rate of thinning was 10% or more.

  From the above experimental results, as in the first embodiment, if the bulge amount is 1.2 times, the occurrence of thinning may not be a problem when the laser irradiation angle θ is in the range of 5 degrees to 80 degrees. found. In particular, when the laser irradiation angle θ is in the range of 5 degrees to 60 degrees, if resistance welding of the noble metal tip 70 is performed so that the amount of swelling is 1.2 times or more, thinning does not occur after laser welding, which is more preferable. is there.

  Next, the manufacturing method of the spark plug of 3rd Embodiment is demonstrated. The third embodiment is another embodiment of the spark plug 200. Also in the third embodiment, the noble metal tip 70 is welded to the inner surface 63 of the ground electrode 60 as in the first embodiment. At this time, similarly to the second embodiment, a base chip 75 having a thermal expansion coefficient between the thermal expansion coefficient of the noble metal tip 70 and the thermal expansion coefficient of the ground electrode 60 is interposed therebetween. The welding process of the noble metal tip 70 to the inner surface 63 of the ground electrode 60 in the third embodiment will be described below with reference to FIGS. 17 and 18 are views showing a welding process of the noble metal tip 70 to the inner surface 63 of the ground electrode 60 in the third embodiment.

  As shown in FIG. 17, in the method for manufacturing the spark plug 200 according to the third embodiment, the spark plug 200 in which the ground electrode 60 is joined to the metal shell 5 is held by a welding jig (not shown), and the same as described above. The welding position of the noble metal tip 70 is positioned. At this time, the noble metal tip 70 in which the pedestal tip 75 similar to that of the second embodiment is bonded to the bottom surface 72 in advance is held by the welding electrode 90 similar to that of the first embodiment.

  As in the second embodiment, the welding electrode 90 causes the bottom surface 72 of the noble metal tip 70 to be pressed against the inner surface 63 of the ground electrode 60 while the pedestal tip 75 is interposed therebetween. (Resistance welding process). At this time, as shown in FIG. 18, as in the second embodiment, this resistance welding is performed so that the cross-sectional area of the flange 73 of the noble metal tip 70 is 1.2 times or more the area of the facing surface 71. Sometimes pressing force is applied. The base chip 75 is crushed so as to surround the flange 73 of the noble metal chip 70.

  Then, similarly to the first embodiment, a laser welding process of the noble metal tip 70 is performed. In addition, it is only necessary to make the cross-sectional area of the flange 73 of the noble metal tip 70 1.2 times or more the area of the facing surface 71 based on the above-described second embodiment by interposing the base tip 75. This is the same as the embodiment.

  As described above, in the spark plug manufacturing method according to the first embodiment, the noble metal tip 70 is temporarily joined to the inner surface 63 of the ground electrode 60 by resistance welding, and is joined by laser welding. At the time of resistance welding, the noble metal tip 70 was pressed against the inner surface 63 and swelled in the vicinity of the bottom surface 72 (bottom) so as to have a cross-sectional area of 1.3 times or more of the area of the facing surface 71 of the noble metal tip 70. A collar 73 is formed. When laser welding is performed on the flange portion 73 during laser welding, even if sink marks occur in a portion (melted portion 80) irradiated with the laser beams after welding, occurrence of thinning due to the sink marks. The cross-sectional area of the portion is made larger than 0.8 times the area of the opposing surface 71, and the bonding strength is not impaired.

  In the spark plug manufacturing method according to the second embodiment, the pedestal tip 75 having a thermal expansion coefficient between the thermal expansion coefficient of the noble metal tip 70 and the ground electrode 60 is temporarily attached to the ground electrode 60. Join. The pedestal tip 75 is interposed between the noble metal tip 70 and the ground electrode 60, and resistance welding of the noble metal tip 70 is performed. Thus, the flange 73 formed near the bottom surface 72 (bottom) of the noble metal tip 70 has the same effect as that of the first embodiment as long as the cross-sectional area is 1.2 times or more the area of the facing surface 71. Can be obtained. Thereby, the pressing force required at the time of resistance welding of the noble metal tip 70 or the time required for processing can be reduced.

  In the spark plug manufacturing method according to the third embodiment, the pedestal tip 75 is interposed between the noble metal tip 70 and the ground electrode 60 as in the second embodiment. It is bonded in advance to the bottom surface 72 of the noble metal tip 70. Then, similarly to the second embodiment, the flange 73 is formed at the time of resistance welding between the noble metal tip 70 and the ground electrode 60, and both are joined by laser welding. Since the base chip 75 is interposed, it is sufficient that the cross-sectional area of the flange 73 to be formed is 1.2 times or more the area of the facing surface 71.

  The present invention is not limited to the above embodiment, and various modifications can be made. For example, although the noble metal tip 70 is a cylinder, it may be a prism, a pyramid or a cone. In addition, the noble metal tip 70 is joined while the ground electrode 60 joined to the metal shell 5 is in an unbent state. What is the direction in which the inner surface 63 and the center electrode 2 are bent after the noble metal tip 70 is joined? The noble metal tip 70 may be joined by bending in the opposite direction.

  The present invention is not limited to a spark plug, and the manufacturing method of the present embodiment can be applied to various workpieces in which columnar tips are welded and joined to a plane.

1 is a partial cross-sectional view of a spark plug 100. FIG. It is a figure which shows the welding process of the noble metal tip 70 to the inner surface 63 of the ground electrode 60 in 1st Embodiment. It is a figure which shows the welding process of the noble metal tip 70 to the inner surface 63 of the ground electrode 60 in 1st Embodiment. It is a figure which shows the welding process of the noble metal tip 70 to the inner surface 63 of the ground electrode 60 in 1st Embodiment. It is a table | surface which shows the relationship between the laser irradiation angle and the presence or absence of generation | occurrence | production of a chip | tip taper in case the amount of swelling is 1.3 times. It is a table | surface which shows the relationship between the laser irradiation angle and the presence or absence of generation | occurrence | production of chip | tip taper in case the amount of swelling is 1.2 times. It is a table | surface which shows the relationship between the laser irradiation angle and the presence or absence of generation | occurrence | production of a chip | tip taper in case the amount of swelling is 1.1 times. It is a table | surface which shows the relationship between the laser irradiation angle in case there is no swelling, and the presence or absence of generation | occurrence | production of a chip taper. 3 is an enlarged cross-sectional view of a main part of a joint portion between a ground electrode 60 and a noble metal tip 70 of a spark plug 200. It is a figure which shows the welding process of the noble metal tip 70 to the inner surface 63 of the ground electrode 60 in 2nd Embodiment. It is a figure which shows the welding process of the noble metal tip 70 to the inner surface 63 of the ground electrode 60 in 2nd Embodiment. It is a figure which shows the welding process of the noble metal tip 70 to the inner surface 63 of the ground electrode 60 in 2nd Embodiment. It is a figure which shows the welding process of the noble metal tip 70 to the inner surface 63 of the ground electrode 60 in 2nd Embodiment. It is a table | surface which shows the relationship between the laser irradiation angle and the presence or absence of generation | occurrence | production of chip | tip taper in case the amount of swelling is 1.2 times. It is a table | surface which shows the relationship between the laser irradiation angle and the presence or absence of generation | occurrence | production of a chip | tip taper in case the amount of swelling is 1.1 times. It is a table | surface which shows the relationship between the laser irradiation angle in case there is no swelling, and the presence or absence of generation | occurrence | production of a chip taper. It is a figure which shows the welding process of the noble metal tip 70 to the inner surface 63 of the ground electrode 60 in 3rd Embodiment. It is a figure which shows the welding process of the noble metal tip 70 to the inner surface 63 of the ground electrode 60 in 3rd Embodiment. It is sectional drawing of the noble metal chip | tip which the chip | tip thinness generate | occur | produced by sink.

DESCRIPTION OF SYMBOLS 1 Insulator 2 Center electrode 5 Metal shell 12 Center through-hole 60 Ground electrode 61 Tip part 62 Base 63 Inner surface 70 Precious metal chip 71 Opposing surface 72 Bottom surface 73 Gutter part 75 Base chip 100,200 Spark plug

Claims (6)

A central electrode, an insulator having an axial hole in the axial direction, and holding the central electrode on a tip end side of the axial hole; a metal shell surrounding the insulator and holding the insulator; and one end portion Is connected to the metal shell, and a ground electrode to which the columnar noble metal tip facing the center electrode is bonded to the other end, and a spark plug manufacturing method comprising:
Protruding the noble metal tip by performing resistance welding between the inner surface of the other end which is the surface facing the center electrode of the other end of the ground electrode and the bottom surface opposite to the facing surface of the noble metal tip A resistance welding step of forming a flange that expands the outer diameter of the noble metal tip at the bottom of the noble metal tip, with a size of 0.3 mm to 1.5 mm,
Laser beam irradiation is performed over the entire circumference of the flange portion of the noble metal tip at an irradiation angle of 5 ° to 80 ° with respect to the inner surface of the other end portion of the ground electrode to melt the entire flange portion. A laser welding process in which the noble metal tip and the ground electrode are welded by being melted into the ground electrode,
With
In the resistance welding step, resistance welding of the noble metal tip is performed such that a cross-sectional area of the flange in the axial direction of the noble metal tip is 1.3 times or more of an area of the facing surface. Manufacturing method of spark plug. A central electrode, an insulator having an axial hole in the axial direction, and holding the central electrode on a tip end side of the axial hole; a metal shell surrounding the insulator and holding the insulator; and one end portion Is connected to the metal shell, and a ground electrode to which a columnar noble metal chip facing the center electrode is bonded at the other end with a pedestal chip in between, and a coefficient of thermal expansion of the pedestal chip Is a method of manufacturing a spark plug having a coefficient of thermal expansion between the noble metal tip and the ground electrode,
Resistance welding is performed between the pedestal tip joined to the inner surface of the other end, which is the surface facing the center electrode, of the other end of the ground electrode, and the bottom surface opposite to the facing surface of the noble metal tip. A resistance welding step of forming a flange portion in which the outer diameter of the noble metal tip is expanded at the bottom of the noble metal tip, with the protruding dimension of the noble metal tip being 0.3 mm or more and 1.5 mm or less,
The laser beam is irradiated over the entire circumference of the flange of the noble metal tip at an irradiation angle of 5 to 80 degrees with respect to the inner surface of the other end of the ground electrode, and the noble metal tip and the ground A laser welding process for welding with an electrode;
With
The noble metal tip is a cylindrical tip, and in the resistance welding step, the cross-sectional area of the flange in the axial direction of the noble metal tip is 1.2 times or more the area of the facing surface. A spark plug manufacturing method, wherein resistance welding of a noble metal tip is performed. A central electrode, an insulator having an axial hole in the axial direction, and holding the central electrode on a tip end side of the axial hole; a metal shell surrounding the insulator and holding the insulator; and one end portion Is connected to the metal shell, and a ground electrode to which a columnar noble metal chip facing the center electrode is bonded at the other end with a pedestal chip in between, and a coefficient of thermal expansion of the pedestal chip Is a method of manufacturing a spark plug having a coefficient of thermal expansion between the noble metal tip and the ground electrode,
Resistance welding between the inner surface of the other end, which is the surface facing the center electrode, of the other end of the ground electrode and the base chip joined to the bottom surface of the noble metal tip opposite to the facing surface And performing a resistance welding step of forming a flange portion in which the outer diameter of the noble metal tip is expanded at the bottom of the noble metal tip, with the protruding dimension of the noble metal tip being 0.3 mm or more and 1.5 mm or less,
The laser beam is irradiated over the entire circumference of the flange of the noble metal tip at an irradiation angle of 5 degrees to 80 degrees with respect to the inner surface of the other end of the ground electrode, and the noble metal tip and the ground A laser welding process for welding with an electrode;
With
The noble metal tip is a cylindrical tip, and in the resistance welding step, the cross-sectional area of the flange in the axial direction of the noble metal tip is 1.2 times or more the area of the facing surface. A spark plug manufacturing method, wherein resistance welding of a noble metal tip is performed.   The laser beam irradiation in the laser welding process is performed at an irradiation angle of 5 degrees to 60 degrees with respect to the inner surface of the other end of the ground electrode. The manufacturing method of the spark plug in any one of 1 thru | or 3.   The noble metal tip is made of an alloy containing iridium as a main component and at least one of rhodium, platinum, nickel, tungsten, palladium, ruthenium, and osmium added thereto. Spark plug manufacturing method.   6. The noble metal tip is made of an alloy containing platinum as a main component and at least one of rhodium, iridium, nickel, tungsten, palladium, ruthenium, and osmium added thereto. Spark plug manufacturing method.

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