JP6510971B2 - Method of manufacturing joined body, and method of manufacturing spark plug - Google Patents

Description

  In the present invention, two members, for example, two small columnar members are butt-to-face with each other at their end faces, the outer peripheral edge of the butting surface is irradiated with laser light, and the butting surface is surrounded including the outer peripheral edge Method for producing a joined body by laser welding along a direction, and a method for producing a joined body, wherein the joined body is a tip for a spark plug electrode (composite tip), and for an electrode produced by this production method The present invention relates to a method of manufacturing a spark plug using a tip.

  Conventionally, a joined body is a tip of a spark plug electrode as described above, two columnar members are butted at the end faces thereof, and laser light is applied to the outer peripheral edge of the butted surfaces (contacting mutual surfaces) The following is known as a method of irradiating, and laser welding along the circumferential direction the butting surfaces including the outer peripheral edge (Patent Document 1). One member (for example, a Ni alloy member) is chucked to a chuck device on a rotatably provided base so as to be coaxial with the rotation center, and the other member (for example, for this member) Noble metals such as Pt, Pt, etc. are butted, coaxially positioned and held. Then, while rotating the both members (workpieces) around the axis together with the chuck device, the laser beam irradiation head of one (one) laser welding device directs the laser toward the outer peripheral edge of the butting surface. The light (hereinafter also referred to as a laser) is irradiated, for example, by pulse oscillation in correspondence with or in synchronization with the rotation speed (set rotation angle). By this irradiation, the butted surface is laser welded along the outer periphery. The laser welding method by such a rotation method not only requires a rotating means, but, for example, in the case of welding by pulse oscillation at an interval of 45 degrees during one rotation (360 degrees rotation), eight times of irradiation Because of the (welding process), the welding process becomes longer accordingly. On the other hand, when two laser welding apparatuses are provided in the opposite arrangement, the process can be halved, but in addition to requiring the welding process for the number of times of irradiation, there are the following problems.

  The reason is that the laser welding is not limited to pulse oscillation or continuous oscillation, but sequentially and circumferentially along the circumferential direction, so that welding distortion and the like are caused due to the end of the time or the like. Bonding bodies such as cylinders for obtaining spark plug electrode tips are small pieces whose diameter (butting surface) is about 1 mm or less, and their dimensional accuracy is extremely high in view of their applications And high bonding strength are required. For this reason, in such a joined body, as uniform as possible including the central portion of the butting surface (herein referred to as the center or the center or a portion near these portions) located behind the outer peripheral edge of the butt surface It is necessary to be welded (welded) on the entire surface with high accuracy and as much as possible. Thus, if welding is desired over the entire surface, although it is not 100%, sufficient melting (melting from the outer peripheral edge of the butting surface to the deep central portion of the surface from the start of laser beam irradiation) Heating is required, ie, its irradiation at the laser intensity (power). However, even if the laser is repeatedly irradiated with the same output, the melting depth (range) becomes gradually deeper at the start of irradiation and in the middle of the irradiation, and at the end, with the increase of the stored heat energy continued to be applied in the welding process. Become. That is, the melting (melting) depth from the outer peripheral edge toward the central portion increases or changes. For this reason, if laser irradiation is performed in such a setting that sufficient melting (melting) can be obtained from the start of laser beam irradiation, then excessive melting (over melting) occurs due to overheating, and welding spatter occurs (the molten metal Problems such as scattering, adhesion), and the resulting buildup of welding may occur.

  On the other hand, one laser beam is branched into a large number of laser beams toward a virtual plane to be irradiated using a diffractive optical element (DOE), and each laser beam branched through a condenser lens is a mirror There is also known a welding method in which multiple parts are simultaneously welded by being reflected by a reflector or the like and simultaneously irradiated toward the multiple parts (Patent Document 2). By this method, the laser light is split into a plurality of diffused shapes so as to be arranged in an annular (for example, annular) shape at intervals, and reflected by the reflector, along the circumferential direction of the outer peripheral edge of the butting surface. If irradiation and welding are performed at various places on the outer peripheral edge, no rotating means is required, and laser irradiation can be performed only once in the process. And since it becomes simultaneous irradiation, since the welding distortion based on the difference of the irradiation time before and after and the variation in the heat input in the circumferential direction can also be eliminated, the fusion depth in each position of the circumferential direction can also be fixed.

JP, 2008-277272, A JP 2005-219070 A

  However, even in the simultaneous welding of a large number of places using such a diffractive optical element (DOE), it melts up to the central part (center or center of these butting parts), that is, in all areas In the case of welding, it is necessary to set the strength of the laser so that the thermal energy of each branched laser can be melted at the central portion of the butting surface. On the other hand, in the case of such welding, the heat input ranges of many lasers overlap at the same time in the center of the butting surface, and as a result, there is no imbalance in heat input in the circumferential direction. Rather, it is likely to cause local melting excess in the central area. As a result, the problem of the occurrence of spatter (scattering and adhesion of molten metal) and the occurrence of thinning of the weld may be greater than the method of sequentially welding in the circumferential direction. However, if the power of each of the branched lasers is reduced as a whole, melting at the center of the butting surface can not be obtained, and the desired bonding strength can not be obtained.

  The present invention has been made in view of such problems, and generation of spatter due to excessive melting (scattering) in a welding method by simultaneous welding of a large number of portions by a large number of laser beams branched using a diffractive optical element (DOE) It is an object of the present invention to provide a manufacturing method and the like which can reduce the occurrence of welding build-up (elation) due to it and yet obtain a joined body of high joint strength.

According to the present invention, the two members are butted, the outer peripheral edge of the butted surface is irradiated with laser light, and the butted surfaces including the outer peripheral edge are laser welded along the circumferential direction. A method of producing a joined body by
One laser beam is split into multiple laser beams using a diffractive optical element, and multiple split laser beams are respectively reflected by multiple reflectors provided in an annular arrangement surrounding the outer peripheral edge, By irradiating each of the reflected laser beams toward a number of locations along the circumferential direction of the outer peripheral edge, simultaneously including the outer peripheral edge, the multiple points along the circumferential direction of the butting surface In manufacturing a joined body by welding,
Laser welding is performed such that the intensities of the branched laser beams are at least two different values, and the depths of the laser beams melted toward the central portion of the buttizing surface from the outer peripheral edge are not the same. It is characterized by

The present invention according to claim 2 is that, in the laser light irradiated toward the outer peripheral edge, the melting range generated on the butting surface by the adjacent laser light at the outer peripheral edge is at least the outer peripheral edge The method according to claim 1, wherein each of the laser beams is irradiated so as not to overlap.
According to a third aspect of the present invention, in the laser light irradiated toward the outer peripheral edge, a melting range generated on the butting surface by a plurality of laser beams not adjacent to each other at the outer peripheral edge is the butt. The method according to any one of claims 1 and 2, wherein the intensities of the respective laser beams are differentiated so as to overlap at the central portion of the mating surfaces.

The present invention according to claim 4 is that each of the butting surfaces has a line symmetrical shape, and the laser light irradiated toward the outer peripheral edge has a symmetrical arrangement corresponding to the line symmetrical shape of the butting surfaces. The method according to any one of claims 1 to 3, wherein the irradiation is performed in a symmetrical intensity distribution from the direction.
The present invention according to claim 5 is characterized in that the joined body is a tip of a spark plug electrode, and one of the two members is a noble metal tip. It is a manufacturing method of the zygote of a statement.
According to a sixth aspect of the present invention, an insulator having an axial hole in the axial direction, a center electrode disposed so as to project from the tip in the axial hole, and a metal shell surrounding the periphery of the insulator. And a ground side electrode provided at a base end thereof to a tip end of the metal shell so that the tip end faces the tip end of the center electrode so as to hold a spark discharge gap therebetween. Manufacturing method of
In a method of manufacturing a spark plug, an electrode tip is fixed to at least one of the tip of the center electrode and the tip of the ground side electrode,
The electrode tip manufactured using the method of manufacturing a joined body according to claim 5 is used as the electrode tip, and the electrode tip is fixed so that the noble metal tip is positioned on the spark discharge gap side. It is a manufacturing method of a spark plug characterized by things.

  In the present invention, the intensities of the respective laser beams are made to differ by at least two types of strength so that the depths of melting from the outer peripheral edge toward the central portion of the butting surface are not the same. Thus, according to the present invention, welding (welding in a desired state) is desired over the entire area of the butting surfaces so as not to cause excessive melting due to local excessive heat input according to the shape, size, etc. of the butting surfaces. ) Can be obtained. For this reason, even if it is desired to weld the entire area of the butt surfaces by simultaneous welding at a large number of points, spatter scattering that has occurred due to excessive melting or the like, or the thickness of the welded portion due to it (recess Without welding, a high weld strength welding can be obtained with a sufficient weld area. In addition, since the intensity (intensity) of each laser beam to be branched is obtained depending on the shape and structure of the diffractive optical element (DOE) together with the branched form (irradiation direction), both welding objects are made. A diffractive optical element formed so as to obtain a desired intensity distribution for the branched laser beam may be used according to the shape of the butting surfaces of the members.

  In the case where the butting surfaces are melted 100% and welded, not only is it likely to cause excessive melting, but also the accuracy of the height, inclination and the like of the joined body may be affected due to the melting. The melting ranges generated on the butting surfaces by the adjacent laser beams at the outer peripheral edge may overlap, but as described in claim 2, at least at the outer peripheral edge, they do not overlap. Good. That is, the melting range may overlap at the outer peripheral edge and be continuous in the circumferential direction, but by doing so, excessive melting tends to occur, as in the invention according to claim 2, Excessive melting is easily avoided. Moreover, even if there is overlap of the melting range at the central portion, the influence is less likely to extend to the outer peripheral surface, as there is no overlap of the melting ranges by adjacent laser beams at the outer peripheral edge, and therefore generation of spatter etc. Can also be reduced. When it is desired to increase the bonding strength, excessive melting is suppressed and bonding at the central portion of the butting surfaces is also secured by the invention described in claim 3, so that the bonding strength is improved. Be enhanced.

  The shape of the butting surface is arbitrary, but when it is axisymmetric as in the case of a circular or regular polygon, it is irradiated toward the outer peripheral edge as in the fourth aspect. It is preferable that the laser beam be irradiated with symmetrical intensity distribution from each direction of symmetrical arrangement corresponding to the line symmetrical shape of the butting surface. This is because the balance of melting at the butt face can be enhanced. In the present invention, the butting surface of the member (base material) to be welded is not limited to a circle or a regular polygon. On the other hand, the form (arrangement) of the split of the laser beam obtained by the structure of the diffractive optical element (DOE) is one circumference which is concentric with that when the shape "contour" of the outer peripheral edge of the butting surface is circular. Although it is preferable to set equal angular intervals above, the present invention is not limited to this, and any outer peripheral shape may be arbitrary according to the welding conditions. Further, the number of branches may be set according to the size of the butting surface, the shape of the outer periphery thereof, and the like. Then, the intensity (intensity distribution) of each of the branched laser beams may be set so as to obtain melting at a desired depth at the irradiation location, and diffraction is made so as to obtain the desired intensity. An optical element (DOE) may be used.

  The reflector may be branched as long as the laser beam irradiated through the condenser lens can be directed toward the welding point for irradiation by desired reflection, and the reflector is not limited to a flat mirror, and a curved mirror may be used. May be Then, the reflection may be performed before or after the focal point so that the focal point of the irradiation spot from which the desired heat input is obtained can be obtained at the outer peripheral edge of the butting surface. Furthermore, in the simultaneous welding process in the present invention, a tack welding process may be included prior to it, if necessary, as in the case of ordinary welding. When each member is small and light, as in the case of a spark plug electrode chip (composite chip), the joint is temporarily attached in this way or an appropriate surface pressure is applied to the butt joint surface. It should be applied, and in that case, it may be pressed by an appropriate means so as not to interfere with the laser light. As in the manufacturing method of the invention according to the fifth aspect, when the joined body is a spark plug electrode tip, one of the two members may be a noble metal tip. Then, according to the present invention as set forth in claim 6, in the method of manufacturing a spark plug, an electrode tip is fixed to at least one of the tip of the center electrode and the tip of the ground side electrode. The electrode chip manufactured by the method for manufacturing a joined body according to claim 5 is used as the chip, and the electrode chip is fixed so that the noble metal chip is positioned on the spark discharge gap side. Thus, a spark plug excellent in ignition performance and durability can be obtained without causing an increase in cost.

The bonded body to be manufactured (welded) in the embodiment of the manufacturing method of the present invention will be described. A is a side view (front view) of each member (base material) before welding, B is both before welding The side view (front view) of the state which faced the member, C is a side view of the joined body after welding. BRIEF DESCRIPTION OF THE DRAWINGS The welding of the joined body which consists of a laser irradiation apparatus etc. used in this example, the typical perspective view which shows notionally the whole manufacturing apparatus. The schematic diagram for description which looked at the welding of FIG. 2, and the whole manufacturing apparatus from the side (front) side. The figure seen from the upper side explaining the state which the branched laser beam irradiates the outer periphery of a butted surface in FIG.2 and FIG.3. The expansion schematic diagram explaining the fusion | melting range of the butt surface in the joined body after welding. The longitudinal half section explaining the spark plug, and the principal part enlarged view. The expansion schematic diagram explaining another example of the fusion | melting range of the butt surface in the joined body after welding. The expansion schematic diagram explaining another example of the fusion | melting range of the butt surface in the joined body after welding.

  An embodiment embodying the present invention will be described in detail based on FIGS. 1 to 5. However, a joined body to be manufactured (welded) in this example is a composite chip (tip for an electrode) fixed by welding or the like to each end of the center electrode or the ground side electrode of the spark plug. This is fixed to each end of the spark discharge gap (spark gap) side of each electrode in order to enhance the ignitability without increasing the cost, as shown in the left diagram (A) of FIG. Two members (hereinafter both members 11, 21 or members) of a nickel member 11 forming a cylindrical body (or a disc) and a noble metal tip (for example, a cylindrical body or a disc) 21 such as platinum or iridium 11 and member 21). In this example, as shown in the center (B) of FIG. 1, the both members 11 and 21 are butted to each other at each end face (plane) 13 and 23 and shown in the right figure (C) of FIG. Thus, the butted surfaces (between each other) are melted and welded including the outer peripheral edge 17 of the both end surfaces (hereinafter also referred to as butted surfaces) 13 and 23 to obtain a joined body 30 as an electrode tip If and when. The welding is performed by the welding and manufacturing apparatus 100 described below toward the outer periphery 17 of the butt surface from the outside along a number of straight lines extending radially from the center of the butt surface forming a circle. By irradiating and welding a large number of laser beams branched by the diffraction optical element (DOE).

  FIG. 2 is a schematic perspective view conceptually showing the entire welding and manufacturing apparatus 100 of a joined body 30 composed of a laser irradiation apparatus and the like used in this embodiment. The apparatus 100 is provided with a laser generation apparatus (not shown) for irradiating the laser light downward from above in the figure, and as shown in the figure, the laser light La generated by this is irradiated with the laser light The light is emitted downward from the head (also referred to as an optical head or simply as a head) 110. And, under the head 100, a DOE support plate 130 provided with a diffractive optical element (for example, made of quartz) 120 on the upper surface is disposed, and under that, a condensing lens 140 and this condensing lens A base 150 for positioning, placing and holding the two members 11 and 21 to be welded is disposed at a predetermined distance under the lower portion 140.

  In this example, the diffraction optical elements 120 are arranged at equal angular intervals so that the laser light La incident from the head 100 is directed along a virtual plane perpendicular to the extension line in the irradiation direction and along the generatrix of the cone (this example In the above, it is configured to be branched in a diffusion manner at 8). Then, each branched laser beam (solid line in the figure) passes through the condensing lens 140 provided under the diffraction optical element 120, and each of the laser beams L1 and L2 passed passes under the both. End surfaces to be welded (butting surfaces) of both members 11 and 21 which are reflected by a large number of reflectors (for example, mirrors) 160 arranged at various places surrounding the members 11 and 21 and positioned and held on the base 150 It is set to be irradiated toward a predetermined position (equal angle interval position) in the circumferential direction in the outer peripheral edge 17 of. For this reason, in the virtual plane perpendicular to the extension line of the irradiation direction of the laser beam La incident on the diffraction optical element 120, a large number (eight in this example) of mirrors 160 is a virtual circle drawn around the extension line. The laser beams L1 and L2 which are disposed at positions where 8 (Kc) is divided at equal angular intervals, are branched, and are incident on the respective mirrors 160 via the condenser lens 140 are reflected, and welding at both members 11 and 21 is performed. In order to irradiate the predetermined position in the circumferential direction of the outer peripheral edge 17 of the butt face to be formed, the inclination and the like are set and arranged (see FIG. 4). In the present embodiment, the intensity distribution (output distribution) of the branched laser beams L1 and L2 is set to be strong and weak, and two adjacent ones alternately become strong laser beams L1 and weak laser beams L2. It is done. The optical axes of the laser beam L1 and the laser beam L2 are illustrated by solid lines.

  In this example, the branched laser beams L1 and L2 are incident on the mirrors 160 before the focal point, and the focal point (irradiation spot) is obtained at the outer peripheral edge 17 to be irradiated. . The irradiation angles of the laser beams L1 and L2 to the outer peripheral edge 17 may be substantially parallel to the butting surfaces 13 and 23, but in this example, an appropriate inclination angle is provided (see FIG. 3). Then, in the present example, as described above, of the eight branched laser beams, four lasers orthogonal to each other at 90 degrees (in the X-axis and Y-axis directions) in plan view (see FIGS. 4 and 5) The intensity of the light L1 is high, and the intensity of the laser light L2 between the high-intensity laser light L1 is low (low), so that the two types of laser light L1 and L2 become strong and weak (see FIG. 4th grade). In FIG. 4 and FIG. 5, the thick arrow line is the high intensity laser beam L1, and the thin arrow line is the low intensity laser beam L2. As a result, the laser beam L2 having a low depth and a deep depth where it is melted from the outer peripheral edge 17 to be laser welded by the irradiation of the high-intensity laser beam L1 toward the centers (central portions) of the butting surfaces 13 and 23 is The depth to be melted toward the center of the butting surfaces 13 and 23 from the outer peripheral edge 17 to be laser-welded by the irradiation of (1) is made shallow and made to be the same.

  In this example, as shown in FIG. 5, the depths melted by the four high-intensity laser beams L1 include the centers of the butting surfaces 13 and 23. The range is set to be superimposed as indicated by double hatching. And, as shown by single hatching, the depth to be melted by the other four low-intensity laser beams L2 is set so that it does not include the center and that the melting range does not overlap with the deeper one. There is. That is, in this example, the melting ranges generated on the butting surfaces 13 and 23 by the four high-intensity laser beams L1 not adjacent to each other on the outer peripheral edge 17 overlap at the central portion of the butting surfaces 13 and 23 It is set, and welding at the central part is made to be surely performed. Note that the melting range of the butt surfaces 13 and 23 by the laser beams L1 and L2 becomes smaller as the heat energy is less likely to reach as the distance from the outer peripheral edge 17 increases, so that the width becomes narrower. Among them, the melting range generated on the butting surfaces 13 and 23 by the adjacent laser beams L1 and L2 at the outer peripheral edge 17 is set so as not to overlap at the outer peripheral edge 17. Note that these settings may be adjusted and set based on the material etc. of the members to be welded so that the desired welding can be obtained appropriately in the setup process, such as performing test welding.

  Next, welding and manufacturing processes will be described. In this example, both members 11 and 21 are concentrically placed on the upper surface of the predetermined position of the base 150 in the above-described welding and manufacturing apparatus 100 in a state where they are vertically butted in a row, as shown in FIG. , See Figure 3). The holding of the positioning can be performed by holding the concentric state of both members 11 and 21 and pushing the upward end face of the upper member 21 downward with an appropriate fixing force so as not to move on the base 150 Any appropriate means may be used. Specifically, as shown by a two-dot chain line in FIG. 2 to FIG. 4 from between the laser beams so as not to interfere with each luminous flux of the branched eight laser beams L1 and L2. An appropriate fixing force F may be used to press by P (for example, a presser bar (bar) made of ceramic or metal having appropriate rigidity). Although not shown, a chuck may be provided on the base 150, and the lower member 11 may be fixed so as not to affect the irradiation of the laser beam.

  After both members 11 and 21 are positioned and held on the base 150 by the above-described welding and manufacturing apparatus 100, the laser light La output from the laser oscillation device is irradiated with a predetermined output through the optical head 100. Do. As a result, when the laser beams L1 and L2 are branched and reflected by the mirror 160, the butt surfaces 13, 23 including the outer peripheral edge 17 of the butt surfaces 13, 23 of both members 11, 21 are 8 Welded simultaneously from the direction. That is, the laser light La of a predetermined output irradiated through the optical head 100 is incident on the diffraction optical element 120 therebelow, branched into eight equal parts in the annular arrangement as described above, and arranged below this The light is incident on each mirror 160 provided in an arrangement surrounding the two members 11 and 21 to be welded through the focused condenser lens 140, and at the same time, is reflected to be a bonded body 30, preferably of both members 11 and 21. The outer peripheral edge 17 of the butting surfaces 13 and 23 is irradiated at equal angular intervals. By this irradiation, the heat is received toward the center of the butting surfaces 13 and 23 including the outer peripheral edge 17, and both members 11 and 21 are melted. Therefore, when the irradiation is stopped, the butt surface including the outer peripheral edge 17 13 and 23 can be welded to obtain a joined body 30. The bonding surface (butting surfaces 13 and 23) of the bonded body 30 thus obtained is in the melting range as schematically shown in FIG.

  As described above, in the present invention, since the welding is performed simultaneously at a large number of places, the laser light oscillated from one optical head as in the prior art sequentially circulates in the circumferential direction and gives a time difference. There is no problem of occurrence of welding distortion as in the case of welding. Further, the laser beams branched and irradiated in the circumferential direction are the laser beams L1 and L2 having different magnitudes (intensity distributions) as described above in the intensity, and the laser beams L1 and L2 The melting depth towards the central part is assumed to be different. Therefore, unlike in the case of securing melting at the central portion with each laser without making a difference in the strength and welding, it is possible to prevent or suppress generation of excessive heat input and excessive melting at the central portion. . On the other hand, the melting range generated on the butting surfaces 13 and 23 by the four high-intensity laser beams L1 not adjacent to each other on the outer peripheral edge 17 is made to overlap at the central portion, including the central portion Bonding in the desired state is obtained in the entire area of the butting surfaces 13 and 23. In particular, in the present embodiment, the melting range generated on the butt surfaces 13 and 23 by the adjacent laser beams L1 and L2 at the outer peripheral edge 17 is set so as not to overlap at the outer peripheral edge 17. Even if there is an overlap of the melting range in the part, the effect is difficult to extend to the outer peripheral edge 17 or the outer peripheral surface of the joined body 30, and therefore spatter scattering and therefore the welding portion thickened (recessed welding surface A desired welded joint 30 is obtained without any deterioration and with less decrease in joint strength. Furthermore, in the present example, the laser light is irradiated on the butt surfaces 13 and 23 so as to be symmetrical with respect to the X axis and Y axis and also in terms of intensity. The balance of bonding throughout is also maintained. As a result, a highly accurate bonded body 30 without inclination can be obtained.

  And, in this example, the joined body 30 which is the object of manufacture is the tip for the electrode of the spark plug. Therefore, since the bonded body (tip for electrode) 30 manufactured by such a manufacturing method has high accuracy and bonding strength, the center electrode 221 and the ground side electrode 231 in the spark plug 201 as shown in FIG. The noble metal tip 21 is fixed to each spark discharge gap (spark gap) side by welding or the like so that the noble metal tip 21 is positioned on the spark discharge gap (spark gap) side. In such a case, it is expected to improve not only the ignition performance but also the durability etc. without increasing the cost. That is, the spark plug 201 of FIG. 6 includes an insulator 251 having an axial hole 241 in the direction of the axis G, a center electrode 221 disposed so as to project toward the tip end in the axial hole 241, and an insulator 251. A cylindrical metal shell 261 surrounding the periphery and a ground side electrode 231 provided so that a base end which is one end is joined to a tip of the metal shell 261 and a tip which is the other end faces the tip of the center electrode 221 And the structure itself is conventionally known, but using the bonded body 30 (tip for electrode) manufactured by the manufacturing method of this example, the noble metal tip 21 is on the spark discharge gap side. As it is positioned, it is fixed to each end (tip) of the center electrode 221 and the ground side electrode 231 on the spark discharge gap side via one end face in the joined body 30, so the ignition performance and durability are also high. It can be made with the spark plug. The noble metal tip 21 of such a bonded body (tip for electrode) 30 is positioned on the spark discharge gap side not on both the tip of the center electrode 221 and the tip of the ground side electrode 231 but only on one of them. It may be fixed in this way.

  In this example, one laser beam La emitted from the laser beam irradiation head 100 is branched at equal angular intervals into eight on one circumference by a plan view, the diffractive optical element 120, and is branched. As described above, among the laser beams, the laser beams L1 from the four orthogonal directions have two types of intensities that are relatively greater in intensity than the other laser beams L2. The number of branches, the arrangement, the intensity distribution of light, the type of strength, etc. depend on the shape of the butting surfaces of the two members to be welded and the material (melting point) of the members to be welded, etc. The diffraction optical element designed and manufactured may be used to obtain the desired welding specifications. The difference in the intensity of each laser beam is excessive melting which causes the occurrence of spattering or the like from the outer peripheral edge toward the central portion of the butting surface depending on the shape of the butting surface, the material (melting point) of the welding target member, etc. Instead, appropriate differences may be set so as to obtain desired melting depths so as to obtain high bonding strength in the entire butting surface.

  That is, in the above-mentioned example, the melting range by 4 laser beams L1 which are not adjacent to each other among 8 branched laser beams is overlapped at the central part of the butting surfaces 13 and 23, and the melting range by other laser beams L2 In the case where the intensity of each of the laser beams L1 and L2 has two differences so as not to overlap, but the butting surfaces 13 and 23 are large and melting at the center is difficult to obtain In order to increase the number of laser beams to be branched, the number of laser beams may be further increased so that the melting range is largely overlapped at the central portions of the butting surfaces 13 and 23. Conversely, if the butting surfaces 13 and 23 are small and melting at the center (central portion) is easy to obtain, it is assumed that the number of laser beam branches is eight as shown in FIG. Also, the melting range of the two opposing laser beams L1 may be merely superimposed at the central portion of the butting surfaces 13 and 23. Then, the intensities of the laser beams L2 and L3 having relatively low intensities may be changed so that the melting depths thereof become three. That is, the intensity of the laser light may be three or more.

  In addition, since the member to be welded is a prismatic body (square bar), as shown in FIG. 8, even if the shape of the butting surfaces 13 and 23 is, for example, a square, it has the circular shape shown in FIG. Similarly, in the central portion of the butting surfaces 13 and 23, the melting range by the four laser beams L1 of the branched eight laser beams is overlapped, and the melting ranges by the other laser beams L2 are not overlapped, The present invention can be embodied by giving an appropriate number of intensity differences regardless of the shapes of the butting surfaces, such as making the intensities of the laser beams L1 and L2 different. Further, the patterns of a large number of laser beams branched by the diffractive optical element may be set according to the shape of the butting surfaces of the members to be welded and the like. If the surface is a circle or a regular polygon, it may be arranged at the corresponding annular line, but the arrangement is not limited thereto.

  In the above example, both members to be welded have been described as cylindrical or prismatic ones, but the present invention is not limited to this, and it is possible to simultaneously weld a large number of locations on the outer peripheral edge of the butting surface. The present invention is applicable to the joint body to be bonded, and is not limited to small pieces such as spark plug electrode tips. The present invention can be applied even if the end faces of both members forming the butting surfaces have different diameters from each other. However, in such a case, if necessary, the laser light is branched without problems to the outer peripheral edge of the butting surface, if necessary, with respect to the butting surface of the larger member among the butting surfaces. The irradiation may be performed as appropriate so as to have an incident angle. The present invention can also be applied to, for example, overlapping two rectangular (or rectangular) plates and welding the outer peripheral edge of the overlapping surface along the outer periphery. In the present invention, the butt surface means a contact surface when the two members are put together for welding. And in the case of joining of such a board, even if it is not a board of the same size, it is applicable.

  If the butting surface is rectangular, the patterns of a large number of diverging laser beams may be set to be disposed on a rectangular annular line surrounding the same, but the invention is not limited thereto. Then, depending on the aspect ratio of the butted surface (rectangle), the direction and intensity of the laser beam to be branched and irradiated may be appropriately set so that the entire area of the butted surface can be efficiently welded. Good. Furthermore, regardless of the shape of the butt surfaces, it is not necessary to overlap at the central portion, for example, in the case where welding can be performed near the entire area of the butt surfaces, the melting ranges may not be overlapped.

  In the present invention, as described above, the diffraction optical element should be given as the number of branches of the laser light, the irradiation direction (branch pattern, arrangement) of the branched laser light, and the laser light intensity (output). It should be designed based on the required specifications such as Also, the output of the laser beam incident on the diffractive optical element, that is, the intensity of the laser beam generated by the laser beam oscillator and emitted from the head is based on the total intensity of the branched laser beam, It may be set to one that can be obtained. And, if necessary, this output can be set while trying so that the desired melting can be obtained based on the melting point of the member (metal) to be welded, the size of the butting surface, the diameter thereof, etc. Just do it. When the branched laser beam is reflected by the reflector after the focusing point, a concave mirror with an appropriate curvature may be used to condense light at the outer peripheral edge of the butted surface. Furthermore, the anti-diagonal body may be an optical element that can reflect each laser beam to be irradiated, in addition to the mirror.

11, 21 members 12, 23 butting surfaces (end faces of members)
17 Bonded outer peripheral edge 30 Bonding body (tip for spark plug electrode)
120 diffraction optics 160 mirror (reflector)
La One laser beam L1, L2 A large number of laser beams 201 branched by the diffraction optical element Spark plug 221 Center electrode 231 Ground side electrode

Claims (6)

A method of manufacturing a joined body by butting two members together, irradiating the outer peripheral edge of the butted surface with laser light, and laser welding the butted surfaces including the outer peripheral edge along the circumferential direction. ,
One laser beam is split into multiple laser beams using a diffractive optical element, and multiple split laser beams are respectively reflected by multiple reflectors provided in an annular arrangement surrounding the outer peripheral edge, By irradiating each of the reflected laser beams toward a number of locations along the circumferential direction of the outer peripheral edge, simultaneously including the outer peripheral edge, the multiple points along the circumferential direction of the butting surface In manufacturing a joined body by welding,
Laser welding is performed such that the intensities of the branched laser beams are at least two different values, and the depths of the laser beams melted toward the central portion of the buttizing surface from the outer peripheral edge are not the same. A method for producing a joined body characterized by:   Among the laser beams irradiated toward the outer peripheral edge, each laser beam is irradiated such that the melting range generated on the butting surface by the adjacent laser light at the outer peripheral edge does not overlap at least the outer peripheral edge A method of producing a joined body according to claim 1, characterized in that:   In the laser beam irradiated toward the outer peripheral edge, a melting range generated on the butting surface by a plurality of laser beams not adjacent to each other at the outer peripheral edge is overlapped at the central portion of the butt interface. The method of manufacturing a joined body according to any one of claims 1 and 2, wherein the intensities of the respective laser beams are differentiated.   The butting surfaces have a line-symmetrical shape, and laser light emitted toward the outer peripheral edge is irradiated with symmetrical intensity distribution from each direction of the symmetrical arrangement corresponding to the line-symmetrical shape of the butting surfaces. The method for producing a joined body according to any one of claims 1 to 3, characterized in that   The method for manufacturing a joined body according to any one of claims 1 to 4, wherein the joined body is a tip of an electrode of a spark plug, and one of the two members is a noble metal tip. . An insulator having an axial hole in the axial direction, a center electrode arranged to project to the tip in the axial hole, a metal shell surrounding the periphery of the insulator, and a base end at the front end of the metal shell A method of manufacturing a spark plug, comprising: a grounded side electrode joined so as to face the tip of the center electrode so as to hold a spark discharge gap between the tip and the tip of the center electrode,
In a method of manufacturing a spark plug, an electrode tip is fixed to at least one of the tip of the center electrode and the tip of the ground side electrode,
The electrode tip manufactured using the method of manufacturing a joined body according to claim 5 is used as the electrode tip, and the electrode tip is fixed so that the noble metal tip is positioned on the spark discharge gap side. A method of manufacturing a spark plug, characterized in that

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