WO2016133079A1

WO2016133079A1 - Method for producing joined structure, and joined structure

Info

Publication number: WO2016133079A1
Application number: PCT/JP2016/054420
Authority: WO
Inventors: 和義西川
Original assignee: オムロン株式会社
Priority date: 2015-02-19
Filing date: 2016-02-16
Publication date: 2016-08-25
Also published as: JP6398778B2; JP2016150375A

Abstract

Provided are: a method for producing a joined structure obtained by joining a first member, and a second member comprising resin; and the joined structure obtained by joining the first member and the second member. The method for producing the joined structure includes: a boring step in which a first-member surface section forming the surface to be joined to the second member is irradiated with a laser to form a plurality of bore holes, such that the surface area of first bore holes per unit volume in a region corresponding to a stress concentration section is greater than the surface area of second bore holes per unit volume in a region excluding the aforementioned region; and a joining step in which the first member and the second member are joined by filling the plurality of bore holes with the second member. The joined structure is obtained by: irradiating, with a laser, the first-member surface section to form the plurality of bore holes, such that the surface area of the bore holes per unit volume in the stress concentration section is greater than the surface area of the bore holes per unit volume in a section excluding the stress concentration section; and filling the plurality of bore holes with the second member.

Description

Manufacturing method of bonded structure and bonded structure

The present invention relates to a method for manufacturing a bonded structure and a bonded structure.

Conventionally, a joint structure in which members made of different materials are joined is known. In such a bonded structure, since different members that are originally difficult to bond are bonded to each other, it is one of the problems to increase the bonding strength.

For example, in Patent Document 1, a recess having an average diameter of 0.01 to 50 μm or a groove having an average width of 0.01 to 50 μm is formed on a joint surface of a metal molded body with a resin molded body. In the first step, the average diameter of the openings is 1.0 to 1000 μm and the maximum depth is 10 to 1000 μm or the average width is 1.0 to 1000 μm and the maximum with respect to the joint surface where the recess or groove is formed There is disclosed a method for producing a composite molded body having a second step of forming a groove having a depth of 10 to 1000 μm and a third step of obtaining a composite molded body by insert molding. According to the thing of this patent document 1, it is supposed that joint strength can be raised.

Here, in the joint structure, the concave portion is formed on the joint surface of one member with the other member because the other member (for example, resin) melted when the two members are joined is filled in the concave portion. Often this is to obtain a so-called anchor effect.

And, although the reason why the bonding strength is improved is not described in Patent Document 1, from FIG. 4 to FIG. 8 of Patent Document 1, recesses and the like are formed in the same shape pattern on the entire bonding surface of the metal member, It is considered that the bonding strength is increased by filling the recesses with resin.

Japanese Laid-Open Patent Publication No. 2014-051040

In the above-mentioned Patent Document 1, since the concave portions and the like are formed in the same shape pattern on the entire bonding surface of the metal member, it is considered that the bonding strength of the entire bonding surface is improved uniformly.

However, in a bonded structure in which different types of members are bonded together, stress is likely to occur due to the difference in linear expansion coefficient between the two members. As in Patent Document 1, the bonding strength of the entire bonding surface is simply uniform. However, if the thermal shock is repeatedly applied to the bonded structure, there is a risk that stress breakage may occur at the stress concentration portion on the bonded surface.

Here, in order to suppress the stress fracture at the stress concentration part, the joint creepage surface is extended (the joint area is increased), the processing depth of the concave portion is increased over the entire joint surface, the concave portion, etc. It is possible to increase the number of However, extending the joint creepage imposes restrictions on product design, and if the processing depth of the recesses is increased or the number of recesses is increased over the entire connection surface, The problem arises that time is increased and productivity is lowered.

The present invention has been made in view of such points, and the object of the present invention is to provide a bonding surface in a method for manufacturing a bonded structure and a bonded structure, while ensuring design freedom and suppressing a decrease in productivity. It is to provide a technique for suppressing stress fracture at the time.

In order to achieve the above object, in the method for manufacturing a joint structure and the joint structure according to the present invention, the contact area between the perforated part and the filling resin at a place where stress fracture is likely to occur is The contact area with the resin is made larger.

Specifically, the present invention is a method for manufacturing a joined structure in which a first member and a second member made of resin are joined, and the first member constituting a joint surface with the second member The surface area of the perforated part per unit volume of the surface part corresponding to the stress concentration part in the surface part is larger than the surface area of the perforated part per unit volume of the other part of the surface part. A perforation step of forming a plurality of perforations by irradiating a laser; and a joining step of joining the first member and the second member by filling the plurality of perforations with the second member. , Including.

In the present invention, the “location corresponding to the stress concentration portion in the surface portion” (hereinafter also referred to as the stress concentration portion) refers to a location that becomes a stress concentration portion on the bonding surface (bonding portion) of the manufactured bonded structure. It means a corresponding location on the surface of the first member. Note that the stress concentration portion of the bonded structure can be specified by CAE (Computer Aided Engineering) analysis, a destructive test, or the like in the pre-production stage.

And where stress is a force per unit area that acts on a small area inside the continuum, according to this configuration, the surface area of the perforated part per unit volume is greater at the stress concentration locations than at other locations. Since it becomes large, the contact area of the hole wall of a perforation part and the 2nd member (resin member) with which the perforation part was filled becomes large. As described above, since the contact area between the hole wall of the perforated part and the filling resin is increased, the force acting on the hole wall (or the surface of the filled resin) of the perforated part is dispersed and the stress is reduced. Stress fracture at the part can be suppressed.

In addition, since the surface area of the perforated portion per unit volume at the stress concentration location is increased instead of extending the joint creepage surface, the degree of freedom in design can be ensured. In addition, the surface area of the perforated part is not increased uniformly over the entire joining surface, but the surface area of the perforated part is increased according to the degree to which the joining strength is required, so that a reduction in productivity can be suppressed. .

In the manufacturing method of the bonded structure, in the drilling step, the processing depth of the drilling portion at a location corresponding to the stress concentration portion is deeper than the processing depth of the drilling portion at the other location. It is preferable to form a plurality of perforations.

According to this configuration, even when the perforated part is formed on the surface portion of the first member at the same pitch, for example, when the perforated part is formed at a stress concentration location, the laser output is increased, or the number of scans is increased. By doing so, the surface area of the perforated portion at the stress concentration location can be easily made larger than the surface area of the perforated portion at other locations.

Further, in the case where there is a difference in the depth of the perforated part between the stress concentration part and the other part in this way, in the manufacturing method of the bonded structure, the perforated part in the other part is the stress concentration part. It is preferable to form such that the closer to the part corresponding to the part, the deeper the processing depth.

In a joined structure in which different types of members are joined together, the stress distribution is disturbed in areas other than the stress concentration part due to the difference in the linear expansion coefficient between the two members. Since the processing depth is formed deeper as the portion is, stress fracture other than the stress concentration portion can be efficiently suppressed.

In the method for manufacturing a bonded structure, in the punching step, the number of perforated parts per unit area at a location corresponding to the stress concentration portion is larger than the number of perforated parts per unit area at the other locations. Preferably, the plurality of perforations are formed.

According to this configuration, even when the perforated portion having the same processing depth is formed on the surface portion of the first member, for example, the laser irradiation interval at the stress concentration location is shorter than the laser irradiation interval at other locations. By doing so, the surface area of the perforated portion at the stress concentration location can be easily made larger than the surface area of the perforated portion at other locations.

Further, in the case of providing a difference in the number of perforated portions between the stress concentration location and other locations as described above, in the manufacturing method of the joined structure, the perforation portion at the other locations is used as the stress concentration portion. It is preferable to form so as to increase the number per unit area closer to the corresponding portion.

According to this configuration, it is possible to efficiently suppress the stress fracture other than the stress concentration portion.

In the manufacturing method of the bonded structure, in the drilling step, one pulse is irradiated with a laser composed of a plurality of sub-pulses, thereby forming projecting portions projecting inwardly on the hole walls of the respective drilled portions. preferable.

According to this configuration, since the irradiated laser is composed of a plurality of sub-pulses, the melted first member is difficult to be scattered and deposited inside the perforated part. The protrusion part which protrudes in can be formed. As a result, even when a force that peels the second member from the first member is applied, the protruding portion is pulled out and resists against a portion of the second member filled in the perforated portion on the back side of the protruding portion. Therefore, the bonding strength in the peeling direction can be improved.

In the method for manufacturing a bonded structure, the first member is preferably made of a metal, a thermoplastic resin, or a thermosetting resin.

In the method for manufacturing a bonded structure, the second member is preferably made of a thermoplastic resin or a thermosetting resin.

In the method for manufacturing a bonded structure, in the bonding step, it is preferable that the plurality of perforated portions are filled with the second member by laser irradiation, injection molding, or hot pressing.

The present invention is also directed to a joined structure in which the first member and the second member are joined.

Specifically, the present invention is a bonded structure in which a first member and a second member made of resin are bonded, and the surface portion of the first member that forms a bonding surface with the second member The laser is irradiated so that the surface area of the perforated part per unit volume of the stress concentration part in the surface part is larger than the surface area of the perforated part per unit volume of the other part in the surface part. A plurality of perforations are formed by the above-mentioned, and the plurality of perforations are filled with the second member.

According to this configuration, since the contact area between the hole wall of the perforated portion and the second member (resin member) is larger in the stress concentration portion than in other portions, the hole wall (or filling) of the perforated portion is larger. Since the force acting on the resin surface) is dispersed and the stress is reduced, the stress breakdown at the stress concentration portion can be suppressed.

Moreover, since the surface area of the perforated part per unit area at the stress concentration point is increased rather than extending the joint creepage surface, the design freedom can be ensured and the perforated part according to the required degree of joint strength. Since the surface area is increased, a decrease in productivity can be suppressed.

As described above, according to the method for manufacturing a bonded structure and the bonded structure according to the present invention, it is possible to secure stress in the bonded surface while ensuring a degree of design freedom and suppressing a decrease in productivity.

It is an expanded sectional view showing typically the joined part in the joined structure concerning Embodiment 1 of the present invention. It is a figure which illustrates typically the drawing area of the apparatus which irradiates a laser. It is sectional drawing which illustrates the manufacturing method of a joining structure typically. It is a figure which shows typically the metal case and resin cover of the photoelectric sensor which concern on the modification of Embodiment 1, FIG. 4 (a) is a perspective view of a metal case and a resin cover, FIG.4 (b) FIG. 5 is an enlarged cross-sectional view taken along the line bb in FIG. It is a perspective view which shows typically the 1st member in the joining structure body of an Example. It is a top view which shows typically the 1st member used for the joining structure which concerns on Embodiment 2 of this invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(Embodiment 1)
-Overall structure of the joint structure-
FIG. 1 is an enlarged cross-sectional view schematically showing a joint portion in the joint structure 1 according to the present embodiment. In the bonded structure 1 shown in FIG. 1, reference numeral 1A indicates a stress concentration portion, and reference numeral 1B indicates a portion other than the stress concentration portion (hereinafter also referred to as a normal portion). As shown in FIG. 1, the bonded structure 1 is formed by bonding a first member 2 and a second member 3 made of resin. The first perforated part 4 and the second perforated opening on the surface of the first member 2 are formed on the surface of the first member 2 constituting the joint interface between the first member 2 and the second member 3 in the joint structure 1. Part 5 is formed. The first perforated part 4 and the second perforated part 5 are formed such that the processing depth of the first perforated part 4 in the stress concentration part 1A is deeper than the processing depth of the second perforated part 5 in the normal part 1B. ing. Thus, in the joined structure 1, the second member 3 filled in the first perforated part 4 and the second perforated part 5 in the melted or softened state is formed in the first perforated part 4 and the second perforated part. The first member 2 and the second member 3 are joined by being solidified in the part 5. In FIG. 1, only two of the first perforation part 4 and the second perforation part 5 are shown for easy understanding of the drawing. However, in actuality, the first perforation part 4 and the second perforation part 5 are more Many are formed.

-First member and second member-
The first member 2 is preferably made of a metal, a thermoplastic resin, or a thermosetting resin. On the other hand, the second member 3 is preferably made of a thermoplastic resin or a thermosetting resin.

Examples of the metal constituting the first member 2 include iron metal, stainless steel metal, copper metal, aluminum metal, magnesium metal and alloys thereof. Further, the first member 2 may be a metal molded body, or may be zinc die casting, aluminum die casting, powder metallurgy, or the like.

Examples of the thermoplastic resin constituting the first member 2 or the second member 3 include PVC (polyvinyl chloride), PS (polystyrene), AS (acrylonitrile styrene), ABS (acrylonitrile butadiene styrene), PMMA (polymethyl methacrylate), PE (polyethylene), PP (polypropylene), PC (polycarbonate), m-PPE (modified polyphenylene ether), PA6 (polyamide 6), PA66 (polyamide 66), POM (polyacetal), PET ( Polyethylene terephthalate), PBT (polybutylene terephthalate), PSF (polysulfone), PAR (polyarylate), PEI (polyetherimide), PPS (polyphenylene sulfide), PES (polyethersulfone), PE K (polyetheretherketone), PAI (polyamideimide), LCP (liquid crystal polymer), PVDC (polyvinylidene chloride), PTFE (polytetrafluoroethylene), PCTFE (polychlorotrifluoroethylene) and PVDF (polyvinylidene fluoride) Is mentioned. The first member 2 or the second member 3 may be TPE (thermoplastic elastomer), and examples of TPE include TPO (olefin-based), TPS (styrene-based), TPEE (ester-based), and TPU. (Urethane type), TPA (nylon type) and TPVC (vinyl chloride type).

Furthermore, as an example of the thermosetting resin constituting the first member 2 or the second member 3, EP (epoxy), PUR (polyurethane), UF (urea formaldehyde), MF (melamine formaldehyde), PF (phenol formaldehyde) , UP (unsaturated polyester) and SI (silicone). Further, the first member 2 or the second member 3 may be FRP (fiber reinforced plastic).

It should be noted that a filler may be added to the thermoplastic resin and the thermosetting resin constituting the first member 2 or the second member 3. Examples of the filler include inorganic fillers (glass fibers, inorganic salts, etc.), metal fillers, organic fillers, and carbon fibers.

-Perforated part-
In the present embodiment, the processing depth of the first perforated portion 4 at the location corresponding to the stress concentration portion 1A on the surface portion of the first member 2 is the processing depth of the second perforated portion 5 at the location corresponding to the normal portion 1B. The first perforated part 4 and the second perforated part 5 are formed by irradiating a processing laser beam (hereinafter simply referred to as a laser) so as to be deeper than the above. First, the reason why the stress concentration portion 1A and the normal portion 1B have a difference in the processing depth of the

perforated portions

4 and 5 will be described. In the following, “location corresponding to the stress concentration portion” is also simply referred to as “stress concentration portion”, and “location corresponding to the normal portion” is also simply referred to as “normal portion”.

In the joint structure 1, the second perforated part 5 is formed on the surface part of the first member 2 when the second member 3 that is melted or softened when the first member 2 and the second member 3 are joined. This is to obtain a so-called anchor effect caused by filling the second perforated part 5.

However, in the bonded structure 1 in which different types of members are bonded to each other, stress is likely to occur due to the difference in the linear expansion coefficient between the first member 2 and the second member 3. If only the perforated part 5 is formed, when a thermal shock or the like is repeatedly applied to the bonded structure 1, stress breakage may occur in the stress concentration part 1A in the bonded part.

Here, in order to suppress the stress fracture at the stress concentration portion 1A, the joining creepage surface is extended (the joining area is increased), or the processing depth of the second punched portion 5 is increased over the entire joining surface. It is possible to do. However, extending the joint creepage imposes restrictions on product design, and if the machining depth of the second perforated part 5 is increased over the entire joining surface, the machining time becomes longer and the productivity decreases. Problem arises.

Therefore, in the present embodiment, the surface area of the first perforated part 4 per unit volume of the stress concentration part 1A in the surface part of the first member 2 is the second perforation per unit volume of the normal part (other part) 1B. The first perforated part 4 and the second perforated part 5 are formed by irradiating the surface of the first member 2 with a laser so as to be larger than the surface area of the part 5. Then, various aspects are available as "the surface area of the first perforated part 4 per unit volume of the stress concentration part 1A is larger than the surface area of the second perforated part 5 per unit volume of the normal part 1B". In this embodiment, the first perforation unit 4 and the second perforation unit 5 are formed so that the processing depth of the first perforation unit 4 is deeper than the processing depth of the second perforation unit 5. Yes.

As a result, even when the first perforated portion 4 and the second perforated portion 5 are formed on the surface portion of the first member 2 at the same pitch, the surface area of the first perforated portion 4 in the stress concentration portion 1A is reduced to the normal portion 1B. The surface area of the second perforated part 5 can be easily increased. Therefore, since the contact area between the hole wall 8 of the first perforated part 4 and the filled second member 3 becomes large, the hole wall 8 of the first perforated part 4 (or the surface of the filled second member 3). ) Is dispersed and the stress is reduced, so that the stress fracture at the stress concentration portion 1A can be suppressed.

The first perforated part 4 and the second perforated part 5 are formed, for example, by being irradiated with a processing laser. As the type of laser, a laser capable of pulse oscillation is preferable, and a fiber laser, a YAG laser, a YVO ₄ laser, a semiconductor laser, a carbon dioxide gas laser, and an excimer laser can be selected. A fiber laser, a YAG laser, A second harmonic of a YAG laser, a YVO ₄ laser, or a semiconductor laser is preferable.

[Identification of stress concentration part]
Since the stress concentration portion 1A differs depending on the shape of the joining structure 1 as a product, the difference in linear expansion coefficient between the first member 2 and the second member 3 used, etc., prior to the manufacture of the joining structure 1, The generation position is specified beforehand. Specifically, for example, the stress concentration portion 1A may be specified from the distribution of linear expansion stress generated in the joint portion by stress simulation using CAE (Computer Aided Engineering). Also, a bonded structure in which a drilled portion (for example, the second drilled portion 5) having a relatively shallow processing depth is prepared over the entire bonded surface is prepared, and the bonded structure is subjected to, for example, an environment of −40 ° C. For example, a portion where peeling or breakage in the joint portion is generated may be specified as the stress concentration portion 1A by applying 100 times of repeated thermal shock for 30 minutes in an environment of 85 ° C. for 30 minutes.

[First perforated part and second perforated part]
Both the first perforated part 4 and the second perforated part 5 are non-through holes having a substantially circular cross section that open on the surface of the first member 2. The opening diameter R1 of the first perforation part 4 and the opening diameter R2 of the second perforation part 5 are preferably 30 μm or more and 100 μm or less. This is because, when the opening diameters R1 and R2 are less than 30 μm, the filling property to the first perforated part 4 and the second perforated part 5 of the second member 3 melted or softened at the time of joining deteriorates and the joining strength decreases. Because there is a case to do. On the other hand, if the opening diameters R1 and R2 exceed 100 μm, the number of the first perforated portions 4 and the second perforated portions 5 per unit area may decrease, and a desired joint strength may not be obtained.

The interval between the first perforations 4 (the distance between the center of a certain first perforation 4 and the center of the first perforation 4 adjacent to the first perforation 4) is 200 μm or less. Is preferred. This is because if the interval between the first perforated portions 4 exceeds 200 μm, the number of the first perforated portions 4 per unit area may decrease and a desired bonding strength may not be obtained. For the same reason, the interval between the second perforated portions 5 (the distance between the center of a certain second perforated portion 5 and the center of the second perforated portion 5 adjacent to the certain second perforated portion 5) is also 200 μm or less. It is preferable that

If the relationship that the processing depth of the first drilling portion 4 is made deeper than the processing depth of the second punching portion 5 is satisfied, the processing depth of the first punching portion 4 and the second punching portion 5 is set. There is no upper limit. In particular, the processing depth of the first perforated part 4 depends on the number and inner diameter of the first perforated parts 4 based on the stress value obtained when the stress concentration part 1A is specified by stress simulation using CAE or the like. What is necessary is just to set suitably. However, the lower limit of the processing depth is preferably more than 30 μm for both the first perforated part 4 and the second perforated part 5 from the viewpoint of resistance to stress caused by the difference in linear expansion coefficient.

As shown in FIG. 1, the first perforated portion 4 is formed with a narrowed portion 6 in which the hole wall 8 is narrowed inward. In other words, the hole wall 8 of the first perforated part 4 has a first wall part 8a whose diameter increases in the depth direction (Z direction) from the bottom side to the surface side, and a surface side of the first wall part 8a. The second wall portion 8b that is reduced in diameter toward the surface side from the end portion is formed so as to be continuous, and the portion constituting the opening portion in the second wall portion 8b that is reduced in diameter constitutes the throttle portion 6 at the same time. is doing. Similarly to this, the second perforated part 5 is also formed with a narrowed part 7 in which the hole wall is narrowed inward. The narrowed

portions

6 and 7 correspond to the “projecting portions projecting inward” in the present invention, and the “projecting portions” are holes of the first perforated portion 4 and the second perforated portion 5 having a substantially circular cross section. It is an example at the time of forming over the perimeter of a wall. In addition, the dashed-two dotted line in FIG. 1 is a virtual line which shows the division | segmentation with the 1st wall part 8a and the 2nd wall part 8b.

As described above, by forming the narrowed

portions

6 and 7 in the first perforated portion 4 and the second perforated portion 5, even when a force that peels the second member 3 from the first member 2 is applied, In the second member 3 filled in the perforated part 4 and the second perforated part 5, the restricting

parts

6 and 7 are pulled out from the bottom part of the restricting

parts

6 and 7, and the resistance in the peeling direction. The joint strength can be improved. Thereby, in addition to the improvement in the joining strength in the shearing direction by filling the first perforating part 4 and the second perforating part 5 with the second member 3, the joining strength in the peeling direction can also be improved.

The first perforation unit 4 and the second perforation unit 5 are formed by irradiating the surface portion of the first member 2 with laser light in which one pulse is composed of a plurality of sub-pulses. Such a method of irradiating a laser beam composed of a plurality of sub-pulses makes it easy to concentrate the energy of the laser beam in the depth direction, so that the first punching portion 4 and the second punching portion 5 are formed. It is suitable for. Specifically, when the first member 2 is irradiated with the laser beam, the first member 2 is locally melted, so that the formation of the first perforated part 4 and the second perforated part 5 proceeds. At this time, since the laser beam is composed of a plurality of sub-pulses, the melted first member 2 is not easily scattered and easily deposited in the vicinity of the first perforated part 4 and the second perforated part 5. Then, as the formation of the first perforated part 4 and the second perforated part 5 proceeds, the melted first member 2 is deposited inside the first perforated part 4 and the second perforated part 5, thereby reducing the throttle part 6. , 7 are formed.

As an example of an apparatus for irradiating such a laser in which one pulse is composed of a plurality of subpulses, fiber laser marker MX-Z2000 or MX-Z2050 manufactured by OMRON can be mentioned.

As processing conditions by the fiber laser marker, it is preferable that one period of the sub-pulse is 15 ns or less. This is because if one period of the sub-pulse exceeds 15 ns, energy is easily diffused by heat conduction, and it is difficult to form the first perforated part 4 and the second perforated part 5. Note that one cycle of the subpulse is a total time of the irradiation time for one subpulse and the interval from the end of the irradiation of the subpulse to the start of the irradiation of the next subpulse.

Further, as processing conditions by the fiber laser marker, the number of subpulses of one pulse is preferably 2 or more and 50 or less. This is because if the number of subpulses exceeds 50, the output per unit of subpulses becomes small, and it becomes difficult to form the first perforated part 4 and the second perforated part 5.

When forming the first perforated part 4 and the second perforated part 5 in the stress concentrated part 1A and the normal part 1B, for example, the drawing area 10 of the fiber laser marker shown in FIG. Corresponding first drawing area 10A as shown in FIG. 2 (c) and second drawing area 10B as shown in FIG. 2 (b) corresponding to normal portion 1B are cut and divided. . Then, for the first drawing area 10A, the first perforated part of the stress concentrating part 1A can be obtained by increasing the processing output of the fiber laser or increasing the number of scans as compared with the second drawing area 10B. 4 can be made deeper easily than the processing depth of the second perforated portion 5 of the normal portion 1B.

Such a bonded structure 1 is applicable, for example, when a resin cover 13 is bonded to a metal case 12 of a photoelectric sensor (see FIG. 4). In this case, the metal case 12 corresponds to the first member 2, and the resin cover 13 corresponds to the second member 3.

-Manufacturing method of bonded structure-
Next, with reference to FIG. 3, the manufacturing method of the junction structure 1 which concerns on this embodiment is demonstrated.

First, prior to the formation of the first perforated part 4 and the second perforated part 5, based on the stress simulation using CAE, the test result when repeated thermal shock is applied, etc., the stress concentration part 1A in the bonded structure 1 Is specified. Next, the drawing area 10 on the surface of the first member 2 is, for example, as shown in FIG. 2, the first drawing area 10A corresponding to the identified stress concentration portion 1A and the second drawing area 10 corresponding to the normal portion 1B. It is divided into the drawing area 10B.

Then, as shown by the arrow in FIG. 3A, the surface of the first member 2 corresponding to the normal portion 1B is irradiated with a laser, and the processing depth is relatively set as shown in FIG. The shallow second perforated portion 5 is formed (perforating step). Next, as shown by the arrow in FIG. 3B, the surface of the first member 2 corresponding to the stress concentration portion 1A is irradiated with a laser, and the processing depth is the second as shown in FIG. The first perforation part 4 deeper than the perforation part 5 is formed (perforation process). At this time, the narrowed

portions

6 and 7 are formed in the hole walls of the first perforated portion 4 and the second perforated portion 5 by irradiating a laser in which one pulse is composed of a plurality of subpulses.

The formation of the first perforation part 4 and the formation of the second perforation part 5 are not particularly precedent. For example, the second perforation part is formed after the formation of the first perforation part 4 in the reverse order shown in FIG. 5 may be formed.

Thereafter, for example, the surface of the first member 2 is irradiated with a laser in a state where the first member 2 and the second member 3 are overlapped to melt or soften the second member 3 (laser irradiation). Is injected into the mold (not shown) and the melted second member 3 is injected (injection molding) to fill the first member 4 and the second member 5 with the second member 3. Then, the second member 3 filled in the first perforation unit 4 and the second perforation unit 5 is solidified in the first perforation unit 4 and the second perforation unit 5, whereby the first member 2 and the second member 3 are solidified. The two members 3 are joined together to form a joined structure 1 as shown in FIG.

-Modification of Embodiment 1-
Next, a modified example of the bonded structure 1 according to the first embodiment will be described.

FIG. 4 is a diagram schematically showing the metal case 12 and the resin cover 13 of the photoelectric sensor according to this modification, and FIG. 4A is a perspective view of the metal case 12 and the resin cover 13. FIG. 4B is an enlarged cross-sectional view taken along line bb in FIG. In FIG. 4B, reference numeral 11A indicates a stress concentration part, and reference numeral 11B indicates a normal part. This modification is different from the first embodiment in that the processing depth of the second perforated part 15 becomes deeper in steps as it approaches the stress concentration part 11A.

As shown in FIG. 4A, the bonded structure 11 is formed by bonding a first member 12 constituting a metal case 12 and a second member 13 constituting a resin cover 13. A first perforated portion 14 and a second perforated hole opened on the surface of the first member 12 are formed on the surface portion of the first member 12 constituting the joint interface between the first member 12 and the second member 13 in the joint structure 11. A portion 15 is formed. The first perforated part 14 and the second perforated part 15 are formed such that the processing depth of the first perforated part 14 in the stress concentration part 11A is deeper than the processing depth of the second perforated part 15 in the normal part 11B. ing.

Thus, in this modification, as shown in FIG. 4B, the second perforated portion 15 of the normal portion 11B is formed so that the processing depth is closer to the stress concentration portion 11A. . That is, in this modification, the second drilling portion 15B farthest from the stress concentration portion 11A among the second drilling portions 15 of the normal portion 11B is the shallowest, and the second drilling portion 15B approaches the stress concentration portion 11A. The machining depth becomes deeper in the order of the second drilling portion 15C, and the machining depth of the second drilling portion 15D closest to the stress concentration portion 11A becomes the deepest.

In the bonded structure 11 in which different members are bonded to each other, the stress distribution is disturbed in areas other than the stress concentration portion 11A due to the difference in the linear expansion coefficient between the two

members

12 and 13. According to this configuration, Since the machining depth of the second perforated part 15 closer to the concentrated part 11A is formed deeper, stress fracture other than the stress concentrated part 11A (normal part 11B) can also be efficiently suppressed.

-Experimental example-
Next, Experimental Example 1 and Experimental Example 2 performed in order to confirm the effects of the manufacturing method of the bonded structure and the bonded structure according to the present invention will be described.

[Experimental Example 1]
In Experimental Example 1, in the bonded structure in which the metal member and the resin member are bonded, the processing depth of the punched portion of the stress concentration portion is made deeper than the processed depth of the punched portion of the normal portion. It was confirmed how much the resistance to stress fracture was improved.

Specifically, as shown in FIG. 5, two plate-like first members 32 each having a length of 100 mm, a width of 29 mm, and a thickness of 3 mm, each made of stainless steel (SUS304), were prepared. The laser beam marker MX-Z2000 made by OMRON is used for one first member 32, and a laser is applied to a predetermined region R of 12.5 mm × 20.0 mm under the following laser irradiation conditions 1-1 and 1-2. A perforated part was formed by irradiation. More specifically, an outer edge portion R _A (black frame portion in FIG. 5) corresponding to the stress concentration portion in the predetermined region R is irradiated with laser under the following laser irradiation condition 1-1. by so as to form a perforated portion of the working depth 65 .mu.m, for an area R _B of 10.5 mm × 18.0 mm, except for the outer edge R _a of the predetermined region R, the laser in the laser irradiation conditions 1-2 below Irradiation formed a perforated portion with a processing depth of 39 μm.

Further, by irradiating the other first member 32 with a laser under the following laser irradiation condition 1-2 using the same fiber laser marker MX-Z2000, a predetermined region R of 12.5 mm × 20.0 mm is obtained. Only a perforated part with a processing depth of 39 μm was formed.

<Laser irradiation condition 1-1>
Laser: Fiber laser (wavelength 1062nm)
Frequency: 10kHz
Output: 3.8W
Scanning speed: 650mm / sec
Number of scans: 40 times Irradiation interval: 65 μm
Number of subpulses: 20

<Laser irradiation condition 1-2>
Laser: Fiber laser (wavelength 1062nm)
Frequency: 10kHz
Output: 3.8W
Scanning speed: 650mm / sec
Number of scans: 20 times Irradiation interval: 65 μm
Number of subpulses: 20

In the present experimental example, perforations in order to increase the depth of the perforated part of the stress concentration portion, the number of scans for forming the perforations in the outer part R _A of one of the first member 32, the region R _B The number of scans was set to 40, which is 20 times greater than the number of scans when forming the portion. Moreover, both the 1st members 32 set the irradiation space | interval to 65 micrometers, and made the space | interval of a perforation part uniform.

Furthermore, both the first members 32 are set to a frequency of a pulse composed of 20 subpulses when the perforated part is formed. That is, under these irradiation conditions 1-1 and 1-2, laser (pulse) was irradiated 10,000 times at an interval of 65 μm while moving 650 mm per second, and the pulse was composed of 20 subpulses. Thus, the perforation part which has an aperture | diaphragm | squeezing part was formed by irradiating the laser comprised with 20 subpulses per pulse.

Next, a bonded structure in which a second member (not shown) is bonded to a predetermined region R is produced by insert molding with respect to the first member 32 in which the drilled portions having a processing depth of 65 μm and 39 μm are formed. Was taken as Example 1. In addition, a bonded structure in which the second member is bonded to the predetermined region R is manufactured by insert molding with respect to the other first member 32 in which only the perforated portion with a processing depth of 39 μm is formed. . As for the second member, in both Example 1 and Comparative Example 1, polybutylene terephthalate (PBT) (Juranex (registered trademark) 3316 made by Wintech Polymer) was used as a material, and a plate of length 100 mm × width 25 mm × thickness 3 mm Formed into a shape. Moreover, J35EL3 made from Japan Steel Works was used for the molding machine. The molding conditions are as follows.

<Molding conditions>
Pre-drying: 120 ° C x 5 hours Mold temperature: 120 ° C
Cylinder temperature: 270 ° C
Holding pressure: 100 MPa

For Example 1 and Comparative Example 1 produced as described above, a thermal shock test was performed using a thermal shock apparatus TSD-100 manufactured by ESPEC. Specifically, a thermal shock of one cycle and one hour of 30 minutes in an environment of −40 ° C. and 30 minutes in an environment of 85 ° C. is continuously applied to Example 1 and Comparative Example 1 until the bonding interface reaches peeling. It was. The confirmation of whether or not the bonding interface had been peeled was performed after applying thermal shocks of 0, 100, 250, 500, 750, 1000, 1500 and 2000 cycles (times), respectively. And when the joining interface reached peeling in a certain cycle, the cycle in which peeling of the previous joining interface was not confirmed was adopted as the thermal shock test resistance. For example, when peeling of the bonding interface was confirmed after 1000 thermal shocks were applied, the previous 750 times were regarded as thermal shock test resistance. The thermal shock test resistance obtained for Example 1 and Comparative Example 1 is shown in Table 1.

From Table 1, in Example 1, in which the working depth of the perforated part of the stress concentrated part is deeper than the processed depth of the perforated part of the normal part in the joined structure in which the metal member and the resin member are joined, It was confirmed that the thermal shock test resistance was improved by a factor of 1.5 compared to Comparative Example 1 in which the drilling depth of each of the drill holes was the same as the drilling depth of the normal hole.

[Experiment 2]
In Experimental Example 2, in the bonded structure in which the resin members are bonded to each other, the depth of drilling of the stress concentration portion is made deeper than the depth of drilling of the normal portion, thereby preventing stress fracture at the bonding surface. We confirmed how much resistance improved.

Specifically, two plate-shaped first members each having a length of 100 mm, a width of 29 mm, and a thickness of 3 mm, each made of polyphenylene sulfide (PPS) (Polyplastics Fortron (registered trademark) 1140) were prepared. . For one of the first members, using a fiber laser marker MX-Z2000 made by OMRON, corresponding to the stress concentration portion in the predetermined region R of 12.5 mm × 20.0 mm, similar to that shown in FIG. With respect to the outer edge portion R _{A having} a width of 1.0 mm (corresponding to the black frame portion in FIG. 5), a laser-irradiated laser is applied under the laser irradiation condition 2-1 below to form a punched portion having a processing depth of 71 μm. In the region R _B of 10.5 mm × 18.0 mm excluding the outer edge portion R _A in the predetermined region R, a perforated portion having a processing depth of 49 μm is formed by irradiating a laser under the following laser irradiation condition 2-2. Formed. Further, the other first member is processed into a predetermined region R of 12.5 mm × 20.0 mm by irradiating a laser under the following laser irradiation condition 2-2 using the same fiber laser marker MX-Z2000. Only a perforated part having a depth of 49 μm was formed.

<Laser irradiation condition 2-1>
Laser: Fiber laser (wavelength 1062nm)
Frequency: 10kHz
Output: 1.1W
Scanning speed: 650mm / sec
Number of scans: 10 times Irradiation interval: 65 μm
Number of subpulses: 5

<Laser irradiation condition 2-2>
Laser: Fiber laser (wavelength 1062nm)
Frequency: 10kHz
Output: 1.1W
Scanning speed: 650mm / sec
Number of scans: 3 times Irradiation interval: 65 μm
Number of subpulses: 5

Next, a joined structure in which the second member was joined to the predetermined region R was produced by insert molding with respect to one of the first members in which the perforated portions having a processing depth of 71 μm and 49 μm were formed. . In addition, a joined structure in which the second member was joined to the predetermined region R was produced by insert molding with respect to the other first member in which only the perforated portion having a processing depth of 49 μm was formed. In addition, the 2nd member used the polybutylene terephthalate as a material similarly to the said Experimental example 1. The molding machine and molding conditions were the same as in Experimental Example 1 above.

For Example 2 and Comparative Example 2 produced as described above, the same thermal shock test as in Experimental Example 1 was performed, and the thermal shock test resistance was obtained by the same evaluation method. Table 2 shows the thermal shock test resistance obtained for Example 2 and Comparative Example 2.

From Table 2, in Example 2 in which the processing depth of the perforated portion of the stress concentration portion was deeper than the processing depth of the perforated portion of the normal portion in the joined structure in which the resin members were joined, the perforated portion of the stress concentration portion It was confirmed that the thermal shock test resistance was improved twice as much as that of Comparative Example 2 in which the machining depth was the same as the machining depth of the perforated part of the normal part.

(Embodiment 2)
The present embodiment is different from the first embodiment in that the number per unit area of the first perforated part 24 in the stress concentration part 21A is different from the number per unit area of the second perforated part 25 in the normal part 21B. It is. Hereinafter, a description will be given focusing on differences from the first embodiment.

FIG. 6 is a plan view schematically showing the first member 22 used in the joint structure according to the present embodiment. In FIG. 6, reference numeral 21A indicates a portion corresponding to the stress concentration portion, and reference numeral 21B indicates a portion corresponding to the normal portion.

Also in the present embodiment, as in the first embodiment, the surface area of the first perforated portion 24 per unit volume of the stress concentration portion 21A in the surface portion of the first member 22 is the second per unit volume of the normal portion 21B. The first perforated part 24 and the second perforated part 25 are formed by irradiating the surface of the first member 22 with a laser so as to be larger than the surface area of the perforated part 25. However, in the present embodiment, unlike the first embodiment, “the surface area of the first perforated part 24 per unit volume of the stress concentration part 21A is larger than the surface area of the second perforated part 25 per unit volume of the normal part 21B. As a mode, the first perforated part 24 is so formed that the number of the first perforated parts 24 per unit area in the stress concentration part 21A is larger than the number of the second perforated parts 25 per unit area in the normal part 21B. And the 2nd perforation part 25 is formed.

Thus, even when the first perforated part 24 and the second perforated part 25 are formed at the same processing depth, the surface area of the first perforated part 24 per unit volume in the stress concentration part 21A is determined as the unit in the normal part 21B. The surface area of the second perforated part 25 per volume can be easily increased. Therefore, since the contact area between the hole wall of the first perforated part 24 and the filled second member 3 is increased, the hole wall of the first perforated part 24 (or the surface of the filled second member 3) is formed. Since the acting force is dispersed and the stress is reduced, the stress fracture at the stress concentration portion 21A can be suppressed.

The types of the metal, thermoplastic resin, and thermosetting resin that constitute the first member 22 are the same as the metal, thermoplastic resin, and thermosetting resin that constitute the first member 2 described in the first embodiment. It is.

-Experimental example-
Next, Experimental Example 3 and Experimental Example 4 performed for confirming the effects of the manufacturing method of the bonded structure and the bonded structure according to the present invention will be described.

[Experiment 3]
In Experimental Example 3, in the joint structure in which the metal member and the resin member are joined, the number of perforated portions per unit area of the stress concentration portion is made larger than the number of perforated portions per unit area of the normal portion. The degree to which the resistance against stress fracture at the joint surface is improved was confirmed.

Specifically, two plate-shaped first members each having a length of 100 mm, a width of 29 mm, and a thickness of 3 mm, each made of stainless steel (SUS304), were prepared. For one of the first members, using an Omron fiber laser marker MX-Z2000, an outer edge portion R _A (width 1.0 mm) corresponding to the stress concentration portion in a predetermined region R of 12.5 mm × 20.0 mm. 5), a perforated portion is formed at an irradiation interval of 50 μm by irradiating a laser under the following laser irradiation condition 3-1, and the outer edge portion _RA of the predetermined region R is excluded. and for region R _B of 10.5 mm × 18.0 mm, to form the perforations in irradiation interval 65μm by irradiating a laser in a laser irradiation conditions 3-2 below. Further, by irradiating the other first member with a laser under the following laser irradiation condition 3-2 using the fiber laser marker MX-Z2000, the predetermined region R of 12.5 mm × 20.0 mm is irradiated. Perforated portions were formed at intervals of 65 μm.

<Laser irradiation condition 3-1>
Laser: Fiber laser (wavelength 1062nm)
Frequency: 10kHz
Output: 3.8W
Scanning speed: 650mm / sec
Number of scans: 20 times Irradiation interval: 50 μm
Number of subpulses: 20

<Laser irradiation condition 3-2>
Laser: Fiber laser (wavelength 1062nm)
Frequency: 10kHz
Output: 3.8W
Scanning speed: 650mm / sec
Number of scans: 20 times Irradiation interval: 65 μm
Number of subpulses: 20

Next, a joined structure in which the second member was joined to the predetermined region R was produced by insert molding with respect to one of the first members having the perforations formed at irradiation intervals of 50 μm and 65 μm. Further, a joined structure in which the second member was joined to the predetermined region R was produced by insert molding with respect to the other first member in which the perforated part was formed with an irradiation interval of 65 μm, and this was designated as Comparative Example 3. In addition, the 2nd member used the polybutylene terephthalate as a material similarly to the said Experimental example 1. The molding machine and molding conditions were the same as in Experimental Example 1 above.

For Example 3 and Comparative Example 3 produced as described above, the same thermal shock test as in Experimental Example 1 was performed, and thermal shock resistance was obtained by the same evaluation method. Table 3 shows thermal shock test resistance obtained for Example 3 and Comparative Example 3.

From Table 3, in the joined structure in which the metal member and the resin member are joined, Example 3 in which the number of perforated parts per unit area of the stress concentration part was larger than the number of perforated parts per unit area of the normal part. Thus, it was confirmed that the thermal shock test resistance was improved 1.5 times as compared with Comparative Example 3 in which the number of perforated parts per unit area of the stress concentration part was the same as the number of perforated parts per unit area of the normal part. It was. In addition, since the thermal shock test resistance obtained in this experimental example is the same as the thermal shock test resistance obtained in experimental example 1, stress concentration is caused in a bonded structure in which a metal member and a resin member are bonded. There was no difference between the method of increasing the drilling depth of the perforated part and the method of increasing the number of perforated parts per unit area of the stress concentration part, and it was also confirmed that both methods could be used selectively .

[Experimental Example 4]
In Experimental Example 4, in the bonded structure in which the resin members are bonded to each other, the number of the perforated portions per unit area of the stress concentration portion is larger than the number of the perforated portions per unit area of the normal portion. It was confirmed how much the resistance to stress fracture at the time of improvement was improved.

Specifically, two plate-shaped first members each having a length of 100 mm, a width of 29 mm, and a thickness of 3 mm, each made of polyphenylene sulfide (PPS) (Polyplastics Fortron (registered trademark) 1140) were prepared. . For one of the first members, using an Omron fiber laser marker MX-Z2000, an outer edge portion R _A (width 1.0 mm) corresponding to the stress concentration portion in a predetermined region R of 12.5 mm × 20.0 mm. 5), a perforated portion is formed at an irradiation interval of 50 μm by irradiating a laser under the following laser irradiation condition 4-1, and an outer edge portion _RA of the predetermined region R is excluded. and for region R _B of 10.5 mm × 18.0 mm, to form the perforations in irradiation interval 65μm by irradiating a laser in a laser irradiation conditions 4-2 below. Further, by irradiating the other first member with a laser under the following laser irradiation condition 4-2 using the same fiber laser marker MX-Z2000, a predetermined region R of 12.5 mm × 20.0 mm is irradiated. Perforated portions were formed at intervals of 65 μm.

<Laser irradiation condition 4-1>
Laser: Fiber laser (wavelength 1062nm)
Frequency: 10kHz
Output: 1.1W
Scanning speed: 650mm / sec
Number of scans: 3 times Irradiation interval: 50 μm
Number of subpulses: 5

<Laser irradiation condition 4-2>
Laser: Fiber laser (wavelength 1062nm)
Frequency: 10kHz
Output: 1.1W
Scanning speed: 650mm / sec
Number of scans: 3 times Irradiation interval: 65 μm
Number of subpulses: 5

Next, a joined structure in which the second member was joined to the predetermined region R was produced by insert molding with respect to the first member in which the perforated part was formed at irradiation intervals of 50 μm and 65 μm. Further, a joined structure in which the second member was joined to the predetermined region R was produced by insert molding with respect to the other first member in which the perforated part was formed with an irradiation interval of 65 μm, and this was designated as Comparative Example 4. In addition, the 2nd member used the polybutylene terephthalate as a material similarly to the said Experimental example 1. The molding machine and molding conditions were the same as in Experimental Example 1 above.

For Example 4 and Comparative Example 4 produced as described above, the same thermal shock test as in Experimental Example 1 was performed, and the thermal shock test resistance was obtained by the same evaluation method. Table 4 shows thermal shock test resistance obtained for Example 4 and Comparative Example 4.

From Table 4, in Example 4 in which the number of perforated parts per unit area of the stress concentration part is larger than the number of perforated parts per unit area of the normal part in the joined structure in which the resin members are joined together, It was confirmed that the thermal shock test resistance was improved twice as much as that of Comparative Example 4 in which the number of perforated portions per unit area of the concentrated portion was the same as the number of perforated portions per unit area of the normal portion. In addition, since the thermal shock test resistance obtained in this experimental example is the same as the thermal shock test resistance obtained in experimental example 2, even in a joined structure in which resin members are joined together, It was also confirmed that there is no difference between the method of increasing the processing depth of the punched portion and the method of increasing the number of punched portions per unit area of the stress concentration portion, and both methods can be selectively used.

(Other embodiments)
The present invention is not limited to the embodiments, and can be implemented in various other forms without departing from the spirit or main features thereof.

In each of the above-described embodiments and the modifications thereof, the first perforated part 4 and the second perforated part 5 having the

throttle parts

6 and 7 are formed, but not limited thereto, the first perforated part 4 and the second perforated part 5 The shape may be a straight shape without the

throttle portions

6 and 7.

In the second embodiment, the number of first perforations 24 per unit area in the stress concentration portion 21A is simply larger than the number of second perforations 25 per unit area in the normal portion 21B. Although the 1st perforation part 24 and the 2nd perforation part 25 were formed, it is not restricted to this, For example, the 2nd perforation part 25 is formed so that the number per unit area may increase so that it may be near the stress concentration part 21A. May be.

Thus, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention. This application claims priority based on Japanese Patent Application No. 2015-030369. By this reference, the entire contents thereof are incorporated into the present application.

According to the present invention, since it is possible to suppress the stress breakdown at the joint surface while ensuring the degree of freedom of design and suppressing the decrease in productivity, the manufacturing method of the joined structure in which the dissimilar members are joined together, and the dissimilarity This is extremely useful when applied to a joined structure in which members are joined together.

DESCRIPTION OF SYMBOLS 1 Junction structure 1A Stress concentration part 2 1st member 3 2nd member 4 1st drilling part 5 2nd drilling part 6 Protrusion part 7 Protrusion part 11 Bonding structure 11A Stress concentration part 12 1st member 13 2nd member 14 1st 1 perforation part 15 2nd perforation part 21A stress concentration part 22 first member 24 first perforation part 25 second perforation part 32 first member

Claims

A method for manufacturing a joined structure in which a first member and a second member made of resin are joined,
In the surface portion of the first member constituting the joint surface with the second member, the surface area of the perforated portion per unit volume of the portion corresponding to the stress concentration portion in the surface portion is the other portion in the surface portion. A perforation step of forming a plurality of perforations by irradiating with a laser so as to be larger than the surface area of the perforations at a unit volume of
A joining step of joining the first member and the second member by filling the plurality of perforated portions with the second member;
The manufacturing method of the joining structure characterized by including.
In the manufacturing method of the joined structure according to claim 1,
In the punching step, forming the plurality of punched portions so that a processing depth of the punched portion at a location corresponding to the stress concentration portion is deeper than a processing depth of the punched portion at the other location. A method for producing a featured bonded structure.
In the manufacturing method of the joined structure according to claim 1,
In the perforating step, the plurality of perforated parts so that the number of perforated parts per unit area in the part corresponding to the stress concentration part is larger than the number of perforated parts per unit area in the other part. The manufacturing method of the joining structure characterized by forming.
In the manufacturing method of the junction structure according to claim 2,
The method for manufacturing a joined structure according to claim 1, wherein the perforated portion at the other portion is formed such that the closer to the portion corresponding to the stress concentration portion, the deeper the processing depth.
In the manufacturing method of the joined structure according to claim 3,
A method for manufacturing a joint structure, wherein the perforated portions in the other locations are formed such that the number per unit area increases as the location is closer to the location corresponding to the stress concentration portion.
In the method for manufacturing a bonded structure according to any one of claims 1 to 5,
In the perforating step, a projecting portion projecting inward is formed on the hole wall of each perforated portion by irradiating a laser in which one pulse is composed of a plurality of sub-pulses. .
In the method for manufacturing a bonded structure according to any one of claims 1 to 6,
The method for manufacturing a joined structure, wherein the first member is made of a metal, a thermoplastic resin, or a thermosetting resin.
In the method for manufacturing a joined structure according to any one of claims 1 to 7,
The method for manufacturing a joined structure, wherein the second member is made of a thermoplastic resin or a thermosetting resin.
In the method for manufacturing a joined structure according to any one of claims 1 to 8,
In the joining step, the second member is filled in the plurality of perforated portions by laser irradiation, injection molding, or hot pressing.
A joined structure in which a first member and a second member made of resin are joined,
In the surface portion of the first member constituting the joint surface with the second member, the surface area of the perforated portion per unit volume of the stress concentration portion in the surface portion is the unit volume of the other portion in the surface portion. A plurality of perforations are made by irradiating a laser so as to be larger than the surface area of the perforation.
The joining structure, wherein the plurality of perforated portions are filled with the second member.