JP5479758B2 - Laser welding method and housing - Google Patents

Description

  The present invention relates to a laser welding method suitable for laser welding a first resin material and a second resin material, and a housing realized by using this laser welding method.

  The housing of the photoelectric sensor contains a light emitting element and a light receiving element therein and seals it in a watertight manner. Generally, the first and second members that form a box-shaped sealed container are brought into contact with each other. The abutting surfaces are joined to each other. Incidentally, the first and second members are generally made of a resin material, and the joining is performed by adhering the butted surfaces, secondary molding, or ultrasonic welding. Although not intended for a photoelectric sensor, a so-called laser welding technique is also proposed in which different types of synthetic resin materials are spot-welded using laser light (see, for example, Patent Document 1).

  Incidentally, the laser welding described above is performed from the first resin material side to the second resin material in a state where the first resin material that transmits the laser light and the second resin material that absorbs the laser light face each other. The laser beam is irradiated toward the second resin material at the abutting surface, and the first member is melted by the heat of fusion, and then the melt is solidified integrally. To achieve.

JP-A-60-214931

  By the way, if the joint surface of the first and / or second member described above is warped, warped, sinked, or distorted, even if these members are brought into contact with each other, they do not completely adhere to each other. It cannot be denied that the welding state becomes unstable due to this. Incidentally, the variation in the welded state is not a problem as long as the joining strength between the first and second members is only ensured. However, when watertightness (sealability) is required at the welded portion, such as when the first member and the second member are joined to form an airtight container, leakage may occur at a poorly welded portion. There is. In order to prevent such problems, it may be possible to increase the manufacturing accuracy of the first member and the second member in advance. However, there is a problem that the manufacturing cost of the first and second members is increased. is there.

The present invention has been made in view of such circumstances, and the object thereof is to laser-weld a first resin material that transmits laser light and a second resin material that absorbs laser light. At this time, it is an object of the present invention to provide a laser welding method capable of easily forming a welded portion having a high bonding strength and a stable state capable of sufficiently ensuring water tightness (sealability).
Another object of the present invention is to provide a housing having a structure suitable for, for example, a photoelectric sensor, which is realized by using the laser welding method.

  In the present invention, a first resin material that easily transmits laser light and a second resin material that does not easily transmit laser light compared to the first resin material are butted together, and the width of the butted surface In the experimental process of laser welding the first and second resin materials while moving the irradiation position of the laser beam with a small spot diameter, compared to the first laser welding trace in which the welded portion is linearly formed, The second laser welding trace in which a linear weld portion is formed in the vicinity is more uniform and there is no variation in the welding width. Then, when the first laser welding trace and the second laser welding trace are verified, the second laser welding trace has a stable state of welding, such as a decrease in foaming observed in the first laser welding trace. The present invention has been made based on this fact.

Therefore, in order to achieve the above-described object, the laser welding method according to the present invention includes a first resin material that transmits a laser beam and a second resin material that absorbs the laser beam, which are brought into contact with each other. When the laser beam is irradiated from the side toward the second resin material to bond the first resin material and the second resin material to each other,
After irradiating laser light from the first resin material side to preliminarily form a weld portion at the abutting portion with the first and second resin materials, laser light is again irradiated in the vicinity of the weld portion. The first resin material and the second resin material are welded to each other in close contact (main welding).

Incidentally, as the laser beam, the spot diameter at the irradiation site is smaller than the width of the butt portion between the first resin material and the second resin material, and the irradiation of the laser beam is as follows. It is desirable to carry out in a state where a pressure is applied between the first resin material and the second resin material which are abutted with each other.
Further, in the case where the first resin material and the second resin material are bonded to each other to form a sealed container, a butt portion between the first resin material and the second resin material The welding position of the laser beam is moved along the continuous direction of the joining end surfaces of the sealed container to form the welded portion in a linear shape (preliminary welding treatment), and further in the vicinity of the linear welded portion. It is desirable to weld the first resin material and the second resin material in a water-tight manner (main welding process) by continuously moving the irradiation position of the laser beam along the welding portion.

Further, a housing according to the present invention includes a first resin material having translucency with respect to laser light, and a second resin material that is less likely to transmit laser light than the first resin material, The first resin material and the second resin material are irradiated with laser light from the first resin material side toward the second resin material with respect to the butted portions of the first and second resin materials that are butted against each other. The butt portion with the resin material is formed in close contact with each other,
The first and second resin materials are linearly formed in the vicinity of the first laser welding portion formed linearly with respect to the longitudinal direction of the joint portion and the first laser welding portion. It is characterized by being joined by the second laser welding portion.

  By the way, the first resin material and the second resin material are formed to be in contact with each other to form a sealed container.

  According to the laser welding method of the present invention, the first resin material and the second resin material can be easily and stably joined (laser) by the main weld portion formed in the vicinity of the preliminarily formed weld portion. Welding). In particular, it is possible to sufficiently increase the bonding strength between the first resin material and the second resin material, and even when water tightness (sealability) at the butt portion (joining portion) is necessary, A laser welding portion in a stable state that can sufficiently satisfy the requirement can be easily formed.

  Moreover, according to the housing | casing which concerns on this invention, the structure which fully heightened the joint strength of the 1st resin material and the 2nd resin material can be implement | achieved.

The figure which shows the structural example of the photoelectric sensor assembled using the laser welding method which concerns on this invention. The figure which shows schematic sectional structure of the housing | casing of the photoelectric sensor shown in FIG. The figure which shows the structure of the laser welding part of the 1st member and the member of the site | part 2 typically. The figure which shows the process concept of the laser welding method which concerns on this invention. The figure which shows the form of the verification experiment for confirming the effect by the laser welding method which concerns on this invention. The figure which shows the form of another verification experiment for confirming the effect by the laser welding method which concerns on this invention.

Hereinafter, a laser welding method according to an embodiment of the present invention will be described.
The laser welding method according to the present invention basically includes each of a first resin material that transmits laser light (for example, PAR; polyarylate) and a second resin material that absorbs laser light (for example, PC; polycarbonate). The joining surfaces are brought into contact with each other, and laser light having a spot diameter smaller than the width of the joining surface (joining surface) is irradiated from the first resin material side toward the second resin material to irradiate laser light on the joining surface. After the part is melted, the melted portion is solidified by cooling (heat removal), thereby joining (welding) the first and second resin materials to each other.

  Such a laser welding method is used, for example, for assembling a housing of an optical sensor device as shown in FIG. Incidentally, the optical sensor device is configured by housing a circuit board 3 on which the light emitting element 1 and the light receiving element 2 are mounted in a sealed housing 4 made of synthetic resin. The hermetic casing 4 has, for example, a rising wall that surrounds the periphery of a flat bottom surface, and each of the open end faces 5a of the box-shaped first member 5 and the second member 6 with one end thereof open. 6a is abutted against each other, and the abutting surfaces (joint surfaces) are joined in a watertight manner.

  The first and second members 5 and 6 have, for example, an external shape having a vertical width of 10 mm, a horizontal width of 5 mm, and a height of about 2 mm, and the thickness of the bottom plate portion and the wall portion is set to about 0.8 mm. And a box-shaped injection-molded product in which the space for accommodating the circuit board 3 is formed in a concave shape. In particular, the second member 6 is made of the above-described second resin material that absorbs the laser beam, and the circuit board 3 is positioned and accommodated in each direction (width, depth, depth) inside thereof. A boss (not shown) is provided. The first member 5 is made of the first resin material that transmits the laser light described above, and lenses 5b and 5b are integrally formed on the bottom surface thereof. It should be noted that the lenses 5b and 5b manufactured separately can be integrated with each other by bonding them to the first member 5. These lenses 5b and 5b are light-emitting elements mounted on the circuit board 3 when the circuit board 3 is housed inside and the open end surfaces 5a and 6a of the first and second members 5 and 6 are brought into contact with each other. The optical system is formed facing the element 1 and the light receiving element 2, respectively.

  In the laser welding of the first and second members 5 and 6, first, the first and second members 5 and 6 having the above-described structure are brought into contact with each other, and the first and second members are used using a jig (not shown). The above-mentioned state is maintained by applying a pressure that does not cause distortion to the fifth and sixth members. Next, in this state, as shown in FIG. 2, from the first member 5 side toward the open end surfaces 5a and 6a that are the butting surfaces, for example, the beam diameter is narrowed to 0.1 to 0.4 mm, An infrared laser beam L having a wavelength of 800 to 1000 nm is irradiated, and the first and second members 5 and 6 are welded (laser welding) at the irradiated portion of the laser beam. At this time, the irradiation position of the laser beam L is continuously moved along the open end surfaces 5a and 6a in a so-called one-stroke manner, so that the entire circumference of the open end surfaces 5a and 6a is extended. Continuous seam welding. The seam welding referred to in the present invention is a water-tightness (sealing property) that does not cause an abnormality in the operation of the sensor device when, for example, ambient moisture enters the sensor device in the environment where the sensor device is used. ).

  The laser welding here is performed as described above while leaving an unwelded region A between the open end surfaces (butting surfaces) 5a and 6a of the first and second members 5 and 6 butted to each other as shown in FIG. Only the irradiated portion of the laser beam L having a small diameter is locally melted, and thereby the first and second members 5 and 6 are welded. At this time, the melting of the second member 6 is locally generated by generating heat by absorbing the energy of the laser beam transmitted through the first member 5, and the melting of the first member 5 is the second This is caused by the propagation of the heat of fusion of the member 6. Then, as the irradiation position of the laser beam L is moved, the temperature of the portion where the laser beam is not irradiated is lowered, and the constituent materials of the first and second members 5 and 6 melted as described above are mixed with each other. Harden. The portion where the first and second members 5 and 6 are welded in a short time due to the curing of these melted portions and the laser beam L is not irradiated is the unwelded region A as the laser beam L. Are left on both sides of the irradiation locus (broken line X in FIG. 1).

  This unwelded region A defines the mechanical assembly positional relationship between the first and second members 5 and 6 and ensures the assembly accuracy (dimensional accuracy). In other words, assuming that all of the open end faces (butting faces) 5a, 6a of the first and second members 5, 6 are laser welded, the above-mentioned butting faces 5a of the first and second members 5, 6 are as follows. , 6a and pressurization between the first and second members 5 and 6 may cause a deviation in the assembly dimensions. In order to prevent such a problem, laser welding is performed between the first and second members 5 and 6 while maintaining the assembly size by the unwelded region A.

  Here, the laser welding method according to the present invention will be described. As shown in FIGS. 4 (a) to 4 (c), the concept is as follows. First, as a preliminary welding process, the first member (first resin material) 5 side is used. After irradiating the laser beam L to form the welded portion B1 at the abutting portion with the first and second resin materials (first resin material) 6, the laser is again applied in the vicinity of the welded portion B1 as the main welding process. By irradiating light L, the first and second members (resin materials) 5 and 6 are brought into close contact with each other and completely welded.

  Specifically, the joint surfaces of the first and second members 5 and 6 are butted against each other, and pressure is applied to the first and second members 5 and 6 so as not to cause distortion. To maintain. In this state, first, the first laser welding process is performed as the preliminary welding process (see FIG. 4B), and then the second laser welding process is performed as the main welding process in the vicinity of the first laser welding part. Is executed (see FIG. 4C).

  Here, when the first and second members 5 and 6 are linearly laser welded, the welding mark C1 in the first (first) welding process (preliminary welding) and the second (second) welding process are performed. When examining the welding mark C2 in (main welding), the width of the welding mark C1 by the preliminary welding is irregular as shown in FIG. 4 (a). It was confirmed that the width of the welding mark C2 was uniform and stable. Further, when the cross section of the joint was examined, as shown in FIG. 4C, a minute gap exists between the first member 5 and the second member 6 in the vicinity of the welded portion B1 formed by the preliminary welding. It was confirmed that the first and second members 5 and 6 were in close contact with each other in the vicinity of the welded part B2 by the main welding.

  Incidentally, the minute gap existing in the vicinity of the welded portion B1 is caused by the accuracy of parts (flatness of the joint surface) such as warpage or sinking (sink) present in the first and second members 5 and 6. It is thought to be a thing. The reason why the vicinity of the second welding portion B2 by the main welding is highly adhered and a uniform and stable laser welding mark C2 is obtained is that the first and second members in the first laser welding (preliminary welding). When 5 and 6 are heated locally (for example, at 300 ° C.) and then returned to room temperature, shrinkage due to cooling occurs in the thickness direction even in the vicinity of the irradiated portion of the laser beam L, and the above-described minute gap is compressed. In the first laser welding (preliminary welding), the irradiated portion of the laser beam L in the first and second members 5 and 6 and the vicinity thereof are equal to or higher than the thermal deformation temperature, This is considered to be a result of the first and second members 5 and 6 being thermally deformed so as to fill the minute gap described above. Then, by applying the second laser welding (main welding) to the portion where the minute gap is compressed as described above in the vicinity of the first laser welding mark C1 by the preliminary welding, the first and second members 5, It is presumed that 6 was welded in close contact with each other, and a good laser welding mark C2 was obtained.

  In order to confirm the effects of such preliminary welding and main welding, the present inventors conducted the following verification experiment. Specifically, a first resin material (PAR; polyarylate) 5 and a second resin material (PC: polycarbonate) 6 made of a flat plate having a thickness of 3 mm are prepared, and are superposed and a pair of glass plates ( The first and second resin materials 5 and 6 were laser welded in a circular shape as shown in FIGS. 5 (a) to 5 (e).

  5 (a) and 5 (b) show how laser welding (fine welding) is performed by drawing circles having a diameter of 10 mm and a diameter of 20 mm with laser light L narrowed down to a spot diameter of 0.05 mm. ing. FIG. 5C shows a state in which the spot diameter is increased to 0.15 mm and laser welding (strong welding) is performed by drawing a circle having a diameter of 15 mm with the laser beam L having an increased intensity. In FIG. 5 (d), a laser welded portion strongly welded as shown in FIG. 5 (c) is used as a preliminary weld, and a laser beam L having a spot diameter of 0.05mm is used for laser welding of a circle having a diameter of 10mm. It shows the appearance of fine welding. Further, FIG. 5 (e) shows a laser welding portion preliminarily welded with laser welding as shown in FIG. 5 (c), and a laser beam L having a spot diameter of 0.05mm is used as a laser beam L on the outer side. The state of welding (fine welding) is shown.

  When laser welding traces of these laser welded samples were observed, as shown in FIGS. 5 (a) and 5 (b), the laser welding traces in which a circle having a diameter of 10 mm and a diameter of 20 mm was finely welded were Unstable phenomena such as bubbles were included and the weld width varied. Further, even in the laser welding traces that were strongly welded as shown in FIG. 5 (c), unstable phenomena such as the inclusion of air bubbles and fluctuations in the welding width were observed. On the other hand, as shown in FIGS. 5 (d) and 5 (e), the laser-welded portion strongly welded as shown in FIG. 5 (c) is pre-welded, and has a diameter of 10 mm and a diameter of 20 mm inside and outside thereof. It was confirmed that bubbles were reduced in the laser welding trace formed by finely welding the circle (main welding), and that the welding width was substantially uniform over the entire circumference. In other words, when a laser beam L having a spot diameter of 0.05 mm is used to laser weld (finely weld) a circle having a diameter of 10 mm or 20 mm, the vicinity of a circular weld mark preliminarily welded as shown in FIG. It was confirmed that very stable laser welding can be performed by forming the film in the thickness.

  It should be noted that the pressure for overlapping the first resin material (PAR) 5 and the second resin material (PC) 6 is reduced from 0.5 MPa to 0.3 MPa, and the other conditions are the same as described above. When laser welding experiment was conducted, it was confirmed that the same effect as the previous experiment was obtained. From this, the pressure for sandwiching the first resin material (PAR) 5 and the second resin material (PC) 6 hardly depends on the result of laser welding, and rather whether or not good laser welding can be obtained. This is considered to be whether or not preliminary welding has been performed.

  Moreover, it verified also about the case where the 1st resin material (PAR; polyarylate) 5 and the 2nd resin material (PC; polycarbonate) 6 which were mentioned above were used and laser-welded linearly. FIG. 6 (a) shows a state where laser welding (fine welding) is performed linearly with a laser beam L narrowed down to a spot diameter of 0.05 mm, and FIG. 6 (b) shows a spot diameter of 0.5mm. The figure shows a state in which laser welding (strong welding) is linearly performed with a laser beam L which is as thick as 15 mm and has an increased intensity. In FIG. 6C, the laser welding portion strongly welded as shown in FIG. 6B is used as a preliminary welding, and the above welding is performed using a laser beam L having a spot diameter of 0.05 mm at a position 1 mm away from the welding portion. A state in which laser welding (fine welding) is performed linearly in parallel with the portion is shown. Further, in FIG. 6D, the laser welding portion strongly welded as shown in FIG. 6B is used as a preliminary welding, and a laser beam L having a spot diameter of 0.05 mm is used at positions 1 mm and 2 mm away from the welding portion. The laser welding (fine welding) is shown in a straight line parallel to the welded portion.

  Even when laser welding is performed linearly in this way, as shown in FIGS. 6A and 6B, when laser welding is performed by simply forming one line, It was found that bubbles were observed at the center of the welding mark and that the welding width became unstable. However, as shown in FIGS. 6 (a) and 6 (b), the first laser welding shown in FIG. 6 (b) is used as a preliminary welding, and the second laser welding (main welding) is performed in the vicinity of the welding portion. When it performed, it has confirmed that the laser welding trace in this welding was very stable.

  Thus, as shown in the laser welding method according to the present invention, when the first resin material that transmits laser light and the second resin material that absorbs laser light are brought into contact with each other and laser welding is performed, first and After the second resin material is pre-welded, the first and second resin materials can be welded very well by performing main welding in the vicinity thereof. In particular, when the first resin material and the second resin material are continuously welded in a linear shape, the first resin material and the second resin material are securely adhered along the linear laser welding trace. Since the welded portion can be stably formed with a uniform width, it is possible to stably and reliably ensure water tightness (sealability) at the welded portion. Moreover, it is possible to achieve a practically excellent effect that a stable and high-quality welding can be realized simply by performing the main welding in the vicinity of the pre-welded portion.

  Therefore, only a certain degree of manufacturing accuracy (finished surface accuracy) of the first and second parts made of the first and second resin materials is ensured, in other words, the finished surface accuracy of the joint surface is sufficiently increased. Without this, the first component and the second component can be reliably laser-welded. Further, even when water tightness (sealability) at the welded portion is required, such an effect that the request can be satisfied easily and reliably is exhibited.

  The present invention is not limited to the embodiment described above. For example, polymethyl methacrylate (PMMA) or the like may be used as the first resin material, and acrylonitrile-butadiene-styrene (ABS) containing a carbon filler may be used as the second resin material. That is, various materials can be used as appropriate for the first resin material and the second resin material. Further, here, the case where the laser welded portion is formed in a linear shape and the water tightness (sealability) at the welded portion is secured has been described as an example. However, the welded portion is formed in a spot shape and the first resin material is formed. The second resin material can be reliably laser-welded to increase the bonding strength.

  In particular, the casing according to the present invention is particularly suitable for use as a casing of a device that encloses an electronic circuit in the casing and requires a predetermined water tightness or a device that requires a predetermined strength. For example, the first resin material is used to form a box with one side opened, and the second resin material is used to form a lid that closes the opening of the box, and the electronic circuit is stored in the box. It is suitable for forming a sealed container-like casing by closing the opening of the box with the lid. In this case as well, the first resin material and the second resin material are joined by two weldings in the same manner as described above, thereby increasing the bonding strength between the two resin materials and ensuring the sealing performance at the welded portion. What is necessary is just to manufacture a housing | casing.

  In addition, when it is necessary to lay a cable for mutually connecting other electronic devices or batteries provided outside the casing and an electronic circuit built in the casing, the cable is attached to the casing. It is necessary to provide a cable pull-out hole for inserting the cable. In this case, in addition to the sealing performance at the welded portion described above, the sealing performance as the housing is ensured by using an appropriate technique such as separately sealing the cable drawing hole after inserting the cable. It is possible.

  In addition, with regard to the preliminary welding, only the portion where it is assumed that the main welding cannot be reliably performed, specifically, the vicinity of the welding start portion in the case of laser welding in a linear shape, the first and second portions It is also possible to perform the assisting only on the part where the part is easily affected by warpage or sinking. In addition, when a site (welding line) to be laser-welded between the first and second parts is determined in advance, it is sufficient to perform preliminary welding in parallel with the welding line. In addition, the separation distance between the pre-welded part and the main-welded part varies depending on the materials (specifications) of the first and second resin materials, the intensity of the laser beam, and the like, but a general resin material is laser-welded. In that case, it is sufficient if it is within a range of about 2 mm. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 1 Light emitting element 2 Light receiving element 3 Circuit board 5 1st member (1st resin material)
5b Lens 6 Second member (second resin material)

Claims (3)

A first resin material having translucency with respect to laser light and a second resin material that is less likely to transmit laser light than the first resin material are brought into contact with each other, and the first resin material side When the first resin material and the second resin material are bonded to each other by irradiating a laser beam toward the second resin material,
The first and second resin materials are irradiated from the first resin material side with a laser beam having a spot diameter smaller than the width of the abutting portion between the first resin material and the second resin material. After performing preliminary welding to form a welded portion at the abutting portion, a laser beam having a spot diameter smaller than that of the preliminary welding and having a lower intensity than the preliminary welding is irradiated again in the vicinity of the welded portion. And performing a laser welding process.   2. The laser welding method according to claim 1, wherein the laser light irradiation is performed in a state in which a pressure is applied between the first resin material and the second resin material that face each other. The first resin material and the second resin material are butted against each other to form a sealed container,
The irradiation of the laser beam is performed by moving the irradiation position along the continuous direction of the joining end surface of the sealed container formed by the abutting portion of the first resin material and the second resin material. The first resin is formed by carrying out the main welding by continuously moving the irradiation position along the welded portion in the vicinity of the linear welded portion after the preliminary welding is performed. The laser welding method according to claim 1, wherein water-tight welding is performed between a material and the second resin material.

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