Laser joining method and laser joined product

Abstract

To provide a laser joining method which can suppress deformation of an inner surface of an inside cylindrical member when two cylindrical members are welded and joined to each other with a laser beam.SOLUTION: A laser joining method includes: an insertion step of welding and joining a first cylindrical member 2 having a first inner cavity 21 and a second cylindrical member 3 having a second inner cavity 31 by irradiation of a laser beam L, and inserting at least a part of the second cylindrical member 3 into the first inner cavity 21; a rotation step of integrally rotating the first cylindrical member 2 and the second cylindrical member 3; and a laser irradiation step of irradiating a part where the first cylindrical member 2 and the second cylindrical member 3 overlap each other in the first cylindrical member 2 and the second cylindrical member 3 rotated in the rotation step, with the laser beam L from outside in a radial direction of the first cylindrical member 2. The laser irradiation step radiates the laser beam L to a position where it passes through boundaries a1 and a2 between the first cylindrical member 2 and the second cylindrical member 3 and does not advance the second inner cavity 31.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a laser bonding method and a laser-bonded formed body for welding and joining two cylindrical members by irradiating them with laser light.

Background Art

[0002] Conventionally, in the medical field, automotive field, etc., a laser bonding method has been proposed for welding and joining two resin-made cylindrical members by laser (see, for example, Patent Document 1). The laser bonding method proposed in Patent Document 1 is a method of joining by laser by irradiating laser light from the outside in the radial direction to a portion where the outer cylindrical member and the inner cylindrical member overlap in a state where at least a part of the inner cylindrical member is arranged in the space inside the outer cylindrical member and they overlap in the radial direction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When two cylindrical members are welded by laser, the inside of the inner cylindrical member arranged inside may expand and deform due to heat, and the inner surface of the inner cylindrical member may be deformed. If the inner surface of the inner cylindrical member is deformed, for example, when the cylindrical member is used as a flow path for a liquid or gas, the uniformity of the flow path may be impaired, and the transportability of the liquid or gas may be reduced.

[0005] Therefore, an object of the present invention is to provide a laser bonding method and a laser-bonded formed body capable of suppressing deformation of the inner surface of the inner cylindrical member when two cylindrical members are welded and joined by laser light.

Means for Solving the Problems

[0006] The present invention relates to a laser welding method for welding and joining a first cylindrical member having a first inner cavity and through which laser light can pass and a second cylindrical member having a second inner cavity and through which laser light can pass by irradiating the laser light. The method includes an insertion step of inserting at least a part of the second cylindrical member into the first inner cavity with an outer peripheral surface thereof in contact with the first inner cavity, a rotation step of integrally rotating the first cylindrical member and the second cylindrical member about a central axis of the first cylindrical member and the second cylindrical member as a rotation center, and a laser irradiation step of irradiating laser light from an outer side in a radial direction of the first cylindrical member to a portion where the first cylindrical member and the second cylindrical member overlap each other in the first cylindrical member and the second cylindrical member rotated in the rotation step. In the laser irradiation step, the laser light is irradiated to a position that passes through a boundary between the first cylindrical member and the second cylindrical member and does not enter the second inner cavity.

[0007] Further, in the laser irradiation step, when a position of the laser light when the optical path is incident on the first cylindrical member at an incident angle of 90 degrees and passes through the central axes of the first cylindrical member and the second cylindrical member is defined as a reference position, a distance in a plane orthogonal to a direction of the central axis between an incident position of the irradiated laser light on the first cylindrical member and the reference position is defined as x, a distance between an incident position of the laser light when the optical path of the irradiated laser light contacts the second inner cavity and the reference position is defined as x1, and a distance between an incident position of the laser light when the optical path of the irradiated laser light contacts the first inner cavity and the reference position is defined as x2, it is preferable to satisfy the following formula (1): x1 ≦ x ≦ x2 ··· (1).

[0008] In the laser irradiation step, when the optical path enters the first cylindrical member at an incident angle of 90 degrees and passes through the central axes of the first cylindrical member and the second cylindrical member, and the position of the laser beam is taken as the reference position, when the distance in the plane perpendicular to the direction of the central axis between the incident position of the irradiated laser beam on the first cylindrical member and the reference position is x, the following formula (2): di*Na / 2N 0 ≦x≦do*Na / 2N 0 ····(2) (where di is the inner diameter of the second cylindrical member, do is the outer diameter of the second cylindrical member, Na is the refractive index of the first cylindrical member and the second cylindrical member, N 0 represents the refractive index of air) is preferably satisfied.

[0009] The present invention also relates to a laser-bonded formed body manufactured by a laser bonding method in which a first cylindrical member having a first inner cavity and through which laser light can pass and a second cylindrical member having a second inner cavity and through which laser light can pass are welded and joined by irradiating laser light. The laser bonding method includes an insertion step of inserting at least a part of the second cylindrical member into the first inner cavity with the outer peripheral surface in contact with the first inner cavity, a rotation step of integrally rotating the first cylindrical member and the second cylindrical member about the central axes of the first cylindrical member and the second cylindrical member as the rotation center, and a laser irradiation step of irradiating laser light from the outside in the radial direction of the first cylindrical member to the overlapping portion of the first cylindrical member and the second cylindrical member in the first cylindrical member and the second cylindrical member rotated in the rotation step. In the laser irradiation step, the laser-bonded formed body is manufactured such that the laser light is irradiated to a position that passes through the boundary between the first cylindrical member and the second cylindrical member and does not enter the second inner cavity, so that the blockage rate of the second inner cavity is less than 50%.

Advantages of the Invention

[0010] According to the present invention, when two cylindrical members are welded and joined by laser light, it is possible to provide a laser bonding method capable of suppressing deformation of the inner surface of the inner cylindrical member.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0012] Hereinafter, an embodiment of the laser joining method of the present invention will be described with reference to the drawings. The laser joining method of the present invention is used, for example, when manufacturing the extension tube 10 of the infusion circuit 100 for drug administration.

[0013] As shown in FIG. 1, the infusion circuit 100 for drug administration includes an extension tube 10 manufactured by the laser joining method according to the present invention. The extension tube 10 has a plurality of connectors 11 (one - end connector 12, intermediate connector 13, the other - end connector 14) and a plurality of tubes 15, and the plurality of tubes 15 are connected by the plurality of connectors 11 to be configured.

[0014] In this embodiment, the extension tube 10 includes a one-end connector 12, an intermediate connector 13, an other-end connector 14, a tube 15 connecting the one-end connector 12 and the intermediate connector 13, and a tube 15 connecting the intermediate connector 13 and the other-end connector 14. The one-end connector 12 and the tube 15 are welded and joined by irradiating laser light. The intermediate connector 13 and the tube 15 are welded and joined by irradiating laser light. The other-end connector 14 and the tube 15 are welded and joined by irradiating laser light.

[0015] For example, the one-end connector 12 is disposed at the end of the extension tube 10. Therefore, when welding and joining the one-end connector 12 and the tube 15 by irradiating laser light, with the one-end connector 12 disposed outside the tube 15, a core material for suppressing deformation of the inner surface of the tube 15 is disposed inside the tube 15, and by irradiating laser light from the outside of the one-end connector 12, the one-end connector 12 and the tube 15 can be welded and joined. The same applies when welding and joining the other-end connector 14 and the tube 15 by irradiating laser light.

[0016] On the other hand, for example, the intermediate connector 13 is disposed in the middle of the extension tube 10. Therefore, when welding and joining the intermediate connector 13 and the tube 15 by irradiating laser light, when the tube 15 is connected to both ends of the intermediate connector 13, it is difficult to insert the core material. Further, it is similarly difficult to remove the core material after welding.

[0017] Therefore, when welding and joining the intermediate connector 13 and the tube 15 by irradiating laser light, with the intermediate connector 13 disposed outside the tube 15, without disposing the core material inside the tube 15, by irradiating laser light from the outside of the intermediate connector 13, the intermediate connector 13 and the tube 15 are welded and joined.

[0018] As shown in FIG. 2, the present invention is a laser bonding method suitably used when, with an intermediate connector 13 disposed outside a tube 15, a core material is not disposed inside the tube 15 and laser light L is irradiated from the outside of the intermediate connector 13 for welding and joining.

[0019] As shown in FIG. 2, in the present embodiment, the intermediate connector 13 will be described as an outer cylindrical member 2 (first cylindrical member). The outer cylindrical member 2 is formed in a cylindrical shape extending in the direction in which the central axis O extends. The ends of the tube 15 as the inner cylindrical member 3 are inserted inside both ends of the outer cylindrical member 2 in the direction in which the central axis O extends.

[0020] Also, the tube 15 will be described as an inner cylindrical member 3 (second cylindrical member). The inner cylindrical member 3 is formed in a cylindrical shape extending in the direction in which the central axis O extends. The end of the inner cylindrical member 3 is disposed inside the end of the intermediate connector 13 as the outer cylindrical member 2.

[0021] The laser bonding method of the present embodiment is a method of welding and joining an intermediate connector 13 as an outer cylindrical member 2 (first cylindrical member) and a tube 15 as an inner cylindrical member 3 (second cylindrical member) by irradiating laser light L. By welding and joining the outer cylindrical member 2 and the inner cylindrical member 3 by the laser bonding method of the present embodiment, a laser-bonded formed body 1 is manufactured.

[0022] As shown in FIG. 2, the outer cylindrical member 2 is formed in a cylindrical shape and extends in the direction of the central axis O. The outer cylindrical member 2 has a first inner cavity 21. The first inner cavity 21 extends with the same diameter in the direction of the central axis O. The outer cylindrical member 2 is transmissive to the laser light L. In the present embodiment, the outer cylindrical member 2 is constituted by, for example, an intermediate connector 13 made of resin.

[0023] The inner cylindrical member 3 is formed in a cylindrical shape and extends in the direction of the central axis O. The inner cylindrical member 3 is inserted into the first inner cavity 21 of the outer cylindrical member 2 with its outer peripheral surface in contact with the first inner cavity 21. The inner cylindrical member 3 has a second inner cavity 31. The second inner cavity 31 extends with the same diameter in the direction of the central axis O. The inner cylindrical member 3 is transmissive to the laser light L. In the present embodiment, the inner cylindrical member 3 is constituted by, for example, a long resin tube 15.

[0024] The outer cylindrical member 2 and the inner cylindrical member 3 are molded bodies formed of a resin material. The resin materials forming the outer cylindrical member 2 and the inner cylindrical member 3 may be the same type of resin material or different types of resin materials. The outer cylindrical member 2 and the inner cylindrical member 3 are formed of, for example, a polyolefin resin such as polypropylene (PP) or a resin such as polycarbonate (PC).

[0025] In the present embodiment, as shown in FIG. 3, for example, for the outer cylindrical member 2, the outer diameter is Do, the inner diameter is Di, and the refractive index is Na. Also, for example, for the inner cylindrical member 3, the outer diameter is do, the inner diameter is di, and the refractive index is Nb.

[0026] In the present embodiment, for example, since both the outer cylindrical member 2 and the inner cylindrical member 3 are formed of the same type of resin material such as polypropylene (PP), the refractive index Na is approximately equal to the refractive index Nb. For example, in the case of polypropylene (PP), the refractive index is 1.48.

[0027] Also, when both the outer cylindrical member 2 and the inner cylindrical member 3 are made of a resin material, even if the types of the resin materials are different, the difference in the refractive indices between different types of resin materials is almost negligible compared to the difference between the refractive index of the resin material and the refractive index of air. Therefore, even if the types of the resin materials of the outer cylindrical member 2 and the inner cylindrical member 3 are different, the refractive index Na of the outer cylindrical member 2 and the refractive index Nb of the inner cylindrical member 3 can be approximated to be almost the same.

[0028] Even when the refractive index Na ≠ refractive index Nb, at the boundary between the outer cylindrical member 2 and the inner cylindrical member 3, the refraction angle based on Snell's law is calculated, and the refracted laser light passes through the boundaries a1, a2 between the outer cylindrical member 2 and the inner cylindrical member 3 and does not enter the second inner cavity 31 of the inner cylindrical member 3 as described later. By controlling the distance x so that the refracted laser light is located between the distance x1 and the distance x2 in the following formula (1), the same effect can be obtained.

[0029] When joining the outer cylindrical member 2 and the inner cylindrical member 3 by the laser joining method of the present invention, the laser joining method performs an insertion step, a rotation step, and a laser irradiation step to join the outer cylindrical member 2 and the inner cylindrical member 3. Thereby, the laser joined molded body 1 is manufactured.

[0030] In the insertion step, as shown in FIGS. 2 and 3, at least a part of the inner cylindrical member 3 is inserted into the first inner cavity 21 of the outer cylindrical member 2. More specifically, in the insertion step, as shown in FIGS. 2 and 3, the portion on one end side of the inner cylindrical member 3 is inserted into the first inner cavity 21 of the outer cylindrical member 2 with the outer peripheral surface in contact with the first inner cavity 21. Thereby, a part of the outer cylindrical member 2 and a part of the inner cylindrical member 3 overlap in the radial direction.

[0031] In the rotation step, as shown in FIG. 3, with at least a part of the inner cylindrical member 3 inserted into the first inner cavity 21 of the outer cylindrical member 2, the outer cylindrical member 2 and the inner cylindrical member 3 are integrally rotated about the central axis O of the outer cylindrical member 2 and the inner cylindrical member 3 as the rotation center. In the present embodiment, in the rotation step, the outer cylindrical member 2 and the inner cylindrical member 3 are integrally rotated counterclockwise about the central axis O of the outer cylindrical member 2 and the inner cylindrical member 3 as the rotation center.

[0032] In the laser irradiation step, as shown in FIG. 3, in the outer cylindrical member 2 and the inner cylindrical member 3 that are being rotated in the rotation step, laser light L is irradiated from the outside in the radial direction of the outer cylindrical member 2 to the overlapping portion of the outer cylindrical member 2 and the inner cylindrical member 3. In the laser irradiation step, the laser light L is irradiated to a position that passes through the boundaries a1 and a2 between the outer cylindrical member 2 and the inner cylindrical member 3 and does not enter the second inner cavity 31 of the inner cylindrical member 3.

[0033] As the laser light, laser light having a wavelength in the near-infrared region or the mid-infrared region (700 to 4000 nm) can be used. For example, laser light having a wavelength of 1200 to 2500 nm is preferable. For example, as the laser light, a Tm laser (thulium laser, wavelength: 2000 nm) having appropriate absorbability can be used in consideration of the absorbability to the resin material.

[0034] In the laser irradiation step, as shown in FIG. 3, when the position of the laser light L when the optical path is incident on the outer cylindrical member 2 at an incident angle of 90 degrees and passes through the central axis O of the outer cylindrical member 2 and the inner cylindrical member 3 is defined as the reference position RP, the distance x in the plane perpendicular to the direction of the central axis O between the incident position of the irradiated laser light L on the outer cylindrical member 2 and the reference position RP is configured to satisfy the relationship of the following formula (1).

[0035] Distance x1 ≤ Distance x ≤ Distance x2 ··· (1) The distance x1 is the distance between the incident position P1 of the laser light L1 when the optical path of the irradiated laser light L is in contact with the second inner cavity 31 of the inner cylindrical member 3 and the reference position RP. The distance x2 is the distance between the incident position P2 of the laser light L2 when the optical path of the irradiated laser light L is in contact with the first inner cavity 21 of the outer cylindrical member 2 and the reference position RP.

[0036] When the relationship of formula (1) is satisfied, as shown in FIG. 3, the laser light L incident in the range from the distance x1 to the distance x2 passes through the boundaries a1 and a2 between the outer cylindrical member 2 and the inner cylindrical member 3 and is irradiated to a position that does not enter the second inner cavity 31 of the inner cylindrical member 3.

[0037] Here, the position where the laser beam L does not enter the second inner cavity 31 of the inner cylindrical member 3 means a position where the optical axis of the laser beam L does not enter the second inner cavity 31 of the inner cylindrical member 3. If the optical axis of the laser beam L is a position where it does not enter the second inner cavity 31 of the inner cylindrical member 3, even if the light spreading from the optical axis of the laser beam L enters the second inner cavity 31 of the inner cylindrical member 3, it is a position where the laser beam L does not enter the second inner cavity 31 of the inner cylindrical member 3.

[0038] For example, the laser beam L1 irradiated at a position at a distance x1 from the reference position RP of the laser beam L is incident on the outer cylindrical member 2 at an incident angle α1 at the incident position P1 of the outer cylindrical member 2, refracted at a refraction angle β1, passes through the boundary a1 between the outer cylindrical member 2 and the inner cylindrical member 3, and passes through the position C1 in contact with the second inner cavity 31 of the inner cylindrical member 3. Thereby, at the boundary a1 between the outer cylindrical member 2 and the inner cylindrical member 3, the outer cylindrical member 2 and the inner cylindrical member 3 are welded and joined.

[0039] Also, for example, the laser beam L2 irradiated at a position at a distance x2 from the reference position RP of the laser beam L is incident on the outer cylindrical member 2 at an incident angle α2 at the incident position P2 of the outer cylindrical member 2, refracted at a refraction angle β2, and passes through the boundary a2 between the outer cylindrical member 2 and the inner cylindrical member 3. The boundary a2 between the outer cylindrical member 2 and the inner cylindrical member 3 coincides with the position C2 in contact with the second inner cavity 31 of the inner cylindrical member 3. Thereby, at the boundary a2 between the outer cylindrical member 2 and the inner cylindrical member 3, the outer cylindrical member 2 and the inner cylindrical member 3 are welded and joined.

[0040] Also, regarding the range of the distance x in the above formula (1), it will be more specifically described with reference to FIG. 4. Here, assuming that the outer cylindrical member 2 and the inner cylindrical member 3 are made of the same resin material, the case where the refractive index Na of the outer cylindrical member 2 and the refractive index Nb of the inner cylindrical member 3 are set to the same refractive index Na will be described.

[0041] As shown in FIG. 4, the irradiated laser beam L is a light parallel to the reference laser beam L passing through the reference position RP, and when the refractive index of the outer cylindrical member 2 and the refractive index of the inner cylindrical member 3 are the same refractive index, the distance x in the plane orthogonal to the direction of the central axis O between the incident position of the irradiated laser beam L on the outer cylindrical member 2 and the reference position RP is configured to satisfy the relationship of the following formula (2).

[0042] di*Na / 2N 0 ≦x≦do*Na / 2N 0 ····(2) In formula (2), di is the inner diameter of the inner cylindrical member 3, do is the outer diameter of the inner cylindrical member 3, Na is the refractive index of the outer cylindrical member 2 and the inner cylindrical member 3, and N 0 represents the refractive index of air. Note that the refractive index of the outer cylindrical member 2 and the refractive index of the inner cylindrical member 3 are set to the same refractive index Na.

[0043] For example, the laser beam L1 incident at a distance x1 from the reference position RP is incident at an angle of incidence α1 with respect to the perpendicular to the surface of the outer cylindrical member 2 at the incident position P1, and is refracted at an angle of refraction β1 according to Snell's law and transmitted into the outer cylindrical member 2. The relationship between the angle of incidence α1 and the angle of refraction β1 at this time is given by formula (3a). Na*sinβ1=N 0 *sinα1····(3a) Here, N 0 is the refractive index of air ≒1, and Na is the refractive index of the resin (for example, PP: 1.48).

[0044] As shown in FIG. 4, the relationships of the following formula (3b) and formula (3c) hold. In △OP1R1, sinα1=x1 / (Do / 2)···(3b) In △OP1C1, sinβ1=(di / 2) / (Do / 2)···(3c) Here, Do is the outer diameter of the outer cylindrical member 2, and di is the inner diameter of the inner cylindrical member 3.

[0045] Substituting Eqs. (3b) and (3c) into Eq. (3a) and arranging them, the relationship of the following Eq. (3d) can be obtained. x1 = di * Na / 2N 0 ····(3d)

[0046] Also, for example, the laser beam L2 incident at a distance x2 from the reference position RP is incident at an incident angle α2 with respect to the perpendicular to the surface of the outer cylindrical member 2 at the incident position P2, and is refracted at an angle of the refraction angle β2 according to Snell's law and transmitted into the outer cylindrical member 2. The relationship between the incident angle α2 and the refraction angle β2 at this time is Eq. (4a). Na * sinβ2 = N 0 * sinα2····(4a) Here, N 0 is the refractive index of air ≒ 1, and Na is the refractive index of the resin (for example, PP: 1.48).

[0047] As shown in Fig. 4, the relationships of the following Eqs. (4b) and (4c) hold. In △OP2R2, sinα2 = x2 / (Do / 2)···(4b) In △OP2C2, sinβ2 = (do / 2) / (Do / 2)···(4c) Here, Do is the outer diameter of the outer cylindrical member 2, and do is the outer diameter of the inner cylindrical member 3.

[0048] Substituting Eqs. (4b) and (4c) into Eq. (4a) and arranging them, the relationship of the following Eq. (4d) can be obtained. x2 = do * Na / 2N 0 ····(4d)

[0049] By substituting the thus-derived Eqs. (3d) and (4d) into Eq. (1), Eq. (2) can be obtained.

[0050] Next, the overall flow of the laser bonding method of the present invention will be briefly described. The laser bonding method of this embodiment is a method of welding and bonding the outer cylindrical member 2 and the inner cylindrical member 3 by laser.

[0051] First, as shown in FIGS. 2 and 3, at least a part of the inner cylindrical member 3 is inserted and disposed in the first inner cavity 21 inside the outer cylindrical member 2 (insertion step). Thereby, at least a part of the inner cylindrical member 3 and at least a part of the outer cylindrical member 2 are disposed in a state of being radially overlapped.

[0052] Next, the outer cylindrical member 2 and the inner cylindrical member 3 are integrally rotated about the central axis O of the outer cylindrical member 2 and the inner cylindrical member 3, for example, as shown in FIG. 3 (rotation step).

[0053] Subsequently, laser light L is irradiated from the outside in the radial direction of the outer cylindrical member 2 to the portion where the outer cylindrical member 2 and the inner cylindrical member 3 overlap (laser light irradiation step).

[0054] Here, the laser light L is irradiated so as to satisfy the relationship of x1 ≦ x ≦ x2. Thereby, the laser light L passes between the boundaries a1 and a2 of the outer cylindrical member 2 and the inner cylindrical member 3, but does not pass through the second inner cavity 31 of the inner cylindrical member 3. Therefore, the laser-bonded molded body 1 can be manufactured by satisfactorily joining the outer cylindrical member 2 and the inner cylindrical member 3 while suppressing the melting and deformation of the second inner cavity 31 of the inner cylindrical member 3. The laser-bonded molded body 1 is manufactured such that the closing rate of the second inner cavity 31 of the inner cylindrical member 3 becomes less than 50% by joining the outer cylindrical member 2 and the inner cylindrical member 3.

[0055] The closing rate of the second inner cavity 31 of the inner cylindrical member 3 is the ratio of the second inner cavity 31 being blocked with respect to the diameter of the second inner cavity 31 of the inner cylindrical member 3 before joining the outer cylindrical member 2 and the inner cylindrical member 3. A state where the second inner cavity 31 is not blocked at all is set to 0%, and a state where the second inner cavity 31 is completely blocked is set to 100%. If the closing rate of the second inner cavity 31 of the inner cylindrical member 3 is less than 50%, the transport performance of transporting liquid or gas can be ensured.

[0056] According to the laser bonding method of the present embodiment described above, the following effects can be obtained.

[0057] In the laser bonding method of this embodiment, an outer cylindrical member 2 having a first inner cavity 21 and an inner cylindrical member 3 having a second inner cavity 31 are welded and joined by irradiating a laser beam L, and at least a part of the inner cylindrical member 3 is inserted into the first inner cavity 21. The method includes an insertion step, a rotation step of integrally rotating the outer cylindrical member 2 and the inner cylindrical member 3, and a laser irradiation step of irradiating the laser beam L from the outside in the radial direction of the outer cylindrical member 2 to a portion where the outer cylindrical member 2 and the inner cylindrical member 3 overlap in the outer cylindrical member 2 and the inner cylindrical member 3 being rotated in the rotation step. In the laser irradiation step, the laser beam L is configured to be irradiated to a position that passes through the boundaries a1, a2 between the outer cylindrical member 2 and the inner cylindrical member 3 and does not enter the second inner cavity 31 of the inner cylindrical member 3. Thereby, the laser beam L can be irradiated to a position that does not enter the second inner cavity 31 of the inner cylindrical member 3. Therefore, the outer cylindrical member 2 and the inner cylindrical member 3 can be welded and joined at the boundaries a1, a2 between the outer cylindrical member 2 and the inner cylindrical member 3 while suppressing deformation of the second inner cavity 31 of the inner cylindrical member 3.

[0058] Further, in the laser irradiation step, the distance x in a plane orthogonal to the direction of the central axis O between the incident position of the irradiated laser beam L on the outer cylindrical member 2 and the reference position RP is configured to satisfy the relationship of the following formula (2). di*Na / 2N 0 ≦x≦do*Na / 2N 0 ····(2) In formula (2), di is the inner diameter of the inner cylindrical member 3, do is the outer diameter of the inner cylindrical member 3, Na is the refractive index of the outer cylindrical member 2 and the inner cylindrical member 3, and N 0 represents the refractive index of air. Thereby, by using the inner diameter di of the inner cylindrical member 3, the outer diameter do of the inner cylindrical member 3, the refractive index Na of the outer cylindrical member 2 and the inner cylindrical member 3, and the refractive index N 0 of air, the range of the distance x of the laser beam L can be determined. Further, even if the refractive indices of the outer cylindrical member 2 and the inner cylindrical member 3 are not exactly the same refractive index Na but only slightly different, the range of the distance x of the laser beam L can be simply determined.

[0059] Further, in the laser irradiation step of the laser bonding method, the laser light L is irradiated at a position that passes through the boundary between the outer cylindrical member 2 and the inner cylindrical member 3 and does not enter the second inner cavity 31 of the inner cylindrical member 3, so that the laser-bonded molded body 1 of the present embodiment is manufactured such that the blockage rate of the second inner cavity 31 of the inner cylindrical member 3 is less than 50%. Thereby, a favorable laser-bonded molded body 1 in which deformation of the second inner cavity 31 of the inner cylindrical member 3 is suppressed can be manufactured.

[0060] Note that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within the scope that can achieve the object of the present invention are included in the present invention.

Example

[0061] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. Examples and comparative examples of the laser bonding method according to the present invention will be described.

[0062] In the examples and comparative examples, with a part of the inner cylindrical member 3 inserted into the first inner cavity 21 inside the outer cylindrical member 2 and arranged, the outer cylindrical member 2 and the inner cylindrical member 3 were integrally rotated counterclockwise, and the laser light L was irradiated onto the outer peripheral surface of the outer cylindrical member 2 under the following test conditions. Thereby, the laser-bonded molded body 1 was manufactured.

[0063] In the examples and comparative examples, the outer cylindrical member 2 had an outer diameter (Do) of 5.35 mm, an inner diameter (Di) of 2.7 mm, a material of polypropylene (PP), and a refractive index of 1.48. Further, the inner cylindrical member 3 had an outer diameter (do) of 2.7 mm, an inner diameter (di) of 1.0 mm, a material of polypropylene (PP), and a refractive index of 1.48. Also, the rotation speeds of the outer cylindrical member 2 and the inner cylindrical member 3 were set to 3.5 mm / s, and they were rotated one and a half turns. The scan width of the laser light L was set to 1 mm.

[0064] Also, as shown in FIG. 3, the rotational directions of the outer cylindrical member 2 and the inner cylindrical member 3 are such that when the incident positions P1 and P2 of the laser beam L on the first cylindrical member 2 are shifted from the reference position RP when the laser beam passes through the central axis O of the outer cylindrical member 2 and the inner cylindrical member 3, the rotational direction is the direction in which the incident positions P1 and P2 of the laser beam L on the outer cylindrical member 2 approach the reference position RP side. In the case of this embodiment, the outer cylindrical member 2 and the inner cylindrical member 3 are rotated counterclockwise.

[0065] <Test conditions> In Example 1, the laser beam L was irradiated so that the laser beam L passed through the boundary between the outer cylindrical member 2 and the inner cylindrical member 3 and the relationship x = x1 was satisfied so that the laser beam L did not enter the second inner cavity 31 of the inner cylindrical member 3. In Example 2, the laser beam L was irradiated so that the laser beam L passed through the boundary between the outer cylindrical member 2 and the inner cylindrical member 3 and the relationship x1 < x < x2 was satisfied so that the laser beam L did not enter the second inner cavity 31 of the inner cylindrical member 3.

[0066] In Comparative Example 1, the laser beam L was irradiated so that the relationship x < x1 was satisfied so that the laser beam entered the second inner cavity 31 of the inner cylindrical member 3. In Comparative Example 2, the laser beam L was irradiated so that the relationship x > x2 was satisfied so that the laser beam L did not pass through the boundary between the outer cylindrical member 2 and the inner cylindrical member 3 and did not enter the second inner cavity 31 of the inner cylindrical member 3.

[0067] <Test results> As shown in Fig. 5, in Example 1 and Example 2, no deformed collapse occurred in the second inner cavity 31 of the inner cylindrical member 3 (blockage rate less than 50%) (judgment: OK). The laser beam L passed through the boundary between the outer cylindrical member 2 and the inner cylindrical member 3, and the outer cylindrical member 2 and the inner cylindrical member 3 were well joined (joining state: OK). Therefore, in Example 1 and Example 2, the outer cylindrical member 2 and the inner cylindrical member 3 were well joined without any deformed collapse occurring in the second inner cavity 31 of the inner cylindrical member 3. Thus, the overall judgment was good (OK).

[0068] That is, in Example 1 and Example 2, when the laser beam L passed through the boundary where the outer cylindrical member 2 (first cylindrical member) and the inner cylindrical member 3 (second cylindrical member) overlapped and the laser welded formed body 1 that was well joined was cut along the radial direction of the outer cylindrical member 2 and the inner cylindrical member 3, the deformation of the second inner cavity 31 of the inner cylindrical member 3 was small, and the overlapping part of the outer cylindrical member 2 and the inner cylindrical member 3 was melted and joined.

[0069] In Comparative Example 1, the second inner cavity 31 of the inner cylindrical member 3 was deformed, collapsed, and blocked (blockage rate 100%) (judgment: NG). The laser beam L passed through the boundary between the outer cylindrical member 2 and the inner cylindrical member 3, and the outer cylindrical member 2 and the inner cylindrical member 3 were well joined (joining state: OK). Therefore, since the second inner cavity 31 of the inner cylindrical member 3 was deformed, collapsed, and blocked, the overall judgment was bad (NG).

[0070] In Comparative Example 2, since the laser beam L did not pass through the boundary between the outer cylindrical member 2 and the inner cylindrical member 3, the outer cylindrical member 2 and the inner cylindrical member 3 were not welded (joining state: NG). Therefore, since the outer cylindrical member 2 and the inner cylindrical member 3 were not welded, the overall judgment was bad (NG).

[0071] In the above test results, regarding the deformation of the second inner cavity 31 of the inner cylindrical member 3, when the laser beam L was irradiated so as not to enter the second inner cavity 31 of the inner cylindrical member 3, as in Example 1 and Example 2, no deformed collapse occurred in the second inner cavity 31 of the inner cylindrical member 3. Therefore, it was found that the deformation of the second inner cavity 31 of the inner cylindrical member 3 can be suppressed. On the other hand, when the laser beam L was irradiated so as to enter the second inner cavity 31 of the inner cylindrical member 3, as in Comparative Example 1, the second inner cavity 31 of the inner cylindrical member 3 was deformed, collapsed, and blocked. Therefore, it was found that the deformation of the second inner cavity 31 of the inner cylindrical member 3 cannot be suppressed.

Explanation of Reference Numerals

[0072] 1 Laser welded formed body 2 Outer cylindrical member (first cylindrical member) 3 Inner cylindrical member (second cylindrical member) 21 First inner cavity 31 Second inner cavity L Laser beam O Central axis

Claims

1. A laser joining method for joining a first cylindrical member having a first inner cavity and capable of transmitting laser light to a second cylindrical member having a second inner cavity and capable of transmitting laser light by irradiating the first cylindrical member with laser light, the method comprising the steps of: an inserting step of inserting at least a portion of the second cylindrical member into the first cavity with an outer circumferential surface of the second cylindrical member in contact with the first cavity; a rotating step of rotating the first cylindrical member and the second cylindrical member integrally about central axes of the first cylindrical member and the second cylindrical member; a laser irradiation step of irradiating a laser beam from a radial outside of the first cylindrical member in a direction from the first cylindrical member toward the second cylindrical member to an overlapping portion of the first cylindrical member and the second cylindrical member being rotated in the rotation step, A laser joining method, in which, in the laser irradiation step, laser light is irradiated at a position that passes through the boundary between the first cylindrical member and the second cylindrical member but does not enter the second inner cavity.

2. In the laser irradiation step, When the position of the laser light when the optical path is incident on the first cylindrical member at an incident angle of 90 degrees and passes through the central axes of the first cylindrical member and the second cylindrical member is set as a reference position, a distance on a plane perpendicular to the direction of the central axis between an incident position of the irradiated laser light on the first cylindrical member and the reference position is defined as x; The distance between the incident position of the laser light and the reference position when the optical path of the irradiated laser light is in contact with the second lumen is defined as x1; When the optical path of the irradiated laser light is in contact with the first lumen, the distance between the incident position of the laser light and the reference position is defined as x2, and the following formula (1) is satisfied: x1≦x≦x2 . . . (1) The laser joining method according to claim 1 , which satisfies the following relationship:

3. In the laser irradiation step, When the position of the laser light when the optical path is incident on the first cylindrical member at an incident angle of 90 degrees and passes through the central axes of the first cylindrical member and the second cylindrical member is set as a reference position, When the distance on a plane perpendicular to the direction of the central axis between the incident position of the irradiated laser light on the first cylindrical member and the reference position is defined as x, the following formula (2): <h2 style=";text-align:left;direction:ltr">di*Na / 2N<h2 style=";text-align:left;direction:ltr"> ０ <h2 style=";text-align:left;direction:ltr"> ≦x≦do*Na / 2N<h2 style=";text-align:left;direction:ltr"> ０ <h2 style=";text-align:left;direction:ltr">・・・・(22) (wherein di is the inner diameter of the second cylindrical member, do is the outer diameter of the second cylindrical member, Na is the refractive index of the first cylindrical member and the second cylindrical member, N ０ indicates the refractive index of air) The laser joining method according to claim 1 or 2, which satisfies the relationship:

4. A laser-joined molded product manufactured by a laser joining method in which a first cylindrical member having a first inner cavity and capable of transmitting laser light and a second cylindrical member having a second inner cavity and capable of transmitting laser light are welded and joined by irradiating the first cylindrical member with a laser light, The laser joining method includes: an inserting step of inserting at least a portion of the second cylindrical member into the first cavity with an outer circumferential surface of the second cylindrical member in contact with the first cavity; a rotating step of rotating the first cylindrical member and the second cylindrical member integrally about central axes of the first cylindrical member and the second cylindrical member; a laser irradiation step of irradiating a laser beam from a radial outside of the first cylindrical member to an overlapping portion of the first cylindrical member and the second cylindrical member being rotated in the rotation step, In the laser irradiation process, a laser-jointed molded product is produced by irradiating laser light at a position that passes through the boundary between the first cylindrical member and the second cylindrical member but does not enter the second cavity, so that the blockage rate of the second cavity is less than 50%.

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