JP4584683B2 - Condensing head for laser welding - Google Patents

Description

  The present invention relates to a laser welding condensing head for condensing laser light emitted from, for example, a laser light source on a member to be welded and performing laser welding.

  In the present invention, “substantially parallel” includes “parallel”, “substantially orthogonal” includes “orthogonal”, and “substantially match” includes “match”.

  2. Description of the Related Art Conventionally, a laser beam machine for applying a laser beam to a member to be welded made of metal for welding has been put to practical use. This laser processing machine includes, for example, a laser light source that emits laser light, a condensing head that faces a member to be welded, an optical fiber that guides laser light emitted from the laser light source to the condensing head, a shield gas supply unit, and the like. When laser welding is performed using such a laser processing machine, if a material having a total plate thickness of, for example, 8 mm or more is laser-welded, spherical or substantially spherical cavities generated in the weld metal, so-called blow holes, are likely to occur. As a means for preventing the blowhole, it is possible to expand the keyhole formed during construction, which is a hole formed by penetrating the heat source to the back side of the base material at the tip of the molten pool. Can be mentioned. In order to extend this keyhole, the following techniques (1) to (4) have been proposed (see, for example, Patent Document 1).

  (1) A laser beam is irradiated to a member to be welded from a plurality of positions. (2) The laser beam is emitted while being tilted with respect to the thickness direction of the member to be welded, and is formed into an elliptical beam that becomes elliptical at the condensing position. (3) Irradiate an elliptical beam at the condensing position using a reflective optical system. (4) One cylindrical lens is arranged in the middle of the optical path of the laser beam, and the condensed beam is distorted to make an elliptical beam.

JP-A-6-190575

  In the technique (1) of irradiating laser light from a plurality of positions, the optical system becomes complicated, and it is difficult to configure the optical system only with generally available optical components. In the technique (2) for tilting the laser beam, for example, the condensing head must be tilted with respect to the thickness direction of the member to be welded, so that the arrangement of the apparatus is restricted and the irradiation density of the laser energy is not uniform. become. In the technique using the reflection optical system of (3), not only the optical system becomes complicated, but also the optical axis adjustment at the time of assembly is difficult. In the technique using the cylindrical lens of (4), since the light is condensed at the defocus position, the irradiation density of the laser energy becomes non-uniform as in (2).

  An object of the present invention is to provide a laser welding condensing head capable of making the irradiation density of laser energy uniform and simplifying its structure.

The present invention is a condensing head for laser welding comprising an optical component that condenses laser light emitted from a laser light source onto a member to be welded to be laser welded,
The optical component is
A first lens that substantially parallelizes the laser light emitted from the laser light source;
A second lens disposed between the condensing position of the member to be welded to be laser-welded and the first lens and having a condensing action only in a first direction substantially orthogonal to the optical axis direction;
A third lens disposed between the optical path between the condensing position and the second lens and having a condensing function only in a second direction substantially orthogonal to the optical axis direction and the first direction, A third lens disposed so that a focal position of the third lens substantially coincides with a focal position of the second lens;
A fourth lens disposed between the condensing position and the optical path between the third lens, and a concave lens group, and a convex lens group disposed closer to the condensing position than the concave lens group; The distance from the convex lens arranged on the most downstream side in the optical axis direction to the condensing position by the fourth lens in the convex lens group is longer than the distance between the focal position of the third lens and the third lens. a laser welding condenser head, characterized in that it comprises a fourth lens that will be set.

  According to the present invention, the laser light emitted from the laser light source is focused on the member to be welded via the optical component. The optical component includes first to third lenses. Of these lenses, the first lens collimates the laser light emitted from the laser light source. The second lens is disposed between the condensing position of the member to be welded to be laser welded and the optical path between the first lens. The second lens has a condensing function only in a first direction substantially orthogonal to the optical axis direction. The third lens is disposed between the condensing position and the optical path between the second lens. The third lens has a light collecting function only in the second direction substantially orthogonal to the optical axis direction and the first direction. Further, the third lens is disposed so that the focal position of the third lens substantially coincides with the focal position of the second lens. The second lens has a condensing function only in the first direction, and the third lens has a condensing function only in the second direction, and the focal positions of the second and third lenses are substantially coincident. The laser light emitted from the laser light source is substantially elliptical at the focal position.

The fourth lens is disposed between the optical path between the focusing position and the third lens. This fourth lens expands the focal length of the second and third lenses.

Further, by arranging a combination of a concave lens and a convex lens group, it is possible to increase the focal length of the second and third lens. Therefore, the work distance can be expanded.

The present invention, prior of Kitotsu lens group, wherein the light collection ratio of the optical axis direction upstream and downstream of the convex lens is configured to be changed.

  According to the present invention, among the concave lens group and the convex lens group, the convex lens group is disposed on the most downstream side in the light emitting direction. The condensing size can be similarly changed by changing the condensing ratio of the convex lenses on the upstream side and the downstream side in the light emitting direction of the convex lens group. That is, it is possible to easily change the major and minor axis sizes of the elliptical laser beam that is substantially elliptical at the focal position.

  According to the present invention, the second lens has a focusing function only in the first direction, and the third lens has a focusing function only in the second direction, and the focal points of the second and third lenses. Since the positions substantially coincide with each other, the laser light emitted from the laser light source is substantially elliptical at the focal position. Therefore, it is possible to expand a hole, that is, a keyhole formed by the heat source penetrating to the back side of the base material of the welded member at the tip of the molten pool. This can eliminate blowholes during laser welding. Thus, according to the present invention, it is possible to make the laser beam elliptical at the focal position without irradiating the laser beam with a tilt as in the prior art. Therefore, it is possible to make the irradiation density of the laser energy uniform and simplify the structure.

Also, the fourth lens is disposed between the optical path between the focusing position and the third lens. This fourth lens expands the focal length of the second and third lenses. As a result, it is possible to reduce the contamination of the lens disposed at the tip of the condensing head, that is, the tip facing the member to be welded. Moreover, the influence by radiant heat can be avoided. In addition, it is possible to secure a space in which equipment necessary for welding can be arranged.

Also, by arranging a combination of a concave lens group and the lens group, it is possible to increase the focal length of the second and third lens. Therefore, the work distance can be expanded.

  Further, according to the present invention, the condensing size can be changed similarly by changing the condensing ratio of the convex lenses on the upstream side and the downstream side in the light emitting direction in the convex lens group. That is, it is possible to easily change the major and minor axis sizes of the elliptical laser beam that is substantially elliptical at the focal position. As a result, it is possible to obtain an optimum laser beam according to the construction object.

  FIG. 1 is a system diagram schematically showing a configuration of a laser beam machine 1 according to an embodiment of the present invention. The laser beam machine 1 is for irradiating a member 2 to be welded with laser light for welding. This laser beam machine 1 is applied to, for example, joining of a frame of a vehicle structure and a side structure. However, the application target of the present invention is not limited to a vehicle, that is, a railway vehicle, and includes, for example, an automobile. The laser processing machine 1 mainly includes a laser light source 3, a laser welding condensing head 4, an optical fiber 5, and a shield gas supply means 6. The laser light source 3 can emit laser light. In this embodiment, the laser light source 3 is, for example, a YAG laser that is a solid-state laser, for example, a YAG laser having an oscillator output of 4000 watts. However, the laser light source 3 is not necessarily limited to the YAG laser.

  The condensing head 4 for laser welding is disposed so as to face the member 2 to be welded. Hereinafter, the laser welding condensing head 4 may be simply referred to as the condensing head 4. The condensing head 4 has a function of condensing the laser light emitted from the laser light source 3 on the member 2 to be welded to be laser welded. The optical fiber 5 guides the laser light emitted from the laser light source 3 to the condensing head 4. For example, a fiber having a core diameter of 0.6 mm is applied to the optical fiber 5. The shield gas supply means 6 supplies a gas for blocking the melted portion formed in the member 2 to be welded from the atmosphere. For the member 2 to be welded, for example, a SUS304 stainless steel plate defined in Japanese Industrial Standard (JIS) G4305 is applied.

  FIG. 2 is a perspective view showing an elliptical condensing optical system of the condensing head 4. FIG. 3 shows an elliptical condensing optical system of the condensing head 4, and FIG. 3A shows the elliptical condensing optical system from a direction parallel to the major axis direction of the elliptical shape to be formed at the condensing position F1. FIG. 3B is a view of the elliptical condensing optical system viewed from a direction parallel to the elliptical minor axis direction. This will be described with reference to FIG.

  The condensing head 4 includes a head body 7 and an optical component 8. The condensing head 4 is configured to be movable in the welding line direction. Specifically, the condensing head 4 is mounted on a mount (not shown), for example, and driving means is provided on this mount. By moving the mount, the converging head 4 can be moved in the welding line direction. Conversely, the member to be welded 2 is placed and supported on one surface portion of a table (not shown) that can move in the multi-axis direction, and by moving the table, the condensing head 4 is moved relatively in the welding line direction. You may make it make it.

  The head main body 7 holds an optical component 8 (described later) and one end portion 5a of the optical fiber 5, and is made of, for example, a metal and has a bottomed substantially cylindrical shape. The head body 7 includes, in order along the optical axis direction, one end portion 5a of the optical fiber 5, a collimating lens 9 as a first lens, a first cylindrical lens 10, and a second cylindrical lens 11. Retained. A cylindrical lens is synonymous with a “cylindrical lens”. The other end of the optical fiber 5 is held by the laser light source 3. The first cylindrical lens 10 corresponds to a second lens, and the second cylindrical lens 11 corresponds to a third lens. In the present embodiment, a collimating lens 9 having a focal length of 120 mm and a diameter of 50 mm is used, for example. The collimating lens 9 makes laser light emitted from one end portion 5a of the optical fiber 5 supported by the head body 7 substantially parallel light. The “substantially parallel light” includes “parallel light”. In the present embodiment, only the collimating lens 9 is applied as the first lens, but it is not necessarily limited to this form. In other words, the first lens may include a lens group, and the laser light may be made substantially parallel by the lens group.

  In the present embodiment, the first cylindrical lens 10 having a focal length of 250 mm and a 30 mm square is used, for example. The first cylindrical lens 10 is disposed slightly apart from the collimating lens 9 in the optical axis direction. That is, the first cylindrical lens 10 is disposed between the light converging position F1 of the member 2 to be welded and the collimating lens 9 to be laser welded. The first cylindrical lens 10 has a condensing function only in a first direction substantially orthogonal to the optical axis direction. 2 and 3B, the first direction is indicated by an arrow x. The first cylindrical lens 10 is a cylindrical lens including at least one cylindrical surface 10 a and is disposed so that the cylindrical surface 10 a faces the collimating lens 9. In the present embodiment, only the first cylindrical lens 10 is applied as the second lens, but it is not necessarily limited to this form. That is, the second lens includes a lens group, and the lens group can be configured to have a condensing function only in the first direction substantially orthogonal to the optical axis direction.

  In the present embodiment, as the second cylindrical lens 11, for example, a lens having a focal length of 100 mm and a 30 mm square is applied. The second cylindrical lens 11 is disposed between the optical path between the condensing position F1 and the first cylindrical lens 10. The second cylindrical lens 11 has a condensing function only in the optical axis direction and the second direction substantially orthogonal to the first direction. 2 and 3 (a), the second direction is indicated by an arrow y. The second cylindrical lens 11 is a cylindrical lens including at least one cylindrical surface 11 a and is disposed so that the cylindrical surface 11 a faces the first cylindrical lens 10. In the present embodiment, only the second cylindrical lens 11 is applied as the third lens, but it is not necessarily limited to this form. In other words, the third lens includes a lens group, and the lens group can be configured to have a light collecting function only in the optical axis direction and in the second direction substantially orthogonal to the first direction.

  The focal positions of the first and second cylindrical lenses 10 and 11 are arranged so as to substantially coincide with each other. In other words, the second cylindrical lens 11 is spaced apart from the first cylindrical lens 10 by 150 mm, which is obtained by subtracting the focal length 100 mm of the second cylindrical lens 11 from the focal length 250 mm of the first cylindrical lens 10. Arranged. As shown in FIG. 4, the laser beam guided from the optical fiber 5 having a diameter of 0.6 mm is converted into the minor axis direction length α (α is, for example, 0.5 mm) and the major axis at the focal position. The light can be condensed into an ellipse having a direction length β (β is, for example, 1.25 mm). In addition, according to this configuration, the laser beam can be made elliptical at the focal position without irradiating the laser beam with a tilt as in the prior art.

FIG. 4 is a plan view of the member 2 to be welded to be laser welded as seen in the thickness direction. FIG. 5 is a chart comparing the test results of the construction beads with the circular focused beam and the test results of the construction beads with the elliptical focused beam. In the present embodiment, Ar gas or N ₂ gas is used as the shield gas supplied from the shield gas supply means 6. For example, 30 liters of shielding gas is supplied per minute. In some cases, seal gas is not used. The relative moving speed of the condensing head 4 with respect to the welded member 2 in the welding line direction is, for example, 30 cm / min. Or 40 cm / min. Or 50 cm / min. Set to As the SUS304 stainless steel plate applied as the member 2 to be welded, for example, those having a thickness of 2 mm and those having a thickness of 4 mm are adopted, and these members 2 to be welded are overlapped in the thickness direction and laser-welded.

  According to the laser processing machine 1 described above, the first cylindrical lens 10 has a condensing function only in the first direction, and the second cylindrical lens 11 has a condensing function only in the second direction. Since the focal positions of the first and second cylindrical lenses 10 and 11 substantially coincide with each other, the laser light emitted from the laser light source 3 is substantially elliptical at the focal position F1. Therefore, it is possible to expand a hole, that is, a keyhole formed by melting the base material of the member to be welded at the tip of the molten pool. Thus, according to the laser beam machine 1 of the present embodiment, the laser beam can be made elliptical at the focal position without irradiating the laser beam with a tilt as in the prior art. Therefore, it is possible to make the irradiation density of the laser energy uniform and simplify the structure.

  FIG. 6 is a perspective view showing an elliptical condensing optical system for extending the work distance. FIG. 7 is a diagram showing an elliptical condensing optical system for extending the work distance. However, the same reference numerals are given to the same members as those in the above embodiment, and the detailed description thereof is omitted. The condensing head 4A includes a head body (not shown), a collimating lens 9, a first cylindrical lens 10, and a second cylindrical lens 11, and further includes a spherical plano-concave lens group 12 and a spherical plano-convex lens group 13. And have. Among these, the spherical plano-concave lens group 12 is disposed between the optical path between the condensing position F2 and the second cylindrical lens 11.

  In the present embodiment, the spherical plano-concave lens group 12 includes two spherical plano-concave lenses 14. Each spherical plano-concave lens 14 has a focal length of 100 mm and a diameter of 50 mm, for example. These spherical plano-concave lenses 14 are arranged so that the respective concave surfaces 14a face each other and the opposed outer peripheral edge portions 14b abut against each other. The spherical plano-convex lens group 13 is disposed between the optical path between the condensing position F2 and the spherical plano-concave lens group 12. In the present embodiment, the spherical plano-convex lens group 13 includes two spherical plano-convex lenses 15. Each spherical plano-convex lens 15 has a focal length of 200 mm and a diameter of 50 mm, for example. These spherical plano-convex lenses 15 are arranged so that the convex surfaces 15a face each other and are close to each other.

  With the above configuration, the laser light guided from the optical fiber 5 having a diameter of 0.6 mm is collected in an oval shape having a short axis length of 0.5 mm and a long axis length of 1.25 mm, for example, at the focal position F2. Can be light. In addition, according to this configuration, the laser beam can be made elliptical at the focal position without irradiating the laser beam with a tilt as in the prior art. At this time, the distance from the lens 15 on the most downstream side in the light emitting direction to the focal position F2 (the distance is also referred to as a work distance) is about 170 mm.

  In other words, the distance from the second cylindrical lens 11 to the focal position can be extended. That is, the focal lengths of the first and second cylindrical lenses 10 and 11 can be increased by the spherical plano-concave lens group 12 and the spherical plano-convex lens group 13. The spherical plano-concave lens group 12 and the spherical plano-convex lens group 13 correspond to a fourth lens. As a result, it is possible to reduce the contamination of the lens 15 disposed at the tip of the light condensing head 4A, that is, the tip facing the member 2 to be welded. Moreover, the influence by radiant heat can be avoided. In addition, it is possible to secure a space in which equipment necessary for welding work, specifically, a shield gas supply nozzle, an air ejection nozzle for preventing spatter and fume from contaminating the optical system, and the like can be provided. If an attempt is made to expand the work distance without using the spherical plano-concave lens group 12 and the spherical plano-convex lens group 13, for example, a lens of about 60 mm square is required, but such a lens is difficult to obtain.

  FIG. 8 is a diagram of an elliptical condensing optical system capable of changing the condensing dimension. However, the same reference numerals are given to the same members as those in the above embodiment, and the detailed description thereof is omitted. The condensing head 4B includes a head body (not shown), a collimating lens 9, a first cylindrical lens 10, and a second cylindrical lens 11, and further includes a spherical plano-concave lens group 12 and a spherical plano-convex lens group 16. And have. Among these, the spherical plano-convex lens group 16 is disposed on the most downstream side in the light emitting direction.

  The spherical plano-convex lens group 16 includes two spherical plano-convex lenses 15 and 17. The spherical plano-convex lenses 15 and 17 are arranged so that the convex surfaces 15a and 17a are opposed to each other and are close to each other. As the spherical plano-convex lens 17 on the most downstream side in the light emitting direction, for example, a lens having a focal length of 150 mm and a diameter of 50 mm is applied. In the present embodiment, in particular, the condensing ratio of the spherical plano-convex lenses 15 and 17 on the upstream side and the downstream side in the light emitting direction of the spherical plano-convex lens group 16 is configured to be changeable. In other words, the elliptical dimension can be changed by simply changing the spherical plano-convex lens 17 on the most downstream side in the light emitting direction with respect to the optical systems shown in FIGS. Specifically, the laser beam guided from the optical fiber having a diameter of 0.6 mm is, for example, 0.38 mm in the short axis direction and 0.92 mm in the long axis direction at the focal position F3. It can be condensed into an ellipse. At this time, the distance from the lens 17 on the most downstream side in the light emitting direction to the focal position F3 is about 130 mm. Therefore, several types of lenses 17 on the most downstream side in the light emitting direction are prepared, and the distance from the lens 17 on the most downstream side in the light emitting direction to the focal position F3 can be made variable. Therefore, the present condensing head 4B can be applied to various uses, and the versatility of the present condensing head 4B can be enhanced. Other effects similar to those of the optical system shown in FIGS.

  In the present embodiment, a solid-state laser is applied to the laser light source. However, for example, a semiconductor laser can be applied to the laser light source. The laser processing machine may have a configuration in which the optical fiber is omitted. There may be a case where the seal gas is not supplied from the seal gas supply means. You may apply metal materials other than a stainless steel plate to a to-be-welded member.

1 is a system diagram schematically showing a configuration of a laser beam machine 1 according to an embodiment of the present invention. 4 is a perspective view showing an elliptical condensing optical system of the condensing head 4. FIG. FIG. 3A shows an elliptical condensing optical system of the condensing head 4, and FIG. 3A is a view of the elliptical condensing optical system viewed from a direction parallel to the major axis direction of the elliptical shape to be formed at the condensing position F <b> 1; FIG. 3B is a view of the elliptical condensing optical system viewed from a direction parallel to the elliptical minor axis direction. It is the top view which looked at the to-be-welded member 2 laser-welded in the thickness direction. It is a table | surface which compares the test result of the construction bead by a circular focused beam with the test result of the construction bead by an elliptical focused beam. It is a perspective view which shows the elliptical condensing optical system for extending a work distance. It is a figure which shows the elliptical condensing optical system for extending a work distance. It is a figure of the elliptical condensing optical system which can change a condensing dimension.

Explanation of symbols

2 Welded member 3 Laser light source 4, 4A, 4B Condensing head 9 Collimating lens 10 1st cylindrical lens 11 2nd cylindrical lens 12 Spherical plano-concave lens group 13 Spherical plano-convex lens group 15, 17 Spherical plano-convex lens F1-F3 Focus position

Claims (2)

A laser welding condensing head comprising an optical component for condensing laser light emitted from a laser light source on a member to be welded to be laser welded,
The optical component is
A first lens that substantially parallelizes the laser light emitted from the laser light source;
A second lens disposed between the condensing position of the member to be welded to be laser-welded and the first lens and having a condensing action only in a first direction substantially orthogonal to the optical axis direction;
A third lens disposed between the optical path between the condensing position and the second lens and having a condensing function only in a second direction substantially orthogonal to the optical axis direction and the first direction, A third lens disposed so that a focal position of the third lens substantially coincides with a focal position of the second lens;
A fourth lens disposed between the condensing position and the optical path between the third lens, and a concave lens group, and a convex lens group disposed closer to the condensing position than the concave lens group; The distance from the convex lens arranged on the most downstream side in the optical axis direction to the condensing position by the fourth lens in the convex lens group is longer than the distance between the focal position of the third lens and the third lens. laser welding condenser head, characterized in that it comprises a fourth lens that will be set. Of front Kitotsu lens group, an optical axis direction upstream and downstream of the laser welding condensing head according to claim 1, condensing ratio of the convex lens is characterized in that it is configured to be changed.

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