JPH1119787A - Laser welding method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cope with scanning speed of a laser beam and also to enable laser welding while a weld line position is detected with high precision. SOLUTION: In butt welding between a sheet 15 and a plate 17, a plane mirror 23 is oscillated in an area of a specific angle around the shaft 29 by a oscillating unit 31, thereby oscillating a laser beam 19 in a diagram orthogonally crossing a weld line W in the direction vertical to the paper surface. A plasma beam 41 generating each from the sheet 15 and the plate 17 in laser beam irradiation is such that the intensity is different mutually because the focal position of the laser beam 19 is different between the sheet 15 and the plate 17, and that the timewise change of this plasma beam intensity is detected by a photo sensor 39; then, a computer 49 judges whether the oscillation center of the laser beam 19 is deviated to the sheet 15 or to the plate 17 with respect to the weld line W, controlling the operation of the oscillating unit 31 so as to correct the deviation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a stepped joint formed by welding plates, such as butt welding of plates having different thicknesses or fillet welding when the plates are overlapped. The present invention relates to a laser welding method and a laser welding apparatus which are formed and irradiate a laser beam to a joining portion at the step portion to perform welding.

[0002]

2. Description of the Related Art In laser welding, a high-quality joint can be obtained with high productivity. However, since the focused spot diameter of the laser beam is as small as about 0.1 to 0.6 mm, the laser beam is An error is likely to occur at the target position, and the strength of the welded joint is likely to be reduced. For example, as shown in FIG. 6, a joining portion 5 in the butt welding of the plate materials 1 and 3 having different thicknesses, and a joining portion 11 in the fillet welding when the plate materials 7 and 9 shown in FIG. Even in the case where a step is provided between the plate materials, it is required that the laser beam 13 be accurately scanned along the welding line W.

Conventionally, as a technique for detecting the position of a welding line, a capacitance or optical cutting method (Kazuo Nakayama, Seiichiro Kimura, Sadao Sugiyama, "Detection of Welding Line in Laser Welding", 26th edition, Toshiba Heavy Industries, Ltd.) The application of image processing such as the Laser Thermal Processing Research Group Transactions, July 1991, pp.31-41) is being considered.

[0004]

However, the conventional method of detecting a welding line described above is not practical because of the following problems.

(1) It is impossible to perform position control on the order of 0.01 mm corresponding to a processing speed of several tens mm / sec, which is a scanning speed of laser welding.

(2) When irradiating a laser beam, the material melts and evaporates, and high-temperature plasma induced at this time generates light, sound, and electromagnetic waves, and is a strong noise source for the sensor unit. And the detection accuracy decreases.

Accordingly, an object of the present invention is to make it possible to perform laser welding while detecting the position of a welding line with high accuracy, which can correspond to the scanning speed of a laser beam.

[0008]

To achieve the above object, according to the first aspect of the present invention, a step portion is formed at a joining portion for joining plates by welding, and the step portion moves along a welding line at the step portion. The laser beam to be irradiated is vibrated so as to reciprocate across the plates in a direction orthogonal to the welding line, and the intensity of the plasma light generated by the laser beam irradiation on each of the plates is changed over time due to the vibration. Calculating a shift direction and a shift amount of the center of vibration of the laser beam with respect to the welding line, and correcting the center of vibration of the laser beam to coincide with the weld line based on the obtained shift direction and shift amount. There is.

According to the above-described laser welding method, the intensity of plasma light generated between one plate material and the other plate material is different, and the center of vibration is at the welding line due to the time change of the plasma light intensity due to the laser beam vibration. On the other hand, it is possible to obtain the position and the amount of the deviation, that is, the deviation direction and the deviation amount of the oscillation center of the laser beam. Based on the determined shift direction and shift amount, the center of vibration of the laser beam is corrected to coincide with the welding line, whereby the laser beam is accurately scanned along the welding line.

According to a second aspect of the present invention, a step portion is formed at a joining portion where the plate members are welded to each other, and a laser beam irradiated while moving along the welding line at the step portion is directed in a direction orthogonal to the welding line. A vibration generating means for oscillating the plate material so as to reciprocate, a plasma light detecting means for detecting the intensity of plasma light generated by irradiating the plate material with a laser beam, and the plasma detected by the plasma light detecting means. The intensity of light, based on the time change due to the vibration, while determining the direction and amount of deviation of the center of vibration of the laser beam with respect to the welding line,
A control means for correcting the center of vibration of the laser beam so as to coincide with the welding line based on the obtained shift direction and shift amount and operating the vibration generating means is provided.

According to the above construction, the laser beam is vibrated by the vibration generating means in a direction orthogonal to the welding line, and the laser beam is scanned along the welding line in this vibration state to perform laser welding. Here, the intensity of the plasma light generated by irradiating the plate material with the laser beam is different between one plate material and the other plate material. On the other hand, the difference and the shift amount, that is, the shift direction and the shift amount of the oscillation center of the laser beam are obtained. The vibration generating means is operated to correct the center of vibration of the laser beam so as to coincide with the welding line based on the determined direction and amount of deviation, whereby the laser beam is accurately scanned along the welding line.

According to a third aspect of the present invention, in the configuration of the second aspect of the present invention, the vibration generating means vibrates a mirror that focuses the laser beam toward the joining portion to be welded and joined.

[0013] According to the above configuration, the converged laser beam vibrates in a direction orthogonal to the welding line, that is, in a direction reciprocating between one plate and the other plate by vibrating the mirror.

According to a fourth aspect of the present invention, in the configuration of the third aspect of the present invention, the vibration generating means for vibrating the mirror comprises a shaft portion connected to one end of the mirror in parallel with the reflection surface of the mirror, and It is configured to be connected and fixed to one of the permanent magnet and the coil, which rotate by the interaction of the magnetic field generated by the permanent magnet and the coil to which a voltage is applied.

According to the above configuration, one of the permanent magnet and the coil vibrates in the rotational direction within a certain angle range under the influence of the magnetic field, and accordingly, the mirror connected via the shaft vibrates. Thus, the laser beam condensed by the mirror vibrates in a direction orthogonal to the welding line, that is, in a direction of reciprocating between one plate and the other plate.

According to a fifth aspect of the present invention, in the configuration of the second aspect of the invention, the step portion is formed by abutting end faces of plate members having different plate thicknesses.

According to the above construction, when the end faces of the plate materials having different plate thicknesses are abutted against each other, a step is formed at the abutting portion, and the laser beam is formed along the welding line of the joint between the plate materials at the step. Is irradiated while oscillating so as to reciprocate between the plate materials about the welding line, thereby performing laser welding.

According to a sixth aspect of the invention, in the configuration of the second aspect of the invention, the step portion is formed by overlapping the plate members.

According to the above arrangement, when the plate materials are overlapped with each other, a step portion is formed at the joining portion, and the laser beam is applied along the welding line of the joint portion between the plate materials at the step portion with the welding line as the center. Laser welding is performed by irradiating while oscillating to reciprocate between the plate materials.

[0020]

According to the first aspect of the present invention, the intensity of plasma light generated between one plate material and the other plate material is different, and the plasma light intensity changes with time due to the vibration of the laser beam. The deviation direction and deviation amount of the beam vibration center are determined, and the laser beam vibration center is corrected to match the welding line based on the determined deviation direction and deviation amount. Can be scanned.

According to the second aspect of the present invention, the intensity of the plasma light generated between the one plate material and the other plate material is different, and the change of the plasma light intensity with time due to the vibration of the laser beam causes the change of the laser beam with respect to the welding line. The shift direction and the shift amount of the vibration center are obtained, and based on the obtained shift direction and the shift amount, the laser beam is corrected so that the vibration center coincides with the welding line. And can be scanned accurately. In this case, since the detection speed of the plasma light and the response speed of the correction mechanism depend on the oscillation frequency of the laser beam, it can sufficiently cope with the laser processing speed, and a photosensor can be used as a means for detecting the intensity of the plasma light. Therefore, it is possible to detect a welding line with high accuracy without being affected by noise.

According to the third aspect of the invention, the converged laser beam vibrates in a direction orthogonal to the welding line, that is, in a direction reciprocating between one plate and the other plate by vibrating the mirror. Therefore, the direction and amount of deviation of the center of oscillation of the laser beam with respect to the welding line can be obtained, and based on this, the center of oscillation of the laser beam can be corrected and the laser beam can be accurately scanned along the welding line. Become.

According to the fourth aspect of the present invention, the vibration generating means can freely set the center position of the vibration range when the permanent magnet or the coil rotationally vibrates, so that the vibration center of the laser beam can be easily corrected. be able to.

According to the fifth aspect of the present invention, when the end faces of the plate materials having different plate thicknesses abut against each other, a step is formed at the abutting portion, and the step is formed along the welding line of the joint of the plate materials at the step. By irradiating a laser beam while vibrating so as to reciprocate between the sheet materials around the welding line, laser welding along the welding line is accurately performed.

According to the sixth aspect of the present invention, when the sheet materials are overlapped with each other, a step is formed at the joining portion, and the laser beam is applied along the welding line of the joint between the plate materials at the step. Irradiation while oscillating so as to reciprocate between the plate materials around the center allows laser welding along the welding line to be performed accurately.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of a laser welding apparatus showing an embodiment of the present invention. Here, two kinds of plate materials having different plate thicknesses, that is, respective end surfaces of a thin plate 15 and a thick plate 17 are butted to each other. This is applied to the butt welding shown in FIG. FIG. 1 is a view of the thick plate 17 viewed from the thin plate 15 side.
The joining portion 18 has a stepped portion formed by a thickness difference, and the joining portion 18 having the stepped portion is provided with a linear welding line W extending in the left-right direction in the drawing. The laser beam 19 output from a laser oscillator (not shown) is a circular parabolic mirror 21 and a circular plane mirror 23.
Then, the light is reflected and directed toward the joint 18 between the thin plate 15 and the thick plate 17 while being scanned along the welding line W.

The parabolic mirror 21 is fixed below the housing 27 at an angle of 45 degrees with respect to the vertical direction parallel to the output direction from the laser oscillator, while the flat mirror 23 is attached to the parabolic mirror 21. It is arranged outside of the housing 27 at the opposing position. This plane mirror 23
It is connected to a vibration unit 31 as a vibration generating means via a shaft portion 29 parallel to the reflection surface. The housing 27 is movable left and right in the drawing so that the laser beam 19 can scan along the welding line W.

The vibration unit 31 is mounted on the side of the housing 27 via a mounting bracket 33.
The shaft portion 29 is oscillated in a rotational direction about the axis thereof within a certain angle range, and accordingly, the plane mirror 23 also oscillates in the same direction. As a result, the laser beam 19 is directed in a direction orthogonal to the welding line W. That is, it vibrates in a direction perpendicular to the paper surface in FIG. 1 and reciprocates across the thin plate 15 and the thick plate 17 with the welding line W as a boundary. Vibration unit 31
As a specific example, a moving coil disposed in a magnetic field is incorporated, and a galvanometer that changes the angle according to a voltage is used.
9 is connected.

A function generator (waveform generator) 35 is connected to the vibration unit 31 via an amplifier 33, and the waveform signal generated by the function generator 35 is amplified by the amplifier 33 and the vibration unit 31
And the vibration unit 31 is driven.

The laser beam 19 below the housing 27
A photo sensor 39 is mounted via a bracket 37 on the front side in the scanning direction (right direction in FIG. 1).
The photo sensor 39 constitutes a plasma light detecting means for detecting the intensity of the plasma light 41 generated by melting, evaporating and ionizing when the thin plate 15 and the thick plate 17 are irradiated with the laser beam 19, It is composed of a photodiode.

Here, the output of the photo sensor 39 changes as shown in FIG. 2 depending on the thickness of the plate material and the focal position of the laser beam. In FIG. 2, the data indicated by a solid line is a plate having a thickness of 1 mm, and the data indicated by a broken line is a plate having a thickness of 2 mm. When the focus position shown on the horizontal axis is "0", the focus is located on the surface of the plate material, and when the value is "1" or "2", the focus position is 1 mm or 2 mm above the surface of the plate material, respectively. And
Conversely, when the values are negative values of "-1" and "-2", it is assumed that the focal point is located 1 mm and 2 mm inside from the surface of the plate material, respectively.

According to FIG. 2, at any plate thickness, the focus position is shifted to the plus side and the minus side with respect to "0", and the plasma emission intensity is increased, and the plus side is "1.5". , The minus side is the focal position near “−2.5” and is the maximum. Here, when the thin plate 15 and the thick plate 17 are butt-welded to each other, when the focal position is set to “0” with respect to the thin plate 15, that is, when the focal position is set to the surface of the thin plate 15, the output level on the vertical axis is Is a value corresponding to “A” for the thin plate 15, whereas a value corresponding to “B” for the thick plate 17 because the focal position is located at “−1” inside the material. And is higher than the thin plate 15 side.

For this reason, the laser beam 19 is vibrated by the vibration unit 31 in a direction orthogonal to the welding line W,
If the thin plate 15 and the thick plate 17 are reciprocated, the focal position with respect to the plate material changes between the thin plate 15 and the thick plate 17, so that any one of the types shown in FIGS. 3 (a), 3 (b) and 3 (c) can be used. Will be obtained. FIG. 3A shows a case where the oscillation center of the laser beam 19 is shifted toward the thick plate 17 as shown in FIG. 4A, and the output level B shown in FIG. I have. On the other hand, FIG. 3B shows a case where the vibration center is shifted to the thin plate 15 side as shown in FIG. 4B, and has a long output time of the output level A shown in FIG. FIG. 3 (c) shows a case where the center of vibration does not shift to any side and coincides with the welding line W between the plate members as shown in FIG. 4 (c). Each output time of B is equal.

The obtained waveform, that is, the output value of the photo sensor 39 is input to the A / D converter 47 via the filter 43 and the amplifier 45, and further input to the computer 49 as control means. Computer 49
3C, the center of vibration of the laser beam 19 coincides with the welding line W, as shown in FIG. 3A, or on the thick plate 17 side, or as shown in FIG. It is determined how much the sheet 15 is displaced.

The data of the shift amount and the shift direction are D / A
The signal is input to the amplifier 33 via the converter 51 as an offset signal. That is, the offset signal is
, The vibration unit 31 can correct the vibration center of the laser beam 19 so as to coincide with the welding line W in accordance with the displacement amount and the displacement direction. Since the vibration unit 31 can freely set the center position of the vibration range when the built-in moving coil vibrates rotationally, the vibration center of the laser beam 19 can be easily corrected. In addition,
The vibration unit may have a configuration in which a magnet is rotatably arranged instead of the moving coil, and the coil is arranged around the magnet.

FIG. 5 is a flowchart showing the operation of the laser welding apparatus described above. First, the computer 49
Receives the input of the synchronization signal serving as the trigger signal from the function generator 35 (step 101), the measurement start processing of the emission intensity of the plasma light is executed (step 103). That is, the vibration unit 31 operates from the function generator 35 via the amplifier 33, and the laser beam 19 reciprocates between the thin plate 15 and the thick plate 17. At this time, the laser beam 19 scans rightward in FIG. 1 along the welding line W by moving the housing 27, and the irradiation of the laser beam 19 generates plasma light 41 from the thin plate 15 and the thick plate 17. ing.

When one cycle of the reciprocating oscillation of the laser beam 19 is completed (step 105), the light emission intensity of the plasma light 41 detected by the photo sensor 39, as shown in FIGS. 3 (a), 3 (b) and 3 (c). (Step 107). Next, the output time T of the output level signal A corresponding to the plasma light intensity on the thin plate 15 side
It is determined how much the ratio of “a” to the output time Tb of the output level signal B corresponding to the plasma light intensity on the thick plate 17 is different from the case where both are equal (step 109).

Here, if Ta <Tb, the vibration center of the laser beam 19 is shifted toward the thick plate 17 by the difference as shown in FIGS. The center of vibration is shifted to the thin plate 15 side by a predetermined amount so as to coincide with the welding line W (step 111). Conversely, if Ta> Tb, FIG.
4 (b) and FIG. 4 (b), the center of vibration of the laser beam 19 is shifted toward the thin plate 15 by that difference. It is made to match (step 113). When Ta = Tb, the center of vibration of the laser beam 19 coincides with the welding line W, so that the position of the center of vibration is not corrected. And
When the laser welding is completed (step 115), the measurement operation is completed.

Thus, the welding line W of the laser beam 19 is
The deviation of the vibration center in the direction orthogonal to
The deviation is corrected by detecting the plasma light having different light emission intensity between the thin plate 15 and the thick plate 17 and correcting the deviation, so that the laser beam 19 can be reliably scanned along the welding line W. Since the intensity of the plasma light 41 is detected by the photo sensor 39, the plasma light 41
The detection accuracy does not decrease due to the light, sound, and electromagnetic waves generated by this, and it is possible to detect the welding line with high accuracy. In addition, the detection speed and the response speed of the correction mechanism depend on the frequency of the vibration unit 31 and can normally be about 100 Hz or more, and can sufficiently cope with a processing speed of several tens mm / sec.

In the above-described embodiment, the present invention is applied to the butt welding of the thin plate 15 and the thick plate 17 having different plate thicknesses, but the corner when the two plate materials shown in FIG. Also applicable to meat welding.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a laser welding apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the relationship between the focal position of a laser beam on a plate and the intensity of plasma light generated from the plate by laser beam irradiation.

3A and 3B are sensor output waveform diagrams of the laser welding apparatus of FIG. 1, wherein FIG. 3A shows a case where the vibration center of the laser beam is shifted to the thick plate side, and FIG. 3B shows a case where the vibration center is shifted to the thin plate side. , (C) show the case where the vibration center coincides with the welding line.

4A and 4B show a vibration state of a laser beam in the laser welding apparatus of FIG. 1; FIG. 4A shows a case where the vibration center of the laser beam is shifted to the thick plate side; (C) is a case where the vibration center coincides with the welding line.

FIG. 5 is a flowchart showing an operation of the laser welding apparatus of FIG. 1;

FIG. 6 is a perspective view showing an operation of butt welding when end faces of two plate materials having different plate thicknesses are butted to each other.

FIG. 7 is a perspective view showing an operation of fillet welding when two sheet materials are overlapped with each other.

[Explanation of symbols]

 Reference Signs List 15 thin plate 17 thick plate 19 laser beam 23 plane mirror (mirror) 29 shaft part 31 vibration unit (vibration generating means) 39 photo sensor (plasma light detecting means) 41 plasma light 49 computer (control means)

Claims (6)

[Claims] 1. A step portion is formed in a joining portion for welding and joining sheet materials to each other, and a laser beam irradiated while moving along a welding line at the step portion is applied across the sheet materials in a direction orthogonal to the welding line. Vibration is caused to reciprocate, and the direction and amount of deviation of the center of vibration of the laser beam with respect to the welding line based on the time change of the intensity of plasma light generated by irradiating the plate material with the laser beam based on the vibration. And correcting the center of vibration of the laser beam so as to coincide with the welding line based on the determined shift direction and shift amount. 2. A step portion is formed at a joining portion where the plate members are welded to each other, and a laser beam irradiated while moving along a welding line at the step portion is applied to the plate members in a direction orthogonal to the welding line. Vibration generating means for vibrating to reciprocate, plasma light detecting means for detecting the intensity of plasma light generated by irradiating the plate material with a laser beam, and the intensity of the plasma light detected by the plasma light detecting means, Based on the time change due to the vibration, the shift direction and the shift amount of the center of vibration of the laser beam with respect to the welding line are determined, and based on the determined shift direction and the shift amount, the center of vibration of the laser beam is determined. And a control means for operating the vibration generating means by making a correction so as to match the welding line. 3. The laser welding apparatus according to claim 2, wherein the vibration generating means is configured to vibrate a mirror for converging a laser beam toward a joining portion to be welded and joined. 4. A vibration generating means for vibrating a mirror, wherein the other end of a shaft connected to one end of the mirror in parallel with the reflection surface has a magnetic field generated by a permanent magnet and a coil to which a voltage is applied. 4. The laser welding apparatus according to claim 3, wherein the laser welding apparatus is connected and fixed to one of the permanent magnet and the coil rotating by interaction. 5. The laser welding apparatus according to claim 2, wherein the step portion is formed by abutting end faces of plate members having different plate thicknesses. 6. The laser welding apparatus according to claim 2, wherein the step portion is formed by overlapping plate members.