JPH0228433B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a laser welding state management device.

(Conventional technology) Laser welding is a non-contact welding method, so
Unlike resistance welding, it is not possible to measure changes in current and voltage during welding to manage the quality of the welding condition. Therefore, in the past, workers had to judge the quality of laser welding one by one with their naked eyes after welding was completed, which was not only extremely inefficient, but also made it difficult for each worker to judge the quality of the laser welding. There is a problem that the quality is not constant due to the difference in quality, and there is a strong demand for automation of this work.

(Problems to be Solved by the Invention) Therefore, the inventor conducted various experiments on the case where two members to be welded are overlapped and welded, and obtained the results shown in FIG. 1. That is, FIG. 1a shows a case where the upper first member to be welded 1 and the lower second member to be welded 2 are reliably welded with sufficient strength, and the first member to be welded at this time 1
Let d ₁ be the fusion diameter of the first welded member _1. If _the welding conditions shown in FIG _. I found it. That is, FIG. 1b shows a case where there is a slight gap between the first workpiece 1 and the second workpiece 2, and in this case, the melt diameter d ₂ is larger than the above-mentioned d ₁ . Ta. Further, FIG. 1c shows a case where the output of the laser beam is lower than that in FIG. 1a, and the melt diameter _d3 at this time is smaller than _d1 . Although not shown, the output of the laser beam is as shown in Figure 1a.
If it becomes larger than when , the melt diameter at this time is
It is clear that d is larger than ₁ .

Accordingly, based on the above experiments, it is an object of the present invention to provide a management device that can determine whether the welding state of lap welding using a laser is good or not based on the molten diameter of a member to be welded.

[Structure of the Invention] (Means and Effects for Solving the Problems) An irradiation spot of a laser beam irradiated on an upper welded member to be overlap-welded is provided with an irradiation spot of at least this diameter along the diameter direction of the irradiation spot. A light projecting means for illuminating the width, a light receiving means provided at a location corresponding to the light projecting means and receiving light at a predetermined interval within a light receiving area exceeding the diameter of the irradiation spot, and an amount of reflected light received by the light receiving means. It is equipped with a signal processing means that compares the signal with a signal based on a reference amount of reflected light, and can detect a change in the melt diameter by receiving the light.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 2 to 4. In the figure, 11 is a laser oscillator. The laser beam L output from this laser oscillator 11 irradiates the first welded member 12 located on the upper side of the superimposed first and second welded members 12 and 13 with a predetermined spot diameter. It's starting to melt. Diagonally above the first workpiece 12, there are a plurality of projectors, five projectors 1 in this embodiment.
4a to 14e are the first and second members to be welded 12, 1
3 are arranged at predetermined intervals along the longitudinal direction. He-Ne is emitted from these projectors 14a to 14e.
Detection light l ₁ to _{l 5} such as laser light is output,
These detection lights l ₁ to _{l 5} are adapted to irradiate the portion of the first member to be welded 12 that is irradiated with the laser beam L along the diameter direction.

Further, diagonally above the first member to be welded 12, the above-mentioned light projectors 14a to 14 are arranged around the optical path of the laser beam L.
Five light receivers 15a to 15e are arranged symmetrically to 14e, and these light receivers 15a to 15e receive the detection lights _l1 to _l5 reflected on the upper surface of the first member to be welded 12, respectively. It's becoming like that.
A signal processing and display device 16 is connected to each of the light receivers 15a to 15e, and this device 16 calculates and displays the amount of light received by each of the light receivers 15a to 15e.

Next, the effect will be explained. First, when the laser oscillator 11 is activated to output the laser beam L having the output shown in FIG. Begins to melt. At this time, the energy distribution within the spot of the laser beam L is as follows:
Since the distribution is Gaussian, with the largest value at the center and decreasing toward the periphery, the first member 12 to be welded begins to melt from a location corresponding to the center of the spot.

On the other hand, along with the laser oscillator 11, the projector 14a
- 14e are activated, and each of the light receivers 15a to 15e detects detection lights _l1 to _l5 outputted from each of the light projectors 14a to 14e and reflected by the first member to be welded 12.
Then, the amount of light detected by each of the light receivers 15a to 15e becomes the state shown in FIGS. 4b to 4d. That is,
The detection light _l3 reflected from the central part of the spot of the laser beam L that irradiated the first workpiece 12 melts fastest in the central part and the reflectance decreases, as shown in FIG. 4b. Immediately after the laser beam L is output, the amount of reflected light decreases, and this is detected by the light receiver 15c. In addition, the detection lights l ₂ and l ₄ reflected from the periphery of the spot melt later than the central part, so
As shown in FIG. 4c, after the amount of reflected light of the detection light l ₃ decreases, the amount of reflected light of these detection lights l ₂ and l ₄ decreases. Furthermore, the detection beams l ₁ and l ₅ that irradiated the portions of the first workpiece 12 that were deviated from the spot of the laser beam L are such that these deviated portions are irradiated with the laser beam L.
Since the light is not melted by the welding process and the reflectance does not decrease, the amount of the detected light beams l ₁ and l ₅ reflected from the first member to be welded 12 does not change and remains constant, as shown in FIG. 4d.

Therefore, by calculating and displaying the state of the amount of reflected light detected by each of the light receivers 15a to 15e on the signal processing display device 16, the first member to be welded 12
The approximate melt diameter is known. The quality of the welding condition can be determined from this melt diameter. for example,
In the above embodiment, the interval between the detection lights l ₂ and l ₄ is set to the first
If the dimensions are set to be slightly smaller than the molten diameter in a good welding condition as shown in Figure a, then the amount of reflected light of the detection lights _L2 and _L4 will lag behind the amount of reflected light of detection light _L3 . If the amount of reflected light of detection beams l ₁ and l ₅ is constant, the melt diameter will be smaller than that of detection beams l ₂ and l _4.
In other words, if the amount of reflected light from detection light _l2 and _l4 does not decrease, the molten diameter is small and the detection light _l1 When the amount of reflected light of l ₅ decreases, it can be determined that the molten diameter is too large and that good welding is not being achieved.
By setting the reference signal based on the reference melt diameter in this way, it is possible to judge as defective anything that deviates from the reference on both the plus and minus sides.

In the above embodiment, each of the five projectors outputs detection light for illumination, but by scanning one detection light at high speed, the amount of reflected light from each point on the workpiece to be welded can be detected. The welding state may also be determined.

[Effects of the Invention] As described above, the present invention compares the amount of light reflected from the molten part of the welded parts overlap-welded by laser with the amount of reflected light based on the reference fusion diameter. It was possible to judge whether the welding condition of lap welding was good or bad. Since the above-mentioned detection can be performed automatically and optically in parallel with the welding operation, it is possible to improve the efficiency and reliability of quality control in laser welding.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the relationship between the quality of the welding state and the molten diameter in lap welding, Fig. 2 is a perspective view showing the schematic configuration of an embodiment of the present invention, and Fig. 3 is a side view, and Fig. 3 is a side view. 4A to 4D are explanatory diagrams showing the temporal relationship between the output of laser light and the amount of reflected light. 12, 13... members to be welded, 14a to 14e...
...Emitter, 15a-15e...Receiver, 16...
Signal processing display device, L...Laser light, _l1 to _l5 ...
detection light.

Claims (1)

[Claims] 1. A light projection means for illuminating a width at least equal to or larger than the diameter of the irradiation spot of the laser beam irradiated on the upper workpiece to be overlap welded, along the diameter direction of the irradiation spot, and a light projection means corresponding to the above-mentioned light projection means. and a light receiving means provided at a position to receive light at predetermined intervals within a light receiving area exceeding the diameter of the irradiation spot, and a signal processing means for comparing a signal based on the amount of reflected light received by the light receiving means. Features: Laser welding status management device.