JP2809106B2 - Processing state monitoring device in laser processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser welding machine capable of judging the quality of a welded state of a workpiece at the same time as welding without destroying the workpiece in welding by a laser welding machine. And a method for monitoring the welding condition.

[0002]

2. Description of the Related Art As shown in FIG. 3, a conventional welding condition monitoring apparatus uses a total reflection mirror 34 and a reflection mirror 35 to irradiate light from a monitor light source 32 installed outside a welding machine 31.
The irradiating light is guided to the workpiece 13 by the optical system, and the reflected and scattered light from the workpiece 13 is monitored by the detector 33. Examples of the detection device 33 include an image sensor that detects a shape of a welded portion, an image sensor that detects a heat ray from the workpiece 13, and the like. And based on the detection result in the detecting device 13, the state of the welded part of the workpiece 13 was monitored.

[0003] This conventional welding condition monitoring device is, for example,
JP-A-61-199577 and JP-A-3-278.
No. 82 is disclosed.

[0004]

With this conventional welding condition monitoring device, only the condition of the surface of the welded portion can be monitored. Therefore, the quality of the welding must be determined by estimation only based on the information on the surface condition of the welded portion, and there is a problem that the reliability is extremely poor.

[0005] In addition to the light source (heat source) for welding,
Since a dedicated light source for the monitor is required, there is also a problem that the device becomes complicated and large-scale.

Further, in the case of a monitor in a laser welding machine, there is a problem that laser light used for welding affects irradiation light for monitoring and makes reflected light to be monitored extremely unstable. There was also.

[0007]

In order to solve the above-mentioned problems, the present invention monitors a laser beam before it is irradiated on a workpiece, and uses the monitoring result as a first indicator showing a change with time in light intensity. A first light detecting means for outputting laser light irradiated on the workpiece and reflecting the same, and a second light for outputting a result of the monitoring as second data indicating a temporal change in light intensity. Detecting means, means for calculating a difference value between the first data and the second data, and outputting the difference data as difference data; and using the difference data obtained when laser processing is normally performed as reference data , Means for comparing the difference data with the reference data and determining a machining state of the workpiece based on a result of the comparison.

[0008]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the overall configuration of a laser welding machine to which a welding state monitoring device for a laser welding machine according to the present invention is applied.

The laser oscillator 1 emits a laser beam 10 for welding a workpiece 13. The laser light 10 is reflected by the reflection mirror 2 toward the reflection mirror 3, and a part of the laser light 10 is transmitted and input to the photodetector 7.
The reflection mirror 3 receives the laser light 1 reflected by the reflection mirror 2.
0, and this laser beam 10
Part 3 (about 1%) of the light reflected on 3 is transmitted. The laser light 10 reflected by the reflection mirror 3 is coupled to the coupling lens 4
And incident on the optical fiber 5. The optical fiber 5 guides the laser light 10 incident by the coupling lens 4 onto the workpiece 13. The laser beam 10 guided by the optical fiber 5 is focused on the workpiece 13 by the focusing lens 6. The photodetector 7 detects the directly transmitted light 11 transmitted through the reflection mirror 2 and outputs a direct light monitor output 15. The light detector 8 detects the reflected and transmitted light 12 transmitted through the reflection mirror 3 and outputs a reflected light monitor output 16. The comparison unit 9 outputs the direct light monitor output 1 output from the photodetector 7.
5 is compared with the direct light monitor output 16 output from the photodetector 8 to determine the welding state on the workpiece 13. If the welding state is poor, an abnormal output 17 is output.

In the laser welding machine having such a configuration, the laser beam 10 emitted from the laser oscillator 1 is turned back by the total reflection mirror 2 and the total reflection mirror 3 and is coupled by the coupling lens 4 to the optical fiber 5. Incident.

On the other hand, a part of the laser light 10 emitted from the laser oscillator 1 is transmitted through the reflection mirror 2. Then, the transmitted directly transmitted light 11 is detected by the photodetector 7, and a direct light monitor output 15 is output.

Next, the laser beam 10 is guided to the workpiece 13 by the optical fiber 5 and is focused on the workpiece 13 by the condenser lens 6. This focused laser beam 10
Is partially absorbed by the workpiece 13 and used for welding, and the rest is reflected and scattered.

The light reflected and scattered by the workpiece 13 is condensed by the condenser lens 6 and is incident on the optical fiber 5. After the light is emitted from the optical fiber 5, most of the light is turned back by the total reflection mirror 3, but a part thereof (about 1%)
Is transmitted. The reflected light 12 transmitted through the total reflection mirror 3 is detected by the photodetector 8 and a reflected light monitor output 16 is output.

Normally, in laser beam welding, when the workpiece is irradiated with the laser beam, the workpiece is melted and welded. And as the melting progresses,
The reflectance of the laser beam changes every moment. The manner in which the reflectance changes varies depending on various factors such as the material and surface condition of the workpiece, laser output, and laser beam mode. Therefore, the photodetector 7 and the photodetector 8 must not only detect the amount of reflected and transmitted light but also detect a change in the intensity of the reflected and transmitted light in real time. That is, the direct light monitor output 15 and the reflected light monitor output 16
Is output as data indicating a change over time in light intensity.

Next, the direct light monitor output 15 output from the photodetector 7 and the reflected light monitor output 16 output from the photodetector 8 are input to the comparator 9. The direct light monitor output 15 and the reflected light monitor output 16
, The absorptance of the laser beam 10 on the workpiece 13 is calculated. Further, the comparing unit 9 detects whether or not the calculated absorption rate matches the absorption rate when normal welding is performed, and detects whether the calculated absorption rate matches the absorption rate. The quality of the welding condition is determined. Here, when it is determined that the welding condition is bad,
An abnormal output 17 is output. When the abnormal output 17 is output, for example, appropriate measures such as immediately interrupting the welding process and performing the process again, or performing laser beam output control depending on the determination result of the welding state. Is applied.

Next, the comparison section will be described with reference to FIGS.

FIG. 2 is a diagram showing the configuration of the comparison unit. The difference circuit 21 includes a direct light monitor output 15 output from the photodetector 7 and a reflected light monitor output 16 output from the photodetector 8. Is input, and the difference data 24 is calculated. The comparison circuit 22 compares the difference data 24 between the direct light monitor output 15 and the reflected light monitor output 16 calculated by the difference circuit 21 with reference data 25 set in the reference data setting unit 23 in advance.
By comparing with, the welding state of the workpiece 13 is determined,
If it is determined that the welding state is bad, an abnormal output 17 is output.

In the comparing section 9 having such a configuration, first, in the difference circuit 21, difference data 24 is calculated in real time based on the direct light monitor output 15 and the reflected light monitor output 16. This difference data 24 is
The absorptance of the laser beam 10 on the workpiece 13 that changes with time is shown. That is, the difference circuit 21 can detect how the laser beam 10 is absorbed by the workpiece 13.

Next, the difference data output from the difference circuit 21 is sequentially input to the comparison circuit 22. The reference data 25 set in the reference data setting unit 23 is also input to the comparison circuit 22 in synchronization with the difference data 24. Here, the reference data 25 is data indicating a temporal change in the absorptance of the laser beam 10 on the workpiece 13 when normal welding is performed.

In the comparison circuit 22, the difference data 24 and the reference data 25 are sequentially compared, and if the respective data are different, an abnormal output 17 is output.

[0022]

As described above, the welding condition monitoring apparatus for a laser welding machine according to the present invention does not need to be provided with a plurality of light sources because the laser light for processing is also used for monitoring. The configuration is simple.

Further, since the processing light beam and the monitoring light beam do not interfere with each other, stable monitoring can be performed.

Further, since the intensity of the direct light and the intensity of the reflected light of the laser light emitted from the laser oscillator are compared, not only the surface condition of the workpiece but also the Can be directly detected whether or not
Further, since the intensity of the direct light and the reflected light is monitored as a time waveform, a change in the welding process can be detected, and the quality of the welding state can be determined with higher reliability.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a comparison unit in FIG. 1;

FIG. 3 is a diagram showing a configuration of a conventional welding state monitoring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser oscillator 2, 3 Total reflection mirror 4 Coupling lens 5 Optical fiber 6 Condensing lens 7, 8 Photodetector 9 Comparison part 10 Laser light 11 Direct transmission light 12 Reflection transmission light 13 Workpiece 15 Direct light monitor output 16 Reflection Optical monitor output 17 Abnormal output 21 Difference circuit 22 Comparison circuit 23 Reference data setting unit 24 Difference data 25 Reference data

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B23K 26/00-26/04

Claims (2)

(57) [Claims] A first light detecting means for monitoring a laser beam before being irradiated on a workpiece, and outputting a result of the monitoring as first data indicating a temporal change in light intensity; A second light detection unit that monitors the laser light irradiated and reflected on the object, and outputs a result of the monitoring as second data indicating a temporal change in light intensity; and the first data and the second data. A difference means for calculating a difference value of the difference data and outputting the difference data as difference data; comparing the difference data with the reference data, using the difference data obtained when laser processing is normally performed as reference data, and comparing the comparison result. Determination means for determining a processing state of the workpiece based on the difference data and the reference data.
Data showing the change over time of the absorption rate on the workpiece
A processing state monitoring device in a laser processing device, which is equivalent to the above . 2. A processing state monitoring device for monitoring a processing state of a workpiece when irradiating the workpiece with laser light, wherein the processing of the laser light is performed during laser processing. Means for detecting, as first data, data corresponding to an absorptivity that changes over time on an object; and changes over time on the workpiece of the laser beam obtained when laser processing is performed normally. Means for determining the processing state of the workpiece by comparing the first data and the second data with data corresponding to the absorption rate to be performed as second data. Processing state monitoring device in laser processing equipment