JPH11147189A - Instrument for detecting defect in laser beam welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To unnecessitate the countermeasure of noises, to improve the quality control technique and to save the number and the labor of inspectors by arranging a sensor for detecting the sound generated at a welding position of a work irradiated with laser beam in a box and executing the detection of defect at the welded position based on the level of sound signal detected with the sensor. SOLUTION: A microphone 17 for detecting the welding sound is arranged in the inner part at the upper end of a laser beam torch 12 by utilizing the cylindrical box of the laser beam torch. Further, a sound absorbing (or sound insulating)material 18 for reducing the detection of the outer noise, is arranged in the inner part of the box. The sound signal from the microphone 17 is converted into a digital signal with an A/D converter by using a welding condition decision processing device 20 and the decision whether the welding condition in the detection of defect, etc., is good or not, is executed according to a treating algorithm predecided in a CPU and a high speed treating processor. If necessary, this result is displayed and stored with a displaying device 21 and a storing device 22.

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 and, more particularly, to a laser welding defect detecting apparatus for detecting sound from a welding portion and detecting a welding defect based on the level of the detected sound signal.

[0002]

2. Description of the Related Art In laser welding, welding is performed by irradiating a target workpiece with pulsed laser light output from a laser oscillator. Weld defect inspection in laser welding,
Inspection is often performed by an inspector off-line visually or by using inspection equipment. In this case, mass production lines such as automobile manufacturing require inspection of a large number of places, and the burden on inspectors is large. Further, the inspection time needs to be short from the viewpoint of the productivity of the production line, and it is most desirable to perform the defect inspection in parallel with the welding.

The following method has been proposed as a technique for online measurement of a welding state in laser welding. According to this method, a sound generated in a welding process from a welding portion is detected by a detector, and a normal or defective welding state is determined based on the detection level.
7 is disclosed.

By the way, in such an apparatus, as shown in FIG. 3, a detector 31 is externally attached to a laser torch 30 for irradiating a work 32 with laser light. The laser torch 30 can be moved up and down in the direction of the optical axis of the laser light in order to adjust the focal position of the laser light. Has been enabled.

[0005]

However, the configuration shown in FIG. 3 has the following problems.

[0006] 1. The detector 31 easily picks up external noise other than the welded portion, and requires noise countermeasures.

[0007] 2. When the laser torch 30 fluctuates up and down or tilts, the detection direction of the detector 31 may deviate from the welding location. This means that when a detector having a high directivity is used as the detector 31, the detection performance is reduced.

[0008] 3. When the work 32 has a complicated shape,
Since the attitude of the laser torch 30 changes variously, and in some cases, the detector 31 may hit the workpiece 32,
The installation position of the detector 31 is restricted.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a laser welding defect detecting apparatus which detects a sound from a welding location without being affected by noise other than the welding location and detects a defect.

Another object of the present invention is to provide a laser welding defect detecting apparatus which detects a sound from a welding portion without being affected by the attitude of a laser torch and performs defect detection.

Still another object of the present invention is to provide a laser welding defect detecting apparatus which can save labor and labor of inspectors and can realize online inspection.

[0012]

A laser welding defect detecting apparatus according to the present invention is directed to a laser for guiding a laser beam to a laser torch having a cylindrical housing and irradiating the work through a lower end opening of the cylindrical housing to perform welding. In the welding machine, a sensor for detecting a sound generated at a welding portion of the workpiece irradiated with the laser light is provided in the housing, and a defect of the welding portion is detected based on a level of a sound signal detected by the sensor. Is performed.

Preferably, a sound absorbing material is provided on the inner wall of the housing.

Further, it is preferable that the sensor is provided at an upper end in the housing.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described with reference to FIGS. In FIG. 1, a pulsed laser beam generated by a laser oscillator 11 is guided to a laser torch 12 by a transmission fiber. The work 15 is irradiated with the introduced laser beam through the laser reflecting mirror 13 and the condenser lens 14 in the laser torch 12 from the lower end opening of the laser torch 12 to perform welding. The configuration shown in FIG. 1 is a basic configuration, and actually incorporates various elements in addition to the above-described elements.

In the present embodiment, a microphone 17 for detecting a welding sound is installed inside the upper end of the laser torch 12, utilizing the fact that the laser torch 12 has a cylindrical housing. A sound absorbing (or soundproofing) material 18 is provided on the inner wall of the housing.

In this way, the welding sound generated from the welding portion of the work 15 is collected by the microphone 17, and the voltage-converted sound signal is output to the welding state determination processing device 20. The welding state determination processing device 20 performs a determination process such as a defect detection based on a voltage signal from the microphone 17, and outputs the result as necessary to the display device 21 or the storage device 2.
Display and record with 2.

FIG. 2 shows the configuration of the welding state determination processing device 20. The sound signal from the microphone 17 is converted into a digital signal by the A / D converter 20-1, and is converted into a digital signal by the CPU 20-2.
In the high-speed signal processor 20-3, the quality of the welding state such as defect detection is determined online according to a predetermined processing algorithm. Such a device configuration is generally used as a signal processing device, and can be easily realized using a personal computer.

The predetermined processing algorithm in the welding state determination processing device 20 is not the gist of the present invention, but, in a simple example, the pass / fail judgment is made based on the level of the voltage signal obtained from the welding sound. Do. That is, it is known that the level of the voltage signal due to the welding sound is higher than the level of the voltage signal due to the welding sound generated in a poor welding state when the welding is performed well. Therefore, a lower limit value and an upper limit value are set for the level of the voltage signal due to the welding sound. What is necessary is just to perform the determination processing which makes a determination.

In the present embodiment, a microphone 17 is installed on the upper part inside a general cylindrical laser torch 12 and a sound absorbing material 18 is provided inside the laser torch 12 to reduce the detection of external noise. It also solves the problem of the installation position. At the same time, the laser torch 12 itself serves as a sound collecting tube, and has directivity, sound collecting property,
From the viewpoint, the welding sound can be detected efficiently. In addition, the laying of the sound absorbing material 18 can suppress the reflection and resonance of sound in the laser torch 12.

The lower part of the laser torch 12 is
The welding sound enters the laser torch 12 because it is located so as to cover the welding location of No. 5. The sound that hits the inner wall of the laser torch 12 in the entered sound is absorbed by the sound absorbing material 18, so that the reflection of the sound is suppressed.
The sound traveling upward is detected by the microphone 17. Therefore, it is possible to detect a sound equivalent to a raw welding sound in which reflection and resonance of the sound are suppressed. Further, since the sound absorbing material 18 absorbs noise from outside the laser torch 12, the welding sound can be detected stably. Further, the laser reflecting mirror 13
The condensing lens 14 becomes an obstacle to the progress of sound, but does not cause a serious problem. When the reflection of sound by the sound absorbing material 18 is not sufficiently suppressed, the inner wall of the laser torch 12 is made to have a structure in which sound is not easily reflected, so that high-quality (near raw) welding sound can be detected.

The laser oscillator 11 is a YAG
A laser oscillator, a CO ₂ laser oscillator, an excimer laser oscillator, or the like can be used.

[0023]

According to the present invention, the following effects can be obtained.

1. Detection of external noise other than welding noise can be suppressed, and noise countermeasures become unnecessary.

2. Even when the shape of the work is complicated and the posture of the laser torch changes variously, the welding sound can be detected without being affected by the change.

3. By utilizing the shape of the cylindrical laser torch, the sound collecting property and the directivity for the welding sound can be improved, and the welding sound can be detected efficiently.

4. Performing online welding judgment based on welding sound makes it possible to improve the quality control of welded products and save labor and labor for inspectors.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a welding defect detection device according to a preferred embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a welding state determination processing device shown in FIG.

FIG. 3 is a diagram showing a positional relationship between a laser torch and a detector provided on the laser torch for explaining a problem of the conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Laser oscillator 12, 30 Laser torch 13 Laser reflection mirror 14 Condensing lens 15, 32 Work 17 Microphone 18 Sound absorbing material

Claims (3)

[Claims] In a laser welding machine for guiding a laser beam to a laser torch having a cylindrical housing and irradiating the work through a lower end opening of the cylindrical housing to perform welding, the laser light is applied to the inside of the housing. Laser welding defect detection characterized by providing a sensor for detecting a sound generated at a welding portion of the work, and detecting a defect at the welding portion based on a level of a sound signal detected by the sensor. apparatus. 2. The laser welding defect detecting device according to claim 1, wherein a sound absorbing material is provided on an inner wall of the housing. 3. The laser welding defect detecting device according to claim 2, wherein said sensor is provided at an upper end portion in said housing.