JPH10202378A - Laser beam welding method by optical fiber transmission and its welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of heat, the damage to optical parts, injuries to human bodies or the like by interrupting the emission of a laser beam with an interlocking means operated when the intensity of the light beam from a weld zone is monitored and the intensity exists outside the normal intensive range. SOLUTION: In a controller 19, the intensity of the light beam 12 from the weld zone is monitored, an interlocking signal 20, turning on when the value exists within the light emission intensity range in normal welding and turning off when the value outside this range is detected, is outputted to a shutter interlock 4. In the shutter interlock 4, the interlocking signal 20 and the output of a discontinuity detecting circuit 2 are electrically connected in series, a safety shutter 5 is operated to close when either one or both turn off. That is, the shutter 5 is closed with the shutter interlock 4 when either one or both of the off signal of the interlocking signal 20 when welding is not normally executed in the weld zone and the welding light beam 12 exists outside the normal range and the off signal when the breakage of the optical fiber 1, the discontinuity or the like are generated are inputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser welding method and apparatus using optical fiber transmission in which laser light is condensed on the surface of a workpiece through an optical fiber to perform welding.

[0002]

2. Description of the Related Art FIG. 5 shows an example of a conventional laser welding apparatus using optical fiber transmission. In FIG. 5, reference numeral 10 denotes a workpiece, 3 denotes a laser oscillator for transmitting a laser beam 6, 1 denotes an optical fiber, 8 denotes an incident optical system, 9 denotes an output optical system, and 11 denotes a molten pool. The interlock system applied to the transmission optical system of the laser welding by the optical fiber transmission includes a disconnection detecting circuit 2 for detecting the disconnection of the optical fiber 1 around the optical fiber 1 and the laser oscillator 3.
And a shutter interlock 4, a safety shutter 5, a beam damper 7, and the like.

In such an optical fiber transmission optical system, when the optical fiber 1 is damaged or disconnected, the disconnection detecting circuit 2 is blown, and when the blow is detected, the shutter interlock 4 is operated to move the safety shutter 5 to the position shown in FIG. , And the laser beam 6 is dropped on the beam damper 7.

[0004]

In an interlock system of a transmission optical system using an optical fiber according to the prior art as shown in FIG. 5, the disconnection detecting circuit 2 is provided only around the optical fiber 1. The interlock does not operate at all with respect to the abnormality of the emitting optical system attached to the emitting end of the optical fiber 1 and the welding state. For this reason, when an abnormality occurs in the emission optical system or the welding state, there is a problem that the safety shutter 5 cannot be closed immediately and the laser beam continues to be emitted. In addition, when an abnormality occurs in the transmission optical system of the high-power laser used for welding, the laser beam 6 is absorbed at the abnormal location and instantaneously generates heat, which may cause a fire or a laser beam to cause an obstacle to the human body. In addition, there is also a problem that a secondary damage of an optical component is caused in a short time.

The present invention has been made in view of the above-mentioned problems of the prior art, so that even when an abnormality occurs in a welded portion, it is possible to detect the abnormality and activate an interlock so that the laser beam is emitted when the abnormality occurs. An object of the present invention is to cut off and prevent heat generation of an optical fiber transmission system and occurrence of secondary damage caused thereby.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a first aspect of the present invention is to perform welding by condensing a laser beam emitted from a laser oscillator on the surface of a workpiece through an optical fiber. In detecting the light from the welded portion, the intensity is monitored, and when the intensity is outside the normal intensity range, the interlock is activated to cut off the laser light, and the laser by optical fiber transmission is characterized in that We propose a welding method.

According to the present invention, there is provided a laser welding apparatus for performing welding by converging laser light emitted from a laser oscillator on the surface of a workpiece through an optical fiber as an apparatus for performing the laser welding method. Light detecting means for detecting light from the light source, measuring means for measuring the intensity of the detected light, and monitoring the intensity of the measured light, and interlocking when the intensity is out of the range of the normal light intensity. Control means for transmitting a signal, and interlock means for interrupting transmission of the laser light to the optical fiber when an interlock signal is input when the signal is outside the normal light intensity range. We propose a laser welding device using optical fiber transmission.

According to the first aspect, the light from the weld detected by the light detecting means is measured by the light intensity measuring means such as a photodiode, and is input to the control section. In the control unit, the input intensity is monitored to determine whether or not the intensity is within a normal light intensity range. When the intensity is outside the normal intensity range, that is, the intensity of the light detected from the welded portion. Is compared with the light intensity when normal welding is performed, and when the intensity is out of the range corresponding to normal welding, it is determined that there is an abnormality in the transmission optical system, and the interface is determined. A lock signal is output to the interlock means. In the interlock means, the transmission of the laser light to the optical fiber transmission system is interrupted by operating a shutoff means such as a safety shutter for interrupting the laser light in response to the interlock signal.

In this way, even when there is an abnormality in the welding state at the welded portion, this is detected and the blocking device such as a safety shutter is operated by the interlock means to block the laser beam. It is possible to prevent generation of heat, damage to optical components caused by the heat, and damage to the human body.

According to a second aspect of the present invention, when a laser beam emitted from a laser oscillator is condensed on the surface of a workpiece through an optical fiber and welding is performed, light reflected from a welded portion is reflected by the incident light. A laser welding method using optical fiber transmission, characterized in that the intensity is detected through an optical fiber for use to monitor the intensity, and when the intensity is out of a normal intensity range, an interlock is activated to cut off the laser light. suggest.

As means for carrying out the second invention, the light detecting means is configured to detect light from a welded portion through the incident optical fiber.

According to the second aspect of the invention, the light from the welded portion is detected through the optical fiber for incidence (laser light transmission), so that the detection optical system and the detection optical system for detecting the light from the welded portion are provided. Since it is not necessary to provide an optical fiber or the like around the welding head, the welding head can be downsized and the number of parts of the welding device can be reduced.

Further, preferably, in addition to the apparatus of the first invention, failure detecting means for detecting a failure such as disconnection or breakage of the optical fiber is provided, and the interlock means is provided outside the normal light intensity range. When one or both of the interlock signal at the time of (1) or the failure detection signal from the failure detection means is detected, the laser beam is cut off.

According to this invention, both the abnormality in the welded portion and the abnormality such as breakage or disconnection of the optical fiber are detected together to activate the interlock means. It is enlarged.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. It's just

FIG. 1 is a configuration diagram (system diagram) showing an interlock system of a transmission optical system using an optical fiber according to a first embodiment of the present invention. In FIG. 1, reference numeral 10 denotes an object to be welded, 3 denotes a laser oscillator for transmitting a laser beam 6, 1 denotes an optical fiber, and 2 denotes a disconnection which is provided around the optical fiber 1 and detects breakage or disconnection of the optical fiber 1. Detection circuit, 4 is shutter interlock, 5 is safety shutter, 7
Denotes a beam damper, and 8 denotes an incident optical system.

When the shutter interlock 4 is operated (opened), the safety shutter 5 is closed as shown by the broken line in FIG. 1, and the laser beam 6 is dropped by the beam damper 7. Has become. When the safety shutter 5 is open (the position indicated by the solid line in FIG. 1), the laser beam 6 is condensed by the incident optical system 8 and enters the optical fiber 1, and exits from an exit optical system 9 through an exit 1a. The light is emitted toward.

Reference numeral 9 denotes a processing emission optical system which focuses the laser beam 6 emitted from the optical fiber 1 on the workpiece 10. As a result, a molten pool 11 is formed on the surface of the workpiece 10, laser welding is performed, and light 12 such as plasma from a welded portion is generated. 13
Is a detection optical system, 14 is a detection optical fiber, 15 is an interference filter, 16 is a monitoring optical system, 17 is a photodiode, 18 is an amplifier, and 19 is a control unit.

In the transmission optical system using the optical fiber having the above-described configuration, the laser beam 6 emitted from the laser oscillator 3 passes through the safety shutter 5 which is normally open, and is condensed by the incident optical system 8 so that the light is condensed. After passing through the fiber 1, the light is condensed by the emission optical system 9 and is irradiated on the welded part on the workpiece 10. Thereby, laser welding is performed.

Light 12 such as reflected light and plasma from a laser beam welding portion on the workpiece 10 is condensed by the detection optical system 13 and enters the detection optical fiber 14.
The light 12 emitted from the exit of the detection optical fiber 14 is condensed by the monitor optical system 16 through the interference filter 15, and the intensity thereof is measured by the photodiode 17. The output of the photodiode 17 is amplified by an amplifier 18 and input to a control unit 19.

The control unit 19 monitors the intensity of the light 12 from the welding portion, and turns on when a light emission intensity range of normal welding is detected, and turns off when a value outside the range is detected. 20 is output to the shutter interlock 4. In the shutter interlock 4,
The interlock signal 20 and the output of the disconnection detection circuit 2 are electrically connected in series, and the operation is performed so as to close the safety shutter 5 when one or both of them are turned off.

That is, the shutter interlock 4 is used to turn off the interlock signal 20 when the welding light 12 is out of the normal range and the welding light 12 is out of the normal range, damage to the optical fiber 1, breakage of the optical fiber 1, etc. O when the occurrence of
When one or both of the FF signals are input, the safety shutter 5 is closed and the laser beam 6 is dropped to the beam damper 7.

[0023]

【Example】

[Example 1] An experimental example of the interlock system according to the first embodiment of the present invention shown in Fig. 1 will be described below. (FIGS. 3 and 4
reference).

Laser: Nd ³ + YAG (wavelength 1.06 μm) Laser beam output: average output 2 kW, peak output 5 k
W, rectangular modulation 100 Hz ・ Laser beam spot diameter: 0.5 mm ・ Material for welding: carbon steel sheet ・ Shielding gas: N ₂・ Welding speed: 20-40 cm / min ・ Interference filter (15): center value 900 nm, half Price range 2
5 nm, transmittance 80% Photodiode (17): Si photodiode

FIG. 3 shows an example of the laser output and the relative intensity of light from the weld. In the present embodiment, the light intensity when the laser beam 6 is emitted as shown by a and c in the figure is monitored, and the light intensity, that is, the relative intensity is set to a threshold value on the assumption that the transmission optical system is damaged. It was determined that an abnormality had occurred when the value fell below d. FIG. 4 shows an example of the shutter interlock operation when the intensity of light from the weld is arbitrarily reduced during welding. 3 and 4, the light intensity is monitored after the start of welding, and when the light intensity decreases, the shutter interlock 4 operates and the safety shutter 5 is closed.

FIG. 2 shows an interlock system of a transmission optical system using an optical fiber according to a second embodiment of the present invention. In this embodiment, a detection mirror 21 is provided in an optical transmission path between the incident optical system 8 and the entrance of the optical fiber 1, and light from a welding portion passing through the optical fiber 1 is reflected by the mirror 21. And input to the interference filter 15.

That is, in FIG.
A detection mirror provided between the entrance optical system 8 in the path of the laser beam 6 transmitted from the optical fiber 1 and the entrance of the optical fiber 1. The laser beam 6 is incident when the safety shutter 6 is open. The light is condensed by 8 and passes through the detection mirror 21 to enter the optical fiber 1 for transmission. The laser beam 6 is focused on the workpiece 10 by the emission optical system 9 to form a molten pool 11, and laser welding is performed. At this time, light such as plasma reflected by the laser beam 6 and plasma is generated from the welded portion. Light 12 from these welds is condensed by the emission optical system 9 and enters the transmission optical fiber 1 from the opposite direction to the time when the light enters the transmission optical fiber 1. The light is condensed by 16 and enters a photodiode 17, where the intensity is monitored. The output of the photodiode 17 is amplified by the amplifier 18 and input to the control unit 19.

The control unit 19 monitors the intensity of the light 12 from the welded portion, and turns on when an emission intensity range of normal welding is detected, and turns off when a value outside this range is detected. 20 is output to the shutter interlock 4. In the shutter interlock 4,
The interlock signal 20 and the output of the disconnection detection circuit 2 are electrically connected in series, and the operation is performed so as to close the safety shutter 5 when one or both of them are turned off.

The other structure and operation are the same as those of the first embodiment shown in FIG. 1, and the same members and elements are denoted by the same reference numerals.

In this embodiment, the light 12 reflected from the welded portion is detected through the optical fiber 1 for incidence (laser light transmission), so that the light from the welded portion as in the first embodiment is detected. It is not necessary to provide an optical system (detection optical system 13, detection optical fiber 14, etc.) around the welding head for detecting, so that the welding head can be downsized and the number of parts of the welding device can be reduced. You.

Example 2 An experimental example of the interlock system according to the second embodiment of the present invention shown in FIG. 2 is shown below (see FIGS. 3 and 4).

Laser: Nd ³ + YAG (wavelength 1.06 μm) Laser beam output: average output 2 kW, peak output 5 k
W, rectangular modulation 100 Hz ・ Laser beam spot diameter: 0.5 mm ・ Welding specimen: carbon steel plate ・ Shielding gas: N ₂・ Welding speed: 20-40 cm / min ・ Detector mirror (21): quartz plate ・ Interference Filter (15): center value 900 nm, half width 2
5 nm, transmittance 80% Photodiode (17): Si photodiode

FIG. 3 shows an example of the laser output and the relative intensity of light from the weld. In the present embodiment, as in the first embodiment, the intensity of light when the laser beam 6 is emitted as shown in FIGS. It was determined that an abnormality had occurred when the intensity, that is, the relative intensity, became lower than the threshold value d. FIG. 4 shows an example of the shutter interlock operation when the intensity of light from the weld is arbitrarily reduced during welding. 3 and 4, the light intensity is monitored after the start of welding, and when the light intensity decreases, the shutter interlock 4 operates and the safety shutter 5 is closed.

[0034]

As described above, according to the present invention, by monitoring the intensity of light from the welded portion, an abnormality in the welded portion is detected, the interlock means is operated, and the safety shutter or the like is operated. The emission of the laser beam can be blocked by the blocking unit. Thus, when an abnormality occurs in the welded portion, it is possible to prevent heat generated by the emission of the laser beam, damage to the optical components caused by the emission of the laser beam, and the occurrence of obstacles to the human body.

According to the fourth and fifth aspects of the present invention, light from the welded portion is detected through the incident optical fiber.
It is not necessary to provide a special device for detecting the light around the welding head, so that the size of the welding head can be reduced, and the number of parts of the welding device is reduced and the cost is reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an interlock system of a transmission optical system using an optical fiber according to a first embodiment of the present invention.

FIG. 2 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 3 is an operation explanatory view (part 1) in the embodiment of the present invention.
It is.

FIG. 4 is an explanatory diagram of an operation in the embodiment of the present invention (part 2).
It is.

FIG. 5 is a configuration diagram showing a conventional interlock system of a transmission optical system using an optical fiber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Disconnection detection circuit 3 Laser oscillator 4 Shutter interlock 5 Safety shutter 7 Beam damper 8 Incident optical system 9 Emission optical system 10 Workpiece 13 Detection optical system 14 Detection optical fiber 15 Interference filter 16 Monitoring optical system 17 Photodiode 19 Control unit 21 Detection mirror

 ──────────────────────────────────────────────────の Continued from the front page (72) Yoshimi Ueto Inventor 5-717-1 Fukabori-cho, Nagasaki-shi Nagasaki Research Laboratory, Mitsubishi Heavy Industries, Ltd.

Claims (5)

[Claims] 1. When welding laser light emitted from a laser oscillator through an optical fiber onto a surface of a workpiece to be welded, light from a weld is detected and its intensity is monitored, and the intensity is monitored. A laser welding method using optical fiber transmission, wherein an interlock is activated to cut off the laser light when the intensity is outside a normal intensity range. 2. A laser welding apparatus for performing welding by converging laser light emitted from a laser oscillator on the surface of a workpiece through an optical fiber, wherein light detecting means for detecting light from a welded portion; Measuring means for measuring the intensity of the measured light; control means for monitoring the intensity of the measured light and transmitting an interlock signal when the intensity is out of the range of the normal light intensity; and And an interlock means for interrupting the transmission of the laser light to the optical fiber when an interlock signal when the signal is out of the range is input. 3. A fault detecting means for detecting a fault such as disconnection or breakage of the optical fiber, wherein the interlock means detects an interlock signal when the optical fiber is out of the normal light intensity range, or detects the fault. 3. The laser welding apparatus using optical fiber transmission according to claim 2, wherein the laser beam is cut off when any one or both of the failure detection signals from the means are detected. 4. A laser beam emitted from a laser oscillator is condensed on the surface of a workpiece through an optical fiber to perform welding, and light reflected from a weld is detected through the incident optical fiber. A laser welding method using optical fiber transmission, characterized in that the intensity is monitored, and when the intensity is out of a normal intensity range, an interlock is activated to block the laser light. 5. The laser welding apparatus using optical fiber transmission according to claim 2, wherein said light detecting means is configured to detect light from a welding portion through said incident optical fiber.