JPH06155056A - Method and device for controlling laser beam welding - Google Patents

Abstract

PURPOSE:To detect the abnormality of a laser beam welding with an AE sensor and to enable the optimum control in the laser beam welding. CONSTITUTION:Sound generated at the time of executing the laser beam welding, is detected with an AE sensor 6 and the AE signal is compared with a reference data 10a. Then, in the case the actual AE signal is more than or less than the reference signal, this AE signal is compared with AE signal patterns 10b in various kinds of non-suitable welding conditions through a CPU 9. This AE signal pattern is the one stored by beforehand examining this pattern at the time of welding generated in the case of being the various kinds of the welding conditions, such as laser beam output, focus positioning of the laser beam, shield gas flow rate, assist gas flow rate, to out of the permissible range. In the case, the AE signal is similar with either one in the AE signal patterns, the welding condition corresponding to this pattern is corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser welding control device, and more particularly to a control technique for monitoring a laser welding state by an AE sensor and performing welding under optimum conditions.

[0002]

2. Description of the Related Art Conventionally, as a control technique for laser welding or the like, there has been proposed a technique for detecting AE (Acoustic Emission) generated during welding and monitoring and controlling the welding state from this detection signal.

For example, in the work condition monitoring method disclosed in Japanese Patent Laid-Open No. 60-22657, ultrasonic welding is taken as an example, and the welding quality indicates the waveform of AE, energy, frequency spectrum, etc. generated during the welding. Focusing on the relationship with the physical quantity, by processing the information of the AE wave, the working state of welding is monitored, and based on this, the current and voltage of the welding power source are controlled, and the work piece is processed. Techniques for controlling the positioning of a cradle have been proposed.

Other similar control methods include, for example,
As disclosed in Japanese Patent Laid-Open No. 64-40192, an AE signal associated with laser processing of a workpiece is detected through one or a plurality of AE sensors fixed to the workpiece, and this AE signal is calculated. A processing control method for processing and monitoring the laser processing state in real time while monitoring is proposed. Further, as disclosed in Japanese Patent Laid-Open No. 1-210185, the quality of a product is determined from the AE signal generated during welding. State monitoring devices and the like have been proposed.

[0005]

The welding conditions necessary for laser welding are: laser beam output, welding speed,
The distance between the focus position of the laser beam and the work piece, the flow rate of the shield gas, and the flow rate of the assist gas are listed. That is, even if one of these conditions changes beyond the allowable value, it may affect the quality of welding.

Specifically, when the actual output value of the laser beam is higher than the set value, unevenness and undercut are likely to occur in the welding beam. On the contrary, if it is lower than the set value, the penetration depth becomes shallow.

Further, when the distance between the focal position of the laser beam and the object to be welded is shorter than the set value, unevenness or undercut of the welding beam is likely to occur, and conversely, when the distance is long, the penetration depth becomes shallow.

If the flow rate of the shield gas and the flow rate of the assist gas are low, blowholes are likely to occur,
Even if the flow rate is high, irregularities are likely to occur on the blowholes and weld beads.

However, the above-mentioned conventional laser processing control and laser processing monitoring and control method using an AE sensor are not designed to deal with all of these problems, and simply use an AE signal and a welding power source (welding output). ), And when a welding abnormality is detected from the AE signal, the output current or voltage of the welding power source is controlled, or the position of the work piece is controlled. When the cause, for example, the flow rate of the shield gas, the flow rate of the assist gas, or the like is abnormal, it cannot be dealt with, so that it is impossible to perform sufficient laser welding control, which makes practical application difficult.

Further, at the site where laser welding control is performed,
Since various work noises are generated in the environment, the AE sensor detects noises other than welding, and there is a high possibility that the welding state is monitored incorrectly.

The present invention has been made in view of the above points, and an object thereof is to specifically diagnose what kind of the above-mentioned various welding conditions the abnormal condition corresponds to when the abnormal laser welding is detected by the AE sensor. The purpose of the present invention is to provide a laser welding control device that enables optimum control of laser welding based on the diagnosis result.

Another object of the present invention is to provide a laser welding monitoring and control device which can accurately perform laser welding monitoring and control by an AE signal without being influenced by noise.

[0013]

In order to achieve the above object, the following laser welding control system is basically proposed.

One of them is that, when performing laser welding, the sound generated during laser welding is detected by an AE sensor, and this AE signal is previously generated as reference data (this reference data is generated when the welding is performed under appropriate welding conditions). The AE signal that has been checked and stored in advance), and if the actual AE signal is equal to or more than the reference data, the AE signal is changed to an AE signal pattern of various unsuitable welding conditions (this AE signal). (The signal pattern is obtained by previously examining and storing the AE signal pattern during welding that occurs when various welding conditions such as laser output, laser beam focus positioning, shield gas flow rate, assist gas flow rate, etc. are outside the allowable range.) If the AE signal is similar to any of the AE signal patterns, the welding condition corresponding to the pattern is corrected (this is the first method). And control system).

The other is to detect the sound generated during laser welding with an AE sensor and compare this AE signal with reference data similar to that of the first control method described above so that the actual AE signal is equal to or greater than the reference data. In the following cases, laser power, laser beam focus positioning, shield gas flow rate,
Various welding conditions such as the assist gas flow rate are prioritized, the welding conditions are slightly changed according to the order, the AE signal after the slight change and the reference data are compared and calculated, and the difference between the reference data and the AE signal is calculated. If it becomes smaller, it is corrected by further changing the welding condition after this slight change (this change is in the same direction as the direction where the above minute change is made), while the reference data is changed due to this slight change in the welding condition.・ If the AE signal difference becomes large, the welding condition is returned to the original state, the welding condition of the next rank is slightly changed, and the AE signal after the slight change and the reference data are compared and calculated as in the previous rank. A control method for correcting the welding conditions is proposed (this is the second control method).

This second control method can also be adopted as a part of the first control method.

For example, in the first control method, when there is a common indistinguishable AE signal pattern of the unsuitable welding conditions among the various welding conditions (for example, among the welding conditions) Taking the welding conditions of the laser output value and the laser focus position as an example, an AE signal pattern generated when the laser beam output is lower than the allowable range and when the laser focus position is outside the proper range The details are described in the embodiment), prioritizing the welding conditions to be the target, and assigning a second priority according to the priority.
The same correction is performed as in the control method (3rd control method).

Further, in connection with these control methods, the AE signal detected by the AE sensor is other than the detection signal in the transient state at the start and end of laser welding and the welding sound from the work site. A method of cutting noise and comparing it with the reference data is proposed.

[0019]

According to the first control method, A generated during welding
By comparing the E signal with the reference data, it is known that the welding conditions are not appropriate, and by comparing the AE signal with the AE signal patterns of various unsuitable welding conditions, the incorrect welding conditions are various welding conditions ( For example, it can be determined which of the laser output, the focus position of the laser beam, the shielding gas, the assist gas flow rate, etc., corresponds to, and the correction of the welding condition obtained from a wide variety of welding conditions becomes possible. Therefore, the state of laser welding can be monitored in real time and appropriate welding control can be performed.

According to the second control method, it is possible to correct the welding condition as appropriate without creating the AE signal pattern of various unsuitable welding conditions as in the first control method.

That is, in this method, when it is determined that the welding condition is abnormal by comparing the AE signal with the reference data, the laser output, the laser beam focus positioning, the shield gas flow rate, the assist gas flow rate, etc. If various welding conditions are slightly changed in the increasing or decreasing direction according to the setting order, and if the difference between the AE signal and the reference data after the change of welding becomes small, the welding condition of the minute change target is currently in an inappropriate state. Therefore, the so-called welding condition diagnostic action is performed.

Then, if the welding condition recognized as unsuitable is further changed in the direction in which the difference between the AE signal and the reference data becomes smaller, the AE signal falls within the range of the reference data and the optimum welding condition can be restored. .

On the other hand, if the difference between the reference data and the AE signal becomes large due to a slight change (increase / decrease) in the welding conditions, the welding conditions are not in an inappropriate state, so the welding conditions are restored to the next order. The welding conditions are changed by a small amount, and the welding conditions are changed by a small amount until diagnosis is made. Even if the above diagnosis is performed for each welding condition, if the welding state is not improved, if the alarm is issued and the operation is stopped, the reliability of welding monitoring control is further enhanced.

The third control method compensates for a part of the first control method, that is, even when there is a common AE signal pattern of unsuitable welding conditions that cannot be distinguished, Since it is possible to diagnose and correct which welding condition is inappropriate, the real-time improvement function of the welding condition is enhanced.

[0025]

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

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

As shown in FIG. 1, a laser beam 2 output from a laser oscillator 1 is transmitted to a laser welding head 4 via an optical system 3, and the laser welding head 4 condenses and emits the beam 2. An object to be welded 5 is arranged near the focal position.

An AE sensor 6 is fixed to the laser welding head 4, and sound generated during welding is detected by the AE sensor 6 in a wide frequency range. The analog signal output from the AE sensor 6 is input to the preamplifier 7 and amplified. The amplified analog signal is converted into a digital signal by the D / A conversion circuit 11, and the CPU is the center of the welding control device.
(Microprocessor) 9 is input. A signal detected by the AE sensor 6 before welding (a noise detection signal outside welding at the work site) is also stored in the background noise data memory 8 as background noise.

Reference numeral 10a is a reference data memory (reference data storage means) connected to the CPU 9 and stores the AE signal level at the time of optimum welding as reference data for comparing and discriminating the signal from the AE sensor 6.

Reference numeral 10b is a diagnostic data memory (AE pattern storage means) connected to the CPU 9, and various welding conditions (for example, laser output, laser beam focus positioning, seal gas flow rate, assist gas flow rate, etc.) are not appropriate (allowable range). Outside), the diagnostic data for determining which welding condition this is stored. This diagnostic data is obtained by previously examining and storing the pattern of the AE signal generated when various welding conditions such as laser output, laser focal length, shield gas, assist gas, etc. are not appropriate.

The CPU 9 reads the background noise data from the background noise data memory 8 at the time of welding according to the control program 22a, and at the same time, inputs the digital signal (AE signal) output from the D / A conversion circuit 11 and outputs the background noise data to each other. The signal of is calculated to be a signal from which background noise is removed. Further, the actual AE signal and the data read from the reference data memory 10 are compared and calculated. As a result of this comparison operation, if the actual AE signal is within the range of the reference data,
Welding is performed under the current welding conditions.

Here, the welding head positioning control device 12 connected to the CPU 9 is controlled by the control program 22a, gives a control command to the servomotor 13, rotates the screw shaft 23 connected to the servomotor 13, and The laser welding head 4 connected to the shaft 23 is moved up and down. The encoder 14 fixed to the shaft of the servomotor 14 feeds back the position signal of the laser welding head 4 to the welding head positioning controller 12.

The laser output control device 15 connected to the CPU 9 is also controlled by the control program 22a to give a control command to the laser oscillator 1 to increase or decrease the output of the laser beam.

The assist gas flow rate control device 16 connected to the CPU 9 is also controlled by the control program 22a and gives a control command to the assist gas flow rate controller 18 to increase or decrease the flow rate of the assist gas. Assist gas supply cylinder 21
The assist gas filled in is supplied to the laser welding head 4 via the assist gas flow rate controller 18, and is supplied near the focal position of the laser beam.

Similarly, the shield gas flow rate control device 17 connected to the CPU 9 is also controlled by the control program 22a and gives a control command to the shield gas flow rate controller 19.
Increase or decrease the flow rate of shield gas. The shield gas filled in the shield gas supply cylinder 20 is supplied to the laser welding head 4 via the shield gas flow rate controller 19 and is supplied near the focal position of the laser beam.

On the other hand, the CPU 9 judges that welding is being performed under unsuitable welding conditions if the AE signal is equal to or more than the reference data as a result of the comparison calculation of the AE signal and the reference data 22, and corrects it. Diagnosis and correction of welding conditions are executed by the program 22b. That is, the CPU 9 also serves as a welding condition correction means.

Prior to the description of this diagnosis and correction, the relationship between welding and the signals of the AE sensor will be described with reference to FIGS. 2 and 3.

FIG. 2 shows the laser welding from the start to the end.
3 shows a detection signal of the AE sensor 6. From 0 at the time of welding start to time t ₁ and from time t ₂ to the time t _{3 of} welding end, transient and unstable peculiar phenomena are observed. Therefore, the reference data read by the CPU 9 is set by excluding the data of this transitional portion. This improves the reliability of the reference data during steady welding.

FIG. 3 is a graph showing the relationship between the detection signal level of the AE sensor 6 and the time during welding.

The time from the start of welding 0 to the time t ₁ and the time from the end of welding t ₂ to the time t ₃ are excluded from the control range for the above reason.

W ₀ is a detection signal of the AE sensor 6 when uniform and high quality laser welding is performed, and the average value of the detection signal levels of the AE sensor 6 from time t ₁ to time t ₂ is S. _Set to ₀ . Here, in order to perform uniform and high-quality welding, the detection signal level of the AE sensor 6 is centered on S ₀ and the upper limit is S ₀ between times t ₁ and t _2.
+ ΔS, the lower limit value must be S ₀ + ΔS, which is in between. In other words, S ₀ ± ΔS becomes the reference data for normal welding.

For example, the waveform W ₁ is from time t ₁ to time t _2.
, There is a time zone exceeding the upper limit value S ₀ + ΔS, and the waveform W ₂
, There is a time zone below the lower limit value S ₀ −ΔS, so uniform and high quality welding cannot be obtained. For this reason,
In order to perform uniform and high-quality welding, it is necessary to control the optimum welding conditions, that is, control the laser beam output, the laser beam focus position, the shield gas flow rate, and the assist gas flow rate to optimum values. is there.

FIGS. 4 and 5 show specific examples of the waveform of the detection signal of the AE sensor 6 obtained when these welding conditions deviate from the proper ranges.

In FIG. 4, a waveform W ₄₁ is a waveform generated when the output value of the laser beam is lower than the optimum range, or when the focus position of the laser beam is not within the optimum range. The waveform W ₄₂ is a waveform when the output of the laser beam is higher than the optimum range. Both the waveforms W ₄₁ and W ₄₂ have a low frequency and have relatively few irregularities in the waveform.

In FIG. 5, a waveform W ₅₀ is a waveform that appears when the flow rate of the shield gas is not within the optimum range and is high or low. When the flow rate of the assist gas is high, a waveform similar to the waveform ₅₀ appears.
The feature is that the detection signal level of the AE sensor 6 has irregularities.

The waveform W ₆₀ is a waveform when the flow rate of the assist gas is smaller than the optimum range, and is characterized in that the detection signal level is abnormally high and the frequency is high. This is due to the metal plasma generated when the flow rate of the assist gas is low.

In order to carry out uniform and stable welding, it is necessary to constantly monitor the welding state and control each welding condition in real time so as to be within an appropriate range. Here, the welding state is detected by one AE sensor 6,
The procedure for controlling each welding condition based on the correction program 22b is shown below.

FIG. 6 shows a control flow of laser welding conditions executed by the correction program 22b. (A)-(k)
Is a step in the flow.

First, in (a), it is determined whether or not the detection signal level of the AE sensor 6 is within the proper range (within the reference data). When the detection signal level is lower than the lower limit value S ₀ −ΔS or higher than the upper limit value S ₀ + ΔS,
(B) The subsequent welding conditions are corrected. If the detection signal level is within the proper range, the process returns to (k) and again at (a) it is checked whether the detection signal level is within the proper range.

In (b), when the waveform of the detection signal is similar to W ₄₁ or W ₄₂ in FIG. 4, the focus position of the laser beam is outside the proper range, or the output value of the laser beam is Is either outside the proper range, but
In this case, prioritization is performed, and first, in (e), the positioning control of the laser welding head is performed, and the focus position of the laser beam is determined and optimal control is performed. The optimum control of the focus position will be described in detail later.

In (f), it is checked again whether the detection signal is within the proper range, and if it is within the proper range, the process is terminated and the process returns to the initial (k). If it is outside the proper range,
Since there are causes other than the focal length, the output value of the laser beam is controlled so as to fall within an appropriate range in (g). Here, when the detection signal level is equal to or higher than the upper limit value S ₀ + ΔS of the proper range, the output value of the laser beam is decreased, and when the detected signal level is equal to or lower than the lower limit value S ₀ -ΔS of the proper range, the output value of the laser beam is increased, Control so that it falls within the proper range.

When the waveform of the detection signal is neither W ₄₁ nor W ₄₂ in (b), the process proceeds to (c), and it is checked whether the waveform of the detection signal is similar to the waveform ₅₀ of FIG. When the waveform is similar to the waveform W ₅₀ , there are cases where the flow rate of the shield gas is small or large relative to the proper value, and there are cases where the flow rate of the assist gas is large. Here, to determine which of these three,
Prioritize and reduce the flow rate of the shield gas by a very small amount. At this time, if the detection signal waveform is improved, the flow rate is further reduced, and the optimum waveform is brought closer to (k). On the contrary, if the detection signal waveform becomes worse when the flow rate of the shield gas is decreased, the flow rate of the shield gas is returned to the original flow rate. Next, the flow rate of the shield gas is increased by a very small amount. If the detection signal waveform at this time is improved, the flow rate is further increased to approach the optimum waveform and the process proceeds to (k).

On the contrary, if the detected waveform becomes worse when the shield gas flow rate is increased, the shield gas flow rate is returned to the original flow rate. If the welding conditions are improved by adjusting the shield gas, then the flow rate of the assist gas is reduced by a very small amount. At this time, if the detection signal waveform is improved, the flow rate is further reduced, and the optimum waveform is approached to proceed to (k).

If the detection signal becomes worse when the flow rate of the assist gas is increased, the flow rate of the assist gas is returned to the original flow rate, and the process proceeds to (k).

In (c), if the waveform of the detection signal is not similar to the waveform W ₅₀ , proceed to (d), and if the waveform of the detection signal is similar to the waveform W _{60 of} FIG. 5, Since the flow rate of assist gas is less than the proper range, the flow rate is increased so that the detection signal waveform falls within the proper range.

As described above, when the detection signal does not fall within the proper range even if the respective welding conditions are controlled, it is judged as an abnormality and the welding is stopped midway.

Here, the optimum control of the focal position of the laser beam performed in (e) of FIG. 6 will be described with reference to FIGS.

In (1) of FIG. 7, the laser beam becomes the focused laser beam 2 by the parabolic mirror 30. The focal length f ₀ of this laser beam is determined by the physical dimensions of the parabolic mirror. When laser welding is performed, it is optimal that the focus of the laser beam is on the surfaces of the abutting portions of the objects to be welded 5a and 5b.

However, the objects to be welded 5a or 5b are often deformed except those which have been machined, and it is necessary to always properly control the positioning of the laser welding head. 7 (2) shows the case where the focal position is above the surface of the workpiece, and FIG. 7 (3) shows the case where the focal position is inside the workpiece.

A method for detecting the states of these three focus positions by the AE sensor 6 and performing optimum control will be described below.

8 (1) shows the case where the focal position is on the surface of the object to be welded, and the detection signal waveform of the AE sensor 6 at this time is the waveform W ₀ of (1 ') in FIG. .

In FIG. 8B, the laser welding head is Δl.
This represents a state in which the height is increased by mm, and the detected signal waveform at this time is W ₁₁ in (2 ′) of FIG. 8, which is the average signal level S ₀ −ΔP ₁₁ , which is lower than the optimum value S _0. .

In FIG. 8C, the laser welding head is Δl.
It shows a state of being lowered by mm, the detected signal waveform at this time is W ₁₂ in (3 ′) of FIG. 8, and the average signal level is S ₀ −ΔP ₁₂ , which is the optimum value S ₀ . Get lower.

FIG. 9 (1 ') shows the case where the focus position is above the object to be welded. The detection signal waveform of the AE sensor 6 at this time is the waveform ₂₀ of (1) of FIG. The signal level becomes S ₀ −ΔP ₂₀ , which is lower than the optimum value S ₀ .

FIG. 9 (2 ') shows a state in which the laser welding head is further raised by .DELTA.lmm from that shown in FIG. 9 (1'). The detection signal waveform at this time is shown in FIG. ) is a waveform W ₂₁ of the average signal level (S ₀ -ΔP ₂₀₎ -Δ
Next P _21, further detection signal level decreases.

FIG. 9 (3 ') shows a state in which the laser welding head is further lowered by .DELTA.lmm from that shown in FIG. 9 (1'). The detection signal waveform at this time is shown in FIG. 9 (3). Waveform W ₂₂ , and the average signal level is (S ₀ −ΔP ₂₀ ) + ΔP
₂₂ and the detection signal level rises.

(1 ') of FIG. 10 shows the case where the focal position is inside the object to be welded, and the detection signal waveform of the AE sensor 6 at this time is the waveform W ₃₀ of (1) of FIG. The signal level becomes S ₀ −ΔP ₃₀ , which is lower than the optimum value S ₀ .

(2 ') of FIG. 10 shows a state in which the laser welding head is raised by .DELTA.lmm from that of (1'), and the detection signal waveform at this time is the waveform of (2) of FIG. W
₃₁ and the average signal level is (S ₀ −ΔP ₃₀ ) + ΔP ₃₁
And the detection signal level rises.

FIG. 10 (3 ') shows a state in which the laser welding head is lowered by .DELTA.lmm from FIG. 10 (1'), and the detection signal waveform at this time is the waveform of FIG. 10 (3). W
₃₂ , and the average signal level is (S ₀ −ΔP ₃₀ ) −ΔP ₃₂
And the detection signal level decreases.

From the above, FIG. 11 shows a control flow for controlling the laser welding head to bring the focal position of the laser beam to the optimum position.

According to the present embodiment, the state of laser welding is constantly monitored online, and if any of the various laser welding conditions causes an inappropriate state, it is detected and corrected in real time. It is possible to stably manufacture high quality laser welded products.

The above welding control method occurs when various welding conditions such as laser output, laser beam focus positioning, shield gas flow rate, assist gas flow rate, etc. are out of the allowable range as welding condition diagnostic data. A when welding
The E signal pattern is used, but without using such diagnostic data, the various welding conditions are prioritized, each welding condition is minutely changed until the welding is improved, and the change in the welding condition is detected. From the comparison between the signal and the reference data, which welding condition should be corrected may be diagnosed.

[0073]

As described above, according to the present invention, when an abnormality in laser welding is detected by the AE sensor, it is specifically diagnosed as to what of the above various welding conditions the abnormality corresponds to, and the diagnosis is made. Enables optimal control of laser welding based on the results.

Further, by taking measures against noise such as site noise, erroneous control can be prevented and reliability can be improved.

[Brief description of drawings]

FIG. 1 is a system of a laser welding control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a detection signal of an AE sensor from the start to the end of laser welding.

FIG. 3 shows the relationship between the detection signal level of the AE sensor during welding and time.

FIG. 4 is an explanatory diagram of a waveform of a detection signal of the AE sensor obtained when the welding conditions deviate from appropriate ranges.

FIG. 5 is an explanatory diagram of a waveform of a detection signal of the AE sensor obtained when the welding conditions deviate from appropriate ranges.

FIG. 6 is a flowchart for correcting welding conditions during welding.

FIG. 7 is an explanatory diagram of optimum control of the focus position of a laser beam.

FIG. 8 is an explanatory diagram of optimum control of the focus position of a laser beam.

FIG. 9 is an explanatory diagram of optimum control of the focal position of the laser beam.

FIG. 10 is an explanatory diagram of optimum control of the focus position of a laser beam.

FIG. 11 is a flowchart of optimum control of the focal position of the laser beam.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Laser oscillator, 2 ... Laser beam, 4 ... Laser welding head, 5 ... Object to be welded, 6 ... AE sensor, 8 ... Dark noise data memory, 9 ... CPU (welding condition correction means), 10a
... reference data memory, 10b ... diagnosis data memory (AE
Pattern data memory), 12 ... Welding head positioning control device (laser beam focus positioning control device), 15 ...
Laser output controller, 16 ... Assist gas flow controller, 17 ... Shield gas flow controller, 22a ... Control program, 22b ... Correction program.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shigeru Takeuchi Inventor 1-1-1 Kokubun-cho, Hitachi-shi, Ibaraki Inside Kokubun factory, Hitachi, Ltd. (72) Inventor Osamu Matsushima 1-1-1 Kokubun-cho, Hitachi-shi, Ibaraki No. 1 inside the Kokubun Plant of Hitachi Ltd. (72) Inventor Osamu Isshiki 1-1-1 Kokubun-cho, Hitachi City, Ibaraki Prefecture Inside the Kokubun Plant of Hitachi Ltd. (72) Inventor Teruyo Yoshiike Two Aise-cho, Hitachi City, Ibaraki Prefecture 9-1-1, Hitachi Equipment Engineering Co., Ltd.

Claims (9)

[Claims] 1. When performing laser welding, a sound generated during laser welding is detected by an AE sensor, and this AE signal is previously set as reference data (the reference data is an AE signal generated when the welding is performed under appropriate welding conditions). In the case where the actual AE signal is equal to or greater than or equal to the reference data, the AE signal is changed to an AE signal pattern of various unsuitable welding conditions (this AE signal pattern is AE signal pattern during welding that occurs when various welding conditions such as laser output, laser beam focus positioning, shield gas flow rate, assist gas flow rate, etc. are outside the allowable range) , AE signal is similar to any of the AE signal patterns, the welding conditions corresponding to the pattern are corrected. . 2. The welding condition according to claim 1, wherein if there is a common indistinguishable AE signal pattern of the unsuitable welding condition among the various welding conditions, the welding condition to be the target is prioritized. The welding conditions are minutely changed according to the order, the AE signal after the minute change and the reference data are compared and calculated, and if the difference between the reference data and the AE signal becomes small, the welding condition changed by the minute amount. Is further corrected (this change is in the same direction as the direction in which the amount is slightly changed), and on the other hand, if the reference data / AE signal difference becomes large due to this slight change in welding conditions, the welding conditions The welding condition of the next rank is slightly changed, and the AE signal after the slight change and the reference data are compared and calculated in the same manner as the previous rank to correct the welding condition. Les User welding control method. 3. When performing laser welding, a sound generated at the time of laser welding is detected by an AE sensor, and this AE signal is previously set as reference data (the reference data is an AE signal generated when performed under appropriate welding conditions). In the case where the actual AE signal is equal to or higher than the reference data, the laser output, laser beam focus positioning, shield gas flow rate, assist gas flow rate, etc. The welding conditions are prioritized, the welding conditions are slightly changed in accordance with the order, the AE signal after the slight change and the reference data are compared and calculated, and the reference data A
If the E signal difference becomes small, the welding condition changed by this minute amount is further corrected (this change is in the same direction as the direction in which the minute amount is changed), and the small amount of this welding condition is corrected. If the difference between the reference data and the AE signal becomes large due to the change, the welding condition is returned to the original state, the welding condition of the next rank is slightly changed, and the AE signal after the slight change and the reference data are changed in the same manner as the previous rank. A laser welding control method characterized by performing a comparative calculation to correct welding conditions. 4. The AE signal detected by the AE sensor according to any one of claims 1 to 3,
Noises other than welding noise from the work site and the detection signal in the transient state at the start and end of laser welding
The laser welding control method is characterized in that it is set so as to be cut and compared with the reference data. 5. The alarm according to any one of claims 1 to 4, when the AE signal is not within the range of the reference data even after the various welding conditions are corrected. A laser welding control method, characterized in that the welding operation is stopped by starting the operation. 6. (a) an AE sensor for detecting a sound generated by laser welding, (b) a laser output control means,
(C) Laser beam focus positioning control means for controlling the laser beam focus position with respect to the workpiece, (d) shield gas flow rate control means, (e) assist gas flow rate control means, (f) appropriate welding conditions A that occurs when performed
Reference data storage means for checking the E signal in advance and storing it as reference data, and (g) AE signal pattern of various unsuitable welding conditions (this AE signal pattern is laser output, laser beam focus positioning, shield gas flow rate, assist gas). AE signal pattern storage means for storing the AE signal pattern at the time of welding that occurs when various welding conditions such as the flow rate are out of the allowable range.
(H) Actual AE at the time of welding detected by the AE sensor
Comparing the signal with the reference data, and if the AE signal is equal to or greater than or equal to the reference data, the AE signal is compared with the AE signal pattern of the various unsuitable welding conditions,
A welding condition correction means for judging whether or not the AE signal is similar to the AE signal pattern, and if the AE signal is similar to any of the AE signal patterns, a welding condition correction means for correcting the welding condition corresponding to the pattern. A laser welding control device characterized by the above. 7. (a) an AE sensor for detecting a sound generated by laser welding, and (b) a laser output control means,
(C) Laser beam focus positioning control means for controlling the laser beam focus position with respect to the workpiece, (d) shield gas flow rate control means, (e) assist gas flow rate control means, (f) appropriate welding conditions A that occurs when performed
Reference data storage means for checking the E signal in advance and storing it as reference data, and (g) AE signal pattern of various unsuitable welding conditions (this AE signal pattern is laser output, laser beam focus positioning, shield gas flow rate, assist gas). AE signal pattern storage means for storing the AE signal pattern at the time of welding that occurs when various welding conditions such as the flow rate are out of the allowable range.
(H) Actual AE at the time of welding detected by the AE sensor
The signal is compared with the reference data, and if the AE signal is above or below the reference data, a predetermined correction program [this correction program is used for laser output, laser beam focus positioning, shield gas flow rate, assist gas If the welding conditions are minutely changed in accordance with the priorities in which various welding conditions such as the flow rate are given in advance, the AE signal after the slight change and the reference data are compared and calculated, and if the difference between the reference data and the AE signal becomes small, this It is corrected by further changing the welding condition that has been changed by a small amount (this change is in the same direction as the direction in which the amount is slightly changed). On the other hand, the small change in the welding condition causes the reference data / AE signal difference to change. If it becomes larger, the welding condition is returned to the original value, and the welding condition of the next rank is changed by a small amount.
A signal and the reference data are compared and calculated to correct the welding condition.] The laser welding control device. 8. The A according to claim 6 or 7,
Of the signals detected by the E sensor, a detection signal in a transitional state at the start and end of laser welding and a means for cutting noise other than welding noise from the work site are provided. A laser welding control device characterized by the above. 9. The method according to claim 6, further comprising means for outputting an alarm and automatically stopping the welding when the welding is not improved by the correction of the various welding conditions. Characteristic laser welding control device.