JP2008272767A - Laser welding apparatus and method of quality control in laser welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser welding apparatus and a method of quality control in laser welding, by which apparatus and method, the time necessary for the quality control in the laser welding can be shortened and an equipment cost can be suppressed by carrying out the laser welding operation for an object to be welded and the inspection process of the welding quality in the laser welding at the same time. <P>SOLUTION: The laser welding apparatus 1 comprises a laser spot gun 2 for laser-welding the work W to be welded while holding the work W by a pair of arms, and carries out the laser welding operation by means of the laser spot gun 2, and also carries out the inspection of the welded state of the work W. The laser spot gun 2 comprises first arm portions 3, 4 for melting the work W by irradiating the work W with a laser beam L, second arm portions 5, 6 for irradiating the work W to be melted by the first arm portions 3, 4 with an inspection beam S1 having a specified wavelength, and for detecting the intensity of the reflected beam S2, and a control portion 13 for judging the welded state of the work W. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser welding apparatus and a laser welding quality control method, and more particularly to a laser welding apparatus and a laser welding quality control method for performing laser welding on stacked steel sheets and inspecting their joining state.

  For example, when laser welding is performed to join stacked steel sheets and the joining state is inspected, conventionally, a visual inspection or an optical sensor directed to the welded portion is arranged and induced by laser light. There is a method of monitoring the plasma intensity generated in the welded portion by the optical sensor. Among these, the visual inspection has a problem that the yield is low because a highly accurate inspection can only be performed by an operator with long experience.

On the other hand, a laser welding management method using an optical sensor is disclosed in Patent Document 1. The laser welding management method disclosed in Patent Document 1 will be described with reference to FIG.
As shown in FIG. 5, in the laser welding apparatus disclosed in Patent Document 1, laser light L output from a laser oscillator (not shown) such as CO ₂ or YAG with respect to an overlapped workpiece W. Is collected after being condensed by a condensing optical system 50 such as a lens, and welding is performed while relatively moving the work piece W and the laser light L at a predetermined speed.

An optical sensor 51 such as a phototransistor directed to the welded portion B is disposed above the workpiece W, and the intensity of the plasma P generated in the welded portion B induced by the laser light L is monitored by the optical sensor 51. It is made to do.
Further, an optical sensor 52 that is directed to the welded portion B and monitors the intensity of the plasma P generated on the back side of the workpiece W is disposed below (back side) of the workpiece W.
In such a configuration, when the joining state of laser welding is inspected, the value detected by the optical sensors 51 and 52 is compared with a reference value stored in advance in a memory of a computer (not shown). Suitability is determined.
JP-A-6-262377

According to the method disclosed in Patent Document 1, since the welding state is inspected based on the correlation between the emission intensity of the laser-induced plasma and the welding strength, the quality control of laser welding can be performed with high accuracy.
However, in the method disclosed in Patent Document 1, when the optical sensors 51 and 52 are arranged above and below the workpiece W, it is necessary to perform accurate positioning for each welding site, and the inspection process is performed after welding. Therefore, there is a problem that it takes a long time to inspect the joining state for each welded part.
Further, in the apparatus shown in FIG. 5, since a jig for fixing the optical sensors 51 and 52 with high accuracy is required, there is a problem that the cost of the apparatus increases.

  The present invention has been made under the circumstances as described above, and by performing laser welding on the workpiece to be welded and simultaneously performing a laser welding joint quality inspection step, the time required for laser welding quality control is achieved. It is an object of the present invention to provide a laser welding apparatus and a laser welding quality control method capable of reducing the cost and apparatus cost.

In order to solve the above-described problem, a laser welding apparatus according to the present invention includes a laser spot gun for laser welding a workpiece to be welded while holding the workpiece between a pair of arms. A laser welding apparatus for performing laser welding and inspecting a joining state of the workpiece, wherein the laser spot gun irradiates the workpiece with a laser beam and melts the workpiece. A second arm portion that irradiates the workpiece to be welded by the first arm portion with inspection light having a predetermined wavelength and detects the intensity of the reflected light; and A control unit that determines a joining state, wherein the control unit determines the joining state of the workpieces based on the intensity of the reflected light detected by the second arm unit. .
The control unit includes storage means for storing a predetermined light intensity as a reference value, and the intensity of the reflected light detected by the second arm part and the reference value stored in the storage means. It is preferable to determine the joining state of the workpieces by comparison.

According to such a structure, since the inspection process of the joining quality can be performed while performing laser welding on the workpiece, the time required for quality control of laser welding can be shortened.
Moreover, since the second arm portion for detecting the intensity of the reflected light is always arranged at a predetermined position with respect to the workpiece in the state where the laser welding is performed, the arrangement in the inspection process of the joining state is performed. Can be easily.
Further, when the laser welding apparatus according to the present invention is configured, the mechanism of the second arm portion can be realized by providing the mechanism on the lower arm side of a conventional general-purpose spot gun, thereby reducing the apparatus cost. Can do.

In order to solve the problem, the quality control method for laser welding according to the present invention performs laser welding with a laser spot gun for laser welding the workpiece while holding the workpiece between a pair of arms. A quality control method of laser welding for inspecting a joining state of the work piece, wherein the laser spot gun irradiates the work piece with a laser beam by a first arm portion and melts the work piece. , Irradiating the workpiece to be welded melted by the first arm part with inspection light having a predetermined wavelength by the second arm part, detecting the reflected light intensity, and detecting the reflected light intensity. The control unit to which the value is supplied has a feature in determining a joining state of the workpieces based on the reflected light intensity.
When the detection value of the reflected light intensity is supplied by the second arm unit, the control unit reads the reference value from a storage unit that stores a predetermined light intensity as a reference value, and It is preferable to determine the joining state of the workpiece by comparing the supplied detection value of the reflected light intensity.

According to such a method, it is possible to carry out the inspection process of the joining quality while performing laser welding on the work piece, so that the time required for quality control of laser welding can be shortened.
Further, as an apparatus configuration for carrying out this method, the second arm portion for detecting the intensity of the reflected light is always arranged at a predetermined position with respect to the work piece in a state where laser welding is performed. The arrangement can be facilitated.
Further, when the quality control method for laser welding according to the present invention is configured, the mechanism of the second arm portion can be realized by providing the mechanism on the lower arm side of a conventional general-purpose spot gun. Can be suppressed.

  According to the present invention, the time required for quality control of laser welding can be shortened and the cost of the apparatus can be reduced by performing the laser welding joint quality inspection process at the same time as performing laser welding on the workpiece. A laser welding apparatus and a quality control method for laser welding can be obtained.

Embodiments of a laser welding apparatus and a laser welding quality control method according to the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a schematic overall configuration of a laser welding apparatus according to the present invention. As shown in FIG. 1, a laser spot gun for welding a workpiece W on which a plurality of steel plates (two in the figure) are overlapped with a YAG laser beam and inspecting the joining state thereof. 2 is provided. In FIG. 1, the laser spot gun 2 is shown in a sectional view.

As shown in FIG. 1, the laser spot gun 2 is composed of a pair of arm portions whose tips are C-shaped. As shown in the drawing, the workpiece W is sandwiched between the arm portions to hold the workpiece W. Used in state.
Of the pair of arm portions constituting the laser spot gun 2, the arm portion (first arm portion) disposed above the work W is a laser nozzle 4 that emits YAG laser light L, and this laser nozzle. 4 and a gun arm 3 that transmits laser light to the laser nozzle 4 through an optical fiber 10. On the other hand, the arm part (second arm part) arranged below the workpiece W includes a sensor part 6 for detecting data from the lower side (back side) of the welding part B and a sensor for supporting the sensor part 6. It consists of an arm 5.

  The gun arm 3 and the sensor arm 5 are configured so as to be movable in the vertical direction. When performing laser welding and inspection of the welding state, the laser nozzle 4 is provided on the upper surface of the welded part B of the workpiece W. The arm is moved so that the upper end of the sensor unit 6 is in close contact with the lower surface of the welded part B.

Further, as shown in the figure, laser light is supplied to the gun arm 3 from a laser oscillation unit 11 that oscillates YAG laser light. The gun arm 3 transmits laser light to the laser nozzle 4 through the optical fiber 10, and the laser nozzle 4 performs welding by irradiating the welding portion B of the workpiece W with the laser light L.
Further, as shown in the enlarged sectional view of FIG. 2 and the plan view of FIG. 3, the sensor unit 6 has a disk-shaped donut-shaped illumination member 7 locked on the inner peripheral surface 9 a of the cylindrical casing 9 whose upper part is open. Furthermore, the photosensor 8 is locked in the through hole 7b formed in the center of the illumination member 7.

As shown in FIG. 2, from the upper surface 7a of the illumination member 7, the inspection light S1 having a predetermined wavelength is irradiated upward. For example, a plurality of LED elements (not shown) are arranged on the illumination member 7 as highly directional illumination elements, and when the plurality of LED elements emit light, the entire upper surface 7a of the illumination member 7 is welded to the welding site B. On the other hand, the inspection light S1 having a predetermined wavelength is irradiated.
Further, as shown in FIG. 1, a light emission drive unit 12 is connected to the illumination member 7 (the LED element thereof), and the illumination member 7 emits light when power is supplied from the light emission drive unit 12. The light emission drive unit 12 is connected to a control unit 13 that controls the operation of the entire laser welding apparatus 1, and the operation of the light emission drive unit 12 is controlled by the control of the control unit 13.

In addition, the photosensor 8 functions to detect the light intensity of the reflected light S2 that is irradiated and reflected by the illumination member 7 on the welding portion B on the lower side W1 of the workpiece W, and the detected value is sent to the control unit 13. It is made to supply.
Further, a memory 13a (storage means) in which a predetermined light intensity is stored in advance as a reference value is provided in the control unit 13.

In the laser welding apparatus 1 configured as described above, when performing welding on the workpiece W and inspection of the welded state, the following is performed.
First, as shown in FIG. 1, with the workpiece W sandwiched and held by the laser spot gun 2, the laser oscillation unit 11 oscillates the YAG laser according to a command from the control unit 13, and the laser light L is emitted from the laser nozzle 4 Is transmitted.
Laser light is irradiated from the front end (lower end) of the laser nozzle 4 to the welded part B of the workpiece W, whereby the welding of the welded part B starts.

On the other hand, in the sensor unit 6, the illumination member 7 emits light by the drive control of the light emission driving unit 12 simultaneously with the start of laser welding, and the inspection light S 1 is irradiated to the welding site B on the lower side W 1 of the workpiece W.
Then, the reflected light S <b> 2 reflected by the welding part B on the lower side W <b> 1 of the workpiece W is received by the light receiving unit 8 a of the photosensor 8, and the detected value of the received light intensity is supplied to the control unit 13.
The control unit 13 reads the reference value of the light intensity stored in advance in the memory 13a, compares the reference value with the supplied detection value, and determines the welding joint state based on the comparison result.

The determination of the joining state in the control unit 13 is performed based on the correlation between the intensity of the reflected light S2 and the welding intensity.
For example, if the detected value of the reflected light S2 is larger than the reference value, it is determined that the joining is insufficient (NG), and if the detected value is smaller than the reference value, it is determined that the joining is sufficient (OK).
That is, as shown in FIG. 4A, when the melting is insufficient and the melt 15 does not reach the lower side W1 of the workpiece W, the surface of the lower side W1 of the workpiece W is smooth, Most of the reflected light S2 of the inspection light S1 is received by the light receiving portion 8a of the photosensor 8. Therefore, when the welding is insufficient, the received light intensity value becomes a large value.

On the other hand, as shown in FIG. 4B, when melting is sufficient and the melt 15 reaches the lower side W1 of the workpiece W, a bead (unevenness) is formed on the lower side W1 of the workpiece W. Is done. For this reason, the reflected light S2 of the inspection light S1 irradiated from the illumination member 7 is diffused in the casing 9, and the received light intensity of the reflected light S2 received by the light receiving portion 8a of the photosensor 8 is reduced. Therefore, when welding is sufficient, the detected value of the received light intensity is a small value.
In addition, it is desirable that the reference value of the light intensity stored in advance in the memory 13a in order to determine the bonding state is determined by a plurality of data collection by experiments.
The determination process in the control unit 13 is preferably performed continuously at short time intervals, and the result is output to output means (for example, a screen monitor, a speaker, etc.) not shown.

As described above, according to the embodiment of the laser welding apparatus and the quality control method of laser welding according to the present invention, it is possible to carry out the joint quality inspection process while performing laser welding on the workpiece W. The time required for quality control of laser welding can be shortened.
Moreover, since the sensor part 6 is always located under the welding part B in the state which performs laser welding as an apparatus structure, arrangement | positioning of the sensor part 6 can be performed easily.
Moreover, when comprising the laser welding apparatus concerning this invention, since the sensor part 6 should just be provided in the arm side below the conventional general purpose spot gun, apparatus cost can be held down.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for a laser welding apparatus and a laser welding quality control method used for lap welding of thin steel plates in a vehicle assembly process or the like.

FIG. 1 is a diagram showing a schematic overall configuration of a laser welding apparatus according to the present invention. FIG. 2 is an enlarged cross-sectional view of the sensor unit. FIG. 3 is a plan view of the sensor unit. FIG. 4 is a diagram for explaining a change in reflected light with respect to a welding joining state. FIG. 5 is a schematic configuration diagram of a conventional laser welding apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser welding apparatus 2 Laser spot gun 3 Gun arm 4 Laser nozzle 5 Sensor arm 6 Sensor part 7 Illumination member 8 Photosensor 10 Optical fiber 11 Laser oscillation part 12 Light emission drive part 13 Control part (control means)
13a Memory (storage means)
B Welded part L Laser light S1 Inspection light S2 Reflected light W Workpiece

Claims (4)

A laser spot gun for laser welding the workpiece to be welded while holding the workpiece to be welded between a pair of arms, and performing laser welding with the laser spot gun and inspecting a joining state of the workpiece to be welded A welding device,
The laser spot gun includes a first arm portion that irradiates the workpiece with laser light to melt the workpiece, and a workpiece having a predetermined wavelength with respect to the workpiece to be melted by the first arm portion. A second arm portion for irradiating the inspection light and detecting the intensity of the reflected light; and a control portion for determining the joining state of the workpieces;
The said control part determines the joining state of the said to-be-welded object based on the intensity | strength of the said reflected light detected by the said 2nd arm part, The laser welding apparatus characterized by the above-mentioned. The control unit includes storage means for storing a predetermined light intensity as a reference value,
2. The joining state of the workpiece is determined by comparing the intensity of the reflected light detected by the second arm portion with a reference value stored in the storage means. The laser welding apparatus described in 1. A laser welding quality control method for performing laser welding with a laser spot gun for laser welding a workpiece while holding the workpiece between a pair of arms, and inspecting a joining state of the workpiece. ,
The laser spot gun irradiates the workpiece with a laser beam by a first arm portion to melt the workpiece, and at the same time secondly melts the workpiece to be welded by the first arm portion. Irradiate the inspection light of a predetermined wavelength by the arm part of, and detect the reflected light intensity,
A quality control method for laser welding, wherein a control unit to which a detection value of the reflected light intensity is supplied determines a joining state of the workpieces based on the reflected light intensity. The controller is
When the detection value of the reflected light intensity is supplied by the second arm unit,
Reading the reference value from a storage unit that stores a predetermined light intensity as a reference value, and comparing the reference value with the detected value of the supplied reflected light intensity to determine the joining state of the workpieces A quality control method for laser welding according to claim 3.

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