JP3544157B2 - Inspection method and device for electric resistance welding nugget - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
A nugget is formed between the workpieces by electric resistance welding, and it is performed to check whether the nugget is sound. The invention belongs to the field of such nugget inspection.
[0002]
[Prior art]
As a prior art relating to the nugget inspection, Japanese Utility Model Laid-Open No. Hei 5-27663 is known. The technology disclosed herein magnetizes the work with alternating current to generate Barkhausen effect noise in the welded part, detects the stress value of the welded part by detecting this noise value, The focus was on the disappearance of stress. The Barkhausen effect noise means noise generated by the movement of the magnetic domain wall of the metal crystal grain of the welded portion when the welded portion is magnetized. For this reason, a probe for detecting noise is employed.
[0003]
[Problems to be solved by the invention]
According to the technique described above, it is necessary to magnetize a workpiece at a position distant from the welded portion and use another movable probe for the welded portion. Therefore, since the magnetizing means and the probe have to be arranged over a wide area of the work for the judgment, there is a problem that interference with neighboring members occurs and the usability as the judgment device is poor.
[0004]
More importantly, there is a problem with the direction of the nugget measurement. Traditionally, nuggets have been evaluated solely from the perspective of whether or not the workpiece is welded. However, in spot welding of steel sheets, the evaluation of nuggets from the two aspects of the relationship between the thickness of the steel sheet and the thickness of the nugget, and the relationship between the thickness of the steel sheet and the planar size of the nugget, that is, the nugget diameter. Is what is desired as a higher level of quality control. Such a concept is not disclosed in the above-mentioned prior art document.
[0005]
[Means for Solving the Problems and Their Functions]
The present invention has been devised in view of the above-described problems, and is based on a basic idea of determining the quality of a nugget from both sides of a nugget thickness and a nugget width with respect to a thickness of a work. .
[0006]
The invention according to claim 1 is a type in which a nugget formed between works by electric resistance welding is inspected, and a sensor probe for measuring the thickness of the work and a nugget thickness in the same direction as the work is formed by using ultrasonic waves. On the other hand, a sensor for measuring a nugget width in a direction substantially perpendicular to the nugget thickness direction is of a type using electromagnetic induction, and a sensor for measuring the thickness of the work and the nugget thickness in the same direction as the workpiece. A probe and a sensor probe for measuring a nugget width in a direction substantially orthogonal to the nugget thickness direction are integrally mounted on a movable mechanism, and both sensor probes are configured to alternately approach a nugget portion of a workpiece. And a measurement value judging device for comparing the measurement value signals from both sensor probes with a reference value is provided. It is an inspection apparatus of an electric resistance weld nugget, wherein the display device for reading the quality state of a nugget obtained by value determining device is provided. Therefore, the thickness and width of the nugget can be displayed in correlation with the thickness of the work, and a reliable nugget inspection can be realized, and by integrating both sensor probes, as described in the prior art, It is possible to solve the problem that a very wide area is occupied for inspection. The reference value is set from the viewpoint of whether the nugget thickness is appropriate for the thickness of the workpiece, for example, the steel plate, or whether the nugget width (diameter) is appropriate for the thickness of the steel plate. ing. Therefore, in the measured value determination device, data comparison processing is performed based on such a correlation with the work thickness. In addition, by using such a sensor probe, the nugget thickness can be accurately grasped with highly reliable ultrasonic waves, and furthermore, the state of the magnetic field lines passing through the nugget part by electromagnetic induction and the parts other than the nugget penetrate. By comparing the states of the magnetic field lines, the state of the soundly welded wide area can be accurately detected. Also, by attaching both sensor probes to the movable mechanism, the thickness or width can be measured almost simultaneously, which is effective for improving the inspection efficiency. In particular, in a robot welding line such as an automobile body, by incorporating an inspection device into an automation line, abnormality detection and line control can be closely related.
[0007]
According to a second aspect of the present invention, there is provided a type for inspecting a nugget formed between works by electric resistance welding, wherein a sensor probe for measuring a thickness of the work and a nugget thickness in the same direction as the work is formed by using ultrasonic waves. On the other hand, a sensor for measuring a nugget width in a direction substantially perpendicular to the nugget thickness direction is of a type using electromagnetic induction, and a sensor for measuring the thickness of the work and the nugget thickness in the same direction as the workpiece. A probe and a sensor probe for measuring a nugget width in a direction substantially orthogonal to the nugget thickness direction are integrally mounted on a movable mechanism, and both sensor probes are configured to alternately approach a nugget portion of a workpiece. And a measurement value judging device for comparing the measurement value signals from both sensor probes with a reference value is provided. An electric resistance welding nugget inspection device equipped with a display that reads the quality of the nugget obtained by the constant value judgment device is used to measure the nugget thickness and the thickness of the work with a sensor probe using ultrasonic waves, and the nugget width is measured. Is measured with a sensor probe using electromagnetic induction, the thickness of the workpiece, the thickness of the nugget, and the nugget width are measured almost simultaneously, and each measured value is compared with a reference value in a measurement value determination device, and the quality of the measured value is determined. Is read by a display device. Therefore, the inspection function as described above is exhibited. In addition, an inspection function utilizing characteristics of ultrasonic waves and electromagnetic induction can be obtained as described above. Also, by attaching both sensor probes to the movable mechanism, the thickness or width can be measured almost simultaneously, which is effective for improving the inspection efficiency. In particular, in a robot welding line such as an automobile body, by incorporating an inspection device into an automation line, abnormality detection and line control can be closely related.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. In addition, the thickness of the illustrated steel plate is exaggerated and shown thickly for easy understanding. First, referring to FIG. 2, steel plates 1 and 2 are welded by spot welding, and reference numeral 3 is a nugget. The thickness t of the nugget 3 is a dimension in the same direction as the thickness of the steel plate, that is, the workpieces 1 and 2, while the width d of the nugget 3 is a dimension in a direction substantially orthogonal to the nugget thickness. Since the planar shape of the nugget 3 is circular, the width d means the diameter of the nugget 3. Reference numeral 4 is an indentation generated by the electrode.
[0012]
FIG. 1 is a schematic diagram of an apparatus used in the present invention. A sensor 5 for measuring the nugget thickness and the thickness of the work 1 and a sensor 6 for measuring the nugget width are housed side by side in a case 7. The case 7 has the work 1 side opened so that it can handle the nugget 3. The case 7 is moved forward and backward by an air cylinder 8 so that the sensors 5 and 6 can correspond to the nugget 3 alternately, and a piston rod 9 of the air cylinder 8 is connected to the case 7. A slide plate 10 is fixed to the air cylinder 8, and slides on the work 1 to set the relative positions of the sensors 5, 6 and the nugget 3. A magnet 11 is embedded in the slide plate 10 to prevent the slide plate 10 from shifting. The two sensors 5 and 6 are integrated as described above, and the air cylinder 8 and the piston rod 9 correspond to a movable mechanism.
[0013]
There are several methods for measuring the thickness of the work and the thickness of the nugget t, such as a method using an X-ray and a method using an ultrasonic wave. Here, the latter method is employed. FIG. 3 shows a normal vertical probe, which is indicated by reference numeral 12. A vibrator 13, a backing material 14, a protection plate 15, and the like are provided in a case 16. The vibrator 13 is made of, for example, lead zirconate titanate-based porcelain, and the backing material 14 is made of, for example, a mixture of epoxy resin and tungsten fine powder.
[0014]
When the ultrasonic beam is emitted from the probe 12 toward the nugget 3, the nugget thickness t is measured by capturing the echo reflected from each part. That is, in FIG. 2, the nugget thickness can be measured by the time difference between the echo from the upper portion of the nugget 3 and the echo from the lower portion of the nugget 3. Since the thickness t is evaluated in relation to the thickness of the steel plates 1 and 2, the echo from the lower portion of the steel plate 1 and the echo from the lower portion of the steel plate 2 are grasped, so that the thickness t of the steel plates 1 and 2 is determined. The thickness is measured at the same time. The thickness t thus measured and the thickness values of the steel plates 1 and 2 are sent to a measurement value determination device described later, where they are compared with a reference value, and the quality of the nugget is displayed. Further, by combining the echo from the lower portion of the steel plate 1 and the echo from the lower portion of the steel plate 2, it is possible to measure which one of the nuggets 3 is biased when viewed in the thickness direction of FIG.
[0015]
There are several methods for measuring the nugget width d, such as a method using thermography and a method for grasping a change in the magnetic permeability of the nugget portion as a change in inductance. Here, the latter based on the principle of electromagnetic induction is employed. The sensor 6 has an electromagnet 18 installed in a case 17 made of a non-magnetic material. Reference numeral 19 denotes an iron core, and reference numeral 20 denotes an electromagnetic coil. A number of loop coils (referred to as array coils) 21 are arranged so as to cross the lines of magnetic force from the iron core 19. FIG. 5 shows a positional relationship between the nugget 3 and the loop coil.
[0016]
When a magnetic field is changed in the nugget portion by the electromagnet 18, in other words, the drive coil, an eddy current is generated in and around the nugget by electromagnetic induction. The state of the nugget part is grasped by measuring and analyzing the magnetic change caused by the eddy current as a voltage generated in the loop coil 21. Lines of magnetic force pass through the steel plate 1 at the portion where there is no nugget, and head toward the opposite pole. On the other hand, at a part of the nugget, the light passes through the nugget 3 itself and also through the steel plate 2 to the opposite pole. In the transmission of the nugget, the lines of magnetic force passing through the center of the nugget 3 have a straight shape as shown in FIG. 4, but the lines of magnetic force near the end of the nugget 3 have an undulating shape as shown. At this time, the change in the length of the line of magnetic force of each portion of the nugget 3 is captured by the loop coil 21 and measured to estimate the state of welding.
[0017]
In FIG. 4, the magnetic field lines near the end of the nugget 3 are curved, and this is the change in the length of the magnetic field lines. In order to measure the change state of the eddy current in and around the nugget 3 as a voltage value generated in the loop coil, the loop coils 21 are arranged at a small interval as shown in FIG. Many are arranged. Since the change in the length of the line of magnetic force appears as a change in the inductance of the loop coil 21, it can be determined from a decrease in magnetic flux when a static magnetic field is applied to each coil of the loop coil 21 and cut off. Note that a lead wire 22 extends from the loop coil 21 and is connected to a voltmeter.
[0018]
In FIG. 1, the inspection signal from each of the sensors 5 and 6 is sent to a measurement value determination device 23, where the inspection signal is compared with a reference value and the quality of the nugget is displayed on a CRT 24. Since the quality of the nugget is determined based on the correlation with the sheet thickness, the correlation is stored in the measurement value determination device 23. The steel plates 1 and 2 described here are for automobiles, both have a thickness of 0.8 mm, a nugget thickness of 0.5 mm, and a nugget width of 4.5 mm. The quality of the nugget width d is determined based on the relative relationship with the thickness of the steel sheet. Therefore, here, whether the relationship between the thickness of the steel plate measured by the sensor 5 and the measured value d is appropriate or not is compared with the reference value in the measured value determination device 23. Such a determination control circuit can be easily implemented by a generally employed comparison method.
[0019]
The operation of the above embodiment will be described. The air cylinder 8 and the case 7 are set on the work 1 so that the sensor 5 matches the nugget 3. Thereafter, first, an ultrasonic beam is emitted to the nugget 3, and the thickness t of the nugget is measured through the above-described process. Next, the sensor 6 is matched with the nugget 3 by the stroke of the air cylinder 8, and the nugget width d is measured according to the principle described above. These measurement signals are sent to the measurement value determination device 23, where they are compared with a reference value, and the quality is displayed on the CRT 24.
[0020]
In the above embodiment, the movable mechanism is configured by the air cylinder 8 and the piston rod 9 thereof, but may be configured as follows instead. That is, the sensor 5 is attached to an air cylinder that moves up and down, and the other sensor 6 is attached to an air cylinder that moves back and forth in the horizontal direction. By operating both air cylinders alternately, the thickness and width of the nugget can be reduced. You measure. Further, both sensors 5 and 6 may be attached to the swing arm, and the measurement may be alternately performed by swinging the arm.
[0021]
In the above-described alternate measurement, the thickness and the width are measured one after another, but both the measurements may be performed simultaneously. For this purpose, the sensor 5 is slightly tilted so that both sensors 5 and 6 coincide with the nugget 3 at a time. As a result, both sensors 5 and 6 can be operated at the same time, and the movable mechanism can be stopped.
[0022]
Although the above description is directed to spot welding in electric resistance welding, there is projection welding as the same type of welding. Since a welded portion is also formed in projection welding, the present invention can be applied to the determination of a welded portion. For reference, FIG. 6 shows that the projections 25 are formed on one of the two steel plates. FIG. 7 shows a projection bolt having projections 26 and 26 formed on its flange. 6 and 7 show a state before welding.
[0023]
【The invention's effect】
According to the present invention, in a type for inspecting a nugget formed between works by electric resistance welding, a sensor probe for measuring a work thickness and a nugget thickness in the same direction as the work is a type using ultrasonic waves. On the other hand, a sensor probe for measuring a nugget width in a direction substantially orthogonal to the nugget thickness direction is of a type utilizing electromagnetic induction, and a sensor probe for measuring the thickness of the work and the nugget thickness in the same direction as the sensor probe. And a sensor probe for measuring a nugget width in a direction substantially perpendicular to the nugget thickness direction are integrally attached to the movable mechanism, and both sensor probes are configured to alternately approach the nugget portion of the work. And a measurement value judging device for comparing the measurement value signals from both sensor probes with a reference value, and Since the inspection device for electric resistance welding nuggets is provided with a display device that reads the quality of the nuggets obtained by the value judgment device, the thickness and width of the nuggets are displayed in correlation with the thickness of the work. This makes it possible to realize a reliable nugget inspection, and solves the problem that a wide area is occupied for inspection as described in the prior art. The reference value is set from the viewpoint of whether the nugget thickness is appropriate for the thickness of the workpiece, for example, the steel plate, or whether the nugget width (diameter) is appropriate for the thickness of the steel plate. ing. Therefore, in the measured value determination device, data comparison processing is performed based on such a correlation with the work thickness. In addition, by using the sensor probe as described above, the thickness of the nugget can be accurately grasped by highly reliable ultrasonic waves, and furthermore, the state of the lines of magnetic force that pass through the nugget portion by electromagnetic induction and the portions other than the nugget pass through. By comparing the states of the lines of magnetic force, the state of the soundly welded wide area is accurately detected. As described above, since both ultrasonic waves and electromagnetic induction are highly reliable measurement methods, they are very advantageous for measuring two elements of thickness and width. Further, by attaching both sensor probes to the movable mechanism, the thickness or width can be measured almost simultaneously, which is effective for improving the inspection efficiency. In particular, in a robot welding line such as an automobile body, by incorporating an inspection device into an automation line, abnormality detection and line control can be closely related.
[0027]
In a type for inspecting a nugget formed between works by electric resistance welding, a sensor probe for measuring a thickness of a work and a nugget thickness in the same direction as that of the work uses an ultrasonic wave. A sensor probe that measures a nugget width in a direction substantially perpendicular to the thickness direction uses electromagnetic induction, and a sensor probe that measures the thickness of the workpiece and a nugget thickness in the same direction as the sensor probe, and the nugget thickness A sensor probe that measures the nugget width in a direction substantially perpendicular to the direction is integrated and attached to the movable mechanism, and both sensor probes are configured to alternately approach the nugget part of the work, and the A measurement value judgment device for comparing the measurement value signal with a reference value is provided, and the measurement value judgment device The nugget thickness and the thickness of the work are measured with a sensor probe using ultrasonic waves, and the nugget width is electromagnetically induced by an electric resistance welding nugget inspection device equipped with a display device that reads the quality of the nugget obtained by After measuring the thickness of the work, the thickness of the nugget and the nugget width almost simultaneously, comparing each measured value with a reference value in a measured value judging device, a display device showing the quality of the measured value. This is a method for inspecting an electric resistance welding nugget, wherein the method is read by: Therefore, the inspection function as described above is exhibited. In addition, an inspection function utilizing characteristics of ultrasonic waves and electromagnetic induction can be obtained as described above. In addition, by attaching both sensor probes to the movable mechanism, the thickness or width can be measured almost simultaneously, which is effective for improving the inspection efficiency. In particular, in a robot welding line such as an automobile body, by incorporating an inspection device into an automation line, abnormality detection and line control can be closely related.
[Brief description of the drawings]
FIG. 1 is an overall system diagram showing an embodiment of the present invention.
FIG. 2 is a sectional view of a nugget part.
FIG. 3 is a sectional view of an ultrasonic sensor.
FIG. 4 is a sectional view of an electromagnetic induction type sensor.
FIG. 5 is a sectional view taken along line (5)-(5) of FIG. 4;
FIG. 6 is a cross-sectional view showing a state of projection welding of a steel sheet.
FIG. 7 is a sectional view showing a state of welding of the projection bolt.
[Explanation of symbols]
1, 2 Work 3 Nugget t Nugget thickness d Nugget width 23 Measured value judging device 24 Display device 5, 6 Sensor probe 8, 9 Moving mechanism

Claims (2)

In a type for inspecting a nugget formed between works by electric resistance welding, a sensor probe for measuring the thickness of a work and a nugget thickness in the same direction as that of the work uses an ultrasonic wave. The sensor probe that measures the nugget width in a direction almost perpendicular to the thickness direction uses electromagnetic induction,
A sensor probe that measures the thickness of the workpiece and a nugget thickness in the same direction as the workpiece, and a sensor probe that measures a nugget width in a direction substantially orthogonal to the nugget thickness direction are integrally attached to a movable mechanism, and both sensors are attached. A probe configured to alternately approach the nugget portion of the workpiece, a measurement value judging device for comparing the measurement value signals from both sensor probes with a reference value, and a nugget obtained by the measurement value judging device. An inspection device for an electric resistance welding nugget, comprising a display device for reading a pass / fail state of the nugget. In a type for inspecting a nugget formed between works by electric resistance welding, a sensor probe for measuring the thickness of a work and a nugget thickness in the same direction as that of the work uses an ultrasonic wave. The sensor probe that measures the nugget width in a direction almost perpendicular to the thickness direction uses electromagnetic induction,
A sensor probe that measures the thickness of the workpiece and a nugget thickness in the same direction as the workpiece, and a sensor probe that measures a nugget width in a direction substantially orthogonal to the nugget thickness direction are integrally attached to a movable mechanism, and both sensors are attached. A probe configured to alternately approach the nugget portion of the workpiece, a measurement value judging device for comparing the measurement value signals from both sensor probes with a reference value, and a nugget obtained by the measurement value judging device. The nugget thickness and the thickness of the workpiece are measured with a sensor probe that uses ultrasonic waves, and the nugget width is a sensor probe that uses electromagnetic induction, using an electric resistance welding nugget inspection device equipped with a display device that reads the pass / fail status of the The thickness of the work, the thickness of the nugget, and the width of the nugget are measured almost simultaneously. After comparison with a reference value in the measured value determination device, inspection method of an electric resistance welding nugget, characterized in that as read by the display device the quality of the measurements.

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