JP2002045976A - Spot welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that conventional spot welding equipment provided with a monitoring function of a welding state is applicable only to an expensive servo gun, and such a characteristic of high speed and fine vibration as an expulsion direction generated during a welding, for example, is hardly detected. SOLUTION: The spot welding equipment is provided with a multi-axis vibration sensor 310, which detects vibrations of at least two axial directions of an electrode tip during the welding work, and a detection means 313 for welding state, which detects the behavior of the electrode tip on the basis of the vibration information detected by the multi-axis vibration sensor 310 and judges the normal/defective welding condition and the normal/defective welding point on the basis of the behavior of the electrode tip. The judgment of the normal/ defective condition of the welding is surely performed with a simple construction, thus the equipment contributes to the improvement of the welding quality and decrease in the cost for the equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spot welding apparatus having a monitoring function for judging the quality of a welding state during welding.

[0002]

2. Description of the Related Art As a spot welding apparatus of this type, for example, as described in Japanese Patent Application Laid-Open No. 10-263839, in a spot welding apparatus having a servo gun, a load cell or a servo motor provided on a pressure shaft is used. The pressing force between the electrode tips is detected from the amount of supplied power, and based on the pressing force, deformation of the workpieces and excessive gaps at the mating surfaces of the workpieces are detected. There is one in which good welding is performed by correcting and controlling the pressure. In addition, JP-A-9-1502
No. 78 discloses that in a spot welding apparatus equipped with a servo gun, the rotation angle information of a servomotor or the stroke amount of a pressurizing shaft is detected, and the detected value is compared with a predetermined reference value to determine the amount of wear of the electrode tip. Is described, the shaping or replacement of the electrode tip is instructed according to the result, and the welding current and the pressure between the electrode tips are corrected and controlled.

[0003]

However, in a spot welding apparatus, factors that hinder good welding include an excessive gap (plate gap) in the mating surface between the materials to be welded, a pressure shaft of the electrode tip, and a large gap. Excessive angular deviation (hitting angle) from the vertical axis with respect to the welding material, half-chip welding (end-hitting) of the end of the material to be welded due to the relative displacement between the setting point of the welding robot and the material to be welded, and electrode tip Dispersion that occurs constantly due to uneven wear or deformation of the material to be welded, welding at the interface between the electrode tip and the material to be welded, and the like are included. In particular, the factors (1) to (4) mainly change the welding current density, so that it is not possible to obtain appropriate resistance heat generation to obtain the required welding strength, and the spot nugget diameter is insufficient, and scattering and blowholes due to abnormal heating are generated. Cause.

However, in the conventional spot welding apparatus, since the state of the material to be welded and the wear state of the electrode tip are detected by using a sensor and a servo function of the servo gun, the application is limited to an expensive servo gun. In addition, since the specifications of the sensor are for executing the servo function, it is not possible to detect a high-speed and fine vibration characteristic such as a direction of scattering generated at the time of welding. There was a problem to solve such problems.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and it is possible to accurately judge the quality of a welding state with a simple structure, to improve welding quality and reduce equipment costs. It is an object of the present invention to provide a spot welding device that can contribute to the above.

[0006]

According to a first aspect of the present invention, there is provided a spot welding apparatus in which a material to be welded is pressed by opposed electrode tips and welded by resistance heating. A multi-axis vibration sensor for detecting vibrations of the tip in at least two axial directions, detecting the behavior of the electrode tip based on vibration information detected by the multi-axis vibration sensor, and determining whether the welding state is good or bad based on the behavior of the electrode tip It has a configuration provided with a welding state detecting means for judging the quality of the position, and the above configuration serves as means for solving the conventional problems.

[0007] In the above-described structure, the excessive plate gap between the materials to be welded, the excessive hitting angle of the pressurizing shaft with respect to the materials to be welded, the edge hitting, the scattering, and the electrode tip which are factors that hinder good welding. In order to detect all of the welding, it is desirable to detect vibrations in three orthogonal axes. At least vibrations in two orthogonal directions are detected, and the behavior of the electrode tip is determined based on the vibration information in the welding state detecting means. , It is possible to detect some of the factors that hinder good welding, thereby judging the quality of the welding state and the quality of the hitting position.

The spot welding apparatus according to the present invention is characterized in that, according to a second aspect of the present invention, the welding automatic control means for automatically controlling the spot welding apparatus is provided with a welding state for each of the hitting positions based on a history of the detection results of the welding state detecting means. A welding control correction instructing means for obtaining correction tendency information and outputting control correction information, and determining whether the spot nugget formation state is good or bad based on vibration information detected by the multi-axis vibration sensor. Nugget quality determination means, and a welding quality monitoring means for monitoring the quality of the finished workpiece based on the detection result of the welding state detection means and the quality determination result of the nugget quality determination means, wherein the welding is performed. A gap detecting means for detecting a gap state of the material to be welded by comparing a time required for the amount of advance of the electrode tip with respect to the material to be welded to reach a predetermined amount to a reference value. According to a fifth aspect of the present invention, the welding state detecting means includes a plate gap detecting means for detecting a plate gap state of the material to be welded by comparing an advance speed of the electrode tip with respect to the material to be welded to a reference value. Claim 6
The welding state detecting means includes a hitting angle detecting means for detecting the inclination of the pressing shaft with respect to the workpiece before pressing contact based on the behavior of the electrode tip when pressing in a direction perpendicular to the pressing shaft. Claim 7 wherein the welding state detecting means detects the presence or absence of the edge of the material to be welded based on a change in the envelope of the one amplitude of the welding vibration detected by the multi-axis vibration sensor. And as claim 8,
The welding state detecting means detects the direction of the dispersion based on the vibration in the direction perpendicular to the pressure axis, and based on the detection result and the detection result of the hitting angle detecting means, determines whether the defective part is on the electrode tip side or not. According to a ninth aspect, the welding state detecting means compares a time when the retreat amount of the electrode tip with respect to the material to be welded reaches a predetermined amount with a reference value. The electrode tip welding detecting means for detecting the welding of the electrode tip to the material to be welded is provided, and the above-mentioned structure is used as means for solving the conventional problems.

[0009]

According to the spot welding apparatus according to the first aspect of the present invention, in a spot welding apparatus in which a material to be welded is pressurized by opposing electrode tips and welded by resistance heating, a welding state between the multi-axis vibration sensor and the welding state is obtained. Due to the adoption of the detection means, despite the relatively simple structure, the excessive plate gap between the materials to be welded, the excessive hitting angle, It is possible to detect hitting, scattering, welding of the electrode tip, and the like, and it is possible to accurately judge the quality of the welding state and the quality of the hitting position. As a result, it is possible to contribute to the improvement of welding quality and productivity, and it is very easy to apply to an existing spot welding apparatus, and it is possible to contribute to reduction of equipment cost.

According to the spot welding apparatus of the second aspect of the present invention, the same effect as that of the first aspect can be obtained, and the welding control correction instruction means is provided to the automatic welding control means of the spot welding apparatus. By adopting, it is possible to quickly and automatically eliminate the cause of poor welding,
It is possible to maintain ideal welding conditions. Further, since the welding control correction instructing means obtains the tendency of the welding state for each hitting point from the history of the detection results of the welding state detecting means and outputs the control correction information, the correction amount of the welding control can be reduced. Thus, power saving, cost reduction, and further improvement in productivity can be realized.

According to the spot welding apparatus of the third aspect of the present invention, the same effects as those of the first and second aspects can be obtained, and the nugget quality judgment means and the welding quality monitoring means are employed. The finished quality of the material to be welded can be accurately monitored, which can contribute to further improvement in welding quality.

According to the spot welding apparatus of the fourth aspect of the present invention, the same effects as those of the first to third aspects can be obtained, and the welding state detecting means can perform welding on the basis of the advance amount of the electrode tip. Since it is equipped with a gap detection means that detects the gap of the material, it is possible to accurately detect the gap of the material to be welded with a simple structure, to prevent an excessive gap that causes welding failure, It can contribute to further improvement of welding quality.

According to the spot welding apparatus of the fifth aspect of the present invention, the same effects as those of the first to third aspects can be obtained, and the welding state detecting means can perform welding on the basis of the advance speed of the electrode tip. Since the apparatus is provided with the sheet gap detecting means for detecting the sheet gap of the material, the sheet gap of the material to be welded can be accurately detected with a simple structure, as in the case of the fourth aspect, which causes welding defects. It can contribute to prevention of excessive plate gap and further improvement of welding quality.

According to the spot welding apparatus of the sixth aspect of the present invention, the same effects as those of the first to fifth aspects can be obtained, and the welding state detecting means is provided with the hitting angle detecting means. With a simple structure, it is possible to accurately detect the inclination of the pressurizing shaft (hitting angle) with respect to the material to be welded, which contributes to prevention of excessive hitting angle which causes welding defects and further improvement of welding quality. it can.

According to the spot welding apparatus of claim 7 of the present invention, the same effects as those of claims 1 to 6 can be obtained, and in addition, the welding state detecting means is provided with the end strike detecting means. With a simple structure, it is possible to accurately detect the edge of the material to be welded, and to prevent the edge of the welding to cause poor welding and to further improve the welding quality.

According to the spot welding apparatus of the eighth aspect of the present invention, the same effect as in the sixth and seventh aspects can be obtained, and the welding state detecting means is provided with the scatter direction detecting means. With a simple structure, the direction of scattering, uneven wear of the electrode tip or deformation of the workpiece can be detected, and it is also possible to accurately estimate whether the defective part is on the electrode tip side or the workpiece side. Thus, it is possible to quickly solve the problem and contribute to further improvement in welding quality.

According to the spot welding apparatus of the ninth aspect of the present invention, the same effects as those of the first to eighth aspects can be obtained, and the welding state detecting means includes the electrode tip welding detecting means. Therefore, the welding of the electrode tip to the material to be welded can be accurately detected with a simple structure, and when the welding of the electrode tip occurs, it can be dealt with promptly.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a spot welding apparatus according to the present invention will be described below with reference to the drawings.

The spot welding apparatus shown in FIGS. 1 and 2 is provided with electrode tips 303 and 304 opposed to a pair of welding gun arms 1 and 2, and sandwiches two superposed workpieces W1 and W2. The material to be welded W1, W2 is welded by pressurization and resistance heating by energization. The electrode tips 303 and 304 are respectively attached to the welding gun arms 1 and 2 by electrode holders 301 and 305 and electrode adapters 302 and 30.
6. One welding gun arm 1 shown on the upper side in FIG. 1 is driven forward and backward with respect to the other welding gun arm 2 by an air cylinder 5. The other welding gun arm 2 is in a fixed state at least during welding.
The welding gun arms 1 and 2 are attached to, for example, a multi-axis control type welding robot.

The above-described spot welding apparatus uses the automatic welding control means 315 shown in FIG.
The welding current, energizing time and energizing timing with respect to 4 are controlled, and the primary current is amplified by the welding transformer 7 to the current Iw required for welding. This welding current Iw
On the other hand, the spot welding device is
2, electrode holders 301 and 305, electrode adapter 302,
306, electrode tips 303 and 304 and workpiece W
1, W2 forms a welding current circuit. The arrow Fm in FIG. 1 indicates the electromagnetic force acting on the parallel lines of the welding gun arms 1 and 2 when the welding current Iw is supplied. Also,
The automatic welding control means 315 includes the electrode tips 303 and 304.
Not only controlling the energization of the welding gun arms 1 and 2
It also controls the welding robot that determines the posture of the welding robot.

As shown in FIG. 3, the above-described spot welding apparatus includes a multi-axis vibration sensor 310 for detecting vibrations of the electrode tip 303 in one of three welding gun arms 1 in three orthogonal directions during welding, and the multi-axis vibration sensor 310. A processing unit 311 having the vibration sensor 310 as an input source is provided. Further, the processing unit 311 includes a nugget quality determination unit 312 that determines the quality of the formation state of the spot nugget based on the vibration information detected by the multi-axis vibration sensor 310, and a multi-axis vibration sensor 310
Electrode tips 303, 30 based on the vibration information detected in
The welding state detecting means 313 for detecting the behavior of No. 4 and judging the quality of the welding state and the hitting position based on the behavior of the electrode tip, and the history of the detection results of the welding state detecting means 313 and the automatic welding control means 315 A welding control correction instructing unit 314 for obtaining a tendency of the welding state for each of the hitting positions from the detected hitting position information and outputting control correction information to the automatic welding control unit 315;
The welding quality monitoring means 322 for monitoring the finished quality of the material to be welded based on the detection result of No. 13 and the quality determination result of the nugget quality determination means 312 is provided.

The multi-axis vibration sensor 310 is a three-axis acceleration sensor, and as shown in FIG.
2 is attached to a bracket 308 fixed with a screw 307, and vibration in the X-axis direction, which is the left-right direction in FIG.
The vibration in the Y-axis direction perpendicular to the plane of FIG.
Vibration in the Z-axis direction (pressing axis direction), which is the vertical direction, is detected. The reason why using an acceleration sensor to multi-axis vibration sensor 310 is particularly easy to detect the high-frequency vibration, wide detection dynamic range thermal expansion displacement that requires the acceleration ^twice the sensitivity ω relative displacement is obtained This is because it is easy to cope with certain applications, and because it is small, it can be easily applied to a welding gun with a large installation space restriction.

As shown in FIG. 4, the welding state detecting means 313 in the processing means 311 is an electrode behavior detecting means for detecting the behavior of the electrode tip 303 in the three axial directions from the vibration information of the multiaxial vibration sensor 310 in the three axial directions. 316, and using the electrode behavior detecting means 316 as an input source, a plate gap detecting means 317, a hitting angle detecting means 318, an end striking detecting means 319, a scattering direction detecting means 320, and an electrode chip welding detecting means 321. It has.

The electrode behavior detecting means 316 performs a double integration process on the three-axis vibration signals obtained by the multi-axis vibration sensor 310,
Displacement Xd, Y in three axial directions, which is the behavior of the electrode tip 303
d and Zd are calculated. Here, FIG. 5 is a diagram showing a reference pattern of the behavior of the electrode tip during welding and an actual behavior pattern of the electrode tip 303 detected by the electrode behavior detecting means 316 during welding.

The spot welding apparatus, as shown in FIG.
After the electrode tip 303 is lowered (moved forward with respect to the material to be welded), energization is performed after a predetermined pressurizing period, and thereafter, the electrode tip 303 is raised (retracted) once after a predetermined holding period, so as to be performed once. Is completed.

In the meantime, in the spot welding apparatus, during the descending process of the electrode tip 303, the plate gap detecting means 317 takes a time Td when the descending amount (advance amount) B1 of the electrode tip 303 with respect to the workpieces W1 and W2 reaches a predetermined amount. Or the descent speed of the electrode tip 303 (descent angle A1)
Is compared with a reference value to detect the gap state of the workpieces W1, W2. The displacement Zd in the Z-axis direction is used for detecting the gap. In the pressurization period, the hitting angle detecting means 318 determines the position of the electrode tip 303 during pressurization in a direction perpendicular to the pressurization axis, that is, the displacement Xd and Yd in the X and Y axis directions. The inclination B2 (α in FIG. 2) of the pressing shaft with respect to the welding materials W1 and W2 is detected.

Thereafter, during the energization period, the edge strike detecting means 319 detects the edges of the workpieces W1 and W2 based on the change in the envelope B3 of the one-sided amplitude in the welding vibration in the Z-axis direction detected by the multi-axis vibration sensor 316. The presence or absence of hitting is detected, and the direction of the scattering B4 is detected by the scattering direction detecting means 320 based on the vibration in the X and Y axis directions perpendicular to the pressing axis. Then, during the ascending process of the electrode tip 303, the workpieces W1, W
The welding time of the electrode tip 303 to the material to be welded W1 is detected by comparing a time Tu in which the rising amount (retreat amount) B5 of the electrode tip 303 with respect to 2 reaches a predetermined amount with a reference value.

FIG. 6 is a flow chart for explaining a basic detection process using the means 317 to 321 described above. That is, in Step S1 of the welding state detection, Step S1 is performed.
At 100, a gap is detected, and if it is determined that there is a gap at step S110, a warning of the gap is output at step S120. Then, step S200
In step S210, the hitting angle, which is the angle of the pressing shaft with respect to the workpieces W1 and W2, is detected. If it is determined in step S210 that the hitting angle is excessive, a warning of the hitting angle is output in step S220.

Subsequently, in step S300, the end is detected, and if it is determined in step S310 that there is an end, an alarm for the end is output in step S320. Next, the direction of the scattering is detected in step S400, and if it is determined in step S410 that there is a steady dispersion, a warning of the scattering is output in step S420. Thereafter, in step S500, the welding state of the electrode tip 303 is detected, and in step S51
If it is determined at 0 that welding has occurred, a warning of welding is output at step S520.

Then, as a processing step in the welding control correction instructing means 314, in step S600, the history of each welding state of the plate gap, hitting angle, edge hitting, scattering, and electrode tip welding is accumulated, and in step S700, the welding state is recorded. The control correction amount for the welding automatic control means 315 is detected based on the history of the control.

Next, the detection procedure of each of the means 317 to 321 will be described in detail with reference to the flowcharts of FIGS. 5 and 9 to 14.

The plate gap detecting means 317 includes the electrode chip 303
In the descending process, the gap is detected using the displacement Zd in the Z-axis direction detected by the electrode behavior detecting means 316. The plate gap detecting means 317 includes a reference pattern shown in FIG. 5, that is, a drop amount B1 of the electrode tip 303 when the normal workpieces W1 and W2 having no plate gap are pressurized, and a time until the drop amount B1 is reached. The time Td is stored as a reference value for determination.

When the actual welding is started, in step S101 of the flowchart shown in FIG. 9, the time T required for the electrode tip 303 to reach the predetermined amount of drop B1 is set.
The measurement of d is started, and it is repeatedly determined in step S102 whether or not the predetermined descending amount B1 has been reached. When the predetermined descending amount B1 has been reached, the measurement of the time Td ends in step S103.

If there is a gap between the workpieces W1 and W2, the gap is crushed by the descending electrode tip 303, and it takes a corresponding amount of time. It takes extra time T1 to reach. Therefore, the plate gap detecting means 317 determines in step S1
At step S04, an additional time T1 is calculated from the difference between the measured time Td and the reference time Td. At step S105, it is determined whether or not the additional time T1 is within an allowable value.
If 1 exceeds the allowable value, it is determined that there is a gap in step S106, and if the additional time T1 is within the allowable value, it is determined that there is no gap in step S107.

The gap detecting means 317 can also detect the gap based on the speed at which the electrode tip 303 descends. The descent speed is represented by the inclination angle A1 of descent of the electrode tip 303 in FIG. In other words, when there is a gap, it takes time to reach the predetermined amount of drop B1, so that the inclination angle A1 is smaller than when there is no gap.

In this case, the plate gap detecting means 317 is provided as shown in FIG.
In step S131 of the flowchart shown in FIG. 7, measurement of the change amount ΔZd of the Z-axis direction displacement Zd during the predetermined period Δt is started, and it is repeatedly determined in step S132 whether the predetermined period Δt has elapsed. In S133, the measurement of the change amount ΔZd ends. Then, in step S134, the descending speed (inclination angle A1) is calculated. This inclination angle A1 is obtained by the following equation (1).

[0037]

[Formula 1]

Thereafter, in step S135, it is determined whether or not the inclination angle A1 is within an allowable value.
If 1 exceeds the allowable value, it is determined in step S136 that there is a gap, and if the inclination angle A1 is within the allowable value, it is determined that there is no gap in step S137. As shown in FIG. 5, the hitting angle detecting means 318 detects a time T2 until the electrode tip 303 reaches a predetermined amount of drop B1.
During the pressurization period after the lapse of the time, the hit angle is detected.
That is, step S2 of the flowchart shown in FIG.
01, it is repeatedly determined whether or not the time T2 has elapsed. After the time T2 has elapsed, in step S202, the displacements Xd and Xd in the X and Y axis directions, which are the behaviors of the electrode tip 303 in the direction orthogonal to the pressure axis. Yd is input, and the hitting angle α shown in FIG. 2A is calculated in step S203.
The hitting angle α is the inclination of the vertical line of the workpiece W1 with respect to the pressurizing shaft before coming into contact with the workpieces W1 and W2, and is obtained by the following equation (2).

[0039]

[Formula 2]

Thereafter, the hitting angle detecting means 318 determines in step S204 whether or not the hitting angle α exceeds an allowable value. If the hitting angle α does not exceed the allowable value, no hitting angle is detected in step S205. If the hitting angle α exceeds the allowable value, it is determined in step S205 that there is a hitting angle (excessive hitting angle). The end detection means 319 includes:
During the energization period shown in FIG. 5, the presence or absence of edge striking is detected using the displacement Zd in the Z-axis direction. That is, the displacement Zd in the Z-axis direction of the electrode tip 303 is a combination of the displacement due to the electromagnetic vibration, the welding vibration, and the thermal expansion. When the welding is performed at a normal position, the displacement is shown in the reference pattern of FIG. Thus, the envelope of the composite wave monotonically increases. However, in the case of the end striking, the crushing of the materials to be welded W1 and W2 progresses rapidly due to the heat generated during energization, and as shown in the behavior pattern of FIG.
As the axial displacement Zd changes abruptly, the envelope of the composite wave also changes abruptly. Therefore, the end strike detection means 319
Detects the envelope of the synthesized wave by the amplitude detection circuit or the like in step S301 of the flowchart shown in FIG.
In step S302, it is determined whether or not there is a sharp edge that appears as a rapid change in the envelope. If there is no sharp edge, it is determined whether or not the energization has been terminated in step S303.
If the energization has been completed, it is determined in step S304 that there is no end-punching. If it is determined in step S303 that the energization has not been completed, the process proceeds to step S30.
Returning to step 2, if there is an edge hit in step S302, it is determined in step S305 that an edge hit is present.
The scatter direction detecting means 320 detects scatter generated in the same direction every time due to uneven wear of the electrode tip 303 or the like. The detection of the scattering is performed using displacements Xd and Yd in the X and Y axis directions which are directions orthogonal to the pressing axis of the electrode tip 303 during the energization period shown in FIG. That is, in step S401 of the flowchart shown in FIG. 13, the scattering vibration is detected based on the displacements Xd, Yd in the X and Y axis directions, and in step S402, the scattering direction α shown in FIG.
s is detected. The direction αs of this scattering is obtained by the following equation (3).

[0041]

[Equation 3]

In step S403, a history of a predetermined number of times of the scattering direction αs is accumulated, and if the scattering is statistically detected in substantially the same direction each time, uneven wear of the electrode tip 303 or the material to be welded is detected. It can be determined that the deformation of W1 and W2 is occurring chronically. In addition,
The scattering is detected by using a differentiating circuit, a high-pass filter, or the like, and extracting a vibration having a large amplitude in a short time. Further, the dispersal direction detecting means 320 performs step S40.
In step S4, the hitting angle α detected by the hitting angle detecting means 318 is compared with the direction αs of scattering, and if the angle α does not coincide with the direction αs of scattering, the work pieces W1, W2 side are determined in step S405. It is presumed that a defect such as deformation has occurred on the electrode tip 303, and if the hitting angle α and the scattering direction αs coincide with each other, it is presumed that a defect such as uneven wear has occurred on the electrode tip 303 side in step S406. . The reason for estimating the defect as described above is as follows. The defects on the side of the workpieces W1 and W2 are, for example, deformation, dirt and scratches on the welding surface, and have no relation to the hitting angle. Therefore, when the hitting angle α and the scattering direction αs do not match, the workpiece W
It can be said that there is a very high possibility that there is a defect on the W1 side. Further, due to uneven wear of the electrode tip 303, the material to be welded W
When the hitting angle α of the pressurizing shaft is generated with respect to 1 and W2, the overpressure by the electrode tip 303 on the side in the hitting angle direction (P in FIG. 2) becomes insufficient. Is easily formed, and the striking angle direction P matches the scattering direction αs. Therefore, when the hitting angle α and the scattering direction αs coincide with each other, it can be said that there is a very high possibility that the electrode tip 303 has a problem. Electrode tip welding detection means 32
In the process of raising the electrode tip 303, the electrode tip 303 is connected to the workpiece W1 based on the displacement Zd in the Z-axis direction.
It is detected whether or not it is welded. The electrode chip welding detecting means 321 stores a predetermined amount of rise B5 of the electrode chip in the reference pattern shown in FIG. 5 and a time Tu until the electrode chip reaches the amount of rise B5 as a reference value for determination. Then, step S501 of the flowchart shown in FIG.
The measurement of the time Tu is started in step S50.
It is repeatedly determined whether or not the predetermined amount of rise B5 has been reached in step 2, and if the predetermined amount of rise B5 has been reached, step S50
At 3, the measurement of the time Tu is completed. Here, the material to be welded W1
When the electrode tip 303 is welded, an additional additional time T5 is required until the electrode tip 303 reaches a predetermined rising amount B5 due to the resistance due to the welding. Therefore, the electrode tip welding detection means 321 calculates the additional time T5 from the difference between the measurement time Td and the reference time Td in step S504, and determines whether or not the additional time T5 is within an allowable value in step S505. If the additional time T5 exceeds the allowable value, it is determined in step S506 that there is welding, and if the additional time T5 is within the allowable value, it is determined that there is no welding in step S507. As described above, when the detection, determination, and determination of the plate gap, the hitting angle, the end striking, the scattering, and the welding of the electrode tip are performed, the welding control correction instructing means 314 includes the detection results from the respective means 317 to 321 and the welding automatic control means. The welding point position information from 315 is input.
The welding control correction instructing means 314 records the history of each detection result, and obtains the statistics of the welding state for each of the hit points on the workpieces W1 and W2 from the history. Then, for example, at a specific hitting point position, a gap determination, a deviation of a hitting angle, a defect determination of a welding state such as the occurrence of edge hitting or the like is performed, and based on a predetermined determination map as shown in Table 1, whether or not the control is corrected is determined. Outputs the contents of the correction as correction information.

[0043]

[Table 1]

The processing steps of the welding control correction instructing means 314 are shown in the flowchart of FIG. That is, step S
In 701, for example, the quality of the welding is determined based on the degree of melting of the welded portion obtained from the vibration information in the Z-axis direction. If the welding is not good, the welding conditions such as the current and the pressing force to the electrode tip 303 are corrected in step S702. If it is set, and welding is good, it is set in step S703 that there is no correction. In step S704, the presence or absence of a plate gap is determined. If there is a plate gap, positioning correction of the workpieces W1 and W2 is set in step S705, and if there is no plate gap, no correction is set in step S706. . Further, in step S707, the hitting angle is determined. If the hitting angle is larger than the allowable value, the positioning correction of the welding robot is set in step S708. If the hitting angle is smaller than the allowable value, step S708 is performed.
At 709, no correction is set. Next, step S
At 710, it is determined whether or not the end is set. If the end is set, the positioning correction of the welding robot is set at Step S711. If the end is not set, Step S71 is performed.
In step 2, no correction is set. Step S71
In 3, the presence or absence of welding of the electrode tip 303 is determined. If there is welding, the replacement of the electrode tip 303 is set in step S714. If there is no welding, step S714 is performed.
At 75, no correction is set. And step S
At 716, each correction information is output based on the determination map shown in Table 1 above. This correction information is input to the automatic welding control means 315, and a process for stopping the welding control or performing a correction operation is executed. In the above processing steps whose basic configuration is shown in FIG. 6, the case where sequential determination is performed in real time while detecting vibration during welding has been described. In addition, as shown in FIG. After once storing the vibration signal in the middle, step S
The method of judging the welding condition collectively in 1 and also,
As shown in FIG. 8, a method may be employed in which a vibration signal during welding is temporarily stored in step S800, and after an average vibration is detected in step S801, the welding state is collectively determined in step S1. In other words, when real-time determination is required, such as in-process control, the sequential determination method shown in FIG. 6 is preferably used. In order to reduce the variation in determination and simplify the quality control data, , FIG. 7 and FIG. 8 are preferably used, and these methods are properly used depending on the application. Next, the nugget quality determination means 312 in the processing means 311 shown in FIG. 3 determines the quality of the spot nugget formation state based on the vibration information in the Z-axis direction detected by the multi-axis vibration sensor 310. Here, FIG. 17 shows that the welding current was changed on a 1.6 mm-thick SPCC steel plate (cold-rolled steel plate) to perform welding, and the formation state of each spot nugget, welding vibration waveform, and welding vibration waveform. FIG. FIG. 18 is similar to FIG.
In the case where welding is not possible as shown in FIG. 7 (a) and the case where welding is successful as shown in FIG. 17 (c), the amplitude spectra of both welding vibration waveforms are divided into a melting start period and a spot nugget advance period and compared. is there. As is clear from FIG.
The features of the welding vibration waveform include the correlation between the amplitude level of the welding vibration waveform and the spot nugget formation, the correlation between the time change pattern of the envelope of the welding vibration waveform and the spot nugget formation, and the time change pattern of the frequency distribution of the welding vibration waveform. And spot nugget formation. FIG.
As is clear from FIG. 8, when the formation state of the spot nugget is not possible, there is no significant difference in the amplitude spectrum between the melting start stage (a) and the spot nugget formation progressing stage (c), but the spot nugget formation When the state is acceptable, a large difference can be confirmed in the amplitude spectrum of the spot nugget formation progressing stage (d) with respect to the melting start period (b). Therefore, in the nugget pass / fail determination means 312, Z
As the vibration information in the axial direction, the amplitude level of the welding vibration waveform,
The quality of the spot nugget can be determined based on the time change pattern of the envelope of the welding vibration waveform, the time change of the frequency distribution of the welding vibration waveform, and the like. Further, processing means 3
The welding quality monitoring means 322 in 11 monitors the finish quality of the material to be welded based on the detection result of the welding state detection means 313 and the quality determination result of the nugget quality determination means 312. As shown in Table 2, the welding quality monitoring means 322 stores a judgment map set based on each alarm output of the welding state detecting means 313 and the quality of the spot nugget. Then, each time the quality judgment result of the spot nugget and each alarm are output, the welding quality is judged and output with reference to the judgment map of Table 1.

[0045]

[Table 2]

The processing steps of the welding quality monitoring means 322 are shown in FIG.
6 is shown in the flowchart. That is, step S90
In step 1, for example, the quality of welding is determined based on the degree of melting of the welded portion obtained from the vibration information in the Z-axis direction. If the welding is defective, the welding quality is set to a defective level in step S902. If welding is good, the presence or absence of welding of the electrode tip 303 is determined in step S903, and if there is welding, the welding quality is set to a poor level in step S904. Further, if there is no welding, it is determined in step S905 whether or not there is an edge. If there is an edge, the welding quality is set to a defective level in step SS906. Next, if there is no edge striking, the presence or absence of a plate gap is determined in step S907, and if there is a plate gap, the welding quality is set to a slightly defective level in step S908. If there is no gap, the hitting angle is determined in step S909. If the hitting angle is larger than the allowable value, the welding quality is set to a quasi-pass level in step S910, and the hitting angle is smaller than the allowable value. In this case, in step S911, the welding quality is set to an acceptable level. Then, in step S912, the entire welding quality level is output. Here, the determination map shown in Table 2 will be described. If an alarm indicating that there is a gap is output when the quality of the spot nugget is judged to be acceptable, the quality as the welding strength is acceptable, but a wavy deformation may occur at the welded spot due to the gap. If the deformation is remarkable, the appearance quality cannot be said to be good. In addition, unnecessary power is consumed because the correction control is operating. For this reason, the determination map is set so as to output information indicating that inspection is required. By removing the cause of the occurrence of the gap based on the alarm, the welding quality and productivity can be managed and maintained well. In addition, when the hitting angle is determined to be acceptable when the quality of the spot nugget is determined to be acceptable, it is determined that the quality of the welding location is within an allowable value and the fact that the welding quality is good is output. The judgment map is set as follows. Further, when the spot nugget is judged to be acceptable and an alarm indicating that there is edged end is output, it cannot be said that both the welding strength and the appearance quality are acceptable. Therefore, the determination map is set to output that the welding quality is poor. Further, if the quality of the spot nugget is determined to be rejected, in order to prevent the material to be welded having insufficient welding strength from flowing out, the welding quality is poor in all combinations with the alarm output. The judgment map is set so as to output. The alarm output from each of the above-described units is connected to an alarm unit such as a lamp or a buzzer and a computer, and is used as welding monitoring result information for worker recognition and recognition in a production management system. In addition, the spot welding apparatus according to the present invention is not limited to the detailed configuration described in the above embodiment, and it is needless to say that various modifications can be made without changing the gist of the present invention. Further, each means can be separated and used as a single function according to the purpose.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a welding gun of a spot welding apparatus.

2A is a side view showing the vicinity of an electrode tip of the welding gun shown in FIG. 1, and FIG. 2B is a bottom view showing an inclination of a pressing shaft.

FIG. 3 is an explanatory diagram showing a circuit configuration in an embodiment of the spot welding apparatus according to the present invention.

FIG. 4 is an explanatory diagram showing an internal configuration of the welding state detecting means shown in FIG.

FIG. 5 is an explanatory diagram showing a reference pattern of the behavior of the electrode tip and a behavior pattern of the electrode tip when welding is actually performed.

FIG. 6 is a flowchart illustrating a basic detection process of a welding state detection unit based on a sequential determination method.

FIG. 7 is a flowchart illustrating a detection process according to a batch determination method.

FIG. 8 is a flowchart illustrating another detection process according to the batch determination method.

FIG. 9 is a flowchart illustrating a detection process based on a descending amount of an electrode tip of a plate gap detection unit.

FIG. 10 is a flowchart illustrating a detection process based on the descending speed of the electrode tip of the gap detection means.

FIG. 11 is a flowchart illustrating a detection process of a hit angle detection unit.

FIG. 12 is a flowchart illustrating a detection process of an edge strike detection unit.

FIG. 13 is a flowchart illustrating a detection process of a scattering direction detection unit.

FIG. 14 is a flowchart illustrating a detection process of an electrode tip welding detection unit.

FIG. 15 is a flowchart illustrating a detection process of a welding control correction instruction unit.

FIG. 16 is a flowchart illustrating a detection process of welding quality monitoring means.

FIG. 17 is an explanatory diagram showing a formation state of a spot nugget at different welding currents, a welding vibration waveform, and an amplitude spectrum.

FIG. 18 shows a case where welding is impossible in FIG.
It is explanatory drawing which shows the amplitude spectrum of the welding vibration waveform of each of the melting start period and the spot nugget formation progress stage in case of welding success of (c).

[Explanation of symbols]

 W1 W2 Workpiece to be welded 303 304 Electrode tip 310 Multi-axis vibration sensor 312 Nugget quality judgment means 313 Welding state detection means 314 Welding control correction instructing means 315 Welding automatic control means 317 Plate gap detection means 318 Strike angle detection means 319 Edge detection means 320 Scattering direction detecting means 321 Electrode tip welding detecting means 322 Weld quality monitoring means

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G01H 17/00 G01H 17/00 Z

Claims (9)

[Claims] 1. A multi-axis vibration sensor for detecting vibration in at least two axial directions of an electrode tip during welding in a spot welding apparatus in which a material to be welded is pressurized by opposed electrode tips and welded by resistance heating. A welding state detecting means for detecting the behavior of the electrode tip based on the vibration information detected by the shaft vibration sensor and determining the quality of the welding state and the quality of the hitting position based on the behavior of the electrode tip. Spot welding equipment. 2. A welding control system for automatically controlling a spot welding apparatus, wherein a welding state tendency at each hitting point is obtained from a history of detection results of the welding state detecting means and correction information of the control is output. The spot welding apparatus according to claim 1, further comprising a correction instruction unit. 3. A nugget quality judging means for judging the quality of the spot nugget formation state based on vibration information detected by the multi-axis vibration sensor, a detection result of the welding state detection means and a quality judgment result of the nugget quality judging means. The spot welding apparatus according to claim 1, further comprising a welding quality monitoring unit that monitors a finish quality of the workpiece based on the welding quality. 4. A welding condition detecting means comprising a sheet gap detecting means for detecting a sheet gap state of a material to be welded by comparing a time required for an amount of advance of an electrode tip with respect to a material to be welded to reach a predetermined amount to a reference value. The spot welding apparatus according to claim 1, wherein: 5. The welding state detecting means includes a sheet gap detecting means for detecting a sheet gap state of the material to be welded by comparing an advance speed of the electrode tip with respect to the material to be welded to a reference value. The spot welding apparatus according to claim 1. 6. A hitting angle detection, wherein a welding state detecting means detects an inclination of a pressing shaft with respect to a workpiece before pressing contact based on a behavior of an electrode tip when pressing in a direction perpendicular to the pressing shaft. The spot welding apparatus according to any one of claims 1 to 5, further comprising means. 7. The welding state detection means includes end detection means for detecting the presence or absence of the end of the work to be welded based on a change in the envelope of the one amplitude of the welding vibration detected by the multi-axis vibration sensor. The spot welding apparatus according to claim 1, wherein: 8. A welding state detecting means for detecting a direction of dispersion based on vibration in a direction perpendicular to the pressure axis, and detecting a defective portion on the electrode tip side based on a result of the detection and a result of detection by the hitting angle detecting means. The spot welding apparatus according to claim 6, further comprising a scatter direction detecting unit for estimating whether the direction is the side of the workpiece or the material to be welded. 9. An electrode tip welding detecting means for detecting welding of the electrode tip to the material to be welded by comparing a time required for the amount of retreat of the electrode tip to the material to be welded to reach a predetermined amount to a reference value. The spot welding apparatus according to any one of claims 1 to 8, further comprising: