JP2006122950A - Spot-welding monitoring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spot-welding monitoring instrument capable of correctly determining acceptance/rejection of the welding by a simple configuration. <P>SOLUTION: The spot-welding monitoring instrument 1 to monitor acceptance/rejection of the spot welding to be continuously performed on a plurality of parts of a metal plate 102 by a pair of electrodes 101 comprises a detection means to detect the voltage between the electrodes 101, a storage means to continuously store voltage information 21 based on the voltage detected by the detection means, a comparison means to acquire difference information 22 on the difference in the voltage information 21 by comparing the voltage information 21 stored in the storage means and with the predetermined time interval therebetween, and a determination means to determine acceptance/rejection of the welding based on the difference information 22 acquired by the comparison means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a spot welding monitoring device that monitors the quality of spot welding continuously applied to a plurality of locations on a metal plate by a pair of electrodes.

  For products that use metal plates such as iron and aluminum, spot welding is used in which two or more metal plates are sandwiched between a pair of electrodes and energized to weld the metal plates together. In a relatively large product such as an automobile vehicle, a spot gun having each electrode is installed at the tip of a robot arm on a production line, and spot welding is continuously performed at a plurality of locations on one product.

  In spot welding, if dust or the like adheres to the metal plate that is the workpiece, the pressure applied to the workpiece by each electrode is insufficient, or the electrode (tip) is worn, an overvoltage is generated between the electrodes during welding. And poor welding occurs. Even during such welding, since current flows between the electrodes, it is difficult to detect poor welding.

Therefore, the voltage value and current value between the electrodes are measured to continuously calculate the impedance at the time of welding, and compared with the data relating to the impedance stored in advance, it is judged whether the welding is “good” or “bad”. A spot welding monitoring device has been proposed (see, for example, Patent Document 1). In this spot welding monitoring device, impedance data is cumulatively updated for each hitting point where welding is performed, and is used to determine whether or not the subsequent welding hit points are acceptable.
JP 2002-210567 A

  However, in the spot welding monitoring device, when all the spots are welded under the same conditions, it is possible to detect a welding failure. However, when spot welding is performed at a plurality of locations of one product, the welding state is different for each spot. Since it is often different, it is not preferable to judge all the hit points in the same way. Accordingly, even if the welding point is in a normal welding state, it is judged as “bad” when the welding state is different from other welding points, and conversely, even if the welding point is abnormal in the welding state, it is the same as other welding points. There was a possibility that it was judged as “good” when the welding state was. In addition, both the voltage and current values of each electrode must be monitored with high accuracy, resulting in a problem that the apparatus configuration becomes complicated.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a spot welding monitoring apparatus capable of accurately determining the quality of welding with a simple apparatus configuration.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a spot welding monitoring device for monitoring the quality of spot welding continuously applied to a plurality of locations on a metal plate by a pair of electrodes, and between each electrode. A detection means for detecting the voltage of the current, a storage means for continuously storing voltage information based on the voltage detected by the detection means, and a comparison between the voltage information stored in the storage means and separated by a predetermined time. The comparison means for obtaining the difference information regarding the difference between the voltage information and the determination means for judging the quality of the welding based on the difference information acquired by the comparison means are provided.

According to the first aspect of the present invention, voltage information is stored in the storage means every time spot welding is performed on the metal plate, and the voltage information separated by a predetermined time is compared by the comparison means, and difference information is obtained. To be acquired. Here, for example, the predetermined time may be set so that the two pieces of voltage information to be compared correspond to the same welding point.
Therefore, it is possible to make a fine pass / fail judgment for all the points depending on the welding state. That is, it is possible to dramatically improve the accuracy of the determination as compared with the case where all the hit points are determined uniformly.
Moreover, since the voltage between each electrode should just be detected, the quality of welding can be judged with a simple apparatus structure.

  According to a second aspect of the present invention, in the spot welding monitoring apparatus according to the first aspect, the voltage information includes voltage data of a plurality of continuous weldings.

According to the second aspect of the invention, in addition to the operation of the first aspect, the voltage information to be compared with each other includes the voltage data at the time of continuous plural times of welding, so that it is not determined by one single point, The difference information is acquired based on the welding state of the hit points that are continuous only a plurality of times.
In other words, if a single spot is judged alone, misjudgment will increase, and if it is difficult to judge welding abnormalities without examining the welding state of the spot that has been continuously repeated several times, the quality of the weld will be judged accurately. can do.

According to a third aspect of the present invention, in the spot welding monitoring apparatus according to the first or second aspect, the voltage information relates to a voltage waveform during welding.
Here, the “voltage waveform” refers to a locus drawn with two axes orthogonal to each other between the voltage value and the time.

  According to the third aspect of the invention, in addition to the operation of the first or second aspect, the voltage waveform can be acquired by continuously detecting the voltage value, so that the creation of voltage information is simple and easy. Therefore, it is extremely advantageous for practical use.

  According to a fourth aspect of the present invention, in the spot welding monitoring apparatus according to the third aspect, the difference information includes information obtained by comparing areas of voltage waveforms.

  According to invention of Claim 4, in addition to the effect | action of Claim 3, since difference information contains the information regarding the area of a voltage waveform, it judges a welding state based on the difference of the calorie | heat amount added to the welding part. Can do. That is, when the combination of the metal plate and each electrode tends to cause poor welding due to the amount of heat, the welding state can be effectively monitored.

  According to a fifth aspect of the present invention, in the spot welding monitoring device according to the third or fourth aspect, the difference information includes information obtained by comparing amplitudes of voltage waveforms.

  According to the fifth aspect of the present invention, in addition to the operation of the third or fourth aspect, the difference information includes information on the amplitude of the voltage waveform, so that the welding state is determined based on the maximum value of the voltage applied to the welded portion. can do. That is, when the combination of the metal plate and each electrode tends to cause poor welding due to the maximum voltage value, the welding state can be effectively monitored.

  According to a sixth aspect of the present invention, in the spot welding monitoring device according to any one of the first to fifth aspects, the difference information is a difference relating to a predetermined amount between the voltage information separated by a predetermined time. The determination means determines whether or not welding is good depending on whether or not the difference is larger than a preset threshold value.

  According to the sixth aspect of the present invention, in addition to the operation of any one of the first to fifth aspects, the quality of the welding is determined based on whether or not the predetermined amount of voltage is greater than a threshold value. It can be done easily. In addition, when the quality of welding required for each product is different, it is possible to flexibly cope with the change of the threshold value, which is extremely advantageous in practical use.

  As described above, according to the spot welding monitoring apparatus of the present invention, the voltage information separated by a predetermined time is compared to acquire the difference information. It is possible to accurately determine the quality of welding with a simple apparatus configuration.

  FIGS. 1 to 5 show an embodiment of the present invention. FIG. 1 is a schematic configuration diagram of a spot welding monitoring device, FIG. 2 is a block diagram of the spot welding monitoring device, and FIG. FIG. 4 is a graph showing the waveform of the voltage when the welding is performed, FIG. 4 is a graph showing the waveform of the voltage including the weld failure point, and FIG.

  As shown in FIG. 1, the spot welding monitoring device 1 includes an A / D converter 2 connected to each electrode 101 of a spot welder 100, and a control unit 3 connected to the A / D converter 2. The touch panel display 4 connected to the control unit 3 is provided. The spot welding monitoring device 1 monitors the quality of spot welding continuously applied to a plurality of locations on the metal plate 102 by a pair of electrodes 101. In the present embodiment, the control unit 3 is called a high-speed sequencer, and the A / D converter 2 and the touch panel display 4 are connected to the I / O interface 10 of the control unit 3.

  The A / D converter 2 converts an analog signal related to the voltage between the electrodes 101 into a digital signal and transmits the digital signal to the control unit 3. In the present embodiment, the A / D converter 2 and the electric wire 5 connecting the electrode 101 to the A / D converter 2 constitute detection means for detecting the voltage between the electrodes 101.

  As shown in FIG. 2, the control unit 3 includes a CPU 11, a ROM 12, a RAM 13, and the like in addition to the I / O interface 10 described above, and these are connected to each other via a bus 14. The ROM 12 compares the storage program 31 for storing the voltage information 21 based on the voltage input from the A / D converter 2 in the RAM 13 with the voltage information 21 stored in the RAM 13 and separated by a predetermined time. A comparison program 32 for acquiring the difference information 22 regarding the difference of the information 21 and a determination program 33 for determining the quality of welding based on the difference state 22 are stored. That is, in the present embodiment, the control unit 3 serves as a storage unit, a comparison unit, and a determination unit.

  Specifically, the voltage information 21 is information relating to a waveform of a voltage value for the hitting point that the spot welder 100 in one product handles. FIG. 3 shows a waveform of a voltage when welding is performed continuously 10 times and welding is normally performed for 10 consecutive hit points. That is, in one product process, the voltage value has a fluctuation cycle of 10 cycles. In the present embodiment, as shown in FIG. 4, the voltage information 21 used for comparison is voltage data of two consecutive weldings.

  The difference information 22 of the second cycle, the third cycle, the fifth cycle, and the sixth cycle among the difference information 22 of all the points is the waveform area of the second cycle and the third cycle, and the fifth cycle and the sixth cycle. It is the difference in the area of the waveform (see FIG. 4). And the determination program 33 is comprised so that the quality of welding may be determined by whether this difference is larger than the preset threshold value 34 or not. In the present embodiment, the second and third hit points and the fifth and sixth hit points are in the same welding state in the process of one product.

  The operation of the control unit 3 configured as described above will be described with reference to the flowchart shown in FIG.

  First, it is determined whether or not product welding has started (step S1). If it is determined that welding has started, the voltage waveform is measured and the voltage information 21 shown in FIG. (Step S2). If it is determined in step S1 that welding has not started, the process returns to step S1 and enters a standby state.

After step S2, the areas of the voltage waveforms of the second and third cycles and the areas of the voltage waveforms of the fifth and sixth cycles are calculated (step S3). Next, a difference is calculated by comparing these areas, and it is determined whether or not the difference is larger than the threshold value 34 (step S4). When the difference is larger than the threshold value 34 in step S4, it is determined that the welding is defective (step S5), the welding defect is displayed on the touch panel display 4, and the operation is terminated. If the difference is equal to or smaller than the threshold value 34 in step S4, it is determined that the welding is normal (step S6), the normal welding is displayed on the touch panel display 4, and the operation is terminated.
The flowchart in FIG. 5 shows what determines the quality of the second cycle, third cycle, fifth cycle and sixth cycle welding, but the control unit 3 performs welding in other cycles of these cycles. Whether the quality is good or bad is judged sequentially.

As described above, according to the spot welding monitoring apparatus 1 of the present embodiment, the voltage information 21 is stored in the RAM 13 every time the metal plate 102 is spot welded, and the voltage information 21 separated by a predetermined time is compared. Thus, the difference information 22 is acquired.
Therefore, it is possible to make a fine pass / fail judgment for all the points depending on the welding state. That is, it is possible to dramatically improve the accuracy of the determination as compared with the case where all the hit points are determined uniformly.
Moreover, since the voltage between each electrode 101 should just be detected, the quality of welding can be judged with a simple apparatus structure.

Moreover, according to the spot welding monitoring apparatus 1 of this embodiment, since the voltage information 21 compared with each other includes voltage data at the time of continuous multiple times of welding, it is determined only a plurality of times without judging by one single spot. The difference information 22 is acquired based on the welding state of the continuous hit points.
In this embodiment, regarding the second and third cycles, and the fifth and sixth cycles, there are many misjudgments when judging by one single spot, and the welding state of the spots that have been continuous multiple times is examined. Otherwise, it is difficult to determine the welding abnormality, and it is possible to accurately determine the quality of the welding.

Further, according to the spot welding monitoring apparatus 1 of the present embodiment, the voltage waveform can be obtained by continuously detecting the voltage value, so that the creation of the voltage information 21 is easy and easy, and is extremely practical. It is advantageous.
Here, since the difference information 22 includes information regarding the area of the voltage waveform, the welding state can be determined based on the difference in the amount of heat applied to the welded portion. In this embodiment, the metal plate 102 and each electrode 101 are a combination that easily causes poor welding due to the amount of heat, and the welding state can be effectively monitored.

  Moreover, according to the spot welding monitoring apparatus 1 of this embodiment, since the quality of welding is determined by whether it is larger than the threshold value 34 regarding the difference of the area | region of the waveform of a voltage, determination can be performed easily and easily. In addition, when the quality of welding required for each product is different, the threshold value 34 can be changed to cope flexibly, which is extremely advantageous in practical use.

  In the above embodiment, the voltage information 21 is voltage data of a plurality of continuous weldings. However, if the reliability is high even if it is determined by one single spot, the voltage information 21 is The voltage data of one welding can be used.

In the above embodiment, the difference information 22 is obtained by comparing the areas of the voltage waveforms. However, the difference information is information obtained by comparing the amplitudes of the voltage waveforms. May be.
In this case, since the difference information includes information regarding the amplitude of the voltage waveform, the welding state can be determined based on the maximum value of the voltage applied to the welded portion. That is, when the combination of the metal plate 102 and each electrode 101 tends to cause poor welding due to the maximum voltage value, the welding state can be effectively monitored.
Also in this case, if it is configured to determine whether the welding is good or not based on whether or not the difference in the maximum voltage value is greater than a preset threshold value, it is possible to easily determine whether the welding is good or not, and the welding required for the product. Can be flexibly adapted to the quality of the product.

  Furthermore, the voltage information is not related to the waveform of the voltage, but may be related to a numerical value such as a voltage change rate, etc. Of course.

It is a schematic block diagram of the spot welding monitoring apparatus which shows one Embodiment of this invention. It is a block diagram of the configuration of the spot welding monitoring device. It is a graph which shows the waveform of the voltage when all the spots are welded normally. It is a graph which shows the waveform of the voltage containing the spot of poor welding. It is a flowchart which shows operation | movement of a control part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spot welding monitoring apparatus 2 A / D converter 3 Control part 5 Electric wire 10 I / O interface 11 CPU
12 ROM
13 RAM
21 Voltage information 22 Difference information 31 Storage program 32 Comparison program 33 Judgment program 100 Spot welder 101 Electrode 102 Metal plate

Claims (6)

A spot welding monitoring device that monitors the quality of spot welding continuously applied to a plurality of locations on a metal plate by a pair of electrodes,
Detection means for detecting the voltage between the electrodes;
Storage means for continuously storing voltage information based on the voltage detected by the detection means;
Comparing means for comparing the voltage information stored in the storage means at a predetermined time and obtaining difference information regarding the difference between the voltage information; and
A spot welding monitoring apparatus comprising: a determination unit that determines whether or not welding is good based on the difference information acquired by the comparison unit.   The spot welding monitoring apparatus according to claim 1, wherein the voltage information includes voltage data of a plurality of continuous weldings.   The spot welding monitoring apparatus according to claim 1, wherein the voltage information relates to a voltage waveform during welding.   The spot welding monitoring apparatus according to claim 3, wherein the difference information includes information acquired by comparing areas of voltage waveforms.   5. The spot welding monitoring apparatus according to claim 3, wherein the difference information includes information acquired by comparing amplitudes of voltage waveforms. The difference information is a difference regarding a predetermined amount between the voltage information separated by a predetermined time,
The spot welding monitoring apparatus according to claim 1, wherein the determination unit determines whether the welding is good or not based on whether the difference is larger than a preset threshold value.

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