JPH0251713B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a device for determining whether the welding strength of electric welding is good or bad.

[Technical background of the invention and its problems] As a welding method, two types of metals are brought together,
There is resistance welding, which welds by passing a constant electric current. Conventionally, the strength of this welding has been determined by visually inspecting each welded location after welding.
In contrast, the present inventors have discovered that the strength of welding can be determined by observing the waveform of welding current or welding voltage. For example, the welding waveform generated during welding is guided to an oscilloscope, the waveform is displayed, and the welding waveform is observed and discriminated. However, in this method, it takes time to discriminate the waveform, resulting in poor work efficiency, and there are disadvantages in that accurate waveform discrimination requires skill.

[Purpose of the Invention] This invention has been made in consideration of the above points, and is a method for improving the quality of electric welding, which can quickly and accurately determine the welding strength and can be automated to improve work efficiency. The purpose is to provide a discrimination device.

[Summary of the Invention] This invention reads welding waveform data in advance, determines a reference waveform based on it, determines a non-defective acceptable range, and performs a calculation to determine whether or not the welding waveform data falls within the acceptable range. It is used to determine quality.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 and 2 are welding electrodes, 3 and 4 are metal wires supported by the electrodes 1 and 2 and in contact with each other, and 5
6 is a welding power supply transformer, 6 is a standard resistance for measurement, 7 is an analog-to-digital converter section that takes in the voltage generated in the standard resistance for measurement 6 when welding current is applied and converts it into a digital value, 8 is a memory section, and 9 is a This is a processing device such as a microcomputer that performs comparison processing based on the output from the memory section 8.

The processing device 9 includes a continuous failure counter that counts the number of consecutive failures based on the comparison results, and a total failure counter that counts the total number of failures based on the comparison results.

In the above device, welding power transformer 5
When a current is supplied from the welding electrodes 1 and 2, current flows through the metal wires 3 and 4.
is welded. During this welding, a welding voltage is generated in the standard measuring resistor 6, and this voltage is converted into a digital signal by the analog-to-digital converter section 7. This digital signal is stored in advance in the memory section 8 with respect to the voltage of the voltage waveform for each welding operation, and a non-defective waveform when welding with sufficient strength is used as a reference waveform. In this case, instead of using one non-defective waveform as the reference waveform, the average value of a plurality of welding waveforms may be used as the non-defective waveform, and this may be stored as the reference waveform.

In the present invention, this reference waveform and the measurement waveform are compared based on voltages at a plurality of sample points.
Here, the waveform shown in Figure 2a is used as the reference waveform,
Using the waveform shown in FIG. 2b as the measured waveform, the comparison operation will be explained with reference to the flowchart in FIG. 3.
First, in Figure 2 a and b, A and A' are the comparison start voltages, B and B' are the times until the comparison starts, C and C' are the comparison start points, D and D' are the sample sampling time intervals, and E is the sample sampling time interval. 1 tolerance, F is the second tolerance, G is the time to the tolerance change point, and H and H' are the sweep times. Note that each of the counters is cleared prior to the comparison operation.

When the welding operation starts, the analog-to-digital converter section 7
The measurement data is output. The output of this analog-digital converter section 7 is the comparison start voltage A,
Count the sweep time until A′ is reached.
When the comparison start voltage A' is reached, the comparison start points C and C' with the reference waveform coincide. Next, it is compared whether the counted sweep time value has reached the tolerance change time G or not. This is because, as is clear from the drawing, the voltage changes in the first half and the second half of the voltage waveform are different, so the tolerance value is changed accordingly to enable more accurate comparison.
That is, when the tolerance change time G has not been reached, the data of the first tolerance value E is taken in, and when the tolerance change time G has been exceeded, the data of the second tolerance value F is taken in and the comparison operation is started. do. Then, the data value of the measured waveform and the reference waveform are compared for each sample point. That is, if the measurement is within the tolerance change time G, the first tolerance value E is used for comparison for each sample point, and if the measurement exceeds the tolerance change time G, the second tolerance value E is used for each sample point. Compare using difference F. And the measurement data is the tolerance value E, F
If it is within the range, the continuous failure counter is cleared and a comparison is made to determine whether the sweep time has reached the predetermined values H, H'. As a result, if H and H' are exceeded, the predetermined comparison is completed, a non-defective product is determined, and a non-defective product signal is generated. Further, as a result of the comparison between the measured data value and the reference waveform, if the tolerance values E and F are exceeded, the count of the continuous failure counter is set to +1, and the count of the total failure counter is set to +1.
If the value of the consecutive defective counter exceeds a predetermined value before the sweep time exceeds the predetermined values H, H', a defective determination is made and a defective signal is generated. Also, when the value of the total defective counter exceeds a preset value, a defective determination is made and a defective signal is generated.

In this way, the comparison operation for each sample point is repeated at the sample sampling time interval from the comparison start point until the predetermined sweep time H, H' has elapsed, and the comparison at all sample points is completed by the tolerance value E. , F, a non-defective product signal is generated, and a non-defective product signal is also generated when both the consecutive number of defective points and the total number of times are within predetermined values. Further, when either the consecutive number of defective points or the total number of defective points exceeds a predetermined value set in advance, a defective signal is generated. In this case, the reference setting values for consecutive failures and total failures are determined experimentally or empirically.

In this way, the predetermined welding waveform data is read, a reference waveform is set based on it, the tolerance range of the product is set, and the measurement data for each weld is then checked to see if it is within the tolerance range. Since the quality of welding is automatically determined, welding strength can be determined quickly and accurately, and it can be easily incorporated into a production line, improving work efficiency. In addition, since the starting point for comparison between the reference waveform and the measured waveform is determined when the voltages of both match at A and A', even if the start of welding is at the reference waveform due to the influence of welding resistance, etc. Even if the waveforms are delayed or advanced, the two waveforms can be matched reliably, and in this respect as well, it is possible to accurately determine the quality of welding. Furthermore, since the allowable range for the reference waveform is changed between the first half and the second half of the sweep time, it is possible to determine the quality of the welding waveform in accordance with the properties of the welding waveform, making it possible to more accurately determine the quality of the welding.

In addition, in the above embodiment, the welding current was controlled by resistor 6.
The welding waveform was measured by converting it into a voltage waveform with The welding waveform may also be measured. In addition, in the above embodiment, the pass/fail determination was performed based on the number of consecutive defective points at each point and the total number of times, but the invention is not necessarily limited to this. It is also possible to determine the quality of the product by performing a test, and various changes can be made without departing from the gist of the present invention.

[Effects of the Invention] As described in detail above, according to the present invention, the welding waveform is read in advance, a reference waveform is set based on it, a tolerance range is determined, and thereafter, it is determined whether the measured welding waveform is within the tolerance range. Since the quality of welding is determined based on whether the quality of the welding is good or not, it is possible to quickly and accurately determine the welding strength, and furthermore, it is possible to provide a quality determination device for electric welding that can be automated and improve work efficiency. .

[Brief explanation of the drawing]

The figures show one embodiment of the present invention, in which Fig. 1 is a schematic configuration diagram, Fig. 2 is a waveform diagram showing an example of a reference waveform and a measured waveform, and Fig. 3 is a flowchart showing a pass/fail determination process. . 1, 2... Welding electrode, 3, 4... Metal wire, 5...
…Welding power supply transformer, 6…Standard resistance for measurement, 7
... Analog-digital converter section, 8 ... Memory section, 9 ... Processing device.

Claims (1)

[Scope of Claims] 1. Means for digitizing and reading welding waveform data of electric welding, means for obtaining and storing reference waveform data from welding waveform data read in advance, and determining acceptable product tolerance range based on the reference waveform data. A device for determining quality of electric welding, characterized in that it comprises means for setting, and calculation determining means for determining whether newly read welding waveform data is within the permissible range by calculating whether or not it is acceptable. 2. Claim 1, wherein the welding waveform data is a welding current waveform corresponding to time.
A device for determining quality of electric welding as described in Section 1. 3. The electric power according to claim 1 or 2, wherein the calculation and determination means performs a calculation to compare the read welding waveform data at a plurality of points sampled at regular time intervals with a non-defective acceptable range. A device to determine the quality of welding. 4. Claims 1, 2, or 3, characterized in that the upper and lower limits of the acceptable range for non-defective products are set by adding and subtracting a certain value from the reference waveform data.
A device for determining quality of electric welding as described in Section 1. 5. The electric welding quality determination device according to claim 4, wherein the fixed values determining the upper and lower limits of the acceptable range of non-defective products are changed within the sweep time of the welding waveform.