JP2023135151A - Circuit resistance measurement device - Google Patents

Abstract

To provide a technique capable of highly accurately measuring a circuit resistance.SOLUTION: A circuit resistance measurement device in spot welding of welding an object comprises: an acquisition unit which acquires a measurement resistance value being each resistance value measured when performing plural times of electric conduction using a current value that is used in actual spot welding of the object and is equal to or greater than a predetermined threshold; a calculation unit which calculates any of an average value, a central value and a most frequent value of the plurality of measurement resistance values as a correction value; and a determination unit which determines a value obtained by correcting the resistance value measured in the actual spot welding of the object using the correction value as a circuit resistance value.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a circuit resistance measuring device.

In spot welding, there is a technique for adjusting the current in welding based on circuit resistance. Patent Document 1 describes a technique for adjusting current according to the amount of change in resistance value calculated by measuring current value and voltage value.

Japanese Patent Application Publication No. 6-71457

However, in the technique described in Patent Document 1, the current is not adjusted in accordance with the exact resistance value of the workpiece. Therefore, a technology that can measure circuit resistance with high accuracy has been desired.

The present disclosure has been made to solve the above-mentioned problems, and can be realized as the following forms.

According to one embodiment of the present disclosure, a circuit resistance measuring device for spot welding a target is provided. This circuit resistance measuring device measures the current value used in the actual spot welding of the target, and each resistance value is measured when energization is performed multiple times using a current value that is equal to or higher than a predetermined threshold value. an acquisition unit that acquires a certain measured resistance value; a calculation unit that calculates one of the average value, median value, and mode of the plurality of measured resistance values as a correction value; and the actual spot welding of the target. a determination unit that determines a value obtained by correcting the resistance value measured in the circuit using the correction value as the circuit resistance value.
The resistance value measured when applying current using the current used in actual spot welding is higher than the resistance value measured when applying current using a lower current than that used in actual spot welding. Variations are less likely to occur. Furthermore, according to this type of circuit resistance device, since the correction value is calculated by using a statistical method from the resistance value measured by energizing multiple times, the resistance value measured once is simply determined as the correction value. It is possible to suppress the adoption of abnormal values more than in the case of Therefore, circuit resistance can be measured with high accuracy.

Note that the present disclosure can be realized in various forms, such as a method for measuring circuit resistance in spot welding, a correction value calculation device, and the like.

FIG. 1 is a schematic diagram showing a schematic configuration of a circuit resistance measuring device. It is a graph which shows the example of the measured resistance value which an acquisition part acquires. It is a graph showing the relationship between current and resistance value. It is a graph showing a resistance waveform when correction is performed using a correction value in a comparative example. It is a graph showing a resistance waveform when correction is performed using a correction value. It is a graph showing the relationship between the resistance value and the number of measurements in a comparative example. It is a graph showing the relationship between resistance value and the number of measurements.

A. First embodiment:
FIG. 1 is a schematic diagram showing a schematic configuration of a circuit resistance measuring device 100 according to an embodiment of the present disclosure. The circuit resistance measuring device 100 is connected to a welding device 200 that performs spot welding, and measures the circuit resistance value during spot welding. The circuit resistance value measured by the circuit resistance measuring device 100 is used for various analyzes such as estimating the nugget diameter of a target welded by spot welding performed by the welding device 200, for example. Welding device 200 can control current and voltage using the circuit resistance value measured by circuit resistance measuring device 100.

The circuit resistance measuring device 100 includes an acquisition section 10, a calculation section 20, and a determination section 30. The circuit resistance measuring device 100 consists of a computer configured with a central processing unit (CPU), RAM, and ROM, and realizes the functions of the acquisition unit 10 and the calculation unit 20 by having the computer execute a program installed in advance. do. However, some or all of the functions of these parts may be realized by a hardware circuit.

The acquisition unit 10 acquires a measured resistance value that is a resistance value when the welding device is energized. More specifically, the current measured by the ammeter and the voltage measured by the voltmeter are acquired, and the resistance value is calculated. The acquisition unit 10 acquires each measured resistance value that is a current value used in actual spot welding of a certain target and is measured when energization is performed multiple times using a current value that is equal to or higher than a predetermined threshold value. . In this embodiment, the acquisition unit 10 acquires the resistance value when energized at 8 kA.

The calculation unit 20 calculates a value determined by a statistical method from the plurality of measured resistance values acquired by the acquisition unit 10 as a correction value. More specifically, the calculation unit 20 calculates one of the average value, median value, and mode of the plurality of measured resistance values acquired by the acquisition unit 10 as the correction value.

The determining unit 30 determines, as the circuit resistance value, a value obtained by correcting the resistance value measured during actual spot welding of a certain target using the correction value calculated by the calculating unit 20. The determining unit 30 may determine the circuit resistance value by correcting the resistance value measured during spot welding using a correction value, and after the completion of spot welding, the resistance value measured during spot welding may be corrected using a correction value. The circuit resistance value may be determined by correcting the resistance value using a correction value.

FIG. 2 is a graph showing an example of measured resistance values acquired by the acquisition unit 10. The upper graph on the left shows changes in current, the lower graph on the left shows changes in voltage, and the graph on the right shows changes in resistance value calculated from these currents and voltages. In the present embodiment, the acquisition unit 10 acquires the resistance value at time t1 when a predetermined time has elapsed since the start of energization, as the measured resistance value.

FIG. 3 is a graph showing the relationship between current and measured resistance value. The horizontal axis of the graph shown in FIG. 3 shows the current during energization, and the vertical axis shows the measured resistance value. FIG. 3 shows the relationship between the current and the measured resistance value of each of the six welding devices. As shown in FIG. 3, the larger the current, the smaller the variation in circuit resistance. The measured resistance value when current is applied at 8kA, which is the current used in actual spot welding, is the measured resistance value when electricity is applied at 2.5kA, which is a lower current than the current used in actual spot welding. Variations are less likely to occur. Note that if it is too large, variations in circuit resistance will occur due to resistance heat generation.

FIG. 4 is a graph showing the resistance waveform of the circuit resistance value when correction is performed using the correction value in the comparative example, and FIG. 5 is a graph showing the resistance waveform of the circuit resistance value when correction is performed using the correction value according to the present embodiment. It is a graph showing a resistance waveform. FIG. 4 shows, as a comparative example, measured resistance values when a resistance value measured by applying a current of 2.5 kA is adopted as a correction value. 4 and 5 show respective resistance waveforms in three welding devices that perform spot welding under the same conditions. Since spot welding is performed under the same conditions, it is preferable that similar resistance waveforms can be obtained by correction even if the welding equipment is different. By using an approximated resistance waveform, various analyzes can be easily performed. As shown in FIG. 4, in the comparative example, the resistance waveform differs greatly depending on the welding device. As shown in FIG. 5, the resistance waveforms in this embodiment are similar to each other compared to the comparative example shown in FIG. Therefore, it is easy to perform various analyzes to compare welding devices using the resistance waveform.

According to the circuit resistance measuring device 100 of the present embodiment described above, the correction value is calculated using the resistance value measured when energization is performed using the current used in actual spot welding. The resistance value measured when applying current using the current used in actual spot welding is higher than the resistance value measured when applying current using a lower current than that used in actual spot welding. , variation is less likely to occur. In addition, since the correction value is calculated using a statistical method from the resistance value measured by energizing multiple times, an abnormal value is adopted rather than simply determining the resistance value measured once as the correction value. can be suppressed. Therefore, the circuit resistance value can be measured with high accuracy.

B. Second embodiment:
The second embodiment differs from the first embodiment in that the calculation unit 20 calculates, as the measured resistance value, the average value of the measured resistance values after repeating the energization a predetermined number of times from the start of the energization. The configuration of the circuit resistance measurement device 100 of the second embodiment is the same as the configuration of the circuit resistance measurement device 100 of the first embodiment, so a description of the configuration of the circuit resistance measurement device 100 will be omitted.

FIG. 6 is a graph showing the relationship between the resistance value and the number of measurements in the comparative example, and FIG. 7 is a graph showing the relationship between the resistance value and the number of measurements in the present embodiment. FIG. 6 shows the resistance value when a current of 2.5 kA is applied as a comparative example. The horizontal axis of the graphs shown in FIGS. 6 and 7 shows the number of measurements, and the vertical axis shows the resistance value. When the electrode attached to the tip of a gun in a welding device is new, the surface of the electrode may have large surface roughness due to irregularities caused by processing during manufacturing. Therefore, at the initial stage of starting resistance value measurement, the surface of the electrode is not familiar, and the contact state may become unstable. As shown in FIGS. 6 and 7, the resistance value at the first time is significantly different from the resistance value at the fifth and subsequent times.

According to the circuit resistance measuring device 100 of the second embodiment described above, the calculation unit 20 calculates, as a correction value, the average value of the measured resistance values after repeating energization a predetermined number of times from the start of energization. The resistance value immediately after the start of energization may be significantly different from the resistance value after energization is repeated several times after the start of energization. Therefore, it is possible to suppress the adoption of abnormal values. Therefore, the circuit resistance value can be measured with high accuracy.

C. Other embodiments:
In the embodiment described above, the acquisition unit 10 acquires, as the measured resistance value, the resistance value at the time when a predetermined time has elapsed since the start of energization. However, the acquisition unit 10 is not limited to this, and the acquisition unit 10 may set one of the average value, median value, and mode of resistance values per unit time during a predetermined time period after starting energization as the measured resistance value. You may obtain it.

The present disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments that correspond to the technical features in each form described in the column of the summary of the invention are for solving the above-mentioned problems or achieving some or all of the above-mentioned effects. It is possible to replace or combine them as appropriate. Further, unless the technical feature is described as essential in this specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10... Acquisition part, 20... Calculation part, 30... Determination part, 100... Circuit resistance measuring device, 200... Welding device

Claims (1)

A circuit resistance measuring device for spot welding a target,
Obtain a measured resistance value, which is a current value used in the actual spot welding of the target, and is each resistance value measured when energization is performed multiple times using a current value equal to or higher than a predetermined threshold value. an acquisition department;
a calculation unit that calculates one of the average value, median value, and mode value of the plurality of measured resistance values as a correction value;
A circuit resistance measuring device, comprising: a determination unit that determines, as a circuit resistance value, a value obtained by correcting a resistance value measured in the actual spot welding of the object using the correction value.

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