KR101563126B1

KR101563126B1 - Expulsion detection method of spot welder and recording medium for storing program thereof

Info

Publication number: KR101563126B1
Application number: KR1020140072388A
Authority: KR
Inventors: 강문진; 김동철; 김철희; 황인성; 윤현준
Original assignee: 한국생산기술연구원
Priority date: 2014-06-13
Filing date: 2014-06-13
Publication date: 2015-10-26

Abstract

The present invention can accurately detect the deflection during the resistance spot welding process, thereby making it possible to accurately determine the occurrence of defects in the welded joint, thereby reducing errors in the determination of the welded products, The present invention relates to a method of detecting a spark of a welder and a recording medium on which the program is stored, the method comprising: detecting a peak dynamic resistance (R _peak ) of a weld material; (Ra, Rb) is detected at a first time interval when the peak dynamic resistance (R _peak ) is detected, and when the ratio of the dynamic resistance (Ra, Rb) is less than a first predetermined ratio ; And calculating average dynamic resistance (Ra _AVE , Rb _AVE ) of the second and third time intervals before and after the predicted deflection, respectively, and calculating the average dynamic resistance (Ra _AVE , Rb _AVE ) And determining that a skidding has occurred if the ratio of the first to the second set ratios is equal to or less than the second set rate.

Description

TECHNICAL FIELD [0001] The present invention relates to a spot welding machine and a spot welding machine,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for detecting a warp of a spot welder and a recording medium on which the program is stored. More particularly, the present invention relates to a method of detecting a warp of a spot welder, .

Generally, spot welding is a welding method belonging to electric resistance welding, and refers to a method of welding while applying pressure using heat generated when a current flows through the metal.

Spot welding is a process in which two metals to be bonded are put together and current is applied while applying appropriate mechanical pressure, and heat of resistance is generated, thereby utilizing the property of bonding the pressure parts. Such spot welding is a very common welding method for assembling a car body.

An apparatus for resistance spot welding includes a fixed lower electrode and an upper electrode that moves up and down on the lower electrode. Therefore, the welding material is seated on the lower electrode, and welding is performed by movement of the upper electrode.

1. Korean Patent Publication No. 2003-0082114 (published on October 22, 2003) 2. Korean Patent No. 10-0722132 (registered on May 18, 2007)

However, in the conventional resistance spot welding, expulsion occurs in the welding process, and the molten metal in the nugget explodes between the two metal materials and blows off, thereby lowering the strength of the joint. For example, in the case of conventional resistance spot welding, if the pressing force is lowered among the three elements, or if the overall current density of the current decreases due to other reasons, the current density increases and the heat quantity increases, Thereby causing welding defects.

The idea of the present invention is to provide a method and apparatus for detecting a deflection of a spot welder that can accurately detect a deflection during a resistance spot welding process, And to provide the stored recording medium. However, these problems are illustrative, and thus the scope of the present invention is not limited thereto.

According to an aspect of the present invention, there is provided a method for detecting a deflection of a spot welder, the method comprising: detecting a peak dynamic resistance (R _peak ) of a weld material; (Ra, Rb) is detected at a first time interval when the peak dynamic resistance (R _peak ) is detected, and when the ratio of the dynamic resistance (Ra, Rb) is less than a first predetermined ratio ; And calculating average dynamic resistance (Ra _AVE , Rb _AVE ) of the second and third time intervals before and after the predicted deflection, respectively, and calculating the average dynamic resistance (Ra _AVE , Rb _AVE ) Is less than or equal to a second set rate, determining that a skidding has occurred.

According to an aspect of the present invention, the step of detecting the prediction error may correspond to a range of the first time interval of 5 to 15 ms.

According to an aspect of the present invention, the step of detecting the predicted track may detect the predicted track from a point in time after the fourth time interval from when the peak dynamic resistance (R _peak ) is detected.

According to an aspect of the present invention, the step of detecting the prediction error may correspond to a range of 5 to 15 ms in the fourth time interval.

According to an aspect of the present invention, the step of detecting the predicted skew includes: when a ratio of the dynamic resistance (Ra, Rb) exceeds the first set ratio, a new dynamic resistance (Ra, Rb) can be calculated.

According to an aspect of the present invention, the fifth time interval may correspond to a range of 0.1 to 1.0 ms.

According to an aspect of the present invention, the step of detecting the prediction error may include calculating a ratio of the dynamic resistance (Ra, Rb) by the following equation (1), and the first setting ratio may be 70 to 90% .

[Equation 1]

Ra; Dynamic Resistance at the Time of Prediction

Rb; Dynamic resistance of the forecasting end point

According to an aspect of the present invention, the step of discriminating the jump may include calculating a ratio of the average dynamic resistance (Ra _AVE , Rb _AVE ) by the following equation (2), and the second setting ratio is 70 to 90% .

&Quot; (2) "

Ra _AVE ; The average of the dynamic resistance during the second time interval before the forecasting point

Rb _AVE ; The average of the dynamic resistance during the third time interval after the predicted end point

According to an aspect of the present invention, the step of discriminating the jump may be the same as the second and third time intervals, and may be in a range of 1 to 10 ms.

According to another aspect of the present invention, there is provided a recording medium on which a program for detecting a deflection of a spot welder is stored, wherein a program for performing the deflection detection method of the spot welder according to the present invention can be stored.

According to the embodiments of the present invention as described above, it is possible to accurately detect the deflection during the resistance spot welding process, thereby precisely determining the occurrence of defects in the welded joint, And also contributes to minimizing the possibility of welding failure due to subsequent measures. Of course, the scope of the present invention is not limited by these effects.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart illustrating a method of detecting deflection of a spot welder in accordance with some embodiments of the present invention.
2 is a block diagram showing a spot welder used in a method of detecting a deflection of a spot welder according to some embodiments of the present invention.
3 is a dynamic resistance graph showing a case where no deflection occurs in the deflection detecting method of a spot welder according to some embodiments of the present invention.
FIG. 4 is a graph of dynamic resistance in the case where a deflection occurs in a deflection detecting method of a spot welder according to some embodiments of the present invention. FIG.
5 is a graph for explaining a step of detecting a predicted skip in the skip detection method of a spot welder according to some embodiments of the present invention.
FIG. 6 is a graph for explaining the step of determining deflection in a deflection detecting method of a spot welder according to some embodiments of the present invention. FIG.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments of the present invention are described in order to more fully explain the present invention to those skilled in the art, and the following embodiments may be modified in various other forms, The present invention is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the concept of the invention to those skilled in the art. In the drawings, the thickness and size of each layer are exaggerated for convenience and clarity of explanation.

It is to be understood that throughout the specification, when an element such as a film, region or substrate is referred to as being "on", "connected to", "laminated" or "coupled to" another element, It will be appreciated that elements may be directly "on", "connected", "laminated" or "coupled" to another element, or there may be other elements intervening therebetween. On the other hand, when one element is referred to as being "directly on", "directly connected", or "directly coupled" to another element, it is interpreted that there are no other components intervening therebetween do. Like numbers refer to like elements. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items.

Although the terms first, second, etc. are used herein to describe various elements, components, regions, layers and / or portions, these members, components, regions, layers and / It is obvious that no. These terms are only used to distinguish one member, component, region, layer or section from another region, layer or section. Thus, a first member, component, region, layer or section described below may refer to a second member, component, region, layer or section without departing from the teachings of the present invention.

Also, relative terms such as "top" or "above" and "under" or "below" can be used herein to describe the relationship of certain elements to other elements as illustrated in the Figures. Relative terms are intended to include different orientations of the device in addition to those depicted in the Figures. For example, in the figures the elements are turned over so that the elements depicted as being on the top surface of the other elements are oriented on the bottom surface of the other elements. Thus, the example "top" may include both "under" and "top" directions depending on the particular orientation of the figure. If the elements are oriented in different directions (rotated 90 degrees with respect to the other direction), the relative descriptions used herein can be interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" include singular forms unless the context clearly dictates otherwise. Also, " comprise "and / or" comprising "when used herein should be interpreted as specifying the presence of stated shapes, numbers, steps, operations, elements, elements, and / And does not preclude the presence or addition of one or more other features, integers, operations, elements, elements, and / or groups.

Hereinafter, embodiments of the present invention will be described with reference to the drawings schematically showing ideal embodiments of the present invention. In the figures, for example, variations in the shape shown may be expected, depending on manufacturing techniques and / or tolerances. Accordingly, the embodiments of the present invention should not be construed as limited to the particular shapes of the regions shown herein, but should include, for example, changes in shape resulting from manufacturing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart illustrating a method of detecting deflection of a spot welder in accordance with some embodiments of the present invention.

As shown in FIG. 1, a method for detecting a deflection of a point welder according to some embodiments of the present invention includes detecting a peak dynamic resistance (R _peak ) (S11), detecting a predicted deflection (S12, S13 And steps S14, S15, and S16 for determining the jump. The spot welder shown in FIG. 2 will be described as an example.

According to step S11 of detecting the peak dynamic resistance (R _peak ), at least one welding material 10 for spot welding is first prepared and the welding material 10 is placed on at least one electrode 20 . At this time, for example, the welding members 10 may be positioned between the upper and lower electrodes 20 as a pair. Then, a current for spot welding is applied to the welding material 10 through the electrode 20, and the peak dynamic resistance (R _peak ) of the welding material is detected by using the current applied to the welding material 10.

The peak dynamic resistance (R _peak ) can be detected by the control unit 30 and can be a peak value among the resistance measuring resistors. The measurement resistance of the welding material can be calculated from the voltage across the welding member 10 and the current applied to the electrode 20 by the control unit 30. When the power is constant, Or the like. Also, the peak dynamic resistance (R _peak ) may vary depending on the type and thickness of the weld material 10 and the like.

The control unit 30 is configured to control the welding current to be applied to the welding material 10, to calculate the peak copper resistance (R _peak ), to measure the copper resistances Ra and Rb of the welding material 10 to be described later, The resistance of the spot welder according to some embodiments of the present invention, including the resistance (Ra _AVE , Rb _AVE ) and its ratio calculation, counting of a fixed time interval, determining whether a given condition is satisfied, The control, calculation, storage and judgment necessary for performing the detection method can be performed according to a predetermined process.

3 is a dynamic resistance graph showing a case where no deflection occurs in the deflection detecting method of a spot welder according to some embodiments of the present invention.

As shown in Fig. 3, after the peak dynamic resistance (R _peak ) is measured, as the spot welding proceeds, the continuously generated heat increases the melting portion 40 (shown in Fig. 2) at the contact surface , The cross-sectional area of the current flow is widened, resulting in a decrease in resistance. At this time, the dynamic resistance is reduced at a constant slope if no skipping occurs.

FIG. 4 is a graph of dynamic resistance in the case where a deflection occurs in a deflection detecting method of a spot welder according to some embodiments of the present invention. FIG.

As shown in FIG. 4, when the dynamic resistance is decreased, the dynamic resistance is abruptly decreased (a) as soon as the deflection occurs, and it can be predicted that deflection occurs therefrom, and the corresponding step detects the predicted deflection Are steps S12 and S13. However, in order to finally determine the prediction error, it is possible to improve the discrimination accuracy of the error by performing steps S14, S15, and S16.

The dynamic resistance Ra and the dynamic resistance Rb are respectively detected at a first time interval after detecting the peak dynamic resistance R _peak at step S12, Rb) is less than or equal to the first set rate (S13).

The first time interval may correspond to a range of, for example, 5 to 15 ms when the dynamic resistance Ra or Rb is detected at the first time interval in each of the steps S12 and S13 of detecting the predicted skew, . On the other hand, the prediction error detection step S12 and S13 may detect the prediction error from the fourth time interval after the detection of the peak dynamic resistance (R _peak ). The fourth time interval may correspond to a range of, for example, 5 to 15 ms, and may be, for example, 10 ms.

If the ratio of the resistances Ra and Rb exceeds the first set ratio in the step S13 of detecting the predicted track at the ratio of the resistances Ra and Rb, , The ratio of the new copper resistance (Ra, Rb) is calculated at the first time interval after the elapse of the fifth time interval, and this process can be repeated until the welding is finished. The fifth time interval may correspond to a range of, for example, 0.1 to 1.0 ms, and may be, for example, 0.5 ms. The ratio of the dynamic resistance Ra and the dynamic resistance Rb can be calculated by the following equation 1 in the step S13 of detecting the predicted flywheel at the ratio of the dynamic resistance Ra and the dynamic resistance Ra, 70% to 90%, for example 80%.

[Equation 1]

Here, Ra is the dynamic resistance at the predicted breaking point, and Rb is the dynamic resistance at the predicted flying end point.

According to the steps S14, S15, and S16 of determining the jump, the average dynamic resistance (Ra _AVE , Rb _AVE ) of the second and third time intervals after the predicted jump is calculated before and after the predicted jump, (S14). When the ratio of the average dynamic resistance (Ra _AVE , Rb _AVE ) is equal to or less than the second set ratio (S15), it is determined that the jump has occurred (S16).

In the steps S14, S15 and S16 for determining the _jump , the ratio of the average copper resistance (Ra _AVE , Rb _AVE ) can be calculated by the following equation (2), and the second setting ratio may be 70 to 90% .

&Quot; (2) "

Where Ra _AVE is the average of the dynamic resistance during the second time interval before the predicted breaking point and Rb _AVE is the average of the dynamic resistance during the third time interval after the predicted end point. Also, the second and third time intervals may be different from each other, but may be the same as each other, but may range from 1 to 10 ms, for example, 5 ms. On the other hand, in order to calculate the dynamic resistance average during the second and third time intervals before and after the first time interval, The third time interval), and the dynamic resistance corresponding to the average dynamic resistance value before and after the predicted dynamic resistance can be extracted from the stored dynamic resistance values and used to calculate the average value. Also, each of the average dynamic resistance (Ra _AVE , Rb _AVE ) may be an average value of the dynamic resistance measured in a plurality of times within the corresponding time interval (second and third time intervals), for example, The third time interval) and the average value of the dynamic resistance at the end point.

If the ratio of the average dynamic resistance (Ra _AVE , Rb _AVE ) is equal to or less than the second predetermined ratio in the steps S14, S15, and S16 of determining the _jump , it can be determined that the predicted jump is the final jump, If the ratio of the average dynamic resistance (Ra _AVE , Rb _AVE ) exceeds the second set ratio, steps (S12, S13) for determining the predicted jump again are performed until welding is completed.

The method of detecting the deflection of the spot welder according to the embodiments of the present invention described above can be formed by a computer program. At this time, the codes and code segments constituting the computer program can be easily deduced by a computer programmer in the field. Also, the computer program may be stored in a computer-readable recording medium, read and executed by a computer, thereby implementing or implementing a method of detecting the spot welder's warpage.

According to the method for detecting the deflection of the spot welder and the recording medium storing the program according to the present invention, it is possible to accurately detect the deflection during the resistance spot welding process, and thereby to precisely identify the occurrence of defects in the welded joint. This can reduce errors in the determination of the quality of the welded product and can contribute to minimizing the possibility of welding failure due to subsequent actions.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

10: welding material 20: electrode
30: control unit 40:

Claims

Detecting a peak copper resistance (R _peak ) of the weld material;
(Ra, Rb) is detected at a first time interval when the peak dynamic resistance (R _peak ) is detected, and when the ratio of the dynamic resistance (Ra, Rb) is less than a first predetermined ratio ; And
(Ra _AVE , Rb _AVE ) of the second and third time intervals before and after the predicted skew, and calculates the average dynamic resistance (Ra _AVE , Rb _AVE ) of the average dynamic resistance Determining that a skidding has occurred if the ratio falls below a second set rate;
And detecting the warp of the spot welder.

The method according to claim 1,
Wherein the step of detecting the prediction error comprises:
Wherein the first time interval corresponds to a range of 5 to 15 ms.

The method according to claim 1,
Wherein the step of detecting the prediction error comprises:
Wherein the prediction error is detected from a fourth time interval after the peak dynamic resistance (R _peak ) is detected.

The method of claim 3,
Wherein the step of detecting the prediction error comprises:
And the fourth time interval corresponds to a range of 5 to 15 ms.

The method according to claim 1,
Wherein the step of detecting the prediction error comprises:
Wherein the ratio of the new dynamic resistance (Ra, Rb) is calculated at a first time interval after the elapse of the fifth time interval when the ratio of the dynamic resistance (Ra, Rb) exceeds the first predetermined ratio Way.

The method of claim 5,
And the fifth time interval corresponds to a range of 0.1 to 1.0 ms.

The method according to claim 1,
Wherein the step of detecting the prediction error comprises:
Wherein the ratio of the dynamic resistance (Ra, Rb) is calculated by the following equation (1), and the first setting ratio is 70 to 90%
[Equation 1]

Ra; Dynamic Resistance at the Time of Prediction
Rb; Dynamic resistance of the forecasting end point

The method according to claim 1,
Wherein the step of determining the jump comprises:
_Wherein a ratio of the average dynamic resistance (Ra _AVE , Rb _AVE ) is calculated by the following equation (2), and the second setting ratio is 70 to 90%
&Quot; (2) "

Ra _AVE ; The average of the dynamic resistance during the second time interval before the forecasting point
Rb _AVE ; The average of the dynamic resistance during the third time interval after the predicted end point

The method of claim 8,
Wherein the step of determining the jump comprises:
Wherein the second and third time intervals are equal to each other and correspond to a range of 1 to 10 ms.

A recording medium on which a program for carrying out the method of detecting a spot welder according to any one of claims 1 to 9 is stored.