JP4933407B2 - Spatter detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spatter detecting method capable of early detecting spatter. <P>SOLUTION: The spatter detecting method detects, as follows, the spatter that is generated when resistance-welding a weld workpiece 2 prepared by superposing two plate materials 21, 22 on each other. A pair of electrodes 31, 32 is arranged while putting the weld workpiece 2 between themselves. By applying an electric current across the pair of electrodes 31, 32 while pressurizing the weld workpiece 2 with the electrodes 31, 32, the two plate materials 21, 22 are resistance-welded. Here, the contact state of the front ends of the electrodes 31, 32 and the weld workpiece 2 is monitored during the time when the electric current is applied across the electrodes 31, 32. When a clearance between the front ends of the electrodes 31, 32 and the weld workpiece 2 is detected, generation of spatter is decided. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a sputtering detection method. Specifically, the present invention relates to a sputter detection method for detecting spatter generated when resistance welding is performed on a welded workpiece in which a plurality of plate materials are overlapped.

Conventionally, in a manufacturing process of an automobile, a plurality of plate materials are stacked and resistance-welded. For example, when manufacturing an automobile body, two inner panels having a high rigidity and a thick inner panel and a thin outer panel having a lower rigidity than the inner panel are overlapped and resistance-welded.
In this resistance welding, the contact area is locally reduced by pressing a welding work in which a plurality of metal plates are overlapped between a pair of electrodes. And by flowing an electric current between a pair of electrodes, a large electric current is caused to flow through this narrow contact surface, and a melted portion is generated at the contact surface between the plate members.

By the way, when the heat generated by resistance welding becomes excessive, spatter that causes a part of the melted part to scatter is generated, and there is a possibility that poor welding may occur in the melted part and its surroundings.
Therefore, in order to detect the welding failure due to the occurrence of this spatter, for example, a method has been proposed in which the resistance value of the welding workpiece is measured and, when the resistance value rapidly decreases, it is determined that spatter has occurred ( Patent Document 1).
Japanese Utility Model Publication No. 6-44542

  However, when spatter occurs, the thickness of the welded workpiece is instantaneously reduced, and a gap is formed between the electrode and the welded workpiece. Therefore, a delay occurs until the resistance value changes after the occurrence of spatter. Therefore, the above-described proposed method has a problem that it takes time until spatter is detected after spatter has occurred.

  An object of this invention is to provide the sputter | spatter detection method which can detect a sputter | spatter early.

  The sputter detection method of the present invention is a sputter detection method for detecting spatter generated when resistance welding is performed on a welded workpiece (for example, a welded workpiece 2 described later) in which a plurality of plates (for example, plate materials 21, 22 described later) are overlapped. A method in which an electrode (for example, a welding electrode 31, 31A, 31B, 32, 32A, 32B, which will be described later) is arranged on the welding workpiece, and the electrode is energized while pressurizing the welding workpiece with the electrode. When the plurality of plate members are resistance-welded to each other, and when the electrode is energized, the contact state between the tip of the electrode and the welding workpiece is monitored, and a gap between the tip of the electrode and the welding workpiece is detected Is characterized in that it is determined that sputtering has occurred.

The present inventors have found that when spatter occurs, the plate thickness of the weld work is instantaneously reduced, and a gap is formed between the electrode and the weld work.
Therefore, according to the present invention, the contact state between the tip of the electrode and the welding workpiece is monitored, and when a gap between the electrode and the welding workpiece is detected, it is determined that spatter has occurred. Therefore, since it is only necessary to detect the gap, spatter can be detected accurately and quickly by a simple method.

  In this case, while the electrode is energized, a transverse wave is output to the welding workpiece from an oscillator (for example, an ultrasonic oscillator 311 described later) built in the electrode, and a sensor (for example, described later) is built in the electrode. Sensor 312) detects the reflected wave of the transverse wave, measures the round-trip time of the transverse wave, and if the round-trip time decreases and exceeds the first reference value, the tip of the electrode and the welding workpiece It is preferable to determine that a gap has occurred between the two.

  In this case, while energizing the electrode, a longitudinal wave is output to the welding workpiece from an oscillator (for example, an ultrasonic oscillator 311A described later) built in the electrode, and a sensor (for example, an electrode built in the electrode (for example, When the reflected wave of the longitudinal wave is detected by a sensor 312A) to be described later and the intensity of the reflected wave rises and exceeds the second reference value, there is a gap between the tip of the electrode and the welding workpiece. It is preferable to determine that has occurred.

  In this case, a pair of the electrodes are provided across the welding workpiece, and an oscillator (for example, an ultrasonic oscillator 311B to be described later) built in one of the pair of electrodes is energized between the pair of electrodes. A longitudinal wave is output to the welding workpiece, and a transmitted wave of the longitudinal wave is detected by a sensor (for example, a sensor 312B described later) built in the other electrode of the pair of electrodes. It is preferable to determine that a gap has occurred between the tip of the pair of electrodes and the welded workpiece when the strength of the electrode decreases and exceeds the third reference value.

  According to this invention, a longitudinal wave and a transverse wave are output from the oscillator toward the welding workpiece, and a transmitted wave and a reflected wave of these output waves are detected by the sensor. When the detected transmitted wave or reflected wave intensity or the round-trip time of the reflected wave changes and exceeds the reference value, it is determined that a gap has occurred. Therefore, the gap can be easily detected.

  In this case, when the state exceeding the reference value continues for a first predetermined time or more, it is preferable to determine that a gap has occurred between the tip of the electrode and the welding workpiece.

  In this case, when the state exceeding the reference value continues in a range from the first predetermined time to the second predetermined time, it is determined that a gap has occurred between the tip of the electrode and the welding workpiece. preferable.

  According to the present invention, since the occurrence of the gap is determined based on the time during which the state exceeding the reference value continues, erroneous determination due to noise and other causes can be prevented.

  According to the present invention, when the contact state between the tip of the electrode and the welded workpiece is monitored and a gap between the electrode and the welded workpiece is detected, it is determined that spatter has occurred. Therefore, since it is only necessary to detect the gap, spatter can be detected accurately and quickly by a simple method.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the embodiments, the same constituent elements are denoted by the same reference numerals, and the description thereof is omitted or simplified.
[First Embodiment]
FIG. 1 is a diagram showing a configuration of a resistance welding system 1 to which a sputter detection method according to a first embodiment of the present invention is applied.

The resistance welding system 1 performs resistance welding on a welding work 2 in which two metal plate materials 21 and 22 are overlapped.
The resistance welding system 1 includes a pair of welding electrodes 31 and 32 disposed with a welding work 2 interposed therebetween, a drive mechanism 33 that moves the welding electrodes 31 and 32 closer to and away from each other, and a control device 34 that controls the drive mechanism 33. And a welding power source 35 for supplying a current to the welding electrodes 31 and 32.

  The welding electrode 31 includes an ultrasonic oscillator 311 that outputs a transverse wave and a sensor 312 that detects a reflected wave of the transverse wave. The ultrasonic oscillator 311 and the sensor 312 are connected to the control device 34.

The operation of the resistance welding system 1 will be described.
First, the drive mechanism 33 is driven by the control device 34, the welding workpiece 2 is pressurized by the welding electrodes 31, 32, and the welding workpiece 2 is clamped.

  In this state, the welding power source 35 energizes between the welding electrodes 31 and 32. Then, due to the contact resistance between the plate materials 21 and 22, heat is generated between the plate materials 21 and 22, and a melting part 23 is generated between the plate materials 21 and 22. Thereafter, the melted portion 23 gradually grows, whereby the plate material 21 and the plate material 22 are welded.

  Here, while the welding electrodes 31 and 32 are energized, the control device 34 outputs a transverse wave from the ultrasonic oscillator 311 to the welding workpiece 2 and detects a reflected wave of the transverse wave by the sensor 312, thereby producing a transverse wave. Measure the round trip time. Since the shear wave has a property of passing through the solid and reflecting in the space, the shear wave is reflected by the molten portion 24 of the weld work 2 when the tip of the weld electrode 31 and the weld work 2 are in contact with each other. In this way, the contact state between the tips of the welding electrodes 31 and 32 and the welding workpiece 2 is monitored.

  As shown in FIG. 2, when a gap is generated between the tips of the welding electrodes 31 and 32 and the welding work 2, the transverse wave is reflected by the tip surface of the welding electrode 31, so that the reciprocation time is abruptly shortened. Therefore, when this reciprocation time rapidly decreases and exceeds the reference value for a predetermined time range, a gap is generated between the tip of the pair of welding electrodes 31 and 32 and the welding workpiece 2. This is determined, and it is determined that sputtering has occurred.

Next, the procedure for detecting spatter will be described with reference to the flowchart of FIG.
First, in ST1, initial setting is performed. That is, the round trip time abnormal value detection flag s, the reflected wave detection number i, and the round trip time abnormal value detection count k are set to zero. In the flowchart of FIG. 3, when the abnormal value of the round trip time is measured, the detection flag s is changed from zero to 1, and the normal mode is shifted to the sputtering confirmation mode for confirming whether or not the abnormal value is sputtering. Shall.
In ST2, it is determined whether or not a nugget (melting portion) is generated. If this determination is No, the process returns to ST2 again, and if Yes, the process moves to ST3.

In ST3, the detection number i of the reflected wave is incremented, and in ST4, the round trip time t _i of the detected reflected wave is measured.
In ST5, it is determined whether or not the abnormal value detection flag S is 1. If this determination is Yes, since it is the sputter confirmation mode, the process proceeds to ST8, and if it is No, it is the normal mode. , Move to ST6.

In ST6, it determines whether the round trip time t _i is in the range of round trip time t _i-1 ± predetermined value α to the previously measured. If the determination is Yes, the order round trip time _{t i} is not the abnormal value, the process returns to ST3. On the other hand, when the determination is No, since the round-trip time _{t i} is the abnormal value, the process proceeds to ST7.
In ST7, the detection flag S outliers 1 increments the detection number k of outliers, the reference value t _S outliers round trip time as t _i, shifted to the sputtering confirmation mode, returns to ST3.

In ST8, it is determined whether or not the round trip time ti is within the range of the reference value t _S ± predetermined value β. If this determination is Yes, the round trip time t _i falls within a predetermined range centered on the reference value t _S , and the process moves to ST9. If the determination is No, the round trip time t _i is because out of the predetermined range around the reference value t _S, proceeds to ST10, determines whether or not the sputtering occurs.

In ST9, the abnormal value detection count k is incremented, and the process returns to ST3.
In ST10, it is determined whether or not the number k of abnormal value detections is a predetermined value γ or more and a predetermined value δ or less. If this determination is No, the number k of abnormal value detections does not fall within the range of the predetermined number, so it is determined as noise, and the process proceeds to ST12. On the other hand, if this determination is Yes, the process moves to ST11.

  In ST11, it is determined that sputtering has occurred. In ST12, the abnormal value detection flag S and the abnormal value detection count k are reset, and the process returns to ST3.

FIG. 4 is a timing chart of the resistance welding system.
Between the time t ₀ of time t _1, since the sputtering does not occur, the round-trip time is constant at r _1.
At time _{t 1,} the sputtering occurs. Then, the gap is generated between the welding electrode welding workpiece, round-trip time is rapidly reduced, and r _2.
At time t _2, the by resistance welding system, spatter is detected.
At time t ₃ , the welding electrode and the welding work are brought into close contact again, and the reciprocation time becomes r ₁ again.

According to this embodiment, there are the following effects.
(1) When the contact state between the tips of the welding electrodes 31 and 32 and the welding workpiece 2 is monitored and a gap between the electrodes 31 and 32 and the welding workpiece 2 is detected, it is determined that spatter has occurred. . Therefore, since it is only necessary to detect the gap, spatter can be detected accurately and quickly by a simple method.

  (2) A transverse wave is output from the ultrasonic oscillator 311 toward the welding workpiece 2, and the reflected wave of the outputted transverse wave is detected by the sensor 312. And when the round-trip time of the detected reflected wave changes rapidly and exceeds a reference value, it determines with the gap having arisen. Therefore, the gap can be easily detected.

  (3) Since it is determined that a gap has occurred between the tip of the electrodes 31 and 32 and the welded work 2 only when the state exceeding the reference value continues for a predetermined time range, errors due to noise or other causes are determined. Judgment can be prevented.

[Second Embodiment]
FIG. 5 is a diagram showing a configuration of a resistance welding system 1A to which the sputtering detection method according to the second embodiment of the present invention is applied.
In the present embodiment, the configurations of the welding electrodes 31A and 32A and the control device 34A are different from those of the first embodiment.
That is, the welding electrode 31A includes an ultrasonic oscillator 311A that outputs a longitudinal wave and a sensor 312A that detects a reflected wave of the longitudinal wave. The ultrasonic oscillator 311A and the sensor 312A are connected to the control device 34A.

  Further, the control device 34A outputs a longitudinal wave from the ultrasonic oscillator 311A to the welding workpiece 2 while energizing between the welding electrodes 31A and 32A, and detects a reflected wave of the longitudinal wave by the sensor 312A. Since the longitudinal wave has a property of transmitting solids and liquids and reflecting in space, the longitudinal wave passes through the welding workpiece 2 when the tip of the welding electrode 31A and the welding workpiece 2 are in contact with each other. In this manner, the contact state between the tips of the welding electrodes 31A and 32A and the welding workpiece 2 is monitored.

  Then, as shown in FIG. 6, when a gap is generated between the tip of the welding electrodes 31A and 32A and the welding workpiece 2, the transverse wave is reflected by the tip surface of the welding electrode 31A, so that the intensity of the reflected wave rapidly increases. To do. Therefore, when the intensity of the reflected wave increases and exceeds the reference value for a predetermined time range, a gap is generated between the tip of the pair of welding electrodes 31A and 32A and the welding workpiece 2. This is determined, and it is determined that sputtering has occurred.

  According to this embodiment, there are the same effects as the effects (1) to (3) described above.

[Third Embodiment]
FIG. 7 is a diagram showing a configuration of a resistance welding system 1B to which the sputtering detection method according to the third embodiment of the present invention is applied.
In the present embodiment, the configurations of the welding electrodes 31B and 32B and the control device 34B are different from those in the first embodiment.
That is, the welding electrode 31B includes an ultrasonic oscillator 311B that outputs a longitudinal wave, and the welding electrode 32B includes a sensor 312B that detects a reflected wave of the longitudinal wave. The ultrasonic oscillator 311B and the sensor 312B are connected to the control device 34B.

  Further, the control device 34B outputs a longitudinal wave from the ultrasonic oscillator 311B to the welding workpiece 2 while energizing between the welding electrodes 31B and 32B, and detects a reflected wave of the longitudinal wave by the sensor 312B. Since the longitudinal wave has a property of transmitting solids and liquids and reflecting in space, the longitudinal wave passes through the welding workpiece 2 when the tip of the welding electrode 31B is in contact with the welding workpiece 2. In this manner, the contact state between the tips of the welding electrodes 31B and 32B and the welding workpiece 2 is monitored.

  As shown in FIG. 8, when a gap is generated between the tip of the welding electrodes 31B and 32B and the welding workpiece 2, the transverse wave is reflected by the tip surface of the welding electrode 31B, so that the intensity of the transmitted wave is drastically reduced. To do. Therefore, when the intensity of the transmitted wave suddenly decreases and exceeds the reference value for a predetermined time range, there is a gap between the tip of the pair of welding electrodes 31B and 32B and the welding workpiece 2. It is determined that it has occurred, and it is determined that sputtering has occurred.

  According to this embodiment, there are the same effects as the effects (1) to (3) described above.

[Example]
An embodiment of the sputtering detection method will be described.
FIG. 9 is an example of the sputtering detection method according to the first embodiment described above, and is a diagram showing the relationship between the energization time and the round trip time of the reflected wave.
As shown in FIG. 9, the round-trip time of the reflected wave is substantially constant at b ₁ at first, but when the spatter occurs at time a ₁ and a gap is generated, the round trip time decreases rapidly to the first reference value b _0. Exceeds b and becomes b ₂ , and thereafter, when the welding electrode and the welded work are brought into close contact again, b ₁ is obtained again. Here, after the spatter is generated at time a ₁ and a gap is generated, if this gap remains, the round-trip time of the reflected wave remains b ₂ as shown by the one-dot chain line in FIG. .

FIG. 10 is an example of the sputtering detection method according to the second embodiment described above, and is a diagram illustrating the relationship between the energization time and the intensity of the reflected wave.
As shown in FIG. 10, the intensity of the reflected wave is initially substantially constant at c ₁ , but when the spatter occurs at time a ₂ and a gap is generated, it rapidly rises and becomes the second reference value c ₀ . beyond c _2, and the subsequently when the welding electrode and the welding workpiece comes into close contact again, a c ₁ again. Here, after the spatter is generated at time a ₂ and a gap is generated, when this gap remains, the intensity of the reflected wave remains c ₂ as indicated by a one-dot chain line in FIG.

FIG. 11 is an example of the sputtering detection method according to the third embodiment described above, and is a diagram showing the relationship between the energization time and the intensity of the transmitted wave.
As shown in FIG. 11, the intensity of the transmitted wave is initially substantially constant at d ₁ , but when the spatter occurs at time a ₃ and a gap is generated, the intensity decreases sharply to obtain the third reference value d ₀ . beyond d _2, and the subsequently when the welding electrode and the welding workpiece comes into close contact again, the d ₁ again. Here, when the gap remains after spattering occurs at time a ₃ , the intensity of the transmitted wave remains d ₂ as indicated by the one-dot chain line in FIG.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.

It is a figure which shows the structure of the resistance welding system to which the sputtering detection method which concerns on 1st Embodiment of this invention was applied. It is a figure which shows the state which the clearance gap generate | occur | produced in the welding workpiece | work about the resistance welding system which concerns on the said embodiment. It is a flowchart which detects a spatter with the resistance welding system which concerns on the said embodiment. It is a timing chart of the resistance welding system which concerns on the said embodiment. It is a figure which shows the structure of the resistance welding system to which the sputtering detection method which concerns on 2nd Embodiment of this invention was applied. It is a figure which shows the state which the clearance gap generate | occur | produced in the welding workpiece | work about the resistance welding system which concerns on the said embodiment. It is a figure which shows the structure of the resistance welding system to which the sputtering detection method which concerns on 2nd Embodiment of this invention was applied. It is a figure which shows the state which the clearance gap generate | occur | produced in the welding workpiece | work about the resistance welding system which concerns on the said embodiment. It is an Example of the sputtering detection method which concerns on 1st Embodiment of this invention. It is an Example of the sputtering detection method which concerns on 2nd Embodiment of this invention. It is an Example of the sputtering detection method which concerns on 3rd Embodiment of this invention.

Explanation of symbols

2 Welding work 21, 22 Plate material 31, 31A, 31B, 32, 32A, 32B Welding electrode (electrode)
311, 311A, 311B Ultrasonic oscillator
312, 312A, 312B sensor

Claims (4)

A sputter detection method for detecting spatter generated when resistance welding is performed on a welded workpiece in which a plurality of plate materials are overlapped,
An electrode is disposed on the welding workpiece, and the electrodes are energized while pressurizing the welding workpiece with the electrode, whereby the plurality of plate members are resistance-welded to each other,
Sputtering that determines that spatter has occurred when the contact state between the tip of the electrode and the welding workpiece is monitored while a gap between the tip of the electrode and the welding workpiece is detected while the electrode is energized. In the detection method,
While energizing the electrode, output a transverse wave to the welding work from the oscillator built in the electrode, and detect the reflected wave of the transverse wave with a sensor built in the electrode,
The reciprocation time of the transverse wave is measured, and when the reciprocation time decreases and exceeds a first reference value, it is determined that a gap is generated between the tip of the electrode and the welding workpiece. Sputter detection method. A sputter detection method for detecting spatter generated when resistance welding is performed on a welded workpiece in which a plurality of plate materials are overlapped,
An electrode is disposed on the welding workpiece, and the electrodes are energized while pressurizing the welding workpiece with the electrode, whereby the plurality of plate members are resistance-welded to each other,
Sputtering that determines that spatter has occurred when the contact state between the tip of the electrode and the welding workpiece is monitored while a gap between the tip of the electrode and the welding workpiece is detected while the electrode is energized. In the detection method,
While energizing the electrode, it outputs a longitudinal wave from the oscillator built in the electrode to the welding workpiece, and detects a reflected wave of the longitudinal wave with a sensor built in the electrode,
When the intensity of the reflected wave rises and exceeds a second reference value, it is determined that a gap has occurred between the tip of the electrode and the welding workpiece . A sputter detection method for detecting spatter generated when resistance welding is performed on a welded workpiece in which a plurality of plate materials are overlapped,
An electrode is disposed on the welding workpiece, and the electrodes are energized while pressurizing the welding workpiece with the electrode, whereby the plurality of plate members are resistance-welded to each other,
Sputtering that determines that spatter has occurred when the contact state between the tip of the electrode and the welding workpiece is monitored while a gap between the tip of the electrode and the welding workpiece is detected while the electrode is energized. In the detection method,
A pair of the electrodes are provided across the welding workpiece,
While energizing between the pair of electrodes, a longitudinal wave is output to the welding workpiece from an oscillator built in one of the pair of electrodes, and built in the other electrode of the pair of electrodes. Detect the longitudinal transmitted wave with a sensor,
When the intensity of the transmitted wave decreases and exceeds a third reference value, it is determined that a gap is generated between the tip of the pair of electrodes and the welding workpiece . In the spatter detection method according to any one of claims 1 to 3 ,
A sputter detection method comprising: determining that a gap has occurred between the tip of the electrode and the welding workpiece when the state exceeding the reference value continues for a first predetermined time or more.

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