JP5203331B2 - Design method of welding electrode with built-in ultrasonic sensor - Google Patents

Description

  The present invention relates to a welding electrode design technique in which an ultrasonic sensor for identifying a reflected wave of a nugget during welding is incorporated.

  In spot welding, for example, a melted and solidified weld metal generated at the contact portion between two steel plates after welding is called a nugget, and the joint strength of the welded portion is evaluated by a nugget diameter indicating the size of the nugget.

  Thus, an electrode having an ultrasonic probe therein has been proposed (for example, see Patent Document 1 (FIG. 1)).

Patent document 1 is demonstrated based on the following figure.
FIG. 10 is a diagram for explaining the basic configuration of the prior art. The welding electrode 100 is connected to a hollow shaft 102 to which a welding cap 101 is attached at the tip and a connection pad 104 placed on the inner bottom surface 103 of the welding cap 101. An ultrasonic probe 106 built in the welding cap 101 and the distal end portion 105 of the hollow shaft 102, a probe holder 107 for holding the ultrasonic probe 106 from the rear and inserting it into the hollow shaft 102, and the probe holder 107 And a signal line 109 extending from the rear end of the ultrasonic probe 106 to the top of the figure and inserted into the probe holder 107 and the cooling water pipe 108.

FIG. 11 is a diagram for explaining the arrival time of the reflected wave. When the time during which the ultrasonic wave moves in the connection pad (hereinafter referred to as a signal transmission member) 104 is Td, the welding cap (hereinafter referred to as a welding tip) is illustrated. .) The arrival time of the reflected wave 116 reflected by the upper surface of 101 is 2Td.
Similarly, when the time for the ultrasonic wave to move in the welding tip 101 is Tt, the arrival time of the reflected wave 118 reflected from the upper surface of the workpiece 117A is 2 (Td + Tt).

Assuming that the time required for the ultrasonic wave to travel to the nugget 119 is Tn, the arrival time of the reflected wave 121 reflected by the nugget 119 is 2 (Td + Tt + Tn).
Furthermore, when the time for which the ultrasonic wave moves in the workpiece 117A is Tw, the arrival time of the reflected wave 122 reflected by the lower surface of the workpiece 117A (that is, on the workpiece 117B) is 2 (Td + Tt + Tw).

  FIG. 12 is a waveform diagram of the reflected wave. As shown in FIG. 12A, when the horizontal axis represents time and the vertical axis represents intensity, the reflected waves 116, 118, 121, and 122 appear in this order. The reflected wave 121 is a wave related to nugget evaluation.

  In FIG. 11, the reflected wave 116 is reflected on the lower surface of the ultrasonic probe (hereinafter referred to as an ultrasonic sensor) 106, and the reflected component passes through the signal transmission member 104 again at the tip of the signal transmission member 104. The phenomenon of reflection inevitably occurs. This wave is the secondary wave 123 shown in FIG.

  When (b) is superimposed on (a), it can be seen that the secondary wave 123 overlaps the reflected wave 121. This makes it difficult to distinguish between the reflected wave 121 and the secondary wave 123 in the waveform diagram, which adversely affects nugget evaluation.

  Therefore, a welding electrode with a built-in ultrasonic sensor that can eliminate the influence of secondary waves is required.

JP 2005-527374 A

  It is an object of the present invention to provide a design technique for a welding electrode with a built-in ultrasonic sensor that can eliminate the influence of a secondary wave.

The invention according to claim 1 is a welding tip that contacts a workpiece and supplies a spot welding current to the workpiece, an ultrasonic sensor that emits an ultrasonic wave and receives a reflected wave, and the ultrasonic sensor and the welding tip. An ultrasonic sensor built-in welding electrode including a signal transmission member that transmits ultrasonic waves emitted by the ultrasonic sensor to the welding tip and transmits reflected waves received by the welding tip to the ultrasonic sensor. Design method,
When the time for the ultrasonic wave to move in the signal transmission member is Td, the time for the ultrasonic wave to move in the welding tip is Tt, and the time for the ultrasonic wave to move in the workpiece is Tw ( The signal transmission member is designed to satisfy the condition of Tt + Tw <Td), and the welding tip is designed to satisfy the condition of (Tw <Tt).

According to a second aspect of the present invention, there is provided a welding tip that contacts a workpiece and supplies a spot welding current to the workpiece, an ultrasonic sensor that emits an ultrasonic wave and receives a reflected wave, and the ultrasonic sensor and the welding tip. An ultrasonic sensor built-in welding electrode including a signal transmission member that transmits ultrasonic waves emitted by the ultrasonic sensor to the welding tip and transmits reflected waves received by the welding tip to the ultrasonic sensor. Design method,
Td is the time for the ultrasonic wave to move in the signal transmission member, Tt is the time for the ultrasonic wave to move in the welding tip, Tα is the time for the ultrasonic wave to move the maximum wear length of the welding tip, The signal transmission member is designed so as to satisfy the condition of (Tt−Tα + Tw <Td), where Tw is the time during which the ultrasonic wave moves within the workpiece, and the condition of (Tw <Tt−Tα) is satisfied. The welding tip is designed as described above.

According to a third aspect of the present invention, there is provided a welding tip that contacts a workpiece and supplies a spot welding current to the workpiece, an ultrasonic sensor that emits an ultrasonic wave and receives a reflected wave, and the ultrasonic sensor and the welding tip. An ultrasonic sensor built-in welding electrode including a signal transmission member that transmits ultrasonic waves emitted by the ultrasonic sensor to the welding tip and transmits reflected waves received by the welding tip to the ultrasonic sensor. Design method,
The time for the ultrasonic wave to move in the signal transmission member is Td, the time for the ultrasonic wave to move in the welding tip is Tt, the time delay of the ultrasonic wave due to the temperature rise of the welding tip is Tβ, The signal transmission member is designed to satisfy the condition of (Tt + Tβ + Tw + Tγ <Td), where Tw is a time during which the sound wave moves within the work and Tγ is a time delay of the ultrasonic wave accompanying the temperature rise of the work. , (Tw−Tβ + Tγ <Tt), the welding tip is designed to satisfy the condition.

According to a fourth aspect of the present invention, there is provided a welding tip that contacts a workpiece and supplies a spot welding current to the workpiece, an ultrasonic sensor that emits ultrasonic waves and receives reflected waves, and the ultrasonic sensor and the welding tips. An ultrasonic sensor built-in welding electrode including a signal transmission member that transmits ultrasonic waves emitted by the ultrasonic sensor to the welding tip and transmits reflected waves received by the welding tip to the ultrasonic sensor. Design method,
Td is the time for the ultrasonic wave to move in the signal transmission member, Tt is the time for the ultrasonic wave to move in the welding tip, Tα is the time for the ultrasonic wave to move the maximum wear length of the welding tip, When the time delay of the ultrasonic wave accompanying the temperature rise of the welding tip is Tβ, the time for the ultrasonic wave to move in the work is Tw, and the time delay of the ultrasonic wave due to the temperature rise of the work is Tγ. , (Tt−Tα + Tβ + Tw + Tγ <Td), and the signal transmission member is designed to satisfy the condition (Tw + Tα−Tβ + Tγ <Tt), and the welding tip is designed to satisfy the condition (Tw + Tα−Tβ + Tγ <Tt).

  In the first aspect of the invention, by satisfying the conditions of (Tt + Tw <Td) and (Tw <Tt), the reflected wave from the nugget and the secondary wave can be temporally separated. Therefore, according to this invention, the technique which can design the welding electrode with a built-in ultrasonic sensor which can exclude the influence of a secondary wave is provided.

  In the invention according to claim 2, by satisfying the conditions of (Tt−Tα + Tw <Td) and (Tw <Tt−Tα), even if welding tip wear occurs, the reflected wave and the secondary wave by the nugget Can be separated in time. Therefore, according to this invention, the technique which can design the welding electrode with a built-in ultrasonic sensor which can exclude the influence of a secondary wave is provided.

  In the invention according to claim 3, by satisfying the conditions of (Tt + Tβ + Tw + Tγ <Td) and (Tw−Tβ + Tγ <Tt), the reflected wave and the secondary wave by the nugget are generated even when the welding tip and the workpiece are at a high temperature. Can be separated in time. Therefore, according to this invention, the technique which can design the welding electrode with a built-in ultrasonic sensor which can exclude the influence of a secondary wave is provided.

  In the invention according to claim 3, by satisfying the conditions of (Tt−Tα + Tβ + Tw + Tγ <Td) and (Tw + Tα−Tβ + Tγ <Tt), even if wear of the welding tip occurs and the welding tip and the workpiece become high temperature, The reflected wave from the nugget and the secondary wave can be temporally separated. Therefore, according to this invention, the technique which can design the welding electrode with a built-in ultrasonic sensor which can exclude the influence of a secondary wave is provided.

It is a figure explaining the arrival time of the reflected wave which concerns on Example 1. FIG. 3 is a waveform diagram of a reflected wave according to Embodiment 1. FIG. It is a figure explaining the arrival time of the reflected wave which concerns on Example 2. FIG. 6 is a waveform diagram of a reflected wave according to Example 2. FIG. It is a figure explaining the arrival time of the reflected wave which concerns on Example 3. FIG. 6 is a waveform diagram of a reflected wave according to Example 4. FIG. It is a figure explaining how to obtain Tβ. It is a figure explaining how to obtain Tγ. It is a figure explaining duration Ts. It is a figure explaining the basic composition of the conventional technology. It is a figure explaining the arrival time of a reflected wave. It is a wave form diagram of a reflected wave.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.

First, Embodiment 1 of the present invention will be described with reference to the drawings.
FIG. 1A is a diagram for explaining the arrival time of the reflected wave. The welding electrode 10 with a built-in ultrasonic sensor is in contact with the workpiece 11A to supply a spot welding current to the workpieces 11A and 11B. An ultrasonic sensor 13 that emits a sound wave and receives a reflected wave, and an ultrasonic wave that is interposed between the ultrasonic sensor 13 and the welding tip 12 and is emitted from the ultrasonic sensor 13 are transmitted to the welding tip 12 and the welding tip 12. And a signal transmission member 14 that transmits the reflected wave received by the ultrasonic sensor 13.

If the time for the ultrasonic wave to move in the signal transmission member 14 is Td, the arrival time of the reflected wave 15 reflected from the upper surface of the welding tip 12 is 2Td.
Similarly, when the time for the ultrasonic wave to move in the welding tip 12 is Tt, the arrival time of the reflected wave 16 reflected from the upper surface of the workpiece 11A is 2 (Td + Tt).
If the time required for the ultrasonic wave to travel to the nugget 17 is Tn, the arrival time of the reflected wave 18 reflected by the nugget 17 is 2 (Td + Tt + Tn).
Furthermore, when the time for the ultrasonic wave to move in the workpiece 11A is Tw, the arrival time of the reflected wave 19 reflected by the lower surface of the workpiece 11A (that is, the upper surface of the workpiece 11B) is 2 (Td + Tt + Tw).

Next, the secondary wave will be described.
As shown in (b), the ultrasonic wave moving in the signal transmission member 14 is reflected by the welding tip 12, this reflected wave is reflected by the ultrasonic sensor 13, and this reflected wave is reflected again by the welding tip 12. Such a reflected wave 21 is read by the ultrasonic sensor 13. The reflected wave 21 is called a secondary wave, and the arrival time of the reflected wave 21 is 4Td.

  Further, the ultrasonic wave moving in the signal transmission member 14 and the welding tip 12 is reflected by the workpiece 11A, the reflected wave is reflected by the welding tip 12, and this reflected wave is reflected again by the welding workpiece 11A. The reflected wave 22 is read by the ultrasonic sensor 13. The reflected wave 22 is called a secondary wave, and the arrival time of the reflected wave 22 is 2 (Td + 2Tt).

FIG. 2 is a waveform diagram corresponding to FIG.
As shown in FIG. 2A, when the horizontal axis is time and the vertical axis is intensity, reflected waves 15, 16, 18, and 19 appear in this order. The reflected wave 18 is a wave related to nugget evaluation.
(B) is a waveform diagram showing the secondary wave 21 of the reflected wave 15, and the secondary wave 21 appears at 4Td on the horizontal axis (that is, twice Td).
(C) is a waveform diagram showing the secondary wave 22, and this secondary wave 22 appears at 2 (Td + 2Tt) on the horizontal axis.

If the secondary wave 21 shown in (b) is on the right side of the reflected wave 19 shown in (a) and the secondary wave 22 shown in (c) is on the right side, at least the most important reflected wave 18 is shown. There is no worry that the secondary waves 21 and 22 overlap.
Specifically, a conditional expression 2 (Td + Tt + Tw) <4Td is derived by comparing (a) and (b). By arranging this conditional expression, (Td + Tt + Tw) <2Td, and (Tt + Tw) <Td.
Similarly, by comparing (a) and (c), a conditional expression of 2 (Td + Tt + Tw) <2 (Td + 2Tt) is derived. When this conditional expression is arranged, (Td + Tt + Tw) <(Td + 2Tt) and Tw <Tt.

  That is, when Td is the time for the ultrasonic wave to move within the signal transmission member, Tt is the time for the ultrasonic wave to move within the welding tip, and Tw is the time for the ultrasonic wave to move within the workpiece, (Tt + Tw <Td The method of designing a welding electrode with a built-in ultrasonic sensor in which the signal transmission member is designed so as to satisfy the condition (2) and the welding tip is designed so as to satisfy the condition (Tw <Tt) is recommended.

That is, the above design method is achieved by adjusting the generation time of Td and Tt by adjusting the length of the welding tip and the signal transmission member and changing the material. In order to shorten the wavelength, it is possible to adjust the damper material built in the ultrasonic sensor or to make the vibration element thinner.
The same applies below.

Next, Example 2 of the present invention in consideration of wear of a welding tip will be described based on the drawings.
FIG. 3A is a diagram for explaining the arrival time of the reflected wave, and the basic configuration is the same as that in FIG. However, the welding tip 12 is worn by use. The tip line 24 shown by the imaginary line is worn at the maximum.

  The time for which the ultrasonic wave moves is Tt in the welding tip 12, but when the time for wear is Tα, the time in the welding tip 12 after wear is (Tt−Tα).

Then, all “Tt” shown in FIG. 1A may be replaced with “(Tt−Tα)”.
As a result, FIG. 1A is rewritten to FIG.

The waveform diagram of FIG. 2 is revised to FIG.
In FIG. 4, by comparing (a) and (b), a conditional expression of 2 (Td + Tt−Tα + Tw) <4Td is derived. By arranging this conditional expression, (Td + Tt−Tα + Tw) <2Td, and (Tt−Tα + Tw) <Td.
Similarly, by comparing (a) and (c), a conditional expression of 2 (Td + Tt−Tα + Tw) <2 (Td + 2Tt−2Tα) is derived. If this conditional expression is arranged, (Td + Tt−Tα + Tw) <(Td + 2Tt−2Tα) and Tw <Tt−Tα.

  That is, Td is the time for the ultrasonic wave to move in the signal transmission member, Tt is the time for the ultrasonic wave to move in the welding tip, Tα is the time for the ultrasonic wave to move the maximum wear length of the welding tip, The signal transmission member is designed so as to satisfy the condition of (Tt−Tα + Tw <Td) when the time for moving in the workpiece is Tw, and the welding tip is set so as to satisfy the condition of (Tw <Tt−Tα). The design method of the welding electrode with a built-in ultrasonic sensor to be designed is recommended.

  By the way, the speed of the ultrasonic wave decreases as the temperature increases. Since a large current flows through the welding tip and the workpiece and is heated, it is necessary to consider the temperature at the welding tip and the workpiece. There is no need to consider the signal transmission member because the temperature change is small.

Then, Example 3 of the present invention in consideration of heating is described based on a drawing.
FIG. 5 is a diagram for explaining the arrival time of the reflected wave, and the ultrasonic wave passing time Tt in the welding tip 12 is increased by Tβ by heating. Similarly, the ultrasonic wave passing time Tw in the workpiece 11A is increased by Tγ by heating.

Then, “Tt” shown in FIG. 1A may be replaced with “(Tt + Tβ)” and “Tw” may be replaced with “(Tw + Tγ)”. A method for obtaining Tβ and Tγ will be described later.
As a result, the time shown in FIG. 5 is obtained.

The waveform diagram of FIG. 2 is revised to FIG.
In FIG. 6, by comparing (a) and (b), a conditional expression of 2 (Td + Tt + Tβ + Tw + Tγ) <4Td is derived. When this conditional expression is arranged, (Td + Tt + Tβ + Tw + Tγ) <2Td and further (Tt + Tβ + Tw + Tγ) <Td.

  As Tβ increases, the secondary wave 21 shown in (b) approaches the reflected wave 18 shown in (a), and the risk of overlapping increases. That is, since the time with the largest delay is the most likely to overlap, Tβ is the delay time when the latest delay occurs due to the temperature rise of the new welding tip (when the tick is maximum).

  Similarly, by comparing (a) and (c), a conditional expression of 2 (Td + Tt + Tβ + Tw + Tγ) <2 (Td + 2Tt + 2Tβ) is derived. If this conditional expression is rearranged, (Td + Tt + Tβ + Tw + Tγ) <(Td + 2Tt + 2Tβ), and Tw−Tβ + Tγ <Tt.

Next, how to determine the delay time Tβ in the welding tip 12 will be described.
As shown in FIG. 7A, the time taken by the reflected wave 24 from the upper surface of the workpiece 11A is 2 (Td + Tt).
When the welding tip 12 is heated, the ultrasonic wave is delayed. 2 (Td + Tt + Tβ) to which the delay time Tβ is added is the moving time of the reflected wave 25 during heating.

As shown in (b), the appearance time of the reflected waves 24 and 25 is taken on the horizontal axis. Then, welding is performed with a pulse current. With the first pulse as “reception number 1” and the nth pulse as “reception number n”, the appearance times of the reflected waves 24 and 25 are plotted along the vertical axis from bottom to top.
Then, the curve 26 is obtained. As the welding tip 12 is heated, a difference of “delay Tβ” is recognized on the horizontal axis. This difference is the delay time Tβ.

However, the method shown in (a) is called an ultrasonic wave (transverse wave) reflection method. When the nugget 17 is formed, a reflected wave on the lower surface of the workpiece 11 cannot be obtained, and therefore the delay time Tγ at the workpieces 11A and 11B cannot be measured.
Therefore, Tγ is obtained by the following ultrasonic (longitudinal wave) transmission method.

  As shown in FIG. 8A, the workpieces 11A and 11B are sandwiched between the upper welding tip 12A and the lower welding tip 12B. Then, ultrasonic waves are transmitted from the upper ultrasonic sensor 13A, transmitted through the workpieces 11A and 11B, and received by the lower ultrasonic sensor 13B. The time required for moving the ultrasonic waves is affected by the temperature. Therefore, the delay time at the upper welding tip 12A is Tβ ', the delay time at the workpieces 11A and 11B is Tγ, and the delay time at the lower welding tip 12B is Tβ'.

As shown in (b), welding is performed with a pulse current. The first pulse is “reception number 1” and the nth pulse is “reception number n”, and the transmission time is plotted along the vertical axis from bottom to top.
Then, the curve 27 is obtained. As the welding tips 12A and 12B and the workpieces 11A and 11B are heated, a difference of “delay Tβ ′ + Tγ + Tβ ′” is recognized on the horizontal axis. This difference is the delay time Tβ ′ + Tγ + Tβ ′. The delay time Tγ can be obtained by assuming that Tβ obtained in FIG. 7 is substantially equivalent to Tβ ′.

  That is, Td is the time for the ultrasonic wave to move in the signal transmission member, Tt is the time for the ultrasonic wave to move in the welding tip, Tβ is the time delay of the ultrasonic wave accompanying the temperature rise of the welding tip, and the ultrasonic wave is in the workpiece. The signal transmission member is designed to satisfy the condition of (Tt + Tβ + Tw + Tγ <Td), where Tw is the moving time and Tγ is the time delay of the ultrasonic wave accompanying the temperature rise of the workpiece, and (Tw−Tβ + Tγ <Tt) Provided is a method for designing a welding electrode with a built-in ultrasonic sensor in which a welding tip is designed to satisfy a condition.

  Next, a fourth embodiment of the present invention that considers the wear of the welding tip and the influence of heating will be described. Since the fourth embodiment is a combination of the second embodiment and the third embodiment and is derived based on FIGS. 3 to 8, detailed description thereof is omitted.

  That is, Td is the time for the ultrasonic wave to move in the signal transmission member, Tt is the time for the ultrasonic wave to move in the welding tip, Tα is the time for the ultrasonic wave to move the maximum wear length of the welding tip, When the time delay of the ultrasonic wave accompanying the temperature rise is Tβ, the time that the ultrasonic wave moves in the work is Tw, and the time delay of the ultrasonic wave accompanying the temperature rise of the work is Tγ, (Tt−Tα + Tβ + Tw + Tγ <Td) A signal transmission member is designed to satisfy the condition, and a welding tip is designed to satisfy the condition of (Tw + Tα−Tβ + Tγ <Tt).

First, the above design method is achieved by adjusting the generation time of Td and Tt by adjusting the length of the welding tip and the signal transmission member and changing the material, and in order to shorten the wavelength, an ultrasonic sensor is used. It was explained that it can be implemented by adjusting the built-in damper material or making the vibration element thinner.
Then, next, the effectiveness of shortening the wavelength will be described in detail.

As shown in FIG. 9A, a reflected wave 18 having a long duration (the duration will be described in (b) and (c)) may appear. This reflected wave 18 tends to overlap the front and rear reflected waves 16 and 19. If they overlap, it becomes difficult to identify the reflected wave 18.
(B) is a waveform diagram redrawn by taking an absolute value from the reflected wave 18 shown in (a).
In (c), an envelope of the redrawn waveform is drawn. The maximum height of this envelope is “1”, a horizontal line is drawn with “0.1” corresponding to 10%, and the interval between the intersections (two) of this horizontal line and the envelope is defined as the duration Ts. .

The duration Ts can be shortened by adjusting a damper material built in the ultrasonic sensor or by thinning the vibration element. As a result, a reflected wave 18 having a short duration Ts as shown in (d) can be obtained.
That is, when designing the welding electrode with a built-in ultrasonic sensor, it is effective to use an ultrasonic sensor with a short duration Ts.

  The present invention is suitable for a welding electrode with a built-in ultrasonic sensor used for spot welding.

  DESCRIPTION OF SYMBOLS 10 ... Welding electrode with built-in ultrasonic sensor, 11A ... Workpiece, 12 ... Welding tip, 13 ... Ultrasonic sensor, 14 ... Signal transmission member.

Claims (4)

A welding tip that contacts the workpiece and supplies a spot welding current to the workpiece; an ultrasonic sensor that emits an ultrasonic wave and receives a reflected wave; and the ultrasonic sensor that is interposed between the ultrasonic sensor and the welding tip. A method for designing a welding electrode with a built-in ultrasonic sensor, including a signal transmission member that transmits ultrasonic waves emitted from a ultrasonic sensor to the welding tip and transmits reflected waves received by the welding tip to the ultrasonic sensor,
When the time for the ultrasonic wave to move in the signal transmission member is Td, the time for the ultrasonic wave to move in the welding tip is Tt, and the time for the ultrasonic wave to move in the workpiece is Tw ( The signal transmission member is designed so as to satisfy the condition of Tt + Tw <Td), and the welding tip is designed so as to satisfy the condition of (Tw <Tt). . A welding tip that contacts the workpiece and supplies a spot welding current to the workpiece; an ultrasonic sensor that emits an ultrasonic wave and receives a reflected wave; and the ultrasonic sensor that is interposed between the ultrasonic sensor and the welding tip. A method for designing a welding electrode with a built-in ultrasonic sensor, including a signal transmission member that transmits ultrasonic waves emitted from a ultrasonic sensor to the welding tip and transmits reflected waves received by the welding tip to the ultrasonic sensor,
Td is the time for the ultrasonic wave to move in the signal transmission member, Tt is the time for the ultrasonic wave to move in the welding tip, Tα is the time for the ultrasonic wave to move the maximum wear length of the welding tip, The signal transmission member is designed so as to satisfy the condition of (Tt−Tα + Tw <Td), where Tw is the time during which the ultrasonic wave moves within the workpiece, and the condition of (Tw <Tt−Tα) is satisfied. The method of designing a welding electrode with a built-in ultrasonic sensor, wherein the welding tip is designed as described above. A welding tip that contacts the workpiece and supplies a spot welding current to the workpiece; an ultrasonic sensor that emits an ultrasonic wave and receives a reflected wave; and the ultrasonic sensor that is interposed between the ultrasonic sensor and the welding tip. A method for designing a welding electrode with a built-in ultrasonic sensor, including a signal transmission member that transmits ultrasonic waves emitted from a ultrasonic sensor to the welding tip and transmits reflected waves received by the welding tip to the ultrasonic sensor,
The time for the ultrasonic wave to move in the signal transmission member is Td, the time for the ultrasonic wave to move in the welding tip is Tt, the time delay of the ultrasonic wave due to the temperature rise of the welding tip is Tβ, The signal transmission member is designed to satisfy the condition of (Tt + Tβ + Tw + Tγ <Td), where Tw is a time during which the sound wave moves within the work and Tγ is a time delay of the ultrasonic wave accompanying the temperature rise of the work. , (Tw−Tβ + Tγ <Tt), wherein the welding tip is designed to satisfy the condition of (Tw−Tβ + Tγ <Tt). A welding tip that contacts the workpiece and supplies a spot welding current to the workpiece; an ultrasonic sensor that emits an ultrasonic wave and receives a reflected wave; and the ultrasonic sensor that is interposed between the ultrasonic sensor and the welding tip. A method for designing a welding electrode with a built-in ultrasonic sensor, including a signal transmission member that transmits ultrasonic waves emitted from a ultrasonic sensor to the welding tip and transmits reflected waves received by the welding tip to the ultrasonic sensor,
Td is the time for the ultrasonic wave to move in the signal transmission member, Tt is the time for the ultrasonic wave to move in the welding tip, Tα is the time for the ultrasonic wave to move the maximum wear length of the welding tip, When the time delay of the ultrasonic wave accompanying the temperature rise of the welding tip is Tβ, the time for the ultrasonic wave to move in the work is Tw, and the time delay of the ultrasonic wave due to the temperature rise of the work is Tγ. , (Tt−Tα + Tβ + Tw + Tγ <Td), and the signal transmission member is designed to satisfy the condition (Tw + Tα−Tβ + Tγ <Tt), and the welding tip is designed to satisfy the condition (Tw + Tα−Tβ + Tγ <Tt) Design method for built-in welding electrode.

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