JP5963508B2 - Spot welding method - Google Patents

Description

  The present invention relates to a spot welding method.

  Conventionally, a plurality of laminated metal plate members are sandwiched between a pair of electrode chips, and the contact is generated by energizing the pair of electrode chips to generate resistance heat at the contact interface of the metal plate members. Spot welding for forming a nugget at the interface is known. The nugget is formed by melting the metal plate near the contact interface by the resistance heat generation.

  In the spot welding, when the metal plate material is melted, spatter and sparks may occur if the pressure force of the electrode tip is large. Therefore, in order to avoid the occurrence of the spatter and spark, an ultrasonic transmitter / receiver is provided in the electrode tip, and an ultrasonic wave is oscillated toward the contact interface, thereby monitoring a molten state of the metal plate material. Has been proposed (see, for example, Patent Document 1).

  When doing in this way, generation | occurrence | production of the said sputter | spatter and a spark can be avoided by controlling the applied pressure of the said electrode tip according to the fusion | melting state of the said metal board | plate material.

JP 2011-200908 A

  However, spot welding has a disadvantage that spatter is generated even when the current density becomes excessive. As an example in which the current density is excessive, when the contact area between the metal plate members is smaller than the contact area of the electrode tip with the metal plate member, the electrode tip is in contact with the metal plate member obliquely, It is conceivable that the chip is in contact with a metal plate.

  Moreover, in spot welding, when the contact area with respect to a metal plate material is increased due to wear of the electrode tips, the current density is lowered, and an excellent quality nugget may not be formed. .

  Accordingly, the present invention provides a spot welding method capable of solving the above inconveniences and forming an excellent quality nugget regardless of the contact state of the electrode tip with the metal plate material or the contact state between the metal plate materials. The purpose is to do.

In order to achieve this object, the spot welding method of the present invention includes a plurality of laminated metal plate members sandwiched between a pair of electrode tips, and energized between the pair of electrode tips. In a spot welding method in which a nugget is formed at the contact interface of a sheet of metal plate material, an ultrasonic transmitter / receiver is provided on the electrode tip, and ultrasonic waves are oscillated from the ultrasonic transmitter / receiver to the plurality of metal plate materials and received. The contact area of the electrode tip with respect to the metal plate material or the contact area between the metal plate materials is detected from the reflected wave, and the contact area of the electrode tip with respect to the metal plate material and the contact area between the metal plate materials And a current value to be passed between the pair of electrode chips is controlled according to the smaller contact area .

In the spot welding method of the present invention, the metal plate material of the electrode tip is obtained by oscillating ultrasonic waves to the plurality of metal plate materials and receiving reflected waves from the ultrasonic transmitter / receiver provided on the electrode tip. Or the contact area between the metal plate members is detected. Then, the contact area of the electrode tip with respect to the metal plate material is compared with the contact area between the metal plate members, and the current value supplied between the pair of electrode tips is controlled according to the smaller contact area. To do.

If a current between before Symbol pair of electrode tips, the current density, the contact area with the metal plate of the electrode tip, is determined by the area of the smaller the contact area between the metallic plate material. Therefore, performing the out of one of the contact area, by controlling the current value to be supplied between the pair of electrode tip according to the contact area of the smaller, and stable spot welding at a current density of constant it is possible, it is possible to form the excellence in quality nugget.

  Here, when the contact area of the electrode tip with respect to the metal plate material is smaller than the contact area between the metal plate members, the current is applied in advance before applying a current for welding between the pair of electrode tips. It is preferable to apply a weaker current. Since the metal plate material is softened by energization, by applying a current that is weaker than the current in advance before applying the current for welding, the contact area of the electrode tip to the metal plate material is increased. By increasing, it can be brought close to the contact area between the metal plate members.

  As a result, the current density at the contact interface between the electrode tip and the metal plate material can be made closer to the current density at the contact interface between the metal plate materials, and the spot welding can be made more stable with a constant current density. Can be performed, and even better quality nuggets can be formed.

  In addition, when the contact area between the metal plate members is smaller than the contact area of the electrode tips with respect to the metal plate member, it is preferable to increase the pressure applied to the pair of electrode tips. The metal plate member can increase the contact area between the metal plate members by increasing the pressing force of the pair of electrode tips, and can approach the contact area of the electrode tip with the metal plate member. .

  As a result, the current density at the contact interface between the metal plate materials can be made closer to the current density at the contact interface between the electrode tip and the metal plate material, and spot welding can be made more stable with a constant current density. Can be performed, and even better quality nuggets can be formed.

Explanatory sectional drawing which shows the spot welding method of the 1st aspect of this embodiment. The graph which shows the waveform of the ultrasonic wave received by the ultrasonic transmitter / receiver in the 1st aspect of the spot welding method of this embodiment. Explanatory sectional drawing which shows the spot welding method of the 2nd aspect of this embodiment. The graph which shows the waveform of the ultrasonic wave received by the ultrasonic transmitter / receiver in the 2nd aspect of the spot welding method of this embodiment.

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

  First, the first aspect of the present embodiment will be described.

  The spot welding method of this embodiment can be implemented with the apparatus shown in FIG. The spot welding apparatus shown in FIG. 1 includes electrode tips 2a and 2b that are in contact with two laminated metal plates 1a and 1b, and an ultrasonic transmitter / receiver 3 is built in the electrode tip 2a. The ultrasonic transmitter / receiver 3 is connected to the main controller 4.

  The main controller 4 controls the ultrasonic transmitter / receiver 3 and analyzes the ultrasonic waves received by the ultrasonic transmitter / receiver 3. The main control device 4 controls the current supplied to the electrode tips 2 a and 2 b via the energization control device 5 and also controls the pressure applied to the electrode tips 2 a and 2 b via the pressurization control device 6.

  In the spot welding method of the present embodiment, first, two stacked metal plate materials 1a and 1b are sandwiched between a pair of electrode tips 2a and 2b. Here, in the first aspect, the metal plate materials 1a and 1b are laminated so that there is no gap at the contact interface between them, and the axis of the electrode chips 2a and 2b is perpendicular to the metal plate materials 1a and 1b. The pressure control device 6 is in pressure contact with the metal plates 1a and 1b.

  Next, the nugget 7 is formed at the contact interface between the metal plates 1a and 1b by energizing the electrode tips 2a and 2b with the energization control device 5. Here, as shown in FIG. 1, when the metal plate materials 1a and 1b are laminated so that there is no gap between the contact surfaces of the two, the current density at the contact interface of the electrode chip 2a with the metal plate material 1a remains as it is. This is the current density at the contact interface between the metal plate materials 1a and 1b. Therefore, the quality of the nugget 7 is determined by the current supplied to the contact area of the electrode tip 2a with the metal plate 1a.

  Therefore, in this embodiment, the main control device 4 oscillates ultrasonic waves from the ultrasonic transmitter / receiver 3 toward the contact interface between the metal plate materials 1a and 1b, and analyzes the received reflected waves, whereby the electrode chip 2a. The contact area with respect to the metal plate 1a is detected. And according to the said contact area, the electric current control apparatus 5 controls the electric current value supplied between electrode tip 2a, 2b. Specifically, the current value is controlled such that a current value (current density) per unit area is constant with respect to the contact area.

  Next, a method for detecting the contact area of the electrode tip 2a with the metal plate 1a will be described. First, when the electrode tip 2a is not in contact with the metal plate 1a, the ultrasonic wave oscillated from the ultrasonic transmitter / receiver 3 is totally reflected at the tip of the electrode tip 2a. The total reflection is due to the fact that the density of the transmission medium changes abruptly when an ultrasonic wave using the electrode tip 2a made of metal as a transmission medium comes into contact with air at the tip of the electrode chip 2a. At this time, the waveform of the ultrasonic wave received by the ultrasonic transceiver 3 is shown in FIG. In FIG. 2A, A is the amplitude of the ultrasonic wave when totally reflected.

  Next, when the electrode tip 2a is in contact with the metal plate 1a, the ultrasonic wave oscillated from the ultrasonic transmitter / receiver 3 is partly metal at the contact interface between the electrode tip 2a and the metal plate 1a. It is transmitted to the plate-making material 1a and the remaining part is reflected. A part of the ultrasonic wave is transmitted to the metal plate 1a because the electrode chip 2a and the metal plate 1a are both made of metal, and there is little change in the density of the transmission medium at the contact interface between them. At this time, the waveform of the ultrasonic wave received by the ultrasonic transceiver 3 is shown in FIG.

Figure 2 (b) the amplitude X ₁ of ultrasonic wave in is smaller than the ultrasonic amplitude A totally reflected in FIG. 2 (a), the main control unit 4 at this time, the ultrasonic wave is a metal sheet The ultrasonic transmittance indicating the ratio transmitted to 1a can be obtained by the following equation (1).

Ultrasonic transmittance = (1−X ₁ / A) (1)
The contact area of the electrode tip 2a with the metal plate 1a can be expressed by the product of the ultrasonic transmittance and the tip area of the electrode tip 2a. Therefore, when the radius of the electrode tip 2a is r and the circumference is π, the contact area can be obtained by the following equation (2).

Contact area = (1−X ₁ / A) × πr ² (2)
Therefore, in the spot welding method of the present embodiment, as described above, the main controller 4 detects the contact area of the electrode tip 2a with the metal plate 1a, and the current value per unit area is constant with respect to the contact area. The current value supplied between the electrode tips 2a and 2b is controlled by the power supply control device 5 so that As a result, regardless of the contact area of the electrode tip 2a with the metal plate 1a, the current density can be made constant, the spot welding can be performed stably, and an excellent quality nugget 7 is formed. can do.

Next, when the contact area of the electrode tip 2a with the metal plate 1a is small, the portion of the ultrasonic wave oscillated from the ultrasonic transmitter / receiver 3 is transmitted to the metal plate 1a and the portion of reflection is large. . As a result, the waveform of the ultrasonic wave received by the ultrasonic transmitter / receiver 3 has an amplitude X ₂ larger than X ₁ as shown in FIG.

  At this time, the contact area of the electrode tip 2a with the metal plate 1a can be obtained by the following equation (3) in the same manner as in the equation (2).

Contact area = (1−X ₂ / A) × πr ² (3)
In this case, as in the case the amplitude of the ultrasonic wave received by the ultrasonic transducer 3 is X _1, so that the current value per unit area with respect to the contact area is constant, the electrode by electrification control apparatus 5 You may control the electric current value supplied between chip | tip 2a, 2b. However, in this case, it is preferable to apply a current that is weaker than the current value that is applied between the electrode tips 2a and 2b for spot welding by the energization control device 5 in advance.

  If it does in this way, the metal plate material 1a will soften with the said weak electric current, and the contact area with respect to the metal plate material 1a of the electrode chip 2a will increase. Therefore, the increase in the contact area is monitored by the main control device 4, and when the contact area reaches a required size, the current supplied between the electrode tips 2a and 2b by the energization control device 5 is used for spot welding. By switching to the current value of n, the nugget 7 of excellent quality can be formed.

  Next, a second aspect of the present embodiment will be described. In the second mode, as shown in FIG. 3, there is a gap 8 between the two laminated metal plates 1a and 1b. At this time, the contact area of the metal plate materials 1a and 1b is smaller than the contact area of the electrode tip 2a with the metal plate material 1a.

  Therefore, in this embodiment, the main control device 4 oscillates ultrasonic waves from the ultrasonic transmitter / receiver 3 toward the contact interface between the metal plate materials 1a and 1b, and analyzes the received reflected wave, thereby obtaining the metal plate material. The contact areas 1a and 1b are detected. Then, the current value supplied between the electrode tips 2a and 2b is controlled by the power supply control device 5 so that the current value (current density) per unit area becomes constant with respect to the contact area.

  Next, a method for detecting the contact area between the metal plates 1a and 1b will be described.

  In the embodiment shown in FIG. 3, a part of the ultrasonic wave oscillated from the ultrasonic transceiver 3 is transmitted to the metal plate 1a at the contact interface between the electrode tip 2a and the metal plate 1a, and the remaining part is reflected. At the same time, a reflected wave is also generated in the gap 8. At this time, the waveform of the ultrasonic wave received by the ultrasonic transceiver 3 is shown in FIG.

The ultrasonic wave amplitude X ₁ in FIG. 4 is the amplitude of the reflected wave at the contact interface between the electrode tip 2 a and the metal plate 1 a, and the amplitude Y ₁ is the amplitude of the reflected wave in the gap 8. Therefore, the main control device 4 can obtain the ultrasonic transmittance indicating the rate at which the ultrasonic waves are transmitted to the metal plate 1a at this time by the following equation (4). A is synonymous with the case of Formula (1)-(3), and is the amplitude of the totally reflected ultrasonic wave.

Ultrasonic transmittance = (1− (X ₁ + Y ₁ ) / A) (4)
The contact area between the metal plate materials 1a and 1b can be expressed by the product of the ultrasonic transmittance and the tip area of the electrode tip 2a. Therefore, when the radius of the electrode tip 2a is r and the circumference is π, the contact area can be obtained by the following equation (5).

Contact area = (1− (X ₁ + Y ₁ ) / A) × πr ² (5)
Therefore, in the spot welding method of the present embodiment, as described above, the main controller 4 detects the contact area of the metal plate materials 1a and 1b, and the current value per unit area is constant with respect to the contact area. As described above, the energization control device 5 controls the current value to be energized between the electrode tips 2a and 2b. As a result, the current density can be made constant regardless of the contact area of the metal plates 1a and 1b, the spot welding can be performed stably, and an excellent quality nugget 7 is formed. Can do.

  In this case, it is preferable to increase the pressure applied by the electrode tips 2 a and 2 b by the pressurization control device 6. If it does in this way, the contact area with respect to the metal board | plate material 1a of the electrode tip 2a will increase by the increase in the said applied pressure. Therefore, the increase in the contact area is monitored by the main control device 4, and when the contact area reaches a required size, the current supplied between the electrode tips 2a and 2b by the energization control device 5 is used for spot welding. By switching to the current value of n, the nugget 7 of excellent quality can be formed.

  DESCRIPTION OF SYMBOLS 1a, 1b ... Metal plate material, 2a, 2b ... Electrode tip, 3 ... Ultrasonic transmitter / receiver, 7 ... Nugget, 8 ... Gap | interval.

Claims (3)

A spot welding method for forming a nugget at a contact interface between a plurality of metal plate members by sandwiching a plurality of metal plate members laminated with a pair of electrode tips and energizing between the pair of electrode tips In
An ultrasonic transmitter / receiver is provided in the electrode chip, ultrasonic waves are oscillated from the ultrasonic transmitter / receiver to the plurality of metal plate members, and a contact area of the electrode chip with respect to the metal plate member from a received reflected wave or the The contact area between the metal plate materials is detected, the contact area of the electrode tip with respect to the metal plate material is compared with the contact area between the metal plate materials, and the pair of electrodes according to the smaller contact area A spot welding method characterized by controlling a current value to be passed between chips. In claim 1 Symbol placement of the spot welding method, the contact area with respect to the metal plate of the electrode tip and smaller than the contact area between the metallic plate material, the current for the welding between the pair of electrode tips A spot welding method, wherein a current weaker than the current is applied in advance before applying. In claim 1 Symbol placement of the spot welding method, the contact area of the metal plate to each other and smaller than the area of contact with the metal plate of the electrode tip, increasing the pressure of the pair of electrode tips A spot welding method characterized by the above.

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