JP7636964B2 - How to join electric wires - Google Patents

Description

The present invention relates to a method for joining electric wires.

Conventionally, there is a technology for ultrasonically joining electric wires. Patent Document 1 discloses a method for manufacturing an electric wire bundle that includes a process for ultrasonically welding together multiple core wires extending from multiple electric wires bundled together by a holder.

JP 2017-055623 A

When ultrasonically joining the core wire of an electric wire, it is desirable to be able to suppress damage to the core wire. For example, during the ultrasonic joining process, standing waves are generated in the electric wire. The inventors of the present application have discovered a problem in that if the antinode of the standing wave is located near the ultrasonically vibrating member, excessive deformation is likely to occur in the core wire.

The object of the present invention is to provide a method for joining electric wires that can ultrasonically join the core wires while minimizing damage to the core wires.

The method for joining electric wires of the present invention includes the steps of holding a portion of an electric wire having a first end and a second end with a jig, and sandwiching the core wire of the first end and the object to be joined with a joining member, and applying ultrasonic vibrations from the joining member to the core wire and the object to be joined to join the core wire and the object to be joined, and is characterized in that in the joining step, the length of the electric wire from the jig to the joining member is a multiple of half the wavelength of the standing wave generated in the electric wire by the ultrasonic vibration.

In the electric wire joining method according to the present invention, in the joining process, the length of the electric wire from the jig to the joining member is a multiple of half the wavelength of the standing wave generated in the electric wire by ultrasonic vibration. Therefore, the node of the standing wave is located near the joining member. The electric wire joining method according to the present invention has the effect of being able to ultrasonically join the core wire while suppressing damage to the core wire.

FIG. 1 is a diagram showing an electric wire joining device according to an embodiment. FIG. 2 is a diagram for explaining standing waves occurring in an electric wire. FIG. 3 is a diagram showing deformation of the core wire. FIG. 4 is a diagram illustrating a method for joining electric wires according to an embodiment. FIG. 5 shows the experimental results. FIG. 6 is a diagram for explaining the position adjustment of the jig main body. FIG. 7 is a diagram for explaining a method for adjusting the length of the electric wire. FIG. 8 is a diagram showing a jig according to a first modified example of the embodiment.

Below, a method for joining electric wires according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment. Furthermore, the components in the following embodiment include those that a person skilled in the art would easily imagine or that are substantially the same.

[Embodiment]
An embodiment will be described with reference to Fig. 1 to Fig. 7. The embodiment relates to a method for joining electric wires. Fig. 1 is a diagram showing an electric wire joining device according to the embodiment, Fig. 2 is a diagram explaining standing waves generated in an electric wire, Fig. 3 is a diagram showing deformation of a core wire, Fig. 4 is a diagram explaining a method for joining electric wires according to the embodiment, Fig. 5 is a diagram showing experimental results, Fig. 6 is a diagram explaining adjustment of the position of a jig main body, and Fig. 7 is a diagram explaining a method for adjusting the length of an electric wire.

As shown in FIG. 1, the electric wire joining device 1 according to this embodiment has a vibration device 2 and a jig 3. The vibration device 2 is a device that joins the core wire 11 of the electric wire 10 to an object to be joined. The electric wire 10 has a core wire 11 and an insulating coating 12. The core wire 11 is composed of a wire formed of a conductive metal. The illustrated core wire 11 has multiple wires. The coating 12 covers the core wire 11 from the outer periphery. The electric wire 10 has a first end 10a and a second end 10b. The first end 10a is one end of the electric wire 10, and the second end 10b is the other end of the electric wire 10.

The core wire 11 is exposed from the coating 12 at the first end 10a. That is, the core wire 11 has an exposed portion 11a exposed from the coating 12. The length of the exposed portion 11a is, for example, about 10 mm to 20 mm. A terminal 13 is connected to the second end 10b. The illustrated terminal 13 is a female terminal having a cylindrical connection portion 13a. The terminal 13 has a core wire clamping piece 13b that is clamped to the core wire 11, and a coating clamping piece 13c that is clamped to the coating 12.

The vibration device 2 has a joining member 20 that joins the core wire 11 and the object to be joined. The joining member 20 includes an anvil 21 and a horn 22. The anvil 21 and the horn 22 are, for example, flat in shape. The anvil 21 presses the core wire and the object to be joined toward the horn 22. The horn 22 is excited by an ultrasonic oscillator to vibrate ultrasonically. The horn 22 applies ultrasonic vibrations to the core wire 11 and the object to be joined to join the core wire 11 and the object to be joined.

The vibration direction of the horn 22 is the axial direction X of the electric wire 10. In other words, the horn 22 applies a force along the axial direction X to the core wire 11 and the object to be joined. More specifically, the horn 22 applies a compressive force F1 and a tensile force F2 alternately to the core wire 11.

The object to be joined is, for example, an electric wire 40 as shown in FIG. 1. The electric wire 40 has a core wire 41, and an end of the core wire 41 is exposed. The anvil 21 clamps the core wire 11 and the core wire 41 between the anvil 21 and the horn 22. The horn 22 applies ultrasonic vibrations to the core wires 11 and 41 to join the core wires 11 and 41. There may be multiple electric wires 40 as the object to be joined. In this case, the vibration device 2 can join multiple core wires 41 to the core wire 11.

The jig 3 holds a part of the electric wire 10. The jig 3 has a jig body 31 and an actuator 32. The jig 3 is arranged so that the distance between the joining member 20 and the jig body 31 in the axial direction X is a desired distance. The jig body 31 is a member that contacts the electric wire 10 and holds the electric wire 10. The jig body 31 has a first holding portion 33 and a second holding portion 34. The first holding portion 33 and the second holding portion 34 may be formed of a resin such as urethane, or may be formed of a metal. The first holding portion 33 and the second holding portion 34 have a hardness that can regulate the vibration of the electric wire 10 in the portion sandwiched by the first holding portion 33 and the second holding portion 34.

The first retaining portion 33 and the second retaining portion 34 face each other. The first retaining portion 33 and the second retaining portion 34 are, for example, plate-shaped. The first retaining portion 33 and the second retaining portion 34 are capable of relative movement along the facing direction Y in which they face each other. In other words, the first retaining portion 33 and the second retaining portion 34 are configured to be able to approach and move away from each other in the facing direction Y.

The actuator 32 is a drive mechanism that moves the first holding portion 33 and the second holding portion 34 relative to each other along the opposing direction Y. The actuator 32 in this embodiment applies a force F3 that moves the first holding portion 33 and the second holding portion 34 closer to the jig body 31. In other words, the actuator 32 applies a holding force that holds the electric wire 10 to the jig body 31. The actuator 32 may be, for example, an air cylinder or a hydraulic cylinder.

In the electric wire joining method according to this embodiment, ultrasonic joining is performed by the vibration device 2 while the electric wire 10 is held by the jig 3. This reduces damage to the core wire 11, as described below.

First, referring to FIG. 2, a standing wave W3 generated in the electric wire 10 during ultrasonic bonding will be described. The electric wire 10 shown in FIG. 2 is not held by the jig 3. When the electric wire 10 is not held by the jig 3, the second end 10b of the electric wire 10 becomes a free end as shown in FIG. 2. When the horn 22 vibrates, an incident wave W1 is input from the horn 22 to the electric wire 10. The incident wave W1 is reflected at the free end of the electric wire 10 and becomes a reflected wave W2. The incident wave W1 and the reflected wave W2 are longitudinal waves along the axial direction X. The incident wave W1 and the reflected wave W2 generate a standing wave W3 in the electric wire 10. The standing wave W3 is a longitudinal wave similar to the incident wave W1 and the reflected wave W2.

As shown in FIG. 2, the standing wave W3 has a node Nd and an antinode An. The node Nd is the position where the vibration amplitude along the axial direction X is the smallest, and the antinode An is the position where the vibration amplitude along the axial direction X is the largest. The standing wave W3 in FIG. 2 has an antinode An near the horn 22. The position of the antinode An in the axial direction X is, for example, a position between the horn 22 and the end of the coating 12. If the antinode An is located near the horn 22, the core wire 11 is likely to be damaged. For example, it is thought that the core wire 11 is likely to be significantly deformed at the antinode An position due to the interaction between the vibration along the axial direction X caused by the standing wave W3 and the force received from the horn 22.

Figure 3 shows the deformation of the core wire 11 during ultrasonic bonding. The anvil 21 and horn 22 hold the wire 10 so that a free section 11b is generated in the core wire 11. The free section 11b is a section of the exposed portion 11a that is not restrained by the bonding member 20 and is not covered by the coating 12. In the free section 11b, the wires 14 are more likely to bend and deform than in other sections of the core wire 11.

The wires 14 of the core wire 11 bend in a direction perpendicular to the axial direction X due to the interaction between the vibration caused by the standing wave W3 and the force received from the horn 22. If the distance between the position of the antinode An of the standing wave W3 and the horn 22 is short, the amount of deformation of the wires 14 is likely to be large. As a result, the core wire 11 may buckle or break due to fatigue due to excessive repeated stress.

As described below, the electric wire joining device 1 according to this embodiment uses a jig 3 to move the position of the antinode An of the standing wave W3 away from the horn 22. Therefore, the electric wire joining device 1 according to this embodiment and the electric wire joining method according to this embodiment can suppress damage to the core wire 11 during ultrasonic joining.

As shown in FIG. 4, the jig 3 holds a part of the electric wire 10 by the jig body 31. As a result, when ultrasonic vibration is applied to the electric wire 10, a standing wave W3 is generated with the part held by the jig body 31 as a node Nd. More specifically, the position of the node Nd of the standing wave W3 is the position of the end face 31a of the jig body 31. The end face 31a is the end face of the jig body 31 on the side of the vibration device 2. The value of the wavelength λ of the standing wave W3 varies depending on, for example, the material of the core wire 11. The half wavelength λ/2 of the standing wave W3 is the length from one node Nd to the adjacent node Nd in the standing wave W3. Note that the wavelength λ and the half wavelength λ/2 are the lengths along the electric wire 10. For example, when the electric wire 10 is bent, the wavelength λ and the half wavelength λ/2 are the lengths along the bent electric wire 10.

In the following description, the process of holding the electric wire 10 with the jig 3 is referred to as the holding process. Also, the process of joining the core wire 11 to the joining object with the joining member 20 is referred to as the joining process. In the holding process, the worker holds the electric wire 10 with the jig 3. The holding process may be performed with the core wire 11 of the first end 10a clamped by the joining member 20. Alternatively, the holding process may be performed with the first end 10a not clamped. In this case, the worker clamps the first end 10a with the joining member 20 after the holding process.

The joining process is performed, for example, as shown in FIG. 4, with a part of the exposed portion 11a being the free section 11b. The core wire 11 of the free section 11b is exposed to the external space between the joining member 20 and the coating 12. The length of the free section 11b in the joining process is, for example, 2 mm or less.

The joining process is started, for example, by an operator operating the vibration device 2. The vibration device 2 ultrasonically vibrates the horn 22 while the core wire 11 and the objects to be joined are sandwiched between the joining member 20. The vibration device 2 applies ultrasonic vibrations from the joining member 20 to the core wire 11 and the objects to be joined, joining the core wire 11 and the objects to be joined.

In the holding process of this embodiment, the position where the jig 3 holds the electric wire 10 is a position where the length L1 shown in FIG. 4 is a multiple of half a wavelength λ/2. The length L1 is the length of the electric wire 10 between the jig 3 and the joining member 20. In FIG. 4, the length L1 is equal to the wavelength λ of the standing wave W3.

The position on the jig 3 side that is the reference for the length L1 is, for example, the end face 31a. The end face 31a is the end face of the jig body 31 on the joining member 20 side. When the electric wire 10 is held by the jig body 31, the incident wave W1 is reflected at the position of the end face 31a. In other words, the position of the end face 31a is the position of the node Nd of the standing wave W3.

The position on the first end 10a side that is the reference for length L1 may be, for example, the end face 21a of the anvil 21 or the end face 22a of the horn 22. The end face 21a is the end face of the anvil 21 that faces the jig body 31. The end face 22a is the end face of the horn 22 that faces the jig body 31. The position on the first end 10a side that is the reference for length L1 may be a position between the joining member 20 and the end of the coating 12. In other words, the position on the first end 10a side that is the reference for length L1 may be a position corresponding to the free section 11b.

By making the length L1 a multiple of half the wavelength λ/2, the node Nd of the standing wave W3 is located near the joining member 20. This makes it possible to reduce the amplitude of the standing wave W3 near the joining member 20. Therefore, according to the electric wire joining method of this embodiment, it is possible to reduce the amount of deformation of the core wire 11 in the ultrasonic joining process. For example, it is possible to reduce the deformation of the exposed portion 11a as shown in FIG. 3. Therefore, according to the electric wire joining method of this embodiment, it is possible to perform ultrasonic joining while suppressing damage to the core wire 11.

The length L1 may be, for example, a length that generates a node Nd of the standing wave W3 between the end of the coating 12 and the joining member 20. In other words, the jig 3 may hold the wire 10 so that the node Nd is located at any position in the free section 11b of the exposed portion 11a. In this case, the length L1 in the joining process is a length that generates a node Nd of the standing wave W3 between the end of the coating 12 and the joining member 20.

It is also believed that the closer the node Nd is to the joining member 20, the easier it is to reduce the deformation of the core wire 11. Therefore, the node Nd may be generated at a position closer to the joining member 20 than the midpoint between the end of the coating 12 and the joining member 20. In other words, in the joining process, the length L1 may be a length that generates the node Nd at a position closer to the joining member 20 than the midpoint between the end of the coating 12 and the joining member 20. In this case, the position of the node Nd is closer to the joining member 20 than the midpoint of the free section 11b.

The node Nd may be located in a portion of the exposed portion 11a that is sandwiched between the joining members 20. In this case, the length L1 in the joining process is a length that generates a node Nd of the standing wave W3 at the position of the joining member 20.

The length L1 may be determined with a focus on the position of the antinode An of the standing wave W3. For example, if the antinode An of the standing wave W3 is not located in the exposed portion 11a, it is considered that damage to the core wire 11 is unlikely to occur. Therefore, the length L1 in the joining process may be a length that generates the antinode An of the standing wave W3 at a position other than the exposed portion 11a of the core wire 11. It is desirable that the length L1 in the joining process is determined so that the antinode An is not located at least in the free section 11b.

The allowable range of length L1 will be explained with reference to FIG. 5. FIG. 5 shows the results of an ultrasonic joining experiment. The electric wire 10 used in the experiment had 10 wires 14. The wavelength λ of the standing wave W3 in this electric wire 10 was 148 mm. In the experiment, the length L1 from the jig 3 to the joining member 20 was set to each value shown in FIG. 5, and the presence or absence of broken wires 14 was confirmed. In FIG. 5, the unbroken wires 14 are marked with a "○" and the broken wires 14 are marked with a "×". The percentage of broken wires 14 (hereinafter simply referred to as the "breakage rate") is shown in the lower part of FIG. 5.

When the length L1 is the same as the wavelength λ (148 mm), no strands 14 broke, and the breakage rate is 0%. When the length L1 is shorter than the wavelength λ, no strands 14 broke when L1 = 137 mm. In other words, even if the length L1 is shortened to 93.5% of the wavelength λ, no strands 14 break. When the length L1 is 132 mm, one strand 14 breaks. In other words, when the length L1 is shortened to 89.2% of the wavelength λ, the breakage rate is 10%. From the above results, it is considered that if the length L1 is 90% or more of the wavelength λ, no strands 14 break, or the breakage rate is less than 10%.

When the length L1 is longer than the wavelength λ, even when L1 = 174 [mm], no wire 14 breaks. In other words, even if the length L1 is increased to 117.6 [%] of the wavelength λ, the wire 14 does not break. From the above results, it is considered that the wire 14 will not break if the length L1 is set to 110 [%] or less of the wavelength λ. Therefore, the range R2 shown in Figure 5 may be set as the allowable range for the length L1. The range R2 is, for example, a range of ±10 [%] of the wavelength λ. It is considered that the possibility of the wire 14 breaking increases in the range R1 below the range R2 and in the range R3 above the range R1.

The value of the wavelength λ varies depending on the material of the core wire 11. Examples of materials for the core wire 11 include copper and aluminum. FIG. 6 shows the wavelength λ1 of the first electric wire 10A and the wavelength λ2 of the second electric wire 10B. The material of the first electric wire 10A and the material of the second electric wire 10B are different from each other. When the lengths of the wavelengths λ are different in this way, the position of the jig body 31 may be adjusted. The jig 3 shown in FIG. 6 has an adjustment mechanism for adjusting the position of the jig body 31. The jig body 31 is configured to be movable along the axial direction X.

In the holding process, the worker positions the jig body 31 at a position determined according to the material of the core wire 11. For example, when the first electric wire 10A is held by the jig 3, the worker moves the jig body 31 so that the length L1 from the jig 3 to the joining member 20 is equal to the wavelength λ1. When the second electric wire 10B is held by the jig 3, the worker moves the jig body 31 so that the length L1 from the jig 3 to the joining member 20 is equal to the wavelength λ2. The worker then operates the jig 3 to hold the electric wire 10 with the jig body 31.

The worker may adjust the length L1 by bending the electric wire 10 in the holding process. FIG. 7 shows the electric wire 10 held by the jig 3 in a bent state. The electric wire 10 is bent between the jig 3 and the joining member 20. In this case, the length L1 is a length that follows the curved shape of the electric wire 10. When the worker holds the first electric wire 10A by the jig 3, the worker bends the first electric wire 10A so that the length L1 is the length of the wavelength λ1. When the worker holds the second electric wire 10B by the jig 3, the worker bends the second electric wire 10B so that the length L1 is the length of the wavelength λ2.

The electric wire joining device 1 may have a guide member having a desired curved shape. In this case, the operator can easily shape the electric wire 10 into the desired curved shape by bending the electric wire 10 along the guide member.

As described above, the method for joining electric wires according to this embodiment includes a holding step and a joining step. In the holding step, a portion of the electric wire 10 having the first end 10a and the second end 10b is held by the jig 3. In the joining step, the core wire 11 of the first end 10a and the object to be joined are sandwiched by the joining member 20, and ultrasonic vibrations are applied from the joining member 20 to the core wire 11 and the object to be joined, joining the core wire 11 and the object to be joined.

In the joining process, the length L1 of the electric wire 10 from the jig 3 to the joining member 20 is a multiple of half the wavelength λ/2 of the standing wave W3 generated in the electric wire 10 by ultrasonic vibration. According to the electric wire joining method of this embodiment, it is possible to join the electric wire 10 and the joining object while suppressing damage to the core wire 11.

In the electric wire joining method according to this embodiment, during the joining process, an exposed portion 11a where the core wire 11 is exposed exists between the end of the coating 12 of the electric wire 10 and the joining member 20, and the length L1 of the electric wire 10 from the jig 3 to the joining member 20 is a length that generates a node Nd of the standing wave W3 between the end of the coating 12 and the joining member 20. Therefore, excessive deformation is unlikely to occur in the core wire 11 of the exposed portion 11a.

In the joining process, the length L1 of the wire 10 from the jig 3 to the joining member 20 may be a length that generates a node Nd at a position closer to the joining member 20 than the midpoint between the end of the coating 12 and the joining member 20. This makes it possible to appropriately suppress deformation of the core wire 11 in the exposed portion 11a.

The electric wire 10 to be joined is not limited to a terminal-attached electric wire having a terminal 13. For example, the electric wire 10 may be an electric wire that does not have a terminal 13 attached to the second end 10b. In this case, the end of the core wire 11 may be exposed to the external space at the second end 10b.

The electric wire 10 joined by the electric wire joining method according to this embodiment may have a holding mark formed by being held by the jig 3. For example, the coating 12 has a holding mark formed by being held by the jig 3.

[First Modification of the Embodiment]
A first modified example of the embodiment will be described. Fig. 8 is a diagram showing a jig according to the first modified example of the embodiment. The jig 3 shown in Fig. 8 is configured to be able to hold two electric wires 10A and 10B having different wavelengths λ at appropriate positions. The jig 3 in Fig. 8 has a first holding portion 33, a second holding portion 34, a third holding portion 35, a fourth holding portion 36, a first loading plate 37, a second loading plate 38, and a third loading plate 39.

The first holding portion 33, the second holding portion 34, the first loading plate 37, and the second loading plate 38 constitute a first loading unit. The third holding portion 35, the fourth holding portion 36, the second loading plate 38, and the third loading plate 39 constitute a second loading unit.

The first load plate 37, the second load plate 38, and the third load plate 39 are plate-shaped members parallel to each other. The second load plate 38 is located between the first load plate 37 and the third load plate 39. The first load plate 37 is disposed on one side of the second load plate 38 in the facing direction Y, and faces the second load plate 38. The third load plate 39 is disposed on the other side of the second load plate 38 in the facing direction Y, and faces the second load plate 38. The second load plate 38 may be fixed. In this case, the first load plate 37 and the third load plate 39 are configured to be movable relative to the second load plate 38 along the facing direction Y.

The first retaining portion 33 is disposed on the first loading plate 37 and is pressed by the first loading plate 37. The first retaining portion 33 may be movable relative to the first loading plate 37 along the axial direction X. The second retaining portion 34 is disposed on the second loading plate 38 and is supported by the second loading plate 38. The second retaining portion 34 may be movable relative to the second loading plate 38 along the axial direction X. The first retaining portion 33 and the second retaining portion 34 may be connected to each other so that they can move together along the axial direction X.

The third retaining portion 35 is disposed on the second loading plate 38 and is supported by the second loading plate 38. The third retaining portion 35 is movable relative to the second loading plate 38 along the axial direction X. The fourth retaining portion 36 is disposed on the third loading plate 39 and is pressed by the third loading plate 39. The fourth retaining portion 36 is movable relative to the third loading plate 39 along the axial direction X. The third retaining portion 35 and the fourth retaining portion 36 may be connected to each other so that they can move together along the axial direction X.

The third holding portion 35 and the fourth holding portion 36 are movable along the axial direction X between the first position P1 and the second position P2. The first position P1 is a position corresponding to the wavelength λ1 of the first electric wire 10A. The positions of the first holding portion 33 and the second holding portion 34 in FIG. 8 are the first position P1. The length L11 of the electric wire 10 when the holding portions 33, 34, 35, and 36 hold the electric wire 10 at the first position P1 is determined based on the wavelength λ1 of the first electric wire 10A. More specifically, the length L11 is a multiple of a half wavelength of the wavelength λ1. In other words, the first position P1 is determined so that the standing wave W3 generated in the first electric wire 10A generates a node Nd in the vicinity of the joining member 20.

The length L12 of the electric wire 10 when the holding portions 35, 36 hold the electric wire 10 at the second position P2 is determined based on the wavelength λ2 of the second electric wire 10B. More specifically, the length L12 is a multiple of half the wavelength λ2. In other words, the second position P2 is determined so that the standing wave W3 generated in the second electric wire 10B generates a node Nd in the vicinity of the joining member 20.

The actuator 32 exerts a holding force on the first load plate 37 and the third load plate 39 to hold the electric wire 10. That is, the actuator 32 presses the first load plate 37 toward the third load plate 39, and presses the third load plate 39 toward the first load plate 37. In FIG. 8, the first holding portion 33 and the second holding portion 34 hold the first electric wire 10A at the first position P1. The third holding portion 35 and the fourth holding portion 36 hold the second electric wire 10B at the second position P2. The jig 3 of the first modified example can hold electric wires 10 having different vibration characteristics in appropriate positions.

The contents disclosed in the above embodiments and variations can be implemented in any suitable combination.

REFERENCE SIGNS LIST 1 electric wire joining device 2 vibration device 3 jig 10: electric wire, 10a: first end portion, 10b: second end portion,
DESCRIPTION OF SYMBOLS 11: Core wire, 11a: Exposed portion, 12: Coating 13: Terminal, 13a: Connection portion, 13b: Core wire clamping piece, 13c: Coating clamping piece 14: Wire 20: Joining member, 21: Anvil, 21a: End face 22: Horn, 22a: End face 31: Jig body, 32: Actuator, 33: First holding portion, 34: Second holding portion 35: Third holding portion, 36: Fourth holding portion, 37: First loading plate, 38: Second loading plate 39: Third loading plate 40: Electric wire F1: Compressive force, F2: Tensile force, W1: Incident wave, W2: Reflected wave, W3: Standing wave, Nd: Node, An: Antinode, X: Axial direction, Y: Opposite direction, λ: Wavelength

Claims (3)

holding a portion of an electric wire having a first end and a second end with a jig;
a step of sandwiching the core wire at the first end portion and the object to be joined by a joining member, and applying ultrasonic vibration from the joining member to the core wire and the object to be joined to join the core wire and the object to be joined;
Including,
a length of the electric wire between the jig and the joining member being a multiple of a half wavelength of a standing wave generated in the electric wire by the ultrasonic vibration, In the joining step,
The core wire has a section exposed toward an external space between an end of the coating of the electric wire and the joining member,
The method for joining electric wires according to claim 1 , wherein a length of the electric wire between the jig and the joining member is a length that generates a node of the standing wave between an end of the coating and the joining member. 3. The method for joining electric wires according to claim 2, wherein in the joining step, a length of the electric wire between the jig and the joining member is a length that generates the node at a position closer to the joining member than a midpoint between the end of the coating and the joining member.

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