JP7548067B2 - Resistance welding device and resistance welding method - Google Patents

Description

This disclosure relates to a resistance welding apparatus and a resistance welding method.

Conventionally, as described in, for example, Patent Document 1, resistance welding devices and methods are known that use a metal rivet with a head and a shank to join dissimilar metal members by resistance welding. In such welding devices and methods, for example, the rivet, aluminum plate, and iron plate are sandwiched between two electrodes so that they are arranged in the order of head, shank, aluminum plate, and iron plate, and pressure is applied to these to generate a nugget between the shank that penetrates the aluminum plate and the iron plate, and the aluminum plate is sandwiched between the head and the iron plate to join the aluminum plate and the iron plate.

In the device described in Patent Document 1, when pressure is applied and current is applied, air is blown near the boundary between the shaft and the aluminum plate, gradually blowing away the molten metal, thereby suppressing the generation of burrs and increasing the joining strength between the rivet head and the aluminum plate.

JP 2020-69499 A

However, in the device described in Patent Document 1, there was a possibility that the molten metal blown away by the air would adhere to the tip of the holder that holds one of the electrodes and the rivet. If the molten metal adheres to and accumulates at the tip of the holder, it will fall onto the head of the rivet and be joined in that state, which could result in burrs on the product and a decrease in quality.

This disclosure can be realized in the following forms:

(1) According to one aspect of the present disclosure, there is provided a resistance welding device for joining a rivet and a plurality of metal members made of different materials by resistance welding by overlapping and sandwiching the plurality of metal members and applying pressure and current thereto, the resistance welding device including a pair of electrodes sandwiching the rivet and the plurality of metal members, the pair of electrodes being made up of a first electrode and a second electrode that contact the rivet when pressure and current are applied, a holder that houses the first electrode and has a portion including a tip that faces an outermost metal member of the plurality of metal members on the first electrode side that is movable in a pressure application direction and an opposite direction relative to the first electrode and is capable of holding the rivet at the portion including the tip, an outlet that is provided at the tip of the holder and ejects air from inside the holder in the pressure application direction toward the outermost metal members, and an elastic member that urges the holder in the pressure application direction with an urging force smaller than a reaction force in the opposite direction that is generated in the holder by the ejection of air.
According to the above embodiment, when air is ejected from the nozzle formed at the tip of the holder, a reaction force acts on the tip of the holder in the direction opposite to the pressurizing direction, i.e., in the direction away from the metal member. At this time, the urging force of the elastic member receiving the reaction force in the pressurizing direction is smaller than the reaction force, so the elastic member elastically deforms in the direction in which the reaction force acts, and the tip of the holder moves away from the metal member. By starting the application of pressure and current and welding with the tip of the holder separated from the metal member, it is possible to prevent the molten metal blown away by the air during welding from adhering to the holder.
(2) In the above embodiment, the elastic member may be a coil spring that contracts when subjected to the reaction force and expands to return to its original state when the reaction force is eliminated. According to this embodiment, when the reaction force caused by the ejection of air is reduced by reducing the amount of ejected air, the elastic member expands from the contracted state to return to its original state. Therefore, as the elastic member expands, the holder can be separated from the metal member or returned to its original state.
(3) In the above embodiment, the holder has a first holder portion that houses the elastic member therein and a second holder portion that includes the tip, and the second holder portion is configured to be movable relative to the first holder portion in the pressure direction and the opposite direction, and the second holder portion may be moved in the opposite direction relative to the first electrode and the first holder portion due to the reaction force.
According to this embodiment, the second holder part moves in the opposite direction relative to the first electrode and the first holder part due to the reaction force. This allows the tip of the second holder part where the nozzle is formed to be separated from the metal member when air is injected. In addition, since there is no need to move the first holder part in the opposite direction, the reaction force generated by the injection of air can be kept small compared to a configuration in which the first holder part moves in the opposite direction in addition to the second holder part. This allows the amount of air injected to be reduced.
(4) According to another aspect of the present disclosure, there is provided a resistance welding method for joining a plurality of metal members made of different materials by sandwiching a rivet and the plurality of metal members made of different materials in a stacked manner and applying pressure and electricity to the plurality of metal members using a resistance welding device. In the resistance welding method of this aspect, the resistance welding device includes a pair of electrodes sandwiching the rivet and the plurality of metal members, the pair of electrodes including a first electrode that contacts the rivet when pressure and electricity are applied and a second electrode, a holder that houses the first electrode and has a portion including a tip that faces an outermost metal member of the plurality of metal members on the first electrode side that is movable in the pressure application direction and the opposite direction relative to the first electrode and is capable of holding the rivet at the portion including the tip, an outlet that is provided at the tip of the holder and ejects air from inside the holder in the pressure application direction toward the outermost metal members, and an elastic member that urges the holder in the pressure application direction with an urging force smaller than a reaction force in the opposite direction generated in the holder by the ejection of the air. This form of resistance welding method includes a clamping process in which the rivet and the multiple metal members are clamped by the pair of electrodes, a separating process in which the tip of the holder is separated from the outermost metal member by ejecting air from the nozzle, and an embedding process in which the rivet is embedded into at least a portion of the multiple metal members by applying pressure and current to the pair of electrodes while maintaining the state in which the tip of the holder is separated from the outermost metal member by the separating process.
According to the above embodiment, in the separating process, the tip of the holder is separated from the outermost metal member, and while maintaining this separated state, pressurization and current are applied by a pair of electrodes in the embedding process, thereby preventing molten metal blown away by air during welding from adhering to the holder.
(5) In the above embodiment, the method may further include a return step of returning the tip of the holder to its original position by utilizing the biasing force of the elastic member by reducing the amount of the air ejected from the ejection port after the embedding step. According to this embodiment, the holder can be easily returned to its original state by the biasing force of the elastic member.

1 is a cross-sectional view showing a schematic configuration of a resistance welding device according to a first embodiment of the present disclosure. 1 is a cross-sectional view showing a schematic configuration of a resistance welding device according to a first embodiment of the present disclosure. 1 is a cross-sectional view showing a schematic configuration of a resistance welding device according to a first embodiment of the present disclosure. 1 is a process diagram showing a resistance welding method according to a first embodiment of the present disclosure. FIG.

A. Embodiments:
A1. Overall configuration of resistance welding equipment:
A resistance welding apparatus and a resistance welding method according to a first embodiment of the present disclosure will be described with reference to Fig. 1 to Fig. 4. First, the configuration of the resistance welding apparatus will be described. Fig. 1 to Fig. 3 are cross-sectional views showing a schematic configuration of the resistance welding apparatus according to an embodiment of the present disclosure. Fig. 1 to Fig. 3 show schematic configurations of the resistance welding apparatus at different steps in a resistance welding method described below.

In the resistance welding device and resistance welding method of the first embodiment, a rivet 11 and multiple (two in this embodiment) metal members 12, 13 made of different materials are sandwiched between each other and pressurized with electricity, thereby joining the multiple metal members 12, 13 by resistance welding. In this embodiment, an aluminum plate 12 and an iron plate 13 are joined as the multiple metal members 12, 13. The aluminum plate 12 corresponds to the "outermost metal member on the first electrode side of the metal members." The "outermost metal member" is the outermost metal member located on the first electrode 14 side along the overlapping direction of the metal members 12, 13.

As shown in each of Figures 1 to 3, the resistance welding device 10 includes a pair of electrodes consisting of a first electrode 14 and a second electrode 15, a holder 30, a coil spring 40, an air flow path 36, and an outlet 37. The resistance welding device 10 further includes a pressurizing current unit, an air supply unit, a power supply unit, a power control unit, and connection cables, etc., which are not shown.

The first electrode 14 has a first shank 16 and a first electrode portion 18. The first electrode 14 contacts the rivet 11 when pressure is applied. The second electrode 15 has a second shank and a second electrode portion 19 (not shown). The second electrode 15 contacts the iron plate 13, which is the metal member on the lower layer side, when pressure is applied. In each electrode 14, 15, the electrode portions 18, 19 on the side of the metal members 12, 13 to be joined gradually become gradually thinner at the tip. The diameter of each electrode portion 18, 19 gradually decreases from the shank 16, 17 to the tip. The tip surface may be flat or may be a curved surface with an R. Each electrode 14, 15 is formed of a copper alloy containing chromium. The tip side of the first electrode 14 and the holder 30 that is on the side of the metal members 12, 13 is also called the "lower" and the base end side is also called the "upper".

The rivet 11 is made of iron and has a head 21 and a shaft 22. The head 21 is disk-shaped. The shaft 22 is formed in a roughly cylindrical shape and protrudes from the center of the head 21 to one side (downward). The diameter of the shaft 22 gradually decreases toward the tip of the protruding side, i.e., the downward tip. In addition, an annular wall 23 that protrudes in the same direction as the shaft 22 is provided around the entire outer periphery of the head 21. As a result, an annular groove 24 is formed around the shaft 22, defined by the outer periphery of the shaft 22, one surface of the head 21, and the inner periphery of the annular wall 23.

The holder 30 is a cylindrical member, and houses the first electrode 14 inside the entire holder 30. The holder 30 is configured to have a first holder part 31 and a second holder part 32 arranged coaxially with the first holder part 31. The base end of the first shank 16 is fixed to the first holder part 31. The diameter of the second holder part 32 is smaller than the diameter of the first holder part 31. The axial length of the second holder part is longer than the axial length of the first holder part 31, approximately three times as long.

The second holder part 32 has an upper cylinder part 33, an intermediate cylinder part 34, and a lower cylinder part 35. The upper cylinder part 33, the intermediate cylinder part 34, and the lower cylinder part 35 are arranged coaxially in that order from the first holder part 31 side. The diameter of the intermediate cylinder part 34 is larger than the upper cylinder part 33. The diameter of the lower cylinder part 35 is smaller than the diameter of the upper cylinder part 33. The second holder part 32 is movable in the pressure direction and the opposite direction relative to the first holder part 31 and the first electrode 14.

The "pressure direction" refers to the direction in which the first electrode 14 applies pressure to the rivet 11 and the two metal members 12, 13 when applying pressure and electricity. The "pressure direction" and its "opposite direction" are along the axis of the first electrode 14 (first shank 16). The "pressure direction" is downward as indicated by arrow A1 in FIG. 1. The "opposite direction" is upward as indicated by arrow A2 in FIG. 1, and coincides with the "direction in which the tip of the second holder portion 32 (holder 30) moves away from the metal members 12, 13." Hereinafter, these are referred to as the "pressure direction A1" and the "opposite direction A2."

When the second holder part 32 receives a reaction force in the opposite direction A2 during air injection, which will be described later, it rises and the upper tube part 33 of the second holder part 32 enters the inside of the first holder part 31, and the upper end of the intermediate tube part 34 engages with the lower end of the second holder part 32. The amount of movement of the second holder part 32 in the lifting and lowering operation is approximately equal to the vertical length of the upper tube part 33.

A magnet (not shown) is built into the second holder part 32 (lower tube part 35) near the lower end. This allows the rivet 11 to be held below the first electrode part 18 inside the second holder part 32 by magnetic force when clamped. The second holder part 32 corresponds to "the part including the tip of the outermost metal member (aluminum plate 12) on the first electrode 14 side of the multiple metal members 12, 13."

The coil spring 40 is accommodated in the first holder part 31 so as to surround the outer periphery of the first shank 16 and be expandable and contractible in the axial direction of the first shank 16. The lower end of the coil spring 40 is fixed to the upper bottom surface of the second holder part 32. The upper end of the coil spring 40 is fixed to the upper bottom surface of the first holder part 31. The coil spring 40 biases the second holder part 32 toward the metal members 12 and 13 with a biasing force smaller than the reaction force generated in the holder 30 when the air jet hits the aluminum plate 12 and bounces off due to the air being ejected from the ejection port 37 described later. In other words, the coil spring 40 biases the second holder part 32 in the pressure direction A1 with a biasing force smaller than the reaction force generated in the second holder part 32 in the opposite direction A2 away from the metal members 12 and 13. Such a biasing force can be realized, for example, by identifying the reaction force in the opposite direction A2 through an experiment or the like, and setting a spring constant and stroke length that will make the biasing force smaller than the reaction force. The coil spring 40 is disposed inside the first holder portion 31 in a natural length state when no pressurizing current is being applied.

Note that Figure 1 illustrates the state of clamping process P20 in which the rivet 11, aluminum plate 12, and iron plate 13 are clamped between a pair of electrodes 14, 15, but the positional relationship between the holder 30, coil spring 40, and first electrode 14 before the rivet 11 is held in the holder 30 is the same as in Figure 1.

The air flow passage 36 is formed inside the second holder part 32 along the axial direction of the first shank 16. In this embodiment, the air flow passage 36 and the nozzle 37 are formed in three portions at approximately equal intervals in the circumferential direction in a cross section perpendicular to the axial direction of the second holder part 32. The air flow passage 36 is formed as a cavity partitioned between the inner wall of the second holder part 32 and the outer wall of the first electrode 14. The lower end of the air flow passage 36 is formed as the nozzle 37. In other words, the position where the nozzle 37 is formed coincides with the position of the tip of the holder 30.

Air flows from an air inlet (not shown) formed in the holder 30 through an air flow path 36 inside the holder 30 and out of the nozzle 37. The nozzle 37 is located at the lower end of the holder 30 and ejects air from inside the holder 30 toward the aluminum plate 12.

A2. Regarding the resistance welding method:
Next, a method for resistance welding dissimilar metal members using the resistance welding apparatus 10 described above in detail will be described. Fig. 4 is a process diagram showing a resistance welding method according to a first embodiment of the present disclosure. As shown in Fig. 4, the resistance welding method according to this embodiment includes a preparation step P10, a clamping step P20, a separation step P30, an embedding step P40, and a return step P50, which are performed in this order. Each step will be described below in order. First, in the preparation step P10, a rivet 11, an aluminum plate 12, an iron plate 13, a first electrode 14, and a second electrode 15 are prepared.

In the clamping process P20, as shown in FIG. 1, the rivet 11 is held at the lower end within the second holder part 32, and the various components are arranged in the following order: head 21, shank 22, aluminum plate 12, and iron plate 13. In other words, with the shank 22 of the rivet 11 in contact with the aluminum plate 12 stacked on the iron plate 13 so as to be perpendicular to the aluminum plate 12, the rivet 11, aluminum plate 12, and iron plate 13 are clamped between the first electrode 14 and the second electrode 15. At this time, the first electrode part 18 is contacted with the head 21 side of the rivet 11, and the second electrode part 19 is contacted with the iron plate 13 side.

In the separation process P30, as shown in FIG. 2, air is ejected from the nozzle 37 to generate a reaction force in the opposite direction A2 on the holder 30, and the reaction force separates the tip of the second holder part 32 from the aluminum plate 12.

The amount of air ejected is set appropriately, but for example, the air ejection pressure is set to a high pressure of 0.8 MPa or more, and the air flow rate is set to approximately 100 to 200 L/min. When air is supplied to the air inlet from an air supply unit (not shown), the air passes through the air flow path 36 inside the second holder part 32 and flows out from the ejection port 37 as shown by arrow A3 in FIG. 2. The lower end of the second holder part 32 receives a reaction force in the opposite direction A2 from the ejected air. The air ejected in the axial direction hits the aluminum plate 12 as shown by arrow A3, and flows around the shaft part 22 of the rivet 11 and to the outside. This air flow causes the molten aluminum to be blown out from around the rivet 11 in the embedding process P40 described later.

At this time, the second holder part 32 receives the reaction force of the air and moves upward relative to the first holder part 31 and the first shank 16, away from the aluminum plate 12. That is, as shown in FIG. 1, the tip of the second holder part 32 (the position where the nozzle 37 is formed) moves upward by the vertical length of the upper tube part 33 from a state in which the tip is in contact with the aluminum plate 12, to a state in which the tip is away from the aluminum plate 12, as shown in FIG. 2. The coil spring 40 is pressed between the upper end surface of the upper tube part 33 and the upper bottom surface of the first holder part 31 in the first holder part 31, and contracts in the axial direction.

At this time, the force urging the second holder part 32 in the pressure direction A1 toward the metal members 12, 13 caused by the contraction of the coil spring 40 is smaller than the reaction force in the opposite direction A2 that moves the second holder part 32 away from the metal members 12, 13 caused by the air being ejected. Therefore, while the air injection continues, as shown in FIG. 2, the second holder part 32 is maintained in a state in which the lower end of the second holder part 32 is lifted up so as to be separated from the aluminum plate 12. In other words, the tip of the second holder part 32 is separated from the aluminum plate 12 by a sufficient distance so that the molten aluminum does not blow off and adhere to it.

In the embedding process P40, as shown in FIG. 3, while maintaining the tip of the second holder portion 32 separated from the aluminum plate 12 in the separating process P30, the rivet 11, the aluminum plate 12, and the iron plate 13 are pressurized and electrified by a pair of electrodes, thereby embedding the shaft portion 22 of the rivet 11 into the aluminum plate 12.

More specifically, the first electrode 14 and the second electrode 15 are brought close to each other, pressure is applied to the head 21 of the rivet 11 and the steel plate 13, and a current is applied between the electrodes 14, 15 to apply pressure and electricity to the rivet 11, the aluminum plate 12, and the steel plate 13, which causes the aluminum plate 12 to melt due to the Joule heat generated while the shaft 22 penetrates the aluminum plate 12. Note that in the embedding process P40, the molten aluminum is blown to the outside from around the rivet 11 by the air flow.

Then, the current flow and air injection are continued to generate a nugget 41 between the penetrating shaft portion 22 and the iron plate 13, and the aluminum plate 12 is sandwiched between the head portion 21 and the iron plate 13, joining the aluminum plate 12 and the iron plate 13. A portion of the molten aluminum fills the annular groove 24 of the rivet 11.

Air injection continues during the pressurization and current application from this embedding process P40 to the generation of the nugget 41. Therefore, the second holder part 32 is always kept in a lifted upward state so that its lower end is a sufficient distance away from the aluminum plate 12 so that the molten aluminum blown away by the air does not adhere to it. When the generation of the nugget 41 is completed, the current application is stopped.

After that, in the return process P50, the second holder part 32 is lowered by stopping the air injection. That is, when the air injection is stopped, the reaction force in the opposite direction A2 is eliminated, and the coil spring 40 extends to its natural length due to the restoring force (biasing force) in the pressure direction A1. Therefore, due to the restoring force of the coil spring 40, the second holder part 32 is lowered relative to the first holder part 31 and the first electrode 14, and naturally returns to its original state (see FIG. 1). In this way, in the return process P50, the amount of air ejected from the ejection port 37 is reduced, and the tip of the holder 30 is returned to its original position using the biasing force of the coil spring 40. Therefore, the next rivet 11 can be held by the holder 30 again, and continuous welding work is possible.

When joining n metal members (n is an integer of 2 or more) in the above joining method, the metal member closest to the first electrode 14 is designated as the first metal member, and the metal members arranged overlapping the second electrode 15 are designated as the second metal member, ..., the nth metal member, in that order. In the embedding process P40, the shaft portion 22 is penetrated through the first metal member to the (n-1)th metal member. A nugget is then generated between the shaft portion 22 and the nth metal member.

(1) According to the resistance welding apparatus 10 and the resistance welding method of the above embodiment, when air is ejected from the nozzle 37 formed at the tip of the holder 30, a reaction force acts on the tip of the second holder part 32 in the opposite direction A2, which moves the tip away from the metal members 12, 13. At this time, the biasing force of the coil spring 40 in the pressure direction A1, which receives the reaction force, is smaller than the reaction force, so the coil spring 40 contracts in response to the reaction force, and the tip of the second holder part 32 moves away from the aluminum plate 12.

In this way, by starting the application of pressure and current while the tip of the second holder part 32 is separated from the aluminum plate 12, which is the outermost metal member, and welding, it is possible to prevent the molten metal blown away by the air during welding from adhering to the holder 30. As a result, spatter generated during welding does not adhere to and accumulate on the holder 30, and the occurrence of burrs in the product can be avoided.

(2) According to the resistance welding apparatus 10 and the resistance welding method of the above embodiment, the coil spring 40 is used as the elastic member, and when the air jet is terminated, the coil spring 40 expands to its original length due to a restoring force, so that the second holder part 32 can be naturally returned to its original position.

(3) According to the resistance welding apparatus 10 and the resistance welding method of the above embodiment, the holder 30 is composed of a first holder part 31 and a second holder part 32, and only the second holder part 32 moves relative to the first electrode 14 in response to the air jet. Therefore, since there is no need to move the first holder part 31 in the opposite direction A2, the reaction force generated by the jet of air can be kept small compared to a configuration in which the first holder part 31 moves in the opposite direction A2 in addition to the second holder part 32. Therefore, the amount of air jetted can be suppressed.

(4) Furthermore, by allowing air to flow inside the holder 30, components such as nozzles that generate air flow from the outside are not required, and interference between components such as nozzles and the holder 30, etc. can be suppressed, and the interference area can be significantly reduced.

(5) In addition, since an actuator such as an air cylinder is not required as a mechanism for raising and lowering the second holder portion 32, welding work can be performed even in a narrow working area.

B. Other embodiments:
(B1) In the resistance welding apparatus 10 of the first embodiment, the coil spring 40 is accommodated in the first holder portion 31 so as to surround the outer periphery of the first shank 16, but is not limited to this configuration. The coil spring 40 may be accommodated in the first holder portion 31 in any form as long as it can move the second holder portion 32 in the opposite direction A2 away from the metal members 12, 13 by being deformed when it receives a reaction force.

(B2) In the resistance welding device 10 of the first embodiment described above, the coil spring 40 is arranged in a natural length state, but it may also be arranged in a slightly contracted state.

(B3) In the resistance welding device 10 of the first embodiment, the elastic member may be something other than the coil spring 40. For example, it may be a leaf spring or an air spring.

(B4) In the resistance welding device 10 of the first embodiment described above, the holder 30 is configured to have a first holder portion 31 and a second holder portion 32, but is not limited to this configuration. For example, the holder 30 may be a single unit, and the entire holder 30 may be biased by an elastic member.

(B5) In the resistance welding method of the first embodiment described above, air injection continues from the embedding step P40 until the formation of the nugget 41. However, since the amount of molten aluminum that is ejected during nugget formation is smaller than that during the embedding step P40, air may be injected only during the embedding step P40 while the holder 30 is raised.

(B6) The rivet 11 used in the resistance welding device 10 and resistance welding method of the first embodiment described above has an annular wall 23 and annular groove 24 on the head 21, but this does not have to be the case. The material and shape of the rivet 11 can be changed as appropriate.

The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features in each embodiment corresponding to the technical features in each form described in the Summary of the Invention column can be replaced or combined as appropriate to solve some or all of the above-described problems or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described in this specification as essential, it can be deleted as appropriate.

10...resistance welding device, 11...rivet, 12...aluminum plate (metal member), 13...iron plate (metal member), 14...first electrode, 15...second electrode, 16...first shank, 18...first electrode portion, 19...second electrode portion, 21...head, 22...shaft portion, 23...annular wall, 24...annular groove, 30...holder, 31...first holder portion, 32...second holder portion, 33...upper cylinder portion, 34...middle cylinder portion, 35...lower cylinder portion, 36...air flow path, 37...air outlet, 40...coil spring (elastic member), 41...nugget, P10...preparation process, P20...clamping process, P30...separation process, P40...embedding process, P50...return process

Claims (5)

A resistance welding device that joins a plurality of metal members made of different materials by resistance welding by overlapping a rivet and the plurality of metal members and applying pressure and current thereto,
a pair of electrodes sandwiching the rivet and the plurality of metal members, the pair of electrodes including a first electrode that contacts the rivet when a current is applied thereto; and a second electrode;
a holder that accommodates the first electrode therein, a portion including a tip that faces an outermost metal member on the first electrode side among the plurality of metal members that is movable relative to the first electrode in a pressure application direction and in an opposite direction, and that can hold the rivet at the portion including the tip;
an air outlet provided at the tip of the holder and configured to eject air from inside the holder toward the outermost metal member in the pressurizing direction;
an elastic member that biases the holder in the pressure direction with a biasing force smaller than the reaction force in the opposite direction that is generated in the holder by the ejection of the air;
A resistance welding apparatus comprising: The resistance welding device according to claim 1, wherein the elastic member is a coil spring that contracts when subjected to the reaction force and expands to return to its original state when the reaction force is released. the holder has a first holder portion that houses the elastic member therein and a second holder portion that includes the tip,
The second holder portion is configured to be movable relative to the first holder portion in the pressure application direction and the opposite direction,
3. The resistance welding device according to claim 1, wherein the second holder portion is moved in the opposite direction relative to the first electrode and the first holder portion by the reaction force. A resistance welding method for joining a plurality of metal members made of different materials to each other by overlapping and clamping a rivet and the plurality of metal members by applying pressure and current thereto using a resistance welding device,
The resistance welding apparatus includes:
a pair of electrodes sandwiching the rivet and the plurality of metal members, the pair of electrodes including a first electrode that contacts the rivet when a current is applied thereto; and a second electrode;
a holder that accommodates the first electrode therein, a portion including a tip that faces an outermost metal member on the first electrode side among the plurality of metal members that is movable relative to the first electrode in a pressure application direction and in an opposite direction, and that can hold the rivet at the portion including the tip;
an air outlet provided at the tip of the holder and configured to eject air from inside the holder toward the outermost metal member in the pressurizing direction;
an elastic member that biases the holder in the pressure direction with a biasing force smaller than the reaction force in the opposite direction that is generated in the holder by the ejection of the air;
Equipped with
a clamping step of clamping the rivet and the plurality of metal members between the pair of electrodes;
a separating step of separating the tip of the holder from the outermost metal member by ejecting the air from the ejection port;
an embedding step of embedding the rivet into at least a portion of the plurality of metal members by applying pressure and current using the pair of electrodes while maintaining a state in which the tip of the holder is separated from the outermost metal member in the separating step;
A resistance welding method comprising: a return step of returning the tip of the holder to its original position by utilizing the biasing force of the elastic member by reducing the amount of the air ejected from the ejection port after the embedding step;
The resistance welding method of claim 4 further comprising:

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