JP2003062672A - Method and equipment for welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an equipment and a method for welding by which the distortion due to welding is suppressed and high precision welding is performed. SOLUTION: A plurality of members to be welded 13 is welded to the whole outer peripheral wall of a cylindrical welding base material 10 in the cylindrical axis direction. Following processes are repeated: a disposing process where a prescribed number of members to be welded 13, which is simultaneously welded, is abutted to the outer peripheral wall of the welding base material 10 and disposed thereon in the cylindrical axis direction in such a way that they are radially disposed at equal intervals; a welding process where each abutted portion of the member and the base material is welded by simultaneously applying a welding voltage thereto while pressing the abutted portions; and a turning process where the welded portions are turned around the cylindrical axis by a prescribed angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding method and a welding apparatus, and more particularly, to a method for efficiently welding a heat radiating member or the like to an outer peripheral wall of a motor case or the like while suppressing distortion.

[0002]

2. Description of the Related Art Conventionally, metal welding methods include fusion welding for melting and adhering a joint portion, pressure welding for pressing the joint portion in a heated and softened state, or a metal bonding agent melted at the joint portion. Brazing is known in which pressure is applied so as to sandwich. A wide variety of such welding methods have been put to practical use, but as fusion welding, TIG welding (Tungsten Inert-gas a
rc welding), arc welding, stud welding, etc.
Moreover, resistance welding, ultrasonic welding, etc. are mentioned as pressure welding.

FIG. 8A is a side view showing an example of welding a heat radiating member 101 to an outer peripheral wall of a cylindrical case member 100 of a motor or a generator. In this example, the heat dissipation member 101 is brought into contact with the outer peripheral wall of the case member 100 in the axial direction, the external electrode 102 is inserted into the heat dissipation member 101, and the internal electrode 103 is provided so as to face the external electrode 102. It is brought into contact with the inner peripheral wall of the case member 103. Then, while applying pressure to the external electrode 102 and the internal electrode 103 in a direction in which they are close to each other, a welding voltage is applied to each electrode to perform projection welding. This welding is repeated along the outer peripheral wall of the case member 100 at predetermined intervals.

[Problems to be Solved by the Invention]

However, since pressure and heat input are applied to the cylindrical case member 100 during welding, as shown in FIG.
As shown in (b), the case member 100 was deformed as the heat dissipation member 101 was welded to the outer peripheral wall of the case member 100, and the roundness was impaired. As described above, in the conventional welding, it is difficult to perform the welding while maintaining the roundness of the case member 100, and it is not possible to perform the manufacturing in which the roundness is maintained despite the demand. there were. For this reason, conventionally, motor cases that require roundness are
In many cases, the case member and the heat dissipation member are integrally formed by casting, but the casting has coarse particles and is easily cracked and has low thermal conductivity, resulting in an increase in weight and shape, resulting in an increase in cost.

The present invention has been proposed in view of the above circumstances, and develops a welding method for efficiently welding an object to be welded to the outer peripheral wall of a cylindrical member while maintaining the circularity. Is intended. Moreover, the present invention proposed at the same time aims at developing a welding apparatus for effectively carrying out this welding method.

[0006]

A welding method according to the present invention, which is proposed to achieve the above object, is a welding base material having a cylindrical shape, which is a cylinder over the entire circumference of an outer peripheral wall. A welding method for welding a plurality of members to be welded in the axial direction, in which a predetermined number of members to be welded at the same time are directed in the cylindrical axis direction radially at equal intervals on the outer peripheral wall of the welding base material. A welding step in which the welding voltage is simultaneously applied to each abutting portion while pressing each abutting portion between the member to be welded and the welding base material, and the welding position. It is configured to repeatedly perform a rotating step of rotating around a cylindrical axis by a predetermined angle.

When the members to be welded are sequentially welded to the outer peripheral surface of the cylindrical welding base metal at predetermined intervals, the welding base metal is deformed due to the pressing force and heat input during welding. The present invention does not sequentially weld the members to be welded to the outer peripheral surface of the welding base metal at predetermined intervals as in the prior art. That is, according to the present invention, a predetermined number of members to be welded at the same time are arranged at equal intervals radially on the outer peripheral wall of the welding base material, and the predetermined number of the members to be welded and the welding base material are arranged. The step of simultaneously welding the contacting portions with and is repeatedly performed while moving the welding position. As a result, the welding pressure applied to the welding base metal is radially balanced, and the welding that suppresses the deformation due to heat input is repeated along the outer peripheral direction of the welding base metal, thereby suppressing the uneven deformation associated with the welding. This is to maintain the roundness of the material.

The number of members to be welded at one time may be two or more. For example, when a three-phase AC power source is used, it is preferable to weld three members to be welded at the same time. is there. The welding method of the present invention includes a motor, a generator,
It can be suitably used when welding a heat dissipation member (welded member) to various case members (welding base material) such as a circular transformer, a compressor, a high temperature pump, and a high temperature gas exhaust tank.

According to a second aspect of the present invention, in the welding method according to the first aspect, the welding base material is a cylindrical motor case or a generator case, and the member to be welded is a heat dissipation member, In the arranging step, three heat radiating members to be welded at the same time are arranged so as to be in contact with the outer peripheral wall of the case in the radial direction at equal intervals in the axial direction of the motor. In the welding step, each of the heat radiating member and the case is arranged. While pressurizing the abutting portions, a three-phase AC voltage is applied to the abutting portions so that the loads of the respective phases are balanced, and the welding is performed simultaneously.

According to the present invention, three heat radiation members are radially arranged at equal intervals on the outer peripheral wall of the case, and are simultaneously welded by a three-phase AC voltage. As a result, the pressure applied to the case is radially balanced around the case, and it is possible to effectively suppress the deformation of the motor case that is easily deformed by heat input. Further, a three-phase AC voltage is applied to the three contact portions of the motor case and the heat dissipation member so that the loads of the respective phases are balanced. As a result, the energized currents are balanced, and the occurrence of flicker noise or the like that accompanies unbalanced energization is suppressed, and the problem that the control computer or the like malfunctions due to noise does not occur.

As described above, in the present invention, in order to maintain the roundness of the case, the steps of performing simultaneous welding by arranging the heat radiating members radially at equal intervals along the outer circumference of the case are repeated. In other words, in order to maintain the roundness of the case, it is desirable that no member other than the heat dissipation member is welded to the outer peripheral wall of the case. Therefore, the fixing member for fixing the motor case or generator case to the body, the hanging member for hanging, or the name plate (name plate) indicating the name and rating of the equipment, etc. are directly welded to the case. Instead of welding, it is better to weld to a heat radiation member fixed by welding. Further, a lead wire or the like led out from the device can be taken out to the outside through an opening provided between the heat dissipation members.

The present invention according to claim 3 is a welding device for welding a plurality of heat radiating members to a cylindrical case member in the axial direction of the cylinder over the entire circumference of the outer peripheral wall of the case member. Then, a predetermined number of heat radiation members to be welded at the same time are held in contact with the outer peripheral wall of the case member in the radial direction at equal intervals in the axial direction of the cylinder to hold the heat radiation member, and the heat radiation member and the case member. It is configured to include an energizing and pressing unit that applies a welding voltage to each of the abutting parts while pressurizing the abutting parts, and a power supply part that supplies a welding voltage required for welding to the energizing and pressing part.

According to the welding apparatus of the present invention, the above-mentioned claim 1
Alternatively, the welding method described in 2 can be effectively implemented. In particular, by adopting a structure in which the impedance of the transformer used in the power supply section (the inductance of the primary and secondary side coils) is reduced, the power factor is improved and the transformer from the secondary side is A large current can be applied to the contact portion in a short time. As a result, sufficient heat input can be applied to each abutting portion to melt it, and good welding can be performed.

According to a fourth aspect of the present invention, the energizing and pressurizing section is disposed in contact with the heat radiating member, and an external electrode for applying a welding voltage while pressing the heat radiating member toward the outer peripheral wall of the case member. An inner electrode that is disposed in contact with the inner peripheral wall of the case member so as to face the outer electrode, and that applies a welding voltage while supporting the inner peripheral wall of the case member so as to face the applied pressure of the outer electrode. It is configured.

According to the present invention, the external electrode is pressed toward the internal electrode without applying pressure to the internal electrode. In other words, the external electrode presses the heat dissipation member against the outer peripheral wall of the case member, and the inner peripheral wall of the case member is fixedly supported by the inner electrode to generate a pressing force for pressing the heat dissipation member against the outer peripheral wall of the case member. There is. With this configuration, the pressurizing mechanism can be simplified as compared with the configuration in which both the internal electrode and the external electrode are pressed so as to be close to each other, and moreover, the pressing force can be made uniform.

The structure of the external electrode and the internal electrode may be an electrode structure for projection welding in which the electrode used for resistance welding is deformed. In other words, by structuring the external and internal electrodes to extend linearly along the outer peripheral wall of the case member in the direction of the cylinder axis, melting occurs over the entire length between the external and internal electrodes. The projection welding can be performed. As a result, the heat dissipation member can be evenly welded to the case member.

In the present invention, the heat radiating member has a groove portion formed by bending a plate material so that its cross section has a substantially U shape, and the bottom portion of the groove portion is directed to the outer peripheral wall of the case member. Welded,
Both side surfaces of the groove portion may be configured to project from the outer peripheral wall of the case member to radiate heat. According to this structure, the equivalent surface area of the case member is expanded and the heat of the case member is effectively released into the air only by welding the heat dissipation member having a simple structure in which the plate member is bent to the case member. be able to. As a result, the heat radiation effect is improved as compared with the case in which the case member and the heat radiation member are integrally molded using a casting or the like, and the size, weight and cost of the device can be reduced.

Further, the heat dissipation member is provided with heat dissipation promoting processing for enlarging a heat dissipation area on both side surfaces of the groove-like portion, or
A heat dissipation promoting member that expands the heat dissipation area can be attached. According to the present invention as set forth in claims 3 and 4, a heat dissipating member separate from the case can be welded while maintaining the roundness of the case. It is not integrally molded. This makes it possible to easily adopt a structure for promoting the heat dissipation effect in the heat dissipation member.

As the heat radiation promoting processing, for example, openings, protrusions or cut and raised portions are provided on both side surfaces of the groove-like portion,
A burring-shaped opening can be provided. Further, both sides of the groove portion may be formed in a corrugated shape so that the heat dissipation area is enlarged. As the heat dissipation promoting member, for example, a metal net or the like can be used, and by mounting the metal net on both side surfaces of the groove-like portion, the heat dissipation area of the heat dissipation member can be effectively expanded. According to this configuration,
Since the heat dissipation effect of the heat dissipation member is improved, it is possible to reduce the size of the heat dissipation member, and thereby to reduce the size and weight of the device.

The heat dissipating member may have cooling pipes attached to both side surfaces of the groove, and a cooling medium may be passed through the cooling pipe for cooling. According to this configuration, even if the heat dissipation area of the heat dissipation member is small, the heat of the case member can be effectively dissipated through the refrigerant flowing through the cooling pipe, and the device can be further downsized. As the cooling medium for the cooling pipe, for example, water or oil can be used.

[0021]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 are perspective views showing the steps of the welding method of the embodiment according to the present invention, and FIG. 4 is a side view of a welding apparatus for carrying out the welding method of the present embodiment. The welding method of the present embodiment is to weld a heat dissipation member to the outer peripheral wall of a cylindrical motor case while maintaining the roundness of the case.

The welding method of this embodiment will be described below in the order of welding steps. The first step is the placement step. In this step, the heat dissipation member 13 is placed in contact with the outer peripheral wall of the motor case, and the welding electrode is placed. As shown in FIG. 1A, the internal electrode 12 is inserted inside the motor case 10. The motor case 10 has a cylindrical shape made of metal. The internal electrodes 12 are three sets of internal electrodes 12 fixed to the outer peripheral wall of a cylindrical core member 11 made of an insulating material in the radial direction at equal intervals in the cylindrical axial direction. The internal electrode 12 has a substantially rectangular cross section, is divided at the central portion in the cylinder axial direction to form one set of internal electrodes 12, and three sets of these internal electrodes 12 are provided. Internal electrode 1
The length of 2 is substantially the same as the length of the motor case 10. When the internal electrodes 12 are inserted into the motor case 10, the electrodes 12 radially contact the inner peripheral wall of the motor case 10.

Next, as shown in FIG. 1B, three heat radiating members 13 are arranged on the outer peripheral wall of the motor case 10, and the external electrodes 14 are brought into contact with each of the heat radiating members 13 to make the motor case 1
Press on the outer peripheral wall of 0. The heat dissipation member 13 is a groove-shaped member formed by bending a metal plate and having a substantially U-shaped cross section, and has substantially the same length as the motor case 10. The external electrode 14 is a rod-shaped electrode having a substantially rectangular cross section, and has a shape in which the external electrode 14 is divided into two at the central portion in the axial direction of the cylinder to form a set of external electrodes 14 and is fitted into the groove portion of the heat dissipation member 13. . The heat dissipation member 13 faces the internal electrode 12, and the motor case 10
Is arranged on the outer peripheral wall of the cylinder in the axial direction of the cylinder. In other words, Figure 2
As shown in (a), the heat dissipation member 13 faces the internal electrode 12 so that the heat dissipation member 13 is removed from the motor case 10.
Are radially arranged on the outer peripheral wall at equal intervals. Then, the external electrode 14 is fitted into the groove portion of the heat dissipation member 13.

A welding process is performed subsequent to the placing process.
In the welding process, welding is performed by applying a welding voltage at the same time while pressurizing a contact portion between the heat dissipation member 13 and the motor case 10. As shown in FIG. 2A, in a state where the heat dissipation member 13 is in contact with the outer peripheral wall of the motor case 10, the three outer electrodes 14 are pressed toward the inner electrodes 12. As a result, the heat dissipation member 13 is pressed against the outer peripheral wall of the motor case 10. With the heat radiating member 13 pressed against the outer peripheral wall of the motor case 10, welding is performed by simultaneously applying a three-phase AC voltage between the facing outer electrode 14 and the facing inner electrode 12. As shown in FIG. 2 (a), the three-phase AC voltage is the interphase voltage a−b,
b-c and c-a are respectively connected between the internal electrode 12 and the external electrode 14 so that the loads of the respective phases are simultaneously applied so as to be balanced.

As shown in FIG. 2B, in the welding process, the three heat radiation members 13 are welded to the outer peripheral wall of the motor case 10. After that, the pressure on the external electrode 14 is released,
Once dissipated from the heat dissipation member 13. The rotating process is performed following the welding process. In the rotating step, the welding position is rotated by a predetermined angle with respect to the cylindrical axis. When rotating the welding position, there are a configuration in which the motor case 10 including the heat dissipation member 13 is rotated and a configuration in which the internal electrode 12 and the external electrode 14 are rotated. In the present embodiment, the former is adopted to simplify the structure. I am trying to In the rotating step, as shown in FIGS. 2B and 3A, the motor case 10 is rotated around the cylindrical axis by a predetermined angle and moved to the next welding position.

After that, the arrangement step, the welding step, and the rotating step described above are repeated to obtain the structure shown in FIG.
As shown in, the heat dissipation member 13 is welded to the outer peripheral wall of the motor case 10 at predetermined intervals. And all the heat dissipation members 1
When the welding of No. 3 is completed, the internal electrode 12 is taken out from the motor case 10, and a series of working steps is completed.

As described above, according to the welding method of the present embodiment, the step of simultaneously welding three radially arranged heat radiation members 13 to the motor case 10 by using a three-phase AC voltage is repeated. As a result, the pressure applied to the motor case 10 in each welding process is radially balanced around the cylindrical shaft, and the deformation of the motor case 10 that is easily deformed by heat input is effectively suppressed.
Further, even if the motor case 10 is slightly deformed by welding, the deformed portion is located radially on the outer periphery of the motor case 10, so that the heat dissipation member 13 is welded over the entire outer peripheral wall of the motor case 10. As a result, it is possible to secure the roundness.

A three-phase AC voltage is applied to the three contact portions of the motor case and the heat radiation member so that the loads of the respective phases are balanced. As a result, the energization currents are balanced, and the occurrence of flicker noise or the like caused by unbalanced energization is suppressed, and the influence of noise on the control computer and the like is also eliminated.

FIG. 4 is a side view showing a welding apparatus 1 for carrying out the welding method of this embodiment. Figure 4
As shown in (a), an internal electrode 12 is attached to a substantially central portion of the welding device 1. By inserting the motor case 10 over the internal electrode 12, the motor case 10 is attached to the welding device 1. It is held in the approximate center. Further, three external electrodes 14 fixed to the cylinder 15 so as to face the internal electrodes 12 are radially arranged. Further, on the left and right lower parts of the welding device 1, there is arranged a power source section P including transformers 16 for supplying a welding voltage to the external electrode 14 and the internal electrode 12.

In the welding apparatus 1 of this embodiment, the internal electrode 1
2 and the external electrode 14 form a holding portion H that abuts and holds the heat dissipation member 13 on the motor case 10, and the inner electrode 12 and the external electrode 14 form the energizing and pressing portion T.
Is formed.

In this welding device 1, as shown in FIG. 4 (b), the cylinder 15 is driven to bring the external electrode 14 into contact with the heat dissipation member 13, thereby causing the heat dissipation member 13 to move to the outer peripheral wall of the motor case 10. It is a structure that energizes while pressing.

Here, in the welding method of this embodiment, the pressure applied to the motor case 10 at the time of welding is radially balanced around the cylindrical shaft so that the motor case 10 is easily deformed by heat input. It was a restraint. Therefore, it is preferable that no member other than the heat dissipation member 13 is welded to the outer peripheral wall of the motor case 10. But,
It is necessary to provide the motor case 10 with a fixing member for fixing the case 10 itself to the body and a hanging member for hanging. Therefore, as shown in FIG. 5, instead of welding the fixing member 17 and the hanging member 18 directly to the motor case 10, the members are fixed to the heat dissipation member 13 by welding.

The fixing member 17 is welded to the fin 13a so as to straddle the two heat radiating members 13 below the motor case 10. The fixing members 17 are provided on both ends of the motor case 10 in the cylindrical axis direction in a total of 4 symmetrically with respect to the cylindrical axis.
It is fixed by welding. An opening (not shown) is provided in the lower portion of the fixing member 17, and the bolt B is inserted into the opening to be fixed to the body (fixing place of the motor). Further, the hanging member 18 is welded to the fin 13a so as to straddle the two heat radiating members 13 on the upper portion of the motor case 10. The hanging member 18 is a member whose cross section is bent into a substantially M-shape, and is provided on the upper portion of the hanging member 18.
The hanging metal fitting 18a is passed through the individual openings (not shown).
The suspension members 18 are fixed near the both ends of the motor case 10 in the axial direction of the cylinder.

Further, in the present embodiment, the motor case 10
The opening 10a is opened in the outer peripheral wall between the heat dissipation members 13 of
A bush 19 is attached to this opening 10a.
Then, through the bush 19, the motor case 10
The lead wire L derived from is taken out to the outside. Although not shown in the drawing, the nameplate of the motor M can be welded to the heat dissipation member 13 or fixed with a screw.

As described above, in this embodiment, the circular shape can be maintained by suppressing the deformation of the motor case 10 due to welding by a simple method of radially welding the heat dissipation member 13 to the outer peripheral wall of the motor case 10. I have to.

By the way, according to the present invention, the motor case 1
It is now possible to fix the heat dissipation member 13, which is a separate member, by welding. Thereby, unlike the case where the heat dissipation member is integrally formed with the motor case as in the case of casting, the heat dissipation member 13 can be easily structured to promote the heat dissipation effect, for example.

FIG. 6 shows an example in which the heat dissipation member 13 is processed to promote the heat dissipation effect. Figure 6
In (a), a large number of openings 13b are provided in the fins 13a, 13a of the heat dissipation member 13, whereby the surface area of the fins 13a is increased and the heat dissipation effect is improved. Further, FIG. 6B shows the fins 13 a and 13 a of the heat dissipation member 13.
A large number of slit-shaped extrusion openings 13b are arranged in a to increase the surface area.

Further, in FIG. 6C, instead of providing the opening, the fin 13a is formed in a corrugated shape, and the surface area is enlarged to improve the heat radiation effect. In addition to the one shown in the drawing, various structures such as a structure in which a large number of protrusions or the like are provided on the fin 13a or a structure in which another heat dissipation member such as a metal net is fixed to the fin 13a are used to improve the heat dissipation effect. It is possible to improve. Further, as shown in FIG. 6D, a pipe P may be welded to the fins 13a, 13a of the heat dissipation member 13, and a cooling structure may be adopted in which a refrigerant (water or oil) is passed through the pipe P.

As described above, according to the welding method of the present embodiment, the heat dissipation member 13 of the motor or the generator is attached to the motor case 1.
It is possible to weld to the outer peripheral wall while maintaining the roundness of 0. As a result, the weight of the motor and the generator can be significantly reduced as compared with the case using a conventional casting. Moreover, since the heat dissipation effect of the heat dissipation member 13 can be improved, the weight and size of the device itself can be reduced, and the cost can be reduced.

The welding method of the present embodiment is not limited to a motor or a generator, and can be applied to the case where a heat dissipation member is welded to a high temperature circular container such as a circular transformer, a compressor, a high temperature pump, a high temperature gas exhaust tank, or the like. Is possible.

Here, when the case for welding the heat radiating member is a thin material, the heat radiating member and the case are likely to be non-uniformly melted, and stable welding may be difficult. For example, in FIG.
As shown in (a), when the thickness of the case 10 is approximately 2 mm or less, the melting tends to be non-uniform. So, case 1
At the portion where the heat dissipation member 13 is welded to 0, slit-like protrusions 10b are provided at predetermined intervals so as to be orthogonal to the longitudinal direction of the heat dissipation member 13. As a result, the contact portion between the protrusion 10b and the heat dissipation member 13 is melted in advance and stable welding can be obtained.

The heat dissipation member is not limited to the U-shaped section shown in FIG. 1, but for example, as shown in FIG. 7B, two U-shaped sections are arranged in parallel. You may use the heat dissipation member 13 'of the side-by-side shape. When welding the heat dissipation member 13 ′, it is possible to connect the electrodes 12, 12 and the electrodes 14, 14 in the same phase and perform simultaneous welding.

[0043]

According to the welding method of the present invention as set forth in claim 1, a member to be welded can be welded while maintaining the roundness of the welding base metal, and a product having improved dimensional accuracy is provided. it can. According to the welding method of the present invention as set forth in claim 2, it is possible to easily weld the heat dissipation member while maintaining the roundness of the case of the motor or the generator, and it is possible to provide a lightweight device.
In particular, since the heat dissipation effect of the heat dissipation member is improved, the heat dissipation member itself can be downsized, and the device can be further reduced in weight and size. According to the welding device of the present invention described in claim 3, it is possible to effectively carry out the welding method described in claim 1 or 2. According to the present invention described in claim 4, the pressing force can be uniformly applied radially with a simple configuration, and good welding can be performed while maintaining the roundness of the case member.

[Brief description of drawings]

1A and 1B are perspective views showing a welding process of an embodiment according to the present invention.

2A and 2B are perspective views showing a welding process following FIG.

3 (a) and 3 (b) are perspective views showing a welding process following FIG.

4 (a) and 4 (b) are sectional views of a welding apparatus for carrying out the welding method shown in FIGS. 1 to 3.

5 is a side view of the motor case shown in FIG. 3 (b).

6A to 6D are a perspective view and a plan view showing a modified example of the heat dissipation member.

FIG. 7A is a perspective view showing an example of welding when the case has a thin wall, and FIG. 7B is an explanatory diagram when welding is performed using a modified example of the heat dissipation member.

8 (a) and 8 (b) show a conventional welding method.
It is a side view which shows the process of welding a heat dissipation member to a motor case.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Welding device 10 Welding base material (motor case, generator case, case member) 11 Internal electrode 13 Member to be welded (heat dissipating member) 14 External electrode H Holding part T Energizing pressurizing part P Power supply part

Claims (4)

[Claims] 1. A welding method for welding a plurality of members to be welded to a cylindrical welding base material in the axial direction of a cylinder over the entire circumference of an outer peripheral wall, wherein a predetermined number of the members to be welded are welded at the same time. The member is placed on the outer peripheral wall of the welding base material so as to be radially abutted toward the cylindrical axial direction so as to be evenly spaced, and a pressure is applied to each contact portion of the welded member and the welding base material. Meanwhile, a welding method characterized in that a welding step of simultaneously applying a welding voltage to each abutting portion to perform welding and a rotating step of rotating a welding position around a cylindrical axis by a predetermined angle are repeatedly performed. 2. The welding base material is a cylindrical motor case or generator case, and the member to be welded is a heat radiating member, and in the arranging step, three heat radiating members to be welded at the same time are arranged.
The outer peripheral wall of the case is arranged so as to be radially abutted toward the motor axial direction so as to be evenly spaced, and in the welding step, each abutting portion is pressed while pressing each abutting portion between the heat dissipation member and the case. The welding method according to claim 1, wherein a three-phase alternating current voltage is applied to the wires so that the loads of the respective phases are balanced, and the welding is performed simultaneously. 3. A welding device for welding a plurality of heat dissipating members to a case member having a cylindrical shape along the entire circumference of an outer peripheral wall of the case member in the axial direction of the cylinder. While holding the heat dissipation member in contact with the outer peripheral wall of the case member in the radial direction at equal intervals in the cylindrical axial direction to hold the heat dissipation member, and pressing the contact parts of the heat dissipation member and the case member, A welding apparatus, comprising: an energizing / pressurizing unit that applies a welding voltage to each contact portion; and a power supply unit that supplies a welding voltage required for welding to the energizing / pressurizing unit. 4. The external pressure applying section is disposed in contact with the heat dissipation member and applies a welding voltage while pressing the heat dissipation member toward the outer peripheral wall of the case member, and the external electrode is opposed to the external electrode. And an internal electrode that is disposed in contact with the inner peripheral wall of the case member to face the pressing force of the external electrode and supports the inner peripheral wall of the case member while applying a welding voltage. The welding device according to claim 3.