Core manufacturing method and core

A core manufacturing method for manufacturing a core for a rotating electrical machine having a stator and a rotor by using a welding device, the core manufacturing method comprising:

• stacking a plurality of electromagnetic steel plates in an axial direction;
• performing first welding on an inner surface of a through hole formed in a stack of the electromagnetic steel plates and continuous in the axial direction, the first welding being performed toward a first side in the axial direction which is one side in the axial direction;
• and
• performing second welding on the inner surface of the through hole, the second welding being performed toward a second side in the axial direction which is the other side in the axial direction, wherein
• a first welding region and a second welding region overlap each other in the axial direction, the first welding region being a region in the axial direction which is welded in the first welding, and the second welding region being a region in the axial direction which is welded in the second welding.

A core manufacturing method for manufacturing a core for a rotating electrical machine having a stator and a rotor by using a welding device, the core manufacturing method comprising:

• stacking a plurality of electromagnetic steel plates in an axial direction;
• performing first welding on a stack of the electromagnetic steel plates, the first welding being performed toward a first side in the axial direction which is one side in the axial direction;
• and
• performing second welding on the stack, the second welding being performed toward a second side in the axial direction which is the other side in the axial direction, wherein
• each of the first welding and the second welding includes an output increase period during which welding is performed while gradually increasing output energy of the welding device, and
• a first increase region and a second increase region overlap each other in the axial direction, the first increase region being a region in the axial direction which is welded during the output increase period of the first welding, the second increase region being a region in the axial direction which is welded during the output increase period of the second welding.

A core for a rotating electrical machine, the core comprising:

• a stack formed by stacking a plurality of electromagnetic steel plates in an axial direction, wherein:
• the stack has a through hole that is continuous in the axial direction,
• a first melted portion and a second melted portion are formed in an inner surface of the through hole, the first melted portion extending through a plurality of the electromagnetic steel plates in the axial direction from an end on a first side in the axial direction which is one side in the axial direction, and the second melted portion extending through a plurality of the electromagnetic steel plates in the axial direction from an end on a second side in the axial direction which is the other side in the axial direction, and
• the first melted portion and the second melted portion are located at different positions in a circumferential direction and overlap each other in the axial direction.