Coil winding method and transformer

A coil winding method in a manufacturing method of a coil in which unit coil portions formed by spirally winding at least one conductive wire are repeatedly placed side by side in a winding axis direction, each of the unit coil portions is formed of a plurality of unit wound portions having mutually different inner circumferential lengths, and at least a part of the unit wound portion having a small inner circumferential length enters inside the unit wound portion having a large inner circumferential length,

• the coil winding method comprising:
• an outward wound unit coil portion forming step of spirally winding the conductive wire from an inner circumferential side toward an outer circumferential side and forming an outward wound unit coil portion formed of the plurality of unit wound portions laminated along a surface orthogonal to a winding axis;
• and
• an inward wound unit coil portion forming step of spirally winding the conductive wire from the outer circumferential side toward the inner circumferential side and forming an inward wound unit coil portion formed of the plurality of unit wound portions laminated along the surface orthogonal to the winding axis,
• wherein by alternately repeating the outward wound unit coil portion forming step and the inward wound unit coil portion forming step, the outward wound unit coil portion and the inward wound unit coil portion are alternately placed along the winding axis,
• in the outward wound unit coil portion forming step, a step of forming the unit wound portion on an outer circumferential side by laminating on an outer circumferential surface of the unit wound portion on an inner circumferential side is repeated from the inner circumferential side toward the outer circumferential side, and
• in the inward wound unit coil portion forming step, a step of forming the unit wound portion at a position spaced apart from a side surface of the outward wound unit coil portion formed immediately before and pushing in the unit wound portion along the winding axis direction until the unit wound portion makes contact with the side surface of the outward wound unit coil portion is repeated from the outer circumferential side toward the inner circumferential side.

A transformer including a primary winding and a secondary winding, comprising:

• a coil configuring any one or both of the primary winding and the secondary winding, including:
• an outward wound unit coil portion formed of a plurality of unit wound portions which is formed by spirally winding a conductive wire from an inner circumferential side toward an outer circumferential side and is laminated along a surface orthogonal to a winding axis;
• and
• an inward wound unit coil portion formed of a plurality of unit wound portions which is formed by spirally winding the conductive wire from the outer circumferential side to the inner circumferential side and is laminated along the surface orthogonal to the winding axis,
• wherein the outward wound unit coil portion and the inward wound unit coil portion are alternately placed along the winding axis,
• in the outward wound unit coil portion and the inward wound unit coil portion which are adjacent to each other, the unit wound portions in the outermost circumference or the unit wound portions in the innermost circumference are connected with each other, and
• a connecting wire which connects the unit wound portions in the outermost circumference with each other or the unit wound portions in the innermost circumference with each other is bent into an S shape between the adjacent unit coil portions.