Patent ID: 8790747

Claim:
A method of producing an insulated electric wire, in which a primary coating layer including at least an enamel-baking layer is formed on a conductor formed of a metal to form a primary coated electric wire, and a secondary coating layer is extruded on the primary coating layer of the primary coated electric wire to produce the insulated electric wire, comprising: a conductor supply process of continuously supplying the conductor with a conductor supply unit; a coat baking process of baking and forming the primary coating layer on the conductor with a coat baking unit; a first pull-out step of pulling the conductor with the primary coating layer formed thereon at a first pulling speed with a first pull-out unit; an electric wire pre-heating process of pre-heating the primary coated electric wire with the primary coating layer formed thereon in the coat baking process with an electric wire pre-heating unit; a resin extrusion process of extruding an extrusion resin to be the secondary coating layer on the primary coating layer of the primary coated electric wire with a resin extrusion unit; a second pull-out step of pulling the primary coated electric wire with the secondary coating layer formed thereon at a second pulling speed with a second pull-out unit; and an electric wire winding process of winding the insulated electric wire with the extrusion resin coated thereon in the resin extrusion process with an electric wire winding unit, wherein the conductor supply unit, the coat baking unit, the first pull-up unit, the electric wire pre-heating unit, the resin extrusion unit, the second pull-unit, and the electric wire winding unit are arranged in a tandem arrangement, an entire process from the conductor supply process to the electric wire winding process is consistently carried out, in the electric wire pre-heating process, a surface of the primary coating layer is pre-heated up in a non-contact state with the primary coated electric wire to a temperature above a glass transition point of an adhesive layer and below a thermal decomposition temperature of the primary coating layer and the secondary coating layer when the adhesive layer is formed on the enamel-baking layer of the primary coating layer to be bonded to the secondary coating layer, and the adhesive layer is an outermost layer of the primary coating layer, and said second pulling speed is set higher than the first pulling speed.