MOTOR CORE HAVING SMALL DETERIORATION IN IRON LOSS UNDER COMPRESSIVE STRESS AND METHOD OF MANUFACTURING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a motor core having small deterioration in the iron loss characteristics at high frequencies even under presence of a compressive stress, and to provide a method of manufacturing the same.SOLUTION: An electromagnetic steel sheet applied with an insulation coating, preferably, containing Si:7 mass% or less, Al:3 mass% or less, Mn:5 mass% or less, S:0.01 mass% or less, N:0.005 mass% or less, and O:0.01 mass% or less is punched using a die having multiple micro protrusions formed entirely or partially on the surface of a motor core in contact with the back yoke. A core material where micro recesses having a depth of 10-50 m and a diameter of 0.05-2 mm are formed entirely or partially in the back yoke on the surface of the punched electromagnetic steel sheet at such intervals as the closest distance becomes 0.2-5 mm is thereby obtained. The core materials are then laminated and a compressive stress of 10 MPa or more is imparted in the circumferential direction thus obtaining a motor core.