Conventionally, for heightening output of motors, or attaining small size, light weight and high performance of the same, rotor cores or stator cores have been applied with laminated cores of predetermined thickness made by laminating many core pieces punched from thin steel sheets by pressing works. When laminating many sheets of thin core pieces, caulk-connection portions such as a V-shaped projections or a cut-and-rising portions (or embossed projections) are provided per each of core pieces, and core pieces are caulked one another via caulk-connection portions and laminated one another.
However, if thickness of the core piece is, e.g., less than 0.2 mm, at the caulk-connection portion such as the V-shaped projections or the cut-and-rising portions, length for connecting upper and lower cores is too short, it has been difficult to realize enough caulking strength. Therefore, since the caulking strength between the respective core pieces composing the laminated core is low, problems have been involved with assembled laminated core being peeled or caused with poor shape.
The invention has been made in view of these circumstances, and it is an object of the invention to provide a laminated core which has the caulk-connecting strength though core pieces have thickness of less than 0.2 mm, and causing neither peel nor poor shapes, and a method of producing the same.