US Patent 7449810 Electric motor and electric tool having the motor

In a circular saw, an end plate provided on an end of a rotor core has a cylindrical shaft insulator and a plate extending radially from the shaft insulator. The plate is disposed at a position separated from the end of the rotor core. The plate includes slot parts, and air holes that penetrate the plate in the axial direction of the rotor shaft at areas adjacent to the rotor shaft. Protruding parts are provided on the shaft insulator on both sides of each air hole, extending in the axial direction of the rotor shaft and protruding radially outward with respect to the rotor shaft. The shaft insulator has an outer diameter D1 that is smaller than a diameter D2 of the plate in the slot parts adjacent to the rotor shaft.