Abstract: An adhesion structure of a motor that adheres a rotor having a first linear expansion coefficient and a magnet having a second linear expansion coefficient, which differs from the first linear expansion coefficient, with an adhesive agent. The adhesion structure includes a thickness determining groove extending parallel to the axis of the rotor and arranged on the rotor in order to determine the thickness of an adhesive agent layer, which is formed from the adhesive agent. The thickness determining groove absorbs shearing stress produced by the difference between the first and second linear expansion coefficients at a surface adhered to the magnet. This effectively suppresses exfoliation of the adhesive agent layer.

Abstract: In a rotor having plural permanent magnets secured on a rotary shaft for use in, e.g., an electric motor which is incorporated preferably into a rack-type electric power steering device, a cylindrical cover is fit on the rotary shaft to cover the external surfaces of the plural permanent magnets, and one or both axial end portions of the cylindrical cover are plastically deformed thereby to secure the cylindrical cover onto the rotary shaft. Thus, the cylindrical cover is firmly secured to the rotary shaft and, even when one or more permanent magnets are separated from the rotary shaft or broken, prevents the separated permanent magnets or the broken fragments from scattering within a housing of the motor.

Abstract: An adhesion structure of a motor that adheres a rotor having a first linear expansion coefficient and a magnet having a second linear expansion coefficient, which differs from the first linear expansion coefficient, with an adhesive agent. The adhesion structure includes a thickness determining groove extending parallel to the axis of the rotor and arranged on the rotor in order to determine the thickness of an adhesive agent layer, which is formed from the adhesive agent. The thickness determining groove absorbs shearing stress produced by the difference between the first and second linear expansion coefficients at a surface adhered to the magnet. This effectively suppresses exfoliation of the adhesive agent layer.

Abstract: In a rotor having plural permanent magnets secured on a rotary shaft for use in, e.g., an electric motor which is incorporated preferably into a rack-type electric power steering device, a cylindrical cover is fit on the rotary shaft to cover the external surfaces of the plural permanent magnets, and one or both axial end portions of the cylindrical cover are plastically deformed thereby to secure the cylindrical cover onto the rotary shaft. Thus, the cylindrical cover is firmly secured to the rotary shaft and, even when one or more permanent magnets are separated from the rotary shaft or broken, prevents the separated permanent magnets or the broken fragments from scattering within a housing of the motor.