| 摘要 |
PROBLEM TO BE SOLVED: To enhance heat radiating capability, durability and productivity, by forming on the circumferential surface of a cylindrical portion at equal intervals a plurality of cooling fins which have rectangular or trapezoidal cross sections, are parallel with one another in the direction of the length and equal in height, and satisfy specific conditions. SOLUTION: Cooling fins (hereafter, referred to as 'fins') 3 are formed on the circumferential surface of the cylindrical portion 2 of a rotor 1. Letting the length and height of the fins 3 be L and h, respectively, the fins 3 are in a straight and flat plate shape with h being constant in the direction of L. These fins 3 are installed on the circumferential surface of the cylindrical portion 2 at equal intervals at the angle of inclination ofθto the rotating direction of the rotor 1. The distance d between the fins 3 is set to a value not less than 6 mm and not more than 11 mm. The inclinationθto the direction of the rotation of the rotor in the lengthwise direction of the fins 3 is set to a value not less than 25 deg. and not more than 55 deg.. The range of 2h<2> /(t1 +t2 )(=H) is set to a value not less than 20 mm and not more than 200 mm, where t1 is the thickness of the bottom of the fins 3 (unit: mm) and t2 is the thickness of the top of the fins 3 (unit: mm). As a result, the heat radiating capability, durability and productivity of the rotor can be enhanced.
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