ノート型パソコン用小形軸流送風機における漏れ磁束と騒音との関係  [in Japanese] Relationship between the Noise and the Magnetic Flux Leakage of a Small Fan for Notebook Personal Computers  [in Japanese]

Fans are used to control the temperature rise of the central processing units of notebook PCs. They are generally located inside the body of the PC. The magnetic flux leakage sometimes affects the performance of other electric devices. It is said that, 3 dB noise difference is very sigificant when such a PC is used in a silent room at midnight. The main factor in the magnetic flux leakage and the noise is the performance of the fan. This paper deals with a method of reducing the magnetic flux leakage and the noise of the fan without changing the outer body design and the performance. The magnetic flux leakage and the noise characteristics of two types of fans are discussed. One is a resin impeller fan (resin motor), and the other is a metal (steel) impeller fan (metal motor). The main findings are as follows: (1) If the resin impeller is replaced by a metal one, the magnetic flux leakage of the metal motor is 49.5% lower on the upper surface of case, and 50.8% lower on the side than the magnetic flux leakage of the reisin motor. (2) According to the experimental data, the noise of the metal motor is from 4 to 8 dB lower than that of the resin motor.