| 摘要 |
PROBLEM TO BE SOLVED: To obtain an electromagnet for noncontact control which has small leakage magnetic flux, even when the distance between the electromagnet and a controlled object becomes large. SOLUTION: An interval (liftoff) between the controlled object 1 and electromagnet 2 is L (mm), the length of the leg part of the electromagnet is F (mm), and the length of the window part of the core of the electromagnet is W (mm). The magnetic permeability of air is set toμ0, and the magnetic permeability of the core and controlled object object is set toμ. The magnetic resistance of leakage luminous flux short-circuiting and flowing in air is (W+2F)/(μ*S)+ W/(μ0*S). The magnetic resistance of magnetic flux having reached the controlled object 1 is (W+2F)/(μ*S)+2L/(μ0S)+W(μ*S). When the former is larger than the latter, majority of the magnetic flux passes through the path shown by the solid line passes through the controlled object. Here, W*(1/μ0-1/μ)S>2L/(μ0*S) is obtained. Takingμ0≪μinto account, W>2L is eventually obtained. If W>2L, the leakage magnetic flux can be made small, even if the distance between the electromagnet and controlled object becomes large.
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