| 摘要 |
<p>PURPOSE:To prevent the generation of the positional displacement of a reading means and a scale by mounting the scale and the scale and the reading means at the center or periphery of thrust. CONSTITUTION:A center yoke (CY) 2 and side yokes (SY) 3 are fixed onto a base 1. Permanent magnets 4 are arranged inside the CY2 and the SYs 3 so that the polarities of adjacent magnetic poles mutually differ. The magnetic poles of the permanent magnets 4a, 4b also differ mutually, and are disposed through a constant magnetic air gap 5. Armature coils (EC) 6 are arranged in the magnetic air gap 5. The ECs 6 are composed of polyphase coils, and currents flowing through each coil are changed over, thus moving the ECs 6, then shifting a needle B. A position sensing means C is mounted for sensing the position of the needle B. The position sensing means C is constituted of a reading head 7 and a linear scale (LS) 8. The LS 8 is provided on the top face of the CY2 so that the center of the LS 8 aligns with the center D of thrust. The reading head 7 is fitted to the needle B so as to be oppositely faced to the LS 8.</p> |
