| 摘要 |
PURPOSE:To certainly and magnetically shield a magnetic detection element against external magnetic fields from all of directions, by arranging the magnetic detection element at the position between a magnetic disc equipped with a magnetic scale and a cover member comprising a soft magnetic material. CONSTITUTION:When a magnetic detection element 7 receives external magnetic fields from the directions shown by arrows B, C, said element 7 is magnetically shielded because a cover member 10 made of a soft magnetic material is interposed and the effect on the magnetic detection element 7 is removed. When the magnetic detection element 7 receives an external magnetic field from the direction shown by an arrow A when a rotary shaft 2 is directly connected to the output shaft of a motor, said magnetic field passes because a housing 1 is made of a non-magnetic material such as an aluminum alloy but, because a magnetic disc 6 made of a hard magnetic material is present in this side of the magnetic detection element 7, the external magnetic field is absorbed by the magnetic disc 6 and, therefore, the effect of the external magnetic field from the direction A to be exerted on the magnetic detection element 7 is also removed. |
