| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a sealing structure of a clearance between a rotation shaft and a casing, preventing intrusion of external dust, moisture, and the like without causing friction load and noise by contact, and also to provide a rotary encoder using it. <P>SOLUTION: Between the rotation shaft which is borne by a device frame and a casing for covering the device frame and the rotation shaft, a pair of magnetic pole forming members for forming a magnetic field around the rotation shaft is provided to the casing side and a sealing layer holding magnetic fluid is provided in the magnetic field. As for the magnetic pole forming member, for example, a permanent magnet with N-S magnet poles is shaped in a ring shape and fit around the rotation shaft and a magnetic field is generated between an end face of the magnet and the rotation shaft or the magnet shaped in the ring shape in the same way is connected with a york of a soft magnetic material and an tip end of the york is confronted with a peripheral wall face of the rotation shaft. By providing a york like this, a magnetic gap is precisely formed because soft magnetic materials such as iron are easy to machine and accuracy of finishing is ensured. <P>COPYRIGHT: (C)2007,JPO&INPIT |
