| 摘要 |
<p>PURPOSE:To reduce the size of a rotational phase detector by using a rotor magnet as a tachmagnet and by making a detecting element thin. CONSTITUTION:A plate 18, which is placed in contact with a rotor magnet 15 and which is made of a highly magnetically permeable material such as iron, is formed with first and second apertures 19 and 20. The magnetic flux density of the magnet 15, which leaks through the apertures 19 and 20, is detected to detect the rotational positions of video heads 4 and 5. A thin Hall element 21 is used as a magneticism detecting element. Thus, the techmagnet for detecting the rotational phase can be dispensed with to attain the cost reducing purpose so that the Hall element 24 can be mounted in a lower stationary cylinder 6. Thus, the mounting cost can be reduced while eliminating the requirement for the spare space.</p> |
