| 摘要 |
<P>PROBLEM TO BE SOLVED: To inexpensively provide a drive unit for improving position detection precision of a plunger. <P>SOLUTION: The drive unit is obtained by: fixing a reflection plate 51 changing a contrast along a drive direction to the plunger 41, then fixing the reflection plate 51 which is fixed to the plunger 41 so that an angle θ making an orthogonal direction Y1 orthogonal to a plate face of the reflection plate 51 and a horizontal direction Y2 of a white key 10 is 90 degrees; emitting light toward the reflection plate 51 by a light emitting element incorporated in an optical sensor 52; receiving light from the light emitting element reflected on the reflection plate 51 by a light receiving element incorporated in the optical sensor 52; and outputting electric signals in response to the light receiving amount as a position of the plunger 41. <P>COPYRIGHT: (C)2009,JPO&INPIT |
