Absolute encoder
An absolute encoder includes a spindle gear fixed to a motor shaft, a permanent magnet provided on the spindle gear, and a first driven gear having a center axis perpendicular to a center axis of a worm gear portion, and engaging the worm gear portion. The absolute encoder includes a second driving gear provided coaxially with the first driven gear and rotating according to a rotation of the first driven gear, and a second driven gear having a center axis perpendicular to the center axis of the first driven gear, and engaging the second driven gear. The spindle gear includes a magnet holder which is fit onto a tip end of the motor shaft, coaxially with the motor shaft, and a resin gear portion provided with the worm gear portion on an outer side in a radial direction.
1. An absolute encoder comprising:
a first driving gear, fixed to a spindle, coaxially with the spindle, and configured to rotate according to a rotation of the spindle;
a first magnet provided on the first driving gear;
a first driven gear, having a center axis perpendicular to a center axis of the first driving gear, and configured to engage the first driving gear;
a second driving gear, provided coaxially with the first driven gear, and configured to rotate according to a rotation of the first driven gear; and
a second driven gear, having a center axis perpendicular to the center axis of the first driven gear, and configured to engage the second driving gear,
wherein the first driving gear includes:
a cylindrical portion fit onto a tip end of the spindle, coaxially with the spindle, and
an annular portion having a teeth portion, configured to engage the first driven gear, and provided on an outer side thereof in a radial direction, and
wherein the annular portion is provided coaxially with the spindle and adjacent to the cylindrical portion,
the cylindrical portion is a separate element from the annular portion,
an inner peripheral surface of the annular portion is fit onto an outer peripheral surface of the spindle,
the cylindrical portion and the spindle contact each other at a first contact portion,
the annular portion and the spindle contact each other at a second contact portion,
the first contact portion and the second contact portion are arranged along a plane parallel to a radial direction of the first driving gear, perpendicular to an axial direction of the spindle, and
the inner peripheral surface of the annular portion includes a surface portion opposing the outer peripheral surface of the cylindrical portion with a gap formed therebetween.
2. The absolute encoder as claimed in claim 1 , wherein the first magnet is fixed to the cylindrical portion formed of a non-magnetic metallic material, via an adhesive.
3. The absolute encoder as claimed in claim 1 , wherein the first driven gear has an outer diameter smaller than an outer diameter of the first driving gear.
4. The absolute encoder as claimed in claim 1 , further comprising:
a second magnet provided on the second driven gear,
wherein the second driven gear is decelerated and rotates unitarily with the second magnet, according to the rotation of the spindle.