Planetary gear assembly, drive unit including the planetary gear assembly, and image forming apparatus including the drive unit, and installation method for planetary gear assembly

Abstract

A planetary gear mechanism includes a plurality of planetary gears, an outer gear, a sun gear, a carrier, and a stick mount. The outer gear meshes with the plurality of planetary gears. The sun gear is coaxially disposed on the same axis as the outer gear and transmits force to the planetary gears. The carrier rotatably supports the plurality of planetary gears and is rotatably and floatingly supported. The carrier includes a hole through which a stick member penetrates in a direction of axis of rotation of the carrier. The stick member penetrates through the hole and is mounted on the stick mount. The stick mount is disposed opposite the carrier. The outer gear and the sun gear are held such that one of the outer gear and the sun gear does not rotate.

What is claimed is: 
     
         1 . A planetary gear mechanism, comprising:
 a plurality of planetary gears;   an outer gear to mesh with the plurality of planetary gears;   a sun gear coaxially disposed on the same axis as the outer gear, to transmit force to the planetary gears;   a carrier to rotatably support the plurality of planetary gears, the carrier rotatably and floatingly supported and including a hole through which a stick member penetrates in a direction of axis of rotation of the carrier; and   a stick mount on which the stick member penetrating through the hole is mounted, the stick mount disposed opposite the carrier,   one of the outer gear and the sun gear being unrotatably held.   
     
     
         2 . The planetary gear mechanism according to  claim 1 , wherein the hole of the carrier is formed at the center of rotation of the carrier, and the sun gear includes the stick mount on a plane facing the carrier in an axial center thereof. 
     
     
         3 . The planetary gear mechanism according to  claim 1 , further comprising a gear mount to which one of the sun gear and the outer gear is fixed, the gear mount including a plane facing the carrier,
 wherein the carrier includes a plurality of the holes evenly formed on a circumference of a lateral surface of the carrier,   wherein the gear mount includes a plurality of the stick mounts on the plane facing the carrier.   
     
     
         4 . The planetary gear mechanism according to  claim 1 , wherein a clearance is provided between the stick member and the hole, and the clearance does not allow the carrier to tilt relative to a direction of insert of the stick member. 
     
     
         5 . The planetary gear mechanism according to  claim 1 , wherein one of the stick mount and the tip of the stick member includes a conical concavity, and another of the stick mount and the tip of the stick member has a conical convex shape,
 wherein the tip of the stick member is fitted to the stick mount.   
     
     
         6 . The planetary gear mechanism according to  claim 1 , further comprising a plurality of groups of the sun gear, the outer gear, the planetary gears, and the carrier,
 wherein the plurality of groups is disposed in series in the axial direction,   wherein the outer gears have the same number of teeth and are constituted as a single integrated member common to each group and fixed unrotatably.   
     
     
         7 . The planetary gear mechanism according to  claim 6 , wherein the position of the hole in the carrier is the same for all groups. 
     
     
         8 . The planetary gear mechanism according to  claim 1 , wherein the hole is formed at the center of rotation of the carrier, and the sun gear includes the stick mount on a plane facing the carrier in the axial center,
 wherein the stick member has a noncircular shape in cross section, and the hole of the carrier has a noncircular shape to allow the stick member to fit therein.   
     
     
         9 . The planetary gear mechanism according to  claim 1 , wherein the stick member has a rounded rectangular shape in cross section, and the hole of the carrier has a rounded rectangular shape to allow the stick member to fit therein. 
     
     
         10 . The planetary gear mechanism according to  claim 1 , wherein the hole of the carrier has a tubular shape extending in the direction of insert of the stick member. 
     
     
         11 . A drive transmission unit, comprising:
 a drive source;   the planetary gear mechanism of  claim 1  including an output shaft; and   a shaft to support a target to be driven and transmit rotary force output from the output shaft of the planetary gear mechanism to the target.   
     
     
         12 . An image forming apparatus, comprising:
 a plurality of targets to be driven; and   the drive transmission unit of  claim 11  to drive at least one of the plurality of targets.   
     
     
         13 . A method for assembling a planetary gear mechanism,
 the planetary gear mechanism comprising:   a plurality of planetary gears;   an outer gear to mesh with the plurality of planetary gears;   a sun gear to transmit force to the planetary gears, the sun gear coaxially disposed on the same axis as the outer gear;   a carrier to rotatably support the plurality of planetary gears, the carrier rotatably and floatingly supported and including a hole through which a stick member penetrates in a direction of axis of rotation of the carrier; and   a stick mount on which the stick member penetrating through the hole is mounted, the stick mount disposed opposite the carrier,   one of the outer gear and the sun gear being unrotatably held,   the method comprising:   inserting the stick member to the hole of the carrier;   mounting the stick member at the stick mount;   meshing the plurality of planetary gears with the sun gear and the outer gear by moving the carrier along the stick member, to mount the carrier in the outer gear; and   removing the stick member after carrier is mounted.