Reduction gear

Abstract

A reduction gear includes a reduction mechanism and a component which constitutes the reduction gear and in which a cavity portion is provided, in which the component includes a reinforcement structure which is provided in the cavity portion and forms a void in the cavity portion.

What is claimed is: 
     
         1 . A reduction gear comprising:
 a reduction mechanism; and   a component which constitutes the reduction gear and in which a cavity portion is provided,   wherein the component includes a reinforcement structure which is provided in the cavity portion and forms a void in the cavity portion.   
     
     
         2 . The reduction gear according to  claim 1 ,
 wherein the component is a casing which accommodates the reduction mechanism.   
     
     
         3 . The reduction gear according to  claim 2 ,
 wherein a first space and a second space are provided in the casing, and   wherein the cavity portion allows the first space and the second space to communicate with each other.   
     
     
         4 . The reduction gear according to  claim 1 ,
 wherein the component includes a bearing disposition portion in which a bearing is disposed, and   wherein the cavity portion is provided at a position overlapping the bearing disposition portion when viewed in a radial direction.   
     
     
         5 . The reduction gear according to  claim 4 ,
 wherein the component is a casing accommodating the reduction mechanism, and   wherein the cavity portion is provided radially outward of the bearing disposition portion.   
     
     
         6 . The reduction gear according to  claim 1 ,
 wherein a metal member formed of a metal-based material and a resin member formed of a resin-based material are provided, and   wherein the component is the metal member.