Machining method, method for manufacturing planetary carrier, and planetary carrier

Abstract

A planetary carrier includes a plurality of plate portions, and column portions connecting the plurality of plate portions. The column portions each have an outer circumferential surface, an inner circumferential surface, and sidewall surfaces. The sidewall surfaces are each formed in a circular arc shape and the circular arc shape has a center on an outer circumferential side in a cross section perpendicular to a shaft of the planetary carrier. An angle formed between the outer circumferential and each of the sidewall surfaces is an obtuse angle and an angle formed between the inner circumferential and each of the sidewall surfaces is an acute angle. The plurality of plate portions and the column portions are integrally formed as one sintered body.

1 . A planetary carrier comprising:
 a plurality of plate portions; and   column portions connecting the plurality of plate portions; wherein   the column portions each have an outer circumferential surface, an inner circumferential surface, and sidewall surfaces,   the sidewall surfaces are each formed in a circular arc shape, the circular arc shape having a center on an outer circumferential side in a cross section perpendicular to a shaft of the planetary carrier,   an angle formed between the outer circumferential and each of the sidewall surfaces is an obtuse angle and an angle formed between the inner circumferential and each of the sidewall surfaces is an acute angle, and   the plurality of plate portions and the column portions are integrally formed as one sintered body.   
     
     
         2 . The planetary carrier according to  claim 1 , wherein each of the side wall surfaces has no chip. 
     
     
         3 . A planetary carrier manufactured by a method including:
 preparing a green compact by integrally forming plate portions on both ends of a body portion having a circular tubular shape;   forming openings through the body portion by using a milling tool to cut the body portion of the green compact, so as to form column portions between the openings; and   sintering the machined green compact,   wherein, in the forming of the openings,   among inner wall surfaces defining a first one of the openings, respective cut surfaces are defined as a first sidewall surface and a second sidewall surface, the respective cut surfaces being cut by cutting edges on an outer periphery of the milling tool and the second sidewall surface being opposite the first sidewall surface, a side from which the milling tool enters is defined as an outer circumferential surface of the body portion, a surface opposite to the outer circumferential surface is defined as an inner circumferential surface of the body portion, a corner where the first sidewall surface and the outer circumferential surface meet is defined as a first obtuse angle corner, a corner where the second sidewall surface and the outer circumferential surface meet is defined as a second obtuse angle corner, a corner where the first sidewall surface and the inner circumferential surface meet is defined as a first acute angle corner, a corner where the second sidewall surface and the inner circumferential surface meet is defined as a second acute angle corner, and the milling tool includes a first milling tool and a second milling tool, and   wherein the forming of the openings includes using the first milling tool, and forming the first sidewall surface by rotating the first milling tool so as to cause cutting edges of the first milling tool to cut the body portion from the first acute angle corner to the first obtuse angle corner, while leaving a cutting allowance on the second sidewall surface; and   using the second milling tool whose cutting edges are reversed from the cutting edges of the first milling tool, and forming the second sidewall surface by rotating the second milling tool so as to cause the cutting edges of the second milling tool to cut the cutting allowance from the second acute angle corner to the second obtuse angle corner, a rotation direction of the second milling tool being opposite to a rotation direction of the first milling tool, a direction in which the first milling tool moves to cut the workpiece being a same as a direction in which the second milling tool moves to cut the workpiece.