Patent ID: 8341997
Filing Date: 2013-01-01
Classification: B21J,B21K,Y10T

Abstract:
1. A method of forging a bevel gear, comprising: a first forging step in which a first intermediate article is obtained by pressing a blank, such that there is formed a preliminary one-end recessed part that is axially recessed in an axis-center part on an axially one-end side and/or a preliminary other-end recessed part that is axially recessed in an axis-center part on an axially other-end side; a second forging step in which a second intermediate article is obtained by pressing the first intermediate article in a hermetically sealed cavity space defined by a first die and a second die that is positioned opposedly to the first die in the axial direction, such that there are formed: a body part including a tooth part on a radially circumference thereof and a one-end recessed part that is axially recessed in an axis-center part on the axially one-end side; and a projecting part projecting from a rear surface part of the body part on the axially other-end side in a columnar shape whose cross-section is smaller than that of the body part; and a through-hole forming step in which a bevel gear having a through hole in an axis-center part is formed by removing the axis-center part extending from a bottom surface of the one-end recessed part to the projecting part of the second intermediate article; wherein: the tooth part provides a tooth-crest surface which is tapered from the axially other-end side to the axially one-end side; when the second forging step is started, the first intermediate article is placed in the hermetically sealed cavity space such that there is a space under the axis-center part on the axially other-end side of the first intermediate article; in the second forging step, the axis-center part on the axially one-end side of the first intermediate article is axially pressed; and upon completion of the second intermediate article in the second forging step, there remains an unfilled space between the projecting part of the second intermediate article and a wall surface of the dies defining the cavity space.