| 摘要 |
PROBLEM TO BE SOLVED: To provide a cold forging method of a crank having a disk-like weight part and a shaft part without making any overlapping portion on a lower side of the weight part. SOLUTION: The relationship on the area ratio betweenϕA<SB>1</SB>,ϕA<SB>11</SB>,ϕA<SB>2</SB>,ϕA<SB>22</SB>, L<SB>1</SB>, L<SB>11</SB>, L<SB>2</SB>and L<SB>22</SB>are (ϕA<SB>11</SB>)<SP>2</SP>/(ϕA<SB>1</SB>)<SP>2</SP>=1.2, and (ϕA<SB>22</SB>)<SP>2</SP>/(ϕA<SB>2</SB>)<SP>2</SP>=1.07, and the relationship on the length (height) ratio are L<SB>1</SB>/L<SB>11</SB>=1.33, and L<SB>2</SB>/L<SB>22</SB>=1.7, whereϕA<SB>11</SB>is the diameter of a shaft part immediately below the weight part, L<SB>11</SB>is the length thereof along the axis,ϕA<SB>22</SB>is the diameter of a lower shaft part of the shaft part immediately below the weight part, L<SB>22</SB>is the length from the lower side of the weight part along the axis, and the angle of inclination of a boundary part to the shaft part immediately below the weight part is 55°, and the angle of inclination of a boundary part to the lowest shaft part is 90°. COPYRIGHT: (C)2003,JPO
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