Tooling and method for fabricating helical sector gear and related helical sector gear
A helical sector gear having a body and a gear segment having a plurality of helical teeth. The gear segment has a toothed sector, on which all of the helical teeth are formed, and spacing segments on the opposite circumferential ends of the toothed sector. Each of the spacing segments has a circumferential surface, which is longer than a pitch of the helical teeth, and a radial surface that is formed in a helical manner that conforms to the helix angle of helical teeth. A die set for forming the helical sector gear and a related method are also provided.
1. A die set for forming a helical sector gear, the die set comprising:
a die having a die cavity with an interior circumferential die surface that is disposed about a central axis, the interior circumferential die surface being configured to form an exterior circumferential surface of the helical sector gear, the interior circumferential die surface including a first die spacing segment, a second die spacing segment and a toothed die sector, the toothed die sector being disposed circumferentially between the first and second die spacing segments and defining a plurality of helical die teeth, each of the helical die teeth extending over a width of the die and having a root that is spaced radially from the central axis by a predetermined root dimension, the first die spacing segment consisting of a first helical die land having a first circumferential die surface and a first radial die surface, the first circumferential die surface extending radially from the central axis by a first dimension, the first radial die surface extending radially inward from the first circumferential die surface, the first radial die surface having a first helical die contour that conforms to a helix angle of the helical die teeth, the second die spacing segment consisting of a second helical die land having a second circumferential die surface and a second radial die surface, the second circumferential die surface extending radially from the central axis by a second dimension, the second radial die surface extending radially inward from the second circumferential die surface, the second radial die surface having a second helical die contour that conforms to the helix angle of the helical die teeth;
an upper punch assembly that is configured to mate with the die to form a first axial end of the helical sector gear, the upper punch assembly having a first upper punch spacing segment, which is configured to matingly engage with the first die spacing segment, a second upper punch spacing segment, which is configured to matingly engage with the second die spacing segment, and a toothed upper punch sector that is configured to matingly engage the toothed die sector; and
a lower punch assembly that is configured to mate with the die to form a second axial end of the helical sector gear, the lower punch assembly having a gear tooth compacting portion with a first lower punch spacing segment, which is configured to matingly engage with the first die spacing segment, a second lower punch spacing segment, which is configured to matingly engage with the second die spacing segment, and a toothed lower punch sector that is configured to matingly engage the toothed die sector;
wherein one of the die, the upper punch assembly and the gear tooth compacting portion is non-rotatable about the central axis and wherein the other two of the die, the upper punch assembly and the gear tooth compacting portion are rotatable about the central axis.
2. The die set of claim 1 , wherein the lower punch assembly includes a body compacting portion that is disposed radially inwardly of the gear tooth compacting portion and wherein the gear tooth compacting portion is movable along the central axis relative to the body compacting portion.
3. The die set of claim 1 , wherein the upper punch assembly and the die are the other two of the die, the upper punch assembly and the gear tooth compacting portion that are rotatable about the central axis.
4. A method for forming a helical sector gear, the method comprising:
providing a die having a die cavity with an interior circumferential die surface that is disposed about a central axis, the interior circumferential die surface being configured to form an exterior circumferential surface of the helical sector gear, the interior circumferential die surface including a first die spacing segment, a second die spacing segment and a toothed die sector, the toothed die sector being disposed circumferentially between the first and second die spacing segments and defining a plurality of helical die teeth, each of the helical die teeth extending over a width of the die and having a root that is spaced radially from the central axis by a predetermined root dimension, the first die spacing segment consisting of a first helical die land having a first circumferential die surface and a first radial die surface, the first circumferential die surface extending radially from the central axis by a first dimension, the first radial die surface extending radially inward from the first circumferential die surface, the first radial die surface having a first helical die contour that conforms to a helix angle of the helical die teeth, the second die spacing segment consisting of a second helical die land having a second circumferential die surface and a second radial die surface, the second circumferential die surface extending radially from the central axis by a second dimension, the second radial die surface extending radially inward from the second circumferential die surface, the second radial die surface having a second helical die contour that conforms to the helix angle of the helical die teeth;
providing an upper punch assembly that is configured to mate with the die to form a first axial end of the helical sector gear, the upper punch assembly having a first upper punch spacing segment, which is configured to matingly engage with the first die spacing segment, a second upper punch spacing segment, which is configured to matingly engage with the second die spacing segment, and a toothed upper punch sector that is configured to matingly engage the toothed die sector;
providing a lower punch assembly that is configured to mate with the die to form a second axial end of the helical sector gear, the lower punch assembly having a gear tooth compacting portion with a first lower punch spacing segment, which is configured to matingly engage with the first die spacing segment, a second lower punch spacing segment, which is configured to matingly engage with the second die spacing segment, and a toothed lower punch sector that is configured to matingly engage the toothed die sector;
loading the die cavity with a predetermined amount of a powdered metal material;
compacting the powdered metal material in the die cavity between the upper punch assembly and the lower punch assembly, wherein one of the die, the upper punch assembly and the gear tooth compacting portion is non-rotatable about the central axis when the powdered metal material is compacted in the die, and wherein the other two of the die, the upper punch assembly and the gear tooth compacting portion are rotatable about the central axis when the powdered metal material is compacted in the die.
5. The method of claim 4 , wherein a plurality of circumferential grooves are formed into an axial end of the helical sector gear when the powdered metal material is compacted in the die.
6. The method of claim 5 , wherein the upper punch assembly and the die are the other two of the die, the upper punch assembly and the gear tooth compacting portion that are rotatable about the central axis.