Forging device for crown-shaped helical gear

A forging device for forming a crown-shaped helical gear comprising:

• a die holder having an axially central part bore diminishing in diameter from one end thereof to the other end thereof defining a tapered surface,
• a finishing die fitted for axial sliding in the axial direction in the axially central part of the die holder, the finishing die having a corresponding tapered surface engaging the tapered surface of the central part bore,
• twist forming teeth formed on the inside circumferential surface of the finishing die for forming a crown-shaped helical gear with the thickness of each tooth being thinner in a middle part than toward both ends in an axial direction of the die, wherein a half-finished work having an outside circumferential surface with rough-formed twist teeth is brought into screw engagement with the twist forming teeth of the finishing die,
• a first punch for axially pressing the half-finished work,
• a second punch for axially pressing the finishing die, and
• a rotary device rotating the die holder in a direction opposite a direction in which the half-finished work is rotated with the finishing die when the first and second punches respectively press the half-finished work to form the crown-shaped helical gear,
• wherein a taper angle of the tapered surface of the die holder is slightly smaller than a taper angle of the corresponding tapered surface of the finishing die.

A forging device for forming a crown-shaped helical gear comprising:

• a die holder having an axially central part bore diminishing in diameter from one end thereof to the other end thereof defining a tapered surface,
• a finishing die fitted for axial sliding in the axial direction in the axially central part of the die holder, the finishing die having a corresponding tapered surface engaging the tapered surface of the central part bore,
• twist forming teeth formed on the inside circumferential surface of the finishing die for forming a crown-shaped helical gear with the thickness of each tooth being thinner in a middle part than toward both ends in an axial direction of the die, wherein a half-finished work having an outside circumferential surface with rough-formed twist teeth is brought into screw engagement with the twist forming teeth of the finishing die,
• a first punch for axially pressing the half-finished work,
• a second punch for axially pressing the finishing die, and
• a rotary device rotating the die holder in a direction opposite a direction in which the half-finished work is rotated with the finishing die when the first and second punches respectively press the half-finished work to form the crown-shaped helical gear,
• wherein a taper angle of the tapered surface of the die holder is slightly smaller toward a smaller diameter end of the central part bore than a taper angle of the corresponding tapered surface of the finishing die, and the taper angle of the tapered surface of the die holder is slightly larger toward a large diameter end of the central part bore than the taper angle of the corresponding tapered surface of the finishing die.