Multi-stage helical gear manufacturing apparatus and multi-stage helical gear manufacturing method

A multi-stage helical gear manufacturing method for manufacturing a multi-stage helical gear including a first gear and a second gear arranged on a same axis, wherein

• the multi-stage helical gear includes a center hole extending along a center line of the first gear and the second gear,
• a linear spline extending along the center line is formed on an inner circumferential surface of the center hole,
• first helical teeth are formed on an outer circumferential surface of the first gear,
• second helical teeth are formed on an outer circumferential surface of the second gear, the second helical teeth having an inclination different from that of the first helical teeth of the first gear,
• the multi-stage helical gear manufacturing method comprises:
• injecting a plastic into a cavity between a first mold member and a second mold member when the first mold member and the second mold member are clamped;
• and
• after the injecting the plastic into the cavity, taking out the multi-stage helical gear formed of the plastic when the first mold member and the second mold member are opened,
• the first mold member rotatably supports a first gear rotation core for forming the first gear and the first helical teeth,
• the first mold member supports a sleeve pin for forming the center hole and the spline, the sleeve pin being permitted to advance and retreat in directions approaching and separating from the second mold member,
• the second mold member rotatably supports a second gear rotation insert for forming the second gear and the second helical teeth,
• the second mold member supports an insert pin inserted into the second gear rotation insert, the insert pin being permitted to advance and retreat in directions approaching and separating from the first mold member in relation to the second gear rotation insert,
• the cavity is formed between the first mold member and the second mold member by the first gear rotation core, the sleeve pin, the second gear rotation insert, and the insert pin at a time of mold clamping,
• when advancing in relation to the second gear rotation insert at the time of mold clamping, the insert pin prohibits the second gear rotation insert from rotating relative to the second mold member,
• when retreating in relation to the second gear rotation insert at a time of mold opening, the insert pin permits the second gear rotation insert to rotate relative to the second mold member, and
• the multi-stage helical gear manufacturing method further comprises:
• when the first mold member and the second mold member are opened, causing the insert pin to retreat in relation to the second gear rotation insert, thereby permitting the second gear rotation insert to rotate relative to the second mold member;
• moving the insert pin, which has been caused to retreat in relation to the second gear rotation insert, and the second gear rotation insert, which is permitted to rotate relative to the second mold member by the retreat of the insert pin, away from the first mold member;
• and
• after the moving the insert pin and the second gear rotation insert, permitting rotation of the first gear rotation core relative to the first mold member, which has been prohibited at the time of mold clamping, and causing the sleeve pin to advance toward the second mold member in relation to the plastic after the insert pin and the second gear rotation insert are separated from the plastic by the movement.