| 摘要 |
PURPOSE: To provide a gear made of a thermoplastic resin suppressed in shrinkage, enhanced in mold transfer properties, reduced in error as an involute gear and having good accuracy. CONSTITUTION: In a gear made of a thermoplastic resin having a hollow part therein, at least one partition wall 6 is provided in the gear and the min. thickness thereof is 0.5-5mm. In the hollow injection molding of the gear, a mold having a structure capable of expanding the vol. in a mold cavity 7 is used and the expansion of the vol. in the cavity 7 is started simultaneously with the start of the injection of a pressure fluid or before 10sec is elapsed after the completion of injection and the pressure of the pressure fluid in a molded product is held for 5-90sec in such a state that expansion is completed. |
