| 摘要 |
PROBLEM TO BE SOLVED: To provide an injection molded plastic gear capable of securing enhanced rigidity by which smooth power transmission is achieved and capable of fully meeting recent requirements for reducing noise. SOLUTION: A cavity part 7 for reducing a thickness of a tooth 2 is formed on both ends of the tooth 2 along a tooth width direction over a predetermined depth L1 from side surfaces 5 and 6 of the tooth 2 to the tooth width direction. A tooth thickness of a part wherein the cavity part 7 is formed is made thicker than a tooth thickness of a part wherein the cavity part 7 is not formed by a shrinkage differenceδafter injection molding. At initial engagement with a counterpart gear, the injection molded plastic gear 1 is softly deformed and absorbs impact when the part wherein the cavity part 7 is formed is engaged with the counterpart gear so that generation of the noise is reduced. When the tooth 2 of the injection molded plastic gear 1 deforms to an extent by which the tooth thickness of the part wherein the cavity part 7 is formed is equal to the tooth thickness of the part wherein the cavity part 7 is not formed, the rigid part wherein the cavity part 7 is not formed transmits large rotational torque. |
