Plastic gear

A plastic gear comprising:

• a gear peripheral portion made of plastic, including gear teeth;
• and
• an inner circumferential member with an annular shape or a disk shape, positioned at an inner circumferential side of the gear peripheral portion,
• wherein the gear peripheral portion includes an inner core having inner tooth portions corresponding to respective gear teeth, and a surface layer member covering the inner core and having obverse tooth portions which cover respective inner tooth portions, wherein the inner core and the surface layer member are made of plastic, the plastic of the inner core having a higher elastic modulus and strength than the plastic of the surface layer member, in which the inner core is fitted and slidably engaged around a periphery portion of the inner circumferential member so that the periphery portion extends over the entire periphery of the inner circumferential member with an even cross sectional shape so as to allow relative displacement of the inner core in the circumferential direction thereof, and an engaging portion is provided at an interface between a lateral layer portion of the surface layer member and the inner circumferential member so as to prevent relative displacement in the circumferential direction thereof.