| 摘要 |
PROBLEM TO BE SOLVED: To provide a fixing device low in cost and capable of preventiing the strength of a drive gear from being reduced. SOLUTION: Many projections 94 and recessions 96 are alternately formed on the part other than a projecting part 92 of a inner circumferential surface of the drive gear 90. The profile of a projection 94 is trapezoidal, and spreads from the upper base (top surface part) 94a toward the bottom base. The top surface part 94a is a contact surface (engagement surface) M in contact with the outer circumferential surface of a fixing roller 50. The width W of the top surface part 94a is approximately a half of a distance L between the center lines (center lines of teeth) of teeth 91 adjacent to each other. Therefore, the contact area of the driving gear in contact with the outer circumferential surface of the fixing roller 500 is a half compared with the case that lots of the convexes 94 and the concaves 96 are not present. Moreover, the convexes 94 are formed on the rear side between a tooth 91 and a tooth 91 (tooth bottom 91a) adjacent to each other. The profile of a recession 96 is circular and formed behind each tooth 91. COPYRIGHT: (C)2004,JPO&NCIPI
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