| 摘要 |
PROBLEM TO BE SOLVED: To surely couple a photoreceptor drum and a driving gear for driving the photoreceptor drum and to release the coupling by using a coupling by setting the relation of the backlash amount of a driving side coupling to a specified value. SOLUTION: A coupling shaft 18 slides to the photoreceptor drum 7 side while rotating on the small-diameter shaft part of a stepped caulking shaft along a gear side coupling recess 21 having the twisted shape of the almost regular triangle of a drum driving gear 22. As a result, a coupling shaft recess 17 and a drum shaft protrusion 16 are coupled. The relation between the diameterϕD1 of the inscribed circle of the hole of the recess 17 and the diameterϕD2 of the inscribed circle of the protrusion 16 is shown by (ϕD3-ϕD4)<=(ϕD1-ϕD2), that is, a difference (ϕD1-ϕD2) between the diameters of the above inscribed circles is set to be larger than or equal to a difference (ϕD3-ϕD4) between the diameterϕD3 of the inscribed circle of the hole of the recess 21 and the diameterϕD4 of the inscribed circle of a coupling shaft protrusion 20. |
