JPH0745095Y2 - Image forming drum - Google Patents

Description

TECHNICAL FIELD The present invention relates to an image forming drum used in an electrophotographic apparatus.

2. Description of the Related Art Conventionally, as shown in FIG. 3, an image forming drum in which a flange 20 is press-fitted into a metal cylindrical drum body 1 and a gear 21 is fixed to an end surface of the flange 20 by a plurality of screws 22. There is. The flange 20 is formed of a conductive aluminum die cast for grounding the drum body 1, while the gear 22 is formed of a synthetic resin for cost reduction, weight reduction, reduction of rotation transmission sound, and the like. Further, as shown in FIG. 4, in order to fix the flange 20 and the gear 21, there is a method of press-fitting a boss 23 formed in the center of the flange 20 into a hole 24 formed in the center of the gear 21.

The problem to be solved by the present invention is shown in FIG. As a result, the rotational force of the motor is not accurately transmitted to the drum body 1 and a rotating drum is generated. Further, as shown in FIG. 4, in the method of press-fitting the flange 20 and the gear 21, one is made of metal and the other is made of synthetic resin, so that there is a difference in shrinkage rate with respect to temperature, which causes the press-fitted portion The bond strength is unstable.

Means for Solving the Problems A metal flange is press-fitted into the inner circumference of a metal cylindrical drum body, and gears made of elastic synthetic resin are coaxially arranged on the end surface of the flange. In the combined image forming drum, a fitting portion that fits with each other is formed at the center of the flange and the gear, and a plurality of holes are formed on the circumference centered on the fitting portion of the flange. , Having a detent protrusion that abuts on both side edges of the hole along the radial direction of the flange and is fitted into the hole and a claw protruding at the tip end in the radial direction of the flange, and is inserted into the hole A plurality of elastic locking pieces are integrally formed with the gear, and an inclined surface is formed at an engaging portion between the claw and the flange.

Action The fitting parts of the flange and the gear that are press-fitted into the drum body are fitted to each other, and the detent protrusion of the gear and the elastic locking piece are engaged with the hole of the flange, so that both use a tool. Easily combined without. In this case, the axial centers of the flange and the gear are accurately aligned by fitting the mating parts together, and the flanges are secured by the contact between the both side edges of the hole along the radial direction of the flange and the detent protrusion of the gear. The movement in the rotational direction with the gear is securely fixed, and the inclined portion is formed at the engaging portion between the claw of the elastic locking piece of the gear and the flange, so that the elastic locking piece bends to cause the claw and the flange to move. Always contact with each other, and the axial movement of the gear with respect to the flange is securely fixed.

Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 and 2. Reference numeral 1 is a cylindrical drum body, and 2 is a flange made of aluminum die cast. A fitting portion 3 that is press-fitted into the inner circumference of the drum body 1, an expanding portion 4 that expands from one end of the fitting portion 3, and a bush 6a that rotatably holds a support shaft 5 are attached to the flange 2. A hub 6 to which is mounted, three holes 7 and one hole 8 arranged in a radial direction, and a fitting portion 10 located at an end portion of the hub 6 are formed. Reference numeral 9 denotes a gear made of elastic synthetic resin. The gear 9 has a fitting hole 11 which is a fitting portion fitted to the fitting portion 10 of the flange 2.
Three elastic locking pieces 12 inserted into the hole 7 and a rotation preventing projection 13 engaged with the hole 8 are integrally formed. A claw 14 is integrally formed at the tip of each of these elastic locking pieces 12 so as to project outward (or inside) in the radial direction of the flange 2. An inclined surface 14a is formed at the base of each of the claws 14 and is inclined outward in the radial direction toward the tip of the claw 14. Further, the width of the anti-rotation protrusion 13 in the circumferential direction of the gear 9 is narrower than the width of the hole 8 in the circumferential direction of the flange 2 of the hole 8, but the width of the intermediate portion is the width of the hole 8. Wider than. That is, both sides of the anti-rotation protrusion 13 are formed in a taper shape from the intermediate portion toward the tip, and a slit 15 is formed at the center to allow the inward bending motion of the anti-rotation protrusion 13. .

When the flange 2 is formed of aluminum die cast, the dimensional accuracy is slightly deteriorated. Therefore, the outer circumference of the fitting portion 3 and the fitting portion of the flange 2 fitted in the fitting hole 11 of the gear 9 are fitted.
10, etc. should be finished by cutting. Further, as shown in FIG. 2, the end surface 16 of the flange 2 and the inner peripheral surface 17 orthogonal to the end surface 16 are cut to form an end surface.
A sharp edge 18 is formed at the intersection of 16 and the inner peripheral surface 17. Further, the flange 2 may be formed by zinc die casting or precision forging. Furthermore, the elastic locking piece 12
It is good to use a part of the as a rotation stop protrusion.

With such a configuration, when assembling, the fitting portion 3 of the flange 2 is press-fitted into the inner circumference of the drum body 1, and then the fitting portion 10 of the flange 2 and the fitting hole 11 of the gear 9 are fitted together. In addition, the detent 13 of the gear 9 is attached to the hole 8 of the flange 2.
The elastic locking piece 12 is inserted into the hole 7 while being fitted into. At this time, since the anti-rotation protrusion 13 is tapered on both sides, it can be easily engaged with the hole 8. Further, since the claw 14 receives resistance from the inner surface of the hole 7, the elastic locking piece 12 elastically flexes inward, but when the claw 14 passes through the hole 7, it returns outward due to its elasticity. The claw 14 is the end surface 16 of the flange 2.
Elastically engages.

In this way, the drum body 1, the flange 2, and the gear 9 are extremely easily coupled without using a tool. Further, since the difference in shrinkage ratio between the metal drum main body 1 and the flange 2 due to temperature is small, the dimensions of the inner diameter of the drum main body 1 and the outer shape of the engaging portion 3 of the flange 2 are stable. Be combined with. Further, the flange 2 and the gear 9 have their axes aligned with each other by fitting the fitting portion 10 and the fitting hole 11 to each other.
The anti-rotation protrusion 13 bends while narrowing the slit 15 and elastically engages with the hole 8 of the flange 2, whereby the rotational movements of the both are securely fixed, and the slanted surface 14a of the claw 14 is When the edge 18 formed on the end face 16 of the flange 2 is engaged, the inclined surface 14a and the edge 18 of the end face 16 of the flange 2 are always brought into contact with each other due to the bending motion of the elastic locking piece 12, whereby the flange The axial movement of the gear 9 with respect to 2 is reliably fixed.

Alternatively, the flange 2 may be formed with an inclined surface that intersects with the end surface 16 thereof, and an edge that abuts this inclined surface may be formed on the claw 14.

EFFECTS OF THE INVENTION Since the present invention is configured as described above, the fitting portions of the flange and the gear that are press-fitted into the drum body are fitted to each other, and the rotation preventing protrusion of the gear and the elastic locking piece are inserted into the hole of the flange. By engaging with each other, it is possible to easily connect both without using a tool. In this case, by fitting the fitting parts together, the axis of the flange and the gear can be accurately aligned. The rotation of the flange and the gear in the rotational direction can be reliably fixed by the contact between both side edges of the hole along the radial direction of the flange and the detent protrusion of the gear. By forming the inclined surface in the engaging portion between the claw and the flange of the stop piece, the claw and the flange are always brought into contact with each other due to the bending operation of the elastic locking piece, and accordingly,
This has the effect of reliably fixing the movement of the gear in the axial direction with respect to the flange.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of the present invention, FIG. 2 is an enlarged vertical side view showing an assembled state thereof, and FIGS. 3 and 4 are exploded perspective views showing a conventional example. 1 ... Drum body, 2 ... Flange, 7,8 ... Hole, 9 ... Gear, 1
0,11 ... Fitting part, 12 ... Elastic locking piece, 13 ... Rotation stop protrusion, 14
… Nail, 14a… Sloping surface

Claims (1)

[Scope of utility model registration request] 1. A metal flange is press-fitted into the inner circumference of a metal cylindrical drum main body, and gears made of elastic synthetic resin are coaxially arranged and joined to the end surface of the flange. In the image forming drum, the fitting portion that fits with each other is formed at the center of the flange and the gear, and a plurality of holes are formed on the circumference centered on the fitting portion of the flange, and the flange is formed. A plurality of elastic members that are inserted into the hole by contacting both side edges of the hole along the radial direction of the hole and having a detent projection that is fitted into the hole and a claw protruding at the tip in the radial direction of the flange. An image forming drum, wherein an engaging piece is integrally formed with the gear, and an inclined surface is formed at an engaging portion between the claw and the flange.