JPH11223970A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device so as to correctly stop a multicolor developing unit of a rotary type at a desired rotating position for a photoreceptor drum. SOLUTION: A sliding bearing 41, made of a resin, comprising a large- diameter part 41a and a small-diameter part 41b is fixed at one end of a rotary shaft 55 of a multicolor developing unit 5 and by inserting the small diameter part 41b into a shaft hole 73 opened in a device frame 70, the rotary shaft 55 is freely rotatably supported in the state that the displacement of it in the direction of the other end is restricted by the large-diameter part 41a. The other end of the rotary shaft 55 is freely rotatably supported with a rotary knob 80 incorporating an elastic support tool which always draws the rotary shaft 55 toward the other end direction by the elastic force of a spring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer, a copying machine or a facsimile apparatus for forming a toner image on recording paper, and more particularly to an electrostatic latent image formed on a photosensitive drum. Using a rotary developing unit provided with a plurality of developing units.

[0002]

2. Description of the Related Art An electrophotographic full-color image forming apparatus is equipped with three developing devices each filled with a developer of three primary colors, or four developing devices further filled with a black developer. Then, these are arranged to face one or a plurality of photosensitive drums, and an electrostatic latent image is visualized with a plurality of colors of developer and superimposed to form an image.

In general, when importance is attached to downsizing and cost reduction of an apparatus, a configuration is adopted in which a plurality of developing units are sequentially arranged facing one photosensitive drum. For this reason, as shown in FIG. 5, a rotary multi-color developing unit 5 holding four developing units 5a to 5d is arranged near one photosensitive drum 1, and the multi-color developing unit 5 is rotated. By doing so, an image forming apparatus has been proposed in which each developing unit is sequentially moved to a position facing the photosensitive drum 1, and each developer sequentially visualizes an electrostatic latent image.

The rotary multicolor developing unit 5 includes a helical gear 50 fixed coaxially with a rotation shaft 55 thereof.
As shown in FIG. 6, a helical gear 60 fixed to a rotating shaft 65 of the step motor 6 is engaged with the helical gear 50. When a desired developing device is arranged to face the photosensitive drum 1, a predetermined number of pulses are supplied to the step motor 6 to rotate the multicolor developing unit 5 to a predetermined rotation position.

FIG. 7 is a view showing a method of supporting the multicolor developing unit 5 on the apparatus frame 70. The developing unit 5 has both ends of a rotating shaft 55 rotatably supported by the apparatus frame 70. I have. The position of the multicolor developing unit 5 in the axial direction is determined by a stop ring 7 such as an E-ring.
1 is fixed by fitting it to the rotating shaft 55.

[0006]

FIGS. 8 and 9 are schematic views showing the engagement between the helical gear 50 of the multicolor developing unit 5 and the helical gear 60 of the step motor 6 in a plan view. When the stepping motor 6 is driven to rotate the multi-color developing unit 5, as shown in FIG. 8, each of the helical gears 50 and 60 is composed of the helical gear 60 (step motor) and the helical gear 50a. The bosses 50a of the color developing unit) are engaged so as to be pushed in the rotation direction.

The stepping motor 6 includes a multicolor developing unit 5
Is stopped when it reaches a desired rotation position, but does not stop immediately because inertial force acts on the multicolor developing unit 5 in the rotation direction. For this reason, when the stepping motor 6 is stopped, as shown in FIG.
Of the helical gear 60 pushes the helical gear 60a of the helical gear 60 in the rotational direction by the inertia force.

At this time, the helical gear 50 of the helical gear 50
a, an inertial force W acts in the rotation direction, and
a, the contact surface of 60a is smooth.
, A normal force N acts from the contact surface. Therefore, the resultant force F acts on the helical gear 50 to the left in the rotational direction in parallel with the contact surface.

As described above, the displacement of the multicolor developing unit 5 in the axial direction is restricted by the stop ring 71 fitted to the rotating shaft 55. However, due to play and dimensional tolerance, the displacement can be completely reduced. Cannot be set to "0". Therefore, when the resultant force F is generated, the helical gear 50 is displaced in the left direction parallel to the contact surface, that is, in the direction of arrow B in FIG. At this time, if the amount of movement of the rotation shaft 55 along the contact surface is L and the torsion angle of the boss is θ, L is
・ It will advance further by sin θ. For this reason, the contact position of the developing device with respect to the photosensitive drum 1 is L · s
There has been a problem that the image is shifted by inθ, causing uneven development and a change in density.

Incidentally, in order to solve such a problem, the rotating shaft 55 of the multicolor developing unit 5 is attached to the apparatus frame 7.
Although it is sufficient that the positioning and fixing are accurately performed with respect to zero, an adjustment work or the like is required after assembly, which causes a new problem that the manufacturing process becomes complicated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an image forming apparatus capable of accurately stopping a rotary multicolor developing unit at a desired rotational position without performing an adjustment operation or the like. It is to provide a device.

[0012]

In order to achieve the above object, according to the present invention, there is provided a rotary type developing unit for holding a plurality of developing units concentrically about a rotation axis, wherein each of the developing units is a photosensitive unit. In an image forming apparatus for controlling rotation so as to be opposed to a body drum at a predetermined position, a first helical gear fixed coaxially with a rotation axis of the developing unit engages with the first helical gear. A second helical gear, a motor for rotating the second helical gear, and a rotational shaft are elastically prevented from being displaced in one end direction and fixedly prevented from being displaced in the other end direction. And a supporting means for rotatably supporting the supporting member.

According to the above arrangement, when the rotating shaft of the developing unit is rotatably supported, even if there is a play in the axial direction, the displacement of the rotating shaft in the other end direction is completely prevented, and the rotating shaft of the developing unit is moved in one end direction. Is also prevented unless a large force exceeding the elastic force is applied. Therefore, it is possible to prevent the rotation of the rotating shaft in the axial direction without performing an adjustment operation or the like for reducing the play of the rotating shaft, and as a result, the multicolor developing unit can be accurately stopped at a desired rotating position. Become.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration of a main part of a full color printer to which the present invention is applied. The color printer of the present embodiment primarily transfers the unfixed toner image formed on the photosensitive drum 1 to a belt-shaped intermediate transfer member 9 stretched by rolls 10, 11, 12, and 13, and The unfixed toner image is configured to be secondarily transferred from the intermediate transfer belt 9 to recording paper on the conveyance path 21 again. Around the photoreceptor drum 1, a charging roll 3, an exposing device 4, a multicolor developing unit 5, a transfer roll 7, a cleaner device 8, and the like are arranged. The roll 10 is coupled to a drive source (not shown) and functions as a drive roll that drives the belt 9.

The photosensitive drum 1 is driven to rotate at a constant speed in the direction of arrow 2 by a main motor (not shown). The surface of the photosensitive drum 1 is uniformly charged by a charging roll 3 and then exposed by an exposure device 4. An electrostatic latent image is formed. This electrostatic latent image is developed by a rotary multicolor developing unit 5. The multicolor developing unit 5 includes four developing units 5Y to 5C corresponding to respective colors of yellow (Y), magenta (M), cyan (C) and black (K), and is formed on the photosensitive drum 1. If the electrostatic latent image corresponds to the yellow image information, the developing unit 5 </ b> Y containing the yellow (Y) toner is aligned and developed so as to be in contact with the photosensitive drum 1, and is developed. A yellow toner image is formed thereon. The unfixed yellow toner image formed on the photoconductor drum 1 is transferred to the surface of the intermediate transfer belt 9 by the transfer roll 7 at a primary transfer position where the photoconductor drum 1 and the intermediate transfer belt 9 are in contact.

In the case of forming a single-color image, the unfixed toner image primarily transferred to the intermediate transfer belt 9 is secondarily transferred to paper immediately, but in the case of forming a full-color image in which a plurality of color toner images are superimposed. The formation of the toner image on the photosensitive drum 1 and the primary transfer of the toner image to the intermediate transfer belt 9 are repeated by the number of colors. When a full-color image is formed by superimposing four color toner images as in the present embodiment, unfixed yellow, magenta, cyan, and black toner images are formed on the photosensitive drum 1 every one rotation thereof. The unfixed toner images are sequentially primary-transferred onto the intermediate transfer belt 9 in order.

On the other hand, the intermediate transfer belt 9 rotates at the same cycle as the photosensitive drum 1 while holding the yellow first-transferred unfixed toner image. The magenta, cyan, and black unfixed toner images are transferred and superimposed on the yellow unfixed toner image every one rotation.

The unfixed toner image primary-transferred onto the intermediate transfer belt 9 in this manner is conveyed to a secondary transfer position facing the conveyance path 21 as the belt 9 rotates. At the secondary transfer position, the secondary transfer roll 14 is in contact with the intermediate transfer body belt 9, and the paper carried out of the paper trays 16 and 17 by the feed rollers 18 and 19 at a predetermined timing is in contact with the secondary transfer roll 14. It is sandwiched between the intermediate transfer belt 9.

At this secondary transfer position, a backup roll 12 is provided at a position facing the transfer roll 14, and a reverse polarity between the transfer roll 14 and the intermediate transfer belt 9, which has a polarity opposite to that of the toner. When a voltage is applied, the unfixed toner images for the four colors carried on the intermediate transfer belt 9 are electrostatically transferred to paper. The paper on which the toner images of four colors are formed is conveyed to the fixing device 23 and fixed.

FIG. 2 shows a multicolor developing unit 5 according to the present invention.
7A and 7B are views showing a method of supporting the device frame 70 on the device frame 70, and the same reference numerals as those described above denote the same or equivalent parts.

At one end (left side in the figure) of the rotating shaft 55 of the multicolor developing unit 5, for example, a large diameter portion 41a and a small diameter portion 4 are provided.
A resin slidable bearing 41 made of 1b is fixed, and by inserting the small-diameter portion 41b into a shaft hole 73 opened in the device frame 70, the rotating shaft 55 moves in the other end direction (right side in the figure). Is rotatably supported in a state in which the displacement to is restricted by the large diameter portion 41a. The other end of the rotating shaft 55 is rotatably supported on the apparatus frame 70 by a rotating knob 80 having a built-in elastic support for attracting the rotating shaft 55 toward the other end by the elastic force of a spring.

FIG. 3 is a sectional view of a rotary knob 80 having the elastic support therein, and FIG. 4 is an assembly view showing the configuration thereof.

The rotary knob 80 according to the present embodiment is provided so as to cover the screw member 81 and a screw member 81 fitted and fixed to the other end of the rotary shaft 55 of the multicolor developing unit 5. A cap-shaped grip 83, a ring-shaped plate 87 screwed to the open end side of the grip 83, and the screw member 81 inserted through the outer peripheral portion of the outer cylindrical portion 81 a of the screw member 81. A spring 85 for elastically pressing the plate member 87 against the grip portion 83 side, and a slidable bearing 84 inserted through the outer peripheral portion of the inner cylindrical portion 81b of the screw member 81 to the screw member 81. A spring 86 that elastically presses against the plate 87 and a resin support cap that is inserted through the shaft hole 73 of the device frame 70 and rotatably supports the slidable bearing 84. It is constituted by a 82.

In the shaft hole 81d of the screw member 81, a claw portion 81c engaged with a groove 52 provided at an end of the rotating shaft 55 elastically protrudes. Therefore, when the rotating shaft 55 of the multicolor developing unit 5 is inserted into the shaft hole 81d of the screw member 81, as shown in FIG.
The claw portion 81c engages with the groove 52 of the fifth member, and the screw member 81
Are fixed to the rotation shaft 55.

A plurality of projections 81e are formed coaxially with the shaft hole 81d on the end face of the screw member 81 on the grip portion 83 side, and inside the grip portion 83 are engaged with the projections 81e. A projection 83e that forms a clutch mechanism together with the spring 85 is formed. With this clutch mechanism,
If the grip 83 is manually turned in the direction of the arrow, the rotary shaft 55 can also be rotated in the same direction. If the grip 83 is rotated in the direction opposite to the arrow, the grip 83 can be rotated without rotating the rotary shaft 55. Only one can be reversed.

On the other hand, the screw member 81 is
6, the rotating shaft 55 of the multicolor developing unit 5 is constantly attracted toward the other end (right side in the figure) by the elastic force of the spring 86. become. Further, at one end of the rotating shaft 55, the large-diameter portion 41a of the slidable bearing 41 is fixedly prevented from displacing in the other end direction. It is always held at the limit position on the right side in the figure determined by the position by the elastic force of the spring 86.

Therefore, when the rotary shaft 55 of the multicolor developing unit 5 is rotatably supported with respect to the apparatus frame 70, even if there is play in the axial direction, the displacement of the rotary shaft 55 in the other end direction is slid. It is completely prevented by the dynamic bearing 41, and the displacement in one end direction is also completely prevented unless a large force exceeding the elastic force by the rotary knob 80 is applied. Therefore, the rotation of the rotating shaft 55 in the axial direction can be prevented without performing an adjusting operation or the like for reducing the play of the rotating shaft 55, and as a result, the multicolor developing unit 5 can be accurately stopped at a desired rotating position. become able to.

In the above embodiment, the rotation shaft 55
Is rotatably supported by the slidable bearing 41 so that displacement in the other end direction is fixedly prevented, and the other end of the rotating shaft 55 is always provided with the rotating shaft 55 at the other end. Although it has been described as being supported by an elastic support tool (rotary knob 80) that is attracted in the direction by the elastic force of the spring, on the contrary, one end of the rotary shaft 55 is fixedly displaced in the one end direction. The rotating shaft 55 may be rotatably supported so as to be prevented, and may be rotatably supported on the other end of the rotating shaft 55 by an elastic support that constantly presses the rotating shaft 55 toward one end by the elastic force of a spring. good.

[0029]

According to the present invention, the following effects are achieved. (1) When the rotating shaft of the developing unit is rotatably supported, even if there is play in the axial direction, the displacement of the rotating shaft in one end direction is fixedly prevented, and the displacement in the other end direction is also supported. It is completely prevented unless a large force exceeding the elastic force of the elastic means of the means is applied. Therefore, it is possible to prevent the rotation of the rotating shaft in the axial direction without performing an adjustment operation or the like for reducing the play of the rotating shaft, and as a result, the multicolor developing unit can be accurately stopped at a desired rotating position. Become. (2) Since the elasticity indicator is provided in the rotary knob, the multicolor developing unit can be stopped accurately at a desired rotational position without increasing the size of the apparatus.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a main part of a full color printer to which the present invention is applied.

FIG. 2 is a view showing a method for supporting a multicolor developing unit according to the present invention.

FIG. 3 is a sectional view of a rotary knob according to an embodiment of the present invention.

FIG. 4 is an assembly view of a rotary knob according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating an operation of the multicolor developing unit.

FIG. 6 is a perspective view illustrating a configuration of a drive system of the developing unit.

FIG. 7 is a diagram illustrating a method of supporting a multicolor developing unit according to the related art.

FIG. 8 is a schematic plan view of the engagement between the helical gear of the multicolor developing unit and the helical gear of the step motor during rotation.

FIG. 9 is a schematic plan view illustrating an engagement state between the helical gear of the multicolor developing unit and the helical gear of the step motor immediately after the rotation is stopped.

[Description of Signs] 1 ... Photoreceptor drum, 5 ... Rotary developing unit, 6 ... Step motor, 50 ... Helix gear of rotary developing unit,
55: rotating shaft of rotary developing unit, 60: helical gear of step motor, 65: rotating shaft of step motor, 7
0: device frame, 80: rotary knob, 81: screw member, 82: support cap, 83: grip, 84: slidable bearing, 85, 86: spring, 87: ring-shaped plate

Claims (4)

[Claims] 1. An image forming apparatus comprising: a rotary developing unit that concentrically holds a plurality of developing units around a rotation axis such that each of the developing units is opposed to a photosensitive drum at a predetermined position; In the apparatus, a first helical gear fixed coaxially with a rotation axis of the developing unit, a second helical gear engaged with the first helical gear, and rotationally driving the second helical gear A motor, and supporting means for rotatably supporting the rotating shaft of the developing unit such that displacement in one end thereof is elastically prevented and displacement in the other end is fixedly prevented. An image forming apparatus comprising: 2. The support means comprises: a fixed support for fixedly blocking one end of the rotary shaft in the axial direction so as to prevent displacement in the other end direction; and the other end of the rotary shaft. The image forming apparatus according to claim 1, further comprising: an elastic support that supports the rotation shaft so as to be elastically attracted to the other end. 3. The support means comprises: a fixed support for fixedly blocking one end of the rotary shaft in the axial direction so as to prevent displacement in one end direction; and the other end of the rotary shaft. The image forming apparatus according to claim 1, further comprising: an elastic support that supports the rotation shaft so that the rotation shaft is elastically pressed toward the one end. 4. The image forming apparatus according to claim 1, wherein the elastic support is provided in a grip member for manually turning the developing unit.