JP2000147853A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain maximum banding improvement effect with minimum inertia by stabilizing unevenness of rotation in not only an image carrier but also in an intermediate transfer body as well with a simple construction and improving banding and by efficiently stabilizing any unevenness in the simultaneous rotation of the image carrier and the intermediate transfer body. SOLUTION: This color image forming device is provided with flywheels 70 and 69 respectively in a drive shaft 68 of the image carrier and a drive shaft 64 of the intermediate transfer body. In order to make the inertia of the flywheel 70 provided in the drive shaft 68 of the image carrier greater than the inertia of the flywheel 69 provided on the drive shaft 64 of the intermediate transfer body, the former diameter is made greater than the latter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus which stabilizes the rotation of an image carrier and an intermediate transfer member, and is applicable to a laser beam printer, a digital copying machine, a plain paper facsimile, and the like. .

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. Hei 9-171327 discloses an image forming apparatus using a flywheel for stabilizing rotation unevenness of an image carrier. It is fixed to a wheel shaft different from the drum shaft, and the rotation of the motor is transmitted to the drum shaft of the photosensitive drum via a gear mechanism, and the rotation of the drum shaft is transmitted via a large-diameter pulley, an endless belt, and a small pulley. There is disclosed an image forming apparatus in which the angular velocity of the flywheel is transmitted to the wheel shaft to make the angular velocity of the flywheel larger than the angular velocity of the drum shaft.

[0003]

However, according to this, a wheel shaft is provided separately from the drum shaft of the photosensitive drum, and rotation of the drum shaft is transmitted to the wheel shaft via a large-diameter pulley, an endless belt, and a small pulley. Although it only stabilizes the rotation unevenness of the photoconductor drum,
The structure is too complicated.

A first object of the present invention is to improve banding in a color image forming apparatus by stabilizing the rotation unevenness of not only an image carrier but also an intermediate transfer member with a simple structure. The second object is to make it possible to efficiently stabilize rotation unevenness due to simultaneous rotation of the image carrier and the intermediate transfer member, and to obtain the maximum banding improvement effect with minimum inertia. .

[0005]

The invention according to claim 1 is
In order to achieve the first object, in a color image forming apparatus having an image carrier and an intermediate transfer body in an apparatus main body and having a drive unit for driving these with a common motor, a drive shaft of the image carrier and an intermediate A flywheel is provided on each drive shaft of the transfer body.

According to a second aspect of the present invention, in order to achieve the second object, in the above structure, the drive shaft of the image carrier is provided rather than the inertia of the flywheel provided on the drive shaft of the intermediate transfer member. The inertia of the flywheel is increased.

[0007]

Next, embodiments of the present invention will be described in detail with reference to the drawings. 1 and 2 are schematic central sectional views of a color image forming apparatus to which the present invention is applied. FIG. 1 shows a state in which a front frame is closed, and FIG. 2 shows a state in which it is opened.

The belt-shaped photosensitive member 1 serving as an image carrier is rotatably supported by rotating rollers 2 and 3 and circulated in the direction of arrow A. A charging unit 4, a discharge lamp 5, and a cleaning unit 1 for cleaning the photoconductor 1 are provided on an outer peripheral portion of the photoconductor 1.
5 are arranged. At a position downstream of the charging device 4, there is an optical writing unit to which the laser light L emitted from the laser writing unit LW is irradiated. At a position downstream of the optical writing unit, a multicolor developing device 6 in which a plurality of developing units are supported so as to be switchable is arranged. Multicolor developing device 6
Has a yellow developing unit, a magenta developing unit, and a cyan developing unit for each of the three colors of toner to be accommodated. Above the multicolor developing device 6, a black developing unit containing black toner is provided. One of these developing units is moved to a position where development with respect to the photoconductor 1 is possible in synchronization with a corresponding developing timing.

In this embodiment, the multi-color developing device 6 has a mechanism for selecting the three-color developing units by rotating 120 degrees on the circumference. When these developing units operate, the black developing unit moves to a position separated from the photoconductor 1. The movement is controlled, for example, by rotation of a cam.

Although not shown, in the laser writing unit LW, the light from the laser light source is scanned by a polygon mirror rotated by a motor, and fθ
After passing through a lens, a mirror and the like, the writing light L reaches the photoconductor 1 and forms a latent image (toner image) corresponding to the written information on the photoconductor 1 charged by the charging device 4.

The latent image on the photoreceptor 1 is developed by the above-mentioned developing device, and a visible image by toner is formed and held on the surface of the photoreceptor. The upper portion of the photoconductor 1 is in contact with an intermediate transfer belt 10 which is an intermediate transfer member.

The intermediate transfer belt 10 includes a rotating roller 11
12, it is rotatably supported and circulated in the direction of arrow B. The toner image on the photoreceptor 1 is transferred to the surface of the intermediate transfer belt 10 by bias means 13 on the back side of the intermediate transfer belt 10.

The photoreceptor 1 is cleaned for each color by a cleaning blade 15A of a cleaning unit 15, and a toner image of a predetermined color is sequentially formed on the photoreceptor 1, and each time the intermediate transfer belt 10 makes one rotation. Each time, the color toner image is transferred to the same position on the surface, and a color toner image in which several colors are overlapped on the intermediate transfer belt 10 is formed. Then, this color toner image is transferred to a recording medium such as paper or plastic.

At the time of transfer to paper, a paper 17A stored in a paper feeder (paper feed cassette) 17 passes through a paper feed roller 18, a pair of transport rollers 19A and 19B, and a pair of registration rollers 20A and 20B, and then intermediately. The paper and the image are conveyed to the nip between the transfer belt 10 and the transfer roller 14 at a timing such that the positions of the sheet and the image become normal. The sheet on which the toner images of several colors on the intermediate transfer belt 10 are collectively transferred by the action of the transfer roller 14 is sent to the fixing device 80, where the toner image on the sheet is fixed, and the discharge roller pair 81A
The sheet is discharged to the discharge stack section 82 at the top of the main body frame 9 by 81B.

On the outer periphery of the intermediate transfer belt 10, a cleaning device 16 for the intermediate transfer belt is
The cleaning blade 16A is configured to be able to freely contact and separate via a cleaning blade contacting / separating arm 16C. This cleaning blade 16A
In the process in which the intermediate transfer belt 10 receives the toner image from the photoreceptor 1, the intermediate transfer belt 10 is separated from the intermediate transfer belt 10, comes into contact with the toner image after being transferred from the intermediate transfer belt 10 to the paper, and remains after the transfer. Scrape off toner.

The waste toner scraped off from the intermediate transfer belt 10 is transported by an auger 16B provided inside the intermediate transfer belt cleaning device 16, and the cleaning unit 15 can be replaced by transport means (not shown). Is collected in a simple collection container 15C. In addition, the waste toner scraped from the photoconductor 1 by the cleaning blade 15A as described above is also collected in the collection container 15C.

The photosensitive member 1, the charging device 4, the intermediate transfer belt 10, the cleaning unit 15, the cleaning device 16, the transport guide 30 for forming the paper transport path, and the like are integrally unitized as a process cartridge 31. It can be replaced at the end of its life.

In addition to replacing the process cartridge 31, the multi-color developing device 6, the black developing unit, and the like are also replaced at the end of their service life. The front frame 8 is not shown in FIG. As shown in FIG. 2, the main frame 9 is pivotally supported by a support shaft 9A so that the main frame 9 can be opened.

An electric equipment / control device E is accommodated in a rear portion of the main body frame 9, and a fan for exhausting air is disposed above the electric device / control device E in order to prevent an excessive temperature rise in the device. Further, another relatively small-sized paper feeding device can be attached to the main body frame 9.

Next, the structure of the drive unit, which is a main part of the present invention, will be described with reference to FIG. An intermediate transfer drive shaft 64 for driving the intermediate transfer belt 10 of the process cartridge 31 shown in FIGS. 1 and 2 and an image carrier drive shaft 68 for rotating the photosensitive member 1
It is supported in parallel with the inner fixed plate 9B. When the process cartridge 31 is set at a predetermined position in the main body frame 9, the drive coupling 71 at one end of the intermediate transfer drive shaft 64 is connected to the coupling 72 of the intermediate transfer drive roller shaft 73 on the process cartridge 31 side. , Drive-side coupling 7 at one end of image carrier drive shaft 68
4 is connected to the coupling 75 of the image carrier driving roller shaft 76 on the process cartridge 31 side, and rotation is transmitted to the roller shafts 73 and 76 from the common motor 61 by the following mechanism.

That is, a large pulley 63A and a small pulley 63B integral therewith are fixed to the intermediate transfer drive shaft 64. A small pulley 66A and a gear 66B integral with the small pulley 66A are fixed to the relay shaft 77 supported by the fixing plate 9B. A gear 67 meshing with the gear 66B is fixed to the image carrier driving shaft 68. A pulley 65 is stretched between the small pulley 63B and the small pulley 66A.

Therefore, the rotation of the motor 61 is controlled by the belt 62
Is transmitted to the intermediate transfer drive shaft 64 by the large pulley 63A via the
The intermediate transfer belt 10 shown in FIGS. 1 and 2 is driven by being transmitted to an intermediate transfer drive roller shaft 73 via 72.

The belt 6 is moved from the intermediate transfer drive shaft 64 to the belt 6.
5, transmitted to the image carrier driving shaft 68 via the gears 66B and 67, and transmitted from the image carrier driving shaft 68 to the couplings 74.7
The photosensitive member 1 is transmitted to the image carrier driving roller shaft 76 via the driving member 5.

In the above configuration, the present invention provides:
In order to stabilize the rotation of the intermediate transfer belt 10 and the photoconductor 1, a flywheel 69 is fixed to the intermediate transfer drive shaft 64, and a flywheel 70 is fixed to the image carrier drive shaft 68, respectively. In order to make the inertia of the flywheel 70 of the image carrier driving shaft 68 larger than the inertia of the flywheel 69 of the intermediate transfer drive shaft 64, the latter flywheel 70 has a larger diameter than the former flywheel 69. Has become. By doing so, rotation unevenness due to simultaneous rotation of the intermediate transfer belt 10 and the photoconductor 1 can be efficiently stabilized.

FIG. 4 is a graph showing the frequency of uneven rotation of the intermediate transfer drive shaft 64 and the image carrier drive shaft 68 when neither the intermediate transfer drive shaft 64 nor the image carrier drive shaft 68 has a flywheel. is there.

FIG. 5 is a graph showing the frequency of rotation unevenness of the intermediate transfer drive shaft 64 and the image carrier drive shaft 68 when the flywheel 70 is attached only to the image carrier drive shaft 68.

FIG. 6 is a graph showing the frequency of uneven rotation of the intermediate transfer drive shaft 64 and the image carrier drive shaft 68 when the flywheel 69 is mounted only on the intermediate transfer drive shaft 64.

FIG. 7 shows the frequency of uneven rotation of the intermediate transfer drive shaft 64 and the image carrier drive shaft 68 when the flywheels 69 and 70 are attached to the intermediate transfer drive shaft 64 and the image carrier drive shaft 68, respectively. It is a graph shown.

By comparing these graphs, it can be seen that the frequency of rotation unevenness (frequency 15 Hz to 130 Hz which appears in the image) cannot be eliminated when only one of the intermediate transfer drive shaft 64 and the image carrier drive shaft 68 is fitted with a flywheel.
Hz) can be eliminated by attaching a flywheel to each of the two drive shafts.

[0030]

According to the first aspect of the present invention, only the flywheel is provided on each of the drive shaft of the image carrier and the drive shaft of the intermediate transfer member, so that not only the image carrier but also the rotation of the intermediate transfer member can be rotated. Since unevenness can be stabilized, banding can be easily improved.

According to the second aspect of the invention, the inertia of the flywheel provided on the drive shaft of the intermediate transfer member is larger than that of the flywheel.
Since the inertia of the flywheel provided on the drive shaft of the image carrier is increased, the rotation unevenness due to the simultaneous rotation of the image carrier and the intermediate transfer member is also stabilized efficiently, and the maximum inertia with the minimum inertia is achieved. An effect of improving banding can be obtained. When the thickness of the flywheel is minimized, the height of the machine body can be reduced by reducing the diameter of the flywheel provided on the drive shaft of the intermediate transfer body, thereby achieving compactness.

[Brief description of the drawings]

FIG. 1 is a schematic center sectional view of an example of a color image forming apparatus to which the present invention is applied, with a front frame closed.

FIG. 2 shows a state in which a front frame is opened in the embodiment.

FIG. 3 is a schematic configuration diagram showing a main mechanism of the present invention.

FIG. 4 is a graph showing the frequency of uneven rotation of the intermediate transfer drive shaft and the image carrier drive shaft when neither the intermediate transfer drive shaft nor the image carrier drive shaft has a flywheel.

FIG. 5 is a graph showing the frequency of rotation unevenness of the intermediate transfer drive shaft and the image carrier drive shaft when the flywheel is attached only to the image carrier drive shaft.

FIG. 6 is a graph showing the frequency of uneven rotation of the intermediate transfer drive shaft and the image carrier drive shaft when a flywheel is attached only to the intermediate transfer drive shaft.

FIG. 7 is a graph showing the frequency of uneven rotation of the intermediate transfer drive shaft and the image carrier drive shaft when a flywheel is attached to each of the intermediate transfer drive shaft and the image carrier drive shaft.

[Explanation of symbols]

 Reference Signs List 1 photoreceptor (image carrier) 10 intermediate transfer belt (intermediate transfer member) 31 process cartridge 61 motor 62 belt 63A large pulley 63B small pulley 64 intermediate transfer drive shaft 65 belt 66A small pulley 66B gear 67 gear 68 image carrier drive shaft 69/70 Flywheel 71/72 Coupling 73 Intermediate transfer drive roller shaft 74/75 Coupling 76 Image carrier drive roller shaft 77 Relay shaft

Continuing from the front page (72) Inventor Hiroyuki Goto 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2H030 AA07 BB24 BB42 BB46 BB71 2H032 AA05 BA05 BA09 2H071 CA05 DA09 DA15 DA26 EA14 EA18

Claims (2)

[Claims] 1. A color image forming apparatus having an image carrier and an intermediate transfer member in an apparatus main body and having a drive unit for driving these with a common motor, wherein a drive shaft of the image carrier and the intermediate transfer member are provided. Wherein a flywheel is provided on each of the drive shafts. 2. The apparatus according to claim 1, wherein the inertia of a flywheel provided on the drive shaft of the image carrier is larger than the inertia of a flywheel provided on the drive shaft of the intermediate transfer member. 3. The color image forming apparatus according to 1.