JP2007264292A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer device and an image forming apparatus, in which shock can be reduced when the tip of a sheet is rushed into a second transfer device using a transfer roller, and a high-quality image having no image disturbance can be obtained. <P>SOLUTION: In the transfer device in the electrophotographic image forming apparatus comprising an image carrier, a latent image forming apparatus for forming a latent image on the image carrier, a developing device for developing the latent image, a first transfer device 30 for transferring the developed image on the image carrier to an intermediate image carrier 20, a recording body carrying device for carrying a recording body, a second transfer device for transferring an image on the intermediate image carrier to the recording body, and a fixing device for fixing the image on the recording body; the intermediate image carrier 20 is tensed between a drive roller 3 and a driven roller 26 and a rotation inertia control means 23 is arranged on the driven roller 26. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus having a configuration that reduces shock jitter during intermediate transfer.

Conventionally, in a transfer device in an electrophotographic image forming apparatus, when a transfer roller is used as a second transfer device that transfers a toner image on an intermediate transfer belt to a sheet, the sheet enters the second transfer unit. There is a problem that the transfer speed of the intermediate transfer belt fluctuates due to an impact when the image is transferred, and shock jitter that disturbs the image occurs.
To solve this problem, a method has been proposed in which a transfer roller pressed by a spring is held apart by a cam, and the holding is released and the transfer roller is pressed in accordance with the entry of a sheet (see, for example, Patent Document 1).
JP-A-6-274051

However, in such a configuration, the separated transfer rollers are caused to collide with the back surface of the paper by the pressing force, and thus the image is frequently disturbed by the impact. As a countermeasure against this, in the conventional example, it has been proposed to reduce the impact by a damper, but basically a discontinuous state occurs, which causes a rotational fluctuation that disturbs the image.
The present invention has been made in consideration of the above-mentioned circumstances, and reduces the impact when the leading edge of the paper enters the second transfer device using the transfer roller, thereby transferring a high-quality image without image distortion. An apparatus and an image forming apparatus are provided.

  In order to solve the above problems, the invention described in claim 1 includes an image carrier, a latent image forming device that forms a latent image on the image carrier, a developing device that develops the latent image, and An endless intermediate transfer belt that partially travels close to the image carrier, a first transfer device that transfers a developed visible image to the intermediate image carrier belt, and a recording medium An electrophotographic image forming apparatus having a recording material transport device, a second transfer device for transferring an image on the intermediate image carrying belt to the recording material, and a fixing device for fixing the image on the recording material. The intermediate image carrying belt is stretched between a driving roller and a driven roller, and a rotary inertia control means is connected to a rotating shaft of the driven roller.

According to a second aspect of the present invention, in the first aspect, the rotary inertia control means is disposed on a driven roller on the downstream side of the drive roller.
According to a third aspect of the present invention, in the first or second aspect, the rotary inertia control means is disposed on a driven roller in the vicinity of the first transfer device.
According to a fourth aspect of the present invention, in the first or second aspect, the rotary inertia control means is arranged on a driven roller constituting the second transfer device.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, rotation is transmitted to the driven roller by the rotary inertia control unit having a buffer unit having elasticity and viscosity. It is characterized by that.

  According to the present invention, an image is provided with a transfer device that does not cause image disturbance in the first transfer device due to impact at the time of entry of the leading edge of the paper in the second transfer device, and disturbance in exposure position on the photosensitive member. A forming apparatus can be provided. In particular, the effect increases when the impact is large, such as in high-speed printing or cardboard printing, and a transfer device and image forming apparatus that can form high-quality images in high-speed cardboard printing in addition to normal printing are realized. it can.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, in order to facilitate understanding of the present invention, an outline of an image forming apparatus to which the present invention is applied will be described. FIG. 5 is a side view of the image forming apparatus 1 using the intermediate transfer belt unit of the present invention.
The image forming apparatus 1 arranges development units corresponding to the respective colors on the intermediate transfer belt 20, forms a color image with toner on the intermediate transfer belt 20 by the development unit, and conveys the color image from the paper cassette 4. The toner image is transferred to a paper sheet, and the fixing device 60 melts and fixes the toner with heat and pressure to form a color image.

  The developing unit is composed of four units: a K developing unit 501 having black toner, a C developing unit 502 having cyan toner, an M developing unit 503 having magenta toner, and a Y developing unit 504 having yellow toner. Yes. The developing unit includes a toner hopper 53 for storing toner, a developing roller 52 for forming a toner layer and bringing the toner into contact with the photosensitive drum 54, a drum cleaner 57 for cleaning the photosensitive drum 54, and a charger for charging the photosensitive drum 54. (Latent image forming device) 55 and an exposure device (latent image forming device) 56 for writing an electrostatic latent image on the photosensitive drum 54. In FIG. 5, as a representative example, the details have been described using the K developing unit 501, but the remaining developing units 502, 503, and 504 also adopt the same configuration, and thus description thereof is omitted.

The intermediate transfer belt 20 is stretched between the first driven roller 21, the second driven roller 26, and the third driven roller 31, and is conveyed by the driving roller 3. The flywheel 23 which is the gist of the present invention to be described later is attached to the first driven roller 21.
The belt cleaner 91 removes residual toner on the intermediate transfer belt 20. The primary transfer roller 58 constituting the first transfer device is disposed inside the intermediate transfer belt 20 so as to face the photosensitive drum 54.
A paper conveyance path (recording material conveyance device) 8 passes between the transfer roller 30 and the intermediate transfer belt 20 from the paper cassette 4 on which the paper is stacked, passes through the pick roller 9 and the separation roller 11, and is fixed from the conveyance belt 81. To vessel 60.
The fixing device 60 includes a backup roller 64, an elastic roller 63, a heating roller 62, and a fixing belt 61. The fixing belt 61 is stretched over the elastic roller 63 and the heating roller 62 and is conveyed by the rotation of the heating roller 62 or other rollers.

The sheet is pressed against the elastic roller 63 side by the backup roller 64. The heating roller 62 has heating means such as a halogen heater in a metal hollow shaft, and heats the fixing belt 61. The surface of the elastic roller 63 is formed of an elastic material such as silicon rubber, and the nip portion is convex toward the elastic roller 63 by pressing the backup roller 64 to prevent the paper from being wound around the fixing belt 61.
When an image is formed in this image forming apparatus, the photosensitive drum 54 is charged by the charger 55 and light corresponding to the image is irradiated by the exposure device 56 to form a latent image on the photosensitive drum 54. The formed latent image reaches the developing roller 52 by the rotation of the photosensitive drum 54 and is developed in contact with the toner layer.
The toner image on the photosensitive drum 54 is transferred onto the intermediate transfer belt 20 at a portion where the primary transfer roller 58 presses the intermediate transfer belt 20. The toner image on the photosensitive drum of each developing unit is transferred onto the intermediate transfer belt 20, and a color toner image is formed. As the intermediate transfer belt 20 is conveyed, the toner image is transferred onto the sheet conveyed by the transfer roller 30. The sheet on which the toner image is transferred is conveyed to the fixing device 60 by the conveying belt 81, and the toner is melted and fixed by heat and pressure to form a color image.

Next, the intermediate transfer belt unit of the present invention will be described. FIG. 1 is a perspective view of an essential part of the intermediate transfer belt unit of the present invention.
The intermediate transfer belt 20 is stretched between the driving roller 3, the first driven roller 21, the second driven roller 26, and the third driven roller 31, and is rotated by a driving roller 3 that is rotated by a driving unit 25 that is a motor. It is conveyed in the direction of the middle arrow A. The second driven roller 26 is configured to apply a tension to the intermediate transfer belt 20 by a load applying unit (not shown) and generate a frictional force between the driving roller 3 and the intermediate transfer belt 20 to obtain a driving force. Yes.
The running surface located between the driving roller 3 and the second driven roller 26 of the intermediate transfer belt 20 has a first transfer roller 58 and the like facing each other with the intermediate transfer belt 20 therebetween as described above with reference to FIG. On the transfer device side.

The second transfer device is composed of a transfer roller 30 and is pressed against the intermediate transfer belt 20 so as to face the third driven roller 31 by a pressing means such as a spring (not shown). The sheet is conveyed from the direction of arrow B in the figure, and is conveyed between the transfer roller 30 and the intermediate transfer belt 20.
The first driven roller 21 rotates due to friction with the intermediate transfer belt 20. Along with this, the flywheel (rotational inertia control means) 23 attached to the rotary shaft 22 of the first driven roller 21 also rotates accordingly.
Normally, an impact when a sheet enters between the transfer roller 30 and the intermediate transfer belt 20 is transmitted toward the downstream side in the transport direction of the intermediate transfer belt 20, and is transferred at the position of the first transfer device. In addition to disturbing the image at the time, the image is disturbed by vibrating the photosensitive member to change the exposure position.

As in the present invention, a flywheel (rotational inertia control means) 23 is provided on the shaft 22 of the first driven roller 21 disposed between the transfer roller 30 constituting the second transfer device and the first transfer device. When arranged, it is possible to prevent the impact of paper entry from being transmitted to the first transfer device due to its inertia.
Further, since the driving roller 3 is disposed on the upstream side of the second transfer device 30, the intermediate transfer belt 20 between the second transfer device 30 and the driving roller 3 is loosened by driving. Therefore, the impact is not transmitted to the drive roller 3, and the transfer speed of the intermediate transfer belt 20 hardly changes on the first transfer device side at this point, and the image is not disturbed.

  As described above, the image forming apparatus of the present invention includes an image carrier (photosensitive member) 54, a latent image forming device (charger 55, exposure device 56) for forming a latent image on the image carrier, and the latent image. A developing device (developing unit) 57 that develops, an endless intermediate transfer belt 20 that partially travels close to the image carrier, and a developed visible image on the image carrier are transferred to the intermediate image carrier belt. A first transfer device 58; a recording material transport device for transporting the recording material; a second transfer device 30 for transferring an image on the intermediate image carrying belt to the recording material; and a fixing device for fixing the image on the recording material. The intermediate image carrier belt is stretched between the driving roller and the driven roller, and the rotary inertia control means 30 is connected to the rotating shaft of the driven roller. The configuration is characteristic.

FIG. 2 is a perspective view of an essential part of the intermediate transfer belt unit of the image forming apparatus according to the second embodiment of the present invention.
The difference from the first embodiment is that the flywheel 23 is attached to the shaft 22 of the second driven roller 26. Since the second driven roller 26 to which the flywheel 23 is attached is close to the first transfer device side where the image is disturbed, the effect of reducing the impact is great. In addition, since the distance between the impact transfer source and the second transfer device 30 is long, the spring constant of the intermediate transfer belt 20 during this time is lowered, and the effect as a damper is increased, so that impact of particularly high frequency components can be reduced.

FIG. 3 is a perspective view of an essential part of the intermediate transfer belt unit of the image forming apparatus according to the third embodiment of the present invention.
The difference from the first and second embodiments is that the flywheel 23 is attached to the shaft 22 of the third driven roller 31 facing the transfer roller 30.
The transfer roller 30 is pressed against the third driven roller 31 via the intermediate transfer belt 20. Therefore, the frictional force between the third driven roller 31 and the intermediate transfer belt 20 can be increased, and the flywheel 23 having higher inertia can be used. Therefore, it is possible to reliably prevent the impact by obtaining a large inertia force without slipping the third driven roller 31 even with respect to a high frequency component included in the impact when the leading edge of the paper enters.

4 (a) and 4 (b) are a front view and a side view showing a flywheel mounting configuration.
The disc-shaped flywheel 23 is supported so as to be rotatable with its rotation center coincided with the driven rotation shaft 22. The rotation of the driven rotary shaft 22 is transmitted from the support member 27 to the flywheel 23 via the elastic member 28. As the elastic member 28, a material such as rubber having elasticity and viscosity is suitable. In this example, four elastic members 28 are provided at 90 ° intervals with the rotation shaft 22 as the center, but the number is not limited. The elastic member 28 penetrates and is fixed to the hole 23a provided in the flywheel 23 and is fixed to the support member 27 at one end surface, but this support structure is only an example. The elastic member 28 may be simply integrated without penetrating through the hole provided in the flywheel 23. Further, the elastic member 28 need not be cylindrical.

The impact transmitted through the intermediate transfer belt 20 is transmitted from the driven roller to the driven rotating shaft 22, and when it is transmitted from the elastic member 28 to the flywheel 23, the elastic member 28 is deformed by the inertia of the flywheel 23. This deformation is converted into heat. As a result, vibration due to impact is further reduced.
By applying the flywheel structure described in FIG. 4 to the flywheel 23 of the first, second, and third embodiments shown in FIGS. 1 to 3, the impact of paper entry can be greatly reduced. Is possible.

FIG. 3 is a perspective view of a main part of the intermediate transfer belt unit according to the first embodiment of the present invention. It is a principal part perspective view of the intermediate transfer belt unit of the 2nd Example of this invention. It is a principal part perspective view of the intermediate transfer belt unit of the 3rd Example of this invention. It is explanatory drawing which shows the attachment structure of the flywheel of this invention. 1 is a side view of an image forming apparatus using an intermediate transfer belt unit of the present invention.

Explanation of symbols

  20 intermediate transfer belt, 21 first driven roller, 22 driven rotating shaft, 23 flywheel, 25 driving means, 26 second driven roller, 27 support member, 28 elastic member, 30 transfer roller, 31 third driven roller , 81 Conveyor belt, 60 Fixing device, 61 Fixing belt, 62 Heating roller, 63 Pressure roller, 64 Backup roller, 501 K developing unit, 52 Developing roller, 56 Charging device, 55 Exposure device, 57 Drum cleaner, 54 Photoconductor Drum, 58 Primary transfer roller, 91 Belt cleaner

Claims (5)

An image carrier, a latent image forming device that forms a latent image on the image carrier, a developing device that develops the latent image, and an endless intermediate transfer belt that travels partially close to the image carrier A first transfer device that transfers the developed visible image on the image carrier to the intermediate image carrier belt, a recording material carrier device that conveys the recording material, and the image on the intermediate image carrier belt to the recording material. An electrophotographic image forming apparatus having a second transfer device for transferring and a fixing device for fixing an image on a recording medium,
2. The image forming apparatus according to claim 1, wherein the intermediate image carrying belt is stretched between a driving roller and a driven roller, and a rotary inertia control unit is connected to a rotating shaft of the driven roller.   2. The image forming apparatus according to claim 1, wherein the rotary inertia control unit is disposed on a driven roller downstream of the drive roller.   3. The image forming apparatus according to claim 1, wherein the rotary inertia control unit is disposed on a driven roller in the vicinity of the first transfer device.   3. The image forming apparatus according to claim 1, wherein the rotary inertia control unit is arranged on a driven roller constituting the second transfer device.   5. The image forming apparatus according to claim 1, wherein rotation is transmitted to the driven roller by the rotation inertia control unit including a buffer unit having elasticity and viscosity. 6. Forming equipment.

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