JPH10268601A - Image recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the fluctuation of driving force caused by an image forming member forming images onto a belt, by forming both end sides of the pressing member of a belt rear side face outside than the width of the body to be recorded out of a member having a hardness higher than that at the center part, and transmitting constant driving force to the belt from the image forming member. SOLUTION: An endless belt 1081 is streched over four rollers including a pressing roller 1085 at a transfer belt unit 108, and the outer peripheral side of a core bar is covered with a rubber material or a sponge material at the pressing roller 1085. Then, both end sides abutting on the outside of the width of the body to be recorded 1 carried are constituted of end side roller parts formed of the rubber material for instance such as EPDM, and a part abutting on the carrying part of the body to be recorded 1 is constituted of a center side roller part formed of the sponge material such as foamed EPDM. Thus, the hardness of the end side roller part is set higher than that of the center side roller part. The driving force from a photoreceptor drum 1 is not affected by the body to be recorded 1, so that a high-definition image is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus using a toner to visualize an image on a recording medium, and more particularly to an image recording apparatus using a belt in a sheet transporting and image transferring section.

[0002]

2. Description of the Related Art Conventionally, as shown in JP-A-6-230683, the surface of a photoreceptor is uniformly charged, and a latent image is formed by exposing the surface of the photoreceptor with light according to an image. Developed with the developed toner, electrostatically transfers the developed image onto the recording medium, and further fixes the toner on the recording medium made of paper or plastic sheet with a fixing machine to form a permanent image. Various image recording apparatuses for recording an image on a recording medium using toner have been put to practical use.
The image recording apparatus using a belt for conveying the recording medium and transferring the toner image to the recording medium is provided with a transfer corotron on the back surface of the belt opposite to the photoconductor on which the toner image is formed. This has the advantage that the influence of the transfer unit on the environmental change of the recording medium can be reduced.

Further, Japanese Patent Application Laid-Open No. 7-295393 discloses a technique in which a roller for pressing a belt against the surface of a photoreceptor is provided upstream of the transfer unit in order to reduce the influence of environmental changes in the transfer unit. ing.

[0004]

When the above-mentioned belt is used for conveying a recording medium and transferring a toner image, the belt is an endless belt, a plurality of rollers are provided in the belt, and the belt is formed by the rollers. The belt is rotated in the same direction and speed as the photoconductor by applying tension and driving one of the rollers.

Ideally, the speed of the surface of the belt driven by the rollers is set equal to the speed of the surface of the photosensitive member, and the recording medium is sandwiched between the belt and the photosensitive member and equals the respective speeds. Conveyed at speed. However, in actuality, when driving both the photoconductor and the belt, it is impossible to achieve the exact same speed due to mechanical precision, and therefore, the respective speeds are designed to have a value that does not adversely affect the transferred image.

If a roller for pressing the photosensitive member is provided in the belt and the endless belt is driven by the photosensitive member, no speed difference occurs between the photosensitive member and the belt, so that the transferred image is not adversely affected.

However, in the belt driven system, when the recording medium enters the transfer section, that is, when the recording medium enters between the photosensitive member and the belt, the frictional force of the recording medium and the frictional force of the belt are reduced. Due to the difference, the driving force transmitted to the belt changes, which may cause speed fluctuation.

According to the present invention, an image is formed on an image forming member using a toner, the image is transferred onto the image forming member, and the image is recorded on the image forming apparatus. It is an object of the present invention to provide an image recording apparatus using a belt for a transfer portion, in which the fluctuation of the driving force by the image forming member on the belt is reduced even when the recording medium enters the transfer section.

[0009]

In order to solve the above problems, an image is formed on an image forming member using toner,
In an image recording apparatus using a belt for transferring a recording medium of an image recording apparatus that records the image by transferring the image onto the recording medium and transferring the toner image, a portion of the back surface of the belt that contacts an image forming member. A pressing member formed of a roller is provided, and both end portions of the pressing member outside the width of the recording medium are formed of members having hardness higher than that of the central portion, and a constant driving force is transmitted from the image forming member to the belt. It was configured to be.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a laser printer according to an embodiment of the image recording apparatus of the present invention. FIG. 2 is a perspective view showing a transfer belt unit of the image recording apparatus of FIG. FIG. 3 is a cross-sectional view of the pressing roller unit shown in FIG. 1, and FIG. 4 is a cross-sectional view of the pressing roller unit when the transfer target is conveyed.

The overall configuration of the image recording apparatus of the present invention will be described with reference to FIG.

A hopper 200 for stocking the recording medium 1 made of paper or plastic film is provided at the bottom of the recording section, and a pickup for taking out the recording medium 1 from the hopper is provided above the hopper 200 in the recording medium discharge direction. A roller 201 is provided. Further, when two or more recording media 1 are fed in the recording
A separation roller 202 for separating sheets into sheets, and conveyance rollers 203 and 20 for conveying the recording medium 1 to the photosensitive drum 101
In order to transfer the image formed on the photosensitive drum 101 onto the recording medium 1 with high accuracy, registration rollers 206 for correcting the skew posture of the recording medium 1 are provided.

As the image forming member for forming a toner image, in this embodiment, a photosensitive drum 101 in which a photosensitive layer is applied to a metal drum surface is used. Although not shown, a drive motor for rotating the photosensitive drum 101 around its axis is connected to the photosensitive drum 101. Around the outer peripheral side of the photosensitive drum 101, a charger 102 for uniformly charging the surface of the photosensitive drum 101, a laser emitting unit for forming an electrostatic latent image on the photosensitive drum 101, and an optical system including a mirror and a lens A system 104 and a developing unit 105 for visualizing the electrostatic latent image with toner to form a toner image are arranged. The developing unit includes a toner hopper 106 for supplying toner into the unit and a toner box 107 for supplying toner to the toner hopper 106. A transfer belt unit 108 for transporting the recording medium 1 and transferring the toner image on the photosensitive drum 101 to the recording medium 1;
A drum cleaner 109 for removing residual toner after transfer on the photosensitive drum 101 is provided.

Next, the details of the transfer belt unit 108 will be described with reference to FIG.

FIG. 2 is a perspective view of the transfer belt unit 108. As shown, the transfer belt unit 108
Means that the endless belt 1081 is
3. It is mounted on four rollers of a belt cleaner backup roller 1084 and a pressing roller 1085. Further, a belt cleaner roller 1086 is provided opposite to the belt backup roller 1084 with the endless belt 1081 interposed therebetween to remove toner attached to the endless belt. A transfer corotron 1087, which is a transfer unit for electrostatically transferring the toner image on the photosensitive drum 101 onto the recording medium 1, is provided at a transfer position in the endless belt 1081.

FIG. 3 is a sectional view of the pressing roller 1085 shown in FIG.

As shown in FIG. 3, the pressing roller 1085
Is covered with a core metal 10851 and an outer peripheral side thereof with a rubber material or a sponge material. That is, both end portions corresponding to the outer side of the width of the recording medium 1 to be conveyed are an end-side roller portion 10852 formed of a rubber material such as EPDM, and a portion corresponding to the conveying portion of the recording medium is formed of foamed EPDM. And a center roller portion 10853 made of a sponge material. That is, the hardness of the end-side roller portion 10852 is
The hardness is set higher than the hardness of the center roller portion 10853. In this way, by making the hardness of the end portion larger than the hardness of the center portion, the pressing force against the photosensitive drum is applied from the end portion side. As described above, the recording medium 1 to be transferred includes the photosensitive drum 101 and the pressing roller 1085.
Even when the photosensitive drum 101 comes between the upper endless belts 1081, the driving force from the photosensitive drum 101 is maintained at the end of the pressing roller 1085, and the end roller 1085 made of rubber material is provided.
2, a high-definition image can be obtained without being affected by the recording medium 1.

The pressing roller 1085 is provided in the vicinity of a transfer corotron provided on the upstream side of the transfer corotron 1087 in the transport direction of the recording medium 1.
1 is pressed against the photosensitive drum 101 to apply a driving force to the endless belt 1081 from the photosensitive drum 101 and rotate. In addition, as shown in FIG. 1, by providing the pressing roller close to the transfer corotron,
There is also an effect of increasing the contact area between the photosensitive drum 101 and the endless belt and increasing the transfer efficiency.

As shown in FIG. 1, a recording medium 1 is transferred from a transfer portion.
On the downstream side in the transport direction, a fixing device including a heat roller 91 having a halogen lamp therein and a backup roller 92 is provided. An auxiliary roller 93 for guiding the recording medium 1 to the outside is provided downstream of the fixing device.

Next, the operation of one embodiment of the present invention will be described with reference to FIGS.

The photosensitive drum 101 is uniformly charged by the charger 102, and the optical system 104 scans the drum with a laser beam that is turned on and off in accordance with an image signal to form an electrostatic latent image. The electrostatic latent image is developed by the developing unit 105 to form a toner image. On the other hand, in parallel with the image recording, the recording medium 1 is sent to the separation roller 202 by the rotation of the pickup roller 201 provided on the upper part of the hopper 200, and is separated into one by the separation roller 202. At 203, 204, and 205, the sheet is conveyed to the registration roller 206 with the conveyance direction reversed. After correcting the skew of the recording medium 1 by abutting the leading end of the recording medium 1 against the registration roller 206, the registration roller 206 is rotated to convey the recording medium 1 to the transfer belt unit 108. The driving force of the endless belt 1081 of the transfer belt unit 108 is transmitted from the photosensitive drum 101 by the pressing roller 1085, and the endless belt 1081 rotates at the same speed as the photosensitive drum 101. At this time, since the hardness of both ends of the pressing roller 1085 is high, the driving force is mainly transmitted at both ends. The recording medium 1 has a pressing roller 10
When the paper is conveyed to 85 parts, the hardness of the central portion of the pressing roller 1085 is low, so that the occurrence of torque fluctuation due to the rush is suppressed low, and the fluctuation of the speed of the endless belt 1081 hardly occurs. In addition, since the sponge material is provided at the center of the pressing roller, the contact between the recording medium 1 and the photosensitive drum 101 is kept good, and the electric charge of the polarity opposite to that of the toner on the photosensitive drum 101 at the transfer unit. By the transfer corotron 1086, the toner image can be transferred without causing disturbance. The recording medium 1 after the image transfer is sent to a fixing device. Here, the unfixed toner image on the recording medium 1 is melted and fixed while passing between the heat roller 91 and the backup roller 92 constituting the fixing device, and then discharged outside the apparatus by the auxiliary roller 93.

The embodiment of the pressing roller is not limited to the above-described embodiment. For example, by making the diameter of both ends of the pressing member larger than the diameter of the center, the recording medium 1 can be used.
Of the endless belt 1081 is less likely to occur.

[0024]

According to the image recording apparatus having the above-described structure, in an image recording apparatus using a belt for transferring a recording medium and transferring a toner image, a portion of the rear surface of the belt that is in contact with an image forming member is pressed. A member is provided, and both ends of the pressing member are formed of members having hardness higher than that of the center portion, and the driving force is transmitted to the belt by the image forming member. Therefore, even when entering the pressing member portion, the fluctuation of the driving force can be reduced, and the fluctuation of the speed can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an image recording apparatus of the present invention.

FIG. 2 is a perspective view showing a transfer belt unit of the image recording apparatus of FIG.

FIG. 3 is a sectional view of a pressing roller unit of FIG. 1;

FIG. 4 is a cross-sectional view of a pressing roller portion during transfer of a transfer object.

[Explanation of symbols]

Reference numeral 1 denotes a recording medium, 108 denotes a transfer belt unit, 1081
... endless belt, 1082 ... drive roller, 1085 ... pressing roller.

Continued on the front page (72) Inventor Hiromitsu Fukuda 502 Kandachicho, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratory, Hitachi, Ltd. (72) Inventor Yuji Furuya 2-6-1, Otemachi, Chiyoda-ku, Tokyo (72) Inventor Minoru Oshima 2-6-1 Otemachi, Chiyoda-ku, Tokyo Nippon Koki Co., Ltd.

Claims (5)

[Claims] An image forming member for forming a toner image; a transfer unit for transferring the toner image onto a recording medium; and an image recording apparatus in which the transfer unit is formed by a belt. An image recording apparatus, wherein a driving force is transmitted by a member. 2. An image forming member for forming a toner image, a transfer unit for transferring the toner image onto a recording medium, and an image formed by a transfer unit provided on a belt and a back surface of the belt. In the recording apparatus, a pressing member is provided on a portion of the back surface of the belt that comes into contact with the image forming member, and both end portions of the pressing member are formed of members having higher hardness than a central portion, and the image forming member is formed on the belt. An image recording apparatus, wherein a driving force is transmitted by a computer. 3. An image recording apparatus according to claim 2, wherein both ends of said pressing member are made of rubber members, and a central part is made of sponge. 4. An image recording apparatus according to claim 2, wherein said transfer device and said pressing member are provided adjacent to each other. 5. An image forming member for forming a toner image, and a transfer unit for transferring the toner image onto a recording medium,
In an image recording apparatus in which the transfer unit is formed by a belt and a transfer device provided on a back surface side thereof, a pressing member is provided on a portion of the back surface of the belt that comes into contact with the image forming member, and the diameter of both ends of the pressing member is set to An image recording apparatus which is formed larger than a portion and transmits a driving force to the belt by an image forming member.