JPH06124026A - Image forming device - Google Patents

Abstract

PURPOSE:To synchronize a photosensitive drum with a belt in a simple constitution. CONSTITUTION:This image forming device is provided with the photosensitive drum 8 on the surface of which an electrostatic latent image corresponding to the image information of an original is formed, a driving motor 28 for rotating the photosensitive drum 8, the belt 12 formed so as to circulate and sucking/ carrying a form paper on the surface, a transfer charger 17 for transferring a toner image on the photosensitive drum 8 on the form paper carried by the belt 12, and a connecting means connecting the photosensitive drum 8 to the belt 12 so as to synchronously rotate the belt 12 and the photosensitive drum 8. The connecting means is composed of, for instance, a carrying hole 21 and a projection 23.

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,
In particular, the present invention relates to an image forming apparatus provided with a circulation belt for adsorbing and conveying a transfer material such as paper.

[0002]

2. Description of the Related Art An image forming apparatus such as a copying machine, which uses a circulation belt for transferring an image on a sheet and for conveying the sheet, is disclosed in, for example, Japanese Patent Laid-Open No. 63-8377. . In this apparatus, a circulating belt is arranged below the photoconductor drum, and a transfer charger for charging the belt is arranged so as to face the photoconductor drum with the belt interposed therebetween. And
The sheet conveyed from the sheet feeding cassette is electrostatically attracted to this belt and is supplied between the photosensitive drum and the transfer charger. Then, the toner image on the photoconductor drum is transferred onto this sheet, and is further sent to the fixing device side by a belt.

[0003]

In an apparatus that conveys a sheet by using the belt and transfers a toner image onto the sheet, it is necessary to synchronize the peripheral speeds of the photosensitive drum and the belt to synchronize them. . If they are not synchronized, image shift occurs and image quality is degraded. But,
In the conventional image forming apparatus, the drive system for driving the belt and the drive system for driving the photoconductor drums are separate systems, and it is very difficult to synchronize the peripheral speeds of both. is there.

An object of the present invention is to provide an image forming apparatus capable of making the peripheral speeds of the photosensitive drum and the belt equal to each other with a simple structure and with high accuracy, and preventing deviation of images.

[0005]

In the image forming apparatus according to the present invention, the image according to the image information of the original is held on the surface of the image carrier. The image carrier is rotated by a driving means such as a motor.
On the other hand, the transfer material is supplied to the image carrier by the circulation belt, and the image held on the image carrier is transferred to the transfer material.

At this time, the circulation belt that conveys the transfer material is connected to the image carrier by the connecting means. Therefore, the circulation belt and the image carrier surely rotate in synchronization,
It is possible to prevent image shift. Further, a motor or the like for driving the circulation belt is not required, which simplifies the configuration.

[0007]

1 shows a copying machine according to an embodiment of the present invention. In the figure, a document table 2 is provided on the upper surface of the copying machine main body 1.
Is fixed, and a document holder 3 is provided on the document table 2 so as to be openable and closable. A bypass paper feed guide 4 for feeding paper is mounted on the right side of the copying machine body 1 in the figure. Further, on the right side of the copying machine main body 1 below the bypass paper feed guide 4, a paper feed cassette 5 is detachably mounted. On the left side of the copying machine body 1 in the drawing, a paper discharge tray 6 for discharging copied paper is mounted.

Inside the copying machine main body 1, an exposure device 7 for reading a document is provided on the upper part thereof. The exposure device 7 is composed of a light source, a mirror, a lens unit and the like. A photoconductor drum 8 on the surface of which an electrostatic latent image is formed is arranged in the center of the copying machine body 1. A charging device 9, a developing device 10, and a cleaning device 11 are arranged around the photosensitive drum 8.

Below the photoconductor drum 8, a belt 12 is disposed which circulates in the sheet conveying direction. The belt 12 is provided so as to be circulated by two upper guide rollers 13 and 14 and two lower guide rollers 15 and 16 provided below the upper guide rollers 13 and 14, respectively. The belt 12 has a semiconductor characteristic and is formed of an elastic member. For example, it is formed of rubber such as urethane rubber or chloroprene rubber, urethane resin, or the like. As described above, by making the belt 12 semiconductive, it is possible to charge the belt 12 and electrostatically adsorb the sheet on the belt 12 for conveyance. In order to charge the belt 12 with electric charges, a bias voltage having the same polarity as that of the photosensitive drum 8 is applied to the lower guide roller 16 on the side of the sheet feeding cassette 5. Further, the upper guide roller 13 on the downstream side in the paper transport direction is grounded, and the electric charge of the belt 12 is removed at this portion, and the paper is separated from the belt 12.

Inside the circulating belt 12, below the photosensitive drum 8, a transfer charger 17 for charging the belt 12 with electric charges (positive electric charges) of the same polarity as the photosensitive drum 8 is provided. . Further, a paper feed / conveyance path 18 is provided between the image forming unit including the photoconductor drum 8 and the like, and the bypass paper feed guide 4 and the paper feed cassette 5. Further, a fixing device 19 for fixing the toner image transferred on the sheet is provided between the image forming section and the sheet discharge tray 6.
And a discharge roller 20 for discharging the sheet on which the toner image is fixed to the discharge tray 6.

FIG. 2 shows the details of the drive units for the photosensitive drum 8 and the belt 12. 2. FIG. 2 is a perspective view of the copying machine main body 1 as viewed from the rear.

A plurality of holes 21 for conveyance are formed at both ends of the belt 12 along the circulation direction at a predetermined pitch. On the other hand, a plurality of protrusions 22 are formed at both ends of the upper guide roller 13 at positions corresponding to the transport holes 21 of the belt 12 at the same pitch as the transport holes 21. The projection 22 engages with the transport hole 21 of the belt 12 so that the two mesh with each other. Similarly, a plurality of protrusions 23 are formed on both end portions of the photosensitive drum 8 at the same pitch as the transport holes 21 of the belt 12, and the protrusions 23 are sequentially meshed with the transport holes 21. ing. The photoconductor drum 8 has a rotary shaft 24 at its center.
A first pulley 25 is fixed to one end of 4. Also,
The first pulley 25 is connected to the second pulley 26 via a belt 27. The second pulley 26 is the drive motor 2
It is designed to be rotated by 8. The rollers 13, 14, 15, 16 for guiding the belt 12
Are rotatably supported by subframes (not shown).

In the apparatus having such a structure, the pulley 26, the belt 27 and the pulley 25 are driven by the drive motor 28.
The photosensitive drum 8 is rotated via the. Since the protrusions 23 provided on both side ends of the photoconductor drum 8 sequentially mesh with the transport holes 21 of the belt 12, the belt 12 is circulated in the same direction as the photoconductor drum 8 rotates. The belt 12 is further guided by the protrusions 22 of the upper guide roller 13, wraps around downward, and is circulated through the guide rollers 15, 16 and 14.

When the sheet is conveyed through the sheet feeding / conveying path 18, the belt 12 is charged with a positive electric charge by the lower guide roller 16, so that the sheet is electrostatically attracted to the belt 12. , And is conveyed between the photoconductor drum 8 and the transfer charger 17. When the transfer charger 17 is turned on in such a state, positive charges forming an electric field larger than the positive charges charged on the photoconductor drum 8 are induced on the surface of the paper on the photoconductor drum 8 side. The negatively charged toner is transferred from the photosensitive drum 8 side to the sheet side by the induced positive charges on the sheet.

The sheet on which the toner image is transferred is further conveyed by the belt 12. Then, the upper guide roller 13
At the portion, since the upper guide roller 13 is grounded, the electric charge of the belt 12 is removed at the guide roller 13 portion, and the electrostatic attraction force of the belt 12 disappears. As a result, the paper is separated from the belt 12 and sent to the fixing device 19 side. In the sheet thus sent to the fixing device 19, the toner image on the sheet is fixed, and the sheet is discharged to the sheet discharge tray 6 side by the discharge roller 20.

In such an embodiment, the belt 12 is formed with the hole 21 for carrying, and the hole 23 for carrying is engaged with the projection 23 of the photosensitive drum 8 and the projection 22 of the upper guide roller 13. The deviation of the belt 12 in the roller axis direction is significantly suppressed. Further, for the same reason, the deviation in the circulation direction orthogonal to the roller axis direction is significantly reduced, the deviation of the image when the toner image is transferred from the photosensitive drum 8 to the sheet on the belt 12 is prevented, and a stable image is always obtained. Is obtained.

Further, since the belt 12 and the photosensitive drum 8 are connected by the connecting means consisting of the conveying hole 21 and the protrusion 23, both are surely rotated in synchronization with each other, and the image shift is prevented as described above. , The image quality will be good.

Other Embodiments (a) In the above embodiment, the photosensitive drum 8 and the belt 12 are
Although the projections 23 and the transport holes 21 are connected to each other, the structure for connecting them is not limited to the above embodiment. For example, both may be connected using a gear train or a belt and rotated in synchronization.

(B) When the photoconductor drum 8 and the belt 12 are connected by using the projection 23 and the transport hole 21,
The protrusion 22 of the upper guide roller 13 may be omitted.

(C) In the above embodiment, the projection 22 is provided on the upper guide roller 13, but the projection may be provided on another guide roller.

[0021]

As described above, according to the present invention, since the circulation belt and the image carrier are connected by the connecting means and both are rotated in synchronization, the peripheral speeds of the both can be adjusted with a simple structure. It is possible to prevent image shift and always obtain an image of stable quality.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional configuration diagram of a copying machine according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a circulation belt portion of the copying machine.

[Explanation of symbols]

 8 Photoreceptor Drum 12 Belt 13-16 Guide Roller 21 Transport Holes 22, 23 Protrusion 28 Drive Motor

Claims (1)

[Claims] 1. An image carrier which holds an image according to image information of a document on a surface thereof and is rotatable, a driving means for rotating the image carrier, and a surface which is circulated and is formed on the surface. A circulation belt for adsorbing and conveying the transfer material, a transfer unit for transferring the image held on the image carrier to the transfer material conveyed by the circulation belt, the circulation belt and the image carrier An image forming apparatus comprising: a connecting unit that connects the image bearing member and the circulation belt so that and rotate in synchronization with each other.