JPH07168453A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent image quality from being deteriorated by faulty transfer by setting the radius of a latent image carrier, the radius of a driven roller, the thickness of a transfer belt, and a gap between the transfer belt and the surface of the latent image carrier expressed by a straight line distance linking the center of the latent image carrier and the center of the driven roller to specified values. CONSTITUTION:When it is assumed that the radius of the latent image carrier 1 is R, the radius of the driven roller 5 is (r), the thickness of the transfer belt 3 is (t), and the straight line distance linking the center of the latent image carrier 1 and the center of the roller 5 is L; a transfer belt device 2 is arranged with reference to the latent image carrier 1 so that a gap G expressed as L-(R+r+t) becomes <=0.5mm, that is, so as to satisfy G=L-(R+r+t)<=0.5mm. Thus, the fluttering of the transfer material 9 is reduced and an abnormal image such as transfer dust is prevented. More desirably, by coating the outer peripheral surface of the roller 5 with an elastic member, a gap is prevented from being rather open caused by the dispertion of the accuracy of parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a latent image forming means for forming an electrostatic latent image on a latent image carrier, and a developing means for developing the electrostatic latent image formed by the latent image forming means with toner. , And a transfer belt device for transferring the toner image onto a transfer material,
The transfer belt device is a transfer belt made of a rubber material of medium resistance wound around a driven roller arranged on the entrance side of the transfer material and a plurality of rollers including a driving roller arranged on the exit side of the transfer material. The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, etc.

[0002]

2. Description of the Related Art Image forming apparatuses of the above type are known, and in this type of apparatus, a conventional transfer belt apparatus is
As shown in FIG. 4, the transfer belt 3 is wound around a driving roller 4 and a driven roller 5, and the transfer belt 3 is in sliding contact with the surface of the photoconductor 1. An application roller 6 is provided slightly downstream of the position where the transfer belt 3 is in sliding contact with the photoreceptor, and a high applied voltage of 2 KV to 5 KV may be applied to the application roller 6. Further, a current also flows through the driven roller 5 via the intermediate resistance transfer belt 3, and the same applied voltage is also applied to the roller. Therefore, the application roller 6 or the driven roller 5
When the transfer belt 3 is pressed against the photoconductor 1 through the transfer belt 3 and the transfer belt 3 has a minute pinhole or the like, the roller is directly discharged to the photoconductor 1 and a hole is formed in the belt. Occurs.

For this reason, as shown in FIG. 5, a method may be considered in which the driven roller 5 is arranged directly below the photoconductor 1 so that the driven roller also serves as the applying roller. However, as described above, the belt has holes. It is difficult to implement because of problems. Generally, as shown in FIG. 4, the photosensitive member 1 and the driven roller 5 are largely separated from each other.

[0004]

However, if the photosensitive member 1 and the driven roller 5 are separated from each other by a large distance, the space becomes large, which is an obstacle to downsizing of the machine, and the belt length becomes long. Further, the gap G becomes large in the straight line connecting the centers of the photoconductor 1 and the driven roller 5. If this gap G is large, there is a problem in that the transfer paper is fluttered before transfer, blurring transfer occurs, and the image such as transfer dust is disturbed.

The present invention solves the above-mentioned conventional problems,
An object of the present invention is to provide an image forming apparatus that defines a gap between a transfer belt and a surface of a photoconductor to prevent deterioration of image quality due to defective transfer.

[0006]

In order to achieve the above object, the present invention provides a latent image forming means for forming an electrostatic latent image on a latent image carrier, and an electrostatic latent image formed by the latent image forming means. A developing roller for developing the image with toner, and a transfer belt device for transferring the toner image onto a transfer material, the transfer belt device being disposed on the inlet side of the transfer material, and an outlet for the transfer material. In the image forming apparatus including a transfer belt made of a rubber material having a medium resistance wound around a plurality of rollers including a driving roller arranged on the side, the radius of the latent image carrier is R, and the radius of the driven roller is When the radius is r, the thickness of the transfer belt is t, and the distance of the straight line connecting the center of the latent image carrier and the center of the driven roller is L, L- (R +
a gap represented as r + t) is formed, such that the gap satisfies L− (R + r + t) ≦ 0.5 mm,
The transfer belt device is arranged.

Further, in order to achieve the above object, the present invention is characterized in that an outer peripheral surface of the driven roller is covered with an elastic member.

[0008]

According to the above structure, a gap represented by L- (R + r + t) is formed, and the gap is L- (R + t).
Since the transfer belt device is arranged with respect to the latent image carrier so as to satisfy r + t) ≦ 0.5 mm, fluttering of the transfer material is reduced and the occurrence of abnormal images such as transfer dust can be prevented.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory diagram showing a main part of an image forming apparatus according to the present invention. In FIG. 1, a transfer belt device 2 which is in sliding contact with at least a transfer position at a transfer position is provided on a drum-shaped photosensitive member 1 serving as a latent image carrier. The transfer belt device 2 includes a transfer belt 3 formed of a medium-resistance rubber material. The transfer belt 3 includes a driving roller 4 whose core is made of metal and whose outer periphery is covered with a rubber material, and a metal roller which rotates together. It is wound around the driven roller 5. While the transfer belt 3 is running upward, a metallic applying roller 6 that is in contact with the transfer belt 3 from the back side is arranged, and a current I ₁ applied from a power source 7 is passed to the transfer belt 3. Further, during the upper running of the transfer belt 3, a metallic earth roller 8 which is in contact with the transfer belt 3 at a position approaching the driving roller 4 is arranged to return the current I ₂ flowing from the transfer belt 3 to the power supply 7.

In the current control of the transfer belt device 2, the difference between the current I ₁ applied from the power source 7 and the current I ₂ returned to the power source 7, that is, the value of current I ₁ -current I ₂ = K is constant. Is controlled so as to stabilize the current value flowing to the side of the photoconductor 1 so that good transfer can always be performed. In addition,
Although the differential constant current method is shown as the control of this example, there is no problem even if the normal constant current method or the constant voltage method is used.

The transfer belt device 2 is arranged with respect to the photosensitive member 1 so that a gap G is formed between the photosensitive member 1 and the transfer belt 3 on the inlet side thereof. This gap G has a radius R of the photoconductor 1, a radius r of the driven roller 5 and a thickness t of the transfer belt 3,
When the distance of the straight line connecting the center of the photoconductor 1 and the center of the driven roller 5 is L, it is expressed as G = L- (R + r + t). The image forming apparatus according to the present invention regulates the gap G to be 0.5 mm or less. That is, the transfer belt device 2 is arranged with respect to the photoconductor 1 so as to satisfy G = L− (R + r + t) ≦ 0.5 mm.

In the image forming apparatus having the above structure, the toner image formed on the photoconductor 1 by the electrophotographic process by the image forming means (not shown) is transferred to the transfer position where the transfer belt 3 slides as the photoconductor 1 rotates. When it arrives, the transfer material 9 is fed from a paper feed unit (not shown) in synchronization with this toner image. The transfer material 9 is guided to the gap G between the photoconductor 1 and the transfer belt 3 by the guide plate 10, and is electrostatically attracted to the transfer belt 3 there. Then, as the transfer belt 3 runs, the toner image is transferred at the transfer position where the transfer belt 3 contacts the photoconductor 1. At this time, since the gap G between the photoconductor 1 and the transfer belt 3 is configured to be 0.5 mm or less, the fluttering of the transfer material 9 is suppressed, and the image turbulence such as transfer dust is caused by the fluttering. To be prevented. In this way, the transfer material 9 without fluttering and subjected to good transfer is sent to the end portion of the transfer belt 3 while being electrically adsorbed, and is subjected to curvature separation. Then, the toner is sent to a fixing unit (not shown), the toner is melted and fixed on the transfer material 9 by the action of heat and pressure, and is discharged to the outside of the machine or the like.

By the way, the unit of the transfer belt device 2 is constructed so as to be able to come into contact with and separate from the photoconductor 1 in order to remove jammed paper or the like. Therefore, the position of the driven roller 5 is determined by the positioning means shown in FIG. It is configured to be positioned. The positioning means forms a downward convex shape 12 on a part of the photosensitive body side plate 11 that supports the photosensitive body 1, and forms an upward convex shape 14 on the unit side plate 13 of the transfer belt device 2.
Then, by matching the upper and lower convex shapes 12 and 13,
The position of the driven roller 5 with respect to the photoconductor 1 is determined so that the gap G is 0.5 mm or less. In addition,
The positioning means may be a combination of a convex shape and a concave shape, instead of the convex shapes.

FIG. 3 is an explanatory view showing another embodiment of the present invention. In this embodiment, an elastic member 15 such as rubber or sponge is wound around the peripheral surface of the driven roller 5.

With such a structure, even if the positioning is set such that the surface of the photosensitive member 1 is bitten into the driven roller 5 by way of the transfer belt 3, the provision of the elastic member 15 causes a minute pinhole or the like. Therefore, there is no possibility that the driven roller 5 directly discharges to the photoconductor 1 due to the presence of. Therefore, even if the gap G between the surface of the photoconductor 1 before transfer and the transfer belt 3 becomes wide due to variations in component accuracy, the gap G of 0.5 mm or less can be guaranteed. In addition, the above L- (R
The value of + r + t) can be set to 0 or less, and in this case, the fluttering of the transfer material 9 before the transfer can be completely eliminated.

[0016]

According to the structure of claim 1, L- (R + r
+ T) forms a gap, and the transfer belt device is arranged with respect to the latent image carrier so that the gap satisfies L- (R + r + t) ≤0.5 mm. Therefore, fluttering of the transfer material is reduced. It is possible to prevent the occurrence of abnormal images such as transfer dust.

According to the second aspect of the invention, since the outer peripheral surface of the driven roller is covered with the elastic member, the latent image carrier can be set to the driven roller via the transfer belt so that the positioning can be set to the extent necessary for the component accuracy. It is possible to prevent the gap from being widened due to variations.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a main part of an image forming apparatus according to the present invention.

FIG. 2 is a perspective view of a positioning unit that determines a position of a driven roller 5 with respect to a photoconductor.

FIG. 3 is an explanatory diagram showing another embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a relationship between a conventional photoconductor and a transfer belt.

FIG. 5 is an explanatory diagram showing a relationship between another conventional photosensitive member and a transfer belt.

[Explanation of symbols]

 1 Photoconductor 2 Transfer Belt Device 3 Transfer Belt 4 Driving Roller 5 Driven Roller 6 Applying Roller 9 Transfer Material 15 Elastic Member G Gap

Claims (2)

[Claims] 1. A latent image forming means for forming an electrostatic latent image on a latent image carrier, a developing means for developing the electrostatic latent image formed by the latent image forming means with toner, and a transfer of the toner image. A transfer belt device for transferring to a material, and the transfer belt device is wound around a driven roller arranged on the inlet side of the transfer material and a plurality of rollers including a driving roller arranged on the outlet side of the transfer material. In an image forming apparatus equipped with a transfer belt made of a rubber material having a medium resistance applied, the radius of the latent image carrier is R, the radius of the driven roller is r, the thickness of the transfer belt is t, and the latent image carrier is When a distance of a straight line connecting the center of the image carrier and the center of the driven roller is L, a gap represented by L- (R + r + t) is formed, and the gap is L- (R + r + t) ≤0.5.
An image forming apparatus, wherein the transfer belt device is arranged so as to satisfy mm. 2. The image forming apparatus according to claim 1, wherein an outer peripheral surface of the driven roller is covered with an elastic member.