JPH1010885A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excellently transfer the high density part of an image to a transfer material, regardless of the kind of transfer material by changing the winding degree of the transfer material on a developing carrier, in accordance with the kind of transfer material. SOLUTION: A pressing member 80 presses a transfer material carrying belt 10 against a photoreceptor drum 1. A sliding mechanism 83X has a supporting member 82 which is provided to support the base end part of the pressing member 80 and be turnable around a shaft 81 and a sliding arm 84 for freely rotatably supporting the supporting member 82, so that a transfer baffle 8 is slid in the directions of arrows P and Q by specific amounts, in a direction where the transfer material is carried away. A tension spring 85 is connected to the supporting member 82, to exert energizing force for pressing the pressing member 80 against the drum 1 to the transfer baffle 8. For instance, when a cardboard mode is selected, the transfer baffle 8 is slid in the direction of the arrow Q by the sliding mechanism 83X, to be moved to the upstream side in the carrying direction of a paper sheet from a position just under the drum 1.

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 such as a copying machine and a printer.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, for example, the surface of a photosensitive drum as an image carrier is uniformly charged and then exposed to form an electrostatic latent image. This electrostatic latent image is developed into a toner image. on the other hand,
The transfer material is fed into the transfer section by the transfer material transporter so that the transfer material contacts the surface of the image carrier in synchronization with the formation of the toner image, and the toner image on the photosensitive drum is electrostatically transferred to the transfer material. Transferred to the surface.

In such an image forming apparatus, in order to reliably transfer the toner image on the image carrier to the surface of the transfer material at the transfer section, the back side of the transfer material transport body, that is, the side opposite to the transfer surface. Is elastically pressed toward the image carrier by a pressing means. This pressing means,
The back surface of the transfer material is pressed via the transfer material transporter so that the surface of the transfer material follows the curved surface of the image carrier.

On the other hand, as a transfer material, not only ordinary plain paper but also thick paper or OHP sheets may be used in some cases. With regard to these various transfer materials, when the transfer operation was performed in the above color image forming apparatus, when the pressing means was adjusted so that the high-density portion of the image was transferred to the transfer material in a good manner with thick paper, the OHP sheet could not be used. If the pressing means is adjusted so that the high-density portion of the image is not transferred to the transfer material satisfactorily and the high-density portion of the image is transferred to the transfer material satisfactorily on the OHP sheet, the high-density portion of the image is good with thick paper. It was found that a phenomenon of not being transferred to the transfer material occurred.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to enable a high-density portion of an image to be successfully transferred to a transfer material regardless of the type of transfer material in an image forming apparatus.

[0006]

According to the present invention, there is provided a transfer material transporter for holding and moving a developed image or a transfer material, a developed image carrier provided in close proximity to the transfer material transporter, In an image forming apparatus having a pressing member provided at a position opposed to the developed image carrier via a material transporter, a winding amount of the transfer material around the developed image carrier is changed according to a type of a transfer material. And means for causing it to be provided.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing a main part of a color image forming apparatus to which the present invention is applied.

A color image forming apparatus shown in FIG. 1 is a photosensitive drum lk, l as an image carrier which rotates in the direction of an arrow.
y, lm, and lc. Around these four photosensitive drums lk, ly, lm, and lc, the chargers 2k, 2y, 2m, 2c,
Laser scanning type image exposure devices 3k, 3y, 3m, 3c, developing devices 4k, 4y, 4m, 4c, pre-transfer chargers 5k, 5
y, 5m, 5c, transfer units 6k, 6y, 6m, 6c, cleaning devices 7k, 7y, 7m, 7c, and the like, respectively, whereby each of the photosensitive drums 1k, 1y, 1
Monochromatic toner images of each color of k (black), y (yellow), m (magenta), and c (cyan) are formed on m and 1c, respectively.

For example, when the color image forming apparatus is configured as a digital color copying machine, a document set on a document table (not shown) is read by a color image reading device, and the read signal is read by a digital image processing means. Signals are temporarily stored in a memory after conversion into signals, and toner images of each color can be formed based on the stored digital image signals of four colors (k, y, m, c). That is, the image exposure devices 3k and 3k are operated in accordance with digital image signals of respective colors input from the image signal processing means.
y, 3m, and 3c, respectively, and the chargers 2k, 2y,
The photosensitive drum lk, which is uniformly charged by 2m and 2c,
The electrostatic latent images are written to ly, lm, and lc, respectively. Then, the electrostatic latent images are developed by the developing devices 4k, 4y, 4m, and 4c containing the toners of the respective colors (k, y, m, and c) to form the toner images of the respective colors. When the color image forming apparatus is configured as a device such as a printer, it is only necessary to form toner images of each color based on an image signal input from outside to the image signal processing means.

In the color image forming apparatus, a transfer material formed of a seamless belt is provided so as to be in a non-contact state below the transfer positions of the four photosensitive drums lk, ly, lm, and lc. The belt 10 is arranged close to. The transfer material conveying belt 10 is stretched around a driving roll 11, a peeling roll 12, a tension roll 13, an idler roll 14, and the like, and is configured to rotate in the direction of the arrow. Further, each transfer unit 6k, which is disposed on the side opposite to each photosensitive drum 1 of the transfer material transport belt 10,
Transfer baffles 8k, 8y, 8m, 8c are provided as pressing means on the front side of 6y, 6m, 6c, respectively. Further, around the belt 10 for transferring the transfer material,
An adsorbing charger 15 and an adsorbing roll 16 for adsorbing the fed transfer material P onto the belt, and a transfer material P
A peeling claw 17 for peeling from above, a fixing device 18 for fixing an unfixed toner image on the transfer material P, a charge removing device 19 for removing charge from the belt 10, and a device for removing residual deposits on the belt 10. Cleaning device 20 and the like are provided. On the transfer material transport belt 10, a plurality of transfer materials P are suction-held in respective holding areas and can be simultaneously transported.

FIG. 2 shows transfer baffles 8k, 8y, 8m,
It is a schematic diagram for demonstrating operation | movement of 8c. here,
The photosensitive drums lk, ly, lm, and lc are replaced with the photosensitive drum 1
The transfer baffles 8k, 8y, 8m, and 8c will be described as transfer baffles 8.

As shown in FIG. 2, the transfer baffle 8 has a pressing member 80 for pressing the transfer material conveying belt 10 in the direction of the photosensitive drum 1, and a shaft 81 for supporting the base end of the pressing member 80. Support member 8 provided rotatably about
A slide mechanism 83X having a slide arm 84 for rotatably supporting the support member 82 and sliding the transfer baffle 8 by a predetermined amount in the directions of arrows P and Q along the direction of the transfer surface of the transfer material P; A tension spring 8 that is connected to the support member 82 and applies an urging force to the transfer baffle 8 so that the pressing member 80 is pressed in the direction of the photosensitive drum 1.
5, the main part is constituted.

The slide operation by the transfer baffle 8 is performed, for example, when the thick paper mode is selected.
Is slid in the direction of arrow Q by the slide mechanism 83X and moves from immediately below the photosensitive drum 1 to a position of 0.5 mm upstream in the sheet transport direction. When the OHP mode is selected, the transfer baffle 8 is
3X, the photosensitive drum 1 slides in the direction of arrow P.
From just below to the position of 1.3 mm upstream.

FIG. 3 shows the relationship between cardboard and OHP sheets.
9 is a graph showing the relationship between the tip position of a transfer baffle and high-density transfer characteristics. As can be seen from the graph shown in FIG. 3, in the case of thick paper, the smaller the amount of movement of the leading end position of the transfer baffle, the better the high-density transfer characteristic. The higher the amount of movement, the better the high density transfer characteristics. The reason why such a phenomenon occurs will be described below. FIG. 4 is an explanatory diagram illustrating a difference in the transfer operation due to a difference in the tip position of the transfer baffle.

As shown in FIG. 4A, in the case of the thick paper P1, the transfer electric field does not effectively act on the toner on the surface of the photosensitive drum 1 due to the thickness of the thick paper P1. By moving the leading end position to a position immediately below the photosensitive drum 1 and shortening the distance D1 between the leading end position of the transfer baffle 8 and the position directly below the photosensitive drum 1, transfer is performed by the transfer baffle 8 functioning as a discharge regulating member. Since the discharge area of the container 6 is narrowed and the electric charges are concentrated, the high-density transfer characteristic for the thick paper P1 is improved.

As shown in FIG. 4B, in the case of the OHP sheet P2, the position of the leading end of the transfer baffle 8 is moved from immediately below the photosensitive drum 1 to the upstream side, and the leading end of the transfer baffle 8 is moved. By increasing the distance D2 between the position and the position immediately below the photosensitive drum 1, the discharge area of the transfer unit 6 is widened and the electric charge is dispersed.
While keeping the same as in the case of 1, the thin OHP sheet P2
The electric field suitable for the above can be applied to the toner on the surface of the photosensitive drum 1 via the OHP sheet. In addition,
Since the OHP sheet P2 is thin and flexible, the OHP sheet P2 is in contact with the surface of the photosensitive drum 1 with a certain width in the circular direction of the photosensitive drum 1. The toner on the surface of the body drum 1 does not scatter to unnecessary portions.

As described above, in this embodiment, the leading end position of the transfer baffle is changed according to the type of the transfer material. Thereby, regardless of the type of the transfer material, high-density transfer characteristics are improved. In the case of plain paper, the leading end position of the transfer baffle is moved to an intermediate position between the position for thick paper and the position for OHP sheets.

In the example shown in FIG. 2, the leading end position of the transfer baffle is moved according to the type of the transfer material, but the same effect as moving the leading end position of the transfer baffle by changing the transfer baffle pressure can be obtained. You can also.

FIG. 5 is a schematic diagram showing an embodiment of the present invention in which the transfer baffle pressure is changed according to the type of transfer material. The transfer baffle 8 includes, as shown in FIG.
A support member 82 supporting the base end portion of the pressing member 80 and rotatably provided about a shaft 81 is provided. The support member 82 is slid by a predetermined amount in the directions of arrows S and T so that the support member 82 is provided about the shaft 81. A slide mechanism 8 that rotates and moves the tip of the pressing member 80 along a direction perpendicular to the transfer surface of the transfer material P.
The main part is constituted by 3Y.

In the slide operation by the transfer baffle 8 shown in FIG. 5, for example, when the thick paper mode is selected, the transfer baffle 8 is pulled in the S direction by the slide mechanism 83Y to increase the transfer baffle pressure. . In the OHP mode, the transfer baffle moves in the T direction to lower the transfer baffle pressure. In the experiment,
The spring force is 140 g / cm for plain paper and 18 for thick paper.
Good image quality could be obtained by setting the OHP mode to 0 g / cm and 0 g / cm to 110 g / cm.

FIG. 6 shows the relationship between cardboard and OHP sheets.
9 is a graph showing a relationship between a bubbling force for applying pressure to a transfer baffle and high-density transfer characteristics. As can be seen from the graph shown in FIG. 6, in the case of thick paper, the higher the bubbling force, the better the high-density transfer characteristics. In the case of an OHP sheet, the smaller the bubbling force, the better the high-density transfer characteristics. Therefore, in the present embodiment, the bubbling force, that is, the transfer baffle pressure is changed according to the type of the transfer material. Thereby, regardless of the type of the transfer material, high-density transfer characteristics are improved.

Further, as shown in FIG. 7, a slide support mechanism 83X for slidably supporting a slide arm 84 rotatably supporting the support member 82 along the direction of the transfer surface of the transfer material is provided. The end of the member 82 opposite to the pressing member 80 is pulled by a spring 85
, A slide mechanism 83Y for moving the transfer baffle in the vertical direction may be provided, and both the leading end position of the transfer baffle and the bubbling force may be changed according to the type of the transfer material.

In the case of the example shown in FIG. 7, the slide mechanism 83Y
Is fixed to a fixed portion such as a frame, and by moving the driving member of the slide mechanism 83Y in the vertical direction, the spring length of the tension spring 85 changes,
As a result, the transfer baffle pressing force, baffle tip position,
The amount of winding of the transfer material changes. For example, in consideration of the pressing force of the transfer baffle, the pressing force increases by increasing the length of the sling, so in the case of thick paper,
What is necessary is just to move the position of the drive member of the slide mechanism 83Y below the OHP sheet and to increase the length of the swing.

Now, as described above, each photosensitive drum 1
The monochromatic toner images of the respective colors formed on k, 1y, 1m, and 1c are adjusted to a charging state optimal for transfer by the pre-transfer charger 5 as necessary, and then subjected to the operation of the transfer unit 6. The transfer material P is successively superposed and transferred onto the transfer material P sucked and transported by the transfer material transport belt 10. That is,
When the transfer material P is transported by the belt 10, each photosensitive drum 1
By passing the transfer positions of k, 1y, 1m, and 1c in contact with the belt 10 in this order, the respective toner images are transferred so as to overlap each other. Transfer material P on which multi-color toner image is formed after the transfer process on photosensitive drum lc is completed
Is released from the belt 10 by the peeling claw 17 and sent to the fixing device 18, and is discharged to the outside after the fixing process.

After completion of the transfer process, the photosensitive drums are cleaned by the cleaning device 7 to remove electricity, and then the image forming process is continuously repeated as described above, or the next image forming process is performed. To wait for. On the other hand, the transfer material transport belt 10 from which the transfer material P has been peeled off is cleaned by the cleaning device 20 after being neutralized by the neutralizer 19.

In the above-described embodiment, each toner image is sequentially transferred onto the transfer material P conveyed by the transfer material conveying belt 10, but an intermediate transfer belt is used instead. Then, the toner images may be sequentially transferred onto the intermediate transfer belt to form a multi-color toner image on the intermediate transfer belt, and the multi-color toner images may be collectively transferred to the transfer material.

Further, the transfer baffle and the transfer device are integrally assembled to form a transfer unit, and the position of the transfer baffle with respect to the photosensitive drum is changed by moving the support member of the transfer unit up and down by a clutch cam. be able to.

In the above-described embodiment, the transfer baffle is moved with respect to the photosensitive drum 1 at the stationary position. 1 may be moved up and down. For example, in the color image forming apparatus shown in FIG. 1, 1k, 1y, 1m, 1c of each photosensitive drum
Since the peripheral components constitute an integrated image forming unit for each photosensitive drum, the support member of this image forming unit is moved up and down by a clutch cam, whereby the photosensitive drum is moved relative to the transfer baffle. You can change the position. Further, as shown in FIG. 8, the tension control mechanism 21 is connected to the tension roll 13 and the belt tension is changed to change the position of the tip of the transfer baffle,
Alternatively, the pressure of the transfer baffle can be changed. The tension control mechanism 21 includes, for example, a plunger 22
And a spring 23 for connecting the shaft of the tension roll 13 with the plunger 22. By driving the plunger 22, the belt tension can be changed. In the case of thick paper, the belt tension is increased, and in the case of an OHP sheet, the belt tension is decreased, thereby changing the position of the leading end of the transfer baffle from immediately below the image carrier or the pressure of the transfer baffle. And high-density transfer characteristics are improved irrespective of the type of paper.

[0030]

As described above, according to the present invention, in an image forming apparatus in which transfer is performed while a transfer material is pressed against an image carrier by a transfer baffle, from just below the image carrier according to the type of paper. Transfer baffle tip position,
Alternatively, the pressure of the transfer baffle was changed,
The high-density transfer characteristics are good regardless of the type of paper.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a main part of a color image forming apparatus to which the present invention is applied.

FIG. 2 is a schematic diagram for explaining the operation of a transfer baffle 8;

FIG. 3 is a graph showing the relationship between the position of the leading end of a transfer baffle and high-density transfer characteristics in thick paper and an OHP sheet.

FIG. 4 is an explanatory diagram illustrating a difference in a transfer operation due to a difference in a tip position of a transfer baffle.

FIG. 5 is a schematic diagram showing an embodiment of the present invention in which a transfer baffle pressure is changed according to a type of a transfer material.

FIG. 6 is a graph showing a relationship between a blowing force for applying pressure to a transfer baffle and high-density transfer characteristics in a thick paper and an OHP sheet.

FIG. 7 is a schematic diagram showing an embodiment of the present invention in which both the leading end position of the transfer baffle and the bubbling force are changed according to the type of transfer material.

FIG. 8 is a schematic diagram showing an embodiment of the present invention in which belt tension is changed according to the type of transfer material.

[Explanation of symbols]

lk, ly, lm, lc photoconductor drums, 2k, 2y,
2m, 2c: charger, 3k, 3y, 3m, 3c: image exposure device, 4k, 4y, 4m, 4c: developing device, 5k, 5
y, 5m, 5c: pre-transfer charger, 6k, 6y, 6m, 6
c: transfer unit, 7k, 7y, 7m, 7c: cleaning device, 8: transfer baffle, 10: transfer material transport belt, 1
DESCRIPTION OF SYMBOLS 1 ... Driving roll, 12 ... Peeling roll, 13 ... Tension roll, 14 ... Idler roll, 15 ... Suction charger, 16 ... Suction roll, 17 ... Peeling claw, 18 ... Fixing device,
19: static eliminator, 20: cleaning device, 21: tension control mechanism, 22: plunger, 23: spring,
80 ... pressing member, 81 ... shaft, 82 ... support member, 83X,
83Y: slide mechanism, 84: slide arm, 85 ...
Tension spring, P… Transfer material

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mikio Kobayashi 2274 Hongo, Fuji Xerox Co., Ltd., Ebina City, Kanagawa Prefecture (72) Inventor Ryoichi Tsuruoka 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Junichiro Samejima 2274 Hongo, Ebina City, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd.

Claims (12)

[Claims] 1. A transfer material transporter that holds and moves a developed image or a transfer material, a developed image carrier that is provided in close proximity to the transfer material transporter, and the developing device via the transfer material transporter. An image forming apparatus having a pressing member provided at a position facing an image carrier, wherein a means for changing a winding amount of the transfer material around the developed image carrier according to a type of the transfer material is provided. Image forming apparatus. 2. The method according to claim 1, further comprising: means for sliding the pressing member along the direction of the transfer surface of the transfer material, and changing a winding amount by changing a tip position of the pressing member according to a type of the transfer material. The image forming apparatus according to claim 1, wherein: 3. A device for sliding the pressing member in a direction perpendicular to the transfer material conveying surface, wherein the amount of winding is changed by changing the pressing force of the pressing member according to the type of the transfer material. The image forming apparatus according to claim 1, wherein: 4. A means for sliding the pressing member in a direction of a transfer surface of the transfer material and in a direction perpendicular to the transfer surface, wherein a tip position of the pressing member and a pressing position of the pressing member are selected according to a type of the transfer material. 2. The image forming apparatus according to claim 1, wherein the winding amount is changed by changing a pressure. 5. An elastic member for connecting between the pressing member and a fixed portion, wherein a distal end position of the pressing member is changed by expansion and contraction of the elastic member to change a winding amount. 2. The image forming apparatus according to 1. 6. An elastic member for connecting between the pressing member and a fixed portion, wherein a pressing force of the pressing member is changed by expansion and contraction of the elastic member to change a winding amount. 2. The image forming apparatus according to 1. 7. An elastic member for connecting between the pressing member and a fixed portion is provided, and a winding amount is changed by changing a tip position and a pressing force of the pressing member by expansion and contraction of the elastic member. The image forming apparatus according to claim 1. 8. The image forming apparatus according to claim 1, wherein an amount of winding of the transfer material and the developed image carrier is changed by moving the transfer material transporting member in a photoconductor position direction. 9. The image forming apparatus according to claim 1, wherein an amount of winding of the transfer material and the developed image carrier is changed by moving the developed image carrier in a position direction of the transfer material carrier. apparatus. 10. The image forming apparatus according to claim 1, wherein the developed image carrier is a photoreceptor. 11. The image forming apparatus according to claim 1, wherein the developed image carrier is an intermediate transfer body, and the transfer material conveying body is an electrostatic transfer unit that performs transfer to a sheet. An image forming apparatus according to claim 1. 12. The image forming apparatus according to claim 1, wherein the transfer material transporting body is an endless belt, and a change in a leading end position is performed by a change in belt tension.