JPH08314294A - Image transferring device for image forming device - Google Patents

Abstract

PURPOSE: To provide a device capable of excellently demonstrating the operation pressing a paper sheet with a simple constitution, and excellently demonstrating the toner image transferring operation with low-voltage, by composing a transferring member adopting a conductive resin sheet provided with conductivity and elasticity. CONSTITUTION: The device is provided with the transferring member 10 constituted of the resinous conductive resin sheet 11, for transferring a toner image T formed on a photoreceptor drum 1 on a paper sheet P, and means for applying voltage from a power source device 6, for supporting the transferring member 10 through a base part supporting member 5. The conductive resin sheet 11 is composed of the resin material such as polyolefin provided with the conductivity and the elasticity, so that the transferring operation is performed so as to prevent the transfer unevenness from occurring, by the elasticity of a free side end part of the conductive resin sheet, by imparting the uniform pressing force toward the photoreceptor drum, with respect to the whole paper sheet P in the width direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image transfer apparatus used for transferring a toner image formed on an image bearing member such as a photosensitive drum of an image forming apparatus to a recording medium such as paper, and more particularly to an electrophotographic apparatus. Printers and ionography printers use a sheet-shaped conductive member from the back of the paper to transfer the toner image formed on the photoconductor or dielectric to a recording medium such as paper. The present invention relates to an image transfer device of an image forming apparatus that is capable of applying an electric charge and a pressing action.

[0002]

2. Description of the Related Art In an electrophotographic printer or an ionography printer, an electrostatic latent image is formed by irradiating a photosensitive drum or a dielectric (image carrier) with light of an image to form the electrostatic latent image. In contrast, a method is used in which toner is supplied from a developing device to form a toner image. Then, the toner image formed on the image carrier as described above is transferred to a recording medium such as a sheet using a transfer unit arranged in the image transfer area, and the sheet carrying the toner image is fixed through a fixing device, It is configured to be ejected as a copy. Examples of the transfer means include, for example, JP-A-60-244979.
It is known to use a corona transfer device that uses a corotron as disclosed in Japanese Patent Publication No. 56-143473, or a roller transfer device as disclosed in Japanese Patent Laid-Open Publication No. 56-143473. Also in the roller transfer device, the transfer roller is made of an elastic material having conductivity so that the function of pressing the paper against the photosensitive drum can be performed in a good state. .

[0003]

However, in recent years, printers have become smaller and less expensive, and when used in combination with a device such as a personal computer, they are often arranged at a position close to the operator. Has become. A transfer device that uses a corona transfer method that generates ozone tends to be shunned because of the problem of harmfulness of ozone. Further, the printer using the roller transfer method using a conductive roller has the following problems with respect to the generation of ozone, although it does not have the drawbacks of the device using the corona transfer method. For example, in a printer using the roller transfer method, a pressing action is applied from the back side of a sheet of paper or the like to press the sheet of paper against a photosensitive drum carrying a toner image and to apply a voltage in the width direction of the sheet of paper. There is a problem that it is difficult to keep the pressure constant.

The transfer roller is relatively thin,
When setting the pressing force on the photoconductor drum via the bearing members that hold both ends, the bending action is applied to the roller, so that all parts in the length direction of the roller are pressed uniformly on the photoconductor drum. There is a drawback that it will not be in a state where it will be. Then, in a state where the pressing force of the roller against the photosensitive drum is insufficient, transfer failure or transfer unevenness is likely to occur, and in a state where the pressing force is strongly exerted, transfer omission due to aggregation of toner occurs. Therefore, in order to solve the problems described above, a pressing roller using a tracking roll or a spring is arranged on the transfer roller so that a uniform pressing operation can be provided. The roller itself is made of conductive rubber or the like having high mechanical accuracy so as to have flexibility.

However, there is a problem that the electrical characteristics of the conductive foam rubber used in the conventional transfer roller are affected by environmental changes such as temperature and humidity. Therefore, the transfer roller is provided with an environment detecting means and the like, a means for controlling the voltage applied to the transfer roller, and the like so as to provide a mechanism for preventing the transfer action of the toner image from being influenced by the environment. I am configuring. However, as described above, arranging the auxiliary control means with respect to the transfer roller causes a problem that not only the structure of the apparatus becomes complicated but also the manufacturing cost of the apparatus is greatly affected.

[0006]

It is an object of the present invention to solve the above-mentioned problems of the conventional transfer device, in which the transfer member is composed of a sheet-shaped conductive member, and the elasticity of the conductive member is utilized to make a paper sheet. By applying a pressing action from the back of the to the photoconductor drum, the pressing force can be kept uniform and
It is an object of the present invention to provide a transfer device having a simple structure and a low cost.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a transfer device for transferring a toner image on an image carrier to a recording medium.
In the present invention, a flexible conductive member that is disposed on the back surface of a recording medium that moves while being in contact with an image carrier and that has a pressing action on the recording medium, and one end of the conductive member are provided. There are provided a holding member that is fixedly held and has a free end protruding toward the image carrier, and a member that applies a voltage to the conductive member. In the present invention, the flexible conductive member has an electric resistance of 10
It can be composed of a sheet-shaped member having a thickness of ² to 10 ⁹ Ω and a thickness of 10 to 100 μm.

Further, in the present invention, the flexible conductive member is folded back through a curved surface and both ends are held together by a holding member, and the folded back portion is used as a pressing portion of a recording medium. Is also possible. In addition to the above-mentioned structure, in the present invention, the flexible conductive member is formed into a cylindrical shape, and small holes are provided in the end portion of the conductive member at regular intervals in the circumferential direction. Is provided as a cylindrical conductive member, the cylindrical conductive member is arranged on the back surface of a recording medium that moves while being in contact with an image carrier, and the cylindrical conductive member is provided with a pressing action. It is also possible to configure the elastic member as a device that rotates following the rotation of the image carrier.

[0009]

As described above, a flexible sheet-shaped conductive member is used as the transfer member, and the elasticity of the sheet is used to configure the means for pressing the sheet from the back side. The pressing action on the paper can be uniformly exerted. Further, when the sheet is formed as a looped shape and the arcuate portion of the sheet is used to perform the pressing action on the sheet, the elasticity of the arcuate portion of the sheet should be greatly exerted. Can
It is possible to make the action of bringing the paper into contact with the photosensitive drum or the like in a good state. Furthermore, when the sheet member is configured in a cylindrical shape, it is possible to provide rigidity in the length direction even when a very thin sheet is used, and to exert the pressing action on the paper in a better state. It is possible to let By configuring the transfer device using the sheet member as described above, the pressure for pressing the paper against the photoconductor drum can be set arbitrarily, and the transfer is simple and inexpensive. The device can be configured.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image transfer device of an image forming apparatus of the present invention will be described with reference to the illustrated example. In the example shown in FIG. 1, a structure of an apparatus for transferring a toner image T formed on a photosensitive drum 1 as an image carrier to a sheet P is shown, and it is composed of a conductive resin sheet member 11. The transfer member 10 is fixedly provided on the base supporting member 5, and constitutes a device for applying a voltage from the power supply device 6 via the base supporting member 5. The power supply device 6 controls the voltage applied to the transfer member in accordance with the water content of the paper and the environmental conditions, as in the case of the voltage application device for the transfer corotron that has been conventionally used in devices such as general printers. It can be configured as such a device. Further, the conductive resin sheet 11 constituting the transfer member 10 is arranged such that the base portion 12 is fixed to the base portion supporting member 5 and the free side end portion 13 is projected toward the photosensitive drum, and is arranged in the arrow x direction. With respect to the paper P moving in contact with the rotating photosensitive drum 1, the free side end of the conductive resin sheet 11 is brought into contact with the back surface, and the elasticity of the conductive resin sheet is used to make the paper P.
It is possible to exert a pressing action against.

The conductive resin sheet 11 forming the transfer member 10 is formed as a flexible conductive member, and has, for example, an electric resistance of 10 ² to 10 ⁹ Ω and a thickness of 10 to 100 μm. It can be composed of a sheet-shaped member. In the example shown in FIG. 1, the thickness is 80 μm.
Conductive resin sheet 11 prepared by dispersing a conductive material such as carbon black in a polyolefin resin film of m.
The surface resistance value is set to 10 ⁴ Ω. Further, the flexible conductive member as described above, elasticity and thickness, and, as long as the electrical resistance value can be obtained, a fluorine-based resin, or a polyester-based resin,
Alternatively, it is also possible to form the conductive resin sheet by using a polycarbonate resin or the like. In the transfer member 10 configured as described above, the photosensitive drum 1
When the paper P is pressed against, the free-side tip of the conductive resin sheet is curved following the movement of the paper, and the elasticity of the curved portion of the sheet exerts a good pressing action on the paper. can do. When the toner image formed on the photoconductor drum is transferred, the conductive resin sheet 1 is attached to the photoconductor drum 1.
1 makes it possible to perform a uniform pressing action in the width direction of the paper.

Therefore, when the transfer member 10 constructed as described above is used, it can be constructed as a device capable of obtaining a high transfer efficiency at a low voltage as shown by a chain line in the graph of FIG. In the example shown in the graph of FIG. 2, the voltage applied from the power supply device 6 to the transfer member is set on the abscissa and the transfer efficiency is shown on the ordinate, but the case of the conventional transfer roller system is shown. In contrast to the solid curve, when the transfer member of the present invention is used, the pressing effect of the transfer member can be satisfactorily exerted, so that high transfer efficiency can be achieved at a low voltage. By constructing the transfer member 10 as shown in FIG. 1, the structure of the transfer member can be simplified and can be incorporated in a small and low-priced printer, such as a photosensitive drum. It is possible to efficiently perform the operation of transferring the toner image formed on the image carrier.

[0013]

Embodiment 2 As shown in FIG. 1, the photosensitive drum 1
In addition to configuring the device that presses the paper toward the photoconductor drum by arranging the transfer member 10 configured by the conductive resin sheet 11 in accordance with
A loop-shaped transfer member 15 as shown in FIG. 3 can also be used. In the loop-shaped transfer member 15 shown in FIG. 3, the conductive resin sheet 16 is folded back through the loop portion 18 in a state where both ends of the conductive resin sheet 16 are stacked in parallel, and the end portion of the conductive resin sheet is stacked. Is configured to be attached to the base support member 5 via the fixing portion 17.
Further, the conductive resin sheet 16 forming the loop-shaped transfer member 15 can be formed of a resin sheet member having flexibility and conductivity as described with reference to FIG. 5 is configured as a device that applies a voltage from a power supply device. Then, while applying a voltage of a predetermined value to the loop-shaped transfer member 15 through the base supporting member, the loop-shaped transfer member 15 is pressed toward the photoconductor drum from the back surface of the paper P, so that the photoconductor drum 1 is pressed. The formed toner image T is transferred to a sheet.

When the sheet is pressed toward the photosensitive drum 1 by the loop-shaped transfer member 15, the sheet P is pressed by the elasticity of the loop portion 18 of the loop-shaped transfer member 15, and the sheet is pressed by the loop portion. The pressure can be set as a large value as compared with the case where the sheet is used alone as shown in FIG. Then, as shown in FIG. 3, when the sheet is pressed by the loop portion 18 of the loop-shaped transfer member 15, a high transfer efficiency can be obtained even if the voltage applied from the power supply device is lowered.

When the loop-shaped transfer member 15 having the above-mentioned structure is used, the position of the loop-shaped transfer member 15 with respect to the photosensitive drum is, as shown in FIG. The loop portion 18 of the transfer member 15 can be arranged at a position where it does not contact the surface of the photosensitive drum 1. Then, when the toner image is transferred from the photosensitive drum to the paper, when the paper is conveyed, the paper presses the loop-shaped transfer member and tilts the loop portion of the loop-shaped transfer member in the moving direction of the paper. Since the process proceeds in this manner, the state shown in FIG. 5 is obtained. Therefore, the loop portion 18 of the loop-shaped transfer member 15 strongly exerts the action of pressing the sheet P toward the photoconductor drum 1, and the action of transferring the toner image to the sheet can be performed in a good state.

The loop-shaped transfer member of the present invention is shown in FIG.
As shown in, even if there is no paper, the loop portion 18 may be in contact with the surface of the photosensitive drum. Then, when the sheet penetrates into the loop portion 18 of the loop-shaped transfer member 15 which is in constant contact with the surface of the photoconductor drum 1 so as to cut in between the photoconductor drum and the loop portion, it is shown in FIG. As described above, the loop-shaped transfer member 15 is largely curved in the moving direction of the paper P. Therefore, due to the elasticity of the loop portion 18 and the action of greatly curving the entire conductive resin sheet, the action of pressing the sheet toward the photoconductor drum is exerted as a large value. That is, as shown in each of FIGS. 4 and 6, even if the conditions such as the arrangement position of the base support member 5 and the length for projecting the loop-shaped transfer member are arbitrarily set, the paper is set on the photosensitive drum. It is possible to exert the action of pressing toward a favorable state. Therefore, it is possible to easily form the transfer nip with respect to the paper without strictly setting the mechanical position accuracy unlike the conventional device using the transfer roller and the like. It can be simplified.

As described above, when a device for moving the paper while pressing the transfer member or the loop-shaped transfer member against the photoconductor drum is constructed, as in the case where the transfer roller or the like is used, There is a concern that the transporting action for the can not be exhibited in a good state. Therefore, when the conveying action on the sheet cannot be satisfactorily achieved only by the photosensitive drum, the conveying roller device 3 is arranged between the photosensitive drum 1 and the fixing device 4 to convey the sheet P as shown in FIG. Means may be provided to assist the action. The carrying roller device 3 is arranged at a position outside the image area of the paper. For example, in a printer or the like using a general electrophotographic system, an area of about 5 mm on which no image is formed on both sides in the paper carrying direction. Therefore, it is preferable to arrange the rollers so that the rollers are in contact with the non-transferred portions of the image on both sides of the sheet.

In the case of using the paper transporting device configured as described above, the paper transporting operation is performed by the paper feeding device and the transporting roller device arranged corresponding to the paper feeding tray or the like in the upstream portion of the photosensitive drum. Be seen. After that, while the trailing edge of the sheet is being fed by the upstream transport device, the leading edge of the sheet is nipped by the transport roller device 3 and transported to the fixing device 4. Then, the sheet is conveyed and discharged by the roller member of the fixing device, so that the sheet can be conveyed in a good state. Even in the apparatus using the transfer member of the present invention, when the distance between the photoconductor drum and the fixing device is very narrow and the carrying roller device at the upstream portion of the photoconductor drum sufficiently performs the carrying operation to the fixing device. In some cases, the transport roller device 3 may not be provided. Further, it is naturally possible to dispose other sheet carrying means instead of the carrying roller device.

[0019]

Third Embodiment In addition to using the above-mentioned transfer member or loop-shaped transfer member, in the present invention, a transfer member arranged corresponding to the photosensitive drum is formed of a conductive resin sheet as shown in FIG. It can also be configured as a cylindrical member. In the example shown in FIG. 9, the conductive resin sheet 21 made of a resin having flexibility and conductivity is formed into a cylindrical shape to form the cylindrical transfer member 20, and the cylindrical transfer member 20 is formed on both sides of the cylindrical transfer member 20. Shafts 23 and 23a are provided at the ends so as to project through a support disk 24. Further, in order to apply a voltage to the conductive resin sheet, the conductive ring member 25 is integrally attached to the end of the cylinder, and the shoe 26 connected to the power supply device 27 is brought into contact with the cylindrical transfer member 20. It constitutes a means for supplying power to. Further, with respect to the cylindrical transfer member 20, driven hole rows 22 and 22a are arranged near both ends of the cylinder, and the driven hole rows are provided at both end portions of the photosensitive drum. The cylindrical transfer member can be rotated in a state of being interlocked with the photoconductor drum by meshing with the conductive tooth member arranged in the above.

The cylindrical transfer member 2 constructed as described above.
For example, 0 is formed into a cylinder having a diameter of about 15 mm in a rolled state of a sheet member having conductivity and elasticity as described in FIG. The holes arranged in the driven hole row are
Holes of 1.5 mm square are arranged in rows at 1.5 mm intervals 3 mm inward from the end of the conductive resin sheet. The shape and arrangement interval of the holes in the driven hole row are set arbitrarily. be able to. Even if the cylindrical transfer member 20 is made of a relatively thin sheet member, the cylindrical transfer member has a very small diameter, and therefore the cylindrical transfer member has a large rigidity. When the cylindrical transfer member is pressed against the photoconductor drum, sufficient elasticity can be exerted on the paper to exert the pressing action.

Then, as shown in FIG. 10, with respect to the cylindrical transfer member 20 provided with the interlocking means as described above, the drive tooth rows 2 are arranged at both ends in the axial direction of the photosensitive drum, The teeth of the driving tooth row 2 are combined so as to mesh with the driven hole rows 22 and 22a of the cylindrical transfer member, respectively. As shown in FIG. 10, when the photosensitive drum 1 and the cylindrical transfer member 20 are combined, the cylindrical transfer member 2
Since 0 is rotated following the rotation of the photosensitive drum 1,
At the nip position of both members, the conveying action on the sheet P can be exhibited in a good state, and the sheet conveying action can be performed without using the auxiliary conveying means as shown in FIG.

[0022]

As described above, the image transfer device of the image forming apparatus of the present invention uses a flexible sheet-shaped conductive member as the transfer member and utilizes the elasticity of the sheet to transfer the sheet. Since the means for performing the pressing action from the back surface is configured, it is possible to uniformly exert the pressing action on the paper. In addition, when the sheet is formed as a curved loop, and when the arc-shaped portion of the loop-shaped transfer member is used to press the sheet, the elasticity of the loop-shaped portion of the sheet is increased. It can be exerted, and the action of bringing the paper into contact with the photosensitive drum or the like can be performed in a good state. Furthermore, when the sheet member is configured in a cylindrical shape, it is possible to provide rigidity in the length direction even when a very thin sheet is used, and to exert the pressing action on the paper in a better state. It is possible to let

By constructing the transfer device using the above-mentioned sheet member, the pressure for pressing the paper against the photosensitive drum can be set arbitrarily, and the construction is simple and the cost is low. It is possible to configure a cheap transfer device. Therefore, in the device of the present invention, it is possible to reduce the generation of ozone and to configure a device with good transfer efficiency, and also to simplify the structure of the transfer member, which can be easily incorporated in a device such as a small printer. it can.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a transfer device of the present invention.

FIG. 2 is a graph showing the relationship between transfer efficiency and applied voltage in the transfer device of the present invention.

FIG. 3 is an explanatory diagram showing the configuration of a second embodiment of the transfer device of the present invention.

FIG. 4 is an explanatory diagram showing an arrangement relationship of a transfer member with respect to a photosensitive drum.

5 is an explanatory diagram of a state where a sheet is nipped by the apparatus of FIG.

FIG. 6 is an explanatory diagram showing a positional relationship of a transfer member with respect to a photosensitive drum different from that in FIG.

7 is an explanatory diagram of a state where a sheet is nipped by the apparatus of FIG.

FIG. 8 is an explanatory diagram of a case where a conveyance roller device is provided in the middle of the paper conveyance path.

FIG. 9 is an explanatory diagram of a cylindrical transfer member configured by using a conductive resin sheet.

FIG. 10 is an explanatory diagram showing a configuration of a transfer device using a cylindrical transfer member.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 photoconductor drum, 2 driving tooth row, 5 base support member, 10 transfer member, 11 conductive resin sheet, 15 loop transfer member, 18 loop portion, 20 cylindrical transfer member, 22 driven hole row, 24 Support disk, 25 conductive ring member.

Claims (4)

[Claims] 1. A transfer device for transferring a toner image on an image carrier to a recording medium, the flexibility being arranged on the back surface of the recording medium moving while being in contact with the image carrier, and imparting a pressing action to the recording medium. And a holding member that holds one end of the conductive member fixedly and projects the free side end toward the image carrier, and a member that applies a voltage to the conductive member. An image transfer apparatus for an image forming apparatus, wherein: 2. The flexible conductive member is a sheet-shaped member having an electric resistance of 10 ² to 10 ⁹ Ω and a thickness of 10 to 100 μm. Image transfer device of the image forming apparatus of. 3. The flexible conductive member is folded back through a curved surface and both ends are held together by a holding member, and the folded back portion is used as a pressing portion of a recording medium. Item 1. The image transfer device of the image forming apparatus according to item 1. 4. A transfer device for transferring a toner image on an image carrier to a recording medium, wherein a flexible conductive member is formed in a cylindrical shape, and is fixed at an end of the conductive member in a circumferential direction. Small holes are provided at intervals of
It is configured as a cylindrical conductive member provided with a driven portion, the cylindrical conductive member is arranged on the back surface of a recording medium that moves while being in contact with an image carrier, and a pressing action is applied to the recording medium, and An image transfer apparatus for an image forming apparatus, characterized in that a cylindrical conductive member is rotated following the rotation of an image carrier.