JP2004177857A - Transfer device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer device having constitution to prevent toner scattering or the like from occurring when transfer paper is separated from the transfer device without increasing the number of parts. <P>SOLUTION: In the transfer device 6 having a transfer feeding belt 60 laid on a plurality of supporting members and carrying and feeding the transfer paper, and a transfer bias applying member 67 arranged inside the transfer paper feeding surface of the belt 60 and applying bias in the case of transferring a visible image on an image carrier 11 to the transfer paper, the supporting member 62 positioned on the most downstream side in a transfer paper feeding direction out of the supporting members for supporting the transfer paper feeding surface of the belt 60 is a conductive member, and the device 6 is provided with a bias applying means 621 for applying bias having the same polarity as the transfer bias to the conductive member. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transfer device that transfers a toner image formed on an image carrier by an electrophotographic process to transfer paper, and more particularly, to a transfer device that has a transfer conveyance belt that carries and conveys transfer paper.
[0002]
[Prior art]
2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer using an electrophotographic process, a toner image formed on an image carrier is applied to a transfer unit with a voltage having a polarity opposite to that of the toner. An electrostatic transfer system is used in which a transfer electric field is formed between the transfer member and the transfer means to electrostatically transfer the toner image on the image carrier to the transfer paper surface. The transfer means includes a transfer roller, a means for applying a predetermined bias to the transfer roller at the nip portion between the image carrier and the transfer roller to transfer the image, and a transfer conveyance belt. Means are known in which a bias is applied from the inner peripheral surface side of the transfer conveyance belt to transfer at the nip portion between the image carrier and the transfer conveyance belt.
When such an electrostatic transfer method is used, high-resistance transfer paper is separated from a contacting member when the image carrier is separated from the transfer paper or when the transfer conveyance belt is separated from the transfer paper. In such a case, peeling discharge occurs due to the voltage applied to the air gap that rapidly increases between the transfer paper and the member in the separation process. Due to the peeling discharge, the unfixed toner on the transfer paper scatters, causing a problem that the image is disturbed or the peripheral members are stained.
[0003]
Conventionally, the following proposals have been made regarding the problem of toner scattering as described above. In the image forming apparatus described in Patent Document 1, a static eliminator is arranged downstream of the transfer unit in the transfer paper transport direction in a state separated from the back surface of the transfer paper that has passed through the transfer unit. The static eliminator has needle-like protrusions facing the downstream side in the transfer paper transport direction. When a bias having the same polarity as that of the toner is applied to the static eliminator, the transfer paper is discharged from the tip of the needle-like protrusions. A bias of the same polarity is applied to the back surface. Further, in the image forming apparatus described in Patent Document 2, a static elimination corotron is disposed immediately above the transport belt where the transfer paper is separated from the transport belt that transports the transfer paper, and a bias having the same polarity as the toner is applied. In this way, a local atmosphere containing a large amount of ions is created to prevent peeling discharge that occurs when the transfer paper and the conveyor belt are separated.
[0004]
[Patent Document 1]
JP-A-10-282798 [Patent Document 2]
JP-A-2000-147911 (FIG. 1)
[0005]
[Problems to be solved by the invention]
However, each of the image forming apparatuses described in the above-mentioned patent documents has a configuration in which a static eliminator is separately provided, and there are problems such as an increase in the number of components and a sufficient installation space.
[0006]
SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a transfer device having a configuration for preventing toner scattering or the like that occurs when transfer paper is separated from the transfer device without increasing the number of components. Still another object of the present invention is to provide an image forming apparatus which is equipped with the transfer device and does not cause disturbance of an image and toner contamination on a peripheral member of the transfer device.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 includes a transfer / transport belt that is wrapped around a plurality of support members and carries / transfers a transfer sheet, and a transfer / transport belt inside the transfer sheet / transport surface of the transfer / transport belt. When transferring the visible image on the image carrier to the transfer paper, in a transfer device having a transfer bias application member that applies a bias, among the support members that support the transfer paper transport surface of the transfer transport belt, The transfer device is a transfer device in which a support member located on the most downstream side in the transfer paper transport direction is a conductive member, and a bias applying unit that applies a bias having the same polarity as the transfer bias to the conductive member.
[0008]
According to a second aspect of the present invention, in the transfer device according to the first aspect, the bias applying means provided on the conductive member is configured to connect the bias to the conductive member and the conductive member during a transfer process of the transfer sheet. This is a transfer device that applies a bias when the transfer paper straddles a transfer portion to which a transfer bias is applied at a contact position.
According to a third aspect of the present invention, in the transfer device according to the first or second aspect, the bias applying unit provided on the conductive member applies a bias while the transfer paper passes over the conductive member. It is a transfer device that keeps performing.
According to a fourth aspect of the present invention, in the transfer device of the first aspect, the bias applying unit provided on the conductive member always applies a bias during the operation of the transfer conveyance belt.
[0009]
According to a fifth aspect of the present invention, there is provided the transfer device according to any one of the first to fourth aspects, wherein the conductive member is configured by using a member that is thermally insulated or has a lower thermal conductivity than metal. .
[0010]
According to a sixth aspect of the present invention, there is provided an image carrier for carrying a latent image, a latent image forming means for forming a latent image on the image carrier, and supplying toner to the latent image on the image carrier. An image forming apparatus comprising: a developing unit for visualizing the image; a transfer unit for transferring a visible image on the image carrier to a transfer sheet; and a fixing unit for fixing the visible image on the transfer sheet. An image forming apparatus, which is the transfer apparatus according to any one of claims 1 to 5.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of a transfer device according to the present invention. The transfer device 6 includes photoconductor drums 11Y, 11M, 11C, and 11K as image carriers on which yellow (Y), magenta (M), cyan (C), and black (K) toner images are formed. This is a transfer device of a so-called tandem type image forming apparatus. A transfer conveyor belt 60 is provided which comes into contact with the photosensitive drums 11Y, 11M, 11C, and 11K, conveys the transfer paper, and transfers each toner image onto the transfer paper. The transfer conveyance belt 60 is a high-resistance endless single-layer belt having a volume resistivity of 10 ⁹ to 10 ¹¹ Ωcm, and the material thereof may be PVDF (polyvinylidene fluoride) or the like.
The transfer conveyance belt 60 is wound around a drive roller 63 and support rollers 61, 62, 65, 66 to form a belt loop. The drive roller 63 is connected to a drive source (not shown), rotates in the direction of the arrow, and frictionally drives the transfer conveyance belt 60. Further, a bending roller 64 is provided downstream of the driving roller 63 in the traveling direction of the transfer conveyance belt 60 so as to contact the outer peripheral surface of the transfer conveyance belt 60 and curve the belt toward the inside of the belt loop. By providing the curved roller 64, the amount of belt winding of the driving roller 63 is increased, and the transmission of the driving force of the driving roller 63 is ensured. Further, a tension roller 65 for adjusting the tension of the belt with a pressing member 69 is provided in the belt loop further downstream than the curving roller 64.
[0012]
An electrostatic attraction roller 80 to which a predetermined voltage is applied from a power supply 80a is disposed on the outer peripheral surface of the transfer conveyance belt 60 so as to face the support roller 61 as a transfer paper entrance roller. The transfer paper passing between the support roller 61 and the electrostatic attraction roller 80 is electrostatically attracted onto the transfer and transport belt 60 and is transported.
Transfer bias applying members 67Y, 67M, 67C, 67K are provided at positions facing the respective photosensitive drums 11Y, 11M, 11C, 11K so as to contact the inner peripheral surface of the transfer / conveyance belt 60. The transfer bias applying member 67 is a bias roller provided with a sponge or the like on the outer periphery, and a transfer bias is applied to the roller core from each of the transfer bias power supplies 9Y, 9M, 9C, and 9K. By the action of the applied transfer bias, transfer charges are applied to the transfer / conveyance belt 60, and a transfer electric field having a predetermined strength is formed between the transfer / conveyance belt 60 and the surface of the photosensitive drum 11 in each transfer portion. Further, a backup roller 68 is provided in order to appropriately maintain the contact between the transfer paper and the photosensitive drum 11 in the area where the transfer is performed and to obtain the best transfer nip.
[0013]
The support roller 62 is a transfer paper exit roller that separates the transfer paper on which the toner image has been transferred from the transfer / conveyance belt 60 and conveys the transfer paper to the next process. The support roller 62 is made of a conductive member, is connected to a bias application power supply 621, and has a configuration in which a predetermined bias is applied to the core of the support roller 62.
As described above, when the transfer paper carrying the toner image is separated from the transfer conveyance belt 60 and is conveyed at the position of the support roller 62, the separation discharge occurs between the transfer conveyance belt 60 and the transfer paper. And the toner is scattered. Therefore, when the transfer paper passes over the support roller 62, a bias having the same polarity as the bias applied to the transfer bias application member 67 is applied to the support roller 62 to attract the toner onto the transfer paper and prevent scattering. is there.
[0014]
In addition, it is preferable that a bias is applied when the transfer paper straddles the support roller 62 and the transfer portion of the photoconductor drum 11 </ b> K located closest to the support roller 62 at least in the transport process. When a transfer sheet whose resistance is reduced by moisture absorption is used, the bias applied to the support roller 62 wraps around the transfer portion of the photosensitive drum 11 </ b> K close to the support roller 62 via the transfer sheet. Therefore, by applying a bias having the same polarity as the transfer bias to the support roller 62, such a wraparound of the bias can be prevented, and a bias of an appropriate value of the transfer portion can be maintained.
[0015]
Further, it is preferable that the bias application power supply 621 continues to apply the bias while the transfer paper passes over the support roller 62. This is because if the bias is turned ON / OFF during the passage of the transfer sheet, a sharp change in the electric field occurs, and toner scattering and dust on the transfer sheet occur.
More preferably, a bias is always applied to the support roller 62 during the operation of the transfer conveyance belt 60. It has already been described that the toner is prevented from being scattered on the transfer paper carried and conveyed by the transfer / conveyance belt 60 during the image forming operation. On the other hand, the toner scattered in each step of development, transfer, cleaning, etc. adheres to the transfer conveyance belt 60 to a considerable extent. Therefore, as long as the transfer conveyance belt 60 is operating, there is a possibility that the toner directly adhering on the transfer conveyance belt 60 scatters to other members. For example, if toner adheres to a transport guide for transporting the transfer sheet to the next fixing step, the transfer sheet becomes dirty, which is a problem. Therefore, during the operation of the transfer conveyance belt 60, a bias is always applied to the support roller 62 to attract the toner adhered on the transfer conveyance belt 60 so as not to be scattered.
Note that a cleaning device 85 including a brush roller and a cleaning blade is disposed so as to contact the outer peripheral surface of the transfer conveyance belt 60 where the drive roller 63 is located. The cleaning device 85 removes foreign matters such as toner adhered to the transfer conveyance belt 60.
[0016]
Next, the configuration of the support roller 62 will be described.
FIG. 2 is a front view illustrating the configuration of the support roller 62. The support roller 62 is provided with a circling portion 62a around which the transfer conveyance belt 60 is wound along the axial direction, and a heat non-conductive portion 62b. The circling portion 62a is a metal surface capable of forming an optical reflection surface, and the heat non-conductive portion 62b is loaded on the outer peripheral surface of the base having a smaller diameter than the circulating portion 62a and is a flexible material capable of abutting on the transfer conveyance belt 60. A member 62c is used, and a non-metallic material such as a resin having a lower thermal conductivity than metal is used as the flexible member.
[0017]
The orbiting portion 62a is used to mirror-finish the metal surface used as the base material of the support roller 62, or to deposit a highly flat metal film on the surface when a resin material is used as the base material of the support roller 62. Thus, a metal surface is formed, and is used as a detection unit for detecting the image density and the belt position on the transfer / conveyance belt 60. In other words, it is used as a reflection surface of irradiation light from an optical sensor (not shown) provided opposite to the transfer conveyance belt 60 for detecting the density of the transfer image and aligning the transfer conveyance belt 60. ing. This makes it possible to detect the image density in accordance with the state of reflection of the irradiation light from the optical sensor, or to serve also as the detection unit for the marking for alignment.
[0018]
The flexible member used for the heat non-conductive portion 62b has an outer diameter equal to or slightly smaller than that of the orbiting portion 62a, and is used as a backing portion of the transfer / transport belt 60. The flexible member is made of conductive rubber or the like in order to apply a bias, and has a specific resistance of 10 ⁻³ to 10 ⁻¹ Ω / cm ² .
[0019]
Next, another embodiment of the heat non-conductive portion 62b will be described.
FIG. 3 shows a configuration in which the heat non-conductive portion 62b is provided with a flexible flocking, which is provided on a base portion having a smaller diameter than the orbiting portion 62a and has a front end capable of contacting the transfer conveyance belt 60 and has flexibility. The flocking PF has the same formation positional relationship and electrical properties as the flexible member 62c used for the heat non-conductive portion 62b shown in FIG. 2, and has a flocking density of 1,000 to 50,000 fibers / cm ² . In addition, the height (H) of the bristle is set to an outer diameter equal to that of the orbital portion 62a, or to a height at which a relationship capable of making contact with the back surface of the transfer conveyance belt 60 is obtained.
Both the flocking density and the height of the bristle are set to obtain a function as a backing portion for the transfer conveyance belt 60 in the heat non-conductive portion 62b, while suppressing heat transfer to the transfer conveyance belt 60. This prevents the transfer conveyance belt 60 from waving. In addition, the height (H) of the hair is a condition in consideration of preventing an increase in the heat transfer coefficient due to a decrease in the air space generated when the hair is shortened, and the dimension is about 1 ± 0.8 mm. Is preferred.
[0020]
As described above, in the present embodiment, the supporting roller 62 is configured using heat insulating material or a member having a lower thermal conductivity than metal because the supporting roller 62 is located at the most downstream side in the traveling direction of the transfer conveyance belt 60. It is a member, and therefore, takes into account the positional relationship that it is close to the fixing device in the next step. The fixing device, which will be described in detail with reference to the configuration of the image forming apparatus later, is a device for fusing and fixing the toner on the transfer paper by heat and pressure, and serves as a heat source in the image forming apparatus. With the above-described configuration of the support roller 62, even when heat from the fixing device is accumulated in the support roller 62, heat transfer to the transfer conveyance belt 60 is suppressed, and a partial temperature increase in the transfer conveyance belt 60 is performed. Therefore, the elongation of the transfer conveyance belt 60 due to thermal expansion can be prevented.
[0021]
Another configuration of the transfer apparatus will be described with reference to FIG.
The transfer bias applying members 67Y, 67M, 67C and the backup roller 68 disposed near the transfer bias applying members 67Y are rotatably integrally held by a swing bracket 93, and are configured to be rotatable about a rotary shaft 94. . This rotation rotates clockwise as the cam 96 fixed to the cam shaft 97 rotates in the direction of the arrow.
The support roller 61 and the electrostatic attraction roller 80 located at the entrance of the transfer paper are integrally supported by the entrance roller bracket 90, and are rotatable clockwise from the state of FIG. . A hole 95 provided in the swing bracket 93 and a pin 92 fixed to the entrance roller bracket 90 are engaged with each other, and rotate in conjunction with the rotation of the swing bracket 93. By the clockwise rotation of these brackets 90 and 93, the transfer bias applying members 67Y, 67M and 67C and the backup roller 68 disposed near the transfer bias applying members 67Y, 67M and 67C are separated from the photoconductors 11Y, 11M and 11C, and are statically connected to the entrance roller 61. The electro attraction roller 80 also moves downward. With such a configuration, it is possible to avoid contact between the photoconductors 11Y, 11M, and 11C and the transfer conveyance belt 60 when forming an image of only black.
On the other hand, the transfer bias applying member 67K and the backup roller 68 adjacent thereto are rotatably supported by the outlet bracket 98, and are rotatable about a shaft 99 coaxial with the support roller 62 located at the transfer paper outlet. When the transfer device 6 is attached to and detached from the main body, the transfer device 6 is rotated clockwise by operating a handle (not shown) to move the transfer bias applying member 67K and the backup roller 68 adjacent thereto from the black image forming photoconductor 11K. It is made to separate.
[0022]
Next, an image forming apparatus equipped with the present transfer device will be described.
FIG. 4 is a diagram showing a schematic configuration of the image forming apparatus according to the present invention. This image forming apparatus includes four image forming units 1Y, 1M, 1C, and 1K for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K). Each of the image forming units 1Y, 1M, 1C, and 1K includes a photosensitive drum 11Y, 11M, 11C, and 11K as an image carrier, and a charging unit, a developing unit, and a cleaning unit. The arrangement of the image forming units 1Y, 1M, 1C, and 1K is set so that the rotation axes of the photosensitive drums are parallel to each other and are arranged at a predetermined pitch in the transfer paper moving direction.
Above the image forming units 1Y, 1M, 1C, and 1K, a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like are provided, and based on image data, a surface of each of the photosensitive drums 11Y, 11M, 11C, and 11K is provided. The optical writing device 2 that irradiates the laser beam while scanning it has a transfer drive belt 60 that has a transfer paper 100 below and transfers the transfer paper 100 so as to pass through the transfer unit of each image forming unit. A transfer device 6 is provided. The detailed configuration of the transfer device 6 is as described above.
A fixing device 7, a paper discharge tray 8, and the like are provided beside the transfer device 6. The fixing device 7 is a belt fixing type fixing device including a fixing belt stretched by a heating roller having a heating element therein and a driven roller, and a pressure roller having a heating element therein.
Paper feed cassettes 3 and 4 on which transfer paper 100 is placed are provided below the image forming apparatus. Also, a manual feed tray MF for manually feeding paper from the side of the image forming apparatus is provided.
In addition, a toner supply container TC is provided, and a waste toner bottle, a duplex / reversing unit, a power supply unit, and the like (not shown) are also provided in a space S indicated by a two-dot chain line.
[0023]
Hereinafter, the operation of the image forming apparatus will be described.
The transfer paper 100 fed from the paper feed cassettes 3 and 4 or the manual feed tray MF is transported by transport rollers while being guided by a transport guide (not shown), and is transported to a temporary stop position where the registration roller pair 5 is provided. The transfer paper 100 sent out at a predetermined timing by the registration roller pair 5 is carried on a transfer / conveyance belt 60, is conveyed toward each of the image forming units 1Y, 1M, 1C, and 1K and passes through each of the transfer units.
The toner images developed on the photoconductor drums 11Y, 11M, 11C, and 11K of the image forming units 1Y, 1M, 1C, and 1K are superimposed on the transfer paper 100 at the respective transfer units, and the transfer electric field and the nip pressure are set. Is transferred onto the transfer paper 100 under the action of By the transfer of the superposition, a full-color toner image is formed on the transfer paper 100.
On the other hand, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11K after the transfer of the toner image are cleaned by a cleaning device, and are further neutralized to prepare for the formation of the next electrostatic latent image.
After the full-color toner image is formed on the transfer paper 100 by the fixing device 7, the transfer paper 100 is fixed to the first discharge direction B or the second In the paper discharge direction C. When the sheet is discharged onto the sheet discharge tray 8 from the first sheet discharge direction B, the sheets are stacked in a so-called face-down state in which the image surface is down. On the other hand, when the paper is discharged in the second paper discharge direction C, the paper is conveyed to another post-processing device (a sorter, a binding device, or the like) (not shown), or is again sent for double-sided printing via a switchback unit. The sheet is conveyed to the registration roller pair 5.
[0024]
The transfer device 6 mounted on the image forming apparatus applies a bias having the same polarity as the transfer bias to the support roller 62 when the transfer paper 100 carried and transported by the transfer transport belt 60 passes over the support roller 62. Therefore, it is possible to prevent the separation discharge from occurring between the transfer conveyance belt 60 and the transfer paper 100, and to prevent the toner on the transfer paper 100 from scattering. As a result, it is possible to prevent the image from being disturbed or stained, and from being stained on peripheral members.
[0025]
【The invention's effect】
As described above, according to the present invention, there is provided a transfer device having a configuration that prevents toner scattering caused when transfer paper carried and conveyed on a transfer conveyance belt is separated from the transfer conveyance belt without increasing the number of components. Can be provided. In addition, the image forming apparatus equipped with the present transfer device can output a high-quality image free from image disturbance, dirt, and the like, and can prevent contamination of peripheral members of the transfer device.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a transfer device according to the present invention.
FIG. 2 is a front view illustrating a configuration of a support roller.
FIG. 3 is a front view showing another configuration of the support roller.
FIG. 4 is a diagram illustrating a schematic configuration of an image forming apparatus according to the present invention.
[Explanation of symbols]
1 Image forming unit 11 Photoconductor drum (image carrier)
6 transfer device 60 transfer / transport belt 62 support roller 621 bias application power supply 67 transfer bias application member 7 fixing device 100 transfer paper

Claims (6)

A transfer transport belt that is wrapped around a plurality of support members and carries and transports the transfer paper;
A transfer bias applying member for applying a bias when a visible image on an image carrier is transferred to the transfer paper, the transfer device being on the inner side of the transfer paper transport surface of the transfer transport belt,
Among the support members that support the transfer paper transport surface of the transfer transport belt, the support member located on the most downstream side in the transfer paper transport direction is a conductive member, and a bias having the same polarity as the transfer bias is applied to the conductive member. A transfer device, comprising: The transfer device according to claim 1,
The bias applying means provided on the conductive member, when the transfer paper crosses the conductive member and the transfer portion where the transfer bias of the closest position is applied to the conductive member in the transport process, A transfer device for applying a voltage. The transfer device according to claim 1, wherein
A transfer apparatus, wherein the bias applying means provided on the conductive member continuously applies a bias while the transfer paper passes over the conductive member. The transfer device according to claim 1,
A transfer apparatus, wherein the bias applying means provided on the conductive member always applies a bias during the operation of the transfer / conveying belt. The transfer device according to any one of claims 1 to 4,
The transfer device according to claim 1, wherein the conductive member is configured using heat insulating or a member having a lower thermal conductivity than metal. An image carrier for carrying a latent image,
Latent image forming means for forming a latent image on the image carrier,
Developing means for supplying toner to the latent image on the image carrier and visualizing the toner;
Transfer means for transferring the visible image on the image carrier to transfer paper,
A fixing unit for fixing the visible image on the transfer paper,
6. The image forming apparatus according to claim 1, wherein the transfer unit is the transfer device according to claim 1.

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