JP2010026227A - Transfer unit and image forming apparatus employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer unit in which the occurrence of scratches of a belt member is suppressed by suppressing a slip of a bending roller on the belt member, and to provide an image forming apparatus employing the same. <P>SOLUTION: The transfer unit includes: a loop-like conductive intermediate transfer belt 11 which is stretched around tension rollers 13, 15, 16, and 17 and is endlessly moved; a surface roller 19 which is brought into contact with a front surface being an outside surface of the loop of the intermediate transfer belt 11, to bend the intermediate transfer belt 11 to the inside of the loop and is rotated with endless movement of the intermediate transfer belt 11; and a power source 81 which applies a prescribed-polarity bias for electrostatically attracting the intermediate transfer belt 11 to the surface roller 19, to the surface roller 19. A conductive elastic member is used for a surface layer of the surface roller 19. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transfer device used in an image forming apparatus such as a printer, a facsimile machine, and a copying machine, and an image forming apparatus including the transfer device.

  In an image forming apparatus for forming a color image of this type, a configuration in which a toner image on an image carrier is transferred to a recording medium via an intermediate transfer member serving as a belt member is often used. The belt member is usually stretched by a tension roller composed of at least three axes of a drive roller, a tension roller, and a speed control roller. If the quality of each color (magenta, cyan, yellow) toner image, such as color misregistration, is divisible, a configuration using a biaxial stretching roller can be used without using the speed control roller. When a high-quality image without color misregistration is required, the belt member needs to be stretched by a stretching roller having three or more axes. However, as the number of shafts of the stretching roller increases, the space occupied by the belt member increases, and it becomes difficult to cope with the space saving required for recent apparatuses.

  For such a problem, Patent Document 1 discloses that a loop-shaped belt member stretched by a plurality of stretching rollers comes into contact with a front surface that is an outer surface of the loop, and the belt member is curved inward of the loop. A transfer device having a curved roller is disclosed. By curving a part of the belt member inside the loop, a useless space inside the loop can be reduced, and a space occupied by the transfer device in the image forming apparatus is reduced. The degree of freedom of layout is expanded.

JP 2004-177773 A

  In the transfer device described in Patent Document 1, the bending roller is configured to follow the surface movement of the belt member, and friction generated at the contact portion between the belt member and the bending roller due to the surface movement of the belt member. The bending roller is rotated by the force. However, if toner or paper dust adheres to the front surface of the belt member, the frictional force generated at the contact point between the belt member and the curved roller is reduced, and the curved roller is moved with respect to the surface movement. When rotating, it may slip on the belt member. When the bending roller slips on the belt member in this way, the front surface of the belt member is rubbed by the bending roller and the front surface of the belt member is damaged, and the life of the belt member is shortened. Arise. In addition, when the intermediate transfer member, which is a belt member, is damaged, an abnormal image may be generated.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a transfer device that can prevent the curved roller from slipping on the belt member and suppress damage to the belt member, and An image forming apparatus is provided.

According to the first aspect of the present invention, there is provided a belt member having a loop-like conductivity that is endlessly moved while being stretched by a plurality of stretching rollers, and a belt member that abuts against a front surface that is a loop outer surface of the belt member. A biasing device having a predetermined polarity for electrostatically attracting the belt member to the curved roller in a transfer device comprising a curved roller that curves the member inwardly and rotates along with the endless movement of the belt member; Bias applying means for applying to the curved roller is provided, and a conductive elastic member is used for the surface layer of the curved roller.
According to a second aspect of the present invention, in the transfer apparatus according to the first aspect, the conductive elastic member is a rubber material.
According to a third aspect of the present invention, in the transfer device of the second aspect, the conductive elastic member is foamed rubber.
According to a fourth aspect of the present invention, in the transfer device according to the first, second, or third aspect, the bias applying unit applies a bias having the same polarity as the charged polarity of the toner carried and conveyed on the belt member. Is.
According to a fifth aspect of the present invention, in the transfer device according to the fourth aspect, the bias applying means can switch and apply a bias having the same polarity and a reverse polarity as the charged polarity of the toner carried on the belt member. It is characterized by being.
According to a sixth aspect of the present invention, in the transfer device according to the fifth aspect, the bias applying means switches the bias having the same polarity and the opposite polarity to the charged polarity of the toner carried on the belt member and applies it a plurality of times. It is a feature.
A seventh aspect of the present invention is the transfer apparatus according to the fifth or sixth aspect, wherein the bias applying unit applies a bias having the same polarity while the curved roller makes at least one rotation.
According to an eighth aspect of the present invention, in the transfer device of the first, second, third, fourth, fifth, sixth or seventh aspect, an axial length of the curved roller is longer than a width direction length of the belt member. To do.
According to a ninth aspect of the present invention, in the transfer device according to the first, second, third, fourth, fifth, sixth, seventh, or eighth aspect, the curved roller has a larger diameter at the central portion in the axial direction than the diameter at both axial end portions. It has a crown shape.
According to a tenth aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier; and a transfer unit that transfers a toner image on the image carrier to a recording medium via a belt member. 2, 3, 4, 5, 6, 7, 8 or 9 transfer device is used.
In the present invention, the belt member and the bending roller can be brought into electrostatic close contact with each other by applying a bias having a predetermined polarity to the bending roller by the bias applying means. Further, since the surface layer of the bending roller is made of an elastic member, the frictional force at the contact point between the belt member and the bending roller can be increased as compared with the case where the surface layer is made of a rigid material. Therefore, the bending roller can be reliably rotated with respect to the endless movement of the belt member, and the bending roller can be prevented from slipping on the belt member.

  According to the present invention, there is an excellent effect that it is possible to provide a transfer device that can prevent the bending roller from slipping on the belt member and prevent the belt member from being damaged, and an image forming apparatus including the transfer device.

  Hereinafter, an electrophotographic printer (hereinafter simply referred to as a printer) will be described as an example of an embodiment of an image forming apparatus to which the present invention is applied. First, the basic configuration of the printer will be described. FIG. 1 is a schematic configuration diagram illustrating the overall configuration of the printer. In the drawing, the printer includes four process units 60Y, M, C, and K for generating toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and Bk). . These use Y, M, C, and K toners of different colors, but other than that, they have the same configuration and are replaced when the lifetime is reached.

  FIG. 2 is a schematic configuration diagram showing a configuration of a Y process unit 60Y for generating a Y toner image. Here, the process unit for Y will be described as an example. As shown in FIG. 2, the process unit includes a charging device 30Y that uniformly charges the surface of the photoreceptor around the drum-shaped photoreceptor 20Y, a cleaning device 40Y that cleans transfer residual toner on the photoreceptor, and a photoreceptor. A developing device 50Y for developing the upper latent image is provided. The developing device 50Y carries a developer sleeve 51Y that carries and conveys a two-component developer composed of a carrier and Y toner, a doctor blade 52Y that regulates the layer thickness of the developer on the developer sleeve 51Y, and agitates and conveys the developer in the device. Conveying screws 54Y and 55Y are provided. This process unit is detachably integrated with the printer main body as one unit with these members held in a common unit casing.

  In the process unit 60Y having the above-described configuration, the surface of the photoreceptor 20Y uniformly charged by the charging device 30Y is exposed and scanned by the laser light L emitted from the optical writing unit 8 serving as a latent image forming unit. The electrostatic latent image is carried. The electrostatic latent image of Y is developed into a Y toner image in a developing area facing the developing sleeve 51Y of the developing device 50Y. The Y toner image developed on the photoconductor 20Y is intermediately transferred onto the intermediate transfer belt 11 by a primary transfer roller 12Y provided in a transfer unit described later. Transfer residual toner remaining on the photoreceptor 20Y after the transfer is cleaned by the cleaning device 40Y. Thereafter, the photoconductor 20Y is charged simultaneously with the charge removal by the charging device 30Y to which the bias of the alternating current component is applied to the direct current, and is prepared for the next image formation. In the process units 60M, C, and K for other colors, M, C, and K toner images are similarly formed on the photoreceptors 20M, C, and K, and sequentially superimposed on the Y toner images on the intermediate transfer belt 11. Intermediate transfer. As a result, a four-color superimposed toner image is formed on the intermediate transfer belt 11.

  As shown in FIG. 1, an optical writing unit 8 is disposed below the process units 60Y, 60M, 60C, and 60K in the drawing. The optical writing unit 8 individually scans the laser light L from the four light sources onto the respective photosensitive members in the process units 60Y, 60M, 60C, and 60K based on the image information. As a result, electrostatic latent images for Y, M, C, and K are formed on the photoconductors 20Y, 20M, 20C, and 20K. Here, the optical writing unit 8 deflects the laser light L emitted from the light source in the photosensitive body axial direction (main scanning direction) by reflection on a regular polygon reflecting surface of a polygon mirror that is rotationally driven by a motor. The photoconductor 20 is optically scanned in the main scanning direction.

  A paper feed cassette 1 having a paper feed roller 3 is disposed on the lower side of the optical writing unit 8 in the drawing. The paper feed cassette 1 stores a plurality of recording papers P as transfer materials in a stack of paper sheets, and presses the paper feed roller 3 against the uppermost recording paper P. When the paper feed roller 3 is driven to rotate counterclockwise in the drawing by a driving means (not shown), the uppermost recording paper P is sent out toward the paper feed path.

  Near the end of the paper feed path, a registration roller pair 4 is disposed, and the recording paper P fed to the paper feed path is sandwiched between the rollers of the registration roller pair 4. As soon as the recording paper P is sandwiched between the rollers, the registration roller pair 4 temporarily stops the rotational driving of the roller pair. Then, the rotational driving of the roller pair is resumed at a timing at which the recording paper P can be superimposed on the four-color superimposed toner image on the intermediate transfer belt 11, and the recording paper P is sent out to a secondary transfer nip described later.

  Above the process units 60Y, 60M, 60C, and 60K, a transfer unit 10 is disposed that moves the intermediate transfer belt 11 endlessly in the direction of arrow A in the drawing. FIG. 3 is a schematic configuration diagram showing the configuration of the transfer unit. As shown in FIG. 3, the transfer unit 10 is energized by four primary transfer rollers 12Y, 12M, 12C, and 12K, a driving roller 13 that rotates and a pressure spring 14 in a loop of the intermediate transfer belt 11. A tension roller 15 that applies tension to the intermediate transfer belt 11 and rollers 16 and 17 that rotate following the intermediate transfer belt 11 are provided. The intermediate transfer belt 11 is endlessly moved counterclockwise in the figure by the rotational drive of the driving roller 13 while being stretched by these rollers.

  The belt speed of the intermediate transfer belt 11 is detected by the entrance roller 16 by a speed detector (not shown). The drive roller 13 does not detect the speed because the speed fluctuation due to the belt thickness fluctuation cannot be eliminated. The tension roller 15 does not detect the speed because it is difficult to maintain the distance between the speed detection device and the tension roller 15 with respect to the belt swing.

  The primary transfer rollers 12Y, 12M, 12C, and 12K sandwich the intermediate transfer belt 11 that is moved endlessly in this manner between the photoreceptors 20Y, 20M, 20C, and 20K. As a result, primary transfer nips for Y, M, C, and K are formed by contact between the photoconductors 20Y, M, C, and K and the front surface of the intermediate transfer belt 11. To the primary transfer rollers 12Y, 12M, 12C, and 12K, a primary transfer bias having a polarity opposite to the charging polarity of the toner (in this embodiment, a positive polarity) is applied by a transfer power source (not shown). The intermediate transfer belt 11 sequentially passes through the primary transfer nips for Y, M, C, and K along with the endless movement thereof, and Y, M, and C on the photoreceptors 20Y, 20M, 20C, and 20K. , K toner images are sequentially superimposed and transferred intermediately.

  In addition to the members described so far, the transfer unit 10 includes a transfer counter roller 5 and a belt cleaning device 18 outside the loop of the intermediate transfer belt 11. The transfer facing roller 5 is in contact with the front surface of the belt at a position facing the driving roller 13 in the belt loop via the intermediate transfer belt 11 to form a secondary transfer nip. The recording paper P is sent out from the registration roller pair 4 toward the secondary transfer nip at the timing when the four-color superimposed toner image formed on the intermediate transfer belt 11 enters the secondary transfer nip.

  A secondary transfer bias having the same polarity as the toner charging polarity (negative polarity in the present embodiment) is applied to the driving roller 13 in the belt loop by the power source 80. The secondary transfer roller 5 outside the belt loop is grounded. As a result, a secondary transfer electric field for electrostatically moving the toner on the intermediate transfer belt 11 from the belt side toward the secondary transfer roller 5 side is formed in the secondary transfer nip. Then, the four-color superimposed toner image is collectively transferred to the recording paper P in close contact with the four-color superimposed toner image on the intermediate transfer belt 11 in the secondary transfer nip by the action of the secondary transfer electric field or nip pressure. Thus, a full color image is formed in combination with the white color of the recording paper P.

  The transfer residual toner that has not been secondarily transferred to the recording paper P adheres to the intermediate transfer belt 11 after passing through the secondary transfer nip. This is removed from the belt surface by the belt cleaning device 18.

  A fixing device 6 is disposed above the secondary transfer nip in the drawing. The recording paper P discharged from the secondary transfer nip while being peeled off from the intermediate transfer belt 11 and the secondary transfer roller 5 is fed into the fixing device 6. Then, the full color image is fixed on the surface by heating or pressurizing when passing through a fixing nip by contact between a fixing roller containing a heat source such as a halogen lamp and a pressure roller pressed against the fixing roller. The Thereafter, the recording paper P is discharged out of the apparatus through a pair of paper discharge rollers 7. A stack unit 70 is formed on the upper surface of the printer main body, and the recording sheets P discharged to the outside by the discharge roller pair 7 are sequentially stacked on the stack unit 70.

  A bottle accommodating portion 71 is disposed between the transfer unit 10 and the stack portion 70 located above the transfer unit 10. The bottle storage portion 71 stores toner bottles 9Y, M, C, and K that store Y, M, C, and K toners for supply. The Y, M, C, and K toners in the toner bottles 9Y, 9M, 9C, and 9K are supplied from Y, M, C, and K toner replenishing devices (not shown) to develop the process units 60Y, M, C, and K, respectively. Is replenished as needed. These toner bottles 9Y, 9M, 9C, and 9K are attached to and detached from the printer main body independently of the process units 60Y, 60M, 60C, and 60K.

  Meanwhile, in the transfer unit 10, a front roller 19 that is a curved roller is disposed outside the loop of the intermediate transfer belt 11. The front roller 19 abuts the intermediate transfer belt 11 on the surface outside the loop, curls the intermediate transfer belt 11 inward and pushes it down, and rotates along with the intermediate transfer belt 11. The surface roller 11 is configured to rotate with the rotation of the intermediate transfer belt 11 in order to prevent a speed difference between the intermediate transfer belt 11 and the surface roller 19. This is because if the speed difference occurs between the intermediate transfer belt 11 and the front roller 19, the front roller 19 damages the intermediate transfer belt 11. The front roller 19 is disposed downstream of the drive roller 13 in the intermediate transfer belt rotation direction and upstream of the Y primary transfer double-up in the intermediate transfer belt rotation direction. This suppresses the problem that the toner image is disturbed by the contact between the toner image before being transferred to the recording paper P by the secondary transfer two-up formed on the intermediate transfer belt 11 and the front roller 19. To do.

  Here, a conductive elastic member made of a rubber material is used for the surface layer portion of the front roller 19. FIG. 4 is a cross-sectional view showing the configuration of the front roller. As shown in FIG. 4, the front roller 19 includes a metal core 19a made of metal and a surface layer 19b made of a conductive elastic member made of a rubber material. As the rubber material, rubber having high frictional force such as EP (ethylene propylene) rubber may be used. In this way, by using a conductive elastic member made of a rubber material for the surface layer 19b, the frictional force between the intermediate transfer belt 11 and the front roller 19, that is, the accompanying force becomes larger, and more reliable accompanying is possible. It becomes.

  A bias having the same polarity as the toner is applied to the front roller 19 by a power source 81 as a bias applying means. In this embodiment, a bias is applied to the front roller 19 to conduct to the ground of the secondary transfer roller 5 through the surface of the intermediate transfer belt 11 (shown in the direction of arrow B). In this way, by applying a bias to the front roller 19, an electrostatic close contact force is generated between the intermediate transfer belt 11 and the front roller 19, and reliable follow-up is performed. Even if the toner is input between the intermediate transfer belt 11 and the front roller 19 to reduce the frictional force, reliable follow-up is performed by the electrostatic adhesion force. In this embodiment, the power supply 81 for applying a bias to the front roller 19 and the power supply 80 for applying a bias to the driving roller 13 are provided separately, but it goes without saying that these may be used together. Further, the power source for applying a bias to the front roller 19 may be combined with another power source provided in the apparatus main body.

  The bias applied to the front roller 19 is the same polarity as the toner (negative polarity in this embodiment), so that the toner adhering on the front roller 19 is transferred to the intermediate transfer belt 11 and the front roller 19 is cleaned. Can do. As described above, the front roller 19 is cleaned, so that the frictional force between the endless belt 11 and the front roller 19 is maintained to enable reliable follow-up.

  Furthermore, the front roller 19 may be applied by switching bias application of the same polarity and reverse polarity as the toner at an arbitrary timing. FIG. 5 is a schematic configuration diagram illustrating a configuration of a transfer unit according to another embodiment. In FIG. 5, the same reference numerals as those shown in FIG. By applying a bias having the same polarity as the toner to the front roller 19, the toner adhering to the front roller 19 is transferred to the intermediate transfer belt 11, and the front roller 19 is cleaned. However, there is a possibility that some toners are charged in the opposite polarity to the normal polarity. Therefore, there is a possibility that the toner attached to the front roller 19 cannot be cleaned with a single polarity as shown in FIG. Therefore, as shown in FIG. 5, the power supply 82 as bias applying means is configured to be able to apply a bias having a polarity opposite to that of the toner to the front roller 19. As a result, the toner adhering to the front roller 19 in a state of being charged with a reverse polarity is also transferred to the intermediate transfer belt 11 and the front roller 19 can be cleaned. For example, the polarity may be repeatedly switched in the order of minus polarity → brass polarity → minus polarity → brass polarity →. Thereby, compared with the case where only a single polarity is applied, the front roller can be more reliably cleaned, and the reduction of the frictional force can be prevented.

FIG. 6 is a partially enlarged configuration diagram showing the configuration of the transfer unit. FIG. 7 is a characteristic diagram showing the relationship between the bias application time to the front roller and the applied bias. In the transfer unit having the configuration shown in FIG. 6, the time T of each bias applied to the front roller 19 is expressed by the following equation (1). In equation (1), a is the surface roller diameter, π is the circumferential ratio, and V1 is the endless belt conveyance speed.
T> (a × π) / V1 (1)
As shown in FIG. 7, when the number of repetitions for switching the applied bias is required three times, the total bias application time is as shown in (T × 6). Thereby, the front roller can be more reliably cleaned, and the follow-up structure is ensured.

  FIG. 8 is a configuration diagram showing the configuration of the front roller. The front roller 19 shown in FIG. 8 includes a metal core 19'a made of metal and a surface layer 19'b made of foamed rubber. By using foam rubber for the surface layer portion 19′b, the toner adhering to the intermediate transfer belt 11 can be taken into the bubbles of the foam rubber, so that the toner interposed between the intermediate transfer belt 11 and the front roller 19 ′. And the frictional force can be prevented from being reduced. Further, as described above, the toner inside the bubbles can be removed by applying a bias to the front roller 19 ', so that it is possible to prepare for the next toner input.

  In order to reliably rotate the intermediate transfer belt 11 and the front roller 19, it is preferable to adopt a configuration as described below. FIG. 9 is a schematic diagram for explaining the lengths of the intermediate transfer belt and the front roller. As shown in FIG. 9, the front roller 19 has a length (length in the longitudinal direction) L1 that is L0 <L1 with respect to the width of the intermediate transfer belt 11 (length in the direction orthogonal to the moving direction) L0. It is comprised so that. As a result, a bias can be applied across the entire width of the intermediate transfer belt 11. That is, since the electrostatic adhesion force is effective over the entire belt width of the intermediate transfer belt 11, the force that causes the accompanying rotation increases.

  FIG. 10A is a plan view showing the configuration of a surface roller in which the shape of the surface layer portion is formed flat in the longitudinal direction (hereinafter referred to as a straight shape), and FIG. 10B shows the surface roller and the intermediate transfer belt. It is a characteristic view explaining the contact area of. FIG. 11A is a plan view showing the configuration of a surface roller in which the outer layer has a larger outer diameter at the center in the longitudinal direction than the both ends in the longitudinal direction (hereinafter referred to as a crown shape). FIG. 4B is a characteristic diagram illustrating the contact area between the front roller and the intermediate transfer belt. In general, the front roller 19 is bent by a reaction force from the intermediate transfer belt 11. Therefore, as shown in FIGS. 10A and 10B, when the surface layer portion of the front roller 19 ″ has a straight shape, the area that contacts the intermediate transfer belt 11 at the center of the front roller 19 ″. Will become smaller. If the contact area between the intermediate transfer belt 11 and the front roller 19 ″ is small, it is considered that the force that causes the accompanying rotation is weakened, causing a problem. On the other hand, as shown in FIGS. 11A and 11B, when the surface layer portion of the front roller 19 has a crown shape, even if the front roller 19 is bent, the contact between the intermediate transfer belt 11 and the front roller 19 is caused. The amount of area reduction can be suppressed. As a result, the intermediate transfer belt 11 and the front roller 19 can be reliably rotated.

As described above, according to the transfer unit 10 that is the transfer device according to the present embodiment, a bias is applied to the front roller 19 that is a curved roller by the power supply 81 that is a bias applying unit. For this reason, an electrostatic close contact force is generated between the intermediate transfer belt 11 that is a belt member and the front roller 19, and reliable follow-up is performed. Even if the toner is input between the intermediate transfer belt 11 and the front roller 19 to reduce the frictional force, reliable follow-up is performed by the electrostatic adhesion force. Further, since the surface layer portion of the front roller 19 is made of rubber which is a conductive elastic member, the frictional force between the intermediate transfer belt 11 and the front roller 19 is increased, and more reliable follow-up is performed.
Further, according to the transfer unit 10 according to the present embodiment, since the rubber material is used for the surface layer portion 19b of the front roller 19, the frictional force between the intermediate transfer belt 11 and the front roller 19 is increased, so that more reliable. A companion is performed.
Further, according to the transfer unit 10 according to the present embodiment, foamed rubber is used for the surface layer portion 19′b of the front roller 19 ′. Therefore, the toner adhering to the intermediate transfer belt 11 can be taken into the foamed rubber bubbles, and the toner interposed between the intermediate transfer belt 11 and the front roller 19 ′ is reduced, thereby preventing the frictional force from being reduced. Can do.
Further, according to the transfer unit 10 according to the present embodiment, a bias having the same polarity as the toner is applied to the front roller 19. As a result, the toner adhering to the front roller 19 is transferred to the intermediate transfer belt 11 and the front roller 19 can be cleaned. As described above, the front roller 19 is cleaned, so that the frictional force between the endless belt 11 and the front roller 19 is maintained to enable reliable follow-up.
Further, according to the transfer unit 10 according to the present embodiment, a bias having the same polarity and reverse polarity as the toner is switched and applied to the front roller 19. As a result, the regular charged toner and the reverse charged toner adhering to the front roller 19 are both transferred to the intermediate transfer belt 11 and the front roller 19 can be cleaned. As described above, the front roller 19 is cleaned, so that the frictional force between the endless belt 11 and the front roller 19 is maintained to enable reliable follow-up.
Further, according to the transfer unit 10 according to the present embodiment, a bias having the same polarity and reverse polarity as the toner is switched and applied to the front roller 19 a plurality of times. Thus, even if the toner attached to the front roller 19 cannot be removed by applying a single bias, the toner attached to the front roller 19 by applying a plurality of biases can be reliably removed.
Further, according to the transfer unit 10 according to the present embodiment, a bias having the same polarity is applied while the front roller 19 rotates at least once. Thereby, the toner adhering to the front roller 19 can be reliably removed.
Further, according to the transfer unit 10 according to the present embodiment, the axial length L1 of the front roller 19 is formed longer than the width direction length L0 of the intermediate transfer belt 11. As a result, the electrostatic adhesion force is effective over the entire belt width of the intermediate transfer belt 11, and the front roller 19 can be reliably rotated.
Further, according to the transfer unit 10 according to the present embodiment, the shape of the front roller 19 is a crown shape. Thus, the contact area between the intermediate transfer belt 11 and the front roller 19 is constant in the axial direction, and the front roller 19 can be reliably rotated.
Further, according to the printer of the present embodiment, the photoconductor 20 and a transfer unit that transfers the toner image formed on the photoconductor 20 to the recording paper P that is a recording medium via the intermediate transfer belt 11. A unit 10 is provided. Therefore, the effects as described above can be obtained, and as a result, the life can be extended and the occurrence of abnormal images can be suppressed.

1 is a schematic configuration diagram illustrating an overall configuration of a printer according to an embodiment. FIG. 2 is a schematic configuration diagram illustrating a configuration of a Y process unit of the printer. FIG. 2 is a schematic configuration diagram illustrating a configuration of a transfer unit of the printer. Sectional drawing which shows the structure of the surface roller of the transfer unit. The schematic block diagram which shows the structure of the transfer unit which concerns on another embodiment. FIG. 3 is a partially enlarged configuration diagram illustrating a configuration of a transfer unit. The characteristic view which shows the relationship between the bias application time to the surface roller of a transfer unit, and an applied bias. The block diagram which shows the structure of the surface roller which concerns on another embodiment. FIG. 3 is a schematic diagram illustrating the lengths of an intermediate transfer belt and a front roller. (A) is a top view which shows the structure of a straight-shaped surface roller, (b) is a characteristic view explaining the contact area of this surface roller and an intermediate transfer belt. (A) is a top view which shows the structure of a crown-shaped surface roller, (b) is a characteristic view explaining the contact area of this surface roller and an intermediate transfer belt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Intermediate transfer unit 11 Intermediate transfer belt 12 Primary transfer roller 13 Drive roller 15 Tension roller 16 Entrance roller 18 Belt cleaning device 19 Front roller 20 Photoconductor 80, 81, 82 Power supply

Claims (10)

A belt member having a loop-like conductivity that is endlessly moved while being stretched by a plurality of stretching rollers, and abuts against the front surface that is the outer surface of the loop of the belt member, so that the belt member is curved inwardly A transfer device comprising a curved roller that rotates with the endless movement of the belt member.
A transfer device comprising bias applying means for applying a bias having a predetermined polarity for electrostatically attracting the belt member to the curved roller, and using a conductive elastic member as a surface layer of the curved roller. . The transfer device according to claim 1.
The transfer device, wherein the conductive elastic member is a rubber material. The transfer device according to claim 2.
The transfer device, wherein the conductive elastic member is foamed rubber. The transfer device according to claim 1, 2, or 3,
The transfer device, wherein the bias applying means applies a bias having the same polarity as the charging polarity of the toner carried on the belt member. The transfer device according to claim 4.
The transfer apparatus according to claim 1, wherein the bias applying means is capable of switching and applying a bias having the same polarity and a reverse polarity as a charging polarity of the toner carried and conveyed on the belt member. The transfer device according to claim 5.
The transfer device, wherein the bias applying means switches a bias having the same polarity and opposite polarity to the charged polarity of the toner carried and conveyed on the belt member, and applies a plurality of times. The transfer device according to claim 5 or 6,
The transfer device, wherein the bias applying unit applies a bias having the same polarity while the curved roller makes at least one rotation. The transfer device according to claim 1, 2, 3, 4, 5, 6 or 7.
2. A transfer apparatus according to claim 1, wherein an axial length of the curved roller is longer than a width direction length of the belt member. The transfer apparatus according to claim 1, 2, 3, 4, 5, 6, 7 or 8.
The transfer device according to claim 1, wherein the curved roller has a crown shape in which a diameter at a central portion in the axial direction is larger than a diameter at both end portions in the axial direction. In an image forming apparatus comprising: an image carrier; and a transfer unit that transfers a toner image on the image carrier to a recording medium via a belt member.
An image forming apparatus using the transfer device according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9 as the transfer means.

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