JP2012042748A - Transfer device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer device capable of obtaining an output image with less roughening, regardless of surface irregularity of a transfer material, and an image formation device using the same.SOLUTION: A transfer device 47 comprises an image carrier 13 which is in an endless belt shape and capable of traveling with a toner image carried on a surface thereof and transfer rollers 50, 51 that make pressure-contact, through intermediary of the image carrier 13, with backup members 48, 49 arranged on a back face side of the image carrier 13, to form nip parts N1, N2 and transfers the toner image to a recording medium P at the nip parts N1, N2. In the transfer device 47, a plurality of nip parts N1, N2 respectively have different transfer pressures against the recording medium P.

Description

  The present invention relates to a transfer device of an electrophotographic image forming apparatus that forms an image using toner such as a copying machine, a facsimile machine, and a printer.

  A transfer material such as a recording sheet is sandwiched between a transfer nip portion formed by an intermediate transfer belt and a contact member such as a transfer roller that contacts the intermediate transfer belt, and a toner image on the intermediate transfer belt is transferred by a transfer pressure and an electric field in the transfer nip portion. An image forming apparatus including a transfer device that transfers to a material is known. In this transfer device, the surface of a coated paper or the like is relatively smooth and can be transferred with a relatively small transfer pressure to a transfer material that has less unevenness when viewed microscopically, whereas high-quality paper or ordinary paper When the surface of paper is rougher than coated paper and microscopically, it is necessary to perform transfer at a transfer pressure that is higher than the transfer pressure for transferring to coated paper for transfer materials that are uncoated paper with many irregularities. There is. This is because if the transfer material is uneven, the transfer material deteriorates in the transfer material in the transfer nip because the contact with the toner image on the intermediate transfer belt is worse than the protrusion in the transfer nip. The print image is likely to have white spots (hereinafter referred to as “bokeh”) due to poor transfer, but by increasing the transfer pressure at the transfer nip, the transfer material is crushed to reduce the unevenness, This is because it is possible to reduce the blur by making the transferability at approximately the same (the unevenness transferability can be improved).

  Furthermore, in recent years, a technology has been adopted in which the surface of the transfer belt follows the unevenness of the transfer material to further reduce the blur by using an elastic transfer belt provided with an elastic layer such as rubber on the surface of the transfer belt. In this case, the change in the transfer pressure tends to contribute to the change in the uneven transfer property. However, when the transfer pressure is increased, there is a problem that the transfer material such as thin paper is wrinkled or the durability of the apparatus is lowered. A thin paper has a low unevenness and a transfer material having a high unevenness is generally a thick paper, and a transfer device capable of increasing the transfer pressure only when the unevenness of the transfer material is high is required. Therefore, it has a mechanism that makes the transfer pressure variable, and by setting the optimal transfer pressure according to the type of recording medium, the occurrence of blur is suppressed even when a highly uneven transfer material is used. The technique is disclosed in, for example, “Patent Document 1”.

  However, the above-described technique has a problem that it cannot sufficiently cope with unevenness (thickness) of the transfer material used. For example, when a 300 kg transfer material with high unevenness is used, it is necessary to significantly increase the transfer pressure. In a general transfer device, a transfer pressure is applied to the transfer nip portion by applying an urging force to both ends of the transfer roller. However, when the urging force is increased, the transfer roller is bent and the transfer nip portion is bent. There arises a problem that the transfer pressure has a deviation in the axial direction of the transfer roller. As means for solving the deviation of the nip transfer pressure caused by the deflection of the roller, (1) a method of changing the thickness of the roller in the longitudinal direction, and (2) making the thickness of the roller variable in the longitudinal direction. A method (for example, “Patent Document 2”) is known. However, the method (1) can achieve a uniform nip transfer pressure in the longitudinal direction only with a specific pressure, and the method (2) makes it difficult to make the transfer roller thin and the transfer belt after passing through the nip. The separation of the transfer material from the roller deteriorates and the mechanism becomes complicated, and even if the transfer pressure is variable, there are problems in ensuring the uniformity of the transfer pressure in the longitudinal direction of the transfer roller and simplifying the apparatus. ing.

  The present invention solves the above-mentioned problems, can ensure the uniformity of the transfer pressure in the axial direction of the transfer roller in response to the diversification of the transfer material, suppress the complication of the apparatus, and improve the unevenness of the transfer material. It is an object of the present invention to provide a transfer apparatus capable of obtaining an output image with little blur regardless of the above, and an image forming apparatus using the transfer apparatus.

  According to the first aspect of the present invention, there is provided an endless belt-like image carrier capable of carrying a toner image on its surface and a backup member disposed on the back side of the image carrier via the image carrier. And a transfer device having a transfer roller for transferring the toner image to a recording medium at the nip, the plurality of nips having different transfer pressures to the recording medium can be formed. Features.

  A second aspect of the present invention is the transfer apparatus according to the first aspect, further comprising a plurality of the transfer roller and / or the backup member.

  According to a third aspect of the present invention, in the transfer device according to the second aspect, the plurality of transfer rollers and / or the backup member are different in hardness.

  According to a fourth aspect of the present invention, in the transfer device according to the third aspect, the plurality of transfer rollers and / or the backup member are further arranged on the downstream side than those arranged on the upstream side in the recording medium conveyance direction. It is characterized by a low hardness of the fish.

  According to a fifth aspect of the present invention, in the transfer device according to any one of the first to fourth aspects, the pressure contact force of the transfer roller with respect to the backup member in each of the nip portions is different.

  According to a sixth aspect of the present invention, in the transfer device according to the fifth aspect, the pressure contact force of the transfer roller with respect to the backup member in each nip portion is lower than that in the nip portion located upstream in the recording medium conveyance direction. The nip portion located on the side is low.

  According to a seventh aspect of the present invention, in the transfer device according to any one of the first to sixth aspects, the pressure contact force of the transfer roller with respect to the backup member can be changed.

  According to an eighth aspect of the present invention, in the transfer device according to any one of the first to seventh aspects, a bias applied to the nip portion can be changed.

  The invention described in claim 9 is the transfer apparatus according to any one of claims 1 to 8, further comprising means for detecting or setting the thickness or unevenness of the recording medium, One of the nip portions is selected according to the unevenness.

  According to a tenth aspect of the present invention, in the transfer device according to the ninth aspect, the selection of the nip portion is performed by bringing a plurality of the transfer rollers and / or the backup member into contact with each other.

  According to an eleventh aspect of the present invention, in the transfer device according to the ninth aspect, the selection of the nip portion is performed by displacing a position of a guide member for guiding a recording medium to the nip portion.

  A twelfth aspect of the invention is an image forming apparatus having the transfer device according to any one of the first to eleventh aspects.

  According to the present invention, it is possible to form an image with little blur on a thick paper or a recording medium with high unevenness, and to prevent wrinkles from occurring on a thin paper or a recording medium with low unevenness.

1 is a schematic front view of an image forming apparatus to which an embodiment of the present invention can be applied. It is the schematic of the transfer apparatus used for the 1st Embodiment of this invention. It is the schematic explaining the secondary transfer roller pair used for the 1st Embodiment of this invention. It is the schematic of the transfer apparatus used for the 1st Embodiment of this invention. It is the schematic explaining operation | movement of the transfer apparatus used for the 1st Embodiment of this invention. It is the schematic of the transfer apparatus used for the 2nd Embodiment of this invention. It is the schematic of the transfer apparatus used for the 3rd Embodiment of this invention. It is the schematic of the transfer apparatus used for the 4th Embodiment of this invention. It is the schematic of the transfer apparatus used for the 5th Embodiment of this invention.

  FIG. 1 is a schematic front view showing a copying machine as an image forming apparatus to which an embodiment of the present invention can be applied. In FIG. 1, a copying machine 1 includes a printer unit 2 that forms an image on a recording sheet P that is a recording medium, a paper feeding device 3 that supplies the recording sheet P to the printer unit 2, a scanner 4 that reads an original image, and a scanner 4 Are provided with an automatic document feeder (ADF) 5 for automatically feeding originals.

  The scanner 4 is placed on the contact glass 8 as the first traveling body 6 mounted with a light source for document illumination, a mirror, and the like and the second traveling body 7 mounted with a plurality of reflecting mirrors reciprocate. The scanning of a document (not shown) is performed. The scanning light sent out from the second traveling body 7 is focused on the imaging surface of the reading sensor 10 installed behind the imaging lens 9 and then read as an image signal by the reading sensor 10.

  On the side surface of the housing of the printer unit 2, there are a manual feed tray 11 for manually placing the recording paper P to be fed into the housing, and a paper discharge tray 12 for stacking the image-formed recording paper P discharged from the housing. Is provided.

  Inside the housing of the printer unit 2 is disposed a transfer unit 14 that supports an intermediate transfer belt 13 as an endless belt-shaped image carrier so that the intermediate transfer belt 13 can run freely by a plurality of rollers. The intermediate transfer belt 13 is driven by a driving means (not shown) in a clockwise direction in the drawing, a secondary transfer backup roller 16 as a backup member, a driven roller 17, four primary transfer rollers 18Y, 18C, It is stretched by 18M and 18K, and is driven to run in the clockwise direction in the drawing by the rotation of the driving roller 15. The intermediate transfer belt 13 is stretched around the rollers 15, 16, and 17 so as to have an inverted triangular shape with the bottom side facing upward, and the belt upper portion corresponding to the bottom side of the triangle extends in the horizontal direction. Above the top of the belt, four process units 19Y, 19C, 19M, and 19K are juxtaposed in the horizontal direction along the extending direction of the top of the belt.

  An optical writing unit 20 is disposed above each process unit 19Y, 19C, 19M, 19K. The optical writing unit 20 emits four laser lights L by driving four semiconductor lasers (not shown) by a laser control unit (not shown) based on the image information of the original read by the scanner 4. The surfaces of the photosensitive drums 21Y, 21C, 21M, and 21K provided in the process units 19Y, 19C, 19M, and 19K are scanned by the laser beams L, respectively, and the surfaces of the photosensitive drums 21Y, 21C, 21M, and 21K are scanned. An electrostatic latent image is formed.

  In the present embodiment, the optical writing unit 20 is configured to perform optical scanning by deflecting laser light emitted from a semiconductor laser by a polygon mirror (not shown) and reflecting it with a reflection mirror (not shown) or passing it through an optical lens. However, instead of this, a configuration in which light scanning is performed by an LED array may be adopted.

  Each process unit 19 has a known charging member 22, a charge removal device 23, a cleaning device 24, a developing device 25, a potential sensor 26, and the like around the photosensitive drum 21. These are held by a common casing and configured to be integrally attached to and detached from the printer unit 2 as one unit.

  Each of the photosensitive drums 21Y, 21C, 21M, and 21K rotates while abutting on the upper surface of the intermediate transfer belt 13 that is moved in the clockwise direction to form a primary transfer nip portion. The primary transfer rollers 18Y, 18C, 18M, and 18K are in contact with the back surface of the intermediate transfer belt 13 on the back side of the portion. Each primary transfer roller 18Y, 18C, 18M, 18K is applied with a primary transfer bias having a polarity opposite to the toner charging polarity by a bias supply means (not shown). A primary transfer electric field for electrostatically moving the toner from the photosensitive drum 21 side to the intermediate transfer belt 13 side is formed in the transfer nip portion. The Y (yellow), C (blue), M (red), and K (black) toner images formed on the photosensitive drums 21Y, 21C, 21M, and 21K are respectively represented by the photosensitive drums 21Y, 21C, 21M, and 21D. With the rotation of 21K, the ink enters the respective primary transfer nip portions, and is primarily transferred onto the intermediate transfer belt 13 by being sequentially superimposed on the primary transfer electric field and the nip portion pressure. As a result, a full-color toner image in which the four colors are superimposed is formed on the surface of the intermediate transfer belt 13. Instead of the primary transfer rollers 18Y, 18C, 18M, and 18K, a conductive brush to which a primary transfer bias is applied, a non-contact type corona charger, or the like may be employed.

  A secondary transfer roller 27 as a transfer roller is disposed below the intermediate transfer belt 13. The secondary transfer roller 27 is rotationally driven in a counterclockwise direction in the figure by a driving means (not shown), and comes into contact with the surface of the intermediate transfer belt 13 via the secondary transfer backup roller 16 and is a secondary transfer nip portion which is a nip portion. Form. A secondary transfer bias having the same polarity as the toner charging polarity is applied to the secondary transfer backup roller 16 by a secondary transfer power source (not shown), and the secondary transfer roller 27 is grounded. As a result, a secondary transfer electric field is formed between the secondary transfer backup roller 16 and the secondary transfer roller 27. The full-color toner image formed on the surface of the intermediate transfer belt 13 enters the secondary transfer nip portion as the intermediate transfer belt 13 travels. A transfer device 46 is configured by the secondary transfer roller 27 and the transfer unit 14 including the secondary transfer backup roller 16.

  A sheet feeding device 3 disposed immediately below the printer unit 2 includes a sheet feeding cassette 28 that stores the recording sheet P, a sheet feeding roller 29 that feeds the recording sheet P stored in the sheet feeding cassette 28, and a recording that has been sent out. A plurality of separation roller pairs 30 for separating the paper P one by one, a plurality of conveyance roller pairs 32 for conveying the separated recording paper P along the paper feed path 31, and the like are provided. The paper feed path 31 of the paper feed device 3 is connected to the paper feed path 33 of the printer unit 2, and the recording paper P fed from the paper feed cassette 28 is fed to the printer unit 2 via the paper feed path 31. It is sent into the paper path 33.

  A registration roller pair 34 is disposed near the end of the paper feed path 33, and the secondary transfer nip portion is synchronized with the full color toner image on the intermediate transfer belt 13 when the recording paper P temporarily stopped between the rollers is arranged. To send. At the secondary transfer nip, the full color toner image on the intermediate transfer belt 13 is secondarily transferred to the recording paper P by the influence of the secondary transfer electric field and the nip pressure, and the full color toner image is transferred onto the recording paper P. The When the recording paper P on which the full-color toner image is formed is discharged from the secondary transfer nip portion, the recording paper P is separated from the intermediate transfer belt 13.

  On the left side of the secondary transfer nip portion, a conveyance belt unit 36 is disposed that travels in the counterclockwise direction in the figure while supporting an endless conveyance belt 35 by a plurality of rollers. The recording paper P separated from the intermediate transfer belt 13 is transferred to the conveyance belt unit 36 and conveyed to the fixing device 37 disposed on the left side thereof.

  The fixing device 37 includes a heating roller 38 containing a heat source such as a halogen lamp (not shown) and a pressure roller 39 pressed against the heating roller 38, and the recording paper P sent into the fixing device 37 is each of the recording paper P. The full color toner image is fixed on the surface by being heated while being pressed by the rollers 38 and 39, and sent to the outside of the fixing device 37.

  A small amount of secondary transfer residual toner that has not been transferred to the recording paper P adheres to the surface of the intermediate transfer belt 13 after passing through the secondary transfer nip, and this secondary transfer residual toner is transferred to the intermediate transfer belt 13. Cleaning is performed by a belt cleaning device 40 that contacts the surface of the belt 13.

  Below the fixing device 37, a switchback device 41 is disposed. When the recording paper P discharged from the fixing device 37 is sent to the conveyance path switching position by the swingable switching claw 42, it is sent to the paper discharge roller pair 43 or the switchback device 41 according to the stop position of the switching claw 42. Sent to. When the paper is sent toward the paper discharge roller pair 43, the paper is discharged to the outside of the apparatus and then stacked on the paper discharge tray 12.

  On the other hand, when it is sent to the switchback device 41, it is turned upside down by the switchback conveyance by the switchback device 41 and then conveyed toward the registration roller pair 34 again. Then, the toner again enters the secondary transfer nip portion, and the full color toner image is transferred to the back surface. The recording paper P manually fed onto the manual feed tray 11 provided on the side surface of the housing of the printer unit 2 is sent to the registration roller pair 34 after passing through the manual feed roller 44 and the manual separation roller pair 45.

  When image formation is performed by the copying machine 1 described above, if the unevenness (thickness) of the transfer material is diversified, it is difficult to ensure the uniformity of the transfer pressure in the axial direction of the secondary transfer roller 27 as described above. There are problems such as a problem that the separation property of the recording paper P from the intermediate transfer belt 13 is deteriorated, a problem that the transfer device 46 is complicated, and a problem that the output image is blurred. Therefore, a transfer apparatus according to an embodiment of the present invention that can suppress the occurrence of these problems will be described below.

  FIG. 2 shows a transfer device 47 according to the first embodiment of the present invention. Compared with the transfer device 46 described above, this transfer device 47 uses secondary transfer backup rollers 48 and 49, which are two backup members, instead of the secondary transfer backup roller 16, and instead of the secondary transfer roller 27. The secondary transfer roller 50 serving as a transfer roller that is pressed against the backup roller 48 via the intermediate transfer belt 13 to form the first nip portion N1 and the backup roller 49 via the intermediate transfer belt 13 are pressed against each other. The difference is only in that the secondary transfer roller 51 is used as a transfer roller for forming the second nip portion N2, and in that the tension roller 54 is used, and the other configurations are the same. The backup roller 48 and the secondary transfer roller 50 form a secondary transfer roller pair 52, and the backup roller 49 and the secondary transfer roller 51 form a secondary transfer roller pair 53.

  In FIG. 2, the pressure applied to the recording medium P by each of the secondary transfer roller pairs 52 and 53, that is, the pressure contact force of the secondary transfer rollers 50 and 51 to the secondary transfer backup rollers 48 and 49 at the nip portions N1 and N2, respectively. By differentiating, the problem that the output image is blurred by guiding the recording paper P to one of the nip portions N1 and N2 according to the thickness or unevenness of the recording paper P is solved. Can do.

  In order to make the pressure applied to the recording medium P of each secondary transfer roller pair 50, 51 different, for example, the roller hardness of each roller pair 50, 51 can be made different. The hardness of the secondary transfer roller 50 is higher than the hardness of the secondary transfer roller 51 when the pressure contact force of the secondary transfer rollers 50 and 51 to the backup rollers 48 and 49 and the hardness of the backup rollers 48 and 49 are equal. In this case, the pressing force of the secondary transfer roller pair 52 against the recording medium P can be made higher than the pressing force of the secondary transfer roller pair 53 against the recording medium P. Further, if the pressure contact force of the secondary transfer roller 50 to the backup roller 48 and the pressure contact force of the secondary transfer roller 51 to the backup roller 49 are different, the pressure applied to the recording medium P of the secondary transfer roller pair 52 and the secondary transfer roller 52 are different. The pressure applied to the recording medium P by the roller pair 53 can be made different.

  In the above-described configuration, the secondary transfer rollers 50 and 51 are bent due to the pressing force of the secondary transfer rollers 50 and 51 against the backup rollers 48 and 49, and there is a risk that a deviation occurs in the transfer pressure in the roller axial direction. There is. Since the pressing force acts on both ends of each of the secondary transfer rollers 50 and 51, the transfer pressure at both ends of the rollers tends to increase. Here, as shown in FIG. 3, the shape of one of the rollers 52 and 53 (in this embodiment, the backup roller 48) is made to be a drum shape with both ends narrower than the center. Thus, the transfer pressure at the end can be lowered and the above-mentioned problems can be solved. As described above, since each roller pair 52, 53 has a shape that takes into account the bending due to the applied pressure, there is no deviation in the transfer pressure in the axial direction in any roller pair 52, 53, and a plurality of types of transfer pressures can be obtained. Can be realized without causing a deviation in the axial direction.

  In order to change the transfer pressure without causing a deviation in the axial direction, it is conceivable that when the pressure contact force is made variable, the roller cored bar is not bent even if any pressure contact force is applied. In such a case, the cored bar becomes thicker and the roller diameter becomes larger, which is not preferable because the peelability of the recording paper deteriorates. Further, if the roller diameter is to be suppressed, the rubber layer of the roller becomes thin and the durability is deteriorated. In the above-described configuration, since the occurrence of deviation in the axial direction can be suppressed without preventing the roller from being bent, a plurality of types of transfer pressure can be realized, which is superior to the above-described conventional technology.

  If the difference between the thick part and the thin part is large when the roller is formed in a drum shape, wrinkles will occur when attempting to transfer to a low-rigidity recording such as thin paper. This is because the linear velocity at the central portion of the roller is faster than the linear velocity at the end portion, and a force that moves the recording paper toward the central portion is generated. In this embodiment, even if a low-rigidity recording paper such as thin paper is used by changing the roller shape (difference between the thick and thin drum-like portions) according to the recording paper to be used, Can be suppressed.

  FIG. 4 shows a more detailed configuration of the transfer device 47. In the drawing, reference numeral 55 denotes a guide plate for guiding the recording paper P to the nip portion N1 or the nip portion N2, and the guide plate 55 is movably supported by a guide plate support member (not shown). A guide plate support member (not shown) is configured to be rotatable about a fulcrum 56 shown in FIG. 5A, and is rotated by a drive means (not shown). A guide plate support member (not shown) includes a first position where the guide plate 55 occupies a position for guiding the recording paper P to the nip portion N1 as shown in FIG. 5A, and a guide as shown in FIG. 5B. The plate 55 selectively occupies a second position that occupies a position for guiding the recording paper P to the nip portion N2. Each of the secondary transfer rollers 50 and 51 is rotatably supported by a movable roller support member (not shown), and the secondary transfer roller 50 passes through the intermediate transfer belt 13 by moving the roller support member (not shown). A first position where the secondary transfer roller 51 is separated from the intermediate transfer belt 13 while the nip portion N1 is formed in pressure contact with the secondary transfer backup roller 48, and the secondary transfer roller 51 passes through the intermediate transfer belt 13 through the second position. A nip portion N2 is formed in pressure contact with the next transfer backup roller 49, and the secondary transfer roller 50 selectively occupies a second position separated from the intermediate transfer belt 13. The roller support member (not shown) occupies the first position when the guide plate support member (not shown) occupies the first position, and the second position when the guide plate support member (not shown) occupies the second position. Occupy. The registration roller pair 34 is also rotatably supported by a registration roller pair support member (not shown) that is movable, and is optimal for feeding the recording paper P to the guide plate 55 in accordance with the movement of the guide plate 55. Moved to position.

  4, reference numeral 57 denotes a paper thickness detecting means, reference numeral 58 denotes a control means for controlling movement of a roller support member (not shown), and reference numeral 59 denotes control means for a driving means (not shown) for rotating a guide plate support member (not shown). Reference numeral 60 denotes a secondary transfer bias applying device and bias application amount control means applied to the nip portions N1 and N2, and reference numeral 61 denotes a control means for controlling the movement of a resist roller pair supporting member (not shown). Reference numeral 62 denotes control means for controlling the transfer pressure of each of the secondary transfer roller pairs 52 and 53. Instead of the paper thickness detecting means 57, a means for setting and inputting the paper thickness by an operator may be used.

  In the above-described configuration, for example, when the transfer pressure, transfer bias, and roller hardness of the secondary transfer roller pair 52 are set higher than those of the secondary transfer roller pair 53 and the recording paper P is a thick paper or a sheet having high unevenness is used. The secondary transfer roller pair 52 is brought into contact with the secondary transfer roller pair 53 and the recording paper P is guided to the nip portion N1. When the recording paper P is thin paper or low in unevenness, 2 is used. The recording paper P is guided to the nip portion N2 by separating the secondary transfer roller pair 52 and bringing the secondary transfer roller pair 53 into contact with each other, thereby forming an image with less blur on the thick paper or the recording paper P with high unevenness. In addition, wrinkles can be prevented from occurring on the thin paper or the recording paper P having low unevenness.

  FIG. 6 shows a transfer apparatus used in the second embodiment of the present invention. Compared with the transfer device 47 shown in the first embodiment, this transfer device 63 uses a secondary transfer backup roller 64 having a large diameter as a backup member in place of the secondary transfer backup rollers 48 and 49, and this secondary transfer backup roller 48, 49. The only difference is that the secondary transfer rollers 50 and 51 can be brought into and out of contact with the transfer backup roller 64, and the other configurations are the same.

  Each of the secondary transfer rollers 50 and 51 is configured to be freely contacted and separated from the secondary transfer backup roller 64 via the intermediate transfer belt 13 and is rotated by a separate or two identical roller support members (not shown). It is supported freely. A roller support member (not shown) is configured to be movable. The secondary transfer roller 50 is pressed against the secondary transfer backup roller 64 via the intermediate transfer belt 13 and the secondary transfer roller 51 is separated from the intermediate transfer belt 13. 6A is a diagram in which the secondary transfer roller 50 is separated from the intermediate transfer belt 13 and the secondary transfer roller 51 is pressed against the secondary transfer backup roller 64 via the intermediate transfer belt 13 from the first position shown in FIG. It selectively occupies the second position shown in FIG. The guide plate 55 also occupies the first position when the unillustrated roller support member occupies the first position and the unillustrated roller support member occupies the second position due to the movement of the unillustrated guide plate support member. Occupy a second position. In this configuration, by setting the transfer pressure, transfer bias, and roller hardness in the same manner as in the first embodiment, it is possible to obtain the same effects as those in the first embodiment.

  FIG. 7 shows a transfer device 65 used in the third embodiment of the present invention, and FIG. 8 shows a transfer device 66 used in the fourth embodiment of the present invention. The transfer device 65 includes a large-diameter secondary transfer backup roller 67 and a plurality of (two or more, four in this embodiment) secondary transfer rollers 68 as backup members, and the transfer device 66 includes a large-diameter secondary transfer roller 69. And a plurality of (two or more, four in this embodiment) secondary transfer backup rollers 70 as backup members. Each of the rollers 68 and 70 is configured to be able to contact and separate from the corresponding rollers 67 and 69, respectively, and only one of the rollers 68 and 70 is configured to contact the corresponding roller 67.69. ing. In this configuration, by setting the transfer pressure, transfer bias, and roller hardness in the same manner as in the first embodiment, it is possible to obtain the same effects as those in the first embodiment.

  FIG. 9 shows a transfer device 71 used in the fifth embodiment of the present invention. The transfer device 71 includes a large-diameter secondary transfer backup roller 72 that is a backup member and a plurality (two or more, four in this embodiment) of secondary transfer rollers 73, and each secondary transfer roller 73. Are supported on the support member 74 at regular intervals and rotatably. The support member 74 is configured to be rotatable about a fulcrum 75, and each secondary transfer roller 73 is configured to contact with and separate from the secondary transfer backup roller 72 when the fulcrum 75 moves. The support member 74 moves downward from the state shown in FIG. 9 (a) and rotates, and then moves upward again from the state shown in FIG. 9 (b) to become the state shown in FIG. 9 (c). The secondary transfer roller 73 that has been in pressure contact with the secondary transfer backup roller 72 is changed. In this configuration, by setting the transfer pressure, transfer bias, and roller hardness in the same manner as in the first embodiment, it is possible to obtain the same effects as those in the first embodiment.

  In the above-described embodiment, an example in which a color copying machine is used as the image forming apparatus has been described. However, the image forming apparatus to which the present invention can be applied is not limited to this, and other printers, plotters, facsimiles, composite machines of these, and the like. The present invention can also be applied to an image forming apparatus.

1 Image forming device (copier)
13 Image carrier (intermediate transfer belt)
47, 63, 65, 66, 71 Transfer device 48, 49, 64, 67, 70, 72 Backup member (secondary transfer backup roller)
50, 51, 68, 69, 73 Transfer roller (secondary transfer roller)
N1, N2 Nip part P Recording medium (recording paper)

JP 2009-175696 A JP 2009-128877 A

Claims (12)

An endless belt-shaped image carrier capable of carrying a toner image on its surface and a backup member disposed on the back side of the image carrier via the image carrier to form a nip portion A transfer apparatus having a transfer roller for transferring the toner image to a recording medium at the nip portion;
A transfer device, wherein a plurality of the nip portions having different transfer pressures with respect to the recording medium can be formed. The transfer apparatus according to claim 1, wherein
A transfer apparatus comprising a plurality of the transfer roller and / or the backup member. The transfer device according to claim 2.
A plurality of the transfer rollers and / or the backup members have different hardnesses. The transfer apparatus according to claim 3.
The transfer device, wherein the plurality of transfer rollers and / or the backup member are arranged on the downstream side in comparison with those arranged on the upstream side in the conveyance direction of the recording medium. In the transfer device according to any one of claims 1 to 4,
The transfer device according to claim 1, wherein the pressure contact force of the transfer roller with respect to the backup member in each nip portion is different. The transfer device according to claim 5, wherein
The transfer apparatus according to claim 1, wherein the nip portion located on the downstream side has a lower pressing force of the transfer roller against the backup member in each nip portion than the nip portion located on the upstream side in the recording medium conveyance direction. The transfer device according to any one of claims 1 to 6,
A transfer device, wherein a pressure contact force of the transfer roller with respect to the backup member is changeable. The transfer apparatus according to any one of claims 1 to 7,
A transfer device, wherein a bias applied to the nip portion is changeable. The transfer device according to any one of claims 1 to 8,
A transfer apparatus having means for detecting or setting the thickness or unevenness of a recording medium, and selecting any one of the nip portions according to the thickness or unevenness of the recording medium. The transfer device according to claim 9, wherein
The nip portion is selected by a plurality of the transfer rollers and / or the backup member coming into contact with and separating from each other. The transfer device according to claim 9, wherein
The transfer device is characterized in that selection of the nip portion is performed by displacing a position of a guide member for guiding a recording medium to the nip portion.   An image forming apparatus comprising the transfer device according to claim 1.

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