JP2008009192A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of reducing influence due to contamination by toner on the inner peripheral surface side of a belt body, arranged adjacent to an image carrier on the surface of which a toner image is formed and is capable of moving around in a circle. <P>SOLUTION: The image forming apparatus 100 has the belt body 51 arranged adjacent to the image carrier 1, on the surface of which the toner image is formed and capable of moving around in a circle; a rotating body 56, arranged on the inner peripheral surface side of the belt body 51 and rotating with the movement of the belt body 51; a bias output means 58 outputting bias inducing a current flowing in a circuit via the rotating body 57; and a cleaning member 91 removing the toner from the surface of the rotating body 56. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer using an electrophotographic system or an electrostatic recording system. More specifically, the present invention relates to an image forming apparatus having an intermediate transfer member or a transfer material carrier as a belt member that is arranged adjacent to an image carrier on which a toner image is formed and which can move around.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic copying machine or a laser beam printer, the surface of an electrophotographic photosensitive member (hereinafter referred to as a “photosensitive drum”) that is generally cylindrical as an image carrier. A toner image is formed, and the toner image is transferred to a transfer material such as paper. In such an image forming apparatus, untransferred toner (transfer residual toner) remaining on the surface of the photosensitive drum after the toner image transfer process is removed and collected by a cleaning device.

  Conventionally, as a color image forming apparatus capable of forming a full-color image, for example, the following direct transfer type and intermediate transfer type image forming apparatuses are known. In the direct transfer method, a toner image formed on one or a plurality of photosensitive drums is transferred to a transfer material carried on a belt body (hereinafter referred to as a “transfer belt”) that can move around as a transfer material carrier. . In the intermediate transfer method, a toner image formed on one or a plurality of photosensitive drums is temporarily transferred (primary transfer) to a belt body (hereinafter referred to as an “intermediate transfer belt”) that can move around as an intermediate transfer body. . Thereafter, the toner image on the intermediate transfer belt is transferred (secondary transfer) to a transfer material. In the intermediate transfer method, it is easy to form an image on various transfer materials, and the selectivity of the transfer material can be improved. In an intermediate transfer type image forming apparatus, normally, untransferred toner (secondary transfer residual toner) remaining on the outer peripheral surface (surface) of the intermediate transfer belt after the secondary transfer step is removed by an intermediate transfer member cleaning device. Collected.

  The cleaning device as described above has a cleaning blade in which an elastic member such as urethane rubber is formed in a plate shape as a cleaning member. Then, the edge of the cleaning blade is brought into contact with the surface of the photosensitive drum or the surface of the intermediate transfer member with a predetermined pressure, and the toner adhering to the surface of the photosensitive drum or the surface of the intermediate transfer member is scraped off. ing.

  A cleaning device using a cleaning blade has a relatively simple structure, can be miniaturized, is advantageous in terms of cost, and has an advantage of excellent toner removal performance, and thus has been widely put into practical use. .

  In a color image forming apparatus that requires high speed and high image quality, the following method may be introduced in order to minimize vibration and damage given to the intermediate transfer member. That is, introduction of a light pressure type brush cleaner and a cleaningless type which are simpler than the cleaning blade.

  On the other hand, in recent years, the pursuit of high image quality has become remarkable, and the toner of the developer tends to have a small particle size. As the toner particle size is reduced, the speed of the image forming apparatus is increased, which tends to cause the toner scattering in the machine more than ever. For such a tendency, improvement of airflow in the machine and electrostatic aggregation by increasing the electrostatic amount of toner have been common solutions. However, there is a limit to improving the airflow in the aircraft. That is, for example, if the suction force for causing the airflow in the machine is increased, scattered toner from the developing device or waste toner from the waste toner box of the cleaning device may be sucked out. May be encouraged.

  In addition, with the recent demand for full color, many image forming apparatuses of the multiple transfer system using the above-described intermediate transfer belt and transfer belt are often seen. In such an image forming apparatus, when the intermediate transfer belt, the inner peripheral surface (back surface) of the transfer belt, the transfer roller as a transfer member disposed on the inner peripheral surface side of the intermediate transfer belt, and the like are contaminated with scattered toner. Image defects due to transfer charge defects are likely to occur. Further, when the belt driving roller or the like as the belt driving means is contaminated by the scattered toner, the belt itself is prevented from rotating, and the belt is liable to slip, skew, wrinkle and the like.

  Conventionally, the problem of contamination of the inner peripheral surface of the belt due to the scattered toner as described above has been generally dealt with by arranging a cleaning member for cleaning the inner peripheral surface of the belt. Patent Document 1 describes a configuration in which an inner peripheral surface of a belt is cleaned with a blade. Patent Document 2 describes a configuration in which the inner peripheral surface of a belt is cleaned with a brush-like member.

On the other hand, Patent Document 3 describes an apparatus in which a plate-like blade is brought into contact with the surface of a roller facing a means for cleaning a transfer material conveying surface of a transfer belt.
JP 2001-343841 A Japanese Patent Laid-Open No. 11-038774 JP 05-333709 A

  However, the cleaning member that cleans the inner peripheral surface of the belt may damage the belt itself and cause image defects. Further, the cleaning member that cleans the inner peripheral surface of the belt may scrape the inner peripheral surface of the belt, and the scraped residue may contaminate the transfer roller, the drive roller, and the like.

  Further, according to the study by the present inventor, it has been found that the surface of a rotating body, for example, a transfer roller, through which a current flows by the bias output from the bias output means on the inner peripheral surface side of the belt body is significantly contaminated. . As described above, when the surface of the transfer roller or the like is contaminated with toner, an image defect due to transfer charging failure is likely to occur.

  Further, for example, a configuration in which the rotating body through which the current flows also serves as a driving unit for the belt body, or the rotating body through which the current flows is rotated by driving the belt body to drive power from the rotating body to another member. The following problem may occur in the configuration that transmits the message. That is, the surface of the rotating body is contaminated with toner, causing a slip between the rotating body and the belt body, resulting in poor rotation of the belt body and poor power transmission.

  Therefore, an object of the present invention is to reduce the influence of toner contamination on the inner peripheral surface side of a belt body that can be circulated and arranged adjacent to an image carrier on which a toner image is formed. A forming apparatus is provided.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, the first aspect of the present invention relates to a belt body that can be moved around and disposed adjacent to an image carrier on which a toner image is formed on the surface, and the belt that is disposed on the inner peripheral surface side of the belt body. A rotating body that rotates as the body moves, a bias output unit that outputs a bias that induces a current that flows through a circuit that passes through the rotating body, and a cleaning member that removes toner from the surface of the rotating body. An image forming apparatus characterized by the above.

  According to the second aspect of the present invention, a belt body that can move around and is disposed adjacent to an image carrier on which a toner image is formed on the surface, and a movement of the belt body that is disposed on the inner peripheral surface side of the belt body. First and second rotating bodies that rotate with the first rotating body, first bias output means for outputting a bias that induces a current flowing through a circuit passing through the first rotating body, and the second rotating body. A second bias output means for outputting a bias for inducing a current flowing through the circuit passing through, and a cleaning member for removing the toner from the surface of the second rotating body. The bias output means outputs a bias for inducing a current for moving the toner charged to the first polarity from the first rotating body toward the inner peripheral surface of the belt body, and the second bias output means. Is charged to the first polarity Image forming apparatus characterized by having a cleaning mode for outputting a bias that induces a current to move toward the second rotating body of the toner from the inner circumferential surface of the belt body is provided.

  According to the present invention, it is possible to reduce the influence of toner contamination on the inner peripheral surface side of a belt body that can be moved around and is disposed adjacent to an image carrier on which a toner image is formed.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
[Overall Configuration and Operation of Image Forming Apparatus]
First, the overall configuration and operation of an image forming apparatus according to an embodiment of the present invention will be described. FIG. 1 shows a schematic cross-sectional configuration of an image forming apparatus 100 of the present embodiment. The image forming apparatus 100 according to the present exemplary embodiment is a full-color electrophotographic image forming apparatus that includes four photosensitive drums and uses an intermediate transfer method.

  The image forming apparatus 100 includes first, second, third, and fourth image forming units (process units) Sa, Sb, Sc, and Sd as a plurality of image forming units. The image forming portions Sa, Sb, Sc, and Sd are for forming colors of yellow, magenta, cyan, and black, respectively.

  In this embodiment, the configuration of each of the image forming units Sa to Sd is substantially the same except that the color of the toner used is different. Therefore, in the following, unless there is a particular distinction, the subscripts a, b, c, and d given to the reference numerals in the drawing are omitted to indicate that they are elements provided for any color, and are summarized Explained.

  The image forming unit S includes a photosensitive drum 1 as an image carrier. Around the photosensitive drum 1, a charging roller 2 as a primary charging unit, a laser scanner 3 as an exposure unit, a developing device 4 as a developing unit, a drum cleaner 6 as a drum cleaning unit, and the like rotate the photosensitive drum 1. They are sequentially arranged along the direction. Further, adjacent to the photosensitive drums 1a to 1d of the image forming portions Sa to Sd, a belt body that can be rotated around as an intermediate transfer body, that is, an intermediate transfer belt 51 is disposed.

  The intermediate transfer belt 51 is stretched around a driving roller 54, a driven roller 55, and a secondary transfer inner roller 56 as a plurality of support members. The intermediate transfer belt 51 is rotated in a direction indicated by an arrow R <b> 3 when a driving force is transmitted by a driving roller 54 that is a belt driving unit. Further, primary transfer rollers 52a to 52d as primary transfer members are disposed at positions facing the respective photosensitive drums 1a to 1d on the inner peripheral surface side of the intermediate transfer belt 51. The intermediate transfer belt 51 is urged toward the photosensitive drums 1a to 1d by the primary transfer rollers 52a to 52d, and the primary transfer portions (primary transfer portions) where the photosensitive drums 1a to 1d and the intermediate transfer belt 51 come into contact with each other. Nip) N1a to N1d are formed. Further, a secondary transfer outer roller 57 as a secondary transfer member is disposed at a position facing the secondary transfer inner roller 56 on the outer peripheral surface side of the intermediate transfer belt 51. The secondary transfer outer roller 57 contacts the outer peripheral surface of the intermediate transfer belt 51 to form a secondary transfer portion (secondary transfer nip) N2.

  The images on the photosensitive drums 1a to 1d formed by the respective image forming units Sa to Sd are sequentially multiplex-transferred onto the intermediate transfer belt 51 that moves and passes adjacent to the photosensitive drums 1a to 1d. Thereafter, the image transferred onto the intermediate transfer belt 51 is further transferred onto a transfer material P such as paper at the secondary transfer portion N2.

  FIG. 2 shows the image forming unit S in more detail. Further description will be made with reference to FIG. 2 as well. The photosensitive drum 1 is rotatably supported by the image forming apparatus main body. The photosensitive drum 1 is a cylindrical electrophotographic photosensitive member that basically includes a conductive substrate 11 such as aluminum and a photoconductive layer 12 formed on the outer periphery thereof. The photosensitive drum 1 has a support shaft 13 at the center thereof. The photosensitive drum 1 is rotationally driven about a support shaft 13 in the direction of an arrow R1 by a driving unit (not shown). In this embodiment, the charging polarity of the photosensitive drum 1 is negative.

  Above the photosensitive drum 1 in the figure, a charging roller 2 as a primary charging means is disposed. The charging roller 2 is in contact with the surface of the photosensitive drum 1 and uniformly charges the surface of the photosensitive drum 1 to a predetermined polarity and potential. The charging roller 2 includes a conductive core 21 disposed in the center, a low resistance conductive layer 22 formed on the outer periphery thereof, and a medium resistance conductive layer 23, and is configured in a roller shape as a whole. Yes. The charging roller 2 is disposed in parallel with the photosensitive drum 1 while both ends of the cored bar 21 are rotatably supported by bearing members (not shown). The bearing members at both ends are urged toward the photosensitive drum 1 by pressing means (not shown). As a result, the charging roller 2 is pressed against the surface of the photosensitive drum 1 with a predetermined pressing force. The charging roller 2 is driven to rotate in the direction indicated by the arrow R2 as the photosensitive drum 1 rotates in the direction indicated by the arrow R1. A charging bias voltage is applied to the charging roller 2 by a charging bias power source 24 as a charging bias output unit. Thereby, the surface of the photosensitive drum 1 is uniformly charged by contact.

  A laser scanner 3 is disposed on the downstream side of the charging roller 2 in the rotation direction of the photosensitive drum 1. The laser scanner 3 scans the laser light based on the image information while turning the laser light OFF / ON, and exposes the photosensitive drum 1. As a result, an electrostatic image (latent image) corresponding to the image information is formed on the photosensitive drum 1.

  A developing device 4 is disposed on the downstream side of the laser scanner 3 in the rotation direction of the photosensitive drum 1. The developing device 4 includes a developing container 41 that contains a two-component developer including non-magnetic toner particles (toner) and magnetic carrier particles (carrier) as a developer. A developing sleeve 42 as a developer carrying member is rotatably installed in an opening of the developing container 41 facing the photosensitive drum 1. In the developing sleeve 42, a magnet roller 43 as a magnetic field generating unit is fixedly disposed so as not to rotate with respect to the rotation of the developing sleeve 42. The two-component developer is carried on the developing sleeve 42 by the magnetic field formed by the magnet roller 43. Further, a regulating blade 44 as a developer regulating member that regulates the two-component developer carried on the developing sleeve 42 and thins it is installed at a position below the developing sleeve 42 in the drawing. The developing container 41 is divided into a developing chamber 45 and an agitating chamber 46, and a replenishing chamber 47 containing replenishing toner is provided in the upper portion of the drawing.

  A thin layer of the two-component developer on the developing sleeve 42 is conveyed to a developing area facing the photosensitive drum 1 as the developing sleeve 42 rotates. The two-component developer on the developing sleeve 42 rises in the developing region by the magnetic force of the developing main pole of the magnet roller 43 located in the developing region, and a magnetic brush for the two-component developer is formed. The surface of the photosensitive drum 1 is rubbed by the magnetic brush, and a developing bias voltage is applied to the developing sleeve 42 by a developing bias power source 48 as a developing bias output means. Thereby, the toner adhering to the carrier constituting the ears of the magnetic brush adheres to the exposed portion of the electrostatic image on the photosensitive drum 1 to form a toner image. In this embodiment, a toner image is formed on the photosensitive drum 1 by reversal development in which toner charged to the same polarity as the charging polarity of the photosensitive drum 1 is attached to a portion of the photosensitive drum 1 where the charge is attenuated by exposure. .

  A primary transfer roller 52 is disposed below the photosensitive drum 1 on the downstream side of the developing device 4 in the rotational direction of the photosensitive drum 1 in the drawing. The primary transfer roller 52 includes a cored bar 521 and a conductive layer 522 formed in a cylindrical shape on the outer peripheral surface thereof. Both ends of the primary transfer roller 52 are urged toward the photosensitive drum 1 by a pressing member (not shown) such as a spring. As a result, the conductive layer 522 of the primary transfer roller 52 is pressed against the surface of the photosensitive drum 1 via the intermediate transfer belt 51 with a predetermined pressing force. Further, a primary transfer bias power source 53 as a primary transfer bias output means is connected to the metal core 521. A primary transfer portion N1 is formed between the photosensitive drum 1 and the primary transfer roller 52. An intermediate transfer belt 51 is sandwiched between the primary transfer portion N1. The primary transfer roller 52 contacts the inner peripheral surface of the intermediate transfer belt 51 and rotates as the intermediate transfer belt 51 moves. At the time of image formation, the primary transfer roller 52 is supplied with a primary transfer bias power source 53 by a reverse polarity (second polarity) of the normal charging polarity of the toner (first polarity: negative polarity in this embodiment). : Positive transfer in this embodiment) is applied. Then, an electric field is formed between the primary transfer roller 52 and the photosensitive drum 1 in a direction in which the toner having the first polarity moves from the photosensitive drum 1 toward the intermediate transfer belt 51. As a result, the toner image on the photosensitive drum 1 is transferred (primary transfer) to the surface of the intermediate transfer belt 51.

  Deposits such as toner (primary transfer residual toner) remaining on the surface of the photosensitive drum 1 after the primary transfer process are cleaned by the drum cleaner 6. The drum cleaner 6 includes a cleaning blade 61 as a drum cleaning member, a conveying screw 62, and a drum cleaner housing 63. The cleaning blade 62 is brought into contact with the photosensitive drum 1 at a predetermined angle and pressure by a pressurizing unit (not shown). As a result, the toner remaining on the surface of the photosensitive drum 1 is scraped and removed from the photosensitive drum 1 by the cleaning blade 62 and collected in the drum cleaner housing 63. The collected toner or the like is transported by the transport screw 62 and discharged to a waste toner container (not shown).

  Below the photosensitive drums 1a to 1d in the figure, there are an intermediate transfer belt 51, primary transfer rollers 52a to 52d, a secondary transfer inner roller 56, a secondary transfer outer roller 57, an intermediate transfer belt cleaner 59, and the like. An intermediate transfer unit 5 is configured. The secondary transfer inner roller 56 is electrically grounded. The secondary transfer outer roller 57 is connected to a secondary transfer bias power source 58 as a secondary transfer bias output means. The secondary transfer inner roller 56 contacts the inner peripheral surface of the intermediate transfer belt 51 and rotates as the intermediate transfer belt 51 moves.

  For example, when a full-color image is formed, toner images of the respective colors are formed on the photosensitive drums 1a to 1d of the first to fourth image forming units Sa to Sd. The toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 51 by receiving a primary transfer bias from the primary transfer rollers 52 facing the photosensitive drums 1a to 1d with the intermediate transfer belt 51 interposed therebetween (primary transfer). ) This toner image is conveyed to the secondary transfer portion N2 as the intermediate transfer belt 51 rotates.

  On the other hand, by this time, the transfer material P is transported to the secondary transfer portion N2 by the transfer material supply means 8. That is, in the transfer material supply means 8, the transfer material P taken out one by one by the pickup roller 82 from the cassette 81 as the transfer material storage unit is conveyed to the secondary transfer unit N2 by the conveyance roller 83 and the like.

  In this embodiment, during image formation, the secondary transfer outer roller 57 is charged by a secondary transfer bias power source 58 with a polarity opposite to the normal charging polarity of the toner (first polarity: negative polarity in this embodiment) ( A secondary transfer bias voltage having a second polarity (positive polarity in this embodiment) is applied. An electric field is formed between the secondary transfer inner roller 56 and the secondary transfer outer roller 57 in a direction in which the first polarity toner is moved from the intermediate transfer belt 51 toward the transfer material P. As a result, the toner image on the intermediate transfer belt 51 is transferred (secondary transfer) onto the transfer material P. The transfer material P onto which the toner image has been transferred in the secondary transfer portion N2 is conveyed to a fixing device 7 as a fixing unit.

  Note that deposits such as toner (secondary transfer residual toner) remaining on the outer peripheral surface of the intermediate transfer belt 51 after the secondary transfer process are removed and collected by the intermediate transfer belt cleaner 59. The intermediate transfer belt cleaner 59 has the same configuration as the drum cleaner 6.

  The fixing device 7 includes a fixing roller 71 that is rotatably arranged, and a pressure roller 72 that rotates while being pressed against the fixing roller 71. A heater 73 such as a halogen lamp is disposed inside the fixing roller 71. The surface temperature of the fixing roller 71 is adjusted by controlling the voltage supplied to the heater 73 and the like. When the transfer material P is conveyed to the fixing device 7, when the transfer material P passes between the fixing roller 71 and the pressure roller 72 that rotate at a constant speed, the transfer material P is almost from both sides. Pressurized and heated at a constant pressure and temperature. As a result, the unfixed toner image on the surface of the transfer material P is melted and fixed to the transfer material P. Thus, a full color image is formed on the transfer material P.

  In this embodiment, the process speed corresponding to the surface moving speed of the photosensitive drum 1 and the intermediate transfer belt 51 is 100 mm / sec.

Here, the intermediate transfer belt 51 can be made of a dielectric resin such as PC (polycarbonate), PET (polyethylene terephthalate), and PVDF (polyvinylidene fluoride). In this embodiment, the intermediate transfer belt 51 has a volume resistivity of 10 ^8.5 Ω · cm (using a probe conforming to the JIS-K6911 method, applied voltage of 100 V, applied time of 60 sec, 23 ° C./50% RH), and PI ( A polyimide resin was used. However, the present invention is not limited to this, and other materials, volume resistivity, and thickness may be used.

The primary transfer roller 52 includes a cored bar 521 having an outer diameter of 8 mm and a conductive urethane sponge layer 522 having a thickness of 4 mm. The electric resistance value of the primary transfer roller 52 was about 10 ⁵ Ω (23 ° C./50% RH). The electrical resistance value of the primary transfer roller 52 is determined by rotating the primary transfer roller 52 in contact with a metal roller that is electrically grounded under a load of 500 g at a peripheral speed of 50 mm / sec. It is obtained from a current value measured by applying a voltage of 500 V to the gold 521.

The secondary transfer inner roller 56 includes a cored bar 561 having an outer diameter of 18 mm and a conductive and solid silicone rubber layer 562 having a thickness of 2 mm. The electrical resistance value of the secondary transfer inner roller 56 was about 10 ⁴ Ω in the same measurement method as that for the primary transfer roller 52.

Further, the secondary transfer outer roller 57 includes a core metal 571 having an outer diameter of 20 mm and a conductive EPDM rubber sponge layer 572 having a thickness of 4 mm. The electrical resistance value of the secondary transfer outer roller 57 was about 10 ⁸ Ω when the applied voltage was 2000 V in the same measurement method as the primary transfer roller 52.

[Cleaning of the inner peripheral surface of the intermediate transfer belt and the surface of the secondary transfer inner roller]
Next, the most characteristic method for cleaning the inner peripheral surface of the intermediate transfer belt 51 and the surface of the secondary transfer inner roller 56 in this embodiment will be described.

  As described above, according to the study by the present inventor, it has been found that the surface of the rotating body where current flows due to the bias output from the bias output means on the inner peripheral surface side of the belt body is significantly contaminated with scattered toner. The reason is considered as follows.

  In the image forming apparatus 100 shown in FIG. 1, the primary transfer roller 52 and the secondary transfer inner roller 56 are rotating bodies through which a current flows due to a bias output by a bias output unit. In this embodiment, the primary transfer bias power source 53 and the secondary transfer bias power source 58 output a bias that induces a current flowing through a circuit passing through the primary transfer roller 52 and the secondary transfer inner roller 56, respectively. It is an output means. First, in this embodiment, a method for reducing the influence of toner contamination on the surface of the secondary transfer inner roller 56 will be described.

  In this embodiment, the toner is negatively charged in the developing device 4. However, scattered toner is usually scattered because it is difficult to receive electrostatic binding force, and there are many toners with a relatively small charge amount, and both the positive polarity and the negative polarity are included. It is.

  In the image forming apparatus 100 of this embodiment, a negatively charged toner on the intermediate transfer belt 51 is applied by applying a positive secondary transfer bias to the secondary transfer outer roller 57 in the secondary transfer portion N2. Is transferred to the transfer material P. At this time, of the toner adhering to the inner peripheral surface (back surface) of the intermediate transfer belt 51, the scattered toner charged to the positive polarity is transferred to the surface of the secondary transfer inner roller 56 by the secondary transfer bias. In this way, toner gradually accumulates on the surface of the secondary transfer inner roller 56, and eventually slips between the inner surface of the intermediate transfer belt 51 and the transfer charging failure. Will cause.

  In other words, in this embodiment, the secondary transfer bias power source 58 is opposite in polarity (second polarity: negative polarity in this embodiment) to the normal charging polarity of the toner (first polarity: negative polarity in this embodiment) during image formation. In this case, a positive polarity bias is output to the secondary transfer outer roller 57. As a result, a current flows in the secondary transfer inner roller 56 in a direction to move the toner charged to the second polarity from the inner peripheral surface of the intermediate transfer belt 51 toward the secondary transfer inner roller 56.

  Therefore, in this embodiment, a cleaning member 91 that removes toner from the surface of the secondary transfer inner roller 56 is installed.

  As the cleaning member 91, a blade formed of an elastic member such as resin or rubber, a brush, or the like can be used. In this embodiment, as described above, the surface layer of the secondary transfer inner roller 56 is a solid silicone rubber. In this embodiment, a PET film plate member (blade) having a thickness of 250 μm and a free length of 10 mm is used as the cleaning member 91 so as to obtain a good cleaning effect on the surface of the secondary transfer inner roller 56. Using. The cleaning member 91 has its free end abutted in the counter direction with respect to the rotational direction of the secondary transfer inner roller 56 over substantially the entire length of the secondary transfer inner roller 56. That is, the free end of the cleaning member 91 faces the upstream side in the rotational direction of the secondary transfer inner roller 56, and the secondary transfer inner roller 56 is located downstream of the contact portion with the secondary transfer inner roller 56 in the rotational direction. The distance between the two was gradually increased.

  Such a cleaning member 91 is attached to the housing 92 to constitute the roller cleaner 9. The toner removed from the secondary transfer inner roller 56 by the cleaning member 91 is collected in the roller cleaner housing 92. The toner collected in the roller cleaner housing 92 can be discharged to a waste toner container (not shown) by an appropriate conveying means (not shown).

  The transfer current flowing from the secondary transfer outer roller 57 to the secondary transfer inner roller 56 at the secondary transfer portion N2 at the time of image formation is +20 μA (process speed 100 mm / sec). Due to this transfer current, the scattered toner on the inner peripheral surface of the intermediate transfer belt 51 is transferred to the surface of the secondary transfer inner roller 56. The toner transferred to the surface of the secondary transfer inner roller 56 is removed from the surface of the secondary transfer inner roller 56 by the cleaning member 91 and collected.

  As described above, according to this embodiment, it is possible to effectively remove stains due to scattered toner on the inner peripheral surface of the intermediate transfer belt 51 and the surface of the secondary transfer inner roller 56 with a simple configuration.

  Further, in this embodiment, the drive of the secondary transfer inner roller 56 rotated by the intermediate transfer belt 51 being rotated is transmitted to the secondary transfer outer roller 57 by a drive transmission means (not shown). ing. With such a configuration, it is possible to perform slip-free image formation at the secondary transfer portion N2 on a wide variety of transfer materials P. In such a configuration, it is extremely important that the secondary transfer inner roller 56 does not slip between the inner peripheral surface of the intermediate transfer belt 51. Accordingly, in such a configuration, it is particularly effective to clean the secondary transfer inner roller 56 that is easily soiled by the scattered toner. By adopting the configuration of this embodiment, the transfer material P can be stably conveyed. be able to.

  The drive transmission means includes the following configuration. A first gear that rotates coaxially with the secondary transfer inner roller 56 is provided at the end in the rotation axis direction of the secondary transfer inner roller 56. Further, a second gear that rotates coaxially with the secondary transfer outer roller 57 is provided at the end of the secondary transfer outer roller 57 in the rotation axis direction. Then, the first gear and the second gear are directly meshed with each other, or one or a plurality of gears are introduced and engaged between the first gear and the second gear so that the rotational force of the secondary transfer inner roller 56 is secondary. This is transmitted to the transfer outer roller 57. However, the drive transmission means is not limited to this, and may be configured using other elements such as a belt and a chain.

  Further, for example, in the image forming apparatus 100 as shown in FIG. 1, the secondary transfer inner roller 56 can also serve as a driving roller as a belt driving unit that transmits a driving force to the intermediate transfer belt 51. Even in such a configuration, it is extremely important that the secondary transfer inner roller 56 does not slip between the inner peripheral surface of the intermediate transfer belt 51. Therefore, even in such a configuration, it is particularly effective to clean the secondary transfer inner roller 56 according to the present embodiment.

  As described above, according to the present embodiment, the secondary transfer inner roller 56 in which a current flows due to the bias output from the bias output means on the inner peripheral surface of the intermediate transfer belt 51 and the inner peripheral surface side of the intermediate transfer belt 51. The scattered toner can be effectively removed and collected from the surface of the toner. As a result, slippage of the secondary transfer inner roller 56 with respect to the inner peripheral surface of the intermediate transfer belt 51, transfer charging failure, and the like can be prevented. Therefore, sufficient cleaning performance can be achieved without providing a cleaning member for other rollers, and stable image formation can be performed with a simple configuration. Further, according to this embodiment, there is no slip due to the stain on the inner peripheral surface of the intermediate transfer belt 51, and the occurrence of color misregistration or the like can be prevented.

  That is, according to the present embodiment, it is possible to ensure the cleaning performance for the rotating body through which current flows by the output bias of the bias output means arranged on the inner peripheral surface of the belt body and the inner peripheral surface side. As a result, with a simple configuration, problems such as image quality degradation due to toner contamination of the rotating body through which current flows due to the output bias of the bias output means arranged on the inner peripheral surface of the belt body and the inner peripheral surface side. Can be prevented.

Example 2
Next, another embodiment according to the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the first embodiment. Accordingly, elements having the same or corresponding functions and configurations as those of the image forming apparatus according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, the image forming apparatus 100 has a cleaning mode that effectively removes the scattered toner attached to the inner peripheral surface of the intermediate transfer belt 51. This will be described in detail below.

  In this embodiment, apart from the normal image forming operation, the toner adhering to the inner peripheral surface (back surface) of the intermediate transfer belt 51 is collected on the surface of the secondary transfer inner roller 56 and cleaned during non-image formation. A cleaning mode. Here, the time of non-image formation may be any timing other than when an image to be transferred to the transfer material P and output is formed. For example, an adjustment operation immediately after power-on of the image forming apparatus 100, a preparation operation before the start of image formation (pre-rotation operation), an arrangement operation after image formation (at the time of post-rotation operation), and the like can be given. Further, the non-image formation may be a period between the transfer material P and the transfer material P during the continuous series of image formation on the plurality of transfer materials P, that is, a so-called timing between papers.

  In other words, the scattering toner adhering to the inner peripheral surface of the intermediate transfer belt 51 includes the bipolar toner as described above. In the configuration in which an image composed of negatively charged toner is transferred, positively charged toner is accumulated on the surface of the secondary transfer inner roller 56. The positive toner on the surface of the secondary transfer inner roller 56 can be removed and collected during image formation in the same manner as in the first embodiment. On the other hand, the negative-polarity toner is accumulated while being rotated on the inner peripheral surface of the intermediate transfer belt 51, and eventually causes slipping and transfer charging failure.

  Therefore, in this embodiment, in a cleaning mode different from the normal image forming operation, a bias having a polarity opposite to the normal secondary transfer bias at the time of image formation is applied to the secondary transfer portion N2. That is, in this embodiment, a negative bias is applied to the outer secondary transfer roller 57 by the secondary transfer bias power source 58. As a result, the transfer current during image formation is +20 μA in the direction from the secondary transfer outer roller 57 to the secondary transfer inner roller 56, whereas a transfer current of −20 μA flows. As described above, in this embodiment, during non-image formation, the secondary transfer bias power source 58 outputs a bias having a polarity different from that during image formation to induce a current flowing through the circuit via the secondary transfer inner roller 56. A cleaning mode.

  That is, in this embodiment, during image formation, as in the first embodiment, the secondary transfer bias power source 58 has a polarity (first polarity) opposite to the normal charging polarity of the toner (first polarity: negative polarity in this embodiment). 2 with a polarity of 2 (positive in this embodiment) is output to the secondary transfer outer roller 57. As a result, a current flows in the secondary transfer inner roller 56 in a direction to move the toner charged to the second polarity from the inner peripheral surface of the intermediate transfer belt 51 toward the secondary transfer inner roller 56.

  In contrast, in the cleaning mode during non-image formation, the secondary transfer bias power supply 58 applies a bias having the same polarity as the normal charging polarity of the toner (first polarity: negative polarity in this embodiment) to the outside of the secondary transfer. Output to the roller 57. As a result, a current flows in the secondary transfer inner roller 56 in a direction to move the toner charged to the first polarity from the inner peripheral surface of the intermediate transfer belt 51 toward the secondary transfer inner roller 56.

  As shown in FIG. 3, in this embodiment, the secondary transfer bias power source 58 includes a first bias output unit 581 that outputs a secondary transfer bias during image formation, and a second bias that outputs a bias during the cleaning mode. Bias output unit 582. The secondary transfer bias power source 58 has a bias switching means 583 for switching both biases. The operation of the secondary transfer bias power source 58 is controlled by a controller as a control unit that comprehensively controls the operation of the image forming apparatus 100.

  By the operation in the cleaning mode as described above, the negative-polarity toner accompanying the inner peripheral surface of the intermediate transfer belt 51 is collected on the surface of the secondary transfer inner roller 56 and cleaned by the cleaning member 91.

  Here, in order to remove and collect the negative scattering toner over the entire inner peripheral surface of the intermediate transfer belt 51, the secondary transfer during the image formation as described above is performed while the intermediate transfer belt 51 makes one or more turns. It is preferable to apply a bias having a polarity opposite to that of the transfer bias. In other words, the cleaning mode is preferably performed while the intermediate transfer belt 51 makes one or more rounds.

  Further, it is effective to apply a strong bias so that the absolute value of the current flowing through the secondary transfer portion N2 in the cleaning mode is larger than the absolute value of the current flowing therethrough during image formation. Next, this point will be described.

  According to the study of the present inventor, the scattering toner that rotates around the inner peripheral surface of the intermediate transfer belt 51 is a toner having an extremely low charge amount (hereinafter referred to as “uncharged”) having an absolute value of the charge amount of about 5 μc / g or less. "Toner")). Such uncharged toner adheres to the inner peripheral surface of the intermediate transfer belt 51 by a non-electrostatic force, and as it is, the secondary transfer is electrostatically performed by a bias applied to the secondary transfer portion N2. There is no transfer onto the surface of the inner roller 56. Therefore, it is preferable to collect such uncharged toner on the surface of the secondary transfer inner roller 56 by applying a strong electric field to recharge the toner.

  This phenomenon will be further described with reference to FIG. First, the positive toner attached to the inner peripheral surface of the intermediate transfer belt 51 is transferred to the surface of the secondary transfer inner roller 56 by the positive bias applied to the outer secondary transfer roller 57 during image formation. And removed and collected by the cleaning member 91.

  On the other hand, in the cleaning mode, a negative bias having a polarity opposite to that at the time of image formation is applied to the secondary transfer outer roller 57. As a result, the negative toner on the inner peripheral surface of the intermediate transfer belt 51 is transferred to the surface of the secondary transfer inner roller 56 and is removed and collected by the cleaning member 91. If the negative polarity bias is strong at this time, peeling discharge occurs at the separation portion (the portion indicated by A in FIG. 3) between the intermediate transfer belt 51 and the secondary transfer inner roller 56, thereby causing uncharged toner. Are also charged positively or negatively. For example, in the configuration of this embodiment, the transfer current at the time of image formation is +20 μA in the direction from the secondary transfer outer roller 57 to the secondary transfer inner roller 56, whereas by passing a −30 μA transfer current, Recharging of the toner could be achieved. As described above, in this embodiment, the absolute value of the current flowing through the circuit via the secondary transfer inner roller 56 induced by the bias output from the secondary transfer bias power source 58 during non-image formation is greater than that during image formation. Also has a large cleaning mode.

  The toner charged to the negative polarity in the recharging process as described above is transferred to the surface of the secondary transfer inner roller 56 and removed and collected by the cleaning member 91. On the other hand, the positively charged toner remains on the inner peripheral surface of the intermediate transfer belt 51. The toner charged to the positive polarity and remaining on the inner peripheral surface of the intermediate transfer belt 51 is typically transferred to the surface of the secondary transfer inner roller 56 by a normal secondary transfer bias during subsequent image formation. And removed and collected by the cleaning member 91. In the cleaning mode, the positively charged toner may be collected on the surface of the secondary transfer inner roller 56 by a normal secondary transfer bias and cleaned by the cleaning member 91.

  Here, to recharge and remove and collect the uncharged toner over the entire inner peripheral surface of the intermediate transfer belt 51, a strong bias as described above is applied while the intermediate transfer belt 51 makes one or more turns. It is preferable to do. In other words, the cleaning mode is preferably performed while the intermediate transfer belt 51 makes one or more rounds.

  In this embodiment, a negative bias having a polarity opposite to that at the time of image formation is applied as a stronger bias than that at the time of image formation. However, the present invention is not limited to this. For example, the same effect can be obtained by applying a bias having the same polarity as that at the time of image formation and stronger than that at the time of image formation, and then applying a bias having a polarity opposite to that at the time of image formation.

  As described above, according to this embodiment, the image forming apparatus 100 has the cleaning mode in which a bias having a polarity opposite to that at the time of image formation is applied to the secondary transfer portion N2. By the operation in the cleaning mode, the scattered toner on the inner peripheral surface of the intermediate transfer belt 51 can be more reliably cleaned. In addition, according to the present exemplary embodiment, the image forming apparatus 100 can have a cleaning mode in which a bias that induces a stronger current in the secondary transfer portion N2 than that during image formation is applied. As a result, even when uncharged toner adheres to the inner peripheral surface of the intermediate transfer belt 51, the toner can be recharged and cleaned more reliably.

Example 3
Next, still another embodiment according to the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the first embodiment. Accordingly, elements having the same or corresponding functions and configurations as those of the image forming apparatus according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present exemplary embodiment, the image forming apparatus 100 has a cleaning mode that effectively removes toner attached to the surface of the primary transfer roller 52 during non-image formation, in addition to the normal image forming operation. This will be described in detail below.

  When image formation is performed in the image forming apparatus 100 illustrated in FIG. 1, a positive polarity bias is applied to the primary transfer roller 52 as a primary transfer bias, and thus the surface of the primary transfer roller 52 has a negative polarity. The toner adheres and is easy to accumulate.

  Here, in order to remove the toner adhering to the surface of the primary transfer roller 52, a cleaning member as described above can be further arranged for each primary transfer roller 52. For example, in such a configuration, during image formation, the primary transfer bias power source 53 has a polarity (second polarity) opposite to the normal charging polarity of the toner (first polarity: negative polarity in this embodiment). A bias of polarity (positive polarity in this embodiment) is output to the primary transfer roller 52. As a result, a current in a direction to move the toner charged to the first polarity from the inner peripheral surface of the intermediate transfer belt 51 toward the primary transfer roller 52 flows to the primary transfer roller. Further, at the time of image formation, the secondary transfer bias power source 58 has a polarity (second polarity: positive polarity in this embodiment) opposite to the normal charging polarity of the toner (first polarity: negative polarity in this embodiment). A bias is output to the secondary transfer outer roller 57. As a result, a current flows in the secondary transfer inner roller 56 in a direction to move the toner charged to the second polarity from the inner peripheral surface of the intermediate transfer belt 51 toward the secondary transfer inner roller 56. Thus, both the first and second polarity toners can be removed and collected by the cleaning members respectively provided on the primary transfer roller 52 and the secondary transfer inner roller 56.

  On the other hand, in this embodiment, the toner accumulated on the primary transfer roller 52 is removed and collected with a simpler configuration.

  This will be described with reference to FIG. In this embodiment, in a cleaning mode different from the normal image forming operation, the primary transfer roller N1 is biased so that a transfer current in the direction opposite to the normal transfer current at the time of image formation flows through the primary transfer portion N1. Apply to 52. That is, in this embodiment, a negative bias is applied to the primary transfer roller 52 by the primary transfer bias power source 52. As a result, the transfer current during image formation is +10 μA in the direction from the primary transfer roller 52 to the photosensitive drum 1, whereas a transfer current of −10 μA flows.

  In other words, in this embodiment, during image formation, the primary transfer bias power source 53 has a polarity (second polarity: this embodiment) opposite to the normal charging polarity of the toner (first polarity: negative polarity in this embodiment). In this case, a positive polarity bias is output to the primary transfer roller 52. As a result, a current flows in the primary transfer roller 52 in a direction to move the toner charged to the first polarity from the inner peripheral surface of the intermediate transfer belt 51 toward the primary transfer roller 52.

  In contrast, in the cleaning mode during non-image formation, the primary transfer bias power source 53 applies a bias having the same polarity as the normal charging polarity of the toner (first polarity: negative polarity in this embodiment) to the primary transfer roller. 52 for output. As a result, a current flows in the primary transfer roller 52 in the direction in which the toner charged to the first polarity attached to the surface of the primary transfer roller 52 moves toward the inner peripheral surface of the intermediate transfer belt 51.

  As shown in FIG. 4, in this embodiment, the primary transfer bias power source 53 includes a first bias output unit 531 that outputs a primary transfer bias during image formation, and a second bias that outputs a bias during a cleaning mode. Bias output section 532. The primary transfer bias power supply 53 has a bias switching means 533 for switching both biases. The operation of the primary transfer bias power source 53 is controlled by a controller as a control unit that comprehensively controls the operation of the image forming apparatus 100.

  By such an operation, the negative toner accumulated on the surface of the primary transfer roller 52 is transferred to the inner peripheral surface of the intermediate transfer belt 51. Subsequently, until the negative toner reaches the surface of the secondary transfer inner roller 56, a bias having a polarity opposite to the secondary transfer bias at the time of image formation is applied to the secondary transfer portion N. That is, as in the cleaning mode of the second embodiment, a negative bias is applied to the secondary transfer outer roller 57 by the secondary transfer bias power source 58. In the present embodiment, a transfer current of −20 μA flows from the secondary transfer outer roller 57 to the secondary transfer inner roller 56 in the secondary transfer portion N2 in the cleaning mode. Due to the transfer current in the direction opposite to that at the time of image formation, the negative toner attached to the inner peripheral surface of the intermediate transfer belt 51 is transferred to the surface of the secondary transfer inner roller 56 and removed and collected by the cleaning member 91. The

  In the same manner as described in the second embodiment, the absolute value of the current flowing through the primary transfer portion N1 and / or the secondary transfer portion N2 in the cleaning mode is greater than the absolute value of the current flowing therethrough during image formation. Can be applied.

  As described above, according to the cleaning mode of this embodiment, the scattered toner accumulated on the primary transfer roller 52 can be removed with a simple configuration. As the primary transfer roller 52, a sponge roller is often used in order to ensure contact stability. It is difficult to remove the toner on the surface of the sponge roller with a blade or a fur brush. In such a case, the cleaning mode of this embodiment is extremely effective.

Example 4
Next, still another embodiment according to the present invention will be described.

[Overall Configuration and Operation of Image Forming Apparatus]
FIG. 5 shows a schematic cross-sectional configuration of the image forming apparatus 200 of the present embodiment. The image forming apparatus 100 of this embodiment is a full-color electrophotographic image forming apparatus using a direct transfer method.

  In the image forming apparatus 200 of the present embodiment shown in FIG. 5, elements having substantially the same functions and configurations as those of the image forming apparatus 100 shown in FIG. To do. In the image forming apparatus 200 of the present embodiment, the configuration of each of the image forming units Sa to Sd is substantially the same except that the color of the toner used is different. Therefore, in the following, unless there is a particular distinction, the subscripts a, b, c, and d given to the reference numerals in the drawing are omitted to indicate that they are elements provided for any color, and are summarized Explained.

  The image forming apparatus 200 according to the present exemplary embodiment includes a belt body that can move around as a transfer material carrier, that is, a transfer belt 201, adjacent to the photosensitive drums 1a to 1d of the image forming units Sa to Sd. The transfer belt 201 is stretched around a driving roller 202 and a driven roller 55 as a plurality of support members. The transfer belt 201 is driven to rotate by a driving roller 202 as a belt driving means, and moves around in the direction indicated by an arrow R4.

  Further, transfer rollers 205a to 205d as transfer members are arranged at positions facing the respective photosensitive drums 1a to 1d on the inner peripheral surface side of the transfer belt 201. The transfer belt 201 is urged toward the photosensitive drums 1a to 1d by the transfer rollers 205a to 205d, and transfer portions (transfer nips) Na to Nd where the photosensitive drums 1a to 1d and the transfer belt 201 come into contact are formed. ing.

  Further, in this embodiment, the transfer rollers 205a to 205b, which are rotating members, are in contact with power supply rollers 204a to 204d as power supply members for applying a bias thereto. As will be described in detail later, in this embodiment, cleaning members 91a to 91d for cleaning the power supply rollers 204a to 204d are provided.

  In the image forming apparatus 200 of this embodiment, the images on the photosensitive drums 1a to 1d formed by the image forming units Sa to Sd are on the transfer belt 201 that moves and passes adjacent to the photosensitive drums 1a to 1d. Multiple transfer is sequentially performed on a transfer material P such as paper.

  At the time of image formation, the transfer material P is conveyed to the transfer belt 201 by the transfer material supply unit 8. That is, in the transfer material supply unit 8, the transfer material P taken out one by one by the pickup roller 82 from the cassette 81 serving as the transfer material storage unit is conveyed toward the transfer belt 201 by the conveyance roller 83 and the like. Then, the transfer material P is electrostatically attracted onto the transfer belt 201 by the attracting means 84 and is conveyed to the transfer portions Na to Nd of the image forming portions Sa to Sd.

  For example, when a full-color image is formed, toner images of the respective colors are formed on the photosensitive drums 1a to 1d of the first to fourth image forming units Sa to Sd. The toner images of the respective colors receive transfer biases from the transfer rollers 205a to 205d and the power supply rollers 204a to 204d facing the photosensitive drums 1a to 1d across the transfer material P and the transfer belt 201, and sequentially transfer belts. The image is transferred onto the transfer material P on 201.

  When the transfer process at each of the transfer portions Na to Nd is completed, the transfer material P is separated from the transfer belt 201 and conveyed to a fixing device 7 as a fixing unit.

  Incidentally, toner (transfer residual toner) remaining on the transfer belt 201 after the transfer process is removed and collected by the transfer belt cleaner 59.

Here, the transfer belt 201 can be made of a dielectric resin such as PC (polycarbonate), PET (polyethylene terephthalate), PVDF (polyvinylidene fluoride), like the above-described intermediate transfer belt 51. In this example, a volume resistivity of 10 ¹⁴ Ω · cm (using a probe conforming to the JIS-K6911 method, an applied voltage of 1000 V, an application time of 60 sec, 23 ° C./50% RH) and a thickness of 80 μm of carbon dispersed PI ( A polyimide resin was used. However, the present invention is not limited to this, and other materials, volume resistivity, and thickness may be used.

In this embodiment, the transfer roller 205 has the same configuration as the primary transfer roller 52 described above. That is, the transfer roller 205 is constituted by a core metal having an outer diameter of 8 mm and a conductive urethane sponge layer having a thickness of 4 mm. The electric resistance value of the transfer roller 205 was about 10 ^6.5 Ω (23 ° C./50% RH). The electrical resistance value of the transfer roller 205 is such that the transfer roller 205 in contact with a metal roller electrically grounded under a load of 500 g is rotated at a peripheral speed of 50 mm / sec, and the core metal is 500 V. It is obtained from the relationship of current measured by applying voltage.

  In this embodiment, a metal roller made of SUS (stainless steel) having an outer diameter of 16 mm was used as the power supply roller 204. The power supply roller 204 is in contact with the transfer roller 205 over substantially the entire longitudinal direction of the transfer roller 205.

[Cleaning of inner surface of transfer belt and surface of transfer roller]
Next, a method for cleaning the inner peripheral surface of the transfer belt 201, the surface of the transfer roller 205, and the surface of the power supply roller 204, which is the most characteristic feature of this embodiment, will be described.

  As described above, in this embodiment, the transfer roller 205, the power supply roller 204 for supplying a transfer current to the transfer roller 205, and the power supply roller 204 are provided on the inner peripheral surface side of the transfer belt 201 of each transfer portion N. A cleaning member 91 for cleaning is provided. A transfer bias power source 206 as a transfer bias output unit is connected to the power supply roller 204.

  In the image forming apparatus 200 shown in FIG. 5, the power supply roller 204 is a rotating body in which a current flows due to a bias output from the bias output unit on the inner peripheral surface side of the belt body. The power supply roller 204 comes into contact with the transfer roller 205 which is a rotating body that contacts the inner peripheral surface of the transfer belt 201, and rotates as the transfer belt 201 moves. In this embodiment, the transfer bias power source 206 is a bias output unit that outputs a bias that induces a current flowing through a circuit passing through the power supply roller 204.

  When image formation is performed in a direct transfer type image forming apparatus, scattered toner tends to accumulate on the surface of the transfer roller 205. Therefore, in order to avoid slip and transfer charging failure, it is effective to clean the toner on the transfer roller 205. For this purpose, for example, a cleaning member as described above can be installed on the transfer roller 205.

  However, the transfer roller 205 usually has elasticity in order to ensure the stability of contact. In this embodiment, as the transfer roller 205, a roller having Asker C of 30 degrees and having an outermost layer formed of urethane sponge is employed. It is difficult to clean the surface layer of the roller having such elasticity.

  Therefore, in this embodiment, a power supply roller 204 for supplying a transfer current to the transfer roller 205 is installed. The transfer roller 205 is electrically floated, and a positive bias is applied to the power supply roller 204 by a transfer bias power source 206. The transfer current supplied from the power supply roller 204 by this bias flows into the photosensitive drum 1 facing the transfer roller 205 via the transfer roller 205. As a result, the toner on the photosensitive drum 1 is transferred to the transfer material P on the transfer belt 201.

  In this embodiment, the toner attached to the surface of the transfer roller 205 is accumulated in the power supply roller 204. That is, when a positive bias is applied to the power supply roller 204 at the time of image formation, the negatively charged scattered toner is transferred from the inner peripheral surface of the transfer belt 51 to the surface of the transfer roller 205 and further to the power supply roller 206. Transcribed.

  The power supply roller 204 is formed of a high hardness surface layer that can be easily cleaned. For example, as the power supply roller 204, a roller in which the whole or at least the outermost layer is made of metal can be suitably used. In the present embodiment, as described above, a metal roller formed of SUS (stainless steel) having an outer diameter of 16 mm was used as the power supply roller 204.

  In this embodiment, a cleaning member 91 for cleaning the surface of the power supply roller 204 is installed. Accordingly, the toner on the surface of the power supply roller 204 is removed and collected by the cleaning member 91.

  Although only the cleaning member 91 is shown in FIG. 5, in this embodiment, the cleaning member 91 is attached to the housing and constitutes a roller cleaner as in the above-described embodiments.

  That is, in this embodiment, at the time of image formation, the transfer bias power source 206 has a polarity (second polarity: positive in this embodiment) opposite to the normal charging polarity of the toner (first polarity: negative in this embodiment). ) Bias is output to the power supply roller 204. As a result, a current in a direction in which the toner charged to the first polarity moves from the inner peripheral surface of the transfer belt 201 and the surface of the transfer roller 205 toward the power supply roller 204 flows to the power supply roller 204.

  Further, a cleaning mode is provided in which the transfer bias power source 206 outputs a bias having the same polarity as the normal charging polarity of the toner (first polarity: negative polarity in this embodiment) to the power supply roller 204 during non-image formation. Also good. As a result, a current flows in the secondary transfer inner roller 56 in a direction in which the toner charged to the second polarity moves from the inner peripheral surface of the transfer belt 201 and the surface of the transfer roller 205 toward the secondary transfer inner roller 56. . Therefore, the toner having the second polarity can be removed and collected from the surface of the power supply roller 204 by the cleaning member 91. In the same manner as described in the second embodiment, a bias is applied so that the absolute value of the current flowing through the transfer portion N in the cleaning mode is larger than the absolute value of the current flowing therethrough during image formation. You can also.

  As described above, according to this embodiment, even in a configuration in which a bias is applied via a plurality of rollers such as the power supply roller 204 and the transfer roller 205, a cleaning member is provided for the roller into which current flows. The scattered toner can be collected effectively. Further, according to the present embodiment, there is no slip due to dirt on the inner peripheral surface of the transfer belt 201, and the occurrence of color misregistration or the like can be prevented.

  As mentioned above, although this invention was demonstrated according to the specific Example, it should be understood that this invention is not limited to the above-mentioned embodiment.

  For example, the cleaning member is provided as the secondary transfer inner roller 56 in the first to third embodiments and the power supply roller in the fourth embodiment, but the present invention is not limited to this. If the rotating body is arranged on the inner peripheral surface side of a belt body that can be moved around and arranged adjacent to the image carrier on which the toner image is formed, and the current flows by the bias output from the bias output means, You may provide a cleaning member with respect to another rotary body. For example, the object to be provided with the cleaning member may be a primary transfer roller or a counter roller of a corona charger. Therefore, for example, in the third embodiment, the configuration in which the dirt on the primary transfer roller is collected by the secondary transfer inner roller is shown, but the present invention is not limited to this, and may be collected by another rotating body. Good.

  Further, a power supply roller similar to that provided for the transfer roller in the image forming apparatus 200 shown in FIG. 5 may be provided for the primary transfer roller in the image forming apparatus 100 shown in FIG. As described in the third embodiment, instead of providing a cleaning member for the primary transfer roller, a cleaning member may be provided for the power supply roller.

  In the first to third embodiments, in the secondary transfer portion, a secondary transfer bias is applied to the secondary transfer outer roller disposed on the outer peripheral surface side of the intermediate transfer belt, and on the inner peripheral surface side of the intermediate transfer belt. The arranged secondary transfer inner roller was electrically grounded. However, conversely, a secondary transfer bias is applied to the secondary transfer inner roller disposed on the inner peripheral surface side of the intermediate transfer belt, and the secondary transfer outer roller disposed on the outer peripheral surface side of the intermediate transfer belt. May be electrically grounded. In this case, the polarity of the bias applied to the secondary transfer unit during the image formation and cleaning operation described in the above embodiment may be reversed.

  In each of the above embodiments, the normal charging polarity of the toner is negative, and the polarity of the bias and the direction of current flow are set accordingly. However, the charging polarity of the toner and the bias The polarity and the direction of current flow are not limited to those in the above embodiments.

  Further, although cases have been described with the above embodiments as examples where the image forming apparatus has a plurality of image carriers, the present invention is equally applicable to image forming apparatuses having a single image carrier. For example, as is well known to those skilled in the art, a plurality of developing devices are provided for a single image carrier, and toner images sequentially formed on the image carrier are transferred to a transfer material on the transfer material carrier. There are image forming apparatuses that directly transfer or sequentially transfer to an intermediate transfer member and then transfer to a transfer material.

1 is a schematic cross-sectional configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional configuration diagram illustrating an image forming unit of the image forming apparatus in FIG. 1 in more detail. FIG. 2 is a schematic diagram showing the vicinity of a secondary transfer unit of the image forming apparatus of FIG. 1 in more detail. FIG. 2 is a schematic diagram showing in more detail the vicinity of a primary transfer unit and a secondary transfer unit of the image forming apparatus of FIG. FIG. 6 is a schematic cross-sectional configuration diagram of an image forming apparatus according to another embodiment of the present invention.

Explanation of symbols

1 Photosensitive drum (image carrier)
51 Intermediate transfer belt (belt body)
52 Primary transfer roller (primary transfer member, rotating body)
56 Secondary transfer inner roller (rotating body)
57 Secondary transfer outer roller (secondary transfer member)
58 Secondary transfer bias power supply (bias output means)
91 Cleaning member 201 Transfer belt (belt body)
204 Power supply roller (rotating body)
205 Transfer roller (transfer member, rotating member)
206 Transfer bias power supply (bias output means)

Claims (29)

  A belt body that can be moved around and disposed adjacent to an image carrier on which a toner image is formed; and a rotating body that is disposed on the inner peripheral surface side of the belt body and rotates as the belt body moves. An image forming apparatus comprising: a bias output unit that outputs a bias that induces a current that flows through a circuit that passes through the rotating body; and a cleaning member that removes toner from the surface of the rotating body.   The belt body is an intermediate transfer body for primary transfer of a toner image on the image carrier onto an outer peripheral surface of the belt body and then secondary transfer of the toner image to a transfer material. The image forming apparatus according to 1.   The rotating body is disposed on the inner peripheral surface side of the intermediate transfer body in a secondary transfer portion for secondary transfer of the toner image on the intermediate transfer body to a transfer material, and the bias output means includes the secondary output section. Inducing an electric current by outputting a bias for the secondary transfer to a member disposed on the outer peripheral surface side of the intermediate transfer member facing the rotating body or the rotating body in the transfer unit. The image forming apparatus according to claim 2.   The rotating body is disposed on an inner peripheral surface side of the intermediate transfer body in a primary transfer portion that primarily transfers a toner image on the image carrier onto the intermediate transfer body, and the bias output unit includes: The image forming apparatus according to claim 2, wherein the current is induced by outputting a bias for the primary transfer to the rotating body.   2. The belt member according to claim 1, wherein the belt member is a transfer material carrier for carrying a transfer material on an outer peripheral surface thereof and transferring a toner image on the image carrier onto the transfer material. Image forming apparatus.   The rotating body is disposed on an inner peripheral surface side of the transfer material carrier in a transfer portion that transfers a toner image on the image carrier to a transfer material on the transfer material carrier, and the bias output unit includes: The image forming apparatus according to claim 5, wherein the current is induced by outputting a bias for the transfer to the rotating body.   The image forming apparatus according to claim 1, wherein the bias output unit is capable of outputting both positive and negative biases.   The image forming apparatus according to claim 1, wherein the bias output unit is capable of outputting biases having different absolute values.   The image forming apparatus according to claim 1, wherein the non-image forming apparatus has a cleaning mode in which the bias output unit outputs a bias having a polarity different from that during image formation to induce the current.   10. The image forming apparatus according to claim 1, wherein the image forming apparatus has a cleaning mode in which an absolute value of the current induced by the bias output from the bias output unit during non-image formation is larger than that during image formation.   At the time of image formation, the bias output means outputs a bias for the secondary transfer, so that the toner charged to a polarity opposite to the normal charging polarity is directed from the inner peripheral surface of the belt body toward the rotating body. The image forming apparatus according to claim 3, wherein a current to be moved is induced.   At the time of non-image formation, the bias output means outputs a bias having a polarity opposite to the bias for the secondary transfer, so that the toner charged with a normal charging polarity is transferred from the inner peripheral surface of the belt body to the rotating body. The image forming apparatus according to claim 11, wherein the image forming apparatus has a cleaning mode in which a current to be moved toward the head is induced.   At the time of image formation, the bias output means outputs a bias for the primary transfer, so that a current for moving the toner charged to a normal charging polarity from the inner peripheral surface of the belt body toward the rotating body is generated. The image forming apparatus according to claim 4, wherein the image forming apparatus is induced.   At the time of non-image formation, the bias output means outputs a bias having a polarity opposite to the bias for the primary transfer, so that the toner charged to a polarity opposite to the normal charging polarity is used as the inner peripheral surface of the belt body. The image forming apparatus according to claim 13, wherein the image forming apparatus has a cleaning mode in which a current to be moved toward the rotating body is induced.   At the time of image formation, the bias output means outputs a bias for the transfer, thereby inducing a current to move the toner charged to a normal charging polarity from the inner peripheral surface of the belt body toward the rotating body. The image forming apparatus according to claim 6.   At the time of non-image formation, the bias output means outputs a bias having a polarity opposite to the bias for the transfer, so that the toner charged to a polarity opposite to a normal charging polarity is transferred from the inner peripheral surface of the belt body to the toner. The image forming apparatus according to claim 15, wherein the image forming apparatus has a cleaning mode in which a current to be moved toward the rotating body is induced.   The image forming apparatus according to claim 12, wherein the absolute value of the current induced in the cleaning mode is larger than the absolute value of the current induced in image formation.   The image forming apparatus according to claim 9, wherein the cleaning mode is performed while the belt body makes one round or more.   The image forming apparatus according to claim 1, wherein the rotating body is in contact with an inner peripheral surface of the belt body.   The image forming apparatus according to claim 1, wherein the rotating body is in contact with a rotating member that is in contact with an inner peripheral surface of the belt body.   21. The image forming apparatus according to claim 20, wherein the bias output unit outputs a bias to the rotating body, and the rotating body supplies the bias output by the bias output unit to the rotating member. . A belt body that can be moved around and disposed adjacent to an image carrier on which a toner image is formed, and a first and a second belt that are disposed on the inner peripheral surface side of the belt body and rotate as the belt body moves. A second rotating body, a first bias output means for outputting a bias for inducing a current flowing through the circuit passing through the first rotating body, and a current flowing through the circuit passing through the second rotating body. Second bias output means for outputting a bias to be removed, and a cleaning member for removing toner from the surface of the second rotating body,
At the time of non-image formation, the first bias output means outputs a bias for inducing a current for moving the toner charged to the first polarity from the first rotating body toward the inner peripheral surface of the belt body. And a cleaning mode in which the second bias output means outputs a bias for inducing a current for moving the toner charged to the first polarity from the inner peripheral surface of the belt body toward the second rotating body. An image forming apparatus.   The belt body is an intermediate transfer body for primary transfer of a toner image on the image carrier onto an outer peripheral surface of the belt body and then secondary transfer of the toner image to a transfer material. The image forming apparatus according to 22.   The first rotating body is disposed on an inner peripheral surface side of the intermediate transfer body in a primary transfer portion that primarily transfers the toner image on the image carrier onto the intermediate transfer body. 1 bias output means outputs a bias to the first rotator, and the second rotator is a secondary transfer unit that secondarily transfers the toner image on the intermediate transfer member to a transfer material. The second bias output means is disposed on the outer peripheral surface side of the intermediate transfer body in the secondary transfer portion so as to face the second rotating body. 24. The image forming apparatus according to claim 23, wherein a bias is output to the formed member or the second rotating body. At the time of image formation, the first bias output means outputs a bias for the primary transfer, whereby the toner charged to the first polarity is transferred from the inner peripheral surface of the belt body to the first rotating body. The second bias output means outputs a bias for the secondary transfer, so that the second polarity is charged to a second polarity opposite to the first polarity. A current is induced to move the toner from the inner peripheral surface of the belt body toward the second rotating body,
In the cleaning mode, the first bias output means outputs a bias having a polarity opposite to the bias for the primary transfer, so that the toner charged with the first polarity is discharged from the first rotating body. A current to be moved toward the inner peripheral surface of the belt body is induced, and the second bias output means outputs a bias having a polarity opposite to the bias for the secondary transfer. An electric current is induced to move the toner charged to the polarity of the belt from the inner peripheral surface of the belt body toward the second rotating body.
25. The image forming apparatus according to claim 24, wherein:   26. The image forming apparatus according to claim 22, wherein the first polarity is a regular charging polarity of toner.   27. The image forming apparatus according to claim 22, wherein the first and second rotating bodies are in contact with an inner peripheral surface of the belt body.   28. The image forming apparatus according to claim 22, wherein the cleaning mode is performed while the belt body makes one round or more.   The belt body is rotated by rotating the rotating body, or the rotating body is rotated by rotating the belt body and power is transmitted from the rotating body to another member. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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