JP6000793B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic or electrostatic recording type image forming apparatus, and more particularly to an image forming apparatus having a brush-like transfer means.

  2. Description of the Related Art Conventionally, as an image forming apparatus such as a copying machine or a printer using an electrophotographic system, there is an intermediate transfer system using an intermediate transfer belt. In an intermediate transfer belt type image forming apparatus, a full-color image is formed through a primary transfer process and a secondary transfer process. In the primary transfer step, a toner image formed on the surface of an electrophotographic photosensitive member (photosensitive member) as an image carrier is transferred onto an intermediate transfer belt. This primary transfer process is repeatedly executed for a plurality of color toner images, whereby a plurality of color toner images are formed on the surface of the intermediate transfer belt. In the secondary transfer process, toner images of a plurality of colors formed on the surface of the intermediate transfer belt are collectively transferred onto the surface of a transfer material such as paper. The toner image transferred onto the surface of the transfer material is then fixed to the transfer material by a fixing unit. Thereby, a full color image is obtained.

  For example, as the primary transfer unit in the above-described intermediate transfer type image forming apparatus, a roller-type transfer unit, a blade-type transfer unit, a brush-type transfer unit, or the like is used. These transfer units are brought into contact with the back surface of the intermediate transfer belt at a position facing the photoconductor, and are used with a primary transfer voltage applied.

  As a brush-shaped transfer means, a pile fabric type brush member is known (Patent Document 1).

  A pile fabric type brush member is a pile of conductive filament yarns woven in the gap between the weft yarn and the warp yarn of the base fabric formed by crossing the warp yarn and the weft yarn extending in directions orthogonal to each other. It is the brush member comprised by this. By using such a brush member, it is possible to obtain a relatively inexpensive brush-shaped transfer means.

JP 2000-293016 A

  However, the image forming apparatus using the brush-like transfer unit composed of a pile fabric type brush member has the following problems.

  For example, in an intermediate transfer type image forming apparatus, in order to suppress image defects in a vertical streak shape (direction along the moving direction of the intermediate transfer belt) caused by uneven contact between the brush-like transfer unit and the intermediate transfer belt. If the pile density is increased, the conveyance torque of the intermediate transfer belt increases. If the conveyance torque of the intermediate transfer belt increases, the load on the motor for driving the intermediate transfer belt increases. In some cases, the rotation of the intermediate transfer belt becomes unstable.

  On the other hand, if the pile density is lowered in order to reduce the conveyance torque of the intermediate transfer belt, a vertical stripe-like image defect occurs.

  Although the conventional problems have been described with an intermediate transfer type image forming apparatus as an example, a direct transfer type image in which a toner image is directly transferred from a photosensitive member onto a transfer material carried on a transfer material conveyance belt. In the forming apparatus, a similar problem may occur with respect to the transfer portion.

  Accordingly, an object of the present invention is to suppress vertical streak-like image defects and to reduce the torque for conveying the belt in a configuration having a belt and a brush-like transfer means that contacts the belt. An image forming apparatus is provided.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention provides an image forming apparatus including an image carrier that carries a toner image, a movable endless belt, and a transfer unit that transfers the toner image from the image carrier toward the belt. In the apparatus, the transfer unit is formed by weaving a pile in a gap portion between the yarns of a base fabric formed by yarns extending along the moving direction of the belt and a direction substantially orthogonal to the moving direction. In the direction substantially perpendicular to the moving direction of the belt, the gap portion in which the pile is flocked is a flocked portion, the gap portion in which the pile is not flocked is a non-flocked portion. A region on the belt to which a toner image from the image carrier is transferred is an image forming region, and a first contact portion where the image carrier and the belt are in contact with each other in the moving direction of the belt; An area on the belt where the belt and the second contact portion where the transfer means comes into contact is defined as an overlapping area, and the pile contacting the belt in the image forming area and the overlapping area is planted. When an area on the base fabric including the gap is defined as an effective area, at least one of the gap rows formed of a plurality of the gaps arranged in the effective area along the moving direction of the belt. An image forming apparatus, wherein a flocked portion and at least one non-flocked portion are provided.

  According to the present invention, in the configuration having the belt and the brush-like transfer means that abuts on the belt, it is possible to suppress the vertical streak-like image defect and reduce the torque for conveying the belt.

1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing a positional relationship between each member of the primary transfer portion and a nip in an embodiment of the present invention. It is (a) perspective view, (b) sectional drawing, and (c) top view showing some primary transfer brushes in one example of the present invention. It is a schematic diagram for demonstrating a pile length and a pile diameter. It is (a) perspective view, (b) sectional drawing, and (c) top view showing some primary transfer brushes in one comparative example. It is (a) perspective view, (b) sectional drawing, and (c) top view showing some primary transfer brushes in other comparative examples. It is (a) perspective view, (b) sectional view, and (c) top view showing a part of a primary transfer brush concerning other examples of the present invention. FIG. 6 is a schematic diagram for explaining the influence of the displacement of the primary transfer brush in the moving direction of the intermediate transfer belt when using the primary transfer brush in one embodiment of the present invention. FIG. 10 is a schematic diagram for explaining the influence of the displacement of the primary transfer brush in the moving direction of the intermediate transfer belt when using the primary transfer brush according to another embodiment of the present invention. It is a partial top view of the primary transfer brush for demonstrating the modification of the pile arrangement | positioning of the primary transfer brush in the other Example of this invention. FIG. 10 is a schematic cross-sectional view illustrating a configuration example of another image forming apparatus to which the present invention can be applied.

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

Example 1
1. First, the overall configuration and operation of an image forming apparatus according to an embodiment of the present invention will be described.

  FIG. 1 is a schematic cross-sectional view of a main part of the image forming apparatus 100 of the present embodiment. The image forming apparatus 100 according to the present exemplary embodiment is a tandem type full color laser beam printer that employs an intermediate transfer method and can form a full color image using an electrophotographic method.

  The image forming apparatus 100 primarily superimposes each color toner image formed according to the image information separated into a plurality of color components on the intermediate transfer belt 6 as an intermediate transfer member, and then primarily transfers the toner image onto the transfer material P. Secondary transfer at once. A recorded image is obtained by fixing the toner image on a transfer material. The image forming apparatus 100 includes first, second, third, and fourth stations Sa, Sb, Sc, and Sd as a plurality of image forming units. In the present embodiment, the first to fourth stations Sa to Sd form toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K).

  In the present embodiment, the configurations and operations of the first to fourth stations Sa to Sd are substantially the same except that the color of the toner used is different. Therefore, in the following, when there is no need for distinction, a description will be given collectively with a, b, c, and d at the end of a symbol indicating an element provided for any color being omitted.

  The station S includes a photosensitive drum 1 that is a drum-type electrophotographic photosensitive member (photosensitive member) as an image carrier. The photosensitive drum 1 is rotationally driven in the direction of arrow R1 (counterclockwise) in the figure by a motor (not shown) as a driving means. Around the photosensitive drum 1, the following units are provided in order along the rotation direction. First, the charging roller 2 is a roller-shaped charging member as charging means. Next, an exposure apparatus (laser scanner) 3 as an exposure unit. Next, there is a developing device 4 as a developing unit. Next, a primary transfer brush 5 which is a brush-like transfer member as a primary transfer means. Next, a drum cleaner 7 as a photosensitive member cleaning unit.

  Further, an intermediate transfer belt 6 that is an endless belt as an intermediate transfer member is disposed so as to face each photosensitive drum 1 of each station S. The intermediate transfer belt 6 is formed of a cylindrical and endless film, and is stretched around three rollers: a driving roller 61, a secondary transfer counter roller 62, and a tension roller 63. The intermediate transfer belt 6 rotates (rotates) in the direction indicated by the arrow R3 (clockwise) in the figure by driving the drive roller 61 in the direction indicated by the arrow R2 (clockwise) in the figure. In this embodiment, the moving speed (peripheral speed) of the surface of the photosensitive drum 1 and the moving speed (peripheral speed) of the surface of the intermediate transfer belt 6 are substantially the same speed. Each primary transfer brush 5 is disposed on the inner peripheral surface (back surface) side of the intermediate transfer belt 6 at a position facing each photosensitive drum 1 with the intermediate transfer belt 6 interposed therebetween. As will be described in detail later, the primary transfer brush 5 is pressed against the back surface of the intermediate transfer belt 6. Thus, the primary transfer portion B1 is formed by the contact between the photosensitive drum 1 and the intermediate transfer belt 6. On the outer peripheral surface (front surface) side of the intermediate transfer belt 6, a secondary transfer member, which is a roller-like transfer member, is disposed at a position facing the secondary transfer counter roller 62 across the intermediate transfer belt 6. A transfer roller 8 is disposed. The secondary transfer roller 8 is pressed against the secondary transfer counter roller 62 via the intermediate transfer belt 6. As a result, the intermediate transfer belt 6 and the secondary transfer roller 8 come into contact with each other to form the secondary transfer portion B2. A belt cleaner 65 serving as an intermediate transfer member cleaning unit is disposed at a position facing the driving roller 61 with the intermediate transfer belt 6 interposed therebetween.

  At the time of image formation, the surface of the rotating photosensitive drum 1 is uniformly charged by the charging roller 2. At this time, a predetermined charging voltage (charging bias) is applied to the charging roller 2 from a charging power source (not shown) as a charging voltage applying means. The surface of the charged photosensitive drum 1 is irradiated with laser light L according to the image information from the exposure device 3. As a result, an electrostatic latent image (electrostatic image) is formed on the photosensitive drum 1.

  The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) as a toner image by the developing device 4. The developing device 4 carries toner as a developer on a rotatable developer carrying member and conveys the toner to a portion facing the photosensitive drum 1 (development position). The developing device 4 performs photosensitivity according to the electrostatic latent image on the photosensitive drum 1. Toner is supplied onto the drum 1. At this time, a predetermined developing voltage (developing bias) is applied to the developer carrying member from a developing power source (not shown) as a developing voltage applying means. In this embodiment, the developing device 4 develops the electrostatic latent image on the photosensitive drum 1 by a reversal development method. That is, the developing device 4 is exposed to the charged polarity (negative polarity in this embodiment) of the photosensitive drum 1 on the image portion (exposure portion) on the photosensitive drum 1 that has been exposed after the charging process and the absolute value of the potential has decreased. The electrostatic latent image is developed by attaching toner charged to the same polarity.

  The toner image formed on the rotating photosensitive drum 1 is transferred (primary transfer) onto the rotating intermediate transfer belt 6 by the action of the primary transfer brush 5 in the primary transfer portion B1. At this time, the primary transfer brush 5 has a polarity opposite to the normal charging polarity (negative polarity in this embodiment) of the toner that forms the toner image from the primary transfer power supply 50 as the primary transfer voltage application means. In this case, a primary transfer voltage (primary transfer bias) which is a DC voltage of positive polarity is applied.

  Toner remaining on the photosensitive drum 1 without being transferred to the intermediate transfer belt 6 in the primary transfer step (primary transfer residual toner) is cleaned by a drum cleaner 7. The drum cleaner 7 includes a cleaning blade 71 that is a plate-like elastic body that comes into contact with the surface of the photosensitive drum 1, and a collected toner container 72. The cleaning blade 71 is a cleaning member for removing toner adhering to the surface of the photosensitive drum 1. The toner removed from the surface of the photosensitive drum 1 rotated by the cleaning blade 71 is collected in a collected toner container 72.

  For example, when a full-color image is formed, the charging, exposure, development, and primary transfer processes as described above are performed in order from the upstream side in the movement direction of the surface of the intermediate transfer belt 6 in order from the first to fourth stations Sa to Sd. Done in As a result, a multi-toner image for a full-color image is formed on the intermediate transfer belt 6 by transferring toner images of four colors of yellow, magenta, cyan, and black.

  The toner image on the intermediate transfer belt 6 is transferred (secondary transfer) onto the transfer material P by the action of the secondary transfer roller 8 in the secondary transfer portion B2. That is, in the transfer material supply unit 20, the transfer material P accommodated in the cassette 21 is fed by the supply roller 22 and then supplied to the secondary transfer unit B 2 by the registration roller 23 at a predetermined timing. At substantially the same time, the secondary transfer roller 8 receives a secondary transfer voltage from the secondary transfer power supply 80 as a secondary transfer voltage application unit, which is a DC voltage having a polarity opposite to the normal charging polarity of the toner forming the toner image. A voltage (secondary transfer bias) is applied.

  The toner remaining on the intermediate transfer belt 6 without being transferred to the transfer material P in the secondary transfer process (secondary transfer residual toner) is cleaned by the belt cleaner 65. The belt cleaner 65 includes a cleaning blade 64 that is a plate-like elastic body that comes into contact with the surface of the intermediate transfer belt 6, and a collected toner container 66. The cleaning blade 64 is a cleaning member for removing toner adhering to the surface of the intermediate transfer belt 6. The toner removed from the surface of the intermediate transfer belt 6 rotated by the cleaning blade 64 is collected in a collected toner container 66.

  The transfer material P onto which the toner image is secondarily transferred is conveyed to a fixing device 9 as a fixing unit. The fixing device 9 heats and pressurizes the transfer material P while conveying it. The unfixed toner image on the transfer material P is fixed on the transfer material P by heat and pressure. Thereafter, the transfer material P is conveyed outside the apparatus by a conveyance roller (not shown).

  Here, the image forming apparatus 100 of the present embodiment is a printer that supports image formation on an A4 size transfer material P having a process speed corresponding to the peripheral speed of the photosensitive drum 1 and the intermediate transfer belt 6 of 116 mm / s. is there. In this embodiment, the photosensitive drum 1 has a diameter of 20 mm.

In this embodiment, a polyimide resin film having a thickness of 60 μm and a volume resistivity adjusted to 10 ⁹ Ωcm by mixing a conductive agent was used as the intermediate transfer belt 6. The intermediate transfer belt 6 is stretched around three axes of a drive roller 61, a secondary transfer counter roller 62, and a tension roller 63, and a tension of about 20 N is applied by the tension roller 63.

In this embodiment, an elastic roller having a volume resistivity of 10 ⁷ to 10 ⁹ Ωcm and a hardness of 30 ° to 40 ° is used as the secondary transfer roller 8. The secondary transfer roller 8 is pressed against the secondary transfer counter roller 62 via the intermediate transfer belt 6 with a total pressure of about 39.2N. The secondary transfer roller 8 is driven to rotate as the intermediate transfer belt 6 rotates. A secondary transfer voltage of 0 to 4.0 kV can be applied to the secondary transfer roller 8 from a secondary transfer power supply 80.

2. Next, the arrangement of the primary transfer brush 5 in the primary transfer portion B1 will be described.

  As will be described in detail later, as the primary transfer brush 5, a pile fabric type brush member is used as a brush member in which brush fibers 51 formed of conductive fibers (conductive fibers) are arranged.

  FIG. 2 is a schematic cross-sectional view showing the positional relationship between each member and the nip in the primary transfer portion B1. In the present embodiment, the configurations of the primary transfer portions B1a to B1d of the stations Sa to Sd are the same.

  In this embodiment, the primary transfer brush 5 is held on the pedestal 102 and is disposed so as to contact the back surface of the intermediate transfer belt 6 with a predetermined amount of penetration. As a result, the primary transfer brush 5 contacts the back surface of the intermediate transfer belt 6 in a state where the brush fibers 106 are tilted downstream along the moving direction R3 of the intermediate transfer belt 6. In this embodiment, the intrusion amount is 1.0 mm. Here, the amount of intrusion is the primary transfer from the back surface of the intermediate transfer belt 6 in the normal direction of the intermediate transfer belt 6 when it is assumed that the primary transfer brush 5 is not deformed by contacting the intermediate transfer belt 6. The longest distance to the tip of the brush fiber 106 of the brush 5 is taken.

  The length of the brush fiber 106, that is, the pile length will be described later. In FIG. 2, illustration of the base fabric constituting the pile fabric of the primary transfer brush 5 is omitted.

  In the present embodiment, the dimension W in the short direction of the primary transfer brush 5 is 3.0 mm. The short side direction of the primary transfer brush 5 is a direction in which the primary transfer brush 5 is arranged substantially perpendicular to the rotation axis direction of the photosensitive drum 1 (substantially parallel to the moving direction R3 of the intermediate transfer belt 6). In this embodiment, the length L1 (FIG. 3C) in the longitudinal direction of the primary transfer brush 5 is 250 mm. The longitudinal direction of the primary transfer brush 5 is a direction arranged substantially parallel to the rotational axis direction of the photosensitive drum 1 (substantially perpendicular to the moving direction R3 of the intermediate transfer belt 6).

  In FIG. 2, N <b> 1 represents a first nip that is a first contact portion formed between the photosensitive drum 1 and the intermediate transfer belt 6. In this embodiment, the width of the first nip N1 in the moving direction of the intermediate transfer belt 6 is 1.0 mm.

  On the other hand, N2 in FIG. 2 represents a second nip which is a second contact portion formed between the intermediate transfer belt 6 and the primary transfer brush 5. Here, the second nip N <b> 2 ends from the contact start point (start point) between the primary transfer brush 5 composed of the plurality of brush fibers 106 and the back surface of the intermediate transfer belt 6 in the moving direction of the intermediate transfer belt 6. The area up to the point (end point). In this embodiment, the width of the second nip N2 in the moving direction of the intermediate transfer belt 6 is 3.0 mm.

  In FIG. 2, s indicates that the first nip N1 where the photosensitive drum 1 and the intermediate transfer belt 6 are in contact and the second nip N2 where the intermediate transfer belt 6 and the primary transfer brush 5 are in contact are the intermediate transfer belt. 6 represents an overlapping region (physical nip) in the moving direction. The physical nip s that is the overlapping region is a region where a transfer electric field is formed. If the physical nip s is not formed, good primary transfer efficiency cannot be obtained. Further, when there is a region in the physical nip s where the intermediate transfer belt 6 and the primary transfer brush 5 do not contact with each other in the longitudinal direction of the primary transfer brush 5, a transfer electric field is not formed in that region, and a transfer failure occurs. Sometimes. As a result, a vertical stripe (band) -like image defect (direction along the moving direction of the intermediate transfer belt 6) may occur. In this embodiment, the width of the physical nip s in the moving direction of the intermediate transfer belt 6 is 1.0 mm.

  In FIG. 2, t represents a region (downstream tension nip) where only the primary transfer brush 5 contacts the intermediate transfer belt 6 on the downstream side of the physical nip s in the moving direction of the intermediate transfer belt 6. That is, t in FIG. 2 indicates that the second nip N2 where the intermediate transfer belt 6 and the primary transfer brush 5 are in contact with the first nip N1 where the photosensitive drum 1 and the intermediate transfer belt 6 are in contact with each other. A region that protrudes downstream in the moving direction of the intermediate transfer belt 6 is shown. The downstream tension nip t is applied by a transfer electric field formed in the overlap nip s, and excessive charge remaining on the intermediate transfer belt 6 flows back to the primary transfer brush 5 after passing through the overlap nip s. It is an area. The downstream tension nip s is a region necessary for preventing the occurrence of an image defect due to abnormal discharge caused by the excessive charge. In this embodiment, the width of the downstream tension nip t in the moving direction of the intermediate transfer belt 6 is 1.8 mm.

  In FIG. 2, “u” represents a first nip N1 where the photosensitive drum 1 and the intermediate transfer belt 6 are in contact with each other, and a second nip N2 where the intermediate transfer belt 6 and the primary transfer brush 5 are in contact with each other is an intermediate transfer. A region (upstream tension nip) that protrudes upstream in the moving direction of the belt 6 is shown. That is, u in FIG. 2 represents a region where only the primary transfer brush 5 contacts the intermediate transfer belt 6 on the upstream side of the physical nip s in the movement direction of the intermediate transfer belt 6. When the upstream tension nip u becomes large, a gap in which a transfer electric field is formed is formed between the photosensitive drum 1 and the intermediate transfer belt 6 on the upstream side in the movement direction of the intermediate transfer belt 6 in the primary transfer portion B1. For this reason, a phenomenon may occur in which the toner is transferred from the photosensitive drum 1 to the intermediate transfer belt 6 before entering the primary transfer portion B1, resulting in an image in which the toner is scattered (transfer scattering due to pre-transfer). For this reason, the upstream tension nip u needs to be as narrow as possible within a range in which the physical nip s can be sufficiently secured in consideration of variations in the position of the primary transfer brush 5. In the present embodiment, the width of the upstream tension nip u in the moving direction of the intermediate transfer belt 6 is 0.2 mm.

3. Primary Transfer Brush Next, the configuration of the primary transfer brush 5 will be described.

  3A, 3B, and 3C are a perspective view, a cross-sectional view, and a plan view as seen from the tip of the pile, respectively, showing a part of the primary transfer brush 5. FIG.

  As the primary transfer brush 5, a pile woven fabric type is used. The pile woven fabric is formed by weaving a pile 105 in which filament yarns serving as brush fibers 106 are bundled into a gap 107 of a lattice-like base fabric 101 composed of warp yarns 103 and weft yarns 104. The primary transfer brush 5 which is a brush member is obtained by fixing it on the pedestal 102 with a conductive adhesive or the like.

As the pile 105, what consists of 10-100 filament yarns per bundle can be used preferably. In this embodiment, a pile 105 composed of 48 filament yarns per bundle of piles 105 was used. The pile density is preferably 100 to 1000 bundles / cm ² . In this example, the pile density was 630 bundles / cm ² . In this embodiment, the base fabric 101 having a pitch f of the gap 107 of 0.4 mm is used in the direction along the axial direction of either the warp yarn 103 or the weft yarn 104.

As the brush fiber 106, a conductive fiber (conductive fiber), in particular, a synthetic fiber containing a conductive agent can be preferably used. For example, a material made of nylon, polyester or the like in which carbon powder is dispersed can be preferably used. In this embodiment, conductive fibers made of a material in which carbon powder is dispersed in nylon are used as the brush fibers 106. The single yarn fineness is preferably in the range of 2 to 15 dtex. In this embodiment, the single yarn fineness is 7 dtex. The resistivity ρfiber of the brush fiber 106 is preferably in the range of 10 ² to 10 ⁸ Ωcm from the viewpoint of improving transfer efficiency. In this embodiment, the resistivity ρfiber is 10 ⁶ Ωcm.

The resistivity ρfiber is measured by the following method. A bundle of 50 fibers is made, and a metal probe is brought into contact with the surface of the bundle at an interval of about 1 cm. Then, using a high resistance meter Advantest R8340A (manufactured by Advantest Co., Ltd.) or the like, the resistance value Rfiber is measured with an applied voltage of 100 V, and the resistivity ρfiber is calculated by the following equation.
ρfiber = Rfiber × (fiber diameter / 2) ² × 3.14 × 50

4). Pile Arrangement Next, the weaving method of the pile fabric and the arrangement of the piles in the primary transfer brush 5 will be described.

  As shown in FIGS. 3A, 3B, and 3C, the warp yarn 103 and the weft yarn 104 extending in a substantially orthogonal direction are alternately crossed in a lattice shape, whereby the base fabric 101 is formed. Yes. A pile fabric constituting the primary transfer brush 5 is formed by weaving the pile 105 in the gap 107 formed by the warp yarn 103 and the weft yarn 104.

  Here, in this embodiment, the warp yarn 103 of the base fabric 101 is disposed substantially parallel to the rotational axis direction of the photosensitive drum 1 (substantially perpendicular to the moving direction R3 of the intermediate transfer belt 6). Further, the weft 104 is arranged substantially perpendicular to the rotational axis direction of the photosensitive drum 1 (substantially parallel to the moving direction R3 of the intermediate transfer belt 6). Note that the fact that the warp yarn 103 and the weft yarn 104 are substantially parallel and substantially perpendicular to the direction of the rotation axis of the photosensitive drum 1 is not limited to the case where they are completely parallel and perpendicular, but also the effects described in this embodiment. May be tilted within a range in which a sufficient value can be obtained, for example, within 30 °. A region surrounded by two adjacent warp yarns 103 and 103 arranged substantially in parallel and two adjacent weft yarns 104 and 104 arranged almost in parallel is a gap 107. Further, the gap portion 107 in which the pile 105 is woven is referred to as a flocked portion 108, and the gap portion 107 in which the pile 105 is not woven is referred to as a non-flocked portion 109.

  As the warp yarn 103 and the weft yarn 104 constituting the base fabric 101, those made of polyester, rayon, cupra or the like can be preferably used. In this embodiment, both the warp yarn 103 and the weft yarn 104 are polyester spun yarns. The fineness of the warp yarn 103 and the weft yarn 104 is preferably in the range of 30 to 200 dtex. In this embodiment, the warp yarn 103 and the weft yarn 104 are both 110 dtex.

  In this embodiment, the pile 105 is a flat surface of the base fabric 101 (the base fabric 101 is fixed) in which the warp yarn 103 and the weft yarn 105 are knitted before being brought into contact with the back surface of the intermediate transfer belt 6. (Represented by the surface in contact with the upper surface of the pedestal 102). Here, the term “substantially parallel to the normal direction” includes the case where the normal direction is inclined at an angle of 30 ° or less due to the spread of a pile 105 described later.

  Pile weaving methods include U weaving and W weaving. In this embodiment, U weaving was used. As shown in FIG. 3B, the U weave is woven into the base fabric 101 so that the pile 105 passes under a single weft thread 104 in a U shape. In FIG. 3 (b), the warp yarn 103 is not shown in order to avoid complication of the drawing.

  As shown in FIG. 3B, the pile 105 converges at a portion close to the base fabric 101, but the filament yarn as the brush fiber 106 is released toward the tip, and has a certain diameter (pile diameter) R. It contacts the back surface of the intermediate transfer belt 6. In this embodiment, the pile diameter R is about 0.4 mm.

  As shown in FIG. 4A, when the pile length B is long and the pile diameter R is too large, the adjacent piles 105 interfere with each other at the overlap e of the pile diameter R, and the intermediate transfer belt 6 is in contact with the intermediate transfer belt 6. Unevenness may occur in contact. As a result, image defects due to transfer unevenness may occur.

  On the other hand, as shown in FIG. 4B, when the pile length B is short and the pile diameter R is too small, the interval c between the adjacent piles 105 becomes large. If the distance c is too large, a region where the back surface of the intermediate transfer belt 6 and the brush fiber 106 do not contact with each other in the longitudinal direction of the primary transfer brush 5 occurs. As a result, a transfer defect may occur, and a vertical stripe-like image defect may occur.

  By examining the pile diameter R by changing the pile length B, the following was found. In other words, if the ratio e / R = (R−f) / R of the overlap of pile diameter R between adjacent piles 105 to the pile diameter R is 0.5 or more, slight transfer unevenness It was found that may occur. Further, it has been found that when the ratio e / R is 0.7 or more, clear transfer unevenness may occur. On the other hand, it was found that if the distance c = f−R between the adjacent piles 105 in the longitudinal direction of the primary transfer brush 5 is 0.1 mm or more, a slight vertical stripe-like image defect may occur. Further, it has been found that when the distance c is 0.2 mm or more, clear vertical stripes may occur.

  Therefore, it is preferable to use a pile length B having an appropriate length according to the interval between the piles 105, that is, the pitch f of the gap 107. In this embodiment, as described above, the pitch f is 0.4 mm, the pile length B is 3.0 mm, the pile diameter R is 0.4 mm, the interval c is 0 mm, and the overlap e is 0 mm.

  Note that the pitch f is a length along the plane of the base fabric 101 formed by knitting the warp yarn 103 and the weft yarn 105 (represented by the surface in contact with the upper surface of the pedestal 102 to which the base fabric 101 is fixed). The pile diameter R, the interval c, and the overlap e are lengths along the back surface of the intermediate transfer belt 6 in a state where the pile 105 is in contact with the back surface of the intermediate transfer belt 6. The pile diameter R is represented by the diameter of the circumscribed circle at the tip of the pile 105. The interval c is represented by the shortest distance between the tips of the piles 105 made of a bundle of brush fibers 106 woven into the adjacent flocks 108 in the direction along the axial direction of the warp yarn 103. The overlap e is represented by the maximum amount of overlap between the tips of the piles 105 made of a bundle of brush fibers 106 woven into the adjacent flocked portions 108 in the direction along the axial direction of the warp yarn 103. The pile length B is piled along the normal direction from the plane of the base fabric 101 formed by knitting the warp yarn 103 and the weft yarn 105 (represented by the surface in contact with the upper surface of the pedestal 102 to which the base fabric 101 is fixed). The length up to the tip of 105 is represented.

  Referring to FIGS. 3A and 3C, a pile 105 in contact with the back surface of the intermediate transfer belt 6 in a range (image forming region) where an image is formed in a direction along the longitudinal direction of the primary transfer brush 5 is shown. A range on the base cloth 101 including the gap portion 107 that is planted is defined as a longitudinal effective range D1. The direction along the longitudinal direction of the primary transfer brush 5 is a direction R4 that is substantially perpendicular to the moving direction R3 of the intermediate transfer belt 6. Further, in the direction along the short direction of the primary transfer brush 5, the range on the base cloth 101 including the gap portion 107 in which the pile 105 contacting the back surface of the intermediate transfer belt 6 of the physical nip s is planted is short-effective. The range is D2. The direction along the short direction of the primary transfer brush 5 is a direction substantially parallel to the moving direction R3 of the intermediate transfer belt 6. And let the area | region on the base fabric 101 enclosed by the long effective range D1 and the short effective range D2 be the effective area D3 (shaded part of FIG.3 (c)). A group of gaps 107 including a plurality of gaps 107 arranged substantially parallel to the moving direction R3 of the intermediate transfer belt 6 is defined as a gap row α. A group of gaps 107 formed of a plurality of gaps 107 arranged in a direction R4 substantially perpendicular to the moving direction R3 of the intermediate transfer belt 6 is defined as a gap row β.

  At this time, in this embodiment, at least one flocked portion is present in all the gap portion rows α in the effective region D3 (α5 to α8... Α′1 to α′4 in FIGS. 3A and 3C). 108 and at least one non-flocked portion 109 are provided. In addition, in this embodiment, the gap portion rows β in the effective region D3 (β2 to β4 in FIGS. 3A and 3C) are all the gap portion rows β of the flocked portion 108 and all of the non-flocked portion 109. It consists of gap part row β. For example, in the present embodiment, as shown in FIGS. 3A and 3C, the gap portion rows β <b> 2 and β <b> 4 are all the flocked portions 108, and the gap portion rows β <b> 3 are all the non-flocked portions 109.

  Thus, in this embodiment, at least one flocked portion 108 is provided in all the gap portion rows α in the effective region D3. Therefore, a region where the back surface of the intermediate transfer belt 6 and the brush fiber 106 do not contact with each other in the longitudinal direction of the primary transfer brush 5 does not substantially occur in the physical nip s. Accordingly, it is possible to suppress the occurrence of transfer failure without forming a transfer electric field in the physical nip s.

5. Effect confirmation [Comparative Example 1]
Here, the comparative example for showing the effect of a present Example is demonstrated. Note that the image forming apparatus of the comparative example (this comparative example and other comparative examples described later) has substantially the same configuration as the image forming apparatus of the embodiment according to the present invention, except for the differences particularly mentioned. . In the comparative example (this comparative example and other comparative examples described later), the elements having the same or equivalent functions and configurations as those of the image forming apparatus of the embodiment according to the present invention will be described with the same reference numerals.

  FIGS. 5A, 5B, and 5C are a perspective view, a cross-sectional view, and a plan view as seen from the tip of the pile, respectively, showing a part of the primary transfer brush 5 in Comparative Example 1. FIG.

  In Comparative Example 1, the pile fabric constituting the primary transfer brush 5 is woven with a W weave. In the W weave, as shown in FIG. 5B, the pile 105 passes under one weft thread 104, then climbs over the adjacent weft thread 104, and further passes under the adjacent weft thread 104. It is woven into the base fabric 101.

  As shown in FIGS. 5 (a) and 5 (c), unlike Comparative Example 1, Comparative Example 1 does not have one flocked portion 108 in the effective region D3 (shaded portion in FIG. 5 (c)). There is a gap row α.

  For example, as shown in FIGS. 5A and 5C, the gap portion rows α6 and α7 and the gap portion rows α′2 and α′3 do not have one flocked portion 108. Similarly, between the gap portion row α8 and the gap portion row α′1 omitted in FIGS. 5A and 5C, there is a gap portion row α that does not have one flocked portion 108 as well.

  As described above, in the gap portion row α in the effective region D3, if there is a gap portion row α that does not have one flocked portion, the back surface of the intermediate transfer belt 6 and the brush fibers 106 are in the longitudinal direction of the primary transfer brush 5. A non-contact area D4 occurs in the physical nip s.

[Comparative Example 2]
6A, 6 </ b> B, and 6 </ b> C are a perspective view, a cross-sectional view, and a plan view as seen from the tip of the pile, respectively, showing a part of the primary transfer brush 5 in Comparative Example 2. FIG.

  In Comparative Example 2, the pile fabric constituting the primary transfer brush 5 is woven with a U weave as in the present embodiment.

  As shown in FIGS. 6A and 6C, in the comparative example 2, unlike the present example, all the gaps 107 in the effective region D3 (shaded portions in FIG. 6C) are the flocked portions 108. is there.

  Therefore, in Comparative Example 2, a region where the back surface of the intermediate transfer belt 6 and the brush fiber 106 do not contact with each other in the longitudinal direction of the primary transfer brush 5 does not substantially occur in the physical nip s.

<Image evaluation 1>
Using the image forming apparatus in which the primary transfer brush 5 of this embodiment, Comparative Example 1 or Comparative Example 2 is disposed in each of the primary transfer portions B1a to B1d of the stations Sa to Sd, an image output durability test is performed. An image evaluation on the vertical stripe (band) was performed.

  As the evaluation image, an image obtained by mixing halftone images of yellow, magenta, cyan, and black was used. The number of images formed in the durability test was 50,000, and the level evaluation of vertical streak-like image defects in the evaluation image was performed visually at appropriate timing throughout the entire period. When no vertical stripe-like image defect occurred, it was evaluated as ◯, and when a vertical stripe-like image defect occurred, it was evaluated as x. Table 1 shows the image evaluation results.

  As shown in Table 1, in this example and comparative example 2, no vertical stripe-like image defect occurred during the entire period of the durability test. On the other hand, in Comparative Example 1, vertical streak-like image defects occurred from the beginning of the durability test.

  In this example and comparative example 2, a region where the back surface of the intermediate transfer belt 6 and the brush fiber 106 do not contact with each other in the longitudinal direction of the primary transfer brush 5 does not substantially occur in the physical nip s. Therefore, in this embodiment and Comparative Example 2, it is considered that transfer unevenness does not occur in the longitudinal direction of the primary transfer brush 5.

  On the other hand, in Comparative Example 1, a region D4 in which the back surface of the intermediate transfer belt 6 and the brush fiber 106 do not contact with each other in the longitudinal direction of the primary transfer brush 5 is generated in the physical nip s. Therefore, in Comparative Example 1, it is considered that a transfer failure occurred in that region, and a vertical stripe-like image failure along the moving direction of the intermediate transfer belt 6 occurred due to transfer unevenness in the longitudinal direction of the primary transfer brush 5. .

  If a region D4 where the back surface of the intermediate transfer belt 6 does not contact the brush fiber 106 in the longitudinal direction of the primary transfer brush 5 is generated, a transfer electric field necessary for primary transfer is not formed in that region. Therefore, it is considered that a transfer defect occurs in that region, and as a result, a vertical stripe-like image defect occurs.

<Torque measurement 1>
The primary transfer brush 5 of the present embodiment, comparative example 1 or comparative example 2 conveys the intermediate transfer belt 6 by using the image forming apparatuses arranged in the primary transfer portions B1a to B1d of the stations Sa to Sd, respectively. The torque on the shaft of the driving roller 61 was measured.

  Table 2 shows both the measurement result when the primary transfer bias is not applied and the measured torque value when the primary transfer bias is applied under the image forming conditions. The unit of torque is Kg · cm.

  As shown in Table 2, the torque measurement values in the state where the primary transfer bias was not applied and in the state where the primary transfer bias was applied were the highest in Comparative Example 2 and were 2.2 kg · cm and 3.3 kg · cm, respectively. Further, the measured torque values in the present example and the comparative example 1 were almost equal. That is, the measured torque values when the primary transfer bias is not applied and when the primary transfer bias is applied are 1.3 Kg · cm and 2.0 Kg · cm in this example, respectively, and 1.5 Kg · cm in Comparative Example 1 respectively. It was 2.2 Kg · cm. In this example and Comparative Example 1, the measured torque values in the state where the primary transfer bias was not applied and in the state where the primary transfer bias was applied were both lower than in Comparative Example 2.

  In Comparative Example 2, all the gaps 107 in the effective region D3 are the flocked portions 108, whereas in this example and Comparative Example 1, there are many non-flocked portions 109. Therefore, in this embodiment and Comparative Example 1, the total area (number) of contact between the back surface of the intermediate transfer belt 6 and the brush fibers 106 is smaller than that in Comparative Example 2. As a result, in this example and Comparative Example 1, it is considered that the sliding frictional force between the back surface of the intermediate transfer belt 6 and the brush fiber 106 is lower than that in Comparative Example 2.

  Further, the reason why the measured torque value when the primary transfer bias is applied is higher than the measured torque value when the primary transfer bias is not applied is considered to be as follows. That is, when a primary transfer bias is applied, an electrostatic attraction force acts between the intermediate transfer belt 6 and the brush fibers 106. As a result, it is considered that the sliding frictional force acting between the back surface of the intermediate transfer belt 6 and the brush fiber 106 is increased, and the torque measurement value is increased.

  As described above, in Comparative Example 1, the driving torque for conveying the intermediate transfer belt 6 can be suppressed to a low level, but a vertical stripe-like image defect occurs. In Comparative Example 2, the occurrence of vertical stripe-like image defects can be suppressed, but the driving torque for conveying the intermediate transfer belt 6 becomes large. On the other hand, according to the present embodiment, it is possible to suppress the occurrence of vertical streak-like image defects and to reduce the driving torque for conveying the intermediate transfer belt 6.

  Thus, in this embodiment, the image forming apparatus 100 transfers the toner image from the image carrier 1 toward the belt 6, the image carrier 1 that carries the toner image, the movable endless belt 6, and the like. And transfer means 5 to be transferred. The transfer means 5 is formed by weaving a pile 105 in a gap portion 107 between yarns of a base fabric 101 formed by yarns extending along a moving direction of the belt 6 and a direction substantially orthogonal to the moving direction. It is like a brush. The gap portion 107 in which the pile 105 is flocked is referred to as a flocked portion 108, and the gap portion 107 in which the pile 105 is not flocked is referred to as a non-flocked portion 109. An area on the belt to which the toner image from the image carrier in a direction substantially orthogonal to the moving direction of the belt 6 is transferred is defined as an image forming area. Further, in the moving direction of the belt 6, the first contact portion N1 where the image carrier 1 and the belt 6 are in contact with the second contact portion N2 where the belt 6 and the transfer means 5 are in contact with each other is on the belt. Let the region be an overlapping region s. Further, an area on the base fabric including the gap portion 107 in which the pile 105 contacting the belt 6 in the image forming area and the overlapping area is planted is defined as an effective area D3. At this time, at least one flocked portion 108 and at least one non-flocked portion 109 are present in all of the gap portion row α including the plurality of gap portions 107 arranged along the moving direction of the belt 1 in the effective region D3. Is provided. In particular, in the present embodiment, in the effective region D3, the gap portion row β including the plurality of gap portions 107 arranged along the direction substantially orthogonal to the moving direction of the belt 6 is all the gap portion row β of the flocked portion 108, All are composed of the gap row β of the non-flocked portion 109. More specifically, in the present embodiment, the base fabric 101 is arranged such that the warp yarn 103 is arranged along a direction substantially orthogonal to the moving direction of the belt 6, the weft yarn 104 is arranged along the moving direction of the belt 6, and the pile 105 It is woven into the weft thread 104. In this embodiment, the pile is woven into the weft thread 104 with a U weave. Further, an area where only the transfer means 5 of the image carrier 1 and the transfer means 5 contacts the belt 6 is provided on the downstream side of the overlapping area s in the moving direction of the belt 6.

  As described above, according to the present embodiment, in the configuration having the belt 6 and the brush-like transfer means 5 in contact with the belt 6, vertical streak-like image defects are suppressed and torque for conveying the belt 6 is reduced. It becomes possible.

Example 2
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of the present embodiment are the same as those of the image forming apparatus 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.

  7A, 7B, and 7C are a perspective view, a cross-sectional view, and a plan view as seen from the tip of the pile, respectively, showing a part of the primary transfer brush 5 in the present embodiment.

  In the present embodiment, the pile fabric constituting the primary transfer brush 5 is woven in a U-weave as in the first embodiment.

  In the present embodiment, all the gap portion rows α in the effective region D3 (shaded portion in FIG. 7C) (α5 to α8 in FIGS. 7A and 7C, α′1 to α′4). , At least one hair transplantation part 108 and at least one non-flocking part 109 are provided. In addition, in this embodiment, the positions of the flocked portions 108 in the gap portion rows β in the effective region D3 (β2 to β4 in FIGS. 7A and 7C) are located between the adjacent gap portion rows β. This is a position where the position of the flocked portion 108 is shifted in the longitudinal direction of the primary transfer brush 5. In particular, in the present embodiment, adjacent gap portion rows β in the effective region D3 each have a flocked portion 108 in a different gap row α.

  For example, in this embodiment, as shown in FIGS. 7A and 7C, in the gap portion rows α5 and α6, the hair portion 108 is provided in the gap portion rows β2 and β4, and the non-flocked portion is provided in the gap portion row β3. Part 109. On the other hand, in the gap portion rows α7 and α8, the flocked portion row β3 has the hair transplanted portion 108, and the gap portion rows β2 and β4 have the non-flocked portion 109. The same applies to the gap portion rows α′1 to α′4 as well as the gap portion rows α5 to α8. Similarly, between the gap portion row α8 and the gap portion row α′1 which are omitted in FIGS. 7A and 7C, the positions of the gap portion rows α which are similarly different between the adjacent gap portion amounts β. The flocked portion 108 appears regularly.

  Thus, in this embodiment, at least one flocked portion 108 is provided in all the gap portion rows α in the effective region D3. Therefore, as in the first embodiment, a region where the back surface of the intermediate transfer belt 6 and the brush fiber 106 do not contact with each other in the longitudinal direction of the primary transfer brush 5 does not substantially occur in the physical nip s.

<Image evaluation 2>
Evaluation similar to the above-described image evaluation 1 was also performed on this example. As a result, in this example, no vertical stripe-like image defect occurred during the entire period of the durability test.

  In this embodiment, as in the first embodiment, a region where the back surface of the intermediate transfer belt 6 and the brush fiber 106 do not contact with each other in the longitudinal direction of the primary transfer brush 5 does not substantially occur in the physical nip s. For this reason, in this embodiment, it is considered that transfer unevenness does not occur in the longitudinal direction of the primary transfer brush 5.

<Torque measurement 2>
The torque measurement similar to the torque measurement 1 described above was also performed for this example. As a result, as shown in Table 3 together with the results of torque measurement 1, the torque measurement values of the present example were almost equivalent to those of Example 1 and Comparative Example 1. That is, the measured torque values when the primary transfer bias is not applied and when the primary transfer bias is applied are 1.4 kg · cm and 2.1 kg · cm, respectively, in this embodiment.

  In this example, as in Example 1 and Comparative Example 1, it has a large number of non-flocked portions 109. Therefore, in this embodiment, the total area (number) of contact between the back surface of the intermediate transfer belt 6 and the brush fibers 106 is smaller than that in Comparative Example 2. As a result, in this embodiment, it is considered that the sliding frictional force between the back surface of the intermediate transfer belt 6 and the brush fiber 106 is lower than that in the comparative example 2.

<Image evaluation 3>
Next, using the primary transfer brush 5 of Example 1 and the primary transfer brush 5 of this example, the position of the primary transfer brush 5 is shifted from the nominal position by a certain amount along the moving direction R3 of the intermediate transfer belt 6. The image evaluation result in the case is shown. As the primary transfer bias value, an optimum voltage value in the case where the primary transfer brush 5 is in the nominal position was used.

  As an evaluation image, an image obtained by mixing halftone images of each color of yellow, magenta, cyan, and black was used as in image evaluation 1. The number of images formed in the durability test was 50,000, and the level of image defects in the evaluation image was visually evaluated at appropriate timing throughout the entire period. When no image defect occurred, it was evaluated as “◯”, when a minor image defect sometimes occurred but at a level where there was no practical problem, Δ, and when an image defect occurred, evaluated as “X”. Table 4 shows the image evaluation results. In Table 4, the positional deviation amount of −0.5 mm indicates a case where the primary transfer brush 5 is displaced by 0.5 mm upstream from the nominal position in the moving direction of the intermediate transfer belt 6, and is +0.5 mm. Indicates a case where it is shifted by 0.5 mm to the downstream side.

  As shown in Table 4, in Example 1, a slight image defect due to abnormal discharge sometimes occurred, whereas in this example, no image defect occurred.

  Here, FIG. 8 is a plan view seen from the front end direction of the pile of the primary transfer brush 5 for explaining the influence of the displacement of the primary transfer brush 5 when the primary transfer brush 5 of Example 1 is used. is there. 8B shows the case where the primary transfer brush 5 is in the designated position in the moving direction of the intermediate transfer belt 6, FIG. 8A shows the case where the primary transfer brush 5 is shifted to the upstream side, and FIG. The case of deviation is shown. FIG. 9 is a plan view seen from the front end direction of the pile of the primary transfer brush 5 for explaining the influence of the displacement of the primary transfer brush 5 when the primary transfer brush 5 of this embodiment is used. . 9B shows the case where the primary transfer brush 5 is in the designated position in the moving direction of the intermediate transfer belt 6, FIG. 9A shows the case where the primary transfer brush 5 is shifted to the upstream side, and FIG. The case of deviation is shown.

  In Example 1, as shown in FIGS. 8A and 8C, when the position of the primary transfer brush 5 is shifted along the moving direction R3 of the intermediate transfer belt 6, the flocked portion 108 entering the effective region D3. The number of may decrease. Therefore, it is considered that the optimum transfer voltage value may be shifted.

  On the other hand, in the second embodiment, as shown in FIGS. 9A and 9C, even when the position of the primary transfer brush 5 is shifted along the moving direction R3 of the intermediate transfer belt 6, it is within the effective region D3. The number of the flocked portions 108 that enter does not change, or the amount of change in the number is smaller. Therefore, it is considered that the optimum transfer voltage value does not change.

  Note that the pile arrangement is not limited to that of the present embodiment. For example, as shown in FIG. 10, the positions of the flocked portions 108 between adjacent gap portion rows β may be shifted in the longitudinal direction of the primary transfer brush 5 by one gap portion row α.

  In this embodiment, the pile 105 is woven with a U weave, but the pile arrangement shown in FIGS. 7 and 10 can also be achieved by weaving the pile 105 with a W weave in each gap row β ( (See FIG. 5). Further, the pile arrangement shown in FIGS. 7 and 10 may be achieved by, for example, alternately weaving the piles 105 of adjacent gap portion rows β by W weave and U weave.

  As described above, in the present embodiment, the position of each flocked portion 108 in the gap portion row β in the effective region D3 is substantially the same as the movement direction of the belt 6 between the adjacent gap portion rows. The position is shifted along the orthogonal direction. The gap part row β is a group of gap parts 107 including a plurality of gap parts 107 arranged along a direction substantially orthogonal to the moving direction of the belt 6. In particular, in the present embodiment, adjacent gap portion rows β in the effective region D3 each have a flocked portion 108 in a different gap row α.

  As described above, according to the present exemplary embodiment, as in the first exemplary embodiment, it is possible to suppress the occurrence of vertical streak-like image defects and to reduce the driving torque for conveying the intermediate transfer belt 6. it can. In this embodiment, even when the position of the primary transfer brush 5 is shifted along the moving direction R3 of the intermediate transfer belt 6, it is possible to provide a more stable and high-quality image.

Other Embodiments Although the present invention has been described with reference to specific embodiments, the present invention is not limited to the above-described embodiments.

  In the above-described embodiments, the image forming apparatus is described as an intermediate transfer type image forming apparatus using an intermediate transfer belt. However, an image forming apparatus having another configuration is also conceivable as an image forming apparatus of a type in which the brush-shaped transfer unit is brought into contact with the image carrier via a belt-shaped member. For example, there is a direct transfer type image forming apparatus that sequentially directly transfers toner images on a plurality of photosensitive drums onto a transfer material conveyed on a transfer material conveyance belt. FIG. 11 is a schematic cross-sectional view of a main part of an example of a direct transfer type image forming apparatus. In FIG. 11, elements having the same or corresponding functions and configurations as those of the intermediate transfer type image forming apparatus shown in FIG. The direct transfer type image forming apparatus has a transfer conveyance belt 160 as a transfer material carrier instead of the intermediate transfer belt as an intermediate transfer body in the intermediate transfer type image forming apparatus. Then, the transfer material P is carried on the transfer material conveying belt 160 by the toner image formed on each photosensitive drum 1 of each station S by the action of the transfer brush 5 as the transfer means in each transfer portion B. The images are transferred in such a manner that they are sequentially superimposed on each other. Thereafter, the toner image is fixed on the transfer material P. As the configuration of each transfer unit of such a direct transfer type image forming apparatus, the configuration of the primary transfer unit in each of the above embodiments can be equally applied, and the same effect as in each of the above embodiments can be obtained.

1 Photosensitive drum (image carrier)
5 Primary transfer brush (brush-shaped transfer means)
6 Intermediate transfer belt (belt)
DESCRIPTION OF SYMBOLS 101 Base fabric 102 Base 103 Warp thread 104 Weft thread 105 Pile 106 Brush fiber 107 Crevice part 108 Planted part 109 Non-grafted part

Claims (9)

In an image forming apparatus comprising: an image carrier that carries a toner image; a movable endless belt; and a transfer unit that transfers a toner image from the image carrier toward the belt.
The transfer means is a brush-like shape formed by weaving piles in gaps between the yarns of a base fabric formed by yarns extending along the moving direction of the belt and a direction substantially orthogonal to the moving direction. And
The gap where the pile is flocked is a flocked portion,
The gap where the pile is not planted is a non-planted portion,
An area on the belt to which a toner image from the image carrier in a direction substantially perpendicular to the moving direction of the belt is transferred is an image forming area.
In the moving direction of the belt, a first contact portion where the image carrier and the belt are in contact with a second contact portion where the belt and the transfer means are in contact with each other. Area and
When the area on the base fabric including the gap portion in which the pile contacting the belt in the image forming area and the overlapping area is planted is an effective area,
In the effective area, at least one of the flocked portions and at least one of the non-flocked portions are provided in all the gap portion rows formed of the plurality of gap portions arranged along the moving direction of the belt. An image forming apparatus.   In the effective region, the gap portion rows composed of the plurality of gap portions arranged along the direction substantially orthogonal to the moving direction of the belt are all the gap portion rows of the flocked portion and all the gaps of the non-flocked portion. The image forming apparatus according to claim 1, further comprising:   In the effective region, the position of the flocked portion of each of the gap portion rows composed of a plurality of the gap portions arranged along a direction substantially orthogonal to the moving direction of the belt is between the adjacent gap portion rows. The image forming apparatus according to claim 1, wherein the position of the flocked portion is a position shifted along a direction substantially orthogonal to the moving direction of the belt.   The image forming apparatus according to claim 3, wherein the adjacent gap portion rows in the effective region have the flocked portions in different gap row columns.   The warp yarn is arranged along a direction substantially perpendicular to the moving direction of the belt, the weft yarn is arranged along the moving direction of the belt, and the pile is woven into the weft yarn. Item 5. The image forming apparatus according to any one of Items 1 to 4.   The image forming apparatus according to claim 5, wherein the pile is woven into the weft with a U weave.   The region where only the transfer unit of the image carrier and the transfer unit contacts the belt is provided on the downstream side of the overlapping region in the moving direction of the belt. The image forming apparatus according to claim 6.   The image forming apparatus according to claim 1, wherein the belt is an intermediate transfer belt to which a toner image is transferred from the image carrier.   The image forming apparatus according to claim 1, wherein the belt is a transfer material conveyance belt that carries and conveys a transfer material onto which a toner image is transferred from the image carrier. .

Images