JP2020003589A - Transfer and conveyance unit and image forming apparatus - Google Patents

Abstract

To provide a transfer and conveyance unit that is suitable for performing smooth conveyance of a medium without the occurrence of clogging with the medium.SOLUTION: A transfer and conveyance unit has a belt that transfers toner images carried on image carriers to a medium and conveys the medium, and static eliminating means that eliminates static electricity on the belt.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus that forms an image using an electrophotographic method, and a transfer / conveyance unit mounted on the image forming apparatus.

  Heretofore, there has been proposed an image forming apparatus of a so-called direct transfer type in which a toner image formed on a photoreceptor is transferred onto a medium while conveying a medium to be printed (for example, see Patent Document 1). ). Patent Literature 1 discloses an image forming apparatus including a belt transport unit detachably provided to an apparatus main body.

JP 2014-44297 A

  In such an image forming apparatus, it is desired that a smooth image forming process is performed without causing a medium jam in a medium conveying process.

  Therefore, it is desirable to provide a transfer / transport unit suitable for carrying out a medium smoothly without causing a medium clogging, and an image forming apparatus including the same.

  A transfer and conveyance unit according to an embodiment of the present invention includes a belt that transfers a toner image carried on an image carrier to a medium and conveys the medium, and a charge removing member that removes charges on the belt.

  An image forming apparatus as one embodiment of the present invention includes an image forming unit including an image carrier that carries a toner image, a belt that transfers a toner image to a medium and conveys the medium, and removes a charge of the belt. A transfer / conveying unit having a charge removing member.

  In the transfer conveyance unit and the image forming apparatus according to an embodiment of the present invention, since a charge removing member that removes a charge of a belt that conveys a medium is provided, a perforated medium provided with holes such as thin paper and perforations is provided. Even so, the attraction force due to the electrostatic phenomenon between the medium and the belt is reduced.

The transfer / transport unit and the image forming apparatus as one embodiment of the present invention are suitable for performing smooth media transport without causing media jam.
This is an example of the effect of the present invention, and the effect of the present invention is not limited to this, and may be any of the effects described below.

FIG. 1 is a schematic diagram illustrating an overall configuration example of an image forming apparatus according to an embodiment of the present disclosure. FIG. 2 is a front view illustrating an appearance of a transfer conveyance unit in the image forming apparatus illustrated in FIG. 1. FIG. 2 is a perspective view illustrating an appearance of a transfer conveyance unit in the image forming apparatus illustrated in FIG. 1. FIG. 3 is a schematic diagram illustrating main components of the transfer / conveyance unit illustrated in FIG. 2. FIG. 3 is a schematic plan view illustrating a state in which the transfer conveyance unit illustrated in FIG. 2 is viewed from above. FIG. 3 is a first explanatory diagram illustrating an operation of the transfer / conveyance unit illustrated in FIG. 2. FIG. 3 is a second explanatory diagram illustrating the operation of the transfer / conveyance unit illustrated in FIG. 2. FIG. 11 is a schematic diagram illustrating main components of a transfer and transport unit according to a first modification of the present invention. FIG. 13 is a schematic diagram illustrating main components of a transfer / transport unit as a second modified example of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description is a specific example of the present invention, and the present invention is not limited to the following embodiments. In addition, the present invention is not limited to the arrangement, dimensions, dimensional ratios, and the like of the components shown in the drawings.

<1. Embodiment>
[Schematic Configuration of Image Forming Apparatus 1]
FIG. 1 is a schematic diagram illustrating an example of the overall configuration of an image forming apparatus 1 equipped with a transfer and transport unit 600 according to an embodiment of the present invention. The image forming apparatus 1 is an electrophotographic printer that forms an image (for example, a color image) on a medium (for example, a print medium or a transfer material) 101 such as paper. In this specification, a direction perpendicular to the transport direction of the medium 101 (a direction perpendicular to the plane of FIG. 1) is referred to as a width direction. Further, in this specification, a position near the medium tray 100 (described later) or a direction toward the medium tray 100 when viewed from an arbitrary position on the transport path on which the medium 101 is transported is referred to as upstream. Further, when viewed from an arbitrary position on the transport path, a position near the stacking unit 805 (described later) where the medium 101 is discharged and stacked, or a direction toward the stacking unit 805 is referred to as downstream.

  As shown in FIG. 1, the image forming apparatus 1 includes, for example, a medium tray 100, a medium feeding unit 200, a medium conveying unit 300, and an image forming unit inside a main body frame 2 which is a housing of the apparatus main body. 500, a transfer / conveyance unit 600, a fixing unit 700, and a reversing unit 800.

(Medium tray 100)
The medium tray 100 is a storage unit that stores the medium 101. The medium tray 100 has a plurality of media 101 loaded therein. A medium feeding section 200 is provided downstream of the medium tray 100.

(Medium feeding unit 200)
The medium feeding section 200 is a mechanism for feeding the medium 101 one by one to the downstream. The medium feeding unit 200 includes a pickup roller 201, a feed roller 203, and a separation piece 204. The pickup roller 201 is a rotating member that comes into pressure contact with the surface of the medium 101 and feeds the medium 101 downstream. The feed roller 203 and the separating piece 204 separate the sheet 101 one by one by sandwiching the medium 101 fed by the pickup roller 201 between them.

(Medium transport unit 300)
The medium transport unit 300 is a mechanism that transports the medium 101 fed by the medium feeding unit 200 to the image forming unit 400. In the present embodiment, the medium transport unit 300 is configured to bend the medium 101 and transport the medium 101 toward the image forming unit 400. The medium transport unit 300 includes medium transport rollers 301a and 301b disposed to face each other via a transport path. One of the medium transport rollers 301a and 301b is a driving roller, and the other is a driven roller. The medium conveying rollers 301a and 301b convey the medium 101 toward the image forming unit 400 by rotating while pinching the medium 101.

(Image forming unit 400)
The image forming unit 400 is a mechanism that forms a toner image (developer image) and transfers the toner image to the medium 101. The image forming section 400 includes an image forming unit 500 and a transfer and transport unit 600.

  The image forming unit 500 uses a toner as a developer based on print data transmitted from a higher-level device such as a personal computer to convert a toner image into a photosensitive drum 511 provided therein (see FIG. 2 described later). ) Mechanism on the surface. The transfer and transport unit 600 is a mechanism that transports the medium 101 while transferring the toner image formed on the surface of the photosensitive drum 511 to the surface of the medium 101 by Coulomb force. The detailed configuration of the image forming unit 500 will be described later. The transfer / conveyance unit 600 conveys the medium 101 onto which the toner image has been transferred toward the fixing unit 700.

  In the present embodiment, the image forming section 400 is detachable (can be freely attached and detached) with respect to the main body frame 2 (hereinafter, also referred to as “apparatus main body”). Further, in the present embodiment, the image forming apparatus 1 corresponds to the image forming units 500K, 500Y, 500M, and 500M corresponding to each color of black (K), yellow (Y), magenta (M), and cyan (C). 500C is provided. The image forming units 500K, 500Y, 500M, and 500C are provided so as to be arranged in series from upstream to downstream. The four image forming units 500K, 500Y, 500M, and 500C have substantially the same configuration except that the color of the developer (toner) accommodated therein is different. Therefore, in the present specification, when it is not necessary to distinguish the image forming units 500K, 500Y, 500M, and 500C, they are collectively referred to as an image forming unit 500.

  In the present embodiment, the transfer / transport unit 600 is detachable from the main body frame 2 (apparatus main body).

(Fixing unit 700)
The fixing unit 700 is a mechanism that applies heat and pressure to the toner image transferred onto the medium 101 conveyed from the transfer conveyance unit 600 to fix the toner image on the medium 101. When the toner image is fixed on the medium 101 by the fixing unit 700, the image forming apparatus 1 conveys the medium 101 toward the stacking unit 805 by the discharge rollers 801a and 801b, and discharges the medium 101 to the stacking unit 805. The loading unit 805 is provided outside the main body frame 2 and is a portion on which the medium 101 on which the toner image is fixed is loaded. The medium 101 is discharged to the stacking unit 805 between the discharge rollers 801a and 801b.

(Reversing unit 800)
This mechanism is a mechanism for reversing the medium 101 when performing double-sided printing, and includes a transport roller pair 802, a medium retreat path 803, a medium transport path 804, and a plurality of transport roller pairs 806. The reversing unit 800 can temporarily retract the medium 101 discharged from the fixing unit 700 to the medium evacuation path 803 by rotating the pair of conveying rollers 802. The reversing unit 800 reversely rotates the conveying roller pair 802 to introduce the medium 101 retracted to the medium evacuation path 803 into the medium conveying path 804 while reversing the medium 101, and further rotates the plurality of conveying roller pairs 806. The medium 101 can pass through the medium conveyance path 804 and return to the medium conveyance unit 300.

[Configuration of Image Forming Unit 500 and Transfer Conveying Unit 600]
Hereinafter, the detailed configurations of the image forming unit 500 and the transfer / conveyance unit 600 will be described with reference to FIGS. FIG. 2 is an enlarged cross-sectional view of the image forming unit 400, which is orthogonal to the width direction. FIG. 3 is a perspective view illustrating the overall configuration of the transfer / conveyance unit 600. FIG. 4 is a conceptual diagram showing only the main components of the transfer / conveyance unit 600 in a simplified manner. FIG. 5 is a schematic plan view showing the transfer and transport unit 600 as viewed from above.

  The image forming unit 500 has a housing including a guide surface 510 that is a flat inclined surface. The guide surface 510 guides the medium 101 traveling between the transfer unit 600 and the transfer unit 600. Both the image forming unit 500 and the transfer / conveyance unit 600 are detachable from the main body frame 2 (apparatus main body).

(Image forming unit 500)
As shown in FIG. 2, the image forming unit 500 includes a photosensitive drum 511, a charging roller 512, a developing roller 513, a supply roller 514, a developing blade 515, a toner storage section 516, and a cleaning member 517. The image forming apparatus 1 has an exposure head 520 disposed outside the image forming unit 500 and at a position facing the surface of the photosensitive drum 511. The exposure head 520 is an LED head having a plurality of light sources, for example, a plurality of LED (Light Emitting Diode) elements, and a plurality of lenses for condensing each light from the plurality of LED elements on the surface of the photosensitive drum 511. . The exposure head 520 selectively exposes the surface of the photosensitive drum 511 to form an electrostatic latent image on the surface of the photosensitive drum 511. In the image forming apparatus 1, a laser light source or the like can be used as the exposure head 520 instead of the LED head.

  The photosensitive drum 511 is a columnar member that carries an electrostatic latent image on its surface (surface layer portion), and is configured using a photosensitive member (for example, an organic photosensitive member).

  The charging roller 512 is a member (charging member) that charges the surface (surface layer) of the photosensitive drum 511, and is arranged so as to be in contact with the surface (peripheral surface) of the photosensitive drum 511. In the image forming apparatus 1, after the charging roller 512 uniformly charges the surface of the photosensitive drum 511, the exposure head 520 selectively exposes the surface of the photosensitive drum 511 based on print data. An electrostatic latent image is formed on the surface.

  The developing roller 513 is a developer carrier that carries a toner for developing an electrostatic latent image on its surface, and is arranged so as to be in contact with the surface (peripheral surface) of the photosensitive drum 511. The developing roller 513 supplies the toner to the photosensitive drum 511 having a surface on which an electrostatic latent image is formed, and develops (visualizes) the electrostatic latent image as a toner image.

  The supply roller 514 is a member (supply member) for supplying toner to the developing roller 513, and is arranged so as to be in contact with the surface (peripheral surface) of the developing roller 513.

  The developing blade 515 is a toner regulating member that forms a toner layer made of toner adhered to the surface of the rotating developing roller 513 and regulates (controls and adjusts) the thickness of the toner layer. The developing blade 515 is a plate-like elastic member (leaf spring) made of, for example, stainless steel or the like, and the tip of the plate-like elastic member is arranged near the surface of the developing roller 513.

  The toner container 516 is a space in which the toner to be supplied to the supply roller 514 is stored.

  The cleaning member 517 is a member that contacts the surface of the photosensitive drum 511 and scrapes residual toner remaining on the surface of the photosensitive drum 511 from the surface of the photosensitive drum 511. Here, the “residual toner” refers to toner remaining on the surface of the photosensitive drum 511 after the transfer process of the toner from the photosensitive drum 511 to the medium 101 performed by the transfer / conveyance unit 600. The cleaning member 517 is disposed so as to abut against the surface of the photosensitive drum 511 by a counter (projects in a direction opposite to the rotation direction of the photosensitive drum 511). The cleaning member 517 is made of, for example, an elastic body such as polyurethane rubber.

(Transfer transport unit 600)

  As shown in FIGS. 2 to 4, the transfer conveyance unit 600 includes a conveyance belt 601, a driving roller 602, a driven roller 603, transfer rollers 604K, 604Y, 604M, 604C, a spring 604a, and a waste toner box. 605, a charging member 607, a belt blade 608, a counter roller 609, a medium guide 610, and a separator 611.

  The transport belt 601 is an endless belt that transports the medium 101, and is a specific example corresponding to the “belt” of the invention. The drive roller 602 is, for example, a rotating body that rotates in the rotation direction R <b> 602 (FIG. 4) and drives the transport belt 601. The driven roller 603 is a rotator that is disposed alongside the drive roller 602 along the transport direction of the medium 101, and rotates in the rotation direction R603 (FIG. 4) following the transport belt 601 rotated by the drive roller 602. The transfer rollers 604K, 604Y, 604M, and 604C are arranged to face the photosensitive drums 511K, 511Y, 511M, and 511C of the four image forming units 500K, 500Y, 500M, and 500C, respectively, with the conveyance belt 601 interposed therebetween. The driving roller 602, the driven roller 603, and the transfer rollers 604K, 604Y, 604M, and 604C are substantially cylindrical rotating members extending in the width direction.

  In the present embodiment, four image forming units 500K, 500Y, 500M, and 500C are arranged on outer surface 601B of transport belt 601. The transport belt 601 transports the medium 101 so that the medium 101 passes between the four photosensitive drums 511K, 511Y, 511M, 511C and the four transfer rollers 604K, 604Y, 604M, 604C. The transport belt 601 is made of, for example, a resin such as a polyimide resin and has elasticity. The transport belt 601 is stretched (stretched) by a driving roller 602, a driven roller 603, transfer rollers 604K, 604Y, 604M, 604C and a charging member 607, and circulates and rotates in the direction of arrow F in FIGS. It has become. The spring 604a is a member that presses the transfer rollers 604K, 604Y, 604M, and 604C against the photosensitive drums 511K, 511Y, 511M, and 511C.

  The transfer rollers 604K, 604Y, 604M, and 604C electrostatically transfer the toner images formed in the image forming units 500K, 500Y, 500M, and 500C onto the medium 101 while conveying the medium 101 in the conveyance direction. It is a member for. The transfer rollers 604K, 604Y, 604M, and 604C are made of, for example, a foamed semiconductive elastic rubber material.

The charging member 607 is a member for removing electric charges charged on the transport belt 601 and is fixed, for example, so as to be in contact with the inner surface 601A. The charging member 607 is made of, for example, a dielectric such as polytetrafluoroethylene (PTFE), which is easily charged by friction. The charging member 607 is a push-up member that urges the transport belt 601 toward the outer surface 601B so as to push it up from the inner surface 601A. The charging member 607 is located on a straight line L (shown by a broken line in FIG. 4) connecting the driving roller 602 and the driven roller 603. Alternatively, the charging member 607 may be located outside the straight line L. Since the charging member 607 urges the transport belt 601 so as to push up the transport belt 601 from the inner surface 601A side to the outer surface 601B side, the leading end of the medium 101 discharged from the transfer transport unit 600 to the fixing unit 700 is moved. 601 is easily separated from the outer surface 601B.
Note that the charging member 607 is a specific example corresponding to the “static elimination member” and the “push-up member” of the present invention.

  The belt blade 608 is a member for scraping and cleaning (cleaning) the waste toner remaining on the surface of the transport belt 601 after the transfer process, and the waste toner box 605 is a member for scraping the waste toner scraped by the belt blade 608. Is collected and stored. Note that the belt blade 608 holds the transport belt 601 between itself and the counter roller 609.

  The medium guide 610 is a member that guides the running of the medium 101 by sandwiching the medium 101 between the medium guide 610 and a transport unit guide 310 described below. The medium guide 610 is arranged between the medium transport unit 300 and the image forming unit 500K located at the most upstream position in the image forming unit 400.

  The separator 611 is a flat or film-like separating member that separates the medium 101 conveyed by the conveyance belt 601 from the conveyance belt 601. The separator 611 is located downstream of the transport belt 601 and has an edge 611E facing the drive roller 602 with the transport belt 601 interposed therebetween. The edge 611E is arranged slightly apart from the transport belt 601.

  5 corresponds to the transport direction of the medium 101 to be transported, and the horizontal direction of FIG. 5 corresponds to the width direction of the transported medium 101.

  As shown in FIG. 5, the drive roller 602 extends in a width direction orthogonal to the transport direction of the medium 101. The edge 611E of the separator 611 faces the drive roller 602 with the conveyance belt 601 interposed therebetween. The edge 611E has a middle part 611EC extending in the width direction, and a pair of ends 611EL, 611ER that sandwich the middle part 611EC in the width direction and are inclined so as to be away from the drive roller 602 as the distance from the middle part 611EC increases. Contains.

  In the present embodiment, in the image forming apparatus 1, the medium transport unit 300 causes the medium 101 to bend and transport the medium 101 toward the image forming unit 500 </ b> K located at the most upstream position of the image forming unit 400. ing. Therefore, the medium 101 is easily lifted before the image forming unit 500K. The medium guide 610 presses the medium 101 from above to prevent the medium 101 from rising due to curved conveyance.

  The medium guide 610 is provided so as to be movable with respect to the transfer / conveyance unit 600. When the transfer / conveyance unit 600 is mounted on the main body frame 2, the medium guide 610 comes into contact with the guide positioning portion 26a (see FIG. 2) and its position. Is regulated.

  In the present embodiment, as shown in FIG. 3, the medium guide 610 is supported by a shaft 606 provided in the waste toner box 605 of the detachable unit 60. Therefore, the medium guide 610 is rotatable about the shaft 606. When the transfer / conveyance unit 600 is mounted on the main body frame 2, the abutment portion 610 a (see FIGS. 2 and 3) abuts the guide positioning portion 26 a (see FIG. 2). Is determined.

  As shown in FIG. 3, the medium guide 610 has an opening 610d at a portion where the medium 101 passes. Further, the medium guide 610 has an abutment portion 610a, a guide portion 610b, and a handle portion 610c.

  As shown in FIG. 2, the abutting portion 610a is a portion where the distal end portion of the guide positioning portion 26a of the sheet metal 26 provided on the main body frame 2 arranged upstream abuts. The abutment portion 610a is formed so as to project toward the sheet metal 26 (see FIG. 2).

  The guide section 610b contacts the medium 101 transported by the medium transport section 300 to guide the traveling of the medium 101. The guide part 610b is formed so as to protrude downward from the handle part 610c (that is, inward of the opening 610d). The lower surface of the lower end of the guide portion 610b is formed as a guide surface 610ba. The guide surface 610ba is a surface that comes into contact with the upper surface of the medium 101. The guide surface 610ba is formed in a round shape.

  The handle 610c is a grip that is gripped by the user. The user can lift the transfer / conveyance unit 600 by gripping the handle 610c. The handle 610c is provided above the opening 610d.

  In the image forming apparatus 1, as shown in FIG. 2, a transport unit guide 310 is provided in a medium transport unit 300. The transport unit guide 310 is a member that guides the traveling of the medium 101 by sandwiching the medium 101 between the medium guide 610 and the medium guide 610. The transport section guide 310 is provided at a position where the upper end thereof faces a guide surface 610ba formed on the medium guide 610.

  Further, as shown in FIG. 2, the image forming apparatus 1 includes a sheet metal 26 provided on the main body frame 2. The sheet metal 26 is a contact member that contacts the medium guide 610. The sheet metal 26 has a guide positioning portion 26a protruding in the direction of the medium guide 610 in a part thereof. The leading end of the guide positioning portion 26a abuts against the abutting portion 610a of the medium guide 610. Thereby, the sheet metal 26 can position the abutting portion 610a of the medium guide 610 at a predetermined position.

  In the image forming apparatus 1, the conveyance unit guide 310 (see FIG. 2) has a predetermined gap between the shaft 606 (see FIG. 3) and the guide surface 610 ba (see FIG. 3) of the medium guide 610. And are disposed so as to face each other. Further, the guide surface 610ba (see FIG. 3) is disposed so as to be located between the guide positioning portion 26a (see FIG. 2) and the shaft portion 606 (see FIG. 3). Furthermore, the distance from the guide surface 610ba (see FIG. 3) to the guide positioning portion 26a (see FIG. 2) is shorter than the distance from the guide surface 610ba (see FIG. 3) to the shaft 606 (see FIG. 3). Placed in

  By arranging the respective components in this manner, the image forming apparatus 1 has a guide surface 610ba (see FIG. 3) associated with a mounting error and a manufacturing error of the guide positioning portion 26a (see FIG. 2) in the transport direction of the medium 101. Of the positional relationship between the transport unit guide 310 and the transport unit guide 310 (see FIG. 2) can be reduced.

[Action / Effect]
(A. Basic operation)
In the image forming apparatus 1, a toner image is transferred to the medium 101 as described below.

  First, the overall operation of the image forming apparatus 1 will be described with reference to FIGS. When the image forming apparatus 1 receives the print data from the host device, the image forming unit 500 rotates the photosensitive drum 511 to perform an image forming process.

  At this time, after the charging roller 512 uniformly charges the surface of the photosensitive drum 511, the exposure head 520 selectively exposes the surface of the photosensitive drum 511 based on print data. As a result, the image forming apparatus 1 forms an electrostatic latent image on the surface of each photosensitive drum 511.

  In the image forming apparatus 1, the toner is supplied from the toner container 516 to the supply roller 514 in advance. When the developing roller 513 rotates with the rotation of the photosensitive drum 511, the supply roller 514 supplies toner to the developing roller 513 and causes the toner to adhere to the surface of the developing roller 513. The toner adhering to the surface of the developing roller 513 comes into contact with the developing blade 515 with the rotation of the developing roller 513, and its layer thickness is regulated.

  Thereafter, in the image forming apparatus 1, the developing roller 513 supplies the toner to the photosensitive drum 511. At this time, the toner is developed on the electrostatic latent image formed on the surface of the photosensitive drum 511. As a result, a toner image is formed on the surface of the photosensitive drum 511.

  On the other hand, in the image forming apparatus 1, the medium feeding unit 200 feeds the medium 101 from the medium tray 100 toward the medium conveying unit 300 by driving the motor provided on the main body frame 2, and the medium conveying roller of the medium conveying unit 300 301 a and 301 b transport the medium 101 toward the image forming unit 400.

  At this time, the image forming unit 400 guides the medium 101 between the guide unit 610b of the medium guide 610 and the conveyance unit guide 310 provided in the medium conveyance unit 300 while being guided by the guide unit 610b and the conveyance unit guide 310. Conveyed toward.

  After that, the medium 101 is conveyed toward the fixing unit 700 by the circulation rotation of the conveyance belt 601. At this time, the medium 101 passes between the guide surface 510 of the image forming unit 500 of the image forming unit 400 and the transport belt 601, and passes between the photosensitive drum 511 and the transfer roller 604.

  In the image forming apparatus 1, when the toner image is formed on the surface of the photosensitive drum 511, the transfer / conveyance unit 600 performs a transfer process. At that time, in the transfer / conveyance unit 600, the transfer roller 604 draws the toner image formed on the surface of the photosensitive drum 511 while the conveyance belt 601 conveys the medium 101. As a result, the toner image is transferred from the photosensitive drum 511 to the medium.

  When the toner image is transferred from the photosensitive drum 511 to the medium 101, the image forming apparatus 1 conveys the medium 101 to the fixing unit 700 (see FIG. 1). The fixing unit 700 performs a fixing process when the medium 101 is transported. At that time, the fixing unit 700 applies heat and pressure to the toner image transferred to the surface of the medium 101, melts the toner image, and fixes the toner image to the medium 101.

  When the toner image is fixed on the medium 101, the image forming apparatus 1 conveys the medium 101 to the stacking unit 805 and discharges the medium 101 onto the stacking unit 805.

  When printing is also performed on the back surface, the medium 101 is reversed in the reversing unit 800 and then the medium 101 is returned to the medium transport unit 300, so that the transfer and fixing of the toner image to the back surface of the medium 101 are sequentially performed. To do. Specifically, the reversing unit 800 temporarily retracts the medium 101 discharged from the fixing unit 700 to the medium evacuation path 803 by rotation of the pair of conveying rollers 802. Next, the reversing unit 800 rotates the conveying roller pair 802 in a direction opposite to the direction in which the medium 101 is retracted to the medium evacuation path 803, thereby reversing the medium 101 retracted to the medium evacuation path 803. Introduced to road 804. The reversing unit 800 further sends the medium 101 to the medium conveying unit 300 by passing the medium 101 through the medium conveying path 804 by rotating a plurality of conveying roller pairs 806. After that, the medium transport unit 300 transports the inverted medium 101 to the image forming unit 400. In the image forming unit 400, the image forming unit 500 forms a toner image on the surface of the photosensitive drum 511 (see FIG. 2), and the transfer / conveyance unit 600 places the toner image formed on the surface of the photosensitive drum 511 on the back surface of the medium 101. Transcribe. The image forming unit 400 conveys the medium 101 on which the toner image has been transferred to the fixing unit 700 again. As a result, the fixing unit 700 heats and pressurizes the toner image transferred to the back surface of the medium 101, melts the toner image transferred to the back surface of the medium 101, and fixes the toner image to the medium 101. When the toner image is fixed on the medium 101, the image forming apparatus 1 conveys the medium 101 toward the stacking unit 805 by the discharge rollers 801a and 801b, and discharges the medium 101 onto the stacking unit 805.

  The overall operation of the image forming apparatus 1 is as described above.

(B. Function of Charging Member 607)
In the image forming apparatus 1, the toner forming the toner image has, for example, a negative charge, and the toner is attracted to the transfer roller 604 and the outer surface 601 </ b> B of the transport belt 601 having the positive charge. Therefore, the medium 101 is also charged, and as a result, the transport belt 601 and the medium 101 may be attracted to each other by an electrostatic phenomenon. For example, as illustrated in FIG. 6A, the toner T forming the toner image IMG usually has a negative charge. Therefore, a voltage is applied to the transfer roller 604 so that the surface of the transfer roller 604 is positively charged. Apply. As a result, negative charges gather near the inner surface 601A of the transport belt 601 that is in contact with the surface of the transfer roller 604, while positive charges gather near the outer surface 601B of the transport belt 601. Further, of the medium 101 conveyed in contact with the outer surface 601B of the conveyor belt 601, negative charges are collected near the back surface 101A, while positive charges are collected near the front surface 101B of the medium 101. As a result, the toner T is adsorbed on the surface 101B of the medium 101. Here, when the medium 101 is thick paper or plain paper and has some rigidity, when the medium 101 is discharged from the transfer / conveyance unit 600 to the fixing unit 700, the medium 101 is compared with the conveyance belt 601. Easily separated. However, when the medium 101 is thin paper, a perforated medium partially provided with holes, or a perforated medium partially formed with perforations, that is, when the rigidity of the medium is relatively weak In such a case, there is a possibility that the medium 101 is hard to be separated from the transport belt 601, and the medium 101 may fall off the transport path. In such a case, the medium may be jammed.

  Therefore, in the image forming apparatus 1, the charging member 607 is provided. Since the charging member 607 is in contact with the inner surface 601A of the conveyor belt 601, frictional charging occurs between the charging member 607 and the inner surface 601A of the conveyor belt 601 as the conveyor belt 601 rotates. At this time, the charge on the charging member 607 has the same polarity as the charge on the toner T. For example, as shown in the explanatory view of FIG. 6B, the charging member 607 is charged with a negative charge similarly to the toner T. Therefore, in the region RR downstream of the charging member 607 shown in FIG. 5B, the negative charges near the inner surface 601A of the transport belt 601 are removed. Further, when the charging member 607 is charged with a negative charge, a positive charge comes near the inner surface 601A of the transport belt 601. As a result, the polarity of the charge near the inner surface 601A of the transport belt 601 is opposite to the polarity of the charge of the toner T. Therefore, the polarity of the charge near the outer surface 601B of the transport belt 601 becomes the same as the polarity of the charge near the back surface 101A of the medium 101, and the medium 101 and the transport belt 601 are repelled (at least change in a direction that is hardly attracted). To do). Therefore, the medium 101 is easily separated from the transport belt 601.

(C. Effect)
As described above, according to the image forming apparatus 1 of the present embodiment, frictional charging occurs due to the rotation of the conveyor belt 601 due to the contact with the conveyor belt 601, and the negative charge near the inner surface 601 </ b> A of the conveyor belt 601 is removed. The charging member 607 is provided. Thereby, the adhesion between the medium 101 and the transport belt 601 due to the electrostatic phenomenon is reduced, and the medium 101 can be separated from the transport belt 601 smoothly. Therefore, it is possible to avoid a medium jam in the image forming apparatus 1.

  Further, in the image forming apparatus 1, the charging member 607 urges the conveyor belt 601 toward the outer surface 601B so as to push up the conveyor belt 601 from the inner surface 601A. As a result, the charging member 607 is located on a straight line L (shown by a broken line in FIG. 4) connecting the driving roller 602 and the driven roller 603, or is located outside the straight line L. Since the charging member 607 urges the transport belt 601 so as to push up the transport belt 601 from the inner surface 601A side to the outer surface 601B side, the leading end of the medium 101 discharged from the transfer transport unit 600 to the fixing unit 700 is transferred to the transport belt. 601 can be more easily separated from the outer surface 601B. Therefore, the possibility of the medium clogging in the image forming apparatus 1 can be sufficiently reduced.

<2. Modification>
As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, an image forming apparatus for forming a color image has been described. However, the present invention is not limited to this. For example, an image forming apparatus for transferring only a black toner image and forming a monochrome image It may be a device. Further, in the above embodiment, the image forming apparatus of the primary transfer system (direct transfer system) has been described, but the present invention can be applied to the secondary transfer system.

  Further, in the above-described embodiment, the charging member 607 sliding on the inner surface 601A of the transport belt 601 is exemplified as the charge removing member, but the present invention is not limited to this. For example, as in a transfer transport unit 600A according to a first modification of the present invention shown in FIG. 7, a charging roller 612 as a charge removing member may be provided instead of the charging member 607. The surface of the charging roller 612 is in contact with the inner surface 601 </ b> A of the transport belt 601 that is rotated and rotated by the driving roller 602. For this reason, the charging roller 612 rotates in the rotation direction R612 indicated by the arrow following the circulating rotation of the transport belt 601. The same effect as the transfer conveyance unit 600 can be expected in the transfer conveyance unit 600A. In addition, in the transfer conveyance unit 600A, since the charging roller 612 rotates following the circulating rotation of the conveyance belt 601, the external force on the conveyance belt 601 is reduced as compared with the transfer conveyance unit 600 having the charging member 607 that does not rotate. In addition, the speed fluctuation of the circulation rotation of the conveyor belt 601 can be reduced. Note that by providing a speed difference between the rotation speed of the charging roller 612 and the speed of the transport belt 601, the frictional resistance may be adjusted so that a required charge amount is obtained. For example, when conveying normal paper having a relatively low conveying load, the electromotive force is increased by making the peripheral speed of the charging roller slower than the conveying speed of the conveying belt. Further, when a thick paper having a relatively high transport load is transported, the electromotive force is increased by increasing the peripheral speed of the charging roller with respect to the transport speed of the transport belt.

  Further, in the above-described embodiment, the charging member 607 made of a dielectric is exemplified as the charge removing member, but the present invention is not limited to this. For example, a conductive member 613 may be mounted as a charge removing member as in a transfer transport unit 600B according to a second modification of the present invention shown in FIG. The conductive member 613 is a conductor such as stainless steel, and is disposed slightly apart from the inner surface 601A of the transport belt 601. In the transfer and transport unit 600B, for example, by applying a negative potential to the conductive member 613, the electric charges on the inner surface 601A of the transport belt 601 can be removed. Therefore, the adhesion between the medium 101 and the transport belt 601 due to the electrostatic phenomenon is reduced, and the medium 101 can be separated from the transport belt 601 smoothly. Therefore, it is possible to avoid a medium jam in the image forming apparatus 1.

  Further, in the above-described embodiment and the like, the image forming apparatus having the printing function is described as a specific example of the “image forming apparatus” in the present invention, but the present invention is not limited to this. That is, the present invention can be applied to an image forming apparatus that functions as a multifunction peripheral having, for example, a scan function and a fax function in addition to the print function.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 100 ... Medium tray, 101 ... Medium, 200 ... Medium feeding part, 300 ... Medium conveying part, 400 ... Image forming part, 500 ... Image forming unit, 600 ... Transfer conveying unit, 601 ... Conveying belt, 602: drive roller, 603: driven roller, 604K, 604Y, 604M, 604C: transfer roller, 605: waste toner box, 606: shaft, 607: charging member, 608: belt blade, 609: counter roller, 610: medium Guide, 611: separator, 612: charging roller, 613: conductive member, 700: fixing unit, 800: reversing unit.

Claims (17)

A belt that transfers the medium while transferring the toner image carried on the image carrier to the medium,
And a charge removing member for removing charges from the belt. A first rotating body and a second rotating body that are arranged side by side along the transport direction of the medium and stretch the belt.
The belt is an endless belt,
The transfer / conveying unit according to claim 1, wherein the static elimination member is in contact with an inner surface of the endless belt and is located on a straight line connecting the first rotator and the second rotator or outside the straight line. . The belt has a first surface in contact with the medium, and a second surface opposite to the first surface,
The said static elimination member is a push-up member which contacts the said 2nd surface in the area | region where the said 1st surface and the said medium contact, and pushes up the said 2nd surface toward the said 1st surface. Transfer transport unit. The transfer / conveyance unit according to claim 1, wherein the static elimination member is a dielectric. The transfer / transport unit according to claim 1, wherein the charge removing member is a third rotating body. The transfer / conveyance unit according to claim 1, wherein the static elimination member is a conductor, and is disposed apart from the belt. An image forming unit including an image carrier that carries a toner image,
An image forming apparatus, comprising: a belt that transfers the toner image onto a medium and conveys the medium; and a transfer / convey unit that includes a charge removing member that removes charges on the belt. A medium supply unit that is provided upstream of the transfer and transport unit and supplies the medium to the transfer and transport unit;
The image forming apparatus according to claim 7, further comprising: a fixing unit that is provided downstream of the transfer and conveyance unit and fixes the toner image on the medium. The transfer transport unit further includes a first rotary body and a second rotary body that are arranged side by side along the transport direction of the medium and stretch the belt.
The belt is an endless belt,
The said static elimination member is in contact with the inner surface of the said endless belt, and is located on the straight line which connects the said 1st rotating body and the said 2nd rotating body, or is located outside the said straight line. Image forming apparatus. The belt has a first surface in contact with the medium, and a second surface opposite to the first surface,
The said static elimination member is a push-up member which contacts the said 2nd surface in the area | region where the said 1st surface and the said medium contact, and pushes up the said 2nd surface toward the said 1st surface. Item 10. The image forming apparatus according to Item 8. The image forming apparatus according to claim 7, wherein the static elimination member is a dielectric. The image forming apparatus according to claim 7, wherein the charge removing member is a third rotating body. The image forming apparatus according to claim 7, wherein the static elimination member is a conductor, and is disposed apart from the belt. An endless belt that transfers the toner image carried on the image carrier to the medium and conveys the medium,
A first rotating body and a second rotating body arranged side by side along the transport direction of the medium and stretching the endless belt;
A transfer member that is in contact with the inner surface of the endless belt and that is located on a straight line connecting the first rotator and the second rotator or that is located outside the straight line. The transfer / transport unit according to claim 14, wherein the push-up member is a charge removing member that removes electric charges from the endless belt. The transfer / conveyance unit according to claim 14, further comprising a plate-shaped or film-shaped separation member that separates the medium conveyed by the endless belt from the endless belt. The first rotating body extends in a width direction orthogonal to the transport direction of the medium,
The separation member has an edge facing the first rotating body across the endless belt,
The edge is an intermediate portion extending in the width direction, and a pair of end portions that sandwich the intermediate portion in the width direction and are inclined so as to be more distant from the first rotating body as the distance from the intermediate portion increases. The transfer conveyance unit according to claim 16, comprising:

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