JP5125043B2 - Image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer, a facsimile, and an image forming apparatus using an electrophotographic system having these functions, and in particular, a toner image carried on the surface of a toner image carrier or the like is transferred by a contact transfer member. The present invention relates to an image forming apparatus that transfers to a transfer material, or a color image forming apparatus that superimposes a plurality of color toner images formed on an intermediate transfer body and transfers them onto a transfer material by a contact transfer member.

  An image forming apparatus such as a laser printer includes a photoconductive drum and a transfer roller disposed to face the photoconductive drum. A toner image based on image data is carried on the photosensitive drum, and the toner image carried on the photosensitive drum passes between the photosensitive drum and the transfer roller by applying a transfer bias voltage to the transfer roller. Is transferred to a transfer material. In this type of image forming apparatus, the transfer material may be wound around the transfer roller.

  As an example of an intermediate transfer type color image forming apparatus, a developing device for each color component of yellow, magenta, cyan, and black is provided around an image carrier such as a photosensitive drum, and an intermediate with respect to the image carrier. The transfer body is placed opposite to each other, and the unfixed toner image of each color component formed on the image carrier for each color component image forming cycle of the image carrier is firstly transferred to the intermediate transfer body in sequence, and then superimposed on the intermediate transfer body. In some cases, each color toner image is secondarily transferred to a transfer material such as paper to form a desired color image on the transfer material.

  As a secondary transfer device for transferring each color toner image on the intermediate transfer member to the transfer material, for example, the transfer roller is pressed against the surface side (the surface side on which the toner image is transferred) of the intermediate transfer member supported by the backup roller. The intermediate transfer member and the transfer roller sandwich and convey the transfer material, and a transfer bias voltage is applied to one or both of the backup roller and the transfer roller to transfer the toner image on the intermediate transfer member to the transfer material. In this case, a batch transfer is used.

  Even in this type of color image forming apparatus, the transfer material may be wound around the transfer roller during the secondary transfer.

  In order to prevent the transfer material from being wound around these transfer rollers, there is a conventional transfer roller having a rough surface. However, in recent years, in order to reliably clean the surface of the transfer roller, it is desirable that the surface of the transfer roller be a smooth surface in the transfer means in which the cleaning blade is in contact with the transfer roller.

  As a transfer roller wrapping prevention means attached to a transfer means for transferring a toner image carried on the surface of an image carrier or the like onto a transfer material by a transfer roller, those described in Patent Document 1 and Patent Document 2 are known. ing.

  The wrapping prevention means of the image forming apparatus of Patent Document 1 is provided with a blower fan and a nozzle on the downstream side in the rotation direction of the transfer fixing roller, and blows air discharged from the nozzle between the separation plate and the transfer fixing roller. Thus, the sheet after fixing is prevented from being wound around the transfer fixing roller.

The wrapping prevention means of the image forming apparatus of Patent Literature 2 is provided with a lower cover that covers at least a part of the peripheral surface of the transfer roller. A protruding contact portion that protrudes toward the transfer roller on the transfer roller facing surface of the lower cover and faces the transfer roller with a gap therebetween, and a stay portion on the upstream side of the sheet conveyance direction of the contact portion , And the paper is retained in a bent state in the retention portion, thereby preventing the paper from being wound around the transfer roller.
Japanese Patent Laying-Open No. 2005-258035 JP 2005-338399 A

  In recent years, in image forming apparatuses such as copiers, printers, facsimiles, and multifunction devices having these functions and color image forming, there is a demand for higher image quality in the transfer process by using polymerized toner and small particle size toner. Is getting bigger. The speed of image forming apparatuses is also increasing. In order to obtain a good image against these trends, paper jamming due to the transfer material wrapping around the transfer roller or intermediate transfer member is prevented, the toner image on the transfer material is transferred well, and stable at high speed. It is necessary to achieve image formation.

  In the image forming apparatus described in Patent Document 1, if air is sent to the transfer unit, the toner image is likely to be disturbed. In addition, when electrostatically attracting from the tip, air cannot be sent to the tip of the transfer material.

  The image forming apparatus described in Patent Document 2 prevents damage to the transfer roller when wound due to poor separation, and does not improve the poor separation of paper itself.

  The present invention has been made to solve the above technical problems, and prevents the back surface of the transfer material from being soiled, reduces the adhesion between the transfer roller and the transfer material, and facilitates separation of the transfer material. Accordingly, the present invention provides an image forming apparatus that prevents paper jamming due to winding of a transfer material around a transfer roller.

  The object is achieved by the configurations described below.

An image carrier that carries a toner image, a contact transfer member that contacts the image carrier and transfers the toner image on the image carrier to a transfer material, and a rotation shaft of the image carrier on the image carrier possess the additional toner image forming means for forming an additional toner image of the strip extending in the longitudinal direction parallel to the direction, and control means for causing the additional toner image on the contact transfer member is formed at a predetermined timing, wherein the image The timing of forming the additional toner image on the carrier is a timing at which the additional toner image is formed on the surface of the contact transfer member corresponding to the tip of the transfer material. apparatus.

  The following effects can be obtained by the image forming apparatus of the present invention.

By forming an additional toner image in contact touch transfer member at a predetermined timing, and hardly generate stains of the transfer material tip, it is possible to prevent the winding of the transfer material into contact transfer member.

  The present invention will be described using embodiments, but the present invention is not limited to the embodiments described below.

  FIG. 1 is a cross-sectional view showing a main part of an image forming apparatus A according to an embodiment of the present invention.

  This image forming apparatus A is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 20Y, 20M, 20C, and 20K, a belt-like image carrier (intermediate transfer member) 1, a primary transfer roller. 25Y, 25M, 25C, 25K, an intermediate transfer unit including a transfer member (secondary transfer roller) 3, a fixing device 16, and a paper feeding device.

  The document placed on the document table is scanned and exposed by the optical system of the document image scanning exposure apparatus of the image reading apparatus, and read by the line image sensor. The analog signal photoelectrically converted by the line image sensor is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in the image processing unit, and then input to the exposure means 23Y, 23M, 23C, and 23K. .

  The image forming unit 20Y that forms a yellow (Y) image includes a charging unit 22Y, an exposing unit 23Y, a developing unit 24Y, and a cleaning unit 26Y disposed around an image carrier (photoconductor) 21Y.

  The image forming unit 20M that forms a magenta (M) color image includes an image carrier 21M, a charging unit 22M, an exposure unit 23M, a developing unit 24M, and a cleaning unit 26M.

  The image forming unit 20C that forms a cyan (C) color image includes an image carrier 21C, a charging unit 22C, an exposure unit 23C, a developing unit 24C, and a cleaning unit 26C.

  The image forming unit 20K that forms a black (K) color image includes an image carrier 21K, a charging unit 22K, an exposure unit 23K, a developing unit 24K, and a cleaning unit 26K.

  The charging unit 22Y and the exposure unit 23Y, the charging unit 22M and the exposure unit 23M, the charging unit 22C and the exposure unit 23C, and the charging unit 22K and the exposure unit 23K constitute a latent image forming unit.

  As the image carriers 21Y, 21M, 21C, and 21K, known ones such as an OPC photosensitive member and an aSi photosensitive member are used. An OPC photosensitive member is preferable, and a negatively charged OPC photosensitive member is particularly preferable. In the form, negatively chargeable OPC is used.

  As the charging means 22Y, 22M, 22C, and 22K, a corona discharge means such as a scorotron or a corotron is used, and a scorotron discharge means is preferably used.

  As the exposure means 23Y, 23M, 23C, and 23K, light emitting elements that emit light according to image data, such as lasers and LED arrays, are used.

  The belt-like intermediate transfer member 1 is semiconductive and is wound by a transfer counter roller 2, a support roller 2B, a driving roller 2C, a driven roller 2D, a tension roller 2E, a cleaning roller 2F, and a roller 2G facing the sensor PS. And supported so as to be able to circulate. In the present embodiment, the intermediate transfer body 1 is supported between the driving roller 2C and the driven roller 2D in a planar shape.

  The toner images of the respective colors formed by the image forming units 20Y, 20M, 20C, and 20K are sequentially transferred (primary transfer) to the rotating intermediate transfer body 1 by the primary transfer rollers 25Y, 25M, 25C, and 25K, and combined. A toner image T of the color image thus formed is formed.

  The transfer material P accommodated in the paper feeding cassette of the paper feeding device is fed by a paper feeding means (first paper feeding unit) (not shown), and feeds a paper feeding roller 12 and a registration roller (second paper feeding unit) 13. Then, the transfer roller 3 of the secondary transfer unit and the transfer counter roller 2 are conveyed to the transfer nip N where they abut via the intermediate transfer body 1, and the toner image is transferred onto the transfer material P (secondary). Transcription).

  Alternatively, the transfer material P sent out from the manual paper feed unit is conveyed to the transfer nip N through the paper feed roller 11 and the registration roller 13.

  The cleaning blade 4 and the coating unit 5 shown in FIG. 1 are in contact with the transfer roller 3 in the transfer nip N. The coating means 5 supplies the transfer material adhesion preventive agent t to the transfer roller 3.

  The transfer material P onto which the color image has been transferred is transported by the transport belt 15, heat and pressure are applied in the fixing device 16, and the intermediate transfer body 1 separated by the curvature separation and separation claw 14 is cleaned. Residual toner is removed by the roller 2F.

  FIG. 2 is a cross-sectional view showing an image forming unit 40 according to another embodiment of the image forming apparatus A.

  Around the image carrier (photosensitive member) 41, a charging unit 42, an exposing unit 43, a developing unit 44, a transfer roller 45, a separation claw 46, and a cleaning unit 47 are arranged in the order of the image forming process.

  The transfer roller 45 is formed of a conductive elastic layer formed on the surface of the rotating shaft. A DC power source 48 connected to the transfer roller 45 transfers residual toner attached to the transfer roller 45 in contact with the image carrier 41 to the image carrier 41 by applying a reverse bias. The image carrier 41 carrying the residual toner is cleaned by a cleaning unit 47.

  On the outer peripheral surface of the transfer roller 45, the cleaning blade 4 and the coating means 5 shown in FIG.

  FIG. 3 is a cross-sectional view of the transfer means according to the present invention in which an image carrier (intermediate transfer member) 1 and a contact transfer member (hereinafter referred to as a transfer roller) 3 abut. FIG. 4 is a perspective view of the transfer means. FIG. 5 is a block diagram showing the control of the transfer means.

  The belt-shaped image carrier 1 is made of a resin such as polyimide, polycarbonate, polyester, or various rubbers containing a conductive agent, and is adjusted to have a volume resistivity of 10E + 5 to 10E + 12 Ω · cm.

  The belt-shaped intermediate transfer body image carrier 1 is rotated by winding a transfer counter roller 2 and a plurality of later-described roller groups (see FIG. 1).

  The transfer facing roller 2 is disposed on the inner surface side of the belt-shaped image carrier 1 so as to face the transfer roller 3.

  The transfer roller 3 presses the transfer counter roller 2 through the image carrier 1 to transfer the toner image T formed on the image carrier 1 to the transfer material P.

  As the transfer roller 3, an elastic member such as acrylonitrile / butadiene rubber (NBR) or urethane rubber coated with a fluorine resin, or a fluorine or nylon tube coated on the surface of the elastic member is used. It is done. The transfer roller 3 is controlled to have a volume resistance of 10E + 3Ω to 10E + 12Ω by introducing a conductive agent. The transfer roller 3 is rotated by driving means (not shown).

  On the outer peripheral surface of the transfer roller 3, a cleaning blade 4 and a coating unit 5 are arranged. The cleaning blade 4 is made of urethane rubber, and abuts in the counter direction with respect to the direction in which the transfer roller 3 rotates in the forward direction (the counterclockwise direction in the drawing) to remove the toner transferred to the transfer roller 3.

  The application means 5 disposed on the downstream side in the rotation direction of the transfer roller 3 of the cleaning blade 4 has, for example, a brush structure in which conductive fibers are planted on a base cloth and adhered to the outer peripheral portion of a cylindrical core made of polycarbonate. Eggplant.

  The driving means 5M connected to the applying means 5 rotates the rotating brush-like applying means 5 in the counterclockwise direction and causes the tip of the rotating brush of the applying means 5 to contact or separate from the transfer roller 3. The conductive fiber of the coating means 5 is connected to a high voltage power source 5E.

  An additional toner container 6 for storing a transfer material adhesion preventing agent t such as a transparent toner is installed below the coating means 5. The driving unit 5M separates the coating unit 5 from the surface of the transfer roller 3, and contacts and adsorbs the transfer material adhesion preventing agent t in the additional toner container 6 below. Further, the driving unit 5M moves the applying unit 5 that has adsorbed the transfer material adhesion preventing agent t to contact the transfer roller 3, and applies the transfer material adhesion preventing agent t to the transfer roller 3.

  The transfer material P conveyed by the transfer material conveying means 7 is sandwiched between the registration rollers 13 and passes through the transfer nip portion N where the transfer counter roller 2 and the transfer roller 3 are pressed against each other via the image carrier 1 of the transfer means. Then, it is conveyed to 16 by a fixing device described later.

  The control unit 8 controls a driving unit 5M that drives rotation of the coating unit 5 and contact / separation with the transfer roller 3, a high-voltage power source 5E that applies a bias voltage to the coating unit 5, and a transfer material transport unit 7. The control unit 8 performs control to apply the transfer material adhesion preventing agent t to the contact transfer member 3 at a predetermined timing. Further, the control means 8 performs control to apply the transfer material adhesion preventing agent t to the contact transfer member 3 on the surface of the contact transfer member 3 corresponding to the front end portion of the transfer material P being conveyed.

In this embodiment, the negative electrode charging toner is used as the transfer material adhesion preventing agent t. Transfer counter roller 2 is connected to a DC power source 2 E applying a negative transfer voltage. The transfer roller 3 is grounded.

The rotating brush-shaped application unit 5 rotates in contact with the transfer roller 3 by the driving unit 5M at an appropriate timing, and applies the transfer material adhesion prevention agent t. For example, when the user selects and sets a specific transfer material P such as thin paper or coated paper that is easy to be wound around the transfer roller 3 on the operation panel of the image forming apparatus A, or below the position detected by the curl detection means. When the curved transfer material P is conveyed, the additional toner image K to which the transfer material adhesion preventing agent t is applied is formed at the front end of the transfer material P in the conveyance direction as shown in FIG. The transfer material adhesion preventing agent t is applied by the applying means 5 at the same timing. Alternatively, as shown in FIG. 4, the driving means 5M is set to a predetermined position so that the transfer material adhesion preventing agent t is applied to the corresponding non-image forming area between the preceding transfer material P and the subsequent transfer material P. You may control by timing. Alternatively, as a predetermined timing, the transfer material adhesion preventing agent t may be applied to the entire surface of the transfer roller 3 as well as a portion corresponding to the tip of the transfer material P and a portion corresponding to a position between the transfer materials P.
The surface of the rotating brush of the application unit 5 is previously contacted and adsorbed to the transfer material adhesion preventing agent t in the additional toner container 6 by the swing of the application unit 5 driven by the drive unit 5M.

  The toner applied to the surface of the transfer roller 3 mainly has the same polarity as the charging polarity of the toner for image formation, and is difficult to adhere to the transfer material P during transfer, and the transfer material P and the transfer roller 3 Can be reduced.

  The toner attached to the transfer roller 3 is removed and cleaned by the cleaning blade 4. The cleaning means is not limited to the method using the cleaning blade 4, and a cleaning roller or the like can also be used.

  Further, the transfer material adhesion preventing agent t is not limited to powder toner, and the charging polarity is not limited. However, toner for image formation is preferable. The application means 5 of the transfer material adhesion preventing agent t is not limited to a rotating brush, and may be a non-woven fabric or a sponge roller. The transfer means is not limited to the illustrated transfer roller 3 but may be an endless transfer belt.

  FIG. 6 is a sectional view showing another embodiment of the transfer means according to the present invention. FIG. 7 is a perspective view of the transfer means. FIG. 8 is a block diagram showing the control of the transfer means.

  In addition, about the code | symbol used in this drawing, the same code | symbol is attached | subjected to the part which has the same function as FIG. Further, differences from the above-described embodiment will be described.

  The cleaning blade 4 is brought into contact with and separated from the surface of the transfer roller 3 by the driving means 4M. At the time of image formation, the toner transferred to the transfer roller 3 is removed by abutting in the counter direction with respect to the direction in which the transfer roller 3 rotates in the forward direction (counterclockwise direction in the drawing).

  As shown in FIG. 7, the belt-like additional toner image K on the outer peripheral surface of the transfer roller 3 is formed in advance before the transfer material P reaches the nip portion N. That is, the image forming apparatus A has a charging unit, an exposure unit, a developing unit, and the like in advance at a position calculated so as to reach the transfer nip N when the transfer material leading end reaches the transfer nip N. An additional toner image K is formed on the image carrier 1 by the image forming device 9 and then transferred to the transfer material P.

  Before the belt-like additional toner image K passes through the transfer nip portion N and reaches the cleaning position of the cleaning blade 4, the pressure applied to the cleaning blade 4 is reduced or the cleaning blade 4 is separated from the transfer roller 3, The belt-like additional toner image K is passed through. The additional toner image K has a low image density with an inconspicuous color such as yellow toner, and makes it difficult for the transfer material P to be stained.

  In the secondary transfer at the time of color image formation in the image forming apparatus A shown in FIG. 1, the secondary transfer that transfers the multicolor toner image formed on the intermediate transfer member by the winding of the transfer material is prevented and the transfer is performed satisfactorily. An image forming apparatus including a member is provided.

  In the above embodiment, the powder is used as the transfer material adhesion preventing agent t. However, the present invention is not limited to this, and a liquid transfer material adhesion preventing agent can also be used. is there. Further, the applying means 5 may be a foamed elastic roller instead of a rotating brush. Further, the contact transfer member 3 may be a transfer belt stretched by a plurality of rollers.

Sectional drawing which shows the image formation part of other embodiment of an image forming apparatus. Sectional drawing which shows the image formation part of other embodiment of an image forming apparatus. FIG. 3 is a cross-sectional view of a transfer unit according to the present invention in which an image carrier and a transfer member abut. The perspective view of a transfer means. Sectional drawing which shows other embodiment of the transfer means which concerns on this invention. The block diagram which shows control of the transfer means by a control means. 6 is a timing chart for controlling the transfer means. FIG. 3 is a cross-sectional view showing a main part of the image forming apparatus according to the embodiment of the present invention.

Explanation of symbols

1 Image carrier (intermediate transfer member)
2 Transfer counter roller 3 Contact transfer member (transfer roller)
DESCRIPTION OF SYMBOLS 4 Cleaning blade 4M, 5M Drive means 5 Application | coating means 5E High voltage power supply 6 Additional toner container 7 Transfer material conveyance means 8 Control means 9 Image forming device 13 Registration roller 21Y, 21M, 21C, 21K Image carrier (photoreceptor)
40 Image forming section 41 Image carrier (photosensitive member)
45 Transfer roller 47 Cleaning means 48 DC power source A Image forming apparatus K Additional toner image N Transfer nip P Transfer material T Toner image t Transfer material adhesion preventive agent

Claims (5)

An image carrier for carrying a toner image;
A contact transfer member that contacts the image carrier and transfers the toner image on the image carrier to a transfer material;
An additional toner image forming means for forming, on the image carrier, a belt-like additional toner image extending in a longitudinal direction parallel to the rotation axis direction of the image carrier;
Control means for forming the additional toner image on the contact transfer member at a predetermined timing;
I have a,
The timing at which the additional toner image is formed on the image carrier is a timing at which the additional toner image is formed on the surface of the contact transfer member corresponding to the front end portion of the transfer material. Image forming apparatus. The image forming apparatus according to claim 1, wherein when a specific transfer material is selected and conveyed, control is performed to form the additional toner image on the image carrier. The image forming apparatus according to claim 1, further comprising a cleaning unit that cleans a surface of the contact transfer member, wherein the cleaning unit is capable of varying a pressing force with respect to the contact transfer member or being able to contact and separate. . The image forming apparatus according to claim 1, wherein the image carrier is a photosensitive member or an intermediate transfer member. The image forming apparatus according to claim 1, wherein the contact transfer member has a roller shape or a belt shape.

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