JP2018120014A - Dirt prevention device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dirt prevention device or the like that, when fixing processing is performed on a label sheet that is a cut sheet, can prevent a fixing member from getting dirty by an adhesive contained in the label sheet.SOLUTION: A dirt prevention device comprises: a pressing part that is provided, in a sheet conveyance direction of a label sheet that is a cut sheet in which a release sheet having an adhesive coated on the back is attached onto a substrate, on the upstream side of a fixing part that fixes an unfixed toner image onto the label sheet, and presses the full width of the release sheet in a sheet width direction orthogonal to the sheet conveyance direction; and a removing part that removes an adhesive protruded from the sheet due to pressing by the pressing part.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an antifouling device and an image forming apparatus.

  In general, an image forming apparatus (printer, copying machine, facsimile, etc.) using an electrophotographic process technology irradiates (exposes) a charged photosensitive drum (image carrier) with laser light based on image data. To form an electrostatic latent image. Then, by supplying toner from the developing device to the photosensitive drum on which the electrostatic latent image is formed, the electrostatic latent image is visualized to form a toner image. Further, after the toner image is directly or indirectly transferred to the sheet, the toner image is formed on the sheet by fixing it by heating and pressing at the fixing nip.

  In the image forming apparatus, label paper having a seal on the back surface may be used as paper. This label paper is obtained by adhering a release sheet coated with glue on the back surface (the surface corresponding to the release material) on the base material coated with the release material. After an image is formed on the surface of the release sheet, the release sheet is used by being peeled off from a base material and attached to a target object.

  By the way, when the label paper passes through the fixing nip, the pressure applied by the fixing nip is large, and the glue of the label paper is softened by heating, so that the glue may protrude from the end of the label paper. . In this case, there is a problem that the protruding glue adheres to a fixing member (for example, a fixing roller, a fixing belt, and a pressure roller) that forms a fixing nip and soils the fixing member.

  In Patent Document 1, an end pressing portion (hereinafter also simply referred to as a pressing portion) that presses the end of the label roll paper is provided on the upstream side of the fixing portion, and the glue of the label roll paper is prevented from protruding from the fixing portion. Techniques to do this are disclosed. Specifically, in Patent Document 1, the amount of glue on the end side of the label roll paper is reduced by reducing the pressing force from the end side of the pressing part toward the center side and pushing the glue toward the center side. Thus, a technique for preventing the glue from protruding at the fixing portion is disclosed. Further, in Patent Document 1, there is provided a removal unit that increases the pressing force from the end side of the pressing unit toward the center side, discharges the glue from the end of the label roll paper, and removes the discharged glue. Thus, a technique is disclosed in which the amount of glue on the end side of the label roll paper is reduced to prevent the glue from sticking out at the downstream fixing portion.

JP, 2006-090813, A

  However, the technique of Patent Document 1 is based on the premise that label roll paper is used, and is configured to press only the edge of such paper, and the fixing member may become dirty when label paper as cut paper is used. is there. That is, when label paper, which is cut paper, is used in the technique of Patent Document 1, when the entire area of the paper is pressed by the fixing unit, the sticking of the paper from the edge in the width direction of the paper can be prevented, but the paper transport direction There is a problem that the paste is pushed out from the rear end and protrudes, and the fixing member is contaminated by the protruded paste.

  An object of the present invention is to provide an anti-smudge device and an image forming apparatus capable of preventing a fixing member from being soiled by glue contained in the label paper when a fixing process is performed on the label paper which is a cut paper. It is.

The antifouling device according to the present invention is
In the paper transport direction of the label paper, which is a cut paper with a release sheet coated with glue on the back surface, provided on the upstream side of the fixing unit for fixing the unfixed toner image on the label paper, A pressing portion that presses the entire width of the release sheet in the paper width direction orthogonal to the paper transport direction;
A removing unit that removes the glue protruding from the sheet by the pressing of the pressing unit.

An image forming apparatus according to the present invention includes:
The above-described anti-smudge device,
An image forming unit that forms a toner image on paper;
A fixing unit that fixes the toner image on the paper.

  According to the present invention, it is possible to prevent the fixing member from being soiled by the glue contained in the label paper when the fixing processing is performed on the label paper that is cut paper.

1 is a diagram schematically showing an overall configuration of an image forming apparatus in the present embodiment. FIG. 2 is a diagram illustrating a main part of a control system of the image forming apparatus according to the present embodiment. It is a figure explaining the arrangement position of the press part in this Embodiment. It is a figure which shows the structure of the press part in this Embodiment, and the removal part, FIG. 4A is a figure shown from the front side, and FIG. 4B is a figure shown from the side surface side. It is a figure which shows the modification of a structure of the removal part in this Embodiment. FIG. 6A is a diagram showing a modification of the configuration of the pressing portion in the present embodiment, FIG. 6A is an example of a crown-shaped pressing portion, and FIG. 6B is an example in which an elastic layer is provided on the surface layer of the pressing portion of FIG. Show. 7A and 7B are diagrams illustrating a case where the pressing force of the pressing portion in the present embodiment is increased on the rear end side of the paper, in which FIG. 7A is a plan view and FIG. 7B is a side view. FIG. 8A is a diagram illustrating a modification example of the configuration of the pressing unit according to the present embodiment, FIG. 8A is a diagram illustrating a range in which label is desired to be removed from the label paper, and FIG. 8B is a plan view illustrating a modification example of the configuration of the pressing unit. . It is a figure explaining the example of control of the pressing force by a press part in case a peeling sheet exists in a part of base material of the label paper in this Embodiment.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically showing an overall configuration of an image forming apparatus 1 according to the present embodiment. FIG. 2 is a diagram illustrating a main part of a control system of the image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 uses paper (cut paper) cut into a predetermined paper size as a recording medium. In particular, as the paper, a label paper is used in which a release sheet coated with glue on the back surface (the surface corresponding to the release material) is attached on the base material coated with the release material. After an image is formed on the surface of the release sheet, the release sheet is used by being peeled off from a base material and attached to a target object. In the following description, label paper and cut paper other than label paper are collectively referred to as paper S (or simply paper), and label paper P is referred to when describing label paper.

  As shown in FIG. 1, the image forming apparatus 1 is an intermediate transfer type color image forming apparatus using an electrophotographic process technology. That is, the image forming apparatus 1 primarily transfers the Y (yellow), M (magenta), C (cyan), and K (black) toner images formed on the photosensitive drum 413 to the intermediate transfer belt 421. After the four color toner images are superposed on the intermediate transfer belt 421, an image is formed by secondary transfer onto the paper S sent from the paper feed tray units 51a to 51c.

  Further, in the image forming apparatus 1, the photosensitive drums 413 corresponding to the four colors of YMCK are arranged in series in the running direction of the intermediate transfer belt 421, and the respective color toner images are sequentially transferred to the intermediate transfer belt 421 in one step. Tandem system is adopted.

  As shown in FIG. 2, the image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper transport unit 50, a fixing unit 60, and a control unit 101.

  The control unit 101 includes a CPU (Central Processing Unit) 102, a ROM (Read Only Memory) 103, a RAM (Random Access Memory) 104, and the like. The CPU 102 reads out a program corresponding to the processing content from the ROM 103 and develops it in the RAM 104, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the developed program. At this time, various data stored in the storage unit 72 is referred to. The storage unit 72 includes, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive.

  The control unit 101 transmits and receives various data to and from an external device (for example, a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 71. Do. For example, the control unit 101 receives image data (input image data) transmitted from an external device, and forms an image on the paper S based on the image data. The communication unit 71 is composed of a communication control card such as a LAN card, for example.

  As shown in FIG. 1, the image reading unit 10 includes an automatic document feeder 11 called an ADF (Auto Document Feeder), a document image scanning device 12 (scanner), and the like.

  The automatic document feeder 11 transports the document D placed on the document tray by a transport mechanism and sends it out to the document image scanning device 12. The automatic document feeder 11 can continuously read images (including both sides) of a large number of documents D placed on the document tray all at once.

  The document image scanning device 12 optically scans a document conveyed on the contact glass from the automatic document feeder 11 or a document placed on the contact glass, and reflects light from the document to a CCD (Charge Coupled Device). ) An image is formed on the light receiving surface of the sensor 12a, and an original image is read. The image reading unit 10 generates input image data based on the reading result by the document image scanning device 12. The input image data is subjected to predetermined image processing in the image processing unit 30.

  As shown in FIG. 2, the operation display unit 20 is configured by, for example, a liquid crystal display (LCD) with a touch panel, and functions as a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, image states, operation states of functions, and the like according to a display control signal input from the control unit 101. The operation unit 22 includes various operation keys such as a numeric keypad and a start key, receives various input operations by the user, and outputs an operation signal to the control unit 101.

  The image processing unit 30 includes a circuit that performs digital image processing on input image data according to initial settings or user settings. For example, the image processing unit 30 performs gradation correction based on the gradation correction data (gradation correction table) under the control of the control unit 101. Further, the image processing unit 30 performs various correction processes such as color correction and shading correction, a compression process, and the like on the input image data in addition to the gradation correction. The image forming unit 40 is controlled based on the image data subjected to these processes.

  As shown in FIG. 1, the image forming unit 40 is based on input image data, and image forming units 41Y, 41M, and 41C for forming an image using colored toners of Y component, M component, C component, and K component. , 41K, intermediate transfer unit 42 and the like.

  The Y component, M component, C component, and K component image forming units 41Y, 41M, 41C, and 41K have the same configuration. For convenience of illustration and explanation, common constituent elements are denoted by the same reference numerals, and Y, M, C, or K are added to the reference numerals when distinguished from each other. In FIG. 1, only the components of the Y-component image forming unit 41Y are denoted by reference numerals, and the constituent elements of the other image forming units 41M, 41C, and 41K are omitted.

  The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413, a charging device 414, a drum cleaning device 415, and the like.

  The photoreceptor drum 413 is made of an organic photoreceptor in which a photosensitive layer made of a resin containing an organic photoconductor is formed on the outer peripheral surface of a drum-shaped metal substrate, for example.

  The control unit 101 rotates the photosensitive drum 413 at a constant peripheral speed by controlling a driving current supplied to a driving motor (not shown) that rotates the photosensitive drum 413.

  The charging device 414 is, for example, a charging charger, and uniformly charges the surface of the photosensitive drum 413 having photoconductivity by generating corona discharge.

  The exposure device 411 is composed of, for example, a semiconductor laser, and irradiates the photosensitive drum 413 with laser light corresponding to the image of each color component. As a result, an electrostatic latent image of each color component is formed in the image area irradiated with laser light on the surface of the photosensitive drum 413 due to a potential difference from the background area.

  The developing device 412 is a two-component reversal developing device, and attaches a developer of each color component to the surface of the photosensitive drum 413 to visualize the electrostatic latent image and form a toner image.

  For example, a DC developing bias having the same polarity as the charging polarity of the charging device 414 or a developing bias in which a DC voltage having the same polarity as the charging polarity of the charging device 414 is superimposed on an AC voltage is applied to the developing device 412. As a result, reverse development is performed in which toner is attached to the electrostatic latent image formed by the exposure device 411.

  The drum cleaning device 415 is in contact with the surface of the photoconductive drum 413 and has a flat drum cleaning blade made of an elastic material, etc., and remains on the surface of the photoconductive drum 413 without being transferred to the intermediate transfer belt 421. Remove toner.

  The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a plurality of support rollers 423, a secondary transfer roller 424, a belt cleaning device 426, and the like.

  The intermediate transfer belt 421 is an endless belt, and is stretched around a plurality of support rollers 423 in a loop shape. At least one of the plurality of support rollers 423 is configured by a driving roller, and the other is configured by a driven roller. For example, it is preferable that the roller 423A disposed downstream of the K component primary transfer roller 422 in the belt traveling direction is a drive roller. This makes it easy to keep the belt running speed constant in the primary transfer portion. As the driving roller 423A rotates, the intermediate transfer belt 421 travels in the direction of arrow A at a constant speed.

  The intermediate transfer belt 421 is a belt having conductivity and elasticity, and has a high resistance layer on the surface. The intermediate transfer belt 421 is rotationally driven by a control signal from the control unit 101.

  The primary transfer roller 422 is disposed on the inner peripheral surface side of the intermediate transfer belt 421 so as to face the photosensitive drum 413 of each color component. The primary transfer roller 422 is pressed against the photosensitive drum 413 with the intermediate transfer belt 421 interposed therebetween, thereby forming a primary transfer nip for transferring a toner image from the photosensitive drum 413 to the intermediate transfer belt 421.

  The secondary transfer roller 424 is disposed on the outer peripheral surface side of the intermediate transfer belt 421 so as to face the backup roller 423B disposed on the downstream side in the belt traveling direction of the drive roller 423A. The secondary transfer roller 424 is pressed against the backup roller 423B with the intermediate transfer belt 421 interposed therebetween, thereby forming a secondary transfer nip for transferring the toner image from the intermediate transfer belt 421 to the paper S.

  When the intermediate transfer belt 421 passes through the primary transfer nip, the toner images on the photoconductive drum 413 are primarily transferred onto the intermediate transfer belt 421 in sequence. Specifically, a primary transfer bias is applied to the primary transfer roller 422, and an electric charge having a polarity opposite to that of the toner is applied to the back side of the intermediate transfer belt 421, that is, the side in contact with the primary transfer roller 422. It is electrostatically transferred to the intermediate transfer belt 421.

  Thereafter, when the sheet S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to the sheet S. Specifically, a secondary transfer bias is applied to the secondary transfer roller 424, and an electric charge having a polarity opposite to that of the toner is applied to the back side of the sheet S, that is, the side in contact with the secondary transfer roller 424. Is electrostatically transferred to the paper S. The sheet S to which the toner image is transferred is conveyed toward the fixing unit 60.

  The belt cleaning device 426 removes transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer.

  The fixing unit 60 is disposed on the fixing surface of the sheet S, that is, the upper fixing unit 60A having a fixing surface side member disposed on the surface on which the toner image is formed, and on the back surface of the sheet S, that is, on the surface opposite to the fixing surface. A lower fixing unit 60B having a back-side support member, a heating source, and the like. When the back surface side support member is pressed against the fixing surface side member, a fixing nip for nipping and transporting the sheet S is formed.

  The fixing unit 60 fixes the toner image on the paper S by heating and pressurizing the paper S on which the toner image is secondarily transferred and conveyed at the fixing nip. The fixing unit 60 is disposed in the fixing device F as a unit.

  The upper fixing unit 60A includes an endless fixing belt 61, a heating roller 62, and a fixing roller 63, which are fixing surface side members. The fixing belt 61 is stretched between a heating roller 62 and a fixing roller 63.

  The lower fixing unit 60B includes a pressure roller 64 that is a back side support member. The pressure roller 64 forms a fixing nip that sandwiches and conveys the sheet S with the fixing belt 61.

  The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, a transport path unit 53, and the like. In the three paper feed tray units 51a to 51c constituting the paper feed unit 51, paper S (standard paper, special paper) identified based on basis weight, size, etc. is stored for each preset type. . The conveyance path unit 53 includes a plurality of conveyance roller pairs including a registration roller pair 53a. The registration roller portion in which the registration roller pair 53a is disposed corrects the inclination and deviation of the paper S.

  The sheets S stored in the sheet feed tray units 51 a to 51 c are sent one by one from the top and are conveyed to the image forming unit 40 by the conveyance path unit 53. In the image forming unit 40, the toner image on the intermediate transfer belt 421 is secondarily transferred onto one side of the sheet S at a time, and the fixing unit 60 performs a fixing process. The sheet S on which the image has been formed is discharged out of the apparatus by a discharge unit 52 having a discharge roller 52a.

  By the way, when the label paper P is used as a recording medium, when the label paper P passes through the fixing nip, the pressure applied by the fixing nip is large, and the glue of the label paper P is softened by heating. In some cases, the paste protruded from the ends of P, that is, both the left and right ends and the rear end. In this case, there is a problem that the glue that protrudes adheres to the fixing member that forms the fixing nip (in this embodiment, the fixing belt 61 and the pressure roller 64) and stains the fixing member.

  With respect to such a problem, as described above, in the configuration in which the end in the width direction of the label paper P is pressed upstream of the fixing unit 60, the end in the width direction of the label paper P is pressed when the entire paper is pressed by the fixing unit 60. Even if the glue can be prevented from sticking out, the glue may be pushed out from the rear end of the label paper P in the transport direction, and the sticking out may occur.

  Specifically, a configuration in which the glue on the label paper P is pushed into the center in the width direction by the end pressing portion, and a configuration in which the glue on the label paper P is pushed out (extruded) from the end in the width direction by the end pressing portion. In any of the cases, when passing through the fixing nip, there is a problem that the fixing member extrudes from the rear end of the label paper P in the conveying direction and protrudes, and the fixing member is contaminated by the protruding adhesive.

  Therefore, in the present embodiment, as shown in FIGS. 1, 3, and 4, the upstream side of the fixing unit 60 and the image forming unit 40 in the paper conveyance direction of the label paper P (the direction of arrow B in FIG. 3). Further, a pressing unit 80 that presses the entire width of the release sheet in the sheet width direction orthogonal to the sheet conveyance direction is provided. As shown in FIGS. 3 and 4 (FIGS. 4A and 4B), the pressing portion 80 has a pair of upper and lower pressing rollers 82 and 84 that press the entire width of the label paper P from the vertical direction. In the present embodiment, the pressing rollers 82 and 84 are provided on the upstream side of the registration roller pair 53a in the paper transport direction (see FIG. 1), and the registration roller pair 53a is not shown in FIG.

  As shown in FIG. 4A, the pressing rollers 82 and 84 have a width longer than the entire width in the conveyance direction of the label paper P. One of the pressing rollers 82 and 84 is rotationally driven by a driving source such as a motor (not shown).

  Further, scrapers 92 and 94 as removal portions for removing the glue protruding from the label paper P are provided on the pressing rollers 82 and 84 so as to contact the surfaces of the corresponding pressing rollers 82 and 84. The scrapers 92 and 94 have substantially the same width as the corresponding pressing rollers 82 and 84 (see FIG. 4A).

  In the image forming apparatus 1 having such a configuration, when an image is formed on the label paper P, the label paper P is pressed so as to be sandwiched from above and below by the pressing rollers 82 and 84 on the upstream side of the image forming unit 40 in the transport direction. In this state, the sheet is fed toward the image forming unit 40. At this time, as shown in FIG. 4A, the glue P2 between the base material P1 and the release sheet P3 is pushed out of the paper, and is pressed from the ends of the label paper P, that is, the left and right ends and the rear end in the paper transport direction. It protrudes on 82,84. Specifically, the glue P2 that protrudes from both the left and right ends in the paper conveyance direction of the label paper P adheres to the width direction end portions of the pressure rollers 82 and 84 and protrudes from the rear end of the label paper P in the paper conveyance direction. The glue P2 adheres over substantially the entire width direction of the pressing rollers 82 and 84.

  In this manner, the paste P2 that protrudes from the label paper P and adheres to the pressing rollers 82 and 84 is scraped off by the scrapers 92 and 94 that come into contact with the surfaces of the pressing rollers 82 and 84. With this operation, the surfaces of the pressure rollers 82 and 84 to which the paste P2 is attached are cleaned by the scrapers 92 and 94.

  Therefore, according to the image forming apparatus 1, the amount of glue P2 at both the left and right ends and the rear end in the paper conveyance direction of the label paper P is reduced, and the entire label paper P is pressed by the fixing nip so that the glue P2 is at the end (left and right). Even if it is brought close to both ends and the rear end), it is possible to prevent the adhesive P2 from protruding from the sheet and soiling the fixing member.

  In addition, as a structure which removes the glue P2 adhering to the outer peripheral surfaces of the pressing rollers 82 and 84, as shown in FIG. 5, the cleaning webs 97 and 99 are brought into contact with the outer peripheral surfaces of the pressing rollers 82 and 84, and the adhesive P2 is removed. May be wiped off (removed) by the cleaning webs 97 and 99. Cleaning units 96 and 98 are provided in the vicinity of the pressing rollers 82 and 84, respectively. The cleaning unit 96 includes an original winding portion 96A in which a cleaning web 97 made of paper or cloth is wound in a roll shape, a pressing roller 96B that presses the cleaning web 97 fed from the original winding portion 96A against the pressing roller 82, and a cleaning unit 96 And a winding portion 96 </ b> C for winding the subsequent cleaning web 97. The cleaning unit 98 includes an original winding portion 98A in which a cleaning web 99 made of paper or cloth is wound in a roll shape, a pressing roller 98B that presses the cleaning web 99 fed from the original winding portion 98A against the pressing roller 84, and a cleaning unit. And a winding portion 98C for winding the subsequent cleaning web 99.

  In the example shown in FIG. 4, the pressing rollers 82 and 84 have a cylindrical shape, in other words, have an outer shape that extends straight in parallel to the axis.

  On the other hand, as shown in FIG. 6A, the pressing rollers 82 and 84 may have a crown shape, that is, an outer shape in which the outer diameter at the center in the axial direction is larger than the outer diameter at the end in the axial direction. By adopting such a shape, the pressing force of the pressing rollers 82 and 84 becomes smaller from the center side to the end side of the label paper P as shown by the arrows in FIG. Since a force pushing outward from the direction center acts, the paste P2 can be more protruded.

  FIG. 6B shows another configuration example of the pressing rollers 82 and 84. Although FIG. 6B shows only the pressure roller 82 side, the pressure roller 84 has the same configuration, and the configuration of the pressure roller 82 will be described below. As shown in FIG. 6B, the pressing roller 82 has a cylindrical shape that extends straight in parallel to the axis by forming an elastic layer 82B made of silicon rubber or the like on the outer peripheral surface of a cored bar 82A made of aluminum or the like. It has an outer shape.

  Here, the cored bar 82A has the crown shape described in FIG. 6A, that is, a shape in which the outer diameter at the center in the axial direction is larger than the outer diameter at the end in the axial direction. On the other hand, the elastic layer 82B has a shape in which the outer diameter at the center in the axial direction is smaller than the outer diameter at the end in the axial direction. By adopting such a shape, the pressing force of the pressing rollers 82 and 84 becomes smaller from the center side in the width direction of the label paper P toward the end side as in the case of FIG. Since a force pushing outward from the direction center acts, the paste P2 can be more protruded.

  Although not shown, as another configuration example of the pressing roller 82, the cored bar 82A has a cylindrical shape that extends straight in parallel with the axis (see FIG. 4), and the outer shape of the elastic layer 82B also has a shape that extends straight in parallel with the axis, The hardness of the elastic layer 82B may be configured such that the axial center side is higher and the axial end side is lower. Also in such a configuration, the pressing force of the pressing rollers 82 and 84 decreases from the center side to the end side of the label paper P, and a force that pushes the glue P2 outward from the axial center acts. Therefore, more paste P2 can be protruded.

  Next, a configuration for controlling the pressing force of the pressing unit 80 against the label paper P will be described with reference to FIG. As described above, in the present embodiment in which the pressing rollers 82 and 84 are longer than the full width in the transport direction of the label paper P and the full width in the transport direction of the label paper P is pressed, the entire width of the label paper P is reached. The paste P2 is protruded, and the protruded paste P2 can be attached and removed over substantially the entire width of the pressing rollers 82 and 84.

  On the other hand, in such a configuration, when the pressing force of the pressure rollers 82 and 84 against the label paper P is always constant, the size (length, width, thickness) of the label paper P, the amount of glue P2 per unit area, etc. Thus, there may be an excess or deficiency in the amount of glue P2 protruding from the pressing portion 80. Here, when the amount of the paste P2 protruding from the pressing portion 80 is excessively large, the function of the label paper P as a label is lowered, and the release sheet P3 may not be attached to the object. On the other hand, if the amount of glue P2 protruding from the pressing portion 80 is too small, the glue P2 may protrude from the fixing nip as described above, and the fixing member may be soiled.

  Therefore, in the present embodiment, a mechanism for changing the pressing force of the pressing rollers 82 and 84 against the label paper P is provided, and the pressing force is controlled by the control unit 101. Specifically, a known load variable mechanism (see Japanese Patent Application Laid-Open No. 2003-287932, etc.), which includes a stepping motor, a cam, and the like and is provided on the fixing member of the fixing unit 60, is also disposed on the pressing rollers 82 and 84. By controlling the stepping motor with the control unit 101, the pressing force of the pressing rollers 82 and 84 can be adjusted.

  The control unit 101 controls the stepping motor so as to switch the pressing force of the pressing rollers 82 and 84 at the timing (see FIGS. 7A and 7B) when the rear end side in the conveyance direction of the label paper P passes the pressing rollers 82 and 84. . More specifically, the control unit 101 uses the pressing rollers 82 and 84 at a position that assumes the amount of paste P2 that protrudes from the rear end side of the label paper P during conveyance of the label paper P by the pressing rollers 82 and 84. The stepping motor is controlled so that the pressing force is larger than the pressing force before switching.

  By such control, the paste P2 protrudes more on the rear end side in the conveyance direction of the label paper P, and the protruded paste P2 is attached to the pressing unit 80 and removed by the removing unit (not shown in FIG. 7B). In this way, by performing control to switch the pressing force of the pressure rollers 82 and 84 so that the paste P2 at the trailing edge of the sheet is protruded mainly, the glue P2 protrudes from the trailing edge side of the label sheet P at the fixing nip. This can be prevented even better.

  FIG. 7B shows a state in which the pressing force is switched so as to increase the pressing force of the pressing rollers 82 and 84 on the rear end side in the conveyance direction of the label paper P. Here, it is desirable that the pressing force of the pressing rollers 82 and 84 after switching the pressing force is set to be larger than the pressing force of the fixing nip.

  The pressing force of the pressing rollers 82 and 84 may be set to be larger than the pressing force of the fixing nip from the leading edge in the conveyance direction of the label paper P before switching the pressing force, but in this case, the paste P2 protrudes excessively. May end up. Therefore, as described above, it is desirable to switch the pressing force of the pressing rollers 82 and 84 on the rear end side in the conveyance direction of the label paper P so as to be larger than the pressing force of the fixing nip. Further, until the pressing force is switched from the leading end in the conveyance direction of the label paper P, the pressing force of the pressing rollers 82 and 84 is zero, that is, an arbitrary value of the pressing force weaker than the fixing nip from the pressed release state is used. can do.

  Regarding the configuration for switching the pressing force, FIG. 7 illustrates the configuration of the pressing rollers 82 and 84 having a cylindrical outer shape, but the crown-shaped pressing rollers 82 and 84 described in FIG. 6 can also be used. .

  Next, another configuration example of the pressing portion will be described with reference to FIG. The hatched portion in FIG. 8A indicates a range P2a where the paste P2 on the label paper P is to be removed. In this example, as shown in FIG. 8A, the range P2a where the glue P2 is desired to be removed is set in a substantially U shape including both the left and right ends and the rear end in the sheet transport direction of the label paper P.

  When removing the paste P2 in such a range P2a, as shown in FIG. 8B, the pressing portion is provided with an end pressing portion 85 that protrudes the adhesive at the end of the paper in addition to the pressing rollers 82 and 84 described above. Good.

  Here, the end pressing portion 85 is provided with a pair of upper and lower end pressing rollers that press the end of the label paper P from the vertical direction at both ends (left end and right end) of the label paper P in the paper width direction. It is done. FIG. 8B shows only the upper end pressing rollers 85L and 85R, and the lower end pressing rollers have the same configuration. As shown in the drawing, the outer diameters of the upper end pressing rollers 85L and 85R are smaller on the center side than on the end side of the label paper P in the paper width direction. Similarly, the outer diameter of the lower end pressing roller is smaller on the center side than on the end side of the label paper P in the paper width direction.

  Further, a removal portion (scraper or cleaning web) having the same configuration as described above is in contact with each end portion pressing roller of the end portion pressing portion 85, and the removal portion is not shown for simplicity. One of the upper end pressing rollers 85L and 85R or the lower end pressing roller is rotationally driven by a driving source such as a motor (not shown).

  In the example shown in FIG. 8B, each end pressing roller of the end pressing portion 85 is provided on the upstream side of the pressing rollers 82 and 84 in the paper transport direction. As another example, each end pressing roller of the end pressing unit 85 may be provided on the downstream side of the pressing rollers 82 and 84 in the paper transport direction.

  Each end pressing roller of the end pressing portion 85 configured as described above has the end of the label paper P so that the pressing force decreases from the center side to the end side of the label paper P in the paper width direction. Press the part. By such pressing, the glue P2 positioned between the base material P1 and the release sheet P3 is pushed from the center side to the end side of the label paper P in the paper width direction and protrudes from the end portion. The protruding paste P2 adheres to the outer peripheral surfaces of the end pressing rollers 85L and 85R, and the attached adhesive P2 is removed by a removing portion (such as a scraper) provided so as to contact the outer peripheral surface.

  On the other hand, as described with reference to FIG. 7, the pressing force of the pressing rollers 82 and 84 against the label paper P is controlled by the control unit 101. That is, the control unit 101 switches the pressure by the pressing rollers 82 and 84 (increases the pressing force) at a position that assumes the amount of the adhesive P2 that protrudes during the conveyance of the label paper P, thereby increasing the adhesive P2 on the rear end side of the sheet. The adhesive paste P2 that protrudes adheres to the pressing portion 80 and is removed by a removing portion (not shown in FIG. 8B).

  With this configuration, the glue P2 in the substantially U-shaped range P2a including the left and right ends and the rear end in the sheet conveyance direction of the label paper P protrudes from the label paper P and is removed. The fixing nip can prevent the paste P from protruding from the left and right ends and the rear end in the conveyance direction of the label paper P. In addition, according to such a configuration, the paste P2 in the center region of the label paper P can be left, and the paste P2 can be easily pushed out from the label paper P without excess or deficiency.

  FIG. 9 shows another configuration example of the label paper P. 4 to 8 exemplify the label paper P having a configuration in which the substrate P1 and the release sheet P3 have the same shape, that is, the release sheet P3 is disposed on the entire surface of the substrate P1.

  On the other hand, as shown in FIG. 9, the label paper P has a configuration in which the release sheet P3 is smaller than the base material P1 and is disposed on a part of the base material P1. In the label paper P illustrated in FIG. 9, two release sheets P3 are arranged on a base material P1 at predetermined positions. In such a case, the control of the position for switching the pressing force of the pressing unit 80 may be performed with reference to the rear end of each release sheet P3.

  As described above in detail, according to the image forming apparatus 1, when the fixing process is performed on the label paper P that is a cut sheet, the fixing member is prevented from being soiled by the glue P2 included in the label paper P. Can do.

  In the above-described embodiment, as the pressing unit 80, when the label paper P is pressed, the configuration in which the pressing force decreases from the center side to the end side in the paper width direction is illustrated. As another example, in the opposite case, that is, when the label paper P is pressed, the pressing force may be increased from the center side to the end side in the paper width direction. In this case, for example, the pressing rollers 82 and 84 may have a reverse crown shape.

  In addition, each of the above-described embodiments is merely an example of actualization in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the gist or the main features thereof.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 40 Image forming part 50 Paper conveyance part 60 Fixing part 80 Press part 82,84 Press roller 92,94 Scraper (removal part)
97,99 Cleaning web (removal part)
101 Control Unit P Label Paper P1 Base Material P2 Glue P3 Release Sheet

Claims (5)

In the paper transport direction of the label paper, which is a cut paper with a release sheet coated with glue on the back surface, provided on the upstream side of the fixing unit for fixing the unfixed toner image on the label paper, A pressing portion that presses the entire width of the release sheet in the paper width direction orthogonal to the paper transport direction;
A removing unit that removes the glue protruding from the paper by the pressing of the pressing unit,
Antifouling device. The pressing portion is a pair of upper and lower pressing rollers that press the entire width of the label paper from the vertical direction,
The removing portion removes the protruding glue by being brought into contact with the surface of the pressing roller,
The antifouling device according to claim 1. A control unit for controlling the pressing force of the pressing unit against the label paper;
The control unit is configured to increase the pressing force of the pressing unit at a timing when the rear end side in the conveyance direction of the label paper passes the pressing unit.
The antifouling device according to claim 1 or 2. The pressing portion is configured such that when the label paper is pressed, the pressing force decreases from the center side to the end side in the paper width direction.
The antifouling device according to any one of claims 1 to 3. The antifouling device according to any one of claims 1 to 4,
An image forming unit that forms an image on the label paper;
Image forming apparatus.

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