JP2016161856A - Sheet posture adjustment unit, fixation device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform highly reliable sheet posture adjustment for preventing the center part of a sheet from entering a fixation nip prior to entrance of both end parts.SOLUTION: A sheet posture adjustment device for adjusting the posture of a sheet entering a fixation nip comprises: a guide member which is composed of a flexible plate-like member provided in the vicinity of the fixation nip on the upstream side in the sheet conveyance direction with respect to the fixation nip and guides the sheet with the upper surface thereof; regulation members which are arranged on the ends of the guide member on both sides of a sheet conveyance path and regulate the sheet conveyance path; and a drive part which drives the regulation members so as to change the interval between the regulation members. When the sheet enters the fixation nip, the drive part drives the regulation members so as to narrow the interval, and the driven regulation members press the guide member to curve the guide member into a circular arc shape.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a sheet orientation adjusting device, a fixing device, and an image forming apparatus.

  In general, an image forming apparatus (printer, copier, facsimile, etc.) using an electrophotographic process technology generates an electrostatic latent image by irradiating (exposing) a charged photoconductor with a laser beam based on image data. Form. Then, by supplying toner from the developing device to the photosensitive member (image carrier) 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 paper, it is fixed by heating and pressurizing to form an image on the paper.

  The fixing device for fixing the toner image transferred to the paper includes a fixing surface side member such as a fixing roller and a fixing belt disposed on the fixing surface side, and a back surface side such as a pressure roller and a pressure belt disposed on the back surface side. A fixing member including a supporting member, a heat source, and the like, and the fixing surface side member and the back surface side supporting member are pressed against each other to form a fixing nip for nipping and conveying the sheet.

  FIG. 8 is a perspective view illustrating an example of a configuration of a main part of a conventional fixing device. The fixing device 500 shown in the figure includes a fixing roller 501, a pressure roller 502, a fixing intrusion guide 503, and two regulation plates 504. In the fixing device 500, the fixing roller 501 and the pressure roller 502 are pressed against each other to form a fixing nip 506. The fixing intrusion guide 503 is a plate-like member having the same width (length in the axial direction) as that of the fixing roller 501 or the pressure roller 502, and an opening is provided at the center thereof, and upward from the opening. An actuator 505 is projected. The fixing rush guide 503 guides the paper S that rushes into the fixing nip 506. The actuator 505 detects the sheet S and slightly lifts the central portion of the sheet S, thereby facilitating the entry of the sheet S into the fixing nip 506. The two restriction plates 504 restrict the displacement of the sheet S in the sheet conveyance path width direction (hereinafter simply referred to as “width direction”) by restricting the sheet conveyance path, and both ends of the fixing intrusion guide 503 in the width direction. It is arranged in contact with.

  In the fixing device 500, when the paper S on which the toner image has been transferred is conveyed, the paper S on the fixing intrusion guide 503 is detected by the actuator 505. The sheet S enters the fixing nip 506 in a state where its central portion is lifted by the action of the actuator 505, and is heated and pressurized in the fixing nip 506. As a result, the toner image is fixed on the sheet S.

  As an image forming apparatus having a fixing rush guide in the fixing device, there is one described in Patent Document 1, for example. Further, as an image forming apparatus having a regulating plate in the fixing device, for example, there is one described in Patent Document 2. The image forming apparatus described in Patent Document 1 includes a fixing rush guide having a protruding portion formed at the center, and the protruding portion of the fixing rush guide is changed according to the basis weight and the paper size (so that it rises up). ) To adjust the orientation of the paper. The image forming apparatus described in Patent Document 2 adjusts the posture of the paper by changing the interval between the both-end restricting plates before the paper enters the fixing nip and directly pushing the paper with the both-end restricting plates. I have to.

JP 2003-084595 A JP 2014-157329 A

  In the fixing device 500 described above, the actuator 505 provided in the fixing entry guide 503 lifts the central portion of the paper S, so that the central portion of the paper S easily enters the fixing nip 506 before both ends. When the central portion of the paper S first enters the fixing nip 506, a force that pulls the paper S from the both ends to the central side acts in the fixing nip 506, which causes the paper S to swell, paper wrinkles, or wrinkles (hereinafter referred to as the paper S). , Simply called “paper wrinkles”).

  FIG. 9 is a perspective view illustrating a state before and after the sheet S enters the fixing nip 506. (A) in the figure is a state immediately before the leading edge of the sheet S enters the fixing nip 506, and (b) in the same figure is a state immediately after the leading edge of the sheet S enters. FIG. 10 is a view of FIG. 9B as viewed from above. In FIG. 9, the sheet S conveyed along the conveyance direction y <b> 1 is lifted by the actuator 505 and then enters the fixing nip 506 from the center portion Sc at the leading end. At the moment when the center portion Sc of the leading end that has entered the fixing nip 506 is held by the fixing nip 506, a difference in sheet speed (corresponding to the length of the arrow y2 in FIG. 10) occurs in the width direction, and at the center portion Sc of the leading end. An external force that is drawn toward (in the direction of the arrow y3 in FIG. 10) acts on the paper S. As a result, the paper S undulates and the wrinkle 600 is generated.

  Regarding such a problem, as in the image forming apparatus described in Patent Document 1, even when the paper posture is adjusted by controlling the rising of the protruding portion of the fixing rush guide, the paper is bent depending on the direction and stiffness of the paper. Since the posture becomes unstable, the paper wrinkles as described above may eventually occur. Further, as in the image forming apparatus described in Patent Document 2, even if the paper posture adjustment is performed by directly pressing the paper with the gap between the both end regulating plates being narrowed, the paper may be bent or the paper may be bent unexpectedly. There is also a possibility that jam may occur due to the above. In other words, both the technique of Patent Document 1 and the technique of Patent Document 2 have certain limitations in terms of improving the reliability of paper posture adjustment.

  The present invention provides a sheet orientation adjusting device, a fixing device, and an image forming apparatus that can perform sheet orientation adjustment that prevents the central portion of the sheet from entering the fixing nip before both end portions with high reliability. Objective.

The paper posture adjusting apparatus according to the present invention is
A paper orientation adjusting device that adjusts the orientation of the paper entering the fixing nip,
A flexible plate-like member provided in the vicinity of the fixing nip on the upstream side in the paper conveyance direction with respect to the fixing nip, and a guide member for guiding the paper by its upper surface;
A regulating member that is disposed at an end of the guide member on both sides of the paper conveyance path and regulates the paper conveyance path;
A drive unit that drives the restriction member to change the interval between the restriction members;
Have
When the sheet enters the fixing nip, the driving unit drives the restricting member so as to narrow the interval, and the driven restricting member presses the guide member to make the guide member into an arc shape. Curve.

The fixing device according to the present invention includes:
The paper attitude adjusting device;
A fixing surface side member and a back surface side member forming the fixing nip;
Have

An image forming apparatus according to the present invention is
The fixing device is provided.

  According to the present invention, it is possible to perform the paper posture adjustment that prevents the paper from entering the fixing nip first from the central portion of the paper, so that paper wrinkles do not occur.

1 is a diagram schematically showing an overall configuration of an image forming apparatus according to an embodiment of the present invention. 2 is a block diagram illustrating a main part of a control system of the image forming apparatus. FIG. FIG. 3 is a perspective view illustrating a main part configuration of the fixing device. It is a figure for demonstrating the shape change of a fixing rush guide. FIG. 5 is a perspective view illustrating a state before and after a sheet enters a fixing nip. FIG. 5 is a view of the state after the paper has entered the fixing nip as viewed from above. It is a figure which shows the conditions which change the shape of the fixing rush guide. FIG. 10 is a perspective view illustrating an example of a configuration of a main part of a conventional fixing device. It is a figure for demonstrating the subject of the fixing device of FIG. It is a figure for demonstrating the subject of the fixing device of FIG.

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 an embodiment of the present invention. FIG. 2 is a block diagram showing the main part of the control system of the image forming apparatus 1 according to the present embodiment. An image forming apparatus 1 shown in FIGS. 1 and 2 is an intermediate transfer type color image forming apparatus using electrophotographic process technology. In other words, the image forming apparatus 1 transfers Y (yellow), M (magenta), C (cyan), and K (black) toner images formed on the photosensitive drum 413 to an intermediate transfer belt (first transfer member). The image is transferred (primary transfer) to 421, and the four color toner images are superimposed on the intermediate transfer belt 421, and then transferred (secondary transfer) to the paper S to form an image.

  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, a storage unit 70, a communication unit 80, An actuator 90, a regulation plate drive unit 91 (drive unit), and a control unit 100 are provided.

  The control unit 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, and the like. The CPU 101 reads a program corresponding to the processing content from the ROM 102 and develops it in the RAM 103, 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 70 are referred to. The storage unit 70 is configured by, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive.

  The control unit 100 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 80. Do. For example, the control unit 100 receives image data transmitted from an external device, and forms an image on the paper S based on the image data (input image data). The communication unit 80 is configured by 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 a 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.

  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, an image status display, an operation status of each function, and the like in accordance with a display control signal input from the control unit 100. 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 100.

  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 100. 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.

  The image forming unit 40 is based on the input image data, and image forming units 41Y, 41M, 41C, 41K, and an intermediate transfer unit 42 for forming an image using colored toners of Y component, M component, C component, and K component. Etc. 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 photosensitive drum 413 has an undercoat layer (UCL) and a charge generation layer (CGL) on the peripheral surface of an aluminum conductive cylinder (aluminum tube) having a drum diameter of 80 mm, for example. It is a negatively charged organic photoconductor (OPC) in which a generation layer (CTL) and a charge transport layer (CTL) are sequentially stacked. The charge generation layer is made of an organic semiconductor in which a charge generation material (for example, phthalocyanine pigment) is dispersed in a resin binder (for example, polycarbonate), and generates a pair of positive charges and negative charges by exposure by the exposure device 411. The charge transport layer consists of a material in which a hole transport material (electron donating nitrogen-containing compound) is dispersed in a resin binder (eg, polycarbonate resin), and transports positive charges generated in the charge generation layer to the surface of the charge transport layer. To do.

  The control unit 100 controls a drive current supplied to a drive motor (not shown) that rotates the photosensitive drum 413, so that the photosensitive drum 413 rotates at a constant peripheral speed.

  The charging device 414 uniformly charges the surface of the photoconductive drum 413 to a negative polarity. 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. A positive charge is generated in the charge generation layer of the photosensitive drum 413 and is transported to the surface of the charge transport layer, whereby the surface charge (negative charge) of the photosensitive drum 413 is neutralized. An electrostatic latent image of each color component is formed on the surface of the photosensitive drum 413 due to a potential difference from the surroundings.

  The developing device 412 is, for example, a two-component developing type developing device, and visualizes an electrostatic latent image by attaching toner of each color component (oilless toner containing wax in toner particles) to the surface of the photosensitive drum 413. Thus, a toner image is formed. The drum cleaning device 415 includes a drum cleaning blade that is slidably contacted with the surface of the photosensitive drum 413, and removes transfer residual toner remaining on the surface of the photosensitive drum 413 after primary transfer.

  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 (second transfer member) 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 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 a roller 423B (hereinafter referred to as “backup roller 423B”) disposed on the downstream side of the driving roller 423A in the belt traveling direction. 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 (transfer nip) for transferring the toner image from the intermediate transfer belt 421 to the paper S. The

  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 (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, the toner image is applied by applying a secondary transfer bias to the secondary transfer roller 424 and applying a charge having a polarity opposite to that of the toner to the back side of the paper S (the side in contact with the secondary transfer roller 424). Is electrostatically transferred onto the paper S. The sheet S to which the toner image is transferred is conveyed toward the fixing unit 60.

  The belt cleaning unit 426 includes a belt cleaning blade that is in sliding contact with the surface of the intermediate transfer belt 421 and removes transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer. Instead of the secondary transfer roller 424, a configuration (so-called belt-type secondary transfer unit) in which a secondary transfer belt is looped around a plurality of support rollers including the secondary transfer roller is adopted. Also good.

  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 transferred and conveyed.

  In the fixing unit 60, a fixing roller 61, which is a fixing surface side member, is disposed on the surface side on which the toner image of the paper S is formed, and is a back surface side member on the back surface (surface opposite to the fixing surface) side of the paper S. A pressure roller 62 is disposed. The pressure roller 62 is pressed against the fixing roller 61 with a predetermined fixing load (for example, 1000 [N]). When the pressure roller 62 is in pressure contact with the fixing roller 61, a fixing nip 65 is formed between the fixing roller 61 and the pressure roller 62 so as to sandwich and convey the paper S. The fixing roller 61 incorporates a heating source (for example, a halogen heater), and the fixing roller 61 is heated by this heating source. The fixing roller 61 contacts the paper S on which the toner image is formed, and heat-fixes the toner image on the paper S at a fixing temperature (for example, 160 to 200 [° C.]).

  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, or the like is stored for each preset type. . The conveyance path unit 53 includes a plurality of conveyance roller pairs such as registration roller pairs 53a.

  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. At this time, the registration roller portion provided with the registration roller pair 53a corrects the inclination of the fed paper S and adjusts the conveyance timing. 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.

  FIG. 3 is a perspective view illustrating a configuration of a main part of the fixing device incorporated in the image forming apparatus 1. The fixing device shown in the figure includes a fixing roller 61 (fixing surface side member), a pressure roller 62 (back surface side member), a fixing inrush guide (guide member) 63, two restriction plates (regulation members) 64, And an actuator 90.

  The fixing rush guide 63 is a flexible plate-like member made of, for example, SUS, and guides the paper S by its upper surface. The fixing intrusion guide 63 adjusts the orientation of the sheet S on the upper surface (loop formation) by bending the section in the sheet transport direction (hereinafter simply referred to as “cross section”) into an arc shape, while controlling the sheet S. It is guided to the fixing nip 65 and enters the fixing nip 65, and is arranged upstream of the fixing nip 65 in the sheet conveyance direction. The width of the fixing entry guide 63 is approximately the same as the axial length of the fixing roller 61 or the pressure roller 62, and the thickness of the fixing entry guide 63 is, for example, 0.3 mm. An opening is provided in the central portion of the fixing rush guide 63, and an actuator 90 is projected from the opening. The actuator 90 detects the arrival of the paper S, and outputs a detection signal indicating the detection result to the control unit 100.

  The two restriction plates 64 are disposed in contact with both ends of the fixing intrusion guide 63 (ends on both sides of the sheet conveyance path) so as to restrict the displacement in the width direction of the sheet S by regulating the sheet conveyance path. Each regulating plate 64 is configured to be able to advance and retreat in the width direction, that is, to change the interval between the regulating plates 64. Specifically, each regulating plate 64 is pushed toward the center or pulled back by the regulating plate drive unit 91 (see FIG. 4). When the arrival of the sheet S by the actuator 90 is detected by the actuator 90 (that is, when the sheet S is about to enter the fixing nip 65), the restriction plate driving unit 91 moves the restriction plates 64 so as to narrow the interval between the restriction plates 64. To drive. When the restricting plates 64 are driven in this manner, the fixing rush guides 63 interposed therebetween are pressed, and the fixing rush guides 63 are curved into an arc shape by the pressing force received from the restricting plates 64. At this time, the fixing intrusion guide 63 has a middle concave shape in which both end portions rise upward from the central portion and the central portion is recessed.

  The combination of the fixing inrush guide 63, the restricting plate 64, and the restricting plate driving unit 91 constitutes a paper posture adjusting device that adjusts the posture of the paper S that enters the fixing nip 65.

  FIG. 4 is a diagram showing a change in the cross-sectional shape of the fixing rush guide 63. The left side of the figure shows the cross-sectional shape of the fixing rush guide 63 at normal time, that is, when the curve is not curved, and the right side of the figure shows the cross section of the fixing rush guide 63 when bent. If the height of the central portion at the normal time is the reference height, the height of the central portion is the same as the reference height at the time of bending. In other words, when the fixing rush guide 63 is pushed toward the center (in the direction of the arrow Y1) by the restricting plate 64, both ends of the fixing rush guide 63 are pushed up (in the direction of the arrow Y2) while fixing. The height position of the central portion of the entry guide 63 is unchanged. If the reference height of the central portion of the fixing rush guide 63 changes, the distance between the paper S and the actuator 90 is not always constant, and accordingly, the accuracy of paper detection by the actuator 90 becomes unstable, which is desired. This is because the loop formation may not be performed. If the desired loop is not formed, the trailing edge of the sheet may jump up when the sheet S enters the fixing nip 65, which may cause image blurring. Therefore, by not changing the height of the central portion of the fixing rush guide 63, it is possible to more reliably suppress the occurrence of a rush failure to the fixing nip 65.

  In FIG. 4, when the 360 mm-wide fixing intrusion guide 63 is pressed by the restriction plate 64, both end portions are raised by 2.5 mm, thereby showing that the apparent width becomes 359 mm. These dimensions are merely examples, and various changes can be made.

  In FIG. 4, the restriction plate driving unit 91 includes an elastic support member (for example, a spring) that presses the restriction plate 64 against the fixing intrusion guide 63 and a cam mechanism (not shown) that moves the elastic support member in the width direction. Composed.

  The effect of the change in the shape of the fixing rush guide 63 will be described with reference to FIGS. FIG. 5 is a perspective view showing a state before and after the sheet S enters the fixing nip 65, and FIG. 6 is a top view of the state after the sheet enters the fixing nip 65.

  Since the sheet S conveyed to the fixing rush guide 63 along the conveyance direction Y3 follows the shape of the fixing rush guide 63, the sheet S also has a shape in which both ends thereof are lifted above the central portion (that is, a center recess). Shape) ((a) of FIG. 5). Since the shape of the sheet S is a concave shape, both end portions Se of the leading end of the sheet S enter the fixing nip 65 before the central portion. When both end portions Se of the leading end enter the fixing nip 65 and are pinched, a difference in paper speed (corresponding to the length of the arrow Y4 in FIG. 6) occurs in the width direction, and both end portions Se of the leading end are separated. An external force that pulls away in the direction of the arrow Y5 in FIG. As a result, the paper S is tensioned in the width direction, so that generation of paper wrinkles can be prevented.

  In addition, after the both end portions Se of the leading edge of the sheet S enter the fixing nip 65, the restricting plate driving unit 91 retracts the restricting plates 64 (that is, in order to prevent the trailing end of the sheet from jumping more reliably (that is, It is preferable to widen the interval between the regulating plates 64 to stop the pressing from the regulating plate 64 against the fixing rush guide 63 and restore the fixing rush guide 63 to a normal flat shape by its own restoring force.

  FIG. 7 is a diagram showing conditions for changing the shape of the fixing inrush guide 63. In the figure, “◯” indicates that it can be used in a flat state, and “Δ” indicates that the shape is changed depending on conditions. Further, “×” indicates that the shape is always changed and used. As illustrated, for example, the paper type is “uncoated paper” or “coated paper”, the basis weight is “128 gsm” or “129 gsm”, and the paper size is “A4”. Alternatively, it is possible to determine whether or not the fixing rush guide 63 is a shape change based on whether it is “A3”. As for “Δ”, the fixing intrusion guide 63 is formed in a concave shape under the following conditions.

Environment: thin paper and high temperature and humidity Coverage: 200%
Curl amount: Large Print mode: During double-sided printing (because the amount of curl increases during double-sided printing)

  According to the embodiment configured as described above, when the sheet S enters the fixing nip 65, the restriction plate driving unit 91 drives and drives the restriction plate 64 so as to narrow the interval between the restriction plates 64. The restricting plate 64 presses the fixing rush guide 63 to bend the fixing rush guide 63 into an arc shape. For this reason, the shape of the sheet S on the fixing intrusion guide 63 also has a stable arc shape, and the both ends Se of the leading edge of the sheet S surely enter the fixing nip 65 before the central portion of the leading edge of the sheet S. . That is, it is possible to reliably prevent the central portion of the leading edge of the paper S from entering the fixing nip 65 before both the end portions Sc of the leading edge of the paper S, and to suppress the occurrence of paper wrinkles.

  The above-described embodiment is merely an example of the implementation of the present invention, and the technical scope of the present invention should not be construed in a limited manner. That is, the scope of the present invention is shown not by the above description but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

  For example, in the above embodiment, assuming that a so-called “upwardly convex” fixing nip 65 is formed in which the flesh of the fixing roller 61 is slightly crushed by the pressure contact with the pressure roller 62, the curved sheet S has a concave shape. The arcuate shape of the fixing entry guide 63 at the time of bending is made to be a middle concave shape. When adopting a so-called “down-convex” fixing nip in which the pressure roller 62 is slightly crushed by the pressure contact with the fixing roller 61, the curved sheet S is curved so that the curved sheet S has a middle convex shape. The arc shape of the fixing entry guide 63 may be a middle convex shape.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image reading part 20 Operation display part 21 Display part 22 Operation part 30 Image processing part 40 Image forming part 50 Paper conveyance part 60 Fixing part 61 Fixing roller 62 Pressure roller 63 Fixing intrusion guide 64 Regulating plate 65 Fixing nip 70 Storage Unit 80 Communication Unit 90 Actuator 91 Restriction Plate Drive Unit 100 Control Unit 101 CPU
102 ROM
103 RAM
F fixing device S paper

Claims (5)

A paper orientation adjusting device that adjusts the orientation of the paper entering the fixing nip,
A flexible plate-like member provided in the vicinity of the fixing nip on the upstream side in the paper conveyance direction with respect to the fixing nip, and a guide member for guiding the paper by its upper surface;
A regulating member that is disposed at an end of the guide member on both sides of the paper conveyance path and regulates the paper conveyance path;
A drive unit that drives the restriction member to change the interval between the restriction members;
Have
When the sheet enters the fixing nip, the driving unit drives the restricting member so as to narrow the interval, and the driven restricting member presses the guide member to make the guide member into an arc shape. Curving,
Paper orientation adjustment device. After the sheet enters the fixing nip, the driving unit drives the regulating member to widen the interval, and the guide member bent into an arc shape by flexibility is flattened by the restoring force of the guide member. To restore,
The sheet orientation adjusting apparatus according to claim 1. The central portion of the curved guide member between the regulating members has the same height position when curved and when not curved.
The sheet orientation adjusting device according to claim 1 or 2. A sheet orientation adjusting device according to any one of claims 1 to 3,
A fixing surface side member and a back surface side member forming the fixing nip;
A fixing device.   An image forming apparatus comprising the fixing device according to claim 4.

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