JP2019003124A - Image forming apparatus and sheet conveyance control method - Google Patents

Abstract

To provide an image forming apparatus and a sheet conveyance control method that can form images on both sides of a long sheet without increasing the size of the apparatus.SOLUTION: An image forming apparatus comprises a path that branches, as both-side conveyance paths, into a first both-side path connected to the upstream of an image forming unit in a main conveyance path, and a second both-side conveyance path folding back before being connected to the main conveyance path. When the image forming apparatus forms toner images on both sides of a long sheet, a conveyance control unit controls the long sheet to pass through one of the first and second both-side paths.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus and a paper conveyance control method.

  Conventionally, an image forming apparatus that forms an image on a sheet using toner is known. In such an image forming apparatus, in order to be able to form an image on both sides by reversing the front and back sides of the paper, a conveyance path is configured to reverse the front and back of the paper by switching back and forth (that is, reverse) in the front and back directions of the paper. Some have a reversing conveyance path (see, for example, Patent Document 1).

  In the conventional image forming apparatus, a sheet having a size that can be stored in the sheet feed tray unit can be switched back through the reverse conveyance path.

JP 2006-124100 A

  In recent years, there is an increasing demand for sheets that are called long paper exceeding the size that can be stored in the paper feed tray unit so that images can be formed on both sides. On the other hand, in realizing double-sided printing of long paper, there are problems in increasing the size of the apparatus associated with increasing the length of the reverse conveyance path, and measures against jamming that is likely to occur compared to standard paper.

  In many image forming apparatuses, a space is secured by hanging a sheet from the opening of the apparatus at the time of the above switchback. On the other hand, in such a configuration, for example, a main body unit in which an image forming unit is disposed between a plurality of units, and an automatic duplex reversing transport unit (Auto Duplex Unit, hereinafter referred to as “ADU”) in which the reversing transport path is configured. ) And a job is stopped and the job is stopped, a phenomenon may occur in which the paper is torn off when the paper is removed. Such a phenomenon (so-called guillotine) is not preferable because the remaining portion of the sheet remains in the apparatus and causes a further jam of the subsequent sheet due to the remaining portion.

  In order to prevent such a paper tearing phenomenon, it is conceivable to secure a large opening of the apparatus. On the other hand, such a configuration can increase the size of the apparatus main body or ensure sufficient rigidity of the apparatus main body. There is a possibility of disappearing.

  An object of the present invention is to provide an image forming apparatus and a paper conveyance control method capable of forming images on both sides of a long sheet without increasing the size of the apparatus.

An image forming apparatus according to the present invention includes:
An image forming unit for forming a toner image on a long paper;
A fixing unit for fixing the toner image formed on the long paper;
A main conveyance path for conveying the long paper to the image forming unit and the fixing unit;
Branches from the downstream side of the fixing unit in the main conveyance path in the conveyance direction, and reverses the conveyance direction of the long paper at a switchback point so that the front and back of the long paper are reversed to the upstream side of the image forming unit. A double-sided conveyance path
A conveyance control unit for controlling conveyance of the long paper,
The double-sided conveyance path branches into a first double-sided path connected to the upstream side of the image forming unit in the main conveying path and a second double-sided path folded back before connecting to the main conveying path,
When the toner image is formed on both sides of the long paper, the conveyance control unit controls the long paper to pass through one of the first and second double-side paths.

The paper transport control method according to the present invention includes:
In order for the image forming unit to form an image on both sides of a long paper whose length in the transport direction is a predetermined length or more, a path in the transport direction before the transport direction of the long paper is reversed at the switchback point, A paper conveyance control method in an image forming apparatus comprising a double-sided conveyance path branched into a first double-sided path connected to the upstream side of the image forming unit and a second double-sided path folded before being connected to a main conveyance path. And
When a toner image is formed on both sides of the long paper, the long paper is conveyed so as to pass through one of the first and second double-side paths.

  According to the present invention, images can be formed on both sides of a long sheet without increasing the size of the apparatus.

1 is a configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment. FIG. 2 is a diagram illustrating a main part of a control system in the image forming apparatus of FIG. 1. It is a figure which expands and shows the conveyance path | route for double-sided printing containing ADU. It is a figure explaining the case where double-sided printing is performed on a long paper. FIG. 10 is a diagram illustrating a case where an image is formed on the back side of a sheet by passing a long sheet through a first double-side path. It is a figure explaining the case where double-sided printing is performed on a long paper, and shows the state of the long paper LS after switchback. It is a figure explaining the case where double-sided printing is performed through a 2nd double-side path | route, and the state of the long paper LS before switchback is shown. 6 is a flowchart illustrating a sheet conveyance process of the image forming apparatus according to the present embodiment.

  Embodiments of an image forming apparatus to which the present invention is applied will be described below 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 shows the main part of the control system of the image forming apparatus 1 in the present embodiment.

  The image forming apparatus 1 according to the present embodiment is an apparatus that uses long paper LS or paper S (non-long paper) as a recording medium and forms an image on the long paper LS or paper S.

  In the present embodiment, the long paper LS is a sheet having a longer length in the transport direction than commonly used A4 size paper, A3 size paper, etc., and is stored in the paper feed tray units 51a to 51c. Has a length that cannot be. The size of the long paper LS, that is, the dimension such as the length in the transport direction is stored as definition data in the memory of the apparatus. Hereinafter, when simply referred to as “paper”, both the long paper LS and the paper S may be included.

  The image forming apparatus 1 is an intermediate transfer type color image forming apparatus using 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 superimposed on the intermediate transfer belt 421, the toner images are formed by secondary transfer onto the paper.

  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 100.

  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 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 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 71. Do. For example, the control unit 100 receives image data transmitted from an external device, and forms a toner image on a sheet based on the image data (input image data). The communication unit 71 is composed of a communication control card such as a LAN card, for example.

  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 the display unit 21 and the 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 LUT) in the storage unit 72 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 description, common components are denoted by the same reference numerals, and in order to distinguish each, Y, M, C, or K is added to the reference numerals. 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, for example, an undercoat layer (UCL), a charge generation layer (CGL), a charge transport layer (CGL) on the peripheral surface of an aluminum conductive cylinder (aluminum tube). It is a negatively charged organic photoreceptor (OPC: Organic Photo-conductor) in which CTL (Charge Transport Layer) is sequentially laminated. 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 (for example, 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 the drive current supplied to a drive motor (not shown) that rotates the photosensitive drum 413 to rotate the photosensitive drum 413 at a constant peripheral speed (linear 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 forms a toner image by visualizing the electrostatic latent image by attaching toner of each color component to the surface of the photosensitive drum 413.

  The drum cleaning device 415 includes a drum cleaning blade (hereinafter simply referred to as a cleaning blade) as a cleaning member that is in sliding contact with the surface of the photosensitive drum 413. The drum cleaning device 415 removes the transfer residual toner remaining on the surface of the photosensitive drum 413 after the primary transfer with a cleaning blade.

  The intermediate transfer unit 42 includes an intermediate transfer belt 421 as an image carrier, 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 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 (the side in contact with the primary transfer roller 422). It is electrostatically transferred to the intermediate transfer belt 421.

  Thereafter, when the sheet passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to the sheet. Specifically, 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 (the side in contact with the secondary transfer roller 424), the toner image becomes It is electrostatically transferred to the paper. The sheet on which the toner image has been transferred is conveyed toward the fixing unit 60.

  The belt cleaning device 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 is arranged on the upper fixing unit 60A having a fixing surface side member arranged on the fixing surface (surface on which the toner image is formed) side of the paper, and on the back surface (surface opposite to the fixing surface) side of the paper. A lower fixing unit 60B having a back-side support member and a heating source 60C. When the back surface side support member is pressed against the fixing surface side member, a fixing nip for nipping and transporting the sheet is formed.

  The fixing unit 60 fixes the toner image on the sheet by secondarily transferring the toner image and heating and pressurizing the conveyed sheet at the fixing nip. The fixing unit 60 is disposed in the fixing device F as a unit. The fixing device F is provided with an air separation unit 60D that separates the sheet S from the fixing surface side member by blowing air.

  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 (rigidity), size, etc. is set for each preset type. Be contained. The conveyance path unit 53 includes a plurality of conveyance rollers such as a pair of registration rollers 53a, a double-sided conveyance path for forming an image on both sides of a sheet, and the like. Details of the transport path unit 53 will be described later.

  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 a fixing process is performed in the fixing unit 60. 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.

  Next, the conveyance path unit 53 will be described in detail.

  The conveyance path unit 53 is a path through which a sheet forms an image on one side (upper surface) thereof, and includes a main conveyance path 530 through which a sheet on which an image is formed by the image forming unit 40 is conveyed. . The main conveyance path 530 is a path for conveying a sheet from the upstream side in the conveyance direction via the registration roller 53a (registration nip), the secondary transfer nip of the image forming unit 40, and the fixing unit 60 (fixing nip). The conveyance path unit 53 includes a reverse conveyance path 533 that reverses the front and back of the sheet.

  The conveyance path unit 53 is fed from an external sheet feeding conveyance path 531 that conveys a sheet such as a long sheet LS fed from the external sheet feeding port 2a to the main conveyance path 530, and the sheet feeding tray units 51a to 51c. A paper feed conveyance path 532 is provided for conveying the sheet S to the main conveyance path 530.

  The main transport path 530 is provided above the paper feed tray units 51 a to 51 c inside the apparatus main body 2 and extends from one side of the apparatus main body 2 to the other side. One end of the main transport path 530 is connected to the external paper feed transport path 531 and the paper feed transport path 532. The other end of the main transport path 530 is connected to the discharge port of the paper discharge unit 52 provided on the other side of the apparatus main body 2.

  One end of the external sheet feed conveyance path 531 is connected to the external sheet feed port 2 a, and the other end is connected to the main conveyance path 530. The paper feed conveyance path 532 is provided in the vicinity of one side in the apparatus main body 2, and extends in the vertical (substantially vertical) direction from the paper feed tray units 51 a to 51 c to the main conveyance path 530. In the paper feed conveyance path 532, an unillustrated open / close door provided on one side of the apparatus main body 2 is opened, so that a part of the path of the paper feed conveyance path 532 is exposed to the outside, jam processing, etc. Is possible. The paper feed transport path 532 has an upper end connected to the main transport path 530 and a lower end connected to the paper feed tray units 51a to 51c.

  The reverse conveyance path 533 is provided between the paper feed tray units 51 a to 51 c and the main conveyance path 530 inside the apparatus main body 2, and extends from the other side of the apparatus main body 2 to one side. The reverse conveyance path 533 includes a first reflux conveyance path 533 a that branches downward from the main conveyance path 530 on the downstream side of the fixing unit 60 in the conveyance direction of the sheet conveyed through the main conveyance path 530, and the image forming unit 40. A second reflux conveyance path 533b that joins the main conveyance path 530 is provided upstream of the secondary transfer nip.

  One end of the reverse conveyance path 533 is connected to the first reflux conveyance path 533a and the second reflux conveyance path 533b. Here, one end of the reverse conveyance path 533 connected to the first reflux conveyance path 533a and the second reflux conveyance path 533b is a switchback that switches between forward and reverse of the paper traveling direction (conveyance direction) during duplex printing. Point SBP. Hereinafter, in the reverse conveyance path 533, the conveyance direction indicated by the arrow a in which the sheet is conveyed from the first reflux conveyance path 533a is referred to as a positive direction, and is indicated by the arrow b in which the sheet is conveyed to the second reflux conveyance path 533b. The conveyance direction is referred to as the reverse direction.

  The reverse conveyance path 533 includes a conveyance roller 53b and a conveyance roller 53c as switchback rollers on the downstream side in the normal conveyance direction with respect to the switchback point SBP. These transport rollers 53b and 53c receive the driving force of a motor (not shown) and transport the paper in both the forward and reverse directions. Specifically, the transport rollers 53b and 53c rotate synchronously under the control of the control unit 100, and are driven to rotate so that the transport direction and the peripheral speed (paper transport speed) are the same.

  Further, the downstream side in the forward conveyance direction of the reverse conveyance path 533, in other words, the portion near the terminal end in the conveyance direction before switchback is curved upward and folded in the opposite direction as shown in the figure. Branch to the route. More specifically, the downstream side of the conveyance roller 53c in the forward direction of the reverse conveyance path 533 is a merging conveyance path P1 as a first double-sided path connected to the upstream side of the image forming unit 40 in the main conveyance path 530, and the main conveyance path P1. Branches to a parallel conveyance path P2 as a second double-sided path that is folded back before being connected to the conveyance path 530. As shown in FIG. 3, the branch path is provided with a switching gate 533g as a switching mechanism for switching the transport direction of the long paper LS to either the merging transport path P1 or the parallel transport path P2.

  The switching gate 533g is connected to an actuator or the like (not shown) controlled by the control unit 100 and rotates so as to guide the leading end of the long paper LS conveyed in the forward direction to either the merging conveyance path P1 or the parallel conveyance path P2. Operates (see FIGS. 4 and 5). In FIG. 3, the switching gate 533g is located at the position where the leading edge of the long paper LS is guided to the parallel transport path P2. When the switching gate 533g is rotated in the arrow direction shown in FIG. 4 from this state, the leading edge of the long paper LS is moved to the merging transport path P1. It is displaced to the guiding position (see FIG. 5). Although not shown for the sake of brevity, a branch path that branches from the main transport path 530 to the paper discharge unit 52 or the first reflux transport path 533a, and the reverse transport path 533 to the first reflux transport path 533a in the reverse transport. Alternatively, the switching gates are also provided on the branch paths that branch to the second reflux conveyance path 533 b, and these switching gates are controlled by the control unit 100.

  The merged conveyance path P1 is a double-sided path used for duplex printing of paper (mainly long paper LS), and the main conveyance path 530 is upstream of the registration rollers 53a in the conveyance direction of the sheet conveyed in the forward direction. And the reverse conveyance path 533 and the main conveyance path 530 are connected. In this example, the merging conveyance path P1 merges upstream from the merging point between the main conveyance path 530 and the second reflux conveyance path 533b. Further, the merged conveyance path P1 merges with the main conveyance path 530 in a direction in which the sheet is conveyed in the left direction of the main conveyance path 530 in the drawing.

  The parallel conveyance path P2 is a double-sided path used for double-sided printing of paper (mainly long paper LS), like the merging conveyance path P1. As shown in FIGS. 1 and 3, the parallel conveyance path P2 is a path that does not merge with the main conveyance path 530, and below the merge conveyance path P1 and the main conveyance path 530 in the space within the ADU, these merge conveyance paths P1. And it is provided in parallel so as to extend in the same direction as the main transport path 530. The front end (end) of the parallel transport path P2 extends to the vicinity of the end portion connected to the main transport path 530 in the second reflux transport path 533b. By providing such a parallel conveyance path P2 as the second double-side path in the ADU, it is possible to improve the productivity in double-sided printing of the long paper LS while effectively using the dead space in the ADU. .

  As described above, in the present embodiment, the forward downstream side of the reverse conveyance path 533 in the double-side conveyance path is branched into two, the merging conveyance path P1 and the parallel conveyance path P2. When images are formed on both sides of the LS, double-sided printing can be performed using either the merging conveyance path P1 or the parallel conveyance path P2.

  In the present embodiment, the reverse conveyance path 533 including the above-described merge conveyance path P1 and the parallel conveyance path P2 and the rollers disposed in the reverse conveyance path 533 are part of the ADU as a part of the apparatus main body 2. Thus, it can be pulled out integrally on the front side in FIG.

  Next, a case where duplex printing is performed on the paper S fed from the paper feed tray units 51a to 51c will be described. In the image forming apparatus 1, the sheet S that has been conveyed in the forward direction (left direction in FIG. 1) through the main conveyance path 530 and passed through the image forming unit 40 and the fixing unit 60 faces upward (first surface). A toner image is transferred and fixed to the toner image. Subsequently, the sheet S is transported and controlled by the control unit 100 so that the sheet S is transported from the main transport path 530 to the reverse transport path 533 via the first reflux transport path 533a. Further, when the trailing end of the sheet S in the transport direction passes the switchback point SBP, the control unit 100 switches the rotation direction of the transport roller 53b to reverse the transport direction, and the sheet S is transferred from the reverse transport path 533 to the second reflux. The conveyance control is performed so as to convey to the main conveyance path 530 via the conveyance path 533b.

  With this conveyance control, the sheet S, which is a non-long sheet, is conveyed in the forward direction indicated by the arrow a before the leading edge of the sheet S enters the merging conveyance path P1 or the parallel conveyance path P2. The end passes through the switchback point SBP. Subsequently, the sheet S passes through the second reflux conveyance path 533b, and is conveyed to the main conveyance path 530 with the first surface, which is the image forming surface, facing downward, and the image is formed on the second surface facing upward. It will be possible. Thus, the sheet S on which the toner images are formed on both sides is transport-controlled by the control unit 100 so that the sheet S is discharged from the main transport path 530 to the sheet discharge unit 52. Therefore, when the paper S, which is a non-long paper, is printed on both sides, the paper S is not transported to either the merging transport path P1 or the parallel transport path P2.

  Next, a case where double-sided printing of the long paper LS is performed using the merging conveyance path P1 will be described. The long sheet LS is conveyed in the forward direction (left direction in FIG. 1) from the external sheet feed port 2a of the apparatus main body 2 via the external sheet feed conveyance path 531. Thereafter, in the same manner as described above, the long paper LS that has passed through the image forming unit 40 and the fixing unit 60 has the toner image transferred and fixed on the upper first surface, and the first reflux conveyance path from the main conveyance path 530. It is conveyed to the reverse conveyance path 533 via 533a (see FIG. 4). When the long sheet LS is conveyed in the forward direction indicated by the arrow a in the reverse conveyance path 533, the control unit 100 controls the conveyance so that the leading end in the conveyance direction enters the merging conveyance path P1 by the operation of the switching gate 533g. (See FIG. 5). Then, as shown in FIG. 5, when the trailing end of the long paper LS in the transport direction passes the switchback point SBP, the control unit 100 switches the rotation direction of the transport rollers 53 b and 53 c and reverses the transport direction. Execute the back operation. After this operation, the long paper LS is transported and controlled by the control unit 100 so as to be transported from the reverse transport path 533 to the main transport path 530 via the second reflux transport path 533b.

  With this conveyance control, in the conveyance in the forward direction on the reverse conveyance path 533, the leading edge of the long paper LS enters the merging conveyance path P1, and depending on the size of the long paper LS (length in the conveyance direction), FIG. As shown in FIG. In this case, when the paper is conveyed in the reverse direction due to the reversal of the conveyance direction, the rear end of the long paper LS in the conveyance direction moves in the reverse direction (right direction in FIG. 5) on the main conveyance path 530.

  Thereafter, as in the case of the sheet S, the long sheet LS is conveyed to the main conveyance path 530 through the second reflux conveyance path 533b with the first surface as the image forming surface facing downward ( 6), an image can be formed on the second surface facing upward. The long paper LS on which the toner images are formed on both sides is transported and controlled by the control unit 100 so as to be discharged from the main transport path 530 to the paper discharge unit 52.

  Next, a case where double-sided printing of the long paper LS is performed using the parallel conveyance path P2 will be described. Similarly to the above, the long paper LS is conveyed in the forward direction (left direction in FIG. 1) from the external sheet feed port 2a of the apparatus main body 2 through the external sheet feed conveyance path 531. . Thereafter, the long paper LS having passed through the image forming unit 40 and the fixing unit 60 has the toner image transferred and fixed on the upper first surface, and passes from the main conveyance path 530 via the first reflux conveyance path 533a. It is conveyed to the reverse conveyance path 533. When the long sheet LS is conveyed in the forward direction indicated by the arrow a in the reverse conveyance path 533, the switching gate 533g is switched (see FIG. 7) so that the leading end in the conveyance direction enters the parallel conveyance path P2. In addition, the conveyance is controlled by the control unit 100. Then, as illustrated in FIG. 7, when the trailing end of the long paper LS in the conveyance direction passes through the switchback point SBP, the control unit 100 switches the rotation direction of the conveyance roller 53 b to reverse the conveyance direction, The conveyance control is performed so that the paper LS is conveyed from the reverse conveyance path 533 to the main conveyance path 530 via the second reflux conveyance path 533b.

  With such conveyance control, in the conveyance in the forward direction on the reverse conveyance path 533, as shown in FIG. 7, the portion on the leading end side of the long paper LS in the conveyance direction enters the parallel conveyance path P2, and the main conveyance path It will be in the state stored in the apparatus main body 2 below 530. Thereafter, when the sheet is conveyed in the reverse direction by the switchback operation, that is, the reversal of the conveyance direction, the rear end side of the long paper LS in the conveyance direction is drawn into the main conveyance path 530 through the second reflux conveyance path 533b. (See FIG. 6).

  By the way, the merging conveyance path P1 and the parallel conveyance path P2 have different properties and characteristics (advantages, disadvantages, etc.) as described below. In view of such different properties, in the present embodiment, in a print job for forming an image on both sides of the long paper LS, the control unit 100 passes the long paper LS through the parallel conveyance path P2 as much as possible. Control. Further, in the present embodiment, in a print job for forming an image on both sides of the long paper LS, it is determined which of the merging conveyance path P1 and the parallel conveyance path P2 is to be used with reference to the image forming conditions, The conveyance of the long paper LS is controlled so as to use the determined conveyance path.

  Here, the image forming conditions include the type (length and stiffness) of the long paper LS to be subjected to double-sided printing, the setting state (such as setting information by the user) of the image forming apparatus 1, and the physical form of the image forming apparatus 1. The state (for example, temperature or humidity state) is included.

  Hereinafter, the difference in properties and the like of the merging conveyance path P1 and the parallel conveyance path P2 and the conveyance control at the time of duplex printing of the long paper LS will be described.

(Double-sided printing productivity perspective)
As described above, the merging conveyance path P1 is a path that merges with the main conveyance path 530. Therefore, when double-sided printing of the long paper LS is performed using the merging conveyance path P1, depending on the size (length) of the long paper LS in the conveyance direction, as shown in FIG. Since the long sheet LS re-enters the sheet conveyance path 530 during the conveyance of the sheet, the conveyance of the subsequent sheet to the main conveyance path 530 may be limited. Specifically, in the example shown in FIG. 5, the long paper LS has such a length that the front end side enters the main transport path 530 when the rear end in the transport direction passes through the switchback point SBP. Yes. In this case, when the succeeding paper S or long paper LS is transported to the main transport path 530 from the state shown in FIG. 5, the papers may interfere with each other and cause a jam or the like. Therefore, until the leading edge of the long paper LS shown in FIG. 5 leaves the main transport path 530 by the switchback operation, the operation of transporting the subsequent paper S or the long paper LS to the main transport path 530 is limited. .

  On the other hand, since the parallel conveyance path P2 is a path that does not merge with the main conveyance path 530, such inconvenience does not occur when double-sided printing of the long paper LS is performed using the parallel conveyance path P2. Specifically, in the example illustrated in FIG. 7, the long paper LS has a leading end side close to the end (end) of the parallel transport path P <b> 2 when the rear end in the transport direction passes through the switchback point SBP. The length reached, in other words, has a length close to a limit value at which the parallel conveyance path P2 can be used. Even in such a case, even if the succeeding paper S or the long paper LS is transported to the main transport path 530 from the state shown in FIG.

  Therefore, it is more advantageous to use the parallel conveyance path P2 from the viewpoint of productivity of double-sided printing. In other words, in the present embodiment, when a plurality of long sheets LS are continuously printed on both sides, each sheet is transported using the parallel transport path P2, so that a high PPM (Page Per Minute) is obtained without reducing productivity. ) To improve printing productivity.

(Perspective from the ease of jam handling)
When performing double-sided printing of the long paper LS, the long paper LS may be jammed in the apparatus, that is, jammed, regardless of which of the merging transport path P1 and the parallel transport path P2. Here, even when a jam occurs in any of the merging conveyance path P1 and the parallel conveyance path P2, the conveyance paths P1 and P2 are integrated from the apparatus main body 2 together with the reverse conveyance path 533 by pulling out the ADU as described above. Pulled out. At this time, since the conveyance path for double-sided printing of the present embodiment has a substantially annular shape as shown in the drawing, the jammed long paper LS is wound around the conveyance path (inner guide member). Remain in. Therefore, according to the present embodiment, the occurrence of so-called guillotine at the time of jam occurrence of the long paper LS can be prevented, and the labor of the jam processing work can be reduced.

  On the other hand, the merged conveyance path P1 is a path that merges with the main conveyance path 530, and has a longer path length than the parallel conveyance path P2, as shown in FIG. Further, in the main conveyance path 530 where the merge conveyance path P1 merges, various conveyance rollers are arranged at a relatively short distance in order to convey various sizes of paper such as standard paper. For this reason, when the jam of the long paper LS occurs during the double-sided printing operation using the merging conveyance path P1, there is a possibility that the work labor when the ADU is pulled out and the long paper LS is taken out increases.

  On the other hand, since the parallel conveyance path P2 is shorter than the merging conveyance path P1 and does not merge with the main conveyance path 530 and a sheet having a short conveyance direction size is not conveyed, There is no need to place them. For this reason, when the jam of the long paper LS occurs during the operation of double-sided printing using the parallel transport path P2, the removal work of the jammed long paper LS is performed as compared with the case of the merging transport path P1 described above. It is easy and jam processing can be performed relatively easily.

  Therefore, it is more advantageous to use the parallel transport path P2 from the viewpoint of ease of jam processing.

  In view of such a point, in the present embodiment, in a print job for forming an image on both sides of the long paper LS, the control unit 100 conveys the long paper LS so as to pass through the parallel conveyance path P2. Basic (default). On the other hand, as will be described below, depending on the image forming conditions, it may not be suitable to use the parallel conveyance path P2. In such a case, the control unit 100 causes the long paper LS to flow along the merged conveyance path P1. The conveyance is controlled so as to pass through.

(Perspective from the paper length)
As described above and illustrated, the parallel transport path P2 is provided below the main transport path 530 and is a relatively short path. Therefore, the size of the long paper LS that can use the parallel transport path P2 (transport direction) The limit value) is shorter than when the merging conveyance path P1 is used. In this example, the path length from the switchback point SBP to the end of the parallel transport path P2 is approximately 600 mm. For this reason, when the length of the long paper LS in the transport direction exceeds 600 mm (threshold), when the leading edge of the paper in the traveling direction reaches the end of the parallel transport path P2 in the forward transport, The rear end does not pass through the switchback point SBP and cannot be switched back.

  Therefore, in the job for forming an image on both sides of the long paper LS, the control unit 100 moves the long paper LS to the merging conveyance path P1 when the length of the long paper LS exceeds a threshold value (600 mm in this example). The conveyance is controlled so as to pass through. On the other hand, when the length of the long paper LS is equal to or smaller than the threshold, the control unit 100 controls the conveyance so that the long paper LS passes through the parallel conveyance path P2.

(Perspective from paper stiffness)
As illustrated, the merging conveyance path P1 and the parallel conveyance path P2 are both paths having a curvature. Here, since the merging conveyance path P1 is a path located outside the parallel conveyance path P2, it has a smaller curvature (gradual curve) than the parallel conveyance path P2. In other words, the degree of bending of the parallel conveyance path P2 is tighter than that of the merging conveyance path P1. For this reason, when using the long paper LS having high rigidity, the sheet conveyance resistance (conveying load) is relatively smaller when the joining conveyance path P1 is used than when the parallel conveyance path P2.

  From this point of view, in the job for forming images on both sides of the long paper LS, the control unit 100 passes the parallel transport path P2 when the rigidity of the long paper LS is low, and joins and transports when the rigidity is high. The long paper LS is controlled to pass through the path P1. In one example, the control unit 100 conveys the long paper LS through the parallel conveyance path P2 when the rigidity of the long paper LS is up to 128 gsm, and passes through the merging conveyance path P1 when the rigidity is 129 gsm or more. Control.

(Perspective from temperature and humidity)
As described above, since the parallel conveyance path P2 has a larger curvature than the merging conveyance path P1, the curl of the conveyed paper (long paper LS) tends to remain relatively when the temperature and humidity in the apparatus is high. .

  From this point of view, the control unit 100 refers to the output of a temperature / humidity sensor (not shown) in the apparatus main body 2 when executing a job for performing double-sided printing on the long paper LS, and the temperature / humidity around the image forming apparatus 1 is determined. Specify whether the environment is HH, NN, or LL. Then, in the HH environment, the control unit 100 performs conveyance control so that the merging conveyance path P1 is used as being easily affected by curl (paper curl is likely to remain). On the other hand, in the case of the NN environment or the LL environment, the control unit 100 controls the conveyance so that the parallel conveyance path P2 is used, assuming that the sheet is hardly affected by the sheet curl (the sheet curl hardly remains).

(Other viewpoints such as usability)
The merged transport path P1 and the parallel transport path P2 have the advantages and disadvantages described above, but in actuality, either path may be used. Therefore, from the viewpoint of usability and the like, prior to double-sided printing of the long paper LS, the user can set the transport path (P1 or P2) to be used in advance as user setting information through a user setting screen (not shown) or the like. May be. In this case, the control unit 100 controls the conveyance of the long paper according to the setting contents of the user setting information at the time of executing a job for performing double-sided printing of the long paper LS.

  Hereinafter, an example of long paper conveyance control performed by the control unit 100 in a print job in which the long paper LS is printed on both sides will be described with reference to the flowchart of FIG. FIG. 8 illustrates an example of conveyance control when duplex printing is performed on a plurality of long papers LS having the same size.

  In step S1 to step S3, the control unit 100 refers to the image forming conditions. In this example, as an image forming condition, the control unit 100 refers to paper information, input image information, and apparatus status information.

  In step S1, the control unit 100 refers to the sheet information. Here, the paper information is information on one long paper LS to be printed, and in the present embodiment, for example, the length in the transport direction of the long paper LS set by a paper setting profile (not shown). Includes information on height and basis weight (rigidity).

  In step S <b> 2, the control unit 100 refers to the information on the temperature and humidity in the machine from the output signal of the temperature and humidity sensor.

  In step S3, the control unit 100 refers to the user setting information described above.

  In step S4, the control unit 100 determines whether or not the second double-side path (parallel transport path P2) is usable based on each information (that is, image forming conditions) referred to in steps S1 to S3. When it is determined that the second double-sided path is usable (step S4, YES), the control unit 100 proceeds to step S5, and when it is determined that the second double-sided path cannot be used (step S4, NO). ) Goes to Step S6.

  In step S <b> 5, the control unit 100 performs double-sided printing of the long paper LS through the parallel conveyance path P <b> 2 and performs conveyance control so that the long paper LS after double-sided printing is discharged from the main conveyance path 530 to the paper discharge unit 52. To do. On the other hand, in step S6, the control unit 100 performs double-sided printing of the long paper LS through the merged conveyance path P1, and discharges the long paper LS after double-sided printing from the main conveyance path 530 to the paper discharge unit 52. Transport control.

  In step S7 after step S5 or step S6, the control unit 100 determines whether or not the print job has ended. If it is determined that the print job has not ended yet (step S7, NO), the control unit 100 returns to step S2. The processes in steps S2 to S7 described above are repeated. On the other hand, when the control unit 100 determines that the print job is finished (step S7, YES), the series of processing is finished.

  The determination conditions in step S4, in other words, the conditions for using the second double-sided path (priority of each information, etc.) can have various modes. For example, when the length of the long paper LS in the conveyance direction is shorter than a threshold value (for example, 600 mm) and the rigidity (basis weight) is smaller than 128 gsm, the control unit 100 sets the second value regardless of other conditions. Are determined to be usable. As another example, when the length of the long paper LS in the conveyance direction is shorter than a threshold (for example, 600 mm), the control unit 100 can use the second double-sided path regardless of other conditions. Judge that there is.

  As described above, in the present embodiment, since the two double-side paths (P1, P2) for switchback conveyance of the long paper LS are provided in the apparatus main body 2, the apparatus is enlarged. And images can be formed on both sides of the long paper.

  Further, according to the image forming apparatus 1 having two double-sided paths (P1, P2) for the long paper LS, the length and rigidity of the long paper LS to be printed at the time of double-side printing of the long paper LS. In consideration of various image forming conditions such as the temperature / humidity environment and the duplex path setting information set by the user, the duplex path to be used can be appropriately switched and printed.

  In the present embodiment, when double-sided printing of the long paper LS is performed, the long paper LS is placed on the second double-side path (parallel transport path P2) provided in the apparatus main body in parallel with the main transport path 530. By transporting a part of the paper to temporarily store the long paper LS, the long paper LS can be returned to the second reflux transport path 533b, and the jam handling property is improved.

  In the present embodiment, since the two-sided path (P1, P2) is selectively used based on various image forming conditions and the conveyance control is performed so as to perform the double-sided printing of the long paper LS, the optimum path is used. Double-sided printing of the long paper LS can be executed, and the long paper LS image-formed on both sides can be discharged out of the machine in a good state.

  In the present embodiment, since conveyance control is performed so that the second double-side path (parallel conveyance path P2) is preferentially used, a high PPM (Page Per Minute) is realized depending on the paper size, and printing is performed. Productivity can be improved.

  In addition, a first double-sided path (merging conveyance path P1) connected to the upstream side of the image forming unit 40 in the main conveyance path 530 and a second double-sided path (inside the main conveyance path 530) provided in the apparatus main body 2 ( According to the present embodiment provided with the parallel conveyance path P2), it is possible to meet each request in, for example, a thick paper / thin paper system, and the paper passing performance is improved.

  The above-described embodiments and modifications are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. . 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 2 Apparatus main body 2a External paper feed port 10 Image reading part 20 Operation display part 30 Image processing part 40 Image forming part 50 Paper transport part 51 Paper feed part 51a-51c Paper feed tray unit 52 Paper discharge part 53 Transport path Portion 53a Registration roller 53b Transport roller 53c Transport roller 530 Main transport path 531 External paper feed transport path 532 Paper feed transport path 533 Reverse transport path 533a First reflux transport path 533b Second reflux transport path 533g Switching gate 60 Fixing section 100 Control unit (transport control unit)
P1 confluence conveyance path (first double-sided path)
P2 Parallel transport path (second double-sided path)
SBP switchback point LS long paper

Claims (7)

An image forming unit for forming a toner image on a long paper;
A fixing unit for fixing the toner image formed on the long paper;
A main conveyance path for conveying the long paper to the image forming unit and the fixing unit;
Branches from the downstream side of the fixing unit in the main conveyance path in the conveyance direction, and reverses the conveyance direction of the long paper at a switchback point so that the front and back of the long paper are reversed to the upstream side of the image forming unit. A double-sided conveyance path
A conveyance control unit for controlling conveyance of the long paper,
The double-sided conveyance path branches into a first double-sided path connected to the upstream side of the image forming unit in the main conveying path and a second double-sided path folded back before connecting to the main conveying path,
The transport control unit controls the long paper to pass through one of the first and second double-side paths when a toner image is formed on both sides of the long paper.
Image forming apparatus. The conveyance control unit controls whether the long paper is passed through the first and second double-sided paths based on image forming conditions.
The image forming apparatus according to claim 1. When the length of the long paper in the conveyance direction is longer than a threshold as the image forming condition, the conveyance control unit passes the long paper through the first double-side path, and the conveyance direction of the long paper If the length is less than or equal to the threshold, control the long paper to pass through the second double-sided path;
The image forming apparatus according to claim 2. The conveyance control unit passes through the first double-side path when the rigidity of the long paper is high and passes through the second double-side path when the rigidity is low as the image forming condition. Control the transport of paper
The image forming apparatus according to claim 2. The conveyance control unit refers to the temperature and humidity around the image forming apparatus as the image forming condition, passes through the first double-sided path when the temperature and humidity are high, and when the temperature and humidity are low. Carrying the long paper so as to pass through the second double-sided path;
The image forming apparatus according to claim 2. The conveyance control unit controls the conveyance of the long paper according to the setting content of user setting information for setting the conveyance path of the long paper as the image forming condition.
The image forming apparatus according to claim 2. In order for the image forming unit to form an image on both sides of a long paper whose length in the transport direction is a predetermined length or more, a path in the transport direction before the transport direction of the long paper is reversed at the switchback point, A paper conveyance control method in an image forming apparatus comprising a double-sided conveyance path branched into a first double-sided path connected to the upstream side of the image forming unit and a second double-sided path folded before being connected to a main conveyance path. And
When a toner image is formed on both sides of the long paper, the long paper is conveyed so as to pass through either of the first and second double-side paths.
Paper transport control method.

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