JP5935642B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus.

  In general, in an image forming apparatus (printer, copying machine, facsimile, etc.) using an electrophotographic process technology, a charged photoconductor is irradiated (exposed) with a laser beam based on image data. An electrostatic latent image is formed on the surface. Then, toner is supplied from the developing device to the photosensitive member (image carrier) on which the electrostatic latent image is formed, so that the electrostatic latent image is visualized and a toner image is formed. This toner image is transferred directly or indirectly to the sheet via an intermediate transfer belt, and then fixed by heating and pressing, whereby an image is formed on the sheet.

  The image forming apparatus described above includes a paper transport unit that transports paper fed from a paper feed tray, a manual feed tray, or an external paper feed device to the image forming unit. FIG. 1 shows a specific configuration example of the paper transport unit included in the image forming apparatus.

  As shown in FIG. 1, the paper transport unit 50 includes a plurality of transport roller units such as intermediate transport roller units 53 and 54, a loop roller unit 55, and a registration roller unit 56. The sheet S is nipped and conveyed by at least one of the plurality of conveyance roller units 53 to 56. Further, the plurality of transport roller units 53 to 56 are incorporated in one unit, and are collectively mounted on the image forming apparatus main body as a paper transport unit ADU.

In the paper transport unit 50, for example, the paper S fed from an external paper feeder is transported by the first intermediate transport roller unit 53 and delivered to the second intermediate transport roller unit 54. Similarly, the paper S is sequentially delivered and conveyed from the second intermediate conveyance roller unit 54 to the loop roller unit 55 and from the loop roller unit 55 to the registration roller unit 56.
When the loop roller unit 55 conveys the sheet S in a state where the leading edge of the sheet S is in contact with the registration roller unit 56, the bending of the sheet S is formed in the loop forming unit 57, and the inclination of the sheet S is corrected. After the conveyance timing is adjusted in the registration roller unit 56, the sheet S is conveyed to the image forming unit (toner image transfer unit).

  In addition, in order to correct the deviation (position in the width direction) of the paper S, a so-called registration rocking mechanism in which the registration roller unit 56 conveys the paper S while rocking in the width direction (axial direction of the registration roller). An image forming apparatus provided is also proposed (for example, Patent Documents 1 and 2).

  Here, when the paper S is conveyed while the registration roller unit 56 swings, if the paper S is nipped by the loop roller unit 55 on the upstream side, the paper S is distorted. Therefore, the pair of rollers of the loop roller portion 55 are configured to be capable of being pressed and separated, and are brought into a separated state when the registration roller portion 56 is conveyed while being swung. In general, the intermediate transport roller portions 53 and 54 are also configured to be capable of being pressed and separated, and after the paper S is delivered to the loop roller portion 55, the intermediate transport roller portions 53 and 54 are brought into a separated state.

In the image forming apparatus including the paper transport unit 50 described above, when a jam occurs in the paper transport unit ADU, the user pulls out the paper transport unit ADU from the main body of the image forming apparatus and exists in the paper transport unit 50. The paper S is removed and jam processing is performed.
At this time, the trailing edge of the paper S may protrude from the paper transport unit ADU depending on the jam occurrence location, the paper transport path length, and the paper length (so-called crying, (See FIG. 2). In this case, if the sheet transport unit ADU is pulled out from the image forming apparatus main body as it is, the sheet S is broken (sheet breakage, so-called guillotine), and the jam handling operation becomes complicated. Therefore, conventionally, the paper S is further transported by the transport roller unit that was driven when the jam occurred, and the paper S is forcibly drawn into the paper transport unit ADU, thereby pulling out the paper transport unit ADU from the image forming apparatus main body. Paper breakage is avoided (guillotine prevention processing, for example, Patent Document 3).

JP-A-11-189355 JP-A-3-94275 JP 2009-47997 A

However, when a jam occurs, the conveyance of the sheet is hindered, so that the conveyance force necessary for the guillotine prevention process is larger than the conveyance force during normal sheet conveyance. For this reason, if a jam occurs when the upstream transport roller portion is in the separated state, it may be difficult to reliably perform the guillotine prevention process.
For example, as shown in FIG. 2, when the sheet is being conveyed by the registration roller unit 56, the upstream loop roller unit 55 and the intermediate conveyance roller units 53 and 54 are in a separated state. If a jam occurs in this state, the sheet is conveyed only by the registration roller unit 56, and the guillotine prevention process is performed. At this time, if the sheet conveying force by the registration roller unit 56 is not sufficient, the sheet is not completely pushed into the sheet conveying unit ADU, and the sheet breaks when the sheet conveying unit ADU is pulled out.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can prevent paper breakage when a paper conveyance unit having a plurality of conveyance roller portions is pulled out to perform jam processing, and can facilitate a jam processing operation.

The image forming apparatus according to the present invention includes a first transport roller unit that sandwiches and transports a sheet, and the sheet is transported by the first transport roller unit that is disposed upstream of the first transport roller unit. A paper transport unit in which a plurality of transport roller units including a second transport roller unit that is separated when
When a jam occurs during the conveyance of the sheet by the first conveyance roller unit and the rear end of the sheet is outside the sheet conveyance unit, the second conveyance roller unit is brought into a pressure-bonded state to remove the sheet. And a control unit to be conveyed.

  According to the image forming apparatus of the present invention, it is possible to reliably prevent paper breakage when a paper conveyance unit having a plurality of conveyance roller portions is pulled out to perform jam processing, thereby facilitating jam processing work. it can.

It is a figure which shows the state of the conveyance roller part at the time of paper conveyance. It is a figure which shows the state of the conveyance roller part at the time of jam generation. 1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment. FIG. 2 is a diagram illustrating a main part of a control system of the image forming apparatus according to the embodiment. It is a figure which shows a some conveyance roller part in detail. It is a flowchart which shows an example of a guillotine prevention process. FIG. 10 is a diagram illustrating a guillotine prevention operation when a jam occurs during sheet conveyance by a registration roller unit. It is a figure which shows a guillotine prevention operation | movement when jam occurs during the paper conveyance by a loop roller part.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 3 is a diagram showing an overall configuration of the image forming apparatus 1 according to the embodiment of the present invention. FIG. 4 is a diagram illustrating a main part of a control system of the image forming apparatus 1 according to the embodiment.
An image forming apparatus 1 shown in FIGS. 3 and 4 is an intermediate transfer type color image forming apparatus using electrophotographic process technology. 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 (vertical direction) of the intermediate transfer belt 421, and each color toner image is formed on the intermediate transfer belt 421 in one procedure. The vertical tandem method is used to transfer the images sequentially.
That is, the image forming apparatus 1 transfers the toner images of Y (yellow), M (magenta), C (cyan), and K (black) formed on the photosensitive drum 413 to the intermediate transfer belt 421 (primary transfer). Then, after superposing four color toner images on the intermediate transfer belt 421, the toner images are transferred to the paper S (secondary transfer) to form an image.

  As shown in FIGS. 3 and 4, 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 also exchanges various data with 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. Send and receive. 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 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 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 includes, based on input image data, an image forming unit 41, an intermediate transfer unit 42, and a secondary transfer unit for forming an image using colored toners of Y component, M component, C component, and K component. 43 and the like.

  The image forming unit 41 includes four image forming units 41Y, 41M, 41C, and 41K for Y component, M component, C component, and K component. Since the image forming units 41Y, 41M, 41C, and 41K have the same configuration, for convenience of illustration and description, common constituent elements are denoted by the same reference numerals, and when distinguished from each other, the reference numerals Y, M, and C are used. Or K. In FIG. 3, only the components of the image forming unit 41Y for the Y component are given 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) and a charge generation layer (CGL) on the peripheral surface of an aluminum conductive cylinder (aluminum tube) having a drum diameter of 80 mm. A negatively charged organic photoreceptor (OPC: Organic Photo-conductor) in which a charge transport layer (CTL) is 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 hole transport material (electron donating nitrogen-containing compound) 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 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 contains a developer of each color component (for example, a two-component developer composed of a toner having a small particle diameter and a magnetic material), and causes the toner of each color component to adhere to the surface of the photosensitive drum 413. Thus, the electrostatic latent image is visualized to form a toner image.
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 including a backup roller 423A, 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. The intermediate transfer belt 421 travels at a constant speed in the direction of arrow A by the rotation of the support roller 423 serving as a drive roller. When the intermediate transfer belt 421 is pressed against the photosensitive drum 413 by the primary transfer roller 422, the respective color toner images are sequentially superimposed and primarily transferred onto the intermediate transfer belt 421.

The secondary transfer unit 43 includes, for example, a secondary transfer roller 431. The secondary transfer unit 43 may have a configuration in which a secondary transfer belt is stretched around a plurality of support rollers including a secondary transfer roller in a loop shape.
The secondary transfer roller 431 is pressed against the backup roller 423A via the intermediate transfer belt 421, thereby forming a transfer nip. When the sheet S passes through the transfer nip, the toner image carried on the intermediate transfer belt 421 is secondarily transferred to the sheet S. Specifically, the toner image is electrostatically transferred onto the paper S by applying a voltage (transfer bias) having a polarity opposite to that of the toner to the secondary transfer roller 431. The sheet S to which the toner image is transferred is conveyed toward the fixing unit 60.

  The belt cleaning device 426 includes a belt cleaning blade that is slidably contacted 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.

  The fixing unit 60 includes a fixing surface side member 61 (for example, a fixing belt) and a back surface side supporting member 62 (for example, a pressure roller). A fixing nip is formed by the fixing surface side member 61 and the back surface side support member 62. The fixing unit 60 fixes the toner image on the sheet S by heating and pressing the conveyed sheet S at the fixing nip. The fixing unit 60 may be provided with an air separation unit that separates the sheet S from the fixing surface side member 61 or the back surface side support member 62 by blowing air.

The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, a plurality of transport roller units 53 to 56, 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 paper S fed from the paper feed tray units 51a to 51c or the external paper feeder is conveyed to the image forming unit 40 (secondary transfer unit) by a plurality of conveyance roller units 53 to 56. When the sheet S passes through the transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to one side (image forming surface) of the sheet S at a time, and a fixing process is performed in the fixing unit 60. The paper S on which the image is formed is discharged out of the apparatus by a paper discharge unit 52 having a paper discharge roller 52a.

FIG. 5 is a diagram illustrating in detail the plurality of transport roller units 53 to 56 of the sheet transport unit 50.
As shown in FIG. 5, the sheet conveyance unit 50 includes a first intermediate conveyance roller unit 53, a second intermediate conveyance roller unit 54, a loop roller unit 55, and a registration roller unit 56 as a plurality of conveyance roller units 53 to 56. Prepare. The intervals between the first intermediate conveyance roller unit 53 and the second intermediate conveyance roller unit 54, the second intermediate conveyance roller unit 54 and the loop roller unit 55, and the loop roller unit 55 and the registration roller unit 56 can be applied to image formation, respectively. It is set to be shorter than the length in the conveyance direction of the minimum size paper. That is, the sheet S is held and conveyed by at least one of the first intermediate conveyance roller unit 53, the second intermediate conveyance roller unit 54, the loop roller unit 55, and the registration roller unit 56.
The plurality of transport roller units 53 to 56 are incorporated in one unit together with the fixing unit 60 and are collectively attached to the image forming apparatus 1 as a sheet transport unit ADU.

The first intermediate transport roller unit 53 transports the paper S fed from the paper feed unit 51 or the external paper feed device and delivers it to the second intermediate transport roller unit 54 on the downstream side. The first intermediate transport roller unit 53 includes a drive roller 531a connected to the drive motor 532 via a power transmission unit (not shown), and a driven roller 531b arranged to face the drive roller 531a. When the driven roller 531b is pressed against the driving roller 531a, a nip portion (first intermediate conveyance nip) for nipping and conveying the sheet S is formed.
The driven roller 531b is held in a pressure-bonded state or a separated state with respect to the driving roller 531a by a pressure-bonding / separating portion 533 having a biasing member or the like. The control unit 100 controls the sheet conveyance operation (rotation driving of the driving roller 531a) by the first intermediate conveyance roller unit 53 and the pressure separation / separation operation by the pressure separation / separation unit 533.

The second intermediate transport roller unit 54 is disposed on the downstream side of the first intermediate transport roller unit 53, transports the paper S delivered from the first intermediate transport roller unit 53, and receives it on the downstream loop roller unit 55. hand over. The second intermediate transport roller unit 54 includes a drive roller 541a connected to the drive motor 542 via a power transmission unit (not shown), and a driven roller 541b arranged to face the drive roller 541a. When the driven roller 541b is pressed against the driving roller 541a, a nip portion (second intermediate conveyance nip) for nipping and conveying the sheet S is formed.
The driven roller 541b is held in a pressure-bonded state or a separated state with respect to the drive roller 541a by a pressure-bonding / separating portion 543 having a biasing member or the like. The control unit 100 controls the sheet conveyance operation (rotation driving of the driving roller 541a) by the second intermediate conveyance roller unit 54 and the pressure separation / separation operation by the pressure separation / separation unit 543.

The loop roller unit 55 is disposed on the downstream side of the second intermediate conveyance roller unit 54, conveys the paper S delivered from the second intermediate conveyance roller unit 54, and delivers it to the registration roller unit 56 on the downstream side. The paper is bent in the loop forming portion 57 between the registration roller portion 56 and the registration roller portion 56. The loop roller unit 55 includes a drive roller 551a connected to the drive motor 552 via a power transmission unit (not shown), and a driven roller 551b arranged to face the drive roller 551a. When the driven roller 551b is pressed against the driving roller 551a, a nip portion (loop nip) for nipping and transporting the paper S is formed.
The driven roller 551b is held in a pressure-bonded state or a separated state with respect to the driving roller 551a by a pressure-bonding / separating portion 553 having a biasing member or the like. The control unit 100 controls the sheet conveyance operation (rotation drive of the driving roller 551a) by the loop roller unit 55 and the pressure separation / separation operation by the pressure separation / separation unit 553.

The registration roller unit 56 is disposed on the downstream side of the loop roller unit 55 (upstream side of the secondary transfer unit), and corrects the inclination and deviation of the sheet S. The registration roller unit 56 includes a drive roller 561a connected to the drive motor 562 via a power transmission unit (not shown), and a driven roller 561b arranged to face the drive roller 561a. When the driven roller 561b is pressed against the driving roller 561a, a nip portion (registration nip) for nipping and transporting the paper S is formed.
In the registration roller unit 56, the driven roller 561b is always held in a pressure-bonded state with respect to the driving roller 561a. The sheet conveying operation by the registration roller unit 56 (rotation driving of the driving roller 561a) is controlled by the control unit 100.

  Further, the registration roller unit 56 moves the driving roller 561a and the driven roller 561b in the width direction (the axial direction of the driving roller 561a) in order to correct the deviation (position in the width direction) of the paper S. Have The resist swinging portion 563 includes, for example, a drive motor (not shown) and a power transmission portion (not shown) such as a rack and pinion.

  Further, a deviation detection sensor 564 that detects the deviation of the sheet S is disposed on the downstream side of the registration roller unit 56. The deviation detection sensor 564 is composed of, for example, a line sensor arranged in parallel with the driving roller 561a and the driven roller 561b.

  The control unit 100 controls the resist swinging unit 563 based on the detection result by the deviation detection sensor 564. In the resist swinging portion 563, the rotational motion of a drive motor (not shown) is converted into a linear motion by a power transmission portion (not shown) and transmitted to the drive roller 561a and the driven roller 561b. Thereby, the drive roller 561a and the driven roller 561b move in the width direction. As the driving roller 561a and the driven roller 561b rotate, that is, swing in the width direction while conveying the sheet S, the position in the width direction of the sheet S is corrected.

  When the paper S fed from the paper feed tray units 51a to 51c or the external paper feeder is transported, the intermediate transport roller portions 53 and 54 and the loop roller portion 55 are brought into a pressure-bonded state. In the paper transport unit 50, for example, the paper S fed from an external paper feeder is transported by the first intermediate transport roller unit 53 and delivered to the second intermediate transport roller unit 54. Then, the sheet S is transported by the second intermediate transport roller unit 54 and transferred to the loop roller unit 55. After the sheet S is delivered to the loop roller unit 55, the first intermediate conveyance roller unit 53 and the second intermediate conveyance roller unit 54 are separated from each other, and the sheet S is conveyed by the loop roller unit 55.

  The sheet S is transported by the loop roller unit 55 and delivered to the registration roller unit 56. Even after the leading edge of the sheet S reaches the registration roller unit 56, the rotation by the registration roller unit 56 (drive roller 561a) is stopped and the conveyance by the loop roller unit 55 is continued. As a result, the leading edge of the sheet S is brought into contact with the registration nip, and the bending of the sheet S is formed in the loop forming portion 57. The inclination of the paper S is corrected by the stress generated in the paper S.

After the inclination of the paper S is corrected, the rotation of the registration roller unit 56 (drive roller 561a) is started, and the paper S is conveyed toward the transfer nip of the image forming unit 40. At this time, the deviation of the sheet S is corrected by the resist swinging portion 563.
Further, when the conveyance of the sheet by the registration roller unit 56 is started, the loop roller unit 55 is separated. This is because, when the sheet S is conveyed while the registration roller unit 56 swings, if the sheet S is held by the upstream loop roller unit 55, the sheet S is distorted.

  A jam detection sensor 58 that detects the occurrence of a jam is arranged in the paper conveyance path where the plurality of conveyance roller units 53 to 56 are arranged. A paper detection sensor 59 (paper detection unit) that detects the conveyed paper S is disposed in the paper transport path. The sheet detection sensor 59 is disposed immediately before the registration roller unit 56, for example.

In the image forming apparatus 1, when a jam occurs in the paper transport unit ADU, the user pulls out the paper transport unit ADU from the image forming apparatus main body, removes the paper S present in the paper transport unit 50, and performs jam processing. Will be done.
At this time, the trailing edge of the paper S may protrude from the paper transport unit ADU depending on the jam occurrence location, the paper transport path length, and the paper length (so-called crying, (See FIG. 1). In this case, if the paper transport unit ADU is pulled out from the image forming apparatus 1 as it is, the paper breaks and the jam handling operation becomes complicated. In the present embodiment, when the paper transport unit ADU is pulled out from the image forming apparatus 1, the paper S is further transported after the jam occurs, and the guillotine prevention process for forcibly pulling the paper S into the paper transport unit ADU is performed. Avoid paper tearing.

  In this guillotine prevention process, the control unit 100 is in a separated state when a jam occurs during the conveyance of the paper S and the rear end of the paper S is outside the paper conveyance unit ADU. The sheet S is transported in a pressure-bonded state. Specifically, the control part 100 performs drive control of the conveyance roller parts 53-56 according to the flowchart shown in FIG.

  FIG. 6 is a flowchart illustrating an example of a guillotine prevention process. The guillotine prevention process shown in FIG. 6 is realized, for example, when the CPU 101 executes a predetermined program stored in the ROM 102 when the image forming process is started.

  In step S <b> 101 of FIG. 6, the control unit 100 determines whether or not a jam has occurred based on the detection result of the jam detection sensor 58. If the control unit 100 determines that a jam has occurred, the control unit 100 proceeds to the process of step S102.

  In step S102, the control unit 100 determines whether the trailing edge of the paper S is outside the paper transport unit ADU, based on the detection result of the paper detection sensor 59 disposed on the paper transport path and the paper length, for example. . When the control unit 100 determines that the trailing edge of the sheet S is outside the sheet transport unit ADU, the control unit 100 proceeds to the process of step S103 and determines that the trailing edge of the sheet S is in the sheet transport unit ADU. In this case, the process proceeds to step S106.

  When the trailing edge of the paper S is in the paper transport unit ADU, in step S106, the control unit 100 causes the display unit 21 to display a jam processing display indicating that a jam has occurred. In this case, there is no tearing of the paper when the paper transport unit ADU is pulled out from the image forming apparatus 1, so that the user only needs to perform jam processing according to the jam processing display.

  In step S103, the control unit 100 determines whether or not the sheet S is being conveyed by the registration roller unit 56 when a jam occurs, that is, the first intermediate conveyance roller unit 53, the second intermediate conveyance roller unit 54, and the loop roller. It is determined whether the unit 55 is in the separated state. When the control unit 100 determines that the sheet S is being conveyed by the registration roller unit 56, the control unit 100 proceeds to the process of step S <b> 104, and when it is determined that the sheet S is not being conveyed by the registration roller unit 56. The process proceeds to step S107.

  In step S <b> 104, the control unit 100 brings the first intermediate transport roller unit 53, the second intermediate transport roller unit 54, and the loop roller unit 55 that are in a separated state into a press-bonded state. In order to increase the conveyance force of the paper S, the loop roller portion 55 closest to the registration roller portion 56 may be at least in a pressure-bonded state.

In step S105, the control unit 100 drives the first intermediate conveyance roller unit 53, the second intermediate conveyance roller unit 54, and the loop roller unit 55 that are brought into the pressure-bonded state, and the trailing edge of the sheet S is set to the sheet conveyance unit ADU. The paper S is conveyed until it is pulled in. As shown in FIG. 7, the conveyed paper S is buckled and stored in, for example, the loop forming unit 57.
When it is difficult to push the sheet S downstream of the registration roller unit 56, the sheet S is conveyed by the first intermediate conveyance roller unit 53, the second intermediate conveyance roller unit 54, and the loop roller unit 55, and the registration roller unit 56 may remain stopped.

  In step S106, the control unit 100 causes the display unit 21 to display a jam processing display indicating that a jam has occurred. The user performs the jam processing work according to the jam processing display.

  When the sheet S is transported in step S105, a sufficient transport force can be obtained by driving the first intermediate transport roller unit 53, the second intermediate transport roller unit 54, and the loop roller unit 55, so that a jam has occurred. However, the paper S can be reliably pulled into the paper transport unit ADU. Therefore, when the user pulls out the paper transport unit ADU from the image forming apparatus 1 and performs the jam processing operation, the paper is not torn.

  On the other hand, when it is determined that the sheet S is not being conveyed by the registration roller unit 56 ("NO" in step S103), in step S107, the control unit 100 causes the loop roller unit 55 to remove the sheet S when a jam occurs. It is determined whether or not the sheet is being conveyed, that is, whether or not the first intermediate conveyance roller unit 53 and the second intermediate conveyance roller unit 54 are in a separated state. When the control unit 100 determines that the sheet S is being conveyed by the loop roller unit 55, the control unit 100 proceeds to the process of step S <b> 108, and when it is determined that the sheet S is not being conveyed by the loop roller unit 55. The process proceeds to step S106 and a jam processing display is performed.

  In step S108, the control unit 100 puts the first intermediate transport roller unit 53 and the second intermediate transport roller unit 54 in the separated state into a press-bonded state. In order to increase the conveyance force of the paper S, the second intermediate conveyance roller unit 54 closest to the loop roller unit 55 may be at least in a pressure-bonded state.

  In step S <b> 109, the control unit 100 drives the first intermediate conveyance roller unit 53 and the second intermediate conveyance roller unit 54 in the pressure-bonded state until the trailing edge of the sheet S is drawn into the sheet conveyance unit ADU. S is conveyed. At this time, the loop roller unit 55 is preferably driven together with the first intermediate conveyance roller unit 53 and the second intermediate conveyance roller unit 54. As shown in FIG. 8, the conveyed paper S is buckled and stored in, for example, the loop forming unit 57.

  In step S106, the control unit 100 causes the display unit 21 to display a jam processing display indicating that a jam has occurred. The user performs the jam processing work according to the jam processing display.

  When the sheet S is transported in step S109, a sufficient transport force can be obtained by driving the first intermediate transport roller unit 53, the second intermediate transport roller unit 54, and the loop roller unit 55, so that a jam has occurred. However, the paper S can be reliably pulled into the paper transport unit ADU. Therefore, when the user pulls out the paper transport unit ADU from the image forming apparatus 1 and performs the jam processing operation, the paper is not torn.

As described above, the image forming apparatus 1 is disposed on the upstream side of the first transport roller unit that sandwiches and transports the paper S, and the paper S is transported by the first transport roller unit. A sheet transport unit ADU having a second transport roller unit that is separated when the first transport roller unit and the second transport roller unit are incorporated in one unit; A jam occurs during conveyance of the sheet S by the conveyance roller unit (“YES” in step S101 in FIG. 6), and the rear end of the sheet S is outside the sheet conveyance unit ADU (in step S102 in FIG. 6). “YES”) includes a control unit 100 that transports the paper S with the second transport roller unit in a pressure-bonded state.
When the first transport roller unit is the registration roller unit 56, the second transport roller unit is the first intermediate transport roller unit 53, the second intermediate transport roller unit 54, and the loop roller unit 55. Further, when the first transport roller unit is the loop roller unit 55, the second transport roller unit becomes the first intermediate transport roller unit 53 and the second intermediate transport roller unit 54.

  According to the image forming apparatus 1, it is possible to reliably prevent paper breakage when a paper transport unit ADU having a plurality of transport roller units 53 to 56 is pulled out to perform jam processing, thereby facilitating jam processing work. Can do.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the above embodiment, and can be changed without departing from the gist thereof.

  For example, according to the paper type of the paper S used for image formation, the conveyance roller unit that is driven in paper conveyance (steps S105 and S109 in FIG. 6) when a jam occurs may be changed. In the case of thick paper, a larger transport force is required compared to thin paper, and therefore it is preferable that there are more transport roller sections to be driven.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image reading part 20 Operation display part 30 Image processing part 40 Image forming part 50 Paper conveyance part 53 1st intermediate conveyance roller part 54 2nd intermediate conveyance roller part 55 Loop roller part 56 Registration roller part 57 Loop formation part 58 Jam detection sensor 59 Paper detection sensor 60 Fixing unit 100 Control units 531a, 541a, 551a, 561a Drive rollers 531b, 541b, 551b, 561b Drive rollers 532, 542, 552, 562 Drive motors 533, 543, 553 Pressing and separating unit 563 Resist oscillating unit 564 Deviation detection sensor ADU Paper transport unit

Claims (5)

A first transport roller unit that sandwiches and transports the paper, and a first state that is separated when the paper is transported by the first transport roller unit that is disposed upstream of the first transport roller unit. A paper transport unit in which a plurality of transport roller units including two transport roller units are incorporated in one unit;
When a jam occurs during the conveyance of the sheet by the first conveyance roller unit and the rear end of the sheet is outside the sheet conveyance unit, the second conveyance roller unit is brought into a pressure-bonded state to remove the sheet. An image forming apparatus comprising: a control unit that conveys the image forming apparatus. The plurality of transport roller units are arranged on the upstream side of a transfer unit that transfers a toner image to a sheet, and a registration roller unit that corrects the inclination and deviation of the sheet;
A loop roller portion that is disposed on the upstream side of the registration roller portion and deflects a sheet to a loop forming portion between the registration roller portion, and
2. The image formation according to claim 1, wherein the control unit controls the loop roller unit as the second conveyance roller unit when the first conveyance roller unit is the registration roller unit. apparatus. The plurality of transport roller units are arranged on the upstream side of a transfer unit that transfers a toner image to a sheet, and a registration roller unit that corrects the inclination and deviation of the sheet;
A loop roller portion that is arranged on the upstream side of the registration roller portion and deflects the sheet to a loop forming portion between the registration roller portion, and
An intermediate conveyance roller unit disposed on the upstream side of the loop roller unit,
The said control part controls the said intermediate | middle conveyance roller part as a said 2nd conveyance roller part, when the said 1st conveyance roller part is the said loop roller part, The Claim 1 or 2 characterized by the above-mentioned. Image forming apparatus. The paper transport unit has a paper detection unit for detecting the transported paper,
4. The control unit according to claim 1, wherein the control unit determines whether or not a rear end of the sheet is outside the sheet transport unit based on a detection result and a sheet length by the sheet detection unit. The image forming apparatus according to any one of the above.   5. The image forming apparatus according to claim 1, wherein the paper transport unit includes a paper storage unit that buckles and stores the drawn paper.

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