JP2017171476A - Sheet conveyance device, image forming apparatus including the same, and image forming system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet conveyance device capable of reducing labor and time for a sheet removing operation by a user as much as possible by a purge function.SOLUTION: When a sheet SH3 is passing a branch point BP toward a relay unit 140 at the time of detecting jam in a post-processing device 150, the conveyance of the sheet SH3 is continued by separating a nip section of each conveyance roller 141 to 143 of the relay unit 140, and the sheet is fed to be overlapped on a sheet SH2 in the relay unit 140. When a rear end of the sheet SH3 passes the branch point BP, a conveyance destination is switched to a reversing port 44 side by a switching claw 41, a sheet SH4 reaching the branch point BP next is guided to the reversing port 44 direction, a reversing roller 45 is normally rotated, and the sheet is purged on a reversing tray 47.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a sheet conveyance technique, and more particularly to a purge technique.

In general, a sheet conveying device mounted on an image forming apparatus such as a printing machine or a copying machine continuously conveys a plurality of sheets along one path. By performing processing such as printing in order on these sheets, high-speed processing of several tens to hundred ppm or more is realized.
When a jam (paper jam) occurs at a certain point on the path, the image forming apparatus interrupts the processing and prompts the user to remove the jammed sheet. At this time, another sheet is generally forcibly stopped also before and after the sheet on the path. In principle, all these sheets must also be removed from the path to resume processing. However, removing these sheets is a troublesome operation for the user.

Some conventional sheet conveying devices can move out of the path when the image forming device interrupts processing due to a jam, etc., in order to relieve the user of the troublesome removal work. There is a model that automatically ejects all the important sheets.
This paper discharge operation performed by the sheet conveying device when the processing of the image forming apparatus is interrupted is referred to as “purge”. In general, the sheet to be purged is discharged to a dedicated tray provided separately from a normal discharge tray.

JP 2013-88604 A

Since a certain amount of space is required to install a purge-dedicated tray, image forming apparatuses that can be equipped with a purge function have been limited to relatively large models. However, in recent years, with the enhancement of functions of image forming apparatuses, it is desired to provide a purge function for small and medium-sized models such as those for offices.
On the other hand, if an attempt is made to provide a purge-dedicated tray for a medium-sized model, this is contrary to the downsizing and cost reduction that are strongly demanded for these small-sized models.

As an example of a small and medium model for an office, there is an image forming system capable of printing on both sides of a sheet as shown in FIG.
An image forming system 950 illustrated in FIG. 15 includes an image forming apparatus 900, a relay apparatus 910, and a post-processing apparatus 920. The image forming apparatus 900 is a color copying machine capable of performing double-sided printing. When double-sided printing is performed, the image forming system 950 performs the following operation.

First, the Y, M, C, and K color toner images formed by the image forming unit 901 are multiple-transferred onto the intermediate transfer belt 906 that circulates in the direction of the arrow. The respective color toner images transferred onto the intermediate transfer belt 906 are secondarily transferred at the secondary transfer position 907 to the surface of the sheet SHT fed out from the cassette 902.
When the sheet SHT after the secondary transfer passes through the fixing unit 903, the toner image is fixed on the surface of the sheet SHT, and is guided to the reversing unit 904 via the branch point 960.

  The reversing unit 904 is a reversing roller immediately before the trailing end of the sheet SHT reaches the reversing roller 941 with the reversing roller 941 protruding the front end of the sheet SHT from the reversing port 940 provided in the apparatus housing. 941 is reversed. As a result, the conveyance direction of the sheet SHT is switched back (reversed). The inverted sheet SHT is guided to the circulation unit 905.

The sheet SHT guided to the circulation unit 905 is conveyed along the circulation path 951 and returned to the secondary transfer position 907. In parallel with this circulation conveyance operation, a toner image forming operation is performed by the image forming unit 901. When the sheet SHT passes the secondary transfer position 907, the toner image on the intermediate transfer belt 906 is formed on the back surface of the sheet SHT. Is secondarily transferred.
When the sheet SHT passes through the fixing unit 903 after the secondary transfer, the toner image is fixed on the back surface of the sheet SHT, and the sheet SHT is conveyed from the branch point 960 to the post-processing device 920 via the relay device 910. In the post-processing device 920, post-processing such as stapling is performed on the sheet SHT, and the post-processed sheet SHT is discharged.

The sheet reversing mechanism having such a reversing opening 940 saves the space necessary for the switch back of the sheet SHT. Therefore, if the outside of the reversing port 940 can also be used as a purge destination, the purge function can be implemented while keeping the casing of the image forming apparatus 900 small.
As the purge function, for example, when the sheet SH0 is jammed in the post-processing device 920, and the sheets SH1 to SH3 are being conveyed in the image forming apparatus 900, the sheets SH1 to SH3 are moved out of the apparatus from the reversing port 940. It is possible to discharge.

  However, for example, when a jam is detected, if the sheet SH1 guided to the relay device 910 via the branch point 960 is passing through the branch point 960, even if the sheet SH1 is immediately stopped, the sheet SH1 is no longer transported to the reversing port 940. If the stopped sheet SH1 stays in the position of the branch point 960 in time and the conveyance path from the branch point 960 to the reverse port 940 is blocked, the subsequent sheets SH2 to SH3 cannot be guided to the reverse port 940. .

Such a problem is not limited to the sheet conveying apparatus provided in the image forming apparatus, and may occur in general in a sheet conveying apparatus having the reversing mechanism as described above.
The present invention has been made in view of the above-described problems, and in a configuration having a reversing mechanism for reversing a part of a sheet to be conveyed outside the reversing opening, the purge function is provided. Accordingly, it is an object of the present invention to provide a sheet conveying apparatus capable of reducing the trouble of a sheet removing operation by a user as much as possible, and an image forming apparatus and an image forming system including the sheet conveying apparatus.

  In order to achieve the above object, the sheet conveying apparatus according to the present invention conveys a sheet to a conveying destination apparatus during normal operation, and interrupts conveyance of the sheet to the conveying destination apparatus when a jam is detected. A sheet conveying apparatus that conveys a sheet along a conveying path, and a first delivery path that directs a sheet conveying destination from a branch point that is a downstream end of the conveying path to the conveying destination apparatus. And a switching means for switching to any one of the second delivery paths toward the reversing port that is an opening of the casing for using the space outside the casing of the sheet conveying apparatus as a space for reversing the sheet conveying direction. Relay transport means for transporting the sheet on the first delivery path toward the transport destination device by one or more transport roller pairs, and separation means for separating the transport roller pairs in the relay transport means; When a jam of the first sheet is detected in the transport destination apparatus, the second sheet transported to the first delivery path is passing through the branch point and is upstream of the second sheet on the transport path. When there is a third sheet on the side, each pair of conveying rollers in the relay conveying means is separated, and the second sheet is conveyed until the rear end in the conveying direction of the second sheet passes the branch point. Then, after the rear end in the transport direction of the second sheet passes the branch point, the transport destination of the third sheet is switched to the second delivery path side, and the third sheet is discharged from the reversing port to the outside of the housing. And a control means for controlling the separation means, the transport means and the switching means so as to execute the purge operation.

Here, the control unit includes a conveyance path length L1 from the branch point to the nip portion of the conveyance roller pair on the most upstream side in the sheet conveyance direction of the relay conveyance unit, and a conveyance direction length Ls of the second sheet. Only when L1 <Ls, the pair of conveyance rollers of the relay conveyance unit may be separated by the separation unit.
In addition, a plurality of transport roller pairs of the relay transport unit exist along the first delivery path, and the control unit determines whether the plurality of transport roller pairs correspond to the length Ls in the transport direction of the second sheet. Of these, a pair of transport rollers to be separated may be selected and separated.

  Further, the control means includes a time T1 until the leading edge of the second sheet reaches the nip portion of the conveyance roller pair on the most upstream side in the sheet conveyance direction of the relay conveyance means, and the sheet conveyance direction by the separation means. It is possible to compare the time T2 until the separation of the conveying roller pair on the most upstream side is completed. When T1 ≦ T2, the conveyance of each sheet may be stopped and the purge operation may be prohibited.

In addition, the control unit compares the conveyance path length L2 from the branch point to the nip portion of the conveyance roller on the most upstream side in the sheet conveyance direction of the conveyance destination apparatus with the conveyance direction length Ls of the second sheet. When L2 ≦ Ls, the conveyance of each sheet may be stopped and the execution of the purge operation may be prohibited.
An image forming apparatus according to the present invention is an image forming apparatus that forms an image on a sheet conveyed by a sheet conveying unit, and includes the sheet conveying device as the sheet conveying unit.

  An image forming system according to the present invention includes the above-described image forming apparatus, and a post-processing apparatus that performs predetermined post-processing on a sheet on which an image is formed by the image forming apparatus, and the sheet conveyance in the image forming apparatus The apparatus to which the sheet is conveyed by the apparatus is the post-processing apparatus.

  In this way, when the sheet jam is detected, by separating the transport roller pair of the relay transport means, another sheet is interposed between the transport destination device and the second sheet passing through the branch point. Also, the second sheet can be conveyed along the second delivery path until the rear end of the second sheet in the conveyance direction passes through the branch point, and the second sheet is positioned at the branch point. Therefore, the conveyance path from the conveyance path to the reversing port is ensured through the branch point. As a result, the succeeding third sheet can be purged from the reversing port, and it is possible to reduce the trouble of the user's sheet removal operation at the time of jam detection.

1 is a perspective view showing an external appearance of an image forming system according to an embodiment of the present invention. It is a schematic front view which shows the internal structure of an image forming system. FIG. 4 is a schematic diagram illustrating a sheet conveyance path formed by a conveyance unit in the image forming system. 2 is a block diagram illustrating a configuration of an electronic control system of the MFP. FIG. (A), (b), (c) is a schematic diagram showing an example of purge control when there is no sheet passing through a branch point when a jam is detected by the post-processing apparatus. (A) And (b) is a schematic diagram which shows an example of the purge control when there is a sheet passing through the branching point when a jam is detected by the post-processing apparatus. (A) And (b) is a schematic diagram which shows the continuation of the purge control of FIG. (A) And (b) is a figure which shows the mode before the nip part of the conveyance roller of a relay unit was spaced apart by the separation mechanism, respectively. 6 is a flowchart illustrating the content of sheet conveyance control when a print job is executed. 10 is a flowchart showing the contents of a purge control subroutine in step S8 of FIG. It is a flowchart which shows the content of the subroutine of the 1st control of step S105 of FIG. It is a flowchart which shows the content of the subroutine of the 2nd control of step S106 of FIG. It is a flowchart which shows the content of the subroutine of the 3rd control of step S110 of FIG. It is a flowchart which shows the content of the subroutine of the 4th control of step S113 of FIG. It is a figure which shows schematic structure of the conventional tandem type color printer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a sheet conveying apparatus according to the present invention, an image forming apparatus including the same, and an image forming system will be described below with reference to the drawings.
[Appearance of image forming system]
FIG. 1 is a perspective view showing an external appearance of an image forming system according to an embodiment of the present invention. The image forming system includes a multi-function peripheral (MFP) 100, a relay unit 140, and a post-processing device 150.

  The MFP 100 has functions of a scanner, a color copier, and a color laser printer. As shown in FIG. 1, an automatic document feeder (ADF) 110 is mounted on the upper surface of the casing of the MFP 100 so as to be openable and closable. A scanner 120 is built in the upper part of the casing located directly under the ADF 110, and a printer 130 is built in the lower part of the casing. A paper feed cassette 133 is attached to the bottom of the printer 130 so that it can be pulled out.

MFP 100 is an in-body discharge type. That is, the paper discharge tray 46 is detachably installed in the gap DSP between the scanner 120 and the printer 130, and accommodates the sheet discharged from the paper discharge port 42 at the back of the gap DSP. A reverse tray 47 is further installed on the paper discharge tray 46 in the gap DSP.
During duplex printing, the sheet on which the front surface (first surface) is printed (printed) is switched back (reversed) on the reversing tray 47. That is, the sheet is once conveyed from the reversing port 44 opened above the paper discharge port 42 to a position where it protrudes onto the reversing tray 47, and then the conveyance direction is reversed and the sheet is again drawn into the reversing port 44.

The relay unit 140 is incorporated in the casing portion of the MFP 100 from which the relay tray 140 is removed instead of the paper discharge tray 46. The relay unit 140 receives a sheet from the paper discharge port 42 and relays it to the post-processing device 150.
In response to an instruction from the MFP 100, the post-processing device 150 performs post-processing on a bundle of sheets received from the paper discharge outlet 42 through the relay unit 140. This post-processing includes, for example, processing for aligning a bundle of sheets and processing for binding the bundle with staples.

As shown in FIG. 1, the post-processing device 150 includes two paper discharge trays 151 and 152. On the upper tray 151, the sheets are stacked in the state when they are delivered from the paper discharge outlet 42. The lower tray 152 is loaded with a bundle of sheets aligned or closed with staples.
[Internal structure of image forming system]
FIG. 2 is a front view schematically showing the internal structure of the image forming system shown in FIG. As shown in FIG. 2, the printer 130 includes a feeding unit 10, an image forming unit 20, a fixing unit 30, and a sending unit 40. These elements cooperate to function as an image forming unit of the MFP 100, and form a toner image on the sheet based on the image data.

The feeding unit 10 uses the feeding roller groups 12P, 12R, 12F, 13, 14, and 15 to produce sheets SH1 one by one from the sheet bundle SHT stored in the sheet feeding cassette 11 or the manual feed tray 16. The image is fed to the image unit 20.
The size of the sheet SHT that can be stored in the paper feed cassette 11 and the manual feed tray 16 is A3, A4, A5, or B4. The sizes of the sheets stored in the paper feed cassette 11 and the manual feed tray 16 are automatically detected by a sensor (not shown). The length Ls in the sheet conveyance direction can be obtained by this size detection.

The image forming unit 20 forms a toner image on the sheet SH2 sent from the feeding unit 10. Specifically, each of the four image forming units 21Y, 21M, 21C, and 21K first uses the laser light from the exposure unit 26 to base the surface of the photosensitive drums 25Y, 25M, 25C, and 25K on the basis of image data. Then, an electrostatic latent image is formed on the surface.
Each image forming unit 21Y,... Then develops the electrostatic latent image with yellow (Y), magenta (M), cyan (C), and black (K) toners. The obtained four-color toner images are formed on the surface of the intermediate transfer belt 23 in order from the surface of the photosensitive drums 25Y,... By the electric field between the primary transfer rollers 22Y, 22M, 22C, 22K and the photosensitive drums 25Y,. It is transferred to the same position above. Thus, one color toner image is formed at that position.

The color toner image passes through the nip portion between the intermediate transfer belt 23 and the secondary transfer roller 24 simultaneously with the sheet SH2 sent from the feeding portion 10, and receives the electric field between the both 23 and 24 to receive the color toner image. Transferred to the surface of the sheet SH2. Thereafter, the secondary transfer roller 24 sends the sheet SH2 to the fixing unit 30.
The fixing unit 30 heat-fixes the toner image on the sheet SH2 sent from the image forming unit 20. Specifically, when the sheet SH2 is passed through the nip portion between the fixing roller 31 and the pressure roller 32, the fixing roller 31 applies heat from the built-in heater to the surface of the sheet SH2 to apply pressure. The roller 32 applies pressure to the heated portion of the sheet SH2 and presses it against the fixing roller 31. The toner image is fixed on the surface of the sheet SH <b> 2 by the heat from the fixing roller 31 and the pressure from the pressure roller 32. Thereafter, the pre-discharge roller 33 sends the sheet SH2 to the sending unit 40.

The sending unit 40 sends the sheet SH <b> 2 sent from the pre-discharge roller 33 to the relay unit 140 or reverses it by the reverse tray 47. As shown in FIG. 2, the delivery unit 40 includes a switching claw 41, a paper discharge port 42, a paper discharge roller 43, a reverse port 44, a reverse roller 45, and a circulation path 48.
Each roller such as the paper discharge roller 43 conveys the sheet with its rotational force by rotating with a pair of rotating members sandwiching the sheet in the nip between the two, but there is no need for explanation in the following. Is simply called a roller without a pair.

  The switching claw 41 is a claw-like or plate-like member whose base end is rotatably fixed between the paper discharge port 42 and the reversing port 44, and swings around the base end to move the tip up and down. Move to. The switching claw 41 raises the tip to form a path (hereinafter referred to as “sending path”) to the sheet discharge port 42 when the sheet sent by the pre-discharge roller 33 is sent to the relay unit 140, and the sheet. When reversing at the reversing port 44, the tip is lowered to form a passage to the reversing port 44 (hereinafter referred to as "reversing path").

The paper discharge port 42 and the reversing port 44 are both slits that are elongated in the horizontal direction and open in the casing of the MFP 100 facing the gap DSP. The inversion port 44 corresponds to an opening of the housing for using the space outside the housing of the MFP 100 as a space for reversing the sheet conveyance direction.
The paper discharge roller 43 is disposed inside the paper discharge port 42 and, while rotating, sends the sheet SH3 that has moved along the switching claw 41 to the relay unit 140 from the paper discharge port 42. The reversing roller 45 is disposed inside the reversing port 44 and is rotatable in both forward and reverse directions.

The reversing roller 45 first feeds the sheet SH4 that has moved along the switching claw 41 on its peripheral surface while rotating normally, and temporarily places it on the reversing tray 47. The reversing roller 45 further reverses immediately before passing the rear end of the sheet SH4, pulls the sheet SH4 from the reversing tray 47 into the reversing port 44, that is, reverses it and sends it to the circulation path 48.
In the circulation path 48, the plurality of transport rollers 48 a to 48 d turn the sheet SH <b> 5 sent from the reverse roller 45 upside down and return it to the transport path in the feeding unit 10. The rotation direction when each of the transport rollers 48a to 48d transports the sheet SH5 is referred to as normal rotation.

Thereafter, the feeding unit 10 sends the sheet SH5 again to the image forming unit 20, and the image forming unit 20 forms a toner image on the back surface (second surface) of the sheet SH5. The fixing unit 30 heat-treats the sheet SH5 again, and the sending unit 40 sends the sheet SH5 to the relay unit 140 this time.
The relay unit 140 relays the sheet sent from the paper discharge port 42 to the post-processing device 150 using the transport roller pairs 141, 142, and 143.

Each of the transport roller pairs 141, 142, and 143 is configured to be separable during purge control. Details will be described later.
In addition to the paper discharge trays 151 and 152, the post-processing device 150 includes an introduction roller 161, a sorting claw 162, an upper paper discharge roller 163, a transport roller group 164, a reverse roller 165, a post-processing unit 166, and a lower paper discharge. A roller 167.

  The introduction roller 161 receives the sheet from the relay unit 140 and pulls it into the housing. The sorting claw 162 is a claw-like or plate-like member whose base end is rotatably fixed, and moves the tip up and down by swinging around the base end. The sorting claw 162 lowers the leading end to form a passage to the upper sheet discharge roller 163 when the sheet pulled by the introduction roller 161 is sent to the upper sheet discharge roller 163, and when the sheet is sent to the post-processing unit 166. The path to the transport roller group 164 is formed by raising the tip.

The upper discharge roller 163 is disposed in the vicinity of the base end portion of the upper discharge tray 151 and discharges the sheet that has moved from the introduction roller 161 along the sorting claw 162 to the upper discharge tray 151. The transport roller group 164 transports the sheet that has moved from the introduction roller 161 along the sorting claw 162 toward the post-processing unit 166 to the reverse roller 165.
The reversing roller 165 is disposed at the entrance of the post-processing unit 166 and can rotate in both forward and reverse directions. The reversing roller 165 first feeds the sheet sent out by the conveying roller group 164 to the post-processing unit 166 on its peripheral surface while rotating normally. The reversing roller 165 then pulls out the post-processed sheet bundle from the post-processing unit 166 on the peripheral surface while reversing.

The post-processing unit 166 accumulates a predetermined number of sheets received from the reversing roller 165 to form a bundle, and performs post-processing such as alignment processing and staple binding processing on the bundle. The lower discharge roller 167 is disposed in the vicinity of the base end portion of the lower discharge tray 152, and discharges a bundle of sheets pulled out from the post-processing unit 166 by the reverse roller 165 to the lower discharge tray 152.
[Sheet Conveying Section]
As shown in FIG. 2, in the MFP 100, in addition to the feeding unit 10 and the sending unit 40, the driving roller 23R of the intermediate transfer belt 23, the secondary transfer roller 24, the fixing roller 31, the pressure roller 32, and before paper discharge A part of the image forming unit 20 and the fixing unit 30 such as the roller 33 functions as a sheet conveying unit.

FIG. 3 is a schematic diagram illustrating a sheet conveyance path formed by the conveyance unit.
As shown in FIG. 3, this route is configured as follows. First, the three paper feed paths from the paper feed cassettes 11a and 11b and the manual feed tray 16 are grouped into a single path (hereinafter referred to as “conveyance path”) 1a at the first junction MP1. The conveyance path 1a passes through the image forming unit 20 and the fixing unit 30, and is divided into two paths, that is, a transmission path 4a and a reversing path 4b at a branch point BP facing the switching claw 41 of the transmission section 40.

The delivery path 4 a is connected to the transport path in the relay unit 140 through the paper discharge port 42, and the reversing path 4 b is connected to the circulation path 48 at the reversing port 44. The circulation path 48 is connected to the transport path 1a at a second junction MP2 located in the vicinity of the timing roller 14. Hereinafter, the path for transporting the sheet such as the transport path and the delivery path may be collectively referred to as a transport path.
The relay unit 140 plays a role of relaying between the printer 130 and the post-processing device 150. However, when the post-processing device 150 is a sheet transport destination device, the transport path of the relay unit 140 transports the sheet. It can be regarded as a part of the delivery path 4a that delivers to the previous device. Hereinafter, the delivery path 4a includes the transport path of the relay unit 140.

Further referring to FIG. 3, a plurality of optical sensors 1FS, 2FS, CS, TS, ES, 1RS, and 2RS are installed on these transport paths in addition to the roller group 12P shown in FIG. . Each optical sensor 1FS,... Detects a sheet passing through the installation location.
Specifically, each optical sensor includes a light emitting unit and a light receiving unit. The light emitting unit emits light of a predetermined wavelength such as infrared rays, and the light receiving unit detects light of that wavelength. While one sheet passes through the installation location of each optical sensor, the sheet blocks the light emitted from the light emitting unit before the light receiving unit or reflects it toward the light receiving unit. Since the output of the light receiving unit changes according to the blocking or reflection of the emitted light, the sheet passing through the installation location of each optical sensor is detected.

The feeding unit 10, the sending unit 40,... Notify these detections to a main control unit 60 (see FIG. 5) described later. In response to this notification, as shown below, the main control unit 60 determines whether a normal operation is performed without a jam or the like, or whether or not an abnormality has occurred in the conveyance timing due to the jam or the like.
Paper feed sensors 1FS and 2FS are installed at the beginning of the conveyance path shown in FIG. 3, that is, in the vicinity of the paper feed cassettes 11a and 11b. Depending on whether or not there is a delay in the sheet passing timing indicated by these outputs, it is determined whether or not the feeding roller group 12P, 12F, 12R is feeding each sheet to the path at a normal timing. .

In addition to the vertical transport roller 13, a vertical transport sensor CS is installed in front of the first junction MP <b> 1 in the path from the second-stage paper feed cassette 11 b. Depending on whether or not there is a delay in the sheet passing timing indicated by this output, it is determined whether or not the longitudinal conveying roller 13 is sending each sheet to the first junction MP1 at a normal timing.
In the vicinity of the boundary between the feeding unit 10 and the image forming unit 20, a timing sensor TS is installed in addition to the timing roller 14 downstream of both the first confluence point MP1 and the second confluence point MP2. The timing roller 14 is generally stopped, and the sheet moving from any of the sheet feeding cassettes 11a and 11b, the manual feed tray 16, and the circulation path 48 is temporarily stopped on the spot. The timing roller 14 further starts to rotate at the timing indicated by the drive signal from the main control unit 60, thereby sending the stopped sheet to the image forming unit 20 at that timing.

  Depending on whether or not there is a delay in the sheet passing timing indicated by the output of the timing sensor TS, whether or not those sheets have arrived at the timing roller 14 at a normal timing, and are sent from the timing roller 14 at a normal timing. It is determined whether or not it has been done. Furthermore, from the time required for the timing roller 14 to send out each sheet, the size of the sheet can be measured.

A paper discharge sensor ES is installed on the upstream side of the branch point BP. Depending on whether or not there is a delay in the sheet passing timing indicated by this output, whether or not the pre-discharge roller 33 is feeding the sheet at a normal timing, and whether the discharge roller 43 or the reverse roller 45 is the sheet It is determined whether or not it is pulled in at a normal timing.
In the circulation path 48, conveyance sensors 1RS and 2RS are installed. Depending on whether or not there is a delay in the sheet passage timing indicated by these outputs, it is determined whether or not the conveyance roller groups 48a to 48d of the circulation path 48 convey the sheet at a normal timing.

  Although not shown in FIG. 3, a plurality of optical sensors are similarly installed in the conveyance path between the relay unit 140 and the post-processing device 150. Using these sensors, post-processing device 150 detects the position of the sheet being conveyed on the path and notifies main control unit 60 of MFP 100 of the position. In response to this notification, it is determined whether or not an abnormality has occurred in the conveyance timing, and it is further determined whether or not there is a conveyance failure such as a jam on the conveyance path between the relay unit 140 and the post-processing device 150.

  When a jam occurring on the sheet being conveyed is detected, a job such as printing being executed is interrupted. The user manually opens and closes exterior covers (not shown) of the MFP 100, the relay unit 140, and the post-processing device 150, and manually removes a sheet that is stopped without being purged on the conveyance path due to the occurrence of a jam from the inside of the apparatus. By performing the operation, the generated jam can be released. When the jam is released, the suspended job is resumed.

  Referring further to FIG. 3, there are drive motor groups M <b> 1-M <b> 12, TM, MM, FM, SM, RM of the roller groups 12 </ b> P,. Driving solenoids SL1 and SL2 are installed. These motors M1,... Are, for example, direct current brushless (BLDC) motors, and are generally rotatable in both forward and reverse directions. Each of the motors M1,... Applies a rotational force to the roller to be driven through a transmission system such as a gear and a belt. The solenoids SL1 and SL2 move the movable iron core (blanger) back and forth in the axial direction using an electromagnet, and push and pull the switching claw 41 and the distribution claw 162, thereby swinging them up and down.

In the vicinity of the paper feed cassettes 11a and 11b, the feed motors M1 and M2 rotate the feed roller groups 12P, 12F, and 12R. In the vicinity of the path from the second-stage sheet feeding cassette 11b, the longitudinal transport motor M3 rotates the longitudinal transport roller 13. In the vicinity of the path from the manual feed tray 16, the feed motor M <b> 4 rotates the feed roller 15.
The timing motor TM rotates the timing roller 14 near the boundary between the feeding unit 10 and the image forming unit 20. In the image forming unit 20, the main motor MM rotates the driving roller 23 </ b> R of the intermediate transfer belt 23. In the fixing unit 30, the fixing motor FM rotates the fixing roller 31 and the pre-discharge roller 33.

  In the delivery unit 40, the paper discharge motor SM rotates the paper discharge roller 43, and the reverse motor RM rotates the reverse roller 45 in both the forward and reverse directions. Here, the rotation of the reverse motor RM when the reverse roller 45 is rotated forward is referred to as normal rotation, and the rotation of the reverse motor RM when the reverse roller 45 is rotated reverse is referred to as reverse rotation. The switching solenoid SL1 swings the switching claw 41 up and down. In the circulation path 48, one motor M5 rotates the first half transport rollers 48a and 48b, and the other motor M6 rotates the second half transport rollers 48c and 48d.

  In the relay unit 140, the transport motor M7 rotates the transport roller group 141,. In the post-processing device 150, the first motor M8 rotates the introduction roller 161, the solenoid SL2 swings the sorting claw 162 up and down, the second motor M9 rotates the upper discharge roller 163, and the third motor M10. Rotates the transport roller group 164. The fourth motor M11 rotates the reverse roller 165 in both forward and reverse directions, and the fifth motor M12 rotates the lower paper discharge roller 167.

[Electronic control system of image forming system]
FIG. 4 is a block diagram showing a configuration of the electronic control system of MFP 100. As shown in the figure, in this electronic control system, in addition to the ADF 110, the scanner 120, and the printer 130, the operation unit 50, the external interface (I / F) 52, and the main control unit 60 can communicate with each other through the bus 90. It is connected.

-Operation part-
The operation unit 50 receives a job request and image data to be printed through a user operation or communication with an external electronic device, and transmits them to the main control unit 60. As shown in FIG. 4, the operation unit 50 includes an operation panel 51. As shown in FIG. 1, operation panel 51 is installed on the front surface of the housing of MFP 100 and includes a push button, a touch panel, and a display.

  The operation unit 50 controls the operation panel 51 to display a GUI screen such as an operation screen and an input screen for various parameters on the display. The operation unit 50 also identifies the position of the push button or touch panel operated by the user, and transmits information related to the identification to the main control unit 60 as operation information. The information for accepting input includes, for example, setting of the types of sheets stored in the paper feed cassette 11 and the manual feed tray 16 and designation of the number of sheets to be stapled. Further, the screen display includes a message display indicating that a jam (paper jam) has occurred on the sheet being conveyed.

-External I / F-
The external I / F 52 includes a USB port or a memory card slot, and directly captures image data to be printed from an external storage device such as a USB memory or a hard disk drive (HDD). The external I / F 52 is also wired or wirelessly connected to an external network (not shown in FIG. 4), and receives image data to be printed from other electronic devices on the network. The external I / F 52 is further connected to the electronic control system of the post-processing device 150 and relays data exchange between the electronic control system and the main control unit 60.

−Main control unit−
As shown in FIG. 4, the main control unit 60 includes a CPU 61, a RAM 62, and a ROM 63. The CPU 61 controls the other elements 10, 20,... Connected to the bus 90 according to the firmware.
The RAM 62 provides a work area for the CPU 61 to execute the firmware to the CPU 61 and stores image data to be printed received by the operation unit 50.

The ROM 63 includes a non-writable semiconductor memory device and a rewritable semiconductor memory device such as an EEPROM or an HDD. The former stores firmware, and the latter provides the CPU 61 with a storage area for environment variables and the like.
As the CPU 61 executes various types of firmware, the main control unit 60 controls other elements in the MFP 100 based on operation information from the operation unit 50. Specifically, the main control unit 60 displays an operation screen on the operation unit 50 to accept an operation by the user.

  For example, when the operation unit 50 receives a print job from the user, the main control unit 60 first causes the operation unit 50 to transfer image data to be printed to the RAM 62. Next, the main control unit 60 designates the type of sheet to be fed and the timing of the feeding in the feeding unit 10 according to the printing conditions indicated by the job, and the toner to be formed in the image forming unit 20. Image data representing an image is provided, the surface temperature of the fixing roller 31 to be maintained is specified for the fixing unit 30, and the transport destination at the branch point BP and the switching timing are specified for the sending unit 40.

The main control unit 60 further monitors the operation state of each element 10, 20,... Of the MFP 100 or the sheet conveyance state, and when any failure is detected, the operation mode is appropriately changed to solve the failure.
For example, when an abnormal delay in sheet conveyance timing is detected through the optical sensor 1FS shown in FIG. 3, the printer 130 is interrupted and a message “jammed” is displayed on the operation panel 51. Encourage users to resolve it. When it is detected that the paper cassettes 11a, 11b are out of paper or the image forming units 21Y,... Have a shortage of toner, the printer 130 is interrupted and the operation panel 51 displays “paper cut / toner is insufficient”. To prompt the user to replenish them.

  As shown in FIG. 4, the main control unit 60 includes a transport control unit 401 and a purge control unit 402. These functional units 401 and 402 are realized by the CPU 61 executing dedicated firmware. That is, the function units 401 and 402 together with the transport unit 410 constitute a sheet transport apparatus 400 in the MFP 100. A conveyance control unit 401 controls the operation of the sheet conveying apparatus 400 in normal job processing. The purge control unit 402 causes the sheet conveying apparatus 400 to perform a purge when the printer 130 interrupts processing in response to a problem such as a jam. Details of the function units 401 and 402 will be described later.

-Printer-
As shown in FIG. 4, each element 10, 20, 30, 40 of the printer 130 includes a drive unit 10D, 20D, 30D, 40D, respectively. Each drive unit 10D controls a motor M1,... And a solenoid SL1 for driving various movable members included in the transport unit 410, including the transport roller group 12P.

Each of the drive units 10D, 20D,... Uses a variety of sensors to monitor the operation state of each element 10, 20,. Notify the controller 60.
[Transport control unit]
The conveyance control unit 401 controls the driving units 10D, 20D,... According to the operation mode of the MFP 100 and job conditions as follows, and conveys an appropriate type of sheet to the conveyance unit 410 at an appropriate timing. Let

  The conveyance control unit 401 first causes the driving unit 10D of the feeding unit 10 to select a sheet feeding cassette to be selected as a sheet feeding source, and a timing at which the feeding rollers 12P,. Instruct. In response to these instructions, the conveyance control unit 401 causes the driving units 10D,... To monitor the conveyance state of each sheet fed by the feeding unit 10, and particularly tracks the position on the conveyance path. Specifically, the conveyance control unit 401 measures the elapsed time from that point with a timer each time the sheet is picked up by the feeding rollers 12P,.

  Since the standard value (that is, the system speed) of the sheet conveyance speed is defined for each operation mode, the conveyance control unit 401 determines the movement distance of each sheet based on the standard conveyance speed and the elapsed time from the pickup time. Periodically, for example, every tens to hundreds of milliseconds, and the current position of the sheet is determined from the value. The conveyance control unit 401 stores information regarding the position of each sheet thus determined in the RAM 62 as one item of the sheet position information 421. This position information 421 defines the items of each sheet in the order of conveyance, for example.

Further, based on the position information 421, the conveyance control unit 401 predicts the installation location of the optical sensor 1FS,. The conveyance control unit 401 corrects the current position of the sheet from the error between the predicted time and the actual passing time represented by the output of the optical sensor, and updates the position information 421 with the corrected value.
Next, the conveyance control unit 401 uses the position information 421 to instruct the timing roller 14 to send the sheet to the image forming unit 20 to the driving unit 10D of the feeding unit 10 to drive the sending unit 40. The section 40D is instructed to indicate the direction of the tip of the switching claw 41 and the timing to switch to that direction, and the timing at which the reverse roller 45 should switch the normal rotation to the reverse rotation.

  Further, based on the position information 421 and the output of the optical sensor 1FS,... Notified from the driving unit 10D, the conveyance control unit 401 detects an abnormal delay in the conveyance timing of the sheet due to a conveyance failure such as a jam. Detect. For an event determined to be an abnormal delay, for example, an error between the passage time of the installation location of the optical sensor 1FS,... Predicted from the position information 421 and the actual passage time represented by the output of the optical sensor exceeds an allowable range. In this case, there is a case where the output of the optical sensor does not represent the actual passage even if the elapsed time from the predicted passage time exceeds the allowable range.

[Purge control unit]
When the main control unit 60 causes the printer 130 to suspend processing, the main control unit 60 activates the purge control unit 402 to execute purging. “Purge” refers to an operation of automatically ejecting a sheet that can continue to be conveyed from the conveyance path. The purge destination is not limited to the original paper discharge destination, such as a paper discharge tray, but a place where paper can be discharged for each sheet is set.

  A typical reason for causing the printer 130 to interrupt processing is the occurrence of a jam. When the occurrence of a jam is detected, the purge control unit 402 starts from the sheet position information 421 on the upstream side in the sheet conveyance direction (hereinafter, simply referred to as “upstream side”) with respect to the sheet that cannot be conveyed due to the jam. A sheet that can be continuously conveyed is identified as a purge target, and then a purge destination and a conveyance order of each sheet are determined, and further, the conveyance unit 410 continues to convey these sheets to perform a purge destination in the conveyance order. Eject the paper.

-Example of purge control-
(1) When there is no sheet passing through the branch point BP at the time of jam occurrence FIGS. 5A to 5C are passing through the branch point BP when a jam of the sheet SH1 is detected in the post-processing device 150. It is an example of purge control when there is no sheet.
As shown in FIG. 5A, when the sheet SH1 is jammed in the post-processing apparatus 150, the leading end of the sheet SH2 on the upstream side is at the position P1, and the position of the trailing end is downstream from the branch point BP. At position P2. The leading end of the further upstream sheet SH3 is at a position P3 before the branch point BP.

In such a case, since there is no hindrance to the switching of the conveyance path by the switching claw 41, the switching claw 41 is turned to the left side, and the delivery destination of the sheet SH3 is switched to the reversing port 44 side (see FIG. 5B). The reverse roller 45 is driven to rotate forward to discharge (purge) the sheet SH3 onto the reverse tray 47 (see FIG. 5C).
(2) When there is a sheet passing through the branching point BP when a jam occurs FIGS. 6A, 6B, 7A, and 7B show that a jam of the sheet SH1 is detected in the post-processing device 150. This is an example of the purge control when the sheet SH3 is passing through the branch point BP at the time.

As shown in FIG. 6A, when the jam of the sheet SH1 occurs in the post-processing device 150, the leading edge of the upstream sheet SH2 is at the position P3, and the trailing edge is a position downstream from the branch point BP. Although at P4, the leading end position of the next sheet SH3 is at the position P5, and its lower end side is upstream from the branch point BP.
In such a state, the switching claw 41 cannot be switched at the branch point BP, and it becomes difficult to purge the upstream sheet to the reverse tray 47. Even if it is attempted to move the sheet SH3 further forward so that the rear end of the sheet SH3 passes through the branch point BP, it is impossible because the sheet SH3 collides with the stopped conveyance roller 141 due to jam detection.

Therefore, in the present embodiment, the upper rollers 141a to 143a of the transport rollers 141 to 143 of the relay unit 140 are configured to move upward by a predetermined amount (for example, about 10 mm), and the transport rollers 141 to 143 are configured to move. They can be separated (see FIG. 6B).
In this way, the sheet SH3 can be further advanced by overlapping the sheet SH2 by driving the sheet discharge roller 43 so that the rear end of the sheet SH3 passes through the branch point BP. If the delivery destination is switched to the reversing port 44 side by the switching claw 41 (see FIG. 7A), the subsequent sheet SH4 can be conveyed to the reversing tray 47 as it is and purged (FIG. 7B). )reference).

FIGS. 8A and 8B are diagrams for explaining the configuration example of the separation mechanism 200 of the conveyance rollers 141 to 143 in the relay unit 140 with respect to the conveyance roller 141.
The upper roller 141a of the transport roller 141 is rotatably supported by a pair of L-shaped frames 201 at both ends of the shaft, and the lower roller 141b is rotationally driven by the transport motor M7 (see FIG. 3).

The frame 201 is held on a main frame (not shown) of the relay unit 140 so as to be swingable by a support shaft 202. The upper roller 141a is pressed against the lower roller 141b with a predetermined pressing force by the urging force of the tension spring 203. (FIG. 8A).
When separating the upper roller 141a from the lower roller 141b, the drive shaft 204a of the cam 204 is rotated by a drive source (not shown) so that the frame 201 is tilted in the arrow direction against the urging force of the tension spring 203. (FIG. 8B).

A similar separation mechanism 200 is also provided for the transport rollers 142 and 143, and all of them are separated in synchronization. Of course, the separation mechanism 200 may use various other known moving means such as solenoids, and each pair of the transport rollers 141 to 143 is not individually separated, but by the same drive source. It may be configured to be separated at the same time.
5 (a) to 5 (c) and FIGS. 6 (a), 6 (b), 7 (a), and 7 (b), an example of typical purge control in the present embodiment has been described. This is a little more complicated because of the influence of the length in the conveyance direction of the sheet being conveyed, the time required to complete the separation of the conveyance rollers 141 to 143 by the separation mechanism 200, the time required to complete the switching of the switching claw 41, and the like. . Hereinafter, the content of the sheet conveyance control centering on the purge control in the present embodiment will be described in more detail based on a flowchart.

<Sheet conveyance control>
FIG. 9 is a main flowchart illustrating processing contents of sheet conveyance control in the image forming system according to the embodiment.
This control is executed by the main control unit 60 in units of print jobs. Note that the print job here is a double-sided print job in which post-processing is not executed by the post-processing device 150 for convenience.

First, sheet feeding / conveying is started in which a plurality of sheets are fed one by one from the sheet feeding cassette 11 or the manual feed tray 16 (step S1).
This sheet feeding conveyance is reversed for each sheet at a predetermined timing, for example, a sheet interval from the preceding sheet when feeding the sheet from the sheet feeding cassette 11, a conveyance timing to the image forming unit 20, and the like. The reversal start timing by the reversing roller 45 in this case, the conveyance timing by the conveyance roller 48d when returning the sheet from the circulation path 48 to the conveyance path 1a, and the like are executed.

In this sheet feeding and conveyance, the switching claw 41 guides the sheet printed on the front surface from the conveyance path 1a to the reversing path 4b, and guides the sheet printed on the back surface from the conveyance path 1a to the sending path 4a. Operations are also included.
Then, it is determined whether or not a jam has been detected during job execution (step S2). If it is determined that a jam is not detected (“NO” in step S2), it is determined whether or not the last sheet of the plurality of sheets has been discharged from the post-processing device 150 (step S3).

  If it is determined that the last sheet is not discharged from the post-processing apparatus 150 (“NO” in step S3), the process returns to step S2. If a jam does not occur before the last sheet is discharged from the post-processing device 150, the processes in steps S2 and S3 are repeated, and the last sheet is discharged from the post-processing device 150 (step S3). "YES"), the control is terminated.

  If it is determined that the occurrence of a jam is detected during job execution (“YES” in step S2), the conveyance of the jammed sheet is interrupted (step S4). This interruption is performed by identifying the roller that was actually transporting the jammed sheet and stopping the motor that rotationally drives the identified roller. The roller can be identified by identifying a roller located at the current position on the conveyance path of the jammed sheet among the rollers arranged on each conveyance path. The current position of the sheet where the jam has occurred is detected when the jam occurs. Information on which roller is disposed at which position in each transport path is stored in advance.

Then, it is determined whether or not a jam has occurred in the post-processing device 150 (step S5). This determination is made based on whether or not the main control unit 60 has received a jam detection notification from the post-processing device 150. If it is determined that no jam has occurred in the post-processing device 150 (“NO” in step S5), downstream paper discharge control is performed (step S6).
The downstream paper discharge control is a control for continuously conveying the sheet existing downstream of the sheet in which the jam has occurred at the time when the occurrence of the jam is detected, and discharging the sheet from the post-processing device 150. As a result, the sheet existing downstream in the conveyance direction from the jammed sheet does not stop while remaining in the machine, so that it is not necessary to perform a jam removing operation on the sheet, and the labor for the user is reduced. .

Then, a message indicating that a jam has occurred is displayed on the operation panel 51 (step S7), and the sheet conveyance control is terminated.
If a jam removal operation is performed to remove the jammed sheet from the machine, the message indicating that a jam has occurred is turned off, and the interrupted print job is resumed. Yes.

When it is determined that a jam has occurred in the post-processing device 150 (“YES” in step S5), purge control is performed (step S8), and after the message indicating the occurrence of a jam is displayed (step S7), the control is terminated. The display at this time includes information such as the presence / absence of a remaining sheet in the machine and the position of the remaining sheet.
FIG. 10 is a flowchart showing the contents of the purge control subroutine in step S8. In this purge control, the main controller 60 activates the purge controller 402 (see FIG. 4).

  As shown in the figure, the purge control unit 402 first specifies a sheet to be purged (step S101). Specifically, the purge control unit 402 reads the sheet position information 421 from the RAM 62 and specifies the position of the sheet currently being conveyed on the conveyance path. Next, it is determined whether or not each sheet can be conveyed from the current position to the reverse tray 47 without being disturbed by a jam. This transportable sheet is specified as a purge target. Of course, this purge control is performed on the assumption that there is a sheet to be purged.

Then, it is determined whether there is a sheet passing through the branch point BP toward the relay unit 140 (step S102). When the sheet toward the relay unit 140 passes the branch point BP, the leading edge of the sheet passes the branch point BP toward the relay unit 140 on the conveyance path, and the rear end passes the branch point BP. When not in a state.
If it is determined that there is a sheet passing through the branch point BP (“YES” in step S102), the length (conveyance direction length) Ls of the sheet passing through the branch point BP and the relay unit 140 from the branch point BP are determined. The distance L1 to the nip portion of the transport roller 141 on the most upstream side is compared (step S103), and when the former length Ls is not longer than the latter distance L1 (see FIG. 5A) (step S103) In step S103, “NO”), the first control in step S105 is executed, the sheet conveying operation is terminated (step S114), and the process returns to the flowchart of FIG.

FIG. 11 is a flowchart showing the contents of the first control subroutine.
First, the conveyance of the sheet passing through the branch point BP is continued by the paper discharge roller 43 (step S201), and it is determined whether or not the trailing edge of the sheet has passed the branch point BP (step S202). When the sheet length Ls is equal to or less than the distance L1 as in this example, the trailing edge of the sheet can pass through the branch point BP without separating the conveyance roller pairs 141 to 143.

When the trailing edge of the sheet passes the branch point BP (“YES” in step S202), the conveyance destination is switched to the reversing port 44 side by the switching claw 41 in preparation for purging the next sheet (step S203).
Then, the conveyance of the sheet that reaches the branch point BP is purged on the reversing tray 47 by rotating the reversing roller 45 in the normal direction, and then the process returns to the flowchart of FIG.

  When it is determined in step S103 in FIG. 10 that the length Ls of the sheet passing through the branch point BP is longer than the distance L1 from the branch point BP to the nip portion of the first transport roller 141 of the relay unit 140. ("YES" in step S103), then, the length Ls of the sheet passing through the branch point BP is from the branch point BP to the nip portion of the introduction roller 161 that is the most upstream roller of the post-processing device 150. It is determined whether or not it is longer than the distance L2 (see FIG. 5 (a)) (step S104).

  If the determination in step S104 is affirmative (“YES” in step S), even if the sheet is conveyed until the leading edge of the sheet comes into contact with the nip portion of the introduction roller 161 of the post-processing device 150, the trailing edge is not detected. Since the branch point BP cannot be passed, the purge of the sheet is abandoned, the sheet conveying operation is terminated (step S114), and the process returns to the flowchart of FIG. Such a condition can be established mainly when a long sheet is supplied from the manual feed tray 16.

In step S104, the length Ls of the sheet passing through the branch point BP is a distance L2 from the branch point BP to the nip portion of the introduction roller 161 that is the most upstream roller of the post-processing device 150 (FIG. 5). If it is determined that it is not longer than (see (a)) (“NO” in step S104), the second control (step S106) is executed.
FIG. 12 is a flowchart showing the contents of this second control subroutine.

First, when the conveyance of the sheet passing through the branch point BP is continued, a time T1 until the leading end reaches the nip portion of the conveyance roller 141 on the most upstream side of the relay unit 140 is estimated (step S301).
As described above, the position of each sheet is grasped by the main control unit 60 based on the detection of each sensor. Therefore, the T1 can be obtained based on the position information and the sheet conveyance speed.

Next, a time T2 required from the start to the end of the separating operation of the transport rollers 141 to 143 of the relay unit 140 is acquired (step S302).
This time T2 is obtained in advance and stored in the ROM 63, and the CPU 61 reads out and acquires the value of the time T2 from the ROM 63.
Then, it is determined whether or not T1> T2 (step S303). If T1> T2 is not satisfied ("NO" in step S303), the sheet leading edge collides with the conveying roller pair 141 when the sheet conveyance is continued. Since there is a fear, the process returns to the flowchart of FIG. 10 without executing the purge operation, and after all the sheet conveyance is completed (step S114 of FIG. 10), the process returns to the main flowchart of FIG.

If T1> T2 (“YES” in step S303), separation of the conveying rollers 141 to 143 is started and conveyance of the sheet passing through the branch point is continued (step S304).
Then, it is determined whether or not the trailing edge of the sheet has passed the branch point BP (step S305). If it has passed (“YES” in step S305), the switching claw 41 moves the conveyance destination to the reversing port 44 side. (Step S306), and after purging the reverse tray 47 sequentially from the sheet that reaches the branch point BP (step S307), the process returns to the flowchart of FIG.

On the other hand, if it is determined in step S102 of FIG. 10 that there is no sheet passing through the branch point BP toward the relay unit 140 (“NO” in step S102), the leading edge of the next sheet reaches the branch point. It is determined whether or not the transfer destination can be switched in time (step S107).
Whether or not the transfer destination can be switched by the switching claw 41 in time can be determined as follows. That is, since the sheet conveyance speed V is constant at the system speed, the time required for switching the switching claw 41 is Ts, and the position retroactive to the upstream side in the conveyance direction by a predetermined distance (V × Ts) from the branch point BP is Ps. When this occurs (see FIG. 5A), if the current position of the leading edge of the sheet at the time of jam detection is a position upstream of the position Ps in the transport direction, it can be determined that the switching is in time. If this switching condition is satisfied (“YES” in step S107), the sheet after the sheet that reaches the branch point BP earliest (the sheet SH4 in FIG. 6B) can be purged. The conveyance destination is switched to the reversing port 44 side by the claw 41 (step S111), and the next sheet reaching the branch point BP is sequentially purged onto the reversing tray 47 (step S112). Is ended (step S114), and the process returns to the flowchart of FIG.

  If it is determined in step S107 that the transport destination cannot be switched before the leading edge of the next sheet reaches the branch point (“NO” in step S107), the next sheet is transferred to the relay unit 140. First, the sheet length Ls is compared with the distance L1 from the branch point BP to the nip portion of the conveying roller 141 on the most upstream side of the relay unit 140 (step S108). When the former sheet length Ls is longer than the latter distance L1 (see FIG. 5A) (“YES” in step S108), the length Ls of the next sheet is further from the branch point BP. It is determined whether or not it is longer than the distance L2 to the nip portion of the introduction roller 161 that is the most upstream roller of the processing device 150 (step S109).

  If the determination in step S109 is affirmative (“YES” in step S109), the sheet is conveyed until the leading edge thereof contacts the nip portion of the introduction roller 161 of the post-processing device 150 of the post-processing device 150. Even so, since the rear end cannot pass the branch point BP, the purging of the sheet is abandoned, the sheet conveying operation is terminated (step S114), and the process returns to the flowchart of FIG.

If a negative determination is made in step S109, that is, the length Ls of the next sheet is a distance L2 from the branch point BP to the nip portion of the introduction roller 161 that is the most upstream roller of the post-processing device 150. If it is not longer, the third control is executed (step S110).
FIG. 13 is a flowchart showing the contents of this third control subroutine.

First, when the next sheet is transported toward the relay unit 140, a time T3 until the leading end reaches the nip portion of the transport roller 141 on the most upstream side of the relay unit 140 is estimated (step S401).
As described above, since the position of each sheet is grasped by the main control unit 60 based on the detection of each sheet passing sensor, T3 can be easily obtained based on the position information and the sheet conveyance speed. .

Next, the time T2 required from the start to the end of the separating operation of the transport rollers 141 to 143 of the relay unit 140 is read from the ROM 63 and acquired (step S402).
Then, it is determined whether or not T3> T2 (step S403). If T3> T2 is not satisfied (“NO” in step S403), the sheet leading edge collides with the conveying roller pair 141 when the sheet conveyance is continued. Therefore, the process returns to the flowchart of FIG. 10 without executing the purge operation, and after completing all the sheet conveying operations (step S114 of FIG. 10), the main flowchart of FIG. Return.

If T3> T2 (“YES” in step S403), the separating operation of the conveying roller pairs 141 to 143 is started, and the next sheet is conveyed toward the relay unit 140 (step S404).
Then, it is determined whether or not the trailing edge of the sheet has passed the branch point BP (step S405). If it has passed (“YES” in step S405), the switching claw 41 moves the conveyance destination to the reversing port 44 side. (Step S406), and after purging on the reverse tray 47 sequentially from the next sheet reaching the branch point BP (Step S407), the process returns to the flowchart of FIG. Step S114 in FIG. 10 returns to the main flowchart in FIG.

  On the other hand, when it is determined in step S108 in FIG. 10 that the length Ls of the next sheet is not larger than the distance L1 from the branch point BP to the nip portion of the transport roller 141 on the most upstream side of the relay unit 140. ("NO" in step S108), the rear end of the sheet passing through the branch point can pass through the branch point BP without separating the conveying roller pairs 141 to 143. 4 control is executed, all the sheet conveying operations are finished (step S114), and the process returns to the flowchart of FIG.

FIG. 14 is a flowchart showing the contents of the fourth control subroutine.
First, the pre-discharge roller 33 and the discharge roller 43 convey the next sheet toward the relay unit 140 (step S501), and it is determined whether the trailing edge of the sheet has passed the branch point BP (step S501). Step S502).
When the trailing edge of the sheet passes the branch point BP (“YES” in step S502), the conveyance of the sheet is stopped, and the conveyance destination is moved to the reversing port 44 side by the switching claw 41 in preparation for purging the next sheet. Switching is performed (step S503).

Then, after sequentially purging on the reverse tray 47 via the reverse roller 45 from the next sheet that reaches the branch point BP (step S504), the process returns to the flowchart of FIG. In step S114, the process returns to the main flowchart of FIG.
By performing the purge control as described above, it is possible to purge the sheet in the conveyance path of the MFP 100 onto the reverse tray 47 as much as possible when a jam occurs in the post-processing apparatus 150.

  Note that the present invention is not limited to the sheet conveying apparatus, the image forming apparatus and the image forming system including the sheet conveying apparatus, and may be a purge control method. Furthermore, the method may be a program executed by a computer. The program according to the present invention includes various computer-readable recording media such as optical recording media such as DVD-ROM, DVD-RAM, CD-ROM, CD-R, MO, and PD, and flash memory recording media. In some cases, production, transfer, etc. may be made in the form of the recording medium, and various wired and wireless networks including the Internet in the form of programs, broadcasting, telecommunication lines, satellite communications, etc. In some cases, the data is transmitted and supplied via the Internet.

(Modification)
As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above-described embodiment, and the following modifications may be considered.
(1) In the above embodiment, control is performed so that all the nip portions of the transport rollers 141 to 143 of the relay unit 140 are separated in step S304 of FIG. 12 and step S404 of FIG. However, in practice, it is only necessary to feed the rear end of the sheet fed to the relay unit 140 (for example, the sheet SH3 in FIG. 7A) as much as it passes through the branch point BP. Only the rollers need be separated. In the state of FIG. 7A, since the rear end of the sheet SH3 has already passed through the branch point BP, the conveyance roller pairs 142 and 143 do not need to be separated from each other. In other words, the conveyance roller that is separated from the upstream side of the relay unit 140 may be selected and separated in accordance with the length in the conveyance direction of the sheet fed to the relay unit 140.

If the roller pair is separated and then returned and pressed repeatedly, the rollers may be partially deformed or damaged, and from the viewpoint of power saving, the unnecessary separation operation should be avoided as much as possible. This is desirable.
(2) When the transport rollers 141 to 143 of the relay unit 140 are separated from each other, the upper rollers 141a to 143a are moved upward in the embodiment described above. In some cases, the lower rollers 141b to 143b may be moved downward, or the upper rollers 141a to 143a and the lower rollers 141b to 143b may be moved away from each other. Configuration is also conceivable.

  (3) In the above embodiment, after the nip portions of the transport rollers 141 to 143 of the relay unit 140 are separated from each other in step S304 of FIG. 12 or step S404 of FIG. Although not specifically described, for example, it may be restored after the upstream sheet purge operation is completed, or it is detected that the sheet remaining in the relay unit 140 has been removed by the user. You may make it return after a while.

  (4) In the above embodiment, an example in which the image forming apparatus including the sheet conveying apparatus according to the present invention is applied to the tandem type printer 130 is described. However, the image forming apparatus is not limited to the tandem type, and color and monochrome images Regardless of the forming function, the present invention can be applied to general image forming apparatuses having a double-sided image forming function for forming an image such as a toner image on both surfaces (first and second surfaces) of a sheet, such as a copying machine and a facsimile machine. . Further, the present invention is not limited to the electrophotographic method, and can be applied to, for example, an inkjet image forming apparatus. Furthermore, the present invention is not limited to an image forming apparatus, and can be applied to a sheet conveying apparatus in general that conveys a sheet to a conveying destination apparatus.

The types of post-processing performed by the post-processing device 150 include processing for aligning a bundle of sheets, processing for binding a bundle of sheets with staples, processing for sorting sheets, and forming binding holes in the sheets. A process, a process of folding a sheet in half, or a process of inserting another sheet into a bundle of sheets may be included.
(5) Further, the configurations of the above embodiment and the above modification may be combined as much as possible.

  The present invention can be widely applied to a sheet conveying apparatus that conveys a sheet.

100 MFP
140 relay unit 150 post-processing apparatus 1a transport path 4a delivery path (first delivery path)
4b Inversion path (second delivery path)
DESCRIPTION OF SYMBOLS 11 Paper feed cassette 12P, 12F, 12R Feed roller group 14 Timing roller 23R Intermediate transfer belt drive roller 24 Secondary transfer roller 30 Fixing part 33 Pre-discharge roller 40 Sending part 41 Switching claw 42 Paper discharge port 43 Paper discharge roller 44 reversing port 45 reversing roller 47 reversing tray 48 circulation path 50 operation unit 140 relay unit 141 to 143 conveyance roller 161 introduction roller 200 separation mechanism 401 conveyance control unit 402 purge control unit BP branch point between delivery path and reversing path

Claims (7)

A sheet conveying apparatus that conveys a sheet to a conveyance destination apparatus during normal operation, and interrupts conveyance of the sheet to the conveyance destination apparatus when a jam is detected;
Conveying means for conveying the sheet along the conveying path;
A space for reversing the sheet conveyance direction between a first conveyance path toward the conveyance destination apparatus, a sheet conveyance destination from a branch point that is a downstream end of the conveyance path, and a space outside the housing of the sheet conveyance apparatus Switching means for switching to any one of the second delivery paths toward the reversing port that is the opening of the housing for use as
Relay conveying means for conveying the sheet on the first delivery path toward the conveying destination apparatus by one or more pairs of conveying rollers;
Separating means for separating each pair of conveying rollers in the relay conveying means;
When the jam of the first sheet is detected in the transport destination apparatus, the second sheet transported to the first delivery path is passing through the branch point and is upstream of the second sheet on the transport path. If there is a third sheet on the side,
Each pair of conveyance rollers in the relay conveyance unit is separated, and the second sheet is conveyed until the rear end in the conveyance direction of the second sheet passes the branch point, and after the conveyance direction of the second sheet. After the end passes through the branch point, the separation unit is configured to perform a purge operation of switching the third sheet conveyance destination to the second delivery path side and discharging the third sheet from the reversing port to the outside of the housing. Control means for controlling the conveying means and the switching means;
A sheet conveying apparatus comprising: The control means includes
The conveyance path length L1 from the branch point to the nip portion of the conveyance roller pair on the most upstream side in the sheet conveyance direction of the relay conveyance means is compared with the conveyance direction length Ls of the second sheet, and L1 <Ls. 2. The sheet conveying apparatus according to claim 1, wherein only in this case, the pair of conveying rollers of the relay conveying unit is separated by the separating unit. A plurality of transport roller pairs of the relay transport means exist along the first delivery path,
3. The control unit according to claim 2, wherein the control unit selects and separates a transport roller pair to be separated from the plurality of transport roller pairs according to a transport direction length Ls of the second sheet. Sheet conveying device. The control means includes
The time T1 until the leading edge of the second sheet reaches the nip portion of the conveying roller pair on the most upstream side in the sheet conveying direction of the relay conveying unit, and the conveying roller pair on the most upstream side in the sheet conveying direction by the separating unit. 4. The sheet according to claim 2, wherein a time T <b> 2 until the separation of the sheet is completed is compared, and when T <b> 1 ≦ T <b> 2, the conveyance of each sheet is stopped and the purge operation is prohibited. Conveying device. The control means includes
The conveyance path length L2 from the branch point to the nip portion of the conveyance roller on the most upstream side in the sheet conveyance direction of the conveyance destination apparatus is compared with the conveyance direction length Ls of the second sheet, and when L2 ≦ Ls, The sheet conveying apparatus according to claim 1, wherein conveyance of each sheet is stopped and execution of a purge operation is prohibited. An image forming apparatus that forms an image on a sheet conveyed by a sheet conveying unit,
An image forming apparatus comprising the sheet conveying device according to claim 1 as the sheet conveying unit. An image forming apparatus according to claim 6;
A post-processing device that performs predetermined post-processing on a sheet on which an image is formed by the image forming device;
With
An image forming system, wherein a sheet transport destination device by a sheet transport device in the image forming apparatus is the post-processing device.

Images