JP2022096194A - Image forming device and image forming method - Google Patents

Abstract

To provide an image forming device capable of avoiding an error of being incapable of supplying a sheet which occurs when the continuous printing is instructed in a state in which only one sheet longer than a prescribed length is left in a sheet feed tray.SOLUTION: An image forming device comprises a conveyance control unit 231C for controlling conveyance of a sheet, a sheet presence/absence determination unit 231A for determining whether or not a sheet is present in a sheet feed tray, and a length determination unit 231E for determining whether or not the length of the sheet being conveyed by a conveyance unit 30 is a prescribed length. The conveyance control unit 231C causes the conveyance unit 30 to further continue the conveyance of a long sheet determined to be longer than the prescribed length by the length determination unit 231E, and passes a rear end of the long sheet through a detection position detected by a resist sensor 33. The sheet presence/absence determination unit 231A determines the presence/absence of a sheet P in the sheet feed tray based on the detection information from a tray sensor 23 accompanying the conveyance control of the long sheet by the conveyance control unit 231C.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image forming apparatus and an image forming method.

An image forming apparatus for forming an image on a sheet such as paper is known. For example, the image forming apparatus described in Patent Document 1 is provided with a sheet length detecting means for detecting the length of a sheet in a transport direction, and erroneously detects the sheet length due to the sheet feeding / double feeding. It is preventing.
In this image forming apparatus, the length of each sheet (the length of the sheet detected by the paper length detecting means) constituting the sheet bundle set in the accommodating portion in the accommodating portion and the set sheet in the control unit. The absolute value of the difference in length is calculated. Then, the control unit determines that the length of the set sheet is inappropriate when the absolute value obtained by the calculation is larger than the predetermined value, and notifies the user that the length is inappropriate.

In the image forming apparatus, a sheet having the same size as the specified size is accommodated in the accommodating portion for accommodating the sheet bundle, but a sheet having a size different from the specified size may be accommodated.
In the image forming apparatus of Patent Document 1, when continuous image formation is instructed with only one sheet longer than the specified size remaining in the accommodating portion, the accommodating portion does not accommodate the sheet. Despite the presence, there was a possibility that it would be falsely detected as having a seat.
In the image forming apparatus of Patent Document 1, if it is erroneously detected that there is a sheet, the sheet is supplied in a state where the sheet is not accommodated in the accommodating portion at the time of printing on the next sheet of the sheet to be detected. Therefore, there was a problem that an error of supply failure occurred.

The present invention has been made in view of the above circumstances, and an object of the present invention is that continuous image formation is instructed with only one sheet longer than the setting remaining in the accommodating portion, and the present invention cannot be supplied. The purpose is to suppress the inconvenience that causes the error.

In order to solve the above problems, the invention according to claim 1 comprises a storage unit for accommodating a sheet bundle, a transport unit for transporting sheets taken out one by one from the top of the sheet bundle, and the transport unit. An image forming apparatus including an image forming unit that forms an image on a conveyed sheet, a sheet presence / absence detection sensor that detects the presence / absence of the sheet in the accommodating portion, and the sheet conveyed by the conveyed unit. A passage detection sensor that detects the passage of the sheet, a transfer control unit that controls the transfer by the transfer unit, and a sheet presence / absence determination unit that determines the presence / absence of the sheet in the accommodation unit based on the detection information from the sheet presence / absence detection sensor. And a length determination unit for determining whether or not the length of the sheet conveyed by the transfer unit is a specified length based on the detection information of the passage detection sensor, and the transfer control unit. Passes the rear end of the specific sheet through the detection position by the passage detection sensor by further continuing the transportation of the specific sheet determined by the length determination unit to be longer than the specified length. The sheet presence / absence determination unit is characterized in that, in accordance with the transfer control of the specific sheet by the transfer control unit, the presence / absence of the sheet in the accommodation unit is determined based on the detection information from the sheet presence / absence detection sensor. And.

According to the present invention, even when continuous image formation is instructed with only one sheet longer than the setting remaining in the accommodating portion, it is possible to suppress the inconvenience of causing an error that the sheet cannot be supplied.

It is a schematic explanatory drawing which shows the image forming apparatus which concerns on one Embodiment of this invention. It is a hardware block diagram of the image forming apparatus which concerns on one Embodiment of this invention. (A) is a hardware configuration diagram of the engine control unit, and (b) is a functional block diagram of the main control unit. (A) to (f) are diagrams for explaining the transport of paper in a state where a plurality of sheets of a specified size are stored. (A) to (g) are diagrams for explaining the transport of paper in a state where paper of a specified size is accommodated under long paper. (A) to (e) are diagrams for explaining the transport of paper in a state where only one long paper is stored. It is a flowchart explaining the continuous printing process. It is a flowchart explaining the process at the time of a resist sensor ON. It is a flowchart explaining the long paper processing.

Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. However, unless there is a specific description, the components, types, combinations, shapes, relative arrangements, etc. described in the embodiments are merely explanatory examples, not the purpose of limiting the scope of the present invention to that alone. ..

<Characteristics of the image forming apparatus 1 according to this embodiment>
First, the features of the image forming apparatus 1 will be described. FIG. 1 is a schematic explanatory view of an image forming apparatus 1.
The image forming apparatus 1 exemplified in FIG. 1 includes a paper feed tray 21 (accommodation unit), a transport unit 30, an image forming unit 40, and a fixing unit 50, and is a sheet-shaped paper P (accommodated in the paper feed tray 21). The image is printed (formation and fixing of the toner image) on the sheet). The paper feed tray 21 accommodates a paper bundle PS (sheet bundle). That is, the paper P of the specified size is housed in the paper feed tray 21 in a laminated state. Above the paper feed tray 21, a tray sensor 23 (sheet presence / absence detection sensor) for determining the presence / absence of paper P in the paper feed tray 21 is provided. The transport unit 30 transports the paper P taken out one by one from the top of the paper bundle PS. The image forming unit 40 forms a toner image on the paper P conveyed by the conveying unit 30. A resist sensor 33 (passage detection sensor) is provided immediately before the image forming unit 40 to detect the paper P fed to the image forming unit 40. The fixing unit 50 fixes the toner image on the paper P.

Originally, paper P of a specified size should be stored in the paper feed tray 21 in a laminated state, but paper P (long paper) longer than the specified size may be stored due to a mistake or the like. Therefore, the image forming apparatus 1 is provided with a function of determining whether the paper P transported by the transport unit 30 is a paper of a specified size or a long paper.
For example, the main control unit 231 (see FIG. 3) causes the paper P to stand by at a predetermined standby position based on the change in the detection signal from the resist sensor 33, and then starts the transfer from the standby position. After that, the main control unit 231 acquires the passing timing of the rear end of the paper P based on the change of the detection signal from the resist sensor 33, the elapsed time from the start of transporting the paper P, and the transport speed of the paper P. The length of the paper P is obtained based on the above. Further, the main control unit 231 determines whether or not the acquired length of the paper P is longer than the specified length of the paper P accommodated in the paper feed tray 21.

When the main control unit 231 determines that the paper P transported by the transport unit 30 is a long paper (specific sheet) longer than the specified length, the main control unit 231 continues the transport to the long paper and lengthens the paper P. The rear edge of the scale paper is passed through the detection position by the resist sensor 33.
Further, the main control unit 231 determines the presence or absence of the paper P in the paper feed tray 21 as the paper is continuously conveyed to the long paper, based on the detection signal (detection information) from the tray sensor 23, and causes the paper feed tray 21 to determine the presence or absence of the paper P. If it is determined that there is no paper P, the user is notified that there is no paper P. The user supplies the paper P to the paper feed tray 21 based on the notification that there is no paper P, and then instructs the image forming apparatus 1 to print.
Therefore, the main control unit 231 can recognize that there is no paper P even when continuous printing is instructed with only one sheet of long paper remaining in the paper feed tray 21, and the paper is present. The inconvenience of false detection can be suppressed.

<Details of the image forming apparatus 1 according to this embodiment>
Next, the details of the image forming apparatus 1 will be described. The image forming apparatus 1 shown in FIG. 1 is, for example, an MFP (Multifunction Peripheral / Product / Printer), and includes a printer unit 10, a scanner unit 110, and a post-processing device 120.
The image forming apparatus 1 is not limited to the MFP. For example, the image forming apparatus 1 may be a copying machine, a printer, or a facsimile transceiver.

The printer unit 10 prints on the paper P. The printer unit 10 will be described in detail later. The scanner unit 110 reads the original and converts it into image data.
The post-processing device 120 receives the paper P discharged from the printer unit 10 and performs various post-processing processes such as bookbinding, sorting, and stacking. Therefore, the post-processing device 120 includes a post-processing device main body 121 for performing post-processing, and a paper discharge tray 122 for accumulating the paper P discharged from the post-processing device main body 121. The image forming apparatus 1 may or may not be provided with the post-processing apparatus 120.

The printer unit 10 includes a paper feeding unit 20, a transport unit 30, an image forming unit 40, and a fixing unit 50.
The paper feed unit 20 includes a paper feed tray 21, a paper feed roller 22, and a tray sensor 23, accommodates the paper bundle PS, and takes out the paper P one by one from the top of the paper bundle PS to convey the paper. Supply to 30.
The paper feed tray 21 includes a tray body 21a and a bottom plate 21b. The tray body 21a is a container for accommodating a bundle of paper PS (sheet bundle, a plurality of stacked sheets), and has, for example, a box shape with an open upper surface. The bottom plate 21b is a plate-shaped member on which the paper bundle PS is placed, and is arranged so as to be movable along the vertical direction in the inner space of the tray main body 21a.
The tray body 21a is manufactured to a size that can accommodate the maximum size of the paper P among the plurality of sizes of the paper P that can be printed by the image forming apparatus 1, and is produced by, for example, a movable partition provided on the bottom plate 21b. A storage space of a size suitable for each size of paper P is formed.

The paper feed roller 22 takes out one sheet of paper P located at the uppermost position from the paper bundle PS housed in the paper feed tray 21 and feeds it toward the transport unit 30. The tray sensor 23 detects the presence or absence of paper P in the paper feed tray 21, and is manufactured by, for example, a photoelectric sensor. The tray sensor 23 of the present embodiment is turned on when the paper P is detected, and turned off when the paper P is not detected. The tray sensor 23 is not limited to the photoelectric sensor, and may be any type of sensor that can detect the presence or absence of paper P in the paper feed tray 21.
In the present embodiment, the paper feed unit 20 includes two sets of a paper feed tray 21, a paper feed roller 22, and a tray sensor 23. The upper set (21A, 22A, 23A) and the lower set (21B, 22B, 23B) may contain the same size paper P or different sizes of paper P.

The transport unit 30 is a means for transporting the paper P taken out from the paper feed unit 20 along the transport path TP, and is composed of a roller, a belt, a motor for driving these, a guide rail, and the like. That is, the transfer unit 30 includes a transfer roller pair 31, a resist roller pair 32, a resist sensor 33, a secondary transfer roller 34, a secondary transfer belt 35, a transfer belt 36, a paper ejection roller 37, a paper ejection sensor 38, and a paper sensor. It has 39.
The transport roller pair 31 sandwiches the paper P from both the front surface and the back surface and rotates about the axis to feed the paper P along the transport path TP. Therefore, a plurality of transport roller pairs 31 are arranged at intervals along the transport path TP.

The resist roller pair 32 is provided immediately before the image forming unit 40 in the transport path TP, and when the transfer timing of the toner image formed on the intermediate transfer belt arrives, the nipped paper P is sent to the image forming unit 40. .. The paper P is temporarily stopped at the nip position of the resist roller pair 32 where the rotation drive is stopped. Then, the paper P is fed to the image forming unit 40 by rotationally driving the resist roller pair 32 in time with the toner image moving together with the intermediate transfer belt.
The resist sensor 33 is provided, for example, between the resist roller pair 32 and the image forming unit 40, and detects the presence or absence of the paper P fed to the image forming unit 40. Since the resist sensor 33 also detects the rear end of the paper P fed to the image forming unit 40, it can be said to be a passage detection sensor that detects the passage of the paper P being transported by the transport unit 30.
The resist sensor 33 of the present embodiment is manufactured by, for example, a photoelectric sensor, and is turned on in the detection state of the paper P and turned off in the non-detection state of the paper P. The tray sensor 23 is not limited to the photoelectric sensor, and may be any type of sensor that can detect the presence or absence of the paper P being conveyed by the conveying unit 30.
The image forming unit 40 forms a toner image transferred to the paper P. The image forming unit 40 will be described later.

The secondary transfer roller 34 nips the intermediate transfer belt 48 and the secondary transfer belt 35 of the image forming unit 40 together with the secondary transfer facing roller 49 of the image forming unit 40. When the paper P passes through the secondary transfer roller 34 and the secondary transfer facing roller 49, the multicolor toner image formed by the image forming unit 40 is transferred to the paper P.
The secondary transfer belt 35 transports the paper P on which the toner image is transferred to the downstream side in the transport direction of the transport path TP. The transfer belt 36 is arranged between the secondary transfer belt 35 and the fixing section 50, and supplies the paper P conveyed by the secondary transfer belt 35 to the fixing section 50. The paper ejection roller 37 and the paper ejection sensor 38 are provided immediately before the post-processing device 120 in the transport path TP. The paper ejection roller 37 ejects the paper P after passing through the fixing portion 50 toward the post-processing device 120. The paper ejection sensor 38 detects the paper P ejected toward the post-processing device 120. A plurality of paper sensors 39 are provided at intervals along the transport path TP, and detect the paper P on the transport path TP.

The image forming unit 40 forms a toner image to be transferred to the paper P in response to a printing command (printing job). The image forming unit 40 includes an image forming unit 41, a primary transfer roller 46, an exposure unit 47, an intermediate transfer belt 48, and a secondary transfer opposed roller 49.
The image forming unit 41 is a part for producing a toner image, for example, an image forming unit 41Y for producing a yellow toner image, an image forming unit 41M for producing a magenta toner image, and an image forming unit 41C for producing a cyan toner image. , And an image forming unit 41K for producing a black toner image. Since each image forming section 41Y, 41M, 41C, and 41K have the same configuration, the image forming section 41K will be described as an example.

The image forming unit 41K includes a photoconductor drum 42, a charging unit 43, a developing unit 44, and a cleaning unit 45. In the image forming unit 41K, an image forming process (charging step, exposure step, developing step, transfer step, cleaning step, static elimination step) is performed on the photoconductor drum 42, and a black toner image is formed on the surface of the photoconductor drum 42. Is formed.

The photoconductor drum 42 is rotationally driven in the direction of arrow R by a drum motor, and the surface of the photoconductor drum 42 is uniformly charged at the position of the charging unit 43. After that, the surface of the photoconductor drum 42 reaches the irradiation position of the laser beam emitted from the exposed portion 47, and the electrostatic latent image corresponding to black is formed by the exposure scanning by the irradiation of the laser beam.
After that, the surface of the photoconductor drum 42 reaches a position facing the developing unit 44, the electrostatic latent image is developed by the developing unit 44, and a black toner image is formed on the surface of the photoconductor drum 42. After that, the surface of the photoconductor drum 42 reaches the opposite position of the primary transfer roller 46. An intermediate transfer belt 48 is sandwiched between the photoconductor drum 42 and the primary transfer roller 46. The black toner image formed on the surface of the photoconductor drum 42 is primarily transferred to the surface of the intermediate transfer belt 48 at the position of the primary transfer roller 46.
After that, the surface of the photoconductor drum 42 reaches a position facing the cleaning unit 45, and the cleaning unit 45 (cleaning blade) collects the untransferred toner remaining on the photoconductor drum 42. Finally, the surface of the photoconductor drum 42 reaches a position facing the static elimination portion, and the residual potential on the photoconductor drum 42 is removed at this position.

The above image-forming process is also performed in the other image-forming units 41Y, 41M, and 41C in the same manner as in the image-forming unit 41K. The toner images of each color formed on the surface of the photoconductor drum 42 in the respective image forming portions 41Y, 41M, 41C, and 41K are superimposed on the intermediate transfer belt 48 and primaryly transferred. As a result, a multicolor toner image is formed on the intermediate transfer belt 48.

The intermediate transfer belt 48 on which the multicolor toner image is formed reaches a position facing the secondary transfer roller 34 (secondary transfer belt 35). At this position, the secondary transfer facing roller 49 forms the secondary transfer nip by sandwiching the intermediate transfer belt 48 and the secondary transfer belt 35 with the secondary transfer roller 34. Then, the multicolor toner image formed on the intermediate transfer belt 48 is secondarily transferred to the paper P conveyed to the position of the secondary transfer nip.
After that, the intermediate transfer belt 48 reaches the position of the intermediate transfer cleaning unit 45. Then, the deposits such as untransferred toner adhering to the surface of the intermediate transfer belt 48 are removed by the intermediate transfer cleaning unit 45. Removal of deposits completes a series of transfer processes performed on the intermediate transfer belt 48.

The paper P on which the multicolor toner image is secondarily transferred is supplied to the fixing portion 50 by the secondary transfer belt 35 and the transport belt 36. The fixing portion 50 includes a fixing belt 51 and a pressure roller 52. Heat and pressure from the fixing belt 51 and the pressure roller 52 are applied to the paper P, and the secondary transferred multicolor toner image is fixed.
After that, the paper P is sent out to the post-processing device 120 by the paper ejection roller 37, and is post-processed by the post-processing device 120. The post-processed paper P is discharged to the output tray 122. By ejecting the paper P to the output tray 122, a series of printing operations by the image forming apparatus 1 is completed.

<Hardware configuration of image forming apparatus 1>
FIG. 2 is a hardware configuration diagram of the image forming apparatus 1 (MFP). As shown in FIG. 2, the image forming apparatus 1 includes a controller 210, a short-range communication circuit 220, an engine control unit 230, an operation panel 240, and a network I / F (InterFace) 250. The hardware configuration of the image forming apparatus 1 is not limited to the configuration shown in FIG. For example, the operation panel 240 may be configured to be connected to the SB instead of the ASIC (Application Specific Integrated Circuit).
Of these, the controller 210 is the CPU 201, which is the main part of the computer, the system memory (MEM-P) 202, the north bridge (NB) 203, the south bridge (SB) 204, the ASIC 206, and the local memory (MEM-) which is a storage unit. It has a C) 207, an HDD controller 208, and a magnetic disk (HD) 209 that is a storage unit. The NB 203 and the ASIC 206 are connected by an AGP (Accelerated Graphics Port) bus 221.
However, the configuration of the controller 210 is not limited to this. For example, two or more components such as CPU201, NB203, and SB204 may be realized by SoC (System on Chip). In this case, the SoC and the ASIC 206 may be connected by a PCI-express (registered trademark) bus.

The CPU 201 is a control unit that controls the entire image forming apparatus 1. The NB 203 is a bridge for connecting the CPU 201 to the MEM-P202, SB204, and the AGP bus 221. The NB 203 includes a memory controller that controls reading and writing to the MEM-P202, a PCI (Peripheral Component Interconnect) master, and an AGP target. Has.
The MEM-P202 includes a ROM 202a which is a memory for storing programs and data that realizes each function of the controller 210, and a RAM 202b which is used as a memory for developing programs and data and a memory for drawing at the time of memory printing. The program stored in the RAM 202b is configured to be recorded and provided as a file in an installable format or an executable format on a computer-readable recording medium such as a CD-ROM, CD-R, or DVD. You may.

SB204 is a bridge for connecting NB203 to a PCI device and peripheral devices. The ASIC 206 is an IC (Integrated Circuit) for image processing applications having hardware elements for image processing. The ASIC 206 serves as a bridge connecting the AGP bus 221 and the PCI bus 222, the HDD controller 208, and the MEM-C207, respectively. The ASIC 206 includes an arbiter (ARB), a memory controller, a plurality of DMACs (Direct Memory Access Controllers), and a PCI unit. The arbiter is the core of the PCI target, AGP master and ASIC. The memory controller controls MEM-C. The DMAC is configured by hardware logic or the like to rotate image data or the like. The PCI unit transfers data between the printer unit 10, the scanner unit 110, and the post-processing device 120 via the PCI bus 222.
A USB (Universal Serial Bus) interface or an IEEE 1394 (Institute of Electrical and Electronics Engineers 1394) interface may be connected to the ASIC 206.

The MEM-C207 is a local memory used as a copy image buffer and a code buffer. The HD209 is a storage for accumulating image data, accumulating font data used at the time of printing, and accumulating forms. The HDD controller 208 controls reading or writing of data to the HD 209 according to the control of the CPU 201. The AGP bus 221 is a bus interface for a graphics accelerator card proposed to speed up graphics processing, and the graphics accelerator card can be speeded up by directly accessing the MEM-P202 with a high throughput. .. However, MEM-C207 may not be installed.

Further, the short-range communication circuit 220 is provided with an antenna 220a for transmitting and receiving data. The short-range communication circuit 220 is a communication circuit such as NFC or Bluetooth.
Further, the engine control unit 230 includes a printer unit 10, a scanner unit 110, and a post-processing device 120. Further, the operation panel 240 displays the current setting value, the selection screen, and the like, and displays the panel display unit 241 such as a touch panel that accepts the input from the operator, and the setting value of the condition related to image formation such as the density setting condition. It includes a panel operation unit 242 including a numeric keypad for receiving, a start key for receiving a copy start instruction, and an application switching key for receiving a function switching instruction performed by the image forming apparatus 1.

The controller 210 controls the entire image forming apparatus 1, for example, drawing, communication, input from the operation panel 240, and the like. The scanner unit 110 or the printer unit 10 includes an image processing portion such as error diffusion and gamma conversion.
The image forming apparatus 1 can sequentially switch and select the document box function, the copy function, the printer function, and the facsimile function by the application switching key of the operation panel 240. When the document box function is selected, the document box mode is set, when the copy function is selected, the copy mode is set, when the printer function is selected, the printer mode is set, and when the facsimile mode is selected, the facsimile mode is set. The operation panel 240 includes a display unit such as an LCD for displaying various information and an LED for displaying an operating state by turning on / off, and an input unit having a touch panel and a hard key switch. If the operation panel 240 is provided with a touch panel, the hard key switch may not be provided.
Further, the network I / F 250 is an interface for performing data communication using a communication network. The short-range communication circuit 220 and the network I / F 250 are electrically connected to the ASIC 206 via the PCI bus 222.

Next, the engine control unit 230 will be described. FIG. 3A is a hardware configuration diagram of the engine control unit 230, and FIG. 3B is a functional block diagram of the main control unit 231.
As shown in FIG. 3A, the engine control unit 230 includes a main control unit 231, a printer unit 10, a scanner unit 110, and a post-processing device 120.
The main control unit 231 controls the printer unit 10, the scanner unit 110, and the post-processing device 120 in cooperation with the controller 210, and includes a CPU 231a and a memory 231b.
The CPU 231a is a central part of the control of the engine control unit 230, and reads out and executes a computer program stored in the memory 231b. The memory 231b stores a computer program executed by the CPU 231a. Further, the memory 231b expands a computer program and temporarily stores various data during the operation of the CPU 231a.

As described above, the printer unit 10 includes a paper feeding unit 20, a transport unit 30, an image forming unit 40, and a fixing unit 50. In addition to the tray sensor 23 described above, the paper feed unit 20 includes a paper feed motor 321 (sheet supply motor) that rotationally drives the paper feed roller 22. In addition to the paper sensor 39, the resist sensor 33, and the paper ejection sensor 38 described above, the transport unit 30 includes a transport motor 331 that rotationally drives the transport roller pair 31, a resist roller drive motor 332 that rotationally drives the resist roller pair 32, and a paper discharge sensor 38. It includes a paper ejection motor 333 that rotationally drives the paper ejection roller 37.
The image forming unit 40 includes a transfer belt drive motor 341 for rotationally driving the transfer belt, in addition to the image forming units 41Y, 41M, 41C, and 41K described above.
The fixing portion 50 includes a fixing belt drive motor 351 that rotationally drives the fixing belt 51, and a heater 352 that heats the fixing portion 50 (for example, the pressure roller 52).

As shown in FIG. 3B, the main control unit 231 includes a paper presence / absence determination unit 231A, a supply control unit 231B, a transfer control unit 231C, and an image formation control unit 231D as the CPU 231a executes a computer program. It functions as a length determination unit 231E, a stop control unit 231F, and a notification control unit 231G.

The paper presence / absence determination unit 231A determines the presence / absence of paper P (sheet) in the paper feed tray 21 based on the detection signal from the tray sensor 23. The supply control unit 231B controls the operation of the paper feed motor 321 to take out the paper P one by one from the top of the paper bundle PS accommodated in the paper feed tray 21, and the taken out paper P is transferred to the transport unit 30. Supply towards. The transport control unit 231C controls the operation of the transport unit 30 (conveyor motor 331, resist roller drive motor 332, and paper ejection motor 333) based on the detection signals from the paper sensor 39, the resist sensor 33, and the paper ejection sensor 38. Then, the transport of the paper P in the transport unit 30 is controlled. The image formation control unit 231D controls the image formation unit 40 based on a print command (print job) to form a multicolor toner image on the paper P.

The length determination unit 231E acquires the length of the paper P conveyed by the transfer unit 30 based on the detection signal from the resist sensor 33, and whether or not the acquired length of the paper P is the specified length. Is determined. In the following description, among the papers P to be determined by the length determination unit 231E, the paper P determined by the length determination unit 231E to be longer or shorter than the specified length is referred to as a specific paper (the specific paper). Long paper, short paper).
The transfer control unit 231C further continues the transfer of the specified paper by the transfer unit 30. As a result, the specific paper is discharged toward the post-processing device 120 after the rear end has passed through the resist sensor 33. When the stop control unit 231F determines that there is no paper P in the paper feed tray 21 by the paper presence / absence determination unit 231A, or the length determination unit 231E determines that the paper P is longer or shorter than the specified length. If so, the printing is stopped (the printing operation is canceled).
The notification control unit 231G controls the panel display unit 241 and the like when the length determination unit 231E determines that the paper P is longer or shorter than the specified length, or when the tray sensor 23 detects that there is no paper. Notify the user of the judgment result and the detection result.

<Transportation of paper P during continuous printing>
Next, the transfer of the paper P at the time of continuous printing performed by the image forming apparatus 1 according to the present embodiment will be described.
FIG. 4 is a diagram illustrating the transfer of the paper P in a state where a plurality of sheets P of the specified size are stored, and FIG. 5 is a diagram of the paper P in a state where the paper P of the specified size is stored under the long paper. FIG. 6 is a diagram illustrating transport, and FIG. 6 is a diagram illustrating transport of paper P in a state where only one sheet of long paper is accommodated.

<About the state where multiple sheets of paper P of the specified size are stored>
First, the transport of paper P in a state where a plurality of sheets P of a specified size are accommodated in the paper feed tray 21 will be described.
As shown in FIG. 4A, when a plurality of sheets P of a specified size are accommodated and continuous printing is instructed on the paper P, the main control unit 231 (paper presence / absence determination unit 231A) is instructed. Based on the detection signal from the tray sensor 23, the presence or absence of the paper P in the paper feed tray 21 is determined.
As shown in FIG. 4B, the main control unit 231 (supply control unit 231B) controls the operation of the paper feed motor 321 based on the determination result that the paper P is present, and is housed in the paper feed tray 21. One sheet of paper P1 (first sheet of paper, preceding paper) is taken out from the top of the paper bundle PS and supplied to the transport unit 30.

As shown in FIG. 4C, in the main control unit 231 (conveyance control unit 231C, paper presence / absence determination unit 231A), the rear end of the first sheet of paper P1 in which the transfer path TP is conveyed by the transfer unit 30 is a determination criterion. When it is determined that the paper has passed the position RP, the presence or absence of the paper P in the paper feed tray 21 is determined based on the detection signal from the tray sensor 23.
The determination reference position RP is used to determine whether or not to start supplying the topmost paper P2 (second sheet, subsequent paper) of the paper bundle PS. Therefore, the determination reference position RP is set at a position with a necessary distance from the tip position of the paper P2 accommodated in the paper feed tray 21.

In the present embodiment, the main control unit 231 estimates the rear end position of the first sheet P1 when the tip of the first sheet P1 reaches the detection position of the resist sensor 33. The estimation of the rear end position of the paper P1 by the main control unit 231 is performed based on the paper size information indicating the paper size (paper length, paper width) in the setting. Specifically, the rear end position of the first sheet P1 is the upstream side in the transport direction from the detection position of the resist sensor 33 at the timing when the tip of the first sheet P1 passes the detection position of the resist sensor 33. It is estimated that the position is traced back by the set paper length toward.
In the example of FIG. 4C, since the length of the first sheet P1 is equal to the set sheet length, the actual rear end position of the first sheet P is the same as the controlled rear end position. be. Therefore, the main control unit 231 determines that the rear end of the first sheet P1 has passed the determination reference position RP when the tip of the first sheet P1 reaches the detection position of the resist sensor 33. do.
The method for estimating the rear end position of the first sheet of paper P1 is not limited to the above method. For example, the rear end position of the first sheet P1 is set to the set sheet length of the first sheet P, the transfer speed of the first sheet P on the transfer path TP, and the first sheet P. May be estimated based on the elapsed time from the start of supply to the transport unit 30.

When the tip of the first sheet of paper P1 reaches immediately before the image forming unit 40, the main control unit 231 (conveyance control unit 231C, image formation control unit 231D) suspends the transfer of the first sheet of paper P1. In the example of FIG. 4C, when the tip of the first sheet P1 reaches the detection position of the resist sensor 33, the main control unit 231 suspends the transfer of the first sheet P1.
After that, when the transfer timing of the toner image arrives, the main control unit 231 feeds the first sheet P1 to the image forming unit 40. Printing is performed on the first sheet of paper P1 by the image forming unit 40 and the fixing unit 50. That is, when the first sheet of paper P1 passes through the image forming unit 40 (the above-mentioned secondary transfer nip), the toner image is transferred to the first sheet of paper P1. After that, when the first sheet P1 on which the toner image is transferred passes through the fixing portion 50, the toner image is fixed on the first sheet P1.

In the main control unit 231 (conveyance control unit 231C, paper presence / absence determination unit 231A), the rear end of the first sheet P is the determination reference position RP before the toner image is transferred to the first sheet P1. If it is not determined that the sheet has passed, it is determined whether or not the rear end of the first sheet of paper P1 has passed the determination reference position RP during the transfer period of the toner image.
Since the transport speed of the first sheet P1 during the transfer period is known, the main control unit 231 sets the rear end position of the first sheet P1 to the set sheet length of the first sheet P1. It is estimated based on the transport speed (transfer speed) of the first sheet P1 and the elapsed time from the start of transfer of the toner image.

As shown in FIG. 4D, the main control unit 231 (supply control unit 231B) controls the operation of the paper feed motor 321 based on the determination result that the paper P is present, and is housed in the paper feed tray 21. The uppermost paper (second sheet) P2 of the paper bundle PS is taken out and supplied to the transport unit 30. As described above, at the time when the supply of the second sheet P2 is started, the rear end of the first sheet P1 has passed the determination reference position RP, and the front end of the second sheet P2 and the first sheet. Since a necessary space is provided between the rear end of the paper P1 and the rear end of the paper P1, the inconvenience that the two sheets P1 and P2 are supplied in an overlapping manner is suppressed.

Further, the main control unit 231 (length determination unit 231E) monitors the detection signal from the resist sensor 33 (passage detection sensor) with the start of transfer of the toner image to the first sheet P1, and the first sheet. It is determined whether or not the length of the paper P1 of the above is the specified length.
For example, the main control unit 231 measures the elapsed time from the start of transfer of the toner image to the first sheet of paper P1 while monitoring the detection signal from the resist sensor 33. Then, the main control unit 231 is within the determination time range corresponding to the predetermined length of the elapsed time from the start of transcription (within the range of the first determination time (S7) or more and less than the second determination time (S13) shown in FIG. 7). In addition, when the detection signal from the resist sensor 33 is switched from ON (with paper) to OFF (without paper), it is determined that the first sheet P1 has a specified length.
Since the first sheet P1 shown in FIG. 4D has a specified length, the main control unit 231 (length determination unit 231E, image formation control unit 231D) prints on the first sheet P1. (Formation and fixing of toner image) is performed.

As shown in FIG. 4 (e), the main control unit 231 (conveyance control unit 231C, paper presence / absence determination unit 231A) is 2 when the tip of the second sheet P2 reaches the detection position of the resist sensor 33. When it is determined that the rear end of the second sheet of paper P2 has passed the determination reference position RP, the presence or absence of the paper P in the paper feed tray 21 is determined based on the detection signal from the tray sensor 23. Further, the main control unit 231 (conveyance control unit 231C) ejects the first sheet of paper P1 from the printer unit 10 toward the post-processing device 120.
As shown in FIG. 4 (f), the main control unit 231 (supply control unit 231B) controls the operation of the paper feed motor 321 based on the determination result that the paper P is in the paper feed tray 21 to supply the paper. The uppermost paper (third paper) P3 of the paper bundle PS housed in the paper tray 21 is supplied to the transport unit 30.
By repeating the above operation, the main control unit 231 continuously prints an image on a paper P having a specified size.

<About the state where the specified size paper P is stored under the long paper>
Next, a state in which long paper longer than the specified length is stored at the top of the paper bundle PS housed in the paper feed tray 21 or in the middle of the stacking direction, in other words, a specified size under the long paper. The transport of the paper P in the state where the paper P is housed will be described.
As shown in FIG. 5A, continuous printing on paper P is performed in a state where the uppermost paper (first sheet) P11 of the paper bundle PS accommodated in the paper feed tray 21 is long paper. Is instructed, the main control unit 231 (paper presence / absence determination unit 231A) determines the presence / absence of paper P in the paper feed tray 21 based on the detection signal from the tray sensor 23.
As shown in FIG. 5B, the main control unit 231 (supply control unit 231B) controls the operation of the paper feed motor 321 based on the determination result that the paper P is present, and is located at the top of the paper bundle PS. The first sheet of paper P11 located is supplied toward the transport unit 30.

As shown in FIG. 5C, in the main control unit 231 (conveyance control unit 231C, paper presence / absence determination unit 231A), the rear end of the first sheet of paper P11 for transporting the transport path TP by the transport unit 30 is a determination criterion. When it is determined that the position RP has been reached, the presence or absence of the paper P in the paper feed tray 21 is determined based on the detection signal from the tray sensor 23.
The main control unit 231 (conveyance control unit 231C) estimates the rear end position of the first sheet P11 prior to determining the presence or absence of the sheet P. As described above, the estimation of the rear end position of the first sheet of paper P11 by the main control unit 231 is the set paper length of the first sheet of paper P11 and the transport speed (transfer speed) of the first sheet of paper P11. ), And based on the elapsed time from the start of transfer of the toner image.

As described with reference to FIG. 4C, the paper length on the setting of the first sheet P11 is determined by the rear end of the paper P when the front end of the paper P reaches the detection position of the resist sensor 33. It is the length that passes through the reference position RP. Therefore, the main control unit 231 (conveyance control unit 231C) determines that the rear end of the first sheet of paper P11 has passed the determination reference position RP.
However, as shown in FIG. 5C, since the first sheet of paper P11 is a long sheet of paper longer than the set sheet length, the actual rear end position of the first sheet of paper P11 is estimated. It is located on the downstream side in the transport direction from the rear end position. In the example of FIG. 5C, when the front end of the first sheet P11 reaches the detection position of the resist sensor 33, the rear end of the first sheet P11 is downstream of the tray sensor 23 in the transport direction. Is located in.

In the example shown in FIG. 5C, the main control unit 231 (paper presence / absence determination unit 231A) puts paper on the paper feed tray 21 based on the fact that the tray sensor 23 detects the rear end portion of the first sheet of paper P11. It is determined that there is P. The main control unit 231 (supply control unit 231B) controls the paper feed motor 321 to rotate the paper feed roller 22 when it is determined that the paper P is in the paper feed tray 21. Due to the rotation of the paper feed roller 22, the rear end portion of the first sheet of paper P11 is fed to the downstream side in the transport direction.

As shown in FIG. 5D, the main control unit 231 (length determination unit 231E) monitors the detection signal from the resist sensor 33 as the transfer of the toner image to the first sheet of paper P11 starts. It is determined whether or not the length of the first sheet P11 is the specified length.
As described above, the main control unit 231 measures the elapsed time from the start of transfer to the first sheet P11 while monitoring the detection signal from the resist sensor 33. Then, even if the elapsed time from the start of transfer exceeds the second determination time (FIGS. 7, S13) corresponding to the set length of the first sheet of paper P11, the main control unit 231 is still from the resist sensor 33. When the detection signal remains ON (with paper), it is determined that the first sheet P11 is a long sheet longer than the specified length.

In the example of FIG. 5D, the main control unit 231 determines that the first sheet P11 is a long sheet. When the main control unit 231 (length determination unit 231E, stop control unit 231F, transfer control unit 231C) determines that the first sheet P11 is a long sheet, the main control unit 231 cancels the printing operation on the first sheet P11. And continue the transportation. In other words, the first sheet of paper P11 is determined to be a long sheet of paper, and the ejection to the post-processing device 120 is started.
When the main control unit 231 (notification control unit 231G) determines that the first sheet of paper P11 is a long sheet of paper, it controls the panel display unit 241 and the like to notify the user of the determination result. Further, since the main control unit 231 has canceled the printing operation, the panel display unit 241 displays information for prompting continuous printing again.
If the main control unit 231 (stop control unit 231F, transfer control unit 231C) supplies the second sheet P to the transfer unit 30 before determining that the paper is long, the main control unit 231 has already supplied the second sheet P. The printing operation of the second sheet P of No. 1 is also canceled, the transfer is continued, and the second sheet of paper P is ejected toward the post-processing device 120. In this case, the post-treatment device 120 discharges each paper P to be ejected to the output tray 122 without performing post-treatment.

The main control unit 231 (conveyance control unit 231C, paper presence / absence determination unit 231A) continues to transport the first sheet (long paper) P11 in the transport unit 30 (start of discharge control), and the tray sensor 23 The presence or absence of paper P in the paper feed tray 21 is determined by monitoring the detection signal from. In the present embodiment, the main control unit 231 determines whether or not the paper P is present, and the paper P (the first paper P11 and the supplied subsequent paper) to be ejected is ejected to the post-processing device 120. Continue until.
In the example of FIG. 5D, since the paper feed tray 21 accommodates other paper P (paper P12 or the like located at the top of the paper bundle PS), the detection signal from the tray sensor 23 is to be ejected. It is kept ON until the designated paper P is ejected. The main control unit 231 determines that the paper P is in the paper feed tray 21 based on the fact that the detection signal from the tray sensor 23 remains ON.

As shown in FIG. 5E, when continuous printing is instructed again by the user, the main control unit 231 (paper presence / absence determination unit 231A) sets the paper feed tray 21 based on the detection signal from the tray sensor 23. Determines the presence or absence of paper P.
As shown in FIG. 5 (f), the main control unit 231 (supply control unit 231B) controls the operation of the paper feed motor 321 based on the determination result that the paper P is in the paper feed tray 21 to supply the paper. The uppermost paper P (first sheet of paper P12) of the paper bundle PS housed in the paper tray 21 is supplied toward the transport unit 30.
As shown in FIG. 5 (g), in the main control unit 231 (conveyance control unit 231C, paper presence / absence determination unit 231A), the rear end of the first sheet of paper P12 for transporting the transport path TP by the transport unit 30 is a determination criterion. When it is determined that the position RP has been reached, the presence or absence of the paper P in the paper feed tray 21 is determined based on the detection signal from the tray sensor 23. Since the subsequent processing is as described with reference to FIG. 4, the description thereof will be omitted.

<About the state where only one sheet of long paper is stored>
Next, the transfer of the paper P in a state where only one sheet of long paper is stored in the paper feed tray 21 will be described.
As shown in FIG. 6A, when only one sheet of paper P21 longer than the specified length is accommodated in the paper feed tray 21, continuous printing on the paper P is instructed, and the main control unit 231 ( The paper presence / absence determination unit 231A) determines the presence / absence of paper P in the paper feed tray 21 based on the detection signal from the tray sensor 23.
As shown in FIG. 6B, the main control unit 231 (supply control unit 231B) controls the operation of the paper feed motor 321 based on the determination result that the paper P is present, and is housed in the paper feed tray 21. The paper P21 is supplied toward the transport unit 30.
As shown in FIG. 6C, in the main control unit 231 (conveyance control unit 231C, paper presence / absence determination unit 231A), the rear end of the paper P21 that conveys the transfer path TP by the transfer unit 30 reaches the determination reference position RP. When it is determined that the paper has been processed, the presence or absence of the paper P in the paper feed tray 21 is determined based on the detection signal from the tray sensor 23.
The operation up to this point is the same as the state in which the paper P of the specified size is accommodated under the paper P11 (the state of FIGS. 5A to 5C). Therefore, in the state of FIG. 6C, the main control unit 231 (paper presence / absence determination unit 231A) determines that the paper P is in the paper feed tray 21.

As shown in FIG. 6D, the main control unit 231 (length determination unit 231E) monitors the detection signal from the resist sensor 33 as the paper P21 starts to be supplied to the image forming unit 40, and the paper It is determined whether or not the length of P21 is the specified length.
In the example of FIG. 6D, the main control unit 231 (length determination unit 231E, stop control unit 231F, transfer control unit 231C) exceeds the second determination time for long paper in the elapsed time from the start of supply. However, since the detection signal from the resist sensor 33 remains ON (with paper), it is determined that longer paper than specified has been supplied to the image forming unit 40, and the printing operation on the paper P21 is cancelled. And, the transfer of the paper P21 is continued. As a result, as shown in FIG. 6E, the paper P21 is discharged toward the aftertreatment device 120.

Returning to FIG. 6D, the main control unit 231 (transfer control unit 231C, paper presence / absence determination unit 231A) is based on the detection signal from the tray sensor 23 as the transfer to the paper P21 continues (start of discharge control). It is determined whether or not the paper P is present in the paper feed tray 21. Since the detection signal from the tray sensor 23 is OFF, the main control unit 231 (paper presence / absence determination unit 231A) determines that there is no paper P in the paper feed tray 21.
That is, the main control unit 231 (paper presence / absence determination unit 231A) determines that the paper P is housed in the paper feed tray 21 in the state of FIG. 6 (c), but after that, the state of FIG. 6 (d). Redetermines that there is no paper P in the paper feed tray 21.
The main control unit 231 (notification control unit 231G) controlled the panel display unit 241 and the like as the long paper was supplied to the image forming unit 40, and the long paper was housed in the paper feed unit 20. Notify the user to that effect. Further, since the main control unit 231 determines that there is no paper P in the paper feed tray 21, the panel display unit 241 displays information for prompting the paper feed tray 21 to be replenished with the paper P.

As is clear from the above description, in the image forming apparatus 1 according to the present embodiment, the main control unit 231 has determined that the paper P21 transported by the transport unit 30 is a long paper longer than the specified length. Along with this, the printing operation is canceled and the paper P21 is continued to be conveyed (long paper is ejected toward the post-processing device 120). Further, the main control unit 231 causes the tray sensor 23 to detect the presence / absence of the paper P in the paper feed tray 21 as the paper P21 continues to be conveyed.
Therefore, according to the image forming apparatus 1 according to the present embodiment, even when continuous printing is instructed with only one sheet of paper P21 longer than specified in the paper feed tray 21, the paper P21 is instructed to print continuously. It is possible to suppress the inconvenience of falsely detecting that there is paper after the paper is ejected.

<Operation flowchart of main control unit 231 during continuous printing processing>
Next, the operation flowchart of the main control unit 231 at the time of continuous printing processing will be described. FIG. 7 is a flowchart for explaining the continuous printing process, FIG. 8 is a flowchart for explaining the process when the resist sensor is ON, and FIG. 9 is a flowchart for explaining the long paper process.
Each flowchart shows the operation by the main control unit 231. In other words, the main control unit 231 executes the operation shown in each flowchart by reading the computer program stored in the memory 231b by the CPU 231a, expanding the computer program into the memory 231b, and executing the program.

When the main control unit 231 receives a continuous print command from the controller 210 of the image forming apparatus 1 (S1, Yes), the main control unit 231 acquires a detection signal from the tray sensor 23 (S2). The main control unit 231 determines that there is paper P in the paper feed tray 21 when the detection signal of the tray sensor 23 is ON (S2, Yes), and feeds paper when the detection signal of is OFF. It is determined that there is no paper P in the tray 21 (S2, No).
When the main control unit 231 determines that there is no paper P in the paper feed tray 21, the main control unit 231 cancels the printing operation based on the continuous printing command (S21) and performs the paper end processing (S22). In the paper end process, the main control unit 231 causes the panel display unit 241 to display information for prompting the paper feed tray 21 to be replenished with the paper P.
When the paper end processing is performed, a series of processing is completed. After that, the user of the image forming apparatus 1 supplies the paper P to the paper feed tray 21 and instructs the continuous printing again, so that the processing from step S1 is performed.

When the main control unit 231 determines that the paper P is in the paper feed tray 21 (S2, Yes), the main control unit 231 controls the operation of the paper feed motor 321 so that the paper P is housed in the paper feed tray 21. The topmost paper P (preceding paper) is supplied toward the transport unit 30 (S3).
After starting the supply of the preceding paper in step S3, the main control unit 231 determines whether or not the tip of the preceding paper has reached the resist sensor 33 (S4), and determines that it has reached (S4, Yes). , Performs the process (S5) when the resist sensor is turned on.
When the tip of the preceding paper reaches a predetermined standby position (for example, the detection position of the resist sensor 33), the main control unit 231 stops the feeding of the preceding paper, and the transfer timing of the toner image by the image forming unit 40 arrives. The preceding paper is put on standby in the meantime.

As shown in FIG. 8, in the process when the resist sensor is turned on, the main control unit 231 estimates the rear end position of the preceding paper based on the paper size information (S31), and the estimated rear end position is the determination reference position RP ( (See FIGS. 4 to 6) is determined (S32).
When the main control unit 231 determines that the rear end position of the preceding paper has passed the determination reference position RP (S32, Yes), the main control unit 231 determines whether or not the tray sensor 23 is ON (S33). When the tray sensor 23 is ON (S33, Yes), the supply of the succeeding paper located at the top of the sheet bundle accommodated in the paper feed tray 21 to the conveying unit 30 is started (S34). On the other hand, when the tray sensor 23 is OFF (S33, No), the main control unit 231 cancels the printing operation based on the continuous printing command (S21) and performs the paper end process (S22).
After starting the supply of the succeeding paper to the transport unit 30, the main control unit 231 determines whether or not the transfer start timing of the toner image for the preceding paper has arrived (S35), and when the transfer start timing has arrived. (S35, Yes) supplies the preceding paper to the image forming unit 40, starts the transfer of the toner image (S36), and returns to the continuous printing process.

When the main control unit 231 determines that the rear end position of the preceding paper has not passed the determination reference position RP (S32, No), the main control unit 231 determines whether or not the transfer start timing of the toner image with respect to the preceding paper has arrived. When the determination is made (S37) and the transfer start timing is reached (S37, Yes), the transfer of the toner image to the preceding paper is started (S38).
The main control unit 231 estimates the rear end position of the preceding paper based on the elapsed time from the start of transfer of the toner image (S39), and determines whether or not the estimated rear end position has passed the determination reference position RP. (S40). When the estimated rear end position does not pass through the determination reference position RP (S40, No), the main control unit 231 proceeds to step S39 and estimates the rear end position of the preceding paper again.
When the main control unit 231 determines that the estimated rear end position has passed the determination reference position RP (S40, Yes), the main control unit 231 determines whether or not the tray sensor 23 is ON (S41). When the tray sensor 23 is ON (S41, Yes), the supply of the uppermost paper P (subsequent paper) in the paper bundle PS housed in the paper feed tray 21 to the transport unit 30 is started (S42) and continuous. Return to print processing. On the other hand, when the tray sensor 23 is OFF (S41, No), the main control unit 231 cancels the printing operation based on the continuous printing command (S21) and performs the paper end process (S22).

Returning to FIG. 7, the main control unit 231 determines whether or not the resist sensor 33 has been turned off, in other words, the rear end of the preceding paper passes through the position of the resist sensor 33, following the process (S5) when the resist sensor 33 is turned on. It is determined whether or not it has been done (S6).
When the resist sensor 33 is kept ON (S6, No), the main control unit 231 determines whether or not the second determination time has elapsed from the start of transfer of the toner image to the preceding paper (S13). The second determination time is set to determine whether or not the paper P (preceding paper) to be transferred of the toner image is a long paper longer than the specified size.
Therefore, the main control unit 231 repeats the processes of steps S6 and S13 while the resist sensor 33 is kept ON, and even if the second determination time elapses from the start of transfer of the toner image. When the resist sensor 33 is kept ON (S13, Yes), it is determined that the preceding paper is a long paper.

When the resist sensor 33 is switched to OFF (S6, Yes) before the second determination time elapses from the start of transfer of the toner image to the preceding paper, the main control unit 231 first determines the elapsed time from the start of transfer. Determine if it is more than an hour. The first determination time is set to determine whether or not the preceding paper has a specified size. Therefore, when the elapsed time from the start of transfer is equal to or longer than the first determination time (S7, Yes), the main control unit 231 determines that the length of the preceding paper is the same as the set length, and determines that the first determination time. If it is less than (S7, No), it is determined that the preceding paper is a short paper shorter than the set length.

When the main control unit 231 determines that the preceding paper is a short paper (S7, No), the main control unit 231 sets a size error flag indicating that the preceding paper is a short paper (S8), and registers from the start of transfer of the toner image to the preceding paper. The paper size of the preceding paper is acquired based on the elapsed time until the sensor 33 is switched to OFF (S9). After that, the main control unit 231 performs short paper processing (S10), cancels the printing operation based on the continuous printing command, discharges the preceding paper and the supplied paper P to the post-processing device 120, and notifies the size error. ..
When the short paper processing is performed, a series of processing is completed. When the user of the image forming apparatus 1 instructs the continuous printing again, the processing from step S1 is performed. The size error flag set in step S8 is cleared by the initialization process accompanying the execution of the process from step S1.

When the main control unit 231 determines that the preceding paper is the regular length paper P (S7, Yes), the main control unit 231 determines whether or not the print data corresponding to the preceding paper is the print data of the last page (S11). ), If it is not the print data of the last page (S11, No), the process proceeds to step S4 and the printing operation is continued. On the other hand, when the print data corresponding to the preceding paper is the print data of the last page (S11, Yes), the main control unit 231 determines whether or not the printing of the last page is completed (S12), and the final page. When the printing of is completed (S12, Yes), the continuous printing process is terminated.

When the resist sensor 33 remains ON even after the second determination time has elapsed from the start of transfer of the toner image to the preceding paper (S13, Yes), the main control unit 231 indicates that the preceding paper is a long paper. A size error flag indicating that this is set (S14), and then long paper processing is performed (S15).
As shown in FIG. 9, in the long paper processing, the main control unit 231 cancels the printing operation based on the continuous printing command (S50). Subsequently, the main control unit 231 starts ejection control of the preceding paper (referred to as long paper in the description of FIG. 9 for convenience) (S51), and if the succeeding paper has already been supplied to the transport unit 30, (S52, Yes). ), Discharge control is also started for the supplied subsequent paper (S53).

The main control unit 231 determines whether or not the third determination time has elapsed from the start of transfer of the toner image to the long paper (S54). The third determination time is set to determine whether or not the long paper or the supplied subsequent paper cannot be ejected due to a paper jam. Therefore, when the third determination time has elapsed from the start of the ejection control (S54, Yes), the main control unit 231 determines that the long paper or the supplied subsequent paper cannot be ejected due to a paper jam. , Paper jam processing is performed (S55).
The main control unit 231 causes the panel display unit 241 to display information indicating that a paper jam has occurred and information for promoting the elimination of the paper jam in the paper jam processing.
When the paper jam process is performed, a series of processes is completed. After that, the user of the image forming apparatus 1 clears the paper jam and instructs the continuous printing again, so that the processing from step S1 is performed.

When it is determined that the third determination time has not elapsed from the start of the discharge control (S54, No), the main control unit 231 acquires the detection signal from the tray sensor 23 (S56).
The main control unit 231 determines that there is paper P in the paper feed tray 21 when the detection signal of the tray sensor 23 is ON (S56, Yes), and feeds paper when the detection signal of is OFF. It is determined that there is no paper P in the tray 21 (S56, No).
When the main control unit 231 determines that there is no paper P in the paper feed tray 21, the main control unit 231 cancels the printing operation based on the continuous printing command (S21) and performs the paper end processing (S22).

On the other hand, when the main control unit 231 determines that the paper P is in the paper feed tray 21, it determines whether or not the rear end of the long paper has passed the detection position of the resist sensor 33 (S57). ).
The main control unit 231 determines whether or not the detection signal of the resist sensor 33 is switched from ON to OFF when the rear end of the long paper has not passed the detection position of the resist sensor 33 (S57, Yes). Judgment (S58). On the other hand, when the rear end of the long paper has passed the detection position of the resist sensor 33 (S57, No), the main control unit 231 shifts to the process of step S61 described later.

When the detection signal of the resist sensor 33 is determined to remain ON (S58, No), the main control unit 231 determines whether or not the third determination time has elapsed after shifting to step S54. On the other hand, when the main control unit 231 determines that the detection signal of the resist sensor 33 has been switched from ON to OFF (S58, Yes), the main control unit 231 acquires the length of the long paper (S59). The length of the long paper is, for example, the elapsed time from the start of transfer of the toner image to the long paper (start of supply of the long paper to the image forming unit 40) to the switching of the detection signal of the resist sensor 33 from ON to OFF. , Can be determined based on the transport speed of long paper.

After acquiring the length of the long paper, the main control unit 231 determines whether or not there is a succeeding paper being ejected (S60). When the main control unit 231 determines that there is a succeeding paper being ejected (S60, Yes), the main control unit 231 determines whether or not the succeeding paper has been ejected (S61). The conditions for determining whether or not the subsequent paper has been ejected can be appropriately determined. For example, it may be determined that the succeeding paper has been ejected when the trailing edge of the succeeding paper has passed the detection position of the resist sensor 33, or the succeeding paper may be determined when the succeeding paper is supplied to the post-processing device 120. It may be determined that it has been discharged.
When it is determined that the succeeding paper has not been ejected (S61, No), the main control unit 231 determines whether or not the third determination time has elapsed after shifting to step S54.

On the other hand, when the main control unit 231 determines that the succeeding paper has been ejected (S61, Yes), or when it determines that there is no succeeding paper being ejected (S60, No), the detection signal from the tray sensor 23 (S62), and it is determined whether or not the paper P in the paper feed tray 21 is present.
When the main control unit 231 determines that there is no paper P in the paper feed tray 21 (S62, No), the main control unit 231 cancels the printing operation based on the continuous printing command (S21) and performs the paper end process (S22). .. On the other hand, when the main control unit 231 determines that the paper P is in the paper feed tray 21 (S62, Yes), the main control unit 231 controls the panel display unit 241 and the like to indicate that a size error based on the long paper has occurred. Is notified to the user (S63).
When the user is notified that a size error has occurred, the series of processes ends. When the user of the image forming apparatus 1 instructs the continuous printing again, the processing from step S1 is performed. The size error flag set in step S14 is cleared by the initialization process accompanying the execution of the process from step S1.

<About modification>
In the above-described embodiment, the electrophotographic image forming unit 40 has been described as an example, but the present invention is not limited to this. For example, the image forming unit 40 may be an inkjet method, a thermal transfer method, or a thermal recording method.
In the above-described embodiment, the sheet P has been described as an example, but the sheet is not limited to the sheet P. For example, it may be a postcard, an envelope, a coated paper (coated paper, art paper, etc.), and tracing paper. Further, it may be an OHP sheet or an OHP film.

Further, each function of the above-described embodiment can be realized by one or a plurality of processing circuits. Here, the "processing circuit" as used herein is a processor programmed to perform each function by software, such as a processor implemented by an electronic circuit, or a processor designed to execute each function described above. It shall include devices such as ASIC (Application Specific Integrated Circuit), DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array) and conventional circuit modules.

[Summary of Examples of Embodiments of the Present Invention, Actions, and Effects]
<First embodiment>
In this embodiment, a paper feed tray 21 (accommodation unit) for accommodating a bundle of paper PS (sheet bundle), a transport unit 30 for transporting paper P (sheets) taken out one by one from the top of the bundle of paper PS, and a transport unit 30. An image forming apparatus 1 including an image forming unit 40 for forming an image on the conveyed paper P by the conveying unit 30, and a tray sensor 23 (sheet presence / absence detection sensor) for detecting the presence / absence of the paper P in the paper feed tray 21. ), The resist sensor 33 (passage detection sensor) that detects the passage of the paper P being conveyed by the transfer unit 30, the transfer control unit 231C that controls the transfer of the paper P by the transfer unit 30, and the tray sensor 23. The paper presence / absence determination unit 231A (sheet presence / absence determination unit) that determines the presence / absence of paper P in the paper feed tray 21 based on the detection signal (detection information) and the transfer unit 30 that determines the presence / absence of paper P in the paper feed tray 21 are conveyed based on the detection information of the resist sensor 33. A length determination unit 231E for determining whether or not the length of the paper P is a specified length is provided, and the transport control unit 231C determines that the length determination unit 231E is longer than the specified length. By further continuing the transport of the paper (specific sheet) by the transport unit 30, the rear end of the long paper is passed through the detection position by the resist sensor 33, and the paper presence / absence determination unit 231A is the length of the transfer control unit 231C. It is characterized in that the presence or absence of paper P in the paper feed tray 21 is determined based on the detection information from the tray sensor 23 in accordance with the paper transport control.
According to the image forming apparatus 1 according to this aspect, even when continuous image forming is instructed with only one sheet of long paper longer than the setting remaining in the paper feed tray 21 (accommodation portion). , It is possible to suppress the inconvenience of causing an error that the paper P cannot be supplied.

<Second embodiment>
In this embodiment, a paper feed tray 21 (accommodation unit) for accommodating a bundle of paper PS (sheet bundle), a transport unit 30 for transporting paper P (sheets) taken out one by one from the top of the bundle of paper PS, and a transport unit 30. The image forming unit 40 that forms an image on the paper P conveyed by the conveying unit 30, the tray sensor 23 (sheet presence / absence detection sensor) that detects the presence / absence of the paper P in the paper feed tray 21, and the conveying unit 30 convey the image. An image forming method using an image forming apparatus 1 including a resist sensor 33 (passing detection sensor) for detecting the passage of paper P, and a conveying unit 30 conveys based on a detection signal (detection information) of the resist sensor 33. The step of determining whether or not the length of the paper P being made is the specified length, and the long paper (specific sheet) determined to be longer than the specified length are further continued to be conveyed by the conveying unit 30. As a result, the paper in the paper feed tray 21 is based on the detection signal (detection information) from the tray sensor 23 along with the step of passing the rear end of the long paper through the detection position by the resist sensor 33 and the transport control of the long paper. It is characterized by having a step of determining the presence or absence of P.
According to the image forming method according to this aspect, the same effect as that of the first embodiment is obtained.

<Third embodiment>
The program according to this aspect is characterized in that each step in the image forming method described in the second embodiment is executed by a computer.

1 ... image forming device, 10 ... printing unit, 20 ... paper feeding unit, 21 ... paper feeding tray, 21a ... tray body, 21b ... bottom plate, 22 ... paper feeding roller, 23 ... tray sensor (sheet presence / absence detection sensor), 30 ... Conveying unit, 31 ... Conveying roller pair, 32 ... Resist roller pair, 33 ... Resist sensor (passage detection sensor), 34 ... Secondary transfer roller, 35 ... Secondary transfer belt, 36 ... Conveying belt, 37 ... Paper ejection roller , 38 ... Paper ejection sensor, 39 ... Paper sensor, 40 ... Image forming section, 41 (41Y, 41M, 41C, 41K) ... Image forming section, 42 ... Photoreceptor drum, 43 ... Charging section, 44 ... Developing section, 45 ... Cleaning section, 46 ... Primary transfer roller, 47 ... Exposure section, 48 ... Intermediate transfer belt, 49 ... Secondary transfer facing roller, 50 ... Fixing section, 51 ... Fixing belt, 52 ... Pressure roller, 110 ... Scanner section, 120 ... Post-processing device, 121 ... Post-processing device main body, 122 ... Paper output tray, 210 ... Controller, 201 ... CPU, 202 ... MEM-P, 203 ... NB, 204 ... SB, 206 ... ASIC, 207 ... MEM-C , 208 ... HDD controller, 209 ... HD, 221 ... AGP bus, 222 ... PCI bus, 220 ... short-range communication circuit, 220a ... antenna, 230 ... engine control unit, 231 ... main control unit, 231a ... CPU, 231b ... memory , 231A ... Paper presence / absence determination unit, 231B ... Supply control unit, 231C ... Transfer control unit, 231D ... Image formation control unit, 231E ... Length determination unit, 231F ... Cancellation control unit, 231G ... Notification control unit, 240 ... Operation panel , 241 ... Panel display unit, 242 ... Panel operation unit, 250 ... Network I / F, 321 ... Paper feed motor, 331 ... Conveyor motor, 332 ... Resist roller drive motor, 333 ... Paper discharge motor, 341 ... Transfer belt drive motor , 351 ... Fixing belt drive motor, 352 ... Heater, PS ... Paper bundle (sheet bundle), P ... Paper (sheet), TP ... Transport path, RP ... Judgment reference position

Japanese Unexamined Patent Publication No. 2014-56161

Claims (2)

It is provided with a storage unit for accommodating a sheet bundle, a transport unit for transporting sheets taken out one by one from the uppermost portion of the sheet bundle, and an image forming unit for forming an image on the sheets transported by the transport unit. It is an image forming device
A seat presence / absence detection sensor that detects the presence / absence of the seat in the accommodation portion,
A passage detection sensor that detects the passage of the sheet being conveyed by the transfer unit, and
A transport control unit that controls the transport of the sheet by the transport unit,
A sheet presence / absence determination unit that determines the presence / absence of the sheet in the accommodation unit based on the detection information from the sheet presence / absence detection sensor, and a sheet presence / absence determination unit.
A length determination unit for determining whether or not the length of the sheet conveyed by the transfer unit is a specified length based on the detection information of the passage detection sensor is provided.
The transfer control unit further continues the transfer of the specific sheet determined by the length determination unit to be longer than the specified length by the transfer unit, whereby the rear end of the specific sheet is determined by the passage detection sensor. Pass the detection position and
The sheet presence / absence determination unit is characterized in that, in accordance with the transfer control of the specific sheet by the transfer control unit, the presence / absence of the sheet in the accommodation unit is determined based on the detection information from the sheet presence / absence detection sensor. Image forming device. An accommodating section for accommodating a bundle of sheets, a transport section for transporting sheets taken out one by one from the top of the bundle of sheets, an image forming section for forming an image on the sheets transported by the transport section, and the accommodating section. An image forming method using an image forming apparatus including a sheet presence / absence detection sensor for detecting the presence / absence of the sheet and a passage detection sensor for detecting the passage of the sheet being conveyed by the conveying unit.
A step of determining whether or not the length of the sheet being conveyed by the conveying unit is a specified length based on the detection information of the passing detection sensor, and
A step of passing the rear end of the specific sheet through the detection position by the passage detection sensor by further continuing the transfer of the specific sheet determined to be longer than the specified length by the transfer unit.
A step of determining the presence or absence of the sheet in the accommodating portion based on the detection information from the sheet presence / absence detection sensor in accordance with the transfer control of the specific sheet.
An image forming method characterized by being provided with.

Images