JP2019211686A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can reduce an operation to take out a sheet from a sheet conveyance path to improve convenience for a user.SOLUTION: A control unit 110 counts a passing time that is a time from when a sensor for determination PS3 detects arrival of a sheet until when the sensor detects passing of the sheet on the basis of an output value from the sensor for determination PS3. When the passing time passes a first determination time based on a reference passing time indicating a standard passing time for one sheet, the control unit 110 causes an image forming unit 4 to stop formation of an image and causes a printing unit 2 to continue conveyance of the sheet. When the sensor for determination PS3 detects passing of the sheet before the passing time passes a second determination time based on a reference passing time for two sheets, the control unit 110 causes the sheet to be ejected to an ejection tray 20T so as to remove the sheet in a sheet conveyance path 20.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming apparatus that prints an image on a sheet.

  A conventional image forming apparatus is disclosed in Patent Document 1. This image forming apparatus has a paper feed nip, a transfer nip, and a fixing nip. The paper feed nip feeds paper. The transfer nip transfers an image to a sheet. The fixing nip fixes the image transferred on the paper. The paper is transported along a paper transport path that passes through a paper feed nip, a transfer nip, and a fixing nip, and is discharged from a paper discharge tray.

  A plurality of determination sensors are provided in the paper transport path. The transported paper is timed at the detection position of the determination sensor, and it is determined whether or not a paper jam error has occurred in the paper transport path. If the paper is jammed in the paper conveyance path during the execution of the print job, the passage of the paper is not detected within the determination time indicating the standard passage time for one sheet. At this time, the print job is interrupted to notify the operation panel that a jam error has occurred. The user takes out the sheet causing the jam error from the sheet conveyance path, and resumes the interrupted print job.

JP 2002-182531 A

  According to the conventional image forming apparatus, when two sheets are supplied to the sheet conveyance path in a state where they are connected, the two sheets that are connected cannot pass the detection position of the determination sensor within the determination time. For this reason, it is determined that the paper is jammed in the paper conveyance path, and the occurrence of a jam error is notified. The user needs to take out the two sheets that caused the jam error from the sheet conveyance path.

  In order to achieve the above object, an object of the present invention is to provide an image forming apparatus capable of reducing the work of taking out paper from a paper transport path and improving user convenience.

  In order to achieve the above object, an image forming apparatus having a first configuration according to the present invention includes a paper discharge tray from which paper is discharged, a printing unit that prints on the paper, a determination sensor that detects arrival and passage of the paper, And a control unit for controlling the sheet conveyance. The printing unit includes a paper feeding unit, an image forming unit, a fixing unit, and a paper conveyance path. The paper feed unit includes a paper feed rotator that forms a paper feed nip. The image forming unit includes a transfer rotator that forms a transfer nip, conveys a sheet, forms an image, and transfers the formed image onto the sheet. The fixing unit includes a fixing rotating body that forms a fixing nip, conveys the sheet, and fixes the image transferred onto the sheet to the sheet. The paper transport path reaches the paper discharge tray via the paper feed nip, transfer nip and fixing nip. The determination sensor is provided upstream of the transfer nip in the paper conveyance direction. Based on the output value of the determination sensor, the control unit counts the passage time, which is the time from when the determination sensor detects the arrival of the paper until the detection of the passage of the paper. When the first determination time based on the reference passage time indicating the passage time of the paper has passed, the image forming unit stops the image formation and the printing unit continues the paper conveyance so that the passage time becomes the reference passage time for two sheets. When the determination sensor detects the passage of the paper before the second determination time based on the paper, the paper is discharged to the paper discharge tray so that the paper in the paper conveyance path runs out.

  In the configuration of the present invention, the control unit counts the passing time, which is the time from when the determination sensor detects the arrival of the paper until it detects the passage of the paper, based on the output value of the determination sensor, However, when the first determination time based on the reference passage time indicating the standard passage time of one sheet has passed, the image forming unit stops image formation and the printing unit continues paper conveyance. In addition, when the determination sensor detects passage of paper before the passage of time passes the second determination time based on the reference passage time for two sheets, the control unit discharges the paper so that there is no paper in the paper transport path. Eject paper into the tray. When the two sheets are conveyed in a continuous state and the trailing edge of the leading sheet overlaps with the leading edge of the succeeding sheet, the determination sensor does not detect passage of the trailing edge of the leading sheet. For this reason, the passage time of the paper in the determination sensor passes the first determination time. At this time, the control unit causes the image forming unit to stop forming an image and causes the printing unit to continue paper conveyance. As a result, the top sheet is continuously printed by the sheet conveyance of the printing unit. Further, the subsequent sheets are not printed because the image forming unit stops the image formation. Further, when the two sheets are conveyed in a continuous state, the determination sensor detects passage of the trailing edge of the subsequent sheet after the first determination time has elapsed and before the second determination time has elapsed. . At this time, the control unit discharges the sheet to the sheet discharge tray so that the sheet in the sheet conveyance path runs out. As a result, the user can reduce the work of taking out the paper from the paper transport path, and the convenience can be improved.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. 1 is an enlarged view showing a sheet conveyance path of an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram showing a hardware configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a diagram illustrating a conveyance state of a sheet conveyed on a sheet conveyance path of the image forming apparatus according to the embodiment of the present disclosure. 6 is a flowchart showing the operation of the image forming apparatus according to the embodiment of the invention. FIG. 6 is a diagram illustrating a conveyance state of a sheet conveyed on a sheet conveyance path of the image forming apparatus according to the embodiment of the present disclosure. FIG. 6 is a diagram illustrating a conveyance state of a sheet conveyed on a sheet conveyance path of the image forming apparatus according to the embodiment of the present disclosure. FIG. 6 is a diagram illustrating a conveyance state of a sheet conveyed on a sheet conveyance path of the image forming apparatus according to the embodiment of the present disclosure.

<Configuration of image forming apparatus>
FIG. 1 is a diagram illustrating an overall configuration of the image forming apparatus 100. The image forming apparatus 100 includes an image reading unit 1, a printing unit 2, a paper discharge tray 20T, a determination sensor PS, and a control unit 110. The image reading unit 1 reads a document and generates image data of the document. The printing unit 2 includes a paper feeding unit 3, an image forming unit 4, a fixing unit 6, and a paper conveyance path 20. Then, the printing unit 2 transports the paper P along the paper transport path 20, prints an image on the paper P being transported, and finally discharges the printed paper P to the paper discharge tray 20T.

  The paper feed unit 3 includes a pickup roller 31 and a paper feed roller pair 32. The paper feed roller pair 32 forms a paper feed nip PN for feeding the paper P to the paper transport path 20. That is, the paper feed roller pair 32 corresponds to a “paper feed rotator”. The paper feeding unit 3 pulls out the paper P from the paper cassette 30 and enters the paper feeding nip PN, and supplies the paper P to the paper transport path 20 (performs primary paper feeding).

  The image forming unit 4 includes mechanism units 40Bk, 40Y, 40C, and 40M corresponding to the respective colors of black (Bk), yellow (Y), cyan (C), and magenta (M).

  Each of the mechanism units 40Bk, 40Y, 40C, and 40M includes a photosensitive drum 41, a charging device 42, a developing device 43, and a cleaning device 44 so that the photosensitive drum 41 contacts the intermediate transfer belt 51 described later. Be placed.

  The image forming unit 4 includes an exposure device 45 that is used in common for each color. Then, the image forming unit 4 forms each color toner image on the surface of the corresponding photosensitive drum 41.

  The image forming unit 4 includes an intermediate transfer belt 51, a primary transfer roller 52, and a secondary transfer roller 53.

  The intermediate transfer belt 51 is stretched by a driving roller 54 and a driven roller 55. The primary transfer roller 52 is disposed inside the intermediate transfer belt 51 and sandwiches the intermediate transfer belt 51 with the photosensitive drum 41. The secondary transfer roller 53 is disposed so as to face the driving roller 54 with the intermediate transfer belt 51 interposed therebetween, and forms a transfer nip TN with the intermediate transfer belt 51.

  The transfer nip TN is a nip for transferring a toner image onto the paper P. That is, the intermediate transfer belt 51 and the secondary transfer roller 53 correspond to a “transfer rotator”. The image forming unit 4 primarily transfers the toner image onto the surface of the intermediate transfer belt 51, and then secondarily transfers the toner image onto the paper P while conveying the paper P entering the transfer nip TN.

  The fixing unit 6 includes a fixing roller pair 61. One roller of the fixing roller pair 61 incorporates a heat source. The other roller is in pressure contact with the one roller, and forms a fixing nip FN with the one roller. The fixing nip FN is a nip for fixing the toner image transferred onto the paper P. That is, the fixing roller pair 61 corresponds to a “fixing rotating body”. The fixing unit 6 fixes the toner image on the paper P by heating and pressurizing the paper P that has entered the fixing nip FN while being conveyed.

<Configuration of paper transport path>
FIG. 2 is an enlarged view of the paper conveyance path. The sheet conveyance path 20 provided in the image forming apparatus 100 includes a main conveyance path 2A and a reverse conveyance path 2B. In FIG. 2, the main conveyance path 2A is indicated by a solid line, and the reverse conveyance path 2B is indicated by a broken line.

  The main transport path 2A reaches the paper discharge tray 20T via the paper feed nip PN (paper feed unit 3), the transfer nip TN (image forming unit 4), and the fixing nip FN (fixing unit 6). When the print job is executed, the paper P fed to the main transport path 2A is transported through the paper feed nip PN, the transfer nip TN, and the fixing nip FN in this order. Hereinafter, a description will be given by adding a symbol D to the transport direction of the paper P at this time.

  The reverse conveyance path 2B is a conveyance path used during duplex printing. The reverse conveyance path 2 </ b> B has a first conveyance path 21 and a second conveyance path 22. In FIG. 2, the first transport path 21 and the second transport path 22 are indicated by different broken lines.

  The first transport path 21 branches from the main transport path 2A at a position downstream of the fixing nip FN in the transport direction D of the paper P and reaches the paper discharge tray 20T. The second conveyance path 22 branches from the first conveyance path 21 at a predetermined branch position P1, and at a predetermined merge position P2 (a position on the upstream side in the conveyance direction D of the paper P from the transfer nip TN). Merge into the main transport path 2A. Note that during double-sided printing, the single-sided printing paper P is conveyed in a first direction D1 that is a direction toward the paper discharge tray 20T and a second direction D2 opposite to the first direction D1.

  The paper transport path 20 is provided with a plurality of transport roller pairs 71 to 77 for transporting the paper P along the paper transport path 20.

  Between the paper feed nip PN and the transfer nip TN of the main transport path 2A, transport roller pairs 71 and 72 are provided in this order in the transport direction D of the paper P. Among these, the transport roller pair 72 located downstream in the transport direction D of the paper P temporarily stops the paper P that has reached the transport roller pair 72 and then sends the paper P to the transfer nip TN (secondary feeding). Do paper). Hereinafter, the conveyance roller pair 72 is referred to as a registration roller pair 72.

  A pair of transport rollers 73 is provided on the paper discharge tray 20T side of the main transport path 2A (the most downstream side in the transport direction D of the paper P). The transport roller pair 73 transports the paper P that has passed through the fixing nip FN along the main transport path 2A, and finally discharges the paper P to the paper discharge tray 20T. Hereinafter, the conveyance roller pair 73 is referred to as a discharge roller pair 73.

  A pair of transport rollers 74 is provided on the first transport path 21 on the paper discharge tray 20T side. As will be described in detail later, the transport roller pair 74 switches back the paper P at the time of duplex printing (reverses the traveling direction of the paper P). Hereinafter, the conveyance roller pair 74 is referred to as a reverse roller pair 74. Further, between the branch position P1 and the merge position P2 of the second transport path 22, transport roller pairs 75, 76, and 77 are provided in this order toward the second direction D2.

  A switching claw 78 for switching the transport path of the paper P is provided at a branch position between the main transport path 2A and the reverse transport path 2B (first transport path 21). The switching claw 78 is supported so as to be able to rotate. By rotating, the switching claw 78 blocks or opens the conveyance path from the main conveyance path 2A to the reverse conveyance path 2B.

  The paper transport path 20 is provided with a plurality of determination sensors PS (PS1 to PS7) for detecting the presence or absence of the paper P at a predetermined position on the transport path. The determination sensor PS is, for example, an optical sensor that changes an output value according to the presence or absence of the paper P at a corresponding detection position. That is, the determination sensors PS (PS1 to PS7) detect the arrival and passage of the paper P.

  The determination sensor PS1 is a sensor having a detection position in the vicinity of the installation position of the paper feed roller pair 32 (a position downstream of the paper feed nip PN in the transport direction D of the paper P).

  The determination sensor PS2 is a sensor having a detection position in the vicinity of the installation position of the conveyance roller pair 71 (a position on the upstream side in the conveyance direction D of the paper P from the installation position of the conveyance roller pair 71).

  The determination sensor PS3 is a sensor having a detection position in the vicinity of the installation position of the registration roller pair 72 (a position on the upstream side in the transport direction D of the paper P from the installation position of the registration roller pair 72).

  The determination sensor PS4 is a sensor having a detection position in the vicinity of the installation position of the drive roller 54 (a position downstream of the transfer nip TN in the transport direction D of the paper P).

  The determination sensor PS5 is a sensor having a detection position in the vicinity of the installation position of the fixing roller pair 61 (a position on the downstream side in the transport direction D of the paper P from the fixing nip FN).

  The determination sensor PS6 is a sensor having a detection position in the vicinity of the branch position P1 (downstream in the second direction D2 from the branch position P1).

  The determination sensor PS7 is a sensor having a detection position in the vicinity of the installation position of the transport roller pair 77 (upstream in the second direction D2 from the installation position of the transport roller pair 77).

  Returning to FIG. 1, the image forming apparatus 100 includes an operation panel 200. Operation panel 200 includes a touch panel display 201. The touch panel display 201 displays a screen for accepting various settings from the user. The operation panel 200 is provided with a plurality of hard keys 202. Examples of the hard keys 202 provided on the operation panel 200 include a start key for accepting a job execution instruction from the user and a numeric keypad for accepting numerical input from the user. The operation panel 200 displays that a jam error and a size mismatch error have occurred. At this time, the operation panel 200 functions as a notification unit.

<Hardware configuration of image forming apparatus>
FIG. 3 is a block diagram illustrating the hardware configuration of the image forming apparatus. The image forming apparatus 100 includes a control unit 110 that controls the entire apparatus. The control unit 110 includes a CPU 111 that executes various processes, a memory 112 that stores a control program for operating the CPU 111, and the like.

  The control unit 110 is connected to the image reading unit 1 and the printing unit 2 and controls the reading operation of the image reading unit 1 and the printing operation of the printing unit 2. The control unit 110 is connected to the operation panel 200 and controls the display operation of the operation panel 200 and detects an operation performed on the operation panel 200.

  Here, the control unit 110 controls the transport operation of a plurality of processing units (rotating bodies for transporting the paper P) responsible for transporting the paper P as control of the printing operation. That is, the control unit 110 controls driving of the motors M1, M2, M3, and M4 for causing each processing unit to perform a transport operation. Further, the control unit 110 controls on / off of the clutches C1, C2, and C3.

  The processing unit that performs the transport operation by the driving force of the motor M <b> 1 includes a pickup roller 31 and a paper feed roller pair 32. That is, the processing unit that performs the transport operation by the driving force of the motor M1 is the paper feeding unit 3. The pickup roller 31 and the paper feed roller pair 32 rotate by receiving the driving force of the motor M1, and feed (convey) the paper P.

  The pickup roller 31 is connected to the motor M1 via the clutch C1. Thereby, only the paper feed roller pair 32 can be rotated.

  The processing unit that performs the transport operation by the driving force of the motor M2 includes an intermediate transfer belt 51, a secondary transfer roller 53, a drive roller 54, a transport roller pair 71, a registration roller pair 72, and transport roller pairs 76 and 77. In the following description, the processing unit that performs the conveying operation by the driving force of the motor M2 is referred to as an image forming unit 4. Each rotating body of the image forming unit 4 receives the driving force of the motor M2 and rotates to convey the paper P.

  The driving roller 54 rotates upon receiving the driving force of the motor M2. When the driving roller 54 rotates, the intermediate transfer belt 51 rotates, and the secondary transfer roller 53 rotates following the rotation of the intermediate transfer belt 51. Thereby, the paper P is conveyed.

  The conveyance roller pairs 76 and 77 rotate so that the sheet P advances toward the merge position P2 when the image forming unit 4 performs an operation of conveying the sheet P in the same direction as the conveyance direction D of the sheet P at the time of job execution. When the image forming unit 4 performs an operation of transporting the paper P in the direction opposite to the transport direction D of the paper P at the time of executing the job, the paper P rotates so as to advance toward the branch position P1.

  The registration roller pair 72 is connected to the motor M2 via the clutch C2. Thereby, only the registration roller pair 72 can be rotated or the rotation can be stopped while the transport roller pair 71 is rotating. Thereby, the secondary paper feeding can be performed at an appropriate timing.

  The processing unit that performs the conveying operation by the driving force of the motor M <b> 3 includes a fixing roller pair 61. That is, the processing unit that performs the transport operation by the driving force of the motor M3 is the fixing unit 6. The fixing roller pair 61 receives the driving force of the motor M3 and rotates to convey the paper P.

  The processing unit that performs the transport operation by the driving force of the motor M4 includes a reverse roller pair 74 and a transport roller pair 75. That is, the processing unit that performs the transport operation by the driving force of the motor M4 is the reversing unit 8. The reverse roller pair 74 and the transport roller pair 75 rotate by receiving the driving force of the motor M4 and transport the paper P.

  The discharge roller pair 73 is also configured to rotate by the driving force of the motor M4. In the case of this configuration, for example, the reverse roller pair 74 and the transport roller pair 75 are connected to the motor M4 via the clutch C3. Thereby, only the discharge roller pair 73 can be rotated in a state where the rotation of the reverse roller pair 74 (conveyance roller pair 75) is stopped.

  Further, the control unit 110 detects the presence or absence of the paper P at the corresponding detection position based on the output values of the plurality of determination sensors PS in order to control the printing operation. In other words, the control unit 110 detects the arrival of the leading edge of the paper P and the passage of the trailing edge of the paper P at each detection position. For example, when executing a print job, the control unit 110 determines whether a jam error has occurred based on the detection result. Details will be described later.

<Single-sided printing and double-sided printing>
The conveyance path on the downstream side in the conveyance direction D of the paper P from the fixing nip FN varies depending on whether a single-sided print job or a double-sided print job is executed. Hereinafter, a specific description will be given with reference to FIG.

  First, when executing a single-sided print job, the control unit 110 discharges the single-sided printing paper P (paper P that has passed through the fixing nip FN) to the paper discharge tray 20T as it is. That is, the control unit 110 blocks the conveyance path from the main conveyance path 2 </ b> A to the reverse conveyance path 2 </ b> B by the switching claw 78. As a result, the single-sided printing paper P that has passed through the fixing nip FN is guided to the paper discharge tray 20T.

  When executing a duplex printing job, the control unit 110 uses the reversing unit 8 to perform switchback processing (processing to switch back the paper P). Specifically, the controller 110 opens the transport path from the main transport path 2A to the reverse transport path 2B by rotating the switching claw 78. As a result, the single-sided printing paper P that has passed through the fixing nip FN is drawn from the main transport path 2A to the reverse transport path 2B (first transport path 21).

  At this time, the control unit 110 rotates the pair of reverse rollers 74 so that the single-sided printing paper P drawn into the first transport path 21 proceeds in the first direction D1. And the control part 110 reversely rotates the inversion roller pair 74 at the timing when the rear end of the single-sided printing paper P passes the branch position P1. As a result, the single-sided printing paper P travels in the second direction D2 and is fed into the second transport path 22.

  Thereafter, the control unit 110 continues to rotate the reverse roller pair 74 and the transport roller pair 75 as they are. As a result, the single-sided printing paper P sent to the second transport path 22 travels in the second transport path 22 in the second direction D2, and enters the main transport path 2A from the joining position P2 (returns to the main transport path 2A). ).

  The single-sided printing paper P that has returned to the main transport path 2A is transported along the main transport path 2A, so that it again passes through the transfer nip TN and the fixing nip FN in this order. At this time, since the front and back sides of the single-sided printing paper P are reversed, an image is printed on the back side (unprinted side) of the single-sided printing paper P. Then, the paper P on which images are printed on both sides is conveyed as it is along the first conveyance path 21 and is discharged to the paper discharge tray 20T.

<Detection of jam error>

  The control unit 110 is a transit time from when a determination sensor PS among a plurality of determination sensors PS detects the arrival of the leading edge of the paper P at the detection position until it detects passage of the trailing edge of the paper P. Time. Then, when the measured passing time has passed the first determination time, it is determined that a jam error has occurred. The first determination time in this case is the time required for the trailing edge of the paper P to pass through the same detection position after the leading edge of one sheet P reaches the detection position of a certain determination sensor PS. Yes, it is a time that can be calculated in advance based on the paper size (length in the carrying direction) and the paper carrying speed. That is, the first determination time is based on the reference passage time indicating the standard passage time for one sheet.

  However, when the passage time in the determination sensor PS3 provided near the installation position of the registration roller pair 72 and upstream of the registration roller pair 72 in the paper transport direction has passed the first determination time, the control unit 110 Does not immediately determine that a jam error has occurred. When the passage time in the determination sensor PS3 has passed the first determination time, there is a possibility that two sheets are conveyed in succession as will be described later. For this reason, the control unit 110 does not determine that a jam error has occurred until the measured passage time has passed the first determination time and has passed the second determination time.

  The second determination time in this case is a time based on the reference passage time for two sheets, and is a time obtained by adding a predetermined margin time to a time twice the reference passage time for one sheet. Here, by adding a predetermined margin time, it is determined that a jam error has occurred when the passage time is slightly increased due to misalignment or bending of the sheet even though one sheet is normally conveyed. This can be prevented.

  In addition, the control unit 110 starts timing from the start of paper feeding by the rotation of the pickup roller 31 when executing a print job. Then, the control unit 110 checks whether or not the leading edge of the paper P has reached the detection position of a certain determination sensor PS when the jam detection time has elapsed from the start of paper feeding. As a result, if the arrival of the leading edge of the paper P cannot be confirmed, the control unit 110 determines that a jam error (paper jam in the paper transport path 20) has occurred. The jam detection time in this case is the time required for one sheet of paper P to travel between the detection start position of the determination sensor PS from the start of paper supply, and is detected by the pickup roller 31 and the determination sensor PS. This is a time that can be calculated in advance based on the distance to the position and the sheet conveyance speed.

  In addition, when executing a print job, the control unit 110 measures the time after detecting the arrival of the leading edge of the paper P at a detection position of a determination sensor PS (referred to as a first sensor) among the plurality of determination sensors PS. You may start. At this time, when the jam detection time has elapsed since the control unit 110 detected the arrival of the leading edge of the paper P at the detection position of the first sensor, the control unit 110 is located on the downstream side in the transport direction of the paper P with respect to the first sensor. It is confirmed whether or not the leading edge of the paper P has reached the detection position of the sensor PS (referred to as a second sensor).

  When the control unit 110 determines that a jam error has occurred, the control unit 110 interrupts the print job being executed. Then, the control unit 110 causes the operation panel 200 to display an error message indicating that a jam error has occurred. That is, the control unit 110 notifies the user that a jam error has occurred (the operation panel 200 functions as a notification unit).

  In a jam processing operation performed by a user (operation for removing the jammed paper P, which is the jammed paper P), the side cover (not shown) of the image forming apparatus 100 is opened. When the side cover is opened, the sheet conveyance path 20 is exposed. As a result, the jammed paper P can be removed from the paper transport path 20. Alternatively, when the paper cassette 30 is pulled out from the image forming apparatus 100, the paper feeding unit 3 is exposed. Therefore, when the jammed paper P remains in the paper feeding unit 3, the jammed paper P can be removed by pulling out the paper cassette 30.

  After detecting the occurrence of a jam error, the control unit 110 determines whether or not the jam processing operation by the user has been completed. For example, when the control unit 110 detects that the side cover opened after the occurrence of the jam error is closed, the control unit 110 determines that the jam processing operation is finished. Further, when the control unit 110 detects that the paper cassette 30 pulled out after the occurrence of the jam error has been returned to its original state, the control unit 110 determines that the jam processing operation has been completed.

  If the paper P does not remain in the paper transport path 20 after the jam processing operation is completed, the control unit 110 resumes the print job that was interrupted by detecting the occurrence of a jam error. At this time, the control unit 110 stops displaying the error message.

  FIG. 4 is a diagram illustrating an example of a conveyance state of a sheet conveyed on a sheet conveyance path. During execution of a print job, the trailing edge side of the leading sheet Pa overlaps with the leading edge side of the succeeding sheet Pb. This shows a state in which the papers Pa and Pb are continuously conveyed. In FIG. 4, the leading paper Pa is indicated by a solid line, and the subsequent paper Pb is indicated by a broken line.

  When the paper feed unit 3 pulls out the paper P from the paper cassette 30 and supplies it to the paper transport path 20, the subsequent paper Pb may follow the leading paper Pa due to static electricity or the like. In this case, during the execution of the print job, the two sheets Pa and Pb are conveyed in a continuous state. Note that the sheet conveyance speed of the two sheets Pa and Pb conveyed in a continuous state is substantially the same as the sheet conveyance speed when one sheet P is normally conveyed.

  At this time, when the trailing edge of the leading paper Pa passes the detection position of the determination sensor PS3, the leading edge of the succeeding paper Pb overlaps the trailing edge of the leading paper Pa. For this reason, the determination sensor PS3 does not detect the trailing edge passage of the leading paper Pa. Therefore, the passage time measured at the detection position of the determination sensor PS3 exceeds the first determination time. At this time, the control unit 110 causes the image forming unit 4 to stop forming an image and causes the printing unit 2 to continue paper conveyance. As a result, the top paper Pa is continuously printed by the paper conveyance of the printing unit 2. Further, the subsequent paper Pb is not printed on the image forming unit 4 and is not printed.

  When the two sheets of paper Pa and Pb are further conveyed in a continuous state, the determination sensor PS3 detects the trailing edge of the subsequent sheet Pb after the first determination time has elapsed and before the second determination time has elapsed. Detect passage. At this time, the control unit 110 discharges the sheet to the sheet discharge tray 20T so that the sheets Pa and Pb in the sheet conveyance path 20T are exhausted.

  As a result, the user can reduce the work of taking out the paper from the paper transport path 20, and the convenience can be improved. Further, the paper is not damaged during the jam handling operation. In addition, an image is printed on the first paper Pa, and a delay in the printing process can be suppressed.

  It should be noted that, based on the output value of the determination sensor PS3 provided upstream of the transfer nip TN in the paper conveyance direction, it is determined whether or not two sheets of paper Pa and Pb are being conveyed in succession. This determination can be made reliably before the sheet Pb is sent to the transfer nip NP. Further, the determination sensor PS3 is disposed in the vicinity of the registration roller pair 72, and when the rear end of the leading sheet Pa passes the determination sensor PS3, most of the subsequent sheet Pb is fed to the sheet feeding unit. It is drawn from 3. Therefore, based on the output value of the determination sensor PS3, the control unit 110 determines whether the two sheets Pa and Pb are continuously conveyed by determining whether or not the two sheets Pa and Pb are conveyed continuously. It can be determined with higher accuracy that the sheet is being conveyed.

  In general, it is unlikely that two sheets of paper Pa and Pb are continuously conveyed from the sheet feeding unit 3 to the sheet conveying path 20 twice in succession. Further, when the paper size set in the paper cassette 30 is larger than the paper size set in the print job, the passing time of the set paper is shorter than the first determination time of the set paper. Also gets longer. For this reason, jam errors are continuously determined by the control unit 110.

  Therefore, the determination sensor PS3 detects the passage of paper before the passage of the first judgment time and the second judgment time, and the judgment of the first fed paper after completion of paper ejection. When the passage time in the sensor PS3 again exceeds the first determination time, the control unit 110 determines that a paper size mismatch error has occurred.

  If it is determined that the paper size mismatch error has occurred, the image forming unit 4 stops image formation and the printing unit 2 stops paper conveyance. Further, an error message indicating that a paper size mismatch error has occurred is displayed on the operation panel 200. This prompts the user to change the paper size setting.

  FIG. 5 is a flowchart showing the operation of the image forming apparatus 100. The print job execution procedure will be specifically described with reference to the steps of FIG. For the sake of explanation, it is assumed that two sheets Pa and Pb are transported in succession during execution of a print job.

  When the user inputs the start key of the operation panel 200 and executes a single-sided print job, the following operation is performed. In step S <b> 1, the paper feeding unit 3 pulls out the paper Pa from the paper cassette 30 and supplies it to the paper transport path 20. At this time, the paper Pb is supplied to the paper transport path 20 following the paper Pa. Further, the control unit 110 starts measuring time from the start of paper feeding.

  In step S2, the leading paper Pa that has reached the registration roller pair 72 is temporarily stopped by the registration roller pair 72 and then sent to the transfer nip TN. At this time, the control unit 110 starts timing after the determination sensor PS3 detects the leading edge of the leading paper Pa. The leading sheet Pa enters the transfer nip TN, and the toner image is secondarily transferred from the intermediate transfer belt 51 while being conveyed.

  In step S3, as shown in FIG. 6, when the leading edge of the leading paper Pa reaches the detection position of the determination sensor PS4, the control unit 110 determines within a predetermined jam detection time from the start of paper feeding. It is confirmed whether or not the sensor PS4 detects the arrival of the paper Pa.

  Here, the sheet conveyance speed of the two sheets Pa and Pb conveyed in a continuous state is substantially the same as the sheet conveyance speed when one sheet P is normally conveyed. Therefore, even when two sheets Pa and Pb are conveyed in a continuous state, it can be determined whether or not a jam error has occurred based on the jam detection time.

  When the determination sensor PS4 detects the arrival of the paper Pa within the jam detection time, the control unit 110 determines that the paper is normally conveyed from the registration roller pair 72 to the transfer nip TN, and proceeds to step S4. Transition.

  On the other hand, if the determination sensor PS4 cannot detect the arrival of the paper Pa within the jam detection time, the control unit 110 determines that a jam error due to a paper jam has occurred around the transfer nip TN, and performs step. The process proceeds to S41.

  In step S41, the control unit 110 causes the printing unit 2 to stop paper conveyance, causes the operation panel 200 to display an error message indicating that a jam error has occurred due to a paper jam, and proceeds to step S42. In step S42, 0 is stored in the flag F in the memory 112, and the print job is terminated. Accordingly, when the next print job is executed, the control unit 110 does not determine that a paper size mismatch error has occurred.

  In step S4, the leading paper Pa that has passed through the transfer nip TN is sent out to the fixing nip FN. The leading sheet Pa enters the fixing nip FN and is heated and pressurized while being conveyed, whereby the toner image is fixed on the sheet P.

  In step S5, as shown in FIG. 7, when the leading edge of the leading sheet Pa reaches the detection position of the determination sensor PS5, the control unit 110 performs the determination within a predetermined jam detection time from the start of sheet feeding. It is confirmed whether or not the sensor PS5 detects the arrival of the paper Pa.

  When the determination sensor PS5 detects the arrival of the paper Pa within the jam detection time, the control unit 110 determines that the paper is normally conveyed from the transfer nip TN to the fixing nip FN, and proceeds to step S6. To do.

  On the other hand, if the determination sensor PS5 cannot detect arrival of the paper Pa within the jam detection time, the control unit 110 determines that a jam error has occurred around the fixing unit 6 due to a paper jam. The process proceeds to S41.

  In step S6, as shown in FIG. 4, when the trailing edge of the leading paper Pa has passed the detection position of the determination sensor PS3, the control unit 110 passes the paper through the detection position of the determination sensor PS3. Time. Then, it is determined whether or not the passage time has passed the first determination time. That is, the control unit 110 determines whether or not the determination sensor PS3 has detected the passage of the sheet when the first determination time has elapsed since the arrival of the leading edge of the leading sheet Pa at the detection position of the determination sensor PS3. Determine whether.

  When the determination sensor PS3 detects passage of paper when the first determination time has elapsed, it is determined that one sheet is normally conveyed along the sheet conveyance path 20, and the process proceeds to step S21 to continue the print job. To do.

  On the other hand, if the determination sensor PS3 cannot detect paper passage when the first determination time has elapsed, it is determined that there is a possibility that some error has occurred in the paper transported along the paper transport path 20, and step S7. Migrate to

  In step S7, the control unit 110 reads the value of the flag F stored in the memory 112, and determines whether 1 is stored in the flag F. When 0 is stored in the flag F, the process proceeds to step S8. On the other hand, when 1 is stored in the flag F, the determination sensor PS3 passes after the first determination time and before the second determination time when the previous print job is executed. PS3 detects the passage of the sheet, and the process proceeds to step S31.

  In step S31, the control unit 110 determines whether a paper size mismatch error has occurred. At this time, the control unit 110 causes the printing unit 2 to stop paper conveyance, causes the operation panel 200 to display an error message indicating that a paper setting error has occurred, and proceeds to step S32. In step S32, 0 is stored in the flag F in the memory 112, and the print job is terminated. Thus, when the next print job is executed, the control unit 110 does not determine again that a paper size mismatch error has occurred.

  In step S8, the control unit 110 causes the image forming unit 4 to stop forming an image and causes the printing unit 2 to continue paper conveyance. As a result, the top paper Pa is continuously printed by the paper conveyance of the printing unit 2. Further, the subsequent paper Pb is not printed on the image forming unit 4 and is not printed.

  In addition, thereafter, the criterion for determining whether or not a jam error has occurred in the determination sensors PS4 and PS5 is changed. Specifically, even if the paper passage time in the determination sensors PS4 and PS5 exceeds the first determination time, the control unit 110 does not immediately determine that a jam error has occurred.

  In step S9, as shown in FIG. 8, when the trailing edge of the succeeding paper Pb passes the detection position of the determination sensor PS3, the control unit 110 passes the paper through the detection position of the determination sensor PS3. Measure. Then, it is determined whether or not the passage time has passed the second determination time. That is, the control unit 110 determines whether or not the determination sensor PS3 detects the passage of the sheet when the second determination time has elapsed since the arrival of the leading edge of the leading sheet Pa at the detection position of the determination sensor PS3. Determine whether.

  When the determination sensor PS3 detects passage of paper before the second determination time has elapsed, the control unit 110 determines that the two sheets of paper Pa and Pb are being conveyed and proceeds to step S10.

  On the other hand, when the determination sensor PS3 cannot detect paper passage even after the second determination time has elapsed, the control unit 110 determines that a jam error due to paper jam has occurred in the paper transport path 20, and step S41. Migrate to

  In step S10, the control unit 110 discharges the sheet to the sheet discharge tray 20T so that the sheets Pa and Pb in the sheet conveyance path 20T are exhausted. As a result, the user can reduce the work of taking out the paper from the paper transport path 20, and the convenience can be improved. Further, the paper is not damaged during the jam handling operation. In addition, an image is printed on the first paper Pa, and a delay in the printing process can be suppressed. When the papers Pa and Pb are discharged to the paper discharge tray 20T, the paper Pb becomes an invalid paper without image formation.

  Further, when the paper Pa and Pb pass the determination sensors PS4 and PS5, the determination sensors PS4 and PS5 detect the passage of the paper before the second determination time elapses. Then, the control unit 110 determines that a jam error has not occurred. As a result, the sheets Pa and Pb pass through the determination sensors PS4 and PS5 in a continuous state.

  On the other hand, when the determination sensors PS4 and PS5 cannot detect paper passage within the second determination time, the control unit 110 determines that a jam error has occurred in the paper conveyance path 20.

  After the sheets Pa and Pb are discharged to the discharge tray 20T, the process proceeds to step S11. In step S11, 1 is stored in the flag F in the memory 112, and the print job is terminated. As a result, when the next print job is executed and the passage time of the determination sensor PS3 again passes the first determination time, the control unit 110 determines that a paper size mismatch error has occurred.

  In step S21, one sheet is normally conveyed along the sheet conveyance path 20, a print job is executed, and the process proceeds to step S22. In step S22, one sheet is discharged to the discharge tray 20T. In step S23, 0 is stored in the flag F in the memory 112, and the print job is terminated.

  According to the present embodiment, when the two sheets are conveyed in a continuous state and the trailing edge side of the leading sheet Pa and the leading edge side of the succeeding sheet Pb overlap, the determination sensor (determination sensor) PS3 is , The passage of the trailing edge of the leading sheet is not detected. For this reason, the passage time of the sheet in the determination sensor PS3 passes the first determination time. At this time, the control unit 110 causes the image forming unit 4 to stop forming an image and causes the printing unit 2 to continue paper conveyance. As a result, the top paper Pa is continuously printed by the paper conveyance of the printing unit 2. Further, the subsequent paper Pb is not printed on the image forming unit 4 and is not printed. Further, when the two sheets are conveyed in a continuous state, the determination sensor PS3 passes the trailing edge of the subsequent sheet Pb after the first half time has elapsed and before the second determination time has elapsed. Detect. At this time, the control unit 110 discharges the sheet to the sheet discharge tray 20T so that the sheet in the sheet conveyance path 20 runs out. As a result, the user can reduce the work of taking out the paper from the paper transport path 20, and the convenience can be improved.

  In addition, when the passage time of the sheet in the determination sensor PS3 has passed the second determination time, the control unit 110 determines that a jam error has occurred because the two sheets are not conveyed in a continuous state, and printing is performed. The unit 2 stops the sheet conveyance. Thereby, it is possible to prevent the printing unit 2 from failing by continuing paper conveyance when a jam error occurs.

  Further, the control unit 110 confirms whether or not the determination sensor PS4 detects the arrival of the paper within a predetermined jam detection time from the start of paper feeding, and the determination sensor PS4 detects whether or not the paper is within the jam detection time. If arrival cannot be detected, it is determined that a jam error has occurred, and the image forming unit 4 stops image formation and the printing unit 2 stops paper conveyance. As a result, even when two sheets of paper Pa and Pb are conveyed in series, the occurrence of a jam error in the sheet conveyance path 20 can be detected.

  In general, it is unlikely that two sheets of paper Pa and Pb are continuously conveyed from the sheet feeding unit 3 to the sheet conveying path 20 twice in succession. Therefore, if the determination sensor PS3 detects the passage of paper before the passage of the first determination time and the passage of the second determination time, the control unit 110 determines that a paper size mismatch error has occurred. Then, the printing unit 2 stops the paper conveyance. A paper size mismatch error can be easily detected.

  The determination sensor PS3 is provided in the vicinity of the installation position of the registration roller pair 72 and upstream of the registration roller pair 72 in the paper transport direction. Thus, when the trailing edge of the leading paper Pa passes the determination sensor PS3, most of the succeeding paper Pb is drawn out from the paper feeding unit 3. For this reason, by making a determination based on the output value of the determination sensor PS3, the control unit 110 can more accurately determine whether or not the two sheets of paper Pa and Pb are being conveyed. it can.

  It should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is shown not by the description of the above-described embodiment but by the scope of claims for patent, and further includes meanings equivalent to the scope of claims for patent and all modifications within the scope.

  For example, the control unit 110 determines whether or not the two sheets Pa and Pb are transported in succession based on the passage time of the sheet passing the detection position of the determination sensor PS3, but more than the transfer nip TN. It may be determined whether or not the two sheets of paper Pa and Pb are being conveyed in series based on the passage time of the sheet passing through the detection position of the determination sensor PS2 arranged on the upstream side in the sheet conveyance direction.

DESCRIPTION OF SYMBOLS 3 Paper feed part 4 Image formation part 6 Fixing part 8 Inversion part 20 Paper conveyance path 20T Paper discharge tray 21 1st conveyance path 22 2nd conveyance path 30 Paper cassette 31 Pickup roller 31 Mounting plate 32 Paper feed roller pair 34 Friction body 35 Pickup Roller 40Bk, 40Y, 40C Mechanism 41 Photoconductor Drum 42 Charging Device 43 Developing Device 44 Cleaning Device 45 Exposure Device 78 Switching Claw 100 Image Forming Device 110 Control Unit 111 CPU
112 memory 200 operation panel 201 touch panel display PN paper feed nip PS judgment sensor Pa, Pb paper TN transfer nip

Claims (5)

A paper exit tray that ejects paper,
A printing section for printing on paper;
A sensor for detecting the arrival and passage of paper,
A control unit for controlling paper conveyance,
The printing unit
A paper feed unit that feeds paper, including a paper feed rotator that forms the paper feed nip;
An image forming unit that includes a transfer rotator that forms the transfer nip, conveys paper, forms an image, and transfers the formed image to the paper;
A fixing unit that includes a fixing rotator that forms the fixing nip, conveys the paper, and fixes the image transferred to the paper to the paper;
A paper conveyance path that reaches the paper discharge tray via the paper feed nip, the transfer nip, and the fixing nip, and
The determination sensor is provided upstream of the transfer nip in the paper conveyance direction,
The controller is
Based on the output value of the determination sensor, the passage time that is the time from when the determination sensor detects the arrival of the paper until the passage of the paper is detected,
When the passage time has passed a first determination time based on a reference passage time indicating the standard passage time for one sheet, the image forming unit is stopped from forming an image and the paper is continuously conveyed to the printing unit. Let
When the determination sensor detects the passage of paper before the passage of the second determination time based on the reference passage time for two sheets, the paper discharge is performed so that there is no paper in the paper conveyance path. An image forming apparatus that discharges a sheet to a tray.   2. The image forming apparatus according to claim 1, wherein when the passing time has passed the second determination time, the control unit determines that a jam error has occurred, and causes the printing unit to stop paper conveyance. . The determination sensor is provided along the paper conveyance path,
The controller is
Check whether the determination sensor detects the arrival of the paper within a predetermined jam detection time from the start of paper feeding,
If the determination sensor cannot detect the arrival of the paper within the jam detection time, it is determined that a jam error has occurred, and the image forming unit stops image formation and the printing unit stops paper conveyance. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. Including an informing unit for informing,
The controller is
When the passage time exceeds the first determination time, and the determination sensor detects passage of paper before the second determination time,
When the passage time of the first fed paper after completion of paper discharge exceeds the first determination time, it is determined that a paper size mismatch error has occurred, and the paper conveyance is stopped in the printing unit,
The image forming apparatus according to claim 1, wherein a paper size mismatch error is notified. A registration roller pair for feeding paper to the transfer nip;
5. The determination sensor according to claim 1, wherein the determination sensor is provided in the vicinity of an installation position of the registration roller pair and upstream of the registration roller pair in a paper conveyance direction. Image forming apparatus.

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