Paper sheet conveyance device

Abstract

To determine occurrence of a paper jam and the number of jammed paper sheets even in an undetected range of a paper sheet where a paper sheet detection unit cannot be provided in a paper sheet conveyance passage.SOLUTION: A paper sheet conveyance device 3 comprises: a carried-in paper sheet sensor 62 for detecting a paper sheet on an upstream side from a heating area of a heating part 61 in the conveyance direction of the paper sheet; a carried-out paper sheet sensor 63 for detecting the paper sheet on a downstream side from the heating area of the heating part 61 in the conveyance direction of the paper sheet; and a control part 66 which counts a first number of the paper sheets detected by the carried-in paper sheet sensor 62, and counts a second number of the paper sheets detected by the carried-out paper sheet sensor 63, and, on the basis of the first number of the paper sheets and the second number of the paper sheets, determines paper sheet jam in an undetected range of the paper sheet between each of detection positions, and determines the number of residual paper sheets in the undetected range.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a paper transport device that includes a paper transport path that receives and transports paper transported from an image forming device, and a heat generating section that heats the paper being transported along the paper transport path, and relates to a technology for detecting paper jams in the area heated by the heat generating section. [Background technology]

[0002] Inkjet image forming devices include those that eject ink onto recording paper to form an image on the recording paper. In this inkjet method, the surface of the recording paper becomes wet with ink, so it is desirable to heat the surface of the recording paper to dry it quickly.

[0003] For example, the image forming system described in Patent Document 1 includes a printer and a drying device. The drying device includes a transport unit that transports sheets transported from the printer and a drying section that emits infrared rays toward a portion of the transport section of the transport unit, promoting evaporation of ink adhering to the paper. Additionally, multiple jam detection sections are provided at different locations along the transport section of the transport unit, and a sheet jam is determined when any of the jam detection sections continues to detect the sheet for a predetermined period of time or longer.

[0004] The image forming device described in Patent Document 2 is provided with a paper feed sensor that detects paper fed from a paper feed means and accumulates the number of sheets, and a paper discharge sensor that detects paper discharged from a discharge means and accumulates the number of sheets.When a jam occurs along the paper transport path from the paper feed sensor to the paper discharge sensor, the total number of sheets remaining on the paper transport path is calculated from the difference between the accumulated numbers of sheets measured by each sensor.

[0005] The image forming apparatus described in Patent Document 3 has multiple detectors installed along the paper transport path. Each detector has its own detection area, and when the leading edge of the paper approaches the detection area, the output of the detector is turned ON, and when the trailing edge of the paper passes through the detection area, the output of the detector is turned OFF. For example, if the output of the next detector does not turn ON even after a predetermined time has passed since the output of the previous detector turned OFF, it is determined that a jam has occurred. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-121194 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-171371 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-145694 Summary of the Invention [Problem to be solved by the invention]

[0007] In Patent Document 1, a sheet jam is determined when a jam detection unit provided in a transport section of a transport unit detects a sheet continuously for a predetermined period of time or more. However, a jam detection unit cannot be provided in a portion of the transport section where infrared rays are emitted by the drying unit, and this technology cannot determine whether a sheet jam has occurred in this portion of the transport section. This is because the jam detection unit (sensor) receives infrared rays and heats up, which can lead to false detection or malfunction.

[0008] Furthermore, in Patent Document 2, when a jam occurs in the paper transport path from the paper feed sensor to the paper discharge sensor, the total number of sheets remaining in the paper transport path is calculated from the difference between the accumulated number of sheets measured by each sensor. However, this technology uses a separate paper detection switch to detect jams, and does not determine whether a jam has occurred using each sensor. Therefore, even if the technology in Patent Document 2 is applied to Patent Document 1 and sensors are installed on both sides of a portion of the transport section where infrared rays are emitted, it is not possible to determine whether a jam has occurred in that portion of the transport section.

[0009] Furthermore, in Patent Document 3, multiple detectors are provided along a paper transport path, and if the output of the next detector does not turn on even after a predetermined time has passed since the output of the previous detector turned off, it is determined that a jam has occurred. However, even if it is possible to determine whether a single sheet of paper has jammed between the previous and next detectors, it does not determine whether multiple sheets of paper have jammed. For this reason, even if the technology in Patent Document 3 is applied to Patent Document 1 and each detector is provided on both sides of a portion of the transport section where infrared rays are emitted, it is not sufficient to determine both the occurrence of a jam in that portion of the transport section and the number of jammed sheets.

[0010] The present invention has been developed in consideration of the above circumstances, and aims to determine the occurrence of paper jams and the number of jammed sheets of paper in an undetected paper range where a paper detection unit for detecting paper cannot be installed. [Means for solving the problem]

[0011] A paper transport device according to one aspect of the present invention comprises a paper transport path having a transport roller for receiving and transporting paper transported from an image forming device; a heat generating section arranged along the paper transport path for heating paper being transported by the paper transport path; a first paper detection section for detecting the paper upstream of the heat generating area of the heat generating section in the direction of paper transport by the paper transport path; a second paper detection section for detecting the paper downstream of the heat generating area of the heat generating section in the direction of paper transport by the paper transport path; and a control section for counting the number of sheets of paper detected by the first paper detection section as a first number of sheets and counting the number of sheets of paper detected by the second paper detection section as a second number of sheets, and for determining whether the paper has jammed in an undetected range of the paper on the paper transport path between the detection position by the first paper detection section and the detection position by the second paper detection section based on the first number of sheets and the second number of sheets, and for determining the number of remaining sheets of paper in the undetected range. [Effects of the Invention]

[0012] According to the present invention, it is possible to determine the occurrence of a paper jam and the number of jammed sheets even in a paper undetected area in the paper transport path where a paper detection unit cannot be provided. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram showing a configuration of an image forming system having a paper transport device according to an embodiment of the present invention; [Figure 2] 1 is a side view schematically showing a paper transport device according to an embodiment of the present invention; [Figure 3] 10A and 10B are diagrams showing the order of transport paths through which normal-sized paper that has been printed on one side is transported in a paper transport device. [Figure 4] 10 is a diagram showing the order of transport paths through which medium-sized paper that has been printed on one side is transported in a paper transport device; FIG. [Figure 5] 10 is a diagram showing the order of transport paths through which long size paper that has been printed on one side is transported in a paper transport device. FIG. [Figure 6] (A) and (B) are diagrams showing the order of the transport paths through which standard-sized paper, which has been printed on the front side only and is then returned from the paper transport device to the image forming device for further printing on the back side, is transported. [Figure 7] 10 is a diagram showing the order of transport paths along which a medium-sized sheet of paper that has been printed on only the front side and is then returned from the paper transport device to the image forming device for further printing on the back side is transported. FIG. [Figure 8] 10 is a diagram showing the order of transport paths through which long size paper, which has been printed on only the front side and is then returned from the paper transport device to the image forming device for further printing on the back side, is transported. FIG. [Figure 9] 10 is a diagram showing the order of transport paths through which normal-size, medium-size, and long-size sheets printed on both sides are transported in a sheet transport device. FIG. [Figure 10] 1 is a diagram showing a main configuration of a paper transport device according to an embodiment of the present invention; [Figure 11] 10 is a flowchart showing a process for detecting a paper jammed in an infrared irradiation area of the paper transport device. [Figure 12] 10A and 10B are diagrams illustrating the order of the transport paths in which a sheet is transported from an undetected range of a main transport path to an exit transport path and then exits in a sheet transport device. [Figure 13] 10A and 10B are diagrams showing messages and the like displayed on a display unit of the paper transport device. DETAILED DESCRIPTION OF THE INVENTION

[0014] A paper transport device and an image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a diagram showing the configuration of an image forming system 1 having a paper transport device 3 according to this embodiment.

[0015] As shown in FIG. 1, the image forming system 1 includes an image forming device 2, a paper transport device 3, and a discharge device 4.

[0016] The paper transport device 3 is connected to the image forming device 2. The discharge device 4 is connected to the paper transport device 3. The paper transport device 3 is connected to the image forming device 2 on the downstream side in the paper transport direction by the image forming device 2. The discharge device 4 is connected to the paper transport device 3 on the downstream side in the paper transport direction by the paper transport device 3.

[0017] The image forming device 2 acquires image data from an original document, or acquires image data from an external server, cloud, or terminal. The image forming device 2 forms and outputs an image on paper based on the image data. The image forming device 2 may be a device that combines an image data transmission / reception function, an image reading function, and an image forming function. For example, the image forming device 2 has the functions of a scanner, printer, copier, telephone, printing machine, and facsimile.

[0018] The image forming device 2 forms an image on a sheet of paper. The image forming device 2 includes a feeding section 20, a feeding section 21, a paper feed conveying path 22, a paper feed conveying path 23, a discharge conveying path 24, an image forming section 25, a conveying belt 26, and a reverse conveying path 27.

[0019] Feeding section 20 stores and feeds sheets of paper. Feeding section 21 mainly performs manual feeding. Paper feed transport path 22 transports the sheets fed from feeding section 20 toward image forming section 25. Paper feed transport path 22 has transport roller 22A.

[0020] The paper feed path 23 transports the paper that has been manually fed from the feeding unit 21 toward the image forming unit 25. The discharge path 24 transports the paper to the paper transport device 3.

[0021] The image forming unit 25 is an inkjet printer that forms an image on paper using ink, and includes an ink cartridge, an ink tank, a pump, a head, a nozzle, and an electrode.

[0022] The ink cartridges and ink tanks store, for example, water-based inks of the colors Y (yellow), M (magenta), C (cyan), and K (black). The pump supplies ink from the ink tanks to the head.

[0023] The head has a large number of nozzles that make up pixels. Based on the image data, ink of a color corresponding to the image data is supplied to the head from an ink tank. The ink is ejected from the nozzles onto the paper.

[0024] The electrodes include, for example, a charging electrode and a deflection electrode. The charging electrode charges the ink ejected from the nozzle. The deflection electrode controls the direction in which the charged ink is ejected.

[0025] The conveyor belt 26 is disposed opposite the nozzles of the head and conveys the paper. An image is formed on the paper conveyed by the conveyor belt 26 using ink ejected from the nozzles of the head.

[0026] The reversing conveying path 27 reverses the face-up paper conveyed from the paper conveying device 3 and conveys it to the image forming unit 25 face-down.

[0027] The discharge device 4 receives the paper conveyed from the paper conveying device 3 and discharges the paper. The discharge device 4 may have a paper discharge tray 4A for accommodating the discharged paper.

[0028] 2 is a side view schematically showing the paper transport device 3 according to this embodiment. As shown in FIG. 2, the paper transport device 3 includes a main transport path 31 that receives and transports paper transported through the discharge transport path 24 of the image forming device 2, a branch transport path 32 branched from the main transport path 31, a second communication transport path 33 connected to the branch transport path 32, a second drum-shaped transport path 34 and a first communication transport path 35 branched from the second communication transport path 33, a first drum-shaped transport path 36 connected to the first communication transport path 35, and a first switchback transport path 37 branched from the first drum-shaped transport path 36. It is equipped with a second switchback conveying path 38 branching off from the second drum-shaped conveying path 34, a third connecting conveying path 39 connecting the second connecting conveying path 33 to the second switchback conveying path 38, an intermediate conveying path 40 connecting the first switchback conveying path 37 and the second switchback conveying path 38 to the reversing conveying path 27 of the image forming section 25, an auxiliary conveying path 41 connecting the first switchback conveying path 37 and the second switchback conveying path 38 to the main conveying path 31, and an exit conveying path 45 branching off from the main conveying path 31.

[0029] Furthermore, the paper transport device 3 is provided with a plurality of transport rollers 42 that are arranged along each of the transport paths 31 to 41 and transport the paper.

[0030] The paper conveying device 3 also includes a branch claw 51 provided at the branch point of the main conveying path 31 and the branch conveying path 32, a branch claw 52 provided at the branch point from the second connecting conveying path 33 to the second drum-shaped conveying path 34 or the first connecting conveying path 35, a branch claw 53 provided at the branch point from the first drum-shaped conveying path 36 to the first switchback conveying path 37, a branch claw 54 provided at the branch point from the second drum-shaped conveying path 34 to the second switchback conveying path 38, a branch claw 55 provided at the branch point from the first switchback conveying path 37 or the second switchback conveying path 38 to the relay conveying path 40 or the auxiliary conveying path 41, a branch claw 56 provided at the branch point from the second connecting conveying path 33 to the third connecting conveying path 39, and a branch claw 57 provided at the branch point from the main conveying path 31 to the exit conveying path 45.

[0031] The paper transport device 3 also includes a heat generating section 61 arranged above the main transport path 31, an incoming paper sensor 62 provided on the paper entrance side of the main transport path 31, and an outgoing paper sensor 63 provided on the paper exit side of the main transport path 31.

[0032] The heating unit 61 includes, for example, a near-infrared halogen lamp. The heating unit 61 irradiates the upper surface of the paper being transported on the main transport path 31 with infrared rays to promote drying of the ink adhering to the upper surface of the paper.

[0033] The incoming paper sensor 62 is located upstream in the paper transport direction from the infrared radiation area (heating area) RA of the heat generating section 61, and detects paper that has been transported from the discharge transport path 24 of the image forming section 25 to the main transport path 31.

[0034] The discharged paper sensor 63 is provided downstream in the paper transport direction from the infrared radiation area RA of the heat generating unit 61, and detects the paper discharged from the infrared radiation area RA.

[0035] The incoming paper sensor 62 and the outgoing paper sensor 63 are equipped with, for example, a light-emitting element that emits light toward the transported paper and a light-receiving element that receives light reflected by the paper, and detect the presence of paper when the light-receiving element can receive the light emitted by the light-emitting element, and detect the absence of paper when the light-receiving element cannot receive the light emitted by the light-emitting element. In the incoming paper sensor 62 and the outgoing paper sensor 63, the timing when the light-receiving element starts receiving light is the timing when the leading edge of the paper is detected, and the timing when the light-receiving element subsequently stops receiving light is the timing when the trailing edge of the paper is detected.

[0036] The incoming paper sensor 62 and the outgoing paper sensor 63 are located at positions outside the infrared radiation area RA of the heat generating unit 61. This prevents the incoming paper sensor 62 and the outgoing paper sensor 63 from being heated by the infrared rays, and prevents false detections and malfunctions caused by the infrared rays.

[0037] The paper transport device 3 also includes an opening / closing door 64 provided on the front side of the main transport path 31, and an opening / closing sensor 65 that detects whether the opening / closing door 64 is open. When the opening / closing door 64 is in the open state, it opens the infrared irradiation area RA (undetected range) on the main transport path 31. When a jam occurs on the main transport path 31, the opening / closing door 64 is opened to remove the jammed paper, and is then closed. The opening / closing door 64 is an example of an opening / closing section in the claims.

[0038] The opening / closing sensor 65 is, for example, a limit switch that turns on and off in response to the opening and closing of the opening / closing door 64.

[0039] The paper transport device 3 is also provided with another door (not shown) for removing paper jammed in another transport path.

[0040] In the paper transport device 3, the paper transport operation is performed under the operational control of the control unit 66 (FIG. 10).

[0041] In such a paper transport device 3, when single-sided (front surface) printing is performed on a paper sheet, the paper sheet is transported face-up (front surface facing up) from the discharge transport path 24 of the image forming device 2 to the main transport path 31 under the operational control of the control unit 66, and each branch claw 51 to 56 is switched appropriately so that the paper sheet is transported to the sub-transport path 41 via several transport paths, and the paper sheet is transported face-down (front surface facing down) from the sub-transport path 41 through the main transport path 31 to the discharge device 4.

[0042] In addition, when double-sided printing is performed on a sheet of paper, under the operational control of the control unit 66, the sheet of paper that has been printed on one side (front side) is transported face-up (front side facing up) from the discharge transport path 24 of the image forming unit 2 to the main transport path 31, and each branch claw 51 to 56 is switched appropriately so that the sheet of paper is transported via several transport paths to the relay transport path 40, and the sheet of paper is transported face-up from the relay transport path 40 to the reverse transport path 27 of the image forming device 2.

[0043] In the image forming device 2, under the operational control of the control unit 66, the paper is transported through the inversion transport path 27, the front and back of the paper are inverted, and the paper is transported face-down (front surface facing downwards) to the image forming unit 25, where an image is also formed on the back side of the paper, and the paper that has been printed on both sides is transported face-down (front surface facing downwards) from the discharge transport path 24 of the image forming device 2 to the main transport path 31 of the paper transport device 3.

[0044] In the paper transport device 3, when a sheet of paper that has been printed on both sides is transported face down (surface downward) from the discharge transport path 24 of the image forming unit 2 to the main transport path 31, the sheet is transported face down (surface downward) from the main transport path 31 to the discharge device 4.

[0045] 3A and 3B show the order of the transport paths through which a normal-sized sheet of paper that has been printed on one side is transported. In Fig. 3A, when face-up paper is transported from the discharge transport path 24 of the image forming device 2 to the main transport path 31, the paper is transported in the order of the main transport path 31 → branch claw 51 → branch transport path 32 → second connecting transport path 33 → branch claw 52 → first connecting transport path 35 → first drum-shaped transport path 36, where it is temporarily stopped, and the rear end of the paper passes through the branch claw 53. Next, the conveying roller 42 of the first drum-shaped conveying path 36 is rotated in the reverse direction, and the paper is conveyed in the opposite direction (called switchback conveying), and the paper is conveyed in the following order: first drum-shaped conveying path 36 → branch claw 53 → first switchback conveying path 37 → branch claw 55 → auxiliary conveying path 41, the paper is turned over, and the paper is conveyed face-down (front side facing downward) from the auxiliary conveying path 41 through the main conveying path 31 to the discharge device 4.

[0046] 3(B), when a face-up sheet of paper is conveyed from discharge conveyance path 24 of image forming device 2 to main conveyance path 31, the sheet is conveyed in the order of main conveyance path 31 → branch claw 51 → branch conveyance path 32 → second connecting conveyance path 33 → branch claw 52 → second drum-shaped conveyance path 34, and is then temporarily stopped, and the rear end of the sheet passes branch claw 54. Subsequently, conveyance roller 42 of second drum-shaped conveyance path 34 is reversed, and the sheet is conveyed in a switchback manner, and the sheet is conveyed in the order of second drum-shaped conveyance path 34 → branch claw 54 → second switchback conveyance path 38 → branch claw 55 → auxiliary conveyance path 41, whereupon the sheet is turned over, and the sheet is conveyed face-down from auxiliary conveyance path 41 through main conveyance path 31 to discharge device 4.

[0047] 4 shows the order of the transport paths through which a medium-sized sheet (longer than a regular size) that has been printed on one side is transported. In FIG. 4, when a face-up sheet of paper is transported from the discharge transport path 24 of the image forming device 2 to the main transport path 31, the sheet is transported in the order of the main transport path 31 → branch claw 51 → branch transport path 32 → second connecting transport path 33 → branch claw 52 → second drum-shaped transport path 34, where it is temporarily stopped, and the rear end of the sheet is stopped at the second connecting transport path 33. Subsequently, the conveying rollers 42 of the second drum-shaped conveying path 34 and the conveying rollers 42 of the second connecting conveying path 33 are rotated in the reverse direction, causing the paper to be conveyed in a switchback manner, and the paper is conveyed in the following order: second connecting conveying path 33 → branch claw 56 → third connecting conveying path 39 → second switchback conveying path 38 → branch claw 55 → auxiliary conveying path 41, the front and back of the paper is turned over, and the paper is conveyed face-down (front surface facing downward) from the auxiliary conveying path 41 through the main conveying path 31 to the discharge device 4.

[0048] 5 shows the order of the transport paths through which long-size paper (longer than medium-size paper) that has been printed on one side is transported. In Fig. 5, when face-up paper is transported from discharge transport path 24 of image forming device 2 to main transport path 31, the paper is transported in the order of main transport path 31 → branch claw 51 → branch transport path 32 → second connecting transport path 33 → branch claw 52 → first connecting transport path 35 → first drum-shaped transport path 36, and is then temporarily stopped, and the rear end of the paper is stopped at second connecting transport path 33. Next, the conveying rollers 42 of the first drum-shaped conveying path 36, the conveying rollers 42 of the first connecting conveying path 35, and the conveying rollers 42 of the second connecting conveying path 33 are rotated in reverse, and the paper is conveyed in a switchback manner, and the paper is conveyed in the following order: second connecting conveying path 33 → branch claw 56 → third connecting conveying path 39 → second switchback conveying path 38 → branch claw 55 → auxiliary conveying path 41, the front and back of the paper is turned over, and the paper is conveyed face-down (front surface facing downward) from the auxiliary conveying path 41 through the main conveying path 31 to the discharge device 4.

[0049] 6(A) and (B) show the order of transport paths through which normal-sized paper that has been printed on only the front side and is then returned from the paper transport device 3 to the image forming device 2 for printing on the back side is transported. In Fig. 6(A), when face-up paper is transported from the discharge transport path 24 of the image forming device 2 to the main transport path 31, the paper is transported in the order of main transport path 31 → branch claw 51 → branch transport path 32 → second connecting transport path 33 → branch claw 52 → first connecting transport path 35 → first drum-shaped transport path 36, where it is temporarily stopped, and the rear end of the paper passes through branch claw 53. Subsequently, the conveying roller 42 of the first drum-shaped conveying path 36 is rotated in the reverse direction, causing the paper to be conveyed in a switchback manner, and the paper is conveyed in the following order: first drum-shaped conveying path 36 → branch claw 53 → first switchback conveying path 37 → branch claw 55 → relay conveying path 40, and the paper is returned from relay conveying path 40 to the reverse conveying path 27 of the image forming device 2 with the paper still face up.

[0050] 6(B), when a face-up sheet of paper is conveyed from the discharge conveyance path 24 of the image forming device 2 to the main conveyance path 31, the sheet is conveyed in the order of the main conveyance path 31 → branch claw 51 → branch conveyance path 32 → second connecting conveyance path 33 → branch claw 52 → second drum-shaped conveyance path 34, and is then temporarily stopped, and the rear end of the sheet passes through the branch claw 54. Subsequently, the conveyance roller 42 of the second drum-shaped conveyance path 34 is rotated in the reverse direction, and the sheet is conveyed in the order of the second drum-shaped conveyance path 34 → branch claw 54 → second switchback conveyance path 38 → branch claw 55 → relay conveyance path 40, and the sheet is returned from the relay conveyance path 40 to the reverse conveyance path 27 of the image forming device 2 while still facing up.

[0051] 7 shows the order of the transport paths along which medium-sized paper that has been printed on only the front side and is then returned from the paper transport device 3 to the image forming device 2 for printing on the back side is transported. In Fig. 7, when face-up paper is transported from the discharge transport path 24 of the image forming device 2 to the main transport path 31, the paper is transported in the order of the main transport path 31 → branch claw 51 → branch transport path 32 → second connecting transport path 33 → branch claw 52 → second drum-shaped transport path 34, where it is temporarily stopped, and the rear end of the paper is stopped at the second connecting transport path 33. Subsequently, the conveying rollers 42 of the second drum-shaped conveying path 34 and the conveying rollers 42 of the second connecting conveying path 33 are rotated in the reverse direction, and the paper is conveyed in a switchback manner in the following order: second connecting conveying path 33 → branch claw 56 → third connecting conveying path 39 → second switchback conveying path 38 → branch claw 55 → relay conveying path 40, and the paper is returned from relay conveying path 40 to the reverse conveying path 27 of the image forming device 2 with the paper still face up.

[0052] 8 shows the order of transport paths along which long-size paper that has been printed on only the front side and is then returned from the paper transport device 3 to the image forming device 2 for printing on the back side is transported. In Fig. 8, when face-up paper is transported from the discharge transport path 24 of the image forming device 2 to the main transport path 31, the paper is transported in the order of the main transport path 31 → branch claw 51 → branch transport path 32 → second connecting transport path 33 → branch claw 52 → first connecting transport path 35 → first drum-shaped transport path 36, and is then temporarily stopped, and the rear end of the paper is stopped at the second connecting transport path 33. Subsequently, the conveying rollers 42 of the first drum-shaped conveying path 36, the conveying rollers 42 of the first connecting conveying path 35, and the conveying rollers 42 of the second connecting conveying path 33 are rotated in the reverse direction, and the paper is conveyed in the following order: second connecting conveying path 33 → branch claw 56 → third connecting conveying path 39 → second switchback conveying path 38 → branch claw 55 → relay conveying path 40, and the paper is returned face-up from relay conveying path 40 to the reverse conveying path 27 of the image forming device 2.

[0053] 9 shows the order of the transport paths through which double-sided printed normal-size, medium-size, and long-size paper is transported. In FIG. 9, when face-down (front side facing down, back side facing up) paper is transported from the discharge transport path 24 of the image forming device 2 to the main transport path 31, the paper is transported face-down from the main transport path 31 to the discharge device 4 via the branch claw 51.

[0054] In the paper transport device 3 configured as described above, for standard-size paper, the first drum-shaped transport path 36 and the second drum-shaped transport path 34 are linked together to transport each paper alternately to the drum-shaped transport paths 36, 34. This increases the job processing volume per unit time and achieves high productivity compared to when only the first drum-shaped transport path 36 is operated. Also, medium-sized and long-sized paper can be received face-up from the image forming device 2, returned face-up to the image forming device 2, and transported face-down to the discharge device 4. Also, because the first drum-shaped transport path 36 and the second drum-shaped transport path 34, through which paper is evacuated, are drum-shaped, the paper transport device 3 can be made smaller than when a direct transport path through which paper is evacuated is provided.

[0055] On the other hand, in the paper transport device 3, as described above, the incoming paper sensor 62 and the outgoing paper sensor 63 are provided in positions outside the infrared radiation area RA of the heat generating unit 61, so that the incoming paper sensor 62 and the outgoing paper sensor 63 are not heated by the infrared rays. Therefore, paper cannot be directly detected between the incoming paper sensor 62 and the outgoing paper sensor 63, and the area between the incoming paper sensor 62 and the outgoing paper sensor 63 is an undetected area for paper. This undetected area for paper is the infrared radiation area RA of the heat generating unit 61, and is part of the main transport path 31.

[0056] In this embodiment, the paper transport device 3 executes a process to detect whether or not paper is jammed in the undetected range, using the detection results from the incoming paper sensor 62 and the outgoing paper sensor 63. When paper is jammed in the undetected range, the user opens the opening / closing door 64 (FIG. 2) provided on the front side of the main transport path 31, removes the paper jammed in the undetected range (part of the main transport path 31), and then closes the opening / closing door 64.

[0057] Fig. 10 is a block diagram showing the configuration of a control system for detecting a paper jam in the infrared irradiation area RA of the paper transport device 3. As shown in Fig. 10, the paper transport device 3 is configured to include a heat generating unit 61, an incoming paper sensor 62, an outgoing paper sensor 63, an opening / closing sensor 65 that detects the opening / closing state of the opening / closing door 64, a control unit 66, a storage unit 67, a non-volatile memory 68, and a display unit 69. These components are capable of transmitting and receiving data or signals to and from each other via a bus.

[0058] The incoming paper sensor 62 and the outgoing paper sensor 63 are equipped with a light-emitting element and a light-receiving element as described above, and the timing at which the light-receiving element starts to receive light is the timing at which the leading edge of the paper is detected, and the timing at which the light-receiving element subsequently stops receiving light is the timing at which the trailing edge of the paper is detected.

[0059] The opening / closing sensor 65 is a limit switch that turns on and off in response to the opening and closing of the opening / closing door 64 as described above.

[0060] The control unit 66 is composed of a processor, RAM (Random Access Memory), ROM (Read Only Memory), etc., and executes a control program stored in the memory unit 67 to control the overall operation of the paper transport device 3 and to perform controls such as detecting paper jammed in the infrared irradiation area RA (part of the main transport path 31) of the paper transport device 3.

[0061] The nonvolatile memory 68 is an EEPROM, etc. The display unit 69 is a liquid crystal display (LCD), an organic light-emitting diode (OLED) display, or the like.

[0062] The control unit 66, the storage unit 67, the nonvolatile memory 68, and the display unit 69 may be provided in the image forming device 2. In this case, the paper conveying device 3 includes the control unit 66, the storage unit 67, the nonvolatile memory 68, and the display unit 69 provided in the image forming device 2 as part of the paper conveying device 3.

[0063] The control unit 66 also drives and controls motors (not shown) that rotate the transport rollers 42 in the paper transport device 3, and actuators (not shown) that reciprocate the branch claws 51 to 57, to transport the paper along the path shown in Figures 3 to 10. The control unit 66 drives the motors to rotate, thereby rotating the transport rollers 42.

[0064] Next, the process of detecting a paper jammed in the infrared irradiation area RA of the paper transporting device 3 will be described with reference to the flowchart shown in FIG.

[0065] When the control unit 66 starts paper transport by the paper transport device 3, it initially sets the number of input sheets J, which indicates the number of sheets transported to the main transport path 31, to "0", and also initially sets the number of output sheets K, which indicates the number of sheets transported out of the infrared irradiation area RA, to "0", and stores the number of input sheets J (= 0) and the number of output sheets K (= 0) in the non-volatile memory 68 (S101).

[0066] The control unit 66 acquires the detection output of the incoming paper sensor 62 and the detection output of the outgoing paper sensor 63 (S102), and when the incoming paper sensor 62 detects the leading edge of the first sheet of paper (S103 "Yes"), it counts up the number of incoming sheets J stored in the non-volatile memory 68 and updates the number of incoming sheets J (=1) (S104). The control unit 66 starts measuring the transport time T1 of the first sheet of paper (S105).

[0067] If the trailing edge of the paper is not detected by the output paper sensor 63 (S106 "No"), the control unit 66 determines whether the number of sheets (K+m) is less than the number of input sheets J when the transport time T1 for the first sheet has passed a specified time t (for example, 3 seconds) (S108). "m" will be described later.

[0068] At this time, if the control unit 66 determines that the transport time T1 of the first sheet has not elapsed the specified time t (S108 "No"), it repeats the process from S103.

[0069] On the other hand, when the control unit 66 repeats the process from S103 and the trailing end of the first sheet of paper is detected by the output sheet sensor 63 (S106 "Yes"), it counts up the number of sheets K output stored in the non-volatile memory 68, updates the number of sheets K output (=1) (S107), and determines whether the number of sheets (K+m) is less than the number of sheets J input when the transport time T1 of the first sheet of paper has elapsed the specified time t (S108).

[0070] Here, if the time interval from when the leading edge of the paper is detected by the incoming paper sensor 62 to when the trailing edge of the paper is detected by the outgoing paper sensor 63 while the paper is being transported normally along the main transport path 31 is defined as standard transport time T0, then the specified time t is set to be longer than the standard transport time T0 by a fixed percentage or a small amount of time. The standard transport time T0 is calculated by dividing the sum of the distance from the detection position of the incoming paper sensor 62 to the detection position of the outgoing paper sensor 63 and the length of the paper by the transport speed of the paper along the main transport path 31. Therefore, the longer the paper length, the longer the standard transport time T0 is set, and the specified time t is set to be a time obtained by extending this standard transport time T0 by a fixed percentage or a small amount of time.

[0071] The control unit 66 is notified of the paper size from the control system (not shown) of the image forming device 2 (for example, the paper size is set by the user and stored in the memory unit of the control system), and calculates the standard transport time T0 for the paper using the paper length in the transport direction according to the paper size as described above, and calculates and sets a specified time t that is longer than the standard transport time T0 by a certain percentage.

[0072] Furthermore, the number of sheets of paper that approach the undetected area between the incoming paper sensor 62 and the outgoing paper sensor 63 varies depending on the size of the sheets. Let the number of approaching sheets be m. In the paper transport device 3, the spacing between multiple sheets of paper is narrowed and multiple sheets are transported continuously. For this reason, multiple sheets of paper may approach the undetected area. For this reason, the concept of the number of approaching sheets m is used. For example, if the number of approaching sheets m is "2" when the trailing edge of the first sheet of paper is detected by the outgoing paper sensor 63 (when the trailing edge of the first sheet of paper leaves the undetected area), the leading edges of two more sheets of paper have passed the position where the incoming paper sensor 62 is located. Therefore, when the trailing edge of the first sheet of paper is detected by the outgoing paper sensor 63, the number of sheets whose leading edges have been detected by the incoming paper sensor 62 will be "3."

[0073] For example, for normal-size paper (e.g., standard A4 size), the number of sheets m is set to two. In this case, the leading edges of the second and third sheets are detected by the incoming paper sensor 62 in succession (S103 "Yes"), and the number of incoming sheets J in the nonvolatile memory 68 is counted up to "3" (S104), after which the trailing edge of the first sheet is detected by the outgoing paper sensor 63 (S106 "Yes"). At this time, the control unit 66 counts up the number of outgoing sheets K in the nonvolatile memory 68 to "1" (S107), and when the transport time T1 for the first sheet has elapsed the specified time t, i.e., after the trailing edge of the first sheet has been detected, it determines that the number of sheets (K + m) = 3 is not less than the number of incoming sheets J = 3 (S108 "No"), and repeats the process from S103.

[0074] For the fourth sheet of paper, the leading edge of the fourth sheet of paper is detected by the incoming sheet sensor 62 (S103 "Yes"), and the number of incoming sheets J in nonvolatile memory 68 is counted up and updated to "4" (S104), after which the trailing edge of the second sheet of paper is detected by the outgoing sheet sensor 63 (S106 "Yes"), and the number of outgoing sheets K in nonvolatile memory 68 is counted up and updated to "2" (S107), and when the transport time T2 for the second sheet of paper has elapsed the specified time t, it is determined that the number of sheets (K+m) = 4 is not less than the number of incoming sheets J = 4 (S108 "No"). The process from S103 is similarly repeated for the fifth and subsequent sheets of paper.

[0075] For example, for medium-sized paper whose length in the transport direction is longer than the standard A4 size, the number of sheets m is set to 1. In this case, the leading edge of the second sheet is detected by the incoming paper sensor 62 (S103 "Yes"), and the number of incoming sheets J in the nonvolatile memory 68 is counted up to "2" (S104), after which the trailing edge of the first sheet is detected by the outgoing paper sensor 63 (S106 "Yes"). At this time, the control unit 66 counts up the number of outgoing sheets K in the nonvolatile memory 68 to "1" (S107), and when the transport time T1 of the first sheet has elapsed the specified time t, and therefore after the trailing edge of the first sheet has been detected, determines that the number of sheets (K + m) = 2 is not less than the number of incoming sheets J = 2 (S108 "No"), and repeats the process from S103.

[0076] For the third sheet of paper, the leading edge of the third sheet of paper is detected by the incoming sheet sensor 62 (S103 "Yes"), and the number of incoming sheets J in nonvolatile memory 68 is counted up and updated to "3" (S104), after which the trailing edge of the second sheet of paper is detected by the outgoing sheet sensor 63 (S106 "Yes"), and the number of outgoing sheets K in nonvolatile memory 68 is counted up and updated to "2" (S107), and when the transport time T2 for the second sheet of paper has elapsed the specified time t, it is determined that the number of sheets (K+m) = 3 is not less than the number of incoming sheets J = 3 (S108 "No"). The process from S103 is similarly repeated for the fourth and subsequent sheets of paper.

[0077] Also, for example, for long-size paper, which is longer in the conveying direction than medium-size paper, the number of unconveyed sheets m is set to 0. In this case, the leading edge of the first sheet is detected by the incoming paper sensor 62 (S103 "Yes"), the number of incoming sheets J in the nonvolatile memory 68 is counted up and updated to "1" (S104), and then the trailing edge of the first sheet is detected by the outgoing paper sensor 63 (S106 "Yes"). At this time, the control unit 66 counts up the number of outgoing sheets K in the nonvolatile memory 68 and updates it to "1" (S107), and when the conveying time T1 of the first sheet has elapsed the specified time t, i.e., after the trailing edge of the first sheet has been detected, it determines that the number of sheets (K + m) = 1 is not less than the number of incoming sheets J = 1 (S108 "No") and repeats the process from S103.

[0078] For the second sheet of paper, the leading edge of the second sheet of paper is detected by the incoming sheet sensor 62 (S103 "Yes"), the number of incoming sheets J in the nonvolatile memory 68 is counted up and updated to "2" (S104), the trailing edge of the second sheet of paper is then detected by the outgoing sheet sensor 63 (S106 "Yes"), the number of outgoing sheets K in the nonvolatile memory 68 is counted up and updated to "2" (S107), and when the transport time T2 for the second sheet of paper has elapsed the specified time t, it is determined that the number of sheets (K+m) = 2 is not less than the number of incoming sheets J = 2 (S108 "No"). For the third and subsequent sheets of paper, the process from S103 onwards is repeated in the same manner.

[0079] On the other hand, when the control unit 66 determines that the number of sheets (K+m) is less than the number of sheets J fed in when the transport time Tn of the nth sheet has elapsed the specified time t (S108 "Yes"), the control unit 66 determines that a paper jam has occurred because the paper has become stuck in the undetected range and the rear end of the paper has not been detected (S109). If the sum (K+m) of the number of sheets K fed out and the number m is less than the number of sheets J fed in, the paper has become stuck in the undetected range and a jam has occurred.

[0080] The control unit 66 notifies the control system of the image forming device 2 to temporarily suspend image formation and paper transport, causes the control unit of the image forming device 2 to stop paper transport from the image forming device 2, and further switches the branch claw 57 as shown in Figure 12, so that for paper that can be transported, the paper is transported from the undetected range of the main transport path 31 to the exit transport path 45 and exits (S110). At this time, when the trailing end of the paper is detected by the exit paper sensor 63, the control unit 66 counts up the number of sheets transported K in the non-volatile memory 68 and updates the number of sheets transported J (S111).

[0081] The control unit 66 temporarily stops the heat generation of the heat generating unit 61 (S112), calculates the number of remaining sheets of paper (JK) that are jammed in the undetected range (S113), and displays a message E indicating the occurrence of a jam and the number of remaining sheets of paper (JK) on the display unit 69 as shown in Figure 13 (S114).

[0082] Here, the number of sheets brought in J is the number of sheets of paper brought into the undetected area, and the number of sheets taken out K is the number of sheets of paper taken out from the undetected area, so the difference (JK) obtained by subtracting the number of sheets taken out K from the number of sheets brought in J indicates the number of remaining sheets of paper left jammed in the undetected area.

[0083] The user sees the message E displayed on the display unit 69, opens the opening / closing door 64 located on the front side of the main conveying path 31, removes the remaining number of sheets (JK) of paper in the undetected area, and closes the opening / closing door 64.

[0084] When the control unit 66 determines whether the opening / closing door 64 is open or closed based on the detection output of the opening / closing sensor 65 (S115 "Yes"), it causes the paper transport device 3 to resume transport of paper while the image forming device 2 is stopped and no paper is being transported from the image forming device 2 to the paper transport device 3 (S116). That is, after determining that a paper jam has occurred in the undetected range, the control unit 66 drives the transport rollers to eject the paper in the undetected range before paper transport in the main transport path 31 is resumed. The control unit 66 starts measuring the elapsed time from the time when paper transport was resumed (S117), and determines whether the leading or trailing edge of the paper is detected by the discharged paper sensor 63 before the elapsed time reaches a predetermined time (S118).

[0085] For example, if the control unit 66 determines that the leading edge or trailing edge of the paper has been detected (S118 "Yes"), it stops the paper transport device 3 again and displays an error message on the display unit 69 indicating that the paper jam has not been cleared (S119). After this, the process returns to S115. If the leading edge or trailing edge of the paper is detected by the discharged paper sensor 63 in this way, it means that the user has not removed the paper from the undetected position, and that the paper has been detected. This is because the paper is jammed and there is a risk of some kind of error occurring during transport.

[0086] The user sees the message displayed on the display unit 69, reopens the door 64, redoes the work to clear the jam, and then closes the door 64.

[0087] The control unit 66 determines whether the opening and closing door 64 is open or closed based on the detection output of the opening and closing sensor 65, waits for the opening and closing of the opening and closing door 64 to be completed (S115 "No"), and when the opening and closing of the opening and closing door 64 is completed (S115 "Yes"), repeats S116 to S118.

[0088] Furthermore, if the control unit 66 determines that the leading edge or trailing edge of the paper has not been detected by the paper output sensor 63 as described above ("No" in S118), it causes the paper transport device 3 to resume transport of the paper and the heating unit 61 to resume heat generation. After this, the process returns to S101. The control unit 66 initializes the number of input sheets J and the number of output sheets K stored in the non-volatile memory 68 to "0" and repeats the process from S102. At the same time, the control unit 66 instructs the control system of the image forming device 2 to resume operation. If the leading edge or trailing edge of the paper has not been detected by the paper output sensor 63 as described above, this is because the user has successfully removed the paper, no paper is present in the undetected area, and the state is such that paper can be transported normally thereafter.

[0089] Furthermore, if the paper jammed in the undetected area is not removed but the paper transport device 3 resumes transporting the paper and the leading or trailing edge of the paper is not detected by the paper output sensor 63 until a certain time has elapsed since the paper transport was resumed (S118 "No"), the process returns to S101 and the processing from S102 is repeated, but when the paper transport time Tn has reached the specified time t, it is determined that the number of sheets (K+m) is less than the number of sheets input J (S108 "Yes"), and a jam is detected again (S109).

[0090] In this manner, in this embodiment, when a paper jam occurs in the undetected range between the incoming paper sensor 62 and the outgoing paper sensor 63, the outputs from the incoming paper sensor 62 and the outgoing paper sensor 63 are used to determine that paper has jammed in the undetected range, the number of jammed sheets is calculated, and a notification is sent to the user that a jam has occurred and the number of jammed sheets. This allows the user to quickly remove the paper from the undetected range after determining the number of jammed sheets in the undetected range.

[0091] Furthermore, since the number of sheets carried in J and the number of sheets carried out K are stored in non-volatile memory 68, even if the user turns off the power to paper transport device 3 when a jam occurs, when the power to paper transport device 3 is turned back on, the number of sheets carried in J and the number of sheets carried out K can be read from non-volatile memory 68 and displayed on display unit 69 for confirmation.

[0092] Furthermore, if the number of consecutively printed sheets is large and the number of input sheets J and the number of output sheets K cannot all be stored in the nonvolatile memory 68, the number of input sheets J and the number of output sheets K may be periodically cleared.

[0093] The configurations and processes of the above-described embodiments explained with reference to FIGS. 1 to 13 are merely examples of the present invention, and the present invention is not limited to these configurations and processes. [Explanation of symbols]

[0094] 1. Image forming system 2. Image forming device 3 Paper transport device 4 Discharge device 61 Heat generating part 62 Paper input sensor 63 Paper output sensor 64 Opening and Closing Doors 65 Open / close sensor 66 Control Unit 67 Memory section 68 Non-volatile memory 69 Display section

Claims

1. a paper transport path having a transport roller for receiving and transporting paper transported from an image forming device; a heat generating unit provided along the paper transport path and configured to heat the paper being transported along the paper transport path; a first paper detection unit that detects the paper upstream of a heat generating region of the heat generating unit in a paper transport direction along the paper transport path; a second paper detection unit that detects the paper downstream of a heat generating region of the heat generating unit in a paper transport direction along the paper transport path; A paper transport device comprising: a control unit that counts the number of sheets of paper detected by the first paper detection unit as a first number of sheets, and counts the number of sheets of paper detected by the second paper detection unit as a second number of sheets, and based on the first number of sheets and the second number of sheets, determines whether the paper has jammed in an undetected range of the paper transport path between the detection position by the first paper detection unit and the detection position by the second paper detection unit, and determines the number of remaining sheets of paper in the undetected range.

2. The control unit measures the time it takes for the paper to be transported from the detection position of the leading edge of the paper by the first paper detection unit to the detection position of the trailing edge of the paper by the second paper detection unit, and determines that a paper jam has occurred in the undetected range if the first number of sheets is greater than the second number of sheets at the point when the transport time has elapsed a specified time calculated based on the distance between the detection positions, the length of the paper, and the transport speed of the paper.

3. The paper transport device of claim 1, wherein the control unit, after determining that the paper is jammed in the undetected range, drives the transport roller to eject the paper in the undetected range before paper transport is resumed in the paper transport path.

4. A display unit is provided, The paper transport device according to claim 3 , wherein the control unit determines the number of remaining sheets of paper in the undetected range based on the first number and the second number of sheets, and causes the display unit to display the number of remaining sheets of paper.

5. It has non-volatile memory, The paper transport device according to claim 1, wherein the control unit stores the first number of sheets in the non-volatile memory each time the first number of sheets is counted, and stores the second number of sheets in the non-volatile memory each time the control unit counts the second number of sheets.

6. an opening / closing section that opens and closes to expose the undetected area in the paper transport path; an opening / closing detection unit that detects the opening / closing of the opening / closing unit, The control unit, when determining that the paper is jammed in the undetected range, stops the transport of the paper along the paper transport path by the transport roller, and when the open / close detection unit detects the opening and closing of the open / close unit, resumes the transport of the paper along the paper transport path by the transport roller, and if no paper is detected by the second paper detection unit after a certain time has elapsed since the paper transport was resumed, resumes the transport of the paper along the paper transport path.

7. It has non-volatile memory, The paper transport device described in claim 6, wherein the control unit stores the first number in the non-volatile memory each time it counts the first number, stores the second number in the non-volatile memory each time it counts the second number, and initializes the first number and the second number stored in the non-volatile memory when it determines that the paper has been removed.

8. the image forming apparatus forms an image on paper by an inkjet method; The paper transport device according to claim 1 , wherein the heat generating section heats an image forming surface of the paper being transported along the paper transport path.

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