Image forming device

Abstract

To provide an image forming device capable of suppressing the occurrence of waste sheets at the time of double feeding of sheets.SOLUTION: An image forming device comprises sheet sensors 28A and 28B and a controller 11 which are disposed on the upstream side of a registration roller 31 in the sheet conveyance direction of a normal route RC. The controller 11 has: a measurement part for measuring an actual elapsed time from the start of the sheet feeding of a sheet P to the detection of the sheet P by the sheet sensors 28A and 28B in the sheet feed operation from a sheet feeding part 2 to the normal route RC; a counting part for counting the number of occurrences of the sheet feed operation in which the actual elapsed time is shorter by a predetermined time or more than a theoretical required sheet feeding time of the sheet P from the sheet feeding part 2 to the sheet sensors 28A and 28B; and a control part for interrupting the sheet feed operation when the number of occurrences reaches a specified number, and resuming the sheet feed operation after a predetermined sheet-separating operation for the sheet P of the sheet feeding part 2 cuts in.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] A paper feeding device is known that measures the arrival time of paper to a multi-feed detection sensor, and even if a multi-feed of paper is detected, transports paper from a paper feed cassette other than the paper feed cassette where the multi-feed occurred within the time it takes for the multi-fed paper to reach the destination (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5350341 Summary of the Invention [Problem to be solved by the invention]

[0004] The paper feeder of Patent Document 1 can prevent toner used to develop the latent image on the transfer drum from being wasted when multiple sheets of paper are fed, but does not provide a fundamental solution to the problem of multiple sheet feeding.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress the occurrence of paper waste when multiple sheets of paper are fed. [Means for solving the problem]

[0006] In order to achieve the above object, an image forming apparatus according to one aspect of the present invention comprises: a paper sensor disposed upstream of the registration roller in the paper transport direction of the paper transport path; a measuring unit that measures an actual elapsed time from the start of paper feeding to the paper transport path when the paper sensor detects the paper; a counting unit that counts the number of occurrences of the paper feeding operation in which the actual elapsed time is shorter than a theoretical paper feeding time required for the paper from the paper feeding unit to the paper sensor by a predetermined time or more; a control unit that, when the number of occurrences reaches a predetermined number, suspends the paper feeding operation and resumes the paper feeding operation after interrupting the paper feeding unit with a predetermined paper separation operation; Equipped with. [Effects of the Invention]

[0007] According to the present invention, it is possible to prevent the occurrence of an error operation caused by the overlapped paper being transported downstream of the registration rollers, and to prevent the occurrence of wasted paper when the paper is overlapped. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a flowchart showing an example of a procedure for the paper separation operation of the paper feed unit performed by the controller of FIG. [Figure 3] FIG. 3 is a diagram showing an example of the specific contents of the paper separation operation of FIG. [Figure 4] FIG. 4 is a diagram showing an example of the specific contents of the paper separation operation of FIG. [Figure 5] FIG. 5 is a diagram showing an example of the specific contents of the paper separation operation of FIG. [Figure 6] FIG. 6 is a diagram showing an example of the specific contents of the paper separation operation of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or equivalent parts and components are designated by the same or equivalent reference numerals throughout the drawings. However, it should be noted that the drawings are schematic and may differ from the actual product. Furthermore, it goes without saying that the dimensional relationships and ratios may differ between the drawings.

[0010] Furthermore, the embodiments shown below are merely examples of devices that embody the technical concept of the present invention, and the technical concept of the present invention does not limit the arrangement of each component to that shown below. Various modifications can be made to the technical concept of the present invention within the scope of the claims.

[0011] FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to one embodiment of the present invention. In the following description, the top, bottom, left, and right directions on the plane of FIG. 1 are defined as the top, bottom, left, and right directions. The path indicated by the thick line in FIG. 1 is the transport path along which paper P is transported. Of the transport paths, the path indicated by the solid line is the normal path RC, the path indicated by the dashed line is the reversal path RR, the paths indicated by the broken lines are the paper discharge paths RD1 and RD2, and the path indicated by the two-dot chain line is the paper feed path RS. In the following description, upstream and downstream refer to the upstream and downstream directions of the transport path.

[0012] The image forming apparatus 1 of this embodiment includes a paper feed section 2, a printing transport section 3, a printing section 4, a first paper discharge section 5, an upper transport section 6, a second paper discharge section 7, an inversion section 8, a controller 11, and a housing 12 that houses or holds each section.

[0013] When a print job is input, the paper feed unit 2 sequentially picks up unprinted paper P from the external paper feed tray 21 or the internal paper feed tray 23 using external paper feed rollers 22 or internal paper feed rollers 24, and sends it to a paper feed path RS. A paper feed path RS is provided corresponding to each of the external paper feed tray 21 and the internal paper feed tray 23. The paper feed unit 2 detects the paper P sent to each paper feed path RS using paper sensors 28A and 28B along the paper feed path RS. The paper feed unit 2 relays the paper P picked up from the internal paper feed tray 23 to the paper feed path RS using vertical transport rollers 25. The paper feed paths RS converge just before the print transport unit 3. The paper P sent by the paper feed unit 2 passes the junction of the paper feed paths RS, is sent to the normal path RC, and is transported to the registration rollers 31 of the print transport unit 3.

[0014] Normal path RC corresponds to the "paper transport path." The direction of normal path RC from paper feed unit 2 toward print transport unit 3 corresponds to the "paper transport direction of the paper transport path." Paper sensors 28A and 28B correspond to "paper sensors arranged upstream of the registration rollers in the paper transport direction of the paper transport path." Hereinafter, paper sensors 28A and 28B will be referred to as registration sensors 28A and 28B to distinguish them from other paper sensors 28C to 28L, which will be described later.

[0015] The print conveying unit 3 sends out the paper P conveyed from the paper feed unit 2 or the reversing unit 8 (described later) to the normal path RC downstream of the registration rollers 31 in synchronization with the printing operation of the printing unit 4. The print conveying unit 3 conveys the paper P on the normal path RC sent out by the registration rollers 31 using the belt platen unit 33. The print conveying unit 3 detects the paper P conveyed on the normal path RC from the registration rollers 31 to the belt platen unit 33 using the paper sensor 28C, and detects the paper P conveyed on the normal path RC from the belt platen unit 33 to the switching unit 36 ​​(described later) using the paper sensor 28D.

[0016] The printing unit 4 has a plurality of inkjet heads (not shown), and performs printing by ejecting ink from the inkjet heads onto the paper P transported by the belt platen unit 33. The printing unit 4 is disposed above the belt platen unit 33.

[0017] The first paper discharge unit 5 sends out the printed paper P conveyed from the belt platen unit 33 to be discharged to a post-processing device (not shown) connected to the image forming apparatus 1, to a paper discharge path RD1 branched from the normal path RC by switching the switching unit 36. The first paper discharge unit 5 detects the paper P sent to the paper discharge path RD1 by the paper sensor 28E midway along the paper discharge path RD1.

[0018] Of the printed sheets P transported from the belt platen unit 33, the upper surface transport unit 6 further transports the sheets P to be discharged or returned to the printing unit 4 to be printed on the back side to the second discharge unit 7 or the inversion unit 8 by the rising and horizontal transport rollers 41, 43 of the normal path RC. The upper surface transport unit 6 detects the sheets P to be transported to the second discharge unit 7 or the inversion unit 8 by the sheet sensors 28F to 28I at various points along the normal path RC of the upper surface transport unit 6.

[0019] The second paper discharge unit 7 sends out the paper P to be discharged in the image forming apparatus 1, among the printed paper sheets P transported by the upper transport unit 6, to a paper discharge route RD2 connected to the normal route RC by switching of the switching unit 51. The second paper discharge unit 7 transports the paper P sent out to the paper discharge route RD2 to a paper discharge tray 54 arranged at the downstream end of the paper discharge route RD2 by a paper discharge roller 52. The second paper discharge unit 7 detects the paper P to be transported to the paper discharge tray 54 midway along the paper discharge route RD2 with a paper sensor 28K.

[0020] The reversing unit 8 sends out, by switching unit 51, the upstream side of the reversing path RR, which is connected to the normal path RC, one of the printed sheets P conveyed by the upper conveying unit 6 and to be returned to the printing unit 4 to be printed on the back side. The reversing path RR is connected to the normal path RC in parallel with the paper discharge path RD2. The reversing unit 8 conveys the sheet P sent out to the upstream side of the reversing path RR to the terminal end of the switchback portion of the reversing path RR by the horizontal conveying roller 43 and the reversing roller 61 of the reversing path RR. The reversing unit 8 detects the sheet P being conveyed to the terminal end of the switchback portion by the paper sensor 28J midway along the reversing path RR.

[0021] The reversing unit 8 reverses the paper P conveyed to the end of the switchback unit by the reversely rotating reversing rollers 61. The reversing unit 8 sends the paper P conveyed in the reverse direction from the switchback unit to the downstream side of the reversing path RR, which is connected to the upstream side of the reversing path RR by switching the switching unit 65 just before the paper sensor 28J of the reversing path RR. The reversing unit 8 detects the paper P sent to the downstream side of the reversing path RR by the paper sensor 28L midway along the downstream side of the reversing path RR. The reversing unit 8 conveys the paper P that has passed the paper sensor 28L downstream of the reversing path RR in an inverted state to the registration rollers 31 of the print conveying unit 3 by the paper refeed rollers 63. The paper P conveyed to the registration rollers 31 in an inverted state is sent to the normal path RC by the registration rollers 31 in synchronization with the printing operation of the printing unit 4.

[0022] The controller 11 controls the above-mentioned operations of the respective units 2 to 8 of the image forming apparatus 1. Furthermore, when the controller 11 suspects that a double feed of the sheets P sent from the external sheet feed tray 21 or the internal sheet feed tray 23 to the sheet feed path RS has occurred, the controller 11 interrupts the sheet feed from both the sheet feed trays 21 and 23 to the sheet feed path RS by the sheet feed unit 2, and causes the sheet feed unit 2 to execute an interrupt operation to separate the sheets P.

[0023] The controller 11 has, for example, a general-purpose microcontroller. The general-purpose microcontroller includes a CPU and a memory. The memory includes a ROM and a RAM. In the control unit 6 of this embodiment, the CPU executes a control program stored in the memory, thereby virtually constructing multiple information processing circuits. The multiple information processing circuits can constitute a measurement unit, a counting unit, and a control unit.

[0024] The measurement unit measures the actual elapsed time from the start of feeding paper P to the registration sensors 28A, 28B during the paper feeding operation from the paper feeding unit 2 to the normal route RC until the paper P is detected by the registration sensors 28A, 28B. The counting unit counts the number of occurrences of paper feeding operations in which the above-mentioned actual elapsed time is shorter than a predetermined time or more compared to the theoretical paper feeding time required for paper P from the paper feeding unit 2 to the registration sensors 28A, 28B. When this number of occurrences reaches a predetermined number, the control unit interrupts the paper feeding operation and resumes the paper feeding operation after interrupting the paper feeding unit 2 with a predetermined paper separation operation for the paper P. The specific content of the paper separation operation will be described later. The measurement unit, counting unit, and control unit may be configured as separate information processing circuits, or may be configured as a single information processing circuit.

[0025] In this embodiment, an example is shown in which multiple information processing circuits built in the controller 11 are realized by software. The information processing circuits may be configured using dedicated hardware. The dedicated hardware performs the information processing of the detection unit and the adjustment unit, which will be described later. Multiple information processing circuits may be configured by one piece of hardware, or one information processing circuit may be configured by one piece of hardware. The dedicated hardware includes devices such as application specific integrated circuits (ASICs) and conventional circuit components arranged to perform the functions of the detection unit and the adjustment unit.

[0026] Multi-feeding of paper P occurs, for example, when paper P from the external paper feed tray 21 or the internal paper feed tray 23 is continuously fed to the paper feed path RS, and the paper P sent later catches up with the paper P sent earlier and sent to the normal path RC by the registration roller 31.

[0027] For example, when the top sheet P on the paper feed tray 21, 23 is fed, if that sheet P drags the second-highest sheet P, the second-highest sheet P will move to a position where it has been partially fed from the paper feed tray 21, 23 by the time the feeding of the top sheet P is completed. If the same thing continues to happen after the next paper feed operation, there is a possibility that the amount of paper P next to the fed sheet P fed from the paper feed tray 21, 23 by the time the feeding operation is completed may increase suddenly or cumulatively. If the amount of paper P fed out of the top sheet P on the paper feed tray 21, 23 before the start of the paper feed operation increases, the transport distance of the paper P until it reaches the registration rollers 31 decreases. If the transport distance of the paper P until it reaches the registration rollers 31 decreases, the paper P fed from the paper feed tray 21, 23 to the print transport unit 3 may catch up with the previously fed paper P just before the registration rollers 31, resulting in double feeding of the paper P. Therefore, when the controller 11 suspects that a double feed of paper P has occurred based on the time it takes for paper P from the paper feed trays 21 and 23 picked up by the paper feed rollers 22 and 24 to be fed to the registration rollers 31, it performs a separation operation of the paper P in the paper feed section 2.

[0028] Next, an example of the procedure for the separation operation of the paper P in the paper feed unit 2 performed by the controller 11 will be described with reference to the flowchart in Fig. 2. The controller 11 checks whether or not there is a subsequent paper (step S1). If there is a print job to print an image on the paper P, the confirmation result indicates that there is a subsequent paper. If there is no subsequent paper (NO in step S1), the process ends, and if there is a subsequent paper (YES in step S1), the controller 11 feeds the topmost paper P in the paper feed unit 2 to the print transport unit 3 and starts measuring the paper feed time (step S3). The topmost paper P is fed by the paper feed rollers 22 and 24 corresponding to the paper feed trays 21 and 23 specified in the print job.

[0029] The controller 11 checks whether the paper P fed to the print transport unit 3 has reached the registration sensors 28A, 28B (step S5). If the paper P has not reached the registration sensors 28A, 28B (NO in step S5), step S5 is repeated. If the paper P has reached the registration sensors 28A, 28B (YES in step S5), the controller 11 counts the actual elapsed time from the start of paper feeding using the measurement unit, and calculates the difference from the theoretical arrival time (step S7). The theoretical arrival time is the theoretical paper feeding time it takes for the paper P to reach the registration sensors 28A, 28B from the start of paper feeding. The theoretical arrival time may be determined individually for each paper feed tray 21, 23 depending on the distance from the paper feed tray 21, 23 to the corresponding registration sensor 28A, 28B.

[0030] Based on the calculated difference, the controller 11 checks whether the actual elapsed time is shorter than the theoretical arrival time by a predetermined time or more (step S9). If the actual elapsed time is longer than the predetermined time shorter than the theoretical arrival time (NO in step S9), the process returns to step S1. If the actual elapsed time is shorter than the theoretical arrival time by a predetermined time or more (YES in step S9), the controller 11 increments the count value of the paper P whose actual elapsed time is shorter than the theoretical arrival time by a predetermined time or more (step S11). This count corresponds to the number of occurrences of paper feeding operations whose actual elapsed time is shorter than the theoretical arrival time by a predetermined time or more, and this counting can be performed by a counting unit.

[0031] The controller 11 checks whether the count of paper sheets P whose actual elapsed time is shorter than the theoretical arrival time by a predetermined time or more has reached a predetermined number or more (step S13). If the count is less than the predetermined number (NO in step S13), the controller 11 returns to step S1, and if the count is equal to or greater than the predetermined number (YES in step S13), the controller 11 interrupts the paper feed operation and executes a paper separation operation (step S15). The paper separation operation can be executed by the control unit. The specific content of the paper separation operation will be described later. After executing the paper separation operation, the controller 11 clears the count of paper sheets P whose actual elapsed time is shorter than the theoretical arrival time by a predetermined time or more, which is counted by the counting unit, to 0 (step S17), and returns to step S1.

[0032] Next, an example of the specific contents of the paper separation operation will be described with reference to Figures 3 to 6. Figures 3 to 6 illustrate an example of the paper separation operation for paper P fed from the external paper feed tray 21 to the print transport unit 3. First, Figure 3 shows a state in which the topmost paper P on the external paper feed tray 21 is dragged by a paper sheet (not shown) that was fed previously, and is partially sent out from the external paper feed tray 21 before the feeding of the previous paper sheet is completed. If paper P is fed from this position to the print transport unit 3, the actual elapsed time from the start of paper feeding until paper P reaches registration sensor 28A will be shorter than the theoretical arrival time of paper P fed from the external paper feed tray 21 to the print transport unit 3.

[0033] When the actual elapsed time of the paper P fed to the print transport unit 3 is shorter than the theoretical arrival time by a predetermined time or more, the paper feeding operation is interrupted and the paper separation operation is executed as an interrupt. This specified number can be determined by experimentally determining, for example, how many times the phenomenon of the next paper P being dragged when feeding a paper P occurs until the paper P before being fed is sent out from the external paper feed tray 21 to the amount that is the guideline for causing double feeding.

[0034] 4, in the paper separation operation of the external paper feed tray 21, first, the external paper feed tray 21 is lowered to separate the stack of papers P on the external paper feed tray 21 from the external paper feed roller 22. The leading edge of the topmost paper P partially fed from the external paper feed tray 21 rides up and is guided by a paper guide (not shown) on the paper feed path RS, and is held in pressure contact with the external paper feed roller 22. Next, the external paper feed roller 22 is rotated in the opposite direction to that during paper feeding.

[0035] 5, the reverse rotation of the external paper feed roller 22 moves the topmost sheet P that has been partially fed out from the external paper feed tray 21 toward the external paper feed tray 21, and returns the topmost sheet P to its original position before being fed out from the external paper feed tray 21. The other sheets P on the external paper feed tray 21 are separated from the external paper feed roller 22 and are therefore not moved by the reverse rotation of the external paper feed roller 22.

[0036] After the top sheet P on the external paper feed tray 21 is returned to its original position, the reverse rotation of the external paper feed roller 22 is stopped. As shown in FIG. 6, after the external paper feed roller 22 has stopped, the external paper feed tray 21 is raised and the top sheet P is pressed against the external paper feed roller 22. The paper separation operation according to the example of this embodiment is as described above. After the paper separation operation is completed, the controller 11 can cause the paper feed unit 2 to resume feeding the paper P.

[0037] In the case of the internal paper feed tray 23, for example, the internal paper feed roller 24, which is relatively separated from the internal paper feed tray 23, may be rotated in reverse and then brought relatively closer to the internal paper feed tray 23, thereby performing a paper separation operation in the same manner as the external paper feed tray 21.

[0038] In the image forming apparatus 1 of this embodiment, when it is suspected that a double feed of paper P has occurred, the paper feed is stopped and the paper separation operation of the paper feed unit 2 is executed as an interrupt, thereby preventing the double-fed paper P from being transported downstream of the registration rollers 31 and causing an error. In addition, since an error operation due to a double feed of paper P is prevented, it is also possible to prevent the occurrence of wasted paper due to a paper P jamming due to a double feed of paper P.

[0039] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied in practice without departing from the spirit of the invention. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all the components shown in the embodiments.

[0040] For example, during the paper separation operation, in addition to stopping the paper feeding operation, a paper feeding operation may be performed on a paper feeding tray 23, 21 other than the paper feeding tray 21, 23 on which the paper feeding operation has been stopped, which tray has paper P of the same size and type stacked thereon. In this case, during the paper separation operation, the paper feeding operation of the other paper feeding tray 23, 21 continues to feed paper P to the print transport unit 3, allowing the printing operation to continue.

[0041] Furthermore, if the actual elapsed time from the start of feeding of the sheet P in the sheet feed unit 2 to the detection of the sheet P by the registration sensors 28A and 28B is longer than a predetermined time from the theoretical required sheet feeding time, the controller 11 may detect that a jam error for the sheet P has occurred in the sheet feed path RS. In this case, the controller 11 suspends detection of a jam error for the sheet P in the sheet feed path RS during the sheet separation operation, similar to the sheet feeding operation. If the controller 11 resumes detection of a jam error for the sheet P in the sheet feed path RS after the sheet separation operation, similar to the sheet feeding operation, the controller 11 may extend the predetermined time for the sheet feeding operation immediately after the resumption. For example, if an extra sheet P is returned from the topmost sheet of paper P on the sheet feed trays 21 and 23 during the sheet separation operation, causing the position of the topmost sheet P to shift upstream from the position of the second-highest sheet P, the controller 11 can avoid falsely detecting a jam error for the sheet feed path RS.

[0042] [Note] The above-described embodiments disclose the invention in the following aspects.

[0043] That is, as one aspect of the invention, a paper sensor disposed upstream of the registration roller in the paper transport direction of the paper transport path; a measuring unit that measures an actual elapsed time from the start of paper feeding to the paper transport path when the paper sensor detects the paper; a counting unit that counts the number of occurrences of the paper feeding operation in which the actual elapsed time is shorter than a theoretical paper feeding time required for the paper from the paper feeding unit to the paper sensor by a predetermined time or more; a control unit that, when the number of occurrences reaches a predetermined number, suspends the paper feeding operation and resumes the paper feeding operation after interrupting the paper feeding unit with a predetermined paper separation operation; An image forming apparatus comprising:

[0044] According to the above aspect of the invention, when a double feed of paper is suspected, the paper feed is stopped and the paper separation operation of the paper feed unit is interrupted, thereby preventing the double-fed paper from being transported downstream of the registration rollers and causing an error. Also, the occurrence of paper waste during a double feed of paper can be prevented. [Explanation of symbols]

[0045] 1. Image forming device 2 Paper feed section 11 Controller (measurement unit, counting unit, control unit) 28A, 28B Paper sensor (resist sensor) 31 Registration roller P paper RC Normal path (paper transport path)

Claims

[Claim 1] a paper sensor disposed upstream of the registration roller in the paper transport direction of the paper transport path; a measuring unit that measures an actual elapsed time from the start of paper feeding to the paper transport path when the paper sensor detects the paper; a counting unit that counts the number of occurrences of the paper feeding operation in which the actual elapsed time is shorter than a theoretical paper feeding time required for the paper from the paper feeding unit to the paper sensor by a predetermined time or more; a control unit that, when the number of occurrences reaches a predetermined number, suspends the paper feeding operation and resumes the paper feeding operation after interrupting the paper feeding unit with a predetermined paper separation operation; An image forming apparatus comprising:

Images