Sheet conveying device, image forming device and determining method

Abstract

To provide a sheet conveying device, an image forming device and a determining method which can determine whether a sheet has an abnormal shape or not, by a simple process.SOLUTION: An image forming device is provided with: a sheet conveying part that conveys a sheet; an imaging part 5 that includes a plurality of imaging elements arranged side by side in a width direction of the sheet at a passing position on which the sheet conveyed by the sheet conveying part passes and outputs imaging data showing imaged results by the plurality of imaging elements in a predetermined imaging period; a count processing part 63 that counts the number of pixel of the sheet included in the imaging data, every time when the imaging part 5 outputs the imaging data; and a determination processing part 64 that determines whether the sheet has an abnormal shape or not, on the basis of transition of the counted values by the count processing part 63.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a sheet conveying device, an image forming apparatus, and a determination method.

Background Art

[0002] An image forming apparatus such as a printer includes a sheet conveying unit that conveys a sheet on which an image is formed. Further, an imaging unit that images the sheet conveyed by the sheet conveying unit is provided, and an image reading device that determines whether or not the sheet has a missing portion based on imaging data output from the imaging unit is known (see Patent Document 1). In this image reading device, an edge of the sheet included in the imaging data is detected, and it is determined whether or not the sheet has a missing portion based on the detected edge of the sheet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a configuration in which it is determined whether or not the sheet has a missing portion based on the detection result of the edge of the sheet included in the imaging data, the processing for determining whether or not the sheet has an abnormal shape becomes complicated.

[0005] An object of the present invention is to provide a sheet conveying device, an image forming apparatus, and a determination method capable of determining whether or not the sheet has an abnormal shape with simple processing.

Means for Solving the Problems

[0006] A sheet conveyance device according to one aspect of the present invention includes a sheet conveyance unit, an imaging unit, a count processing unit, and a determination processing unit. The sheet conveyance unit conveys a sheet. The imaging unit includes a plurality of imaging elements arranged side by side in a width direction orthogonal to the conveyance direction of the sheet at a passing position through which the sheet conveyed by the sheet conveyance unit passes, and outputs imaging data indicating imaging results by the plurality of imaging elements at a predetermined imaging cycle. The count processing unit counts the number of sheet pixels indicating the sheet included in the imaging data each time the imaging data is output by the imaging unit. The determination processing unit determines whether the sheet has an abnormal shape based on the transition of the count value by the count processing unit.

[0007] An image forming apparatus according to another aspect of the present invention includes the sheet conveyance device and an image forming unit. The image forming unit forms an image on the sheet conveyed by the sheet conveyance unit.

[0008] A determination method according to another aspect of the present invention is executed in a sheet conveyance device including a sheet conveyance unit that conveys a sheet and an imaging unit that includes a plurality of imaging elements arranged side by side in a width direction orthogonal to the conveyance direction of the sheet at a passing position through which the sheet conveyed by the sheet conveyance unit passes, and outputs imaging data indicating imaging results by the plurality of imaging elements at a predetermined imaging cycle, and includes a count step and a determination step. In the count step, the number of sheet pixels indicating the sheet included in the imaging data is counted each time the imaging data is output by the imaging unit. In the determination step, it is determined whether the sheet has an abnormal shape based on the transition of the count value in the count step.

Advantages of the Invention

[0009] According to the present invention, it is possible to determine whether the sheet has an abnormal shape with simple processing.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the following embodiments are an example of embodying the present invention and do not limit the technical scope of the present invention.

[0012] [Configuration of Image Forming Apparatus 100] First, with reference to FIGS. 1 to 3, the configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described. In FIG. 1, a sheet conveyance path R11 is shown by a two-dot chain line. Also, in FIG. 3, the flow of imaging data is shown by a solid arrow line. Further, in FIG. 3, the flow of an electrical signal is shown by a broken arrow line.

[0013] The image forming apparatus 100 is a printer capable of forming an image on a sheet SH10 (see FIG. 1) by an inkjet method. Note that the present invention may be applied to a facsimile apparatus, a copying machine, or a multifunction machine capable of forming an image on a sheet SH10 by an inkjet method. Further, the present invention may be applied to an image forming apparatus capable of forming an image on a sheet SH10 by a method different from the inkjet method, such as an electrophotographic method.

[0014] As shown in FIG. 1, the image forming apparatus 100 includes a housing 1, a sheet conveyance unit 2, an image forming unit 3, and a conveyance unit 4. Further, the image forming apparatus 100 includes an imaging unit 5, a shape determination unit 6, a control unit 7, and an operation display unit 8 shown in FIG. 3.

[0015] The housing 1 houses each component of the image forming apparatus 100. A paper feed cassette 11 (see FIG. 1) is detachably provided on the housing 1. The paper feed cassette 11 houses the sheet SH10 on which an image is to be formed. A paper discharge tray 12 (see FIG. 1) is provided on the outer surface of the housing 1. The sheet SH10 on which an image is formed by the image forming unit 3 is discharged onto the paper discharge tray 12. Inside the housing 1, the sheet SH10 housed in the paper feed cassette 11 is conveyed along a sheet conveyance path R11 (see FIG. 1) that leads from the paper feed cassette 11 to the paper discharge tray 12 via the image forming position by the image forming unit 3.

[0016] The sheet conveyance unit 2 conveys the sheet SH10 housed in the paper feed cassette 11 along the sheet conveyance path R11 (see FIG. 1). As shown in FIG. 1, the sheet conveyance unit 2 includes a pickup roller 21 and a plurality of conveyance rollers 22. The pickup roller 21 picks up the uppermost sheet SH10 in the sheet stack housed in the paper feed cassette 11 and sends out the sheet SH10 to the sheet conveyance path R11. The plurality of conveyance rollers 22 are arranged side by side along the sheet conveyance path R11. Each of the conveyance rollers 22 conveys the sheet SH10 along the sheet conveyance path R11. Each of the conveyance rollers 22 conveys the sheet SH10 in the conveyance direction D11 (see FIG. 1) from the paper feed cassette 11 toward the paper discharge tray 12.

[0017] The image forming unit 3 forms an image on the sheet SH10 conveyed by the sheet conveying unit 2. As shown in FIG. 1, the image forming unit 3 includes line heads 31 to 34 and a head frame 35.

[0018] As shown in FIG. 2, each of the line heads 31 to 34 is long in the width direction D12 orthogonal to the conveyance direction D11. Specifically, each of the line heads 31 to 34 has a length corresponding to the width of the largest-sized sheet SH10 among the sheets SH10 that can be accommodated in the paper feed cassette 11 in the width direction D12. The line heads 31 to 34 are arranged at equal intervals along the conveyance direction D11.

[0019] As shown in FIG. 2, each of the line heads 31 to 34 has a plurality of recording heads 30. Each of the recording heads 30 discharges ink toward the sheet SH10 conveyed by the conveyance unit 4. Each of the recording heads 30 provided in the line head 31 discharges black ink. Each of the recording heads 30 provided in the line head 32 discharges cyan ink. Each of the recording heads 30 provided in the line head 33 discharges magenta ink. Each of the recording heads 30 provided in the line head 34 discharges yellow ink.

[0020] Each of the recording heads 30 includes a plurality of nozzles 30A (see FIG. 2) for discharging ink. Each of the nozzles 30A is provided on the opposing surface of the recording head 30 with the sheet SH10 conveyed by the conveyance unit 4.

[0021] Each recording head 30 includes a pressure chamber (not shown) corresponding to each nozzle 30A, a piezoelectric element (not shown), and an individual flow path (not shown). The pressure chamber communicates with the nozzle 30A and stores ink. The piezoelectric element discharges ink from the nozzle 30A in response to the application of a predetermined driving voltage. The individual flow path is an ink flow path provided between the pressure chamber and a common flow path (not shown) common to a plurality of nozzles 30A. A plurality of the individual flow paths corresponding to the plurality of nozzles 30A are connected to the common flow path. The common flow path is connected to an ink supply unit (not shown) that supplies ink to each of the pressure chambers.

[0022] In the present embodiment, in the line head 31, three recording heads 30 are arranged in a staggered manner along the width direction D12. Also, in each of the other line heads 32 to 34, three recording heads 30 are arranged in a staggered manner along the width direction D12, similar to the line head 31.

[0023] The head frame 35 supports the line heads 31 to 34. The head frame 35 is supported by the housing 1. Note that the number of line heads provided in the image forming unit 3 does not have to be four. Also, the number of recording heads 30 provided in each of the line heads 31 to 34 does not have to be three.

[0024] As shown in FIG. 1, the conveyance unit 4 is disposed below the line heads 31 to 34. The conveyance unit 4 conveys the sheet SH10 while facing it to the recording head 30. For example, each time ink is ejected by the recording head 30, the conveyance unit 4 conveys the sheet SH10 by a predetermined conveyance amount. Also, while ink is being ejected by the recording head 30, the conveyance unit 4 stops the conveyance of the sheet SH10. As shown in FIG. 1, the conveyance unit 4 includes a conveyance belt 41 on which the sheet SH10 is placed, a first tension roller 42, a second tension roller 43, and a third tension roller 44 that stretch the conveyance belt 41, and a conveyance frame 45 that supports these. The gap between the conveyance belt 41 and the recording head 30 is adjusted so that the gap between the surface of the sheet SH10 and the recording head 30 during image formation becomes a predetermined distance (for example, 1 mm).

[0025] The first tension roller 42 is rotationally driven by a rotational driving force supplied from a motor (not shown). Thereby, the conveyance belt 41 rotates in a direction in which the sheet SH10 can be conveyed in the conveyance direction D11 (see FIG. 1). The conveyance unit 4 is also provided with a suction unit (not shown) that sucks air from a number of through-holes formed in the conveyance belt 41 in order to adsorb the sheet SH10 to the conveyance belt 41. Also, above the first tension roller 42, a pressure roller 46 is provided for pressing and conveying the sheet SH10 against the conveyance belt 41.

[0026] The imaging unit 5 images the sheet SH10 conveyed by the sheet conveyance unit 2 at the imaging position P11 (see FIG. 1) on the upstream side in the conveyance direction D11 from the image forming unit 3 in the sheet conveyance path R11.

[0027] As shown in FIG. 3, the imaging unit 5 includes a line sensor 51 and an AFE (analog front end) circuit 52.

[0028] As shown in FIG. 1, the line sensor 51 is provided at an imaging position P11 (an example of the passing position of the present invention) (see FIG. 1) through which the sheet SH10 conveyed by the sheet conveyance unit 2 passes. For example, the line sensor 51 is a CIS (Contact Image Sensor). The line sensor 51 includes a plurality of imaging elements arranged side by side in the width direction D12 (see FIG. 2) orthogonal to the conveyance direction D11 of the sheet SH10 (see FIG. 1). Each of the imaging elements includes a light emitting unit and a light receiving unit. The light emitting unit emits light toward the imaging position P11. The light receiving unit is provided so as to be able to receive the light emitted from the light emitting unit and reflected by the sheet SH10 passing through the imaging position P11, and outputs an analog electrical signal according to the amount of received light.

[0029] The AFE circuit 52 is an electronic circuit that converts the analog electrical signal output from each of the imaging elements of the line sensor 51 into a digital electrical signal (image data). For example, the AFE circuit 52 converts the analog electrical signal output from each of the imaging elements into image data expressed in 256 gradations with the pixel density ranging from 0 to 255.

[0030] The imaging unit 5 outputs imaging data indicating the imaging result by the line sensor 51 at a predetermined imaging cycle. The imaging cycle is set based on the conveyance speed of the sheet SH10 by the sheet conveyance unit 2.

[0031] The control unit 7 comprehensively controls the image forming apparatus 100. As shown in FIG. 3, the control unit 7 includes a CPU 7A, a ROM 7B, and a RAM 7C. The CPU 7A is a processor that executes various arithmetic processes. The ROM 7B is a non-volatile storage device in which information such as control programs for causing the CPU 7A to execute various processes is stored in advance. The RAM 7C is a volatile or non-volatile storage device used as a temporary storage memory (working area) for various processes executed by the CPU 7A. The CPU 7A comprehensively controls the image forming apparatus 100 by executing various control programs stored in advance in the ROM 7B.

[0032] The operation display unit 8 includes a display unit such as a liquid crystal display that displays various types of information according to a control instruction from the control unit 7, and an operation key that inputs various types of information to the control unit 7 according to a user's operation, or an operation unit such as a touch panel.

[0033] Incidentally, an image reading apparatus that determines whether or not the sheet SH10 has a missing portion based on the imaging data output from the imaging unit 5 is known. In this image reading apparatus, the edge of the sheet SH10 included in the imaging data is detected, and based on the detected edge of the sheet SH10, it is determined whether or not the sheet SH10 has a missing portion.

[0034] However, in a configuration that determines whether or not the sheet SH10 has a missing portion based on the detection result of the edge of the sheet SH10 included in the imaging data, the process for determining whether or not the sheet SH10 has an abnormal shape becomes complicated. The abnormal shape includes an ear fold SH12 (see FIG. 7) formed by folding the corner of the sheet SH10 and a partial defect SH13 (see FIG. 8) where a part of the sheet SH10 is chipped.

[0035] On the other hand, as will be described below, the image forming apparatus 100 according to an embodiment of the present invention can determine whether or not the sheet SH10 has the abnormal shape with a simple process.

[0036] The shape determination unit 6 determines whether or not the sheet SH10 has the abnormal shape based on the imaging data output from the imaging unit 5. The shape determination unit 6 is composed of an electronic circuit such as an integrated circuit (ASIC, DSP). Note that the CPU 7A of the control unit 7 may function as the shape determination unit 6 by executing the control program stored in the ROM 7B.

[0037] As shown in FIG. 3, the shape determination unit 6 includes an imaging processing unit 61, a binarization unit 62, a count processing unit 63, and a determination processing unit 64. An apparatus including the sheet conveyance unit 2, the imaging unit 5, the shape determination unit 6, and the control unit 7 is an example of the sheet conveyance apparatus of the present invention.

[0038] The imaging processing unit 61 causes the imaging unit 5 to output the imaging data at the imaging period.

[0039] For example, when the leading end SH11 of the sheet SH10 (see FIG. 5) is detected by a sheet sensor (not shown) provided upstream of the imaging position P11 in the sheet conveyance path R11 in the conveyance direction D11, the imaging processing unit 61 causes the imaging unit 5 to start outputting the imaging data. Further, when a predetermined time has elapsed after the trailing end of the sheet SH10 is detected by the sheet sensor, the imaging processing unit 61 causes the imaging unit 5 to end the output of the imaging data.

[0040] The binarization unit 62 performs a binarization process of binarizing each pixel included in the imaging data output from the imaging unit 5 into a value indicating the presence or absence of the sheet SH10. In the binarization process, based on whether or not the density value of the pixel exceeds a predetermined threshold value, the density value of the pixel is converted into a first value indicating the presence of the sheet SH10 or a second value indicating the absence of the sheet SH10.

[0041] The count processing unit 63 counts the number of sheet pixels indicating the sheet SH10 included in the imaging data each time the imaging data is output by the imaging unit 5.

[0042] For example, the count processing unit 63 counts the number of the sheet pixels included in the imaging data after the binarization process is performed by the binarization unit 62.

[0043] The determination processing unit 64 determines whether or not the sheet SH10 has the abnormal shape based on the transition of the count value by the count processing unit 63.

[0044] For example, when the change time of the count value by the count processing unit 63 exceeds a first predetermined time, the determination processing unit 64 determines that the sheet SH10 has the abnormal shape.

[0045] Here, while referring to FIGS. 5 to 8, the relationship between the state of the sheet SH10 conveyed by the sheet conveyance unit 2 and the transition of the count value by the count processing unit 63 will be described.

[0046] FIG. 5 shows the transition of the count value by the count processing unit 63 when the sheet SH10 having no abnormal shape and not inclined with respect to the conveyance direction D11 is conveyed.

[0047] Further, FIG. 6 shows the transition of the count value by the count processing unit 63 when the sheet SH10 having no abnormal shape and inclined with respect to the conveyance direction D11 is conveyed.

[0048] Further, FIG. 7 shows the transition of the count value by the count processing unit 63 when the sheet SH10 having an ear fold SH12 on the leading end SH11 side and not inclined with respect to the conveyance direction D11 is conveyed.

[0049] Further, FIG. 8 shows the transition of the count value by the count processing unit 63 when the sheet SH10 having a partial defect SH13 on the leading end SH11 side and inclined with respect to the conveyance direction D11 is conveyed.

[0050] Note that the timing T0 shown in FIGS. 5 to 8 is the timing when the leading end SH11 of the sheet SH10 is detected by the sheet sensor. Further, the timing T1 shown in FIGS. 5 to 8 is the timing when the leading end SH11 of the sheet SH10 reaches the imaging position P11. Further, the timing T2 shown in FIGS. 5 to 8 is the timing when the conveyance distance of the sheet SH10 from the timing T1 reaches the length in the conveyance direction D11 of the sheet SH10. Further, in FIGS. 5 to 8, the leading end SH11 of the sheet SH10 at each of the timing T1 and the timing T2 is indicated by a broken line.

[0051] As shown in FIG. 5, when the sheet SH10 does not have the abnormal shape and is not inclined with respect to the conveyance direction D11, the count value by the count processing unit 63 instantaneously rises from zero to a value corresponding to the length L1 (see FIG. 5) in the width direction D12 of the sheet SH10 from the timing T1. Further, it instantaneously falls from the value corresponding to the length L1 to zero from the timing T2.

[0052] As shown in FIG. 6, when the sheet SH10 does not have the abnormal shape and is inclined with respect to the conveyance direction D11, the count value by the count processing unit 63 rises from zero to a value corresponding to the length L1 (see FIG. 6) until the change time X1 (see FIG. 6) elapses from the timing T1. Further, it falls from the value corresponding to the length L1 to zero until the change time X1 elapses from the timing T2. The change time X1 becomes longer as the inclination angle of the sheet SH10 with respect to the conveyance direction D11 becomes larger.

[0053] As shown in FIG. 7, when the sheet SH10 has the ear fold SH12 on the tip SH11 side and is not inclined with respect to the conveyance direction D11, the count value by the count processing unit 63 rises from zero to a value corresponding to the length L1 (see FIG. 7) until the change time X2 (see FIG. 7) elapses from the timing T1. Further, it instantaneously falls from the value corresponding to the length L1 to zero from the timing T2. The change time X2 becomes longer as the size of the ear fold SH12 in the conveyance direction D11 becomes larger.

[0054] As shown in FIG. 8, when the sheet SH10 has the partial defect SH13 on the tip SH11 side and is inclined with respect to the conveyance direction D11, the count value by the count processing unit 63 rises from zero to a value corresponding to the length L1 (see FIG. 8) until the change time X3 (see FIG. 8) elapses from the timing T1. Further, it falls from the value corresponding to the length L1 to zero until the change time X1 (see FIG. 8) elapses from the timing T2. The change time X3 becomes longer as the size of the partial defect SH13 in the conveyance direction D11 becomes larger.

[0055] As is clear from FIGS. 5 to 8, when the sheet SH10 has the abnormal shape on the tip portion SH11 side, the change time of the count value by the count processing unit 63 from zero to the value corresponding to the length L1 (see FIGS. 5 to 8) becomes longer. Further, when the sheet SH10 has the abnormal shape on the rear end portion side, the change time of the count value by the count processing unit 63 from the value corresponding to the length L1 (see FIGS. 5 to 8) to zero becomes longer. Therefore, when the change time of the count value by the count processing unit 63 exceeds the first time, it is possible to determine that the sheet SH10 has the abnormal shape. Further, by adjusting the first time, it is possible to ignore the abnormal shape having a certain degree of small size.

[0056] Here, the determination processing unit 64 determines whether or not the sheet SH10 has the abnormal shape based on the transition of the count value by the count processing unit 63 from the detection of the tip portion SH11 in the conveyance direction D11 of the sheet SH10 based on the imaging data until the second time corresponding to the size in the conveyance direction D11 of the sheet SH10 elapses. Thereby, when the sheet SH10 is a tabbed sheet having a tab protruding from the rear end portion, it is possible to avoid an erroneous determination that the tab portion has the abnormal shape.

[0057] For example, the determination processing unit 64 acquires the second time using table data indicating the correspondence relationship between the size of the sheet SH10 and the second time. The table data may be stored in a non-volatile storage device (not shown) provided in the shape determination unit 6 in advance. Further, the size of the sheet SH10 may be set by the user in advance.

[0058] Note that the determination processing unit 64 may determine that the sheet SH10 has the abnormal shape when the change speed of the count value changes during the change of the count value by the count processing unit 63 (see FIGS. 7 and 8).

[0059] On the one hand, as shown in FIG. 3, the control unit 7 includes a stop processing unit 71. Specifically, the control unit 7 executes the control program stored in the ROM 7B using the CPU 7A. Thereby, the control unit 7 functions as the stop processing unit 71.

[0060] When the determination processing unit 64 determines that the sheet SH10 has the abnormal shape, the stop processing unit 71 stops the conveyance of the sheet SH10 by the sheet conveyance unit 2. Thereby, it is possible to avoid a collision between the ear fold SH12 of the sheet SH10 and components of the image forming apparatus 100 such as the recording head 30.

[0061] For example, the stop processing unit 71 stops the conveyance of the sheet SH10 by the sheet conveyance unit 2 and causes the operation display unit 8 to display a message indicating that the sheet SH10 is determined to have the abnormal shape.

[0062] [Shape determination processing] Hereinafter, with reference to FIG. 4, an example of the procedure of the shape determination processing executed by the shape determination unit 6 in the image forming apparatus 100 will be described together with the determination method of the present invention. Here, steps S11, S12,... represent the numbers of the processing steps (steps) executed by the shape determination unit 6. The shape determination processing is executed when the leading end portion SH11 of the sheet SH10 is detected by the sheet sensor.

[0063] [Step S11] First, in step S11, the shape determination unit 6 determines whether or not the second time has elapsed since the detection of the leading end portion SH11 in the conveyance direction D11 of the sheet SH10 based on the imaging data.

[0064] Specifically, when the second time has elapsed since the timing when it is determined that the change in the count value starts for the first time in the process of step S17 described later, the shape determination unit 6 determines that the second time has elapsed since the detection of the leading end portion SH11.

[0065] Here, when the shape determination unit 6 determines that the second time has elapsed since the detection of the tip SH11 (Yes side of S11), it ends the shape determination process. Also, if the second time has not elapsed since the detection of the tip SH11 (No side of S11), the shape determination unit 6 shifts the process to step S12.

[0066] <Step S12> In step S12, the shape determination unit 6 determines whether the imaging timing of the sheet SH10 has arrived.

[0067] Specifically, when the number of executions of the process in step S12 is 1, the shape determination unit 6 immediately determines that the imaging timing has arrived. Also, when the number of executions of the process in step S12 is 2 or more, the shape determination unit 6 determines that the imaging timing has arrived when the time corresponding to the imaging period has elapsed since the arrival of the immediately preceding imaging timing.

[0068] Here, when the shape determination unit 6 determines that the imaging timing has arrived (Yes side of S12), it shifts the process to step S13. Also, if the imaging timing has not arrived (No side of S12), the shape determination unit 6 waits for the arrival of the imaging timing in step S12.

[0069] <Step S13> In step S13, the shape determination unit 6 causes the imaging unit 5 to output the imaging data. The process of step S13 is executed by the imaging processing unit 61 of the shape determination unit 6.

[0070] <Step S14> In step S14, the shape determination unit 6 executes the binarization process on the imaging data output in step S13. The process of step S14 is executed by the binarization unit 62 of the shape determination unit 6.

[0071] <Step S15> In step S15, the shape determination unit 6 counts the number of sheet pixels included in the captured data after the binarization process is executed. The process of step S15 is an example of the counting step of the present invention and is executed by the counting processing unit 63 of the shape determination unit 6.

[0072] <Step S16> In step S16, the shape determination unit 6 determines whether it is in a non-measurement state in which the change time of the count value counted by the process of step S15 is not measured.

[0073] Here, when the shape determination unit 6 determines that it is in the non-measurement state (Yes side of S16), the process is shifted to step S17. If it is not in the non-measurement state (No side of S16), the shape determination unit 6 shifts the process to step S19.

[0074] <Step S17> In step S17, the shape determination unit 6 determines whether the change of the count value counted by the process of step S15 has started.

[0075] Specifically, the shape determination unit 6 determines that the change of the count value has started when the difference between the last two obtained count values exceeds a predetermined reference value. The reference value is set based on the variation amount of the count value until the leading end SH11 of the sheet SH10 reaches the imaging position P11.

[0076] Here, when the shape determination unit 6 determines that the change of the count value has started (Yes side of S17), the process is shifted to step S18. If the change of the count value has not started (No side of S17), the shape determination unit 6 shifts the process to step S11.

[0077] <Step S18> In step S18, the shape determination unit 6 starts measuring the change time of the count value.

[0078] <Step S19> In step S19, the shape determination unit 6 determines whether or not the change in the count value counted by the process of step S15 has ended.

[0079] Specifically, when the difference between the last two acquired count values is equal to or less than the reference value, the shape determination unit 6 determines that the change in the count value has ended.

[0080] Here, when the shape determination unit 6 determines that the change in the count value has ended (Yes side in S19), the process is shifted to step S20. Also, if the change in the count value has not ended (No side in S19), the shape determination unit 6 shifts the process to step S21.

[0081] <Step S20> In step S20, the shape determination unit 6 ends the measurement of the change time of the count value.

[0082] <Step S21> In step S21, the shape determination unit 6 determines whether or not the change time of the count value during measurement exceeds the first time. The process of step S21 is an example of the determination step of the present invention and is executed by the determination processing unit 64 of the shape determination unit 6.

[0083] Here, when the shape determination unit 6 determines that the change time of the count value during measurement exceeds the first time (Yes side in S21), the process is shifted to step S22. Also, if the change time of the count value during measurement does not exceed the first time (No side in S21), the shape determination unit 6 shifts the process to step S11.

[0084] <Step S22> In step S22, the shape determination unit 6 notifies the control unit 7 that the abnormal shape has been detected from the conveyed sheet SH10.

[0085] Thus, in the image forming apparatus 100, every time the imaging data is output by the imaging unit 5, the number of the sheet pixels included in the imaging data is counted. Then, based on the transition of the count value of the sheet pixels, it is determined whether the sheet SH10 has the abnormal shape. Thereby, it is possible to determine whether the sheet SH10 has the abnormal shape with a simple process.

[0086] [Supplementary Note of the Invention] Hereinafter, the outline of the invention extracted from the above-described embodiment will be appended. Note that each configuration and each processing function described in the following supplementary note can be arbitrarily combined by making selections.

[0087] <Supplementary Note 1> A sheet conveyance device including: a sheet conveyance unit that conveys a sheet; an imaging unit including a plurality of imaging elements arranged side by side in a width direction orthogonal to a conveyance direction of the sheet at a passage position through which the sheet conveyed by the sheet conveyance unit passes, and outputting imaging data indicating imaging results by the plurality of imaging elements at a predetermined imaging period; a count processing unit that counts the number of sheet pixels indicating the sheet included in the imaging data every time the imaging data is output by the imaging unit; and a determination processing unit that determines whether the sheet has an abnormal shape based on a transition of a count value by the count processing unit.

[0088] <Supplementary Note 2> The sheet conveyance device according to Supplementary Note 1, wherein the determination processing unit determines that the sheet has the abnormal shape when a change time of the count value exceeds a predetermined first time.

[0089] <Supplementary Note 3> The sheet conveyance device according to Supplementary Note 1, wherein the determination processing unit determines that the sheet has the abnormal shape when a change speed of the count value changes during the change of the count value.

[0090] <Supplementary Note 4> The determination processing unit determines whether the sheet has the abnormal shape based on the transition of the count value from the detection of the leading end of the sheet in the conveyance direction in the sheet based on the imaging data until the elapse of a second time corresponding to the size of the sheet. The sheet conveyance device according to any one of Appendices 1 to 3.

[0091] <Appendix 5> When it is determined by the determination processing unit that the sheet has the abnormal shape, the sheet conveyance device according to any one of Appendices 1 to 4, comprising a stop processing unit that stops the conveyance of the sheet by the sheet conveyance unit.

[0092] <Appendix 6> An image forming apparatus comprising the sheet conveyance device according to any one of Appendices 1 to 5, and an image forming unit that forms an image on the sheet conveyed by the sheet conveyance unit.

[0093] <Appendix 7> A determination method executed by a sheet conveyance device including a sheet conveyance unit that conveys a sheet and an imaging unit that includes a plurality of imaging elements arranged side by side in a width direction orthogonal to the conveyance direction of the sheet at a passing position through which the sheet conveyed by the sheet conveyance unit passes, and outputs imaging data indicating imaging results by the plurality of imaging elements at a predetermined imaging cycle. The determination method includes a counting step of counting the number of sheet pixels indicating the sheet included in the imaging data each time the imaging data is output by the imaging unit, and a determination step of determining whether the sheet has an abnormal shape based on the transition of the count value in the counting step.

Explanation of Signs

[0094] 1 Housing 2 Sheet conveyance unit 3 Image forming unit 4 Conveyance unit 5 Imaging unit 6 Shape determination unit 7 Control unit 8 Operation display unit 21 Pickup roller 22 Conveyor roller 30 Recording head 31 Line head 32 Line head 33 Line head 34 Line head 35 Head frame 51 Line sensor 52 AFE circuit 61 Imaging processing unit 62 Binarization unit 63 Count processing unit 64 Judgment processing unit 71 Stop processing unit 100 Image forming apparatus

Claims

1. A sheet conveyance unit that conveys a sheet, including a plurality of image sensors arranged side by side in the width direction orthogonal to the conveyance direction of the sheet at a passing position through which the sheet conveyed by the sheet conveyance unit passes, and outputting imaging data indicating imaging results by the plurality of image sensors at a predetermined imaging period; an imaging unit, a count processing unit that counts the number of sheet pixels indicating the sheet included in the imaging data each time the imaging data is output by the imaging unit, a determination processing unit that determines whether the sheet has an abnormal shape based on the transition of the count value by the count processing unit, A sheet conveyance device comprising:

2. The determination processing unit determines that the sheet has the abnormal shape when the change time of the count value exceeds a predetermined first time. The sheet conveyance device according to claim 1.

3. The determination processing unit determines that the sheet has the abnormal shape when the change speed of the count value changes during the change of the count value. The sheet conveyance device according to claim 1.

4. The determination processing unit determines whether the sheet has the abnormal shape based on the transition of the count value from the detection of the leading end of the sheet in the conveyance direction in the sheet based on the imaging data until a second time corresponding to the size of the sheet has elapsed. The sheet conveyance device according to claim 1.

5. When the determination processing unit determines that the sheet has the abnormal shape, it includes a stop processing unit that stops the conveyance of the sheet by the sheet conveyance unit. The sheet conveyance device according to claim 1.

6. A sheet conveyance device according to any one of claims 1 to 5, and an image forming unit that forms an image on the sheet conveyed by the sheet conveyance unit. An image forming apparatus comprising:

7. A determination method executed by a sheet conveyance device including a sheet conveyance unit that conveys a sheet and an imaging unit that includes a plurality of image sensors arranged side by side in the width direction orthogonal to the conveyance direction of the sheet at a passing position through which the sheet conveyed by the sheet conveyance unit passes, and outputs imaging data indicating imaging results by the plurality of image sensors at a predetermined imaging period, a count step of counting the number of sheet pixels indicating the sheet included in the imaging data each time the imaging data is output by the imaging unit, A determination step of determining whether the sheet has an abnormal shape based on the transition of the count value according to the count step; A determination method including the above.

Images