Image forming device and image quality adjusting method

Abstract

To provide an image forming device that can suppress a formed image from expanding or contracting in a conveying direction of a sheet, without consuming ink, and an image quality adjusting method.SOLUTION: An image forming device 100 comprises an expanding / contracting processing part 67 that when a sheet which is same as a sheet conveyed by a first conveying processing part 64 is conveyed, in a direction which is different from the conveying direction thereof by the first conveying processing part 64, by a second conveying processing part 65, expands or contracts a size along the conveying direction of the sheet of an image formed by an image forming part 3, on the basis of a size of the sheet measured when the sheet is conveyed by the first conveying processing part 64 and a size of the sheet measured when the sheet is conveyed by the second conveying processing part 65.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and an image quality adjustment method. [Background technology]

[0002] In an inkjet image forming apparatus, ink is ejected from an ejection unit such as a line head onto a sheet being conveyed, thereby forming an image on the sheet. Also, a configuration including an imaging unit that captures an image of the sheet being conveyed is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-76637 Summary of the Invention [Problem to be solved by the invention]

[0004] In the image forming apparatus, the image formed by the ejection unit may expand or contract in the sheet transport direction compared to the original image, such as a document image. To address this issue, a configuration is conceivable in which the ejection unit forms a predetermined detection image on the sheet, the imaging unit measures the size of the detection image formed on the sheet in the transport direction, and the ejection cycle of the ink by the ejection unit is adjusted based on the measurement results. However, in this configuration, the ink is consumed when adjusting the ejection cycle.

[0005] An object of the present invention is to provide an image forming apparatus and an image quality adjustment method that can suppress expansion and contraction of a formed image in the sheet transport direction without consuming ink. [Means for solving the problem]

[0006] According to one aspect of the present invention, an image forming apparatus includes a conveying belt, a discharge unit, an imaging unit, a first conveying processing unit, a first acquisition processing unit, a second conveying processing unit, a second acquisition processing unit, a determination processing unit, and an expansion / contraction processing unit. The conveying belt conveys a sheet along a predetermined conveying direction. The discharge unit discharges ink toward the sheet conveyed by the conveying belt. The imaging unit captures an image of the sheet conveyed by the conveying belt. The first conveying processing unit conveys the sheet along a conveying path including a conveying section of the conveying belt. The first acquisition processing unit uses the imaging unit to acquire the size of the sheet conveyed by the first conveying processing unit in the conveying direction and the size of the sheet in a width direction perpendicular to the conveying direction. The second conveying processing unit conveys the sheet along the conveying path after the sheet has been conveyed by the first conveying processing unit. The second acquisition processing unit uses the imaging unit to acquire the size of the sheet conveyed by the second conveying processing unit in the conveying direction and the size of the sheet conveyed by the second conveying processing unit. The determination processing unit determines whether the same sheet as the sheet transported by the first transport processing unit has been transported by the second transport processing unit in a different orientation from that when transported by the first transport processing unit, based on the results acquired by the first acquisition processing unit and the second acquisition processing unit. When it is determined that the same sheet as the sheet transported by the first transport processing unit has been transported by the second transport processing unit in a different orientation from that when transported by the first transport processing unit, the expansion / contraction processing unit expands or contracts the size of the image formed by the discharge unit along the transport direction, based on the results acquired by the first acquisition processing unit and the second acquisition processing unit.

[0007] An image quality adjustment method according to another aspect of the present invention is executed by an image forming apparatus including a conveyor belt that conveys a sheet along a predetermined conveying direction, an ejection unit that ejects ink toward the sheet conveyed by the conveyor belt, and an imaging unit that images the sheet conveyed by the conveyor belt, and includes a first conveying step, a first obtaining step, a second conveying step, a second obtaining step, a determining step, and an expanding / contracting step. In the first conveying step, the sheet is conveyed along a conveying path including a conveying section of the conveyor belt. In the first obtaining step, the imaging unit is used to obtain the size in the conveying direction and the size in a width direction perpendicular to the conveying direction of the sheet conveyed in the first conveying step. In the second conveying step, the sheet is conveyed along the conveying path after being conveyed in the first conveying step. In the second obtaining step, the imaging unit is used to obtain the size in the conveying direction and the size in the width direction of the sheet conveyed in the second conveying step. In the determining step, it is determined whether the same sheet as the sheet transported in the first transport step has been transported in the second transport step in a different orientation from when it was transported in the first transport step, based on the results obtained in the first obtaining step and the second obtaining step. In the expanding / contracting step, if it is determined that the same sheet as the sheet transported in the first transport step has been transported in the second transport step in a different orientation from when it was transported in the first transport step, the size of the image formed by the discharge unit along the transport direction is expanded or contracted based on the results obtained in the first obtaining step and the second obtaining step. [Effects of the Invention]

[0008] According to the present invention, it is possible to prevent the formed image from expanding or contracting in the sheet transport direction without consuming ink. [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 1 is a cross-sectional view showing the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view showing the configuration of the image forming section, the transport unit, and the line sensor in the image forming apparatus according to the embodiment of the present invention. [Figure 3] FIG. 3 is a block diagram showing the system configuration of the image forming apparatus according to the embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart showing an example of image quality adjustment processing executed by the image forming apparatus according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following embodiment is an example of a specific embodiment of the present invention and does not limit the technical scope of the present invention.

[0011] [Configuration of image forming apparatus 100] First, the configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described with reference to Figures 1 to 3. In Figure 1, a sheet transport path R11 is indicated by a two-dot chain line.

[0012] The image forming apparatus 100 is a printer capable of forming an image on a sheet by inkjet printing. The present invention may also be applied to a fax machine, a copier, or a multifunction peripheral capable of forming an image on a sheet by inkjet printing.

[0013] 1, the image forming apparatus 100 includes a housing 1, a sheet conveying section 2, an image forming section 3, a conveying unit 4, and a shape reading section 5. The image forming apparatus 100 also includes an operation display section 6, a control section 7, and an image processing section 8 shown in FIG.

[0014] The housing 1 houses each component of the image forming apparatus 100. A paper feed cassette 11 (see FIG. 1) is removably provided in the housing 1. The paper feed cassette 11 stores sheets on which images are to be formed. A paper output tray 12 (see FIG. 1) is provided on the outer surface of the housing 1. Sheets on which images are formed by the image forming unit 3 are discharged to the paper output tray 12. Inside the housing 1, the sheets stored in the paper feed cassette 11 are transported along a sheet transport path R11 (see FIG. 1) that passes through an image formation position by the image forming unit 3 and reaches the paper output tray 12.

[0015] The sheet transport unit 2 transports sheets stored in the paper feed cassette 11 along a sheet transport path R11 (see FIG. 1). As shown in FIG. 1, the sheet transport unit 2 includes a pickup roller 21 and multiple transport rollers 22. The pickup roller 21 picks up the top sheet of the stack of sheets stored in the paper feed cassette 11 and sends the sheet to the sheet transport path R11. The multiple transport rollers 22 are arranged side by side along the sheet transport path R11. Each transport roller 22 transports the sheet along the sheet transport path R11. Each transport roller 22 transports the sheet in a transport direction D11 (see FIG. 1) from the paper feed cassette 11 to the paper output tray 12.

[0016] The image forming unit 3 forms an image on a sheet transported along a sheet transport path R11 (see FIG. 1). As shown in FIG. 1, the image forming unit 3 includes line heads 31 to 34 and a head frame 35.

[0017] 2, each of the line heads 31 to 34 is elongated in a width direction D12 perpendicular to the conveying direction D11. Specifically, each of the line heads 31 to 34 has a length in the width direction D12 corresponding to the width of the largest size sheet that can be accommodated in the paper feed cassette 11. The line heads 31 to 34 are arranged side by side at equal intervals along the conveying direction D11.

[0018] 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 ejects ink toward a sheet transported by the transport belt 41 of the transport unit 4. Each of the recording heads 30 provided in the line head 31 ejects black ink. Each of the recording heads 30 provided in the line head 32 ejects cyan ink. Each of the recording heads 30 provided in the line head 33 ejects magenta ink. Each of the recording heads 30 provided in the line head 34 ejects yellow ink. The line heads 31 to 34 are examples of ejection sections of the present invention.

[0019] Each of the recording heads 30 includes a plurality of nozzles 30A (see FIG. 2) that eject ink. The plurality of nozzles 30A are provided on the surface of the recording head 30 that faces the sheet transported by the transport unit 4.

[0020] Each recording head 30 also includes a pressure chamber (not shown), a piezoelectric element (not shown), and an individual flow path (not shown) corresponding to each nozzle 30A. The pressure chamber communicates with the nozzle 30A and stores ink. The piezoelectric element ejects ink from the nozzle 30A in response to application of a predetermined drive voltage. The individual flow path is an ink flow path provided between the pressure chamber and a common flow path (not shown) shared by the multiple nozzles 30A. A plurality of the individual flow paths corresponding to the multiple 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.

[0021] 2, the line head 31 includes three recording heads 30 arranged in a staggered pattern along the width direction D12. Similarly to the line head 31, each of the other line heads 32 to 34 also includes three recording heads 30 arranged in a staggered pattern along the width direction D12.

[0022] The head frame 35 supports the line heads 31 to 34. The head frame 35 is supported by the housing 1. 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.

[0023] The image forming unit 3 forms an image on a sheet based on image data input from the image processing unit 8. Specifically, the image forming unit 3 controls the ejection of ink from each of the line heads 31 to 34 based on the image data input from the image processing unit 8.

[0024] As shown in FIG. 1, the transport unit 4 is disposed below the line heads 31 to 34. The transport unit 4 transports a sheet while facing the recording head 30. Each of the line heads 31 to 34 ejects ink toward the sheet being transported by the transport unit 4. As shown in FIG. 1, the transport unit 4 includes a transport belt 41 on which the sheet is placed, a first tension roller 42, a second tension roller 43, and a third tension roller 44 that tension the transport belt 41, and a transport frame 45 that supports these. The gap between the transport belt 41 and the recording head 30 is adjusted so that the gap between the surface of the sheet and the recording head 30 during image formation is a predetermined distance (for example, 1 mm).

[0025] The first tension roller 42 is driven to rotate by a rotational driving force supplied from a motor (not shown). As a result, the conveyor belt 41 rotates in a direction that allows the sheet to be conveyed in the conveying direction D11 (see FIG. 1). The conveyor belt 41 conveys the sheet placed on its outer circumferential surface along the conveying direction D11. The conveying unit 4 is also provided with a suction unit (not shown) that sucks air through a number of through holes formed in the conveyor belt 41 to attract the sheet to the conveyor belt 41.

[0026] The shape reading unit 5 reads the shape of the sheet being conveyed along the sheet conveying path R11.

[0027] As shown in FIG. 3, the shape reading 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 on the sheet transport path R11 upstream of the image forming unit 3 in the sheet transport direction D11. The line sensor 51 is also provided above the transport belt 41. As shown in FIG. 2, the line sensor 51 is also provided elongated along the width direction D12. The line sensor 51 captures an image of the sheet transported by the transport belt 41. The line sensor 51 is an example of an imaging unit of the present invention.

[0029] For example, the line sensor 51 is a CIS (contact image sensor). The line sensor 51 includes multiple imaging elements arranged side by side in the width direction D12 (see FIG. 2). Each of the imaging elements includes a light-emitting unit and a light-receiving unit. The light-emitting unit emits light toward the conveyor belt 41. The light-receiving unit is configured to receive light emitted from the light-emitting unit and reflected by the conveyor belt 41 or the conveyed sheet, and outputs an analog electrical signal corresponding to the amount of received light. The line sensor 51 captures an image of the sheet conveyed along the sheet conveyance path R11 at a predetermined imaging cycle. Specifically, the line sensor 51 outputs an analog electrical signal corresponding to an image of the object (sheet and conveyor belt 41) facing the line sensor 51 at the imaging cycle. The outer circumferential surface of the conveyor belt 41 is colored, such as black, to suppress reflection of light emitted from the light-emitting unit compared to the background color (white) of the sheet.

[0030] The AFE circuit 52 is an electronic circuit that performs predetermined processing on the analog electrical signal output from the line sensor 51. Specifically, the AFE circuit 52 includes a signal conversion unit that converts the analog electrical signal output from the line sensor 51 into a digital electrical signal (image data). The AFE circuit 52 also includes a binarization unit that performs binarization processing on the image data output from the signal conversion unit. The binarization processing is a process of binarizing each pixel included in the image data output from the signal conversion unit into a value that indicates the presence or absence of a sheet. The image data binarized by the binarization unit (hereinafter referred to as "line data") is input to the image processing unit 8.

[0031] The shape reading unit 5 outputs shape data indicating the shape of the sheet imaged by the line sensor 51. The shape data is data configured from a plurality of line data output from the AFE circuit 52 while the shape reading unit 5 is reading the shape of the sheet.

[0032] The operation display unit 6 is a user interface of the image forming apparatus 100. The operation display unit 6 includes a display unit and an operation unit. The display unit displays various information in response to control instructions from the control unit 7. For example, the display unit is a flat panel display such as a liquid crystal display. The operation unit inputs various information to the control unit 7 in response to user operations. For example, the operation unit includes operation keys and a touch panel.

[0033] The control unit 7 performs overall control of the image forming apparatus 100. As shown in FIG. 3, the control unit 7 includes a CPU 61, a ROM 62, and a RAM 63. The CPU 61 is a processor that executes various types of arithmetic processing. The ROM 62 is a non-volatile storage device that stores in advance information such as control programs for causing the CPU 61 to execute various types of processing. The RAM 63 is a volatile or non-volatile storage device that is used as a temporary storage memory (work area) for the various types of processing executed by the CPU 61. The CPU 61 performs overall control of the image forming apparatus 100 by executing the various control programs that are stored in advance in the ROM 62.

[0034] The image processing unit 8 adjusts the image data input to the image forming unit 3, i.e., the image data used to form an image on a sheet, based on the shape data input from the shape reading unit 5. For example, the image processing unit 8 masks a portion of the image data input to the image forming unit 3 that is used to form an image on the outside of the sheet transported along the sheet transport path R11, based on the shape data input from the shape reading unit 5. This prevents ink from being ejected onto the outside of the sheet. The image processing unit 8 is composed of electronic circuits such as integrated circuits (ASIC, DSP).

[0035] In the image forming apparatus 100, the images formed by the line heads 31 to 34 may expand or contract in the transport direction D11 compared to the original image such as the document image. To address this issue, a configuration is conceivable in which a predetermined detection image is formed on a sheet using the line heads 31 to 34, the size of the detection image formed on the sheet in the transport direction D11 is measured using the line sensor 51, and the ink ejection cycle of the line heads 31 to 34 is adjusted based on the measurement results. However, in this configuration, ink is consumed when adjusting the ejection cycle.

[0036] In contrast to this, in the image forming apparatus 100 according to the embodiment of the present invention, as will be described below, it is possible to prevent the formed image from expanding or contracting in the transport direction D11 without consuming ink.

[0037] 3, the control unit 7 includes a first conveyance processing unit 64, a second conveyance processing unit 65, a determination processing unit 66, and an expansion / contraction processing unit 67. Specifically, the CPU 61 of the control unit 7 functions as each of the above-mentioned processing units by executing the control program stored in the ROM 62. Note that each of the above-mentioned processing units may be realized by an electronic circuit.

[0038] 3, the image processing unit 8 includes a first acquisition processing unit 71 and a second acquisition processing unit 72. The CPU 61 of the control unit 7 may execute the control program stored in the ROM 62 to function as each of the above-mentioned processing units.

[0039] The first conveying processing unit 64 performs a first conveying process of conveying the sheet along a sheet conveying path R11 (an example of a conveying path of the present invention) including a conveying section by the conveying belt 41.

[0040] For example, the first conveyance processing unit 64 displays a first guide screen on the operation display unit 6 in response to a predetermined user operation on the operation display unit 6. The first guide screen includes a message urging the user to place a rectangular sheet in the paper feed cassette 11. The first guide screen also includes a first execution key used to perform the first conveyance processing.

[0041] When the first execution key is operated by the user, the first conveying processing unit 64 executes the first conveying process. In the first conveying process, the sheet conveying unit 2 and the conveying unit 4 are used to convey the sheet placed in the sheet feed cassette 11 along the sheet conveying path R11.

[0042] The first acquisition processing unit 71 executes a first acquisition process using the line sensor 51 to acquire the size of the sheet conveyed by the first conveying processing unit 64 in the conveying direction D11 (see Figure 2) and the size in the width direction D12 (see Figure 2) perpendicular to the conveying direction D11.

[0043] For example, when the leading edge of a sheet is detected by a sheet sensor (not shown) provided upstream of the line sensor 51 in the sheet conveyance path R11 (see FIG. 1) in the conveyance direction D11, the first acquisition processing unit 71 starts reading the shape of the sheet by the shape reading unit 5. This causes the AFE circuit 52 to output the line data at the imaging cycle. Furthermore, the first acquisition processing unit 71 ends reading the shape of the sheet by the shape reading unit 5 when a predetermined time has elapsed since the trailing edge of the sheet was detected by the sheet sensor. The predetermined time is set so that reading of the shape of the sheet by the shape reading unit 5 ends after the trailing edge of the sheet has passed a position facing the line sensor 51. Then, the first acquisition processing unit 71 acquires the plurality of line data (the shape data) output from the AFE circuit 52 during the period in which the shape reading unit 5 is reading the shape of the sheet.

[0044] The first acquisition processing unit 71 also counts the number of sheet pixels in the line data that includes sheet pixels indicating the presence of a sheet, among the line data included in the shape data. The first acquisition processing unit 71 then multiplies the count result by the size in the width direction D12 of the image sensor included in the line sensor 51 to calculate the size in the width direction D12 of the sheet conveyed by the first conveying processing unit 64.

[0045] The first acquisition processing unit 71 also counts the number of sheet pixels in pixel rows extending in a direction (a direction corresponding to the conveying direction D11) perpendicular to the extension direction of the line data in the shape data. The first acquisition processing unit 71 then multiplies the count result by the conveying distance per imaging cycle by the conveyor belt 41 to calculate the size in the conveying direction D11 of the sheet conveyed by the first conveying processing unit 64. The conveying distance per imaging cycle by the conveyor belt 41 is acquired by multiplying the design value of the sheet conveying speed by the conveyor belt 41 by the imaging cycle.

[0046] Here, the actual transport distance per imaging cycle by the transport belt 41 may differ from the design value due to individual errors in the diameter of the first tension roller 42, wear of the first tension roller 42, and the like.

[0047] If the actual conveying distance per imaging cycle by the conveyor belt 41 is faster than the design value, the image formed by the line heads 31 to 34 will be elongated in the conveying direction D11 more than the original image. Also, if the actual conveying distance per imaging cycle by the conveyor belt 41 is faster than the design value, the line sensor 51 will have fewer opportunities to capture an image of the sheet, and the size of the sheet in the conveying direction D11 acquired by the first acquisition processing unit 71 will be smaller than the actual size.

[0048] On the other hand, if the actual conveyance distance per imaging cycle by the conveyor belt 41 is slower than the design value, the image formed by the line heads 31 to 34 will be smaller in the conveyance direction D11 than the original image. Also, if the actual conveyance distance per imaging cycle by the conveyor belt 41 is slower than the design value, the line sensor 51 will have more opportunities to capture an image of the sheet, and the size of the sheet in the conveyance direction D11 acquired by the first acquisition processing unit 71 will be larger than the actual size.

[0049] After the sheet is conveyed by the first conveyance processing section 64, the second conveyance processing section 65 performs a second conveyance process to convey the sheet along the sheet conveyance path R11.

[0050] For example, after the first conveyance processing unit 64 conveys the sheet, the second conveyance processing unit 65 displays a second guide screen on the operation display unit 6. The second guide screen includes a message urging the user to place the sheet discharged to the paper discharge tray 12 (the sheet conveyed by the first conveyance processing unit 64) in the paper feed cassette 11 in an orientation different from that at the time of conveyance by the first conveyance processing unit 64. The second guide screen also includes a second execution key used to perform the second conveyance process.

[0051] Then, when the second execution key is operated by the user, the second conveyance processing unit 65 executes the second conveyance process. In the second conveyance process, the sheet conveyance unit 2 and the conveyance unit 4 are used to convey the sheet placed in the sheet feed cassette 11 along the sheet conveyance path R11.

[0052] Here, if the user acts in accordance with the message on the second guide screen, the same sheet as that conveyed by the first conveyance processing unit 64 is conveyed by the second conveyance processing unit 65 in a different orientation from that when conveyed by the first conveyance processing unit 64. For example, an A4 size sheet that was conveyed in portrait orientation in the first conveyance processing is conveyed in landscape orientation in the second conveyance processing.

[0053] The second acquisition processing unit 72 executes a second acquisition process using the line sensor 51 to acquire the size of the sheet conveyed by the second conveying processing unit 65 in the conveying direction D11 (see Figure 2) and the size in the width direction D12 (see Figure 2).

[0054] Specifically, the second acquisition processing unit 72 acquires the size of the sheet conveyed by the second conveyance processing unit 65 in the conveyance direction D11 and the size of the sheet in the width direction D12 in the same manner as the first acquisition processing unit 71.

[0055] Based on the results acquired by the first acquisition processing unit 71 and the results acquired by the second acquisition processing unit 72, the judgment processing unit 66 determines whether the same sheet as the sheet transported by the first conveying processing unit 64 was transported by the second conveying processing unit 65 in a different orientation than when transported by the first conveying processing unit 64.

[0056] For example, when the ratio between the size of the sheet in the conveying direction D11 acquired by the first acquisition processing unit 71 and the size of the sheet in the width direction D12 acquired by the second acquisition processing unit 72 is within a predetermined allowable range, and the ratio between the size of the sheet in the width direction D12 acquired by the first acquisition processing unit 71 and the size of the sheet in the conveying direction D11 acquired by the second acquisition processing unit 72 is within the allowable range, the determination processing unit 66 determines that the same sheet as that conveyed by the first conveying processing unit 64 has been conveyed by the second conveying processing unit 65 in a different orientation from when it was conveyed by the first conveying processing unit 64. The allowable range is a range that includes "1".

[0057] When it is determined that the same sheet as that transported by the first transport processing unit 64 has been transported by the second transport processing unit 65 in a different orientation than when it was transported by the first transport processing unit 64, the expansion / contraction processing unit 67 expands or contracts the size of the image formed by the line heads 31 to 34 along the transport direction D11 (see Figure 2) based on the results acquired by the first acquisition processing unit 71 and the results acquired by the second acquisition processing unit 72.

[0058] For example, the expansion / contraction processing unit 67 expands or contracts the size along the conveying direction D11 of the image formed using the line heads 31 to 34 based on the larger of the two sizes acquired by the first acquisition processing unit 71 and the larger of the two sizes acquired by the second acquisition processing unit 72.

[0059] For example, the expansion / contraction processing unit 67 changes the ink ejection cycle of the line heads 31 to .

[0060] For example, if the sheet is transported vertically in the first transport process and horizontally in the second transport process, the expansion / contraction processing unit 67 obtains the correction value as the result of dividing the size of the sheet in the transport direction D11 obtained by the first acquisition processing unit 71 by the size of the sheet in the width direction D12 obtained by the second acquisition processing unit 72.

[0061] In addition, when the sheet is transported horizontally in the first transport process and when the sheet is transported vertically in the second transport process, the expansion / contraction processing unit 67 obtains the correction value as the result of dividing the size of the sheet in the transport direction D11 obtained by the second acquisition processing unit 72 by the size of the sheet in the width direction D12 obtained by the first acquisition processing unit 71.

[0062] Then, the expansion / contraction processing unit 67 changes the discharge period by multiplying the acquired correction value by the discharge period.

[0063] The correction value is smaller than 1 when the actual transport distance per imaging cycle by the transport belt 41 is shorter than the design value. In this case, the ejection cycle is shortened.

[0064] Furthermore, when the actual transport distance per imaging cycle by the transport belt 41 is slower than the design value, the correction value becomes greater than 1. In this case, the ejection cycle is extended.

[0065] For example, the expansion / contraction processing unit 67 changes the image capturing period together with the discharge period. Specifically, the expansion / contraction processing unit 67 changes the image capturing period by multiplying the image capturing period by the acquired correction value.

[0066] The expansion / contraction processing unit 67 may expand or contract the size of the image formed by the line heads 31 to 34 along the conveyance direction D11 by changing the conveyance speed of the sheet by the conveyance belt 41.

[0067] In addition, the expansion / contraction processing unit 67 may expand or contract the size along the conveying direction D11 of the image formed using the line heads 31 to 34 based on the smaller of the two sizes acquired by the first acquisition processing unit 71 and the smaller of the two sizes acquired by the second acquisition processing unit 72.

[0068] [Image quality adjustment processing] 4, the image quality adjustment method of the present invention will be described below, along with an example of the procedure of the image quality adjustment process executed by the control unit 7 and image processing unit 8 in the image forming apparatus 100. Here, steps S11, S12, etc. represent the numbers of the processing procedures (steps) executed by the control unit 7 or the image processing unit 8. The image quality adjustment process is executed when a user operation to instruct execution of the image quality adjustment process is accepted on the operation display unit 6.

[0069] <Step S11> First, in step S11, the control unit 7 causes the first guide screen to be displayed on the operation display unit 6. The process of step S11 is executed by the first transfer processing unit 64 of the control unit 7.

[0070] <Step S12> In step S12, the control unit 7 determines whether or not a user operation on the first execution key included in the first guide screen has been accepted.

[0071] Here, if the control unit 7 determines that the user's operation on the first execution key has been accepted (Yes in S12), it shifts the process to step S13. On the other hand, if the user's operation on the first execution key has not been accepted (No in S12), the control unit 7 waits for the user's operation on the first execution key in step S12.

[0072] <Step S13> In step S13, the control unit 7 executes the first transfer process. The process of step S13 is an example of the first transfer step of the present invention, and is executed by the first transfer process unit 64 of the control unit 7.

[0073] <Step S14> In step S14, the image processing unit 8 executes the first acquisition process. The process of step S14 is an example of the first acquisition step of the present invention, and is executed by the first acquisition processing unit 71 of the image processing unit 8.

[0074] <Step S15> In step S15, the control unit 7 causes the second guide screen to be displayed on the operation display unit 6. The process of step S15 is executed by the second transfer processing unit 65 of the control unit 7.

[0075] <Step S16> In step S16, the control unit 7 determines whether or not the user's operation on the second execution key included in the second guide screen has been accepted.

[0076] Here, if the control unit 7 determines that the user's operation on the second execution key has been accepted (Yes in S16), it shifts the process to step S17. On the other hand, if the user's operation on the second execution key has not been accepted (No in S16), the control unit 7 waits for the user's operation on the second execution key in step S16.

[0077] <Step S17> In step S17, the control unit 7 executes the second transfer process. The process of step S17 is an example of the second transfer step of the present invention, and is executed by the second transfer process unit 65 of the control unit 7.

[0078] <Step S18> In step S18, the image processing unit 8 executes the second acquisition process. The process of step S18 is an example of the second acquisition step of the present invention, and is executed by the second acquisition processing unit 72 of the image processing unit 8.

[0079] <Step S19> In step S19, the control unit 7 determines whether or not the adjustment condition is met.

[0080] Specifically, the control unit 7 determines that the adjustment condition is satisfied when the ratio between the size of the sheet in the conveying direction D11 acquired in the first acquisition process and the size of the sheet in the width direction D12 acquired in the second acquisition process is within the allowable range, and the ratio between the size of the sheet in the width direction D12 acquired in the first acquisition process and the size of the sheet in the conveying direction D11 acquired in the second acquisition process is within the allowable range. Here, the process of determining whether the adjustment condition is satisfied is an example of a determination step of the present invention, and is executed by the determination processing unit 66 of the control unit 7.

[0081] Here, if the control unit 7 determines that the adjustment condition is satisfied (Yes in S19), it shifts the process to step S20. On the other hand, if the adjustment condition is not satisfied (No in S19), the control unit 7 shifts the process to step S15. In this case, the control unit 7 may cause the operation display unit 6 to display a message indicating that the same sheet as that conveyed in the first conveying process is not conveyed in the second conveying process in a different orientation from that when conveyed in the first conveying process.

[0082] <Step S20> In step S20, the control unit 7 changes the ink ejection cycle of the line heads 31 to 34 based on the results obtained in the first acquisition process and the results obtained in the second acquisition process. The process of step S20 is an example of an expansion / contraction step of the present invention, and is executed by the expansion / contraction processing unit 67 of the control unit 7.

[0083] Here, the control unit 7 changes the image capturing period along with the ejection period. This allows the image quality adjustment process to be repeatedly performed. Therefore, the ejection period can be adjusted in accordance with changes in the conveying distance per image capturing period by the actual conveyor belt 41.

[0084] The control unit 7 may accept a manual setting operation for the discharge cycle and the image capture cycle outside the execution period of the image quality adjustment process.The control unit 7 may then change the discharge cycle and the image capture cycle in response to the manual setting operation.This allows a user who is not satisfied with the execution result of the image quality adjustment process to manually adjust the discharge cycle and the image capture cycle.

[0085] In this way, in the image forming apparatus 100, when it is determined that the same sheet as that conveyed by the first conveyance processing unit 64 has been conveyed by the second conveyance processing unit 65 in a different orientation from that when conveyed by the first conveyance processing unit 64, the ink ejection cycle of the line heads 31 to 34 is adjusted based on the results obtained by the first acquisition processing unit 71 and the second acquisition processing unit 72. In other words, in the image forming apparatus 100, it is possible to prevent the formed image from expanding or contracting in the conveyance direction D11 without consuming ink.

[0086] [Notes on the Invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0087] <Appendix 1> a conveyance belt that conveys a sheet along a predetermined conveyance direction; a discharge unit that discharges ink toward the sheet conveyed by the conveyance belt; an imaging unit that images the sheet conveyed by the conveyance belt; a first conveyance processing unit that conveys the sheet along a conveyance path including a conveyance section of the conveyance belt; a first acquisition processing unit that uses the imaging unit to acquire a size in the conveyance direction and a size in a width direction perpendicular to the conveyance direction of the sheet conveyed by the first conveyance processing unit; a second conveyance processing unit that conveys the sheet along the conveyance path after conveyance of the sheet by the first conveyance processing unit; an image forming apparatus comprising: a second acquisition processing unit that acquires a size along the conveying direction; a determination processing unit that determines, based on the acquisition results by the first acquisition processing unit and the second acquisition processing unit, whether the same sheet as the sheet conveyed by the first conveying processing unit has been conveyed by the second conveying processing unit in a different orientation than when it was conveyed by the first conveying processing unit; and an expansion / contraction processing unit that expands or contracts the size along the conveying direction of an image formed by the ejection unit, based on the acquisition results by the first acquisition processing unit and the second acquisition processing unit, when it is determined that the same sheet as the sheet conveyed by the first conveying processing unit has been conveyed by the second conveying processing unit in a different orientation than when it was conveyed by the first conveying processing unit.

[0088] <Appendix 2> 2. The image forming apparatus according to claim 1, wherein the expansion / contraction processing unit changes a period during which the ink is ejected by the ejection unit.

[0089] <Appendix 3> The image forming apparatus according to claim 1 or 2, wherein the expansion / contraction processing unit expands or contracts the size of the image formed using the ejection unit along the conveying direction based on the larger of the two sizes acquired by the first acquisition processing unit and the larger of the two sizes acquired by the second acquisition processing unit.

[0090] <Appendix 4> An image quality adjustment method executed by an image forming apparatus including a conveyance belt that conveys a sheet along a predetermined conveyance direction, an ejection unit that ejects ink toward the sheet conveyed by the conveyance belt, and an imaging unit that images the sheet conveyed by the conveyance belt, the method including: a first conveyance step of conveying the sheet along a conveyance path including a conveyance section of the conveyance belt; a first acquisition step of acquiring, using the imaging unit, a size in the conveyance direction and a size in a width direction perpendicular to the conveyance direction of the sheet conveyed by the first conveyance step; a second conveyance step of conveying the sheet along the conveyance path after conveying the sheet by the first conveyance step; and an image capturing unit that captures, using the imaging unit, an image of the sheet conveyed by the second conveyance step in the conveyance direction. a second acquisition step of acquiring a size in the conveying direction and a size in the width direction; a determination step of determining, based on the results acquired by the first acquisition step and the second acquisition step, whether the sheet identical to the sheet conveyed by the first conveying step has been conveyed by the second conveying step in a different orientation from when it was conveyed by the first conveying step; and an expansion / contraction step of expanding or contracting the size along the conveying direction of the image formed by the ejection unit, based on the results acquired by the first acquisition step and the second acquisition step, when it is determined that the sheet identical to the sheet conveyed by the first conveying step has been conveyed by the second conveying step in a different orientation from when it was conveyed by the first conveying step. [Explanation of symbols]

[0091] 1 chassis 2 Sheet transport section 3 Image forming unit 4 Transport unit 5 Shape reading unit 6 Operation display section 7 Control Unit 8 Image processing section 11 Paper cassette 12 Paper output tray 21 Pickup roller 22 Transport roller 30 Recording head 30A nozzle 31 Line Head 32 Line Head 33 Line Head 34 Line Head 35 Head Frame 41 Conveyor belt 42 First tension roller 43 Second tension roller 44 Third tension roller 45 Transport frame 51 Line Sensor 52 AFE circuit 61 CPU 62 ROM 63 RAM 64 First transport processing section 65 Second transport processing section 66 Judgment processing unit 67 Stretching processing part 71 First acquisition processing unit 72 Second acquisition processing unit 100 Image forming device

Claims

1. a conveyor belt that conveys a sheet along a predetermined conveyance direction; a discharge unit that discharges ink toward the sheet conveyed by the conveyor belt; an imaging unit that images the sheet being conveyed by the conveying belt; a first conveying processing section that conveys the sheet along a conveying path including a conveying section of the conveying belt; a first acquisition processing unit that acquires, using the imaging unit, a size in the conveying direction and a size in a width direction perpendicular to the conveying direction of the sheet conveyed by the first conveying processing unit; a second conveying processing unit that conveys the sheet along the conveying path after the sheet has been conveyed by the first conveying processing unit; a second acquisition processing unit that acquires, using the imaging unit, a size in the conveyance direction and a size in the width direction of the sheet conveyed by the second conveyance processing unit; a determination processing unit that determines whether the same sheet as the sheet conveyed by the first conveying processing unit has been conveyed by the second conveying processing unit in a different orientation from when the sheet was conveyed by the first conveying processing unit, based on the acquisition result by the first acquisition processing unit and the acquisition result by the second acquisition processing unit; an expansion / contraction processing unit that expands or contracts a size of the image formed by the ejection unit along the conveying direction based on the acquisition results by the first acquisition processing unit and the second acquisition processing unit when it is determined that the same sheet as the sheet conveyed by the first conveying processing unit has been conveyed by the second conveying processing unit in a different orientation from when the sheet was conveyed by the first conveying processing unit; An image forming apparatus comprising:

2. the expansion / contraction processing unit changes the ink ejection cycle of the ejection unit; The image forming apparatus according to claim 1 .

3. the expansion / contraction processing unit expands or contracts a size along the transport direction of the image formed using the discharge unit, based on the larger of the two sizes acquired by the first acquisition processing unit and the larger of the two sizes acquired by the second acquisition processing unit.

3. The image forming apparatus according to claim 1.

4. An image quality adjustment method executed in an image forming apparatus including a conveyor belt that conveys a sheet along a predetermined conveyance direction, an ejection unit that ejects ink toward the sheet conveyed by the conveyor belt, and an imaging unit that images the sheet conveyed by the conveyor belt, a first conveying step of conveying the sheet along a conveying path including a conveying section of the conveying belt; a first obtaining step of obtaining a size in the conveying direction and a size in a width direction perpendicular to the conveying direction of the sheet conveyed by the first conveying step using the imaging unit; a second conveying step of conveying the sheet along the conveying path after the sheet has been conveyed in the first conveying step; a second obtaining step of obtaining a size in the conveying direction and a size in the width direction of the sheet conveyed by the second conveying step using the imaging unit; a determination step of determining whether the same sheet as that conveyed in the first conveying step has been conveyed in the second conveying step in a different orientation from that in the first conveying step, based on the results of the first and second acquisition steps; an expansion / contraction step of expanding or contracting a size of an image formed by the ejection unit along the conveying direction based on the results obtained by the first acquisition step and the second acquisition step when it is determined that the same sheet as the sheet conveyed by the first conveying step has been conveyed by the second conveying step in a different orientation from when the sheet was conveyed by the first conveying step; An image quality adjustment method including:

Images