Image forming device

Abstract

To correct the inclination of reading means by a simpler method.SOLUTION: An image forming device conveys a sheet in a predetermined conveying direction and forms an image on the sheet. The image forming device forms a first test image on the sheet and causes reading means to read the first test image from the sheet. The image forming device corrects the inclination of the reading means with respect to conveying means on the basis of the reading result of the first test image.SELECTED DRAWING: Figure 13

Description

Technical Field

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

Background Art

[0002] In recent years, electrophotographic or inkjet printing methods have been spreading in the commercial printing market, which has been mainly offset printing. In order for printers using electrophotographic or inkjet printing methods to further spread in the commercial printing market, image quality equivalent to that of the offset printing method must be achieved. Therefore, such an image forming apparatus includes a reading device for reading a test sheet used for calibration of the image forming apparatus while transporting it along a transport path.

[0003] The image forming apparatus described in Patent Document 1 forms a test image on a sheet, reads the test image by an image reading device, and performs registration adjustment to correct the misregistration (shift of the image forming position) of the image formed on the sheet based on the reading result.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, if the mounting position of the reading means is inclined with respect to the direction orthogonal to the transport direction, the image detected by the reading means is distorted into a parallelogram, and there has been a problem that calibration cannot be performed with high accuracy. Therefore, an object of the present invention is to correct the inclination of the reading means.

Means for Solving the Problems

[0006] The present invention is, for example, Conveying means for conveying a sheet in a predetermined conveying direction, Forming means for forming an image on the sheet conveyed by the conveying means, Reading means for reading a first test image from the sheet conveyed by the conveying means, the first test image being formed by the forming means, Correction means for correcting the inclination of the reading means with respect to the conveying means based on the reading result of the first test image, To provide an image forming apparatus having the above.

Effect of the Invention

[0007] According to the present invention, it becomes possible to correct the inclination of the reading means.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant descriptions are omitted.

[0010] <Example 1> (1) Image forming apparatus FIG. 1 is a schematic diagram showing an example of the schematic configuration of an inkjet recording apparatus 100. The Z direction is the height direction of the inkjet recording apparatus 100. The Y direction is parallel to the sheet conveyance direction. The X direction is the width direction of the sheet S. The X direction is also a direction orthogonal to the sheet conveyance direction (Y direction) of the sheet S. Note that the width direction of the sheet S may be referred to as the main scanning direction. A direction parallel to the sheet conveyance direction of the sheet S may be referred to as the sub-scanning direction.

[0011] The inkjet recording apparatus 100 is a single-sheet type image forming apparatus that forms an ink image on a sheet S using two liquids, a reaction liquid and ink. The sheet S on which the ink image is formed may be called a recording material, an output material, or a product. The ink contains, for example, a resin component, water, a water-soluble organic solvent, a colorant, wax, and an additive. However, this is only an example.

[0012] The inkjet recording apparatus 100 includes a feeding module 1000, a printing module 2000, a drying module 3000, a fixing module 4000, a cooling module 5000, a reversing module 6000, a discharge stacking module 7000, and the like. The cut-sheet-like sheet S supplied from the feeding module 1000 is conveyed along the conveyance path, processed by each module, and discharged to the discharge stacking module 7000.

[0013] The feeding module 1000 has three storage bins 1100a to 1100c for accommodating the sheet S. The storage bins 1100a to 1100c can be pulled out to the front side of the inkjet recording apparatus 100. The sheet S is fed one by one by a separation belt and a conveyance roller in the storage bins 1100a to 1100c and conveyed to the printing module 2000. Note that the number of the storage bins 1100a to 1100c may be one or more.

[0014] The print module 2000 has a sheet correction unit 2100, a belt unit 2200, and a recording unit 2300. The sheet correction unit 2100 corrects the inclination and position of the sheet S conveyed from the feeding module 1000, and conveys the sheet S to the belt unit 2200. The recording unit 2300 is arranged to face the belt unit 2200 with the conveyance path therebetween. The recording unit 2300 performs a recording process (printing) on the conveyed sheet S from above with a recording head to form an image. The sheet S is adsorbed and conveyed by the belt unit 2200. Thereby, an appropriate clearance is secured between the recording head and the sheet S. Also, a plurality of recording heads may be arranged along the conveyance direction. In the embodiment, four line-type recording heads corresponding to four colors (Y: yellow, M: magenta, C: cyan, Bk: black) of ink and one line-type recording head for discharging the reaction liquid C0 are provided. The number of colors and the number of recording heads are not limited to five respectively. For example, three line-type recording heads for special colors C1, C2, C3 different from Y, M, C, and Bk may be added. As the inkjet recording method, for example, there are a method using a heating element, a method using a piezo element, a method using an electrostatic element, or a method using a MEMS element. MEMS is an abbreviation for a micro electro mechanical system.

[0015] Each of the four colors of ink is supplied from an ink tank (not shown) to the recording head via an ink tube. The belt unit 2200 further conveys the sheet S on which an image has been printed by the recording unit 2300 downstream. An in-line scanner 1 may be arranged on the downstream side of the recording unit 2300. The in-line scanner 1 detects the deviation and color density of the image formed on the sheet S. The detection result is used to correct a subsequent printed image.

[0016] The drying module 3000 reduces the liquid content included in the ink applied onto the sheet S by the recording unit 2300, and enhances the fixing property between the sheet S and the ink. The drying module 3000 includes a decoupling unit 3200, a drying belt unit 3300, and a warm air blowing unit 3400. The sheet S printed with an image by the recording unit 2300 of the printing module 2000 is conveyed to the decoupling unit 3200 disposed within the drying module 3000. While holding the sheet S by the wind pressure from above and the frictional force of the belt, the decoupling unit 3200 further conveys the sheet S downstream. Thereby, the deviation of the sheet S on the belt unit 2200 is suppressed. The sheet S is conveyed from the decoupling unit 3200 to the drying belt unit 3300. The drying belt unit 3300 conveys the sheet S while adsorbing it. The warm air blowing unit 3400 is disposed above the drying belt unit 3300. The warm air blowing unit 3400 applies hot air to the sheet S to dry the ink-applied surface of the sheet S. The drying belt unit 3300 conveys the sheet S to the fixing module 4000.

[0017] The drying module 3000 heats and dries the reaction liquid and the liquid components of the ink applied to the sheet S. Thereby, the evaporation of moisture in the reaction liquid and the ink is promoted, and the cockling of the sheet S is suppressed.

[0018] The drying module 3000 would be sufficient as long as it is a device capable of performing heat drying. For example, the drying module 3000 may have a warm air dryer or a heater. There is no particular limitation on the type of the heater either. For example, as the heater, a heating wire heater or an infrared heater may be adopted.

[0019] The fixing module 4000 has a fixing belt unit 4100. The fixing belt unit 4100 has an upper belt unit and a lower belt unit. The upper belt unit and the lower belt unit are heated, and the sheet S passes therebetween. Thereby, the ink solvent sufficiently penetrates into the sheet S.

[0020] The cooling module 5000 has a plurality of cooling units 5100 that cool the high-temperature sheet S conveyed from the fixing module 4000. The cooling unit 5100, for example, takes in outside air into the cooling box with a fan, increases the pressure inside the cooling box, and blows air onto the sheet S from nozzles formed in the conveyance guide. As a result, the sheet S is cooled. The cooling units 5100 are arranged on both sides of the conveyance path in the height direction. Thereby, both sides of the sheet S are cooled. A switching unit 5200 for switching the conveyance path may be provided inside the cooling module 5000. The switching unit 5200 switches between conveying the sheet S to the inversion module 6000 and conveying the sheet S to the duplex conveyance path used during duplex printing. During duplex printing, the sheet S is conveyed to a duplex conveyance path 5300 provided below the cooling module 5000. Further, the sheet S is conveyed through the fixing module 4000, the drying module 3000, the printing module 2000, and the feeding module 1000. As a result, the sheet S is conveyed again to the sheet correction unit 2100, the belt unit 2200, and the recording unit 2300 of the printing module 2000. Then, the recording unit 2300 prints an image on the second side of the sheet S.

[0021] An inversion unit 4200 for inverting the front and back of the sheet S may be provided in the duplex conveyance path of the fixing module 4000. The inversion module 6000 also has an inversion unit 6400. The inversion unit 6400 inverts the front and back of the conveyed sheet S. Thereby, the front and back (face down / face up) of the discharged sheet S can be freely selected.

[0022] The discharge stacking module 7000 has a top tray 7200 and a stacking unit 7500. The top tray 7200 and the stacking unit 7500 align and stack the sheets S conveyed from the inversion module 6000.

[0023] (2) Printing Module FIG. 2 is a schematic cross-sectional view of the print module 2000. The print module 2000 is an image forming unit that performs a recording process on a conveyed sheet S by using five recording heads 10 (eight recording heads 10 when using special color recording heads) from above, and forms an ink image on the sheet S. The sheet S needs to be stably conveyed in the image forming unit. In particular, the sheet S passing directly below the recording head 10 needs to be stably conveyed. Therefore, the belt unit 2200 sucks and conveys the sheet S.

[0024] The print belt 25 of the belt unit 2200 is stretched over the stretching rollers 21 to 24. The belt surface (conveying surface) stretched between the stretching roller 21 and the stretching roller 24 is called the image forming surface 26. The recording head 10 discharges ink (droplets) onto the sheet S conveyed by the image forming surface 26 to form an image. The print belt 25 has a plurality of suction holes (not shown) for sucking the sheet S. By sucking the sheet S from the plurality of suction holes existing on the image forming surface 26, the sheet S is firmly adsorbed to the image forming surface 26, and the sheet S is stably conveyed. Note that the print belt 25 is not limited to a configuration in which the sheet S is adsorbed to the print belt 25 by sucking the sheet S from the suction holes of the print belt 25. For example, a charge applying unit for applying a charge to the surface of the print belt 25 may be added. Thereby, the sheet S may be electrostatically adsorbed to the print belt 25. In this way, the print belt 25 functions as a sheet supporting member for supporting the sheet S. The print belt 25 is manufactured from a single belt-like PET sheet wound in a roll shape. PET is an abbreviation for polyethylene terephthalate. A plurality of suction holes are formed in the PET sheet. Next, the PET sheet is cut so that the length of the PET sheet becomes a predetermined length. The front end and the rear end of the PET sheet are joined by laser welding. Thereby, an endless print belt 25 is manufactured.

[0025] (3) Belt Unit FIG. 3 shows the belt unit 2200. The print belt 25 is stretched over the stretching rollers 21 to 24. In particular, the stretching roller 21 is a driving roller that rotationally drives the print belt 25. The rotation axis of the stretching roller 21 is rotatably supported by a bearing 40a. The motor M2a moves the stretching roller 21 in the X direction by moving the bearing 40a in the X direction.

[0026] The stretching roller 22 is a tension roller that stretches the print belt 25 by pressing the print belt 25 from the inner peripheral surface side to the outer peripheral surface side. The stretching roller 23 is a steering roller. The motor M1 moves one shaft end of the stretching roller 23 and tilts the stretching roller 23. Thereby, the meandering of the print belt 25 is suppressed.

[0027] The stretching roller 24 is a driven roller that rotates following the rotation of the print belt 25. The rotation axis of the stretching roller 24 is rotatably supported by a bearing 40b. The motor M2b moves the stretching roller 24 in the X direction by moving the bearing 40b in the X direction.

[0028] The sheet S is adsorbed to the image forming surface 26 and is integrated with the print belt 25. Therefore, by accurately positioning the image forming surface 26, the accuracy (e.g., squareness) of the image formed on the sheet S is also improved. The two stretching rollers 21 and 24 form the image forming surface 26.

[0029] The belt sensor 30a is arranged near the stretching roller 21 and detects the detection shape 35 arranged at the end of the print belt 25. The belt sensor 30b is arranged near the stretching roller 24 and detects the detection shape 35 arranged at the end of the print belt 25. The detection results of the belt sensors 30a and 30b are used to specify the passing position of the end of the print belt 25 and the conveyance direction of the print belt 25. Based on the detection results of the belt sensors 30a and 30b, the motors M2a and M2b independently move the stretching rollers 21 and 24 in the X direction, thereby adjusting the position of the print belt 25.

[0030] The detection shape 35 may be, for example, a plurality of holes having a major axis of about 1 mm. The plurality of holes may be provided at intervals of about 6 mm over one circumference of the print belt 25. The line connecting the center positions of the plurality of holes is a straight line, and this straight line is parallel to the end of the print belt 25. The belt sensors 30a and 30b may be contact image sensors (CIS). The center positions of the holes read by the belt sensors 30a and 30b may be calculated. If the center position of the hole detected by the belt sensor 30a in the X direction coincides with the center position of the hole detected by the belt sensor 30b, the print belt 25 is parallel to the Y direction. Also, when the print belt 25 is moved in the X direction, the amount of movement of the center position of the hole detected by the belt sensor 30a in the X direction and the amount of movement of the center position of the hole detected by the belt sensor 30b are calculated. If the two amounts of movement are equal, it means that the print belt 25 has moved parallel in the X direction. By intentionally making the two amounts of movement different, it is possible to change the conveyance direction of the print belt 25.

[0031] (4) Recording head FIG. 4 is a perspective view of the recording head 10. As shown in FIG. 4, the recording head 10 has a plurality of nozzle plates 103 arranged side by side in the X direction. Each of the plurality of nozzle plates 103 has a plurality of nozzles for discharging ink (droplets). The positioning portions 101L and 101R are arranged at both ends of the recording head 10 and position the recording head 10 in the X, Y, and Z directions. A first contact portion 101a is provided on the bottom surface of the positioning portion 101L. The first contact portion 101a has a concave portion with a conical slope. A second contact portion 101b and a third contact portion 101c are provided on the bottom surface of the positioning portion 101R. The second contact portion 101b has a groove portion. The Z-Y cross section of the groove portion is substantially V-shaped. The third contact portion 101c has a flat portion.

[0032] At one end of the recording head 10 in the longitudinal direction (X direction), a first pin 107a extending in the X direction is provided. At the other end of the recording head 10 in the longitudinal direction (X direction), a second pin 107b and a third pin 107c extending in the X direction are provided. The straight line connecting the center of the first contact portion 101a and the center of the second contact portion 101b is parallel to the arrangement direction of the plurality of nozzle plates 103.

[0033] (5) Support structure of the recording head FIG. 5(A) shows four recording heads 10 and a positioning member 811a provided on the housing 81 of the belt unit 2200. FIG. 5(B) shows a state where the four recording heads 10 are positioned with respect to the housing 81. The positioning member 811a has a shape corresponding to the first contact portion 101a. In this example, the positioning member 811a is a hemispherical convex portion. As the recording head 10 descends toward the housing 81, the positioning member 811a fits into the first contact portion 101a. Thereby, the recording head 10 is positioned with respect to the housing 81.

[0034] FIG. 6(A) shows one end side of the recording head 10. FIG. 6(B) shows the other end side of the recording head 10. FIG. 6(C) is a perspective view of the recording head 10. The head holders 106R and 106L are support members that support the recording head 10. As the head holders 106R and 106L descend from the retracted position toward the printing position, the recording head 10 also descends. Thereby, the first contact portion 101a and the positioning member 811a fit together. Also, the second contact portion 101b fits into a positioning member 811b provided on the housing 81. The third contact portion 101c abuts or engages with the positioning member 811c. Thereby, both ends of the recording head 10 in the longitudinal direction are firmly positioned.

[0035] The head holder 106R is provided with an opening 161 having an area larger than the cross-sectional shape of the first pin 107a. At the bottom of the opening 161, a first groove portion 161a for engaging the first pin 107a of the recording head 10 is provided.

[0036] The head holder 106L is provided with substantially U-shaped openings 162 and 163. A second groove portion 162a is provided at the bottom of the opening 162. A third groove portion 163a is provided at the bottom of the opening 163. The second pin 107b of the recording head 10 engages with the second groove portion 162a. The third pin 107c of the recording head 10 engages with the third groove portion 163a.

[0037] In this way, by engaging the first pin 107a with the first groove portion 161a, the second pin 107b with the second groove portion 162a, and the third pin 107c with the third groove portion 163a, the recording head 10 is positioned in the Z direction and the Y direction.

[0038] (6) Inline scanner FIG. 7 shows the inline scanner 1. The inline scanner 1 is an image reading device provided on the downstream side of the recording head 10 in the conveyance direction (Y direction) of the sheet S. The inline scanner 1 can read an image formed on the sheet S conveyed by the print belt 25.

[0039] Inside the housing 2 of the inline scanner 1, an optical box 3, a reading glass 4, and an image processing board 7 are provided. The optical box 3 reads the shape of the sheet S itself and the test image through the reading glass 4. The optical box 3 is movable in the Y direction. The reading position 5 of the optical box 3 can move between the position for reading the sheet S and the shading sheet 6. The reading result of the shading sheet 6 is used to perform shading correction on the image acquired by the optical box 3. The shading sheet 6 is sometimes called a white reference plate. The inline scanner 1 may be positioned in contact with a positioning member provided on the housing 81 of the belt unit 2200, like the recording head 10.

[0040] Incidentally, the optical box 3 has a reduction optical system including a CMOS type image sensor and a lens. CMOS is an abbreviation for complementary metal oxide semiconductor. When the ambient temperature of the in-line scanner 1 rises, the temperature of the optical box 3 also rises. Due to this temperature rise, thermal expansion occurs in the holding member that holds the lens in the optical box 3 or in the lens itself. As a result, the reading position 5 of the optical box 3 changes. In particular, the reading positions 5 arranged linearly in the X direction may become non-orthogonal to the conveyance direction. This can occur when the amount of temperature change at each position of the optical box 3 in the X direction is not uniform. Therefore, it may be necessary to correct the inclination of the image read by the in-line scanner 1 (hereinafter referred to as the inclination of the in-line scanner 1).

[0041] (7) Position correction and magnification correction FIG. 8 shows position correction and magnification correction in the inkjet recording apparatus 100. The position correction includes, for example, sheet position correction and image position correction. The sheet position correction means correcting the position (conveyance position) of the sheet S with respect to the recording head 10 in the width direction (X direction) of the print belt 25. The image position correction means correcting the position of the image 800 with respect to the sheet S (the position in the main scanning direction and the position in the sub-scanning direction). The magnification correction means correcting the magnification in the sub-scanning direction and the magnification in the main scanning direction of the image 800. These correction processes are executed based on correction values obtained by reading a test image described later by the in-line scanner 1.

[0042] (8) Test image FIG. 9 shows a sheet S on which a test image is formed. The test image may be four cross marks respectively provided near the four corners of the sheet S. It may be used to correct the conveyance position of the sheet S with respect to the recording head 10. This test image may be used to correct the writing position in the main scanning direction with respect to the sheet S and the writing position in the sub-scanning direction with respect to the sheet S. This test image may be used to adjust the magnification in the sub-scanning direction of the image and the magnification in the main scanning direction of the image. Further, the test image can also be used to obtain the inclination θ of the in-line scanner 1. Here, the inclination θ of the in-line scanner 1 is used to correct the image read by the in-line scanner 1. The test image is printed on the sheet S by the recording head 10 provided most downstream in the conveyance direction (Y direction) in which the sheet S is conveyed. The test image described in the present embodiment is printed by the black recording head 10.

[0043] According to FIG. 9, the coordinates of the first corner of the sheet S are defined as (X1, Y1). The coordinates of the second corner of the sheet S are defined as (X2, Y2). The coordinates of the third corner of the sheet S are defined as (X3, Y3). The coordinates of the fourth corner of the sheet S are defined as (X4, Y4). The coordinates of the first mark are defined as (X5, Y5). The coordinates of the second mark are defined as (X6, Y6). The coordinates of the third mark are defined as (X7, Y7). The coordinates of the fourth mark are defined as (X8, Y8).

[0044] Note that the direction parallel to the conveyance direction (Y direction) may be called the sub-scanning direction. The X direction orthogonal to the conveyance direction may also be called the main scanning direction. (X1, Y1) to (X8, Y8) are calculated from the reading result of the in-line scanner 1 of the sheet S on which the test image is formed.

[0045] Sheet position correction, image position correction, and magnification correction are performed from (X1, Y1) to (X8, Y8). However, since these specific correction methods are already known, the description thereof is omitted here.

[0046] (9) Method for obtaining the inclination When the in-line scanner 1 is inclined with respect to the conveyance direction of the sheet S, the reading result of the in-line scanner 1 also becomes inclined. The in-line scanner 1 can reduce the influence of the inclination θ in the reading result by rotating the reading result (read image) according to the inclination θ. This rotation process may be executed in the in-line scanner 1 or may be executed in an image processing apparatus provided outside the in-line scanner 1.

[0047] FIG. 10 shows a method for obtaining the inclination θ. Here, it is assumed that the orthogonality of the image is ensured by adjusting the conveyance direction of the print belt 25 and the attachment angle of the recording head 10 in advance. According to FIG. 10, it shows that the in-line scanner 1 is inclined with respect to the direction orthogonal to the conveyance direction of the sheet S. The inclination is expressed as θ.

[0048] The correction chart S0 is a sheet S on which four test images are accurately formed with respect to the sheet S. FIG. 11 shows the reading result (read image) of the correction chart S0.

[0049] The print belt 25 conveys the correction chart S0, and the in-line scanner 1 reads the correction chart S0. The inclination θ of the in-line scanner 1 is measured from the coordinates of the four test images included in the reading result of the correction chart S0. In this case, the inclination θ which is a correction value is calculated from the following formula.

[0050] θ = (θa + θb) / 2 ···(1) As shown in FIG. 11, the inclination θa is the inclination of the in-line scanner 1 obtained from the two test images on the downstream side (front end side) in the conveyance direction. The inclination θb is the inclination of the in-line scanner 1 obtained from the two test images on the upstream side (rear end side) in the conveyance direction. The inclinations θa and θb are obtained from the following formulas.

[0051] θa = arctan((Y6 - Y5) / (X6 - X5)) ···(2) θa represents the measured value of the inclination of the image on the leading edge side in the conveyance direction of the sheet S.

[0052] θb = arctan((Y8 - Y7) / (X8 - X7)) ···(3) θb represents the measured value of the inclination of the image on the trailing edge side in the conveyance direction of the sheet S. In this way, the inclination θ is calculated from the statistical values (e.g., average value) of the measured values θa and θb. For the sake of simplifying the calculation, the following calculation may be used. That is, the inclination θ may be calculated from two test images on the leading edge side or two test images on the trailing edge side.

[0053] θ = θa ···(4) θ = θb ···(5) The inclination θ obtained in this way is used as the correction value for the inclination of the in-line scanner 1. The inclination θ obtained using equation (1) is stored in the storage device of the in-line scanner 1 or the like. θ may be obtained by installing the inkjet recording device 100 in the customer's living room and forming a test image on the sheet S. In this case, the sheet S may be called a correction chart. Alternatively, as described in the second embodiment, θ may be obtained using the non-discharge detection chart printed on the sheet S to detect non-discharge of ink.

[0054] (10) Controller FIG. 12 shows the controller 1200 of the inkjet recording apparatus 100. The controller 1200 has a CPU 1201 and a memory 1210. The CPU 1201 realizes various functions by executing a control program stored in the memory 1210. All or part of the functions realized by the CPU 1201 may be realized by other hardware circuits such as a DSP, an ASIC, or an FPGA. DSP is an abbreviation for a digital signal processor. ASIC is an abbreviation for an application-specific integrated circuit. FPGA is an abbreviation for a field-programmable gate array. The memory 1210 is a storage device that may include a volatile memory (e.g., RAM), a non-volatile memory (e.g., ROM), a hard disk drive (HDD), and a solid state drive (SSD). The controller 1200 may be connected to an input device 1451 for receiving user input and a display device 1452 for displaying information to the user.

[0055] The test unit 1202 controls the inkjet recording apparatus 100 to form a test image on the sheet S. The image acquisition unit 1203 controls the in-line scanner 1 to read the test image formed on the sheet S. Thereby, the image acquisition unit 1203 acquires the reading result of the test image. The correction unit 1204 obtains a position correction value of the sheet S, a correction value of the image position, and a correction value of the magnification from the reading result of the test image, and executes position correction and magnification correction according to these correction values. The inclination acquisition unit 1205 acquires the inclination θ of the in-line scanner 1 based on the reading result of the test image.

[0056] The recording unit 2300 has a head control unit 1230. The head control unit 1230 controls the recording head 10 according to the image signal output from the CPU 1201. The head control unit 1230 drives the motor M3 according to the control command output from the CPU 1201 to adjust the mounting angle of the recording head 10. The motor M3 is an option. Also, the head control unit 1230 adjusts the ejection timing of the recording head 10 or selects which nozzle among the plurality of nozzles included in the recording head 10 to use according to the control command output from the correction unit 1204. Thereby, the image position is corrected.

[0057] The belt unit 2200 has a belt control unit 1220. The belt control unit 1220 controls the motor M1 to reduce the meandering of the print belt 25. The belt control unit 1220 controls the belt sensors 30a and 30b to detect the conveyance direction of the print belt 25. The belt control unit 1220 may control the motors M2a and M2b according to the control command from the CPU 1201. Thereby, the conveyance direction of the print belt 25 may be corrected, and the conveyance position of the sheet S with respect to the recording head 10 may be corrected.

[0058] FIG. 13 shows the details of the correction unit 1204. The sheet position correction unit 1301 calculates, for example, a correction value for the position of the sheet S so that the coordinates (X1, Y1) in the reading result of the sheet S match the target coordinates. Note that the use of the coordinates (X2, Y2), (X3, Y3), and the coordinates (X4, Y4) also improves the accuracy of the position correction. The belt adjustment unit 1306 transmits a control command to the belt control unit 1220 so as to control the conveyance direction of the print belt 25 according to the correction value of the sheet position.

[0059] The image position correction unit 1302 corrects the sub-scanning position and the main-scanning position of the image based on the coordinates (X5, Y5) obtained from the reading result of the test image. For example, the image position correction unit 1302 corrects the writing position of the image in the main-scanning direction and the writing position of the image in the sub-scanning direction so that the coordinates (X5, Y5) become the target coordinates. The writing position of the image in the main-scanning direction is realized by correcting the conveyance position of the sheet S or by selecting the nozzle to be ejected from among the plurality of nozzles in the recording head 10. That is, the correction value of the image position is set in the bed adjustment unit 1307 or the timing adjustment unit 1308. Alternatively, the correction of the image position may be realized by deforming the original image by the image deformation unit 1309. In this case, the correction value of the image position is set in the image deformation unit 1309.

[0060] The magnification correction unit 1303 corrects the magnification of the image in the main-scanning direction and the magnification of the image in the sub-scanning direction. For example, the magnification correction unit 1303 measures the current sub-scanning magnification and the current main-scanning magnification from the reading result of the test image. The magnification correction unit 1303 obtains a correction value for the magnification in the main-scanning direction from the error between the measured value in the main-scanning direction and the target value in the main-scanning direction. Similarly, the magnification correction unit 1303 obtains a correction value for the magnification in the sub-scanning direction from the error between the measured value in the sub-scanning direction and the target value in the sub-scanning direction. The image deformation unit 1309 deforms the original image based on the correction value for the magnification in the main-scanning direction and the correction value for the magnification in the sub-scanning direction. Thereby, the magnification in the main-scanning direction and the magnification in the sub-scanning direction are corrected. Thus, pre-deforming the original image (document image) may be called pre-distortion.

[0061] FIG. 14 shows the details of the inclination acquisition unit 1205. The inclination acquisition unit 1205 acquires the inclination θ from the reading result of the test image formed on the sheet S. Note that the inclination acquisition unit 1205 may calculate the inclination θ using, for example, equation (1).

[0062] The θa calculation unit 1402 calculates the inclination θa from the test image reading result by the in-line scanner 1. For example, the θa calculation unit 1402 may calculate the inclination θa using the formula (2).

[0063] The θb calculation unit 1403 calculates the inclination θb from the test image reading result by the in-line scanner 1. For example, the θb calculation unit 1403 may calculate the inclination θb using the formula (3).

[0064] The statistics unit 1404 obtains a statistical value (e.g., the average value of the inclination θa and the inclination θb) based on the inclination θa and the inclination θb. The θ calculation unit 1405 obtains the inclination θ (correction value θ) from the statistical values of the inclination θa and the inclination θb. For example, the θ calculation unit 1405 may apply the formula (1) to the statistical value of the inclination θa and the statistical value of the inclination θb to calculate the inclination θ.

[0065] FIG. 15 shows the image processing board 7 of the in-line scanner 1. The image processor 1502 is composed of a CPU or an ASIC, etc. The image processor 1502 generates image data from the reading result of the in-line scanner 1 and transmits it to the controller 1200. The image processor 1502 has an image data generation unit 1503 and an inclination correction unit 1504. The image data generation unit 1503 generates image data from the image signal output from the image sensor 1501. The inclination correction unit 1504 reversely rotates the image data by the inclination θ based on the inclination θ acquired by the inclination acquisition unit 1205 and stored in the memory 1505. Thereby, the influence of the inclination θ in the image data is reduced. Since the influence of the inclination θ is reduced from the reading result of the test image, the reading accuracy of the test image is improved.

[0066] (11) Flowchart FIG. 16 is a flowchart showing a control method executed by the CPU 1201.

[0067] In S1601, the CPU 1201 (test unit 1202) controls the inkjet recording apparatus 100 to form a test image on the sheet S. For example, the feeding module 1000 starts feeding and transporting the sheet S according to the feeding command from the CPU 1201. The printing module 2000 forms a test image on the sheet S while transporting the sheet S according to the command from the CPU 1201.

[0068] In S1602, the CPU 1201 (image acquisition unit 1203) reads the test image using the in-line scanner 1. As a result, the reading result (image data) of the test image is acquired.

[0069] In S1603, the CPU 1201 (correction unit 1204) acquires the coordinates of the test image based on the reading result of the test image. As shown in FIG. 8, the coordinates (X5, Y5) to (X8, Y8) of the four test images are acquired.

[0070] In S1604, the CPU 1201 (θa calculation unit 1402, θb calculation unit 1403) acquires the inclinations θa and θb from the coordinates (X5, Y5) to (X8, Y8) of the four test images. For example, the inclinations θa and θb may be calculated using equations (2) and (3).

[0071] In S1605, the CPU 1201 (statistics unit 1404) performs statistical processing on the inclinations θa and θb. As shown in equation (1), the statistical processing may be processing to obtain the average values of the inclinations θa and θb. Further, when there are reading results of N sheets S, the average value of the N average values obtained from the N sheets S may be further obtained.

[0072] In S1606, the CPU 1201 (θ calculation unit 1405) determines the inclination θ based on the statistical values of the inclinations θa and θb. This is as described with respect to equation (1).

[0073] In S1607, the CPU 1201 (tilt acquisition unit 1205) stores the tilt θ in the memory 1505 of the in-line scanner 1, and ends the acquisition process of the tilt θ of the in-line sensor 1. Next, the sheet position correction performed by the CPU 1201 using the tilt θ stored in the memory 1505 will be described. While continuously forming images, the CPU 1201 reads the shape of the sheet S itself using the in-line scanner 1. The CPU 1201 rotates the reading result (image data) of the shape of the sheet S itself based on the tilt θ stored in the memory 1505. Then, the CPU 1201 corrects the position (conveying position) of the sheet S conveyed to the recording head 10 based on the rotated reading result (image data) of the shape of the sheet S itself. Note that the configuration for correcting the position (conveying position) of the sheet S conveyed to the recording head 10 may be a known configuration that corrects the conveying position of the sheet S using a roller, for example. Here, the description of the detailed configuration for correcting the position (conveying position) of the sheet S conveyed to the recording head 10 is omitted.

[0074] According to this embodiment, the tilt θ of the in-line scanner 1 is obtained from the test image formed on the sheet S. Thereby, it becomes possible to correct the tilt of the reading means. Further, in the position correction and the magnification correction, the influence of the tilt of the in-line scanner 1 is reduced. As a result, the deviation of the printing position with respect to the sheet S is also reduced.

[0075] <Example 2> In the first embodiment, the tilt θ (correction value θ) of the in-line scanner 1 is obtained from a dedicated correction chart S0. However, this is only an example. In the second embodiment, a case where a test image for other purposes and a test image for obtaining the tilt θ (correction value θ) of the in-line scanner 1 are formed on the same sheet S will be described. Note that the description of matters common to the first embodiment in the second embodiment is incorporated by reference to the description of the first embodiment. Therefore, hereinafter, the specific parts of the second embodiment will be described in detail.

[0076] (1) Correction chart FIG. 17 shows a non-discharge detection chart S1 with two test images for obtaining the inclination θ (correction value θ) of the in-line scanner 1. The non-discharge detection chart S1 includes a test image 1710 for detecting clogging of a plurality of nozzles included in the recording head 10.

[0077] In addition to the test image 1710 for non-discharge detection, the non-discharge detection chart S1 has two test images 1717 and 1718 for obtaining the inclination θ (correction value θ) of the in-line scanner 1. In this case, the inclination θb is obtained from the coordinates (X7, Y7) and (X8, Y8) of the two test images 1717 and 1718 included in the read image of the in-line scanner 1. Also, the inclination θ (correction value θ) of the in-line scanner 1 is equal to the inclination θb. Thus, two test images 1717 and 1718 for obtaining the inclination θ (correction value θ) of the in-line scanner 1 may be formed in the empty area on the rear end side of the non-discharge detection chart S1 in the conveyance direction.

[0078] FIG. 18 shows another non-discharge detection chart S1 with four test images for obtaining the inclination θ (correction value θ) of the in-line scanner 1. In this example, in addition to the test image 1710 for non-discharge detection, the non-discharge detection chart S1 has four test images 1717, 1718, 1805, and 1806 for obtaining the inclination θ (correction value θ) of the in-line scanner 1. That is, by shifting the formation position of the test image 1710 for non-discharge detection in the non-discharge detection chart S1, an empty area is secured on the front end side of the non-discharge detection chart S1 in the conveyance direction. Then, the test images 1805 and 1806 are formed in this empty area. Thereby, the inclination θa is obtained from the coordinates (X5, Y5) and (X6, Y8) of the two test images 1805 and 1806 included in the read image of the in-line scanner 1. Further, similarly to the first embodiment, the CPU 1201 obtains the inclination θ (correction value θ) of the in-line scanner 1 from the inclination θa and the inclination θb.

[0079] (2) Flowchart (2-1) Case where the non-discharge detection chart has two test images FIG. 19 is a flowchart showing a method for obtaining the inclination θ (correction value θ) of the in-line scanner 1 using the non-ejection detection chart S1 shown in FIG. 17.

[0080] In S1901, the CPU 1201 determines whether to start non-ejection detection based on an instruction input from the input device 1451. If the instruction indicates to start non-ejection detection, the CPU 1201 proceeds from S1901 to S1902. If the instruction does not indicate to start non-ejection detection, the CPU 1201 skips each process from S1902 to S1907.

[0081] In S1902, the CPU 1201 controls the inkjet recording device 100 to form a non-ejection detection chart S1 with test images 1717 and 1718 on the sheet S.

[0082] In S1903, the CPU 1201 controls the in-line scanner 1 to read the test images 1717 and 1718 of the non-ejection detection chart S1. As a result, the reading results (read images) of the test images 1717 and 1718 are obtained.

[0083] In S1904, the CPU 1201 obtains the coordinates of the two test images 1717 and 1718 from the reading result (read image) of the test image. As illustrated in FIG. 17, (X7, Y7) and (X8, Y8) are obtained.

[0084] In S1905, the CPU 1201 obtains the inclination θb based on the coordinates of the test image. For example, the CPU 1201 may calculate the inclination θb according to equation (3).

[0085] In S1906, the CPU 1201 obtains the correction value θ, which is the inclination of the in-line scanner 1, based on the inclination θb. For example, the CPU 1201 substitutes the inclination θb into the correction value θ.

[0086] In S1907, the CPU 1201 stores the correction value θ in the memory 1210.

[0087] Note that by repeating a series of processes from S1903 to S1907 multiple times, a plurality of correction values θ may be calculated, and an average value of the plurality of correction values θ may be obtained. Thereby, the influence of the reading error by the in-line scanner 1 may be reduced.

[0088] (2-2) Case where the non-ejection detection chart has four test images FIG. 20 is a flowchart showing a method of obtaining the inclination θ (correction value θ) of the in-line scanner 1 using the non-ejection detection chart S1 shown in FIG. 18.

[0089] In S2001, the CPU 1201 determines whether or not to start non-ejection detection based on an instruction input from the input device 1451. If the instruction indicates to start non-ejection detection, the CPU 1201 proceeds from S2001 to S2002. If the instruction does not indicate to start non-ejection detection, the CPU 1201 skips each process after S2002.

[0090] In S2002, the CPU 1201 controls the inkjet recording device 100 to form a non-ejection detection chart S1 with test images 1717, 1718, 1805, and 1806 on the sheet S.

[0091] In S2003, the CPU 1201 controls the in-line scanner 1 to read the test images 1717, 1718, 1805, and 1806 of the non-ejection detection chart S1. Thereby, reading results (read images) of the test images 1717, 1718, 1805, and 1806 are obtained.

[0092] Thereafter, for the test images 1717, 1718, 1805, and 1806, S1603 to S1607 described in the first embodiment are executed. Then, the CPU 1201 generates correction data (correction conditions) for correcting the image formed on the sheet based on the corrected image data. Further, based on the correction data (correction conditions), the CPU 1201 performs an affine transformation on the image formed on the sheet by image processing so as to correct the geometric characteristics of the image formed on the sheet.

[0093] According to the second embodiment as described above, the process of obtaining the inclination θ (correction value θ) of the in-line scanner 1 is executed in parallel with the non-ejection detection process. As a result, while suppressing a decrease in the productivity of the inkjet recording apparatus 100, the inclination θ (correction value θ) of the in-line scanner 1 can be obtained.

[0094] <Technical idea derived from the embodiment> (Item 1) The print belt 25 is an example of a conveying unit that sucks the sheet S and conveys it in a predetermined conveying direction. The recording head 10 is an example of a forming unit that forms an image on the sheet S conveyed by the conveying unit. The in-line scanner 1 is an example of a reading unit that reads the first test image from the sheet S formed with the first test image by the recording head 10 and conveyed by the print belt 25. The CPU 1201 and the correction unit 1204 are an example of a correction unit that corrects the inclination of the reading unit with respect to the conveying unit based on the reading result of the first test image. As described above, according to this embodiment, a rotating body having a position reference member as described in Patent Document 1 is not required. Therefore, in this embodiment, it is possible to correct the inclination of the reading unit by a simpler method. Further, the shape of the image in the image forming apparatus is maintained inexpensively and with high accuracy. (Item 2) The CPU 1201 and the inclination acquisition unit 1205 are an example of an acquisition unit that acquires the inclination of the reading unit based on at least two first test images formed on the sheet. In this way, by using the two first test images formed on the sheet S, the inclination θ of the reading unit can be accurately acquired. (Item 3) The CPU 1201 and the θa calculation unit 1402 are an example of first calculation means for calculating a first inclination θa on the leading edge side of the sheet S based on two first test images formed on the leading edge side of the sheet S in the conveyance direction of the sheet S. The CPU 1201 and the θa calculation unit 1402 are an example of second calculation means for calculating a second inclination θb on the trailing edge side of the sheet S based on two first test images formed on the trailing edge side of the sheet S in the conveyance direction of the sheet S. The θ calculation unit 1405 is an example of third calculation means for calculating the inclination θ of the reading means based on the first inclination and the second inclination. As a result, since the inclination θ (correction value θ) is accurately calculated, the alignment between the in-line scanner 1 and the print belt 25 is accurately adjusted. (Item 4) The coordinates (X5, Y5) and (X6, Y6) are an example of a first coordinate and a second coordinate for two first test images formed on the leading edge side of the sheet S. The θa calculation unit 1402 may calculate the first inclination θa by calculating the arctangent between the first coordinate and the second coordinate. As a result, since the inclination θ (correction value θ) is accurately calculated, the alignment between the in-line scanner 1 and the print belt 25 is accurately adjusted. (Item 5) The coordinates (X7, Y7) and (X8, Y8) are an example of a third coordinate and a fourth coordinate for two first test images formed on the trailing edge side of the sheet S. The θa calculation unit 1402 may calculate the second inclination θb by calculating the arctangent between the third coordinate and the fourth coordinate. As a result, the inclination θ between the in-line scanner 1 and the print belt 25 will be accurately obtained. (Item 6) The θ calculation unit 1405 may calculate the statistical value (e.g., average value) of the first inclination and the second inclination as the inclination of the reading means. As a result, since the influence of the reading error is reduced, the inclination θ between the in-line scanner 1 and the print belt 25 will be accurately obtained. (Item 7) As described in Example 2, the recording head 10 may form, together with the first test image, a second test image for detecting image formation defects of the recording head 10 on the sheet S. Thereby, since the common sheet S can be used for both the inclination correction and the non-ejection detection, the number of sheets S is reduced. Further, since the inclination θ can be obtained in parallel with the non-ejection detection, the processing time is reduced. (Item 8) As illustrated in FIG. 17, the recording head 10 may form at least two first test images on the rear end side of the sheet S and also form a second test image for detecting image formation defects on the sheet S. Thereby, since the common sheet S can be used for both the inclination correction and the non-ejection detection, the number of sheets S is reduced. Further, since the inclination θ can be obtained in parallel with the non-ejection detection, the processing time is reduced. (Item 9) As illustrated in FIG. 18, the recording head 10 may form at least two first test images on the front end side of the sheet S and also form a second test image for detecting image formation defects on the sheet. Thereby, since the common sheet S can be used for both the inclination correction and the non-ejection detection, the number of sheets S is reduced. Further, since the inclination θ can be obtained in parallel with the non-ejection detection, the processing time is reduced. (Item 10) The CPU 1201 and the inclination acquisition unit 1205 may acquire the inclination θ of the reading means based on at least two first test images formed on the sheet S. (Item 11) As illustrated in FIG. 18, the recording head 10 may form at least two first test images on the front end side of the sheet S, form at least two first test images on the rear end side of the sheet S, and also form a second test image for detecting image formation defects on the sheet S. Thereby, since the common sheet S can be used for both the inclination correction and the non-ejection detection, the number of sheets S is reduced. Further, since the inclination θ can be obtained in parallel with the non-ejection detection, the processing time is reduced. Also, since four first test images are used, the calculation accuracy of the inclination θ will be improved. (Item 12) As illustrated in FIG. 11, the CPU 1201 and the correction unit 1204 may acquire the inclination θ of the reading means based on at least two first test images formed on the leading end side of the sheet S and at least two first test images formed on the trailing end side of the sheet S. (Item 13) The in-line scanner 1 may be configured to read a third test image formed on another sheet. That is, the third test image may be a test image for position correction or magnification correction. In this embodiment, the test image for obtaining the inclination θ of the in-line scanner 1 and the test image for position correction or magnification correction are common, but this is only an example. These test images may be different. The CPU 1201, the correction unit 1204, or the inclination correction unit 1504 may be configured to correct (e.g., rotate) the reading result of the third test image according to the inclination θ. Thereby, the influence of the inclination θ of the in-line scanner 1 may be reduced from the reading result of the third test image. As a result, the accuracy of various controls using the reading result of the third test image will be improved. (Item 14) The sheet position correction unit 1301 or the belt adjustment unit 1306 may function as adjustment means for adjusting the conveyance position of the print belt 25 or the sheet S based on the reading result of the third test image corrected according to the inclination θ. (Item 15) The print belt 25 is an example of an endless belt. The endless belt may be configured to be stretched over at least two rollers (e.g., tension rollers 21, 24) and rotate. The sheet S is carried and conveyed on the outer peripheral surface (e.g., image formation surface 26) of the endless belt between the first roller (e.g., tension roller 21) and the second roller (e.g., tension roller 24) among the two or more rollers. The CPU 1201 and the correction unit 1204 move at least one of the first roller or the second roller in the rotation axis direction by adjustment means (e.g., belt adjustment unit 1306, motors M2a, M2b). Thereby, the conveyance position of the print belt 25 or the sheet S may be corrected. (Item 16) The image position correction unit 1302, the magnification correction unit 1303, etc. are examples of adjustment means for adjusting the formation position of the image formed on the sheet S by the recording head 10 or the magnification of the image based on the reading result of the third test image corrected according to the inclination θ. (Item 17) As illustrated in FIG. 4, the recording head 10 is arranged along the longitudinal direction of the recording head 10 and has a plurality of nozzles that eject ink respectively. The CPU 1201, the correction unit 1204, and the timing adjustment unit 1508 may adjust the formation position of the image formed on the sheet S by adjusting the ejection timing of the plurality of nozzles. (Item 18) The CPU 1201 and the correction unit 1204 may correct the image data that is the source of the image formed by the recording head 10 based on the reading result of the third test image corrected according to the inclination θ. Thereby, the formation position of the image formed on the sheet S or the magnification of the image may be adjusted. (Item 19) The reversing unit 4200 is an example of reversing means for reversing the sheet S on which an image is formed on the first surface. The double-sided conveyance path 5300 is an example of a conveyance path for conveying the sheet S reversed by the reversing means to the conveying means. The recording head 10 forms an image on the second surface of the sheet S on which an image is formed on the first surface. By correcting the perpendicularity of the image, the front-back shift is also reduced.

[0095] The invention is not limited to the above embodiments, and various changes and modifications are possible without departing from the spirit and scope of the invention. Therefore, claims are attached to disclose the scope of the invention.

Explanation of Reference Numerals

[0096] 25: Print belt, 10: Recording head, 1: Inline scanner, 1201: CPU, 1502: Image processor

Claims

1. Conveying means for conveying a sheet in a predetermined conveying direction, Forming means for forming an image on the sheet conveyed by the conveying means, Reading means for reading a first test image formed by the forming means from the sheet conveyed by the conveying means, Correction means for correcting the inclination of the reading means with respect to the conveying means based on the reading result of the first test image, An image forming apparatus having the above.

2. The correction means, has acquisition means for acquiring the inclination of the reading means based on at least two of the first test images formed on the sheet. The image forming apparatus according to claim 1.

3. The acquisition means, has first calculation means for calculating a first inclination on the leading end side of the sheet based on two of the first test images formed on the leading end side of the sheet in the conveying direction of the sheet, has second calculation means for calculating a second inclination on the trailing end side of the sheet based on two of the first test images formed on the trailing end side of the sheet in the conveying direction of the sheet, and has third calculation means for calculating the inclination of the reading means based on the first inclination and the second inclination. The image forming apparatus according to claim 2.

4. The first calculation means is configured to calculate a first coordinate and a second coordinate for the two first test images formed on the leading end side of the sheet, and calculate the arctangent between the first coordinate and the second coordinate to calculate the first inclination. The image forming apparatus according to claim 3.

5. The second calculation means is configured to calculate a third coordinate and a fourth coordinate for the two first test images formed on the trailing end side of the sheet, and calculate the arctangent between the third coordinate and the fourth coordinate to calculate the second inclination. The image forming apparatus according to claim 3.

6. The third calculation means calculates a statistical value of the first inclination and the second inclination as the inclination of the reading means. The image forming apparatus according to claim 3.

7. The forming means forms a second test image for detecting an image forming defect of the forming means on the sheet together with the first test image. The image forming apparatus according to claim 1.

8. The forming means forms at least two of the first test images on the rear end side of the sheet, and forms a second test image for detecting a defective image formation of the forming means on the sheet, according to the image forming apparatus of claim 1.

9. The forming means forms at least two of the first test images on the front end side of the sheet, and forms a second test image for detecting a defective image formation of the forming means on the sheet, according to the image forming apparatus of claim 1.

10. The correction means has an acquisition means for acquiring the inclination of the reading means based on at least two of the first test images formed on the sheet, according to the image forming apparatus of claim 8 or 9.

11. The forming means forms at least two of the first test images on the front end side of the sheet, forms at least two of the first test images on the rear end side of the sheet, and forms a second test image for detecting a defective image formation of the forming means on the sheet, according to the image forming apparatus of claim 1.

12. The correction means has an acquisition means for acquiring the inclination of the reading means based on at least two of the first test images formed on the front end side of the sheet and at least two of the first test images formed on the rear end side of the sheet, according to the image forming apparatus of claim 11.

13. The reading means is configured to read a third test image formed on another sheet, The correction means is configured to correct the reading result of the third test image according to the inclination of the reading means, according to the image forming apparatus of claim 1.

14. has an adjustment means for adjusting the conveyance position of the conveyance means based on the reading result of the third test image corrected by the correction means according to the inclination of the reading means, according to the image forming apparatus of claim 13.

15. The conveyance means includes an endless belt, The endless belt is configured to be stretched over at least two rollers and rotate, The sheet is configured to be carried while being supported on an outer peripheral surface of the endless belt between a first roller and a second roller among the two or more rollers. The image forming apparatus according to claim 14, wherein the correction means adjusts the conveyance position of the endless belt by moving at least one of the first roller and the second roller in the axial direction of the rotation axis by the adjustment means.

16. The image forming apparatus according to claim 13, further comprising adjustment means configured to adjust a formation position of an image formed on a sheet by the forming means or a magnification of the image based on a reading result of the third test image corrected by the correction means according to the inclination of the reading means.

17. The forming means is arranged along the longitudinal direction of the forming means and has a plurality of nozzles that each eject ink. The image forming apparatus according to claim 16, wherein the adjustment means adjusts the formation position of the image formed on the sheet by the forming means by adjusting the ejection timing of the plurality of nozzles.

18. The image forming apparatus according to claim 16, wherein the adjustment means corrects image data serving as a basis for the image formed by the forming means based on a reading result of the third test image corrected by the correction means according to the inclination of the reading means, thereby adjusting the formation position of the image formed on the sheet by the forming means or the magnification of the image.

19. An inversion means for inverting a sheet on which an image is formed on a first surface by the forming means. A conveyance path for conveying the sheet inverted by the inversion means to the conveyance means, and The image forming apparatus according to claim 1, wherein the forming means forms an image on a second surface of the sheet on which the image is formed on the first surface.

Images