Image forming device

Abstract

To enable flushing to be properly executed, even if a conveying belt is displaced in a main scanning direction in performing the flushing through flushing-opening parts formed in the conveying belt.SOLUTION: A conveying belt 2 comprises a plurality of flushing-opening parts 31 and a sensing hole 32. The plurality of flushing-opening parts 31 are arranged along a main scanning direction at least in two lines. A discharge timing control part makes a belt sensor 29 detect a position of the sensing hole 32 in the main scanning direction (a), identifies the flushing-opening part 31 corresponding to a nozzle, on the basis of the position of the sensing hole 32 in the main scanning direction (b), and makes a print engine execute flushing of the nozzle, at a timing corresponding to the identification of the flushing-opening part 31.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] In inkjet recording devices such as inkjet printers, the ink may thicken due to drying, causing the nozzles of the recording head to become clogged. Therefore, flushing is performed, in which the thickened ink is ejected and discarded. In one image forming device, holes corresponding to the size of the unit recording heads in the recording heads are provided in the conveyor belt, and ink is ejected through the holes to perform flushing (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-96116 Summary of the Invention [Problem to be solved by the invention]

[0004] When the conveyor belt rotates, it may be displaced in the main scanning direction (the direction perpendicular to the conveying direction, i.e., the width direction of the conveyor belt). If the conveyor belt is displaced in the main scanning direction, the ink ejected by flushing may not be accurately discarded downward through the holes, but may hit the conveyor belt, causing the conveyor belt to become dirty.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an image forming device that can properly perform flushing even when the conveying belt is displaced in the main scanning direction when flushing is performed through a flushing opening formed in the conveying belt. [Means for solving the problem]

[0006] The image forming apparatus according to the present invention includes a conveyor belt for conveying a print sheet, a print engine having a plurality of nozzles arranged in a main scanning direction and for ejecting ink from the nozzles onto the print sheet, and an ejection timing control unit for controlling the ink ejection timing of the print engine. The conveyor belt includes a plurality of flushing openings and detection holes, and the plurality of flushing openings are arranged in at least two rows along the main scanning direction. The ejection timing control unit (a) detects the positions of the detection holes in the main scanning direction with a sensor, (b) identifies the flushing openings corresponding to the nozzles based on the positions of the detection holes in the main scanning direction, and (c) causes the print engine to perform flushing of the nozzles at the timing corresponding to the flushing openings. The ink jet head further includes the following configuration (A) or (B): (A) the ejection timing control unit (a) detects the size of the detection hole with the sensor, and (b1) if the detected size matches a predetermined reference value, causes the print engine to execute flushing of the nozzle at a timing corresponding to the flushing opening, and (b2) if the detected size does not match the predetermined reference value, causes the print engine to not execute flushing of the nozzle. (B) The ejection timing control unit does not attempt to detect the detection hole from the timing at which the position of the detection hole is detected until a detection range set for a timing after a detection period corresponding to the arrangement period of the detection holes arrives, but instead attempts to detect the detection hole within the detection range. [Effects of the Invention]

[0007] According to the present invention, an image forming apparatus can be obtained that can properly perform flushing through a flushing opening formed in a conveyor belt even if the conveyor belt is displaced in the main scanning direction.

[0008] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a side view illustrating the mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view of the image forming apparatus shown in FIG. [Figure 3] FIG. 3 is a diagram showing an example of the conveyor belt 2 in FIG. [Figure 4] FIG. 4 is a block diagram showing the electrical configuration of the image forming apparatus 10 according to the embodiment of the present invention. [Figure 5] FIG. 5 is a diagram (1 / 2) for explaining the identification of the flushing opening 31 corresponding to each nozzle. [Figure 6] FIG. 6 is a diagram (2 / 2) for explaining the identification of the flushing opening 31 corresponding to each nozzle. [Figure 7] FIG. 7 is a diagram for explaining the determination of whether or not flushing is to be performed based on the width of the detection hole in the main scanning direction in the second embodiment. [Figure 8] FIG. 8 is a diagram for explaining the determination of whether or not flushing is performed based on the length of the detection hole in the transport direction in the second embodiment. [Figure 9] FIG. 9 is a diagram illustrating the detection range of the detection hole in the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] Embodiment 1

[0012] Fig. 1 is a side view illustrating the mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention, and Fig. 2 is a plan view of the image forming apparatus shown in Fig. 1.

[0013] The image forming apparatus 10 according to this embodiment is a device such as a printer, a copier, a facsimile machine, or a multifunction machine, and in this embodiment is equipped with a line-head inkjet color printing mechanism.

[0014] The image forming apparatus 10 shown in FIG. 1 includes a print engine 10a and a sheet transport unit 10b. The print engine 10a physically prints an image to be printed on a print sheet (such as print paper). An ink cartridge is detachably attached to the print engine 10a, and the print engine 10a performs printing using ink supplied from the ink cartridge. The sheet transport unit 10b transports the print sheet to the print engine 10a.

[0015] In this embodiment, print engine 10a is equipped with line-head type inkjet recording units 1a to 1d corresponding to four ink colors: cyan, magenta, yellow, and black, and ink is ejected onto a print sheet by inkjet recording units 1a to 1d.

[0016] As shown in Figure 2, in this embodiment, each of the inkjet recording units 1a, 1b, 1c, and 1d has one or more (three in this example) head units 11. These head units 11 are arranged along the main scanning direction and are detachable from the device body. The head unit 11 (i.e., each of the inkjet recording units 1a, 1b, 1c, and 1d) has multiple nozzles arranged in the main scanning direction, and ejects ink from the nozzles onto a print sheet.

[0017] In this embodiment, the sheet conveying section 10b includes a circular conveying belt 2 arranged opposite the print engine 10a to convey the print sheet, a drive roller 3, a driven roller 4, and a tension roller 4a around which the conveying belt 2 is suspended, an adsorption roller 5 that nips the print sheet together with the conveying belt 2, a downstream conveying belt 6, and a dryer 7.

[0018] A drive roller 3, a driven roller 4, and a tension roller 4a rotate the conveyor belt 2. The print sheet 101 conveyed from a paper feed cassette 20 (described later) is nipped by an attraction roller 5, and the nipped print sheet 101 is conveyed by the conveyor belt 2 to the printing positions of the inkjet recording units 1a-1d in order, where an image of each color is printed by the inkjet recording units 1a-1d. The sheet sensor 2a detects the passage of the print sheet, and the current position of the print sheet on the conveyance path is determined based on the detection timing. The image is then printed at the appropriate position on the print sheet. After printing, the print sheet is discharged to a discharge tray 10c or the like by a subsequent conveyor belt 6. At this time, a dryer 7 dries the print sheet on which the ink has been discharged.

[0019] 3 is a diagram showing an example of the conveyor belt 2 in FIG. 1. The conveyor belt 2 is provided with a plurality of flushing openings 31. For example, as shown in FIG. 3, a plurality of flushing openings 31 are formed in the conveyor belt 2, and the flushing openings 31 are formed in at least two rows (two rows in FIG. 3) along the main scanning direction. In other words, there are flushing openings 31 arranged at different positions in the conveying direction. Furthermore, the plurality of flushing openings 31 are arranged so as to cover the entire range of the plurality of nozzles arranged in the inkjet recording units 1a to 1d in the main scanning direction (that is, so that there are no missing portions).

[0020] In the area other than the flushing opening 31, sheet suction holes are arranged approximately uniformly at a predetermined density.

[0021] 1, ink receiving units 8a to 8d are provided below the head unit 11 of the inkjet recording units 1a to 1d. Flushing (e.g., line flushing) for each nozzle of each of the inkjet recording units 1a, 1b, 1c, and 1d is performed when one of the flushing openings 31 is located directly below the head unit 11 of the inkjet recording units 1a, 1b, 1c, and 1d, and the ink ejected from the nozzles during flushing is received by the corresponding ink receiving unit 8a, 8b, 8c, and 8d through the flushing opening 31 and is then collected in a waste ink tank.

[0022] The sheet suction units 9 are arranged along the sheet transport path at a location other than the ink receiving units 8a to 8d. A negative pressure is applied to the sheet suction units 9, causing the print sheet to adhere to the transport belt 2 through the sheet suction holes. A negative pressure lower than that applied to the sheet suction units 9 is applied to the ink receiving units 8a to 8d.

[0023] Furthermore, the sheet transport unit 10b is equipped with a paper feed cassette 20 as a paper feed source. The paper feed cassette 20 stores print sheets 101, and a lift plate 21 pushes the print sheets 101 upward to abut against a pickup roller 22. The print sheets 101 placed in the paper feed cassette 20 are picked up one by one from above by the pickup roller 22 onto a paper feed roller 23. The paper feed roller 23 is a roller that transports the print sheets 101 fed from the paper feed cassette 20 by the pickup roller 22 onto a transport path one by one.

[0024] The transport rollers 27 are rollers that transport the print sheet 101 on a predetermined transport path. When the transported print sheet 101 is detected by the resist sensor 28a, the resist rollers 28 temporarily stop the print sheet 101 and transport the print sheet 101 to the print engine 10a (specifically, to the nip position between the attraction roller 5 and the transport belt 2) at the secondary paper feed timing. The secondary paper feed timing is specified by the control unit 81, which will be described later, so that an image is formed at a specified position on the print sheet 101.

[0025] Furthermore, a belt sensor 29 is provided above the conveyor belt 2. The belt sensor 29 is an optical sensor, for example, a line sensor arranged along the main scanning direction, and for example, irradiates light from an LED or the like onto the conveyor belt 2, detects the reflected light with each light-receiving element such as a photodiode, and identifies the color at each position within a predetermined range in the main scanning direction.

[0026] The conveyor belt 2 also has a detection hole 32. As will be described later, the detection hole 32 is formed to detect the position (amount of displacement) of the conveyor belt 2 in the main scanning direction. In the conveyance direction, the detection hole 32 is arranged ahead of the leading flushing opening 31.

[0027] The detection hole 32 (image) is detected by the belt sensor 29 in a color different from the surface (image) of the conveyor belt 2, and the position (displacement amount) of the conveyor belt 2 in the main scanning direction is determined based on the position of the detection hole 32 (image).

[0028] As shown in FIG. 3, the width of the inkjet recording units 1a, 1b, 1c, and 1d (i.e., the width of the nozzle array) is equal to or greater than the width of the print sheet 101, and the width of the array of flushing openings 31 is equal to or greater than the width of the inkjet recording units 1a, 1b, 1c, and 1d (i.e., the width of the nozzle array).

[0029] Fig. 4 is a block diagram showing the electrical configuration of image forming apparatus 10 according to an embodiment of the present invention. As shown in Fig. 4, image forming apparatus 10 includes a printing device 71 having the mechanical configuration shown in Figs. 1 and 2, as well as an operation panel 72, a storage device 73, an image reading device 74, and a processing unit 75.

[0030] The operation panel 72 is arranged on the surface of the housing of the image forming device 10 and is equipped with a display device 72a such as an LCD display and an input device 72b such as hard keys or a touch panel, and displays various messages to the user on the display device 72a and accepts user operations on the input device 72b.

[0031] The storage device 73 is a non-volatile storage device (such as a flash memory or a hard disk drive) that stores data, programs, and the like required for controlling the image forming apparatus 10.

[0032] The image reading device 74 is equipped with a platen glass and an automatic document feeder, and optically reads the image of a document placed on the platen glass or a document transported by the automatic document feeder, and generates image data of that image.

[0033] The arithmetic processing device 75 includes a computer that operates according to a program, an ASIC (Application Specific Integrated Circuit) that executes predetermined operations, and the like, and operates as various processing units. The computer includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and the like, and operates as various processing units (together with the ASIC as necessary) by loading a program stored in the ROM, storage device 73, etc. into the RAM and executing it on the CPU.

[0034] Here, the arithmetic processing unit 75 operates as a control unit 81 and an image processing unit 82 .

[0035] The control unit 81 controls the printing device 71 (print engine 10a, sheet conveying unit 10b, etc.) to execute a print job requested by a user. In this embodiment, the control unit 81 causes the image processing unit 82 to execute predetermined image processing, and controls the print engine 10a (head unit 11) to eject ink to form a print image on a print sheet. The image processing unit 82 executes predetermined image processing such as RIP (Raster Image Processing), color conversion, and halftoning on the image data of the image to be printed on the print sheet.

[0036] The control unit 81 causes the printing device 71 to print an image specified by the user. Specifically, the control unit 81 causes the print engine 10a to print a user's original image based on print image data specified by the user. The control unit 81 causes the print engine 10a to eject ink when printing the user's original image.

[0037] The control unit 81 also includes a discharge timing control unit 81a that controls the ink discharge timing of the print engine 10a. The discharge timing control unit 81a causes the print engine 10a to discharge ink from each nozzle at a flushing timing corresponding to each nozzle of the print engine 10a. This flushing is performed to discard ink that has thickened in the nozzles.

[0038] 5 and 6 are diagrams for explaining the identification of the flushing openings 31 corresponding to the respective nozzles.

[0039] The ejection timing control unit 81a (a) detects the position Xd of the detection hole 32 in the main scanning direction (the center position of the detection hole 32) using the belt sensor 29, (b) identifies the flushing opening 31-i (i=1, 2, . . . , Nf, where Nf is the number of flushing openings 31) corresponding to each nozzle (nozzle number 0, . . . , Nn, where Nn is the number of nozzles) based on the position Xd of the detection hole 32 in the main scanning direction, and (c) causes the print engine 10a to perform flushing of the nozzle at the timing corresponding to the flushing opening 31-i.

[0040] Specifically, the ejection timing control unit 81a (a) identifies the flushing opening 31-i corresponding to a nozzle based on the position Xd of the detection hole 32 in the main scanning direction, the distance DPi from the detection hole 32 to the flushing opening 31-i (the center position of the flushing opening 31-i), the width of the flushing opening 31-i (here, the radius of the circular flushing opening 31-i), and the position of the nozzle in the main scanning direction, (b) identifies the ejection timing (= the detection timing of the detection hole 32 + DSj / linear speed) for flushing of the nozzle based on the detection timing of the detection hole 32, the distance DSj (j = 1, 2) from the detection hole 32 to the identified flushing opening 31-i in the transport direction, and the linear speed of the transport belt 2, and (c) causes the print engine 10a to perform flushing of the nozzle at the identified ejection timing. As a result, flushing of the nozzle is performed when the identified flushing opening 31-i arrives at a position directly below the corresponding nozzle.

[0041] Figure 5 shows a case where there is no deviation in the position of the conveying belt 2 in the main scanning direction. In the case shown in Figure 5, the position Xd of the detection hole 32 is the reference position Xref, the flushing opening 31-1 corresponds to the nozzles with nozzle numbers 0 to Nr1, and the flushing opening 31-2 corresponds to the nozzles with nozzle numbers Nr1+1 to Nr2 (the same applies to the flushing openings 31-3 to 31-Nf).

[0042] On the other hand, Figure 6 shows a case where there is a positional deviation of the conveying belt 2 in the main scanning direction. In the case shown in Figure 6, the position Xd of the detection hole 32 is different from the reference position Xref, and the flushing opening 31-1 corresponds to the nozzles with nozzle numbers 0 to N1 (N1 ≠ Nr1), and the flushing opening 31-2 corresponds to the nozzles with nozzle numbers N1+1 to N2 (N2 ≠ Nr2) (the same applies to the flushing openings 31-3 to 31-Nf).

[0043] In this way, the positional deviation of the conveyor belt 2 is detected by the detection holes 32, and the nozzles corresponding to each flushing opening 31-i are identified taking the positional deviation into consideration.

[0044] The nozzles (nozzle numbers) corresponding to the respective flash openings 31 are individually identified for each of the inkjet recording units 1a to 1d (that is, for each ink color).

[0045] Next, the operation of the image forming apparatus 10 will be described.

[0046] When printing an image, the ejection timing control unit 81a controls the print engine 10a to eject ink onto the print sheet from the nozzles of the inkjet recording units 1a, 1b, 1c, and 1d at the ink ejection timing for pixels in the image to which ink should be ejected.

[0047] The ejection timing control unit 81a also performs flushing in accordance with predetermined flushing conditions (such as the passage of a predetermined length of unused time for the image forming apparatus 10a). At this time, the ejection timing control unit 81a selects the nozzles to be flushed (some or all of the nozzles) and performs flushing for the selected nozzles. Specifically, when the belt sensor 29 detects a detection hole 32 while the conveyor belt 2 is rotating, the ejection timing control unit 81a identifies the position of the detection hole 32 in the main scanning direction based on the image obtained by the belt sensor 29, identifies the flushing opening 31-i corresponding to the selected nozzle, and determines the flushing timing for each selected nozzle based on the relative position of the identified flushing opening 31-i with respect to the detection hole 32, etc. Then, when the flushing timing arrives for each nozzle, the ejection timing control unit 81a ejects ink to perform flushing.

[0048] As described above, according to the first embodiment, the conveyor belt 2 includes a plurality of flushing openings 31 and detection holes 32, and the plurality of flushing openings 31 are arranged in at least two rows along the main scanning direction. The ejection timing control unit 81a then (a) detects the positions of the detection holes 32 in the main scanning direction using the belt sensor 29, (b) identifies the flushing openings 31 corresponding to the nozzles based on the positions of the detection holes 32 in the main scanning direction, and (c) causes the print engine 10a to perform flushing of the nozzles at the timing corresponding to the flushing openings 31.

[0049] As a result, when flushing is performed through the flushing opening 31 formed in the conveying belt 2, even if the conveying belt 2 is displaced in the main scanning direction, flushing is performed appropriately (without ink being ejected onto the surface of the conveying belt 2).

[0050] Embodiment 2

[0051] In the second embodiment, flushing is prohibited when a foreign object (such as a piece of paper) adheres to the detection hole 32 and the position (center position) of the detection hole 32 cannot be accurately identified.

[0052] In the second embodiment, the ejection timing control unit 81a (a) detects the size of the detection hole 32 (size based on the image obtained by the belt sensor 29) using the belt sensor 29, (b1) if the detected size matches a predetermined reference value (i.e., if the difference (absolute value) between the detected size and the predetermined reference value is less than a predetermined value), causes the print engine 10a to perform flushing of the nozzle at the timing corresponding to the flushing opening 31-i, and (b2) if the detected size does not match the predetermined reference value, does not cause the print engine 10a to perform flushing of the nozzle.

[0053] Fig. 7 is a diagram for explaining the determination of whether flushing is possible based on the width of the detection hole in the main scanning direction in embodiment 2. Fig. 8 is a diagram for explaining the determination of whether flushing is possible based on the length of the detection hole in the transport direction in embodiment 2.

[0054] The size of the detection hole 32 is, for example, the width Wd of the detection hole 32 in the main scanning direction as shown in FIG. 7, or the length Ld of the detection hole 32 in the transport direction as shown in FIG.

[0055] In the image obtained by the belt sensor 29, if the color of the detection hole 32 is not the same as the color of the foreign matter, the width Wd or length Ld of the detection hole 32 will be detected as being smaller than the predetermined reference values ​​Wref, Lref (the width Wd and length Ld of the detection hole 32 when there is no foreign matter), as shown in Figures 7 and 8, for example.

[0056] On the other hand, if the color of the detection hole 32 in the image obtained by the belt sensor 29 is the same as the color of the foreign matter, the width Wd or length Ld of the detection hole 32 is detected to be greater than the predetermined reference values ​​Wref, Lref, as shown in Figures 7 and 8, for example.

[0057] Therefore, if the size of the detected detection hole 32 does not match the predetermined reference value, the ejection timing control unit 81a determines that foreign matter (of the same color or a different color) is attached to the detection hole 32, and prohibits flushing because the position (center position) of the detection hole 32 cannot be accurately identified and the flushing openings 31-i corresponding to each nozzle to be flushed cannot be accurately identified.

[0058] The other configurations and operations of the image forming apparatus according to the second embodiment are the same as those of the first embodiment, and therefore the description thereof will be omitted.

[0059] Embodiment 3

[0060] In the third embodiment, the period during which detection of the detection hole 32 is attempted is limited so that foreign matter (such as a piece of paper) adhering to the conveyor belt 2 is not erroneously detected as the detection hole 32.

[0061] FIG. 9 is a diagram illustrating the detection range of the detection hole 32 in the third embodiment.

[0062] Specifically, as shown in Figure 9, for example, multiple sets of detection holes 32 and flash openings 31 are formed on the conveying belt 2, and the ejection timing control unit 81a does not attempt to detect the detection hole 32 from the time the belt sensor 29 detects the position of a certain detection hole 32 until the detection range set for the timing after the detection period corresponding to the arrangement period HP of the detection holes 32 arrives, but instead attempts to detect the detection hole within that detection range.

[0063] The arrangement period HP is the interval (distance) between the plurality of arranged detection holes 32, and the detection period is the time length obtained by dividing the arrangement period HP by the linear speed of the conveyor belt 2.

[0064] 9, the temporal detection range corresponds to a range a distance R forward from the position of the next detection hole 32 and a range DR a distance R backward. Therefore, detection of the detection hole 32 is not performed outside this range DR, and even if a foreign object of the same color as the detection hole 32 adheres to an image in a location outside this range DR (approximately the same position as the detection hole 32 in the main scanning direction), the foreign object will not be erroneously detected as the detection hole 32, and inappropriate flushing will not be performed. Furthermore, if a foreign object adheres within this range DR, flushing may be prohibited, as described in the second embodiment.

[0065] The other configurations and operations of the image forming apparatus according to the third embodiment are the same as those of the first or second embodiment, and therefore, description thereof will be omitted.

[0066] It should be noted that various changes and modifications to the above-described embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. In other words, it is intended that such changes and modifications be included within the scope of the claims.

[0067] For example, in the first to third embodiments, instead of providing the detection hole 32 separately from the flushing opening 31, one of the flushing openings 31 at the front in the transport direction may be used as the detection hole.

[0068] Furthermore, in the first to third embodiments, a line sensor (not shown) that detects the position of the print sheet 101 in the main scanning direction may be used as the belt sensor 29. [Industrial Applicability]

[0069] The present invention is applicable to, for example, an inkjet type image forming apparatus. [Explanation of symbols]

[0070] 2 conveyor belt 10 Image forming device 10a Print Engine 29 Belt sensor 31, 31-i Flashing opening 32 Detection hole 81a Discharge timing control section

Claims

1. a conveyor belt for conveying a print sheet; a print engine having a plurality of nozzles arranged in a main scanning direction and ejecting ink from the nozzles onto the print sheet; an ejection timing control unit that controls the ink ejection timing of the print engine; the conveyor belt has a plurality of flushing openings and detection holes; the plurality of flushing openings are arranged in at least two rows along the main scanning direction, the ejection timing control unit (a) detects the position of the detection hole in the main scanning direction with a sensor, (b) identifies the flushing opening corresponding to the nozzle based on the position of the detection hole in the main scanning direction, and (c) causes the print engine to execute flushing of the nozzle at a timing corresponding to the flushing opening; the ejection timing control unit (a) detects the size of the detection hole with the sensor, (b1) if the detected size matches a predetermined reference value, causes the print engine to execute flushing of the nozzle at a timing corresponding to the flushing opening, and (b2) if the detected size does not match the predetermined reference value, does not cause the print engine to execute flushing of the nozzle; An image forming apparatus comprising:

2. The image forming apparatus according to claim 1, characterized in that the ejection timing control unit (a) identifies the flushing opening corresponding to the nozzle based on the position of the detection hole in the main scanning direction, the distance from the detection hole to the flushing opening, and the position of the nozzle, (b) identifies the ejection timing for flushing of the nozzle based on the detection timing of the detection hole, the distance from the detection hole to the identified flushing opening in the transport direction, and the linear speed of the transport belt, and (c) causes the print engine to perform flushing of the nozzle at the identified ejection timing.

3. 2. The image forming apparatus according to claim 1, wherein the size is a width of the detection hole in the main scanning direction or a length of the detection hole in the transport direction.

4. A conveyor belt for conveying a print sheet; a print engine having a plurality of nozzles arranged in a main scanning direction and ejecting ink from the nozzles onto the print sheet; an ejection timing control unit that controls the ink ejection timing of the print engine; the conveyor belt has a plurality of flushing openings and detection holes; the plurality of flushing openings are arranged in at least two rows along the main scanning direction, the ejection timing control unit (a) detects the position of the detection hole in the main scanning direction with a sensor, (b) identifies the flushing opening corresponding to the nozzle based on the position of the detection hole in the main scanning direction, and (c) causes the print engine to execute flushing of the nozzle at a timing corresponding to the flushing opening; The image forming apparatus is characterized in that the ejection timing control unit does not attempt to detect the detection hole from the time when the position of the detection hole is detected until the detection range set for the timing after the detection period corresponding to the arrangement period of the detection hole arrives, but instead attempts to detect the detection hole within the detection range.

Images