Image forming apparatus

Abstract

An image forming apparatus is provided. A conveyance belt includes a plurality of flush opening portions and a detection hole, the plurality of flush opening portions being arranged in at least two rows along a main scanning direction. Also, an ejection timing control section performs the following processes: (a) detecting a position of the detection hole in the main scanning direction by a belt sensor, (b) determining a flush opening portion corresponding to a nozzle based on the position of the detection hole in the main scanning direction, (c) causing a print engine to perform flushing of the nozzle at a timing corresponding to the flush opening portion.

Description

TECHNICAL FIELD

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

[0002] In an inkjet recording apparatus such as an inkjet printer, sometimes the nozzles of a recording head are clogged due to ink thickening caused by drying. Therefore, flushing is performed in which the ink after thickening is ejected and discarded. In a certain image forming apparatus, a hole portion corresponding to the size of a unit recording head among recording heads is provided on a conveyance belt, and ink is ejected through the hole portion to perform flushing.

[0003] When the conveyance belt is in a looped motion, the conveyance belt sometimes shifts in a main scanning direction (a direction perpendicular to the conveyance direction, i.e., a width direction of the conveyance belt). In the case where the conveyance belt shifts in the main scanning direction, the ink ejected by flushing does not accurately fall downward through the above-described hole portion, but comes into contact with the conveyance belt, which can contaminate the conveyance belt.

[0004] The present application was made in view of the above-described problem, and aims to obtain an image forming apparatus in which, in the case where flushing is performed through a flushing opening portion formed in a conveyance belt, even if the conveyance belt shifts in a main scanning direction, flushing can be properly performed. SUMMARY

[0005] The image forming apparatus of the present application includes a conveyance belt that conveys a print sheet; a print engine that has a plurality of nozzles arranged in a main scanning direction, and that ejects ink from the nozzles toward the print sheet; and an ejection timing control section that controls the ink ejection timing of the print engine, the conveyance belt having a plurality of flushing opening portions arranged in at least two rows along the main scanning direction, and a detection hole. The ejection timing control section performs the following processes: (a) detects the position of the detection hole in the main scanning direction using a sensor, (b) determines the flushing opening portion corresponding to the nozzles based on the position of the detection hole in the main scanning direction, and (c) causes the print engine to perform flushing of the nozzles at a timing corresponding to the flushing opening portion.

[0006] According to the present application, an image forming apparatus in which, in the case where flushing is performed through a flushing opening portion formed in a conveyance belt, even if the conveyance belt shifts in a main scanning direction, flushing can be properly performed can be obtained.

[0007] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description and accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a side view that illustrates the mechanical internal structure of an image forming apparatus of an embodiment of the present application.

[0009] Figure 2 is Figure 1 a plan view of the image forming apparatus.

[0010] Figure 3 is a view showing an example of the conveyance belt 2 in Figure 1

[0011] Figure 4 is a block diagram showing an electrical structure of the image forming apparatus 10 of the embodiment of the present application.

[0012] Figure 5 is a view for explaining determination of the flushing opening portion 31 corresponding to each nozzle (1 / 2).

[0013] Figure 6 is a view for explaining determination of the flushing opening portion 31 corresponding to each nozzle (2 / 2).

[0014] Figure 7 is a view for explaining determination of flushability based on a width of the detection hole in the main scanning direction in the embodiment 2.

[0015] Figure 8 is a view for explaining determination of flushability based on a length of the detection hole in the conveyance direction in the embodiment 2.

[0016] Figure 9 is a view for explaining a detection range of the detection hole in the embodiment 3. DETAILED DESCRIPTION

[0017] Hereinafter, an embodiment of the present application will be described with reference to the drawings.

[0018] First Embodiment

[0019] Figure 1 is a side view showing a mechanical internal structure of the image forming apparatus of the embodiment of the present application. Figure 2 is Figure 1 a plan view of the image forming apparatus.

[0020] The image forming apparatus 10 of the embodiment is a printer, a copier, a facsimile, a multifunction peripheral, or the like, and has a color printer mechanism of a line head type inkjet method in the embodiment.

[0021] Figure 1 The image forming apparatus 10 shown in FIG. 1 includes a print engine 10a and a sheet conveyance portion 10b. The print engine 10a physically prints an image to be printed on a print sheet (print paper or the like). An ink cartridge is attachable to and detachable from the print engine 10a, and the print engine 10a performs printing using ink supplied from the ink cartridge. In addition, the sheet conveyance portion 10b conveys the print sheet to the print engine 10a. ​

[0022] In this embodiment, the printing engine 10a has inkjet recording units 1a to 1d of line printhead types corresponding to the four ink colors of cyan, magenta, yellow, and black, and ink is ejected onto the printing sheet through the inkjet recording units 1a to 1d.

[0023] like Figure 2 As shown, in this embodiment, each inkjet recording unit 1a, 1b, 1c, 1d has one or more (three in this case) heads 11. These heads 11 are arranged along the main scanning direction and can be attached and detached relative to the device body. The heads 11 (i.e., each inkjet recording unit 1a, 1b, 1c, 1d) have a plurality of nozzles arranged in the main scanning direction, from which ink is ejected onto the printing sheet.

[0024] In addition, in this embodiment, the sheet conveying section 10b includes: an annular conveyor belt 2, which is configured opposite to the printing engine 10a and conveys the printing sheet; a drive roller 3, a driven roller 4, and a tension roller 4a, which suspend the conveyor belt 2; an adsorption roller 5, which clamps the printing sheet together with the conveyor belt 2; a rear conveyor belt 6; and a dryer 7.

[0025] The drive roller 3, driven roller 4, and tension roller 4a cause the conveyor belt 2 to rotate. Then, the suction roller 5 clamps the printing sheet conveyed from the paper feed cassette 20 (described later). The clamped printing sheet 101 is sequentially conveyed by the conveyor belt 2 to the printing positions of the inkjet recording units 1a to 1d, where images of various colors are printed. At this time, the passing of the printing sheet is detected by the sheet sensor 2a, and the current position of the printing sheet on the conveyor path is determined based on this detection timing. Therefore, an image is printed at the appropriate position on the printing sheet. After printing, the printed sheet is discharged via the subsequent conveyor belt 6 to the discharge tray 10c, etc. At this time, the ink-sprayed printing sheet is dried using a dryer 7.

[0026] Figure 3 It means Figure 1 A diagram showing an example of a conveyor belt 2. The conveyor belt 2 includes multiple flushing openings 31. For example, as shown... Figure 3 As shown, a plurality of rinsing openings 31 are formed on the conveyor belt 2, and the rinsing openings 31 are formed in at least two rows along the main scanning direction (in Figure 3 (There are two columns in the middle). That is, in the transport direction, there are flushing openings 31 arranged at different positions. In addition, the multiple flushing openings 31 are arranged to cover the entire area of ​​the multiple nozzles arranged in the inkjet recording sections 1a to 1d in the main scanning direction (that is, without any omissions).

[0027] In addition, sheet suction holes are arranged at a predetermined density in a generally uniform manner in the area outside the rinsing opening 31.

[0028] For example,Figure 1 As shown, ink receiving portions 8a to 8d are provided below the head 11 of each of the inkjet recording sections 1a to 1d. The flushing (e.g., line flushing) of each nozzle in each of the inkjet recording sections 1a, 1b, 1c, 1d is performed when any one of the flushing opening portions 31 is located directly below the head 11 of the inkjet recording section 1a, 1b, 1c, 1d. The ink ejected from the nozzle at the time of flushing is received by the corresponding ink receiving portion 8a, 8b, 8c, 8d via the flushing opening portion 31, and is recovered to the waste ink tank.

[0029] In addition, sheet suction portions 9 are arranged along the conveying path of the sheet at portions other than the ink receiving portions 8a to 8d. A negative pressure is applied to the sheet suction portions 9, whereby the print sheet is adsorbed on the conveying belt 2 via the sheet suction holes. In addition, a lower negative pressure than that of the sheet suction portions 9 is applied to the ink receiving portions 8a to 8d.

[0030] Furthermore, the sheet conveying portion 10b has a paper feed cassette 20 as a paper feed source. The paper feed cassette 20 houses the print sheet 101, and the print sheet 101 is pushed upward by a lift plate 21 to abut against a pickup roller 22. The print sheet 101 placed on the paper feed cassette 20 is picked up one sheet at a time from the upper side by the pickup roller 22 to a paper feed roller 23. The paper feed roller 23 is a roller that conveys the print sheet 101 fed one sheet at a time from the paper feed cassette 20 to the conveying path.

[0031] The conveying roller 27 is a roller that conveys the print sheet 101 on a prescribed conveying path. The registration roller 28 temporarily stops the print sheet 101 being conveyed when the print sheet 101 is detected by a registration sensor 28a, and conveys the print sheet 101 to the print engine 10a (specifically, to the pinch position of the suction roller 5 and the conveying belt 2) at a secondary paper feed timing. The secondary paper feed timing is specified by a control portion 81 described later, so that an image is formed on the print sheet 101 at a prescribed position.

[0032] Further, a belt sensor 29 is provided above the conveying belt 2. The belt sensor 29 is an optical sensor, for example, a line sensor arranged in the main scanning direction, and for example, irradiates light to the conveying belt 2 with an LED or the like, and detects the reflected light with each light receiving element such as a photodiode, to determine the color of each position in a prescribed range in the main scanning direction.

[0033] In addition, the conveying belt 2 has a detection hole 32. As described later, the detection hole 32 is formed to detect the position (displacement amount) of the conveying belt 2 in the main scanning direction. In the conveying direction, the detection hole 32 is arranged before the flushing opening portion 31 of the front head.

[0034] The (image of the) detection hole 32 is detected by the belt sensor 29 in a color different from that of the (image of the) surface of the conveyance belt 2, and based on the position of the (image of the) detection hole 32, the position (displacement amount) of the conveyance belt 2 in the main scanning direction is determined.

[0035] In addition, as shown in FIG. 1, for example, the width of the inkjet recording sections 1a, 1b, 1c, 1d (i.e., the width of the nozzle arrangement) is equal to or greater than the width of the print sheet 101, and the arrangement width of the flush opening sections 31 is equal to or greater than the width of the inkjet recording sections 1a, 1b, 1c, 1d (i.e., the width of the nozzle arrangement). Figure 3

[0036] Figure 4 is a block diagram showing an electrical structure of the image forming apparatus 10 according to the embodiment of the present application. As shown in Figure 4 , the image forming apparatus 10 has, in addition to the printing device 71 having the mechanical structure as shown in Figure 1 and Figure 2 , an operation panel 72, a storage device 73, an image reading device 74, and an arithmetic processing device 75.

[0037] The operation panel 72 is arranged on the surface of the frame of the image forming apparatus 10, and has a display device 72a such as a liquid crystal display and an input device 72b such as a hard key, a touch panel, etc., displays various messages to the user through the display device 72a, and accepts the user's operation through the input device 72b.

[0038] The storage device 73 is a nonvolatile storage device (flash memory, hard disk drive, etc.) that stores data, programs, etc. required for the control of the image forming apparatus 10.

[0039] The image reading device 74 has a platen glass and an automatic document feeder, optically reads the image of a document placed on the platen glass or a document fed by the automatic document feeder, and generates image data of the image.

[0040] The arithmetic processing device 75 has a computer that operates according to a program, an ASIC (Application Specific Integrated Circuit) that performs a prescribed operation, etc., and functions as various processing sections. The computer has a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., loads a program stored in the ROM, the storage device 73, etc. into the RAM and executes the program by the CPU, and functions as various processing sections (together with the ASIC as necessary).

[0041] ​Here, the operation processing device 75 functions as the control section 81 and the image processing section 82.

[0042] The control section 81 controls the printing device 71 (the print engine 10a, the sheet conveyance section 10b, etc.) to execute a print job requested by a user. In this embodiment, the control section 81 causes the image processing section 82 to execute a prescribed image processing, and controls the print engine 10a (the head 11) to eject ink to form a print image on a print sheet. The image processing section 82 executes a prescribed image processing such as RIP (Raster Image Processing), color conversion, halftone processing, etc. on image data of an image to be printed on a print sheet.

[0043] The control section 81 causes the printing device 71 to print an image specified by a user. Specifically, the control section 81 causes the print engine 10a to print a user original image based on print image data specified by a user. The control section 81 causes the print engine 10a to eject ink at the time of printing of the user original image.

[0044] In addition, the control section 81 is provided with an ejection timing control section 81a that controls the timing of ink ejection of the print engine 10a. The ejection timing control section 81a causes the print engine 10a to eject ink from each nozzle at a purging timing corresponding to each nozzle of the print engine 10a. This purging is performed in order to discard thickened ink in the nozzle.

[0045] Figure 5 and Figure 6 is a view that explains the determination of the purging opening 31 corresponding to each nozzle.

[0046] The ejection timing control section 81a performs the following processing: (a) detects the position Xd of the detection hole 32 (the center position of the detection hole 32) in the main scanning direction with the tape sensor 29, (b) determines the purging opening 31-i (i = 1, 2, ··· Nf, Nf is the number of purging openings 31) corresponding to each nozzle (nozzle number 0, ···, Nn, Nn is the number of nozzles) based on the position Xd of the detection hole 32 in the main scanning direction, (c) causes the print engine 10a to perform purging of the nozzle at a timing corresponding to the purging opening 31-i.

[0047] Specifically, the ejection timing control section 81a performs the following processing: (a) 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 section 31-i (the center position of the flushing opening section 31-i), the width of the flushing opening section 31-i (in this case, the radius of the circular flushing opening section 31-i), and the position of the nozzle in the main scanning direction, the flushing opening section 31-i corresponding to the nozzle is determined, (b) based on the detection timing of the detection hole 32, the distance DSj (j = 1, 2) from the detection hole 32 in the conveyance direction to the determined flushing opening section 31-i, and the linear velocity of the conveyance belt 2, the ejection timing for flushing of the nozzle (= the detection timing of the detection hole 32 + DSj / linear velocity) is determined, (c) flushing of the nozzle is performed toward the print engine 10a at the determined ejection timing. Thus, at the timing at which the determined flushing opening section 31-i reaches the position directly below the corresponding nozzle, flushing of the nozzle is performed.

[0048] Figure 5 The case where the position of the conveyance belt 2 in the main scanning direction is not shifted is shown in FIG. 8. In this case, the position Xd of the detection hole 32 becomes the reference position Xref, the flushing opening section 31-1 corresponds to the nozzles with nozzle numbers 0 to Nr1, and the flushing opening section 31-2 corresponds to the nozzles with nozzle numbers Nr1 + 1 to Nr2 (the same applies to the flushing opening sections 31-3 to 31-Nf). Figure 5

[0049] On the other hand, the case where the position of the conveyance belt 2 in the main scanning direction is shifted is shown in FIG. 9. In this case, the position Xd of the detection hole 32 is different from the reference position Xref, the flushing opening section 31-1 corresponds to the nozzles with nozzle numbers 0 to N1 (N1 ≠ Nr1), and the flushing opening section 31-2 corresponds to the nozzles with nozzle numbers N1 + 1 to N2 (N2 ≠ Nr2) (the same applies to the flushing opening sections 31-3 to 31-Nf). Figure 6 Figure 6

[0050] In this way, the position shift of the conveyance belt 2 is detected by the detection hole 32, and the nozzles corresponding to each flushing opening section 31-i are determined taking the position shift into account.

[0051] In addition, the nozzles (nozzle numbers) corresponding to each of the flash lamp opening sections 31 are determined individually for each of the ink ejection sections 1a to 1d (i.e., for each of the ink colors).

[0052] Next, the operation of the above-described image forming apparatus 10 will be described.

[0053] ​​​When printing an image, the ejection timing control section 81a controls the print engine 10a to eject ink from the nozzles of the ink ejection sections la, lb, lc, Id to the print sheet at the ink ejection timing with respect to the pixels of the image for which ink should be ejected.

[0054] In addition, the ejection timing control section 81a performs purging in accordance with a prescribed purging condition (a prescribed length of non-use time of the image forming apparatus 10a, etc.). At this time, the ejection timing control section 81a selects the nozzles (part or all of the nozzles) that should be purged, and performs purging with respect to the selected nozzles. Specifically, while the conveyance belt 2 is being looped, the ejection timing control section 81a determines the position of the detection hole 32 in the main scanning direction based on the image obtained by the belt sensor 29 when the detection hole 32 is detected by the belt sensor 29, determines the purging opening portion 31-i corresponding to the selected nozzles based on the relative position of the determined purging opening portion 31-i with respect to the detection hole 32, etc., and determines the purging timing with respect to each of the selected nozzles. Then, the ejection timing control section 81a ejects ink to perform purging with respect to each of the nozzles when the purging timing arrives.

[0055] As described above, according to the first embodiment described above, the conveyance belt 2 is provided with a plurality of purging opening portions 31 and a detection hole 32, and the plurality of purging opening portions 31 are arranged in at least two rows in the main scanning direction. Also, the ejection timing control section 81a performs the following processes: (a) detects the position of the detection hole 32 in the main scanning direction by the belt sensor 29, (b) determines the purging opening portion 31 corresponding to the nozzles based on the position of the detection hole 32 in the main scanning direction, and (c) causes the print engine 10a to perform purging of the nozzles at the timing corresponding to the purging opening portion 31.

[0056] Thus, in the case of performing purging via the purging opening portion 31 formed in the conveyance belt 2, even if the conveyance belt 2 is displaced in the main scanning direction, purging can be appropriately performed (ink is not ejected onto the surface of the conveyance belt 2).

[0057] Second Embodiment

[0058] In the second embodiment, in the case where a foreign substance (a piece of paper, etc.) is attached to the detection hole 32 and the position (center position) of the detection hole 32 cannot be accurately determined, purging is prohibited.

[0059] In the second embodiment, the ejection timing control section 81a performs the following processing: (a) detects the size of the detection hole 32 (size based on the image obtained by the tape sensor 29), (b1) in the case where the detected size coincides with the prescribed reference value (i.e., in the case where the difference (absolute value) between the detected size and the prescribed reference value is less than the prescribed value), causes the print engine 10a to perform purging of the nozzle corresponding to the timing of the purging opening section 31-i, (b2) in the case where the detected size does not coincide with the prescribed reference value, does not cause the print engine 10a to perform purging of the nozzle.

[0060] Figure 7 is a view that explains the decision of the possibility of purging based on the width of the detection hole in the main scanning direction in the second embodiment. Figure 8 is a view that explains the decision of the possibility of purging based on the length of the detection hole in the conveyance direction in the second embodiment.

[0061] The size of the detection hole 32 described above is, for example, the width Wd of the detection hole 32 in the main scanning direction as shown in Figure 7 or the length Ld of the detection hole 32 in the conveyance direction as shown in Figure 8 .

[0062] In the image obtained by the tape sensor 29, in the case where the color of the detection hole 32 and the color of the foreign matter are not the same color, for example, as shown in Figure 7 and Figure 8 , the width Wd or the length Ld of the detection hole 32 is detected to be smaller than the prescribed reference value Wref, Lref (width Wd and length Ld of the detection hole 32 in the absence of the foreign matter).

[0063] On the other hand, in the image obtained by the tape sensor 29, in the case where the color of the detection hole 32 and the color of the foreign matter are the same color, for example, as shown in Figure 7 and Figure 8 , the width Wd or the length Ld of the detection hole 32 is detected to be larger than the prescribed reference value Wref, Lref.

[0064] Therefore, in the case where the detected size of the detection hole 32 does not coincide with the prescribed reference value, the ejection timing control section 81a determines that a foreign matter (of the same color or of a different color) is attached to the detection hole 32, the position (center position) of the detection hole 32 is not correctly determined, and the purging opening section 31-i corresponding to each nozzle of the purging target is not correctly determined, and thus purging is prohibited.

[0065] In addition, other structures and operations of the image forming apparatus of the second embodiment are the same as those of the first embodiment, and thus the description thereof is omitted.

[0066] Third Embodiment

[0067] In the third embodiment, in order not to erroneously detect a foreign matter (a paper sheet or the like) adhering to the conveyance belt 2 as the detection hole 32, the period in which the detection hole 32 is to be detected is limited.

[0068] Figure 9 is a view illustrating the detection range of the detection hole 32 in the third embodiment.

[0069] Specifically, for example, as shown in Figure 9 , a plurality of sets of the detection hole 32 and the flush opening 31 are formed on the conveyance belt 2, and the ejection timing control section 81a does not attempt to detect the detection hole 32 from the timing at which the position of the detection hole 32 is detected by the belt sensor 29 until the detection range set for the timing after the detection period corresponding to the arrangement period HP of the detection hole 32 arrives, but attempts to detect the detection hole in the detection range.

[0070] Further, the arrangement period HP is the interval (distance) at which a plurality of the detection holes 32 are arranged, and the detection period is the length of time obtained by dividing the arrangement period HP by the linear velocity of the conveyance belt 2.

[0071] Further, the detection range in time corresponds to a range DR of only a distance R in the forward direction from the position of the next detection hole 32 and a range of only a distance R in the backward direction in space, for example, as shown in Figure 9 . Therefore, outside the range DR, the detection of the detection hole 32 is not performed, and even if a foreign matter of the same color as the detection hole 32 adheres to the image at a position (a position substantially the same as the detection hole 32 in the main scanning direction) outside the range DR, the foreign matter is not erroneously detected as the detection hole 32, and thus inappropriate flushing is not performed. Further, in the case where a foreign matter adheres within the range DR, as explained in the second embodiment, flushing can also be prohibited.

[0072] Further, the other structures and operations of the image forming apparatus of the third embodiment are the same as those of the first or second embodiment, and thus the explanation thereof is omitted.

[0073] Further, it is understood by those skilled in the art that various changes and modifications can be made with respect to the above-described embodiments. Such changes and modifications can be made without departing from the scope of the present application and without impairing the advantages of the present application. That is, such changes and modifications should be included in the scope of the present application.

[0074] For example, in the above-described first to third embodiments, the above-described detection hole 32 can not be provided separately from the flush opening 31, but one of the flush openings 31 at the front end in the conveyance direction can be used as the detection hole.

[0075] Further, in the first to third embodiments described above, a line sensor (not shown) that detects the position of the print sheet 101 in the main scanning direction can be used as the tape sensor 29.

[0076] Industrial applicability

[0077] The present application can be applied to an image forming apparatus of, for example, an inkjet system.

Claims

1. An image forming apparatus characterized by comprising: An image forming apparatus includes: a conveyance belt that conveys a print sheet; a print engine that has a plurality of nozzles arranged in a main scanning direction, and that ejects ink from the nozzles toward the print sheet; a ejection timing control section that controls ink ejection timing of the print engine, the conveyance belt has a plurality of flush opening sections and a detection hole, the plurality of flush opening sections are arranged in at least two rows along the main scanning direction, the ejection timing control section performs the following processes: (a) acquires an image of a partial region of the conveyance belt including the detection hole using a sensor, and detects a center position of the detection hole in the main scanning direction from the acquired image, (b) determines the flush opening section corresponding to the nozzle based on the center position of the detection hole in the main scanning direction, and (c) causes the print engine to perform flushing of the nozzle at a timing corresponding to the flush opening section.

2. The image forming apparatus according to claim 1, wherein the ejection timing control section performs the following processes: (a) determines the flush opening section corresponding to the nozzle based on the center position of the detection hole in the main scanning direction, a distance from the detection hole to the flush opening section, and a position of the nozzle, (b) determines an ejection timing for flushing of the nozzle based on a detection timing of the detection hole, a distance from the detection hole to the determined flush opening section in a conveyance direction, and a linear velocity of the conveyance belt, and (c) causes the print engine to perform flushing of the nozzle at the determined ejection timing.

3. The image forming apparatus according to claim 1, wherein the ejection timing control section performs the following processes: (a) detects a size of the detection hole from the image, (b1) in a case where the detected size coincides with a prescribed reference value, causes the print engine to perform flushing of the nozzle at a timing corresponding to the flush opening section, and (b2) in a case where the detected size does not coincide with the prescribed reference value, does not cause the print engine to perform flushing of the nozzle.

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

5. The image forming apparatus according to claim 1, wherein the ejection timing control section does not attempt to detect the detection hole until a detection range set from a timing at which the center position of the detection hole is detected to a timing after a detection period corresponding to a configuration period of the detection hole, and attempts to detect the detection hole within the detection range. ​

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