Inkjet recording device

Abstract

The present invention provides an inkjet recording device. When printing on a recording medium of a first size and then printing on a recording medium of a second size larger than the first size, a control unit causes the recording head to perform a preliminary flushing process after the recording medium of the first size passes through a position opposite to the recording head and before the recording medium of the second size reaches a position opposite to the recording head. The preliminary flushing process is to eject ink from a predetermined first nozzle that was not set as a target nozzle when printing on the recording medium of the first size but is newly set as a target nozzle when printing on the recording medium of the second size to an opening.

Description

Technical Field

[0001] The present invention relates to an inkjet recording device. Background Art

[0002] Conventionally, an inkjet recording device including a recording head is known. Conventional inkjet recording devices use a conveyor belt to convey a recording medium. Ink is ejected from the recording head onto the recording medium conveyed by the conveyor belt to form an image on the recording medium.

[0003] Conventional inkjet recording devices perform a flushing process to forcibly eject ink from all nozzles in order to prevent nozzle clogging of the recording head. Performing the flushing process can prevent image quality from being degraded.

[0004] For example, in the past, an opening area for flushing is formed on the conveyor belt. In the flushing process, ink is ejected to the opening area. The ejected ink passes through the opening area. Thus, it is possible to prevent the ink ejected during the flushing process (ink that does not contribute to printing) from adhering to the conveyor belt and the recording medium.

[0005] In the conventional flushing process, for example, the same amount of ink is ejected from all nozzles. That is, in the flushing process, the same amount of ink is ejected from nozzles that do not contribute to printing as from nozzles that contribute to printing. In the conventional control, the undesirable phenomenon of increased ink consumption in the flushing process occurs. Summary of the invention

[0006] In order to solve the above-mentioned problems, an object of the present invention is to provide an inkjet recording apparatus capable of suppressing a decrease in image quality and reducing the amount of ink consumed in a flushing process.

[0007] In order to achieve the above-mentioned object, the present invention provides an inkjet recording device, which includes: a conveyor belt supported so as to be rotatable in a circumferential direction and conveying a recording medium by the circumferential rotation; a recording head arranged at a position opposite to the recording medium, having a plurality of nozzles arranged in a width direction perpendicular to the circumferential rotation direction of the conveyor belt, and printing on the recording medium by ejecting ink from the nozzles; and a control unit controlling a flushing process performed by the recording head, the conveyor belt having a flushing area formed with an opening, the flushing area being arranged in a plurality of intervals in the circumferential rotation direction, the control unit setting the nozzle opposite to the recording medium when printing on the recording medium as a target nozzle, and when the flushing area that does not overlap with the recording medium is opposite to the recording head, The recording head is caused to perform a process of ejecting ink from the object nozzle toward the opening as the flushing process. When printing on the recording medium having a first size in the width direction and then printing on the recording medium having a second size in the width direction that is larger than the first size, the control unit causes the recording head to perform a preliminary flushing process after the recording medium of the first size passes through a position relative to the recording head and before the recording medium of the second size reaches a position relative to the recording head. The preliminary flushing process ejects ink toward the opening from a predetermined first nozzle that was not set as the object nozzle when printing on the recording medium of the first size but is newly set as the object nozzle when printing on the recording medium of the second size.

[0008] According to the present invention, it is possible to suppress degradation of image quality and reduce the amount of ink consumed in the flushing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of an inkjet recording apparatus according to one embodiment of the present invention.

[0010] Figure 2 It is a top view of a recording section of an inkjet recording device according to one embodiment of the present invention.

[0011] Figure 3 It is a block diagram of an inkjet recording apparatus according to one embodiment of the present invention.

[0012] Figure 4 It is a schematic diagram of the periphery of a conveyor belt of an inkjet recording apparatus according to one embodiment of the present invention.

[0013] Figure 5 It is a top view of a conveyor belt of an inkjet recording device according to one embodiment of the present invention.

[0014] Figure 6This is a diagram showing the positional relationship between the flushing area of ​​the conveyor belt and the recording head of the inkjet recording apparatus according to one embodiment of the present invention.

[0015] Figure 7 This is a diagram showing the positional relationship between a flushing area of ​​a conveyor belt and paper in an inkjet recording apparatus according to one embodiment of the present invention.

[0016] Figure 8 This is a diagram showing a state where a paper is conveyed by a conveyor belt of an inkjet recording apparatus according to an embodiment of the present invention.

[0017] Fig. 9 This is a diagram showing a target nozzle of an inkjet recording device according to one embodiment of the present invention.

[0018] Fig.10 This is a diagram for explaining control of a flushing process and a preliminary flushing process performed in an inkjet recording apparatus according to one embodiment of the present invention.

[0019] Fig.11 This is a diagram showing a first nozzle and a second nozzle of an inkjet recording device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] Next, the inkjet recording device of this embodiment is described by taking a printer as an example. For example, the printer prints an image on a paper as a recording medium. Various sheets such as OHP sheets can also be used as recording media.

[0021] <Overall Structure of Printer>

[0022] like Figure 1 As shown, the printer 100 of this embodiment includes a first conveying unit 1 and a second conveying unit 2. The first conveying unit 1 supplies the paper S placed in the paper supply cassette CA and conveys it to the printing position. In the printing operation using the printer 100, the paper S passing the printing position is printed. The second conveying unit 2 conveys the printed paper S and discharges it to the discharge tray ET.

[0023] For example, although not shown, a plurality of paper feed cassettes CA are installed in the printer 100. The sizes of the paper S placed in the plurality of paper feed cassettes CA may be the same as or different from each other. In a printing operation using the printer 100, a paper feed cassette CA in which the paper S used in the printing operation is placed among the plurality of paper feed cassettes CA is set as a paper source, and the paper S is supplied from the paper feed cassette CA set as the paper source.

[0024] The first conveying unit 1 includes a plurality of conveying roller components including a registration roller pair 11. The plurality of conveying roller components convey the paper S by rotating respectively. The registration roller pair 11 is composed of a pair of rollers in pressure contact with each other. An registration gap is formed between the pair of rollers. The paper S supplied from the paper supply box CA enters the registration gap. The registration roller pair 11 conveys the paper S entering the registration gap to the belt conveying unit 3 described later by rotating.

[0025] The registration roller pair 11 stops rotating when the leading end of the paper S reaches the registration nip. At this time, the conveying roller member upstream of the registration roller pair 11 in the paper conveying direction rotates. Thus, the skew of the paper S is corrected.

[0026] The printer 100 includes a belt conveying unit 3. The belt conveying unit 3 receives the paper S from the first conveying unit 1 and conveys it. The belt conveying unit 3 includes a conveying belt 30. The conveying belt 30 is annular and supported so as to be rotatable in the circumferential direction. In addition, the belt conveying unit 3 includes a plurality of tensioning rollers 301. The plurality of tensioning rollers 301 are supported so as to be rotatable. The conveying belt 30 is tensioned and stretched by the plurality of tensioning rollers 301 and rotates in the circumferential direction.

[0027] One of the plurality of tension rollers 301 is connected to a belt motor (not shown) and rotates when the driving force of the belt motor is transmitted. The conveyor belt 30 rotates in the circumferential direction by the rotation of the tension roller 301 connected to the belt motor, and the other tension rollers 301 rotate accordingly.

[0028] Furthermore, the belt conveyor 3 includes a suction unit 300. The suction unit 300 is disposed inside the conveyor belt 30. The conveyor belt 30 is formed with a plurality of suction holes (not shown) penetrating in the thickness direction.

[0029] The paper S transported from the first transport unit 1 reaches the outer peripheral surface of the transport belt 30. The suction unit 300 attracts the paper S through the suction holes. The paper S on the outer peripheral surface of the transport belt 30 is sucked on the outer peripheral surface of the transport belt 30. The transport belt 30 absorbs and holds the paper S on the outer peripheral surface and rotates in the circumferential direction. In this way, the paper S is transported.

[0030] In this way, the belt conveying unit 3 conveys the paper S in the circumferential rotation direction of the conveying belt 30. That is, the circumferential rotation direction of the conveying belt 30 is the conveying direction of the paper S (the direction in which the paper S travels).

[0031] The printer 100 includes a recording unit 4. The recording unit 4 is disposed to face the outer peripheral surface of the conveyor belt 30. When the paper S is held by suction on the outer peripheral surface of the conveyor belt 30, the paper S faces the recording unit 4 with a gap therebetween.

[0032] like Figure 2As shown, the recording unit 4 includes four line print heads 41 corresponding to the respective colors of cyan, magenta, yellow and black. Figure 2 In the figure, the cyan line print head 41 is marked with the reference mark “C”, the magenta line print head 41 is marked with the reference mark “M”, the yellow line print head 41 is marked with the reference mark “Y”, and the black line print head 41 is marked with the reference mark “K” to distinguish them.

[0033] The line print head 41 of each color is composed of a plurality of (for example, three) recording heads 40. For example, the plurality of recording heads 40 of each color are arranged in a staggered manner in a direction perpendicular to the circumferential rotation direction of the conveyor belt 30 (the conveying direction of the paper S). In the following description, the direction perpendicular to the circumferential rotation direction of the conveyor belt 30 is simply referred to as the "width direction".

[0034] Each recording head 40 is arranged at intervals in the vertical direction relative to the outer peripheral surface of the conveyor belt 30. In other words, each recording head 40 is arranged at a position opposite to the paper S conveyed by the conveyor belt 30 in the vertical direction. In addition, the vertical direction is a direction perpendicular to the circumferential rotation direction and the width direction of the conveyor belt 30.

[0035] Each recording head 40 has a nozzle surface facing the conveyor belt 30 (paper S on the conveyor belt 30). The nozzle surface of each recording head 40 has a plurality of nozzles 4N. The plurality of nozzles 4N of each recording head 40 eject ink of corresponding colors. For example, the number of nozzles 4N of each recording head 40 is the same. The plurality of nozzles 4N of each recording head 40 are arranged along the width direction of the conveyor belt 30. Figure 2 The nozzles 4N are indicated by dotted lines in FIG. 1 . Actually, more nozzles 4N are provided in each recording head 40 .

[0036] The recording unit 4 (recording head 40) ejects ink from the nozzle 4N toward the paper S based on the image data to be printed in the printing operation. The ink ejected from the recording unit 4 adheres to the paper S. Thus, an image is printed on the paper S. That is, the position between the conveyor belt 30 and the recording head 40 is the printing position. In other words, the position opposite to the nozzle surface (nozzle 4N) of the recording head 40 in the up-down direction is the printing position.

[0037] Here, the viscosity of the ink in the nozzle 4N with a small number of ink ejection times among the plurality of nozzles 4N increases over time. As a result, clogging occurs, resulting in reduced image quality. In order to suppress such undesirable phenomena, each recording head 40 performs a flushing process. In the flushing process performed by each recording head 40, the ink retained in the nozzle 4N is ejected. Thus, clogging is suppressed. Details will be described later.

[0038] Back to Figure 1The printer 100 includes a drying unit 51 and a decurler 52. The drying unit 51 conveys the paper S to the decurler 52 and dries the ink attached to the conveyed paper S. The decurler 52 corrects the curl of the paper S. The decurler 52 conveys the curl-corrected paper S to the second conveying unit 2.

[0039] In addition, if Figure 3 As shown, the printer 100 includes a control unit 6. The control unit 6 includes a processing circuit such as a CPU and an ASIC. The control unit 6 controls the printing job performed by the printer 100. In other words, the control unit 6 controls the operations of the first conveying unit 1, the second conveying unit 2, the belt conveying unit 3, the recording unit 4, the drying unit 51, and the decurler 52. In further other words, the control unit 6 controls the conveyance of the paper S and the ejection of ink by each recording head 40. In addition, the control unit 6 controls the flushing process performed by each recording head 40.

[0040] The control unit 6 is connected to a registration sensor 61 , a paper sensor 62 , and a belt sensor 63 . Figure 4 The detection positions (arrangement positions) of the registration sensor 61 , the paper sensor 62 , and the belt sensor 63 are schematically shown.

[0041] The alignment sensor 61 detects a position upstream of the alignment nip in the paper conveying direction. The alignment sensor 61 is, for example, a reflective or transmissive optical sensor. The alignment sensor 61 changes its output value depending on whether the paper S is present at the corresponding detection position.

[0042] The control unit 6 detects the arrival of the front end and the passage of the rear end of the paper S at the detection position of the calibration sensor 61 based on the output value of the calibration sensor 61. In other words, the control unit 6 detects the arrival of the front end and the passage of the rear end of the paper S in the alignment nip based on the output value of the calibration sensor 61. The control unit 6 estimates the timing of starting to convey the paper S by the registration roller pair 11 (the timing of starting to rotate the registration roller pair 11) based on the elapsed time from the detection of the arrival of the front end of the paper S at the detection position of the calibration sensor 61. Even if the paper S is skewed, the paper S is started to be conveyed by the registration roller pair 11 in a state where the skew is corrected.

[0043] The paper sensor 62 uses the printing position of the line print head 41 located most upstream in the paper conveying direction among the plurality of line print heads 41 and the position between the alignment nip as the detection position. The paper sensor 62 changes the output value according to whether the paper S exists at the corresponding detection position. As the paper sensor 62, a CIS (Contact Image Sensor) can be used, or a reflective or transmissive optical sensor can be used. For example, a CIS is used as the paper sensor 62.

[0044] The control unit 6 detects the arrival of the front end and the passing of the rear end of the paper S at the detection position of the paper sensor 62 based on the output value of the paper sensor 62. The control unit 6 estimates the timing of ejecting ink onto the paper S transported by the transport belt 30 based on the output value of the paper sensor 62. Alternatively, the timing of ejecting ink onto the paper S transported by the transport belt 30 may be estimated based on the elapsed time from the start of transport of the paper S by the registration roller pair 11.

[0045] Furthermore, the control unit 6 measures the paper passage time from when the leading end of the paper S reaches the detection position of the paper sensor 62 to when the trailing end of the paper S passes the detection position of the paper sensor 62. The paper passage time at the detection position of the paper sensor 62 changes according to the size of the paper S in the conveying direction. Therefore, the control unit 6 recognizes the size of the paper S in the conveying direction conveyed by the conveyor belt 30 based on the paper passage time. Thus, even if the paper S conveyed by the conveyor belt 30 is not of a standard size, the control unit 6 can recognize the size of the paper S in the conveying direction.

[0046] In addition, the control unit 6 detects the positional deviation (skewness) of the paper S based on the output value of the paper sensor 62 (the read data obtained by reading the paper sensor 62). For example, the paper S may be positionally deviated after the paper S is conveyed by the registration roller pair 11. In this case, the positional deviation of the paper S is detected by the control unit 6.

[0047] In addition, the number of paper sensors 62 to be provided may be plural. For example, two paper sensors 62 may be provided.

[0048] The belt sensor 63 is a sensor for detecting a predetermined reference position (starting point) of the conveyor belt 30. A predetermined mark is provided at the reference position of the conveyor belt 30. Thus, the reference position of the conveyor belt 30 can be detected based on the output value of the belt sensor 63. For example, a CIS is used as the belt sensor 63. The belt sensor 63 may also be configured using a transmission type or reflection type optical sensor.

[0049] The control unit 6 detects the reference position of the conveyor belt 30 based on the output value of the belt sensor 63. In other words, the control unit 6 detects the position of the flushing area 31 (opening 310) described later in the circumferential rotation direction based on the output value of the belt sensor 63.

[0050] In addition, if Figure 3 As shown, the printer 100 includes a storage unit 7. The storage unit 7 includes storage devices such as ROM, RAM, HDD, and SSD. The storage unit 7 is connected to the control unit 6. The control unit 6 reads information from the storage unit 7. In addition, the control unit 6 writes information to the storage unit 7.

[0051] The printer 100 includes an operation panel 8. For example, a touch screen is provided on the operation panel 8. The touch screen displays software buttons and information, etc., and accepts touch operations from the user. In addition, hardware buttons for accepting settings and instructions, etc. are also provided on the operation panel 8. The operation panel 8 is connected to the control unit 6. The control unit 6 controls the display operation of the operation panel 8 (touch screen). In addition, the control unit 6 detects operations performed on the operation panel 8.

[0052] The printer 100 includes a communication unit 9. The communication unit 9 includes a communication circuit and the like. The communication unit 9 is connected to a user terminal PC via a network NT. The user terminal PC is an information processing device such as a personal computer. The control unit 6 communicates with the user terminal PC using the communication unit 9. For example, print data (including data such as PDL data) of a print job is sent from the user terminal PC to the printer 100. In other words, a request to execute a print job is sent from the user terminal PC to the printer 100. The print data of the print job includes various setting data related to printing, such as the size of the paper S used in the print job.

[0053] <Conveyor belt structure>

[0054] like Figure 5 As shown, the conveyor belt 30 has a flushing area 31. Figure 5 In the embodiment, the flushing area 31 is surrounded by a dotted line. The flushing area 31 is a region where an opening 310 is formed to penetrate the conveyor belt 30 in the thickness direction. In the flushing process, ink is ejected from each recording head 40, and the ejected ink passes through the opening 310 and reaches the receiving portion 302 (see FIG. 1 ) disposed inside the conveyor belt 30. Figure 4 ). The ink in the receiving unit 302 is recovered and discarded.

[0055] The conveyor belt 30 is provided with a plurality of flushing areas 31. The plurality of flushing areas 31 are arranged at predetermined intervals from each other in the circumferential rotation direction of the conveyor belt 30.

[0056] Each flushing area 31 has a plurality of (the same number of) openings 310. The openings 310 are long holes that are long in the width direction of the conveyor belt 30. The shape of the openings 310 (the shape when viewed from the thickness direction of the conveyor belt 30) is not particularly limited, and may be rectangular, circular, elliptical, or oblong.

[0057] For example, each flushing area 31 includes two rows of openings. The opening rows are rows of openings 310 arranged at equal intervals in the width direction of the conveyor belt 30. One opening row has six openings 310, and the other opening row has five openings 310. In addition, the center position of any opening row in the width direction is consistent with the center position of the conveyor belt 30 in the width direction. That is, the multiple openings 310 of each flushing area 31 are arranged in a staggered manner in the width direction. In addition, the length of the opening 310 in the width direction (opening width) is greater than the interval between one opening 310 and another opening 310 adjacent to each other in the width direction.

[0058] In addition, if Figure 6 As shown, the width W1 (mm) is smaller than the width W2 (mm). In addition, the width W1 corresponds to the length of the line print head 41 in the width direction. Specifically, the width W1 corresponds to the length in the width direction from the end of the recording head 40 located on one side in the width direction to the end of the recording head 40 located on the other side in the width direction. The width W2 corresponds to the length in the width direction of the flushing area 31. Specifically, the width W2 corresponds to the length in the width direction from the end of the opening 310 located on the one side most in the width direction to the end of the other side of the opening 310 located on the other side most in the width direction.

[0059] Thus, by rotating the conveyor belt 30 in the circumferential direction, the plurality of nozzles 4N of each recording head 40 can be vertically opposed to at least one of the openings 310. As a result, during the flushing process, although ink that does not contribute to printing is ejected from each nozzle 4N, the ink can be controlled to pass through the opening 310 (the ink can be controlled not to adhere to the conveyor belt 30 and the paper S).

[0060] <Paper Transport>

[0061] When printing is continuously performed on a plurality of sheets of paper S of the same size that are sequentially conveyed by the conveyor belt 30, the control unit 6 controls so that the interval in the conveying direction between the rear end of the leading sheet S and the front end of the trailing sheet S (the sheet S that is conveyed next to the leading sheet S), that is, the paper feed interval (the width in the conveying direction of the area between the rear end of the leading sheet S and the front end of the trailing sheet S) is constant. That is, in this case, the control unit 6 controls so that the plurality of sheets of paper S are conveyed at a fixed interval (the paper feed intervals of the plurality of sheets of paper S are maintained at a fixed interval). Continuous printing of a plurality of sheets of paper S of the same size that are sequentially conveyed by the conveyor belt 30 at intervals corresponds to "continuous printing", which is simply referred to as "continuous printing" in the following description.

[0062] Here, during the continuous printing, the flushing process is performed in each recording head 40. The control unit 6 controls the flushing process performed by each recording head 40. The ink ejected during the flushing process does not contribute to printing. Therefore, the control unit 6 controls so that the ink ejected during the flushing process passes through the opening 310. That is, the control unit 6 ejects ink from each nozzle 4N at a timing facing the opening 310 that does not overlap with the paper S.

[0063] In order to perform such control, the control unit 6 recognizes the size of the paper S conveyed by the conveyor belt 30. In addition, the control unit 6 detects the reference position of the conveyor belt 30. Furthermore, the control unit 6 estimates the timing of starting to convey the paper S from the registration roller pair 11 to the conveyor belt 30 so that the flushing area 31 appears at a fixed period in the paper feeding interval. The control unit 6 changes the timing of starting to convey the paper S from the registration roller pair 11 to the conveyor belt 30 according to the size of the paper S conveyed by the conveyor belt 30. Before executing the printing job, the control unit 6 recognizes the size of the paper S (the paper S conveyed by the conveyor belt 30) used in the printing job based on the print data of the printing job executed this time.

[0064] Figure 7 The positional relationship between the paper S conveyed by the conveyor belt 30 and the flushing area 31 is shown. Figure 7 The circumferential rotation direction of the conveyor belt 30 (the conveying direction of the paper S) is from right to left on the paper surface. Figure 7 In FIG. 3 , the flushing area 31 is indicated by a hatched pattern and the opening 310 is omitted. Figure 7 In the figure, the reference numerals of the paper S are omitted, and instead, the size of the paper S is marked in the figure representing the paper S. In addition, for convenience, Figure 7 A plurality of sheets S of different sizes are collectively shown in the figure.

[0065] Here, refer to Figure 8 , detailed instructions are given around the A4 vertical size. Figure 8 The circumferential rotation direction of the conveyor belt 30 (the conveying direction of the paper S) is the direction from bottom to top of the paper surface. Figure 8 In the figure, three sheets of paper S are shown, and the reference numerals of the sheets of paper S are given numbers 1 to 3 indicating the conveyance order.

[0066] When the size of the paper S is A4 longitudinal size, the flushing area 31 does not appear in the paper feeding interval between the first paper S1 and the second paper S2. The flushing area 31 appears in the paper feeding interval between the second paper S2 and the third paper S3. The flushing area 31 in the paper feeding interval between the paper S2 and the paper S3 does not overlap with any of the paper S2 and S3 at all. Although not shown in the figure, the flushing area 31 does not appear in the paper feeding interval between the third paper S3 and the fourth paper S, and the flushing area 31 appears in the paper feeding interval between the fourth paper S and the fifth paper S.

[0067] <Flushing treatment>

[0068] Hereinafter, the control of the flushing process performed by each recording head 40 will be described with focus on a certain recording head 40. The same control as that of the recording head 40 is performed on the other recording heads 40. Therefore, the description of the control of the other recording heads 40 will be omitted.

[0069] In the continuous printing of a plurality of sheets of paper S of the same size, the control unit 6 sets the period from when the leading end of the first printed sheet of paper S (the first sheet of paper S) reaches the printing position of the recording head 40 (the position opposite to the recording head 40) to when the last printed sheet of paper S (the final sheet of paper S) in the continuous printing passes the printing position of the recording head 40 (the position opposite to the recording head 40) as the control period of the flushing process in the continuous printing. Furthermore, during the set control period, the control unit 6 causes the target nozzle 4Nt (see Fig. 9 ) for flushing treatment.

[0070] Here, the target nozzle 4Nt is described in detail. The control unit 6 sets the target of the flushing process among the plurality of nozzles 4N. The set nozzle 4N is the target nozzle 4Nt. The control unit 6 performs a process of ejecting ink from the target nozzle 4Nt as the flushing process during the control period of the flushing process.

[0071] When setting the target nozzle 4Nt, the control unit 6 recognizes the size of the paper S used in continuous printing (the paper S conveyed by the conveyor belt 30 ), and sets any one of the plurality of nozzles 4N as the target nozzle 4Nt based on the size of the paper S in the width direction.

[0072] For example, the paper S used in continuous printing and the recording head 40 (plurality of nozzles 4N) are Fig. 9The positional relationship shown in FIG. 1 is shown in FIG. 1 . In this case, the control unit 6 sets the nozzle 4N located in the area inside the width direction of the range R1, which is equivalent to the width direction size of the paper S used in the continuous printing, as the target nozzle 4Nt. In other words, the control unit 6 sets the nozzle 4N that is opposite to the paper S in the up-down direction when printing on the paper S as the target nozzle 4Nt. The target nozzle 4Nt is a nozzle 4N that contributes to printing on the paper S. On the other hand, the nozzle 4N located in the area outside the width direction of the range R1 (the nozzle 4N that is not opposite to the paper S in the up-down direction when printing on the paper S) does not contribute to printing and is not set as the target nozzle 4Nt.

[0073] During the execution of continuous printing (during the control period of the flushing process), when the flushing area 31 that does not overlap with the paper S at all faces the recording head 40, the control unit 6 causes the recording head 40 to perform a process of ejecting ink from the target nozzle 4Nt to the opening 310 as the flushing process. Hereinafter, the flushing area 31 that does not overlap with the paper S at all is referred to as a non-overlapping flushing area 31 to distinguish it from other flushing areas 31.

[0074] exist Figure 8 In the example shown, if the first sheet to be printed continuously is paper S1, the time when the leading end of paper S1 reaches the printing position of the recording head 40 becomes the starting point of the control period. Figure 8 In the example shown, the flushing process is performed when the non-overlapping flushing area 31 located in the paper feeding interval between the paper S2 and the paper S3 faces the recording head 40. In addition, although not shown, the non-overlapping flushing area 31 also appears in the paper feeding interval between the fourth paper S and the fifth paper S, and the flushing process is performed when the non-overlapping flushing area 31 faces the recording head 40. Thereafter, the non-overlapping flushing area 31 appears in the paper feeding interval between the even-numbered paper S and the odd-numbered paper S, and the flushing process is performed when the non-overlapping flushing area 31 faces the recording head 40. That is, the flushing process is performed once each time the non-overlapping flushing area 31 located in the paper feeding interval between the paper S conveyed by the conveyor belt 30 reaches a position facing the recording head 40.

[0075] During the control of the flushing process, even if the flushing area 31 partially overlapping the paper S (the flushing area 31 only partially overlapping the paper S) faces the recording head 40, the control unit 6 does not cause the recording head 40 to perform the flushing process. Figure 8 In the example shown, even if the flushing area 31 overlapping with the paper S1 , the flushing area 31 overlapping with the paper S2 , and the flushing area 31 overlapping with the paper S3 are respectively opposed to the recording head 40 , the flushing process is not performed.

[0076] Fig.10 An example of controlling the flushing process (including the preliminary flushing process described later) is shown. Fig.10 As shown, during the period Tn when the non-overlap flushing area 31 faces the recording head 40, the control unit 6 causes each target nozzle 4Nt to perform n 1 Lines of ink ejected (n 1 Each time the non-overlap flushing area 31 faces the recording head 40 (each time the period Tn comes), the control unit 6 causes each target nozzle 4Nt to perform n 1 The ink ejection process of each row is regarded as a flushing process. 1 The row is 30 rows.

[0077] Furthermore, when receiving a request to execute a print job, the control unit 6 adds the received print job to the queue. When there are a plurality of print jobs in the queue, the control unit 6 executes the plurality of print jobs in the order in which they were received.

[0078] When the sizes of the paper S used in the first print job whose receiving order is N and the second print job whose receiving order is N+1 are the same, the control unit 6 executes the first print job and the second print job as a single job. In this case, the control unit 6 sets the period from when the first paper S of the first print job arrives at the printing position of the recording head 40 to when the last paper S of the second print job passes through the printing position of the recording head 40 as the control period of the flushing process.

[0079] <Preliminary flushing treatment>

[0080] Hereinafter, the control of the preliminary flushing process performed by each recording head 40 will be described with focus on a certain recording head 40. The same control as that of the recording head 40 is performed on the other recording heads 40. Therefore, the description of the control of the other recording heads 40 will be omitted.

[0081] When the size of the first paper S (corresponding to the "first recording medium") conveyed and printed by the conveyor belt 30 is different from the size of the second paper S (corresponding to the "second recording medium") conveyed and printed after the first paper S, the control unit 6 performs a switching process to switch the paper source. Therefore, the paper feeding interval between the first paper S and the second paper S becomes larger. As a result, the viscosity of the ink in the nozzle 4N becomes higher before the second paper S is printed, causing clogging.

[0082] For example, the sizes of the paper S used in the first print job whose receiving order is N and the second print job whose receiving order is N+1 may be different from each other. In this case, the control unit 6 performs the switching process after the paper feeding process of the last paper S (first paper S) of the first print job, and starts the paper feeding process of the first paper S (second paper S) of the second print job. As a result, the paper feeding interval between the first paper S and the second paper S becomes larger.

[0083] When the width dimension of the second paper S is larger than the width dimension of the first paper S, the nozzle 4N not used in the printing of the first paper S is used in the printing of the second paper S. Since the unused time of the nozzle 4N becomes longer, the viscosity of the ink in the nozzle 4N tends to increase. Therefore, it is preferable to perform a process (i.e., flushing process) of forcibly ejecting the ink in the nozzle 4N not used in the printing of the first paper S before printing the second paper S.

[0084] Therefore, when printing on a sheet S (first sheet S) having a first size in the width direction and then printing on a sheet S (second sheet S) having a second size larger than the first size in the width direction, the control unit 6 causes the recording head 40 to perform the following processing as a preliminary flushing processing after the first sheet S passes through the printing position of the recording head 40 (a position opposite to the recording head 40) and before the second sheet S reaches the printing position of the recording head 40: that is, ink is ejected from a predetermined nozzle 4N (equivalent to the “first nozzle”) that was not set as the target nozzle 4Nt when printing on the first sheet S but is newly set as the target nozzle 4Nt when printing on the second sheet S, toward the opening 310. Hereinafter, the nozzle 4N equivalent to the “first nozzle” is denoted by reference numeral 401 and is referred to as the first nozzle 401.

[0085] In addition, the control unit 6 causes the recording head 40 to further perform the following process as a preliminary flushing process: that is, ink is ejected from the nozzle 4N (corresponding to the "second nozzle") set as the target nozzle 4Nt when printing on the first paper S to the opening 310. Hereinafter, the nozzle 4N corresponding to the "second nozzle" is denoted by the reference numeral 402 and is referred to as the second nozzle 402.

[0086] For example, when the flushing area 31 located downstream in the conveying direction of the second paper S and closest to the second paper S faces the recording head 40, the control unit 6 causes the recording head 40 to perform the preliminary flushing process. Hereinafter, the flushing area 31 located downstream in the conveying direction of the second paper S and closest to the second paper S is referred to as the preliminary flushing area 31 to distinguish it from other flushing areas 31. In addition, the preliminary flushing area 31 is a flushing area 31 that does not overlap with the paper S at all.

[0087] exist Figure 8 In the example shown, the second sheet S is the sheet S1. In this case, the flushing area 31 shown just above the sheet S1 is the preliminary flushing area 31. Figure 8 The flushing area 31 shown as being located downstream in the paper conveying direction relative to the flushing area 31 just above the paper S1 is set as a preliminary flushing area 31 .

[0088] Here, refer to Fig.11, the first nozzle 401 and the second nozzle 402 are described in detail. Fig.11 In the figure, the first paper S is denoted by reference symbol Sa, and the second paper S is denoted by reference symbol Sb for distinction.

[0089] Fig.11 The first paper Sa is a paper S of the first size, which is Fig. 9 That is, when printing the first paper Sa, the nozzles 4N located in the area in the width direction inside the range R1 corresponding to the width direction size of the first paper Sa are set as the target nozzles 4Nt (see Fig. 9 ) On the other hand, when printing the first paper Sa, the nozzles 4N located in the area outside the width direction of the range R1 are not set as the target nozzles 4Nt.

[0090] Fig.11 The second paper Sb is a paper S of a second size larger in the width direction than the first size. When printing the second paper Sb, the nozzles 4N located in the area in the width direction inside the range R2 corresponding to the size of the second paper Sb in the width direction are set as the target nozzles 4Nt. On the other hand, when printing the second paper Sb, the nozzles 4N located in the area in the width direction outside the range R2 are not set as the target nozzles 4Nt.

[0091] exist Fig.11 In the example shown, the switching process is performed after the paper feeding process of the first paper Sa. Therefore, the paper feeding interval between the first paper Sa and the second paper Sb becomes larger. Fig.11 In the figure, for convenience, the figure mark 4Nt is omitted.

[0092] exist Fig.11 In the example shown, when printing on the first paper Sa, the nozzles 4N located in the area outside the width direction of the range R1 are not set as the target nozzles 4Nt. When printing on the second paper Sb, the nozzles 4N located in the area inside the width direction of the range R2 are set as the target nozzles 4Nt. Fig.11 In the example shown, the nozzles 4N located in the area outside the width direction of the range R1 and in the area inside the width direction of the range R2 are the first nozzles 401. The nozzles 4N located in the area inside the width direction of the range R1 are the second nozzles 402.

[0093] When the preliminary flushing area 31 faces the recording head 40, the control unit 6 causes the recording head 40 to perform a process of ejecting a first amount of ink from each first nozzle 401 as a preliminary flushing process. In addition, at this time, the control unit 6 causes the recording head 40 to perform a process of ejecting a second amount of ink less than the first amount from each second nozzle 402 as a preliminary flushing process.

[0094] The first amount is greater than the second amount. That is, the amount of ink ejected from each first nozzle 401 in the preliminary flushing process is greater than the amount of ink ejected from each second nozzle 402 in the preliminary flushing process. In addition, the amount of ink ejected from each second nozzle 402 in the preliminary flushing process is greater than the amount of ink ejected from each target nozzle 4Nt in the normal flushing process.

[0095] For example, Fig.10 As shown, during the period T0 when the preliminary flushing area 31 faces the recording head 40, the control unit 6 ejects n more lines of ink from each first nozzle 401 than the normal flushing process of the target nozzle 4Nt. 2 Lines of ink ejected (n 2 For example, n 2 The rows are 100 rows.

[0096] In addition, during the period T0 when the preliminary flushing area 31 faces the recording head 40, the control unit 6 ejects n lines or more of ink from each second nozzle 402 for the normal flushing process of the target nozzle 4Nt. 3 Lines of ink ejected (n 3 For example, n 3 The rows are 50 rows.

[0097] In the present embodiment, as described above, when printing the first paper Sa (paper S of the first size) and then printing the second paper Sb (paper S of the second size larger than the first size in the width direction), the control unit 6 causes the recording head 40 to perform a preliminary flushing process after the first paper Sa passes the printing position of the recording head 40 (the position opposite to the recording head 40) and before the second paper Sb reaches the printing position of the recording head 40. The preliminary flushing process is to eject ink toward the opening 310 from a predetermined first nozzle 401 that was not set as the object nozzle 4Nt when printing the first paper Sa but is newly set as the object nozzle 4Nt when printing the second paper Sb.

[0098] Here, the first nozzle 401 is a nozzle 4N that does not contribute to printing during continuous printing. Therefore, even if the nozzle 4N corresponding to the first nozzle 401 is not set as the target nozzle 4Nt (even if the flushing process of the nozzle 4N is not performed), it will not affect the image quality. By performing control in the above manner, the flushing process of the nozzle 4N that does not contribute to printing is not performed, and the ink consumption in the flushing process can be reduced.

[0099] On the other hand, the first nozzle 401 is a nozzle 4N that helps printing in the next printing. Therefore, if the viscosity of the ink in the nozzle 4N corresponding to the first nozzle 401 becomes high, the image quality in the next printing is affected. Therefore, before the next printing, a preliminary flushing process is performed to forcibly eject the ink of the first nozzle 401. Thus, even if the flushing process of the first nozzle 401 is not performed in the continuous printing, the clogging of the first nozzle 401 in the next printing can be suppressed. That is, the degradation of the image quality in the next printing can be suppressed.

[0100] As a result, in the present embodiment, it is possible to reduce the amount of ink consumed in the flushing process while suppressing a decrease in image quality.

[0101] In addition, in the present embodiment, as described above, the control unit 6 causes the recording head 40 to further perform the following process as a preliminary flushing process: that is, ink is ejected from the second nozzle 402 set as the target nozzle 4Nt when printing on the first paper Sa to the opening 310. In this structure, clogging of the second nozzle 402 can be suppressed. As a result, degradation of image quality can be further suppressed in the next printing.

[0102] In addition, in the present embodiment, as described above, the amount of ink ejected from each first nozzle 401 in the preliminary flushing process is greater than the amount of ink ejected from each second nozzle 402 in the preliminary flushing process. Here, since the first nozzle 401 is not used in continuous printing, it is more likely to be clogged than the second nozzle 402 used in continuous printing. However, the amount of ink ejected from the first nozzle 401 in the preliminary flushing process is greater than that from the second nozzle 402. Thus, clogging of the first nozzle 401 can be reliably suppressed.

[0103] In addition, in the present embodiment, as described above, the amount of ink ejected from each second nozzle 402 in the preliminary flushing process is greater than the amount of ink ejected from each target nozzle 4Nt in the normal flushing process. That is, the amount of ink ejected from each first nozzle 401 in the preliminary flushing process is greater than the amount of ink ejected from each target nozzle 4Nt in the normal flushing process. Thus, clogging of the first nozzle 401 can be more reliably suppressed.

[0104] Here, in the case where the second paper Sb (the second size of paper S) is printed after the plurality of first papers Sa (the first size of paper S) sequentially conveyed by the conveyor belt 30 are continuously printed, the more the number of first papers Sa used in the continuous printing (the number of printed sheets in the continuous printing) is, the longer the unused time of the first nozzle 401 is. In addition, by performing a capping process of covering the nozzle surface of the recording head 40 with a cap, the nozzle surface of the recording head 40 (the ink in the nozzle 4N) is suppressed from drying. However, during the execution of printing, the capping process of the recording head 40 is not performed. Therefore, the longer the continuous printing time is, the longer the unused time of the first nozzle 401 is, and the higher the viscosity of the ink in the first nozzle 401 is (the easier it is to dry in the first nozzle 401).

[0105] Therefore, in the present embodiment, when printing is performed on the second paper Sb after printing on the plurality of first paper Sa sequentially conveyed by the conveyor belt 30, the control unit 6 identifies the number of printed sheets in the continuous printing, and increases the ink ejection amount of each first nozzle 401 in the preliminary flushing process as the number of printed sheets identified increases. Thus, in the next printing of the continuous printing with a large number of printed sheets, even when using paper S having a larger size in the width direction than the paper S used in the continuous printing, it is possible to suppress a decrease in image quality.

[0106] The embodiments disclosed this time are all illustrative and should not be considered restrictive. The scope of the present invention is indicated by the claims rather than the description of the embodiments above, and includes equivalents to the claims and all modifications within the scope of the claims.

Claims

1. An inkjet recording device, characterized in that include: A conveyor belt is supported to be rotatable in a circumferential direction and conveys the recording medium by the circumferential rotation; a recording head, arranged at a position opposite to the recording medium, having a plurality of nozzles arranged in a width direction perpendicular to the circumferential rotation direction of the conveyor belt, and performing printing on the recording medium by ejecting ink from the nozzles; as well as a control unit that controls flushing processing performed by the recording head, The conveyor belt has a flushing area formed with openings, The flushing area is arranged in plurality at intervals in the circumferential rotation direction. The control unit sets the nozzle facing the recording medium when printing on the recording medium as a target nozzle, and when the flushing area that does not overlap with the recording medium faces the recording head, causes the recording head to perform a process of ejecting ink from the target nozzle toward the opening as the flushing process, When printing on the recording medium having a first size in the width direction and then printing on the recording medium having a second size in the width direction that is larger than the first size, the control unit causes the recording head to perform a preliminary flushing process after the recording medium of the first size passes through a position relative to the recording head and before the recording medium of the second size reaches a position relative to the recording head. The preliminary flushing process ejects ink toward the opening from a predetermined first nozzle that was not set as the target nozzle when printing on the recording medium of the first size but is newly set as the target nozzle when printing on the recording medium of the second size.

2. The inkjet recording device according to claim 1, wherein In addition to the preliminary flushing process, the control unit causes the recording head to further perform a process of ejecting ink from a second nozzle set as the target nozzle when printing on the recording medium of the first size toward the opening.

3. The inkjet recording device according to claim 2, wherein: The amount of ink ejected from each of the first nozzles in the preliminary flushing process is greater than the amount of ink ejected from each of the second nozzles in the process of ejecting ink from the second nozzle to the opening, which is performed other than the preliminary flushing process.

4. The inkjet recording device according to claim 2, wherein: The amount of ink ejected from each of the second nozzles in the process of ejecting ink from the second nozzle to the opening is equal to or greater than the amount of ink ejected from each of the target nozzles in the flushing process.

5. The inkjet recording device according to any one of claims 1 to 4, characterized in that: When printing on the recording medium of the second size after continuously printing on a plurality of recording media of the first size conveyed sequentially by the conveyor belt, the control unit identifies the number of sheets of the continuous printing, and the greater the number of sheets of printing, the greater the amount of ink ejected from each of the first nozzles in the preliminary flushing process.

Images