Inkjet recording device

Abstract

The present invention provides an inkjet recording device. When printing continuously on a plurality of recording media of the same size, a control unit sets the period from when the first recording medium reaches a position opposite to a recording head to when the last recording medium passes the position opposite to the recording head as a control period for flushing processing, sets a nozzle that is not opposite to the recording medium during the control period as a first nozzle, and sets a nozzle that is opposite to the recording medium during the control period as a second nozzle, and performs control so that the total ejection amount of ink from each first nozzle in the flushing processing during the control period is less than the total ejection amount of ink from each second nozzle.

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 transport a recording medium. Ink is ejected from the recording head onto the recording medium transported 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 clogging of the nozzles of the recording head. Performing the flushing process can prevent degradation of image quality.

[0004] For example, conventionally, an opening area for flushing is formed on the conveyor belt. During the flushing process, ink is ejected into the opening area. The ejected ink passes through the opening area. This prevents the ink ejected during the flushing process (ink that does not contribute to printing) from adhering to the conveyor belt and recording medium.

[0005] In conventional flushing processes, for example, the same amount of ink is ejected from all nozzles. That is, nozzles not contributing to printing eject the same amount of ink as nozzles contributing to printing. Conventional control methods can lead to increased ink consumption during flushing. 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 that can suppress degradation of image quality and reduce ink consumption in flushing processing.

[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 that controls a flushing process performed by the recording head, wherein the conveyor belt has a flushing area formed with an opening, and the flushing area is arranged in plurality at intervals in the circumferential rotation direction. When continuously printing on a plurality of recording media of the same size conveyed sequentially by the conveyor belt, the control unit controls the flushing process from the first recording medium of the continuous printing to the recording medium adjacent to the recording head. The period from the relative position to the final position of the continuous printing when the recording medium passes through the position relative to the recording head is set as the control period of the flushing process. During the control period, when the flushing area that does not overlap with the recording medium is opposite to the recording head, the control unit causes the recording head to perform a process of ejecting ink from all the nozzles to the opening as the flushing process. The control unit sets the nozzles that are not opposite to the recording medium during the control period as first nozzles among the multiple nozzles, and sets the nozzles that are opposite to the recording medium during the control period as second nozzles, and controls so that the total ejection amount of ink from each of the first nozzles in the flushing process during the control period is less than the total ejection amount of ink from each of the second nozzles.

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

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

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

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

[0012] Figure 4 This 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 This is a top view of a conveyor belt of an inkjet recording apparatus 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 in the inkjet recording apparatus according to one embodiment of the present invention.

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

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

[0017] Figure 9 This is a diagram showing a first nozzle and a second nozzle of an inkjet recording device according to one embodiment of the present invention.

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

[0019] The following describes the inkjet recording device of this embodiment using a printer as an example. For example, the printer prints an image on paper as a recording medium. Various sheets such as OHP sheets can also be used as recording media.

[0020] <Overall Structure of Printer>

[0021] like Figure 1 As shown, the printer 100 of this embodiment includes a first conveyor unit 1 and a second conveyor unit 2. The first conveyor unit 1 supplies paper S placed in the paper cassette CA and conveys it to the printing position. During a print job using the printer 100, printing is performed on the paper S passing through the printing position. The second conveyor unit 2 conveys the printed paper S and discharges it to the discharge tray ET.

[0022] For example, although not shown, the printer 100 is equipped with multiple paper cassettes CA. The sizes of the papers S placed in the multiple paper cassettes CA may be the same or different. During a print job using the printer 100, the paper cassette CA containing the papers S used in the print job is set as a paper source, and the papers S are supplied from the paper cassette CA set as the paper source.

[0023] The first conveying unit 1 includes multiple conveying roller components, including a registration roller pair 11. Each of the multiple conveying roller components rotates to convey a sheet of paper S. The registration roller pair 11 comprises a pair of rollers in pressure contact with each other. An registration nip is formed between the pair of rollers. Sheets of paper S fed from the paper cassette CA enter the registration nip. The registration roller pair 11 rotates to convey the sheets of paper S entering the registration nip to the belt conveying unit 3, described later.

[0024] The registration roller pair 11 stops rotating when the leading end of the paper S reaches the registration nip. At this point, the conveying roller member upstream of the registration roller pair 11 in the paper conveying direction rotates, thereby correcting the skew of the paper S.

[0025] The printer 100 includes a belt conveyor unit 3. The belt conveyor unit 3 receives and conveys paper S from the first conveyor unit 1. The belt conveyor unit 3 includes a conveyor belt 30. The conveyor belt 30 is annular and supported for circumferential rotation. Furthermore, the belt conveyor unit 3 includes a plurality of tension rollers 301. The plurality of tension rollers 301 are supported for circumferential rotation. The conveyor belt 30 is tensioned and supported by the plurality of tension rollers 301, allowing the conveyor belt 30 to rotate circumferentially.

[0026] One of the plurality of tension rollers 301 is connected to a belt motor (not shown) and rotates when the belt motor's driving force is transmitted thereto. The conveyor belt 30 rotates circumferentially as the tension roller 301 connected to the belt motor rotates, and the other tension rollers 301 rotate accordingly.

[0027] 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 has a plurality of suction holes (not shown) formed therein that penetrate in the thickness direction.

[0028] The paper S conveyed from the first conveying unit 1 arrives on the outer circumference of the conveyor belt 30. The suction unit 300 sucks the paper S through the suction holes. The paper S on the outer circumference of the conveyor belt 30 is attracted to the outer circumference of the conveyor belt 30. The conveyor belt 30 rotates while holding the paper S on its outer circumference. This conveys the paper S.

[0029] In this manner, the belt conveying section 3 conveys the paper S along 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).

[0030] The printer 100 includes a recording unit 4. The recording unit 4 is disposed opposite to the outer peripheral surface of the conveyor belt 30. When a sheet S is sucked and held by the outer peripheral surface of the conveyor belt 30, the sheet S faces the recording unit 4 with a gap therebetween.

[0031] like Figure 2 As 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.

[0032] The line print head 41 for each color is composed of a plurality (e.g., three) of recording heads 40. For example, the plurality of recording heads 40 for each color are arranged in a staggered pattern in a direction perpendicular to the circumferential rotation direction of the conveyor belt 30 (the conveyance 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."

[0033] The recording heads 40 are arranged at intervals in the vertical direction relative to the outer circumferential surface of the conveyor belt 30. In other words, the recording heads 40 are arranged at positions vertically opposed to the paper S being conveyed by the conveyor belt 30. The vertical direction is perpendicular to the circumferential rotational direction and width direction of the conveyor belt 30.

[0034] Each recording head 40 has a nozzle surface facing the conveyor belt 30 (the 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. In reality, more nozzles 4N are provided in each recording head 40 .

[0035] The recording unit 4 (recording head 40) ejects ink from nozzles 4N onto the paper S based on the image data to be printed during the print job. The ink ejected from the recording unit 4 adheres to the paper S. This prints the image on the paper S. Specifically, the position between the conveyor belt 30 and the recording head 40 is the printing position. In other words, the position vertically opposite the nozzle face (nozzles 4N) of the recording head 40 is the printing position.

[0036] Here, the viscosity of the ink in nozzles 4N that eject ink less frequently among the multiple nozzles 4N increases over time. This results in clogging, which degrades image quality. To prevent this undesirable phenomenon, each recording head 40 performs a flushing process. During the flushing process, each recording head 40 ejects any ink remaining in the nozzles 4N, thereby preventing clogging. Details will be described later.

[0037] Return to Figure 1 The 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 adhering to the paper S during conveyance. The decurler 52 corrects the curl of the paper S. The decurler 52 conveys the paper S with the corrected curl to the second conveying unit 2.

[0038] In addition, if Figure 3As shown, the printer 100 includes a control unit 6. The control unit 6 includes processing circuits such as a CPU and an ASIC. The control unit 6 controls the printing jobs executed by the printer 100. Specifically, the control unit 6 controls the operations of the first conveyor unit 1, the second conveyor unit 2, the belt conveyor unit 3, the recording unit 4, the drying unit 51, and the decurler 52. Furthermore, the control unit 6 controls the conveyance of the paper S and the ejection of ink by each recording head 40. Furthermore, the control unit 6 controls the flushing process performed by each recording head 40.

[0039] The control unit 6 is connected to a registration sensor 61 , a paper sensor 62 , and a belt sensor 63 . Figure 4 The respective detection positions (arrangement positions) of the registration sensor 61 , the paper sensor 62 , and the belt sensor 63 are schematically shown.

[0040] The alignment sensor 61 detects a position upstream of the registration 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.

[0041] Based on the output value of the alignment sensor 61, the control unit 6 detects the arrival and passage of the leading edge of the paper S at the detection position of the alignment sensor 61. In other words, based on the output value of the alignment sensor 61, the control unit 6 detects the arrival and passage of the leading edge of the paper S in the alignment nip. The control unit 6 estimates the timing for the registration roller pair 11 to start conveying the paper S (the timing for starting rotation of the registration roller pair 11) based on the elapsed time since the arrival of the leading edge of the paper S at the detection position of the alignment sensor 61. Even if the paper S is skewed, conveyance of the paper S by the registration roller pair 11 begins after the skew is corrected.

[0042] The paper sensor 62 detects the position between the printing position of the line head 41 located furthest upstream in the paper transport direction and the registration nip. The paper sensor 62 changes its output value depending on the presence or absence of paper S at the corresponding detection position. A CIS (Contact Image Sensor) or a reflective or transmissive optical sensor can be used as the paper sensor 62. For example, a CIS is used as the paper sensor 62.

[0043] The control unit 6 detects the arrival and passage of the leading 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 being conveyed by the conveyor belt 30 based on the output value of the paper sensor 62. Alternatively, the timing of ejecting ink onto the paper S being conveyed by the conveyor belt 30 may be estimated based on the elapsed time since the registration roller pair 11 started conveying the paper S.

[0044] Furthermore, the control unit 6 measures the paper transit time from the time the leading edge of the paper S reaches the detection position of the paper sensor 62 until the trailing edge of the paper S passes the detection position of the paper sensor 62. The paper transit time at the detection position of the paper sensor 62 varies depending on the size of the paper S in the conveyance direction. Therefore, the control unit 6 identifies the size of the paper S in the conveyance direction being conveyed by the conveyor belt 30 based on the paper transit time. This allows the control unit 6 to identify the size of the paper S in the conveyance direction even if the paper S being conveyed by the conveyor belt 30 is not a standard size.

[0045] Furthermore, the control unit 6 detects positional deviation (skewness) of the paper S based on the output value of the paper sensor 62 (data obtained by reading by the paper sensor 62). For example, the paper S may become positionally deviated after the registration roller pair 11 starts conveying the paper S. In such cases, the control unit 6 detects the positional deviation of the paper S.

[0046] In addition, the number of paper sensors 62 provided may be multiple. For example, two paper sensors 62 may be provided.

[0047] 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. This allows the reference position of the conveyor belt 30 to be detected based on the output value of the belt sensor 63. For example, a CIS is used as the belt sensor 63. Alternatively, a transmissive or reflective optical sensor may be used as the belt sensor 63.

[0048] 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 direction based on the output value of the belt sensor 63.

[0049] 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 and writes information to the storage unit 7.

[0050] The printer 100 includes an operation panel 8. The operation panel 8 is provided with, for example, a touch screen. The touch screen displays software buttons and information, and accepts touch operations from the user. The operation panel 8 also includes hardware buttons for accepting settings and instructions. The operation panel 8 is connected to a control unit 6. The control unit 6 controls the display operation of the operation panel 8 (touch screen). Furthermore, the control unit 6 detects operations performed on the operation panel 8.

[0051] The printer 100 includes a communication unit 9. The communication unit 9 includes a communication circuit, etc. 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, the control unit 6 transmits print data (including data such as PDL data) for a print job from the user terminal PC to the printer 100. In other words, a request to execute a print job is transmitted from the user terminal PC to the printer 100. The print data for a print job includes various setting data related to printing, such as the size of the paper S used in the print job.

[0052] <Conveyor Belt Structure>

[0053] like Figure 5 As shown, the conveyor belt 30 has a flushing area 31. Figure 5 In the figure, the flushing area 31 is surrounded by a dotted line. The flushing area 31 is a region where openings 310 are formed that penetrate the conveyor belt 30 in the thickness direction. During the flushing process, ink is ejected from each recording head 40, and the ejected ink passes through the openings 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.

[0054] The conveyor belt 30 is provided with a plurality of flushing areas 31. The plurality of flushing areas 31 are arranged at predetermined intervals in the circumferential rotation direction of the conveyor belt 30.

[0055] Each flushing area 31 has a plurality (the same number) of openings 310. The openings 310 are elongated holes extending in the width direction of the conveyor belt 30. The shape of the openings 310 (when viewed from the thickness direction of the conveyor belt 30) is not particularly limited and can be rectangular, circular, elliptical, or oblong.

[0056] 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. Furthermore, the center position of each opening row in the width direction coincides with the center position of the conveyor belt 30 in the width direction. That is, the multiple openings 310 in each flushing area 31 are arranged in a staggered pattern in the width direction. Furthermore, the width length (opening width) of the openings 310 is greater than the distance between adjacent openings 310 in the width direction.

[0057] In addition, if Figure 6As shown, width W1 (mm) is smaller than width W2 (mm). Furthermore, width W1 corresponds to the widthwise length of the line head 41. Specifically, width W1 corresponds to the widthwise length from the end of the recording head 40 located on one side in the widthwise direction to the end of the recording head 40 located on the other side in the widthwise direction. Width W2 corresponds to the widthwise length of the flushing area 31. Specifically, width W2 corresponds to the widthwise length from the end of the opening 310 located closest to one side in the widthwise direction to the end of the opening 310 located closest to the other side in the widthwise direction.

[0058] Thus, by rotating the conveyor belt 30 in the circumferential direction, the plurality of nozzles 4N of each recording head 40 can be aligned vertically with 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, this ink can be controlled to pass through the openings 310 (this ink can be controlled to prevent it from adhering to the conveyor belt 30 and the paper S).

[0059] <Paper Transport>

[0060] When printing continuously on multiple sheets of paper S of the same size, which are sequentially conveyed by the conveyor belt 30, the control unit 6 controls the conveyance direction between the rear end of the leading sheet S and the front end of the trailing sheet S (the sheet S conveyed next to the leading sheet S), i.e., the paper feed interval (the width in the conveyance direction of the area between the rear end of the leading sheet S and the front end of the trailing sheet S). In other words, in this case, the control unit 6 controls the conveyance of the multiple sheets of paper S at fixed intervals (maintaining the paper feed intervals of the multiple sheets of paper S at fixed intervals). Continuous printing on multiple sheets of paper S of the same size, which are sequentially conveyed by the conveyor belt 30 at intervals, is referred to as "continuous printing" and will be referred to simply as "continuous printing" in the following description.

[0061] During continuous printing, each recording head 40 performs a flushing process. The control unit 6 controls the flushing process performed by each recording head 40. Ink ejected during the flushing process does not contribute to printing. Therefore, the control unit 6 controls the ink ejected during the flushing process so that it passes through the opening 310. In other words, the control unit 6 ejects ink from each nozzle 4N at a timing when the nozzle faces the opening 310 that does not overlap with the paper S.

[0062] To perform this control, the control unit 6 identifies the size of the paper S being conveyed by the conveyor belt 30. Furthermore, the control unit 6 detects the reference position of the conveyor belt 30. Furthermore, the control unit 6 estimates the timing for 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 interval between paper feeds. The control unit 6 changes the timing for starting to convey the paper S from the registration roller pair 11 to the conveyor belt 30 based on the size of the paper S being conveyed by the conveyor belt 30. Before executing a print job, the control unit 6 identifies the size of the paper S used in the print job (the paper S being conveyed by the conveyor belt 30) based on the print data for the currently executed print job.

[0063] 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, 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 2 and 3. A plurality of paper sheets S of different sizes are shown in a summary diagram.

[0064] Here, refer to Figure 8 , detailed description around 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 FIG, three sheets S are shown, and the reference numerals of the sheets S are denoted by numbers 1 to 3 indicating the order in which the sheets are conveyed.

[0065] When the paper S is A4 size (portrait), the flushing region 31 does not occur between the first and second paper S1, S2. However, the flushing region 31 occurs between the second and third paper S3. The flushing region 31 between paper S2 and S3 does not overlap with either paper S2 or S3. Although not shown, the flushing region 31 does not occur between the third and fourth paper S3, but does occur between the fourth and fifth paper S.

[0066] <Flushing treatment>

[0067] 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.

[0068] In continuous printing of multiple sheets S of the same size, the control unit 6 sets the period from the time the leading edge of the first sheet S to be printed (the first sheet S) reaches the printing position (the position facing the recording head 40) of the recording head 40 to the time the last sheet S to be printed (the final sheet S) in the continuous printing passes the printing position (the position facing the recording head 40) as a control period for the flushing process in the continuous printing. The control unit 6 causes the recording head 40 to perform the flushing process during this set control period.

[0069] Specifically, during the flushing process control period, when the flushing area 31 that does not completely overlap with the paper S faces the recording head 40, the control unit 6 causes the recording head 40 to perform a process of ejecting ink from all nozzles 4N of the recording head 40 toward the opening 310 as the flushing process. Hereinafter, the flushing area 31 that does not completely overlap with the paper S will be referred to as a non-overlapping flushing area 31 to distinguish it from other flushing areas 31.

[0070] exist Figure 8 In the example shown, if the first sheet to be printed continuously is paper S1, the moment 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 between the paper feeds of sheets S2 and S3 faces the recording head 40. Furthermore, although not shown, a non-overlapping flushing area 31 also appears between the paper feeds of the fourth and fifth sheets S, and the flushing process is performed when this non-overlapping flushing area 31 faces the recording head 40. Subsequently, a non-overlapping flushing area 31 appears between the paper feeds of the even-numbered and odd-numbered sheets S, and the flushing process is performed when this non-overlapping flushing area 31 faces the recording head 40. In other words, the flushing process is performed each time the non-overlapping flushing area 31 located between the paper feeds of sheets S conveyed by the conveyor belt 30 reaches a position facing the recording head 40.

[0071] Here, if Figure 9 As shown, the control unit 6 sets the nozzle 4N that is not opposite to the paper S during the control of the flushing process among the multiple nozzles 4N of the recording head 40 as the first nozzle 4Na, and sets the nozzle 4N that is opposite to the paper S during the control of the flushing process as the second nozzle 4Nb. Specifically, the multiple nozzles 4N are classified into nozzles 4N located in an area outside the width direction of a range corresponding to the size of the paper S in the width direction and nozzles 4N located in an area inside the width direction of the range. And, the former nozzle 4N is set as the first nozzle 4Na, and the latter nozzle 4N is set as the second nozzle 4Nb. The first nozzle 4Na is a nozzle 4N that does not contribute to printing, and the second nozzle 4Nb is a nozzle 4N that contributes to printing. In Figure 9In FIG, the edge of the paper S is indicated by a dotted line.

[0072] The control unit 6 performs control such that the total amount of ink ejected from each first nozzle 4Na during the flushing process is less than the total amount of ink ejected from each second nozzle 4Nb during the flushing process control period. To perform this control, the control unit 6 causes each first nozzle 4Na to eject a first amount of ink during a single flushing process, and causes each second nozzle 4Nb to eject a second amount of ink during a single flushing process. The first amount is less than the second amount. In other words, the second amount is greater than the first amount. The first and second amounts are predetermined by the manufacturer of the printer 100.

[0073] For example, the control unit 6 makes the total number of ink ejections from each of the first nozzles 4Na smaller than the total number of ink ejections from each of the second nozzles 4Nb during the flushing process during the control period of the flushing process. Thus, the control unit 6 makes the total amount of ink ejected from each of the first nozzles 4Na smaller than the total amount of ink ejected from each of the second nozzles 4Nb during the flushing process during the control period of the flushing process.

[0074] Furthermore, during the flushing process control period, when the flushing region 31 that partially overlaps the paper S (the flushing region 31 that only partially overlaps the paper S) faces the recording head 40, the control unit 6 causes the recording head 40 to further perform a process of ejecting ink from the first nozzle 4Na toward the opening 310 as the flushing process. Hereinafter, the flushing region 31 that partially overlaps the paper S will be referred to as the partially overlapping flushing region 31 to distinguish it from other flushing regions 31.

[0075] The control unit 6 causes the recording head 40 to perform the flushing process on the first nozzle 4Na every time the partially overlapped flushing area 31 faces the recording head 40. At this time, the flushing process on the second nozzle 4Nb is not performed.

[0076] exist Figure 8 In the example shown, when the flushing region 31 overlapping the sheet S1 faces the recording head 40, ink is ejected from the nozzle 4N (first nozzle 4Na) located outside the width direction of the sheet S1 toward the opening 310. Furthermore, when the flushing region 31 overlapping the sheet S2 faces the recording head 40, ink is ejected from the nozzle 4N (first nozzle 4Na) located outside the width direction of the sheet S2 toward the opening 310. Furthermore, when the flushing region 31 overlapping the sheet S3 faces the recording head 40, ink is ejected from the nozzle 4N (first nozzle 4Na) located outside the width direction of the sheet S3 toward the opening 310.

[0077] Figure 10 An example of controlling the flushing process (including the preliminary flushing process described later) is shown. Figure 10As shown, during the period Tn when the non-overlapping flushing area 31 faces the recording head 40, the control unit 6 causes each first nozzle 4Na to eject ink for n1 lines (n1 ink ejections) less than 10 lines, and further causes each second nozzle 4Nb to eject ink for n lines (e.g., 30 lines) greater than 10 lines (n ink ejections). Furthermore, during the period Tp when the partially overlapping flushing area 31 faces the recording head 40, the control unit 6 causes each first nozzle 4Na to eject ink for n1 lines.

[0078] For example, the amount of ink ejected per ejection by each nozzle 4N during the flushing process is the same. By making the number of ink ejections by the first nozzle 4Na and the second nozzle 4Nb different during one flushing process, the amount of ink ejected by the first nozzle 4Na can be made smaller than the amount of ink ejected by the second nozzle 4Nb, even if the amount of ink ejected per ejection by the first nozzle 4Na and the second nozzle 4Nb are the same.

[0079] Furthermore, upon receiving a print job execution request, the control unit 6 adds the received print job to the queue. If there are multiple print jobs in the queue, the control unit 6 executes the multiple print jobs in the order in which they were received.

[0080] If the paper S used in the first print job (Nth) and the second print job (N+1th) are the same size, the control unit 6 executes the first and second print jobs as a single job. In this case, the control unit 6 sets the flushing process control period from the time the first paper S of the first print job arrives at the print position of the recording head 40 to the time the last paper S of the second print job passes the print position of the recording head 40.

[0081] <Preliminary flushing treatment>

[0082] 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.

[0083] If the size of the first sheet S (corresponding to the "first recording medium"), the sheet S previously conveyed and printed on by the conveyor belt 30, differs from the size of the second sheet S (corresponding to the "second recording medium"), the control unit 6 switches the paper source. Consequently, the paper feed interval between the first and second sheets S increases. As a result, the ink viscosity in the nozzles 4N increases before printing on the second sheet S, causing clogging.

[0084] For example, the sizes of the sheets S used in the first print job (Nth) and the second print job (N+1th) may differ. In this case, the control unit 6 switches after feeding the final sheet S (first sheet S) of the first print job and starts feeding the first sheet S (second sheet S) of the second print job. This increases the feeding interval between the first sheet S and the second sheet S.

[0085] Here, if the width dimension of the second sheet S is larger than that of the first sheet S, the nozzles 4N not used for printing on the first sheet S are used for printing on the second sheet S. Since the nozzles 4N are not used for a longer period of time, the viscosity of the ink within the nozzles 4N tends to increase. Therefore, before printing on the second sheet S, it is preferable to perform a process (i.e., flushing process) to forcibly eject the ink within the nozzles 4N not used for printing on the first sheet S.

[0086] Therefore, when the width dimension of the second paper S is larger than the width dimension of the first paper S, the control unit 6 causes the recording head 40 to perform a preliminary flushing process after the first paper S passes the printing position of the recording head 40 (the position opposite to the recording head 40) and before the second paper S reaches the printing position of the recording head 40 (the position opposite to the recording head 40). The preliminary flushing process is to eject a specified amount of ink greater than the first amount from each nozzle 4N set as the first nozzle 4Na when printing on the first paper S to the opening 310.

[0087] For example, when the flushing area 31 located downstream in the conveyance direction relative to the second sheet S and closest to the second sheet S faces the recording head 40, the control unit 6 causes the recording head 40 to perform a preliminary flushing process. Hereinafter, the flushing area 31 located downstream in the conveyance direction relative to the second sheet S and closest to the second sheet S will be referred to as the preliminary flushing area 31 to distinguish it from other flushing areas 31. Furthermore, the preliminary flushing area 31 is a flushing area 31 that does not completely overlap with the sheet S.

[0088] 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. Although not shown, Figure 8 The flushing area 31 shown as being located downstream in the paper conveyance direction relative to the flushing area 31 immediately above the paper S1 is set as a preliminary flushing area 31 .

[0089] When the preliminary flushing area 31 faces the recording head 40, the control unit 6 causes the recording head 40 to perform the following processing as preliminary flushing processing: namely, eject a predetermined amount of ink, which is greater than the first amount, from each nozzle 4N set as the first nozzle 4Na when printing on the first sheet of paper S, into the opening 310 of the preliminary flushing area 31. Here, the predetermined amount is an amount greater than the second amount. Furthermore, as preliminary flushing processing, the control unit 6 causes the recording head 40 to further perform the following processing as preliminary flushing processing: eject ink from each nozzle 4N set as the second nozzle 4Nb when printing on the first sheet of paper S into the opening 310. For example, during the preliminary flushing processing, the recording head 40 ejects an amount of ink greater than the second amount (e.g., the same amount as the second amount) from each nozzle 4N set as the second nozzle 4Nb when printing on the first sheet of paper S.

[0090] For example, Figure 10 As shown, during the period T0 in which the preliminary flushing area 31 faces the recording head 40, the control unit 6 causes each nozzle 4N, which is designated as the first nozzle 4Na during printing on the first sheet of paper S, to eject ink for n2 lines (n2 ink ejections), which is greater than the number of lines ejected by the second nozzle 4Nb during normal flushing processing. Furthermore, during the period T0 in which the preliminary flushing area 31 faces the recording head 40, the control unit 6 causes each nozzle 4N, which is designated as the second nozzle 4Nb during printing on the first sheet of paper S, to eject ink for n lines, which is the same number of lines (30 lines) as the number of lines ejected by the second nozzle 4Nb during normal flushing processing. Alternatively, each nozzle 4N, which is designated as the second nozzle 4Nb during printing on the first sheet of paper S, may be caused to eject ink for a number greater than n lines.

[0091] In this embodiment, as described above, the control unit 6 sets the nozzles 4N among the multiple nozzles 4N that are not facing the paper S during the flushing process as the first nozzle 4Na, and sets the nozzles 4N that are facing the paper S during the flushing process as the second nozzle 4Nb. Here, the second nozzle 4Nb contributes to printing, while the first nozzle 4Na does not. Therefore, even if ink ejection is poorly caused by clogging in the first nozzle 4Na during continuous printing, this does not degrade image quality. In other words, even if the amount of ink ejected from the first nozzle 4Na is reduced during the flushing process, the impact on image quality is minimal. Furthermore, to prevent degradation of image quality during continuous printing, it is sufficient to perform the flushing process on the second nozzle 4Nb.

[0092] Therefore, in this embodiment, as described above, the control unit 6 performs control such that the total amount of ink ejected from each of the first nozzles 4Na during the flushing process is smaller than the total amount of ink ejected from each of the second nozzles 4Nb during the flushing process control period. This can suppress degradation of image quality and reduce ink consumption during the flushing process.

[0093] Furthermore, in this embodiment, as described above, during the flushing process control, when the flushing area 31 that partially overlaps the sheet S faces the recording head 40, the control unit 6 causes the recording head 40 to further perform a flushing process by ejecting ink from the first nozzle 4Na toward the opening 310. This configuration allows the flushing process to be performed more frequently for the first nozzle 4Na than when the flushing process is performed only when the non-overlapping flushing area 31 faces the recording head 40. Consequently, clogging of the first nozzle 4Na can be suppressed. Consequently, if the nozzle 4N designated as the first nozzle 4Na in the current print is to contribute to printing in the next print, degradation of image quality in the next print can be suppressed.

[0094] Furthermore, in this embodiment, as described above, the control unit 6 reduces the total number of ink ejections (ink ejection lines) from each of the first nozzles 4Na during the flushing process compared to the total number of ink ejections (ink ejection lines) from each of the second nozzles 4Nb during the flushing process. This makes it possible to easily reduce the total amount of ink ejected from each of the first nozzles 4Na during the flushing process compared to the total amount of ink ejected from each of the second nozzles 4Nb during the flushing process.

[0095] Furthermore, in this embodiment, as described above, when the width dimension of the second sheet S conveyed subsequent to the first sheet S is larger than the width dimension of the first sheet S, the control unit 6 causes the recording head 40 to perform a preliminary flushing process after the first sheet S passes the position opposing the recording head 40 and before the second sheet S reaches the position opposing the recording head 40. This preliminary flushing process causes each nozzle 4N, which was set as the first nozzle 4Na when printing on the first sheet S, to eject a predetermined amount of ink, greater than the first amount, into the opening 310. This configuration can suppress degradation of image quality during printing on the second sheet S.

[0096] In the present embodiment, as described above, the predetermined amount is larger than the second amount. This makes it possible to more reliably suppress clogging of the nozzle 4N set as the first nozzle 4Na when printing on the first sheet S.

[0097] Furthermore, in this embodiment, the control unit 6 causes the recording head 40 to further perform the following process as a preliminary flushing process: namely, ink is ejected from each nozzle 4N set as the second nozzle 4Nb when printing on the first sheet of paper S toward the opening 310. This can more reliably prevent the nozzles 4N set as the second nozzle 4Nb when printing on the first sheet of paper S from clogging.

[0098] The embodiments disclosed herein are for illustrative purposes only and should not be construed as limiting. The scope of the present invention is indicated by the claims rather than the description of the embodiments above, and includes all modifications within the scope of the claims and equivalents thereof.

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. When a plurality of recording media of the same size conveyed sequentially by the conveyor belt are continuously printed, the control unit sets the period from when the first recording medium of the continuous printing reaches the position opposite to the recording head to when the last recording medium of the continuous printing passes the position opposite to the recording head as the control period of the flushing process, During the control, when the flushing area that does not overlap the recording medium faces the recording head, the control unit causes the recording head to perform a process of ejecting ink from the nozzle to the opening as the flushing process each time the flushing area faces the recording head. The control unit sets the nozzle that is not opposite to the recording medium during the control period among the multiple nozzles as the first nozzle, and sets the nozzle that is opposite to the recording medium during the control period as the second nozzle, and controls so that the total ejection amount of ink from each of the first nozzles in the flushing process during the control period is less than the total ejection amount of ink from each of the second nozzles.

2. The inkjet recording device according to claim 1, wherein In addition to the flushing process, during the control period, when the flushing region partially overlapping the recording medium faces the recording head, the control unit causes the recording head to further perform a process of ejecting ink from the first nozzle toward the opening.

3. The inkjet recording device according to claim 1 or 2, characterized in that: The control unit makes the total ejection amount of ink from each of the first nozzles in the flushing process during the control period less than the total ejection amount of ink from each of the second nozzles by reducing the total ejection number of ink from each of the first nozzles in the flushing process during the control period compared to the total ejection number of ink from each of the second nozzles.

4. The inkjet recording device according to claim 1 or 2, characterized in that: The ejection amount of the ink in the flushing process of the first nozzle is set to a first amount, When the dimension in the width direction of the second recording medium, which is the recording medium conveyed subsequently to the first recording medium, is larger than the dimension in the width direction of the first recording medium, which is the recording medium conveyed in front by the conveyor belt, the control unit causes the recording head to perform a preliminary flushing process after the first recording medium passes through a position opposite to the recording head and before the second recording medium reaches a position opposite to the recording head. The preliminary flushing process is to eject a specified amount of ink greater than the first amount from the nozzle set as the first nozzle when printing on the first recording medium to the opening.

5. The inkjet recording device according to claim 4, characterized in that the ejection amount of ink in the flushing process of the second nozzle is set to a second amount which is larger than the first amount, The prescribed amount is greater than the second amount.

6. The inkjet recording device according to claim 5, characterized in that In addition to the preliminary flushing process, the control unit causes the recording head to further perform a process of ejecting ink from the nozzle set as the second nozzle when printing on the first recording medium to the opening.

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