Inkjet recording device

Abstract

To provide an inkjet recording device that efficiently directs ink droplets discharged during flushing to an ink receiving part with a simple configuration, and can suppress contamination inside the machine due to mist.SOLUTION: An inkjet recording device includes a recording head, a transport member, a control part, an ink collection part, an ink passage, and a suction part. The transport member has an opening through which ink discharged from the recording head passes. When the transport speed of the transport member is Vp [mm / s], the wind speed of the suction air generated in the ink passage by the suction part is Vh [m / s], the discharge speed of the ink at the position where it passes through the transport member is Vi [m / s], the distance from the transport member to the impact surface of the ink receiving part is Ld [mm], and the distance from the position where the last ink droplet passing through the opening has passed through the opening to the upstream side end of the opening is Ls [mm], {(Vh+Vi) / 1000}×(Ls / Vp)≥Ld is satisfied.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to an inkjet recording apparatus. [Background technology]

[0002] Conventionally, in inkjet recording devices such as inkjet printers, flushing (empty ejection) is performed periodically to eject ink from the nozzles in order to reduce or prevent clogging of the nozzles due to drying of the ink. For example, in the inkjet recording device of Patent Document 1, an opening is provided in a conveyor belt that conveys the recording medium, and ink is ejected from each nozzle of the recording head to pass through the opening of the conveyor belt.

[0003] In the inkjet recording device described above, the ink droplets that have passed through the openings in the transport belt by flushing reach an ink receiving section that normally receives ink, are collected, and are discharged from the ink receiving section as waste liquid. If the ink receiving section could be located near the ink ejection surface of the recording head, almost all of the ink droplets could be collected by the ink receiving section. However, since the transport belt is located between the recording head and the ink receiving section, it is difficult to locate the ink receiving section near the ink ejection surface. As a result, the ink droplets turn into mist before reaching the ink receiving section, contaminating the inside of the device.

[0004] As a method for improving the recovery of ejected ink droplets, for example, Patent Document 2 discloses a waste ink tank for an inkjet recording device in which an ink absorber made of a porous polymer is loaded into the waste ink tank and an ink discharge tube is placed on the ink absorber so as to divide the ink absorber evenly. The ink discharge tube has many openings in the longitudinal direction, and waste ink discharged by the ejection recovery mechanism is introduced into the waste ink tank from a connection port so that the waste ink can be evenly absorbed by the ink absorber. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-23374 A [Patent Document 2] Japanese Patent Application Publication No. 6-340092 Summary of the Invention [Problem to be solved by the invention]

[0006] The method of Patent Document 2 was unable to efficiently collect mist that occurs when the distance from the ink ejection nozzles of the recording head to the ink receiving portion is long, or ink droplets that have lost speed.

[0007] In view of the above problems, an object of the present invention is to provide an inkjet recording apparatus that can efficiently cause ink droplets ejected by flushing to reach an ink receiving section with a simple configuration, thereby suppressing contamination inside the apparatus due to mist. [Means for solving the problem]

[0008] In order to achieve the above object, a first configuration of the present invention is an inkjet recording device including a recording head, a transport member, a control unit, an ink recovery unit, an ink passage, and a suction unit. The recording head has a plurality of nozzles that eject ink. The transport member has an opening through which ink ejected from the recording head passes, and transports a recording medium. The control unit controls the driving of the recording head and the transport member to perform flushing, which ejects ink from the nozzles of the recording head and passes through the opening at a timing different from the timing contributing to image recording. The ink recovery unit is disposed opposite the recording head across the transport member, and has an ink receiving unit that receives ink that has passed through the opening during flushing. The ink passage is formed between the transport member and the ink receiving unit, and the ink that has passed through the opening passes through the ink passage. The suction unit is connected to the ink receiving unit, and sucks the ink that has passed through the opening together with air in the ink passage. When the transport speed of the transport member is Vp [mm / s], the wind speed of the suction air generated in the ink passage by the suction section is Vh [m / s], the ink ejection speed at the position passing through the transport member is Vi [m / s], the distance from the transport member to the landing surface of the ink receiving section is Ld [mm], and the distance from the position where the last ink droplet to pass through the opening passes through the opening to the upstream end of the opening is Ls [mm], the following formula (1) is satisfied. {(Vh+Vi) / 1000}×(Ls / Vp)≧ Ld ···(1) Effect of the Invention

[0009] According to the first aspect of the present invention, there is no risk of the upper portion of the ink passage being blocked by the transport member until the ink droplets that last passed through the opening reach the landing surface of the ink receiving section. This ensures that the ink droplets are collected in the ink receiving section, making it possible to prevent the ink droplets ejected during flushing from adhering to the transport member. Therefore, it is possible to maintain image quality by flushing while preventing internal contamination of the inkjet recording device. [Brief description of the drawings]

[0010] [Figure 1]FIG. 1 is an explanatory diagram showing a schematic configuration of a printer 100 as an inkjet recording apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a plan view of a recording unit 9 included in a printer 100 according to an embodiment of the present invention. [Diagram 3] FIG. 1 is an explanatory diagram showing a schematic configuration of the vicinity of a transport path of a paper P from a paper feed cassette 2 to a second transport unit 12 via a first transport unit 5 of a printer 100 according to an embodiment of the present invention; [Figure 4] FIG. 1 is a block diagram showing the hardware configuration of the main part of a printer 100 according to an embodiment of the present invention. [Diagram 5] FIG. 13 is a schematic diagram showing an ink recovery unit 31Y and a paper transport area adjacent to the ink recovery unit Y. [Figure 6] FIG. 1 is a side cross-sectional view of the ink recovery unit 31Y taken along a direction perpendicular to the transport direction. [Figure 7] A plan sectional view of the waste ink tank 33 constituting the ink recovery unit 31Y. [Figure 8] FIG. 1 is a partially enlarged view of the periphery of an opening group 82 of a first conveyor belt 8 of a first conveyor unit 5. [Figure 9] FIG. 3 is a plan view showing the positional relationship between the opening group 82 of the first conveyor belt 8 and the ink receiving portions 32a to 32c. [Figure 10] FIG. 11 is a side cross-sectional view showing a state in which the most upstream opening 81 of the first conveyor belt 8 passes through the ink receiving sections 32a to 32c. [Figure 11] FIG. 1 is a plan view of the most upstream opening 81 of the first conveyor belt 8, showing the relationship between the position through which the last ink droplet IL passes during flushing and the upstream end 81a of the most upstream opening 81. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 1. Configuration of the Inkjet Recording Apparatus Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is an explanatory diagram showing the general configuration of a printer 100 as an inkjet recording device according to one embodiment of the present invention. The printer 100 is equipped with a paper feed cassette 2 which is a paper storage section. The paper feed cassette 2 is located at the bottom inside the printer main body 1. Inside the paper feed cassette 2, paper P, which is an example of a recording medium, is stored.

[0012] A paper feeder 3 is disposed downstream of the paper feed cassette 2 in the paper transport direction, i.e., above the right side of the paper feed cassette 2 in Fig. 1. The paper feeder 3 separates and sends out the paper P one by one toward the upper right of the paper feed cassette 2 in Fig. 1.

[0013] The printer 100 has a first paper transport path 4a inside. The first paper transport path 4a is located in the upper right corner, which is the paper feed direction, of the paper feed cassette 2. The paper P sent out from the paper feed cassette 2 is transported vertically upward along the side of the printer body 1 by the first paper transport path 4a.

[0014] A pair of registration rollers 13 is provided at the downstream end of the first paper transport path 4a in the paper transport direction. Furthermore, a first transport unit 5 and a recording unit 9 are arranged immediately downstream in the paper transport direction of the pair of registration rollers 13. The paper P sent out from the paper feed cassette 2 reaches the pair of registration rollers 13 through the first paper transport path 4a. The pair of registration rollers 13 corrects skewed feed of the paper P and sends the paper P toward the first transport unit 5 (particularly the first transport belt 8 described later) in time with the ink ejection operation performed by the recording unit 9.

[0015] The paper P sent to the first transport unit 5 by the registration roller pair 13 is transported by the first transport belt 8 to a position facing the recording unit 9 (particularly recording heads 17a to 17c described below). An image is recorded on the paper P by ejecting ink from the recording unit 9 onto the paper P. At this time, the ejection of ink in the recording unit 9 is controlled by a control device 110 inside the printer 100.

[0016] In the paper transport direction, a second transport unit 12 is disposed downstream of the first transport unit 5 (on the left side in FIG. 1). The paper P on which an image has been recorded by the recording unit 9 is sent to the second transport unit 12. The ink ejected onto the surface of the paper P is dried while passing through the second transport unit 12.

[0017] In the paper transport direction, a decurler unit 14 is provided downstream of the second transport unit 12 and near the left side surface of the printer body 1. The paper P from which the ink has been dried by the second transport unit 12 is sent to the decurler unit 14, where any curls in the paper P are straightened out.

[0018] In the paper transport direction, a second paper transport path 4b is provided downstream of the decurler unit 14 (upper in FIG. 1). If double-sided recording is not performed, the paper P that has passed through the decurler unit 14 passes through the second paper transport path 4b and is discharged to a paper discharge tray 15a provided outside the left side of the printer 100. A sub-discharge tray 15b is provided below the paper discharge tray 15a to discharge unnecessary paper P (broken paper) that has experienced printing defects or the like.

[0019] A reversing transport path 16 for double-sided recording is provided at the top of the printer body 1, above the recording unit 9 and the second transport unit 12. When double-sided recording is performed, after recording on one side (first side) of the paper P is completed and the paper P passes through the second transport unit 12 and the decurler unit 14, it is sent to the reversing transport path 16 via the second paper transport path 4b.

[0020] After being sent to the reversing transport path 16, the transport direction of the paper P is then switched so that recording can be performed on the other side (second side) of the paper P. The paper P then passes over the top of the printer body 1 and is transported to the right side, passes through the pair of registration rollers 13, and is sent again to the first transport unit 5 with the second side facing up. In the first transport unit 5, the paper P is transported to a position facing the recording section 9, and an image is recorded on the second side by ink ejection from the recording section 9. After double-sided recording, the paper P passes through the second transport unit 12, the decurler section 14, and the second paper transport path 4b in that order, and is discharged to the paper discharge tray 15a.

[0021] In addition, a maintenance unit 19 and a cap unit 20 are disposed below the second transport unit 12. The maintenance unit 19 moves horizontally below the recording unit 9 when performing purging, wipes off ink extruded from the ink ejection ports of the recording head, and collects the wiped ink. Purging refers to the operation of forcibly pushing out ink from the ink ejection ports of the recording head in order to expel thickened ink, foreign matter, and air bubbles from the ink ejection ports. The cap unit 20 moves horizontally below the recording unit 9 when capping the ink ejection surface of the recording head, and then moves further upward to be attached to the underside of the recording head.

[0022] FIG. 2 is a plan view of the recording unit 9. The recording unit 9 includes a head housing 10 and line heads 11Y, 11M, 11C, and 11K. The line heads 11Y to 11K are held in the head housing 10 at a height that forms a predetermined gap (for example, 1 mm) with respect to the conveying surface of the endless first conveyor belt 8 that is stretched around a plurality of rollers including a driving roller 6a, a driven roller 6b, and tension rollers 7a and 7b (see FIG. 3). The driving roller 6a drives the first conveyor belt 8 in the conveying direction of the paper P (the direction of the arrow A). The driving of the driving roller 6a is controlled by a main control unit 110a of the control device 110 (see FIG. 4). The above-mentioned plurality of rollers are arranged in the following order along the running direction of the first conveyor belt 8: tension roller 7a, tension roller 7b, driven roller 6b, and driving roller 6a (see FIG. 3).

[0023] Each of the line heads 11Y to 11K has a plurality of (three in this example) recording heads 17a to 17c. The recording heads 17a to 17c are arranged in a staggered pattern along the paper width direction (arrow BB' direction) perpendicular to the paper transport direction (arrow A direction). The recording heads 17a to 17c have a plurality of ink ejection openings 18 (nozzles). The ink ejection openings 18 are arranged at equal intervals in the width direction of the recording head, that is, the paper width direction (arrow BB' direction). From the line heads 11Y to 11K, inks of yellow (Y), magenta (M), cyan (C), and black (K) are ejected toward the paper P transported by the first transport belt 8 through the ink ejection openings 18 of the recording heads 17a to 17c.

[0024] The recording heads 17a to 17c constituting each of the line heads 11Y to 11K are supplied with ink of four colors (yellow, cyan, magenta, and black) stored in ink tanks (not shown) for each of the line heads 11Y to 11K.

[0025] Each of the recording heads 17a to 17c ejects ink from the ink ejection orifices 18 toward the paper P that is adsorbed and held on the conveying surface of the first conveyor belt 8 and conveyed in accordance with image data received from an external computer by a control signal from the control device 110 (see FIG. 4). As a result, a color image is formed on the paper P on the first conveyor belt 8 by overlapping four colors of ink: yellow, cyan, magenta, and black.

[0026] In the printer 100, in order to clean the ink ejection surfaces of the recording heads 17a to 17c, when printing starts after a long period of inactivity and between printing operations, ink is extruded (purged) from the ink ejection ports 18 of all of the recording heads 17a to 17c, and a recovery operation of the recording heads 17a to 17c is performed in which the ink ejected on the ink ejection surfaces is wiped off with a wiper (not shown) in preparation for the next printing operation. The ink wiped off from the ink ejection surface F1 is collected by ink recovery units 31Y to 31K (see FIG. 3), which will be described later.

[0027] Fig. 3 shows a schematic configuration of the vicinity of the transport path of the paper P from the paper feed cassette 2 to the second transport unit 12 via the first transport unit 5. Fig. 4 is a block diagram showing the hardware configuration of the main parts of the printer 100. In addition to the above configuration, the printer 100 further includes a registration sensor 21, a first paper sensor 22, a second paper sensor 23, and belt sensors 24 and 25.

[0028] The registration sensor 21 detects the paper P transported by the paper feeder 3 from the paper cassette 2 and sent to the registration roller pair 13. The registration sensor 21 is located upstream of the registration roller pair 13 in the supply direction of the paper P. The control device 110 (e.g., paper supply control unit 110c) controls the timing at which the registration roller pair 13 starts to rotate based on the detection result of the registration sensor 21. For example, the control device 110 controls the timing at which the paper P is supplied to the first transport belt 8 after skew (oblique movement) correction by the registration roller pair 13 based on the detection result of the registration sensor 21.

[0029] The first paper sensor 22 detects the widthwise position of the paper P sent from the registration roller pair 13 to the first conveyor belt 8. Based on the detection result of the first paper sensor 22, the control device 110 (e.g., the main control unit 110a) can record an image on the paper P by ejecting ink from the ink ejection openings 18 corresponding to the width of the paper P, among the ink ejection openings 18 of the recording heads 17a to 17c of the line heads 11Y to 11K.

[0030] The second paper sensor 23 detects the passage of the paper P supplied to the first conveyor belt 8 by the registration roller pair 13. In other words, the second paper sensor 23 detects the position in the conveying direction of the paper P conveyed by the first conveyor belt 8. The second paper sensor 23 is located upstream of the recording unit 9 and downstream of the first paper sensor 22 in the paper conveying direction. Based on the detection result by the second paper sensor 23, the control device 110 (for example, the main control unit 110a) can control the timing of ink ejection onto the paper P that reaches a position opposing the line heads 11Y to 11K (recording heads 17a to 17c) by the first conveyor belt 8.

[0031] The belt sensors 24 and 25 are reference detection sensors that detect a reference identification portion (not shown) provided on the first conveyor belt 8. The reference identification portion is a portion that indicates the reference for one revolution of the first conveyor belt 8. Since the positional relationship between the reference identification portion and the opening 80 (see FIG. 8) is known in advance, the belt sensors 24 and 25 detect the reference identification portion of the first conveyor belt 8, and based on the position of the detected reference identification portion, the belt sensors 24 and 25 can detect the position of each opening 80 (opening group 82) provided in the first conveyor belt 8 in the conveying direction. Therefore, the belt sensors 24 and 25 function as opening position detection portions that detect the positions of the openings 80 in the first conveyor belt 8.

[0032] In addition, marks may be formed at positions corresponding to each opening group 82 on the end of the first conveyor belt 8 in the belt width direction, and the belt sensors 24 and 25 may detect the marks to detect the positions of the opening groups 82 (openings 80) corresponding to the marks.

[0033] The belt sensor 24 is located downstream of the recording unit 9 in the paper conveying direction (the running direction of the first conveyor belt 8). The belt sensor 25 is located upstream of the driven roller 6b that stretches the first conveyor belt 8 in the paper conveying direction. In this embodiment, the belt sensor 25 is located between the driven roller 6b and the tension roller 7b, but it may be located between the tension roller 7a and the roller 7b. The driven roller 6b is located upstream of the recording unit 9 in the running direction of the first conveyor belt 8. The belt sensor 24 also has the same function as the second paper sensor 23. The control device 110 (for example, the paper supply control unit 110c) can control the registration roller pair 13 to supply the paper P to the first conveyor belt 8 at a predetermined timing based on the detection result of the belt sensor 24 or 25.

[0034] In addition, by detecting the position of the paper P with multiple sensors (first paper sensor 22, second paper sensor 23) and detecting the reference specific portion of the first conveyor belt 8 with multiple sensors (belt sensors 24 and 25), it is possible to correct errors in the detected position and detect abnormalities.

[0035] The above-mentioned first paper sensor 22, second paper sensor 23, and belt sensors 24 and 25 may be configured with a transmissive or reflective optical sensor, a CIS sensor (Contact Image Sensor), or the like.

[0036] Alternatively, the printer 100 may be configured to include a meandering detection sensor that detects meandering of the first transport belt 8, and to correct the meandering of the first transport belt 8 based on the detection result.

[0037] The printer 100 further includes an operation panel 27, a storage unit 28, and a communication unit 29.

[0038] The operation panel 27 is an operation unit for receiving various setting inputs. For example, the user can operate the operation panel 27 to input information on the size of the paper P to be set in the paper feed cassette 2, that is, the size of the paper P to be transported by the first transport belt 8. The user can also operate the operation panel 27 to input the number of sheets of paper P to be printed and to instruct the start of a print job. The operation panel 27 also functions as a notification device that notifies users about the operating status of the printer 100 (image recording and flushing, which will be described later).

[0039] The storage unit 28 is a memory that stores the operation program of the control device 110 as well as various types of information, and is configured to include a ROM (Read Only Memory), a RAM (Random Access Memory), a non-volatile memory, etc. Information set by the operation panel 27 (e.g., information on the size and number of sheets of paper P) is stored in the storage unit 28.

[0040] The communication unit 29 is a communication interface for transmitting and receiving information to and from an external device (e.g., a personal computer (PC)). For example, when a user operates a PC and sends a print command together with image data to the printer 100, the image data and print command are input to the printer 100 via the communication unit 29. In the printer 100, the main control unit 110a controls the recording heads 17a to 17c based on the image data to eject ink, thereby recording an image on the paper P.

[0041] The printer 100 of this embodiment also includes a control device 110. The control device 110 includes, for example, a CPU (Central Processing Unit) and a memory. Specifically, the control device 110 includes a main control unit 110a, a flushing control unit 110b, a paper supply control unit 110c, and a maintenance control unit 110d. Each control unit that constitutes the control device 110 is configured with one CPU, but may of course be configured with separate CPUs.

[0042] The main control unit 110a controls the operation of each unit of the printer 100. For example, the driving of each roller inside the printer 100, the ejection of ink from the recording heads 17a to 17c during image formation (other than during flushing), and the like are controlled by the main control unit 110a.

[0043] The flushing control unit 110b causes the recording heads 17a to 17c to perform flushing based on the position of the opening 80 detected by the belt sensor 24 or 25.

[0044] The paper supply control unit 110c is a recording medium supply control unit that controls the pair of registration rollers 13 as a recording medium supply unit. For example, the paper supply control unit 110c controls the pair of registration rollers 13 based on the position detection of the opening 80 by the belt sensor 24 or 25. Note that the paper supply control unit 110c can also control the pair of registration rollers 13 independently of the position detection of the opening 80 by the belt sensor 24 or 25 (regardless of the position detection).

[0045] The maintenance control unit 110d controls the recording heads 17a to 17c to execute the above-mentioned purging, which forcibly pushes out ink from each ink ejection port 18. When the maintenance control unit 110d causes the recording heads 17a to 17c to execute the purging, it also controls the driving of the above-mentioned maintenance unit 19 (for example, the movement of the recording unit 9 downward and the retraction).

[0046] 3, the printer 100 has ink recovery units 31Y, 31M, 31C, and 31K on the inner circumferential surface side of the first transport belt 8. The ink recovery units 31Y to 31K receive and recover ink that is ejected from the recording heads 17a to 17c and passes through the openings 80 of the first transport belt 8 when the recording heads 17a to 17c are caused to perform flushing. Therefore, the ink recovery units 31Y to 31K are provided at positions facing the recording heads 17a to 17c of the line heads 11Y to 11K across the first transport belt 8.

[0047] The second transport unit 12 has a second transport belt 12a and a dryer 12b. The second transport belt 12a is stretched around two drive rollers 12c and a driven roller 12d. The paper P transported by the first transport unit 5 and having an image recorded thereon by ink ejection by the recording unit 9 is transported by the second transport belt 12a, dried by the dryer 12b during transport, and transported to the decurler unit 14 described above.

[0048] [2. Details of the ink recovery section] Next, the configuration of the ink recovery units 31Y to 31K will be described in detail. Fig. 5 is a schematic diagram showing the ink recovery unit 31Y and a paper transport area adjacent to the ink recovery unit 31Y. For ease of explanation, the first transport belt 8 is omitted from Fig. 5. Below, the configuration around the ink recovery unit 31Y will be described, but since the ink recovery units 31M to 31K have the same configuration, their explanations will be omitted.

[0049] The ink recovery section 31Y is disposed between the pair of side frames 100a so as to face the recording heads 17a to 17c (see FIG. 2) constituting the line head 11Y. On the upper surface of the ink recovery section 31Y, ink receiving sections 32a to 32c for receiving ink droplets ejected from the recording heads 17a to 17c are provided.

[0050] The suction fan 40, which is a suction unit, is attached to two places on the side frame 100a, and one end of the suction duct 37 is connected to the suction fan 40. The other end of the suction duct 37 is provided with a plurality of suction ports 41. The suction ports 41 are arranged facing the inner peripheral surface of the first conveyor belt 8 (see FIG. 3). The first conveyor belt 8 is provided with a number of suction holes 8a (see FIG. 8) for suctioning air. By operating the suction fan 40, air on the outer peripheral surface side of the first conveyor belt 8 is sucked through the suction holes 8a. More specifically, air in the paper suction region R (hatched region in FIG. 5) excluding the ink receiving portions 32a to 32c is sucked. With this configuration, the paper P is sucked onto the conveying surface of the first conveyor belt 8 by the suction wind generated in the paper suction region R and conveyed.

[0051] Fig. 6 is a side cross-sectional view of the ink recovery unit 31Y taken in a direction perpendicular to the transport direction (cross-sectional view taken along the CC' arrow in Fig. 5). Fig. 7 is a plan cross-sectional view of the waste ink tank 33 constituting the ink recovery unit 31Y. The waste ink tank 33 is disposed below the ink receiving units 32a to 32c. A suction path 35 and an ink recovery path 36 are provided inside the waste ink tank 33.

[0052] The suction path 35 is formed of, for example, a resin material, and has a first flow path 35a, a junction chamber 35b, and a second flow path 35c. The first flow path 35a communicates with the ink receiving portions 32a to 32c. The junction chamber 35b is where the three first flow paths 35a, which communicate with the ink receiving portions 32a to 32c, merge into one. The second flow path 35c has an upper end that communicates with the junction chamber 35b and a lower end that opens into the duct 37. With the above configuration, the ink receiving portions 32a to 32c are connected to the suction fan 40 via the suction path 35 and the duct 37.

[0053] Ink droplets contained in the air flow passing through the suction path 35 collide with the inner wall surfaces of the first flow path 35a and the merging chamber 35b and accumulate below. The ink accumulated below the waste ink tank 33 is discharged to the outside through the ink recovery path 36.

[0054] The ink recovery path 36 has an inclined portion 36a and an ink discharge tube 36b. The inclined portion 36 is formed adjacent to and below the first flow path 35a and the merging chamber 35b, and the ink discharge tube 36b is connected to the lowermost portion (bottom) of the inclined portion 36a. Ink droplets adhering to the inner wall surfaces of the first flow path 35a and the merging chamber 35b flow downward along the inner wall surfaces and then flow along the inclined portion 36a to be collected at one location (the lowermost portion). The ink then passes through the ink discharge tube 36b and is collected in a waste ink recovery bottle (not shown).

[0055] Although an ink recovery path 36 is provided here to recover ink accumulated inside the waste ink tank 33, an ink absorbent such as a melamine sponge may be placed inside the waste ink tank 33 instead of the ink recovery path 36. In that case, the ink absorbed by the ink absorbent is stored inside the waste ink tank 33 as it is, and is discarded or recovered when the waste ink tank 33 is replaced.

[0056] [3. Details of the first conveyor belt] Next, a detailed description will be given of the first transport belt 8 of the first transport unit 5. Fig. 8 is a partially enlarged view of the periphery of the opening group 82 of the first transport belt 8 used in the printer 100.

[0057] In this embodiment, a negative pressure suction method is adopted in which the paper P is adsorbed to the first transport belt 8 and transported by negative pressure suction by the suction fan 40. Therefore, a large number of suction holes 8a are formed over the entire area of ​​the first transport belt 8 to allow passage of an air flow (suction wind) for adsorbing the paper P to the first transport belt 8 by negative pressure suction.

[0058] The first conveyor belt 8 has a plurality of openings 80 that pass ink ejected from each nozzle (ink ejection port 18) of the recording heads 17a to 17c during flushing. In this embodiment, an opening group 82 consisting of the plurality of openings 80 is formed in a straight line across the entire width of the first conveyor belt 8. The openings 80 include a row of upstream-most openings 81 located on the upstream side (lower side in FIG. 8) with respect to the conveying direction (direction of arrow A) of the first conveyor belt 8.

[0059] 8, the shape of each opening 80 in plan view may be a circle, or may be a hole elongated in the belt width direction (arrow BB' direction) (e.g., an ellipse). The number of openings 80 in one row may be the same as the number of openings 80 (upstream-most openings 81) in the other row.

[0060] With the opening group 82 shown in FIG. 8 taken as one set, a plurality of sets of opening groups 82 are formed in one cycle of the first transport belt 8. The intervals in the transport direction between the sets of opening groups 82 are not the same, and the opening groups 82 are formed irregularly at positions according to the size of the paper P being transported. That is, the intervals between two sets of opening groups 82 adjacent to each other in the paper transport direction are not constant but different. In this case, the maximum interval between two sets of opening groups 82 adjacent to each other in the paper transport direction is longer than the length in the paper transport direction of the paper P of the smallest printable size (e.g., A4 size landscape) when the paper P is placed on the first transport belt 8.

[0061] FIG. 9 is a plan view showing the positional relationship between the opening group 82 of the first conveyor belt 8 and the ink receiving portions 32a to 32c. As shown in FIG. 9, when the first conveyor belt 8 moves in the conveying direction (the direction of the arrow A) and the opening group 82 overlaps with the ink receiving portions 32a and 32c, the recording heads 17a and 17c perform flushing. When the first conveyor belt 8 further moves in the conveying direction from the state of FIG. 9 and the opening group 82 overlaps with the ink receiving portion 32b, the recording head 17b performs flushing. Ink discharged from each ink discharge port 18 of the recording heads 17a to 17c passes through one of the openings 80 of the opening group 82. Therefore, it is possible to reduce clogging due to drying of ink in all the ink discharge ports 18 by causing the recording heads 17a to 17c to perform flushing over the entire head width.

[0062] [4. Relationship between flushing conditions and distance to ink receiver] Next, the conditions for performing flushing and the configuration of the ink recovery units 31Y-31K, which are characteristic parts of the printer 100 of this embodiment, will be described. Fig. 10 is a side cross-sectional view showing how the most upstream opening 81 of the first transport belt 8 passes through the ink receiving units 32a-32c. Fig. 11 is a plan view of the most upstream opening 81 of the first transport belt 8, showing the relationship between the position where the last ink droplet IL passes when flushing is performed and the upstream end 81a of the most upstream opening 81.

[0063] As shown in Fig. 10, a belt support plate 60 is disposed between the first transport belt 8 and the ink receiving portions 32a to 32c. The belt support plate 60 is disposed opposite the inner peripheral surface of the first transport belt 8 and supports the first transport belt 8 from the inside. There is no belt support plate 60 below the recording heads 17a to 17c, and an ink passage 60a is formed between the ink receiving portions 32a to 32c and the belt support plate 60. The ink passage 60a also functions as a duct through which suction air generated by the suction fan 40 (see Fig. 5) passes to suck in ink droplets discharged from the recording heads 17a to 17c.

[0064] The ink receiving portions 32a to 32c are filled with an ink absorber 61. The ink absorber 61 is made of a porous material such as a sponge. The upper surface of the ink absorber 61 becomes the landing surface F of the ink droplets.

[0065] After the most upstream opening 81 of the opening group 82 of the first transport belt 8 passes through the ink passage 60a, the upper part of the ink passage 60a is blocked by the first transport belt 8. When the upper part of the ink passage 60a is blocked, the suction fan 40 cannot suck the air inside the ink passage 60a. Therefore, it is no longer possible to suck the ink droplets together with the suction wind and collect them in the ink receivers 32a to 32c, and the mist of ink droplets accumulates inside the ink passage 60a.

[0066] In addition, as the first transport belt 8 moves, turbulence of the airflow occurs, which approaches the first transport belt 8 from the front side and the back side, and then reverses. Influenced by this airflow, mist-like ink droplets that have accumulated in the ink passage 60a adhere to and accumulate on the back side of the first transport belt 8. This leads to internal contamination of the printer 100.

[0067] Therefore, in this embodiment, the configuration of the ink recovery units 31Y-31K and the conditions for executing flushing are set so that, during flushing, the last ink droplets IL ejected from the recording heads 17a-17c reach the landing surfaces F of the ink receiving units 32a-32c before the upper part of the ink passage 60a is blocked by the first conveyor belt 8. This prevents ink from accumulating in the ink passage 60a, and prevents contamination of the rear surface of the first conveyor belt 8.

[0068] In this specification, the "last ink droplet IL" refers to the ink droplet that passes through the most upstream opening 81 at the latest timing among the many ink droplets that pass through the most upstream opening 81 when flushing is performed.

[0069] Specifically, the conveying speed of the first conveying belt is Vp [mm / s], the wind speed of the suction air in the ink passage 60a is Vh [m / s], the ejection speed of the ink droplets at the position where they pass through the first conveying belt 8 (the position of the belt support plate 60) is Vi [m / s], the distance from the first conveying belt 8 to the landing surface F of the ink receiving sections 32a to 32c is Ld [mm], and the distance from the position where the last ink droplet IL passes through the most upstream opening 81 to the upstream end 81a of the most upstream opening 81 is Ls [mm].

[0070] The moving speed of the ejected ink droplets IL is expressed as Vh+Vi [m / s], which is the sum of the ink speed Vi [m / s] at the position where the ink droplets IL pass through the first conveyor belt 8 and the wind speed Vh [m / s] of the suction wind in the ink passage 60a. Here, the upper part of the ink passage 60a is not blocked and air can be sucked in from the position where the last ink droplet IL passes through the most upstream opening 81 to the upstream end 81a of the most upstream opening 81.

[0071] The time it takes for the first conveyor belt 8 to travel the distance Ls [mm] between the position where the last ink droplet IL passed and the upstream end 81a of the most upstream opening 81 is expressed as Ls / Vp [s]. Therefore, since it is sufficient for the ink droplet IL to reach the landing surface F of the ink receiving sections 32a to 32c within the time Ls / Vp [s], it is sufficient that the travel distance of the ink droplet IL, calculated by multiplying the moving speed Vh+Vi [m / s] of the ink droplet IL by the time Ls / Vp [s] during which air can be sucked from the ink passage 60a, is equal to or greater than the distance Ld [mm] from the first conveyor belt 8 to the landing surface F. In other words, Vp, Vh, Vi, Ld, and Ls are set so as to satisfy the following formula (1). {(Vh+Vi) / 1000}×(Ls / Vp)≧ Ld ···(1)

[0072] By satisfying the relationship of formula (1), there is no risk of the upper part of the ink passage 60a being blocked by the first transport belt 8 until the last ink droplet IL reaches the landing surface F of the ink receiving units 32a to 32c. This ensures that the ink droplets are collected in the ink absorbers 61 of the ink receiving units 32a to 32c, making it possible to prevent the ink droplets ejected during flushing from adhering to the rear surface of the first transport belt 8. Therefore, it is possible to maintain image quality by flushing while preventing internal contamination of the printer 100.

[0073] [5. Other] The present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, in the above embodiment, the ink receiving sections 32a to 32c are filled with the ink absorber 61, but the ink absorber 61 is not an essential component, and the ink receiving sections 32a to 32c may not be filled with the ink absorber 61. When the ink receiving sections 32a to 32c are not filled with the ink absorber 61, the bottom surfaces of the ink receiving sections 32a to 32c become the landing surface F of the ink droplets.

[0074] In the above embodiment, the three recording heads 17a to 17c are arranged in a staggered pattern for each color of the line heads 11Y to 11K, but the present invention is not limited to this configuration. For example, the present invention is also applicable to a configuration in which the line heads 11Y to 11K are arranged in a straight line.

[0075] In addition, in the above embodiment, a configuration was described in which a first conveyor belt 8 is used in which opening groups 82 consisting of a plurality of openings 80 are irregularly arranged at positions according to the paper size in the conveying direction, but it is also possible to use a first conveyor belt 8 in which sets of opening groups 82a to 82c are arranged side by side at regular intervals in the paper conveying direction.

[0076] In the above embodiment, in order to ensure the strength of the first conveyor belt 8, a plurality of small-diameter openings 80 are provided in the first conveyor belt 8 to cover the entire widthwise ejection range of the recording heads 17a to 17c, but this configuration is not limited to this. For example, depending on the configuration of the printer 100, if the strength of the first conveyor belt 8 can be ensured by supporting it with the belt support plate 60, it is also possible to cover the entire widthwise ejection range of the recording heads 17a to 17c with a single opening 80 that is elongated in the width direction. In this case, the distance from the position where the last ink droplet IL has passed through the single opening 80 to the upstream end of the opening 80 may be set to Ls [mm].

[0077] In the above embodiment, the paper P is attracted to the first transport belt 8 by negative pressure suction and transported, but the first transport belt 8 may be charged and the paper P may be electrostatically attracted to the first transport belt 8 and transported (electrostatic adsorption method). When the paper P is electrostatically attracted, the suction holes 8a of the first transport belt 8 are not necessary.

[0078] In addition, in the above embodiment, a color printer that records color images using four colors of ink has been described as an inkjet recording device, but the present invention can also be applied to a monochrome printer that records monochrome images using black ink. [Industrial Applicability]

[0079] The present invention can be used in inkjet recording devices such as inkjet printers. [Explanation of symbols]

[0080] 8 First conveyor belt (conveyor member) 17a~17c Recording head 18 Ink outlet (nozzle) 31Y~31K Ink recovery section 32a~32c Ink receiving section 33 Waste ink tank 35 Suction Path 36 Ink collection route 37 Duct 40 Suction fan (suction section) 60 Belt support plate (support plate) 60a Ink passage 61 Ink absorber 80 Opening 81 Uppermost opening 81a Upstream end 82 Openings 100 Printers (inkjet recording devices) 110b Flushing control unit 110d Main control unit P Paper (recording medium)

Claims

1. a recording head having a plurality of nozzles for ejecting ink; a conveying member that has an opening through which the ink ejected from the recording head passes and conveys a recording medium; a control unit that controls driving of the recording head and the transport member to perform flushing by ejecting the ink from the nozzles of the recording head and causing the ink to pass through the opening at a timing different from a timing contributing to image recording; an ink recovery unit disposed opposite the recording head with the transport member interposed therebetween, the ink recovery unit having an ink receiving unit that receives the ink that has passed through the opening during the flushing process; an ink passage formed between the transport member and the ink receiving portion, through which the ink passes after passing through the opening; a suction section connected to the ink receiving section and configured to suck the ink that has passed through the opening together with air within the ink passage; In an inkjet recording apparatus comprising: The conveying speed of the conveying member is Vp [mm / s], The wind speed of the suction wind generated in the ink passage by the suction unit is Vh [m / s], The ejection speed of the ink at the position passing through the conveying member is Vi [m / s], The distance from the transport member to the landing surface of the ink receiving portion is Ld [mm], Ls [mm] is the distance from the position where the last ink droplet passing through the opening passes through the opening to the upstream end of the opening, and wherein the following formula (1) is satisfied: {(Vh+Vi) / 1000}×(Ls / Vp)≧Ld...(1)

2. the conveying member is formed with one or more opening groups each including a plurality of openings aligned in a conveying direction of the recording medium and in a width direction perpendicular to the conveying direction, the opening group including a most upstream opening positioned on the most upstream side with respect to the conveying direction, 2. The inkjet recording apparatus according to claim 1, wherein a distance from a position where the last ink droplet to pass through the most upstream opening has passed through the most upstream opening to an upstream end of the most upstream opening is defined as Ls [mm].

3. a support plate for supporting the transport member is disposed between the transport member and the ink receiving portion, 2. The ink jet recording apparatus according to claim 1, wherein the ink passage is formed in the support plate.

4. 4. An ink jet recording apparatus according to claim 1, wherein the ink receiving section is filled with an ink absorber made of a porous material, and an upper surface of the ink absorber is a landing surface of the ink receiving section.

Images