Inkjet recording apparatus

Abstract

An inkjet recording apparatus includes a recording head, a transport member, a control unit, an ink recovery unit, an ink passage, and a suction unit. An opening through which the ink ejected from the recording head passes is formed in the transport member. Vp [mm / s] is set as the conveying speed of the conveying member, Vh [m / s] is set as the wind speed of the suction wind generated in the ink passing path by the suction unit, Vi [m / s] is set as the ejection speed of the ink at the position passing through the conveying member, Ld [mm] is set as the distance from the conveying member to the contact surface of the ink receiving unit, and Vh [m / s] is set as the distance from the conveying member to the contact surface of the ink receiving unit. When Ls [mm] is the distance from the position at which the ink droplet finally passing through the opening passes through the opening to the upstream end of the opening, {(Vh + Vi) / 1000} * (Ls / Vp) > = Ld is satisfied.

Description

Technical Field

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

[0002] Conventionally, in order to reduce or prevent nozzle clogging caused by drying of ink, flushing (empty ejection) of ink ejected from the nozzle is performed regularly in inkjet recording devices such as inkjet printers. For example, in an inkjet recording device, an opening is provided on a conveyor belt that conveys a recording medium, so that ink is ejected from each nozzle of a recording head and passes through the opening of the conveyor belt.

[0003] In the above-mentioned inkjet recording device, the ink droplets passing through the opening of the conveyor belt due to flushing usually reach the ink receiving part that receives the ink and are recovered, and then discharged from the ink receiving part as waste liquid. Here, as long as the ink receiving part can be arranged near the ink ejection surface of the recording head, almost all the ink droplets can be recovered by the ink receiving part. However, since the conveyor belt is arranged between the recording head and the ink receiving part, it is difficult to arrange the ink receiving part near the ink ejection surface. As a result, the ink droplets are atomized before reaching the ink receiving part and contaminate the inside of the device. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] An object of the present invention is to provide an inkjet recording apparatus which can allow ink droplets ejected by flushing to efficiently reach an ink receiving portion with a simple structure and can suppress contamination inside the apparatus due to mist.

[0006] (II) Technical solution

[0007] The inkjet recording device of the first structure of the present invention is characterized in that it comprises: a recording head having a plurality of nozzles for ejecting ink; a conveying member having an opening through which the ink ejected from the recording head passes and conveying a recording medium; a control unit controlling the driving of the recording head and the conveying member to perform flushing at a time different from a time that contributes to image recording, that is, to cause the ink to be ejected from the nozzles of the recording head and pass through the opening; an ink recovery unit having an ink receiving unit, the ink receiving unit being arranged opposite to the recording head with the conveying member interposed therebetween and receiving the ink passing through the opening when the flushing is performed; an ink passage path formed between the conveying member and the ink receiving unit and through which the ink passing through the opening passes; and a suction portion connected to the ink receiving portion and sucking the air in the ink passage and the ink passing through the opening, wherein the conveying speed of the conveying component is set to Vp [mm / s], the wind speed of the suction wind generated by the suction portion in the ink passage is set to Vh [m / s], the ejection speed of the ink at the position passing through the conveying component is set to Vi [m / s], the distance from the conveying component to the contact surface of the ink receiving portion is set to Ld [mm], and 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 is set to Ls [mm], and the following formula (1) is satisfied: {(Vh+Vi) / 1000}×(Ls / Vp)≧Ld ··· (1).

[0008] (III) Beneficial effects

[0009] According to the first structure of the present invention, before the ink droplets that finally pass through the opening reach the contact surface of the ink receiving portion, the upper portion of the ink passage path is not blocked by the conveying member. As a result, the ink droplets can be reliably recovered in the ink receiving portion, thereby suppressing the adhesion of the ejected ink droplets to the conveying member when flushing is performed. Therefore, the internal contamination of the inkjet recording device can be suppressed, and the image quality can be maintained by flushing. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This 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.

[0011] Figure 2 It is a plan view of the recording unit 9 included in the printer 100 according to the present embodiment.

[0012] Figure 3 1 is an explanatory diagram schematically showing the peripheral configuration 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 of the printer 100 according to the present embodiment.

[0013] Figure 4 This is a block diagram showing the hardware configuration of the main parts of the printer 100 according to the present embodiment.

[0014] Figure 5 Schematic diagram showing the ink recovery section 31Y and a paper conveyance area adjacent to the ink recovery section 31Y.

[0015] Figure 6 This is a side cross-sectional view of the ink recovery section 31Y cut along a direction perpendicular to the conveyance direction.

[0016] Figure 7 It is a plan cross-sectional view of the waste ink tank 33 constituting the ink recovery unit 31Y.

[0017] Figure 8 It is a partially enlarged view of the periphery of the opening portion group 82 of the first conveyor belt 8 included in the first conveyor unit 5 .

[0018] Fig. 9 It is a plan view showing the positional relationship between the opening portion group 82 of the first conveyor belt 8 and the ink receiving portions 32a to 32c.

[0019] Fig.10 It is a side cross-sectional view showing a state where the most upstream opening 81 of the first conveyor belt 8 passes through the ink receiving portions 32a to 32c.

[0020] Fig.11 1 is a plan view of the most upstream opening 81 of the first conveyor belt 8 , and shows the relationship between the position where the last ink droplet IL passes when flushing is performed and the upstream end 81 a of the most upstream opening 81 . DETAILED DESCRIPTION

[0021] (1. Structure of inkjet recording device)

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 1 is an explanatory diagram showing a schematic structure of a printer 100 as an inkjet recording device according to an embodiment of the present invention. The printer 100 includes a paper feed cassette 2 as a paper storage portion. The paper feed cassette 2 is disposed at the lower portion of the printer body 1. Paper P as an example of recording medium is stored in the paper feed cassette 2.

[0023] On the downstream side of the paper feeding cassette 2 in the paper conveying direction, that is, Figure 1 A paper feeding device 3 is arranged above the right side of the paper feeding box 2. Figure 1 As shown, the paper P is separated and fed out one by one toward the upper right of the paper feeding cassette 2 by the paper feeding device 3 .

[0024] The printer 100 includes a first paper conveyance path 4a located in the paper feed direction, that is, above and to the right of the paper feed cassette 2. The paper P fed from the paper feed cassette 2 is conveyed vertically upward along the side of the printer body 1 through the first paper conveyance path 4a.

[0025] In the paper conveying direction, a registration roller pair 13 is provided at the downstream end of the first paper conveying path 4a. In addition, the first conveying unit 5 and the recording section 9 are arranged immediately downstream of the registration roller pair 13 in the paper conveying direction. The paper P fed from the paper feed cassette 2 passes through the first paper conveying path 4a and reaches the registration roller pair 13. The registration roller pair 13 corrects the oblique conveyance of the paper P, measures the timing of the ink ejection operation performed by the recording section 9, and outputs the paper P toward the first conveying unit 5 (especially the first conveying belt 8 described later).

[0026] The paper P fed to the first conveying unit 5 by the registration roller pair 13 is conveyed by the first conveying belt 8 to a position facing the recording unit 9 (particularly, recording heads 17a to 17c described later). By ejecting ink from the recording unit 9 to the paper P, an image is recorded on the paper P. At this time, the ejection of ink in the recording unit 9 is controlled by the control device 110 inside the printer 100.

[0027] In the paper conveying direction, on the downstream side of the first conveying unit 5 ( Figure 1 On the left side of the sheet of paper 10, a second conveying unit 12 is provided. The sheet of paper P on which an image is recorded by the recording unit 9 is conveyed to the second conveying unit 12. The ink sprayed onto the surface of the sheet of paper P dries while passing through the second conveying unit 12.

[0028] A decurling unit 14 is provided downstream of the second conveying unit 12 in the paper conveying direction and near the left side of the printer body 1. The paper P dried by the second conveying unit 12 is conveyed to the decurling unit 14, and the curl generated in the paper P is corrected.

[0029] In the paper conveying direction, on the downstream side of the decurling section 14 ( Figure 1 ), a second paper conveying path 4b is provided above the de-curling unit 14. When double-sided recording is not performed, the paper P that has passed through the de-curling unit 14 is discharged to a paper discharge tray 15a through the second paper conveying path 4b. The paper discharge tray 15a is provided outside the left side of the printer 100. A secondary discharge tray 15b is provided below the paper discharge tray 15a, and the secondary discharge tray 15b discharges unnecessary paper P (damaged paper) that has a poor print or the like.

[0030] A reversing conveying path 16 for double-sided recording is provided at the upper portion of the printer body 1 and above the recording unit 9 and the second conveying unit 12. In the case of double-sided recording, the paper P that has been recorded on one side (first side) of the paper P and has passed through the second conveying unit 12 and the de-curling unit 14 passes through the second paper conveying path 4b and is conveyed to the reversing conveying path 16.

[0031] The paper P conveyed to the reversing conveying path 16 then switches its conveying direction for recording on the other side (second side) of the paper P. Then, the paper P passes through the upper part of the printer body 1 and is conveyed to the right side, passes through the registration roller pair 13, and is conveyed to the first conveying unit 5 again with the second side facing upward. In the first conveying unit 5, the paper P is conveyed to a position facing the recording unit 9, and an image is recorded on the second side by ejecting ink from the recording unit 9. The paper P after double-sided recording passes through the second conveying unit 12, the de-curling unit 14, and the second paper conveying path 4b in sequence, and is discharged to the paper discharge tray 15a.

[0032] In addition, a maintenance unit 19 and a cap unit 20 are arranged below the second conveying unit 12. When performing flushing, the maintenance unit 19 moves horizontally below the recording unit 9, wipes the ink extruded from the ink ejection port of the recording head, and recovers the wiped ink. In addition, flushing refers to the action of forcibly squeezing out the ink from the ink ejection port of the recording head in order to discharge the viscous ink, foreign matter, and bubbles in the ink ejection port. The cap unit 20 moves horizontally below the recording unit 9 when capping the ink ejection surface of the recording head, and then moves upward and is assembled on the lower surface of the recording head.

[0033] Figure 2 1 is a top view of the recording unit 9. The recording unit 9 includes a head cover 10 and line heads 11Y, 11M, 11C, and 11K. The line heads 11Y to 11K are held by the head cover 10 at a height that forms a predetermined interval (e.g., 1 mm) relative to the conveying surface of the endless first conveyor belt 8, wherein the first conveyor belt 8 is stretched over a driving roller 6a, a driven roller 6b, and tension rollers 7a and 7b (see FIG. Figure 3 ) of the plurality of rollers. The driving roller 6a causes the first conveyor belt 8 to move in the conveying direction (arrow A direction) of the paper P. The driving of the driving roller 6a is controlled by the main control unit 110a of the control device 110 (see Figure 4 ) control. In addition, the above-mentioned plurality of rollers are sequentially arranged along the traveling direction of the first conveyor belt 8: a tension roller 7a, a tension roller 7b, a driven roller 6b, and a driving roller 6a (refer to Figure 3 ).

[0034] Each of the line heads 11Y to 11K has a plurality of (three in this case) recording heads 17a to 17c. The recording heads 17a to 17c are arranged in a staggered manner along the paper width direction (arrow BB' direction) that is orthogonal to the paper conveying direction (arrow A direction). The recording heads 17a to 17c have a plurality of ink ejection ports 18 (nozzles). The ink ejection ports 18 are arranged at equal intervals along the width direction of the recording head, that is, the paper width direction (arrow BB' direction). Ink of yellow (Y), magenta (M), cyan (C), and black (K) is ejected from the line heads 11Y to 11K via the ink ejection ports 18 of the recording heads 17a to 17c toward the paper P conveyed by the first conveyor belt 8.

[0035] Inks of four colors (yellow, cyan, magenta, and black) stored in ink cartridges (not shown) are supplied to the recording heads 17 a to 17 c constituting the line heads 11Y to 11K, respectively, according to the colors of the line heads 11Y to 11K.

[0036] Each of the recording heads 17a to 17c is controlled by the control device 110 (see Figure 4 ), and according to the image data received from the external computer, ink is ejected from the ink ejection port 18 to the paper P which is held and transported by the first conveyor belt 8. Thus, a color image in which the four colors of ink, yellow, cyan, magenta and black, are superimposed is formed on the paper P on the first conveyor belt 8.

[0037] In order to clean the ink ejection surfaces of the recording heads 17a to 17c in the printer 100, a recovery operation of the recording heads 17a to 17c is performed when printing starts after a long period of inactivity and between printing operations. Ink is squeezed out (flushed) from the ink ejection ports 18 of all the recording heads 17a to 17c, and the ink ejected toward the ink ejection surfaces is wiped with a wiper (not shown) to prepare for the next printing operation. The ink wiped from the ink ejection surfaces is recovered by the ink recovery units 31Y to 31K described later (see Figure 3 )Recycle.

[0038] Figure 3 The structure of the periphery of the conveying path of the paper P from the paper feed cassette 2 to the second conveying unit 12 via the first conveying unit 5 is schematically shown. Figure 4 1 is a block diagram showing the hardware configuration of the main parts of the printer 100. The printer 100 includes a registration sensor 21, a first paper sensor 22, a second paper sensor 23, and belt sensors 24 and 25 in addition to the above configuration.

[0039] The registration sensor 21 detects the paper P that is fed from the paper cassette 2 by the paper feeding device 3 and sent to the registration roller pair 13. The registration sensor 21 is located on the upstream side of the registration roller pair 13 in the feeding direction of the paper P. The control device 110 (for example, the paper feeding control unit 110c) controls the rotation start timing of the registration roller pair 13 based on the detection result of the registration sensor 21. For example, the control device 110 controls the timing of feeding the paper P to the first conveyor belt 8 after the skew (skew) is corrected by the registration roller pair 13 based on the detection result of the registration sensor 21.

[0040] The first paper sensor 22 detects the position in the width direction of the paper P conveyed from the registration roller pair 13 to the first conveyor belt 8. The control device 110 (for example, the main control unit 110a) can eject ink from the ink ejection outlets 18 corresponding to the width of the paper P among the ink ejection outlets 18 of the recording heads 17a to 17c of the line heads 11Y to 11K based on the detection result of the first paper sensor 22, and record an image on the paper P.

[0041] 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. That is, the second paper sensor 23 detects the position of the paper P conveyed by the first conveyor belt 8 in the conveying direction. The second paper sensor 23 is located on the upstream side of the recording unit 9 and on the downstream side of the first paper sensor 22 in the paper conveying direction. The control device 110 (for example, the main control unit 110a) can control the timing of ejecting ink to the paper P that reaches the position opposite to the line heads 11Y to 11K (recording heads 17a to 17c) by the first conveyor belt 8 based on the detection result of the second paper sensor 23.

[0042] The belt sensors 24 and 25 are reference detection sensors that detect a reference determination portion (not shown) provided on the first conveyor belt 8. The reference determination portion is a portion indicating a reference of one cycle of the first conveyor belt 8. Since the reference determination portion and the opening 80 (see FIG. 1 ) are known in advance, Figure 8 ), the reference determination portion of the first conveyor belt 8 can be detected by the belt sensors 24 and 25, and the position of each opening 80 (opening group 82) provided in the first conveyor belt 8 in the conveying direction can be detected based on the position of the detected reference determination portion. Therefore, the belt sensors 24 and 25 function as an opening position detection unit that detects the position of the opening 80 of the first conveyor belt 8.

[0043] Alternatively, marks may be formed in advance at positions corresponding to the opening groups 82 at the ends 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.

[0044] The belt sensor 24 is located on the downstream side of the recording section 9 in the paper conveying direction (the traveling direction of the first conveyor belt 8). The belt sensor 25 is located on the upstream side of the paper conveying direction than the driven roller 6b that tensions the first conveyor belt 8. In the present embodiment, the belt sensor 25 is located between the driven roller 6b and the tension roller 7b, but it may also be located between the tension roller 7a and the tension roller 7b. The driven roller 6b is located on the upstream side of the traveling direction of the first conveyor belt 8 relative to the recording section 9. In addition, the belt sensor 24 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 time based on the detection result of the belt sensor 24 or 25.

[0045] Furthermore, since the position of the paper P is detected by multiple sensors (the first paper sensor 22 and the second paper sensor 23 ), and the reference determination portion of the first conveyor belt 8 is detected by multiple sensors (the belt sensors 24 and 25 ), error correction and abnormality detection of the detection position can also be performed.

[0046] The first paper sensor 22 , the second paper sensor 23 , and the belt sensors 24 and 25 may be formed of a transmissive or reflective optical sensor, a CIS sensor (Contact Image Sensor), or the like.

[0047] Furthermore, the printer 100 may be configured to include a fluctuation advance detection sensor for detecting the fluctuation advance of the first conveyor belt 8 , and to correct the fluctuation advance of the first conveyor belt 8 based on the detection result.

[0048] The printer 100 also includes an operation panel 27 , a storage unit 28 , and a communication unit 29 .

[0049] 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 the size of the paper P placed in the paper feed cassette 2, that is, the size information of the paper P conveyed by the first conveyor belt 8. In addition, the user can also operate the operation panel 27 to input the number of sheets of paper P to be printed or to instruct the start of a printing job. In addition, the operation panel 27 also has a function as a notification device, that is, it can make notifications related to the operating status of the printer 100 (image recording, flushing described later).

[0050] The storage unit 28 is a memory that stores the operating program of the control device 110 and various information, and is configured to include a ROM (Read Only Memory), a RAM (Random Access Memory), a nonvolatile memory, etc. Information set through the operation panel 27 (for example, information on the size and number of sheets of paper P) is stored in the storage unit 28 .

[0051] The communication unit 29 is a communication interface for transmitting and receiving information with an external device (such as a personal computer (PC)). For example, when a user operates the PC to send image data and a printing command to the printer 100, the image data and the printing command are input to the printer 100 via the communication unit 29. In the printer 100, the main control unit 110a can control the recording heads 17a to 17c to eject ink based on the image data, thereby recording an image on the paper P.

[0052] In addition, the printer 100 of the present embodiment includes a control device 110. The control device 110 is configured to include, 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 constituting the control device 110 is composed of one CPU, but may also be composed of different CPUs.

[0053] The main control unit 110 a controls the operation of each unit of the printer 100. For example, the main control unit 110 a controls the driving of each roller inside the printer 100 and the ejection of ink from the recording heads 17 a to 17 c during image formation (except during flushing).

[0054] The flushing control unit 110 b causes the recording heads 17 a to 17 c to execute flushing based on the position detection of the opening 80 by the belt sensor 24 or 25 .

[0055] The paper supply control unit 110c is a recording medium supply control unit that controls the registration roller pair 13 as a recording medium supply unit. For example, the paper supply control unit 110c controls the registration roller pair 13 based on the position detection of the opening 80 by the belt sensor 24 or 25. In addition, the paper supply control unit 110c can also control the registration roller pair 13 in a manner independent of the position detection of the opening 80 by the belt sensor 24 or 25 (regardless of the position detection).

[0056] The maintenance control unit 110d controls the recording heads 17a to 17c to perform the above-mentioned flushing for forcibly squeezing out the ink from the ink ejection ports 18. When the maintenance control unit 110d causes the recording heads 17a to 17c to perform the flushing, it also controls the driving of the above-mentioned maintenance unit 19 (for example, movement to the bottom of the recording unit 9 and retreat).

[0057] In addition, if Figure 3 As shown, the printer 100 has ink recovery units 31Y, 31M, 31C, and 31K on the inner peripheral surface side of the first conveyor belt 8. When the recording heads 17a to 17c are flushed, the ink recovery units 31Y to 31K receive and recover the ink ejected from the recording heads 17a to 17c and passing through the opening 80 of the first conveyor belt 8. Therefore, the ink recovery units 31Y to 31K are provided at positions opposite to the recording heads 17a to 17c of the line heads 11Y to 11K across the first conveyor belt 8.

[0058] The second conveying unit 12 includes a second conveying belt 12a and a dryer 12b. The second conveying belt 12a is stretched by two rollers, namely, a driving roller 12c and a driven roller 12d. The paper P conveyed by the first conveying unit 5 and having an image recorded thereon by the inkjet of the recording unit 9 is conveyed by the second conveying belt 12a, dried by the dryer 12b during the conveying process, and conveyed to the above-mentioned unwinding unit 14.

[0059] (2. Details of the ink recovery department)

[0060] Next, the configuration of the ink recovery units 31Y to 31K will be described in detail. Figure 5 31Y and the paper conveying area adjacent to the ink recovery unit 31Y. Figure 5 In the figure, the description of the first conveyor belt 8 is omitted. Hereinafter, the structure of the ink recovery unit 31Y and its surroundings will be described, but the ink recovery units 31M to 31K also have the same structure, and thus the description thereof will be omitted.

[0061] The ink recovery unit 31Y is disposed between the pair of side frames 100 a so as to be aligned with the recording heads 17 a to 17 c (see FIG. 1 ) constituting the line head 11Y. Figure 2 ) are opposite. Ink receiving portions 32a to 32c for receiving ink droplets ejected from the recording heads 17a to 17c are provided on the upper surface of the ink recovery portion 31Y.

[0062] The suction fan 40 as the suction unit is installed at two locations of the side frame 100a and connected to one end of the suction duct 37. A plurality of suction ports 41 are provided at the other end of the suction duct 37. The suction ports 41 are connected to the first conveyor belt 8 (see Figure 3) are disposed opposite to the inner circumference of the first conveyor belt 8. A plurality of suction holes 8a for air suction are provided on the first conveyor belt 8 (refer to Figure 8 ). By operating the suction fan 40, air on the outer peripheral surface side of the first conveyor belt 8 is sucked through the suction hole 8a. More specifically, the paper suction area R (excluding the ink receiving parts 32a to 32c) is sucked. Figure 5 According to this structure, the paper P is sucked onto the conveying surface of the first conveyor belt 8 by the suction wind generated in the paper suction area R and conveyed.

[0063] Figure 6 is a side sectional view of the ink recovery unit 31Y cut along a direction perpendicular to the conveying direction ( Figure 5 CC′ section view). Figure 7 2 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.

[0064] The suction path 35 is formed of, for example, a resin material, and includes: a first flow path 35a, a confluence chamber 35b, and a second flow path 35c. The first flow path 35a is connected to the ink receiving parts 32a to 32c. The confluence chamber 35b is used to merge the three first flow paths 35a connected to the ink receiving parts 32a to 32c into one place. The upper end of the second flow path 35c is connected to the confluence chamber 35b, and the lower end of the second flow path 35c opens in the duct 37. According to the above structure, the ink receiving parts 32a to 32c are connected to the suction fan 40 via the suction path 35 and the duct 37.

[0065] Ink droplets contained in the air flow passing through the suction path 35 contact the inner wall surfaces of the first flow path 35a and the merging chamber 35b and remain below. The ink remaining below the waste ink tank 33 is discharged to the outside through the ink recovery path 36.

[0066] The ink recovery path 36 includes an inclined portion 36a and an ink discharge pipe 36b. The inclined portion 36a is formed adjacent to the first flow path 35a and the confluence chamber 35b below, and the ink discharge pipe 36b is connected to the lowest part (bottom) of the inclined portion 36a. Ink droplets attached to the inner wall surfaces of the first flow path 35a and the confluence chamber 35b flow downward along the inner wall surfaces, and then flow along the inclined portion 36a and gather at one place (the lowest part). Ink droplets are recovered to a waste ink recovery bottle (not shown) through the ink discharge pipe 36b.

[0067] In addition, although the ink recovery path 36 for recovering the ink retained in the waste ink tank 33 is provided here, an ink absorber such as melamine sponge may be arranged in the waste ink tank 33 instead of the ink recovery path 36. In this case, the ink absorbed by the ink absorber is stored in the waste ink tank 33 and is discarded or recovered when the waste ink tank 33 is replaced.

[0068] (3. Details of the first conveyor belt)

[0069] Next, the first conveyor belt 8 of the first conveyor unit 5 will be described in detail. Figure 8 This is a partially enlarged view of the periphery of the opening portion group 82 of the first conveyor belt 8 used in the printer 100 .

[0070] In this embodiment, a negative pressure suction method is adopted, that is, the paper P is sucked to the first conveyor belt 8 for conveyance by the negative pressure suction of the suction fan 40. Therefore, a plurality of suction holes 8a are formed throughout the first conveyor belt 8, and the air flow (suction wind) for sucking the paper P to the first conveyor belt 8 by negative pressure suction passes through the suction holes 8a.

[0071] The first conveyor belt 8 has a plurality of openings 80, and the openings 80 allow the ink ejected from the nozzles (ink ejection ports 18) of the recording heads 17a to 17c to pass through when flushing is performed. In the present embodiment, an opening group 82 composed of a plurality of openings 80 is formed in a straight line over the entire width direction of the first conveyor belt 8. The openings 80 include: an opening located on the upstream side (in the direction of arrow A) relative to the conveying direction of the first conveyor belt 8; Figure 8 A row of upstream side openings 81) on the lower side.

[0072] In this embodiment, the shape of each opening 80 when viewed from above is as follows: Figure 8 The holes shown are circular, but may also be rectangular or may be elongated in the belt width direction (arrow BB′ direction) (e.g., elliptical). In addition, the number of openings 80 in one row may be the same as the number of openings 80 in another row (most upstream openings 81).

[0073] Will Figure 8 The opening section group 82 shown is formed as a group, and a plurality of opening section groups 82 are formed in one cycle of the first conveyor belt 8. The intervals of the groups of opening section groups 82 in the conveying direction are different, and they are formed irregularly at positions corresponding to the size of the paper P to be conveyed. That is, the intervals between two adjacent opening section groups 82 in the paper conveying direction are not constant, but different. At this time, the maximum interval between the two adjacent opening section groups 82 in the paper conveying direction is longer than the length of the paper P in the paper conveying direction when the paper P of the minimum size that can be printed (for example, A4 size horizontally) is placed on the first conveyor belt 8.

[0074] Fig. 9 8 is a top view showing the positional relationship between the opening group 82 of the first conveyor belt 8 and the ink receiving portions 32a to 32c. Fig. 9 As shown, when the first conveyor belt 8 moves in the conveying direction (arrow A direction) and the opening group 82 overlaps with the ink receiving portion 32a, 32c, the recording head 17a, 17c performs flushing. Fig. 9 When the opening group 82 overlaps with the ink receiving portion 32b and further moves in the conveying direction from the state of the recording head 17a to 17c, the recording head 17b performs flushing. The ink ejected from each ink ejection port 18 of the recording heads 17a to 17c passes through any opening 80 of the opening group 82. Therefore, the recording heads 17a to 17c can be flushed over the entire head width, so that all the ink ejection ports 18 are less clogged due to ink drying.

[0075] (4. Relationship between flushing execution conditions and distance from the ink receiving part)

[0076] Next, the characteristic parts of the printer 100 according to the present embodiment, namely, the execution conditions of flushing and the configurations of the ink recovery units 31Y to 31K will be described. Fig.10 It is a side cross-sectional view showing a state where the most upstream opening 81 of the first conveyor belt 8 passes through the ink receiving portions 32a to 32c. Fig.11 1 is a plan view of the most upstream opening 81 of the first conveyor belt 8 , and shows the relationship between the position where the last ink droplet IL passes when flushing is performed and the upstream end 81 a of the most upstream opening 81 .

[0077] like Fig.10 As shown in FIG. 1 , a belt support plate 60 is disposed between the first conveyor belt 8 and the ink receiving parts 32a to 32c. The belt support plate 60 is disposed opposite to the inner circumference of the first conveyor belt 8 and supports the first conveyor 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 recording heads 17a to 17c and the ink receiving parts 32a to 32c. The ink passage 60a also functions as a duct, which is supplied by the suction fan 40 (see FIG. 1 ). Figure 5 ) passes through the suction wind generated by the recording heads 17a to 17c for sucking ink droplets ejected from the recording heads 17a to 17c.

[0078] The ink receiving parts 32a to 32c are filled with an ink absorber 61. The ink absorber 61 is formed of a porous material such as sponge. The upper surface of the ink absorber 61 serves as a contact surface F with ink droplets.

[0079] After the most upstream opening 81 in the opening group 82 of the first conveyor belt 8 passes through the ink passage 60a, the upper portion of the ink passage 60a is blocked by the first conveyor belt 8. When the upper portion of the ink passage 60a is blocked, the suction fan 40 cannot suck the air in the ink passage 60a. Therefore, the ink droplets cannot be sucked together with the suction wind and recovered to the ink receiving parts 32a to 32c, and the atomized ink droplets are retained in the ink passage 60a.

[0080] In addition, as the first conveyor belt 8 moves, the airflow approaches the first conveyor belt 8 from the front side and the back side of the first conveyor belt 8, and the airflow is turned upside down and turbulent. Under the influence of the airflow, the mist-like ink droplets retained in the ink passage 60a adhere to the back side of the first conveyor belt 8 and accumulate. As a result, the inside of the printer 100 is contaminated.

[0081] Therefore, in the present embodiment, the structure of the ink recovery parts 31Y to 31K and the execution conditions of flushing are set in such a manner that the last ink droplets IL ejected from the recording heads 17a to 17c when flushing is performed reach the contact surfaces F of the ink receiving parts 32a to 32c before the upper part of the ink passage 60a is blocked by the first conveyor belt 8. Thus, the ink does not remain in the ink passage 60a, and contamination of the back side of the first conveyor belt 8 can be suppressed.

[0082] In addition, the “last ink droplet IL” in this specification refers to an ink droplet that passes through the most upstream opening 81 at the latest timing among a plurality of ink droplets that pass through the most upstream opening 81 when flushing is performed.

[0083] Specifically, the conveying speed of the first conveyor belt 8 is set to Vp [mm / s], the wind speed of the suction wind in the ink passage path 60a is set to Vh [m / s], the ejection speed of the ink droplets at the position passing through the first conveyor belt 8 (the position of the belt support plate 60) is set to Vi [m / s], the distance from the first conveyor belt 8 to the contact surface F of the ink receiving part 32a~32c is set to 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 set to Ls [mm].

[0084] The moving speed of the ejected ink droplet 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 droplet IL passes through the first conveyor belt 8 and the wind speed Vh[m / s] of the suction wind in the ink passage 60a. Here, 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, the upper part of the ink passage 60a is not blocked, and air can be sucked.

[0085] Ls / Vp[s] represents the time for the first conveyor belt 8 to move a distance Ls[mm], which is the distance between the position where the last ink droplet IL passes and the upstream end 81a of the most upstream opening 81. Therefore, since the ink droplet IL only needs to reach the contact surface F of the ink receiving portion 32a to 32c within the time Ls / Vp[s], the moving distance of the ink droplet IL only needs to be greater than the distance Ld[mm] from the first conveyor belt 8 to the contact surface F, where the moving distance of the ink droplet IL is the product of the moving speed Vh+Vi[m / s] of the ink droplet IL and the time Ls / Vp[s] for air suction in the ink passage 60a. That is, Vp, Vh, Vi, Ld, and Ls are set to satisfy the following formula (1).

[0086] {(Vh+Vi) / 1000}×(Ls / Vp)≧Ld ··· (1)

[0087] Since the relationship of formula (1) is satisfied, the upper part of the ink passage 60a is not blocked by the first conveyor belt 8 before the last ink droplet IL reaches the contact surface F of the ink receiving parts 32a to 32c. As a result, the ink droplets can be reliably recovered in the ink absorber 61 of the ink receiving parts 32a to 32c, thereby suppressing the adhesion of the ejected ink droplets to the back side of the first conveyor belt 8 when flushing is performed. Therefore, the internal contamination of the printer 100 can be suppressed, and the image quality can be maintained by flushing.

[0088] (5. Others)

[0089] The present invention is not limited to the above-mentioned embodiment, and various changes can be made without departing from the scope of the present invention. For example, in the above-mentioned embodiment, the ink absorber 61 is filled inside the ink receiving parts 32a to 32c, but the ink absorber 61 is not an essential component, and the structure without the ink absorber 61 can also be used. When the ink absorber 61 is not filled, the bottom surface of the ink receiving parts 32a to 32c is the contact surface F of the ink droplets.

[0090] In the above embodiment, the three recording heads 17a to 17c for each color of the line heads 11Y to 11K are arranged in a staggered pattern, but the present invention is not limited to this structure. For example, the present invention can also be applied to a structure in which the line heads 11Y to 11K are arranged in a straight line.

[0091] In addition, in the above-mentioned embodiment, the structure of using the first conveyor belt 8 in which the opening portion group 82 composed of a plurality of opening portions 80 is irregularly arranged at positions corresponding to the paper size in the conveying direction is described, but it is also possible to use the first conveyor belt 8 in which the group of opening portion groups 82 is arranged at constant intervals in the paper conveying direction.

[0092] In addition, in the above-mentioned embodiment, in order to ensure the strength of the first conveyor belt 8, a plurality of openings 80 with a small diameter are provided on the first conveyor belt 8, thereby covering the entire width direction range of the ejection range of the recording heads 17a to 17c, but the present invention is not limited to this structure. For example, according to the structure of the printer 100, as long as 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 use a single opening 80 that is elongated in the width direction to cover the entire width direction range of the ejection range of the recording heads 17a to 17c. In this case, it is sufficient to set the distance from the position where the last ink droplet IL passes through the single opening 80 to the upstream end of the opening 80 to Ls [mm].

[0093] In the above embodiment, the paper P is transported by being attracted to the first conveyor belt 8 by negative pressure suction. However, the first conveyor belt 8 may be charged so that the paper P is electrostatically attracted to the first conveyor belt 8 for transport (electrostatic attraction method). When the paper P is electrostatically attracted, the suction hole 8a of the first conveyor belt 8 is not required.

[0094] In the above embodiment, a color printer that records color images using four-color inks is described as the inkjet recording apparatus, but the present invention is also applicable to a monochrome printer that records monochrome images using black ink.

[0095] The present invention can be used in inkjet recording devices such as inkjet printers.

Claims

1. An inkjet recording device comprising: a recording head having a plurality of nozzles for ejecting ink; a conveying member having an opening through which the ink ejected from the recording head passes and conveying a recording medium; a control unit that controls the driving of the recording head and the conveying member to perform flushing at a timing different from a timing that contributes to image recording, that is, to cause the ink to be ejected from the nozzle of the recording head and pass through the opening; an ink recovery unit including an ink receiving unit disposed opposite to the recording head with the transport member interposed therebetween and receiving the ink passing through the opening when the flushing is performed; an ink passage formed between the conveying member and the ink receiving portion and through which the ink passing through the opening portion passes; and a suction portion connected to the ink receiving portion and sucking air in the ink passage and the ink passing through the opening, The inkjet recording device is characterized in that The conveying speed of the conveying member is set to Vp [mm / s], The wind speed of the suction wind generated by the suction unit in the ink passage is set to Vh [m / s], The ejection speed of the ink at the position where the ink passes through the transport member is set to Vi [m / s], The distance from the conveying member to the contact surface of the ink receiving portion is set to Ld [mm], The distance from the position where the last ink droplet that passed through the opening passes through the opening to the upstream end of the opening is set to Ls [mm]. At this time, the following formula (1) is satisfied: {(Vh+Vi) / 1000}×(Ls / Vp)≧Ld··· (1).

2. The inkjet recording device according to claim 1, wherein The conveying member is provided with one or more opening groups, the opening group being composed of a plurality of openings arranged in a conveying direction of the recording medium and in a width direction orthogonal to the conveying direction, the opening group including an upstream-most opening located on an upstream side relative to the conveying direction, The distance from the position where the ink droplet that last passed through the most upstream opening passes through the most upstream opening to the upstream end of the most upstream opening is set to Ls [mm].

3. The inkjet recording device according to claim 2, wherein: A support plate for supporting the conveying member is arranged between the conveying member and the ink receiving portion. The ink passage is formed on the support plate.

4. The inkjet recording device according to any one of claims 1 to 3, characterized in that: The ink receiving portion is filled with an ink absorber formed of a porous material, and an upper surface of the ink absorber is a contact surface of the ink receiving portion.

Images