Inkjet printer and ink deaeration method

Abstract

To suppress volumes of gas mixing in ink supplied to a discharge head, by arranging a deaeration module properly, so that discharging of ink from the discharge head can be appropriately maintained.SOLUTION: An inkjet printer is provided with a deaeration module 61 (a first deaeration unit) arranged in piping 461 (a return passage) through which ink is returned from a recovery tank 451 to a supply tank 441, where the deaeration module 61 removes gas from ink flowing through the piping 461. The inkjet printer is further provided with a deaeration module 62 (a second deaeration unit) arranged in piping 471 (a supply passage) through which ink is supplied from a buffer tank 42 (an ink tank) to the recovery tank 451, where the deaeration module 62 removes gas from ink flowing through the piping 471.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a degassing technique for removing gas from ink supplied to an ejection head that ejects ink from nozzles. [Background technology]

[0002] Inkjet printers are known that print images by ejecting ink from nozzles using an inkjet method. In such inkjet printers, in order to eject ink from the nozzles well, it is important to keep the amount of gas (dissolved oxygen) mixed in the ink low. In contrast, the inkjet printer of Patent Document 1 uses two degassing modules to remove gas from the ink.

[0003] Incidentally, this inkjet printer uses four tanks to supply ink to the head (ejection head). Specifically, ink stored in the ink tank is supplied to the head via the supply sub-tank, and ink collected from the head in the collection sub-tank is returned to the ink tank. In this way, ink circulates between the ink tank and the head. Also, a main tank that stores a large amount of ink is provided, and ink is replenished from the main tank to the ink tank. A degassing module is provided between the main tank and the ink tank, and a degassing module is provided between the ink tank and the supply sub-tank. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-233952 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the arrangement of the degassing module as described above is not necessarily optimal, and there are cases where the amount of gas mixed into the ink supplied to the ejection head cannot be sufficiently suppressed, making it difficult to maintain good ejection of the ink from the ejection head.

[0006] This invention has been developed in consideration of the above-mentioned problems, and aims to reduce the amount of gas that becomes mixed into the ink supplied to the ejection head by appropriately positioning the degassing module, thereby making it possible to maintain good ink ejection from the ejection head. [Means for solving the problem]

[0007] The inkjet printing machine of the present invention comprises a head unit having an ejection head that ejects ink from nozzles, a supply tank that supplies ink to the ejection head, a recovery tank that recovers ink from the ejection head, an ink return section having a return flow path connecting the recovery tank and the supply tank and returning ink from the recovery tank to the supply tank via the return flow path, an ink tank that stores ink, and an ink supply section having a supply flow path connecting the ink tank and the recovery tank and replenishing ink from the ink tank to the recovery tank via the supply flow path, wherein the ink return section has a first degassing unit arranged in the return flow path, the first degassing unit removes gas from ink flowing through the return flow path, and the ink supply section has a second degassing unit arranged in the supply flow path, the second degassing unit removes gas from ink flowing through the supply flow path.

[0008] The ink degassing method of the present invention includes the steps of supplying ink from a supply tank to an ejection head which ejects ink from a nozzle, recovering ink from the ejection head to a recovery tank, returning ink from the recovery tank to the supply tank via a return flow path connecting the recovery tank and the supply tank, and replenishing ink from the ink tank to the recovery tank via a resupply flow path connecting the ink tank and the recovery tank, wherein a first degassing unit is disposed in the return flow path, which removes gas from ink flowing through the return flow path, and a second degassing unit is disposed in the resupply flow path, which removes gas from ink flowing through the resupply flow path.

[0009] In the present invention (inkjet printer, ink degassing method) configured as above, the ejection head ejects ink supplied from a supply tank. Therefore, in order to maintain good ink ejection from the ejection head, it is important to sufficiently suppress the amount of gas mixed in the ink in the supply tank, which is the supply source of ink to the ejection head. On the other hand, while ink is supplied to the supply tank via a recovery tank, gas that has entered from the ejection head via the nozzle is likely to be mixed into the ink in the recovery tank. Therefore, the present invention has a first degassing unit arranged in a return flow path that returns ink from the recovery tank to the supply tank, and this first degassing unit removes gas from the ink flowing in the return flow path. In this way, the gas is removed from the ink that flows out from the recovery tank toward the supply tank. Furthermore, the present invention has a second degassing unit arranged in a refill flow path that refills ink from the ink tank to the recovery tank, and this second degassing unit removes gas from the ink flowing in the refill flow path. In this way, the gas is removed from the ink that flows toward the recovery tank. That is, in the present invention, a degassing unit is provided at each of the inlet and outlet of the recovery tank through which the ink flows into the supply tank, making it possible to sufficiently reduce the amount of gas mixed in with the ink in the supply tank, which is the ink supply source for the ejection head, and to maintain good ink ejection from the ejection head.

[0010] The inkjet printer may be configured to further include a conveying section that conveys the printing medium, and a head holding unit that is movable in a predetermined movable direction and holds the head unit, and the head holding unit moves in the movable direction to move the head unit between a facing position facing the printing medium conveyed by the conveying section and a retracted position retracted from the facing position in the movable direction, and the first degassing unit is held by the head holding unit and moves integrally with the head holding unit. That is, the head unit may be moved as needed for maintenance or the like. In contrast, the first degassing unit provided immediately before the supply tank that is the supply source of ink to the ejection head is disposed relatively close to the head unit. Therefore, it is expected that the first degassing unit may interfere with the movement of the head unit. Therefore, in the above configuration, a head holding unit that movably holds the head unit is provided, and the first degassing unit is held by the head holding unit and moves integrally with the head holding unit. Therefore, the first degassing unit can be disposed relatively close to the head unit while preventing the first degassing unit from interfering with the movement of the head unit.

[0011] Furthermore, the inkjet printer may be configured so that the number of first degassing units held by the head holding unit is 1. In this configuration, the size of the moving body including the head unit, the head holding unit, and the first degassing unit can be reduced, and the device configuration can be prevented from becoming complicated.

[0012] The inkjet printer may be configured so that the second degassing unit is provided separately from the head holding unit. In other words, the second degassing unit does not necessarily need to be located close to the head unit. Therefore, by providing the second degassing unit separately from the head holding unit, the size of the moving body can be reduced.

[0013] The inkjet printer may be configured so that the ink return section has a pump disposed in the return flow path for driving the ink in the return flow path from the recovery tank to the supply tank, and the pump is held by the head holding unit and moves integrally with the head holding unit. In this configuration, the pump can be disposed relatively close to the head unit while preventing the pump from interfering with the movement of the head unit.

[0014] The inkjet printer may be configured so that the pump and the first degassing unit are arranged on the head holding unit so as to be offset from each other in the moving direction. In this configuration, the pump and the first degassing unit can be arranged compactly in the width direction perpendicular to the moving direction. As a result, the width of the inkjet printer can be reduced. Effect of the Invention

[0015] As described above, according to the present invention, by appropriately positioning the degassing module, it is possible to reduce the amount of gas that becomes mixed into the ink supplied to the ejection head, thereby maintaining good ink ejection from the ejection head. [Brief description of the drawings]

[0016] [Figure 1] 1 is a front view showing a schematic diagram of an example of an inkjet printer according to the present invention; [Diagram 2] FIG. 2 is a bottom view illustrating a schematic configuration of the head unit. [Diagram 3] FIG. 2 is a cross-sectional view illustrating a schematic internal configuration of the ejection head. [Figure 4] FIG. 2 is a diagram illustrating an ink circulation mechanism that circulates ink to an ejection head of a head unit. [Diagram 5] FIG. 2 is an overall perspective view of an inkjet printer showing the positional relationship between a head unit and an ink return section provided for the head unit. [Figure 6] FIG. [Figure 7]13 is a diagram showing an example of the results of an experiment on the relationship between the arrangement of the degassing module and the dissolved oxygen concentration in the ink returning section. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Fig. 1 is a front view showing a schematic diagram of an example of an inkjet printer according to the present invention. In this specification, the horizontal X direction, the horizontal Y direction perpendicular to the X direction, and the vertical Z direction are indicated as appropriate. The inkjet printer 1 prints an image on a long strip-shaped web W by ejecting ink onto the web W by an inkjet method while transporting the web W in a roll-to-roll manner. The material of the web W is paper or film, and the web W is flexible.

[0018] The inkjet printer 1 includes a transport section 2 that transports the web W in the web transport direction Dw. The transport section 2 includes a feed roller 21 and a take-up roller 22, and transports the web W in a roll-to-roll manner by winding the web W fed by the feed roller 21 with the take-up roller 22. The transport section 2 includes a take-up section 23 that takes in the web W fed from the feed roller 21, between the feed roller 21 and the take-up roller 22. The take-up section 23 includes two drive rollers 231, two nip rollers 232, and an edge position adjustment section 234 provided between the two drive rollers 231. Each drive roller 231 rotates by the driving force of a motor while winding the web W around it, thereby driving the web W. The two nip rollers 232 are provided corresponding to the two drive rollers 231, respectively, and each nip roller 232 sandwiches the web W between the corresponding drive roller 231. The edge position adjustment unit 234 adjusts the position of the edge of the web W in the X direction, which is the width direction of the web W.

[0019] The transport section 2 also has a plurality of support rollers 24 that support the web W between the take-in section 23 and the winding roller 22. The support rollers 24 transport the web W in the Y direction while supporting the web W from below, on which ink is discharged by the inkjet method. In particular, the support rollers 24 are arranged at an incline so that the support rollers 24 on the downstream side of the transport direction (Y direction) of the web W are positioned at a higher position. Therefore, the web W transported by the support rollers 24 is transported at an incline so as to rise toward the Y direction. The transport section 2 also has a plurality of support rollers 25 that support the web W between the support rollers 24 and the winding roller 22, and a drive roller 281 and a nip roller 282 that are arranged between the support rollers 25 and the winding roller 22. The drive roller 281 drives the web W by rotating by the driving force of a motor while winding the web W around it. The nip roller 282 sandwiches the web W between the drive roller 281 and the nip roller 282.

[0020] The inkjet printer 1 has a plurality of (four) head units 3 (FIG. 2) that face from above the web W supported by a plurality of support rollers 24. The head units 3 eject different color inks, specifically yellow, magenta, cyan and black inks, by an inkjet method onto the web W transported by the transport section 2. The number of head units 3 and the colors of the inks are not limited to the example given here. The ink ejected by the head units 3 can be UV ink or water-based ink, etc.

[0021] 1, the posture of each of the multiple head units 3 is set according to the inclination of the web W supported by the multiple support rollers 24. In other words, the multiple head units 3 are arranged such that the more upstream the head unit 3 is in the transport direction of the web W, the greater the inclination with respect to the Z direction. However, the most downstream head unit 3 in the transport direction (Y direction) of the web W is arranged horizontally and is not inclined with respect to the Z direction, and the head units 3 other than the most downstream head unit 3 are inclined so as to become higher toward the transport direction of the web W. The inclination of the head unit 3 can be evaluated by the angle that the nozzle opening plane 310 of the ejection head 31 in which the nozzles 311 are formed makes with respect to the Z direction.

[0022] The inkjet printer 1 also includes a plurality of lifting and lowering drive units 11 respectively provided corresponding to the plurality of head units 3. Each lifting and lowering drive unit 11 can raise and lower the corresponding head unit 3, thereby positioning the head unit 3 at one of a plurality of positions at different heights. In FIG. 1, each head unit 3 is positioned at a printing height h0 that is closest to the web W. Such lifting and lowering drive unit 11 can be realized by a known specific configuration, and can be configured to raise and lower the head unit 3 by, for example, driving a ball screw or an eccentric cam with a motor.

[0023] FIG. 2 is a bottom view showing a schematic configuration of the head unit. Each head unit 3 has a plurality of (five) ejection heads 31. The ejection heads 31 are arranged at different positions in the X direction, and are arranged in two rows in a staggered pattern in the X direction. In other words, a head column C31 consisting of three ejection heads 31 arranged parallel to the X direction and a head column C31 consisting of two ejection heads 31 arranged parallel to the X direction are provided in the Y direction. The bottom surface of each ejection head 31 is a nozzle opening plane 310 facing the web W, and the nozzle opening plane 310 has a rectangular shape in a bottom view. A plurality of nozzles 311 are opened in the nozzle opening plane 310. The plurality of nozzles 311 are arranged in a staggered pattern in the X direction and face the web W from above, and each nozzle 311 ejects ink onto the web W by an inkjet method.

[0024] The head unit 3 has a head holding member 32 that holds each ejection head 31. The bottom surface of the head holding member 32 is a web-facing plane 320 that faces the web W, and the web-facing plane 320 has a rectangular shape when viewed from the bottom. A plurality of head insertion holes 321 corresponding to the plurality of ejection heads 31 are opened in the web-facing plane 320. The plurality of ejection heads 31 are fixed to the head holding member 32 in a state where they are inserted into the corresponding head insertion holes 321. The head holding member 32 can be made of a non-elastic member such as metal or resin.

[0025] FIG. 3 is a cross-sectional view showing a schematic internal configuration of the ejection head. As shown in FIG. 3, the ejection head 31 has a housing 312. As described above, a plurality of nozzles 311 are opened in a staggered arrangement in the Y direction on a nozzle opening plane 310 provided on the bottom surface of the housing 312. Inside the housing 312, a plurality of cavities 313 each communicating with the plurality of nozzles 311 and an ink supply chamber 314 communicating with the plurality of cavities 313 are provided, and ink supplied from the ink supply chamber 314 is stored in the cavity 313. In addition, a piezoelectric element 315 is provided in each cavity 313, and the piezoelectric element 315 is displaced in response to a drive signal (electrical signal), thereby applying a pressure fluctuation to the ink in the cavity 313. Due to this pressure fluctuation, ink is pushed out of the cavity 313, and ink is ejected from the nozzle 311 communicating with the cavity 313. In addition, an ink inlet 316 and an ink outlet 317 are opened at the top of the ejection head 31, and ink flows into the ink supply chamber 314 from the outside through the ink inlet 316 and flows out from the ink supply chamber 314 to the outside through the ink outlet 317.

[0026] 4 is a schematic diagram showing an ink circulation supply mechanism that circulates ink to the ejection heads of the head units. In the inkjet printer 1, a plurality of ink circulation supply mechanisms 4 are provided corresponding to the plurality of head units 3, respectively. In other words, one ink circulation supply mechanism 4 is provided for each head unit 3.

[0027] The ink circulation supply mechanism 4 has a main tank 41 and a buffer tank 42 that store ink. The volume of ink that the buffer tank 42 can store is smaller than the volume of ink that the main tank 41 can store. Since the ink in the buffer tank 42 has not been degassed, there is a possibility that a large amount of gas may be mixed in. In addition, the ink circulation supply mechanism 4 has a main supply unit 43 that supplies ink from the main tank 41 to the buffer tank 42. The main supply unit 43 has a pipe 431 that connects the main tank 41 and the buffer tank 42, and the main tank 41 and the buffer tank 42 communicate with each other via the pipe 431. Furthermore, the ink circulation supply mechanism 4 has a main pump 432 attached to the pipe 431 between the main tank 41 and the buffer tank 42. The main pump 432 drives the ink in the pipe 431 from the main tank 41 to the buffer tank 42, so that the ink is supplied from the main tank 41 to the buffer tank 42.

[0028] Furthermore, the ink circulation supply mechanism 4 has an ink supply unit 44 that supplies ink to each ejection head 31 of the head unit 3. The ink supply unit 44 has a supply tank 441 that stores ink to be supplied to each ejection head 31, and a plurality of pipes 442 that connect the supply tank 441 and the plurality of ejection heads 31, respectively, and the supply tank 441 and the ejection heads 31 communicate with each other through the pipes 442. Therefore, the ink flowing out from the supply tank 441 flows into the ejection heads 31 through the pipes 442. More specifically, the ink flowing out from the supply tank 441 to the pipes 442 flows into the ink supply chamber 314 through the ink inlet 316. Furthermore, the ink supply unit 44 has a pressure adjustment unit 443 that adjusts the pressure in the supply tank 441, and the pressure adjustment unit 443 applies a predetermined pressure P44 (negative pressure) to the ink stored in the supply tank 441 (specifically, the gas-liquid interface in the supply tank 441).

[0029] The ink circulation supply mechanism 4 also has an ink recovery section 45 that recovers ink from each ejection head 31 of the head unit 3. The ink recovery section 45 has a recovery tank 451 that stores ink recovered from each ejection head 31, and a plurality of pipes 452 that connect the ejection heads 31 to the recovery tank 451, respectively, and the ejection heads 31 and the recovery tank 451 communicate with each other through the pipes 452. Therefore, ink flowing out from the ejection heads 31 flows into the recovery tank 451 through the pipes 452. More specifically, ink flowing out from the ink supply chamber 314 to the pipes 452 through the ink outlet 317 flows into the recovery tank 451. Furthermore, the ink recovery section 45 has a pressure adjustment section 453 that adjusts the pressure in the recovery tank 451, and the pressure adjustment section 453 applies a predetermined pressure P45 (negative pressure) to the ink stored in the recovery tank 451 (specifically, the gas-liquid interface in the recovery tank 451).

[0030] At this time, pressure P45 applied to the ink in the recovery tank 451 is lower than pressure P44 applied to the ink in the supply tank 441. Due to this pressure difference (P44-P45), a flow of ink is formed from the supply tank 441 toward the recovery tank 451 via the ejection head 31.

[0031] Furthermore, the ink circulation supply mechanism 4 has an ink return unit 46 that returns the ink that has flowed into the recovery tank 451 to the supply tank 441. The ink return unit 46 has a pipe 461 that connects the recovery tank 451 and the supply tank 441, and the recovery tank 451 and the supply tank 441 communicate with each other via the pipe 461. The ink return unit 46 also has a circulation pump 462 attached to the pipe 461 between the recovery tank 451 and the supply tank 441. The circulation pump 462 drives the ink in the pipe 461 from the recovery tank 451 to the supply tank 441, so that the ink is returned from the recovery tank 451 to the supply tank 441 via the pipe 461.

[0032] Thus, in the ink circulation supply mechanism 4, an ink circulation path is formed in which the ink that flows from the supply tank 441 through the ejection head 31 into the recovery tank 451 is returned to the supply tank 441 by the ink return section 46. Then, the ejection head 31 ejects the ink supplied through the circulation path.

[0033] The ink return unit 46 also has a filter 51 attached to the pipe 461 between the circulation pump 462 and the supply tank 441. This filter 51 removes foreign matter from the ink in the pipe 461. In other words, the filter 51 removes foreign matter from the ink passing through the filter 51 along the pipe 461 from the recovery tank 451 toward the supply tank 441.

[0034] Furthermore, the ink return unit 46 has a degassing module 61 attached to the pipe 461 between the filter 51 and the supply tank 441. This degassing module 61 removes gas from the ink in the pipe 461. That is, the degassing module 61 removes gas from the ink passing through the degassing module 61 along the pipe 461 from the recovery tank 451 to the supply tank 441. This degassing module 61 removes gas from the ink by applying a negative pressure generated by a vacuum pump to the ink through a hollow fiber membrane. In addition, in the flow of ink from the recovery tank 451 to the supply tank 441, the degassing module 61 is located downstream of the filter 51. Therefore, the degassing module 61 removes gas from the ink from which foreign matter has been removed by the filter 51.

[0035] The ink circulation supply mechanism 4 also has an ink supply unit 47 that supplies ink from the buffer tank 42 to the recovery tank 451. The ink supply unit 47 has a pipe 471 that connects the buffer tank 42 and the recovery tank 451, and the buffer tank 42 and the recovery tank 451 communicate with each other via the pipe 471. The ink supply unit 47 also has a supply pump 472 attached to the pipe 471 between the buffer tank 42 and the recovery tank 451. The supply pump 472 drives the ink in the pipe 471 from the buffer tank 42 to the recovery tank 451, whereby the ink is supplied from the buffer tank 42 to the recovery tank 451.

[0036] Furthermore, the ink supply unit 47 has a degassing module 62 attached to the pipe 471 between the supply pump 472 and the recovery tank 451. This degassing module 62 removes gas from the ink in the pipe 471. In other words, the degassing module 62 removes gas from the ink passing through the degassing module 62 along the pipe 471 from the buffer tank 42 toward the recovery tank 451. This degassing module 62 removes gas from the ink by applying negative pressure generated by a vacuum pump to the ink via a hollow fiber membrane.

[0037] The ink circulation supply mechanism 4 also has an ink return unit 48 that returns ink from the supply tank 441 to the buffer tank 42. The ink return unit 48 has a pipe 481 that connects the supply tank 441 and the buffer tank 42, and the supply tank 441 and the buffer tank 42 communicate with each other via the pipe 481. The ink return unit 48 also has a return pump 482 attached to the pipe 481 between the supply tank 441 and the buffer tank 42. The return pump 482 drives the ink in the pipe 481 from the supply tank 441 to the buffer tank 42, thereby returning the ink from the supply tank 441 to the buffer tank 42.

[0038] In addition, in the ink circulation supply mechanism 4, the ink return section 46 arranged adjacent to the head unit 3 is configured to move integrally with the head unit 3. Next, this point will be described with reference to Figs. 5 and 6.

[0039] FIG. 5 is an overall perspective view of an inkjet printer showing the positional relationship between a head unit and an ink return section provided for the head unit, and FIG. 6 is a partial perspective view showing the ink return section.

[0040] As shown in FIG. 5, the inkjet printer 1 has a moving and holding mechanism 7 provided above the transport section 2. This moving and holding mechanism 7 has a guide section 71 attached to the upper end of the transport section 2 and a holding unit 72 guided by the guide section 71, and the guide section 71 guides the movement of the holding unit 72 in the X direction. The guide section 71 has a pair of guide rails 711 spaced apart in the Y direction. Each guide rail 711 extends parallel to the X direction, and a portion 711A on one side X1 of each guide rail 711 faces the transport section 2 in the Z direction, whereas a portion 711B on the other side X2 of the guide rail 711 protrudes from the transport section 2 in the X direction and does not face the transport section 2 in the Z direction.

[0041] The holding unit 72 moves in the X direction along the guide rails 711 while engaging with the pair of guide rails 711. The holding unit 72 has a holding frame 73 and a holding frame 74 provided on the other side X2 in the X direction of the holding frame 73. The holding frames 73 and 74 are fixed to each other and configured as an integral unit.

[0042] The holding frame 73 holds a plurality of (four) print bars B corresponding to inks of different colors. The print bar B is a unit formed by integrating a head unit 3 with a supply tank 441, a pipe 442, a recovery tank 451, and a pipe 452 corresponding to the head unit 3. The holding frame 73 also holds a lifting drive unit 11 that raises and lowers the print bar B. That is, the lifting drive unit 11 raises and lowers the print bar B, thereby raising and lowering the head unit 3 included in the print bar B. As shown in FIG. 5, the lifting drive unit 11 has a lifting hold unit 12 that holds the print bar B on one side X1, and a lifting hold unit 13 that holds the print bar B on the other side X2.

[0043] When the holding unit 72 is located at a portion 711A of the guide rail 711, the head unit 3 of the print bar B is located at a facing position L1 facing the web W transported by the transport section 2. On the other hand, when the holding unit 72 is located at a portion 711B of the guide rail 711, the head unit 3 of the print bar B retreats from the facing position L1 to a retreat position L2 on the other side X2 in the X direction and does not face the web W transported by the transport section 2. In this way, the holding unit 72 moves in the X direction, and can selectively perform an operation of positioning the head unit 3 at the facing position L1 and an operation of positioning the head unit 3 at the retreat position L2. The movement of the holding unit 72 in the X direction may be performed manually or by a short-axis robot.

[0044] The holding frame 74 holds four ink return units 46 corresponding to the four print bars B (in other words, the head units 3), respectively. As shown in FIG. 6, the ink return unit 46 has a circulation pump 462, a filter 51, and a bottom plate 463 that holds the degassing module 61, and the bottom plate 463 is attached to the holding frame 74.

[0045] One end of piping 461A (part of piping 461) is attached to an input port 462I of the circulation pump 462, and the other end of piping 461A is connected to a recovery tank 451 of the print bar B via a flexible piping. This flexible piping is held by a cable carrier 75 connected to the print bar B and a holding frame 74. Here, a Cablebear (registered trademark) can be used as the cable carrier 75. The ink that flows into the input port 462I of the circulation pump 462 is driven by the circulation pump 462 and output from an output port 462O of the circulation pump 462.

[0046] The filter 51 has a single housing 511 having a substantially cylindrical shape, a single inlet port 512 protruding upward from the upper end of the housing 511, and a single outlet port 513 protruding downward from the lower end of the housing 511. The output port 462O of the circulation pump 462 and the inlet port 512 of the filter 51 are connected by a pipe 461B (a part of the pipe 461), and ink output from the output port 462O of the circulation pump 462 flows into the inlet port 512 via the pipe 461B. The ink that flows into the housing 511 from the inlet port 512 flows out from the outlet port 513 after foreign matter is removed by the filter 51.

[0047] The degassing module 61 has a single housing 611 having a substantially cylindrical shape, a single inlet port 612 protruding upward from the upper end of the housing 611, and a single outlet port 613 protruding laterally from a side wall of the housing 611. A hollow fiber membrane is stored in the housing 611. The outlet port 513 of the filter 51 and the inlet port 612 of the degassing module 61 are connected by a pipe 461C (a part of the pipe 461), and ink flowing out from the outlet port 513 of the filter 51 flows into the inlet port 612 via the pipe 461C. The ink flowing into the housing 611 from the inlet port 612 passes outside the hollow fiber membrane in the housing 611, and then flows out from the outlet port 613.

[0048] Furthermore, the degassing module 61 has an exhaust port 614 that protrudes downward from the lower end of the housing 611. This exhaust port 614 is connected to a vacuum pump by a vacuum pipe 69, and negative pressure generated by the vacuum pump is applied to the inside of the hollow fiber membrane in the housing 611 via the vacuum pipe 69 and the exhaust port 614. As a result, gas is sucked and removed from the ink through the hollow fiber membrane.

[0049] One end of piping 461D (part of piping 461) is attached to outlet port 613 of degassing module 61, and the other end of piping 461D is connected to supply tank 441 of printbar B via flexible piping. This flexible piping is held by cable carrier 75 which is connected to printbar B and holding frame 74.

[0050] In the X direction, the circulation pump 462 and the degassing module 61 are disposed at different positions. That is, the degassing module 61 is disposed on the other side X2 of the circulation pump 462. In a front view from the X direction, a lower end portion (exhaust port 614) of the degassing module 61 at least partially overlaps with the circulation pump 462.

[0051] The filter 51 is adjacent to the degassing module 61 in the Y direction. In addition, the circulation pump 462 and the filter 51 are disposed at different positions in the X direction. That is, the filter 51 is disposed on the other side X2 of the circulation pump 462. In a front view from the X direction, a lower end portion (outlet port 513) of the filter 51 at least partially overlaps with the circulation pump 462.

[0052] In the embodiment described above, the ejection head 31 ejects ink supplied from the supply tank 441. Therefore, in order to maintain good ejection of ink from the ejection head 31, it is important to sufficiently suppress the amount of gas mixed in the ink in the supply tank 441, which is the supply source of ink to the ejection head 31. On the other hand, while ink is supplied to the supply tank 441 via the recovery tank 451, the ink in the recovery tank 451 is likely to be mixed with gas that has entered from the ejection head 31 via the nozzle 311. Therefore, in this embodiment, a degassing module 61 (first degassing unit) is provided in a pipe 461 (return flow path) that returns ink from the recovery tank 451 to the supply tank 441, and this degassing module 61 removes gas from the ink that may have a large amount of gas mixed in and flows through the pipe 461. In this way, gas is removed from the ink that flows from the recovery tank 451 toward the supply tank 441. Furthermore, in this embodiment, a degassing module 62 (second degassing unit) is provided in a pipe 471 (supply flow path) that supplies ink from the buffer tank 42 (ink tank) to the recovery tank 451, and this degassing module 62 removes gas from the ink flowing through the pipe 471. In this way, gas is removed from the ink flowing toward the recovery tank 451. That is, in this embodiment, the degassing modules 61 and 62 are provided at the inlet and outlet of the recovery tank 451, respectively, through which the ink flows before flowing into the supply tank 441 passes. As a result, it is possible to sufficiently suppress the amount of gas mixed in the ink in the supply tank 441, which is the supply source of ink to the ejection head 31, and to maintain good ejection of ink from the ejection head 31.

[0053] Also provided are a transport section 2 that transports the web W (printing medium) and a holding unit 72 (head holding unit) that is movable in the X direction (movable direction) and holds the head unit 3. The holding unit 72 moves in the X direction to move the head unit 3 between a facing position L1 that faces the web W transported by the transport section 2 and a retracted position L2 that retracts from the facing position L1 in the X direction. Meanwhile, the degassing module 61 is held by the holding unit 72 and moves integrally with the holding unit 72. That is, the head unit 3 may be moved appropriately in the X direction for maintenance or the like. Meanwhile, the degassing module 61 provided immediately before the supply tank 441 that is the supply source of ink to the ejection head 31 is disposed relatively close to the head unit 3. Therefore, it is assumed that the degassing module 61 may interfere with the movement of the head unit 3. Therefore, in this embodiment, a holding unit 72 that movably holds the head unit 3 is provided, and the degassing module 61 is held by the holding unit 72 and moves integrally with the holding unit 72. Therefore, the degassing module 61 can be disposed relatively close to the head unit 3 while preventing the degassing module 61 from interfering with the movement of the head unit 3.

[0054] Furthermore, the number of degassing modules 61 held in the holding unit 72 is one. With this configuration, the size of the moving body including the head unit 3, the holding unit 72, and the degassing module 61 can be reduced, and the device configuration can be prevented from becoming complicated.

[0055] Moreover, the degassing module 62 is provided separately from the holding unit 72. In other words, the degassing module 62 does not necessarily need to be disposed close to the head unit 3. Thus, by providing the degassing module 62 separately from the holding unit 72, the size of the moving body can be reduced.

[0056] Furthermore, the ink return section 46 has a circulation pump 462 (pump) that is disposed in a pipe 461 (return flow path) and drives the ink in the pipe 461 from the recovery tank 451 to the supply tank 441. This circulation pump 462 is held by the holding unit 72 and moves integrally with the holding unit 72. With this configuration, the circulation pump 462 can be disposed relatively close to the head unit 3, while preventing the circulation pump 462 from interfering with the movement of the head unit 3.

[0057] Furthermore, the circulation pump 462 and the degassing module 61 are arranged in the holding unit 72 so as to be offset from each other in the X direction. In this configuration, the circulation pump 462 and the degassing module 61 can be arranged compactly in the Y direction (width direction) perpendicular to the X direction. As a result, the width of the inkjet printing machine 1 can be reduced.

[0058] In the embodiment described above, the nozzle 311 corresponds to an example of a "nozzle" of the present invention, the ejection head 31 corresponds to an example of an "ejection head" of the present invention, the head unit 3 corresponds to an example of a "head unit" of the present invention, the supply tank 441 corresponds to an example of a "supply tank" of the present invention, the recovery tank 451 corresponds to an example of a "recovery tank" of the present invention, the piping 461 corresponds to an example of a "return flow path" of the present invention, the ink return section 46 corresponds to an example of an "ink return section" of the present invention, the buffer tank 42 corresponds to an example of an "ink tank" of the present invention, the piping 471 corresponds to an example of a "supply flow path" of the present invention, and the ink supply section 47 corresponds to an example of an "ink supply section" of the present invention. the degassing module 61 corresponds to an example of a "first degassing unit" of the present invention, the degassing module 62 corresponds to an example of a "second degassing unit" of the present invention, the inkjet printing machine 1 corresponds to an example of an "inkjet printing machine" of the present invention, the web W corresponds to an example of a "printing medium" of the present invention, the transport section 2 corresponds to an example of a "transport section" of the present invention, the X direction corresponds to an example of a "movable direction" of the present invention, the holding unit 72 corresponds to an example of a "head holding unit" of the present invention, the opposing position L1 corresponds to an example of a "opposing position" of the present invention, the retracted position L2 corresponds to an example of a "retracted position" of the present invention, and the circulation pump 462 corresponds to an example of a "pump" of the present invention.

[0059] The present invention is not limited to the above-mentioned embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the specific configuration of the degassing module 61 is not limited to the above-mentioned example. Therefore, a degassing module having a configuration in which ink passes through the inside of a hollow fiber filter and the outside of the hollow fiber filter is sucked can be used as the degassing module 61. The same applies to the degassing module 62.

[0060] In addition, the positional relationship between the print bar B and the ink return unit 46 is not limited to the example in Figure 5, and it is not essential that the ink return unit 46 be movable integrally with the print bar B. In addition, the positional relationship between the circulation pump 462 and the degassing module 61 is not limited to the example in Figure 6, and these positional relationships can be changed as appropriate.

[0061] Fig. 7 is a diagram showing an example of the results of an experiment on the relationship between the arrangement of degassing modules and the dissolved oxygen concentration in the ink return section. That is, in Fig. 7, the item "arrangement of degassing modules" shows the number of degassing modules arranged relative to the ink supply section 47 and the ink return section 46, and the item "dissolved oxygen concentration" shows the results of judging the dissolved oxygen concentration in the ink return section 46 according to a predetermined standard.

[0062] In an example where one degassing module 61 was arranged in the ink supply unit 47 and no degassing module was arranged in the ink return unit 46, the dissolved oxygen concentration in the ink return unit 46 was high and was rated C. In an example where no degassing module was arranged in the ink supply unit 47 and one degassing module was arranged in the ink return unit 46, the dissolved oxygen concentration in the ink return unit 46 was moderate and was rated B. In an example where two degassing modules 61 were arranged in the ink supply unit 47 and no degassing module was arranged in the ink return unit 46, the dissolved oxygen concentration in the ink return unit 46 was moderate and was rated B. In an example where one degassing module 61 was arranged in the ink supply unit 47 and one degassing module was arranged in the ink return unit 46, the dissolved oxygen concentration in the ink return unit 46 was low and was rated A.

[0063] In other words, it was found that by placing one degassing module 61 in the ink supply section 47 and one degassing module in the ink return section 46, the dissolved oxygen concentration in the ink return section 46 can be kept low, and good results can be obtained. [Industrial Applicability]

[0064] The present invention is applicable to all degassing techniques for removing gas from ink supplied to an ejection head that ejects ink from nozzles. [Explanation of symbols]

[0065] 1. Inkjet printer 2...Transport section 3. Head unit 31...Discharge head 311…Nozzle 42…Buffer tank 441…Supply tank 451…Recovery tank 46…Ink return section 461…Plumbing 462…Circulation pump 47…Ink supply section 471…Plumbing 61…Degassing module 62…Degassing module 72…Holding unit L1…opposite position L2…Evacuation position W…Web

Claims

1. a head unit having an ejection head that ejects ink from nozzles; a supply tank for supplying ink to the ejection head; a recovery tank for recovering ink from the ejection head; an ink return section having a return flow path connecting the recovery tank and the supply tank, and returning ink from the recovery tank to the supply tank through the return flow path; an ink tank for storing ink; an ink supply unit having a supply flow path connecting the ink tank and the recovery tank, and supplying ink from the ink tank to the recovery tank through the supply flow path; Equipped with the ink return section has a first degassing unit disposed in the return flow path, The first degassing unit removes gas from the ink flowing through the return flow path, the ink supply section has a second degassing unit disposed in the supply passage, The second degassing unit of the inkjet printer removes gas from the ink flowing through the supply passage.

2. A transport unit that transports the print medium; a head holding unit that is movable in a predetermined movable direction and holds the head unit; Further equipped with the head holding unit moves in the movable direction to move the head unit between a facing position facing the print medium transported by the transport unit and a retracted position retracted from the facing position in the movable direction, The inkjet printer according to claim 1 , wherein the first degassing unit is held by the head holding unit and moves integrally with the head holding unit.

3. 3. The inkjet printer according to claim 2, wherein the number of the first degassing units held by the head holding unit is one.

4. The inkjet printer according to claim 2 , wherein the second degassing unit is provided separately from the head holding unit.

5. the ink return unit has a pump disposed in the return flow path and configured to drive the ink in the return flow path from the recovery tank to the supply tank; 5. The inkjet printer according to claim 2, wherein the pump is held by the head holding unit and moves integrally with the head holding unit.

6. The inkjet printer according to claim 5 , wherein the pump and the first degassing unit are disposed on the head holding unit so as to be shifted from each other in the movable direction.

7. supplying ink from a supply tank to an ejection head that ejects ink from a nozzle; recovering ink from the ejection head into a recovery tank; returning ink from the recovery tank to the supply tank through a return flow path connecting the recovery tank and the supply tank; replenishing ink from the ink tank to the recovery tank through a replenishing flow path connecting the ink tank and the recovery tank; Equipped with A first degassing unit is disposed in the return flow path, The first degassing unit removes gas from the ink flowing through the return flow path, A second degassing unit is disposed in the supply passage; The second degassing unit removes gas from the ink flowing through the supply passage.

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