Liquid supply system, liquid circulation method, and printing system

Abstract

Provided are a liquid supply system, a liquid circulation method and a printing system in which the generation of distribution of liquid contained in a buffer tank can be suppressed. The liquid supply system comprises: a buffer tank (12) in which the liquid to be supplied to a liquid supply target device (15) is stored; liquid level changing devices (78, 82) that change the liquid level in the buffer tank; liquid flow paths (16, 18) that communicate the liquid supply target device and the buffer tank; a pump (98A) provided in the liquid flow path; and a valve (97A) that opens and closes the liquid flow path, wherein when the liquid supply target device does not operate, the liquid is discharged from the buffer tank to lower the liquid level in the buffer tank, and the pump and the valve are controlled to allow the liquid to flow from the liquid flow path to the buffer tank.

Description

[Technical Field]

[0001] The present invention relates to a liquid supply system, a liquid circulation method, and a printing system. [Background technology]

[0002] Inkjet printing devices are known that are provided with a buffer tank for temporarily storing ink and supply ink from the buffer tank to an inkjet head to accommodate fluctuations in ink consumption. Inkjet printing devices that include a buffer tank circulate ink between the inkjet head and the buffer tank to cause the ink to flow, thereby stabilizing the physical properties of the ink, such as the viscosity and temperature, of the ink supplied to the inkjet head.

[0003] Patent Document 1 describes a liquid ejection device in which a liquid storage portion and a liquid ejection portion are connected via a supply flow path and a return flow path. and others The device supplies liquid to the liquid ejection unit. In addition, in a circulation mode, the device circulates the liquid between the liquid storage unit and the liquid flow path. Specifically, in the circulation mode of the device, the liquid flows from the liquid storage unit through the supply flow path, the liquid storage chamber, the return flow path, and the liquid storage unit in this order.

[0004] Patent Document 2 describes an inkjet printing device equipped with an ink ejection unit that ejects white ink. The device described in this document includes an ink supply pipe that supplies ink to the ink ejection unit that ejects white ink, and an ink delivery pipe that delivers ink from the ink ejection unit to the ink supply unit. The device circulates ink between the ink ejection unit and the ink supply unit using the ink supply pipe and the ink delivery pipe, preventing the colorant from settling.

[0005] Patent Document 3 describes an inkjet recording device equipped with an ink supply system that circulates ink between a head and a buffer tank. In the device described in this document, ink is supplied from the buffer tank to the head via a supply flow path. In addition, the device also performs ink circulation, recovering ink from the head to the buffer tank via a recovery flow path.

[0006] The buffer tank of the device is equipped with a liquid level sensor. When the amount of ink contained in the buffer tank falls below a reference value, ink is supplied from the main tank to the buffer tank.

[0007] Patent Document 4 describes an inkjet recording apparatus that can circulate ink between a buffer tank and an ink tank, thereby effectively stirring the ink in the ink tank.

[0008] Patent Document 5 describes an inkjet ejection device equipped with a stirring motor and stirring blades as stirring means for stirring the inside of an ink tank. The device described in this document stirs the ink contained inside the ink tank to prevent the precipitation of ink solids such as colored particles.

[0009] Patent Document 6 describes an inkjet recording device that forms images using pigment-based ink. The device described in this document agitates the pigment-based ink contained in an ink container to prevent pigment particles from settling at the bottom of the ink container. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-128850 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-119355 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-083021 [Patent Document 4] Japanese Patent Application Laid-Open No. 2010-099855 [Patent Document 5] Japanese Patent Application Laid-Open No. 2002-273867 [Patent Document 6] Japanese Patent Application Laid-Open No. 2015-071263 Summary of the Invention [Problem to be solved by the invention]

[0011] However, the ink inside the buffer tank may have distributions such as temperature distribution and particle settling. If the distributions in the ink inside the buffer tank cause distributions in the ink inside the inkjet head, there is a concern that the ejection performance of the inkjet head may be affected.

[0012] The invention described in Patent Document 1 can suppress the occurrence of ink distribution in the supply flow path and the circulation flow path due to the implementation of the circulation mode, but it is difficult to suppress the ink distribution in the liquid storage portion corresponding to the buffer tank. The inventions described in Patent Document 2, Patent Document 3, and Patent Document 4 may also have similar problems.

[0013] The invention described in Patent Document 5 rotates an agitating blade inside the ink tank to prevent ink from being distributed unevenly inside the ink tank, but the provision of an agitating blade and agitating motor increases the cost of the device. Furthermore, such a configuration makes the device configuration and control complicated, and makes the device more susceptible to breakdowns.

[0014] Furthermore, when the stirring blade is rotated to stir the ink inside the ink tank, the ink around the stirring blade is stirred, but it is difficult to stir the ink in an area that is a certain distance away from the stirring blade. While a stirrer or a stirring bar can be used instead of a stirring blade to stir the ink inside the ink tank, there is a concern that the agitator may wear out due to friction between the agitator and the inner wall of the ink tank. The invention described in Patent Document 6 may also have the same problem.

[0015] The problem of distribution of ink contained in a buffer tank is not unique to inkjet printing devices, and similar problems can arise in liquid supply devices that supply liquid to liquid supply recipient devices that perform processing using liquid.

[0016] The present invention has been made in view of the above circumstances, and has an object to provide a liquid supply system, a liquid circulation method, and a printing system that can suppress uneven distribution of the liquid contained in the buffer tank. [Means for solving the problem]

[0017] The liquid supply system according to the present disclosure comprises a buffer tank that stores liquid to be supplied to a liquid supply target device and is equipped with a liquid inlet and outlet through which the liquid flows in and out, a liquid level varying device that varies the liquid level in the buffer tank, a liquid flow path that connects the liquid supply target device and the buffer tank, a pump that is equipped in the liquid flow path, a valve that opens and closes the liquid flow path, and one or more processors, wherein the processor controls the liquid level varying device to discharge liquid from the buffer tank when the liquid supply target device is not operating, thereby lowering the liquid level in the buffer tank relative to the liquid level in the buffer tank when the liquid supply target device is operating, and controls the pump and valve to allow liquid to flow from the liquid flow path into the buffer tank when the liquid supply target device is not operating.

[0018] According to the liquid supply device disclosed herein, when the liquid circulation is performed while the liquid supply target device is not operating, the liquid level in the buffer tank is lowered compared to when the liquid supply target device is operating. This relatively reduces the cross-sectional area through which the liquid flows in the buffer tank, relatively increases the flow rate of the liquid in the buffer tank, promotes agitation of the liquid in the buffer tank, and can suppress uneven distribution of the liquid contained in the buffer tank.

[0019] The liquid supply target device is a device that uses the liquid supplied from the liquid supply device. Examples of the liquid supply target device include a printing device, a print head, and an application device.

[0020] The liquid level varying device may include components such as a discharge flow path connected to the subtank, a valve provided in the discharge flow path, and a pump provided in the discharge flow path. The valve and the pump may be controlled based on a control signal sent from the processor.

[0021] When the liquid level is lowered, the liquid level is preferably at a position above the upper end of the liquid inlet / outlet.

[0022] The liquid flow path that connects the liquid supply target device and the buffer tank may include a plurality of flow paths. The liquid flow path may be provided with a liquid reservoir for temporarily storing the liquid, a damper for suppressing pulsation of the liquid, and the like.

[0023] The processor may operate the pump to supply liquid from the buffer tank to the liquid supply target device through the liquid flow path, operate the pump in reverse relative to when supplying the liquid to cause the liquid to flow back, and use the same liquid flow path to cause the liquid to flow from the liquid supply target device to the buffer tank.

[0024] Liquid according to another aspect supply The system is applied with a liquid in which particles are dispersed in a solvent that can settle into the solvent.

[0025] According to this aspect, it is possible to suppress the settling of particles inside the buffer tank.

[0026] Examples of particles include colorant particles such as titanium oxide particles contained in white ink, and resin particles contained in coating liquid.

[0027] Liquid according to another aspect supply The system is a liquid having a particle density of 2.0 grams per cubic centimeter or greater.

[0028] In such an embodiment, the particles may have a density of 5.0 grams per cubic centimeter or less.

[0029] Liquid according to another aspect supply In the system, the buffer tank has a supply port and a recovery port as liquid inlets and outlets, the liquid flow path includes a supply flow path communicating with the supply port and a recovery flow path communicating with the recovery port and the supply flow path, and the pump includes a supply pump provided in the supply flow path and a recovery pump provided in the recovery flow path.

[0030] According to this aspect, liquid can be circulated by supplying the liquid from the buffer tank to the liquid supply target device via the supply flow path and recovering the liquid from the liquid supply target device to the buffer tank via the recovery flow path.

[0031] The supply flow path and the recovery flow path may be connected via a flow path structure such as a liquid reservoir, or may be connected via another flow path.

[0032] Liquid according to another aspect supply In the system, the processor controls at least one of the supply pump and the recovery pump to perform reverse circulation, which causes liquid to flow in a direction different from normal circulation, by causing liquid to flow out through the supply port and into the buffer tank through a liquid inlet / outlet different from the supply port.

[0033] According to this aspect, reverse circulation is performed to allow the liquid to flow into the buffer tank through the supply port, thereby generating a liquid flow inside the buffer tank that differs from that in the case of normal circulation, and making it possible to disperse settling particles, such as those that settle on the bottom of the buffer tank.

[0034] Liquid according to another aspect supply In the system, the liquid flow path is connected to the buffer tank and the supply flow path and includes a bypass flow path that is a flow path separate from the recovery flow path, the buffer tank has a bypass port that is connected to the bypass flow path as a liquid inlet and outlet, and the processor reverses the operation of the supply pump relative to normal circulation to perform reverse circulation in which liquid flows in a different direction through the bypass flow path and the supply flow path relative to normal circulation.

[0035] According to this aspect, the liquid is allowed to flow into the buffer tank through the bypass port, which generates a liquid flow inside the buffer tank that differs from that occurring when normal circulation is performed, and can disperse settling particles, such as those that settle on the bottom of the buffer tank.

[0036] In this embodiment, normal circulation can be performed in which liquid is supplied from the buffer tank to the device to which the liquid is supplied via the supply flow path, and the liquid in the buffer tank is returned from the device to which the liquid is supplied via the bypass flow path.

[0037] Liquid according to another aspect supply The system includes a filter provided in the supply flow path, and after reverse circulation is performed, the processor controls at least one of the supply pump and the recovery pump to perform normal circulation to return the liquid that does not pass through the filter to the buffer tank.

[0038] According to this aspect, when the liquid is supplied to the liquid supply target device after reverse circulation has been performed, the supply of the liquid that has not passed through the filter to the liquid supply target device is suppressed.

[0039] Liquid according to another aspect supply In the system, the liquid level varying device includes a supply flow path and a supply pump, and the processor controls the supply pump to send liquid from the buffer tank to the liquid supply target device via the supply port and the supply flow path.

[0040] According to this aspect, when the liquid level in the buffer tank is lowered, the liquid can be discharged from the buffer tank via the supply flow path and the liquid supply target device.

[0041] Liquid according to another aspect supply The system includes a liquid level varying device that includes a replenishment flow path connected to the liquid inlet / outlet, a replenishment pump provided in the replenishment flow path, and a main tank that is connected to the replenishment flow path, and the processor controls the replenishment pump to send liquid from the buffer tank to the main tank via the liquid inlet / outlet and replenishment flow path.

[0042] According to this aspect, when the liquid level in the buffer tank is lowered, the liquid can be discharged from the buffer tank to the main tank via the refilling passage.

[0043] Liquid according to another aspect supply The system processor controls the pump to increase the flow rate of the liquid when the liquid-supplied device is in operation within the range where the pump performance is acceptable.

[0044] According to this aspect, the flow of liquid in the buffer tank can be made relatively fast within the range allowed by the performance of the pump.

[0045] The range in which the pump's performance is allowable can be the range set as the operating conditions of the pump when the liquid supply target device is operated.

[0046] Liquid according to another aspect supply The system's processor stops supplying liquid to the liquid supply target device when liquid circulation is performed while the liquid supply target device is not in operation.

[0047] According to this aspect, it is possible to prevent the occurrence of abnormalities such as liquid leakage in the liquid supply target device.

[0048] Liquid according to another aspect supply In the system, the buffer tank has a bottom surface having a structure that prevents stagnation of the liquid flow.

[0049] According to this aspect, stagnation of the liquid at the bottom surface of the buffer tank is suppressed.

[0050] In this embodiment, a structure that prevents stagnation of the liquid flow may also be applied to the side surface of the buffer tank.

[0051] Liquid according to another aspect supply In the system, the buffer tank has a bottom surface that is subjected to a coating treatment in which a fluororesin is applied as a coating material.

[0052] According to this aspect, the flow of liquid at the bottom surface of the buffer tank is promoted.

[0053] In this embodiment, the side surface of the buffer tank may also be coated with a fluororesin.

[0054] Liquid according to another aspect supply In the system, the buffer tank has a distance from a side intersecting the plane on which the liquid inlet / outlet is arranged to the center of the liquid inlet / outlet that is at least half the inner diameter of the liquid inlet / outlet and no more than three times the inner diameter of the liquid inlet / outlet.

[0055] According to this aspect, the liquid inlet / outlet is disposed near the side surface of the buffer tank, which prevents liquid from stagnating at the edge of the buffer tank.

[0056] In the embodiment having a plurality of liquid inlets and outlets, it is preferable that the liquid inlets and outlets through which liquid flows into the buffer tank during normal circulation are located near the side surfaces of the buffer tank.

[0057] The liquid circulation method according to the present disclosure is a liquid circulation method applied to a liquid supply device that supplies liquid from a buffer tank via a liquid flow path to a liquid supply target device, and when the liquid supply target device is not operating, the liquid is discharged from the buffer tank to lower the liquid level in the buffer tank relative to the liquid level in the buffer tank when the liquid supply target device is operating, and when the liquid supply target device is not operating, a pump and a valve provided in the liquid flow path are controlled to allow liquid to flow from the liquid flow path into the buffer tank.

[0058] According to the liquid circulation method of the present disclosure, it is possible to obtain the same effects as the liquid supply system of the present disclosure. The constituent elements of the liquid supply system of the other aspects can be applied to the constituent elements of the liquid circulation method of the other aspects.

[0059] The printing system according to the present disclosure comprises a buffer tank that stores ink to be supplied to the print head and is equipped with a liquid inlet and outlet through which the ink flows in and out, a liquid level varying device that varies the liquid level in the buffer tank, a liquid flow path that connects the print head and the buffer tank, a pump that is equipped in the liquid flow path, a valve that opens and closes the liquid flow path, and one or more processors, wherein the processor controls the liquid level varying device to discharge ink from the buffer tank when the print head is not operating, thereby lowering the liquid level in the buffer tank relative to the liquid level in the buffer tank when the print head is operating, and controls the pump and valve to allow ink to flow from the liquid flow path into the buffer tank when the print head is not operating.

[0060] According to the printing system of the present disclosure, it is possible to obtain the same effects as those of the liquid supply system of the present disclosure. The constituent elements of the liquid supply system of other aspects can be applied to the constituent elements of the printing system of other aspects. [Effects of the Invention]

[0061] According to the present invention, in liquid circulation performed when the liquid supply target device is not operating, the liquid level in the buffer tank is lowered compared to when the liquid supply target device is operating, which relatively reduces the cross-sectional area through which the liquid flows in the buffer tank, relatively increases the flow rate of the liquid in the buffer tank, promotes agitation of the liquid in the buffer tank, and can suppress uneven distribution of the liquid contained in the buffer tank. [Brief explanation of the drawings]

[0062] [Figure 1] FIG. 1 is a diagram showing the overall configuration of an ink supply device according to an embodiment. [Figure 2] FIG. 2 is a functional block diagram showing the electrical configuration of the ink supply device shown in FIG. [Figure 3] FIG. 3 is a perspective view of the buffer tank shown in FIG. [Figure 4] FIG. 4 is a diagram showing the flow of ink in the ink circulation during printing. [Figure 5] FIG. 5 is an explanatory diagram of the liquid level in the buffer tank during printing. [Figure 6] FIG. 6 is a schematic diagram showing the flow of ink in the buffer tank during printing. [Figure 7] FIG. 7 is a diagram showing the flow of ink in normal circulation during a non-printing period. [Figure 8] FIG. 8 is an explanatory diagram of the liquid level in the buffer tank during a non-printing period. [Figure 9] FIG. 9 is a schematic diagram showing the flow of ink in the buffer tank during a non-printing period. [Figure 10] FIG. 10 is an explanatory diagram of the liquid level in the buffer tank during a non-printing period. [Figure 11] FIG. 11 is a diagram showing the flow of ink in normal circulation using a bypass flow path. [Figure 12] FIG. 12 is a diagram showing the ink flow in reverse circulation using a bypass flow path. [Figure 13] FIG. 13 is a cross-sectional view of a buffer tank showing an example of the structure of the buffer tank according to a modified example. [Figure 14] FIG. 14 is an explanatory diagram of an example of the arrangement of the recovery ports. [Figure 15] FIG. 15 is a diagram showing the flow of ink in reverse circulation using a supply flow path and a recovery flow path. [Figure 16] FIG. 16 is a diagram showing the flow of ink in normal circulation using the recovery flow path and the bypass flow path. [Figure 17] FIG. 17 is a diagram showing the flow of ink in reverse circulation using a recovery flow path and a bypass flow path. [Figure 18] FIG. 18 is a diagram showing the flow of ink in normal circulation applied to the ink supply device according to the modified example. [Figure 19] FIG. 19 is a diagram showing the flow of ink in reverse circulation applied to an ink supply device according to a modified example. [Figure 20] FIG. 20 is a flowchart showing the procedure of the ink circulation method according to the embodiment. [Figure 21] FIG. 21 is a diagram showing the overall configuration of an inkjet printing system to which the ink supply device according to the embodiment is applied. [Figure 22] FIG. 22 is a plan perspective view showing an example of the structure of a head module. [Figure 23] 23 is a cross-sectional view taken along the line XXIII-XXIII shown in FIG. [Figure 24] FIG. 24 is a functional block diagram showing the electrical configuration of the inkjet printing system shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0063] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In this specification, the same components are designated by the same reference numerals, and redundant explanations will be omitted where appropriate.

[0064] [Overall configuration of ink supply device] 1 is a diagram showing the overall configuration of an ink supply device according to an embodiment. The ink supply device 10 supplies ink to an inkjet bar 14, and includes a buffer tank 12, a supply flow path 16, and a recovery flow path 18.

[0065] The buffer tank 12 temporarily stores ink to be supplied to the inkjet bar 14. The ink supply device 10 stably supplies ink from the buffer tank 12 to the inkjet bar 14 in response to the ink consumption of the inkjet bar 14.

[0066] The buffer tank 12 has a supply port 12A, a recovery port 12B, a bypass port 12C, and an overflow port 12D. The supply port 12A is connected to the supply flow path 16 via a joint. The recovery port 12B is connected to the recovery flow path 18 via a joint. The bypass port 12C is connected to the replenishment flow path 78 via a joint. The overflow port 12D is connected to the overflow flow path 80 via a joint. Note that in FIG. 1, the joints connecting the buffer tank 12 to each flow path are not shown.

[0067] The supply flow path 16 connects the buffer tank 12 and the inkjet bar 14 via a joint F1. The recovery flow path 18 connects the inkjet bar 14 and the buffer tank 12 via a joint F2. Ink stored in the buffer tank 12 is supplied to the inkjet bar 14 via the supply flow path 16. Ink not used by the inkjet bar 14 is recovered into the buffer tank 12 via the recovery flow path 18.

[0068] The supply flow path 16 and the recovery flow path 18 are configured to include flow path components such as tubes etc. The supply flow path 16 and the recovery flow path 18 are connected to flow path control devices such as pumps and valves using joints F.

[0069] The supply flow path 16 is connected to a degassing module 22, a supply pump 24, a supply-side filter 26, and a heat exchanger 28 as flow path control devices.

[0070] The degassing module 22 degasses the ink passing through the supply flow path 16. The supply pump 24 applies pressure to the ink inside the supply flow path 16, causing the ink to flow inside the supply flow path 16. A tube pump may be used as the supply pump 24. The supply-side filter 26 removes air bubbles, foreign matter, and the like from the ink. The heat exchanger 28 adjusts the temperature of the ink.

[0071] A recovery pump 50 and a recovery channel valve 52 are connected to the recovery channel 18 as a channel control device. The recovery pump 50 applies pressure to the ink inside the recovery channel 18, causing the ink inside the recovery channel 18 to flow. A tube pump may be used as the recovery pump 50. The recovery channel valve 52 operates in response to a control signal to switch between opening and closing the recovery channel 18 between the recovery pump 50 and the buffer tank 12.

[0072] The ink supply device 10 includes an ink main tank 76, a refill passage 78, an overflow passage 80, and a refill pump 82. The refill passage 78 and the overflow passage 80 are equipped with joints F.

[0073] The main ink tank 76 stores ink to be supplied to the buffer tank 12. A refill flow path 78 connects the main ink tank 76 to the recovery port 12B of the buffer tank 12 via a joint F. An overflow flow path 80 connects the main ink tank 76 to the overflow port 12D of the buffer tank 12 via a joint F.

[0074] The refill pump 82 applies pressure to the ink inside the refill passage 78, causing the ink to flow inside the refill passage 78. A tube pump may be used as the refill pump 82. In response to the driving of the refill pump 82, ink is refilled from the main ink tank 76 to the buffer tank 12.

[0075] A main tank filter 76A is provided at the end of the refill passage 78 on the side of the main ink tank 76. The main tank filter 76A removes foreign matter from the ink refilled from the main ink tank 76 to the buffer tank 12.

[0076] When the buffer tank 12 is replenished with ink exceeding the specified amount of the buffer tank 12, the ink is returned from the buffer tank 12 to the main ink tank 76 via the overflow port 12D and the overflow passage 80.

[0077] The ink supply device 10 includes a first safety valve 84 , a second safety valve 86 , a third safety valve 88 , a recovery-side filter 90 , and a recovery-side filter valve 92 .

[0078] In the ink supply device 10, when the internal pressure of the supply flow path 16 rises above a specified value, the first safety valve 84 and the second safety valve 86 operate to reduce the internal pressure of the supply flow path 16. In addition, in the ink supply device 10, when the internal pressure of the recovery flow path 18 rises above a specified value, the third safety valve 88 operates to reduce the internal pressure of the recovery flow path 18.

[0079] The recovery-side filter valve 92 operates in response to a control signal to switch between an open state and an closed state between the recovery pump 50 and the degassing module 22. The ink supply device 10 opens the recovery-side filter valve 92 and allows the ink that has passed through the degassing module 22 to pass through the recovery-side filter 90.

[0080] The ink supply device 10 includes a bypass flow path 54. The bypass flow path 54 connects the joint F3 of the inkjet bar 14 with the bypass port 12C of the buffer tank 12. The bypass flow path 54 is a flow path that sends ink from the inkjet bar 14 to the buffer tank 12 without passing through the recovery flow path 18. The bypass flow path 54 is equipped with a joint F.

[0081] The ink supply device 10 described in the embodiment is an example of a liquid supply system. The supply port 12A, the recovery port 12B, and the bypass port 12C described in the embodiment are each an example of a liquid inlet / outlet through which a liquid flows in and out. The ink described in the embodiment is an example of a liquid.

[0082] The refilling flow path 78 and the refilling pump 82 described in the embodiment are examples of components of the liquid level varying device. Men allowed 1 is an example of a component of a transforming device.

[0083] The supply flow path 16, the recovery flow path 18, and the bypass flow path 54 described in the embodiment are examples of liquid flow paths. The supply-side back pressure tank 30, the supply-side head manifold 32, the recovery damper 40, the recovery valve 42, the drain flow path 47, the drain flow path 49, the first bypass flow path 64, and the second bypass flow path 66 described in the embodiment are examples of liquid flow paths.

[0084] [Example of inkjet bar flow path structure] The inkjet bar 14 shown in Fig. 1 is a line-type inkjet head that includes a plurality of head modules 15 and has a structure in which the plurality of head modules 15 are connected together. Fig. 1 illustrates an inkjet bar 14 that includes n head modules 15. Of the n head modules, Fig. 1 illustrates three head modules labeled 15-1, 15-2, and 15-n. The same applies to Fig. 4 and the like.

[0085] The inkjet bar 14 is not limited to a configuration including a plurality of head modules 15, and may include a single head module 15. In other words, n, which represents the number of head modules 15, may be an integer equal to or greater than one.

[0086] The inkjet bar 14 includes a supply-side back-pressure tank 30. The supply-side back-pressure tank 30 is a pressure buffer device that suppresses fluctuations in the internal pressure of the supply flow path 16. The supply-side back-pressure tank 30 communicates with the supply flow path 16 via an ink inlet 30A and a joint F1.

[0087] The supply-side back pressure tank 30 includes an ink outlet 30B, a liquid chamber 30C, an air chamber 30D, an elastic membrane 30E, an air bubble discharge port 30F, and an air flow path communication port 30G. Ink that flows in through the ink inlet 30A passes through the liquid chamber 30C and flows out from the ink outlet 30B.

[0088] The elastic film 30E is disposed between the liquid chamber 30C and the air chamber 30D, and separates the liquid chamber 30C from the air chamber 30D. The elastic film 30E deforms in response to pressure fluctuations of the ink passing through the liquid chamber 30C, thereby reducing the pressure fluctuations of the ink passing through the liquid chamber 30C.

[0089] The air chamber 30D communicates with an air flow path 58 via an air flow path communication port 30G. The air flow path 58 communicates the air chamber 30D with an air tank 60 via an air connect valve 59. The air tank 60 communicates with an atmosphere communication passage 61. The atmosphere communication passage 61 is equipped with an air valve 62.

[0090] The bubble discharge port 30F of the liquid chamber 30C communicates with the bypass flow path 54 via the drain flow path 47 and a joint F3. The drain flow path 47 is equipped with a drain valve 56. The drain valve 56 operates in response to a control signal to switch the drain flow path 47 between open and closed states.

[0091] The inkjet bar 14 includes a supply head manifold 32. The supply head manifold 32 communicates with an ink outlet 30B via a flow path. The ink discharged from the supply back pressure tank 30 flows into the supply head manifold 32.

[0092] The supply-side head manifold 32 includes a supply-side pressure sensor 34. The supply-side pressure sensor 34 detects the internal pressure of the supply-side head manifold 32. The supply-side head manifold 32 is subjected to pressure control in accordance with the detection result of the supply-side pressure sensor 34.

[0093] The supply-side pressure sensor 34 may be a semiconductor piezo-resistance type, a capacitance type, a silicon resonant type, or the like. The same applies to the recovery-side pressure sensor 46.

[0094] The inkjet bar 14 has the same number of ink supply channels 35 as the head modules 15. The supply-side head manifold 32 communicates with the head modules 15 via the ink supply channels 35, and supplies ink to the head modules 15 via the ink supply channels 35 and ink supply ports 15A.

[0095] Each of the ink supply flow paths 35 is equipped with a supply valve 36 and a supply damper 38. Note that in Fig. 1, only one of the n ink supply flow paths 35 is labeled with a reference symbol. The same applies to the n supply valves 36 and the n supply dampers 38.

[0096] The inkjet bar 14 has the same number of ink recovery channels 39 as the number of head modules 15. Each of the head modules 15 is connected to an ink recovery channel 39.

[0097] The inkjet bar 14 includes a recovery-side head manifold 44. Each head module 15 communicates with the recovery-side head manifold 44 via an ink recovery flow path 39, and discharges ink from an ink discharge port 15B to the recovery-side head manifold 44 via the ink recovery flow path 39.

[0098] The recovery side head manifold 44 includes a recovery side pressure sensor 46. The recovery side pressure sensor 46 detects the internal pressure of the recovery side head manifold 44. The recovery side head manifold 44 is subjected to pressure control in accordance with the detection result of the recovery side pressure sensor 46.

[0099] Each of the ink recovery channels 39 is provided with a recovery damper 40 and a recovery valve 42. In Fig. 1, only one of the n recovery dampers 40 is labeled with a reference symbol. The same applies to the n recovery valves 42.

[0100] The inkjet bar 14 includes a recovery-side back pressure tank 48. The recovery-side back pressure tank 48 is connected to the recovery-side head manifold 4. 4 and This is a pressure buffer device that suppresses fluctuations in the internal pressure of the flow path between the joint F3.

[0101] An ink inlet 48A of the recovery-side back-pressure tank 48 communicates with the recovery-side head manifold 44 via a flow path. The recovery-side back-pressure tank 48 has an ink outlet 48B. The recovery-side back-pressure tank 48 communicates with the recovery flow path 18 via the ink outlet 48B and a joint F2.

[0102] The recovery-side back-pressure tank 48 includes a liquid chamber 48C, an air chamber 48D, an elastic membrane 48E, and an air flow path communication port 48G. The liquid chamber 48C, the air chamber 48D, and the elastic membrane 48E have the same structures and functions as the liquid chamber 30C, the air chamber 30D, and the elastic membrane 30E provided in the supply-side back-pressure tank 30, respectively.

[0103] Air chamber 48D communicates with air flow path 71 via air flow path communication port 48G. Air flow path 71 communicates air chamber 48D with air tank 73 via air connect valve 72. Air tank 73 communicates with atmosphere communication path 74. Air communication path 74 is equipped with air valve 75.

[0104] The bubble discharge port 48F of the liquid chamber 48C is connected to the bypass flow path 54 via a drain flow path 49 and a joint F3. The drain flow path 49 is equipped with a drain valve 70. The drain valve 70 operates in response to a control signal to switch the drain flow path 49 between open and closed states.

[0105] The inkjet bar 14 includes a first bypass flow path 64 and a second bypass flow path 66. The first bypass flow path 64 and the second bypass flow path 66 connect the supply head manifold 32 and the recovery head manifold 44 to each other.

[0106] The first bypass flow path 64 is provided with a first bypass flow path valve 68. The first bypass flow path valve 68 operates in response to a control signal to switch between opening and closing of the first bypass flow path 64. The second bypass flow path 66 is provided with a second bypass flow path valve 69. The second bypass flow path valve 69 switches between opening and closing of the second bypass flow path 66 in response to a control signal.

[0107] 1 illustrates an inkjet bar 14 including a plurality of head modules 15, the inkjet bar 14 may include one or more head modules 15. Furthermore, of the components of the inkjet bar 14 shown in FIG. 1, the components other than the head modules 15, such as the supply-side back pressure tank 30 and the supply-side head manifold 32, may be included as components of the ink supply device 10. In such an embodiment, the positions of the joints F1 and the like that connect the ink supply device 10 and the inkjet bar 14 are changed as appropriate.

[0108] 1 illustrates an ink supply device 10 that supplies one color of ink to one inkjet bar 14. A printing system that includes multiple inkjet bars 14 corresponding to multiple colors of ink is provided with the same number of ink supply devices 10 as the number of colors.

[0109] In the present embodiment, the ink supply device 10 supplies ink to the inkjet bar 14, but the ink supply device 10 may supply a liquid other than ink to a liquid supply target device.

[0110] [Electrical configuration of ink supply device] Fig. 2 is a functional block diagram showing the electrical configuration of the ink supply device shown in Fig. 1. The ink supply device 10 includes a general control unit 94, a valve control unit 97, and a pump control unit 98.

[0111] The overall control unit 94 transmits command signals to the valve control unit 97 and the pump control unit 98, and controls the overall operation of the ink supply device 10. The overall control unit 94 includes one or more processors 95 and one or more memories 96.

[0112] The processor 95 executes a program stored in the memory 96. Examples of the hardware structure of the processor 95 include a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a PLD (Programmable Logic Device), and an ASIC (Application Specific Integrated Circuit).

[0113] A CPU is a general-purpose processor that executes programs and functions as a variety of functional units. A GPU is a processor specialized for image processing. Note that the term "program" is synonymous with the term "software."

[0114] A PLD is a processor whose electrical circuit configuration can be changed after the device is manufactured. An example of a PLD is an FPGA (Field Programmable Gate Array). An ASIC is a processor with dedicated electrical circuitry designed specifically to perform a specific task.

[0115] A processing unit may be configured with one of these various processors, or may be configured with two or more processors of the same or different types. Examples of combinations of various processors include a combination of one or more FPGAs and one or more CPUs, and a combination of one or more FPGAs and one or more GPUs. Another example of a combination of various processors is a combination of one or more CPUs and one or more GPUs.

[0116] A single processor may be used to configure multiple functional units. An example of using a single processor to configure multiple functional units is a configuration in which a single processor is configured by applying a combination of one or more CPUs and software, such as an SoC (System On Chip), which is typified by a computer such as a client or server, and this processor operates as multiple functional units.

[0117] Another example of using one processor to configure multiple functional units is to use a processor that uses one IC chip to realize the functions of an entire system including multiple functional units. Note that IC is an abbreviation for Integrated Circuit.

[0118] In this way, the various functional units are configured as hardware structures using one or more of the various processors described above.More specifically, the hardware structures of the various processors described above are electric circuits (circuitry) that combine circuit elements such as semiconductor elements.

[0119] The memory 96 stores programs executed by the processor 95. The memory 96 stores control parameters used when the processor executes the programs. The memory 96 may include one or more RAMs (Random Access Memories) and one or more ROMs (Read Only Memories).

[0120] The processor 95 uses the RAM as a work area and various parameters stored in the ROM to execute a control program applied to the ink supply device 10 and perform various processes of the ink supply device 10.

[0121] The memory 96 can store various types of data applied to the ink supply device 10. The various types of data applied to the ink supply device 10 can be acquired from a device external to the ink supply device 10. Examples of the external device include a server device and a storage device that are connected to the ink supply device 10 via a network so that data communication is possible.

[0122] The valve control unit 97 controls the operation of the valve 97A in response to a command signal sent from the overall control unit 94. The valve 97A shown in Fig. 2 includes the recovery passage valve 52 and the recovery-side filter valve 92 shown in Fig. 1. The valve 97A shown in Fig. 2 may include various valves such as the supply valve 36 provided in the inkjet bar 14 shown in Fig. 1.

[0123] That is, the valve control unit 97 opens and closes various valves provided in the flow path through which ink passes from the buffer tank 12 via the inkjet bar 14 and returns to the buffer tank 12, thereby defining the flow path through which the ink passes.

[0124] The pump control unit 98 controls the operation of the pump 98A in response to a command signal sent from the overall control unit 94. The pump 98A shown in Fig. 2 includes various pumps provided in the ink supply device 10, such as the supply pump 24 shown in Fig. 1.

[0125] That is, the pump control unit 98 controls the operation of various pumps provided in the flow path through which ink passes from the buffer tank 12 via the inkjet bar 14 and returns to the buffer tank 12, thereby determining the ink flow speed and ink flow direction.

[0126] One or more processors may be used in the valve control unit 97. One or more processors may be used in the pump control unit 98. The valve control unit 97 and the pump control unit 98 may be configured using one or more processors.

[0127] The overall control unit 94 acquires the detection signals transmitted from the sensors 99. Based on the acquired detection signals, the overall control unit 94 controls each part of the ink supply device 10. The sensors 99 include the supply-side pressure sensor 34 and the recovery-side pressure sensor 46 shown in FIG.

[0128] The sensor 99 includes a liquid level detection sensor that detects the liquid level in the buffer tank 12. Based on the detection result of the liquid level, the integrated control unit 94 adjusts the liquid level of the ink contained in the buffer tank 12. The liquid level detection sensor is indicated by the reference numeral 99A in FIG.

[0129] [Buffer tank configuration example] 3 is a perspective view of the buffer tank shown in FIG. 1. A supply port 12A, a recovery port 12B, a bypass port 12C, and an overflow port 12D are formed on a side surface 13A of the buffer tank 12. The supply port 12A is connected to a joint F 11 The supply flow path 16 is connected to the recovery port 12B via a joint F. 12 The bypass port 12C is connected to the recovery passage 18 via a joint F. 13 The overflow port 12D is connected to the bypass flow path 54 via a joint F. 14 is connected.

[0130] A liquid level detection sensor 99A is attached to the top surface 13B of the buffer tank 12. A wiring 99B that transmits a detection signal output from the liquid level detection sensor 99A is attached to the liquid level detection sensor 99A. The liquid level detection sensor 99A detects the liquid level of the ink in the buffer tank 12.

[0131] The integrated control unit 94 controls the operation of the pumps 98A, such as the refill pump 82, via the pump control unit 98 based on the detection signal sent from the liquid level detection sensor 99A, and adjusts the amount of ink contained in the buffer tank 12.

[0132] [Ink circulation during non-printing periods] [Normal circulation] The normal circulation during the non-printing period of the ink supply device 10 will now be described. Figure 4 is a diagram showing the flow of ink during the ink circulation during the printing period. The arrows in Figure 4 indicate the direction of ink flow.

[0133] During the printing period when ink is consumed in the inkjet bar 14, the ink supply device 10 circulates ink. During the printing period, ink flows out of the supply port 12A of the buffer tank 12 and is supplied to the inkjet bar 14 via the supply flow path 16. Ink that is not consumed in the inkjet bar 14 is returned to the recovery port 12B of the buffer tank 12 via the recovery flow path 18. Of the various valves shown in FIG. 4, the supply valve 36 and the like are shown in white, indicating an open state. Of the various valves, the drain valve 56 and the like are shown in black, indicating a closed state. The same applies to FIGS. 7, 11, 12, and 15 to 19.

[0134] 5 is an explanatory diagram of the liquid level in the buffer tank during printing. During printing, the liquid level 302 of the ink 300 contained in the buffer tank 12 is sufficiently higher than the upper end position of the recovery port 12B.

[0135] That is, the buffer tank 12 stores a sufficient amount of ink during printing, which can accommodate the ink consumption of the inkjet bar 14 and contribute to the stability of the ink temperature.

[0136] 6 is a schematic diagram showing the flow of ink in the buffer tank 12 during printing. When a sufficient amount of ink 300 is stored in the buffer tank 12, the flow of ink 300 generated inside the buffer tank 12 spreads throughout the entire buffer tank 12.

[0137] That is, the ink flow 304 flowing from the recovery port 12B into the buffer tank 12 collides with the inner surface 13C of the inner surface of the buffer tank 12 that faces the recovery port 12B, generating a downward ink flow 306 and an upward ink flow 308.

[0138] As a result, the effects of uniforming the ink distribution, such as the effect of flushing out settling particles such as pigment particles that settle on the bottom surface 13D of the buffer tank 12, which are caused by the flow of ink 300 generated inside the buffer tank 12, and the effect of uniforming the ink temperature distribution, are insufficient. Here, downward refers to a direction that has a component in the direction of gravity. Upward refers to a direction that has a component in the opposite direction to the direction of gravity.

[0139] 7 is a diagram showing the flow of ink in normal circulation during non-printing periods. Ink circulation during non-printing periods uses a flow path that does not allow ink to flow to the head module 15, with the supply valve 36 and the recovery valve 42 in a closed state.

[0140] In the example shown in FIG. 7, the ink supply device 10 operates the supply pump 24 to supply ink from the supply port 12A of the buffer tank 12 through the supply flow path 16 to the inkjet bar 14.

[0141] The ink supplied to the inkjet bar 14 is discharged from the joint F2 to the recovery flow path 18 via the supply-side back pressure tank 30, the supply-side head manifold 32, the first bypass flow path 64, the second bypass flow path 66, the recovery-side head manifold 44, and the recovery-side back pressure tank 48.

[0142] The ink supply device 10 operates the recovery pump 50 to recover ink discharged from the inkjet bar 14 into the recovery passage 18 into the buffer tank 12 via the recovery passage 18 and the recovery port 12B.

[0143] Figure 8 is an explanatory diagram of the liquid level in the buffer tank during a non-printing period. When performing ink circulation during a non-printing period, the ink supply device 10 discharges the ink 300 contained in the buffer tank 12, lowering the liquid level 302 of the ink 300. Figure 8 shows an example in which the liquid level 302 of the ink 300 is lowered to a position where the recovery port 12B is connected.

[0144] 9 is a schematic diagram showing the flow of ink in the buffer tank during a non-printing period. If the amount of ink circulating per unit period during a non-printing period is not changed compared to a printing period, the cross-sectional area of ​​the ink flowing inside the buffer tank 12 during the non-printing period decreases compared to a printing period. This increases the ink flow rate during the non-printing period compared to a printing period, and sufficiently achieves the effect of uniforming the ink distribution, such as flushing out settling particles such as pigment particles that settle on the bottom surface 13D of the buffer tank 12.

[0145] 9, ink flow 304 flowing into the buffer tank 12 from the recovery port 12B collides with the inner surface 13C of the buffer tank 12, generating a downward ink flow 306. On the other hand, the upward ink flow 308 shown in FIG. 6 does not occur.

[0146] That is, the ink circulation method according to the embodiment has the effect of suppressing the settling of pigment particles onto the bottom surface 13D of the buffer tank 12. Furthermore, the ink circulation method according to the embodiment has the effect of promoting uniformity in the temperature of the ink stored in the buffer tank 12.

[0147] Increasing the ink flow rate relatively promotes agitation of the ink inside the buffer tank 12, and it is preferable to control the recovery pump 50 to increase the amount of ink flowing into the buffer tank 12 per unit time within the range allowed by the performance of the recovery pump 50.

[0148] However, if pressure control in the head module 15 becomes unstable, an abnormality in the head module 15 may occur, such as ink leakage from the head module 15 or air entering the head module 15. Therefore, when ink circulation is performed during non-printing periods, the flow of ink into the head module 15 is blocked. Note that the increased ink amount described in the embodiment is an example of the increased liquid flow rate.

[0149] The ink circulation according to the embodiment is preferably performed when starting up and shutting down a printing system including the inkjet bar 14. The ink circulation according to the embodiment may also be performed when the printing system is not in operation. In particular, when starting up the printing system, it is preferable to perform the ink circulation according to the embodiment before performing the ink circulation shown in FIG.

[0150] Inks where pigment particle settling is a problem are primarily white inks, in which titanium dioxide is applied to the pigment particles. An example of the density of pigment particles in white ink is 4.2 grams per cubic centimeter.

[0151] To check whether pigment particles have settled to the bottom surface 13D of the buffer tank 12, a method can be applied in which ink is extracted from the upper and lower portions of the buffer tank 12 and the mass of the pigment particles contained therein is compared. In the case of white ink, the water in each of the ink in the upper and lower portions of the buffer tank 12 is evaporated, and the mass of the remaining solid pigment particles is measured. Based on the results of this mass measurement, it can be determined whether the ink 300 inside the buffer tank 12 is within the appropriate concentration range.

[0152] [Liquid level] 10 is an explanatory diagram of the liquid level in the buffer tank during a non-printing period. It is desirable to lower the liquid level 302 of the ink 300 in the buffer tank 12 as much as possible during a non-printing period. When lowering the liquid level 302 of the ink 300 to the position of the recovery port 12B, if it is lowered to a position below the upper end position 12E of the recovery port 12B, there is a possibility that air will be sucked into the buffer tank 12 from the recovery port 12B. Therefore, the liquid level 302 of the ink 300 is set to a position above the upper end position 12E of the recovery port 12B.

[0153] Considering the fluctuation in ink flow caused by pulsation of the recovery pump 50 and the solid dispersion of the recovery pump 50, the distance between the liquid level 302 of the ink 300 and the upper end position 12E of the recovery port 12B is preferably 2 mm or more and 3 mm or less.

[0154] When the heights of the supply port 12A, the recovery port 12B, and the bypass port 12C are different, it is preferable that the liquid level 302 of the ink 300 is higher than the upper end position of the supply port 12A, the recovery port 12B, and the bypass port 12C that has the highest upper end position.

[0155] An example of lowering the liquid level 302 of the ink 300 in the buffer tank 12 is to operate the refill pump 82 to send ink from the recovery port 12B through the refill flow path 78 to the main ink tank 76.

[0156] Another example of lowering the liquid level 302 of the ink 300 in the buffer tank 12 is to operate the supply pump 24 to send ink from the supply port 12A to the inkjet bar 14 via the supply flow path 16, and then discharge the ink through the head module 15.

[0157] Alternatively, the buffer tank 12 may be provided with an outlet, and the liquid level 302 of the ink 300 in the buffer tank 12 may be lowered by opening a valve provided at the outlet and discharging the ink from the buffer tank 12 through the outlet.

[0158] When the liquid level 302 of the ink 300 during the non-printing period is returned to the liquid level 302 of the ink 300 during the printing period, the refill pump 82 is operated to supply ink from the main ink tank 76 to the buffer tank 12 .

[0159] [Circulation using a bypass flow path] In the buffer tank 12, ink is ejected from a narrow flow path connected to the recovery port 12B into the portion of the buffer tank 12 where the ink is pooled, so that the ink flows vigorously from the recovery port 12B from which the ink is ejected to the inner surface 13C opposite the recovery port 12B. As a result, the ink tends to flow downward inside the buffer tank 12, which has the effect of mobilizing settling particles.

[0160] On the other hand, when ink is caused to flow in the opposite direction to normal circulation and is caused to flow into the buffer tank 12 from the supply port 12A and the bypass port 12C, the ink does not return to the buffer tank 12 with great force, and it is difficult to use the force of the ink being sprayed out to flush out particles that settle near the bottom surface 13D of the buffer tank 12.

[0161] Therefore, an ink flow different from the normal circulation is generated, the ink is returned to the buffer tank 12 from the supply port 12A and the bypass port 12C, and the particles settling near the bottom surface 13D of the buffer tank 12 are sprayed up.

[0162] 11 is a diagram showing the flow of ink in normal circulation using the bypass flow path. In normal circulation using the bypass flow path 54, when ink is sent from the inkjet bar 14 to the buffer tank 12, the bypass flow path 54 is used, and the ink flows into the buffer tank 12 from the bypass port 12C. This causes the ink to flow vigorously into the buffer tank 12 from the bypass port 12C, making it easier for settling particles to flow away near the bypass port 12C.

[0163] 12 is a diagram showing the flow of ink in reverse circulation using a bypass flow path. In reverse circulation using a bypass flow path, the ink flows in the opposite direction to normal circulation. That is, when ink is sent from the buffer tank 12 to the inkjet bar 14, the supply pump 24 operates in a reverse direction relative to normal circulation, discharging ink from the bypass port 12C, and using the bypass flow path 54, sending ink from the buffer tank 12 to the inkjet bar 14.

[0164] Furthermore, when ink is sent from the inkjet bar 14 to the buffer tank 12, the supply flow path 16 is used to allow the ink to flow from the supply port 12A into the buffer tank 12. This allows the ink to flow vigorously from the supply port 12A into the buffer tank 12, making it easier for settling particles to flow away near the supply port 12A.

[0165] In reverse circulation using the bypass flow path 54, a problem can occur in that ink that does not pass through the supply-side filter 26 flows into the inkjet bar 14. The ink that does not pass through the supply-side filter 26 may contain particles of a size that may affect the ejection of ink from the head module 15.

[0166] Therefore, when reverse circulation using the bypass flow path 54 is performed, normal circulation is performed after the reverse circulation, and ink that does not pass through the supply-side filter 26 is collected in the buffer tank 12. This prevents ejection abnormalities in the head module 15 from occurring due to the supply of ink that does not pass through the supply-side filter 26 to the head module 15.

[0167] The normal circulation after the reverse circulation is performed before the start of the circulation during the printing period. During the normal circulation after the reverse circulation, a volume of ink exceeding the volume of ink supplied to the inkjet bar 14 during the reverse circulation is collected in the buffer tank 12.

[0168] For example, the rotation speed of the supply pump 24 is fixed, and the period exceeding the period during which reverse circulation is performed is set as the period during which normal circulation is performed after reverse circulation. Alternatively, the volume of ink flowing out of the buffer tank 12 and the volume of ink recovered into the buffer tank 12 may be calculated using the detection result of the liquid level detection sensor 99A provided in the buffer tank 12, and the supply pump 24 may be controlled based on the comparison result between the two.

[0169] The ink that does not pass through the supply-side filter 26 described in the embodiment is an example of a liquid that does not pass through a filter. The normal circulation and reverse circulation described in the embodiment are examples of liquid circulation.

[0170] [Modification of buffer tank] 13 is a cross-sectional view of a buffer tank showing an example of the structure of a buffer tank according to a modified example. The buffer tank 312 shown in the figure faces an inner surface 314 on which a recovery port 312B is formed, and has a downward surface 316 including a position facing the recovery port 312B.

[0171] The ink that flows into the buffer tank 12 from the recovery port 312B has an ink flow 318 directed toward the downward surface 316. The ink that collides with the downward surface 316 is guided downward, generating a downward ink flow 320. This causes a flow of ink 322 contained inside the buffer tank 312, suppressing the settling of particles.

[0172] When the liquid level 323 of the ink 322 in the buffer tank 312 is lowered, at least a portion of the downward surface 316 is immersed in the ink 322. The height H of the portion of the downward surface 316 immersed in the ink 322 may be equal to or greater than the diameter D of the recovery port 312B. The length of the downward surface 316 in the width direction may be equal to or greater than the diameter D of the recovery port 312B.

[0173] Here, the height of downward surface 316 is the length of downward surface 316 in a direction perpendicular to bottom surface 324. The width direction of downward surface 316 is a direction parallel to bottom surface 324 and a direction parallel to the surface on which recovery port 312B is formed. The diameter D of recovery port 312B is the inner diameter of recovery port 312B.

[0174] The angle of the downward surface 316 relative to the bottom surface 324 may be any angle greater than 0 degrees and less than 90 degrees. The angle of the downward surface 316 relative to the bottom surface 324 is preferably any angle greater than 30 degrees and less than 45 degrees. Figure 13 shows a downward surface 316 that is flat. As long as it generates a downward ink flow 320, the downward surface 316 may be a curved surface, or a combination of multiple types of surfaces, such as a combination of flat and curved surfaces.

[0175] The bottom surface of the buffer tank 12 shown in FIG. 13D 13 has a flat structure that prevents ink from stagnating. The term "flat" means that the bottom surface 13D, etc. has a certain degree of flatness. The term "flat" may also mean that the surface roughness of the bottom surface 13D, etc. is smaller than a specified value.

[0176] 14 is an explanatory diagram of an example of the location of the recovery port. It is preferable that the recovery port 12B be located near the end 13E of the buffer tank 12. In other words, the distance between the end 13E of the buffer tank 12 on the recovery port 12B side and the center 12F of the recovery port 12B can be at least half the inner diameter D of the recovery port 12B and no more than three times the inner diameter D of the recovery port 12B. This can prevent ink from stagnating in the area of ​​the buffer tank 12 on the end 13E side of the recovery port 12B.

[0177] 3 and the like, the distance from the end of the buffer tank 12 on the supply port 12A side can be set to at least half the diameter of the supply port 12A and no more than three times the diameter of the supply port 12A, thereby making it possible to prevent ink from stagnating in the area closer to the end than the supply port 12A.

[0178] In a preferred embodiment, the buffer tank 12 has a bottom surface 13D coated with a coating that makes it difficult for particles contained in the ink to adhere to it. An example of such a coating is a fluorine coating. The buffer tank 12 may have an inner surface other than the bottom surface 13D coated with a coating that makes it difficult for particles contained in the ink to adhere to it. The same applies to the buffer tank 312 shown in FIG. 13.

[0179] The end 13E of the buffer tank 12 on the recovery port 12B side described in the embodiment is an example of a side surface that intersects with the surface on which the liquid inlet and outlet ports are arranged. The fluorine coating described in the embodiment is an example of a coating process in which a fluororesin is used as the coating material.

[0180] [Modification of ink circulation during non-printing periods] 15 is a diagram showing the flow of ink in reverse circulation using a supply flow path and a recovery flow path. In the reverse circulation shown in the figure, ink flows out from the recovery port 12B and is sent to the inkjet bar 14 via the recovery flow path 18. In addition, ink is sent from the inkjet bar 14 to the buffer tank 12 via the supply flow path 16, and ink flows into the buffer tank 12 from the supply port 12A.

[0181] After the reverse circulation, normal circulation is performed in which ink is sent from the buffer tank 12 to the inkjet bar 14 via the supply flow path 16, and ink is sent from the inkjet bar 14 to the buffer tank 12 via the recovery flow path 18.

[0182] 16 is a diagram showing the flow of ink in normal circulation using the recovery flow path and bypass flow path. In normal circulation shown in the figure, ink is discharged from the supply port 12A, and by operating the recovery pump 50, the ink is sent from the buffer tank 12 to the inkjet bar 14 via the degassing module 22, the recovery filter valve 92, and the recovery filter 90.

[0183] Furthermore, the ink that has flowed into the inkjet bar 14 passes through the recovery damper 40 and the drain passage 49, and is discharged from the inkjet bar 14 via the joint F3. Inside the inkjet bar 14, the first bypass passage valve 68 and the second bypass passage valve 69 are closed, and no ink flows from the recovery-side head manifold 44 to the supply-side head manifold 32. The ink that has flowed out of the inkjet bar 14 via the joint F3 flows through the bypass passage 54 and into the buffer tank 12 from the bypass port 12C.

[0184] 17 is a diagram showing the flow of ink in reverse circulation using the recovery flow path and the bypass flow path. In the reverse circulation shown in the figure, the recovery pump 50 is operated to cause ink to flow out from the bypass port 12C, and the ink is sent from the buffer tank 12 to the inkjet bar 14 via the bypass flow path 54.

[0185] The ink flowing into the inkjet bar 14 passes through the drain passage 49 and the recovery damper 40, and then flows out of the inkjet bar 14 via the joint F2. The ink is then sent from the inkjet bar 14 to the buffer tank 12 via the recovery passage 18, the recovery-side filter valve 92, and the degassing module 22. The ink sent from the inkjet bar 14 to the buffer tank 12 flows into the buffer tank 12 via the supply port 12A.

[0186] Ink circulation between the buffer tank 12 and the inkjet bar 14 may be achieved by operating the supply pump 24 to send ink from the buffer tank 12 to the inkjet bar 14 via the supply flow path 16, and then operating the supply pump 24 in the reverse direction to send ink from the inkjet bar 14 to the buffer tank 12 via the supply flow path 16. In this embodiment, the recovery flow path 18 and the bypass flow path 54 may be used instead of the supply flow path 16, and the recovery pump 50 may be used instead of the supply pump 24.

[0187] [Modifications of the liquid supply device and inkjet bar] Figure 18 is a diagram showing the flow of ink in normal circulation applied to an ink supply device according to a modified example. The ink supply device 400 shown in the figure supplies ink to an inkjet bar 414. The inkjet bar 414 includes a supply-side back-pressure tank 430 and components related to the supply-side back-pressure tank 430, but does not include the recovery damper 40 and components related to the recovery damper 40 shown in Figure 1. Note that in Figure 18, the reference numerals for the components related to the supply-side back-pressure tank 430 are omitted.

[0188] The inkjet bar 414 includes a head module 415. The head module 415 includes an ink supply port 415A, but does not include an ink discharge port 15B shown in FIG.

[0189] The inkjet bar 414 includes a supply-side head manifold 432, a supply-side pressure sensor 434, an ink supply flow path 435, a supply valve 436, and a supply damper 438, but does not include the ink recovery flow path 39, the recovery damper 40, the recovery valve 42, and the recovery-side head manifold 44 shown in FIG. 1, etc.

[0190] The inkjet bar 414 includes a drain flow path 447, a drain valve 456, a joint F1, and a joint F3, but does not include the drain flow path 49, the drain valve 70, and the joint F2 shown in FIG.

[0191] The ink supply device 400 includes a buffer tank 412, a supply flow path 416, a degassing module 422, a supply pump 424, a supply-side filter 426, and a heat exchanger 428. The ink supply device 400 includes a bypass flow path 454 and a plurality of joints F. The buffer tank 412 includes a supply port 412A, a recovery port 412B, a bypass port 412C, and an overflow port 412D.

[0192] The ink supply device 400 includes a main ink tank 476 , a main tank filter 476A, a refill passage 478 , an overflow passage 480 , a refill pump 482 , a first safety valve 484 , and a second safety valve 486 .

[0193] On the other hand, the ink supply device 400 does not include the recovery flow path 18, the recovery pump 50, the recovery-side filter 90, and the recovery-side filter valve 92 shown in Fig. 1 etc. Note that the degassing module 422 etc. shown in Fig. 18 has the same configuration and function as the degassing module 22 etc. shown in Fig. 1.

[0194] In normal circulation during non-printing periods applied to the ink supply device 400 and the inkjet bar 414, the supply pump 424 is operated to cause ink to flow out of the supply port 412A, and ink is sent from the buffer tank 412 to the inkjet bar 414.

[0195] The ink that flows into the inkjet bar 414 flows out from the joint F3 via the joint F1, the supply-side back pressure tank 430, and the drain flow path 447. The ink that flows out of the inkjet bar 414 flows through the bypass flow path 454 and the bypass port 412C into the buffer tank 412.

[0196] 19 is a diagram showing the flow of ink in reverse circulation applied to the ink supply device according to the modified example. In reverse circulation during non-printing periods applied to the ink supply device 400 and the inkjet bar 414, the supply pump 424 operates in a reverse direction relative to normal circulation, causing ink to flow out from the bypass port 412C and sending ink from the buffer tank 412 to the inkjet bar 414.

[0197] The ink that flows into the inkjet bar 414 flows through the joint F3, the drain channel 447, and the supply-side back pressure tank 430, and then flows out from the joint F1. 414 The ink flowing out from the supply port 412A passes through the supply flow path 416 and flows out of the supply port 412B. Raba The refrigerant flows into the buffer tank 412.

[0198] After the reverse circulation, the normal circulation shown in FIG. 18 is performed, and the ink that flows into the inkjet bar 414 without passing through the supply-side filter 426 is returned to the buffer tank 412 via the bypass flow path 454.

[0199] In this way, ink circulation during non-printing periods is also performed in ink supply devices 400 that do not have the recovery flow path 18 shown in Fig. 1. This promotes the flow of ink inside the buffer tank 412 and suppresses the occurrence of ink distribution such as particle settling. Note that Fig. 19 illustrates three of the n head modules 415.

[0200] [Ink circulation method] Figure 20 is a flowchart showing the steps of the ink circulation method according to the embodiment. In the non-printing period determination step S10, the overall control unit 94 shown in Figure 2 determines whether or not it is a non-printing period. In the non-printing period determination step S10, if the overall control unit 94 determines that it is a printing period, the determination is No. If the determination is No, the steps of the ink circulation method for the non-printing period are terminated, and ink circulation is not performed.

[0201] On the other hand, if the integrated control unit 94 determines that it is a non-printing period in the non-printing period determination step S10, a Yes determination is made. If a Yes determination is made, the process proceeds to the ink circulation implementation determination step S12.

[0202] In the ink circulation execution determination step S12, the overall control unit 94 determines whether or not to execute ink circulation. In the ink circulation execution determination step S12, the overall control unit 94 can determine whether or not an ink circulation execution condition is satisfied. An example of the ink circulation execution condition being satisfied is the passage of a specified period of time since the most recent ink circulation was executed.

[0203] In the ink circulation execution determination step S12, if the integrated control unit 94 determines that ink circulation is not to be executed, the determination is No. If the determination is No, the ink circulation method is terminated and ink circulation is not executed.

[0204] On the other hand, if the integrated control unit 94 determines that ink circulation should be performed in the ink circulation determination step S12, the determination is Yes. If the determination is Yes, the process proceeds to the liquid level adjustment step S14.

[0205] In the liquid level adjusting step S14, the integrated control unit 94 discharges ink from the buffer tank 12 shown in FIG. 1, and lowers the ink level in the buffer tank 12 to a specified position.

[0206] In the liquid level adjusting step S14, the general control unit 94 can perform feedback control based on the detection result of the liquid level detection sensor 99 A. After the liquid level adjusting step S14, the process proceeds to the circulation start valve switching step S16.

[0207] In the circulation start valve switching step S16, the valve control unit 97 switches various valves, such as the drain valve 56 shown in Fig. 1, between open and closed states to set a flow path through which ink passes. The valve control unit 97 also closes the supply valve 36 and the recovery valve 42 to set no ink supply to the head module 15. After the circulation start valve switching step S16, the process proceeds to the pump control step S18.

[0208] In the pump control step S18, the pump control unit 98 sets operating conditions for pumps applied to ink circulation, such as the supply pump 24 shown in Fig. 1, starts operation of the supply pump 24, etc., and controls the operation of the supply pump 24, etc. In the pump control step S18, the pump control unit 98 may feedback control the supply pump 24, etc., depending on the detection results of the supply-side pressure sensor 34, etc. After the pump control step S18, the process proceeds to the ink circulation completion determination step S20.

[0209] In the ink circulation end determination step S20, the overall control unit 94 determines whether or not to end the ink circulation. In the ink circulation end determination step S20, the overall control unit 94 can determine whether or not an ink circulation end condition is satisfied. Examples of satisfying the ink circulation end condition include the passage of a specified period of time and the acquisition of a signal indicating the end of ink circulation.

[0210] In the ink circulation end determination step S20, if the integrated control unit 94 determines not to end the ink circulation, the determination is No. If the determination is No, the ink circulation continues, and the ink circulation end determination step S20 continues.

[0211] On the other hand, if the integrated control unit 94 determines to end the ink circulation in the ink circulation end determination step S20, the determination is Yes. If the determination is Yes, the process proceeds to the pump stop step S22.

[0212] In the pump stopping step S22, the pump control unit 98 stops the operation of the supply pump 24 and other components used in ink circulation. After the pump stopping step S22, the process proceeds to the circulation termination valve switching step S24.

[0213] In the circulation end valve switching step S24, the valve control unit 97 switches the opening and closing of the drain valve 56, etc., to set the ink flow path according to the process after the ink circulation. After the circulation end valve switching step S24, the process proceeds to the liquid level recovery step S26.

[0214] In the liquid level restoration step S26, the pump control unit 98 operates the refill pump 82 to supply ink from the main ink tank 76 to the buffer tank 12, thereby restoring the ink liquid level in the buffer tank 12. After the liquid level restoration step S26, the overall control unit 94 ends the ink circulation method.

[0215] After the non-printing period determination step S10, a circulation direction selection step may be performed to select whether to perform normal circulation or reverse circulation. If reverse circulation is selected, it is preferable to perform normal circulation after reverse circulation. Note that the ink circulation method described in the embodiment is an example of a liquid circulation method.

[0216] [Effects of the embodiment] The ink supply device according to the embodiment can achieve the following advantageous effects.

[0217] [1] During non-printing periods when the inkjet bar 14 is not operating, if ink circulation is performed, the liquid level of the ink contained in the buffer tank 12 is lowered compared to during printing periods. This promotes the flow of ink at and near the bottom surface 13D of the buffer tank 12, and suppresses the settling of particles contained in the ink and the occurrence of ink distribution such as ink temperature distribution.

[0218] [2] When ink circulation is performed during non-printing periods, the ink flow rate is relatively increased within the range allowed by the pump performance, thereby promoting agitation of the ink in the buffer tank 12.

[0219] [3] When ink circulation is performed during non-printing periods, the flow of ink to the head module 15 is blocked. This prevents abnormalities in the head module 15, such as ink leakage from the head module 15 and air entering the head module 15.

[0220] [4] The distance between the liquid level in the buffer tank 12 and the upper end position 12E of the recovery port 12B through which ink flows into the buffer tank 12 is 2 millimeters or more. 3 minutes This makes it possible to both promote the agitation of the ink in the buffer tank 12 and prevent air from entering the recovery passageway 18 and the like from the recovery port 12B.

[0221] [5] The distance between center 12F of recovery port 12B, through which ink flows into buffer tank 12 when circulating ink during non-printing periods, and edge 13E of buffer tank 12 is set to be at least half the diameter D of recovery port 12B and no more than three times the inner diameter D of recovery port 12B. This prevents ink from stagnating near edge 13E of buffer tank 12. If a similar configuration is applied to the edge on the supply port 12A side and supply port 12A, similar effects can be obtained.

[0222] [6] Ink is circulated normally through the bypass flow path 54. This causes ink to flow vigorously into the buffer tank 12 from the bypass port 12C, and suppresses ink settling around the bypass port 12C.

[0223] [7] The ink is circulated in the reverse direction via the bypass flow path 54. This causes the ink to flow vigorously from the supply port 12A into the buffer tank 12, and suppresses the ink from settling around the supply port 12A.

[0224] [8] After reverse circulation of the ink, normal circulation is performed, which allows any ink that has entered the inkjet bar 14 without passing through the supply-side filter 26 to be expelled from the inkjet bar 14.

[0225] [9] The buffer tank 312 has a downward surface 316 on the surface facing the recovery port 312B. fart The incoming ink collides with the downward surface 316, promoting the generation of a downward ink flow 320.

[0226]

[10] A flat structure is applied to the bottom surface 13D of the buffer tank 12. This prevents ink from stagnating on the bottom surface 13D of the buffer tank 12.

[0227]

[11] A coating process that promotes the flow of ink is applied to the bottom surface 13D of the buffer tank 12. This promotes the flow of ink on the bottom surface 13D of the buffer tank 12.

[0228] [Application example to inkjet printing system] 21 is a diagram showing the overall configuration of an inkjet printing system to which an ink supply device according to an embodiment is applied. The inkjet printing system 110 applies a single-pass method and performs single-pass printing.

[0229] In the inkjet printing system 110, a continuous roll of paper 1 is used as the printing medium. However, the paper 1 may be a single sheet.

[0230] General-purpose printing paper can be used as paper 1. General-purpose printing paper does not refer to paper specifically for inkjet printing, but refers to paper that is primarily made of cellulose, such as coated paper used for general offset printing. Paper 1 can also be made of materials other than paper, such as resin, metal, and cloth.

[0231] The inkjet printing system 110 includes a conveying device 120, a sending device 130, a pretreatment liquid application device 140, a printing device 150, a drying device 170, and a winding device 180. Each device will be described in detail below.

[0232] [Transportation device] A roll-to-roll system is applied to the conveying device 120. The conveying device 120 conveys the paper 1 along a conveying path from the sending device 130 to the winding device 180. The conveying direction of the paper 1 refers to the direction in which the paper 1 travels along the conveying path of the paper 1 from the sending device 130 to the winding device 180. In the following description, the conveying direction of the paper 1 may be referred to as the paper conveying direction.

[0233] The transport device 120 includes a plurality of pass rollers 122. The pass rollers 122 function as guide rollers that support the paper 1 in the transport path of the paper 1. Each of the above-described parts of the inkjet printing system 110 includes one or more pass rollers 122.

[0234] The conveying device 120 includes conveying members that convey the paper 1 through each part of the inkjet printing system 110. An example of a conveying member is a print drum 152 provided in the printing device 150. Note that the conveying device 120 may adopt a mode in which it includes the sending device 130 and the winding device 180 as components.

[0235] [Delivery device] The delivery device 130 has a delivery roll 132 mounted thereon. The delivery roll 132 has a configuration in which the unprinted paper 1 is wound around a reel that is rotatably supported. The reel is not shown in the drawing.

[0236] [Take-up device] The winding device 180 has a winding roll 182 placed thereon. The winding roll 182 has a configuration in which printed paper 1 is wound around a rotatably supported reel. One end of the paper 1 is connected to the reel. The winding roll 182 is connected to the rotating shaft of a motor that rotates the reel. The reel and motor are not shown in the figure.

[0237] [Pretreatment liquid application device] The pretreatment liquid application device 140 is disposed on the paper transport path, at a position upstream of the printing device 150 in the paper transport direction. The pretreatment liquid application device 140 applies a pretreatment liquid to the printing surface of the paper 1. The pretreatment liquid is a liquid that contains water and a component that aggregates or insolubilizes colorant components in the aqueous ink and thickens the aqueous ink. The aqueous ink thickens by reacting with the pretreatment liquid.

[0238] The pretreatment liquid application device 140 includes an application roller 142, an opposing roller 144, and a pretreatment liquid drying device 146. The paper 1 conveyed from the delivery device 130 is guided by a pass roller 122 and conveyed to a position facing the application roller 142.

[0239] The pretreatment liquid application device 140 employs a roller application method in which the paper 1 is sandwiched between an application roller 142, to which the pretreatment liquid is supplied, and an opposing roller 144, and the pretreatment liquid is applied to the printing surface of the paper 1. Note that a liquid reservoir and the like for storing the pretreatment liquid to be supplied to the application roller 142 are not shown in the drawings.

[0240] The method of applying the pretreatment liquid applied to the pretreatment liquid application device 140 is not limited to the roller application method. For example, an application method other than the roller application method, such as a blade application method using a blade, may be applied.

[0241] The sheet 1 to which the pretreatment liquid has been applied is dried using a pretreatment liquid drying device 146. The pretreatment liquid drying device 146 may employ a method in which hot air is blown onto the sheet 1 from a hot air heater. The sheet 1 to which the pretreatment liquid application device 140 has been applied is transported to a printing device 150.

[0242] [Printing device] Printing device 150 prints a color image on the printing surface of paper 1. Printing device 150 includes inkjet bar 14K, inkjet bar 14C, inkjet bar 14M, inkjet bar 14Y, and inkjet bar 14W. Inkjet bar 14K, inkjet bar 14C, inkjet bar 14M, inkjet bar 14Y, and inkjet bar 14W eject black ink, cyan ink, magenta ink, yellow ink, and white ink, respectively.

[0243] Each of the inkjet bar 14K, inkjet bar 14C, inkjet bar 14M, inkjet bar 14Y, and inkjet bar 14W shown in FIG. 21 corresponds to the inkjet bar 14 shown in FIG.

[0244] The printing device 150 includes an ink supply device 10K, an ink supply device 10C, an ink supply device 10M, an ink supply device 10Y, and an ink supply device 10W. Each of the ink supply devices 10K, etc. supplies ink of a corresponding color to each of the inkjet bars 14K, etc.

[0245] Each of the ink supply device 10K, the ink supply device 10C, the ink supply device 10M, the ink supply device 10Y, and the ink supply device 10W shown in FIG. 21 corresponds to the ink supply device 10 shown in FIG.

[0246] In the following description, inkjet bar 14K, inkjet bar 14C, inkjet bar 14M, inkjet bar 14Y, and inkjet bar 14W may be collectively referred to as inkjet bar 14. Similarly, ink supply device 10K, ink supply device 10C, ink supply device 10M, ink supply device 10Y, and ink supply device 10W may be collectively referred to as ink supply device 10. Note that inkjet bar 14K and the like described in the embodiment are an example of a print head.

[0247] The paper 1 is supported and transported using the print drum 152, and droplets of water-based ink such as black and cyan are ejected onto the paper 1 directly below the inkjet bar 14, printing a color image.

[0248] Water-based ink includes ink in which pigment particles are dispersed in a solvent such as water. White ink uses titanium oxide as the pigment particle material that can settle in the solvent. The average particle diameter of the titanium oxide particles contained in the white ink may be greater than 100 nanometers. The average particle diameter may be the particle diameter at which the integrated value in the particle size distribution derived using a laser diffraction scattering method is 50%.

[0249] The density of the pigment particles in the white ink may be 2.0 grams per cubic centimeter or more. The density of the pigment particles in the white ink may be 5.0 grams per cubic centimeter or more.

[0250] The printing device 150 includes a scanner 156. The scanner 156 includes an imaging device that captures an image, such as a test image, printed on the printing surface of the paper 1 and generates an imaging signal corresponding to the image. The imaging device may be a color CCD linear image sensor. Alternatively, a color CMOS linear image sensor may be used.

[0251] The imaging device is not shown in the figure. CCD is an abbreviation for Charge Coupled Device. CMOS is an abbreviation for Complementary Metal Oxide Semiconductor. The paper 1 on which a color image has been printed using the printing device 150 is transported to the drying device 170.

[0252] [Drying equipment] The drying device 170 dries the printed surface of the paper 1 by blowing hot air toward the printed surface of the paper 1 supported by the drying drum 172. The paper 1 whose printed surface has been dried by the drying device 170 is transported to the winding device 180.

[0253] [Configuration of inkjet bar and head module] The inkjet bar 14 may have a structure in which multiple head modules 15 are connected together in the width direction of the paper 1. The multiple head modules 15 may have the same structure. The width direction of the paper 1 is a direction perpendicular to the paper transport direction. Hereinafter, the width direction of the paper 1 may be referred to as the paper width direction.

[0254] Figure 22 is a planar perspective view showing an example of the structure of a head module. Figure 22 is a schematic diagram showing the flow path structure of the head module 15. Note that the symbol X in this figure indicates the paper width direction. The symbol Y indicates the paper transport direction. The symbol Z is the normal direction to the outer circumferential surface of the print drum 152, which is a direction parallel to the direction in which the nozzle surface of the inkjet bar 14 faces.

[0255] The head module 15 includes a plurality of nozzles 202. The plurality of nozzles 202 are arranged two-dimensionally. Fig. 22 shows an example in which the plurality of nozzles 202 are arranged in a matrix.

[0256] Each of the plurality of nozzles 202 communicates with a pressure chamber 204. The pressure chamber 204 communicates with a supply branch 210. The supply branch 210 communicates with a common flow path 212. The common flow path 212 communicates with the ink supply port 15A.

[0257] Each nozzle 202 is also connected to a tributary recovery channel 218 via an ink circulation channel. The tributary recovery channel 218 is connected to a common circulation channel 220. The common circulation channel 220 is connected to the ink discharge port 15B. The ink circulation channel is not shown in FIG. 22. The ink circulation channel is shown in FIG. 23 using the reference numeral 216. In FIG. 22, a circle is shown as an example of the opening shape of the nozzle 202, but the opening shape of the nozzle 202 may be a shape other than a circle, such as a rectangle.

[0258] Figure 23 is a cross-sectional view taken along the line XXIII-XXIII shown in Figure 22. Figure 23 illustrates the three-dimensional structure of the head module 15. The head module 15 includes a nozzle plate 230, a flow path plate 232, and an actuator 228. The head module 15 has a structure in which the nozzle plate 230, the flow path plate 232, and the actuator 228 are stacked in this order.

[0259] A plurality of nozzles 202 are formed in the nozzle plate 230. The nozzles 202 have openings formed in the nozzle surface 200 and have a structure that penetrates the nozzle plate 230.

[0260] The flow path plate 232 is formed with pressure chambers 204, supply restrictors 208, supply tributaries 210, common flow paths 212, descenders 214, ink circulation paths 216, recovery tributaries 218, and circulation common flow paths 220. Note that the common flow paths 212 and circulation common flow paths 220 are not shown in FIG.

[0261] Silicon may be used as the material for the nozzle plate 230 and the flow path plate 232. The nozzle plate 230 and the flow path plate 232 may be processed using a semiconductor manufacturing process to form structures such as the nozzles 202 and the pressure chambers 204.

[0262] The nozzle 202 is in communication with a pressure chamber 204 via a descender 214. The pressure chamber 204 is in communication with a supply tributary 210 via a supply restrictor 208. The nozzle 202 is also in communication with a recovery tributary 218 via an ink circulation path 216.

[0263] 22 flows through the common flow path 212, the supply tributary 210, the supply restrictor 208, the pressure chamber 204, and the descender 214, and a portion of the ink is ejected from each nozzle 202. Ink that is not ejected from the nozzle 202 passes through the ink circulation path 216, the recovery tributary 218, and the circulation common flow path 220 and is discharged from the ink discharge port 15B.

[0264] It is preferable that the ink circulation path 216 is configured to be arranged in the periphery of the nozzle 202. In the head module 15 shown in Fig. 23, the ink circulation path 216 is arranged in a region that communicates with the descender 214 and that contacts the nozzle plate 230 of the flow path plate 232. This makes it possible to circulate ink in the vicinity of the nozzle 202, suppressing the increase in viscosity of the ink inside the nozzle 202, and enabling stable ejection from the head module 15.

[0265] An actuator 228 is bonded to a vibration plate 226, which is the top surface of the pressure chamber 204 and also serves as a common electrode. A piezoelectric element including a piezoelectric layer and individual electrodes is used as the actuator 228. The piezoelectric layer and individual electrodes are not shown in the figure.

[0266] The actuator 228 flexes and deforms in response to the application of a drive voltage to the individual electrode, deforming the pressure chamber 204. Ink is ejected from the nozzle 202 in response to the contraction of the pressure chamber 204. In response to the expansion of the pressure chamber 204 after the ink is ejected from the nozzle 202, new ink is supplied to the pressure chamber 204 from the common flow path 212 through the supply tributary 210 and the supply orifice 208.

[0267] Although the present embodiment has exemplified a piezoelectric method as an ink ejection method, other ink ejection methods may also be used, such as a thermal method or an electrostatic method. Furthermore, the arrangement of the nozzles 202 is not limited to a matrix arrangement, and a single row arrangement, a two-row zigzag arrangement, or the like may also be used.

[0268] [Electrical Configuration of Inkjet Printing System] Fig. 24 is a functional block diagram showing the electrical configuration of the inkjet printing system shown in Fig. 21. The inkjet printing system 110 includes a transport control unit 250, a pretreatment liquid application control unit 252, a print control unit 254, a drying control unit 256, a general control unit 258, and a user interface 264.

[0269] The transport control unit 250 controls the operations of the transport device 120, the delivery device 130, and the winding device 180 based on specified transport conditions, and controls the transport of the paper 1 from the delivery device 130 to the winding device 180.

[0270] Examples of the transport conditions include the transport speed of the paper 1, the suction pressure when the paper 1 is suction-supported, and the transport tension applied to the paper 1. Note that the term "speed" can also mean the speed as an absolute value.

[0271] That is, the transport control unit 250 controls the speed at which the paper 1 is transported by controlling the rotation of a motor connected to a transport member such as the print drum 152.

[0272] In addition, the operation of the pumps connected to the suction holes formed on the outer peripheral surface of the printing drum 152 and the suction holes formed on the outer peripheral surface of the drying drum 172 is controlled to control the suction pressure of the paper 1 onto the outer peripheral surface of the printing drum 152 and the suction pressure of the paper 1 onto the outer peripheral surface of the drying drum 172.

[0273] Furthermore, the transport control unit 250 controls the operation of a transport tension applying mechanism that applies transport tension to the paper 1 in each device, thereby controlling the transport tension applied to the paper 1.

[0274] The pretreatment liquid application control unit 252 applies specified application conditions and controls the operation of the pretreatment liquid application device 140 to control the application of the pretreatment liquid to the paper 1. In other words, the pretreatment liquid application control unit 252 controls the application timing of the pretreatment liquid to the paper 1 and the application amount of the pretreatment liquid applied to the paper 1.

[0275] The pretreatment liquid application control unit 252 applies specified drying conditions and controls the operation of the pretreatment liquid drying device 146 to control the drying process of the sheet 1 on which the pretreatment liquid has been applied. That is, the pretreatment liquid application control unit 252 controls the temperature control of the drying process and the timing of performing the drying process.

[0276] The print control unit 254 controls the overall operation of the ink supply device 10 shown in Fig. 21. The print control unit 254 includes the overall control unit 94, valve control unit 97, and pump control unit 98 shown in Fig. 2, and controls the supply of ink to the inkjet bar 14 and the circulation of ink.

[0277] The print control unit 254 applies specified print conditions and print data to control the ejection of ink from the inkjet bar 14. The print control unit 254 includes an image processing unit that generates halftone data for each color from print data such as raster data.

[0278] The print control unit 254 includes a drive voltage generation unit that generates drive voltages to be supplied to the inkjet bar 14 based on halftone data for each color. The print control unit 254 includes a drive voltage output unit that outputs drive voltages to be supplied to the inkjet bar 14.

[0279] The print control unit 254 performs correction processing on the inkjet bar 14 based on an image signal corresponding to a test image or the like sent from the scanner 156 shown in Fig. 21. Examples of correction processing include density correction, color correction, and abnormal nozzle correction processing.

[0280] The print control unit 254 includes a maintenance control unit that controls maintenance of the inkjet bar 14. Examples of maintenance of the inkjet bar 14 include wiping the nozzle surface 200, purging to discharge ink from the nozzles 202, and moisturizing the nozzle surface 200.

[0281] The drying control unit 256 applies specified drying conditions and controls the operation of the drying device 170 to control the drying process for the paper 1 on which an image is printed. In other words, the drying control unit 256 controls the temperature and volume of the hot air blown onto the paper 1.

[0282] The overall control unit 258 sends command signals to the transport control unit 250 , the pretreatment liquid application control unit 252 , the print control unit 254 , and the drying control unit 256 , and performs overall control of the operation of the inkjet printing system 110 .

[0283] The overall control unit 258 includes one or more processors 260 and one or more memories 262. The overall control unit 258 of the inkjet printing system 110 shown in FIG. 24 includes the overall control unit 94 of the ink supply device 10 shown in FIG. 2. The processor 260 shown in FIG. 24 includes the processor 95 shown in FIG. 2. The memory 262 shown in FIG. 24 includes the memory 96 shown in FIG. 2.

[0284] The user interface 264 is used when a user operates the inkjet printing system 110. The user interface 264 may include input devices such as a keyboard and a mouse. The user interface 264 may also include a display device that displays various types of information in the inkjet printing system 110. A touch panel type display device may be used, and the display device and input device may be integrated into one unit.

[0285] [Modification of Inkjet Printing System] The inkjet printing system 110 may perform a modification treatment on the paper 1 before the pretreatment liquid is applied, to change the surface properties, such as the surface roughness, of the paper 1. Corona discharge treatment may be used as the modification treatment.

[0286] The inkjet printing system 110 may employ a one-liquid method that performs printing on the paper 1 without using a pretreatment liquid. The inkjet printing system 110 to which the one-liquid method is applied does not include the pretreatment liquid application device 140.

[0287] Various functions applicable to various inkjet printing devices can be added to the inkjet printing system 110. An example of the various functions is an inspection process for determining whether the printed paper 1 is good or bad.

[0288] [Example of application to a program] A program can be configured in a computer to realize various functions in ink circulation that are applied to the ink supply device 10. That is, a program can be configured in a computer to realize functions such as a non-printing period determination function, an ink circulation determination function, a liquid level adjustment function, a valve switching function, and a pump selection function.

[0289] A program that causes a computer to realize the various functions described above can be stored in a computer-readable information storage medium, which is a tangible, non-transitory information storage medium, and the program can be provided through the information storage medium.

[0290] Alternatively, the program may be provided by storing it on a non-transitory information storage medium, or by providing a signal corresponding to the program via a communication network.

[0291] The above-described embodiments of the present invention may be modified, added, or deleted as appropriate within the scope of the spirit of the present invention. The present invention is not limited to the above-described embodiments, and many modifications may be made by a person skilled in the art within the technical concept of the present invention. Furthermore, the embodiments, modifications, and applications may be implemented in appropriate combinations. [Explanation of symbols]

[0292] 1 sheet of paper 10 Ink supply device 10C Ink Supply Unit 10K ink supply unit 10M ink supply unit 10W ink supply unit 10Y ink supply unit 12 Buffer Tank 12A supply port 12B Collection port 12C Bypass Exit 12D Overflow port 12E Upper end position 12F center 13A side 13B Top surface 13C Inner surface 13D bottom 13E end 14 Inkjet Bar 14C Inkjet Bar 14K Inkjet Bar 14M Inkjet Bar 14W Inkjet Bar 14Y Inkjet Bar 15 Head Module 15A ink supply port 15B Ink outlet 16 Supply channel 18 Recovery channel 22 Degassing module 24 Supply Pump 26 Supply side filter 28 Heat exchanger 30 Supply side back pressure tank 30A ink inlet 30B Ink outlet 30C liquid chamber 30D air chamber 30E Elastic membrane 30F Air bubble outlet 30G Air flow passage connection port 32 Supply side head manifold 34 Supply side pressure sensor 35 Ink supply channel 36 Supply valve 38 Supply damper 40 Recovery Damper 42 Recovery valve 44 Recovery side head manifold 46 Recovery side pressure sensor 47 Drain channel 48 Recovery side back pressure tank 48A Ink inlet 48B ink outlet 48C Liquid chamber 48D air chamber 48E Elastic membrane 48F Air bubble outlet 48G Air flow passage connection port 49 Drain channel 50 Recovery Pump 52 Recovery flow path valve 54 Bypass flow path 56 Drain valve 58 Air flow path 59 Air connect valve 60 Air Tank 61 Atmospheric communication passage 62 Air valve 64 First bypass flow path 66 Second bypass flow path 68 First bypass flow valve 69 Second bypass flow valve 70 Drain valve 71 Air flow path 72 Air connect valve 73 Air Tank 74 Atmospheric communication passage 75 Air valve 76 Ink main tank 76A Main Tank Filter 78 Refill Channel 80 Overflow channel 82 Refill pump 84 First safety valve 86 Second safety valve 88 Third safety valve 90 Recovery filter 92 Recovery side filter valve 94 General Control Unit 95 processors 96 memory 97 Valve control section 97A Valve 98 Pump control section 98A Pump 99 Sensors 99A Liquid Level Sensor 99B Wiring 110 Inkjet Printing System 120 Transport Device 122 Pass Roller 130 Delivery device 132 Feed-out roll 140 Pre-treatment liquid application device 142 Application roller 144 opposing roller 146 Pretreatment liquid drying device 150 Printing equipment 152 Printing drum 156 Scanner 170 Drying equipment 172 Drying drum 180 Winding device 182 Winding roll 200 Nozzle surface 202 Nozzle 204 Pressure Chamber 210 Supply tributary 212 Common flow path 214 Descender 216 Ink circulation path 218 Recovery Tributary 220 Circulation common flow path 226 Diaphragm 228 Actuator 230 Nozzle Plate 232 Flow path plate 250 Transport control unit 252 Pre-treatment liquid application control unit 254 Printing control unit 256 Drying control unit 258 General Control Unit 260 processor 262 memory 264 User Interface 300 ink 302 Liquid level 306 Downward ink flow 308 Upward ink flow 312 Buffer Tank 312B Collection port 314 Inner surface 316 Downward surface 322 Ink 324 bottom 400 Ink supply unit 412 Buffer Tank 412A Supply port 412C Bypass Exit 414 Inkjet Bar 415 Head Module 416 Supply channel 422 Degassing Module 424 Supply Pump 426 Supply Side Filter 428 Heat Exchanger 430 Supply side back pressure tank 432 Supply side head manifold 434 Supply side pressure sensor 435 Ink supply channel 436 Supply Valve 438 Supply Damper 447 Drain channel 454 Bypass flow path 456 Drain Valve 476 Ink main tank 478 Refill Channel 480 Overflow Channel 482 Refill Pump 484 First safety valve 486 Second safety valve F fitting F1 fitting F2 fitting F3 fitting F 11 Joints F 12 Joints F 13 Joints F 14 Joints S10~S26 Ink circulation method steps

Claims

1. a buffer tank that contains the liquid to be supplied to the liquid supply target device and is provided with a liquid inlet / outlet through which the liquid flows in and out; a liquid level varying device for varying the liquid level of the buffer tank; a liquid flow path that connects the liquid supply target device and the buffer tank; a pump provided in the liquid flow path; a valve that opens and closes the liquid flow path; one or more processors; Equipped with The processor: When the liquid supply target device is not operating, the liquid level varying device is controlled to discharge the liquid from the buffer tank, thereby lowering the liquid level in the buffer tank relative to the liquid level in the buffer tank when the liquid supply target device is operating; a liquid supply system that controls the pump and the valve to allow liquid to flow from the liquid flow path into the buffer tank when the liquid supply target device is not in operation;

2. A liquid supply system as described in claim 1, comprising a pressure buffer device that buffers pressure fluctuations in the liquid flow path.

3. A liquid supply system as described in claim 1 or 2, wherein the pump is arranged between the buffer tank and the pressure buffer device.

4. 4. The liquid supply system according to claim 1, wherein the liquid is a liquid in which particles capable of settling in a solvent are dispersed.

5. 5. The liquid supply system of claim 4, wherein the liquid has particles with a density of 2.0 grams per cubic centimeter or greater.

6. the buffer tank includes a supply port and a recovery port as the liquid inlet and outlet ports; The liquid flow path is a supply flow path communicating with the supply port; a recovery flow path communicating with the recovery port and the supply flow path, The pump a supply pump provided in the supply flow path; The liquid supply system according to claim 1 , further comprising: a recovery pump provided in the recovery passage.

7. A liquid supply system as described in Claim 6, wherein the supply port and the recovery port are arranged on surfaces of the buffer tank facing in the same direction.

8. A liquid supply system as described in claim 6 or 7, wherein the supply port and the recovery port are positioned at the same height from the bottom surface of the buffer tank.

9. A liquid supply system described in any one of claims 6 to 8, wherein the buffer tank has a downward surface that faces the inner surface on which the recovery port is formed, faces the bottom surface of the buffer tank, and includes a position that faces the recovery port.

10. 10. A liquid supply system according to claim 6, wherein the processor controls at least one of the supply pump and the recovery pump to perform reverse circulation, which causes liquid to flow in a direction different from normal circulation, by causing liquid to flow out through the supply port and into the buffer tank through a liquid inlet / outlet different from the supply port.

11. the liquid flow path includes a bypass flow path that is in communication with the buffer tank and the supply flow path and is separate from the recovery flow path; the buffer tank includes a bypass port that communicates with the bypass flow path as the liquid inlet / outlet port, The liquid supply system according to claim 10 , wherein the processor reverses the operation of the supply pump relative to the normal circulation to perform the reverse circulation in which liquid flows in a direction different from the normal circulation in the bypass flow path and the supply flow path.

12. a filter provided in the supply flow path; 12. A liquid supply system as described in claim 10 or 11, wherein the processor controls at least one of the supply pump and the recovery pump to perform the normal circulation, returning the liquid that has not passed through the filter to the buffer tank, after the reverse circulation has been performed.

13. the liquid level varying device includes the supply flow path and the supply pump, The liquid supply system according to claim 10 , wherein the processor controls the supply pump to send the liquid from the buffer tank to the liquid supply target device via the supply port and the supply flow path.

14. The liquid level varying device is a refill channel communicating with the liquid inlet / outlet; a refill pump provided in the refill flow path; a main tank connected to the refilling passage; Equipped with The liquid supply system according to claim 1 , wherein the processor controls the refill pump to send the liquid from the buffer tank to the main tank via the liquid inlet / outlet and the refill flow path.

15. A liquid supply system according to any one of claims 1 to 14, wherein the processor controls the pump to increase the flow rate of the liquid when the liquid supply target device is operating, within an acceptable range for the performance of the pump.

16. The liquid supply system according to claim 1 , wherein the processor stops supplying liquid to the liquid supply target device when liquid circulation is performed while the liquid supply target device is not in operation.

17. The liquid supply system according to claim 1 , wherein the buffer tank has a bottom surface having a structure that prevents stagnation of the liquid flow.

18. The liquid supply system according to claim 1 , wherein the buffer tank has a bottom surface that is subjected to a coating process using a fluororesin as a coating material.

19. A liquid supply system according to any one of claims 1 to 18, wherein the distance from the side of the buffer tank that intersects with the plane on which the liquid inlet / outlet is arranged to the center of the liquid inlet / outlet is at least half the inner diameter of the liquid inlet / outlet and not more than three times the inner diameter of the liquid inlet / outlet.

20. A liquid circulation method applied to a liquid supply device that supplies liquid from a buffer tank to a liquid supply target device through a liquid flow path, comprising: When the liquid supply target device is not operating, the liquid is discharged from the buffer tank to lower the liquid level in the buffer tank relative to the liquid level in the buffer tank when the liquid supply target device is operating; A liquid circulation method comprising controlling a pump and a valve provided in the liquid flow path to cause liquid to flow from the liquid flow path into the buffer tank when the liquid supply target device is not in operation.

21. a buffer tank containing ink to be supplied to the print head and having a liquid inlet / outlet for ink to enter and exit; a liquid level varying device for varying the liquid level of the buffer tank; a liquid flow path that connects the print head and the buffer tank; a pump provided in the liquid flow path; a valve that opens and closes the liquid flow path; one or more processors; Equipped with The processor: when the print head is not operating, the liquid level varying device is controlled to discharge ink from the buffer tank, thereby lowering the liquid level in the buffer tank relative to the liquid level in the buffer tank when the print head is operating; A printing system that controls the pump and the valve to allow ink to flow from the liquid flow path to the buffer tank when the print head is not in operation.

Images