Printing device and printing method

Abstract

The present invention suppresses pressure fluctuation in an ink flow path at the start of ejection when ink is ejected from a head.　This printing device comprises: an ink supply source that supplies ink; a sub-tank that stores the ink supplied from the ink supply source; an ink flow path that has one end connected to the sub-tank and through which the ink stored in the sub-tank flows; a head that is connected to the other end of the ink flow path and from which the ink supplied from the sub-tank through the ink flow path is ejected; and a branch pipe part that branches from the ink flow path and can supply the ink to the ink flow path while containing the ink and air therein.

Description

Printing Apparatus and Printing Method

[0001] The present invention relates to a printing apparatus and a printing method.

[0002] Printing apparatuses equipped with a piezoelectric head that ejects ink supplied from an ink supply source are known (see, for example, Patent Document 1).

[0003] Japanese Unexamined Patent Application Publication No. 2003-1850

[0004] In a printing apparatus such as that disclosed in Patent Document 1, when ink is ejected from the head, the pressure inside the ink flow path may suddenly fluctuate significantly toward the negative pressure side at the start of ejection due to flow path resistance of the ink flow path or the like. This pressure fluctuation may prevent the ink from being properly ejected from the head, leading to the possibility of ink missing on printed matter.

[0005] The present invention has been made in view of the above, and an object thereof is to provide a printing apparatus and a printing method capable of suppressing pressure fluctuations in the ink flow path at the start of ejection when ink is ejected from a head.

[0006] A printing apparatus according to the present invention includes: an ink supply source that supplies ink; a sub-tank that stores the ink supplied from the ink supply source; an ink flow path having one end connected to the sub-tank, through which the ink stored in the sub-tank flows; a head connected to the other end of the ink flow path, that ejects the ink supplied from the sub-tank via the ink flow path; and a branch pipe section that branches off from the ink flow path, and is capable of supplying ink to the ink flow path while containing the ink and air inside.

[0007] A printing method according to the present invention is a printing method using the above printing apparatus, comprising: an ink circulation step of causing the ink to flow through the entire ink flow path; an ink and air arrangement step of filling the ink up to a predetermined distance from a branch portion of the ink flow path in the branch pipe section, and taking in air at an end portion on the side opposite to the branch portion; and an ejection step of ejecting the ink from the head in a state where the ink and the air are arranged in the branch pipe section by the ink and air arrangement step.

[0008] According to the present invention, when ink is ejected from the print head, pressure fluctuations in the ink flow path at the start of ejection can be suppressed.

[0009] Figure 1 is a schematic diagram showing an example of a printing apparatus according to an embodiment. Figure 2 is a flowchart showing an example of a printing method using the printing apparatus. Figure 3 is a diagram showing the operation process of the printing apparatus, showing an example of the ink flow step. Figure 4 is a diagram showing the operation process of the printing apparatus, showing an example of the ink-air arrangement step (placing the syringe). Figure 5 is a diagram showing the operation process of the printing apparatus, showing an example of the ink-air arrangement step (injecting ink into the branch pipe section with the syringe). Figure 6 is a diagram showing the operation process of the printing apparatus, showing an example of the ink-air arrangement step (removing the syringe and sealing it with a stopper member). Figure 7 is a diagram showing the operation process of the printing apparatus, showing an example of the ejection step (state at the start of ejection). Figure 8 is a diagram showing the operation process of the printing apparatus, showing an example of the ejection step (state during ejection). Figure 9 is a diagram showing the operation process of the printing apparatus, showing an example of the ejection step (state after ejection). Figure 10 is a graph showing the relationship between the passage of time and the pressure inside the head when ejecting ink.

[0010] Hereinafter, embodiments of the printing apparatus and printing method according to the present invention will be described with reference to the drawings. However, the present invention is not limited by these embodiments. Furthermore, the components in the following embodiments include those that are easily substituted or substantially identical to those that are easily substituted by those skilled in the art.

[0011] Figure 1 is a schematic diagram showing an example of a printing apparatus 100 according to this embodiment. As shown in Figure 1, the printing apparatus 100 comprises an ink supply source 10, a sub-tank 20, a head 30, an ink flow path 40, an ink pump 50, a pneumatic pump 51, and a control unit 60.

[0012] The ink supply source 10 is a source that supplies ink to the print head 30. The ink supply source 10 may have a configuration that includes one or more cartridges that contain ink.

[0013] The sub-tank 20 temporarily stores the ink supplied from the ink supply source 10. A sub-tank 20 is provided for each ink supply source 10. A pneumatic pump 51 is connected to the sub-tank 20. The pneumatic pump 51 manages the pressure in the sub-tank 20, the second flow path 42, and the head 30. The pneumatic pump 51 circulates the ink Q from the sub-tank 20 to the head 30.

[0014] The print head 30 is connected to the other end of the ink channel 40 and ejects ink supplied from the sub-tank 20 via the second channel 42. The print head 30 has one or more nozzles 31 for ejecting ink. The print head 30 is positioned below the sub-tank 20 in the direction of gravity. Ink Q flows from the sub-tank 20 to the print head 30 due to the difference in water head between the sub-tank 20 and the print head 30.

[0015] Ink flows through the ink channel 40 from the ink supply source 10 to the sub-tank 20 and the head 30. The ink channel 40 has a first channel 41, a second channel 42, and a branch pipe section 43.

[0016] The first channel 41 connects the ink supply source 10 and the sub-tank 20. An ink pump 50 (described later) for circulating ink is provided in the first channel 41.

[0017] The second flow path 42 connects the sub-tank 20 and the head 30. One end of the second flow path 42 is connected to the sub-tank 20, and the other end is connected to the head 30. A filter 45 is provided in the second flow path 42. The filter 45 removes foreign matter from the ink. The filter 45 is optional.

[0018] The branch pipe section 43 branches off from the branch section 44 of the second flow path 42. The branch pipe section 43 has an open end 43a (hereinafter referred to as the end 43a) opposite to the branch section 44. The open end 43a of the branch pipe section 43 is sealed by a plug member 46. The plug member 46 is detachably attached to the end 43a of the branch pipe section 43. When the plug member 46 is attached, the branch pipe section 43 is sealed. When the plug member 46 is removed, the branch pipe section 43 is released to the atmosphere.

[0019] The branched pipe section 43 can supply ink to the second flow path 42 while containing ink and air inside. The branched pipe section 43 has an open tip 43a extending from the branched portion 44 of the ink flow path 40. The branched pipe section 43 can be sealed by inserting a stopper member 46 into the open portion of the tip 43a. When the tip 43a of the branched pipe section 43 is sealed, the tip 43a is positioned higher than the branched portion 44 of the ink flow path 40.

[0020] The ink pump 50 is installed in the first flow path 41, for example, between the ink supply source 10 and the sub-tank 20. The ink pump 50 circulates ink Q from the ink supply source 10 to the sub-tank 20 via the first flow path 41.

[0021] The control unit 60 controls the operation of the printing device 100. The control unit 60 controls the operation of the head 30.

[0022] Next, the operation of the printing apparatus 100 configured as described above will be explained. Figure 2 is a flowchart showing an example of a printing method using the printing apparatus 100. As shown in Figure 2, the printing method according to this embodiment includes an ink distribution step S10, an ink-air arrangement step S20, and an ejection step S30. Hereinafter, each step will be specifically explained with reference to Figures 3 to 9. Figures 3 to 9 are diagrams showing the process of operation of the printing apparatus 100.

[0023] In the ink distribution step S10, the ink pump 50 supplies ink Q from the ink supply source 10 to the sub-tank 20 via the first flow path 41. Furthermore, the pneumatic pump 51 pressurizes the sub-tank 20, supplying ink Q from the sub-tank 20 to the print head via the second flow path 42. Figure 3 shows the state where ink Q has circulated throughout both the first flow path 41 and the second flow path 42. In step S10, ink Q is circulated through at least the entire second flow path 42.

[0024] In the ink-air placement step S20, ink Q is filled from the branching portion 44 of the branched pipe section 43 up to a predetermined height H, and air is drawn in towards the tip section 43a.

[0025] Specifically, first, as shown in Figure 4, the stopper member 46 is removed from the tip 43a of the branched pipe section 43, and the syringe 70 is inserted into the tip 43a with the stopper member 46 removed. Next, as shown in Figure 5, the syringe 70 is made negatively pressurized to draw ink Q from the second flow path 42 to the branched pipe section 43. At this time, ink Q is filled to a position that is distance H from the branched section 44. After that, as shown in Figure 6, the syringe 70 is removed, and the tip 43a is sealed with the stopper member 46. As a result, the branched pipe section 43 holds ink Q on the branched section 44 side and air A on the tip 43a side.

[0026] In the discharge step S30, ink Q is discharged from the head 30 with ink Q and air A positioned in the branch pipe section 43. When ink Q is discharged, the pressure inside the head 30 fluctuates. In this embodiment, as shown in Figure 7, air A is positioned at the tip 43a side of the branch pipe section 43. Air A has a larger volume fluctuation due to pressure fluctuations and lower piping resistance compared to ink Q. Therefore, the volume of air A increases due to the pressure fluctuation at the start of ink Q discharge, causing ink Q in the branch pipe section 43 to flow towards the head 30. As the volume of air A increases, ink Q in the branch pipe section 43 moves down to a position H1 (H1 < H) from the branch section 44. This supply of ink Q from the branch pipe section 43 suppresses pressure fluctuations inside the head 30.

[0027] Subsequently, as shown in Figure 8, ink Q is ejected from the nozzle 31 of the head 30. After the ink Q is ejected from the head 30, the pressure inside the head 30 returns to a predetermined negative pressure. Due to this pressure fluctuation, as shown in Figure 9, the volume of air A in the branch pipe section 43 returns to its volume before ejection, and ink Q returns from the second flow path 42 to the branch pipe section 43.

[0028] Figure 10 is a graph showing the relationship between the passage of time when ink Q is ejected and the pressure inside the print head 30. The horizontal axis of Figure 10 represents the passage of time, and the vertical axis represents the pressure inside the print head 30. The solid line L in Figure 10 is an example using the printing apparatus 100 according to this embodiment, and the dashed line L0 is a comparative example using a configuration without the branch pipe section 43.

[0029] As shown by the solid line L and dashed line L0 in Figure 10, the pressure inside the head 30 is set to a nearly constant negative pressure (pressure P1). When ink Q is ejected, the pressure inside the head 30 fluctuates so that the negative pressure increases to pressure P2. Specifically, at the start of ejection, the pressure overshoots to pressures P3 and P4 (time t1), and then settles at pressure P2. In the configuration of this embodiment, the pressure overshoot is suppressed to be smaller compared to the configuration of the comparative example. If the pressure overshoot is large, as in the comparative example, ink Q may not be ejected from the nozzle 31 of the head 30 afterward, resulting in ink bleed-through in the printed material. In contrast, in the configuration of this embodiment, since the pressure overshoot is suppressed, ink Q is properly ejected from the nozzle 31 of the head 30, and ink bleed-through in the printed material is avoided.

[0030] Furthermore, as shown in Figure 10, in the configuration of this embodiment, even when the pressure inside the head 30 returns from pressure P2 to pressure P1 after ink Q is ejected from the head 30, the pressure overshoot is suppressed to be smaller compared to the configuration of the comparative example. As a result, the meniscus of ink Q in the nozzle 31 is stabilized.

[0031] As described above, the printing apparatus 100 according to this embodiment includes an ink supply source 10 for supplying ink Q, a sub-tank 20 for storing the ink Q supplied from the ink supply source 10, a second flow path 42 through which the ink Q stored in the sub-tank 20 flows, a head 30 connected to the other end of the second flow path 42 for discharging the ink Q supplied from the sub-tank 20 via the second flow path 42, and a branch pipe section 43 that branches off from the second flow path 42 and is capable of supplying ink Q to the second flow path 42 while containing ink Q and air inside.

[0032] By housing ink Q and air inside the branched pipe section 43, the volume of air inside the branched pipe section 43 can be varied in accordance with pressure fluctuations inside the head 30 when ink Q is ejected from the head 30. This suppresses pressure fluctuations inside the head 30 compared to a configuration without the branched pipe section 43.

[0033] In the printing apparatus 100 according to this embodiment, the branch pipe section 43 has an open tip 43a extending from the branch portion 44 of the second flow path 42, and can be sealed by inserting a plug member 46 into the open portion of the tip 43a.

[0034] With this configuration, ink Q and air A can be held inside the branched pipe section 43 from the tip section 43a.

[0035] In the printing apparatus 100 according to this embodiment, the branch pipe section 43 is positioned such that its tip 43a is sealed and the tip 43a is higher than the branch section 44 of the second flow path 42.

[0036] With this configuration, the ink Q can be positioned towards the branching section 44 by gravity inside the branching pipe section 43.

[0037] The printing method according to this embodiment is a printing method using the printing apparatus 100 according to this embodiment, and includes an ink distribution step S10 for circulating ink Q throughout the second flow path 42; an ink-air arrangement step S20 for filling the branch pipe section 43 with ink Q up to a predetermined distance H from the branch portion 44 of the second flow path 42 and taking in air at the end opposite to the branch portion 44; and a discharge step S30 for discharging ink Q from the head 30 with ink Q and air arranged in the branch pipe section 43 by the ink-air arrangement step S20.

[0038] This configuration makes it possible to suppress pressure fluctuations within the head 30 when ink Q is ejected.

[0039] In the ink-air arrangement step S20 of this embodiment, the stopper member 46 is removed from the tip 43a of the branch pipe section 43, a syringe is inserted into the tip 43a, and the inside of the syringe is made negatively pressurized to draw ink Q from the second flow path 42 to the buffer side.

[0040] With this configuration, ink Q can be easily filled into the branch portion 44 side of the branched pipe section 43, and air A can be placed on the tip portion 43a side.

[0041] In the printing apparatus 100 according to this embodiment, in the ink flow step S10, the air arrangement step S20, and the discharge step S30, the end of the branch pipe section 43 opposite to the branch portion 44 is positioned above the branch portion 44.

[0042] With this configuration, the ink Q can be positioned towards the branching section 44 within the branching pipe section 43 by gravity.

[0043] The technical scope of the present invention is not limited to the embodiments described above, and modifications can be made as appropriate without departing from the spirit of the invention.

[0044] A...Air, H, H1...Distance, L...Solid line, L0...Dotted line, Q...Ink, P1, P2, P3, P4...Pressure, 10...Ink supply source, 20...Sub-tank, 40...Ink flow path, 30...Head, 31...Nozzle, 41...First flow path, 42...Second flow path, 43...Branch pipe section, 43a...Tip section, 44...Branching section, 45...Filter, 46...Stopper member, 50...Ink pump, 51...Pneumatic pump, 60...Control unit, 70...Syringe, 100...Printing device

Claims

1. A printing apparatus comprising: an ink supply source for supplying ink; a sub-tank for storing the ink supplied from the ink supply source; an ink channel, one end of which is connected to the sub-tank, through which the ink stored in the sub-tank flows; a head connected to the other end of the ink channel for discharging the ink supplied from the sub-tank via the ink channel; and a branch pipe section that branches off from the ink channel and contains the ink and air inside, and is capable of supplying the ink to the ink channel.

2. The printing apparatus according to claim 1, wherein the branched pipe portion has an open tip extending from the branched portion of the ink flow path, and can be sealed by inserting a plug member into the open portion of the tip.

3. The printing apparatus according to claim 2, wherein the branched pipe section is positioned higher than the branched section while the tip is sealed.

4. A printing method using the printing apparatus described in claim 1, comprising: an ink distribution step of circulating the ink throughout the entire ink flow path; an ink-air arrangement step of filling the branch pipe section with ink up to a predetermined distance from the branch portion of the ink flow path and taking in air at the end opposite to the branch portion; and a discharge step of discharging the ink from the head with the ink and air arranged in the branch pipe section by the ink-air arrangement step.

5. The printing method according to claim 4, wherein in the ink-air placement step, the stopper member is removed from the end opposite to the branch portion of the branch pipe, a syringe is inserted into the opened end, and the ink is drawn from the ink flow path to the branch pipe side by creating negative pressure inside the syringe.

6. The printing method according to claim 4, wherein in the ink distribution step, the ink-air arrangement step, and the discharge step, the end of the branched pipe opposite to the branched portion is positioned above the branched portion.

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