JP2023170408A - Inkjet printing device and ink recovery method - Google Patents

Abstract

To provide an inkjet printing device that can readily and properly recover ink.SOLUTION: An inkjet printing device includes: an ink tank for storing ink; a head unit including a plurality of droplet discharge parts for discharging ink; a circulation pipeline for circulating ink between the ink tank and the head unit; and a recovery pipeline for recovering internal ink from the head unit and the circulation pipeline.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an inkjet printing device and an ink recovery method.

In recent years, methods of manufacturing devices using inkjet apparatuses have been attracting attention. An inkjet device has a plurality of nozzles that eject droplets, and prints a print object by ejecting droplets from the nozzles while controlling the positional relationship between the nozzles and the print object. As one type of inkjet printing device, a configuration including a line head is known (see, for example, Patent Document 1). The line head includes a plurality of module heads arranged in parallel in the width direction of the printing target, in other words, a droplet ejection head having a plurality of ejection ports. By arranging these line heads side by side in the sub-scanning direction, which is a direction orthogonal to the main-scanning direction within the same horizontal plane, ink can be applied all at once to large printing objects in one transport process. can do.

JP2013-28040A

When replacing the old ink filled in the printing device with new ink, the old ink remaining in the circulation piping can be removed by filling the cleaning liquid into the circulation piping after collecting the pure old ink present in the circulation piping. dilute. Thereafter, the recovery of the liquid in the circulation pipe and the filling of the cleaning liquid into the circulation pipe are repeated until the concentration of the old ink in the circulation pipe reaches a target concentration that does not cause any operational problems. When the concentration of the old ink in the circulation piping reaches the target concentration, the liquid in the circulation piping is recovered and the new ink is filled into the circulation piping until the concentration of the new ink in the circulation piping reaches the target concentration. Repeat until.

However, since there are restrictions on the configuration of the circulation piping in order to appropriately discharge ink, the apparatus described in Patent Document 1 cannot flexibly design the ink recovery method and recovery means. Therefore, it becomes difficult to properly collect ink.

An object of the present disclosure is to provide an inkjet printing device and an ink recovery method that can easily realize appropriate recovery of ink.

An inkjet printing apparatus of the present disclosure includes an ink tank that stores ink, a head unit that has a plurality of droplet ejection sections that eject ink, and a circulation system that circulates ink between the ink tank and the head unit. and a collection pipe for collecting ink within the head unit and the circulation pipe.

The ink recovery method of the present disclosure includes an ink tank for storing ink, a head unit having a plurality of droplet ejection sections for ejecting ink, and a circulation system for circulating ink between the ink tank and the head unit. An ink recovery method performed by an inkjet printing apparatus including piping and a collection piping, wherein the inkjet printing apparatus collects ink in the head unit and the circulation piping via the collection piping.

According to the inkjet printing device and ink collection method of the present disclosure, it is possible to easily collect ink appropriately.

A schematic diagram showing a schematic configuration of an inkjet printing device according to an embodiment A sectional view showing a state when the inner diameter of the recovery pipe according to the embodiment is not appropriately set. A sectional view showing a state when the inner diameter of the recovery pipe according to the embodiment is appropriately set. A vertical cross-sectional view showing a method of setting the inner diameter of the recovery pipe according to the embodiment. Cross-sectional view along line BB in Figure 3A Schematic diagram showing the general configuration of a conventional inkjet printing device Cross-sectional view of circulation piping showing conventional issues Cross-sectional view of circulation piping showing conventional issues An explanatory diagram of a simplified ink collection method in an inkjet printing device according to an embodiment An explanatory diagram of an ink recovery method in an inkjet printing device according to an embodiment Flowchart showing ink replacement processing in the inkjet printing device according to the embodiment A schematic diagram showing a schematic configuration of an inkjet printing device according to a modified example

[Embodiment]
Embodiments of the present disclosure will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a schematic configuration of an inkjet printing apparatus. FIG. 2A is a cross-sectional view showing a state in which the inner diameter of the recovery pipe is not set appropriately. FIG. 2B is a sectional view showing a state when the inner diameter of the recovery pipe is appropriately set. FIG. 3A is a longitudinal cross-sectional view showing a method of setting the inner diameter of the recovery pipe. FIG. 3B is a cross-sectional view taken along line BB in FIG. 3A. In the following explanation and each figure, the direction parallel to the ink ejection direction from the inkjet printing device is the Z-axis direction, the scanning direction of the head unit that constitutes the inkjet printing device is the Y-axis direction, and the Z-axis direction and the Y-axis. The direction perpendicular to this direction is defined as the X-axis direction. In this embodiment, a case will be described in which the Z-axis direction is the vertical direction and the ink ejection direction is the -Z direction.

First, a schematic configuration of an inkjet printing device will be described. As shown in FIG. 1, the inkjet printing apparatus 1 includes an ink tank unit 10, a head unit 20, a circulation pipe 30, and a recovery pipe 40. Note that in FIG. 1, only one set of each head unit 20, circulation pipe 30, and recovery pipe 40 is shown in order to facilitate understanding of the configuration, but the inkjet printing apparatus 1 , a plurality of sets of head units 20, circulation piping 30, and recovery piping 40.

The ink tank unit 10 is an example of an ink tank according to the present disclosure. The ink tank unit 10 includes an in tank 11, an out tank 12, a buffer tank 13, a supply tank 14, a recovery tank 15, and an intermediate tank 16. The in-tank 11, the out-tank 12, and the buffer tank 13 are arranged above the head unit 20.

One end (upper end) of an outgoing pipe 31 that constitutes the circulation pipe 30 is connected to the in-tank 11 . The in-tank 11 stores liquid to be sent to the head unit 20 via the outgoing pipe 31.

One end (upper end) of a return pipe 32 that constitutes the circulation pipe 30 is connected to the out tank 12 . The out tank 12 stores the liquid that returns from the head unit 20 via the return pipe 32.

Buffer tank 13 is arranged between in-tank 11 and out-tank 12. Buffer tank 13 is connected to in-tank 11 via piping 17A in which first pump P1 is arranged. The buffer tank 13 is connected to the out tank 12 via a pipe 17B in which a second pump P2 is arranged. The buffer tank 13 supplies ink to the in-tank 11 and collects ink from the out-tank 12.

Supply tank 14 is connected to buffer tank 13 via piping 17C. Supply tank 14 supplies liquid to buffer tank 13 .

The recovery tank 15 is connected to the buffer tank 13 via a pipe 17D branched from the pipe 17C. The recovery tank 15 stores ink or cleaning liquid sent from the buffer tank 13 and used for cleaning the inside of the head unit 20 and the circulation pipe 30.

One end (upper end) of a recovery pipe 40 is connected to the intermediate tank 16 . Intermediate tank 16 is connected to buffer tank 13 via piping 17E.

Further, each tank 11, 12, 13, 14, 15, 16 is provided with a pneumatic circuit. Liquid level sensors are arranged in the in-tank 11, out-tank 12, and buffer tank 13 necessary for liquid circulation. The positions of the liquid levels in the in-tank 11, out-tank 12, and buffer tank 13 are controlled by the driving states of the first and second pumps P1 and P2.

The inkjet printing apparatus 1 applies a driving pressure to the liquid by a liquid circulation device including a pneumatic circuit and first and second pumps P1 and P2, and during operation, a liquid circulation device is used to circulate the liquid between the ink tank unit 10 and the head unit 20. Preferably, the liquid is constantly circulated.

The head unit 20 includes an upstream distribution tank 21, a plurality of droplet discharge sections 22 (only one droplet discharge section 22 is shown in FIG. 1), and a downstream distribution tank 23.

The other end (lower end) of the outgoing pipe 31 is connected to the upstream distribution tank 21 . The upstream distribution tank 21 supplies ink supplied from the in-tank 11 via the outgoing pipe 31 to the droplet ejection unit 22 .

The droplet discharge section 22 includes a piezoelectric actuator, a diaphragm, a pressure chamber, a nozzle, and the like. The droplet ejection unit 22 ejects ink supplied from the upstream distribution tank 21 from a nozzle by driving a piezoelectric actuator.

The other end (lower end) of the return pipe 32 is connected to the downstream distribution tank 23 . Ink that has not been ejected from the droplet ejection section 22 among the ink supplied to the droplet ejection section 22 flows into the downstream distribution tank 23 . The ink that has flowed into the downstream distribution tank 23 returns to the out tank 12 via the return pipe 32.

The circulation pipe 30 circulates ink between the ink tank unit 10 and the head unit 20. The circulation pipe 30 includes an outgoing pipe 31 and a return pipe 32. The outgoing pipe 31 includes a first outgoing vertical part 31A extending vertically downward, an outgoing inclined part 31B extending diagonally downward from the lower end of the first outgoing vertical part 31A, and a second outgoing pipe extending vertically downward from the lower end of the outgoing inclined part 31B. A vertical portion 31C is provided. The return piping 32 includes a first return vertical section 32A extending vertically downward, a return slope 32B extending diagonally downward from the lower end of the first return vertical section 32A, and a second return line extending vertically downward from the lower end of the return slope 32B. A vertical portion 32C is provided. The first and second outward vertical sections 31A and 31C and the first and second return vertical sections 32A and 32C guide the liquid in the vertical direction. The outward slope portion 31B and the return slope portion 32B guide the liquid in a direction inclined with respect to the horizontal plane. In other words, the circulation pipe 30 is configured to have a portion that extends in the horizontal direction and does not have a portion that guides the liquid in the horizontal direction.

An outgoing flow path switching section 51 is disposed in the middle of the second outgoing vertical section 31C. A return path switching section 52 is disposed in the middle of the second return path vertical section 32C. The outward flow path switching section 51 and the return flow path switching section 52 are examples of the flow path switching section of the present disclosure. The other end (lower end) of the recovery pipe 40 is connected to the forward flow path switching section 51 . The outward flow path switching section 51 and the return flow path switching section 52 are connected by a flow path switching section connection pipe 53. The forward flow path switching section 51 and the return flow path switching section 52 are configured by, for example, valves, and are configured to cause liquid flowing in from a predetermined pipe connected thereto to flow out into at least one of the remaining pipes. It is composed of

The portion of the outgoing piping 31 that includes the first outgoing vertical portion 31A and the outgoing inclined portion 31B, and the portion of the incoming piping 32 that includes the first incoming vertical portion 32A and the incoming inclined portion 32B are defined by the movement of the head unit 20 in the Y-axis direction. It is curved to follow. In this embodiment, the inclination angles of the outward slope portion 31B and the return slope portion 32B with respect to the horizontal plane are as follows. Although the angle is set to 3 degrees, the angle may be greater than 3 degrees or less than 3 degrees. When the inclination angles of the forward slope portion 31B and the return slope portion 32B increase, the water head difference between the liquid level of the ink tank unit 10 and the nozzle surface of the head unit 20 increases, and the inside of the tank constituting the ink tank unit 10 increases accordingly. It becomes necessary to reduce the pressure. In this case, as the evaporation of the solvent contained in the ink is accelerated, the viscosity of the ink increases, and the ink with increased viscosity may clog the nozzles of the head unit 20. When designing the inclination angles of the outward slope portion 31B and the return slope portion 32B, the design may be performed in consideration of factors such as the above-mentioned factors or the height restrictions of the equipment.

The lengths of the outgoing piping 31 and the incoming piping 32 depend on the position of each head unit 20, and are therefore different. The length of the outgoing piping 31 and the returning piping 32 from the ink tank unit 10 to the farthest head unit 20 is set to 4720 mm, and the length of the outgoing piping 31 and the returning piping 32 to the nearest head unit 20 is set to 880 mm. ing.

The inner diameters of the outgoing piping 31 and the incoming piping 32 are calculated for each head unit 20 connected to the outgoing piping 31 and the incoming piping 32, based on the Hagen-Poiseuille pressure loss formula shown in equation (1).

In equation (1), it is possible to consider the fluid density ρ, viscosity μ, and flow rate Q as constants, so if they are constant C ₁ , the pressure loss ΔF for each head unit 20 is 10 ⁻¹ [kPa]. The inner diameter D and length L of the outgoing piping 31 and the incoming piping 32 were calculated so that they were equal to each other up to the digit.

The recovery pipe 40 is arranged to recover ink within the head unit 20 and the circulation pipe 30. The recovery pipe 40 includes a first recovery vertical section 40A extending vertically downward, a recovery inclined section 40B extending diagonally downward from the lower end of the first recovery vertical section 40A, and a second recovery section 40B extending vertically downward from the lower end of the recovery inclined section 40B. It includes a vertical section 40C and a recovery connecting section 40D that connects the lower end of the second recovery vertical section 40C and the outgoing flow path switching section 51. The first and second recovery vertical sections 40A and 40C guide the liquid in the vertical direction. The recovery inclined portion 40B guides the liquid in a direction inclined with respect to the horizontal plane.

A portion of the recovery pipe 40 including the first recovery vertical section 40A and the recovery inclined section 40B is curved to follow the movement of the head unit 20 in the Y-axis direction. In the present embodiment, the angle of inclination of the collection slope portion 40B with respect to the horizontal plane is as follows. Although the angle is set to 3 degrees, the angle may be greater than 3 degrees or less than 3 degrees.

An intermediate portion of the recovery connection section 40D is connected to a flow path switching section connection pipe 53 via a bypass pipe 54. With such a configuration, the liquid flowing out from the return flow path switching section 52 can be made to flow into the recovery pipe 40 without passing through the outbound flow path switching section 51.

Further, as the recovery pipe 40, a thin pipe whose inner diameter is smaller than the inner diameter of the outgoing pipe 31 and the return pipe 32 is used. If the inner diameter of the recovery pipe 40 is not set appropriately, the meniscus Em of the ink E in the recovery pipe 40 will break, and gas-liquid separation of the ink E will occur, as shown in FIG. 2A. However, if the inner diameter of the recovery pipe 40 is appropriately set, as shown in FIG. E can be delivered. The inner diameter of the recovery piping 40 is such that when applying negative pressure to the intermediate tank 16 and sucking up ink through the recovery piping 40, even if there is a part of the recovery piping 40 parallel to the horizontal plane, the ink meniscus is The size is set to ensure that it does not break (does not break).

A method for setting the inner diameter of the recovery pipe 40 will be explained using FIGS. 3A and 3B. In FIG. 3A, T represents the interfacial tension of the ink E with respect to the piping 81, θ represents the contact angle of the ink E with the piping 81, and R represents the inner radius of the piping 81, respectively. Mg shown in FIG. 3B represents the gravity of the ink E per unit length, φ represents the angle with respect to the horizontal plane, and r represents the radial length. As shown in FIG. 3B, if the upward component of the interfacial tension Tsinθ is larger than the gravity Mg of the ink E per unit length, the meniscus of the ink E is broken, and the ink in the radial direction of the pipe 81 is It can be said that the gas-liquid separation of E does not occur. The equation used to set the inner diameter of the recovery pipe 40 is shown in equation (2) below.

The interfacial tension T, contact angle θ, and fluid density ρ of the ink E are 30 [mN/m], 65°, and 950 [kg/m ³ ], respectively, and when these are substituted into equation (2), the inside of the pipe 81 is The radius R will be less than 1.8 mm. In this embodiment, the inner diameter of the recovery pipe 40 is set to 2 mm, which satisfies the result obtained from equation (2). Note that the inner radius R of the recovery pipe 40 that satisfies the above formula (2) changes depending on the physical property values T, θ, and ρ of the liquid used.

Next, before explaining the operation of the inkjet printing apparatus 1 of this embodiment, a conventional inkjet printing apparatus 9 will be explained. FIG. 4 is a schematic diagram showing a schematic configuration of a conventional inkjet printing device. FIGS. 5A and 5B are cross-sectional views of circulation piping illustrating conventional problems. Note that the same components in the inkjet printing device 9 as in the inkjet printing device 1 are given the same reference numerals and names, and the explanation will be omitted or simplified.

As shown in FIG. 4, the inkjet printing device 9 includes an ink tank unit 91, a plurality of head units 20, and a circulation pipe 92. In FIG. 4, only one set of the head unit 20 and circulation piping 92 is shown in order to facilitate understanding of the configuration. A plurality of sets of piping 92 are provided.

The ink tank unit 91 includes the components of the ink tank unit 10 except for the intermediate tank 16 and the piping 17E.

The circulation pipe 92 includes an outgoing pipe 93 and a return pipe 94. The outgoing pipe 93 includes a first outgoing vertical part 31A, an outgoing horizontal part 93B extending horizontally from the lower end of the first outgoing vertical part 31A, and a second outgoing vertical part 31C connected to the lower end of the outgoing horizontal part 93B. Equipped with. The return piping 94 includes a first return vertical section 32A, a return horizontal section 94B extending horizontally downward from the lower end of the first return vertical section 32A, and a second return vertical section 32C connected to the return horizontal section 94B. . The outward horizontal portion 93B and the backward horizontal portion 94B guide the liquid in the horizontal direction. That is, the circulation pipe 92 is configured to have a portion that extends in the horizontal direction and guides the liquid in the horizontal direction.

Comparing the conventional inkjet printing device 9 and the inkjet printing device 1 of this embodiment, it is found that the inkjet printing device 9 is not provided with the recovery pipe 40, and that the circulation pipe 92 guides the liquid horizontally in the outgoing horizontal section. 93B and a return horizontal portion 94B. The conventional inkjet printing apparatus 9 having such a difference, for example, applies negative pressure to the out tank 12 while applying positive pressure to the in tank 11, thereby printing air in the direction shown by the arrow D9. form a flow. The ink in the circulation pipe 92 and the head unit 20 is guided in the same direction as the air flow shown by the arrow D9 and is collected in the out tank 12. That is, the conventional inkjet printing apparatus 9 uses the circulation pipe 92 having an inner diameter larger than that of the recovery pipe 40 to collect ink inside the circulation pipe 92 and the head unit 20 .

Since the inkjet printing apparatus 9 shown in FIG. 4 has more nozzles than a printing apparatus using one head unit 20, the amount of ink divided is increased. When the divided flow rate increases, the pressure loss changes rapidly due to a temporary change in the flow rate. Therefore, in order to suppress this change, in the inkjet printing apparatus 9, the inner diameter of the circulation pipe 92 is increased. However, if the inner diameter of the circulation pipe 92 is increased, when the ink in the inkjet printing device 9 is recovered, the meniscus Em of the ink E in the circulation pipe 92 is broken, as shown in FIG. 5A, and the diameter of the circulation pipe 92 is Gas-liquid separation occurs in this direction, and only the gas layer is fluidly sucked up, making it difficult to recover the ink E, which is a liquid layer. Therefore, when collecting the ink E in the circulation pipe 92, there is a possibility that the ink E may stay in the circulation pipe 92, as shown in FIG. 5B. As described above, in the conventional inkjet printing device 9, there are restrictions on the design of the circulation piping 92 in order to achieve both appropriate ink ejection and appropriate ink recovery.

Furthermore, since the ink is not guided downward by gravity in the outward horizontal portion 93B, if the ink meniscus breaks, there is a risk that the ink will remain in the outward horizontal portion 93B. As explained above, in the conventional inkjet printing apparatus 9, it is difficult to completely collect the ink inside the circulation pipe 92 and the head unit 20.

Note that the cleaning liquid used when replacing ink in the inkjet printing device 9 is also recovered in the same manner as ink. Therefore, in the inkjet printing apparatus 9, it may be difficult to completely recover the cleaning liquid inside the circulation pipe 92 and the head unit 20.

Next, the operation of the inkjet printing apparatus 1 of this embodiment will be explained. First, a method for circulating ink during operation of the inkjet printing apparatus 1 will be described with reference to FIG. 1.

The inkjet printing apparatus 1 controls the outgoing flow path switching section 51 so that a portion of the outgoing piping 31 above the outgoing path switching section 51 is in a circulating state in which the portion above the outgoing path switching section 51 communicates only with the lower portion. The inkjet printing apparatus 1 controls the return flow path switching section 52 so that the region above the return flow path switching section 52 in the return path piping 32 is in a circulating state in which the region above the return flow path switching section 52 communicates only with the lower region. As shown by arrow J in FIG. 1, the liquid circulation device always causes ink to flow in one direction. That is, ink flows from the in-tank 11 to the head unit 20 via the outgoing pipe 31 and flows to the out tank 12 via the incoming pipe 32. The liquid circulation device controls liquid levels in the out tank 12, buffer tank 13, and in tank 11, and circulates ink between the ink tank unit 10 and the head unit 20. Note that the cleaning liquid used when replacing ink in the inkjet printing apparatus 1 is also circulated in the same manner as the ink.

Next, a method for collecting ink in the inkjet printing apparatus 1 will be described with reference to FIG. 6. FIG. 6 is an explanatory diagram of a simplified ink recovery method in an inkjet printing device. FIG. 7 is an explanatory diagram of an ink recovery method in an inkjet printing device. When recovering ink from the inkjet printing apparatus 1, recovery processing for ink in the outbound piping 31, recovery processing for ink in the return piping 32, and recovery processing for ink in the head unit 20 are performed separately. Note that the cleaning liquid used when replacing ink in the inkjet printing apparatus 1 is also recovered in the same manner as ink.

First, when recovering ink in the outgoing pipe 31 , the inkjet printing apparatus 1 is set in a collecting state in which a portion of the outgoing pipe 31 above the outgoing flow path switching section 51 communicates only with the collecting pipe 40 . Then, the forward flow path switching section 51 is controlled. The inkjet printing apparatus 1 applies negative pressure to the intermediate tank 16 while applying positive pressure to the in-tank 11 . Through such control, an air flow is formed in the direction shown by the arrow D1 in FIG. It is guided to the intermediate tank 16 via the intermediate tank 16.

When performing the recovery process for ink in the return pipe 32, the inkjet printing apparatus 1 is in a recovery state in which a portion of the return pipe 32 above the return flow path switching section 52 communicates only with the flow path switching section connection pipe 53. The return flow path switching unit 52 is controlled so that The inkjet printing apparatus 1 controls the outgoing flow path switching unit 51 so as to enter a recovery state in which ink is prevented from flowing to the recovery pipe 40 or the outgoing path piping 31 via the flow path switching unit connection pipe 53. The inkjet printing apparatus 1 applies negative pressure to the intermediate tank 16 while applying positive pressure to the out tank 12 . Through such control, an air flow is formed in the direction shown by the arrow D2 in FIG. It is guided to the intermediate tank 16 via the connection pipe 53, bypass pipe 54, and recovery pipe 40. Note that the outgoing flow path switching unit 51 is controlled so that the flow path switching unit connecting pipe 53 is in the recovery state communicating only with the recovery pipe 40, and the ink in the flow path switching unit connecting pipe 53 is transferred to the outgoing flow. It may also be guided to the intermediate tank 16 via the path switching section 51 and recovery piping 40.

When performing the ink recovery process in the head unit 20, the inkjet printing apparatus 1 is set in a recovery state in which a portion of the return piping 32 above the return flow path switching section 52 communicates only with a lower portion. , controls the return flow path switching section 52. The inkjet printing apparatus 1 controls the outgoing flow path switching section 51 so that a portion of the outgoing path piping 31 below the outgoing flow path switching section 51 is in a recovery state in which it communicates only with the recovery piping 40 . The inkjet printing apparatus 1 applies negative pressure to the intermediate tank 16 while applying positive pressure to the out tank 12 . Through such control, an air flow is formed in the direction shown by the arrow D3 in FIG. The liquid is also guided to the intermediate tank 16 via the lower part, the outgoing flow path switching section 51 and the recovery pipe 40. Furthermore, due to the air flow in the direction shown by arrow D3 in FIG. The ink in the lower region is also guided to the intermediate tank 16.

Note that the ink recovery process within the head unit 20 may be performed as follows. The inkjet printing apparatus 1 controls the outgoing flow path switching section 51 so that a section of the outgoing piping 31 above the outgoing channel switching section 51 is in a recovery state in which the section above the outgoing channel switching section 51 communicates only with the lower section. The inkjet printing apparatus 1 operates the return flow path switching section 52 such that a portion of the return flow path switching section 52 in the return path piping 32 is in a recovery state in which a portion of the return flow path switching section 52 is in communication with only the flow path switching section connecting pipe 53. Control. The inkjet printing apparatus 1 applies negative pressure to the intermediate tank 16 while applying positive pressure to the in-tank 11 . Through such control, an air flow is formed that flows in the order of the forward flow path switching section 51, the head unit 20, the return flow path switching section 52, the flow path switching section connection pipe 53, the bypass pipe 54, and the recovery pipe 40. The ink in the head unit 20 is guided to the intermediate tank 16 by the air flow. In addition, ink in a portion of the outgoing piping 31 below the outgoing flow path switching portion 51 and in a portion of the returning piping 32 below the incoming flow path switching portion 52 is also guided to the intermediate tank 16. Ru.

After the inkjet printing apparatus 1 performs the above-described recovery process for the ink in the outgoing piping 31, the incoming piping 32, and the head unit 20, the ink stored in the intermediate tank 16 is collected as indicated by arrow D4 in FIG. The liquid is sent to the recovery tank 15 via the buffer tank 13 so that the liquid is transferred to the recovery tank 15.

Note that under the control of the forward flow path switching section 51 and the return flow path switching section 52, the ink inside at least one of the outbound path piping 31 and the return path piping 32 and the ink inside the head unit 20 are recovered at the same time. Also good. Alternatively, the ink stored in the intermediate tank 16 may be directly sent to a waste liquid tank (not shown). Alternatively, the intermediate tank 16 in which ink is stored may be removed from the inkjet printing apparatus 1, and the ink in the removed intermediate tank 16 may be collected.

Although FIG. 6 was used in the above description, as shown in FIG. 7, the inkjet printing apparatus 1 includes a plurality of sets of a head unit 20, a circulation pipe 30, and a recovery pipe 40 (only two sets are shown in FIG. 7). ). When recovering ink from the inkjet printing device 1, the inkjet printing device 1, as described above, uses the in-tank 11, the out-tank 12, the intermediate tank 16, the outgoing path flow path switching unit 51 of each set, and the incoming path The flow path switching unit 52 is controlled to be in the recovery state to form air flows in the directions shown by arrows D1, D2, and D3, and the ink in the head units 20 and circulation pipes 30 of each set is removed. Guide to intermediate tank 16. The inkjet printing apparatus 1 then sends the ink stored in the intermediate tank 16 to the recovery tank 15 via the buffer tank 13, as shown by arrow D4.

As described above, the inkjet printing apparatus 1 uses the collection pipe 40 different from the circulation pipe 30 to collect ink in the head unit 20 and the circulation pipe 30. Therefore, the circulation piping 30 can be designed so that the ink can be appropriately ejected without considering the destruction of the meniscus of the ink (liquid) during ink recovery. Further, by making the inner diameter of the recovery pipe 40 large enough to prevent the meniscus of the ink from breaking, the ink can be easily recovered. Further, by making the inner diameter of the recovery pipe 40 large enough to prevent the meniscus of the cleaning liquid (liquid) from breaking, the cleaning liquid can be easily recovered. Therefore, it is possible to provide the inkjet printing device 1 that can easily realize appropriate collection of ink without any restrictions on the configuration of the circulation pipe 30.

In addition, in the inkjet printing apparatus 1 that collects ink using a collection pipe 40 different from the circulation pipe 30, a pump can also be disposed within the collection pipe 40. With this configuration, the ink recovery efficiency can be increased by driving the pump in the recovery pipe 40 during recovery, while the ink discharge using the circulation pipe 30 is not affected. Furthermore, when the circulation piping 30 has flexibility, at least one of the first outgoing vertical section 31A and the outgoing inclined section 31B can be deformed to be orthogonal to the horizontal plane when collecting ink or cleaning liquid. With this configuration, the ink or cleaning liquid in the outgoing piping 31 or the incoming piping 32 can flow downward due to its own weight, and it is possible to suppress the ink or cleaning liquid from remaining in the outgoing piping 31 or the incoming piping 32. can.

The inner diameter of the recovery pipe 40 is smaller than the inner diameter of the circulation pipe 30. In piping with a small inner diameter, the value obtained by dividing the liquid volume by the surface area is small, and surface force becomes dominant over body force. That is, the influence of interfacial tension becomes significant. Therefore, during recovery of the liquid (at least one of ink and cleaning liquid) using the recovery pipe 40, it is possible to prevent the meniscus of the liquid from breaking within the recovery pipe 40, and the liquid can be easily recovered. . Furthermore, by making the inner diameter of the circulation pipe 30 sufficiently large, it is possible to suppress sudden changes in pressure loss during printing.

The circulation pipe 30 is configured so as not to have a portion that guides liquid in the horizontal direction. Therefore, the liquid in the circulation pipe 30 can be moved downward by gravity. Therefore, by recovering the liquid that has moved downward using the recovery pipe 40, the efficiency of liquid recovery can be increased.

The inkjet printing apparatus 1 circulates the ink between the ink tank unit 10 and the head unit 20 by setting the forward flow path switching section 51 and the return flow path switching section 52 to the circulation state, while also circulating the ink between the ink tank unit 10 and the head unit 20. By doing so, the ink inside the head unit 20 and the circulation pipe 30 is collected. Therefore, by simply controlling the states of the forward flow path switching section 51 and the return flow path switching section 52, it is possible to switch between the ink circulation state and the recovery state.

Next, ink replacement processing in the inkjet printing apparatus 1 will be described with reference to FIG. 8. FIG. 8 is a flowchart showing ink replacement processing in the inkjet printing apparatus 1.

When replacing old ink with new ink while the inkjet printing device 1 contains old ink, the inkjet printing device 1 stops circulating the old ink, as shown in FIG. 8 (step S1). After that, the inkjet printing apparatus 1 collects the old ink in the circulation pipe 30 and the head unit 20 using the above-described ink collection method (step S2).

Next, the inkjet printing apparatus 1 cleans the circulation pipe 30 and the head unit 20 (step S3). In the process of step S3, the inkjet printing apparatus 1 fills the inside of the circulation pipe 30 and the inside of the head unit 20 with the cleaning liquid supplied from the supply tank 14, and fills the inside of the circulation pipe 30 and the inside of the head unit 20 with the cleaning liquid supplied from the supply tank 14, and uses The process of recovering the liquid in the head unit 20 is repeated until the concentration of the cleaning liquid contained in the recovered liquid reaches, for example, 99.9% or more. The concentration of the cleaning liquid contained in the collected liquid can be measured using a refractometer. Since the refractive index of the cleaning liquid and the concentration of the cleaning liquid contained in the liquid are in a proportional relationship, by measuring the refractive index of the cleaning liquid in advance, the concentration of the cleaning liquid contained in the liquid can be measured. Note that the concentration of the cleaning liquid contained in the liquid may be measured using a spectrometer or other measuring device instead of a refractometer.

When the cleaning process for the circulation pipe 30 and the head unit 20 is completed, the inkjet printing apparatus 1 removes the cleaning liquid from the circulation pipe 30 and the head unit 20 (step S4). In the process of step S4, the inkjet printing apparatus 1 fills the inside of the circulation pipe 30 and the inside of the head unit 20 with new ink supplied from the supply tank 14, and fills the inside of the circulation pipe 30 with new ink supplied from the supply tank 14, and fills the inside of the circulation pipe 30 with new ink supplied from the supply tank 14. and the process of recovering the liquid in the head unit 20 are repeated until the concentration of the new ink contained in the recovered liquid reaches, for example, 99.9% or more. The concentration of the new ink contained in the collected liquid may be measured by the same method as the concentration measurement of the cleaning liquid in the process of step S3. When the concentration of the new ink contained in the collected liquid reaches, for example, 99.9% or more, the inkjet printing apparatus 1 fills the inside of the circulation pipe 30 and the inside of the head unit 20 with the new ink (step S5). With the above, the ink replacement process in the inkjet printing apparatus 1 is completed. Note that in this embodiment, the ink is not only a colorant but also a semi-solid and liquid material for manufacturing solder, liquid crystal displays (for example, color filters), perovskite solar cells, battery separators, etc. Including etc.

As described above, by using the collection pipe 40 that is different from the circulation pipe 30, the liquid in the head unit 20 and the circulation pipe 30 can be easily collected, thereby reducing the time required for ink replacement processing. can do.

[Modified example]
Note that the present disclosure is not limited to the above embodiments, and can be modified as appropriate without departing from the spirit.

For example, an inkjet printing apparatus 100 shown in FIG. 9 includes an ink tank unit 110, a head unit 20, a circulation pipe 30, and a recovery pipe 40. In FIG. 9, in order to facilitate understanding of the configuration, only one set of each head unit 20, circulation pipe 30, and recovery pipe 40 is shown. A plurality of sets of units 20, circulation piping 30, and recovery piping 40 are provided. The ink tank unit 110 includes an ink tank 111 and an intermediate tank 16. The ink tank 111 is connected to one end (upper end) of the outgoing pipe 31, one end (upper end) of the return pipe 32, and the upper end of the pipe 17C. Ink tank 111 is connected to intermediate tank 16 via piping 117A. A pump P3 is disposed in the middle of the first outgoing vertical section 31A of the outgoing piping 31. When recovering ink from the inkjet printing apparatus 100, the inkjet printing apparatus 100 uses the same method as the recovery method of the above embodiment, except that positive pressure is applied to the ink tank 111 instead of the in-tank 11 or the out-tank 12. Then, the intermediate tank 16, the forward flow path switching section 51, and the return flow path switching section 52 are controlled to form air flows in the directions shown by arrows D1, D2, and D3, and the ink is transferred to the intermediate tank 16. I will guide you to. The inkjet printing apparatus 100 sends the ink stored in the intermediate tank 16 to the recovery tank 15 via the ink tank 111, as shown by arrow D4.

The outgoing piping 31 may be provided with an outgoing horizontal part 93B instead of the outgoing inclined part 31B, and the inward piping 32 may be provided with a returning horizontal part 94B in place of the incoming inclined part 32B.

The present disclosure can be applied to an inkjet printing device and an ink recovery method.

1,9,100 Inkjet printing device 10,91,110 Ink tank unit 11 In tank 12 Out tank 13 Buffer tank 14 Supply tank 15 Recovery tank 16 Intermediate tank 17A, 17B, 17C, 17D, 17E, 81, 117A Piping 20 Head Unit 21 Upstream distribution tank 22 Droplet discharge section 23 Downstream distribution tank 30, 92 Circulation piping 31, 93 Outbound piping 31A First outbound vertical section 31B Outbound inclined section 31C Second outbound vertical section 32, 94 Return piping 32A First Return vertical section 32B Return inclined section 32C Second return vertical section 40 Recovery piping 40A First recovery vertical section 40B Recovery inclined section 40C Second recovery vertical section 40D Recovery connecting section 51 Outward flow path switching section 52 Return path switching section 53 Flow path switching section connection piping 54 Bypass piping 93B Outward horizontal section 94B Return horizontal section 111 Ink tank E Ink Em Meniscus K Air layer P1 1st pump P2 2nd pump P3 Pump

Claims (5)

an ink tank that stores ink;
a head unit having a plurality of droplet ejection sections that eject ink;
circulation piping for circulating ink between the ink tank and the head unit;
a collection pipe for collecting ink within the head unit and the circulation pipe;
Inkjet printing equipment. The inner diameter of the recovery pipe is smaller than the inner diameter of the circulation pipe.
The inkjet printing device according to claim 1. The ink tank is arranged above the head unit,
The circulation piping does not have a portion that guides the ink in a horizontal direction.
The inkjet printing device according to claim 1. The recovery piping is connected to the circulation piping,
A flow path switching unit is disposed at a connection portion between the recovery piping and the circulation piping to switch between a circulation state in which the ink is circulated within the circulation piping and a recovery state in which the ink is collected through the recovery piping. There is,
The inkjet printing device according to claim 1. An ink tank for storing ink, a head unit having a plurality of droplet ejection sections for ejecting ink, a circulation pipe for circulating ink between the ink tank and the head unit, and a collection pipe. An ink recovery method performed by an inkjet printing device comprising:
The inkjet printing device includes:
collecting ink in the head unit and the circulation pipe via the collection pipe;
How to collect ink.

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