Ink supply device

Abstract

To provide an art which can properly supply an ink from an external tank to an ink circulation circuit in a printer including the ink circulation circuit having a temperature adjustment function.SOLUTION: An ink supply device includes: an ink tank; an ink supply route and an ink feedback route along which an ink is circulated between the ink tank and a head; an ink heating part that heats the ink in the ink tank; and an external tank for storing the ink to be supplied to the ink tank. A controller allows the ink to be replenished from the external tank to the ink tank in a flow rate regulation mode in which a flow rate is regulated in such a manner that a temperature of the ink in the ink tank falls within a predetermined temperature range. A regulation flow rate for ink replenishment in the flow rate regulation mode is calculated on the basis of at least a temperature in the ink tank and an ink storage amount.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an ink supply device that supplies ink to an inkjet head in an inkjet printing device. [Background technology]

[0002] Some inks used in inkjet printers tend to aggregate and form precipitates. For example, aqueous pigment inks that tend to aggregate are used for flexible packaging.

[0003] In inkjet printing devices, ink is exposed to the outside air in the nozzles of the head, which makes it easier for the solvent to evaporate and aggregate in nozzles that are not printing. For this reason, a circulation system is adopted that supplies ink to the head and collects ink from the head, preventing ink from accumulating in the head and preventing aggregation in the nozzles. A printing device that employs a circulation system is described, for example, in Patent Document 1.

[0004] In the printing device of Patent Document 1, an ink circulation circuit is formed by a buffer tank (103), an ink temperature control tank (108), a sub-tank (104), and a head (101). Ink is supplied to the buffer tank (103) from an external ink supply unit (ink tank 102) in the circulation circuit.

[0005] Furthermore, in inkjet printing devices, the temperature of the ink sent to the head may be controlled to appropriately adjust the viscosity of the ink in the head. Patent Document 1 discloses a printing device that maintains the ink temperature in the head within a desired range by keeping the total flow rate of temperature-controlled ink sent from a subtank (104) upstream of the head to the head (101) constant, regardless of the amount of ink ejected from the head. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-151528 Summary of the Invention [Problem to be solved by the invention]

[0007] In printing devices with such ink circulation circuits, ink is generally supplied to the circulation circuit from an external large-capacity ink tank (external tank) purchased from an ink manufacturer. When the ink in this external tank runs out and the external tank is replaced, it is not always possible to replace it immediately because the ink level has run out. In such cases, the problem of the ink level remaining in the ink tank in the ink circulation circuit becoming low arises.

[0008] The same problem occurs when there is a malfunction in the pump on the supply path from the external tank to the circulation circuit. For example, if the pump malfunction can be resolved within a certain amount of time, it can be addressed without stopping the printing process, but during that time, the remaining amount of ink in the ink tank in the ink circulation circuit decreases.

[0009] In such a case, if ink is supplied at a large flow rate after the supply of ink from the external tank to the circulation circuit is resumed, the temperature may not be adjusted in time, and the temperature of the ink in the circulation circuit may drop suddenly.

[0010] The present invention has been developed in consideration of the above circumstances, and aims to provide a technology that can properly supply ink from an external tank to an ink circulation circuit in a printing device that includes an ink circulation circuit with a temperature adjustment function. [Means for solving the problem]

[0011] In order to solve the above problems, a first invention of the present application is an ink supply device for supplying ink to a plurality of heads in an inkjet printing device, comprising an ink tank for storing the ink, an ink supply path for supplying the ink from the ink tank to the head, an ink return path for returning the ink from the head to the ink tank, an ink heating unit for heating the ink in the ink tank, an external tank for storing the ink to be supplied to the ink tank, an ink refill path for supplying the ink from the external tank to the ink tank, an ink refill pump inserted in the ink refill path, and a heater for heating the ink in the ink tank or the ink supply path. the ink supply pump is operable in a flow rate adjustment mode that adjusts the flow rate of the ink supply pump so that the temperature of the ink in the ink tank is within a predetermined temperature range, and the control unit calculates the flow rate of the ink supply pump in the flow rate adjustment mode based on at least the temperature inside the tank detected by the temperature detection unit and the ink storage amount detected by the storage amount detection unit.

[0012] A second invention of the present application is an ink supply device of the first invention, wherein the control unit drives the ink refill pump in a normal mode in which the flow rate of the ink refill pump is a predetermined flow rate when the ink storage amount detected by the storage amount detection unit is equal to or greater than a predetermined low remaining amount threshold, and drives the ink refill pump in the flow rate adjustment mode when the ink storage amount detected by the storage amount detection unit is less than the low remaining amount threshold.

[0013] A third invention of the present application is an ink supply device of the first invention, further comprising an external temperature detection unit that detects the outside air temperature around the external tank or the external temperature, which is the temperature of the ink inside the external tank, and the control unit calculates the flow rate of the ink refill pump in the flow rate adjustment mode based on at least the temperature inside the tank detected by the temperature detection unit, the ink storage amount detected by the storage amount detection unit, and the external temperature detected by the external temperature detection unit.

[0014] A fourth invention of the present application is an ink supply device of the first invention, further comprising an outflow amount detection unit that detects the amount of ink flowing out from the ink tank to the ink supply path, and the control unit calculates the flow rate of the ink refill pump in the flow rate adjustment mode based on at least the temperature inside the tank detected by the temperature detection unit, the ink storage amount detected by the storage amount detection unit, and the ink outflow amount detected by the outflow amount detection unit.

[0015] A fifth aspect of the present invention is the ink supply device of the fourth aspect, wherein the outflow amount detection unit is a flow rate sensor that directly detects the outflow amount of ink.

[0016] A sixth aspect of the present invention is the ink supply device of the fourth aspect, wherein the outflow amount detection unit is a calculation unit included in the control unit, and calculates the outflow amount of ink from the amount of ink ejected from the head.

[0017] The seventh invention of the present application is an ink supply device of the second invention, wherein, in the normal mode, the control unit drives the ink refill pump so that the ink storage amount detected by the storage amount detection unit is greater than or equal to a first reference amount and less than a second reference amount, and both the first reference amount and the second reference amount are greater than the low remaining amount threshold. [Effects of the Invention]

[0018] According to the first to seventh aspects of the present invention, in a printing device including an ink circulation circuit with a temperature adjustment function, ink can be appropriately supplied from an external tank to the circulation circuit. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram of a printing device. [Figure 2] FIG. 2 is a schematic diagram of an ink supply device. [Figure 3] 10 is a flowchart showing a flow of mode selection for ink refill processing in the ink supply device. [Figure 4] 10 is a flowchart showing the flow of ink refill processing in a normal mode. [Figure 5] 10 is a flowchart showing the flow of an ink refill process in a flow rate adjustment mode. [Figure 6] 10 is a flowchart showing a flow of mode selection for ink refill processing in an ink supply device according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] <1. Printer configuration> A printing device 9 having an ink supply device 1 according to one embodiment of the present invention will be described below with reference to Fig. 1. Fig. 1 is a schematic diagram of the printing device 9. The printing device 9 performs coating, printing, and drying processes on the long strip-shaped printing medium M while transporting the printing medium M by controlling each device component with a control unit 90.

[0022] Specifically, the printing device 9 is a printing device that ejects aqueous pigment ink onto a long strip of film sheet for flexible packaging using an inkjet method. The material of the printing medium M is a film such as OPP (oriented polypropylene) or PET (polyethylene terephthalate). However, the material of the printing medium M is not limited to a resin film, and it may be other materials such as paper. Of the two surfaces of the printing medium M, the surface on which an image is printed is referred to as the front surface, and the surface opposite the front surface is referred to as the back surface.

[0023] The printing device 9 includes a transport mechanism 91 , a coating processing section 92 , a printing processing section 93 , and a drying processing section 94 .

[0024] The transport mechanism 91 is a device for transporting the printing medium M along a predetermined transport path. The transport mechanism 91 has a feed roller 911, a take-up roller 912, and a number of other transport rollers 913. The feed roller 911, the take-up roller 912, and some of the transport rollers 913 are rotating rollers that are rotated by a motor or the like. In addition, some of the transport rollers 913 are driven rollers that rotate in accordance with the movement of the printing medium M.

[0025] When the printing device 9 is in operation, the feeding roller 911, the winding roller 912, and some of the rotating rollers of the transport roller 913 rotate, causing the printing medium M to be fed from the feeding roller 911, and after undergoing coating processing by the coating processing unit 92, printing processing by the printing processing unit 93, and drying processing by the drying processing unit 94, the printing medium M is wound up by the winding roller 912. Note that in Figure 1, an arrow indicating the transport direction is attached to the front side of the printing medium M.

[0026] The coating processing unit 92 is a device for coating a liquid primer (coating liquid) on the surface of the printing medium M. The coating processing unit 92 has a pan 921 and a gravure roller 922. The pan 921 stores the liquid primer. The gravure roller 922 is a roller for coating the primer on the surface of the printing medium M transported by the transport mechanism 91. The gravure roller 922 is positioned so that it is partially immersed in the primer stored in the pan 921.

[0027] The gravure roller 922 holds a primer on its outer circumferential surface and rotates while transporting the print medium M with its surface facing downward, thereby applying the primer to the surface of the print medium M. The direction of travel of the print medium M and the direction of rotation of the gravure roller 922 (indicated by the arrow in FIG. 1) are opposite directions. In other words, the gravure roller 922 applies the primer to the surface of the print medium M using a so-called reverse kiss method.

[0028] The print processing unit 93 has a housing 930, a color printing unit 931, and a white printing unit 932. The color printing unit 931 and the white printing unit 932 are arranged inside the housing 930. The color printing unit 931 ejects ink of multiple colors from above onto the printing medium M, which is transported with its front side facing up. In this embodiment, the color printing unit 931 has four head units 20 that eject ink of different colors. The inks ejected by the color printing unit 931 are, for example, cyan, magenta, yellow, and black. The white printing unit 932 ejects white ink from above onto the printing medium M, which is transported with its front side facing up. The white printing unit 932 has one head unit 20 that ejects white ink.

[0029] The detailed configuration of the head unit 20 and the ink supply device 1 for supplying ink to the multiple heads 21 of the head unit 20 will be described later.

[0030] In addition, the print processing unit 93 further has pre-drying units (not shown) downstream of the color printing unit 931 and upstream of the white printing unit 932, and downstream of the white printing unit 932, which dry the ink ejected onto the surface of the printing medium M.

[0031] The drying processing unit 94 is a device that dries the ink ejected onto the surface of the printing medium M in the print processing unit 93. The drying processing unit 94 has a drying oven 941, which is a housing. Inside the drying oven 941, the transport path for the printing medium M formed by the transport mechanism 91 is S-shaped. Note that the transport mechanism 91 has an air turn bar 914 instead of a transport roller 913 at the location that comes into contact with the surface of the printing medium M inside the drying oven 941.

[0032] The control unit 90 is configured by, for example, a computer having a processor such as a CPU, a memory such as RAM, and a storage unit such as a hard disk drive. The printing device 9 controls the operations of the above-mentioned transport mechanism 91, coating processing unit 92, print processing unit 93, drying processing unit 94, and each unit of the ink supply device 1 described below in accordance with a computer program. In this way, the printing process in the printing device 9 progresses.

[0033] <2. Configuration of the ink supply device> Next, the configuration of the ink supply device 1 for supplying ink to the plurality of heads 21 of the head unit 20 will be described with reference to FIG.

[0034] 2, the head unit 20 has a plurality of heads 21 arranged in a horizontal direction (a direction perpendicular to the plane of the paper in FIG. 1). In FIG. 2, the plurality of heads 21 connected to the recovery reservoir 23 and indicated by dashed lines are the same as the plurality of heads 21 connected to the supply reservoir 22 and indicated by solid lines, and are shown redundantly for the sake of the configuration of the drawing.

[0035] The ink supply device 1 has, as ink storage sections, a supply reservoir 22 and a recovery reservoir 23 of the head unit 20, an external tank 31, and an ink tank 32. The ink supply device 1 also has a first transport section 41, a second transport section 42, a third transport section 43, and a fourth transport section 44 as means for transporting ink between each storage section.

[0036] The head unit 20 is provided with a plurality of heads 21, a supply reservoir 22, and a recovery reservoir 23. The heads 21 have a plurality of ejection nozzles that eject ink onto the print medium M on the surface of their lower part.

[0037] The supply reservoir 22 is an ink storage unit that stores ink to be supplied to the head 21. The supply reservoir 22 has a first horizontal reservoir 51 and a first vertical reservoir 52.

[0038] The first horizontal reservoir 51 is a cylindrical storage section that extends substantially horizontally along the direction in which the multiple heads 21 are arranged. One end of the first horizontal reservoir 51 is connected in communication with the first vertical reservoir 52. The other end of the first horizontal reservoir 51 is closed. A plurality of supply ports 510 that vertically connect the inside and outside of the first horizontal reservoir 51 are provided at the bottom of the first horizontal reservoir 51. Each supply port 510 is connected in communication with a head 21 arranged below the supply port 510 via a supply pipe 211.

[0039] The first vertical reservoir 52 is a cylindrical storage unit with a bottom and a lid. The first vertical reservoir 52 is larger in the vertical direction than the first horizontal reservoir 51. The first vertical reservoir 52 has a first opening 520 on its side surface that directly communicates with one end of the first horizontal reservoir 51.

[0040] The first vertical reservoir 52 is equipped with a level sensor 521. Based on a detection signal from the level sensor 521, the control unit 90 can determine the amount of ink stored in the supply reservoir 22. The level sensor 521 may be a float-type level sensor or may be a level sensor of another type.

[0041] In the supply reservoir 22, the first horizontal reservoir 51 is filled with ink, and the amount of ink stored in the first vertical reservoir 52 is adjusted so that a gas layer of a certain level or more is generated in the upper part. The gas layer in the first vertical reservoir 52 is connected to a pressure adjustment unit 522. This maintains the pressure in the first vertical reservoir 52 at a predetermined negative pressure for the supply reservoir.

[0042] The recovery reservoir 23 is an ink storage unit that stores ink recovered from the head 21. The recovery reservoir 23 has a second horizontal reservoir 61 and a second vertical reservoir 62.

[0043] The second horizontal reservoir 61 is a cylindrical storage section that extends substantially horizontally along the direction in which the multiple heads 21 are arranged. One end of the second horizontal reservoir 61 is connected in communication with the second vertical reservoir 62. The other end of the second horizontal reservoir 61 is closed. A plurality of recovery ports 610 that connect the inside and outside of the second horizontal reservoir 61 in the vertical direction are provided at the bottom of the second horizontal reservoir 61. Each recovery port 610 is connected in communication with a head 21 arranged below the recovery port 610 via a recovery pipe 212.

[0044] The second vertical reservoir 62 is a cylindrical storage unit with a bottom and a lid. The second vertical reservoir 62 is larger in the vertical direction than the second horizontal reservoir 61. The second vertical reservoir 62 has a second opening 620 on its side surface that directly communicates with one end of the second horizontal reservoir 61.

[0045] The second vertical reservoir 62 is equipped with a level sensor 621. Based on a detection signal from the level sensor 621, the control unit 90 can determine the amount of ink stored in the recovery reservoir 23. The level sensor 621 may be a float-type level sensor or may be a level sensor of another type.

[0046] In the recovery reservoir 23, the second horizontal reservoir 61 is filled with ink, and the amount of ink stored in the second vertical reservoir 62 is adjusted so that a certain amount of gas layer is generated at the top. The gas layer in the second vertical reservoir 62 is connected to a pressure adjustment unit 622. This maintains the pressure inside the second vertical reservoir 62 at a predetermined recovery reservoir negative pressure. The recovery reservoir negative pressure is lower than the supply reservoir negative pressure. In other words, the difference between atmospheric pressure and the recovery reservoir negative pressure is greater than the difference between atmospheric pressure and the supply reservoir negative pressure.

[0047] The external tank 31 is an ink storage unit that has the largest maximum ink storage capacity. The external tank 31 stores ink to be supplied to the ink tank 32. For example, ink purchased from an ink manufacturer is used in the external tank 31 as is. The external tank 31 is located in an area away from the head unit 20 and the ink tank 32.

[0048] The external tank 31 is equipped with an external temperature sensor 311. The external temperature sensor 311 in this embodiment is an "external temperature detection unit" that detects the "external temperature," which is the temperature of the ink inside the external tank 31. Note that the external temperature sensor 311 as an external temperature detection unit may also detect the outside air temperature around the external tank 31 as the external temperature.

[0049] The ink tank 32 temporarily stores ink. The ink storage capacity of the ink tank 32 is smaller than that of the external tank 31, but is larger than that of the supply reservoir 22 and the recovery reservoir 23.

[0050] The ink tank 32 is provided with a temperature sensor 321 , a heater 322 , a level sensor 323 , and a stirring unit 324 .

[0051] The temperature sensor 321 detects the temperature of the ink stored in the ink tank 32. The temperature sensor 321 is a “temperature detection unit” that detects the “internal tank temperature” which is the temperature of the ink in the ink tank 32.

[0052] The heater 322 is attached to the outer wall of the ink tank 32. The heater 322 is an “ink heating unit” that heats the ink in the ink tank 32. The control unit 90 controls the heater 322 based on the ink temperature detected by the temperature sensor 321.

[0053] The level sensor 323 detects the level of ink stored in the ink tank 32 and outputs the detection result to the control unit 90. In other words, the level sensor 323 is a "storage amount detection unit" that detects the amount of ink stored in the ink tank 32. In addition, the stirring unit 324 stirs the ink stored in the ink tank 32 to prevent uneven heating and uneven density.

[0054] The first transport unit 41 transports ink from the external tank 31 to the ink tank 32. The first transport unit 41 has a pipe 411, a valve 412 inserted in the pipe 411, an ink refill pump 413, and a valve 414. One end of the pipe 411 is disposed in an ink storage area in the external tank 31. The other end of the pipe 411 communicates with the interior of the ink tank 32. When the control unit 90 opens the valves 412 and 414 and operates the ink refill pump 413, the ink stored in the external tank 31 is sent to the ink tank 32 via the pipe 411.

[0055] The second transport unit 42 transports ink from the ink tank 32 to the recovery reservoir 23. The second transport unit 42 includes a pipe 421, a pump 422, a filter 423, a degassing unit 424, and a valve 425 that are inserted into the pipe 421. One end of the pipe 421 is disposed in an ink storage area in the ink tank 32. The other end of the pipe 421 communicates with the interior of the second vertical reservoir 62 of the recovery reservoir 23. The filter 423 removes solid components (aggregates and precipitates) contained in the ink. The degassing unit 424 removes air bubbles contained in the ink and some of the gas components dissolved in the ink. When the control unit 90 opens the valve 425 and operates the pump 422, the ink stored in the ink tank 32 is sent to the second vertical reservoir 62 via the pipe 421. The pipe 421 is also provided with a flow rate sensor 426 that detects the ink flow rate in the pipe 421.

[0056] The third transport unit 43 transports ink from the recovery reservoir 23 to the supply reservoir 22. The third transport unit 43 has a pipe 431, a pump 432, a filter 433, and a degassing unit 434 attached to the pipe 431. One end of the pipe 431 is disposed in an ink storage area in the second vertical reservoir 62 of the recovery reservoir 23. The other end of the pipe 431 communicates with the interior of the first vertical reservoir 52 of the supply reservoir 22. The filter 433 removes solid components (aggregates, precipitates) contained in the ink. The degassing unit 434 removes air bubbles contained in the ink and some of the gas components dissolved in the ink. When the control unit 90 operates the pump 432, the ink stored in the second vertical reservoir 62 of the recovery reservoir 23 is sent to the first vertical reservoir 52 of the supply reservoir 22 via the pipe 431.

[0057] The fourth transport unit 44 transports ink from the supply reservoir 22 to the ink tank 32. The fourth transport unit 44 has a pipe 441, and a valve 442 and a pump 443 inserted in the pipe 441. One end of the pipe 441 is disposed in the ink storage area of ​​the first vertical reservoir 52 of the supply reservoir 22. The other end of the pipe 441 communicates with the interior of the ink tank 32. When the control unit 90 operates the pump 443, the ink stored in the first vertical reservoir 52 of the supply reservoir 22 is sent to the ink tank 32 via the pipe 441.

[0058] With this configuration, an ink circulation path is formed by the supply reservoir 22, the multiple supply pipes 211, the head 21 and recovery pipe 212, the recovery reservoir 23, and the third transport unit 43. When the pump 432 of the third transport unit 43 is driven, ink is supplied from the second vertical reservoir 62 of the recovery reservoir 23 to the first vertical reservoir 52 of the supply reservoir 22, causing an ink flow from the first vertical reservoir 52 through the first horizontal reservoir 51, the multiple supply pipes 211, the head 21 and recovery pipe 212, and the second horizontal reservoir 61 of the recovery reservoir 23, and back to the second vertical reservoir 62. This ink circulation path is called circulation within the head unit.

[0059] As described above, the negative pressure for the recovery reservoir is lower than the negative pressure for the supply reservoir. That is, the pressure in the second horizontal reservoir 61 of the recovery reservoir 23 is lower than the pressure in the first horizontal reservoir 51 of the supply reservoir 22. Therefore, for each head 21, the pressure in the second horizontal reservoir 61 communicating with the recovery pipe 212 is lower than the pressure in the first horizontal reservoir 51 communicating with the supply pipe 211, and therefore, a flow of ink occurs in the head 21 from the supply pipe 211 to the recovery pipe 212.

[0060] An ink circulation path is formed by the ink tank 32, the second transport unit 42, the recovery reservoir 23, the third transport unit 43, the supply reservoir 22, and the fourth transport unit 44. When transportation in the second transport unit 42, the third transport unit 43, and the fourth transport unit 44 is performed simultaneously, an ink flow occurs from the ink tank 32, passing through the second transport unit 42, the recovery reservoir 23, the third transport unit 43, the supply reservoir 22, and the fourth transport unit 44, and returning to the ink tank 32. This ink circulation path is called the head unit extra-circulation.

[0061] When ink is ejected from the head 21 during the printing process or the maintenance process of the head 21 and the ink in the supply reservoir 22 decreases, the ink level in the first vertical reservoir 52 drops. In such a case, the control unit 90 recognizes the drop in the ink level in the first vertical reservoir 52 based on a detection signal from the level sensor 521. The control unit 90 then starts transporting ink in the second transport unit 42 and the third transport unit 43 so that the ink level detected by the level sensor 521 and the level sensor 621 falls within a predetermined range. Note that if ink is already being transported by circulation within the head unit or circulation outside the head unit, the control unit 90 increases the amount of ink transported in the second transport unit 42 and the third transport unit 43.

[0062] Furthermore, when the ink in the ink tank 32 decreases due to ink supply from the ink tank 32 to the head unit 20, the ink level in the ink tank 32 drops. In such a case, the control unit 90 recognizes the drop in the ink level in the ink tank 32 based on a detection signal from the level sensor 323. The control unit 90 then controls the transport of ink in the first transport unit 41 so that the ink level detected by the level sensor 323 falls within the treatment range.

[0063] In this embodiment, the first transport unit 41 is an "ink refill path" 71 that supplies ink from the external tank 31 to the ink tank 32. The second transport unit 42, the recovery reservoir 23, the third transport unit 43, and the supply reservoir 22 are an "ink supply path" 72 that supplies ink from the ink tank 32 to the head 21. The recovery reservoir 23, the third transport unit 43, the supply reservoir 22, and the fourth transport unit 44 are an "ink return path" 73 that returns ink from the head 21 to the ink tank 32. The flow rate sensor 426 is an "outflow amount detection unit" that detects the amount of ink flowing from the ink tank 32 to the second transport unit 42, which serves as the ink supply path. Note that the outflow amount detection unit is not limited to a unit that directly detects the amount of ink outflow, like the flow rate sensor 426 of this embodiment. The outflow amount detection unit may be, for example, a calculation unit included in the control unit 90 that calculates the amount of ink outflow from the amount of ink ejected from the head 21.

[0064] The control unit 90 controls the flow rate of ink in the ink refill path 71, the ink supply path 72, and the ink return path 73. When the amount of ink stored detected by the level sensor 323 is equal to or greater than a predetermined threshold, the control unit 90 drives the ink refill pump 413 in normal mode. When the amount of ink stored detected by the level sensor 323 is less than the predetermined threshold, the control unit 90 drives the ink refill pump 413 in flow rate adjustment mode.

[0065] The ink supply path 72 and the ink return path 73 constitute an ink circulation circuit with a temperature adjustment function. In contrast, the ink refill path 71 refills the ink circulation circuit with temperature-unadjusted ink from the external tank 31. In the conventional normal mode, the control unit 90 sets the flow rate of the ink refill pump 413 to a predetermined flow rate and refills ink from the external tank 31 to the ink tank 32. If the ink tank 32 has a sufficient amount of ink remaining, the problem of the temperature of the ink in the ink tank 32 dropping suddenly in normal mode is unlikely to occur.

[0066] However, if some time has passed since the external tank 31 became empty before it was replaced, the ink remaining in the ink tank 32 will be low. At this time, if ink is replenished from the external tank 31 to the ink tank 32 in normal mode by setting the ink refill pump 413 to a predetermined flow rate until the desired ink storage amount is reached, a problem is likely to occur in which the temperature of the ink in the ink tank 32 drops suddenly.

[0067] Therefore, in this ink supply device 1, in addition to the normal mode, a flow rate adjustment mode is provided for the process of refilling ink from the external tank 31 to the ink tank 32. In the flow rate adjustment mode, the control unit 90 adjusts the flow rate of the ink refill pump 413 so that the temperature of the ink in the ink tank 32 is within a predetermined temperature range. At this time, the control unit 90 calculates the flow rate of the ink refill pump 413 based on at least the temperature inside the tank detected by the temperature sensor 321 and the amount of ink stored detected by the level sensor 323. In this embodiment, the control unit 90 further calculates the flow rate of the ink refill pump 413 based on the external temperature detected by the external temperature sensor 311 and the amount of ink flowing out detected by the flow rate sensor 426. As a result, In the printing device 9 including an ink circulation circuit (ink supply path 72 and ink return path 73) with a temperature adjustment function, ink can be appropriately supplied from the external tank 31 to the ink tank 32 in the circulation circuit.

[0068] <3. Adjusting the ink refill amount in normal mode and flow rate adjustment mode> Next, a description will be given of the ink refilling process from the external tank 31 to the ink tank 32 by the ink supply device 1. In the ink refilling process by the ink supply device 1, the control unit 90 uses two modes: a normal mode and a flow rate adjustment mode.

[0069] In normal mode, the control unit 90 refills the ink tank 32 with ink so that the amount of ink stored in the ink tank 32 is within a range equal to or greater than a predetermined first reference amount and less than a second reference amount. The normal mode is performed when the amount of ink stored in the ink tank 32 detected by the level sensor 323 is equal to or greater than a predetermined low remaining amount threshold. Here, the low remaining amount threshold is a value smaller than the first reference amount. In normal mode, the control unit 90 drives the ink refill pump 413 at a predetermined normal flow rate when the amount of ink stored in the ink tank 32 falls below the first reference amount, and stops the ink refill pump 413 when the amount of ink reaches the second reference amount.

[0070] At this time, the "normal flow rate" is set to a flow rate that can maintain the ink temperature in the ink tank 32 within a desired range, even if ink is replenished from the external tank 31 with a lower ink temperature, from the first reference amount to the second reference amount. Depending on each setting value, including the difference between the first reference amount and the second reference amount, the "normal flow rate" may be the maximum flow rate of the ink replenishment pump 413.

[0071] In the flow rate adjustment mode, the control unit 90 drives the ink refill pump 413 while adjusting the flow rate so that the temperature of the ink in the ink tank 32 is within a predetermined temperature range. The flow rate adjustment mode is performed when the amount of ink stored in the ink tank 32 detected by the level sensor 323 is below a predetermined low remaining amount threshold due to, for example, the external tank 31 running out of ink. In this embodiment, the condition for performing the flow rate adjustment mode is that the amount of ink stored in the ink tank 32 is below the predetermined low remaining amount threshold, and also that the determination in step S104, which will be described later, is performed.

[0072] The following describes the mode switching of the ink refill process and the adjustment of the ink refill amount in each mode with reference to Figures 3 to 5. Figure 3 is a flowchart showing the flow of mode selection of the ink refill process in the ink supply device 1. Figure 4 is a flowchart showing the flow of the ink refill process in the normal mode. Figure 5 is a flowchart showing the flow of the ink refill process in the flow rate adjustment mode.

[0073] As shown in FIG. 3, when the ink supply device 1 starts refilling the ink tank 32 with ink from the external tank 31, the control unit 90 first refills the ink in the normal mode (step S101).

[0074] 4, in the ink refill process in normal mode, the control unit 90 periodically determines whether the amount of ink stored in the ink tank 32 detected by the level sensor 323 is less than a first reference amount (step S201). If the amount of ink stored in the ink tank 32 is equal to or greater than the first reference amount (step S201: No), the process returns to step S201.

[0075] If the amount of ink stored in the ink tank 32 is less than the first reference amount (step S201: Yes), the control unit 90 opens the valves 412 and 414 and drives the ink refill pump 413 to start refilling ink at a normal flow rate (step S202).

[0076] When ink replenishment at the normal flow rate is started in step S202, the control unit 90 periodically determines whether the amount of ink stored in the ink tank 32 detected by the level sensor 323 is equal to or greater than a second reference amount (step S203). If the amount of ink stored in the ink tank 32 is less than the second reference amount (step S203: No), the control unit 90 continues ink replenishment at the normal flow rate and returns to step S203.

[0077] If the amount of ink stored in the ink tank 32 is equal to or greater than the second reference amount (step S203: Yes), the control unit 90 stops the ink refill pump 413 and closes the valves 412 and 414 to stop ink refilling (step S204), and then returns to step S201.

[0078] Returning to Figure 3, after starting the ink refill process in normal mode in step S101, the control unit 90 monitors whether the external tank 31 has been replaced (step S102). In order for the control unit 90 to detect that the external tank 31 has been replaced, for example, a sensor that detects the removal / installation of the external tank 31 may be provided, or an operator may input a signal to the control unit 90 when replacing the external tank 31.

[0079] If it is determined that the external tank 31 has been replaced (step S102: Yes), the control unit 90 then determines whether the amount of ink stored in the ink tank 32 detected by the level sensor 323 is less than the low remaining amount threshold (step S103). If the amount of ink stored in the ink tank 32 is equal to or greater than the low remaining amount threshold (step S103: No), the control unit 90 continues the ink refill process in normal mode and returns to step S102.

[0080] In step S103, if the amount of ink stored in the ink tank 32 is less than the low remaining amount threshold (step S103: No), the control unit 90 determines whether printing processing of any print job is currently being performed in the printing device 9 (step S104).

[0081] In step S104, if it is determined that printing processing is not in progress (step S104: No), the control unit 90 continues refilling ink at the normal flow rate in the normal mode, and returns to step S102.

[0082] In step S104, if it is determined that printing processing is in progress in the printing device 9 (step S104: Yes), the control unit 90 ends the normal mode for the ink refill processing mode and starts the flow rate adjustment mode (step S105).

[0083] Next, the flow rate adjustment mode will be described. As shown in Fig. 5, when the flow rate adjustment mode is started, the control unit 90 first acquires each value required to calculate the adjusted flow rate (step S301). Specifically, the control unit 90 acquires the tank internal temperature detected by the temperature sensor 321, the ink storage amount detected by the level sensor 323, the external temperature detected by the external temperature sensor 311, and the ink outflow amount detected by the flow rate sensor 426.

[0084] Thereafter, the control unit 90 calculates the adjusted flow rate of the ink refill pump 413 based on the values ​​acquired in step S301 so that the temperature of the ink in the ink tank 32 falls within a predetermined temperature range (step S302).

[0085] Once the adjusted flow rate is calculated, the control unit 90 opens the valves 412 and 414 and drives the ink refill pump 413 to start refilling ink at the calculated adjusted flow rate (step S303).

[0086] For example, if it is desired to set the ink temperature inside the ink tank 32 to To±α [°C], the lowest allowable ink temperature is To-α [°C]. If the current ink temperature inside the ink tank 32 is Ta [°C], the amount of ink stored in the ink tank 32 is Va [L], and the external temperature, which is the ink temperature inside the external tank 31, is Tb [°C], and the flow rate of ink sent from the external tank 31 to the ink tank 32 is Vb [L / sec], then, ignoring heating by the heater 322, the ink temperature Ta' [°C] inside the ink tank 32 after one second will be calculated as shown in the following equation (1). Ta'=(Va*Ta+Vb*Tb) / (Va+Vb) ···(1)

[0087] On the other hand, if the heater 322 can raise the ink temperature Va+Vb[L] by ΔT [°C] in one second, the ink temperature Ta″ [°C] in the ink tank 32 after one second, taking into account the heating capacity of the heater 322, is Ta″=Ta′+ΔT, as shown in the following equation (2). Ta”=(Va*Ta+Vb*Tb) / (Va+Vb)+ΔT ···(2)

[0088] The control unit 90 calculates the liquid transfer flow rate Vb [L / sec] from the external tank 31 to the ink tank 32 so that Ta″ [°C] does not fall below To−α [°C].

[0089] When ink replenishment at the adjusted flow rate is started in step S302, the control unit 90 periodically determines whether the amount of ink stored in the ink tank 32 detected by the level sensor 323 is equal to or greater than the low remaining amount threshold (step S304). If the amount of ink stored in the ink tank 32 is less than the low remaining amount threshold (step S304: No), the process returns to step S303 while continuing ink replenishment at the adjusted flow rate.

[0090] If the amount of ink stored in the ink tank 32 is equal to or greater than the low remaining amount threshold (step S304: Yes), the control unit 90 stops the ink refill pump 413 and closes the valves 412 and 414 to stop ink refill (step S204), then ends the flow rate adjustment mode and returns to step S101.

[0091] <4. Modifications> Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments.

[0092] In the above embodiment, when the ink supply device 1 refills the ink tank 32 from the external tank 31, the condition for switching the mode from the normal mode to the flow rate adjustment mode is that the amount of ink stored in the ink tank 32 detected by the level sensor 323 is less than a predetermined low remaining amount threshold, and the condition in step S104 must also be satisfied. However, the present invention is not limited to this. The condition for switching the mode from the normal mode to the flow rate adjustment mode may be simply that the amount of ink stored in the ink tank 32 detected by the level sensor 323 is less than a predetermined low remaining amount threshold.

[0093] Fig. 6 is a flowchart showing a modified example of the flow of mode selection for ink refill processing in the ink supply device 1. In the example of Fig. 6, the condition for switching from the normal mode to the flow rate adjustment mode is simply that the amount of ink stored in the ink tank 32 detected by the level sensor 323 is less than a predetermined low remaining amount threshold.

[0094] In this modified example, steps S101A to S103A are performed in the same manner as steps S101 to S103 in the above embodiment. If, in step S103A, the amount of ink stored in the ink tank 32 is equal to or greater than the low remaining amount threshold (step S103A: No), the ink refill process in normal mode continues and the process returns to step S102A. On the other hand, if, in step S103A, the amount of ink stored in the ink tank 32 is less than the low remaining amount threshold (step S103A: No), the control unit 90 ends the normal mode and starts the flow rate adjustment mode for the ink refill process without making any other determination (step S105A).

[0095] As in the example of FIG. 6, the condition for switching from the normal mode to the flow rate adjustment mode may simply be one.

[0096] Furthermore, in the above embodiment, water-based pigment ink is used as the ink, but the present invention is not limited to this. The ink may be oil-based ink or dye ink.

[0097] In the above embodiment, the printing device 9 has the coating processing unit 92 and the drying processing unit 94, but the present invention is not limited to this. The ink supply device of the present invention may be used in a printing device that only performs printing processing.

[0098] Furthermore, the elements appearing in the above-described embodiments and modifications may be combined as appropriate within the scope of not causing any contradiction. [Explanation of symbols]

[0099] 1: Ink supply device 9:Printing device 20: Head unit 21: Head 22: Supply reservoir 23: Recovery reservoir 31: External tank 32: Ink tank 41: First Transportation Department 42: Second Transportation Department 43: 3rd Transportation Department 44: 4th Transportation Department 71: Ink refill path 72: Ink supply path 73: Ink return path 90: Control unit 311: External temperature sensor 321: Temperature sensor 322: Heater 323: Level sensor 413: Ink refill pump 426: Flow sensor

Claims

1. In an inkjet printing device, an ink supply device that supplies ink to a plurality of heads, an ink tank for storing the ink; an ink supply path that supplies the ink from the ink tank to the head; an ink return path for returning the ink from the head to the ink tank; an ink heating unit that heats the ink in the ink tank; an external tank that stores the ink to be supplied to the ink tank; an ink refill path for supplying the ink from the external tank to the ink tank; an ink refill pump inserted in the ink refill path; a temperature detection unit that detects an internal tank temperature, which is the temperature of the ink in the ink tank or the ink supply path; a storage amount detection unit that detects the amount of ink stored in the ink tank; a control unit that controls the flow rate of the ink in the ink supply path, the ink return path, and the ink refill path; and The control unit the ink refill pump can be driven in a flow rate adjustment mode in which the flow rate of the ink refill pump is adjusted so that the temperature of the ink in the ink tank is within a predetermined temperature range; The control unit controls the flow rate of the ink refill pump in the flow rate adjustment mode by at least The temperature inside the tank detected by the temperature detection unit; and the ink storage amount detected by the storage amount detection unit; An ink supply device that calculates based on the above.

2. 2. The ink supply device according to claim 1, The control unit When the ink storage amount detected by the storage amount detection unit is equal to or greater than a predetermined low remaining amount threshold, the ink refill pump is driven in a normal mode in which the flow rate of the ink refill pump is set to a predetermined flow rate; When the ink storage amount detected by the storage amount detection unit is less than the low remaining amount threshold, the ink refill pump is driven in the flow rate adjustment mode. Ink supply device.

3. 2. The ink supply device according to claim 1, an external temperature detection unit that detects the external temperature, which is the temperature of the ink in the external tank or the ambient temperature around the external tank; and The control unit controls the flow rate of the ink refill pump in the flow rate adjustment mode by at least The temperature inside the tank detected by the temperature detection unit; and the ink storage amount detected by the storage amount detection unit; the external temperature detected by the external temperature detection unit; An ink supply device that calculates based on the above.

4. 2. The ink supply device according to claim 1, an outflow amount detection unit that detects the amount of ink outflow from the ink tank to the ink supply path; and The control unit controls the flow rate of the ink refill pump in the flow rate adjustment mode by at least The temperature inside the tank detected by the temperature detection unit; and the ink storage amount detected by the storage amount detection unit; the outflow amount of ink detected by the outflow amount detection unit; An ink supply device that calculates based on the above.

5. 5. The ink supply device according to claim 4, The ink supply device, wherein the outflow amount detection unit is a flow rate sensor that directly detects the outflow amount of ink.

6. 5. The ink supply device according to claim 4, The outflow amount detection unit is a calculation unit included in the control unit, and calculates the outflow amount of ink from the ink ejection amount in the head.

7. 3. The ink supply device according to claim 2, the control unit drives the ink refill pump in the normal mode so that the ink storage amount detected by the storage amount detection unit is equal to or greater than a first reference amount and less than a second reference amount; The ink supply device, wherein the first reference amount and the second reference amount are both greater than the low remaining amount threshold.

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