Ink supply device

Abstract

To provide a technique of suppressing ink leakage from a nozzle and suppressing condensation in a head when an abnormality occurs in a pressure adjustment mechanism.SOLUTION: This ink supply device comprises a supply reservoir and a recovery reservoir connected to a plurality of heads. A control unit executes, when detecting an abnormality in one of first and second pressure adjustment units for respectively supplying negative pressure to the supply and recovery reservoirs, a) an abnormality side cutting-off step of cutting off the a pressure control unit of the abnormality side and the reservoirs from each other, b) a bypass opening step of opening a bypass valve inserted into a bypass pipe through which an air layer of the supply reservoir and an air layer of the recovery reservoir communicate with each other, c) a pressure change step of adjusting the negative pressure supplied by a pressure control unit of a normal side to third negative pressure between first negative pressure supplied by the first pressure adjustment unit at normal time and second negative pressure supplied by the second pressure adjustment unit at the normal time, and d) a pressure maintenance step of maintaining the third negative pressure.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] Among the inks used in inkjet printing devices, there are some that are prone to aggregation of the ink components, resulting in precipitation. For example, water-based pigment inks that are prone to aggregation are used for flexible packaging.

[0003] In an inkjet printer, the ink is exposed to the outside air in the nozzles of the head, so the solvent evaporates and coagulation is likely to occur in the 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, thereby preventing ink from accumulating in the head and preventing coagulation in the nozzles. A printer that employs a circulation system is described in, for example, Patent Document 1.

[0004] The ink supply section of the printing device described in Patent Document 1 has, in addition to a main reservoir (91m) which is an ink supply source, ink storage sections called a feed reservoir (91f) located upstream of the head (H) and a return reservoir (91r) located downstream of the head. The feed-side adjustment section (98f) of the pressure adjustment mechanism (98) applies negative pressure to the feed reservoir (91f), and the return-side adjustment section (98r) of the pressure adjustment mechanism (98) applies negative pressure to the return reservoir (91r).

[0005] The pressure adjustment mechanism (98) applies a stronger negative pressure to the return reservoir (91r) than to the feed reservoir (91f), and the pressure difference causes an ink flow from the feed reservoir (91f) to the return reservoir (91r) via the head (H). In this way, the difference in negative pressure between the reservoirs located upstream and downstream of the head is used to generate an ink flow in the head, suppressing coagulation in the head. [Prior art documents] [Non-patent literature]

[0006] [Patent Document 1] Patent Publication No. 2021-45932 Summary of the Invention [Problem to be solved by the invention]

[0007] In such a mechanism, if an abnormality occurs in one of the two pressure adjustment mechanisms that apply negative pressure to the two reservoirs located upstream and downstream of the head, conventionally, both pressure adjustment mechanisms were kept disconnected from the reservoirs immediately after the abnormality was detected until a maintenance worker arrived and the maintenance work was completed.

[0008] With such conventional measures, the pressure inside the head is not kept negative, and the meniscus of the nozzle cannot be maintained, which may cause ink to leak out. In addition, when both pressure adjustment mechanisms are cut off from the reservoir, it is difficult to circulate the ink and generate an ink flow inside the head. For this reason, if it takes a long time to complete the maintenance work, there is a risk of coagulation occurring in the head.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a technology that suppresses ink leakage from the nozzles while suppressing aggregation within the head when an abnormality occurs in the pressure adjustment mechanism. [Means for solving the problem]

[0010] In order to solve the above problems, a first invention of the present application is an ink supply device for supplying ink to a head in an inkjet printing device, comprising: a supply reservoir for storing the ink to be supplied to the head; a recovery reservoir for storing the ink recovered from the head; an inter-reservoir ink flow path for sending the ink from the recovery reservoir to the supply reservoir; a first pressure adjustment unit for supplying negative pressure to the supply reservoir; a first communication tube for communicating between the first pressure adjustment unit and an air space in the supply reservoir; a first valve inserted in the first communication tube; a second pressure adjusting unit that supplies a negative pressure to the reservoir, a second communication pipe that communicates the second pressure adjusting unit with an air layer of the recovery reservoir, a second valve inserted in the second communication pipe, a bypass pipe that communicates the air layer of the supply reservoir with the air layer of the recovery reservoir, a bypass valve inserted in the bypass pipe, detection means that detects abnormalities in the first pressure adjusting unit and the second pressure adjusting unit, and a control unit that controls the operation of the first pressure adjusting unit, the first valve, the second pressure adjusting unit, the second valve, and the bypass valve, wherein the control unit the control unit opens the first valve and the second valve, closes the bypass valve, causes the first pressure adjustment unit to supply a first negative pressure to the supply reservoir, and causes the second pressure adjustment unit to supply a second negative pressure stronger than the first negative pressure to the recovery reservoir, and when the detection means detects an abnormality in one of the first pressure adjustment unit and the second pressure adjustment unit, a) an abnormality side blocking step of closing one of the first valve and the second valve corresponding to the one pressure adjustment unit in which the detection means has detected an abnormality; and b) a blocking step of the step a). Then, a bypass opening step of opening the bypass valve is performed; c) after step a), a pressure changing step of adjusting the negative pressure supplied by the other pressure adjustment unit, of the first pressure adjustment unit and the second pressure adjustment unit, for which no abnormality has been detected by the detection means, to a third negative pressure that is stronger than the first negative pressure and weaker than the second negative pressure; and d) after step c), an ink circulating step of generating a flow of ink from the supply reservoir to the recovery reservoir via the multiple heads while maintaining the negative pressure supplied by the other pressure adjustment unit at the third negative pressure.

[0011] A second invention of the present application is the ink supply device of the first invention, further comprising an inter-reservoir pump inserted in the inter-reservoir ink flow path and pumping the ink from the recovery reservoir to the supply reservoir, wherein the control unit in the step d) includes: d1) a head difference generating step of driving the inter-reservoir pump to pump the ink from the recovery reservoir to the supply reservoir through the inter-reservoir ink flow path so that the liquid level of the ink in the supply reservoir becomes higher than the liquid level of the ink in the recovery reservoir; and d2) a waiting step after d1), of stopping the inter-reservoir pump and waiting until the ink moves from the supply reservoir through the multiple heads to the recovery reservoir by the head difference and the difference in liquid level between the supply reservoir and the recovery reservoir becomes small.

[0012] A third invention of the present application is the ink supply device of the first invention, further comprising a tank for storing the ink to be supplied to the supply reservoir, an ink supply path connecting the tank and the supply reservoir, a supply pump inserted in the ink supply path and pumping the ink from the tank toward the supply reservoir, an ink recovery path connecting the recovery reservoir and the tank, a recovery pump inserted in the ink recovery path and pumping the ink from the recovery reservoir toward the tank, and an inter-reservoir pump inserted in the inter-reservoir ink flow path and pumping the ink from the recovery reservoir toward the supply reservoir, and in step d), the control unit operates the supply pump and the recovery pump at the same or similar liquid delivery rates, and operates the inter-reservoir pump at a smaller liquid delivery rate than the supply pump and the recovery pump. Effect of the Invention

[0013] According to the first to third aspects of the present application, when an abnormality occurs in the pressure adjustment mechanism, ink leakage from the nozzles can be suppressed. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram of a printing device. [Diagram 2] FIG. 2 is a schematic diagram of an ink supply device. [Diagram 3] 4 is a simplified diagram showing the flow of ink in a small circulation path and a large circulation path in a normal state. FIG. [Figure 4] 10 is a flowchart showing the flow of an ink circulation maintenance process when an abnormality is detected in the first pressure adjustment unit or the second pressure adjustment unit. [Diagram 5] 13 is a simplified diagram showing the ink flows in the small circulation path and the large circulation path at the beginning of step S104 when an abnormality occurs in the first pressure adjustment unit. FIG. [Figure 6] 13 is a simplified diagram showing the ink flows in the small circulation path and the large circulation path upon completion of step S104 in the case where an abnormality occurs in the first pressure adjustment unit. FIG. [Figure 7] 13 is a flowchart showing a flow of an ink circulation process using only the small circulation path when an abnormality occurs. [Figure 8] 11 is a simplified diagram showing the ink flows in a small circulation path and a large circulation path in a head difference generating step (step S211). FIG. [Figure 9] 11 is a simplified diagram showing the ink flows in the small circulation path and the large circulation path in the standby step (step S212). [Figure 10] 11 is a simplified diagram showing the ink flows in the small circulation path and the large circulation path in an ink circulation process in the event of an abnormality caused by the small circulation path and the large circulation path; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] <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 unit with a control unit 90.

[0017] Specifically, the printing device 9 is a printing device that ejects aqueous pigment-type ink by an inkjet method onto a long strip-shaped film sheet for flexible packaging. 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 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.

[0018] 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 .

[0019] 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, the other part of the transport rollers 913 is a driven roller that rotates in accordance with the movement of the printing medium M.

[0020] 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 being subjected to a coating process by the coating processing unit 92, a printing process by the printing processing unit 93, and a drying process by the drying processing unit 94, the printing medium M is wound up by the winding roller 912. Note that in FIG. 1, an arrow indicating the transport direction is indicated on the front side of the printing medium M.

[0021] 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 liquid primer is stored in the pan 921. 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 disposed so as to be partially immersed in the primer stored in the pan 921.

[0022] The gravure roller 922 holds a primer on its outer peripheral surface while rotating, with the print medium M being transported with its surface facing down, thereby applying the primer to the surface of the print medium M. The traveling direction of the print medium M and the rotation direction of the gravure roller 922 (indicated by an 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 by a so-called reverse kiss method.

[0023] 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 that is transported with the 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 in 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 that is transported with the front side facing up. The white printing unit 932 has one head unit 20 that ejects white ink.

[0024] A 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.

[0025] In addition, the print processing unit 93 further includes pre-drying units (not shown) that dry the ink ejected onto the surface of the printing medium M, respectively downstream of the color printing unit 931 and upstream of the white printing unit 932, and downstream of the white printing unit 932.

[0026] The drying processing unit 94 is a device that dries the ink discharged 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 of the printing medium M formed by the transport mechanism 91 has an S-shape. Note that the transport mechanism 91 has an air turn bar 914 instead of the transport roller 913 at a location that comes into contact with the surface of the printing medium M inside the drying oven 941.

[0027] The control unit 90 is configured by, for example, a computer having a processor such as a CPU, a memory such as a RAM, and a storage unit such as a hard disk drive. The processor of the control unit 90 controls the operations of the above-mentioned transport mechanism 91, the coating processing unit 92, the printing processing unit 93, the drying processing unit 94, and each unit of the ink supply device 1 described later in accordance with a computer program. This allows the printing process in the printing device 9 to proceed.

[0028] <2. Configuration of the ink supply device> Next, the configuration of the ink supply device 1 for supplying ink to the multiple heads 21 of the head unit 20 will be described with reference to Fig. 2. One ink supply device 1 is provided corresponding to each of the four head units 20 of the color printing section 931 and one head unit 20 of the white printing section 932. These multiple ink supply devices 1 have the same configuration.

[0029] The head unit 20 has a plurality of heads 21 arranged in a horizontal direction (a direction perpendicular to the plane of FIG. 1). In addition, a supply reservoir 22 and a recovery reservoir 23 are provided within the head unit 20.

[0030] The ink supply device 1 has, as ink storage sections, a supply reservoir 22, a recovery reservoir 23, a drum tank 31, and a buffer tank 32. The ink supply device 1 also has, as ink transport means between the storage sections, a first transport section 41, a second transport section 42, a third transport section 43, and a fourth transport section 44.

[0031] 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 for ejecting ink onto the print medium M on the lower surface thereof.

[0032] The supply reservoir 22 is an ink storage unit that stores ink to be supplied to the head 21. One ends of a plurality of supply pipes 211 are connected in communication with the bottom of the supply reservoir 22. The other ends of the plurality of supply pipes 211 are respectively connected to different heads 21. In this way, the supply reservoir 22 is connected in communication with the head 21 via the supply pipes 211.

[0033] The supply reservoir 22 is equipped with a first level sensor 221. A detection signal from the first level sensor 221 enables the control unit 90 to determine the amount of ink stored in the supply reservoir 22. The first level sensor 221 may be a float-type level sensor, or may be another type of level sensor, such as an electrode-type, vibration-type, or optical-type.

[0034] The ink storage amount is adjusted so that an air layer of a certain volume or more is generated in the upper part of the internal space of the supply reservoir 22. The air layer of the supply reservoir 22 is connected to the first pressure adjustment unit 50.

[0035] The first pressure adjustment unit 50 is a mechanism for supplying negative pressure to the supply reservoir 22. The first pressure adjustment unit 50 has a first air tank 51, a first atmosphere release valve 52 for opening the internal space of the first air tank 51 to the atmosphere, a first vacuum pump 53 for creating a negative pressure in the internal space of the first air tank 51, and a first pressure gauge 54 for measuring the internal pressure of the first air tank 51.

[0036] The first air tank 51 and the air layer of the supply reservoir 22 are connected in communication with each other by a first communication pipe 55. That is, the first communication pipe 55 communicates between the first pressure adjustment unit 50 and the air layer of the supply reservoir 22. A first valve 56 is inserted into the first communication pipe 55. The first valve 56 is an electromagnetic valve that opens / closes the first communication pipe 55.

[0037] When the pressure in the first air tank 51 is to be reduced, the first vacuum pump 53 is driven with the first atmosphere release valve 52 kept closed. When the pressure in the first air tank 51 is to be increased, the first atmosphere release valve 52 is opened. The pressure in the first air tank 51 is detected by a first pressure gauge 54.

[0038] In the first pressure adjustment section 50, the pressure in the first air tank 51 is maintained at a predetermined "first negative pressure" and the first valve 56 is opened, so that the pressure in the supply reservoir 22 is maintained at the first negative pressure.

[0039] The recovery reservoir 23 is an ink storage unit that stores ink recovered from the head 21. One ends of a plurality of recovery pipes 212 are connected in communication with the bottom of the recovery reservoir 23. The other ends of the plurality of recovery pipes 212 are respectively connected to different heads 21. In this way, the recovery reservoir 23 is connected in communication with the head 21 via the recovery pipes 212.

[0040] The recovery reservoir 23 is equipped with a second level sensor 231. Based on a detection signal from the second level sensor 231, the control unit 90 can determine the amount of ink stored in the recovery reservoir 23. The second level sensor 231 may be a float-type level sensor, or may be another type of level sensor, such as an electrode-type, vibration-type, or optical-type.

[0041] In the recovery reservoir 23, the amount of ink stored is adjusted so that an air layer of a certain volume or more is generated in the upper part of the internal space. The air layer in the recovery reservoir 23 is connected to the second pressure adjustment unit 60.

[0042] The second pressure adjustment unit 60 is a mechanism for supplying negative pressure to the collection reservoir 23. The second pressure adjustment unit 60 has a second air tank 61, a second atmosphere release valve 62 for opening the internal space of the second air tank 61 to the atmosphere, a second vacuum pump 63 for creating a negative pressure in the internal space of the second air tank 61, and a second pressure gauge 64 for measuring the internal pressure of the second air tank 61.

[0043] The second air tank 61 and the air space of the recovery reservoir 23 are connected in communication with each other through a second communication pipe 65. That is, the second communication pipe 65 communicates between the second pressure adjustment unit 60 and the air space of the recovery reservoir 23. A second valve 66 is inserted into the second communication pipe 65. The second valve 66 is an electromagnetic valve that opens and closes the second communication pipe 65.

[0044] When the pressure in the second air tank 61 is to be reduced, the second vacuum pump 63 is driven with the second atmosphere release valve 62 kept closed. When the pressure in the second air tank 61 is to be increased, the second atmosphere release valve 62 is opened. The pressure in the second air tank 61 is detected by a second pressure gauge 64.

[0045] In the second pressure adjustment section 60, the pressure in the second air tank 61 is maintained at a predetermined "second negative pressure" and the second valve 66 is opened, so that the pressure in the supply reservoir 22 is maintained at the second negative pressure.

[0046] The second negative pressure is stronger than the first negative pressure. That is, the second negative pressure is lower than the first negative pressure, and the absolute value of the second negative pressure is greater than the absolute value of the first negative pressure. Therefore, the difference between the atmospheric pressure and the second negative pressure is greater than the difference between the atmospheric pressure and the first negative pressure. As a result, the pressure in the recovery reservoir 23 becomes smaller than the pressure in the supply reservoir 22, and ink flows from the supply reservoir 22 through the multiple heads 21 toward the recovery reservoir 23.

[0047] The drum tank 31 is an ink storage unit that has the largest maximum ink storage amount. Ink is supplied from the drum tank 31 to the supply reservoir 22 and the recovery reservoir 23 in the head unit 20 via a buffer tank 32.

[0048] The buffer tank 32 is a tank that temporarily stores ink to be supplied to the supply reservoir 22. The amount of ink stored in the buffer tank 32 is smaller than that of the drum tank 31, and is larger than that of the supply reservoir 22 and the recovery reservoir 23. The drum tank 31 and the buffer tank 32 are disposed in an area away from the head unit 20.

[0049] The buffer tank 32 is equipped with a temperature sensor 321 , a heater 322 , a level sensor 323 , and a stirring unit 324 .

[0050] The temperature sensor 321 detects the temperature of the ink stored in the buffer tank 32. The heater 322 is attached to the outer wall of the buffer tank 32, and heats the ink in the buffer tank 32. The control unit 90 controls the heater 322 based on the ink temperature detected by the temperature sensor 321.

[0051] The level sensor 323 detects the level of the ink stored in the buffer tank 32, and outputs the detection result to the control unit 90. In addition, the stirring unit 324 stirs the ink stored in the buffer tank 32 to prevent uneven heating and uneven density.

[0052] The first transport unit 41 transports ink from the drum tank 31 to the buffer tank 32. The first transport unit 41 has a pipe 411, a valve 412, a pump 413, and a valve 414 that are inserted in the pipe 411. One end of the pipe 411 is disposed in an ink storage area in the drum tank 31. The other end of the pipe 411 communicates with the inside of the buffer tank 32.

[0053] When the control unit 90 opens the valves 412 and 414 and operates the pump 413 , the ink stored in the drum tank 31 is sent to the buffer tank 32 via the pipe 411 .

[0054] The second transport unit 42 transports ink from the buffer tank 32 to the supply reservoir 22. The second transport unit 42 has an ink supply path 421, a supply pump 422, a filter 423, a degassing unit 424, and a supply valve 425 that are inserted in the ink supply path 421.

[0055] The ink supply path 421 communicates between the buffer tank 32 and the supply reservoir 22. One end of the ink supply path 421 is disposed in an ink storage area in the buffer tank 32. The other end of the ink supply path 421 communicates with the interior of the supply reservoir 22. The supply pump 422 pumps ink from the buffer tank 32 toward the supply reservoir 22.

[0056] The filter 423 removes solid components (aggregates, 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. The supply valve 425 is an electromagnetic valve that opens / closes the ink supply path 421. When the control unit 90 opens the supply valve 425 and operates the supply pump 422, the ink stored in the buffer tank 32 is sent to the supply reservoir 22 via the ink supply path 421.

[0057] The third transport unit 43 transports ink from the recovery reservoir 23 to the buffer tank 32. The third transport unit 43 has an ink recovery path 431, and a recovery pump 432 and a recovery valve 433 that are inserted in the ink recovery path 431.

[0058] The ink recovery path 431 communicates between the recovery reservoir 23 and the buffer tank 32. One end of the ink recovery path 431 is disposed in an ink storage area in the recovery reservoir 23. The other end of the ink recovery path 431 communicates with the interior of the buffer tank 32. The recovery pump 432 pumps ink from the recovery reservoir 23 toward the buffer tank 32. The recovery valve 433 is an electromagnetic valve that opens / closes the ink recovery path 431.

[0059] When the control unit 90 opens the recovery valve 433 and operates the recovery pump 432 , the ink stored in the recovery reservoir 23 is sent to the buffer tank 32 via the ink recovery path 431 .

[0060] The fourth transport unit 44 transports ink from the recovery reservoir 23 to the supply reservoir 22. The fourth transport unit 44 has an inter-reservoir ink flow path 441 and an inter-reservoir pump 442 inserted in the inter-reservoir ink flow path 441.

[0061] The inter-reservoir ink flow path 441 communicates between the supply reservoir 22 and the recovery reservoir 23. One end of the inter-reservoir ink flow path 441 is disposed in an ink storage area in the recovery reservoir 23. The other end of the inter-reservoir ink flow path 441 is disposed in an ink storage area in the supply reservoir 22.

[0062] The inter-reservoir pump 442 is inserted in the inter-reservoir ink flow path 441, and pumps ink from the recovery reservoir 23 toward the supply reservoir 22. When the control unit 90 operates the inter-reservoir pump 442, the ink stored in the recovery reservoir 23 is sent to the supply reservoir 22 via the inter-reservoir ink flow path 441.

[0063] The ink supply device 1 also has a bypass pipe 71 that connects the first communication pipe 55 and the second communication pipe 65, and a bypass valve 72 that is inserted in the bypass pipe 71.

[0064] One end of the bypass pipe 71 is connected in communication with the first communicating pipe 55 on the supply reservoir 22 side relative to the first valve 56. The other end of the bypass pipe 71 is connected in communication with the second communicating pipe 65 on the recovery reservoir 23 side relative to the second valve 66. As a result, the bypass pipe 71 indirectly connects the air layer of the supply reservoir 22 and the air layer of the recovery reservoir 23 via a part of the first communicating pipe 55 and a part of the second communicating pipe 65.

[0065] The bypass valve 72 is an electromagnetic valve that opens / closes the communication of the bypass pipe 71. Therefore, when the bypass valve 72 is opened, the air layer of the supply reservoir 22 and the air layer of the recovery reservoir 23 communicate with each other, and when the bypass valve 72 is closed, the air layer of the supply reservoir 22 and the air layer of the recovery reservoir 23 are blocked from each other. In a normal state, the bypass valve 72 is closed to make the pressures of the supply reservoir 22 and the recovery reservoir 23 different.

[0066] With this configuration, in the ink supply device 1, two ink circulation paths, that is, the small circulation path 11 and the large circulation path 12, are formed.

[0067] The small circulation path 11 is formed by the supply reservoir 22, a plurality of sets of supply pipes 211, the head 21 and the recovery pipes 212, the recovery reservoir 23, and the fourth transport section 44.

[0068] When circulating ink in the small circulation path 11, a pressure difference is generated between the supply reservoir 22 and the recovery reservoir 23 by the first pressure adjustment unit 50 and the second pressure adjustment unit 60, and the inter-reservoir pump 442 of the fourth transport unit 44 is driven. As a result, due to the pressure difference between the supply reservoir 22 and the recovery reservoir 23, an ink flow is generated from the supply reservoir 22 toward the recovery reservoir 23 via the respective supply pipes 211, head 21, and recovery pipes 212. In addition, due to the driving of the inter-reservoir pump 442, an ink flow is generated from the recovery reservoir 23 toward the supply reservoir 22 via the inter-reservoir ink flow path 441.

[0069] The large circulation path 12 is formed by the buffer tank 32, the second transport section 42, the supply reservoir 22, a plurality of sets of supply pipes 211, heads 21 and recovery pipes 212, the recovery reservoir 23, and the third transport section 43.

[0070] When circulating ink in the large circulation path 12, the supply valve 425 of the second transport section 42 is opened to drive the supply pump 422, the recovery valve 433 of the third transport section 43 is opened to drive the recovery pump 432, and a pressure difference is created between the supply reservoir 22 and the recovery reservoir 23 by the first pressure adjustment section 50 and the second pressure adjustment section 60.

[0071] As a result, by driving the supply pump 422, a flow of ink is generated from the buffer tank 32 through the ink supply path 421 toward the supply reservoir 22. Also, due to the pressure difference between the supply reservoir 22 and the recovery reservoir 23, a flow of ink is generated from the supply reservoir 22 through the respective supply pipes 211, head 21, and recovery pipes 212 toward the recovery reservoir 23. Furthermore, by driving the recovery pump 432, a flow of ink is generated from the recovery reservoir 23 through the ink recovery path 431 toward the buffer tank 32.

[0072] In order to prevent ink from coagulating in the head 21 even during standby for printing, during the printing process, and during a maintenance process for the head 21, the control unit 90 controls each unit to constantly generate a flow of ink in the head 21. Specifically, the control unit 90 circulates the ink in the small circulation path 11, the ink in the large circulation path 12, or both.

[0073] At this time, the control unit 90 adjusts the liquid sending amounts of the supply pump 422, the recovery pump 432, and the inter-reservoir pump 442 so that the liquid level of the ink in the supply reservoir 22 detected by the level sensor 221 and the liquid level of the ink in the recovery reservoir 23 detected by the level sensor 231 are within a predetermined range. That is, when the liquid level in the supply reservoir 22 detected by the level sensor 221 falls below the predetermined level, the supply pump 422 is driven to replenish ink to the supply reservoir 22. Also, when the liquid level in the recovery reservoir 23 detected by the level sensor 231 rises above the predetermined level, the recovery pump 432 or the inter-reservoir pump 442 is driven depending on the ink storage amount in the supply reservoir 22 at that time to discharge ink from the recovery reservoir 23 to the buffer bank 32 or the supply reservoir 22.

[0074] When ink is ejected from the head 21 during the printing process or during the maintenance process of the head 21, and the amount of ink in the supply reservoir 22 decreases, the ink level in the supply reservoir 22 drops. In such a case, the control unit 90 recognizes the drop in the liquid level in the supply reservoir 22 based on a detection signal from the level sensor 221. Then, for example, the control unit 90 increases the amount of ink sent by the supply pump 422 to raise the ink level in the supply reservoir 22 and adjust it to be within a predetermined range.

[0075] Furthermore, when the ink in the buffer tank 32 decreases due to the supply of ink from the buffer tank 32 to the head unit 20, the ink level in the buffer tank 32 drops. In such a case, the control unit 90 recognizes the drop in the ink level in the buffer tank 32 based on a detection signal from the level sensor 323. Then, the control unit 90 transports ink in the first transport unit 41 so that the ink level detected by the level sensor 323 falls within a predetermined range.

[0076] <3. How to maintain ink circulation when an abnormality is detected in the pressure adjustment unit> Next, a method for maintaining ink circulation in the ink circulation path including the head 21 when an abnormality is detected in the first pressure adjustment unit 50 or the second pressure adjustment unit 60 will be described with reference to FIGS.

[0077] The control unit 90 detects abnormalities in the first pressure adjustment unit 50 and the second pressure adjustment unit 60 based on pressure values ​​measured by the first pressure gauge 54 of the first pressure adjustment unit 50 and the second pressure gauge 64 of the second pressure adjustment unit 60. That is, the first pressure gauge 54 and the second pressure gauge 64 are detection means for detecting abnormalities in the first pressure adjustment unit 50 and the second pressure adjustment unit 60.

[0078] When the pressure value measured by the first pressure gauge 54 exceeds a predetermined pressure range, the control unit 90 detects an abnormality in the first pressure adjustment unit 50. When the pressure value measured by the second pressure gauge 64 exceeds a predetermined pressure range, the control unit 90 detects an abnormality in the second pressure adjustment unit 60.

[0079] Fig. 3 is a simplified diagram showing the flow of ink in the small circulation path 11 and the large circulation path 12 in a normal state. In Fig. 3 and Figs. 5, 6, 8 to 10 described later, among the first valve 56, the second valve 66, the bypass valve 72, the supply valve 425, and the recovery valve 433, valves in an open state are not shown. Furthermore, out of the multiple heads 21, only one representative head 21 is shown. Fig. 4 is a flowchart showing the flow of the ink circulation maintenance process when an abnormality is detected in the first pressure adjustment unit 50 or the second pressure adjustment unit 60.

[0080] 3, in a normal state, the bypass valve 72 is closed to isolate the air layer in the supply reservoir 22 from the air layer in the recovery reservoir 23, and the pressure in the supply reservoir 22 is maintained at a first negative pressure (weak negative pressure), and the pressure in the recovery reservoir 23 is maintained at a second negative pressure (strong negative pressure). As a result, ink flows in the head 21 disposed between the supply reservoir 22 and the recovery reservoir 23, and the pressure in the head 21 is maintained at a medium negative pressure that is stronger than the first negative pressure (weak negative pressure) and weaker than the second negative pressure (strong negative pressure). Meanwhile, the supply pump 422, the recovery pump 432, and the inter-reservoir pump 442 operate at a timing according to the ink levels in the supply reservoir 22 and the recovery reservoir 23, and ink is circulated through both the small circulation path 11 and the large circulation path 12.

[0081] 4, when an abnormality is detected in the first pressure adjustment unit 50 or the second pressure adjustment unit 60, the control unit 90 first closes the valves 56, 66 on the pressure adjustment unit 50, 60 side where the abnormality was detected (step S101: abnormal side shutoff process). Specifically, when an abnormality is detected in the first pressure adjustment unit 50, the control unit 90 closes the first valve 56 on the first pressure adjustment unit 50 side. Furthermore, when an abnormality is detected in the second pressure adjustment unit 60, the control unit 90 closes the second valve 66 on the second pressure adjustment unit 60 side.

[0082] Furthermore, in step S101, the control unit 90 stops all pumps in operation in parallel. That is, the supply pump 422, the recovery pump 432, and the inter-reservoir pump 442, which are operating in the normal state, are stopped. The supply valve 425 and the recovery valve 433 are also closed.

[0083] When step S101 is completed, the control unit 90 opens the bypass valve 72 (step S102: bypass opening step). At the same time as the start of step S102, or following step S102, the control unit 90 adjusts the negative pressure supplied by the normal pressure adjustment unit 50, 60 that has not detected an abnormality to a third negative pressure (step S103: pressure change step). Specifically, when an abnormality of the first pressure adjustment unit 50 is detected, the control unit 90 adjusts the negative pressure supplied by the second pressure adjustment unit 60 to a third negative pressure. Also, when an abnormality of the second pressure adjustment unit 60 is detected, the control unit 90 adjusts the negative pressure supplied by the first pressure adjustment unit 50 to a third negative pressure. Here, the third negative pressure is a medium negative pressure that is stronger than the first negative pressure (weak negative pressure) and weaker than the second negative pressure (strong negative pressure).

[0084] Fig. 5 is a simplified diagram showing the flow of ink in the small circulation path 11 and the large circulation path 12 at the beginning of step S103 when an abnormality occurs in the first pressure adjustment unit 50. Fig. 6 is a simplified diagram showing the flow of ink in the small circulation path 11 and the large circulation path 12 at the completion of step S103 when an abnormality occurs in the first pressure adjustment unit 50.

[0085] 5, at the start of step S103, the bypass valve 72 is opened, the supply reservoir 22 and the recovery reservoir 23 have the same pressure, and the flow of ink is stopped. In this state, the negative pressure supplied by the second pressure adjustment unit 60 is changed from the second negative pressure (strong negative pressure) to the third negative pressure (medium negative pressure). As a result, at the completion of step S103, the pressures of the supply reservoir 22 and the recovery reservoir 23 both become the third negative pressure (medium negative pressure), and the pressure inside the head 21 communicating with the supply reservoir 22 and the recovery reservoir 23 also becomes the third negative pressure (medium negative pressure) (see FIG. 6).

[0086] As a result, the pressure inside the head 21 upon completion of step S103 becomes close to the pressure inside the head 21 in the normal state. This maintains a meniscus in the nozzle of the head 21, and prevents ink from leaking from the nozzle.

[0087] After completing step S103, the control unit 90 maintains the negative pressure supplied by the normal side pressure adjustment units 50, 60 that have not detected an abnormality at the third negative pressure. The control unit 90 also executes an abnormality ink circulation process (step S200) that generates a flow of ink from the supply reservoir 22 through the multiple heads 21 toward the collection reservoir 23.

[0088] As examples of the abnormality-induced ink circulation process (step S200), an abnormality-induced ink circulation process using only the small circulation path 11 and an abnormality-induced ink circulation process using both the small circulation path 11 and the large circulation path 12 will be described below.

[0089] FIG. 7 is a flow chart showing the flow of the ink circulation process (step S200) when an abnormality occurs using only the small circulation path 11. As shown in FIG. 7, in the ink circulation process when an abnormality occurs using only the small circulation path 11, the control unit 90 repeatedly executes a head difference generating process (step S211) and a standby process (step S212). FIG. 8 is a simplified diagram showing the ink flow in the small circulation path 11 and the large circulation path 12 in the head difference generating process (step S211). FIG. 9 is a simplified diagram showing the ink flow in the small circulation path 11 and the large circulation path 12 in the standby process (step S212).

[0090] In the head difference generating step (step S211), the control unit 90 drives the inter-reservoir pump 442 to send ink from the recovery reservoir 23 to the supply reservoir 22 via the inter-reservoir ink flow path 441 so that the ink level in the supply reservoir 22 is higher than the ink level in the recovery reservoir 23. This generates a head difference between the supply reservoir 22 and the recovery reservoir 23, as shown in Fig. 8. When the control unit 90 determines from the measurement values ​​of the level sensors 221, 231 that a predetermined head difference has occurred, it ends the head difference generating step (step S211).

[0091] Next, in the standby step (step S212), the control unit 90 stops the inter-reservoir pump 442 and waits until ink moves from the supply reservoir 22 to the recovery reservoir 23 via the multiple heads 21 due to the head difference, and the difference in liquid level between the supply reservoir 22 and the recovery reservoir 23 becomes small. This reduces the head difference between the supply reservoir 22 and the recovery reservoir 23, as shown in Fig. 9. When the control unit 90 determines from the measurement values ​​of the level sensors 221, 231 that the head difference has become equal to or less than a predetermined threshold, it ends the standby step (step S212) and returns to the head difference generating step (step S211).

[0092] By using this method, a head difference is created between the supply reservoir 22 and the recovery reservoir 23, thereby circulating ink in the small circulation path 11, and by ensuring back pressure against the nozzles of the head 21, ink leakage from the nozzles is suppressed while a flow of ink is generated within the head 21, thereby suppressing ink aggregation within the head 21.

[0093] In this way, ink is circulated within the small circulation path 11 by utilizing the head difference occurring between the supply reservoir 22 and the recovery reservoir 23. It is desirable to continue this ink circulation process during an abnormality (step S200) until the pressure adjustment mechanism 50 or 60 is repaired by a serviceman or the like. Note that ink may continue to be ejected from the head 21 during the period from when an abnormality in the pressure adjustment mechanism 50 or 60 is detected until the repair is completed. This makes it possible to more reliably prevent the nozzles from drying out. On the other hand, it is also possible not to eject ink from the head 21 during the period. This makes it possible to more reliably maintain the shape of the meniscus.

[0094] 10 is a simplified diagram showing the flow of ink in an abnormal ink circulation process using the small circulation path 11 and the large circulation path 12. In this method, the control unit 90 operates the supply pump 422 and the recovery pump 432 at the same or similar liquid delivery rates, and operates the inter-reservoir pump 442 at a smaller liquid delivery rate than the supply pump 422 and the recovery pump 432.

[0095] 10, an ink flow from the supply reservoir 22 to the recovery reservoir 23 occurs within the head 21. In this method, the supply pump 422 supplies ink from the buffer tank 332 to the supply reservoir 22, and the inter-reservoir pump 442 supplies ink from the recovery reservoir 23 to the supply reservoir 22.

[0096] In this manner, the ink flow rate in the head 21 can be increased by generating an ink flow in the head 21 using the large circulation path 12. Therefore, even if the head unit 20 has a large number of heads 21 and the flow path resistance of the multiple heads 21 is high, an ink flow can be reliably generated inside each head 21. As a result, ink coagulation in the head 21 can be suppressed by generating an ink flow in the head 21 while ink leakage from the nozzles is suppressed by ensuring back pressure against the nozzles.

[0097] <4. Modifications> Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

[0098] In the above embodiment, a water-based pigment ink is used as the ink, but the present invention is not limited to this. The ink may be an oil-based ink or a dye ink.

[0099] 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.

[0100] In the above embodiment, the first valve 56, the second valve 66, the bypass valve 72, the supply valve 425, and the recovery valve 433 are described as solenoid valves, but they do not necessarily have to be solenoid valves. For example, motor-operated valves can also be used for these valves.

[0101] Furthermore, the elements appearing in the above-described embodiments and modifications may be combined as appropriate to the extent that no contradiction arises. [Explanation of symbols]

[0102] 1: Ink supply device 9:Printing device 11: Small circulation pathway 12: Major circulation route 21: Head 22: Supply reservoir 23: Recovery reservoir 31: Drum Tank 32: Buffer tank 50: First pressure adjustment section 51: First air tank 54: First pressure gauge 55: 1st communication pipe 56: First valve 60: Second pressure adjusting section 61: Second air tank 64: Second pressure gauge 65:Second communication pipe 66: Second valve 71: Bypass pipe 72: Bypass valve 90: Control section 221: First level sensor 231: Second level sensor 332: Buffer tank 421: Ink supply path 422: Supply pump 425: Supply valve 431: Ink recovery passage 432: Recovery pump 433: Recovery valve 441: Ink flow path between reservoirs 442: Reservoir pump

Claims

1. An ink supply device for supplying ink to a head in an inkjet printing device, comprising: a supply reservoir that stores the ink to be supplied to the head; a recovery reservoir that stores the ink recovered from the head; an inter-reservoir ink flow path that transfers the ink from the recovery reservoir to the supply reservoir; A first pressure regulator that supplies a negative pressure to the supply reservoir; a first communication pipe that communicates the first pressure adjustment unit with an air layer of the supply reservoir; a first valve inserted in the first communication pipe; A second pressure regulator that supplies a negative pressure to the collection reservoir; a second communication pipe that communicates the second pressure adjustment unit with an air space in the recovery reservoir; a second valve inserted in the second communication pipe; a bypass pipe communicating an air space of the supply reservoir with an air space of the recovery reservoir; A bypass valve inserted in the bypass pipe; a detection means for detecting an abnormality in the first pressure adjustment unit and the second pressure adjustment unit; a control unit that controls the operation of the first pressure adjustment unit, the first valve, the second pressure adjustment unit, the second valve, and the bypass valve; Equipped with The control unit, during normal operation, opening the first valve and the second valve and closing the bypass valve; causing the first pressure regulator to supply a first negative pressure to the supply reservoir; causing the second pressure adjusting unit to supply a second negative pressure to the collection reservoir, the second negative pressure being stronger than the first negative pressure; When the detection means detects an abnormality in one of the first pressure adjustment unit and the second pressure adjustment unit, a) an abnormality side shutoff step of closing one of the first valve and the second valve, which corresponds to one of the pressure adjustment units in which an abnormality has been detected by the detection means; b) a bypass opening step of opening the bypass valve after the step a); c) a pressure changing step of adjusting, after the step a), a negative pressure supplied by the other pressure adjustment unit, of the first pressure adjustment unit and the second pressure adjustment unit, for which the detection means has not detected an abnormality, to a third negative pressure that is stronger than the first negative pressure and weaker than the second negative pressure; d) an ink circulation step of, after the step c), generating a flow of the ink from the supply reservoir through the plurality of heads toward the recovery reservoir while maintaining the negative pressure supplied by the other pressure adjustment unit at the third negative pressure; and An ink supply device that performs the above steps.

2. 2. The ink supply device according to claim 1, an inter-reservoir pump that is inserted in the inter-reservoir ink flow path and pumps the ink from the recovery reservoir toward the supply reservoir; and The control unit, in the step d), d1) a head difference generating step of driving the inter-reservoir pump to send the ink from the recovery reservoir to the supply reservoir through the inter-reservoir ink flow path so that the ink level in the supply reservoir is higher than the ink level in the recovery reservoir; d2) after d1), stopping the inter-reservoir pump and waiting until the ink moves from the supply reservoir to the recovery reservoir via the heads due to a head difference and a difference in liquid level between the supply reservoir and the recovery reservoir becomes small; 2. An ink supply device comprising:

3. 2. The ink supply device according to claim 1, a tank for storing the ink to be supplied to the supply reservoir; an ink supply passage communicating between the tank and the supply reservoir; a supply pump that is inserted in the ink supply path and pumps the ink from the tank toward the supply reservoir; an ink recovery passage communicating between the recovery reservoir and the tank; a recovery pump that is inserted in the ink recovery path and pumps the ink from the recovery reservoir toward the tank; an inter-reservoir pump that is inserted in the inter-reservoir ink flow path and pumps the ink from the recovery reservoir toward the supply reservoir; and In the ink supply device, in step d), the control unit operates the supply pump and the recovery pump at the same or similar liquid delivery rates, and operates the inter-reservoir pump at a smaller liquid delivery rate than the supply pump and the recovery pump.

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