Deaeration unit, inkjet recording device, deaeration method and program

Abstract

To provide a deaeration unit, an inkjet recording device, a deaeration method and a program which can reduce printing downtime.SOLUTION: The deaeration unit is provided with an external reflux-type deaeration module 451 in which a gas permeation film (a hollow fiber film 4512) that can deaerate dissolved gas in ink is provided, and a control part 50 that executes ejection control of ejecting ink infiltrating into the gas permeation film. The control part executes control of ejecting ink of a plurality of colors simultaneously. The control part 50 determines the number of colors of ink to which the ejection control is executed simultaneously, according to degrees of clogging of the gas permeation film sensed by a sensing part (the control part 50).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a degassing device, an inkjet recording device, a degassing method, and a program. [Background technology]

[0002] Inkjet recording devices are known that eject ink from the nozzles of an inkjet head to form an image on the recording surface of a recording medium. In inkjet recording devices, residual bubbles of gas dissolved in the ink can cause problems such as ink not being ejected from the nozzles. For this reason, inkjet recording devices equipped with an external reflux degassing module on the ink supply path that supplies ink from an ink tank to the inkjet head are known. The degassing module contains multiple gas-permeable membranes, such as hollow fiber membranes, within a hollow cylindrical body. The degassing module has a vacuum pump connected to at least one end of the gas-permeable membrane, allowing the pressure inside the gas-permeable membrane to be reduced. When ink comes into contact with the interface of the gas-permeable membrane, the internal pressure of which has been reduced, the dissolved gas in the ink passes through the gas-permeable membrane and is removed (degassed).

[0003] As the degassing module is used, it becomes clogged with ink components that have infiltrated into the gas-permeable membrane. As a result, the degassing performance of the degassing module deteriorates. Because degassing modules are expensive, it is not cost-effective to replace the degassing module every time its degassing performance deteriorates. Therefore, a configuration has been disclosed in which ink components that have infiltrated into the tube of the hollow fiber membrane are discharged by opening a hollow fiber valve (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-168257 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the configuration described in Patent Document 1 has a problem in that when ink component discharge control is performed for multiple colors, it takes time for the number of colors. Since printing is not possible during discharge control, if the time required for the number of colors is required, long periods of printing downtime occur.

[0006] An object of the present invention is to provide a degassing device, an inkjet recording device, a degassing method, and a program that can reduce printing downtime. [Means for solving the problem]

[0007] The invention described in claim 1 has been made to achieve the above object, In the degassing device, an external circulation type degassing module having a gas permeable membrane therein capable of degassing dissolved gas in ink; a control unit that performs discharge control to discharge the ink that has permeated the gas-permeable membrane; Equipped with The control unit is characterized in that it simultaneously performs the discharge control for a plurality of colors.

[0008] The invention described in claim 2 is the degassing device described in claim 1, a detection unit capable of detecting a degree of clogging of the gas-permeable membrane; The control unit determines the number of colors for which the discharge control is to be performed simultaneously in accordance with the degree of clogging detected by the detection unit.

[0009] The invention described in claim 3 is the degassing device described in claim 2, The control unit determines the number of colors for which the discharge control is to be performed simultaneously based on the degree of clogging and a predetermined threshold value.

[0010] The invention described in claim 4 is the degassing device described in claim 2, The detection unit detects the degree of clogging of the gas-permeable membrane using a difference between the pressure on the upstream side of the degassing module and the pressure on the downstream side of the degassing module.

[0011] The invention described in claim 5 is the degassing device described in claim 2, The detection unit is characterized in that it detects the degree of clogging of the gas-permeable membrane by using the time it takes for the air pressure inside the gas-permeable membrane to reach a predetermined air pressure when the inside of the gas-permeable membrane, which is open to the atmosphere, is evacuated.

[0012] The invention described in claim 6 is the degassing device described in claim 2, The detection unit is characterized in that it detects the degree of clogging of the gas-permeable membrane using the flow rate of air inside the gas-permeable membrane when the inside of the gas-permeable membrane, which has been depressurized, is opened to the atmosphere.

[0013] The invention described in claim 7 is the degassing device described in claim 1, The ink is characterized by being a UV ink.

[0014] The invention described in claim 8 is In the inkjet recording apparatus, an external circulation type degassing module provided between an ink storage section that stores ink and an ink ejection head that ejects ink from nozzles, the external circulation type degassing module having an internal gas permeable membrane that can degas dissolved gas in the ink; a control unit that performs discharge control to discharge the ink that has permeated the gas-permeable membrane; Equipped with The control unit is characterized in that it simultaneously performs the discharge control for a plurality of colors.

[0015] The invention described in claim 9 is A degassing method for a degassing device equipped with an external circulation type degassing module having an internal gas permeable membrane capable of degassing dissolved gas in ink, comprising: a control step of performing discharge control to discharge ink that has infiltrated into the gas-permeable membrane; The control step is characterized in that the discharge control is performed simultaneously for a plurality of colors.

[0016] The invention described in claim 10 is a computer of a degassing device equipped with an external reflux type degassing module having an internal gas permeable membrane capable of degassing dissolved gas in ink; functioning as a control unit that performs discharge control to discharge ink that has infiltrated into the gas-permeable membrane; The control unit is a program that performs the discharge control for a plurality of colors simultaneously. [Effects of the Invention]

[0017] According to the present invention, printing downtime can be reduced. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram illustrating a schematic configuration of an inkjet recording apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a functional block diagram showing a control structure of the inkjet recording apparatus according to the present embodiment. [Figure 3] FIG. 2 is a diagram showing a schematic configuration of a liquid delivery unit. [Figure 4] FIG. 2 is a diagram showing the configuration of a degassing module. [Figure 5] 5 is a flowchart illustrating an example of control of the inkjet recording apparatus according to the present embodiment. [Figure 6] FIG. 1 is a diagram showing an example of a simplified flow path diagram in the vicinity of a degassing module. [Figure 7] FIG. 10 is a diagram showing an example of pressure transition during discharge control. [Figure 8] FIG. 10 is a diagram illustrating an example of the relationship between the pressure difference increase rate and the discharge amount. [Figure 9] 6 is a flowchart showing an example of simultaneous discharge control performed in step S118 of FIG. 5. [Figure 10] 10A and 10B are diagrams illustrating an example of the calculated upstream pressure, downstream pressure, and pressure difference for each color. [Figure 11] FIG. 10 is a diagram in which the calculated pressure differences Δi for each color are sorted in ascending order. [Figure 12] FIG. 10 is a diagram showing an example of the results of grouping the pressure differences of the respective colors arranged in ascending order. [Figure 13] FIG. 10 is a diagram showing an example of a transition of the upstream pressure when the vacuum pump is driven. [Figure 14] FIG. 10 is a diagram showing another example of a simplified flow path diagram in the vicinity of the degassing module. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0020] 1 and 2, the inkjet recording apparatus 1 according to this embodiment includes a paper feed unit 10, an image forming unit 20, a paper discharge unit 30, a liquid delivery unit 40, a control unit 50, and a notification unit 60. The liquid delivery unit 40 and the control unit 50 function as a degassing device 100 of the present invention.

[0021] The inkjet recording device 1 transports the recording medium P from the paper feed unit 10 to the image forming unit 20 under the control of the control unit 50. Then, the control unit 50 forms an image on the recording medium P in the image forming unit 20 using ink supplied from the liquid delivery unit 40. After the image formation, the control unit 50 ejects the recording medium P to the paper ejection unit 30.

[0022] The paper feed unit 10 stores recording media P before image formation. The paper feed unit 10 transports the recording media P to the image forming unit 20 under the control of the control unit 50. The paper feed unit 10 includes a paper feed tray 11 and a transport unit 12.

[0023] The paper feed tray 11 is a plate-like member that stores recording media P. The paper feed tray 11 is provided so that one or more recording media P can be placed on it. The paper feed tray 11 moves up and down depending on the amount of recording media P placed on it. By this up and down movement, the paper feed tray 11 is held at a position where the top recording medium P can be transported by the transport unit 12.

[0024] The conveying unit 12 conveys the recording medium P from the paper feed tray 11 to the image forming unit 20. The conveying unit 12 includes a conveying mechanism. The conveying mechanism drives a belt 123 to convey the recording medium P on the belt 123. The belt 123 is ring-shaped, and the inside of the ring is supported by multiple rollers 121 and 122. The conveying unit 12 includes a supplying unit. The supplying unit delivers the top recording medium P placed on the paper feed tray 11 onto the belt 123. The conveying unit 12 uses the supplying unit to convey the recording medium P along the belt 123.

[0025] Under the control of the control unit 50, the image forming unit 20 cooperates with the liquid supply unit 40 to record an image on the recording medium P. The image forming unit 20 includes an image forming drum 21, a delivery unit 22, a paper heating unit 23, a head unit 24, an irradiation unit 25, and a delivery unit 26.

[0026] The image forming drum 21 carries the recording medium P along its cylindrical outer circumferential surface and transports the recording medium P as it rotates. The transport surface of the image forming drum 21 faces the paper heating unit 23, the head unit 24, and the irradiation unit 25, and performs an image forming process on the transported recording medium P.

[0027] The delivery unit 22 is provided at a position interposed between the conveying section 12 and the image forming drum 21. The delivery unit 22 includes a claw portion 221 and a delivery drum 222.

[0028] The claw portion 221 is a cylindrical member that holds one end of the recording medium P conveyed by the conveying unit 12. The delivery drum 222 is a member that guides the recording medium P held by the claw portion 221.

[0029] The delivery unit 22 picks up the recording medium P on the conveying section 12 with the claw portion 221 and moves it along the outer circumferential surface of the delivery drum 222. The delivery unit 22 delivers the recording medium P to the image forming drum 21 by this operation.

[0030] The paper heating unit 23 includes, for example, an electric heating wire, and generates heat in response to the passage of electricity. The paper heating unit 23 is controlled by the control unit 50, and generates heat so that the recording medium P passing nearby reaches a predetermined temperature. The paper heating unit 23 is located near the outer circumferential surface of the image forming drum 21 and is positioned upstream of the head unit 24 in the conveying direction of the recording medium P.

[0031] A temperature sensor (not shown) is provided near the paper heating unit 23. The control unit 50 uses the temperature sensor to detect the temperature near the paper heating unit 23. The control unit 50 controls the heat generation of the paper heating unit 23 based on the detected temperature.

[0032] The head units 24 form an image by ejecting ink droplets from nozzles onto the recording medium P. The head units 24 are provided corresponding to the colors C (cyan), M (magenta), Y (yellow), and K (black). In FIG. 1, the head units 24 corresponding to the colors Y, M, C, and K are provided in this order from upstream in the conveyance direction of the recording medium P.

[0033] Here, in a plan view, the direction perpendicular to the transport direction of the recording medium P is defined as the width direction. In this embodiment, a plurality of head units 24 are arranged in the width direction with a length (width) that covers the entire recording medium P. In other words, the inkjet recording apparatus 1 is a one-pass line head type inkjet recording apparatus. The head unit 24 is configured by arranging a plurality of inkjet heads 24a (see FIG. 3). The inkjet heads 24a are ink ejection heads of the present invention that eject ink from nozzles. The number of head units 24 may be five or more or three or less. Alternatively, the head unit 24 may be configured by a single inkjet head 24a.

[0034] The ink ejected by the head unit 24 is, for example, ultraviolet curable ink (UV ink). The ultraviolet curable ink is a gel ink that changes phase between a gel state and a liquid state depending on the temperature when not irradiated with ultraviolet light from the irradiation unit 25. The ultraviolet curable ink has a phase change temperature of, for example, about 40 to 100°C, and is uniformly liquefied (solized) when heated to or above the phase change temperature. On the other hand, the ultraviolet curable ink gels at about normal room temperature, that is, about 0 to 30°C.

[0035] The irradiation unit 25 includes, for example, a fluorescent tube such as a low-pressure mercury lamp. The irradiation unit 25 emits energy rays such as ultraviolet light by emitting light from the fluorescent tube. The irradiation unit 25 is provided near the outer peripheral surface of the image forming drum 21. The irradiation unit 25 is also provided so as to be located downstream of the head unit 24 in the transport direction of the recording medium P. The irradiation unit 25 irradiates the recording medium P onto which ink has been ejected with energy rays. The ink on the recording medium P is cured by the action of the energy rays.

[0036] The fluorescent tube that emits ultraviolet light is not limited to a low-pressure mercury lamp. The fluorescent tube may be a mercury lamp with an operating pressure of, for example, several hundred Pa to 1 MPa. The fluorescent tube may also be a light source that can be used as a germicidal lamp. Light sources that can be used as germicidal lamps include, for example, cold cathode fluorescent lamps, ultraviolet laser light sources, metal halide lamps, and light-emitting diodes. Among these, it is desirable that the fluorescent tube is a light source that can irradiate ultraviolet light with higher illuminance and is energy-saving. The fluorescent tube is, for example, a light-emitting diode. The energy rays are not limited to ultraviolet light, and may be any energy rays that have the property of curing ink depending on the properties of the ink. The light source is also replaced depending on the energy rays.

[0037] Although the above description exemplifies a case in which the head unit 24 ejects ultraviolet curable ink, the present invention is not limited to this. The ink ejected by the head unit 24 may be a water-based ink or ink having other physical properties.

[0038] The delivery unit 26 includes a transport mechanism. The transport mechanism drives a ring-shaped belt 263, the inside of which is supported by a plurality of rollers 261 and 262, to transport the recording medium P. The delivery unit 26 includes a cylindrical delivery roller 264. The delivery roller 264 delivers the recording medium P from the image forming drum 21 to the transport mechanism. The delivery unit 26 transports the recording medium P delivered onto the belt 263 by the delivery roller 264, and sends it out to the paper discharge unit 30.

[0039] The recording medium P on which an image has been formed in the image forming unit 20 is discharged to the paper discharge unit 30. The paper discharge unit 30 includes a plate-shaped paper discharge tray 31. The recording medium P sent out from the image forming unit 20 by the delivery unit 26 is placed on the paper discharge tray 31. The paper discharge unit 30 stores the recording medium P until the user removes it.

[0040] FIG. 3 shows a schematic configuration of the liquid delivery section 40. The liquid supply unit 40 includes a plurality of main tanks 41 that store ink of each color. The liquid supply unit 40 supplies the ink of each color in the main tanks 41 to each head unit 24. Through this control, the liquid supply unit 40 enables the ink of each color to be ejected from the nozzles.

[0041] The liquid delivery unit 40 includes a main tank 41, which is an ink storage unit, a first sub-tank 42, and a second sub-tank 43. The liquid delivery unit 40 also includes a degassing module 451 that degasses dissolved gas in the ink before delivery to the head unit 24.

[0042] The main tank 41 is a tank that stores ink to be supplied to each part of the liquid delivery unit 40. The main tank 41 is, for example, a rigid, sealed tank made of metal. The main tank 41 is in communication with the first sub-tank 42 via a supply pipe 44. A supply pump 441 and a supply valve 442 are provided in the supply pipe 44.

[0043] The supply pump 441 and the supply valve 442 operate under the control of the control unit 50. When the supply valve 442 is open, the ink in the main tank 41 is supplied to the first sub-tank 42 via the supply pipe 44 by driving the supply pump 441. The main tank 41 is replaceable as a whole. Furthermore, the main tank 41 is detachable from the supply pipe 44 regardless of the driving status of the supply pump 441.

[0044] The first sub-tank 42 is one or more ink chambers having a smaller volume than the main tank 41. The first sub-tank 42 stores ink pumped from the main tank 41 by the supply pump 441. The first sub-tank 42 reduces pressure fluctuations caused by pulsation when the supply pump 441 supplies ink from the main tank 41. The first sub-tank 42 recovers ink that has not been discharged from the inkjet head 24a from an outlet. The first sub-tank 42 is in communication with the second sub-tank 43 via a liquid supply pipe 45. The liquid supply pipe 45 is provided with a degassing module 451, a liquid supply pump 452, a liquid supply valve 453, etc.

[0045] The liquid supply pump 452 sends the ink flowing out from the ink outlet 4511b (see FIG. 4) of the degassing module 451 to the second sub-tank 43. A check valve (not shown) is provided between the liquid supply pump 452 and the second sub-tank 43 to prevent the ink sent to the second sub-tank 43 from flowing back.

[0046] The liquid supply valve 453 is an electromagnetic valve that selectively opens and closes the liquid supply pipe 45 under the control of the control unit 50 when the liquid supply pump 452 is operating.

[0047] The second subtank 43 is a small tank chamber in which ink degassed by the degassing module 451 is temporarily stored. The capacity of the second subtank 43 is, for example, approximately the same as that of the first subtank 42. The second subtank 43 is connected to the inlets of each inkjet head 24a via a supply path 46. The ink in the second subtank 43 is supplied to each inkjet head 24a in accordance with the amount of ink ejected from the nozzle. The second subtank 43 is also provided with a back pressure adjustment means (not shown). The back pressure adjustment means applies an appropriate negative pressure to the inkjet head 24a to prevent ink from leaking.

[0048] Figure 4 shows the configuration of the degassing module. The degassing module 451 removes dissolved gas from the ink that has flowed in and discharges the degassed ink. The degassing module 451 includes an ink flow chamber 4511, a hollow fiber membrane 4512, a first vacuum chamber 4513, and a second vacuum chamber 4514. In other words, the degassing module 451 is an external reflux type degassing module that has the hollow fiber membrane 4512 inside. The degassing module 451 is provided between the ink storage section (main tank 41, first sub-tank 42) and the inkjet head 24a.

[0049] The ink circulation chamber 4511 is provided in the center of the interior of the casing that forms the degassing module 451. The ink circulation chamber 4511 is provided with an ink inlet 4511a and an ink outlet 4511b. The ink circulation chamber 4511 receives ink flowing in from the first sub-tank 42 via the ink inlet 4511a. The ink circulation chamber 4511 also allows ink to flow out to the second sub-tank 43 via the ink outlet 4511b.

[0050] It is preferable that ink inlet 4511a is provided on the first end side of ink flow chamber 4511. It is also preferable that ink outlet 4511b is provided on the second end side of ink flow chamber 4511. With this configuration, ink can more easily come into contact with hollow fiber membrane 4512, thereby improving the degassing efficiency of degassing module 451.

[0051] The hollow fiber membrane 4512 is tubular, and its membrane surface is gas permeable. The hollow fiber membrane 4512 is a gas permeable membrane of the present invention, and has a multiplicity of hollow fine fiber structures. The hollow fiber membrane 4512 is arranged so that the multiplicity of hollow fine fiber structures form a bundle and extend in the axial direction of the ink flow chamber 4511.

[0052] Hollow fiber membrane 4512 is disposed so as to communicate with first vacuum chamber 4513 and second vacuum chamber 4514. Therefore, a first end of hollow fiber membrane 4512 is connected to the atmosphere via hollow fiber valve 4513c. A second end of hollow fiber membrane 4512 is connected to vacuum pump 4514e.

[0053] The first vacuum chamber 4513 is provided at a first end of the degassing module 451. The first vacuum chamber 4513 is separated from the ink flow chamber 4511 by a partition wall. The side of the first vacuum chamber 4513 facing the ink flow chamber 4511 is connected to the atmosphere by a first vacuum path 4513a. A first pressure sensor 4513b, a hollow fiber valve 4513c, and the like are provided in the first vacuum path 4513a.

[0054] The first pressure sensor 4513b detects the pressure value inside the first vacuum chamber 4513 and transmits the pressure value to the control unit 50. Hollow fiber valve 4513c is an electromagnetic valve, and in response to a control signal from control unit 50, hollow fiber valve 4513c opens first vacuum path 4513a to the atmosphere.

[0055] Second vacuum chamber 4514 is provided on the second end side of degassing module 451. Second vacuum chamber 4514 is separated from ink flow chamber 4511 by a partition wall. Second vacuum chamber 4514 communicates with reduced pressure tank 4514c via second vacuum path 4514a. Second vacuum path 4514a is provided with second pressure sensor 4514b that detects the pressure value therein.

[0056] Second pressure sensor 4514b detects the pressure inside second vacuum chamber 4514 and transmits the pressure value to control unit 50. Control unit 50 controls the operation of degassing module 451 according to the pressure values ​​acquired from first pressure sensor 4513b and second pressure sensor 4514b. Note that, although the configuration in which second pressure sensor 4514b is provided in the flow path between degassing module 451 and reduced pressure tank 4514c is illustrated, the present invention is not limited to this. Second pressure sensor 4514b may also be provided in the flow path between reduced pressure tank 4514c and vacuum pump 4514e.

[0057] The reduced pressure tank 4514c includes an ink discharge valve 4514d and a vacuum pump 4514e. The reduced pressure tank 4514c can store a predetermined volume of gas and can suppress pressure fluctuations inside the hollow fiber membrane 4512 due to pulsation of the vacuum pump 4514e. The reduced pressure tank 4514c stores ink that has permeated the hollow fiber membrane 4512 and entered the second vacuum path 4514a. Storing ink in the reduced pressure tank 4514c prevents the ink from reaching the vacuum pump 4514e and causing it to break down. The ink stored inside the reduced pressure tank 4514c is discharged to the outside by the ink discharge valve 4514d.

[0058] The vacuum pump 4514e is a diaphragm pump. Specifically, the vacuum pump 4514e includes a pump chamber with an expandable diaphragm. The vacuum pump 4514e includes a drive source and the like that operates the diaphragm so that the volume of the pump chamber expands and contracts. The pump chamber includes an intake port with a check valve that only allows fluid to flow in from the outside. The pump chamber includes an exhaust port with a check valve that only allows fluid to flow out from the inside.

[0059] Under the control of control unit 50, vacuum pump 4514e sucks air from hollow fiber membrane 4512 when hollow fiber valve 4513c is open. This operation of vacuum pump 4514e removes foreign matter from hollow fiber membrane 4512 and reduces the pressure inside hollow fiber membrane 4512. Therefore, when ink flowing into ink flow chamber 4511 comes into contact with the membrane surface of hollow fiber membrane 4512, dissolved gas selectively permeates the membrane surface and is degassed. In other words, dissolved gas (dissolved oxygen) in the ink can be degassed (removed). The dissolved gas that has passed through hollow fiber membrane 4512 then flows down to decompression tank 4514c via second vacuum chamber 4514.

[0060] In the present invention, an external reflux type degassing module 451 configured as described above is employed. The form of the degassing module 451 is not limited, but it is preferable to use, for example, a sheet in which a plurality of hollow fiber membranes 4512 are woven together in a mesh pattern. This is because the mesh of the hollow fiber membranes 4512 becomes finer, making it easier for all of the ink to pass through the mesh of the hollow fiber membranes 4512, thereby making it easier to improve degassing efficiency. Furthermore, with this configuration, even flexible hollow fiber membranes 4512 can easily achieve a certain level of strength.

[0061] The control unit 50 controls each unit that constitutes the inkjet recording apparatus 1. The control unit 50 is connected to each unit that constitutes the inkjet recording apparatus 1. The control unit 50 includes a CPU 51, a RAM 52, and a ROM 53. The control unit 50 performs discharge control to discharge the ink that has soaked into the hollow fiber membrane 4512. The control unit 50 also functions as a detection unit of the present invention that can detect the degree of clogging of the hollow fiber membrane 4512.

[0062] The CPU 51 reads and executes various programs and data according to the processing content from a storage device such as the ROM 53. The CPU 51 also controls the operation of each part of the inkjet recording apparatus 1 according to the processing content executed. The RAM 52 temporarily stores various programs and data to be processed by the CPU 51 . The ROM 53 stores various programs and data that are read by the CPU 51 and the like.

[0063] The notification unit 60 notifies various pieces of information under the control of the control unit 50. The notification unit 60 is, for example, a display unit having a screen, or a communication unit capable of communicating with other devices via a network.

[0064] Next, the control of the inkjet recording apparatus 1 according to this embodiment will be described with reference to the flowchart of Fig. 5. The control of Fig. 5 is a control in which the inkjet recording apparatus 1 simultaneously performs discharge control for multiple colors. The control of Fig. 5 is started, for example, when the inkjet recording apparatus 1 is turned on. The control of Fig. 5 may be executed automatically at regular time intervals or manually.

[0065] In this control, the control unit 50 determines the number of colors for which discharge control is to be performed simultaneously depending on the detected degree of clogging of the hollow fiber membranes 4512. In the example shown in Fig. 5, the control unit 50 detects the degree of clogging using the difference (pressure difference) between the upstream pressure and the downstream pressure of the degassing module 451. 6 shows an example of a simplified flow path diagram near the degassing module 451. For convenience of explanation, the two color CK degassing modules 451 out of the four color YMCK degassing modules 451 are omitted. A first pressure sensor 4513b is provided upstream of the degassing module 451 for each color (on the hollow fiber valve 4513c side). A second pressure sensor 4514b is provided downstream of the degassing module 451 for each color (on the vacuum pump 4514e side). This makes it possible to detect the difference between the pressure upstream and the pressure downstream of the degassing module 451 for each color. FIG. 7 shows an example of pressure transition during discharge control. Reference symbol L1 in FIG. 7 indicates the pressure upstream of the degassing module 451 (on the hollow fiber valve 4513c side). Reference symbol L2 indicates the pressure downstream of the degassing module 451 (on the vacuum pump 4514e side). In the example shown in FIG. 7, it can be seen that the pressure difference while the hollow fiber valve is open (reference symbol T1) is larger than the pressure difference during steady operation (reference symbol T2). This is because the flow rate is high while the hollow fiber valve is open, and the difference in resistance due to clogging of the hollow fiber membrane 4512 is easily detected as a pressure difference. The timing for acquiring (detecting) the pressure difference is not particularly limited, and may be while the hollow fiber valve is open or during steady operation. However, considering that the pressure difference is easier to detect, it is more preferable to acquire (detect) the pressure difference while the hollow fiber valve is open. Hereinafter, the control for simultaneously performing discharge control for a plurality of colors will be described with reference to the flowchart of FIG.

[0066] First, the control unit 50 defines a serial number as a variable i and the total number of colors as a constant n (step S101). For example, if the total number of colors is four, YMCK, then n=4.

[0067] Next, the control unit 50 sets the serial number i to an initial value of 1 (i=1) (step S102).

[0068] Next, the control unit 50 determines whether i≦n (step S103). If the control unit 50 determines that i≦n (step S103: YES), the process proceeds to the next step S104. On the other hand, if the control unit 50 determines that i>n is true (step S103: NO), the process proceeds to step S108.

[0069] Next, the control unit 50 opens (OPEN) the hollow fiber valve 4513c of the ith color and drives (ON) the vacuum pump 4514e (step S104).

[0070] Next, the control unit 50 measures the upstream pressure i and downstream pressure i of the ith color (step S105). The upstream pressure is the pressure on the upstream side (hollow fiber valve 4513c side) of the degassing module 451, measured by the first pressure sensor 4513b. The downstream pressure is the pressure on the downstream side (vacuum pump 4514e side) of the degassing module 451, measured by the second pressure sensor 4514b.

[0071] Next, the control unit 50 closes (CLOSE) the hollow fiber valve 4513c for the ith color, and stops (OFF) the driving of the vacuum pump 4514e (Step S106).

[0072] Next, the control unit 50 adds 1 to the serial number i (i=i+1) (step S107).

[0073] In step S108, the control unit 50 calculates the pressure difference Δi for each color. Specifically, the control unit 50 calculates the pressure difference Δi using the following formula (1). Pressure difference Δi = upstream pressure i - downstream pressure i...(1) The calculated pressure difference Δi for each color represents the degree of clogging of the hollow fiber membrane 4512 of each color. As described above, the control unit 50 detects the degree of clogging of the hollow fiber membranes 4512 using the difference between the upstream pressure and the downstream pressure of the degassing module 451.

[0074] Next, the control unit 50 sorts the pressure differences Δi of the respective colors in ascending order (step S109). The pressure differences Δi of the respective colors sorted in ascending order in step S109 are referred to as Δi_sort (see FIG. 11).

[0075] Next, the control unit 50 defines the group number as a variable j (step S110).

[0076] Next, the control unit 50 sets the serial number i and the group number j to initial values ​​of 1 (i=1, j=1) (step S111).

[0077] Next, the control unit 50 determines whether i≦n (step S112). When the control unit 50 determines that i ≤ n (step S112: YES), it proceeds to the next step S113. On the other hand, when the control unit 50 determines that i > n (step S112: NO), it proceeds to step S118.

[0078] Next, the control unit 50 adds Δi_sort to group j (step S113).

[0079] Next, the control unit 50 determines whether (max(group j) - min(group j)) / max(group j) < A (step S114). max(group j) is the maximum value of Δi_sort within group j, that is, the maximum pressure difference within group j. min(group j) is the minimum value of Δi_sort within group j, that is, the minimum pressure difference within group j. A is a predetermined threshold value. The predetermined threshold value A is a reference value for the pressure difference such that there is no problem even when discharge control is simultaneously implemented. The predetermined threshold value A is determined by the ink used, the performance of the degassing module 451, and the vacuum pump 4514e. For example, when using UV ink, a silicone degassing module, and a vacuum pump (ULVAC Kiko DTC - 22), when the increase rate of the pressure difference reaches 40%, the target discharge amount of the ink component (monomer) becomes 16 g or less (see FIG. 8). The increase rate of the pressure difference is the ratio of the difference between the maximum and minimum pressure differences within group j to the maximum pressure difference within group j. Therefore, the predetermined threshold value A in the example shown in FIG. 8 is 0.4. In this step S114, when the ratio of the difference between the maximum and minimum pressure differences within group j to the maximum pressure difference within group j exceeds the predetermined threshold value A, it is determined that simultaneous implementation of discharge control is not possible. When the control unit 50 determines that (max(group j) - min(group j)) / max(group j) < A (step S114: YES), it determines that simultaneous implementation of discharge control is possible and proceeds to the next step S115. On the other hand, if the control unit 50 determines that (max(group j)-min(group j)) / max(group j)≧A is satisfied (step S114: NO), it determines that simultaneous discharge control cannot be performed, and proceeds to step S116.

[0080] Next, the control unit 50 adds 1 to the serial number i (i=i+1) (step S115), and then proceeds to step S112.

[0081] In step S116, the control unit 50 excludes Δi_sort from group j.

[0082] Next, the control unit 50 adds 1 to the group number j (j=j+1) (step S117), and then proceeds to step S112.

[0083] In step S118, the control unit 50 performs simultaneous discharge control. Simultaneous discharge control refers to control in which discharge control is performed simultaneously for the colors belonging to all groups. Discharge control is control in which hollow fiber valve 4513c is opened (OPEN) and vacuum pump 4514e is driven (ON). For example, in the case where YMC is in group 1 and K is in group 2, discharge control for YMC is performed simultaneously first, and then discharge control for K is performed. This allows colors with similar clogging conditions to be discharged simultaneously.

[0084] FIG. 9 is a flowchart showing an example of the simultaneous discharge control performed in step S118 of FIG. First, the control unit 50 defines the group number as a variable j and the total number of groups as a constant f (step S201). For example, if the number of groups is two, f=2.

[0085] Next, the control unit 50 sets the group number j to an initial value of 1 (j=1) (step S202).

[0086] Next, the control unit 50 determines whether j≦f (step S203). If the control unit 50 determines that j≦f (step S203: YES), the process proceeds to the next step S204. On the other hand, if the control unit 50 determines that j≦f (step S203: NO), the process ends.

[0087] In step S204, the control unit 50 opens (OPEN) the hollow fiber valves 4513c of the colors belonging to group j.

[0088] Next, the control unit 50 drives (turns on) the vacuum pump 4514e (step S205).

[0089] Next, the control unit 50 determines whether a predetermined time has elapsed (step S206). The predetermined time is the driving time of the vacuum pump 4514e, and is, for example, 300 seconds, and more preferably, 600 seconds. If the control unit 50 determines that the predetermined time has elapsed (step S206: YES), the process proceeds to the next step S207. On the other hand, if the control unit 50 determines that the predetermined time has not elapsed (step S206: NO), it repeats the process until the predetermined time has elapsed.

[0090] Next, the control unit 50 stops (turns off) the vacuum pump 4514e (step S207).

[0091] Next, the control unit 50 closes (CLOSE) the hollow fiber valves 4513c of the colors belonging to group j (step S208).

[0092] Next, the control unit 50 adds 1 to the group number j (j=j+1) (step S209), and then proceeds to step S203.

[0093] The processing of steps S112 to S117 in Fig. 5 will be specifically described with reference to Figs. 10 to 12. Fig. 10 is a diagram showing an example of the calculated upstream pressure, downstream pressure, and pressure difference Δi for each color. Fig. 11 is a diagram showing the calculated pressure difference Δi for each color sorted in ascending order. Fig. 12 is a diagram showing an example of the results of grouping the pressure differences (Δi_sort) for each color sorted in ascending order. Note that n=4 and A=0.4. First, when i=1, Δ1_sort=10 is added to group 1 in step S113. Next, since max(group 1) and min(group 1) are both 10, (10-10) / 10=0<0.4 is satisfied in step S114. Therefore, i=1+1=2 is satisfied in step S115, and the process proceeds to step S112. When i=2, Δ2_sort=10 is added to group 1 in step S113. Next, since max(group 1) and min(group 1) are both 10, (10-10) / 10=0<0.4 is satisfied in step S114. Therefore, i=2+1=3 is satisfied in step S115, and the process proceeds to step S112. When i=3, in step S113, Δ3_sort=12.5 is added to group 1. Next, max(group 1) is 12.5 and min(group 1) is 10, so in step S114, (12.5-10) / 12.5=0.2<0.4. Therefore, in step S115, i=3+1=4, and the process proceeds to step S112. When i=4, Δ4_sort=20 is added to group 1 in step S113. Next, max(group 1) is 20 and min(group 1) is 10, so (20-10) / 20=0.52≧0.4 in step S114. Therefore, Δ4_sort=20 is excluded from group 1 in step S116, j=1+1=2 in step S117, and the process proceeds to step S112. Thereafter, Δ4_sort=20 is added to group 2 in step S113. Next, max(group 2) and min(group 2) are both 20, so (20-20) / 20=0<0.4 in step S114. Therefore, i=4+1=5 in step S115, and the process proceeds to step S112, where i=5>4, so the process proceeds to step S118. As described above, the control unit 50 determines the number of colors for which discharge control is to be performed simultaneously based on the degree of clogging and a predetermined threshold value through the processes of steps S112 to S117. This allows colors with similar degrees of clogging to be simultaneously discharge-controlled.

[0094] As described above, the degassing device 100 of the inkjet recording apparatus 1 according to this embodiment includes the degassing module 451 and the control unit 50. The degassing module 451 is an external circulation type degassing module having an internal gas-permeable membrane (hollow fiber membrane 4512) capable of degassing dissolved gas in the ink. The control unit 50 simultaneously controls the discharge of ink that has infiltrated the gas-permeable membrane for multiple colors. Therefore, the degassing device 100 can shorten the time required for discharge control, thereby reducing printing downtime.

[0095] The degassing device 100 also includes a detection unit (control unit 50) that can detect the degree of clogging of the gas-permeable membrane. The control unit 50 determines the number of colors for which discharge control is to be performed simultaneously, depending on the degree of clogging detected by the detection unit. If discharge control is performed simultaneously for multiple colors, and the hollow fibers of the degassing modules 451 for each color are clogged to different degrees, air will flow only through the less clogged module. This raises concerns about reduced discharge efficiency. However, the degassing device 100 can simultaneously discharge and control degassing modules 451 of colors with similar degrees of clogging. This makes it possible to achieve efficient discharge with well-balanced flow rates, improving discharge efficiency during discharge control.

[0096] Furthermore, according to the degassing device 100, the control unit 50 determines the number of colors for which discharge control is to be performed simultaneously based on the degree of clogging and a predetermined threshold value. Therefore, according to the degassing device 100, it is possible to easily identify colors that indicate similar levels of clogging in the degassing module 451. Therefore, it is possible to easily achieve efficient discharge, and it is possible to easily improve the discharge efficiency in discharge control.

[0097] Furthermore, according to the degassing device 100, the detection unit detects the degree of clogging of the gas-permeable membrane using the difference between the pressure on the upstream side of the degassing module 451 and the pressure on the downstream side of the degassing module 451. Therefore, the degassing device 100 can detect the degree of clogging of the degassing module 451 of each color with a simple configuration. This makes it possible to easily achieve efficient discharge, and easily improve the discharge efficiency in discharge control.

[0098] Although the present invention has been specifically described above based on the embodiments thereof, the present invention is not limited to the above embodiments and can be modified within the scope of the present invention.

[0099] (Variation 1) For example, in the above embodiment, the degree of clogging is detected using the difference (pressure difference) between the upstream pressure and the downstream pressure of degassing module 451, but the present invention is not limited to this. For example, instead of the pressure difference, the degree of clogging may be detected using the time it takes for the pressure value inside hollow fiber membrane 4512 to reach a predetermined value when vacuum pump 4514e is driven while hollow fiber valve 4513c is open. That is, control unit 50 may detect the degree of clogging using the time it takes for the air pressure inside hollow fiber membrane 4512 to reach a predetermined air pressure when the inside of hollow fiber membrane 4512, which is open to the atmosphere, is evacuated. Fig. 13 shows an example of the transition of the upstream pressure when vacuum pump 4514e is driven. In the example shown in Fig. 13, the predetermined air pressure is -90 kPa. In the example shown in Fig. 13, it can be seen that when hollow fiber membrane 4512 is clogged (symbol L3), it takes longer to reach the predetermined air pressure (-90 kPa) compared to when there is no clog (symbol L4). In the first modification, the control unit 50 detects the degree of clogging based on the difference in time it takes for a predetermined air pressure to be reached when there is clogging and when there is no clogging. Note that specific control is performed by replacing the pressure difference in the flowchart of FIG. 5 with the time difference.

[0100] As described above, the detection unit detects the degree of clogging of the gas-permeable membrane by using the time it takes for the air pressure inside the gas-permeable membrane to reach a predetermined air pressure when the inside of the gas-permeable membrane that is open to the atmosphere is evacuated. Therefore, the degassing device 100 can detect the degree of clogging of the degassing module 451 of each color with a simple configuration. This makes it possible to easily achieve efficient discharge, and easily improve the discharge efficiency in discharge control.

[0101] (Variation 2) The degree of clogging may also be detected using the flow rate of air inside hollow fiber membrane 4512 when hollow fiber valve 4513c is opened after the pressure inside hollow fiber membrane 4512 is reduced. That is, control unit 50 may detect the degree of clogging using the flow rate of air inside hollow fiber membrane 4512 when the inside of hollow fiber membrane 4512, which has been reduced in pressure, is opened to the atmosphere. FIG. 14 shows another example of a simplified flow path diagram near the degassing module 451. In the example shown in FIG. 14, a flow sensor 47 is provided in the flow path between the degassing module 451 and the vacuum pump 4514e. The flow sensor 47 detects the flow rate of air inside the hollow fiber membrane 4512. Generally, if there is a blockage inside the hollow fiber membrane 4512, the flow rate of air decreases. That is, the lower the air flow rate detected by the flow sensor 47, the more clogged the hollow fiber membrane 4512 is. The control unit 50 detects the degree of blockage based on the air flow rate detected by the flow sensor 47. In the second modification, the step of calculating the difference between the upstream and downstream sides (see step S108 in FIG. 5) is omitted, and the detected flow rates of each color are used directly to detect the degree of blockage and perform discharge control. Specifically, the flow rates of each color are first detected (acquired). Next, the flow rates of each color are sorted in ascending order (corresponding to step S109 in FIG. 5). Thereafter, following the process from step S110 onwards in FIG. 5, the objects are divided into groups, and discharge control is performed for each group.

[0102] As described above, the detection unit detects the degree of clogging of the gas-permeable membrane using the flow rate of air inside the gas-permeable membrane when the inside of the gas-permeable membrane is opened to the atmosphere after the pressure inside the gas-permeable membrane has been reduced. Therefore, the degassing device 100 can detect the degree of clogging of the degassing module 451 of each color with a simple configuration. This makes it possible to easily achieve efficient discharge, and easily improve the discharge efficiency in discharge control.

[0103] (Other variations) In addition, although the above embodiment illustrates a configuration using UV ink, the present invention is not limited to this. That is, the ink is not limited to UV ink. Furthermore, the configuration of the external circulation type degassing module is not particularly limited. However, when using a degassing module made of UV ink or a hollow fiber membrane made of silicone, more ink will penetrate into hollow fiber membrane 4512. In other words, when using a degassing module made of UV ink or a hollow fiber membrane made of silicone, clogging is more likely to occur. Therefore, a configuration using a degassing module made of UV ink or a hollow fiber membrane made of silicone is more effective because it makes it easier to achieve the effects of the present invention.

[0104] In addition, the detailed configuration and operation of each device constituting the inkjet recording apparatus can be modified as appropriate without departing from the spirit of the present invention. [Explanation of symbols]

[0105] 1. Inkjet recording device 10 Paper feed section 11 Paper feed tray 12 Conveyor 20 Image forming unit 21 Image forming drum 22 Delivery Unit 23 Paper heating section 24 Head Unit 24a Inkjet head (ink ejection head) 25 Irradiation unit 26 Delivery Department 30 Paper output section 31 Paper output tray 40 Liquid delivery section 41 Main tank (ink storage section) 42 First subtank (ink storage section) 43 Second subtank (ink storage section) 451 Degassing Module 4511 Ink Distribution Room 4512 Hollow fiber membrane (gas permeable membrane) 4513 First vacuum chamber 4513b First Pressure Sensor 4513c hollow fiber valve 4514 Second vacuum chamber 4514b Secondary pressure sensor 4514e Vacuum Pump 47 Flow Sensor 50 control unit (detection unit) 51 CPU 52 RAM 53 ROM 60 Information Department 100 Degassing device P Recording medium

Claims

1. an external circulation type degassing module having a gas permeable membrane therein capable of degassing dissolved gas in the ink; a control unit that performs discharge control to discharge the ink that has infiltrated into the gas-permeable membrane; Equipped with The degassing device is characterized in that the control unit performs the discharge control for a plurality of colors simultaneously.

2. A detection unit capable of detecting a degree of clogging of the gas-permeable membrane is provided, 2. The degassing device according to claim 1, wherein the control unit determines the number of colors for which the discharge control is to be performed simultaneously depending on the degree of clogging detected by the detection unit.

3. 3. The degassing device according to claim 2, wherein the control unit determines the number of colors for which the discharge control is to be performed simultaneously based on the degree of clogging and a predetermined threshold value.

4. 3. The degassing device according to claim 2, wherein the detection unit detects the degree of clogging of the gas-permeable membrane by using a difference between a pressure on the upstream side of the degassing module and a pressure on the downstream side of the degassing module.

5. 3. The degassing device according to claim 2, wherein the detection unit detects the degree of clogging of the gas-permeable membrane by using the time it takes for the air pressure inside the gas-permeable membrane to reach a predetermined air pressure when the inside of the gas-permeable membrane that is open to the atmosphere is evacuated.

6. 3. The degassing device according to claim 2, wherein the detection unit detects the degree of clogging of the gas-permeable membrane using the flow rate of air inside the gas-permeable membrane when the inside of the gas-permeable membrane, which has been depressurized, is opened to the atmosphere.

7. 2. The degassing device according to claim 1, wherein the ink is a UV ink.

8. an external reflux type degassing module provided between an ink storage section that stores ink and an ink ejection head that ejects ink from a nozzle, the external reflux type degassing module having an internal gas permeable membrane that can degas dissolved gas in the ink; a control unit that performs discharge control to discharge the ink that has infiltrated into the gas-permeable membrane; Equipped with The inkjet recording apparatus is characterized in that the control unit performs the discharge control for a plurality of colors simultaneously.

9. A degassing method for a degassing device including an external circulation type degassing module having an internal gas permeable membrane capable of degassing dissolved gas in ink, comprising the steps of: a control step of performing discharge control for discharging the ink that has infiltrated into the gas-permeable membrane; The degassing method, wherein the control step performs the discharge control for a plurality of colors simultaneously.

10. A computer of a degassing device including an external reflux type degassing module having an internal gas permeable membrane capable of degassing dissolved gas in ink, a control unit that performs discharge control to discharge the ink that has infiltrated into the gas-permeable membrane; The control unit performs the discharge control for a plurality of colors simultaneously.

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