Degassing device and ink jet recording apparatus

Abstract

The invention provides a degassing device. The degassing device removes air dissolved in the liquid in a reduced pressure atmosphere. The degassing device is provided with a liquid storage tank, a decompression device, an impregnation component and a lifting device. The liquid storage tank is used for storing liquid. And the pressure reducing device is used for reducing the pressure in the liquid storage tank. And the dipping part is dipped in the liquid in the liquid storage tank. The lifting device is used for lifting the dipping component between a dipping state and a retreating state, and the dipping state refers to a state that the dipping component is positioned on the liquid level of the liquid in the liquid storage tank; the retracted state is a state in which the immersion member is retracted from the liquid level in the liquid tank. Thus, redissolution of air can be suppressed without lowering degassing efficiency.

Description

Technical Field

[0001] This invention relates to a degassing device and an inkjet recording apparatus. Background Technology

[0002] In inkjet recording devices, an increase in the amount of dissolved air in the ink can lead to the formation of air bubbles inside the recording head, causing poor air removal. Therefore, existing technologies have been researching structures to reduce the amount of dissolved air in the ink. For example, there are structures that degas the ink by reducing pressure inside the ink reservoir.

[0003] In the above structure, a floating body is placed on the liquid surface to prevent air from redissolving into the ink in the ink tank. However, in this structure, the floating body narrows the liquid surface, thus reducing the degassing efficiency. Summary of the Invention

[0004] In view of the above, the object of the present invention is to suppress the redissolution of air without reducing the degassing efficiency.

[0005] The degassing device of this invention removes dissolved air from a liquid under reduced pressure. The degassing device includes a liquid storage tank, a pressure reducing device, an immersion component, and a lifting device. The liquid storage tank is used to store liquid. The pressure reducing device is used to reduce the pressure inside the liquid storage tank. The immersion component is immersed in the liquid inside the liquid storage tank. The lifting device is used to move the immersion component between an immersion state and a retraction state; the immersion state refers to the state where the immersion component is positioned at the surface of the liquid inside the liquid storage tank; the retraction state refers to the state where the immersion component is retracted from the surface of the liquid inside the liquid storage tank.

[0006] The inkjet recording apparatus of the present invention includes the degassing device and the recording head, the recording head being used to discharge liquid degassed by the degassing device onto the sheet. Attached Figure Description

[0007] Figure 1 This is a schematic diagram illustrating an inkjet recording apparatus according to an embodiment of the present invention.

[0008] Figure 2 This is a schematic diagram illustrating the ink supply structure according to an embodiment of the present invention.

[0009] Figure 3 This is a schematic diagram illustrating a circulating pump according to an embodiment of the present invention.

[0010] Figure 4 This is a schematic cross-sectional view of a degassing apparatus according to an embodiment of the present invention.

[0011] Figure 5 This is a schematic cross-sectional view of a degassing apparatus according to an embodiment of the present invention.

[0012] Figure 6 This is a perspective view showing the float and lifting device according to an embodiment of the present invention.

[0013] Figure 7 This is a diagram showing the result of performing cyclic degassing in an embodiment of the present invention and in the structure of the prior art.

[0014] Figure 8 This is a cross-sectional view showing a degassing apparatus according to a first modified embodiment of the present invention.

[0015] Figure 9 This is a cross-sectional view showing a degassing apparatus according to a first modified embodiment of the present invention.

[0016] Figure 10 This is a cross-sectional view showing the degassing apparatus according to a second variation of an embodiment of the present invention.

[0017] Figure 11 This is a cross-sectional view showing the degassing apparatus according to a second variation of an embodiment of the present invention.

[0018] Figure 12 This is a cross-sectional view showing the degassing apparatus according to a second variation of an embodiment of the present invention.

[0019] Figure 13 This is a cross-sectional view showing the degassing apparatus according to a second variation of an embodiment of the present invention.

[0020] Figure 14 This is a cross-sectional view showing the degassing apparatus according to the third variation of an embodiment of the present invention.

[0021] Figure 15 This is a cross-sectional view showing the degassing apparatus according to the third variation of an embodiment of the present invention. Detailed Implementation

[0022] Below, refer to the appendix. Figure 1 The inkjet recording apparatus 1 of this embodiment will be described. Figure 1 This is a schematic diagram illustrating the inkjet recording apparatus 1 according to this embodiment. For ease of explanation, it is shown below. Figure 1The front side of the paper in the diagram is the front side (front) of the inkjet recording device 1. The left and right orientations are explained based on the direction when viewing the inkjet recording device 1 from the front. The arrows L, R, U, and Lo marked in each figure represent the left, right, top, and bottom sides of the inkjet recording device 1, respectively.

[0023] The inkjet recording device 1 prints by ejecting ink from each inkjet recording head 21 onto a sheet S, which serves as the recording medium. The inkjet recording device 1 has a box-shaped housing 10 that houses various devices. A paper tray 11 for placing the sheet S is housed in the lower part of the housing 10, and a manual tray 12 for manually placing the sheet S is provided on the right side of the housing 10. A paper discharge tray 13 for stacking the recorded sheets S is provided on the upper side of the left side of the housing 10.

[0024] A first transport path 14 is formed on the right side of the housing 10, transporting sheet S from the paper feed cassette 11 to the recording head 21 in the center of the housing 10. A first paper feed unit 15 is provided upstream of the first transport path 14, which picks up sheet S from the sheet stack of the paper feed cassette 11. A alignment roller 18 is provided downstream of the first transport path 14 to adjust the feed time of sheet S. Furthermore, the paper feed path 16 of the manual tray 12 merges with the first transport path 14 downstream, and a second paper feed unit 17 is provided on the paper feed path 16, which picks up sheet S from the sheet stack of the manual tray 12.

[0025] Downstream of the alignment roller 18 is a conveying device 22 and recording heads 21 arranged by color (e.g., black, cyan, magenta, yellow). The alignment roller 18 corrects the skewness of the sheet S and, in coordination with the ink discharge action of each recording head 21, feeds the sheet S to the conveying device 22. On the housing 10, an ink container 31 and an ink reservoir 32 are provided for each recording head 21. The ink in each ink container 31 is temporarily stored in the ink reservoir 32, and the ink is degassed as needed and supplied from the ink reservoir 32 to the recording head 21.

[0026] The conveying device 22 is configured by winding a conveyor belt 24 around a plurality of mounting rollers 23 disposed below each recording head 21. Downstream of the conveying device 22, a drying device 25 is provided for drying the ink on the sheet S. Downstream of the drying device 25, a straightening device 26 is provided to correct any curling that occurs on the sheet S due to ink drying. Downstream of the straightening device 26, a second conveying path 27 is formed for conveying the sheet S to the paper discharge tray 13. Downstream of the second conveying path 27, a paper discharge section 28 is provided to discharge the recorded sheet S to the paper discharge tray 13.

[0027] Below the drying unit 25 are a maintenance unit 35 for cleaning the recording head 21 and a cover unit 36 ​​for covering the recording head 21. The maintenance unit 35 has a scraper-like wiping blade that scrapes away ink residue on the nozzle surface of the recording head 21. The cover unit 36 ​​has a recording head cover that covers the nozzle surface of the recording head 21. The recording head cover helps to prevent the ink inside the nozzle from drying. Further measures can be taken to prevent the ink from drying by storing a cleaning solution or other liquid inside the recording head cover.

[0028] Furthermore, the inkjet recording apparatus 1 includes a control unit 38 that encompasses the entire control unit. The control unit 38 can be configured as a processor or as logic circuitry (hardware) formed in an integrated circuit or similar component. When configured as a processor, the processor performs various processes by reading and executing programs stored in memory. For example, a CPU (Central Processing Unit) can be used as the processor. Depending on its purpose, the memory may consist of one or more storage devices such as ROM (Read Only Memory) or RAM (Random Access Memory).

[0029] During image recording, sheet S is taken from paper tray 11 and manual tray 12 via first paper feed unit 15 and second paper feed unit 17 respectively, and conveyed to registration roller 18. In coordination with ink discharge timing, sheet S is conveyed from registration roller 18 to conveyor belt 24, and degassed ink is discharged from each recording head 21, recording a color image on the surface of sheet S. Sheet S is dried by drying device 25, and curling of sheet S is corrected by straightening device 26. Sheet S is conveyed to paper discharge unit 28 via second conveying path 27, and the recorded sheet S is discharged to paper discharge tray 13 via paper discharge unit 28.

[0030] However, the ink surface comes into contact with air within the ink reservoir 32, causing air dissolution. Sometimes, air bubbles within the ink can clog the nozzles of the recording head 21. Therefore, it is desirable to appropriately suppress the amount of dissolved air within the ink. For example, a method has been proposed where, after depressurization around a hollow fiber filter, ink is passed through the hollow fiber filter, causing air to move from the wall of the hollow fiber towards the depressurization side for degassing. However, this method requires expensive hollow fiber filters and necessitates regular replacement, thus increasing costs.

[0031] In addition, to prevent nozzle clogging, a method for degassing the ink by agitating it with a stirrer while the pressure inside the ink reservoir 32 is reduced to below atmospheric pressure (hereinafter referred to as the agitation degassing method). In the agitation degassing method, a magnetic force is applied to the stirrer inside the ink reservoir 32 from the outside, causing the stirrer to rotate and agitate the ink inside the ink reservoir 32. When the ink depth is large or the diameter of the ink reservoir is large, it is difficult to agitate the ink, resulting in a decrease in degassing efficiency. Increasing the speed of the stirrer makes agitation easier, but if the speed of the stirrer becomes too high, a loss of synchronization will occur, and the rotation noise of the stirrer will also increase. Therefore, the circulating degassing method shown below is adopted in this embodiment.

[0032] [Degassing device] The degassing device 40 involved in this embodiment will be described. Figure 2 This is a schematic diagram illustrating the ink supply structure involved in this embodiment. Figure 3 This is a schematic diagram showing the circulating pump 67 involved in this embodiment. Figure 4 , Figure 5 This is a schematic cross-sectional view of the degassing device 40. In the inkjet recording apparatus 1 according to this embodiment, ink supply structures are provided according to the color of the ink. These ink supply structures have the same structure, so one ink supply structure will be described here.

[0033] [Ink Storage Tank] The ink reservoir 32 has a side wall portion 32W, a bottom portion 32B, and a cover portion 32C. The side wall portion 32W is cylindrical, with its axial direction defined by the vertical direction. The bottom portion 32B blocks the lower end of the side wall portion 32W. The cover portion 32C blocks the upper end of the side wall portion 32W. The horizontal cross-section of the inner surface of the side wall portion 32W is preferably circular. Preferably, the side wall portion 32W and the bottom portion 32B are integrally formed.

[0034] [Supply Flow] The replenishment flow path 41 is connected to the ink container 31 and the ink reservoir 32. One end of the replenishment flow path 41 is connected to a portion below the liquid level of the side wall portion 32W of the ink reservoir 32. A replenishment pump 61 and a replenishment valve 51 are provided in the replenishment flow path 41.

[0035] [Open Atmospheric Flow Path] The atmospheric open flow path 43 is connected to the cover portion 32C and communicates with the upper space 34 of the ink storage tank 32. An atmospheric open valve 53 is provided in the atmospheric open flow path 43.

[0036] [Decompression Flow Path] The pressure-reducing flow path 42 is connected to the cover portion 32C and communicates with the upper space 34 of the ink reservoir 32. A pressure-reducing pump 62 and a pressure-reducing valve 52 are provided in the pressure-reducing flow path 42.

[0037] [Supply Flow] The supply path 44 is connected to the ink reservoir 32 and the recording head 21. One end of the supply path 44 is connected to the bottom 32B of the ink reservoir 32. A supply valve 54 and a supply pump 64 are provided in the supply path 44.

[0038] [Recycle Flow] The recovery flow path 45 is connected to the ink reservoir 32 and the recording head 21. One end of the recovery flow path 45 is connected to the side wall 32W of the ink reservoir 32. A recovery valve 55 is provided in the recovery flow path 45.

[0039] [Bypass Flow] A bypass flow path 46 is provided in the supply flow path 44, bypassing the supply valve 54 and the supply pump 64. A bypass valve 56 is provided in the bypass flow path 46.

[0040] [Circular Flow Path] The circulation path 47 communicates with the area near the bottom and surface of the ink in the ink reservoir 32. The circulation path 47 has an outlet 71 for ink to flow out of the ink reservoir 32 and an inlet 72 for ink to flow into the ink reservoir 32. The outlet 71 is connected to the bottom 32B of the ink reservoir 32, and the inlet 72 is connected to the portion near the surface of the ink on the side wall 32W of the ink reservoir 32. That is, the inlet 72 is located higher than the outlet 71. A circulation pump 67 is provided in the circulation path 47. The ink circulates through the circulation path 47 via the circulation pump 67.

[0041] [Circulation Pump] During the degassing process, the ink reservoir 32 is under reduced pressure, making reciprocating pumps such as diaphragm pumps susceptible to the effects of this pressure reduction. Therefore, the circulation pump 67 is preferably a pump that delivers ink via a rotating body. For example, non-positive displacement pumps such as centrifugal pumps, mixed-flow pumps, and axial-flow pumps can be used as the circulation pump 67, as well as positive displacement rotary pumps such as vane pumps, gear pumps, and screw pumps. By using these pumps, unlike reciprocating pumps, the effects of pressure reduction within the ink reservoir 32 can be suppressed, thus enabling ink circulation.

[0042] Furthermore, generally speaking, the circulation path 47 in the degassing process can include the recording head 21, but in this embodiment, the circulation path 47 does not include the recording head 21. That is, the circulation path 47 is separate from the path that supplies ink to the recording head 21. Since the recording head 21 is not included in the circulation path 47, the possibility of external air entering the recording head 21 due to the disruption of the meniscus formed in the nozzle of the recording head 21 under depressurization during degassing can be reduced.

[0043] like Figure 3As shown, the pump shaft 73 and motor shaft 75 of the circulating pump 67 can transmit power in a non-contact manner through a partition wall 77. A pump casing 76 is formed along the circulation path 47, and the pump shaft 73 with an impeller 74 is housed within the pump casing 76. A motor (not shown) is provided on the outside of the circulation path 47. Discs 78 and 79 are provided at the ends of the pump shaft 73 and motor shaft 75, and the discs 78 and 79 face each other through the partition wall 77 of the pump casing 76. On the facing surfaces of the discs 78 and 79, magnets with alternating S and N poles are arranged circumferentially (not shown).

[0044] The pump shaft 73 and the motor shaft 75 are magnetically connected (magnetically coupled), and power is transmitted from the motor shaft 75 to the pump shaft 73 using magnetic force. The motor shaft 75 does not penetrate the pump housing 76; instead, the impeller 74 inside the pump housing 76 can rotate while the pump housing 76 is liquid-tightly sealed. The disks 78 and 79 of the pump shaft 73 and the motor shaft 75 are separated by a partition wall 77 in the pump housing 76. Therefore, even if a pressure difference occurs inside and outside the pump housing 76 when the ink reservoir 32 is depressurized, ink leakage due to this pressure difference is reliably prevented.

[0045] [Control Device] The replenishment pump 61, pressure reducing pump 62, supply pump 64, circulation pump 67, and replenishment valve 51, pressure reducing valve 52, atmospheric vent valve 53, supply valve 54, recovery valve 55, and bypass valve 56 are controlled by control device 38. Control device 38 includes a determination unit 39 that determines whether degassing is required based on the ink's storage time. If determination unit 39 determines that degassing is not necessary, degassing is not performed. Even if air redissolves due to ink storage, the ink can be used without degassing as long as it is within the permissible time.

[0046] [Barometer] A barometer 33 is installed in the ink reservoir 32 to measure the air pressure in the upper space 34 of the ink reservoir 32. The control device 38 obtains air pressure data from the barometer 33.

[0047] Next, the basic operation of the degassing device 40 will be explained. Here, the standby state will be used as the initial state for explanation.

[0048] [Standby mode] In standby mode, the replenishment valve 51, pressure reducing valve 52, and supply valve 54 are closed, while the atmospheric vent valve 53, recovery valve 55, and bypass valve 56 are opened. Ink is stored in the ink tank 32, and the liquid surface is in contact with the air in the upper space 34 open to the atmosphere, thereby dissolving in the ink over time.

[0049] In standby mode, the determination unit 39 of the control device 38 determines whether degassing is required. For example, the control device 38 is equipped with a timer to time the ink placement time. The amount of dissolved air in the ink can be estimated based on one or more parameters such as air pressure, ink temperature, and the elapsed time since the last printing. Therefore, the determination unit 39 stores conversion information showing the correspondence between each parameter and the amount of dissolved air in the ink, and estimates the amount of dissolved air in the ink based on each parameter. In addition, the determination unit 39 stores conversion information showing the correspondence between the amount of dissolved air in the ink and the allowable time, and sets the allowable time based on the amount of dissolved air in the ink. The allowable time refers to the time during which printing is allowed even if ink is placed without degassing. Furthermore, mapping data, lookup tables, conversion formulas, etc., are used in the conversion information showing the correspondence between each parameter and ink viscosity, and the conversion information showing the correspondence between the amount of dissolved air in the ink, viscosity, and allowable time. These mapping data, lookup tables, and conversion formulas use information obtained in advance through experiments, experience, and theory.

[0050] If the ink has been left to stand for a period of time within the allowable time, the oxygen saturation is low, and therefore the determination unit 39 determines that degassing is not required. If the ink has been left to stand for a period of time exceeding the allowable time, the oxygen saturation is high, and therefore the determination unit 39 determines that degassing is required. If degassing is required, the control device 38 performs the following decompression and degassing processes.

[0051] [Decompression Process] During the pressure reduction process, control device 38 closes supply valve 51, atmospheric vent valve 53, supply valve 54, recovery valve 55, and bypass valve 56, opens pressure reducing valve 52, and drives pressure reducing pump 62. Air is then drawn out from the upper space 34 of ink reservoir 32, thus reducing the pressure in the upper space 34. When the pressure in the upper space 34, as indicated by barometer 33, reaches a target value (e.g., -50 kPa), control device 38 stops pressure reducing pump 62.

[0052] [Degassing process] When the depressurization process ends, the control device 38 performs the degassing process. During the degassing process, the control device 38 closes the supply valve 51, pressure reducing valve 52, atmospheric release valve 53, supply valve 54, recovery valve 55, and bypass valve 56, and drives the circulation pump 67 at a predetermined time. When the circulation pump 67 is driven, the ink in the ink tank 32 circulates through the circulation path 47. Ink near the bottom surface of the ink tank 32 with a higher amount of dissolved air flows out through the outlet 71 into the circulation path 47, while ink in the circulation path 47 flows into the ink tank 32 near the liquid surface through the inlet 72. The ink surface is exposed to the depressurized atmosphere, and the air dissolved in the ink near the liquid surface is removed. The ink near the liquid surface with less dissolved air and the ink near the bottom surface with more dissolved air exchange smoothly, improving degassing efficiency. Furthermore, unlike agitation degassing methods, it is not affected by ink depth or tank diameter, and the driving noise of the circulation pump 67 is suppressed compared to the rotation noise of an agitator, improving quietness.

[0053] [Record Head Loop Process] The recording head circulation process can be performed before or after the degassing process, or it can be performed at a separate time. During the recording head circulation process, control device 38 closes the supply valve 51, pressure reducing valve 52, and bypass valve 56, opens the atmospheric vent valve 53, supply valve 54, and recovery valve 55, and drives the supply pump 64. Ink is then supplied from the ink tank 32 to the recording head 21 through the supply flow path 44, and ink is recovered from the recording head 21 to the ink tank 32 through the recovery flow path 45. By circulating the ink between the recording head 21 and the ink tank 32, ink with increased viscosity is exchanged within the recording head 21, and air bubbles are removed from the recording head 21.

[0054] [Printing Process] During the printing operation by the recording head 21, the replenishment valve 51, pressure reducing valve 52, and supply valve 54 are closed, while the atmospheric vent valve 53, recovery valve 55, and bypass valve 56 are opened. That is, during the printing operation, the ink reservoir 32 is open to the atmosphere and becomes atmospheric pressure. During the printing operation, the ink reservoir 32 does not undergo pressure reduction to produce substantial degassing. Whenever ink is discharged from the recording head 21, ink is supplied from the ink reservoir 32 to the recording head 21 through the bypass flow path 46 and the recovery flow path 45. Sometimes, ink is replenished midway through an ink exchange operation or a printing operation. During this ink replenishment operation, the replenishment valve 51 is opened and the replenishment pump 61 is activated. Driven by the replenishment pump 61, ink is replenished from the ink container 31 to the ink reservoir 32 through the replenishment flow path 41.

[0055] also, Figure 1While schematically depicted, in reality, the recording head 21 is positioned above the ink reservoir 32. The ink within the recording head 21 is subjected to negative pressure due to the head difference between it and the ink in the ink reservoir 32, causing a meniscus to form at the nozzle of the recording head 21. After ink is discharged from the recording head 21, the surface tension of the ink acts to reduce the surface area of ​​the meniscus, thereby introducing a reduced amount of ink from the ink reservoir 32 to the recording head 21 through the resulting negative pressure. Alternatively, the recovery valve 55 can be closed, supplying ink to the recording head 21 only from the bypass flow path 46.

[0056] Furthermore, when the recording head 21 is connected to the ink reservoir 32, if the ink reservoir 32 is depressurized to the point of causing substantial degassing, the meniscus of the nozzle may be damaged. Even if the meniscus is not damaged, the shape of the meniscus inside the nozzle is different from when the ink reservoir 32 is open to the atmosphere, and the ink discharge characteristics may change. In this embodiment, the ink reservoir 32 is not depressurized to the point of causing substantial degassing during printing, therefore the meniscus inside the nozzle of the recording head 21 is not damaged, and there is no change in shape that alters the discharge characteristics.

[0057] Next, the features of this embodiment will be described in detail. Figure 6 This is a perspective view showing the float 81 and the lifting device 82.

[0058] The degassing device 40 described in this embodiment is a device for removing air dissolved in a liquid (e.g., ink) under reduced pressure. It includes a liquid storage tank (e.g., ink storage tank 32), a pressure reducing device (e.g., pressure reducing pump 62), an immersion component (e.g., float 81), and a lifting device 82. The liquid storage tank stores the liquid; the pressure reducing device reduces the pressure inside the liquid storage tank; the immersion component is immersed in the liquid within the liquid storage tank; and the lifting device 82 moves the immersion component between an immersion state and a retraction state. The immersion state refers to the state where the immersion component is positioned at the surface of the liquid within the liquid storage tank; the retraction state refers to the state where the immersion component is retracted from the surface of the liquid within the liquid storage tank. Here, immersion also includes the state where the lower end of the immersion component is in contact with the liquid surface. Furthermore, the term "the liquid surface where the immersion component is positioned within the liquid storage tank" means that the liquid surface is located at any position between the lower end and the upper end of the immersion component. In other words, the liquid level of the immersed component within the liquid tank means that a portion of the immersed component is immersed in the liquid within the liquid tank, while the entire immersed component is not immersed in the liquid within the liquid tank. This will be explained in detail below. Furthermore, as previously described, the ink tank 32 and the pressure reducing pump 62 are also present; therefore, the float 81 and the lifting device 82 will be primarily described below.

[0059] [Floating body] The mass per unit volume of float 81 is smaller than that of ink. Float 81 is formed as a plate with dimensions smaller than the horizontal cross-section of the inner surface of the sidewall portion 32W. In this embodiment, the horizontal cross-section of the inner surface of the sidewall portion 32W is circular; therefore, float 81 is also formed as a circular plate. The outer diameter of float 81 is smaller than the inner diameter of the sidewall portion 32W. A through hole 81H is provided at the center of float 81.

[0060] [Lifting device] The lifting device 82 includes a guide portion 82G, a magnetic body 82M, and an electromagnet 82E. The guide portion 82G is a rod-shaped component with its length along the vertical direction. The upper end of the guide portion 82G is fixed to the lower surface of the cover portion 32C. The lower end of the guide portion 82G can be fixed to the bottom 32B of the ink reservoir 32, or a gap can be provided between the lower end of the guide portion 82G and the bottom 32B (illustration omitted). The guide portion 82G is inserted into the through hole 81H of the float 81. The float 81 can slide along the guide portion 82G. An electromagnet 82E is provided at the upper end of the guide portion 82G. A magnetic body 82M (a strongly magnetic body) that is attracted and moved by the electromagnet 82E is provided on the upper surface of the float 81. A gap G is formed covering the entire circumference between the inner surface of the side wall portion 32W of the ink reservoir 32 and the outer edge of the float 81. This gap G reduces the contact between the float 81 and the side wall 32W when the float 81 rises and falls.

[0061] Electromagnet 82E is controlled by control device 38. When control device 38 is not energizing electromagnet 82E (refer to...), Figure 4 ), float 81 floats on the liquid surface, with its lower part immersed in the liquid (immersion state). When control device 38 energizes electromagnet 82E (refer to...) Figure 5 The magnetic body 82M is attracted and moved by the electromagnet 82E, thus causing the float 81 to retreat upwards from the liquid surface (retreat state). Alternatively, a magnetized magnetic body 82M can be used, and its movement can be achieved by using repulsive force.

[0062] In the standby state, decompression process, recording head circulation process, and printing process, the control device 38 moves the float 81 towards the immersion state. In this state, the liquid surface is formed only inside the gap G, thus suppressing the redissolution of air.

[0063] On the other hand, during the degassing process, the control device 38 moves the float 81 to a retracted state. In this state, the liquid surface expands entirely to the inner side of the sidewall portion 32W, thus preventing the float 81 from reducing the degassing efficiency.

[0064] [experiment] Figure 7This graph shows the results of the cyclic degassing process. The comparative example is a structure where the float 81 remains floating on the liquid surface without moving towards a retrenched state during the degassing process. Assuming the ink viscosity is 7 [mPa·s], the ink temperature is 25 [°C], the diameter of the ink tank 32 is 60 [mm], the ink depth is 28 [mm], and the ink circulation flow rate is 770 [ml / min], the change in oxygen solubility over time is compared. The vertical axis represents the oxygen solubility [%], and the horizontal axis represents the ink circulation time [min]. The solubility rate represents the ratio of the amount dissolved relative to the saturated state, with an initial value of 100 [%. As can be seen from the graph, compared to the comparative example, the tendency for the solubility rate to decrease significantly in this embodiment begins from the initial stage, decreasing to 50% in approximately 14 minutes. In contrast, in the comparative example, even after 40 minutes, it did not reach 50%.

[0065] The degassing apparatus 40 according to the above-described embodiment is a degassing apparatus 40 for removing air dissolved in a liquid (e.g., ink) under a reduced pressure atmosphere. It includes a liquid storage tank (e.g., ink storage tank 32), a pressure reducing device (e.g., pressure reducing pump 62), an immersion member (e.g., float 81), and a lifting device 82. The liquid storage tank stores the liquid; the pressure reducing device reduces the pressure inside the liquid storage tank; the immersion member is immersed in the liquid inside the liquid storage tank; and the lifting device 82 moves the immersion member between an immersion state and a retraction state. The immersion state refers to the state where the immersion member is positioned at the surface of the liquid inside the liquid storage tank; the retraction state refers to the state where the immersion member is retracted from the surface of the liquid inside the liquid storage tank. With this structure, the redissolution of air can be suppressed without reducing the degassing efficiency.

[0066] Furthermore, according to the degassing device 40 of this embodiment, in the retracted state, the lifting device 82 retracts the immersion member to a position above the liquid level in the liquid reservoir. For example, consider a case where the inkjet recording device 1 can continue printing using the ink in the ink reservoir 32 even if the ink container 31 is empty. In this case, due to the continuation of printing, the liquid level in the ink reservoir 32 drops from its normal height, therefore, based on the liquid level, it is considered that the immersion member cannot be retracted downwards. In contrast, in this embodiment, the immersion member is retracted upwards, so even when the liquid level is dropping, the immersion member can be retracted from the liquid level. Therefore, according to this embodiment, even when degassing is performed when the liquid level is dropping, a decrease in degassing efficiency can be prevented.

[0067] Furthermore, in the degassing device 40 according to this embodiment, the immersion member is a float 81. With this structure, no driving force is required to immerse the immersion member in the liquid, thus simplifying the structure. Additionally, energy can be saved.

[0068] Furthermore, according to the degassing device 40 of this embodiment, the lifting device 82 has an electromagnet 82E, and the float 81 has a magnetic body 82M that moves via the electromagnet 82E. With this structure, the float 81 can be retracted using a simple configuration.

[0069] Furthermore, according to the degassing device 40 of this embodiment, the degassing device 40 has a circulation path 47 and a circulation device (circulation pump 67). The circulation path 47 connects different positions of the liquid storage tank; the circulation device (circulation pump 67) circulates the liquid through the circulation path 47. With this structure, it is possible to promote the exchange between liquid with a high amount of dissolved air near the bottom of the liquid storage tank and liquid with a low amount of dissolved air near the liquid surface. Therefore, even when the amount of liquid is large, the degassing efficiency can be improved.

[0070] Furthermore, the inkjet recording apparatus 1 according to this embodiment includes a degassing device 40 and a recording head 21, the recording head 21 discharging the degassed liquid from the degassing device 40 to the sheet S. With this structure, image quality degradation due to bubble formation can be suppressed.

[0071] The above implementation method can also be modified as follows.

[0072] [First Variation] Figure 8 , Figure 9 This is a cross-sectional view showing the degassing device 40 according to the first modification of the above embodiment. In the above embodiment, an example is shown where the lifting device 82 retracts the immersion member to a position above the liquid level in the liquid tank in the retracted state. However, in this modification, the lifting device 82 retracts the immersion member to a position below the liquid level in the liquid tank in the retracted state. For example, imagine that the ink tank 32 is nearly full (see...). Figure 8 In this case, the inkjet recording apparatus 1 is configured to form an image under certain conditions. In this case, based on the ink level, it is considered impossible to retract the immersion member upwards. In contrast, in this modified example, an electromagnet 82E is provided at the lower end of the guide portion 82G to retract the immersion member downwards (see reference 82G). Figure 9 Therefore, even when the ink reservoir 32 is nearly full, the immersed component can be retracted from the liquid surface. Accordingly, according to this modified example, even when degassing is performed when the ink reservoir 32 is nearly full, a decrease in degassing efficiency can be prevented.

[0073] [Second Variation] Figures 10 to 13This is a cross-sectional view of the degassing device 40 according to the second modification of the above embodiment. In this modification, the degassing device 40 has a detection device 83 for detecting the height of the liquid level in the liquid tank. In the retracted state, the lifting device 82 retracts the immersion member either upward or downward according to the height of the liquid level in the liquid tank detected by the detection device 83. Specifically, electromagnets 82E are provided at the upper and lower ends of the guide portion 82G. The detection device 83 is provided, for example, on the lower surface of the cover portion 32C, and illuminates light onto the float 81 or the liquid surface, calculating the distance to the liquid surface based on the phase difference between the incident light and the reflected light.

[0074] When the height of the liquid level detected by the detection device 83 is such that the immersed part cannot retract upwards (see reference). Figure 10 The control device 38 energizes the electromagnet 82E below, causing the impregnated part to retract downwards (see reference). Figure 11 On the other hand, if the height of the liquid level detected by the detection device 83 is too low for the immersed component to retract downwards (see reference...). Figure 12 The control device 38 energizes the electromagnet 82E above, causing the impregnated part to retract upwards (see reference). Figure 13 According to this embodiment, the degassing efficiency can be prevented from decreasing regardless of the liquid level.

[0075] [3rd Variation] Figure 14 , Figure 15 This is a cross-sectional view showing the degassing device 40 according to the third variation of the above embodiment. The lifting device 92 has a shaft 92S and a propeller 92P, wherein the shaft 92S is arranged in the vertical direction and can slide in the vertical direction; the propeller 92P is arranged on the shaft 92S, and the immersion member is arranged above the propeller 92P on the shaft 92S, and is a large-diameter portion 91 with a diameter larger than that of the shaft 92S. When the propeller 92P is not driven, the immersion member is in an immersion state; when the propeller 92P is driven in the direction of pushing liquid downward, the immersion member is in a retracted state.

[0076] Specifically, a cylindrical bearing portion 92B is provided at the upper end of the support shaft 92S in the cover portion 32C. The shaft 92S can slide relative to the bearing portion 92B in the vertical direction. The propeller 92P is formed of, for example, a strongly magnetic material. A permanent magnet 92M and a motor 92D for rotating the permanent magnet 92M are provided on the outer side of the bottom 32B of the ink reservoir 32.

[0077] The propeller 92P is constrained by a magnetic field generated by a permanent magnet 92M. The magnetic field rotates as the permanent magnet 92M rotates, therefore, the propeller 92P also rotates. The propeller 92P generates thrust in the direction that pushes the shaft 92S upwards (in the direction that pushes the liquid downwards). The large-diameter portion 91 is formed with a dimension smaller than the horizontal cross-section of the inner surface of the sidewall portion 32W. In this embodiment, the horizontal cross-section of the inner surface of the sidewall portion 32W is circular; therefore, the large-diameter portion 91 is also formed as a circular plate. The outer diameter of the large-diameter portion 91 is smaller than the inner diameter of the sidewall portion 32W.

[0078] When the control device 38 does not rotate the propeller 92P (see reference) Figure 14 The shaft 92S descends under the influence of gravity, and its lower end contacts the upper surface of the bottom 32B. In this case, since the large-diameter portion 91 is immersed, the liquid level narrows. On the other hand, when the control device 38 rotates the propeller 92P (see...). Figure 15 The propeller 92P generates thrust that pushes the shaft 92S upward, and the upper end of the shaft 92S contacts the lower surface of the cover portion 32C. In this case, the large-diameter portion 91 is in a retracted state, thus expanding the liquid surface. The propeller 92P is provided to agitate the liquid and promote degassing, but in this modified example, since the driving force of the propeller 92P is used to retract the immersion component, a dedicated driving force for retracting the immersion component is not required.

[0079] [Other variations] In the above embodiment, an example is shown in which a degassing device 40 is provided in the inkjet recording apparatus 1. However, the degassing device 40 can also be applied to apparatuses used in other fields such as semiconductor manufacturing and display manufacturing. That is, it can also be applied to the degassing of liquid medicines, electrolytes, liquid resins, adhesives, solvents, lubricants, liquid foods, cosmetics, etc., other than inks.

[0080] In the above embodiment, a pressure reducing pump 62 is exemplified as a pressure reducing device, but any device capable of reducing pressure in the ink reservoir 32 is acceptable, such as an ejector.

[0081] In the above embodiment, a circulation pump 67 is exemplified as a circulation device, but any device that can circulate ink through the circulation path 47 is acceptable, such as a jet injector.

Claims

1. A degassing device for removing air dissolved in a liquid under reduced pressure, characterized in that, It includes a liquid storage tank, a pressure reducing device, an impregnated component, and a lifting device, among which, The liquid storage tank is used to store liquid; The pressure reducing device is used to reduce the pressure inside the liquid storage tank; The immersion component is immersed in the liquid in the liquid storage tank; The lifting device is used to move the immersion component up and down between an immersion state and a retraction state. The immersion state refers to the state in which the immersion component is located at the liquid surface in the liquid storage tank; the retraction state refers to the state in which the immersion component is retracted from the liquid surface in the liquid storage tank.

2. The degassing device according to claim 1, characterized in that, In the retracted state, the lifting device retracts the immersion component to a position above the liquid level in the liquid storage tank.

3. The degassing device according to claim 1, characterized in that, In the retracted state, the lifting device retracts the immersion component to a position lower than the liquid level in the liquid storage tank.

4. The degassing device according to claim 1, characterized in that, It has a detection device for detecting the liquid level in the liquid storage tank. In the retracted state, the lifting device retracts the immersion component either upward or downward based on the height of the liquid level in the liquid storage tank detected by the detection device.

5. The degassing device according to claim 1, characterized in that, The impregnated component is a float.

6. The degassing device according to claim 5, characterized in that, The lifting device has an electromagnet. The buoy has a magnetic body that moves via the electromagnet.

7. The degassing device according to claim 5, characterized in that, It has a circulating flow path and a circulating device, wherein, The circulation path connects different locations of the liquid storage tank. The circulation device circulates the liquid through the circulation path.

8. The degassing device according to claim 2, characterized in that, The lifting device has a shaft and a propeller, wherein... The shaft is arranged in the vertical direction and can slide in the vertical direction. The propeller is mounted on the shaft. The impregnated component is positioned above the propeller of the shaft, and is a large-diameter portion with a diameter larger than that of the shaft. When the propeller is not driven, the immersion component is in the immersion state; when the propeller is driven in the direction of pushing the liquid downward, the immersion component is in the retraction state.

9. An inkjet recording device, characterized in that, It has a recording head and the degassing device according to claim 1, wherein, The recording head is used to discharge the liquid degassed by the degassing device onto the sheet.

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