Deaeration device and liquid discharge device

Abstract

To improve air bubble removal performance of a deaeration device using a gas-liquid separation membrane and inhibit reduction of moisture in a liquid.SOLUTION: A deaeration device 30 includes: a passage 31 in which a liquid (for example, an ink) containing moisture flows; a decompression chamber 34 which contacts with the passage 31; a gas-liquid separation membrane 35 which is provided at a border part between the passage 31 and the decompression chamber 34 and allows a gas to penetrate therethrough; a decompression pump 36 which decompresses the decompression chamber 34; and an air bubble removal part 40 which removes air bubbles from the liquid. The air bubble removal part 40 includes: a water tank 41 which stores water; a storage part 42 which temporarily stores the liquid flowing through the passage 31, allows a liquid surface to be opened to the atmospheric air, and is immersed in water in the water tank 41; an ultrasonic sound generator 43 which transmits ultrasonic waves to the storage part 42 through water in the water tank 41; and a communication pipe 44 which allows a space above a water surface of the water tank 41 and the decompression chamber 34 to communicate with each other.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a degassing device for degassing a liquid and a liquid ejection device provided with the degassing device. [Background technology]

[0002] In an inkjet recording device, if the amount of dissolved air in the ink increases, air bubbles may be generated inside the inkjet head, which may cause ejection failure. Therefore, conventionally, techniques for reducing the amount of dissolved air in the ink have been considered. For example, Patent Documents 1 and 2 describe a configuration in which a decompression chamber that houses a hollow fiber membrane connected to an ink flow path and the ink inside the hollow fiber membrane is degassed by decompressing the decompression chamber with a vacuum pump. Patent Document 3 describes a configuration that includes a defoaming chamber for removing air from a liquid and a decompression chamber for decompressing the defoaming chamber, and the wall between the defoaming chamber and the decompression chamber is permeable to gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-147365 A [Patent Document 2] JP 2019-217712 A [Patent Document 3] JP 2010-46820 A Summary of the Invention [Problem to be solved by the invention]

[0004] The hollow fiber membranes described in Patent Documents 1 and 2 have a high gas separation performance, but have a problem of low durability. The gas-permeable wall described in Patent Document 3 has the advantage of being more durable and less expensive than the hollow fiber membrane, but when a water-based ink is used, the wall is more susceptible to water vapor generated by evaporation of water in the ink than the hollow fiber membrane, resulting in a problem of high ink viscosity.

[0005] In addition, the gas separating members (hereinafter referred to as gas-liquid separation membranes) described in Patent Documents 1 to 3 have high performance in removing gas dissolved in liquid, but low performance in removing air bubbles. In order to improve the performance in removing air bubbles, it is conceivable to increase the area of ​​the gas-liquid separation membrane, but this would result in an increase in the size of the device.

[0006] In consideration of the above circumstances, an object of the present invention is to improve the bubble removal performance of a degassing device using a gas-liquid separation membrane and to suppress a decrease in moisture content in a liquid. [Means for solving the problem]

[0007] In order to solve the above problems, the degassing device of the present invention comprises a flow path through which a water-containing liquid flows, a pressure reduction chamber in contact with the flow path, a gas-liquid separation membrane provided at the boundary between the flow path and the pressure reduction chamber and allowing gas to pass through, a pressure reduction pump for reducing the pressure in the pressure reduction chamber, and a bubble removal unit for removing air bubbles from the liquid, the bubble removal unit comprising a water tank for storing water, a storage unit for temporarily storing the liquid flowing through the flow path, the liquid surface of which is open to the atmosphere and immersed in the water in the water tank, an ultrasonic generator for propagating ultrasonic waves to the storage unit via the water in the water tank, and a connecting pipe for connecting the space above the water surface of the water tank with the pressure reduction chamber.

[0008] The bubble removing units may be provided on the upstream side and downstream side of the decompression chamber.

[0009] A liquid ejection device according to the present invention includes the degassing device and an inkjet head that ejects liquid supplied from the flow path. Effect of the Invention

[0010] According to the present invention, the bubble removal performance of a degassing device using a gas-liquid separation membrane can be improved, and a decrease in moisture content in liquid can be suppressed. [Brief description of the drawings]

[0011] [Figure 1]FIG. 1 is a front view illustrating a schematic internal configuration of a printer according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating an ink supply path according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic cross-sectional view of a degassing device. [Figure 4] FIG. 2 is a schematic cross-sectional view of a degassing device. [Diagram 5] FIG. 2 is a schematic cross-sectional view of a degassing device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An inkjet recording apparatus 1 (an example of a liquid ejection apparatus) according to one embodiment of the present invention will now be described with reference to the drawings.

[0013] Fig. 1 is a front view showing a schematic internal configuration of inkjet recording apparatus 1. Fig. 2 is a schematic diagram showing ink supply path 60. In the following description, the front side of the paper in Fig. 1 is the front side (front side) of inkjet recording apparatus 1, and the left and right directions are described based on the direction seen from the front of inkjet recording apparatus 1. In each figure, U, Lo, L, R, Fr, and Rr respectively indicate up, down, left, right, front, and rear.

[0014] The inkjet recording device 1 (see FIG. 1) includes a rectangular parallelepiped main housing 3. A paper feed cassette 4 that stores individual sheets S, such as plain paper and coated paper, and a paper feed roller 5 that feeds the sheets S from the paper feed cassette 4 are provided in the lower part of the main housing 3. A transport unit 7 that attracts the sheets S and transports them in the Y direction is provided above the paper feed cassette 4. An image creating unit 6 that ejects ink to form an image is provided above the transport unit 7. An ejection roller 8 that ejects the sheets S on which an image has been formed, and an ejection tray 9 on which the ejected sheets S are stacked are provided in the upper right part of the main housing 3.

[0015] A transport path 10 is provided inside the main body housing 3, which extends from the paper feed roller 5 through the gap between the transport unit 7 and the imaging unit 6 to the discharge roller 8. The transport path 10 is mainly formed of plate-like members facing each other with a gap therebetween to allow the sheet S to pass through. The transport path 10 is provided with transport rollers 17 that hold and transport the sheet S. A registration roller 18 is provided upstream of the imaging unit 6 in the transport direction Y.

[0016] The transport unit 7 includes an endless transport belt 21, a support plate 23, and a suction unit 24. The transport belt 21 has many ventilation holes (not shown), and is wound around a drive roller 25 and a driven roller 22. The support plate 23 has many ventilation holes, and its upper surface is in contact with the inner surface of the transport belt 21. The suction unit 24 sucks air through the ventilation holes of the support plate 23 and the transport belt 21, thereby adsorbing the sheet S to the transport belt 21. The drive roller 25 is driven in the counterclockwise direction by a drive unit (not shown) including a motor and a reduction gear, so that the transport belt 21 rotates in the counterclockwise direction, and the sheet S adsorbed to the transport belt 21 is transported in the Y direction.

[0017] The imaging unit 6 includes head units 11Y, 11Bk, 11C, and 11M (collectively referred to as head unit 11). The head unit 11 includes one or more inkjet heads 12 (see FIG. 2), for example, three inkjet heads 12 arranged in a staggered pattern. Ink containers 20Y, 20Bk, 20C, and 20M (collectively referred to as ink containers 20) filled with yellow, black, cyan, and magenta inks, respectively, are connected to the head units 11Y, 11Bk, 11C, and 11M via ink supply paths 60 (see FIG. 2).

[0018] In FIG. 2, an ink supply path 60 corresponding to one color of ink is illustrated, but in this embodiment, four colors of ink are used, so that four ink supply paths 60 are actually provided. The inkjet recording device 1 includes a container mounting section 61 to which an ink container 20 is attached, a filter 62 for filtering ink, a pump 63 for sucking ink from the ink container 20 through the filter 62, and a sub-tank 64 for storing ink sent from the pump 63 and supplying ink to the inkjet head 12. A flow path 31 is provided that runs from the container mounting section 61 through the filter 62, the pump 63, and the sub-tank 64 to the inkjet head 12. Note that, although one inkjet head 12 is illustrated in FIG. 2, three inkjet heads 12 belonging to one head unit 11 are actually connected to one sub-tank 64.

[0019] The control unit 2 (see FIG. 1) includes a calculation unit and a storage unit (not shown). The calculation unit is, for example, a CPU (Central Processing Unit). The storage unit includes storage media such as a ROM (Read Only Memory), a RAM (Random Access Memory), and an EEPROM (Electrically Erasable Programmable Read Only Memory). The calculation unit performs various processes by reading and executing control programs stored in the storage unit. The control unit 2 may be realized by an integrated circuit that does not use software.

[0020] A display operation unit 19 is provided on the upper part of the main body housing 3 (see FIG. 1). The display operation unit 19 includes a display panel, a touch panel laminated on the display panel, and a keypad (not shown). The control unit 2 displays a screen showing the operation menu and status of the inkjet recording device 1 on the display panel, and controls each part of the inkjet recording device 1 in response to operations detected by the touch panel and the keypad.

[0021] The basic image forming operation of the inkjet recording device 1 is as follows. When an image formation job is input to the inkjet recording device 1 from the display operation unit 19, an external computer, or the like, the paper feed rollers 5 feed the sheet S from the paper feed cassette 4 to the transport path 10, and the registration rollers 18, whose rotation has been stopped, correct any skew of the sheet S. When the registration rollers 18 feed the sheet S to the transport unit 7 at a predetermined timing, the transport unit 7 attracts the sheet S to the transport belt 21 and transports it in the Y direction. Ink is ejected from the inkjet head 12, and an image is formed on the sheet S. The ejection rollers 8 eject the sheet S on which the image has been formed to an ejection tray 9.

[0022] [Degassing device] Figures 3 to 5 are schematic cross-sectional views of the degassing device 30. Figure 4 shows a cross-section taken along line II in Figure 3. Figure 5 shows a cross-section taken along line III-III in Figure 3. Figure 3 shows a cross-section taken along line II-II in Figures 4 and 5.

[0023] The degassing device 30 according to the present embodiment includes a flow path 31 through which a liquid (e.g., ink) containing water flows, a reduced pressure chamber 34 in contact with the flow path 31, a gas-liquid separation membrane 35 that is provided at the boundary between the flow path 31 and the reduced pressure chamber 34 and allows gas to pass through, a reduced pressure pump 36 that reduces the pressure in the reduced pressure chamber 34, and a bubble removal unit 40 that removes bubbles from the liquid. The bubble removal unit 40 includes a water tank 41 that stores water, a storage unit 42 that temporarily stores the liquid flowing through the flow path 31, the liquid surface of which is open to the atmosphere and is immersed in the water in the water tank 41, an ultrasonic generator 43 that propagates ultrasonic waves to the storage unit 42 through the water in the water tank 41, and a communication pipe 44 that communicates the space above the water surface of the water tank 41 with the reduced pressure chamber 34. Specifically, the structure is as follows. The ink according to the present embodiment is a water-based ink (aqueous ink) that contains water, a pigment or dye, glycerin, an organic solvent, and the like.

[0024] [Flow passage (ink chamber)] Ink is supplied along the flow path 31 in a direction from the ink container 20 to the inkjet head 12 (hereinafter referred to as the supply direction F). A section of the flow path 31 between the pump 63 and the subtank 64 has a cross section perpendicular to the ink supply direction F enlarged compared to the upstream and downstream sides of the supply direction F. This section with an enlarged cross section is called an ink chamber 33. The ink chamber 33 constitutes a part of the flow path 31. In this example, the cross section of the ink chamber 33 is rectangular, but the cross section of the ink chamber 33 may have any shape. The pump 63 is, for example, a diaphragm pump, and is driven by a control signal output by the control unit 2.

[0025] [Gas-liquid separation membrane] An opening 33A is provided in a part of the ink chamber 33 (in this example, a part corresponding to the bottom). The opening 33A is closed by a gas-liquid separation membrane 35. The gas-liquid separation membrane 35 is made of silicone rubber with a thickness of about 0.1 mm, for example. Note that the gas-liquid separation membrane 35 may be made of a film such as polyethylene or polypropylene.

[0026] [Decompression chamber] The decompression chamber 34 is in contact with the ink chamber 33 via a gas-liquid separation membrane 35. An opening 34A having the same dimensions as the opening 33A of the ink chamber 33 is provided in a part of the decompression chamber 34 (in this example, a part corresponding to the ceiling). The opening 33A of the ink chamber 33 and the opening 34A of the decompression chamber 34 are joined with the gas-liquid separation membrane 35 in between. In other words, the gas-liquid separation membrane 35 is provided at the boundary between the ink chamber 33 (part of the flow path 31) and the decompression chamber 34.

[0027] [Pressure reducing pump, valve] A pressure reduction flow path 38 is connected to the pressure reduction chamber 34. A pressure reduction pump 36 and a valve 37 are provided in the pressure reduction flow path 38. The pressure reduction pump 36 is, for example, a diaphragm pump, and is driven by a control signal output by the control unit 2. The valve 37 is, for example, a solenoid valve, and is opened and closed by a control signal output by the control unit 2.

[0028] [Air pressure sensor] The air pressure sensor 52 is provided inside the decompression chamber 34 and is connected to the control unit 2. The air pressure sensor 52 measures the air pressure inside the decompression chamber 34 and outputs air pressure data indicating the measured air pressure value to the control unit 2.

[0029] [Air bubble removal section] The air bubble removing section 40 is provided downstream in the ink supply direction F of the ink chamber 33. The air bubble removing section 40 includes a water tank 41, a storage section 42, an ultrasonic generator 43, and a communication tube 44.

[0030] Water is contained in the water tank 41. The water tank 41 has a ceiling portion 41T. The storage portion 42 is provided on the flow path 31 and is immersed in the water in the water tank 41. The storage portion 42 has a box-shaped structure with a cross section larger than that of the flow path 31 when viewed from the supply direction F. The storage portion 42 temporarily stores the ink flowing from the ink chamber 33. The stored ink is supplied to the sub-tank 64. The storage portion 42 has a ceiling portion 42T. The ceiling portion 42T is provided with an air vent pipe 42P that protrudes upward. The tip of the air vent pipe 42P penetrates the ceiling portion 41T of the water tank 41 and protrudes above the ceiling portion 41T. The space above the ink liquid level in the storage portion 42 (hereinafter referred to as the upper space 42U) is open to the atmosphere.

[0031] The water tank 41 is provided with an ultrasonic generator 43. The ultrasonic generator 43 is provided, for example, so as to cover the side and bottom surfaces of the water tank 41, and transmits ultrasonic waves to the storage section 42 through the water in the water tank 41. The communication pipe 44 communicates the water tank 41 with the decompression chamber 34. One end of the communication pipe 44 is connected to the water tank 41 at a location above the water surface in the water tank 41. The other end of the communication pipe 44 is connected to the decompression chamber 34. In other words, the communication pipe 44 communicates the space above the water surface of the water tank 41 (hereinafter referred to as the upper space 41U) with the decompression chamber 34. Therefore, when the decompression chamber 34 is decompressed, the upper space 41U is also decompressed.

[0032] Next, the operation of the degassing device 30 will be described. The control unit 2 operates the decompression pump 36 and determines whether the air pressure in the decompression chamber 34 measured by the air pressure sensor 52 has dropped to a predetermined value (for example, 0.6 kPa). When the air pressure has dropped to the predetermined value, the control unit 2 closes the valve 37 and stops the decompression pump 36. With the valve 37 closed, the air pressure in the decompression chamber 34 is maintained at the predetermined value.

[0033] In the bubble removal section 40, ultrasonic waves are transmitted to the ink temporarily stored in the storage section 42, causing the ink to vibrate, and air bubbles present in the ink are released from the ink surface through the upper space 42U into the atmosphere. In addition, ultrasonic waves are transmitted to the water stored in the water tank 41, causing the water to vibrate, promoting the generation of water vapor. In addition, the upper space 41U of the water tank 41 is depressurized, further promoting the generation of water vapor. The water vapor is supplied to the depressurized chamber 34 through the communication pipe 44.

[0034] The gas-liquid separation membrane 35 has a mesh-like molecular structure, so that microscopically, the ink chamber 33 and the decompression chamber 34 are connected via gaps between the molecules. The gaps between the molecules are large enough for gas molecules to pass through, so ink and gas coexist near the surface of the gas-liquid separation membrane 35 on the ink chamber 33 side. This gas includes air that was dissolved in the ink. Because the decompression chamber 34 is decompressed, the air that was dissolved in the ink passes through the gas-liquid separation membrane 35 and is sucked into the decompression chamber 34.

[0035] Conventionally, when the pressure in the reduced pressure chamber 34 is reduced, the amount of water vapor in the reduced pressure chamber 34 also decreases, and so the water vapor resulting from evaporation of the moisture in the ink, together with the air dissolved in the ink, is sucked into the reduced pressure chamber 34. In contrast, in this embodiment, the reduced pressure chamber 34 is humidified by supplying water vapor from the water tank 41 through the communicating tube 44 to the reduced pressure chamber 34, and the reduction in the amount of water vapor in the reduced pressure chamber 34 is suppressed, so that evaporation of the moisture in the ink is also suppressed.

[0036] According to the degassing device 30 of the present embodiment described above, the degassing device 30 includes a flow path 31 through which a liquid containing water (e.g., ink) flows, a reduced pressure chamber 34 in contact with the flow path 31, a gas-liquid separation membrane 35 that is provided at the boundary between the flow path 31 and the reduced pressure chamber 34 and allows gas to pass through, a reduced pressure pump 36 that reduces the pressure in the reduced pressure chamber 34, and a bubble removal unit 40 that removes bubbles from the liquid, the bubble removal unit 40 including a water tank 41 that stores water, a storage unit 42 that temporarily stores the liquid flowing through the flow path 31 and is immersed in the water in the water tank 41 with the liquid surface open to the atmosphere, an ultrasonic generator 43 that propagates ultrasonic waves to the storage unit 42 via the water in the water tank 41, and a communication pipe 44 that communicates the space above the water surface of the water tank 41 with the reduced pressure chamber 34. This configuration improves the bubble removal performance of the degassing device 30 using the gas-liquid separation membrane 35 and suppresses a decrease in water in the liquid.

[0037] The above embodiment may be modified as follows.

[0038] In the above embodiment, an example is shown in which the degassing device 30 is provided between the pump 63 and the sub-tank 64 , but the degassing device 30 may be provided at any position on the flow path 31 .

[0039] In the above embodiment, an example has been shown in which the bubble removal unit 40 is provided on the downstream side of the decompression chamber 34 in the supply direction F, but the bubble removal unit 40 may be provided on the upstream side of the decompression chamber 34 in the supply direction F. With this configuration, the same effects as those of the above embodiment can be obtained.

[0040] Moreover, the air bubble removal section 40 may be provided on both the upstream side and the downstream side of the decompression chamber 34 in the supply direction F. According to this configuration, it is possible to improve the air bubble removal performance compared to the case where the air bubble removal section 40 is provided on either the upstream side or the downstream side.

[0041] In the above embodiment, an example in which the present invention is applied to the inkjet recording device 1 has been shown, but the present invention may also be applied to an inkjet type liquid ejection device that ejects liquids other than ink, including water. For example, the present invention may be applied to a liquid ejection device that ejects a treatment liquid for performing base treatment on the sheet S, a liquid in which a conductor is dispersed and used to form an electric circuit, a light-emitting material used to manufacture an organic EL (Electro-Luminescence) panel, a dye for textile printing, or liquefied resin or ceramics used to form a three-dimensional object by a 3D printer. [Explanation of symbols]

[0042] 1 Inkjet recording device (liquid ejection device) 12 Inkjet head 30 Deaeration device 31 Flow Path 34 Decompression Chamber 35 Gas-liquid separation membrane 36 Pressure reducing pump 40 Air bubble removal section 41 Aquarium 42 Storage section 43 Ultrasonic generator 44 Communication pipe

Claims

1. A flow path through which a liquid containing water flows; A decompression chamber in contact with the flow path; a gas-liquid separation membrane provided at a boundary between the flow path and the decompression chamber and allowing gas to pass therethrough; A decompression pump that decompresses the decompression chamber; and an air bubble removing unit that removes air bubbles from the liquid. The air bubble removal unit includes: A tank for containing water; a reservoir that temporarily stores the liquid flowing through the flow path, the liquid level of the reservoir being open to the atmosphere and immersed in the water in the water tank; an ultrasonic generator that propagates ultrasonic waves to the storage section through the water in the water tank; a communication pipe that connects a space above the water surface of the water tank with the reduced pressure chamber.

2. 2. The degassing device according to claim 1, wherein the bubble removing section is provided on the upstream side and downstream side of the decompression chamber.

3. A degassing device according to claim 1 or 2; an inkjet head that ejects the liquid supplied from the flow path.

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