Deaeration device and liquid discharge device

Abstract

To improve deaeration efficiency 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 humidification chamber 71 which contacts with the passage 31 at a position different from that of the decompression chamber 34 and contains water; a first 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 second gas-liquid separation membrane 72 which is provided at a border part between the passage 31 and the humidification chamber 71 and allows the gas to penetrate therethrough; and a decompression pump 36 which decompresses the decompression chamber 34.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 consideration of the above circumstances, an object of the present invention is to improve the degassing efficiency of a degassing device using a gas-liquid separation membrane and to suppress a decrease in moisture in a liquid. [Means for solving the problem]

[0006] 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 humidification chamber in contact with the flow path at a location different from the pressure reduction chamber and containing water, a first gas-liquid separation membrane provided at the boundary between the flow path and the pressure reduction chamber and permeable to gas, a second gas-liquid separation membrane provided at the boundary between the flow path and the humidification chamber and permeable to gas, and a pressure reduction pump that reduces the pressure in the pressure reduction chamber.

[0007] The area of ​​the first gas-liquid separation membrane may be different from the area of ​​the second gas-liquid separation membrane.

[0008] The first gas-liquid separation membrane and the second gas-liquid separation membrane may have a different thickness.

[0009] The first gas-liquid separation membrane and the second gas-liquid separation membrane may be made of different materials.

[0010] 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

[0011] According to the present invention, the degassing efficiency of a degassing device using a gas-liquid separation membrane can be improved, and a decrease in the moisture content of the liquid can be suppressed. [Brief description of the drawings]

[0012] [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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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).

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] [Degassing device] 3 and 4 are diagrams that typically show a cross section of the degassing device 30. Fig. 4 shows a cross section taken along line II in Fig. 3. Fig. 3 shows a cross section taken along line II-II in Fig. 4.

[0024] The degassing device 30 according to this embodiment includes a flow path 31 through which a liquid containing water (e.g., ink) flows, a pressure reduction chamber 34 in contact with the flow path 31, a humidification chamber 71 that is in contact with the flow path 31 at a location different from the pressure reduction chamber 34 and contains water, a first gas-liquid separation membrane 35 that is provided at the boundary between the flow path 31 and the pressure reduction chamber 34 and is permeable to gas, a second gas-liquid separation membrane 72 that is provided at the boundary between the flow path 31 and the humidification chamber 71 and is permeable to gas, and a pressure reduction pump 36 that reduces the pressure in the pressure reduction chamber 34. Specifically, they are as follows. The ink according to this embodiment is a water-based ink (aqueous ink) and contains water, a pigment or dye, glycerin, an organic solvent, and the like.

[0025] [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.

[0026] [First 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 ceiling), and the opening 33A is closed by a first gas-liquid separation membrane 35. The first gas-liquid separation membrane 35 is made of silicone rubber with a thickness of about 0.1 mm, for example. Note that the first gas-liquid separation membrane 35 may be made of a membrane such as polyethylene or polypropylene.

[0027] [Decompression chamber] The decompression chamber 34 is in contact with the ink chamber 33 via a first 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 bottom). The opening 33A of the ink chamber 33 and the opening 34A of the decompression chamber 34 are joined with the first gas-liquid separation membrane 35 in between. In other words, the first 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.

[0028] [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.

[0029] [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.

[0030] [Second gas-liquid separation membrane] An opening 33B is provided in a part of the ink chamber 33 (in this example, a part corresponding to the bottom), and the opening 33B is closed by a second gas-liquid separation membrane 72. The second gas-liquid separation membrane 72 is made of silicone rubber with a thickness of about 0.1 mm, for example. Note that the second gas-liquid separation membrane 72 may be made of a membrane such as polyethylene or polypropylene.

[0031] [Humidification room] The humidification chamber 71 is in contact with the ink chamber 33 via a second gas-liquid separation membrane 72. An opening 71B having the same dimensions as the opening 33B of the ink chamber 33 is provided in a part of the humidification chamber 71 (in this example, a part corresponding to the ceiling). The opening 33B of the ink chamber 33 and the opening 71B of the humidification chamber 71 are joined with the second gas-liquid separation membrane 72 sandwiched between them. In other words, the second gas-liquid separation membrane 72 is provided at the boundary between the ink chamber 33 (part of the flow path 31) and the humidification chamber 71.

[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] Since the first gas-liquid separation membrane 35 has a mesh-like molecular structure, 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 first gas-liquid separation membrane 35 on the ink chamber 33 side. This gas includes air that was dissolved in the ink. Since the decompression chamber 34 is decompressed, the air that was dissolved in the ink passes through the first gas-liquid separation membrane 35 and is sucked into the decompression chamber 34.

[0034] Due to the mesh-like molecular structure of the second gas-liquid separation membrane 72, the ink chamber 33 and the humidification chamber 71 are connected microscopically through 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 second gas-liquid separation membrane 72 on the ink chamber 33 side. This gas contains water vapor produced by evaporation of water contained in the humidification chamber 71. The water vapor in the humidification chamber 71 has reached saturated water vapor pressure. Therefore, the water vapor passes through the second gas-liquid separation membrane 72 and enters the ink chamber 33.

[0035] Conventionally, when the pressure in the decompression chamber 34 is reduced, the amount of water vapor in the decompression chamber 34 also decreases, and the water vapor resulting from the evaporation of moisture in the ink is sucked out together with the air dissolved in the ink into the decompression chamber 34. In contrast, in this embodiment, water vapor is supplied to the ink chamber 33 through the second gas-liquid separation membrane 72, so that the water vapor sucked out into the decompression chamber 34 can be replenished.

[0036] Here, consider a comparative example in which the humidification chamber 71 also serves as the decompression chamber 34. Specifically, the humidification chamber 71 is provided with the decompression flow path 38, the decompression pump 36, and the valve 37, but is not provided with the opening 33A, the first gas-liquid separation membrane 35, or the decompression chamber 34. In this case, it is known that the amount of water vapor that permeates the second gas-liquid separation membrane 72 from the ink chamber 33 and moves to the humidification chamber 71 is different from the amount of water vapor that permeates the second gas-liquid separation membrane 72 from the humidification chamber 71 and moves to the ink chamber 33. In order to suppress a decrease in the moisture of the ink in the ink chamber 33, it is necessary to make the amount of water vapor leaving the ink chamber 33 close to the amount of water vapor entering the ink chamber 33, but this is difficult with the configuration of the comparative example.

[0037] In contrast, in this embodiment, by making the specifications of the first gas-liquid separation film 35 and the second gas-liquid separation film 72 different, it is possible to make the amount of water vapor leaving the ink chamber 33 and the amount of water vapor entering the ink chamber 33 closer to each other. For example, if the first gas-liquid separation film 35 and the second gas-liquid separation film 72 have the same thickness and material, then, if A1 is the area of ​​the first gas-liquid separation film 35, A2 is the area of ​​the second gas-liquid separation film 72, and R is the molar fraction of water in the ink, then by setting the relationship between A1 and A2 according to formula (1), it is possible to make the amount of water vapor leaving the ink chamber 33 and the amount of water vapor entering the ink chamber 33 substantially the same. A2=A1×R / (1-R) ​​Formula (1)

[0038] Generally, the molar fraction of water in water-based inks is about 0.9, so A2 should be about 9 times A1, but by making A2 at least larger than A1, it is possible to suppress the loss of water in the ink more than in the comparative example.

[0039] The degassing device 30 according to the present embodiment described above includes a flow path 31 through which a liquid containing moisture (e.g., ink) flows, a pressure reduction chamber 34 in contact with the flow path 31, a humidification chamber 71 that is in contact with the flow path 31 at a location different from the pressure reduction chamber 34 and contains water, a first gas-liquid separation membrane 35 that is provided at the boundary between the flow path 31 and the pressure reduction chamber 34 and is permeable to gas, a second gas-liquid separation membrane 72 that is provided at the boundary between the flow path 31 and the humidification chamber 71 and is permeable to gas, and a pressure reduction pump 36 that reduces the pressure in the pressure reduction chamber 34. This configuration improves the degassing efficiency of a degassing device that uses a gas-liquid separation membrane, and suppresses a decrease in moisture in the liquid.

[0040] Furthermore, in the degassing apparatus 30 according to this embodiment, the area of ​​the first gas-liquid separation membrane 35 is different from the area of ​​the second gas-liquid separation membrane 72. With this configuration, even if the first gas-liquid separation membrane 35 and the second gas-liquid separation membrane 72 are the same in thickness and made of the same material, the reduction in moisture in the liquid can be suppressed by simply changing the area, thereby reducing costs.

[0041] The above embodiment may be modified as follows.

[0042] In the above embodiment, an example has been shown in which the area of ​​the first gas-liquid separation membrane 35 and the area of ​​the second gas-liquid separation membrane 72 are different, but the thickness of the first gas-liquid separation membrane 35 and the thickness of the second gas-liquid separation membrane 72 may be different. Specifically, making the second gas-liquid separation membrane 72 thinner than the thickness of the first gas-liquid separation membrane 35 has the same effect as making the area of ​​the second gas-liquid separation membrane 72 larger than the area of ​​the first gas-liquid separation membrane 35, so that the area of ​​the second gas-liquid separation membrane 72 can be reduced, and as a result, the size of the degassing device 30 can be reduced.

[0043] However, making the second gas-liquid separation membrane 72 thinner than the first gas-liquid separation membrane 35 may result in a decrease in durability of the second gas-liquid separation membrane 72. Therefore, when priority is placed on durability rather than the size of the degassing device 30, it is desirable not to make the second gas-liquid separation membrane 72 thinner.

[0044] Furthermore, the material of the first gas-liquid separation membrane 35 may be different from the material of the second gas-liquid separation membrane 72. For example, using a material that is more permeable to water vapor than the first gas-liquid separation membrane 35 as the second gas-liquid separation membrane 72 has the same effect as making the area of ​​the second gas-liquid separation membrane 72 larger than the area of ​​the first gas-liquid separation membrane 35, so that the area of ​​the second gas-liquid separation membrane 72 can be reduced, and as a result, the size of the degassing device 30 can be reduced.

[0045] Furthermore, using a material for the second gas-liquid separation membrane 72 that is more permeable to water vapor than the first gas-liquid separation membrane 35 has the same effect as making the second gas-liquid separation membrane 72 thinner than the first gas-liquid separation membrane 35, thereby improving the durability of the second gas-liquid separation membrane 72.

[0046] Furthermore, any two of the area, thickness, and material may be different between the first gas-liquid separation membrane 35 and the second gas-liquid separation membrane 72, or all of the area, thickness, and material may be different. With this configuration, it is possible to achieve both a reduction in the size of the degassing device 30 and durability of the second gas-liquid separation membrane 72.

[0047] 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 .

[0048] 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]

[0049] 1 Inkjet recording device (liquid ejection device) 12 Inkjet head 30 Deaeration device 31 Flow Path 34 Decompression Chamber 35 First gas-liquid separation membrane 36 Pressure reducing pump 71 Humidification room 72 Second gas-liquid separation membrane

Claims

1. A flow path through which a liquid containing water flows; A decompression chamber in contact with the flow path; a humidification chamber that is in contact with the flow path at a location different from the decompression chamber and that contains water; a first gas-liquid separation membrane provided at a boundary between the flow path and the decompression chamber and permeable to gas; a second gas-liquid separation membrane provided at a boundary between the flow path and the humidification chamber and allowing gas to permeate; and a decompression pump for decompressing the decompression chamber.

2. 2. The degassing apparatus according to claim 1, wherein an area of ​​the first gas-liquid separation membrane is different from an area of ​​the second gas-liquid separation membrane.

3. 3. The degassing apparatus according to claim 1, wherein the first gas-liquid separation membrane and the second gas-liquid separation membrane have different thicknesses.

4. 3. The degassing apparatus according to claim 1, wherein the first gas-liquid separation membrane and the second gas-liquid separation membrane are made of different materials.

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

Images