Deaeration unit and liquid discharge device

Abstract

To improve deaeration efficiency of a deaeration unit using a gas / liquid separation film and suppress moisture in liquid from reducing.SOLUTION: A deaeration unit 30 comprises: a flow passage 31 (for instance, an ink chamber 33) through which liquid (for instance, ink) including moisture flows; a decompression chamber 34 which contacts the flow passage 31 to store water; a gas / liquid separation film 35, arranged at a boundary part between the flow passage 31 and the compression chamber 34, through which gas is transmitted; a decompression pump 36 that decompresses the decompression chamber 34; and a heater 42 that heats at least either of the flow passage 31 and 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 content 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 and containing water, a gas-liquid separation membrane provided at the boundary between the flow path and the pressure reduction chamber and allowing gas to permeate, a pressure reduction pump for reducing the pressure in the pressure reduction chamber, and a heater for heating at least one of the flow path and the pressure reduction chamber.

[0007] The degassing device may include an exterior member covering an outer surface of at least one of the flow path and the reduced pressure chamber, and the heater may heat at least one of the flow path and the reduced pressure chamber via the exterior member.

[0008] The exterior member may be made of metal.

[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 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]

[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. 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] 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.

[0023] The degassing device 30 according to this embodiment includes a flow path 31 (e.g., an ink chamber 33) through which a liquid containing water (e.g., ink) flows, a reduced pressure chamber 34 that is in contact with the flow path 31 and contains water, 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 heater 42 that heats at least one of the flow path 31 and the reduced pressure chamber 34. More specifically, they are as follows. The ink according to this 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, the bottom part). 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 (the ceiling portion in this example). 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. Water is contained in 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] [Exterior materials] The ink chamber 33 and the decompression chamber 34 are covered with an exterior member 41 made of a metal, such as stainless steel or an aluminum alloy.

[0030] [Heater] The heater 42 is provided at the bottom of the exterior member 41 on the side of the reduced pressure chamber 34. The heater 42 is, for example, an electric heating wire stretched in a planar shape.

[0031] 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.

[0032] The heat generated by the heater 42 is transferred to the decompression chamber 34 and the ink chamber 33 via the exterior member 41. Because the flow path 31 and the decompression chamber 34 are in contact with each other, even if the heater 42 is disposed on one side of the flow path 31 and the decompression chamber 34, heat is transferred from one to the other, heating both the flow path 31 and the decompression chamber 34. In addition, the heat generated by the heater 42 is transferred uniformly within the range in which the exterior member 41 is provided.

[0033] 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.

[0034] 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 evaporation of the moisture in the ink is sucked into the decompression chamber 34 together with the air dissolved in the ink. In contrast, in this embodiment, heating the decompression chamber 34 promotes the evaporation of the water contained in the decompression chamber 34, so that the reduction in the amount of water vapor in the decompression chamber 34 is suppressed, and the evaporation of the moisture in the ink is suppressed. Furthermore, heating the ink chamber 33 reduces the amount of saturated dissolved air in the ink, improving degassing efficiency.

[0035] The degassing device 30 according to the present embodiment described above includes a flow path 31 (e.g., ink chamber 33) through which a liquid containing moisture (e.g., ink) flows, a reduced pressure chamber 34 that is in contact with the flow path 31 and contains water, 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 heater 42 that heats at least one of the flow path 31 and the reduced pressure chamber 34. This configuration improves the degassing efficiency of the degassing device 30 that uses the gas-liquid separation membrane 35, and suppresses a decrease in moisture in the liquid.

[0036] Moreover, the degassing device 30 according to this embodiment includes an exterior member 41 that covers the outer surface of at least one of the flow path 31 and the reduced pressure chamber 34, and the heater 42 heats at least one of the flow path 31 and the reduced pressure chamber 34 via the exterior member 41. With this configuration, heat can be uniformly transferred to at least one of the flow path 31 and the reduced pressure chamber 34.

[0037] Moreover, in the degassing device 30 according to this embodiment, the exterior member 41 is made of metal. With this configuration, the efficiency of heat transfer to the flow path 31 and the decompression chamber 34 can be improved.

[0038] The above embodiment may be modified as follows.

[0039] In the above embodiment, an example has been shown in which the heater 42 is provided at the bottom of the exterior member 41 on the side of the reduced pressure chamber 34, but the heater 42 may be provided at any position on the exterior member 41.

[0040] In addition to the configuration of the above embodiment, a water tank for storing water, a pump for supplying water from the water tank to the reduced pressure chamber 34, and a sensor for detecting the amount of water in the reduced pressure chamber 34 may be provided, and the device may be configured to replenish water when the amount of water in the reduced pressure chamber 34 falls below a predetermined value (not shown).

[0041] 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 .

[0042] 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]

[0043] 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 41 Exterior materials 42 Heater

Claims

1. A flow path through which a liquid containing water flows; a pressure reduction chamber in contact with the flow path and containing water; 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; a heater for heating at least one of the flow path and the decompression chamber.

2. an exterior member for covering an outer surface of at least one of the flow path and the decompression chamber; 2. The degassing device according to claim 1, wherein the heater heats at least one of the flow path and the decompression chamber through the exterior member.

3. 3. The degassing device according to claim 2, wherein the exterior member is made of metal.

4. A degassing device according to any one of claims 1 to 3; an inkjet head that ejects the liquid supplied from the flow path.

Images