Degassing device and liquid ejection device

Abstract

The purpose of the present invention is to minimize reduction in moisture in liquid when the liquid is to be deaerated using a gas-permeable membrane. A deaeration apparatus (30) comprises: a flow passage (31) through which liquid flows; a decompression chamber (34); a membrane (35) that allows gas to pass therethrough; a decompression pump (36); and a humidification device (41). The decompression chamber (34) is in contact with the flow passage (31). The membrane (35) is disposed at the boundary between the flow passage (31) and the decompression chamber (34). The decompression pump (36) reduces the air pressure within the decompression chamber (34). The humidification device (41) humidifies the decompression chamber 34.

Description

[Technical Field]

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

[0002] In inkjet recording apparatuses, the amount of dissolved gas in ink can increase, which can cause air bubbles to form inside the inkjet head and lead to ink ejection failure.

[0003] Therefore, conventionally, techniques for reducing the amount of dissolved gas in ink have been studied. For example, Patent Document 1 describes a configuration including a decompression chamber and a vacuum pump. The decompression chamber houses a hollow fiber membrane connected to an ink flow path. The vacuum pump degasses the ink inside the hollow fiber membrane by reducing the pressure in the decompression chamber.

[0004] Patent Document 2 describes a second configuration in addition to the first configuration similar to that of Patent Document 1. In the second configuration, ultrasonic vibrations are used to release minute air bubbles adhering to pigments or metal particles contained in the ink.

[0005] Patent Document 3 describes a third configuration including a defoaming chamber and a decompression chamber. In the third configuration, the decompression chamber decompresses the defoaming chamber to remove air from the liquid, and a wall between the defoaming chamber and the decompression chamber is permeable to gas. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-147365 [Patent Document 2] Japanese Patent Application Publication No. 2019-217712 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-46820 Summary of the Invention [Problem to be solved by the invention]

[0007] The hollow fiber membrane has a high gas separation performance but a low durability, and the gas-permeable wall member has the advantage of being more durable and less expensive than the hollow fiber membrane.

[0008] However, when a water-based ink is used, the wall member is more permeable to water vapor formed by evaporation of water in the ink than the hollow fiber membrane, which can easily cause a problem of increased viscosity of the ink.

[0009] An object of the present invention is to provide a degassing device and a liquid ejection device that can suppress a decrease in moisture content in a liquid when the liquid is degassed using a gas-permeable membrane. [Means for solving the problem]

[0010] A degassing device according to one aspect of the present invention includes a flow path through which a water-containing liquid flows, a pressure reduction chamber, a membrane, a pressure reduction pump, and a humidifier. The pressure reduction chamber is disposed in contact with the flow path. The membrane is provided at the boundary between the flow path and the pressure reduction chamber. Gas can permeate through the membrane. The pressure reduction pump reduces the pressure in the pressure reduction chamber. The humidifier humidifies the pressure reduction chamber.

[0011] The humidifier may include a reservoir for storing water, and a water supply pump. The water supply pump supplies water from the reservoir to the decompression chamber.

[0012] The degassing device may include a water sensor and a control unit. The water sensor detects a predetermined amount of water in the decompression chamber. The control unit controls the water supply pump. The control unit operates the water supply pump when the water sensor does not detect the predetermined amount of water.

[0013] The control unit may be configured to operate the water supply pump while the decompression pump is stopped.

[0014] The membrane may be silicone rubber.

[0015] A liquid ejection device according to another aspect of the present invention includes the degassing device and a head that ejects the liquid supplied from the flow path. [Effects of the Invention]

[0016] According to the present invention, when a liquid is degassed using a gas-permeable membrane, it is possible to suppress a decrease in the moisture content of the liquid. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a front view schematically illustrating the internal configuration of a printer according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing the arrangement of inkjet heads according to one embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view of an inkjet head according to one embodiment of the present invention. [Figure 4] FIG. 4 is a diagram schematically illustrating an ink supply path according to one embodiment of the present invention. [Figure 5] FIG. 5 is a diagram schematically illustrating the configuration of a degassing device according to one embodiment of the present invention. [Figure 6] FIG. 6 is a diagram schematically illustrating the configuration of a degassing device according to one embodiment of the present invention. [Figure 7] FIG. 7 is a flow chart showing the control of the degassing device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] A printer 1 according to an embodiment of the present invention will be described below with reference to the drawings. The printer 1 is an example of an inkjet recording device.

[0019] First, we will explain the overall configuration of the printer 1. In the following explanation, the front side of the paper in Figure 1 will be the front side (front side) of the printer 1. Furthermore, the left and right directions will be explained based on the direction when viewing the printer 1 from the front. In each figure, U, Lo, L, R, Fr, and Rr represent up, down, left, right, front, and rear, respectively.

[0020] The printer 1 includes a rectangular parallelepiped main body housing 3 (see FIG. 1). A paper feed cassette 4 and a paper feed roller 5 are provided in the lower part of the main body housing 3.

[0021] The paper feed cassette 4 stores sheets S such as plain paper, coated paper, etc. The paper feed roller 5 feeds the sheets S from the paper feed cassette 4 to the right.

[0022] A transport unit 7 that adsorbs and transports the sheet S in the Y direction is provided above the paper feed cassette 4. An image forming unit 6 that ejects ink to form an image is provided above the transport unit 7.

[0023] A paper discharge roller 8 and a paper discharge tray 9 are provided in the upper right portion of the main body housing 3. Inside the main body housing 3, a transport path 10 is provided that runs from the paper feed roller 5 through the gap between the transport unit 7 and the imaging unit 6 to the paper discharge roller 8.

[0024] The sheet ejection rollers 8 eject the sheet S on which the image has been formed from the conveyance path 10. The ejected sheet S is stacked on a sheet ejection tray 9.

[0025] The conveying path 10 is mainly composed of plate-like members that face each other with a gap therebetween to allow the sheet S to pass through. Conveying rollers 17 that hold and convey the sheet S are provided at multiple locations in the conveying direction Y on the conveying path 10. Registration rollers 18 are provided upstream of the imaging unit 6 in the conveying direction Y.

[0026] The transport unit 7 includes an endless transport belt 21, a support plate 23, and a suction unit 24. The transport belt 21 has a large number of ventilation holes (not shown), and is wound around a drive roller 25 and a driven roller 22.

[0027] The support plate 23 has a large number of ventilation holes. The upper surface of the support plate 23 is in contact with the inner surface of the conveyor belt 21. The suction unit 24 sucks air through the ventilation holes in the support plate 23 and the ventilation holes in the conveyor belt 21, thereby adsorbing the sheet S to the conveyor belt 21.

[0028] The drive roller 25 is driven counterclockwise by a drive unit (not shown) including a motor and a reduction gear, causing the conveyor belt 21 to rotate counterclockwise, and the sheet S attracted to the conveyor belt 21 is conveyed in the Y direction.

[0029] The imaging unit 6 includes head units 11Y, 11Bk, 11C, and 11M that eject yellow, black, cyan, and magenta ink, respectively. Ink containers 20Y, 20Bk, 20C, and 20M filled with yellow, black, cyan, and magenta ink, respectively, are connected to the head units 11Y, 11Bk, 11C, and 11M.

[0030] In the following description, the head unit 11 is a general term for the head units 11Y, 11Bk, 11C, and 11M, and the ink container 20 is a general term for the ink containers 20Y, 20Bk, 20C, and 20M.

[0031] The head unit 11 includes one or more inkjet heads 12. For example, the head unit 11 includes three inkjet heads 12 arranged in a staggered pattern (see FIG. 2). The inkjet head 12 includes a housing 12H and a nozzle plate 12P (see FIG. 3). The housing 12H is a rectangular parallelepiped with its longitudinal direction extending in the front-to-rear direction. The nozzle plate 12P is provided at the bottom of the housing 12H.

[0032] The nozzle plate 12P has a large number of nozzles 12N arranged in the front-rear direction. Each nozzle 12N includes a branch flow path 12B and an ejection port 12A. The branch flow path 12B branches off from a flow path 31 that connects to a sub-tank 64. The ejection port 12A is provided in a nozzle surface 12F.

[0033] The diaphragm 12V forms a part of the inner wall of the branch flow path 12B. Each of the diaphragms 12V is provided with a pressure element 12Z. The housing 12H is provided with a driver 50 and a control circuit 40. The driver 50 drives the pressure element 12Z. The control circuit 40 controls the driver 50.

[0034] For example, a piezoelectric element, an electrostatic element (electrostatic actuator), or a heating element () used in a thermal inkjet system is used as the pressure element 12Z.

[0035] The printer 1 is equipped with ink supply paths 60 (see FIG. 4). In FIG. 4, the ink supply path 60 corresponding to one color of ink is shown. However, in this embodiment, four colors of ink are used, so four similar ink supply paths 60 are provided.

[0036] The printer 1 includes a container mounting unit 61, an ink supply pump 63, and a sub-tank 64. The container mounting unit 61 is where the ink container 20 is mounted. The ink supply pump 63 sucks ink from the ink container 20. The sub-tank 64 stores the ink pumped from the ink supply pump 63.

[0037] The control unit 2 (see FIG. 1) includes a calculation unit and a storage unit. The calculation unit is, for example, a CPU (Central Processing Unit). The storage unit includes a storage medium such as a ROM (Read Only Memory), a RAM (Random Access Memory), or an EEPROM (Electrically Erasable Programmable Read Only Memory).

[0038] The calculation unit performs various processes by reading and executing the control program stored in the storage unit. Note that the control unit 2 may be realized by an integrated circuit without using software.

[0039] A display / operation unit 19 is provided on the top of the main body housing 3 (see FIG. 1). The display / operation unit 19 includes a display panel, a touch panel, and a keypad. The touch panel is provided over the display surface of the display panel. The keypad is disposed adjacent to the display panel.

[0040] The control unit 2 causes the display panel to display screens showing operation menus, status, etc. of the printer 1. Furthermore, the control unit 2 controls each part of the printer 1 in response to operations detected on the touch panel or the keypad.

[0041] The basic image formation operation of the printer 1 is as follows: When an image formation job is input to the printer 1 from the display operation unit 19 or an external computer, the paper feed roller 5 sends the sheet S from the paper feed cassette 4 to the conveyance path 10. Furthermore, the registration roller 18, whose rotation has been stopped, corrects any skew in the sheet S.

[0042] The registration rollers 18 send out the sheet S at a predetermined timing to the transport unit 7. As a result, the transport unit 7 transports the sheet S in the Y direction while adsorbing the sheet S to the transport belt 21.

[0043] When the control unit 2 supplies raster format image data to the control circuit 40 in synchronization with the conveyance of the sheet S, the driver 50 supplies an ejection signal corresponding to the gradation data to the pressure element 12Z. This causes ink to be ejected from the nozzle 12N, forming an image on the sheet S. The paper ejection roller 8 ejects the sheet S on which the image has been formed onto the paper ejection tray 9.

[0044] Next, a description will be given of the configuration of the degassing device 30. Figures 5 and 6 are diagrams that schematically show the configuration of the degassing device 30. Figure 5 shows a cross section taken along line II-II in Figure 6, and Figure 6 shows a cross section II in Figure 5.

[0045] The degassing device 30 includes a flow path 31, a pressure reduction chamber 34, a gas-liquid permeable membrane 35, a pressure reduction pump 36, and a humidifying device 41. Ink flows through the flow path 31. Ink is an example of a liquid that contains water.

[0046] The decompression chamber 34 is disposed in contact with the flow path 31. The gas-liquid permeable membrane 35 is provided at the boundary between the flow path 31 and the decompression chamber 34. The gas-liquid permeable membrane 35 is an example of a membrane that is permeable to gas.

[0047] The decompression pump 36 decompresses the decompression chamber 34. The humidifier 41 humidifies the decompression chamber 34.

[0048] The ink according to this embodiment is a water-based ink (aqueous ink), which contains, for example, water, a pigment or dye, glycerin, an organic solvent, and the like.

[0049] [Flow path (ink chamber)] A section of the flow path 31 between the ink supply pump 63 and the subtank 64 is the ink chamber 33. The cross section of the ink chamber 33 perpendicular to the ink supply direction F is larger than the cross sections of the ink chamber 33 on the upstream and downstream sides in the ink supply direction F in the flow path 31. The ink chamber 33 constitutes a part of the flow path 31.

[0050] 5 and 6, the ink chamber 33 has a rectangular cross section, but the ink chamber 33 may have any cross section. The ink supply pump 63 is, for example, a diaphragm pump. The ink supply pump 63 operates in accordance with a control signal output by the control unit 2.

[0051] [Gas-liquid permeable membrane] An opening is formed in a part of the ink chamber 33. In the example shown in Figures 5 and 6, the opening is formed in the bottom of the ink chamber 33. The opening is covered with a gas-liquid permeable membrane 35.

[0052] The gas-liquid permeable membrane 35 is, for example, silicone rubber with a thickness of about 0.1 mm. Alternatively, the gas-liquid permeable membrane 35 may be made of polyethylene, polypropylene, or the like.

[0053] [Decompression chamber] The decompression chamber 34 is in contact with the ink chamber 33 via a gas / liquid permeable membrane 35. An opening having the same dimensions as the opening of the ink chamber 33 is formed in a part of the decompression chamber 34 (the ceiling in this example). In the example shown in Figures 5 and 6, the opening is formed in the ceiling of the decompression chamber 34.

[0054] The opening of the ink chamber 33 and the opening of the decompression chamber 34 are joined together with the gas-liquid permeable membrane 35 sandwiched therebetween. In other words, the gas-liquid permeable membrane 35 is provided at the boundary between the ink chamber 33 and the decompression chamber 34, which are part of the flow path 31.

[0055] [Reducing pump, valve] A decompression pump 36 is connected to the decompression chamber 34. The decompression pump 36 is, for example, a diaphragm pump. The decompression pump 36 operates in accordance with a control signal output by the control unit 2.

[0056] A valve 37 is provided between the decompression pump 36 and the decompression chamber 34. The valve 37 is, for example, a solenoid valve. The valve 37 opens and closes in accordance with a control signal output by the control unit 2.

[0057] [humidifier] The humidifier 41 includes a reservoir 42 for storing water and a water supply pump 43. The water supply pump 43 supplies water from the reservoir 42 to the decompression chamber 34. The reservoir 42 is a tank.

[0058] The water supply pump 43 is, for example, a tube pump. The water supply pump 43 operates in accordance with a control signal output from the control unit 2.

[0059] [Water sensor] The water sensor 51 is provided at the bottom of the decompression chamber 34 and is connected to the control unit 2.

[0060] The water sensor 51 includes, for example, a pair of electrodes facing each other in the horizontal direction and provided at a predetermined height from the bottom of the decompression chamber 34. When the water level supplied to the decompression chamber 34 reaches the position of the pair of electrodes, a current flows between the pair of electrodes via the water.

[0061] When a current flows between the pair of electrodes, the water sensor 51 outputs a detection signal indicating that water has been detected to the control unit 2. In other words, the water sensor 51 detects a predetermined amount of water in the decompression chamber 34.

[0062] [Barometric pressure sensor] The air pressure sensor 52 is provided at the top of 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.

[0063] Next, we will explain the operation of the degassing device 30. Fig. 7 is a flowchart showing the control content of the degassing device 30. When the printer 1 is turned on, the control unit 2 controls the degassing device 30 according to the flowchart shown in Fig. 6.

[0064] First, the control unit 2 opens the valve 37 (step S01). Next, the control unit 2 determines whether the water sensor 51 has detected a predetermined amount of water (step S02).

[0065] When the control unit 2 determines that the water sensor 51 has detected a predetermined amount of water, the process proceeds to step S06, which will be described later (YES in step S02).

[0066] On the other hand, if the control unit 2 determines that the water sensor 51 has not detected the predetermined amount of water, it activates the water supply pump 43 (NO in step S02, step S03).

[0067] After the water supply pump 43 is activated, the control unit 2 determines whether or not the water sensor 51 has detected a predetermined amount of water (step S04). If the control unit 2 determines that the water sensor 51 has not detected the predetermined amount of water, it repeats the determination of step S04 (NO in step S04).

[0068] On the other hand, when the control unit 2 determines that the water sensor 51 has detected the predetermined amount of water, it stops the water supply pump 43 (YES in step S04, step S05).

[0069] Next, the control unit 2 activates the decompression pump 36 (step S06). Furthermore, the control unit 2 determines whether the air pressure in the decompression chamber 34 measured by the air pressure sensor 52 has decreased to a predetermined value (step S07). The predetermined value of the air pressure is, for example, 0.6 kPa.

[0070] If the control unit 2 determines that the air pressure has not decreased to the predetermined value, it repeats the determination in step S07 (NO in step S07).

[0071] On the other hand, when the control unit 2 determines that the air pressure has dropped to the predetermined value, it closes the valve 37 and stops the decompression pump 36 (YES in step S07, step S08). When the valve 37 is closed, the air pressure in the decompression chamber 34 is maintained at the predetermined value.

[0072] Next, the control unit 2 determines whether or not a print job has started (step S09). If the control unit 2 determines that a print job has not started, it repeats the determination in step S09 (NO in step S09).

[0073] On the other hand, when the control unit 2 determines that the print job has started, it opens the valve 37 and activates the decompression pump 36 (NO in step S09, step S10). That is, the pressure in the decompression chamber 34 is reduced in parallel with the execution of the print job.

[0074] Next, the control unit 2 determines whether the print job has ended (step S11). If the control unit 2 determines that the print job has not ended, it repeats the determination in step S11 (NO in step S11).

[0075] On the other hand, if the control unit 2 determines that the print job has ended, it stops the pressure reducing pump 36 and repeats the processes from step S02 onwards (YES in step S11, step S12).

[0076] As described above, the degassing device 30 includes the flow path 31, the decompression chamber 34 in contact with the flow path 31, the gas-liquid permeable membrane 35, the decompression pump 36, and the humidifier 41. Ink, which is an example of a liquid containing water, flows through the flow path 31. The gas-liquid permeable membrane 35 is provided at the boundary between the flow path 31 and the decompression chamber 34. The gas-liquid permeable membrane 35 is an example of a membrane that is permeable to gas. The decompression pump 36 decompresses the decompression chamber 34. The humidifier 41 humidifies the decompression chamber 34.

[0077] The gas-liquid permeable film 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 in the gas-liquid permeable film 35.

[0078] The gaps between the molecules are large enough to allow gas molecules to pass through. Therefore, liquid and water vapor coexist near the surface of the gas-liquid permeable membrane 35 on the ink chamber 33 side. In conventional devices, when the pressure in the decompression chamber 34 is reduced, the amount of water vapor in the decompression chamber 34 also decreases, so the water in the ink vaporizes and is sucked into the decompression chamber 34.

[0079] On the other hand, in this embodiment, the decompression chamber 34 is humidified, thereby suppressing a decrease in the amount of water vapor in the decompression chamber 34. This suppresses the phenomenon in which the moisture in the ink evaporates and is sucked into the decompression chamber 34. According to this embodiment, when degassing a liquid using a gas-permeable membrane, it is possible to suppress a decrease in the moisture in the liquid.

[0080] Furthermore, in the degassing device 30 according to this embodiment, the humidifying device 41 includes a reservoir 42 that stores water, and a water supply pump 43. The water supply pump 43 supplies water from the reservoir 42 to the reduced pressure chamber 34. With this configuration, the reduced pressure chamber 34 is humidified by water vapor that is naturally generated from the water. Therefore, the reduced pressure chamber 34 can be humidified at low cost.

[0081] Furthermore, the degassing device 30 according to this embodiment includes a water sensor 51 that detects a predetermined amount of water in the decompression chamber 34, and a control unit 2 that controls the water supply pump 43. The control unit 2 operates the water supply pump 43 when the water sensor 51 does not detect the predetermined amount of water. This configuration prevents the humidifying device 41 from becoming unable to perform humidification.

[0082] Furthermore, in the degassing device 30 according to this embodiment, the control unit 2 operates the water supply pump 43 while the decompression pump 36 is stopped. With this configuration, the decompression chamber 34 returns to atmospheric pressure when the decompression pump 36 is stopped. Therefore, a decrease in the moisture content of the liquid is prevented when water is being supplied to the decompression chamber 34.

[0083] Furthermore, in the degassing device 30 according to this embodiment, the gas-liquid permeable membrane 35 is made of silicone rubber. Silicone rubber is inexpensive. However, the use of silicone rubber can easily cause the inconvenience of moisture in the ink evaporating and being sucked into the decompression chamber 34. However, in this embodiment, the humidifying device 41 suppresses the loss of moisture in the ink, so the cost of the gas-liquid permeable membrane 35 can be suppressed while avoiding the above-mentioned inconvenience.

[0084] The above embodiment may be modified as follows.

[0085] In the above embodiment, an example has been shown in which the opening of the ink chamber 33 and the opening of the decompression chamber 34 are joined together with the gas-liquid permeable membrane 35 sandwiched therebetween. However, in a modified example, a partial section of the flow path 31 may be formed by the tubular gas-liquid permeable membrane 35, and the decompression chamber 34 may be configured to surround the section formed by the gas-liquid permeable membrane 35. With this configuration, the same effects as in the above embodiment can be obtained.

[0086] In the above embodiment, an example has been shown in which the present invention is applied to a degassing device 30 that uses a gas-liquid permeable membrane 35. However, in a modified example, the present invention may be applied to a degassing device that uses a hollow fiber membrane instead of the gas-liquid permeable membrane 35. This is because even when a hollow fiber membrane is used, the phenomenon of moisture in the ink being sucked into the decompression chamber can still occur.

[0087] In the above embodiment, the degassing device 30 is provided in the flow path 31 between the ink supply pump 63 and the subtank 64. However, in a modified example, the degassing device 30 may be provided at any position in the flow path 31 from the ink container 20 to the inkjet head 12.

[0088] In the above embodiment, an example in which the present invention is applied to an inkjet recording apparatus is shown, but the present invention may also be applied to a liquid ejection apparatus that ejects liquids other than ink, including water.

[0089] For example, the heating unit may heat various liquids. For example, the objects to be heated by the heating unit may include a treatment liquid for performing a surface treatment on the sheet S, a liquid containing dispersed conductors used to form electrical circuits, a light-emitting material used to manufacture organic electroluminescence (EL) panels, dyes for textile printing, or liquefied resin or ceramics used to form three-dimensional objects using a 3D printer. In this case, the present invention may be applied to the heating unit.

Claims

1. a liquid chamber that is a part of a flow path through which a liquid containing water flows; a decompression chamber in contact with the liquid chamber; a gas-permeable membrane provided at a boundary between the liquid chamber and the decompression chamber; a decompression pump connected to the decompression chamber and decompressing the decompression chamber; a humidifier for humidifying the decompression chamber; a storage section for storing water; a water supply pump that supplies water from the reservoir to the decompression chamber, A degassing device in which the cross section of the liquid chamber perpendicular to the direction of passage of the liquid is formed larger than both the cross section of the inlet portion of the liquid into the liquid chamber in the flow path and the cross section of the outlet portion of the liquid from the liquid chamber.

2. a water sensor for detecting a predetermined amount of water in the decompression chamber; a control unit that controls the water supply pump, The degassing device according to claim 1 , wherein the control unit activates the water supply pump when the water sensor does not detect the predetermined amount of water.

3. The degassing device according to claim 2 , wherein the control unit operates the water supply pump while the pressure reducing pump is stopped.

4. 4. The degassing device according to claim 1, wherein the membrane is made of silicone rubber.

5. A head that ejects a liquid containing water supplied through a flow path through which the liquid flows; A liquid ejection device comprising: the degassing device according to claim 1 , which is disposed in the flow path.

Images