JP2019018527A - Droplet discharge device and inkjet printer - Google Patents

Abstract

To provide a droplet discharge device including a filter unit which can inhibit gas from remaining therein.SOLUTION: A droplet discharge device includes a droplet discharge head and a filter unit 2A. The droplet discharge head includes a nozzle 45 which discharges droplets. The filter unit includes: a casing 21 disposed in a passage of liquid to be supplied to the droplet discharge head; and a filter which is disposed so as to partition the interior of the casing into a primary side chamber and a secondary side chamber. In the filter, a bubble point of a filter area located at an upstream side in a direction of flow of the liquid in the casing is smaller than a bubble point of a filter area located at a downstream side.SELECTED DRAWING: Figure 4

Description

  Embodiments described herein relate generally to a droplet discharge device and an inkjet printer.

  2. Description of the Related Art A droplet discharge device including a droplet discharge head that supplies a predetermined amount of droplets to a predetermined position is known. The droplet discharge device is mounted on, for example, an ink jet printer, a 3D printer, a dispensing device, or the like. An ink jet printer ejects ink droplets from an ink jet head to form an image or the like on the surface of a recording medium. The 3D printer discharges a droplet of a modeling material such as a liquid resin from a modeling material discharge head and cures it to form a three-dimensional modeled object. The dispensing device is a device that supplies a predetermined amount of sample to a plurality of containers or the like.

  In the droplet discharge device, a filter unit is provided in the flow path of the liquid supplied to the droplet discharge head. For example, when a foreign substance is mixed in the liquid, the filter unit captures the foreign substance with the filter and prevents the droplet discharge head from being clogged. In the filter unit, for example, air may remain inside when the liquid is initially passed. Air remaining in the filter unit may reduce the effective filtration area of the filter.

JP-A-2005-161617 JP 2009-12316 A JP 2014-124946 A

  The problem to be solved by the present invention is to provide a droplet discharge device and an ink jet printer provided with a filter unit capable of suppressing gas from remaining inside, for example, when liquid is initially passed.

  In order to solve the above problems, a droplet discharge device according to an embodiment includes a droplet discharge head and a filter unit. The droplet discharge head includes a nozzle that discharges droplets. The filter unit includes a casing disposed in a flow path of a liquid supplied to the droplet discharge head, and a filter disposed so as to partition the inside of the casing into a primary side chamber and a secondary side chamber. In the filter, the bubble point of the filtration region located on the upstream side in the flow direction of the liquid in the casing is smaller than the bubble point of the filtration region located on the downstream side.

It is a longitudinal cross-sectional view which shows schematic structure of the inkjet printer carrying the droplet discharge apparatus of 1st Embodiment. It is a side view which shows schematic structure of the droplet discharge apparatus of 1st Embodiment. It is a perspective view of the droplet discharge device of a 1st embodiment. It is an expanded view of the droplet discharge apparatus of 1st Embodiment. It is an expanded view of the filter unit of 1st Embodiment. It is a longitudinal cross-sectional view of the filter unit of 1st Embodiment. It is explanatory drawing which shows an example of the bubble point of the filter of 1st Embodiment. It is explanatory drawing which shows typically the liquid flow in the filter unit of 1st Embodiment. It is explanatory drawing which shows typically the flow of the liquid in the filter unit with the bubble point of a filter uniform. It is a longitudinal cross-sectional view of the filter unit of the droplet discharge device of the second embodiment. It is explanatory drawing which shows typically the liquid flow in the filter unit of 2nd Embodiment. It is a perspective view of the filter unit of the droplet discharge device of a 3rd embodiment.

  Hereinafter, a droplet discharge device and an ink jet printer according to an embodiment will be described in detail with reference to the accompanying drawings. In the drawings, the same components are denoted by the same reference numerals.

(First embodiment)
An inkjet printer 100 that prints an image on a recording medium such as a sheet S will be described as an example of an inkjet printer equipped with the droplet discharge device 1 of the embodiment. The droplet discharge device 1 of the embodiment includes an inkjet head 10A (10B to 10D) that is an example of a droplet discharge head. Further, the droplet discharge device 1 includes a filter unit 2A that captures foreign matter when, for example, foreign matter is mixed into the ink supplied to the ink jet head 10A (10B to 10D) (see FIG. 2).

  FIG. 1 shows a schematic configuration of an inkjet printer 100 equipped with inkjet heads 10A to 10D. The ink jet printer 100 includes a box-shaped housing 101 that is an exterior body, for example. Inside the housing 101 are cassettes 102A and 102B for storing sheets S as an example of a recording medium, an upstream conveyance path 106 for the sheets S, a conveyance belt 110 for holding the sheets S for image forming processing, and sheets. Ink jet heads 10 </ b> A to 10 </ b> D that discharge ink droplets toward S, a downstream conveyance path 120 of the sheet S, and a discharge tray 123 are arranged. The ink jet printer 100 further includes an operation unit 144 including a display screen as a user interface and a control board 140 as a control unit.

  Data of an image formed on the sheet S by the ink jet printer 100 is generated by the computer 150, for example. Image data generated by the computer 150 is input to the inkjet printer 100 through the cable 143 and the connectors 141A and 141B. The inkjet heads 10 </ b> A to 10 </ b> D discharge, for example, cyan, magenta, yellow, and black ink droplets to a predetermined position of the sheet S on the conveyance belt 110 to print an image corresponding to the image data on the sheet S. .

  The cassette 102A and the cassette 102B store sheets S of different sizes, for example. The upstream conveyance path 106 is composed of a pair of feed rollers 105a, 105b, and 105c and sheet guide plates 106a and 106b that define the sheet conveyance path. The pickup roller 104 supplies the sheets S from the cassette 102A to the upstream conveyance path 106 one by one. The sheet S is conveyed by the pair of rotating feed rollers 105a and 105b, and after passing through the pair of feed rollers 105a, is fed to the upper surface of the conveyor belt 110 by the sheet guide plate 106a. An arrow A1 in the drawing indicates a conveyance path of the sheet S from the cassette 102A. On the other hand, the pickup roller 109 supplies the sheets S from the cassette 102B to the upstream conveyance path 106 one by one. The sheet S is conveyed by a pair of rotating feed rollers 105a, 105b, and 105c. After passing through the pair of feed rollers 105c, the sheet S is fed to the upper surface of the conveyor belt 110 by sheet guide plates 106a and 106b. An arrow A2 in the drawing indicates a conveyance path of the sheet S from the cassette 102B.

  The conveyor belt 110 is a net-like endless belt having a large number of through holes formed on the surface thereof. The conveyor belt 110 is rotatably supported by three rollers, that is, a driving roller 112a and driven rollers 112b and 112c. The driving roller 112a is rotated by a motor 111 which is an example of a driving device. A3 in the figure indicates the direction of rotation of the conveyor belt 110. A negative pressure container 113 is disposed on the back side of the conveyor belt 110. The upper surface of the negative pressure container 113 is in contact with the back surface of the conveyor belt 110. Many fine holes 114 are formed on the upper surface of the negative pressure vessel 113. The negative pressure container 113 is connected to a decompression fan 115, and the inside of the container is decompressed by an air flow formed by the fan 115. A4 in the figure indicates the flow of airflow. The sheet S is adsorbed and held on the upper surface of the conveyance belt 110 when the negative pressure container 113 is depressurized. The cassettes 102A and 102B, the upstream conveyance path 106, and the conveyance belt 110 constitute a recording medium conveyance device that conveys the sheet S to a position facing the inkjet heads 10A to 10D. When the sheet S sucked and held on the upper surface of the conveyance belt 110 passes under the inkjet heads 10A to 10D, an image is formed.

  The ink jet heads 10 </ b> A to 10 </ b> D are arranged so as to face the sheet S sucked and held on the conveyance belt 110 through a slight gap of 1 mm, for example. The ink jet heads 10A to 10D have the same structure except that the colors of ink to be ejected are different. The detailed structure of the inkjet heads 10A to 10D will be described later.

  Ink tanks 130 </ b> A to 130 </ b> D and ink supply pressure adjusting devices 131 </ b> A to 131 </ b> D are connected to the inkjet heads 10 </ b> A to 10 </ b> D via ink flow paths 135, respectively. The ink flow path 135 is, for example, a resin tube. Further, a filter unit 2A described later is disposed on the side surface of the ink jet head 10A (see FIG. 2). The inkjet heads 10B to 10D are the same as the inkjet head 10A. The ink tanks 130A to 130D are containers that store ink. Further, maintenance units 132A to 132D are arranged in the vicinity of the inkjet heads 10A to 10D. For example, the maintenance unit 132A of the ink jet head 10A includes a cap 133 that protects the surface of the ink discharge nozzle of the ink jet head 10A, and a blade 134 that removes deposits remaining on the surface of the ink discharge nozzle. The maintenance units 132B to 132D of the other inkjet heads 10B to 10D have the same configuration.

  Each ink tank 130A-130D is arrange | positioned above each inkjet head 10A-10D. In order to prevent ink from leaking out from the ink discharge nozzles of the inkjet heads 10A to 10D during standby, the ink supply pressure adjusting devices 131A to 131D are negative in the inkjet heads 10A to 10D with respect to atmospheric pressure. I try to become pressure. The negative pressure is set to −1 kPa, for example. At the time of image formation, the ink in each of the ink tanks 130A to 130D is supplied to each of the inkjet heads 10A to 10D by the ink supply pressure adjusting devices 131A to 131D.

  A temperature adjustment unit 3 that further adjusts the temperature of the ink jet heads 10 </ b> A to 10 </ b> D is disposed in the housing 101. The temperature adjustment unit 3 includes a constant temperature tank 31 that stores hot water that is an example of a temperature adjustment fluid, and a pump 32 that is an example of a liquid feeding device that supplies the hot water to each of the inkjet heads 10A to 10D. The flow path of the warm water has a supply path 33 that supplies the warm water in the constant temperature tank 31 to each of the inkjet heads 10A to 10D, and a recovery path 34 that returns the warm water discharged from each of the inkjet heads 10A to 10D to the constant temperature tank 31. The hot water circulates through the ink jet heads 10 </ b> A to 10 </ b> D and the constant temperature tank 31 through the supply path 33 and the recovery path 34. The hot water flow paths 33 and 34 are formed of, for example, a resin tube. The constant temperature tank 31 may further include a heating or cooling device and a temperature sensor for keeping the hot water at a predetermined temperature. In addition, although the figure has shown the structure which supplies warm water to each inkjet head 10A-10D from the common temperature adjustment unit 3, it makes it arrange | position the separate temperature adjustment unit 3 for each inkjet head 10A-10D. May be.

  The sheet S on which the image is formed is sent from the conveyance belt 110 to the downstream conveyance path 120. The downstream conveyance path 120 includes feed roller pairs 120a, 120b, 120c, and 120d and sheet guide plates 121a and 121b that define the conveyance path of the sheet S. The sheet S is sent from the discharge port 122 to the discharge tray 123 by the feed roller pairs 120a, 120b, 120c, and 120d. An arrow A5 in the figure indicates the conveyance path of the sheet S.

  Next, the configurations of the inkjet heads 10A to 10D and the filter units 2A to 2D will be described with reference to FIGS. The inkjet heads 10A to 10D are provided with filter units 2A to 2D, respectively. The following describes the inkjet head 10A and the filter unit 2A. However, the inkjet heads 10B to 10D and the filter units 2B to 2D have the same structure as the inkjet head 10A and the filter unit 2A.

  The inkjet head 10 </ b> A has a configuration in which a pair of symmetrical inkjet head portions 4 </ b> A and 4 </ b> B that can eject ink droplets of the same color are arranged on both side surfaces of the temperature control member 5. Hot water from the constant temperature tank 31 is supplied to the temperature adjustment member 5. As shown in the developed view of FIG. 4 in particular, the inkjet head unit 4A includes a nozzle head unit 41, an ink supply unit 42, a flexible printed wiring board 43, a driving circuit board 44, and a flexible printed wiring board 43 and a driving circuit board 44. A protective cover 48 is provided. The nozzle head portion 41 includes a nozzle plate 45, a flow path substrate 46 constituting an actuator, and a cover member 47 for forming a pressure chamber. In addition, the inkjet head part 4B arrange | positioned on the opposite surface of the temperature control member 5 has the same structure as 4A of inkjet head parts.

  The nozzle plate 45 is a rectangular plate formed of, for example, a resin such as polyimide or a metal such as stainless steel. In particular, as shown in a partial cross-section in FIG. 2, a plurality of nozzles 45 a that are ejection holes for ejecting ink droplets are formed on the surface of the nozzle plate 45. The nozzle density of the nozzle plate 45 is set within a range of 150 to 1200 dpi, for example. The cover member 47 for forming the pressure chamber is a box-shaped member in which a surface on the flow path substrate 46 side and a surface on the nozzle plate 45 side are opened. The cover member 47 may be formed by adhering a top plate to one surface of a U-shaped frame. On one surface of the flow path substrate 46 surrounded by the cover member 47, a plurality of ink pressure chambers 46a extending along the direction of gravity and a plurality of piezoelectric bodies 46b serving as walls defining the pressure chambers 46a are formed. The plurality of pressure chambers 46a having side walls formed of the piezoelectric body 46b communicate with the nozzle 45a so as to be in a one-to-one relationship. The piezoelectric body 46b which is the side wall of the pressure chamber 46a is formed by bonding two plate-like piezoelectric bodies made of, for example, lead zirconate titanate (PZT) so that the polarization directions are opposite to each other. Has been.

  An electrode (not shown) such as a nickel thin film is formed on the side wall and the bottom surface of each pressure chamber 46a. When a predetermined pulse voltage is applied to the electrodes, the piezoelectric body 46a is deformed and further returns to the original state. The volume change of the pressure chamber 46a generated by the deformation and return of the piezoelectric body 46a becomes a driving force for ejecting ink in the pressure chamber 46a from the nozzle 45a. That is, the pressure chamber 46a and the piezoelectric body 46b constitute an actuator that performs shear mode deformation. The width and depth of the pressure chamber 46a can be changed as appropriate according to the specifications of the inkjet printer 100 and the like. As an example, it is set within a range of several tens to several hundreds of μm. The ink droplets ejected by the deformation of the piezoelectric body 46b are set, for example, within a range of 1 to 180 picoliters. The nozzle 45a, the pressure chamber 46a, the piezoelectric body 46b, etc. are drawn larger than the actual dimensions for the convenience of drawing.

  The electrodes of each pressure chamber 46 a are electrically connected to the drive circuit board 44 through the flexible printed wiring board 43. An IC (Integrated Circuit) 44a for driving is mounted on the driving circuit board 44 serving as a discharge operation control unit. The drive circuit board 44 temporarily stores image data from the control board 140 of the inkjet printer 100 in a buffer, and operates an actuator so that ink droplets are ejected at a predetermined timing for forming an image. Is output. The electric signal is a pulse voltage applied to the electrode of each pressure chamber 45a. A cable (not shown) that electrically connects the drive circuit board 44 and the control board 140 of the inkjet printer 100 is wired using the opening 48 a of the protective cover 48. One end of the cable is connected to, for example, a connector 44b of the drive circuit board 44.

  The ink supply unit 42 is fixedly disposed on the surface of the pressure chamber forming cover member 47. The ink supply unit 42 is a rectangular member having an ink flow path formed therein. One end side of the ink flow path of the ink supply unit 42 communicates with a common ink chamber which is a space in the cover member 47, and the other end side is connected to the filter unit 2A. The ink that has passed through the filter unit 2A is supplied to the common ink chamber in the cover member 47 through the ink supply unit 42, and is further supplied to each pressure chamber 46a that communicates with the common ink chamber.

  The flexible printed wiring board 43 and the protective cover 48 of the drive circuit board 44 are made of, for example, a resin material. The protective cover 48 is fixed to the temperature adjustment member 5 so as to be detachable.

  The temperature control member 5 is made of ceramics, for example. A hot water supply port 51 and a discharge port 52 are respectively formed on the upper surface of the temperature control member 5. The hot water supply port 51 and the discharge port 52 communicate with a hot water flow path 53 formed inside the temperature control member 5. The temperature adjustment member 5 also serves as a support member that supports the nozzle head portion 41 and the drive circuit board 44. The temperature adjustment member 5 maintains the temperature of the nozzle head portion 41 and / or the drive circuit board 44 at a predetermined temperature by heat transfer from the hot water. For example, when using a high viscosity ink, the temperature of the hot water is set so that the nozzle head 41 has a predetermined temperature in order to reduce the viscosity of the ink. Alternatively, the temperature of the hot water is set so as to keep the temperature of the drive circuit board 44, which becomes high due to current flow, at a relatively low temperature. The temperature adjustment of the hot water is performed by changing the temperature setting of the constant temperature tank 31, for example. On the side surface on the short side of the temperature adjustment member 5, a support member 54 that is used when the inkjet head 10 </ b> A is attached to the inkjet printer 100 is provided.

  The ink is a liquid in which a dye or pigment is dissolved or dispersed in a solvent as a colorant. Ink solvents include aqueous, oily, and solvent.

  Next, the filter unit 2A will be described. The filter unit 2A is arranged vertically on the side surface on the short side of the inkjet head 10A. The filter unit 2A includes a casing 21 whose outer shape extending in the direction of gravity is substantially rectangular. The casing 21 is formed of a resin material such as polyether ether ketone (PEEK). On the upper surface side of the casing 21, an inflow port 22 for ink sent from the ink supply pressure adjusting device 131 </ b> A via the flow path 135 is formed. On the other hand, an outlet 23 for ink that has passed through the filter 6 is formed on the bottom side of the casing 21. The outflow port 23 is formed by, for example, a cylindrical nozzle. Two outlets 23 are provided on the bottom surface of the casing 21 and are connected to the ink supply portions 42 of the pair of ink jet head portions 4A and 4B, respectively.

  The filter unit 2A is installed to prevent foreign matter from entering the ink jet head portions 4A and 4B when foreign matter is mixed into the ink. The filter unit 2A needs to widen the filtration area in order to prevent the ink flow rate from changing even if the foreign matter is captured and the effective filtration area is reduced. On the other hand, since the inkjet head 10A is required to be downsized, the filter unit 2A must also realize a small capacity. In particular, in the filter unit 2A, since the ink supplied to both of the pair of ink jet head portions 4A and 4B flows, the flow rate is larger than that in the case of a single ink jet head portion. As an example, the size of the inkjet head 10A is 80 to 90 mm in length, 60 to 70 mm in width, and 20 to 30 mm in thickness. As an example, the casing 21 serving as an exterior body of the filter unit 2A is set to have a height of 50 mm, a width direction length of 10 mm, and a thickness direction length of 10 mm.

  The filter 6 is provided in the casing 21 of the filter unit 2A as shown in the cross-sectional views of FIGS. The filter 6 is arranged vertically so that the filtration surface is along the direction of gravity. The filter 6 divides the internal space of the casing 21 into a primary side chamber 24 before filtration and a secondary side chamber 25 after filtration. The filter 6 is arrange | positioned in the center position so that the internal space of the casing 21 may be equally divided, for example. The ink inflow port 22 and the outflow port 23 are connected to a primary side chamber 24 and a secondary side chamber 25 in the casing 21, respectively.

  The casing 21 has a split structure at the primary side chamber 24 and the secondary side chamber 25. An edge portion where the casing 21a forming the primary side chamber 24 and the casing 21b forming the secondary side chamber 25 are joined to each other has a stepped shape so as to be joined by, for example, a step joint. And the filter unit 2A is formed by joining the casing 21a and the casing 21b with the annular gasket 26 and the filter 6 interposed therebetween. The casing 21a and the casing 21b are fixed with, for example, an adhesive. The gasket 26 is, for example, a fluorine-based resin or rubber.

  The filter 6 has a plate shape formed of a metal such as nickel electroformed foil, stainless steel, titanium, or the like. The dimensions of the filter 6 are set to a height of 50 mm, a width of 10 mm, and a thickness of 10 μm, for example. A large number of flow holes 61 (61a, 61b) having a size of several μm to several tens of μm are formed on the surface of the filter 6 so that ink can pass from the primary side chamber 24 to the secondary side chamber 25. It has become. Foreign matter that cannot pass through the flow holes 61 (61a, 61b) is captured by the filter 6. The foreign matter includes, for example, dust mixed from the outside when the ink tank 130A is replaced. The through holes 61 (61a, 61b) are formed by etching a metal plate, for example. The shape of the flow hole 61 (61a, 61b) is preferably a circle, but may be an ellipse or a rectangle. Further, a mesh filter may be used.

  In the above configuration, the ink flows in the casing 21 from the upper side toward the lower side. Accordingly, when viewed from the ink flow, the upper side of the entire filtering surface of the filter corresponds to the filtering region 62a positioned on the upstream side, and the lower side corresponds to the filtering region 62b positioned on the downstream side. And the through-hole 61a in the filtration area | region 62a located in an upstream is set larger than the through-hole 61b in the filtration area | region 62b located in a downstream.

  As shown in FIG. 7, the shape of the flow holes 61 (61 a, 61 b) is circular, and the flow holes 61 a of the upstream filtration region 62 a are set to have a hole diameter D 1 of 10 μm and a pitch P 1 of 18 μm. The through holes 61b in the downstream filtration region 62b have a hole diameter D2 of 9.25 μm and a pitch P2 of 18 μm. The diameters of the through holes 61a and 61b are set based on bubble points. For example, referring to the Japanese Industrial Standard (JIS K3802), the bubble point is: “When the filter is sufficiently wetted and pressurized from the opposite side of the filter surface with a gas that is poorly soluble in the solvent, bubbles first appear on the filter surface. This is the pressure that occurs. The test method for bubble point is based on the method specified in Japanese Industrial Standard (JIS K3832). Furthermore, when the hole diameter of the flow hole 61 (61a, 61b) is D [m], the surface tension of the ink is γ [N / m], the contact angle is θ [rad], and the bubble point is P [Pa], The calculation formula of D = 4γcos θ / P is established.

  The table of FIG. 7 is a value obtained by calculating the hole diameter D and the bubble point P of the flow hole 61 at intervals of 1 mm from the upper end to the lower end of the filter 6 using the above calculation formula. The value (default value) at the upper end of the table is adopted as the hole diameter 10 μm of the flow hole 61a in the upstream filtration region 62a. On the other hand, the value at the lower end of the table is adopted as the hole diameter 9.25 μm of the flow hole 61b in the downstream filtration region 62b. In the casing 21, as shown in the table, the liquid pressure increases as it falls from the upper end toward the lower end, so the hole diameter D is reduced to adjust the bubble point. The value of each hole diameter D [mm] shown in the table indicates that if the hole diameter is set smaller than this value, the ink flows first from the through hole having a hole diameter of 10 μm. As can be seen from the bubble point values of the pore diameter of 10 μm and the pore diameter of 9.25 μm, the bubble point (7300 [Pa]) of the upstream filtration region 62a is the bubble point (7888 [Pa]) of the downstream filtration region 62b. Smaller than).

  The upstream filtration region 62 a is set so as to occupy one third of the entire filtration surface of the filter 6. As described above, since the ink supplied to both of the pair of ink jet head portions 4A and 4B flows through the filter unit 2A, the ink jet head portion is set to one third of the entire filtration surface of the filter 6 by setting it to one third. The pressure loss in one case is the same. Of course, the upstream filtration region 62a can be changed according to the type of ink flowing through the filter unit 2A, the maximum flow rate, and the like. As an example, the upstream filtration region 62a can be appropriately changed within a range that is half or less of the entire filtration surface of the filter 6. Moreover, you may make it divide | segment by three or more several hole diameters instead of dividing by the two hole diameters like the flow-through holes 61a and 61b of the filtration surface of the filter 6. FIG.

  When the ink I is filled in the filter unit 2A having the above-described configuration, first, the primary side chamber 24 is filled with ink, as schematically shown in FIG. Since the ink I has a relatively high viscosity and the pore diameters of the flow holes 61 (61a, 61b) are fine, it is less resistance to flow to fill the primary side chamber 24 than to pass through the filter 6. It is. The ink I flows into the secondary chamber side 25 preferentially from the upper filtration region 62a where the bubble point is set to be small, and flows through the secondary chamber side 25 from the upper side toward the lower side, thereby forming the casing. 21 is filled with ink I. When the entire inside of the casing 21 is filled with the ink I, there is no large bias in pressure loss as in the initial liquid flow, so that the ink I flows almost uniformly through the entire filter 6.

  On the other hand, when the bubble point of the upstream filtration region 62a and the bubble point of the downstream filtration region 62b are uniformly the same, that is, the hole diameters of the flow hole 61a and the flow hole 62b of the filter 6 are set to be the same. In this case, since the hydraulic pressure on the lower side is higher by the height of the filter 6, as shown schematically in FIG. 9, the ink I enters the secondary chamber side 25 before the upper side from the lower side. Flows in. Since the pressure loss that passes through the filter 6 is greatest during the initial passage, if the flow of the ink I from the lower side is first formed, the ink I flows preferentially from the lower side. Therefore, air often remains in the upper part of the secondary side chamber 25. If air remains on the upper side, the effective filtration area of the filter 6 decreases.

  According to the above-described embodiment, the bubble point of the upstream filtration region 62a is made smaller than the bubble point of the downstream filtration region 62b, so that the secondary side chamber 25 of the casing 21 can be formed in the initial filling of ink. It is possible to suppress the air from remaining in the upper part. Although the above-mentioned embodiment uses the plate-like filter 6, it is not limited to the plate shape as long as it is a porous body. Further, an intermediate filtration region having a different hole diameter may be added between the upstream filtration region 62a and the downstream filtration region 62b.

(Second Embodiment)
Next, the filter unit provided in the droplet discharge device of the second embodiment will be described. The droplet discharge device of the second embodiment has the same configuration as the droplet discharge device of the first embodiment except that the configuration of the filter unit is different. Accordingly, the same components as those of the droplet discharge device of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the filter unit 7 of the second embodiment, as shown in FIG. 10, the upper side of the casing 71 is inclined toward the primary side chamber 24, and the separation distance from the filter 6 is small. As an example, the inclined surface 71a is formed by inclining the surface (inner surface) of the casing 71 facing the filtration region 62a having a small bubble point. As shown in FIGS. 5 to 7, when the filtration region 62a occupies one third of the entire filtration surface, the casing 71 also has an inclined surface 71a inclined by inclining the upper side that occupies one third of the surface. Form. The inclined surface 71 a forms an angle θ formed with the filtering surface of the filter 6. An angle θ formed by the inclined surface 71a and the filter 6 is, for example, 17 °. However, the inclined surface 71a is not limited to one third of the surface of the casing 71, and may be appropriately changed within a range of, for example, half or less. Furthermore, you may change suitably the angle (theta) which the inclined surface 71a and the filtration surface of the filter 6 make within the range of 15-25 degrees, for example.

  When the filter unit 71 having the above configuration is filled with the ink I, the primary side chamber 24 is first filled with the ink I, as schematically shown in FIG. This is because the ink I has a relatively high viscosity and the pore diameters of the flow holes 61 a and 61 b are fine, and therefore the resistance is smaller when flowing to fill the primary side chamber 24 than passing through the filter 6. Then, the ink I flows into the secondary side chamber 25 preferentially from the filtration region 62a having a small bubble point. Since the filtration area 62a and the inclined surface 71a of the secondary side chamber 25 are close to each other, the ink I that has flowed into the secondary side chamber 25 immediately comes into contact with the surface of the secondary side chamber 25. The ink I flows along the surface of the casing 71 to the lower side of the secondary side chamber 25 due to the affinity between the liquid ink I and the solid casing 71 surface.

  According to the above-described embodiment, the filter 6 has a smaller bubble point in the filtration region 62a located on the upstream side than the bubble point in the filtration region 62b located on the downstream side. It is possible to prevent air from remaining in the upper part of the secondary side chamber 25 of 71. Further, the surface (inner surface) of the casing 71 facing the filtration region 62a is inclined so that the separation distance from the filter 6 is reduced, so that the ink moves from the upper side to the lower side in the secondary side chamber 25. Can be promoted. Instead of the configuration in which the surface of the casing 71 is inclined, the filter 6 may be inclined to reduce the separation distance.

(Third embodiment)
Next, the filter unit provided in the droplet discharge device of the third embodiment will be described. The droplet discharge device of the third embodiment has the same configuration as the droplet discharge device of the first embodiment, except that the configuration of the filter unit is different. Accordingly, the same components as those of the droplet discharge device of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 12, the filter unit 8 of 3rd Embodiment has arrange | positioned the casing 81 horizontally. As an example, the casing 81 has a configuration in which a casing 81b serving as a top plate is attached to a lower casing 81a where the filter 6 is disposed. The ink inflow port 82 is disposed on the side surface on one end side of the casing 81, and the ink outflow port 83 that has passed through the filter 6 is disposed on the side surface on the other end side of the casing 81. The filter 6 is disposed horizontally with the filtration surface in a direction along the direction of gravity. Also in this case, since the ink flows in the casing 8 from the inlet 82 toward the outlet 83, when viewed from the ink flow, one end side of the entire filtration surface of the filter 6 hits the filtration region 62 a located on the upstream side, and the other The end side corresponds to the filtration region 62b located on the downstream side. And the flow hole 61a of the filtration area | region 62a located in an upstream is larger than the flow hole 61b of the filtration area | region 62b located in a downstream, similarly to 1st Embodiment.

  Further, the casing 81 has a shape in which a portion located on the upstream side is inclined upward from below. Therefore, the filter 6 has a shape in which the upper corner on the upstream side is notched into an inverted triangle. When the casing 81 is placed horizontally, the end face on the upstream side of the secondary chamber 25 is inclined upward from below to form an inclined surface 84. Using the affinity between the inclined surface 84 and the ink, air is prevented from remaining on the upper side.

  The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 100 Inkjet printer 10A-10D Inkjet head 2A-2D Filter unit 21 Casing 22 Inlet 23 Outlet
6 Filter 61a Upstream flow hole 61b Downstream flow hole 62a Upstream filtration area 62b Downstream filtration area 71 Casing 71a Inclined surface

Claims (5)

A droplet discharge head comprising a nozzle for discharging droplets;
A casing disposed in a flow path of a liquid supplied to the droplet discharge head, and disposed in such a manner as to partition the inside of the casing into a primary side chamber and a secondary side chamber, and is located upstream of the liquid flow direction in the casing. A droplet discharge device comprising: a filter unit comprising: a filter in which a bubble point of the filtration region is smaller than a bubble point of the filtration region located on the downstream side.   The separation distance to the surface of the secondary chamber of the casing facing the filtration region located on the upstream side is larger than the separation distance to the surface of the secondary chamber of the casing facing the filtration region located on the downstream side. The droplet discharge device according to claim 1, which is small. The filter is a plate-like filter having a filtration surface arranged in the direction of gravity,
3. The droplet according to claim 1, wherein the casing is fixedly disposed on a side surface of the droplet discharge head in a vertical position in which a liquid inflow port is located on an upper side and a liquid outflow port is located on a lower side. Discharge device. The droplet discharge device includes a plurality of droplet discharge heads,
4. The droplet discharge device according to claim 3, wherein the filter unit is connected to the plurality of droplet discharge heads through a supply path that supplies the liquid that has passed through the filter to each of the plurality of droplet discharge heads. An inkjet head having a nozzle for ejecting ink droplets;
A casing disposed in a flow path of ink to be supplied to the inkjet head, and a filtration region that is disposed so as to partition the inside of the casing into a primary side chamber and a secondary side chamber, and is located on the upstream side in the ink flow direction in the casing. A filter unit comprising a filter smaller than the bubble point of the filtration region where the bubble point is located on the downstream side,
A recording medium conveying device for conveying a recording medium to a position facing the inkjet head;
An ink jet printer comprising: a control unit that controls the ink jet head to eject ink to a predetermined position of the recording medium.