JP2007008157A - Droplet ejector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a droplet ejecting apparatus capable of preventing ink ejected from an ejecting nozzle at the time of purging from adhering to the vicinity of an exit port of the ejecting nozzle as much as possible.
A flow path unit 2 of an inkjet head 1 includes a plurality of recovery nozzles 25 formed in the vicinity of a plurality of ejection nozzles 20 and a recovery flow path 28 communicating with the plurality of recovery nozzles 25, respectively. The recovery port 25 a of the recovery nozzle 25 opened on the ink ejection surface 40 is formed close to the emission port 20 a of the ejection nozzle 20. The inkjet printer 100 causes the suction pump 66 to eject ink from the emission port 20a in a state where the cap 65 covers both the emission port 20a and the collection port 25a, and further, the ejected ink is ejected from the collection port 25a. To the recovery channel 28.
[Selection] Figure 2

Description

  The present invention relates to a droplet ejecting apparatus that ejects liquid from a nozzle.

  An ink jet head ejects ink droplets from nozzles onto an object such as recording paper, but the nozzles are clogged with dust or thickened ink, or in the ink flow path including the nozzles. When air bubbles are mixed in, the ejection characteristics of the nozzle (droplet ejection amount, droplet flight direction, etc.) may become abnormal, and ink may not be ejected from the nozzle at all. For this reason, when a general inkjet head cannot eject ink normally from a nozzle, the so-called purge operation that forcibly ejects ink from the nozzle and discharges dust and bubbles to eliminate the abnormal state The structure for performing is provided.

  For example, an inkjet head (printing head) described in Patent Document 1 (Japanese Patent Application Laid-Open No. 5-220970) includes a cap (capping member) attached to an ink ejection surface so as to cover the emission ports of a plurality of nozzles, and the cap. And a suction pump connected via a tube. Then, with the cap attached to the ink ejection surface, the ink is sucked from a plurality of nozzles by a suction pump, and the ink is forcibly ejected into the space in the cap, thereby causing an abnormal ink ejection state of the inkjet head. Can be eliminated.

JP-A-5-220970

  However, during the purge operation, part of the ink that has flowed out of the nozzle tends to adhere to the vicinity of the emission port of the ink ejection surface in a bubbled state. Since the inside of the ink jet head is maintained at a negative pressure, the foamed ink returns to the inside of the nozzle and bubbles are mixed therein, and there is a possibility that the ink cannot be ejected from the nozzle again. . In addition, in order to collect and reuse the ink sucked by the suction pump during the purge operation, a complicated mechanism such as a tube connecting the ink sub tank and the cap provided in the movable inkjet head is required. Therefore, the sucked ink has been discarded in the ink waste liquid chamber without being reused.

  An object of the present invention is to provide a droplet ejecting apparatus capable of preventing as much as possible ink that has flowed out of an ejection nozzle during purging from adhering to the vicinity of the ejection opening of the ejection nozzle.

Means for Solving the Problems and Effects of the Invention

  According to the first aspect of the present invention, there is provided a liquid droplet ejecting apparatus that ejects liquid droplets, the liquid ejecting nozzle communicating with the ejecting nozzle, the collecting nozzle, and communicating with the collecting nozzle. A recovery channel, a channel unit having a droplet ejection surface on which an ejection port that is an opening of the ejection nozzle and a recovery port that is an opening of the recovery nozzle are formed; and a liquid in the ejection channel An injection pressure applying mechanism for applying an injection pressure, a cap capable of abutting on the droplet ejection surface so as to cover and cover both the ejection port of the ejection nozzle and the recovery port of the recovery nozzle, and the cap A purge pressure applying mechanism that causes the liquid in the ejection flow path to flow to the recovery flow path in a state of covering both the emission port and the recovery port, and the purge pressure applying mechanism The liquid flows out from the outlet Thereby, further, the droplet ejection apparatus is provided for recovering the liquid from the collection port to the recovery channel. In the droplet ejection surface, the collection port of the collection nozzle may be formed close to the emission port of the injection nozzle.

  According to the first aspect of the present invention, when an injection pressure is applied to the liquid in the ejection channel by the ejection pressure application mechanism, the liquid is ejected from the ejection nozzle communicating with the ejection channel. On the other hand, when the ejection of the liquid from the ejection nozzle becomes abnormal due to clogging of the ejection nozzle or mixing of bubbles into the ejection flow path, the purge pressure is maintained with the ejection nozzle outlet covered by the cap. By the applying mechanism, for example, the liquid in the ejection channel is caused to flow out from the ejection nozzle to the space between the cap and the droplet ejection surface.

  Here, for example, a recovery nozzle is formed in the vicinity of the injection nozzle, and the exit of the recovery nozzle may be provided close to the exit of the injection nozzle. At the time of purging the ejection nozzle, the ejection port of the ejection nozzle and the recovery port of the recovery nozzle are covered with a single cap so that the liquid that has flowed out of the ejection nozzle is separated from the space between the cap and the droplet ejection surface. To the recovery channel through the recovery nozzle. For this reason, most of the liquid foamed when flowing out from the ejection nozzle is collected and hardly adheres to the droplet ejection surface, and the amount of liquid adhering to the vicinity of the ejection port of the droplet ejection surface is reduced. Therefore, it is possible to prevent as much as possible that the liquid that is foamed when flowing out from the injection nozzle returns into the injection nozzle and causes an abnormal injection in the injection nozzle.

  In the droplet ejecting apparatus according to the aspect of the invention, the purge pressure applying mechanism may include a suction device that sucks from the recovery flow path side and decompresses the space formed between the cap and the droplet ejecting surface. But you can. Accordingly, by reducing the pressure in the space between the cap and the droplet ejection surface by the suction device, the liquid flows out from the ejection port of the ejection nozzle to the space between the cap and the droplet ejection surface, and the ejection nozzle While purging, the liquid that has flowed out can be recovered from the recovery nozzle to the recovery channel.

  In the liquid droplet ejecting apparatus according to the aspect of the invention, the purge pressure applying mechanism may further include a pressurizing device that pressurizes the liquid in the ejection flow path. According to this configuration, when the spray nozzle is purged, the flow rate can be increased by pressurizing the liquid in the spray flow path with the pressurizing device, so that the spray nozzle can be purged more reliably.

  In the liquid droplet ejecting apparatus according to the aspect of the invention, the recovery nozzle includes a plurality of individual recovery nozzles, and two openings of the individual recovery nozzles are provided at positions opposite to each other with respect to the emission port on the liquid droplet ejection surface. Individual recovery ports may be arranged respectively. In this configuration, the liquid that has flowed out from the outlet of the ejection nozzle during the purge is reliably recovered from the recovery ports of the individual recovery nozzles arranged on both sides of the outlet, so that the liquid adhering to the vicinity of the outlet is removed. It can be further reduced.

  In the droplet ejecting apparatus of the present invention, the ejection nozzle of the flow path unit has a plurality of individual ejection nozzles, the recovery nozzle of the flow path unit has a plurality of individual recovery nozzles, and the droplet ejection surface In addition, an individual emission port that is an opening of the individual injection nozzle and an individual recovery port that is an opening of the individual recovery nozzle may be formed. By forming a plurality of individual ejection nozzles and individual recovery nozzles in the flow path unit, a large amount of liquid can be ejected and recovered at a time.

  In the droplet ejection device of the present invention, the individual ejection ports are arranged in a predetermined direction on the droplet ejection surface, and the individual recovery ports are respectively disposed between the plurality of individual ejection ports. May be. In this configuration, the liquid that has flowed out from the two individual emission ports can be collected from the individual collection ports arranged between them, and the number of collection ports can be reduced. In addition, since the collection port can be arranged efficiently, the apparatus can be downsized.

  In the droplet ejecting apparatus of the present invention, the individual emission ports are arranged in a predetermined direction on the droplet ejection surface, and the individual emission ports are arranged on both sides of the row of the individual ejection ports on the droplet ejection surface. A plurality of the individual recovery ports may be arranged in parallel with the arrangement direction of the mouths. In this configuration, the liquid flowing out from the individual emission port can be reliably collected from the individual collection ports arranged on both sides of the individual emission port, and the liquid adhering to the vicinity of the individual emission port can be reduced.

  In the droplet ejecting apparatus according to the aspect of the invention, the plurality of individual emission ports may be arranged in a plurality of rows at a predetermined pitch along a predetermined direction on the droplet ejection surface, and the adjacent two rows of the individual emission ports may be arranged. With respect to the row of mouths, the individual outlets belonging to one row are arranged to be shifted from the individual outlets belonging to the other row by half of the predetermined pitch in the predetermined one direction, and the plurality of individual recovery ports are The two individual outlets are arranged at the predetermined pitch along the predetermined one direction between the adjacent two rows of individual outlets, and each of the individual recovery ports is arranged on both sides thereof. May be positioned on a straight line connecting two individual emission ports arranged in a predetermined direction and shifted from each other by half of the predetermined pitch. In this configuration, the liquid that has flowed out from the plurality of individual injection nozzles at the time of purging can be efficiently recovered by the number of individual recovery nozzles that is half the number of the individual injection nozzles. Therefore, since a wide area for arranging the individual ejection nozzles can be secured, the individual ejection nozzles can be arranged at high density, and the droplet ejection apparatus can be downsized.

  The liquid droplet ejecting apparatus according to the aspect of the invention may include a communication unit that communicates the ejection flow path and the recovery flow path outside the flow path unit. According to this configuration, the liquid that has flowed out of the ejection nozzle during the purge can be recovered by the recovery nozzle and then returned to the ejection flow path via the communication portion, so that the liquid can be reused.

  In the liquid droplet ejecting apparatus according to the aspect of the invention, the communication unit may be provided with a filter that removes foreign matters contained in the liquid recovered from the recovery channel. According to this configuration, since the foreign matter contained in the liquid is removed by the filter before the recovered liquid is returned to the ejection flow path, the foreign matter flows into the ejection flow path and clogs the ejection nozzle. Can be prevented.

  In the liquid droplet ejecting apparatus according to the aspect of the invention, the communication unit may include a storage unit that stores the liquid recovered from the recovery channel, and the filter may be provided in the storage unit. According to this configuration, since the liquid that has flowed into the storage portion from the recovery channel passes through the filter in the storage portion and then flows into the ejection channel, the foreign material flows into the ejection channel. It is possible to prevent the injection nozzle from being clogged.

  In the liquid droplet ejecting apparatus according to the aspect of the invention, the liquid recovered from the recovery channel may be ejected from the ejection nozzle through the ejection channel. In this case, since the liquid collected from the collection channel can be circulated and re-injected, the amount of liquid discarded can be reduced. For example, when the droplet ejecting apparatus is an ink jet printer, the amount of ink discarded when the head is purged can be drastically reduced, so there is no need to provide a waste liquid chamber for discarding ink inside the printer. . Furthermore, since it is not necessary to anticipate the amount of ink discarded during the purge operation, the substantial amount of ink necessary for printing a predetermined number of sheets can be reduced. Accordingly, the capacity of the ink tank can be reduced.

  In the droplet ejecting apparatus of the present invention, the liquid repellency of the region around the emission port on the droplet ejection surface can be made higher than the liquid repellency of the region around the recovery port. In this case, it is possible to reduce the amount of liquid adhering around the emission port, and it is possible to efficiently recover the liquid adhering around the recovery port.

  In the liquid droplet ejecting apparatus according to the aspect of the invention, the cap may be partitioned into a plurality of regions, and each region of the cap may cover the individual emission port and the individual recovery port independently. In this case, the liquid can be efficiently recovered by dividing the cap into a plurality of regions in accordance with the arrangement of the individual emission ports and the individual recovery ports.

  A flow path unit having an injection nozzle and a flow path for injection communicating with the injection nozzle; a recovery nozzle and a maintenance mechanism for maintaining the flow path unit having a recovery flow path communicating with the recovery nozzle; and the injection A head having an ejection port that is an opening of a nozzle and a droplet ejection surface on which a recovery port that is an opening of the recovery nozzle is formed; and an ejection pressure application mechanism that applies an ejection pressure to the liquid in the ejection channel; The recovery flow path is liquid-coupled to the recovery flow path and a cap capable of contacting the droplet ejection surface so as to cover and cover both the ejection port of the ejection nozzle and the recovery port of the recovery nozzle. A purge pressure applying mechanism that applies a purge pressure to the liquid in the liquid, and the purge pressure applying mechanism causes the liquid to flow out from the emission port, and this liquid is further discharged from the recovery port to the recovery channel. Droplet ejection apparatus is provided to yield.

  According to the second aspect of the present invention, the maintenance mechanism is provided in the head, and the cap and the maintenance mechanism are not integrated. Therefore, the area where the cap of the droplet ejecting apparatus is disposed is reduced in size. It is possible to reduce the installation area of the droplet ejection device.

  In the present application, the term “purge pressure” means a pressure applied to the liquid or the like in the recovery channel in order to recover the liquid through the recovery channel, and includes both negative pressure and positive pressure.

  An embodiment of the present invention will be described. This embodiment is an example in which the present invention is applied to an ink jet printer that records an image or the like by ejecting ink from a nozzle onto a recording sheet as a droplet ejecting apparatus.

  As shown in FIG. 1, an inkjet printer 100 includes a carriage 101 that can move in a scanning direction (left and right direction in FIG. 1), and a serial type inkjet that is provided on the carriage 101 and ejects ink onto a recording sheet P. A head 1 and a transport roller 102 for transporting the recording paper P in the paper feed direction (forward) in FIG. 1 are provided. Ink is supplied to the inkjet head 1 from a sub tank 61 connected to the ink tank 60 through a tube 62. The inkjet head 1 moves in the scanning direction integrally with the carriage 101, and the ejection port 20a of the ejection nozzle 20 formed on the lower surface of the ink ejection surface 40 (droplet ejection surface) (see FIG. 4). Ink is ejected onto the recording paper P to record an image or the like on the recording paper P. The recording paper P recorded by the inkjet head 1 is discharged in the paper feeding direction by the transport roller 102.

  Furthermore, the inkjet printer 100 includes a cap 65 that can contact the ink ejection surface 40 so as to cover the emission ports 20 a of the plurality of ejection nozzles 20, and the ejection nozzle 20 with the cap 65 in contact with the ink ejection surface 40. A suction pump 66 (a suction device, a purge pressure applying mechanism) that sucks the ink from the ink and forcibly flows it out. Then, the inkjet printer 100 cannot normally eject ink from the ejection nozzle 20 due to clogging of the ejection nozzle 20 due to foreign matters such as dust or the mixing of bubbles into the ink flow path of the inkjet head 1. In some cases, with the cap 65 in contact with the ink ejection surface 40, the suction pump 66 is operated to perform a purge operation for forcibly ejecting ink from the ejection nozzle 20.

  Next, the inkjet head 1 will be described in detail with reference to FIGS. As shown in FIGS. 2 to 7, the inkjet head 1 is disposed on a flow path unit 2 in which an individual ink flow path 21 including a pressure chamber 14 (see FIG. 6) is formed, and on the upper surface of the flow path unit 2. And a piezoelectric actuator 3 (an injection pressure applying mechanism).

  First, the flow path unit 2 will be described. As shown in FIGS. 3 and 5 to 7, the flow path unit 2 includes a cavity plate 10, a base plate 11, a manifold plate 12, and a nozzle plate 13, and these four plates 10 to 13 are stacked. It is joined. Among these, the cavity plate 10, the base plate 11 and the manifold plate 12 are stainless steel plates, and ink flow paths such as a manifold 17 and a pressure chamber 14 described later can be easily etched in these three plates 10-12. Can be formed. The nozzle plate 13 is formed of, for example, a polymer synthetic resin material such as polyimide, and is bonded to the lower surface of the manifold plate 12. Or this nozzle plate 13 may be formed with metal materials, such as stainless steel, similarly to the three plates 10-12.

  As shown in FIGS. 2, 3, and 5 to 7, the cavity plate 10 is formed with a plurality of pressure chambers 14 (for example, ten) arranged along a plane. The pressure chamber 14 is open upward. The plurality of pressure chambers 14 are arranged in two rows in the paper feeding direction (up and down direction in FIG. 2). Each pressure chamber 14 is formed in a substantially elliptical shape that is long in the scanning direction (left-right direction in FIG. 2) in plan view.

  Communication holes 15 and 16 are formed at positions where the base plate 11 overlaps both ends of the pressure chamber 14 in plan view. The manifold plate 12 is formed with a manifold 17 extending in the paper feeding direction (vertical direction in FIG. 2). The manifold 17 is arranged so as to overlap with the left half of the pressure chambers 14 arranged on the left side and the right half of the pressure chambers 14 arranged on the right side in plan view. The manifold 17 communicates with an ink supply port 18 formed in a vibration plate 30 described later, and ink is supplied from the sub tank 61 (see FIG. 1) to the manifold 17 via the tube 62 and the ink supply port 18. Is done. A plurality of communication holes 19 that are continuous with the plurality of communication holes 16 are also formed at positions where the manifold plate 12 overlaps the ends of the pressure chambers 14 opposite to the manifolds 17 in plan view.

  Furthermore, a plurality of injection nozzles (individual injection nozzles) 20 are formed at positions where the nozzle plate 13 respectively overlaps the plurality of communication holes 19 in plan view. As shown in FIGS. 2 and 4, the plurality of injection nozzles 20 (the emission ports (individual emission ports) 20 a of the plurality of injection nozzles 20) are opposite to the manifolds 17 of the plurality of pressure chambers 14 arranged in two rows. Are arranged in two rows at equal intervals in the paper feed direction (vertical direction in FIG. 2) in the substantially central portion in the left-right direction of the inkjet head 1. When the nozzle plate 13 is made of a synthetic resin material, the injection nozzle 20 can be formed by excimer laser processing or the like. Further, when the nozzle plate 13 is made of a metal material, it can be formed by press working or the like.

  As shown in FIG. 6, the manifold 17 communicates with the pressure chamber 14 through the communication hole 15, and the pressure chamber 14 communicates with the nozzle 20 through the communication holes 16 and 19. As described above, a plurality of individual ink flow paths 21 extending from the manifold 17 to the ejection nozzle 20 through the pressure chamber 14 are formed in the flow path unit 2. The manifold 17 and the plurality of individual ink channels 21 constitute an ejection channel 22 for ejecting ink from the plurality of ejection nozzles 20 to the recording paper P.

  By the way, in the inkjet printer 100 of the present embodiment, when the ejection nozzle 20 is clogged or bubbles are mixed into the ejection flow path 22 in the flow path unit 2, the cap 65 and the suction pump 66 A purge operation for forcibly flowing out the ink from the ejection nozzle 20 is performed. The flow path unit 2 collects ink that has flowed out from the ejection nozzles 20 during the purge operation, separately from the ejection flow path 22 including the manifold 17 and the plurality of individual ink flow paths 21 described above. A maintenance mechanism 300 having a nozzle 25 and a recovery flow path 28 is provided.

  As shown in FIGS. 2, 4, and 7, a plurality of recovery nozzles (individual recovery nozzles) 25 are formed around the injection nozzle 20 of the nozzle plate 13. A collection port (individual collection port) 25a, which is an opening in the ink ejection surface 40, of the plurality of collection nozzles 25 is emitted from the plurality of ejection nozzles 20 arranged in the paper feeding direction (vertical direction in FIGS. 2 and 4). Between the openings 20a, they are arranged close to the exit openings 20a. The plurality of recovery ports 25a are arranged in two rows in the paper feed direction, like the plurality of emission ports 20a.

  Further, in the flow path unit 2, a recovery flow path 28 communicating with the plurality of recovery nozzles 25 is formed. The collection channel 28 is formed in the manifold plate 12 and communicates with the plurality of collection nozzles 25, and the merge channel 27 formed by joining the plurality of individual collection channels 26. Including. As shown in FIG. 2 and FIG. 4, the plurality of individual recovery flow paths 26 extend in the scanning direction (left-right direction) from the plurality of recovery nozzles 25 arranged in two rows in plan view, and the flow path unit 2. Are joined to a joining flow path 27 extending in the paper feeding direction at the center in the scanning direction (left-right direction in FIG. 2). Further, the confluence channel 27 is bent at one end (the upper end in FIGS. 2 and 4), and from the connection port 29 formed in the cavity plate 10, as shown in FIG. The tube 64 is connected to the sub tank 61.

  During the purging operation, a later-described cap 65 that receives the ejected ink is disposed on the ink ejection surface 40 (lower surface of the nozzle plate 13) of the inkjet head 1 in which the ejection ports 20a of the plurality of ejection nozzles 20 are formed. It abuts so as to cover 20a. In this state, air or the like is sucked from the collection flow path 28 side by the suction pump 66 (see FIG. 1), and the space 50 (see FIG. 3) formed between the cap 65 and the ink ejection surface 40 is decompressed. As a result, the ink is forced to flow out from the ejection nozzle 20. Here, as shown in FIG. 4, since the plurality of recovery ports 25 a are arranged between the plurality of emission ports 20 a, the plurality of recovery ports 25 a are also covered with this cap 65. Then, the ink that has flowed out from the emission port 20 a of the ejection nozzle 20 into the space 50 formed between the cap 65 and the ink ejection surface 40 is collected from the collection nozzle 25 through the collection channel 28 to the sub tank 61. The The ink recovery during the purge operation will be described in more detail later.

  Next, the piezoelectric actuator 3 will be described. As shown in FIGS. 2 to 7, the piezoelectric actuator 3 includes a vibration plate 30 disposed on the upper surface of the flow path unit 2, a piezoelectric layer 31 formed on the upper surface of the vibration plate 30, and the piezoelectric layer 31. Individual electrodes 32 formed respectively corresponding to the plurality of pressure chambers 14 are provided on the upper surface.

  The diaphragm 30 is a plate made of a substantially rectangular metal material in plan view, and is made of, for example, an iron-based alloy such as stainless steel, a copper-based alloy, a nickel-based alloy, or a titanium-based alloy. The diaphragm 30 is disposed on the upper surface of the cavity plate 10 so as to cover the plurality of pressure chambers 14, and is joined to the upper surface of the cavity plate 10. The metal diaphragm 30 has conductivity, and also serves as a common electrode for applying an electric field to the piezoelectric layer 31 sandwiched between the diaphragm 30 and the individual electrode 32.

  On the upper surface of the diaphragm 30, a piezoelectric layer 31 mainly composed of lead zirconate titanate (PZT), which is a solid solution and is a ferroelectric substance, is formed of lead titanate and lead zirconate. As shown in FIGS. 2 and 3, the piezoelectric layer 31 is continuously formed over the plurality of pressure chambers 14. Here, the piezoelectric layer 31 can be formed using, for example, an aerosol deposition method (AD method) in which particles of very small piezoelectric material are sprayed onto a substrate to collide at high speed and deposited on the substrate. Alternatively, it can be formed by a sputtering method, a chemical vapor deposition method (CVD method), a sol-gel method, a hydrothermal synthesis method, or the like. Alternatively, the piezoelectric layer 31 may be formed by cutting a piezoelectric sheet generated by firing a green sheet of PZT into a predetermined size and attaching the cut piezoelectric sheet to the vibration plate 30.

  On the upper surface of the piezoelectric layer 31, a plurality of individual electrodes 32 having an elliptical shape in plan view that is slightly smaller than the pressure chamber 14 are formed. Each of the plurality of individual electrodes 32 is formed at a position overlapping the central portion of the corresponding pressure chamber 14 in plan view. The individual electrode 32 is made of a conductive material such as gold, copper, silver, palladium, platinum, or titanium. Furthermore, on the upper surface of the piezoelectric layer 31, a plurality of wiring portions 35 extending in parallel with the longitudinal direction of the individual electrodes 32 (left and right direction in FIG. 2) are formed from the end portions on the manifold 17 side of the plurality of individual electrodes 32, respectively. Has been. The plurality of individual electrodes 32 and the plurality of wiring portions 35 can be formed by, for example, screen printing, sputtering, vapor deposition, or the like.

  A flexible wiring member (not shown) such as a flexible printed circuit (FPC) is joined to the plurality of wiring portions 35, and as shown in FIG. 6, the driver IC 37 is interposed via the wiring member. And are electrically connected. Then, a drive voltage is selectively supplied from the driver IC 37 to the plurality of individual electrodes 32 via the wiring portion 35.

  Next, the operation of the piezoelectric actuator 3 will be described. When a drive voltage is selectively applied from the driver IC 37 to the desired individual electrode 32, the potential of the individual electrode 32 on the upper side of the piezoelectric layer 31 to which the drive voltage is supplied and the piezoelectric layer 31 held at the ground potential. The potentials of the diaphragm 30 as the lower common electrode are in different states, and an electric field in the thickness direction is generated in the portion of the piezoelectric layer 31 sandwiched between the individual electrode 32 and the diaphragm 30. At this time, when the polarization direction of the piezoelectric layer 31 and the direction of the electric field are the same, the piezoelectric layer 31 contracts in a horizontal direction orthogonal to the thickness direction that is the polarization direction. At this time, the diaphragm 30 is deformed so as to protrude toward the pressure chamber 14 as the piezoelectric layer 31 contracts, so that the volume in the pressure chamber 14 is reduced and the ejection pressure is applied to the ink in the pressure chamber 14. The ink is ejected from the ejection nozzle 20 that is applied and communicates with the pressure chamber 14.

  Next, the cap 65 and the suction pump 66 used during the purge operation will be described. As shown in FIG. 1, the cap 65 is disposed below the retreat position of the inkjet head 1 on the outer side (left side in FIG. 1) in the scanning direction than the conveyance path of the recording paper P. As shown in FIG. 3, the cap 65 is moved in the vertical direction (arrow direction in FIG. 3) by a drive motor (not shown). When the purge operation is performed, the cap 65 is driven upward and comes into contact with the ink ejection surface 40 after the inkjet head 1 has moved to the retracted position.

  As shown in FIGS. 3 and 4, the cap 65 has a long shape in the paper feed direction, which is the arrangement direction of the injection nozzles 20, so as to cover all the emission ports 20 a of the injection nozzles 20 arranged in two rows. In addition, the ink ejecting surface 40 can be brought into contact with the central portion in the scanning direction (left-right direction in FIG. 4). Here, as described above, the collection ports 25a of the plurality of collection nozzles 25 are respectively disposed between the plurality of emission ports 20a arranged in the paper feed direction (vertical direction in FIG. 4), and thus the cap 65 is provided. As shown in FIG. 4, the plurality of emission ports 20 a and the plurality of recovery ports 25 a are all covered with a cap 65 when the ink comes into contact with the ink ejection surface 40.

  As shown in FIG. 1, the suction pump 66 is connected via a tube 63 to a connection port 29 (see FIGS. 2 and 4) that is an open end of a recovery flow path 28 formed in the flow path unit 2. Yes. Further, the suction pump 66 is connected to the sub tank 61 via a tube 64. In the purge operation, as shown in FIGS. 3 and 4, the cap 65 comes into contact with the ink ejection surface 40, so that the emission ports 20 a of the plurality of ejection nozzles 20 and the recovery ports 25 a of the plurality of recovery nozzles 25 are arranged. The cap 65 is hermetically covered. In this state, the suction pump 66 sucks air or the like from the recovery flow path 28 through the tube 63, and decompresses the space 50 between the cap 65 and the ink ejection surface 40. Then, the ink is ejected into the space 50 from the emission port 20a of the ejection nozzle 20. Here, since the recovery port 25a of the recovery nozzle 25 is disposed close to the emission port 20a on the ink ejection surface 40, the ejection nozzle 20 passes through the space 50 and reaches the recovery nozzle 25 (recovery channel 28). An ink flow is generated, and most of the ink that has flowed out of the ejection nozzle 20 into the space 50 is sucked into the collection port 25a and collected in the collection channel 28, and thus adheres to the vicinity of the emission port 20a of the ink ejection surface 40. Less ink is used. Therefore, it is possible to prevent as much as possible that the ink which is bubbled when flowing out from the ejection nozzle 20 returns from the ejection nozzle 20 to the inside of the flow path unit 2 and causes an ejection abnormality in the ejection nozzle 20. .

  Further, the ink sucked into the recovery flow path 28 from the recovery port 25 a by the suction pump 66 is sent to the sub tank 61 (storage part) through the tube 64. As shown in FIG. 8, the sub tank 61 is provided on the side of the sub tank 61 and connected to the ink tank 60 (see FIG. 1), and the sub tank 61 is provided on the bottom of the sub tank 61 and the flow path unit 2. The ink supply section 71 connected to the ejection flow path 22 (ink supply port 18: see FIG. 2), and the recovery flow path 28 of the flow path unit 2 provided above the sub tank 61 via the suction pump 66. (Connection port 29: see FIG. 2) and an ink recovery unit 72 connected to the connection port 29. The sub tank 61 has an ink supply space 73 that communicates with both the tank connection portion 70 and the ink supply portion 71, and an ink recovery portion 72 that communicates with the ink supply space 73 via a partition wall 75. A partitioned ink collection space 74 is formed. The partition wall 75 is formed with a communication hole 76 that allows the ink supply space 73 and the ink recovery space 74 to communicate with each other. Therefore, the ink recovered from the recovery port 25 a to the recovery flow path 28 and flowing into the sub tank 61 flows from the ink recovery space 74 through the communication hole 76 to the ink supply space 73 and is ejected from the ink supply portion 71 again. Supplied to the use flow path 22 and reused. The communication hole 76 is provided with a filter 77 that removes foreign matters contained in the ink recovered from the recovery flow path 28. Accordingly, the ink that has flowed into the sub tank 61 from the recovery flow path 28 flows into the ejection flow path 22 after the foreign matter is removed by the filter 77 in the sub tank 61, so that the foreign matter flows into the ejection flow path 22. It is possible to prevent the injection nozzle 20 from being clogged. The sub tank 61 and the tubes 62, 63, 64 correspond to the communication portion of the present invention, and communicate the injection flow path 22 and the recovery flow path 28 outside the flow path unit 2.

  According to the inkjet printer 100 described above, the following effects can be obtained. The ink ejection surface 40 is provided with a recovery port 25a of the recovery nozzle 25 in proximity to the output port 20a of the ejection nozzle 20, and during the purge operation, the ejection port 20a of the ejection nozzle 20 and the recovery port of the recovery nozzle 25 are provided. 25a is covered with one cap 65. Therefore, most of the ink that is sucked from the collection flow path 28 side by the suction pump 66 and flows out from the ejection nozzle 20 is collected from the collection port 25a close to the emission port 20a to the collection flow path 28. For this reason, it is difficult for the foamed ink to adhere to the ink ejection surface 40 when it flows out from the ejection nozzle 20, and the foamed ink returns from the ejection nozzle 20 to the inside of the flow path unit 2 and is ejected to the ejection nozzle 20. Abnormality can be prevented as much as possible.

  The plurality of recovery ports 25a are respectively disposed between the plurality of emission ports 20a arranged in the paper feeding direction. Therefore, the ink ejected from the two emission ports 20a can be collected from one collection port 25a disposed between them, and the number of collection ports 25a can be reduced. Therefore, the recovery ports 25a can be arranged efficiently, and the jet nozzles 20 can be arranged with high density, so that the inkjet head 1 can be downsized.

  Further, the ejection flow path 22 and the recovery flow path 28 formed in the flow path unit 2 communicate with each other via the sub tank 61 and the tubes 62, 63, 64 outside the flow path unit 2. Therefore, since the liquid ejected from the ejection nozzle 20 during the purge operation can be recovered by the recovery nozzle 25 and then returned to the ejection flow path 22 via the sub tank 61 and the tubes 62, 63, 64, the purge operation Sometimes the ejected ink can be reused. Therefore, the inkjet printer 100 does not need to be provided with a waste liquid chamber for discarding the ink collected during the purge operation, and the number of parts of the inkjet printer 100 can be reduced and the size can be reduced. In addition, since it is not necessary to anticipate the amount of ink discarded during the purge operation, the size of the ink tank 60 can be suppressed. In the present embodiment, the cap is not provided with a mechanism for sucking ink. Therefore, it is possible to reduce the installation area of the printer main body as compared with the case where the cap and the purge mechanism are integrated.

  Next, modified embodiments in which various modifications are made to the embodiment will be described. However, components having the same configuration as in the above embodiment are given the same reference numerals and description thereof is omitted as appropriate.

<First modification>
As shown in FIG. 9, the recovery ports 25a are also provided at positions on both ends in the arrangement direction (positions on both the upper and lower ends in FIG. 9) of the plurality of emission ports 20a arranged in the paper feed direction (up and down direction in FIG. 9). The two recovery ports 25a may be disposed at positions on both sides (opposite to the output port 20a) with respect to the arrangement direction of each of the output ports 20a. In this inkjet head 1A, the ink that has flowed out from the outlet 20a to the cap 65A during the purge operation can be recovered from the two recovery ports 25a located on both sides in the arrangement direction of the outlet 20a to the recovery channel 28A. Therefore, the amount of ink adhering to the vicinity of the emission port 20a is further reduced.

<Second modification>
Further, as shown in FIG. 10, a plurality of recovery ports are provided at positions on both sides in the scanning direction (left-right direction in FIG. 10) with respect to the row of emission ports 20a arranged in the paper feed direction (up-down direction in FIG. 10). 25a are arranged in parallel to the row of the emission ports 20a, and two recovery ports 25a are arranged at positions on both sides (opposite to the emission port 20a) with respect to the scanning direction with respect to each of the emission ports 20a. May be arranged. Also in the inkjet head 1B, the ink ejected from the emission port 20a to the cap 65B can be collected from the two collection ports 25a located on both sides in the scanning direction of the emission port 20a to the collection channel 28B. The amount of ink adhering to the vicinity of the emission port 20a is reduced.

<Third modification>
The emission ports 20a of the plurality of ejection nozzles 20 may be arranged in a plurality of rows at equal intervals, and a plurality of recovery ports 25a may be arranged between the rows of the plurality of rows of emission ports 20a. For example, in the inkjet head 1C shown in FIG. 11, the recovery ports 25a of the plurality of recovery nozzles 25 arranged in one row are arranged between the rows of the emission ports 20a arranged in two rows. Are arranged in parallel with each other. In this configuration, as compared with the embodiment and the first and second modified embodiments described above, the area where the ejection nozzles 20 are arranged on the ink ejection surface 40 can be secured widely. Therefore, the ejection nozzles 20 are arranged at a high density, The inkjet head 1C can be downsized.

  Further, in the inkjet head 1C of FIG. 11, with respect to the two adjacent rows of the emission ports 20a, the emission ports 20a belonging to one row are in the paper feed direction (see FIG. 11) with respect to the emission ports 20a belonging to the other row. 11 in the vertical direction) is shifted by half the pitch. The plurality of recovery ports 25a are arranged at the same pitch as the rows of the emission ports 20a. Furthermore, each collection port 25a is included in a row of two rows of emission ports 20a arranged on both sides thereof, and two emission ports arranged by being shifted by half the pitch in the paper feed direction which is the arrangement direction. On the straight line L which connects 20a, it is located in the position where the distance between the two output ports 20a becomes equal. In the inkjet head 1C, the ink ejected from the plurality of ejection nozzles 20 to the cap 65C can be efficiently collected by a small number (half the number of the ejection nozzles 20) of the collection nozzles 25. However, according to this configuration, the number of recovery ports 25a (recovery nozzles 25) is reduced as compared with the above-described embodiment, so that the overall ink recovery amount is also reduced. Therefore, in order to collect more ink with a small number of collection ports 25a, for example, as shown in FIG. 11, the diameter of the collection port 25a may be larger than the diameter of the emission port 20a.

<Fourth modification>
As shown in FIG. 12, an individual recovery flow path 26D communicating with the recovery nozzle 25 may be formed in the nozzle plate 13D instead of the manifold plate 12D.

<Fifth modification>
Like the ink jet printer 100E shown in FIG. 13, instead of the suction pump 66 (see FIG. 1) of the above embodiment, between the sub tank 61 and the ejection flow path 22 of the ink jet head 1 (flow path unit 2), A pressurizing pump 80 (pressurizing device) may be provided that causes ink to flow out of the ejection nozzle 20 by pressurizing the ink in the ejection flow path 22 during the purge operation. Also in this case, a purge pressure for recovering the ink can be applied to the ink in the recovery channel 28 that is in fluid communication with the ejection channel 22.

<Sixth modification>
Further, as in the ink jet printer 100F shown in FIG. 14, a suction pump 66 is provided between the recovery flow path 28 of the ink jet head 1 (flow path unit 2) and the sub tank 61, and the sub tank 61 and the ejection flow path 22 are provided. A pressure pump 80 may be provided between the two. According to this configuration, at the time of the purge operation, the suction pump 66 sucks the ink from the collection flow path 28 side, and the pressure pump 80 pressurizes the ink from the ejection flow path 22 side to eject the ink from the ejection nozzle 20. Therefore, the injection speed can be further increased, and the injection nozzle 20 can be purged more reliably.

  Alternatively, the purge operation may be performed using a mechanism (piezoelectric actuator 3) that applies pressure to the ink in the ejection flow path 22 without providing a dedicated pump. In this case, it is desirable to control the mechanism that applies pressure to the ink so that the pressure applied to the ink during the purge operation is greater than the pressure applied during recording. Also in this case, a purge pressure for recovering the ink can be applied to the ink in the recovery channel 28 that is in fluid communication with the ejection channel 22.

  Note that the mechanism for applying pressure to the ink in the ejection flow path is not limited to the piezoelectric actuator. For example, the pressure may be applied to the ink by heating / boiling the ink with a heater, or the pressure may be applied to the ink by deforming a thin plate actuator by electrostatic force.

<Seventh modification>
The shape of the cap that covers the ink ejection surface of the ink jet head during the purging operation is not limited to the shape shown in the above-described embodiment and modification, and may be any shape. In particular, the internal shape of the cap can be arbitrarily changed according to the arrangement of the injection nozzle 20 and the recovery nozzle 25. For example, a cap whose interior is not partitioned as shown in the above embodiment can be used. In this case, when the cap covers the ink ejection surface, one continuous space is formed by the inner surface of the cap and the ink ejection surface. Further, for example, a cap 165A as shown in FIG. 15 is used for the inkjet head 1 including the ejection nozzles 20 and the recovery nozzles 25 arranged in a row as described with reference to FIG. it can. The inside of the cap 165A is partitioned for each nozzle row. In this case, ink does not scatter in the portion between the nozzle rows during the purge operation. Further, since the volume of the space to be sucked per collection nozzle is reduced, the suction efficiency of the collection nozzle can be increased. Further, for example, for an inkjet head 1B including the recovery nozzles 25 arranged in rows on both sides of the ejection nozzles 20 arranged in a row as described with reference to FIG. A cap 165B as shown can be used. The inside of the cap 165B is divided into 10 sections each having one injection nozzle 20 and recovery nozzles 25 on both sides thereof. Also in this case, there is no possibility that the ink will be scattered beyond the section during the purge operation, and the volume of the space to be sucked per collection nozzle becomes very small, so that the suction efficiency can be improved. In FIG. 15 and FIG. 16, the recovery channel is omitted.

<Eighth modification>
The degree of liquid repellency of the ink ejection surface of the inkjet head can be arbitrarily adjusted. For example, as shown in FIG. 17, a high liquid repellency region 120 and a low liquid repellency region 125 can be formed around the ejection nozzle 20 and the recovery nozzle 25 of the ink jet head 1 shown in FIG. . Thus, by forming the highly liquid repellent region 120 around the ejection nozzle 20, it is possible to prevent ink from adhering to the circumference of the ejection nozzle 20. Further, by forming the low liquid repellency region 125 around the collection nozzle 25, it is possible to efficiently collect the ink adhering to the circumference of the collection nozzle 25 during the purge operation. The highly liquid-repellent region 120 formed around the injection nozzle 20 can be formed by coating a film of a fluorine resin, for example. The low liquid repellency region 125 formed around the collection nozzle 25 can be formed by coating a hydrophilic film, for example. Alternatively, when the nozzle plate 13 is formed of a material such as polyimide, the low liquid repellency region 125 irradiates the surface of the nozzle plate 13 with weak output laser light, and the laser of the nozzle plate 13 irradiates. It can also be formed by reducing the liquid repellency of the formed area. Further, only one of the high liquid repellency region and the low liquid repellency region can be formed on the ink ejection surface of the nozzle plate 13, and even in such a case, the above-described effect can be obtained. it can.

  As described above, the embodiment in which the present invention is applied to the ink jet printer that records by ejecting ink onto the recording paper as the liquid droplet ejecting apparatus has been described, but the form to which the present invention can be applied is not limited to these forms, The present invention can also be applied to various droplet ejecting apparatuses that eject liquid other than ink onto various objects.

1 is a schematic configuration diagram of an inkjet printer according to an embodiment of the present invention. It is a top view of an inkjet head. It is the III-III sectional view taken on the line of FIG. It is a bottom view of an inkjet head. FIG. 3 is a partially enlarged view of FIG. 2. FIG. 6 is a sectional view taken along line VI-VI in FIG. 5. It is the VII-VII sectional view taken on the line of FIG. It is sectional drawing of a sub tank. It is a bottom view of the ink jet head of the 1st modification. It is a bottom view of the inkjet head of the 2nd modification. It is a bottom view of the inkjet head of the 3rd change form. It is sectional drawing equivalent to FIG. 7 of a 4th modification. It is a schematic block diagram of the inkjet printer of a 5th modification form. It is a schematic block diagram of the inkjet printer of the 6th modification form. FIG. 15 is a bottom view of an ink jet head according to a seventh modification. FIG. 16 is a bottom view of an ink jet head according to a seventh modification. FIG. 17 is a bottom view of an ink jet head according to an eighth modification.

Explanation of symbols

1, 1A, 1B, 1C Inkjet head 2 Flow path unit 3 Piezoelectric actuator 20 Injection nozzle 22 Injection flow path 25 Recovery nozzle 25a Recovery port 28, 28A, 28B Recovery flow path 40 Ink injection surface 50 Space 61 Sub tanks 62, 63 , 64 Tube 65, 65A, 65B, 65C Cap 66 Suction pump 77 Filter 80 Pressure pump 100, 100E, 100F Inkjet printer

Claims (16)

A liquid droplet ejecting apparatus that ejects liquid droplets,
An ejection nozzle, an ejection channel communicating with the ejection nozzle, a recovery nozzle, a recovery channel communicating with the recovery nozzle, an emission port that is an opening of the ejection nozzle, and a recovery port that is an opening of the recovery nozzle A flow path unit having a formed droplet ejection surface;
An injection pressure applying mechanism for applying an injection pressure to the liquid in the injection flow path;
A cap capable of contacting the droplet ejection surface so as to seal and cover both the ejection port of the ejection nozzle and the recovery port of the recovery nozzle;
A purge pressure applying mechanism for causing the liquid in the ejection channel to flow to the recovery channel in a state where the cap covers both the emission port and the recovery port;
A liquid droplet ejecting apparatus that causes the liquid to flow out from the emission port by the purge pressure applying mechanism and further collects the liquid from the recovery port to the recovery channel.   2. The droplet ejecting apparatus according to claim 1, wherein a recovery port of the recovery nozzle is formed in proximity to an emission port of the injection nozzle on the droplet ejection surface.   3. The droplet ejection according to claim 2, wherein the purge pressure applying mechanism includes a suction device that suctions from the collection flow path side and decompresses the space formed between the cap and the droplet ejection surface. apparatus.   The droplet ejecting apparatus according to claim 3, wherein the purge pressure applying mechanism further includes a pressurizing device that pressurizes the liquid in the ejection flow path.   The recovery nozzle includes a plurality of individual recovery nozzles, and two individual recovery ports, which are openings of the individual recovery nozzles, are disposed at positions on the droplet ejection surface opposite to each other with respect to the emission port. The liquid droplet ejecting apparatus according to claim 2.   The ejection nozzle of the flow path unit has a plurality of individual ejection nozzles, the recovery nozzle of the flow path unit has a plurality of individual recovery nozzles, and the droplet ejection surface has an opening of the individual ejection nozzle. The liquid droplet ejecting apparatus according to claim 2, wherein an individual outlet and an individual recovery port that is an opening of the individual recovery nozzle are formed. In the droplet ejection surface, the individual emission ports are arranged in a predetermined direction,
The liquid droplet ejecting apparatus according to claim 6, wherein the individual recovery ports are respectively disposed between the plurality of individual emission ports. In the droplet ejection surface, the individual emission ports are arranged in a predetermined direction,
The liquid droplet ejecting apparatus according to claim 6, wherein a plurality of the individual recovery ports are arranged in parallel to the arrangement direction of the individual emission ports on both sides of the row of the individual emission ports on the droplet ejection surface. In the droplet ejection surface, the plurality of individual emission ports are arranged in a plurality of rows at a predetermined pitch along a predetermined direction,
With respect to the two rows of the individual emission ports adjacent to each other, the individual emission ports belonging to one row are arranged so as to be shifted by half the predetermined pitch in the predetermined one direction with respect to the individual emission ports belonging to the other row. ,
The plurality of individual recovery ports are arranged at the predetermined pitch along the predetermined one direction between the rows of the two adjacent individual emission ports,
Each individual recovery port belongs to a row of two individual output ports arranged on both sides of the individual recovery port, and connects two individual output ports arranged so as to be shifted from each other by half of the predetermined pitch in the predetermined direction. The droplet ejecting apparatus according to claim 6, which is located on a straight line.   The droplet ejecting apparatus according to claim 2, further comprising a communication portion that communicates the ejection flow path and the recovery flow path outside the flow path unit.   The droplet ejecting apparatus according to claim 10, wherein the communication portion is provided with a filter that removes foreign matters contained in the liquid recovered from the recovery flow path.   The droplet ejecting apparatus according to claim 11, wherein the communication unit includes a storage unit that stores the liquid recovered from the recovery channel, and the filter is provided in the storage unit.   The liquid droplet ejecting apparatus according to claim 10, wherein the liquid recovered from the recovery channel is ejected from the ejection nozzle through the ejection channel.   2. The droplet ejecting apparatus according to claim 1, wherein a liquid repellency of a region around the emission port is higher than a liquid repellency of a region around the recovery port on the droplet ejection surface.   The liquid droplet ejecting apparatus according to claim 6, wherein the cap is divided into a plurality of regions, and each region of the cap independently covers the individual emission port and the individual recovery port. A liquid droplet ejecting apparatus that ejects liquid droplets,
A flow path unit having an injection nozzle and a flow path for injection communicating with the injection nozzle; a recovery nozzle and a maintenance mechanism for maintaining the flow path unit having a recovery flow path communicating with the recovery nozzle; and the injection A head having an emission port that is an opening of a nozzle and a droplet ejection surface on which a recovery port that is an opening of the recovery nozzle is formed;
An injection pressure applying mechanism for applying an injection pressure to the liquid in the injection flow path;
A cap that can be in contact with the droplet ejection surface so as to hermetically cover and cover both the ejection port of the ejection nozzle and the recovery port of the recovery nozzle, and a liquid connection to the recovery channel, A purge pressure applying mechanism for applying a purge pressure to the liquid of
A liquid droplet ejecting apparatus that causes the liquid to flow out from the emission port by the purge pressure applying mechanism and further collects the liquid from the recovery port to the recovery channel.

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