JP4696764B2 - Inkjet recording device - Google Patents

Description

  The present invention relates to an ink jet recording apparatus.

  Conventionally, a plurality of nozzles that eject ink, a plurality of pressure chambers that supply ink to the plurality of nozzles, a cavity unit that temporarily stores ink to be supplied to the pressure chamber, and a pressure unit that pressurizes the pressure chamber. There is known an ink jet recording apparatus that includes a pressurizing unit that ejects ink from the nozzle and that records the ink by ejecting the ink toward a recording medium (for example, see Patent Document 1).

In such an ink jet recording apparatus, there is a case where it is desired to increase the amount of droplets ejected per unit area of the recording medium in order to increase the recording density (paper surface density).
Japanese Patent Laid-Open No. 2002-19102

  In order to increase the amount of ejected droplets per unit area, it is conceivable to increase the size of ink droplets. However, in order to increase the size of ink droplets, there are limits to not impairing ejection stability and limitations on drive frequency. Exists. Although it is conceivable to increase the number of ejections by increasing the number of scans per unit area, increasing the number of scans decreases the recording speed.

  Therefore, the inventor has a configuration in which each nozzle is provided with a set of two nozzle holes, and during normal recording, ink droplets are ejected from only one of the two sets of nozzle holes, while per unit area. At the time of recording in which it is desired to increase the recording density by increasing the amount of ejected liquid droplets, the inventors have conceived that the above problem can be solved by ejecting ink droplets simultaneously from the two nozzle holes. It is a thing.

  An object of the present invention is to provide an ink jet recording apparatus that can increase the amount of ejected droplets per unit area without increasing the size of ink droplets or increasing the number of scans.

The invention according to claim 1 is a cavity unit including a plurality of nozzles for ejecting ink, a plurality of pressure chambers for supplying ink to the plurality of nozzles, and a manifold for temporarily storing ink to be supplied to the pressure chamber; Pressurizing means for pressurizing a pressure chamber and ejecting ink from the nozzle, and in the ink jet recording apparatus for recording by ejecting the ink on a recording medium, each nozzle has a pair of nozzle holes. Two pressure chambers communicating with the set of two nozzle holes are vertically overlapped, and one pressurizing means is provided for the two pressure chambers, The opposing walls of the two pressure chambers are formed of an elastic body capable of propagating pressure from one pressure chamber to the other pressure chamber, and the pressurizing means pressurizes the one pressure chamber. With that Serial other pressure chamber is also characterized in that it is pressurizable configured.

  In this way, by simultaneously pressurizing both pressure chambers arranged in the upper and lower directions by the pressurizing means, ink droplets are ejected from both nozzle holes, and the amount of ejected droplets per unit area is reduced. You can record more. Therefore, the recording density can be increased.

In addition, since the opposing walls of the pressure chambers, which are arranged in an overlapping manner in the vertical direction, are made of an elastic body capable of propagating pressure from one pressure chamber to the other pressure chamber, this elastic body Due to the elastic deformation, the applied pressure applied to the upper pressure chamber is propagated to the lower pressure chamber.

According to a second aspect of the present invention, in the ink jet recording apparatus of the first aspect, a damper chamber, which is a space portion, is disposed between the pressure chambers disposed above and below the upper and lower portions.

  In this way, the applied pressure from the upper pressure chamber is attenuated by the damper chamber and propagated to the lower pressure chamber. Therefore, the pressure applied to the lower pressure chamber is smaller than the pressure applied to the upper pressure chamber by the pressurizing means.

A third aspect of the present invention, in the ink jet recording apparatus according to claim 1 or 2, pairwise nozzle holes constituting the respective nozzles, arranged side by side in a direction perpendicular to the longitudinal direction of the pressure chamber It is characterized by being.

  In this way, a set of two nozzle holes constituting each nozzle is provided side by side in a direction orthogonal to the longitudinal direction of the pressure chamber, so that the ink droplets ejected from the two nozzle holes Is landed at a close position on the recording medium.

According to a fourth aspect of the present invention, in the ink jet recording apparatus according to any one of the first to third aspects, a set of two nozzle holes constituting each of the nozzles is an array of the two nozzle holes with respect to a recording medium. Scanning is performed in a direction crossing the direction.

  By doing so, the nozzle holes of each pair constituting each nozzle are scanned in the direction intersecting the arrangement direction of the two nozzle holes with respect to the recording medium. The ink droplets are landed with high density in the direction crossing the scanning direction.

According to a fifth aspect of the present invention, in the ink jet recording apparatus according to any one of the first to fourth aspects, the pressure chambers disposed so as to overlap the upper and lower sides are planarly viewed, the central portions in the longitudinal direction overlap, and the end portions Is shifted in correspondence with the position of the nozzle hole.

  In this way, the communication path that communicates the pressure chamber and the nozzle hole and the communication path (throttle section) that communicates the common ink chamber (manifold) and the pressure chamber are formed without a complicated structure. Can do.

According to a sixth aspect of the present invention, in the ink jet recording apparatus according to any one of the first to fifth aspects, the pressurizing unit ejects ink using only one of the two nozzle holes as the control mode. And a second mode in which ink is ejected using both the nozzle holes.

  In this way, when it is necessary to increase the amount of ejected droplets per unit area, the second mode is selected. When it is not necessary to increase the amount, the first mode is selected. Then, such switching between the first and second modes can be realized simply by controlling the magnitude of the pressure applied by the pressurizing means.

According to a seventh aspect of the present invention, in the ink jet recording apparatus according to the sixth aspect, the first mode is a normal recording mode, and the second mode is a method of overprinting ink more than the normal recording mode. It is a recording mode in which the number of times is reduced.

  In this way, since the ink is ejected using both nozzle holes in the recording mode in which the number of ink overstrikes is smaller than that in the normal recording mode, the normal recording mode can be achieved even if the number of overstrikes is small. As a result, the amount of ejected droplets per unit area can be increased. Therefore, in the recording mode (second recording mode) in which the number of ink overstrikes is smaller than that in the normal recording mode (first recording mode), a recording density comparable to that in the normal recording mode is secured. The recording quality can be improved.

According to an eighth aspect of the present invention, in the ink jet recording apparatus according to any one of the first to seventh aspects, the nozzle provided with the set of two nozzle holes ejects at least black ink.

  In this way, when, for example, character data is recorded with black ink, the amount of ejected droplets per unit area is increased without increasing the ink droplets or increasing the number of scans, thereby increasing the recording density. It can be secured and recorded at high speed.

According to a ninth aspect of the present invention, in the ink jet recording apparatus according to any one of the first to eighth aspects, the pair of nozzle holes have different hole diameters.

  In this way, the amount of ejected droplets per unit area that one nozzle is responsible for is a combination of controlling the amount of pressure applied by the pressurizing means and making the diameters of the two nozzle holes different. Further control can be performed on

  In the present invention, as described above, each nozzle is provided with a set of two nozzle holes, and the pressure chambers communicating with the nozzle holes of the nozzles are vertically overlapped, and the nozzles are overlapped vertically. Since the pressure chambers are pressurized simultaneously, ink droplets can be ejected from both nozzle holes, and the amount of ejected droplets per unit area can be easily increased.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the recording apparatus according to the present embodiment has a well-known ink jet type in which a recording head is mounted on a carriage that reciprocates along a recording medium, and ink droplets are ejected from the recording head toward the recording medium. It is a recording device.

  FIG. 1 is a cross-sectional view of a piezoelectric ink jet head used in an ink jet recording apparatus according to the present invention, and FIG. 2 is a plan view of a cavity unit in the ink jet head.

  As shown in FIG. 1, the inkjet head 1 has a plate-type piezoelectric actuator 3 (pressurizing means) joined to an upper side of a cavity unit 2 having a plurality of metal plates, and an upper side of the plate-type piezoelectric actuator 3. A flexible flat cable 4 for connection with an external device is overlapped and joined. Then, ink is ejected downward from nozzles (nozzle holes 5a and 5b described later) opened on the lower surface side of the cavity unit 2.

  As shown in FIG. 1, the cavity unit 2 has a structure in which each of the eight plates 11 to 18 and the elastic sheets 19 and 20 are laminated and bonded with an adhesive in a laminated state. That is, a total of eight thin layers of the upper cavity plate 11, the damper plate 12, the lower cavity plate 13, the base plate 14, the two manifold plates 15 and 16, the spacer plate 17, and the nozzle plate 18 are stacked in order from the upper side. The plate includes two elastic sheets 19 and 20 interposed between the lower cavity plate 13 and the damper plate 12 and between the damper plate 12 and the upper cavity plate 11. Each of the plates 11 to 18 has a thickness of about 50 to 150 μm and is a metal plate made of 42% nickel alloy steel plate.

  Each of the cavity plates 11 and 13 has a plurality of elongate pressure chambers 11a and 13a in plan view so that the longitudinal direction thereof is along the short side direction of the cavity plates 11 and 13 (the left-right direction in FIG. 1). Are formed as through holes. The pressure chambers 11a and 13a are arranged in a positional relationship overlapping in the vertical direction (the stacking direction of the plates) in plan view, and the long sides of the cavity plates 11 and 13 (the direction perpendicular to the paper surface of FIG. 1, the X direction of FIG. 2) ) Are arranged in two rows in a staggered pattern. Moreover, since both the pressure chambers 11a and 13a are arranged overlapping in the vertical direction, they can be simultaneously pressurized by the piezoelectric actuator 3 from above.

  In addition, a damper chamber 12a is formed as a through hole in the damper plate 12, so that a damper chamber 12a, which is a space portion, is disposed between the pressure chambers 11a and 13a that are disposed overlapping above and below. The pressure chambers 11a, 13a and the damper chamber 17a are partitioned by elastic sheets 19, 20. These elastic sheets 19 and 20 serve as walls on the opposite sides of the pressure chambers 11a and 13a that are arranged so as to overlap in the vertical direction, and the elastic sheet 19 is a pressure chamber due to a change in the pressure of ink in the pressure chamber 11a. 11a and the damper chamber 12a can be deformed in a direction in which the volume of the damper chamber 12a is changed, and the elastic sheet 20 has the damper chamber 12a and the pressure chamber 13a formed by the pressure change of the air in the damper chamber 12a based on the volume change of the damper chamber 12a. It is composed of an elastic body that can be deformed in the direction of volume change.

  In the two manifold plates 15 and 16, two common ink chambers 41 that are long along the long side direction are formed through the plate thickness so as to extend along each row of nozzles (nozzle holes 5a and 5b). Has been. That is, as shown in FIG. 1, two common ink chambers 41 are hermetically sealed by stacking two manifold plates 15 and 16 and covering the upper surface with the base plate 14 and the lower surface with the spacer plate 17. It is formed into a shape. Each common ink chamber 41 overlaps with a part of the pressure chambers 11a and 13a when viewed in plan from the stacking direction of the plates, as shown in FIG. 2, in the row direction of the pressure chambers 11a and 13a (the nozzle holes 5a and 5b). It extends long along the column direction. One end portion of each common ink chamber 41 communicates with an ink supply source via an ink supply port (not shown).

  As shown in FIG. 2, the nozzle plate 18 has a plurality of nozzle holes 5a and 5b each having a very small diameter (about 25 μm in this embodiment) as a nozzle for ejecting ink. ing. The nozzles (nozzle holes 5a and 5b) are arranged in two rows in a staggered arrangement along the long side direction (the direction perpendicular to the paper surface of FIG. 1, the X direction of FIG. 2) of the nozzle plate 18. These two nozzle holes 5a, 5b are arranged close to each other in a direction perpendicular to the longitudinal direction of the pressure chambers 11a, 13a. The pair of nozzle holes 5a and 5b are scanned in a direction intersecting the arrangement direction of the two nozzle holes 5a and 5b with respect to the recording medium.

  One end portion 11aa of the pressure chamber 11a is formed in the elastic sheet 19, the damper plate 12, the lower cavity plate 13, the base plate 14, the two manifold plates 15 and 16, and the spacer plate 17 in the same staggered arrangement. It communicates with the nozzle hole 5a in the nozzle plate 18 through the small-diameter communication path 31. Similarly, the one end portion 13aa of the pressure chamber 13a is connected to the base plate 14, the two manifold plates 15, 16 and the spacer plate 17 through a small-diameter communication passage 32 which is also drilled in a staggered arrangement. The nozzle plate 18 communicates with the nozzle hole 5b.

  The elastic sheet 19, the damper plate 12, the lower cavity plate 13 and the base plate 14 below the upper cavity plate 11 are provided with communication passages 33 connected to the other end portions 11ab of the pressure chambers 11a. Yes. A communication passage 34 connected to the other end 13ab of each pressure chamber 13a is formed in the lower base plate 14 of the lower cavity plate 13. The communication passages 33 and 34 are formed with a small cross-sectional area so as to supply ink from the common ink chamber 41 to the pressure chambers 11a and 13a and to serve as a flow path resistance and function as a throttle portion.

  Then, the one end portion 13aa of the lower pressure chamber 13a is displaced from the one end portion 11aa of the upper pressure chamber 11a in accordance with the positions of the nozzle holes 5a, 5b, and the pressure chambers 11a, 13a and the nozzle holes 5a, The configuration of the communication passages 31 and 32 communicating with 5b is facilitated. Further, the other end portion 13ab of the lower pressure chamber 13a is also displaced with respect to the other end portion 11ab of the upper pressure chamber 11a, and the pressure chambers 11a, 13a and the common ink chamber 41 (manifold holes 15a, 16a) communicate with each other. The communication passages 33 and 34 are configured easily.

  Thus, in the ink flow path from the ink supply port to the nozzle holes 5a and 5b, the ink is supplied from the ink supply port to the common ink chamber 41 as an ink supply channel, and then passes through the communication paths 33 and 34. The pressure chambers 11a and 13a are distributed and supplied. By driving the piezoelectric actuator 3, the ink passes from the pressure chambers 11a and 13a through the communication passages 31 and 32 to the nozzle holes 5a and 5b corresponding to the pressure chambers 11a and 13a. .

  On the other hand, the piezoelectric actuator 3 has a structure in which a plurality of piezoelectric sheets 51 are laminated in the same manner as the known one disclosed in Japanese Patent Laid-Open No. 4-341833 etc., and each piezoelectric sheet having a thickness of about 30 μm. In the upper surface (wide surface) of the even-numbered piezoelectric sheet 51a from the lower side, narrow individual electrodes 52 are provided along the long side direction at locations corresponding to the pressure chambers 11a and 13a in the cavity unit 2. It is formed in a row. A common electrode 53 common to the plurality of pressure chambers 11a and 13a is formed on the upper surface (wide surface) of the odd-numbered piezoelectric sheet 51b from the bottom.

  An adhesive sheet (not shown) made of a non-ink-permeable synthetic resin material as an adhesive is formed on the entire lower surface (the wide surface facing the pressure chamber 111a) of the plate-type piezoelectric actuator 3 having such a configuration. Next, the piezoelectric actuator 3 is bonded and fixed to the cavity unit 2 with the individual electrodes 52 corresponding to the respective pressure chambers 11 a in the cavity unit 2. A flexible flat cable 4 having a wiring pattern connected to each electrode 52 is fixed to the upper surface of the piezoelectric actuator 3.

  As a control mode, the piezoelectric actuator 3 (pressurizing means) first ejects ink using only one nozzle hole 5a (nozzle hole 5a communicating with the upper pressure chamber 11a) of both nozzle holes 5a and 5b. In the recording mode (normal recording mode) and the pressure chambers 11a and 13a from the upper side, a larger pressing force is applied than in the first recording mode, and ink is applied using both nozzle holes 5a and 5b. A second recording mode to be ejected. FIG. 3 shows a schematic circuit diagram for controlling the recording mode. The control device converts the serially transferred recording data into parallel conversion so as to correspond to the arrangement of the nozzle holes 5a and 5b, and the converted recording data has a pulse waveform with a voltage or pulse width corresponding to the recording mode. Generating circuit 62, scanning control means for scanning the recording head in a direction (Y in FIG. 3) that intersects (for example, a right angle) with the arrangement direction of the nozzle holes 5a and 5b of the set, and the recording medium in the scanning direction. Conveyance control means for conveying the sheet by a predetermined amount in a direction perpendicular to it.

  In the first recording mode, a pulse waveform having a voltage lower than that in the second recording mode is applied between the individual electrode 52 and the common electrode 53, and the ink in the upper pressurizing chamber 11a is applied to the ink. Thus, a pressure necessary for spraying from the nozzle hole 5a is applied. However, when the applied pressure is propagated to the lower pressurizing chamber 13a, the applied pressure is attenuated by the damper chamber 12a, and the applied pressure to the ink in the lower pressure chamber 13a is weakened. Ink droplets are not ejected. For this reason, as shown in FIG. 3B, dots are formed at a pitch P1 of the nozzle holes 5a of the pressurizing chamber 11a in a direction perpendicular to the Y direction by scanning in the Y direction of the recording head. However, in the first recording mode, ink droplets are not ejected from the other nozzle hole 5b, but the meniscus is vibrated by the applied pressure, so that the ink in the nozzle hole 5b is agitated, and as a result, the viscosity of the ink is increased. Or drying is prevented. Accordingly, it is possible to reduce periodic non-printing ink ejection (so-called purge processing).

  In the second recording mode, a high voltage pulse waveform is applied between the electrodes so that sufficient pressure is applied to the ink in the lower pressure chamber 13a regardless of the attenuation by the damper chamber 12a. The For this reason, as shown in FIG. 3A, since the dots formed by the nozzles 5b are formed between the dots formed by the nozzle holes 5a, the amount of ejected droplets per unit area increases, that is, recording is performed at a high density. . In addition, since the pressure applied to the upper pressure chamber 11a is larger than that in the first recording mode, the size of the ink droplet ejected from one nozzle hole 5a is larger than that in the first recording mode. Since it becomes large, the amount of ejected droplets per unit area also increases from this point.

  In both of the recording modes, the medium transport amount is such that dots are not formed in one scan, but more dots are formed in the medium transport direction of the dots formed in (A) and (B) above. After the medium is transported by controlling the recording head, the recording head can be scanned. In the first recording mode, scanning is performed twice as many times as in the second recording mode, and a recording density equivalent to that in the second recording mode is obtained. In other words, the second recording mode can be a high-speed recording mode in which the number of scans (that is, the number of ink overstrikes) is smaller than that in the first recording mode.

  The present invention is not limited to the above embodiment, and can be modified as follows.

  (i) In addition to the second recording mode in which ink droplets are ejected from both nozzle holes 5a and 5b, in the first recording mode, the size is such that no ink droplets are ejected from the other nozzle hole 5b. By changing the pressing force in two steps within the range, a mode in which medium droplets are ejected from the nozzle hole 5a when the pressing force is large, and a small droplet is ejecting from the nozzle hole 5a when the pressing force is small. It is also possible to adopt a configuration having two modes, i.e. In this case, since the second recording mode is provided in addition to the two modes of the first recording mode, three types of large, medium, and small sizes can be substantially obtained by changing the pressing force in three stages. Ink droplets can be ejected.

  (ii) The pair of two nozzle holes have the same hole diameter, but may have different hole diameters. In this way, in addition to controlling the magnitude of the applied pressure by the pressurizing means (for example, the control as described in (i) above), it is possible to change one nozzle hole by changing the hole diameter of the two nozzle holes. Further control can be performed on the amount of ejected droplets per unit area.

  (iii) In the case of an ink jet recording apparatus that performs color recording, the nozzles having a set of two nozzle holes do not need to be applied to all nozzles, but are only applied to nozzles that eject at least black ink. But you can. In this way, recording with black ink, such as character data, can be ensured by increasing the amount of ejected droplets per unit area without increasing ink droplets or increasing the number of scans. Can be done at high speed.

FIG. 3 is a cross-sectional view taken along the line II of FIG. 2, which is a piezoelectric ink jet head used in the ink jet recording apparatus according to the present invention. It is a top view of the cavity unit in the same inkjet head. Schematic circuit diagram for controlling a first recording mode in which ink is ejected using only one of the two nozzle holes, and a second recording mode in which ink is ejected using two nozzle holes It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head 2 Cavity unit 3 Piezoelectric actuator 5a, 5b Nozzle hole 11 Upper cavity plate 11a Pressure chamber 12 Damper plate 12a Damper chamber 13 Lower cavity plate 13a Pressure chamber 14, 15 Manifold plate 14a, 15a Manifold hole 19, 20 Elastic sheet (Elastic body)
41 Common ink chamber

Claims (9)

A plurality of nozzles that eject ink, a plurality of pressure chambers that supply ink to the plurality of nozzles, and a cavity unit that temporarily stores ink to be supplied to the pressure chamber; and An ink jet recording apparatus that includes a pressurizing unit that ejects ink from a nozzle and that records the ink by ejecting the ink onto a recording medium
Each of the nozzles includes a pair of nozzle holes,
Two pressure chamber communicating are arranged overlapping vertically with the two set of nozzle holes,
One pressurizing means is provided for the two pressure chambers,
The opposing walls of the two pressure chambers are composed of an elastic body capable of propagating pressure from one pressure chamber to the other pressure chamber,
An ink jet recording apparatus, wherein the pressurizing unit pressurizes the one pressure chamber so that the other pressure chamber can also be pressurized . Wherein between upper and lower pressure chambers which are arranged overlapping, the ink jet recording apparatus according to claim 1, characterized in that it is arranged a damper chamber is a space unit. 3. The ink jet recording apparatus according to claim 1, wherein a set of two nozzle holes constituting each of the nozzles is provided side by side in a direction orthogonal to a longitudinal direction of the pressure chamber. Pairwise nozzle holes constituting the respective nozzles, the recording medium, any one of claims 1-3, characterized in that it is scanned in a direction crossing the arrangement direction of the two nozzle holes 2. An ink jet recording apparatus according to 1. The pressure chambers arranged to overlap vertically are overlapped in a longitudinal direction in a plan view, and end portions thereof are shifted corresponding to the positions of the nozzle holes. 4. An ink jet recording apparatus according to any one of 4 above. As the control mode, the pressurizing means has a first mode in which ink is ejected using only one of the nozzle holes, and a second mode in which ink is ejected by using both nozzle holes in each nozzle. an ink jet recording apparatus according to any one of claims 1 to 5, characterized in that it has and. The first mode is a normal recording mode, the second mode, in claim 6, wherein the normal printing mode number overstrike an ink is less than the recording mode The ink jet recording apparatus described. Nozzles comprising the pairwise nozzle holes, an ink jet recording apparatus according to any one of claims 1 to 7, characterized in that to inject at least a black ink. It said two pair of nozzle holes, an ink jet recording apparatus according to any one of claims 1 to 8, characterized in that different hole diameters.

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