JP2007125798A - Inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and surely carry out removal of bubbles that stay at a bending part in the constitution where ink flows bending nearly perpendicularly from a communication hole of a cavity unit into a pressure chamber. <P>SOLUTION: The pressure chamber 24 covered with an actuator 21 is formed to flow the ink from one end 24a connected with the communication hole 28 towards the other end 24b connected with a nozzle 23. Moreover, the communication hole 28 is formed opened in a nearly perpendicular direction to a flow direction of the ink in the pressure chamber 24 to one end of the pressure chamber 24. A cross section of the one end 24a of the pressure chamber among cross sections nearly perpendicular to the ink flow in the pressure chamber 24 is made flat with a depth in a center axis O direction of the communication hole 28 smaller than a width in a nearly perpendicular direction to the direction. An end 28d opened in the one end 24a of the pressure chamber 24 of the communication hole 28 is formed to make one of dimensions in the nearly perpendicular direction to the center axis O almost equal to a depth of the pressure chamber 24. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inkjet head, and more particularly, to an inkjet head having a cavity unit configured to supply ink through a communication hole to a pressure chamber that receives discharge pressure.

  In recent inkjet heads, miniaturization has been promoted, and the applicant of the present invention has also disclosed a plurality of thin plates with a cavity unit having an ink flow path in the inkjet head as disclosed in, for example, Patent Document 1. By stacking and configuring, the entire head is made thinner.

  As the plurality of plates of the cavity unit, a plate in which a plurality of nozzles are formed, a plate in which a pressure chamber for each nozzle is formed, and a common ink chamber in which ink supplied from an ink supply source is temporarily stored are formed. A plate, a plate in which communication holes for distributing the ink in the common ink chamber to the respective pressure chambers (described as communication passage 38 in Patent Document 1) are formed. An actuator that applies discharge pressure to the ink filled in the pressure chamber is stacked on the cavity unit so as to cover the pressure chamber.

In such a thin cavity unit, in order to effectively utilize the thickness dimension of the entire cavity unit and secure an ink flow path necessary for ejection, the ink flow path is disposed inside the cavity unit in the plate stacking direction ( (Thickness direction) or extends parallel to the surface direction of each plate. Specifically, the pressure chamber that receives the discharge pressure from the actuator is placed on the back plate facing the actuator, the nozzle is placed on the front plate, and the common ink chamber is placed on the intermediate plate in the stacking direction. Yes. Then, after the ink is supplied to the common ink chamber, the ink advances through the communication hole 28 along the plate stacking direction to the one end 24a of the pressure chamber 24 as schematically shown in FIG. The flow direction at one end 24a of the pressure chamber 24 is bent at a substantially right angle, proceeds to the other end 24b of the pressure chamber 24 along the surface of the actuator 21, and the flow direction at the other end 24b again at a substantially right angle. It is configured to be bent to reach the nozzle provided on the front side of the cavity unit.
Japanese Patent Laying-Open No. 2005-41047 (see FIGS. 4 and 5)

  By the way, in the ink jet head, if air bubbles are mixed in the ink inside the cavity unit, ink ejection failure is caused. For this reason, the ink is forced by sucking ink from the nozzle side of the cavity unit or pushing it from the ink supply source side. Maintenance (purge process) is performed to pressurize and discharge bubbles together with ink.

  However, as described above, if the ink flow path is configured to bend at a substantially right angle, bubbles are stagnated at the bent portion, and the stagnant bubbles merge with bubbles that come later and grow into large bubbles. Easy to do. In particular, in order to give a large discharge pressure to the ink, the pressure chamber needs to increase the rate of change of the cross-sectional area accompanying the operation of the actuator, and the width facing the actuator (W in the plan view of FIG. 12C). It is preferably a flat cross-sectional shape having a large depth and a small depth (vertical direction in FIG. 12A). Further, the plate in which the communication hole is formed is preferably a plate thicker than the plate forming the pressure chamber in order to give rigidity to the entire cavity unit, and a communication hole that is smaller than the thickness is formed. Therefore, the communication hole has a diameter approximately equal to its thickness. For this reason, as shown in FIG. 12 (b), the bubble A that has grown greatly inside the communication hole 28 is spherical, so that it is difficult to enter the pressure chamber 24 having a depth smaller than the diameter of the bubble. It stagnates on the ceiling surface of 24. As a result, the pressure applied to the ink in the pressure chamber 24 by the actuator is absorbed by the bubbles, and the pressure for discharging from the nozzle is insufficient, resulting in a discharge failure.

  In order to remove the bubbles, it is necessary to perform a purging process in which a pressure is applied to the ink to cause a flow from the communication hole 28 to the pressure chamber 24. As shown in FIG. Since W is sufficiently larger than the diameter L of the communication hole 28, the ink flow due to the purge process escapes in the width direction of the pressure chamber 24, and the bubbles A cannot be pushed out. For this reason, if the purge process is not performed by applying a large pressure on the ink to deform the spherical shape of the bubble A into a flat shape, the bubbles cannot be reliably removed, and wasteful discharge of ink accompanying the purge process, There has been a problem that the purge processing pump is also increased in size.

  The present invention solves the above-described problem, and in the structure in which the ink flows while bending at a substantially right angle from the communication hole of the cavity unit into the pressure chamber, the bubbles accumulated in the bent portion are removed. It is an object of the present invention to provide an ink jet head capable of easily and reliably performing the above.

  In order to solve the above-described problem, an ink jet head according to the first aspect of the present invention includes a pressure chamber provided corresponding to each of a plurality of nozzles that eject ink, and a method for distributing ink to the plurality of pressure chambers. A cavity unit in which a common ink chamber, a communication hole connecting the common ink chamber and the pressure chamber are formed, and an actuator that applies discharge pressure to the ink filled in the pressure chamber; Is formed so that ink flows from one end connected to the communication hole to the other end connected to the nozzle, and the communication hole is substantially the same as the direction of ink flow in the pressure chamber with respect to one end of the pressure chamber. An ink jet head that is formed in a right angle direction and is configured to bend the direction in which ink that has passed through the communication hole flows at one end of the pressure chamber at a substantially right angle. Of the cross section substantially perpendicular to the flow of ink in the pressure chamber, the cross section of one end of the pressure chamber is formed in a flat shape in which the thickness in the central axis direction of the communication hole is smaller than the width in the direction substantially perpendicular thereto. An end portion of the communication hole that opens to one end of the pressure chamber is formed so that one of the dimensions in a direction substantially perpendicular to the central axis is substantially equal to the depth of the pressure chamber. is there.

  According to a second aspect of the present invention, in the ink jet head according to the first aspect, the cavity unit includes a plate that forms the pressure chamber, a plate that forms the communication hole, and a plate that forms the common ink chamber. The actuator is laminated on a plate forming the pressure chamber on a side opposite to the plate forming the communication hole.

  According to a third aspect of the present invention, in the ink jet head according to the first or second aspect, the communication hole has a cross-sectional area on the upstream side of the communication chamber, as compared with an end opening at one end of the pressure chamber. The end of the pressure chamber opens at one end of the pressure chamber so that one of the dimensions in a direction substantially perpendicular to the central axis is substantially equal to the depth of the pressure chamber. To do.

  According to a fourth aspect of the present invention, in the ink jet head according to the second aspect, the plate forming the communication hole is composed of a plurality of plates stacked in the stacking direction, and at least of the plurality of plates. The communication hole having a dimension in a direction substantially perpendicular to the central axis substantially equal to the depth of the pressure chamber is formed in the pressure chamber side plate.

  According to a fifth aspect of the present invention, in the inkjet head according to the second aspect, an end portion of the communication hole that opens to one end of the pressure chamber is in a direction parallel to the ink flow direction of the pressure chamber. The pressure chamber has a size approximately equal to the depth of the pressure chamber, and is larger than that in a direction substantially perpendicular thereto.

  According to a sixth aspect of the present invention, in the ink jet head according to the second aspect, the plate forming the pressure chamber covers a part of the communication hole, and the remaining part of the communication hole is the pressure chamber. It is laminated on a plate forming the communication hole in a state of opening at one end.

  The invention according to claim 7 is the inkjet head according to any one of claims 1 to 6, wherein an aspect ratio of a cross section at one end of the pressure chamber is 0.4 or less. is there.

  The invention according to claim 8 is the ink jet head according to claim 2, wherein the plate forming the communication hole is thicker in the stacking direction than the plate forming the pressure chamber. It is.

  According to the first aspect of the present invention, the end portion of the communication hole that opens to one end of the pressure chamber has a dimension substantially perpendicular to the central axis of the communication hole so as to be substantially equal to the depth of the pressure chamber. Since it is formed, the bubbles flowing into the pressure chamber from the communication hole have a dimension that is approximately equal to or smaller than the depth dimension of the pressure chamber, and can quickly enter the pressure chamber. As a result, bubbles are less likely to stagnate at one end of the pressure chamber, and by applying a relatively small pressure to the ink in the purge process, the bubbles can flow further downstream with the ink and be discharged to the outside. .

  According to the second aspect of the present invention, since the cavity unit is formed by laminating a plurality of plates each having an ink flow path formed therein, the cavity unit having a complicated and finely shaped ink flow path therein. It can be easily and thinly configured.

  According to the third aspect of the present invention, the communication hole has a shape having a larger cross-sectional area on the upstream side than the end opening at one end of the pressure chamber. Since the end area is reduced along the advancing direction, the ink flowing through the communication hole has the highest flow velocity at the end of the communication hole, and the discharge of bubbles is promoted.

  According to the invention described in claim 4, since the plate forming the communication hole is composed of a plurality of plates, the rigidity of the entire cavity unit can be increased. In addition, since it is difficult to make a hole having a diameter smaller than the plate thickness in the plate, it is difficult to form a communication hole having a small diameter almost equal to the depth of the pressure chamber in the plate having a large plate thickness. However, as described above, it is possible to form a communication hole having a size substantially equal to the depth of the pressure chamber in at least the plate on the pressure chamber side by using a plurality of plates forming the communication holes.

  According to the fifth aspect of the present invention, at the end of the communication hole that opens to one end of the pressure chamber, the dimension in the direction parallel to the ink flow direction of the pressure chamber is substantially equal to the depth dimension of the pressure chamber, Further, since the dimension in the direction substantially perpendicular to the dimension is larger than this dimension, the communication hole is formed in a long hole shape in plan view. Therefore, the difference in flatness from the communication hole to one end of the pressure chamber is reduced, and bubbles are less likely to stagnate at one end of the pressure chamber, and are easily discharged to the outside through the pressure chamber. Further, since the communication hole has a long hole shape with respect to the spherical bubble, there is an effect that the ink flow path can be secured even if the bubble is stagnated in the communication hole.

  According to the invention described in claim 6, since a part of the communication hole is covered with the plate forming the pressure chamber, even if the communication hole is drilled with a relatively large inner diameter in the thick plate, The opening of the communication hole with respect to one end of the pressure chamber can be substantially reduced.

  According to the seventh aspect of the present invention, the cross section at one end of the pressure chamber has a high flatness with an aspect ratio of 0.4 or less, and the volume change rate of the pressure chamber due to the operation of the actuator is increased. be able to. Furthermore, since the dimension of the end portion of the communication hole that opens to one end of the pressure chamber is approximately equal to the dimension on the short side of the cross section of the pressure chamber, it can be pushed away to the pressure chamber side without causing bubbles to stagnate. It becomes possible.

  According to the eighth aspect of the present invention, in order to increase the volume change rate of the pressure chamber due to the operation of the actuator, the plate forming the pressure chamber is thin, and the pressure chamber has a large opening area, so the pressure chamber is formed. However, the rigidity of the entire stacking direction can be increased by making the plate forming the communication hole thicker in the stacking direction than the plate forming the pressure chamber.

  Below, 1st Embodiment of this invention is described using FIGS.

  FIG. 1 is a perspective view of a cavity unit 20, a piezoelectric actuator 21, and a flexible flat cable 22 in an inkjet head 1 according to an embodiment of the present invention. A plate-type piezoelectric actuator 21 is provided on a cavity unit 20 composed of a plurality of plates. A flexible flat cable 22 for connection to an external device is overlapped and bonded to the upper surface of the plate-type piezoelectric actuator 21. Then, it is assumed that ink is ejected downward from the nozzle 23 opened on the lower surface side of the cavity unit 20 (see FIG. 3).

  As shown in FIG. 2, the cavity unit 20 includes a total of seven thin plates including a nozzle plate 30, a spacer plate 31, two manifold plates 33a and 33b, a supply plate 34, a base plate 35, and a cavity plate 36. It has a structure in which it is overlapped with an adhesive.

  In the embodiment, each of the plates 30 to 36 has a thickness of about 40 to 150 μm, the nozzle plate 30 is made of a synthetic resin such as polyimide, and the other plates 31 to 36 are made of 42% nickel alloy steel plate. The nozzle plate 30 is provided with a large number of ink discharge nozzles 23 having a minute diameter (about 20 μm) at minute intervals. The nozzles 23 are arranged in two rows parallel to the long side direction (X direction) of the nozzle plate 30.

  In the cavity plate 36, as shown in FIG. 2, a plurality of pressure chambers 24 are arranged in two rows parallel to the long side of the cavity plate 36 (the X direction). In the embodiment, as shown in FIGS. 3 and 4, each of the pressure chambers 24 is an elongated shape in plan view, and the longitudinal direction of the pressure chamber 24 is along the short side direction (Y direction) of the cavity plate 36. Drilled through the thickness. A communication hole 28 is connected to one longitudinal end 24 a of each pressure chamber 24, and the one end 24 a communicates with the common ink chamber 25 through the communication hole 28 and the connection flow path 29. The other end 24 b in the longitudinal direction of each pressure chamber 24 is connected to the base plate 35, the supply plate 34, the two manifold plates 33 a and 33 b, and the through-passage 26 formed in the spacer plate 31. The nozzles 23 communicate with the nozzles 23.

  As shown in FIG. 4, the pressure chamber 24 has a depth dimension D and a width dimension W in a direction substantially perpendicular to the depth direction and substantially perpendicular to the ink flow. The depth dimension D of the pressure chamber 24 is a thickness in a direction parallel to the direction of the central axis O of the communication hole 28 described later. As described above, the pressure chamber 24 is formed through the thickness of the cavity plate 36. Therefore, it is the same as the thickness dimension T1 of the cavity plate 36. The cross-sectional area perpendicular to the ink flow in the pressure chamber 24 is determined by the width dimension W and the depth dimension D (see FIGS. 4 and 5A). The pressure chamber 24 needs to have a large change rate of the cross-sectional area accompanying the operation of the actuator in order to give a large discharge pressure to the ink, and is set to a relationship of W> D. Specifically, the width dimension W is , Approximately 250 μm to 300 μm, and the depth dimension D is approximately 40 μm to 60 μm. Therefore, the cross section of the pressure chamber 24 is formed in a flat shape that is long in a direction substantially perpendicular to the ink flow (see FIG. 5C), and in detail, the aspect ratio (D / W) is 0.4 or less ( Preferably, the shape has a high flatness of about 0.2).

  In the base plate 35 adjacent to the lower surface of the cavity plate 36, a communication hole 28 connected to one end 24 a of each pressure chamber 24 is formed for each pressure chamber 24, and the communication hole 28 faces the actuator 21. Ink flows (see FIGS. 2 and 3). The base plate 35 is preferably a plate thicker than the cavity plate 36 in order to give rigidity to the entire cavity unit, but it is difficult to drill the communication hole 28 having a diameter smaller than the thickness.

  In the first embodiment, the base plate 35 is configured by laminating two base plates 35a and 35b (indicated by reference numerals 35a and 35b in order from the side close to the cavity plate 36), and the plate thickness per base plate 35a and 35b. The rigidity of the entire base plate 35 is ensured so that the total thickness of these two sheets is increased (approximately 100 μm to 150 μm). The communication hole 28 is configured such that holes formed in the two base plates 35a and 35b (individually referred to as communication holes 28a and 28b, respectively) are overlapped in the ink flow direction (FIGS. 4 and 4). 5 (a)).

  Each of the communication holes 28a, 28b has a cylindrical shape (circular shape in plan view from the stacking direction), is concentric with respect to the central axis O, and has a cross-sectional area in stages along the direction in which the ink advances ( The inner diameter is small, and the cross-sectional area of the communication hole 28b is 1.5 times or more the cross-sectional area of the communication hole 28a. That is, the inner diameter La of the communication hole 28a and the inner diameter Lb of the communication hole 28b are in a relationship of La <Lb, and the end portion 28d of the communication hole 28 that opens to the one end 24a of the pressure chamber 24 is connected to the communication hole 28a. The diameter La is substantially equal to the depth dimension D of the pressure chamber 24 (La≈D) (see FIG. 5D).

  The total thickness of the two base plates 35a and 35b is thicker than the thickness T1 of the cavity plate 36. In particular, the base plate 35a has a communication hole 28a having a small inner diameter that is the same as the depth D of the pressure chamber 24. In order to pierce, it is a thin plate having a thickness dimension substantially equal to or smaller than the thickness dimension T1 of the cavity plate 36.

  The supply plate 34 adjacent to the lower surface of the base plate 35 is provided with a connection channel 29 for supplying ink from the common ink chamber 25 to the pressure chambers 24. Each connection channel 29 is located between the inlet hole into which ink enters from the common ink chamber 25, the outlet hole facing the communication hole 28, and the inlet hole and the outlet hole. And a throttle portion formed with a reduced cross-sectional area so as to provide road resistance. One end of the connection channel 29 communicates with the common ink chamber 25, and the other end communicates with the pressure chamber 24 through the communication hole 28. In order to discharge ink from the nozzle 23, the throttle portion prevents the ink from moving backward toward the common ink chamber 25 when the pressure chamber 24 receives discharge pressure, and efficiently advances the ink toward the nozzle 23. It is provided to make it happen. In addition, if a predetermined flow path resistance can be obtained by the communication hole 28 instead of the connection flow path 29 having the throttle portion, it may be configured by only a simple cylindrical communication hole 28.

  The two manifold plates 33a and 33b are formed with two common ink chambers 25 extending through the plate thickness so as to extend along each row of the nozzles 23 along the long side direction (X direction). ing. That is, as shown in FIGS. 2 and 3, two manifold plates 33a and 33b are stacked, and the upper surface thereof is covered with the supply plate 34, and the lower surface is covered with the spacer plate 31, so that a total of two common plates are used. An ink chamber (manifold chamber) 25 is formed. Each common ink chamber 25 overlaps with a part of the pressure chamber 24 and extends in the row direction of the pressure chambers 24 (row direction of the nozzles 23) when viewed in plan from the stacking direction of the plates.

  In addition, as shown in FIG. 2, two ink supply ports 40 are formed in the end portions on one short side of the cavity plate 36, the base plate 35, and the supply plate 34 so as to correspond to the upper and lower positions. Has been. Ink from the ink supply source is supplied from the ink supply port 40 to one end of the common ink chamber 25. In addition, a filter body 40a is attached to the ink supply port 40 with an adhesive or the like.

  In the ink flow path in the cavity unit 20, after ink is supplied from the ink supply port 40 to the common ink chamber 25, as shown in FIG. 3, the ink flows through the connection flow path 29 of the supply plate 34 and the communication hole 28 of the base plate 35. The pressure is distributed and supplied to each pressure chamber 24. Then, the ink passes through the through passage 26 from each pressure chamber 24 and reaches the nozzle 23 corresponding to the pressure chamber 24.

  On the other hand, the piezoelectric actuator 21 has a flat shape having a size extending over all the pressure chambers 24 and a direction perpendicular to the flat direction, similar to the known one disclosed in JP-A-4-341853. And a plurality of electrode layers disposed on the flat surface of the plurality of ceramic layers. Here, an appropriate number of sheet surfaces among a plurality of piezoelectric ceramic material sheets (green sheets) formed by mixing ceramic powder, binder and solvent into a flat shape so that the thickness of each sheet is about 30 μm. The piezoelectric actuator 21 is formed by forming an electrode layer with a conductive paste on the substrate by a printing method or the like, and laminating and firing the plurality of green sheets. Thereby, each green sheet becomes a ceramic layer of a sintered body.

  As the electrode layer, an electrode layer for each electrode formed for each pressure chamber 24 and an electrode layer for a common electrode formed across the plurality of pressure chambers 24 make a pair in the stacking direction of the ceramic layers. And a layer of a surface electrode 46 disposed on the uppermost surface and electrically connected to the flexible flat cable 22 (see FIG. 1). In the piezoelectric actuator 21 provided with the electrode layer in this manner, as is well known, by applying a high voltage between the individual electrode and the common electrode, the portion of the ceramic layer sandwiched between the two electrodes is polarized and activated. Formed as part.

  The piezoelectric actuator 21 thus formed is fixed on the cavity plate 36 so as to cover the pressure chambers 24 with the individual electrodes corresponding to the pressure chambers 24. By selectively applying a drive voltage between the individual electrode and the common electrode, a portion of the ceramic layer sandwiched between the two electrodes is deformed to cause a volume change in the pressure chamber 24. As a result, a discharge pressure is applied to the ink in the pressure chamber, and the ink is discharged from the nozzle 23.

  In the ink jet head 1 configured as described above, the ink flowing into the pressure chamber 24 ascends the communication hole 28, hits the piezoelectric actuator 21, and changes its direction at a substantially right angle. It flows toward the other end 24b of 24. As described in the section “Problems to be Solved by the Invention”, when the entire communication hole 28 is formed in a cylindrical shape having an inner diameter sufficiently larger than the depth D of the pressure chamber 24. The bubbles that grow larger than the depth D in the communication hole 28 are not easily deformed along the flat shape of the pressure chamber 24 even by the pressure of the purge process, so that it takes a long time to discharge the bubbles. Will be wasted.

  However, in the first embodiment, among the cross sections substantially perpendicular to the ink flow, the cross section of the one end 24a of the pressure chamber 24 has a flat shape in which the depth dimension D is smaller than the width dimension W. The communication hole 28 connected to the one end 24 a is formed so that its inner diameter gradually decreases as it approaches the pressure chamber 24, and an end portion 28 d connected to the one end 24 a of the pressure chamber 24 is formed in the pressure chamber 24. The inner diameter La is substantially equal to the depth dimension D. Therefore, even if a bubble that has grown greatly inside the communication hole 28 is stagnant, the bubble is pushed to the pressure chamber 24 side by the pressure of the ink during the purge process, and depending on the inner shape of the communication hole 28, It is deformed into an elongated shape so that the cross-sectional area substantially perpendicular to the ink flow becomes small. Then, at the end portion 28 d of the communication hole 28, the bubble has a dimension La that is substantially equal to the depth dimension D of the pressure chamber 24. As a result, even when a large bubble flows into the pressure chamber 24, it has already been deformed into a shape that is easy to flow into the pressure chamber 24, so that it can be swept downstream with the ink and discharged to the outside. It becomes.

  In addition, since the inner diameter of the communication hole 28 decreases along the direction of ink flow, the flow velocity of the ink is gradually increased, and the flow velocity increases most at the end portion 28d. There is an effect of promoting the inflow of bubbles to the 24 side.

  In the above-described embodiment, the case where the inkjet head is arranged horizontally so that the nozzle 23 faces downward and bubbles rise vertically upward from the communication hole 28 has been described. However, the inkjet head is oriented so that the nozzle 23 faces sideways or upward. Even when the head is arranged, if the ink is pressurized by the purge process, the ink and bubbles flow in the same manner, so the same effect can be obtained.

  Thus, in the first embodiment, even if large bubbles are stagnating in the bent portion from the communication hole 28 to the pressure chamber 24, the purge process can be performed easily, that is, in a short time. The amount of ink ejected along with the bubbles can be suppressed, and wasteful consumption of ink can be prevented. Furthermore, since the pressure of the pump used for the purging process can be reduced, the pump capacity can be lowered and the cost of parts can be reduced.

  When the plate of the cavity unit 20 is made of metal as in the first embodiment, the recesses and through holes for forming the ink flow path are often processed by a wet etching method. In the wet etching method, since etching proceeds in the plate surface direction at the same speed as the plate thickness direction, it is extremely difficult to process a recess or a through hole having an inner diameter smaller than the plate thickness. Therefore, in order to increase the rigidity of the cavity unit 20 as a whole, if the plate thickness T2 of the base plate 35 in which the communication holes 28 are formed is increased, the diameter L of the communication holes 28 (see FIG. 12C) must be increased. I don't get it. On the other hand, in the cavity plate 36 having the pressure chamber 24, the plate thickness T1 is reduced in order to increase the change rate of the cross-sectional area of the pressure chamber 24 due to the operation of the actuator, and is perpendicular to the ink flow in the pressure chamber 24. The cross section has a flat shape. Therefore, for these reasons, the cross-sectional area is small and flat while bending at a substantially right angle from the communication hole 28 to the one end 24a of the pressure chamber.

  However, in the first embodiment, the base plate 35 is constituted by a plurality of plates, and the rigidity of the cavity unit is ensured by the whole of the plurality of plates, so that the plate thickness per base plate can be reduced. Since a small inner diameter hole can be drilled in the thin base plate 35, a communication hole 28a having a small inner diameter La (La≈D), which is difficult with a thick plate, is formed in the base plate 35a. It can be arranged so as to open to one end 24 a of the chamber 24, and can be configured so as not to cause a sudden change in cross section from the communication hole 28 to the pressure chamber 24.

  In addition, when ink flows from the other end 24b of the pressure chamber 24 to the through passage 26, the ink is bent at a substantially right angle. However, as the ink flows at the bent portion, the cross section is orthogonal to the ink flow. Therefore, the air bubbles can flow quickly downstream.

  In the above embodiment, the actuator is exemplified as a piezoelectric type, but is not limited to the piezoelectric type, and can be applied to other driving methods such as static electricity.

  The present invention can be applied not only to the first embodiment but also to various forms. Other embodiments will be described below with reference to the drawings. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 6, the communication hole 28 of the second embodiment has a communication hole 28a having an inner diameter La and a communication hole 28b having an inner diameter larger than the communication hole 28a, as in the first embodiment. The configured communication hole 28 is formed in one base plate 35. The communication hole 28 a has a depth dimension substantially equal to or smaller than the depth D of the pressure chamber 24 with respect to the thickness of the base plate 35, and the communication hole 28 b has the remaining thickness of the base plate 35. Each has a depth dimension, and can be formed by processing each from the front and back surfaces of the base plate 35.

  Further, like the communication hole 28 of the third embodiment shown in FIGS. 7A and 7B, communication holes 28a and 28b each having an inner diameter La are formed in the two base plates 35a and 35b. And may be stacked in the stacking direction. When the thickness of the entire base plate exceeds twice the inner diameter La, three or more base plates may be stacked.

  As shown in FIGS. 8A and 8B, the communication hole 28 of the fourth embodiment covers a part of the communication hole 28 formed in the base plate 35 with a cavity plate 36, and the remaining communication holes 28 are formed. The portion is an end portion 28 d that opens to one end 24 a of the pressure chamber 24, and the length dimension La in the short direction of the opening area of the end portion 28 d is substantially equal to the depth dimension D of the pressure chamber 24. Further, the communication hole 28 is covered with the cavity plate 35. Thereby, even if the plate thickness of the base plate 35 is thick and the inner diameter of the communication hole 28 is larger than the depth dimension D of the pressure chamber, the opening end to the pressure chamber 24 at the end portion 28d is the length dimension in the short direction. La has a flat shape substantially equal to the depth dimension D of the pressure chamber 24, the difference in flatness from the communication hole to one end of the pressure chamber is reduced, and bubbles are less likely to stagnate at one end of the pressure chamber. It is easy to be discharged outside through the room. Further, since the communication hole has a long hole shape with respect to the spherical bubble, the ink flow path can be secured even if the bubble is about to stay in the communication hole.

  As shown in FIGS. 9A and 9B, the communication hole 28 of the fifth embodiment is formed in an elliptical shape in plan view on the base plate 35, and the elliptical ink in the pressure chamber 24 is formed. The dimension La in the direction parallel to the flow direction is approximately equal to the thickness D of the pressure chamber, and the dimension in the direction substantially perpendicular to La is larger than La. Thus, the end portion 28 d of the communication hole 28 that opens to the one end 24 a of the pressure chamber 24 does not necessarily have a circular shape, and one of the dimensions in a direction substantially perpendicular to the central axis is the depth dimension D of the pressure chamber 24. If they are approximately equal, the same effects as in the fourth embodiment can be obtained.

  As shown in FIGS. 10A and 10B, the communication hole 28 of the sixth embodiment is composed of two base plates 35 a and 35 b obtained by dividing the base plate 35 in the longitudinal direction of the pressure chamber 24. Side surfaces orthogonal to the wide surfaces of 35a and 35b are arranged on the supply plate 34 so as to face each other. The communication holes 28 are formed by abutting the notches 28a and 28b formed on the side surfaces of the base plates 35a and 35b, respectively. Since the communication hole 28 is a combination of notches formed on the side surface of the plate, the communication hole 28 has an effect that it can be easily formed with a smaller opening area than the hole formed through the plate thickness. In this case, the communication hole 28 can be formed in either a circular shape or an oval shape in plan view.

  Moreover, like the communication hole 28 of 7th Embodiment shown to Fig.11 (a) and FIG.11 (b), the opening by the side of the one end 24a of the pressure chamber 24 has the internal diameter La and the small diameter side in the baseplate 35. The form drilled in the tapered communication hole 28 may be used.

  Further, as shown in FIG. 11 (b), the width of the one end 24a of the pressure chamber 24 is smaller than the width W of the pressure chamber portion on the downstream side, and is close to the size of the opening end of the communication hole 28. You may make it do. By doing so, the fast flow of ink flowing from the communication hole 28 to the one end 24a of the pressure chamber 24 is maintained as a relatively fast flow even at the narrow end 24a, and the bubbles are more effectively pushed downstream. be able to. The shape of the one end 24a of the pressure chamber 24 can be applied to the other embodiments described above.

  It goes without saying that the present invention is not limited to the above-described embodiment, and forms in which these are modified or combined are possible.

1 is a perspective view of an inkjet head according to an embodiment of the present invention. It is a disassembled perspective view of an inkjet head. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 1. It is a disassembled perspective view of the principal part of a cavity unit. (A) is a longitudinal cross-sectional view which shows the communicating hole of 1st Embodiment, (b) is a top view of the communicating hole seen from the pressure chamber side. It is a longitudinal cross-sectional view which shows the communicating hole of 2nd Embodiment. (A) is a longitudinal cross-sectional view which shows the communicating hole of 3rd Embodiment, (b) is a top view of the communicating hole seen from the pressure chamber side. (A) is a longitudinal cross-sectional view which shows the communicating hole of 4th Embodiment, (b) is a top view of the communicating hole seen from the pressure chamber side. (A) is a longitudinal cross-sectional view which shows the communicating hole of 5th Embodiment, (b) is a top view of the communicating hole seen from the pressure chamber side. (A) is a longitudinal cross-sectional view which shows the communicating hole of 6th Embodiment, (b) is a top view of the communicating hole seen from the pressure chamber side. (A) is a longitudinal cross-sectional view which shows the communicating hole of 7th Embodiment, (b) is a top view of the communicating hole seen from the pressure chamber side. (A) (b) And (c) is a schematic diagram which shows the flow of the ink of the conventional cavity unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head 20 Cavity unit 21 Piezoelectric actuator 22 Flexible flat cable 23 Nozzle 24 Pressure chamber 24a One end part 24b Other end part 25 Common ink chamber 26 Through path 28 (28a, 28b, 28d) Communication hole 28d End part 29 Connection flow path 30 Nozzle plate 35 (35a, 35b, 35c) Base plate 36 Cavity plate

Claims (8)

A pressure chamber provided corresponding to each of a plurality of nozzles for discharging ink, a common ink chamber for distributing ink to the plurality of pressure chambers, and a communication hole connecting the common ink chamber and the pressure chamber A cavity unit, and an actuator that applies discharge pressure to the ink filled in the pressure chamber,
The pressure chamber is formed so that ink flows from one end connected to the communication hole to the other end connected to the nozzle, and the communication hole flows the ink in the pressure chamber with respect to one end of the pressure chamber. An ink jet head configured to bend substantially perpendicularly to a direction in which the ink flowing through the communication hole flows at one end of the pressure chamber, the opening being formed in a direction substantially perpendicular to the direction;
Of the cross section substantially perpendicular to the ink flow in the pressure chamber, the cross section of one end of the pressure chamber is formed in a flat shape in which the depth in the central axis direction of the communication hole is smaller than the width in a direction substantially perpendicular thereto.
An end portion of the communication hole that opens to one end of the pressure chamber is formed so that one of the dimensions in a direction substantially perpendicular to the central axis is substantially equal to the depth of the pressure chamber. head.   The cavity unit is formed by stacking a plate that forms the pressure chamber, a plate that forms the communication hole, and a plate that forms the common ink chamber, and the actuator is formed on the plate that forms the pressure chamber. 2. The ink jet head according to claim 1, wherein the ink jet head is laminated on a side opposite to a plate forming the communication hole.   The communication hole has a shape having a larger cross-sectional area on the upstream side than the end opening at one end of the pressure chamber, and the end opening at one end of the pressure chamber is substantially the same as the central axis. 3. An ink jet head according to claim 1, wherein one of the dimensions in the perpendicular direction is formed so as to be approximately equal to the depth of the pressure chamber.   The plate forming the communication hole is composed of a plurality of plates stacked in the stacking direction, and at least the plate on the pressure chamber side among the plurality of plates has a dimension in a direction substantially perpendicular to the central axis. The ink jet head according to claim 2, wherein the communication hole having a size substantially equal to a depth of the ink is formed.   The end of the communication hole that opens at one end of the pressure chamber has a size that is substantially equal to the depth of the pressure chamber in a direction parallel to the ink flow direction of the pressure chamber, and in a direction substantially perpendicular thereto. The inkjet head according to claim 2, wherein the inkjet head is also large.   The plate forming the pressure chamber is laminated on the plate forming the communication hole in a state where a part of the communication hole is covered and the remaining part of the communication hole opens at one end of the pressure chamber. The ink-jet head according to claim 2, wherein:   The inkjet head according to claim 1, wherein an aspect ratio of a cross section at one end of the pressure chamber is 0.4 or less. The inkjet head according to claim 2, wherein the plate forming the communication hole is thicker in the stacking direction than the plate forming the pressure chamber.

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