JP2007125808A - 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 nearly perpendicular to a center axis O of the communication hole 28 is made sequentially larger towards the one end 24a of the pressure chamber 24 and in the ink flow direction in 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, as shown schematically in FIG. 10A, the ink advances through the communication hole 28 along the plate stacking direction to the one end 24a of the pressure chamber 24. 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 bend and 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 forcibly pressurized by sucking from the nozzle side of the cavity unit or pushing from the ink supply source side. Thus, maintenance (purging process) for discharging the air bubbles together with the ink is performed.

  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 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. 10C) It is preferably a flat cross-sectional shape having a large depth and a small depth (vertical direction in FIG. 10A). 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. 10B, since the bubble A which has grown greatly inside the communication hole 28 is spherical, 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 depth in the central axis direction of the communication hole is smaller than the width in a direction substantially perpendicular thereto. The cross-sectional area of the communication hole that is substantially perpendicular to the central axis is gradually increased toward one end of the pressure chamber and in the direction of ink flow in the pressure chamber.

  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 extends in an ink flow direction in the pressure chamber at an end opening at one end of the pressure chamber. And a groove-shaped recess that is narrower than the width of the pressure chamber, a portion of the recess is covered with a plate forming the pressure chamber, and the remaining portion of the recess is connected to one end of the pressure chamber. It is characterized by that.

  According to a fourth aspect of the present invention, in the ink jet head according to the first or second aspect, the communication hole is formed with a reduced diameter portion in the middle of the ink flow direction. Is.

  The invention according to claim 5 is the inkjet head according to any one of claims 1 to 4, wherein an aspect ratio of a cross section at one end of the pressure chamber is 0.4 or less. is there.

  According to a sixth aspect of the present invention, in the ink jet head according to the second aspect, 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 cross-sectional area of the communication hole substantially perpendicular to the central axis of the communication hole gradually increases toward one end of the pressure chamber and along the ink flow direction in the pressure chamber. Therefore, the cross section of one end of the pressure chamber is formed into 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 to it, and the bubble grows to a size that makes it difficult to enter the flat portion. However, it is easy to cause the bubbles to be sequentially deformed along the direction of ink flow in the pressure chamber by the pressure of the purge process, and to be discharged together with the ink, thereby preventing ink ejection failure.

  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, a part of the groove-shaped recess formed at the end opening at one end of the pressure chamber of the communication hole is covered with the plate forming the pressure chamber. A flat space is formed at the end of each. Therefore, when ink flows from the communication hole to the flat pressure chamber, it flows through the flat space at the end of the communication hole, so that the flatness does not rapidly increase from the communication hole to the pressure chamber. Bubbles easily flow into the pressure chamber.

  According to the fourth aspect of the present invention, since the reduced diameter portion is provided midway in the ink flow direction of the communication hole, the communication hole has a shape in which the cross-sectional area increases from the reduced diameter portion toward the pressure chamber. Is done. In order to form a reduced diameter portion in the middle of the direction of ink flow in the communication hole, that is, in the middle of the thickness direction of the plate in which the communication hole is formed, a method of simultaneously performing wet etching from both the front and back surfaces of the plate forming the communication hole If it is adopted, the inner surface of the communication hole from the reduced diameter portion to the end of the communication hole is gently formed, so that the ease of inflow of bubbles from the communication hole to the pressure chamber is promoted.

  According to the fifth 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, by forming the communication hole as described in any one of claims 1 to 4, it is possible to suppress a sudden increase in flatness from the communication hole to the pressure chamber. The ink can be sequentially deformed along the ink flow direction, and the bubble discharge performance is improved.

  According to the sixth 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 becomes 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 width dimension W and a depth dimension D. As described above, the pressure chamber 24 is formed through the thickness of the cavity plate 36. The depth dimension D of the cavity plate 36 is the same as the thickness dimension T 1 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 flow of ink. Specifically, the aspect ratio (D / W) is 0.4 or less (preferably approximately 0.2). It has a highly flat shape.

  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 (thickness dimension T2) thicker than the cavity plate 36 in order to give rigidity to the entire cavity unit, but the communication hole 28 having a diameter smaller than the thickness T2 is formed. It is difficult. In the first embodiment, the communication hole 28 has a cross-sectional area that is substantially perpendicular to the central axis O and gradually increases toward the one end 24 a of the pressure chamber 24 and along the ink flow direction in the pressure chamber 24. The two communication holes 28a and 28b having different cross-sectional areas are combined. The cross-sectional area of the communication holes 28a and 28b is 1.5 times or more that the communication hole 28a on the side close to the pressure chamber (exit side) is larger than the communication hole 28b on the far side (inlet side).

  Specifically, as shown in FIGS. 4 and 5B, a communication hole 28a formed as a groove-like recess having a long hole shape in plan view and narrower than the width dimension W of the pressure chamber 24, and a circular shape in plan view. The communication hole 28b is disposed around the central axis O, and the communication hole 28a is overlapped with the communication hole 28b in the stacking direction and the other end 24b of the pressure chamber 24 with respect to the central axis O. It is arranged to extend to the side. As a result, as shown in FIG. 5 (a), the flatness gradually increases from the communication hole 28 to the pressure chamber 24, and the ink bends gently when the flow direction is changed substantially at a right angle. I am doing so. The lower communication hole 28b can be processed without increasing its inner diameter by setting the depth dimension to about half the plate thickness of the base plate 35.

  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 includes an inlet hole into which ink enters from the common ink chamber 25, an outlet hole that opens to face the communication hole 28, and an inlet hole and an outlet hole. And a throttle portion formed with a reduced cross-sectional area so as to have the largest flow path 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. If a predetermined flow path resistance can be obtained by the lower communication hole 28b instead of the connection flow path 29 having the throttle portion as shown in FIGS. 2, 3, and 4, it is constituted only by the communication hole 28. May be.

  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. At this time, the cross-sectional area of the end portion that opens to the pressure chamber 24 side in the communication hole 28 is larger than the cross-sectional area of the communication hole on the upstream side of the communication hole 28. As shown in FIG. 5A, the corner on the inner side of the corner portion where the ink bends from the communication hole 28 toward the pressure chamber 24 is cut as shown in FIG. For this reason, when the ink enters the pressure chamber 24 at a substantially right angle, it bends while gently curving, and the flatness from the communication hole 28 to the pressure chamber 24 does not suddenly increase, but stepwise. Therefore, bubbles can be deformed sequentially along the direction of ink flow in the pressure chamber and easily flow into the pressure chamber 24 by the pressure of the purge process. That is, bubbles can be discharged in a short time with a relatively small pressure of the purge process.

  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.

  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 hole 28 is formed is increased, the diameter L (see FIG. 10C) of the communication hole 28 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. As described in the section “Problems to be Solved by the Invention”, the bubbles that grow larger than the depth D in the communication hole 28 follow the flat shape of the pressure chamber 24 even by the pressure of the purge process. Since it is difficult to deform, the pump used for the purge process becomes larger and the amount of ink to be discharged increases. In the first embodiment, even if large bubbles are stagnating in the communication hole 28, the purge process can be performed easily, that is, in a short time. Unnecessary consumption 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.

  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 communication hole 28 of 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 FIGS. 6 (a) and 6 (b), the communication hole 28 of the second embodiment includes a communication hole 28 in the base plate 35 as in the first embodiment, and a communication hole 28a having a long hole shape in plan view. And a communication hole 28b having a circular shape in plan view are formed so as to communicate with each other in the stacking direction. The cavity plate 36 in which the pressure chamber 24 is formed covers a part of the opening of the communication hole 28a. . As a result, as in the first embodiment, the ink gently curves from the communication hole 28 to the pressure chamber 24 and changes its direction, and a sudden change in flatness toward the pressure chamber 24 is prevented.

  As shown in FIGS. 7A and 7B, the communication hole 28 of the third embodiment is a form obtained by modifying a part of the communication hole 28 of the second embodiment, and the shape of the communication hole 28a. However, in the plan view from the stacking direction, it is formed in a tapered long hole in which the width dimension on the downstream side of the ink flow is smaller than the width dimension on the upstream side. Thereby, when the ink passes through the communication hole 28a, the flow velocity is increased toward the downstream side, and the inflow of the bubbles into the pressure chamber 24 can be promoted.

  As shown in FIGS. 8A and 8B, the communication holes 28 according to the fourth embodiment are respectively provided with holes (communication holes 28a and communication holes) from the front and back surfaces of the base plate 35 on which the communication holes 28 are formed. The hole 28b) is processed by wet etching, and the communication hole 28 is formed in the middle of the thickness direction of the base plate 35 so that both holes are connected. When the hole is processed in the metal plate by wet etching, the hole is gradually reduced in diameter toward the bottom surface thereof, so that the inner diameter narrows in the middle of the ink flow direction in the communication hole 28. The diameter portion can be easily formed. Further, the center axis of the communication hole 28a is shifted in advance to the downstream side of the ink flow in the pressure chamber 24 with respect to the center axis of the communication hole 28b. Therefore, the ink flowing through the communication hole 28 can be gently bent when flowing into the pressure chamber 24 from the communication hole 28b through the communication hole 28a, and the discharge of bubbles can be promoted.

  As shown in FIGS. 9A and 9B, the communication hole 28 of the fifth embodiment is on the side of the other end 24b of the pressure chamber 24 on the inner wall surface of the communication hole 28a having a long hole shape in plan view. This surface is formed in a tapered shape whose diameter increases from a bottom surface connected to the communication hole 28b toward an end portion (end surface) that opens to the pressure chamber 24. That is, the flattening rate is continuously changed from the communication hole 28 toward the pressure chamber 24, whereby the bubbles can be easily deformed and discharged.

  Further, as shown in FIG. 9B, 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, a relatively fast flow can be formed in the ink flowing from the communication hole 28 to the one end 24a of the pressure chamber 24, and the bubbles can be pushed more effectively to the downstream side. The shape of the one end 24a of the pressure chamber 24 can be applied to the other embodiments described above.

  In each embodiment, the upper and lower holes 28a and 28b of the communication hole 28 are formed on one plate, but the upper and lower holes 28a and 28b may be formed on different plates and stacked.

  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 sectional view showing the communication hole of the first embodiment, (b) is a plan view of the communication hole viewed from the pressure chamber side, (c) is a schematic diagram showing a cross section of one end of the pressure chamber, (d) ) Is a schematic view showing a cross section of an end portion opened to the pressure chamber of the communication hole. (A) is a longitudinal cross-sectional view which shows the communicating hole of 2nd 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 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 the longitudinal cross-sectional view which shows the communicating hole of 5th Embodiment, (b) was 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 passage 28 (28a, 28b) Communication hole 28d End part 29 Connection flow path 30 Nozzle plate 35 Base plate 36 Cavity plate

Claims (6)

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.
The inkjet head according to claim 1, wherein a cross-sectional area of the communication hole substantially perpendicular to the central axis is sequentially increased toward one end of the pressure chamber and in an ink flow direction in the pressure chamber.   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 groove-like recess extending at an end opening at one end of the pressure chamber in the ink flow direction in the pressure chamber and narrower than the width of the pressure chamber, and a part of the recess is The inkjet head according to claim 1, wherein the inkjet head is covered with a plate forming the pressure chamber, and is connected to one end of the pressure chamber at a remaining portion of the concave portion.   The inkjet head according to claim 1, wherein a diameter-reduced portion is formed in the communication hole in the middle of the ink flow direction.   The inkjet head according to any one of claims 1 to 4, 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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