JP2006015764A - Inkjet head - Google Patents

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JP2006015764A
JP2006015764A JP2005283463A JP2005283463A JP2006015764A JP 2006015764 A JP2006015764 A JP 2006015764A JP 2005283463 A JP2005283463 A JP 2005283463A JP 2005283463 A JP2005283463 A JP 2005283463A JP 2006015764 A JP2006015764 A JP 2006015764A
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piezoelectric
layer
ink
electrode
piezoelectric layer
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JP4207228B2 (en
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Atsuo Sakaida
惇夫 坂井田
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Brother Ind Ltd
ブラザー工業株式会社
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Abstract

PROBLEM TO BE SOLVED: To maintain high deformation efficiency by enlarging deformation as a whole piezoelectric body based on cooperation between shear mode deformation of a piezoelectric layer and expansion mode deformation of an outer piezoelectric layer even when the thickness of the piezoelectric layer is increased. It is possible to provide a low-cost inkjet head capable of reducing the loss of generated pressure by increasing the rigidity of an ink pressure chamber.
When a switch S is turned on, an electric field perpendicular to the polarization direction is generated on both surfaces of a piezoelectric ceramic layer 23 based on the fact that a drive voltage is applied to each first electrode 26 from a drive power supply V. The electric field parallel to the polarization direction of the outer piezoelectric ceramic layer 24 is generated at the same time, and the outer piezoelectric layer is uniformly deformed in the expansion / contraction mode. As a result, the volume of the ink pressure chamber 21 is reduced, whereby ink in the ink pressure chamber 21 is ejected from the ink ejection port (not shown) toward the printing paper, and characters and the like are printed.
[Selection] Figure 2

Description

  In the present invention, a piezoelectric layer is fixed so as to close an open surface of an ink pressure chamber formed in a cavity plate, and a driving voltage is applied to a predetermined electrode provided on the piezoelectric layer to deform the piezoelectric layer. In particular, an ink jet head that ejects ink from an ink ejection port uses a piezoelectric body in which a piezoelectric layer polarized in the layer thickness direction and an outer piezoelectric layer are stacked, and the polarization direction of the piezoelectric layer when a driving voltage is applied The piezoelectric layer is deformed in the shear mode by generating an electric field orthogonal to the piezoelectric layer, and the electric field parallel to the polarization direction of the outer piezoelectric layer is generated to deform the outer piezoelectric layer in the expansion / contraction mode. It is possible to increase the deformation of the entire piezoelectric body based on the cooperation between the mode deformation and the expansion / contraction mode deformation of the outer piezoelectric layer, and the pressure generated by increasing the rigidity of the ink pressure chamber. It relates an inkjet head capable of reducing the loss.

  Conventionally, various configurations have been proposed for the configuration of an inkjet head mounted on an inkjet printer. As an example, for the drive electrode of a piezoelectric element fixed to the open surface of an ink pressure chamber formed on a cavity plate. Ink jet heads configured to eject ink droplets from ink ejection ports by applying a drive pulse and generating shear mode deformation in a piezoelectric element to change the volume of an ink pressure chamber are known.

  For example, in the specification and drawings of U.S. Pat. No. 4,825,227, an ink pressure chamber is constituted by a chamber plate and a fixed plate, and a single layer piezoelectric layer is fixed to the open surface (upper surface) side of the ink pressure chamber. In addition, there is described an ink jet head in which two electrodes and a common electrode are formed on the entire surface of the other surface (lower surface) of the piezoelectric layer on the peripheral surface of the ink pressure chamber on one surface (upper surface) of the piezoelectric layer. In such an ink jet head, the piezoelectric layer is polarized in parallel along the surface of the piezoelectric layer from the center of the ink pressure chamber, and a piezoelectric layer is generated by applying a driving voltage to the two electrodes to generate an electric field orthogonal to the polarization direction. In this configuration, the shear mode deformation is generated, whereby the volume of the ink pressure chamber is changed to discharge the ink in the ink pressure chamber from the ink discharge port.

  Further, in the specification and drawings of US Pat. No. 4,584,590, an ink pressure chamber is formed in a main body plate, a piezoelectric layer composed of a single layer is fixed to the open surface (upper surface) side of the ink pressure chamber, and ink pressure There is described an ink jet head in which electrodes are formed on both surfaces of a piezoelectric layer corresponding to the peripheral position of the electrodes and both sides of the piezoelectric layer that are out of the ink pressure chamber corresponding to the chamber. In such an ink jet head, the piezoelectric layer is polarized along the layer thickness direction, and the piezoelectric layer is shared by applying a driving voltage to each electrode corresponding to the ink pressure chamber to generate an electric field orthogonal to the polarization direction. Mode deformation is generated, whereby the volume of the ink pressure chamber is changed, and the ink in the ink pressure chamber is discharged from the ink discharge port.

  In this way, in the two ink jet heads described above, although the polarization direction of the piezoelectric layer is different, an electric field perpendicular to the polarization direction is generated by applying a drive voltage between the electrodes spaced apart from the piezoelectric layer, thereby generating the piezoelectric layer. This is common in that it is configured to change the volume of the ink pressure chamber by changing the volume of the ink pressure chamber to discharge ink from the ink discharge port, and to use a single piezoelectric layer as the piezoelectric layer.

  In addition, an ink jet head using a laminated piezoelectric material in which two or more piezoelectric layers are laminated is also known. The laminated piezoelectric material used in this type of ink jet head uses a lateral effect mode or a longitudinal effect mode. The piezoelectric body is deformed in a so-called expansion / contraction mode, and employs a configuration in which a diaphragm or the like is interposed between the piezoelectric body and the ink pressure chamber. In addition, a laminated piezoelectric material is used, and a drive voltage is applied to the laminated piezoelectric material to generate an electric field in a direction substantially perpendicular to the polarization direction of the piezoelectric material so as to deform in the shear mode. An ink jet head that discharges ink while changing its volume is also known (see Japanese Patent Laid-Open No. 4-125157).

U.S. Pat. No. 4,825,227 U.S. Pat. No. 4,584,590 JP-A-4-125157

  However, in the inkjet head described in the specifications and drawings of each of the aforementioned US Pat. Nos. 4,825,227 and 4,584,590, a drive voltage is applied to the electrodes of the piezoelectric layer when ink is ejected from the ink ejection port as described above. Although the ink is ejected from the ink ejection port by generating an electric field orthogonal to the polarization direction of the piezoelectric layer and deforming the shear mode, the piezoelectric layer is only driven to be deformed only by the shear mode deformation. At this time, in order to efficiently eject ink from the ink ejection port, it is necessary to improve the deformation efficiency of the piezoelectric layer with respect to the drive voltage, but the deformation efficiency of the piezoelectric layer is thin if the thickness is thin. It gets higher. Considering the deformation efficiency of the piezoelectric layer, the ink jet head is only driven to be deformed only by the shear mode deformation, so there is a limit to increasing the thickness of the piezoelectric layer. Therefore, the piezoelectric layer itself constitutes one wall of the ink pressure chamber, and the piezoelectric layer cannot be thicker than a predetermined thickness in order to maintain the deformation efficiency of the piezoelectric layer above a certain level. As a result, the strength of the ink is lowered and the ink is deflected when the ink is ejected. As a result, the pressure generated in the ink pressure chamber is lowered.

  Furthermore, in an inkjet head that uses a laminated piezoelectric material, a diaphragm or the like is used for discharging the ink by transmitting the expansion / contraction deformation in the laminated piezoelectric material to the ink pressure chamber because of the deformation of the laminated piezoelectric material in the expansion / contraction mode. Is required, which increases the cost of the inkjet head. In order to realize a high-resolution multi-nozzle head, when using a multilayer piezoelectric body in an expansion / contraction mode, a method of arranging a plurality of piezoelectric bodies at a minute pitch, and a groove processing on a single piezoelectric body at a minute pitch However, in any case, there is a limit to the fine pitch, which is not suitable for a high resolution head.

  In addition, in an inkjet head that discharges ink by deforming a laminated piezoelectric material in a shear mode, the laminated piezoelectric material has a plurality of piezoelectric layers, so that electromechanical conversion efficiency is good and driving voltage is reduced. However, since the multilayer piezoelectric body is only deformed only in the shear mode, it cannot be said that the deformation efficiency of the multilayer piezoelectric body is still sufficient.

  The present invention has been made to solve the above-described problems, and uses a piezoelectric body formed by laminating a piezoelectric layer polarized in the layer thickness direction and an outer piezoelectric layer, and is piezoelectric when a driving voltage is applied. By generating an electric field orthogonal to the polarization direction of the layer and deforming the piezoelectric layer in the shear mode, and generating an electric field parallel to the polarization direction of the outer piezoelectric layer and deforming the outer piezoelectric layer in the expansion and contraction mode, Even when the thickness of the piezoelectric layer is increased, the deformation of the piezoelectric body as a whole can be increased based on the cooperation of the shear mode deformation of the piezoelectric layer and the expansion mode deformation of the outer piezoelectric layer, and the deformation efficiency can be kept high. An object of the present invention is to provide a low-cost inkjet head that can increase the rigidity of the ink pressure chamber and reduce the loss of generated pressure.

  In order to achieve this object, an ink jet head according to claim 1 is fixed to the cavity plate so as to close a surface of the ink pressure chamber and a cavity plate in which an ink pressure chamber is formed. And a first electrode formed at a position corresponding to the ink pressure chamber and a second electrode formed at a peripheral position of the ink pressure chamber, and a piezoelectric layer polarized in the layer thickness direction; A power source provided with a first terminal and a second terminal having different polarities, to which one electrode and the second electrode are connected, respectively, and a driving voltage is applied between the first and second electrodes from the power source In the inkjet head that discharges ink in the ink pressure chamber from the ink discharge port by deforming the piezoelectric layer, the piezoelectric layer is laminated on one surface of the piezoelectric layer and An outer piezoelectric layer polarized in the thickness direction; and an outer electrode formed on one side of the outer piezoelectric layer and connected to the second terminal of the power source, and when the driving voltage is applied from the power source, the piezoelectric The layer is deformed in the shear mode by generating an electric field perpendicular to the polarization direction between the first electrode and the second electrode, and the outer piezoelectric layer is parallel to the polarization direction. By generating a simple electric field between the first electrode and the outer electrode, the outer piezoelectric layer is deformed in the expansion / contraction mode.

  In the ink jet head according to claim 1, during the driving, a driving voltage is applied between the first and second electrodes from the power source, whereby the piezoelectric layer has a polarization direction between the first electrode and the second electrode. The piezoelectric layer is deformed in the shear mode based on the generation of the orthogonal electric field, and between the outer electrode connected to the second terminal of the power source and the first electrode of the piezoelectric layer adjacent to the outer piezoelectric layer. The outer piezoelectric layer is deformed in the expansion / contraction mode based on the generation of an electric field parallel to the polarization direction of the outer piezoelectric layer.

  In this way, the piezoelectric layer is deformed in the shear mode, and at the same time, an electric field parallel to the polarization direction of the outer piezoelectric layer is generated to deform the outer piezoelectric layer in the expansion / contraction mode, thereby increasing the thickness of the piezoelectric layer. Even in this case, it is possible to increase the deformation of the entire piezoelectric body based on the cooperation between the shear mode deformation of the piezoelectric layer and the expansion / contraction mode deformation of the outer piezoelectric layer, and to keep the deformation efficiency high. In addition, since the deformation efficiency can be kept high even if the thickness of the piezoelectric layer is increased, the generated pressure can be increased by increasing the rigidity of the ink pressure chamber as compared with the case of using a single piezoelectric layer. Loss can be reduced.

  An ink jet head according to a second aspect is the ink jet head according to the first aspect, wherein the outer piezoelectric layer is laminated on an upper surface of the piezoelectric layer. In the ink jet head according to the second aspect, the piezoelectric layer on the ink pressure chamber side is deformed in the shear mode, and the outer piezoelectric layer is deformed in the expansion / contraction mode on the upper surface of the piezoelectric layer. As a result, so-called bimorph deformation occurs in the piezoelectric layer based on the deformation of the outer piezoelectric layer, and the deformation amount of the entire piezoelectric body increases.

  The ink jet head according to claim 3 is the ink jet head according to claim 1, wherein the outer piezoelectric layer is laminated on a lower surface of the piezoelectric layer. In the ink jet head according to the third aspect, the outer piezoelectric layer on the ink pressure chamber side is deformed in the expansion / contraction mode, and the piezoelectric layer is deformed in the shear mode on the upper side of the outer piezoelectric layer. In this case, as in the case of the ink jet head of the second aspect, the piezoelectric layer undergoes a so-called bimorph deformation based on the deformation of the outer piezoelectric layer on the lower surface thereof, so that the deformation amount of the entire piezoelectric body is reduced. Becomes larger.

  Furthermore, an ink jet head according to a fourth aspect is the ink jet head according to the third aspect, wherein another piezoelectric layer in contact with the ink in the ink pressure chamber is provided on the lower surface of the outer piezoelectric layer. . In the ink jet head according to claim 4, since another piezoelectric layer that contacts the ink in the ink pressure chamber is provided on the lower surface of the outer piezoelectric layer, the outer electrode formed on one side of the outer piezoelectric layer directly contacts the ink. Never do. In addition, another piezoelectric layer that comes into contact with the ink acts as an insulating layer that prevents the ink from coming into contact with the outer electrode of the outer piezoelectric layer, thereby providing a special insulating layer such as an insulating film, a vibration plate, or the like. The outer electrode can be isolated from the ink in the ink pressure chamber without any further, and another piezoelectric layer acting as the insulating layer can be formed simultaneously with the manufacture of the piezoelectric layer and the outer piezoelectric layer. Therefore, there is no cost increase.

  As is apparent from the above description, in the ink jet head according to claim 1, a driving voltage is applied between the first electrode and the second electrode from the power source at the time of driving, whereby the first electrode and the second electrode are connected. The piezoelectric layer is deformed in the shear mode based on the generation of an electric field perpendicular to the polarization direction between the outer electrode and the outer piezoelectric layer connected to the second terminal of the power source. The outer piezoelectric layer is deformed in the expansion / contraction mode based on the fact that an electric field parallel to the polarization direction is generated in the outer piezoelectric layer between the first electrode of the piezoelectric layer.

  In this way, the piezoelectric layer is deformed in the shear mode, and at the same time, an electric field parallel to the polarization direction of the outer piezoelectric layer is generated to deform the outer piezoelectric layer in the expansion / contraction mode, thereby increasing the thickness of the piezoelectric layer. Even in this case, it is possible to increase the deformation of the entire piezoelectric body based on the cooperation between the shear mode deformation of the piezoelectric layer and the expansion / contraction mode deformation of the outer piezoelectric layer, and to keep the deformation efficiency high. In addition, since the deformation efficiency can be kept high even if the thickness of the piezoelectric layer is increased, the generated pressure can be increased by increasing the rigidity of the ink pressure chamber as compared with the case of using a single piezoelectric layer. Loss can be reduced.

  In the ink jet head according to claim 2, the piezoelectric layer on the ink pressure chamber side is deformed in the shear mode, and the outer piezoelectric layer is deformed in the expansion / contraction mode on the upper surface of the piezoelectric layer. Based on the deformation of the outer piezoelectric layer, so-called bimorph deformation occurs, and the deformation amount of the entire piezoelectric body increases.

  Further, in the ink jet head according to claim 3, the outer piezoelectric layer on the ink pressure chamber side is deformed in the expansion / contraction mode, and the piezoelectric layer is deformed in shear mode on the upper side of the outer piezoelectric layer. As in the case of the inkjet head 2, the piezoelectric layer undergoes so-called bimorph deformation based on the deformation of the outer piezoelectric layer on the lower surface thereof, and the amount of deformation of the entire piezoelectric body increases.

  In the ink jet head according to the fourth aspect, since the other piezoelectric layer that contacts the ink in the ink pressure chamber is provided on the lower surface of the outer piezoelectric layer, the outer electrode formed on one surface of the outer piezoelectric layer is directly There is no contact with ink. In addition, another piezoelectric layer that comes into contact with the ink acts as an insulating layer that prevents the ink from coming into contact with the outer electrode of the outer piezoelectric layer, thereby providing a special insulating layer such as an insulating film, a vibration plate, or the like. The outer electrode can be isolated from the ink in the ink pressure chamber without any further, and another piezoelectric layer acting as the insulating layer can be formed simultaneously with the manufacture of the piezoelectric layer and the outer piezoelectric layer. Therefore, there is no cost increase.

  As described above, the present invention uses a piezoelectric body formed by laminating a piezoelectric layer polarized in the layer thickness direction and an outer piezoelectric layer, and generates an electric field orthogonal to the polarization direction of the piezoelectric layer when a driving voltage is applied. When the piezoelectric layer is deformed in the shear mode and an electric field parallel to the polarization direction of the outer piezoelectric layer is generated to deform the outer piezoelectric layer in the expansion / contraction mode, thereby increasing the thickness of the piezoelectric layer. In addition, the deformation of the piezoelectric body as a whole can be increased based on the cooperation between the shear mode deformation of the piezoelectric layer and the expansion mode deformation of the outer piezoelectric layer, and the deformation efficiency can be kept high. It is possible to provide a low-cost inkjet head capable of reducing the loss of generated pressure by increasing the pressure.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an ink jet head according to the invention will be described in detail with reference to the drawings based on embodiments embodying the invention. First, an outline of an ink jet printer in which the ink jet head according to the first embodiment is mounted will be described with reference to FIG. FIG. 1 is a perspective view showing a main part of an ink jet printer.

  In FIG. 1, a platen 3 is rotatably mounted via a shaft 2 between a pair of frames 1 (only one frame 1 is shown in FIG. 1). The platen 3 is rotationally driven by a motor 4. The A piezoelectric ink jet head 5 is disposed so as to face the platen 3. The piezoelectric inkjet head 5 is placed on a carriage 7 together with an ink supply device 6. The carriage 7 is slidably supported by two guide rods 8 arranged parallel to the axis of the platen 3, and a timing belt 10 that is hooked on a pair of pulleys 9 is coupled to the carriage 7. Has been. Also, one pulley 9 (the right pulley 9 in FIG. 1) is fixed to the drive shaft of the motor 11, and therefore the timing belt 10 is based on the rotation of the right pulley 9 via the motor 11. And the carriage 7 is reciprocated along the platen 3.

Next, the structure of the piezoelectric inkjet head 5 will be described with reference to FIG. FIG. 2 is a cross-sectional view showing a part of the array structure of the piezoelectric inkjet head 5 according to the first embodiment. The inkjet head 5 according to the first embodiment is a so-called push-type inkjet head that ejects ink when a drive voltage is applied.
In FIG. 2, the array 20 of the piezoelectric inkjet head 5 basically includes a cavity plate 22 formed with a plurality of ink pressure chambers 21 whose upper surfaces are opened, and upper surfaces (open surfaces) of the ink pressure chambers 21. The piezoelectric ceramic layer 23 is fixed on the cavity plate 22 with an adhesive or the like, and the outer piezoelectric ceramic layer 24 is laminated on the upper surface of the piezoelectric ceramic layer 23.

  The ink pressure chambers 21 are formed by cutting the cavity plate 22 or the like, and the ink pressure chambers 21 are partitioned by partition walls 25.

  The piezoelectric ceramic layer 23 is formed of a piezoelectric ceramic layer having a piezoelectric / electrostrictive effect, and a first electrode 26 is formed on the upper surface of the piezoelectric ceramic layer 23 at a position corresponding to each ink pressure chamber 21. In addition, a second electrode 27 is formed corresponding to each partition wall 25 at the peripheral position of the ink pressure chamber 21. Further, the first electrode 26 and the second electrode 27 are formed on the lower surface of the piezoelectric ceramic layer 23 at positions corresponding to the first electrode 26 and the second electrode 27 on the upper surface, respectively. The piezoelectric ceramic layer 23 can be formed at the same time as the outer piezoelectric ceramic layer 24 is manufactured, so that the cost is not increased.

  The piezoelectric ceramic layer 23 is polarized in the layer thickness direction as indicated by an arrow A in FIG. The first electrodes 26 on the upper and lower surfaces of the piezoelectric ceramic layer 23 are connected to the positive terminal of the driving power source V via the switch S, and the second electrodes 27 are connected to the negative side of the driving power source V, respectively. Connected to the terminal.

  Further, the outer piezoelectric ceramic layer 24 is formed simultaneously with the production of the piezoelectric ceramic layer 23, and the outer electrode 28 is provided over the entire upper surface thereof. The outer piezoelectric ceramic layer 24 is polarized in the layer thickness direction as indicated by an arrow B. Further, the outer electrode 28 of the outer piezoelectric ceramic layer 24 is connected to the negative terminal of the drive power supply V.

  The manufacturing method of the piezoelectric ceramic layer 23, the outer piezoelectric ceramic layer 24, and the like, and the polarization processing method thereof are the same as the manufacturing method and the polarization processing method described in JP-A-4-125157. Therefore, detailed description of the manufacturing method and the like is omitted here.

  Next, the operation of the array 20 in the inkjet head 5 configured as described above will be described with reference to FIG. FIG. 3 is an enlarged cross-sectional view showing a part of the array 20 that is performing the printing operation by deforming the piezoelectric ceramic layer 23. Here, as shown in FIG. 2, the operation of each piezoelectric ceramic layer 23 and the outer piezoelectric ceramic layer 24 will be described on the assumption that the switch S corresponding to the second ink pressure chamber 21 from the left is turned on. And

  In FIG. 3, when the switch S is turned on via a controller (not shown) based on predetermined print data, the drive voltage is applied to the first electrodes 26 on the upper and lower surfaces of the piezoelectric ceramic layer 23 via the drive power supply V. Applied. At this time, since the first electrode 26 is connected to the positive terminal of the drive power source V and the second electrode 27 is connected to the negative terminal, the first electrode 26 and the second electrode on both the upper and lower surfaces of the piezoelectric ceramic layer 23. 27, an electric field (indicated by arrow C) perpendicular to the polarization direction (indicated by arrow A) of the piezoelectric ceramic layer 23 is generated as shown in FIG. Thereby, the piezoelectric ceramic layer 23 is uniformly deformed as shown in the shear mode based on the piezoelectric / electrostrictive effect.

  Further, since the outer electrode 28 of the outer piezoelectric ceramic layer 24 is connected to the negative terminal of the drive power supply V, when the switch S is turned on as described above, the outer piezoelectric layer 28 is connected to the first electrode 26. An electric field (indicated by arrow D) in a direction parallel to the polarization direction (indicated by arrow B) of the ceramic layer 24 is generated. As a result, the outer piezoelectric ceramic layer 24 is deformed in the expansion / contraction mode based on the piezoelectric / electrostrictive effect. That is, since the outer piezoelectric ceramic layer 24 extends in the thickness direction and contracts in the longitudinal direction, the outer piezoelectric ceramic layer 24 bends downward in the figure due to a bimorph effect between the adjacent piezoelectric ceramic layers 23.

  As described above, when the switch S is turned on, the driving voltage is applied to the first electrodes 26 on the upper and lower surfaces of the piezoelectric ceramic layer 23 from the driving power source V. By generating an electric field orthogonal to and uniformly deforming in the shear mode, and simultaneously generating an electric field parallel to the polarization direction of the outer piezoelectric ceramic layer 24 and deforming the outer piezoelectric ceramic layer 24 in the expansion / contraction mode Then, the volume of the ink pressure chamber 21 is reduced, whereby the ink in the ink pressure chamber 21 is ejected from the ink ejection port (not shown) toward the printing paper, and characters and the like are printed.

  As described above, in the inkjet head 5 according to the first embodiment, the piezoelectric ceramic layer 23 is deformed in the shear mode while the outer piezoelectric ceramic layer 24 is deformed in the expansion / contraction mode at the time of printing driving. The so-called bimorph deformation occurs due to the cooperation of the shear mode deformation of the ceramic layer 23 and the expansion / contraction mode deformation of the outer piezoelectric ceramic layer 24, and the deformation of the entire piezoelectric body can be increased. Further, based on the cooperative action of the shear mode deformation of the piezoelectric ceramic layer 23 and the expansion mode deformation of the outer piezoelectric ceramic layer 24, the deformation efficiency can be kept high even if the thickness of the piezoelectric ceramic layer 23 is increased. Therefore, compared to the case where a single piezoelectric layer is used, the rigidity of the ink pressure chamber 21 can be increased and the loss of generated pressure can be reduced.

  Further, since the piezoelectric ceramic layer 23 can be formed simultaneously with the production of the outer piezoelectric ceramic layer 24, there is no cost increase.

  In the first embodiment, if the relationship between the polarization directions of the piezoelectric ceramic layer 23 and the outer piezoelectric ceramic layer 24 is reversed, the piezoelectric ceramic layer 23 and the outer piezoelectric ceramic layer 24 are moved in the opposite direction, that is, ink. The pressure chamber 21 can be deformed in the direction of increasing the volume, and can be applied to a pulling method described later. Further, in order to isolate the first electrode 26 formed on the lower surface of the piezoelectric ceramic layer 23 from the ink in the ink pressure chamber 21, a protective film made of an organic or inorganic material is appropriately formed on the lower surface of the piezoelectric ceramic layer 23. Is desirable.

  Next, the array structure of the inkjet head 5 according to the second embodiment will be described with reference to FIG. FIG. 4 is a cross-sectional view showing a part of the array structure of the piezoelectric inkjet head 5 according to the second embodiment. The ink jet head 5 according to the second embodiment is a so-called ink jet type ink jet head that discharges ink when the application of the drive voltage is stopped after the ink suction operation is performed when the drive voltage is applied. is there.

  In FIG. 4, the array 30 of the piezoelectric inkjet head 5 basically includes a cavity plate 32 formed with a plurality of ink pressure chambers 31 whose upper surfaces are opened, and upper surfaces (open surfaces) of the ink pressure chambers 31. A piezoelectric ceramic layer 40 fixed on the cavity plate 32 with an adhesive or the like, an outer piezoelectric ceramic layer 34 laminated on the upper surface of the piezoelectric ceramic layer 40, and an upper surface of the outer piezoelectric ceramic layer 34. The piezoelectric ceramic layer 33 is formed. Here, for convenience of explanation, the layers are divided into layers, but the piezoelectric ceramic layer 40, the outer piezoelectric ceramic layer 34, and the piezoelectric ceramic layer 33 are integrally formed.

  Here, each ink pressure chamber 31 is formed by cutting the cavity plate 32 or the like, and each ink pressure chamber 31 is partitioned by a partition wall 35.

  An outer electrode 38 is formed over the entire upper surface of the piezoelectric ceramic layer 40 disposed on the lower surface of the outer piezoelectric ceramic layer 34, and the outer electrode 38 is negative of the drive power supply V as will be described later. It is an electrode necessary to be connected to the side terminal and to deform the outer piezoelectric ceramic layer 34 in the expansion / contraction mode. The piezoelectric ceramic layer 40 is a piezoelectric layer that comes into contact with ink in the ink pressure chamber 31 and acts as an insulating layer that isolates the outer piezoelectric ceramic layer 34 and the piezoelectric ceramic layer 33 from the ink. In this way, the piezoelectric ceramic layer 40 functions as an insulating layer, and the ink is prevented from contacting the outer electrode 38 on the lower surface of the upper outer piezoelectric ceramic layer 34 via the piezoelectric ceramic layer 40. This is because the piezoelectric ceramic layer 33 can be isolated from the ink in the ink pressure chamber without providing a special insulating layer such as an insulating film, a vibration plate, or the like. Further, since the piezoelectric ceramic layer 40 can be formed simultaneously with the manufacture of the piezoelectric ceramic layer 33, there is no increase in cost.

  A first electrode 36 is formed on the upper surface of the outer piezoelectric ceramic layer 34 at a position corresponding to each ink pressure chamber 31, and a second corresponding to each partition wall 23 at the peripheral position of the ink pressure chamber 31. An electrode 37 is formed. Each first electrode 36 is connected to the positive terminal of the drive power supply V via the switch S, and each second electrode 37 is connected to the negative terminal of the drive power supply V. The outer piezoelectric ceramic layer 34 is polarized in the layer thickness direction as indicated by an arrow F, and the outer piezoelectric ceramic layer 34 is formed integrally with the piezoelectric ceramic layer 40, so The electrode 38 is formed over the entire lower surface of the outer piezoelectric ceramic layer 34. The outer electrode 38 is connected to the negative terminal of the drive power supply V.

  The piezoelectric ceramic layer 33 is composed of a piezoelectric ceramic layer having a piezoelectric / electrostrictive effect. Like the outer piezoelectric ceramic layer 34, the first surface thereof is located at a position corresponding to each ink pressure chamber 31. An electrode 36 is formed, and a second electrode 37 is formed corresponding to each partition wall 35 at the peripheral position of the ink pressure chamber 31. The piezoelectric ceramic layer 33 is polarized in the layer thickness direction as indicated by an arrow E. Further, each first electrode 36 is connected to the plus side terminal of the driving power source V via the switch S, and each second electrode 37 is connected to the minus side terminal of the driving power source V, respectively. . As a result, the first electrode 36 and the second electrode 37 are formed on the upper and lower surfaces of the piezoelectric ceramic layer 33 at positions facing each other.

  The manufacturing method of the piezoelectric ceramic layer 33, the outer piezoelectric ceramic layer 34, and the like, and the polarization processing method thereof are the same as the manufacturing method and the polarization processing method described in JP-A-4-125157. Therefore, detailed description of the manufacturing method and the like is omitted here.

  Next, the operation of the array 30 in the inkjet head 5 according to the second embodiment configured as described above will be described with reference to FIG. FIG. 5 is an enlarged cross-sectional view showing a part of the array 30 that performs the printing operation by deforming the piezoelectric ceramic layer 33. Here, as shown in FIG. 4, the operation of each piezoelectric ceramic layer 33 and the outer piezoelectric ceramic layer 34 will be described on the assumption that the switch S corresponding to the second ink pressure chamber 31 from the left is turned on. And

  In FIG. 5, when the switch S is turned on via a controller (not shown) based on predetermined print data, a drive voltage is applied to each first electrode 36 via a drive power supply V. At this time, each first electrode 36 is connected to the positive terminal of the drive power supply V, and each second electrode 37 is connected to the negative terminal, so that the first electrode 36 and the first electrode 36 on the upper surface of the piezoelectric ceramic layer 33 are connected. As shown in FIG. 5, an electric field (indicated by arrow G) perpendicular to the polarization direction (indicated by arrow E) of the piezoelectric ceramic layer 33 is generated between the two electrodes 37. Similarly, an electric field (indicated by an arrow G) orthogonal to the polarization direction (indicated by an arrow E) of the piezoelectric ceramic layer 33 between the first electrode 36 and the second electrode 37 on the lower surface of the piezoelectric ceramic layer 33. Occurs). As a result, the piezoelectric ceramic layer 33 is uniformly deformed in the shear mode based on the piezoelectric / electrostrictive effect.

  Further, since the outer electrode 38 of the outer piezoelectric ceramic layer 34 is connected to the negative terminal of the drive power supply V, the first electrode 36 facing when the switch S is turned on as described above, An electric field (indicated by arrow H) in a direction parallel to the polarization direction (indicated by arrow F) of the outer piezoelectric ceramic layer 34 is generated. Accordingly, the outer piezoelectric ceramic layer 34 is deformed in the expansion / contraction mode based on the piezoelectric / electrostrictive effect. That is, since the outer piezoelectric ceramic layer 34 extends in the thickness direction and contracts in the longitudinal direction, like the outer piezoelectric ceramic layer 24 in the first embodiment, the outer piezoelectric ceramic layer 34 has a bimorph effect between the adjacent piezoelectric ceramic layers 33. , Curved upward in the figure. The piezoelectric ceramic layer 40 in contact with the ink in the ink pressure chamber 31 is composed of the same layers (components) as the piezoelectric ceramic layers 33 and the outer piezoelectric ceramic layer 34. Following the shear mode deformation of the layer 33 and the expansion mode deformation of the outer piezoelectric ceramic layer 34, the layer 33 is deformed as shown in FIG. Since the outer piezoelectric ceramic layer 34 is sandwiched between the piezoelectric ceramic layer 33 and the piezoelectric ceramic layer 40, the bimorph effect generated as described above is slightly weakened. Since it is thick, it is deformed as shown in FIG. At this time, when importance is attached to the deformation efficiency of the piezoelectric ceramic layer 33 and the outer ceramic piezoelectric layer 34, the piezoelectric ceramic layer 40 should be omitted. This is because the outer electrode 38 is connected to the negative terminal (ground) of the drive power source V as shown in FIG. 4 and hardly affects the ink in the ink pressure chamber 31. On the other hand, when importance is attached to the adverse effect that the outer electrode 38 may have on the ink in the ink pressure chamber 31, and the deformation efficiency of the piezoelectric ceramic layer 33 and the outer ceramic piezoelectric layer 34 is also important, Instead of the piezoelectric ceramic layer 40, a flexible insulating film or the like may be disposed on the lower surface of the outer piezoelectric ceramic layer 34. As described above, when the outer piezoelectric ceramic layer 34 is provided on the lower surface of the piezoelectric ceramic layer 33, various deformation modes are conceivable. However, each deformation mode has advantages and disadvantages. It may be determined in consideration of the merit to do.

  As described above, when the switch S is turned on, an electric field orthogonal to the polarization direction is applied to both surfaces of the piezoelectric ceramic layer 33 based on the fact that the drive voltage is applied from the drive power supply V to each first electrode 36. The volume of the ink pressure chamber 21 is increased by generating and deforming in the shear mode, and simultaneously generating an electric field parallel to the polarization direction of the outer piezoelectric ceramic layer 34 to deform the outer piezoelectric layer in the expansion / contraction mode. Thus, after the ink is sucked into the ink pressure chamber 21, the ink is ejected from the ink ejection port (not shown) toward the printing paper when the application of the driving voltage is stopped, and characters and the like are printed. .

  As described above, in the inkjet head 5 according to the second embodiment, the piezoelectric ceramic layer 33 is deformed in the shear mode while the outer piezoelectric ceramic layer 34 is deformed in the expansion / contraction mode at the time of printing driving. The cooperation of the shear mode deformation of the ceramic layer 33 and the expansion / contraction mode deformation of the outer piezoelectric layer 34 causes so-called bimorph deformation, and the deformation of the entire piezoelectric body can be increased. Further, based on the cooperative action of the shear mode deformation of the piezoelectric ceramic layer 33 and the expansion / contraction mode deformation of the outer piezoelectric ceramic layer 34, the deformation efficiency can be kept high even if the thickness of the piezoelectric ceramic layer 33 is increased. Therefore, compared to the case where a single piezoelectric layer is used, the rigidity of the ink pressure chamber 31 can be increased and the loss of generated pressure can be reduced.

  In addition, since the piezoelectric ceramic layer 40 that contacts the ink in the ink pressure chamber 31 is provided on the lower surface of the outer piezoelectric ceramic layer 34, the outer electrode 38 existing on the lower surface of the outer piezoelectric ceramic layer 34 directly contacts the ink. Thus, the outer electrode 38 can be isolated from the ink in the ink pressure chamber 31 without providing a special insulating layer such as an insulating film, a diaphragm, or the like. In addition, the piezoelectric ceramic layer 40 that functions as an insulating layer can be formed at the same time as the manufacture of the piezoelectric ceramic layer 33 and the outer piezoelectric ceramic layer 34, so that the cost is not increased.

  Further, the piezoelectric ceramic layer 40 that comes into contact with the ink in the ink pressure chamber 31 is formed of the same layer as the piezoelectric ceramic layer 33 and the outer piezoelectric ceramic layer 34. Therefore, the piezoelectric ceramic layer 40 is formed of the piezoelectric ceramic layer. Therefore, the piezoelectric ceramic layer 33 is easily deformed according to the shear mode deformation of 33 and the expansion / contraction mode deformation of the outer piezoelectric ceramic layer 34, so that the movement of the piezoelectric ceramic layer 33 and the outer piezoelectric ceramic layer 34 is not restricted. The one electrode 36 and the outer electrode 38 of the outer piezoelectric ceramic layer 34 can be shielded from the ink in the ink pressure chamber 31.

  The present invention is not limited to the first and second embodiments described above, and various improvements and modifications can be made without departing from the scope of the present invention.

It is a perspective view which shows the principal part of an inkjet printer. It is sectional drawing which shows a part of array structure of the piezoelectric inkjet head which concerns on 1st Embodiment. It is sectional drawing which expands and shows a part of array which is deforming a piezoelectric ceramic layer and is performing printing operation. It is sectional drawing which shows a part of array structure of the piezoelectric inkjet head which concerns on 2nd Embodiment. It is sectional drawing which expands and shows a part of array which is deforming a piezoelectric ceramic layer and is performing printing operation.

Explanation of symbols

5 Inkjet head 20, 30 Array 21, 31 Ink pressure chamber 22, 32 Cavity plate 23, 33 Piezoelectric ceramic layer 24, 34 Outer piezoelectric ceramic layer 25, 35 Partition wall 26, 36 First electrode 27, 37 Second electrode 28, 38 Outer electrode 40 Piezoelectric ceramic layer A, B, E, F Polarization direction C, D, G, H Electric field direction S Switch V Drive power supply

Claims (4)

  1. A cavity plate having an ink pressure chamber open on one side, and a first electrode fixed to the cavity plate so as to close one side of the ink pressure chamber and formed at a position corresponding to the ink pressure chamber And a second electrode formed at a peripheral position of the ink pressure chamber, the piezoelectric layer polarized in the layer thickness direction, and the first electrode and the second electrode having different polarities connected to each other A power source provided with a first terminal and a second terminal, and applying a drive voltage between the first and second electrodes from the power source to deform the piezoelectric layer, thereby causing ink in the ink pressure chamber to flow. In an inkjet head that discharges from an ink discharge port,
    An outer piezoelectric layer laminated on one side of the piezoelectric layer and polarized in the layer thickness direction;
    An outer electrode formed on one side of the outer piezoelectric layer and connected to a second terminal of the power source;
    When a drive voltage is applied from the power source, an electric field perpendicular to the polarization direction is generated between the first electrode and the second electrode in the piezoelectric layer, thereby deforming the piezoelectric layer in the shear mode. The inkjet head is characterized in that an electric field parallel to the polarization direction of the outer piezoelectric layer is generated between the first electrode and the outer electrode, whereby the outer piezoelectric layer is deformed in an expansion / contraction mode.
  2.   The inkjet head according to claim 1, wherein the outer piezoelectric layer is laminated on an upper surface of the piezoelectric layer.
  3.   The inkjet head according to claim 1, wherein the outer piezoelectric layer is laminated on a lower surface of the piezoelectric layer.
  4.   4. The ink jet head according to claim 3, wherein another piezoelectric layer in contact with the ink in the ink pressure chamber is provided on the lower surface of the outer piezoelectric layer.
JP2005283463A 2005-09-29 2005-09-29 Inkjet printer Expired - Lifetime JP4207228B2 (en)

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Cited By (4)

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JP2007203515A (en) * 2006-01-31 2007-08-16 Brother Ind Ltd Liquid droplet jet apparatus
JP2012204352A (en) * 2011-03-23 2012-10-22 Konica Minolta Holdings Inc Piezoelectric thin film device
US8382257B2 (en) 2009-03-19 2013-02-26 Fujifilm Corporation Piezoelectric actuator, method of manufacturing piezoelectric actuator, liquid ejection head, method of manufacturing liquid ejection head and image forming apparatus
US8899729B2 (en) 2007-03-30 2014-12-02 Brother Kogyo Kabushiki Kaisha Piezoelectric actuator and liquid transport apparatus provided with piezoelectric actuator

Families Citing this family (1)

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Publication number Priority date Publication date Assignee Title
CN107399165A (en) * 2016-05-20 2017-11-28 中国科学院苏州纳米技术与纳米仿生研究所 A kind of piezo jets for improving shearing deformation quantity and preparation method thereof

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007203515A (en) * 2006-01-31 2007-08-16 Brother Ind Ltd Liquid droplet jet apparatus
JP4702701B2 (en) * 2006-01-31 2011-06-15 ブラザー工業株式会社 Droplet ejector
US8899729B2 (en) 2007-03-30 2014-12-02 Brother Kogyo Kabushiki Kaisha Piezoelectric actuator and liquid transport apparatus provided with piezoelectric actuator
US8382257B2 (en) 2009-03-19 2013-02-26 Fujifilm Corporation Piezoelectric actuator, method of manufacturing piezoelectric actuator, liquid ejection head, method of manufacturing liquid ejection head and image forming apparatus
JP2012204352A (en) * 2011-03-23 2012-10-22 Konica Minolta Holdings Inc Piezoelectric thin film device

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