JP2014144596A - Liquid discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the discharge amount of each nozzle when driving two respective piezoelectric elements corresponding to two adjacent pressure chambers larger than the discharge amount of the nozzle when driving either one piezoelectric element only.SOLUTION: An inkjet head has a plurality of first pressure chambers 53a disposed at one face side of a piezoelectric actuator 44, and a plurality of the second pressure chambers 53b disposed at the other face side of the actuator 44. The pluralities of the first and second pressure chambers 53a and 53b are commonly covered by the actuator 44. When two piezoelectric elements 65 corresponding to the adjacent first and second pressure chambers 53a and 53b, respectively, are driven by a driver IC45, two portions of the actuator 44 covering the adjacent two pressure chambers 53 are displaced in mutually opposite directions.

Description

  The present invention relates to a liquid ejection apparatus.

  Patent Document 1 discloses an ink jet head that ejects ink droplets from nozzles as a liquid ejecting apparatus. This inkjet head includes a flow path unit and a piezoelectric actuator. In the flow path unit, an ink flow path including a plurality of nozzles and a plurality of pressure chambers respectively communicating with the plurality of nozzles is formed. The piezoelectric actuator includes two piezoelectric layers covering a plurality of pressure chambers, a plurality of individual electrodes respectively disposed corresponding to the plurality of pressure chambers on the upper surface of the upper piezoelectric layer, and between the two piezoelectric layers. And a common electrode disposed.

  When a predetermined voltage is applied between one individual electrode and a common electrode, an active portion (hereinafter also referred to as a piezoelectric element) of an upper piezoelectric layer sandwiched between the individual electrode and the common electrode is arranged in a plane direction. Shrink. Accordingly, in the region facing the pressure chamber corresponding to the individual electrode, the two piezoelectric layers are bent so as to protrude toward the pressure chamber. The ink pressure in the pressure chamber rises due to the change in volume of the pressure chamber at this time, and ink droplets are ejected from the nozzles communicating with the pressure chamber.

JP 2011-212901 A

  Incidentally, in the piezoelectric actuator as disclosed in Patent Document 1, it is known that a phenomenon called crosstalk occurs between two pressure chambers when the piezoelectric actuator is displaced in each of two adjacent pressure chambers. ing. FIG. 10 is a diagram for explaining crosstalk between two adjacent pressure chambers. FIG. 10A shows a state in which no voltage is applied to both of the two piezoelectric elements 101 corresponding to the two pressure chambers 102, and the piezoelectric actuator 100 (piezoelectric layers 103 and 104) has two pressures. There is no displacement at each portion facing the chamber 102. FIG. 10B shows a state in which a voltage is applied only to the piezoelectric element 101 corresponding to one pressure chamber 102, and the piezoelectric actuator 100 has a pressure chamber 102 side in a portion facing the one pressure chamber 102. Is displaced. FIG. 10C shows a state in which a voltage is applied to both of the two piezoelectric elements 101 corresponding to the two pressure chambers 102, and the piezoelectric actuator 100 is in two parts facing the two pressure chambers 102. Each is displaced to the pressure chamber 102 side.

  As shown in FIG. 10C, when two piezoelectric elements 101 corresponding to the two pressure chambers 102 are driven simultaneously, a portion of the piezoelectric actuator 100 facing one pressure chamber 102 is convex toward the pressure chamber 102 side. By displacing in this manner, in the other pressure chamber 102, a force is generated in the piezoelectric actuator 100 to displace to the side opposite to the pressure chamber 102. Therefore, compared to the case where only one piezoelectric element 101 is driven as shown in FIG. 10B, in FIG. 10C, the displacement amount of the piezoelectric actuator 100 in each pressure chamber 102 is reduced. In other words, when the piezoelectric elements 101 are driven simultaneously for two adjacent pressure chambers 102, the discharge from the nozzles communicating with each pressure chamber 102 is performed, compared to the case where only the piezoelectric elements 101 corresponding to one pressure chamber 102 are driven. The amount of liquid that is applied is reduced.

  On the other hand, in a general liquid ejecting apparatus such as an ink jet printer, the liquid is ejected simultaneously from a plurality of nozzles in many cases when a large amount of liquid is ejected in a short time. For example, when performing solid printing at a high density in an inkjet printer, a large amount of ink is landed on a recording sheet by simultaneously ejecting ink from a large number of nozzles. In this case, it is naturally preferable that the amount of ink discharged from each nozzle is large. Conversely, when a thin line is formed by ejecting ink from one nozzle, the line becomes thicker if the amount of ink ejected from that nozzle is large. Therefore, it is preferable that the amount of ejection from that nozzle be small. However, in actuality, when discharging liquid from a plurality of nozzles simultaneously, the discharge amount of each nozzle is smaller than when discharging liquid from one nozzle due to the influence of the crosstalk between the adjacent pressure chambers described above. It was the opposite of the originally desirable form of fewer.

  It is an object of the present invention to set the discharge amount of each nozzle when driving two piezoelectric elements corresponding to two adjacent pressure chambers, rather than the discharge amount of nozzles when only one of the piezoelectric elements is driven. To make it bigger.

According to a first aspect of the present invention, there is provided a liquid discharge apparatus including a plurality of nozzles that discharge liquid and a plurality of pressure chambers that respectively communicate with the plurality of nozzles. A piezoelectric actuator provided in a plane along one plane and having a plurality of piezoelectric elements respectively corresponding to the plurality of pressure chambers, and a driving device for individually driving the plurality of piezoelectric elements,
The plurality of pressure chambers include a plurality of first pressure chambers disposed on one surface side of the piezoelectric actuator, and a plurality of second pressure chambers disposed on the other surface side of the piezoelectric actuator, The plurality of first pressure chambers and the plurality of second pressure chambers are alternately arranged at a predetermined pitch along an arrangement direction parallel to the predetermined one plane,
The plurality of first pressure chambers and the plurality of second pressure chambers are commonly covered by the piezoelectric actuator, and the driving device is adjacent to the first pressure chamber and the second pressure chamber in the arrangement direction. When the two piezoelectric elements corresponding to each of the two piezoelectric elements are driven, two portions of the piezoelectric actuator that respectively cover the two adjacent pressure chambers are opposite to each other in a direction perpendicular to the predetermined plane. It is characterized in that it is displaced.

  In the present invention, “driving the piezoelectric element” means changing a voltage applied to the piezoelectric element in order to eject ink from the corresponding nozzle. Also, not only when a predetermined voltage is applied from a state where no voltage is applied to cause piezoelectric deformation, but also when the predetermined voltage is already applied and then the voltage application is released to return the deformation. Including.

  In the present invention, the first pressure chamber and the second pressure chamber which are adjacent in the arrangement direction are arranged on opposite sides of the piezoelectric actuator. Further, the displacement of the piezoelectric actuator when the corresponding piezoelectric element is driven between the two adjacent pressure chambers is in the opposite direction. Therefore, when the two piezoelectric elements corresponding to the two pressure chambers are driven simultaneously, the displacement of the piezoelectric actuator in each pressure chamber can be increased by the crosstalk generated between the two pressure chambers. Alternatively, when only the piezoelectric element corresponding to one pressure chamber is driven, the displacement of the piezoelectric actuator in the one pressure chamber can be suppressed by the crosstalk. Thereby, the discharge amount of each nozzle when driving two piezoelectric elements corresponding to two adjacent pressure chambers is made larger than the discharge amount of nozzles when only one of the piezoelectric elements is driven. Is possible.

According to a second aspect of the present invention, there is provided the liquid ejecting apparatus according to the first aspect, wherein the piezoelectric actuator includes a piezoelectric body having at least two piezoelectric layers formed of a piezoelectric material, and the piezoelectric body includes the plurality of pressure chambers. A plurality of individual electrodes provided so as to face each other, and a common electrode provided so as to face the plurality of individual electrodes in common between the two piezoelectric layers,
The portion of the piezoelectric body sandwiched between one individual electrode and the common electrode constitutes one piezoelectric element, and the two individual electrodes respectively corresponding to the two adjacent pressure chambers are the common electrode It is characterized by being arranged on the opposite sides with respect to each other.

  A common electrode is disposed between the two piezoelectric layers, and two individual electrodes respectively corresponding to the adjacent first pressure chamber and the second pressure chamber are disposed on opposite sides of the common electrode. . That is, two piezoelectric elements corresponding to two adjacent pressure chambers are arranged on the opposite side with the common electrode interposed therebetween. In this configuration, when a voltage is applied to the piezoelectric element sandwiched between the individual electrode and the common electrode, the deformation of the piezoelectric body is reversed between the two pressure chambers, and the displacement of the piezoelectric actuator is also reversed.

  According to a third aspect of the present invention, there is provided the liquid ejection device according to the first or second aspect, wherein the second pressure chamber is provided between the two first pressure chambers adjacent to each other in the arrangement direction of the flow path structure. And a first cavity that opposes the piezoelectric actuator and between the two second pressure chambers adjacent to each other in the arrangement direction of the flow path structure. A second cavity portion facing the actuator is formed.

  In this invention, the 1st cavity part facing a 2nd pressure chamber is provided in the position between adjacent 1st pressure chambers of a flow-path structure. That is, the first cavity exists on the opposite side of the second pressure chamber with the piezoelectric actuator interposed therebetween. Therefore, the deformation of the piezoelectric element corresponding to the second pressure chamber is not hindered by the flow path structure. Similarly, since the second cavity exists on the opposite side of the first pressure chamber across the piezoelectric actuator, deformation of the piezoelectric element corresponding to the first pressure chamber is not hindered by the flow path structure.

  According to a fourth aspect of the present invention, there is provided the liquid ejection device according to the third aspect, wherein the first partition wall that separates the first pressure chamber from the first cavity, the second pressure chamber, and the second cavity. The separated second partition wall portion is arranged so as to be shifted in the arrangement direction.

  Since the piezoelectric actuator is sandwiched between the two partition walls between the first partition wall and the second partition wall, deformation is restricted. The larger the sandwiched width, the stronger the force that restrains the piezoelectric actuator, and the crosstalk between the first pressure chamber and the second pressure chamber is suppressed. In the present invention, since the positions of the first partition wall and the second partition wall are shifted in the arrangement direction of the pressure chambers, the width of the piezoelectric actuator sandwiched between the first partition wall and the second partition wall is reduced. The deformation restraining force by the two partition walls is weakened. Therefore, it is possible to positively generate crosstalk between two adjacent pressure chambers, and to increase the influence on the displacement of the piezoelectric actuator in each pressure chamber.

  According to the present invention, the discharge amount of each nozzle when driving two piezoelectric elements corresponding to two adjacent pressure chambers is larger than the discharge amount of nozzles when only one of the piezoelectric elements is driven. It becomes possible to enlarge.

1 is a schematic plan view of an ink jet printer according to an embodiment. 1 is a block diagram schematically illustrating an electrical configuration of an ink jet printer. It is the side view seen from the scanning direction of the inkjet head. It is a disassembled perspective view of an inkjet head. It is the VV sectional view taken on the line of FIG. It is operation | movement explanatory drawing of a piezoelectric actuator. It is operation | movement explanatory drawing of the piezoelectric actuator which concerns on a change form. It is sectional drawing equivalent to FIG. 5 of the inkjet head which concerns on another modification. FIG. 6 is a cross-sectional view corresponding to FIG. 5 of an ink jet head according to still another modified embodiment. It is a figure explaining the crosstalk between two adjacent pressure chambers in a conventional configuration.

  Next, an embodiment of the present invention will be described. This embodiment is an example in which the present invention is applied to an ink jet printer as a liquid ejection apparatus. FIG. 1 is a schematic plan view of the ink jet printer according to the present embodiment. FIG. 2 is a block diagram schematically showing an electrical configuration of the ink jet printer. In the following description, the front side in FIG. 1 is defined as the upper side, and the other side of the paper in FIG. 1 is defined as the lower side. As shown in FIGS. 1 and 2, the inkjet printer 1 includes a platen 2, a carriage 3, an inkjet head 4, a transport mechanism 5, a control device 6, and the like.

  On the upper surface of the platen 2, a recording sheet 100 as a recording medium is placed. Above the platen 2, two guide rails 10 and 11 extending in parallel along the scanning direction shown in FIG. The carriage 3 is attached to the two guide rails 10 and 11. An endless belt 14 is connected to the carriage 3. By driving the endless belt 14 by the carriage drive motor 15, the carriage 3 reciprocates in the scanning direction while being guided by the two guide rails 10 and 11.

  Four ink jet heads 4 arranged in the scanning direction are mounted on the carriage 3. The four inkjet heads 4 move in the scanning direction together with the carriage 3. A plurality of nozzles 57 arranged in a zigzag pattern along the transport direction are formed on the lower surface of each inkjet head 4 (the surface on the other side of the paper in FIG. 1).

  A cartridge holder 9 is provided in the printer main body 1 a of the printer 1. The cartridge holder 9 is loaded with four ink cartridges 17 each storing black, yellow, cyan and magenta inks. The four inkjet heads 4 mounted on the carriage 3 and the four ink cartridges 17 of the cartridge holder 9 are connected to each other by tubes (not shown). Each inkjet head 4 ejects ink supplied from the corresponding ink cartridge 17 from the plurality of nozzles 57 toward the recording paper 100 placed on the platen 2.

  The transport mechanism 5 includes two transport rollers 18 and 19 disposed so as to sandwich the platen 2 in the transport direction. The two transport rollers 18 are driven in synchronization by a transport motor 20 shown in FIG. The transport mechanism 5 transports the recording paper 100 placed on the platen 2 in the transport direction by two transport rollers 18 and 19.

  2 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an ASIC (Application Specific Integrated Circuit) including various control circuits, and the like. As shown in FIG. 2, the control device 6 is connected to various devices or drive units of the printer 1 such as a driver IC 45 of the inkjet head 4 described later, a carriage drive motor 15, and a carry motor 20. The control device 6 is connected to the operation panel 30 and a PC 31 that is an external device.

  The control device 6 executes the following printing process by the CPU and the ASIC according to the program stored in the ROM. That is, the control device 6 controls the ink jet head 4, the carriage drive motor 15, the transport motor 20, and the like based on the print command transmitted from the PC 31 to print images, characters, and the like on the recording paper 100. More specifically, four colors of ink are ejected from the four inkjet heads 4 mounted on the carriage 3 while moving the carriage 3 in the scanning direction on the recording paper 100 placed on the platen 2. . Further, the recording paper 100 is transported by a predetermined amount in the transport direction by the two transport rollers 18 and 19. The ink ejection operation by the ink jet head 4 and the transport operation of the recording paper 100 by the transport mechanism 5 are alternately and repeatedly executed to print an image or the like on the recording paper 100. In the above description, the control device 6 has been described as including a CPU, a ROM, a RAM, and an ASIC. However, the present invention is not limited to this, and the control device 6 can be realized by any hardware configuration. May be. For example, the functions may be shared by two or more CPUs or two or more ASICs.

  Next, the inkjet head 4 will be described in detail. In addition, since the structure of the four inkjet heads 4 is the same, below, one structure is demonstrated. 3 is a side view of the inkjet head of FIG. 1 as viewed from the scanning direction, FIG. 4 is an exploded perspective view of the inkjet head, and FIG. 5 is a cross-sectional view taken along line VV of FIG. As shown in FIGS. 3 to 5, the inkjet head 4 includes a first flow path member 41, a second flow path member 42, a nozzle plate 43, a piezoelectric actuator 44, a driver IC 45, and the like.

  Both the first flow path member 41 and the second flow path member 42 are rectangular plate-shaped members. A piezoelectric actuator 44 is disposed between the two flow path members 41 and 42.

  A first ink supply port 51 a is formed on the surface of the first flow path member 41 opposite to the piezoelectric actuator 44. A first manifold 52a extending in the transport direction is formed inside the first flow path member 41, and the first manifold 52a is connected to the first ink supply port 51a. A plurality of first pressure chambers 53a arranged in the transport direction are formed on the surface of the first flow path member 41 on the piezoelectric actuator 44 side. A first dummy pressure chamber 54a (first cavity) is formed in the portion of the first flow path member 41 between the adjacent first pressure chambers 53a. As shown in FIG. 5, the first pressure chamber 53a and the first dummy pressure chamber 54a are separated by a first partition wall portion 55a. The first pressure chamber 53a and the first dummy pressure chamber 54a both have an oval planar shape. That is, the first pressure chambers 53a and the first dummy pressure chambers 54a having the same shape are alternately arranged at a predetermined pitch P along the transport direction.

  The plurality of first pressure chambers 53a communicate with the first manifold 52a. On the other hand, the plurality of first dummy pressure chambers 54a do not communicate with the first manifold 52a, and ink is not supplied to these first dummy pressure chambers 54a. In addition, a plurality of openings 56 a communicating with the plurality of first pressure chambers 53 a are formed on the end surface along the longitudinal direction of the first flow path member 41.

  The second flow path member 42 has a flow path structure that is substantially symmetrical to the flow path structure of the first flow path member 41 with the piezoelectric actuator 44 interposed therebetween. That is, the second ink supply port 51 b is formed on the surface of the second flow path member 42 opposite to the piezoelectric actuator 44. Inside the second flow path member 42, the second manifold 52b connected to the second ink supply port 51b extends along the transport direction. In addition, on the surface of the second flow path member 42 on the piezoelectric actuator 44 side, a plurality of second pressure chambers 53b communicating with the second manifold 52b and a plurality of second dummy pressure chambers 54b not communicating with the second manifold 52b are provided. Are alternately arranged at the same pitch P as the arrangement pitch of the first pressure chambers 53a and the second dummy pressure chambers 54a along the transport direction. As shown in FIG. 5, the second pressure chamber 53b and the second dummy pressure chamber 54b are separated by a second partition wall portion 55b. The first partition wall portion of the first flow path member 41 and the second partition wall portion 55b of the second flow path member 42 are opposed to each other, and the piezoelectric actuator 44 is sandwiched between the partition wall portions 55a and 55b. Yes. A plurality of openings 56b communicating with the plurality of first pressure chambers 53a are formed on the end surface along the longitudinal direction of the second flow path member 42.

  However, the first pressure chamber 53a of the first flow path member 41 and the second pressure chamber 53b of the second flow path member 42 are shifted by a pitch P in the transport direction. That is, the plurality of first pressure chambers 53a and the plurality of second pressure chambers 53b are arranged at a pitch P along the transport direction. In other words, the first pressure chamber 53 a of the first flow path member 41 faces the second dummy pressure chamber 54 b of the second flow path member 42 with the piezoelectric actuator 44 interposed therebetween. Further, the second pressure chamber 53 b of the second flow path member 42 faces the first dummy pressure chamber 54 a of the first flow path member 41 with the piezoelectric actuator 44 interposed therebetween. The plurality of openings 56a of the first flow path member 41 and the plurality of openings 56b of the second flow path member 42 are also arranged in the transport direction according to the arrangement relationship between the corresponding first pressure chambers 53a and second pressure chambers 53b. They are shifted by the pitch P, and these openings 56a and 56b are arranged in a staggered pattern along the transport direction.

  As shown in FIGS. 3 and 4, the nozzle plate 43 is formed with a plurality of nozzles 57 arranged in two rows in a staggered manner along the transport direction. The arrangement pitch of the nozzles 57 in the transport direction is equal to the arrangement pitch P of the first pressure chambers 53a and the second pressure chambers 53b. The nozzle plate 43 includes a first flow path member such that the plurality of openings 56 a of the first flow path member 41 and the plurality of openings 56 b of the second flow path member 42 communicate with the plurality of nozzles 57 of the nozzle plate 43. The end face of 41 and the end face of the second flow path member 42 are joined.

  The first flow path member 41, the second flow path member 42, and the nozzle plate 43 of the present embodiment correspond to the “flow path structure” of the present invention.

  The piezoelectric actuator 44 includes a piezoelectric body 60 including two piezoelectric layers 61 and 62, a plurality of first individual electrodes 63a, a plurality of second individual electrodes 63b, and a common electrode 64. The piezoelectric actuator 44 has a flat plate shape as a whole. The piezoelectric actuator 44 includes one surface of the first flow path member 41 in which the plurality of first pressure chambers 53a are disposed, and one surface of the second flow path member 42 in which the plurality of second pressure chambers 53b are disposed. The first flow path member 41 and the second flow path member 42 are arranged in a plane so as to be parallel to each other.

  The two piezoelectric layers 61 and 62 of the piezoelectric body 60 are each made of a piezoelectric material mainly composed of ferroelectric lead zirconate titanate (PZT), which is a solid solution of lead titanate and lead zirconate. . One piezoelectric layer 61 is joined to the first flow path member 41 so as to cover the plurality of first pressure chambers 53a and the plurality of first dummy pressure chambers 54a in common. The other piezoelectric layer 62 is joined to the second flow path member 42 so as to cover the plurality of second pressure chambers 53b and the plurality of second dummy pressure chambers 54b in common. That is, the two piezoelectric layers 61 and 62 have a structure that covers the plurality of first pressure chambers 53a and the plurality of second pressure chambers 53b arranged separately on both sides thereof.

  A plurality of first individual electrodes 63a respectively facing the plurality of first pressure chambers 53a are formed on the surface of the piezoelectric layer 62 opposite to the piezoelectric layer 61 (the surface on the second flow path member 42 side). Yes. A plurality of second individual electrodes 63b respectively facing the plurality of second pressure chambers 53b are formed on the surface of the piezoelectric layer 61 opposite to the piezoelectric layer 62 (the surface on the first flow path member 41 side). Has been. As shown in FIG. 5, since the second dummy pressure chamber 54b exists on the opposite side of the first pressure chamber 53a across the piezoelectric actuator 44, the first individual electrode 63a facing the first pressure chamber 53a is There is no contact with the second flow path member 42. Similarly, since the first dummy pressure chamber 54a exists on the opposite side of the second pressure chamber 53b across the piezoelectric actuator 44, the second individual electrode 63b facing the second pressure chamber 53b has the first flow path. There is no contact with the member 41.

  The common electrode 64 is formed almost entirely between the two piezoelectric layers 61 and 62. Accordingly, the common electrode 64 is opposed to both the plurality of first individual electrodes 63 a formed on the piezoelectric layer 62 and the plurality of second individual electrodes 63 b formed on the piezoelectric layer 61. In other words, the first individual electrode 63a and the second individual electrode 63b are arranged on the opposite side with the common electrode 64 in between. Note that the potential of the common electrode 64 is always held at the ground potential.

  Of the piezoelectric layers 61 and 62, the portion sandwiched between the individual electrodes 63a and 63b and the common electrode 64 is a portion where piezoelectric deformation occurs when a predetermined voltage is applied to the individual electrodes 63a and 63b by a driver IC 45 described later. It is. Hereinafter, the portion of the piezoelectric layers 61 and 62 is referred to as a piezoelectric element 65. Further, the piezoelectric element 65 of the piezoelectric layer 62 sandwiched between the first individual electrode 63a and the common electrode 64 is particularly referred to as a first piezoelectric element 65a. The piezoelectric element 65 of the piezoelectric layer 61 sandwiched between the second individual electrode 63b and the common electrode 64 is particularly referred to as a second piezoelectric element 65b. The plurality of piezoelectric elements 65a and 65b corresponding to the plurality of pressure chambers 53a and 53b are polarized in the thickness direction, respectively.

  The driver IC 45 (driving device) is mounted on a COF 66 (Chip On Film) which is a wiring member in which a large number of wirings are formed. The COF 66 is bonded to one surface of the piezoelectric actuator 44 and electrically connected to the plurality of individual electrodes 63a and 63b. The COF 66 is also connected to the control device 6 shown in FIG. With this COF 66, the driver IC 45 is electrically connected to both the control device 6 and the piezoelectric actuator 44. The driver IC 45 individually drives the plurality of piezoelectric elements 65 a and 65 b based on the control signal sent from the control device 6. More specifically, the driver IC 45 causes a piezoelectric deformation in the piezoelectric element 65 by applying a predetermined voltage to the individual electrode 63 provided in the piezoelectric element 65.

  The operation of the piezoelectric actuator 44 when the piezoelectric element 65 is driven by the driver IC 45 will be described. When a predetermined voltage is applied from the driver IC 45 to the individual electrode 63 of a certain piezoelectric element 65, an electric field in the thickness direction acts on the piezoelectric element 65. Since the direction of the electric field coincides with the polarization direction of the piezoelectric element 65, the piezoelectric element 65 contracts in the surface direction. Due to the contraction of the piezoelectric element 65, the portion of the piezoelectric actuator 44 (piezoelectric body 60) facing the pressure chamber 53 is bent so as to protrude toward the pressure chamber 53. At this time, since the volume in the pressure chamber 53 is changed, pressure (discharge energy) is applied to the ink in the pressure chamber 53, so that the ink is discharged from the nozzle 57 communicating with the pressure chamber 53.

  Here, as shown in FIG. 5r, a second dummy pressure chamber 54b is disposed on the opposite side of the first pressure chamber 53a across the piezoelectric actuator 44, and a first dummy is disposed on the opposite side of the second pressure chamber 53b. A pressure chamber 54a is disposed. Therefore, the deformation of the first piezoelectric element 65a corresponding to the first pressure chamber 53a is not hindered by the second flow path member 42, and the deformation of the second piezoelectric element 65b corresponding to the second pressure chamber 53b is not performed. However, the first flow path member 41 is not hindered.

  In the above-described driving method of the piezoelectric actuator 44, voltage is applied to the piezoelectric element 65 from the standby state where the piezoelectric element 65 is not deformed to displace the piezoelectric actuator 44 toward the pressure chamber 53, and the volume of the pressure chamber 53 is increased. Ink is ejected from the nozzles 57 by reducing. The above system is generally called “pushing”. Incidentally, a driving system called “strike” is also known for this pushing, but application to the striking drive will be described later as an embodiment different from the present embodiment.

  By the way, in this embodiment, a plurality of first pressure chambers 53a of the first flow path member 41 and a plurality of second pressure chambers 53b of the second flow path member 42 arranged at a pitch P along the transport direction. Are disposed on opposite sides of the piezoelectric actuator 44. Therefore, when a voltage is applied, the deformation of the first piezoelectric element 65a and the second piezoelectric element 65b is reversed. Accordingly, the direction in which the two portions of the piezoelectric actuator 44 covering the two pressure chambers 53a and 53b are displaced is also opposite.

  FIG. 6 is an operation explanatory diagram of the piezoelectric actuator. FIG. 6A shows a state where both the first piezoelectric element 65a and the second piezoelectric element 65b are not driven (no voltage is applied). At this time, the piezoelectric actuator 44 is not deformed in both the first pressure chamber 53a and the second pressure chamber 53b.

  FIG. 6B shows a state in which only the second piezoelectric element 65b is driven. FIG. 6C shows a state where both the first piezoelectric element 65a and the second piezoelectric element 65b are driven. As shown in FIG. 6C, when the first piezoelectric element 65a is driven, the portion of the piezoelectric actuator 44 (two piezoelectric layers 61 and 62) facing the first pressure chamber 53a In a direction (a direction orthogonal to the arrangement plane of the pressure chambers 53), it is deformed so as to protrude upward. Further, as shown in FIGS. 6B and 6C, when the second piezoelectric element 65b is driven, the portion of the piezoelectric actuator 44 facing the second pressure chamber 53b is convex downward. Deform.

  Here, as shown in FIG. 6C, when both the first piezoelectric element 65a and the second piezoelectric element 65b are driven simultaneously, when the piezoelectric actuator 44 is displaced in one direction in one pressure chamber 53, Due to the crosstalk, a force is applied to the piezoelectric actuator 44 in the other pressure chamber 53 in a direction opposite to the one direction. At this time, in the configuration of the present embodiment, the direction in which the displacement is promoted by the crosstalk is a direction that protrudes toward the pressure chamber 53 in any pressure chamber 53 (volume decreasing direction), and the two pressure chambers 53a. , 53b, the displacement of the piezoelectric actuator 44 increases. If the displacement of the piezoelectric actuator 44 in the pressure chamber 53 increases, a large energy is applied to the ink in the pressure chamber 53. Therefore, when the two piezoelectric elements 65a and 65b are driven simultaneously, the discharge amount of each nozzle 57 does not decrease due to the crosstalk between the two adjacent pressure chambers 53a and 53b, and conversely, as shown in FIG. Compared to the case where only one piezoelectric element 65 is driven, the discharge amount can be increased.

  Accordingly, the discharge amount of each nozzle 57 when ink is ejected simultaneously from all of the plurality of nozzles 57 as in the case of performing solid printing by landing a large amount of ink on the recording paper 100 is a thin line on the recording paper 100. As compared with the case where ink is ejected from only one nozzle 57 as in the case of forming the ink, it can be made larger.

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

1] In the above-described embodiment, the driving method of the piezoelectric actuator 44 is exemplified by pushing driving (see FIG. 6). However, as a driving method of the piezoelectric actuator 44, in addition to the above-described pushing driving, the piezoelectric actuator 44 is once displaced in a direction in which the volume of the pressure chamber 53 increases, and then the volume of the pressure chamber 53 is increased. A so-called hitting method in which displacement is made in a decreasing direction is also known. The present invention can also be applied to striking driving.

  FIG. 7 shows the operation of the piezoelectric actuator when driven by pulling. FIG. 7A shows a standby state in which ink is not ejected from the nozzles 57. In the standby state, a predetermined voltage is applied to both the first individual electrode 63a and the second individual electrode 63b. Therefore, the portion of the piezoelectric actuator 44 that faces the first pressure chamber 53a and the portion that faces the second pressure chamber 53b are displaced so as to protrude toward the pressure chamber 53, respectively. FIG. 7B shows a state in which only the second piezoelectric element 65b is driven. FIG. 7C shows a state where both the first piezoelectric element 65a and the second piezoelectric element 65b are driven. The driving of the piezoelectric element 65 by the driver IC 45 when ink is ejected from the nozzle 57 is as follows.

  As shown in FIG. 7A, the potential of the individual electrode 63 is once switched to the same ground potential as that of the common electrode 64 by the driver IC 45 from the state in which the voltage is applied to the individual electrode 63. Then, the deformation of the piezoelectric element 65 is eliminated, and the piezoelectric actuator 44 that has been displaced so as to protrude toward the pressure chamber 53 becomes a flat shape, as shown in FIGS. 7B and 7C. The volume in the pressure chamber 53 increases as compared with the above. Thereafter, when a voltage is again applied to the individual electrode 63 by the driver IC 45, the state returns to the state of FIG. 7A and the volume of the pressure chamber 53 decreases. Here, the pressure wave generated when the volume is increased is superimposed on the pressure wave generated when the volume is decreased by appropriately setting the switching timing of the volume increase → volume decrease of the pressure chamber 53. As a result, a large pressure wave is generated in the pressure chamber 53, and ink is pushed out from the nozzle 57 communicating with the pressure chamber 53 and ejected. Even in this modification, the direction of displacement of the piezoelectric actuator when the piezoelectric element 65 is driven (voltage application / voltage application release) is opposite between the two pressure chambers 53a and 53b.

  By the way, when only the second piezoelectric element 65b corresponding to one pressure chamber 53 (here, the second pressure chamber 53b) is driven as shown in FIG. 7B, voltage application to the second piezoelectric element 65b is performed. Once released, the portion of the piezoelectric actuator 44 that faces the second pressure chamber 53b tends to become flat from a state where it protrudes downward (on the second pressure chamber 53b side). Here, since the first pressure chamber 53a and the second pressure chamber 53b are disposed on opposite sides of the piezoelectric actuator 44, the direction of displacement of the piezoelectric actuator 44 is opposite. Further, the portion of the piezoelectric actuator 44 that faces the first pressure chamber 53a remains convex upward. As a result, a force to be displaced downward acts on the portion of the piezoelectric actuator 44 facing the second pressure chamber 53b, so that it cannot return to a completely flat state. On the other hand, as shown in FIG. 7C, when the voltage application is simultaneously canceled for both of the two piezoelectric elements 65a and 65b respectively corresponding to the two adjacent pressure chambers 53a and 53b, The piezoelectric actuator 44 returns to a flat state in each of the first pressure chamber 53a and the second pressure chamber 53b. Therefore, the discharge amount of the nozzle 57 when only one piezoelectric element 65 is driven is suppressed, and is smaller than the discharge amount of each nozzle 57 when both piezoelectric elements 65a and 65b are driven simultaneously.

2] As shown in FIG. 5 of the above-described embodiment, the piezoelectric actuator 44 includes a first partition 55a that separates the first pressure chamber 53a and the first dummy pressure chamber 54a, a second pressure chamber 53b, and a second dummy pressure. It is sandwiched between a second partition wall 55b that separates the chamber 54b. That is, the portion of the piezoelectric actuator 44 between the first pressure chamber 53a and the second pressure chamber 53b is sandwiched between the first partition wall portion 55a and the second partition wall portion 55b, so that the deformation is restrained. . The greater the sandwiched width, the stronger the force that restrains the deformation of the piezoelectric actuator 44 between the first pressure chamber 53a and the second pressure chamber 53b, and the cross between the first pressure chamber 53a and the second pressure chamber 53b. Talk is suppressed. In other words, it is possible to change the degree of crosstalk between the first pressure chamber 53a and the second pressure chamber 53b by adjusting the width between the first partition wall portion 55a and the second partition wall portion 55b. .

  For example, as illustrated in FIG. 8A, the first partition wall portion 55 a and the second partition wall portion 55 b may be displaced in the arrangement direction of the pressure chambers 53. Thereby, the width | variety pinched by the 1st partition part 55a and the 2nd partition part 55b of the piezoelectric actuator 44 becomes small, and the deformation | transformation restraint force by the two partition parts 55a and 55b becomes weak. Accordingly, it is possible to positively generate crosstalk between the two adjacent pressure chambers 53a and 53b, and to increase the influence on the displacement of the piezoelectric actuator 44 in each pressure chamber 53. Further, as shown in FIG. 8B, the width of the first partition wall portion 55a and the width of the second partition wall portion 55b may be different.

  Further, by increasing the width of the first partition wall portion 55a and the width of the second partition wall portion 55b, and by increasing the width in which they face each other (the width in which the piezoelectric actuator 44 is sandwiched), almost no crosstalk occurs. It is also possible to do so. As a result, the discharge amount of the nozzle 57 can be made substantially equal when the two piezoelectric elements 65a and 65b are driven simultaneously and when only one of the piezoelectric elements 65 is driven.

3] The configuration of the piezoelectric actuator 44 is not limited to that of the above embodiment. For example, the piezoelectric body 60 is not limited to a configuration including two piezoelectric layers, and may be configured by three or more piezoelectric layers.

  Further, it is not essential that the piezoelectric body 60 is disposed so as to cover the plurality of pressure chambers 53 in common. For example, in the configuration of FIG. 9, the diaphragm 70 made of a non-piezoelectric material (for example, a metal material or a metal oxide) is provided so as to cover the plurality of first pressure chambers 53 a and the plurality of second pressure chambers 53 b in common. Is provided. A plurality of first piezoelectric elements 75a corresponding to the plurality of first pressure chambers 53a and a plurality of second piezoelectric elements 75b corresponding to the plurality of second pressure chambers 53b are separated on both surfaces of the diaphragm 70. The arrangement may be arranged.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 4 Inkjet head 41 1st flow path member 42 2nd flow path member 43 Nozzle plate 44 Piezoelectric actuator 45 Driver IC
53a 1st pressure chamber 53b 2nd pressure chamber 54a 1st dummy pressure chamber 54b 2nd dummy pressure chamber 55a 1st partition part 55b 2nd partition part 57 Nozzle 60 Piezoelectric body 61, 62 Piezoelectric layer 63 Individual electrode 64 Common electrode 65 Piezoelectric Element 75 Piezoelectric element

Claims (4)

A flow path structure having a plurality of nozzles each discharging liquid and a plurality of pressure chambers respectively communicating with the plurality of nozzles;
A piezoelectric actuator provided in the flow path structure in a plane along a predetermined plane and having a plurality of piezoelectric elements respectively corresponding to the plurality of pressure chambers;
A drive device for individually driving the plurality of piezoelectric elements,
The plurality of pressure chambers include a plurality of first pressure chambers disposed on one surface side of the piezoelectric actuator, and a plurality of second pressure chambers disposed on the other surface side of the piezoelectric actuator,
The plurality of first pressure chambers and the plurality of second pressure chambers are alternately arranged at a predetermined pitch along an arrangement direction parallel to the predetermined one plane,
The plurality of first pressure chambers and the plurality of second pressure chambers are commonly covered by the piezoelectric actuator,
The two adjacent pressures of the piezoelectric actuator when the two piezoelectric elements respectively corresponding to the first pressure chamber and the second pressure chamber adjacent in the arrangement direction are driven by the driving device. 2. A liquid ejecting apparatus according to claim 2, wherein two portions respectively covering the chamber are displaced in directions opposite to each other in a direction orthogonal to the predetermined plane. The piezoelectric actuator is
A piezoelectric body having at least two piezoelectric layers formed of a piezoelectric material;
A plurality of individual electrodes provided on the piezoelectric body so as to respectively face the plurality of pressure chambers;
A common electrode provided so as to face the plurality of individual electrodes in common between the two piezoelectric layers;
A portion of the piezoelectric body sandwiched between one individual electrode and the common electrode constitutes one piezoelectric element,
The liquid ejecting apparatus according to claim 1, wherein the two individual electrodes respectively corresponding to the two adjacent pressure chambers are arranged on opposite sides of the common electrode. Between the two first pressure chambers adjacent to each other in the arrangement direction of the flow path structure, a first cavity portion is formed which is opposed to the second pressure chamber with the piezoelectric actuator interposed therebetween,
A second cavity portion is formed between the two second pressure chambers adjacent to each other in the arrangement direction of the flow path structure so as to oppose the first pressure chamber and the piezoelectric actuator. The liquid ejection apparatus according to claim 1, wherein the liquid ejection apparatus is a liquid ejection apparatus.   The first partition wall that separates the first pressure chamber and the first cavity, and the second partition that separates the second pressure chamber and the second cavity are shifted in the arrangement direction. The liquid ejecting apparatus according to claim 3, wherein the liquid ejecting apparatus is a liquid ejecting apparatus.

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