Inkjet head and image forming device

Abstract

To provide an inkjet head and an image forming device which can reduce influence of electric field crosstalk to prevent a quality of a formed image from deteriorating.SOLUTION: An inkjet head comprises: a piezoelectric element having a plurality of driving regions arranged in a first direction to correspond to a plurality of nozzles; a plurality of individual electrodes, arranged on the piezoelectric element for each of the driving regions, to which driving voltages for making the corresponding nozzles discharge ink are individually applied; a plurality of common electrodes, arranged in the piezoelectric element alternately with the individual electrodes, in the first direction, to which common driving voltages are applied to generate an electric field between the individual electrodes and the common electrodes, in the plurality of driving regions; and a slit formed on the piezoelectric element to divide the piezoelectric element for each of the driving regions.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an inkjet head and an image forming apparatus. [Background technology]

[0002] Inkjet image forming devices have been known in the past that eject ink from a plurality of nozzles arranged in an inkjet head onto a recording medium such as paper to form an image on the recording medium. In such inkjet image forming devices, the inkjet head has a plurality of channels corresponding to the number of nozzles, and each channel is equipped with a pressure chamber that stores ink and a piezoelectric element that deforms the pressure chamber.

[0003] In an inkjet head, when a drive voltage is applied to a piezoelectric element, the piezoelectric element deforms in response to the drive voltage, which in turn deforms the pressure chamber, changing the pressure on the ink in the pressure chamber that is supplied to the nozzle, causing the ink in the pressure chamber to be ejected from the nozzle.

[0004] When a piezoelectric element in a channel deforms to eject ink from a nozzle, this deformation may propagate to an adjacent piezoelectric element, causing crosstalk between adjacent channels, which may result in a deterioration in the quality of the formed image.

[0005] Therefore, various methods for reducing the effects of such crosstalk have been proposed recently. For example, Patent Document 1 discloses an inkjet head in which notches are formed at predetermined positions on both sides of a piezoelectric element and electrodes are arranged so that the polarization direction of the piezoelectric element is parallel to the electric field direction. This inkjet head discloses a technology for reducing the effects of crosstalk on piezoelectric elements in adjacent channels by changing the deformation direction of the piezoelectric element when a drive voltage is applied to the electrodes. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-008095 Summary of the Invention [Problem to be solved by the invention]

[0007] Crosstalk can be divided into structural crosstalk and electric field crosstalk. Structural crosstalk occurs when the deformation of a piezoelectric element in one channel affects the deformation of a piezoelectric element in an adjacent channel. Electric field crosstalk occurs when the electric field generated by applying a drive voltage to one channel affects the adjacent channel.

[0008] In contrast to this, the inkjet head described in Patent Document 1 can suppress the above-mentioned structural crosstalk, but cannot suppress the electric field crosstalk.

[0009] On the other hand, to improve the driving efficiency of an inkjet head that deforms a pressure chamber by shearing a piezoelectric element, it is necessary to increase the thickness of the piezoelectric element. However, if the piezoelectric element is made thicker, the cross-sectional area relative to the adjacent channel increases. Therefore, if the piezoelectric element is made thicker, the amount of leakage of the electric field generated when a driving voltage is applied to a certain channel to the adjacent channel also increases. Therefore, in this case, the effect of electric field crosstalk increases, resulting in a problem of reduced quality of the formed image.

[0010] An object of the present disclosure is to provide an inkjet head and an image forming apparatus that can reduce the influence of electric field crosstalk and prevent degradation in the quality of formed images. [Means for solving the problem]

[0011] The inkjet head according to the present disclosure comprises: a piezoelectric element having a plurality of drive regions aligned in a first direction corresponding to the plurality of nozzles; a plurality of individual electrodes arranged in the piezoelectric element for each of the drive regions, to which drive voltages for ejecting ink from the corresponding nozzles are individually applied; a common electrode disposed on the piezoelectric element alternately with the individual electrodes in the first direction, the common electrode being applied with a common driving voltage so as to generate an electric field between the common electrode and the individual electrodes in the plurality of driving regions; a slit formed in the piezoelectric element so as to divide the piezoelectric element into the driving regions; Equipped with A plurality of the common electrodes are arranged.

[0012] The inkjet head according to the present disclosure further comprises: a piezoelectric element having a plurality of drive regions aligned in a first direction corresponding to the plurality of nozzles; a plurality of individual electrodes arranged in the piezoelectric element for each of the drive regions, to which drive voltages for ejecting ink from the corresponding nozzles are individually applied; a common electrode disposed on the piezoelectric element alternately with the individual electrodes in the first direction, the common electrode being applied with a common driving voltage so as to generate an electric field between the common electrode and the individual electrodes in the plurality of driving regions; a slit formed in the piezoelectric element so as to divide the piezoelectric element into the driving regions; a partition wall separating a plurality of pressure chambers arranged in the first direction corresponding to the plurality of nozzles from each other; Equipped with a surface of the piezoelectric element on which the slit is formed and a surface of the piezoelectric element on which the common electrode is disposed are both parallel to the first direction and positioned opposite to each other in a second direction perpendicular to the respective surfaces; the individual electrodes are disposed at positions corresponding to the centers between the adjacent partition walls when viewed from the second direction, A plurality of the common electrodes are arranged, The slit is formed at a position corresponding to the common electrode and the partition wall when viewed from the second direction.

[0013] Furthermore, the inkjet head according to the present disclosure comprises: a piezoelectric element having a plurality of drive regions aligned in a first direction corresponding to the plurality of nozzles; a plurality of individual electrodes arranged in the piezoelectric element for each of the drive regions, to which drive voltages for ejecting ink from the corresponding nozzles are individually applied; a common electrode disposed on the piezoelectric element alternately with the individual electrodes in the first direction, the common electrode being applied with a common driving voltage so as to generate an electric field between the common electrode and the individual electrodes in the plurality of driving regions; a slit formed in the piezoelectric element so as to divide the piezoelectric element into the driving regions; a partition wall separating a plurality of pressure chambers arranged in the first direction corresponding to the plurality of nozzles from each other; Equipped with a surface of the piezoelectric element on which the slit is formed and a surface of the piezoelectric element on which the common electrode is disposed are both parallel to the first direction and positioned opposite to each other in a second direction perpendicular to the respective surfaces; the individual electrodes are disposed at positions corresponding to the centers between the adjacent partition walls when viewed from the second direction, A plurality of the common electrodes are arranged, the slit is formed at a position corresponding to the common electrode and the partition wall when viewed from the second direction, The piezoelectric element is polarized in the second direction so as to be perpendicular to the electric field generated when the drive voltage is applied to the individual electrode.

[0014] In addition, the image forming apparatus according to the present disclosure includes: The inkjet head is provided. [Effects of the Invention]

[0015] According to the present disclosure, it is possible to reduce the influence of electric field crosstalk and prevent deterioration in the quality of formed images. [Brief explanation of the drawings]

[0016] [Figure 1]FIG. 1 is a schematic diagram showing an example of the configuration of an inkjet image forming apparatus according to this embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically showing an example of the structure of the head of FIG. [Figure 3] FIG. 3 is a cross-sectional view schematically showing an example of the shape of the slit in FIG. [Figure 4] FIG. 4 is a cross-sectional view schematically showing another example of the shape of the slit in FIG. [Figure 5] FIG. 5 is a cross-sectional view schematically showing a first example of the structure of the head according to the present embodiment. [Figure 6] FIG. 6 is a cross-sectional view schematically showing a second example of the structure of the head according to the present embodiment. [Figure 7] FIG. 7 is a cross-sectional view schematically showing a third example of the structure of the head according to the present embodiment. [Figure 8] FIG. 8 is a cross-sectional view schematically showing a fourth example of the structure of the head according to the present embodiment. [Figure 9] FIG. 9 is a cross-sectional view schematically showing a fifth example of the structure of the head according to the present embodiment. [Figure 10] FIG. 10 is a cross-sectional view schematically showing a sixth example of the structure of the head according to the present embodiment. [Figure 11] FIG. 11 is a cross-sectional view schematically showing a seventh example of the structure of the head according to the present embodiment. [Figure 12] FIG. 12 is a cross-sectional view schematically showing an eighth example of the structure of the head according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments, and various modifications are possible without departing from the spirit of the present disclosure. In addition, in each drawing, the same reference numerals are used to denote the same or equivalent parts, and this is common throughout the entire specification.

[0018] An inkjet image forming apparatus according to an embodiment of the present disclosure forms an image by ejecting ink droplets onto a recording medium such as paper.

[0019] [Configuration of inkjet image forming apparatus 1] FIG. 1 is a schematic diagram showing an example of the configuration of an inkjet image forming apparatus 1 according to the present embodiment. As shown in FIG. 1, the inkjet image forming apparatus 1 includes a supply unit 10, an image forming unit 20, and a discharge unit 30. Under the control of a control unit (not shown), the inkjet image forming apparatus 1 transports a recording medium M stored in the supply unit 10 to the image forming unit 20, forms an image on the recording medium M in the image forming unit 20, and transports (discharges) the recording medium M with the image formed to the discharge unit 30. The recording medium M can be paper such as plain paper or coated paper, or various media such as fabric or sheet-like resin, on whose surface ink can be fixed when it lands.

[0020] The supply unit 10 has a paper feed tray 11 that stores the recording medium M, and a medium supply unit 12 that conveys and supplies the recording medium M from the paper feed tray 11 to the image forming unit 20.

[0021] The paper feed tray 11 is a plate-like member that can accommodate one or more recording media M. The paper feed tray 11 is configured to move up and down depending on the amount (number of sheets) of recording media M placed on the paper feed tray 11, and in the direction of the up and down movement, the topmost recording medium M is held at a position where it is transported by the medium supply unit 12.

[0022] The medium supply unit 12 has a circular belt supported by two rollers on the inside, and by rotating the rollers with the recording medium M placed on this belt, the recording medium M is transported from the paper feed tray 11 to the image forming unit 20.

[0023] The image forming section 20 includes a transport drum 21, a delivery unit 22, a medium heating section 23, a head unit 24, a fixing section 26, a delivery section 27, and the like.

[0024] The transport drum 21 holds the recording medium M on its cylindrical outer curved surface (transport surface) and rotates around a rotation axis extending in a direction perpendicular to the paper surface of Figure 1 (hereinafter referred to as the "orthogonal direction"), thereby transporting the recording medium M in a transport direction along the transport surface (see arrow in Figure 1).

[0025] The transport drum 21 has claws and an air intake section (not shown) for holding the recording medium M on its transport surface. The recording medium M is held on the transport surface by having its edges pressed down by the claws and being drawn to the transport surface by the air intake section. The transport drum 21 has a transport drum motor (not shown) for rotating the transport drum 21, and rotates by an angle proportional to the amount of rotation of the transport drum motor. The transport drum 21 and the transport drum motor serve as a transport section that transports the recording medium M facing the head unit 24 (the nozzle surface of the inkjet head).

[0026] The transfer unit 22 transfers the recording medium M transported by the medium supply unit 12 of the supply unit 10 to the transport drum 21. The transfer unit 22 is provided at a position between the medium supply unit 12 of the supply unit 10 and the transport drum 21, and holds and picks up one end of the recording medium M transported from the medium supply unit 12 with a swing arm unit 221, and transfers it to the transport drum 21 via the transfer drum 222.

[0027] The medium heating unit 23 is disposed between the position where the delivery drum 222 is disposed and the position where the head unit 24 is disposed. The medium heating unit 23 heats the conveying surface of the conveying drum 21 and the recording medium M so that the temperature of the recording medium M conveyed by the conveying drum 21 is within a predetermined range. The medium heating unit 23 has, for example, an infrared heater or the like, and causes the infrared heater to generate heat by supplying power to the infrared heater based on a control signal supplied from a control unit (not shown).

[0028] The head unit 24 forms (records) an image by ejecting ink onto the recording medium M from nozzle openings provided on an ink ejection surface facing the transport surface of the transport drum 21 at appropriate timing according to the rotation of the transport drum 21 on which the recording medium M is held. The head unit 24 is disposed so that its ink ejection surface and the transport surface of the transport drum 21 are spaced a predetermined distance apart.

[0029] In the inkjet image forming apparatus 1 of this embodiment, four head units 24 are arranged corresponding to four colors of ink, yellow (Y), magenta (M), cyan (C), and black (K). These head units 24 are arranged at predetermined intervals in the order of Y, M, C, and K from the upstream side in the conveyance direction of the recording medium M.

[0030] Furthermore, when forming an image, the head unit 24 is used while its position is fixed relative to the rotation axis of the transport drum 21. That is, the inkjet image forming apparatus 1 is a single-pass type apparatus.

[0031] Each head unit 24 has an inkjet head (hereinafter referred to as a “head”) 240 and an inkjet head driving section 241.

[0032] When a drive voltage is applied, the head 240 ejects ink in accordance with the drive voltage. Details of the head 240 will be described later. Note that, although a plurality of heads 240 are actually arranged within the head unit 24, the number and arrangement of the heads 240 are the same as in the conventional case, and therefore detailed description thereof will be omitted.

[0033] The inkjet head driving unit 241 drives the head 240 by supplying a driving voltage corresponding to the image data to the piezoelectric actuator 2404 (see FIG. 2) of the head 240 at an appropriate timing under the control of a control unit (not shown).

[0034] The fixing unit 26 has a light-emitting unit arranged across the width of the conveying drum 21 in the perpendicular direction. The fixing unit 26 irradiates the recording medium M placed on the conveying drum 21 with energy rays such as ultraviolet rays from the light-emitting unit, and imparts a predetermined energy to the ink ejected onto the recording medium M. In this way, the fixing unit 26 heats the recording medium M to a predetermined temperature, and hardens and fixes the ink on the recording medium M.

[0035] The delivery unit 27 has a belt loop 272 having a circular belt supported on the inside by two rollers, and a cylindrical transfer drum 271 that transfers the recording medium M from the transport drum 21 to the belt loop 272. The delivery unit 27 transports the recording medium M that has been transferred from the transport drum 21 onto the belt loop 272 by the transfer drum 271, using the belt loop 272, and sends it to the discharge unit 30.

[0036] The discharge unit 30 has a plate-shaped discharge tray 31 on which the recording medium M sent from the image forming unit 20 by the delivery unit 27 is placed. The discharge tray 31 is a plate-shaped member that is provided so that the recording medium M on which an image has been formed can be placed, for example. The discharge tray 31 is provided so as to move up and down according to the amount (number of sheets) of recording media M placed on the discharge tray 31.

[0037] (Head 240) Next, the configuration and structure of the head 240 will be described. FIG. 2 is a cross-sectional view schematically illustrating an example of the structure of the head 240 of FIG. 1. In the following description, the longitudinal direction of the head 240 (left-right direction on the paper) is referred to as the X-axis direction, the lateral direction of the head 240 (depth direction on the paper) is referred to as the Y-axis direction, and the height direction of the head (up-down direction on the paper) is referred to as the Z-axis direction. The X-axis direction, Y-axis direction, and Z-axis direction correspond to the "first direction," "third direction," and "second direction" of the present disclosure, respectively. The X-axis direction in FIG. 2 corresponds to the orthogonal direction in FIG. 1. Furthermore, for each part of the head 240, the surface above the paper in the Z-axis direction may be referred to as the "upper surface," and the surface below the paper in the Z-axis direction may be referred to as the "lower surface."

[0038] As shown in FIG. 2, the head 240 is formed by laminating a nozzle plate 2401, a nozzle communication plate 2402, a pressure chamber plate 2403, and a piezoelectric actuator 2404 in this order.

[0039] The nozzle plate 2401 is formed, for example, in a plate shape and is disposed so that its plate surface is perpendicular to the Z axis. The nozzle connection plate 2402 is formed, for example, in a plate shape and is disposed on the upper surface side of the nozzle plate 2401 in the Z axis direction so that its plate surface is perpendicular to the Z axis. The nozzle connection plate 2402 is sandwiched between the pressure chamber plate 2403 and the nozzle plate 2401.

[0040] The pressure chamber plate 2403 is formed, for example, in a plate shape, and is disposed on the upper surface of the nozzle connection plate 2402 in the Z-axis direction so that the plate surface is perpendicular to the Z-axis. The pressure chamber plate 2403 is sandwiched between a piezoelectric actuator 2404 and the nozzle connection plate 2402. The piezoelectric actuator 2404 is formed by laminating a piezoelectric element 2441 and a protective layer 2442. The piezoelectric actuator 2404 is disposed on the upper surface of the pressure chamber plate 2403 in the Z-axis direction so that the plate surface is perpendicular to the Z-axis.

[0041] The head 240 also includes a nozzle 2411, a communication flow path 2421, a pressure chamber 2431, a piezoelectric element 2441, an individual electrode 2443, and a common electrode 2444. The nozzle 2411, the communication flow path 2421, the pressure chamber 2431, the piezoelectric element 2441, the individual electrode 2443, and the common electrode 2444 are formed inside the nozzle plate 2401, the nozzle communication plate 2402, the pressure chamber plate 2403, and the piezoelectric actuator 2404, or by combining these together.

[0042] A plurality of nozzles 2411 are formed in the nozzle plate 2401 along the X-axis. That is, the X-axis direction, which is a first direction, is the direction in which the nozzles 2411 are arranged. The plurality of nozzles 2411 are holes that penetrate the nozzle plate 2401 in the Z-axis direction. Ink droplets are ejected to the outside in the Z-axis direction through the nozzles 2411.

[0043] In this example, three nozzles 2411 are arranged in the head 240, but the number of nozzles 2411 is not limited to this example. For example, the nozzles 2411 are arranged in a number that can cover the width in the X-axis direction (the perpendicular direction in FIG. 1) of the area on which an image is to be recorded on the recording medium M transported by the transport drum 21 (see FIG. 1).

[0044] A plurality of communication channels 2421 are formed along the X-axis in the nozzle communication plate 2402. The plurality of communication channels 2421 are holes that penetrate the nozzle communication plate 2402 in the Z-axis direction, and are formed corresponding to the plurality of nozzles 2411. The communication channels 2421 communicate between the nozzles 2411 and the pressure chambers 2431.

[0045] The pressure chambers 2431 are formed by closing the open surface (upper surface in the Z-axis direction) of a recess formed in the pressure chamber plate 2403 with a protective layer 2442 of the piezoelectric actuator 2404. The pressure chambers 2431 are spaces that store ink ejected from the nozzles 2411. The pressure chambers 2431 are arranged side by side in the X-axis direction corresponding to each of the multiple nozzles 2411, and communicate with the nozzles 2411 via communication channels 2421.

[0046] Furthermore, the pressure chamber plate 2403 is formed with partition walls 2432 that become the wall surfaces of the pressure chambers 2431. When multiple pressure chambers 2431 are formed side by side in the X-axis direction corresponding to the multiple nozzles 2411, the partition walls 2432 serve to separate the adjacent pressure chambers 2431 from each other.

[0047] The piezoelectric element 2441 is, for example, a plate-shaped piece of lead zirconate titanate (PZT) and is polarized in a predetermined direction. In this embodiment, the piezoelectric element 2441 is polarized in the Z-axis direction (polarization direction P in FIG. 2).

[0048] The piezoelectric elements 2441 are deformed by applying a drive voltage to each individual electrode 2443. This causes the piezoelectric elements 2441 to deform the pressure chambers 2431. In consideration of efficient manufacturing, it is preferable that the thickness (length in the Z-axis direction) of the piezoelectric elements 2441 be, for example, 150 μm or more.

[0049] Here, the nozzle 2411, the communication channel 2421, and the pressure chamber 2431 communicate with each other to form one channel for ejecting ink. The ejection of ink is controlled for each channel.

[0050] The individual electrodes 2443 and the common electrode 2444 are arranged on the surface of at least one of two surfaces perpendicular to the Z axis of the piezoelectric element 2441. Here, the Z axis direction, which is the second direction, is a direction perpendicular to the surface of the piezoelectric element 2441 on which the individual electrodes 2443 and the common electrode 2444, which are parallel to the X axis, are arranged.

[0051] The individual electrodes 2443 are electrodes to which a drive voltage is applied, and are arranged for each channel. The common electrode 2444 is an electrode arranged in common to all channels, and is either grounded or has a common drive voltage applied thereto.

[0052] Here, as a driving method for piezoelectric element 58, for example, there is a method in which common electrode 2444 is grounded to set the voltage at 0 V, and a driving voltage according to each pixel data is applied to individual electrode 2443. Note that in this driving method, the driving voltage applied to individual electrode 2443 may be either a positive or negative voltage, or both a positive and negative voltage.

[0053] Furthermore, for example, when the inkjet head driving unit 241 (see FIG. 1) applies only a positive driving voltage, first, a positive driving voltage corresponding to each pixel data is applied to the individual electrode 2443. Then, in synchronization with the falling timing of the waveform of the applied driving voltage returning from positive to 0, a driving voltage rising from 0 to positive is applied to the common electrode 2444. By applying positive driving voltages with different waveforms to both the individual electrode 2443 and the common electrode 2444 in this way, the displacement of the piezoelectric element 58 can be increased.

[0054] The individual electrodes 2443 are arranged at corresponding positions in the Z-axis direction near the center between two adjacent partition walls 2432 in the X-axis direction. This is because when a drive voltage is applied to the individual electrodes 2443, the piezoelectric elements 2441 are deformed, thereby appropriately deforming the pressure chambers 2431 for each channel.

[0055] The common electrode 2444 is disposed between two individual electrodes 2443 adjacent to each other in the X-axis direction and at a corresponding position in the Z-axis direction. Preferably, the common electrode 2444 is disposed at a corresponding position in the Z-axis direction of the partition wall 2432. That is, the individual electrodes 2443 and the common electrode 2444 are disposed alternately in the X-axis direction.

[0056] 2, the individual electrode 2443 is disposed on the upper surface of the piezoelectric element 2441. The individual electrode 2443 is also disposed near the center between two partition walls 2432 adjacent in the X-axis direction, at a corresponding position in the Z-axis direction. In other words, the individual electrode 2443 is disposed above and near the center of the pressure chamber 2431 formed so as to be sandwiched between the two partition walls 2432.

[0057] The common electrode 2444 is disposed on the lower surface in the Z-axis direction. The common electrode 2444 is also disposed at a position corresponding to the partition wall 2432 in the Z-axis direction.

[0058] 2, both the individual electrode 2443 and the common electrode 2444 may be arranged on one surface of the piezoelectric element 2441 in the Z-axis direction. Specific examples of the arrangement of the individual electrode 2443 and the common electrode 2444 will be described later.

[0059] Furthermore, the piezoelectric element 2441 has a slit 2445 formed on one surface of the piezoelectric element 2441 in the Z-axis direction, the slit 2445 being concave toward the other surface. The slit 2445 is formed by, for example, dicing. In the example of Fig. 2, the slit 2445 is formed on the upper surface of the piezoelectric element 2441. However, the slit 2445 is not limited to this, and may also be formed on the lower surface of the piezoelectric element 2441 so as to be concave toward the upper surface.

[0060] The slit 2445 is formed at a position corresponding to the space between two adjacent individual electrodes 2443 in the X-axis direction. Preferably, the slit 2445 is formed at the same position in the X-axis direction as the common electrode 2444 arranged between the two adjacent individual electrodes 2443 in the X-axis direction, and on the surface of the piezoelectric element 2441 opposite to the surface on which the common electrode 2444 is arranged.

[0061] In this way, the individual electrodes 2443 are arranged on the piezoelectric element 2441 and the slits 2445 are formed, whereby a plurality of driving regions 2440 are formed in the piezoelectric element 2441, each of which includes an individual electrode 2443 and is separated by the slits 2445. The plurality of driving regions 2440 are formed side by side in the X-axis direction corresponding to the plurality of nozzles 2411.

[0062] Fig. 3 is a cross-sectional view schematically showing an example of the shape of the slit 2445 in Fig. 2. Fig. 4 is a cross-sectional view schematically showing another example of the shape of the slit 2445 in Fig. 2.

[0063] The slit 2445 may be formed over the entire Y-axis direction of the piezoelectric element 2441, or may be formed in a part of the Y-axis direction as shown in Fig. 3. Also, as shown in Fig. 4, a part or all of the slit 2445 may be formed so as to divide the piezoelectric element 2441 in the Z-axis direction.

[0064] Furthermore, a plurality of slits 2445 may be arranged at positions corresponding to the gap between two adjacent individual electrodes 2443 in the X-axis direction. In this case, however, at least one slit 2445 is arranged on the surface opposite to the surface on which the common electrode 2444 is arranged in the Z-axis direction.

[0065] By forming such slits 2445, the cross-sectional area of ​​the piezoelectric element 2441 between two channels adjacent in the X-axis direction when cut in the YZ plane is reduced compared to when the slits 2445 are not formed.

[0066] [Head 240 operation] The operation of the head 240 in the inkjet image forming apparatus 1 according to this embodiment having the above configuration will be described below. First, when a drive voltage from the inkjet head drive unit 241 is applied to the individual electrode 2443 of the piezoelectric actuator 2404, the piezoelectric element 2441 is deformed.

[0067] At this time, an electric field in the X-axis direction is generated in the piezoelectric element 2441, extending from the individual electrode 2443 toward the common electrodes 2444 on both sides. Here, the polarization direction P of the piezoelectric element 2441 is the Z-axis direction, and the electric field direction E is the X-axis direction, so the polarization direction P and the electric field direction E of the piezoelectric element 2441 are perpendicular to each other. Therefore, the piezoelectric element 2441 undergoes shear deformation, and is essentially deformed so as to bend in the Z-axis direction (toward the pressure chamber 2431) around the position of the individual electrode 2443.

[0068] As a result, the pressure chamber 2431 is deformed, which changes the pressure on the ink inside the pressure chamber 2431, causing the ink inside the pressure chamber 2431 to be ejected from the nozzle 2411 via the communication flow path 2421. In this way, ink droplets are ejected from the nozzle 2411, thereby forming an image on the recording medium M.

[0069] (electric field leakage) In a conventional inkjet head, when a driving voltage is applied to an individual electrode of a piezoelectric element in a certain channel, the channel is driven to generate an electric field, but the generated electric field may leak to an adjacent channel. When the electric field leaks to an adjacent channel, electric field crosstalk occurs, which affects the ejection speed, ejection volume, and other properties of ink droplets.

[0070] The amount of electric field leakage at this time varies depending on the cross-sectional area of ​​the piezoelectric element between the driven channel and the adjacent channel. Therefore, in order to suppress the effects of electric field crosstalk, it is necessary to reduce the cross-sectional area, i.e., the thickness of the piezoelectric element.

[0071] However, if the thickness of the piezoelectric element is reduced, the rigidity of the piezoelectric element for deforming the pressure chamber decreases, making it impossible to sufficiently deform the pressure chamber. Therefore, in order to suppress the effects of electric field crosstalk, it is necessary to reduce the cross-sectional area between adjacent channels without reducing the thickness of the piezoelectric element.

[0072] In contrast, in head 240 according to this embodiment, slits 2445 are formed in piezoelectric element 2441. By forming slits 2445 in piezoelectric element 2441, it is possible to reduce the cross-sectional area between the drive channel and the adjacent channel without reducing the thickness of piezoelectric element 2441. As a result, in head 240 according to this embodiment, it is possible to reduce the amount of electric field leakage to the adjacent channel.

[0073] [Example of head 240] Next, specific examples of the head 240 according to this embodiment will be described. The head 240 can be formed as shown in the following first to eighth examples, depending on the arrangement positions of the individual electrodes 2443 and the common electrode 2444, and the arrangement position of the slits 2445. Note that here, a case where one slit 2445 is formed between two adjacent individual electrodes 2443 will be illustrated. In addition, in the following description, the "lower surface" and the "upper surface" correspond to the "first surface" and the "second surface" of the present disclosure, respectively.

[0074] (First example) 5 is a cross-sectional view schematically showing a first example of the structure of head 240 according to this embodiment. As shown in FIG. 5, in the first example, slits 2445 are formed on the upper surface of piezoelectric element 2441. Furthermore, individual electrodes 2443 are arranged on the upper surface side of piezoelectric element 2441. Common electrode 2444 is arranged on the lower surface side of piezoelectric element 2441.

[0075] In a first example, the slits 2445 are formed on the top surface of the piezoelectric element 2441. Therefore, after manufacturing the piezoelectric actuator 2404 including the piezoelectric element 2441, the protective layer 2442, the individual electrodes 2443, and the common electrode 2444, the slits 2445 can be formed by dicing.

[0076] (Second example) 6 is a cross-sectional view schematically showing a second example of the structure of head 240 according to the present embodiment. As shown in FIG. 6, in the second example, slits 2445 are formed on the upper surface of piezoelectric element 2441. Individual electrodes 2443 and common electrode 2444 are disposed on the lower surface side of piezoelectric element 2441.

[0077] In the second example, similar to the first example, the slits 2445 are formed on the upper surface of the piezoelectric element 2441. Therefore, after the piezoelectric actuator 2404 is manufactured, the slits 2445 can be formed by dicing.

[0078] (Third example) 7 is a cross-sectional view schematically showing a third example of the structure of head 240 according to the present embodiment. As shown in FIG. 7, in the third example, slits 2445 are formed on the upper surface of piezoelectric element 2441. Furthermore, individual electrodes 2443 are arranged on the lower surface side of piezoelectric element 2441. Common electrode 2444 is arranged on the upper surface side of piezoelectric element 2441.

[0079] In the third example, similar to the first and second examples, the slits 2445 are formed on the upper surface of the piezoelectric element 2441. Therefore, after the piezoelectric actuator 2404 is manufactured, the slits 2445 can be formed by dicing.

[0080] In the third example, the common electrode 2444 and the slit 2445 are both formed on the upper surface of the piezoelectric element 2441 and are arranged at the same position in the X-axis direction. That is, the common electrode 2444 and the slit 2445 are arranged on a common surface of the piezoelectric element 2441. Therefore, when manufacturing the piezoelectric actuator 2404, for example, the piezoelectric actuator 2404 may be manufactured without the common electrode 2444, and after the slit 2445 is formed by dicing, the common electrode 2444 may be arranged on the upper surface of the piezoelectric element 2441.

[0081] In this case, the common electrode 2444 may be arranged inside the slit 2445. In this case, the inner circumferential surface and bottom surface of the slit 2445 are also considered to be part of the upper surface of the piezoelectric element 2441. Therefore, even when the common electrode 2444 is arranged inside the slit 2445, the common electrode 2444 and the slit 2445 are considered to be arranged on a common surface of the piezoelectric element 2441.

[0082] (Example 4) 8 is a cross-sectional view schematically showing a fourth example of the structure of head 240 according to the present embodiment. As shown in FIG. 8, in the fourth example, slits 2445 are formed on the upper surface of piezoelectric element 2441. Furthermore, individual electrodes 2443 and common electrode 2444 are arranged on the upper surface side of piezoelectric element 2441.

[0083] In the fourth example, similarly to the first to third examples, the slits 2445 are formed in the upper surface of the piezoelectric element 2441. Therefore, after the piezoelectric actuator 2404 is manufactured, the slits 2445 can be formed by dicing.

[0084] In the fourth example, similarly to the third example, the common electrode 2444 and the slit 2445 are both formed on the upper surface of the piezoelectric element 2441 and are arranged at the same position in the X-axis direction. That is, the common electrode 2444 and the slit 2445 are arranged on a common surface of the piezoelectric element 2441. Therefore, when manufacturing the piezoelectric actuator 2404, for example, the piezoelectric actuator 2404 may be manufactured excluding the common electrode 2444, and after the slit 2445 is formed by dicing, the common electrode 2444 may be arranged on the upper surface of the piezoelectric element 2441.

[0085] In this case, the common electrode 2444 may be arranged inside the slit 2445. In this case, the inner circumferential surface and bottom surface of the slit 2445 are also considered to be part of the upper surface of the piezoelectric element 2441. Therefore, even when the common electrode 2444 is arranged inside the slit 2445, the common electrode 2444 and the slit 2445 are considered to be arranged on a common surface of the piezoelectric element 2441.

[0086] In this way, the first to fourth examples are examples in which the slits 2445 are formed on the upper surface of the piezoelectric element 2441. In particular, in the first and second examples, the slits 2445 are arranged on the surface (upper surface) opposite to the surface (lower surface) on which the common electrode 2444 is arranged.

[0087] In this case, leakage of the electric field generated in the piezoelectric element 2441 from one individual electrode 2443 to an adjacent individual electrode 2443 is blocked by the slit 2445. In other words, since the slit 2445 suppresses leakage of the electric field from one channel to an adjacent channel, the influence of electric field crosstalk on the adjacent channel can be suppressed.

[0088] (Fifth Example) 9 is a cross-sectional view schematically showing a fifth example of the structure of head 240 according to this embodiment. As shown in FIG. 9, in the fifth example, slits 2445 are formed on the lower surface of piezoelectric element 2441. Furthermore, individual electrodes 2443 are arranged on the lower surface side of piezoelectric element 2441. Common electrode 2444 is arranged on the upper surface side of piezoelectric element 2441.

[0089] In the fifth example, a slit 2445 is formed on the lower surface of the piezoelectric element 2441. In this case, when the piezoelectric actuator 2404 is stacked on the pressure chamber plate 2403, the slit 2445 is formed inside the head 240, so that a decrease in the durability of the piezoelectric actuator 2404 can be suppressed.

[0090] (Example 6) 10 is a cross-sectional view schematically showing a sixth example of the structure of head 240 according to the present embodiment. As shown in FIG. 10, in the sixth example, slits 2445 are formed on the lower surface of piezoelectric element 2441. Furthermore, individual electrodes 2443 and common electrode 2444 are arranged on the upper surface side of piezoelectric element 2441.

[0091] In the sixth example, similarly to the fifth example, a slit 2445 is formed on the lower surface of the piezoelectric element 2441. Therefore, a decrease in the durability of the piezoelectric actuator 2404 can be suppressed.

[0092] (Example 7) Fig. 11 is a cross-sectional view schematically showing a seventh example of the structure of head 240 according to this embodiment. As shown in Fig. 11, in the seventh example, slits 2445 are formed on the lower surface of piezoelectric element 2441. Furthermore, individual electrodes 2443 are arranged on the upper surface side of piezoelectric element 2441. Common electrode 2444 is arranged on the lower surface side of piezoelectric element 2441. In other words, common electrode 2444 and slits 2445 are arranged on a common surface of piezoelectric element 2441.

[0093] In the seventh example, similar to the fifth and sixth examples, a slit 2445 is formed on the lower surface of the piezoelectric element 2441. Therefore, a decrease in the durability of the piezoelectric actuator 2404 can be suppressed.

[0094] When manufacturing the piezoelectric actuator 2404, for example, the piezoelectric actuator 2404 may be manufactured without the common electrode 2444, and after forming the slits 2445 by dicing, the common electrode 2444 may be disposed on the lower surface of the piezoelectric element 2441. Furthermore, without being limited to this, for example, the slits 2445 may be formed by dicing after manufacturing the piezoelectric actuator 2404 including the common electrode 2444.

[0095] Furthermore, in this case, the common electrode 2444 may be arranged inside the slit 2445. In this case, the inner circumferential surface and bottom surface of the slit 2445 are also considered to be part of the lower surface of the piezoelectric element 2441. Therefore, even when the common electrode 2444 is arranged inside the slit 2445, the common electrode 2444 and the slit 2445 are considered to be arranged on a common surface of the piezoelectric element 2441.

[0096] (Example 8) Fig. 12 is a cross-sectional view schematically showing an eighth example of the structure of head 240 according to this embodiment. As shown in Fig. 12, in the eighth example, slits 2445 are formed on the lower surface of piezoelectric element 2441. Furthermore, individual electrode 2443 and common electrode 2444 are arranged on the lower surface side of piezoelectric element 2441. In other words, common electrode 2444 and slit 2445 are arranged on a common surface of piezoelectric element 2441.

[0097] In the eighth example, similarly to the fifth to seventh examples, a slit 2445 is formed on the lower surface of the piezoelectric element 2441. Therefore, a decrease in the durability of the piezoelectric actuator 2404 can be suppressed.

[0098] When manufacturing the piezoelectric actuator 2404, for example, as in the seventh example, the slit 2445 may be formed in the piezoelectric element 2441 and then the common electrode 2444 may be placed on the piezoelectric element 2441, or the slit 2445 may be formed by dicing after manufacturing the piezoelectric actuator 2404 including the common electrode 2444.

[0099] Furthermore, in this case, the common electrode 2444 may be arranged inside the slit 2445. In this case, the inner circumferential surface and bottom surface of the slit 2445 are also considered to be part of the lower surface of the piezoelectric element 2441. Therefore, even when the common electrode 2444 is arranged inside the slit 2445, the common electrode 2444 and the slit 2445 are considered to be arranged on a common surface of the piezoelectric element 2441.

[0100] In this way, the fifth to eighth examples are examples in which the slits 2445 are formed on the lower surface of the piezoelectric element 2441. In particular, in the fifth and sixth examples, the slits 2445 are arranged on the surface (lower surface) opposite to the surface (upper surface) on which the common electrode 2444 is arranged.

[0101] In this case, as in the first and second examples, leakage of the electric field generated in the piezoelectric element 2441 from one individual electrode 2443 to an adjacent individual electrode 2443 is blocked by the slit 2445. In other words, since the slit 2445 suppresses leakage of the electric field from one channel to an adjacent channel, it is possible to suppress the influence of electric field crosstalk on the adjacent channel.

[0102] As described above, in head 240 according to this embodiment, individual electrodes 2443 and common electrodes 2444 are alternately arranged on the surface of piezoelectric element 2441 along the X-axis direction. In addition, piezoelectric element 2441 has slits 2445 formed on the surface along the X-axis direction.

[0103] With this configuration, in the head 240, of the electric fields generated in the piezoelectric elements 2441, leakage of the electric field from one individual electrode 2443 to an adjacent individual electrode 2443 is blocked by the slits 2445. This makes it possible to suppress the influence of electric field crosstalk on adjacent channels and to suppress degradation in the quality of images formed by the inkjet image forming apparatus 1.

[0104] Although the embodiments have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications and applications are possible without departing from the spirit and scope of the present disclosure. In the present embodiment, it has been described that ink droplets are ejected from the nozzles 2411 in the Z-axis direction, but the ejection direction of the ink droplets is not limited to this example. For example, the head 240 may be configured so that the nozzle plate 2401 in which the nozzles 2411 are formed is disposed on the ZX plane, and ink droplets from the nozzles 2411 may be ejected in the Y-axis direction.

[0105] The disclosures of the specification, drawings and abstract contained in Japanese Patent Application No. 2023-108384, filed on June 30, 2023, are incorporated herein by reference in their entirety. [Explanation of symbols]

[0106] 1. Inkjet image forming device 20 Image forming unit 24 Head Unit 240 Inkjet head 241 Inkjet head drive unit 2401 Nozzle plate 2402 Nozzle connection plate 2403 Pressure chamber plate 2404 Piezoelectric Actuator 2440 Drive Area 2441 Piezoelectric element 2442 Protective layer 2411 Nozzle 2421 Connecting flow path 2431 Pressure Chamber 2432 Bulkhead 2443 Individual electrode 2444 Common electrode 2445 Slit

Claims

1. a piezoelectric element having a plurality of drive regions aligned in a first direction corresponding to the plurality of nozzles; a plurality of individual electrodes arranged in the piezoelectric element for each of the drive regions, to which drive voltages for ejecting ink from the corresponding nozzles are individually applied; a common electrode disposed on the piezoelectric element alternately with the individual electrodes in the first direction, the common electrode being applied with a common driving voltage so as to generate an electric field between the common electrode and the individual electrodes in the plurality of driving regions; a slit formed in the piezoelectric element so as to divide the piezoelectric element into the driving regions; Equipped with A plurality of the common electrodes are arranged. Inkjet head.

2. The slit is The individual electrodes are formed at positions between two of the individual electrodes adjacent to each other in the first direction.

2. The ink jet head according to claim 1.

3. The slit is the individual electrodes and the common electrode are formed at positions corresponding to the common electrode when viewed from a second direction perpendicular to a surface of the piezoelectric element parallel to the first direction in which the individual electrodes and the common electrode are arranged; 2. The ink jet head according to claim 1.

4. further comprising partition walls separating a plurality of pressure chambers arranged in the first direction corresponding to the plurality of nozzles, The slit is the individual electrodes and the common electrode are formed at positions corresponding to the partition walls when viewed from a second direction perpendicular to a surface of the piezoelectric element parallel to the first direction in which the individual electrodes and the common electrode are arranged, 2. The ink jet head according to claim 1.

5. further comprising partition walls separating a plurality of pressure chambers arranged in the first direction corresponding to the plurality of nozzles, The individual electrodes are the individual electrodes and the common electrodes are disposed at positions corresponding to the centers between the adjacent partition walls when viewed from a second direction perpendicular to the surface of the piezoelectric element parallel to the first direction in which the individual electrodes and the common electrodes are disposed; 2. The ink jet head according to claim 1.

6. a surface of the piezoelectric element on which the slit is formed and a surface of the piezoelectric element on which the common electrode is disposed are both parallel to the first direction and positioned on opposite sides to each other in a second direction perpendicular to the respective surfaces; 2. The ink jet head according to claim 1.

7. a surface of the piezoelectric element on which the common electrode is disposed faces a plurality of pressure chambers aligned in the first direction corresponding to the plurality of nozzles; the individual electrodes are arranged on a surface of the piezoelectric element on which the slits are formed, the surface not facing the pressure chambers.

7. The ink jet head according to claim 6.

8. a surface of the piezoelectric element on which the slits are formed does not face a plurality of pressure chambers aligned in the first direction corresponding to the plurality of nozzles, the individual electrodes and the common electrode are disposed on a surface of the piezoelectric element facing the pressure chamber.

7. The ink jet head according to claim 6.

9. a surface of the piezoelectric element on which the slits are formed faces a plurality of pressure chambers aligned in the first direction corresponding to the plurality of nozzles; a surface of the piezoelectric element on which the common electrode is disposed is disposed on a surface of the piezoelectric element that does not face the pressure chamber; the individual electrodes are disposed on a surface of the piezoelectric element on which the slits are formed; 7. The ink jet head according to claim 6.

10. a surface of the piezoelectric element on which the slits are formed faces a plurality of pressure chambers aligned in the first direction corresponding to the plurality of nozzles; the individual electrodes and the common electrode are disposed on a surface of the piezoelectric element that does not face the pressure chamber.

7. The ink jet head according to claim 6.

11. The slit and the common electrode are formed on a common surface of the piezoelectric elements parallel to the first direction; 2. The ink jet head according to claim 1.

12. The common electrode is disposed within the slit, The ink jet head according to claim 11.

13. The slit is the individual electrodes and the common electrode are formed on a part or all of the piezoelectric element in a third direction orthogonal to both the first direction and a second direction orthogonal to a surface of the piezoelectric element parallel to the first direction in which the individual electrodes and the common electrode are arranged; 2. The ink jet head according to claim 1.

14. The slit is the individual electrodes and the common electrode are formed so as to penetrate the piezoelectric element in a second direction perpendicular to a surface of the piezoelectric element parallel to the first direction in which the individual electrodes and the common electrode are arranged; 2. The ink jet head according to claim 1.

15. The piezoelectric element is a length in a second direction perpendicular to a surface of the piezoelectric element parallel to the first direction on which the individual electrodes and the common electrode are arranged is 150 μm or more; 2. The ink jet head according to claim 1.

16. The piezoelectric element is the piezoelectric element is polarized in a second direction perpendicular to a surface of the piezoelectric element parallel to the first direction in which the individual electrodes and the common electrode are arranged, so as to be perpendicular to an electric field generated when the drive voltage is applied to the individual electrodes; 2. The ink jet head according to claim 1.

17. a piezoelectric element having a plurality of drive regions aligned in a first direction corresponding to the plurality of nozzles; a plurality of individual electrodes arranged in the piezoelectric element for each of the drive regions, to which drive voltages for ejecting ink from the corresponding nozzles are individually applied; a common electrode disposed on the piezoelectric element alternately with the individual electrodes in the first direction, the common electrode being applied with a common driving voltage so as to generate an electric field between the common electrode and the individual electrodes in the plurality of driving regions; a slit formed in the piezoelectric element so as to divide the piezoelectric element into the driving regions; a partition wall separating a plurality of pressure chambers arranged in the first direction corresponding to the plurality of nozzles from each other; Equipped with a surface of the piezoelectric element on which the slit is formed and a surface of the piezoelectric element on which the common electrode is disposed are both parallel to the first direction and positioned on opposite sides to each other in a second direction perpendicular to the respective surfaces; the individual electrodes are disposed at positions corresponding to the centers between the adjacent partition walls when viewed from the second direction, A plurality of the common electrodes are arranged, the slits are formed at positions corresponding to the common electrode and the partition wall when viewed from the second direction. Inkjet head.

18. a piezoelectric element having a plurality of drive regions aligned in a first direction corresponding to the plurality of nozzles; a plurality of individual electrodes arranged in the piezoelectric element for each of the drive regions, to which drive voltages for ejecting ink from the corresponding nozzles are individually applied; a common electrode disposed on the piezoelectric element alternately with the individual electrodes in the first direction, the common electrode being applied with a common driving voltage so as to generate an electric field between the common electrode and the individual electrodes in the plurality of driving regions; a slit formed in the piezoelectric element so as to divide the piezoelectric element into the driving regions; a partition wall separating a plurality of pressure chambers arranged in the first direction corresponding to the plurality of nozzles from each other; Equipped with a surface of the piezoelectric element on which the slit is formed and a surface of the piezoelectric element on which the common electrode is disposed are both parallel to the first direction and positioned on opposite sides to each other in a second direction perpendicular to the respective surfaces; the individual electrodes are disposed at positions corresponding to the centers between the adjacent partition walls when viewed from the second direction, A plurality of the common electrodes are arranged, the slit is formed at a position corresponding to the common electrode and the partition wall when viewed from the second direction; the piezoelectric element is polarized in the second direction so as to be perpendicular to an electric field generated when the drive voltage is applied to the individual electrode; Inkjet head.

19. An image forming apparatus comprising the inkjet head according to claim 1 , 17 , or 18 .

Images