Liquid droplet discharge head and recording device

Abstract

To provide a liquid droplet discharge head and a recording device in which a driving displacement of a piezoelectric element is unlikely to decrease even when positional deviation occurs between a pressure chamber and a surface electrode.SOLUTION: A liquid droplet discharge head according to the present disclosure comprises a nozzle, a pressure chamber, and a piezoelectric element. The nozzle discharges droplets. The pressure chamber is connected to the nozzle. The piezoelectric element is deformed by applying a voltage thereto, thereby deforming the pressure chamber. The piezoelectric element has a surface electrode and a first groove section. The surface electrode faces the pressure chamber. The first groove section is positioned in the periphery of the surface electrode and extends in a shape corresponding to the outer shape of the surface electrode. When A1 is the maximum value of the distance between the outer edge of the pressure chamber and the outer edge of the first groove section in a perspective plan view, A2 is the minimum value thereof, B1 is the maximum value of the distance between the outer edge of the surface electrode and the outer edge of the first groove section in a plan view, and B2 is the minimum value thereof, formula (1) is satisfied. (1): A1-A2<B1-B2.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a droplet ejection head and a recording apparatus. [Background technology]

[0002] 2. Description of the Related Art Known printing devices include inkjet printers and inkjet plotters that use an inkjet recording method. Such inkjet printing devices are equipped with a droplet ejection head for ejecting liquid.

[0003] The droplet ejection head ejects the liquid in the pressure chamber from the nozzle by driving a piezoelectric element located above the pressure chamber to change the pressure in the pressure chamber. The piezoelectric element has a piezoelectric body, an internal electrode located inside the piezoelectric body, and a surface electrode located on the surface of the piezoelectric body.

[0004] Patent Document 1 discloses an inkjet head having piezoelectric elements in which grooves are formed around the surface electrodes to surround the surface electrodes in order to suppress the occurrence of crosstalk between the piezoelectric elements. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-311954 Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure provides a droplet ejection head and a recording apparatus in which the driving displacement of a piezoelectric element is unlikely to decrease even when misalignment occurs between a pressure chamber and a surface electrode. [Means for solving the problem]

[0007] A droplet ejection head according to one aspect of the present disclosure has a nozzle, a pressure chamber, and a piezoelectric element. The nozzle ejects droplets. The pressure chamber is connected to the nozzle. The piezoelectric element deforms when a voltage is applied to it, thereby deforming the pressure chamber. The piezoelectric element has a surface electrode and a first groove. The surface electrode faces the pressure chamber. The first groove is located around the surface electrode and extends in a shape that corresponds to the outer shape of the surface electrode. If the maximum value of the distance between the outer edge of the pressure chamber and the outer edge of the first groove in a planar perspective view is A1 and the minimum value is A2, and the maximum value of the distance between the outer edge of the surface electrode and the outer edge of the first groove in a planar view is B1 and the minimum value is B2, then the following formula (1) is satisfied. A1-A2 <B1―B2 ···(1) [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a droplet ejection head and a recording apparatus in which the driving displacement of the piezoelectric element is unlikely to decrease even when misalignment occurs between the pressure chamber and the surface electrode. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic side view of a printer according to a first embodiment. [Figure 2] FIG. 2 is a schematic plan view of the printer according to the first embodiment. [Figure 3] FIG. 3 is a schematic exploded perspective view of the droplet ejection head according to the first embodiment. [Figure 4] FIG. 4 is a schematic plan view showing the main part of the head main body according to the first embodiment. [Figure 5] FIG. 5 is a schematic enlarged view of region V shown in FIG. [Figure 6] FIG. 6 is a schematic cross-sectional view taken along the line VI-VI in FIG. [Figure 7] FIG. 7 is a schematic plan view of the piezoelectric element according to the first embodiment. [Figure 8] FIG. 8 is a schematic plan view of the piezoelectric element according to the first embodiment. [Figure 9]FIG. 9 is a schematic plan view of the piezoelectric element according to the first embodiment. [Figure 10] FIG. 10 is a schematic plan view of the piezoelectric element according to the first embodiment. [Figure 11] FIG. 11 is a schematic plan view of the piezoelectric element according to the first embodiment. [Figure 12] FIG. 12 is a schematic cross-sectional view of a reinforcing plate and a flow path member according to the first embodiment. [Figure 13] FIG. 13 is a schematic cross-sectional view showing a main part of the head main body according to the first embodiment. [Figure 14] FIG. 14 is a schematic plan view showing a main part of the head main body according to the first embodiment. [Figure 15] FIG. 15 is a plan view showing the configuration of the reinforcing plate according to the first embodiment. [Figure 16] FIG. 16 is a schematic plan view showing the configuration of the piezoelectric element according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a detailed description will be given of a droplet ejection head and a recording apparatus according to the present disclosure (hereinafter referred to as an "embodiment") with reference to the drawings. Note that the present disclosure is not limited to the embodiment. Furthermore, the embodiments can be appropriately combined as long as the processing content is not contradictory. Furthermore, the same components in the following embodiments are designated by the same reference numerals, and redundant explanations will be omitted.

[0011] Furthermore, in the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in the strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision or installation precision.

[0012] In addition, for ease of understanding, the drawings referred to below may show an orthogonal coordinate system in which the X-axis, Y-axis, and Z-axis directions are defined as being orthogonal to each other, with the positive Z-axis direction being the vertically upward direction. Also, the direction of rotation around the vertical axis may be referred to as the θ direction.

[0013] The groove portion of the inkjet head described in Patent Document 1 is formed by bonding a flow path unit including multiple pressure chambers to an actuator unit having a piezoelectric element, and then performing laser processing based on the position of the surface electrode.

[0014] In order to increase the driving displacement of the piezoelectric element, it is preferable to form a groove portion that follows the edge of the pressure chamber in a planar perspective view. However, when the actuator unit is attached to the flow path unit, the actuator unit may be attached in a state where it is shifted from the desired position relative to the flow path unit. In other words, the position of the surface electrode relative to the pressure chamber may be shifted from the desired position. In the above-mentioned conventional technology, the groove portion is formed based on the position of the surface electrode. Therefore, if the position of the surface electrode is shifted from the desired position, the groove portion will not be positioned along the edge of the pressure chamber, and as a result, the driving displacement of the piezoelectric element may be smaller than the desired value.

[0015] Therefore, it is desired to provide an inkjet head in which the driving displacement of the piezoelectric element is unlikely to decrease even when misalignment occurs between the pressure chamber and the surface electrode.

[0016] (First embodiment) <Printer configuration> First, an overview of a printer 1, which is an example of a recording apparatus according to the first embodiment, will be described with reference to Figures 1 and 2. Figure 1 is a schematic side view of the printer 1 according to the first embodiment, and Figure 2 is a schematic plan view of the printer 1 according to the first embodiment. The printer 1 according to the first embodiment is, for example, a color inkjet printer.

[0017] As shown in Figure 1, the printer 1 includes a paper feed roller 2, a guide roller 3, an applicator 4, a head case 5, a plurality of conveying rollers 6, a plurality of frames 7, a plurality of droplet ejection heads 8, a conveying roller 9, a dryer 10, a conveying roller 11, a sensor unit 12, and a recovery roller 13.

[0018] Furthermore, the printer 1 has a control unit 14 that controls the paper feed roller 2, guide roller 3, coater 4, head case 5, multiple conveying rollers 6, multiple frames 7, multiple droplet ejection heads 8, conveying roller 9, dryer 10, conveying roller 11, sensor unit 12, and recovery roller 13.

[0019] The printer 1 records images or characters on the printing paper P by causing droplets to land on the printing paper P. The printing paper P is an example of a recording medium. Before use, the printing paper P is wound around a paper feed roller 2. The printer 1 then transports the printing paper P from the paper feed roller 2 through a guide roller 3 and a coater 4 into the inside of a head case 5.

[0020] The coater 4 applies the coating agent evenly to the printing paper P. This allows the surface of the printing paper P to be treated, thereby improving the printing quality of the printer 1.

[0021] The head case 5 houses a plurality of transport rollers 6, a plurality of frames 7, and a plurality of droplet ejection heads 8. Inside the head case 5, a space is formed that is isolated from the outside, except for some parts that are connected to the outside, such as the part where the printing paper P enters and leaves.

[0022] At least one of the control factors such as temperature, humidity, and air pressure of the internal space of the head case 5 is controlled by the control unit 14 as necessary. The transport rollers 6 transport the printing paper P inside the head case 5 to the vicinity of the droplet ejection heads 8.

[0023] The frame 7 is a rectangular flat plate, and is positioned above and in close proximity to the print paper P being transported by the transport rollers 6. As shown in FIG. 2, the frame 7 is positioned so that its longitudinal direction is perpendicular to the transport direction of the print paper P. Inside the head case 5, multiple (for example, four) frames 7 are positioned along the transport direction of the print paper P.

[0024] A liquid, such as ink, is supplied from a liquid tank (not shown) to the droplet discharge head 8. The droplet discharge head 8 discharges droplets of liquid supplied from the liquid tank.

[0025] The control unit 14 controls the droplet discharge head 8 based on image or character data, causing it to discharge droplets toward the printing paper P. The distance between the droplet discharge head 8 and the printing paper P is, for example, about 0.5 to 20 mm.

[0026] The droplet ejection head 8 is fixed to the frame 7. For example, both ends of the droplet ejection head 8 in the longitudinal direction are fixed to the frame 7. The droplet ejection head 8 is positioned so that its longitudinal direction is perpendicular to the transport direction of the printing paper P.

[0027] That is, the printer 1 according to the first embodiment is a so-called line printer in which the droplet ejection head 8 is fixed inside the printer 1. Note that the printer 1 according to the first embodiment is not limited to a line printer, and may also be a so-called serial printer. A serial printer is a printer that alternates between recording while moving the droplet ejection head 8 back and forth in a direction intersecting the transport direction of the printing paper P, for example, in a direction approximately perpendicular to the direction, and transporting the printing paper P.

[0028] As shown in Fig. 2, a plurality of (for example, five) droplet ejection heads 8 are fixed to one frame 7. Fig. 2 shows an example in which three droplet ejection heads 8 are positioned in front and two in the rear in the transport direction of the printing paper P, and the droplet ejection heads 8 are positioned in the transport direction of the printing paper P so that the centers of the droplet ejection heads 8 do not overlap.

[0029] A head group 8A is made up of multiple droplet ejection heads 8 positioned on one frame 7. The four head groups 8A are positioned along the transport direction of the printing paper P. The same color ink is supplied to droplet ejection heads 8 belonging to the same head group 8A. This allows the printer 1 to print with four colors of ink using the four head groups 8A.

[0030] The colors of ink ejected from each head group 8A are, for example, magenta (M), yellow (Y), cyan (C), and black (K). The control unit 14 controls each head group 8A to eject ink of multiple colors onto the printing paper P, thereby printing a color image on the printing paper P.

[0031] In order to treat the surface of the printing paper P, a coating agent may be ejected onto the printing paper P from the droplet ejection head 8.

[0032] Furthermore, the number of droplet ejection heads 8 included in one head group 8A, or the number of head groups 8A mounted on the printer 1, can be changed as appropriate depending on the object to be printed or the printing conditions. For example, if a single color is printed on the printing paper P and the printing area is to be printed with one droplet ejection head 8, the number of droplet ejection heads 8 mounted on the printer 1 may be one.

[0033] The printing paper P that has been printed inside the head case 5 is transported to the outside of the head case 5 by transport rollers 9 and passes through the inside of the dryer 10. The dryer 10 dries the printing paper P that has been printed. The printing paper P that has been dried in the dryer 10 is transported by transport rollers 11 and collected by collection rollers 13.

[0034] In the printer 1, by drying the printing paper P in the dryer 10, it is possible to reduce adhesion between overlapping printing paper P wound up on the collection roller 13 and rubbing of undried liquid.

[0035] The sensor unit 12 is configured with a position sensor, a speed sensor, a temperature sensor, etc. The control unit 14 can determine the state of each part of the printer 1 based on information from the sensor unit 12 and control each part of the printer 1.

[0036] The printer 1 described so far uses printing paper P as the printing object (i.e., recording medium), but the printing object in the printer 1 is not limited to printing paper P. For example, the printing object may be a roll of cloth or the like.

[0037] Furthermore, the printer 1 may transport the printing paper P on a conveyor belt instead of directly transporting the printing paper P. By using a conveyor belt, the printer 1 can print on sheets of paper, cut pieces of cloth, wood, tiles, etc.

[0038] The printer 1 may also print wiring patterns for electronic devices by discharging droplets containing conductive particles from the droplet discharging head 8. The printer 1 may also produce chemicals by discharging a predetermined amount of liquid chemicals or droplets containing chemicals from the droplet discharging head 8 toward a reaction vessel or the like.

[0039] <Configuration of droplet ejection head> Next, the configuration of the droplet ejection head 8 according to the first embodiment will be described with reference to Fig. 3. Fig. 3 is a schematic exploded perspective view of the droplet ejection head 8 according to the first embodiment.

[0040] The droplet ejection head 8 has a head main body 20, a wiring section 30, a housing 40, and a pair of heat sinks 45. The head main body 20 has a flow path member 21, a reinforcing plate 172 (see FIG. 4), a piezoelectric actuator 22 (see FIG. 4), and a reservoir 23.

[0041] In the following description, for convenience, the direction in which the head body 20 is provided in the droplet ejection head 8 may be referred to as "downward," and the direction in which the housing 40 is provided relative to the head body 20 may be referred to as "upward."

[0042] The flow path member 21 of the head main body 20 has a generally flat plate shape and has a first surface 21a which is one main surface, and a second surface 21b (see FIG. 6) located on the opposite side of the first surface 21a. The first surface 21a has an opening (not shown), and liquid is supplied from a reservoir 23 to the inside of the flow path member 21 through the opening.

[0043] The second surface 21b has a plurality of discharge holes 163 (see FIG. 6) that discharge droplets onto the printing paper P. The flow path member 21 has therein a flow path that allows liquid to flow from the first surface 21a to the second surface 21b.

[0044] The reinforcing plate 172 is located on the first surface 21a of the flow path member 21. The reinforcing plate 172 has a first surface 172a facing the first surface 21a of the flow path member 21, and a second surface 172b (see FIG. 6) located on the opposite side of the first surface 172a.

[0045] The piezoelectric actuator 22 is located on a first surface 172a of the reinforcing plate 172. The piezoelectric actuator 22 has a plurality of piezoelectric elements 170 (see FIG. 6). The piezoelectric actuator 22 is electrically connected to a flexible substrate 31 of the wiring section 30.

[0046] A reservoir 23 is positioned above the piezoelectric actuator 22. The reservoir 23 has openings 23a at both ends in the main scanning direction, which is perpendicular to the transport direction of the printing paper P and parallel to the printing paper P. The reservoir 23 has a flow path therein, and liquid is supplied from the outside through the openings 23a. The reservoir 23 supplies liquid to the flow path member 21. The reservoir 23 also stores the liquid to be supplied to the flow path member 21.

[0047] The wiring section 30 has a flexible substrate 31, a wiring substrate 32, a plurality of driver ICs 33, a pressing member 34, and an elastic member 35. The flexible substrate 31 transmits a predetermined signal sent from the outside to the head body 20. As shown in FIG. 3, the droplet ejection head 8 according to the first embodiment may have two flexible substrates 31.

[0048] One end of the flexible substrate 31 is electrically connected to the piezoelectric actuator 22 of the head main body 20. The other end of the flexible substrate 31 is drawn upward so as to pass through the slit portion 23b of the reservoir 23, and is electrically connected to the wiring substrate 32. This allows the piezoelectric actuator 22 of the head main body 20 to be electrically connected to the outside.

[0049] The wiring board 32 is located above the head body 20. The wiring board 32 distributes signals to a plurality of driver ICs 33.

[0050] The plurality of driver ICs 33 are located on one main surface of the flexible substrate 31. As shown in Fig. 3, in the droplet ejection head 8 according to the first embodiment, two driver ICs 33 are provided on each flexible substrate 31, but the number of driver ICs 33 provided on each flexible substrate 31 is not limited to two.

[0051] The driver IC 33 drives the piezoelectric actuator 22 of the head main body 20 based on a drive signal sent from the control unit 14 (see FIG. 1). In this way, the driver IC 33 drives the droplet ejection head 8.

[0052] The pressing member 34 has a substantially U-shape in cross section, and presses the driver IC 33 on the flexible substrate 31 from the inside toward the heat sink 45. As a result, in the first embodiment, heat generated when the driver IC 33 is driven can be efficiently dissipated to the outer heat sink 45.

[0053] The elastic member 35 is provided so as to contact the outer wall of the pressing portion (not shown) of the pressing member 34. By providing such elastic member 35, it is possible to reduce the possibility that the pressing member 34 will damage the flexible substrate 31 when the pressing member 34 presses the driver IC 33.

[0054] The elastic member 35 is made of, for example, a double-sided foam tape. Also, by using, for example, a non-silicon heat conductive sheet as the elastic member 35, it is possible to improve the heat dissipation of the driver IC 33. However, the elastic member 35 is not necessarily required.

[0055] The housing 40 is disposed on the head main body 20 so as to cover the wiring portion 30. This allows the housing 40 to seal the wiring portion 30. The housing 40 is made of, for example, resin or metal.

[0056] The housing 40 has a box shape that extends long in the main scanning direction, and has a first opening 40a and a second opening 40b on a pair of side surfaces that face each other in the main scanning direction. The housing 40 also has a third opening 40c on its bottom surface and a fourth opening 40d on its top surface.

[0057] One side of the heat sink 45 is disposed in the first opening 40a so as to cover the first opening 40a, and the other side of the heat sink 45 is disposed in the second opening 40b so as to cover the second opening 40b.

[0058] The heat sink 45 is provided to extend in the main scanning direction and is made of a metal or alloy with high heat dissipation properties. The heat sink 45 is provided to be in contact with the driver IC 33 and dissipates heat generated by the driver IC 33.

[0059] The pair of heat sinks 45 are each fixed to the housing 40 with screws (not shown). Therefore, the housing 40 to which the heat sinks 45 are fixed has a box shape in which the first opening 40a and the second opening 40b are closed and the third opening 40c and the fourth opening 40d are open.

[0060] The third opening 40c is positioned so as to face the reservoir 23. The flexible substrate 31 and the pressing member 34 are inserted into the third opening 40c.

[0061] The fourth opening 40d is provided for inserting a connector (not shown) provided on the wiring board 32. If the space between the connector and the fourth opening 40d is sealed with resin or the like, it becomes difficult for liquid or dust to enter the inside of the housing 40.

[0062] The housing 40 also has a heat insulating portion 40e. The heat insulating portion 40e is disposed adjacent to the first opening 40a and the second opening 40b, and is provided so as to protrude outward from the side surface of the housing 40 along the main scanning direction.

[0063] The heat insulating portion 40e is formed to extend in the main scanning direction. That is, the heat insulating portion 40e is located between the heat sink 45 and the head main body 20. By providing the heat insulating portion 40e in the housing 40 in this way, heat generated in the driver IC 33 is less likely to be transmitted to the head main body 20 via the heat sink 45.

[0064] It should be noted that FIG. 3 shows an example of the configuration of the droplet ejection head 8, and the droplet ejection head 8 may further include members other than those shown in FIG.

[0065] <Head body configuration> Next, a description will be given of the configuration of the head main body 20 according to the first embodiment. Fig. 4 is a schematic plan view showing the main parts of the head main body 20 according to the first embodiment.

[0066] As described above, the head main body 20 has the flow path member 21, the reinforcing plate 172, and the piezoelectric actuator 22. The flow path member 21, the reinforcing plate 172, and the piezoelectric actuator 22 have a flat plate shape, and are positioned in this order from the bottom side of the head main body 20: flow path member 21, reinforcing plate 172, and piezoelectric actuator 22 (see FIG. 6).

[0067] 4, the flow path member 21 and the reinforcing plate 172 are larger than the piezoelectric actuator 22. Specifically, the widths of the flow path member 21 and the reinforcing plate 172 in the longitudinal direction are larger than the width of the piezoelectric actuator 22 in the longitudinal direction. In addition, the widths of the flow path member 21 and the reinforcing plate 172 in the lateral direction are larger than the width of the piezoelectric actuator 22 in the lateral direction.

[0068] The flow path member 21 has first through holes 21c in a region located outside the piezoelectric actuator 22. The first through holes 21c are formed, for example, at both ends of the flow path member 21 in the longitudinal direction.

[0069] The reinforcing plate 172 has second through holes 172g at positions corresponding to the first through holes 21c. Specifically, the second through holes 172g are disposed above the first through holes 21c at positions overlapping with the first through holes 21c in a plan view. The first through holes 21c and the second through holes 172g will be described later with reference to FIG. 13.

[0070] The piezoelectric actuator 22 is located approximately in the center of the reinforcing plate 172. The piezoelectric actuator 22 has a discharge area 24. In the discharge area 24, a plurality of piezoelectric elements 170 are located.

[0071] Fig. 5 is a schematic enlarged view of region V shown in Fig. 4. Fig. 5 is a plan view of piezoelectric element 170 viewed from a direction perpendicular to the surface of piezoelectric ceramic body 171. Note that first groove portions 100, which will be described later, are omitted from Fig. 5.

[0072] 5, the plurality of piezoelectric elements 170 are arranged at positions corresponding to the plurality of pressure chambers 162 of the flow path member 21. Specifically, the plurality of piezoelectric elements 170 are arranged so that an electrode body 174a of a surface electrode 174, which will be described later, is located above the pressure chambers 162.

[0073] Here, the configuration of the flow path member 21 having the pressure chamber 162 will be described. Fig. 6 is a schematic cross-sectional view taken along the arrows VI-VI shown in Fig. 5. Note that the line VI-VI shown in Fig. 5 is a straight line passing through a center point P1 of an electrode body 174a of a surface electrode 174 (described later) and a center point P2 of a connection electrode 175 (described later).

[0074] 6, the flow path member 21 has a laminated structure in which a plurality of plates are stacked. Specifically, the flow path member 21 has a cavity plate 21A, a base plate 21B, an aperture (throttle) plate 21C, a supply plate 21D, manifold plates 21E, 21F, and 21G, a cover plate 21H, and a nozzle plate 21I. These plates are positioned in this order from the first surface 21a side of the flow path member 21. These plates are formed of a metal such as stainless steel (SUS).

[0075] A large number of holes are formed in the plates that make up the flow path member 21. The thickness of each plate is approximately 10 μm to 300 μm. This allows for high accuracy in forming the holes. The plates are aligned and stacked so that these holes communicate with each other to form the individual flow paths 164 and the supply manifold 161.

[0076] In the flow path member 21, the supply manifold 161 and the discharge holes 163 are connected by individual flow paths 164. The supply manifold 161 is located on the second surface 21b side inside the flow path member 21, and the discharge holes 163 are located on the second surface 21b of the flow path member 21.

[0077] The individual flow path 164 has a pressure chamber 162 and an individual supply flow path 165. The pressure chamber 162 is located on the first surface 21a of the flow path member 21, and the individual supply flow path 165 is a flow path that connects the supply manifold 161 and the pressure chamber 162.

[0078] Furthermore, the individual supply flow path 165 includes a restriction 166 that is narrower than the other portions. The restriction 166 has a high flow path resistance because it is narrower than the other portions of the individual supply flow path 165. When the flow path resistance of the restriction 166 is high in this way, the pressure generated in the pressure chamber 162 is less likely to escape to the supply manifold 161.

[0079] Next, the configurations of the piezoelectric element 170 and the reinforcing plate 172 will be described with reference to Figures 5 and 6. As shown in Figures 5 and 6, the piezoelectric element 170 has a piezoelectric ceramic body 171, a reinforcing plate 172, an internal electrode 173, a surface electrode 174, and a connection electrode 175.

[0080] The piezoelectric ceramic body 171 has a flat plate shape and is located on the first surface 21a of the flow path member 21 with a reinforcing plate 172 interposed therebetween.

[0081] The piezoelectric ceramic body 171 includes, for example, a plurality of piezoelectric ceramic layers 171a and 171b. The piezoelectric ceramic layers 171a and 171b each have a thickness of, for example, about 20 μm. Both of the piezoelectric ceramic layers 171a and 171b extend across the plurality of pressure chambers 162. The plurality of piezoelectric elements 170 share one piezoelectric ceramic body 171.

[0082] The piezoelectric ceramic layers 171a and 171b can be made of a ferroelectric ceramic material such as lead zirconate titanate (PZT).

[0083] Here, an example is shown in which the piezoelectric ceramic body 171 includes two piezoelectric ceramic layers 171a and 171b, but the piezoelectric ceramic body 171 may include three or more piezoelectric ceramic layers.

[0084] The piezoelectric ceramic layer 171b is an example of a diaphragm. Note that the diaphragm does not necessarily have to be a piezoelectric ceramic body such as PZT.

[0085] The internal electrode 173 is located inside the piezoelectric ceramic body 171. Specifically, the internal electrode 173 is located between the two piezoelectric ceramic layers 171a and 171b. The internal electrode 173 is formed over substantially the entire surface in the planar direction in the region between the piezoelectric ceramic layers 171a and 171b. In other words, the internal electrode 173 overlaps with all of the pressure chambers 162 in the region facing the piezoelectric actuator 22. The internal electrode 173 functions as a common electrode shared by multiple piezoelectric elements 170.

[0086] For example, a metal material such as Ag—Pd may be used for the internal electrode 173. The thickness of the internal electrode 173 is, for example, about 2 μm.

[0087] The internal electrode 173 is electrically connected through a via hole formed in the piezoelectric ceramic layer 171a to a connection electrode (not shown) located on the surface of the piezoelectric ceramic body 171. The connection electrode for the internal electrode 173 is grounded and maintained at ground potential.

[0088] The surface electrode 174 has an electrode body 174a and an extraction electrode 174b. The electrode body 174a is located in a region facing the pressure chamber 162. The electrode body 174a is slightly smaller than the pressure chamber 162 and has a shape that is approximately similar to the pressure chamber 162.

[0089] 5, the first embodiment shows, as an example, a case where the pressure chamber 162 and the electrode main body 174a are circular in plan view. However, the shapes of the pressure chamber 162 and the electrode main body 174a are not limited to this example. This point will be described later with reference to FIG. 16.

[0090] The extraction electrode 174b is extracted from the electrode body 174a. The extraction electrode 174b extends linearly toward a connection electrode 175, which will be described later. That is, the connection electrode 175 is located at a portion of one end of the extraction electrode 174b that is extracted to the outside of the region facing the pressure chamber 162.

[0091] The electrode body 174a and the extraction electrode 174b of the surface electrode 174 may be made of a metal material such as an Au-based material.

[0092] The connection electrode 175 has a convex shape with a thickness of, for example, about 15 μm. The connection electrode 175 is located on the surface of the piezoelectric ceramic body 171 and is connected to the surface electrode 174. Specifically, the connection electrode 175 is located on the extraction electrode 174b and is electrically connected to the electrode body 174a via the extraction electrode 174b. The connection electrode 175 is electrically joined to an electrode provided on the flexible substrate 31 (see FIG. 3).

[0093] The connection electrode 175 contains a metal that is more likely to cause ion migration than the metal (e.g., Au) contained in the surface electrode 174. For example, the connection electrode 175 contains Ag, Cu, Sn, Pb, and Ni. Specifically, the connection electrode 175 is made of silver-palladium containing glass frit. The connection electrode 175 is an example of a bump.

[0094] Furthermore, the piezoelectric actuator 22 has a dummy connection electrode 25 in addition to the connection electrode 175 required for electrically connecting the surface electrode 174 and the flexible substrate 31. The dummy connection electrode 25 has, for example, a convex shape and is located on the surface of the piezoelectric ceramic body 171. The dummy connection electrode 25 is an example of a bump.

[0095] In order to individually control the potential of the surface electrodes 174, each of them is electrically connected to the control unit 14 (see FIG. 1) via the connection electrodes 175, the flexible substrate 31, and wiring. When the surface electrodes 174 and the internal electrodes 173 are set to different potentials and an electric field is applied in the polarization direction of the piezoelectric ceramic layer 171a, the portion of the piezoelectric ceramic layer 171a to which the electric field is applied operates as an active portion that deforms due to the piezoelectric effect.

[0096] The reinforcing plate 172 has a flat plate shape. The reinforcing plate 172 is located between the flow path member 21 and the piezoelectric element 170. Specifically, the reinforcing plate 172 is located between the first surface 21a of the flow path member 21 and the back surface of the piezoelectric ceramic body 171, which is opposite to the front surface on which the front electrode 174 is located. The reinforcing plate 172 extends across the multiple pressure chambers 162 and forms a ceiling portion of the multiple pressure chambers 162. The multiple piezoelectric elements 170 share one reinforcing plate 172.

[0097] It should be noted that the head main body 20 does not necessarily have to have the reinforcing plate 172. In this case, the piezoelectric ceramic body 171 forms the ceiling portion of the plurality of pressure chambers 162.

[0098] That is, in the piezoelectric actuator 22, the surface electrode 174, the piezoelectric ceramic layer 171a, the reinforcing plate 172, and the portion of the internal electrode 173 that faces the pressure chamber 162 constitute a piezoelectric element 170. When the piezoelectric element 170 undergoes unimorph deformation, the pressure chamber 162 is pressed, and liquid is ejected from the ejection hole 163. The ejection hole 163 is an example of a nozzle that penetrates the nozzle plate 21I.

[0099] <Configuration of the first groove portion> 7 to 9 are schematic plan views of the piezoelectric element 170 according to the first embodiment. Note that in Fig. 7 to Fig. 9, the size of the first groove portion 100 is exaggerated for ease of understanding.

[0100] 7, the piezoelectric element 170 has first grooves 100. The first grooves 100 are located around (outside) the electrode body 174a of the surface electrode 174 in a plan view, and extend in a shape that corresponds to the outer shape of the electrode body 174a. That is, the first grooves 100 have a shape that is approximately similar to the outer shape of the electrode body 174a in a plan view.

[0101] 7, the first groove 100 extends in an arc shape along the outer shape of the circular electrode main body 174a so as to surround the electrode main body 174a. Both ends of the first groove 100 in the longitudinal direction are located outside the extraction electrode 174b so as to sandwich the extraction electrode 174b. Specifically, one end of the first groove 100 in the longitudinal direction faces one side surface of the extraction electrode 174b, and the other end faces the other side surface of the extraction electrode 174b.

[0102] In this way, by providing the first groove portion 100 around the electrode main body 174a, the rigidity of the piezoelectric ceramic body 171 can be reduced, and therefore the driving displacement of the piezoelectric element 170 can be increased compared to when the first groove portion 100 is not provided.

[0103] Here, as shown in Figure 7, when the outer edge of the first groove portion 100 is formed so as to follow the outer edge of the pressure chamber 162 in a planar perspective view, the driving displacement of the piezoelectric element 170 can be made larger than when the outer edge of the first groove portion 100 is formed so as not to follow the outer edge of the pressure chamber 162.

[0104] However, when the piezoelectric actuator 22 is bonded to the flow path member 21, the piezoelectric actuator 22 may be bonded in a state where it is deviated from the desired position relative to the flow path member 21. In other words, the position of the surface electrode 174 relative to the pressure chamber 162 may be deviated from the desired position. FIGS. 8 and 9 show the piezoelectric element 170 when the position of the surface electrode 174 is deviated from the desired position (for example, the position shown in FIG. 7) relative to the pressure chamber 162. For example, if the first groove portion 100 is formed based on the position of the surface electrode 174, there is a problem in that the position of the surface electrode 174 is deviated from the desired position. This results in an arrangement in which the outer edge of the first groove portion 100 does not align with the outer edge of the pressure chamber 162, and as a result, the driving displacement of the piezoelectric element 170 may be smaller than the desired value.

[0105] Therefore, the first groove portion 100 is formed at a position along the outer edge of the pressure chamber 162. Specifically, the configuration of the pressure chamber 162, the surface electrode 174, and the first groove portion 100 may satisfy the following formula (1), as shown in Fig. 8, when the maximum value of the distance between the outer edge of the pressure chamber 162 and the outer edge of the first groove portion 100 is A1 and the minimum value is A2, and the maximum value of the distance between the outer edge of the surface electrode 174 and the outer edge of the first groove portion 100 is B1 and the minimum value is B2. A1-A2 <B1―B2 ···(1)

[0106] With this configuration, the positional deviation between the outer edge of the pressure chamber 162 and the outer edge of the first groove portion 100 is smaller than the positional deviation between the outer edge of the electrode main body 174a and the outer edge of the first groove portion 100. In other words, the first groove portion 100 is disposed closer to the outer edge of the pressure chamber 162 than to the outer edge of the surface electrode 174, and even if a positional deviation occurs between the pressure chamber 162 and the surface electrode 174, the driving displacement of the piezoelectric element 170 is less likely to decrease.

[0107] Furthermore, as shown in FIG. 9, the configuration of the pressure chamber 162, the surface electrode 174, and the first groove portion 100 may satisfy the following formula (2), where the maximum value of the distance between the center point P3 of the pressure chamber 162 and the outer edge of the first groove portion 100 is C1 and the minimum value is C2, and the maximum value of the distance between the center point P1 of the surface electrode 174 and the outer edge of the first groove portion 100 is D1 and the minimum value is D2. C1-C2 <D1-D2 ···(2)

[0108] With this configuration, the positional deviation between the center of the pressure chamber 162 and the outer edge of the first groove portion 100 is smaller than the positional deviation between the center of the electrode main body 174a and the outer edge of the first groove portion 100. In other words, the first groove portion 100 is positioned so as to correspond more closely to the center point P3 of the pressure chamber 162 than to the center point P1 of the surface electrode 174, and therefore, even if a positional deviation occurs between the pressure chamber 162 and the surface electrode 174, the driving displacement of the piezoelectric element 170 is less likely to decrease.

[0109] Furthermore, the first groove portion 100 penetrates the piezoelectric actuator 22 in the thickness direction (see FIG. 10). With this configuration, the rigidity of the piezoelectric ceramic body 171 can be reduced compared to when the first groove portion 100 does not penetrate the piezoelectric actuator 22, and therefore the driving displacement of the piezoelectric element 170 can be further increased.

[0110] It should be noted that the first groove portion 100 does not necessarily need to penetrate the piezoelectric actuator 22 .

[0111] <Positional relationship between the first groove portion, pressure chamber, and surface electrode> Next, a description will be given of the positional relationship between the first groove portion 100 according to the first embodiment and the pressure chamber 162 and the surface electrode 174. Fig. 10 is a schematic plan view of the piezoelectric element 170 according to the first embodiment.

[0112] 10, it is assumed that the extraction electrode 174b extends from the electrode main body 174a in the positive direction of the X-axis (an example of a first direction). In this case, when a part of the outer edge of the first groove portion 100 is located outward from the outer edge of the pressure chamber 162 in a planar perspective view, the outer edge of the first groove portion 100 may be furthest from the outer edge of the pressure chamber in the positive X-axis direction among the positive X-axis direction, the negative X-axis direction (an example of a second direction), the positive Y-axis direction (an example of a third direction), and the negative Y-axis direction (an example of a fourth direction).

[0113] The same may also be true for the positional relationship between the first groove portion 100 and the electrode main body 174a. That is, the outer edge of the first groove portion 100 may be farthest from the outer edge of the electrode main body 174a in the positive X-axis direction among the positive X-axis direction, the negative X-axis direction, the positive Y-axis direction, and the negative Y-axis direction.

[0114] 10, because the extraction electrode 174b is located on the positive X-axis direction side of the electrode body 174a, the first groove portion 100 is not provided around the extraction electrode 174b so as not to overlap with the extraction electrode 174b. Therefore, the area of ​​the first groove portion 100 in the positive X-axis direction of the four directions is smaller than the area of ​​the first groove portion 100 in the other three directions. Therefore, when the outer edge of the first groove portion 100 is farthest from the outer edge of the pressure chamber 162 in the positive X-axis direction of the four directions, the driving displacement of the piezoelectric element 170 is less likely to decrease compared to the other directions.

[0115] The same applies to the positional relationship between the first groove portion 100 and the electrode main body 174a. When the outer edge of the first groove portion 100 is farthest from the center of the electrode main body 174a in the positive X-axis direction among the four directions, the driving displacement of the piezoelectric element 170 is less likely to decrease compared to the other directions.

[0116] <Positional relationship between first groove portion and surface electrode> Next, a description will be given of the positional relationship between the first groove portion 100 and the surface electrode 174 according to the first embodiment. Fig. 11 is a schematic plan view of the piezoelectric element 170 according to the first embodiment.

[0117] As described above with reference to Figure 8, in the first embodiment, in order to prevent the driving displacement of the piezoelectric element 170 from decreasing even if the position of the surface electrode 174 deviates from the desired position relative to the pressure chamber 162, the first groove portion 100 is formed at a position along the outer edge of the pressure chamber 162.

[0118] Here, if the pressure chamber 162 and the surface electrode 174 are misaligned in the left-right direction (Y-axis direction) by more than a threshold value, and the first groove portion 100 is formed in a position along the outer edge of the pressure chamber 162, there is a risk that the first groove portion 100 will overlap with the surface electrode 174. This will result in a portion of the surface electrode 174 being scraped off. In particular, if the extraction electrode 174b of the surface electrode 174 is scraped off, the wiring will be cut, and there is a risk that the ejection function will be reduced (lost).

[0119] Therefore, the first groove 100 is formed so as to ensure a certain distance or more from the extraction electrode 174b. Specifically, as shown in Fig. 11, the configuration of the first groove 100 and the surface electrode 174 may satisfy the following formula (3), where E1 is the distance between one end of the first groove 100 and the other end, E2 is the width of the extraction electrode 174b, and E3 is the average distance between the outer edge of the surface electrode 174 and the inner edge of the first groove 100. (E1-E2) / 2>E3 (3)

[0120] With this configuration, the extraction electrode 174b is less likely to be scraped off even if there is a left-right (Y-axis) misalignment between the surface electrode 174 and the first groove portion 100. As a result, compared to when the extraction electrode 174b of the surface electrode 174 is scraped off, a processing defect can be detected more quickly by a capacitance inspection, and the effect on the ejection function can be reduced.

[0121] <Size relationship between the first through hole and the second through hole> Next, a description will be given of the size relationship between the first through hole 21c and the second through hole 172g according to the first embodiment. Fig. 12 is a schematic cross-sectional view of the reinforcing plate 172 and the flow path member 21 according to the first embodiment.

[0122] As described above with reference to FIG. 4, the flow path member 21 has a first through hole 21c in a region located outside the piezoelectric actuator 22. The reinforcing plate 172 also has a second through hole 172g at a position corresponding to the first through hole 21c. In this case, as shown in FIG. 12, the second through hole 172g may be larger than the first through hole 21c in a planar perspective view. With this configuration, the position of the first through hole 21c in the flow path member 21 is clear in a planar perspective view, and the position of the outer edge of the pressure chamber 162 of the flow path member 21 can be easily grasped using the position of the first through hole 21c as a landmark. Therefore, when forming the first groove portion 100 in the piezoelectric actuator 22 after bonding the piezoelectric actuator 22, the reinforcing plate 172, and the piezoelectric actuator 22, the first groove portion 100 can be easily formed at a position along the outer edge of the pressure chamber 162 using the first through hole 21c as a reference.

[0123] Although the example in which the first through hole 21c and the second through hole 172g are both circular in plan view has been described here, the shapes of the first through hole 21c and the second through hole 172g are not limited to this example. For example, the shapes of the first through hole 21c and the second through hole 172g may be rectangular or elongated.

[0124] <Structure of the reinforcing plate> Next, the configuration of the reinforcing plate 172 according to the first embodiment will be described with reference to Figs. 13 to 15. Fig. 13 is a schematic cross-sectional view showing a main part of the head main body 20 according to the first embodiment. Fig. 14 is a schematic plan view showing a main part of the head main body 20 according to the first embodiment. Fig. 15 is a plan view showing the configuration of the reinforcing plate 172 according to the first embodiment.

[0125] 13, the reinforcing plate 172 may have second grooves 172c on a second surface 172b, which is the bonding surface with the piezoelectric actuator 22. As shown in FIG. 14, the second grooves 172c are formed at positions that do not overlap with the first grooves 100 and the pressure chambers 162 in a planar perspective. Specifically, the second grooves 172c are located outside the first grooves 100 and the pressure chambers 162 in a planar perspective. The dashed dotted lines in FIG. 14 indicate the sidewalls of the second grooves 172c.

[0126] In this way, by forming the second groove portion 172c on the bonding surface of the reinforcing plate 172 with the piezoelectric actuator 22, excess adhesive or air bubbles can be released (flowed into) the second groove portion 172c when bonding the piezoelectric actuator 22 and the reinforcing plate 172. This makes it less likely that transfer unevenness or air bubble entrapment will occur, and as a result, variations in ejection characteristics can be reduced. Furthermore, by forming the second groove portion 172c at a position that does not overlap with the first groove portion 100 and the pressure chamber 162, the possibility that the first groove portion 100 and the pressure chamber 162 will communicate with each other when the first groove portion 100 is formed can be reduced compared to when the second groove portion 172c is formed at a position that overlaps with the first groove portion 100 and the pressure chamber 162.

[0127] 15, the second groove portion 172c has a plurality of individual groove portions 172e and a collecting groove portion 172f. In a planar perspective, the plurality of individual groove portions 172e extend along the periphery of two or more of the plurality of pressure chambers 162. The collecting groove portion 172f communicates with the plurality of individual groove portions 172e.

[0128] The flow path member 21 has a communication hole 21d that communicates with the collecting groove 172f. The communication hole 21d opens to a second surface 21b (see FIG. 6), which is the surface of the flow path member 21 opposite to the surface where the reinforcing plate 172 is joined.

[0129] That is, the communication hole 21d of the flow path member 21 and the individual groove portion 172e of the second groove portion 172c are communicated with each other via the collecting groove portion 172f. Therefore, when the piezoelectric actuator 22 and the reinforcing plate 172 are bonded together, outgassing or bubbles that flow into the second groove portion 172c pass through the individual groove portion 172e, the collecting groove portion 172f, and the communication hole 21d and are released to the outside of the droplet ejection head 8. Therefore, the internal pressure of the second groove portion 172c is less likely to increase, and as a result, variations in the ejection characteristics can be reduced.

[0130] 13, the reinforcing plate 172 has a pillar portion 172d inside the second groove portion 172c. One end of the pillar portion 172d is located at the piezoelectric actuator 22, and the other end is located at the reinforcing plate 172.

[0131] In a planar perspective view, the pillar portion 172d is disposed at a position overlapping the connection electrode 175 or the dummy connection electrode 25 located on the surface of the piezoelectric actuator 22. In other words, no groove is formed in the reinforcing plate 172 vertically below the connection electrode 175 or the dummy connection electrode 25.

[0132] When electrically connecting the flexible substrate 31 and the piezoelectric actuator 22, a certain amount of pressure is applied to the connection electrode 175 and the dummy connection electrode 25. For this reason, if a groove is formed vertically below the connection electrode 175 or the dummy connection electrode 25, the pressure may not be able to be withstood, which may result in cracks occurring in the head main body 20. Therefore, by forming the pillar portion 172d inside the second groove portion 172c at a position that overlaps with the connection electrode 175 or the dummy connection electrode 25 in a planar perspective view as described above, the pressure can be withstood by the pillar portion 172d, making it less likely that cracks will occur in the head main body 20.

[0133] Thus, according to the droplet ejection head 8 according to the first embodiment, even if a positional deviation occurs between the pressure chamber 162 and the surface electrode 174, the driving displacement of the piezoelectric element 170 is unlikely to decrease.

[0134] (Second embodiment) <Piezoelectric element shape> Fig. 16 is a schematic plan view showing the configuration of a piezoelectric element 170 according to the second embodiment. The shape of the piezoelectric element 170 is not limited to the shape shown in Fig. 5. For example, as shown in Fig. 16, the shape of the piezoelectric element 170 may be a bowling pin shape.

[0135] Specifically, the pressure chamber 162 may have a diamond shape with rounded corners in a plan view. In this case, the electrode main body 174a of the surface electrode 174 also has a diamond shape with rounded corners in a plan view, matching the shape of the pressure chamber 162. The extraction electrode 174b extends linearly from an acute corner of the multiple corners of the electrode main body 174a toward the connection electrode 175. The connection electrode 175 is circular in a plan view.

[0136] In this case as well, the piezoelectric element 170 may have a first groove portion 100 (not shown here) that is located around the electrode body 174a of the surface electrode 174 and extends in a shape that corresponds to the outer shape of the electrode body 174a. Also in this case as well, the first groove portion 100 may be formed in a position that follows the outer edge of the pressure chamber 162.

[0137] In one embodiment, (1) a droplet ejection head (for example, droplet ejection head 8) has a nozzle (for example, ejection hole 163), a pressure chamber (for example, pressure chamber 162), and a piezoelectric element (for example, piezoelectric element 170). The nozzle ejects droplets. The pressure chamber is connected to the nozzle. The piezoelectric element deforms when a voltage is applied, thereby deforming the pressure chamber. The piezoelectric element has a surface electrode (for example, surface electrode 174) and a first groove portion (for example, first groove portion 100). The surface electrode faces the pressure chamber. The first groove portion is located around the surface electrode and extends in a shape that corresponds to the outer shape of the surface electrode. If the maximum value of the distance between the outer edge of the pressure chamber and the outer edge of the first groove portion in a planar perspective view is A1 and the minimum value is A2, and the maximum value of the distance between the outer edge of the surface electrode and the outer edge of the first groove portion in a planar perspective view is B1 and the minimum value is B2, the following formula (1) is satisfied. A1-A2 <B1―B2 ···(1)

[0138] (2) The droplet ejection head has a nozzle, a pressure chamber, and a piezoelectric element. The nozzle ejects droplets. The pressure chamber is connected to the nozzle. The piezoelectric element deforms when a voltage is applied to it, thereby deforming the pressure chamber. The piezoelectric element has a surface electrode and a first groove. The surface electrode faces the pressure chamber. The first groove is located around the surface electrode and extends in a shape that corresponds to the outer shape of the surface electrode. The pressure chamber and the surface electrode are circular in planar perspective, and when the maximum value of the distance between the center of the pressure chamber and the outer edge of the first groove in planar perspective is C1 and the minimum value is C2, and when the maximum value of the distance between the center of the surface electrode and the outer edge of the first groove in planar perspective is D1 and the minimum value is D2, the following formula (2) may be satisfied. C1-C2 <D1-D2 ···(2)

[0139] (3) In the droplet ejection head of (1) or (2) above, the surface electrode has an electrode main body (for example, electrode main body 174a) located in an area facing the pressure chamber and an extraction electrode (for example, extraction electrode 174b) extending in a first direction from the electrode main body, and when a part of the outer edge of the first groove portion is located outside the outer edge of the pressure chamber in a planar perspective view, the outer edge of the first groove portion may be farthest from the outer edge of the pressure chamber in the first direction among the first direction, the second direction opposite to the first direction, the third direction perpendicular to the first and second directions, and the fourth direction opposite to the third direction.

[0140] (4) In the droplet ejection head of (1) or (2) above, the surface electrode has an electrode main body located in an area facing the pressure chamber and an extraction electrode extending from the electrode main body in a first direction, and in a planar view, the outer edge of the first groove portion may be farthest from the outer edge of the electrode main body in the first direction among the first direction, a second direction opposite to the first direction, a third direction perpendicular to the first and second directions, and a fourth direction opposite to the third direction.

[0141] (5) In the droplet ejection head of any one of (1) to (4) above, the pressure chamber is circular in plan view, the surface electrode has an electrode body that is circular in plan view and located in an area facing the pressure chamber, and an extraction electrode that extends from the electrode body in a first direction, the first groove portion has an arc shape that surrounds the electrode body and is located outside the extraction electrode so that both ends sandwich the extraction electrode, and when, in plan view, the distance between one end and the other end of the first groove portion is E1, the width of the extraction electrode is E2, and the average value of the distance between the outer edge of the surface electrode and the inner edge of the first groove portion is E3, the following formula (3) may be satisfied. (E1-E2) / 2>E3 (3)

[0142] (6) Any one of the droplet ejection heads (1) to (5) above may have a flat-plate-shaped piezoelectric actuator (for example, piezoelectric actuator 22) having a plurality of piezoelectric elements, a flat-plate-shaped flow path member (for example, flow path member 21) having a plurality of pressure chambers, and a reinforcing plate (for example, reinforcing plate 172) located between the flow path member and the piezoelectric elements, wherein the flow path member and the reinforcing plate are larger than the piezoelectric actuator in a planar perspective view, the flow path member has a first through hole (for example, first through hole 21c) in an area located outside the piezoelectric actuator, and the reinforcing plate has a second through hole (for example, second through hole 172g) at a position corresponding to the first through hole, and the second through hole may be larger than the first through hole in a planar perspective view.

[0143] (7) In the droplet ejection head of (6) above, the first groove portion may penetrate the piezoelectric actuator in the thickness direction, and the reinforcing plate may have a second groove portion (for example, second groove portion 172c) on the adhesive surface with the piezoelectric actuator, outside the first groove portion and the pressure chamber when viewed from above.

[0144] (8) In the droplet ejection head of (7) above, the second groove portion has a plurality of individual groove portions (for example, individual groove portion 172e) extending along the periphery of two or more of the plurality of pressure chambers in a planar perspective view, and a collective groove portion (for example, collective groove portion 172f) communicating with the plurality of individual groove portions, and the flow path member has a communication hole (for example, communication hole 21d) communicating with the collective groove portion, and the communication hole may open on the surface opposite to the bonding surface with the reinforcing plate.

[0145] (9) In the droplet ejection head of (7) or (8) above, the reinforcing plate has a pillar portion (for example, pillar portion 172d) inside the second groove portion that contacts the piezoelectric actuator, and in plan view, the piezoelectric actuator may have a bump (for example, connection electrode 175, dummy connection electrode 25) at a position that overlaps with the pillar portion.

[0146] (10) A recording device (for example, a printer 1) may have a droplet ejection head according to any one of (1) to (9) above, and a control unit (for example, a control unit 14) that controls the droplet ejection head.

[0147] (11) A recording apparatus may have the droplet ejection head according to any one of (1) to (9) above, and an arm that holds the droplet ejection head.

[0148] The disclosed embodiments should be considered in all respects as illustrative and not restrictive. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0149] For example, the present disclosure may be applied to a recording device (painting robot) equipped with a droplet ejection head and an arm that holds the droplet ejection head. The painting robot can be used for painting vehicle bodies. The droplet ejection head used in the painting robot may eject highly viscous paint, have short paint ejection intervals, and eject a large amount of paint. Therefore, a decrease in ejection performance due to a decrease in the driving displacement of the piezoelectric element and ejection failure due to a broken wire may significantly affect the painting quality.

[0150] However, by applying the present disclosure, the reduction in the driving displacement of the piezoelectric element can be suppressed, the variation in displacement between pressure chambers can also be suppressed, and the probability of non-ejection due to broken wires can be reduced, thereby improving painting quality even when used in a painting robot. [Explanation of symbols]

[0151] 1. Printer 8 Droplet ejection head 14 Control Unit 20 Head body 21 Flow path member 21c 1st through hole 21d Communication hole 22 Piezoelectric Actuator 25 Dummy connection electrode 100 First groove 162 Pressure Chamber 163 Discharge hole 170 Piezoelectric element 171 Piezoelectric ceramic body 172 Reinforcement plate 172c 2nd groove 172d Pillar 172e Individual groove section 172f Collecting groove 172g 2nd through hole 173 Internal electrode 174 Surface electrode 174a Electrode body 174b Extraction electrode 175 connecting electrode

Claims

1. a nozzle for ejecting droplets; a pressure chamber connected to the nozzle; a piezoelectric element that deforms when a voltage is applied to the piezoelectric element, thereby deforming the pressure chamber; and The piezoelectric element is a surface electrode facing the pressure chamber; a first groove portion located around the surface electrode and extending in a shape corresponding to the outer shape of the surface electrode; and A droplet ejection head that satisfies the following formula (1), where the maximum value of the distance between the outer edge of the pressure chamber and the outer edge of the first groove portion in a planar perspective view is A1 and the minimum value is A2, and the maximum value of the distance between the outer edge of the surface electrode and the outer edge of the first groove portion in a planar perspective view is B1 and the minimum value is B2. A1-A2<B1-B2...(1)

2. a nozzle for ejecting droplets; a pressure chamber connected to the nozzle; a piezoelectric element that deforms when a voltage is applied to the piezoelectric element, thereby deforming the pressure chamber; and The piezoelectric element is a surface electrode facing the pressure chamber; a first groove portion located around the surface electrode and extending in a shape corresponding to the outer shape of the surface electrode; and the pressure chamber and the surface electrode are circular in plan view, A droplet ejection head that satisfies the following formula (2), where the maximum value of the distance between the center of the pressure chamber and the outer edge of the first groove portion in a planar perspective view is C1 and the minimum value is C2, and the maximum value of the distance between the center of the surface electrode and the outer edge of the first groove portion in a planar perspective view is D1 and the minimum value is D2. C1-C2<D1-D2...(2)

3. The surface electrode is an electrode body located in an area facing the pressure chamber; an extraction electrode extending in a first direction from the electrode body; and 2. The droplet ejection head of claim 1, wherein when a portion of the outer edge of the first groove portion is located outside the outer edge of the pressure chamber in a planar perspective view, the outer edge of the first groove portion is farthest from the outer edge of the pressure chamber in the first direction among the first direction, a second direction opposite to the first direction, a third direction perpendicular to the first direction and the second direction, and a fourth direction opposite to the third direction.

4. The surface electrode is an electrode body located in an area facing the pressure chamber; an extraction electrode extending in a first direction from the electrode body; and 2. The droplet ejection head of claim 1, wherein, in a planar view, the outer edge of the first groove portion is farthest from the outer edge of the electrode body in the first direction among the first direction, a second direction opposite to the first direction, a third direction perpendicular to the first direction and the second direction, and a fourth direction opposite to the third direction.

5. The pressure chamber has a circular shape in plan view, The surface electrode is an electrode body having a circular shape in a plan view and located in an area facing the pressure chamber; an extraction electrode extending in a first direction from the electrode body; and the first groove portion has an arc shape that surrounds the electrode body and is located outside the extraction electrode so that both ends thereof sandwich the extraction electrode, 2. A droplet ejection head as described in claim 1, wherein, in a planar view, when the distance between one end and the other end of the first groove portion is E1, the width of the extraction electrode is E2, and the average value of the distance between the outer edge of the surface electrode and the inner edge of the first groove portion is E3, the following formula (3) is satisfied. (E1-E2) / 2>E3...(3)

6. a flat-plate-shaped piezoelectric actuator having a plurality of the piezoelectric elements; a flat-plate-shaped flow path member having a plurality of the pressure chambers; a reinforcing plate positioned between the flow path member and the piezoelectric element; and When viewed from above, the flow path member and the reinforcing plate are larger than the piezoelectric actuator, the flow path member has a first through hole in a region located outside the piezoelectric actuator, the reinforcing plate has a second through hole at a position corresponding to the first through hole, The droplet ejection head according to claim 1 , wherein the second through-hole is larger than the first through-hole in a planar perspective view.

7. the first groove portion penetrates the piezoelectric actuator in a thickness direction, The reinforcing plate is The droplet ejection head according to claim 6 , wherein a second groove portion is provided on the adhesive surface to be bonded to the piezoelectric actuator, the second groove portion being located outside the first groove portion and the pressure chamber in a planar perspective view.

8. The second groove portion is a plurality of individual grooves extending along the peripheries of two or more of the pressure chambers in a plan view perspective; a collecting groove portion communicating with the plurality of individual groove portions; and the flow path member has a communication hole communicating with the collecting groove portion, The droplet ejection head according to claim 7 , wherein the communication hole opens to a surface opposite to a surface bonded to the reinforcing plate.

9. the reinforcing plate has a column portion in the second groove portion that contacts the piezoelectric actuator, The droplet ejection head according to claim 7 , wherein the piezoelectric actuator has a bump at a position overlapping the column portion in a planar perspective view.

10. The droplet ejection head according to claim 1 ; a control unit that controls the droplet ejection head.

11. The droplet ejection head according to claim 1 ; an arm that holds the droplet ejection head.

Images