Droplet discharge head, droplet discharge unit, and droplet discharge device

Abstract

To provide a technique for reducing a discharge speed difference between both ends and a center part in a single row of nozzle rows.SOLUTION: A droplet discharge head includes: a nozzle plate that forms nozzles for discharging droplets; a flow path plate that forms a pressure generation chamber communicating with the nozzles; a vibration plate that seals one surface of the pressure generation chamber; a laminated piezoelectric element as a pressure generation source that is provided on the side opposed to the pressure generation chamber via the vibration plate and generates pressure for discharging the droplets; and a support body that is fixed to the laminated piezoelectric element. There are the plurality of laminated piezoelectric elements correspondingly to the nozzles. On the basis of the correlation between the response speed time of the plurality of laminated piezoelectric elements and the discharge speed of the droplets from each nozzle, the widths of protrusions of the vibration plate are configured so as to compensate for the discharge speed difference in a single row of nozzle rows.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a droplet ejection head, a droplet ejection unit, and a droplet ejection device. [Background technology]

[0002] A droplet ejection device that ejects droplets is known. The droplet ejection device includes a droplet ejection unit that ejects liquid as droplets. The droplet ejection unit is configured to include a droplet ejection head. The droplet ejection head is formed by bonding a nozzle plate, a liquid chamber plate, a vibration plate, and a laminated piezoelectric element. The laminated piezoelectric element changes the pressure in the liquid chamber, and operates to eject the liquid in the liquid chamber from the nozzle as droplets.

[0003] The droplet ejection head is provided with a nozzle row in which a plurality of nozzles are arranged, and is configured to be able to eject droplets from each nozzle included in the nozzle row. It is known that in conventional droplet ejection heads, the response speed time of the laminated piezoelectric element is different between both ends and the center of one nozzle row. This difference in response time occurs as the ejection speed difference occurs in the manner that the ejection speed is slow in the center of one nozzle row, and the ejection speed continuously increases toward both ends.

[0004] In order to reduce the difference in ejection speed within a row of nozzles, a configuration has been disclosed in which a drive waveform can be selectively applied as a first drive signal or a second drive signal, thereby reducing the difference in ejection speed by using different drive signals at the center and ends (see, for example, Patent Document 1).

[0005] Also, in a high-density head, when the vibration area (diaphragm portion) of the diaphragm member is displaced to eject droplets, pressure fluctuations are transmitted to adjacent liquid chambers, causing unstable droplet ejection when the adjacent liquid chambers eject droplets, or causing liquid to drip from the nozzles when the adjacent liquid chambers do not eject droplets. A configuration has been disclosed that can reduce so-called mutual interference (see, for example, Patent Document 2). Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 1 discloses a configuration in which a drive waveform can be selectively applied as a first drive signal or a second drive signal, and therefore the difference in ejection speed can be reduced by using different drive signals at the center and ends. Patent Document 2 discloses a configuration in which the width of the protrusions on the drive side and the protrusions on the fixed side are made different.

[0007] However, neither Patent Document 1 nor Patent Document 2 can solve the problem that the response speed time of the laminated piezoelectric element differs between both ends and the center of a nozzle row. In other words, the conventional technology cannot solve the problem that a difference in ejection speed occurs in a nozzle row, where the ejection speed is slow in the center and continuously increases toward both ends.

[0008] An object of the present invention is to provide a technique for reducing the difference in ejection speed between the two ends and the center of a nozzle row. [Means for solving the problem]

[0009] In order to solve the above problem, one aspect of the present invention is a droplet ejection head having a nozzle plate forming a nozzle for ejecting droplets, a flow path plate forming a pressure generating chamber communicating with the nozzle, a vibration plate sealing one side of the pressure generating chamber, a laminated piezoelectric element provided on the side facing the pressure generating chamber via the vibration plate as a pressure generating source for generating pressure for ejecting droplets, and a support fixed to the laminated piezoelectric element, wherein there are a plurality of the laminated piezoelectric elements corresponding to the nozzles, and the width of the convex portion of the vibration plate is set so as to offset the difference in ejection speed within one row of the nozzles based on the correlation between the response speed time of the plurality of laminated piezoelectric elements and the ejection speed of droplets from each nozzle.

[0010] According to the present invention, it is possible to reduce the difference in ejection speed between the two ends and the center of one nozzle row. [Brief description of the drawings]

[0011] [Figure 1]FIG. 1 is a perspective view showing an embodiment of a droplet discharge unit according to the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing the configuration of a droplet ejection head according to the present invention. [Diagram 3] 11 is a graph showing the correlation between response time and ejection speed in a conventional droplet ejection head. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of a droplet discharge head, a droplet discharge unit, and a droplet discharge device according to the present invention will be described with reference to the drawings. Fig. 1 is a perspective view illustrating an example of the appearance of a droplet discharge unit 10. As shown in Fig. 1, the droplet discharge unit 10 has a housing formed of a head frame 11 as a support and a head cover 12, and is provided with a plurality of liquid supply ports 13 for introducing liquid into the inside.

[0013] Fig. 2 is an enlarged cross-sectional view of a portion of the droplet discharge head 1 as an internal configuration of the droplet discharge unit 10. As shown in Fig. 2, the droplet discharge head 1 mainly includes a pressure generating chamber 2 and a laminated piezoelectric element 5 that applies pressure to the pressure generating chamber 2 to discharge droplets. The droplet discharge head 1 is configured by laminating a nozzle plate 3 that forms a nozzle 4 that discharges droplets, a flow path plate 2a that forms a plurality of pressure generating chambers 2 that communicate with the nozzle 4, and a vibration plate 6 that seals one surface of the pressure generating chambers 2. The laminated piezoelectric element 5 applies pressure to the vibration plate 6 to vibrate it.

[0014] The diaphragm 6 has a protrusion 6a that receives pressure from the laminated piezoelectric element 5, and a diaphragm portion 6b that vibrates when subjected to pressure.

[0015] The droplet ejection head 1 has a plurality of nozzle rows arranged at high density, and has a plurality of laminated piezoelectric elements 5 arranged corresponding to each nozzle row, which serve as pressure generating sources for ejecting droplets. It also has a flexible printed circuit board (FPC: Flexible Printed Circuit) that transmits electrical signals from a higher-level device, a drive IC that is connected to the FPC and controls the drive of the laminated piezoelectric element 5, a head frame 11 that holds and fixes the droplet ejection head 1, and a liquid supply port 13 that supplies ejection liquid from the outside.

[0016] The droplet ejection head 1 can solve problems that arise when the response speed time of the laminated piezoelectric element 5 differs between both ends and the center of a row of nozzles 4 arranged by a nozzle plate 3 (nozzle row). In particular, it makes it possible to reduce the ejection speed difference that occurs when the ejection speed is slow in the center of a nozzle row and the ejection speed is continuously fast toward both ends.

[0017] The graph in Figure 3 (horizontal axis indicates the position of the nozzle 4 in the nozzle row, vertical axis indicates the ejection speed and response speed time) illustrates the correlation between the "response speed time" and "ejection speed" corresponding to the position of the nozzle 4 in the arrangement direction of the nozzle row. Figure 3 shows that the correlation between the response speed time and the ejection speed at the center and both ends of a nozzle row is such that the response speed time is short, and the ejection speed is slow in correlation with this. It also shows that the response speed time gets longer from the center to both ends of the row, and the ejection speed gets faster in correlation with this.

[0018] That is, the "response speed time" that contributes to the timing at which each piezoelectric element 5 pushes out a droplet becomes shorter when the ejection speed of the nozzle row is slow. On the other hand, the ejection speed becomes faster when the response speed time is long.

[0019] Therefore, the droplet ejection head 1 illustrated in FIG. 2 is configured so that the "response speed time" that contributes to the timing at which each piezoelectric element 5 pushes out a droplet is relatively long in the center of the row and relatively short at both ends.

[0020] That is, the width of the convex portion 6a at the center of the vibration plate 6 (the center of the nozzle row) is made relatively larger than the width of the convex portion 6a at both ends of the row (both ends of the nozzle row).The width of the convex portion 6a is continuously reduced from the center of the row toward both ends of the row.As a result, the internal pressure of the pressure generating chamber 2 at the center of the nozzle row where the width of the convex portion 6a is relatively large is higher than the internal pressure of the pressure generating chamber 2 at both ends, so the ejection speed of droplets from the nozzles 4 at the center of the row is faster than that of the nozzles 4 at both ends of the row.

[0021] In other words, the vibration plate 6 provided in the droplet ejection head 1 is configured such that the dimension in the row direction of the convex portion 6a that presses the diaphragm portion 6b that transmits pressure to the pressure generating chamber 2 is relatively larger at the center of the row than at both ends of the row, and the pressure inside the liquid chamber of the pressure generating chamber 2 is relatively smaller at both ends of the row than at the center of the row.

[0022] In addition, since the width of the protrusions 6a is continuously reduced from the center of the row toward both ends of the row, the pressure inside the liquid chamber of the pressure generating chamber 2 is continuously reduced from the center of the row toward both ends of the row. Therefore, the ejection speed is not relatively and continuously slowed down from the center of the row toward both ends of the row.

[0023] That is, like the droplet ejection head 1, the ejection speed is correlated with the response time that contributes to the timing of ejecting droplets of the laminated piezoelectric elements 5 in one nozzle row, and the ejection speed is slow in the center of the row (=shorter response time) and continuously faster toward both ends of the row (=longer response time), by combining the laminated piezoelectric elements 5 with the vibration plate 6. This makes it possible to reduce the difference in ejection speed within one nozzle row, and obtain stable droplet ejection characteristics.

[0024] The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the technical gist of the present invention. The present invention covers all technical matters included in the technical ideas described in the claims. The above-described embodiments are preferred examples, but a person skilled in the art can realize various modifications from the disclosed contents. Such modifications are also included in the technical scope described in the claims.

[0025] For example, aspects of the present invention are as follows. <1> a nozzle plate forming nozzles for ejecting droplets; a flow path plate forming a pressure generating chamber communicating with the nozzle; a vibration plate that seals one side of the pressure generating chamber; a laminated piezoelectric element as a pressure generation source that generates pressure for ejecting droplets, the laminated piezoelectric element being provided on a side facing the pressure generation chamber with the vibration plate therebetween; A droplet ejection head having The laminated piezoelectric element is provided in a plurality of layers corresponding to the nozzles, Based on the correlation between the response speed of the plurality of laminated piezoelectric elements and the ejection speed of droplets from each nozzle, a width of the convex portion of the vibration plate is set so as to offset a difference in ejection speed within one row of the nozzle rows; The droplet ejection head is characterized by the above. <2> In the case where the response speed of the piezoelectric elements in one row of the nozzles is slow in the center of the row, the ejection speed is slow, and the response speed is continuously fast toward both ends of the row, the ejection speed is fast, The width of the projection at the center of the row of the vibration plate is increased to increase the pressure inside the liquid chamber, thereby increasing the ejection speed, and the width of the projection is successively decreased toward both ends of the row to decrease the pressure inside the liquid chamber, thereby decreasing the ejection speed, thereby reducing the difference in the ejection speed. <1> The droplet ejection head according to claim 1, <3> a driving IC that controls the driving of the laminated piezoelectric element based on a signal transmitted from a host device; <1> or <2> A support that holds and fixes the droplet ejection head described in The droplet ejection unit is characterized by comprising: <4> The above <3> A droplet ejection device including the droplet ejection unit according to claim 1. [Explanation of symbols]

[0026] 1: Droplet ejection head 2: Pressure generating chamber 2a: Flow path plate 3: Nozzle plate 4: Nozzle 5: Multilayer piezoelectric element 6: Vibration plate 6a: Convex part 6b: Diaphragm part 10: Droplet ejection unit 11: Head frame 12: Head cover 13:Liquid supply port [Prior art documents] [Patent documents]

[0027] [Patent Document 1] JP 2021-138043 A [Patent Document 2] JP 2011-177922 A

Claims

1. a nozzle plate forming nozzles for ejecting droplets; a flow path plate forming a pressure generating chamber communicating with the nozzle; a vibration plate that seals one side of the pressure generating chamber; a laminated piezoelectric element as a pressure generating source that generates pressure for ejecting droplets, the laminated piezoelectric element being provided on a side opposite to the pressure generating chamber with the vibration plate therebetween; A droplet ejection head having a support fixed to the laminated piezoelectric element, The laminated piezoelectric element is provided in a plurality of layers corresponding to the nozzles, Based on the correlation between the response speed of the plurality of laminated piezoelectric elements and the ejection speed of droplets from each nozzle, The width of the convex portion of the vibration plate is set so as to offset the difference in ejection speed within one row of the nozzle rows. A droplet ejection head comprising:

2. In the case where the response speed of the piezoelectric elements in one row of the nozzles is slow in the center of the row, the ejection speed is slow, and the response speed is continuously fast toward both ends of the row, the ejection speed is fast, The droplet ejection head of claim 1, wherein the ejection speed difference is reduced by increasing the convex width in the center of the row of the vibration plate to increase the pressure inside the liquid chamber to increase the ejection speed, and by continuously decreasing the convex width toward both ends of the row to decrease the pressure inside the liquid chamber to slow the ejection speed.

3. a drive IC for controlling the driving of the laminated piezoelectric element based on a signal transmitted from a host device; and a frame for holding and fixing the droplet ejection head according to claim 1 or 2; A droplet ejection unit comprising:

4. A droplet ejection device comprising the droplet ejection unit according to claim 3 .

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