Liquid drop discharge head

Abstract

To provide a liquid drop discharge head having a configuration in which two nozzles communicate with one pressure chamber, in which not only selective discharge but also high resolution and high-speed recording are achieved.SOLUTION: Two nozzles 12N1, 12N2 communicate with one pressure chamber 12P. The pressure chamber 12P is arranged along a plane orthogonal to a vertical direction. The two nozzles 12N1, 12N2 are opened in a direction crossing with the plane. The nozzle 12N1 and the pressure chamber 12P are connected with each other by a connection flow path 12D1. The nozzle 12N2 and the pressure chamber 12P are connected with each other by a connection flow path 12D2. An inertance M1 [kg / m4] of a portion including the connection flow path 12D1 and the nozzle 12N1 and an inertance M2 [kg / m4] of a portion including the connection flow path 12D2 and the nozzle 12N2 are different from each other.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a droplet ejection head having a configuration in which two nozzles communicate with one pressure chamber. [Background technology]

[0002] Patent document 1 shows that in a configuration in which two nozzles are connected to one pressure chamber via first and second flow paths, in order to selectively eject droplets from the two nozzles, the positions of the upstream end openings connecting to the pressure chamber are shifted in the longitudinal direction of the pressure chamber between the first flow path and the second flow path, thereby making the propagation time of the pressure wave different. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-246863 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, to achieve selective ejection, the positions of the upstream end openings of the first and second flow paths are shifted in the longitudinal direction of the pressure chamber. As a result, the length of the pressure chamber in the longitudinal direction is long, making it impossible to achieve a high-density arrangement of individual flow paths including the pressure chamber, and therefore high resolution. In addition, because the size of the pressure chamber is large, the natural frequency of the individual flow paths is small, making it impossible to achieve high-speed recording.

[0005] An object of the present invention is to provide a droplet ejection head that is configured such that two nozzles communicate with one pressure chamber, and that is capable of not only selective ejection but also high-resolution and high-speed recording. [Means for solving the problem]

[0006] The droplet ejection head of the present invention comprises a pressure chamber arranged along a plane, a first nozzle opening in a direction intersecting the plane, a second nozzle opening in a direction intersecting the plane, a first connection flow path connecting the first nozzle to the pressure chamber, and a second connection flow path connecting the second nozzle to the pressure chamber, wherein the first connection flow path and the second connection flow path each include a first flow path extending in a direction parallel to the plane and a second flow path extending in a direction intersecting the plane, and are characterized by satisfying the following formula (1): M1≠M2...Equation (1) (where M1 is the inertance [kg / m 4 ], M2 is the inertance [kg / m 4 ].) [Effects of the Invention]

[0007] By satisfying equation (1), the propagation time of the pressure wave can be made different between the first and second connection flow paths, and thus the ejection speed function relative to the pulse width can be made different. This makes it possible to achieve selective ejection from two nozzles by adjusting the pulse width. Furthermore, with this configuration, there is no need to increase the size of the pressure chambers to achieve selective ejection, so small pressure chambers can be densely arranged to achieve high-resolution and high-speed recording. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a plan view of a printer 100 including a head 1 according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the printer 100. [Figure 3] FIG. [Figure 4] FIG. 4 is an enlarged view of region IV in FIG. 3. [Figure 5] FIG. 4 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] 10 is a graph showing an example of a drive signal X applied to a piezoelectric element 13X by a driver IC 14. [Figure 8] 10 is a graph showing the relationship between the width Tm of the main pulse Pm of the drive signal X and the ejection speed of ink droplets from the nozzles 12N1 and 12N2. [Figure 9] 10 is a graph showing the relationship between inertances M1 and M2, primary frequencies F1 and F2, and voltage ratio. [Figure 10] 6 is a cross-sectional view corresponding to FIG. 5, showing a head 2 according to a second embodiment of the present invention. [Figure 11] FIG. 5 is an enlarged view corresponding to FIG. 4 of a head according to a third embodiment of the present invention. [Figure 12A] 10 is a graph showing the relationship between the width Tm of the main pulse Pm of the drive signal X and the ejection speed of ink droplets from the nozzles 12N1 and 12N2 in the region above the curve L1 in FIG. 9. [Figure 12B] 10 is a graph showing the relationship between the width Tm of the main pulse Pm of the drive signal X and the ejection speed of ink droplets from the nozzles 12N1 and 12N2 in the region sandwiched between the curves L1 and L2 in FIG. 9. [Figure 12C] 10 is a graph showing the relationship between the width Tm of the main pulse Pm of the drive signal X and the ejection speed of ink droplets from the nozzles 12N1 and 12N2 in the region below the curve L2 in FIG. 9. [Figure 13] 10 is a graph similar to FIG. 9, showing the range satisfied by a head according to a fifth embodiment of the present invention. [Figure 14] 10 is an enlarged view corresponding to FIG. 4 of a head according to a sixth embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] First Embodiment The head 1 shown in Fig. 1 is a first embodiment of a droplet ejection head according to the present invention. The head 1 is included in a printer 100. The printer 100 comprises a housing 100A, a head unit 1X including four heads 1, a platen 3, a transport mechanism 4, and a control unit 5. The head unit 1X, platen 3, transport mechanism 4, and control unit 5 are arranged inside the housing 100A.

[0010] The length of the head unit 1X in the paper width direction is longer than the length of the head unit 1X in the transport direction. The head unit 1X is fixed to a housing 100A. The head unit 1X is a line type.

[0011] The paper width direction is the direction along the width of the paper 9 and is perpendicular to the vertical direction.

[0012] The four heads 1 included in the head unit 1X are arranged in a staggered pattern in the paper width direction. The length of the heads 1 in the paper width direction is longer than the length of the heads 1 in the transport direction.

[0013] The platen 3 is a plate along a plane perpendicular to the vertical direction, and is disposed below the head unit 1 X. A paper sheet 9 is supported on the upper surface of the platen 3.

[0014] The transport mechanism 4 includes a roller pair 41 having two rollers, a roller pair 42 having two rollers, and a transport motor 43 shown in Fig. 2. In the transport direction, the head unit 1X and the platen 3 are disposed between the roller pair 41 and the roller pair 42. The transport direction is perpendicular to the vertical direction and the paper width direction.

[0015] When the conveying motor 43 is driven under the control of the control unit 5, the rollers of the roller pair 41, 42 rotate. As the rollers of the roller pair 41, 42 rotate, the paper 9 sandwiched between the rollers of the roller pair 41, 42 is conveyed in the conveying direction.

[0016] As shown in FIG. 2, the control unit 5 includes a CPU 51, a ROM 52, and a RAM 53.

[0017] The CPU 51 executes various controls based on data input from an external device and in accordance with programs and data stored in the ROM 52 and RAM 53. The external device is, for example, a personal computer (PC).

[0018] The ROM 52 stores programs and data for the CPU 51 to perform various controls. The RAM 53 temporarily stores data used when the CPU 51 executes the programs.

[0019] Next, the configuration of the head 1 will be described.

[0020] As shown in FIG. 5, the head 1 includes a flow path member 12, an actuator member 13, and a sealing member 15 disposed between the flow path member 12 and the actuator member 13.

[0021] The flow path member 12 has six plates 11A to 11F. The plates 11A to 11F are stacked in the vertical direction and bonded to one another. Holes that form flow paths are formed in the plates 11A to 11F. The flow paths include a common flow path 12A and a plurality of individual flow paths 12B.

[0022] As shown in Fig. 3, the common flow path 12A extends in the paper width direction. A supply port 121 is connected to one end of the common flow path 12A in the paper width direction. A return port 122 is connected to the other end of the common flow path 12A in the paper width direction. The supply port 121 and the return port 122 open to the upper surface of the flow path member 12. The upper surface of the flow path member 12 is the upper surface of the uppermost plate 11A of the six plates 11A to 11F. The supply port 121 and the return port 122 communicate with an ink tank via tubes. The common flow path 12A communicates with the ink tank via the supply port 121 and the return port 122, and also communicates with multiple individual flow paths 12B.

[0023] The multiple individual flow paths 12B are arranged in a staggered pattern in the paper width direction, as shown in Fig. 3. Each of the multiple individual flow paths 12B includes a pressure chamber 12P, two nozzles 12N1 and 12N2, a connection flow path 12D1 that connects the nozzle 12N1 to the pressure chamber 12P, a connection flow path 12D2 that connects the nozzle 12N2 to the pressure chamber 12P, and a communication flow path 12E that connects the pressure chamber 12P to the common flow path 12A.

[0024] The nozzle 12N1 corresponds to the "first nozzle" of the present invention, and the nozzle 12N2 corresponds to the "second nozzle" of the present invention. The connection flow path 12D1 corresponds to the "first connection flow path" of the present invention, and the connection flow path 12D2 corresponds to the "second connection flow path" of the present invention.

[0025] As shown in Figure 4, the pressure chambers 12P are arranged along a plane perpendicular to the vertical direction. This plane corresponds to "one plane" in the present invention. The length of the pressure chambers 12P in the transport direction is longer than the length of the pressure chambers 12P in the paper width direction. The pressure chambers 12P have one end 12PX, which is the downstream end in the transport direction, and the other end 12PY, which is the upstream end in the transport direction.

[0026] The pressure chambers 12P are formed by holes formed in the plate 11A, and open to the upper surface of the flow path member 12, as shown in FIG.

[0027] 6, holes 29 are formed in the flow path member 12, each having one end 29X communicating with the pressure chamber 12P and the other end 29Y communicating with the atmosphere. The holes 29 are formed across the plates 11A to 11F, with the other end 29Y opening to the lower surface of the plate 11F. A meniscus is formed at the other end 29Y to absorb pressure fluctuations of the ink in the pressure chamber 12P. Because the hole 29 has a small flow path cross-sectional area, a long flow path length, and high flow path resistance, ink does not leak from the other end 29Y when ink is ejected from the nozzles 12N1 and 12N2 by driving the piezoelectric elements 13X described below.

[0028] As shown in FIGS. 4 and 5, the connection flow paths 12D1 and 12D2 connect the nozzles 12N1 and 12N2 to the other end 12PY of the pressure chamber 12P, respectively, and include a vertical hole 21, a horizontal flow path 22, and a vertical flow path .

[0029] FIG. 5 shows a cross section passing through the connection flow path 12D2 and the nozzle 12N2, but a cross section passing through the connection flow path 12D1 and the nozzle 12N1 also has a similar configuration.

[0030] As shown in FIG. 5, the vertical hole 21 is formed in the plate 11B and extends downward from the other end 12PY of the pressure chamber 12P.

[0031] As shown in FIG. 5, the horizontal flow path 22 is formed by a hole formed in the plate 11C and extends in the transport direction. The horizontal flow path 22 corresponds to the "first flow path" of the present invention. The transport direction is parallel to the plane in which the pressure chambers 12P are arranged and corresponds to the "extension direction" of the present invention. The horizontal flow path 22 has one end 22X, which is the downstream end in the transport direction, and the other end 22Y, which is the upstream end in the transport direction. The one end 22X is connected to the pressure chamber 12P, and the other end 22Y is connected to the vertical flow path 23. The one end 22X is connected to the pressure chamber 12P via the vertical hole 21.

[0032] As shown in FIG. 5, the vertical flow path 23 is formed by a hole formed in the plate 11E and extends in the vertical direction. The vertical flow path 23 corresponds to the "second flow path" of the present invention. The vertical direction is a direction that intersects with the plane in which the pressure chamber 12P is arranged. The vertical flow path 23 has one end 23X in the vertical direction, which is the upper end, and the other end 23Y in the vertical direction, which is the lower end. The one end 23X is connected to the horizontal flow path 22, and the other end 23Y is connected to the nozzles 12N1 and 12N2.

[0033] 5, the nozzles 12N1 and N2 are formed as holes formed in the plate 11F and open to the lower surface of the plate 11F. The lower surface of the plate 11F is the lower surface of the flow path member 12. The nozzles 12N1 and N2 open downward, that is, in a direction intersecting with the plane in which the pressure chambers 12P are arranged.

[0034] As shown in FIGS. 4 and 5, the communication flow path 12E connects the common flow path 12A and one end 12PX of the pressure chamber 12P, and includes a vertical hole 24, a horizontal flow path 25, and a vertical hole 26.

[0035] As shown in FIG. 5, the vertical hole 24 is formed in the plate 11B and extends downward from one end 12PX of the pressure chamber 12P.

[0036] As shown in FIG. 5, the horizontal flow path 25 is formed by a hole formed in the plate 11C. As shown in FIG. 4, the horizontal flow path 25 extends in a direction intersecting both the transport direction and the paper width direction along a plane perpendicular to the vertical direction, i.e., along the plane in which the pressure chambers 12P are arranged. The horizontal flow path 25 corresponds to the "third flow path" of the present invention. The horizontal flow path 25 has one end 25X and the other end 25Y. The one end 25X is connected to the pressure chamber 12P, and the other end 25Y is connected to the common flow path 12A. The one end 25X is connected to the pressure chamber 12P via a vertical hole 24, and the other end 25Y is connected to the common flow path 12A via a vertical hole 26.

[0037] 5, the plate 11C has both holes that define the horizontal flow paths 22 and holes that define the horizontal flow paths 25. The horizontal flow paths 22 and 25 are arranged throughout the entire thickness of the plate 11C.

[0038] As shown in FIG. 5, the vertical hole 26 is formed in the plate 11D and extends upward from the upper surface of the common flow channel 12A.

[0039] The ink in the ink tank is supplied to the common flow path 12A through the supply port 121 by driving the pump 10 shown in Figure 2 under the control of the control unit 5, and is distributed from the common flow path 12A to multiple individual flow paths 12B (see Figure 3).

[0040] When the volume of the pressure chamber 12P is reduced by driving the piezoelectric element 13X, which will be described later, pressure is applied to the ink in the pressure chamber 12P. The pressurized ink passes through the connection flow path 12D1 and / or the connection flow path 12D2 and is ejected as ink droplets from the nozzle 12N1 and / or the nozzle 12N2.

[0041] The ink that is supplied to the common flow path 12A via the supply port 121 but is not distributed to the individual flow paths 12B returns to the ink tank via the return port 122.

[0042] 5, the sealing member 15 is disposed on the upper surface of the flow path member 12 so as to cover the pressure chambers 12P. The sealing member 15 is made of a material with low ink permeability, such as stainless steel.

[0043] 5, the actuator member 13 is fixed to the upper surface of the flow path member 12 via a sealing member 15. The actuator member 13 includes piezoelectric layers 13A and 13B, a plurality of individual electrodes 13C, and a common electrode 13D. The piezoelectric layers 13A and 13B and the common electrode 13D are arranged to cover the plurality of pressure chambers 12P. An individual electrode 13C is provided for each pressure chamber 12P and is arranged to overlap that individual pressure chamber 12P in the vertical direction.

[0044] The portion of the actuator member 13 that overlaps the pressure chamber 12P in the vertical direction functions as a piezoelectric element 13X. The piezoelectric element 13X can be deformed independently in response to the potential applied to the individual electrode 13C. The piezoelectric element 13X is a bulk piezoelectric element, not a thin-film piezoelectric element. A thin-film piezoelectric element is a micro device, known as a micro electro mechanical system (MEMS), in which multiple piezoelectric elements are integrated by sequentially depositing thin films such as electrode films and piezoelectric films on a substrate. A bulk piezoelectric element is a piezoelectric element formed by stacking multiple piezoelectric sheets obtained by firing.

[0045] The individual electrodes 13C and the common electrode 13D are electrically connected to a driver IC 14. The driver IC 14 maintains the potential of the common electrode 13D at ground potential while changing the potential of the individual electrode 13C. The common electrode 13D is an electrode common to the piezoelectric elements 13X.

[0046] The driver IC 14 generates a drive signal based on a control signal from the control unit 5 and supplies the drive signal to the individual electrode 13C. The drive signal changes the potential of the individual electrode 13C between a predetermined drive potential VDD and the ground potential.

[0047] An example of a drive signal is shown in FIG.

[0048] 7 includes three rectangular pulses within one ejection period (the time from time t0 to time t1) for forming one dot. The three pulses include a main pulse Pm, a pre-pulse Pp applied before the main pulse Pm, and a cancel pulse Pc applied after the main pulse Pm.

[0049] The main pulse Pm is used to eject ink droplets of a predetermined volume from the nozzles 12N1 and 12N2. The pre-pulse Pp and cancel pulse Pc are used to prevent satellite droplets, and have widths Tp and Tc that are smaller than the width Tm of the main pulse Pm. Satellite droplets are generated when the tail of an ink droplet separates from the main ink droplet, and have a smaller volume than the main droplet. The pre-pulse Pp cancels the pressure wave in the pressure chamber 12P that was generated in the previous ejection cycle. The cancel pulse Pc cancels the pressure wave in the pressure chamber 12P that was generated by the application of the main pulse Pm in the current ejection cycle.

[0050] By adjusting the width Tm of the main pulse Pm, it is possible to selectively eject ink droplets from one of the two nozzles 12N1 and 12N2, the other, or both. To achieve this selective ejection and also achieve high resolution and high speed recording, the inventors of the present application have determined the inertance M1 [kg / m] of the portion consisting of the connection flow path 12D1 and the nozzle 12N1. 4 ] and the inertance M2 [kg / m 4 It has been found that it is effective to make the above two different from each other.

[0051] That is, the head 1 satisfies the following formula (1). M1≠M2...Equation (1) By satisfying equation (1), the propagation time of the pressure wave can be made different between the connection flow paths 12D1 and 12D2, and thus the function of the ejection speed with respect to the width Tm (see FIG. 8) can be made different. As a result, by adjusting the width Tm, selective ejection from the two nozzles 12N1 and 12N2 can be achieved. Furthermore, with this configuration, there is no need to increase the size of the pressure chambers 12P to achieve selective ejection, so small pressure chambers 12P can be densely arranged to achieve high-resolution and high-speed recording.

[0052] In this embodiment, the inertance M1a [kg / m 4 ] and the inertance M2a [kg / m 4 That is, the head 1 further satisfies the following formula (2). M1a≠M2a...Equation (2) By adopting a configuration that satisfies the formula (2), the formula (1) can be easily satisfied.

[0053] Specifically, as shown in Fig. 4, the horizontal flow path 22 of the connection flow path 12D1 has a smaller flow path width than the horizontal flow path 22 of the connection flow path 12D2, except for one end 22X and the other end 22Y. The flow path width is the length in the paper width direction. The cross-sectional area of ​​the horizontal flow path 22 of the connection flow path 12D1 is smaller than the cross-sectional area of ​​the horizontal flow path 22 of the connection flow path 12D2. The inertance of a flow path is calculated by dividing the cross-sectional area of ​​the flow path by S [m 2 ], the length of the flow path is L [m], and the density of the ink in the flow path is ρ [kg / m 3 ], then ρL / S [kg / m 4 The horizontal flow paths 22 of the connecting flow paths 12D1 and the horizontal flow paths 22 of the connecting flow paths 12D1 have substantially the same flow path length. Therefore, in this embodiment, M1a>M2a.

[0054] The head 1 further satisfies the following formulas (3) and (4). M1c≦M1n...Equation (3) M2c≦M2n...Equation (4) Here, M1c is the inertance [kg / m 4 ], M1n is the inertance of nozzle 12N1 [kg / m 4 ], M2c is the inertance of the connecting flow path 12D2 [kg / m 4 ], M2n is the inertance of nozzle 12N2 [kg / m 4 ]. If the inertance of the connecting flow paths 12D1 and 12D2 is greater than the inertance of the nozzles 12N1 and 12N2, the pressure wave is likely to be reflected at the connecting flow paths 12D1 and 12D2. In this case, it is necessary to increase the drive voltage applied to the piezoelectric element 13X in order to propagate the pressure wave to the nozzles 12N1 and 12N2. In this regard, with this configuration, since equations (3) and (4) are satisfied, the pressure wave is less likely to be reflected at the connecting flow paths 12D1 and 12D2, and the drive voltage applied to the piezoelectric element 13X can be reduced.

[0055] Furthermore, the inventors of the present application have found that in order to reduce the drive voltage applied to the piezoelectric element 13X, it is effective for the head 1 to satisfy the following formulas (5), (6), and (7). F1=F2...Equation (5) M1≧2.99×10 4 ×F1^2-1.11×10 7 ×F1+1.06×10 9 ...Equation (6) M2≦6.11×10 1 ×F2^3-2.41×10 4 ×F2^2+1.86×10 6 ×F2+1.10×10 8 ...Equation (7) (Here, F1 is the primary frequency [kHz] of the connection flow path 12D1, and F2 is the primary frequency [kHz] of the connection flow path 12D2.) The primary frequencies F1 and F2 are mainly governed by the configuration of the communication flow path 12E, but may also be affected by the configurations of the connection flow paths 12D1 and 12D2 and the nozzles 12N1 and 12N2, the presence or absence of dampers, and the like.

[0056] Figure 9 shows the results of an analysis conducted by the inventors. Figure 9 shows that there is a correlation between the inertances M1 and M2, the primary frequencies F1 and F2, and the voltage ratio. The voltage ratio is a ratio when the drive voltage when the ejection speed reaches a predetermined speed (for example, 7 m / s) is set to "1" when the ink viscosity is 7 cps, the ink tension is 24 mN / m, and the configuration of the individual flow path 12B other than the connecting flow path is predetermined.

[0057] In FIG. 9, curves L1 and L2 are lines along the voltage ratio of 104%. Curve L1 is the line of the formula "2.99 x 10 4 ×F1^2-1.11×10 7 ×F1+1.06×10 9 " and curve L2 is approximated by the formula "6.11 x 10 1 ×F2^3-2.41×10 4 ×F2^2+1.86×10 6 ×F2+1.10×10 8 " is approximated.

[0058] The area above curve L1 is the area where the voltage ratio is 104% or less, and is defined by formula (6). The area below curve L2 is the area where the voltage ratio is 104% or less, and is defined by formula (7). When formulas (5), (6), and (7) are satisfied, the voltage ratio is 104% or less, and the drive voltage applied to piezoelectric element 13X can be reduced.

[0059] The head 1 has a hole 29 having one end 29X that communicates with the pressure chamber 12P and the other end 29Y that communicates with the atmosphere, and the hole 29 has a meniscus formed at the other end 29Y that absorbs pressure fluctuations of the ink in the pressure chamber 12P (see FIG. 6). When two nozzles 12N1 and 12N2 communicate with one pressure chamber 12P as in this embodiment, the high-frequency components of the pressure wave that are generated in the connection flow paths 12D1 and 12D2, reflected by the nozzles 12N1 and 12N2, and returned to the pressure chamber 12P are twice as strong as in a configuration in which one nozzle communicates with one pressure chamber 12P. In this case, the pressure wave generated by driving the piezoelectric element 13X in the pressure chamber 12P is combined with the returned high-frequency components, which complicates the waveform of the pressure wave and may result in the formation of satellite droplets. In this regard, in this configuration, the pressure fluctuations inside the pressure chamber 12P are absorbed by the holes 29, so high frequency components are reduced and satellite droplets can be prevented.

[0060] One plate 11C has both holes that define the horizontal flow path 22 and holes that define the horizontal flow path 25 (see FIG. 5). When the horizontal flow paths 22 and 25 are arranged on separate plates, the horizontal flow paths 22 and 25 are formed in separate processes. In this case, the dimensional variations occurring in each process are compounded, resulting in large dimensional variations between the horizontal flow paths 22 and 25, making it impossible for the desired pressure wave to propagate to the nozzles 12N1 and 12N2. In this regard, in the present configuration, the horizontal flow paths 22 and 25 are arranged on the same plate 11C, so the horizontal flow paths 22 and 25 can be formed in the same process. In this case, the above-mentioned dimensional variations are not compounded, and the dimensional variations between the horizontal flow paths 22 and 25 can be suppressed. Consequently, the desired pressure wave can propagate to the nozzles 12N1 and 12N2.

[0061] The horizontal flow paths 22, 25 are arranged across the entire thickness of the plate 11C. In this case, the vertical lengths of the horizontal flow paths 22, 25 can be made constant, compared to when the horizontal flow paths 22, 25 are arranged in part of the thickness of the plate 11C by half-etching or the like. Consequently, the sizes of the horizontal flow paths 22, 25 can be made as designed.

[0062] The other end 22Y of the horizontal flow path 22 in the connecting flow path 12D1 and the other end 22Y of the horizontal flow path 22 in the connecting flow path 12D1 are positioned in the transport direction (see FIG. 4). In this case, the length of the entire individual flow path including the connecting flow path in the extension direction (in the embodiment, the longitudinal direction of the pressure chamber) can be reduced. This makes it possible to more reliably achieve a high-density arrangement of the individual flow paths, and therefore higher resolution.

[0063] Second Embodiment 10 is a second embodiment of a droplet ejection head according to the present invention. Head 2 differs from head 1 of the first embodiment in that flow path member 12 has five plates 11A, 11C to 11F, i.e., plate 11B of the first embodiment is omitted.

[0064] The connecting flow paths 12D1 and 12D2 of this embodiment each include a horizontal flow path 22 and a vertical flow path 23, and do not include the vertical hole 21 (see FIG. 5) of the first embodiment. One end 22X of the horizontal flow path 22 is connected to the pressure chamber 12P without passing through the vertical hole 21. Similarly, the communicating flow path 12E of this embodiment includes a horizontal flow path 25 and a vertical hole 26, and does not include the vertical hole 24 (see FIG. 5) of the first embodiment. One end 25X of the horizontal flow path 25 is connected to the pressure chamber 12P without passing through the vertical hole 24.

[0065] When the above formula (2) is satisfied, one of the two connecting channels 12D1, 12D2 has a large inertance of the horizontal channel 22. In this case, by directly connecting the horizontal channel 22 with the large inertance to the pressure chamber 12P, the high-frequency components of the pressure wave can be reduced, and satellite droplets can be prevented.

[0066] Furthermore, in this embodiment, the plate 11B is omitted and the number of components of the head 2 is reduced, so the structure is simplified and manufacturing is easy.

[0067] Third Embodiment A head according to a third embodiment of the present invention will be described with reference to Fig. 11. The head of this embodiment differs from the first embodiment (see Fig. 4) in the configuration of the horizontal flow path 322 in the connection flow path 12D2.

[0068] 11, the horizontal flow path 322 includes two flow path sections 22A and 22B. The two flow path sections 22A and 22B are aligned in the paper width direction and extend in the transport direction. The two flow path sections 22A and 22B share one end 322X and the other end 322Y of the horizontal flow path 322.

[0069] A partition wall 22C is disposed within the horizontal flow path 322. The partition wall 22C extends in the transport direction in a region between one end 322X and the other end 322Y of the horizontal flow path 322, dividing the region into two. The two divided regions constitute flow path sections 22A and 22B. The partition wall 22C is interposed between the two flow path sections 22A and 22B.

[0070] The resistance of the horizontal flow path 22 of the connection flow path 12D1 and the combined resistance of the two flow path portions 22A and 22B of the connection flow path 12D2 are the same.

[0071] It is conceivable that formula (2) above can be satisfied by making the flow path cross-sectional areas of the horizontal flow paths 22 different between the connection flow paths 12D1 and 12D2. However, in this case, during initial introduction or purging, ink does not easily flow into the horizontal flow path 22 with the smaller flow path cross-sectional area, making it difficult to discharge air through that horizontal flow path 22. In this regard, in the present configuration, even when the flow path cross-sectional areas of the horizontal flow paths 22 are made different between the connection flow paths 12D1 and 12D2, the resistances of the two horizontal flow paths 22 are the same, so during initial introduction or purging, a sufficient amount of ink flows through both of the two horizontal flow paths 22, and air can be discharged through both of the two horizontal flow paths 22.

[0072] The initial introduction refers to introducing ink from an ink tank into the flow path in the head, and the purging refers to forcibly ejecting ink from the nozzles by driving a pump.

[0073] Furthermore, by providing the partition wall 22C, the two flow path portions 22A and 22B can be easily formed.

[0074] <Fourth embodiment> The head according to the fourth embodiment of the present invention satisfies the following formulas (8), (9), and (10) instead of the above formulas (5), (6), and (7). F1≠F2...Formula (8) M1<2.99×10 4 ×F1^2-1.11×10 7 ×F1+1.06×10 9 ...Equation (9) M2>6.11×10 1 ×F2^3-2.41×10 4 ×F2^2+1.86×10 6 ×F2+1.10×10 8 ...Equation (10)

[0075] If formula (8) is not satisfied, the range of M1 and M2 corresponding to the desired drive voltage is narrow, and M1 is likely to be approximately equal to M2. Specifically, in FIG. 9, when the horizontal axes F1 and F2 are the same value and the voltage ratio is 104% or more, the range that M1 and M2 can take is narrow. For example, when F1=F2=170 kHz, to achieve a voltage ratio of 104% or more, M1 and M2 must be approximately 2.9×10 7 ~3.6×10 7 kg / m 4 If the values ​​of M1 and M2 are similar, the ejection speed function (see FIG. 8) relative to the pulse width will be similar in the connection flow path 12D1 and the connection flow path 12D2, making it difficult to achieve selective ejection. In this regard, according to this configuration, by satisfying formula (8), the range that M1 and M2 can take can be widened, and the values ​​of M1 and M2 can be prevented from becoming similar. This makes it possible to more reliably achieve selective ejection.

[0076] When formulas (9) and (10) are satisfied, the region between curves L1 and L2 in FIG. 9 corresponds to the region, and the voltage ratio exceeds 104%. In this case, the driving voltage applied to the piezoelectric element 13X is high. The inventors of the present application have found that the driving voltage affects the function of the ejection speed relative to the pulse width. Specifically, in the region above curve L1 in FIG. 9, the ejection speed changes relative to the pulse width as shown in FIG. 12A. In the region between curves L1 and L2 in FIG. 9, the ejection speed changes relative to the pulse width as shown in FIG. 12B. In the region below curve L2 in FIG. 9, the ejection speed changes relative to the pulse width as shown in FIG. 12C. In other words, when formulas (9) and (10) are satisfied, the change in the ejection speed relative to the pulse width is gradual, as shown in FIG. 12B. Therefore, ejection speed variation is unlikely to occur among multiple drive signals with different pulse widths. Furthermore, even if the pulse width is changed when ink droplets are ejected from one of the two nozzles 12N1, 12N2, when ink droplets are ejected from the other, or when ink droplets are ejected from both one and the other, variation in the ejection speed is unlikely to occur.

[0077] Fifth Embodiment The head according to the fifth embodiment of the present invention satisfies the following formulas (8), (11), and (12) instead of the above formulas (5), (6), and (7): Formula (8) is the same as in the fourth embodiment. F1≠F2...Formula (8) M1≦-1.23×10 6 ×F1+2.32×10 8 ...Equation (11) M2≦-1.23×10 6 ×F2+2.32×10 8 ...Equation (12)

[0078] When formulas (11) and (12) are satisfied, the voltage ratio is approximately 101% or less, which corresponds to the region below the line L3 in Fig. 13. In this case, the drive voltage applied to the piezoelectric element 13X can be reduced.

[0079] In this embodiment, when F1>F2 and M1>M2, the following formula (13) is further satisfied. M1-M2=-1.23×106 ×(F1 - F2) ··· Equation (13)

[0080] When Equation (13) is satisfied, the peak value of the ejection speed of the ink droplets from one of the two nozzles 12N1 and 12N2 can be aligned with the peak value of the ejection speed of the ink droplets from the other of the two nozzles 12N1 and 12N2. Thereby, landing deviation that may occur when the peak values are different can be prevented.

[0081] <Sixth Embodiment> The head according to the sixth embodiment of the present invention will be described with reference to FIG. 14. In the head of this embodiment, the configuration of the horizontal flow path 625 in the communication flow path 12E is different from that of the first embodiment (see FIG. 4).

[0082] As shown in FIG. 14, one end 625X of the horizontal flow path 625 is located not at the center in the paper width direction of the pressure chamber 12P but near one end in the paper width direction of the pressure chamber 12P. As a result, the distance A1 between one end 22X of the horizontal flow path 22 of the connection flow path 12D1 and one end 25X of the horizontal flow path 25 of the communication flow path 12E is smaller than the distance A2 between one end 22X of the horizontal flow path 22 of the connection flow path 12D2 and one end 25X of the horizontal flow path 25 of the communication flow path 12E (A1 < A2). The distances A1 and A2 are distances along the plane in which the pressure chamber 12P is arranged, respectively.

[0083] The configuration of this embodiment is effective when M1a > M2a. When M1a > M2a, in the configuration of the first embodiment (see FIG. 4), at the time of initial introduction or purging, it is difficult for ink to flow through the horizontal flow path 22 of the connection flow path 12D1, and it is difficult to discharge air through the connection flow path 12D1. In this regard, in this configuration, since A1 < A2, ink easily flows from the horizontal flow path 625 through the pressure chamber 12P into the horizontal flow path 22 of the connection flow path . Therefore, at the time of initial introduction or purging, ink also easily flows through the horizontal flow path 22 of the connection flow path 12D1, and air can be discharged through both of the connection flow paths 12D1 and 12D1.

[0084] <Modification Example> While the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design modifications are possible within the scope of the claims.

[0085] For example, in the above-described embodiment, the other end 29Y of the hole 29 (see FIG. 6) opens to the lower surface of the flow path member 12, but this is not limiting. For example, the other end 29Y may open to the side surface or upper surface of the flow path member 12.

[0086] In the above-described embodiment, the electrodes constituting the piezoelectric element have a two-layer structure including an individual electrode and a common electrode, but may have a three-layer structure. For example, a three-layer structure is a structure including a drive electrode to which a high potential or a low potential is selectively applied, a high-potential electrode that is maintained at a high potential, and a low-potential electrode that is maintained at a low potential.

[0087] The piezoelectric element may be a thin film piezoelectric element.

[0088] In the third embodiment (see FIG. 11), the two flow path portions 22A, 22B are aligned in the paper width direction, but this is not limiting and they may be aligned in the vertical direction, for example. Also, in the third embodiment (see FIG. 11), the partition wall 22C is provided, but the partition wall 22C may be omitted, and a configuration may be adopted which includes a flow path portion formed by the horizontal flow path 22 similar to that of the first embodiment, and another flow path portion which shares the other end 22Y of the horizontal flow path 22 with the flow path portion and extends from the other end 22Y to the pressure chamber 12P.

[0089] In the above-described embodiment, the extension direction of the first flow path is the longitudinal direction of the pressure chamber, but is not limited to this. For example, the extension direction may be a direction that intersects both the transport direction and the paper width direction in the above-described embodiment.

[0090] The positional relationship between the first flow path and the second flow path is not limited. For example, the vertical positional relationship between the horizontal flow path 22 and the vertical flow path 23 may be reversed from that in the above-described embodiment. In this case, the horizontal flow path 22 is connected to the nozzles 12N1 and 12N2, and the vertical flow path 23 is connected to the other end 12PY of the pressure chamber 12P.

[0091] The type of droplet ejection head is not limited to the line type, but may be a serial type.

[0092] The object onto which the droplets are ejected is not limited to paper, but may be, for example, a cloth, a substrate, or plastic.

[0093] The droplets ejected from the nozzles are not limited to ink droplets, but may be droplets of a treatment liquid that aggregates or precipitates components in the ink, for example.

[0094] The present invention is not limited to printers, but can also be applied to facsimiles, copiers, and multifunction peripherals. The present invention can also be applied to droplet ejection devices used for purposes other than image recording. For example, the present invention can be applied to a droplet ejection device that ejects a conductive liquid onto a substrate to form a conductive pattern. [Explanation of symbols]

[0095] 1;2 head (droplet ejection head) 11A~11F Plates 12A Common flow path 12B Individual flow path 12P pressure chamber 12N1 Nozzle (1st Nozzle) 12N2 nozzle (second nozzle) 12D1 Connection channel (first connection channel) 12D2 Connection channel (second connection channel) 22;322 Horizontal channel (first channel) 22A, 22B flow path section 22C Partition wall 22X;322X One end 22Y;322Y other end 23 Vertical flow path (second flow path) 23X one end 23Y other end 25;625 horizontal channel (third channel) 25X;625X one end 25Y other end 29 holes 29X one end 29Y other end

Claims

1. pressure chambers arranged along one plane; a first nozzle opening in a direction intersecting the plane; a second nozzle opening in a direction intersecting the plane; a first connection flow path that connects the first nozzle and the pressure chamber; a second connection flow path that connects the second nozzle and the pressure chamber, the first connection flow path and the second connection flow path each include a first flow path extending in a direction parallel to the one plane and a second flow path extending in a direction intersecting the one plane, A droplet ejection head characterized by satisfying the following formula (1): M1≠M2...Formula (1) (where M1 is the inertance [kg / m 4 ], M2 is the inertance [kg / m 4 ].)

2. The droplet ejection head according to claim 1 , further satisfying the following formula (2): M1a≠M2a...Formula (2) (where M1a is the inertance [kg / m 4 ], M2a is the inertance of the first flow path of the second connecting flow path [kg / m 4 ]

3. One end of the first flow path is connected to the pressure chamber, and the other end of the first flow path is connected to one end of the second flow path, the other end of the second flow path is connected to the first nozzle or the second nozzle, 3. The droplet ejection head according to claim 2, wherein the one end of the first flow path is connected to the pressure chamber without passing through a flow path extending in a direction intersecting the one plane.

4. One end of the first flow path is connected to the pressure chamber, and the other end of the first flow path is connected to one end of the second flow path, the other end of the second flow path is connected to the first nozzle or the second nozzle, a cross-sectional area of ​​the first flow path of the first connection flow path is smaller than a cross-sectional area of ​​the first flow path of the second connection flow path; the first flow path of the second connection flow path includes two flow path portions that share at least a portion of the first flow path from the one end to the other end, 3. The droplet ejection head according to claim 2, wherein a resistance of the first flow path of the first connection flow path and a combined resistance of the two flow path portions of the second connection flow path are the same.

5. The droplet ejection head according to claim 4 , further comprising a partition wall that divides the region between the one end and the other end of the first flow path and is interposed between the two flow path portions.

6. The droplet ejection head according to claim 1 , further satisfying the following formulas (3) and (4): M1c≦M1n...Formula (3) M2c≦M2n...Formula (4) (where M1c is the inertance [kg / m 4 ], M1n is the inertance of the first nozzle [kg / m 4 ], M2c is the inertance of the second connecting flow path [kg / m 4 ], M2n is the inertance of the second nozzle [kg / m 4 ].)

7. 2. The droplet ejection head according to claim 1, further satisfying the following formulas (5), (6), and (7): F1=F2...Formula (5) M1 ≥ 2.99 × 10 4 ×F1^2-1.11×10 7 ×F1 + 1.06 × 10 9 ...Form (6) M2≦6.11×10 1 ×F2^3-2.41×10 4 ×F2^2 + 1.86 × 10 6 ×F2+1.10×10 8 ...Form (7) (Here, F1 is the primary frequency [kHz] of the first connecting flow path, and F2 is the primary frequency [kHz] of the second connecting flow path.)

8. The droplet ejection head according to claim 1 , further satisfying the following formula (8): F1≠F2...Formula (8) (Here, F1 is the primary frequency [kHz] of the first connecting flow path, and F2 is the primary frequency [kHz] of the second connecting flow path.)

9. 9. The droplet ejection head according to claim 8, further satisfying the following formulas (9) and (10): M1 < 2.99 × 10 4 ×F1^2-1.11×10 7 ×F1 + 1.06 × 10 9 ・・・Form (9) M2 > 6.11 × 10 1 ×F2^3-2.41×10 4 ×F2^2 + 1.86 × 10 6 ×F2+1.10×10 8 ・・・Form (10)

10. 9. The droplet ejection head according to claim 8, further satisfying the following formulas (11) and (12): M1≦-1.23×10 6 ×F1 + 2.32 × 10 8 ・・・Form (11) M2≦-1.23×10 6 ×F2+2.32×10 8 ・・・Form (12)

11. 11. The droplet ejection head according to claim 10, further satisfying the following formula (13) when F1>F2 and M1>M2. M1-M2=-1.23×10 6 ×(F1-F2) ・・・Form (13)

12. 2. The droplet ejection head according to claim 1, further comprising a hole having one end communicating with the pressure chamber and the other end communicating with the atmosphere, wherein a meniscus is formed at the other end to absorb pressure fluctuations of the liquid in the pressure chamber.

13. a plurality of individual flow paths each including the pressure chamber, the first nozzle, the second nozzle, the first connection flow path, and the second connection flow path; a common flow path communicating with the plurality of individual flow paths; a third flow path included in each of the plurality of individual flow paths, the third flow path having one end connected to the pressure chamber and the other end connected to the common flow path, and extending in a direction parallel to the one plane; a plurality of plates having holes defining the plurality of individual flow paths; The droplet ejection head according to claim 1 , wherein one of the plurality of plates has both a hole that defines the first flow path and a hole that defines the third flow path.

14. The droplet ejection head according to claim 13, wherein the first flow path and the third flow path are arranged across the entire thickness of the one plate.

15. a plurality of individual flow paths each including the pressure chamber, the first nozzle, the second nozzle, the first connection flow path, and the second connection flow path; a common flow path communicating with the plurality of individual flow paths; a third flow path included in each of the plurality of individual flow paths, the third flow path having one end connected to the pressure chamber and the other end connected to the common flow path and extending in a direction parallel to the one plane, One end of the first flow path is connected to the pressure chamber, and the other end of the first flow path is connected to one end of the second flow path. the other end of the second flow path is connected to the first nozzle or the second nozzle, M1a>M2a, The droplet ejection head described in claim 2, characterized in that the distance along the plane between the one end of the first flow path of the first connecting flow path and the one end of the third flow path is smaller than the distance along the plane between the one end of the first flow path of the second connecting flow path and the one end of the third flow path.

16. the first flow path extends in an extension direction parallel to the one plane, and has one end in the extension direction that is connected to the pressure chamber, and the other end in the extension direction that is connected to the second flow path, A droplet ejection head described in any one of claims 1 to 15, characterized in that the other end of the first flow path in the first connection flow path and the other end of the first flow path in the second connection flow path are positioned in the same direction in the extension direction.

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