Liquid discharge head and recording device

Abstract

This liquid discharge head includes a flow path member and a plurality of pressurizing parts. The flow path member has a plurality of discharge holes, a plurality of pressurizing chamber bodies, one or more second common flow paths, a partial flow path, one or more first common flow paths, and a first flow path. The plurality of pressurizing parts pressurize the plurality of pressurizing chamber bodies, respectively. The first flow path has a first section connected to one discharge hole, and a second section in which two or more first sections of two or more first flow paths are connected in common and further connected to the first common flow path. Two or more second sections of the first flow path are connected to one first common flow path. Of the resonance frequency of the partial flow path and the resonance frequency of the first flow path, the one with the larger value is at least 1.2 times more than the smaller value.

Description

Liquid ejection head and recording apparatus

[0001] The disclosed embodiments relate to a liquid ejection head and a recording apparatus.

[0002] Liquid ejection heads are known that perform various printing operations by ejecting liquid onto a recording medium such as paper. A liquid ejection head has, for example, a large number of ejection holes that are arranged two-dimensionally to eject liquid. Printing is performed by aligning the liquid ejected from each ejection hole and landing it on the recording medium.

[0003] International Publication No. 2019 / 066019 International Publication No. 2020 / 004324

[0004] A liquid ejection head according to one aspect of the embodiment includes a flow path member and multiple pressurizing units. The flow path member has multiple ejection holes, multiple pressure chamber bodies connected to the multiple ejection holes, one or more second common flow paths connected in common to the multiple pressure chamber bodies, partial flow paths connecting the ejection holes to the pressure chamber bodies, one or more first common flow paths connected in common to each of the partial flow paths, and a first flow path connecting the partial flow paths to the first common flow path. The multiple pressurizing units pressurize the multiple pressure chamber bodies, respectively. The first flow paths have a first portion connected to one of the ejection holes and a second portion connected in common to two or more of the first flow paths and further connected to the first common flow path. Two or more of the second portions of the first flow paths are connected to one first common flow path. The larger of the resonant frequencies of the partial flow paths and the first flow paths is at least 1.2 times the smaller of the two.

[0005] FIG. 1A is a side view schematically illustrating an example of a recording apparatus according to an embodiment. FIG. 1B is a plan view schematically illustrating an example of a recording apparatus according to an embodiment. FIG. 2A is a plan view showing an example of a head main body, which is a main part of a liquid ejection head according to an embodiment. FIG. 2B is a plan view obtained by removing a second flow path member and a piezoelectric actuator substrate from FIG. 2A. FIG. 3 is a plan view partially enlarged of the head main body shown in FIG. 2B. FIG. 4 is a plan view partially enlarged of the head main body shown in FIG. 3. FIG. 5A is a partial vertical cross-sectional view schematically illustrating an example of a head main body. FIG. 5B is a partial vertical cross-sectional view schematically illustrating an example of a head main body. FIG. 6 is a perspective view schematically illustrating a part of a flow path provided in the head main body. FIG. 7A is a diagram schematically illustrating an example of liquid ejected from a liquid ejection head whose ejection characteristics have fluctuated. FIG. 7B is a diagram schematically illustrating an example of liquid ejected from a liquid ejection head whose ejection characteristics have fluctuated. FIG. 8A is a perspective view schematically illustrating an example of a main part of a flow path provided in a head main body according to an embodiment. Fig. 8B is a perspective view schematically showing an example of a main part of a flow path included in a head main body according to an embodiment. Fig. 8C is a perspective view schematically showing an example of a main part of a flow path included in a head main body according to an embodiment. Fig. 8D is a perspective view schematically showing an example of a main part of a flow path included in a head main body according to an embodiment. Fig. 9 is a diagram showing evaluation results of ejection stability. Fig. 10A is a side view schematically showing another example of a recording apparatus according to an embodiment. Fig. 10B is a plan view schematically showing another example of a recording apparatus according to an embodiment.

[0006] In the above-described liquid ejection head, the ejection characteristics may fluctuate, causing problems.

[0007] Therefore, there is a need to provide a liquid ejection head and a recording apparatus that can improve ejection stability.

[0008] Hereinafter, embodiments of a liquid ejection head and a recording apparatus disclosed in the present application will be described with reference to the accompanying drawings. Note that the present disclosure is not limited to the embodiments described below. It should be noted that the drawings are schematic, and the dimensional relationships and ratios of elements may differ from reality. Furthermore, the dimensional relationships and ratios may differ between the drawings.

[0009] 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, installation precision, etc.

[0010] Furthermore, the embodiments can be combined as appropriate within the scope of not causing any contradiction in the processing content. Furthermore, the same components in the following embodiments are denoted by the same reference numerals, and redundant explanations will be omitted.

[0011] [Embodiment] <Printer Configuration> First, an overview of a printer 1, which is an example of a recording apparatus according to an embodiment, will be described with reference to Figures 1A and 1B. Figure 1A is a side view that schematically shows an example of a recording apparatus according to an embodiment. Figure 1B is a plan view that schematically shows an example of a recording apparatus according to an embodiment. The recording apparatus according to an embodiment is the printer 1. The printer 1 is, for example, a color inkjet printer.

[0012] The printer 1 transports printing paper P, an example of a recording medium, from roller 82A, which is a guide roller, to roller 82B, which is a transport roller, thereby moving the printing paper P relative to the liquid ejection head 2. The control unit 88 controls the liquid ejection head 2 based on image and character data to eject liquid toward the printing paper P, causing droplets to land on the printing paper P, and performing recording, such as printing, on the printing paper P.

[0013] In this embodiment, the liquid ejection head 2 is fixed to the printer 1, which is a so-called line printer. Another form of recording device is a so-called serial printer, which alternates between recording while moving the liquid ejection head 2 back and forth in a direction intersecting the transport direction of the print paper P, for example, in a direction substantially perpendicular to the direction, and transporting the print paper P. Alternatively, recording may be performed while moving the liquid ejection head 2 with a robot arm or the like relative to a fixed print paper P.

[0014] A flat frame 70 is fixed to the printer 1 so as to be approximately parallel to the printing paper P. Twenty holes (not shown) are formed in the frame 70, and twenty liquid ejection heads 2 are mounted in the respective holes. This allows the portion of the liquid ejection head 2 that ejects liquid to face the printing paper P. The distance between the liquid ejection head 2 and the printing paper P is, for example, approximately 0.5 mm to 20 mm. Five liquid ejection heads 2 make up one head group 72, and the printer 1 has four head groups 72.

[0015] The liquid ejection heads 2 have an elongated shape that is long and narrow in the direction from the front to the back in Fig. 1A, and in the vertical direction in Fig. 1B. Within one head group 72, three liquid ejection heads 2 are lined up in a direction that intersects with the transport direction of the printing paper P, for example, in a direction that is approximately perpendicular to it. The other two liquid ejection heads 2 are lined up one-by-one between the three liquid ejection heads 2, at positions offset along the transport direction.

[0016] The liquid ejection heads 2 are arranged so that the printable range of each liquid ejection head 2 is connected in the width direction of the printing paper P, i.e., in the direction intersecting the conveying direction of the printing paper P, or so that the ends overlap, making it possible to print without gaps in the width direction of the printing paper P.

[0017] The four head groups 72 are arranged along the transport direction of the printing paper P. Each liquid ejection head 2 is supplied with liquid, for example, ink, from a liquid tank (not shown). The liquid ejection heads 2 belonging to one head group 72 are supplied with ink of the same color, and the four head groups 72 can print with ink of four colors. The colors of ink ejected from each head group 72 are, for example, magenta (M), yellow (Y), cyan (C), and black (K). Color images can be printed by controlling these inks with the control unit 88.

[0018] The number of liquid ejection heads 2 mounted on the printer 1 may be one, for example, if printing is performed in a single color within the printable area of ​​one liquid ejection head 2. The number of holes and / or liquid ejection heads 2 included in the head group 72, the number of head groups 72, etc. can be changed as appropriate depending on the object to be printed and the printing conditions. For example, the number of head groups 72 may be increased to print in more colors. Furthermore, by arranging multiple head groups 72 printing in the same color and alternately printing in the transport direction, the transport speed can be increased even when liquid ejection heads 2 with the same performance are used. This allows for a larger printing area per unit time. Furthermore, multiple head groups 72 printing in the same color may be prepared, or they may be arranged offset in a direction intersecting the transport direction. This allows for higher resolution in the width direction of the printing paper P.

[0019] Furthermore, the printer 1 may print a liquid such as a coating agent to treat the surface of the printing paper P, in addition to printing colored ink.

[0020] Before use, the printing paper P is wound around roller 80A, which is a paper feed roller. After passing between two guide rollers, roller 82A, the printing paper P passes below the liquid ejection head 2 mounted on the frame 70. The printing paper P then passes between two transport rollers, roller 82B, and is finally collected by collection roller 80B. When printing, the printing paper P is transported at a constant speed by rotating roller 82B, and is printed by the liquid ejection head 2. The collection roller 80B winds up the printing paper P sent out from roller 82B. The transport speed may be, for example, 100 m / min. Each roller may be controlled by the control unit 88, or may be operated manually.

[0021] Furthermore, the printer 1 may print on rolls of cloth and the like in addition to printing paper P. The printer 1 may also transport the printing paper P on a conveyor belt instead of directly transporting it. In this way, printing targets can be sheets of paper, cut pieces of cloth, wood, tiles, and the like. Furthermore, a liquid containing conductive particles may be ejected from the liquid ejection head 2 to print wiring patterns for electronic devices, and a chemical agent may be produced by ejecting a predetermined amount of liquid chemical or a liquid containing a chemical agent from the liquid ejection head 2 toward a reaction vessel or the like, causing a reaction.

[0022] Furthermore, position sensors, speed sensors, temperature sensors, etc. may be attached to the printer 1, and the control unit 88 may control each part of the printer 1 according to the state of each part of the printer 1 determined from information from each sensor. For example, if the temperature of the liquid ejection head 2, the temperature of the liquid in the liquid tank, or the pressure that the liquid in the liquid tank applies to the liquid ejection head 2 affects the ejection characteristics of the ejected liquid, i.e., the ejection amount and ejection speed, the drive signal for ejecting the liquid may be changed according to this information.

[0023] <Configuration of Liquid Ejection Head> Next, a liquid ejection head 2 according to one embodiment of the present disclosure will be described. Fig. 2A is a plan view showing an example of a head main body 2a, which is a main part of a liquid ejection head according to an embodiment. Fig. 2B is a plan view in which the second flow path member 6 and the piezoelectric actuator substrate 40 are removed from Fig. 2A. Fig. 3 is a partially enlarged plan view of the head main body 2a shown in Fig. 2B. Fig. 4 is a partially enlarged plan view of the head main body 2a shown in Fig. 3. Figs. 5A and 5B are partial vertical cross-sectional views schematically showing an example of the head main body 2a. Fig. 6 is a perspective view schematically showing a part of the flow path provided in the head main body 2a.

[0024] FIG. 3 is a plan view enlarging the area indicated by the dashed line in FIG. 2B. FIG. 4 is a plan view enlarging the area indicated by the dashed line in FIG. 3. In addition, in FIG. 5A, in order to show the connection of the flow paths, flow paths that do not actually exist on the same vertical cross section are depicted as if they exist on the same vertical cross section. More specifically, the vertical cross sections above plate 4g and below plate 4h are different sections. FIG. 5B is a vertical cross section of a portion of the head main body 2a that is different from that shown in FIG. 5A. Note that FIG. 5B also shows a signal transmission unit 60, which is not shown in FIG. 2A.

[0025] To make the drawings easier to understand, the figures are labeled as follows. In Figures 2A to 4, flow paths and the like located below one another are indicated by solid lines. In Figure 4, the first flow path 14 and the like are omitted on the left side of the central two-dot chain line that divides the figure into left and right halves. The pressure chamber main body 10a and the like are omitted on the right side of the figure. Only the individual electrodes 44 and connection electrodes 46 corresponding to some of the pressure chambers 10 on the left side of the figure are shown.

[0026] The head main body 2a includes a first flow path member 4, a second flow path member 6 that supplies liquid to the first flow path member 4, and a piezoelectric actuator substrate 40 on which displacement elements 50, which serve as pressure applying units, are fabricated. The head main body 2a has a flat plate shape that is long in one direction, which is sometimes referred to as the longitudinal direction. The second flow path member 6 also serves as a support member that supports the structure of the head main body 2a, and the head main body 2a is fixed to a frame 70 (see FIGS. 1A and 1B) at both ends of the second flow path member 6 in the longitudinal direction. The liquid ejection head 2 may also include a housing, a driver IC, a wiring board, and the like in addition to the head main body 2a.

[0027] The first flow path member 4 constituting the head main body 2a has a flat plate-like shape and a thickness of approximately 0.5 to 2 mm. A large number of pressure chambers 10 are arranged in a plane on a pressure chamber surface 4-1, which is one surface of the first flow path member 4. A large number of ejection holes 8 from which liquid is ejected are arranged in a plane on an ejection hole surface 4-2, which is the surface of the first flow path member 4 opposite the pressure chamber surface 4-1. Each of the ejection holes 8 is connected to a pressure chamber 10. In the following description, the pressure chamber surface 4-1 will be described as being located above the ejection hole surface 4-2.

[0028] In the first flow path member 4, a plurality of second common flow paths 20 and a plurality of first common flow paths 22 are arranged to extend along the first direction. Hereinafter, the second common flow paths 20 and the first common flow paths 22 may be collectively referred to as the common flow path. The second common flow paths 20 and the first common flow paths 22 are arranged to overlap. A direction intersecting the first direction is referred to as the second direction. There are eight second common flow paths 20 and eight first common flow paths 22, and they are arranged side by side in the second direction. The first direction is the same as the longitudinal direction of the head main body 2a. The direction opposite the first direction is referred to as the third direction, and the direction opposite the second direction is referred to as the fourth direction. In some figures, the first to fourth directions are indicated by D1 to D4.

[0029] The pressure chambers 10 connected to the second common flow path 20 and the first common flow path 22, and the discharge holes 8 connected to the pressure chambers 10, are lined up along both sides of the second common flow path 20 and the first common flow path 22. Two rows of pressure chambers 10 are provided on each side of the second common flow path 20 and the first common flow path 22, forming four pressure chamber rows 11A in total. Two rows of discharge holes 8 are provided on each side of the second common flow path 20 and the first common flow path 22, forming four discharge hole rows 9A in total. Since there are eight second common flow paths 20 and eight first common flow paths 22, there are a total of 32 pressure chamber rows 11A and 32 discharge hole rows 9A.

[0030] The second common flow path 20 and the four rows of pressure chambers 10 lined up on both sides thereof are connected via a second flow path 12. The first common flow path 22 and the four rows of pressure chambers 10 lined up on both sides thereof are connected via a first flow path 14.

[0031] With the above-described configuration, in the first flow path member 4, the liquid supplied to the second common flow path 20 flows into the pressure chambers 10 aligned along the second common flow path 20. A portion of the liquid that flows into the pressure chambers 10 is ejected from the ejection holes 8. The other portion of the liquid that is not ejected flows into the first common flow path 22 and is discharged to the outside from the first flow path member 4. The flow of supply and recovery of the liquid may be reversed.

[0032] The second common flow path 20 is arranged to overlap the first common flow path 22. The second common flow path 20 opens to the outside of the first flow path member 4 at openings 20b located at both ends in the first and third directions outside the range where the second flow paths 12 are connected. The first common flow path 22 opens to the outside of the first flow path member 4 at openings 22b located at both ends in the first and third directions outside the range where the first flow paths 14 are connected and outside the openings 20b of the second common flow path 20. The openings 22b of the lower first common flow path 22 are located outside the openings 20b of the upper second common flow path 20, thereby improving space efficiency. Note that the entire second common flow path main body 20a, excluding both end portions, is arranged below the entire second common flow path main body 20a, excluding both end portions.

[0033] Approximately the same amount of liquid is supplied from the opening 20b on the first direction side and the opening 20b on the third direction side of the second common flow path 20, and flows toward the center of the second common flow path 20. If the amount of liquid discharged from the discharge holes 8 connected to one second common flow path 20 and one first common flow path 22 is approximately constant regardless of location, the flow in the second common flow path 20 slows down toward the center and becomes zero (0) at approximately the center. The flow in the first common flow path 22 is the opposite, being zero at approximately the center and becoming faster toward the outside.

[0034] Because the liquid ejection head 2 records a variety of objects, the amount of liquid ejected from the ejection holes 8 connected to one second common flow path 20 and one first common flow path 22 varies in distribution. When the amount of liquid ejected from the ejection holes 8 on the first direction side is large, the location where the flow becomes zero is closer to the first direction than the center. Conversely, when the amount of liquid ejected from the ejection holes 8 on the third direction side is large, the location where the flow becomes zero is closer to the third direction than the center. In this way, the distribution of ejection changes depending on what is being recorded, and the location where the flow becomes zero moves. As a result, even if the flow becomes zero at a certain moment and the liquid stagnates, the change in the distribution of ejection eliminates the stagnation at that location, making it less likely that the liquid will continue to stagnate in the same location, causing pigment sedimentation or solidification of the liquid.

[0035] The pressure applied to the portion of the second flow path 12 connected to the second common flow path 20 on the second common flow path 20 side varies depending on the position (mainly the position in the first direction) at which the second flow path 12 connects to the second common flow path 20 due to the influence of pressure loss. The pressure applied to the portion of the first flow path 14 connected to the first common flow path 22 varies depending on the position (mainly the position in the first direction) at which the first flow path 14 connects to the first common flow path 22 due to the influence of pressure loss. If the pressure of the liquid in one discharge hole 8 is made almost zero, the above-mentioned pressure change changes symmetrically, so the pressure of the liquid can be made almost zero in all discharge holes 8.

[0036] The lower surface of the second common flow path 20 is a damper 28A. The surface of the damper 28A opposite to the surface facing the second common flow path 20 faces a damper chamber 29A. The damper chamber 29A contains a gas such as air, and its volume changes depending on the pressure applied from the second common flow path 20. The damper 28A can vibrate when the volume of the damper chamber 29A changes, and the damping of this vibration can attenuate pressure fluctuations occurring in the second common flow path 20. By providing the damper 28A, pressure fluctuations such as those caused by resonance of the liquid in the second common flow path 20 can be reduced.

[0037] The lower surface of the first common flow path 22 is a damper 28B. The surface of the damper 28B opposite to the surface facing the first common flow path 22 faces a damper chamber 29B. As in the case of the first common flow path, providing the damper 28B can reduce pressure fluctuations such as resonance of the liquid in the first common flow path 22.

[0038] In one ejection hole row 9A, the ejection holes 8 may be arranged at intervals of 37.5 dpi (37.5 holes per inch (25.4 mm)). There may be 32 ejection hole rows 9A, and the ejection holes 8 included in these rows may be arranged offset from one another in the first direction, so that the ejection holes 8 are arranged at intervals of 1,200 dpi overall.

[0039] 3, when the ejection holes 8 are projected in a direction perpendicular to the first direction, 32 ejection holes 8 are projected within the range of R of an imaginary line parallel to the first direction, and the ejection holes 8 are arranged at intervals of 1200 dpi within the range of R of the imaginary line. As a result, if printing is performed by transporting the printing paper P in a direction perpendicular to the imaginary line, printing can be performed at a resolution of 1200 dpi.

[0040] The second flow path member 6 is joined to the pressurizing chamber surface 4-1 of the first flow path member 4. The second flow path member 6 has a first unified flow path 24 that supplies liquid to the second common flow path 20, and a second unified flow path 26 that recovers liquid from the first common flow path 22. The second flow path member 6 may be thicker than the first flow path member 4. The thickness of the second flow path member 6 may be approximately 5 mm to 30 mm.

[0041] The second flow path member 6 is joined to the pressure chamber surface 4-1 of the first flow path member 4 in an area where the piezoelectric actuator substrate 40 is not connected. More specifically, the second flow path member 6 is joined so as to surround the piezoelectric actuator substrate 40. By doing so, it becomes less likely that a portion of the ejected liquid will become mist and adhere to the piezoelectric actuator substrate 40. Furthermore, because the first flow path member 4 is fixed at its outer periphery so as to surround the piezoelectric actuator substrate 40, it is possible to reduce resonance that occurs when the first flow path member 4 vibrates in response to the driving of the displacement element 50.

[0042] An opening 24b opening to the upper surface of the second flow path member 6 is arranged at the end of the first integrated flow path 24 in the third direction. The first integrated flow path 24 branches into two along the way. One of the branched first integrated flow paths 24 is connected to the opening 20b of the second common flow path 20 on the third direction side, and the other is connected to the opening 20b of the second common flow path 20 on the first direction side. An opening 26b opening to the upper surface of the second flow path member 6 is arranged at the end of the second integrated flow path 26 in the first direction. The second integrated flow path 26 branches into two along the way. One of the branched second integrated flow paths 26 is connected to the opening 22b of the first common flow path 22 on the first direction side, and the other is connected to the opening 22b of the first common flow path 22 on the third direction side. When printing, liquid is supplied from the outside to the opening 24b of the first integrated flow path 24, and any liquid not ejected is collected from the opening 26b of the second integrated flow path 26.

[0043] Furthermore, the second flow path member 6 is provided with a through-hole 6a that passes through the second flow path member 6 from top to bottom. A signal transmission unit 60 such as an FPC (Flexible Printed Circuit) that transmits a drive signal that drives the piezoelectric actuator substrate 40 passes through the through-hole 6a.

[0044] By disposing the first integrated flow path 24 in the second flow path member 6, which is separate from the first flow path member 4 and thicker than the first flow path member 4, the cross-sectional area of ​​the first integrated flow path 24 can be increased, thereby reducing the difference in pressure loss due to the difference in the position where the first integrated flow path 24 and the second common flow path 20 are connected. The flow path resistance of the first integrated flow path 24 may be 1 / 100 or less of that of the second common flow path 20. Here, the flow path resistance of the first integrated flow path 24 more accurately refers to the flow path resistance of the range of the first integrated flow path 24 that is connected to the second common flow path 20.

[0045] By arranging the second integrated flow path 26 in a second flow path member 6 that is separate from and thicker than the first flow path member 4, the cross-sectional area of ​​the second integrated flow path 26 can be increased, thereby reducing the difference in pressure loss due to the difference in the position where the second integrated flow path 26 and the first common flow path 22 are connected.

[0046] The first integrated flow path 24 is disposed at one end of the second flow path member 6 in the short direction, and the second integrated flow path 26 is disposed at the other end of the second flow path member 6 in the short direction, with each flow path facing the first flow path member 4 and connected to the second common flow path 20 and the first common flow path 22, respectively. This structure increases the cross-sectional area of ​​the first integrated flow path 24 and the second integrated flow path 26, thereby reducing flow path resistance. Furthermore, this structure increases the rigidity of the first flow path member 4 because the outer periphery is fixed by the second flow path member 6. Furthermore, this structure makes it possible to provide a through-hole 6a through which the signal transmission unit 60 passes.

[0047] A groove that becomes the first integrated flow path 24 and a groove that becomes the second integrated flow path 26 are arranged on the lower surface of the second flow path member 6. The groove that becomes the first integrated flow path 24 of the second flow path member 6 has a part of its lower surface blocked by the upper surface of the first flow path member 4, and the other part of its lower surface connected to an opening 20b of the second common flow path 20 that is arranged on the upper surface of the first flow path member 4, thereby forming the first integrated flow path 24. The groove that becomes the second integrated flow path 26 of the second flow path member 6 has a part of its lower surface blocked by the upper surface of the first flow path member 4, and the other part of its lower surface connected to an opening 22a of the first common flow path 22 that is arranged on the upper surface of the first flow path member 4, thereby forming the second integrated flow path 26.

[0048] Dampers may be provided in the first integrated flow path 24 and the second integrated flow path 26 to stabilize the supply or discharge of liquid despite fluctuations in the liquid discharge rate. Furthermore, filters may be provided inside the first integrated flow path 24 and the second integrated flow path 26 or between them and the second common flow path 20 or the first common flow path 22 to make it difficult for foreign matter or air bubbles to enter the first flow path member 4.

[0049] The upper surface of the second flow path member 6 is covered by a metal housing or the like. The signal transmission unit 60 is electrically connected to, for example, a wiring board housed in the housing. The wiring board and the control unit 88 are electrically connected by a cable or the like. A driver IC that drives the displacement element 50 may be mounted on the signal transmission unit 60. By bringing the driver IC into contact with the metal housing or a member of the housing that facilitates heat transfer, the heat generated by the driver IC can be released to the outside.

[0050] A piezoelectric actuator substrate 40 including displacement elements 50 is bonded to the pressure chamber surface 4-1, which is the upper surface of the first flow path member 4, and each displacement element 50 is arranged so as to be located above a pressure chamber 10. The piezoelectric actuator substrate 40 occupies an area having substantially the same shape as the pressure chamber group formed by the pressure chambers 10. The opening of each pressure chamber 10 is closed by bonding the piezoelectric actuator substrate 40 to the pressure chamber surface 4-1 of the first flow path member 4. The piezoelectric actuator substrate 40 has a rectangular shape that is long in the same direction as the head main body 2a.

[0051] A signal transmission unit 60 that supplies signals to each displacement element 50 is connected to the piezoelectric actuator substrate 40. The second flow path member 6 has a through-hole 6a that penetrates vertically in the center, and the signal transmission unit 60 is electrically connected to the control unit 88 through the through-hole 6a. The signal transmission unit 60 is shaped to extend in the short direction from one long side end to the other long side end of the piezoelectric actuator substrate 40, and the wiring arranged in the signal transmission unit 60 can be made to extend along the short side direction and lined up in the long direction, thereby increasing the distance between the wiring.

[0052] Individual electrodes 44 are disposed on the upper surface of the piezoelectric actuator substrate 40 at positions facing the pressure chambers 10 .

[0053] The first flow path member 4 has a laminated structure in which multiple plates are stacked. Plate 4a is disposed on the pressure chamber surface 4-1 side of the first flow path member 4, and plates 4b to 4l are stacked in order below plate 4a. Plate 4a, in which holes forming the side walls of the pressure chambers 10 are formed, is sometimes called the cavity plate. Plates 4e, 4f, 4i, and 4j, in which holes forming the side walls of the common flow paths are formed, are sometimes called manifold plates. Plate 4l, in which the ejection holes 8 are opened, is sometimes called the nozzle plate. Numerous holes and grooves are formed in each plate. The holes and grooves can be formed, for example, by fabricating each plate from metal and etching it. The thickness of each plate is approximately 10 μm to 300 μm, allowing for high precision in the formation of the holes. The plates are aligned and stacked so that the holes communicate with each other to form flow paths such as the second common flow path 20.

[0054] A pressure chamber body 10a is opened on the pressure chamber surface 4-1 of the flat plate-shaped first flow path member 4, and a piezoelectric actuator substrate 40 is joined to the pressure chamber body 10a. The pressure chamber surface 4-1 also has an opening 20b for supplying liquid to the second common flow path 20 and an opening 22b for recovering liquid from the first common flow path 22. A discharge hole 8 is opened on the discharge hole surface 4-2, which is the surface of the first flow path member 4 opposite the pressure chamber surface 4-1.

[0055] The structure for discharging liquid includes a pressure chamber 10 and a discharge hole 8. The pressure chamber 10 includes a pressure chamber main body 10a and a partial flow path 10b. The pressure chamber main body 10a is formed in the plate 4a and faces the displacement element 50. In a plan view, the pressure chamber main body 10a has a substantially elliptical shape that is long in the second direction. Note that the pressure chamber main body 10a does not have to be elliptical in shape, and may be rectangular or circular.

[0056] The partial flow path 10b connects the pressure chamber main body 10a and the discharge hole 8. The partial flow path 10b is formed by overlapping holes formed in the plates 4b to 4k. The lower end of the partial flow path 10b is closed by the plate 4l except for the discharge hole 8. Therefore, the partial flow path 10b extends in the height direction of the first flow path 14.

[0057] The second flow path 12 connects the pressure chamber body 10a and the second common flow path 20. The second flow path 12 includes a circular hole that penetrates the plate 4b, a long and narrow through groove that extends in the planar direction of the plate 4c, and a circular hole that penetrates the plate 4d.

[0058] The first flow path 14 connects the partial flow paths 10b and the first common flow path 22. The first flow path 14 has a connection flow path 14b that connects the first common flow path 22 and multiple first individual flow paths 14a that are connected to one pressurizing chamber 10. In other words, the first flow path 14 has a first individual flow path 14a that is connected to only one pressurizing chamber 10A, a first individual flow path 14a that is connected to only the other pressurizing chamber 10B, and a connection flow path 14b that connects these two first individual flow paths 14a and the first common flow path 22. In Figure 4, the connection flow path 14b is formed by joining (connecting) two first individual flow paths 14a that are connected to the two pressurizing chambers 10A, 10B, respectively, and is connected to the first common flow path 22.

[0059] A plurality of sets, each consisting of a connection flow path 14b and a plurality of first individual flow paths 14a, are connected to one first common flow path 22. The term "set" here refers to one first flow path 14. A plurality of connection flow paths 14b are connected to one first common flow path 22. The number of connection flow paths 14b connected to one first common flow path 22 is half the number of pressure chambers 10 connected to one first common flow path 22. By bundling the plurality of first individual flow paths 14a into a connection flow path 14b and then connecting them to the first common flow path 22, space efficiency is improved. Note that the number of first individual flow paths 14a connected to the connection flow path 14b may be three or more.

[0060] The second common flow path 20 is formed by overlapping holes formed in plates 4e and 4f, and is further blocked on the upper side by plate 4d and on the lower side by plate 4g. The first common flow path 22 is formed by overlapping holes formed in plates 4i and 4j, and is further blocked on the upper side by plate 4h and on the lower side by plate 4k.

[0061] To summarize the flow of liquid, the liquid supplied to the first joint flow channel 24 passes through the second common flow channel 20 and the second flow channel 12 in this order, and enters the pressure chamber 10, and some of the liquid is ejected from the ejection hole 8. The liquid that is not ejected passes through the first flow channel 14, enters the first common flow channel 22, then enters the second joint flow channel 26, and is discharged to the outside of the head main body 2a.

[0062] The piezoelectric actuator substrate 40 has a laminated structure made up of two piezoelectric ceramic layers 40a and 40b. Each of the piezoelectric ceramic layers 40a and 40b has a thickness of about 20 μm. That is, the thickness from the top surface of the piezoelectric ceramic layer 40a to the bottom surface of the piezoelectric ceramic layer 40b of the piezoelectric actuator substrate 40 is about 40 μm. The thickness ratio of the piezoelectric ceramic layer 40a to the piezoelectric ceramic layer 40b is set to 3:7 to 7:3, preferably 4:6 to 6:4.

[0063] Both of the piezoelectric ceramic layers 40a and 40b extend across the multiple pressure chambers 10. The piezoelectric ceramic layers 40a and 40b are made of a material such as lead zirconate titanate (PZT) or NaNbO, which has ferroelectricity. ３ system, BaTiO ３ system, (BiNa)NbO ３ system, BiNaNb ５ O １５ Alternatively, the piezoelectric ceramic layer 40b may be made of a ceramic material such as a silicon-based material. In this embodiment, the piezoelectric ceramic layer 40b functions as a vibration plate and does not directly undergo piezoelectric deformation. Instead of the piezoelectric ceramic layer 40b, a ceramic or metal plate that does not have piezoelectric properties may be used as the vibration plate.

[0064] The piezoelectric actuator substrate 40 has a common electrode 42 and individual electrodes 44. The material of the common electrode 42 may be, for example, a metal material such as an Ag-Pd system. The material of the individual electrodes 44 may be, for example, a metal material such as an Au system. The thickness of the common electrode 42 may be about 2 μm. The thickness of the individual electrodes 44 may be about 1 μm.

[0065] Each individual electrode 44 is disposed on the upper surface of the piezoelectric actuator substrate 40 at a position facing each pressure chamber body 10a. Each individual electrode 44 includes an individual electrode body 44a and an extraction electrode 44b. The individual electrode body 44a is slightly smaller than the pressure chamber body 10a in plan view and has a shape substantially similar to the pressure chamber body 10a. The extraction electrode 44b is extracted from the individual electrode body 44a. A connection electrode 46 is formed on one end of the extraction electrode 44b, at a portion that extends outside the region facing the pressure chamber 10. The connection electrode 46 may be made of a conductive resin containing conductive particles such as silver particles, and may be formed to a thickness of approximately 5 μm to 200 μm. The connection electrode 46 is electrically connected to an electrode provided in the signal transmission unit 60.

[0066] A drive signal is supplied to the individual electrodes 44 from the control unit 88 through the signal transmission unit 60. The drive signal is supplied at a constant cycle in synchronization with the transport speed of the printing paper P.

[0067] The common electrode 42 is formed over almost the entire surface in the plane direction in the region between the piezoelectric ceramic layers 40a and 40b. In other words, the common electrode 42 extends so as to cover all of the pressure chambers 10 in the region facing the piezoelectric actuator substrate 40. The common electrode 42 is connected to a surface electrode (not shown) formed on the piezoelectric ceramic layer 40a at a position that avoids the electrode group made up of the individual electrodes 44, via a through conductor that penetrates the piezoelectric ceramic layer 40a. The common electrode 42 is also grounded via the surface electrode and maintained at ground potential. Like the individual electrodes 44, the surface electrode is connected directly or indirectly to the control unit 88.

[0068] The portions of the piezoelectric ceramic layer 40a sandwiched between the individual electrodes 44 and the common electrode 42 are polarized in the thickness direction, forming a displacement element 50 with a unimorph structure that displaces when a voltage is applied to the individual electrodes 44. More specifically, when the individual electrodes 44 are set to a different potential from the common electrode 42 and an electric field is applied to the piezoelectric ceramic layer 40a in the polarization direction, the portions to which this electric field is applied function as active portions that distort due to the piezoelectric effect. In this configuration, when the control unit 88 sets the individual electrodes 44 to a predetermined positive or negative potential relative to the common electrode 42 so that the electric field and polarization are in the same direction, the portions of the piezoelectric ceramic layer 40a sandwiched between the electrodes (active portions) contract in the planar direction. On the other hand, the piezoelectric ceramic layer 40b, which is an inactive layer, is not affected by the electric field and does not contract spontaneously but instead attempts to restrict deformation of the active portions. As a result, a difference in strain in the polarization direction occurs between the piezoelectric ceramic layer 40a and the piezoelectric ceramic layer 40b, causing the piezoelectric ceramic layer 40b to deform so as to be convex toward the pressure chamber 10 (unimorph deformation).

[0069] Next, the liquid ejection operation will be described. The displacement elements 50 are driven (displaced) by drive signals supplied to the individual electrodes 44 via a driver IC or the like under control of the control unit 88. In this embodiment, liquid can be ejected using various drive signals, but here, a so-called pull-and-shoot drive method will be described.

[0070] The individual electrodes 44 are set to a higher potential than the common electrode 42 (hereinafter referred to as the "high potential"). Each time an ejection request is made, the individual electrodes 44 are temporarily set to the same potential as the common electrode 42 (hereinafter referred to as the "low potential"), and then set to the high potential again at a predetermined timing. As a result, when the individual electrodes 44 reach the low potential, the piezoelectric ceramic layers 40a, 40b attempt to return to their original (flat) shape, increasing the volume of the pressure chamber 10 compared to the initial state (when the two electrodes have different potentials). This applies negative pressure to the liquid in the pressure chamber 10, causing the liquid in the pressure chamber 10 to vibrate at its natural vibration period. Specifically, initially, the volume of the pressure chamber 10 begins to increase, and the negative pressure gradually decreases. Then, the volume of the pressure chamber 10 reaches its maximum, and the pressure becomes nearly zero. Then, the volume of the pressure chamber 10 begins to decrease, and the pressure increases. Then, when the pressure reaches its maximum, the individual electrodes 44 are set to the high potential. As a result, the first vibration and the second vibration overlap, and a larger pressure is applied to the liquid. This pressure propagates through the partial flow path 10b, causing the liquid to be ejected from the ejection hole 8.

[0071] In other words, the liquid ejection head 2 can eject droplets by supplying to the individual electrodes 44 a pulse drive signal that sets a high potential as a reference and then sets the potential to a low level for a certain period of time. If the pulse width is set to AL (Acoustic Length), which is half the natural vibration period of the liquid in the pressure chamber 10, then in principle, the ejection speed and ejection volume of the liquid can be maximized. The natural vibration period of the liquid in the pressure chamber 10 is significantly influenced by the physical properties of the liquid and the shape of the pressure chamber 10, but is also influenced by the physical properties of the piezoelectric actuator substrate 40 and the characteristics of the flow path connected to the pressure chamber 10.

[0072] Here, the first flow path 14 includes a first individual flow path 14a (hereinafter sometimes referred to as a first portion) connected to one discharge hole 8, and a connecting flow path 14b (hereinafter sometimes referred to as a second portion) connecting multiple first individual flow paths 14a to the first common flow path 22. In this embodiment, there are two first individual flow paths 14a (first portions) connected to one connecting flow path 14b (second portion), but there may be three or more. Also, there are two or more connecting flow paths 14b (second portions) each having two (or more) first individual flow paths 14a (first portions). In other words, two or more connecting flow paths 14b (second portions) connected to two (or more) first individual flow paths 14a (first portions) are connected to one first common flow path 22. This also means that two or more first flow paths 14 are connected to one first common flow path 22.

[0073] The first individual flow path 14a has a third portion 14aa and a fourth portion 14ab. The third portion 14aa is a portion connected to one discharge hole 8. The third portion 14aa is also connected to a partial flow path 10b of the pressure chamber 10. One third portion 14aa is connected to one fourth portion 14ab. Two fourth portions 14ab are connected to one connecting flow path 14b (second portion). In one first flow path 14, the flow paths between two third portions 14aa and one connecting flow path 14b may be formed as one space. In this case, the portion of the flow path connecting one third portion 14aa and the connecting flow path 14b may be considered as one fourth portion 14ab, and the portion of the flow path connecting another third portion 14aa and the connecting flow path 14b may be considered as another fourth portion 14ab.

[0074] Furthermore, the second common flow path 20 is connected to the pressure chamber main body 10a by the second flow path 12, and the first common flow path 22 is connected by the first flow path 14, thereby ejecting and recovering the liquid and performing printing. At this time, for example, as shown in Figure 6, when the drive state of a set 18 in which two pressure chambers 10 are connected to one connection flow path 14b via two first individual flow paths 14a is switched, there is a possibility that the ejection characteristics will fluctuate and the printed image will not have the desired image quality, resulting in a problem.

[0075] 7A and 7B are schematic diagrams illustrating an example of liquid ejected from a liquid ejection head whose ejection characteristics have fluctuated.

[0076] 7A shows a state where, of the group 18 to which the two channels C1 and C2 shown in Fig. 6 belong, channels C1 and C2 are driven, but channel C2 is stopped, leaving only channel C1 driven. When liquid is being ejected onto a print sheet P transported in the transport direction P1 so that droplets d are spaced equally apart, if the drive state of channel C2 changes, an ejection defect Pd occurs in which the spacing between droplets d becomes larger than in other areas.

[0077] 7B shows the state when, of the group 18 to which the two channels C1 and C2 shown in FIG. 6 belong, driving of channel C2 is started from a state in which only channel C1 is driven, and the state is changed to one in which both channels C1 and C2 are driven. When liquid is being ejected onto a print sheet P transported in the transport direction P1 so that droplets d are spaced equally apart, if the driving state of channel C2 changes, an ejection defect Pd occurs in which the spacing between droplets d becomes smaller than in other areas.

[0078] Such ejection failure Pd occurs when the resonance frequency of the partial flow path 10b connecting the ejection hole 8 and the pressure chamber main body 10a is similar to the resonance frequency of the first flow path 14. When the resonance frequencies are similar, it is thought that resonance of the first flow path 14 always occurs to some extent. However, when the same driving state is continuously repeated, it is thought that resonance of the first flow path 14 occurs stably and the amplitude of the resonance increases. In other words, when continuous driving of two channels or continuous driving of one channel continues, a state occurs in which resonance of a large amplitude corresponding to the driving state occurs in the first flow path 14. When a channel different from the continuous driving is driven in such a state, the pressure propagation caused by the different driving fluctuates due to the resonance that occurred before. This is thought to cause ejection failure Pd.

[0079] For example, the third portion 14aa connected to the partial flow path 10b has a smaller cross-sectional area than the partial flow path 10b. This prevents the pressure generated in the pressure chamber main body 10a from escaping, allowing for efficient ejection of liquid. Furthermore, the pressure is released to the second common flow path 20, making it less likely that unnecessary vibrations will occur in the second common flow path 20.

[0080] On the other hand, it is necessary to avoid an increase in flow path resistance by making the cross-sectional areas of the fourth portion 14ab and the connecting flow path 14b on the second common flow path 20 side larger than those of the third portion 14aa. In such a case, by arranging the third portion 14aa, which has a relatively small cross-sectional area, at the end of the third portion 14aa on the partial flow path 10b side, it is possible to make it difficult for unnecessary vibrations to occur in the pressure chamber 10.

[0081] The resonant frequency of the third portion 14aa is higher than and separate from the resonant frequency of the partial flow path 10b.

[0082] On the other hand, if an attempt is made to compactly integrate the ejection element including the second flow path 12 and the first flow path 14 as in this embodiment, limitations on the arrangement of the flow paths and the available space could result in the resonant frequency of the fourth portion 14ab and the connecting flow path 14b becoming close to the resonant frequency of the partial flow path 10b.

[0083] In contrast to this, in the liquid ejection head 2 according to this embodiment, the larger of the resonant frequency of the partial flow path 10b connecting the ejection hole 8 and the pressure chamber main body 10a and the resonant frequency of the first flow path 14 may be 1.2 times or more, for example, 1.35 times or more, or even 1.5 times or more, of the smaller of the two. Also, if the larger of the resonant frequency of the partial flow path 10b and the resonant frequency of the first flow path 14 is 8 times or less of the smaller of the two, it is possible to suppress an increase in the volume of the first flow path member 4 that is required to have such a flow path.

[0084] Here, the resonant frequency of the partial flow path 10b refers to the resonant frequency of the partial flow path 10b with the largest amplitude among the resonances of the partial flow path 10b that occur when the liquid ejection head 2 is driven to eject the liquid. The resonant frequency of the first flow path 14 refers to the resonant frequency of the first flow path 14 with the largest amplitude among the resonances of the first flow path 14 that occur when the liquid ejection head 2 is driven to eject the liquid. The resonant frequency of the first flow path 14 is basically the resonant frequency of the first flow path 14 with the largest amplitude. Even if this is not the case, the resonant frequency of the first flow path 14 is one of the main resonant frequencies with the largest amplitude among the resonances of the first flow path 14. Furthermore, since the resonant frequency of the third portion 14aa is significantly different from the resonant frequency of the partial flow path 10b as described above, the resonant frequency of the first flow path 14 is essentially the resonant frequency of the portion other than the third portion 14aa, i.e., the resonant frequency of the fourth portion 14ab and the connecting flow path 14b.

[0085] In this way, by making the resonance frequency of the partial flow path 10b and the resonance frequency of the first flow path 14 significantly different, the ejection characteristics are less likely to fluctuate even when the driving state of the channel is switched, and ejection stability is improved. Specifically, even when the channel is repeatedly driven with the same drive signal, the amplitude of the resonance that occurs in the first flow path 14 can be reduced, and therefore, even when the channel is subsequently driven with a different drive signal, the effect of the resonance on ejection can be reduced.

[0086] Furthermore, the resonance frequency of the first flow path 14 may be higher than the resonance frequency of the partial flow path 10b.

[0087] If the cross-sectional shape of the partial flow path 10b is significantly changed midway or the cross-sectional area is changed drastically in order to change the resonance frequency, there is a possibility that the pressure will not be efficiently transmitted from the pressure chamber 10 to the discharge hole 8. Therefore, by designing the first flow path 14 so that the resonance frequency is high, the discharge performance can be further stabilized.

[0088] Next, the liquid ejection head 2 according to this embodiment will be further described using Figures 8A to 8D. Figures 8A to 8D are perspective views that schematically show an example of the main parts of the flow paths of the head main body 2a according to this embodiment. Note that in Figures 8A to 8D, the first common flow path 22 connected to the first flow path 14 and the second common flow path 20 connected to the partial flow path 10b, which are part of the set 18 shown in Figure 6, are not shown.

[0089] 8A, a connecting flow path 14b may be provided that is integrated with the fourth portion 14ab. In this case, the height of the connecting flow path 14b may be reduced to shorten the flow path length. Also, a damper (not shown) may be provided on the upper surface of the connecting flow path 14b.

[0090] By making the shape of the first flow path 14 significantly different in this way, even when the driving state of the channel is switched, for example, the ejection characteristics are less likely to fluctuate, and ejection stability is improved.

[0091] 8B, the cross-sectional area of ​​the partial channel 10b may be increased. For example, the cross-sectional area of ​​the partial channel 10b in a cross section perpendicular to the flow of liquid flowing through the partial channel 10b may be set to, for example, about 250 μm.

[0092] The length of the partial flow path 10b may also be increased. For example, the length of the partial flow path 10b may be 0.5 to 2 times the length of the first flow path 14. Here, the lengths of the partial flow path 10b and the first flow path 14 refer to the flow path lengths. Specifically, the lengths of the partial flow path 10b and the first flow path 14 are defined as the lengths connecting the area centers of gravity in the cross sections of the partial flow path 10b and the first flow path 14 along a direction perpendicular to the liquid flow. Unless otherwise specified, the lengths of the other flow paths are defined similarly.

[0093] In this way, by increasing the cross-sectional area and / or length of the partial flow path 10b and changing the resonant frequency, the ejection characteristics are less likely to fluctuate, even when the driving state of the channel is switched, and ejection stability is improved.

[0094] 8C and 8D, the length of the first flow path 14 may be increased. For example, a fifth portion 14ac may be further provided to connect the third portion 14aa and the fourth portion 14ab. The height of the fourth portion 14ab and / or the connecting flow path 14b may also be increased.

[0095] In this way, by increasing the flow path length of the first flow path 14 and changing the resonance frequency, even when the driving state of the channel is switched, for example, the ejection characteristics are less likely to fluctuate, and ejection stability is improved.

[0096] Furthermore, the height of the second portion of the first flow path 14 may be greater than half the height of the first common flow path 22. This reduces the inertance of the second portion and increases the resonance frequency. Therefore, even when the driving state of the channel is switched, the ejection characteristics are less likely to fluctuate, improving ejection stability.

[0097] The height direction corresponds to the stacking direction of the plates of the first flow path member 4. Since multiple ejection elements (displacement elements 50 and the flow paths provided corresponding to them) are arranged at high density in the planar direction of the plate, there are relatively limitations on changing the size of the flow path in the planar direction. Therefore, changing the size in the height direction is effective in changing the resonant frequency of the flow path.

[0098] Furthermore, the height of the second portion of the first flow path 14 may be equal to or greater than the height of the first common flow path 22. This reduces the inertance of the second portion and increases the resonance frequency. Therefore, even when the driving state of the channel is switched, for example, the ejection characteristics are less likely to fluctuate, improving ejection stability.

[0099] Furthermore, the second portion of the first flow path 14 may have the same height as the first common flow path 22. This allows the volume of the liquid ejection head 2 to be reduced because there is no portion higher than the first common flow path 22, and under such conditions, the inertance of the second portion can be reduced, thereby increasing the resonance frequency.

[0100] Furthermore, the cross-sectional area of ​​the first portion in a cross section perpendicular to the flow of liquid flowing through the first portion may be ⅕ or less of the cross-sectional area of ​​the second portion in a cross section perpendicular to the flow of liquid flowing through the second portion. The entire cross-sectional area of ​​the first portion may be ⅕ or less of the cross-sectional area of ​​the second portion, or a portion of the cross-sectional area of ​​the first portion may be ⅕ or less of the cross-sectional area of ​​the second portion. Furthermore, the resonant frequency of the first flow path 14 may be the resonant frequency of the second portion. That is, of the resonances occurring in various parts of the first flow path 14, the second portion may be the portion that generates the resonance closest to the resonant frequency of the partial flow path 10b.

[0101] Furthermore, two first portions (first individual flow paths 14 a) may be connected independently and spaced apart from each other to an end of the second portion of the first flow path 14 located opposite to the end connected to the first common flow path 22. Specifically, as shown in FIG. 8A , the first portions (first individual flow paths 14 a) may be connected independently and spaced apart from each other to the second portion (connecting flow path 14 b). Furthermore, as shown in FIGS. 8C and 8D , fourth portions 14 ab, which are parts of the first portion (first individual flow path 14 a), may be connected independently and spaced apart from each other to the second portion (connecting flow path 14 b).

[0102] The structure in which the two first portions are separate and independent and connected to the second portion at a distance from each other makes it difficult for a pressure wave generated in the pressure chamber 10 and transmitted from one of the second portions to be transmitted to the other first portion connected via the second portion, and therefore the pressure wave is more likely to escape via the second portion to the first common flow path 22. This reduces the effect on the adjacent ejection hole 8, making it possible to, for example, make it less likely that a deterioration in image quality due to a delay in ejection as shown in FIG.

[0103] 8C and 8D , the first portion may include two horizontal paths (the third portion 14aa and the fifth portion 14ac) and a vertical path (the connection portion between the third portion 14aa and the fifth portion 14ac) connecting these two horizontal paths. Furthermore, the cross-sectional areas of the two horizontal paths perpendicular to the liquid flow may be such that the horizontal path (the fifth portion 14ac) connected to the second portion is larger than the horizontal path (the third portion 14aa) connected to the partial flow path 10b.

[0104] The cross-sectional area of ​​the two horizontal paths is larger in the horizontal path connected to the second portion than in the horizontal path connected to the partial flow path 10b, which allows the liquid such as ink to be efficiently agitated and flowed, and allows the liquid to flow in a state where it is less likely to stagnate, to the first common flow path 22. The first portion may have two or more horizontal paths, for example, three.

[0105] Furthermore, when viewed from a direction along the partial flow path 10b, the two first portions may be connected to the ends of the second portions in a line-symmetrical manner with respect to a line along the direction in which the second portions extend from the first common flow path 22.

[0106] This makes it easier for the pressure wave transmitted from the pressure chamber 10 to the first part to escape to the first common flow path 22, and also reduces the impact on the adjacent ejection hole 8, thereby improving ejection stability.

[0107] Furthermore, when viewed from a direction along the partial flow path 10b, the second portion may extend in a straight line (i.e., without bending along the way) from the first common flow path 22 in a direction perpendicular to the direction along the first common flow path 22.

[0108] This allows the pressure wave transmitted from the pressure chamber 10 to the first portion to escape more easily to the first common flow path 22, and also further reduces the impact on adjacent ejection holes 8, thereby improving ejection stability. Furthermore, the pressure wave transmitted from the second portion to the first common flow path 22 enters the first common flow path 22 perpendicular to the first common flow path 22, making it less likely that unnecessary vibrations will occur within the first common flow path 22. Therefore, the impact on other ejection holes 8 generated via the first common flow path 22 is further reduced, improving ejection stability.

[0109] In addition, in FIGS. 8C and 8D, the two first portions (fourth portions 14ab) may be connected to the second portions at acute angles to each other.

[0110] This allows the pressure wave generated in the pressure chamber 10 to escape more easily to the first common flow path 22, and also reduces the influence on the adjacent ejection holes 8, thereby improving ejection stability.

[0111] In addition, in FIG. 8D, the height of the horizontal path (fourth portion 14ab) connected to the second portion may be less than 50% of the height of the second portion.

[0112] This makes it easier for pressure waves that have leaked to the first section to be lost, making it less likely for pressure waves to interfere with each other in the second section and the first common flow path 22. It also reduces pressure leakage to adjacent channels. Furthermore, when the liquid flows from the horizontal flow path to the second section, a sudden expansion flow is generated, which allows the ink to be efficiently agitated and allows the ink to flow into the first common flow path 22 in a state where stagnation is less likely to occur.

[0113] 9 is a diagram showing the evaluation results of the ejection stability. Using the set 18 shown in FIG. 6 as a reference test sample (sample No. 1), samples with different resonance frequency ratios ((resonance frequency of the first individual flow path 14 a) / (resonance frequency of the partial flow path 10 b)) were prepared, and the ejection performance was evaluated.

[0114] In Samples No. 2 and No. 4, the length of the partial flow path 10b was longer than that of Sample No. 1. In Sample No. 3, the height (thickness) of the connecting flow path 14b was greater than that of Sample No. 1. In Sample No. 5, as shown in FIG. 8C , a fifth portion 14ac was further provided, and the height (thickness) of the second portion was greater than that of Sample No. 1.

[0115] The evaluation criteria shown in FIG. 9 are as follows: ×: Not applicable when high quality is required, but no problem for normal printing. △: A quality improvement effect is observed, and it is applicable even when high quality is required. ○: Meets the expected quality. ◎: Higher ejection stability than the expected quality is observed.

[0116] 9, when the resonance frequency ratio is 1.2 or more, the ejection stability is improved, and when the resonance frequency ratio is 1.35 or more, high ejection stability is observed. Furthermore, when the resonance frequency ratio is 1.5 or more, even higher ejection stability is observed.

[0117] [Other Embodiments] Fig. 10A is a side view schematically illustrating another example of a recording apparatus according to an embodiment. Fig. 10B is a plan view schematically illustrating another example of a recording apparatus according to an embodiment. Below, differences from the printer 1 according to the embodiment will be particularly described. Matters not specifically mentioned may be considered to be the same as the printer 1 shown in Figs. 1A and 1B. In Figs. 1A and 1B, the printer 1 is illustrated so that the print paper P moves from the right side of the paper to the left side of the paper. In Figs. 10A and 10B, the printer 101 is illustrated so that the print paper P moves from the left side of the paper to the right side of the paper, which is the opposite of Figs. 1A and 1B.

[0118] In the above-described embodiment, it has been described that a coating agent may be printed by the liquid ejection head 2. In addition to being printed by the liquid ejection head 2 as in this embodiment, the coating agent may also be uniformly applied by the applicator 84 controlled by the control unit 88. The printing paper P sent out from roller 80A, which is a paper feed roller, passes between rollers 82A, which are two transport rollers, and then passes under the applicator 84. At this time, the applicator 84 applies a coating agent to the printing paper P. The printing paper P is then transported below the liquid ejection head 2.

[0119] The printer 101 according to this embodiment has a head chamber 85 that houses the liquid ejection head 2. The head chamber 85 is connected to the outside in some areas, such as the area where the printing paper P enters and leaves, but is generally a space that is isolated from the outside. The head chamber 85 has at least one of the control factors, such as temperature, humidity, and air pressure, controlled by a control unit 88 or the like as needed. The head chamber 85 is less susceptible to disturbances than the outside, so the fluctuation range of the above-mentioned control factors can be narrower than the outside.

[0120] The head mounting frame 270 on which the liquid ejection heads 2 are mounted is roughly the same as the head mounting frame 270 of the embodiment, divided for each head group 72, and is housed in a head chamber 85. Five rollers 82B serving as guide rollers are arranged in the head chamber 85, and the printing paper P is transported over the rollers 82B. The five rollers 82B are arranged so that the center is convex in the direction in which the head mounting frame 270 is arranged when viewed from the side. As a result, the printing paper P transported over the five rollers 82B has an arc shape when viewed from the side, and by applying tension to the printing paper P, the printing paper P is stretched flat between the rollers 82B. One head mounting frame 270 is arranged between two rollers 85B. The angle at which each head mounting frame 270 is installed is slightly changed so that it is parallel to the printing paper P transported below it.

[0121] The printer 101 according to this embodiment includes a dryer 78. Printing paper P exiting the head chamber 85 passes between two transport rollers 82C and then through the dryer 78. Drying the printing paper P in the dryer 78 reduces adhesion between overlapping sheets of printing paper P wound around the transport rollers 82C and reduces friction between undried liquid. High-speed printing requires fast drying. To speed up drying, the dryer 78 may use multiple drying methods in sequence, or multiple drying methods may be used in combination. Examples of drying methods used in such cases include blowing hot air, irradiating infrared rays, and contact with a heated roller. When irradiating infrared rays, infrared rays within a specific frequency range may be used to speed up drying while minimizing damage to the printing paper P.

[0122] When the printing paper P is brought into contact with a heated roller, the time for heat transfer may be increased by transporting the printing paper P along the cylindrical surface of the roller. The range of transport along the cylindrical surface of the roller is preferably at least ¼ of the circumference of the cylindrical surface of the roller, and more preferably at least ½ of the circumference of the cylindrical surface of the roller. When printing with UV-curable ink or the like, a UV irradiation light source may be provided instead of or in addition to the dryer 78. The UV irradiation light source may be provided between each head mounting frame 270.

[0123] At least one of the coater 82, the head chamber 85 and the dryer 78 may be combined with the frame 70 of the embodiment.

[0124] The printer 1 or 101 may be equipped with a cleaning unit that cleans the liquid ejection head 2. The cleaning unit performs cleaning by, for example, wiping or capping. Wiping involves, for example, using a flexible wiper to rub the surface from which the liquid is ejected, e.g., the ejection surface, to remove any liquid adhering to that surface. Cleaning by capping is performed, for example, as follows: First, a cap is placed over the area from which the liquid is ejected, e.g., the ejection surface (this is called capping), creating a nearly sealed space between the ejection surface and the cap. Repeated liquid ejection in this state removes any liquid that has become more viscous than normal and any foreign matter that has clogged the nozzles. Capping prevents the liquid from splashing onto the printer 1 or 101 during cleaning and prevents the liquid from adhering to the printing paper P, rollers, or other transport mechanisms. The ejection surface after cleaning may then be wiped. Wiping and capping and cleaning may be performed manually by a person using wipers and caps attached to the printer 1 or 101, or may be performed automatically by the control unit 88.

[0125] In one embodiment, (1) a liquid ejection head includes a flow path member having a plurality of ejection holes, a plurality of pressure chamber bodies each connected to the plurality of ejection holes, one or more second common flow paths connected in common to the plurality of pressure chamber bodies, partial flow paths connecting the ejection holes and the pressure chamber body, one or more first common flow paths connected in common to each of the partial flow paths, and a first flow path connecting the partial flow paths and the first common flow path; and a plurality of pressurizing units that pressurize the plurality of pressure chamber bodies, respectively, wherein the first flow paths have: a first portion connected to one of the ejection holes; and a second portion in which two or more of the first portions of two or more of the first flow paths are connected in common and are further connected to the first common flow path, and two or more of the second portions of the first flow paths are connected to one of the first common flow paths, and the larger of the resonant frequencies of the partial flow paths and the first flow paths is 1.2 times or more greater than the smaller of the two.

[0126] (2) In the liquid ejection head of (1) above, the resonance frequency of the first flow path may be higher than the resonance frequency of the partial flow path.

[0127] (3) In the liquid ejection head of (1) or (2) above, the height of the second portion may be greater than half the height of the first common flow path.

[0128] (4) In the liquid ejection head according to any one of (1) to (3) above, the height of the second portion may be equal to or greater than the height of the first common flow path.

[0129] (5) In the liquid ejection head according to any one of (1) to (4) above, the second portion may have the same height as the first common flow path.

[0130] (6) In any one of the liquid ejection heads (1) to (5) above, the cross-sectional area of ​​the first portion in a cross section perpendicular to the flow of liquid flowing through the first portion may be 1 / 5 or less of the cross-sectional area of ​​the second portion in a cross section perpendicular to the flow of liquid flowing through the second portion, and the resonant frequency of the first flow path may be the resonant frequency of the second portion.

[0131] (7) In the liquid ejection head according to any one of (1) to (6) above, the length of the partial flow path may be 0.5 to 2 times the length of the first flow path.

[0132] (8) In the liquid ejection head according to any one of (1) to (7) above, the two first portions may be connected to the second portion independently and spaced apart from each other.

[0133] (9) In any one of the liquid ejection heads (1) to (8) above, the first portion may include two or more horizontal paths and one or more vertical paths connecting the two or more horizontal paths, and the cross-sectional area of ​​the horizontal path connected to the second portion in a cross section perpendicular to the flow of liquid flowing through the two or more horizontal paths may be larger than the cross-sectional area of ​​the horizontal path connected to the partial flow path.

[0134] (10) In any one of the liquid ejection heads (1) to (9) above, when viewed from a direction along the connecting flow path, the two first portions may be connected to the ends of the second portions in line symmetry with respect to a line along the direction in which the second portions extend from the first common flow path.

[0135] (11) In the liquid ejection head of (10) above, when viewed from a direction along the partial flow path, the second portion may extend linearly from the first common flow path in a direction perpendicular to the direction along the first common flow path.

[0136] (12) In the liquid ejection head according to any one of (1) to (11) above, the two first portions may be connected to the second portion at an acute angle to each other.

[0137] (13) In the liquid ejection head of (9) above, the height of the horizontal path connected to the second portion may be less than 50% of the height of the second portion.

[0138] In one embodiment, (14) a recording device includes: a liquid ejection head according to any one of (1) to (13) above; a transport unit that moves a recording medium and the liquid ejection head relatively; and a control unit that controls the liquid ejection head.

[0139] Further advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

[0140] REFERENCE SIGNS LIST 1 Printer 2 Liquid ejection head 4 First flow path member 6 Second flow path member 8 Ejection hole 10 Pressure chamber 10a Pressure chamber body 10b Partial flow path 12 Second flow path 14 First flow path 14a First individual flow path (first portion) 14aa Third portion 14ab Fourth portion 14b Connection flow path (second portion) 20 Second common flow path 22 First common flow path

Claims

1. A liquid ejection head comprising: a flow path member having a plurality of ejection holes, a plurality of pressurizing chamber bodies each connected to the plurality of ejection holes, one or more second common flow paths connected in common to the plurality of pressurizing chamber bodies, partial flow paths connecting the ejection holes and the pressurizing chamber body respectively, one or more first common flow paths connected in common to each of the partial flow paths, and a first flow path connecting the partial flow paths and the first common flow path; and a plurality of pressurizing units for pressurizing the plurality of pressurizing chamber bodies respectively, wherein the first flow paths have a first portion connected to one of the ejection holes, and a second portion in which two or more of the first flow paths have a first portion connected in common and are further connected to the first common flow path, and two or more of the second portions of the first flow paths are connected to one of the first common flow paths, and the larger of the resonant frequency of the partial flow paths and the resonant frequency of the first flow path is 1.2 times or more than the smaller of the two.

2. The liquid ejection head according to claim 1, wherein the resonant frequency of the first flow path is higher than the resonant frequency of the partial flow path.

3. The liquid ejection head according to claim 1 or 2, wherein the height of said second portion is higher than half the height of said first common flow path.

4. A liquid ejection head according to any one of claims 1 to 3, wherein the height of said second portion is equal to or greater than the height of said first common flow path.

5. A liquid ejection head according to any one of claims 1 to 4, wherein the second portion has the same height as the first common flow path.

6. A liquid ejection head described in any one of claims 1 to 5, wherein a cross-sectional area of ​​the first portion in a cross section perpendicular to the flow of liquid flowing through the first portion is 1 / 5 or less of a cross-sectional area of ​​the second portion in a cross section perpendicular to the flow of liquid flowing through the second portion, and a resonant frequency of the first flow path is a resonant frequency of the second portion.

7. The liquid ejection head according to claim 1, wherein the length of the partial flow path is 0.5 to 2 times the length of the first flow path.

8. The liquid ejection head according to any one of claims 1 to 7, wherein the two first portions are independent of the second portion and connected to the second portion at a distance from each other.

9. A liquid ejection head described in any one of claims 1 to 8, wherein the first portion includes two or more horizontal paths and one or more vertical paths connecting the two or more horizontal paths, and the cross-sectional area of ​​the horizontal path connected to the second portion in a cross section perpendicular to the flow of liquid flowing through the two or more horizontal paths is larger than that of the horizontal path connected to the partial flow path.

10. A liquid ejection head described in any one of claims 1 to 9, wherein, when viewed from a direction along the partial flow paths, the two first portions are connected to the ends of the second portions in line symmetry with respect to a line along the direction in which the second portions extend from the first common flow path.

11. A liquid ejection head as described in claim 10, wherein, when viewed from a direction along the partial flow path, the second portion extends linearly from the first common flow path in a direction perpendicular to the direction along the first common flow path.

12. The liquid ejection head according to any one of claims 1 to 11, wherein the two first portions are connected to the second portion at an acute angle to each other.

13. The liquid ejection head according to claim 9, wherein the height of the horizontal path connected to the second portion is less than 50% of the height of the second portion.

14. A recording device comprising: a liquid ejection head according to any one of claims 1 to 13; a transport unit for relatively moving a recording medium and said liquid ejection head; and a control unit for controlling said liquid ejection head.

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