JP2016036984A - Liquid discharge head and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow image quality to be improved by reducing variation in droplet discharge property in a nozzle arraying direction by a simple structure.SOLUTION: A liquid discharge head comprises a plurality of nozzles 4 that discharge liquid droplets, a plurality of individual flow paths 5 communicated with the plurality of nozzles 4 respectively and a common liquid chamber 10 that supplies liquid to the plurality of individual flow paths 5. Between the common liquid chamber 10 and the individual flow paths 5 are provided filter portions 9 for each individual flow path 5. The common liquid chamber 10 has, at an end part in a nozzle arraying direction, a narrowing portion 10Z in which a distance between the filter portion 9 and a surface opposing to the filter portion 9 becomes gradually smaller as approaching the end part. Fluid inductance of a filter portion 9B opposing to the narrowing portion 10Z of the common liquid chamber 10 is larger than fluid inductance of a filter portion 9A opposing to a part other than the narrowing portion 10.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a liquid discharge head and an image forming apparatus.

  As an image forming apparatus, for example, an apparatus using a liquid discharge head (droplet discharge head) for discharging liquid droplets as a recording head, for example, an ink jet recording apparatus is known.

  As a conventional liquid discharge head, a common liquid chamber that supplies liquid to a plurality of individual liquid chambers has a constricted portion at the end in the nozzle arrangement direction, and an external supply port side and an individual liquid chamber side in the common liquid chamber A supply path forming member formed with a plurality of supply paths that communicate with each other is provided, and the supply path forming member has an opening area of the supply path at both ends in the longitudinal direction corresponding to the narrowed portion of the common liquid chamber. The thing of the structure smaller than the opening area of the supply path of a center part is known (patent document 1).

JP 2009-0669904 A

  By the way, in the configuration having the constriction at the end of the common liquid chamber in the nozzle arrangement direction, the natural vibration period (resonance period) of the liquid chamber varies depending on the difference in distance between the individual flow path and the wall surface of the constriction. Occur.

  Therefore, when droplets are ejected simultaneously from a plurality of nozzles including nozzles that lead to the individual liquid chamber corresponding to the narrowed portion, the drop velocity between the nozzles that lead to the individual liquid chamber corresponding to the narrowed portion and the other nozzles is reduced. Variation will occur.

  Here, as in the configuration disclosed in Patent Document 1 described above, the opening area of the supply path on the end portion side corresponding to the narrowed portion is made smaller than the opening area of the supply path on the center side, so that the nozzle arrangement direction The fluid inductance on the end portion side can be increased, and the resonance period of the individual liquid chamber can be increased on the end portion side.

  However, in the configuration disclosed in Patent Document 1, since a common flow path is formed between the supply path forming member that forms the supply path and the individual liquid chamber (individual flow path), the common liquid There is a problem that it is difficult to correct the resonance period of the individual liquid chamber corresponding to the end side in the nozzle arrangement direction of the chamber to be close to the resonance period of the individual liquid chamber corresponding to the center side.

  The present invention has been made in view of the above problems, and an object of the present invention is to improve image quality by reducing variations in droplet discharge characteristics in the nozzle arrangement direction with a simple configuration.

In order to solve the above-described problem, a liquid discharge head according to claim 1 of the present invention includes:
A plurality of nozzles for discharging droplets;
A plurality of individual channels through which the plurality of nozzles respectively communicate;
A common liquid chamber for supplying a liquid to the plurality of individual flow paths,
Between the common liquid chamber and the individual flow path, a filter unit is provided for each individual flow path,
The common liquid chamber has a constricted portion at an end portion in the nozzle arrangement direction, in which a distance between the filter portion and a surface facing the filter portion gradually decreases as it goes toward the end portion,
The fluid inductance of the filter portion facing the narrowed portion of the common liquid chamber is larger than the fluid inductance of the filter portion facing the portion other than the narrowed portion of the common liquid chamber.

  According to the present invention, it is possible to reduce variation in droplet discharge characteristics and improve image quality with a simple configuration.

FIG. 6 is an exploded perspective view of an example of a liquid discharge head according to the present invention. It is a principal part section explanatory drawing which follows a direction which intersects perpendicularly with a nozzle arrangement direction. It is a principal part sectional view similarly along a nozzle arrangement direction. It is a perspective explanatory view of a frame member similarly provided with a damper member. FIG. 5 is a perspective cross-sectional explanatory view along the nozzle arrangement direction of FIG. 4. It is explanatory drawing with which it uses for description of the common liquid chamber shape in the nozzle arrangement direction in 1st Embodiment of this invention. It is the plane explanatory view which looked at the channel portion of the embodiment from the nozzle side. It is explanatory drawing of the droplet discharge state with which the narrow part is provided in the edge part of a common liquid chamber, and it uses for description of the variation in the droplet speed in the nozzle arrangement direction of the comparative example which does not apply this invention. It is explanatory drawing of an example of a drive pulse similarly. It is explanatory drawing of an example of the pulse width characteristic of drop speed similarly. It is explanatory drawing of a droplet discharge state similarly. It is the plane explanatory view which looked at the channel portion of a 2nd embodiment of the present invention from the nozzle side. It is the plane explanatory view which looked at the channel portion of a 3rd embodiment of the present invention from the nozzle side. It is plane explanatory drawing which looked at the flow-path part of 4th Embodiment of this invention from the nozzle side. It is plane explanatory drawing which looked at the flow-path part of 5th Embodiment of this invention from the nozzle side. It is plane explanatory drawing which looked at the flow-path part of 6th Embodiment of this invention from the nozzle side. 1 is a perspective explanatory view of an example of an image forming apparatus according to the present invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings. An example of a liquid discharge head according to the present invention will be described with reference to FIGS. FIG. 1 is an exploded perspective view of the liquid discharge head, FIG. 2 is a cross-sectional view of the main part along the direction orthogonal to the nozzle arrangement direction, and FIG. 3 is a cross-sectional view of the main part along the nozzle arrangement direction.
It is.

  The liquid discharge head includes a nozzle plate 1, a flow path plate 2, a vibration plate 3, a piezoelectric element 11 that is a pressure generating unit, a holding substrate 50, and a frame member 70 that also serves as a common liquid chamber member. Yes. In the present embodiment, a portion constituted by the flow path plate 2, the vibration plate 3 and the piezoelectric element 11 is referred to as an “actuator substrate 20”. However, this does not mean that an independent member is formed as the actuator substrate 20 and is joined to the nozzle plate 1, the holding substrate 50, and the frame member 70.

  A plurality of nozzles 4 for discharging droplets are formed on the nozzle plate 1. Here, four nozzle rows in which the nozzles 4 are arranged are arranged.

  The flow path plate 2, together with the nozzle plate 1 and the vibration plate 3, form an individual liquid chamber 6 that communicates with the nozzle 4, a fluid resistance portion 7 that communicates with the individual liquid chamber 6, and a liquid introduction portion (passage) 8 that communicates with the fluid resistance portion 7. doing. These individual liquid chamber 6, fluid resistance portion 7, and liquid introduction portion 8 are combined to form an individual flow path 5.

  The liquid introducing portion 8 communicates with the common liquid chamber 10 formed by the opening 10 </ b> A of the holding substrate 50 and the frame member 70 through the filter portion 9 formed in the diaphragm 3. The opening 10A is a part of the common liquid chamber 10 described later. In addition, the filter part 9 is comprised by the 1 or several filter hole 91 as shown in FIG.

  The vibration plate 3 forms a deformable vibration region 30 that forms a part of the wall surface of the individual liquid chamber 6. A piezoelectric element 11 is provided integrally with the vibration region 30 on the surface of the vibration plate 3 opposite to the individual liquid chamber 6 in the vibration region 30, and a piezoelectric actuator is configured by the vibration region 30 and the piezoelectric element 11. Yes.

  The piezoelectric element 11 is configured by sequentially laminating a lower electrode 13, a piezoelectric layer (piezoelectric body) 12, and an upper electrode 14 from the vibration region 30 side. An interlayer insulating film 21 is formed on the piezoelectric element 11.

  The lower electrode 13 of the piezoelectric element 11 is drawn out through the common wiring 15 and connected to the connection pad 17. The upper electrode 14 is drawn out via the individual wiring 16 and connected to the connection pad 18 and is connected to a driving IC (driver IC) (not shown).

  The driver IC is mounted on the actuator substrate 20 by a method such as flip chip bonding or wire bonding so as to cover a region between the rows of piezoelectric element rows.

  On the actuator substrate 20, a recess (vibration chamber) 51 that accommodates the piezoelectric element 11 and a holding substrate 50 that forms a wiring space 52 are provided via the passivation layer 22.

  As described above, the holding substrate 50 also forms the opening 10A which is a part of the common liquid chamber. The holding substrate 50 is bonded to the diaphragm 3 side of the actuator substrate 20 with an adhesive.

  In this liquid discharge head configured as described above, by applying a voltage between the upper electrode 14 and the lower electrode 13 of the piezoelectric element 11 from the driver IC, the piezoelectric layer 12 expands in the electrode stacking direction, that is, the electric field direction, Shrink in a direction parallel to the vibration region 30.

  At this time, since the lower electrode 13 side is constrained by the vibration region 30, a tensile stress is generated on the lower electrode 13 side of the vibration region 30, and the vibration region 30 bends toward the individual liquid chamber 6 side and applies the internal liquid. By pressing, a droplet is discharged from the nozzle 4.

  Next, an example of the frame member forming the common liquid chamber will be described with reference to FIGS. 4 is a perspective explanatory view of a frame member provided with a damper member, and FIG. 5 is a perspective cross-sectional explanatory view along the nozzle arrangement direction of FIG.

  The frame member 70 is bonded to the opposite side of the surface of the actuator substrate 20 to which the nozzle plate 1 is bonded, and a common liquid chamber that supplies liquid to the plurality of individual liquid chambers 6 through which the plurality of nozzles 4 that discharge droplets communicate. 10 (having a concave portion that becomes the common liquid chamber 10).

  Further, the frame member 70 is formed with a recess 75 that accommodates the damper member 80 and serves as a damper chamber.

  In addition, the frame member 70 has a connecting pipe part that forms at least a part of a supply pipe part that supplies liquid from the outside to the common liquid chamber 10 at the central part of the concave part 75 in the longitudinal direction (nozzle arrangement direction) 76 is provided. A liquid supply path 71 is formed in the connecting pipe portion 76 (see FIG. 5).

  The damper member 80 is disposed in a region between the wall portion of the frame member 70 constituting the connecting pipe portion 76 and the side wall of the recess in the common liquid chamber longitudinal direction.

  The damper member 83 includes a reversibly deformable damper 81 that forms a part of the wall surface opposite to the individual liquid chamber side of the common liquid chamber 10, and a holding member 82 that is joined to the damper 81 and holds the damper 81. It has. The holding member 82 has an opening 83 (which becomes a part of the damper chamber) that allows deformation of the damper 81.

  On the other hand, a flow path conversion member 90 (see FIG. 1) is joined to the opening side of the recess 75 of the frame member 70.

  The connecting pipe part 76 of the frame member 70 and the connecting pipe part (not shown) of the flow path converting member 90 are connected via a packing.

  Next, a first embodiment of the present invention will be described with reference to FIGS. FIG. 6 is an explanatory diagram for explaining the shape of the common liquid chamber in the nozzle arrangement direction in the same embodiment, and FIG. 7 is an explanatory plan view of the flow path portion of the same embodiment as seen from the nozzle side.

  In the present embodiment, a filter unit 9 is provided for each individual flow path 5 between the common liquid chamber 10 and the individual flow path 5. In addition, although the fluid resistance part 7 is comprised by the flow path branched by the center partition part 7a, it can also be made into one fluid resistance part.

  The common liquid chamber 10 has, at the end in the nozzle arrangement direction, a constricted portion 10Z that gradually decreases as the distance between the filter portion 9 and the surface (wall surface) 10a facing the filter portion 9 approaches the end portion. ing. When the droplet discharge is performed downward, the narrowed portion 10Z becomes lower in the height direction (Z direction) as the position of the wall surface 10a approaches the end portion.

  The wall surface 10a forming the constricted portion 10Z may be a linearly inclined surface as schematically shown in FIG. 6, or may be a curved surface as shown in FIG. .

  Here, the filter unit 9 facing the portion other than the narrowed portion 10Z of the common liquid chamber 10 is referred to as a filter unit 9A, and the filter unit 9 facing the narrowed portion 10Z of the common liquid chamber 10 is referred to as a filter unit 9B.

  The fluid inductance of the filter portion 9B facing the constricted portion 10Z of the common liquid chamber 10 is made larger than the fluid inductance of the filter portion 9A facing the portion other than the constricted portion 10Z of the common liquid chamber 10.

  In the present embodiment, the filter hole 91b of the filter portion 9B has an opening diameter (hereinafter simply referred to as “diameter”) φ1, and the filter hole 91a of the filter portion 9A has a diameter φ0. In the embodiment, the opening area is represented by a diameter.

  Then, by forming the filter hole 91b of the filter portion 9B to have a diameter φ1 smaller than the diameter φ0 of the filter hole 91a of the filter portion 9A (φ1 <φ0), the fluid inductance of the filter portion 9B is greater than the fluid inductance of the filter portion 9A. It is also bigger.

  As a result, the resonance period of each individual flow path 5 in the nozzle arrangement direction can be made substantially the same at the end portion and the central portion, and variations in droplet discharge speed (droplet speed) can be reduced. Can be improved.

  Here, refer to FIGS. 6 to 9 for variations in droplet ejection characteristics (particularly, droplet velocity) in the nozzle arrangement direction of the comparative example having the constricted portion 10Z at the end of the common liquid chamber 10 but not applying the present invention. To explain.

  First, in the case where the end portion of the common liquid chamber 10 has the constricted portion 10Z, as shown in FIG. 6, the droplets ejected from the nozzles on the end side in the nozzle arrangement direction are more than the droplets ejected from the nozzles on the center side. However, the phenomenon that the droplet velocity Vj becomes slow occurs.

  This point will be described in relation to the resonance period (natural vibration period) Tc of the individual flow path.

  As shown in FIG. 7, a drive pulse is applied which includes a waveform element a that is expanded in the individual liquid chamber 6, a waveform element b that holds the expanded state, and a waveform element c that contracts the individual liquid chamber from the expanded state. Thus, the piezoelectric element 11 is driven.

  When the time (holding time) of the waveform element b of the drive pulse is the pulse width Pw, the drop velocity Vj when the pulse width Pw is changed is the pressure vibration of the pressure that caused the individual liquid chamber 6 to expand and the individual liquid. It changes as shown in FIG. 8, for example, depending on the timing at which the pressure for contracting the chamber 6 is superimposed. Note that the droplet velocity Vj in FIG. 8 indicates the numerical value of the ejected droplets from the nozzle located at the center in the nozzle arrangement direction.

  In the example of FIG. 8, the first peak of the drop velocity Vj is present at the pulse width Pw = 1.25 μs, and the second peak of the drop velocity Vj is present near Pw = 5.25 μs.

  On the other hand, FIG. 9 shows the ejection state of the nozzles at the end in the nozzle arrangement direction when the pulse width Pw is changed. Here, thinning driving for driving every four nozzles and multi driving for simultaneously driving all nozzles are shown.

  As can be seen from FIG. 9, in thinning driving with a small number of simultaneously driven nozzles, the droplet velocity Vj ejected from the nozzle at the nozzle array direction end and the droplet velocity ejected from the nozzle at the center in the nozzle array direction are almost the same. The same. That is, in this thinning drive, the first peak is when the pulse width Pw = 1.25 μs, and the second peak is when the pulse width Pw = 5.25 μs.

  On the other hand, when multi-driving with a large number of simultaneously driven nozzles is performed, especially when the pulse width Pw = 5.25 μs, which is the second peak of the droplet velocity Vj ejected from the nozzle in the center of the nozzle arrangement direction, The drop velocity Vj of the droplets ejected from the nozzles at the nozzle array direction end is slow. The droplet velocity Vj ejected from the nozzle in the center of the nozzle arrangement direction is substantially the same as the droplet velocity Vj ejected from the nozzle in the center of the nozzle array in the timing shorter than the nozzle width Pw = 5.25 μs. The pulse width Pw = 4.75 μs.

  As described above, since the end of the common liquid chamber in the nozzle arrangement direction is narrowed, when the number of nozzles simultaneously ejecting droplets is large, the same characteristic as when the pulse width characteristic is substantially shortened is exhibited.

  As a result, variations in the landing position accuracy of the droplets increase, and in particular, when a plurality of pulses that modulate the number of droplets are continuously ejected in the gradation expression, the influence is superimposed, so that the image deterioration occurs. Becomes prominent.

  Therefore, in the present embodiment, the fluid inductance of the filter portion 9B at the nozzle arrangement direction end is set larger than the fluid inductance of the filter portion 9A at the nozzle arrangement direction center.

  In the present embodiment, the filter hole 91b of the filter portion 9B has a diameter φ1, which is smaller than the diameter φ0 of the filter hole 91A of the filter portion 9A (φ1 <φ0). Since the filter parts 9B and 9A have the same number of filter holes 91 and the same thickness of the diaphragm 3 forming the filter part 9, the fluid inductance of the filter part 9B becomes relatively large.

  Here, in general, when a flow path having a circular cross section (corresponding to the filter hole 91 alone) is replaced with a circuit element of R, L, and C as a lumped constant, each value can be obtained as follows.

Ro = k1 · 8 · μ · L0 / (π · r4)
Lo = k2 · ρ · L0 / (π · r ² )
Co = (π · r ² ) · L0 / (c ² · ρ)

  However, k1, k2: correction constant, μ: liquid viscosity, ρ: liquid density, c: liquid sound velocity, L0: flow path length, r: flow path tube diameter.

  The filter unit 9 formed by the plurality of filter holes 91 may be considered as each circuit element of the filter holes 91 being arranged and connected in parallel.

  When the number of filter holes 91 of the filter unit 9 is increased, the inductance L of the filter unit 9 is reduced because of the parallel connection of the inductance Lo.

  Approximately, assuming that the inductance of each filter hole 91 is Lo, the inductance L of the filter portion 9 is Lo / n when n filter holes 91 are connected in parallel.

  In the present embodiment, as described above, the filter hole 91b of the filter portion 9B has a diameter φ1, which is smaller than the diameter φ0 of the filter hole 91a of the filter portion 9A (φ1 <φ0).

Thereby, the filter hole 91b of the filter part 9B has a flow path pipe diameter r in the above equation “L = k2 · ρ · L0 / (π · r ² )” smaller than that of the filter hole 91a of the filter part 9A. Since the duct length (thickness of the diaphragm 3) is the same, the inductance L of each filter hole 91b of the filter portion 9B is larger than the inductance L of each filter hole 91a of the filter portion 9A.

  And since the number of the filter holes 91a and 91b of filter part 9A, 9B is the same, the fluid inductance of filter part 9B becomes larger than the fluid inductance of filter part 9A.

  The resonance period (natural vibration period) Tc of the individual flow path 5 is expressed by “Tc∝√ (LC)” from the inductance L of the entire individual flow path 5 including the filter unit 9 and the compliance C.

  Here, since the compliance Co of each filter hole 91 of the filter unit 9 is very small compared to the compliance of the diaphragm, the inductance Lo of each filter hole 91 of the filter unit 9 acts on the resonance period Tc.

  Therefore, if the fluid inductance L of the filter unit 9 is increased, the individual flow path 5 and the individual filter unit 9 are connected in series, so that the inductance of the entire flow path is increased.

  Thereby, when the pressure resonance (resonance period) including the filter part 9 is considered, since the fluid inductance of the filter part 9 becomes large, the resonance period Tc of pressure becomes long.

  Here, as described above, the constricted portion 10Z of the common liquid chamber 10 behaves as if the pressure resonance period is shortened, so the pressure resonance period of the individual flow path 5 corresponding to the constricted portion 10Z is slightly longer. By setting, it is possible to prevent the drop velocity Vj of the droplets from the nozzle corresponding to the narrowed portion 10Z from being lowered when droplets are ejected by multi-drive.

  Returning to FIGS. 4 and 5, in this embodiment, a plurality (1) not used for image formation is disposed on both sides in the nozzle arrangement direction of the plurality of individual flow paths 5 including the nozzles 4 for discharging the droplets for image formation. The dummy individual flow path 105 may be arranged.

  The dummy individual flow path 105 corresponds to the endmost side of the narrowed portion 10Z of the common liquid chamber 10.

  Here, the two dummy individual flow paths 105 from the extreme end side of the constricted portion 10Z of the common liquid chamber 10 have the same width as the individual liquid chamber width without providing the fluid resistance portion, and the portion corresponding to the filter portion is It is just a large opening 90. Further, the dummy individual flow path 105 adjacent to the individual flow path 5 is provided with a fluid resistance portion, and a portion corresponding to the filter portion is simply a large opening 90.

  Thereby, the fluid resistance value of the dummy individual flow path 105 and the entire opening 90 is reduced, and the flow rate of the dummy individual flow path 105 can be increased when performing maintenance for sucking and discharging the liquid from the nozzle. improves.

  In addition, it is preferable that the dummy individual flow path 105 has the same flow path shape as the individual flow path 5 (except for the partition wall portion that forms the fluid resistance portion). Thereby, while ensuring the rigidity as a structure, the dispersion | variation in the droplet discharge characteristic of the separate liquid chamber 6 of a nozzle arrangement direction edge part can be suppressed. Further, when the flow path is formed by etching, uneven etching occurs due to a pattern change. Therefore, by forming the dummy individual flow path, etching unevenness peculiar to the end can be prevented.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 10 is an explanatory plan view of the channel portion of the same embodiment as viewed from the nozzle side.

  In the present embodiment, the filter portion 9B corresponding to the narrowed portion 10Z and the filter portion 9A corresponding to a portion other than the narrowed portion 10Z are formed with a filter hole 91a having the same diameter, for example, a diameter φ0.

  Then, the number of filter holes 91a in the filter unit 9B is made smaller than the number of filter holes 91a in the filter unit 9A, and the fluid inductance of the filter unit 9B at the end in the nozzle arrangement direction is changed to the filter unit 9A in the center in the nozzle arrangement direction. It is set larger than the fluid inductance.

  Accordingly, similarly to the first embodiment, the resonance period of the filter unit 9 and the individual flow path 5 at the end in the nozzle arrangement direction is set to be long, and the resonance period is substantially reduced due to the pressure interference of the common liquid chamber by the narrowed part 10Z. The phenomenon of the shortening can be alleviated, and the variation in the drop speed can be suppressed.

  Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 11 is an explanatory plan view of the flow path portion of the same embodiment as viewed from the nozzle side.

  In the present embodiment, as the filter portion 9B corresponding to the narrowed portion 10Z, the filter portion 9B1 and the filter portion 9B2 are arranged from the end side toward the center side (side adjacent to the filter portion 9A) in the nozzle arrangement direction. ing.

  The filter portion 9B1 is provided with nine filter holes 91b having a diameter φ1, and the filter portion 9B2 is provided with ten filter holes 91b having a diameter φ1. The filter portion 9A is provided with ten filter holes 91a having a diameter φ0 (φ0> φ1).

  That is, the filter part 9B corresponding to the end part side is provided with a smaller number of filter holes 91b having a smaller diameter than the filter hole 91a of the filter part 9A corresponding to the center part side than the number of the filter holes 91a of the filter part 9A. ing.

  Thereby, the fluid inductance of the filter portion 9B increases stepwise (can be made continuous) from the central portion side in the nozzle arrangement direction toward the end portion.

  Therefore, similarly to the first and second embodiments, the resonance period of the filter unit 9 and the individual flow path 5 at the end in the nozzle arrangement direction is set long, and the resonance period is caused by the pressure interference of the common liquid chamber by the narrowed part 10Z. Can alleviate the phenomenon of substantially shortening the droplet speed and suppress variations in droplet speed.

  The number of filter holes is an example, and is not limited to the above number (the same applies to the following embodiments).

  Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 12 is an explanatory plan view of the flow path portion of the same embodiment as viewed from the nozzle side.

  In the present embodiment, as the filter portion 9B corresponding to the narrowed portion 10Z, the filter portion 9B3 and the filter portion 9B2 are arranged from the end side toward the center side (side adjacent to the filter portion 9A).

  The filter portion 9B3 is provided with ten filter holes 91c having a diameter φ2 (φ2 <φ1). The filter portion 9B2 is provided with ten filter holes 91b having a diameter φ1. The filter portion 9A is provided with ten filter holes 91a having a diameter φ0 (φ0> φ1).

  Thereby, the fluid inductance of the filter portion 9B increases stepwise (can be made continuous) from the central portion side in the nozzle arrangement direction toward the end portion.

  Therefore, similarly to the first and second embodiments, the resonance period of the filter unit 9 and the individual flow path 5 at the end in the nozzle arrangement direction is set long, and the resonance period is caused by the pressure interference of the common liquid chamber by the narrowed part 10Z. Can alleviate the phenomenon of substantially shortening the droplet speed and suppress variations in droplet speed.

  Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 13 is an explanatory plan view of the flow path portion of the same embodiment as viewed from the nozzle side.

  In the present embodiment, a filter portion 9A2 having a filter hole 91d having a diameter φ3 is provided in a part of the filter portion 9A corresponding to a portion other than the narrowed portion 10Z.

  The diameter φ3 of the filter hole 91d is larger than the diameters φ1 and φ2 of the filter holes 91b and 91c of the filter portions 9B and 9C, and smaller than the diameter φ0 of the filter hole 91a of the filter portion 9A (φ2 <φ1 <φ3 <φ0). .

  As a result, the pressure superposition of the common liquid chamber on the center side can be prevented from gradually increasing the peak of the superposition pressure by gradually changing the resonance period including the filter section, and the droplet velocity due to the pressure resonance of the common liquid chamber can be prevented. Variation distribution can be reduced.

  Next, a sixth embodiment of the present invention will be described with reference to FIG. FIG. 14 is an explanatory plan view of the channel portion of the same embodiment as viewed from the nozzle side.

  In this embodiment, a portion corresponding to the filter portion of a part of the dummy individual flow path 105 other than the endmost portion in the nozzle arrangement direction is the damper portion 95. It should be noted that at least the dummy individual channel 105 at the extreme end in the nozzle arrangement direction is not a damper portion in order to ensure bubble discharge performance.

  Thus, by forming the damper part 95 in the part corresponding to the constriction part 10Z, the pressure peak of the pressure superposition of the common liquid chamber 10 can be suppressed small, the fluid inductance of the filter part 9 is increased, and the resonance period is increased. In addition to shifting the pressure, by reducing the pressure peak, it is possible to suppress variations in droplet speed at the nozzles on the end side in the nozzle arrangement direction.

  In each of the above embodiments, the liquid supply port is provided at the center in the nozzle arrangement direction of the common liquid chamber, and the configuration of the center supply in which the liquid flows toward both ends of the nozzle arrangement direction has been described. A liquid supply port may be provided at one end in the nozzle arrangement direction, and a one-sided supply structure in which liquid flows toward the other end in the nozzle arrangement direction may be employed.

  Further, in each of the above embodiments, the configuration has been described in which the narrow portion is provided at the end portion in the nozzle arrangement direction of the common liquid chamber, but the narrow portion is provided at the end portion with the wall surface gradually inclined from the liquid supply port side. The common liquid chamber of the structure formed may be sufficient. Even in this case, in the common liquid chamber, the distance between the filter unit and the surface facing the filter unit in the nozzle arrangement direction is shorter on the end side than on the liquid supply port side, and as it is directed toward the end side as described above. The same phenomenon occurs when the resonance period becomes substantially longer.

  Next, an example of the image forming apparatus according to the present invention will be described with reference to FIG. FIG. 15 is an explanatory perspective view of the image forming apparatus.

  This image forming apparatus is a serial type image forming apparatus, and a carriage 403 is movably supported on a guide member 401, and is moved and scanned by a motor 406 via a belt 407.

  The carriage 403 is equipped with a recording head 411 that is a liquid ejection head according to the present invention that ejects droplets.

  On the other hand, a conveyance roller 412 that conveys the medium 410 facing the recording head 411 is provided. The transport roller 412 is rotationally driven by a motor 413, and the transported medium 410 is guided and supported by a transport guide member 414.

  In this image forming apparatus, the medium 410 is intermittently conveyed by a predetermined amount by the conveying roller 412, and droplets are ejected from the recording head 411 while moving and scanning the carriage 403 with respect to the stopped medium 410. Form.

  Further, during standby, the carriage 403 is moved to the maintenance device 420 side.

  The maintenance device 420 includes a cap for capping the nozzle surface of the recording head 411, a wiping member for wiping the nozzle surface, and the like.

  The maintenance device 420 performs a maintenance recovery operation of capping the nozzle surface with a cap and sucking and discharging the thickened ink from the nozzle with a suction pump, and capping the nozzle surface to prevent the ink from drying.

  Since this image forming apparatus includes the liquid ejection head according to the present invention, the variation in image density is reduced and a high-quality image can be formed.

  The “image” is not limited to a planar image, but includes an image given to a three-dimensionally formed image and an image formed by three-dimensionally modeling a solid itself.

  Further, the image forming apparatus includes both a serial type image forming apparatus and a line type image forming apparatus, unless otherwise limited.

DESCRIPTION OF SYMBOLS 1 Nozzle plate 2 Flow path plate 3 Vibrating plate 4 Nozzle 6 Individual liquid chamber 9, 9A, 9A1, 9B, 9B1, 9B2, 9B3 Filter part 11 Piezoelectric element 20 Actuator substrate 50 Holding substrate 70 Frame member 91, 91a, 91b, 91c 91d Filter hole 411 Recording head

Claims (8)

A plurality of nozzles for discharging droplets;
A plurality of individual channels through which the plurality of nozzles respectively communicate;
A common liquid chamber for supplying a liquid to the plurality of individual flow paths,
Between the common liquid chamber and the individual flow path, a filter unit is provided for each individual flow path,
The common liquid chamber has a constricted portion at an end portion in the nozzle arrangement direction, in which a distance between the filter portion and a surface facing the filter portion gradually decreases as it goes toward the end portion,
A liquid discharge head characterized in that a fluid inductance of the filter portion facing the narrowed portion of the common liquid chamber is larger than a fluid inductance of the filter portion facing a portion other than the narrowed portion of the common liquid chamber. . The filter unit is provided with a plurality of filter holes,
The number of filter holes in the filter portion facing the narrow portion of the common liquid chamber is smaller than the number of filter holes in the filter portion facing portions other than the narrow portion of the common liquid chamber. The liquid discharge head according to claim 1. The filter unit is provided with a plurality of filter holes,
The opening area of one filter hole in the filter portion facing the narrowed portion of the common liquid chamber is larger than the opening area of one filter hole in the filter portion facing the portion other than the narrowed portion of the common liquid chamber. The liquid ejection head according to claim 1, wherein the liquid ejection head is also small. A plurality of the filter parts are opposed to the narrowed part of the common liquid chamber,
4. The liquid according to claim 1, wherein fluid inductances of the plurality of filter parts facing the constriction part increase as approaching the endmost part of the common liquid chamber in the nozzle arrangement direction. Discharge head. 5. The liquid discharge head according to claim 1, wherein an end portion side of the constricted portion of the common liquid chamber communicates with a dummy individual channel that is not used for droplet discharge. 6. The liquid discharge head according to claim 1, further comprising a plurality of the filter portions having different fluid inductances facing a portion other than the narrowed portion of the common liquid chamber. A plurality of nozzles for discharging droplets;
A plurality of individual channels through which the plurality of nozzles respectively communicate;
A common liquid chamber for supplying a liquid to the plurality of individual flow paths,
Between the common liquid chamber and the individual flow path, a filter unit is provided for each individual flow path,
In the common liquid chamber, in the nozzle arrangement direction, the distance between the filter unit and the surface facing the filter unit is shorter on the end side than the liquid supply port side for supplying liquid from the outside,
The liquid discharge head according to claim 1, wherein a fluid inductance of the filter portion corresponding to the end portion side of the common liquid chamber is larger than a fluid inductance of the filter portion corresponding to the liquid supply port side of the common liquid chamber.   An image forming apparatus comprising the liquid discharge head according to claim 1.