Liquid discharge head, liquid discharge device, liquid discharge apparatus, and image forming apparatus

A liquid discharge head includes a nozzle row, individual liquid chambers, a common liquid chamber, a circulation liquid chamber, a supply port, and a delivery port. The nozzle row includes nozzles to discharge liquid. The nozzles are arrayed in a nozzle array direction. The individual liquid chambers are communicated with the nozzles and arrayed in the nozzle array direction. The common liquid chamber extends longer in the nozzle array direction, to supply liquid to the individual liquid chambers. The circulation liquid chamber is communicated with the individual liquid chambers. The supply port is disposed at a center of the common liquid chamber in the nozzle array direction, to supply liquid to the common liquid chamber. The delivery port is disposed outside the common liquid chamber in the nozzle array direction, to deliver liquid from the circulation liquid chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is based on and claims priority pursuant to 35 U.S.C. §119(a) to Japanese Patent Application Nos. 2015-080046, filed on Apr. 9, 2015, and 2016-021504, filed on Feb. 8, 2016, in the Japan Patent Office, the entire disclosure of each of which is hereby incorporated by reference herein.

BACKGROUND

Technical Field

Aspects of the present disclosure relate to a liquid discharge head, a liquid discharge device, and a liquid discharge apparatus, and an image forming apparatus.

Related Art

A circulatory liquid discharge head to circulate liquid is known as a liquid discharge head of an image forming apparatus to discharge liquid.

Such a liquid discharge head includes, for example, a plurality of pressure generation chambers arranged in a nozzle array direction and communicated with respective nozzles of each nozzle row in which the nozzles are arrayed and a common liquid chamber extending longer in the nozzle array direction to supply liquid to the plurality of pressure generation chambers. The liquid discharge head further includes a supply port communicated with the common liquid chamber to supply ink to the common liquid chamber and a delivery port communicated with a circulation channel communicated with the plurality of pressure generation chambers to deliver ink from the circulation channel. The supply port is communicated with an upper portion of one end of the common liquid chamber in the nozzle array direction. The delivery port is disposed at a position outer than the common liquid chamber on an opposite side of the supply port in the nozzle array direction.

SUMMARY

In an aspect of this disclosure, there is provided a liquid discharge head that includes a nozzle row, a plurality of individual liquid chambers, a common liquid chamber, a circulation liquid chamber, a supply port, and a delivery port. The nozzle row includes a plurality of nozzles to discharge liquid. The plurality of nozzles is arrayed in a nozzle array direction. The plurality of individual liquid chambers is communicated with the plurality of nozzles and arrayed in the nozzle array direction. The common liquid chamber extends longer in the nozzle array direction, to supply liquid to the plurality of individual liquid chambers. The circulation liquid chamber is communicated with the plurality of individual liquid chambers. The supply port is disposed at a center of the common liquid chamber in the nozzle array direction, to supply liquid to the common liquid chamber. The delivery port is disposed outside the common liquid chamber in the nozzle array direction, to deliver liquid from the circulation liquid chamber.

In another aspect of this disclosure, there is provided a liquid discharge device that includes the liquid discharge head and at least one of a head tank, a carriage, a supply device, a maintenance device, and a main-scanning moving device.

In still another aspect of this disclosure, there is provided a liquid discharge apparatus that includes the liquid discharge device.

In still yet another aspect of this disclosure, there is provided an image forming apparatus that includes the liquid discharge device to discharge liquid droplets from the liquid discharge head to from an image.

In further yet another aspect of this disclosure, there is provided a liquid discharge apparatus that includes the liquid discharge head.

In still further yet another aspect of this disclosure, there is provided an image forming apparatus that the liquid discharge head to discharge liquid droplets to form an image.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure are described with reference to the attached drawings.

First Embodiment

FIG. 2is a cross-sectional view of a liquid discharge head434as a separately-circulating liquid discharge head according to an embodiment of the present disclosure, cut along a direction perpendicular to a nozzle array direction (indicated by arrow D inFIG. 4) in which nozzles are arrayed.FIG. 3is a cross-sectional view of the liquid discharge head434cut along the nozzle array direction D.FIG. 4is a cross-sectional view of the liquid discharge head434cut along a planar direction of liquid chambers.

The liquid discharge head434according to this embodiment includes a frame1, fluid resistive portions21, a channel plate2, a nozzle pate3, and a diaphragm plate6. The frame1includes recessed portions as an ink supply port11(seeFIG. 4) and a common liquid chamber12. The channel plate2includes recessed portions as pressure generation chambers22and communication channels23communicated with nozzles31. The nozzle pate3includes the nozzles31. The diaphragm plate6includes island-shaped projections61, diaphragm portions62, and ink inlets63. The liquid discharge head434further includes laminated piezoelectric elements5as pressure generating elements joined to the diaphragm plate6via an adhesion layer7and a base4to which the laminated piezoelectric elements5are secured.

The base4is made of barium titanate based ceramic. The laminated piezoelectric elements5are arrayed in two rows and joined to the base4. In the laminated piezoelectric element5, piezoelectric layers made of lead zirconate titanate (PZT), each having a thickness of from 10 μm to 50 μm per layer, and internal electrode layers made of silver-palladium (AgPd), each having a thickness of several μm per layer, are alternately laminated one on another. The internal electrode layers are connected to external electrodes. The laminated piezoelectric elements5are divided in a comb shape by half-cut dicing and alternately used as driving portions56and support portions57(non-driving portions). The outer side of the external electrodes is divided by half-cut dicing and the lengths thereof are limited by processing, e.g., notching to form a plurality of individual electrodes54. The opposite side is conducting without being divided by dicing, to form a common electrode55.

Flexible print circuits (FPC)8are soldered to the individual electrodes54of the driving portions56. For the common electrode55, an electrode layer is disposed at an end portion of the laminated piezoelectric elements5and is turned and joined to a ground (Gnd) electrode of the FPC8. The FPC8is implemented with a head driver109as a head controller to control application of a drive voltage to the driving portions56.

The diaphragm plate6is formed by laminating two layers of Ni plating films by electroforming. The diaphragm plate6includes thin-film diaphragm portions62, island-shaped projections61, thick-film portions, and openings as the ink inlets63. The projection61is joined to the laminated piezoelectric element5as the driving portion56disposed at a central portion of the diaphragm portion62. The thick-film portion includes a beam joined to the frame1. The diaphragm portion62has a thickness of 3 μm and a width of 35 μm (one side). The island-shaped projection61of the diaphragm plate6and the driving portion (movable portion) of the laminated piezoelectric element5are adhered by patterning the adhesion layer7including a gap material. The diaphragm plate6and the frame1are also adhered by patterning the adhesion layer7.

The channel plate2is formed by patterning the fluid resistive portions21, recessed portions to be the pressure generation chambers22, and through-holes to be the communication channel23at positions corresponding to the nozzles31by etching a monocrystalline silicon substrate. Remaining portions after etching form partitions24of the pressure generation chambers22. For the liquid discharge head434, the etching width is partially set smaller to form the fluid resistive portions21.

The nozzle pate3is made of a metal material, for example, a Ni plating film formed by electroforming, and includes a large number of nozzles31that are fine discharge ports to fly ink droplets. The internal shape (interior shape) of the nozzle31is horn-shaped (or may be substantially cylindrical or substantially frustoconical). The diameter of the nozzle31at an exit side of ink droplet is approximately 20 μm to approximately 35 μm. The nozzle pitch of each nozzle row is 150 dots per inch (dpi).

A water-repellent layer32surface-treated for water repellency is disposed on an ink discharge face (a nozzle surface side) of the nozzle pate3. The water-repellent layer32is formed by a treatment selected in accordance with the physical properties of ink from, for example, polytetrafluoroethylene (PTFE)-Ni eutectoid plating, electrodeposition of fluororesin, vapor deposition of exporative fluororesin (e.g., fluorinated pitch), firing after coating of a solution of silicon-based resin or fluorine-based resin. Accordingly, the droplet shape and flying properties are stabilized to obtain a high degree of image quality. The frame1, in which recessed portions to be the ink supply port11and the common liquid chamber12are to be formed, is manufactured by resin molding.

For the liquid discharge head434thus configured, a drive waveform (a pulse voltage of from 10 V to 50 V) constituted of a drive pulse is applied to the driving portions56in accordance with a recording signal. Thus, the driving portions56are displaced in a direction of lamination of the driving portions56and the pressure generation chamber22is pressurized via the diaphragm plate6to increase pressure, discharging ink droplets from the nozzle31. When the discharge of ink droplets ends, the pressure of ink in the pressure generation chamber22decreases. A negative pressure arises in the pressure generation chamber22due to the inertia of ink flow and the electric discharge process of drive voltage (drive pulse) and the process shifts to an ink refilling step. At this time, ink supplied from an ink tank flows into the common liquid chamber12and is refilled into the pressure generation chamber22from the common liquid chamber12through the ink inlet63and the fluid resistive portion21.

The fluid resistive portion21is resistive against the refilled ink due to the surface tension while having an effect of decreasing residual pressure vibration after ink discharge.

By properly selecting the configuration of the fluid resistive portion21, the decay of the residual pressure and the refilling time are balanced, thus allowing a reduction in a transition time (drive cycle) to the next ink-droplet discharge operation.

Next, an example of an ink circulation system using the liquid discharge head434according to this embodiment is described with reference toFIG. 5.

FIG. 5is a block diagram of the ink circulation system according to this embodiment. As illustrated inFIG. 5, the ink circulation system includes, e.g., a main tank410, the liquid discharge head434, a head tank435, a supply pump438a, a circulation pump438b, a liquid feed pump438c, a supply pressure sensor439a, and a circulation pressure sensor439b. The supply pressure sensor439ais disposed between the supply pump438aand the liquid discharge head434and connected to a supply channel connected to a supply port71(seeFIG. 1) of the liquid discharge head434. The circulation pressure sensor439bis disposed between the liquid discharge head434and the circulation pump438band is connected to a circulation channel connected to a circulation port72(seeFIG. 1) of the liquid discharge head434. The supply pump438aand the circulation pump438bflow ink so that the supply pressure sensor439adetects a positive pressure and the circulation pressure sensor439bdetects a negative pressure. Accordingly, ink flows from the head tank435into the liquid discharge head434via the supply port71, exits from the circulation port72, and returns to the head tank435, thus allowing circulation of ink.

The supply pump438aand the circulation pump438bare constantly controlled so that the supply pressure sensor439adetects a constant positive pressure and the circulation pressure sensor439bdetects a constant negative pressure. Such a configuration allows the menisci of ink to be maintained at a constant negative pressure while circulating ink through the inside of the liquid discharge head434. When droplets are discharged from the nozzles31of the liquid discharge head434, the amount of ink in the head tank435decreases.

Accordingly, the liquid feed pump438creplenishes ink from the main tank410to the head tank435. The replenishment of ink from the main tank410to the head tank435is controlled in accordance with a result of detection with, e.g., a liquid level sensor in the head tank435, for example, in a manner in which ink is replenished when the liquid level of ink in the head tank435is lower than a predetermined height.

First Configuration Example

Next, a first configuration example of the liquid discharge head434is described below.

FIG. 6is a cross-sectional view of the liquid discharge head434cut along a direction perpendicular to the nozzle array direction D (a longitudinal direction of the liquid discharge head434). The circulation channel connects the common liquid chamber12to a common circulation channel41through an introduction portion20, the fluid resistive portion21, the pressure generation chamber22, the communication channel23, and a circulation resistive portion42. The nozzle31is disposed at an end of the communication channel23in a course of the circulation channel. The common liquid chamber12is disposed in the frame1and a channel from the introduction portion20to the circulation channel41is disposed in the channel plate2. The channel plate2has a configuration in which a plurality of plate members are laminated.

FIG. 1is an example of a cross-sectional view of the liquid discharge head434cut along line A-A′ ofFIG. 6. The supply port71of the frame1is communicated with the common liquid chamber12and the supply port71is disposed at a center of the common liquid chamber12in the nozzle array direction D. The common liquid chamber12is communicated with a circulation liquid chamber43in the channel plate2via the circulation channel described with reference toFIG. 6and connected to the circulation port72. As illustrated inFIG. 1, two circulation ports72are disposed at both sides of the frame1outer than the common liquid chamber12in the nozzle array direction D. The arrangement of the supply port71and the circulation ports72at the above-described positions allows a smaller width of the liquid discharge head434in the liquid discharge head434than a configuration in which the supply port71is disposed an end portion of the common liquid chamber12in the nozzle array direction D while the circulation port72are disposed at the same positions.

Accordingly, the arrangement allows the circulation channel to be formed while preventing an increased size of the liquid discharge head434in the nozzle array direction D. The arrangement of the supply port71at the center of the common liquid chamber12in the nozzle array direction D also allows the length of a liquid channel from the supply port71to each circulation port72to be the same in any of the pressure generation chambers22. As described above, setting the liquid channel to the same length in any of the pressure generation chambers22allows a sum of a pressure loss arising in the common liquid chamber12and a pressure loss arising in the circulation liquid chamber43to be the same in a route through any of the pressure generation chambers22. Setting the sum of the pressure loss to the same prevents the occurrence of a difference in properties due to pressure loss.

Second Configuration Example

Next, a second configuration example of the liquid discharge head434is described below.

FIG. 7is a cross-sectional view of another example of the liquid discharge head434cut along line A-A′ ofFIG. 6. LikeFIG. 1, the supply port71of the frame1is communicated with the common liquid chamber12and the supply port71is disposed at the center of the common liquid chamber12in the nozzle array direction D (the longitudinal direction of the liquid discharge head434). The common liquid chamber12is communicated with a circulation liquid chamber43in the channel plate2via the circulation channel described with reference toFIG. 6and connected to the circulation port72. As illustrated inFIG. 7, two circulation ports72are disposed at both sides of the frame1outer than the common liquid chamber12in the nozzle array direction D.

For the liquid discharge head434according to the second configuration example, a cross-sectional area of the common liquid chamber12in a direction perpendicular to a direction of flow of liquid is greater than a cross-sectional area of the circulation liquid chamber43in the direction perpendicular to the direction of flow of liquid. The common liquid chamber12has a fluid resistance smaller than the circulation liquid chamber43. For such a configuration, when liquid is discharged while circulated, both liquid for circulation and liquid for discharge flow through the common liquid chamber12. However, the cross-sectional area of the common liquid chamber12is greater than the cross-sectional area of the circulation liquid chamber43, thus reducing pressure loss in the common liquid chamber12.

For example, assume that, when liquid is circulated from the supply port71to the circulation port72at the flow amount of 400 μl/s, a greatest discharge amount of liquid from all the nozzles31of the liquid discharge head434is 200 μl/s. Since liquid to be discharged from all the nozzles31of the liquid discharge head434is supplied from the common liquid chamber12, a greatest flow amount of liquid flowing to the supply port71and the common liquid chamber12is 600 μl/s and a greatest flow amount of liquid flowing to the circulation liquid chamber43and the circulation port72is 400 μl/s. At maximum, liquid flows in the common liquid chamber12at a flow amount of 1.5 times as great as the greatest flow amount of liquid in the circulation liquid chamber43Accordingly, the cross-sectional area of the common liquid chamber12is preferably not smaller than 1.5 times as great as the cross-sectional area of the circulation liquid chamber43.

Third Configuration Example

Next, a third configuration example of the liquid discharge head434is described below.

For the liquid discharge head434according to the above-described second configuration example, the cross-sectional area of the common liquid chamber12in the direction perpendicular to the direction of flow of liquid is greater than the cross-sectional area of the circulation liquid chamber43in the direction perpendicular to the direction of flow of liquid to reduce the fluid resistance value of the channel. By contrast, even when the cross-sectional area of the common liquid chamber12in the direction perpendicular to the direction of flow of liquid is smaller than the cross-sectional area of the circulation liquid chamber43in the direction perpendicular to the direction of flow of liquid, the fluid resistance value of the channel may be small, depending on the shape of the channel. For example, when the aspect ratio of the width to the height of the channel is high, the channel has a relatively high fluid resistance value even if the common liquid chamber12and the circulation liquid chamber43have the same cross-sectional area. Accordingly, as the aspect ratio of the width to the height of the channel is closer to one, the fluid resistance value of the channel is smaller even if the common liquid chamber12and the circulation liquid chamber43have the same cross-sectional area. As described above, setting the fluid resistance value of the common liquid chamber12to be smaller than the fluid resistance value of the circulation liquid chamber43reduces pressure loss due to flow of liquid for circulation and liquid for discharge.

For example, relative to the channel having an aspect ratio of 1:1 in cross section, it is necessary to increase the width to approximately 100 times to obtain the same fluid resistance value by half of the height. That is, the aspect ratio is200. Like the above-described second configuration example, assuming that liquid flows at a flow amount of 600 μl/s in the common liquid chamber12and at a flow amount of 400 μl/s is in the circulation liquid chamber43, the fluid resistance value of the common liquid chamber12is preferably set to be not greater than two third of the fluid resistance value of the circulation liquid chamber43. When the aspect ratio of the common liquid chamber12in cross section is 1:1 and the aspect ratio of the circulation liquid chamber43in cross section is 0.6:1.8, the fluid resistance value of the common liquid chamber12is approximately two third of the fluid resistance value of the circulation liquid chamber43and the cross-sectional area of the common liquid chamber12is approximately 91% of the cross-sectional area of the circulation liquid chamber43. As described above, it is necessary to consider the fluid resistance value rather than the cross-sectional area, depending on the cross-sectional shape of the channel.

Note that, in the above-described embodiment, the configurations of the channel components are described taking several examples. However, the configurations of the channel components are not limited to the above-described embodiment. Generally, an inkjet recording apparatus including a droplet discharge head to discharge, for example, droplets of ink (hereinafter, referred to as ink droplets) is known as a printer, a fax machine, a copier, a plotter, or an image forming apparatus obtained by combining functions of these devices. In the inkjet recording apparatus, ink droplets are adhered to a sheet of paper as a recording medium by a droplet discharge head while the medium is conveyed and an image is formed. In this disclosure, the medium used herein is also referred to as a “sheet.” However, the medium is not limited to a specific material and a recording medium, a transfer material, and a recording sheet may be used. In addition, the image forming apparatus means an apparatus that applies droplets to a medium such as a sheet, thread, fiber, cloth, hides, metal, plastic, glass, wood, and ceramics and forms an image. In addition, the image formation means applying an image not having the meaning such as a pattern (discharging the droplets simply) as well as applying an image having the meaning such as a letter or a figure to the medium. In addition, the ink is used. However, the present disclosure is not limited to the ink and any material becoming a droplet at the time of being discharged may be used. The ink is used as a general term of liquids including a DNA sample, a resist, and a pattern material.

Second Embodiment

A second embodiment is described below.

An example of a liquid discharge head504according to this second embodiment is described with reference toFIGS. 8 to 13.FIG. 8is an outer perspective view of the liquid discharge head504according to this embodiment.FIG. 9is a cross-sectional view of the liquid discharge head504according to this embodiment in a direction perpendicular to the nozzle array direction.FIG. 10is a cross-sectional view of the liquid discharge head504according to this embodiment in a direction parallel to the nozzle array direction.FIG. 11is a plan view of a nozzle plate3of the liquid discharge head504according to this embodiment.FIGS. 12A through 12Fare plan views of members constituting a channel substrate of the liquid discharge head504according to this embodiment.FIGS. 13A and 13Bare plan views of a common liquid chamber substrate of the liquid discharge head504according to this embodiment.

In the liquid discharge head504, a nozzle pate3, a channel plate2, and a diaphragm plate6as a wall face substrate are joined and laminated one on another. The liquid discharge head504includes piezoelectric actuators13to displace the diaphragm plate6, a frame1as a common liquid chamber substrate, and a cover29. The nozzle pate3includes a plurality of nozzles31to discharge liquid. As illustrated inFIG. 11, the nozzles31are arranged in a staggered manner. The channel plate2includes pressure generation chambers22as individual liquid chambers communicated with the nozzles31, fluid resistive portions21communicated with the pressure generation chambers22, and introduction portions20communicated with the fluid resistive portions21. In the channel plate2, a plurality of plate members2a,2b,2c,2d, and2eis joined and laminated one on another in this order from the side of the nozzle pate3. The diaphragm plate6is joined and laminated on the plate members2a,2b,2c,2d, and2eto constitute a channel member40.

The diaphragm plate6includes filter portions9as openings to communicate the introduction portions20with a common liquid chamber12of the frame1. The diaphragm plate6is a wall face substrate constituting wall faces of the pressure generation chambers22of the channel plate2. The diaphragm plate6has a two-layer structure including a first layer including thin portions and facing the channel plate2and a second layer including thick portions. The first layer includes deformable vibration regions30at positions corresponding to the pressure generation chamber22. Note that the diaphragm plate6is not limited to the two-layer structure.

As illustrated inFIG. 12A, the plate member2aconstituting the channel plate2includes through grooves (groove-shaped through holes)22aconstituting the pressure generation chambers22, fluid resistance portions51, and through grooves51aand52aconstituting circulation liquid chambers43. As illustrated inFIG. 12B, the plate member2bincludes through grooves22bconstituting the pressure generation chambers22and through grooves52bconstituting circulation liquid chambers43. As illustrated inFIG. 12C, the plate member2cincludes through grooves22cconstituting the pressure generation chambers22and through grooves53aconstituting circulation channels53and extending in a longitudinal direction parallel to the nozzle array direction. As illustrated inFIG. 12D, the plate member2dincludes through grooves22dconstituting the pressure generation chambers22, through grooves21aas the fluid resistive portions21, through grooves20aconstituting the introduction portions20, and through grooves53bconstituting the circulation channels53and extending in a longitudinal direction parallel to the nozzle array direction. As illustrated inFIG. 12E, the plate member2eincludes through grooves22econstituting the pressure generation chambers22, through grooves as filter-downstream-side chambers constituting the introduction portions20and extending in a longitudinal direction parallel to the nozzle array direction, and through grooves53cconstituting the circulation channels53and extending in a longitudinal direction parallel to the nozzle array direction. As illustrated inFIG. 12F, the diaphragm plate6includes vibration regions30, filter portions9, through grooves53dconstituting the circulation channels53and extending in a longitudinal direction parallel to the nozzle array direction. As described above, the plate members2a,2b,2c,2d, and2eare joined and laminated one on another to constitute the channel member40, thus allowing formation of complicated channels with a simple configuration.

In the above-described configuration, the channel member40made of the channel plate2and the diaphragm plate6includes the fluid resistance portions51communicated with the pressure generation chamber22and extending in a plane direction of the channel plate2, the circulation liquid chamber43, and the circulation channels53communicated with the circulation liquid chamber43and extending in a thickness direction of the channel member40. Note that the circulation channels53are communicated with the common liquid chambers50described below.

The frame1includes the common liquid chamber12, to which liquid is supplied from a supply circulation device594, and circulation common liquid chambers50. As illustrated inFIG. 13A, a first common liquid chamber substrate la constituting the frame1includes a through hole25afor piezoelectric actuator, through grooves10ato be downstream common liquid chambers12A, and grooves50awith bottoms to be the circulation common liquid chambers50. Likewise, as illustrated inFIG. 13B, a second common liquid chamber substrate lb includes a through hole25bfor piezoelectric actuator and grooves10bto be upstream common liquid chambers12B.

The second common liquid chamber substrate lb includes through holes71aas supply port portions to communicate a center portion of the common liquid chamber12in the nozzle array direction with the supply ports71(seeFIG. 8). Likewise, each of the first common liquid chamber substrate la and the second common liquid chamber substrate lb includes through holes72ato communicate each end of the circulation common liquid chambers50in the nozzle array direction and the circulation port72. Note that, inFIGS. 13A and 13B, the grooves with bottoms are illustrated in solid gray.

As described above, the frame1is made of the first common liquid chamber substrate1aand the second common liquid chamber substrate1b. The first common liquid chamber substrate1ais joined to the diaphragm plate6of the channel member40. The second common liquid chamber substrate lb is joined and laminated on the first common liquid chamber substrate la. The frame1includes the common liquid chamber12, to which liquid is supplied from a head tank or liquid cartridge, and the circulation common liquid chambers50.

Here, the first common liquid chamber substrate la includes the downstream common liquid chamber12A constituting part of the common liquid chamber12communicated with the introduction portions20and the circulation common liquid chambers50communicated with the circulation channels53. The second common liquid chamber substrate1bincludes the upstream common liquid chamber12B which is a remaining portion of the common liquid chamber12. At this time, the downstream common liquid chamber12A constituting part of the common liquid chamber12and the circulation common liquid chambers50are arranged side by side in a direction perpendicular to the nozzle array direction. The circulation common liquid chambers50are disposed at positions at which the circulation common liquid chambers50are projected in the common liquid chamber12. Such a configuration prevents the dimension of the circulation common liquid chambers50from being constrained by a dimension required for a channel including the pressure generation chambers22, the fluid resistive portions21, and the introduction portions20of the channel member40. As described above, the circulation common liquid chambers50and the common liquid chamber12are partially arranged side by side and the circulation common liquid chambers50are disposed at the positions at which the circulation common liquid chambers50are projected in the common liquid chamber12. Such a configuration prevents an increase in the width of the liquid discharge head504in the direction perpendicular to the nozzle array direction. Accordingly, the upsizing of the liquid discharge head504is prevented.

Piezoelectric actuators13including electromechanical transducer elements as driving devices to deform the vibration regions30of the diaphragm plate6are disposed at a side of the diaphragm plate6opposite the pressure generation chambers22. As illustrated inFIG. 10, the piezoelectric actuator13includes the laminated piezoelectric element5joined to the base4. For the laminated piezoelectric element5, a single laminated piezoelectric element5is groove-processed by half-cut dicing, so that a desired number of pillar-shaped piezoelectric elements5A and5B are formed in a comb shape at predetermined distances.

In this embodiment, the piezoelectric element5A of the laminated piezoelectric element5is a piezoelectric element to be driven by a drive waveform applied and a piezoelectric element5B is a simple support to which a drive waveform is not applied. However, in some embodiments, all the piezoelectric elements5A and5B may be piezoelectric elements to be driven by application of drive waveforms. The piezoelectric elements5A are joined to projections30aas island-shaped thick portions in the vibration regions30of the diaphragm plate6. The piezoelectric elements5B are joined to projections30bas thick portions of the diaphragm plate6. The laminated piezoelectric element5includes piezoelectric layers and internal electrodes alternately laminated. The internal electrodes are lead out to end faces of the laminated piezoelectric element5to form external electrodes. The external electrodes are connected to a flexible wire member15.

In the liquid discharge head504thus configured, for example, when the voltage applied to the piezoelectric element5A is lowered from a reference potential, the piezoelectric element5A contracts. As a result, the vibration region30of the diaphragm plate6moves downward and the volume of the pressure generation chamber22increases, thus causing liquid to flow into the pressure generation chamber22. When the voltage applied to the piezoelectric element5A is raised, the piezoelectric element5A expands in the direction of lamination. The vibration region30of the diaphragm plate6deforms in a direction toward the nozzle31and contracts the volume of the pressure generation chamber22. Thus, liquid in the pressure generation chamber22is pressurized and discharged from the nozzle31. Then, liquid is drawn from the common liquid chamber12by surface tension and is refilled into the common liquid chamber12. Finally, the meniscus surface of liquid is stabilized by a balance between a negative pressure determined by a supply tank531, a circulation tank532, and a hydraulic head difference and a surface tension of the meniscus, thus allowing a transition to the next discharge operation.

Note that the driving method of the liquid discharge head504is not limited to the above-described example (pull-push discharge). For example, pull discharge or push discharge may be performed by changing the way of applying the drive waveform. In the above-described embodiment, the laminated piezoelectric element is described as an example of the pressure generator to apply pressure fluctuations to the pressure generation chamber22. However, the pressure generator is not limited to the laminated piezoelectric element and may be, for example, a thin-film piezoelectric element. In some embodiments, a thermal resistor may be disposed within the pressure generation chamber22to heat liquid to generate bubbles to apply pressure fluctuations. Alternatively, for example, pressure fluctuations may be generated by electrostatic force.

Next, an example of a liquid circulation system530using the liquid discharge head504according to this embodiment is described with reference toFIG. 14.

FIG. 14is a block diagram of the liquid circulation system530according to this embodiment. As illustrated inFIG. 14, the liquid circulation system530includes, e.g., a main tank502, the liquid discharge head504, a supply tank531, a circulation tank532, a compressor533, a vacuum pump534, a first liquid feed pump535, a second liquid feed pump536, a supply pressure sensor537, a circulation pressure sensor538, a regulator (R)539a, and a regulator (R)539b. The supply pressure sensor537is disposed between the supply tank531and the liquid discharge head504and connected to a supply channel connected to the supply port71(seeFIG. 8) of the liquid discharge head504. The circulation pressure sensor538is disposed between the liquid discharge head504and the circulation tank532and is connected to a circulation channel connected to the circulation port72(seeFIG. 8) of the liquid discharge head504.

One end of the circulation tank532is connected to the supply tank531via the first liquid feed pump535and the other end of the circulation tank532is connected to the main tank502via the second liquid feed pump536. Thus, liquid is flown from the supply tank531into the liquid discharge head504through the supply port71and output to the circulation tank532from the circulation port72. Further, the first liquid feed pump535feeds liquid from the circulation tank532to the supply tank531, thus circulating liquid. The supply tank531is connected to the compressor533and controlled so that a predetermined positive pressure is detected with the supply pressure sensor537. By contrast, the circulation tank532is connected to the vacuum pump534and controlled so that a predetermined negative pressure is detected with the circulation pressure sensor538. Such a configuration allows the menisci of ink to be maintained at a constant negative pressure while circulating ink through the inside of the liquid discharge head504.

When droplets are discharged from the nozzles31of the liquid discharge head504, the amount of liquid in each of the supply tank531and the circulation tank532decreases. Accordingly, preferably, liquid is replenished from the main tank502to the circulation tank532with the second liquid feed pump536. The replenishment of liquid from the main tank502to the circulation tank532is controlled in accordance with a result of detection with, e.g., a liquid level sensor in the circulation tank532, for example, in a manner in which liquid is replenished when the liquid level of liquid in the circulation tank532is lower than a predetermined height.

Next, the circulation of liquid in the liquid discharge head504is described below.

FIG. 15is a cross-sectional view of the liquid discharge head504cut along line A-A′ ofFIG. 9.FIG. 16is a cross-sectional view of the liquid discharge head504cut along line B-B′ ofFIG. 9. As illustrated inFIG. 8, the liquid discharge head504includes the supply port71and the circulation ports72at an end portion of the frame1. The supply port71is communicated with the common liquid chamber12. The circulation port72is communicated with the circulation common liquid chambers50. The supply port71and the circulation ports72are connected to the supply tank531and the circulation tank532(seeFIG. 14), respectively, via tubes. Liquid stored in the supply tank531is supplied to the pressure generation chambers22via the supply port71, the common liquid chamber12, the introduction portions20, and the fluid resistive portions21. Liquid in the pressure generation chamber22is discharged from the nozzles31by driving the piezoelectric elements5A and5B. Meanwhile, a portion or all of liquid stored in the pressure generation chambers22without being discharged is circulated to the circulation tank532through the fluid resistance portions51, the circulation channels52and53, the circulation common liquid chambers50, and the circulation ports72.

Note that the circulation of liquid can be performed not only during operation of the liquid discharge head504but also during the suspension of operation. Circulation during the suspension of operation reduces aggregation and sedimentation of components of liquid while constantly refreshing liquid in the pressure generation chambers22.

In this embodiment, the liquid discharge head434may be employed that has any configuration of the first to third configuration examples of the first embodiment described with reference to, e.g.,FIGS. 1, 6, and 7, thus giving advantages equivalent to the above-described advantages. In such a configuration, the liquid discharge head is downsized, thus allowing the size of a liquid discharge apparatus including the liquid discharge head.

Next, an example of the liquid discharge apparatus1000in which the liquid discharge head434or504according to each of the above-described embodiment is usable is described with reference toFIGS. 17 and 18. Note that, in the example illustrated inFIGS. 17 and 18, the liquid discharge head504is used in the liquid discharge apparatus1000.FIG. 17is a plan view of a portion of the liquid discharge apparatus1000according to this embodiment.

FIG. 18is a side view of a portion of the liquid discharge apparatus1000according to this embodiment. The liquid discharge apparatus1000is a serial discharge apparatus and includes a main-scanning moving device593to reciprocally move a carriage503in a main scanning direction indicated by arrow MSD. The main-scanning moving device593includes, e.g., a guide501, a main scanning motor505, and a timing belt508. The guide501is laterally bridged between side plates591A and591B at both ends in a longitudinal direction of the liquid discharge apparatus1000and supports the carriage503in a manner in which carriage503is movable. The main scanning motor505reciprocally moves the carriage503in the main scanning direction MSD, which is the longitudinal direction of the liquid discharge apparatus1000, via the timing belt508laterally bridged between a drive pulley506and a driven pulley507.

The carriage503includes a liquid discharge device540mounting the liquid discharge head504. The liquid discharge head504of the liquid discharge device540discharges ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (K). The liquid discharge head504includes nozzle rows including a plurality of nozzles arrayed in a sub-scanning direction indicated by arrow SSD inFIG. 17perpendicular to the main scanning direction MSD, with the liquid discharge head504oriented downward. A supply circulation device594supplies liquid, which is stored outside the liquid discharge head504, to the liquid discharge head504through a supply tube556to supply and circulate liquid to the liquid discharge head504. Note that, in this embodiment, the supply circulation device594includes, e.g., the supply tank531, the circulation tank532, the compressor533, the vacuum pump534, the first liquid feed pump535, the second liquid feed pump536, and the regulator (R)539a, and the regulator (R)539b. The supply pressure sensor537is disposed between the supply tank531and the liquid discharge head504and connected to a supply channel connected to the supply port71of the liquid discharge head504. The circulation pressure sensor538is disposed between the liquid discharge head504and the circulation tank532and is connected to a circulation channel connected to the circulation port72of the liquid discharge head504.

The liquid discharge apparatus1000includes a conveyance device595to convey a sheet510. The conveyance device595includes a conveyance belt512as a conveyor and a sub-scanning motor516to drive the conveyance belt512. The conveyance belt512is disposed at a position opposite the liquid discharge head504to attract and convey the sheet510. The conveyance belt512is an endless belt wound around a conveyance roller513and a tension roller514. The attraction of the sheet510onto the conveyance belt512is performed by electrostatic attraction or air suction. The conveyance roller513is rotated by the sub-scanning motor516via a timing belt517and a timing pulley518, so that the conveyance belt512circulates in the sub-scanning direction indicated by arrow SSD inFIG. 17.

At one end in the main scanning direction MSD of the carriage503, a maintenance device520is disposed at a lateral side of the conveyance belt512to maintain and recover the liquid discharge head504. The maintenance device520includes, e.g., a cap521to cap a nozzle face (a face in which nozzles are formed) of the liquid discharge head504and a wiper522to wipe the nozzle face.

The main-scanning moving device593, the supply circulation device594, the maintenance device520, and the conveyance device595are mounted to a housing including, e.g., side plates591A and591B and a back plate591C. For the liquid discharge apparatus1000thus configured, the sheet510is fed and attracted onto the conveyance belt512and conveyed in the sub-scanning direction SSD with rotation of the conveyance belt512. By driving the liquid discharge head504in accordance with an image signal while moving the carriage503in the main scanning direction MSD, liquid is discharged onto the sheet510, which is stopped below the liquid discharge head504, to form an image. As described above, the liquid discharge apparatus1000includes the liquid discharge head504, thus allowing stable formation of high quality images.

Next, another example of the liquid discharge device540is described with reference toFIG. 19.

FIG. 19is a plan view of a portion of another example of the liquid discharge device540. In this example, the liquid discharge device540includes a housing portion including the side plates591A and591B and the back plate591C, the main-scanning moving device593, the carriage503, and the liquid discharge head504. Note that the liquid discharge device540may be configured so that at least one of the above-described maintenance device520and the supply circulation device594is further mounted to, for example, the side plate591B of the liquid discharge device540.

In the above-described embodiments, the term “liquid discharge head” used herein is a functional component to discharge or jet liquid from nozzles. The liquid discharged from the liquid discharge head is not limited to a particular liquid as long as the liquid has a viscosity or surface tension dischargeable from the head. However, preferably, the viscosity of the liquid is not greater than 30 mPa·s under ordinary temperature and ordinary pressure or by heating or cooling. Examples of the liquid include a solution, a suspension, or an emulsion including, for example, a solvent, such as water or an organic solvent, a colorant, such as dye or pigment, a functional material, such as a polymerizable compound, a resin, a surfactant, a biocompatible material, such as DNA, amino acid, protein, or calcium, and an edible material, such as a natural colorant. Such a solution, a suspension, or an emulsion can be used for, e.g., inkjet ink, surface treatment solution, a liquid for forming components of electronic element or light-emitting element or a resist pattern of electronic circuit, or a material solution for three-dimensional fabrication. Examples of an energy source for generating energy to discharge liquid include a piezoelectric actuator (a laminated piezoelectric element or a thin-film piezoelectric element), a thermal actuator that employs a thermoelectric conversion element, such as a thermal resistor, and an electrostatic actuator including a diaphragm and opposed electrodes.

The liquid discharge device is an integrated unit including the liquid discharge head and functional parts, or the liquid discharge head and other structures, and denotes an assembly of parts relative to the liquid discharge. For example, the liquid discharge device may be formed of a combination of the liquid discharge head with at least one of the supply circulation device, the carriage, the maintenance device, and the main-scanning moving device. Herein, examples of the integrated unit include a combination in which the liquid discharge head and a functional part(s) are combined fixedly to each other through, e.g., fastening, bonding, or engaging, and a combination in which one of the liquid discharge head and a functional part(s) is movably held by another. In addition, the liquid discharge head can be detachably attached to the functional parts or structures each other.

For example, the liquid discharge head and the supply circulation device are integrated as the liquid discharge device. The liquid discharge head and the supply circulation device may be connected each other via, e.g., a tube to integrally form the liquid discharge device. Here, a unit including a filter may further be added to a portion between the supply circulation device and the liquid discharge head, thereby forming another liquid discharge device. In another example, the liquid discharge device may include a liquid discharge head integrated with a carriage as a single unit. In still another example, the liquid discharge device includes the liquid discharge head movably held by a guide that forms part of a main-scanning moving device, so that the liquid discharge head and the main-scanning moving device are integrated as a single unit. Furthermore, in another example, the cap that forms part of the maintenance device is secured to the carriage mounted with the liquid discharge head so that the liquid discharge head, the carriage, and the maintenance device are integrated as a single unit to form the liquid discharge device. Further, in another example, the liquid discharge device includes tubes connected to the supply circulation device or the channel member mounted on the liquid discharge head so that the liquid discharge head and the supply device are integrated as a single unit. Liquid is supplied from a liquid reservoir source to the liquid discharge head. The main-scanning moving device may include only a guide, such as the guide501. The supply device may include only a tube(s) or a loading unit.

The term “liquid discharge apparatus” used herein is an apparatus including the liquid discharge head or the liquid discharge device to discharge liquid by driving the liquid discharge head. As the liquid discharge apparatus, there are an apparatus capable of discharging liquid to a material on which liquid can be adhered as well as an apparatus to discharge liquid toward gas or liquid. The liquid discharge apparatus may include devices to feed, convey, and eject the material on which liquid can be adhered. The liquid discharge apparatus may further include a pretreatment apparatus to coat a treatment liquid onto the material, and a post-treatment apparatus to coat a treatment liquid onto the material, onto which the liquid has been discharged.

Examples of the liquid discharge apparatus include an image forming apparatus to form an image on a sheet by discharging ink, and a three-dimensional apparatus to discharge a molding liquid to a powder layer in which powder material is formed in layers, so as to form a three-dimensional article. In addition, the liquid discharge apparatus is not limited to such an apparatus to form and visualize meaningful images, such as letters or figures, with discharged liquid. For example, the liquid discharge apparatus may be an apparatus to form meaningless images, such as patterns, or fabricate three-dimensional objects.

The above-described term “material on which liquid can be adhered” represents a material on which liquid is at least temporarily adhered, a material on which liquid is adhered and fixed, or a material into which liquid is adhered to permeate. Examples of the “material on which liquid can be adhered” include recording media, such as paper sheet, recording paper, recording sheet of paper, film, and cloth, electronic component, such as electronic substrate and piezoelectric element, and media, such as powder layer, organ model, and testing cell. The “material on which liquid can be adhered” includes any material on which liquid is adhered, unless particularly limited. Examples of the material on which liquid can be adhered include any materials on which liquid can be adhered even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, and ceramic.

The “liquid” is not limited to a particular liquid as long as the liquid has a viscosity or surface tension to be discharged from a head. However, preferably, the viscosity of the liquid is not greater than 30 mPa·s under ordinary temperature and ordinary pressure or by heating or cooling. Examples of the liquid include a solution, a suspension, or an emulsion including, for example, a solvent, such as water or an organic solvent, a colorant, such as dye or pigment, a functional material, such as a polymerizable compound, a resin, a surfactant, a biocompatible material, such as DNA, amino acid, protein, or calcium, and an edible material, such as a natural colorant. Such a solution, a suspension, or an emulsion can be used for, e.g., inkjet ink, surface treatment solution, a liquid for forming components of electronic element or light-emitting element or a resist pattern of electronic circuit, or a material solution for three-dimensional fabrication.

The liquid discharge apparatus may be an apparatus to relatively move a liquid discharge head and a material on which liquid can be adhered. However, the liquid discharge apparatus is not limited to such an apparatus. For example, the liquid discharge apparatus may be a serial head apparatus that moves the liquid discharge head or a line head apparatus that does not move the liquid discharge head. Examples of the liquid discharge apparatus further include a treatment liquid coating apparatus to discharge a treatment liquid to a sheet to coat the treatment liquid on the surface of the sheet to reform the sheet surface and an injection granulation apparatus in which a composition liquid including raw materials dispersed in a solution is injected through nozzles to granulate fine particles of the raw materials. The term “image formation” means not only recording, but also printing, image printing, molding, and the like.

The above-described embodiments and examples are limited examples, and the present disclosure includes, for example, the following aspects having advantages.

Aspect A

A liquid discharge head, such as the liquid discharge head434, includes: a nozzle row including a plurality of nozzles, such as the plurality of nozzles31, to discharge liquid, such as ink, the plurality of nozzles arrayed in a nozzle array direction; a plurality of individual liquid chambers, such as the plurality of pressure generation chambers22, communicated with the plurality of nozzles and arrayed in the nozzle array direction; a common liquid chamber, such as the common liquid chamber12, extending longer in the nozzle array direction, to supply liquid to the plurality of individual liquid chambers; a circulation liquid chamber, such as the circulation liquid chamber43, communicated with the plurality of individual liquid chambers; a supply port, such as the supply port71, disposed at a center of the common liquid chamber in the nozzle array direction, to supply liquid to the common liquid chamber; and a delivery port, such as the circulation port72, disposed outside the common liquid chamber in the nozzle array direction, to deliver liquid from the circulation liquid chamber. In aspect A, the supply port is disposed at a center of the common liquid chamber in the nozzle array direction and the delivery port is disposed outside the common liquid chamber in the nozzle array direction. Such a configuration allows a smaller width of the liquid discharge head in the nozzle array direction than a configuration in which the supply port is disposed at one end of the common liquid chamber in the nozzle array direction and the delivery port is disposed outside the common liquid chamber in the nozzle array direction. Thus, such a configuration prevents an increase in the size of the liquid discharge head in the nozzle array direction.

Aspect B

In aspect A, the delivery port is disposed outside each end of the common liquid chamber in the nozzle array direction. As described in the above-described embodiments, such a configuration allows the length of a channel of liquid from the supply port to the delivery port to be the same in any of the individual liquid chambers.

Aspect C

In aspect A or B, the common liquid chamber has a greater cross-sectional area in a direction perpendicular to a direction of flow of liquid than a cross-sectional area of the circulation liquid chamber in the direction perpendicular to the direction of flow of liquid. As described in the above-described embodiments, such a configuration reduces the pressure loss in the common liquid chamber.

Aspect D

In aspects A through C, the common liquid chamber has a fluid resistance value smaller than a fluid resistance value of the circulation liquid chamber. As described in the above-described embodiments, such a configuration reduces the pressure loss due to the flow of liquid for circulation and the flow of liquid for discharge.

Aspect E

A liquid discharge device includes the liquid discharge head according to any one of aspects A through D and at least one of a head tank, such as the supply tank531or the circulation tank532, a carriage, such as the carriage503, a supply device, such as the supply circulation device594, a maintenance device, such as the maintenance device520, and a main-scanning moving device, such as the main-scanning moving device593. As described in the above-described embodiments, such a configuration downsizes the liquid discharge head, thus reducing the size of the liquid discharge device.

Aspect F

A liquid discharge apparatus includes the liquid discharge head according to any one of aspects A through D. As described in the above-described embodiments, such a configuration downsizes the liquid discharge head, thus reducing the size of the liquid discharge apparatus.

Aspect G

A liquid discharge apparatus includes the liquid discharge device according to aspect E. As described in the above-described embodiments, such a configuration downsizes the liquid discharge device, thus reducing the size of the liquid discharge apparatus.

Aspect H

An image forming apparatus, such as a printer, includes the liquid discharge head, such as the liquid discharge head434, according to any one of aspects A through D to discharge liquid droplets to form an image. As described in the above-described embodiments, such a configuration downsizes the liquid discharge head, thus reducing the size of the image forming apparatus.

Aspect I

An image forming apparatus includes the liquid discharge device according to aspect E to discharge liquid droplets from the liquid discharge head to from an image. As described in the above-described embodiments, such a configuration downsizes the liquid discharge device, thus reducing the size of the image forming apparatus.