JP5482130B2 - Piezoelectric actuator, liquid discharge head, and image forming apparatus - Google Patents

Description

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

  As an image forming apparatus such as a printer, a facsimile, a copying machine, a plotter, or a complex machine of these, for example, a liquid discharge recording type image forming using a recording head composed of a liquid discharge head (droplet discharge head) that discharges ink droplets. As an apparatus, an ink jet recording apparatus or the like is known. This liquid discharge recording type image forming apparatus means that ink droplets are transported from a recording head (not limited to paper, including OHP, and can be attached to ink droplets and other liquids). Yes, it is also ejected onto a recording medium or a recording medium, recording paper, recording paper, etc.) to form an image (recording, printing, printing, and printing are also used synonymously). And a serial type image forming apparatus that forms an image by ejecting liquid droplets while the recording head moves in the main scanning direction, and a line type head that forms images by ejecting liquid droplets without moving the recording head There are line type image forming apparatuses using

  In the present application, the “image forming apparatus” of the liquid discharge recording method is an apparatus that forms an image by discharging liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, or the like. In addition, “image formation” means not only giving an image having a meaning such as a character or a figure to a medium but also giving an image having no meaning such as a pattern to the medium (simply It also means that a droplet is landed on a medium). “Ink” is not limited to ink, but is used as a general term for all liquids capable of image formation, such as recording liquid, fixing processing liquid, and liquid. DNA samples, resists, pattern materials, resins and the like are also included. In addition, the “image” is not limited to a planar one, but includes an image given to a three-dimensionally formed image, and an image formed by three-dimensionally modeling a solid itself.

  Conventionally, as a liquid ejection head, a piezoelectric element, particularly a laminated piezoelectric member in which piezoelectric layers and internal electrodes are alternately laminated, is used as pressure generating means (actuator means) for generating pressure to pressurize ink that is liquid in a liquid chamber. Using a so-called piezoelectric actuator that deforms the elastically deformable diaphragm that forms the wall surface of the liquid chamber by the displacement of the laminated pressure member in the direction d33 or d31, and discharges the liquid droplet by changing the volume / pressure in the liquid chamber The piezoelectric head used is known.

  As a piezoelectric actuator of such a piezoelectric head, a conductive member is joined in parallel with an end face electrode serving as a common external electrode facing between two rows of piezoelectric elements, and formed on a base member. There is known one that electrically connects the common electrode patterns that are divided when the division processing is performed (Patent Document 1). In addition, there is also known a device in which a gap member that determines the interval between piezoelectric members before division is provided between two rows of piezoelectric elements (Patent Document 2).

Japanese Patent No. 3311514 Japanese Patent No. 4222882

  By the way, as the image forming apparatus increases in speed, the liquid discharge head also becomes longer. With this increase, the piezoelectric element columns on the end side and the piezoelectric element columns in the central part in the plurality of arranged piezoelectric element columns. There is a problem that the difference in resistance value between the nozzle and the nozzle becomes large, a uniform displacement amount cannot be secured in each piezoelectric element column, and the droplet discharge characteristics vary between nozzles.

  In the technique disclosed in Patent Document 1 described above, a plurality of common electrode patterns formed on a substrate and connected to the substrate from individual piezoelectric element columns are connected to each other by a conductive member. Therefore, it is necessary to provide a connecting portion for connecting the piezoelectric element columns and the substrate with a conductive paste or the like, and the piezoelectric element members must be separated from each other by more than the width of the conductive member. In this case, there is a problem that the head cannot be miniaturized, the manufacturing process becomes complicated, and the manufacturing cost increases.

  The present invention has been made in view of the above-described problems, and it is an object of the present invention to suppress variations in characteristics due to lengthening and increasing the density of actuators and heads with a low-cost configuration without increasing the size of the head. And

In order to solve the above problems, the piezoelectric actuator according to the present invention is:
Having a piezoelectric member fixed to the base member;
In the piezoelectric member, a plurality of piezoelectric element columns which are columnar piezoelectric elements formed by being divided into comb teeth by grooves are arranged in one direction,
A common external electrode connected to at least two piezoelectric element columns to which a drive signal is applied is formed on one surface of the piezoelectric member in a direction orthogonal to the arrangement direction of the piezoelectric element columns,
A metal member is arranged in parallel with the surface of the piezoelectric member on which the common external electrode is formed,
It said metal member and the common external electrodes are electrically directly bonded by melt type electrically conductive material,
The metal member is disposed in a groove formed in the base member along the arrangement direction of the piezoelectric element columns .

  The liquid discharge head according to the present invention includes the piezoelectric actuator according to the present invention.

  The image forming apparatus according to the present invention includes the liquid discharge head according to the present invention.

According to the piezoelectric actuator according to the present invention, actuators and head of elongated, variation in characteristics due to high density, without increasing the size of the head can be suppressed at a low cost configuration.

  According to the liquid discharge head according to the present invention, since the piezoelectric actuator according to the present invention is provided, good droplet discharge characteristics can be obtained.

  According to the image forming apparatus of the present invention, since the liquid discharge head according to the present invention is provided, stable image formation can be performed.

FIG. 3 is an exploded perspective view of an embodiment of a liquid discharge head according to the present invention. It is sectional explanatory drawing which follows the direction (liquid chamber longitudinal direction) orthogonal to the nozzle arrangement direction of the head. It is sectional explanatory drawing in alignment with the nozzle arrangement direction (liquid chamber short direction) of the head. It is a section explanatory view showing the state before solder fusion in the 1st embodiment of the piezoelectric actuator concerning the present invention. It is a perspective explanatory view similarly. It is explanatory drawing with which it uses for description of an example of the solder melting method of a metal member similarly. It is explanatory drawing with which it uses for description of the other example of the solder melting method of a metal member similarly. It is a section explanatory view showing the state after solder melting similarly. It is a section explanatory view showing the state before solder fusion in other examples of the embodiment. It is sectional explanatory drawing which shows the state before the solder melting in the further another example of the embodiment. It is sectional explanatory drawing which shows the state after the solder melting in each example of FIG.9 and FIG.10. It is principal part perspective explanatory drawing which shows the state before the solder melting in 2nd Embodiment of the piezoelectric actuator which concerns on this invention. It is sectional explanatory drawing which shows the state before solder melting in 3rd Embodiment of the piezoelectric actuator which concerns on this invention. 1 is an overall configuration diagram illustrating an example of an image forming apparatus according to the present invention. Similarly it is principal part plane explanatory drawing. It is a whole block diagram which shows the other example of the image forming apparatus which concerns on this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. An embodiment of a liquid discharge head including a piezoelectric actuator according to the present invention will be described with reference to FIGS. 1 is an exploded perspective view of the head, FIG. 2 is a sectional explanatory view along a direction (liquid chamber longitudinal direction) orthogonal to the nozzle arrangement direction of the head, and FIG. 3 is a nozzle arrangement direction (liquid chamber) of the head. It is sectional explanatory drawing in alignment with a transversal direction.

  The liquid discharge head includes a flow path substrate (liquid chamber substrate) 1 formed of a SUS substrate, a vibration plate member 2 bonded to the lower surface of the flow path substrate 1, and a nozzle plate 3 bonded to the upper surface of the flow path substrate 1. And a plurality of nozzles 4 for ejecting droplets (liquid droplets) by these, respectively, as a plurality of liquid chambers (pressurized liquid chamber, pressure chamber, Also referred to as a pressure chamber, a flow path, etc.) 6, a fluid resistance portion 7 that also serves as a supply path for supplying ink to the liquid chamber 6, and a communication portion 8 that communicates with the liquid chamber 6 via the fluid resistance portion 7. Ink is supplied from a common liquid chamber 10 formed in a frame member 17 to be described later to the communication portion 8 through a supply port 9 formed in the diaphragm member 2.

  The flow path substrate 1 is configured by bonding a flow path plate 1A and a communication plate 1B. The flow path substrate 1 is formed by etching the SUS substrate using an acidic etchant or machining such as punching (pressing) to open openings such as the communication path 5, the pressurized liquid chamber 6, and the fluid resistance portion 7. Each is formed.

  The diaphragm member 2 has each vibration region (diaphragm portion) 2a that forms a wall surface corresponding to each liquid chamber 6, and an island-shaped convex portion on the outer side of the vibration region 2a (on the side opposite to the liquid chamber 6). 2b is provided, and the piezoelectric actuator 100 according to the present invention as a driving means (actuator means, pressure generating means) for deforming the vibration region 2a is disposed on the island-shaped convex portion 2b.

  The piezoelectric actuator 100 has two laminated piezoelectric members 12 joined on a base member 13 with an adhesive 50. The piezoelectric member 12 is processed with a groove 31 (FIG. 3) by half-cut dicing to produce one piezoelectric member. A required number of piezoelectric element columns 12A and 12B are formed in a comb shape at a predetermined interval with respect to the member 12. The piezoelectric element columns 12A and 12B of the piezoelectric member 12 are the same, but the piezoelectric element column that is driven by giving a drive waveform is used as the drive piezoelectric element column 12A, and the piezoelectric element is used as a simple column without giving the drive waveform. The columns are distinguished as non-driving piezoelectric element columns 12B. Further, the upper end surface (joint surface) of the drive piezoelectric element column 12 </ b> A is joined to the island-shaped convex portion 2 b of the diaphragm member 2.

  Here, the piezoelectric member 12 is obtained by alternately stacking the piezoelectric material layers 21 and the internal electrodes 22A and 22B. The internal electrodes 22A and 22B are respectively substantially perpendicular to the end face, that is, the diaphragm member 2 of the piezoelectric member 12. By pulling out to the side surface, connecting to the end face electrodes (external electrodes) 23, 24 formed on the side face, and applying a voltage between the end face electrodes (external electrodes) 23, 24, displacement in the stacking direction occurs. Here, the external electrode 23 is used as an individual external electrode (individual electrode), and the external electrode 24 is used as a common external electrode (common electrode). The non-driving piezoelectric element column 12B at the end of the piezoelectric member 12 is a non-driving piezoelectric element column 12Ba formed wider than the other piezoelectric element columns 12A and 12B.

  The metal member 51 includes a metal member 51 such as a Cu wire having a circular cross section disposed in parallel with the surface of the piezoelectric member 12 on which the common external electrode 24 common to the plurality of drive piezoelectric element columns 12A is formed. The surface of the common external electrode 24 is electrically connected. A solder 52 is provided between the metal member 51 and the common external electrode 24. Here, as shown in FIG. 7, the common electrode may be taken out from the metal member 51 by pulling out the lead wire 62 and directly taken out to the outside, or via the piezoelectric element column 12Ba at the end (in this part, The internal electrode 22 is formed across the piezoelectric element member 12, and the common electrode 24 is drawn out to the individual electrode 23 side), and the common electrode may be taken out via the FPC 15 described later. In the former case, since the lead wire is not used to pass through the thin electrode portion, there is an effect that the resistance value of the common electrode portion can be further reduced. In the latter case, all the electrodes are formed only by the FPC 15. There is an effect that it can be taken out.

  The piezoelectric member 12 is connected to an FPC 15 as a flexible wiring member for giving a driving signal to the driving piezoelectric element column 12A. The FPC 15 has individual wiring electrodes connected to the individual electrodes 23 of the driving piezoelectric element pillar 12A. Moreover, as a heating method for connecting the FPC 15 and the piezoelectric member 12, there are a contact heating method using a heater or the like and a non-contact heating method using a laser or the like. The FPC 15 and the piezoelectric member 12 may be bonded to each other with a rigid member, but it is preferable that the FPC 15 and the piezoelectric member 12 be bonded to each other by air pressure while being bonded by a laser.

  The nozzle plate 3 is formed from a nickel (Ni) metal plate, and is formed by an electroforming method (electroforming). From a metal such as stainless steel, a resin such as a polyimide resin film, silicon, and a combination thereof. Can also be used. In this nozzle plate 3, nozzles 4 having a diameter of 10 to 35 μm are formed corresponding to the respective liquid chambers 6 and bonded to the flow path plate 1 with an adhesive. A water repellent layer is provided on the droplet discharge side surface (surface in the discharge direction: discharge surface or surface opposite to the liquid chamber 6 side) of the nozzle plate 3.

  This head is configured to pressurize the ink in the liquid chamber 6 using the displacement in the d33 direction as the piezoelectric direction of the piezoelectric member 12, and the discharge direction of the liquid droplets is the flow direction of the recording liquid in the liquid chamber 6. The liquid droplets are ejected by different side shooter methods. By adopting the side shooter system, the size of the piezoelectric member 12 becomes substantially the size of the head, and the miniaturization of the piezoelectric member 12 can be directly linked to the miniaturization of the head, and the head can be easily miniaturized. Further, since the surfaces of the metal member 51 and the common external electrode 24 are directly connected using the solder 52, the length between the piezoelectric members 12 can be shortened, and the head can be further miniaturized.

  Further, on the outer peripheral side of the piezoelectric actuator 100 according to the present invention composed of the piezoelectric member 12, the base member 13 as a base member, the FPC 15 and the like, a frame member formed by injection molding with epoxy resin or polyphenylene sulfite. 17 is joined. The frame member 17 is formed with the common liquid chamber 10 described above, and further, a supply port 19 for supplying ink from the outside to the common liquid chamber 10 is formed. It is connected to an ink supply source such as a cartridge.

  In the liquid ejection head configured as described above, for example, when driven by a punching method, a drive pulse voltage of 20 to 50 V is selectively applied to the drive piezoelectric element column 12A according to an image recorded from a control unit (not shown). When applied, the driving piezoelectric element column 12A to which the pulse voltage is applied is displaced to deform the vibration region 2a of the vibration plate member 2 in the direction of the nozzle plate 3, and the liquid chamber 6 is changed by the volume (volume) change of the liquid chamber 6. By pressurizing the liquid inside, droplets are ejected from the nozzle 4 of the nozzle plate 3. As the liquid droplets are discharged, the pressure in the liquid chamber 6 decreases, and a slight negative pressure is generated in the liquid chamber 6 due to the inertia of the liquid flow at this time. Under this state, by turning off the application of voltage to the driving piezoelectric element column 12A, the diaphragm 2 returns to the original position and the liquid chamber 6 becomes the original shape, so that further negative pressure is generated. To do. At this time, the recording liquid is filled from the common liquid chamber 10 into the liquid chamber 6, and droplets are ejected from the nozzles 4 in response to the next drive pulse application.

  In addition to the above-described punching, the liquid ejection head has a pulling method (a method in which the diaphragm 2 is released from the pulled state and pressurized with a restoring force), a pull-pushing method (the diaphragm member 2 is placed in the middle). It can also be driven by a method such as a method of holding it at a position, pulling it from this position and then extruding it.

  Here, according to the piezoelectric actuator 100 in the liquid discharge head, the piezoelectric member 12 in which the plurality of piezoelectric element columns 12A and 12B are formed, and two or more piezoelectric elements to which at least a drive signal is applied formed in the piezoelectric member 12 is applied. It has a common external electrode 24 common to the element pillar 12A, and a metal member 51 arranged in parallel with the surface on which the common external electrode 24 is formed, and the metal member 51 and the common external electrode 24 are fused conductive materials. Therefore, without increasing the size of the head, the actuator 100 and the length of the head can be increased between the end portion and the central portion of the piezoelectric member 12 by increasing the density. It is possible to reduce variations in characteristics and to suppress heat generation of the common electrode due to current concentration on the common electrode by simultaneously driving the plurality of piezoelectric element columns 12A. .

  Here, the manufacturing process of the piezoelectric actuator 100 will be described with reference to FIGS. 4 is a cross-sectional explanatory view showing an example of the actuator before solder melting, FIG. 5 is a perspective explanatory view, FIG. 6 is an explanatory view for explaining an example of a solder melting process of a metal member, and FIG. 7 is a metal member. FIG. 8 is an explanatory cross-sectional view for explaining the state after the solder melting of the metal member.

  First, as shown in FIGS. 4 and 5, a Cu wire as a metal member 51 whose periphery is covered with a solder film 52a is fixed to the base member 13 using an adhesive. In this case, the wire (metal member) 51 may be positioned by forming a V-shaped groove in the base member 13. Thereafter, positioning is performed by bringing the two piezoelectric members 12 and 12 into contact with the metal member 15 from opposite directions. Thereby, the piezoelectric members 12 and 12 can be easily positioned with high accuracy. In this case, the metal member 51 can be positioned with higher accuracy by using a cylindrical member. Moreover, the piezoelectric members 12 and 12 and the base member 13 are performed by an adhesive 50 such as a UV adhesive.

  Then, as shown in FIG. 6, a semiconductor laser 61 similar to the semiconductor laser 61 that solders the FPC 15 is used to melt the solder film 52a around the metal member 51, and the periphery of the common external electrode 24 and the metal member 51 And are electrically connected. This bonding is not limited to solder, but any conductive material having heat melting properties can be used. However, by performing solder bonding, the width of the heating means is widened, and the bonding can be performed easily and firmly. Electrical properties can also be obtained.

  As a method of melting the solder film 52a around the metal member 51, a lead wire can be drawn from the metal member 51 and directly heated. Since the resistance of the metal member 51 is low, in such a configuration, a common electrode is formed by passing a high resistance body serving as a heating element in the center of the metal member 51 and energizing the core. As a heating element and a function as a heating element.

  In this way, as shown in FIG. 8, the solder film 52 a around the metal member 51 is melted to become the solder 52, and the metal member 51 and the common external electrode 24 are joined.

  Here, the metal member 51 is preferably a metal material having excellent conductivity, and may be dichrome, Ag, or the like in addition to Cu. Further, the common external electrode 24 of the piezoelectric member 12 is formed with a metal film of about 1 μm by sputtering, but if the metal film is processed as a base, such as Cr, Ni, Cu, Au, etc., the solder 51 and Can be easily joined.

  Further, the base member 13 is preferably a metal material that can fix the piezoelectric member 12 with the adhesive 50, and further, a material such as Cu, dichrome, or Ag as described above, or a treatment such as Cr, Ni, Cu, or Au is performed. As a result, the metal member 51 and the base member 13 can be joined together with the solder 51 simultaneously with the joining of the metal member 51 and the common electrode 24, and the common electrode 24 having a lower resistance is pulled out through the base member 13 that is a metal material. be able to.

  In the present embodiment, the example in which the metal member 51 whose periphery is covered with the solder film 52 a is used has been described. However, as shown in FIG. 9, the solder film 52 a of the metal member 51 is formed on a part of the outer periphery of the metal member 51. A piece having a different structure may be used, and the solder film 52a may be disposed on the upper side. In this way, since the interval between the piezoelectric members 12 is determined by the diameter of the metal member 51, the piezoelectric member can be positioned with higher accuracy without being affected by the thickness variation of the solder film 52a.

  Further, after the piezoelectric member is positioned and joined with the metal member 51 not having the solder film 52a interposed therebetween, a solder member 52b having a smaller diameter than the metal member 51 is placed on the metal member 51 as shown in FIG. It can also be melted with a laser 61. Even if it does in this way, while being able to position a highly accurate piezoelectric member similarly to the former stage, it is not necessary to consider the direction of the solder film 52a of the metal member 51 like the former stage, and it also has an effect of improving workability. Note that the amount of solder used for joining can be adjusted to an appropriate amount by changing the diameter of the solder member.

  9 and 10, after the solder 52 is melted, the solder 52 is unevenly distributed above the metal member 51 as shown in FIG.

Next, a second embodiment of the piezoelectric actuator according to the present invention will be described with reference to FIG. FIG. 12 is an explanatory perspective view of a main part showing a state of the actuator before solder melting.
Here, the two metal members 51 and 51 and the common external electrode 24 of the piezoelectric member 12 are directly electrically connected by a molten conductive material. In this case, the two metal members 51 and 51 are electrically connected by solder bonding. By using a plurality of small-diameter metal members 51 in this way, the heat capacity of the metal members can be reduced, and joining with a small amount of heating becomes possible.

Next, a third embodiment of the piezoelectric actuator according to the present invention will be described with reference to FIG. FIG. 13 is an explanatory sectional view showing a state of the actuator before solder melting.
Here, by arranging the metal member 51 in the groove 13a of the base member 13, the contact position between the metal member 51 and the common external electrode 24 is the depth position of the groove 31 divided into the plurality of piezoelectric element columns 12A and 12B. It is set as the structure which is in a lower position. Thereby, a common electrode can be obtained without being influenced by the processing depth of the groove | channel which divides piezoelectric element pillar 12A, 12B. In addition, the metal member 51 serving as the common electrode forming member can be easily positioned by setting the diameter portion of the metal member 51 to be higher than the bonding surface of the piezoelectric member 12 to the base member 13. Furthermore, it is possible to form an escape portion for the flow of the adhesive 50 that joins the piezoelectric member 12 and the base member 13.

  Note that an ink cartridge in which a tank for supplying ink to the liquid discharge head of each of the above embodiments is integrated can be configured.

Next, an example of the image forming apparatus according to the present invention including the liquid ejection head according to the present invention will be described with reference to FIGS. FIG. 14 is a schematic configuration diagram for explaining the overall configuration of the mechanism unit of the apparatus, and FIG.
This image forming apparatus is a serial type image forming apparatus, and a carriage 233 is slidably held in the main scanning direction by main and slave guide rods 231 and 232 which are guide members horizontally mounted on the left and right side plates 221A and 221B. The main scanning motor that does not perform moving scanning in the direction indicated by the arrow (carriage main scanning direction) via the timing belt.

  The carriage 233 includes a plurality of recording heads 234 including the liquid discharge head unit according to the present invention for discharging ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (K). Nozzle rows consisting of these nozzles are arranged in the sub-scanning direction orthogonal to the main scanning direction, and are mounted with the ink droplet ejection direction facing downward.

  The recording head 234 is configured by attaching liquid ejection heads 234a and 234b each having two nozzle rows to one base member, and one nozzle row of one head 234a has a black (K) droplet. The other nozzle row ejects cyan (C) droplets, the other nozzle row of the other head 234b ejects magenta (M) droplets, and the other nozzle row ejects yellow (Y) droplets. . Note that, here, a two-head configuration is used to eject four color droplets, but a liquid ejection head for each color may be provided.

  The carriage 233 is equipped with sub tanks 235a and 235b (referred to as “sub tank 235” when not distinguished) for supplying ink of each color corresponding to the nozzle rows of the recording head 234. The sub tank 235 is supplied with ink of each color from the ink cartridge 210 of each color by the supply unit 224 via the supply tube 236 of each color.

  On the other hand, as a paper feed unit for feeding the paper 242 loaded on the paper stacking unit (pressure plate) 241 of the paper feed tray 202, a half-moon roller (feed) that feeds the paper 242 from the paper stacking unit 241 one by one. A separation pad 244 made of a material having a large coefficient of friction is provided opposite to the sheet roller 243 and the sheet feeding roller 243, and the separation pad 244 is urged toward the sheet feeding roller 243 side.

  In order to feed the sheet 242 fed from the sheet feeding unit to the lower side of the recording head 234, a guide member 245 for guiding the sheet 242, a counter roller 246, a conveyance guide member 247, and a tip pressure roller. And a conveying belt 251 which is a conveying means for electrostatically attracting the fed paper 242 and conveying it at a position facing the recording head 234.

  The conveyor belt 251 is an endless belt, and is configured to wrap around the conveyor roller 252 and the tension roller 253 so as to circulate in the belt conveyance direction (sub-scanning direction). In addition, a charging roller 256 that is a charging unit for charging the surface of the transport belt 251 is provided. The charging roller 256 is disposed so as to come into contact with the surface layer of the conveyor belt 251 and to rotate following the rotation of the conveyor belt 251. The transport belt 251 rotates in the belt transport direction when the transport roller 252 is rotationally driven through timing by a sub-scanning motor (not shown).

  Further, as a paper discharge unit for discharging the paper 242 recorded by the recording head 234, a separation claw 261 for separating the paper 242 from the transport belt 251, a paper discharge roller 262, and a paper discharge roller 263 are provided. A paper discharge tray 203 is provided below the paper discharge roller 262.

  A double-sided unit 271 is detachably attached to the back surface of the apparatus main body. The duplex unit 271 takes in the paper 242 returned by the reverse rotation of the transport belt 251, reverses it, and feeds it again between the counter roller 246 and the transport belt 251. The upper surface of the duplex unit 271 is a manual feed tray 272.

  Further, a maintenance / recovery mechanism 281 including a recovery means for maintaining and recovering the nozzle state of the recording head 234 is disposed in the non-printing area on one side in the scanning direction of the carriage 233. The maintenance / recovery mechanism 281 includes cap members (hereinafter referred to as “caps”) 282a and 282b (hereinafter referred to as “caps 282” when not distinguished) for capping each nozzle surface of the recording head 234, and nozzle surfaces. A wiper blade 283 that is a blade member for wiping the ink, and an empty discharge receiver 284 that receives liquid droplets for discharging the liquid droplets that do not contribute to recording in order to discharge the thickened recording liquid. ing.

  Further, in the non-printing area on the other side in the scanning direction of the carriage 233, there is an empty space for receiving a liquid droplet when performing an empty discharge for discharging a liquid droplet that does not contribute to the recording in order to discharge the recording liquid thickened during the recording. A discharge receiver 288 is disposed, and the idle discharge receiver 288 is provided with an opening 289 along the nozzle row direction of the recording head 234 and the like.

  In this image forming apparatus configured as described above, the sheets 242 are separated and fed one by one from the sheet feeding tray 202, and the sheet 242 fed substantially vertically upward is guided by the guide 245, and is conveyed to the conveyor belt 251 and the counter. It is sandwiched between the rollers 246 and conveyed, and further, the leading end is guided by the conveying guide 237 and pressed against the conveying belt 251 by the leading end pressing roller 249, and the conveying direction is changed by approximately 90 °.

  At this time, a positive output and a negative output are alternately applied to the charging roller 256, that is, an alternating voltage is applied, and a charging voltage pattern in which the conveying belt 251 alternates, that is, in the sub-scanning direction that is the circumferential direction. , Plus and minus are alternately charged in a band shape with a predetermined width. When the sheet 242 is fed onto the conveyance belt 251 charged alternately with plus and minus, the sheet 242 is attracted to the conveyance belt 251, and the sheet 242 is conveyed in the sub scanning direction by the circumferential movement of the conveyance belt 251.

  Therefore, by driving the recording head 234 according to the image signal while moving the carriage 233, ink droplets are ejected onto the stopped paper 242 to record one line, and after the paper 242 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 242 has reached the recording area, the recording operation is finished and the paper 242 is discharged onto the paper discharge tray 203.

  Thus, since the image forming apparatus includes the liquid discharge head according to the present invention as a recording head, stable droplet discharge characteristics can be obtained, and a high-quality image can be stably formed.

Next, another example of the image forming apparatus according to the present invention including the liquid ejection head according to the present invention will be described with reference to FIG. FIG. 16 is a schematic configuration diagram of the entire mechanism of the apparatus.
This image forming apparatus is a line type image forming apparatus, has an image forming unit 402 and the like inside the apparatus main body 401, and can supply a large number of recording media (sheets) 403 on the lower side of the apparatus main body 401. A paper tray 404 is provided, a sheet 403 fed from the sheet feeding tray 404 is taken in, a required image is recorded by the image forming unit 402 while the sheet 403 is conveyed by the conveying mechanism 405, and then the side of the apparatus main body 401. The paper 403 is discharged to a paper discharge tray 406 attached to the printer.

  Also, a duplex unit 407 that can be attached to and detached from the apparatus main body 401 is provided, and when performing duplex printing, the sheet 403 is conveyed into the duplex unit 407 while being transported in the reverse direction by the transport mechanism 405 after one-side (front) printing is completed. Then, the other side (back side) is sent back to the transport mechanism 405 as the printable side, and the paper 403 is discharged to the paper discharge tray 406 after the other side (back side) printing is completed.

  Here, the image forming unit 402 is, for example, four full-line liquids according to the present invention that discharge droplets of each color of black (K), cyan (C), magenta (M), and yellow (Y). The recording heads 411k, 411c, 411m, and 411y (which are referred to as “recording heads 411” when the colors are not distinguished) are configured with ejection heads, and each recording head 411 has a nozzle surface on which nozzles for ejecting droplets are formed downward. The head holder 413 is attached.

  In addition, a maintenance / recovery mechanism 412k, 412c, 412m, 412y (referred to as “maintenance / recovery mechanism 412” when colors are not distinguished) is provided to maintain and recover the performance of the head corresponding to each recording head 411. During the head performance maintenance operation such as wiping processing, the recording head 411 and the maintenance / recovery mechanism 412 are relatively moved so that the capping member constituting the maintenance / recovery mechanism 412 faces the nozzle surface of the recording head 411.

  Here, the recording head 411 is arranged to eject droplets of each color in the order of black, cyan, magenta, and yellow from the upstream side in the paper conveyance direction, but the arrangement and the number of colors are not limited to this. Further, as the line-type head, one or a plurality of heads provided with a plurality of nozzle rows for discharging droplets of each color at predetermined intervals can be used, and a recording liquid cartridge for supplying a recording liquid to the head and the head. Can be integrated or separated.

  The paper 403 in the paper feed tray 404 is separated one by one by a paper feed roller (half-moon roller) 421 and a separation pad (not shown) and fed into the apparatus main body 401, and is registered along the guide surface 423 a of the transport guide member 423. It is sent between 425 and the conveyor belt 433, and is sent to the conveyor belt 433 of the conveyor mechanism 405 via the guide member 426 at a predetermined timing.

  In addition, the conveyance guide member 423 is also formed with a guide surface 423 b for guiding the paper 403 sent out from the duplex unit 407. Further, a guide member 427 for guiding the sheet 403 returned from the transport mechanism 405 to the duplex unit 407 during duplex printing is also provided.

  The conveyance mechanism 405 includes an endless conveyance belt 433 that is stretched between a conveyance roller 431 that is a driving roller and a driven roller 432, a charging roller 434 that charges the conveyance belt 433, and an image forming unit 402. A platen member 435 that maintains the flatness of the conveyance belt 433 at the opposite portion, a pressing roller 436 that presses the paper 403 fed from the conveyance belt 433 against the conveyance roller 431 side, and other recording liquid that is attached to the conveyance belt 433, although not shown. It has a cleaning roller made of a porous material or the like, which is a cleaning means for removing (ink).

  On the downstream side of the transport mechanism 405, a paper discharge roller 438 and a spur 439 for sending the paper 403 on which an image is recorded to the paper discharge tray 406 are provided.

  In the image forming apparatus configured as described above, the conveyance belt 433 moves in the direction indicated by the arrow, and is charged by contact with the charging roller 434 to which a high potential application voltage is applied. The conveyance belt is charged to this high potential. When the sheet 403 is fed onto the sheet 433, the sheet 403 is electrostatically attracted to the conveyance belt 433. In this way, the sheet 403 that is strongly adsorbed to the transport belt 433 is calibrated for warpage and unevenness, and forms a highly flat surface.

  Then, the paper 403 is moved around the conveyor belt 433 and droplets are ejected from the recording head 411, whereby a required image is formed on the paper 403, and the paper 403 on which the image has been recorded is the paper discharge roller 438. As a result, the paper is discharged to the paper discharge tray 406.

  As described above, since the image forming apparatus includes the recording head including the liquid discharge head according to the present invention, stable droplet discharge characteristics can be obtained, and a high-quality image can be stably formed.

  In the above embodiment, the present invention has been described with reference to an example in which the present invention is applied to an image forming apparatus having a printer configuration. However, the present invention is not limited to this. For example, the present invention may be applied to an image forming apparatus such as a printer / fax / copier multifunction machine. it can. Further, the present invention can be applied to an image forming apparatus using a liquid other than the narrowly defined ink, a fixing processing liquid, or the like.

DESCRIPTION OF SYMBOLS 1 Flow path plate 2 Vibration board member 3 Nozzle plate 4 Nozzle 6 Individual liquid chamber 10 Common liquid chamber 12 Piezoelectric member 12A, 12B Piezoelectric element column 12Ba Piezoelectric element column 13 Base member 15 FPC (wiring member)
23 Individual External Electrode 24 Common External Electrode 51 Metal Member 52 Solder 52a Solder Film 100 Piezoelectric Actuator 233 Carriage 234 Recording Head 411k, 411c, 411m, 411y Recording Head (Liquid Discharge Head)

Claims (8)

Having a piezoelectric member fixed to the base member;
In the piezoelectric member, a plurality of piezoelectric element columns which are columnar piezoelectric elements formed by being divided into comb teeth by grooves are arranged in one direction,
A common external electrode connected to at least two piezoelectric element columns to which a drive signal is applied is formed on one surface of the piezoelectric member in a direction orthogonal to the arrangement direction of the piezoelectric element columns,
A metal member is arranged in parallel with the surface of the piezoelectric member on which the common external electrode is formed,
It said metal member and the common external electrodes are electrically directly bonded by melt type electrically conductive material,
The piezoelectric actuator according to claim 1, wherein the metal member is installed in a groove formed in the base member along an arrangement direction of the piezoelectric element columns .   The piezoelectric actuator according to claim 1, wherein the metal member is a cylindrical member.   The piezoelectric actuator according to claim 1 or 2, wherein the metal member and the common external electrode are joined by solder.   4. A piezoelectric actuator according to claim 1, wherein a common electrode is directly taken out from the metal member.   4. A piezoelectric actuator according to claim 1, wherein the common electrode is taken out via a flexible wiring board.   6. The contact position between the metal member and the common external electrode is at a position lower than a depth position of a groove that is divided into the plurality of piezoelectric element columns. Piezoelectric actuator. A liquid discharge head is characterized in that it comprises a piezoelectric actuator according to any one of claims 1 to 6. An image forming apparatus comprising the liquid discharge head according to claim 7 .

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