JP2011056919A - Liquid delivering head and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a configuration for detecting poor connection of a piezoelectric member and a wiring member becomes complicate following elongation and high-density formation of an actuator. <P>SOLUTION: The liquid delivering head includes both the piezoelectric member 12 with a plurality of piezoelectric element pillars 12A, 12C and 12C, and an FPC 15 which supplies an electricity to the piezoelectric element pillar 12A of the piezoelectric member 12. The piezoelectric member 12 has a driving piezoelectric element pillar 12A and a non-driving piezoelectric element pillar 12B. External electrodes 23 and 25 of the piezoelectric member 12 and a wiring electrode of the FPC 15 are connected with each other. The FPC 15 is equipped with a pair of measurement electrodes 32C1 and 32C1 connected with external electrodes 23 of the measurement piezoelectric element pillars 12C, and has a terminal capable of measuring a resistance value between the pair of measurement electrodes 32C1 and 32C1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  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.

  As a conventional liquid discharge head, a piezoelectric body as pressure generating means for generating pressure by pressurizing ink, which is a liquid in a liquid chamber, particularly a stacked piezoelectric element in which piezoelectric layers and internal electrodes are alternately stacked is used. A so-called piezoelectric device that includes a piezoelectric actuator and deforms an elastically deformable diaphragm that forms a wall surface in a liquid chamber by displacement in the d33 or d31 direction of the multilayer piezoelectric element, and discharges droplets by changing the volume and pressure in the liquid chamber. A mold head is known.

  As a piezoelectric actuator used in such a liquid discharge head, a plurality of driving portions (driving piezoelectric element columns) and non-driving portions (non-driving piezoelectric element columns) are formed by performing groove processing on the laminated piezoelectric member. Then, a wiring electrode of a wiring member such as an FPC (flexible printed cable) is joined to an external electrode (also referred to as an end surface electrode) from which the internal electrode of the laminated piezoelectric member is drawn to the end surface, and each piezoelectric element column is subjected to an image signal. Some drive signals are given.

  For example, in Patent Document 1, it is possible to provide individual external electrodes and common external electrodes on the same surface by providing common external electrodes in the non-driving parts at both ends in the arrangement direction of the driving parts, and to provide a drive signal with one FPC. Yes.

  By the way, in the liquid discharge head, high speed and high precision are required, and the length and density of the head are increased, that is, the length and density of the piezoelectric element are increased. When the length of the piezoelectric element is increased, the length of the FPC (wiring member) is also increased, so that the expansion / contraction of the FPC due to heating when the FPC is joined increases, and the external electrode of the piezoelectric element (hereinafter, “piezoelectric element electrode”) And the FPC wiring electrode (hereinafter also referred to as “FPC electrode”) are likely to be displaced. Further, when the density of the piezoelectric element is increased, the widths of the piezoelectric element electrode and the FPC electrode are reduced. Further, the variation in the distance between the electrodes of the piezoelectric element electrode and the FPC electrode due to the undulation of the FPC, the foreign matter, and the inclination in the direction between the electrodes of the piezoelectric element and the FPC increases.

  As described above, when the piezoelectric element is lengthened and densified, not only the connection area is reduced, but also there is a problem in that a connection failure is likely to occur because the distance between electrodes and the number of connection points increase. In particular, at both ends in the arrangement direction of the drive portions of the piezoelectric member, poor connection is likely to occur due to the positional deviation between the piezoelectric element electrode and the FPC electrode and the inclination between the piezoelectric element and the FPC electrode.

  Conventionally, the connection failure between the piezoelectric element electrode and the wiring electrode has been performed by an appearance (visual) inspection of the connection portion. However, in the appearance inspection, an electrical connection member (for example, solder, conductive adhesive, There is a problem that it is only possible to confirm whether or not the adhesive of the anisotropic conductive film is wet with the piezoelectric element electrode or the FPC electrode.

  Therefore, depending on the capacitance inspection of the piezoelectric element, it is determined whether or not the inspection terminal of the wiring member is peeled off from the bonding surface of the piezoelectric actuator, or the resistance value between the wiring substrate and the piezoelectric element electrode is determined. What is to be measured (Patent Documents 1 and 2), a probe inspection electrode is provided in the vicinity of the connection portion between the piezoelectric element electrode and the FPC electrode, and the connection resistance is measured (Patent Documents 3 and 4), a specific electrode As a shape that protrudes between the electrodes, there is known a technique in which the distance between the electrodes is partially reduced and a short circuit due to the displacement of the electrodes is detected by electrical characteristics such as resistance (Patent Document 5).

Japanese Patent No. 4240124 Japanese Patent No. 4240125 Japanese Patent No. 3389941 JP 2001-179995 A JP 2008-1441078 A

  However, as disclosed in Patent Documents 1 and 2, in the configuration in which the connection failure is inspected by the capacitance inspection of the piezoelectric element, the wiring resistance and the external resistance of the driving IC are large. It can only detect defects (separation or disconnection between electrodes) and shorts between adjacent electrodes (leakage or short circuit). Further, as disclosed in the literatures 1 and 2, in the configuration in which the resistance value between the inspection terminal of the wiring board and the piezoelectric element electrode (common electrode) is measured, the driving IC is connected through the common electrode and the internal electrode. The resistance value including the external resistance is measured, and even if the internal electrode is disconnected, it is misjudged as a joint disconnection, or the error value of the external resistance (usually about 100Ω) of the driving IC is about several Ω. The rise cannot be detected. For this reason, there is a problem that a connection failure having a high connection resistance such that the electrodes come into contact with each other through the electrical connection member and peel with a little external force, which is a problem in connection reliability, cannot be detected.

  Further, in the configuration in which the probe inspection electrode is provided near the connection portion between the piezoelectric element electrode and the FPC electrode and the connection resistance is measured, the size of the wiring member such as the FPC is large in order to secure the probe inspection electrode region. Become. In addition, the inspection electrode area can be reduced by sharing the inspection electrode with a plurality of connection portions, but the wiring for sharing the inspection electrode with the plurality of connection portions must be cut after the inspection. There is a problem that the cost becomes high.

  Furthermore, in a configuration in which a specific electrode protrudes between the electrodes, the distance between the electrodes is partially reduced, and a short circuit due to the displacement of the electrode is detected by electrical characteristics such as resistance, the electrode pitch is reduced. There is a problem that a short circuit will be detected excessively.

  The present invention has been made in view of the above problems, and an object of the present invention is to detect a connection failure with a simple configuration without complicating the electrode structure of a piezoelectric member or a wiring member.

In order to solve the above problems, the piezoelectric actuator according to the present invention is:
A piezoelectric member having a plurality of piezoelectric element columns in which piezoelectric layers and internal electrodes are alternately laminated;
A wiring member that feeds power to the piezoelectric element column of the piezoelectric member,
The piezoelectric member has a driving piezoelectric element column and a non-driving piezoelectric element column,
The external electrode of the piezoelectric member and the wiring electrode of the wiring member are connected,
The wiring member is provided with a pair of measurement electrodes connected to an external electrode of at least one non-driven piezoelectric element column,
The terminal has a terminal capable of measuring the resistance value between the pair of measurement electrodes.

here,
The piezoelectric member is provided with a non-driving piezoelectric element column having common external electrodes formed at both ends,
The non-driving piezoelectric element column to which the pair of measurement electrodes of the wiring member is connected can be configured to be disposed between the driving piezoelectric element column and the non-driving piezoelectric element column on which the common external electrode is formed. .

Also,
A non-driving piezoelectric element column to which a pair of measurement electrodes of the wiring member is connected is disposed between the driving piezoelectric element columns on the piezoelectric member,
The external electrode of the piezoelectric member is divided into a distal end side and a base side,
Of the external electrodes of the two non-drive piezoelectric element columns to which the pair of measurement electrodes of the wiring member sandwiching the drive piezoelectric element column is connected, the base side electrode portion and the pair of measurement electrodes are connected. ,
The electrode portion on the tip side of the external electrode of the driving piezoelectric element column between the two non-driving piezoelectric element columns and the measurement electrode may be connected.

  Further, the measurement electrode of the wiring member may be branched on the base side of the piezoelectric member.

  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 of the present invention, the wiring member is provided with a pair of measurement electrodes connected to the external electrode of at least one non-driven piezoelectric element column, and the resistance value between the pair of measurement electrodes can be measured. Since the terminal is provided, the connection failure can be detected with a simple configuration without complicating the electrode structure of the piezoelectric member and the wiring member.

  According to the liquid discharge head according to the present invention, the piezoelectric actuator according to the present invention is provided, so that the reliability is improved.

  According to the image forming apparatus of the present invention, since the liquid discharge head according to the present invention is provided, high reliability can be obtained and a high-quality image can be formed at high speed.

FIG. 4 is an exploded perspective view illustrating an example 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 of an example along the nozzle arrangement direction (liquid chamber short direction) of the head. It is sectional explanatory drawing of the other example along the nozzle arrangement direction (liquid chamber short direction) of the head. It is front explanatory drawing with which it uses for description of the electrode structure of the piezoelectric member of the piezoelectric actuator which concerns on 1st Embodiment of this invention, and the wiring structure of a wiring member. FIG. 6 is a cross-sectional explanatory view taken along line AA in FIG. 5. It is front explanatory drawing with which it uses for description of the electrode structure of the piezoelectric member of the piezoelectric actuator which concerns on 2nd Embodiment of this invention, and the wiring structure of a wiring member. It is front explanatory drawing with which it uses for description of the electrode structure of the piezoelectric member of the piezoelectric actuator which concerns on 3rd Embodiment of this invention, and the wiring structure of a wiring member. It is sectional explanatory drawing which follows the BB line of FIG. 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 example of a liquid discharge head 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 cross-sectional explanatory view along a direction (liquid chamber longitudinal direction) orthogonal to the nozzle arrangement direction of the head, and FIGS. 3 and 4 are nozzle arrangement directions of the head. FIG. 4 is an enlarged sectional explanatory view of one liquid chamber portion.

  The liquid discharge head includes a flow path plate (flow path substrate, liquid chamber substrate) 1 formed of a SUS substrate, a vibration plate member 2 that forms a vibration plate bonded to the lower surface of the flow path plate 1, and a flow path plate. A plurality of liquid chambers as individual flow paths each having a nozzle plate 3 joined to the upper surface of the nozzle 1 and a plurality of nozzles 4 for discharging droplets (liquid droplets) communicated with each other via a nozzle communication path 5. (Also referred to as a pressurized liquid chamber, a pressure chamber, a pressurized chamber, a flow path, etc.) 6, a fluid resistance section 7 that also serves as a supply path for supplying ink to the liquid chamber 6, and the fluid resistance section 7 A communication portion 8 communicating with the liquid chamber 6 is formed, and ink is supplied from a common liquid chamber 10 formed in a frame member 17 described later through a supply port 9 formed in the diaphragm member 2 in the communication portion 8.

  The flow path plate 1 is configured by bonding a flow path plate 1A and a communication plate 1B. The flow path plate 1 is formed by etching the SUS substrate with 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 is formed of the first layer 2A and the second layer 2B, the first layer 2A forms a thin portion, and the first layer 2A and the second layer 2B form a thick portion. . And this diaphragm member 2 has each vibration field (diaphragm part) 2a formed in the 1st layer 2A which forms the wall surface corresponding to each liquid room 6, and in this vibration field 2a, An island-shaped convex portion 2b formed by the thick portions of the first layer 2A and the second layer 2B is provided on the outer surface (the side opposite to the liquid chamber 6), and the vibration region 2a is deformed into the island-shaped convex portion 2b. A piezoelectric actuator 100 according to the present invention including an electromechanical conversion element as a driving means (actuator means, pressure generating means) is arranged.

  The piezoelectric actuator 100 includes a plurality of (here, two) laminated piezoelectric members 12 that are bonded to an adhesive on a base member 13, and the piezoelectric member 12 has one groove 31 processed by half-cut dicing. A required number of piezoelectric element columns 12A and 12B are formed in a comb shape at a predetermined interval with respect to the piezoelectric 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. Then, 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. The upper end surface of the non-driving piezoelectric element column 12B is joined to the diaphragm member 2 at a position corresponding to the liquid chamber interval wall 6A.

  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. Pulled out to the side surface (surface along the laminating direction), connected to the end face electrodes (external electrodes) 23, 24 formed on this side surface, and a voltage is applied between the end face electrodes (external electrodes) 23, 24 to form the laminating direction Cause displacement.

  The piezoelectric member 12 is connected to an FPC 15 which is a flexible wiring board as a flexible power supply member (wiring member) for supplying a driving signal to the driving piezoelectric element column 12A. Although not shown, the FPC 15 includes a driver IC (drive circuit) that gives a drive waveform to the drive piezoelectric element column 12A.

  Here, as described above, the piezoelectric element columns 12A and 12B of the piezoelectric member 12 are the same, but the piezoelectric element column to be driven by applying a driving waveform is not provided with the driving piezoelectric element column 12A. As shown in FIG. 3, the piezoelectric element column used as a mere support is a non-driving piezoelectric element column 12B, and the driving piezoelectric element column 12A and the support piezoelectric element column 12B are alternately used as shown in FIG. As shown in FIG. 4, it is possible to adopt a normal pitch configuration in which all the piezoelectric element columns are used as the driving piezoelectric element columns 12A.

  The nozzle plate 3 is formed from a nickel (Ni) metal plate, and is manufactured by an electroforming method (electroforming). 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.

  Further, a frame member 17 formed by injection molding with an epoxy resin or polyphenylene sulfite is joined to the outer peripheral side of the actuator portion composed of the piezoelectric element 12, the base member 13, the FPC 15, and the like. The frame member 17 is formed with the common liquid chamber 10 described above, and further, a supply port for supplying recording liquid 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 discharge head configured as described above, for example, when driven by a punching method, a driving pulse voltage of 20 to 50 V is selectively applied to the driving piezoelectric element column 12A according to an image recorded from a control unit (not shown). Is applied to the piezoelectric element column 12A to which the pulse voltage is applied, and the vibration region 2a of the vibration plate 2 is deformed in the direction of the nozzle plate 3, and the liquid chamber 6 changes its volume (volume). A liquid droplet is discharged from the nozzle 4 of the nozzle plate 3 by pressurizing the liquid. 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, when the voltage application to the piezoelectric element column 12A is turned off, the diaphragm 2 returns to the original position and the liquid chamber 6 becomes the original shape, so that further negative pressure is generated. . At this time, the recording liquid is filled into the liquid chamber 6 from the common liquid chamber 10, and droplets are ejected from the nozzle 4 in response to the next drive pulse application.

  In addition to the above-described pushing, the liquid ejection head is not limited to the pulling method (a method of releasing the diaphragm 2 from the pulled state and pressurizing it with a restoring force), and the pulling-pushing method (the diaphragm 2 at the intermediate position). It is also possible to drive by pulling from this position and then extruding.

  Therefore, details of the piezoelectric actuator according to the first embodiment of the present invention in this liquid discharge head will be described with reference to FIGS. 5A is an electrode configuration of the piezoelectric member, FIG. 5B is a wiring configuration of the wiring member, FIG. 5C is a front explanatory view for explaining a bonding state of the piezoelectric member and the wiring member, and FIG. It is sectional explanatory drawing which follows the AA line of c).

  As described above, the piezoelectric actuator 100 includes a piezoelectric member 12 having a plurality of piezoelectric element columns 12A and 12B in which piezoelectric layers 21A and internal electrodes 22A and 22B are alternately stacked, and a driving piezoelectric element column 12A of the piezoelectric member 12. And an FPC 15 as a wiring member for supplying power.

  In this embodiment, a plurality of driving piezoelectric element columns 12A are arranged at the center of the piezoelectric member 12, and a wide non-driving piezoelectric element column 12Ba for a common external electrode is arranged at both ends, so that at least a plurality of driving piezoelectric element columns are arranged. Two non-driving piezoelectric element columns for measurement 12C are arranged between the driving piezoelectric element column 12A and the non-driving piezoelectric element column 12Ba outside the column arrangement direction of 12A.

  Here, individual external electrodes 23 are formed on the side to be joined to the FPC 15 in the driving piezoelectric element column 12A and the non-driving piezoelectric element column 12C. The individual external electrode 12C of the non-driving piezoelectric element 12C is not applied with a driving waveform during operation, but will be described as an individual external electrode. A common external electrode 23 is formed on the non-driving piezoelectric element column 12Ba on the side where the FPC 15 is joined. The common external electrode 24 of the driving piezoelectric element column 12A is connected to a common external electrode 25 formed on the non-driving piezoelectric element column 12Ba through an internal electrode (not shown) that is not divided by slit processing.

  Note that the column widths (electrode widths) of the driving piezoelectric element columns 12A and the measurement non-driving piezoelectric element columns 12C are the same width and the same pitch. In FIG. 5, only one end side of the piezoelectric member 12 is shown, but the other end side has the same configuration. Also, illustration of the internal electrodes is omitted.

  The FPC 15 as a wiring member has a wiring (electrode) 32 formed on the base material 31, a solder resist 33, and a driving IC (not shown), and is fixed to the base member 13 with a hot melt adhesive 16. .

  The FPC 15 is connected to the surface of the piezoelectric member 12 where the individual external electrodes 23 are formed, and the individual electrode wiring 32A connected to the individual external electrodes 23 of the driving piezoelectric element column 12A and the non-driving piezoelectric element columns 12Ba are connected. A common electrode wiring 32B connected to the common external electrode 25 and a measurement wiring 32C (32C1, 32C2, 32C3) connected to the individual external electrode 23 of the measurement non-driving piezoelectric element column 12C are provided.

  Here, the individual electrode wiring 32A is formed up to a connection terminal of a drive IC (not shown). The common electrode wiring 32B is formed wider than the individual electrode wiring 32A.

  The measurement wiring 32C includes a pair of measurement electrodes 32C1 connected to the two measurement non-drive piezoelectric element columns 12C and 12C, a branch electrode 32C2 that branches one measurement wiring 32C1, and a non-drive piezoelectric element column 12C. , 12C, the connecting electrode 32C3 is connected. The branch electrode 32C2 is connected to a measurement terminal (not shown).

  Each electrode and wiring 32 (32A, 32B, 32C1, 32C2, and 32C3) of the FPC 15 are formed of highly conductive Cu with a thickness of 8 μm. In the case of lower resistance, a thick film having a thickness of 12 μm, 18 μm, 35 μm or the like can also be used. Further, the solder resist 33 is formed in a partial region 15B (FIG. 6) of the FPC 15.

  Each electrode and wiring 32 of the FPC 15 (referred to as “FPC electrode”) and each of the electrodes 23 and 25 (referred to as “piezoelectric element electrode”) of the piezoelectric member 12 are connected by solder 41. As a method of connecting the FPC electrode and the piezoelectric element electrode, the electrodes are aligned, the piezoelectric member 12 and the FPC 15 are overlapped, and the heater chip (block) is pressed while pressing the substrate 31 on the back surface of the electrode portion 15A of the FPC 15 with the heater chip. A heater joining method in which the solder 41 is melted and hardened by pulsating the temperature, and the FPC 15 is pressed by a rigid member that transmits a laser such as glass, and laser light is applied to each electrode wiring 32A of the FPC 15; For example, a laser bonding method in which the solder 41 is melted and cured by irradiating the solder 32B or the solder 41 can be used.

  The solder 41 is a metal material having a lower melting point than that of the FPC electrode and the base material 31 of the FPC 15 and may be made of a conductive material and does not contain lead (Pb). It is preferable. For example, as the solder 41, solder containing tin (Sn) and bismuth (Bi) as main components can be used. Since lead is not contained, it is effective from the viewpoint of environmental protection, and the solder 41 mainly composed of tin (Sn) and bismuth (Bi) has a very low melting point among non-lead members. Therefore, the FPC electrode and the piezoelectric element electrode can be easily welded without damaging the FPC 15 and the piezoelectric member 12.

  Here, the solder 41 is used as the electrical connection member, but an anisotropic conductive film, a conductive adhesive, or the like can also be used.

  The solder 41 is formed in advance on the external electrodes 23 and 25 of the piezoelectric member 12 or the electrode wiring 32 (electrode portion 15A) of the FPC 15 by a printing method, a plating method, or the like.

  Here, although FPC is used as the wiring member, it may be any film provided with a plurality of electrodes that are thin and parallel to each other. For example, TAB (Tape Automated Bonding) can also be used. .

  In the piezoelectric actuator configured as described above, after the piezoelectric member 12 and the FPC 15 are connected, the resistance value between the pair of measurement electrodes 32C1 is measured through a measurement terminal (not shown).

  Here, the voltage or current is applied to the branch electrode 32C2 to perform four-terminal measurement to measure the current or voltage, and wiring from the branch portion of one measurement electrode 32C1 to the branch portion of the other measurement electrode 32C1 Resistance values including resistance and connection resistance were measured. As a result, it is possible to detect a defective junction that exhibits a slightly higher resistance (good connection resistance + 1Ω or less) with respect to the good junction.

  Thus, according to the piezoelectric actuator in the liquid discharge head, the wiring member is provided with a pair of measurement electrodes connected to the external electrode of at least one non-driven piezoelectric element column, and the resistance between the pair of measurement electrodes Since the configuration has a terminal capable of measuring a value, it is possible to detect a connection failure with a simple configuration without complicating the electrode structure of the piezoelectric member and the wiring member.

  In this case, the piezoelectric member is provided with a non-driving piezoelectric element column in which common external electrodes are formed at both ends, and the non-driving piezoelectric element column to which the pair of measurement electrodes of the wiring member is connected is the driving piezoelectric element column. Due to the arrangement between the non-driven piezoelectric element column with the common external electrode formed, the poor connection due to the displacement of the piezoelectric element electrode and the wiring electrode and the inclination between the piezoelectric element and the wiring electrode. It is possible to measure the connection resistance at both ends of the driving piezoelectric element columns of the piezoelectric member in which it is likely to occur, and it is possible to easily detect a connection failure.

  In addition, since the external electrode width and pitch of the non-drive piezoelectric element column for measurement and the external electrode width and pitch of the drive piezoelectric element column are made the same, even if the positional deviation between the piezoelectric element electrode and the wiring electrode occurs, the connection state Is almost the same between the driving piezoelectric element column and the non-driving piezoelectric element column for measurement. Therefore, if the connection resistance of the non-driving piezoelectric element column for measurement increases and a connection failure occurs, the connection failure also occurs in the driving piezoelectric element column. It can be determined that it has occurred. As a result, the short circuit failure is not detected excessively.

  Also, since the measurement electrode wiring of the wiring member is branched on the base side of the piezoelectric member, resistance measurement by the four-terminal method can be performed, so from the branching portion to the resistance measurement electrode such as a probe inspection electrode Therefore, it is not necessary to provide a probe inspection electrode in the vicinity of the connection portion of the measurement electrode wiring.

  Also, by using solder as an electrical connection member, not only can the connection resistance be lowered compared to anisotropic conductive films, conductive adhesives, etc., but if a connection failure occurs due to resistance measurement, Bonding can be performed again by melting the solder while pressing the FPC.

  A liquid ejection head having such a piezoelectric actuator is a highly reliable head because the connection failure can be easily detected even if the connection failure of the piezoelectric actuator occurs with an increase in the length and density of the head. Can be obtained.

Next, a piezoelectric actuator according to a second embodiment of the present invention will be described with reference to FIG. 7A is an electrode configuration of the piezoelectric member in the embodiment, FIG. 7B is a wiring configuration of the wiring member, and FIG. 7C is a front explanatory view for explaining a bonding state of the piezoelectric member and the wiring member. is there.
Here, one of the pair of measurement electrodes 32C1 of the FPC 15 in the first embodiment and the connection electrode 32C3 are integrally formed.

  Further, as compared with the first embodiment, the number of non-driven columns can be reduced, and the resistance between the measurement electrodes 32C1 and 32C1 outside the both ends of the piezoelectric member 12 is measured, whereby the common electrodes 12Ba ( It is possible to accurately measure the resistance between the other (not shown).

Next, a piezoelectric actuator according to a third embodiment of the present invention will be described with reference to FIGS. 8A is an electrode configuration of the piezoelectric member according to the embodiment, FIG. 8B is a wiring configuration of the wiring member, and FIG. 8C is a front explanatory view for explaining a bonding state of the piezoelectric member and the wiring member. FIG. 9 is a cross-sectional explanatory view taken along line BB in FIG.
Here, driving piezoelectric element columns 12A and measurement non-driving piezoelectric element columns 12C are alternately arranged on the piezoelectric member 12, and measurement non-driving piezoelectric element columns 12C are arranged at both ends of the driving piezoelectric element column 12A. Non-driving piezoelectric element columns 12Ba in which common external electrodes 25 are formed are arranged outside the measurement non-driving piezoelectric element columns 12C at both ends of the piezoelectric member 12.

  In addition, the external electrodes 23 and 25 on the bonding surfaces of the piezoelectric element columns 12A, 12Ba, and 12C with the FPC 15 are vertically moved to the distal end side portion 23a and the base side (side bonded to the base member 13) portion 23b of the piezoelectric member 12. The structure is divided (divided). As a method of dividing the external electrodes 23 and 25 into the upper and lower sides, a method of forming a groove with a dicer or a method of removing the electrodes with a laser can be used.

  The individual electrode wiring 32A of the FPC 15 is connected to the base portion 23b of the external electrode 23 of the driving piezoelectric element column 12A. Further, the common electrode wiring 32B is connected to the entire external electrode 25 of the non-driving piezoelectric element column 12B.

  The measurement electrode wiring 32C of the FPC 15 includes a pair of measurement electrodes 32C1, a branch electrode 32C2, and a connection electrode 32C3 that connects the piezoelectric element columns 12C, 12A, and 12C.

  The electrode parts (lower part) of the pair of measurement electrodes 32C1 and the coupling electrode 32C3 are connected to the base part 23b of the external electrode 23 of the piezoelectric element column 12C. In addition, the connecting portion of the connecting electrode 32C3 (the portion along the piezoelectric element column arrangement direction) is connected to the tip portion side portion 23a of the external electrode 23 of the piezoelectric element columns 12A and 12C. The connection electrode 32C3 is not electrically connected to the base portion 23b of the external electrode 23 of the drive piezoelectric element column 12A.

  Since it comprised in this way, after connecting the piezoelectric member 12 and FPC15, the resistance value between a pair of electrodes 32C1 for a measurement can be measured. Here, first, the resistance value between a pair of measurement electrodes 32C1 and 32C1 arranged on both sides of the individual electrode 32A at the end is measured by the four-terminal method, and the other measurement electrode is measured from the branch portion of one measurement electrode 32C1. The resistance including the wiring resistance and connection resistance to the branch portion of the electrode 32C1 was measured. Next, in the figure, the resistance between the pair of measurement electrodes 32C1 arranged on both sides of the second individual electrode 32A from the left, and the resistance between the pair of measurement electrodes 32C1 arranged on both sides of the third individual electrode 32A The resistance between a pair of measurement electrodes 32C1 arranged on both sides of all the individual electrodes 32A was measured sequentially.

  As described above, the piezoelectric member is provided with the non-driving piezoelectric element column to which the pair of measurement electrodes of the wiring member is connected between the driving piezoelectric element columns, and the external electrode of the piezoelectric member is divided into the tip side and the base side. Of the external electrodes of the two non-drive piezoelectric element columns to which the pair of measurement electrodes of the wiring member sandwiching the drive piezoelectric element column is connected, and the pair of measurement electrodes are connected to each other. Non-driving adjacent to all the driving piezoelectric element columns by connecting the electrode part on the tip end side of the external electrode of the driving piezoelectric element column between the two non-driving piezoelectric element columns and the measurement electrode The connection resistance of the piezoelectric element column can be measured. As a result, when the connection resistance of the non-driving piezoelectric element columns increases and a connection failure occurs, it can be determined that a connection failure has occurred in the driving piezoelectric element columns between the non-driving piezoelectric element columns.

  That is, it is possible to detect a connection failure in which the distance between the electrodes of the piezoelectric member and the FPC is locally increased due to the undulation of the FPC, foreign matter, or the like, and the connection portion has a high resistance.

  In addition, the external electrodes of each piezoelectric element column are divided into upper and lower sides (tip side and base side), and the outside of the two non-driving piezoelectric element columns to which the pair of measurement electrodes of the wiring member sandwiching the driving piezoelectric element column are connected The electrode portion on the base side of the electrode is connected to the pair of measurement electrodes, and the electrode portion on the distal end side of the external electrode of the drive piezoelectric element column between the two non-drive piezoelectric element columns and the measurement electrode By being connected, resistance measurement can be performed without patterning the external electrode and the internal electrode of the piezoelectric member, and a connection failure can be easily detected at low cost.

  The liquid discharge head according to the present invention can also be configured as a head-integrated cartridge or a cartridge-integrated head in which a cartridge for supplying ink to the head is integrated.

  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 discharge head according to the present invention will be described with reference to FIGS. FIG. 10 is a schematic configuration diagram for explaining the overall configuration of the mechanism section of the apparatus, and FIG. 11 is a plan view for explaining a main portion of the mechanism section.
This image forming apparatus is a serial type image forming apparatus, and a carriage 233 is slidably held in a main scanning direction by main and sub guide rods 231 and 232 which are guide members horizontally mounted on 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 for maintaining and recovering the nozzle state of the recording head 234 is disposed in a 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.

  As described above, since the image forming apparatus includes the liquid discharge head according to the present invention as a recording head, reliable and stable droplet discharge can be performed even if the head is lengthened and densified. And high-quality images can be formed at high speed.

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. 12 is a schematic configuration diagram of the entire mechanism unit 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.

  Further, a maintenance / recovery mechanism 412k, 412c, 412m, 412y for maintaining and recovering the performance of the head corresponding to each recording head 411 (referred to as “maintenance / recovery mechanism 412” when colors are not distinguished) is provided, and purge processing, 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 blank, 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. 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, highly reliable and stable droplet discharge is performed even if the head is lengthened and densified. And high-quality images can be formed at high speed.

  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.

1 Channel plate (channel substrate)
2 vibration plate member 3 nozzle plate 4 nozzle 6 liquid chamber 10 common liquid chamber 12 piezoelectric member 12A driving piezoelectric element column 12B non-driving piezoelectric element column 12C non-driving piezoelectric element column for measurement 13 base member 15 FPC (wiring member)
15A electrode portion 23 individual external electrode 24 common external electrode 25 common external electrode 31 base material 32A individual electrode wiring 32B common electrode wiring 32C measurement wiring 32C1 measurement electrode 32C2 branch electrode 32C3 connecting electrode 100 piezoelectric actuator 233 carriage 234 recording head

Claims (6)

A piezoelectric member having a plurality of piezoelectric element columns in which piezoelectric layers and internal electrodes are alternately laminated;
A wiring member that feeds power to the piezoelectric element column of the piezoelectric member,
The piezoelectric member has a driving piezoelectric element column and a non-driving piezoelectric element column,
The external electrode of the piezoelectric member and the wiring electrode of the wiring member are connected,
The wiring member is provided with a pair of measurement electrodes connected to an external electrode of at least one non-driven piezoelectric element column,
A piezoelectric actuator comprising a terminal capable of measuring a resistance value between the pair of measuring electrodes. The piezoelectric member is provided with a non-driving piezoelectric element column having common external electrodes formed at both ends,
The non-driving piezoelectric element column to which the pair of measurement electrodes of the wiring member is connected is disposed between the driving piezoelectric element column and the non-driving piezoelectric element column on which the common external electrode is formed. The piezoelectric actuator according to claim 1. A non-driving piezoelectric element column to which a pair of measurement electrodes of the wiring member is connected is disposed between the driving piezoelectric element columns on the piezoelectric member,
The external electrode of the piezoelectric member is divided into a distal end side and a base side,
Of the external electrodes of the two non-drive piezoelectric element columns to which the pair of measurement electrodes of the wiring member sandwiching the drive piezoelectric element column is connected, the base side electrode portion and the pair of measurement electrodes are connected. ,
2. The piezoelectric actuator according to claim 1, wherein an electrode portion on a distal end side of an external electrode of the driving piezoelectric element column between the two non-driving piezoelectric element columns is connected to the measurement electrode. .   4. The piezoelectric actuator according to claim 1, wherein the measurement electrode of the wiring member is branched on the base side of the piezoelectric member.   A liquid discharge head comprising the piezoelectric actuator according to claim 1.   An image forming apparatus comprising the liquid discharge head according to claim 5.

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