JP2008062388A - Method and apparatus for inspecting liquid droplet ejection head, and liquid droplet ejector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure a high reliability by accurately detecting an initial failure of a piezoelectric element. <P>SOLUTION: To an inkjet recording head which ejects ink liquid droplets from a plurality of nozzles when a drive voltage is applied to separate piezoelectric elements prepared correspondingly to the plurality of nozzles, a capacitance is measured by applying a low voltage and a high voltage to the separate piezoelectric elements (steps 102-108), and generation of deflection/generation of separation/normal state of the piezoelectric elements is detected on the basis of the capacitance according to each voltage level (steps 110-120). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and apparatus for inspecting a droplet discharge head, and a droplet discharge device, and more particularly, an inspection of a droplet discharge head that discharges droplets by driving individual piezoelectric elements provided in a plurality of nozzles. The present invention relates to a method and apparatus, and a droplet discharge apparatus to which the droplet discharge head inspection method and apparatus are applied.

  In a piezoelectric ink jet recording apparatus that ejects ink droplets from a nozzle by bending displacement caused by application of a driving voltage to a bending mode piezoelectric actuator (piezoelectric element), capacitance measurement and impedance (admittance) frequency characteristics are used as methods for detecting a defect in the piezoelectric element. Measurement is known.

Specifically, a print correction method that changes the applied voltage according to the capacitance of the piezoelectric element (see, for example, Patent Document 1), the current flowing through the piezoelectric element is detected by driving the piezoelectric element, and the detected current is defined. A failure detection method for determining that there is a failure in the piezoelectric element or the piezoelectric element drive circuit when out of range (see, for example, Patent Document 2), an impedance analyzer connected to each nozzle, and provided corresponding to each nozzle An adhesion failure diagnosis method for measuring a natural frequency (resonance frequency) of a piezoelectric element and determining that a piezoelectric element having a natural frequency deviated from the natural frequency in a piezoelectric element having a normal adhesion state is determined as an adhesion failure (for example, Patent Document 3) Reference), the inkjet printer is provided with a measurement unit for measuring the resonance frequency when the piezoelectric element is driven, and the resonance frequency data serving as a reference is stored in the storage unit so that the piezoelectric element is driven. By measuring the change in the resonance frequency, the inspection method of detecting the ink discharge failure due to bubble generation of the failure and the pressure chamber of the piezoelectric element (for example, see Patent Document 4) have been disclosed.
Japanese Patent Laid-Open No. 10-193613 JP 2002-127405 A Japanese Patent Laid-Open No. 11-64175 Japanese Patent Laid-Open No. 2004-9501

  However, even with each of the above-described methods, it is not possible to accurately detect initial deflection and peeling at the manufacturing stage of the piezoelectric element. That is, the defect measurement cannot be sufficiently detected by the manufacturing variation such as the thickness and area of the piezoelectric element only by the capacitance measurement in a low electric field that is normally performed, and cannot be detected by the impedance frequency characteristic measurement.

  For example, in the case of a piezoelectric element having a large amount of deflection at the initial stage (manufacturing stage), it becomes difficult to discharge particularly when discharging a micro droplet, and it cannot be driven under the same driving conditions as other piezoelectric elements. Adopting individual driving means or treating it as a defective product causes an increase in cost.

  In addition, when the piezoelectric element is bent and the degree thereof is increased due to the stress during driving, the discharge droplet amount changes, and the discharge droplet amount is smaller than that of the nozzle provided with the piezoelectric element that is not bent. It will be different and image degradation will occur. This is particularly noticeable when ejecting microdroplets. As described above, in the piezoelectric element in which bending occurs, there is a problem that sufficient reliability cannot be ensured because the ejection characteristics change due to stress during driving or the like, or it becomes easy to peel off with the driving.

  In view of the above facts, the present invention provides a droplet discharge head inspection method and apparatus, and a droplet discharge apparatus, which can detect an initial failure of a piezoelectric element with high accuracy and ensure high reliability. Let it be an issue.

  In order to solve the above-described problem, the invention described in claim 1 is configured such that a droplet is ejected from the plurality of nozzles by applying a driving voltage to each piezoelectric element provided corresponding to the plurality of nozzles. The electrostatic capacitance is measured by applying a voltage of at least two of at least a first voltage and a second voltage higher than the first voltage to the individual piezoelectric elements with respect to the droplet discharge head. The degree of flexure of the piezoelectric element is detected based on the electrostatic capacity corresponding to each voltage level.

  In the first aspect of the present invention, at least two of the first voltage and the second voltage higher than the first voltage are applied to the individual piezoelectric elements provided corresponding to the plurality of nozzles. Is applied to measure the capacitance, and the degree of flexure of the piezoelectric element is detected based on the capacitance corresponding to each voltage level. This inspection method makes it possible to accurately detect the deflection of the piezoelectric element, particularly the initial deflection in the manufacturing stage, which could not be detected by the conventional capacitance measurement only with a low electric field. Measures can be taken to improve recording accuracy (high image quality) and reliability.

  According to a second aspect of the present invention, in the method for inspecting a droplet discharge head according to the first aspect, the second voltage with respect to a capacitance when the first voltage is applied to the individual piezoelectric elements. A reduction rate of the electrostatic capacity when the voltage is applied is calculated, and a piezoelectric element having the reduction rate smaller than the first threshold is determined as a piezoelectric element in which bending occurs.

  For example, with respect to detection of a piezoelectric element in which initial deflection has occurred in the manufacturing stage, as in the invention according to claim 2, the first electrostatic voltage is applied to each piezoelectric element when the first voltage is applied. This can be realized by calculating the rate of decrease of the capacitance when the voltage of 2 is applied, and determining that a piezoelectric element having the rate of decrease smaller than the first threshold is a piezoelectric element in which bending occurs.

  The invention according to claim 3 is directed to a droplet discharge head that discharges droplets from the plurality of nozzles by applying a driving voltage to each piezoelectric element provided corresponding to the plurality of nozzles. At least a first voltage and a second voltage higher than the first voltage are applied to each of the piezoelectric elements to measure the capacitance, and the voltage corresponding to each voltage level is measured. It is characterized in that the peeling of the piezoelectric element is detected based on the capacitance.

  In the third aspect of the present invention, by the same inspection method as that of the first aspect of the present invention, the piezoelectric element peeling, which has not been detected by the conventional capacitance measurement only with a low electric field, particularly in the initial stage of manufacturing. Separation and the like can be accurately detected. Therefore, it is possible to take measures for improving the reliability and recording with high accuracy by equalizing the amount of ejected droplets.

  According to a fourth aspect of the present invention, in the method for inspecting a droplet discharge head according to the third aspect, the second voltage with respect to a capacitance when the first voltage is applied to the individual piezoelectric elements. The rate of decrease in the electrostatic capacity when the voltage is applied is calculated, and a piezoelectric element having the rate of decrease greater than the second threshold is determined as a piezoelectric element in which peeling has occurred.

  For example, with respect to detection of a piezoelectric element in which initial peeling has occurred at the manufacturing stage, as in the invention according to claim 4, with respect to the capacitance when the first voltage is applied to each piezoelectric element. This can be realized by calculating a rate of decrease in capacitance when the second voltage is applied, and determining that a piezoelectric element having a rate of decrease greater than the second threshold is a piezoelectric element in which peeling has occurred.

  According to a fifth aspect of the present invention, in the method for inspecting a droplet discharge head according to any one of the first to fourth aspects, the capacitance is measured by applying at least the second voltage. In addition, a voltage to which a bias voltage is added is applied to the piezoelectric element so that the polarity of the voltage applied to the piezoelectric element is constant during the measurement period.

  For example, when the first voltage and the second voltage applied to each piezoelectric element at the time of capacitance measurement are voltages whose voltage magnitude changes periodically with a constant amplitude, the voltage amplitude must be small. For example, even if a bipolar voltage is applied, the piezoelectric element is not adversely affected. However, if the amplitude of the voltage is large, the piezoelectric element may be destroyed.

  Therefore, as in the fifth aspect of the invention, when measuring the capacitance by applying at least the second voltage, the polarity of the voltage applied to the piezoelectric element during the measurement period is constant. By applying a voltage to which the bias voltage is applied to the piezoelectric element, the polarity of the voltage applied to the piezoelectric element is prevented from being temporarily switched at least during the application period of the second voltage, and the piezoelectric element is adversely affected. Can be prevented. Note that when the capacitance is measured by applying the first voltage, the voltage applied with the bias voltage is applied to the piezoelectric element so that the polarity of the voltage applied to the piezoelectric element is constant during the measurement period. You may make it apply.

  According to a sixth aspect of the present invention, in the liquid droplet ejection head inspection method according to any one of the first to fifth aspects, the liquid droplet ejection head is capable of storing and reading information. , And the detection result of the piezoelectric element in which the bending has occurred or the piezoelectric element in which the peeling has occurred is stored in the information storage means.

  According to the sixth aspect of the present invention, the information storage means included in the droplet discharge head stores the detection result of the piezoelectric element in which the deflection occurs or the piezoelectric element in which the separation occurs, thereby storing the droplet. The state of each piezoelectric element provided corresponding to the plurality of nozzles of the discharge head can be recognized.

  For example, a droplet discharge head is usually used by being incorporated in a droplet discharge device, but the information storage means added to the droplet discharge head is the detection result of the piezoelectric element that is bent or peeled as described above. By storing it, the above detection result can be obtained even when the droplet discharge head is detached from the droplet discharge device. Therefore, even when the droplet discharge head is detached from the droplet discharge device and reused (reuse), the above detection result can be easily obtained by reading the information from the information storage means. Based on the above, by controlling the drive of the droplet discharge head, such as changing the drive frequency or drive voltage of the piezoelectric element in which bending or peeling occurs, the recording accuracy decreases due to variations in the amount of discharged droplets (image quality degradation) In addition, it is possible to easily realize a reduction in reliability.

  The invention according to claim 7 includes information storage means capable of storing and reading out the detection result of the piezoelectric element in which the bending occurs or the piezoelectric element in which the peeling occurs, and corresponds to a plurality of nozzles. By applying a driving voltage to each of the provided piezoelectric elements, a droplet discharge head for discharging droplets from the plurality of nozzles can be detachably mounted, and at least the first piezoelectric element can be mounted on the individual piezoelectric elements. And a second voltage higher than the first voltage, a capacitance measuring means for measuring a capacitance by applying a voltage of two or more of the levels, and a capacitance measured by the capacitance measuring means. And detecting means for detecting a piezoelectric element in which bending or peeling occurs based on an electrostatic capacity corresponding to each voltage level.

  According to the seventh aspect of the present invention, it is possible to detachably mount a droplet discharge head provided with information storage means capable of storing and reading out the state of the piezoelectric element, and the capacitance measuring means is attached to each piezoelectric element. The capacitance is measured by applying a voltage of at least two of the first voltage and the second voltage higher than the first voltage, and measured by the capacitance measuring means. Based on the capacitance corresponding to each voltage level, the piezoelectric element in which the bending or peeling occurs is detected, and information indicating the piezoelectric element in which the bending or peeling occurs is provided in the droplet discharge head. Stored in the information storage means. Thereby, an inspection apparatus for a droplet discharge head can be provided.

  According to an eighth aspect of the present invention, there is provided a liquid droplet ejection head that ejects liquid droplets from the plurality of nozzles by applying a driving voltage to individual piezoelectric elements provided corresponding to the plurality of nozzles. An information storage unit that stores information indicating a piezoelectric element in which bending or peeling detected by the method for inspecting a droplet discharge head according to any one of claims 1 to 6, and the information storage unit Drive control means for controlling the drive of the droplet discharge head so as to change the drive frequency or drive voltage of the piezoelectric element in which bending or peeling occurs based on the information stored in It is characterized by.

  In the invention according to claim 8, the liquid droplet ejection head inspecting method according to any one of claims 1 to 6 causes bending or peeling detected in a manufacturing process, for example. Information indicating the piezoelectric element is stored in the information storage means, and the drive control means determines the drive frequency or drive voltage of the piezoelectric element in which bending or peeling occurs based on the information stored in the information storage means. The drive of the droplet discharge head is controlled to change. As a result, the amount of droplets ejected from the droplet ejection head can be made uniform to improve the recording accuracy (image quality) and improve the reliability.

  According to a ninth aspect of the present invention, there is provided a liquid droplet ejection head that ejects liquid droplets from the plurality of nozzles by applying a driving voltage to each piezoelectric element provided corresponding to the plurality of nozzles. A capacitance measuring means for measuring a capacitance by applying a voltage of at least two of a first voltage and a second voltage higher than the first voltage to each of the piezoelectric elements; and Detection means for detecting a piezoelectric element in which bending or peeling has occurred based on the capacitance corresponding to each voltage level measured by the capacitance measuring means, and bending or peeling detected by the detection means The information storage means for storing information indicating the piezoelectric element in which the occurrence of noise occurs, and the drive frequency or drive voltage of the piezoelectric element in which bending or peeling occurs based on the information stored in the information storage means is changed. As above Is characterized by comprising a driving control means for controlling the driving of the droplet discharging head.

  According to the ninth aspect of the present invention, the capacitance measuring means applies at least the first voltage and the first voltage to each piezoelectric element provided corresponding to the plurality of nozzles of the droplet discharge head. The electrostatic capacity is measured by applying a voltage that is higher than the second voltage and a voltage of 2 or higher, and the detecting means is based on the electrostatic capacity corresponding to each voltage level measured by the electrostatic capacity measuring means. Then, the piezoelectric element in which bending or peeling occurs is detected. Information indicating the piezoelectric element in which bending or peeling is detected, which is detected by the detection means, is stored in the information storage means, and the drive control means is based on the information stored in the information storage means. The drive of the droplet discharge head is controlled so as to change the drive frequency or drive voltage of the piezoelectric element in which peeling occurs.

  As described above, the capacitance measuring means, the detecting means, the information storing means, and the drive control means are provided to detect and store the bending and peeling of the individual piezoelectric elements of the droplet discharge head on the apparatus. Thus, it is possible to provide a droplet discharge device capable of performing drive control based on this.

  According to a tenth aspect of the present invention, in the droplet discharge device according to the ninth aspect, the electrostatic capacity when the first voltage is applied and the electrostatic capacity when the second voltage is applied by the electrostatic capacity measuring means. Capacitance measurement and detection of the piezoelectric element in which the bending or peeling occurs by the detection means are periodically performed.

  In the invention according to claim 10, for example, the electrostatic capacity measurement by the electrostatic capacity measurement means and the detection of the piezoelectric element in which the bending or peeling occurs by the detection means are performed, for example, power ON / OFF of the droplet discharge device During regular maintenance, maintenance, standby (droplet discharge operation non-execution), etc., while the use of the droplet discharge device continues, some of the piezoelectric elements of the droplet discharge head Even when the state changes, it is possible to detect the change in the state of this part of the piezoelectric elements. Accordingly, it is possible to provide a highly reliable device by controlling the driving of the droplet discharge head so as to change the driving frequency or driving voltage of the piezoelectric element whose state has changed.

  According to the method and apparatus for inspecting a droplet discharge head and the droplet discharge device of the present invention, an initial failure of a piezoelectric element can be detected with high accuracy, and high reliability can be ensured.

  Hereinafter, an ink jet recording head according to an embodiment of the present invention and an ink jet recording apparatus including the ink jet recording head will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows an ink jet recording apparatus according to a first embodiment of the present invention. As shown in FIG. 1, the ink jet recording apparatus 10 stocks the paper P and sends it to the recording head unit 16 by controlling the posture of the paper P supplied from the paper supply unit 12 and the paper supply unit 12 sent out during image recording. The registration unit 14 includes a registration adjustment unit 14, a recording head unit 16 that records an image by ejecting ink droplets onto the paper P sent from the registration adjustment unit 14, and a maintenance unit 18 that performs maintenance of the recording head unit 16. 20 and a discharge unit 22 that discharges the paper P on which an image is recorded by the recording unit 20.

  The paper supply unit 12 is provided with a stocker 24 in which a plurality of sheets P are stacked and stocked, and a transport device 26 that transports the sheets one by one from the stocker 24 to the registration adjusting unit 14. The registration adjusting unit 14 is provided with a loop forming unit 28 and a guide member 29 for controlling the posture of the paper. The paper P fed from the paper supply unit 12 is supplied with the loop forming unit 28 and the guide member. By passing through 29, the skew of the paper P is corrected using the stiffness of the paper P, and the conveyance timing is controlled and sent to the recording unit 20.

  In the recording unit 20, a recording head unit 16 and a maintenance unit 18 that are vertically opposed to each other are provided, and a sheet conveyance path through which the sheet P fed from the registration adjusting unit 14 is conveyed is formed between them. Yes. The recording head unit 16 is provided with a plurality of inkjet recording heads (head bars) 30 arranged at predetermined intervals along the paper conveyance path, and upstream and downstream of each inkjet recording head 30 in the paper conveyance path. On the side, a plurality of pairs of star wheels 17 and transport rolls 19 that are vertically opposed to each other are provided.

  The paper P is transported continuously (without stopping) on the paper transport path while being sandwiched between the star wheel 17 and the transport roll 19, and ink droplets are ejected from each ink jet recording head 30 of the recording head unit 16. As a result, an image is recorded. In the discharge unit 22, the paper P on which an image is recorded by the recording unit 20 is conveyed by the paper discharge belt 23 and stored in the tray 25.

  The maintenance unit 18 includes a plurality of maintenance devices 21 arranged to face each of the plurality of inkjet recording heads 30. The maintenance device 21 includes a cap CP (see FIG. 9) for capping the ink jet recording head 30, and can perform other processes such as wiping, dummy jet, and vacuum.

  The ink jet recording apparatus 10 is configured as described above. Next, the ink jet recording head 30 mounted on the ink jet recording apparatus 10 will be described in detail. The present embodiment relates to an ink jet recording head configured by joining and fixing a plurality of special planar recording head units having nozzles formed in a matrix to a long substrate. The configuration and manufacturing method of the ink jet recording head according to this embodiment including the recording head unit having the shape will be described.

  As shown in FIGS. 2 and 3, the ink jet recording head 30 includes a plurality of recording head units 32 arranged along a direction (paper width direction Y) orthogonal to the paper feed direction X. As shown in FIG. 3B, one recording head unit 32 has a substantially parallelogram shape in plan view (the central portion in the paper feed direction X is a parallelogram shape), and ejects ink to the central portion of the nozzle surface 52A. Nozzles 54 to be formed are formed in a matrix, and in one inkjet recording head 30, a plurality of nozzles 54 provided in each recording head unit 32 are formed in a continuous long matrix along the paper width direction Y. ing.

  Each recording head unit 32 records an image on the paper P by ejecting ink droplets from the nozzles 54 in the matrix arrangement on the paper P that is continuously transported through the paper transporting path. The nozzles are arranged in a line (one row) along the paper width direction Y, and higher image quality and higher speed can be achieved compared to the recording head unit. Note that at least four ink jet recording heads 30 mounted on the ink jet recording apparatus 10 are arranged corresponding to each color of YMCK in order to record a so-called full-color image, for example.

  As shown in FIG. 4, the print area width by the nozzles 54 formed in a matrix along the paper width direction Y on one ink jet recording head 30 is the same as that of the paper P on which image recording with this ink jet recording apparatus 10 is assumed. It is longer than the maximum sheet width PW, and image recording over the entire width of the sheet P can be performed without moving the inkjet recording head 30 in the sheet width direction Y (so-called Full Width Array (FWA)). Here, the print area is basically the largest of the recording areas obtained by subtracting the non-printing margin from both ends of the paper P, but is generally larger than the maximum paper width PW to be printed. . This is because there is a possibility that the sheet is conveyed at an angle (skew) with respect to the conveyance direction, and there is a high demand for borderless printing.

  As shown in FIGS. 2 and 3, the ink jet recording head 30 includes a long substrate 40, the plurality of recording head units 32 described above, and a plurality of spacer members 42. The long substrate 40 is long in the paper width direction Y, and has a plurality of openings 40A arranged at predetermined intervals along the longitudinal direction. A pair of attachment plates 41 serving as attachment members to the ink jet recording apparatus 10 are provided at both ends in the longitudinal direction of the long substrate 40, and the long substrate 40 is inside the paper width direction Y of the attachment plate 41. It is arranged so as to span the lower surface of the part. In addition, the width of the long substrate 40 in the paper feed direction X is narrower than the width of the recording head unit 32 in the same direction, whereby the inkjet recording head 30 is configured in a small size.

  A spacer member 42 is attached to the lower surface of the long substrate 40. The spacer members 42 are formed of a transparent resin material and have a plate shape, and two recording head units 32 are arranged obliquely apart from each other in the paper feed direction X as shown in FIG. . As shown in FIGS. 6A and 6B, the spacer member 42 is screwed to the long substrate 40 with screws 46 at two locations. As a result, the spacer member 42 can be detached from the long substrate 40.

  An ink supply unit 44 (see FIG. 5) for supplying ink from an ink tank (not shown) to the recording head unit 32 is disposed between the two spacer members 42. By arranging the two spacer members 42 apart from each other, there is no need to provide a flow path for ink supply in the spacer member 42 itself, and the ink supply unit 44 can be arranged in the separated portion, and an ink supply path is secured. It becomes possible to do. Further, it is not necessary to form an ink supply path in the spacer member 42, and it is possible to select a material that does not take ink resistance into consideration, and a degree of freedom can be obtained in selecting a material to be used for the spacer member 42.

  Here, the case where the two spacer members 42 spaced apart from each other is used for each recording head unit 32 is described. However, the present invention is not limited to this embodiment. For example, the two spacer members 42 spaced apart from each other are used. May be formed as a through hole 42B, for example, so that a part of the spacer member 42 is separated so that the spacer member 42 does not exist in the portion where the ink supply path is arranged (see FIG. 13). .

  In this embodiment, the case where the spacer member 42 is used for each recording head unit 32 has been described. However, the spacer member 42 may be used for a plurality of recording head unit 32 units as necessary. In this case, the plurality of recording head units 32 can be replaced and the number of spacer members 42 to be used can be reduced, so that the manufacturing cost can be reduced (see FIG. 14).

  The recording head unit 32 includes a liquid relay member 50 and a head substrate 52 as shown in FIG. The liquid relay member 50 is disposed on the spacer member 42 side, and an individual supply path 50 </ b> A that communicates with the ink supply unit 44 and supplies ink to the head substrate 52 is formed. The head substrate 52 is disposed on the ink ejection side, and nozzles 54 for ejecting ink are formed in a matrix on a two-dimensional plane in the paper width direction Y and the paper feed direction X on the nozzle surface 52A side (FIG. 3 ( B)).

  As shown in FIG. 15, the head substrate 52 communicates with the ink chamber 56 communicated with the individual supply path 50 </ b> A of the liquid relay member 50, and the ink chamber 56 and one end side communicate with each other via the supply path 58. A pressure chamber 60 whose other end side is in communication with the nozzle 54 is provided. The ink chamber 56 stores ink supplied through the individual supply path 50 </ b> A, and the pressure chamber 60 is filled with ink supplied from the ink chamber 56 through the supply path 58.

  A part of the wall surface on the side opposite to the nozzle surface 52 </ b> A constituting the pressure chamber 60 is formed by a diaphragm 62, and a piezoelectric element 64 is bonded and fixed to the diaphragm 62 by bonding or the like. The ink chamber 56, the supply path 58, the pressure chamber 60, and the piezoelectric element 64 are provided in the same number as the nozzles 54 corresponding to the plurality of nozzles 54 formed on the nozzle surface 52A of the head substrate 52.

  When a driving voltage is applied to the piezoelectric element 64 provided on the head substrate 52 of the recording head unit 32, the piezoelectric element 64 is deflected and displaced to vibrate the diaphragm 62, and the vibration of the diaphragm 62 is converted into a pressure wave as a pressure wave. By propagating through the chamber 60, the ink in the pressure chamber 60 is ejected as ink droplets from the nozzle 54 (arrow I).

  The recording head unit 32 is disposed on the opposite side of the long substrate 40 with the spacer member 42 interposed therebetween. The spacer member 42 and the recording head unit 32 have substantially the same shape (rectangular shape) on the outer side of the long substrate 40 along the paper width direction Y when viewed from the nozzle surface 52A side. The recording head unit 32 is bonded and fixed to the spacer member 42 at both ends along the paper width direction Y, that is, at both ends along the longitudinal direction of the recording head unit 32.

  The recording and fixing of the recording head unit 32 to the spacer member 42 is performed by a UV (ultraviolet) curable adhesive U interposed between the recording head unit 32 and the spacer member 42. A gap G corresponding to the thickness of the adhesive U is formed between the recording head unit 32 and the spacer member 42. By adjusting the gap G, the heights of the nozzle surfaces 52A of the plurality of recording head units 32 are increased. Can be aligned.

  As shown in FIG. 6B, a through hole 42A for electrical wiring is formed in a portion of the spacer member 42 where the long substrate 40 is not overlapped. Electrical wiring (not shown) connects the recording head unit 32 and drive control means 78 as a controller, which will be described later, through the through hole 42A.

  Next, a method for manufacturing the ink jet recording head 30 of the present embodiment will be described with reference to FIGS. 7 (A) to 7 (D). First, as shown in FIG. 7A, all the spacer members 42 are attached to the long substrate 40. The attachment here is performed by screwing with a screw 46.

  Next, as shown in FIG. 7 (B), the long substrate 40 is attached to the bonding descending arm SA provided in the alignment bonding apparatus, and the alignment bonding apparatus arranged in parallel with the attached long substrate 40 is used. On the positioning stage ST, a number of recording head units 32 necessary for constituting one ink jet recording head 30 are arranged in a line. At this time, the recording head unit 32 accurately positions and arranges the positions of the nozzles 54 between the recording head units 32. A UV curable adhesive U is applied to the recording head unit 32 at a predetermined location.

  Next, as shown in FIG. 7C, the joining lowering arm SA is brought close to the positioning stage ST while maintaining a parallel state, and stopped at a position where the nozzle surface 52A constitutes a predetermined nozzle surface. At this time, the adhesive U applied to the recording head unit 32 is pressed against the spacer member 42, and a thickness portion having a predetermined thickness or more is crushed (bonded).

  Next, the adhesive U is irradiated with UV light while maintaining the distance between the bonding descending arm SA and the positioning stage ST in the above state (bonding fixation), as shown in FIG. 7D. Then, the ink jet recording head 30 is completed by detaching from the lowering arm SA and the positioning stage ST. The UV light applied to the adhesive U is irradiated only within a predetermined range including a predetermined location where the adhesive U is applied, for example, using focus irradiation or a mask, that is, the adhesive U is applied. The irradiation range is limited so that no part is irradiated.

  According to the above manufacturing method, the spacer member 42 is attached to the long substrate 40 by screwing. However, since the spacer member 42 is attached to the long substrate 40 before the recording head unit 32 is joined, a slight displacement of the spacer member 42 is recorded. The alignment of the head unit 32 is not affected. Since the recording head unit 32 is bonded to the spacer member 42 attached to the long substrate 40 using the adhesive U, it can be bonded and fixed in an aligned state on the positioning stage ST. Compared with the case where the long substrate 40 and the recording head unit 32 are directly screwed, the long substrate 40 and the recording head unit 32 can be bonded and fixed while being accurately aligned.

  In the above manufacturing method, all the recording head units 32 necessary for configuring the long substrate 40 are arranged on the positioning stage ST and bonded and fixed at a time. However, the bonding and fixing of the recording head unit 32 is performed as follows. You don't have to do it all at once. For example, as shown in FIG. 8, only a part of the recording head units 32 such as one, two, etc. are arranged and bonded and fixed (two in FIG. 8), and the same processing is repeated a plurality of times to thereby perform inkjet. The recording head 30 may be completed.

  Next, the operation of the inkjet recording apparatus 10 of the present embodiment will be described. When a print job is input to the inkjet recording apparatus 10 and a printing (image recording) operation is started, one sheet P is picked up from the stocker 24 and conveyed to the recording unit 20 by the conveying device 26.

  On the other hand, the ink is already stored (filled) in the ink chamber 56 and the pressure chamber 60 of the recording head unit 32 from the ink tank through the ink supply port in the ink jet recording head 30. At this time, a meniscus having a slightly recessed ink surface is formed at the tip (discharge port) of the nozzle 54.

  While conveying the paper P at a predetermined conveyance speed, a driving voltage is applied to each piezoelectric element 64 of the recording head unit 32, the piezoelectric element 64 is deflected and displaced to vibrate the diaphragm 62, and the pressure chamber 60 is pressurized. By selectively ejecting ink droplets from the plurality of nozzles 54, an image based on the image data is recorded on the paper P.

  When maintaining the recording head unit 32, as shown in FIG. 9, the cap CP is disposed at the maintenance position M1, and the recording head unit 32 is capped with the cap CP. At this time, the cap CP is pressed against the end side portion T along the longitudinal direction of the recording head unit 32 (the same direction as the paper width direction Y). Thereby, the nozzle surface 52A side of the inkjet recording head 30 is covered with the cap CP, and the sealed space H is formed. In this state, a pump (not shown) of the maintenance device 21 is operated to make the sealed space H have a negative pressure, and by sucking the nozzle 54, an ink lump that is blocking the nozzle 54 can be discharged.

  In the ink jet recording head 30 according to the present embodiment, the spacer member 42 and the recording head unit 32 are joined at the end T portion pressed by the cap CP during the maintenance. Can be appropriately received at the joint, and deformation of the ink jet recording head 30 can be prevented.

  In addition, as shown in FIG. 10, the inkjet recording head 30 can have both the long substrate 40 and the recording head unit 32 disposed below the spacer member 42, but is disposed as in the present embodiment. Accordingly, the pressing force by the cap CP can be received by both the long substrate 40 and the spacer member 42 during maintenance, and the strength can be improved.

  In the present embodiment, the width of the long substrate 40 in the paper feed direction X is narrower than the width of the recording head unit 32. However, the width of the long substrate 40 in the paper feed direction X is as shown in FIG. In addition, the width of the recording head unit 32 may be approximately the same. In this case, the through hole 42A for electrical wiring is not necessary, and electrical wiring may be performed at a position communicating with the opening 40A of the long substrate 40 between the spaced spacer members 42.

  In addition, since the spacer member 42 of the present embodiment is made of a transparent resin, in the curing process of the adhesive U, the UV light emitted toward the adhesive U passes through the spacer member 42 as shown in FIG. Then, the entire adhesive U is irradiated. In this case, as shown in FIG. 12A, the configuration in which the width of the long substrate 40 in the paper feeding direction X is narrower than the width of the recording head unit 32 is shown in FIG. As described above, the light irradiation area becomes wider than the configuration in which the width of the long substrate 40 in the paper feeding direction is the same as the width of the recording head unit 32, and the irradiation efficiency is improved.

  Next, an inspection method for detecting bending and peeling of individual piezoelectric elements 64 provided in each recording head unit 32 provided in the above-described ink jet recording head 30 will be described. As described above, in the conventional capacitance measurement using only a low electric field (for example, an applied voltage of 1 V), it is not possible to detect bending or peeling of the piezoelectric element due to manufacturing variations. Similarly, it cannot be detected in the impedance frequency characteristic measurement.

  Various investigations and experiments were conducted on this problem, and the results and the found items will be described with reference to FIGS. In the following description, a piezoelectric element having a deflection (a deflection amount is outside a predetermined allowable range) is referred to as “a deflection generating element”, and a piezoelectric element having a separation (a peeling amount is outside a predetermined allowable range) is referred to as “a peeling occurrence”. An “element” or a piezoelectric element in which no bending or peeling occurs (the amount of bending or peeling is within a predetermined allowable range) is referred to as “an ungenerated element” or “normal element”.

  FIG. 16 is a comparative view schematically showing the deflection displacement when a predetermined DC bias voltage is applied to each of the piezoelectric elements where the deflection is generated, the peeling is generated, and the piezoelectric element is not generated. As shown in FIG. 16A, the vibration plate 62 is bent due to the bending generation element 64A in which the piezoelectric element itself is bent, or unevenness of the adhesive layer that bonds the piezoelectric element to the vibration plate 62. In the bending generating element 64A ′, the bending displacement amount (capacitance) Δa due to application of a predetermined voltage becomes small.

  On the other hand, in the normal element 64B (non-generated element) in which the bending and peeling do not occur as shown in FIG. 16B, the bending displacement amount Δb due to the application of the predetermined voltage increases (Δb> Δa), and FIG. C) Even with the peeling generation element 64C partially peeled (without bending), the bending displacement amount Δc due to application of a predetermined voltage increases (Δc> Δa).

  In FIG. 17, the relationship between the predetermined DC bias voltage application (for example, amplitude 1 V, frequency 1 kHz) and capacitance in each of the piezoelectric elements that are bent, peeled, and not generated (non-defective), that is, voltage dependency of the capacitance. Is shown in a graph. As can be seen from FIG. 17, in contrast to the non-generated element whose graph line is indicated by a solid line, the deflection generating element whose graph line is indicated by a one-dot chain line has a smaller inclination of the graph line, and the capacitance changes with respect to the applied voltage. Few. The peeling generating element in which the graph line is indicated by a two-dot chain line has a large inclination of the graph line and a large change in capacitance with respect to the applied voltage.

  In addition, when comparing the capacitance values by applying only a low voltage L (for example, a bias voltage of 0 V), the difference in capacitance values depends on the shape due to variations in the processing shape (thickness, area, etc.) of the piezoelectric elements. It is difficult to determine whether it is due to bending or peeling, and the occurrence of bending or peeling cannot be sufficiently detected. On the other hand, when comparing the capacitance values by applying only a high voltage H (for example, a bias voltage of 30 V), the difference between the capacitance values of the piezoelectric elements is small. It becomes difficult.

  FIG. 18 is a graph showing the relationship between the applied voltage and the resonance frequency in each of the piezoelectric elements that are bent, peeled, and not generated (good product). From FIG. 18, it can be seen that even if the applied voltage level is increased and forcibly bent, the resonance frequency is not observed in each piezoelectric element.

From these results, the following three points were found.
(1) There is a difference in the change rate of the capacitance value with respect to the applied voltage value between the deflection generating element, the peeling generating element, and the non-generating element (see FIG. 17).
(2) In the deflection generating element, the peeling generating element, and the non-generating element, there is almost no change in the resonance frequency with respect to the applied voltage value (see FIG. 18). That is, it is not possible to detect bending or peeling of the piezoelectric element at the resonance frequency.
Therefore,
(3) By applying at least two different voltages (high and low 2 or more) to the piezoelectric element and measuring and comparing the capacitance values, it is possible to detect the presence or absence of occurrence of bending or peeling. Furthermore, it is possible to determine the degree of bending (relative bending magnitude).

  Next, a specific method for detecting whether the piezoelectric element is bent or peeled off will be described. For example, when measuring and comparing the capacitance values by applying two high and low voltages to the piezoelectric element, the low electric field capacitance (Cpl) and the high electric field capacitance (Cph) are measured to reduce the capacitance. The rate (for example, the ratio of the capacitance value change amount (Cpl−Cph) to the voltage value change amount (ΔV)) is calculated by the following equation (1) (see FIG. 17).

  Capacitance reduction rate R = (Cpl−Cph) / ΔV × 100 (1)

  Then, the capacitance reduction rate R is compared with a threshold value Ra of the capacitance reduction rate that distinguishes between the normal state (good product) and the deflection occurrence state, which is determined in advance from an actual value or the like. When R is smaller than the threshold value Ra (R <Ra), it is determined that the measured piezoelectric element is in a bending state. Further, the capacitance reduction rate R is compared with a threshold value Rb of a capacitance reduction rate that distinguishes between a normal state (good product) and a peeling occurrence state, which is determined in advance from an actual value or the like. Is larger than the threshold value Rb (R> Rb), it is determined that the measured piezoelectric element is in a peeled state. Furthermore, when the capacitance reduction rate R is not less than the threshold value Ra and not more than the threshold value Rb (Ra ≦ R ≦ Rb), the measured piezoelectric element is determined to be in a normal state.

  The state of the piezoelectric element (deformation / debonding / normal) can be detected by calculating the capacitance reduction rate based on the above-described capacitance measurement and comparing / determining the calculated value and the threshold value.

  Next, the configuration of the present embodiment to which the above-described inspection method for the inkjet recording head 30 is applied will be described. The present embodiment is an example in which an inspection of the ink jet recording head 30 is performed before use in a manufacturing process of the ink jet recording apparatus 10 or the like.

  As shown in FIG. 19, the ink jet recording head 30 detects the state based on the above-described capacitance measurement from the individual piezoelectric elements 64 provided in each recording head unit 32 (deformation / peeling / normal). An element selection circuit 70 including a switch IC for selecting the piezoelectric element 64 for performing the operation, and an element state storage means 72 including a RAM for storing the detected state of the piezoelectric element 64.

  The inkjet recording apparatus 10 includes a drive voltage / waveform generation unit 74 that generates a drive voltage and a waveform to be applied to the inkjet recording head 30, and a drive voltage / waveform generation unit 74. , A selection circuit 76 that selects the driving voltage from the driving voltage / waveform generation unit 74 or a measurement voltage from the outside of the apparatus, and the selection circuit 76, the element selection circuit 70, and the element state storage means 72 are connected to each other. A selection control circuit 76 and drive control means 78 for driving and controlling the inkjet recording head 30 based on information stored in the state storage means 72 are provided.

  In addition, as shown by a dotted line in the drawing, a series of operations of driving the inkjet recording head 30 for measuring the capacitance of the piezoelectric element 64 and measuring the capacitance are controlled outside the inkjet recording apparatus 10. A drive / measurement control means 80, a first measurement voltage / waveform generator 82 for generating a first measurement voltage and waveform to be applied to the inkjet recording head 30, a second measurement voltage to be applied to the inkjet recording head 30, and The second measurement voltage / waveform generation unit 84 that generates the waveform, the capacitance measurement unit 86 that measures the capacitance of the piezoelectric element 64, and the piezoelectric measurement based on the capacitance measurement by the capacitance measurement unit 86. Element state detection means 88 for determining and detecting the state of the element 64 is provided.

  The drive / measurement control means 80 includes a first measurement voltage / waveform generation unit 82, a second measurement voltage / waveform generation unit 84, a selection circuit 76 of the inkjet recording apparatus 10, and an element selection circuit 70 of the inkjet recording head 30. The first measurement voltage / waveform generation unit 82 and the second measurement voltage / waveform generation unit 84 are connected to the selection circuit 76 together with the drive voltage / waveform generation unit 74. The capacitance measuring means 86 is connected to all the piezoelectric elements 64 of the ink jet recording head 30 and outputs the measured capacitance values of the individual piezoelectric elements 64 to the element state detecting means 88. The element state detection unit 88 is connected to the element state storage unit 72 of the ink jet recording head 30, and the state of each piezoelectric element 64 based on the capacitance value input from the capacitance measurement unit 86 is stored in the element state storage unit. 72 is stored in the memory.

  Next, an inspection method for the ink jet recording head 30 having the above-described configuration will be described. In order to inspect the ink jet recording head 30 before use in the manufacturing process of the ink jet recording apparatus 10 or the like, the head inspection process (A) is performed in step 90 of the head inspection process before use shown in FIG. In the head inspection process (A) shown in FIG. 21, when the process is started, first, the first measurement voltage / waveform generation unit 82 and the second measurement voltage / waveform generation controlled by the drive / measurement control means 80 are performed. The unit 84 generates a DC bias voltage for capacitance measurement and outputs it to the selection circuit 76.

  Here, the first measurement voltage / waveform generation unit 82 has a sine wave (for example, amplitude of 1 V, frequency of 1 kHz) as shown in FIG. 22A, a voltage level of V1, and a capacitance described later. A first DC bias voltage (low voltage) to which a bias voltage is applied so that the polarity of the voltage applied to the piezoelectric element 64 is constant during the measurement period is generated and output to the selection circuit 76. The second measurement voltage / waveform generation unit 84 is a sine wave (for example, amplitude 1 V, frequency 1 kHz) as shown in FIG. 22B and has a voltage level Vh higher than the first DC bias voltage (Vh). > Vl), and a second DC bias voltage (high voltage) is generated by adding a bias voltage that makes the polarity of the voltage applied to the piezoelectric element 64 constant during the capacitance measurement period described later. To the selection circuit 76.

  Then, in step 100, the element selection circuit 70 controlled by the drive / measurement control unit 80 selects a piezoelectric element to be processed from the plurality of piezoelectric elements 64 provided in each recording head unit 32 of the inkjet recording head 30. The element 64 is selected, and in step 102, the selection circuit 76 controlled by the drive / measurement control means 80 selects the input first DC bias voltage and outputs the selected first DC bias voltage to the element selection circuit 70. Applies a first DC bias voltage to the piezoelectric element 64 selected in step 100.

  As the low voltage is applied, the piezoelectric element 64 is deflected and displaced. In step 104, the capacitance measuring means 86 measures the capacitance of the piezoelectric element 64, and the measured value (low electric field capacitance: Cpl). Is output to the element state detecting means 88.

  Next, in step 106, the selection circuit 76 selects the input second DC bias voltage and outputs it to the element selection circuit 70, and the element selection circuit 70 outputs the same piezoelectric element 64 selected in step 100. A second DC bias voltage is applied.

  As the high voltage is applied, the piezoelectric element 64 is deflected and displaced, and in step 108, the capacitance measuring means 86 measures the capacitance of the piezoelectric element 64, and the measured value (high electric field capacitance: Cph). ) To the element state detecting means 88.

  In the subsequent step 110, the element state detecting means 88 detects the state of the piezoelectric element 64 to be processed based on the capacitance measurement value corresponding to the high and low voltage levels. Specifically, as described above, in the calculation process using the equation (capacitance reduction rate R = (Cpl−Cph) / ΔV × 100) for calculating the capacitance reduction rate, Calculate the rate of decline.

  In step 112, the capacitance reduction rate R is greater than the threshold value Ra (first threshold value) of the capacitance reduction rate that distinguishes between the normal state (non-defective product) and the state of occurrence of deflection, which is determined in advance from the actual value or the like. If the determination is affirmative (R <Ra), the process proceeds to step 114, where the element state detecting means 88 determines that the piezoelectric element 64 to be processed is in a state of occurrence of bending, and step 122 is performed. Thus, information indicating that the piezoelectric element 64 is in a state of occurrence of bending is written and stored in the element state storage means 72.

  On the other hand, in the case of a negative determination in step 112 (R ≧ Ra), the process proceeds to step 116, where the capacitance decreases to distinguish between a normal state (non-defective product) and a peeling occurrence state determined in advance from an actual value or the like. It is determined whether or not the capacitance decrease rate R is larger than the rate threshold value Rb (second threshold value). If the determination is affirmative (R> Rb), the process proceeds to step 118, and the element state detection means 88 determines that the piezoelectric element 64 to be processed is in a peeling occurrence state, and writes and stores information indicating that the piezoelectric element 64 is in a peeling occurrence state in the element state storage means 72 in step 122.

  If negative determination is made at step 116 (R ≦ Rb => Ra ≦ R ≦ Rb), the process proceeds to step 120, where the element state detection means 88 determines that the piezoelectric element 64 to be processed is in a normal state (non-defective product). In step 122, information indicating that the piezoelectric element 64 is in a normal state is written and stored in the element state storage means 72. Further, in addition to the detection state of the piezoelectric element 64, the element state storage means 72 also stores information indicating the measured low electric field capacitance (Cpl) and high electric field capacitance (Cph).

  With the above procedure, the state detection of one piezoelectric element 64 that is the processing target is completed. In the following step 124, it is determined whether or not the state detection process has been completed for all the piezoelectric elements 64 of the ink jet recording head 30, and in the case of a negative determination, the process returns to step 100 and the unprocessed piezoelectric elements 64 are changed. On the other hand, the procedure from step 100 to step 122 is repeated. When the detection of the states of all the piezoelectric elements 64 is completed, the inspection process of the ink jet recording head 30 is completed, and the element state storage means 72 stores the states of the individual piezoelectric elements 64 (deformation / peeling / normal). Is stored.

  Here, when the same driving voltage as that of a normal element is applied to, for example, a deflection generating element or a peeling generating element when the head is driven, the displacement amount of each element has the following relationship.

  Peeling generation element> Normal element> Bending generation element (2)

  This causes a difference in the ejection amount of ink droplets ejected from the nozzles corresponding to each element, leading to image degradation. Control over the element is required.

  Therefore, in the inkjet recording apparatus 10 of the present embodiment, when recording an image in a user's usage environment, information indicating the state of each piezoelectric element 64 stored in the element state storage unit 72 of the inkjet recording head 30 is driven. Based on the information read by the control means 78, the selection circuit 76 and the element selection circuit 70 to which the drive voltage is input from the drive voltage / waveform generation unit 74 are controlled, and the inkjet recording head 30 is driven and controlled as follows. (Step 92 in FIG. 20).

For example, with respect to the deflection generating element and the peeling generating element detected by the inspection method of the inkjet recording head 30 described above,
(1) The frequency of use is decreased, and the decrease is compensated for by other normal elements (see FIG. 23).
(2) Stop use and use another normal element (see FIG. 23).
(3) The drive voltage applied for each element is changed (see FIG. 24).
(4) A waveform set is prepared in advance, and the corresponding waveform set is used as necessary (see FIG. 25).
(5) In the case where a temperature correction table is provided, the table is diverted by using, for example, a low temperature bending element and a high temperature peeling element.

  Here, as shown in the above (1) and (2), when the frequency of use of the deflection generating element or the peeling generating element is decreased or when the use is stopped, the bending / peeling occurs as shown in FIG. This is done by increasing the amount of ink droplets ejected from the nozzle adjacent to the nozzle corresponding to the element.

  For example, if all three piezoelectric elements 64 corresponding to three adjacent specific nozzles 54 are normal, when the same drive voltage is applied to those piezoelectric elements 64, the displacement amounts of the respective elements become substantially equal. As shown in FIG. 23A, the ejection amounts of the ink droplets ejected from the nozzles 54 are substantially equal, and the three pixels G1, G2, G3 to be recorded have substantially the same size.

  On the other hand, for example, if one piezoelectric element 64 is bent, the amount of ink droplets discharged from the nozzle 54 corresponding to the deflection generating element is reduced, as shown in FIG. In addition, when the pixel (for example, pixel 2) becomes smaller and peeling occurs, the ink droplet ejection amount is not increased, and as shown in FIG. 23C, the pixel (for example, pixel 2) becomes larger. As a result, missing dots or excessive dots, and ink droplet landing position shift (pixel shift) may occur.

  Therefore, the bending / peeling generation element reduces the use frequency or stops the use, increases the drive voltage applied to the normal element provided corresponding to the adjacent nozzle 54, and increases the ejection amount of the ink droplets. . As a result, as shown in FIG. 23D, adjacent pixels (for example, pixels 1 and 3) are enlarged, and a decrease in defective pixels can be compensated.

  Further, when the drive voltage applied to each element is changed as in (3) above, the drive voltage applied to the deflection generating element is a normal element as shown in FIGS. 24 (A) and (B), for example. In contrast, the drive voltage applied to the peeling generation element is set to be smaller than that of the normal element (−ΔV), and the drive voltage applied to each element is set so as to satisfy the following relationship.

  Peeling generation element <Normal element <Bending generation element (3)

  As a result, the ejection amount of the ink droplets ejected from the nozzles 54 corresponding to the respective occurrences of bending / peeling / normal is made uniform, and image quality deterioration due to missing or excessive dots, displacement of landing positions of ink droplets, etc. can be suppressed. .

  Further, when changing the ejected ink droplet amount for each element using the waveform set prepared in advance as described in (4) above, for example, as shown in FIG. 25, a large droplet waveform / medium droplet waveform for each element. / Use a waveform set with each droplet waveform set. In this waveform set, a normal element waveform set (large droplet (N), medium droplet (N), small droplet (N)) is selected and driven for a normal element. For the deflection generating element, the waveform set for the deflection generating element (large droplet (T), medium droplet (T), small droplet (T)) is selected and driven. For the peeling generating element, a waveform set for the peeling generating element (large droplet (H), medium droplet (H), small droplet (H)) is selected and driven. In addition, these waveform sets may be used only when discharging microdroplets that are particularly susceptible to influence, as required. Thereby, as in (3) above, it is possible to control at a lower cost compared to the case of controlling each element.

  As described above, in the ink jet recording apparatus 10 of the present embodiment, the state of each piezoelectric element 64 is detected, and the ink jet recording head 30 is driven and controlled based on the information, thereby suppressing image deterioration and improving the image quality. Is possible.

  As described above, in the method for inspecting the inkjet recording head 30 (recording head unit 32) of the present embodiment, the first voltage (the first voltage) is applied to each piezoelectric element 64 provided corresponding to the plurality of nozzles 54. DC bias voltage) and a second voltage higher than that (second DC bias voltage) are applied to measure the capacitance, and the capacitance corresponding to each voltage level. The degree of deflection and peeling of the piezoelectric element 64 are detected based on the above, and by this inspection method, the bending and peeling of the piezoelectric element, particularly in the manufacturing stage, which could not be detected by the conventional capacitance measurement only with a low electric field. Initial defects can be detected with high accuracy. Accordingly, it is possible to take measures for improving the image quality and improving the reliability by making the amount of ejected ink droplets uniform, and the yield during manufacturing can be improved.

  In addition, the inspection of the ink jet recording head 30 has been described as an example in which the ink jet recording apparatus 10 is assembled in the ink jet recording apparatus 10 in the manufacturing process of the ink jet recording apparatus 10 before use. It can also be carried out in a process or the like.

  In the capacitance measurement of the piezoelectric element 64, two voltages, high and low, are applied to the piezoelectric element 64. In particular, the high voltage (second voltage) is applied to the piezoelectric element 64 during the measurement period. By applying a voltage (DC bias voltage) obtained by adding a bias voltage so that the polarity of the voltage to be constant is applied, the polarity of the voltage applied to the piezoelectric element 64 is temporarily changed during this high voltage application period. It is possible to prevent the piezoelectric element 64 from being adversely affected.

  Further, in the present embodiment, the element state storage means 72 provided in the ink jet recording head 30 stores the detection results of the piezoelectric elements 64 detected as the occurrence of bending / peeling / normal state, thereby enabling individual piezoelectric elements to be stored. 64 can be recognized, and for example, the detection result can be acquired even when the ink jet recording head 30 is detached from the ink jet recording apparatus 10. Therefore, even when the ink jet recording head 30 is detached from the ink jet recording apparatus 10 and reused, the above detection results can be easily obtained by reading the information of each element from the element state storage means 72. Based on the detection result, it is possible to perform drive control such as changing the drive frequency or drive voltage of the deflection generating element or the peeling generating element.

(Second Embodiment)
Next, the configuration of the second embodiment to which the above-described ink jet recording head inspection method is applied will be described. This embodiment is also an example in which the inspection of the ink jet recording head is performed before use in the manufacturing process of the ink jet recording apparatus.

  As shown in FIG. 26, in the present embodiment, the element state storage means 72 is not mounted on the inkjet recording head 132 but is mounted on the inkjet recording apparatus 130, and the rest is configured in the same manner as in the first embodiment. ing.

  In this way, the element state storage means 72 can be provided on the ink jet recording apparatus 130 side. In this case, when the ink jet recording head 132 is replaced, new information on the ink jet recording head 132 (deflection of all piezoelectric elements) is obtained. Although it is necessary to write and store information indicating occurrence / peeling occurrence / normal state) in the element state storage means 72, the cost of the ink jet recording head 132 can be reduced. Therefore, in a configuration in which a plurality of inkjet recording heads are mounted, such as an FWA (Full Width Array) apparatus as in the present embodiment, the cost of the entire apparatus can be reduced.

(Third embodiment)
Next, the configuration of the ink jet recording apparatus according to the third embodiment and the inspection method of the ink jet recording head will be described. The present embodiment is an example in which the inspection of the ink jet recording head can be performed even after use of the ink jet recording apparatus in a user environment or the like.

  As shown in FIG. 27, the ink jet recording apparatus 140 of the present embodiment is equipped with the ink jet recording head 132 described in the second embodiment and the individual element state storage means 72. The drive / measurement control unit 80, the first measurement voltage / waveform generation unit 82, the second measurement voltage / waveform generation unit 84, the capacitance measurement unit 86, and the element state detection unit 88 described in the embodiment are also mounted. Has been. In addition, the function of the drive control unit 78 described in the first embodiment is incorporated in the drive / measurement control unit 80, and the drive control unit 78 is replaced with the drive / measurement control unit 80.

  Thus, each means for inspecting the ink jet recording head 132 can be provided on the ink jet recording apparatus 140 side. With this configuration, the ink jet recording head 132 can be inspected by the manufacture of the ink jet recording apparatus 140. In addition to the process, etc., it can also be implemented in the user's usage environment.

  Here, a head inspection method after use in the inkjet recording apparatus 140 of the present embodiment will be described. The inspection described below is periodically executed when a predetermined number of heads have been driven, or when the apparatus is turned on / off, during maintenance, or during standby (when ink droplet ejection operation is not performed). .

  In order to inspect the used inkjet recording head 132 in the usage environment or the like of the inkjet recording apparatus 140, the head inspection process (B) is performed in step 150 of the after-use head inspection process shown in FIG. In the head inspection process (B) shown in FIG. 29, when the process is started, the second measurement voltage / waveform generator 84 controlled by the drive / measurement control means 80 causes the DC bias voltage for capacitance measurement. Is output to the selection circuit 76.

  In subsequent step 160, the element selection circuit 70 controlled by the drive / measurement control means 80 selects a piezoelectric element to be processed from among the plurality of piezoelectric elements 64 provided in each recording head unit 32 of the inkjet recording head 132. 64, the selection circuit 76 controlled by the drive / measurement control means 80 outputs the input second DC bias voltage to the element selection circuit 70 in step 162, and the element selection circuit 70 outputs the piezoelectric element 64. In contrast, a second DC bias voltage is applied.

  Next, in step 164, the capacitance measuring unit 86 measures the capacitance of the piezoelectric element 64 and outputs the measured value (high electric field capacitance over time: Cph) to the element state detecting unit 88. Here, the element state detection means 88 reads the low electric field capacitance (Cpl) before use in the piezoelectric element 64 to be processed measured in the manufacturing process etc. from the element state storage means 72 and uses it in step 166. The rate of decrease in capacitance is calculated based on the previous initial low electric field capacitance (Cpl) and the high electric field capacitance (Cph) measured over time after use (see equation (1)).

  Then, the subsequent steps 168 to 180 detect the state (deformation occurrence / separation occurrence / normal) of the piezoelectric element 64 to be processed in the same procedure as in the first embodiment, and store information indicating the detected state in the element state The state is stored in the means 72, and the state detection and information are stored in the same manner for all the piezoelectric elements 64, and the inspection process is terminated.

  After performing this inspection process, the drive / measurement control means 80 performs the same head drive control as in the first embodiment based on the information indicating the detection state of each element newly stored in the element state storage means 72. This is executed (step 152 in FIG. 28), and image recording by the ink jet recording apparatus 140 is performed.

  As described above, by periodically inspecting the ink jet recording head, it is possible to detect the degree of bending and the change in characteristics over time for a piezoelectric element whose characteristics change over time. Then, by reducing the frequency of use according to the degree of failure and performing head drive control such as supplementing the shortage with alternative use of normal elements, ejection characteristic deterioration due to changes in characteristics over time of the piezoelectric element 64 (= (Image quality degradation) can be reduced, and a highly reliable device can be obtained. In particular, in the inspection method of this embodiment, the initial low electric field capacitance (Cpl) is used, and the time-lapse low electric field capacitance measurement is omitted, so that the inspection time can be shortened. .

(Fourth embodiment)
Next, a description will be given of a fourth embodiment in which the inspection method for the inkjet recording head 132 is changed in the inkjet recording apparatus 140 described above. In the case of this embodiment as well, as in the third embodiment, the inkjet recording head 132 is periodically used when the predetermined number of heads have elapsed, or when the apparatus is turned on / off, during maintenance, or during standby. A check is performed.

  As shown in FIG. 30, in the post-use head inspection process of the present embodiment, in step 190, the head inspection process (A) described in the first embodiment is performed (see FIG. 21) and acquired by the inspection process. Based on the information indicating the detection state of each piezoelectric element 64, the head drive control similar to that of the first embodiment is executed in step 192 to perform image recording.

  In this head inspection process (A), the capacitance decrease rate of each piezoelectric element 64 provided in the ink jet recording head 132 is determined by the low electric field capacitance (Cpl) with time measured after use and the high electric field with time. It is calculated based on the electric capacity (Cph). As a result, a change in the degree of bending of the piezoelectric element 64 over time and a deterioration in ejection characteristics can be detected with higher accuracy, and a reduction effect on image quality deterioration is enhanced.

(Fifth embodiment)
Next, the configuration of the ink jet recording apparatus according to the fifth embodiment, which is a partial modification of the third embodiment, will be described. As shown in FIG. 31, the ink jet recording apparatus 200 of the present embodiment is not equipped with the element state storage means 72. Instead of the ink jet recording head 132, the element state storage means described in the first embodiment is used. An ink jet recording head 30 having 72 is mounted.

  Also in the ink jet recording apparatus 200, as in the third embodiment, it is possible to periodically inspect the apparatus after the operation, and to update the detection information regarding the state of the piezoelectric element 64. Similarly to the first embodiment, the detected information is stored in the element state storage unit 72 on the ink jet recording head 30 side, so that information on each element is read out from the element state storage unit 72, thereby replacing the head. And can be easily reused.

(Sixth embodiment)
Next, the configuration of an inkjet recording head inspection apparatus according to a sixth embodiment, which is a partial modification of the first embodiment, will be described. As shown in FIG. 32, the ink jet recording head 30 of the present embodiment is equipped with an element state storage means 72, and the ink jet recording head 30 is detachably mounted on the inspection apparatus 300. The inspection apparatus 300 includes a drive / measurement control unit 80, a first measurement voltage / waveform generation unit 82, a second measurement voltage / waveform generation unit 84, a capacitance measurement unit 86, and an element state detection unit 88. .

  In the inspection apparatus 300 of the present embodiment, the state of each piezoelectric element 64 can be detected, and the state of the piezoelectric element 64 can be stored in the element state storage means 72 of the ink jet recording head 30. It is possible to provide an inspection apparatus for an ink jet recording head.

  As mentioned above, although the present invention was explained in detail by the 1st-6th embodiment mentioned above, the present invention is not limited to those embodiments, and other various forms are within the limits of the present invention. It can be implemented. For example, in the ink jet recording head inspection method described above, two voltages are applied in order to obtain the capacitance reduction rate of the piezoelectric element 64, but the applied voltage may be three or more.

For example, when applying three levels of voltage, low, medium, and high, the capacitance reduction rate R is the capacitance calculated based on the low electric field capacitance (Cpl) and the medium electric field capacitance (Cpm). Capacitance reduction rate calculated based on the reduction rate (R ₁ = (Cpl−Cpm) / ΔV ₁ × 100), medium electric field capacitance (Cpm) and high electric field capacitance (Cph) (R ₂ = The average value of (Cpm−Cph) / ΔV ₂ × 100) is used (R = (R ₁ + R ₂ ) / 2), or an approximate straight line for each capacitance of low, medium, and high electric fields is obtained and its inclination The same calculation method can be used when applying voltages of four or more levels.

  In the above-described ink jet recording heads 30 and 132, the case where the element selection circuit 70 is included has been described as an example. However, the element selection circuit 70 is provided on the ink jet recording apparatus side and the inspection apparatus side according to the head form. It may be.

  In the above-described embodiment, an example in which at least four inkjet recording heads 30 are arranged corresponding to each color of YMCK in order to record a full-color image has been described. It is not limited to this. For example, for each row of a plurality of recording head units arranged in the Y direction in the paper width direction to a plurality of recording head units 32 that are two-dimensionally arranged in the paper width direction Y and the paper feeding direction X for one long substrate 40. Each of the colors of YMCK can be made to correspond to the recording head units 32C, 32M, 32Y, 32K.

  In the above-described embodiment, the example of the FWA corresponding to the paper width has been described. However, the ink jet recording head of the present invention is not limited to this, and a partial width array (PWA) having a main scanning mechanism and a sub-scanning mechanism. It can also be applied to devices.

  In addition, in the inkjet recording apparatus 10 of the above embodiment, ink droplets are selectively ejected from the inkjet recording heads 30 of black, yellow, magenta, and cyan based on image data, and a full color image is recorded on the paper P. However, ink jet recording in the present invention is not limited to recording characters and images on the paper P.

  That is, the recording medium is not limited to paper, and the liquid to be ejected is not limited to ink. For example, industrially used liquids such as creating color filters for displays by discharging ink onto polymer films or glass, or forming bumps for component mounting by discharging solder in a welded state onto a substrate The ink jet recording head (droplet discharge head) according to the present invention can be applied to all droplet discharge (ejection) apparatuses.

1 is a schematic configuration diagram illustrating an overall configuration of an ink jet recording apparatus according to a first embodiment of the present invention. 1 is a perspective view of an ink jet recording head according to a first embodiment of the present invention. 2A is a front view and FIG. 2B is a bottom view of the inkjet recording head of FIG. It is a figure which shows the printing area | region by the inkjet recording head of FIG. FIG. 3 is a top view illustrating a configuration of a mounting portion of a spacer member of the ink jet recording head of FIG. 2. 2A is a front view and FIG. 2B is a side view showing a configuration of a mounting portion of a recording head unit of the ink jet recording head of FIG. It is explanatory drawing which shows the process (A) and (B) which manufacture the inkjet recording head which concerns on the 1st Embodiment of this invention. It is explanatory drawing which shows the process (C) and (D) which manufacture the inkjet recording head which concerns on the 1st Embodiment of this invention. It is explanatory drawing which shows the modification of the process of manufacturing the inkjet recording head which concerns on the 1st Embodiment of this invention. FIG. 3 is a side view showing a positional relationship with a cap during maintenance of the ink jet recording head according to the first embodiment of the present invention. It is a side view which shows the positional relationship with the cap at the time of the maintenance of the inkjet recording head of other embodiment to which this invention was applied. It is a side view which shows the modification of the inkjet recording head which concerns on the 1st Embodiment of this invention. It is a side view which shows the other modification of the inkjet recording head which concerns on the 1st Embodiment of this invention. FIG. 6 is a top view showing another configuration of the attachment portion of the spacer member of the ink jet recording head according to the first embodiment of the present invention. It is a front view which shows the modification of the spacer member in the inkjet recording head which concerns on the 1st Embodiment of this invention. FIG. 2 is a cross-sectional view showing an internal structure of the recording head unit according to the first embodiment of the invention. It is a comparison figure which shows typically deflection displacement when a predetermined DC bias voltage is impressed to each piezoelectric element of (A) occurrence of a flexure, (B) normal, and (C) exfoliation. It is a graph which shows the relationship between predetermined DC bias voltage application and an electrostatic capacitance in each piezoelectric element of bending generation | occurrence | production, peeling generation | occurrence | production, and non-generation (normal). It is a graph which shows the relationship between predetermined DC bias voltage application and resonance frequency in each piezoelectric element of bending generation | occurrence | production, peeling generation | occurrence | production, and non-generation | generation (normal). 1 is a schematic block diagram illustrating a configuration for inspecting an inkjet recording apparatus and an inkjet recording head according to a first embodiment of the present invention. It is a flowchart which shows the procedure of the head inspection process before use which concerns on the 1st Embodiment of this invention. FIG. 21 is a flowchart showing a subroutine of head inspection processing in FIG. 20. FIG. (A) is a waveform of a first measurement voltage to which a bias voltage is added, and (B) is a diagram illustrating a waveform of a second measurement voltage to which a bias voltage is added. In three pixels recorded by ink droplets ejected from three adjacent nozzles, (A) shows that all the piezoelectric elements corresponding to the three nozzles are normal, and (B) shows that the middle piezoelectric element is bent. (C) is an explanatory view showing an example when the middle piezoelectric element is peeled off, and (D) is an example when the middle defective element is corrected. (A) is a waveform of a drive voltage applied to a normal element, and (B) is a diagram showing a waveform of a drive voltage applied to a deflection / separation generating element. It is a table | surface figure which shows an example of the waveform set used in order to change the amount of ejected ink droplets with respect to each element of bending generation | occurrence | production / separation generation | occurrence | production / normal. It is a schematic block diagram which shows the structure for test | inspecting the inkjet recording device which concerns on the 2nd Embodiment of this invention, and an inkjet recording head. It is a schematic block diagram which shows the structure of the inkjet recording device provided with the test | inspection function of the inkjet recording head which concerns on the 3rd Embodiment of this invention. It is a flowchart which shows the procedure of the post-use head test | inspection process which concerns on the 3rd Embodiment of this invention. It is a flowchart which shows the subroutine of the head test | inspection process in FIG. It is a flowchart which shows the procedure of the post-use head test | inspection process which concerns on the 4th Embodiment of this invention. It is a schematic block diagram which shows the structure of the inkjet recording device provided with the test | inspection function of the inkjet recording head which concerns on the 5th Embodiment of this invention. It is a schematic block diagram which shows the structure of the inspection apparatus of the inkjet recording head which concerns on the 6th Embodiment of this invention.

Explanation of symbols

10 Inkjet recording device (droplet ejection device)
30 Inkjet recording head (droplet ejection head)
32 recording head unit 52 head substrate 54 nozzle 64 piezoelectric element 72 element state storage means (information storage means)
78 Drive control means 80 Drive / measurement control means (drive control means)
86 Capacitance measuring means 88 Element state detecting means (detecting means)

Claims (10)

By applying a driving voltage to each piezoelectric element provided corresponding to a plurality of nozzles, a droplet discharge head that discharges droplets from the plurality of nozzles,
At least a first voltage and a second voltage higher than the first voltage are applied to each of the piezoelectric elements to measure the capacitance, and the voltage corresponding to each voltage level is measured. A method for inspecting a droplet discharge head, which detects the degree of deflection of a piezoelectric element based on capacitance.   For each of the piezoelectric elements, a reduction rate of the capacitance when the second voltage is applied to the capacitance when the first voltage is applied is calculated, and the reduction rate is less than the first threshold value. 2. The method for inspecting a droplet discharge head according to claim 1, wherein the small piezoelectric element is determined as a piezoelectric element in which bending occurs. By applying a driving voltage to each piezoelectric element provided corresponding to a plurality of nozzles, a droplet discharge head that discharges droplets from the plurality of nozzles,
At least a first voltage and a second voltage higher than the first voltage are applied to each of the piezoelectric elements to measure the capacitance, and the voltage corresponding to each voltage level is measured. A method for inspecting a droplet discharge head that detects the peeling of a piezoelectric element based on electrostatic capacitance.   For each of the piezoelectric elements, the rate of decrease in capacitance when the second voltage is applied relative to the capacitance when the first voltage is applied is calculated, and the rate of decrease is calculated from a second threshold value. 4. The method for inspecting a droplet discharge head according to claim 3, wherein a large piezoelectric element is determined as a piezoelectric element in which peeling occurs.   When measuring the capacitance by applying at least the second voltage, the voltage applied with the bias voltage is applied to the piezoelectric element so that the polarity of the voltage applied to the piezoelectric element is constant during the measurement period. The method for inspecting a droplet discharge head according to claim 1, wherein the inspection is performed.   The droplet discharge head includes an information storage unit capable of storing and reading information, and a detection result of the piezoelectric element in which the bending occurs or the piezoelectric element in which the separation occurs is stored in the information storage unit. 6. The method for inspecting a droplet discharge head according to claim 1, wherein the inspection method is stored. It is equipped with information storage means that can store and read out the detection results of piezoelectric elements that are deflected or peeled, and are driven by individual piezoelectric elements provided corresponding to multiple nozzles. By applying a voltage, it is possible to detachably mount a droplet discharge head for discharging droplets from the plurality of nozzles,
Capacitance measuring means for measuring the capacitance by applying two or more voltages of at least a first voltage and a second voltage higher than the first voltage to the individual piezoelectric elements. When,
Detecting means for detecting a piezoelectric element in which bending or peeling occurs based on a capacitance according to each voltage level measured by the capacitance measuring means;
An inspection apparatus for a droplet discharge head, comprising: A droplet discharge head for discharging droplets from the plurality of nozzles by applying a driving voltage to each piezoelectric element provided corresponding to the plurality of nozzles;
Information storage means for storing information indicating a piezoelectric element in which bending or peeling detected by the droplet discharge head inspection method according to any one of claims 1 to 6 is generated;
Drive control means for controlling the drive of the droplet discharge head so as to change the drive frequency or drive voltage of the piezoelectric element in which bending or peeling occurs based on the information stored in the information storage means;
A droplet discharge apparatus comprising: A droplet discharge head for discharging droplets from the plurality of nozzles by applying a driving voltage to each piezoelectric element provided corresponding to the plurality of nozzles;
A capacitance measuring means for measuring the capacitance by applying a voltage of at least two of the first voltage and the second voltage higher than the first voltage to the individual piezoelectric elements; ,
Detecting means for detecting a piezoelectric element in which bending or peeling occurs based on a capacitance according to each voltage level measured by the capacitance measuring means;
Information storage means for storing information indicating a piezoelectric element in which bending or peeling detected by the detection means has occurred;
Drive control means for controlling the drive of the droplet discharge head so as to change the drive frequency or drive voltage of the piezoelectric element in which bending or peeling occurs based on the information stored in the information storage means;
A droplet discharge apparatus comprising:   The capacitance measurement by the capacitance measurement unit and the detection of the piezoelectric element in which the bending or peeling occurs by the detection unit are periodically performed. Droplet discharge device.

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