Method of manufacturing liquid discharge head

Abstract

To solve the problem of variations in the degree of deterioration of head chips and variations in discharge performance when head chips incorporated in a liquid discharge head are reused.SOLUTION: A method of manufacturing a second liquid discharge head provided with a second head chip by reusing a first head chip of a first liquid discharge head. Each of the first head chip and the second head chip has an actuator to be driven for discharging liquid. The method includes: a removing step of removing the first head chip from the first liquid discharge head; an assembling step of assembling the first head chip to the second liquid discharge head; and an adjusting step of performing an adjustment process to reduce a difference between discharge performance of the first head chip and discharge performance of the second head chip on the actuator of at least one of the first head chip and the second head chip.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a liquid ejection head. [Background technology]

[0002] BACKGROUND ART There is known an apparatus equipped with a liquid ejection head that is equipped with a plurality of head chips that eject liquid such as ink (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-39804 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional liquid ejection devices, when a liquid ejection head malfunctions or nears the end of its life due to deterioration from use, the device is repaired by replacing the liquid ejection head. Each liquid ejection head is equipped with multiple head chips. Therefore, even if some head chips are deemed unusable or near the end of their life, the entire liquid ejection head is replaced, even usable head chips or head chips with only minor deterioration are discarded. Therefore, it is desirable to recycle liquid ejection heads by reusing usable used head chips. However, if the degree of deterioration of the multiple used head chips incorporated into the recycle liquid ejection head varies, the ejection performance will vary. Therefore, if the liquid ejected from the liquid ejection head is, for example, ink, the quality of the image formed by the ink may be degraded. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms or application examples: A manufacturing method for a liquid ejection head according to the present disclosure is a manufacturing method for manufacturing a second liquid ejection head including a first head chip of a first liquid ejection head and a second head chip different from the head chip incorporated in the first liquid ejection head by reusing the first head chip of the first liquid ejection head, wherein the first head chip and the second head chip each have an actuator that is driven to eject liquid, and the manufacturing method includes a detachment step of removing the first head chip from the first liquid ejection head, an assembly step of incorporating the first head chip into the second liquid ejection head, and an adjustment step of performing an adjustment process on the actuator of at least one of the first head chip and the second head chip to reduce the difference in ejection performance between the first head chip and the second head chip. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 2 is a top view showing a schematic configuration of a liquid ejection apparatus used in the method for manufacturing a liquid ejection head according to the embodiment. [Figure 2] FIG. 1 is a side view showing a schematic configuration of a liquid ejection device. [Figure 3] FIG. 2 is an exploded perspective view showing the structure of the head unit. [Figure 4] FIG. [Figure 5] FIG. 2 is a cross-sectional view of a head chip included in the liquid ejection head. [Figure 6] FIG. 2 is an explanatory diagram showing the functional configuration of the liquid ejection device. [Figure 7] FIG. [Figure 8] FIG. 10 is an explanatory diagram schematically showing the transition of a head chip incorporated in a head unit from collection to reuse. [Figure 9] FIG. 4 is an explanatory diagram schematically showing the initial characteristic values ​​of the head chip and the subsequent changes over time. [Figure 10] 3A to 3C are process diagrams showing the manufacturing process of the liquid ejection head according to the first embodiment. [Figure 11]FIG. 4 is an explanatory diagram showing the state of connection between the relay board of the head unit and the reading device. [Figure 12] FIG. 2 is an explanatory diagram schematically illustrating a manufacturing process according to the first embodiment. [Figure 13] FIG. 10 is an explanatory diagram showing how the characteristics of piezoelectric actuators with different ejection performances change with aging. [Figure 14] FIG. 3 is an explanatory diagram schematically showing a case where a novel head chip is used in the manufacturing process of the first embodiment. [Figure 15] 6A to 6C are process diagrams showing the manufacturing process of the liquid ejection head according to the second embodiment. [Figure 16] FIG. 10 is an explanatory diagram schematically illustrating a manufacturing process according to a second embodiment. [Figure 17] FIG. 10 is an explanatory diagram showing an example of ranking priorities. [Figure 18] 10A to 10C are process diagrams showing the manufacturing process of the liquid ejection head according to the third embodiment. [Figure 19] FIG. 10 is an explanatory diagram schematically illustrating a manufacturing process according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, an embodiment of a method for manufacturing a liquid ejection head will be described with reference to the drawings. The drawings used are for convenience of explanation. The embodiments described below are merely examples of embodiments and do not limit the contents of the present disclosure. Furthermore, the configurations described below should not be construed as essential, except for those described as essential components.

[0008] A. First embodiment: (A1) Overview of the liquid ejection device: A manufacturing method for a liquid ejection head according to the first embodiment will be described below. The manufacturing method according to the first embodiment involves reusing the first head chip of a first liquid ejection head to manufacture a second liquid ejection head including the first head chip and a second head chip different from the head chip incorporated in the first liquid ejection head. Prior to describing the manufacturing method for the liquid ejection head, we will first describe the configuration of a head unit including a plurality of liquid ejection heads 31 corresponding to the first liquid ejection head, and a liquid ejection device including this head unit. In this specification, "ejection" refers to the act of sending liquid outward from a nozzle or the like. Ejection includes various modes of outputting a predetermined amount of liquid to the outside, such as spraying, spurting, spraying or discharging, and intermittent outflow, regardless of the type of liquid, output time, number of times, etc.

[0009] FIG. 1 is a top view showing the schematic configuration of a liquid ejection device 10. FIG. 2 is a side view showing the schematic configuration of the liquid ejection device 10. As shown in these figures, the liquid ejection device 10 used in this embodiment will be described as a so-called line-type inkjet printer, which performs printing simply by transporting a medium P onto which ink is ejected. Note that the liquid ejection device 10 is not limited to a line-type inkjet printer, and may also be a so-called serial-type inkjet printer, in which a head unit moves in synchronization with the transport of the medium P.

[0010] In the following description, the transport direction in which the medium P is transported is referred to as direction X, with the upstream side of the transport of the medium P being the X1 side and the downstream side being the X2 side. Furthermore, in the in-plane direction of the landing surface where ink lands on the medium P, the direction perpendicular to direction X is referred to as direction Y, with one end of the liquid ejection device 10 in direction Y being the Y1 side and the other end being the Y2 side. Furthermore, the direction perpendicular to both directions X and Y, in which ink is ejected from the head unit 3 onto the medium P, is referred to as direction Z, with the ink ejected from the head unit 3 being ejected from the Z2 side toward the Z1 side of direction Z. In this embodiment, directions X, Y, and Z are described as being orthogonal axes, but the configuration of the liquid ejection device 10 is not limited to being arranged orthogonal to each other. These directions X, Y, and Z are also shown in other figures as appropriate.

[0011] 1 and 2, the liquid ejection device 10 has a device main body 2, a head unit 3, a storage section 4, a medium transport mechanism 5, and a maintenance mechanism 6. First, these main components of the liquid ejection device 10 will be described.

[0012] The storage unit 4 stores ink to be supplied to the head unit 3. This storage unit 4 is fixed to the device body 2. Examples of storage units 4 that store such ink include ink cartridges, bag-shaped ink packs made of flexible film, and ink tanks that can be refilled with ink. The ink stored in the storage unit 4 is supplied to the head unit 3 via a supply pipe 40 such as a tube. Here, the storage unit 4 may store ink of multiple colors, such as black, cyan, magenta, yellow, red, and gray. Therefore, the storage unit 4 may include multiple ink cartridges, ink packs, and ink tanks corresponding to the ink colors to be stored, and the supply pipe 40 may further include multiple tubes corresponding to the ink colors to be stored in the storage unit 4. The storage unit 4 may also be mounted on the head unit 3.

[0013] A signal for controlling the ejection of ink is supplied to the head unit 3 from the drive circuit board 7 via a cable 17. The head unit 3 then ejects the ink supplied from the storage section 4 in an amount according to the signal supplied from the drive circuit board 7 and at a timing according to the signal supplied from the drive circuit board 7. Details of the head unit 3 will be described later.

[0014] The medium transport mechanism 5 is composed of a first transport unit 5a and a second transport unit 5b. The first transport unit 5a is located on the X1 side of the head unit 3. At least a portion of the second transport unit 5b is located on the X2 side of the head unit 3. The first transport unit 5a and the second transport unit 5b transport the medium P in the direction X from the X1 side to the X2 side.

[0015] The first transport unit 5a includes a transport roller 51a, a driven roller 52a, and a drive motor 53a. A driving force is supplied to the transport roller 51a from the drive motor 53a. The transport roller 51a is driven to rotate in accordance with the driving force supplied from the drive motor 53a. The transport roller 51a and the driven roller 52a sandwich the medium P and transport the medium P toward the X2 side. The driven roller 52a may include a spring (not shown) that presses the medium P toward the transport roller 51a by stress generated by a biasing member.

[0016] The second conveying section 5b includes a conveying roller 51b, a driven roller 52b, a drive motor 53b, a conveying belt 54b, a tension roller 55b, a biasing member 56b, and a pressure roller 57b.

[0017] The transport roller 51b is located on the X2 side of the head unit 3 in the X direction. A driving force is supplied to the transport roller 51b from a drive motor 53b. The transport roller 51b is then driven to rotate by the driving force supplied from the drive motor 53b. A driven roller 52b is provided at a position spaced a predetermined distance from the transport roller 51b on the X1 side, and an endless transport belt 54b is stretched between the driven roller 52b and the transport roller 51b. When the transport roller 51b is driven to rotate by the driving force supplied from the drive motor 53b, the transport belt 54b is driven by the transport roller 51b and transports the medium P sent by the driven roller 52a and the transport roller 51a downstream, i.e., toward the X2 side. The tension roller 55b is located between the transport roller 51b and the driven roller 52b and abuts against the inner surface of the transport belt 54b. The tension roller 55b applies tension to the transport belt 54b by the biasing force generated by a biasing member 56b, such as a spring.

[0018] The pressure rollers 57b are provided on the Z2 side of the medium P, on both the X1 side and the X2 side of the head unit 3. The medium P is sandwiched between the pressure rollers 57b and the conveyor belt 54b, thereby maintaining a flat posture of the medium P. In order to maintain the position and posture of the medium P more precisely, a flat platen may be provided on the Z1 side of the conveyor belt 54b directly below the head unit 3 (Z1 side).

[0019] In the liquid ejection device 10 configured as described above, the first transport unit 5a and the second transport unit 5b are driven to transport the medium P from the X1 side toward the X2 side in the direction X. Ink is ejected from the head unit 3 at a predetermined timing onto the transported medium P. As a result, the ink ejected from the head unit 3 lands at a desired position on the medium P, and a desired image is formed on the medium P.

[0020] The maintenance mechanism 6 performs maintenance functions to ensure that ink is ejected normally by the head unit 3. The maintenance mechanism 6 is used, for example, to perform wiping, flushing, cleaning, and capping. Wiping is a process in which a wiping member WP (see FIG. 5) provided in the maintenance mechanism 6 wipes the nozzle surface from which ink is ejected (hereinafter referred to as the nozzle surface) to remove ink, paper debris, and the like that has adhered to the nozzle surface. Flushing is a process in which a concave-shaped container (not shown) provided in the maintenance mechanism 6 is placed opposite the nozzle surface to eject ink from the nozzles, thereby restoring the viscosity of the ink stored inside the head unit 3 to an appropriate state if an abnormality occurs in the viscosity of the ink stored inside the head unit 3.

[0021] (A2) Head unit structure: Next, the structure of the head unit 3 will be described. Fig. 3 is a partially exploded perspective view showing the structure of the head unit 3. As shown in the figure, the head unit 3 has a plurality of liquid ejection heads 31, a base member 33, a flow path member 34, and a cover member 35. Fig. 3 shows an example in which the head unit 3 has six liquid ejection heads 31, but the number of liquid ejection heads 31 that the head unit 3 has is not limited to this.

[0022] The liquid ejection head 31 has a plurality of head chips 310 and a holding member 360 that holds the head chips 310. In this embodiment, the liquid ejection head 31 has six head chips 310, but the number of head chips 310 included in one liquid ejection head 31 may be more or less than six.

[0023] FIG. 4 shows an exploded perspective view of the detailed structure of a liquid ejection head 31 equipped with six head chips 310. The multiple head chips 310 included in the liquid ejection head 31 have the same structure within the range of manufacturing tolerance. FIG. 5 also shows the internal structure of the head chip 310. FIG. 5 is a cross-sectional view of the head chip 310 shown in FIG. 4, cut along the YZ plane at the center of its longitudinal direction. As shown in FIG. 5, each head chip 310 includes a case 610, a protective substrate 620, a pressure chamber substrate 630, a flow path substrate 640, and a nozzle plate 650. In the head chip 310, the case 610, the protective substrate 620, the pressure chamber substrate 630, the flow path substrate 640, and the nozzle plate 650 are bonded together with an adhesive or the like. At least one of the multiple adhesives that bond these components together comes into contact with ink flowing through the flow paths within the head chip 310.

[0024] The structure of the head chip 310 will be described with reference to FIG. 5 . The nozzle plate 650 has a plurality of nozzles 651 that eject ink. Specifically, the nozzle plate 650 has a plurality of nozzle rows arranged along the direction Xa, which is the longitudinal direction of the head chip 310, and two rows arranged along the direction Ya. Here, the direction Xa is a direction inclined with respect to the direction X, which is the transport direction of the medium P, and the direction Ya is a direction intersecting the direction Xa in the XY plane defined by the directions X and Y. That is, the liquid ejection head 31 is mounted on the head unit 3 so that the arrangement direction of the nozzles 651 of the head chip 310 is inclined with respect to the direction X, which is the transport direction of the medium P. Note that the number of nozzle rows formed by the nozzles 651 is not limited to two, but may be one row or three or more rows. Here, the surface of the nozzle plate 650 on the Z1 side where the nozzles 651 open is referred to as the nozzle surface 652. The head chip 310 has one nozzle plate 650 .

[0025] The pressure chamber substrate 630 is located on the Z2 side of the nozzle plate 650. The pressure chamber substrate 630 has a plurality of pressure generating chambers 631 partitioned by partitions or the like. Each pressure generating chamber 631 is located corresponding to a nozzle 651 of the nozzle plate 650. That is, the pressure chamber substrate 630 has the same number of pressure generating chambers 631 as the nozzles 651 provided in the nozzle plate 650. Furthermore, the plurality of pressure generating chambers 631 of the pressure chamber substrate 630 are arranged side by side in the direction Xa. The rows of the arranged pressure generating chambers 631 are arranged in two rows in the direction Ya.

[0026] The flow path substrate 640 is located on the Z2 side of the nozzle plate 650 and on the Z1 side of the pressure chamber substrate 630. In other words, the flow path substrate 640 is located between the nozzle plate 650 and the pressure chamber substrate 630 in the direction along the Z direction. The flow path substrate 640 has a common flow path 641, branch flow paths 642, communicating flow paths 643, and individual flow paths 644 for supplying ink supplied from the storage section 4 to each of the multiple nozzles 651.

[0027] The individual flow channels 644 communicate with the corresponding nozzles 651 and pressure generating chambers 631. The common flow channel 641 is provided in common to the multiple pressure generating chambers 631 of the pressure chamber substrate 630 and the multiple nozzles 651 of the nozzle plate 650. Ink is supplied to the common flow channel 641 from the reservoir 4. The ink supplied to the common flow channel 641 is supplied to the pressure generating chambers 631 via branch flow channels 642 and communicating flow channels 643 provided corresponding to the pressure generating chambers 631. In other words, the branch flow channels 642 and communicating flow channels 643 communicate the common flow channel 641 with the corresponding pressure generating chambers 631. In the flow channel substrate 640 configured as described above, the ink supplied to the common flow channel 641 branches at the branch flow channels 642 so as to correspond to each of the multiple pressure generating chambers 631, and then supplies the ink to the pressure generating chambers 631 via the communicating flow channels 643.

[0028] A vibration plate 621 is bonded to the Z2-side surface of the pressure chamber substrate 630. Furthermore, a plurality of piezoelectric elements 60 corresponding to the plurality of pressure generating chambers 631 are provided on the Z2-side surface of the vibration plate 621. These piezoelectric elements 60 function as actuators that are driven to eject liquid such as ink from the nozzles 651. In this embodiment, a piezoelectric actuator such as the piezoelectric element 60 is used as the actuator, but a heat generating element or the like can also be used as the actuator. The piezoelectric element 60 used in this embodiment includes electrodes 602 and 603 and a piezoelectric layer 601, and the electrode 602, piezoelectric layer 601, and electrode 603 are laminated in this order on the Z2-side surface of the vibration plate 621 in the direction Z from the Z1 side to the Z2 side. One of the electrodes 602, 603 of each piezoelectric element 60 is configured as a common electrode that supplies a signal of a common voltage value to the piezoelectric elements 60, and the other of the electrodes 602, 603 is configured as an individual electrode that supplies a signal of an individual voltage value to each piezoelectric element 60. Note that in this embodiment, the electrode 602 is described as an individual electrode and the electrode 603 is a common electrode, but this is not limited to this. A drive signal COM is supplied to the electrode 602, which is an individual electrode, and a reference voltage signal indicating a reference potential Vbs of the drive signal COM is supplied to the electrode 603, which is a common electrode.

[0029] In the piezoelectric element 60 configured as described above, the piezoelectric layer 601 deforms in response to the potential difference generated between the electrode 602 and the electrode 603. That is, the piezoelectric element 60 is driven in response to the potential difference between the voltage value of the signal supplied to the electrode 602 and the voltage value of the signal supplied to the electrode 603. When the piezoelectric element 60 is driven, the vibration plate 621 is displaced. When the vibration plate 621 is displaced toward the Z2 side, the internal pressure of the pressure generating chamber 631 decreases. As a result, ink is supplied to the pressure generating chamber 631 from the common flow path 641 via the branch flow path 642 and the communication flow path 643. On the other hand, when the vibration plate 621 is displaced toward the Z1 side, the internal pressure of the pressure generating chamber 631 increases. As a result, ink stored in the pressure generating chamber 631 is ejected from the nozzle 651 via the individual flow path 644. Here, a configuration including the piezoelectric element 60, the pressure generating chamber 631, the individual flow path 644, and the nozzle 651 is referred to as an ejection unit 600 that ejects ink from the head chip 310.

[0030] The protective substrate 620 is located on the Z2 side of the diaphragm 621. The protective substrate 620 has a holding portion 622 that forms a space for protecting the piezoelectric element 60. The space formed by the holding portion 622 has a size sufficient to accommodate displacement caused by driving the piezoelectric element 60.

[0031] The case 610 is located on the Z2 side of the flow path substrate 640 and the protective substrate 620. The case 610 has a manifold 611 that communicates with a common flow path 641 of the flow path substrate 640. The manifold 611 is a space that stores ink to be supplied to the plurality of nozzles 651, and is provided continuously over the plurality of nozzles 651 and the plurality of pressure generating chambers 631. The ink supplied to this manifold 611 is supplied to the common flow path 641. In other words, the common flow path 641 and the manifold 611 are a common liquid chamber that communicates with the plurality of nozzles 651. The common liquid chamber extends with its longitudinal direction being the direction Xa in which the plurality of nozzles 651 are arranged.

[0032] In the liquid ejection head 31, the protective substrate 620 and the case 610 are provided with through-holes 313 that penetrate in the direction Z. A flexible wiring substrate 311 is inserted into the through-hole 313. One end of the flexible wiring substrate 311 is electrically connected to lead electrodes extending from the electrodes 602 and 603 of the piezoelectric element 60. That is, a signal for driving the piezoelectric element 60 is transmitted to the flexible wiring substrate 311. An integrated circuit 312 is mounted on the flexible wiring substrate 311. The signal for driving the piezoelectric element 60, which is transmitted through the flexible wiring substrate 311, is input to the integrated circuit 312. The integrated circuit 312 controls the timing at which the signal for driving the piezoelectric element 60 is supplied to the electrode 602 based on the input signal. This controls the timing at which the piezoelectric element 60 is driven and the amount of drive of the piezoelectric element 60. Therefore, a predetermined amount of ink is ejected at a predetermined timing from the ejection unit 600 including the piezoelectric element 60. A water-repellent film 658 is formed on the outside of the nozzle plate 650, and when the surface of the head chip 310 becomes dirty, the nozzle plate 650 is wiped by a wiping member WP included in the maintenance mechanism 6.

[0033] Pressure fluctuations for ejecting ink from the nozzles 651 are generated in the head chip 310 by a piezoelectric element 60 including an electrode 603, a piezoelectric layer 601, and an electrode 602, one pressure generating chamber 631, and a vibration plate 621. The piezoelectric element 60, pressure generating chamber 631, and vibration plate 621 are collectively referred to as a segment. The head chip 310 has as many such segments as there are nozzles 651. The segments have various characteristics related to the ejection of liquid, such as the natural frequency of the segment, the weight of the ink droplets ejected from the nozzles 651, the speed of the ink droplets ejected from the nozzles 651, and the displacement of the vibration plate 621 of the segment.

[0034] The natural frequency of a segment can be measured using known devices and methods. For example, a known measuring device called an impedance analyzer is used to input a specific sine wave into the segment and measure its impedance. The impedance of the segment changes by changing the frequency of the input sine wave. The frequency of the input sine wave at which the impedance peaks can be measured as the natural frequency of the segment. This natural frequency is a value correlated to the natural vibration period Tc of the liquid in the pressure generating chamber 631.

[0035] The weight of the ink droplets ejected from the nozzle 651 can be measured using known devices and methods. For example, a drive signal COM including a specific drive waveform (reference drive waveform) that enables droplets to be ejected is applied to the piezoelectric element 60, causing it to eject a certain number of droplets into a receiving container. Then, the weight of the ink droplets ejected from the nozzle 651 can be measured by measuring the weight change of the receiving container and the weight change of the reservoir 4, which is the ink supply source. A high-precision weighing scale such as an electronic balance can be used for this measurement.

[0036] The displacement of the diaphragm 621 of the segment is the difference between the maximum and minimum displacements of the vibrating part where piezoelectric distortion is generated by the piezoelectric element 60. The displacement of the diaphragm 621 of the segment is also simply called the displacement of the segment. The displacement of the segment can be measured using known devices and methods. For example, a Doppler vibrometer utilizing the difference in wavelength that occurs in the round trip path of an irradiated laser when reflected by the vibrating diaphragm 621 can be used to measure the speed at which the diaphragm 621 is moving due to vibration, and the displacement of the diaphragm 621 can be measured by integrating this speed.

[0037] The natural frequency of these segments, the weight of ink droplets ejected from nozzle 651, the speed of ink droplets ejected from nozzle 651, the displacement of diaphragm 621, and the like can be used to rank the head chips, which will be described later. Note that the aforementioned measured values ​​such as the natural frequency may differ between multiple segments included in one head chip 310. In such cases, the ranking may be performed using the average value or mode of the measured values ​​of multiple segments included in one head chip.

[0038] The head chips 310 configured as described above are held by a holding member 360 in the liquid ejection head 31. As shown in Fig. 4, the holding member 360 includes a flow path member 361 common to the multiple head chips 310, a holder 362 that holds the multiple head chips 310, and a first relay substrate 363 that is electrically connected to at least two or more head chips 310. The first relay substrate 363 of this embodiment is electrically connected to all of the head chips 310 that the liquid ejection head 31 includes.

[0039] A flow path is provided inside the flow path member 361 for supplying ink supplied from the reservoir 4 via the flow path member 34 to each head chip 310. This flow path is connected to an ink supply unit 364 provided on the Z2 side surface of the flow path member 361. That is, ink supplied from the reservoir 4 is supplied to the flow path member 361 via the ink supply unit 364. Note that the flow paths provided inside the flow path member 361 are provided corresponding to each ink supply unit 364. Here, although FIG. 4 shows the flow path member 361 having four ink supply units 364, this is not limited to this. A filter may be provided inside the flow path member 361 for removing foreign matter such as dust and air bubbles contained in the supplied ink.

[0040] At both ends of the flow path member 361 in the direction X, cable insertion holes 365 are provided that penetrate in the direction Z. A cable 366 electrically connected to a first relay board 363 (described later) via a connector 368 is inserted into the cable insertion hole 365. Here, the connector 368 is detachably connected to the cable 366, and is electrically connected to a plurality of terminals corresponding to a plurality of wires included in the cable 366.

[0041] The holder 362 is located on the Z1 side of the flow path member 361, and is fixed to the flow path member 361 by screws 381 shown in FIG. 3. The holder 362 also has a holding portion 367. The holding portion 367 is a groove-shaped space that is continuous in the direction Y on the Z1 side surface of the holder 362 and is open to both side surfaces in the direction Y. A plurality of head chips 310 are bonded to the holding portion 367 by an adhesive or the like (not shown). In this way, the plurality of head chips 310 are held by the holding member 360.

[0042] Furthermore, a flow path (not shown) that communicates with the flow path provided inside flow path member 361 is provided inside holder 362. Ink supplied from ink supply unit 364 is supplied to each head chip 310 via the flow path provided inside flow path member 361 and the flow path provided inside holder 362. In other words, holder 362 is a flow path member common to multiple head chips 310.

[0043] The first relay substrate 363 is located between the flow path member 361 and the holder 362. The flexible wiring substrates 311 of the head chips 310 are electrically connected to the first relay substrate 363. A connector 368 is also provided on the first relay substrate 363. The first relay substrate 363 configured as described above transmits signals input via cables 366 electrically connected to the connectors 368 to the corresponding head chips 310, and outputs signals output from the head chips 310 via the flexible wiring substrate 311 to the outside of the liquid ejection head 31 via the connectors 368 and the cables 366. The first relay substrate 363 also includes a memory 201.

[0044] The above-described liquid ejection head 31 includes a cover 32 that covers the multiple head chips 310 between the cover 32 and the holder 362. In other words, the multiple head chips 310 are arranged inside an accommodation space S, which is a space defined by the holding portion 367 of the holder 362 and the cover 32. This reduces the risk of ink droplets floating inside the liquid ejection device 10 adhering to each head chip 310. In other words, the cover 32 protects the head chips 310 of the liquid ejection head 31 from ink droplets.

[0045] The cover 32 is provided on the Z1 side, which is the nozzle surface 652 side, of the multiple head chips 310 provided in the liquid ejection head 31. As shown in FIG. 4, the cover 32 includes a base portion 321 and extension portions 322 and 323. The base portion 321 is a plate-like member provided on the nozzle surface 652 side of the head chip 310 covered by the cover 32. The cover 32, together with the base portion 321, forms a space with the extension portions 322 and 323, and the holder 362 is inserted into the formed space. The base portion 321 is bonded to the Z1 side surface of the holder 362 with an adhesive or the like (not shown).

[0046] Base portion 321 has a plurality of openings 324. Each opening 324 corresponds to a respective head chip 310, and exposes a plurality of nozzles 651 of the corresponding head chip 310 to the outside. This allows ink ejected from each head chip 310 to land on medium P without being obstructed by cover 32.

[0047] Returning to FIG. 3, a plurality of liquid ejection heads 31 are fixed to the base member 33. The base member 33 includes a storage section 332 having a space therein that opens to the Z1 side. The plurality of liquid ejection heads 31 are stored and held in this space. Specifically, the liquid ejection heads 31 are stored in the storage section 332 of the base member 33 so that the nozzle surface 652 side of the liquid ejection heads 31 protrudes further toward the Z1 side than the storage section 332. In this case, each of the plurality of liquid ejection heads 31 is stored in the storage section 332 so that the nozzle row located on the nozzle surface 652 is oriented along the direction Xa that is inclined with respect to the direction X.

[0048] When the liquid ejection head 31 is housed in the base member 33, the liquid ejection head 31 is fixed to the base member 33 via a spacer 37. The spacer 37 is fixed to the Z2-side surface of the liquid ejection head 31 with a screw 382, ​​and is also fixed to the Z1-side surface of the base member 33 with a screw 383. In other words, the liquid ejection head 31 is fixed to the base member 33 via the spacer 37. As described above, by fixing the spacer 37, which is fixed to the liquid ejection head 31 with the screw 382, ​​to the base member 33 with the screw 383, it becomes possible to easily attach and detach the liquid ejection head 31 to and from the base member 33. Note that the method of fixing the spacer 37 and the liquid ejection head 31 is not limited to using the screw 382.

[0049] The base member 33 also has a supply hole 331 that penetrates in the direction Z. An ink supply unit 364 of the liquid ejection head 31 fixed to the base member 33 is inserted into the supply hole 331. The base member 33 also has an opening 333 that penetrates in the direction Z. A cable 366 of the head unit 3 fixed to the base member 33 is inserted into the opening 333.

[0050] Furthermore, steps 334 that open to the Z2 side are provided on the outer periphery of both sides of the accommodation section 332 that face each other in the direction X. A second relay substrate 335 is accommodated in each of the steps 334. Cables 366 that correspond to each of the multiple liquid ejection heads 31 and that are led out from the multiple openings 333 are electrically connected to the second relay substrate 335. As a result, the second relay substrate 335 transmits signals that are input to each of the multiple liquid ejection heads 31 and signals that are output from the multiple liquid ejection heads 31.

[0051] 3 illustrates a case where two second relay boards 335 are provided, and each of the two second relay boards 335 is provided with an integrated circuit 336, but the integrated circuit 336 may be provided on only one of the two second relay boards 335, or the head unit 3 may be provided with only one second relay board 335. The two second relay boards 335 are fixed to the accommodation section 332 with screws 384, respectively.

[0052] A cable 17 is connected to the second relay board 335, which is electrically connected to the drive circuit board 7 fixed to the device body 2. This allows various signals generated by the drive circuit board 7 to be input to the head unit 3. The electrical wiring of each head chip 310, the integrated circuit 312, the first relay board 363, the second relay board 335, etc. will be described later.

[0053] The flow path member 34 is provided on the Z2 side of the base member 33. The flow path member 34 is a flow path member common to the multiple liquid ejection heads 31, and distributes and supplies ink supplied from the storage section 4 to each of the multiple liquid ejection heads 31. A flow path (not shown) is provided inside the flow path member 34 for supplying ink supplied from the storage section 4 to the multiple liquid ejection heads 31. The flow path provided inside this flow path member 34 communicates with a supply pipe 40 connected to the storage section 4, and also communicates with an ink supply section 364 of the liquid ejection head 31. As a result, ink supplied from the storage section 4 is supplied to the corresponding liquid ejection head 31.

[0054] The cover member 35 is provided on the Z2 side of the flow path member 34. The cover member 35 is a box-shaped member that covers the flow path member 34 and the second relay board 335. The cover member 35 is provided with an opening 351 for inserting the cable 17 and an opening 352 for inserting the supply pipe 40. The cover member 35 is fixed to the housing portion 332 of the base member 33 with screws 385.

[0055] As described above, the head unit 3 is a head unit 3 that is assembled into a liquid ejection device 10 that ejects ink onto a medium P, and the head unit 3 has a plurality of liquid ejection heads 31, and each liquid ejection head 31 has a plurality of head chips 310.

[0056] (A3) Functional configuration of the liquid ejection device: Next, the functional configuration of the liquid ejection device 10 will be described. Fig. 6 is a diagram showing the functional configuration of the liquid ejection device 10. As shown in the figure, the liquid ejection device 10 has a head unit 3, a medium conveyance mechanism 5, a maintenance mechanism 6, a drive circuit board 7, a main circuit board 8, and an information output mechanism 9. The configuration of the medium conveyance mechanism 5 has already been explained, so below, the head unit 3, the maintenance mechanism 6, the drive circuit board 7, the main circuit board 8, and the information output mechanism 9 will be briefly explained in order.

[0057] The hardware configuration of the head unit 3 has already been described in detail. The internal electrical configuration of the head unit 3 will be described with reference to FIG. 6. As shown in the figure, the head unit 3 has n liquid ejection heads 31, and each liquid ejection head 31 has m head chips 310. That is, the head unit 3 will be described as having a total of n × m head chips 310, where n and m are both integers equal to or greater than 2. In the liquid ejection head 31, each head chip 310 is connected to a first relay substrate 363 via m flexible wiring substrates 311. The connection between the first relay substrate 363 and each head chip 310 is achieved by connecting a connector 315 provided on the other end of the flexible wiring substrate 311 to a connector 314 on the first relay substrate 363. The connector 315 and the connector 314 are detachably connected. The first relay substrate 363 aggregates drive signal wiring that supplies a common drive signal COM to the m head chips 310.

[0058] In the following description, when distinguishing between n liquid ejection heads 31, they may be referred to as liquid ejection heads 31-1 to 31-n, and similarly when distinguishing between m head chips 310 or flexible wiring boards 311, they may be referred to as head chips 310-1 to 310-m or flexible wiring boards 311-1 to 311-m. When it is not necessary to distinguish between liquid ejection heads 31-1 to 31-n, flexible wiring boards 311-1 to 311-m, or head chips 310-1 to 310-m, they will simply be referred to as liquid ejection heads 31, flexible wiring boards 311, and head chips 310.

[0059] An integrated circuit 312 is provided on each flexible wiring board 311. This integrated circuit 312 includes a memory 200 and a drive signal selection control circuit 210. The memory 200 stores data such as the usage history of the head chip 310 that includes the memory 200. The drive signal selection control circuit 210 also selects signals to be sent to the multiple piezoelectric elements 60 provided in the head chip 310, and ejects liquid, in this case ink, from a desired nozzle 651 out of the multiple nozzles 651 provided in the head chip 310.

[0060] The head chip 310 is provided with piezoelectric elements 60 that generate pressure changes for ejection, corresponding to each of the multiple nozzles 651. When the piezoelectric elements 60 receive a drive signal COM having a predetermined drive waveform via the drive signal selection control circuit 210, they expand and contract along the Z direction in accordance with the applied voltage waveform. The drive signal COM and reference voltage signal are shown in FIG. 7.

[0061] The drive signal selection control circuit 210 includes a plurality of switching elements provided corresponding to the plurality of piezoelectric elements 60. The switching elements select whether or not to supply a drive signal COM to the individual electrode of the corresponding piezoelectric element 60 for each printing cycle TP based on a clock signal, a latch signal, a change signal, a print data signal, and the like (not shown).

[0062] As shown in FIG. 7, the drive signal COM is, for example, a trapezoidal wave, and has a period in which it maintains the minimum potential VL and a period in which it maintains the maximum potential V H The duration of the voltage, the minimum potential VL, and the maximum potential V H The intermediate potential V C The reference voltage signal is a signal in which a constant reference potential Vbs smaller than the minimum potential VL continues. Note that while power is being supplied to the liquid ejection head 31, the intermediate potential V of the drive signal COM is always C is applied to the individual electrodes of the piezoelectric elements 60 during the period when liquid is not being ejected from the nozzles 651, and the reference potential Vbs of the reference voltage signal is applied to the common electrode. Cand the reference voltage signal Vbs, affects the amount of deformation of the piezoelectric element 60 and changes over time in the deformation characteristics. Therefore, the magnitude of this reference voltage Vm may be treated as one of the usage histories of the head chip 310. Another item that can be treated as usage history is the environmental temperature of the head chip 310. The environmental temperature of the head chip 310 can be detected by providing a temperature sensor in the integrated circuit 312, etc., but the temperature inside the housing of the liquid ejection device 10 or the temperature around the head chip 310 may also be treated as the environmental temperature. The environmental temperature of the head chip 310 may also be considered the environmental temperature of the liquid ejection head 31. A method of storing the reference voltage Vm and the environmental temperature in the memory 200 of the head chip 310 and treating them as usage history will be described later.

[0063] Signals from the head chip 310 and drive signals COM to the head chip 310 are collected on the first relay board 363. The n first relay boards 363 are connected to the second relay board 335 by cables 366. The cables 366 are connected to connectors 368 provided on the first relay board 363 and connectors 337 provided on the second relay board 335, electrically connecting the two boards. The second relay board 335 is provided with an integrated circuit 336. The integrated circuit 336 includes a memory 203 and n selectors 202. Each of the n selectors 202 is provided corresponding to one of the liquid ejection heads 31-1 to 31-n. The selectors 202 receive print data signals, memory control signals, latch signals, and change signals input from the drive circuit board 7. Then, depending on the logical levels of the input latch signal and change signal, the selector 202 selects whether to output the print data signal, latch signal, and change signal to the liquid ejection head 31, or whether to output the memory control signal, latch signal, and change signal to the memory 200 of the flexible wiring board 311.

[0064] The head unit 3 described above is electrically connected to the drive circuit board 7 via the second relay board 335. The second relay board 335 and the drive circuit board 7 are connected via a cable 17. One end of the cable 17 is connected to a connector 27b provided on the second relay board 335, and the other end is connected to a connector 27a provided on the drive circuit board 7, thereby mediating the exchange of signals between them.

[0065] The drive circuit board 7 includes a control circuit 71, a drive signal output circuit 72, and a drive state detection circuit 73. The control circuit 71 outputs a memory control signal for controlling the memory 203 of the second relay board 335. Here, control of the memory 203 includes a read process for reading out information stored in the memory 203 and a write process for writing information to the memory 203. The control circuit 71 also generates a drive data signal that defines the voltage waveform of the drive signal COM for driving the piezoelectric element 60, and outputs the signal to the drive signal output circuit 72. The drive signal output circuit 72 amplifies the voltage waveform defined by each of the drive data signals.

[0066] The drive status detection circuit 73 generates a discharge section status signal indicating the status of the corresponding discharge section 600 based on the residual vibration signal input from the head chip 310 via the first relay board 363 and the second relay board 335. The drive status detection circuit 73 outputs this discharge section status signal to the control circuit 71. Based on the input discharge section status signal, the control circuit 71 determines whether or not to cause the maintenance mechanism 6 to perform a wiping process, a flushing process, a cleaning process, etc., generates an operation information signal indicating the determination result, and outputs the signal to the liquid discharger control circuit 81 via the cable 18, etc.

[0067] The main circuit board 8 has a liquid ejection device control circuit 81, a signal conversion circuit 82, a time measurement circuit 83, a power supply circuit 84, and a voltage detection circuit 85. The main circuit board 8 is provided with connectors 25a, 26a, 28a, and 29a. The main circuit board 8 is connected to the drive circuit board 7 via cable 18 connected to connector 28a, to the medium conveyance mechanism 5 via cable 15 connected to connector 25a, to the maintenance mechanism 6 via cable 16 connected to connector 26a, and to the information output mechanism 9 via cable 19 connected to 29a. Connectors 28b, 25b, 26b, and 29b, to which the other ends of the cables 18, 15, 16, and 19 are connected, are provided on each of the destination boards and mechanisms. Note that the types of connectors used in this specification are not limited as long as they have a structure that electrically and detachably connects wiring members without using bonding such as conductive adhesive or soldering. Here, the aforementioned connectors 314 and 315 are each a convex connector and a concave connector, and are detachably electrically connected by inserting and removing the convex connector into the concave connector. In this way, a configuration may be used in which connectors other than connectors 314 and 315 are connected to connectors other than the connectors in question.

[0068] The liquid ejection device control circuit 81 exchanges signals with each component of the liquid ejection device 10 to control the operation of each component. For example, it exchanges instructions for transporting the medium P and transport information for the transported medium P with the medium transport mechanism 5. The liquid ejection device control circuit 81 also exchanges control signals for controlling the operation of the maintenance mechanism 6 with the maintenance mechanism 6. Similarly, the liquid ejection device control circuit 81 exchanges control signals for controlling the operation of the information output mechanism 9 with the information output mechanism 9. Furthermore, the liquid ejection device control circuit 81 inputs image data signals from an external device, such as a host computer, external to the liquid ejection device 10, performs necessary processing on the image data signals, and outputs the processed image data to the signal conversion circuit 82. The signal conversion circuit 82 converts the input image data signals into image signals corresponding to the ink colors used in the liquid ejection device 10 and outputs the converted image data to the drive circuit board 7.

[0069] An external commercial power supply is input to the power supply circuit 84. The power supply circuit 84 converts the input commercial power into, for example, a 42V DC voltage and outputs it. The DC voltage output from the power supply circuit 84 is input to a voltage detection circuit 85 and is also used as a power supply voltage for each component of the liquid ejection device 10. The voltage detection circuit 85 detects whether power is being supplied to the liquid ejection device 10 based on the voltage value of the DC voltage. The voltage detection circuit 85 generates a voltage detection signal of a logic level corresponding to the detection result and outputs it to the time measurement circuit 83. For example, if the voltage value of the DC voltage deviates from a predetermined range, the voltage detection circuit 85 outputs an L-level voltage detection signal to the time measurement circuit 83. If the voltage value of the DC voltage is within the predetermined range, the voltage detection circuit 85 outputs an H-level voltage detection signal VDET to the time measurement circuit 83. The time measurement circuit 83 determines whether power is being supplied to the liquid ejection device 10 based on the voltage detection signal. Then, when the time measurement circuit 83 determines based on the voltage detection signal that power supply voltage is being supplied to the liquid ejection device 10, it generates elapsed time information and outputs it to the liquid ejection device control circuit 81. This elapsed time information is used to count the usage time of the liquid ejection device 10, and in turn, the head chip 310, etc.

[0070] The information output mechanism 9 outputs various types of information to the user of the liquid ejection device 10. The liquid ejection device control circuit 81 generates a control signal for controlling the operation of the information output mechanism 9 and outputs the control signal to the information output mechanism 9 via a cable 19 connected to a connector 29a. The information output mechanism 9 includes, for example, a display for displaying information. The display for displaying information displays various types of information such as information indicating the operating status of the liquid ejection device 10, information indicating the operating status of the maintenance mechanism 6, information regarding the usage history of the head unit 3, and warning information. The information output mechanism 9 may be configured to notify the user of various types of information, and may include, for example, a configuration for notifying the user of information by sound, light, or the like.

[0071] (A4) Head tip reuse cycle: As explained above, the head unit 3 incorporated in the liquid ejection device 10 is provided with a plurality of liquid ejection heads 31, and each of the liquid ejection heads 31 further incorporates a plurality of head chips 310. In order to explain the manufacturing method of the liquid ejection head of this embodiment, a brief description will be given using Figure 8 of the process from when a new head chip 310 is manufactured and released to the market, to when it is collected and reused. The terms used in the explanation are defined as follows.

[0072] Head chips 310: Head chips with no history of use and head chips with a history of use that are being used in products until they are collected. Used head chip 300: A head chip that has been used and has been collected. Even if it is attached to the head unit 3 or the liquid ejection head 31, the head chip that is included in the collected product is called a used head chip 300. First liquid ejection head 31: The liquid ejection head from which the reused used head chips 300 are taken out. In the above explanation of the hardware configuration, this has been consistently referred to as the liquid ejection head 31, but the liquid ejection head from which the reused used head chips 300 are taken out will be called the first liquid ejection head to distinguish it from the liquid ejection head to be manufactured. Second liquid ejection head 31: A liquid ejection head manufactured using at least a part of a used head chip 300 removed from the first liquid ejection head 31. Third liquid ejection head: Like the first liquid ejection head, this is a liquid ejection head from which a second-hand head chip 300 to be reused is taken out, and is a liquid ejection head different from the first liquid ejection head and the second liquid ejection head. Used head chip ejection performance: The ability of the used head chip 300 to eject liquid at the time the used head chip 300 is collected, in other words, information related to the degree of deterioration of the piezoelectric actuator. This is expressed by the usage history of the used head chip 300 or the measurement results of the used head chip 300 itself. Initial characteristic value: Information relating to the ejection performance immediately after manufacturing the head chip 310 or the used head chip 300. It is expressed by information correlated with the ejection performance or information specifying the category to which this ejection performance belongs. · 1st ranking: Ranking of used head chips 300 based on ejection performance. Second ranking: ranking of the used head chips 300 based on the initial characteristic values.

[0073] An example of the cycle of manufacturing head chips 310 and reusing used head chips 300 will be described with reference to Figure 8. When head chips 310 and liquid ejection devices 10 equipped with them are manufactured in the manufacturing process MFG, the products are provided to the market MRT, and are collected due to malfunction, expiration of their useful life, or discontinuation of use by the user, and are reused in the recycling process RCL. In the recycling process RCL, used head chips 300 are removed, ranked, and further used to manufacture second liquid ejection heads 31x.

[0074] In the manufacturing process MFG, first, the head chip 310 is manufactured, which are then assembled into liquid ejection heads 31a and 31b, further formed into a head unit 3, and finally incorporated into the liquid ejection device 10. During this process, information such as the initial characteristic values ​​of the head chip 310 and which liquid ejection head 31 it is incorporated into is linked to each other and stored in a database DB1 prepared in the cloud. Each process from the head chip 310 to the manufacture of the liquid ejection device 10 may be performed by the same manufacturer, but at least some of the processes may also be performed by a manufacturer other than the manufacturer of the head chip 310. Note that even for the same liquid ejection head 31, the voltage waveform of the drive signal COM that drives the piezoelectric element 60 and the reference voltage Vm may differ depending on the user.

[0075] Products such as the liquid ejection device 10 are placed on the market (MRT) for sale or lease, and are withdrawn from the market due to malfunction or expiration of the usage period, and are collected in the recycling process (RCL). The liquid ejection heads incorporating the collected used head chips 300 are illustrated as the first liquid ejection head 31a in the figure. The used head chips 300 removed from the first liquid ejection head 31a are ranked, and the ranking information is stored in a database DB2. The ranking is performed using a first ranking C1 based on the usage history of the used head chips 300 and a second ranking C2 based on the initial characteristic values ​​of the used head chips 300. The used head chips 300 are classified into ranks R11 to R14 and R21 to R24, which are a combination of these rankings.

[0076] The ranked used head chips 300 are incorporated as at least a part of a second liquid ejection head 31x. The second liquid ejection head 31x manufactured in this way is incorporated into a head unit and ultimately into a liquid ejection device, just like the head chips 310 in the manufacturing process MFG, and is then supplied to the market by an MRT, or the second liquid ejection head 31x is supplied to the market by itself by an MRT.

[0077] The manufacturing method of the liquid ejection head of this embodiment is performed in the reuse process RCL described above, and therefore does not directly involve the manufacturing of the liquid ejection head in the manufacturing process MFG. However, the initial characteristic values ​​of the liquid ejection head may be measured in the manufacturing process MFG. Therefore, the manufacturing of the liquid ejection head in the manufacturing process MFG will now be described in detail. In the manufacturing process MFG, the head chip 310 is first manufactured. Each head chip 310 incorporates multiple piezoelectric elements 60 as actuators for ejecting ink. The head chips 310 manufactured in the manufacturing process MFG have their initial characteristic values ​​measured, and are then classified and ranked based on the measured initial characteristic values. In this embodiment, the initial characteristic value is the natural vibration period Tc of the liquid in the pressure generating chamber 631 of the manufactured head chip 310. Note that instead of the natural vibration period Tc, the volume, weight, or ejection speed of the ink droplets ejected when the manufactured head chip 310 is driven by the reference drive signal COM may also be used.

[0078] FIG. 9 shows a schematic diagram of the initial characteristic values ​​of the head chip 310 and the subsequent change in the ejection performance of the head chip 310 over time. In the figure, the vertical axis represents the ejection performance of the head chip 310, and the horizontal axis represents the number of subsequent ejections or the length of time the head chip has been in use. The ejection performance of the head chip 310, in other words, the ejection performance of the piezoelectric element 60, is determined by, for example, the natural vibration period Tc of the liquid in the pressure generating chamber 631, the ejection speed or ink weight of ink droplets ejected when driven by the reference drive signal COM, and the displacement of the vibration plate 621. The ejection performance of the head chip 310 is correlated with the degree of deterioration of the piezoelectric element 60. The piezoelectric element 60 expands and contracts each time the drive signal COM is applied, and its ejection performance changes depending on the cumulative number of ejections (hereinafter referred to as the cumulative ejection number). Therefore, although the change in characteristics due to use is illustrated by the cumulative ejection number, even when the drive signal COM is not applied, as long as the reference voltage Vm is applied to the piezoelectric element 60, the ejection performance changes regardless of whether liquid is being ejected. Therefore, the time during which the drive signal COM and the reference voltage Vm are applied, that is, the usage time, may be treated as equivalent to the cumulative number of ejections.

[0079] The figure shows the long-term change in characteristics when the number of ejections per unit time is kept constant. In this embodiment, the reference voltage Vm is applied to the piezoelectric element 60 regardless of whether liquid is being ejected or not. Therefore, the cumulative number of ejections and the usage time can be considered to be approximately the same as the usage history of the head chip. In the figure, time t0 indicates the time when the head chip 310 is manufactured, and time ta indicates the end of the aging period performed during the manufacturing of the head chip 310. Since the ejection performance of the head chip 310 changes significantly during the initial use period, an aging process is performed in which a load is applied for a predetermined period of time prior to actual use. This process is called the initial aging process. The period of the initial aging process (time t0 to ta) may vary depending on the magnitude of the initial characteristic value. As shown in the figure, the ejection performance in response to the drive signal COM significantly deteriorates during the initial aging period during manufacturing, and the change in ejection performance with subsequent use becomes smaller. The representative characteristics of head chip 310 at the time aging is complete are shown as characteristics CR1, CR2, and CR3, in descending order of ejection performance Ci1, Ci2, and Ci3. Naturally, the characteristics of head chip 310 vary widely, but for ease of understanding, three representative examples of ejection performance, large, medium, and small, are given.

[0080] For the three representative examples, a solid line Cc1 is further drawn, along with a dashed-dotted line Cc2, which shows an example of a characteristic with higher ejection performance than the solid line Cc1, and a dashed-two-dot line Cc3, which shows an example of a characteristic with lower ejection performance than the solid line Cc1. The differences between these lines will be explained using the characteristic CR1, which shows the highest ejection performance corresponding to the initial characteristic value. The solid line Cc1 of the characteristic CR1, which begins at the time ta when aging is complete, shows the change in ejection performance when the ambient temperature Ta during use of the head chip 310 is 25°C, which is assumed to be room temperature, and the reference voltage Vm of the drive signal COM is the average voltage Vav. The dashed-dotted line Cc2 shows the change in ejection performance when the ambient temperature Ta during use of the head chip 310 is 15°C, which is lower than room temperature, and the reference voltage Vm of the drive signal COM is a voltage Vs, which is lower than the average voltage Vav. Furthermore, the two-dot chain line Cc3 shows the change in ejection performance when the ambient temperature Ta during use of the head chip 310 is 45°C, which is higher than room temperature, and the reference voltage Vm of the drive signal COM is a voltage Vl that is higher than the average voltage Vav. This change in characteristics also applies to characteristics CR2 and the like.

[0081] As will be described later, the ejection performance of the head chip 310 varies over time. However, as a whole, it has a strong correlation with the initial characteristic value, which is the ejection performance at the time of manufacture. Therefore, it is possible to classify and rank the head chip 310 based on the initial characteristic value at the time of manufacture, t0. This corresponds to the second ranking C2, and will be referred to as ranks 1, 2, and 3 below as necessary. Ranks 1, 2, and 3 represent the ejection performance ranges "1," "2," and "3" at time t0 shown in Figure 9. As will be described later, used head chips 300 used as products in the market are also ranked based on their usage history, such as the number of ejections. However, at the time of the manufacturing process MFG, there is no usage history other than aging, so ranking based on usage history is not performed. Ranks A to D and a to d based on usage history shown in Figure 9 will be explained in detail later.

[0082] The above has explained the ejection performance of each head chip 310 during the manufacturing process MFG and aging before shipping, but generally, at the time of manufacturing, head chips 310 belonging to the same rank are collected together to manufacture the liquid ejection head 31. This is because the drive signal COM with the same reference voltage Vm is usually applied to the multiple head chips 310 included in one liquid ejection head 31. After manufacturing, the head chips 310 included in liquid ejection devices 10 placed in the market MRT vary widely in terms of frequency of use, applied voltage, and environmental temperature, so even if the ejection performance of each head chip 310 was somewhat consistent at the time of manufacturing, it is expected that it will differ considerably by the time they are collected.

[0083] (A5) Manufacture of second liquid ejection head: Based on the above assumptions, next, a method for manufacturing a new liquid ejection head, the second liquid ejection head 31x, by reclaiming each head chip 310 used in the first liquid ejection head 31a, etc., collected from a market MRT will be described. FIG. 10 is a process diagram showing the manufacturing process of a liquid ejection head according to the first embodiment. The liquid ejection head according to the first embodiment is manufactured in the process shown as the reuse process RCL in FIG. 8. At this point, the first liquid ejection head 31a and the third liquid ejection head 31b have been collected as one or more liquid ejection heads. When the process for manufacturing a new liquid ejection head, the second liquid ejection head 31x, is started, an acquisition process (step S100) is first performed to acquire used head chips from the multiple liquid ejection heads.

[0084] Specifically, this acquisition process (step S100) involves performing, for each of the multiple target liquid ejection heads, here the first liquid ejection head 31a and the third liquid ejection head 31b, a connection process (step S101), a process for acquiring the usage history of the used head chip 300 (step S111), a process for saving various data (step S121), and a removal process for removing the head chip (step S131). In this embodiment, the used head chip 300 removed from the first liquid ejection head 31a corresponds to the first head chip, and the used head chip 300 removed from the third liquid ejection head 31b corresponds to the second head chip.

[0085] In the connection process (step S101), a reading device 65 is connected so as to be able to access the memory 200 provided in the used head chip 300 provided in the liquid ejection head 31a, etc., which is treated as the first liquid ejection head. The reading device 65 is connected by connecting a connection cable 63 of the reading device 65 to, for example, the connector 27b of the second relay board 335 of the head unit 3, as shown in FIG. 11 . At this time, the originally connected cable 17 may be used instead of the connection cable 63.

[0086] In this embodiment, the reading device 65 is connected to the connector 27b of the second relay substrate 335, so that the usage history of each used head chip 300 provided in all of the first liquid ejection heads 31a and the like connected to the second relay substrate 335 can be read out sequentially from the memory 200 provided in each used head chip 300. When the reading device 65 is connected to the connector 315 of the used head chip 300, the usage history of the used head chip 300 can be read out sequentially from the memory 200 provided in the flexible wiring substrate 311. Note that signals and power required to read data such as the usage history from the memory 200 are output from the reading device 65 to the second relay substrate 335, the first relay substrate 363, and the flexible wiring substrate 311 via the connection cable 63.

[0087] Instead of the above connection, the connection cable 63 of the reading device 65 may be connected to the connector 368 of the first relay board 363, in which case the usage history of all head chips 310-1 to 310-m provided in one first liquid ejection head 31a, etc. can be read out sequentially from each memory 200. Furthermore, by connecting the connection cable 63 of the reading device 65 to the connector 315 provided on the flexible wiring board 311 of the used head chip 300 , the usage history of each used head chip 300 may be read out. One end of the connection cable 63 may be provided with a connector that can be connected to any of the connector 27b, the connector 368, and the connector 315.

[0088] Once the reading device 65 is connected, the memory 200 is accessed, and a process is performed to acquire the ejection performance of each used head chip 300 incorporated in the first liquid ejection head 31a, etc. (Step S111). In the first embodiment, the ejection performance may be an initial characteristic value of the ejection performance linked to the serial number (S / N) of the used head chip 300, or the usage history of the used head chip 300, such as the accumulated number of ejections (hereinafter also referred to as the accumulated number of ejections) or the usage time.

[0089] As will be explained in the second embodiment, the ejection performance of each used head chip 300 can be treated as a rank determined by the initial characteristic value of the ejection performance, the cumulative number of ejections, which is the usage history, and further the reference voltage Vm, environmental temperature, etc. However, for ease of understanding, the first embodiment will be explained as the ejection performance being obtained from the initial characteristic value and usage time. The initial characteristic value can be obtained by referencing the database DB1 shown in FIG. 8 using the serial number S / N of each used head chip 300. The usage time of each used head chip 300 can also be read from the memory 200.

[0090] As explained with reference to FIG. 9, the ejection performance of the head chip 310 deteriorates with use. Therefore, the ejection performance can be easily obtained from the initial characteristic value and the length of use. Of course, the ejection performance can also be measured directly. For example, the displacement of the piezoelectric element 60, which serves as the actuator in each used head chip 300, can be directly measured and used as the ejection performance. This is because the amount of ejected liquid is approximately proportional to the displacement of the piezoelectric element 60, which serves as the actuator. Various well-known methods can be used to measure the displacement of the piezoelectric element 60. For example, the nozzle plate 650 of the liquid ejection head 31 can be used as one of the measurement electrodes. An electric field is formed between this electrode (nozzle plate 650) and an electrode member provided on the capping member of the maintenance mechanism 6. Charged ink is then ejected between the two electrodes, and the voltage change is detected. The displacement of the piezoelectric element 60 can be estimated based on the magnitude of this voltage. Another known method involves measuring the back electromotive force generated when the piezoelectric element 60 is driven and estimating the displacement of the piezoelectric element 60 from the magnitude of the back electromotive force. Any method may be used as long as it is possible to measure the displacement of the piezoelectric element 60.

[0091] Once the ejection performance of each used head chip 300 has been acquired in this way (step S115), this data is saved in a storage device built into the reading device 65 (step S121). This is a process of saving the acquired data on the ejection performance for the selection of used head chips 300, which will be described later, and for aging, which will be described later. The data may be saved in a storage device prepared within the reading device 65, or in a storage device prepared in the cloud.

[0092] After acquiring the ejection performance data and storing the data for all used head chips 300 provided in one liquid ejection head 31, the used head chips 300 are removed (step S131). In this embodiment, the reading device 65 is connected to the second relay board 335 to read the data from each used head chip 300 all at once, so the removal process is performed at the end of the acquisition step S100. However, if the connector 315 provided on the flexible wiring board 311 of each used head chip 300 is connected to the reading device 65 so that the data can be read, the removal process for the used head chips 300 may be performed first.

[0093] The above-described acquisition step S100 is performed for the multiple target liquid ejection heads 31. Once acquisition step S100 is completed for all liquid ejection heads 31, the process proceeds to step S151 and subsequent steps for manufacturing the second liquid ejection head 31x. First, it is determined whether the multiple removed used head chips 300 can be used to assemble a new liquid ejection head, the second liquid ejection head 31x (step S151). An example of this step is shown in FIG. 12. In this example, data is acquired from four used head chips 300 from the first liquid ejection head 31a. Of these, head chips A1 and A2 are determined to be reusable and are removed as the first head chips. Data is also acquired from four used head chips 300 from the third liquid ejection head 31b. Of these, head chips B2 and B4 are determined to be reusable and are removed as the second head chips. Head chips A3, A4, B1, and B3, shown in reverse in the figure, are determined to be unreusable due to insufficient ejection performance or malfunction. These illustrated states are the same in other embodiments. Whether the ejection performance is at a level that allows reuse can be determined by whether the cumulative number of ejections exceeds an upper limit, whether the displacement of the piezoelectric element 60 is below a predetermined value, etc.

[0094] If it is determined in step S151 that the second liquid ejection head 31x can be assembled using only the used head chips 300 for which data has been acquired (step S151: "YES"), a reusable first head chip and a reusable second head chip are selected (step S161). The used head chips 300 selected in this manner are then subjected to an aging process and the results of the process are inspected (step S171). The aging process is a type of adjustment process for reducing variations in the characteristics of the selected head chips. In particular, when the actuator is a piezoelectric actuator, the aging process refers to a process for adjusting the ejection performance of the piezoelectric element 60 by applying a predetermined voltage to the piezoelectric element 60, which is directly related to the ejection performance. Generally, the ejection performance deteriorates during the aging process. The adjustment process by aging will be described using FIG. 13. 13 shows the relationship between the ejection performance and usage time of the first head chips A1 and A2, which are used head chips 300 removed from the first liquid ejection head 31a, as a solid line A, and the relationship between the ejection performance and usage time of the second head chips B2 and B4, which are used head chips 300 removed from the third liquid ejection head 31b, as a solid line B. Note that the symbol IV in the figure indicates the initial characteristic value of the ejection performance of each head chip.

[0095] In this example, the reference voltage Vm of the drive waveform applied to the used head chip 300 included in the third liquid ejection head 31b is smaller than the reference voltage Vm of the drive waveform applied to the used head chip 300 included in the first liquid ejection head 31a, so the degradation in ejection performance of the second head chips B2 and B4, which are used head chips 300 included in the third liquid ejection head 31b, is greater than the degradation in ejection performance of the first head chips A1 and A2, which are used head chips 300 included in the first liquid ejection head 31a. Such differences can arise not only from differences in the reference voltage Vm of the drive waveform between head chips with similar initial characteristic values, but also from differences in the operating environment temperature, etc.

[0096] Assume that the first head chips A1 and A2, which are used head chips 300 of the first liquid ejection head 31a, were used until time tA, and the second head chips B2 and B4, which are used head chips 300 of the third liquid ejection head 31b, were used until time tB. Therefore, the ejection performance of the first head chips A1 and A2, which were used until time tA, is significantly superior to the ejection performance of the second head chips B2 and B4, which were used until time tB. Therefore, depending on the difference in ejection performance, an aging process is performed on the first head chips A1 and A2, which have the characteristics of solid line A. In this example, by performing the aging process e.g. on the used head chips 300, which have the characteristics of solid line A, it is expected that the ejection performance of the first head chips A1 and A2, which have the characteristics of solid line A, will, after aging e.g., exhibit a characteristic similar to that of solid line A, if the first and second head chips A1, A2, B2, and B4 are used at the same reference voltage Vm and the same ambient temperature. As a result, in subsequent use, the ejection performance approaches that of the second head chips B2 and B4, which have the characteristics of solid line B, and the difference in ejection performance (here, the ejection amount) between the first and second head chips A1, A2, B2, and B4 becomes smaller. Note that, as shown in Figure 13, in order to reduce the difference in ejection performance by performing a short-term aging process eg, it is sufficient to perform at least one of the following: increasing the voltage applied to the piezoelectric actuator when performing the aging process eg, or performing the aging process eg when the environmental temperature of the used head chip 300 is high.

[0097] Whether or not the difference in ejection performance has been reduced is confirmed by an inspection process that is performed as part of the aging process. The reduction in the difference in ejection performance can be confirmed when at least one of the following conditions is satisfied: <1> The color difference ΔE of the test image when ink of the same color is ejected from each of the first and second head chips A1, A2, B2, and B4 is a predetermined value, for example, a value of 2 or less. It is more preferable to perform an aging process so that the color difference ΔE becomes a value of 1 or less. <2> The weight Iw of ink ejected from each of the first and second head chips A1, A2, B2, and B4 is measured, and the difference between these ink weights IW is found to be smaller than before the aging process. <3> The speed Vs of ink ejected from each of the first and second head chips A1, A2, B2, and B4 is measured, and the difference between these speeds Vs is smaller than before the aging process. <4> The displacement of the piezoelectric element 60 before and after the aging process is measured or estimated, and the displacement of the piezoelectric element 60 before and after the process is compared to determine whether the difference has become smaller. In the above cases of <2> to <4>, the aging process may be performed on a nozzle-by-nozzle basis.

[0098] The inspection process is also performed as part of the aging process because, even if the aging process is performed for a predetermined time, the difference in ejection performance may not be as small as in the example above. In this case, inspection is performed to confirm the difference in ejection performance, and if the difference is not sufficiently small, the aging process is performed again. Note that the aging process does not need to be performed on all used head chips 300; it can be performed on all used head chips 300 except for the used head chip 300 with the lowest ejection performance. In Figure 12, the second head chip B4 has the lowest ejection performance among the used head chips 300. In this case, the aging processes eg1, ge2, and eg3 are performed on the other first head chips A1 and A2 and the second head chip B2. The process of performing such aging processes corresponds to the adjustment process.

[0099] Once the aging process has sufficiently reduced the difference in ejection performance among the multiple used head chips 300, an assembly process is performed in which these used head chips 300 are used to assemble a second liquid ejection head 31x (step S181). When assembling the second liquid ejection head 31x, new components of the liquid ejection head 31 other than the head chips may be used, or used components may be reused if they are usable. Although not shown in the figures, when assembling the second liquid ejection head 31x, data indicating the ejection performance of the incorporated head chips is stored in memory 200, and the second liquid ejection head 31x may be incorporated into a new liquid ejection device 10 such as a printer and shipped as a product.

[0100] On the other hand, in the judgment of the above-mentioned step S151, if it is judged that the used head chips 300 removed from the first liquid ejection head 31a and the third liquid ejection head 31b initially prepared are not enough to assemble a new second liquid ejection head 31x (step S151: "NO"), new head chips 310 are selected in the same number as the missing used head chips 300 to make up for the missing used head chips 300 (step S152). After that, the remaining head chips are selected from the used head chips 300 (step S161).

[0101] After that, the processes from step S171 onward are performed. This process is shown schematically in FIG. 14. In this example, of the four head chips of the third liquid ejection head 31b, all but head chip B2 were determined to be unusable. Therefore, only three used head chips 300 constituting the second liquid ejection head 31x could be removed from the first liquid ejection head 31a and the third liquid ejection head 31b. Therefore, in such cases, a new head chip 310 is used, and a new head chip N1 is added to assemble the second liquid ejection head 31x. In this example, head chip N1 is considered to have the highest ejection performance, so an aging process eg4 is performed. In the illustrated example, head chip B2 is the most severely deteriorated, or in other words, has the lowest ejection performance, so no aging process is performed on it. The initial aging process described with reference to FIG. 9 for the new head chip N1 is preferably performed before the adjustment process. This saves time compared to performing the initial aging process as part of the conditioning process.

[0102] According to the liquid ejection head manufacturing method of the first embodiment described above, head chips installed in the first liquid ejection head 31a or the like that were installed in a liquid ejection device 10, such as a printer, once released to the market can be collected, the condition of the collected used head chips 300 can be determined, and a new liquid ejection head, the second liquid ejection head 31x, can be manufactured using the reusable used head chips 300. This eliminates the need to discard usable head chips unnecessarily, contributing to resource conservation. Reusable used head chips 300 are selected based on the initial characteristic values ​​at the time of shipment stored in the memory 200 of the first liquid ejection head 31a or the like that incorporated the used head chips 300, as well as the usage time and cumulative number of ejections since use in the market. The head chips 300, excluding those with the lowest ejection performance, are subjected to an aging process to reduce differences in ejection performance, and a new liquid ejection head, the second liquid ejection head 31x, can be assembled. Therefore, the characteristics of the head chips in the newly manufactured second liquid ejection head 31x can be uniform.

[0103] According to this embodiment, when there are insufficient used head chips 300 removed from the first liquid ejection head 31a or the like to be reused, new head chips 310 are used and subjected to an aging process to bring the ejection performance closer to that of the used head chips 300. Therefore, even in this case, it is possible to reduce the difference in characteristics between the head chips constituting the second liquid ejection head 31x. Note that instead of using new head chips 310, a third liquid ejection head 31c that was used in another liquid ejection device 10 may be additionally disassembled, and a used head chip 300 may be removed as a second head chip, and usable used head chips 300 may be found and used.

[0104] In the above embodiment, in addition to the first liquid ejection head 31a, second-hand head chips 300 were recovered from the third liquid ejection head 31b that had been used in another printer, but if only the second-hand head chips 300 recovered from the first liquid ejection head 31a are sufficient, the second liquid ejection head 31x may be manufactured without using the third liquid ejection head 31b. Alternatively, if there are insufficient second-hand head chips 300 even after adding the third liquid ejection head 31b, second-hand head chips 300 obtained by further disassembling the liquid ejection head 31c as the third liquid ejection head 31c may be used.

[0105] B. Second embodiment: Next, a method for manufacturing a liquid ejection head according to a second embodiment will be described. The steps of the manufacturing method according to the second embodiment are shown in FIG. 15. The manufacturing process of the liquid ejection head in this case is also shown in FIG. 16. In the second embodiment, in order to manufacture the liquid ejection head, the first liquid ejection head 31a and the third liquid ejection heads 31b and 31c are prepared, and then, as in the first embodiment, a used head chip 300 is removed from a liquid ejection device 10 that has been used, and a new liquid ejection head is manufactured. In the second embodiment, the removed used head chip 300 is ranked, and second liquid ejection heads 31x and 31y, which are new liquid ejection heads, are manufactured based on the rank.

[0106] When this manufacturing process begins, an acquisition process (step S100B) is first executed. The acquisition process of the second embodiment differs from the first embodiment in that a ranking process (step S115) is added after the process (step S111) of reading data such as the number of ejections from the first liquid ejection head 31a and the third liquid ejection heads 31b and 31c. In the ranking process, the used head chips 300 are classified into one of several ranks. In this embodiment, as shown in the top row of FIG. 16, the ranks are determined using the initial characteristic values ​​and the cumulative number of ejections as main parameters, and the reference voltage Vm of the drive signal COM, the environmental temperature of the used head chip 300, and the type of ink ejected by the used head chip 300 as subparameters. As a result, the ranks of the used head chips 300 are classified according to the degree of deterioration of their piezoelectric actuators. The main parameters and sub-parameters required for such ranking are read out from the first liquid ejection head 31a in step S111, or are read out from the serial number (S / N) of the used head chip 300 via the database DB1.

[0107] The ranking step S115 will now be described. Using the main parameters, first ranking C1 and second ranking C2 are performed. The cumulative number of ejections is used as the usage history, and the first ranking C1 is performed based on which of the categories A to D shown in FIG. 9 the cumulative number of ejections belongs to. The second ranking C2 is performed by determining whether the ejection performance of each used head chip 300 immediately after manufacture belongs to category 1 or 2 of the initial characteristic values ​​shown in FIG. 9. While category 3 is also shown in the figure as a category for initial characteristic values, head chips 310 with initial characteristic values ​​in category 3 are considered to be initially defective products with low ejection performance from the start and are not used in the manufacture of any liquid ejection heads 31. Therefore, in the second ranking C2, the used head chips 300 are ranked into category 1 or category 2.

[0108] By combining the first ranking C1 and the second ranking C2, the used head chip 300 can be classified into one of a total of eight ranks, R11 to R14 and R21 to R24, based on the cumulative number of discharges (four divisions: A to D) and the initial characteristic values ​​(two divisions: 1 and 2).

[0109] In the above explanation of ranking, the first ranking C1, which is ranking based on usage history, and the second ranking C2, which is ranking based on initial characteristic values, are described as being performed independently, but it is also possible to combine the two and further rank the products by taking sub-parameters into consideration. This method is described below.

[0110] As shown in Figure 9, the ejection performance of a head chip after a specified aging period changes with increasing ejection counts. The degree of change is affected by factors such as environmental temperature and the reference voltage Vm of the drive signal COM. For used head chips 300, the changes in ejection performance due to initial characteristic values ​​and subsequent use have been investigated for each parameter that affects ejection performance, such as environmental temperature and the reference voltage Vm of the drive signal COM. Therefore, knowing the initial characteristic values ​​and parameters allows for highly accurate prediction of how the ejection performance will change with increasing ejection counts. Therefore, as shown in an example in Figure 9, by assuming ejection performance ranges a, b, c, d, etc. based on the initial characteristic values ​​and various parameters using the ejection performance achieved by aging as a standard, the rank of a used head chip 300 at a given ejection count can be further refined. This is equivalent to ranking used head chips 300 based on their usage history for each initial characteristic value—that is, by combining the initial characteristic values ​​and usage history.

[0111] For example, if a head chip 310 with initial characteristic values ​​of ejection performance Ci1 is used at an ambient temperature of 15°C and a reference voltage Vm of Vs, the rank of the used head chip 300 based on its usage history at ejection time te is rank b, based on the dashed-dotted line Cc2 in the figure. Similarly, if a used head chip 300 with initial characteristic values ​​of ejection performance Ci1 is used at an ambient temperature of 25°C and a reference voltage Vm of VAV, the rank of the used head chip based on its usage history at ejection time te is rank c, based on the solid line Cc1 in the figure. If the used head chip 300 is used at an ambient temperature of 45°C and a reference voltage Vm of Vl, the rank of the used head chip 300 based on its usage history at ejection time te is rank d, based on the dashed-two-dot line Cc3 in the figure. Here, rank d is a rank that exceeds the usage limit and cannot be reused, and used head chips 300 in this category d may be excluded from the selection process.

[0112] Typical parameters of the usage history to be combined with such initial characteristic values ​​are listed below. These parameters correlate with the degree of deterioration of the piezoelectric element 60. Accumulative number of ejections (usage time): The cumulative number of ejections is one of the main parameters, and its influence on ejection performance has been described in detail above, so a detailed explanation will be omitted here. The first ranking C1 regarding the degree of deterioration of the piezoelectric element 60 may be performed based only on the cumulative number of ejections (usage time), without using usage history such as the ambient temperature of use or the reference voltage Vm. In this case, the first ranking C1 classifies the used head chips 300 into ranks A to D. The ranking in the first embodiment is performed based only on the cumulative number of ejections (usage time), and the used head chips 300 are classified into ranks A to D. Ambient temperature during use: This is the temperature during use of the used head chip 300, and is treated as a subparameter. The ambient temperature during use of the used head chip 300 is not always the same, but the average temperature can be calculated as the ambient temperature, or the ambient temperature for each period of use can be calculated and integrated to be treated as the ambient temperature parameter. In other words, the first ranking C1 regarding the degree of deterioration of the piezoelectric element 60 may be determined by combining the reference voltage Vm with the cumulative number of ejections (usage time) to classify the used head chip 300 into ranks a to d. Note that the reference voltage Vm may not be used, and the used head chip 300 may be classified into ranks a to d by combining only the cumulative number of ejections (usage time) and the ambient temperature during use. Reference voltage Vm: This is the potential difference between the reference potential Vbs and the intermediate potential Vc of the drive signal COM applied to the used head chip 300 described above, and is also treated as one of the subparameters. The voltage value itself may be used, or the voltage value may be divided into multiple categories and the category to which the reference voltage Vm belongs may be used. In other words, the first ranking C1 regarding the degree of deterioration of the piezoelectric element 60 may be used in combination with the ambient temperature and the cumulative number of ejections (usage time) to classify the used head chip 300 into ranks a to d. Note that the ambient temperature may not be used, and the cumulative number of ejections (usage time) and the reference voltage Vm alone may be used to classify the used head chip 300 into ranks a to d. Ink type: The higher the viscosity of the ink being ejected, the higher the reference voltage Vm of the drive waveform that must be applied to the piezoelectric actuator for ejection, making it more susceptible to degradation. Furthermore, for inks that require solid ejection (solid jetting) with a high operating rate (duty), such as black ink, white ink, pre-treatment liquids used to pre-treat the media surface, and post-treatment liquids such as overcoats, a large amount of ink must be ejected from the nozzle 651, and the reference voltage Vm applied to the piezoelectric actuator that ejects this ink tends to be large. In other words, the reference voltage Vm can be estimated based on the type of ink. These ranks a to d are provided for ranks 1 and 2 of the initial characteristic values.

[0113] An example of the ranking priority order that combines usage history and initial characteristic values ​​is shown in Figure 17. In the example shown, the following ranking processes Ra and Rb are performed as the first ranking based on usage history, along with the second ranking process based on the initial characteristic values ​​(ranks 1 to 3 in Figure 9). Processing Ra: Ranking processing based on cumulative number of discharges (ranks A to D in Figure 9), Process Rb: Ranking process based on the ambient temperature and the reference voltage Vm (ranks a to d in Figure 9); In the first ranking based on these usage histories, used head chips 300 that are classified as "unreusable rank ZZ" because they are deemed unsuitable for continued use in any one of the processes Ra and Rb should desirably be excluded from the scope of reuse. All or only some of these usage history parameters may be taken into consideration.

[0114] These parameters relating to the usage history, that is, the cumulative number of ejections that increases with use, the environmental temperature during use, the reference voltage Vm, and other usage history information, are counted by the control circuit 71 of the drive circuit board 7 and are written as needed to the memory 200 provided in each head chip 310 via the second relay board 335 and the first relay board 363. As mentioned above, the cumulative number of ejections may be substituted by the usage time of the head chip 310 or liquid ejection head 31a, etc.

[0115] As a result of this process, as illustrated in FIG. 16, an acquisition process (step S100B) is performed on the first liquid ejection head 31a and the third liquid ejection heads 31b and 31c, and a total of 12 used head chips 300 are removed after ranking. While the actual ranking varies widely as shown in FIG. 17, the results of the ranking performed using the above parameters are simplified and shown here as ranks R1, R2, and ZZ. Rank R2 indicates a higher degree of piezoelectric actuator deterioration than rank R1. Therefore, in this embodiment, the first head chips A1 and A2, which are used head chips 300 removed from the first liquid ejection head 31a, and the first head chips B2 and C3, which are used head chips 300 removed from the third liquid ejection heads 31b and 31c, are head chips of rank R1. On the other hand, the third head chip A3, which is the used head chip 300 removed from the first liquid ejection head 31a, and the third head chips B3, B4, and C4, which are the used head chips 300 removed from the third liquid ejection heads 31b and 31c, are head chips of rank R2. As a result, in this example, as shown in the top row of the figure, the first head chips A1, A2, B2, and C3, which are used head chips 300 of rank R1, the third head chips A3, B3, B4, and C4, which are used head chips 300 of rank R2, and the head chips A4, B1, C1, and C2, which are unreusable, of rank ZZ are obtained. In the figure, the head chips of rank R1 are shown as they are, the head chips of rank R2 are shown with diagonal hatching, and the head chips outside the rank are shown in reversed black and white.

[0116] Returning to FIG. 15 , in the liquid ejection head manufacturing method of the second embodiment, following the acquisition process for all target liquid ejection heads (step S100B), the ranks of the removed multiple used head chips 300 are checked (step S153), and only used head chips 300 ranked R1 or R2 are selected (step S161 or S162). The four used head chips 300 ranked R1 or R2 that make up the new second liquid ejection head 31x or 31y, except for the one with the highest degree of deterioration, are subjected to an aging process and subsequent inspection (step S171 or S172). Here, as shown in the middle of FIG. 16 , the aging process is not performed on head chips C3 and C4, while the other head chips are each subjected to an aging process. The setting of the degree of aging and the inspection of the adjustment of ejection performance through aging are the same as in the first embodiment. By repeating the aging process and inspection as necessary, the ejection performance of each head chip is adjusted to a predetermined range. Therefore, thereafter, a process for assembling the second liquid ejection head 31x from only the first head chips A1, A2, B2, and C3 of rank R1 or a process for assembling the second liquid ejection head 40y from only the third head chips A3, B3, B4, and C4 of rank R2 (step S181 or S182) is performed, and this processing step is terminated. When assembling the second liquid ejection heads 31x and 31y, data indicating the ejection performance of the incorporated head chips may be stored in memory 200, or the second liquid ejection heads 31x and 31y may be incorporated into a new liquid ejection device 10 and shipped as a product, as in the first embodiment.

[0117] According to the manufacturing method of the second embodiment described above, used head chips 300 collected from the first liquid ejection head 31a and the third liquid ejection heads 31b and 31c included in multiple liquid ejection devices 10 are ranked. The second liquid ejection head 31x is manufactured using only used head chips 300 ranked R1, and the second liquid ejection head 31y is manufactured using only used head chips 300 ranked R2. Furthermore, the aging process is performed on used head chips 300 of the same rank to approximate the ejection performance of the used head chips 300 incorporated into the second liquid ejection heads 31x and 31y. In other words, the aging process is performed as an adjustment process on used head chips 300 with relatively similar ejection performance, thereby reducing the time required to perform the aging process in the adjustment process. As described in the first embodiment with reference to FIG. 13, the degree of aging can be determined to reduce the difference in ejection performance between the used head chip 300 and the lowest-performing used head chip 300. Therefore, the ejection performance of the used head chips 300 assembled in the second liquid ejection heads 31x and 31y can be adjusted to fall within a predetermined range.

[0118] C. Third embodiment: Next, a method for manufacturing a liquid ejection head according to a third embodiment will be described. The steps of the manufacturing method according to the third embodiment are shown in FIG. 18. The manufacturing process of the liquid ejection head in this case is also shown schematically in FIG. 19. In the third embodiment, in order to repair and manufacture a second liquid ejection head 31s, work begins with one first liquid ejection head 31a prepared in addition to the second liquid ejection head 31s. When the process begins, the second liquid ejection head 31s to be repaired is first subjected to a connection process (step S201), a read process (step S211), a data storage process (step S221), a determination of usability (step S231), and a head chip removal process (step S241).

[0119] The connection process (step S201) is a process of connecting the reading device 65 to the connector 27b of the second relay board 335, as shown in FIG. 11. The subsequent data reading process (step S211) is a process of using the reading device 65 to read data indicating the status of each head chip 310 provided in the second liquid ejection head 31s, such as the cumulative number of ejections and initial characteristic values. Since this data is recorded in the memory 200 of the second liquid ejection head 31s, it is convenient to connect the reading device 65 and read the data before removing the second liquid ejection head 31a, etc. The data saving process (step S221) is a process of saving the read data for use in selecting a used head chip 300 that was provided in the first liquid ejection head 31a, as described below. The data may be saved in a storage device provided within the reading device 65, or in a storage device provided in the cloud.

[0120] The usability determination (step S231) is a step of determining whether each head chip 310 provided in the second liquid ejection head 31s is a head chip that can be used continuously, based on the data read from the memory 200. For the second liquid ejection head 31s illustrated in FIG. 19, main parameters and sub-parameters are read as shown in the top row of the figure, and a rank, including unusable rank ZZ, is determined based on these parameters. The method of determining the rank from the main parameters and sub-parameters is the same as in the second embodiment. Of the four head chips S1 to S4 of the second liquid ejection head 31s, head chips S1 to S3 are determined to belong to rank R1, and head chip S4 is determined to be rank ZZ, that is, unusable. These head chips S1 to S3 correspond to the second head chips. 9 based on the initial characteristic values ​​and the cumulative number of ejections, or the liquid ejection device 10 equipped with the second liquid ejection head 31s may inspect for missing dots and determine that a head chip that does not eject ink even after cleaning or other processes is "faulty," write the determination result into memory 203 of the second relay board 335, and read the determination result from memory 203. Of course, such "faulty" data may be written in step S201 of the first relay board 363 or in memory 200 provided for each head chip, and used.

[0121] Thereafter, a removal process (step S241) is performed to remove the head chip S4 that has been determined to be unusable. This process is shown in the middle part of Figure 19. The removed head chip S4 is discarded. Up to this point, the state of the second liquid ejection head 31s that is required when repairing the second liquid ejection head 31s is obtained, and the second head chips S1 to S3 are identified.

[0122] Next, an acquisition process (step S100) is performed on the first liquid ejection head 31a. This process is the same as the acquisition process described in the first embodiment. As a result, used head chips 300 corresponding to the first head chips are identified and removed from the first liquid ejection head 31a. Thereafter, based on the state of each head chip 310 obtained in the acquisition process (step S100), it is determined whether they can be reassembled for repair into the second liquid ejection head 31s (step S151). In the example shown in FIG. 19, main parameters and sub-parameters for each used head chip 300 of the first liquid ejection head 31a are read out, and the rank of the used head chip 300 is determined based on these. In this example, of the four used head chips 300 provided in the first liquid ejection head 31a, head chips A1 to A3 belong to rank ZZ and are determined to be unusable, but head chip A4 belongs to rank R1 and is determined to be a reusable first head chip.

[0123] If it is determined in step S151 that the second liquid ejection head 31s can be repaired and assembled using only the used head chip 300 for which data was acquired (step S151: "YES"), multiple reusable head chips may be found, and a process of selecting one of them is performed (step S161). In this case, as shown in FIG. 19, the first head chip A4 provided in the first liquid ejection head 31a is selected. Next, a process of assembling the selected head chip into the second liquid ejection head 31s (step S165) is performed, and the selected first head chip A4 is assembled with the second head chips S1 to S3 that were present in the second liquid ejection head 31s to form the second liquid ejection head 31s. An aging process and an inspection of the process results are performed on the necessary used head chips 300 of these four used head chips 300 that form the second liquid ejection head 31s (step S171). In the third embodiment, the used head chip 300 removed from the first liquid ejection head 31a corresponds to the first head chip, and the head chip that was not removed from the second liquid ejection head 31s corresponds to the second head chip. As in the other embodiments, the aging process is a type of adjustment for reducing variation in the characteristics of the used head chip 300. In the example shown in Fig. 19, head chip A4 was determined to have deteriorated the least, and aging processes es1 to es3 were performed on the other head chips S1 to S3.

[0124] When the difference in ejection performance among the multiple used head chips 300 becomes sufficiently small as a result of the aging process, the repair of the second liquid ejection head 31s is considered complete, and a process (step S185) is performed to store data of the used head chips 300 that make up the second liquid ejection head 31s in memory 200, etc., followed by an assembly process (step S195) to assemble the second liquid ejection head 31s, and the manufacturing process exits to "END" to end. Note that if it is determined in step S151 that the second liquid ejection head 31s cannot be assembled using the used head chips 300 that were included in the first liquid ejection head 31a and the second liquid ejection head 31s, the second liquid ejection head 31s is not assembled, and the process exits to "END" to end. Of course, if it is determined that the used head chips 300 of the first liquid ejection head 31a and the second liquid ejection head 31s are not capable of assembling the second liquid ejection head 31s, it is possible to add a selection of usable used head chips 300 from the third liquid ejection head 31b, etc.

[0125] According to the manufacturing method of the third embodiment described above, if one or more of the head chips 310 included in the second liquid ejection head 31s breaks down, it can be repaired using used head chips 300 that were used in the first liquid ejection head 31a, which has a usage history. In this case, there is also no need to wastefully discard the second liquid ejection head 31s in which only one or more of the head chips 310 have broken down. Furthermore, there is no need to use new head chips for repair, which contributes to resource conservation. Furthermore, since the aging process is performed, variation in the ejection performance of the used head chips 300 in the second liquid ejection head 31s can be suppressed.

[0126] In the third embodiment described above, the used head chip 300 used to repair the broken second liquid ejection head 31s was removed from only the first liquid ejection head 31a, but it is also possible to use a used head chip 300 that has been used in a liquid ejection head 31 different from the first liquid ejection head 31a, such as the third liquid ejection head 31b, in addition to the first liquid ejection head 31a.

[0127] D. Other Embodiments: (1) The present disclosure can be implemented in the following embodiments. One possible method for manufacturing a liquid ejection head is a method for manufacturing a second liquid ejection head including a first head chip and a second head chip different from the head chip incorporated in the first liquid ejection head by reusing the first head chip of the first liquid ejection head. The first head chip and the second head chip each have an actuator that drives to eject liquid. The method includes a detachment process for removing the first head chip from the first liquid ejection head, an assembly process for incorporating the first head chip into the second liquid ejection head, and an adjustment process for performing an adjustment process on the actuator of at least one of the first head chip and the second head chip to reduce the difference in ejection performance between the first head chip and the second head chip. This allows the second liquid ejection head to be manufactured by reusing the first head chip included in the first liquid ejection head, and also reduces the difference in ejection performance between the head chips. This reduces variation in the ejection performance of the manufactured second liquid ejection head.

[0128] The results of the adjustment process to reduce the difference in ejection performance between the head chips of the second liquid ejection head may be confirmed through an inspection process, or the amount of displacement before the adjustment process may be estimated based on the usage history and compared with the current amount of displacement or the current amount of displacement estimated taking into account the history of the adjustment process to determine whether the difference in ejection performance has been reduced. It is desirable that the color difference (ΔE) between the test image when ink of the same color is ejected is 2 or less, preferably 1 or less. Alternatively, it may be determined that the weight of the ejected ink is smaller than before the adjustment process, or that the ejection speed of the ejected ink is smaller than before the adjustment process.

[0129] The adjustment process may be performed on all of the first or second head chips, or on all head chips included in the second liquid ejection head. However, if the difference in ejection performance can be minimized, it is sufficient to perform the adjustment process on at least one of them. If the adjustment process, such as aging, results in a decrease in ejection performance, the adjustment process may be performed on head chips other than the one with the lowest ejection performance. If the adjustment process can restore ejection performance, the adjustment process may be performed on head chips other than the one with the highest ejection performance. For example, if the actuator uses an electrostrictive element whose deformation is restored by applying a voltage with a polarity opposite to that applied during ejection, such an adjustment process may be used to minimize the difference in ejection performance. Note that the adjustment process does not include replacing driving elements such as piezoelectric elements in the actuator.

[0130] This manufacturing method can be applied to the manufacture of liquid ejection heads that eject various liquids such as ink, water, alcohol, liquid fuel, chemicals, etc. The ejection performance of the first and second head chips may be determined by extracting and referencing the usage history of each head chip, or may be obtained by extracting the first and second head chips, attaching them to a measuring device, and measuring them.

[0131] (2) In the above configuration, the removing step may further include removing the second head chip from a third liquid ejection head different from the first and second liquid ejection heads, and the assembling step may further include incorporating the second head chip into the second liquid ejection head. This allows the second liquid ejection head to be manufactured using head chips from at least two different liquid ejection heads. For example, if the number of reusable head chips that can be removed from the first liquid ejection head is insufficient to meet the number of head chips required for the second liquid ejection head, the second liquid ejection head can be manufactured using the third liquid ejection head. Alternatively, even if the same head chips are used, but the number of head chips in the second liquid ejection head is greater than the number of head chips in the first liquid ejection head, the second liquid ejection head can be manufactured using the third liquid ejection head.

[0132] Of course, the use of a third liquid ejection head is not essential, and if the number of head chips that can be removed and reused from the first liquid ejection head is equal to or greater than the number of head chips required for the second liquid ejection head, then the second liquid ejection head may be manufactured without using a third liquid ejection head. This may occur, for example, when the first and second liquid ejection heads use the same head chips and the number of head chips provided in the first liquid ejection head is greater than the number of head chips in the second liquid ejection head.

[0133] (3) In the above configuration, the actuator may be a piezoelectric actuator, and the adjustment process may be a process of aging the piezoelectric actuator of at least one of the first head chip and the second head chip. This makes it easy to adjust the ejection performance of a head chip that uses a piezoelectric actuator as an actuator.

[0134] (4) In the above configuration, the adjustment step may include setting conditions for the aging treatment to be performed on at least one of the first head chip and the second head chip based on a reference voltage of the drive waveform applied to the piezoelectric actuator of the first head chip as part of the first liquid ejection head before the removal step and a reference voltage of the drive waveform applied to the piezoelectric actuator of the second head chip as part of the third liquid ejection head before the removal step. This allows adjustment treatment to be performed on head chips recovered from at least two different liquid ejection heads that were used with different drive waveforms by changing the reference voltage without changing the drive waveform itself. Of course, adjustment treatment may also be performed by changing the drive waveform itself.

[0135] In order to reduce the difference in ejection performance between the first head chip and the second head chip assembled as the second liquid ejection head, the adjustment process typically involves determining the degree of deterioration of the head chips and correcting the degree of deterioration of one of the head chips to reduce the difference between the two.

[0136] Further, the following subparameters may be cited as secondarily contributing to the degree of deterioration of the head chip: These subparameters vary significantly depending on the user of the liquid ejection head, including the environment in which the liquid ejection head is used, i.e., the configuration of the liquid ejection device and the type of liquid ejected. Drive waveform: When not ejecting, an intermediate potential is applied to the piezoelectric actuator, and it is known that the greater the potential difference between the intermediate potential of the individual electrodes and the potential of the common electrode, the more likely the piezoelectric actuator is to deteriorate. Ambient temperature: It is known that piezoelectric actuators are more susceptible to deterioration when the ambient temperature is high. Type of liquid: It is known that the higher the viscosity of the liquid being ejected, the more energy the piezoelectric actuator consumes, which ultimately makes it more susceptible to deterioration. The higher the viscosity of the liquid, the higher the drive voltage that must be applied to the piezoelectric actuator to eject it, making it more susceptible to deterioration. In addition, when the liquid is ink ejected onto a medium, a pre-treatment liquid that is applied to the medium before the ink is ejected, or a post-treatment liquid that is applied to the medium after the ink is ejected, a large amount of liquid must be ejected, and the reference voltage applied to these liquids and the ejecting piezoelectric actuator tends to be large.

[0137] The adjustment process to reduce the difference in ejection performance between the first head chip and the second head chip is performed by setting conditions such as the magnitude of the drive waveform, the number of ejections, and the environmental temperature during the adjustment process. Here, the magnitude of the drive waveform can be treated as, for example, the magnitude of the intermediate potential, and by changing the intermediate potential, the displacement amount of the piezoelectric actuator can be adjusted to set the adjustment process conditions. The adjustment process conditions can also be set by changing the number of ejections or the energization time, or by the environmental temperature of the head chip during the adjustment process. Note that if a piezoelectric actuator is provided for each of the multiple liquid ejection nozzles on the head chip, the adjustment process may be performed for each nozzle. However, if common wiring is used to connect the multiple piezoelectric actuators to simplify the connection wiring, it is likely that the degree of deterioration between the multiple piezoelectric actuators will be small, so it is also acceptable to perform the adjustment process on a head chip basis. When the intermediate potential of the drive waveform is applied to all piezoelectric actuators provided for each nozzle, the usage time of each piezoelectric actuator will be the same, and the difference in the degree of deterioration within the head chip can be considered to be sufficiently small.

[0138] (5) In the above configuration, the adjustment step may include setting conditions for the aging treatment to be performed on at least one of the first head chip and the second head chip based on the environmental temperature when the first liquid ejection head was used before the removal step and the environmental temperature when the third liquid ejection head was used before the removal step. This allows the adjustment step to be performed according to the environmental temperature when the head chip was used in the liquid ejection head, and as described above, it is possible to reduce the difference in ejection performance between the first and second head chips.

[0139] (6) In the above configuration, the method may further include setting conditions for the aging treatment to be performed on at least one of the first head chip and the second head chip based on the type of liquid that was supplied to the first head chip as part of the first liquid ejection head before the removal step and the type of liquid that was supplied to the second head chip as part of the third liquid ejection head before the removal step. This allows adjustment treatment to be performed according to the type of liquid that was supplied when the head chip was used in the liquid ejection head, and as described above, it is possible to reduce the difference in ejection performance between the first and second head chips.

[0140] (7) In the above configuration, the first liquid ejection head may have been used in a liquid ejection device for ejecting liquid. This allows for the reuse of head chips of liquid ejection heads used in liquid ejection devices such as printers, contributing to resource conservation.

[0141] (8) In the above configuration, the assembly process may incorporate into the second liquid ejection head only a plurality of head chips, including the first head chip and the second head chip, removed from each of a plurality of liquid ejection heads that have been used in an ejection operation to eject liquid while mounted on one or more liquid ejection devices. This eliminates the need to use newly manufactured head chips, thereby reducing the burden on the environment. It is more preferable to select such a plurality of head chips, including the first head chip and the second head chip, that have the same degree of deterioration and use them by minimizing the difference in ejection performance between the head chips through the adjustment process described above.

[0142] (9) In the above configuration, the removing step may further include removing the second head chip belonging to the first rank from the first liquid ejection head, which includes the first head chip belonging to a first rank in deterioration degree and a third head chip belonging to a second rank in deterioration degree higher than the first rank, and a third liquid ejection head different from the second liquid ejection head. The assembling step may incorporate multiple head chips, including the first head chip and the second head chip, belonging to the first rank into the second liquid ejection head. This allows the second liquid ejection head to be constructed using head chips belonging to the same rank, allowing for a uniform aging process and preventing unnecessary head chip deterioration. Furthermore, the aging process can be reduced. As a result, variation in the ejection performance of the second liquid ejection head can be reduced.

[0143] (10) In the above configuration, the adjustment process may be performed under conditions set based on the usage history of the first head chip. If the adjustment process is performed based on the usage history, there is no need to measure the ejection performance. Of course, the ejection performance of the first head chip may be measured and the adjustment process may be performed based on the measured value. In the latter case, there is no need to store the usage history in a memory or the like or to read it out.

[0144] (11) In the above configuration, the removing step may remove, as the first head chip, a head chip determined to be reusable based on the usage history of the head chip from among the plurality of head chips included in the first liquid ejection head. This prevents the use of a head chip that is unlikely to be reusable or unlikely to be reusable, thereby preventing the lifespan of the assembled liquid ejection head from being shortened unexpectedly. Head chips determined to be non-reusable may be removed from the first liquid ejection head and then discarded, or only the reusable head chips may be removed and then the first liquid ejection head may be discarded.

[0145] (12) In the above configuration, the second liquid ejection head may have drive signal wiring that supplies a common drive signal to the actuators of the first head chip and the second head chip. In this way, since the difference in ejection performance between the first and second head chips is reduced by adjustment processing, the first and second head chips can be driven by a common drive signal supplied by the common drive signal wiring, thereby simultaneously achieving simplification of the configuration of the liquid ejection head and suppression of variations in ejection performance.

[0146] (13) In the above configuration, the second liquid ejection head may have been used for ejecting liquid while mounted on a liquid ejection device, the assembly of the second liquid ejection head in the assembling step may be performed by incorporating the first head chip into the second liquid ejection head from which all head chips except for at least one head chip remaining in the second liquid ejection head have been removed, and the adjustment step may perform the adjustment process on at least the second head chip. In this way, rather than manufacturing a new liquid ejection head, the manufacture of the liquid ejection head can be performed as a repair of an existing liquid ejection head.

[0147] (14) In each of the above embodiments, the liquid ejection device 10 includes a head unit 3 including multiple liquid ejection heads 31. However, this is not limited to this. The liquid ejection device 10 may include a single liquid ejection head 31, i.e., it may not include a head unit 3.

[0148] (15) In each of the above embodiments, instead of performing the second ranking C2 based on the initial characteristic values, a selection process may be performed to select used head chips to be incorporated into the second liquid ejection head 31x, etc., based on a ranking that classifies used head chips 300 into multiple ranks based on the degree of deterioration of the piezoelectric element 60.

[0149] (16) The usage history of the used head chip 300 may be obtained by any of the following methods. The usage history of the used head chip 300 of the liquid ejection head 31 of the seller or leaser (hereinafter sometimes referred to as the customer) may be obtained via a network from the customer's printer connected to the Internet, provided that the printer has access to the memory that stores the usage history. Data on the usage history may be stored in the memory of a circuit board included in the customer's printer. For example, a worker recovering the first liquid ejection head 31 may acquire the usage history data using an electronic device that can be connected to the customer's printer to read and save the usage history data from the printer, and the data may be transmitted wirelessly or via a wired connection from the electronic device to a server of a company that performs the recycling process RCL.

[0150] (17) In each of the above embodiments, the information related to the usage history may be the usage history itself or information correlated with the usage history. For example, the information related to the reference voltage Vm of the drive waveform of the drive signal COM, which is an example of the usage history, may be the reference voltage Vm itself, or, because the reference voltage Vm can be calculated from the intermediate potential Vc and the reference potential Vbs, it may be the intermediate potential Vc of the drive signal COM and the reference potential Vbs of the reference voltage signal.

[0151] (18) In the above-mentioned method for manufacturing a liquid ejection head, <1> Manufacturing a new head chip (process X1), (2) Assembling the newly manufactured head chip into the liquid ejection head (process X2). <3> Management of data related to head chip characteristic information, such as initial characteristic values ​​of the head chip, along with assignment of a unique ID, such as a serial number, for the head chip incorporated in the liquid ejection head (process X3); <4> After the liquid ejection head is supplied to the market, the liquid ejection head with a history of use is collected from the market (process Y1). <5> Removal of used head chips from the collected liquid ejection heads (step Y2), <6> Management of used head chips (process Y3), in which the characteristic information of the used head chips is acquired and the used head chips are ranked, and the ranked used head chips are stored with the characteristic information corresponding to the ranking information; <7> Selecting the ranked used head chips based on the above ranking, and manufacturing a new liquid ejection head using the selected head chips (step Z1); <8> Selecting the ranked used head chips based on the above ranking and using them together with the used head chips of a specific liquid ejection head to manufacture a liquid ejection head (step Z2); <9> Providing used head chips that have been classified and stored in accordance with the requests of the entities Z1 and Z2 (process Z3); At least some of the steps are carried out.

[0152] Processes X1 to X3 correspond to the process up to when new head chips are supplied to the market, processes Y1 to Y3 correspond to the process up to when used head chips are collected and managed, and processes Z1 to Z3 relate to the manufacture and repair of liquid ejection heads using used head chips. Note that processes Y2 and Y3 can also be considered to relate to the manufacture and repair of liquid ejection heads using used head chips. All of these processes X1 to Z3 may be carried out by the same entity such as a company, or processes X1 to X3, processes Y1 to Y3, and processes Z1 to Z3 may each be carried out by different entities. Of course, all of the processes may also be carried out by different entities.

[0153] In each of the above embodiments, some of the configurations implemented by hardware may be replaced with software. At least a portion of the configurations implemented by software may also be implemented by a discrete circuit configuration. Furthermore, when some or all of the functions of the present disclosure are implemented by software, the software (computer program) may be provided in a form stored on a computer-readable recording medium. The term "computer-readable recording medium" is not limited to portable recording media such as floppy disks and CD-ROMs, but also includes internal storage devices within a computer, such as various RAMs and ROMs, and external storage devices fixed to a computer, such as a hard disk. In other words, the term "computer-readable recording medium" has a broad meaning, including any recording medium capable of fixing data packets, not just temporarily.

[0154] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0155] 3...head unit, 4...storage section, 5...medium transport mechanism, 5a...first transport section, 5b...second transport section, 6...maintenance mechanism, 7...drive circuit board, 8...main circuit board, 9...information output mechanism, 10...liquid ejection device, 15-19...cables, 25a, 26a, 27a, 27b, 28a, 28b, 29a...connectors, 30...drive circuit board, 31...liquid ejection head, 31a...first liquid ejection head, 31b, 31c...third liquid ejection head, 31x, 31y...second liquid ejection head, 32...cover, 33...base member, 34...flow path member, 35...cover - member, 37...spacer, 40...supply pipe, 51a, 51b...conveying rollers, 52a, 52b...follower rollers, 53a, 53b...drive motor, 54b...conveying belt, 55b...tension roller, 56b...urging member, 57b...roller, 60...piezoelectric element, 63...connecting cable, 65...reading device, 71...control circuit, 72...drive signal output circuit, 73...drive state detection circuit, 81...liquid ejection device control circuit, 82...signal conversion circuit, 83...time measurement circuit, 84...power supply circuit, 85...voltage detection circuit, 200, 201, 203...memory Lee, 202...selector, 210...drive signal selection control circuit, 300...used head chip, 310...head chip, 311...flexible wiring board, 312...integrated circuit, 313...through hole, 314, 315...connector, 321...base portion, 322...extension portion, 324...opening, 331...supply hole, 332...accommodation portion, 333...opening, 334...step, 335...second relay board, 336...integrated circuit, 337...connector, 351, 352...opening, 360...holding member, 361...flow path member, 362...holder, 363...first relay board, 364...ink supply portion, 365...cable insertion hole, 366...cable, 367...holding portion, 368...connector, 381 to 385...screws, 600...ejection portion, 601...piezoelectric layer, 602, 603...electrodes, 610...case, 611...manifold, 620...protective substrate, 621...diaphragm, 622...holding portion, 630...pressure chamber substrate, 631...pressure generating chamber, 640...flow path substrate, 641...common flow path, 642...branch flow path, 643...communicating flow path, 644...individual flow path, 650...nozzle plate, 651...nozzle, 652...nozzle surface, 658...water-repellent film

Claims

1. A manufacturing method for manufacturing a second liquid ejection head including a first head chip and a second head chip different from the head chip incorporated in the first liquid ejection head by reusing the first head chip of the first liquid ejection head, comprising: each of the first head chip and the second head chip has an actuator that is driven to eject liquid; a removing step of removing the first head chip from the first liquid ejection head; an assembly process of incorporating the first head chip into the second liquid ejection head; an adjustment process for performing an adjustment process on the actuator of at least one of the first head chip and the second head chip to reduce a difference between the ejection performance of the first head chip and the ejection performance of the second head chip; A method for manufacturing a liquid ejection head.

2. the removing step further includes removing the second head chip from a third liquid ejection head different from the first liquid ejection head and the second liquid ejection head; the assembling step further includes incorporating the second head chip into the second liquid ejection head. The method for manufacturing a liquid ejection head according to claim 1 .

3. the actuator is a piezoelectric actuator; the adjustment process is an aging process that deteriorates the piezoelectric actuator of at least one of the first head chip and the second head chip. The method for manufacturing a liquid ejection head according to claim 1 or 2.

4. the adjusting step includes setting conditions for the aging treatment to be performed on at least one of the first head chip and the second head chip based on a reference voltage of the drive waveform that was applied to the piezoelectric actuator of the first head chip as a part of the first liquid ejection head before the removing step and a reference voltage of the drive waveform that was applied to the piezoelectric actuator of the second head chip as a part of the third liquid ejection head before the removing step. The method for manufacturing a liquid ejection head according to claim 3, which relies on claim 2.

5. the adjusting step includes setting conditions for the aging treatment to be performed on at least one of the first head chip and the second head chip based on an environmental temperature when the first liquid ejection head was used before the removing step and an environmental temperature when the third liquid ejection head was used before the removing step. The method for manufacturing a liquid ejection head according to claim 3, which relies on claim 2.

6. the adjusting step includes setting conditions for the aging treatment to be performed on at least one of the first head chip and the second head chip based on a type of liquid that had been supplied to the first head chip as part of the first liquid ejection head before the removing step and a type of liquid that had been supplied to the second head chip as part of the third liquid ejection head before the removing step. The method for manufacturing a liquid ejection head according to claim 3, which relies on claim 2.

7. the first liquid ejection head has been used for an ejection operation of ejecting liquid while being mounted on a liquid ejection device; The method for manufacturing a liquid ejection head according to claim 1 .

8. the assembling step includes incorporating into the second liquid ejection head only a plurality of head chips including the first head chip and the second head chip, which have been removed from each of a plurality of liquid ejection heads that have been used for an ejection operation of ejecting liquid while being mounted on one or a plurality of liquid ejection devices; The method for manufacturing a liquid ejection head according to claim 1 .

9. the removing step further includes removing the second head chip belonging to the first rank from the first liquid ejection head, which includes the first head chip whose degree of deterioration belongs to a first rank and a third head chip whose degree of deterioration belongs to a second rank higher than the first rank, and from the third liquid ejection head different from the second liquid ejection head; the assembling step includes incorporating a plurality of head chips, including the first head chip and the second head chip, belonging to the first rank into the second liquid ejection head; The method for manufacturing a liquid ejection head according to claim 1 .

10. the adjusting step sets conditions for the adjusting process based on a usage history of the first head chip. The method for manufacturing a liquid ejection head according to claim 1 .

11. the removing step includes removing, as the first head chip, a head chip determined to be reusable based on a usage history of the head chip from among a plurality of head chips included in the first liquid ejection head; The method for manufacturing a liquid ejection head according to claim 1 .

12. the second liquid ejection head has a drive signal wiring that supplies a common drive signal to the actuators of the first head chip and the second head chip; The method for manufacturing a liquid ejection head according to claim 1 .

13. the second liquid ejection head has been used for ejecting liquid while being mounted on a liquid ejection device, the assembly of the second liquid ejection head in the assembly step is carried out by incorporating the first head chip into the second liquid ejection head from which the other head chips have been removed except for at least one head chip that remains as the second head chip in the second liquid ejection head, the adjusting step performs the adjusting process on at least the second head chip; The method for manufacturing a liquid ejection head according to claim 1 .

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