Manufacturing method for liquid discharge head

Abstract

To solve the problem that when one head chip deteriorates, all of a plurality of head chips are discarded, in a liquid discharge head configured so that the head chips are incorporated therein.SOLUTION: In a manufacturing method for a liquid discharge head, first rank-classification in which a plurality of used head chips provided in a first liquid discharge head are classified into a plurality of ranks, on the basis of respective characteristic information on the plurality of used head chips provided in the first liquid discharge head, so as to select the used head chips, of the plurality of used head chips, which are incorporated in a second liquid discharge head so that the second liquid discharge head includes the plurality of used head chips classified into different ranks by the first rank-classification. The plurality of used head chips which are selected are incorporated in the second liquid discharge head, so that some of the plurality of head chips provided in the first liquid discharge head are reused to manufacture the second liquid discharge head.SELECTED DRAWING: Figure 15

Description

[Technical Field]

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

[0002] BACKGROUND ART A liquid ejection apparatus is known that includes 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 this conventional technology, when a liquid ejection head included in a liquid ejection device breaks down or reaches the end of its life due to deterioration through use, the liquid ejection head is replaced to repair the liquid ejection device. A single liquid ejection head is equipped with multiple head chips. Therefore, even though the deterioration and failure manifest themselves differently for each head chip, if some head chips are deemed unusable or near the end of their life, the entire liquid ejection head is replaced, resulting in the problem that even usable head chips or head chips with only minor deterioration are subject to disposal. [Means for solving the problem]

[0005] The present disclosure can be implemented as a method for manufacturing a liquid ejection head. The method for manufacturing a liquid ejection head includes manufacturing a second liquid ejection head by reusing some of a plurality of used head chips included in one or more first liquid ejection heads, and includes a first ranking step of classifying the used head chips included in the one or more first liquid ejection heads into a plurality of ranks based on characteristic information of the used head chips included in the one or more first liquid ejection heads, a selection step of selecting one or more used head chips from the plurality of used head chips to be incorporated into the second liquid ejection head so that the second liquid ejection head includes a plurality of used head chips classified into different ranks in the first ranking step, and an assembly step of incorporating the one or more used head chips selected in the selection step into the second liquid ejection head. [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 head chips incorporated in a head unit from collection to ranking. [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] FIG. 4 is an explanatory diagram illustrating a state in which the manufactured head chip is incorporated into a discharge head. [Figure 11] FIG. 4 is an explanatory diagram showing an example of data created and saved during manufacturing of a head chip. [Figure 12A] FIG. 10 is a process diagram illustrating a process for ranking collected used head chips. [Figure 12B] FIG. 10 is an explanatory diagram showing an example of ranking priorities. [Figure 13] FIG. 4 is an explanatory diagram showing the state of connection between the relay board of the head unit and the reading device. [Figure 14] 1 is a process diagram showing the selection and assembly process for manufacturing a new liquid ejection head. [Figure 15] 5A to 5C are explanatory diagrams illustrating an example of a process for manufacturing a new liquid ejection head. [Figure 16] 6A to 6C are process diagrams showing the manufacturing process of the liquid ejection head according to the second embodiment. [Figure 17] FIG. 10 is an explanatory diagram illustrating an example of a combination of used head chips. [Figure 18] 10A and 10B are explanatory diagrams illustrating examples of other combinations of used head chips. [Figure 19] 10A and 10B are explanatory diagrams illustrating examples of other combinations of used head chips. [Figure 20] 1 is a process diagram showing the process of measuring and ranking the condition of used head chips. 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. In the manufacturing method according to the first embodiment, a second liquid ejection head is manufactured by reusing some of the used head chips included in one or more first liquid ejection heads. Here, the first liquid ejection head is a liquid ejection head that has been incorporated into a liquid ejection device or the like and used. The second liquid ejection head is a liquid ejection head manufactured by reusing at least some of the used head chips included 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 heads, 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, discharging, and intermittent outflow, regardless of the type of liquid, output time, or number of times.

[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, and the ink ejected from the head unit 3 will be described as 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, a liquid ejection device 10 includes 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 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 corresponding to the signal supplied from the drive circuit board 7 and at a timing corresponding 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. The cleaning process may be, for example, suction cleaning, in which a capping space formed by covering the nozzle surface with a recessed cap (not shown) provided in the maintenance mechanism 6 is subjected to negative pressure by a negative pressure generating mechanism such as a pump (not shown) provided in the maintenance mechanism 6 connected to the cap, thereby forcibly discharging ink from the nozzles to the outside, or pressure cleaning, in which a flow path located upstream of a pressure generating chamber 631 (described below) is pressurized by a pressure generating mechanism such as a pump (not shown) provided in the maintenance mechanism 6, thereby forcibly discharging ink from the nozzles to the outside. In this embodiment, since a line-type inkjet printer is used as an example of the liquid ejection device 10, the maintenance mechanism 6 is located in a position different from the head unit 3, and a head unit moving mechanism (not shown) moves the head unit 3 to the position of the maintenance mechanism 6 to perform the above-mentioned wiping, flushing, cleaning, and other processes. The number of times of these processes can be treated as one of the characteristic information of the head chip, as described below.

[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 a 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 included in the pressure chamber substrate 630 and the multiple nozzles 651 included in 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. Specifically, each piezoelectric element 60 includes electrodes 602, 603 and a piezoelectric layer 601. The electrode 602, the piezoelectric layer 601, and the electrode 603 are laminated in this order on the Z2-side surface of the vibration plate 621, facing from the Z1 side to the Z2 side in the direction Z. 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 element 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. While this embodiment will be described assuming that the electrode 602 is an individual electrode and the electrode 603 is a common electrode, this is not a limitation. A drive signal COM is supplied to the electrode 602, which is an individual electrode, and a reference voltage signal indicating the 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 a potential difference generated between the electrode 602 and the electrode 603. That is, the piezoelectric element 60 is driven in response to a potential difference between the voltage value of a signal supplied to the electrode 602 and the voltage value of a 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 outer surface 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.

[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 instrument 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 plurality of head chips 310, a holder 362 that holds the plurality of 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 a 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 a flow path provided inside flow path member 361 and a 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, signals input to each of the multiple liquid ejection heads 31 and signals output from the multiple liquid ejection heads 31 propagate through the second relay substrate 335.

[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 Fig. 6, 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, and the main circuit board 8 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 greater than or equal to 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 of the first relay substrate 363. The connector 315 and the connector 314 are detachably connected.

[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 configuration of this drive signal selection control circuit 210 is shown schematically in Figure 8. As shown in the figure, 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 this piezoelectric element 60 receives a drive signal COM via the drive signal selection control circuit 210, it expands and contracts along the Z direction in accordance with the applied voltage. The drive signal COM and reference voltage signal are shown in Figure 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 piece of characteristic information of the head chip 310. Another item that can be treated as characteristic information 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 or the like, 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. 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 characteristic information 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 a cable 18 connected to the connector 28a, to the medium conveyance mechanism 5 via a cable 15 connected to the connector 25a, to the maintenance mechanism 6 via a cable 16 connected to the connector 26a, and to the information output mechanism 9 via a cable 19 connected to the connector 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. The connectors used in this specification are not limited to specific types as long as they are configured to electrically and detachably connect 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 were used in products until they were 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. First position: The position where the head tip is placed, which is expected to be used relatively more frequently than other head tips. Second position: A position where a head tip is placed that is expected to be used less frequently than the head tip placed in the first position, when comparing the frequency of use of the head tip. Used head chip characteristic information: Information related to the liquid ejection ability and various degrees of deterioration of the used head chip 300 at the time of collection of the used head chip 300. 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 capacity immediately after manufacturing the head chip 310 or the used head chip 300. It is expressed by information correlated with the ejection capacity or information specifying the category to which this ejection capacity belongs. First ranking: Ranking of used head chips 300 based on characteristic information. Second ranking: ranking of the used head chips 300 based on the initial characteristic values.

[0073] 8, which shows an example of the cycle of manufacturing head chips 310 and reusing used head chips 300, once 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, discontinuation of use by the user, etc., and are reused in the recycling process RCL. In the recycling process RCL, the used head chips 300 are removed, ranked, and further manufactured into 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 manufacture 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. 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 in the same way as 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. The aging period (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 aging period during manufacturing, and the change in ejection performance with subsequent use becomes smaller. Representative characteristics of the head chip 310 at the time aging is completed are shown as characteristics CR1, CR2, and CR3, in descending order of ejection performance Ci1, Ci2, and Ci3. Of course, the characteristics of the head chip 310 vary widely, but for ease of understanding, three representative examples of large, medium, and small ejection performance 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, overall, it is strongly correlated with the initial characteristic value, which is the ejection performance at the time of manufacture. Therefore, the head chip 310 is classified and ranked based on the initial characteristic value at time t0 when manufactured. 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] FIG. 10 shows how head chips 310 are ranked after manufacture. The top row in the figure indicates the ranks into which manufactured head chips 310 are classified based on initial characteristic values ​​at the time of manufacture. The numbers "1," "2," and "3" assigned to the head chips 310 indicate that the initial characteristic values ​​of the head chips 310 correspond to those represented by the characteristics CR1, CR2, and CR3 shown in FIG. 9. In this embodiment, for example, head chips 310 with rank 3, which have low ejection performance based on initial characteristic values, are not used, and head chips 310 with ranks 1 and 2 are combined to form liquid ejection heads 31a to 31c. However, it is also possible to form a liquid ejection head 31 by combining head chips 310 with rank 3. In this case, as shown in the figure, it is preferable to combine head chips 310 with similar initial characteristic values. Liquid ejection head 31c shows an example composed only of head chips 310 ranked 1. Liquid ejection head 31b shows an example composed only of head chips 310 ranked 2. In this example, when used for the same period of time, the liquid ejection head 31a uses a head chip 310 of rank 1 in the first position where the head chip 310 for black ink K, which normally has the highest number of ejections, in other words has the highest ejection frequency, is placed, and a head chip 310 of rank 2 in the second position where the head chip 310 for CMY, which is assumed to have a lower ejection frequency than the head chip 310 in the first position, is placed.

[0083] Then, a plurality of liquid ejection heads 31a, 31b, and 31c configured in this manner are combined to form head units 3a to 3c. Each of the head units 3a to 3c is used in a respective liquid ejection device. FIG. 10 shows a head unit 3a manufactured by combining only the liquid ejection head 31a, and head units 3b and 3c manufactured by combining only the liquid ejection head 31b and only the liquid ejection head 31c. FIG. 10 also shows a memory 200 that stores information related to usage history. As described above, this memory 200 is a memory provided in each head chip 310. This memory 200 stores usage history, and its contents and ranking using the usage history will be described in detail later. The memory 200 may store initial characteristic values ​​along with the usage history. In this embodiment, the initial characteristic values ​​are recorded in a database DB1 on the cloud, as described below.

[0084] An example of a record of initial characteristic values ​​is shown in Figure 11. In the record shown as table TB1 in the figure, the serial number of the head chip 310 (shown as S / N in the figure) is linked to "data," the serial number of the liquid ejection head 31, and the date of assembly of the head chip 310 into the liquid ejection device 10. The "data" includes ranks 1 and 2 based on the initial characteristic values. These records are stored as database DB1 on a cloud site and are referenced when, for example, a new liquid ejection head 31 corresponding to the second liquid ejection head is constructed using a used head chip removed from a liquid ejection head 31 corresponding to the first liquid ejection head, as will be described later.

[0085] The liquid ejection heads 31a, 31b, 31c, etc. configured in this manner constitute head units 3a, 3b, 3c, and the head units are incorporated into the device main body to manufacture the liquid ejection devices 10a, 10b, 10c, etc. The manufactured liquid ejection devices 10a, 10b, 10c, etc. are shipped to the market MRT and are used by users (see FIG. 8).

[0086] (A5) Liquid ejection head manufacturing method - ranking process: Next, a manufacturing method for the liquid ejection head of this embodiment will be described. This manufacturing method is performed in the reuse process RCL shown in FIG. 8 and broadly includes a ranking process, a selection process, and an assembly process. The ranking process of this embodiment includes a first ranking process in which the multiple used head chips 300 included in the first liquid ejection head 31a, etc. are divided into multiple ranks based on the characteristic information of each of the multiple used head chips 300 included in the first liquid ejection head 31a, etc. The selection process selects used head chips 300 to be incorporated into the second liquid ejection head 31x from the multiple used head chips 300 so that the second liquid ejection head 31x includes multiple used head chips 300 classified into different ranks in the first ranking process. Furthermore, the used head chips 300 selected in the selection process are incorporated into the second liquid ejection head 31x. These processes will be described in order below.

[0087] FIG. 12A is a process diagram showing an example of the ranking process. Prior to the ranking process, head units 3 present in liquid ejection devices 10a and the like collected from market MRTs are removed. Therefore, in the ranking process, a reading device 65 is connected to the head unit 3 so as to access the memory 200 provided in the used head chip 300 provided in the liquid ejection head 31a and the like, which is treated as the first liquid ejection head (step S101). The reading device 65 is connected by connecting the 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. 13. At this time, the originally connected cable 17 may be used instead of the connection cable 63.

[0088] 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 characteristic information of the used head chip 300 can be read out sequentially from the memory 200 provided in the flexible wiring substrate 311. Note that the 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.

[0089] In addition, 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.

[0090] Once the reading device 65 is connected, the memory 200 is accessed to obtain the serial number (S / N) of each used head chip 300 incorporated in the first liquid ejection head 31a, etc. (step S111). Similarly, data on each incorporated used head chip 300, in this case the accumulated number of ejections (hereinafter also referred to as the accumulated number of ejections), which is the usage history, is read from the memory 200 (step S121). Using this read data, each used head chip 300 is classified, and the first ranking C1 process is performed (step S131).

[0091] Characteristic information such as the cumulative number of ejections can be obtained from data stored in each memory 200 mounted on each used head chip 300 of the first liquid ejection head 31a, etc. The memory 200 contains at least the number of ejections of each used head chip 300 as information correlated with ejection performance. The control circuit 71 of the liquid ejection device 10a, etc., accumulates the number of ejections each time it commands each head chip 310 to eject ink droplets and stores the result at a predetermined timing in the memory 200 on the flexible wiring board 311 associated with each head chip. Therefore, by connecting a reading device 65, characteristic information of each used head chip 300 can be obtained from each memory 200 mounted on the head unit 3a, etc. As shown in Figure 9, the ejection performance of a head chip generally deteriorates as the number of times it is used increases. Therefore, the number of ejections can represent the characteristic information of a used head chip 300 and can be used as a guide for reuse, as described below. For this purpose, the number of ejections for each used head chip 300 is read from the memory 200, and it is determined which of the predetermined categories A to D according to the usage history it belongs to, and the first ranking C1 can be performed.

[0092] As shown in FIG. 9, the ejection performance of a head chip when the number of ejections of the head chip reaches a predetermined value is strongly affected by the initial characteristic values ​​of each head chip. For this reason, the initial characteristic values ​​of the head chips constituting one liquid ejection head 31 are often made uniform, as shown for head units 3b and 3c in FIG. 10. This is because the reference voltage Vm of the drive signal COM applied to the piezoelectric elements 60 of the multiple head chips constituting one liquid ejection head 31 can be made uniform. For this reason, it is also considered to rank used head chips 300 according to which category of initial characteristic values ​​they belong to. For this reason, following the first ranking (step 367131), a second ranking process based on the initial characteristic values ​​(steps S141 and S151) is performed.

[0093] In step S141, database DB1 is accessed based on the serial number (S / N) of the head chip acquired in step S111, and initial characteristic values ​​of each used head chip 300 are acquired. Furthermore, in step S151, a second ranking C2 is performed using the acquired initial characteristic values. The second ranking C2 is performed by determining whether the initial characteristic values ​​of the used head chip 300 belong to category 1 or 2 shown in FIG. 9.

[0094] Thereafter, information on each used head chip 300 ranked according to the first ranking C1 and the second ranking C2 is linked to its serial number and stored in database DB2 (step S161). Data on each ranked used head chip 300 is stored in database DB2, with the cumulative number of uses and initial characteristic values ​​linked to the serial number of the head chip. This database DB2 may be stored on the cloud or locally. This database DB2 can be treated as representing the inventory of used head chips 300 sorted into each rank.

[0095] Thereafter, a removal process is carried out to remove the used head chips 300 that were incorporated into the first liquid ejection head 31a, etc. (step S171). The removed used head chips 300 are sorted according to the ranks described above and stored (step S181). This completes the ranking process. In the first ranking C1, the used head chips 300 are classified into categories A to D, with category D being a "non-reusable rank" that has exceeded its usage limit, and used head chips 300 in category D may be excluded from the selection process.

[0096] The first ranking C1 and the second ranking C2 are explained below. In steps S121 and S131, 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. In steps S141 and S151, 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. Fig. 9 also shows category 3 as a category of initial characteristic values, but as already explained, head chips 310 with initial characteristic values ​​in category 3 are not reused and have not been used, so in the second ranking C2, the used head chips 300 are ranked into category 1 or category 2.

[0097] Using these first rankings C1 and second rankings C2, used head chips 300 are ranked according to the cumulative number of ejections and the initial characteristic values, as shown in the lower part of Fig. 8. In this example, the first ranking C1 based on the cumulative number of ejections is divided into four categories, and the second ranking C2 based on the initial characteristic values ​​is divided into two categories. As a result, there are a total of eight ranks, R11 to R14 and R21 to R24.

[0098] In the above ranking process, 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 performed independently, but the first ranking C1 and the second ranking C2 may be performed in a combined state. A method of combining the two rankings will be described below.

[0099] As shown in Figure 9, the ejection performance of a head chip after a specified aging period changes with increasing ejection counts, but the degree of change is affected by differences in 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 examined 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 number of ejections can be determined. 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.

[0100] 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.

[0101] 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. Accumulated number of ejections (usage time): This 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 accumulated 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 first ranking C1 of this embodiment is performed based only on the accumulated number of ejections (usage time), and classifies the used head chips 300 into ranks A to D. Ambient temperature during use: The temperature at which the used head chip 300 is used. The ambient temperature during use of the used head chip 300 is not necessarily the same, but an average temperature may be calculated as the ambient temperature, or the ambient temperature for each period of use may be calculated and integrated to be used as the ambient temperature parameter. In other words, the first ranking C1 relating to the degree of deterioration of the piezoelectric element 60 may be used in combination with the reference voltage Vm and 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: 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. 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. These ranks a to d are provided for ranks 1 and 2 of the initial characteristic values.

[0102] In addition to the parameters related to the degree of deterioration of the piezoelectric element 60, the following are typical parameters of the usage history as characteristic information used in the first ranking. The following are parameters for estimating the degree of deterioration of elements other than the piezoelectric element 60. Ink filling time: The degree of deterioration of the adhesive used in forming the used head chip 300 affects whether the used head chip 300 can continue to be used. The degree of adhesive deterioration is affected by the amount of time the common liquid chamber, pressure generating chamber 631, etc. of the used head chip 300 have been filled with ink. In other words, when performing a first ranking based on the degree of adhesive deterioration, the longer the ink filling time, the higher the rank of the used head chip 300 that has been classified as being at a higher level of deterioration. Note that the type of ink used may be combined with the ink filling time to perform a first ranking based on a more accurate estimation of the degree of adhesive deterioration. For this reason, parameters such as the ink type as well as the ink filling time may be included in the usage history as characteristic information used in the first ranking. Number of wipings: Similarly, the degree of deterioration of the water-repellent film 658 provided on the used head chip 300 affects the determination of whether the used head chip 300 can continue to be used. The degree of deterioration of the water-repellent film 658 is affected by the number of wipings. In other words, when performing first ranking according to the degree of deterioration of the water-repellent film 658, the higher the number of wipings, the higher the rank of the used head chip 300 classified as having a higher degree of deterioration. Note that the first ranking may be performed based on a more accurate estimation of the degree of deterioration of the water-repellent film 658 by combining the number of wipings with the load with which the wiping member WP presses the water-repellent film 658 during wiping and the type of ink adhering to the water-repellent film 658. For this reason, in addition to the number of wipings, parameters such as the wiping load and ink type may also be included in the usage history as characteristic information used in the first ranking. Number of cleaning processes: The degree of deterioration of the nozzles 651 of the used head chip 300 can be grasped, for example, as the frequency and number of clogged nozzles. When a nozzle becomes clogged, a cleaning process is performed, so when first ranking is performed according to the degree of deterioration of the nozzles 651, the used head chip 300 is classified into a rank with a higher degree of deterioration, the more the number of cleaning processes has been performed.

[0103] An example of ranking priorities that combines various usage histories treated as characteristic information with initial characteristic values ​​is shown in Fig. 12B. In the example shown, the following ranking processes Ra to Rc are performed as first rankings based on usage histories, in addition to second rankings based on initial characteristic values ​​(ranks 1 to 3 in Fig. 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); Treatment Rc: Ranking treatment according to the degree of deterioration of the water-repellent film, Treatment Rd: Ranking treatment based on the degree of adhesive deterioration. Although not shown, other rankings may be used in combination, such as a ranking process based on the degree of nozzle deterioration. It is desirable to exclude used head chips 300 that are classified as "unreusable" in the first ranking process based on the usage history, i.e., that they are not suitable for continued use in any one of the processes Ra to Rd, from being eligible for reuse. All or some of these usage history parameters may be considered.

[0104] These parameters relating to the usage history, that is, the usage history such as the cumulative number of ejections and the number of wiping operations that increase with use, the ambient temperature during use, and the reference voltage Vm, 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 the liquid ejection head 31a, etc.

[0105] (A6) Liquid ejection head manufacturing method - selection and assembly process: Next, a process for constructing a new liquid ejection head 31 using each used head chip 300 will be described. Figure 14 is a process diagram showing the selection and assembly process. Here, second liquid ejection heads 31x and 31y, which are liquid ejection heads similar to the first liquid ejection head 31a, etc., are manufactured using used head chips 300 that were assembled to first liquid ejection heads 31a and 31b, which are liquid ejection heads that were used in the liquid ejection device 10a, etc.

[0106] When the assembly process for the second liquid ejection heads 31x and 31y begins, the database DB2 is accessed first (step S201). This database DB2 is the database written and saved in step S161 of FIG. 12. The database DB2 stores information about used head chips 300 that have been collected from the market MRT, sorted based on rank, stored, and managed. Based on the data read from the database DB2, it is determined whether the required number of used head chips 300 for assembling the second liquid ejection heads 31x and 31y can be combined (step S211). Because the database DB2 represents the inventory of used head chips 300 sorted by rank, by reading the database DB2, it is easy to determine whether the required number of used head chips 300 with the desired characteristics are available. If it is determined that the used head chips cannot be combined to form a new second liquid ejection head 31x, etc. (step S211: "NO"), nothing is done and the assembly process ends.

[0107] If it is determined that a combination of used head chips 300 for constituting the second liquid ejection head 31x, etc., is possible (step S211: "YES"), then the used head chips 300 are selected based on the information read from the database DB2 (step S231). An example of the selection is shown in FIG. 15. For ease of understanding, the diagram begins with the disassembly of the used head chips 300 mounted on the head units 3a, 3b collected from the market. The liquid ejection heads 31a, 31b in the diagram correspond to the "first liquid ejection head." The liquid ejection heads 31a, 31b removed from the head units 3a, 3b include multiple used head chips 300, but the ejection performance of each used head chip 300 varies. In the diagram, among the labels such as "1A," "1" and "2" correspond to the initial characteristic value ranks "1" and "2" described with reference to FIG. 8, and "A," "B," "C," and "D" correspond to the ejection count classifications "A," "B," "C," and "D." The used head chips 300 obtained by disassembling the first liquid ejection heads 31a and 31b are ranked according to their initial characteristic values ​​and cumulative number of ejections, and are sorted into ranks R11 to R14 and R21 to R24 and stored in a warehouse or the like. These sorted used head chips 300 correspond to the information recorded in the database DB2. In addition, in FIGS. 8 and 15, the used head chips 300 classified as rank D, which is a "non-reusable rank," in the first ranking C1 are classified as rank R14 or R24 ​​and then stored. However, since the used head chips 300 classified as rank R14 or R24 ​​are not reused, by discarding the used head chips 300 classified as rank D after the first ranking C1, it is not necessary to store the used head chips 300 classified as rank R14 or R24.

[0108] Next, the second liquid ejection heads 31x and 31y are constructed by combining the sorted used head chips 300 with the same initial characteristic value rank. The illustrated second liquid ejection head 31x was constructed by selecting from an inventory with an initial characteristic value of rank "1" and a cumulative ejection count of rank "A," i.e., rank R11. The illustrated second liquid ejection head 31y is a head chip for ejecting black (K) ink, which is assumed to be used relatively frequently, and is selected from an inventory with an initial characteristic value of rank "2" and a cumulative ejection count of rank "A," i.e., rank R21. The other three head chips were constructed by selecting from an inventory with the same initial characteristic value of rank "2" and a cumulative ejection count of rank "B," i.e., rank R22. The latter three head chips are for cyan (C), magenta (M), and yellow (Y), which eject less frequently than black ink. The position where the K ink head chip will be attached is known in advance, and this position corresponds to the first position L1. The positions where the head chips for CMY inks are attached are also known in advance, and these positions correspond to the second position L2. The first position L1 and the second position L2 correspond to any of the positions where the head chips for CMY inks are arranged relative to the storage space S. This allows a head chip with a low cumulative number of ejections to be attached to a head chip with a high ejection frequency. The used head chip 300 attached to the first position L1 corresponds to the "first used head chip," and the used head chip 300 attached to the second position L2 corresponds to the "second used head chip." As mentioned above, used head chips 300 with different cumulative ejection counts exhibit similar degrees of deterioration of the piezoelectric element 60 if the usage time, reference voltage Vm, ambient temperature, etc. are the same. However, used head chips 300 with a high number of ejections tend to be more susceptible to failure than used head chips 300 with a low number of ejections because stress caused by displacement of the diaphragm 621 during ejection is more likely to act on the diaphragm 621. Therefore, the estimated lifespan of a used head chip 300 decreases as the number of ejections increases. Therefore, by using the above-mentioned mounting method, it is possible to extend the usable period of the second liquid ejection head 31y as a whole.Of course, if there are sufficient stocks of head chips of rank R21, a second-hand head chip 300 of "2A" may also be selected for the latter.

[0109] In the above configuration, a used head chip 300 with a low number of ejections is placed at the first position L1, and a used head chip 300 with a high number of ejections is placed at the second position L1. However, this is not limited to this. For example, the deterioration level of elements other than the piezoelectric element 60 of a used head chip 300 as a "first used head chip" attached at the first position L1 may be ranked lower than the deterioration level of elements other than the piezoelectric element 60 of a used head chip 300 as a "second used head chip" attached at the second position L2. For example, a head chip with a high ejection frequency undergoes more wiping and cleaning processes than a head chip with a low ejection frequency. In other words, a head chip with a high ejection frequency is more susceptible to deterioration of the water-repellent film 658 and nozzles 651 than a head chip with a low ejection frequency. Therefore, it is preferable to attach a used head chip 300 with a lower rank of deterioration of the water-repellent film or nozzles 651 to the first position L1 than a used head chip 300 attached at the second position L2.

[0110] The second liquid ejection heads 31x, 31y obtained in this way are constructed using second-hand head chips 300 removed by disassembling head units 3a etc. collected from market MRTs, and the assembled second-hand head chips 300 have sufficient performance to withstand use in market MRTs. Therefore, the second liquid ejection heads 31x, 31y to which the used head chips 300 are assembled in steps S231, S241 can be treated as liquid ejection heads with sufficient ejection capability and lifespan.

[0111] The liquid ejection device 10 is assembled by assembling the second liquid ejection head 31x or 31y to the head unit 3 and incorporating the head unit 3 into the device main body 2 (step S251). Note that step S251 may be omitted, and the second liquid ejection heads 31x, 31y may be reintroduced to the market MRT by themselves. Also, step S251 may be omitted from assembling the liquid ejection device 10, in which case the head unit 3 equipped with the second liquid ejection head 31x or 31y is reintroduced to the market MRT.

[0112] The reading device 65 may be capable of writing data, and in this case, information on the usage history of the used head chip 300 incorporated in the second liquid ejection head 31, i.e., data such as the cumulative number of ejections, is saved in at least one of the memory 201 of the second liquid ejection head 31 and the memory 203 of the head unit 3 including the second liquid ejection head 31, by connecting to the reading device 65 (step S261). Specifically, when the usage history accumulated after re-introduction to the market is stored in the memory 201 of the second liquid ejection head 31, it is preferable to save the information on the usage history of the used head chip 300 in the memory 201 of the second liquid ejection head 31. When the usage history accumulated after re-introduction to the market is stored in the memory 203 of the head unit 3 including the second liquid ejection head 31, it is preferable to save the information on the usage history of the used head chip 300 in the memory 203 of the head unit 3. In addition, since the used head chip 300 of this embodiment stores usage history in memory 200, step S261 may be omitted if the usage history accumulated after re-release on the market is to be stored in memory 200 of the used head chip 300 incorporated in the second liquid ejection head 31.

[0113] Thereafter, information about the used head chips 300 in the second liquid ejection heads 31x, 31y is registered in database DB1 as information about new used head chips 300 (step S271). When registering the used head chips 300 (step S271), the serial number of the head chip 310 is already registered in database DB1, so that data may be overwritten, or, since it has already been released on the market, it may be recorded by adding to the existing data. After the above processing, the process exits to "END" and the manufacture of the liquid ejection head is completed.

[0114] According to the method for manufacturing a liquid ejection head of the first embodiment described above, head chips 310 mounted on liquid ejection heads 31a, etc. mounted on liquid ejection devices 10a, such as printers, that have been released on the market can be collected as used head chips 300, and the collected used head chips 300 can be ranked according to their characteristic information to manufacture new liquid ejection heads, such as second liquid ejection heads 31y, etc. Therefore, there is no need to discard usable used head chips 300, which contributes to resource conservation.

[0115] Furthermore, since the second liquid ejection head 31y includes a plurality of used head chips 300 classified into different ranks, the used head chips 300 corresponding to the first used head chips and the second used head chips can be arranged at the first position L1 and the second position L2, where head chips with different ejection frequencies are used, respectively. This reduces the possibility that some of the used head chips 300 incorporated into the second liquid ejection head 31y will malfunction due to differences in frequency of use, shortening the lifespan of the second liquid ejection head 31y.

[0116] In this embodiment, used head chips 300 are ranked by combining initial characteristic values ​​at the time of manufacture that are stored in association with the serial number of the head chip 310 and a usage history relating to the degree of deterioration of the piezoelectric element 60 due to subsequent use in the market, so that the characteristics of the used head chips 300 in the newly manufactured second liquid ejection head 31y can be made appropriate for the intended use. Note that the ranking does not necessarily have to be performed by combining the initial characteristic values ​​and the usage history, and may be performed by the usage history alone, or may be performed by the usage history relating to the degree of deterioration of elements other than the piezoelectric element 60, or by combining the initial characteristic values, the usage history relating to the degree of deterioration of the piezoelectric element 60, and the usage history relating to the degree of deterioration of elements other than the piezoelectric element 60.

[0117] As described above, according to this embodiment, when configuring the second liquid ejection head 31y, the characteristic information of the used head chips 300, here sorted according to initial characteristic values ​​and usage history, is used to include used head chips 300 with different ejection performance ranks. On the other hand, as in the case of the second liquid ejection head 31x, it is also possible to align the ejection performance of the multiple used head chips 300 incorporated into the second liquid ejection head 31x. This can reduce the possibility that the lifespan of the second liquid ejection head 31x will be shortened due to variations in the ejection performance of the used head chips 300 that configure the second liquid ejection head 31x.

[0118] In this embodiment, the liquid ejection device 10 is a printer that ejects CMYK inks, so even if the ranks based on usage history are different for the used head chips 300 that make up the second liquid ejection head 31y, by using used head chips 300 with the same rank in initial characteristic values, it is easy to ensure image quality in color printing.

[0119] B. Second embodiment: Next, a second embodiment of the method for manufacturing a liquid ejection head will be described. In the second embodiment, as in the first embodiment, a head chip 310 is manufactured, and liquid ejection heads 31a and the like incorporating the head chip 310 are manufactured. Further, head units 3a and the like are assembled using the liquid ejection heads 31a, and liquid ejection devices 10a and the like are manufactured using the head units 3a and then released to the market. At this time, data such as initial characteristic values ​​is linked using the serial number of the head chip 310 and recorded in database DB1. Used head chips 300 collected from the market are ranked and stored, and the data is recorded in database DB2. Furthermore, in the second embodiment, liquid ejection heads collected from the market are designated as first liquid ejection heads 31a and the head chips 310 incorporated therein are reused as used head chips 300 to assemble second liquid ejection heads 31x and 31y. Up to this point, the process is the same as in the first embodiment.

[0120] The second embodiment differs from the first embodiment in that some of the used head chips 300 included in the first liquid ejection head 31a are not removed from the first liquid ejection head 31a but are used as they are as the second liquid ejection head 31y. In the second embodiment, some of the used head chips 300 of the first liquid ejection head 31a are used as they are, and the remaining used head chips 300 are replaced to manufacture the second liquid ejection head 31y.

[0121] FIG. 16 is a process diagram illustrating a manufacturing process for a liquid ejection head in such a case. In this process, first, as illustrated in FIG. 13, a reading device 65 is connected to the head unit 3a incorporating the first liquid ejection head 31a (step S301). The reading device 65 may be connected to the first liquid ejection head 31a. Next, the serial number (S / N) of each used head chip 300 used in the first liquid ejection head 31a is obtained from the memory 200 corresponding to the used head chip 300 (step S311). Next, data on each incorporated used head chip 300, in this case the cumulative number of ejections, which is an example of the usage history of the used head chip 300, is read (step S321).

[0122] Thereafter, the used head chips 300z that cannot be used as the second liquid ejection head 31y as they are are removed from the used head chips 300 provided in the first liquid ejection head 31a (step S331). The used head chips 300z that cannot be used as the second liquid ejection head 31y as they are are: Used head chip 300z that is known to be faulty in advance, - The cumulative number of ejections, which is an example of the usage history, is excessive, and the head chip 300z is classified as category "D", which is a non-reusable rank, for example, The used head chip 300z that has the highest degree of deterioration among the used head chips 300 of the first liquid ejection head 31a, etc. Such a used head chip 300z corresponds to the "third used head chip."

[0123] FIG. 17 illustrates the removal of a used head chip 300z, which cannot be used as the second liquid ejection head 31y as is, from the first liquid ejection head 31a. The first liquid ejection head 31a is shown at the left end of the middle row in the figure. Of the four used head chips 300 incorporated into this first liquid ejection head 31a, the head chip designated by reference numeral 300z has a cumulative ejection count in category "D" and is therefore the third used head chip 300z to be removed. Once the head chip 300z to be removed has been identified, a database DB1 related to the already ranked used head chips 300 is accessed, and the previously read serial number is used to obtain from the database DB1 the initial characteristic values ​​and other information of the used head chips 300 incorporated into the first liquid ejection head 31a, including the used head chip 300z to be removed (step S341). The above processes (steps S301 to S341) are the same as those in the ranking process (FIG. 12, steps S101 to S141), except for the process of removing the head chips 300z (step S331). That is, in the second embodiment, ranking of the used head chips 300 provided in the first liquid ejection head 31a is performed as part of the process of selecting and assembling the used head chips 300, which will be described later. In this respect, the second embodiment differs from the first embodiment.

[0124] Since the ejection performance of the removed used head chip 300z has been identified through the above process, the database DB2 is accessed (step S401) to determine whether a used head chip 300 that can replace the removed used head chip 300x is available in the ranked inventory (step S411). If a used head chip 300 that can be installed in place of the used head chip 300z is available in the ranked inventory, that used head chip 300 is selected (step S421). If not, a replacement head chip 310 is selected from new head chips (step S431). In the example shown in FIG. 17, the used head chip that replaces the removed used head chip 300 is a used head chip 300 that has the same rank in initial characteristic values ​​as the used head chips 300 other than the removed used head chip 300z and is deemed to have a low cumulative ejection count, that is, a used head chip 300 with rank R21 (depicted as ejection performance "2A").

[0125] When selecting such used head chips 300, the reason for selecting a used head chip 300 with a high usage history ranking may be that the head chip located at that position has been used frequently. For example, in FIG. 17, if the used head chip 300 at the left end of the second liquid ejection head 31y is ejecting K ink, this position corresponds to the first position L1, and the used head chip 300 located at this position corresponds to the "first used head chip." The used head chips 300 at positions other than the first position of the second liquid ejection head 31y eject CMY inks, and therefore have a lower expected ejection frequency compared to the used head chips 300 that eject K ink. These positions correspond to the second position L2, and the head chips located at these positions correspond to the "second used head chip." The head chip with a high ejection frequency located at the first position L1 is not limited to one that ejects K ink. For example, if the head chip performs solid printing (solid ejection) with a high operating rate (duty), such as white ink, pre-treatment liquid used before processing the medium surface, or post-treatment liquid such as overcoat, the ejection frequency will be higher than other head chips, and it will correspond to the first used head chip.

[0126] Thereafter, the selected used head chip 300 or head chip 310 is assembled in the location where the used head chip 300z was removed from the first liquid ejection head 31a (step S441). As a result, the liquid ejection head to which the selected used head chip 300 is assembled has one or more used head chips 300 to be assembled into the second liquid ejection head 31y selected from the multiple used head chips so that it includes multiple used head chips 300 classified into different ranks, and the second liquid ejection head 31y is assembled.

[0127] This second liquid ejection head 31y is returned to the head unit 3a, and the liquid ejection device 10 is assembled (step S451). As in step S261 in the first embodiment, when the second liquid ejection head 31y is returned to the head unit 3a, a reading device 65 is connected, and information on the usage history of the head chip (used head chip 300 or new head chip 310) installed in place of the removed used head chip 300, i.e., data such as the cumulative number of ejections, is saved in at least one of memories 201 and 203 (step S461). Thereafter, the information on this head chip is linked to the serial number S / N and registered in database DB1 (step S471).

[0128] When registering the head chip (step S471), if a used head chip 300 is used, its serial number is already registered in database DB1, so that data may be overwritten, or, since it is a product that has already been released on the market, it may be recorded by adding to the existing data. If a new head chip 310 is used, it is registered in database DB1 as new head chip data. After the above processing, the process exits to "END" and the manufacturing of the liquid ejection head, which involves replacing the head chip, is completed. In the above processing, the first liquid ejection head 31a is manufactured as the second liquid ejection head 31y by removing the used head chip 300z, which cannot be used as is, and incorporating the new used head chip 300 together with the other used head chips 300.

[0129] According to the method for manufacturing a liquid ejection head of the second embodiment described above, used head chips 300 that have been installed in printers or the like that have been released to the market are collected and ranked according to their characteristics. The second liquid ejection head 31y can be manufactured by removing some of the used head chips 300 from the first liquid ejection head 31a and replacing them with head chips of a different rank. This eliminates the need to discard usable head chips, contributing to resource conservation. Since the used head chips 300 are ranked based on a combination of their initial characteristic values ​​and the cumulative number of ejections they have performed since then, the characteristics of the head chips in the manufactured second liquid ejection head 31y can be tailored to the desired specifications.

[0130] In the method of the second embodiment, all head chips except the defective one are used as they are, so only some of the head chips need to be replaced. This reduces the number of manufacturing processes required. Other effects are the same as those of the first embodiment.

[0131] As the used head chip 300 to be incorporated into the second liquid ejection head 31x, a used head chip 300 (shown as ejection performance "2B") having a similar degree of deterioration to the used head chip 300 other than the removed used head chip 300z may be selected, as shown in Figure 18.

[0132] 19, from among the used head chips 300 other than the used head chip 300z removed from the first liquid ejection head 31a, used head chips 300 that have a higher degree of deterioration or a higher number of ejections than the used head chip 300 that ejects K ink may be selected. In the example shown, the used head chips 300 other than the removed used head chip 300z include used head chips 300 that have different first ranks C1, which are rankings for the degree of deterioration or the number of ejections, but the same second rank C2, which is rankings for the initial characteristic values, that is, two used head chips 300 of rank R22 (illustrated as ejection performance "2B") and one used head chip 300 of rank R21 (illustrated as ejection performance "2A"). Here, the used head chip 300 of rank R21 is an example of a “first used head chip,” one of the two used head chips 300 of rank R22 is an example of a “second used head chip,” and the used head chip 300z having a first rank C1 lower than the used head chip 300 of rank R22 is an example of a “third used head chip.” In other words, the used head chip 300 incorporated into the second liquid ejection head 31x in the selection process is a used head chip 300 that ejects C ink.

[0133] C. Other Embodiments: (1) In the above embodiments, the manufactured liquid ejection heads are described as being used in printers, but the manufacturing method of the present disclosure can be applied to the manufacture of liquid ejection heads that eject various liquids, such as ink, water, alcohol, liquid fuel, chemical liquids, etc. Liquid ejection is not limited to methods using piezoelectric elements, such as piezo elements, and various other methods can be used, such as a bubble jet method using a heater or a method using a pump.

[0134] (2) In each of the above embodiments, data regarding characteristic information was obtained by reading the usage history of the used head chip 300 from memory 200 and performing first ranking C1 based on that usage history. However, it is also possible to remove the used head chip 300, obtain characteristic information based on detecting the condition of the used head chip 300 using a measuring device, and perform first ranking C1 based on the obtained characteristic information.

[0135] An example of a process for acquiring characteristic information of used head chips by measurement and ranking them is shown in Figure 20. This ranking process differs from the ranking process shown in Figure 12 in that the removal process (S171) is performed before the ejection performance storage process (S161). The used head chips 300 removed in the removal process (S171) are attached to a measuring device, and the state of the used head chips 300 is measured (step S175). Then, the used head chips 300 are ranked based on the characteristic information acquired based on the measured state of the used head chips 300 (step S177), and the data of the ranked used head chips 300 is stored (step S161). Note that sorting and storing the used head chips 300 (step S181) is performed last, similar to the ranking process of the first embodiment.

[0136] As explained in detail in the first and second embodiments, the characteristic information of the used head chip 300, such as the ejection performance, can be used to rank the degree of deterioration of the piezoelectric element 60 using parameters such as the initial characteristic value, the cumulative number of ejections as a usage history, and the environmental temperature. However, the degree of deterioration of the piezoelectric element 60 can also be ranked using the ejection performance obtained by measuring the displacement of the diaphragm 621, which is an example of the state of the used head chip 300, when a standard drive signal COM is applied to the piezoelectric element 60. Of course, to predict the subsequent deterioration of the ejection performance, it is preferable to consider not only the ejection performance obtained by measurement but also the initial characteristic value. Furthermore, it is preferable to predict the subsequent deterioration of the ejection performance by using at least one of the usage history, such as the cumulative number of ejections, the reference voltage Vm of the drive waveform of the drive signal COM, and the environmental temperature, in addition to the initial characteristic value. Furthermore, the degree of deterioration of elements other than the piezoelectric element 60 estimated based on the usage history in the above-mentioned embodiments can also be measured in a similar manner. For example, the degree of deterioration of the water-repellent film 658 can be detected by measuring the contact angle (wettability) of pure water on the surface of the nozzle plate 650. In other words, this contact angle is an example of the state of the used head chip 300.

[0137] (3) In the first embodiment, the process of removing the used head chip 300 from the first liquid ejection head 31 was carried out after obtaining the usage history, etc. However, if the characteristic information of the used head chip 300 is obtained by measurement as described above, or if a dedicated reading device is prepared and the information is read directly from the memory 200 provided in the used head chip 300, the disassembly process may be carried out before reading the usage history.

[0138] (4) Memory 200, which stores the usage history of used head chip 300 used in each embodiment, can be a semiconductor memory, a magnetic memory, or the like. It is preferable to use a non-volatile memory for the semiconductor memory, which retains data even when power is lost, such as an EEPROM, flash memory, or a battery-backed SRAM. The same memory as memory 200 can be used for memories 201 and 203.

[0139] As in the above embodiment, the usage history of the used head chip 300 may be stored in the memory 200 provided in the head chip 310, or the usage history of at least two or more used head chips 300 may be stored in the memory 201 of the first relay substrate 363 connected in common to at least two or more of the multiple head chips 310 of one liquid ejection head 31. In this case, all of the multiple head chips 310 of one liquid ejection head 31 may be connected to the first relay substrate 363, or two or more head chips 310 that are part of the multiple head chips 310 of one liquid ejection head 31 may be connected in common to the first relay substrate 363. When storing the usage history of the used head chips 300 in the memory 201 of the first relay board 363, by connecting the reading device 65 to the connector 27b of the second relay board 335, the usage history of each used head chip 300 provided in the multiple first liquid ejection heads 31 connected to the second relay board 335 can be collectively read out sequentially from the memory 201 provided in each first liquid ejection head 31. Note that 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 the multiple used head chips 300 provided in one first liquid ejection head 31 can be collectively read out sequentially from the memory 201.

[0140] Alternatively, the usage history of the used head chips 300 included in at least two or more of the multiple liquid ejection heads 31 of one head unit 3 may be stored in the memory 203 of the second relay substrate 335 that is commonly connected to at least two or more of the multiple liquid ejection heads 31 of one head unit 3. In this case, all of the multiple liquid ejection heads 31 of one head unit 3 may be connected to the second relay substrate 335, or two or more liquid ejection heads 31 that are part of the multiple liquid ejection heads 31 of one head unit 3 may be connected to the second relay substrate 335. When storing the usage history of the used head chips 300 in the memory 203 of the second relay board 335, by connecting the reading device 65 to the connector 27b of the second relay board 335, the usage history of each used head chip 300 provided in the multiple first liquid ejection heads 31 connected to the second relay board 335 can be collectively read out sequentially from the memory 203 provided in the head unit 3.

[0141] Furthermore, in the above embodiment, the memory 200 is provided on the flexible wiring board 311. However, the memory 200 may be built into an element other than the flexible wiring board 311 of the head chip 310, and part or all of the circuitry for accessing the memory 200 may be provided on the flexible wiring board 311 or the first relay board 363. Furthermore, information regarding the usage history may be stored in the memory 203 provided on the second relay board 335. In this case, the usage histories of the multiple head chips 310 connected to the multiple liquid ejection heads 31 connected to the second relay board 335 can be read all at once or partially at once. Furthermore, the usage history of the used head chip 300 may be stored in two or more of the memories 200, 201, and 203 by dividing the data. Furthermore, at least part of the usage history data may be stored in duplicate in two or more of the memories 200, 201, and 203, and one of the duplicated data may be treated as backup data. Furthermore, in the second embodiment described above, if the memory 201 of the second liquid ejection head 31 stores the usage history of multiple used head chips 300, including the used head chip 300z to be removed, then in step S461, only the usage history of the used head chip 300 incorporated into the second liquid ejection head 31 may be overwritten and saved in the memory 201.

[0142] (5) 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.

[0143] Processes X1 to X3 correspond to the process up to the supply of new head chips to the market, processes Y1 to Y3 correspond to the collection and management of used head chips, 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.

[0144] (6) In each of the above embodiments, some of the configurations realized by hardware may be replaced with software. At least a portion of the configurations realized by software may also be realized by a discrete circuit configuration. Furthermore, when some or all of the functions of the present disclosure are realized 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.

[0145] (7) In each of the above embodiments, the liquid ejection device 10 includes a head unit 3 including a plurality of liquid ejection heads 31. However, this is not limiting. The liquid ejection device 10 may include a single liquid ejection head 31, i.e., it may not include a head unit 3.

[0146] (8) 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 a used head chip to be incorporated into the second liquid ejection head 31 based on the first ranking C1, which classifies the used head chips 300 into multiple ranks based on at least one of the degree of deterioration of the piezoelectric element 60, the degree of deterioration of the adhesive, and the degree of deterioration of the water-repellent film 658.

[0147] (9) In the second embodiment described above, as shown in Figures 17 to 19, the number of used head chips 300 to be incorporated into the second liquid ejection head 31 in the assembly process, in other words, the number of used head chips 300 selected in the selection process as the used head chips 300 to be incorporated into the second liquid ejection head 31, was one, but it may be multiple.

[0148] (10) 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.

[0149] (11) 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 may be the intermediate potential Vc of the drive signal COM and the reference potential Vbs of the reference voltage signal, since the reference voltage Vm can be calculated from the intermediate potential Vc and the reference potential Vbs.

[0150] 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]

[0151] 3, 3a, 3b...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, 10a, 10b...liquid ejection device, 15-19...cable, 25a, 26a, 27a, 27b, 28a, 28b, 29a...connector, 30...drive circuit board, 31, 31a, 31b, 31c...liquid ejection head, 31a...first 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 roller, 52a, 52b...follower roller, 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, 2 02...selector, 210...drive signal selection control circuit, 300...used head chip, 300z...third 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...second 1 relay substrate, 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...protection 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 method for manufacturing a liquid ejection head, in which a second liquid ejection head is manufactured by reusing some of a plurality of used head chips provided in one or a plurality of first liquid ejection heads, a first ranking step of classifying the used head chips included in the one or more first liquid ejection heads into a plurality of ranks based on characteristic information of the used head chips included in the one or more first liquid ejection heads; a selection step of selecting one or more used head chips to be incorporated into the second liquid ejection head from among the plurality of used head chips so that the second liquid ejection head includes the plurality of used head chips classified into different ranks in the first ranking step; an assembly process of incorporating the one or more used head chips selected in the selection process into the second liquid ejection head; A method for manufacturing a liquid ejection head comprising:

2. a second ranking step of classifying the plurality of used head chips included in the one or more first liquid ejection heads into a plurality of ranks based on the initial characteristic values ​​of the plurality of used head chips; the selecting step selects the one or more used head chips to be incorporated into the second liquid ejection head so that the plurality of used head chips included in the second liquid ejection head include only the plurality of used head chips classified into the same rank in the second ranking step. The method for manufacturing a liquid ejection head according to claim 1 .

3. the selecting step selects all of the used head chips provided in the second liquid ejection head to be incorporated into the second liquid ejection head so that the used head chips provided in the second liquid ejection head include the used head chips classified into different ranks in the first ranking step. The method for manufacturing a liquid ejection head according to claim 1 .

4. the selecting step selects the one or more used head chips to be incorporated into the second liquid ejection head as part of all the used head chips included in the second liquid ejection head so that the used head chips included in the second liquid ejection head include the used head chips classified into different ranks in the first ranking step. The method for manufacturing a liquid ejection head according to claim 1 .

5. the plurality of used head chips of the second liquid ejection head include a first used head chip and a second used head chip that is classified in the first ranking step into a rank having a higher degree of deterioration or a higher number of ejections than the first used head chip, a removing step of removing, from the first liquid ejection head, a third used head chip that has been classified in the first ranking step as having a higher degree of deterioration or a higher number of ejections than the second used head chip, the selecting step selects the first used head chip as the one or more used head chips to be incorporated into the second liquid ejection head. The method for manufacturing a liquid ejection head according to claim 4 .

6. the plurality of used head chips of the second liquid ejection head include a first used head chip and a second used head chip that is classified in the first ranking step into a rank having a higher degree of deterioration or a higher number of ejections than the first used head chip, a removing step of removing, from the first liquid ejection head, a third used head chip that has been classified in the first ranking step as having a higher degree of deterioration or a higher number of ejections than the second used head chip, the selecting step selects the second used head chip as the one or more used head chips to be incorporated into the second liquid ejection head. The method for manufacturing a liquid ejection head according to claim 4 .

7. one of the plurality of ranks divided in the first ranking step includes a non-reusable rank for classifying used head chips that exceed a usage limit; The method for manufacturing a liquid ejection head according to claim 1 .

8. the plurality of used head chips of the second liquid ejection head include a first used head chip arranged at a first position of the second liquid ejection head and a second used head chip arranged at a second position of the second liquid ejection head, a discharge frequency of the first used head chip arranged at the first position of the second liquid discharge head is higher than a discharge frequency of the second used head chip arranged at the second position of the second liquid discharge head, the first ranking step classifies the first used head chip into a rank having a lower degree of deterioration or less information about the number of ejections than a rank to which the second used head chip belongs, The method for manufacturing a liquid ejection head according to claim 1 .

9. The characteristic information is acquired based on the usage history of the used head chip. The method for manufacturing a liquid ejection head according to claim 1 .

10. The method for manufacturing a liquid ejection head according to claim 9 , wherein the usage history includes information regarding the number of times liquid has been ejected from the nozzles of the used head chip.

11. the usage history further includes at least one of information regarding a reference voltage of a drive waveform applied to the used head chip and information regarding an environmental temperature when the used head chip was used; The method for manufacturing a liquid ejection head according to claim 10.

12. The usage history is [1] Information about the number of times the nozzle surface of the used head chip has been wiped; [2] Information about the number of cleaning processes performed on the used head chip; [3] Information about the elapsed time since the used head chip was filled with liquid, and [4] Information about the type of liquid supplied to the used head chip; The method for manufacturing a liquid ejection head according to claim 9 , comprising at least one of the steps of:

13. The method for manufacturing a liquid ejection head according to claim 1 , wherein the characteristic information is acquired based on detecting the state of the used head chip.

14. The method for manufacturing a liquid ejection head according to claim 1 , further comprising a removing step of removing the used head chip from the first liquid ejection head.

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