JP6156524B2 - Droplet discharge device - Google Patents

Description

  The present invention relates to a droplet discharge device that discharges droplets for each discharge mechanism.

  It is known to detect abnormality of a nozzle in a printer that ejects droplets by driving a drive element for each of a plurality of nozzles (see Patent Document 1). In Patent Document 1 (paragraph 0054), when there is a nozzle abnormality detection command, the nozzles to be inspected are selected one by one. Then, a driving voltage is applied to the driving element corresponding to the nozzle to be inspected to discharge a droplet, and it is determined whether or not the residual vibration is normal when the droplet is discharged. By repeating the above processing, it is determined whether or not all nozzles are abnormal in order.

JP 2005-305992 A

However, there has been a problem that a normal print job cannot be executed unless the process of determining whether or not all nozzles are abnormal is completed. Further, since it is impossible to determine whether or not the nozzle is abnormal during execution of the print job, there is a problem that abnormal ink droplets continue to be ejected until the print job is completed.
An object of the present invention has been made in view of the above problems, and an object of the present invention is to provide a droplet discharge apparatus that continues a print job while suppressing the influence of an abnormality of the discharge mechanism.

  In order to solve the above problems, a droplet discharge apparatus of the present invention has a discharge head including a plurality of discharge mechanisms including a drive element that discharges droplets from a nozzle. The ejection head includes ejection availability data acquisition means, abnormality determination means, and abnormality handling means. The discharge enable / disable data acquisition unit acquires discharge enable / disable data indicating whether or not to discharge droplets for each of the plurality of discharge mechanisms. The abnormality determination unit determines whether or not the discharge mechanism is abnormal when discharging droplets based on the discharge enable / disable data acquired for the Ath (A is a natural number). The abnormality handling means is an abnormal ejection mechanism that is a ejection mechanism in which the ejection availability data acquired in the (A + B) th (B is a natural number) within the same print job as the Ath ejection availability data is determined to be abnormal. When the normal discharge mechanism, which is a discharge mechanism that has not been determined to be abnormal, indicates that the droplet is not discharged, the normal discharge mechanism discharges the droplet instead of the abnormal discharge mechanism.

  In the above-described configuration, the abnormality handling unit is configured to use the normal discharge mechanism instead of the abnormal discharge mechanism when the discharge availability data indicates that the abnormal discharge mechanism discharges the droplet and the normal discharge mechanism does not discharge the droplet. A droplet is discharged. That is, the abnormality handling unit causes the normal discharge mechanism that can normally discharge the droplets to discharge the droplets instead of the abnormal discharge mechanism that cannot normally discharge the droplets. Thereby, even when an abnormal discharge mechanism exists, it is possible to prevent abnormal droplets from being discharged. In addition, when an abnormal ejection mechanism is detected when a droplet is ejected based on the Ath ejection availability data, the droplet is ejected based on the (A + B) th ejection availability data in the same print job. At the stage of discharging, the droplets can be discharged to the normal discharge mechanism instead of the abnormal discharge mechanism. Accordingly, it is possible to prevent abnormal droplets from being continuously discharged from the abnormal discharge mechanism until the print job is completed. Also, there is no need to cancel the print job. Furthermore, since the abnormality determination unit and the abnormality handling unit are provided in the ejection head, it is not necessary to generate ejection propriety data for causing the normal ejection mechanism to eject droplets instead of the abnormal ejection mechanism. Therefore, it is not necessary to notify the determination result of the abnormal ejection mechanism to the main substrate or the like outside the ejection head so as to generate ejection propriety data that causes the normal ejection mechanism to eject droplets instead of the abnormal ejection mechanism. There is no need to provide a signal line.

  In addition, the abnormality handling unit may cause the (A + 1) th discharge enable / disable data in the same print job as the Ath discharge enable / disable data to cause the abnormal discharge mechanism to discharge a droplet and the normal discharge mechanism to not discharge a droplet. In this case, the normal ejection mechanism may eject droplets instead of the abnormal ejection mechanism. That is, at the stage of discharging the droplet based on the discharge availability data next to the A-th discharge availability data where the abnormal discharge mechanism is detected, the normal discharge mechanism may discharge the droplet instead of the abnormal discharge mechanism. . The smaller the number of times an abnormal droplet is ejected from the abnormal ejection mechanism, the better the quality of the product formed by the droplet.Therefore, abnormal ejection is performed in the ejection based on the next ejection availability data detected by the abnormal ejection mechanism. It is desirable to cause the normal ejection mechanism to eject droplets instead of the mechanism.

  Further, in each of the plurality of ejection mechanisms, the ejection head is connected in series with the drive voltage source and the drive element, and determines whether or not to apply a drive voltage for ejecting droplets to the drive element based on ejection propriety data. You may provide the application switch which switches. Then, the abnormality determination unit obtains an inspection voltage generated between both ends of the application switch for applying a driving voltage to the driving element in each of the plurality of ejection mechanisms, and whether or not the ejection mechanism is abnormal based on the inspection voltage. May be determined. When a drive voltage is applied to the drive element, both ends of the application switch are conducted, and a specific resistance is generated between both ends of the application switch. Therefore, a current flows between both ends of the application switch in accordance with the residual vibration of the drive element, and an inspection voltage proportional to the current is generated. That is, the abnormality determination unit can obtain an inspection voltage corresponding to the residual vibration of the drive element, and can determine whether or not the ejection mechanism is abnormal based on the inspection voltage. Here, since the inspection switch is provided in each of the plurality of ejection mechanisms, the amount of current flowing through the inspection switch can be suppressed. Therefore, the inspection switch can be realized with a small current element, and the ejection head including the inspection switch can be downsized. Further, since the inspection switch is provided for each ejection mechanism, the voltage generated by the residual vibration of the drive element in the ejection mechanism that is not the inspection target can be interrupted by the inspection switch. Accordingly, the droplets can be ejected by the ejection mechanism that is not the inspection target without interfering with the inspection of the ejection mechanism, and the ejection mechanism can be inspected even during a period during which an arbitrary print job is executed.

It is a block diagram of a printer. (2A) is a schematic diagram of the ejection mechanism, and (2B) is a circuit diagram of the ejection head. (3A) is a diagram showing the nozzle, and (3B) is a timing chart showing the operation of the switch. (4A) is a graph of a combined inspection voltage, and (4B) is a diagram showing an inspection table. It is a flowchart of an inspection process. (6A) is a flowchart of the abnormality handling process, and (6B) is a flowchart of the inspection process. (7A) is a circuit diagram of the drive circuit of the first modification, and (7B) is a timing chart showing the operation of the switch of the first modification. (8A), (8B) is a figure which shows the test | inspection table of the modification 1. FIG.

Here, embodiments of the present invention will be described in the following order.
(1) First embodiment:
(1-1) Printer configuration:
(1-2) Inspection process:
(1-3) Abnormal response processing:
(2) Modification 1:
(3) Other variations:

(1) Printer configuration:
FIG. 1 is a block diagram showing a configuration of a printer 1 as a droplet discharge device according to an embodiment of the present invention. The printer 1 includes an ejection head 10 and a main substrate 20. The main board 20 includes a discharge availability data generation circuit 21 and a drive voltage generation circuit 22. The discharge enable / disable data generation circuit 21 is a circuit that generates discharge enable / disable data SI specifying whether or not to discharge ink droplets as droplets for each of a plurality of discharge mechanisms provided in the discharge head 10. The discharge propriety data generation circuit 21 outputs nozzle selection data obtained by serially combining the discharge propriety data SI to permutations of a plurality of discharge mechanisms to the discharge head 10. The discharge availability data generation circuit 21 generates discharge enable / disable data SI for each of a plurality of discharge timings, and outputs the discharge enable / disable data SI in the order of discharge timing. The ejection timing is a timing at which a plurality of ejection mechanisms provided in the ejection head 10 simultaneously eject ink droplets during a print job execution period. Further, the ejection propriety data generation circuit 21 generates a latch signal LAT and a switching signal CH and outputs them to the ejection head 10. The latch signal LAT is a timing signal for defining the ejection timing. The switching signal CH is a timing signal for defining a period in which the ejection timing is subdivided.

  The drive voltage generation circuit 22 is a circuit (drive voltage source) that generates a drive voltage COM for driving the piezo element 12 as a drive element included in the ejection head 10. The drive voltage generation circuit 22 includes a D / A conversion unit that generates a drive voltage COM based on digital data that defines a voltage pattern of the drive voltage, and an amplification unit that amplifies the D / A converted drive voltage COM. . The drive voltage COM output from the drive voltage generation circuit 22 is input to the application switch P of the ejection head 10.

  FIG. 2A is a schematic diagram illustrating a structure of a discharge mechanism provided in the discharge head 10, and FIG. 2B is a circuit diagram of a part of the discharge head 10. As shown in FIG. 1, the ejection head 10 includes a head IC 11, a piezo element 12, an ink chamber 13, a nozzle 14, and a diaphragm 15. The ejection head 10 includes a plurality of (not shown) ejection mechanisms, and each of the plurality of ejection mechanisms includes a piezo element 12, an ink chamber 13, a nozzle 14, and a diaphragm 15 as shown in FIG. 2A. In this embodiment, 90 ejection mechanisms are provided for each ink color of C (cyan), M (magenta), Y (yellow), and K (black), and a total of 360 (= N) ejection mechanisms are provided. ing. The piezo element 12 is a piezoelectric element. By applying the drive voltage COM to the piezo element 12, the piezo element 12 is mechanically distorted, and the diaphragm 15 constituting the wall surface of the ink chamber 13 filled with ink is vibrated. As a result, the pressure in the ink chamber is increased and decreased, and the ink in the ink chamber is ejected from the nozzle 14 as ink droplets. The application switch P is a switch that switches whether to apply the drive voltage COM to the piezo element 12 in each of the plurality of ejection mechanisms. That is, the application switch P selectively applies the drive voltage COM to the piezo elements 12 corresponding to the nozzles 14 designated when ink droplets are ejected by the ejectability data SI.

  As shown in FIG. 2B, in each of the plurality of ejection mechanisms (one-dot chain lines), the wiring for transmitting the drive voltage COM, the piezo element 12, the application switch P, and the ground are connected in series. The application switch P has a source-drain connected in series between the piezo element 12 and the ground. Accordingly, when the application switch P is turned on, the drive voltage COM is applied to the piezo element 12, and when the application switch P is turned off, the drive voltage COM is not applied to the piezo element 12. In addition, the application switch P has a resistance of a size inherent to the element between the source and the drain in the ON state. Accordingly, when a current flows from the piezo element 12 during a period in which the application switch P is on, a voltage proportional to the current (hereinafter referred to as a test voltage) is generated between the source and drain of the application switch P.

  In each of the plurality of ejection mechanisms, an inspection switch M1 is connected between the piezo element 12 and the application switch P. In each of the plurality of ejection mechanisms, the application switch P and the inspection switch M1 are connected to the same data output terminal of the application switch controller 11c. Accordingly, in each of the plurality of ejection mechanisms, the application switch P and the inspection switch M1 are controlled by a control signal based on the same ejection propriety data SI. As shown in FIG. 2B, three terminals of the inspection switch M1 that are not connected to the application switch P are electrically coupled to each other, and the three inspection switches M1 are commonly connected to the inspection switch M2. . A group G indicated by a broken line is formed by 3 (= M) ejection mechanisms to which the application switch P is connected via the inspection switch M1 with respect to the common inspection switch M2. That is, in the present embodiment, the group G is configured by 3 (= M) ejection mechanisms. The inspection switch M2 is provided for each group G, and each of the plurality of inspection switches M2 is connected to the inspection terminal T of the pulse converter 11e by a common wiring. When the inspection switch M2 is turned on and all the S (natural number of 3 (= M) or less) inspection switches M1 connected to the inspection switch M2 are turned on, the S inspection switches M1 are respectively connected. The combined inspection voltage MV, which is a combination of the inspection voltages between the source and drain of the S application switches P, is input to the inspection terminal T of the pulse converter 11e. Note that the voltage drop due to the resistance in the inspection switches M1 and M2 is ignored. Coupling means that voltage waveforms of a plurality of inspection voltages are combined at the coupling inspection voltage MV.

  As shown in FIG. 1, the head IC 11 includes a switch control data generation unit 11a, an abnormality handling unit 11b, an application switch control unit 11c, an application switch P, an inspection switch control unit 11d, inspection switches M1 and M2, a pulse conversion unit 11e, and a cycle. A measurement unit 11f, a voltage determination unit 11g, and an abnormality determination unit 11h are provided. The head IC 11 is an SOC (System on a chip) or the like in which a digital signal processing circuit, an analog signal processing circuit, a RAM, and the like are included in a single semiconductor integrated circuit.

  The switch control data generation unit 11a as the discharge availability data acquisition unit acquires the discharge enable / disable data SI at each discharge timing, and outputs the discharge enable / disable data SI to the subsequent abnormality handling unit 11b. The abnormality handling unit 11b causes the abnormal ejection mechanism, in which the ejection availability data SI is determined to be abnormal by an inspection process to be described later, to eject the ink droplet, and causes the ink ejection to the normal ejection mechanism, which is determined to be normal. When it is indicated that the ejection is not performed, the ejection propriety data SI is corrected. That is, the abnormality handling unit 11b corrects the ejection enable / disable data SI so as to cause the normal ejection mechanism to eject ink droplets instead of the abnormal ejection mechanism, and outputs the data to the subsequent application switch control unit 11c. In this embodiment, the abnormality handling unit 11b causes the normal ejection mechanism adjacent to the abnormal ejection mechanism to eject ink droplets instead of the abnormal ejection mechanism.

  FIG. 3A is a diagram showing the arrangement of the nozzles 14 on the surface (nozzle surface) facing the recording medium in the head IC 11. In this embodiment, the head IC 11 is a line head, and is provided with two nozzle rows for each ink color in which a plurality of nozzles 14 are arranged perpendicular to the conveyance direction (printing direction) of the recording medium. In each nozzle row, the arrangement interval of the nozzles 14 in the direction orthogonal to the printing direction is constant. Further, the position of the nozzle 14 in the direction orthogonal to the printing direction is shifted by a half of the arrangement interval between the nozzle rows adjacent in the printing direction. The normal ejection mechanism adjacent to the abnormal ejection mechanism ejects ink droplets of the same ink color as the abnormal ejection mechanism and has the shortest distance from the nozzle 14 (white circle) included in the abnormal ejection mechanism in the direction orthogonal to the printing direction. It is two discharge mechanisms provided with the nozzle 14 (double circle) used as (half the arrangement interval).

  The abnormality handling unit 11b acquires a determination table D2 indicating whether each of the plurality of ejection mechanisms is abnormal at each ejection timing in the print job, and ejects the ejection mechanism that ejects ink droplets at the ejection timing. It specifies based on the availability data SI. When the ejection mechanism that ejects ink droplets is an abnormal ejection mechanism, the ink ejection is caused to be ejected by a normal ejection mechanism adjacent to the abnormal ejection mechanism instead of the abnormal ejection mechanism. The abnormality determination unit 11h updates the determination table D2 for each ejection timing in the print job. Accordingly, at the (A + 1) th ejection timing, the abnormality handling unit 11b causes the normal ejection mechanism to eject ink droplets instead of the abnormal ejection mechanism that is abnormal by the abnormality determination unit 11h at the Ath ejection timing. Become. Since the discharge availability data SI is output to the discharge mechanism at each discharge timing, the piezo element 12 of the discharge mechanism is controlled based on the Ath discharge availability data SI at the Ath discharge timing in the print job. Become.

  The application switch control unit 11c includes a shift register that restores the discharge enable / disable data SI for each discharge mechanism by performing parallel conversion on the nozzle selection data serially coupled to the discharge enable / disable data SI. That is, the application switch control unit 11c has a plurality of registers corresponding to each of the plurality of ejection mechanisms, and shifts the nozzle selection data for each predetermined clock in the plurality of registers, thereby causing the plurality of registers to be registered. The discharge availability data SI is held. Then, the application switch controller 11c controls the control signal at the data output terminal to which the application switch P is connected based on the discharge availability data SI held in each of the plurality of registers in synchronization with the latch signal LAT and the switching signal CH. Is controlled to 1 or 0. Thereby, in each of the plurality of ejection mechanisms, the application switch P is turned on (control signal: 1) and turned off (control signal: 0), and whether or not the ink droplets are ejected by the piezo element 12 is switched.

  FIG. 3B is a timing chart showing the operation of the drive voltage COM and the switches P, M1, and M2. In the present embodiment, the drive voltage generation circuit 22 performs ejection pulses for driving the piezo elements 12 so as to eject ink droplets at each ejection timing, and piezo so that the diaphragm 15 slightly vibrates to the extent that ink droplets are not ejected. A drive voltage COM including a fine vibration pulse for driving the element 12 is generated. Note that the potential of the voltage pattern generated by the drive voltage generation circuit 22 is a known reference potential VS in a period excluding the output period of the ejection pulse and the output period of the fine vibration pulse. The ejection timing is a period between timings when the pulse of the latch signal LAT rises. The switching signal CH is a timing signal that rises in the middle of the ejection timing and defines the first half and the second half of the ejection timing. The drive voltage COM has a discharge pulse in the first half of the discharge timing, and has a fine vibration pulse in the second half of the discharge timing.

  When the discharge enable / disable data SI for discharging ink droplets is input, the application switch controller 11c turns on the application switch P and the inspection switch M1 of the discharge mechanism in the first half of the discharge timing and turns off in the second half of the discharge timing. In addition, the signal level of the control signal at the data output terminal is controlled based on the discharge availability data SI. That is, the signal level of the control signal at the data output terminal corresponding to the ejection mechanism that ejects ink droplets is set to 1 in the first half of the ejection timing and 0 in the second half of the ejection timing. Thereby, an ejection pulse can be applied to the piezo element 12 in the first half of the ejection timing, and ink droplets can be ejected. On the other hand, when the discharge enable / disable data SI that does not discharge ink droplets is input, the application switch control unit 11c turns off the application switch P and the inspection switch M1 of the discharge mechanism in the first half of the discharge timing and turns on in the second half of the discharge timing. As described above, the signal level of the control signal at the data output terminal is controlled based on the discharge availability data SI. That is, the signal level of the control signal at the data output terminal corresponding to the ejection mechanism that does not eject ink droplets is 0 in the first half of the ejection timing and 1 in the second half of the ejection timing. As a result, a fine vibration pulse is applied to the piezo element 12 in the latter half of the discharge timing, and the vibration plate 15 can be vibrated to the extent that ink droplets are not discharged. Therefore, even in an ejection mechanism that does not eject ink droplets, ink stagnation in the ink chamber 13 can be prevented.

  As shown in FIG. 1, the switch control data generation unit 11a generates inspection control data SG and outputs the inspection control data SG to the inspection switch control unit 11d. As shown in FIG. 2B, the inspection switch control unit 11d converts the serial data of the inspection control data SG into parallel data and outputs the inspection control data SG to the inspection switch M2 provided corresponding to the plurality of groups G. Contains registers. The switch control data generation unit 11a selects one inspection target group G for each ejection timing, and generates inspection control data SG so that only the inspection switch M2 corresponding to the group G is turned on. Therefore, the inspection voltage generated between the source and drain of the application switch P of 3 (= M) or less S discharge mechanisms constituting the inspection target group G is coupled to the inspection terminal T of the pulse converter 11e. The combined inspection voltage MV is input. The switch control data generation unit 11a can select the same group G as an inspection object continuously over a plurality of ejection timings.

  As shown in FIG. 3B, the inspection switch M2 corresponding to the group G to be inspected is controlled based on the inspection control data SG so as to be turned on in the period from the end of the ejection pulse output period to the end of the first half of the ejection timing. Is done. As a result, it is possible to obtain the coupling inspection voltage MV indicating the state of residual vibration of the diaphragm 15 immediately after the output period of the ejection pulse that forcibly vibrates the diaphragm 15. That is, in the ejection mechanism that ejects ink droplets, it is possible to obtain a combined inspection voltage MV in which inspection voltages corresponding to residual vibrations of the piezo element 12 immediately after ejection of the ink droplets are combined in units of groups G. In addition, a current flows between the piezo element 12 and the ground due to a change in the parasitic capacitance of the piezo element 12 due to the residual vibration of the diaphragm 15, and a test voltage proportional to the current flows between the source and drain of the application switch P. Will occur. On the other hand, in the ejection mechanisms that do not eject ink droplets among the ejection mechanisms belonging to the group G to be inspected, the inspection switch M1 is always off during the period in which the inspection switch M2 is on. It is possible to prevent the generated voltage from becoming a noise source of the coupling inspection voltage MV. Similarly, in the group G that is not the inspection target, since the inspection switch M2 is always turned off, the voltage generated at the application switch P of the ejection mechanism belonging to the group G that is not the inspection target becomes the noise source of the combined inspection voltage MV. Can also be prevented.

  The pulse conversion unit 11e amplifies the combined test voltage MV input to the test terminal T, and binarizes the amplified test signal MV depending on whether or not the amplified combined test voltage MV is larger than the threshold voltage. Is a circuit that generates Since one end of the application switch P is connected to the ground, the potential of the inspection terminal T can be acquired as a coupling inspection voltage MV generated between the source and drain of the application switch P.

  FIG. 4A is a graph showing the combined inspection voltage MV and the inspection pulse MP. The pulse converter 11e performs an inspection in which the signal level is 1 in a period in which the coupling inspection voltage MV is equal to or higher than the threshold voltage set in the center of the amplitude, and the signal level is 0 in a period in which the coupling inspection voltage MV is less than the threshold voltage. A pulse MP is generated. The coupling inspection voltage MV has a periodic waveform whose amplitude is attenuated as time t elapses. The period p at which the coupling inspection voltage MV vibrates due to the residual vibration depends on the natural frequency of the diaphragm 15, and the natural frequency when bubbles are mixed in the ink chamber is larger than the natural frequency when bubbles are not mixed. Become. Therefore, when bubbles are mixed in the ink chamber, the cycle p of the coupling inspection voltage MV is shortened.

  The period measuring unit 11f measures the period from the rise of the inspection pulse MP to the next rise of the inspection pulse MP as the period p. If a plurality of periods p can be measured, the period measuring unit 11f may output the average of the plurality of periods p to the voltage determining unit 11g as the period p. The voltage determination unit 11g refers to the determination condition data D1, acquires the normal range of the cycle p, and determines whether or not the cycle p output from the cycle measurement unit 11f belongs to the normal range. The voltage determination unit 11g determines that the coupling inspection voltage MV is abnormal when the period p output from the period measurement unit 11f does not belong within the normal range. On the other hand, the voltage determination unit 11g determines that the coupling inspection voltage MV is normal when the cycle p output from the cycle measurement unit 11f belongs within the normal range.

  The abnormality determination unit 11h acquires the inspection control data SG from the ejection propriety data generation circuit 21, and specifies the group G to be inspected based on the inspection control data SG. Further, the abnormality determination unit 11h acquires the ejection propriety data SI from the abnormality handling unit 11b, and among the 3 (= M) ejection mechanisms belonging to the group G to be inspected based on the ejection propriety data SI, the ink droplets S operating discharge mechanisms that are discharge mechanisms that have performed the discharge are identified. The abnormality determination unit 11h records the determination result of the combined inspection voltage MV for the ejection mechanisms belonging to the group G to be inspected in the determination table D2.

  FIG. 4B is a diagram illustrating a determination table D2 recorded by the abnormality determination unit 11h. In the determination table D2 of FIG. 4B, the inspection result is recorded for each combination of a unique number n (maximum value N) for each discharge mechanism and a discharge timing number A corresponding to the discharge timing. In the determination table D2 of FIG. 4B, the number n column corresponding to the ejection mechanisms other than the three ejection mechanisms belonging to the group G to be inspected is hatched. Of the three ejection mechanisms belonging to the group G to be inspected, a pause character is added to the column of the number n of ejection mechanisms that did not eject ink droplets. On the other hand, among the three ejection mechanisms belonging to the group G to be inspected, the column n of the ejection mechanism that ejected ink droplets has OK (when normal) or NG (when normal) as the determination result of the combined inspection voltage MV. Appears in the case of abnormality).

  When the joint inspection voltage MV is normal, the abnormality determination unit 11h temporarily determines that all of the S operating discharge mechanisms are normal, and adds 1 to the normal count for all of the S discharge mechanisms. Then, the abnormality determination unit 11h determines that the discharge mechanism is normal for the discharge mechanism in which the number of normal times is a predetermined normal threshold. In the present embodiment, the normal threshold is 2 times. For example, in the determination table D2 in FIG. 4B, it is determined that the combined inspection voltage MV is normal at the discharge timings 206 and 207 (= A) for the discharge mechanism No. 31 (= n), and the discharge No. 207 The number of normal times is 2 in the timing. Accordingly, the 31st discharge mechanism is determined to be normal at the 207th discharge timing. In the determination table D2 of FIG. 4B, a letter “O” is attached to the column corresponding to the number n of the ejection mechanism determined to be normal.

  The abnormality determination unit 11h determines that one operating ejection mechanism is an abnormal ejection mechanism when there is one operating ejection mechanism in the group G to be inspected and the combined inspection voltage MV is abnormal. In this embodiment, that the ejection mechanism is abnormal means that the presence of air bubbles in the ink chamber 13 causes the volume of the ink droplet to be reduced from a normal amount. In addition, the abnormality determination unit 11h determines whether any of the S operating discharge mechanisms when the number of operating discharge mechanisms in the group G to be inspected is 2 or more (S is 2 or more) and the combined inspection voltage MV is abnormal. Is temporarily determined to be abnormal, and all of the S ejection mechanisms are determined as abnormal candidates. For example, in the determination table D2 of FIG. 4B, all of the 3 (= S) ejection mechanisms 31 to 33 eject ink droplets at the 205th ejection timing, but the combined inspection voltage MV is abnormal. All three discharge mechanisms are considered as abnormal candidates. In the determination table D2 of FIG. 4B, a letter “Δ” is attached to a column corresponding to the number “n” of the ejection mechanism determined as an abnormality candidate together with a subscript indicating the ejection timing number “A” as an abnormality candidate.

  The abnormality determination unit 11h sets all of the S operating discharge mechanisms as abnormality candidates, and excludes one discharge mechanism among the S discharge mechanisms (S-1) when the discharge mechanisms are normal. When it is determined, it is determined that the one discharge mechanism is an abnormal discharge mechanism. In the determination table D2 of FIG. 4B, all of the 3 (= S) ejection mechanisms 31 to 33 at the 205th ejection timing are regarded as abnormal candidates, but then the 31st and 33rd at the 207th ejection timing. The number of normal discharge mechanisms is 2, and it has been determined that 2 (= S-1) discharge mechanisms 31 and 33 are normal. In this case, the abnormality determination unit 11h is determined to be normal at the 207th discharge timing among the 3 (= S) three (= S) discharge mechanisms 31 to 33 determined as the abnormality candidates at the 205th discharge timing. It is determined that the 32nd ejection mechanism excluding the 33th (2 == S-1) ejection mechanisms is an abnormal ejection mechanism. In the determination table D2 of FIG. 4B, a letter X is attached to the column corresponding to the number n of the ejection mechanism determined to be an abnormal ejection mechanism.

  When it is determined that all of the 3 (= M) ejection mechanisms belonging to the group G to be inspected are normal or abnormal, the abnormality determination unit 11h selects the next group G as the inspection target. To give permission. In response to this, the switch control data generation unit 11a generates inspection control data SG for turning on the inspection switch M2 corresponding to the next group G immediately after the ejection pulse at the next ejection timing. On the other hand, the abnormality determination unit 11h selects the next group G as an inspection target when it cannot be determined that all 3 (= M) ejection mechanisms belonging to the group G to be inspected are normal or abnormal. Not allowed to do. In response to this, the switch control data generation unit 11a continues to generate inspection control data SG for turning on the inspection switch M2 corresponding to the current group G to be inspected immediately after the ejection pulse at the next ejection timing. Accordingly, when the abnormality determination unit 11h specifies S ejection mechanisms as abnormality candidates, the abnormality determination unit 11h excludes one ejection mechanism among the S ejection mechanisms that are regarded as abnormality candidates (S-1). Until it is determined to be normal, the process of determining whether or not the joint inspection voltage MV is normal for the group G is repeated.

  In the configuration of the present embodiment described above, when the drive voltage COM is applied to the piezo element 12, the source and the drain of the application switch P are conducted, and a specific resistance is generated between the source and the drain of the application switch P. It will be. Therefore, a current flows between the source and drain of the application switch P according to the residual vibration of the piezo element 12, and a test voltage proportional to the current is generated. That is, the abnormality determination unit 11h can obtain an inspection voltage corresponding to the residual vibration of the piezo element 12, and can determine whether or not the ejection mechanism is abnormal based on the inspection voltage. Since the inspection switch M1 is provided in each of the plurality of ejection mechanisms, the amount of current flowing through the inspection switch M1 can be suppressed. Accordingly, the inspection switch M1 can be realized with a small current element, and the head IC 11 including the inspection switch M1 can be downsized. Further, since the inspection switch M1 is provided for each ejection mechanism, the voltage generated by the application switch P of the ejection mechanism that does not eject ink droplets among the ejection mechanisms belonging to the group G can be cut off by the inspection switch M1. Furthermore, since the inspection switch M2 is provided for each group G, the voltage generated by the residual vibration of the piezo element 12 in the ejection mechanism belonging to the group G that is not the inspection target can be cut off by the inspection switch M2. Accordingly, the ink droplets can be ejected by the ejection mechanism belonging to the group G that is not the inspection target without interfering with the inspection of the ejection mechanism, and the ejection mechanism can be inspected even during a period during which an arbitrary print job is executed.

  Further, in each of the plurality of ejection mechanisms, the application switch P and the inspection switch M1 are controlled by a control signal output from the same data output terminal of the application switch controller 11c. It is not necessary to separately provide a shift register for controlling the application switch P1 and the inspection switch M1, and the head IC 1 can be downsized. In addition, the abnormality determination unit 11h, the inspection switch, the application switch P, and the application switch control unit 11c are included in a single semiconductor integrated circuit. Thereby, size reduction and cost reduction of the printer 1 are realizable.

  In each of the plurality of ejection mechanisms, one end of the application switch P is set to a known potential (ground), and the other end of the application switch P is connected to the piezo element 12. Then, the inspection switch M1 switches whether to connect the other end of the application switch P and the inspection terminal T. In this way, if one end of the application switch P is set to a known potential, the potential at the other end of the application switch P is measured at the inspection terminal T, so that the difference between the measured potential and the known potential is applied. An inspection voltage between the source and drain of the switch P can be obtained. In particular, in each of the plurality of ejection mechanisms, since one end of the application switch P is connected to the ground as a known potential, the inspection voltage can be easily obtained from the difference between the ground potential and the potential at the other end of the application switch P.

  The abnormality handling unit 11b applies ink droplets to the normal ejection mechanism instead of the abnormal ejection mechanism when the ejection enable / disable data SI indicates that the abnormal ejection mechanism ejects ink droplets and the normal ejection mechanism does not eject ink droplets. Discharge. That is, the abnormality handling unit 11b causes the normal ejection mechanism that can normally eject ink droplets to eject ink droplets instead of the abnormal ejection mechanism that cannot normally eject ink droplets. Thereby, even when an abnormal ejection mechanism is present, it is possible to prevent abnormal ink droplets from being ejected. Further, when an abnormal ejection mechanism is detected when ejecting ink droplets based on the A-th ejection availability data SI, ink droplets are ejected based on the (A + 1) th ejection availability data SI in the same print job. When ejecting (next ejection timing), ink droplets can be ejected to the normal ejection mechanism instead of the abnormal ejection mechanism. Therefore, it is possible to suppress deterioration of the printed image. Also, there is no need to cancel the print job. Furthermore, since the abnormality determination unit 11h and the abnormality handling unit 11b are provided in the ejection head 10, it is not necessary to generate the ejection propriety data SI for causing the normal ejection mechanism to eject ink droplets instead of the abnormal ejection mechanism. Therefore, it is not necessary to notify the determination result of the abnormal ejection mechanism to the main substrate or the like outside the ejection head 10 so as to generate ejection propriety data SI that causes the normal ejection mechanism to eject ink droplets instead of the abnormal ejection mechanism. There is no need to provide a signal line for notification.

  Further, the pulse conversion unit 11e as the coupling inspection voltage acquisition unit is configured such that, out of 360 (= N) ejection mechanisms, 3 (= M = L) or less S ejection mechanisms eject ink droplets. A joint inspection voltage MV is obtained from the inspection terminal T. Therefore, the abnormality determination unit 11h can collectively determine whether or not the S ejection mechanisms are abnormal based on the combined inspection voltage MV. Since the maximum number of ejection mechanisms to which the inspection voltage is coupled is suppressed to 3 (= M = L), it is possible to prevent the number of coupling of the inspection voltage from being excessive and the determination accuracy of the coupling inspection voltage MV from being lowered.

  In addition, 360 (= N) ejection mechanisms are divided into a group G composed of 3 (= M) ejection mechanisms. Then, the pulse conversion unit 11e, when 3 (= M = L) or less S ejection mechanisms out of 3 (= M) ejection mechanisms belonging to the inspection target group G eject ink droplets, A joint inspection voltage MV is obtained from the inspection terminal T. At an ejection timing during execution of an arbitrary print job, it is unlikely that 3 (= M = L) or less S ejection mechanisms out of 360 (= N) ejection mechanisms eject ink droplets. However, even at the ejection timing during execution of an arbitrary print job, the number (S) of ejection mechanisms ejecting ink droplets out of 3 (= M) ejection mechanisms constituting the group G to be inspected is always 3 (= M = L) or less. Accordingly, when 3 (= M = L) or less S ejection mechanisms out of 3 (= M) ejection mechanisms belonging to the group G to be inspected eject ink droplets, the joint inspection is performed from the inspection terminal T. By acquiring the voltage MV, it can be determined at an early stage whether or not the S ejection mechanisms are abnormal. That is, even when a printer 1 having a large number of ejection mechanisms (N is large) executes an arbitrary print job in which the ejection mechanism that ejects ink droplets simultaneously is unspecified, the ejection mechanism The inspection can be completed.

  Here, if all of the inspection voltages in the S discharge mechanisms uniformly show a normal voltage pattern, it is considered that the combined inspection voltage MV obtained by combining the inspection voltages in the S discharge mechanisms also shows a normal voltage pattern. Can do. Therefore, the abnormality determination unit 11h can determine that all of the S ejection mechanisms are normal when the combined inspection voltage MV is not abnormal. In the present embodiment, when the combined inspection voltage MV is not abnormal, the abnormality determination unit 11h tentatively determines that all of the S ejection mechanisms are normal, and adds 1 to the normal count.

  On the other hand, when S is 2 or more and the combined inspection voltage MV obtained by combining the inspection voltages of the S ejection mechanisms is abnormal, it is determined which of the S ejection mechanisms has an abnormal inspection voltage. It cannot be uniquely identified. Therefore, when S is 2 or more and the combined inspection voltage MV is abnormal, it is temporarily determined that any of the S ejection mechanisms is abnormal, and all of the S ejection mechanisms are abnormal candidates. Keep it as The abnormality determination unit 11h determines whether or not the combined inspection voltage MV is abnormal for a single group G a plurality of times. Then, when the abnormality determination unit 11h determines that (S-1) discharge mechanisms are normal among the S discharge mechanisms determined as abnormal candidates except for one discharge mechanism, the single discharge mechanism It is determined that the mechanism is an abnormal discharge mechanism. Thereby, it is not necessary to repeat the process of determining whether or not the combined inspection voltage MV is abnormal for the same group G until the abnormal ejection mechanism ejects ink droplets alone.

  Here, the greater the number of times that the coupling inspection voltage MV is determined to be normal, the higher the reliability that the coupling inspection voltage MV is normal. As in the present embodiment, the abnormality determination unit 11h determines that the ejection mechanism is in a case where the normal number, which is the number of times that the joint inspection voltage MV is tentatively determined to be normal, is equal to or greater than a predetermined normal threshold value (twice). By determining that it is normal, a highly reliable test can be performed.

(1-2) Inspection process:
FIG. 5 is a flowchart of the inspection process executed by the head IC 11 of the ejection head 10. The inspection process is a loop process that is executed at each ejection timing during execution of a print job. The print job that can execute the inspection process is not particularly limited, and the inspection process can be executed in a print job that forms an arbitrary print image. The switch control data generation unit 11a selects the group G to be inspected (S100). For example, the switch control data generation unit 11a may select the group G in ascending order of the number n of ejection mechanisms belonging to the group G. If the inspection process for all the groups G has not been completed at the time of the previous print job, the group G that has not been inspected at the time of the previous print job is referred to the determination table D2. May be selected. Next, the switch control data generation unit 11a generates inspection control data SG for turning on only the inspection switch M2 corresponding to the group G to be inspected, and outputs the inspection control data SG to the inspection switch control unit 11d (S105).

  Next, the switch control data generation unit 11a acquires the discharge availability data SI from the discharge availability data generation circuit 21 (S110). In other words, the switch control data generation unit 11a acquires the discharge availability data SI for the discharge mechanism to discharge the current ink droplet. When the ejection enable / disable data SI is acquired, the abnormality handling unit 11b executes an abnormality handling process (described later). In this abnormality handling process, the abnormality handling unit 11b corrects the discharge feasibility data SI, and after the step S115, each process is performed on the corrected ejection propriety data SI.

  The switch control data generation unit 11a, based on the discharge enable / disable data SI, out of 3 (= M) discharge mechanisms belonging to the group G to be inspected, S operating discharge mechanisms that are discharge mechanisms that discharge ink droplets. Is specified (S115). Then, when the latch signal LAT rises after step S115, all of the ejection mechanisms designated to eject ink droplets by the ejection propriety data SI, including the S operating ejection mechanisms belonging to the group G to be inspected, are used. Ink droplets are ejected.

  The pulse conversion unit 11e and the period measurement unit 11f acquire the coupling inspection voltage MV, and measure the period p at which the coupling inspection voltage MV vibrates (S120). That is, immediately after the ejection pulse output period, the coupling inspection voltage MV is input from the application switches P of the S operating ejection mechanisms to the inspection terminal T of the pulse converter 11e via the inspection switches M1 and M2. Then, the pulse converter 11e converts the combined inspection voltage MV into the inspection pulse MP, and measures the period p based on the inspection pulse MP. Next, the voltage determination unit 11g determines whether or not the period p is abnormal (S125). That is, the voltage determination unit 11g determines that the cycle p is abnormal when it does not belong to the normal range defined in the determination condition data D1, and determines that the cycle p is normal when it belongs to the normal range. .

  When the period p is abnormal (S125: Y), the abnormality determining unit 11h determines whether or not there are 1 (S = 1) operating ejection mechanisms belonging to the group G to be inspected (S130). If there is one operating discharge mechanism belonging to the group G to be inspected (S130: Y), the abnormality determining unit 11h determines that the one operating discharge mechanism is an abnormal discharge mechanism, and the determination table. Record in D2 (FIG. 4B) (S135). On the other hand, when there is not one operating discharge mechanism belonging to the group G to be inspected (S130: N), the abnormality determination unit 11h temporarily determines that all of the S operating discharge mechanisms are abnormal, It records in determination table D2 that all the S operation | movement discharge mechanisms are abnormality candidates (S140). That is, the abnormality determination unit 11h determines that any of the S operating discharge mechanisms is abnormal when S is 2 or more and the coupling inspection voltage MV is abnormal, and the abnormal discharge mechanism Is not uniquely identified.

  When the period p is normal (S125: N), the abnormality determination unit 11h tentatively determines that all of the S operating ejection mechanisms belonging to the group G to be inspected are normal (S145). Then, the abnormality determination unit 11h adds 1 to the number of normal times for each of the S operating discharge mechanisms in the determination table D2. When the group G is first selected as the inspection target, the normal number of times is reset to 0 for all the composition ejection mechanisms belonging to the group G. The abnormality determination unit 11h determines that the composition ejection mechanism whose normal number of times is equal to the normal threshold (2) is normal, and records it in the determination table D2 (S150).

  Furthermore, the abnormality determination unit 11h determines whether (S-1) discharge mechanisms are determined to be normal among S discharge mechanisms that are simultaneously determined as abnormal candidates (S155). As shown in FIG. 4B, since the ejection timing numbers determined as abnormality candidates in the determination table D2 are associated with the ejection mechanisms, it is possible to identify S ejection mechanisms simultaneously regarded as abnormality candidates. At the same time, when (S-1) discharge mechanisms are determined to be normal among the S discharge mechanisms that have been determined as abnormal candidates (S155: Y), the abnormality determination unit 11h is determined to be normal (S -1) It is determined that the remaining one ejection mechanism excluding one ejection mechanism is an abnormal ejection mechanism, and is recorded in the determination table D2 (S160). On the other hand, when (S-1) discharge mechanisms are not determined to be normal among the S discharge mechanisms that are simultaneously determined as abnormal candidates (S155: N), the abnormality determination unit 11h proceeds directly to step S165. To do. As described above, the determination table D2 is updated every discharge timing, that is, every time discharge availability data SI is output.

  Next, the abnormality determining unit 11h determines whether or not determination results have been determined for all the ejection mechanisms belonging to the group G to be inspected (S165). If the determination result is not fixed for all the ejection mechanisms belonging to the group G to be inspected (S165: N), the abnormality determination unit 11h does not select the next group G as the inspection target in step S100. The process returns to step S105. That is, the abnormality determination unit 11h prohibits the switch control data generation unit 11a from selecting the next group G as an inspection target, and repeatedly executes the processing (S105 to S105) for the same group G. On the other hand, when the determination results are confirmed for all the ejection mechanisms belonging to the group G to be inspected (S165: Y), the abnormality determination unit 11h determines whether all the groups G have been selected as inspection targets (S170). ). And when not having selected all the groups G as a test object (S170: N), the abnormality determination part 11h returns to step S100. That is, the abnormality determination unit 11h allows the switch control data generation unit 11a to select the next group G as an inspection target, and causes the next group G to be processed (S105). On the other hand, when all the groups G are selected as inspection targets (S170: Y), the abnormality determination unit 11h ends the inspection process. If the print job is completed before the end of the inspection process, the determination table D2 at that time may be held, and the inspection process may be continued in the next print job.

(1-3) Abnormal response processing:
FIG. 6A is a flowchart of the abnormality handling process executed by the abnormality handling unit 11b. The abnormality handling process is a process that is executed every time the ejection propriety data SI is acquired in the inspection process of FIG. When the discharge enable / disable data SI is acquired in step S110 of FIG. 5, the abnormality handling unit 11b acquires the determination table D2 updated at the previous discharge timing. That is, if the discharge availability data SI at the (A + 1) th discharge timing is acquired in step S110 of FIG. 5, the abnormality handling unit 11b acquires the determination table D2 updated at the Ath discharge timing.

  The abnormality handling unit 11b specifies an operating ejection mechanism that should eject ink droplets based on the current ejection propriety data SI, and selects one of the operating ejection mechanisms (S210). Next, the abnormality handling unit 11b determines whether or not the selected operating discharge mechanism is an abnormal discharge mechanism determined to be abnormal in the determination table D2 (S230). If the selected operating discharge mechanism is not the abnormal discharge mechanism determined to be abnormal in the determination table D2 (S230: N), step S250 is performed without correcting the discharge availability data SI for the selected operating discharge mechanism. Execute. That is, the abnormality handling unit 11b determines whether or not all the operation discharge mechanisms have been selected (S250). If not all the operation discharge mechanisms have been selected (S250: N), the process returns to step S210, and the next operation discharge mechanism is selected. In the abnormality handling process, it is assumed that an uninspected ejection mechanism (a ejection mechanism in which neither abnormality nor normality is determined) is not abnormal.

  On the other hand, when the selected operating discharge mechanism is an abnormal discharge mechanism that is determined to be abnormal in the determination table D2 (S230: Y), the abnormality handling unit 11b determines whether the adjacent operating discharge mechanism adjacent to the selected operating discharge mechanism. It is determined whether or not all of the abnormal ejection mechanisms are determined to be abnormal in the determination table D2 (S260). That is, as shown in FIG. 3A, the abnormality handling unit 11b ejects ink droplets of the same ink color as the abnormal ejection mechanism, and the distance from the nozzle 14 (white circle) provided in the abnormal ejection mechanism in the direction orthogonal to the printing direction. It is determined whether or not the two discharge mechanisms each having the nozzle 14 (double circle) having the shortest (half of the arrangement interval) are abnormal discharge mechanisms. If all the adjacent ejection mechanisms are abnormal ejection mechanisms (S260: Y), the abnormality handling unit 11b executes step S250 without correcting the ejection availability data SI.

  On the other hand, if at least one of the adjacent ejection mechanisms is not an abnormal ejection mechanism (S260: N), the abnormality handling unit 11b determines whether all of the adjacent ejection mechanisms that are not abnormal ejection mechanisms are operating ejection mechanisms that eject ink droplets. Is determined (S270). If at least one of the adjacent discharge mechanisms that are not the abnormal discharge mechanism is not the operating discharge mechanism (S270: N), the abnormality handling unit 11b performs the discharge availability data SI for the selected operating discharge mechanism and the active discharge even in the abnormal discharge mechanism. The discharge availability data SI for an adjacent discharge mechanism that is not a mechanism is exchanged. Accordingly, ink droplets can be ejected to a normal adjacent ejection mechanism instead of the selected abnormal operation ejection mechanism. When there are a plurality of adjacent discharge mechanisms that are neither the abnormal discharge mechanism nor the active discharge mechanism, the abnormality handling unit 11b may exchange any of these adjacent discharge mechanisms with the discharge availability data SI.

  On the other hand, when all of the adjacent ejection mechanisms that are not abnormal ejection mechanisms are operating ejection mechanisms (S270: Y), the abnormality handling unit 11b executes step S250 without correcting the ejection propriety data SI. If the ink droplets cannot be ejected to the normal ejection mechanism instead of the abnormal ejection mechanism (S260: Y, S270: Y), the abnormality handling unit 11b ejects the ink droplets so as not to be ejected from the operating ejection mechanism. The availability data SI may be modified. Further, when ink droplets cannot be ejected by the normal ejection mechanism instead of the abnormal ejection mechanism (S260: Y, S270: Y), the abnormality handling unit 11b widens the existence range of the nozzles 14 to be satisfied by the adjacent ejection mechanism. May be.

  In the present embodiment, even when all of the 3 (= M) ejection mechanisms constituting the group G are ejecting, abnormality determination based on the combined inspection voltage MV is performed. However, by limiting the number of coupling voltages in the coupling test voltage MV to L (L <M), the determination accuracy of the period p at which the coupling test voltage MV vibrates may be improved. Hereinafter, an embodiment in which the number of coupling voltages in the coupling inspection voltage MV is limited to L will be described.

  FIG. 6B shows a flowchart (partial) of the inspection process when the number of coupling voltages in the coupling inspection voltage MV is limited to L. FIG. 6B shows only processing different from the inspection processing of FIG. When an active discharge mechanism is specified among the three discharge mechanisms constituting the group G (FIG. 5: S115), the abnormality determination unit 11h determines whether the number of the active discharge mechanisms is 2 (= L) or less. (S118). If the number of operating discharge mechanisms is not two or less, the abnormality determination unit 11h returns to step S105 (FIG. 5). That is, it waits for the output of the discharge availability data SI at the next discharge timing without determining whether or not the period p at which the coupling inspection voltage MV vibrates is abnormal. On the other hand, when there are two or less operating discharge mechanisms, the abnormality determination unit 11h executes the processing from step S120 onward (FIG. 5) to determine whether or not the period p at which the coupling inspection voltage MV vibrates is abnormal. To do. As described above, if the number of operating discharge mechanisms in the combined inspection voltage MV for determining whether or not the period p is abnormal is limited to a predetermined L, the number of inspection voltages combined in the combined inspection voltage MV can be reduced. It is possible to improve the determination accuracy of the period p.

(2) Modification 1:
FIG. 7A is a circuit diagram of a part of the ejection head 10 of the first modification. In the first modification, the drive voltage generation circuit 22, the application switch P, the piezo element 12, and the ground are connected in series. In the first modification, the application switch P1 is connected to the drive voltage generation circuit 22 side rather than the ground side to the piezo element 12a. One end of the application switch P is connected to the drive voltage generation circuit 22, and the other end of the application switch P is connected to the inspection terminal T of the pulse converter 11 e via the inspection switch M. When the inspection switch M is turned on, the other end of the application switch P and the inspection terminal T of the pulse converter 11e have the same potential. The inspection switch M is provided for each ejection mechanism, and the inspection switch control unit 11d switches the inspection switch M for each ejection mechanism based on the inspection control data SG. In the present embodiment, the switch control data generation unit 11a turns on only the inspection switch M corresponding to a single ejection target ejection mechanism, and turns off all the inspection switches M corresponding to other ejection mechanisms. That is, in the first modification, the inspection is not performed for each group G but for each ejection mechanism.

  FIG. 7B is a timing chart illustrating the operation of the drive voltage COM and the switches P and M according to the first modification. In the first modification, the single ejection timing is divided into the first to fourth periods by the switching signal CH. The same drive voltage COM is generated at each ejection timing, and the drive voltage COM is a known voltage pattern. In the first period, the drive voltage COM includes an ejection pulse for ejecting a large ink droplet that forms a large dot. In the second period, the drive voltage COM includes an ejection pulse for ejecting a medium ink droplet that forms a medium dot. In the third period, the drive voltage COM includes an ejection pulse for ejecting a small ink droplet that forms a small dot. In the fourth period, the drive voltage COM includes a fine vibration pulse for causing the piezoelectric element 12 to vibrate. The volume of ink droplets is the largest for large ink droplets and the smallest for small ink droplets. In addition, the drive voltage COM becomes the reference potential VS in a period excluding the output period of each ejection pulse and micro-vibration pulse.

  When a large ink droplet is ejected by the ejection mechanism, the application switch P is turned on in the first period. When a large ink droplet is ejected by the ejection mechanism and selected as an inspection target, the inspection switch M is turned on immediately after the ejection pulse output period in the first period. When the middle ink droplet is ejected by the ejection mechanism, the application switch P is turned on in the second period. Further, when the middle ink droplet is ejected by the ejection mechanism and is selected as the inspection target, the inspection switch M is turned on immediately after the ejection pulse output period in the second period. When ejecting small ink droplets by the ejection mechanism, the application switch P is turned on in the third period. Further, when a small ink droplet is ejected by the ejection mechanism and is selected as an inspection target, the inspection switch M is turned on immediately after the ejection pulse output period in the third period. When ink droplets are not ejected by the ejection mechanism, the application switch P is turned on in the fourth period.

  Here, when the inspection switch M is turned on immediately after the ejection pulse output period, the drive voltage COM becomes the reference potential VS. Therefore, the inspection voltage generated between the source and drain of the application switch P can be acquired by subtracting the reference potential VS from the potential of the inspection terminal T of the pulse converter 11e during the period in which the inspection switch M is on. Further, since the inspection voltage generated by the residual vibration is an AC component, the inspection voltage may be obtained by removing the DC component corresponding to the reference potential VS with a capacitor or the like. That is, the reference potential VS in the drive voltage COM does not necessarily need to be known up to the magnitude of the potential. If the constant potential is known to be a constant DC component, an inspection caused between the source and drain of the application switch P due to residual vibration. The voltage can be extracted. According to the configuration described above, an inspection voltage indicating a residual vibration state can be acquired for each ejection mechanism selected as an inspection target, and the residual vibration is abnormal for each ejection mechanism selected as an inspection target based on the inspection voltage. It can be determined whether or not. Further, the inspection voltage can be acquired regardless of whether the selected ejection mechanism ejects a large ink droplet, a medium ink droplet, or a small ink droplet.

  The pulse converter 11e generates an inspection pulse MP by binarizing the inspection voltage input to the inspection terminal T. The pulse converter 11e includes an amplifier circuit that amplifies a test voltage obtained by subtracting the reference potential VS from the potential of the test terminal T, and a binarization circuit that binarizes the test voltage amplified by the amplifier circuit. The binarization circuit generates an inspection pulse MP having a signal level of 1 during a period in which the inspection voltage is equal to or higher than a predetermined threshold voltage. In the first modification, the pulse converter 11e includes three first to third amplifier circuits A1 to A3 and a switch (not shown). In the first period, the switch inputs the inspection voltage to the first amplifier circuit A1, in the second period, the switch inputs the inspection voltage to the second amplifier circuit A2, and in the third period, the switch supplies the inspection voltage to the third amplifier circuit A3. To input. The amplification factors in the first to third amplifier circuits A1 to A3 are the smallest in the first amplifier circuit A1 and the largest in the third amplifier circuit A3. That is, the smaller the volume of the ejected ink droplet, the larger the amplification factor of the inspection voltage MV. The smaller the volume of the ejected ink droplet, the smaller the amplitude of the inspection voltage MV before amplification. However, by increasing the amplification factor, the threshold voltage is included in the change range of the inspection voltage MV after amplification. it can. Accordingly, by increasing the amplification factor of the inspection voltage MV as the volume of the ejected ink droplet is smaller, the inspection pulse MP corresponding to the inspection voltage MV can be generated even when the volume of the ejected ink droplet is small.

  The inspection voltage MV has a periodic waveform whose amplitude attenuates as time t passes. Then, when the residual vibration is attenuated as time t elapses and the amplitude of the inspection voltage MV after amplification does not include the predetermined threshold voltage, the signal level of the inspection pulse MP does not change. In the first modification, the head IC 11 includes an attenuation period measurement unit (not shown) instead of the period measurement unit 11f (FIG. 1), and the attenuation period measurement unit finally starts the inspection pulse MP from the end time of the ejection pulse output period. A period until time t when the signal level of the signal changes is specified as an attenuation period. The voltage determination unit 11g reads the normal range of the decay period for each of the first to third periods from the determination condition data D1, and the test voltage is normal when the decay period measured by the decay period measurement unit belongs to the normal range. Judge that there is. In the third period in which the small ink droplets are ejected, the amplitude of the piezo element 12 (the diaphragm 15) is smaller than in the first and second periods in which the large ink droplets and the medium ink droplets are ejected. Is the shortest. However, since the amplification factors of the first to third amplifier circuits A1 to A3 are different from each other, if the normal range of the attenuation period in the third period is set to a shorter value side than the normal range of the attenuation period in the first period. Is not limited. Since the attenuation period becomes shorter as the viscosity of the ink in the ink chamber 13 becomes higher, the attenuation period being in the normal range means that the viscosity of the ink in the ink chamber 13 is normal. That is, in the first modification, that the ejection mechanism is abnormal means that the viscosity of the ink in the ink chamber 13 is abnormal. In the first modification, whether or not the inspection voltage is normal for each ejection mechanism is determined by the voltage determination unit 11g. Therefore, the abnormality determination unit 11h determines the determination result of the inspection voltage (attenuation period) for each ejection mechanism. Record in table D2.

  FIG. 8A shows an example of the determination table D2 recorded in the first modification. In FIG. 8A, the 31st to 33rd ejection mechanisms are sequentially selected as inspection targets. The abnormality determination unit 11h adds 1 to the normal count in the determination table D2 when it is determined that the inspection voltage is normal regardless of whether the inspection voltage is acquired in any of the first to third periods. Then, the abnormality determining unit 11h determines that the ejection mechanism is normal when the normal count reaches 2. If it is determined that the inspection voltage is abnormal even if the inspection voltage is acquired in any of the first to third periods, the abnormality determination unit 11h indicates that the inspection target ejection mechanism is abnormal in the determination table D2. Determine. That is, in the first modification, the normal threshold for the normal number of times is set to 2 times, and the abnormal threshold value for the abnormal number of times is set to 1 time. By setting the normal threshold for the normal number of times to 2 times, it is possible to carefully consider that it is normal, and it is possible to prevent the detection failure of the abnormal discharge mechanism.

  When the abnormality determination unit 11h determines that the ejection mechanism to be inspected is normal or abnormal, the abnormality determination unit 11h permits the switch control data generation unit 11a to select the next ejection mechanism as the inspection target. Thereby, the switch control data generation unit 11a selects the next discharge mechanism as an inspection target, and generates inspection control data SG for turning on the inspection switch M only in the discharge mechanism. Note that it is not always necessary to inspect only the ejection mechanism until an inspection result is confirmed for the ejection mechanism to be inspected. Another ejection mechanism is temporarily inspected at an ejection timing at which the ejection mechanism does not eject ink droplets. You may choose as For example, at the discharge timing No. 208 in FIG. 8A, it may be determined whether or not the inspection voltage is normal by tentatively inspecting an unexamined No. 33 discharge mechanism. Then, at the discharge timing of 209 when the discharge mechanism of number 32 discharges ink droplets, it may be determined whether or not the inspection voltage is normal with the discharge mechanism of number 32 as the inspection target.

  FIG. 8B shows another example of the determination table D2 recorded in the first modification. In FIG. 8B, the numerical value described in the column of the discharge mechanism that is the inspection target represents the total index value, not the normal number of times. When the inspection voltage acquired in the first period is normal, the abnormality determination unit 11h does not add 1 to the normal number of times, but uses 2 (= 2 × 1) is added to the total index value. When the inspection voltage acquired in the second period is normal, the abnormality determination unit 11h adds 1 (= 1 × 1) to the overall index value as an index value obtained by multiplying the normal number of times by 1 with the weight coefficient 1. Furthermore, when the inspection voltage acquired in the third period is normal, the abnormality determination unit 11h uses 0.5 (= 0.5 × 1) as an index value obtained by multiplying the normal number of times by a weighting factor of 0.5. Is added to the total index value. That is, the abnormality determination unit 11h calculates a total index value obtained by adding the index values obtained by multiplying the number of times that the inspection voltage is determined to be normal by a weighting coefficient that is larger as the ink droplet size is larger. Then, when the abnormality determining unit 11h is equal to or greater than 2 which is a predetermined normal threshold, it is determined that the ejection mechanism to be inspected is normal.

  In the example of FIG. 8B, if the number of normal times when the inspection voltage becomes normal when a large ink droplet is ejected is one or more, it is determined that the ejection mechanism is normal. Further, if the normal number of times that the inspection voltage becomes normal when the medium ink droplet is ejected is 2 times or more, it is determined that the ejection mechanism is normal. Furthermore, if the number of normal times when the inspection voltage becomes normal when ejecting small ink droplets is 4 or more, it is determined that the ejection mechanism is normal. That is, in the example of FIG. 8B, the smaller the volume of the ejected ink droplet, the larger the normal count threshold for determining that the ejection mechanism is normal.

  As described above, when a small ink droplet is ejected, the inspection voltage is amplified by the largest amplification factor. Therefore, when a small ink droplet is ejected, even if a minute noise voltage is mixed in the inspection voltage, inspection is performed. A pulse corresponding to the noise voltage can appear in the pulse MP. That is, the smaller the ink droplet ejected when the inspection voltage is acquired, the higher the possibility that a noise component appears in the inspection pulse MP, and the reliability of the inspection voltage determination result based on the inspection pulse MP becomes lower. On the contrary, the larger the ink droplet ejected when the inspection voltage is acquired, the lower the possibility that a noise component appears in the inspection pulse MP, and the reliability of the determination result of the inspection voltage based on the inspection pulse MP becomes higher. Therefore, by determining whether or not the ejection mechanism is normal based on a total index value obtained by summing index values obtained by multiplying a larger weight coefficient as the ink droplet size is larger, a highly reliable test voltage is obtained. It is possible to determine whether or not the ejection mechanism is normal by focusing on the determination result.

  In the first modification, the abnormality handling process (FIG. 6) may be changed as follows. That is, when all adjacent ejection mechanisms that are not abnormal ejection mechanisms are operating ejection mechanisms (S270: Y), the abnormality handling unit 11b increases the volume of ink droplets that are ejected by any adjacent ejection mechanism that is not an abnormal ejection mechanism. As described above, the discharge availability data SI for the adjacent discharge mechanism may be modified. In the first modification, an ink droplet may be ejected to the auxiliary piezo element 12b by the abnormal ejection mechanism.

(3) Other variations:
The abnormality handling unit 11b performs normal ejection instead of the abnormal ejection mechanism at the (A + B) th ejection timing in the same print job as the Ath ejection timing based on the determination table D2 updated at the Ath ejection timing. What is necessary is just to discharge an ink drop to a mechanism. That is, B does not necessarily have to be 1. If the tact time of the abnormality handling process is longer than the ejection timing, B may be 2 or more.

  In the above embodiment, the inspection apparatus inspects the ejection mechanism that ejects ink droplets. However, the ejection mechanism that ejects droplets other than ink droplets may be inspected. In other words, the ejection mechanism may form a planar structure or a three-dimensional structure with the ejected droplets, and the droplets may be any material constituting the planar structure or the three-dimensional structure. Furthermore, the discharge mechanism may discharge a processing liquid for performing processing (cleaning, etching, etc.) at the landing position of the droplet. Further, in the embodiment, the inspection process is performed during execution of an arbitrary print job. However, the printer 1 may perform the inspection process while printing a predetermined inspection image. Furthermore, the droplets are not limited to those ejected by pressurization due to mechanical changes of the piezoelectric element, but may be ejected by pressurization due to the generation of bubbles. Further, inspection parameters other than the residual vibration period p and the attenuation period may be acquired based on the combined inspection voltage. Of course, abnormalities other than the mixing of bubbles in the ink chamber 13 and abnormal ink viscosity may be inspected based on inspection parameters other than the period p of the residual vibration and the attenuation period.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 10 ... Discharge head, 11 ... Head IC, 11a ... Switch control data generation part, 11b ... Abnormal response part, 11c ... Application switch control part, 11d ... Inspection switch control part, 11e ... Pulse conversion part, 11f ... Period measurement unit, 11g ... voltage determination unit, 11h ... abnormality determination unit, 12 ... piezo element, 13 ... ink chamber, 14 ... nozzle, 15 ... vibrating plate, 20 ... main substrate, 21 ... discharge availability data generation circuit, 22 ... Drive voltage generation circuit, A1 to A3: amplification circuit, CH: switching signal, COM: drive voltage, D1: determination condition data, D2: determination table, G ... group, M ... inspection switch, MP ... inspection pulse, MV ... coupling Inspection voltage, P: Application switch, SI: Discharge availability data, T: Inspection terminal, VS: Reference potential.

Claims (2)

A droplet discharge apparatus having a discharge head including a plurality of discharge mechanisms including a drive element for discharging droplets from a nozzle,
The ejection head is
A discharge availability data acquisition unit that acquires discharge availability data indicating whether or not to discharge droplets for each of the plurality of ejection mechanisms;
In each of the plurality of ejection mechanisms, a drive voltage source and the drive element are connected in series, and whether or not to apply a drive voltage for ejecting the droplet based on the ejection propriety data to the drive element is determined. An application switch to switch;
An abnormality determination unit that determines whether the discharge mechanism is normal or abnormal when discharging the droplet;
With
The abnormality determination unit determines whether the discharge mechanism is normal or abnormal based on a combined inspection voltage obtained by combining voltage waveforms of inspection voltages generated between both ends of the plurality of application switches.
Droplet discharge device. The abnormality determination unit determines that the ejection mechanism is normal or abnormal when the number of times that the combination inspection voltage is determined to be normal or abnormal is equal to or greater than a predetermined threshold.
The droplet discharge device according to claim 1 .

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