Liquid dispensing device, head unit control circuit, and liquid dispensing inspection method

Abstract

This reduces the inspection time required to determine the condition of the discharge unit D. [Solution] The inkjet printer 1 includes an ejection unit D capable of ejecting ink in response to an input drive signal COM, a signal generation unit 60 that receives a residual vibration signal VD corresponding to the residual vibration generated in the ejection unit D in response to the input of the drive signal COM and generates a comparison signal CCP based on the residual vibration signal VD, and a determination unit 64 that determines the state of the ejection unit D based on the comparison signal CCP. The signal generation unit 60 has a first inspection mode that generates a first inspection mode signal as a comparison signal CCP corresponding to a first partial signal in a first period TPP1 of the residual vibration signal VD, and a second inspection mode that generates a second inspection mode signal as a comparison signal CCP corresponding to a second partial signal in a second period TPP2 of the residual vibration signal VD. The first period TPP1 is a shorter period than the second period TPP2.

Description

Technical Field

[0001] The present invention relates to a liquid-liquid ejection device, a head unit control circuit for controlling a head unit of the liquid ejection device, and a liquid ejection inspection method.

Background Art

[0002] A liquid ejection device such as an inkjet printer ejects a liquid such as ink filled in a ejection part by driving the ejection part provided in a liquid ejection head in each of a plurality of unit periods defined by a latch signal, and forms an image on a medium. However, in this type of liquid ejection device, ejection abnormalities may occur where the liquid cannot be normally ejected from the ejection part. For this reason, conventionally, techniques for inspecting the ejection state in the ejection part have been proposed. For example, Patent Document 1 discloses a technique for inspecting the ejection state in the ejection part based on a detection signal indicating vibration remaining in the ejection part after driving the ejection part by a drive signal.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, with conventional technology, when inspecting the discharge state at the discharge section, noise is superimposed on the signal immediately after the start of the inspection. Therefore, a mask circuit was used to compensate for the effect of this noise. While this mask circuit is quite effective in improving inspection accuracy, it was a factor in increasing the inspection time. Furthermore, when inspecting the discharge state, for example, period index data indicating the period of the detection signal showing residual vibration is generated after the mask is removed, and requires information for at least one period of the detection signal. The fact that information for one period of the detection signal is required after the mask is removed was also a major constraint on shortening the inspection time. [Means for solving the problem]

[0005] To solve the above problems, the liquid dispensing device according to the present invention comprises: a dispensing unit capable of dispensing liquid in response to an input drive signal; a signal generation unit that receives a residual vibration signal corresponding to the residual vibration generated in the dispensing unit in response to the input drive signal and generates a state inspection signal based on the residual vibration signal; and a determination unit that determines the state of the dispensing unit based on the state inspection signal. The signal generation unit has a first inspection mode that generates a first inspection mode signal as the state inspection signal corresponding to a first partial signal in a first period of the residual vibration signal; and a second inspection mode that generates a second inspection mode signal as the state inspection signal corresponding to a second partial signal in a second period of the residual vibration signal, wherein the first period is shorter than the second period.

[0006] Furthermore, the head unit control circuit according to the present invention is a head unit control circuit that controls a head unit having a discharge unit capable of discharging liquid in response to an input drive signal, and comprises a signal generation unit that receives a residual vibration signal corresponding to the residual vibration generated in the discharge unit in response to the input of the drive signal and generates a state inspection signal based on the residual vibration signal, and a determination unit that determines the state of the discharge unit based on the state inspection signal, wherein the signal generation unit has a first inspection mode that generates a first inspection mode signal as the state inspection signal corresponding to a first partial signal in a first period of the residual vibration signal, and a second inspection mode that generates a second inspection mode signal as the state inspection signal corresponding to a second partial signal in a second period of the residual vibration signal, wherein the first period is shorter than the second period.

[0007] Furthermore, the liquid discharge inspection method according to the present invention is a liquid discharge inspection method for a liquid discharge device equipped with a discharge unit capable of discharging liquid in response to an input drive signal, wherein a state inspection signal is generated based on a residual vibration signal corresponding to the residual vibration generated in the discharge unit in response to the input of the drive signal, the state of the discharge unit is determined based on the state inspection signal, and when a first inspection mode is selected as the inspection mode for determining the state of the discharge unit, a first inspection mode signal corresponding to a first partial signal in a first period of the residual vibration signal is generated as the state inspection signal, and when a second inspection mode is selected as the inspection mode, a second inspection mode signal corresponding to a second partial signal in a second period of the residual vibration signal is generated as the state inspection signal, and the first period is a shorter period than the second period. [Brief explanation of the drawing]

[0008] [Figure 1] This block diagram shows an example of the configuration of an inkjet printer according to the first embodiment of the present invention. [Figure 2] This is a perspective view showing an example of the general internal structure of an inkjet printer. [Figure 3] This is a cross-sectional view illustrating an example of the structure of the discharge section. [Figure 4]This is an explanatory diagram illustrating the ink ejection operation in the ejection section. [Figure 5] This is a plan view showing an example of nozzle arrangement in a head unit. [Figure 6] This is a block diagram showing an example of a head unit configuration. [Figure 7] This is a block diagram showing an example of a measurement circuit configuration. [Figure 8] This is a timing chart showing an example of the operation of an inkjet printer over a unit period. [Figure 9] This is a timing chart showing an example of the operation of the signal generation unit. [Figure 10] This is an explanatory diagram illustrating the relationship between residual vibration signals, reset timing, and comparison signals. [Figure 11] This is an explanatory diagram illustrating the relationship between the reset timing and the amplitude calculated based on the time duration. [Figure 12] This is an explanatory diagram illustrating the relationship between the reset timing, amplitude, and amplitude change rate. [Figure 13] This flowchart shows an example of how an inkjet printer operates when performing a discharge state determination process. [Figure 14] This is a block diagram showing an example of the configuration of an inspection unit according to the second embodiment. [Figure 15] This is an explanatory diagram illustrating the general process for adjusting the reset timing. [Figure 16] This is an explanatory diagram illustrating the relationship between the reset timing, amplitude, and amplitude change rate. [Figure 17] This flowchart shows an example of how an inkjet printer operates when performing a discharge state determination process. [Figure 18] This is a block diagram showing an example of the configuration of an inspection unit according to the third embodiment. [Figure 19] This is an explanatory diagram illustrating the relationship between residual vibration signals, reset timing, and comparison signals. [Figure 20]It is an explanatory diagram for explaining an outline of adjustment of sensitivity when determining the state of the ejection unit. [Figure 21] It is an explanatory diagram for explaining the relationship between the reset timing and the amplitude calculated based on the time duration. [Figure 22] It is an explanatory diagram for explaining the relationship between the time ratio of two time durations, the amplitude, and the amplitude change rate. [Figure 23] It is an explanatory diagram for explaining an example of the variation in amplitude between nozzles calculated based on the time duration. [Figure 24] It is an explanatory diagram for explaining an example of the amplitude calculated based on the time duration when the time ratio of two time durations is changed. [Figure 25] It is a flowchart showing an example of the operation of an inkjet printer when executing the ejection state determination process. [Figure 26] It is a block diagram showing an example of the configuration of an inspection unit according to the first modification. [Embodiments for Carrying Out the Invention]

[0009] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, in each figure, the dimensions and scales of each part are appropriately different from the actual ones. Further, the embodiments described below are preferred specific examples of the present invention, and thus various technically preferable limitations are imposed. However, the scope of the present invention is not limited to these embodiments unless there is a description to specifically limit the present invention in the following description.

[0010] [1. Embodiment] In the present embodiment, a liquid ejection device will be described by exemplifying an inkjet printer that ejects ink onto a recording sheet to form an image. Note that, in the present embodiment, ink is an example of "liquid". First, the configuration of the inkjet printer 1 according to the present embodiment will be described while referring to FIG. 1.

[0011] [First Embodiment] Figure 1 is a block diagram showing an example of the configuration of an inkjet printer 1 according to the first embodiment of the present invention.

[0012] The inkjet printer 1 is supplied with print data (IMG) indicating the image to be formed, for example, from a host computer such as a personal computer or a digital camera. The inkjet printer 1 performs a printing process to form the image indicated by the print data (IMG) supplied from the host computer onto a medium. In this embodiment, the medium is assumed to be the recording paper P shown in Figure 2, which will be described later.

[0013] The inkjet printer 1 includes a head module HM which includes a head unit 3 equipped with an ink ejection unit D for ejecting ink, and a head unit control module HCM which controls the head unit 3. Furthermore, the inkjet printer 1 includes a transport unit 7 for changing the relative position of the recording paper P with respect to the head unit 3, and a maintenance unit 8 which performs maintenance processing to maintain the ink ejection unit D provided on the head unit 3. Note that the head unit control module HCM is an example of a "head unit control circuit".

[0014] The head unit control module HCM includes a control unit 2 that controls various parts of the inkjet printer 1, and a drive signal generation unit 4 that generates a drive signal COM for driving the ejection unit D. The head unit control module HCM also includes a storage unit 5 that stores various information such as print data IMG and the control program PG of the inkjet printer 1, and an inspection module TM that includes an inspection unit 6 that determines the state of the ejection unit D.

[0015] In this embodiment, we assume that the head unit 3 and the inspection unit 6 correspond to each other. For example, the inkjet printer 1 may have multiple head units 3 and multiple inspection units 6 that correspond one-to-one with the multiple head units 3. Alternatively, the inkjet printer 1 may have one head unit 3 and one inspection unit 6 that corresponds to one head unit 3. In this embodiment, we assume that the inkjet printer 1 has four head units 3 and four inspection units 6 that correspond one-to-one with the four head units 3. However, for the sake of explanation, we will focus on one of the four head units 3 and one of the four inspection units 6 that is provided in correspondence with one of the head units 3.

[0016] The control unit 2 is configured to include one or more CPUs (Central Processing Units). Alternatively, the control unit 2 may include a programmable logic device such as an FPGA (field-programmable gate array) instead of, or in addition to, a CPU. Furthermore, the control unit 2 functions as a drive control unit 22 by executing the control program PG stored in the memory unit 5.

[0017] The drive control unit 22 generates signals to control the operation of each part of the inkjet printer 1, such as the print signal SI, the waveform specification signal dCOM, the pulse detection period signal Pcut, and the mask signal MSK. Here, the waveform specification signal dCOM is a digital signal that defines the waveform of the drive signal COM. The drive signal COM is an analog signal for driving the ejection unit D. The print signal SI is a digital signal that specifies the type of operation of the ejection unit D. Specifically, the print signal SI specifies the type of operation of the ejection unit D by specifying whether or not to supply the drive signal COM to the ejection unit D. The pulse detection period signal Pcut and the mask signal MSK will be explained in Figures 7 and 8 below.

[0018] When printing is performed, for example, the drive control unit 22 controls the head unit 3 and the transport unit 7 to print the image indicated by the print data IMG onto the recording paper P. Specifically, when printing is performed, the drive control unit 22 generates signals to control the head unit 3, such as the print signal SI, based on the print data IMG. The drive control unit 22 also generates signals to control the drive signal generation unit 4, such as the waveform specification signal dCOM, when printing is performed. The drive control unit 22 also generates signals to control the transport unit 7 when printing is performed. In this way, the drive control unit 22 controls the transport unit 7 to change the relative position of the recording paper P with respect to the head unit 3 during printing, while also adjusting the presence or absence of ink ejection from the ejection unit D, the amount of ink ejection, and the timing of ink ejection. In this manner, the drive control unit 22 controls each part of the inkjet printer 1 so that an image corresponding to the print data IMG is formed on the recording paper P.

[0019] The drive signal generation unit 4 includes, for example, a DAC (Digital Analog Converter) and generates a drive signal COM based on a waveform specification signal dCOM supplied from the drive control unit 22. For example, the drive signal generation unit 4 generates a drive signal COM that includes a waveform defined by the waveform specification signal dCOM. The drive signal generation unit 4 outputs the drive signal COM generated based on the waveform specification signal dCOM to the switching circuit 31 included in the head unit 3. In this embodiment, it is assumed that the head unit 3 and the drive signal COM correspond to each other. For example, the inkjet printer 1 may have four drive signal generation units 4 that correspond one-to-one with four head units 3.

[0020] The memory unit 5 is composed of one or both of the following: volatile memory such as RAM (Random Access Memory) and non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable ROM). The memory unit 5 may also be included in the control unit 2. The memory unit 5 is an example of a "storage unit".

[0021] The head unit 3 includes a switching circuit 31, a recording head 32, and a detection circuit 33.

[0022] The recording head 32 has J ejection units D. The value J is a natural number greater than or equal to 1. Hereinafter, the j-th ejection unit D among the J ejection units D provided on the recording head 32 may be referred to as ejection unit D[j]. Here, the variable j is a natural number satisfying "1 ≤ j ≤ J". Furthermore, hereinafter, if a component or signal of the inkjet printer 1 corresponds to ejection unit D[j] among the J ejection units D, the subscript [j] may be added to the code used to represent that component or signal.

[0023] The switching circuit 31 switches whether or not to supply the drive signal COM to the ejection unit D[j] based on the print signal SI. In the following, as shown in Figure 6 and other figures described later, the drive signal COM supplied to the ejection unit D[j] may be referred to as the individual drive signal Vin[j]. The drive signal COM and the individual drive signal Vin are examples of "drive signals".

[0024] Furthermore, the switching circuit 31 switches whether or not to electrically connect the ejection unit D[j] and the detection circuit 33 based on the printing signal SI. When the ejection unit D[j] and the detection circuit 33 are electrically connected, for example, the detection signal Vout[j] detected from the ejection unit D[j] is supplied to the detection circuit 33 via the switching circuit 31. The detection signal Vout[j] is an analog signal that indicates, for example, the change in potential of the upper electrode Zu[j] provided on the piezoelectric element PZ[j] of the ejection unit D[j]. For example, the detection signal Vout[j] is a residual vibration signal that occurs due to vibrations remaining in the ejection unit D[j] after the piezoelectric element PZ[j] has been driven by the individual drive signal Vin[j]. In this case, the waveform of the detection signal Vout[j] shows, for example, the waveform of the residual vibration which is the vibration remaining in the ejection unit D[j] after the piezoelectric element PZ[j] has been driven. The residual vibration of the discharge section D[j] after the piezoelectric element PZ[j] is driven corresponds to the residual vibration of the diaphragm 321 after the piezoelectric element PZ[j] is driven. The piezoelectric element PZ, the upper electrode Zu[j], and the diaphragm 321 will be described later in Figure 3.

[0025] The detection circuit 33 generates a residual vibration signal VD[j] corresponding to the detection signal Vout[j] as a signal for determining the state of the discharge section D[j]. For example, the detection circuit 33 shapes the detection signal Vout[j] into a waveform suitable for processing in the inspection unit 6 by amplifying the amplitude of the detection signal Vout[j] or removing noise components contained in the detection signal Vout[j]. This generates the residual vibration signal VD[j]. For example, the detection circuit 33 may include a negative feedback type amplifier for amplifying the detection signal Vout[j], a low-pass filter for attenuating the high-frequency components of the detection signal Vout[j], and a voltage follower that converts the impedance to output a low-impedance residual vibration signal VD[j].

[0026] For example, the residual vibration signal VD[j] generated based on the detection signal Vout[j] is an analog signal that shows the waveform of the residual vibration of the diaphragm 321 after the piezoelectric element PZ[j] has been driven by the individual drive signal Vin[j]. The detection circuit 33 outputs the residual vibration signal VD[j] generated based on the detection signal Vout[j] to the inspection unit 6. In this way, the detection circuit 33 detects the residual vibration of the diaphragm 321 caused by driving the piezoelectric element PZ[j] based on the detection signal Vout[j].

[0027] The inspection unit 6 determines, for example, the state of the ejection unit D[j] based on the residual vibration signal VD[j]. Figure 1 briefly illustrates the overview of the inspection unit 6, and details of the inspection unit 6 will be explained later in Figure 7. In this embodiment, it is assumed that the inspection unit 6 has a first inspection mode and a second inspection mode as inspection modes for determining the state of the ejection unit D. For example, the first inspection mode is an inspection mode that determines the state of the ejection unit D[j] in a shorter inspection time than the second inspection mode. Therefore, in this embodiment, the inspection time can be shortened by selecting the first inspection mode as the inspection mode. In this embodiment, by selecting the second inspection mode as the inspection mode, it is possible to determine multiple abnormal states, including the viscosity state of the ink in the ejection unit D.

[0028] The inspection unit 6 includes, for example, a signal generation unit 60 that generates a state inspection signal based on a residual vibration signal VD, and a determination unit 64 that determines the state of the ejection unit D based on the state inspection signal. For example, the determination unit 64 determines the state of the ejection unit D based on the state inspection signal generated by the signal generation unit 60 and generates state information Cinf that includes information indicating the result of the determination. Examples of the state of the ejection unit D include the viscosity of the ink inside the ejection unit D. For example, the determination unit 64 uses a state inspection signal generated based on a residual vibration signal VD[j] to determine the viscosity of the ink inside the ejection unit D[j]. In this case, it is possible to prevent the printing process from being executed when an abnormality caused by the viscosity of the ink inside the ejection unit D[j] has occurred. Hereinafter, the process of determining the state of the ejection unit D[j] will also be referred to as the ejection state determination process. Also below, the ejection unit D whose state is determined will also be referred to as the ejection unit D to be determined.

[0029] When the ejection state determination process is executed, the drive control unit 22 generates signals for controlling the head unit 3, such as the print signal SI. Also, when the ejection state determination process is executed, the drive control unit 22 generates signals for controlling the drive signal generation unit 4, such as the waveform specification signal dCOM. As a result, the drive control unit 22 drives the ejection unit D[j] as the ejection unit D to be determined.

[0030] Furthermore, when the ejection state determination process is executed, the drive control unit 22 generates a print signal SI, thereby controlling the head unit 3 so that a detection signal Vout[j] corresponding to the ejection unit D[j] driven as the ejection unit D to be determined is supplied to the detection circuit 33. As a result, the detection circuit 33 generates a residual vibration signal VD[j] corresponding to the detection signal Vout[j] detected from the ejection unit D[j] driven as the ejection unit D to be determined. The inspection unit 6 then determines the state of the ejection unit D[j] driven as the ejection unit D to be determined based on the residual vibration signal VD[j] supplied from the detection circuit 33. The inspection unit 6 also outputs state information Cinf, which includes information indicating the determination result of the state of the ejection unit D[j], to the control unit 2.

[0031] The inspection unit 6 may be included in the control unit 2. For example, the control unit 2 may function as the inspection unit 6 by operating according to the control program PG stored in the memory unit 5.

[0032] Furthermore, as described above, in this embodiment, the inkjet printer 1 performs maintenance processing. For example, the maintenance processing includes a flushing process to discharge ink from the ejection unit D, a wiping process to wipe off foreign matter such as ink adhering to the vicinity of the nozzle N of the ejection unit D with a wiper, and a pumping process to suck out the ink inside the ejection unit D with a tube pump or the like. The nozzle N will be described later in Figure 3.

[0033] For example, ink that has undergone thickening, resulting in increased viscosity, is discharged from the discharge unit D through a flushing process. This allows the viscosity of the ink in the nozzle N at the start of the printing process to be kept below a predetermined viscosity. In this case, since the thickened ink is discharged from the discharge unit D, it is possible to suppress a decrease in the quality of the image printed during the printing process.

[0034] The maintenance unit 8 includes an ink discharge receiving unit 80 for receiving ink discharged from the discharge unit D during the flushing process, a wiper for wiping off foreign matter such as ink adhering to the vicinity of the nozzle N of the discharge unit D, and a tube pump for sucking up ink, air bubbles, etc. from the discharge unit D. The ink discharge receiving unit 80 will be described later in Figure 2. The wiper and tube pump are not shown in the illustration. Next, the general internal structure of the inkjet printer 1 will be described with reference to Figure 2.

[0035] Figure 2 is a perspective view showing an example of the schematic internal structure of inkjet printer 1.

[0036] As shown in Figure 2, in this embodiment, it is assumed that the inkjet printer 1 is a serial printer. Specifically, when the inkjet printer 1 performs a printing process, it transports the recording paper P in the sub-scanning direction, and while moving the head module HM back and forth in the main scanning direction intersecting the sub-scanning direction, it ejects ink from the ejection unit D[j] to form dots on the recording paper P corresponding to the print data IMG.

[0037] In the following, for the sake of explanation, a three-axis orthogonal coordinate system with mutually orthogonal X, Y, and Z axes will be introduced as appropriate. For example, in this embodiment, the Y1 direction along the Y axis is the sub-scanning direction, and the X1 and X2 directions along the X axis are the main scanning directions. Note that the X2 direction is the opposite direction to the X1 direction. Also, in this embodiment, as illustrated in Figure 2, the Z1 direction along the Z axis is the ink ejection direction from the ejection unit D[j]. Furthermore, in the following, the X1 and X2 directions will be collectively referred to as the X-axis direction, the Y1 direction and the Y2 direction opposite to the Y1 direction will be collectively referred to as the Y-axis direction, and the Z1 direction and the Z2 direction opposite to the Z1 direction will be collectively referred to as the Z-axis direction. Note that in this embodiment, as described above, it is assumed that the X, Y, and Z axes are mutually orthogonal, but the present invention is not limited to this embodiment. For example, the X, Y, and Z axes only need to intersect each other.

[0038] The inkjet printer 1 according to this embodiment includes a housing 100 and a carriage 110 that can reciprocate within the housing 100 in the X-axis direction. The carriage 110 is equipped with a head module HM including four head units 3.

[0039] In this embodiment, it is assumed that the carriage 110 houses four ink cartridges 120, each corresponding to one-to-one with four inks: cyan, magenta, yellow, and black. Furthermore, in this embodiment, it is assumed that four head units 3 correspond one-to-one with the four ink cartridges 120. Each ejection unit D[j] receives ink from the ink cartridge 120 corresponding to the head unit 3 on which the ejection unit D[j] is located. As a result, each ejection unit D[j] can fill itself with the supplied ink and eject the filled ink from the nozzle N. Note that the ink cartridges 120 may be located outside the carriage 110.

[0040] Furthermore, the inkjet printer 1 according to this embodiment has a transport unit 7, as described in Figure 1. The transport unit 7 has a carriage transport mechanism 71 for reciprocating the carriage 110 in the X-axis direction, and a carriage guide shaft 76 that supports the carriage 110 so that it can reciprocate in the X-axis direction. In addition, the transport unit 7 has a media transport mechanism 73 for transporting the recording paper P, and a platen 75 provided in the Z1 direction relative to the carriage 110. For example, in the printing process, the carriage transport mechanism 71 reciprocates the head module HM together with the carriage 110 along the carriage guide shaft 76 in the X-axis direction, and the media transport mechanism 73 transports the recording paper P on the platen 75 in the Y1 direction. Therefore, in the printing process, the transport unit 7 changes the relative position of the recording paper P with respect to the head module HM by causing the carriage transport mechanism 71 and the media transport mechanism 73 to perform the above operations, thereby enabling ink to land on the entire recording paper P.

[0041] Next, the general structure of the recording head 32 will be described with reference to Figure 3.

[0042] Figure 3 is a cross-sectional view illustrating an example of the structure of the ejection section D. Note that Figure 3 schematically shows a portion of the recording head 32 when the recording head 32 is cut to include the ejection section D[j].

[0043] The ejection unit D[j] includes a cavity CV filled with ink, a nozzle N communicating with the cavity CV, a piezoelectric element PZ[j] that generates pressure fluctuations in the ink within the cavity CV when an individual drive signal Vin[j] is supplied, and a diaphragm 321. The ejection unit D[j] ejects the ink from the cavity CV through the nozzle N when the piezoelectric element PZ[j] is driven by the individual drive signal Vin[j].

[0044] The cavity CV corresponds to a pressure chamber communicating with the nozzle N. For example, the cavity CV is a space partitioned by a cavity plate 324, a nozzle plate 323 on which the nozzle N is formed, and a diaphragm 321. The cavity CV communicates with the reservoir 325 via an ink supply port 326. The reservoir 325 communicates with the ink cartridge 120 corresponding to the ejection section D[j] via an ink intake port 327. The piezoelectric element PZ[j] has an upper electrode Zu[j], a lower electrode Zd[j], and a piezoelectric element Zb[j] provided between the upper electrode Zu[j] and the lower electrode Zd[j]. The piezoelectric element Zb[j] is formed of, for example, a ferroelectric piezoelectric material.

[0045] The upper electrode Zu[j] is electrically connected to wiring Li, to which the individual drive signal Vin[j] is supplied. The lower electrode Zd[j] is electrically connected to wiring Ld, to which the base potential signal VBS is supplied. When the individual drive signal Vin[j] is supplied to the upper electrode Zu[j], a voltage is applied between the upper electrode Zu[j] and the lower electrode Zd[j]. The piezoelectric element PZ[j] is displaced in the Z1 direction or the Z2 direction according to the voltage applied between the upper electrode Zu[j] and the lower electrode Zd[j].

[0046] Thus, the piezoelectric element PZ[j] vibrates in response to the voltage applied between the upper electrode Zu[j] and the lower electrode Zd[j]. The lower electrode Zd[j] is joined to the diaphragm 321. Therefore, when the piezoelectric element PZ[j] is driven and vibrates by the individual drive signal Vin[j], the diaphragm 321 also vibrates. As a result of the vibration of the diaphragm 321, the volume of the cavity CV and the pressure inside the cavity CV change, and the ink filled in the cavity CV is ejected from the nozzle N.

[0047] In this embodiment, as an example, we assume that the piezoelectric element PZ is displaced in the Z1 direction when the potential of the individual drive signal Vin[j] supplied to the discharge unit D[j] changes from a low potential to a high potential. That is, in this embodiment, we assume that when the potential of the individual drive signal Vin[j] supplied to the discharge unit D[j] is high, the volume of the cavity CV provided by the discharge unit D[j] becomes smaller compared to when it is low.

[0048] Next, the ink ejection operation in the ejection unit D will be explained with reference to Figure 4.

[0049] Figure 4 is an explanatory diagram illustrating the ink ejection operation in the ejection unit D.

[0050] The drive control unit 22, for example, in Phase-1, changes the potential of the drive signal COM supplied to the piezoelectric element PZ of the ejection unit D, thereby generating a strain that causes the piezoelectric element PZ to be displaced in the Z2 direction. As a result, the diaphragm 321 of the ejection unit D bends in the Z2 direction. Consequently, as shown in Phase-2 in Figure 4, the volume of the cavity CV of the ejection unit D expands compared to Phase-1. Next, the drive control unit 22, for example, in Phase-2, changes the potential of the drive signal COM, thereby generating a strain that causes the piezoelectric element PZ to be displaced in the Z1 direction. As a result, the diaphragm 321 of the ejection unit D bends in the Z1 direction. Consequently, as shown in Phase-3 in Figure 4, the volume of the cavity CV rapidly contracts, and a portion of the ink filling the cavity CV is ejected as ink droplets from the nozzle N communicating with the cavity CV.

[0051] Thus, the piezoelectric element PZ and the diaphragm 321 of the discharge unit D are displaced in the Z-axis direction when the piezoelectric element PZ of the discharge unit D is driven by the drive signal COM. For this reason, residual vibration occurs in the discharge unit D, including the diaphragm 321, after the piezoelectric element PZ is driven by the drive signal COM.

[0052] Next, an example of nozzle N arrangement will be described with reference to Figure 5.

[0053] Figure 5 is a plan view showing an example of the arrangement of nozzles N in the head unit 3. In Figure 5, when the inkjet printer 1 is viewed from the Z1 direction, an example of the arrangement of the four head units 3 in the head module HM and the total of 4J nozzles N provided on these four head units 3 is shown.

[0054] Each head unit 3 of the head module HM provided on the carriage 110 is provided with a nozzle row NL. Here, the nozzle row NL is a plurality of nozzles N arranged to extend in a row in a predetermined direction. In this embodiment, as an example, we assume that each nozzle row NL consists of J nozzles N arranged to extend in the Y-axis direction.

[0055] Next, we will describe the overview of the head unit 3 with reference to Figure 6.

[0056] Figure 6 is a block diagram showing an example of the configuration of the head unit 3.

[0057] As described in Figure 1, the head unit 3 includes a switching circuit 31, a recording head 32, and a detection circuit 33. The head unit 3 also has wiring La to which the drive signal COM is supplied from the drive signal generation unit 4, and wiring Ls to which the detection signal Vout is supplied to the detection circuit 33. Furthermore, the head unit 3 has wiring Li[j] to which the individual drive signal Vin[j] is supplied to the ejection unit D[j], and wiring Ld to which the base potential signal VBS is supplied.

[0058] The switching circuit 31 includes J switches SWa[1] to SWa[J] that correspond one-to-one with J discharge units D[1] to D[J], J switches SWs[1] to SWs[J] that correspond one-to-one with J discharge units D[1] to D[J], and a connection state specification circuit 310.

[0059] The connection state designation circuit 310 designates the connection state of each of the J switches SWa and J switches SWs. For example, the connection state designation circuit 310 generates connection state designation signals Qa[j] and Qs[j] based on at least some of the print signal SI, latch signal LAT, and period designation signal Tsig supplied from the drive control unit 22. The connection state designation signal Qa[j] is a signal that designates the on / off state of switch SWa[j], and the connection state designation signal Qs[j] is a signal that designates the on / off state of switch SWs[j].

[0060] In this embodiment, it is assumed that each of the J switches SWa and J switches SWs is composed of a transfer gate including a P-channel transistor and an N-channel transistor connected in parallel. However, each of the J switches SWa and J switches SWs may be composed of either a P-channel transistor or an N-channel transistor.

[0061] The switch SWa[j] switches between conductivity and non-conductivity between wiring La and the upper electrode Zu[j] of piezoelectric element PZ[j] provided in the discharge unit D[j], based on the connection status specification signal Qa[j]. That is, the switch SWa[j] switches between conductivity and non-conductivity between wiring La and wiring Li[j] connected to the upper electrode Zu[j], based on the connection status specification signal Qa[j]. In this embodiment, the switch SWa[j] is turned on when the connection status specification signal Qa[j] is high level and turned off when it is low level. When the switch SWa[j] is turned on, the drive signal COM supplied to wiring La is supplied as an individual drive signal Vin[j] to the upper electrode Zu[j] of the discharge unit D[j] via wiring Li[j]. That is, the individual drive signal Vin[j] is the drive signal COM supplied to the piezoelectric element PZ[j] of the discharge unit D[j] via the switch SWa[j].

[0062] The switch SWs[j] switches between continuity and non-continuity between the wiring Ls and the upper electrode Zu[j] of the piezoelectric element PZ[j] provided in the discharge section D[j], based on the connection status specification signal Qs[j]. In other words, the switch SWs[j] switches between continuity and non-continuity between the wiring Ls and the wiring Li[j] connected to the upper electrode Zu[j], based on the connection status specification signal Qs[j]. In this embodiment, the switch SWs[j] is turned on when the connection status specification signal Qs[j] is at a high level and turned off when it is at a low level.

[0063] For example, the connection status specification signal Qs[j] becomes high when detecting residual vibration of the discharge unit D[j]. This allows the residual vibration of the discharge unit D to be detected. When the switch SWs[j] is turned on, a detection signal Vout[j] indicating the potential of the upper electrode Zu[j] of the piezoelectric element PZ[j] of the discharge unit D[j] to be detected is supplied to the detection circuit 33 via the wiring Li[j] and wiring Ls. The detection circuit 33 then generates a residual vibration signal VD[j] based on the detection signal Vout[j]. The residual vibration signal VD[j] is supplied to the signal generation unit 60 of the inspection unit 6.

[0064] The supply of the residual vibration signal VD[j] to the signal generation unit 60 ends when the switch SWs[j] is turned off. For example, when the switch SWs[j] is turned off, the wiring Ls and wiring Li[j] become non-conductive, and the signal path of the residual vibration signal VD from the discharge unit D to the signal generation unit 60 is interrupted. In other words, the signal generation unit 60 becomes electrically disconnected from the discharge unit D[j] by the connection status specification signal Qs[j]. For example, the timing at which the connection status specification signal Qs[j] transitions from a high level to a low level corresponds to the interruption timing at which the signal path of the residual vibration signal VD from the discharge unit D to the signal generation unit 60 is interrupted. Note that the connection status specification signal Qs is an example of a "disconnection signal". Furthermore, in the signal path of the residual vibration signal VD from the discharge unit D[j] to the signal generation unit 60, one of the wirings Ls and Li[j] corresponds to the "first signal path," and the other of the wirings Ls and Li[j] corresponds to the "second signal path."

[0065] Next, we will describe the inspection unit 6 with reference to Figure 7.

[0066] Figure 7 is a block diagram showing an example of the configuration of the inspection unit 6. As described in Figure 1, the inspection unit 6 has a signal generation unit 60 and a determination unit 64.

[0067] The signal generation unit 60 includes, for example, a comparison unit 62 including comparison circuits 620, 621, and 622, and an adjustment unit 63 including adjustment circuits 630, 631, and 632.

[0068] Each of the comparison circuits 620, 621, and 622 included in the comparison unit 62 binarizes the residual vibration signal VD by comparing the residual vibration signal VD with a threshold value.

[0069] The comparison circuit 620, for example, compares the potential of the residual vibration signal VD with the threshold potential VthC and generates a comparison signal CPc indicating the comparison result. Specifically, the comparison circuit 620 generates a comparison signal CPc that becomes a high level when the potential of the residual vibration signal VD is equal to or higher than the threshold potential VthC and becomes a low level when the potential of the residual vibration signal VD is lower than the threshold potential VthC.

[0070] Further, the comparison circuit 621, for example, compares the potential of the residual vibration signal VD with the threshold potential Vth1 and generates a comparison signal CP1 indicating the comparison result. Specifically, the comparison circuit 621 generates a comparison signal CP1 that becomes a high level when the potential of the residual vibration signal VD is equal to or higher than the threshold potential Vth1 and becomes a low level when the potential of the residual vibration signal VD is lower than the threshold potential Vth1.

[0071] Further, the comparison circuit 622, for example, compares the potential of the residual vibration signal VD with the threshold potential Vth2 and generates a comparison signal CP2 indicating the comparison result. Specifically, the comparison circuit 622 generates a comparison signal CP2 that becomes a high level when the potential of the residual vibration signal VD is equal to or higher than the threshold potential Vth2 and becomes a low level when the potential of the residual vibration signal VD is lower than the threshold potential Vth2.

[0072] In this embodiment, the threshold potential VthC is the potential at the amplitude center level of the residual vibration signal VD, and the threshold potentials VthC, Vth1, and Vth2 satisfy "VthC < Vth2 < Vth1". Also, in this embodiment, the threshold potentials VthC, Vth1, and Vth2 satisfy "|Vth2 - VthC| < |Vth1 - VthC|". The threshold potential VthC is an example of the "first potential", and the threshold potentials Vth1 and Vth2 are examples of the "second potential".

[0073] The comparison signals CPc, CP1, and CP2 are supplied to the adjustment circuits 630, 631, and 632 of the adjustment unit 63, respectively. Hereinafter, the comparison signals CPc, CP1, and CP2 may be collectively referred to as the comparison signal CP. The comparison signal CP is an example of a "test signal." Furthermore, among the comparison signals CP, the comparison signal CPc corresponds to the "reference signal."

[0074] The adjustment unit 63 generates comparison signals CCPc, CCP1, and CCP2 based on the pulse detection period signal Pcut and mask signal MSK supplied from the control unit 2, and the comparison signals CPc, CP1, and CP2 supplied from the comparison unit 62. Hereinafter, comparison signals CCPc, CCP1, and CCP2 may be collectively referred to as comparison signal CCP. Comparison signal CCP is an example of a "status check signal".

[0075] The pulse detection period signal Pcut, as shown in Figure 9 later, is a signal that defines the reset timing tep for resetting the comparison signal CCP. For example, the pulse detection period signal Pcut is maintained at a high level during the period when the comparison signal CP is effective as a signal used to generate the comparison signal CCP. The pulse detection period signal Pcut is an example of a "reset signal".

[0076] Furthermore, the mask signal MSK is a signal that defines a mask period in which the comparison signal CP is invalid as a signal used to generate the comparison signal CCP in the second inspection mode. Therefore, the residual vibration signal VD during the mask period is not used to determine the state of the discharge unit D. In this embodiment, it is assumed that the mask signal MSK is maintained at a high level during the mask period. For example, in the second inspection mode, the mask signal MSK is maintained at a high level until a predetermined time has elapsed since the switch SWs[j] was turned on, and then changes to a low level after the predetermined time has elapsed. In the first inspection mode, the mask signal MSK is maintained at a low level.

[0077] For example, the adjustment circuit 630 of the adjustment unit 63 generates a comparison signal CCPc, which is the logical AND of the inverted signal of the mask signal MSK and the pulse detection period signal Pcut and the comparison signal CPc. As a result, the potential of the comparison signal CCPc after the reset timing tep defined by the pulse detection period signal Pcut is maintained at a low level, regardless of the level of the comparison signal CPc. The inverted signal of the mask signal MSK is, for example, a signal that becomes high level when the mask signal MSK is low level, and low level when the mask signal MSK is high level.

[0078] Furthermore, the adjustment circuit 631 of the adjustment unit 63 generates a comparison signal CCP1 which is a logical AND of the inverted signal of the mask signal MSK, the pulse detection period signal Pcut, and the comparison signal CP1. As a result, the potential of the comparison signal CCP1 after the reset timing tep defined by the pulse detection period signal Pcut is maintained at a low level regardless of the level of the comparison signal CP1.

[0079] Furthermore, the adjustment circuit 632 of the adjustment unit 63 generates a comparison signal CCP2, which is a logical AND of the inverted signal of the mask signal MSK, the pulse detection period signal Pcut, and the comparison signal CP2. As a result, the potential of the comparison signal CCP2 after the reset timing tep defined by the pulse detection period signal Pcut is maintained at a low level, regardless of the level of the comparison signal CP2.

[0080] The comparison signals CCPc, CCP1, and CCP2, generated by the adjustment circuits 630, 631, and 632, respectively, are supplied to the determination unit 64. For example, if the cutoff timing is before the reset timing tep, comparison signal CCPc corresponds to the signal in which the potential of comparison signal CPc at the cutoff timing is held until the reset timing tep. Similarly, comparison signal CCP1 corresponds to the signal in which the potential of comparison signal CP1 at the cutoff timing is held until the reset timing tep, and comparison signal CCP2 corresponds to the signal in which the potential of comparison signal CP2 at the cutoff timing is held until the reset timing tep.

[0081] Here, since the potential of the comparison signal CCP after the reset timing tep is maintained at a low level regardless of the level of the comparison signal CP, the reset timing tep can also be considered as the endpoint timing of the pulse of the comparison signal CCP.

[0082] The determination unit 64 includes a specification unit 67 which contains specification circuits 670, 671, and 672, an amplitude calculation circuit 68, and a determination circuit 69.

[0083] The identification unit 67 identifies, for example, the duration of the period during which each of the comparison signals CCPc, CCP1, and CCP2 is maintained at a high level. For example, the identification circuits 670, 671, and 672 of the identification unit 67 are supplied with the comparison signals CCPc, CCP1, and CCP2, respectively. For example, the identification circuit 670 identifies the duration TCc of the period WCc during which the comparison signal CCPc is at a high level, and outputs time information NTCc indicating this duration TCc to the amplitude calculation circuit 68. In this embodiment, the period WCc for which the duration TCc is identified is, as shown in Figure 9 later, the period during which the comparison signal CCPc is first maintained at a high level, after the time t0 when the supply of the residual vibration signal VD to the signal generation unit 60 begins.

[0084] Furthermore, the identification circuit 671 identifies the time length TC1 of the period WC1 in which the comparison signal CCP1 is at a high level, and outputs time information NTC1 indicating this time length TC1 to the amplitude calculation circuit 68. Here, the period WC1 in which the time length TC1 is identified is, as shown in Figure 9, a period after time t0, during which the comparison signal CCP1 is first maintained at a high level.

[0085] Furthermore, the identification circuit 672 identifies the time length TC2 of the period WC2 in which the comparison signal CCP2 is at a high level, and outputs time information NTC2 indicating this time length TC2 to the amplitude calculation circuit 68. Here, the period WC1 in which the time length TC2 is identified is, as shown in Figure 9, the period after time t0 in which the comparison signal CCP2 is first maintained at a high level. Hereafter, time lengths TCc, TC1, and TC2 may be collectively referred to as time length TC, and time information NTCc, NTC1, and NTC2 may be collectively referred to as time information NTC. Time information NTC is an example of "inspection signal information".

[0086] The amplitude calculation circuit 68 calculates an amplitude Vamp that corresponds to the amplitude VPK of the residual vibration signal VD shown in Figure 9, for example. The amplitude Vamp that corresponds to the amplitude VPK of the residual vibration signal VD includes the same amplitude as the amplitude VPK of the residual vibration signal VD, an amplified amplitude of the amplitude VPK of the residual vibration signal VD, and an attenuated amplitude of the amplitude VPK of the residual vibration signal VD. Hereinafter, the amplitude Vamp that corresponds to the amplitude VPK of the residual vibration signal VD may simply be referred to as the amplitude Vamp of the residual vibration signal VD.

[0087] Furthermore, in this embodiment, the amplitude calculation circuit 68 has a first calculation mode and a second calculation mode as calculation modes for calculating the amplitude Vamp of the residual vibration signal VD. For example, in the first calculation mode, the amplitude calculation circuit 68 calculates the amplitude Vamp based on the time lengths TCc and TC1 and the threshold potentials VthC and Vth1. In the second calculation mode, the amplitude calculation circuit 68 calculates the amplitude Vamp based on the time lengths TCc and TC2 and the threshold potentials VthC and Vth2.

[0088] The amplitude Vamp is expressed by equation (1) in the first calculation mode and by equation (2) in the second calculation mode. Equations (1) and (2) below calculate the amplitude Vamp by approximating the waveform of the residual vibration signal VD to a sine wave.

[0089]

number

[0090] The choice of which calculation mode, the first calculation mode or the second calculation mode, to use to calculate the amplitude Vamp may be predetermined for each nozzle N, for example. Alternatively, the amplitude calculation circuit 68 may determine which calculation mode to use to calculate the amplitude Vamp based on the time length TC1. Specifically, for example, the amplitude calculation circuit 68 may calculate the amplitude Vamp in the first calculation mode if the time length TC1 is longer than the first reference time, and calculate the amplitude Vamp in the second calculation mode if the time length TC1 is shorter than the second reference time which is less than or equal to the first reference time. If the time length TC1 is greater than or equal to the second reference time and less than or equal to the first reference time, the amplitude Vamp may be calculated in the previous calculation mode. The initial calculation mode is, for example, the first calculation mode. In the above example, the switching of the calculation mode has a hysteresis characteristic, but the switching of the calculation mode does not have to have a hysteresis characteristic.

[0091] The amplitude calculation circuit 68 outputs amplitude information NVamp, which indicates the amplitude Vamp, to the determination circuit 69 as waveform information that shows the waveform characteristics of the residual vibration signal VD. Here, the waveform characteristics of the residual vibration signal VD refer to information about the shape of the waveform of the residual vibration signal VD, such as the amplitude VPK and period of the residual vibration signal VD. In this embodiment, as described above, it is assumed that amplitude information NVamp, which indicates the amplitude Vamp corresponding to the amplitude VPK of the residual vibration signal VD, is supplied to the determination circuit 69 as waveform information.

[0092] The determination circuit 69 determines the ink ejection state at the ejection unit D based on the amplitude Vamp of the residual vibration signal VD, and generates state information Cinf which includes information indicating the result of the determination. For example, when the inspection mode is the second inspection mode, the determination circuit 69 may acquire, in addition to the amplitude information NVamp, time information NTCc, which indicates the duration TCc of the period WCc during which the comparison signal CCPc is at a high level, as waveform information. In this case, the determination circuit 69 may determine the ink ejection state at the ejection unit D based on the amplitude Vamp and duration TCc of the residual vibration signal VD. As a method for determining the state of the ejection unit D based on the amplitude Vamp of the residual vibration signal VD, etc., known methods for determining the state of the ejection unit D based on the amplitude VPK of the residual vibration signal VD, etc., can be employed.

[0093] Next, the operation of the inkjet printer 1 will be explained with reference to Figure 8.

[0094] Figure 8 is a timing chart showing an example of the operation of the inkjet printer 1 in a unit period TU. In this embodiment, when the inkjet printer 1 performs a printing process or an ejection state determination process, one or more unit periods TU are set as the operating period of the inkjet printer 1. In this embodiment, the inkjet printer 1 can drive each ejection unit D[j] for the printing process or ejection state determination process in each unit period TU. For example, when the inkjet printer 1 performs an ejection state determination process, it can drive the ejection unit D to be determined and detect the detection signal Vout[j] from the ejection unit D to be determined in each unit period TU.

[0095] Control unit 2 outputs a latch signal LAT having a pulse PlsL. This allows control unit 2 to define a unit period TU as the period from the rising edge of one pulse PlsL to the rising edge of the next pulse PlsL.

[0096] The print signal SI includes, for example, J individual designation signals Sd[1] to Sd[J] that correspond one-to-one with J ejection units D[1] to D[J]. The individual designation signals Sd[j] specify the mode of operation of the ejection units D[j] in each unit period TU when the inkjet printer 1 performs printing or ejection state determination processing. For example, the control unit 2 supplies the print signal SI, including the individual designation signals Sd[1] to Sd[J], to the connection state designation circuit 310 in synchronization with the clock signal CL prior to each unit period TU. The connection state designation circuit 310 then generates connection state designation signals Qa[j] and Qs[j] based on the individual designation signals Sd[j] in the unit period TU.

[0097] For example, in a unit period TU in which printing is performed, the ejector unit D[j] is designated by the individual designation signal Sd[j] to be either an ejector unit D that forms dots or an ejector unit D that does not form dots. Also, for example, in a unit period TU in which ejector state determination processing is performed, the ejector unit D[j] is designated by the individual designation signal Sd[j] to determine whether or not to be driven as the ejector unit D to be determined. In Figure 8, the connection status designation signals Qa[j] and Qs[j] etc. are shown when the ejector unit D[j] is designated as the ejector unit D to be determined by the individual designation signal Sd[j] in a unit period TU in which ejector state determination processing is performed. Figure 8 mainly explains the operation of the inkjet printer 1 when ejector state determination processing is performed. Also, Figure 8 assumes that the inspection mode is the first inspection mode. In this case, the mask signal MSK is maintained at a low level in a unit period TU.

[0098] When the discharge state determination process is executed, for example, the control unit 2 outputs a period definition signal Tsig having pulses PlsT1 and PlsT2. As a result, the control unit 2 divides the unit period TU into a control period TSS1 from the start of pulse PlsL to the start of pulse PlsT1, and a control period TSS2 from the start of pulse PlsT1 to the start of the next pulse PlsL.

[0099] Furthermore, the control unit 2 defines the validity period TPval of the comparison signal CP by controlling the pulse detection period signal Pcut. For example, the drive control unit 22 of the control unit 2 sets the pulse detection period signal Pcut to a high level when pulse PlsT1 ends and sets the pulse detection period signal Pcut to a low level when pulse PlsT2 begins. In this case, the period during which the logical AND result of the inverted signal of the mask signal MSK and the pulse detection period signal Pcut is high corresponds to the validity period TPval. In the first inspection mode, as shown in Figure 8, the mask signal MSK is maintained at a low level in the unit period TU, so the period during which the pulse detection period signal Pcut is high corresponds to the validity period TPval.

[0100] Furthermore, the drive signal COM used in the ejection state determination process includes, for example, a pulse PA supplied to wiring La during the control period TSS1. The pulse PA used in the ejection state determination process may be a pulse that does not eject ink from the nozzle N, or a pulse that ejects ink from the nozzle N, as long as it is a pulse that generates vibration in the diaphragm 321. In this embodiment, it is assumed that the pulse PA is a pulse that does not eject ink from the nozzle N. In the printing process, instead of pulse PA, a pulse that ejects ink from the nozzle N is supplied to wiring La during the unit period TU.

[0101] A pulse PA is a waveform in which the potential of the drive signal COM returns to potential V0, passing through a potential VLa lower than potential V0, and then back to potential V0. Potential V0 is the potential at the start and end of pulse PA and is the reference potential of the drive signal COM.

[0102] For example, a pulse PA has a waveform element Pa1 in which the potential changes from potential V0 to potential VLa, a waveform element Pa2 in which the potential is maintained at the potential VLa at the end of waveform element Pa1, and a waveform element Pa3 in which the potential changes from potential VLa to potential V0. Hereafter, waveform elements Pa1, Pa2, and Pa3 may be collectively referred to as waveform element Pa.

[0103] The waveform element Pa1 is an expansion element that displaces the piezoelectric element Zb in the Z2 direction. In the expansion element, the potential of the drive signal COM changes in order to drive the piezoelectric element PZ to expand the volume of the cavity CV. Therefore, in the waveform element Pa1, the potential of the drive signal COM changes to expand the volume of the cavity CV. When the volume of the cavity CV expands, the surface of the ink inside the nozzle N is pulled in the Z2 direction, which is the opposite direction to the ejection direction, as shown in Phase-2 in Figure 4. Hereafter, the pulling of the surface of the ink inside the nozzle N in the opposite direction to the ejection direction may be referred to as "pull".

[0104] Furthermore, the waveform element Pa2 is a maintenance element for maintaining the position of the piezoelectric element Zb in the Z-axis direction. For example, the waveform element Pa2 maintains the potential of the drive signal COM in order to drive the piezoelectric element PZ to maintain the volume of the cavity CV that has been expanded by the waveform element Pa1.

[0105] Furthermore, the waveform element Pa3 is a contraction element for displacing the piezoelectric element Zb in the Z1 direction. In the contraction element, the potential of the drive signal COM changes in order to drive the piezoelectric element PZ to contract the volume of the cavity CV. Therefore, in the waveform element Pa3, the potential of the drive signal COM changes to contract the volume of the cavity CV. When the volume of the cavity CV contracts, the surface of the ink in the nozzle N is pushed out in the Z1 direction, which is the discharge direction. In this embodiment, the waveform element Pa3 pushes the surface of the ink in the nozzle N out in the Z1 direction to the extent that no ink is discharged from the nozzle N. Hereafter, pushing the surface of the ink in the nozzle N in the discharge direction may be referred to as "pushing".

[0106] Thus, the pulse PA is a so-called pull-push waveform. However, the waveform of the drive signal COM, which prevents ink from being ejected from nozzle N, is not limited to a pull-push waveform.

[0107] Furthermore, for example, if the discharge unit D[j] is designated as the discharge unit D to be determined by the individual designation signal Sd[j], the connection state designation circuit 310 sets the connection state designation signal Qa[j] to a high level and the connection state designation signal Qs[j] to a low level during the control period TSS1. Then, during the control period TSS2, the connection state designation circuit 310 sets the connection state designation signal Qa[j] to a low level and the connection state designation signal Qs[j] to a high level. The timing of the transition of the connection state designation signal Qs[j] from a low level to a high level corresponds to the timing when the input of the drive signal COM to the discharge unit D[j] ends and the timing when the residual vibration signal VD[j] is input to the signal generation unit 60.

[0108] Furthermore, when switching between control period TSS1 and control period TSS2, it is preferable that the state of each switch SWa[j] and SWs[j] switches between on and off, passing through a state where both switches SWa[j] and SWs[j] are on. In other words, it is preferable that the timing of the transition of the connection status specification signal Qs[j] from low level to high level is earlier than the timing of the transition of the connection status specification signal Qa[j] from high level to low level. Also, it is preferable that the timing of the transition of the connection status specification signal Qs[j] from high level to low level is later than the timing of the transition of the connection status specification signal Qa[j] from low level to high level. In this case, since a state in which both switches SWa[j] and SWs[j] are off does not occur when switching between control period TSS1 and control period TSS2, it is possible to suppress changes in the potential of the wiring Ls shown in Figure 6 due to switching noise, etc.

[0109] Furthermore, it is preferable that the timing at which the pulse detection period signal Pcut transitions from a high level to a low level is earlier than the timing at which the connection status specification signal Qa[j] transitions from a low level to a high level, and also earlier than the timing at which the connection status specification signal Qs[j] transitions from a high level to a low level. For this reason, in this embodiment, as described above, the drive control unit 22 of the control unit 2 sets the pulse detection period signal Pcut to a low level when the pulse PlsT2 starts. Alternatively, the drive control unit 22 of the control unit 2 may set the pulse detection period signal Pcut to a high level when the pulse PlsT1 starts, and then set the pulse detection period signal Pcut to a low level when the next pulse PlsL starts, provided that the above transition timing is met.

[0110] The timing at which the pulse detection period signal Pcut transitions from a high level to a low level corresponds to the reset timing tep, which resets the comparison signal CCP. In the following, the timing at which the pulse detection period signal Pcut transitions from a high level to a low level may be referred to as the reset timing tep.

[0111] The piezoelectric element PZ[j] of the discharge section D[j] to be judged is driven by the pulse PA of the drive signal COM during the control period TSS1. Specifically, the piezoelectric element PZ[j] of the discharge section D[j] to be judged is displaced by the pulse PA of the drive signal COM during the control period TSS1. As a result, vibration occurs in the discharge section D[j] to be judged. The vibration that occurred during the control period TSS1 persists into the control period TSS2. During the control period TSS2, the potential of the upper electrode Zu[j] of the piezoelectric element PZ[j] of the discharge section D[j] to be judged changes according to the residual vibration occurring in the discharge section D[j] to be judged. That is, during the control period TSS2, the potential of the upper electrode Zu of the piezoelectric element PZ of the discharge section D to be judged becomes a potential corresponding to the electromotive force of the piezoelectric element PZ caused by the residual vibration occurring in the discharge section D to be judged. The potential of the upper electrode Zu is then detected as the detection signal Vout during the control period TSS2. As a result, the change in the potential of the upper electrode Zu is detected as a detection signal Vout during the control period TSS2. Consequently, the detection signal Vout is input to the detection circuit 33 as a residual vibration signal generated by the vibration remaining in the discharge section D.

[0112] The detection signal Vout input to the detection circuit 33 is supplied to the signal generation unit 60 as a residual vibration signal VD during the control period TSS2. As a result, the comparison signal CP is generated by the signal generation unit 60 during the control period TSS2. Furthermore, the comparison signal CCP is generated by the signal generation unit 60 during the effective period TPval.

[0113] Next, the operation of the inkjet printer 1 when printing is performed will be briefly described. Note that in the printing process, the unit period TU does not necessarily have to be divided into a control period TSS1 and a control period TSS2. In this case, the period definition signal Tsig may be kept at a low level and the pulse detection period signal Pcut may be kept at a low level during the unit period TU.

[0114] The connection status designation signal Qs[j] is maintained at a low level for a unit period TU, regardless of whether, for example, the discharge unit D[j] is designated as a discharge unit D that forms a dot. The connection status designation signal Qa[j] is set to a high level or a low level depending on whether the discharge unit D[j] is designated as a discharge unit D that forms a dot.

[0115] For example, if the individual designation signal Sd[j] designates a discharge unit D[j] as a discharge unit D that forms a dot, the connection state designation circuit 310 sets the connection state designation signal Qa[j] to a high level during the unit period TU. Note that the connection state designation signal Qa corresponding to a discharge unit D that does not form a dot is set to a low level during the unit period TU.

[0116] When the connection status specification signal Qa[j] is set to a high level, a drive signal COM, which includes a pulse that ejects ink from nozzle N, is supplied from the drive signal generation unit 4 to the dot-forming ejection unit D. For example, the pulse that ejects ink from nozzle N is supplied to wiring La for a unit period TU. The pulse that ejects ink from nozzle N may also be a pull-push waveform, similar to pulse PA. In this case, the pulse that ejects ink from nozzle N is defined such that the potential difference at the start and end of the contraction element, which is the waveform element that ejects ink, is greater than the potential difference at the start and end of the waveform element Pa3 of pulse PA. Note that the pulse that ejects ink from nozzle N is not limited to a pull-push waveform. For example, the pulse that ejects ink from nozzle N may be a pull-push-pull waveform.

[0117] Each waveform element of the pulse that ejects ink from nozzle N is defined such that a predetermined amount of ink is ejected from ejection unit D[j] when an individual drive signal Vin[j] having the pulse is supplied to ejection unit D[j]. In this embodiment, it is assumed that when the potential of the individual drive signal Vin[j] is high, the volume of the cavity CV provided by ejection unit D[j] is smaller compared to when it is low. Therefore, when ejection unit D[j] is driven by an individual drive signal Vin[j] having an ink ejection pulse, the ink in ejection unit D[j] is ejected from nozzle N by a waveform element that changes the potential of the individual drive signal Vin[j] from low potential to high potential.

[0118] For example, each waveform element of the pulse that ejects ink from nozzle N is determined based on the ink ejection characteristics of the ejection unit D. The ink ejection characteristics include, for example, the amount of ink ejected as ink droplets and the ejection speed of the ejected ink droplets. The ejection speed of the ink droplets changes depending on, for example, the viscosity of the ink. For example, the ejection speed of ink droplets with a viscosity higher than a predetermined viscosity is lower than the ejection speed of ink droplets with a viscosity of less than or equal to the predetermined viscosity. In this embodiment, the viscosity of the ink in the ejection unit D can be determined based on the amplitude Vamp indicated by the amplitude information NVamp.

[0119] In this embodiment, since it is assumed that the pulse PA is a pulse that does not eject ink from the nozzle N, the ejection state determination process can be executed even when the head unit 3 is not located on the ejected ink receiving unit 80. For example, when printing is performed one pass at a time while moving the head unit 3 along the X-axis, the ejection state determination process may be executed between passes. Also, the ejection state determination process may be executed between a print job based on one print data IMG and a print job based on another print data IMG. Alternatively, the ejection state determination process may be executed when maintenance processing is performed.

[0120] Note that the operation of the inkjet printer 1 is not limited to the example shown in Figure 8. For example, the pulse PA may be a pulse that ejects ink from the nozzle N. In this case, the drive signal COM including the pulse PA may be used in both the printing process and the ejection state determination process. However, if the pulse PA used in the ejection state determination process is a pulse that ejects ink from the nozzle N, it is preferable that the ejection state determination process is performed, for example, when the head unit 3 is positioned on the ejected ink receiving unit 80.

[0121] Furthermore, for example, when the discharge state determination process is executed, the control unit 2 may output a period definition signal Tsig having only pulse PlsT1 among pulses PlsT1 and PlsT2. In this case, the drive control unit 22 of the control unit 2 may, for example, set the pulse detection period signal Pcut to a high level when pulse PlsT1 starts or ends, and set the pulse detection period signal Pcut to a low level when the next pulse PlsL starts, in order to satisfy the transition timing described above.

[0122] Furthermore, although Figure 8 illustrates a case where there is one drive signal COM, the present invention is not limited to this embodiment. For example, multiple drive signals COM may be used, including a drive signal COM that does not eject ink from the nozzle N and a drive signal COM that ejects ink from the nozzle N. In this case, during the printing process, a pulse PA that does not eject ink may be used to prevent ink viscosity from increasing. Also, the drive signal COM that ejects ink from the nozzle N may have multiple pulses that eject ink from the nozzle N to form dots of different sizes.

[0123] Next, with reference to Figure 9, the signals supplied to the signal generation unit 60 and the signals generated by the signal generation unit 60 will be described.

[0124] Figure 9 is a timing chart showing an example of the operation of the signal generation unit 60. In Figure 9, the comparison signal CCP when the inspection mode is the first inspection mode is shown with a solid line, and the comparison signal CCP when the inspection mode is the second inspection mode is shown with a dashed line. In Figure 9, the comparison signal CCP and other related information will be explained mainly in the case when the inspection mode is the first inspection mode.

[0125] Time t0 in Figure 9 indicates the timing when the supply of the residual vibration signal VD to the signal generation unit 60 begins. The timing when the supply of the residual vibration signal VD to the signal generation unit 60 begins is, for example, the timing when the connection status designation signal Qs[j] shown in Figure 8 transitions from a low level to a high level. In the first inspection mode, the connection status designation signal Qs[j] transitions from a high level to a low level, for example, between times t15 and t16. However, in Figure 9, for the sake of clarity, the comparison signal CCP, etc., will be explained assuming that the connection status designation signal Qs[j] is maintained at a high level from time t0 to time t45, regardless of the inspection mode.

[0126] In Figure 9, we assume that the potential of the residual vibration signal VD at time t0 is lower than the threshold potential VthC, which corresponds to the potential of the amplitude center level of the residual vibration signal VD, and that the first peak PK1 of the residual vibration signal VD is the peak where the potential of the residual vibration signal VD is at its maximum value. Therefore, in the example shown in Figure 9, the second peak PK2 of the residual vibration signal VD is the peak where the potential of the residual vibration signal VD is at its minimum value, and the third peak PK3 of the residual vibration signal VD is the peak where the potential of the residual vibration signal VD is at its maximum value. Hereafter, the peaks PK1, PK2, and PK3 of the residual vibration signal VD, and the other peaks of the residual vibration signal VD other than peaks PK1, PK2, and PK3 may be collectively referred to as peak PK.

[0127] For example, the potential of the residual vibration signal VD increases with time from time t0 to time t15, and decreases with time from time t15 to time t25. Then, the potential of the residual vibration signal VD increases with time from time t25 to time t35, and decreases with time from time t35 to time t45.

[0128] First, assuming that the connection status specification signal Qs[j] is maintained at a high level from time t0 to time t45, we will explain the comparison signals CPc, CP1, and CP2.

[0129] For example, at time t10, which is later than time t0, the potential of the residual oscillation signal VD reaches the threshold potential VthC. Therefore, the comparator circuit 620 transitions the comparator signal CPc from a low level to a high level at time t10. Hereafter, the timing at which the comparator signal CPc transitions from a low level to a high level may be referred to as timing tsc. For example, in Figure 9, time t10 corresponds to timing tsc.

[0130] Furthermore, at time t12, which is later than time t10, the potential of the residual oscillation signal VD reaches a threshold potential Vth2, which is higher than the threshold potential VthC. Therefore, at time t12, the comparator circuit 622 transitions the comparator signal CP2 from a low level to a high level. Hereafter, the timing at which the comparator signal CP2 transitions from a low level to a high level may be referred to as timing ts2. For example, in Figure 9, time t12 corresponds to timing ts2. Also below, timings tsc, ts1, and ts2 may be collectively referred to as timing ts.

[0131] Furthermore, at time t14, which is later than time t12, the potential of the residual oscillation signal VD reaches a threshold potential Vth1, which is higher than the threshold potential Vth2. Therefore, the comparator circuit 621 transitions the comparator signal CP1 from a low level to a high level at time t14. Hereafter, the timing at which the comparator signal CP1 transitions from a low level to a high level may be referred to as timing ts1. For example, in Figure 9, time t14 corresponds to timing ts1.

[0132] Furthermore, at time t15, which is later than time t14, the potential of the residual oscillation signal VD reaches its peak from the threshold potential Vth1. Therefore, from time t15 onwards, the potential of the residual oscillation signal VD begins to decrease.

[0133] Then, at time t16, which is later than time t15, the potential of the residual oscillation signal VD reaches the threshold potential Vth1. For this reason, the comparator circuit 621 transitions the comparator signal CP1 from a high level to a low level at time t16.

[0134] Furthermore, at time t18, which is later than time t16, the potential of the residual oscillation signal VD reaches the threshold potential Vth2. Therefore, at time t18, the comparator circuit 622 transitions the comparator signal CP2 from a high level to a low level.

[0135] Furthermore, at time t20, which is later than time t18, the potential of the residual oscillation signal VD reaches the threshold potential VthC. Therefore, at time t20, the comparator circuit 620 transitions the comparator signal CPc from a high level to a low level.

[0136] In this way, a comparison signal CPc indicating whether the potential of the residual vibration signal VD is greater than or equal to the threshold potential VthC is generated by the comparison circuit 620, a comparison signal CP1 indicating whether the potential of the residual vibration signal VD is greater than or equal to the threshold potential Vth1 is generated by the comparison circuit 621, and a comparison signal CP2 indicating whether the potential of the residual vibration signal VD is greater than or equal to the threshold potential Vth2 is generated by the comparison circuit 622.

[0137] Next, we will explain the comparison signals CCPc, CCP1, and CCP2.

[0138] The comparison signal CCP is a signal obtained by resetting the comparison signal CP to a low level at the reset timing tep defined by the pulse detection period signal Pcut. In the first test mode, it is preferable that the reset timing tep, when the pulse detection period signal Pcut transitions from a high level to a low level, is earlier than the timing when the comparison signal CCP1 transitions from a high level to a low level. In the example shown in Figure 9, the pulse detection period signal Pcut transitions from a high level to a low level at time t15, which corresponds to the timing of the first peak PK1 of the residual vibration signal VD. Therefore, in the example shown in Figure 9, time t15 corresponds to the reset timing tep.

[0139] For example, the comparison signal CCPc transitions from a low level to a high level at timing tsc, when the comparison signal CPc transitions from a low level to a high level, and transitions from a high level to a low level at the reset timing tep, when the pulse detection period signal Pcut transitions from a high level to a low level. Therefore, the period WCc during which the comparison signal CCPc is at a high level is the period from timing tsc to the reset timing tep, and the duration TCc of the period WCc corresponds to the elapsed time from timing tsc to the reset timing tep.

[0140] Furthermore, for example, the comparison signal CCP2 transitions from a low level to a high level at timing ts2, when the comparison signal CP2 transitions from a low level to a high level, and transitions from a high level to a low level at the reset timing tep. Therefore, the period WC2 during which the comparison signal CCP2 is at a high level is the period from timing ts2 to the reset timing tep, and the duration TC2 of the period WC2 corresponds to the elapsed time from timing ts2 to the reset timing tep.

[0141] Furthermore, for example, the comparison signal CCP1 transitions from a low level to a high level at timing ts1, when the comparison signal CP1 transitions from a low level to a high level, and transitions from a high level to a low level at the reset timing tep. Therefore, the period WC1 during which the comparison signal CCP1 is at a high level is the period from timing ts1 to the reset timing tep, and the duration TC1 of the period WC1 corresponds to the elapsed time from timing ts1 to the reset timing tep.

[0142] Thus, in the first inspection mode, comparison signals CCPc, CCP1, and CCP2 are generated corresponding to the first partial signal in the first period TPP1 of the residual vibration signal VD from time t10 to time t15. In the example shown in Figure 9, the portion of the residual vibration signal VD from time t10 to time t15 corresponds to the first partial signal. It is preferable that the first period TPP1 starts before the first time has elapsed since the residual vibration signal VD was input to the signal generation unit 60. The first time is, for example, shorter than the time corresponding to one-quarter of the period of the residual vibration signal VD. In this case, it is possible to suppress the inspection time from becoming too long. For example, it is possible to suppress the waiting time from when the residual vibration signal VD is input to the signal generation unit 60 until the generation of the comparison signal CCP begins to become too long. The comparison signals CCPc, CCP1, and CCP2 shown by the solid lines in Figure 9 are examples of the "state inspection signal" and the "first inspection mode signal".

[0143] Here, the amplitude Vamp, which corresponds to the amplitude VPK of the peak PK1 of the residual vibration signal VD, is calculated by equation (1) or equation (2) by approximating the waveform of the residual vibration signal VD as a sine wave, as explained in Figure 7. For example, if the elapsed time from time t10 is "t", the angular velocity is "ω", and the potential difference between the potential of the residual vibration signal VD at time t and the threshold potential VthC is "VE", then the potential difference VE can be expressed using the amplitude VPK by equation (3). In the following equations, "·" is used as appropriate to indicate multiplication.

[0144] VE = VPK·sin(ωt) …(3)

[0145] Furthermore, since the duration TCc of the period WCc during which the comparison signal CCPc is at a high level corresponds to one-quarter of the period of the residual vibration signal VD, the angular velocity ω can be expressed using the duration TCc in equation (4).

[0146] ω = π / (2·TCc) …(4)

[0147] Furthermore, the elapsed time from time t10 to time t14 is expressed by the formula "TCc-TC1", which is obtained by subtracting time length TC1 from time length TCc, and the elapsed time from time t10 to time t12 is expressed by the formula "TCc-TC2", which is obtained by subtracting time length TC2 from time length TCc.

[0148] Therefore, the potential difference VE1 between the potential of the residual vibration signal VD at time t14 and the threshold potential VthC is expressed by equation (5), using time lengths TCc and TC1. Similarly, the potential difference VE2 between the potential of the residual vibration signal VD at time t12 and the threshold potential VthC is expressed by equation (6), using time lengths TCc and TC2.

[0149] VE1=VPK·sin(π·(TCc-TC1) / (2·TCc)) …(5) VE2=VPK·sin(π·(TCc-TC2) / (2·TCc)) …(6)

[0150] Furthermore, the amplitude VPK can be expressed as equation (7) by rearranging equation (5). Alternatively, the amplitude VPK can be expressed as equation (8) by rearranging equation (6).

[0151] VPK=VE1 / (sin((π / 2)·(1-TC1 / TCc))) …(7) VPK=VE2 / (sin((π / 2)·(1-TC2 / TCc))) …(8)

[0152] Since the potential of the residual vibration signal VD at time t14 is the threshold potential Vth1, the potential difference VE1 is the value obtained by subtracting the threshold potential VthC from the threshold potential Vth1. Therefore, by substituting the equation "Vth1-VthC", obtained by subtracting the threshold potential VthC from the threshold potential Vth1, into the potential difference VE1 in equation (7), and substituting the amplitude Vamp into the amplitude VPK in equation (7), equation (1) explained in Figure 7 is derived. Also, since the potential of the residual vibration signal VD at time t12 is the threshold potential Vth2, the potential difference VE2 is the value obtained by subtracting the threshold potential VthC from the threshold potential Vth2. Therefore, by substituting the equation "Vth2-VthC", obtained by subtracting the threshold potential VthC from the threshold potential Vth2, into the potential difference VE2 in equation (8), and substituting the amplitude Vamp into the amplitude VPK in equation (8), equation (2) explained in Figure 7 is derived.

[0153] As will be explained in detail in Figure 10 and later, the amplitude Vamp calculated from equation (1) is adjusted by adjusting at least one of the potential difference between the threshold potential VthC and the threshold potential Vth1, and the time ratio, which is the ratio of the time length TC1 to the time length TCc. By adjusting the amplitude Vamp calculated from equation (1), the difference between the amplitude Vamp calculated from equation (1) in a normal discharge unit D and the amplitude Vamp calculated from equation (1) in an abnormal discharge unit D can be adjusted. Therefore, by adjusting the amplitude Vamp calculated from equation (1), the sensitivity when determining the state of the discharge unit D can be adjusted. Similarly, by adjusting the amplitude Vamp calculated from equation (2), the sensitivity when determining the state of the discharge unit D can be adjusted. In this embodiment, the sensitivity when determining the state of the discharge unit D may be adjusted by adjusting the amplitude Vamp calculated from equation (1), or by adjusting the amplitude Vamp calculated from equation (2).

[0154] Next, we will briefly explain the comparison signal CCP, etc., when the inspection mode is the second inspection mode. In the second inspection mode, instead of the amplitude of the peak PK1 of the residual vibration signal VD, the amplitude of the peak PK3 of the residual vibration signal VD is used to determine the state of the discharge unit D. Therefore, for example, the comparison signal CP from time t0 to time t25 is not used to determine the state of the discharge unit D. For this reason, in the second inspection mode, the mask signal MSK is maintained at a high level from time t0 to time t25, as shown by the dashed line in Figure 9, and then transitions from a high level to a low level at time t25. Then, the mask signal MSK is maintained at a low level from time t25 to time t45. During the period when the mask signal MSK is at a high level, that is, from time t0 to time t25, the comparison signal CCP is maintained at a low level regardless of the level of the comparison signal CP.

[0155] Furthermore, in the second inspection mode, the pulse detection period signal Pcut is maintained at a high level until time t45, as shown by the dashed line in Figure 9, and then transitions from a high level to a low level at time t45. Therefore, in the second inspection mode, time t45 corresponds to the reset timing tep.

[0156] As described above, the potential of the residual oscillation signal VD increases with time from time t25 to time t35, and decreases with time from time t35 to time t45.

[0157] For example, at time t30, which is later than time t25, the potential of the residual oscillation signal VD reaches the threshold potential VthC. Therefore, at time t30, the comparator circuit 620 transitions the comparator signal CPc from a low level to a high level.

[0158] Furthermore, at time t32, which is later than time t30, the potential of the residual oscillation signal VD reaches a threshold potential Vth2, which is higher than the threshold potential VthC. Therefore, at time t32, the comparator circuit 622 transitions the comparator signal CP2 from a low level to a high level.

[0159] Furthermore, at time t34, which is later than time t32, the potential of the residual oscillation signal VD reaches a threshold potential Vth1, which is higher than the threshold potential Vth2. Therefore, at time t34, the comparator circuit 621 transitions the comparator signal CP1 from a low level to a high level.

[0160] Furthermore, at time t35, which is later than time t34, the potential of the residual oscillation signal VD reaches its peak from the threshold potential Vth1. Therefore, from time t35 onwards, the potential of the residual oscillation signal VD begins to decrease.

[0161] Then, at time t36, which is later than time t35, the potential of the residual oscillation signal VD reaches the threshold potential Vth1. For this reason, the comparator circuit 621 transitions the comparator signal CP1 from a high level to a low level at time t36.

[0162] Furthermore, at time t38, which is later than time t36, the potential of the residual oscillation signal VD reaches the threshold potential Vth2. Therefore, at time t38, the comparator circuit 622 transitions the comparator signal CP2 from a high level to a low level.

[0163] Furthermore, at time t40, which is later than time t38, the potential of the residual oscillation signal VD reaches the threshold potential VthC. Therefore, at time t40, the comparator circuit 620 transitions the comparator signal CPc from a high level to a low level.

[0164] In the second test mode, the time t45, which corresponds to the reset timing tep, is later than the time t40. Therefore, for example, the comparison signal CCPc, generated by the logical AND of the inverted signal of the mask signal MSK, the pulse detection period signal Pcut, and the comparison signal CPc, will be the same signal as the comparison signal CPc, as shown by the dashed line in Figure 9. Similarly, the comparison signal CCP1, generated by the logical AND of the inverted signal of the mask signal MSK, the pulse detection period signal Pcut, and the comparison signal CP1, will be the same signal as the comparison signal CP1, as shown by the dashed line in Figure 9. And the comparison signal CCP2, generated by the logical AND of the inverted signal of the mask signal MSK, the pulse detection period signal Pcut, and the comparison signal CP2, will be the same signal as the comparison signal CP2, as shown by the dashed line in Figure 9.

[0165] Therefore, in the second inspection mode, the time length TOc of the period WOc when the comparison signal CPc is at a high level becomes the time length TCc of the period WCc when the comparison signal CCPc is at a high level. Similarly, the time length TO1 of the period WO1 when the comparison signal CP1 is at a high level becomes the time length TC1 of the period WC1 when the comparison signal CCP1 is at a high level. Furthermore, the time length TO2 of the period WO2 when the comparison signal CP2 is at a high level becomes the time length TC2 of the period WC2 when the comparison signal CCP2 is at a high level. In the second inspection mode as well, the amplitude Vamp of the residual vibration signal VD is calculated by approximating the waveform of the residual vibration signal VD as a sine wave, using equation (1) or equation (2) as explained in Figure 7.

[0166] Thus, in the second inspection mode, comparison signals CCPc, CCP1, and CCP2 are generated corresponding to the second partial signal in the second period TPP2 from time t30 to time t40 of the residual vibration signal VD. Therefore, in the second inspection mode, the period of the residual vibration signal VD can be identified based on the comparison signal CCPc. In this case, multiple abnormal conditions, including the viscosity of the ink in the ejection unit D, can be determined based on the amplitude Vamp and period of the residual vibration signal VD. In the example shown in Figure 9, the portion of the residual vibration signal VD from time t30 to time t40 corresponds to the second partial signal. The comparison signals CCPc, CCP1, and CCP2 shown by the dashed lines in Figure 9 are examples of "condition inspection signals" and "second inspection mode signals".

[0167] Here, the second period TPP2 is a period that follows the first period TPP1 and is longer than the first period TPP1. Therefore, in the second inspection mode, even if noise is superimposed on the residual vibration signal VD when the control period TSS1 and control period TSS2 shown in Figure 8 switch, the influence of the noise on determining the state of the discharge unit D can be suppressed. On the other hand, in the first inspection mode, the comparison signals CCPc, CCP1, and CCP2 used to determine the state of the discharge unit D are generated according to the first partial signal in the first period TPP1, which is a shorter period than the second period TPP2 of the residual vibration signal VD. Therefore, in the first inspection mode, the unit period TU can be shortened compared to the second inspection mode, and thus the inspection time can be shortened. For example, the first period TPP1 is a period of one-quarter or less of the period of the residual vibration signal VD, and the second period TPP2 is a period of one-half or more of the period of the residual vibration signal VD. In other words, in the second inspection mode, the amplitude Vamp is calculated using the comparison signal CCP in the second period TPP2, which is more than half the period of the residual vibration signal VD, whereas in the first inspection mode, the amplitude Vamp is calculated using the comparison signal CCP in the first period TPP1, which is less than one-quarter the period of the residual vibration signal VD.

[0168] Each comparison signal CCP may be generated by a method other than calculating the logical AND of the comparison signal CP corresponding to the comparison signal CCP, the inverted signal of the mask signal MSK, and the pulse detection period signal Pcut.

[0169] For example, in the first test mode, a comparison signal CCPc may be generated by a latch circuit that transitions the output signal from a low level to a high level when the comparison signal CPc transitions from a low level to a high level, and resets the output signal to a low level when the pulse detection period signal Pcut transitions from a high level to a low level. Similarly, a comparison signal CCP1 may be generated by a latch circuit that transitions the output signal from a low level to a high level when the comparison signal CP1 transitions from a low level to a high level, and resets the output signal to a low level when the pulse detection period signal Pcut transitions from a high level to a low level. Furthermore, a comparison signal CCP2 may be generated by a latch circuit that transitions the output signal from a low level to a high level when the comparison signal CP2 transitions from a low level to a high level, and resets the output signal to a low level when the pulse detection period signal Pcut transitions from a high level to a low level. As described above, in the embodiment in which the comparison signal CCP is generated by a latch circuit, for example, the reset timing tep can be set to a timing later than the timing in which the comparison signal CP1 transitions from a high level to a low level. Furthermore, in a configuration in which a comparison signal CCP is generated by a latch circuit or the like, for example, the interruption timing at which the signal path of the residual vibration signal VD from the discharge unit D to the signal generation unit 60 is interrupted can be set to be earlier than the reset timing tep.

[0170] Furthermore, for example, in the second inspection mode, the comparison signal CPc may be output as the comparison signal CCPc from the adjustment circuit 630 to the specific circuit 670. Similarly, the comparison signal CP1 may be output as the comparison signal CCP1 from the adjustment circuit 631 to the specific circuit 671, and the comparison signal CP2 may be output as the comparison signal CCP2 from the adjustment circuit 632 to the specific circuit 672.

[0171] Furthermore, for example, the pulse detection period signal Pcut and the mask signal MSK may be generated by the connection state specification circuit 310 of the switching circuit 31. Specifically, the connection state specification circuit 310 may generate the pulse detection period signal Pcut and the mask signal MSK based on at least some of the signals of the print signal SI, the latch signal LAT, and the period specification signal Tsig.

[0172] Furthermore, for example, the signal corresponding to the logical AND of the pulse detection period signal Pcut and the inverted mask signal MSK shown in Figure 9 may be used as a signal that serves both as the pulse detection period signal Pcut and the mask signal MSK.

[0173] Furthermore, for example, in the second inspection mode, the amplitude of the peak PK2 of the residual vibration signal VD may be used to determine the state of the discharge unit D. In this case, the comparison circuits 620, 621 and 622 and the pulse detection period signal Pcut and mask signal MSK may operate as follows.

[0174] For example, comparator circuit 620 generates a comparator signal CPc that is high level when the potential of the residual vibration signal VD is below the threshold potential VthC, and low level when the potential of the residual vibration signal VD is higher than the threshold potential VthC. Comparator circuit 621 generates a comparator signal CP1 that is high level when the potential of the residual vibration signal VD is below the threshold potential Vthm1, and low level when the potential of the residual vibration signal VD is higher than the threshold potential Vthm1. Comparator circuit 622 generates a comparator signal CP2 that is high level when the potential of the residual vibration signal VD is below the threshold potential Vthm2, and low level when the potential of the residual vibration signal VD is higher than the threshold potential Vthm2. The mask signal MSK is maintained at a high level from time t0 to time t15, and then transitions from a high level to a low level at time t15. The mask signal MSK is then maintained at a low level, for example, from time t25 to time t45. Furthermore, the pulse detection period signal Pcut is maintained at a high level until time t35, at which point it transitions from a high level to a low level. Note that threshold potential Vthm2 is lower than threshold potential VthC, and threshold potential Vthm1 is lower than threshold potential Vthm2.

[0175] Furthermore, for example, in the second inspection mode, the amplitude of the peak PK1 of the residual vibration signal VD may be used to determine the state of the discharge unit D. In this case, for example, the pulse detection period signal Pcut in the second inspection mode may be maintained at a high level until time t25, and then transition from a high level to a low level at time t25. Also, when the amplitude of the peak PK1 of the residual vibration signal VD is used to determine the state of the discharge unit D in the second inspection mode, the mask signal MSK may be omitted.

[0176] Furthermore, in the first inspection mode, the time ratio, which is the ratio of time length TC1 to time length TCc, and the time ratio, which is the ratio of time length TC2 to time length TCc, may be adjusted by adjusting the reset timing tep. In this case, the amplitude Vamp calculated from equation (1), etc., is adjusted, and the sensitivity when determining the state of the discharge unit D is adjusted. That is, in the first inspection mode, the sensitivity when determining the state of the discharge unit D may be adjusted by adjusting the reset timing tep.

[0177] Next, referring to Figures 10 to 12, we will explain how to adjust the sensitivity when determining the state of the discharge unit D in the first inspection mode. Figures 10 to 12 illustrate the case where the potential of the residual vibration signal VD is compared with the threshold potential Vth1. The case where the potential of the residual vibration signal VD is compared with the threshold potential Vth2 can also be explained in Figures 10 to 12 by substituting the elements related to threshold potential Vth1 with the elements related to threshold potential Vth2.

[0178] Figure 10 is an explanatory diagram illustrating the relationship between the residual vibration signal VD, the reset timing tep, and the comparison signal CCP. Figure 10 shows the pulse detection period signal Pcut, the residual vibration signal VD of a normal nozzle, the comparison signals CCPc and CCP1 of a normal nozzle, the residual vibration signal VD of an abnormal nozzle, and the comparison signals CCPc and CCP1 of an abnormal nozzle. A normal nozzle indicates that the discharge section D is in a normal state, while an abnormal nozzle indicates that the discharge section D is in an abnormal state.

[0179] Furthermore, in the graph of the residual vibration signal VD in Figure 10, the vertical axis represents the voltage [V] relative to the threshold potential VthC, i.e., the potential difference from the threshold potential VthC, and the horizontal axis represents the elapsed time [μs] from the reference timing tref. The unit [μs] means microseconds. In Figure 10, the reference timing tref is the timing when the potential of the residual vibration signal VD of the normal nozzle reaches the threshold potential VthC from a potential lower than VthC. In Figure 10, it is assumed that the potential difference between the threshold potential VthC and the threshold potential Vth1 is 0.5V. In addition, in Figure 10, it is assumed that the amplitude VPK of the residual vibration signal VD of the normal nozzle is 1.0V, the amplitude VPK of the residual vibration signal VD of the abnormal nozzle is 0.9V, and the time TPH corresponding to the phase difference between the residual vibration signal VD of the normal nozzle and the residual vibration signal VD of the abnormal nozzle is 0.5μs. Furthermore, Figure 10 assumes that the period of the residual vibration signal VD of the normal nozzle and the period of the residual vibration signal VD of the abnormal nozzle are the same, and that one-quarter of the period is 2.0 μs. The dashed line shown in the graph of the residual vibration signal VD in Figure 10 represents the slope of the residual vibration signal VD of the normal nozzle at the threshold potential Vth1. Figure 10 assumes that the slope of the residual vibration signal VD at the threshold potential Vth1 is almost the same for both the normal and abnormal nozzles.

[0180] Figure 10 shows the comparison signals CCPc and CCP1 when the reset timing tep, at which the pulse detection period signal Pcut transitions from a high level to a low level, is 2.0 μs after the reference timing tref. Figure 10 also shows an example of an adjusted reset timing tep as a dotted line.

[0181] In both normal and abnormal nozzles, the timing tsc at which the comparison signal CCPc transitions from a low level to a high level is not adjusted by adjusting the reset timing tep. In contrast, the timing at which the comparison signal CCPc transitions from a high level to a low level is adjusted to the same timing as the reset timing tep in both normal and abnormal nozzles by adjusting the reset timing tep. Therefore, in both normal and abnormal nozzles, the duration TCc of the period WCc during which the comparison signal CCPc is at a high level is adjusted by adjusting the reset timing tep.

[0182] Furthermore, in both normal and abnormal nozzles, the timing ts1 at which the comparison signal CCP1 transitions from a low level to a high level is not adjusted even when the reset timing tep is adjusted. In contrast, the timing at which the comparison signal CCP1 transitions from a high level to a low level is adjusted to the same timing as the reset timing tep in both normal and abnormal nozzles by adjusting the reset timing tep. Therefore, in both normal and abnormal nozzles, the duration TC1 of the period WC1 during which the comparison signal CCP1 is at a high level is adjusted by adjusting the reset timing tep.

[0183] Next, referring to Figure 11, we will explain the relationship between the adjustment of the reset timing tep and the amplitude Vamp calculated based on the time lengths TCc and TC1 adjusted by the reset timing tep.

[0184] Figure 11 is an explanatory diagram illustrating the relationship between the reset timing tep and the amplitude Vamp calculated based on the time lengths TCc and TC1. The adjusted waveform in Figure 11 shows a sine wave with an amplitude Vamp calculated from equation (1) explained in Figure 7 using the time lengths TCc and TC1 adjusted by the reset timing tep. In other words, the adjusted waveform is a hypothetical waveform in which the residual vibration signal VD is assumed to have an amplitude Vamp calculated based on the time lengths TCc and TC1, and is not necessarily the same waveform as the residual vibration signal VD actually output from the detection circuit 33.

[0185] In Figure 11, the graphs of the residual vibration signal VD and the adjustment waveform show that the vertical axis represents the voltage [V] relative to the threshold potential VthC, i.e., the potential difference from the threshold potential VthC, and the horizontal axis represents the elapsed time [μs] from the reference timing tref. In Figure 11, the reference timing tref is the timing when the potential of the residual vibration signal VD of a normal nozzle reaches the threshold potential VthC from a potential lower than VthC, and the potential difference between the threshold potential VthC and the threshold potential Vth1 is 0.5V.

[0186] Furthermore, the residual vibration signals VD of the normal nozzle and the abnormal nozzle shown in Figure 11 are the same as those of the normal nozzle and the abnormal nozzle described in Figure 10. For example, the amplitude VPK of the residual vibration signal VD of the normal nozzle is 1.0V, and the amplitude VPK of the residual vibration signal VD of the abnormal nozzle is 0.9V. Also, the time TPH corresponding to the phase difference between the residual vibration signal VD of the normal nozzle and the residual vibration signal VD of the abnormal nozzle is 0.5μs. In addition, the time of one-quarter of the period of the residual vibration signal VD of the normal nozzle and the residual vibration signal VD of the abnormal nozzle is 2.0μs. Therefore, the residual vibration signal VD of the normal nozzle reaches its peak PK1 at a timing 2.0μs after the reference timing tref, and the residual vibration signal VD of the abnormal nozzle reaches its peak PK1 at a timing 2.5μs after the reference timing tref.

[0187] In the following, the timing at which the residual vibration signal VD reaches its peak PK1 may be referred to as the peak timing of the residual vibration signal VD. In the example shown in Figure 10, the peak timing of the residual vibration signal VD corresponds to the time when one-quarter of the period of the residual vibration signal VD has elapsed from the time when the potential of the residual vibration signal VD reaches the threshold potential VthC from a potential lower than VthC.

[0188] Figure 11 shows four adjustment waveforms corresponding to four reset timings tep for both a normal nozzle and an abnormal nozzle. The four reset timings tep shown in Figure 11 are 1.5 μs, 2.0 μs, 2.5 μs, and 3.0 μs after the reference timing tref, respectively.

[0189] As shown in Figure 11, in both normal and abnormal nozzles, the amplitude Vamp of the adjustment waveform is larger when the time from the reference timing tref to the reset timing tep is long compared to when the time from the reference timing tref to the reset timing tep is short.

[0190] For example, the peak timing of the residual vibration signal VD in a normal nozzle is 2.0 μs after the reference timing tref, as described above. Therefore, in a normal nozzle, if the reset timing tep is 2.0 μs after the reference timing tref, the amplitude Vamp of the adjustment waveform will be 1.0 V, which matches the amplitude VPK of the residual vibration signal VD. Also, if the reset timing tep is 1.5 μs after the reference timing tref, the amplitude Vamp of the adjustment waveform will be approximately 0.8 V, which is smaller than the amplitude VPK of the residual vibration signal VD. Furthermore, if the reset timing tep is 2.5 μs after the reference timing tref, the amplitude Vamp of the adjustment waveform will be approximately 1.2 V, which is larger than the amplitude VPK of the residual vibration signal VD. Also, if the reset timing tep is 3.0 μs after the reference timing tref, the amplitude Vamp of the adjustment waveform will be approximately 1.5 V, which is larger than the amplitude VPK of the residual vibration signal VD. Furthermore, the amplitude Vamp of the adjustment waveform when the reset timing tep is 3.0 μs after the reference timing tref is greater than the amplitude Vamp of the adjustment waveform when the reset timing tep is 2.5 μs after the reference timing tref.

[0191] Furthermore, for example, the peak timing of the residual vibration signal VD of an abnormal nozzle is 2.5 μs after the reference timing tref, as described above. Therefore, in the case of an abnormal nozzle, if the reset timing tep is 2.5 μs after the reference timing tref, the amplitude Vamp of the adjustment waveform will be 0.9 V, which matches the amplitude VPK of the residual vibration signal VD. Also, if the reset timing tep is 2.0 μs after the reference timing tref, the amplitude Vamp of the adjustment waveform will be approximately 0.7 V, which is smaller than the amplitude VPK of the residual vibration signal VD. Also, if the reset timing tep is 1.5 μs after the reference timing tref, the amplitude Vamp of the adjustment waveform will be approximately 0.5 V, which is smaller than the amplitude VPK of the residual vibration signal VD. Furthermore, when the reset timing tep is 1.5 μs after the reference timing tref, the amplitude Vamp of the adjustment waveform is smaller than when the reset timing tep is 2.0 μs after the reference timing tref. Also, when the reset timing tep is 3.0 μs after the reference timing tref, the amplitude Vamp of the adjustment waveform is approximately 1.1 V, which is larger than the amplitude VPK of the residual oscillation signal VD.

[0192] The periods WCc and WC1, during which the comparison signal CCPc is at a high level, are fixed at one end each by the reset timing tep. Therefore, the amplitude Vamp calculated based on the time lengths TCc and TC1 includes information on both the change in amplitude VPK and the change in phase. For example, the amplitude Vamp of the adjustment waveform of an abnormal nozzle includes information on the change in both the amplitude VPK and phase of the residual vibration signal VD of the abnormal nozzle relative to the residual vibration signal VD of the normal nozzle. In the example shown in Figure 11, when the reset timing tep is 2.0 μs after the reference timing tref, the amplitude Vamp of the adjustment waveform of the abnormal nozzle is smaller than the amplitude VPK of the residual vibration signal VD of the abnormal nozzle, as described above. Thus, in the first inspection mode, since the change in phase difference can be derived as a change in amplitude Vamp, the parameter for determining the state of the discharge unit D can be reduced from two patterns, amplitude VPK and phase, to one pattern, the amplitude Vamp of the adjustment waveform. This simplifies the discharge state determination process in the first inspection mode.

[0193] Furthermore, in the first inspection mode, since the amplitude Vamp of the adjustment waveform of the abnormal nozzle includes information on both the change in amplitude VPK and the change in phase, it is possible to suppress a decrease in the accuracy of determining whether the state of the discharge unit D is normal or not. For example, in the first inspection mode, even if the amplitude difference DVR or phase difference between the residual vibration signal VD of the normal nozzle and the residual vibration signal VD of the abnormal nozzle is small, it is possible to suppress a decrease in the accuracy of determining whether the state of the discharge unit D is normal or not.

[0194] Specifically, in the example shown in Figure 11, the amplitude difference DVR between the residual vibration signal VD of a normal nozzle and the residual vibration signal VD of an abnormal nozzle is 0.1V. In contrast, for example, when the reset timing tep is 2.0 μs after the reference timing tref, the amplitude difference DV1 between the adjustment waveform of a normal nozzle and the adjustment waveform of an abnormal nozzle is approximately 0.3V, which is larger than 0.1V. That is, when the reset timing tep is 2.0 μs after the reference timing tref, the amplitude difference DV1 between the adjustment waveform of a normal nozzle and the adjustment waveform of an abnormal nozzle is larger than the amplitude difference DVR between the residual vibration signal VD of a normal nozzle and the residual vibration signal VD of an abnormal nozzle. In this case, it is possible to determine whether the state of the discharge unit D is normal or not based on the amplitude difference DV1, which is larger than the amplitude difference DVR between the residual vibration signal VD of a normal nozzle and the residual vibration signal VD of an abnormal nozzle. Therefore, in the first inspection mode, it is possible to determine with greater accuracy whether the discharge unit D is normal or not, compared to when the state of the discharge unit D is determined based on the amplitude difference DVR between the residual vibration signal VD of a normal nozzle and the residual vibration signal VD of an abnormal nozzle. For example, the determination circuit 69 may determine that the state of the discharge unit D is abnormal if the amplitude Vamp calculated by the amplitude calculation circuit 68 is smaller than a predetermined threshold amplitude based on the amplitude Vamp of the adjustment waveform of a normal nozzle.

[0195] Furthermore, for example, when the reset timing tep is 3.0 μs after the reference timing tref, the amplitude difference DV2 between the adjustment waveform of a normal nozzle and the adjustment waveform of an abnormal nozzle is approximately 0.4 V, which is greater than 0.3 V. In other words, the amplitude difference DV2 is greater than the amplitude difference DV1. Hereafter, the amplitude differences DV2 and DV1 may be collectively referred to as the amplitude difference DV. Furthermore, hereafter, the amplitude difference between the adjustment waveform of a normal nozzle and the adjustment waveform of an abnormal nozzle may be referred to as the amplitude difference DV.

[0196] In the example shown in Figure 11, the amplitude difference DV between the adjustment waveform of a normal nozzle and the adjustment waveform of an abnormal nozzle is larger when the time from the reference timing tref to the reset timing tep is long compared to when the time from the reference timing tref to the reset timing tep is short.

[0197] Thus, in the first inspection mode, the sensitivity for detecting changes in the phase of the residual vibration signal VD can be adjusted by the reset timing tep, allowing the sensitivity for determining the state of the discharge section D to be set according to the application.

[0198] Next, referring to Figure 12, we will explain the relationship between the reset timing tep, the amplitude Vamp, and the amplitude change rate.

[0199] Figure 12 is an explanatory diagram illustrating the relationship between the reset timing tep, the amplitude Vamp, and the amplitude change rate. One vertical axis in Figure 12 shows the voltage [V] of the amplitude Vamp relative to the threshold potential VthC, the other vertical axis shows the amplitude change rate [%], and the horizontal axis shows the time [μs] of the reset timing tep. The amplitude change rate represents the ratio [%] of the amplitude Vamp calculated in the abnormal nozzle to the amplitude Vamp calculated in the normal nozzle. The time of the reset timing tep represents the time from the reference timing tref to the reset timing tep. The reference timing tref is the timing when the potential of the residual vibration signal VD in the normal nozzle reaches the threshold potential VthC from a potential lower than VthC, as in Figures 10 and 11. Hereafter, the amplitude Vamp calculated in the normal nozzle may be referred to as the normal nozzle amplitude Vamp, and the amplitude Vamp calculated in the abnormal nozzle may be referred to as the abnormal nozzle amplitude Vamp.

[0200] Figure 12 shows the amplitude Vamp and amplitude change rate when the reset timing tep is adjusted for the residual vibration signal VD of the normal nozzle and the residual vibration signal VD of the abnormal nozzle shown in Figures 10 and 11. The white circles in Figure 12 represent the amplitude Vamp of the normal nozzle, the black circles represent the amplitude Vamp of the abnormal nozzle, and the rectangles in Figure 12 represent the amplitude change rate.

[0201] As shown in Figure 12, in both normal and abnormal nozzles, the amplitude Vamp increases as the time from the reference timing tref to the reset timing tep increases. Also, the amplitude difference DV between the amplitude Vamp of the normal nozzle and the amplitude Vamp of the abnormal nozzle increases as the time from the reference timing tref to the reset timing tep increases. Furthermore, in the example shown in Figure 12, the absolute value of the amplitude change rate, which is the ratio of the amplitude Vamp of the abnormal nozzle to the amplitude Vamp of the normal nozzle, decreases as the time from the reference timing tref to the reset timing tep increases because the amplitude Vamp of the normal nozzle increases.

[0202] Thus, in the first inspection mode, the amplitude Vamp can be adjusted by adjusting the reset timing tep. Therefore, in the first inspection mode, the sensitivity for determining the state of the discharge unit D can be adjusted by adjusting the reset timing tep. For example, if the time from the reference timing tref to the reset timing tep is increased, the amplitude difference DV between the amplitude Vamp of a normal nozzle and the amplitude Vamp of an abnormal nozzle becomes larger compared to when the time from the reference timing tref to the reset timing tep is short. When the amplitude difference DV is large, the resolution is improved compared to when the amplitude difference DV is small, so the accuracy of the determination when determining whether the state of the discharge unit D is normal can be increased.

[0203] As explained in Figure 11, in both normal and abnormal nozzles, if the reset timing tep coincides with the peak timing of the residual vibration signal VD, the amplitude Vamp coincides with the amplitude VPK of the residual vibration signal VD. Therefore, the sensitivity for determining the state of the discharge unit D may be adjusted based on the case where the reset timing tep coincides with the peak timing of the residual vibration signal VD of a normal nozzle.

[0204] Furthermore, the reset timing tep may be adjusted for each nozzle N. In this embodiment, for example, correction information for generating a pulse detection period signal Pcut that defines the reset timing tep corresponding to each nozzle N may be stored in the storage unit 5. Also in this embodiment, for example, two discharge units D each having two nozzles N correspond to the "first discharge unit" and the "second discharge unit," respectively. Among the signals corresponding to the discharge unit D of the "first discharge unit," the comparison signal CPc corresponds to the "first reference signal," the comparison signals CP1 and CP2 correspond to the "first inspection signal," the time information NTCc corresponds to the "first reference signal information," the time information NTC1 and NTC2 correspond to the "first inspection signal information," and the correction information corresponds to the "first correction information." Similarly, among the signals corresponding to the discharge unit D of the "second discharge unit," the comparison signal CPc corresponds to the "second reference signal," the comparison signals CP1 and CP2 correspond to the "second inspection signal," the time information NTCc corresponds to the "second reference signal information," the time information NTC1 and NTC2 correspond to the "second inspection signal information," and the correction information corresponds to the "second correction information."

[0205] Next, referring to Figure 13, the operation of the inkjet printer 1 when performing the ejection state determination process will be described.

[0206] Figure 13 is a flowchart showing an example of the operation of the inkjet printer 1 when performing the ejection state determination process.

[0207] First, in step S100, the control unit 2 of the inkjet printer 1 functions as a drive control unit 22 and selects the ejection unit D to be judged from among the ejection units D[1] to D[J]. In the following explanation, the case in which ejection unit D[j] is selected as the ejection unit D to be judged will be explained as an example.

[0208] Next, in step S120, the control unit 2 functions as a drive control unit 22 and determines whether the state of the ejection unit D is determined in the first inspection mode. For example, the drive control unit 22 may identify the inspection mode based on operation information indicating the content of operations performed on the inkjet printer 1. Alternatively, the drive control unit 22 may determine whether the state of the ejection unit D is determined in the first inspection mode based on the purpose of determining the state of the ejection unit D and the context in which the determination is made. The correspondence between the purpose of determining the state of the ejection unit D and the context in which the determination is made, and the inspection mode, may be set in advance by the manufacturer of the head unit 3, etc. For example, determining the state of the ejection unit D in the first inspection mode can shorten the inspection time compared to the second inspection mode, and is therefore effective when determining the state of the ejection unit D in a short time. Also, immediately after the inkjet printer 1 is started up, the ink in the cavity CV is likely to be stagnant and thickened. For this reason, determining the state of the ejection unit D in the first inspection mode may take precedence over determining the state of the ejection unit D in the second inspection mode after the inkjet printer 1 is started up. Therefore, a first inspection mode may be pre-set as the inspection mode after the inkjet printer 1 is started up.

[0209] If the result of the determination in step S120 is positive, that is, if the state of the discharge unit D is determined in the first inspection mode, the drive control unit 22 moves the process to step S140. On the other hand, if the result of the determination in step S120 is negative, that is, if the state of the discharge unit D is determined in the second inspection mode, the drive control unit 22 moves the process to step S142.

[0210] In step S140, the inkjet printer 1 generates a residual vibration signal VD. The step of generating the residual vibration signal VD includes, for example, the following first and second steps, although not shown in Figure 13. In the first step of generating the residual vibration signal VD, the control unit 2 functions as a drive control unit 22 and controls the switching circuit 31 of the head unit 3 so that the ejection unit D[j] is driven as the ejection unit D to be determined. Then, in the second step of generating the residual vibration signal VD, the detection circuit 33 of the head unit 3 detects a detection signal Vout[j] indicating residual vibration occurring in the ejection unit D[j], and generates the residual vibration signal VD[j] based on the detection signal Vout[j].

[0211] Step 140 also includes, although not shown in Figure 13, supplying the pulse detection period signal Pcut and the mask signal MSK for the first inspection mode to the signal generation unit 60 of the inspection unit 6. For example, the drive control unit 22 may supply the pulse detection period signal Pcut and the mask signal MSK for the first inspection mode to the signal generation unit 60 of the inspection unit 6. Alternatively, the drive control unit 22 may control the switching circuit 31 of the head unit 3 so that the pulse detection period signal Pcut and the mask signal MSK for the first inspection mode are supplied to the signal generation unit 60 of the inspection unit 6. After performing the processing in step S140, the inkjet printer 1 moves the processing to step S160.

[0212] In step S160, the signal generation unit 60 of the inspection unit 6 generates comparison signals CCPc, CCP1, and CCP2 in the first inspection mode. Then, the inspection unit 6 moves the process to step S180.

[0213] Furthermore, if the result of the determination in step S120 is negative, the process in step S142 is executed as described above. In step S142, the inkjet printer 1 operates in the same manner as in step S140 to generate a residual vibration signal VD. However, in step S142, instead of the pulse detection period signal Pcut and mask signal MSK for the first inspection mode, the pulse detection period signal Pcut and mask signal MSK for the second inspection mode are supplied to the signal generation unit 60 of the inspection unit 6. After executing the process in step S142, the inkjet printer 1 moves the process to step S162.

[0214] In step S162, the signal generation unit 60 of the inspection unit 6 generates comparison signals CCPc, CCP1, and CCP2 in second inspection mode. Then, the inspection unit 6 moves the process to step S180.

[0215] In step S180, the identification unit 67 of the determination unit 64 of the inspection unit 6 identifies the time length TCc of the comparison signal CCPc, the time length TC1 of the comparison signal CCP1, and the time length TC2 of the comparison signal CCP2.

[0216] Next, in step S200, the amplitude calculation circuit 68 of the determination unit 64 of the inspection unit 6 identifies the calculation mode. The method for identifying the calculation mode is explained in Figure 7, so the explanation is omitted here.

[0217] Next, in step S220, the amplitude calculation circuit 68 of the determination unit 64 determines whether the calculation mode identified in step S200 is the first calculation mode.

[0218] If the result of the determination in step S220 is positive, that is, if the calculation mode is the first calculation mode, the amplitude calculation circuit 68 calculates the amplitude Vamp in the first calculation mode in step S240 and moves the process to step S260. For example, in step S240, the amplitude calculation circuit 68 calculates the amplitude Vamp based on the time lengths TCc and TC1.

[0219] On the other hand, if the result of the determination in step S220 is negative, that is, if the calculation mode is the second calculation mode, the amplitude calculation circuit 68 calculates the amplitude Vamp in the second calculation mode in step S242 and moves the process to step S260. For example, in step S242, the amplitude calculation circuit 68 calculates the amplitude Vamp based on the time lengths TCc and TC2.

[0220] In step S260, the determination circuit 69 of the determination unit 64 determines the state of the discharge unit D[j] based on the amplitude Vamp calculated in step S240 or step S242, and generates state information Cinf which includes information indicating the result of the determination. The determination circuit 69 then outputs the state information Cinf to the control unit 2 and terminates the discharge state determination process.

[0221] Note that the operation of the inkjet printer 1 when executing the ejection state determination process is not limited to the example shown in Figure 13. For example, the determination in step S120 may be performed before the processing in step S100. Also, for example, the determination in step S220 may be included in the processing in step S200. In other words, the determination in step S220 and the processing in step S200 do not need to be strictly distinguished. Also, for example, the step of supplying the pulse detection period signal Pcut and the mask signal MSK for the first inspection mode to the signal generation unit 60 of the inspection unit 6 may be included in step 160. Similarly, the step of supplying the pulse detection period signal Pcut and the mask signal MSK for the second inspection mode to the signal generation unit 60 of the inspection unit 6 may be included in step 162.

[0222] In this embodiment, the inkjet printer 1 includes an ejection unit D capable of ejecting ink in response to an input drive signal COM, a signal generation unit 60 that receives a residual vibration signal VD corresponding to the residual vibration generated in the ejection unit D in response to the input of the drive signal COM and generates a comparison signal CCP based on the residual vibration signal VD, and a determination unit 64 that determines the state of the ejection unit D based on the comparison signal CCP. The signal generation unit 60 has a first inspection mode that generates a first inspection mode signal as a comparison signal CCP corresponding to a first partial signal in a first period TPP1 of the residual vibration signal VD, and a second inspection mode that generates a second inspection mode signal as a comparison signal CCP corresponding to a second partial signal in a second period TPP2 of the residual vibration signal VD. The first period TPP1 is a shorter period than the second period TPP2.

[0223] In this embodiment, the signal generation unit 60 and determination unit 64 described above are included in a head unit control module HCM that controls a head unit 3 equipped with an ejection unit D capable of ejecting ink in response to an input drive signal COM. In this embodiment, the method for determining the state of the ejection unit D corresponds to a liquid ejection inspection method.

[0224] As described above, in this embodiment, the signal generation unit 60 has a first inspection mode and a second inspection mode as inspection modes for determining the state of the discharge unit D. In the first inspection mode, the state of the discharge unit D is determined using the first partial signal of the first period TPP1, which is shorter than the second period TPP2, of the residual vibration signal VD. Therefore, in this embodiment, by determining the state of the discharge unit D in the first inspection mode, the inspection time for determining the state of the discharge unit D can be shortened. In the second inspection mode, the state of the discharge unit D is determined using the second partial signal of the second period TPP2, which is longer than the first period TPP1, of the residual vibration signal VD. Therefore, in the second inspection mode, multiple pieces of information such as the period of the residual vibration signal VD, the accumulation of the phase difference, and the attenuation of the amplitude can be identified based on the second partial signal of the residual vibration signal VD. Therefore, in this embodiment, by determining the state of the discharge unit D in the second inspection mode, the state of the discharge unit D can be determined with high accuracy.

[0225] Furthermore, in this embodiment, the first period TPP1 may be less than or equal to one-quarter of the period of the residual vibration signal VD, and the second period TPP2 may be more than or equal to half of the period of the residual vibration signal VD. In this embodiment, by determining the state of the discharge unit D in the first inspection mode, the inspection time can be shortened by more than one-quarter of the period of the residual vibration signal VD compared to determining the state of the discharge unit D in the second inspection mode.

[0226] Furthermore, in this embodiment, the second period TPP2 is a period later than the first period TPP1. In the second inspection mode, the signal generation unit 60 generates the second inspection mode signal without using the first partial signal of the residual vibration signal VD. In this embodiment, the first partial signal of the first period TPP1, which is a period earlier than the second period TPP2, is not used to determine the state of the discharge unit D. Therefore, in this embodiment, by determining the state of the discharge unit D in the second inspection mode, even if noise is superimposed on the residual vibration signal VD immediately after it is input to the signal generation unit 60, the influence of such noise on determining the state of the discharge unit D can be suppressed.

[0227] Furthermore, in this embodiment, the first period TPP1 may start before the first time has elapsed since the residual vibration signal VD was input to the signal generation unit 60. The first time is shorter than the time corresponding to one-quarter of the period of the residual vibration signal VD. Therefore, in the first inspection mode, it is possible to suppress the time from when the residual vibration signal VD is input to the signal generation unit 60 until the comparison signal CCP is generated from being extended. As a result, in this embodiment, by determining the state of the discharge unit D in the first inspection mode, the inspection time required to determine the state of the discharge unit D can be shortened.

[0228] Furthermore, in this embodiment, the signal path of the residual vibration signal VD[j] from the discharge unit D[j] to the signal generation unit 60 is interrupted at an interruption timing based on the connection status specification signal Qs[j]. In this embodiment, the determination unit 64 may be understood to operate as follows. For example, the determination unit 64 determines the state of the discharge unit D based on a plurality of time information NTC generated by using a plurality of comparison signals CP as signals reset at a reset timing tep based on the pulse detection period signal Pcut. If the interruption timing is earlier than the reset timing tep, each of the plurality of time information NTC is generated by using each of the plurality of comparison signals CP as a signal whose potential at the interruption timing is held until the reset timing tep. In this embodiment, the period during which the residual vibration signal VD[j] from the discharge unit D[j] is input to the signal generation unit 60 can be shortened, thus shortening the inspection time.

[0229] Furthermore, in this embodiment, a reset timing tep may be set for each discharge unit D. In this embodiment, for example, in each of two discharge units D, the state of the discharge unit D is determined based on time information NTC generated using a pulse detection period signal Pcut and a comparison signal CP that define the reset timing tep corresponding to the discharge unit D. As a result, in this embodiment, even if the detection of residual vibration signal VD varies among multiple discharge units D, the state of each discharge unit D can be determined with high accuracy.

[0230] [Second Embodiment] Figure 14 is a block diagram showing an example of the configuration of the inspection unit 6A according to the second embodiment. Elements similar to those described in Figures 1 to 13 are denoted by the same reference numerals, and detailed descriptions are omitted.

[0231] The inkjet printer 1 according to this embodiment is the same as the inkjet printer 1 shown in Figure 1, except that it has an inspection unit 6A instead of the inspection unit 6 shown in Figure 1. In this embodiment, it is assumed that reset information Ntep is used instead of the pulse detection period signal Pcut shown in Figure 8, etc. Reset information Ntep is an example of a "reset signal" and "timing information". In addition, in this embodiment, it is assumed that the determination of the state of the ejection unit D in the second inspection mode described in the first embodiment above is not performed. For this reason, the mask signal MSK shown in Figure 8, etc. is not used in this embodiment. However, even in this embodiment, the state of the ejection unit D may be determined in the second inspection mode. The inspection unit 6A will be described in detail below.

[0232] The inspection unit 6A includes a signal generation unit 60A and a determination unit 64A. The signal generation unit 60A is configured similarly to the signal generation unit 60 shown in Figure 7, but without the adjustment unit 63. For example, the signal generation unit 60A includes a comparison unit 62 which contains comparison circuits 620, 621, and 622. The signal generation unit 60A outputs the comparison signal CPc generated by the comparison circuit 620, the comparison signal CP1 generated by the comparison circuit 621, and the comparison signal CP2 generated by the comparison circuit 622 to the determination unit 64A.

[0233] The determination unit 64A includes a timing specification circuit 65, a specification unit 67A, an amplitude calculation circuit 68, and a determination circuit 69. The amplitude calculation circuit 68 and the determination circuit 69 are the same as those shown in Figure 7. For example, the amplitude Vamp of the residual vibration signal VD is calculated by approximating the waveform of the residual vibration signal VD as a sine wave, using equation (1) or equation (2) explained in Figure 7.

[0234] The timing specification circuit 65 specifies the reset timing tep to the specification unit 67A by outputting reset information Ntep, which indicates the reset timing tep, to the specification unit 67A. For example, the timing specification circuit 65 outputs reset information Ntep to the specification unit 67A, which indicates the time from the time t0 shown in Figure 9, i.e., the timing when the supply of the residual vibration signal VD to the signal generation unit 60A begins, to the reset timing tep. The reset information Ntep is stored in, for example, the memory unit 5. Hereinafter, the timing when the supply of the residual vibration signal VD to the signal generation unit 60A begins may be referred to as the measurement start timing. The measurement start timing is, for example, the time t0 shown in Figure 9, i.e., the timing when the connection status specification signal Qs[j] shown in Figure 8 transitions from a low level to a high level.

[0235] The identification unit 67A identifies, for example, the time length TC from the timing ts when the comparison signals CPc, CP1, and CP2 transition from a low level to a high level, to the reset timing tep. For example, the identification unit 67A has identification circuits 670A, 671A, and 672A to which the comparison signals CPc, CP1, and CP2 are supplied, respectively. Reset information Ntep is also supplied to each of the identification circuits 670A, 671A, and 672A.

[0236] For example, the specific circuit 670A identifies the time length TCc from the timing tsc, when the comparison signal CPc transitions from a low level to a high level, to the reset timing tep, indicated by the reset information Ntep. Specifically, for example, the specific circuit 670A measures the time from the measurement start timing to timing tsc. Then, the specific circuit 670A identifies the time length TCc as the difference between the time from the measurement start timing to timing tsc and the time from the measurement start timing to the reset timing tep. The time length TCc identified by the specific circuit 670A corresponds, for example, to the time length TCc of the period WCc, where the comparison signal CCPc is at a high level, as shown in Figure 9. The specific circuit 670A outputs the time information NTCc, which indicates the time length TCc identified based on the comparison signal CPc and the reset information Ntep, to the amplitude calculation circuit 68.

[0237] Furthermore, for example, the specific circuit 671A identifies the time length TC1 from the timing ts1 when the comparison signal CP1 transitions from a low level to a high level, to the reset timing tep indicated by the reset information Ntep. Specifically, for example, the specific circuit 671A measures the time from the measurement start timing to timing ts1. Then, the specific circuit 671A identifies the time length TC1 as the difference between the time from the measurement start timing to timing ts1 and the time from the measurement start timing to the reset timing tep. The time length TC1 identified by the specific circuit 671A corresponds, for example, to the time length TC1 of the period WC1 in which the comparison signal CCP1 is at a high level, as shown in Figure 9. The specific circuit 671A outputs time information NTC1, which indicates the time length TC1 identified based on the comparison signal CP1 and the reset information Ntep, to the amplitude calculation circuit 68.

[0238] Furthermore, for example, specific circuit 672A identifies the time length TC2 from the timing ts2 when the comparison signal CP2 transitions from a low level to a high level, to the reset timing tep indicated by the reset information Ntep. Specifically, for example, specific circuit 672A measures the time from the measurement start timing to timing ts2. Then, specific circuit 671A identifies the difference between the time from the measurement start timing to timing ts2 and the time from the measurement start timing to the reset timing tep as the time length TC2. The time length TC2 identified by specific circuit 672A corresponds, for example, to the time length TC2 of the period WC2 in which the comparison signal CCP2 is at a high level, as shown in Figure 9. Specific circuit 672A outputs time information NTC2, which indicates the time length TC2 identified based on the comparison signal CP2 and the reset information Ntep, to the amplitude calculation circuit 68.

[0239] Here, the time length TCc is expressed by equation (9) using timing tsc and reset timing tep, and the time length TC1 is expressed by equation (10) using timing ts1 and reset timing tep. Furthermore, the time length TC2 is expressed by equation (11) using timing ts2 and reset timing tep.

[0240] TCc = tep - tsc …(9) TC1 = tep - ts1 …(10) TC2 = tep - ts2 …(11)

[0241] Thus, in this embodiment, the time length TC can be determined without generating the comparison signals CCPc, CCP1, and CCP2 shown in Figure 9.

[0242] Note that the configuration of the inspection unit 6A is not limited to the example shown in Figure 14. For example, the timing specification circuit 65 may be included in the control unit 2.

[0243] Furthermore, for example, the timing specification circuit 65 may supply the endpoint specification signal, which transitions from a high level to a low level at the reset timing tep, as reset information Ntep to the specific circuits 670A, 671A, and 672A. In this embodiment, for example, the timing specification circuit 65 measures the elapsed time from the measurement start timing and transitions the endpoint specification signal from a high level to a low level at the timing when the measurement result matches the time from the measurement start timing to the reset timing tep. Then, for example, the specific circuit 670A measures the time from the timing tsc, when the comparison signal CPc transitions from a low level to a high level, to the reset timing tep, when the endpoint specification signal transitions from a high level to a low level, and identifies the measurement result as the time length TCc. Similarly, the specific circuit 671A measures the time from timing ts1 to the reset timing tep and identifies the measurement result as the time length TC1. Also, the specific circuit 672A measures the time from timing ts2 to the reset timing tep and identifies the measurement result as the time length TC2. In this embodiment, the initial level of the endpoint designation signal is not particularly limited and may be high or low. However, if the initial level of the endpoint designation signal is low, the endpoint designation signal transitions from low to high at a timing prior to the reset timing tep.

[0244] Furthermore, for example, the timing specification circuit 65 may supply a termination point specification signal that transitions from a low level to a high level at the reset timing tep as reset information Ntep to specific circuits 670A, 671A, and 672A.

[0245] In this embodiment as well, the comparison signal CP may be generated based on the signal in the portion of the residual vibration signal VD in the first period TPP1, which is less than or equal to one-quarter of the period of the residual vibration signal VD. The first period TPP1 is, for example, the first period TPP1 shown in Figure 9. In this embodiment as well, it is preferable that the first period TPP1 is started before a first time has elapsed since the residual vibration signal VD was input to the signal generation unit 60A. The first time is, for example, a time shorter than the time corresponding to one-quarter of the period of the residual vibration signal VD.

[0246] Next, we will explain the overview of adjusting the reset timing tep, referring to Figure 15.

[0247] Figure 15 is an explanatory diagram illustrating the overview of the adjustment of the reset timing tep. The vertical axis of the figure shows the voltage [V] of the residual vibration signal VD relative to the ground potential, and the horizontal axis shows the elapsed time from the start of measurement, for example, the elapsed time from time t0 [μs].

[0248] In the example shown in Figure 15, the first peak PK of the residual vibration signal VD is the peak PK where the potential of the residual vibration signal VD is at its minimum value. Therefore, Figure 15 assumes that the potential of the residual vibration signal VD in the range from the threshold potential VthC to the second peak PK of the residual vibration signal VD is compared with the threshold potential VthC and Vth1, etc. For example, in Figure 15, the potential difference between the ground potential and the threshold potential VthC is 1.5V, and the potential difference between the ground potential and the threshold potential Vth1 is 2.5V.

[0249] Furthermore, the solid line in Figure 15 represents the residual vibration signal VD of a normal nozzle, while the dashed line represents the residual vibration signal VD of an abnormal nozzle where ink flight deviation occurred.

[0250] For example, if paper dust adheres to the vicinity of nozzle N, the surface of the ink inside nozzle N is drawn up in the ejection direction by the paper dust, causing an abnormality in the ink's flight path. In this case, as shown in Figure 15, the period of residual vibration, i.e., the period of the residual vibration signal VD, is slightly longer in the abnormal nozzle with paper dust adhered to the vicinity of nozzle N compared to a normal nozzle. In the example shown in Figure 15, the residual vibration signal VD of the abnormal nozzle differs from that of the normal nozzle by approximately 4% in period and approximately 9% in amplitude. When the change in the residual vibration signal VD of an abnormal nozzle compared to a normal nozzle is small, it becomes difficult to detect abnormalities in the ejection state by simply identifying the waveform characteristics of the residual vibration signal VD from the residual vibration signal VD itself. Therefore, in this embodiment, the accuracy of the determination of whether the state of the ejection unit D is normal is increased by adjusting the reset timing tep.

[0251] For example, by adjusting the reset timing tep, the time lengths TCc and TC1 are adjusted. As a result, the time ratio, which is the ratio of time length TC1 to time length TCc, is adjusted, and thus the amplitude Vamp calculated from equation (1) explained in Figure 7 is adjusted. In this embodiment, since it is not necessary to actually generate pulses with a duration of time length TCc, such as the comparison signal CCPc shown in Figure 9, the time from the start of measurement to the reset timing tep can be made longer than in the first embodiment described above. Therefore, in this embodiment, the adjustment range when adjusting the reset timing tep can be widened. As a result, in this embodiment, the judgment accuracy when determining whether the state of the discharge unit D is normal can be easily adjusted.

[0252] For example, the reset timing tep is adjusted so that when the inspection accuracy of the discharge unit D state is high, the time from the shut-off timing to the reset timing tep is longer compared to when the inspection accuracy is low. Similarly, when the inspection time of the discharge unit D state is shortened, the reset timing tep is adjusted so that the time from the shut-off timing to the reset timing tep is shorter compared to when the inspection time is long.

[0253] Furthermore, in this embodiment, the cutoff timing at which the signal path of the residual vibration signal VD from the discharge unit D[j] to be judged to the signal generation unit 60 is cut off can be set to earlier than the reset timing tep. Therefore, in this embodiment, for example, even if the time from the start of measurement timing to the reset timing tep is increased, the discharge unit D[j] can be made to perform a different operation at a timing later than the cutoff timing, regardless of the reset timing tep. Alternatively, in this embodiment, regardless of the reset timing tep, a discharge unit D other than the discharge unit D[j] can be operated as the discharge unit D to be judged at a timing later than the cutoff timing. In this way, in this embodiment, even if the time from the start of measurement timing to the reset timing tep is increased, it is possible to suppress an increase in the inspection time.

[0254] In the embodiment where the endpoint designation signal, which transitions from a high level to a low level at the reset timing tep, is used as the reset information Ntep, the reset timing tep of the dispensing unit D to be judged is earlier than the measurement start timing of the next dispensing unit D to be judged. However, even in this embodiment, the cutoff timing can be set earlier than the reset timing tep, thus suppressing an increase in inspection time. For example, even in this embodiment, if the timing is later than the cutoff timing of the dispensing unit D to be judged, the drive signal COM can be supplied to the next dispensing unit D to be judged at a timing earlier than the reset timing tep of the dispensing unit D to be judged.

[0255] Furthermore, while Figure 15 assumes a case where the potential of the residual vibration signal VD in the range from the threshold potential VthC to the second peak PK of the residual vibration signal VD is compared with the threshold potentials VthC and Vth1, etc., the present invention is not limited to this embodiment. For example, in the residual vibration signal VD shown in Figure 15, the potential of the residual vibration signal VD in the range from the threshold potential VthC to the first peak PK of the residual vibration signal VD may also be compared with the threshold potentials VthC and Vth1, etc. In this case, for example, instead of comparing the potential of the residual vibration signal VD with the threshold potential Vth1, the potential of the residual vibration signal VD is compared with a threshold potential lower than the threshold potential VthC, for example, the threshold potential Vthm1 shown in Figure 9. The method for generating a comparison signal CP based on the comparison result between a threshold potential lower than the threshold potential VthC and the potential of the residual vibration signal VD is the same as the method using the threshold potential Vthm1 described in Figure 9.

[0256] Next, referring to Figure 16, we will explain the relationship between the reset timing tep, the amplitude Vamp, and the amplitude change rate.

[0257] Figure 16 is an explanatory diagram illustrating the relationship between the reset timing tep, the amplitude Vamp, and the amplitude change rate. In Figure 12, one vertical axis shows the voltage [V] of the amplitude Vamp relative to the threshold potential VthC, the other vertical axis shows the amplitude change rate [%], and the horizontal axis shows the adjustment time [μs] of the reset timing tep. The adjustment time of the reset timing tep is shown as the time in μs from the lower limit of the adjustment range of the reset timing tep. However, the adjustment range of the reset timing tep and the lower limit of said adjustment range are introduced for the sake of explanation and do not necessarily have to be set in reality. Also, the amplitude change rate is shown as the ratio [%] of the amplitude Vamp calculated in the abnormal nozzle to the amplitude Vamp calculated in the normal nozzle, similar to Figure 12.

[0258] In Figure 16, the solid line represents the amplitude Vamp of a normal nozzle, the dashed line represents the amplitude Vamp of an abnormal nozzle where ink flight deviation occurred, and the dotted line represents the amplitude change rate. In addition, in Figure 16, the numerical values ​​of the amplitude difference and amplitude change rate in a comparative example in which the amplitude Vamp of the residual vibration signal VD is calculated in the same way as the second inspection mode described in the first embodiment above are shown in parentheses. For example, the amplitude difference between the amplitude Vamp of a normal nozzle and the amplitude Vamp of an abnormal nozzle calculated using the comparative example is about 0.1V, and the amplitude change rate in the comparative example is also about 0.1V.

[0259] In this embodiment, as shown in Figure 16, the amplitude Vamp increases as the adjustment time of the reset timing tep increases, in both the normal nozzle and the abnormal nozzle. Also, the amplitude difference DV between the amplitude Vamp of the normal nozzle and the amplitude Vamp of the abnormal nozzle increases as the adjustment time of the reset timing tep increases. In the example shown in Figure 16, while the amplitude difference in the comparative example is about 0.1V, the amplitude difference DV can be adjusted in the range of about 0.2V to about 1.0V. Furthermore, the absolute value of the amplitude change rate, which is the ratio of the amplitude Vamp of the abnormal nozzle to the amplitude Vamp of the normal nozzle, decreases as the adjustment time of the reset timing tep increases. In the example shown in Figure 16, while the amplitude difference in the comparative example is about -9%, the amplitude change rate can be adjusted in the range of about -16% to about -42%.

[0260] Thus, in this embodiment, the amplitude Vamp, etc., can be adjusted by adjusting the reset timing tep. For example, when the amplitude difference DV is large, the resolution is improved compared to when the amplitude difference DV is small, so the accuracy of the determination when determining whether the state of the ejection unit D is normal can be increased. Accordingly, in this embodiment, the sensitivity when determining the state of the ejection unit D can be adjusted by adjusting the reset timing tep. For example, in this embodiment, the sensitivity of detecting ink flight deviation can be increased by adjusting the reset timing tep.

[0261] Next, referring to Figure 17, we will explain the operation of the inkjet printer 1 when performing the ejection state determination process.

[0262] Figure 17 is a flowchart showing an example of the operation of the inkjet printer 1 when performing the ejection state determination process. The operation shown in Figure 17 is the same as the operation shown in Figure 13, except that the processes of steps S120, S142, and S162 shown in Figure 13 are omitted, and the processes of steps S164 and S170 are executed. Figure 17 will mainly explain the processes of steps S164 and S170.

[0263] The process in step S164 is executed after the process in step S140 has been completed. For example, inkjet printer 1 performs the process in step S140 and then moves on to step S164.

[0264] In step S164, the signal generation unit 60A of the inspection unit 6A generates comparison signals CPc, CP1, and CP2 by comparing the potential of the residual vibration signal VD with the threshold potentials VthC, Vth1, and Vth2, respectively. Then, the inspection unit 6A moves the process to step S170.

[0265] In step S170, the timing specification circuit 65 of the determination unit 64A of the inspection unit 6A specifies the reset timing tep to the specification unit 67A by outputting reset information Ntep, which indicates the reset timing tep, to the specification unit 67A. Then, the inspection unit 6A moves the process to step S180.

[0266] In step S180, the identification unit 67A of the determination unit 64A of the inspection unit 6A identifies the time lengths TCc, TC1, and TC2 based on, for example, formulas (9), (10), and (11) explained in Figure 14.

[0267] Note that the operation of the inkjet printer 1 when executing the ejection state determination process is not limited to the example shown in Figure 17. For example, the process in step S170 only needs to be executed before the process in step S180, and may be executed before the process in step S100.

[0268] In this embodiment, the inkjet printer 1 comprises an ejection unit D capable of ejecting ink in response to an input drive signal COM, a signal generation unit 60A that receives a residual vibration signal VD corresponding to the residual vibration generated in the ejection unit D in response to the input of the drive signal COM and generates a plurality of comparison signals CP based on the residual vibration signal VD, and a determination unit 64A that determines the state of the ejection unit D. The signal path of the residual vibration signal VD from the ejection unit D[j] to the signal generation unit 60A is interrupted at an interruption timing based on the connection state specification signal Qs[j]. The determination unit 64A determines the state of the ejection unit D based on a plurality of time information NTC generated by using the plurality of comparison signals CP as signals that have been reset at a reset timing tep based on reset information Ntep. If the interruption timing is earlier than the reset timing tep, each of the plurality of time information NTC is generated by using each of the plurality of comparison signals CP as a signal whose potential at the interruption timing is held until the reset timing tep.

[0269] In this embodiment, the signal generation unit 60A and determination unit 64A described above are included in the head unit control module HCM, which controls the head unit 3 equipped with an ejection unit D capable of ejecting ink in response to an input drive signal COM. In this embodiment as well, the method for determining the state of the ejection unit D corresponds to the liquid ejection inspection method.

[0270] Thus, in this embodiment, the signal path of the residual vibration signal VD from the discharge unit D[j] to the signal generation unit 60A is interrupted at the interruption timing. Furthermore, in this embodiment, if the interruption timing is before the reset timing tep, each of the multiple comparison signals CP is used as a signal whose potential at the interruption timing is held until the reset timing tep, thereby generating each of the multiple time information NTCs. For this reason, in this embodiment, for example, the discharge unit D[j] can be made to perform a different operation at a timing after the interruption timing, regardless of the reset timing tep. Alternatively, in this embodiment, regardless of the reset timing tep, a discharge unit D other than the discharge unit D[j] can be operated as the discharge unit D to be judged at a timing after the interruption timing. In other words, in this embodiment, for example, even if the time from the start of supplying the residual vibration signal VD to the signal generation unit 60A to the reset timing tep is increased, the inspection time for determining the state of the discharge unit D can be shortened.

[0271] Furthermore, in this embodiment, when the inspection time for the state of the discharge unit D is shortened, the reset timing tep may be adjusted so that the time from the shut-off timing to the reset timing tep is shorter compared to when the inspection time is longer. In this way, in this embodiment, the inspection time for the state of the discharge unit D can be easily shortened by adjusting the reset timing tep.

[0272] Also, in the present embodiment, when increasing the inspection accuracy of the state of the ejection unit D, the reset timing tep may be adjusted so that the time from the cutoff timing to the reset timing tep becomes longer than when the inspection accuracy is low. Thus, in this aspect, by adjusting the reset timing tep, the inspection accuracy of the state of the ejection unit D can be easily increased. For example, when the time from the cutoff timing to the reset timing tep becomes longer, the time from the timing when the supply of the residual vibration signal VD to the signal generation unit 60A starts to the reset timing tep becomes longer. Therefore, when adjusted so that the time from the cutoff timing to the reset timing tep becomes longer, the amplitude of the adjusted waveform of the sine wave based on the plurality of comparison signals CP becomes larger, so that the resolution is increased and the inspection accuracy can be enhanced.

[0273] Also, in the present embodiment, the signal generation unit 60A may generate a plurality of comparison signals CP based on a signal in a first period TPP1 that is 1 / 4 or less of the period of the residual vibration signal VD among the residual vibration signals VD. Thus, in this aspect, since the time required for generating the comparison signal CP can be shortened, the inspection time for determining the state of the ejection unit D can be shortened.

[0274] Also, in the present embodiment, the signal generation unit 60A is electrically disconnected from the ejection unit D[j] by the connection state designation signal Qs[j]. For example, in the present embodiment, the wiring Li[j] is electrically disconnected from the wiring Ls according to the connection state designation signal Qs[j]. Thus, in the present embodiment, since the signal generation unit 60A is electrically disconnected from the ejection unit D[j] by the connection state designation signal Qs[j], another operation can be executed on the ejection unit D[j] before the determination of the state of the ejection unit D[j] is completed. Alternatively, in the present embodiment, before the determination of the state of the ejection unit D[j] is completed, another ejection unit D different from the ejection unit D[j] can be operated as the ejection unit D to be determined.

[0275] Furthermore, in this embodiment, the multiple comparison signals CP may be generated based on the signal in the portion of the residual vibration signal VD in a first period TPP1 that is less than one-quarter of the period of the residual vibration signal VD. The first period TPP1 starts before a first time has elapsed since the residual vibration signal VD was input to the signal generation unit 60A, and the first time is shorter than the time corresponding to one-quarter of the period of the residual vibration signal VD. In this embodiment, it is possible to suppress the time from when the residual vibration signal VD is input to the signal generation unit 60A until the comparison signals CP are generated from being input. As a result, in this embodiment, the inspection time for determining the state of the discharge unit D can be shortened.

[0276] [Third Embodiment] Figure 18 is a block diagram showing an example of the configuration of the inspection unit 6B according to the third embodiment. Elements similar to those described in Figures 1 to 17 are denoted by the same reference numerals, and detailed descriptions are omitted.

[0277] The inkjet printer 1 according to this embodiment is the same as the inkjet printer 1 shown in Figure 1, except that it has an inspection unit 6B instead of the inspection unit 6 shown in Figure 1. In this embodiment, as with the second embodiment described above, it is assumed that the determination of the state of the ejection unit D in the second inspection mode described in the first embodiment described above is not performed. For this reason, the mask signal MSK shown in Figure 8, etc. is not used in this embodiment. However, in this embodiment as well, the state of the ejection unit D may be determined in the second inspection mode. The inspection unit 6B will be described in detail below.

[0278] In the test unit 6B, reset information Ntec, Nte1, and Nte2 are used instead of reset information Ntep shown in Figure 14. Reset information Ntec indicates the reset timing tec of the comparison signal CPc, reset information Nte1 indicates the reset timing te1 of the comparison signal CP1, and reset information Nte2 indicates the reset timing te2 of the comparison signal CP2. Each of the reset information Ntec, Nte1, and Nte2 is an example of a "reset signal" and "timing information". Hereafter, reset information Ntep, Ntec, Nte1, and Nte2 may be collectively referred to as reset information Nte. Also below, reset timing tep, tec, te1, and te2 may be collectively referred to as reset timing te.

[0279] The inspection unit 6B is the same as the inspection unit 6A shown in Figure 14, except that it has a determination unit 64B instead of the determination unit 64A shown in Figure 14. For example, the inspection unit 6B has a signal generation unit 60A and a determination unit 64B. The signal generation unit 60A is the same as the signal generation unit 60A shown in Figure 14. For example, in this embodiment as well as in the second embodiment described above, timing tsc is the timing when the comparison signal CPc transitions from a low level to a high level. Also, timing ts1 is the timing when the comparison signal CP1 transitions from a low level to a high level, and timing ts2 is the timing when the comparison signal CP2 transitions from a low level to a high level.

[0280] The determination unit 64B is the same as the determination unit 64A shown in Figure 14, except that it has a timing specification circuit 66 and a specific unit 67B instead of the timing specification circuit 65 and specific unit 67A shown in Figure 14. For example, the determination unit 64B has a timing specification circuit 66, a specific unit 67B, an amplitude calculation circuit 68, and a determination circuit 69. The amplitude calculation circuit 68 and the determination circuit 69 are the same as the amplitude calculation circuit 68 and the determination circuit 69 shown in Figure 7. For example, the amplitude Vamp of the residual vibration signal VD is calculated by equation (1) or equation (2) explained in Figure 7 by approximating the waveform of the residual vibration signal VD as a sine wave.

[0281] The specific unit 67B is the same as the specific unit 67A shown in Figure 14, except that it has specific circuits 670B, 671B, and 672B instead of the specific circuits 670A, 671A, and 672A shown in Figure 14. The specific circuit 670B is the same as the specific circuit 670A, except that it uses the reset timing tec instead of the reset timing tep to specify the time length TCc. The specific circuit 671B is the same as the specific circuit 671A, except that it uses the reset timing te1 instead of the reset timing tep to specify the time length TC1. The specific circuit 672B is the same as the specific circuit 672A, except that it uses the reset timing te2 instead of the reset timing tep to specify the time length TC2.

[0282] Thus, in this embodiment, the reset timings tec, te1, and te2 corresponding to the comparison signals CPc, CP1, and CP2 are used to determine the time lengths TCc, TC1, and TC2, respectively. In addition, in this embodiment, the reset timing te is adjusted for each dispensing unit D. Below, the operation of the timing specification circuit 66 will be explained using the case where dispensing unit D[j] is the dispensing unit D to be determined as an example.

[0283] The timing specification circuit 66 specifies the reset timing tec[j] to the specific circuit 670B of the specific unit 67B by outputting reset information Ntec[j] corresponding to the comparison signal CPc to the specific circuit 670B of the specific unit 67B. The timing specification circuit 66 also specifies the reset timing te1[j] to the specific circuit 671B of the specific unit 67B by outputting reset information Nte1[j] corresponding to the comparison signal CP1 to the specific circuit 671B of the specific unit 67B. The timing specification circuit 66 also specifies the reset timing te2[j] to the specific circuit 671B of the specific unit 67B by outputting reset information Nte2[j] corresponding to the comparison signal CP2 to the specific circuit 671B of the specific unit 67B.

[0284] For example, the timing specification circuit 66 has adders 660, 661 and 662 and multipliers 663 and 664.

[0285] The summing unit 660 adds the reference period length RTCc and the reference set timing rtsc[j], and outputs reset information Ntec, which is the result of the addition and indicates the reset timing tec[j], to the specific circuit 670B. The reference period length RTCc is a parameter that determines the reference period length to reduce the variation in amplitude Vamp in multiple discharge units D, and is common to J discharge units D. For example, the reference period length RTCc may be set to about one-quarter of the period of a normal residual vibration signal VD. Information indicating the reference period length RTCc is stored, for example, in the memory unit 5. The reference set timing rtsc[j] is, for example, the timing tsc at which the comparison signal CPc transitions from a low level to a high level when the state of the discharge unit D[j] is normal. Information indicating the reference set timing rtsc[j] is stored, for example, in the memory unit 5 in association with the discharge unit D[j].

[0286] The adder 661 receives the result of the multiplication performed by the multiplier 663. For example, the multiplier 663 multiplies the reference period length RTCc by a coefficient α and outputs the result of this multiplication to the adder 661. The adder 661 then adds the result of the multiplication of the reference period length RTCc and the coefficient α to the reference set timing rts1[j] and outputs reset information Nte1, which indicates the reset timing te1[j] resulting from this addition, to the specific circuit 671B. The reference set timing rts1[j] is, for example, the timing ts1 at which the comparison signal CP1 transitions from a low level to a high level when the state of the ejection unit D[j] is normal. The information indicating the reference set timing rts1[j] is stored in the storage unit 5, for example, in association with the ejection unit D[j].

[0287] Furthermore, the coefficient α is a coefficient that adjusts the sensitivity when determining the state of the dispensing unit D, and is determined so that "α < 100%". For example, the coefficient α may be a coefficient common to J dispensing units D, or it may be a coefficient determined for each dispensing unit D. Alternatively, the coefficient α may be a coefficient determined for each group containing multiple dispensing units D. A group containing multiple dispensing units D may be, for example, a group of multiple dispensing units D corresponding to a nozzle row NL. Information indicating the coefficient α is stored, for example, in the storage unit 5. Note that if the coefficient α is a coefficient determined for each dispensing unit D, the information indicating the coefficient α is stored in the storage unit 5 in association with the dispensing unit D. Also, if the coefficient α is a coefficient determined for each group of multiple dispensing units D, the information indicating the coefficient α is stored in the storage unit 5 in association with the group.

[0288] The adder 662 receives the result of the multiplication performed by the multiplier 664. For example, the multiplier 664 multiplies the reference period length RTCc by a coefficient β and outputs the result of this multiplication to the adder 662. The adder 662 then adds the result of the multiplication of the reference period length RTCc and the coefficient β to the reference set timing rts2[j] and outputs reset information Nte1, which indicates the reset timing te2[j] resulting from this addition, to the specific circuit 672B. The reference set timing rts2[j] is, for example, the timing ts2 at which the comparison signal CP2 transitions from a low level to a high level when the state of the ejection unit D[j] is normal. Information indicating the reference set timing rts2[j] is stored in the storage unit 5, for example, in association with the ejection unit D[j].

[0289] Furthermore, the coefficient β is a coefficient that adjusts the sensitivity when determining the state of the dispensing unit D, and is determined so as to satisfy "α < 100%". For example, the coefficient β may be a coefficient common to J dispensing units D, or it may be a coefficient determined for each dispensing unit D. Alternatively, the coefficient β may be a coefficient determined for each group containing multiple dispensing units D. A group containing multiple dispensing units D may be, for example, a group of multiple dispensing units D corresponding to a nozzle row NL. Information indicating the coefficient β is stored, for example, in the storage unit 5. Note that if the coefficient β is a coefficient determined for each dispensing unit D, the information indicating the coefficient β is stored in the storage unit 5 in association with the dispensing unit D. Also, if the coefficient β is a coefficient determined for each group of multiple dispensing units D, the information indicating the coefficient β is stored in the storage unit 5 in association with the group.

[0290] Here, the reset timing tec[j] is expressed by equation (12), using the reference period length RTCc and the reference set timing rtsc[j]. The reset timing te1[j] is expressed by equation (13), using the reference period length RTCc, the reference set timing rts1[j], and the coefficient α. The reset timing te2[j] is expressed by equation (14), using the reference period length RTCc, the reference set timing rts2[j], and the coefficient β.

[0291] tec[j]=RTCc+rtsc[j] …(12) te1[j]=α·RTCc+rts1[j] …(13) te2[j]=β·RTCc+rts2[j] …(14)

[0292] The reset timing te1[j] can be adjusted by adjusting the coefficient α, as can be seen from equation (13). Similarly, the reset timing te2[j] can be adjusted by adjusting the coefficient β, as can be seen from equation (14).

[0293] Also, the time length TCc[j] is expressed by Equation (15) using the timing tsc[j] and the reset timing tec[j], and the time length TC1[j] is expressed by Equation (16) using the timing ts1[j] and the reset timing te1[j]. Also, the time length TC2[j] is expressed by Equation (17) using the timing ts2[j] and the reset timing te2[j].

[0294] TCc[j]=tec[j]-tsc[j] …(15) TC1[j]=te1[j]-ts1[j] …(16) TC2[j]=te2[j]-ts2[j] …(17)

[0295] Also, the time length TCc[j] is expressed by Equation (18) from Equation (12) and Equation (15), the time length TC1[j] is expressed by Equation (19) from Equation (13) and Equation (16), and the time length TC2[j] is expressed by Equation (20) from Equation (14) and Equation (17).

[0296] TCc[j]=RTCc+rtsc[j]-tsc[j] …(18) TC1[j]=α·RTCc+rts1[j]-ts1[j] …(19) TC2[j]=β·RTCc+rts2[j]-ts2[j] …(20)

[0297] As can be seen from equation (18), the time length TCc[j] is expressed as the sum of the reference period length RTCc and the value obtained by subtracting the timing tsc[j] from the reference set timing rtsc[j]. Also, as can be seen from equation (19), the time length TC1[j] is expressed as the sum of the product of the reference period length RTCc and the coefficient α and the value obtained by subtracting the timing ts1[j] from the reference set timing rts1[j]. Also, as can be seen from equation (20), the time length TC2[j] is expressed as the sum of the product of the reference period length RTCc and the coefficient β and the value obtained by subtracting the timing ts2[j] from the reference set timing rts2[j]. In this embodiment as well, the time length TC can be determined without generating the comparison signals CCPc, CCP1 and CCP2 shown in Figure 9.

[0298] Note that the configuration of the inspection unit 6B is not limited to the example shown in Figure 18. For example, the timing specification circuit 66 may be included in the control unit 2. Alternatively, the timing specification circuit 66 may be included in the specific unit 67B. In the embodiment in which the timing specification circuit 66 is included in the specific unit 67B, the time lengths TCc[j], TC1[j], and TC2[j] may be calculated based on equations (18), (19), and (20) without calculating the reset timings tec[j], te1[j], and te2[j]. Also, for example, the reset information Ntec[j], Nte1[j], and Nte2[j] may be stored in the storage unit 5 in association with the discharge unit D[j]. In this embodiment, the timing specification circuit 66 outputs the reset information Ntec[j], Nte1[j], and Nte2[j] read from the storage unit 5 to the specific unit 67B.

[0299] Furthermore, for example, endpoint designation signals whose levels transition at reset timing tec[j], endpoint designation signals whose levels transition at reset timing te1[j], and endpoint designation signals whose levels transition at reset timing te2[j] may be used as reset information Ntec[j], Nte1[j], and Nte2[j], respectively.

[0300] In this embodiment as well, the comparison signal CP may be generated based on the signal in the portion of the residual vibration signal VD in the first period TPP1, which is less than or equal to one-quarter of the period of the residual vibration signal VD. The first period TPP1 is, for example, the first period TPP1 shown in Figure 9. In this embodiment as well, it is preferable that the first period TPP1 is started before a first time has elapsed since the residual vibration signal VD was input to the signal generation unit 60A. The first time is, for example, a time shorter than the time corresponding to one-quarter of the period of the residual vibration signal VD.

[0301] Next, referring to Figure 19, we will explain the relationship between the residual vibration signal VD and the reset timing te and the comparison signal CP.

[0302] Figure 19 is an explanatory diagram illustrating the relationship between the residual vibration signal VD, the reset timing te, and the comparison signal CP. Note that the subscript [j] is omitted in Figure 19, but it will be used as appropriate in the explanation of Figure 19.

[0303] Time t0 in Figure 19 indicates the timing at which the supply of the residual vibration signal VD[j] to the signal generation unit 60A begins. The timing at which the supply of the residual vibration signal VD[j] to the signal generation unit 60A begins is, for example, the timing at which the connection status specification signal Qs[j] shown in Figure 8 transitions from a low level to a high level. In Figure 19, for the sake of clarity, the comparison signal CP, etc., will be explained assuming that the connection status specification signal Qs[j] is maintained at a high level. However, in this embodiment, the connection status specification signal Qs[j] can be transitioned from a high level to a low level, for example, between timing ts1 and reset timing te1.

[0304] Furthermore, in Figure 19, for the sake of clarity, hypothetical comparison signals VCPc, VCP1, and VCP2 are shown in parentheses. Comparison signals VCPc, VCP1, and VCP2 correspond to comparison signals CCPc, CCP1, and CCP2 shown in Figure 9. Note that comparison signals VCPc, VCP1, and VCP2 are not actually generated signals. Comparison signal VCPc is a hypothetical signal obtained by resetting comparison signal CPc at reset timing tec, comparison signal VCP1 is a hypothetical signal obtained by resetting comparison signal CP1 at reset timing te1, and comparison signal VCP2 is a hypothetical signal obtained by resetting comparison signal CP2 at reset timing te2. In Figure 19, comparison signals VCPc, VCP1, and VCP2 are shown when reset timings tec, te1, and te2 are the same.

[0305] In Figure 19, period Wc is the period from the timing tsc, when the comparison signal CPc transitions from a low level to a high level, to the reset timing tec, and the duration of period Wc is duration TCc. Period W1 is the period from the timing ts1, when the comparison signal CP1 transitions from a low level to a high level, to the reset timing te1, and the duration of period W1 is duration TC1. Period W2 is the period from the timing ts2, when the comparison signal CP2 transitions from a low level to a high level, to the reset timing te2, and the duration of period W2 is duration TC2.

[0306] When the discharge unit D[j] is in a normal state, the time length TCc[j] from timing tsc[j] to reset timing tec[j] is equal to the time length from the reference set timing rtsc[j] to reset timing tec[j], i.e., the reference period length RTCc. Note that "equal to" includes not only cases where they are exactly the same, but also cases where there are differences in the degree of error due to manufacturing errors or operational errors. Furthermore, when the J discharge units D are in a normal state, the time length TCc[j] of the J discharge units D is equal to the reference period length RTCc common to the J discharge units D.

[0307] Furthermore, when the discharge unit D[j] is in a normal state, the time length TC1[j] from timing ts1[j] to reset timing te1[j] is equal to the time length from the reference set timing rts1[j] to reset timing te1[j], i.e., the product of the reference period length RTCc and the coefficient α. Similarly, the time length TC2[j] from timing ts2[j] to reset timing te2[j] is equal to the time length from the reference set timing rts2[j] to reset timing te2[j], i.e., the product of the reference period length RTCc and the coefficient β.

[0308] Here, the reset timing te1[j] is adjusted by adjusting the coefficient α, as explained in Figure 18. For example, by adjusting the coefficient α, the reset timing te1[j] can be the same timing as the reset timing tec[j], later than the reset timing tec[j], or earlier than the reset timing tec[j].

[0309] If the reset timing te1[j] is later than the reset timing tec[j], the amplitude Vamp is determined by assuming that the potential of the residual oscillation signal VD reached the threshold potential Vth1 at a timing earlier than the actual timing ts1[j]. For example, consider the case where the reset timing te1[j] is shifted to match the reset timing tec[j] while maintaining the time length from the reference set timing rts1[j] to the reset timing te1[j]. Let this shift amount be called the first shift amount. In this case, the reference set timing rts1[j] is also shifted to a timing earlier by the first shift amount. As explained in Figure 18, the time length TC1[j] is expressed as the sum of the product of the reference period length RTCc and the coefficient α, and the value obtained by subtracting the timing ts1[j] from the reference set timing rts1[j]. If the measured time length TC1 is maintained, the value obtained by subtracting the timing ts1[j] from the reference set timing rts1[j] is also maintained. Therefore, the timing ts1[j] is also shifted to an earlier timing by the first shift amount. In this case, the amplitude Vamp is determined by assuming that the potential of the residual oscillation signal VD reached the threshold potential Vth1 at a timing that is the first shift amount earlier than the actual timing ts1[j].

[0310] Furthermore, if the reset timing te1[j] is earlier than the reset timing tec[j], the amplitude Vamp is determined by assuming that the potential of the residual oscillation signal VD reached the threshold potential Vth1 at a timing later than the actual timing ts1[j]. For example, consider the case where the reset timing te1[j] is shifted to match the reset timing tec[j] while maintaining the time length from the reference set timing rts1[j] to the reset timing te1[j]. Let's call this shift amount the second shift amount. In this case, the reference set timing rts1[j] is also shifted to a later timing by the second shift amount. Also, if the measured time length TC1 is maintained, the timing ts1[j] will also be shifted to a later timing by the second shift amount. In this case, the amplitude Vamp is determined by assuming that the potential of the residual oscillation signal VD reached the threshold potential Vth1 at a timing later than the actual timing ts1[j] by the second shift amount.

[0311] The reset timing te2[j] is adjusted by adjusting the coefficient β, similar to the reset timing te1[j]. For example, if the reset timing te2[j] is later than the reset timing tec[j], the amplitude Vamp is determined by assuming that the potential of the residual oscillation signal VD reached the threshold potential Vth2 at a timing earlier than the actual timing ts2[j]. Also, for example, if the reset timing te2[j] is earlier than the reset timing tec[j], the amplitude Vamp is determined by assuming that the potential of the residual oscillation signal VD reached the threshold potential Vth2 at a timing later than the actual timing ts2[j].

[0312] Next, with reference to Figure 20, an overview of the adjustment of sensitivity when determining the state of the discharge unit D will be described. In the following, the adjustment of sensitivity when determining the state of the discharge unit D may be simply referred to as sensitivity adjustment.

[0313] Figure 20 is an explanatory diagram illustrating the overview of sensitivity adjustment when determining the state of the discharge unit D. Figure 20 mainly explains sensitivity adjustment by adjusting the reset timing te1. Figure 20 shows the residual vibration signal VD of a normal nozzle and the residual vibration signal VD of an abnormal nozzle. The vertical axis of Figure 20 shows the voltage [V] relative to the threshold potential VthC, i.e., the potential difference from the threshold potential VthC, and the horizontal axis shows the elapsed time [μs] from the reference timing tref. In Figure 20, the reference timing tref is the timing when the potential of the residual vibration signal VD of the normal nozzle reaches the threshold potential VthC from a potential lower than VthC. That is, the reference timing tref is the reference set timing rtsc [j]. Also, Figure 20 assumes that the potential difference between the threshold potential VthC and the threshold potential Vth1 is 0.5V. Furthermore, the dashed line in Figure 20 shows the slope of the residual vibration signal VD of a normal nozzle at the threshold potential Vth1, while the dotted line shows the slope after sensitivity adjustment.

[0314] Furthermore, Figure 20 assumes that the amplitude VPK of the residual vibration signal VD of the normal nozzle is 1.0V, the amplitude VPK of the residual vibration signal VD of the abnormal nozzle is 0.9V, and the phase difference between the residual vibration signal VD of the normal nozzle and the residual vibration signal VD of the abnormal nozzle is 0. Also, Figure 10 assumes that the period of the residual vibration signal VD of the normal nozzle and the residual vibration signal VD of the abnormal nozzle are the same, and that one-quarter of the period is 2.0μs. In other words, Figure 20 assumes that only the amplitude VPK changes between the residual vibration signal VD of the normal nozzle and the residual vibration signal VD of the abnormal nozzle, among the amplitude VPK, period, and phase.

[0315] If only the amplitude VPK changes among the amplitude VPK, period, and phase, the period Wc of the comparison signal CPc remains unchanged between a normal nozzle and an abnormal nozzle, while the period W1 of the comparison signal CP1 changes. For example, the difference in the period W1 of the comparison signal CP1 between a normal nozzle and an abnormal nozzle is the time difference Δts1.

[0316] As shown in Figure 20, before sensitivity adjustment, the time difference Δts1 corresponds to the change in the slope near the threshold potential Vth1 of the residual vibration signal VD of a normal nozzle. During sensitivity adjustment, for example, the reset timing te1 is adjusted by adding the product of the reference period length RTCc and the coefficient α to the reference set timing rtsc, while maintaining the time difference Δts1, so that the slope after sensitivity adjustment becomes steeper. In the example shown in Figure 20, the reset timing te1 is adjusted to a timing that is tc1 time later than the reset timing tec.

[0317] For example, consider the case where the reset timing te1 is shifted by time tc1 to match the reset timing tec, while maintaining the time length from the reference set timing rts1 to the reset timing te1. In this case, the reference set timing rts1 is also shifted by time tc1 to the previous timing. Furthermore, since the time difference Δts1 is maintained, the timing ts1 of the abnormal nozzle is also shifted by time tc1 to the previous timing. As a result, the slope after sensitivity adjustment becomes steeper compared to before sensitivity adjustment, as shown by the dotted line in Figure 20.

[0318] Furthermore, simply amplifying the amplitude VPK of the residual vibration signal VD to make the slope steeper causes the slope of the residual vibration signal VD of the abnormal nozzle to change in the same way as the slope of the residual vibration signal VD of the normal nozzle, thus changing the time difference Δts1. For this reason, it is difficult to appropriately adjust the sensitivity when determining the state of the discharge section D using a method that simply amplifies the amplitude VPK of the residual vibration signal VD to make the slope steeper.

[0319] Next, referring to Figure 21, we will explain the relationship between the reset timing te and the amplitude Vamp calculated based on the time length TC.

[0320] Figure 21 is an explanatory diagram illustrating the relationship between the reset timing te and the amplitude Vamp calculated based on the time length TC. The adjusted waveform in Figure 21 shows a sine wave having an amplitude Vamp calculated from equation (1) explained in Figure 7, using the time length TCc adjusted by the reset timing tec and the time length TC1 adjusted by the reset timing te1. In other words, the adjusted waveform is a hypothetical waveform in which the residual vibration signal VD is assumed to have an amplitude Vamp calculated based on the time lengths TCc and TC1, and is not necessarily the same waveform as the residual vibration signal VD actually output from the detection circuit 33. Furthermore, the comparison signal VCPc in Figure 21 is a hypothetical signal obtained by resetting the comparison signal CPc with the reset timing tec, and the comparison signal VCP1 is a hypothetical signal obtained by resetting the comparison signal CP1 with the reset timing te1.

[0321] In Figure 21, the graphs of the residual vibration signal VD and the adjustment waveform show that the vertical axis represents the voltage [V] relative to the threshold potential VthC, i.e., the potential difference from the threshold potential VthC, and the horizontal axis represents the elapsed time [μs] from the reference timing tref. In Figure 21, the reference timing tref is the timing when the potential of the residual vibration signal VD of a normal nozzle reaches the threshold potential VthC from a potential lower than VthC, and the potential difference between the threshold potential VthC and the threshold potential Vth1 is 0.5V.

[0322] Furthermore, the residual vibration signals VD of the normal nozzle and the abnormal nozzle shown in Figure 21 are the same as those of the normal nozzle and the abnormal nozzle described in Figure 20. For example, the amplitude VPK of the residual vibration signal VD of the normal nozzle is 1.0V, the amplitude VPK of the residual vibration signal VD of the abnormal nozzle is 0.9V, and the phase difference between the residual vibration signal VD of the normal nozzle and the residual vibration signal VD of the abnormal nozzle is 0. Also, the time of one-quarter of the period of the residual vibration signal VD of the normal nozzle and the residual vibration signal VD of the abnormal nozzle is 2.0μs. Therefore, the residual vibration signals VD of the normal nozzle and the residual vibration signal VD of the abnormal nozzle reach their peak PK at a timing 2.0μs after the reference timing tref.

[0323] Figure 21 shows six adjustment waveforms corresponding to six reset timings te1 for both a normal nozzle and an abnormal nozzle. Figure 21 also shows the adjustment waveform and a virtual comparison signal VCP1 when reset timing te1 is shifted to the same position as reset timing tec.

[0324] As shown in Figure 21, by adjusting the reset timing te1, the time ratio, which is the ratio of the time length TC1 to the time length TCc when the discharge unit D is in a normal state, is adjusted. In both the normal nozzle and the abnormal nozzle, the amplitude Vamp of the adjusted waveform becomes larger when the time ratio, which is the ratio of the time length TC1 to the time length TCc when the discharge unit D is in a normal state, is large compared to when the time ratio is small.

[0325] The reset timing te1 is adjusted, for example, by adjusting the coefficient α in equation (13) explained in Figure 18. The coefficient α corresponds to the time ratio, which is the ratio of the time length TC1 to the time length TCc when the discharge unit D is in a normal state. The reset timing te1 may also be adjusted by adjusting the reference set timing rts1. Adjusting the reference set timing rts1 also adjusts the time ratio, which is the ratio of the time length TC1 to the time length TCc when the discharge unit D is in a normal state.

[0326] Here, the amount of adjustment of the time length TC1 in response to the adjustment of the reset timing te1 corresponds to the correction amount of the comparison signal CP1. Also, although not shown in Figure 21, the amount of adjustment of the time length TC2 in response to the adjustment of the reset timing te2 corresponds to the correction amount of the comparison signal CP2. Alternatively, the change in amplitude Vamp due to the adjustment of the time length TC1 can also be considered as the correction amount.

[0327] Next, referring to Figure 22, we will explain the relationship between the time ratio, which is the ratio of time length TC1 to time length TCc when the discharge section D is in a normal state, and the amplitude Vamp and amplitude change rate.

[0328] Figure 22 is an explanatory diagram illustrating the relationship between the time ratio of two time lengths TCc and TC1, and the amplitude Vamp and amplitude change rate. One vertical axis in Figure 22 shows the voltage [V] of the amplitude Vamp relative to the threshold potential VthC, the other vertical axis shows the amplitude change rate [%], and the horizontal axis shows the time ratio [%] of time lengths TCc and TC1. The amplitude change rate, as in Figure 12, shows the ratio [%] of the amplitude Vamp calculated in the abnormal nozzle to the amplitude Vamp calculated in the normal nozzle. The time ratio of time lengths TCc and TC1 shows the ratio [%] of time length TC1 to time length TCc when the discharge section D is in a normal state. For example, the time ratio corresponds to the coefficient α in equations (13) and (19) explained in Figure 18.

[0329] In Figure 22, the white circles indicate the amplitude Vamp of a normal nozzle, the black circles indicate the amplitude Vamp of an abnormal nozzle, and the rectangles indicate the rate of change of amplitude.

[0330] As shown in Figure 22, in both normal and abnormal nozzles, the amplitude Vamp increases as the time ratio of time length TCc to TC1 increases. Furthermore, the amplitude difference DV between the amplitude Vamp of the normal nozzle and the amplitude Vamp of the abnormal nozzle increases as the time ratio of time length TCc to TC1 increases. Also, the absolute value of the amplitude change rate, which is the ratio of the amplitude Vamp of the abnormal nozzle to the amplitude Vamp of the normal nozzle, increases as the time ratio of time length TCc to TC1 increases. In the example shown in Figure 16, when the time ratio of time length TCc to TC1 is set to approximately 90%, the amplitude change rate increases to approximately three times the amplitude change rate when the time ratio of time length TCc to TC1 is approximately 67%.

[0331] Thus, in this embodiment, the amplitude Vamp and amplitude change rate can be adjusted by adjusting the time ratio of time length TCc and TC1, for example, the coefficient α. The time ratio of time length TCc and TC1 may be determined for each ejection unit D according to the amount of ink ejected when the ejection unit D is in a normal state. For example, if the i-th ejection unit D, which is different from the j-th ejection unit D[j] among the J ejection units D, is designated as ejection unit D[i], then the time ratio of time length TCc and TC1 may be adjusted for each of ejection units D[j] and D[i] according to the amount of ink ejected. The variable i is a natural number satisfying "1≦i≦J" and "i≠j". Furthermore, in the following, if a component or signal of the inkjet printer 1 corresponds to ejection unit D[i] among the J ejection units D, the subscript [i] may be added to the symbol used to represent that component or signal.

[0332] For example, if the amount of ink ejected by ejector unit D[i] is less than the amount of ink ejected by ejector unit D[j], the amplitude VPK[i] of the residual vibration signal VD[i] of ejector unit D[i] tends to be smaller than the amplitude VPK[j] of the residual vibration signal VD[j] of ejector unit D[j]. Therefore, if the amount of ink ejected by ejector unit D[i] is less than the amount of ink ejected by ejector unit D[j], the time ratio of time lengths TCc and TC1 is adjusted such that, for example, the adjustment amount of the amplitude Vamp[i] of ejector unit D[i] is larger than the adjustment amount of the amplitude Vamp[j] of ejector unit D[j]. In this case, the time ratio of time lengths TCc and TC1 may be adjusted by adjusting the coefficient α for each ejector unit D. That is, the coefficient α may be different for ejector unit D[j] and ejector unit D[i]. In the following, the coefficient α used to calculate the reset timing te1[j] will be referred to as coefficient α[j], and the coefficient α used to calculate the reset timing te1[i] will be referred to as coefficient α[i]. The reset timing te1[j] is an example of the "first timing".

[0333] In the above example, discharge unit D[j] is an example of a "first discharge unit," and discharge unit D[i] is an example of a "second discharge unit." Furthermore, residual vibration signal VD[j] is an example of a "first residual vibration signal," and residual vibration signal VD[i] is an example of a "second residual vibration signal." Comparison signal CPc[j] of discharge unit D[j] is an example of a "first reference signal," and comparison signals CP1[j] and CP2[j] of discharge unit D[j] are examples of "first inspection signals." Time information NTCc[j] of discharge unit D[j] is an example of "first reference signal information," and time information NTC1[j] and NTC2[j] of discharge unit D[j] are examples of "first inspection signal information." Additionally, information indicating the reference set timing rts1[j] and the coefficient α[j] are examples of "first correction information." Similarly, the comparison signal CPc[i] of the discharge unit D[i] is an example of a "second reference signal," and the comparison signals CP1[i] and CP2[i] of the discharge unit D[i] are examples of "second check signals." The time information NTCc[i] of the discharge unit D[i] is an example of "second reference signal information," and the time information NTC1[i] and NTC2[i] of the discharge unit D[i] are examples of "second check signal information." In addition, the information indicating the reference set timing rts1[i] and the information indicating the coefficient α[i] are examples of "second correction information." However, if the coefficient α is common to both the discharge unit D[j] and the discharge unit D[i], the information indicating the coefficient α does not need to be included in the "first correction information" and "second correction information."

[0334] In this embodiment, as described above, the time ratio of time length TCc and TC1 can be adjusted in each of the ejection sections D[j] and D[i] according to the amount of ink ejected. This allows the ejection sections D[j] and D[i] to be inspected using the same standard in this embodiment.

[0335] Next, with reference to Figure 23, an example of the variation in amplitude Vamp between nozzles N, calculated based on time lengths TCc and TC1, will be described.

[0336] Figure 23 is an explanatory diagram illustrating an example of the variation in amplitude Vamp between nozzles N, calculated based on time lengths TCc and TC1. Figure 23 shows the results obtained from experiments. The vertical axis of Figure 23 shows the voltage [V] relative to the threshold potential VthC, i.e., the potential difference from the threshold potential VthC, and the horizontal axis shows the nozzle number for identifying the J nozzles N. Figure 23 also shows a comparative example in which the amplitude Vamp of the residual vibration signal VD is calculated in the same way as the second inspection mode described in the first embodiment above, without performing adjustment for the variation between nozzles. In the comparative example, the variation ΔVex of amplitude Vamp across the J nozzles N is about 2V, and the amplitude change rate is about -10%.

[0337] In this embodiment, since the reset timing te is adjusted for each discharge unit D, the time lengths TCc and TC1, respectively, when the discharge unit D is in a normal state, are approximately the same for the J nozzles N corresponding to the J discharge units D. Therefore, as shown in Figure 23, the amplitude Vamp calculated based on the time lengths TCc and TC1 is approximately the same for the J nozzles N. That is, the variation in amplitude Vamp ΔVamp across the J nozzles N is approximately 0. However, since the characteristics of each nozzle N change due to environmental changes such as temperature changes, variations in repeated measurements, and aging degradation of the piezoelectric element PZ, the variation in amplitude Vamp ΔVamp across the J nozzles N is not strictly 0. Furthermore, in this embodiment, the amplitude change rate can be improved from approximately -10% to approximately -23% compared to the comparative example.

[0338] Thus, in this embodiment, the amplitude variation rate can be improved compared to the comparative example, while significantly reducing the variation ΔVamp of the amplitude Vamp across the J nozzles N. Furthermore, in this embodiment, by adjusting the coefficient α, for example, the sensitivity when determining the state of the discharge section D can be increased while reducing the variation ΔVamp of the amplitude Vamp across the J nozzles N.

[0339] Next, referring to Figure 24, we will explain an example of the amplitude Vamp calculated when the sensitivity for determining the state of the discharge section D is adjusted.

[0340] Figure 24 is an explanatory diagram illustrating an example of the amplitude Vamp calculated when the sensitivity for determining the state of the discharge unit D is adjusted. Figure 24 shows the results obtained from experiments. Figure 24 shows the amplitude Vamp when the sensitivity for determining the state of the discharge unit D is adjusted by adjusting the time ratio of the time lengths TCc and TC1 when the state of the discharge unit D is normal. In Figure 24, it is assumed that the coefficient α is common to J discharge units D, and that the time ratio of the time lengths TCc and TC1 is adjusted by adjusting this coefficient α.

[0341] As shown in Figure 24, in all cases where the time ratio of time length TCc to TC1 is approximately 70%, 80%, and 90%, the variation in amplitude Vamp across the J nozzles N, ΔVamp, is approximately 0. Furthermore, in the example shown in Figure 24, as explained in Figure 22, as the time ratio of time length TCc to TC1 increases, the amplitude Vamp, the amplitude difference DV between the amplitude Vamp of a normal nozzle and the amplitude Vamp of an abnormal nozzle, and the absolute value of the amplitude change rate all increase. Next, referring to Figure 25, the operation of the inkjet printer 1 when performing the ejection state determination process will be described.

[0342] Figure 25 is a flowchart showing an example of the operation of the inkjet printer 1 when performing the ejection state determination process. The operation shown in Figure 25 is the same as the operation shown in Figure 17, except that a series of processes in steps S172, S174, and S176 are executed instead of the process in step S170 shown in Figure 17. In Figure 25, the series of processes in steps S172, S174, and S175 will be explained, with the case where the ejection unit D to be determined is ejection unit D[j] as an example.

[0343] The series of processes in steps S172, S174, and S175 are performed by the timing designation circuit 66 of the determination unit 64B of the inspection unit 6B after the process in step S164 has been executed. For example, the inkjet printer 1 moves the process to step S172 after executing the process in step S164.

[0344] In step S172, the timing specification circuit 66 acquires information indicating the reference period length RTCc, information indicating the coefficient α, and information indicating the coefficient β. For example, the timing specification circuit 66 reads information indicating the reference period length RTCc, information indicating the coefficient α, and information indicating the coefficient β from the storage unit 5. Then, the inspection unit 6B moves the process to step S174.

[0345] In step S174, the timing specification circuit 66 acquires information indicating the reference set timings rtsc[j], rts1[j], and rts2[j] of the discharge unit D[j] to be judged. For example, the timing specification circuit 66 reads information indicating the reference set timings rtsc[j], rts1[j], and rts2[j] from the storage unit 5. Then, the inspection unit 6B moves the process to step S176.

[0346] In step S176, the timing specification circuit 66 calculates the reset timings tec[j], te1[j], and te2[j] of the discharge unit D[j] to be determined. For example, the timing specification circuit 66 calculates the reset timings tec[j], te1[j], and te2[j] based on equations (12), (13), and (14) explained in Figure 18. The timing specification circuit 66 then outputs reset information Ntec[j] indicating the reset timing tec[j], reset information Nte1[j] indicating the reset timing te1[j], and reset information Nte2[j] indicating the reset timing te2[j] to the specification unit 67B. As a result, the reset timings tec[j], te1[j], and te2[j] are specified to the specification unit 67B. After the timing specification circuit 66 outputs reset information Ntec[j], Nte1[j], and Nte2[j] to the identification unit 67B, the inspection unit 6A moves to step S180.

[0347] In step S180, the identification unit 67B of the determination unit 64B of the inspection unit 6B identifies the time lengths TCc[j], TC1[j], and TC2[j] based, for example, on formulas (15), (16), and (17) as explained in Figure 18.

[0348] Note that the operation of the inkjet printer 1 when executing the ejection state determination process is not limited to the example shown in Figure 25. For example, the series of processes in steps S172, S174, and S175 only need to be executed after the process in step S100 and before the process in step S180, and may be executed before the process in step S140. Also, for example, if each of coefficients α and β is common to J ejection units D, the process in step S172 may be executed before the process in step S100. Alternatively, the reference period length RTCc, coefficients α and β may be set in advance in the timing specification circuit 66. In this case, step S172 is omitted. Also, for example, if each of coefficients α and β is determined for each ejection unit D, in step S172, the timing specification circuit 66 obtains information indicating the coefficients α and β of the ejection unit D[j] to be determined.

[0349] Furthermore, for example, the processing in step S172 and the processing in step S174 do not need to be strictly distinguished. Also, for example, the processing in step S176 and the processing in step S180 do not need to be strictly distinguished. For example, the inspection unit 6B may determine the time lengths TCc[j], TC1[j] and TC2[j] based on equations (18), (19), and (20) explained in Figure 18, without calculating the reset timings tec[j], te1[j] and te2[j]. In this embodiment, for example, the timing specification circuit 66 may output information indicating the reference period length RTCc, information indicating the coefficient α, and information indicating the coefficient β to the specification unit 67B in step S172. Then, in step S174, the timing specification circuit 66 may output information indicating the reference set timings rtsc[j], rts1[j], and rts2[j] of the discharge unit D[j] to be determined to the specification unit 67B.

[0350] In this embodiment, the inkjet printer 1 includes an ejection unit D[j] and an ejection unit D[i] capable of ejecting ink in response to an input drive signal COM; a signal generation unit 60A that generates comparison signals CP1[j] and CPc[j] based on a residual vibration signal VD[j] when a residual vibration signal VD[j] corresponding to residual vibration occurring in the ejection unit D[j] in response to the input drive signal COM is input, and generates comparison signals CP1[i] and CPc[i] based on a residual vibration signal VD[i] when a residual vibration signal VD[i] corresponding to residual vibration occurring in the ejection unit D[i] in response to the input drive signal COM is input; a determination unit 64B that determines the state of each of the ejection units D[j] and D[i]; and a storage unit 5 that stores information indicating a reference set timing rts1[j] and information indicating a reference set timing rts1[i]. The determination unit 64B determines the state of the discharge unit D[j] using time information NTC1[j] generated based on the reference set timing rts1[j] and the comparison signal CP1[j] without using the reference set timing rts1[i], and time information NTCc[j] generated based on the comparison signal CPc[j] without using the reference set timing rts1[j] and rts1[i], and determines the state of the discharge unit D[i] using time information NTC1[i] generated based on the reference set timing rts1[i] and the comparison signal CP1[i] without using the reference set timing rts1[j], and time information NTCc[i] generated based on the comparison signal CPc[i] without using the reference set timing rts1[j] and rts1[i].

[0351] In this embodiment, the signal generation unit 60A and determination unit 64B described above are included in the head unit control module HCM, which controls the head unit 3, which has ejection units D[j] and D[i] capable of ejecting ink according to the input drive signal COM. In this embodiment as well, the method for determining the state of ejection units D[j] and D[i] corresponds to the liquid ejection inspection method.

[0352] Thus, in this embodiment, a reference set timing rts1[j] used for generating time information NTC1[j] and a reference set timing rts1[i] used for generating time information NTC1[i] are provided. Therefore, in this embodiment, it is possible to suppress variations in the time information NTC1, or more precisely, the time length TC1 indicated by the time information NTC1, between the discharge unit D[j] and the discharge unit D[i]. As a result, in this embodiment, the discharge unit D[j] and the discharge unit D[i] can be inspected using the same standard. Furthermore, in this embodiment, since variations in the time length TC1 indicated by the time information NTC1 are suppressed, it is not necessary to perform processing to address variations individually for each discharge unit D in processes such as those that use the time information NTC1 for determination. Therefore, in this embodiment, the state of the discharge unit D can be inspected efficiently. As a result, in this embodiment, it is possible to suppress an increase in the inspection time required to determine the state of the discharge unit D. Furthermore, in this embodiment, the time information NTC1 is generated based on the reference set timing rts1 and the comparison signal CP1. For example, in this embodiment, in order to shorten the inspection time for determining the state of the discharge unit D, time information NTC1 can be generated using a comparison signal CP1 that has been reset based on a reference set timing rts1 or the like. In other words, in this embodiment, the inspection time for determining the state of the discharge unit D can be shortened.

[0353] Furthermore, in this embodiment, the time information NTC1[j] is generated based on information obtained by correcting the comparison signal CP1[j] using the reference set timing rts1[j], and the time information NTC1[i] is generated based on information obtained by correcting the comparison signal CP1[i] using the reference set timing rts1[i]. When the amount of ink ejected by the ejection unit D[i] is less than the amount of ink ejected by the ejection unit D[j], the correction amount using the reference set timing rts1[i] is larger than the correction amount using the reference set timing rts1[j]. Thus, in this embodiment, the correction amount is adjusted in each of the ejection units D[j] and D[i] according to the amount of ink ejected. As a result, in this embodiment, the ejection unit D[j] and the ejection unit D[i] can be inspected using the same standard.

[0354] Furthermore, in this embodiment, the comparison signal CPc[j] is a signal indicating whether or not the residual vibration signal VD[j] is greater than or equal to the threshold potential VthC, the comparison signal CP1[j] is a signal indicating whether or not the residual vibration signal VD[j] is greater than or equal to a threshold potential Vth1 that is different from the threshold potential VthC, and the time information NTC1[j] is information generated by using the comparison signal CP1[j] as a signal indicating that the residual vibration signal VD[j] is greater than or equal to the threshold potential Vth1 until the reset timing te1[j] corresponding to the reference set timing rts1[j], regardless of whether or not the residual vibration signal VD[j] has transitioned to less than the threshold potential Vth1. In this way, in this embodiment, the adjusted sine wave waveform based on the comparison signal CP1[j] can be easily corrected by correcting the period of the comparison signal CP1[j] indicating that the residual vibration signal VD[j] is greater than or equal to the threshold potential Vth1. Furthermore, in this embodiment, even if the time from the start of supplying the residual vibration signal VD[j] to the signal generation unit 60A to the reset timing te1[j] is increased, the inspection time for determining the state of the discharge unit D[j] can be shortened.

[0355] Furthermore, in this embodiment, the signal path of the residual vibration signal VD[j] from the discharge unit D[j] to the signal generation unit 60A is interrupted at an interruption timing based on the connection state specification signal Qs[j]. The determination unit 64B generates time information NTC1[j] by using the comparison signal CP1[j] as a signal that has been reset at a reset timing te1[j] corresponding to the reference set timing rts1[j]. If the interruption timing is earlier than the reset timing te1[j], the time information NTC1[j] is generated by using the comparison signal CP1[j] as a signal whose potential at the interruption timing is held until the reset timing te1[j]. As a result, in this embodiment, for example, the discharge unit D[j] can be made to perform a different operation at a timing later than the interruption timing, regardless of the reset timing te1[j]. Alternatively, in this embodiment, a discharge unit D[i] other than the discharge unit D[j] can be operated as the discharge unit D to be determined at a timing later than the interruption timing, regardless of the reset timing te1[j]. Therefore, in this embodiment, even if the time from the start of supplying the residual vibration signal VD[j] to the signal generation unit 60A to the reset timing te1[j] is increased, for example, the inspection time for determining the state of the discharge unit D[j] can be shortened.

[0356] Furthermore, in this embodiment, the signal generation unit 60A may generate comparison signals CP1[j] and CPc[j] based on the signal in the first period TPP1 portion of the residual vibration signal VD[j], which is one-quarter or less of the period of the residual vibration signal VD[j]. In this way, the time required to generate the comparison signals CP1[j] and CPc[j] can be shortened, and therefore the inspection time required to determine the state of the discharge unit D[j] can be shortened.

[0357] Furthermore, in this embodiment, the signal generation unit 60A is electrically disconnected from the discharge unit D[j] by the connection status specification signal Qs[j]. For example, in this embodiment, wiring Li[j] is electrically disconnected from wiring Ls in accordance with the connection status specification signal Qs[j]. Thus, in this embodiment, since the signal generation unit 60A is electrically disconnected from the discharge unit D[j] by the connection status specification signal Qs[j], the discharge unit D[j] can be made to perform a different operation before the determination of the state of the discharge unit D[j] is completed. Alternatively, in this embodiment, before the determination of the state of the discharge unit D[j] is completed, a different discharge unit D[i] can be made to operate as the discharge unit D to be determined.

[0358] Furthermore, in this embodiment, the comparison signals CP1[j] and CPc[j] may be generated based on the signal in the portion of the residual vibration signal VD[j] that is one-quarter or less of the period of the residual vibration signal VD[j] in the first period TPP1. The first period TPP1 starts before the first time has elapsed since the residual vibration signal VD[j] was input to the signal generation unit 60A, and the first time is shorter than the time corresponding to one-quarter of the period of the residual vibration signal VD[j]. In this embodiment, it is possible to suppress the time from when the residual vibration signal VD[j] is input to the signal generation unit 60A until the comparison signals CP1[j] and CPc[j] are generated. As a result, in this embodiment, the inspection time for determining the state of the discharge unit D[j] can be shortened.

[0359] [2. Variant] Each of the above forms can be modified in various ways. Specific examples of modifications are given below. Two or more forms arbitrarily selected from the following examples can be combined as appropriate, within the bounds of mutual consistency. In the modified examples given below, for elements whose function or action is equivalent to that of the embodiments, the same reference numerals used in the above description will be reused, and detailed explanations of each will be omitted as appropriate.

[0360] [First variation] In the embodiments described above, the inspection units 6, 6A, and 6B may have a switching unit that switches whether or not to supply the residual vibration signal VD to the comparison unit 62. In this modified example, the control signal that switches whether or not to supply the residual vibration signal VD to the comparison unit 62, i.e., the control signal of the switching unit, may be considered as a "cutoff signal".

[0361] Figure 26 is a block diagram showing an example of the configuration of the inspection unit 6C according to the first modified example. Elements similar to those described in Figures 1 to 25 are denoted by the same reference numerals, and detailed explanations are omitted.

[0362] The inkjet printer 1 according to this modified example is the same as the inkjet printer 1 shown in Figure 1, except that it has an inspection unit 6C instead of the inspection unit 6 shown in Figure 1. However, the control unit 2 supplies a timing signal TMSIG to the inspection unit 6C instead of the pulse detection period signal Pcut shown in Figure 8, etc. Furthermore, this modified example assumes that the determination of the state of the ejection unit D in the second inspection mode described in the first embodiment above is not performed. For this reason, the mask signal MSK shown in Figure 8, etc. is not used in this modified example. However, the state of the ejection unit D may be determined in the second inspection mode even in this modified example. The inspection unit 6C will be described in detail below.

[0363] The inspection unit 6C includes a signal generation unit 60B, a determination unit 64, and switches SWc1, SW11, and SW21. The signal generation unit 60B is the same as the signal generation unit 60 shown in Figure 7, except that it includes switches SWc1, SW11, and SW21, inverters INVc1, INVc2, INV11, INV12, INV21, and INV22, and a timing specification circuit 65A. Each of the inverters INVc1, INVc2, INV11, INV12, INV21, and INV22 outputs an inverted signal of the input signal. The determination unit 64 is the same as the determination unit 64 shown in Figure 7.

[0364] The timing specification circuit 65A generates a cutoff signal CSIG and an end point specification signal ESIG based on the timing signal TMSIG supplied from the control unit 2, for example. The timing specification circuit 65A then outputs the cutoff signal CSIG to switches SWc1, SW11, and SW21. The timing specification circuit 65A also outputs the end point specification signal ESIG to the adjustment unit 63.

[0365] The timing signal TMSIG is, for example, a signal that starts at a low level, transitions from low to high at the cutoff timing, and transitions from high to low at the reset timing te, which is after the cutoff timing. That is, the timing based on the rising edge of the timing signal TMSIG is the cutoff timing, and the timing based on the falling edge of the timing signal TMSIG is the reset timing tep. The cutoff timing may also be based on the timing when the connection status specification signal Qs[j] transitions from high to low.

[0366] The cutoff signal CSIG is, for example, a signal whose initial level is low, and which transitions from low to high when the timing signal TMSIG transitions from low to high. The cutoff signal CSIG may also transition from high to low before the start of the next unit period TU following the unit period TU that includes the timing when the timing signal TMSIG transitioned from low to high.

[0367] The endpoint designation signal ESIG is, for example, a signal whose initial level is low, and which transitions from low to high level when the timing signal TMSIG transitions from low to high level. Furthermore, the endpoint designation signal ESIG may transition from low to high level before the start of the control period TSS2, which is included in the next unit period TU following the unit period TU that includes the timing when the timing signal TMSIG transitioned from low to high level.

[0368] Thus, in this modified example, the cutoff signal CSIG and the endpoint designation signal ESIG are signals based on the timing signal TMSIG input to the signal generation unit 60B via a single signal line. The endpoint designation signal ESIG is an example of a "reset signal".

[0369] Switches SWc1, SW11, and SW21 switch between conduction and non-conductivity between the detection circuit 33 of the head unit 3 and the comparison unit 62 of the signal generation unit 60B based on the cutoff signal CSIG. For example, when switch SWc1 is turned off, the signal path of the residual vibration signal VD from the detection circuit 33 to the comparison circuit 620 of the comparison unit 62 is cut off. Similarly, when switch SW11 is turned off, the signal path of the residual vibration signal VD from the detection circuit 33 to the comparison circuit 621 of the comparison unit 62 is cut off. And when switch SW21 is turned off, the signal path of the residual vibration signal VD from the detection circuit 33 to the comparison circuit 622 of the comparison unit 62 is cut off.

[0370] In the example shown in Figure 26, switches SWc1, SW11, and SW21 are turned on when the cutoff signal CSIG is low level and turned off when it is high level. For example, when switch SWc1 is turned on, the residual vibration signal VD from the detection circuit 33 is supplied to the comparator circuit 620. Similarly, when switch SW11 is turned on, the residual vibration signal VD from the detection circuit 33 is supplied to the comparator circuit 621, and when switch SW21 is turned on, the residual vibration signal VD from the detection circuit 33 is supplied to the comparator circuit 622.

[0371] Switch SWc2 switches the input of inverter INVc1 to either the output of comparator circuit 620 or the output of inverter INVc2 based on the cutoff signal CSIG. In the example shown in Figure 26, when the cutoff signal CSIG is low level, switch SWc2 connects the input of inverter INVc1 to the output of comparator circuit 620, and when the cutoff signal CSIG is high level, it connects the input of inverter INVc1 to the output of inverter INVc2. The output of inverter INVc1 is connected to the input of inverter INVc2. Therefore, when the cutoff signal CSIG transitions from low level to high level, the output of inverter INVc2 is held at the potential at the timing when the cutoff signal CSIG transitions from low level to high level. The output of inverter INVc2 is connected to the input of adjustment circuit 630 of adjustment unit 63. Therefore, when the cutoff signal CSIG transitions from low level to high level, the input of adjustment circuit 630 is held at the potential at the timing when the cutoff signal CSIG transitions from low level to high level.

[0372] Switch SW12 switches the input of inverter INV11 to either the output of comparator circuit 621 or the output of inverter INV12 based on the cutoff signal CSIG. In the example shown in Figure 26, when the cutoff signal CSIG is low, switch SW12 connects the input of inverter INV11 to the output of comparator circuit 621, and when the cutoff signal CSIG is high, it connects the input of inverter INV11 to the output of inverter INV12. The output of inverter INV11 is connected to the input of inverter INV12. Therefore, when the cutoff signal CSIG transitions from low to high, the output of inverter INV12 is held at the potential at the timing when the cutoff signal CSIG transitions from low to high. The output of inverter INV12 is connected to the input of adjustment circuit 631 of adjustment unit 63. Therefore, when the cutoff signal CSIG transitions from low to high, the input of adjustment circuit 631 is held at the potential at the timing when the cutoff signal CSIG transitions from low to high.

[0373] Switch SW22 switches the input of inverter INV21 to either the output of comparator circuit 622 or the output of inverter INV22 based on the cutoff signal CSIG. In the example shown in Figure 26, when the cutoff signal CSIG is low level, switch SW22 connects the input of inverter INV21 to the output of comparator circuit 622, and when the cutoff signal CSIG is high level, it connects the input of inverter INV21 to the output of inverter INV22. The output of inverter INV21 is connected to the input of inverter INV22. Therefore, when the cutoff signal CSIG transitions from low level to high level, the output of inverter INV22 is held at the potential at the timing when the cutoff signal CSIG transitions from low level to high level. The output of inverter INV22 is connected to the input of adjustment circuit 632 of adjustment unit 63. Therefore, when the cutoff signal CSIG transitions from low level to high level, the input of adjustment circuit 632 is held at the potential at the timing when the cutoff signal CSIG transitions from low level to high level.

[0374] Thus, in this modified configuration, the signal generation unit 60B, more specifically inverters INVc1 and INVc2, maintain the potential of the comparison signal CPc at the cutoff timing. Similarly, the signal generation unit 60B, more specifically inverters INV11 and INV12, maintain the potential of the comparison signal CP1 at the cutoff timing. Furthermore, the signal generation unit 60B, more specifically inverters INV21 and INV22, maintain the potential of the comparison signal CP2 at the cutoff timing.

[0375] The adjustment unit 63 operates similarly to the adjustment unit 63 shown in Figure 7. However, in the adjustment unit 63 shown in Figure 26, the outputs of inverters INVc2, INV12, and INV22 are input instead of the comparison signals CPc, CP1, and CP2, and the endpoint designation signal ESIG is input instead of the pulse detection period signal Pcut. Note that the mask signal MSK is not used in this modified example, as described above.

[0376] The adjustment circuit 630 in the adjustment unit 63 generates a comparison signal CCPc, which represents the logical AND of the output signal of inverter INVc2 and the endpoint designation signal ESIG. As a result, the comparison signal CCPc is at the level of the comparison signal CPc during the period before the cutoff timing, and is maintained at the level of the comparison signal CPc at the cutoff timing during the period from the cutoff timing to the reset timing tep. After the reset timing tep, the comparison signal CCPc is maintained at a low level. The adjustment circuits 631 and 632 in the adjustment unit 63 operate in the same manner as the adjustment circuit 630. In this way, the signal generation unit 60B generates the comparison signals CCPc, CCP1, and CCP2 assuming that the potential of the residual oscillation signal VD at the cutoff timing is maintained.

[0377] Note that the configuration of the inspection unit 6B is not limited to the example shown in Figure 26. For example, the timing specification circuit 65A may be provided outside the signal generation unit 60B. That is, the signal generation unit 60B may be defined without including the timing specification circuit 65A.

[0378] For example, the adjustment circuit 630 may include a latch circuit that transitions the comparison signal CCPc from a low level to a high level when the output signal of inverter INVc2 transitions from a low level to a high level, and resets the comparison signal CCPc to a low level when the endpoint designation signal ESIG transitions from a high level to a low level. The adjustment circuits 631 and 632 may also include latch circuits. In this embodiment, since the level of the comparison signal CP at the cutoff timing is held by the latch circuit, the switches SWc1, SW11 and SW21 and the inverters INVc1, INVc2, INV11, INV12, INV21 and INV22 may be omitted.

[0379] Alternatively, instead of switches SWc1, SW11, and SW21 and inverters INVc1, INVc2, INV11, INV12, INV21, and INV22, there may be a latch circuit that holds the level of the comparison signal CP at the cutoff timing.

[0380] Furthermore, the endpoint designation signal ESIG may be supplied to the identification unit 67 of the determination unit 64. In this embodiment, the switches SWc1, SW11 and SW21, the inverters INVc1, INVc2, INV11, INV12, INV21 and INV22, and the adjustment circuit 630 may be omitted. For example, in this embodiment, the identification circuit 670 of the identification unit 67 measures the time from the timing tsc when the comparison signal CPc transitions from a low level to a high level to the reset timing tep when the endpoint designation signal ESIG transitions from a high level to a low level, and identifies the measurement result as the time length TCc. The identification circuits 671 and 672 of the identification unit 67 operate in the same manner as the identification circuit 670.

[0381] Furthermore, for example, the reset timing tep, that is, the timing at which the timing signal TMSIG transitions from a high level to a low level, may be adjusted for each nozzle N.

[0382] Furthermore, the polarity of each of the timing signal TMSIG, the cutoff signal CSIG, and the endpoint designation signal ESIG can be appropriately determined according to the characteristics of each element, such as the switch SWc1. For example, the timing signal TMSIG may be a signal that starts at a high level, transitions from a high level to a low level at the cutoff timing, and transitions from a low level to a high level at the reset timing te.

[0383] In this modified example, the same effects as those of the embodiment described above can be obtained.

[0384] Furthermore, in this modified version, the signal generation unit 60B maintains the levels of the comparison signals CPc, CP1, and CP2 at the cutoff timing. This allows the time from when the residual vibration signal VD is input to the signal generation unit 60B until the cutoff timing to be shortened. As a result, the inspection time for determining the state of the discharge unit D can be easily shortened in this modified version.

[0385] Furthermore, in this modified example, the adjustment unit 63 of the signal generation unit 60B resets the levels of each of the comparison signals CCPc, CCP1, and CCP2 in accordance with the input of the endpoint designation signal ESIG. The input of the endpoint designation signal ESIG is, for example, when the level of the endpoint designation signal ESIG transitions from a high level to a low level. In this way, in this modified example, the reset of the comparison signals CCPc, CCP1, and CCP2 is controlled by the endpoint designation signal ESIG. As a result, in this modified example, the comparison signals CCPc, CCP1, and CCP2 can be adjusted more easily than in a configuration in which, for example, the comparison signals CCPc, CCP1, and CCP2 are reset after a predetermined time has elapsed since the input of the cutoff signal CSIG.

[0386] Furthermore, in this modified example, the cutoff signal CSIG and the termination signal ESIG are signals based on the timing signal TMSIG input to the signal generation unit 60B, more specifically to the timing specification circuit 65A, via a single signal line. One of the cutoff timing and the reset timing tep is based on the rising edge of the timing signal TMSIG, and the other of the cutoff timing and the timing signal TMSIG is based on the falling edge of the timing signal TMSIG. In this way, in this modified example, by defining the mutually exclusive cutoff timing and the reset timing tep based on the rising and falling edges of a single timing signal TMSIG, it is possible to suppress an increase in the number of signal lines and interfaces to the signal generation unit 60B.

[0387] Furthermore, in this modified example, when the inspection time for the state of the discharge unit D is shortened, the reset timing tep may be adjusted so that the time from the cutoff timing to the reset timing tep is shorter compared to when the inspection time is longer. In this way, in this embodiment, the inspection time for the state of the discharge unit D can be easily shortened by adjusting the reset timing tep. For example, in this embodiment, the period during which the comparison signal CP is output can be shortened by shortening the time from the cutoff timing to the reset timing tep.

[0388] [Second variation] In the embodiments and modifications described above, examples were given in which the amplitude Vamp is adjusted by adjusting the time ratio of the time lengths TCc and TC1, but the present invention is not limited to such embodiments. For example, the amplitude calculation circuit 68 may calculate the amplitude Vamp by considering the threshold potential Vth1 as a correction potential different from the actual potential.

[0389] Specifically, in the embodiment described above, for example, when calculating the amplitude Vamp of the residual vibration signal VD shown in Figure 10 based on the time lengths TCc and TC1, "0.5" and "0" are substituted for the threshold potentials Vth1 and VthC in equation (1) explained in Figure 7, respectively. In contrast, in this modified example, for example, "0" is substituted for the threshold potential VthC in equation (1), and a value greater than the actual potential difference "0.5V" relative to the threshold potential VthC, or a value less than the actual potential difference "0.5V", is substituted for the threshold potential Vth1. The value substituted for the threshold potential Vth1 in equation (1) is, for example, a value based on a correction potential. Correction information indicating the correction potential is stored, for example, in the memory unit 5. Correction information indicating the correction potential used to determine the state of the discharge unit D[j] is an example of "first correction information", and correction information indicating the correction potential used to determine the state of the discharge unit D[i] is an example of "second correction information".

[0390] If a value greater than the actual potential difference "0.5V" relative to the threshold potential VthC is substituted for the threshold potential Vth1 in equation (1), the calculated amplitude Vamp will be larger than when the actual potential difference "0.5V" relative to the threshold potential VthC is substituted for the threshold potential Vth1. In other words, the amplitude Vamp calculated based on the time lengths TCc and TC1 is adjusted to be larger.

[0391] If a value smaller than the actual potential difference "0.5V" relative to the threshold potential VthC is substituted for the threshold potential Vth1 in equation (1), the calculated amplitude Vamp will be smaller than when the actual potential difference "0.5V" relative to the threshold potential VthC is substituted for the threshold potential Vth1. In other words, the amplitude Vamp calculated based on the time lengths TCc and TC1 is adjusted to be smaller.

[0392] Thus, in this modified example, the threshold potential Vth1, which is compared with the potential of the residual vibration signal VD to generate the comparison signal CP1, is considered a correction potential different from the actual potential, and the amplitude Vamp calculated based on the time lengths TCc and TC1 is adjusted. For example, the determination unit 64B uses the comparison signal CP1[j] as a signal indicating whether the residual vibration signal VD[j] is greater than or equal to the correction potential based on the correction information. The correction potential can be appropriately determined according to the amount of adjustment of the amplitude Vamp. In addition, in this modified example, both adjustment of the amplitude Vamp by considering the threshold potential Vth1 as a correction potential and adjustment of the time ratio of time lengths TCc and TC1 may be performed.

[0393] In this modified example, the inkjet printer 1 has ejection units D[j] and D[i] that can eject ink in response to an input drive signal COM, and when a residual vibration signal VD[j] corresponding to the residual vibration occurring in the ejection unit D[j] in response to the input drive signal COM is input, it generates comparison signals CP1[j] and CPc[j] based on the residual vibration signal VD[j], and when a residual vibration signal VD[i] corresponding to the residual vibration occurring in the ejection unit D[i] in response to the input drive signal COM is input, it generates comparison signals CP1[j] and CPc[j] based on the residual vibration signal VD[i]. The system includes a signal generation unit 60A that generates comparison signals CP1[i] and CPc[i], a storage unit 5 that stores first correction information for comparison signal CP1[j] and second correction information for comparison signal CP1[i], and a determination unit 64B that determines the state of the discharge unit D[j] using the first correction information, comparison signal CP1[j] and comparison signal CPc[j] without using the second correction information, and determines the state of the discharge unit D[i] using the second correction information, comparison signal CP1[i] and comparison signal CPc[i] without using the first correction information. The comparison signal CPc[j] is a signal indicating whether the residual vibration signal VD[j] is greater than or equal to the threshold potential VthC, and the comparison signal CP1[j] is a signal indicating whether the residual vibration signal VD[j] is greater than or equal to a threshold potential Vth1 that is different from the threshold potential VthC. The determination unit 64B uses the comparison signal CP1[j] as a signal indicating whether the residual vibration signal VD[j] is equal to or greater than the correction potential based on the first correction information to determine the state of the discharge unit D[j].

[0394] In this modified example, the same effects as those of the embodiment and modified example described above can be obtained. Furthermore, in this modified example, by considering the threshold potential Vth1 as a correction potential different from the actual potential, the sinusoidal adjustment waveform based on the comparison signal CP1[j] can be easily corrected.

[0395] [Third variation] In the third embodiment described above, an example was given in which the reset timings tec, te1, and te2 are adjusted for each discharge unit D. However, the present invention is not limited to this embodiment. For example, the reset timings tec, te1, and te2 may be determined for each group including multiple discharge units D. A group including multiple discharge units D may be, for example, a group of multiple discharge units D corresponding to a nozzle row NL. In this modified example, the same effects as in the third embodiment described above can be obtained.

[0396] [Fourth variation] In the embodiments and modifications described above, the case in which the piezoelectric element PZ is displaced in the Z1 direction due to a change in the potential of the individual drive signal Vin[j] from a low potential to a high potential was illustrated, but the present invention is not limited to such embodiments. For example, a piezoelectric element PZ that is displaced in the Z1 direction due to a change in the potential of the individual drive signal Vin[j] from a high potential to a low potential may be used. In this case, for example, the potential of the drive signal COM changes from a low potential to a high potential in the part corresponding to the expansion element, and changes from a high potential to a low potential in the part corresponding to the contraction element. The same effects as those of the embodiments and modifications described above can be obtained in this modification as well.

[0397] [Fifth variation] In the embodiments and modifications described above, the case in which each head unit 3 has one nozzle row NL is illustrated, but the present invention is not limited to such embodiments. For example, each head unit 3 may have multiple nozzle rows NL. In this modification as well, the same effects as in the embodiments and modifications described above can be obtained.

[0398] [Sixth variation] The embodiments and modifications described above illustrate the case where the inkjet printer 1 has four head units 3, but the present invention is not limited to such embodiments. For example, the inkjet printer 1 may have one to three head units 3, or five or more head units 3. Alternatively, the inkjet printer 1 may have one to three head units 3A, or five or more head units 3A.

[0399] [7th variation] In the embodiments and modifications described above, the amplitude Vamp is calculated based on the duration of the period during which the potential of the residual vibration signal VD is equal to or greater than the threshold potential. However, the present invention is not limited to these embodiments. For example, the inspection unit 6 may calculate the amplitude Vamp based on the duration of the period during which the potential of the residual vibration signal VD is equal to or less than the threshold potential. In this modification as well, the same effects as in the embodiments and modifications described above can be obtained.

[0400] [8th variation] In the embodiments and modifications described above, an example is provided in which multiple inspection units 6 are provided, each corresponding to a plurality of head units 3 on a one-to-one basis. However, the present invention is not limited to this embodiment. For example, one inspection unit 6 may be provided for multiple head units 3, or multiple inspection units 6 may be provided for one head unit 3. The same effects as those of the embodiments and modifications described above can be obtained in this modification as well.

[0401] [9th variation] In the embodiments and modifications described above, it was assumed that the inkjet printer 1 is a serial printer. However, the present invention is not limited to this embodiment, and the inkjet printer 1 may be a so-called line printer in which a plurality of nozzles N are provided in the head module HM so as to extend wider than the width of the recording paper P. In this modification as well, the same effects as in the embodiments and modifications described above can be obtained.

[0402] [3. Addendum] From the forms exemplified above, for example, the following configuration can be understood.

[0403] [Note A1] The liquid dispensing device according to Appendix A1 comprises a dispensing unit capable of dispensing liquid in response to an input drive signal, a signal generation unit that receives a residual vibration signal corresponding to the residual vibration generated in the dispensing unit in response to the input drive signal and generates a state inspection signal based on the residual vibration signal, and a determination unit that determines the state of the dispensing unit based on the state inspection signal, wherein the signal generation unit has a first inspection mode that generates a first inspection mode signal as the state inspection signal corresponding to a first partial signal in a first period of the residual vibration signal, and a second inspection mode that generates a second inspection mode signal as the state inspection signal corresponding to a second partial signal in a second period of the residual vibration signal, wherein the first period is shorter than the second period. According to Appendix A1, determining the state of the discharge unit in the first inspection mode shortens the inspection time required to determine the state of the discharge unit, and determining the state of the discharge unit in the second inspection mode allows for more accurate determination of the state of the discharge unit.

[0404] [Appendix A2] The liquid dispensing device according to Appendix A2 is the liquid dispensing device according to Appendix A1, wherein the first period is a period of one-quarter or less of the period of the residual vibration signal, and the second period is a period of one-half or more of the period of the residual vibration signal. According to Appendix A2, by determining the state of the discharge unit in the first inspection mode, the inspection time can be reduced by more than one-quarter of the period of the residual vibration signal compared to determining the state of the discharge unit in the second inspection mode.

[0405] [Note A3] The liquid dispensing device according to Appendix A3 is the liquid dispensing device according to Appendix A1 or Appendix A2, wherein the second period is a period later than the first period, and the signal generation unit generates the second inspection mode signal in the second inspection mode without using the first partial signal of the residual vibration signal. According to Appendix A3, by determining the state of the discharge unit in the second inspection mode, even if noise is superimposed on the residual vibration signal immediately after it is input to the signal generation unit, the influence of such noise on determining the state of the discharge unit can be suppressed.

[0406] [Note A4] The liquid dispensing device according to Appendix A4 is a liquid dispensing device according to any one of Appendix A1 to Appendix A3, wherein the first period is started before the first time has elapsed since the residual vibration signal was input to the signal generation unit, and the first time is shorter than the time corresponding to one-quarter of the period of the residual vibration signal. According to Appendix A4, in the first inspection mode, it is possible to suppress the increase in the time from when the residual vibration signal is input to the signal generation unit until the state inspection signal is generated.

[0407] [Note A5] The head unit control circuit according to Appendix A5 is a head unit control circuit that controls a head unit having a discharge unit capable of discharging liquid in response to an input drive signal, and comprises a signal generation unit that receives a residual vibration signal corresponding to the residual vibration generated in the discharge unit in response to the input of the drive signal and generates a state inspection signal based on the residual vibration signal, and a determination unit that determines the state of the discharge unit based on the state inspection signal, wherein the signal generation unit has a first inspection mode that generates a first inspection mode signal as the state inspection signal corresponding to a first partial signal in a first period of the residual vibration signal, and a second inspection mode that generates a second inspection mode signal as the state inspection signal corresponding to a second partial signal in a second period of the residual vibration signal, wherein the first period is shorter than the second period. According to Appendix A5, the same effect as described in Appendix A1 can be obtained.

[0408] [Note A6] The head unit control circuit according to Appendix A6 is the head unit control circuit according to Appendix A5, wherein the first period is a period of one-quarter or less of the period of the residual vibration signal, and the second period is a period of one-half or more of the period of the residual vibration signal. According to Appendix A6, the same effect as described in Appendix A2 can be obtained.

[0409] [Note A7] The head unit control circuit according to Appendix A7 is the head unit control circuit according to Appendix A5 or Appendix A6, wherein the second period is a period later than the first period, and the signal generation unit generates the second inspection mode signal in the second inspection mode without using the first partial signal of the residual vibration signal. According to Appendix A7, the same effect as described in Appendix A3 can be obtained.

[0410] [Note A8] The liquid discharge device according to Appendix A8 is a head unit control circuit according to any one of Appendix A5 to Appendix A7, wherein the first period is started before the first time has elapsed since the residual vibration signal was input to the signal generation unit, and the first time is shorter than the time corresponding to one-quarter of the period of the residual vibration signal. According to Appendix A8, the same effect as described in Appendix A4 can be obtained.

[0411] [Note A9] The liquid discharge inspection method according to Appendix A9 is a liquid discharge inspection method for a liquid discharge device equipped with a discharge unit capable of discharging liquid in response to an input drive signal, wherein a state inspection signal is generated based on a residual vibration signal corresponding to the residual vibration generated in the discharge unit in response to the input of the drive signal, the state of the discharge unit is determined based on the state inspection signal, and if a first inspection mode is selected as the inspection mode for determining the state of the discharge unit, a first inspection mode signal corresponding to the first partial signal in the first period of the residual vibration signal is generated as the state inspection signal, and if a second inspection mode is selected as the inspection mode, a second inspection mode signal corresponding to the second partial signal in the second period of the residual vibration signal is generated as the state inspection signal, and the first period is a shorter period than the second period. According to Appendix A9, the same effect as described in Appendix A1 can be obtained.

[0412] [Note A10] The liquid discharge inspection method according to Appendix A10 is the liquid discharge inspection method according to Appendix A9, wherein the first period is a period of one-quarter or less of the period of the residual vibration signal, and the second period is a period of one-half or more of the period of the residual vibration signal. According to Appendix A10, the same effect as described in Appendix A2 above can be obtained.

[0413] [Note A11] The liquid discharge inspection method according to Appendix A11 is the liquid discharge inspection method according to Appendix A9 or Appendix A10, wherein the second period is a period later than the first period, and in the second inspection mode, the second inspection mode signal is generated without using the first partial signal of the residual vibration signal. According to Appendix A11, the same effect as described in Appendix A3 above can be obtained.

[0414] [Note A12] The liquid discharge inspection method according to Appendix A12 is a liquid discharge inspection method according to any one of Appendix A9 to Appendix A11, wherein the first period is started before a first hour has elapsed since the input of the drive signal to the discharge unit ended, and the first hour is shorter than the time corresponding to one-quarter of the period of the residual vibration signal. According to Appendix A12, the same effect as described in Appendix A4 above can be obtained.

[0415] [Note B1] The liquid dispensing device according to Appendix B1 comprises a dispensing unit capable of dispensing liquid in response to an input drive signal, a signal generation unit that receives a residual vibration signal corresponding to the residual vibration generated in the dispensing unit in response to the input of the drive signal and generates a plurality of inspection signals based on the residual vibration signal, and a determination unit that determines the state of the dispensing unit. The signal path of the residual vibration signal from the dispensing unit to the signal generation unit is interrupted at an interruption timing based on an interruption signal, and the determination unit determines the state of the dispensing unit based on a plurality of inspection signal information generated by using the plurality of inspection signals as signals that have been reset at a reset timing based on a reset signal. If the interruption timing is earlier than the reset timing, each of the plurality of inspection signal information is generated by using each of the plurality of inspection signals as a signal whose potential at the interruption timing is maintained until the reset timing. According to Appendix B1, even if the time from the start of supplying residual vibration signals to the signal generation unit to the reset timing is increased, the inspection time for determining the state of the discharge unit can be shortened.

[0416] [Note B2] The liquid dispensing device according to Appendix B2 is the liquid dispensing device according to Appendix B1, wherein the signal generation unit holds the potential of each of the plurality of inspection signals at the cutoff timing. According to Appendix B2, the time from when the residual vibration signal is input to the signal generation unit until the cutoff timing can be shortened.

[0417] [Note B3] The liquid dispensing device according to Appendix B3 is the liquid dispensing device according to Appendix B1 or Appendix B2, wherein the signal generation unit resets the potential of each of the plurality of inspection signals in accordance with the input of the reset signal. According to Appendix B3, multiple test signals can be easily adjusted.

[0418] [Note B4] The liquid dispensing device according to Appendix B4 is a liquid dispensing device according to any one of Appendix B1 to Appendix B3, wherein the cutoff signal and the reset signal are signals based on a timing signal input to the signal generation unit by a single signal line, one of the cutoff timing and the reset timing is a timing based on the rising edge of the timing signal, and the other of the cutoff timing and the reset timing is a timing based on the falling edge of the timing signal. According to Appendix B4, it is possible to suppress an increase in the number of signal lines and interfaces to the signal generation unit.

[0419] [Note B5] The liquid dispensing device relating to Appendix B5 is a liquid dispensing device relating to any one of Appendix B1 to Appendix B4, wherein when the inspection time for the state of the dispensing section is shortened, the reset timing is adjusted so that the time from the shut-off timing to the reset timing is shorter compared to when the inspection time is longer. According to Appendix B5, the period during which multiple test signals are output can be shortened.

[0420] [Note B6] The liquid dispensing device relating to Appendix B6 is a liquid dispensing device relating to any one of Appendix B1 to Appendix B5, wherein when the inspection accuracy of the state of the dispensing section is increased, the reset timing is adjusted so that the time from the shut-off timing to the reset timing is longer compared to when the inspection accuracy is low. According to Appendix B6, resolution can be increased, improving inspection accuracy.

[0421] [Note B7] The liquid dispensing device according to Appendix B7 is a liquid dispensing device according to any one of Appendix B1 to Appendix B6, wherein the signal generation unit generates the plurality of inspection signals based on the signal in the first period portion of the residual vibration signal, which is one-quarter or less of the period of the residual vibration signal. According to Appendix B7, the time required to generate multiple inspection signals can be reduced, thereby shortening the inspection time required to determine the state of the dispensing unit.

[0422] [Note B8] The liquid dispensing device relating to Appendix B8 is a liquid dispensing device relating to any one of Appendix B1 to Appendix B7, wherein the signal generation unit is electrically disconnected from the dispensing unit by the cutoff signal. According to Appendix B8, the dispensing unit can be made to perform another operation before the determination of the dispensing unit's state is completed.

[0423] [Note B9] The liquid dispensing device according to Appendix B9 is a liquid dispensing device according to any one of Appendix B1 to Appendix B8, wherein the plurality of inspection signals are generated based on the signal in a first period portion of the residual vibration signal that is one-quarter or less of the period of the residual vibration signal, the first period starts before one hour has elapsed since the residual vibration signal was input to the signal generation unit, and the first hour is shorter than the time corresponding to one-quarter of the period of the residual vibration signal. According to Appendix B9, it is possible to suppress the increase in the time between the input of the residual vibration signal to the signal generation unit and the generation of multiple inspection signals.

[0424] [Note B10] The head unit control circuit according to Appendix B10 is a head unit control circuit that controls a head unit having a discharge unit capable of dispensing liquid in response to an input drive signal, and comprises a signal generation unit that receives a residual vibration signal corresponding to the residual vibration generated in the discharge unit in response to the input of the drive signal and generates a plurality of inspection signals based on the residual vibration signal, and a determination unit that determines the state of the discharge unit, wherein the signal path of the residual vibration signal from the discharge unit to the signal generation unit is interrupted at an interruption timing based on an interruption signal, and the determination unit determines the state of the discharge unit based on a plurality of inspection signal information generated by using the plurality of inspection signals as signals that have been reset at a reset timing based on a reset signal, and if the interruption timing is earlier than the reset timing, each of the plurality of inspection signal information is generated by using each of the plurality of inspection signals as a signal whose potential at the interruption timing is held until the reset timing. According to Appendix B10, the same effect as described in Appendix B1 above can be obtained.

[0425] [Note B11] The head unit control circuit according to Appendix B11 is the head unit control circuit according to Appendix B10, wherein the signal generation unit holds the potential of each of the plurality of test signals at the cutoff timing. According to Appendix B11, the same effect as described in Appendix B2 above can be obtained.

[0426] [Note B12] The head unit control circuit according to Appendix B12 is the head unit control circuit according to Appendix B10 or Appendix B11, wherein the signal generation unit resets the potential of each of the plurality of test signals in accordance with the input of the reset signal. According to Appendix B12, the same effect as described in Appendix B3 above can be obtained.

[0427] [Note B13] The head unit control circuit according to Appendix B13 is a head unit control circuit according to any one of Appendix B10 to Appendix B12, wherein the cutoff signal and the reset signal are signals based on a timing signal input to the signal generation unit by a single signal line, one of the cutoff timing and the reset timing is a timing based on the rising edge of the timing signal, and the other of the cutoff timing and the reset timing is a timing based on the falling edge of the timing signal. According to Appendix B13, the same effect as described in Appendix B4 above can be obtained.

[0428] [Note B14] The head unit control circuit relating to Appendix B14 is a head unit control circuit relating to any one of Appendix B10 to Appendix B13, wherein when the inspection time for the state of the discharge unit is shortened, the reset timing is adjusted so that the time from the cutoff timing to the reset timing is shorter compared to when the inspection time is longer. According to Appendix B14, the same effect as described in Appendix B5 above can be obtained.

[0429] [Note B15] The head unit control circuit relating to Appendix B15 is a head unit control circuit relating to any one of Appendix B10 to Appendix B14, wherein when the inspection accuracy of the discharge unit state is increased, the reset timing is adjusted so that the time from the cutoff timing to the reset timing is longer compared to when the inspection accuracy is low. According to Appendix B15, the same effect as described in Appendix B6 above can be obtained.

[0430] [Note B16] The head unit control circuit according to Appendix B16 is a head unit control circuit according to any one of Appendix B10 to Appendix B15, wherein the signal generation unit generates the plurality of inspection signals based on the signal in the portion of the residual vibration signal that is one-quarter or less of the period of the residual vibration signal. According to Appendix B16, the same effect as described in Appendix B7 above can be obtained.

[0431] [Note B17] The head unit control circuit relating to Appendix B17 is a head unit control circuit relating to any one of Appendix B10 to Appendix B16, wherein the signal generation unit is electrically disconnected from the output unit by the cutoff signal. According to Appendix B17, the same effect as described in Appendix B8 above can be obtained.

[0432] [Note B18] The head unit control circuit according to Appendix B18 is a head unit control circuit according to any one of Appendix B10 to Appendix B17, wherein the plurality of inspection signals are generated based on the signal in a first period portion of the residual vibration signal that is one-quarter or less of the period of the residual vibration signal, the first period starts before one hour has elapsed since the residual vibration signal was input to the signal generation unit, and the first hour is shorter than the time corresponding to one-quarter of the period of the residual vibration signal. According to Appendix B18, the same effect as described in Appendix B9 above can be obtained.

[0433] [Note B19] The liquid discharge inspection method described in Appendix B19 is a liquid discharge inspection method for a liquid discharge device equipped with a discharge unit capable of discharging liquid in response to an input drive signal, wherein a residual vibration signal corresponding to the residual vibration generated in the discharge unit in response to the input of the drive signal is input, a plurality of inspection signals are generated based on the residual vibration signal, and the state of the discharge unit is determined based on the plurality of inspection signal information generated by using the plurality of inspection signals as signals reset at a reset timing based on a reset signal, the signal path of the residual vibration signal output from the discharge unit is interrupted at an interruption timing based on an interruption signal, and if the interruption timing is earlier than the reset timing, each of the plurality of inspection signal information is generated by using each of the plurality of inspection signals as a signal whose potential at the interruption timing is maintained until the reset timing. According to Appendix B19, the same effect as described in Appendix B1 above can be obtained.

[0434] [Note B20] The liquid discharge inspection method according to Appendix B20 is the liquid discharge inspection method according to Appendix B19, wherein the potential of each of the plurality of inspection signals at the cutoff timing is maintained. According to Appendix B20, the same effect as described in Appendix B2 above can be obtained.

[0435] [Note B21] The liquid discharge inspection method according to Appendix B21 is the liquid discharge inspection method according to Appendix B19 or Appendix B20, wherein the potential of each of the plurality of inspection signals is reset in accordance with the input of the reset signal. According to Appendix B21, the same effect as described in Appendix B3 above can be obtained.

[0436] [Note B22] The liquid discharge inspection method relating to Appendix B22 is a liquid discharge inspection method relating to any one of Appendix B19 to Appendix B21, wherein the cutoff signal and the reset signal are signals based on a timing signal supplied on a single signal line, one of the cutoff timing and the reset timing is a timing based on the rising edge of the timing signal, the other of the cutoff timing and the reset timing is a timing based on the falling edge of the timing signal, and the cutoff timing is a timing earlier than the reset timing. According to Appendix B22, the same effect as described in Appendix B4 above can be obtained.

[0437] [Note B23] The liquid discharge inspection method relating to Appendix B23 is a liquid discharge inspection method relating to any one of Appendix B19 to Appendix B22, wherein when the inspection time for the state of the discharge unit is shortened, the reset timing is adjusted so that the time from the shut-off timing to the reset timing is shorter compared to when the inspection time is longer. According to Appendix B23, the same effect as described in Appendix B5 above can be obtained.

[0438] [Note B24] The liquid discharge inspection method relating to Appendix B24 is a liquid discharge inspection method relating to any one of Appendix B19 to Appendix B23, wherein when the inspection accuracy of the state of the discharge section is increased, the reset timing is adjusted so that the time from the shut-off timing to the reset timing is longer compared to when the inspection accuracy is low. According to Appendix B24, the same effect as described in Appendix B6 above can be obtained.

[0439] [Note B25] The liquid discharge inspection method relating to Appendix B25 is a liquid discharge inspection method relating to any one of Appendix B19 to Appendix B24, wherein the plurality of inspection signals are generated based on the signal in the first period portion of the residual vibration signal, which is one-quarter or less of the period of the residual vibration signal. According to Appendix B25, the same effect as described in Appendix B7 above can be obtained.

[0440] [Note B26] The liquid discharge inspection method relating to Appendix B26 is a liquid discharge inspection method relating to any one of Appendix B19 to Appendix B25, wherein the signal path includes a first signal path and a second signal path, and the first signal path is electrically disconnected from the second signal path in accordance with the cutoff signal. According to Appendix B26, the same effect as described in Appendix B8 above can be obtained.

[0441] [Note B27] The liquid discharge inspection method according to Appendix B27 is a liquid discharge inspection method according to any one of Appendix B19 to Appendix B26, wherein the plurality of inspection signals are generated based on the signal in a first period portion of the residual vibration signal that is one-quarter or less of the period of the residual vibration signal, the first period starts before one hour has elapsed since the input of the drive signal to the discharge unit ended, and the first hour is shorter than the time corresponding to one-quarter of the period of the residual vibration signal. According to Appendix B27, the same effect as described in Appendix B9 above can be obtained.

[0442] [Note C1] The liquid dispensing device according to Appendix C1 includes a first dispensing unit and a second dispensing unit capable of dispensing liquid in response to an input drive signal; a signal generation unit that generates a first inspection signal and a first reference signal based on the first residual vibration signal when a first residual vibration signal corresponding to residual vibration occurring in the first dispensing unit in response to the input drive signal is input, and generates a second inspection signal and a second reference signal based on the second residual vibration signal when a second residual vibration signal corresponding to residual vibration occurring in the second dispensing unit in response to the input drive signal is input; a determination unit that determines the state of the first dispensing unit and the second dispensing unit, respectively; and first correction information and second correction information. The system includes a storage unit that stores the first correction information, and the determination unit determines the state of the first discharge unit using first inspection signal information generated based on the first correction information and the first inspection signal without using the second correction information, and first reference signal information generated based on the first reference signal without using the first correction information and the second correction information, and determines the state of the second discharge unit using second inspection signal information generated based on the second correction information and the second inspection signal without using the first correction information, and second reference signal information generated based on the second reference signal without using the first correction information and the second correction information. According to Appendix C1, the condition of the dispensing section can be inspected efficiently, thus reducing the time required for inspection to determine the condition of the dispensing section.

[0443] [Note C2] The liquid dispensing device according to Appendix C2 is the same as the liquid dispensing device according to Appendix C1, wherein the first inspection signal information is generated based on information obtained by correcting the first inspection signal using the first correction information, the second inspection signal information is generated based on information obtained by correcting the second inspection signal using the second correction information, and when the amount of liquid discharged by the second dispensing unit is less than the amount of liquid discharged by the first dispensing unit, the correction amount using the second correction information is greater than the correction amount using the first correction information. According to Appendix C2, the first and second discharge sections can be inspected using the same standards.

[0444] [Note C3] The liquid dispensing device according to Appendix C3 includes a first dispensing unit and a second dispensing unit capable of dispensing liquid in response to an input drive signal; a signal generation unit that generates a first inspection signal and a first reference signal based on the first residual vibration signal when a first residual vibration signal corresponding to residual vibration generated in the first dispensing unit in response to the input of the drive signal is input, and generates a second inspection signal and a second reference signal based on the second residual vibration signal when a second residual vibration signal corresponding to residual vibration generated in the second dispensing unit in response to the input of the drive signal is input; a storage unit that stores first correction information for the first inspection signal and second correction information for the second inspection signal; and a device that performs the following without using the second correction information. The device includes a determination unit that determines the state of the first discharge unit using first correction information, the first inspection signal, and the first reference signal, and determines the state of the second discharge unit using second correction information, the second inspection signal, and the second reference signal without using the first correction information, wherein the first reference signal is a signal indicating whether or not the first residual vibration signal is at or above a first potential, and the first inspection signal is a signal indicating whether or not the first residual vibration signal is at or above a second potential different from the first potential, and the determination unit uses the first inspection signal as a signal indicating whether or not the first residual vibration signal is at or above a third potential based on the first correction information to determine the state of the first discharge unit. According to Appendix C3, the same effect as described in Appendix C1 can be obtained. Furthermore, according to Appendix C3, by considering the second potential as a third potential different from the actual potential, the adjustment waveform of the sine wave based on the first test signal can be easily corrected.

[0445] [Note C4] The liquid dispensing device according to Appendix C4 is a liquid dispensing device according to any one of Appendix C1 to C3, wherein the first reference signal is a signal indicating whether or not the first residual vibration signal is at or above the first potential, the first inspection signal is a signal indicating whether or not the first residual vibration signal is at or above the second potential which is different from the first potential, and the first inspection signal information is information generated by using the first inspection signal as a signal indicating that the first residual vibration signal is at or above the second potential until the first timing corresponding to the first correction information, regardless of whether or not the first residual vibration signal has transitioned to below the second potential. According to Appendix C4, even if the time from the start of supplying the residual vibration signal to the signal generation unit to the first timing is increased, the inspection time for determining the state of the first discharge unit can be shortened.

[0446] [Note C5] The liquid dispensing device according to Appendix C5 is a liquid dispensing device according to any one of Appendix C1 to C4, wherein the signal path of the first residual vibration signal from the first dispensing unit to the signal generation unit is interrupted at an interruption timing based on an interruption signal, the determination unit generates the first inspection signal information by using the first inspection signal as a signal reset at a first timing corresponding to the first correction information, and if the interruption timing is earlier than the first timing, the first inspection signal information is generated by using the first inspection signal as a signal in which the potential at the interruption timing is maintained until the first timing. According to Appendix C5, even if the time from the start of supplying the residual vibration signal to the signal generation unit to the first timing is increased, the inspection time for determining the state of the first discharge unit can be shortened.

[0447] [Appendix C6] The liquid dispensing device according to Appendix C6 is a liquid dispensing device according to any one of Appendix C1 to Appendix C5, wherein the signal generation unit generates the first inspection signal and the first reference signal based on the signal in the first period portion of the first residual vibration signal that is one-quarter or less of the period of the first residual vibration signal. According to Appendix C6, the time required to generate the first inspection signal and the first reference signal can be shortened, thereby shortening the inspection time required to determine the state of the first discharge unit.

[0448] [Note C7] The liquid dispensing device according to Appendix C7 is the liquid dispensing device according to Appendix C5, and the signal generation unit is electrically disconnected from the first dispensing unit by the cutoff signal. According to Appendix C7, the first discharge unit can be made to perform another operation before the determination of the state of the first discharge unit is completed. Also, according to Appendix C7, the second discharge unit can be made to operate as the discharge unit to be determined before the determination of the state of the first discharge unit is completed.

[0449] [Note C8] The liquid dispensing device according to Appendix C8 is a liquid dispensing device according to any one of Appendix C1 to C7, wherein the first inspection signal and the first reference signal are generated based on the signal in the portion of the first residual vibration signal that is one-quarter or less of the period of the first residual vibration signal, the first period starts before one hour has elapsed since the first residual vibration signal was input to the signal generation unit, and the first hour is shorter than the time corresponding to one-quarter of the period of the first residual vibration signal. According to Appendix C8, it is possible to suppress the increase in the time from when the residual vibration signal is input to the signal generation unit until the first test signal and the first reference signal are generated.

[0450] [Note C9] The head unit control circuit according to Appendix C9 is a head unit control circuit that controls a head unit having a first discharge unit and a second discharge unit capable of discharging liquid in response to an input drive signal, and includes a signal generation unit that generates a first inspection signal and a first reference signal based on the first residual vibration signal when a first residual vibration signal corresponding to residual vibration generated in the first discharge unit in response to the input drive signal is input, and generates a second inspection signal and a second reference signal based on the second residual vibration signal when a second residual vibration signal corresponding to residual vibration generated in the second discharge unit in response to the input drive signal is input, and a determination unit that determines the state of the first discharge unit and the second discharge unit, respectively. The device comprises a unit and a storage unit that stores first correction information and second correction information. The determination unit determines the state of the first discharge unit using first inspection signal information generated based on the first correction information and the first inspection signal without using the second correction information, and first reference signal information generated based on the first reference signal without using the first correction information and second correction information. The determination unit determines the state of the second discharge unit using second inspection signal information generated based on the second correction information and the second inspection signal without using the first correction information, and second reference signal information generated based on the second reference signal without using the first correction information and second correction information. According to Appendix C9, the same effect as described in Appendix C1 can be obtained.

[0451] [Note C10] The head unit control circuit according to Appendix C10 is the same as the head unit control circuit according to Appendix C9, wherein the first inspection signal information is generated based on information obtained by correcting the first inspection signal using the first correction information, and the second inspection signal information is generated based on information obtained by correcting the second inspection signal using the second correction information, and when the amount of liquid discharged by the second discharge unit is less than the amount of liquid discharged by the first discharge unit, the correction amount using the second correction information is greater than the correction amount using the first correction information. According to Appendix C10, the same effect as described in Appendix C2 can be obtained.

[0452] [Note C11] The head unit control circuit described in Appendix C11 is a head unit control circuit that controls a head unit having a first discharge unit and a second discharge unit capable of discharging liquid in response to an input drive signal, and includes a signal generation unit that generates a first inspection signal and a first reference signal based on the first residual vibration signal when a first residual vibration signal corresponding to residual vibration generated in the first discharge unit in response to the input of the drive signal is input, and generates a second inspection signal and a second reference signal based on the second residual vibration signal when a second residual vibration signal corresponding to residual vibration generated in the second discharge unit in response to the input of the drive signal is input, and a storage unit that stores first correction information for the first inspection signal and second correction information for the second inspection signal. The system includes a unit and a determination unit that determines the state of the first discharge unit using the first correction information, the first inspection signal, and the first reference signal without using the second correction information, and determines the state of the second discharge unit using the second correction information, the second inspection signal, and the second reference signal without using the first correction information, wherein the first reference signal is a signal indicating whether or not the first residual vibration signal is at or above a first potential, and the first inspection signal is a signal indicating whether or not the first residual vibration signal is at or above a second potential different from the first potential, and the determination unit determines the state of the first discharge unit using the first inspection signal as a signal indicating whether or not the first residual vibration signal is at or above a third potential based on the first correction information. According to Appendix C11, the same effect as described in Appendix C3 above can be obtained.

[0453] [Note C12] The head unit control circuit relating to Appendix C12 is a head unit control circuit relating to any one of Appendix C9 to C11, wherein the first reference signal is a signal indicating whether or not the first residual vibration signal is at or above a first potential, the first inspection signal is a signal indicating whether or not the first residual vibration signal is at or above a second potential different from the first potential, and the first inspection signal information is information generated by using the first inspection signal as a signal indicating that the first residual vibration signal is at or above the second potential until a first timing corresponding to the first correction information, regardless of whether or not the first residual vibration signal has transitioned to below the second potential. According to Appendix C12, the same effect as described in Appendix C4 above can be obtained.

[0454] [Note C13] The head unit control circuit according to Appendix C13 is a head unit control circuit according to any one of Appendix C9 to C12, wherein the signal path of the first residual vibration signal from the first discharge unit to the signal generation unit is interrupted at an interruption timing based on an interruption signal, the determination unit generates the first inspection signal information by using the first inspection signal as a signal that has been reset at a first timing corresponding to the first correction information, and if the interruption timing is earlier than the first timing, the first inspection signal information is generated by using the first inspection signal as a signal whose potential at the interruption timing is maintained until the first timing. According to Appendix C13, the same effect as described in Appendix C5 above can be obtained.

[0455] [Note C14] The head unit control circuit according to Appendix C14 is a head unit control circuit according to any one of Appendix C9 to C13, wherein the signal generation unit generates the first inspection signal and the first reference signal based on the signal in the first period portion of the first residual vibration signal that is one-quarter or less of the period of the first residual vibration signal. According to Appendix C14, the same effect as described in Appendix C6 above can be obtained.

[0456] [Note C15] The head unit control circuit related to Appendix C15 is the same as the head unit control circuit related to Appendix C13, wherein the signal generation unit is electrically disconnected from the first discharge unit by the cutoff signal. According to Appendix C15, the same effect as described in Appendix C7 above can be obtained.

[0457] [Note C16] The head unit control circuit according to Appendix C16 is a head unit control circuit according to any one of Appendix C9 to C15, wherein the first inspection signal and the first reference signal are generated based on the signal in a first period portion of the first residual vibration signal that is one-quarter or less of the period of the first residual vibration signal, the first period starts before a first time has elapsed since the first residual vibration signal was input to the signal generation unit, and the first time is shorter than the time corresponding to one-quarter of the period of the first residual vibration signal. According to Appendix C16, the same effect as described in Appendix C8 above can be obtained.

[0458] [Note C17] The liquid discharge inspection method according to Appendix C17 is a liquid discharge inspection method for a liquid discharge apparatus comprising a first discharge section and a second discharge section capable of discharging liquid in response to an input drive signal, wherein a first inspection signal and a first reference signal are generated based on a first residual vibration signal corresponding to residual vibration generated in the first discharge section in response to the input of the drive signal, a second inspection signal and a second reference signal are generated based on a second residual vibration signal corresponding to residual vibration generated in the second discharge section in response to the input of the drive signal, the state of the first discharge section is determined using first inspection signal information generated based on the first correction information and the first inspection signal without using the second correction information among the first and second correction information stored in the memory section, and first reference signal information generated based on the first reference signal without using the first correction information and the second correction information, and the state of the second discharge section is determined using second inspection signal information generated based on the second correction information and the second inspection signal without using the first correction information, and second reference signal information generated based on the second reference signal without using the first correction information and the second correction information. According to Appendix C17, the same effect as described in Appendix C1 above can be obtained.

[0459] [Note C18] The liquid discharge inspection method according to Appendix C18 is the liquid discharge inspection method according to Appendix C17, wherein the first inspection signal information is generated based on information obtained by correcting the first inspection signal using the first correction information, and the second inspection signal information is generated based on information obtained by correcting the second inspection signal using the second correction information, and when the amount of liquid discharged by the second discharge unit is less than the amount of liquid discharged by the first discharge unit, the correction amount using the second correction information is greater than the correction amount using the first correction information. According to Appendix C18, the same effect as described in Appendix C2 can be obtained.

[0460] [Note C19] The liquid discharge inspection method according to Appendix C19 is a liquid discharge inspection method for a liquid discharge device comprising a first discharge unit and a second discharge unit capable of discharging liquid in response to an input drive signal, wherein a first inspection signal and a first reference signal are generated based on a first residual vibration signal corresponding to residual vibration generated in the first discharge unit in response to the input of the drive signal, and a second inspection signal and a second reference signal are generated based on a second residual vibration signal corresponding to residual vibration generated in the second discharge unit in response to the input of the drive signal, and without using the second correction information among the first and second correction information stored in the memory unit, the first correction information, the first inspection signal and the first base The state of the first discharge unit is determined using a quasi-signal, and the state of the second discharge unit is determined using the second correction information, the second inspection signal, and the second reference signal without using the first correction information, wherein the first reference signal is a signal indicating whether or not the first residual vibration signal is at or above a first potential, and the first inspection signal is a signal indicating whether or not the first residual vibration signal is at or above a second potential different from the first potential, and when determining the state of the first discharge unit, the state of the first discharge unit is determined using the first inspection signal as a signal indicating whether or not the first residual vibration signal is at or above a third potential based on the first correction information. According to Appendix C19, the same effect as described in Appendix C3 above can be obtained.

[0461] [Note C20] The liquid discharge inspection metho...

Claims

1. A dispensing unit capable of dispensing liquid in response to an input drive signal, A signal generation unit receives a residual vibration signal corresponding to the residual vibration generated in the discharge section in response to the input of the drive signal, and generates a state inspection signal based on the residual vibration signal. A determination unit that determines the state of the discharge unit based on the state inspection signal, Equipped with, The signal generation unit, A first inspection mode that generates a first inspection mode signal as the state inspection signal corresponding to a first partial signal in the first period of the residual vibration signal, A second inspection mode that generates a second inspection mode signal as the state inspection signal corresponding to the second partial signal in the second period of the residual vibration signal, It has, The first period is shorter than the second period. A liquid dispensing device characterized by the following features.

2. The first period is a period of one-quarter or less of the period of the residual vibration signal. The second period is a period of at least half the period of the residual vibration signal. The liquid dispensing device according to feature 1.

3. The second period is a period that follows the first period. The signal generation unit, In the second inspection mode, the second inspection mode signal is generated without using the first partial signal of the residual vibration signal. The liquid dispensing device according to feature 1.

4. The first period begins before a first time has elapsed since the residual vibration signal was input to the signal generation unit. The first time is shorter than the time corresponding to one-quarter of the period of the residual vibration signal. The liquid dispensing device according to feature 1.

5. A control head unit circuit for a head unit equipped with a discharge unit capable of dispensing liquid in response to an input drive signal, A signal generation unit receives a residual vibration signal corresponding to the residual vibration generated in the discharge section in response to the input of the drive signal, and generates a state inspection signal based on the residual vibration signal. A determination unit that determines the state of the discharge unit based on the state inspection signal, Equipped with, The signal generation unit, A first inspection mode that generates a first inspection mode signal as the state inspection signal corresponding to a first partial signal in the first period of the residual vibration signal, A second inspection mode that generates a second inspection mode signal as the state inspection signal corresponding to the second partial signal in the second period of the residual vibration signal, It has, The first period is shorter than the second period. A head unit control circuit characterized by the following features.

6. The first period is a period of one-quarter or less of the period of the residual vibration signal. The second period is a period of at least half the period of the residual vibration signal. The head unit control circuit according to claim 5.

7. The second period is a period that follows the first period. The signal generation unit, In the second inspection mode, the second inspection mode signal is generated without using the first partial signal of the residual vibration signal. The head unit control circuit according to claim 5.

8. The first period begins before a first time has elapsed since the residual vibration signal was input to the signal generation unit. The first time is shorter than the time corresponding to one-quarter of the period of the residual vibration signal. The head unit control circuit according to claim 5.

9. A liquid discharge inspection method for a liquid discharge device equipped with a discharge unit capable of discharging liquid in response to an input drive signal, A status inspection signal is generated based on a residual vibration signal corresponding to the residual vibration generated in the discharge section in response to the input of the drive signal. Based on the status inspection signal, the state of the discharge unit is determined. When a first inspection mode is selected as the inspection mode for determining the state of the discharge section, a first inspection mode signal corresponding to the first partial signal during the first period of the residual vibration signal is generated as the state inspection signal. When the second inspection mode is selected as the inspection mode, a second inspection mode signal corresponding to the second partial signal in the second period of the residual vibration signal is generated as the state inspection signal. The first period is shorter than the second period. A liquid discharge inspection method characterized by the following features.

10. The first period is a period of one-quarter or less of the period of the residual vibration signal. The second period is a period of at least half the period of the residual vibration signal. The liquid discharge inspection method according to feature 9.

11. The second period is a period that follows the first period. In the second inspection mode, the second inspection mode signal is generated without using the first partial signal of the residual vibration signal. The liquid discharge inspection method according to feature 9.

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