JP2017164973A - Liquid discharge device, head unit of the same, and determination method for discharge state of liquid in the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately calculate amplitude of residual vibration.SOLUTION: A liquid discharge device comprises: a first discharge section comprising a first piezoelectric element displaced according to a potential change of a driving signal supplied to a first electrode; a second discharge section comprising a second piezoelectric element displaced according to a potential change of a driving signal supplied to a second electrode; a switch for detection being disposed between wiring for detection and the first electrode, maintaining an off-state in a first period, and maintaining an on-state in a second period started after completion of the first period; a first switch being disposed between signal wiring supplied with the driving signal and the first electrode, maintaining the on-state in the first period, and maintaining the off-state in the second period; a second switch disposed between the signal wiring and the second electrode, maintaining the on-state in the first period, and maintaining the off-state in the second period; a detection section detecting potential of the wiring for detection in the second period; and a determination section determining a discharge state of liquid in the first discharge section based on a detection result in the detection section.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a liquid ejection apparatus, a head unit of the liquid ejection apparatus, and a method for determining a liquid ejection state in the liquid ejection apparatus.

  A liquid discharge apparatus such as an ink jet printer fills a cavity (pressure chamber) of each discharge unit by driving and displacing a piezoelectric element included in each of a plurality of discharge units provided in the head unit by a drive signal. A printing process for forming an image on a recording medium is performed by discharging a liquid such as ink. In such a liquid ejecting apparatus, there may be a case where the ejection abnormality that the liquid cannot be ejected normally from the ejecting part may occur due to the thickening of the liquid in the cavity or the adhering of foreign matter to the ejecting part. When the ejection abnormality occurs, the dots that are scheduled to be formed on the recording medium cannot be accurately formed by the liquid ejected from the ejection unit, and the image quality of the image formed on the recording medium in the printing process is degraded.

  In Patent Document 1, in order to prevent deterioration of the image quality of an image formed in a printing process, residual vibration generated in the discharge unit when the discharge unit is driven is detected, and the detected residual vibration period, vibration, and the like are detected. There has been proposed a technique related to a discharge state determination process for determining the discharge state of a liquid in the discharge unit based on the characteristics of residual vibration.

JP 2011-189655 A

  By the way, in the liquid ejection apparatus, the ejection state determination process and the printing process may be executed simultaneously. In this case, noise from the ejection unit driven in the printing process can be propagated to the ejection unit (hereinafter referred to as “determination target ejection unit”) that is driven so as to generate residual vibration as a target of the ejection state determination process. There is sex. For this reason, it may be difficult to accurately detect the residual vibration from the determination target discharge unit.

  The present invention has been made in view of the above-described circumstances, and provides a technique for reducing the influence of noise from an ejection unit driven in a printing process and detecting residual vibration with high accuracy. One of the issues.

  In order to solve the above problems, a liquid ejection apparatus according to the present invention has a pair of electrodes including a first electrode, and responds to a potential change of the drive signal when the drive signal is supplied to the first electrode. A first piezoelectric element that displaces the first piezoelectric element, and includes a first ejection unit that can eject liquid in accordance with the displacement of the first piezoelectric element, and a pair of electrodes including a second electrode. A second ejection unit that includes a second piezoelectric element that is displaced in response to a change in potential of the drive signal when a signal is supplied, and that is capable of ejecting liquid in accordance with the displacement of the second piezoelectric element; And a detection switch that is disposed between the first electrode and the first electrode, maintains an off state in a first period, and maintains an on state in a second period that starts after the end of the first period; Disposed between the signal wiring to be supplied and the first electrode; A first switch that maintains an on state in the first period and an off state in the second period, and is disposed between the signal wiring and the second electrode, and maintains the on state in the first period. A second switch that maintains an off state in the second period, a detection unit that detects a potential of the detection wiring in the second period, and a detection result in the detection unit based on a detection result in the detection unit. And a determination unit for determining a liquid discharge state.

  In the present invention, the supply of the drive signal in the second period is stopped with respect to the second ejection unit driven by the drive signal in the first period. For this reason, compared with the case where the drive signal is supplied to the second ejection unit in the second period, the change in the electromotive force of the second piezoelectric element due to the vibration generated in the second ejection unit in the second period is The possibility of propagating as noise to the detection wiring via the signal wiring can be reduced. Accordingly, the detection unit can accurately detect the residual vibration generated in the first ejection unit in the second period as the potential of the detection wiring.

  In the liquid ejection device described above, the signal wiring is set to a predetermined potential in the second period, and the detection unit detects the potential of the detection wiring and the potential of the signal wiring in the second period. This may be a feature.

  According to this aspect, in the second period, the signal wiring and the second electrode are made non-conductive, and therefore, the electromotive force of the second piezoelectric element caused by the vibration generated in the second ejection unit in the second period. It is possible to reduce the possibility that this change will propagate to the signal wiring as noise. Accordingly, the detection unit can accurately detect the residual vibration generated in the first ejection unit in the second period as a potential difference between the potential of the detection wiring and the potential of the signal wiring.

  The liquid ejection apparatus described above includes a third piezoelectric element that has a pair of electrodes including a third electrode and that is displaced in accordance with a change in potential of the drive signal when the drive signal is supplied to the third electrode. A third discharge section capable of discharging a liquid according to the displacement of the third piezoelectric element; and disposed between the signal wiring and the third electrode, and maintains an OFF state in the first period. And a third switch that maintains an ON state during the period.

  According to this aspect, since the third switch is turned on in the second period to fix the potential of the third electrode at a predetermined potential, it is possible to reduce the possibility that the third ejection unit vibrates in the second period. . Thereby, the possibility that noise is superimposed on the detection wiring detected by the detection unit in the second period can be reduced.

  In the liquid ejecting apparatus described above, the signal wiring is set to the predetermined potential in a preparation period before the start of the first period, and the first switch, the second switch, and the third switch are the preparation The on-state may be maintained during the period.

  According to this aspect, since the potential of the signal supplied to the third piezoelectric element is substantially the same before the start of the first period and at the start of the second period, signal supply is started in the second period. Accordingly, displacement of the third piezoelectric element can be prevented. Thereby, it is possible to reduce the possibility of vibrations occurring in the third discharge part in the second period, and to accurately detect residual vibrations generated in the first discharge part.

  The head unit according to the present invention is a head unit provided in a liquid ejection apparatus, and has a pair of electrodes including a first electrode, and when the drive signal is supplied to the first electrode, A first piezoelectric element that is displaced in accordance with a change in potential; a second ejection unit that includes a first ejection unit capable of ejecting a liquid in accordance with the displacement of the first piezoelectric element; and a second electrode that includes a second electrode. A second ejection unit that includes a second piezoelectric element that displaces in response to a change in potential of the drive signal when the drive signal is supplied to the electrode, and that can eject liquid in accordance with the displacement of the second piezoelectric element; A detection switch disposed between the detection wiring and the first electrode, wherein the detection switch maintains an off state in a first period and maintains an on state in a second period started after the end of the first period; The signal wiring to which the drive signal is supplied; and A first switch that is disposed between the first electrode and maintains an on state in the first period and is maintained in an off state in the second period; and is disposed between the signal wiring and the second electrode, A second switch that maintains an on-state in the first period and maintains an off-state in the second period; and a detection unit that detects a potential of the detection wiring in the second period. And

  In the present invention, since the signal wiring and the second electrode are made non-conductive in the second period, the change in the electromotive force of the second piezoelectric element due to the vibration generated in the second ejection part in the second period However, the possibility of propagating as noise to the detection wiring via the signal wiring can be reduced. Thereby, the detection unit can accurately detect the residual vibration generated in the first ejection unit in the second period as the potential of the detection wiring.

  Further, the method for determining the liquid discharge state in the liquid discharge apparatus according to the present invention has a pair of electrodes including the first electrode, and changes the potential of the drive signal when the drive signal is supplied to the first electrode. A first piezoelectric element that is displaced according to the displacement of the first piezoelectric element; and a pair of electrodes including a second electrode that includes a first ejection unit capable of ejecting a liquid according to the displacement of the first piezoelectric element. A second discharge unit that includes a second piezoelectric element that is displaced according to a change in potential of the drive signal when a drive signal is supplied; and a second discharge unit that is capable of discharging liquid according to the displacement of the second piezoelectric element; A detection switch disposed between a wiring and the first electrode; a signal switch to which the driving signal is supplied; a first switch disposed between the first electrode; the signal wiring; A liquid switch comprising: a second switch disposed between the two electrodes In the first period, in the first period, the detection switch is turned off, the first switch is turned on, the second switch is turned on, and the first period is set. In the second period that starts after the end of, the detection switch is turned on, the first switch is turned off, the second switch is turned off, the potential of the detection wiring is detected, and the detection On the basis of the result, the discharge state of the liquid in the first discharge unit is determined.

  In the present invention, since the signal wiring and the second electrode are made non-conductive in the second period, the change in the electromotive force of the second piezoelectric element due to the vibration generated in the second ejection part in the second period However, the possibility of propagating as noise to the detection wiring via the signal wiring can be reduced. Thereby, it is possible to accurately detect the residual vibration generated in the first discharge section in the second period as the potential of the detection wiring.

1 is a block diagram illustrating a configuration of an inkjet printer 1 according to the present invention. 1 is a perspective view showing a schematic internal structure of an ink jet printer 1. FIG. FIG. 6 is an explanatory diagram for explaining the structure of a discharge unit D. It is a top view which shows the example of arrangement | positioning of the nozzle N in the head module HM. It is a block diagram which shows the structure of the head unit HU. It is a timing chart for explaining printing processing and discharge state judging processing. It is explanatory drawing for demonstrating a connection state designation | designated signal. 3 is a block diagram showing a configuration of a connection state designation circuit 11. FIG. 7 is an explanatory diagram for explaining an operation of a measurement circuit 81. FIG. 6 is an explanatory diagram for explaining the operation of a discharge state determination circuit 82. FIG. It is explanatory drawing for demonstrating the connection state designation | designated signal which concerns on comparison. It is explanatory drawing for demonstrating the motion of the discharge part D which concerns on proportionality. It is explanatory drawing for demonstrating the motion of the discharge part D which concerns on this invention. FIG. 10 is a block diagram illustrating a configuration of a head unit HU according to a first modification. 10 is a timing chart for explaining a printing process and an ejection state determination process according to Modification 1; It is explanatory drawing for demonstrating the connection state designation | designated signal which concerns on the modification 1. FIG.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, in each figure, the size and scale of each part are appropriately changed from the actual ones. Further, since the embodiments described below are preferable specific examples of the present invention, various technically preferable limitations are attached thereto. However, the scope of the present invention is particularly limited in the following description. Unless otherwise stated, the present invention is not limited to these forms.

<< A. Embodiment >>
In the present embodiment, the liquid ejecting apparatus will be described by exemplifying an ink jet printer that ejects ink (an example of “liquid”) to form an image on a recording paper P (an example of “medium”).

<< 1. Overview of inkjet printers >>
Hereinafter, the configuration of the inkjet printer 1 according to the present embodiment will be described with reference to FIGS. 1 and 2.

FIG. 1 is a functional block diagram illustrating an example of the configuration of the inkjet printer 1.
In the inkjet printer 1, from a host computer (not shown) such as a personal computer or a digital camera, print data Img indicating an image to be formed by the inkjet printer 1 and information indicating the number of copies of the image to be formed by the inkjet printer 1 And are supplied. The ink jet printer 1 executes a printing process for forming an image indicated by the print data Img supplied from the host computer on the recording paper P.

  As illustrated in FIG. 1, the inkjet printer 1 includes a head module HM including a head unit HU provided with a discharge unit D that discharges ink, and a drive that generates a drive signal Com for driving the discharge unit D. In order to change the relative position of the recording paper P with respect to the head module HM and the determination module JM having the signal generation circuit 5 and the determination unit JU (an example of a “determination unit”) that determines the ink ejection state in the ejection unit D. , A control unit 6 that controls the operation of each unit of the inkjet printer 1, and a storage unit 61 that stores various types of information. Among these, the control unit 6, the drive signal generation circuit 5, the storage unit 61, and the determination unit JU are a control module 60 (an example of a “head unit control circuit”) that controls the head unit HU.

  In the present embodiment, as an example, a case is assumed in which the head module HM includes four head units HU and the determination module JM includes four determination units JU as shown in FIG. In the present embodiment, it is assumed that the head unit HU and the determination unit JU are provided in a one-to-one correspondence. In the following, one head unit HU among the four head units HU and one determination unit JU provided corresponding to one head unit HU among the four determination units JU will be described. The description also applies to other head units HU and other determination units JU.

  The control unit 6 includes a CPU (Central Processing Unit). However, the control unit 6 may include a programmable logic device such as an FPGA (field-programmable gate array) instead of the CPU. The control unit 6 generates signals for controlling the operation of each unit of the inkjet printer 1, such as the print signal SI and the waveform designation signal dCom, by the CPU operating according to the control program stored in the storage unit 61. To do.

Here, the waveform designation 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 drive signal generation circuit 5 includes a DA conversion circuit, and generates a drive signal Com having a waveform defined by the digital waveform designation signal dCom.
The print signal SI is a digital signal for designating the type of operation of the ejection unit D.
Specifically, the print signal SI is a signal for designating the type of operation of the ejection unit D by designating whether or not to supply the drive signal Com to the ejection unit D. Here, the designation of the type of operation of the ejection part D is, for example, whether or not the ejection part D is to be driven or whether ink is ejected from the ejection part D when the ejection part D is driven. Or specifying the amount of ink ejected from the ejection unit D when the ejection unit D is driven.

  As illustrated in FIG. 1, each head unit HU is provided with a recording head HD having M ejection portions D (M is a natural number satisfying 1 ≦ M). In the following, among the M ejection units D provided in each recording head HD, the mth (m-th) ejection unit D may be referred to as a ejection unit D [m] (the variable m is Natural number satisfying 1 ≦ m ≦ M). In addition, when a component or signal of the ink jet printer 1 corresponds to the number of stages m of the discharge unit D [m], a sign indicating that the component or signal corresponds to the number of stages m is appended. The letter [m] may be attached.

As illustrated in FIG. 1, each head unit HU is provided with a supply circuit 10 (an example of a “supply unit”) and a detection circuit 20 (an example of a “detection unit”).
The supply circuit 10 switches whether to supply the drive signal Com to each ejection unit D based on the print signal SI. Hereinafter, among the drive signals Com, the drive signal Com supplied to the ejection unit D may be referred to as a drive signal Vin. Hereinafter, the drive signal Vin supplied to the ejection unit D [m] may be referred to as a drive signal Vin [m]. Further, the supply circuit 10 detects a detection potential signal Vout [m] indicating the potential of the upper electrode Zu [m] of the piezoelectric element PZ [m] provided in the ejection part D [m] based on the print signal SI. Whether to supply to the circuit 20 is switched. The piezoelectric element PZ [m] and the upper electrode Zu [m] will be described later with reference to FIG.
The detection circuit 20 generates the detection signal NSA [m] based on the detection potential signal Vout [m] indicating the potential of the upper electrode Zu [m] of the ejection part D [m]. The detection potential signal Vout [m] is a vibration (hereinafter referred to as “residual”) that remains in the discharge portion D [m] after the supply circuit 10 drives the discharge portion D [m] by the drive signal Vin [m]. Waveform ").

Further, as described above, the ink jet printer 1 according to the present embodiment includes the determination unit JU that determines the ink discharge state in the discharge portion D based on the detection signal NSA as illustrated in FIG. The determination unit JU includes a measurement circuit 81 and a discharge state determination circuit 82.
The measurement circuit 81 generates waveform information Info indicating the waveform characteristics of the detection signal NSA based on the detection signal NSA. Here, the waveform characteristic of the detection signal NSA is information regarding the shape of the waveform of the detection signal NSA, such as the amplitude and period of the detection signal NSA.
The ejection state determination circuit 82 determines the ink ejection state in the ejection unit D based on the waveform information Info, and generates determination information Stt indicating the result of the determination. Hereinafter, the determination in the discharge state determination circuit 82 may be referred to as “discharge state determination”. In the following description, the discharge unit D that is a target of the discharge state determination by the discharge state determination circuit 82 may be referred to as a determination target discharge unit D-H.

FIG. 2 is a perspective view illustrating an example of a schematic internal structure of the inkjet printer 1.
As shown in FIG. 2, in the present embodiment, it is assumed that the ink jet printer 1 is a serial printer. Specifically, when performing the printing process, the ink jet printer 1 is configured to convey the recording paper P in the sub-scanning direction, while reciprocating the head module HM in the main scanning direction intersecting the sub-scanning direction. By ejecting ink from D, dots corresponding to the print data Img are formed on the recording paper P.
In the following, the + X direction and the −X direction that is the opposite direction are collectively referred to as the “X axis direction”, the + Y direction and the −Y direction that is the opposite direction are collectively referred to as the “Y axis direction”, and the + Z direction The −Z direction, which is the opposite direction, is collectively referred to as “Z-axis direction”. In this embodiment, as shown in FIG. 2, the direction from the -X side (upstream side) to the + X side (downstream side) is set as the sub-scanning direction, and the + Y direction and -Y direction are set as the main scanning direction. In this embodiment, as an example, it is assumed that the X-axis direction, the Y-axis direction, and the Z-axis direction are directions orthogonal to each other. However, the X-axis direction, the Y-axis direction, and the Z-axis direction are assumed. May be in any direction that intersects each other.

  As illustrated in FIG. 2, the inkjet printer 1 according to the present embodiment includes a housing 200 and a carriage 100 that can reciprocate in the housing 200 in the Y-axis direction and mounts the head module HM.

Further, as described above, the ink jet printer 1 according to the present embodiment includes the transport mechanism 7.
The transport mechanism 7 changes the relative position of the recording paper P with respect to the head module HM by reciprocating the carriage 100 in the Y-axis direction and transporting the recording paper P in the + X direction when printing processing is executed. In this way, ink can land on the entire recording paper P.
As shown in FIG. 1, the transport mechanism 7 includes a transport motor 71 serving as a drive source for reciprocating the carriage 100, a motor driver 72 for driving the transport motor 71, and a recording paper P. A paper feed motor 73 serving as a drive source and a motor driver 74 for driving the paper feed motor 73 are provided. Further, as shown in FIG. 2, the transport mechanism 7 is stretched between a carriage guide shaft 76 extending in the Y-axis direction, a pulley 711 that is rotationally driven by the transport motor 71, and a rotatable pulley 712. And a timing belt 710 extending in the Y-axis direction. The carriage 100 is supported reciprocally in the Y-axis direction by a carriage guide shaft 76 and is fixed to a predetermined portion of the timing belt 710 via a fixture 101. Therefore, the transport mechanism 7 can reciprocate the head module HM along the carriage guide shaft 76 in the Y-axis direction together with the carriage 100 by rotating the pulley 711 by the transport motor 71.

  Further, as shown in FIG. 2, the transport mechanism 7 rotates according to the drive of the platen 75 provided on the lower side (−Z direction) of the carriage 100 and the paper feed motor 73, and prints the recording paper P one by one. A paper feed roller (not shown) for feeding onto the platen 75, and a paper discharge roller 730 that rotates according to the drive of the paper feed motor 73 and conveys the recording paper P on the platen 75 to the paper discharge port. Prepare. Therefore, the transport mechanism 7 can transport the recording paper P on the platen 75 from the −X direction (upstream side) to the + X direction (downstream side) as shown in FIG.

In the present embodiment, as illustrated in FIG. 2, four ink cartridges 31 are stored in the carriage 100 of the inkjet printer 1. More specifically, in this embodiment, four ink cartridges 31 corresponding to four colors (CMYK) of cyan, magenta, yellow, and black are stored in the carriage 100. Assuming that
In the present embodiment, it is assumed that four ink cartridges 31 are provided in a one-to-one correspondence with the four head units HU. Each ejection unit D receives ink supplied from the ink cartridge 31 corresponding to the head unit HU to which the ejection unit D belongs. Thereby, each discharge part D can fill the supplied ink inside, and can discharge the filled ink from the nozzle N. That is, a total of 4M ejection portions D included in the head module HM can eject inks of four colors CMYK as a whole.
FIG. 2 is merely an example, and the ink cartridge 31 may be provided outside the carriage 100.

  Here, an outline of the operation of the control unit 6 when the printing process is executed will be described.

When the printing process is executed, the control unit 6 first stores the print data Img supplied from the host computer in the storage unit 61. Next, the control unit 6 is a signal for controlling the operation of each head unit HU and the like such as the print signal SI and the waveform designation signal dCom based on various data such as the print data Img stored in the storage unit 61. And a signal for controlling the transport mechanism 7. The control unit 6 controls the transport mechanism 7 so as to change the relative position of the recording paper P with respect to the head module HM based on various signals such as the print signal SI and various data stored in the storage unit 61. However, the supply circuit 10 is controlled so that the discharge part D is driven.
Thus, the control unit 6 adjusts the presence / absence of ink ejection from the ejection unit D, the ink ejection amount, the ink ejection timing, and the like, and forms the image corresponding to the print data Img on the recording paper P. Each unit of the inkjet printer 1 is controlled so that the processing is executed.

  In addition, the inkjet printer 1 according to the present embodiment executes an ejection state determination process.

The discharge state determination process is a series of processes including a discharge state determination and various preparation processes for performing the discharge state determination.
More specifically, the discharge state determination process is a process in which the control unit 6 selects a determination target discharge unit DH that is a target of discharge state determination, and the drive signal generation circuit 5 outputs an output from the control unit 6. Under the process of generating the drive signal Com based on the waveform designation signal dCom to be performed and the control by the control unit 6, the supply circuit 10 uses the drive signal Com output from the control unit 6 as the drive signal Vin as the determination target discharge unit D. -H is supplied to the detection target discharge unit D-H, and the detection circuit 20 detects the detection signal NSA according to the detection potential signal Vout indicating the residual vibration generated in the determination target discharge unit D-H. , The measurement circuit 81 generates waveform information Info based on the detection signal NSA, and the ejection state determination circuit 82 uses the waveform information Info to determine the ink in the determination target ejection unit DH. Perform discharge status determination to determine the discharge status, and It includes a process of generating the determination information Stt indicating a constant results, and a series of processing executed by the ink jet printer 1.

Here, the discharge state determination executed by the discharge state determination circuit 82 is, as described above, whether or not the ink discharge state from the determination target discharge unit D-H is normal, that is, the determination target discharge unit D−. In H, it is determined whether or not a discharge abnormality has occurred.
Further, the ejection abnormality is a general term for a state in which the ink ejection state in the ejection unit D becomes abnormal, that is, a state in which ink cannot be ejected accurately from the nozzles N included in the ejection unit D. More specifically, the ejection abnormality is a state in which ink cannot be ejected according to a mode defined by the drive signal Com even if the ejection unit D is driven by the drive signal Com to eject ink from the ejection unit D. Here, the ink ejection mode defined by the drive signal Com is an ejection mode in which the ejection unit D ejects an amount of ink defined by the waveform of the drive signal Com, and the ejection unit D is ejected by the waveform of the drive signal Com. Ink is ejected at a speed. That is, the state in which ink cannot be ejected due to the ink ejection mode defined by the drive signal Com is different from the ink ejection amount defined by the drive signal Com in addition to the state in which ink cannot be ejected from the ejection unit D. Ink is ejected at a desired landing position on the recording paper P because the ink is ejected at a speed different from the ink ejection speed defined by the drive signal Com and the state in which the ink is ejected from the ejection section D. Including the state that can not be.

Hereinafter, in the printing process or the discharge state determination process, the discharge unit D driven by the drive signal Com (drive signal Vin) is referred to as a drive target discharge unit DD. In the present embodiment, the determination target discharge unit D-H is selected from the drive target discharge units DD driven by the drive signal Com in the printing process. That is, in the present embodiment, it is assumed that the ejection state determination process is executed during the printing process.
In the following, among the drive target discharge units DD, the discharge units D that do not correspond to the determination target discharge units D-H are referred to as print drive discharge units DP. Hereinafter, when the printing process or the ejection state determination process is performed, the ejection unit D that is not driven by the drive signal Com is referred to as a pause ejection unit D-K.
That is, in the present embodiment, when the printing process or the ejection state determination process is executed, each of the M ejection units D provided in the head unit HU is driven by the drive target ejection unit DD driven by the drive signal Com. Or, it operates as any one of the pause discharge portions D-K that are not driven by the drive signal Com. In the present embodiment, each drive target discharge section DD operates as either the determination target discharge section D-H or the print drive discharge section DP.

<< 2. Overview of recording head and discharge section >>
With reference to FIGS. 3 and 4, the recording head HD and the discharge section D provided in the recording head HD will be described.

FIG. 3 is a schematic partial cross-sectional view of the recording head HD in which the recording head HD is cut so as to include the ejection portion D.
As shown in FIG. 3, the ejection part D includes a piezoelectric element PZ, a cavity 320 filled with ink inside (an example of a “pressure chamber”), a nozzle N communicating with the cavity 320, a vibration plate 310, Is provided. The ejection part D ejects ink in the cavity 320 from the nozzles N when the drive signal Vin is supplied to the piezoelectric element PZ and the piezoelectric element PZ is driven by the drive signal Vin. The cavity 320 is a space defined by the cavity plate 340, the nozzle plate 330 in which the nozzles N are formed, and the vibration plate 310. The cavity 320 communicates with the reservoir 350 via the ink supply port 360. The reservoir 350 communicates with the ink cartridge 31 corresponding to the ejection unit D via the ink intake port 370.

In the present embodiment, a unimorph (monomorph) type as shown in FIG. 3 is adopted as the piezoelectric element PZ. The piezoelectric element PZ is not limited to a unimorph type, but may be a bimorph type or a laminated type.
The piezoelectric element PZ includes an upper electrode Zu, a lower electrode Zd, and a piezoelectric body Zm provided between the upper electrode Zu and the lower electrode Zd. The lower electrode Zd is electrically connected to a power supply line LHd (see FIG. 5) set to the potential VBS. When the drive signal Com (drive signal Vin) is supplied to the upper electrode Zu and a voltage is applied between the upper electrode Zu and the lower electrode Zd, the piezoelectric element PZ is moved in the + Z direction according to the applied voltage. Alternatively, the piezoelectric element PZ vibrates as a result of displacement in the −Z direction.

A diaphragm 310 is installed in the upper surface opening of the cavity plate 340. A lower electrode Zd is joined to the vibration plate 310. For this reason, when the piezoelectric element PZ is driven by the drive signal Vin and vibrates, the diaphragm 310 also vibrates. Then, the volume of the cavity 320 (pressure in the cavity 320) is changed by the vibration of the vibration plate 310, and the ink filled in the cavity 320 is ejected from the nozzle N.
More specifically, when ink is ejected from the nozzle N of the ejection part D, the control unit 6 first supplies the piezoelectric element PZ to the piezoelectric element PZ so that the piezoelectric element PZ of the ejection part D is displaced in the + Z direction. The potential of the signal Vin is changed. As a result, the piezoelectric element PZ and the vibration plate 310 are bent in the + Z direction, and the volume of the cavity 320 of the discharge part D is increased. Next, the control unit 6 changes the potential of the drive signal Vin supplied to the piezoelectric element PZ so that the piezoelectric element PZ of the ejection unit D is displaced in the −Z direction. Thereby, the piezoelectric element PZ and the vibration plate 310 are bent in the −Z direction, and the volume of the cavity 320 of the discharge part D is contracted. As a result, a part of the ink filled in the cavity 320 can be ejected from the nozzle N as an ink droplet. Residual vibration occurs in the discharge portion D including the vibration plate 310 after the piezoelectric element PZ and the vibration plate 310 are driven by the drive signal Vin and displaced in the Z-axis direction.
Ink is supplied from the reservoir 350 when the ink in the cavity 320 decreases due to ink ejection. Ink is supplied from the ink cartridge 31 to the reservoir 350 via the ink intake port 370.

  FIG. 4 shows the four recording heads HD provided in the head module HM when the inkjet printer 1 is viewed in a plan view from the + Z direction or the −Z direction, and a total of 4M pieces provided on the four recording heads HD. 5 is an explanatory diagram for explaining an example of an arrangement of nozzles N. FIG.

As shown in FIG. 4, each recording head HD provided in the head module HM is provided with a nozzle row Ln. Here, the nozzle row Ln is a plurality of nozzles N provided so as to extend in a row in a predetermined direction. In the present embodiment, it is assumed that each nozzle row Ln is configured by arranging M nozzles N so as to extend in a row in the X-axis direction.
Hereinafter, as shown in FIG. 4, the four nozzle rows Ln provided in the head module HM are referred to as nozzle rows Ln-BK, Ln-CY, Ln-MG, and Ln-YL. Here, the nozzle row Ln-BK is a nozzle row Ln in which the nozzles N of the discharge portion D that discharges black ink are arranged, and the nozzle row Ln-CY is the nozzle N of the discharge portion D that discharges cyan ink. Are arranged in a nozzle row Ln, the nozzle row Ln-MG is a nozzle row Ln in which the nozzles N of the ejection unit D that ejects magenta ink are arranged, and the nozzle row Ln-YL ejects yellow ink. This is a nozzle row Ln in which the nozzles N of the discharge part D are arranged.

  However, the nozzle row Ln shown in FIG. 4 is an example, and the M nozzles N belonging to each nozzle row Ln are arranged with a predetermined width in a direction intersecting with the extending direction of the nozzle row Ln. May be. That is, in each nozzle row Ln, the M nozzles N belonging to each nozzle row Ln are arranged in a staggered manner so that the even-numbered nozzles N and the odd-numbered nozzles N have different positions in the Y-axis direction from the + X side. May be. Each nozzle row Ln may extend in a direction different from the X-axis direction. Further, in this embodiment, the case where the number of nozzle rows Ln provided in each print head HD is “1” is illustrated, but each print head HD is provided with two or more nozzle rows Ln. May be.

<< 3. Head unit configuration >>
Hereinafter, the configuration of each head unit HU will be described with reference to FIG.

  FIG. 5 is a block diagram showing an example of the configuration of the head unit HU. As described above, the head unit HU includes the recording head HD, the supply circuit 10, and the detection circuit 20. The head unit HU also includes an internal wiring LHa (an example of “signal wiring”) to which the drive signal Com is supplied from the control unit 6 and an internal wiring LHs (“detection”) for supplying the detection potential signal Vout to the detection circuit 20. An example of “wiring for use”).

  As shown in FIG. 5, the supply circuit 10 includes M switches SWa (SWa [1] to SWa [M]), M switches SWs (SWs [1] to SWs [M]), and each switch. And a connection state designating circuit 11 for designating the connection state. As each switch, for example, a transmission gate can be adopted. FIG. 5 shows a case where M = 3 for simplicity.

The connection state designating circuit 11 turns on / off the switches SWa [1] to SWa [M] based on at least a part of the print signal SI, the latch signal LAT, and the period defining signal Tsig supplied from the control unit 6. Connection state designation signals SLa [1] to SLa [M] for designating, and connection state designation signals SLs [1] to SLs [M] for designating ON / OFF of the switches SWs [1] to SWs [M] are generated. To do.
The switch SWa [m] is connected between the internal wiring LHa and the upper electrode Zu [m] of the piezoelectric element PZ [m] provided in the ejection part D [m] in response to the connection state designation signal SLa [m]. Switch between conduction and non-conduction. For example, the switch SWa [m] is turned on when the connection state designation signal SLa [m] is at a high level and turned off when it is at a low level. As described above, the drive signal Vin [m] is a signal that is actually supplied to the piezoelectric element PZ [m] of the ejection section D [m] via the switch SWa [m].
The switch SWs [m] is connected between the internal wiring LHs and the upper electrode Zu [m] of the piezoelectric element PZ [m] provided in the discharge part D [m] in response to the connection state designation signal SLs [m]. Switch between conduction and non-conduction. For example, the switch SWs [m] is turned on when the connection state designation signal SLs [m] is at a high level and turned off when it is at a low level.

A detection potential signal Vout [m] output from the piezoelectric element PZ [m] of the discharge unit D [m] driven as the determination target discharge unit D-H is supplied to the detection circuit 20 via the internal wiring LHs. Is done. Further, the drive signal Com is supplied to the detection circuit 20 through the internal wiring LHa. The detection circuit 20 generates a detection signal NSA based on the detection potential signal Vout [m] and the drive signal Com.
However, the present invention is not limited to such an embodiment, and at least the detection potential signal Vout may be supplied to the detection circuit 20. That is, the drive signal Com may not be supplied to the detection circuit 20.

<< 4. Head unit operation >>
Hereinafter, the operation of each head unit HU will be described with reference to FIGS.

  In the present embodiment, the operation period of the inkjet printer 1 includes one or a plurality of unit periods Tu. Further, the inkjet printer 1 according to the present embodiment can drive each ejection unit D for printing processing in each unit period Tu. In addition, the inkjet printer 1 according to the present embodiment drives the determination target discharge unit D-H in the discharge state determination process and detects the detection potential signal Vout from the determination target discharge unit D-H in each unit period Tu. Can be detected.

  Note that, in general, the inkjet printer 1 causes ink to be ejected, for example, one or more times from each ejection unit D by executing a printing process in a plurality of unit periods Tu provided continuously or intermittently. Then, an image indicated by the print data Img is formed. In addition, the inkjet printer 1 according to the present embodiment performs M discharge state determination processes by executing M discharge state determination processes, for example, in M unit periods Tu provided continuously or intermittently. The ink ejection state in each of [1] to D [M] is determined.

FIG. 6 is a timing chart for illustrating the operation of the inkjet printer 1 in the unit period Tu.
As shown in FIG. 6, the control unit 6 outputs a latch signal LAT having a pulse PlsL. Thereby, the control unit 6 defines the unit period Tu as a period from the rising of the pulse PlsL to the rising of the next pulse PlsL.
Further, as shown in FIG. 6, the control unit 6 outputs a period defining signal Tsig having a pulse PlsT1 and a pulse PlsT2 in the unit period Tu. Then, the control unit 6 divides the unit period Tu into a control period TSS0 (an example of “preparation period”) from the rise of the pulse PlsL to the rise of the pulse PlsT1, and a control period TSS1 from the rise of the pulse PlsT1 to the rise of the pulse PlsT2. (An example of “first period”) and a control period TSS2 (an example of “second period”) from the rise of the pulse PlsT2 to the rise of the pulse PlsL.
In this embodiment, the control period TSS2 is started at the end of the control period TSS1, and the unit period Tu is ended at the end of the control period TSS2. However, the present invention is not limited to such a mode, After the end of the period TSS1, the control period TSS2 may be started with an interval, or after the end of the control period TSS2, the unit period Tu may be ended with an interval.

  The print signal SI according to the present embodiment includes individual designation signals Sd [1] to Sd [M] that designate the type of operation of the ejection units D [1] to D [M] in each unit period Tu. When the printing process or the ejection state determination process is executed in the unit period Tu, the control unit 6 prior to the unit period Tu, as shown in FIG. 6, the individual designation signals Sd [1] to Sd [M ] Is supplied to the connection state designating circuit 11 in synchronization with the clock signal CL. In this case, the connection state designation circuit 11 generates connection state designation signals SLa [m] and SLs [m] based on the individual designation signal Sd [m] in the unit period Tu.

  The individual designation signal Sd [m] according to the present embodiment is the operation as the print drive ejection unit DP and the determination target ejection unit D-H with respect to the ejection unit D [m] in each unit period Tu. One of the three types of operations, that is, the operation or the operation as the pause discharge unit D-K, is designated. In other words, each discharge unit D [m] receives a print drive discharge unit DP, a determination target discharge unit D-H, or a pause discharge unit D-K in response to an individual designation signal Sd [m] in each unit period Tu. It is classified into any one of these.

  In the present embodiment, it is assumed that the individual designation signal Sd [m] is a 2-bit digital signal (see FIGS. 9 to 11).

  As shown in FIG. 6, the drive signal Com has a waveform PS (an example of a “drive waveform”) provided in the control period TSS1. The waveform PS is determined such that when the drive signal Com having the waveform PS is supplied as the drive signal Vin [m] to the discharge portion D [m], the discharge portion D [m] discharges a predetermined amount of ink. It is a waveform. The drive signal Com is maintained at the potential V0 (an example of “predetermined potential”) in the control period TSS0 and the control period TSS2.

  FIG. 7 is an explanatory diagram for explaining the relationship between the individual designation signal Sd [m] and the connection state designation signals SLa [m] and SLs [m] generated in the connection state designation circuit 11.

As shown in FIG. 7, the connection state designating circuit 11 uses the individual designation signal Sd [m] to designate the operation as the print drive ejection unit DP for the ejection unit D [m] in the unit period Tu. The connection state designation signal SLa [m] is set to the high level during the control periods TSS0 and TSS1, and is set to the low level during the control period TSS2. The connection state designation signal SLs [m] is set to the low level over the unit period Tu. Set to. In this case, the switch SWa [m] maintains the on state during the control periods TSS0 and TSS1, maintains the off state during the control period TSS2, and the switch SWs [m] maintains the off state over the unit period Tu. Therefore, when the ejection unit D [m] is the print drive ejection unit DP, the drive signal Vin [m] having the potential V0 is supplied in the control period TSS0, and the waveform PS in the control period TSS1. The ink is ejected by being driven by a drive signal Vin [m] having.
In the present embodiment, as an example, when the individual designation signal Sd [m] indicates (1, 1), the operation as the print drive ejection unit DP is designated for the ejection unit D [m]. I will do it.

Further, as shown in FIG. 7, in the unit period Tu, the connection state designating circuit 11 designates the operation as the determination target ejection unit D-H for the ejection unit D [m] by the individual designation signal Sd [m]. In this case, the connection state designation signal SLa [m] is set to a high level in the control periods TSS0 and TSS1, set to a low level in the control period TSS2, and the connection state designation signal SLs [m] is set to high in the control period TSS2. Set to level and set to low level in the control periods TSS0 and TSS1. In this case, the switch SWa [m] maintains the on state in the control periods TSS0 and TSS1, maintains the off state in the control period TSS2, and the switch SWs [m] maintains the on state in the control period TSS2. The off state is maintained in the periods TSS0 and TSS1. Therefore, when the ejection unit D [m] is the determination target ejection unit D-H, the drive signal Vin [m] having the potential V0 is supplied in the control period TSS0, and the waveform PS in the control period TSS1. Is driven by the drive signal Vin [m] having the above and ejects ink to vibrate, thereby creating a state in which residual vibration occurs in the control period TSS2. Then, the potential of the upper electrode Zu [m] of the discharge part D [m] changes according to the residual vibration generated in the discharge part D [m]. That is, the detection circuit 20 detects the detection potential signal Vout [m] based on the residual vibration generated in the ejection part D [m] through the internal wiring LHs in the control period TSS2.
In the present embodiment, as an example, when the individual designation signal Sd [m] indicates (1, 0), the operation as the determination target ejection unit D-H is designated for the ejection unit D [m]. I will do it.

Further, as shown in FIG. 7, in the unit period Tu, the connection state designating circuit 11 designates the operation as the pause ejection unit D-K for the ejection unit D [m] by the individual designation signal Sd [m]. In this case, the connection state designation signal SLa [m] is set to a high level in the control periods TSS0 and TSS2, and is set to a low level in the control period TSS1, and the connection state designation signal SLs [m] is set to low for the unit period Tu. Set to level. In this case, the switch SWa [m] maintains the ON state in the control periods TSS0 and TSS2, maintains the OFF state in the control period TSS1, and the switch SWs [m] maintains the OFF state over the unit period Tu. Therefore, when the discharge unit D [m] is the pause discharge unit D-K, the drive signal Vin [m] having the potential V0 is supplied in the control periods TSS0 and TSS2, and the drive signal Vin is supplied in the control period TSS1. Since the supply of [m] is stopped, ink is not ejected in the unit period Tu.
In this embodiment, as an example, when the individual designation signal Sd [m] indicates (0, 0), the operation as the pause ejection unit D-K is designated for the ejection unit D [m]. And

FIG. 8 is a diagram illustrating an example of the configuration of the connection state designating circuit 11 according to the present embodiment. FIG. 8 shows a case where M = 3 for the sake of simplicity.
As shown in FIG. 8, the connection state designating circuit 11 includes transfer circuits SR [1] to SR [M] and a latch circuit so as to correspond one-to-one with the discharge units D [1] to D [M]. LT [1] to LT [M] and decoders DC [1] to DC [M]. Among these, the individual designation signal Sd [m] is supplied to the transfer circuit SR [m]. In FIG. 8, the individual designation signals Sd [1] to Sd [M] are supplied serially. For example, the individual designation signal Sd [m] corresponding to m stages is transferred from the transfer circuit SR [1] to the transfer circuit SR. A case is illustrated in which [m] is sequentially transferred in synchronization with the clock signal CL. The latch circuit LT [m] latches the individual designation signal Sd [m] supplied to the transfer circuit SR [m] at the timing when the pulse PlsL of the latch signal LAT rises to a high level. Further, the decoder DC [m] decodes the individual designation signal Sd [m] according to FIG. 7 based on at least a part of the individual designation signal Sd [m], the latch signal LAT, and the period defining signal Tsig. The connection state designation signals SLa [m] and SLs [m] are generated.

As described above, the detection circuit 20 according to the present embodiment generates the detection signal NSA [m] based on the detection potential signal Vout [m] and the drive signal Com. More specifically, the detection circuit 20 according to the present embodiment is a signal indicating a potential difference between the potential indicated by the detection potential signal Vout [m] in the control period TSS2 and the potential V0 indicated by the drive signal Com in the control period TSS2. The detection signal NSA [m] shaped into a waveform suitable for processing by the determination unit JU is generated by amplifying the signal or removing a noise component.
For example, the detection circuit 20 attenuates a high-frequency component of a negative feedback amplifier for amplifying a signal indicating a potential difference between the detection potential signal Vout [m] and the drive signal Com, and a signal indicating the potential difference. And a voltage follower for converting the impedance of the signal indicating the potential difference and outputting a low impedance signal.

<< 5. Judgment unit >>
Next, after describing the residual vibration generated in the discharge unit D, the determination unit JU will be described.

In general, the residual vibration generated in the ejection part D has a natural vibration period determined by the shape of the nozzle N, the weight of the ink filled in the cavity 320, the viscosity of the ink filled in the cavity 320, and the like. .
For example, in general, when a discharge abnormality occurs due to air bubbles mixed in the cavity 320 of the discharge part D, the residual vibration generated in the discharge part D compared to when the discharge state is normal. The period of is shortened. In general, when a discharge abnormality occurs due to a foreign matter such as paper dust adhering to the vicinity of the nozzle N of the discharge portion D, the discharge portion is compared with a case where the discharge state is normal. The period of the residual vibration generated in D becomes longer, and the amplitude of the residual vibration generated in the discharge section D becomes smaller. In general, when the discharge abnormality occurs because the ink in the cavity 320 of the discharge portion D is thickened, the discharge portion D occurs in the discharge portion D as compared with the case where the discharge state is normal. The period of the residual vibration becomes longer, and the amplitude of the residual vibration generated in the discharge part D becomes smaller.
As described above, the residual vibration characteristics such as the period and amplitude of the residual vibration generated in the ejection unit D vary depending on the ink ejection state in the ejection unit D. For this reason, the ink ejection state in the ejection unit D can be determined based on the characteristics of the residual vibration such as the period and amplitude of the residual vibration generated in the ejection unit D.

A detection signal NSA, which is a signal obtained by shaping the waveform of the detection potential signal Vout, shows a waveform corresponding to the residual vibration occurring in the determination target discharge unit DH. Specifically, the detection signal NSA indicates a period corresponding to the period of the residual vibration occurring in the determination target discharge unit DH, and corresponds to the amplitude of the residual vibration occurring in the determination target discharge part D-H. Indicates the amplitude. For this reason, it is possible to determine the ink discharge state in the determination target discharge portion DH based on the cycle and amplitude of the detection signal NSA.
In the following, the period of the residual vibration generated in the determination target discharge part D-H and the period of the detection signal NSA generated based on the detection potential signal Vout indicating the residual vibration generated in the determination target discharge part D-H will be described. In some cases, it is simply referred to as a residual vibration period Tc.

  As described above, the determination unit JU determines the ink discharge state in the determination target discharge portion D-H based on the measurement circuit 81 that generates the waveform information Info based on the detection signal NSA, and the waveform information Info. A discharge state determination circuit 82 that generates determination information Stt indicating the result of the above.

FIG. 9 is an explanatory diagram for explaining the generation of the waveform information Info in the measurement circuit 81. In the present embodiment, the waveform information Info includes period information Info-T indicating the period Tc of the detection signal NSA and amplitude information Info-S which is information related to the amplitude of the detection signal NSA.
As shown in FIG. 9, the measurement circuit 81 measures the period Tc of the detection signal NSA based on the comparison result between the potential of the detection signal NSA and the potential Vth-C of the amplitude center level of the detection signal NSA. Period information Info-T indicating the period Tc is generated.
In addition, the measurement circuit 81 has a potential of the detection signal NSA that is higher than the potential Vth-H higher than the potential Vth-C and lower than the potential Vth-C during the period of measuring the period Tc. Is set to a value “1” indicating that the detection signal NSA has a predetermined amplitude, and in other cases, the amplitude information Info-S is set to a value “1”. The value of the information Info-S is set to a value “0” indicating that the detection signal NSA does not have a predetermined amplitude.
Then, the measurement circuit 81 generates waveform information Info including period information Info-T and amplitude information Info-S.

FIG. 10 is an explanatory diagram for explaining generation of determination information Stt in the discharge state determination circuit 82.
As shown in this figure, when the amplitude information Info-S is “1”, the ejection state determination circuit 82 is configured to have a period Tc indicated by the period information Info-T and at least one of the threshold value Tth1 and the threshold value Tth2. , The ink discharge state in the determination target discharge portion D-H is determined, and determination information Stt indicating the result of the determination is generated.
Here, the threshold value Tth1 is the residual vibration period Tc when the discharge state of the determination target discharge unit DH is normal and the residual vibration when bubbles are mixed into the cavity 320 of the determination target discharge unit D-H. This is a value for indicating the boundary between the cycle Tc. Further, the threshold value Tth2 is larger than the threshold value Tth1, and the residual vibration period Tc when the discharge state of the determination target discharge unit D-H is normal and the vicinity of the nozzle N of the determination target discharge unit D-H This is a value for indicating the boundary between the residual vibration period Tc when the foreign matter adheres to the ink or when the ink in the cavity 320 of the determination target ejection part D-H is thickened.

In the present embodiment, as shown in FIG. 10, when the value of the amplitude information Info-S is “1” and the period Tc indicated by the period information Info-T satisfies “Tth1 ≦ Tc ≦ Tth2”. The ink discharge state in the determination target discharge portion DH is considered to be normal. In this case, the ejection state determination circuit 82 sets a value indicating that the ink ejection state in the determination target ejection unit DH is normal, for example, “1”, for the determination information Stt.
Further, when the value of the amplitude information Info-S is “1” and the period Tc indicated by the period information Info-T satisfies “Tc <Tth1”, the ejection is performed by bubbles in the determination target ejection unit D-H. It is considered that an abnormality has occurred. In this case, the discharge state determination circuit 82 sets a value, for example, “2”, indicating that a discharge abnormality due to air bubbles has occurred in the determination target discharge portion DH in the determination information Stt.
Further, when the value of the amplitude information Info-S is “1” and the period Tc indicated by the period information Info-T satisfies “Tth2 <Tc”, the foreign matter adheres to the determination target ejection unit DH. It is considered that ejection abnormality has occurred due to ink thickening. In this case, the ejection state determination circuit 82 sets a value indicating, for example, “3”, that the ejection abnormality due to foreign matter adhesion or ink thickening has occurred in the determination target ejection unit DH with respect to the determination information Stt. Set.
Further, when the value of the amplitude information Info-S is “0”, it is considered that the ejection abnormality due to foreign matter adhesion or ink thickening has occurred in the determination target ejection unit DH. In this case, the discharge state determination circuit 82 sets a value, for example, “3”, indicating that a discharge abnormality has occurred in the determination target discharge portion DH, for the determination information Stt.
As described above, the ejection state determination circuit 82 generates the determination information Stt based on the waveform information Info including the period information Info-T and the amplitude information Info-S.

<< 6. Conclusion of embodiment >>
As described above, in this embodiment, in the control period TSS2 of the unit period Tu, the supply of the drive signal Com to the print drive discharge unit DP is stopped, and the potential V0 is applied to the pause discharge unit D-K. While detecting the drive signal Com, the detection potential signal Vout indicating the residual vibration generated in the determination target discharge unit DH is detected. In order to clarify the effect of the present embodiment in which the head unit HU is driven according to such a mode, first, in the following, first, a mode in which the head unit HU is driven in a mode different from the present embodiment (hereinafter referred to as “comparative”). Will be described.

FIG. 11 is an explanatory diagram for explaining connection state designation signals SLa [m] and SLs [m] generated in the ink jet printer according to the comparative example. The comparative inkjet printer is configured in the same manner as the inkjet printer 1 according to the present embodiment, except that a connection state designation signal SLa [m] having a signal level as shown in FIG. 11 is output.
As shown in FIG. 11, the inkjet printer according to the comparative example has a connection state designation signal SLa [m when the ejection unit D [m] is designated as the print drive ejection unit DP in the control period TSS2 of the unit period Tu. ] Is set to the high level, and the connection state designation signal SLa [m] is set to the low level when the discharge part D [m] is designated as the pause discharge part D-K. In other words, the proportional inkjet printer supplies the drive signal Com to the print drive discharge unit DP and stops the supply of the drive signal Com to the pause discharge unit D-K in the control period TSS2.

FIG. 12 is an explanatory diagram for explaining the operation of the ejection unit D in the inkjet printer according to the comparative example. As described above, the proportional inkjet printer stops the supply of the drive signal Com to the upper electrode Zu of the piezoelectric element PZ provided in the rest discharge portion D-K in the control period TSS2. Therefore, in the proportional inkjet printer, the piezoelectric element PZ of the rest discharge portion D-K is easily displaced in the control period TSS2 as compared with the case where a signal having a constant potential is supplied to the upper electrode Zu. Vibration is likely to occur in the pause discharge part D-K.
When vibration occurs in one discharge section D, the partition 340A that partitions one discharge section D and another discharge section D adjacent to one discharge section D bends. For this reason, when the pause discharge unit D-K and the determination target discharge unit D-H are adjacent to each other, vibration generated in the pause discharge unit D-K is caused by the pause discharge unit D-K and the determination target discharge unit D. The possibility of propagation to the determination target discharge portion D-H is increased through the partition wall 340A provided between -H.
In particular, as shown in FIG. 12, in the comparative inkjet printer, the pause discharge unit D-K is adjacent to the two discharge units D of the print drive discharge unit DP and the determination target discharge unit D-H. In this case, the vibration remaining in the print drive discharge part DP in the control period TSS2 propagates to the determination target discharge part D-H via the pause discharge part D-K. In this case, noise caused by vibration propagated through the rest discharge portion D-K is superimposed on the detection potential signal Vout detected from the determination target discharge portion DH in the control period TSS2. For this reason, in the example of FIG. 12, there is a high possibility that the ink discharge state in the determination target discharge portion DH cannot be accurately determined.

  On the other hand, in the present embodiment, as shown in FIG. 13, in order to fix the potential of the upper electrode Zu of the rest discharge portion D-K in the control period TSS2, the control is performed as compared with the comparative inkjet printer. It is possible to suppress the displacement of the piezoelectric element PZ in the period TSS2 and to suppress the occurrence of vibrations in the rest discharge portion D-K in the control period TSS2. For this reason, in the present embodiment, it is possible to prevent noise from being superimposed on the detection potential signal Vout due to vibrations from the pause discharge unit D-K, and ink discharge in the determination target discharge unit D-H. It is possible to improve the state determination accuracy.

  Further, the proportional inkjet printer supplies a drive signal Com to the print drive discharge section DP in the control period TSS2. In other words, the proportional inkjet printer switches on the upper electrode Zu [m] and the internal wiring LHa of the discharge unit D [m] selected as the print drive discharge unit DP in the control period TSS2. Electrical connection is made via SWa [m]. In this case, the fluctuation of the potential of the upper electrode Zu [m] due to the vibration remaining in the print drive discharge part DP propagates as noise to the internal wiring LHa. Further, noise due to the vibration of the print drive discharge part DP may propagate to the internal wiring LHs via the internal wiring LHa. When the noise caused by the vibration of the print drive discharge part DP propagates to the internal wiring LHa and the internal wiring LHs, the detection circuit 20 accurately detects the residual vibration generated in the determination target discharge part D-H. It becomes difficult to detect.

  On the other hand, in the present embodiment, since the supply of the drive signal Com to the print drive discharge unit DP is stopped in the control period TSS2, the print drive discharge unit DP is compared with the proportional inkjet printer. It is possible to reduce the possibility that noise caused by the vibration of the noise propagates to the internal wiring LHa and the internal wiring LHs. Thereby, in this embodiment, it becomes possible for the detection circuit 20 to accurately detect the residual vibration generated in the determination target discharge unit DH.

In the present embodiment, the determination target discharge unit DH that is the target of residual vibration detection in the control period TSS2 is an example of the “first discharge unit”, and the piezoelectric element provided in the determination target discharge unit DH. The element PZ is an example of a “first piezoelectric element”, the upper electrode Zu included in the piezoelectric element PZ is an example of a “first electrode”, and the cavity 320 provided in the determination target discharge unit DH is “ It is an example of a “first pressure chamber”.
In addition, the print drive discharge unit DP that discharges ink in the control period TSS1 is an example of a “second discharge unit”, and the piezoelectric element PZ provided in the print drive discharge unit DP is a “second piezoelectric element”. The upper electrode Zu included in the piezoelectric element PZ is an example of a “second electrode”, and the cavity 320 provided in the print driving discharge unit DP is an example of a “second pressure chamber”. .
In addition, the pause discharge unit D-K in which the supply of the drive signal Com is stopped in the control period TSS1 is an example of “third discharge unit”, and the piezoelectric element PZ provided in the pause discharge unit D-K is “third”. The piezoelectric element PZ is an example, the upper electrode Zu included in the piezoelectric element PZ is an example of a “third electrode”, and the cavity 320 provided in the pause discharge portion D-K is an example of a “third pressure chamber”. It is.
The switch SWs [m] provided corresponding to the discharge unit D [m] operating as the determination target discharge unit D-H is an example of a “detection switch” and operates as the determination target discharge unit D-H. The switch SWa [m] provided corresponding to the discharge unit D [m] is an example of a “first switch”, and is provided corresponding to the discharge unit D [m] operating as the print drive discharge unit DP. The switch SWa [m] is an example of a “second switch”, and the switch SWa [m] provided corresponding to the discharge unit D [m] operating as the pause discharge unit D-K is an example of a “third switch”. It is.

<< B. Modification >>
Each of the above forms can be variously modified. Specific modifications are exemplified below. Two or more aspects arbitrarily selected from the following examples can be appropriately combined within a range that does not contradict each other. In addition, about the element which an effect | action and a function are equivalent to embodiment in the modification illustrated below, the code | symbol referred by the above description is diverted and each detailed description is abbreviate | omitted suitably.

<< Modification 1 >>
In the above-described embodiment, the drive signal Com having the same waveform is supplied to the printing drive discharge unit DP and the determination target discharge unit D-H. However, the present invention is limited to such a mode. Instead, the drive signal Com having a different waveform may be supplied to the print drive discharge unit DP and the determination target discharge unit D-H.

FIG. 14 is a block diagram showing an example of the configuration of the head unit HUa included in the ink jet printer according to this modification. The ink jet printer according to this modification is an embodiment except that the head unit HUa is provided instead of the head unit HU, and the drive signal Com includes the drive signal Com-A and the drive signal Com-B. It is comprised similarly to the inkjet printer 1 which concerns on this.
The head unit HUa includes a supply circuit 10a instead of the supply circuit 10, a point including an internal wiring LHb to which the drive signal Com-B is supplied, and a point where the drive signal Com-A is supplied to the internal wiring LHa. Are configured in the same manner as the head unit HU.
The supply circuit 10a includes switches SWb [1] to SWb [M] corresponding to the discharge units D [1] to D [M] on a one-to-one basis, and a connection state designation instead of the connection state designation circuit 11. The configuration is the same as that of the supply circuit 10 except that the circuit 11a is provided.
The connection state designation circuit 11a outputs a connection state designation signal SLb [m] for designating on / off of the switch SWb [m] in addition to the connection state designation signals SLa [m] and SLs [m].

  FIG. 15 is a timing chart for illustrating the operation of the ink jet printer according to this modification. As shown in this figure, the drive signal Com-A has a waveform PS1 provided in the control period TSS1. In the waveform PS1, when the drive signal Com-A having the waveform PS1 is supplied to the discharge section D [m] as the drive signal Vin [m], residual vibration occurs in the discharge section D [m] in the control period TSS2. The waveform is determined as follows. The drive signal Com-B has a waveform PS2 provided in the control period TSS1. The waveform PS2 is such that when the drive signal Com-B having the waveform PS2 is supplied as the drive signal Vin [m] to the ejection unit D [m], the ejection unit D [m] ejects a predetermined amount of ink. It is a defined waveform.

  FIG. 16 illustrates the relationship between the individual designation signal Sd [m] and the connection state designation signals SLa [m], SLb [m], and SLs [m] generated in the connection state designation circuit 11a. It is explanatory drawing of. As shown in this figure, the connection state designating circuit 11a uses the individual designation signal Sd [m] to designate the operation as the print drive ejection unit DP for the ejection unit D [m] in the unit period Tu. The connection state designation signal SLb [m] is set to high level in the control periods TSS0 and TSS1, and is set to low level in the control period TSS2, and the connection state designation signals SLa [m] and SLs [m] are set to the unit period. Set to low level for Tu. Further, the connection state designating circuit 11a connects the connection state when the individual designation signal Sd [m] designates the operation as the determination target ejection unit DH or the rest ejection unit D-K for the ejection unit D [m]. Connection state designation signals SLa [m] and SLs [m] similar to those of the designation circuit 11 are output, and the connection state designation signal SLb [m] is set to a low level over the unit period Tu. For this reason, the determination target discharge unit DH is driven by the drive signal Com-A having the waveform PS1 in the control period TSS1, and the print drive discharge unit DP is driven by the drive signal having the waveform PS2 in the control period TSS1. Driven by Com-B.

<< Modification 2 >>
In the embodiment and the modification described above, the determination unit JU is provided as a circuit separate from the control unit 6, but the present invention is not limited to such a mode, and a part of the determination unit JU is included. Alternatively, all may be implemented as functional blocks realized by the CPU of the control unit 6 operating according to the control program.

<< Modification 3 >>
In the embodiment and the modification described above, the ink jet printer 1 is provided so that the four head units HU and the four ink cartridges 31 correspond to each other in one-to-one. The ink jet printer 1 is not limited to the above, and the ink jet printer 1 only needs to include one or more head units HU and one or more ink cartridges 31.
In the above-described embodiment and modification, the inkjet printer 1 is provided with the determination unit JU corresponding to each head unit HU on a one-to-one basis. However, the present invention is not limited to such an embodiment. Instead, the inkjet printer 1 may be provided with one determination unit JU for a plurality of head units HU, or may be provided with a plurality of determination units JU for one head unit HU.

<< Modification 4 >>
In the above-described embodiments and modifications, it is assumed that the ink jet printer 1 is a serial printer. However, the present invention is not limited to such a mode, and the ink jet printer 1 includes a plurality of head modules HM. A so-called line printer may be used in which the nozzles N are provided so as to extend wider than the width of the recording paper P.

DESCRIPTION OF SYMBOLS 1 ... Inkjet printer, 5 ... Drive signal generation circuit, 6 ... Control part, 7 ... Conveyance mechanism, 10 ... Supply circuit, 20 ... Detection circuit, 60 ... Control module, 61 ... Memory | storage part, 81 ... Measurement circuit, 82 ... Discharge State determination circuit, 320 ... cavity, D ... discharge section, HD ... recording head, HU ... head unit, JU ... determination unit, JM ... determination module, LHa ... internal wiring, LHs ... internal wiring, PZ ... piezoelectric element, SWa ... Switch, SWs ... Switch, Zu ... Upper electrode.

Claims (6)

A first piezoelectric element that has a pair of electrodes including a first electrode and that is displaced in response to a change in potential of the drive signal when a drive signal is supplied to the first electrode; A first discharge unit capable of discharging a liquid according to
A second piezoelectric element that has a pair of electrodes including a second electrode and that is displaced in response to a change in potential of the drive signal when the drive signal is supplied to the second electrode; A second ejection part capable of ejecting liquid according to the displacement;
Arranged between the detection wiring and the first electrode;
Maintaining the off state in the first period;
A detection switch that maintains an ON state in a second period that starts after the end of the first period;
Arranged between the signal wiring to which the drive signal is supplied and the first electrode;
Maintaining the on state in the first period;
A first switch that maintains an off state in the second period;
Arranged between the signal wiring and the second electrode;
Maintaining the on state in the first period;
A second switch that maintains an off state in the second period;
A detection unit for detecting a potential of the detection wiring in the second period;
Based on the detection result in the detection unit,
A determination unit for determining a liquid discharge state in the first discharge unit;
Comprising
A liquid discharge apparatus characterized by that. The signal wiring is
Set to a predetermined potential in the second period;
The detector is
Detecting the potential of the detection wiring and the potential of the signal wiring in the second period;
The liquid ejecting apparatus according to claim 1, wherein the liquid ejecting apparatus is a liquid ejecting apparatus. A third piezoelectric element that has a pair of electrodes including a third electrode and that displaces in response to a change in potential of the drive signal when a drive signal is supplied to the third electrode, the displacement of the third piezoelectric element; A third discharger capable of discharging liquid according to
Arranged between the signal wiring and the third electrode;
Maintaining an off state in the first period;
A third switch that maintains an ON state in the second period;
Comprising
The liquid ejecting apparatus according to claim 2, wherein the liquid ejecting apparatus is a liquid ejecting apparatus. The signal wiring is
Set to the predetermined potential in a preparation period before the start of the first period;
The first switch, the second switch, and the third switch are:
Maintaining the on state during the preparation period;
The liquid ejecting apparatus according to claim 3, wherein the liquid ejecting apparatus is a liquid ejecting apparatus. A head unit provided in the liquid ejection device,
A first piezoelectric element that has a pair of electrodes including a first electrode and that is displaced in response to a change in potential of the drive signal when a drive signal is supplied to the first electrode; A first discharge unit capable of discharging a liquid according to
A second piezoelectric element that has a pair of electrodes including a second electrode and that is displaced in response to a change in potential of the drive signal when the drive signal is supplied to the second electrode; A second ejection part capable of ejecting liquid according to the displacement;
Arranged between the detection wiring and the first electrode;
Maintaining the off state in the first period;
A detection switch that maintains an ON state in a second period that starts after the end of the first period;
Arranged between the signal wiring to which the drive signal is supplied and the first electrode;
Maintaining the on state in the first period;
A first switch that maintains an off state in the second period;
Arranged between the signal wiring and the second electrode;
Maintaining the on state in the first period;
A second switch that maintains an off state in the second period;
A detection unit for detecting a potential of the detection wiring in the second period;
Comprising
A head unit characterized by that. A first piezoelectric element that has a pair of electrodes including a first electrode and that is displaced in response to a change in potential of the drive signal when a drive signal is supplied to the first electrode; A first discharge unit capable of discharging a liquid according to
A second piezoelectric element that has a pair of electrodes including a second electrode and that is displaced in response to a change in potential of the drive signal when the drive signal is supplied to the second electrode; A second ejection part capable of ejecting liquid according to the displacement;
A detection switch disposed between the detection wiring and the first electrode;
A first switch disposed between the signal line to which the drive signal is supplied and the first electrode;
A second switch disposed between the signal wiring and the second electrode;
A method for determining a liquid discharge state in a liquid discharge apparatus comprising:
In the first period,
The detection switch is turned off, the first switch is turned on, the second switch is turned on,
In the second period starting after the end of the first period,
The detection switch is turned on, the first switch is turned off, the second switch is turned off, and the potential of the detection wiring is detected,
Based on a result of the detection, a liquid discharge state in the first discharge unit is determined.
The determination method characterized by this.

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